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FOURTH MEETING

BRITISH ASSOCIATION

FOR THE

ADVANCEMENT OF SCIENCE;

HELD AT EDINBURGH IN 1834.

LONDON:

JOHN MURRAY, ALBEMARLE STREET.

1835.

PRI

RED LION COURT, FLEET

NTED BY RICHARD TAYLOR,
STREET.

CONTENTS.

_——_~<——— -

PROCEEDINGS OF THE MEETING... ceeeeeseeee bine Te aX

REPORTS ON THE STATE OF SCIENCE.

Report on the Geology of North America. Part I. By Henry. -
#). Rogers, HiGoedix soiled SOT) 2 BODO ALR LSS x 1

Report on the State of our Knowledge of the Laws of Contagion.
By Witu1am Henry, M.D., F.R.S., &c., late Physician to the
Manchester Royal Infirmary and Fever-Wards ...... ees ue” Sk

Report on Animal Physiology; comprising a Review of the Pro-
gress and Present State of Theory, and of our Information re-
specting the Blood, and the Powers which circulate it. By
Witriam Crark, M.D., F.R.C., F.G.S., F.C.P.S., late Fellow
of Trinity College, and Professor of Anatumy inthe University ~
of Cambridge.........+-+.+0. Gaate Cane ta nia oat « muir

Report on the Recent Progress and Present State of Zoology. By
the Rev. Lronarp Jenyns, M.A., F.L.S., F.Z.S., F.C.P.S. .. 143

Report on the Theory of Capillary Attraction. By the Rey. Jamzs
Cuattis, late Fellow of Trinity College, Cambridge ........ 253

Report on the Progress and Present State of Physical Optics.
By the Rev. Humpurey Lroyp, A.M., M.R.1.A., Fellow of —
Trinity College, and Professor of Natural and Experimental
Philosophy in the University of Dublin ........ tale Hd ooh aD

Report on the Progress and Present State of our Knowledge of »
Hydraulics as a Branch of Engineering. Part II. By Gores
Renniz, Esq., F.R.S., Acad. Reg. Se. Turin. Corresp., &c. &e. 415

TRANSACTIONS OF THE SECTIONS.

I, Matuematics anp Purysics:

Professor Hamitton on the Application to Dynamics of a General
Mathematical Method previously applied to Optics ........ 513
Professor Hamitton on Conjugate Functions, or Algebraic Couples,
as tending to illustrate generally the Doctrine of Imaginary
Quantities, and as confirming the Results of Mr. Graves re-
specting the Existence of Two independent Integers in the com-
plete expression of an Imaginary Logarithm .......+..+005 519

vi : CONTENTS,
Page.
Joun Tuomas Graves on the Theory of Exponential Functions. 523
Joun S. RussEtt’s Notice of the Reduction of an anomalous Fact
in Hydrodynamics, and of a new Law of the Resistance of
Fluids to the Motion of Floating Bodies .........+eeeeeeee 531
Earon Hopexinson on the Collision of imperfectly Elastic Bodies 534
The Rev. James Cuatuis’s Theoretical Explanations of some Facts
relating to the Composition of the Colours of the Spectrum .. 544
The Rev. Professor Powrxt on the Achromatism of the Eye; in
Continuation of a Paper in the last Volume of the British Asso-

ciation Reports .....+.+seeeeeee cece cereecees seeeeeces 548
The Rev. Professor Powrxt on the Theory of the Dispersion of
Light by the Hypothesis of Undulations ..... ofa suite iets cose: 549

The Rev. Professor Powrtt on the Repulsion excited between
Surfaces at minute distances by the Action of Heat ......... 549
The Rev. Wizt1am Wuewe t's Suggestions respecting Sir John
Herschel’s Remarks on the Theory of the Absorption of Light
. by coloured Media .. +06 e0+ee0s seen dewecececccerccere O00
The Rev. T. R. Rosryson on the Visibility of the Moon in Total
Eclipses ..4... cb eeseenensscrcecesccnecscarecsenceses OOS
Professor Mitier’s Account of some Observations made for the
purpose of determining the Positions of the Axes of Optical .

Elasticity in oblique prismatical Crystals......... ° piel woe 906
R. Appams’s Account of a new Phznomenon of sonorous Inter-
REVENGE eine Coole he Lees ele aes S660 8 Sew a mnte dhe gOOl

Professor Luoxp’s Account of Magnetical Observations in Ireland, _
and of a new Method of observing the Dip and the Force with

the same Instrument... 06.0, 0.4% «lx + dq Siar eidlale “5.0 pig-epibiclen apo
Sir Tuomas M. Brisbane onan apparent Anomaly inthe Measure >
of Rain..... ae sates Li ye arn oie bs web ele bieiel giehna stn onas 04 2/4i5,060

Professor Puitures’s Second Report of the Result of Twelve
Months’ Experiments on the Quantities of Rain falling at different
Elevations above the Surface of the Ground at York, under-
taken at the request of the Association by William Gray, Jun., -
and Professor Phillips, F.R.S, F.G.S., Secretaries of the York- ~~
shire Philosophical Society ...... 6s ceeecedevesecsvessee 560

Luxe Howarp on the difference of the Quantity of Rain at different
Heights above the Surface of the neighbouring Ground...... 563

Professor Strvetty’s Attempt to connect some of the best-known
Phzenomena of Meteorology with established Physical Principles 564

Professor Curistie—Extract of a Letter to Professor Forses .. 566

Lieut.-Col. Syxzs’s Notes on mean Temperatures in India...... 567

The Rev. J. Hairsrone on a peculiar Oscillation of the Barometer 569

H. H. Warson on the use of Leslie’s Hygrometer with a new Scale 569

Avexanpver J, Apir’s Account of Experiments onthe Expansion
of Stone by the Application of Heat .....cccereeeeceenes 569

CONTENTS.

Il. -Cuemisrry.—MIneERALoGy.

vil
Page.

Apam VANDER Toorn’s Table of the Proportions of anhydrous acid

in acetic acid of every degree’ of concentration between pure
water and the hydrated acetic acid, compared with the specific
gravities, water at 59° Fahr. being taken as unity ..........
Rosert W. Fox’s Account of some Experiments on the Electricity
of the Copper Vein in Huel Jewel Mine ......... oe nee eh s

Sir Davin Brewster's Notice respecting a remarkable Specimen ~

of Amber ..... Neha ye ae tens one aaa) 6 Rien scents pis
Sir Davin BrewstEr’s Remarks on the value of Optical Characters

in the discrimination of Mineral Species .......-2.-20+--0- é

The Rev. Wittram Vernon Hancovrt’s Experiments on the ef-
fects of long-continued Heat on Mineral and Organic Substances
Dr. Cuarx’s Explanation of the Successful Application of the Hot
Blast to the Production of Cast Iron .......--sseeeeeeeee
Professor GRAHAM on hydrated’ Salts and metallic Peroxides ;
with Observations on the doctrine of Isomerism ........-.-
Grorcr Lows on some new Chemical products obtained in the
Gas-works of the Metropolis ...........e eens ete ate
Henry Hovex Watson on the quantity of Carbonic Acid in the
Atmosphere .......- 8, CRG O RHI GOEUAC ESOS QeuOD
J. F. W. Jounston on the Chemical Composition of crystallized
Oxichloride of Antimony ........ ee al eer re iat stent ete
Cuartzs J. B. WitxrraMs on the phenomena and products of a
low form of Combustion .......+eseeeeeeeeeees a etok 6 i
Dr. Wm. Grecory’s Abstract of the Discoveries made by Dr.
RercHENBACH, in his examination of the products of destructive
Distillation.... 2 .s2ee5.- eee $2 Fossiess gible Gravee aS

Ill. Matuemaricat InstrumENTs AND MeEcuanicaL Arts.

Professor. Forbes on a new Sympiesometer.....seeeeeseeeees
Davin Dicx on the construction of Achromatic Object-Glasses. .
Joun Dunn on a new Klinometer and portable Surveying Instru-

MENt se ccce cece cece cece eter crew ere seseeeesersovenes
E. J. Denr ona Chronometer with a Glass Balance-spring ....
Mr. Gorpon on the Polyzonal Lens......2.20eeeeeeeeeeeees
Mr. Rennie on an Instrument for taking up Water at great depths

576

578

- 379

582

583

- 587

588

591

593
595
594
595

595
595

Professor StevEtty on the application of a Vernier to a Scale, not '

of equal but of variable parts, and particularly to Wollaston’s
Scale of Chemical Equivalents......sssesseecessevvevecs

IV. Narvurat History, ANATOMY, AND PuysioLoay.

Botany.

_ Rozserr Brown on the plurality and development of Embryos in

the Seeds of Conifere secre eoevpeevoreeseeveeereeoererevrer eee?

596

596

viii CONTENTS,
Page.
Dr. Arnott on the Cocculus Indicus of Commerce.....+.+++4. 597
Dr. Davuseny on Excretions from the Roots of Vegetables...... 598
W. C. Treveryan on the Distribution of the Phenogamous Plants
of the Faroe Islands..........- clertlepe poo jee. 0 sie deme Tee

Zoology.

Joun Granam Datyett on the Propagation of certain Scottish

Zoophytes......csecececcccarescone Perens ee opie 998
J. O. Wxstwoop on the Transformations of the Crustacea ..... 608
P. J. Sexsy’s Observations onthe Orbital Glands in certain tribes

Biba ES AUS 3 nccie? dopaiate wee} unibis weihs apebacon ell las| ayaa tele acne eka malta «» 609
P. J. Sezsy’s Notice of Bata cf geri in Sutherlandshirey June,
Ua al Ca ol Mi tal ni ol tb ieia leis id 610

Sir W. Jarpine’s a bear on the elated a which were eA
with during an Excursion to the North-west of Sutherlandshire
in June 1834. it ais an sian shan Supls, cM ai aed adel “hes oles ca NT a . 613
James Witson’s Notice regarding the Coleopterous Insects. col-
lected during a Tour in Sutherland.........+++++-. neiusieht Ole
M. Agassiz on the different Species of the Genus Salmo. which
frequent the various Rivers and Lakes of Europe ......... . 617
Dr. AtLen Tuomson’s remarks on some specimens of Reptiles.. 623
Dr. Trattx on the Laryngeal Sac of the Reindeer.........- »» 623
J. B. Pentianp on the Ancient Inhabitants of the Andes..... aioe

. Geology.

Davip Mine on the Geology of Berwickshire ........++0+++ 624
Major-General Lord Greenock on the Coal-fields of Scotland .. 639
Dr. Hissert on the Ossiferous Beds contained in the Basins of
the:Forth,. the Clyde,and the Taye esis. oes csiccececclocdses 642
Dr. Traitr on the Geological Structure of the Orkney islands: - 644
Proiessor JamEson’s. remarks on the Fossil Fish Cephalaspis.... 646
M. Aeassiz on the Fossil Fishes of Scotland »............0006 646
Mr. Macraren on the Pentland Hills ..... ete TR IE eM -. 649
W. Macerttivray’s account of the central Portion of the great
Mountain Range of the South of Scotland, in which: arise the

Sources of the T'weed .... SADA ANODE LL Tie 5. SON 650
C.G.S. Menteatu’s notice of the Limestone of Closeburn, in re-

ply to a Query of the Geological Committee ...........505 651
Dr. Kwnicur’s notice of the Flints of Aberdeenshire......... spr Gad
R. I. Murcutson on the Old Red Sandstone and other Forma-

GOs OE ONE. WEUHA SIOTOGT So. se ercs ua os 0 eunwiale ae ais seine 652
C. Lyet on the Change of Level of the Land and Sea in Scandi-

MUEGU URL etaretelatere: Mate Telare ela ese ere erote are. bai. sece'e\\e 1s) eve love Ga fa eimai aie 652
W. Gitsertson on Marine Shells of recent Species found at consi-

derable elevations, near Preston ........2eeee08 coven p slome 654

Professor Puituirs’s Notices in reply to a Question proposed by

CONTENTS. ix
Page.
the Geological Committee at Cambridge, as to the Relations of
Mineral Veins and the Non-metalliferous Joints in Rocks .... 654
James Bryce on some Caverns containing bones, near the Giant’s

Causeway ...csecceeecconcccesces Aeinihte es welts «anos S
Tuomas ANDREWs on some Caves in the Tatand of Rathlin and the
adjoining Coast of the County of Antrim......... vot ean aee

W. Nicot on the Anatomical Structure of recent and fossil Woails 660

V. Anatomy AND PuysioLoey.

Sir C. Betx’s Observations on the proper method of studying the

Nervous System .... cece ee cece ce ee cree crcee seer crecee 667
Dr. ABERCROMBIE on the importance to the Medical Profession
of the study of Mental Philosophy ...........-- cre eae ae 670

Dr. J. Rerp’s notice of some Experiments on the connexion between
the Nervous System and the Irritability of Muscles in Lig

Animals. With Observations by Dr. ALISON........-+0++. 671
Dr. Axtson’s Notice of some Observations on the vital properties
of Arteries leading to inflamed parts ......++.seeeees . 674

Dr. Marsuatt Hatt and Mr. Broventon’s Report of Progress
made in an Experimental Inquiry regarding the Sensibilities of
the Cerebral Nerves, recommended at the last Meeting of the

Association fo eT ee PPL eee me TI Ue ean ora gt ore, ox 676
Dr. Hopexin and Dr. Riirrett on the Effects of Poisons on the
Animal Giconomy.......2..eeceeeececoeees PSS deen ek

Dr. T. J. Arrxtn’s Inquiries into the Varieties of Mechanism by
which the Blood may be accelerated or retarded in the Arterial
and Venous Systems of Mammalia ...... PORN vee 5 oe. OB
Dr. Suarrey’s Observations on the Anatomy of the Blood-vessels
of the Porpoise ........+..-- ey watulvialatetnd Stak Stan eele we
Mr. Dick on the Use of the Omentum ...........04- assaeed 683
Dr. W. Tuomson on the Infiltration of the Lungs with black Matter,
and on black Expectoration ........eseeeeees vir aetee de 68S
Professor Syme on Excision of diseased. Joints Ne
Dr. Josern Crarxe’s account ofa Registry kept in the Lying-in
-» Hospital of Great Britain-street, Dublin, fromthe year 1758 to
thieend of 1983 hoes Mh Gece sh ees oer oee es cede tare bt ORS

VI. Statistics.

Dr. CreLann’s Statistics of Glasgow ....seeecrecsesseseeee 685
Mr. Heywoop—Statistics of Manchester ......++.+++eeee+4 690
Mr. Gorpon’s notice of the new Statistical Account of Scotland.. 692
Earl Firzwitxiam’s remarks on the Statistical Reports regarding
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OBJECTS AND RULES OF THE ASSOCIATION.
:

OBJECTS.

Tue Association contemplates no interference with the ground occu-
pied by other Institutions. Its objects are,—To give a stronger im-
pulse and a more systematic direction to scientific inquiry,—to promote
the intercourse of those who cultivate Science in different parts of the
British Empire, with one another, and with foreign philosophers,—to
obtain a more general attention to the objects of Science, and a removal
of any disadvantages of a public kind, which impede its progress.

RULES.
MEMBERS.

All Persons who have attended the first Meeting shall be entitled to
become Members of the Association, upon subscribing an obligation to
conform to its Rules.

The Fellows and Members of Chartered Literary and Philosophical
Societies publishing Transactions, in the British Empire, shall be en-
titled, in like manner, to become Members of the Association.

The Office-Bearers and Members of the Councils, or managing Com-
mittees, of Philosophical Institutions shall be entitled, in like manner,
to become Members of the Association.

_ All Members of a Philosophical Institution recommended by its
Council or Managing Committee, shall be entitled, in like manner, to
become Members of the Association.

Persons not belonging to such Institutions shall be elected by the
General Committee or Council, to become Members of the Association,
subject to the approval of a General Meeting.

SUBSCRIPTIONS.

The amount of the Annual Subscription shall be One Pound, to be
paid in advance upon admission ; and the amount of the composition
in lieu thereof, Five Pounds. :

Subscriptions shall be received by the Treasurer or Secretaries.

If the annual subscription of any member shall have been in arrear
for two years, and shall not be paid on proper notice, he shall cease
to be a member ; but it shall be in the power of the Committee or
Council to reinstate him, on payment of arrears, within one year.

RULES OF THE ASSOCIATION.

MEETINGS.

The Association shall meet annually, for one week, or longer. The
place of each Meeting shall be appointed by the General Committee at
the previous Meeting ; and the Arrangements for it shall be entrusted
to the Officers of the Association.

GENERAL COMMITTEE.

The General Committee shall sit during the time of the Meeting, or
longer, to transact the Business of the Association. It shall consist of
all Members present, who have communicated any scientific Paper to a
Philosophical Society, which Paper has been printed in its Transactions,
or with its concurrence.

Members of Philosophical Institutions, being Members of this Asso-
ciation, who may be sent as Deputies to any Meeting of the Association,
shall be Members of the Committee for that Meeting, the number
being limited to two from each Institution.

COMMITTEES OF SCIENCE.

The General Committee shall appoint, at each Meeting, Committees,
consisting severally of the Members most conversant with the several
branches of Science, to advise together for the advancement thereof.

The Committees shall report what subjects of investigation they
would particularly recommend. to be prosecuted during the ensuing
year, and brought under consideration at the next Meeting. They
shall engage their own Members, or others, to undertake such inves-
tigations ; and where the object admits of being assisted by the exer-
tions of scientific bodies, they shall state the particulars in which it
might be desirable for the General Committee to solicit the co-opera-
tion of such bodies.

The Committees shall procure Reports on the state and progress of
particular Sciences, to be drawn up from time to time by competent
persons, for the information of the Annual Meetings.

LOCAL COMMITTEES.

Local Committees shall be appointed, where necessary, by the General
Committee, or by the Officers of the Association, to assist in promoting
its objects.

Committees shall have the power of adding to their numbers those
Members of the Association whose assistance they may desire.

OFFICERS.

A President, two Vice-Presidents, two or more Secretaries, and a
Treasurer, shall be annually appointed by the General Committee.

RULES OF THE ASSOCIATION.

COUNCIL.

In the intervals of the Meetings the affairs of the Association shall
be managed by a Council, appointed by the General Committee.

PAPERS AND COMMUNICATIONS.

The General Committee shall appoint at each Meeting a Sub-Com-
mittee, to examine the papers which have been read; and the register of
communications; to report what ought to be published, and to recom-
mend the manner of publication. The Author of any paper or commu-
nication shall be at liberty to reserve his right of property therein. > -

ACCOUNTS. —

The Accounts of the Association shall be audited annually, by) Audi-
tors appointed by the Meeting.

TREASURER.

Joun Taytor, Esq., 14, Chatham Place, London.

LOCAL TREASURERS.

Dr, Davseny, Oxford. Dr. Pricwarp, Bristol.

Cuantus Forsss,Esq. Edinburgh. | Gzorce Parsons, Esq., Birming-
JonatHan Gray, Esq., York. ham.

Prof. Henstow, Cambridge. Rev. JounJ. Tayier, Manchester.

Wit1iam Horton, Esq., Newcas- | Samuet Turner, Esq., Liverpool.

tle-on-Tyne. H, Wootcomss, Esq., Pl t
Dr. Orren, Dublin. » Hsq., Plymouth.

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FOURTH REPORT.

PROCEEDINGS OF THE MEETING.

1834,

THE British Association resumed its sittings on Monday the
8th of September, 1834, in the city of Edinburgh. The Meet-
ing was attended by a greater number of members than had as-
sembled on any former occasion* ; but by means of the arrange-
ments adopted by the Secretaries and local Committee, its pro-
ceedings were conducted with order and facility. All the
public accommodations which this magnificent capital possesses
were opened to the Association: the members received their
tickets in the gallery of the Royal Institution ; the general Com-
mittee sat in the meeting-room of the Royal Society ; the Sec-
tions were distributed through the class-rooms of the Univer-
sity ; the meetings of the entire body were held in the public.
Assembly Rooms and in the hall of the College Library.

GENERAL MEETINGS.

On Monday evening, at eight o’clock, the first General
Meeting was held in the great Assembly Room. The President
of the preceding year (the Rev. Professor Sedgwick) addressed
some remarks to the meeting on the progress of the Associa-
tion; he congratulated them on the increased strength in which
they had assembled, in a place endeared to the feelings of every
lover of science, by so many delightful and elevating recollec-
tions, especially by the recollection of the great men whom it
had fostered or to whom it had given birth. Among the per-
sons congregating together from different countries to this great
philosophical union it had been his good fortune to encounter
on his road thither M. Arago the Perpetual Secretary of the

* The number of tickets issued was 1298.
1834. b

x FOURTH REPORT—1834.

French Institute, a name which the meeting well knew was not
inferior in scientific reputation to any in Europe. To meet with
such men, to breathe the same atmosphere with them, to partake
the same sentiments, to enjoy their conversation, and to gain,
he hoped, their friendship, these were among the highest privi-
leges which such unions bestowed.

If he were to be asked what the power is which this Associa-
tion peculiarly applies to the advancement of science, he would
answer,—the power of combination: how feeble is man for any
purpose when he stands alone, how strong when united with his
fellow-men! It might be true, perhaps, that the greatest philo-
sophical works have been achieved in privacy ; but it is no less
true that those works would never have been accomplished if
their authors had not mingled with men of similar pursuits, and
availed themselves of their assistance. To such a commerce of
ideas they have often been indebted for the germs of their ap-
parently insulated discoveries, and without such mutual aid they
would seldom have been able to carry their investigations to any
valuable conclusion. Even in the highest departments of philo-
sophical reasoning, when a question of fact arises, when a point
of experiment is reached, the greatest masters of analysis are
obliged to call in the cooperation of other labourers, and to wait
for the observations of experimental men.

The manner in which the power of combination is brought
into action by these meetings might, in some measure, be col-
lected from the results which had sprung out of the proceedings
of the last meeting. A discussion, for instance, had then taken
place on the subject of the aurora borealis, and measures were
adopted for promoting the investigation of the circumstances
connected with that remarkable phenomenon. Soon afterwards
a beautiful arch appeared across the heavens; it was simulta-
neously observed by different members of the Association at
distant points ; and thus elements were furnished for a compu-
tation of its height. Again, observations of great value had
long since been made at the Royal Observatory of Greenwich
by Bradley and Maskelyne: these had lain till now unreduced,
like unwrought ore, or raw materials for a valuable manufacture
not worked up ; and they might still have continued useless and
lost to science but for the application to Government resolved
upon at the last meeting of the Association, the success of which
had been announced in the volume of Reports which had since
been printed. The Professor nextreferred to the progress which
by the same agency is making in the observing of the tides and
the discussion of tide observations, and to the experiments on
the effects of long-continued heat, which are going on in the

PROCEEDINGS OF THE MEETING. Xi

iron-furnaces of Yorkshire. He concluded by recommending to
the meeting a strict adherence to the principle of excluding
from their discussions every subject of a nature not strictly
scientific, and expressed the satisfaction with which he resigned
his office into the hands of one who had already been placed at
the head of science in Scotland, and who had added to laurels
gained in fighting the battles of his country the glory of having
kindled up the light of philosophy even at the antipodes.

The President (Sir Thomas Brisbane) assured the meeting of
the strong desire which animated individuals of every rank in
the city of Edinburgh and its neighbourhood to give the warm-
est welcome to the Association, and to uphold, by its reception,
the national character for hospitality. He announced that the
Principal and Professors of the University had given the
free use of their class-rooms and of other apartments in the
College, which would be found admirably adapted for the Sec-
tional meetings of the Association; and he added that other
public bodies had not been backward in making similar offers,
and in contributing whatever lay in their power towards its ac-
commodation.

- The senior Secretary (Mr. Robison) stated the course of pro-
ceeding which it was intended to adopt in conducting the busi-
ness of the present meeting. The principal variation to be
made from the course pursued in former years consisted in de-
voting the entire morning to the meetings of the Sections and
their Committees ; and transacting the detail of scientific business
solely at the morning meetings. In the evening the Chair would
be taken at eight o’clock ; the officers of each Committee would
give a short summary of the proceedings which had taken place
in their respective Sections, and these statements would be fol-
lowed by any communications of a more popular character that
might be selected for the evening meetings. In addition to
_what had been already said of the liberal conduct of public
bodies in Edinburgh, he was bound to mention the peculiar ob-
ligation under which the Association lay to the proprietors of
the building in which they were then assembled, who had not
only granted the gratuitous use of their apartments, but had ex-
pended a large sum of money in preparing and decorating them
for the meeting.

The junior Secretary (Professor Forbes) then delivered the
following address :

- “ It having been suggested that the general view of the pro-

gress of the affairs of the Association, so ably executed last year

by Mr. Whewell, should annually be continued by the Secretary

for the time being, I have undertaken this portion of the duties
b2

xii FOURTH REPORT—1834.

which devolve upon the Secretaries for Edinburgh, at the desire
of my learned colleague Mr. Robison, who, on the other hand,
has engaged briefly to state the nature and motives of the prac-
tical arrangements for the present meeting, of which he has had
the kindness to superintend by far the most laborious part.

I felt anxious that such a periodical report as I have men-
tioned should be continued, because of the necessarily fluctua-
ting state of our Body, and the small number of persons who,
by circumstances, have been enabled to attend all the meetings,
and to become acquainted with the actual operation of a some-
what complicated machine; and I was ready to undertake that
duty, because I hoped that I might be able, by an appeal to
facts, in the first place, to put in a clear point of view, what
has not perhaps been enough insisted on, and has therefore
been very generally misunderstood,—the perfectly wnigue cha-
racter of this Association, and the high aims to which its efforts
are directed ; and, in the second place, to demonstrate that these
aims and objects are in the due course of attainment ; that the
members, and especially the projectors of this institution, are
fulfilling the pledges, of no common character, which they gave
to the public, and this more especially in relation to the pro-
ceedings of the past year.

‘<The character of the Association, I have said, may be con-
sidered as unique. It is not to be confounded with those nu-
merous and flourishing institutions which have sprung up, es-
pecially of late years, for the simple diffusion of scientific truths.
Such diffusion does not even, properly speaking, include any
attempt at extension or accumulation: if in many cases it does
promote such extension, it is indirectly, and beyond a doubt
has sometimes had the opposite tendency. The intellectual
wealth of mankind is no more increased by this operation, than
is the weight of the precious metals under the hand of the gold-
beater. A greater display may indeed be attained, and a more
commodious application to the useful and the elegant purposes
of life; but for actual increase of the stock which may hereafter
be fashioned with ease and expedition by the hands of a thou-
sand artificers, we must recur to the miner toiling in his solitary
nook, and to the labourer who painfully extracts some precious
grains from the bed of the torrent. It is the furtherance of this
species of productive energy that the British Association claims
for its capital object. The diffusion of a taste for science amongst
its numerous members is no doubt also one of the most neces-
sary and most desirable consequences of the principles upon
which it is founded; but it is not the basis of these principles.
To teach those who have never pursued natural knowledge but

PROCEEDINGS OF THE MEETING. xiii

as an occasional amusement,—to feel that for them a field lies
open which tomorrow they may call their own,—to lend them
such aid as may promote the success of their exertions, by re-
moving the preliminary difficulties, and pointing out the exist-
ing boundary betwixt the known and the unknown,—to stimu-
late these exertions and those of others who have already be-
come, to a certain degree, familiarized with the labours and with
the results of intellectual toil, by enabling them to mix with the
yeterans in each department who haye gained, and who still con-
tinue to gain, the highest rewards which the investigation of na-
ture confers,—who will point out the methods which they pur-
sued, the disappointments which they met, and the difficulties
which they surmounted, thus affording at once the gratification
which every generous mind feels in personal communication
with those who have signalized themselves by intellectual achieve-
ment, and the instruction and encouragement for the pursuit of
a similar course which words, and words alone, can impart,—
these we hold out as amongst the first and the most valuable
objects proposed to be attained by the institution of this Asso-
ciation. ’

‘** No doubt societies for the promotion of natural knowledge
have been in existence for near two centuries, and these have
done much to the due-advancement of science itself, as well as
the promotion of a more general taste for its cultivation. They
were admirably adapted to the period of their institution, when
the difficulties of ordinary communication, and the want of sci-
entific journals, made the Royal Society of London the great
centre of philosophical information,—when new experiments
were there first repeated,—when new theories were there first
discussed,—and when its Transactions, and those of the other
academies of Kurope—fraught with the literary treasures which
Hooke and Wren, and Boyle and Leibnitz, and the Bernouillis,
loved to display, and which Newton alone loved to conceal—
were the couriers which published to Europe the intelligence of
the successive intellectual victories of that mighty age. Rarely
even then, however, and latterly still less, did these societies at-
tempt to guide in any specific direction the investigations of their
members, or to form any school of science for the initiation of
fresh inquirers. The formation of such schools of disciples who
voluntarily combined under some philosopher of eminence, partly
did away with the necessity of this on the Continent ; whilst the
total want of anything similar in our own country, and the less
specific objects of those honorary rewards which from time to
time have been given by learned societies in all countries, and
which have occasionally drawn forth all the powers of some mas-

xiv FOURTH REPORT—1834.

ter mind to the solution of a specific difficulty proposed as a
prize question, necessarily produced a greater want of systema-
tic cooperation amongst scientific men in Britain than is to be
found in several countries not her political superiors.

“« The migratory scientific associations of Germany and Swit-
zerlaud—to which we gratefully acknowledge that our British
one owes its rise,—embrace only one class of the objects to
which we have above alluded as characterizing this Body. Their
aim was simply to promote the intercourse of scientific men,
and to diffuse a taste for the prosecution of science. Their ex-
istence is not permanent,—they execute no functions but for the
moments during which their members are once a-year assembled,
—they regard not the past, and have no cares for the future,—
they merely receive and consider the communications which the
zeal of individual members places in their way. Such was at
first proposed to be the character of the Body this day assem-
bled, in imitation of the foreign meetings ; but a more extensive
design was subsequently adopted, and it was determined to
establish a permanent society, of which these annual reunions
should simply be the meetings, but which, by methods and by
influence peculiarly its own, should continue to operate during
the intervals of these public assemblies, and should aspire to
give an impulse to every part of the scientific system, to mature
scientific enterprise, and to direct the labours requisite for dis-
covery*.

“< If we now turn from the aims to the acts of the Associa-
tion, we shall find gratifying proof that these designs were not
chimerical, and that the primary machinery devised for effecting
them was wanting neither in efficiency nor in permanence. The
first and most signal proof which we can cite, is the produc+
tion of those Reports on the Progress of Science, which ap-
peared to be one of the most important objects of such an in-
stitution, and one which, beyond all dispute, no existing society
could have attempted. To call upon persons whose time was
in all cases more or less valuable, for such a devotion of it
as was required for a systematic and precise detail of the re-
cent progress of the sciences which they respectively culti-
vated, was to make a demand, the boldness of which cannot
perhaps well be appreciated but by those who have had expe-
rience in the labour of bringing together the substance of de-
tached, though often profound, papers in the extensive range of
scientific periodicals and academical collections. Yet so obvious

* The author here described the share which some of the founders of the As-
sociation had respectively taken in planning and conducting the institution.

PROCEEDINGS OF THE MEETING. xv

was the utility of the proposed undertaking, that, in the very
infancy of the Association, there were found several distinguished
individuals, and chiefly from the University of Cambridge, who
had not even been present at the first meeting, but who volun-
teered to undertake some of the most valuable of those reports
which appeared in the first volume of the Proceedings of the As-
sociation. As Mr. Whewell enumerated these in his last year’s
address, I will not further allude to them. It ought, however,
specially to be observed, that these reports differ entirely from
the short systematic treatises on scientific subjects with which
the press teems.. They are not primarily intended for the gene-
ral reader—they are not meant for the purpose of popularizing
technical subjects; their main object is so to classify existing
discoveries as to lead the individual who is prepared to grapple
with its difficulties, to start with the most complete and accurate
knowledge of what has already been done in any particular sci-
ence,—not intended itself to contain that knowledge, but merely
to serve the purpose of a catalogue raisonnée, by means of a
lucid analysis and arrangement, at the same time (and here is
the great necessity of securing the cooperation of persons di-
stinguished in the several departments,) that the report should
point out the most important questions which remain for solu-
tion, whether by direct experiment or by mathematical investi-
gation.
‘© The second volume of Reports has amply justified the ex-’
pectations with which it was hailed; and whilst the first was
chiefly occupied with reports upon great and leading divisions
of science, we have here several happy specimens of a still
greater division of labour, by the discussion within moderate
limits of some particular provinces. Thus, Mr. Taylor has
treated of one particular and most interesting question in Geo-
logy, the formation of Mineral Veins,—one of the most impor-
tant, in a theoretical point of view, which could have been stated,
and which, from its intimate connexion with commercial specu-
lation, might have been expected in a country like ours to have
been more specifically treated of than it has been. It strictly
belongs to the dynamics of the science, to which, since the time
of Hutton, but little attention has been paid until very recently.
By the exertions, however, of Mr. Carne, of Dr. Boase, and Mr.
Henwood of Cornwall, whose researches are to form one point
of discussion in the Geological Section at the present meeting,
the question of the origin of mineral veins, though probably by
no means decided, has been brought prominently forward.
“That electric agency was concerned in the disposition of
metalliferous veins can scarcely be doubted ; and the connexion

xvi FOURTH REPORT—1834,

between electricity arid magnetism, now so fully established,
the connexion between metalliferous veins and lines of elevation,
and between the latter and the isodynamical lines of terrestrial
magnetic intensity, as suggested by Professor Necker of Geneva,
—point out a bond of union between this subject and that of ter-
restrial magnetism, on which we have a report by Mr. Christie,
where the very interesting direct observations of Mr. Fox of Fal-
mouth, on the electro-magnetic action of mineral veins, are par-
ticularly noticed. Mr. Christie’s theory of the diurnal variation
of the needle, which he is desirous should be submitted to the
test of a laboratory experiment, is likewise intimately connected
with the actual constitution of our globe*. The whole subject
of Terrestrial Magnetism is one of the most interesting and
progressive of the experimental sciences. The determination of
the direction of the magnetic energy by means of two spheri-
cal coordinates, termed the variation and the dip, and the mea-
sure of the intensity of that force, are the great objects of imme-
diate research, as forming a basis of theory. The existence of
four points on the earth’s surface, to which the needle tends, has
long been known; and the position of two of these (in Northern
Asia and America,) has recently been elucidated by the perse-
vering efforts of Professor Hansteen and Commander Ross. The
precise numerical determination of the elements just alluded to
acquires a deep and peculiar interest from the multiplied varia-
tions which they undergo. Not only are these elements subject
to abrupt and capricious changes, which Baron Humboldt has
termed magnetic storms; but gradual and progressive variations
are undergone at different hours of the day, at different seasons
of the year, and throughout longer periods, which may even per-
haps bear a comparison with the sublime cycles of Astronomy.
‘¢ Natural History forms a more prominent subject in this
volume than in the last, though the reports of Professor Lindley
‘ on the principal questions at present debated in the Philosophy
of Botany’; and of Dr. Charles Henry ‘ on the Philosophy of
the Nervous System’, refer only to particular departments of
widely extended subjects, which are again to be resumed in more
general reports, undertaken for the present meeting,—that by
Mr, Bentham, on Systematic Botany, and by Dr. Clarke of
Cambridge, on Physiology in general. We cannot but remark
with pleasure, that one of the points for inquiry particularly in-
sisted on by Professor Lindley, that of the influence of the che-
mical nature of soils, and of the excretions of plants, was taken
up at an early period of the existence of the Association, by one

* Report, p. 122-3,

PROCEEDINGS OF THE MEETING. xvii

éf its most zealous supporters, Dr. Daubeny ; and that, in re-
ferénce to the review by Dr. Henry of the labours of European
physiologists, we may quote, as a national honour, the disco-
veries of our distinguished associate Sir Charles Bell.

“ Qn the general connexion and occasional apparent opposi-
tion of theory and practice, I would refer to some very pertinent
temarks in the address of Mr. Whewell at the last meeting. The
importance of carrying on both simultaneously and independ-
ently, and of looking to our increased knowledge of both as the
only sure means of ultimately reconciling discrepancies, has been
manifested by the desire of the Council of the Association to
procure two distinct reports on the Theory and Practice of Hy-
dratlics, which have been drawn up with remarkable perspicuity,
aud within a small compass, by Mr. Challis and Mr. Rennie.
Both of these gentlemen have shown their zeal in the objects of
the Association by proniising to continue their valuable labours.
Mr. Rennie, on that part of his subject which relates to the mo-
tion of fluids in open channels, and Mr. Challis on some of those
exceedingly interesting branches of theory altogether modern,
which physically, as well as in their mathematical methods, have
the closest analogy to that case of the motion of fluids treated of
in the present volume, namely, the theory of Sound, and the in-
timate constitution of Liquids. When, in addition to these re-
ports, we shall have received that undertaken by Mr. Whewell
upon the mathematical theory of Magnetism, Electricity, and
Heat, we shall undoubtedly possess the most complete outline
extant of a department of knowledge entirely of recent date.

_ ‘Inthe science of Hydraulics, indeed, some progress in theory
has accompanied the increase of practical information, at least
since the time of Newton ; but in the other strictly practical
report of the present volume, that of Mr. Barlow on the very
interesting subject of the strength of materials, little or nothing
has been done of much theoretical importance since the days of
Galileo. Circumstances, which it would be easy to point out,
prevent our setting out, except in rare cases, from unimpeach-
able data; but several very interesting conclusions of general
application are derivable from well-conducted experiments, and
the Association may claim some credit for having brought into
general notice the ingenious investigations of Mr. Hodgkinson
of Manchester, more particularly alluded to in this paper.

“* One report, and that the longest which has been printed
by the Association, remains to be mentioned. It is by Mr.
Peacock on the present state of Mathematics. When we con-
sider the vast extent of the subject, and the extremely limited
number of persons, even in the whole of Europe, capable of

XVili FOURTH REPORT—1834.

undertaking it, we must consider the production of a work of
so much labour as the present, which, as yet, is incomplete, but
which the author has promised to resume, as the best trophy

to which we can refer in proof of the entire efficiency of the As-

sociation according to its original plan,—as a proof of the
ability and the indefatigable industry which it has enlisted in
its service,—as a proof that its aim is not the dissemination of
superficial literature, stamped with the effigy of science, and
lowered for the demand of the indolent and the careless,—but
that it is intended to refine the precious metal until it reaches
a state of chemical purity, not to alloy and coin it for the pur-
poses of a promiscuous and debased currency. Mr. Peacock
undertook his report in the early days of the Association, when
its friends were yet few and its success dubious; its execution
has been delayed by the extent of the subject and labour of the
task. The report on the Differential and Integral Calculus, which
was intended to form the basis of it, is delayed, and the present
one is devoted to a discussion chiefly of algebraic methods, and
a close examination of the metaphysical principles upon which
this interpretation of analysis is founded. The author has thus
been led to extend the views which, in his recent systematic
treatise, he had developed in regard to the signs of affection of
algebraic quantities, including those of imaginary quantities, of
discontinuous functions, and the interpretations of zero and infi-
nity. The author has then treated of Series, as regards their
fitness for giving directly conclusive results, particularly when
such series are divergent, leaving to the other part of the report
a detail of the progress in the application of series, which is
more practical than metaphysical. The author then treats hi-
storically of the elementary works in use on Algebra and Trigo-
nometry ; and devotes the last part of the report, consisting of
above fifty pages, to the Theory of Equations, in which he has
minutely analysed some of the most remarkable papers on this
abstruse subject. Altogether this report (especially when com-
pleted,) cannot fail to fulfill, in a striking manner, the two great
objects of such works: first, to supply those engaged in colla-
teral branches of science with the means of referring to and ob-
taining the information they may require upon methods which
perhaps are of daily utility in physico-mathematical inquiries,
but with which, from the vast extent of the science of pure ma-
thematics, the shortness of human life prevents the possibility
of a complete and systematic acquaintance, unless it be made
the special object of study; and, in the second place, to point
out, where chasms of reasoning occur, what mathematical me-
thods are impregnable, and what rest upon a still dubious basis,

——— :

PROCEEDINGS OF THE MEETING. xix

in a metaphysical point of view, several of which are very spe-
cifically treated of in Mr. Peacock’s report. It is much to be
desired that nothing may longer postpone the conclusion of a
work which cannot fail to reflect honour upon the Association.
«* Were those annual Reports the only fruits of the labours of
this Society, there would be no reason to complain. But yet more
specific results of its impulsive action on’ science may be quoted.
The questions suggested by the reporters and others, and recom-
mended for investigation, have met with ready attention from se-
veral individuals capable of satisfactorily treating them. Pro-
fessor Airy has himself investigated, from direct observation, the
mass of Jupiter, suggested as a desideratum in his report on As-
tronomy ; and since the last meeting of the Association, has con-
firmed his first results by new observations, which give almost
the same mass by the observed elongations of the satellites, .as
had been deduced from the perturbations of the smal] planets
by Jupiter. Hourly observations of the Thermometer in the
South of England have, in two instances, been commenced ;
and we are assured that the same desirable object is about to
be attained by the zeal of the Committee in India, where the
Association has established a flourishing colony. A series of
the best observations for ascertaining the law which regulates
the fall of rain at different heights, conducted at the sugges-
tion of the Physical Section, by Messrs. Phillips and Gray of
York, have been ably discussed by the former gentleman, in’
last year’s report, and have since been continued. A regu-
lar system of Auroral observation, extending from the Shet-
land Isles to the Land’s End, has been established under the
superintendence of a special committee, and specimens of the
results have been published. Observations on the supposed in-
fluence of the Aurora on the Magnetic Needle have likewise
been pursued in consequence of this proceeding. The condi-
tions of Terrestrial Magnetism in Ireland have been experimen-
tally investigated by Professor Lloyd. An important inquiry
into the law of Isomorphism has been undertaken by a special
committee, which has likewise reported progress ; and an ela-
borate synopsis of the whole Fossil Organic Remains found in
Britain is in progress, under the hands of Professor Phillips.
Many specific inquiries are besides going forward, under parti-
cular individuals, to whom they were confided ; whilst it is not
to be doubted that numberless persons, many of them perhaps
new to the world of science, are at this moment pursuing inves-
tigations recommended in general terms, in one or other of the
publications of the Society.
“'To others the Association has not scrupled to commit a por-
tion of the funds at their disposal, for the purpose of pursuing

XX FOURTH REPORT—1834.

objects which required an outlay not to be expected from in-
dividuals. Among the most important of these is the collec-
tion of the Numerical Constants of Nature and Art, which are
of perpetual recurrence in physical inquiries, and which has
been confided to the superintendence of Mr. Babbage. When
objects of still more peculiar national importance presented
themselves, the Association has fulfilled its pledge of stimu-
lating Government to the aid of science. Five hundred pounds
have been advanced by the Lords of the Treasury towards the
reductions of the Greenwich Observations, at the instance of the
Association ; and more recently the observations recommended
by the Committee on Tides have been undertaken, by order of
the Lords of the Admiralty, at above 500 stations on the coast
of Britain.

“ Individuals, as we have said, have been stimulated by the in-
fluence of the Association; but so may nations and great bodies
of men. Its published proceedings have found their way into
every quarter, and are tending to produce corresponding efforts
in distant lands. Our reports on science have produced some
very interesting counterparts in the literary town of Geneva.
America has taken the lead in several departments of experiment
recommended by the Association ; and the instructions for con-
ducting uniform systems of observation have been reprinted and
circulated in the New World. We must likewise consider it as
an especial proof of the influence and importance of the Associa-
tion, that a Report on the Progress of American Geology has
been undertaken and executed by Professor Rogers of Philadel-
phia*. Similar contributions from some other foreign countries
haye been promised, which will extend the utility of the Asso-
ciation, by making us acquainted with the more characteristic
state of science in the various parts of Europe. Nor can we fail,
on the present occasion, to consider as a most auspicious pro-
mise of the future success of the Association, that the distin-
guished Secretary of the Institute of France has not only ho-
noured this mneeting by his presence, but has promised to interest
that powerful body on behalf of the important objects contem-
plated by the Association, which its cooperation might effec-
tually secure. The formation of a Statistical Section at Cam-

* Some strictures having been made in America on the extracts from this re-
port which appeared in the Edinburgh New Philosophical Journal, it may be
proper to remark that, in requesting from Professor Rogers a general outline
of what is known of the geology of the United States, the Association could not
expect that all parts of such a sketch should be verified by the personal obsex-
vation of the author ; it is also due to him to state that his report is published
under the unavoidable disadvantage of not having been revised by the author
in passing through the press.—Zditor.

PROCEEDINGS OF THE MEETING. XXi

bridge was the prelude to the establishment of a flourishing
society, which acknowledges itself the offspring of this Institu-
tion, and which promises, by a procedure similar to that intro-
duced by the Association, to advance materially the greatly neg-
lected subject of British statistics.

‘* Gentlemen, I shall be satisfied if, in the preceding hasty re-
view, I shall have given you some direct and tangible proof of
the working of a system, the excellence ‘of which may best be
appreciated by such statements. Did it come within the scope
of these observations, (which it does not,) I could quote exam-
ples, equally specific, of the powerful moral influence of the
Association. Yet, in conclusion, I will call upon you to remark,
because IJ believe that it comes home to the breast of every one
who has habitually attended these our annual reunions, what a
spirit is infused into otherwise isolated and perhaps ineffective
exertions, when many minds, conversant. with one class of ob-
jects, and aiming at one great end, unite in friendly and intel-
lectual converse. Thereis an impulse there which no system of
cold calculation can estimate. There is a bond in the sense of
community of purpose, which is the cement of society. There
has been, we fear, a general but most erroneous impression
-abroad, that philosophers are incapable of enjoying, and stoically
superior to, the ordinary sociabilities of life,—that scientific ar-
dour dwells only in the mind of the solitary, and gives place to
narrow-minded jealousy, when another attempts to share the
prize. If, in afew cases, such allegations have not been with-
out a colouring of truth, it is to meetings like these that we
should look for a cure which no mere reasoning can effect. The
most striking feature of these meetings has ever been, the per-
vading sense which has thrown a peculiar character over them,
of the one great and exalted object which united so many di-
sstinct and unconnected individuals,—which not less has drawn
into this great assembly, the single and unaided labourer in the
cause of science, from the solitudes of the country, or the still
greater intellectual solitude of some noisy and commercial city,
and the phalanx of scholars who have shared the advantages, and
sustained the reputation, of the great academical foundations of
the country. ‘

“ True it is that, looking merely to the moral influence of the
Association, some there are whose zeal for the promotion of
science places them above the necessity of such an external sti-
mulant. But we must not legislate for individual and such rare
cases. Those who have once trod the higher walks of science,
need perhaps no inducements to revisit these sublime elevations.
The footway may be sharp and narrow, surrounded with preci-

Xxii ' -FOURTH REPORT—1834.

pices and occasionally enveloped in mists,—but they have there
breathed that pure and elastic air which descends not to lower
regions,—and through the cloudy openings they have caught
rich and extensive views, showing at once the configuration and
the bearing of the country, which less daring spirits must pain-
fully and partially explore. Such men are independent of any
reward but that which the exertion itself bestows; yet, let it
not be called an ignoble motive, if the traveller, embarked on
the discovery of a new, and hitherto untrodden, path, which
leads to the point to which he aspires, feels fresh vigour infused
into his frame, by the consciousness that, in the valley beneath,
a thousand eyes are watching his progress, and that a shout of
applause, unheard except perhaps in imagination by him, will
announce the arrival of the adventurer at the summit of the al-
pine chain.

“We look forward without anxiety to the future fate of the
Association. So long as it continues to be guided by the same
principles as heretofore, it cannot fail to confer a substantial be-
nefit upon the science of Britain. We have enough of energy
in action to communicate to the many the knowledge of the few,
but it is to prevent the stagnation of the stream at the fountain-
head, which should be our especial object. True it is that but a
few are able or disposed to devote themselves unreservedly to
those great enterprises which require the whole man; yet,
though it is morally impossible that any others should under-
take the highest generalizations to which we have just alluded,
a division of labour is as practicable in intellectual as in mecha-
nical science. If one designing mind direct the whole, distinct
labourers may be engaged, unknowing each other’s tasks, yet
happy in the consciousness of being more usefully and more
honourably employed than in imperfectly attempting the execu-
tion of works which they might individually complete. The ex-
quisite piece of mechanism which, in the form of a watch, issues
from. the manufactories at Paris or Geneva, has its various ele-
ments of its wheels and pinions, its balance and fusee, collected
from the detached cottages of the peasantry of the Jura.

‘To combine individual effort, to render parts capable of com-
bination into a whole, to economize time, and thus virtually to
lengthen the lives of those whose exertions are valuable in the
cause of science, may be considered as humble, yet surely most
important, contributions to its advancement. We shall have
little reason to regret the want of a National Institute, whose
existence is the just subject of pride to our continental neigh-
bours, so long as individual exertion can supply the stimulus
which even the sunshine of wealth and patronage has sometimes
failed to excite,”’

PROCEEDINGS OF THE MEETING. Xxiil

The Members reassembled at the same time and place on the
evenings of Tuesday, Wednesday, Thursday, and Friday. At
these meetings lectures on various subjects of science were de-
livered by Dr. Robinson, Dr. Lardner, Dr. Buckland, Professor
Sedgwick, and Mr. Whewell. On each evening the Chairmen or
Secretaries of the Sectional Committees reported the proceed-
ings which had taken place during the morning in their respec-
tive sections. In concluding the last report of the transactions
of the Medical section, Dr. ABERCROMBIE said, ‘‘ The whole
business of the section, Sir, has been conducted in the most
satisfactory manner, and a great variety of important communi-
cations has been laid before it; but considering these as not
adapted in general for a mixed audience, I have alluded to them
in very few words; having, therefore, intruded but little upon
your time, I trust you will indulge me with your attention while
I express in the name of the medical profession of Edinburgh
the high satisfaction we have received from the meeting which’
is now drawing to a close, especially by having been brought
into personal intercourse, and, I trust, personal friendship with
so many distinguished individuals whose names have been long
familiar to us as holding the highest rank in science. From
their combined exertions we expect the most valuable results to
every department of human knowledge. I am none of those
who anticipate from the researches of physical science anything
adverse to the highest interests of man as a moral being. On
the contrary, I am convinced that those who have made the
greatest advances in true science will be the first to acknowledge
their own insignificance when viewed in relation to that incom-
prehensible One who guides the planet in its course, and main-
tains the complicated movements of ten thousand suns and ten
thousand systems in undeviating harmony. Infidelity and irre-
ligion, I am satisfied, are the offspring of ignorance united to
presumption; and the boldest researches of physical science, if
conducted in the spirit of true philosophy, must lead us but to
new discoveries of the power, and wisdom, and harmony, and
beauty which pervade all the works of Him, who is eternal.”

The last General Meeting was held on Saturday the 13th of
September, at 3 p.m., in the hall of the College Library. The
General Secretary reported the Proceedings of the General Com-
mittee, the time and place appointed for the next meeting, the
names of the Officers and Council who had been elected, the
objects and extent of the votes of money for promoting experi-
ments and investigations, the number and nature of the reports
solicited from men eminent in science, and the recommendations
of special subjects for research.

Xxiv FOURTH REPORT—1834.

The thanks of the Association were then voted to the follow-
ing bodies and individuals :—

On the motion of the Rev. Dr. Buckland, seconded by the
Rev. Dr. Lloyd,—To the University of Edinburgh, its Patrons
and Officers, for the ample accommodation afforded to the meet-
ing in the College ;

On the motion of Lord Greenock, seconded by Prof. Forbes,—
To the Royal College of Physicians and the public bodies who
have given or offered the use of their premises to the Association ;

On the motion of the Rev. Baden Powell, seconded by G. B.
Greenough, Esq.,—To the proprietors of the Assembly-rooms,
who have given the gratuitous use of their spacious premises,
and fitted them up in a splendid manner for the reception of the
Association 5

On the motion of R. I. Murchison, Esq., seconded by the
Rev. Prof. Sedgwick,—To the Highland and Agricultural Society
of Scotland.

Mr. Murchison stated that this Society was eminently en-
titled to the thanks of the Association for their liberal and zea-
lous endeavours to promote the geology of their country. Inti-
mately persuaded that the agricultural and mineral resources of
Scotland would be improved by an increased knowledge of its
subsoil and rocks, the Highland Society had advanced premiums
for the completion of a geological map of Scotland, and had
exerted themselves to obtain possession, through His Majesty’s
Government, of the valuable unpublished documents of Dr. Mac-
Culloch, which, without these spirited efforts, might long have
lain dormant. .

On the motion of the Rev. Wm. Whewell, seconded by Prof.
Hamilton, thanks were voted—To the President (Sir Thomas
Brisbane,) and the Vice-Presidents (Sir David Brewster, K. H.,
and the Rev. Dr. Robinson) 5

On the motion of the Rev. W. V. Harcourt, seconded by Prof.
Phillips,—To John Robison, Esq., and Prof. Forbes, Secretaries
for the Edinburgh meeting ;

On the motion of John Taylor, Esq., seconded by John
Robison, Esq.,—To the T asurer and the Committee of Re-
ception,

Mr. Charles Forb } Treasurer,

Dr. Christison, ~

Dr. Borthewick, «

Mr. Cay, ‘S Committee of Reception,

Mr. Craigie,

Mr. Burt, .
and other gentlemen who gave their valuable aid in making ar-
rangements for the meeting ;

PROGEEDINGS OF THE MEETING. XXV

* On the motion of Prof.Sedgwick, seconded by Lord Brougham,
—To M. Arago and other distinguished foreigners who have ho-
noured the meeting with their presence on this occasion ;

' The Lord Chancellor said, ‘I rise to second the motion con-
veying thanks to these most illustrious men. The high honour
of being called upon to perform this duty I owe, not, certainly,
to any service I have done to this Association, because this your
last day of meeting is (owing to an accident of a domestic na-
ture, which retarded my journey,) the first of my appearing
here. I owe it to the circumstance of having the honour, the
very undeserved honour (but yet one of the proudest of my life),
to be a member of the National Institute of France, and the
friend of the distinguished philosopher whose name is mentioned
in this motion. Gentlemen, allow me to say that I look upon
this as one of the most important and unquestionable of all the
benefits this Association is calculated to bestow—that it brings
together men of science from every quarter of the world. The
benefits of this are great to science; but they are great, also, to
society; for in proportion as men know one another, they are
the more disposed to cultivate habits of friendly intercourse,
especially if their intimacy subsists on grounds so mutual as
science: for they who devote themselves to science are of no
country; over them the angry blast and tempest of war rages
innocuous ; the pursuits in which they unite are naturally favour-
able to that greatest of all objects which human rulers ought to
have in mind, I mean the maintenance of peace and goodwill
among men. It has sometimes been remarked, that war is a
game at which, if the people were wise, governments would not
often play ; and it has also been said of men, that the longer they
live the more clearly they see that life is too short to be spent in
personal quarrels; it is the same with nations: the world is grow-
ing too wise and experienced to bear war. As there is no duty
more sacred and imperative on the part of governments than to
promote, by every means, that peace which ought to bind the
great family of mankind together in all its departments and in-
stitutions, so I hold, that whatever brings men into contact on
such mutual ground as science tends to facilitate the task of
rulers, and makes it easy to keep at peace with neighbouring
states. I beg leave, therefore, both on scientific principles and
also on the principles of universal philanthropy, most heartily
to second the motion.” ma aestilg

_ On the motion of the Rev. Dr. Robinson, seconded by Sir
Charles Lemon, thanks were voted to the Rev. William Vernon
Harcourt for his continued and unremitting exertions as General
Secretary. . 1 ocak mania

1834. c

XXvl FOURTH REPORT—1834.

The President, in closing the meeting, said, that it had been
his good fortune to attend all the former meetings of the Asso-
ciation at York, Oxford, and Cambridge, and he was rejoiced to
think that Scotland had not fallen short in the reception which
it had given them on the present occasion ; he had himself shared
in the benefit of those hospitable feelings with which the Associ-.
ation had been welcomed, having had the honour that day of
receiving with several distinguished individuals the freedom of
the City of Edinburgh*. ‘The eminent foreigners,”’ he added,
‘“‘ who have attended the meeting have all expressed their desire
to assist in promoting the objects of the Association, and I have
been requested by my illustrious friend M. Arago, whom I have
had the happiness of knowing for nineteen years, to assure them
of his own willingness and that of the Institute of France to co-.
operate with them in every thing in which mutual assistance
might be serviceable to the advancement of science.” -He then
adjourned the meeting to the 10th of August, 1835, at Dublin.

GENERAL COMMITTEE.

The General Committee met in the apartments of the Royal
Society on Monday the 8th of September, and came to the fol-
lowing Resolutions : )

Rules.—That in Rule 2, respecting privileges of admission,
for the words ‘ Fellows and Members of Royal and Chartered
Societies’, be substituted the words ‘ Fellows and Members of
Chartered Literary and Philosophical Societies publishing Trans-
actions’.

That grants of pecuniary aid for scientific purposes from the
funds of the Association shall expire at the meeting following
that at which they were granted, unless they shall have been
acted upon, or a continuation of them ordered by the General
Committee.

Committee of Recommendations.—That Mr. W. Baily, Sir
D. Brewster, Dr. Brown, Rev. Dr. Buckland, Rev. G. Peacock,
Professor Forbes, Professor Hamilton, Professor Roget, Dr.
Turner, Rey. W. Whewell, Dr. Richardson, and the Rev. W.
V. Harcourt be a Committee to report in what manner the funds
of the Society may be best appropriated to the promotion of sci-

* At an extraordinary meeting of the Town Council, held on Saturday, the
13th of September, diplomas of the freedom of the City of Edinburgh were pre-
sented by the Lord Provost to the following Members of the Association: Sir
Thomas Brisbane, M. Arago, Professor Moll, Dr. Dalton, and Dr. Brown.

ee

PROCEEDINGS OF THE MEETING. XXXVI

ence, and what reports on the state and progress of science it
is desirable to obtain, directing their attention especially to the:
recommendations of the Committees of Science.

That this Committee have power to add to their number the
names of any Members of the Association whose assistance they.
may desire.

‘That this Committee be directed to communicate with M.
Arago, and to report whether there are any scientific objects
which may be advanced by the cooperation of the Association
with the Institute of France.

That the Committees for Science be requested to communicate
to the Committee of Recommendations any suggestions they
may think useful respecting particular scientific objects which
might be advanced by the appropriation of the funds of the
Association, and particular departments of science on the state
and progress of which reports are wanted. .

Committees of Science.—That the Members of the Committees
of Science established at Cambridge be considered as the Sec-
tional Committees of this meeting, with power to add to their
number from the Members of the General Committee.

Two Secretaries were appointed to each Committee.

Corresponding Members.—That MM. Arago, Quételet, Gir-
sted, and De la Rive be elected Corresponding Members of the
Association. :

That the Council be empowered to add to the list of corre-
sponding members the names of foreigners eminent in science,
and desirous to cooperate in the objects of the Association*, —

The Committee met from day to day for the election of Mem-
bers.

On Saturday, the Committee of Recommendations having
made their report, after receiving from the Treasurer an account
of the state of the funds, the General Committee adopted the
recommendations and allowed the grants of money therein con-
tained.

Letters of invitation to the Association having been received
from the Bristol Institution, the Literary and Philosophical So-
ciety of Liverpool, the Royal Dublin Society, the Royal Irish Aca-
demy, the Geological Society of Ireland, the University of Dublin,
—Itwas resolved, That the next meeting of the Association be held
in Dublin, and that the thanks of the Association be returned to the
scientific institutions from which invitations have been received,

»* In consequence of this resolution Baron Humboldt, Professor Berzelius,
Professor Schumacher, Professor Agassiz, and Professor Moll were elected Cor+
responding Members of the British Association,

c2

XXVili - FOURTH REPORT—1834.

That the Council be instructed to make such arrangements
that the Sections may be enabled to meet for scientific business
on the morning of the second Monday in August.

That the salary of the Assistant General Secretary be increased
to the sum of 200/. per annum, to enable him to attend at the
places of meeting for the purpose of making arrangements pre-
vious to the assembly of the Association, and to bear such ex-
penses as the Council may think proper to indicate.

Officers and Council elected.

President elect.—Rev. Dr. Lloyd, Prov. of Trin. Coll. Dublin.
Vice-Presidents elect.—Lord Oxmantown. Rev. W. Whe-

well.

Secretaries for Dublin.—Professor Hamilton. Professor
Lloyd.

Treasurer.—John Taylor.

General Secretary.—Rev. W. V. Harcourt.

Assistant General Secretary.—Professor Phillips.

Council.—Professor Airy. Rey. Dr. Buckland. Dr. Brown.
G. Bentham. William Clift. Professor Christie. J. EK. Drink-
water. Geo. B. Greenough. Dr. Hodgkin. John W. Lubbock.
G. Rennie. Rev. G. Peacock. Dr. Roget. William Yarrell.
Ex officio,—The Trustees (Professor Babbage, R. I. Murchison,
John Taylor,) and the Officers of the Association.

Secretaries.—Dr. E. Turner. Rev. J. Yates.

Members of Committees of Sciences elected.
I. Mathematics and General Physics.

Chairman.—Rev. W. Whewell.
Deputy Chairmen.—Rev. Dr. Lloyd.» Rev. Dr. Robinson.

_ Secretaries.—Professor Forbes. Professor Lloyd.

- Committee —M. Arago. F. Baily. Sir David Brewster. Sir
Thomas Brisbane. Rev. J. Bowstead. E.J. Cooper. Lieute-
nant Drummond. Rev. R. Greswell. Professor Hamilton. Tho-
mas Henderson. William Hopkins. Dr. Jackson. Dr. Knight.
Rey. Dr. Lardner. Professor Moll. Rev. R. Murphy. Lieute-
nant Murphy. Rev. G. Peacock. Rev. Dr. Pearson. Profes-
sor Powell. John Ramage. G. Rennie. Rev. Dr. Robinson.
John Robison. Professor Stevelly. Professor Thomson. Pro-
fessor Wallace. W.L. Wharton. Charles Wheatstone.

PROCEEDINGS OF THE MEETING. XXix

II. Chemistry and Mineralogy.

- Chairman.—Dr. Hope.
Deputy-Chairmen.—Dr. Dalton. Dr. Thomas Thomson.
Secretaries.—Mr. Johnston. Dr. Christison.
Committee.—Dr. Daubeny. Dr. Turner. Dr. Lloyd. Rev.

W.V. Harcourt. Thos. J. Pearsall. William Hatfeild. Pro-

fessor Traill. Dr. William Gregory. Dr. Thomas Clark. Pro-

fessor Graham. Arthur Connell. Luke Howard. Charles Ten-
nant. Charles Mackintosh. William West. Richard Phillips.

III. Geology and Geography.

Chairman.—Professor Jameson. —

Deputy-Chairmen.—Lord Greenock. G. B. Greenough.

Secretaries.—Professor Phillips. T. Jameson Torrie. Rev.
J. Yates.
Committee —Rev. Dr. Buckland. Dr. Boase. J. Bryce.
Major Clerke. Rev. Professor Sedgwick. Colonel Silvertop.
H.T. Witham. William Smith. John Taylor. W. C. Trevelyan.
R. 1. Murchison. William Hutton. Charles Lyell. L. Horner.
J.B. Pentland. R.J. Griffith. William Copland. Dr. Hibbert.
R. Stevenson. Lieut. Murphy. William Clift. Sir Thomas
Dick Lauder. Sir George Mackenzie. Rev. Dr, Fleming.
Dr. Traill. Captain Maconochie. Henry Woolcombe. 8S. P. Pratt.
M. Agassiz. William Nicol. Rev. W. Turner. be

IV. Natural History.

Chairman.—Professor Graham.
_ Deputy-Chairman.—Sir William Jardine, Bart.
- Secretaries—William Yarrell. Professor Burnett.
Committee.—G. A. Walker Arnott. M. Agassiz. Rev. Dr.
Adam. OC. Babington. Dr. Robert Brown. W. Christy.
Dr. Coldstream, Allan Cunningham. John Curtis. David Don.
P.B. Duncan. Dr.R. Dickson. Dr. Daubeny. Rev. L. W. P. Gar-
nons. Dr. Greville. B.D. Greene, Boston, U.S. Professor
Henslow. Professor Hooker. Rev. Dr. Hincks. Professor
Jameson. Rev. L. Jenyns. Mackay. Dr. Richardson.
Commander Ross. J.F. Royle. P.J.Selby. Colonel Sykes.
W. Spence. Richard Taylor. Professor Treviranus. William
Thompson. Dr. Wasse. James Wilson.

xXxXxK . FOURTH REPORT§1834.

V. Anatomy and Medicine.

Chairman.—Dr. Abercrombie.

Deputy-Chairmen.—Sir Charles Bell. Professor Clark.

Secretaries.—Dr. Roget. Dr. William Thomson.

Commitiee——Dr. Alison. Dr. Arnott. Sir G. Ballingall.
8S. D. Broughton. Dr. J. Campbell. Professor Clark. William
Clift. Dr. Davidson. Dr. Hodgkin. Dr. Holme.. Dr. Home.
Dr. Maclagan. Dr. Roget. James Russell. Dr. Thomson.
Dr. A. T. Thomson.. Dr. Wm. Thomson. Professor Trevi-
ranus. Dr. Turner. Dr. Yelloly. ,

VI. Statistics.

Chairman.—Sir Charles Lemon, Bart.

Deputy-Chairmen.—Colonel Sykes. Benjamin Heywood.

Secretaries.—Dr. Cleland. C. Hope Maclean.

Committee.—Howard Elphinstone. | Rev. E. Stanley. J. E.
Drinkwater. Rev. W. Whewell. The Earl Fitzwilliam. Sir
John Sinclair, Bart. Sir Thomas Acland, Bart. John Kennedy.
Captain Churchill. R. I. Murchison. John Whishaw. — Dr.
Chalmers. L. Horner. John Marshall. Neil Malcolm. Fran-
cis Clark. Major Shadwell Clerke. George William Wood.
Right Hon. Lord Jeffrey. John Gordon. Sir Henry Jardine.
Right Hon. Holt Mackenzie. Rev. Dr. Henry Duncan. Dr.
Brunton. Rev. Peter Chalmers. -

COMMITTEE OF RECOMMENDATIONS.

Meetings of this Committee were held on Thursday, Friday,
and Saturday, for the purpose of conferring with M. Arago,
and considering and revising the recommendations to be sub-
mitted to the General Committee.

_ M. Arago, having been requested to state his views as to
any points on which it appeared to him that it might be use-
ful for the British Association to cooperate with the Institute
of France, noticed in particular the great advantage which
might be expected to accrue to magnetical science from the
establishment of observatories furnished with adequate instru-
ments, and under the superintendence of a competent observer,
throughout the extensive possessions of the British empire, and
dwelt upon the necessity of arranging magnetical observations
upon a uniform and well-approved plan. He also spoke of the
value of more extensive and systematic observations on the tem-

PROCEEDINGS OF THE MEETING. xxxi

perature of the earth and springs at small and great depths from
the surface, and mentioned some of the sources of error in such
researches, and the means of obviating them*.

The Committee came to the following Resolutions :

That it be represented to the Government of this country that
the British Association conceive it would be of great service to
science, if magnetical and meteorological observatories were esta-
blished in several parts of the earth, furnished with proper in-
struments well constructed on uniform principles, and if provi-
sion were made for careful and continued observations at those
places ;—that in Great Britain and its colonies there are points
favourable for such observations ; and that it is the more desirable
that the British nation should take a part in carrying them on,
since a system of similar observations, as the Association is
informed, has begun to be established in France and its de-
pendencies. )

That Mr. Baily, Mr. D. Gilbert, Mr. Lubbock, and the Rev.
G. Peacock be a Committee to make the required representation
to the Government, and to solicit the cooperation of the French
Institute.

That the East India Company be requested to further the
same objects, especially at their establishment at Madras.

That notice be given that any persons who may be able to
obtain the temperature of the air, water, and rock, in mines
and borings of known depth, or the indications of thermo-
meters sunk to different depths, in different kinds of soil and
in different parts of the earth, are requested to make known
their names and the places where they have this opportunity, in
order that they may receive instructions for making such ob-
servations, and communicating the results to the Association.

That Mr. Taylor, Prof. Forbes, Prof. Powell, Mr. R. Fox,

Mr. Lubbock, Dr. Dalton, Rev. Dr. Robinson, Prof. Christie,
Prof. Lloyd, and Prof. Phillips be a Committee, with power to
give instructions and to make arrangements on the subject of
the thermometrical observations recommended in the above reso-
lution, and that 100/. be placed at their disposal for these ob-
jectst.
- That M. Arago be respectfully requested, with the least pos-
sible delay, to publish, and to have reduced, his valuable and ex-
tensive collection of magnetical cbservations made at the obser-
vatory at Paris.

_ * On the subject of Artesian wells, see the dnnuaire for 1835.

_ + The Committee has taken steps to have instruments constructed suitable
for the experiments in mines, wells, &c., and to have sufficient instructions con-
veyed to persons who will undertake the researches required at selected points
in various parts of the country.

XXxii FOURTH REPORT—]834.

M. Arago expressed his readiness to comply with the request
of the Committee as soon as it should become practicable ;
and stated that the immense collection referred to (amounting to
more than 100,000 careful observations, and relating to nearly
all parts of magnetical science,) had been some time since des-
tined for publication, but that the printing of them had been post-
poned in consequence of an application which had come from
England for the cooperation of France in furnishing data for the
improvement of the theory of the tides. When Mr. Lubbock ap-
plied to the Bureau des Longitudes, through M. Poisson, for the
loan of the manuscript observations on the tides at Brest, it was
decided, at the earnest recommendation of M. Arago, that an
object in which other nations were thus taking interest should
have the preference given to it; that the observations on the
tides at Brest should be printed at the expense of the French
Government, and that copies should be furnished to those per-
sons in foreign countries who were ready to use them.

The Committee then proceeded to receive and revise the re-
commendations laid before them by the Committees of Science.

COMMITTEES OF SCIENCE.

The several Committees met daily at 10 a.M., to arrange the
business of the Sections and to determine on the recommenda-
tions which were to be presented to the Committee appointed
to receive them.

Committee for Mathematical and Physical Science.

The Committee reported on the part of the Sub-Committee for
discussing observations on the tides (see vol. ii. p.471.), that
the discussion of the tide observations, and the formation of
tide tables, was in considerable progress, and would be conti-
nued with all practicable expedition. That the sum of 50/. only,
out of the 200/. appropriated by the British Association for this
purpose, had at present been paid by the Treasurer ; but that it
was probable that the whole of the sum so appropriated might
be eventually required.

The gentlemen of the Atheneum of Liverpool, on being ap-
plied to on the part of the British Association, with great libe-
rality and kindness sent the original manuscript of Mr. Hutch-
inson’s observations to Mr. Dessiou of the Admiralty, who was
engaged by the Sub-Committee to discuss them. These observa-
tions are now undergoing the requsite calculations. i

PROCEEDINGS OF THE MEETING. XXXiil

‘The Corporation of Liverpool also, at the suggestion of the Sub-
Committee, have established two sets of apparatus for the pur-
pose of making tide observations at Liverpool, the one at the
Clarence Docks, the other at the Black Rock. Mr. Yates of
West Dingle, and Lieut. Drummond, R.N., the director of the
Ordnance Survey of the coast in that neighbourhood, have given
much valuable aid to the objects of the Sub-Committee.

The Committee reported on the part of the Sub-Committee
for superintending the reduction of the Observations of Bradley,
Maskelyne, and Pond, on the Sun, Moon, and Planets, made at
Greenwich, (see vol. ii. p. 469.), that the reduction of these ob-
servations was in progress; that the Royal Society had con
tributed a copy of Maskelyne’s Observations for that purpose ;—
That the Syndicate of the University Press at Cambridge had
given the paper and press-work for the printed forms requisite for
the calculations ;—That one calculator had been employed since
the beginning of March, in which interval the transits have been
taken out of Bradley and Maskelyne; the means of the wires have
also been deduced, some advances made towards completing the
imperfect transits, and considerable progress in preparing the
apparent right ascensions of the fundamental stars ;—that a
temporary stop was put to a portion of the work, in conse-
quence of a very severe illness with which Professor Airy was at-
tacked during the last summer, but that the work was again
proceeding with as much expedition as possible.

The Committee reported the following Recommendations :

_1. That it is desirable that the Constant of Lunar Nutation
should be deduced from observations made with the mural circle
at Greenwich.

2. That it is expedient that the sum of 100/. be appropriated to
the purpose above mentioned by the British Association ; and
that Sir Thomas Brisbane, Rey. Dr. Robinson, and Mr. Baily be
requested to superintend the deductions.

_3. That it is desirable that the Standard Scale made some
years ago by Mr. Troughton for the town of Aberdeen should
be compared with the Standard Scale recently made for the
Royal Astronomical Society; and that application should be
made by the British Association to the magistrates of that town
for the loan of the same for the purpose above mentioned.

4, That Mr. Baily be requested to make the requisite com: —
parisons, provided the loan of the Scale can be obtained*.

5. That the Difference of Meridians between the Observatories
of Greenwich, Cambridge, Oxford, Edinburgh, Dublin, and Ar-

>

. * The scale has been received, and is under examination by Mr. Baily. ~

XXXiV FOURTH REPORT—1834.

magh should be determined by means of chronometers, or by
signals, or by both methods, and that application be made to
Government for their assistance in accomplishing this object.
That the Astronomer Royal, Dr. Robinson, Prof. Airy, Prof.
Rigaud, Prof. Henderson, Prof. Hamilton, Sir Thomas Brisbane
and Lieut. Drummond be requested to carry this recommenda-
tion into effect.

6. That Mr. W. Gray, jun., and Prof. Phillips be requested
to continue their experiments on the Quantities of Rain falling
on the top of York Minster and other adjacent stations.

7. That Mr. Peacock be requested to continue his Report on
certain branches of Analysis for the next meeting.

8. That Mr. Whewell be requested to execute for the next
meeting the Reports on the Mathematical Theories of Heat,
Electricity, and Magnetism.

9. That Mr. Challis be requested to proceed with his Report
on the Mathematical Theory of the Motion of Fluids.

10. That Mr. Rennie be requested to proceed with his Report
on Practical Hydraulics.

11. That Mr. Willis be requested to prepare his Report upon
Acoustics for the next meeting.

Committee for Chemical and Mineralogical Science.

The Committee reported that they had received statements
of the progress of the experiments on the specific gravity of cer-
tain gases, and on the effects of long-continued heat on mineral
and organic substances, for which sums of money had been ap-
propriated at a former meeting, and recommended the conti-
nuance of those appropriations.
~ They reported also the following Recommendations :

1. That Mr. Graham be requested to submit to further investi-

ation the amount of security to be derived from the Safety Lamp.

2. That Mr. Graham and Dr. Williams be requested to investi-
gate further the phenomena of Low Combustion.

3. That a sum of 101. be placed at the disposal of Mr. Johnston
to defray the expense of preparing a specimen of Chemical Con-
stants, in conformity with the suggestions of Mr. Babbage.

4, That Dr. Dalton, Dr. Hope, Dr. T. Thompson, Mr. Whewell,
Dr. Turner, Prof. Miller, Dr. Gregory, Dr. Christison, Mr. R.
Phillips, Mr. Graham, Prof. Johnston, Dr. Faraday, Prof. Da-
niell, Dr. Clark, Prof. Cumming, and Dr. Prout be appointed a
Committee, to report to the next Meeting their opinion on the
adoption of an uniform set of Chemical Symbols; with power to
add to their number. Dr. Turner to be Secretary.

5. That Dr. Roget be requested to report on the progress of

OO

PROCEEDINGS OF THE MEETING. XXXV

Electro-chemistry and Electro-magnetism, so far as regards the
experimental part of the subject.

6. The Committee recommended the researches commenced
by Sir David Brewster into the Optical properties of Minerals to
the attention of chemists.

Committee for Geology and Geography.

The Committee reported the following Recommendations:

1. That Mr. Stevenson be requested to complete the Report
of the relative level of land and sea, and on the waste and exten-
sion of the land, which he has presented to this Meeting.

2. That with a view to perfect our knowledge of the Fossil
Ichthyology of the British islands, a sum not exceeding 105/. be
paid by the Treasurer to Dr. Buckland, Prof. Sedgwick, and
Mr. Murchison, to be applied for the purpose of assisting
M. Agassiz in carrying on his Ichthyological work.

3. That the recommendations relating to the veins and sections
of Flintshire, the heaves of Cornwall, the quantity of mud and
silt, the experiments of Mr. G. Watt, and the desiderata noticed
by Mr. John Taylor and Mr. Conybeare, and the sixth and tenth
queries, be repeated.

4, That a sum not exceeding 20/. be placed at the disposal of
Mr. J. Yates and Mr. G. Rennie, for the purpose of the experi-
ments on the quantity of mud and silt in rivers.

5. That evidence should be collected as to the direction and

probable sources from which drifted blocks and pebbles, referri-
ble to rocks not existing in the neighbourhood where they now
occur, whether in insulated masses, or in beds of superficial gra-
vel, may have been derived *.
_ 6. That evidence should be collected as to the form and direc-
tion of hills or ridges of superficial gravel, and the sources whence
the materials of such gravel hills may have been transported to
their present place.

7. That observations should be made on the direction and depth
of grooves and hollows, such as are often found on the faces of
hard rocks and beneath superficial deposits of drifted clay and
gravel not referrible to the action of any existing currents.

8. The Committee further reported that it appeared to them
that the advancement of various branches of science is greatly
retarded by the want of an accurate map of the whole of the
British Islands :—that it be recommended to the Council to con-
sider of the propriety of representing this opinion to His Ma-

_ * The Assistant-Secretary has forwarded to persons known to possess infor-
mation on these subjects a circular, of which copies may be had on application
to him.

XXxXvi ‘FOURTH REPORT.—1834.

jesty’s Government, with a view of expediting the completion of
the stiil unfinished or unpublished parts of the Ordnance Survey*:

_ * In consequence of this recommendation the following Memorial, upon the
state and progress of the Ordnance Survey of Great Britain, was presented to
the Chancellor of the Exchequer on the part of the Association, by a deputation
from the Council :

Memoria.

“The Trigonometrical Survey of Great Britain, conducted by men of high sci-
entific attainments, commenced its operations in 1798, with a view to the con-
struction of a general map, and in 1805 the first sheets of that work were pub-
lished. Of one hundred and eight sheets required to form the whole map of
England. sixty-five only have yet been published, at which rate of progress
thirty years would elapse before the survey could reach the banks of the Tweed.
Now, although from the exertions recently made in this department, the rate of
publication has been accelerated, yet, on reference to the highest authorities on
this subject, no prospect is held out, even upon the present improved system,
that the desired result can be attained in less than ten years, after which the
entire map of Scotland will remain to be constructed. th

*‘ Your memerialists conceive that this simple statement of the condition
and future prospects of the Survey might in itself be a sufficient reason to in-
duce Parliament to increase the grant allotted to this branch of public service.
But to place the evil complained of in a clear light, they venture to submit to
you the following considerations.

“ Urgent calls for the acceleration of this Map are made by many proprietors of
land and mines both in the North of England and in Scotland, who contend that
in the construction of rail-roads, canals, or other public works, that portion
of the kingdom is subjected to great expenses and difficulties from the want of
it. In forming the Western rail-road from London to Bristol an outlay of several
thousand pounds in surveying has been saved by the possession of those por-
tions of the Map which are published, whilst the correctness of the physical
features laid down upon them has enabled the engineer at once to select his line
of operations, and thus to gain at least a year of time in the commencement of
the work. Similar results have been obtained in Ireland, in forming the Ulster
canal, in consequence of the publication of the Ordnance Map of that country;
Another important benefit will be conferred upon the public by the completion
of this Map, in the correction of the coast surveys, determining the precise posi-
tion of headlands and form of bays; a point of considerable moment in the
northern parts of this maritime country, where the outline of the coast is broken
and dangerous. In illustration of this it may be mentioned, that in the progress
of the yet unpublished parts of this Survey, errors of position in the most ac-
credited charts of this coast have been detected to an extent in one instance of
eleven miles !

“Your memorialists particularly invite attention to the fact, that although
a very large portion of the expense relating to the Scottish survey has been in~
ewred, not only in establishing the great triangulation, but also in minutely and
accurately surveying a large portion of the South-west of Scotland, the mate-
rials so collected are now, they believe, laid by in the archives of the Map-office,
without the prospect of their being made available for many years; whilst it
must be observed that the knowledge thus locked up relates to one of those
tracts of the empire where its diffusion would prove of singular advantage.
Upon this head, indeed, it can be shown that the delay is not only a negative but
a positive evil, in as much as, but for the conviction that many years could
not elapse between the execution of this Survey and its publication, the inhabi-
tants themselves would have endeavoured to improve the maps.

“In this backward state of a national geographical survey, Great Britain

PROCEEDINGS OF THE MEETING. -xxxyii

Committee for Natural History.

‘The Committee reported the following Recommendations :
It was resolved, ‘

1. That, Mr. James Wilson be requested to report on the pre-
sent state of our knowledge of the geographical distribution, of
Insects, particularly Coleoptera.

2. That Dr. Richardson be requested to prepare a Report on
the state of our knowledge of the Zoology of North America.

stands almost alone among the civilized nations of Europe, whilst it is obvious
that in no country can the perfection of its maps be more imperiously called
for. The trigonometrical survey of Austria is completed as respects the Tyrol;
the Eastern Alps, Bohemia, and Austria Proper.

“ Prussia has nearly completed her survey.

* France, though possessing the elaborate maps of Cassini, has still deemed it
essential to institute a new survey of her whole dominions, which is now going
on-in so vigorous a manner, that though only commenced in the year 1828,
there is every reason to suppose that the whole will be finished long before
the British survey (at its present rate of progress) will have been completed.

‘ Bavaria holds forth an example highly worthy of imitation. Her survey,
commencing in 1819, has made such rapid progress that out of one hundred
sheets to illustrate her territories sixty-three have been already published, and
the whole work will be terminated in six years, and this too upon a scale of
three inches to a mile.

“ Now in none of these countries is there the hope that such expenditure of
public money can be repaid, whilst in England and Scotland there are many
districts where the sale of the Trigonometrical Survey will go far towards re~
paying the cost of production.

’ “Though deeply sensible of the advantages which must accrue to physical
science from the diffusion of these maps, seeing that the published portions of
them have already enabled the geologist to develope with precision the mineral
structure of large tracts of England, your memorialists solely avoid dwelling
upon this important point because the subject requires more explanation than
can be well condensed into a short memorial.

“* Anxious for the progress of science, and its application to national uses

‘in every portion of the United Kingdom, your memorialists have had their at-
tention the more powerfully attracted to the languid condition of the Ordnance
Survey of Great Britain, by the contrast which it presents to the active manner
in which the survey of Ireland is now conducted; for whilst they rejoice that
this important object is there so munificently supported as to admit of the rapid
publication of a map constructed upon a scale of siz inches to a mile, they must
at the same time deplore, in regard to some of the most valuable tracts of
England and Scotland, that a survey upon a scale of only one inch to.a mile
is making such feeble progress.
. “Your memorialists therefore trust that His Majesty’s Government: will
suggest to Parliament the propriety of an adequate grant for the acceleration of

a work in which so many public interests are involved, and they feel confi-
dent that enlightened men of all political parties will unite in the support’ of
such a truly useful. and national measure.

* « By order of the Council of the British Association
4f for the Advancement of Science,
May 28, 1835. (Signed) “ ROD. I. MURCHISON,,

“ Chairman.” «> ~

XXXVili FOURTH REPORT—1834.

3. That Dr. Greene and Dr. Hooker be requested to prepare a
Report on the state of our knowledge of the Botany of North
America.

4, That the Zoological Queries introduced in last year’s Re-
commendations be continued, except the 6th and 7th.

5. That the Botanical Inquiries be continued. .

6. As a full and arranged Catalogue of the works on Natural
History (including Memoirs, &c., in Journals and Transactions,)
would greatly facilitate the study of that branch of science, it is
recommended that at the next meeting of the Association a
Committee be appointed for devising the means of forming and
publishing such a catalogue ; and that in the mean time, to aid
the labours of that Committee, gentlemen who have devoted
themselves to the study of particular departments of natural
history be earnestly requested to send in to the Assistant-Secre-
tary lists of the works, memoirs, &c., relating to such depart-
ments.

Medical Committee.

The Medical Committee reported that the sum of 25/. was
placed at the disposal of Dr. Marshall Hall and Mr. Broughton
for the investigation of the subject of the Sensibilities of the
Nerves of the Brain; that these gentlemen have presented a
report, which has been read and highly approved; that their
experiments are not yet complete, but they do not ask for any
further grant for the prosecution of them. (Report received.)

They further reported that a sum of 25/. was placed at the
disposal of Dr. Roupell and Dr. Hodgkin for prosecuting an in-
quiry into the effects of poisons on the animal ceconomy ; that
an interim report has been read from these gentlemen who are
prosecuting the inquiry, and that they do not at present ask for
any further grant. .

The Committee recommended, as an important object of in-
quiry, the anatomical relations of the absorbent and venous sy-
stems in the different classes of animals, to be illustrated by in-
jected preparations and graphic representations.

The Committee, considering the contradictory results ob-
tained by the distinguished anatomists who have prosecuted this
subject of investigation, recommended that two Sub-Committees
be appointed for prosecuting the inquiry, the one to sit at Edin-
burgh and the other in London.

The Edinburgh Sub-Committee to consist of Dr. Allen Thomp-
son, Dr. Alison, Dr. Fletcher, Dr. Sharpus, Dr. Hardyside, Dr.
Reid, Mr. Mackenzie and Mr. Dick ; and the London Sub-Com-
mittee to consist of Dr. Hodgkin, Dr. Roget, Dr. Clark of Cam-
bridge, Mr. Bracey Clark, Mr. Clift and Mr. Broughton, with

PROCEEDINGS OF THE MEETING. XXxix

power to add to their numbers. They further recommended
that a sum not exceeding 25/. should be placed at the disposal
of each Sub-Committee for assisting the prosecution of such re-
searches. :

The Committee recommended the prosecution of inquiries on
the pathology of the Nervous System ; on the successive motions
of the different parts of the heart; and the sounds which accom-
pany them. Three Committees were named for the prosecution
of these researches in London, Edinburgh, and Dublin.

The Committee recommended the appointment of Medical
Sub-Committees, to communicate with the Statistical Com-
mittee of the Association, or with the Statistical Society in Lon-
don, relative to a registration of deaths, comprising particulars
of a medical nature, with the view that if any legislative measure
should hereafter be adopted as to registration, such suggestions
may be offered by the Association as may seem best fitted to at-
tain the requisite information for this desirable object. Two
Committees were named, one in London and the other in Edin-
burgh. London: Drs. Yelloly, Bright, Roget, Bisset Hawkins,
and Clark, 6, George Street, Hanover Square. Edinburgh :
Drs. Abercrombie, Traill, Christison, W. Thomson, and Alison*.

The Committee recommended that Dr. Christison be re-
quested to draw up a Report on the circumstances in vegetation
which influence the medicinal efficacy of plants.

Statistical Committee.

The Committee recommended that a Sub-Committee should
be formed, who should associate with themselves certain gentle-
men connected with the conduct and publication of the new
Statistical Account of Scotland, to be named by that body for
the purpose of drawing up a set of queries by which more mi-
nute information on statistical subjects than that hitherto re-
ceived may be obtained, and that the Committee be autho-
rized to defray the expense which may attend the printing of the

ueries. :

That Mr. Taylor be requested to draw up a series of ques-
tions upon the condition and habits of the mining population
of Cornwall and Wales, with a view to obtain a complete ac-
count of the statistics of that class.

The Committee reported that in pursuance of a recommenda-
tion of the Association, Professor Jones had applied for leave of
access to the archives of the East India Company, and that
that body, with its accustomed liberality, had afforded him every
facility in prosecuting his researches.

* These Committees have been for some time in operation.

xl . FOURTH REPORT—1834.

APPROPRIATION OF FUNDS,

At the instance of the Committee of Recommendations :

For the prosecution of Thermometrical Observations
at various depths from the surface, under the direc-
tion of a Committee named for that purpose. . .

On the recommendation of the Committee for Mathematical
and Physical Science :
For determining the Constant of Lunar Nutation from
the ee Observations . . .
For discussing Observations of the Tides in ofomeen to
improve the Tide Tables (vote of last year continued
and enlarged) :
For the construction of a telescopic lens of tock salt,
(vote of last year enlarged) .

On the recommendation of the Committee for Chemical
and Mineralogical Science :

For the execution of a specimen of chemical constants

on the plan of Professor Babbage
For experiments on the effects of long-continued heat
on mineral and organic bodies, (vote of last year
continued). . .
For determining the specific gravity of hydrogen and
other gases (vote of last year continued). . . .

On the recommendation of the Geological and Geographi-
cal Committee :
For advancing our emul near of British fossil Ichthy-

ology . . : :
For experiments on the quantity ¢ of mud transported

by rivers

On the recommendation of the Committee of Anatomy ee

__ Physiology :
For experimental investigations on the effects of poi-
sons on the animal economy, (vote of last year con-

tinued) . : .
_ For investigating the relations ‘of ‘the absorbent and ve-
nous systems .. 5 .

_ For defraying certain expenses incurred i in the execution
of thermometrical observations at Elymonth si the
lateness Eharvey * 64. .:0-¢10)6 die

Bis

100

100

- 250

80

10

50

50

25

20

£860

PROCEEDINGS OF THE MEETING. xh

SECTIONAL MEETINGS.

The Sections assembled daily at eleven a.m., in the Class
Rooms of the College, to hear the communications in different
departments of science prepared to be laid before them by the
secretaries of their respective committees.

The following is a list of the communications which were
made to the meeting, divided into four classes: Ist, Reports
on the state and progress of science, drawn up at the.request of
the Association; 2nd, Accounts of researches undertaken at the
request of the Association ; 3rd, Notices in answer to queries and
recommendations proceeding from the Association ; 4th, Miscel-
laneous communications.

I. Reports on the State and Progress of Science, drawn up
at the request of the. Association.

On the Geology of North America, Part I. By Professor
Rogers.

On the State of our Knowledge of the Laws of Contagion.
By Dr. Henry.

On Animal Physiology. By Dr. Clark, Professor of Ana-
tomy, Cambridge.

On the recent Progress and present State of Zoology. By
the Rey. L. Jenyns.

On the Theory of Capillary Attraction. By the Rev. James
Challis.

On the Progress and present State of the Science of Physical
Optics. By the Rev. H. Lloyd, Professor of Nat. Phil. Dublin.
» On the Progress of Hydraulics considered as a Branch of En-
gineering: Part II. By George Rennie.

II. Accounts of Researches undertaken at the request of the
Association.

Remarks on the relative Level of Land and Sea, &c. By
Robert Stevenson, Engineer. ‘a

Results of a Second Series of twelve months’ observations
on the Quantities of Rain falling at different elevations above
the ground. By William Gray, jun., and Professor ‘Phillips.

Account of the institution of Experiments on the effects of
long-continued Heat. By the Rev. W. V. Harcourt.

Account of researches in Crystallography. By Professor
Miller. : ?

1834. d

xhii FOURTH REPORT—1834.

Account of the progress of experiments on the nature of the
Secretions from the Roots of Vegetables. By Dr. Daubeny, Pro-
fessor of Chemistry and Botany, Oxford.

Notice of the progress made in the comparative analysis of
Iron in the different stages of its manufacture. By Professor
Johnston.

Notice of the progress made in determining the specific gravi-
ties of Oxygen, Hydrogen, and Carbonic Acid. By Dr. Dalton.

Account of researches on the effects of Poison on the animal
ceconomy. By Dr. Roupell and Dr. Hodgkin.

Account of researches on the Sensibilities of the Nerves of
the Brain. By Dr. Marshall Hall and 8. D. Broughton.

Account of the performance of a Chronometer with a Glass
Balance-spring. By E. J. Dent.

Notice of the performance of an Instrument for ascertaining

the quantities of mud transported by Rivers. By George Ren-
nile. .

III. Notices in reply to Queries and Recommendations of
the Association.

On the electrical condition of Metalliferous Veins. By R. W.
Fox.

On the peculiar circumstances attending certain Coal Di-
stricts inthe midland counties of England. By R.1. Murchison.

On the direction &c. of Non-metalliferous Fissures. By Pro-
fessor Phillips.

On the Limestone of Closeburn. By C. G.S. Menteath.

On the Beds inclosing the Hematite of Dalton. By Professor
Sedgwick.

On the supposed Metamorphosis of Crustacea. By J..O. West-
wood.

On the progress made in inquiries relative to the Secretions
from the Roots of Vegetables. By Dr. Dunbar.

On the nature and quantity of the Gases given off from Ther-
mal Springs. By Dr. Daubeny.

On the purity and specific gravity of Mercury, Dr. Thompson
remarked that he considered the mercury as imported into this
country to be pure, and the specific gravity assigned;to it by
Cavendish to be correct, as it agrees with recent determinations
by Mr. Crichton, from experiments continued through a whole
winter.

On products collected in Chimneys of Furnaces. By Mr.
Lowe.

PROCEEDINGS OF THE MEETING. xliti

IV. Miscellaneous Communications.

Abercrombie, Dr. On the study of Mental Philosophy as a
part of Medica} Literature. ;

Adam, Rev. W. On a Sextant furnished with a Spirit Level,
to be used at-sea or land when the horizon is invisible.

Addams, R. On a phenomenon of Sound.

Adie, J. On the Expansion of Stone.

Agassiz. On the Fossil Fishes of Scotland.

On the recent genus Salmo.

Aitken, Dr. On the Motions of Blood in Mammalia.

Alison, Dr. On the Vital Powers of Arteries leading to in-
flamed parts.

Andrews, T. On certain Caves in Rathlin, &c.

Arago. Remarks on the methods of conducting experimental
researches in Magnetism, especially for the detection of
minute variations of Intensity and Direction.

——— Proposal of submitting M. Poisson’s conclusions regarding
the Change of Density near the Surface of Fluids to an
experimental test, by the observation of the angle of the
complete polarization of light at these’ surfaces.

—— On the hypothesis of Transversal Vibrations in Physical
Optics, and the claims of Dr. Thomas Young as the first
to propose it.

Arnott, G.W. On Cocculus Indicus. .
Auldjo, J. Notice of a work of M. Rotindo on the Statistics
of Naples.

Badnall. On Friction on Railways.
Bell, Sir Charles. Discourse on the Nervous System.
Blackadder. Notice of a Fossil Fish from Glammis.
Boase, Dr. Statement of his views on the question of the Stra-
tification of certain primary Rocks.
—— On Fissures and Veins.
Boujou, Dr. Sur les rapports reciproques de la Médecine ‘et Ia
Philosophie.
Breen, Hugh. On a property of Numbers.
Brewster, Sir David. On Colours in the spaces’ of the Rainbow.
Experiments on the effects of Reflexion from‘ the surfaces
of Crystals when those surfaces have been: altered by’ so-
lution.
—— On a large specimen of Amber from Ava.
—— On the Optical Characters of Minerals.
—— On the Structure of Feathers.
Brisbane, Sir Thomas. Notice of a fact observed in registering
the Fall of Rain. '

d 2

xliv FOURTH REPORT—1834.

Brisbane, Sir Thomas. Notice of Sand from New South Wales

for the manufacture of Glass.

Notice of an Ephemeris of Halley’s Comet by Mr. Rumker.

Brown, Dr. On the Plurality of Embryos in Conifere.

Brown, Capt. On Pecten aspersus.

Brunel. On the Construction of Arches without centering.

Bryce, W. J. On certain Caves in the North of Ireland.

Buckland, Rev. Dr. A Lecture on several remarkable Fossil
Fishes and Reptiles, delivered at an Evening Meeting
of the Association.

——- Notice of a fossil Marine Plant from the Red Sandstone
near Liverpool.

Bushnan, Dr. On the detection of Worms in the Human
Veins.

Challis, Rev. James. Theoretical explanations of some facts
relating to the composition of the Colours of the Spec-
trum.

Christie, Professor. Description of a Meteorological Pheenome-
non.

Christison, Professor. Action of Water on Lead.

Clark, Dr. On the use of the Hot Air Blast in Iron-furnaces.

Clarke, Dr. (deceased.) On the Ventilation of Hospitals.

Cleland, Dr. On the Statistics of Glasgow.

Dalyell, J. G. On the Propagation of Scottish Zoophytes.

Dick, David. On the cementing the internal surfaces of Object-

glasses.

On a new Suspension Railway.

Dick, William. On the use of the Omentum.

—— On the Elastic Tissue of animals.

—— Observations on the Tongue of the Chameleon.

Drake. On the Change of Colour in the Elder.

Drinkwater, J. E. On the Origin of the Statistical Society of
London.

Dunn, John. Description of a new Clinometer.

Fitzwilliam, Earl. On the details desirable in Statistical Re-
ports relating to Agriculture.

Forbes, Professor. On a new Sympiesometer.

Graham, Professor. On Hydrated Salts.

Grant. On Tables of Insurance.

Graves, J. T. On Exponential Functions.

Gilbertson, William. On Marine Shells of existing species at
various elevations near Preston.

Gordon, Alex. On the construction and uses of Polyzonal
Lenses.

Greenock, Lord. On certain Coal Tracts in Scotland.

PROCEEDINGS OF THE MEETING. xlv

Greenock, Lord. . Notice of the section of Trap and Sandstone
in the Castle Hill, Edinburgh.

Greenough, G. B. On the Stratification of certain primary
Rocks.

Gregory, Dr. W. Notice of various Organic Products.

—— Abstract of Reichenbach’s discoveries.

Hailstone; Rev. J. On minute Oscillations of the Barometer.

Hall, Colonel. Account of excursions in Quito.

Hall, Elias. Exhibition of a model of the Geology of Derby-
shire.

Hamilton, Professor. On Conjugate Functions.

On a General Method in Dynamics.

Harlan, Dr. Notice of some Organic Remains of the United
States.

Hibbert, Dr. On the ossiferous beds in the Basins of the Forth,
Clyde, and Tay.

Hodgkinson, E. Experimental Researches on Collision.

Howard, Luke. On the Quantities of Rain at different eleva-
tions. .

Jameson, Professor. Notice concerning the Fossil Fishes of
Scotland, and the geological age of the formations in
which they occur.

Jardine, Sir William. Account of Fishes collected in Suther-
landshire.

Johnston, Professor. On Oxichloride of Antimony.

Jordan, T. B.. Ona construction of the Magnetic Needle.

Kemp, K. T. On the Liquefaction of the Gases.

Knight, Dr. On the Organic Remains inthe Flints of Peters-
head, &c.

—~ On a method of rendering visible the Vibrations of heated
Metals.

Lardner, Rey. Dr. A Lecture. on Professor Babbage’s Calcu-
lating Machine, delivered at an Evening Meeting of the
Association.

Lloyd, Prof. On a method of observing the Magnetic Needle.

Lowe, George. Exhibition of certain products obtained in Gas
Works, &c.

Lyell, Charles. On the relative Level of the Land and Sea on

i the shores of Scandinavia.

—— On the Characters of Stratification in the discussion on
Primary Rocks.

MacConnochie, Captain. Notice of a work by M. Guerry, Sur
laS tatistique morale de la France.

MacDonnell, Dr.. On the Pulse, and the variation of its agi
ness from various causes.

xlvi FOURTH REPORT—1834.

MacGillivray, W. On the Natural History of the Transition
Ranges of Scotland.

—— Exhibition of drawings of the Vertebrate Animals of Great
Britain and Ireland.

Maclaren, Charles. On the Geology of the Pentlands.

Milne, David. On the Geology of Berwickshire.

Murchison, R. I. On the Transition Formations of the Welsh
Border. .
Murphy, Rev. R. Notice of some recent electrical Experi-
ments, by Mr. Snow Harris, on the retention of Elec-

tricity on the surfaces of bodies in vacuo.

Murphy, Lieut. Notice of the progress made in the Ordnance
Survey of Ireland.

Murray. On Rates of Mortality.

Murray, J. On the cultivation of Phormium tenax in Scotland.

On the Chameleon.

On the Ascent of the Sap.

Nicol, W. On the structure of Fossil Wood.

Pentland, J.B. Ona peculiar configuration of the Skull in a
race of men formerly existing in Peru.

Phillips, Professor. On a method of causing the centre of
gravity of a Dipping-needle to coincide with its axis
of motion.

—— On the Stratification of Primary Rocks, (in discussion on
that subject.)

Powell, Professor. On the Repulsion produced by Heat.

On the Achromatism of the Eye.

—— On the Dispersion of Light.

Quetelet. In a letter to Mr. Whewell, M. Quetelet states his

. belief that he has succeeded in reducing the examination .
of the Law of Population to the discussion of ma-
thematical formule, and requests that his. views may be
tested by a comparison of the calculated results with those
furnished by observations in England, the United. States,
and elsewhere.

Ramage, John. On the construction of large reflecting Tele-
scopes.

Reid, Dr. On the Connexion of Muscles with Nerves.

Rennie, G. Notice of the successful performance of an In-
strument to measure the quantity of Mud in the water
of Rivers.

Robinson, Rev. Dr. A Discourse on Halley’s- Comet, delivered

at an Evening Meeting of the Association.

On the Visibility of the Moon in total eclipses.

—— On the Situation of the Edinburgh Observatory.

PROCEEDINGS OF THE MEETING. xlvii

Royle, J. F. On the Character of the Vegetation of the Hi-
malaya Mountains.

Russell, J. On the Resistance to Floating Bodies.

Sang, Edward. On the Geometry of Lines of the third order.

On Vibrating Wires.

On a property of successive Integer Numbers.

Saull, W. D. Drawing of the Incisors and Canine Teeth of the
Hippopotamus, from a gravel-pit near Huntingdon.

Saumarez, Richard. On Light and Colours.

Saxton, Joseph. On an Instrument for measuring minute Va-
riations of Temperature in Metal Rods, &c. .

Secretary to the Society of the Sons of the Clergy in Scotland.
Notices relating to a Statistical Survey of Scotland.

Sedgwick, Rev. Professor. On the Stratification of certain Pri-
mary Rocks, (in reply to Dr. Boase’s views.)

—— A Review of the Geological Proceedings of the Meeting at
Edinburgh, delivered at an Evening Meeting of the As-
sociation. ‘ ’

Selby, P. J. Notice of Birds collected in Sutherland.

On the Postorbital Glands in Natatorial Birds.

Sharpey, Dr. On the Vascular System of the Porpoise.

Smith, William. Observations on the Waste and Extension of
Land on the Kast Coast of England.

Stanley, Rev. E. Notice regarding Statistical Returns for
Parishes.

Statistical Society of Manchester, by Mr. Heywood. Statisti-
cal Returns relating to Manchester.

Stevelly, Professor. On some branches of Meteorological Sci-
ence.

— On a Vernier to be adapted to a scale of unequal parts.

Sykes, Lieut.-Col. On Mean Temperatures in India.

Syme, Professor. On removing portions of Joints.

Taylor, John. On the Directions of Mineral Veins in different
countries.

Thomson, Dr. Allen. On the Structure of the Human Feetus
and that of Mammalia at early periods of development.

—— On the external Gills of the Young of the Skate, and on the
Gills of some Reptilia.

On the Change of Colour observable in the Cuttle-fish.

Thomson, Dr. A. T. On Iodides.

Thomson, Dr. T. Notice of a Fossil Plant (probably marine)
from the Glasgow Coalfield. ;

Thomson, Dr. W. On black Discoloration of the Lungs.

Toorn, M. Vander. On the Water in Sulphate of Zinc.

xlviii FOURTH REPORT— 1834.

Tough, Rev. Mr. On a Glass Celestial Sphere.
Traill, Professor. On the Laryngeal Sac of the Reindeer.
—-~- On the Geology of the Orkneys.
On the Fossil Fishes of the Orkneys.
Trevelyan, A. On theapplication of Vapour of Alcohol to the
purpose of a chemical Lamp Furnace. (See Phil. Mag.
1834.)
. Trevelyan, W.C. On Fossil Wood from Faroe.
On the Geographical distribution of Plants in Faroe.
Turner, Dr. E. On Atomic Weights; that they are not repre-
sentable by whole numbers.
West, William. On the presence of Sulphur in Bar Iron,
Whewell, Rev. W. A Lecture on certain Phenomena of the
Tides, delivered at an Evening Meeting of the Associa-
tion.
—-— Suggestions regarding Sir J. Herschel’s explanation of Di-
spersion according to the Undulatory Theory.
Williams, Dr. C. On the State of Knowledge regarding Sound.
On the Phenomena of Low Combustion.
Wilson, J. On the Coleopterous Insects of Sutherland.
Yates, Rev. J. On some facts regarding the Stratification of
Primary Rocks.

ee ee

REPORTS

ON

THE STATE OF SCIENCE.

Report on the Geology of North America, Part I., by Henry
é D. RoecErs, F.G.S.

IN obedience to the request of the British Association, ex-
pressed to me at the last Annual Meeting, I beg leave to offer
the following Report on the present state of our knowledge of
the geology of North America.

The magnitude of the region, our remoteness from the foun-
tains of science in Europe, and likewise some peculiarities in
the geological structure of the country, have operated hitherto te
make our efforts in exploring its formations tardy and uncertain.
But the friendly interest expressed by the British geologists in
our labours is calculated to cheer and quicken our progress.

It will be seen to be among not the least important of the
good results of this Association, that it can invigorate by its
ample spirit the youthful science of a distant but kindred con-
tinent.

The plan and object of this Report make it necessary to offer
an introductory section on the general physical geography of
the country. In no section of the globe will a more obvious
and marked connexion-be seen between the geographical features
of the surface and the geology. Such a description is indispen-
sable indeed, for certain geographical boundaries will be found
the best, in fact almost the only, guide we possess at present for
judging of the probable range and extent of certain formations
over many extensive districts not yet explored.

Physical Geography.—Owmitting the minor irregularities, and
confining our survey to the great masses which compose the
continent of North America, its structure will be seen to exhibit
great simplicity and regularity. From the Atlantic to the Pa-
cific Ocean, and from the Arctic Sea to the Gulf of Mexico,
the whole area seems naturally divided into two great plains,

1834. B

2 FOURTH REPORT—1834.

bounded by two broad ranges, or rather belts, of mountains.
One plain, the least considerable by far, occupies the space
between the Atlantic and the Appalachian or Alleghany Moun-
tains, and extends from Long Island, or more properly from the
eastern coast of Massachusetts, to the Gulf of Mexico, losing
itself at its south-western termination in the plain of the Mis-
sissippi: this last is a portion of the second great plain, which
we may style the central basin of the continent, and occupies
much the largest portion of the whole surface of North America.
In breadth it spreads from the Alleghanies to the Rocky Moun-
tains, and expands from the Gulf of Mexico, widening as it
extends northward, until it reaches the Arctic Sea and Hudson’s
Bay. Over the whole of this great area occur no: mountain
chains, nor any elevations beyond a few long ranges of hills. It’
is made up of a few very wide and regular slopes, one from the
Appalachians, westward to the Mississippi; another, more ex-
tensive and very uniform, from the Rocky Mountains eastward
to the same ; and a third from the sources of the Mississippi and
the great lakes northward to the Arctic Sea. The most striking
feature of this region is the amazing uniformity of the whole
surface, rising by a perfectly regular and very gentle ascent from
the Gulf of Mexico to the head waters of the Mississippi, and
the lakes reaching in that space an elevation of not more than
700 or 800 feet, and rising again in a similar manner from the
banks of the Mississippi westward to the very foot of the Rocky
Mountains. From the Alleghanies to the Mississippi the sur-
face is more broken into hills, and embraces the most fertile
territory of the United States. Three or four hundred miles
west of the Mississippi a barren desert commences, extending
to the Rocky Mountains, covering a breadth of between four
and five hundred miles, from the Missouri in lat. 46°, the whole
way into Mexico. The territory from the sources of the Missis-
sippi, north, is little known except to fur traders and the Indians,
but is always described as low, level, and abounding in lakes.
Of the two chief mountain belts which range through the con-
tinent, both nearly parallel to the adjacent coasts, the Alleghany,
or Appalachian, is by far the least considerable. This system of
mountains separates the central plain or basin of the Mississippi
from the plain next the Atlantic, though its ridges do not in
strictness divide the rivers which severally water the two slopes.
The northern and southern terminations of these mountains are
nt well defined; they commence, however, in Maine, traverse
New England nearly from north to south, deviate from the sea
and enter New York, cross Pennsylvania in a broad belt, in-
flecting first to the west and then again to the south, and from

REPORT ON THE GEOLOGY OF NORTH AMERICA. 3

thence assume a more decidedly south-western course, penetra-
ting deeper into the continent as they traverse Virginia, the two
Carolinas, and Georgia, into Alabama. Throughout this range,
especially in the middle and southern portions, they are marked
by great uniformity of structure, an obvious feature being the
great length and parallelism of the chains, and the uniform level
outline of their summits. Their total length is about 1200
miles, and the zone they cover about 100 miles broad, two
thirds of which is computed to be occupied by the included
valleys. They are not lofty, rarely exceeding 3000 feet, and in
_ magnitude and grandeur yield. immeasurably to the Rocky or
Chippewayan Mountains which traverse the opposite side of the
continent.

This last system of mountains, the Andes of North America,
skirts the continent on the side of the Pacific ina broad belt from
the Isthmus of Panama almost to the Arctic Sea, its extreme
northern limit, as defined by Captain Franklin, being far north
on the Mackenzie’s River. The chains within this zone are
many of them very lofty, their average direction, until they en-
ter Mexico, being nearly north and south. Within the United
States territory they rise abruptly from the sandy plain before
described, in longitude about 324° west from Washington ; and
from that meridian nearly the whole way to the ocean the region
is mountainous, with elevated sandy plains, and volcanic tracts
resembling those of Mexico. The summits of many of the
Chippewayan chains are far above the limit of perpetual snow,
the highest points being about 12,000 feet above the sea.
~ When we regard the grandeur of the dimensions exhibited in
these several divisions of North America, the extreme regularity
prevailing over great distances both in the plains and systems
of mountains, and the straightness and parallelism of these to
its long coasts, we are prepared to look for a proportionately
wide range and uniformity in its geological features. ‘To com-
prehend the relations of our formations to.each other, and the
true extent of the portion of our geology at present partially
developed, the exhibition of which is in fact the main end and
object of this Report, a further description, rather more in detail,
of our geography is here requisite.

Let us first contemplate that long and comparatively narrow
plain defined above, which lies between the Atlantic Ocean and
the chains of the Alleghany mountains. This tract, which in the
New England States is very narrow, comprising the mere coast
and islands, expands in its course southward, the mountains in
Carolina being more than 200 miles from the sea, It is divided
longitudinally nearly through pe length by a well marked

B

4 FOURTH REPORT—1834.

geographical and geological boundary, commencing on the coast
of Massachusetts and running to Alabama. The boundary meant
is the eastern edge of a well exposed range of primary rocks,
which, from New Jersey as far south as North Carolina, forms a
nearly definite limit to the flowing up of the tide in the Atlantic
rivers. Between it and the ocean the country is throughout
low, flat, and sandy, while westward the rest of the plain rises
in gradually swelling undulations to the base of the blue ridge
or eastern chain of the Alleghanies. The rivers descend from
the mountains over this western portion of the tract, precipitate
themselves over the rocky boundary mentioned, either in falls
or long rapids, and emerge into the tide level to assume at once
a totally new character. South of North Carolina this line of
primary rocks leaves the tide and retires much nearer to the
mountains, though it still preserves its general features, sepa-
rating the rolling and picturesque region of the older rocks from
the tertiary plains next the ocean ; and though the tide does not
any longer lave its base, as in Virginia, Maryland and Pennsyl-
vania, it still produces rapids and cataracts in the southern
rivers which cross-it. Ranging for so very great a distance
with a remarkable uniformity of outline and height, on an
average between 200 and 300 feet above the tide, it consti-
tutes as admirable a geographical limit as it does a commercial
one. Nearly all the chief cities of the Atlantic States have
arisen upon this boundary, from the obvious motive of seek~-
ing the head of navigation ; a striking example of the influence
of geological causes in distributing population and deciding the
political relations of an extensive country. Below this boundary
the aspect of the region is low and monotonous, the general
average elevation of the plain probably not exceeding 100 feet.
Its general width through the Middle and Southern States is
from 100 to 150 miles. As the tide enters this tract so exten-
sively, flowing, except in the more southern States, entirely
across it, a series of very abundant alluvial deposits occurs, dis-
tributed throughout. The surface is everywhere scooped down
from the general level to that of the tide by a multiplicity of
valleys and ravines, the larger of which receive innumerable
inlets and creeks, while the smaller contain marshes and allu-
vial meadows. The whole aspect of the barrier of primary rocks
forming the western limits of this plain forcibly suggests the
idea that at a rather lower level they once formed the Atlantic
shore, and that they exposed a long line of cliffs and hills of
gneiss to the fury of the ocean: a survey of the plain just de-
scribed as strongly suggests the idea that all of it has been lifted
from beneath the waves by a submarine force, and its surface

_arerapemetcallt

REPORT ON THE GEOLOGY OF NORTH AMERICA. 5

cut into the valleys and troughs which it presents by the retreat
of the upheaved waters. The submarine origin of all this tract
will be made apparent in treating of its geology; but in refer-
ence to its valleys, it may be well to remark that it has no doubt
been torn by more than one denuding wave, in as much as the
great current which has evidently rushed over other portions of
the continent has also passed across this tract, and strewed it as
we see with diluvium. How many such denudations of the
strata have operated to form the present broad valleys of its
enormous rivers, or how much of the excavation has been due
to the continued action of the rivers themselves, we have, so far
at least, no sufficient data to form a decision.

The level region here spoken of I propose calling, for conve-
nience, the Atlantic Plain of the United States, while the ter-
ritory between it and the mountains may be fitly entitled the
Atlantic Slope.

The extensive denudation of the surface of this plain will be
found highly favourable to the accurate development of its geo-
logy. It is from this and the accessible nature of its rivers that
we already know more of its strata, and especially of its organic
remains, than we do of any other district of the country. Its
horizontal strata are in many places admirably exposed in the
vertical banks cf the rivers, often through many miles’ extent;
and the mass of appropriate fossils thus procured, as will be
seen from this Report, is already far from insignificant. 'This
plain, widening in its range to the south-west, bends round the
southern termination of the Alleghanies in Alabama, and expands
itself into the great central plain or valley of the Mississippi.
The tract in question embraces the greater portion of the newer
secondary and tertiary formations hitherto investigated upon
this continent, though, notwithstanding the great area it covers
from Long Island to Florida, it may yet be found to constitute
but a small section of the whole range of those deposits, when
we shall, on some future day, have explored in detail the vast
' plains beyond the Mississippi.
~ The ledge of primary rocks, bounding the tertiary and cre-
taceous secondary deposits of the Atlantic coast, may be de-
lineated by commencing at the city of New York, and tracing a
line marked out by the falls in nearly all the rivers from that
point to the Mississippi. It is thus marked in the falls of the
Passaic at Patterson, in the Raritan near New Brunswick, in
the Millstone near Princeton, in the Delaware at Trenton, the
Schuylkill near Philadelphia, the Brandywine near Wilmington,
the Patapsco near Baltimore, the Potomac at Georgetown, the
Rappahanock near Fredericksburg, James River at Richmond,

6 FOURTH REPORT—1834.

Munford Falls on the Roanoke, the Neuse at Smithfield, Cape
Fear River at Averysboro, the Pedee near Rockingham, the
Wateree near Cambden, the Congaree at Columbia, the Falls at
the junction of the Saluda and Broad Rivers, the Savanna at Au-
gusta, the Oconee at Milledgeville, the Ockmulgee at Macon,
Flint River at Fort Lawrence, the Chattahooche at Fort Mit-
chell, &c., deviating thence north-west through the state of
Mississippi. ‘Towards the southern termination of this rocky
ledge, in Alabama for instance, it does not consist, as it generally
does elsewhere, of gneiss, but is formed of the ancient sandstone
and limestone of the Alleghanies. It everywhere, however, ap-
pears as a natural line of division, of great length and unifor-
mity, separating two tracts of very dissimilar geological age and
features. The upper tract, which I have called the Atlantic slope,
possesses a very variable width; it is narrow in New York and the
New England States, where the mountains approach the coast,
and narrow also in Alabama, where they approach the plains oc;
cupied by the cretaceous rocks of the south, but is much expanded
in Virginia and the Carolinas. Here it has a breadth of about
200 miles, ascending from the tide in an undulating hilly sur-
face, to a mean elevation of perhaps 500 or 600 feet near the
mountains. As it approaches these, its hills swell into bolder
dimensions until we gain the foot of the blue ridge or first chain
of the Alleghanies. It consists almost exclusively of the older
sedimentary and stratified primary rocks. This fine hill tract
exhibits a marked uniformity in the direction of its ridges and
valleys, running very generally north-west and south-east, or
parallel with the mountains. The ridges, though not high, are
long, and the fertile intervening valleys very extensive. It em-
braces a variety of fine soils, and an immense water power in its
rivers and running streams.

Geology of the United States——I propose to treat of our
formations in the order of the latest first, commencing the
survey of each group in the districts where it is best known. I
shall therefore, in this first part of my Report, describe whatever
is known of our recent, tertiary, and cretaceous formations, and
shall reserve an account of the rest of the secondary and all the
primary rocks for the next annual meeting of the Association.
By the delay I hope to be able to add materially to the accu-
racy of the geological map, and it will enable me to present
some of the results of the geological surveys now set on foot by
the States of Maryland and Tenessee, together with whatever
else may in the mean while be brought to light.

The tertiary and cretaceous groups yet known to us in North
America are confmed almost exclusively to the Atlantic plain

ee

REPORT ON THE GEOLOGY OF NORTH AMERICA. 7

of the United States, and to the southern part of the great.cen-
tral valley, or basin of the Mississippi. The lines along which
these formations have been traced in the valley of the west are
few and far apart, so that our present survey is chiefly confined
to the tide-water plain along the Atlantic.

The same line, which was before sketched as forming the
boundary of the Atlantic plain, will be observed, in tracing it
through the states of New Jersey, Pennsylvania, Delaware,
Maryland, Virginia, and North and South Carolina, to coincide
almost exactly with the western limit of the tertiary and se-
condary formations here to be discussed. From Long Island,
south, this barrier of primary rocks presents everywhere a re-
markably abrupt and well defined line of separation between
these newer deposits and the rocks of older origin. North of
Long Island, on the main land-of Connecticut, Rhode Island,
and Massachusetts, the precise position of this line is not so
readily traceable. Along the coast of the two first states little
or nothing of the newer formations is seen; and, if we except
the small portions stated by Hitchcock as occurring in the valley
of the Connecticut river, and on the eastern peninsula of Mas-
sachusetts near Cape Cod, they have not been noticed on the
continent east of New York. The islands of Nantucket, Mar-
tha’s Vineyard, and Long Island are all, however, embraced
within the area of the upper strata about to be described.

The acknowledged difficulty of defining the exact era to
which the newest deposits belong, is sensibly felt in treating
of those of the United States. The amount of strata within
this area which have had their origin in the class of geological
causes at present in action, is, no doubt, very considerable.
Indeed, geologists are accustomed to allude to the changes
wrought by the Mississippi and Niagara as among the most
striking within the recent period anywhere to be met with.
Nevertheless, it seems very possible that a large portion of the
alluvial matter which borders the mouths of the rivers and
coast, may have been formed before the earth, or this conti-
nent at least, was tenanted by man. The evidence upon this
point will be given present!y. The first class of phenomena to
be examined are those which are unquestionably recent.

Of volcanic action we have no traces east of the Mississippi.
The earthquakes which convulse the equatorial and southern
sections of the continent rarely reach the United States; and
when felt, they come with such greatly diminished force as to
be hardly sensible. The forces now in action are, therefore,
exclusively aqueous. ‘These, however, prevail over very exten-
sive areas, as will be seen on adverting to the size and num-

8 FOURTH REPORT—1834.

ber of the rivers, the magnitude of the coast, and the enormous
lakes where freshwater deposits are probably accumulating on
a scale of great extent.

Alluvial Deposits —From the mouth of St. Croix River to
Florida Point, the length of the Atlantic coast is about 1800
miles; and along the Gulf of Mexico, from Florida Point to
Sabine River, the boundary of the United States coast, the di-
stance is 1100 miles more. The first section receives the rivers
which descend the Atlantic slope. The several basins drained
by these rivers, according to the view given by Darby, are
forty-two in number, and the total area drained is 252,900
square miles. .

The smaller river basins in the vicinity of the delta of the
Mississippi, from Sabine River to the western slope of Florida
inclusive, are, excluding the great basin of the Mississippi, six-
teen, with an area of 144,240 square miles. The area drained by
the Mississippi and_all its tributaries is computed at 1,099,000
square miles. Ido not extend the survey to the many large
rivers which enter the gulf west of the Sabine. The quantity
of sediment conveyed to the ocean from so wide an area must
be very enormous ; and, as a proof, we behold either an alluvial
‘delta or a bar at the mouth of almost every river. The entire
line of sea-coast, from the Sabine to the mouth of the Pearl,
presents an uninterrupted marsh 400 miles long, and from 30
to 50, or even 70 miles wide, the production solely of the Mis-
sissippi and the rivers adjacent. From the mouth of the Pearl
eastward, the sandy pine tract reaches the gulf, and extends,
with little interruption, along the whole sea-coast of the Missis-
sippi, Alabama, and great part of Florida. Along this part of
the gulf, and along the Atlantic from the point of Florida to
New Jersey, though many extensive marshes occur upon the
coast, the shore is more generally sandy. At the mouths, how-
ever, of nearly all the rivers, low, marshy, alluvial tracts are to
be seen. Low down, towards their mouths, these rivers run
through extensive flats or meadows, most of which are at pre-
sent elevated above the highest spring-tides, though it is pos-
sible that many of them, during unusually heavy storms or
great freshets, may be liable to be partially submerged. These
meadows: are often several miles in width, and bordered on each
side by abrupt banks, consisting of the solid strata of the coun-
try, so that they have all the aspect of having been, at a former
period, permanently beneath the tides, which, on this suppo-
sition, penetrated their valleys in the shape of extensive bays
and estuaries.

The river meadows are never covered by the coating of

REPORT ON THE GEOLOGY OF NORTH AMERICA. 9

~ diluvial sand and gravel which conceals all the other forma-

tions of the country; a circumstance which will enable us to
distinguish between them and another group of more ancient
alluvial deposits to be described further on.

Recent Changes in the Mississippi.—I am informed by Mr.
Tanner, the geographer, that a striking example of the manner
in which this river ordinarily varies its channels was witnessed
about two years ago, at the mouth of the Red River. A re-
markable bend at that place, known as one of the longest and
most circuitous loops in the Mississippi, was cut off by the
simple expedient of digging a very short trench across the
narrow neck which the stream was daily scooping away. In
24 hours steam-boats passed through the new channel, and it
immediately became the outlet of the Red River, which before
entered the Mississippi by the lower side of the bend, but now
discharges itself along the upper. By this change the river has
been shortened 20 miles. .

When it is recollected that in freshets the current of the Mis-
sissippi descends at the rate of five and even six miles an hour,
and at low water at the rate of two miles, it will at once be seen
how great a load of sedimentary matter it can annually sweep
down into its delta, and how rapidly this must augment both in
height and superficial area. As an example of the rate at which
it is growing, the Old Balize, a post erected by the French about
the year 1724, at the very mouth of the river, is now two miles
above it. There was not at that time the smallest appearance
of the island, on which, 42 years after, Ulloa caused barracks
to be erected for the pilots, and which is now known as the
New Balize.

The distance from the mouth of the river, at which the chief
deposit of sediment usually takes place, is about two miles.
When these shoals accumulate sufficiently, they form small
islands, which soon unite and reach the continent; and thus
the delta increases. So enormous has been the growth of such
deposits, not only opposite the mouths of the Mississippi, but
around the whole northern shore of the gulf, that nearly the
entire coast of Louisiana is inaccessible, from the shallowness
of the water, except eapesntely. through the channels of the
rivers.

An almost universal feature in the entrances of the rivers of —
the Atlantic is the bar obstructing their mouths. That of the
principal entrance of the Mississippi had, in 1722, about 25 feet
of water upon it; Ulloa, in 1767, found 20 feet at the highest
flood; and in 1826 the depth was only 16 feet.

Above these obstructions the rivers are generally Saitbhe

10 FOURTH REPORT—1834.

deeper; the Mississippi, at New Orleans, being above 100 feet ~
deep, which depth it preserves to the mouth of the Missouri.
Mobile Bay is crossed by a bar, having only 10 feet of water,
and the bar of the Altamaba of Georgia has 14 feet, which is,
perhaps, about the average depth to be found at the entrance
of most of the southern rivers of the Atlantic coast. é
Alluvial Terraces.—Besides the alluvial flats which border
so many of the rivers at an elevation of only a few feet above
the tide, and which may have been formed during the present
relative level of the land and sea, there are plains of another
class, which often occupy the sides of the valleys in terraces
more remote from the rivers. This common feature on many
of the rivers of the United States, I mention not only from my
own observation, but on the authority of various works, as
Stoddard’s Sketches, Drake’s Picture of Cincinnati, Dar-
by’s Louisiana, and Professor Hitchcock’s Report on the
Geology of Massachusetts; some of them mentioning two,
three, or even more of these river terraces. The latter author
thus describes them on the Connecticut river in Massachusetts:
“If we start from the edge of the stream at low water, and
ascend a bank of 10 or 15 feet high, we shall come upon an
alluvial meadow, which is frequently overflowed, and is conse-
quently receiving yearly deposits: this may be regarded as
the lowest terrace. Crossing this, we ascend the escarpment of
a second terrace, 30 or 40 feet in height, which may be seen at
intervals on the same level on all sides of the meadow. This
second terrace is rarely very wide in any place, and seems to be
only the remnant of a meadow, once much more extensive,
which has been worn away. Ascending from this 40 or 50
feet up another escarpment, we reach the plain that forms the
bottom of the great valley of the continent: this constitutes the
upper terrace.’ He adds, that terraces, more or less distinct,
exist on almost every stream of considerable size in the State,
wherever the banks are low enough to admit of alluvial flats.
Professor Hitchcock imputes these terraced valleys to the sud-
den bursting of the barriers of a lake or pond through which
the stream flowed, or the sudden removal of an obstruction in
the river, by which it cut a new channel into the soft soil above
the obstruction. I would beg leave to suggest, however, whe-
ther, in the case of so many successive terraces, such an ex-
planation is not rendered improbable, from the difficulty of
imagining so many debacles taking place in succession upon
the same river. The circumstance that nearly all our river
valleys which have the structure described, occur in districts
where the rivers could never have been crossed by ridges of

REPORT ON THE GEOLOGY OF NORTH AMERICA. 11

rock—no relics of such barriers being seen, for example, among
the horizontal formations of the Atlantic plain—is, I think,
conclusive evidence that we must seek for some other cause.

That the cause which has given the delta of the Mississippi
its present elevation was the uplifting agency of forces from
within the earth, we shall see additional evidence for admitting,
when I treat presently of some of the newest of our fossilifer-
ous deposits. In the present infancy of geological research in
the United States, we are not prepared to venture any views
upon the age to which the terraces in question belong. It is
very possible that they may be finally referred to several distinct
periods. Many of them are covered by the general capping of
diluvium, which renders it very likely that the date of some
of them is earlier than the recent period. In the absence of
organic remains, it is wisest to leave the discussion of the age
of these formations open until a larger stock of information has
been gathered concerning them.

Of the Coast Islands, and their probable Origin.—Having,
in the previous section, given some account of a few of the
causes now in action on this continent, as a specimen of the
kind of phenomena which in this country present themselves on
a scale of peculiar magnitude, I shall proceed to a feature in
our geology closely connected with the foregoing class of opera-
tions, implying the agency of almost the very same powers,
and, if I mistake not, taking us into a period very little, if at
all, earlier than that of the river deltas and alluvium just de-
scribed. There is to be seen lying a little off from the main
shore, along the chief extent of the Atlantic coast, an interesting
range of shoals and islands, all running parallel with the shore,
and distinguished by the same uniform features. These long,
narrow, and low islands of sand range from Long Island to
Florida, and around nearly the whole northern sweep of the
Gulf of Mexico. They are rarely more than a mile or two
wide, sometimes 20 or 30 miles long, and, on an average,
about 12 feet high. The geology of Anastasia Island, on the
coast of Florida, is a representation of many others, though it
must be confessed we know extremely little respecting them.

Anastasia Island, opposite St. Augustine, upon the eastern
coast of Florida, is, according to Mr. Dietz (Jowr. of the dead.
of Nat. Sci. Philadelphia), about 10 or 12 miles long, 14 broad,
and has not more than 10 or 12 feet of elevation above the level
of the ocean. It lies parallel to the shore, at a distance of from
2to3 miles. The greater part of the northern portion, and
perhaps the whole of the island, is composed of horizontal
layers of a semi-indurated rock, consisting wholly of fragments

12 FOURTH REPORT—1834.

of shells, belonging, as far as examined, almost, though not
exclusively, to species inhabiting the adjoining coast. The
mass is divided, by thin seams of some foreign matter, into
layers from 1 to 18 inches thick, and is so soft before exposure
to the air, that it is easily cut by a tool into slabs of any re-
quired size, and in this form is extensively used for building.
Near the surface the fragments of the shells, generally speak-
ing, are the smallest; but they occur of various sizes, and
frequently in the same layer the shells are entire. Much of
this rock, especially the more comminuted kind, exhibits not
unfrequently a confused crystallization ; this process having
gone so far as to present the fragments in an almost obliter-
ated state. The coarse varieties are composed of some frag-
ments evidently thus altered, and of others which have not
yet lost their colouring matter. The shells belong principally
to the genus Arca; they are 4. pexata, A. ponderosa, A. in-
congrua, A. transversa; also Lutraria canaliculata, all of
Say; besides a Mactra, a Donax, a Crepidula, a Lucina, and
another species of Arca, which is probably either extinct upon
our coast, or extremely rare. Natica, Oliva, and Nassa tri-
villata, of Say, are also mentioned. Mr. Dietz attributes the
formation of this island to the agitation of the tides and winds,
conceiving the shells to be driven first towards the shore, and
deposited afterwards at their present distance from the beach
by the retiring tide. But such an explanation seems not alto-
gether satisfactory, for I cannot learn that this heaping-up of
shells from beneath the water is anywhere noticed upon our sea-
islands at present. The winds do indeed drive the sands from
the beach, and the shoals which are laid bare at low water, upon
them, but mingled with hardly any shells, while the rock of
Anastasia Island is made up of shells exclusively. Such agita-
tion would seem incompatible with the accumulation of so ho-
mogeneous a mass, which is found to contain neither pebbles,
sand, nor other transported matter of any sort. My own pre- -
sent conviction regarding these coast-islands is, That they are
all the portions of a-range of shoals or bars formed along. the
line of junction of the turbid waters from our rivers, and the
great in-setting currents connected with the gulf-stream;—that
since the existence of the gulf-stream and the present drainage
of the Atlantic plain, this growth of sediment opposite the coast
has been going on ;—that in the more tranquil places upon these
bars, vast colonies of shell-fish planted themselves ;—and that
the whole line of shoals has been lifted, with part of the adjacent
continent, by the force of an earthquake or earthquakes, to
their present small elevation above the waves. Traces of more

‘

REPORT ON THE GEOLOGY OF NORTH AMERICA. 13

than one such up-heave of the continent during the tertiary
period, may possibly be found hereafter, when the various sy-
stems of plains and terraces along the rivers and the coast shall
have been more investigated.

There can be no doubt that most of the islands opposite the
coast of the Middle States, New Jersey for instance, are hourly
on the increase. They consist, like the opposite main shore,
of marsh as a substratum, which is seen to: receive a covering
of sand blown in from the sea side whenever the tides and gales
are favourable. Thus, the side of these islands next the sea is
sandy and on the increase, while that adjacent to the continent
is marshy, and in many cases appears to be wearing down
under the action of the rapid current which sweeps through the
intervening sound or strait. As a proof of the daily growth of
some of these islands, or beaches, as they are called, Cranberry
Inlet is now closed up, though it still bears the nate “ Inlet,”
as may be seen upon any map of the Jersey coast.

It is impossible, therefore, to refer them all to the period
which produced Anastasia Island, and the islands and coast in
its neighbourhood, though, regarding the manner of their for-
mation, there can be no doubt that the same combination of
causes, winds and currents, operated in producing them all.
These causes, as I have already shown, are active, in the pre-
sent day, in effecting similar deposits along the delta of the
Mississippi; nor do I perceive any good reason why we should
not admit the agency of the same in remote tertiary periods.
Our rivers, since the appearance of the carboniferous forma-
tions, at least, must have been always. very large, and have
formed vast deposits of sediment in the sea; and there is
every reason to suppose that the gulf-stream, which has evi-
dently much to do in shaping these deposits, has existed since
an early period of our coast formations.’ The true age of that
great ocean current can only be decided when we know more
thoroughly the geology of the isthmus separating North from
South America. In the mean time we may safely apply the
actions which are daily witnessed upon our coast, to forma-
tions so very little older, as that of Anastasia Island.

Raised Estuary Formations ofthe Gulf of Mexico.—A
very extensive bed of shells, bordering on the Gulf of Mexico,
seems to claim a position somewhere in the group of formations
now before us. It appears to hold a place on the confines, as
it were, of the tertiary and the recent formations. It is thus
described by Mr. Conrad: “ An interesting deposit borders the
Gulf of Mexico, and is probably several hundred miles in ex-
tent. It consists entirely of two species of shells, Cyrena Ca-

14 FOURTH REPORT—1834.

rolinensis, and Rangia cyrenoides of Des Moulins (Clathrodon
cuneatus, Gray); the former, however, is rare, the deposit con-
sisting almost entirely of the latter shell. In the vicinity of
Mobile, which is built on a sandy flat, very little elevated above
the tide, the beds in question are superficial, although co-
vered by a vegetable mould bearing a forest of gigantic pines.
When one of the trees is prostrated by the wind, the decom-
posing shells are seen adhering to the roots, but beneath they
are entire, and nearly as hard, when dry, as the recent species.
It is remarkable that they occur in beds with scarcely any ad-
mixture of sand or earth, and they are consequently found
extremely useful in repairing roads, and paving the streets of
the city. They are dug from the surface of the soil, both on
the main shore and the islands of the bay. These deposits
border the bays of the Gulf of Mexico between Mobile and
New Orleans, and they occur in the vicinity of Franklin,
Louisiana. The Chandeleur Isles, between Mobile Bay and
the delta of the Mississippi, consist of deposits of these shells
covered by a fertile soil. The Rangia lives in vast numbers in
the extensive flats below Mobile, burrowing three or four
inches beneath the surface of the sand, in which numerous de-
pressions indicate where they are to be found.’ According to
Mr. Conrad, the Rangia was first seen in a sub-fossil state in
the newer Pleiocene, at the mouth of the Potomac, where, how-
ever, it is rare. Though it there occurs in a deposit of marine
shells, the sea appears not to be the usual resort of the species ;
and it is only in the brackish water in the bays and estuaries
that it is abundant. He is therefore inclined to regard the few
found in marine deposits as coming from some neighbouring
estuary. As it abounds in the recent state in the present shel-
tered sounds which fringe the Gulf of Mexico, the presumption
is very strong that the fossil beds above described are colonies
which, previous to the change of level of the land, flourished in
precisely similar situations. This would account satisfactorily
for the narrow and very long belts in which they run, skirting
round the bays and the coast above its present marshes, from
Pensacola, in Florida, to near Franklin, in Louisiana.
Diluvial Action over North America.—Almost the whole
surface of North America, as far as examined, may be said to
be covered with an investment of earth, pebbles, and boulders,
obviously of diluvial origin. The thickness of this deposit varies,
though its average depth may be said to be from ten to twenty
feet. All that low and level tract described as the Atlantic
plain, and also the lower sections of the great valley of the Mis-
sissippi, appear to be the districts where it conceals the under-

REPORT ON THE GEOLOGY OF NORTH AMERICA, 15

lying strata to the greatest depth. Over the whole of this ex-
tensive territory it covers the horizontal strata of the tertiary
and cretaceous deposits, and obscures them so effectually that,
except in the cliffs, along the rivers, and in the sides of the ra-
vines and valleys, these formations are rarely or never exposed.
If we begin our examination of this great mass of detritus
upon the Atlantic coast, we there find it to consist of fine sand
and gravel, in which form it abounds over the peninsula of
Jersey, Maryland, Virginia, and North Carolina, and all. the
‘states along the Atlantic to the Mississippi. This soil along
the seaboard may very possibly, if we judge from its consisting
so entirely of pure finely comminuted sand, have been reclaimed
from the ocean since the general distribution of diluvial matter
over the continent. But even upon this view, it is to be re-
‘garded as the result of diluvial action. The pebbles are of a
kind, in fact, which could only come from the interior, above
the range of rocks bordering the tide. They do not belong to
the tertiary and cretaceous strata of the Atlantic plain, but to
the older rocks of the Atlantic slope and the mountains. As we
advance inward from the coast, the mass of diluvial matter be-

_ comes less sandy and coarser, the soil somewhat less barren,
and the vegetation more diversified, though still consisting
principally of pine. Over the upper portion of the Atlantic
plain, or nearest its rocky boundary, the mass contains the
gravel in a much coarser state, mingled with clay sufficiently
pure for bricks. Rolled blocks and boulders of no inconsiderable
‘size occur, especially in the valleys of the rivers, when within
‘ten or twelve miles of the boundary mentioned. For many miles
from the coast there is rarely anything but the diluvium. In
‘the central districts of the tract the fossiliferous strata appear
beneath it, though near the upper limits of this tract these
often disappear again, and the region immediately eastward of
the rocky boundary presents the diluvium covering another class
of deposits very different from the tertiary and secondary beds
which underlie it near the sea.

The deposit along the east of the rocky boundary, or, in other
words, at the head of tide in the Middle States, is not diluvium,
as from the absence of fossils many might at first imagine. At
tmany places, as Bordentown on the Delaware, the deep cut of
the Chesapeake and Delaware Canal, Baltimore, &c., the mingled
mass of ordinary diluvium reposes upon very regularly stratified
‘beds of dark blue clay, containing decayed trees, lignite, and
amber; the whole mass precisely such in appearance and con-
tents as to lead to the conviction that it is more probably an al-

16 FOURTH REPORT— 1834.

luvial mass deposited in front of the ancient rocky coast, than a
portion of the detritus left by diluvial action.

Proceeding now from the Atlantic plain towards the moun-
tains, the diluvial matter is more irregularly distributed, in con-
sequence of the undulations of the surface. It may be seen in
greatest quantity in the valleys of the rivers, the boulders which
cover their beds and sides being almost invariably traceable to
formations which lie at some miles’ distance to the xorth-west
and north. This distribution of the diluvium from the north
and north-west is not confined to the rivers whose valleys run
in those directions, but belongs, it is believed, to at least all the
middle and northern latitudes of the continent. It is seen west
of the Alleghanies, throughout the region of the Ohio and Mis-
sissippi, as well as extensively over the Atlantic slope and the
tertiary Atlantic plain. Bigsby and the travellers to the north
have already shown it to prevail in the latitudes north of the
United States.

The very extensive valley which crosses. Pennsylvania, Mary-
land and Virginia, lying immediately east of the blue ridge, though
it consists principally of transition limestone and greywacke slate,
is strewed also with innumerable blocks and boulders of the same
sandstone which composes most of the blue ridge, and appears,
so far as yet examined, to be newer, together with fragments
- from the hills between the valley and the Atlantic. Opposite to
the passes or breaks in this first range of mountains, the quantity
of such»transported matter on the south-east of them is particu-
larly great ; and many of the first ridges of the chain are covered
to an unknown depth upon their flanks and even their summits
by the diluvial matter in a comminuted state. As an instance, the
mountain which bounds this valley im Pennsylvania, running
west from the Susquehannali through Cumberland county, and
called there the North Mountain, is covered with a mass of little
else than sand, such as could not be derived from the limestone
tract to the south-east, but just such as would be formed from
the disintegration of the sandstones of the Alleghanies.

It is stated by Hayden, in his Geological Essays, that in
Washington city itself, which is south of the first primary ridge,
and about fifty miles south-east of the mountains, there is a
small area covered with rolled masses of sandstone, some of
which would weigh from 200 to 500 pounds, and containing
perfect impressions of shells resembling Zerebrutula. Now, no
fossiliferous formations occur until we pass beyond the blue
ridge, and the blocks must have come from the north-east or
north, at least sixty miles. I have myself seen fragments of

REPORT ON THE GEOLOGY OF NORTH AMERICA. 17

similar boulders in the neighbourhood of Columbia, on the Sus-
quehanna, containing several species of Producta and Terebra-
tula, which could only have come from a like region within the
mountains of Pennsylvania, a distance perhaps of fifty miles at
least. Drake, in his Picture of Cincinnati, mentions large
masses of granite in that part of Ohio, resting upon the ordinary
finer diluvium. The nearest granite on the north is at least one
hundred leagues distant ; while no primary rocks occur south or
east within even a much greater limit. We are reminded here
of the great detached blocks which strew the plains of northern
Europe, and the explanation suggested that they have been car-
ried there by floating upon ice. They occur, promiscuously dis-
persed over a great extent of country in Ohio, Kentucky, and
Indiana, and are in no way connected with the present river
valleys.

I may mention as an interesting fact, corroborating the opi-
nion of the northerly origin of the current here advanced, that
Mr. Conrad, who has explored the State of Alabama, was never
once able to perceive a boulder upon its surface.

Besides the fossiliferous deposits of very recent date, described
by Mr. Conrad, around the Gulf of Mexico, many of our rivers
adjacent to the sea present extensive beds of shells, of another
class, but probably referrible to the same origin and the same
period of elevation. They consist of the common Ostrea virgi-
nica, almost exclusively, with a very few of the recent univalves
of the coast, all of these being shells peculiar to the bays and
estuaries of the rivers, and the shallow sounds on the inner side
of the Sea Islands and shoals along the coast. The position in
which these beds of shells are invariably seen is upon the low
level plains adjacent to the tide creeks of our rivers, where they
appear to have dwelt in colonies in the sheltered bays at a time
when these plains were at a small depth beneath the water, and
to have been lifted with them by, perhaps, the last shock which
has changed the level of the coast. These shells, in a sub-fossil
state, occur in Cumberland County, New Jersey, on the bank of
Stow Creek, at Egg Harbour, on the Severn, at Euston, in
Maryland; again, upon the York river in Virginia, and indeed
upon many others of the southern rivers. They occur at the
mouth of the Potomac, resting upon the beds of marine shells,
which were originally described in the Journal of the Academy
of Natural Sciences by Mr. Conrad, and considered by him as
referrible to the newest of our fossiliferous formations. In the
same locality these beds of fossil Ostrea virginica are seen to
be covered by the diluvium, so that there can be no question of
their origin having been during the latest stage, as it. were, of

1834, c

18 FOURTH REPORT—1834.

the tertiary period, and not connected, as imagined by the vulgar,
with human agency. The usual position of these beds of Ostrea
is near the rivers, at a small elevation from the tide. They seem
to hold also nearly the same elevation along the coast of New
Jersey and elsewhere.

Ancient Alluvium.—The above subdivision of our strata is
adopted for the sake of treating, under an independent head, a
group of beds of no inconsiderable extent in the United States,
and which, in their phenomena, seem to cast important light
upon the former revolutions of the Atlantic side of the Continent.
They point to a period when this coast had a very different con-
figuration, and denote in a striking manner one of the revolutions
which have impressed upon the tract included between the sea
and the mountains the peculiar features which it now bears.
The formation I allude to immediately underlies, wherever it
occurs, the general investment of diluvium.

It has produced, hitherto, very few organic remains of the
description proper to enable us to judge of its relative place in
the series ; but. as the few shells occasionally found in it belong
to species now inhabiting our Atlantic waters, and as, from all
its other characters, it has evidently been formed under differ-
ent circumstances from our other tertiary beds, and at'a period
apparently much more recent than any of the rest with which it
can be compared, I am induced to place it thus apart, and to
give it provisionally, from its obvious origin, the convenient and
not too theoretical name of ‘ancient alluvium.’

This deposit is the same which has usually, in this country,
gone under the name of plastic clay formation,—a title suf-
ficiently inappropriate, even were it to express correctly its true.

‘place in the tertiary series, and now particularly ineligible, when,
‘in place of being one of the lowest tertiary deposits, it will be
seen, from the evidence I shall present, to be one of the very
‘uppermost. The beds I am speaking of consist generally of
numerous alternating deposits of gravel, sand, various coloured
tenacious clays, often black and ferruginous conglomerates,
iron ore, and lignite. They occur exposed in the deeper sec-
tions of our canals and rail-roads, and in the banks: of some of
‘the rivers, where they usually reach from the water’s edge to
an elevation of sixty, seventy, or more feet. They extend along
‘the upper edge of the Atlantic plain, ranging along the east-
‘érn base of the rocky Atlantic slope, in a belt several miles
‘wide, and appearing at intervals, where the rivers have cut
‘through them, from the coast of Massachusetts as far at
least, it is’ believed, as the Mississippi.. Professor Hitchcock,
speaking of these beds in the valley of the Connecticut river,

© BB oe 2 ey

REPORT ON THE GEOLOGY OF NORTH AMERICA. 19

describes them under the name of the most recent tertiary,
which I have stated to be my own view. But he makes a di-
stinction between these and other similar beds in Martha’s
Vineyard and elsewhere, which he calls plastic clay. The first,
he says, are horizontal layers of white siliceous sand and blue
plastic clay, almost entirely destitute of any organic remains.
‘These beds constitute most of the level and elevated terraces
along the valley of this and most of the other rivers of New
England: the height of the plains above the water is from
fifty to one hundred feet. Along the Connecticut, in some
places, the clay beds alone compose the cliff, and are from forty
to more than seventy feet thick. They repose beneath fifteen
or twenty feet of diluvial matter. Their position, and all their
features, here and everywhere else, indicate a general uplift of
the strata along the whole line of the primary boundary when
that boundary formed the coast, and a consequent emergence of
these beds from about the water level, where they seem to have
grown as marshy deltas, accumulated along the ancient mouths
_of the rivers. On this supposition, the mouths of the Atlantic
rivers were at the points where they now form their falls, and
break through the boundary of the older rocks ; and it is singular
enough that all the conspicuous deposits of these clays, imbed-
ding the trunks of trees and lignite, are just opposite, or near to,
the same points. At Gay’s Head, on the coast of Martha’s Vine-
yard, are alternating sands and clays, which I refer to this for-
mation, rising in the cliff to a height of between 150 and 200
feet. The clays contain a bed of lignite, which is, in some
-places, five feet thick. It alternates with the clays, especially
the blue, and is often intimately mixed with them, forming a
comminuted dark mass, resembling peat. Woody fibre is often
distinguishable in it, and the whole has the appearance of a
deposit of peat, through which logs are interspersed. The prin-
cipal beds lie not far from the middle of the cliff, and have a dip
.of from 40° to 50° north. In this lignite bed are found impres-
-sions of dicotyledonous leaves, apparently Ulmus, Sulizx, &c.,
trees at present growing in the country. Associated with these
-beds of clay, however, occur several variations of sand; and what
at first seems startling enough, one bed described as a green sand,
containing remains of Crabs, casts of shells, Alcyonites, &c.,
_evidently referrible to the cretaceous formation of New Jersey, and
_-also interstratified with the same osseous conglomerate, from
which were procured the teeth of a Crocodile and several bones,
_some of them very large, being nine inches thick, and as much
in length. The worn and mutilated state of these remains, and
the mixture in which they are found, prove forcibly that the bed
c2

20 FOURTH REPORT—1834.

is derived from the violent disintegration of a much more ancient
formation than that in which it occurs, namely, of a cretaceous
deposit, like that of New Jersey, which may possibly underlie
this island and Long Island also, they being exactly in its range.
The dip and contortion of the strata at Gay’s Head lend consi-
derable probability to the foregoing explanation of the origin of
this bed of detritus from the greensand. In other quarters, the
ancient alluvial beds which I am discussing are usually nearly
horizontal, or when they incline, it is with a gentle dip towards
the ocean ; but in the strata at Martha’s Vineyard the dip is
abrupt and in the contrary direction, being to the north. These
circumstances, taken in conjunction with the fact, that a pre-
cisely similar deposit of detritus from the greensand formation
covers the northern edge of that group of beds in many spots in
New Jersey, where I have seen it not far east of the beds of
so-called plastic clay and lignite,—as, for example, between New
Egypt and Bordentown,—make me venture to put forward the
suggestion that the cretaceous formations of our coast have
probably extended further to the north-east than at present, oc-
cupying what is now Long Island Sound, and its prolongation
eastward. Viewing the island of Martha’s Vineyard and Long
Island as remnants of a more extensive ancient tract in structure,
like the peninsula of New Jersey, we can readily account, I
think, for all the above phenomena, together with some others
which they present.

According to Hitchcock, similar strata of the tertiary clays,
which I have called ancient alluvium, underlie the diluvial
covering in both Nantucket and Long Island. They are con-
spicuously exposed in New Jersey, in the sections of the rail-
road near Amboy, and again very strikingly on the Delaware,
near Bordentown. Here they have all the features which they
display at Martha’s Vineyard, with the exception that they are
nearly horizontal and less brightly variegated in colour. Lignite,
containing pyrites, dicotyledonous wood, and amber, abound in
the dark tenacious clay or ancient peat, which has here a thick-
ness of many feet. The following description of this formation
in New Jersey and the States south of it will serve to show its
extensive range and important character.

In ascending the Raritan it is traced on the south-east shore
to within three miles of Brunswick. Approaching Bordentown
by the rail-road it is conspicuously exposed for several miles
in nearly all the deep cuttings. At Bordentown the banks of
the Delaware consist of its various beds of brilliant sands and
dark and white clays for more than two miles. At Philadelphia
it occurs, but at a lower level, remains of trees having been

centies

REPORT ON THE GEOLOGY OF NORTH AMERICA. 21

found forty-five or fifty feet beneath the city. It is seen in the
sections along the Delaware and Chesapeake Canal, where its
black tenacious vegetable clay and its sands precisely resemble
those above: also in the sections of the Newcastle and French-
town rail-road. Around the harbour of Baltimore these de-
posits occur on a large scale. In excavations made at Baltimore
abundant remains of trees and their fruits, particularly the black
walnut, have been found at the depth of forty-five or fifty feet.
In Virginia, along the same line, as at Richmond for example,
similar facts are well known. Near Baltimore, in sinking a well
in the Star Fort at Fort M’Henry, two miles below the granite
ridge, or supposed ancient coast, the workmen came upon a
mass of carbonized wood in a boggy marsh fifty feet below the
surface. In digging a well in the same Star Fort (perhaps the
same well), a tooth of the Mastodon was found at the depth of
nearly sixty feet. At a point on the Chesapeake Bay, about
twenty miles below Baltimore, called Cape Sable, very extensive
beds of these clays occur, abounding in lignite, pyrites, and
amber. The uppermost stratum is sand, very ferruginous, often
sixty or seventy feet thick, then a stratum of lignite three to
four feet. Below this a bed of sand, intermixed with enormous
quantities of pyrites, nests of this mineral occurring from a foot
to a foot and half in thickness, and of fifteen or twenty square
feet in surface. Next follows a bed’of earthy lignite, from five
to twelve feet deep, containing an abundance of pyritous wood,
with fragments of bituminous wood thirty feet long. In this
stratum of lignite have been also found specimens of a curious
comb or nest, the work of an insect. These are from one to
three inches in length: each cell has several minute holes. The
substance is a resinous matter, resembling amber in properties,
and the whole nidus is generally attached around a stem or car-
bonized twig.

The next stratum is an argillaceous sandstone two to five feet
thick, uneven on its surface, while the beds above are all nearly
horizontal. Below is a bed of whitish grey clay four feet, and
beneath all a bed of sand. The enormous accumulation of car-
bonized trees in this place, now eighty miles in a direct line
from the sea, and at least fifteen from the supposed ancient
coast or boundary of primary rocks, points very clearly to the
existence, at some ancient date, of an extensive delta here.
Whether these beds at Cape Sable may hereafter be found con-
tinuous with those around Baltimore in which the Mastodon’s
tooth was found, time will ascertain, but as yet we have no data
precise enough from which to infer the probable place of these
beds in the series.

22 FOURTH REPORT—1834.

Their geographical position is between the supposed ancient
openings of the Susquehanna and Potomac rivers. No one who
is familiar with the annual floods of these rivers, and has seen
the burden of wood and trees which the former tears up in its
passage through the mountains, and discharges each spring into
the Chesapeake Bay, can doubt that the very same rivers have
probably been employed in olden time in forming these very
tracts of sand, clay, and lignite. There are now in the upper
part of the bay large flats, which consist solely of sand and
drifted timber, the annual scourings of the Susquehanna; and
if we conceive these tracts to become converted into marshes
and swamps, as might readily happen, we have all the circum-
stances, and in the same district, which would be requisite to
produce from these recent deposits beds perfectly similar to the
more ancient ones just described.

Whether those ancient alluvial deposits from Martha’s Vine-
yard to the Chesapeake are all of one date of formation, and
what indeed their precise age is, are matters demanding much
future research to determine. I have called these beds alluvial,
but by no means venture to suppose them all the results of ac-
cumulation in deltas, strictly so called. Our rivers may have
had basins or estuaries through the tracts in question, through-
out which, as well as upon the coast, these beds may have col-
lected. The details of this formation further south are not in a
sufficiently authentic shape to be presented ; we know, however,
that similar beds of clays, sands, and lignites occur largely upon
most of the southern rivers, and upon the Mississippi, on a scale
which is truly gigantic.

I am inclined to consider as a portion of the same formation
an extensive group of variegated clays and sands which spread
themselves very widely over the States of Georgia and South
Carolina. Like the others before treated of, these contain few
fossils. 'They are seen to repose in some places upon the cre-
taceous rocks, as those in New Jersey do; in some places upon
Eocene; and they are also found below the diluvium.

These beds have been already referred by Vanuxem to ancient
alluvial origin. He thus describes them :

“<The ancient alluvial is chiefly composed of red earth. This
earth is pretty uniform in its character, consisting of sand, with
a minute portion of clay, coloured by red oxide of iron. Its in-
ferior parts often contain pebbles, sometimes coarse nodules or
geodes of iron, resting almost invariably on the white or varie-
gated clays, or upon those masses which contain littoral shells.
Though not often met with beyond North Carolina, it is ex-
tremely abundant in all the States south of it. It appears to

—oOoOoO

REPORT ON THE GEOLOGY OF NORTH AMERICA. 23

occupy the highest elevations above the secondary and tertiary
classes, and consequently could not have been formed by our
existing rivers. It is entirely unmixed with the tertiary, and
destitute of the fossils which characterize the latter; it must
therefore be considered as distinct from it, at the same time
that it is unlike the modern alluvial, whose origin is clearly at-
tributable to the overflow and inundation of our rivers.”

This red earth is precisely similar to the mixture of sand and
clay which we may witness discharged from some of the turbid
rivers of the Mississippi in the present day. It is seen covering
tertiaries at Augusta in Georgia, Columbia in South Carolina, &c.
The ancient alluvial beds, resembling in all respects those at
Bordentown, are seen along the Santee canal in Georgia, where
they repose on secondary beds. In excavating this canal, not
only the dark vegetable clay before described, but much lignite
and the remains of a Mastodon were found, marking the agree-
ment of the deposit in all respects with the corresponding beds
at Baltimore and elsewhere. . .

Fossil Mammalia of the United States.—The extinct species
of the higher orders of animals found fossil in the United States °
are Mastodon giganteum, Elephas primigenius, another Ele-
phant (a tooth only being known, differing considerably from
the tooth of either the living or fossil species), Megatherium,
Megalonyx, Bos bhombifrons, Bos Pallasii, Bos latifrons,
Cervus americanus, or fossil Elk of Wistar, and Walrus.

Of living species also found fossil, we may enumerate the
Horse, the Buffalo, and three or four species of Deer. ‘The
situations in which these have been found have been either very
recent undisturbed alluvial bogs, or a slightly disturbed marshy
deposit like Big Bone Lick, neither of them covered by the
general diluvium; thirdly, boggy beds containing lignite re-
ferrible to an ancient alluvium, covered by diluvial sand and
gravel; and lastly, the floors of caves, buried to a very small
depth with earth not described.

The largest collections of bone remains occur in boggy grounds
called Licks, affording salt, in quest of which the herbivorous
animals, wild and domestic, enter the marshy spot and are
sometimes mired. The most noted of these deposits is Big
Bone Lick in Kentucky, occupying the bottom of a boggy val-
ley kept wet by a number of salt springs, which rise over a sur-
face of several acres. The spot is thus described by Mr. Cooper:
“The substratum of the country is.a fossiliferous limestone. At
the Lick the valley is filled up to the depth of not less than thirty
feet with unconsolidated beds of earth of various kinds. The
uppermost of these is a light yellow clay, which apparently is

D4, FOURTH REPORT—1834.

no more than the soil brought down from the high grounds by
rains and land floods. In this yellow earth are found, along
the water courses at various depths, the bones of Buffalos (Bi-
son) and other modern animals, many broken, but often quite
entire. Beneath this is another thinner layer of a different soil,
bearing the appearance of having been formerly the bottom of a
marsh. It is more gravelly, darker coloured, softer, and con-
tains remains of reedy plants, smaller than the cane so abundant
in some parts of Kentucky, with shells of freshwater Mollusca.
In this layer, and sometimes partially imbedded in a stratum of
blue clay, very compact and tenacious, are deposited the bones
of extinct species.’” Mr. Cooper has been at the pains to com-
pute, from the teeth and other parts known to have been re-
moved from Big Bone Lick, the number of individuals requisite
to furnish the specimens already carried off:

Mastodon maximus ....100 individuals,

Elephas primigenius ... 20 —_

Megalonyx Jeffersonii.. 1 —

Bos bombifrons ...... 2 —
Bos Pallasti......... 1 —
Cervus americanus .... 2 —

and it is probable that some still remain behind.

It is possible that the Horse ought to be added to this list of
animals once indigenous to America. During the early settle-
ment of the country, the great bones were either lying on the
surface of the ground, or so near it as to be obtained with very
little labour.

The next most important kind of locality in which such re-
mains are often found, is simply a soft bog or meadow, where
most of the finest specimens known in this country have been
obtained. As an example of the common condition in which
the Mastodon is found, I may describe the situation of one dis-
interred in 1824 near the sea-coast of New Jersey, three miles
from Longbranch. ‘The proprietor of the farm, walking over
a reclaimed marsh, observed something projecting through the
turf, which he struck with his foot, and found to be a grinder
tooth. Two other teeth, some pieces of the skull, the spine, the
humeral, and other bones were afterwards found. ‘The soil
around was a soft dark peat, full of vegetable fibres. Though
the skull and many other bones had been removed before
Messrs. Cooper, Dekay, and Van Ransaeller, examined the spot,
they were able to behold the vertebral column with all the joints,
the ribs articulated to them, resting in their natural position,
about eight or ten inches below the surface. The scapule both
rested upon the heads of the humeri, and these, as in life, in a

REPORT ON THE GEOLOGY OF NORTH AMERICA. 25

vertical position upon the bones of the fore arm. The right fore
arm inclined a little backwards, and the foot immediately below
was a little in advance of the other, in the attitude of walking.
Ten inches below the surface was the sacrum, with the pelvis
united though decayed. The femora were close by, but lay in
a position nearly horizontal, the right less than the left, and
both at right angles with the spine. Both tibie, each with its
fibula, stood nearly erect in their natural place beneath the fe-
mora, and below them were the bones of the hinder feet in their
places: no caudal vertebre were seen. The marsh had been
drained for three years, and the surface had in consequence
been lowered about two feet, producing, it has been conjectured,
the dislocated attitude of the thigh-bones. Beneath the peaty
bed a sandy stratum was seen, and all the feet were noticed to
be standing upon the top of this floor of the bog.”

I have already described the nature of the beds in which the
antediluvian Mastodon tooth was found at Fort M’Henry near
Baltimore; and concerning the bed in which the cane specimens,
the Megalonyx, &c., have been buried, I have no information
sufficiently satisfactory to offer.

Localities of Fossil Mammalia.—ELePHas PRIMIGENIUS:

Big Bone Lick, Kentucky, the teeth especially in great num-
bers. Biggin Swamp, in South Carolina, teeth eight or nine
feet below the surface. (Drayton.) Kentucky has furnished the
greatest number of teeth, but South Carolina the largest col-:
lection of other parts of the skeleton. (Godman.) Monmouth
County, New Jersey. (Mitchell.) Opelousas, west of the Missis-
sippi, bones and teeth in recent alluvium. (See Durald in dnn.
Phil. Trans. vol. vi. p.55., also Darby in Mitchell’s translation
of Cuvier’s Theory of the Earth.) Stone in Carolina, teeth,
(Catesby.) Queen Anne’s County, Maryland, a grinder, dif-
fering considerably from the tooth either of the living or fossil
species, in stiff blue clay by the side of a marsh.
“ Mastopon maximus: Big Bone Lick, Kentucky, in a dark
coloured marsh, the upper stratum somewhat gravelly, the
substratum a blue tenacious clay, both imbedding bones; over
all a light yellow soil, brought apparently from the adjacent
high grounds: all the larger bones broken as if by violent action
(Cooper).

The remains of Mastodon are found indeed in nearly all the
Western States in bogs and soft meadows uncovered by any di-
luvial stratum. White River, Indiana, upper jaw and teeth.
(Mitchell.) The marshes and bogs near the Walkill, west. of
the Hudson, New York. This vicinity yielded the first and
finest skeleton yet procured, viz. the magnificent specimen in
the Philadelphia Museum. (Peale.) Also on the North Holston,

26 FOURTH REPORT—1834.

a branch of the Tennessee river. Carolina, bones, &c., in a
morass like the rest. (Jefferson’s notes on Virginia.)

. Again, in Wythe County, Virginia, at five feet below the sur-
face, near a salt-lick, a large number of bones, almost an entire
skeleton, was found, said to have been accompanied by a mass
of triturated branches, leaves, &c., enveloped in a sac, supposed
to be the stomach, not however correctly. (See Godman’s Wat.
History.) Chester, Orange County, New York, in a peat bog,
four feet beneath the surface, many fine fragments. (Mitchell.)
On the York River some fine members of a skeleton were found,
in marsh mud, surrounded by roots of cypress trees. (Madison,
Medical Repository.) On the coast of New Jersey, near Long
Branch, in a bog, almost an entire skeleton, in the natural erect
posture, the head hardly below the surface. (Cooper’s Annals
of the New York Lyceum.) In Rockland County, New York,
grinders three feet deep in mud. (Mitchell.) Near Baltimore, at
Fort M’ Henry, in digging a well in the Star Fort, in a stratum
of marsh mud, nearly sixty feet below the surface, under a layer
of diluvium. (Hayden’s Geol. Essays.) Remains of Mastodon
abound at the Salines (Licks) of Great Osage River to as great
an extent, it is said, as at Big Bone Lick, or around the Wal-
kill. (Godman.)

MeEGATHERIUM. Fragments of at least two skeletons in re-
cent marsh, Skidaway Island, Georgia. (Cooper.)

MeeAtonyx. A fragment of an arm or thigh-bone, a com-
plete radius, an ulna, three phalangal claw-bones, and some
bones of the feet, found about thirty feet below the surface of
the floor of a cavern in Green Briar County, Virginia. (Godman.)
Big Bone Lick has furnished a large humerus, a metacarpal
bone, a right lower maxillary bone with four teeth, a detached
molar tooth in good preservation, a clavicle, a tibia of the right
side. (Cooper.) Megalonyx bones have also been found in White
Cave, Kentucky.

Bos somBIFRONS: two heads at Big Bone Lick. (Harlan’s
Fauna Americana; Wistar’s Trans. American Phil. Society.)
Bos Patuasit, Dekay: a head, Big Bone Lick, also New Ma-
drid, on the Mississippi,—closely resembles Bos moschatus.
Bos Latirrons (Harlan): a portion of a skull, ten miles from
Big Bone Lick: Cuvier allies it to the Bos Urus of Europe.

CERVUS AMERICANUS (Fossil Elk): two imperfect skulls,
Big Bone Lick (Cooper). Horse: Big Bone Lick (Cooper),
New Jersey (Mitchell). The existence of the Horse pervious to
the occupancy of this country by the Europeans, is: not well
established by the occurrence of its remains, though the evi-
dence is in favour of the opinion. Watrus: anterior portion
of the cranium, fossil, from decomac County, Virginia. Not

REPORT ON THE GEOLOGY OF NORTH AMERICA. 2h

known whether it belongs to the living species. This animal
has not been seen on the American coast south ‘of lat. 47°.
(Annals of the New York Lyceum, vol. ii. p. 271.)

It was suggested, first, I believe, by Mr. Vanuxem, that all the
bones of the Mammoth and other extinct quadrupeds of this
country yet found, have been in either the ancient or modern
alluvium. Some have been inclined to attribute them exclu-
sively to the catastrophe which has strewed the surface of this
continent with transported blocks and gravel, or have supposed,
in other words, that the races perished by that diluvial action
which I have before shown to have occurred, after the period of
the ancient alluvium, and prior to the recent. Notwithstanding
the extreme neglect which has been hitherto evinced in record-
ing the geological situation of the interesting organic remains
of the extinct Mammalia of this country, sufficient information
has been collected to enable us to reason, I think with some
certainty, concerning the date of their disappearance.

It will be observed that we have authentic accounts of the
remains of extinct Mammalia under two entirely dissimilar si-
tuations. In one case, as in the Mastodon tooth discovered
near Baltimore, the fossil occurs in an ancient bog, covered by
a thick bed of sand and diluvium. This is one of the deposits
which I have called ancient alluvium, and which seems to
belong to some era of the tertiary period, but what precise
epoch is at present quite uncertain. Another set, apparently
consisting of the very same species, occurs in the most recent
class of bogs and marshes, buried to a very slight depth be-
neath the surface. The latter is the situation in which by far
the largest number of Mastodon, Elephant, and other bones have
been found. These newer bogs or marshes are in no case seen
to be covered by any diluvial matter, but appear, on the con-
trary, from their low level and their wet state, being often tra-
versed by streams, to have experienced little or no change since
the fossil relics were originally entombed in them. In the re-
gions beyond the Alleghanies, most of these remains occur in
spots which are called Salt Licks, which are meadows and
swampy grounds where the soil on the surface of the ground
is impregnated with muriate of soda, from the springs which
empty themselves from the muriatiferous sandstones which
abound in the Western States. Big Bone Lick, in Kentucky, is
an example of one of these. Here have been found not only vast
numbers of the fossil bones of the extinct races, but quantities
almost as great of the Buffalo, besides many of two or three
species of Deer, now, like the Buffalo, indigenous to the country.
This, therefore, would appear to have been resorted to not -
only in modern times by the living races, but more anciently by

28 FOURTH REPORT—1834.

animals now extinct, for the salt, and it may be for the food and
pleasant coolness produced by the marsh. Our travellers to the
western regions, where the Buffalo or Bison now ranges, have
daily opportunities of witnessing these animals entrapped and
perishing in these licks and swamps; and it seems evident that
the Mastodon and Elephant of former times, from their huge
size and unwieldy forms, must have been equally exposed to
the same fate. Granting such to have been the chief cause
which has buried these races, we see at once why such remains
are found only in meadows or soft places, why they occur at
such small depths, and why in so many cases the head has been
seen resting nearly on the surface of the marsh; the cranium
universally decayed ; and the skeleton either in its natural erect
position, or the ponderous bones below, and the ribs and verte-
bre above. (See Annals of the New York Lyceum, vol. i.
p- 145., also Ossemens Fossiles, 2nd edit. tom. i. pp. 217, 222.)
The state of perfect preservation in which so many of these
bones are found, is another argument that the animals have
perished by such a cause, and not by any violent catastrophe.
There is at present in the Philadelphia Museum a pair of mag-
nificent tusks of the Mastodon, so little acted on by time, that
the beholder almost fancies he sees the marks and scratches on
the enamel which it received in the living state. These beauti-
ful remains were found by a countryman in Ohio when diggin
an ordinary ditch in his meadow, so that it is probable that the
rest of the skeleton lies near, and at very little depth. From all
the facts before me, I have little hesitation in giving my opinion
that the extinct gigantic animals of this continent, the Mastodon,
Elephant, Megalonyx, Megatherium, fussil Bos, and fossil Cervus
lived down to a comparatively recent period, and that some of
them were in existence as long ago as the era anterior to that
which covered the greatest part of this continent with diluvium.

_ Two interesting conclusions seem here naturally to suggest
themselves: first, that the diluvial catastrophe, whatsoever it
may have been, could not have introduced any very material
change of climate or condition upon the continent, or we should
have beheld the races sooner extinguished ; and, secondly, that
the physical features of the surface were the same or very nearly
the same when the Mastodon lived as now; so that his extinc-
tion seems neither traceable to violent revolutions, so called, nor
to any decided change of climate ; which, seeing that no appre-
ciable change of physical geography has taken place since his
day, ought to remain the same now as when he formerly stalked
through the continent, and perished in the same morasses
which at this day entrap and bury our less gigantic living races
of animals.

ee ee ee ee eee

a

REPORT ON THE GEOLOGY OF NORTH AMERICA. 29

~~ It may seem at variance with what I have here advanced of
the recent and tranquil extinction of these animals, that in the
enormous accumulation of their relics at Big Bone Lick, the
boggy matter should be found partially filled with gravel, and
the larger bones universally fractured. However, the small
amount of gravel described as mingling with the peaty mass,
seems hardly to imply that this spot was visited at this time by
any violent action, such as covered the adjoining hills with their
boulders and gravel; so that, on the whole, J am most inclined
to explain the fractured condition of the jaws, femora, &c., by
the constant treading and floundering of the huge animals over
the skeletons of their ancestors.

Tertiary Formations.—Many circumstances tend to give
peculiar interest to the tertiary geology of America at the pre-
sent time. The day appears to have come when some of the
broad conclusions recently arrived at in Europe may be fitly
tested by a comparison with the phenomena of remoter regions,
and America would seem to be so much dissociated from Eu-
rope, both by its insulated position and different physical struc-
ture, that the comparison between them will possess peculiar
weight. The great range which characterizes all the deposits
of America belongs, no less remarkably, to those of the tertiary
age, and affords a very favourable opportunity for ascertaining
to what extent formations so recent may be distributed
without departing materially from an uniform type, or where
they do depart, of determining the causes which influence the
variation. The existing animal and vegetable races of this
hemisphere differ so widely from those of the Old World, that
we are induced to inquire when, or whether at any time, the
species on the opposite sides of the Atlantic were more nearly
identical. These inquiries, bearing intimately on some of the
most important questions of the science, have been recently dis-
cussed with great ability by Mr. Lyell. I do not consider that
our researches have proceeded to a sufficient length to render
them of much weight upon many points in tertiary geology; but
I nevertheless venture to remark, that they will be found to af-
ford a striking corroboration of the soundness of the new prin-
ciple upon which the tertiary formations of Europe have been
arranged in chronological order by Lyell. They will perhaps
be seen at the same time to suggest some slight changes in the
views hitherto entertained respecting the different circumstances
under which tertiary and secondary groups are supposed to have
been severally formed.

The area within which the tertiary deposits of this country

occur, so far as our information at present extends, is that por-
tion of the United States which I have styled the Atlantic

80 FOURTH REPORT—1834.

plain, together with an undefined portion of the part of the
great central plain of the continent which is connected with
the Mississippi.

The northern limit of the tertiaries, so far as at present une-
quivocally ascertained, is in the south-eastern corner of New
Jersey, adjacent to the Delaware Bay. Here it appears to com-
pose the greater part of the counties of Cape May, Cumberland,
and the south-west corner of Salem. From that point it is be-
lieved to extend almost continuously through the eastern por-
tions of Delaware, Maryland, Virginia, and North Carolina, and
in interrupted patches further south through South Carolina,
Georgia, Alabama, and Mississippi into Louisiana, and the ter-
ritory west of the Mississippi river.

The following arrangement will show the range, as far as hi-
therto discovered, of the tertiary and recent formations of this
country.

Synoptical Table of Recent and Tertiary Formations of the
United States.

Periods. Character of Formations. Localities of the Formations.
Modern alluvium, consisting | Deltas of nearly all the rivers,
of sands, clays, and marshes, | especially the Mississippi.
containing trunks of trees;
and occasionally relics of

human workmanship.

ReEceEnNT.

Terraced valleys of alluvial | Connecticut, and many other
origin. rivers, especially in the New
England States.

1. | Loose shell rock, composed of | Anastasia Island, and the sea

comminuted fragments of
shells, exclusively those now
found recent on the coast.

formed almost entirely of
shells of the Rangia Cyre-
noides in-a:subfossil state.

islands and beaches parallel
to the coasts of Georgia and
Florida generally. Probably
most of the other sand
beaches and islands also,
which lie along the coast as
far as Long Island.

2. | Raised estuary formation, | Extends along the whole shore

of the Gulf of Mexico from
Pensacola to ‘Franklin in
Louisiana, bends around
Mobile Bay, Lake Pontchar-
train, and ranges across the
delta of the Mississippi, im-
mediately above its marshes,
a total distance of nearly 300
miles, and probably much
further. 4

REPORT ON THE GEOLOGY OF NORTH AMERICA.

_ Periods. Character of Formations.

_—_—_

to the Indians, contain oc-
casionally fragments of older
tertiary shells, as Pectens,
&c. ; matrix generally sandy,
like that of the beach.

Ditvviat.
rived from the primary and
ancientsecondary rocks of the
interior. Noorganicremains.

LUVIAL. sands. One bed is a deep
black tenacious clay, con-
taining leaves, trunks of trees,
lignite, amber, and vegetable
products generally. It has
all the aspect of having been
once a saltwater marsh, si-
milar to that now at the mouth
of the Mississippi. No re-
mains ‘but such as are sup-
posed to belong to existing
species have hitherto been
found in these clays, and they
are therefore, for the present,
put apart from the true ter-
tiary formations.

Newer Prer-| A’lead-coloured clay.
| OCENE.

Ouper Puzr-| Alternating beds of sand and
-ocenE and | clay, the sandy beds often
Metocene. | abounding in fossil shells,
which are sometimes )in a
friable and pulverulent state,
giving the bed the character
of a shell marl. These fos-
siliferous beds rest almost
invariably on a bed of blue
clay; sometimes the sands
are greenish, but more usu-
ally they are yellow with a
slight admixture of clay.

EEE EERE aaa aaa

3. | Banks of oyster shells, ascribed

Boulders,pebbles, and sand, de- | Surface of the United States

—— ee ainenintienE

|
Ancient At-| Beds of clay and variegated

31

Localities of the Formations.

New Jersey; Choptank River,
Maryland; York Kiver,
Virginia, &c.

generally.

Martha’s Vineyard; Long Is-
land; greater part of New
Jersey from Amboy Bay
along the sections of the rail-
road to Bordentown; Chesa-
peake and Delaware Canal
in Delaware; Telegraph Hill,
Baltimore; near the city of
Richmond, Virginia; Cape
Sable in the Chesapeake Bay,
Maryland. There is little
doubt that the same appears
interruptedly the whole way
to the Mississippi.

Mouth of the Potomac, St.
Mary’s County, Maryland.

Cumberland County, New Jer-
sey; Cantwell’s Bridge, De-
laware; Chester Town; East-
on, and nearly all the eastern
shore of Maryland; the whole
of Charles, St. Mary’s, Cal-
vert, and part of Prince
George Counties, Maryland.
In Virginia, in Lancaster,
Gloucester, ‘and all the pen-
insula between James and
York rivers; ‘also nearly all
Norfolk, Nansemond, Isle of
Wight, Surrey, and Prince
George Counties. ‘In North
Carolina, near the towns of
Wilmington, ‘Murfreesboro’,
and throughout the counties
of Craven, Duplin, &c., across
the State. In South Carolina,
Vances ferry on Santee river
seems to be about the fermi-
nation of the middle tertiary
groups of the United States.

FOURTH REPORT—1834.

Character of Formations.

A series of whitish and lead-
coloured friable limestones,
and ferruginous and siliceous
sands, all abounding in ex-
tinct species of shells and
zoophytes.

Occurs also very frequently in
the form of a fine-grained
siliceous rock, abounding in

Localities of the Formations.

Piscataway, near the Potomac
River, Maryland; « Upper
Marlboro’, Maryland; Vance’s
Ferry, South Carolina; and
across to Three Runs, on Sa-
vanna River; Shell Bluff,
Savanna River; Silver Bluff
onthe same, inBurkisCounty,
Georgia; near Milledgeville

in Georgia; Early County,
Georgia; Wilcox County,
Alabama; Clayborne, Ala-
bama; St. Stephens, Alaba-
ma; Munroe, on the Washi-
taw River, west of the Mis-
sissippi. All these localities
are on the authority of Mr.
Conrad, who has either seen
them in person or received
eocene fossils from them.

casts and impressions of
shells. ‘This is used as a burr
stone in Georgia.

It is necessary, perhaps, that I here explain in what sense I
employ the very useful nomenclature of Lyell. I wish it to be
understood that I apply the terms Pleiocene, Meiocene, and Eo-
cene to our beds, not under the idea of any strict identity, either
in geological character or age, being discoverable between them
and the strata which have severally received those names in
Europe, but to express simply their own comparative chrono-
logical relations, and their connexion with the recent organic
races of this country, independently of any direct comparison
with formations elsewhere. It is possible, indeed it is very
likely, that some of our formations, our newer pleiocene, for ex-
ample, may exhibit in their organic remains nearly the same
proportion of recent species as certain beds in Europe, and yet
differ materially from the latter in positive age; for I conceive
it is afair inference, that throughout a certain period of more or
less duration, the relations of species, from general physical
causes, must be more stable in some regions than in others, va-
rying less rapidly, for instance, upon the tranquil shores of the
United States, than near the often agitated coasts of volcanic
Sicily. If this view be granted, and I think it should not be
overlooked in attempting to establish identity of period in di-
stant strata, the tertiary formations of America will furnish an
instance in illustration of the importance of the caution recently
given us by Mr. Murchison and other eminent geologists of
England, that we make out a classification of our rocks from
their own relations, instead of ranking them, as we have hi-
therto invariably done, merely as members of European types.

REPORT ON THE GEOLOGY OF NORTH AMERICA. 33

-More extended researches in our recent conchology will
doubtless inform us, from time to time, of the existence in the
living state of some shells which we now regard as occurring
only in the extinct and fossil state; and the natural tendency
wil! therefore be, to lessen the apparent antiquity of each for-
mation. It is this prospect of being compelled to modify our
arrangement of the tertiary beds, as the researches multiply,
that has made me hesitate to fasten upon all of them the terms
of the new nomenclature, which they might otherwise claim.
I propose, therefore, to designate them for the present by the
convenient synonyms of ‘newer tertiary’ for the newer pleiocene,
‘middle tertiary’ for the older pleiovcene and meiocene together,
and ‘ older tertiary’ for the eocene. The newer pleiocene and the
eocene certainly exist in well-pronounced characters, and there
will be little or no necessity, now at least, to employ their pro-
posed synonyms ; but the case is very different with the less de-
finéd formations of an intermediate age, and I shall therefore find
it of essential assistance to employ, for these, the term ‘ middle
tertiary’. American geologists will be careful not to confound
the middle tertiary beds, of which I am speaking, with those
which Mr. Conrad has designated by the same name, and which
are clearly of eocene date, as both that gentleman (in his_re-
searches among the fossils of Clairborne, Alabama,) and Mr.
Lea have been prompt to show.

Newer Pleiocene of St. Mary’s County, Maryland.—In the
tertiary mass now before us, the number of well-characterized
shells is such as to enable us to examine their relations to the
species now living in the neighbouring ocean, or peculiar to
other formations. For our knowledge of the formation at the
mouth of the Potomac, we are indebted exclusively to the re-
searches of Mr. Conrad; and it is mainly from his descriptions
and on other information which he has been kind enough to im-
part, that I am enabled to present the following brief account
of the deposit. He justly pointed out its very modern character,
by showing the identity of nearly all the species with the shells
at present living on our coast. Mr. Conrad thus describes the
formation :

** About three miles north of the low sandy point which forms
the southern extremity of the peninsula, the bank of the Poto-
mac rises to an elevation of about fifteen feet at its highest
point: the fossils are visible in this bank to the extent of a
quarter of amile. The inferior stratum is a lead-coloured clay,
containing vast numbers of the Mactra lateralis of Say, which
in many instances appear in nearly vertical veins, as though
they had fullen into fissures. The Pholas costata is also nu-

1834. D

34 FOURTH REPORT—1834.

merous, and each individual remains in the position in which the
living shell is usually buried in the sand or mud; that is, ver-
tical, with the short side pointing downwards: they are so fra-
gile, that they can rarely be taken entire from the matrix. Upon
this stratum of clay, in a matrix of sand, lies a bed of the Ostrea
virginica, in some places a foot in thickness. It is nearly
horizontal ; in some places at least eight or ten, and in others
not more than four feet above high-water mark. The diluvium
above exhibits a vein of small pebbles, traversing it horizontally,
and at a distance resembling a stratum of shells. Not only are
the fossils of this locality the same as existing species, but in
some instances they retain their colour; a circumstance com-
mon to the later deposits of Europe. The distance from the
nearest point on the Atlantic Ocean is about forty-five miles,
but it is at least one hundred by the course of the bay. It will
be observed, that nearly all the shells are known to inhabit
the shores of the United States at the present time: those of
them which are now only known in the fossil state are extremely
rare, or of minute dimensions.”

Mr. Conrad also mentions to me as an indication of the great
tranquillity which has attended the deposition of these beds, that
the underlying blue clay is everywhere penetrated by the Pholas

-costata in its natural position. Theupper bed contains Ostrea
associated with Mytilus, a fragile shell, in a very entire and un-
disturbed condition. Itis nota little curious that the same fel-
lowship of Ostrea virginica and Mytilus recurvus (hamatus,
Say,) should subsist at the present day in the Gulf of Mexico,
though the latter shell has never been seen in the more northern
latitudes of our coast. The Rangia, likewise a gulf shell exclu-
sively, occurs also in the same newer pleiocene, so that we seem
to have indications of a higher temperature even so late as the
newest of our tertiary periods. Several of the species, however,
in the foregoing table were long supposed by our conchologists
to inhabit, in the present day, only the most southern portions
of our Atlantic coast, but the same have been since found as far
north as the shores of Rhode Island.

The bed of Ostrea virginica reposing upon the fossiliferous
blue clay, has already been referred to a somewhat newer date,
from the circumstance of its entire identity with the very recent
beds of fossil oyster seen on the margins of some of our rivers
and bays, in circumstances which prove them to be among the
very newest of all the upheaved accumulations of the waters of

-the coast. Considering these upper remains, therefore, as not
quite contemporary with the subjacent and more diversified
assemblage of marine shells, we may regard the latter as having

eee eee “ ~~, =

— ee eee

REPORT ON THE GEOLOGY OF NORTH AMERICA. 36

colonized a tract in the bed of the ocean, much deeper than
would be compatible with the known habits of the oyster, until
the occurrence of an alteration of the level, from what may be
termed deep sea, to a shallow estuary; the clay enveloping
the lower shells, indicating perhaps the ooze peculiar to the
one, the oysters above lying in a sediment equally characteristic
of the other, namely, sand. The supposed change of circum-
stances would be just such as would tend to banish the pelagian
shells and to introduce in abundance a race like the oyster, de-
lighting in protected coves and shoals. A second elevation of
_the region must have taken place to bring both beds to their
present position above high tide, and to expose them to receive
their covering of diluvial pebbles, which is said to be thick and
well characterized. The deposit at the mouth of the Potomac
is the only one of its exact period at present discovered, though,
from the appearance of successive small upheaves at various
times, along nearly the whole Atlantic plain, it seems reason-
able to look for the occurrence of beds of nearly similar age in
other sections of the coast; if, indeed, we have not already
found one at Charleston, and on the adjoining coast of South
Carolina.

Formations of the older Pleiocene and Meiocene periods.—
These deposits which, before the appearance of Mr. Lyell’s no-
menclature, went under the name of the ‘upper marine’ formation,
from a supposed identity with the beds of that name in certain
basins in Europe, constitute by far the most extensively distri-
buted portion of our tertiary beds yet explored. There is even,
I think, reason to believe that we have deposits of a wide range
which may be separately classed, some in the meiocene, others
in the older pleiocene period, though in many cases it is not
possible, from the present limited catalogue of their fossils, al-
ways to infer with precision their exact comparative age : on this
account, and also from the circumstance that their mutal geo-
graphical connexion has never been yet properly examined, I
prefer, for temporary convenience, to treat them for the present
under one head, as the deposits of one great middle tertiary
group. These are clearly separated by a well-marked and per-
haps wide interval from the more recent newer pleiocene on
the one hand, and the more ancient eocene on the other, though
there is some ground to believe that they will be found to blend
into each other by various shades of approximation,—unless,
indeed, future researches may point out among them an addi-
tional number of distinguishing fossils. It is very probable,
from present indications, that when we have investigated the
deposits of these two periods we shall find it requisite to inter-

pd2

36 FOURTH REPORT—1834.

calate several subordinate new periods between the principal
ones already recognised, fulfilling the plan and the predictions
of Mr. Lyell.

The proportion of species in the tables which are to follow
will show how far these suggestions are pertinent. In the
mean while I shall content myself with establishing, from proper
evidence, the existence of both the older pleiocene and meiocene
in their broader limitations, being assisted by the tables and
notes of Mr. Conrad, whose researches in this field, in Maryland
and Virginia, constitute the chief of what we at present know
touching these formations, and whose expression of concur-
rence in some of my present general views gives me much
satisfaction.

Geographical Range of the older Pleiocene and Meiocene For-
mations.—Commencing most probably, as I have already stated,
in the southern extremity of New Jersey, these tertiary beds
show themselves in a wide and, at present, undefined belt con-
tinuously through Delaware, Maryland, Virginia, and North
Carolina, in the south of which State, and in part of the adjoin-
ing State of South Carolina, they only occur in interrupted
patches, thinning out and disappearing altogether after reaching
the Santee river in South Carolina.

New Jersey.—Hardly anything is known of these formations
in this State, beyond what may be inferred from a small collec-
tion of shells procured by Mr. Conrad, near Stone Creek, Cum-
berland county, and by a few specimens of similar fossils received
from Cape May and other places along the same shore of the
Delaware Bay. In mineral character the middle tertiary beds of
New Jersey appear, from the slight examination which they have
had, to consist of yellowish siliceous sands, resting upon a lead-
coloured clay, the chief receptacle of the fossil shells above enu-
merated. There is reason to believe that tertiary beds are nearly
continuous from Salem to Cape May and Great Egg Harbour, a
tract of at least forty miles long by ten or fifteen broad. How
much more of the peninsula of New Jersey may consist of ter-
tiary beds, we cannot say, as the surface is deeply covered by
diluvium and sea sand.

Deluware.—In this State tertiary formations of the same
period certainly exist, though it is a district which has received
no attention. At Cantwell’s Bridge, fossils have been procured,
which Mr. Conrad is inclined to refer to the middle tertiary,
though we consider the locality to require further investigation
before we can pronounce even thus far.

Maryland.—Formations, the major part at least of which
are fairly of the middle tertiary age, occupy nearly the whole

REPORT ON THE GEOLOGY OF NORTH AMERICA. 37

surface of both shores of the Chesapeake Bay south of an irre-
gular line drawn from Kent county to a few miles below the
city of Washington on the Potomac. Over this great area,
which is nearly one hundred miles long from north to south,
and more than fifty wide, the tertiary beds are seen under
nearly uniform characters in almost every spot where the rivers
or ravines have exposed sections. The upper layers are usually
arenaceous and repose very generally upon a more argillaceous
stratum, often developed as an almost pure lead-coloured clay.
Both deposits are highly fossiliferous, and when seen on the
side of a river, present, sometimes, little else than a bank of
shells and zoophytes, often in a state of fine preservation.

Some of the most conspicuous localities are on the Chester
river, which is about the northern boundary; also at Kaston
and Cambridge, all on the eastern shore; and again on the
western shore of the bay, especially in St. Mary’s county,
where many of the fossils of this formation were first discovered.
Mr. Conrad describes the fossiliferous mass as extending in the
precipitous banks of St. Mary’s river nearly a mile. This bed,
he says, contaius many extinct species; it furnishes a large
number of genera, with very few species of each, while the in-
dividuals are in the greatest abundance. The bank is elevated
perhaps thirty feet in the highest point above tide, and there
the stratum of shells rises fifteen feet above the river. Siliceous
masses with imbedded shells are numerous, and are used for the
foundations of buildings. The inferior stratum of these banks
is clay, which appears to contain the same species of shells as
the sand above it. On the eastern shore of Maryland in the
banks of the Choptank, not far from Easton, Mr, Conrad ob-
served the following section.

1. Diluvium. Feet.

2. Sand, with Pecten Madisonius and Balanus Proteus almost exclu-
BIVel yards, Stet Pay ae Mets Ute Pe ML MMI Se Maeta ee eI Ae

8. Cytherea marylandica, Corbula and Pecten Madisonius, in sand... 7

4. Cytherea marylandica in vast numbers, in sand, with Crassatella
marylandica in abundance... ~~... +--+ sees eee reece
5. Blue clay, with Perna mazillata.

_Virginia.—Tertiary deposits, apparently of the same middle
group, occupy, it is believed, nearly all Virginia east of a few
miles below the primary boundary, and are seen to put on all
the varieties observable in Maryland, being continuous and
identical with those just described as belonging to that region.
The average breadth of the deposit in Virginia may be stated,
therefore, at about sixty miles, and its length the whole extent
of the State, from the Potomac south to the State of North Ca~-

38: FOURTH REPORT—1834.

rolina.. Throughout this great area it has scarcely received any
geological examination, our only accurate information being
that procured by Conrad in his researches among the fossils in
Suffolk county, and again at York town, and some recent exa-
minations made by my brother, W. B. Rogers, along the James
and York rivers and the peninsula embraced between them. The
general distribution of the formation, however, is well known,
because the fossiliferous parts of the deposit are sought over
nearly the whole region for the fertilizing action of their carbo-
nate of lime and shells upon the soil, in consequence of which
the whole deposit bears the name of marl in all the States in
which it occurs. I select for description the beds upon the
James and York rivers, as being best known to us, and probably
characteristic of the deposit generally.

On the James river, along the clifis in the counties of James
city and Warwick, the fossiliferous strata are finely exposed.
My brother, Professor Rogers, thus describes the locality : “ By
far the most striking exhibition of the tertiary strata which I
have yet seen is on the bank of James river, from a little above
King’s Mill upwards. The bank has an average height of sixty
feet, and from the water-line to a few feet from the top is occu-
pied by shells: in some places huge blocks of the deposit have
fallen down, exposing the specimens in a very perfect state. The
mass in which the shells are imbedded is usually a stratum of
sand, sometimes covered by, but mostly resting upon, blueish
clay, which also includes the same fossils. The sand, as in
Maryland, is mostly yellowish, though it has often a green hue,
like that called turtia by the French. It is sometimes indu-
rated into a rough concreted mass by the cementing action of the
carbonate of lime of the shells. An interesting fact is, the oc-
currence among it of the green grains so characteristic of the
secondary greensand of New Jersey.”

My brother states, that after examining at least thirty distinct
localities, he has found the greensand an invariable ingredient
in all, some having as much as thirty per cent. of this mineral.
At Burwell’s Mill the stratum over the shells for five feet is an
olive and red clay, containing from thirty to forty per cent. of
the greensand, from which it receives its colour, olive or green,
precisely as certain beds of similar clay in the secondary tracts
of New Jersey acquire the same tint.

A section upon the side of a mill-pond recently drained near
Williamsburgh, about midway between the York and James
rivers, affords the following arrangement: Ist, reddish sand,
about eight feet, containing near the bottom a stratum two feet
thick of shells, chiefly Venus and Arca idonea, very large;

4
?
}

a

REPORT ON THE GEOLOGY OF NORTH AMERICA. 39

2nd, blue marl, full of Venus, twelve inches; 3rd, blueish
green marl, four feet thick, having at the bottom a mass of
Pecten, and below this a crowded layer of Perna, all perfectly
horizontal.

On the York river the stratification, though it does not ex-
hibit so lofty a precipice filled with shells as before described
on the James river, presents the clay strata very beautifully.
Immediately overlying the shells is a continuous bed of clay,
many miles long, in some places forming a vertical wall, ten or
fifteen feet high, and as smooth as masonry. It is of a blue
coleur, and divided by thin layers of sand, perfectly horizontal,
into portions about eight to twelve inches thick, so that the ap-
pearance is very much like that of a wall. The incumbent clay
in some-places thins out, and changes colour to areddish brown,
which makes it scarcely distinguishable from the diluvium above;
sometimes it is subdivided into two strata, separated by sand
and gravel. This clay is a very common deposit throughout
the tertiary marl region, sometimes beneath, sometimes above
the shells, and often both below and above, and also containing
shells. In appearance it resembles a clay which is a member of
the secondary greensand formation of New Jersey. From York
town, six miles up the river, is the following interesting section :
1st. Near York, acurious rock, containing shells, often in minute
fragments, being somewhat like masses of the crag of England.
Here the strata are not horizontal; but in a ravine below the
town they dip on opposite sides towards the ravine at an angle
of more than thirty degrees. This shell rock is an indurated cal-
careous sand, formed of shells, not partially decomposed, but
comminuted by attrition. It had obviously been subjected, as
Mr. Conrad observes, to a violent action of the waters at a pe-
riod anterior to the tranquil deposition of the perfect shells it
contains. 2nd. From York town to about three miles up the
river, the principal stratum consists of shells, overlaid by the
above-mentioned blue clay, separated near its western end into
two strata. 3rd. At some distance higher up, the shell rock
again takes the place both of the stratum of shells and the over-
lying blue clay. 4th. Beyond this again, and still on the same
level, the blue clay is seen resting once more on the unbroken
Shells. The appearance of the wall of clay in these places is
very curious; it is as smooth as if cut with a spade, and re-
sembles the wall of a fortress. On the Nansemond river, in the
immediate neighbourhood of Suffolk, very nearly the same series
of strata is seen as described upon the York and James rivers.
Yellowish sand reposes most generally upon the blue clay, both
beds containing a profusion of shells, and rising from the river

40 j FOURTH REPORT—1834.

some fifteen or twenty feet. This would appear to be the pre-
vailing order, not only in all the portion of Virginia here de-
scribed but throughout the middle tertiary region, from whatever
part of it accounts have reached us, whether from Maryland or
North Carolina.

North Carolina.—The middle tertiary beds are prolonged
through this State in a belt, the east and west boundaries of
which are not at present ascertained, but which appears to con-
tract both in width and thickness as we proceed south.

Professor Mitchell, of the University of North Carolina, men-
tions it as ranging through the following localities: Near the
northern boundary of the State it appears on the Meherrin river
at Murfreesboro’ ; further south, on the banks of the Roanoke at
Scotland Neck; again on the banks of Fishing Creek near In-
field, in Halifax county, and on the banks of the Tar river near
Greenville, in Pitt county, and also a little below the falls of the
Tar ; in several places in Craven county, and on the banks of the
Neuse, below Newbern. It appears also in Duplin county, and
on the banks of Cape Fear river, at Walker’s Bluffs, and eight
miles above Elizabeth. Walker’s Bluff, like all the other con-
siderable bluffs in this State, is on the western or right bank of
the river as we descend. It extends about three fourths of a mile
along the river, and then recedes and loses itself in the general
plain of the country above. The stratum of shells is from five
to twelve or fifteen feet in thickness, and its upper surface
seventy-five feet above the mean level of the water in the river.
The tide flows a few miles above it. Beneath the shells are al-
ternating and irregular strata of sand and blue tenacious clay,
the latter predominating. Above the shells the surface rises as
we recede from the river, until it gains a height of about one
hundred feet, which is not far from the average level of the sur-
face of this portion of the State above the sea. In Duplin and
many parts of the south-eastern corner of the State, as along
Cape Fear River, near Wilmington, this formation rests imme-
diately upon the upper zoophitic limestone of our southern cre-
taceous rocks. It is here in fact a mere capping, having a
thickness of not more than a very few feet, but still abounding
in characteristic fossils.

South Carolina.—Mr. Conrad has the following observation
in allusion to the southern extremity of these beds, which I have
here termed middle tertiary: ‘‘The formation has not been
found south of Vances Ferry, on the Santee river, in South
Carolina; nor do I believe it occurs in Georgia, Alabama, or
Mississippi. I never myself observed it in any part of South
Carolina, though I explored the country between Charleston and

REPORT ON. THE GEOLOGY OF NORTH AMERICA. 41

the Eutaw springs, which is wholly secondary. The deposit
therefore at Vances Ferry is probably very limited in extent,
and extremely superficial, capping the cretaceous rocks in the
same manner as at Wilmington.

- “The pleiocene probably occurs on the Santee river, near the
junction of the Congaree and Wateree rivers, as Mr. Say de-
scribes two species of -drca, evidently pleiocene fossils, from a
locality near the junction of these two rivers.”

Such, then,.are the principal localities at present known of the
middle tertiary formations in their apparently continuous range
from the Delaware to the Santee, over a tract perhaps eighty
miles in breadth from the coast. In external character, mineral
contents, and organic remains, the sedimentary deposits over
this great tract exhibit a most marked uniformity, and were it
not that the principle. has been furnished us whereby, through
a comparison of recent and extinct fossils, the relative antiquity
of each locality may be determined, at least approximately, we
should, without a doubt, regard the whole tract as one simul-
taneous formation. I look confidently, however, for both older
pleiocene and meiocene proportions among the species, and shall
not be surprised if we discover, ultimately, almost every inter-
mediate ratio. For this intimate association of the two periods
there would seem to exist a natural and obvious cause. The
whole of our tertiary, and even cretaceous groups, are all de-
posits effected under the same general physical exposures, all
accumulations upon the same coast, bearing traces of no con-
vulsions, and therefore interrupted by no hiatus. These for-
mations occupy one extensive plain, where the stratification is
- amazingly horizontal, which is crossed by no ridges, and there-
fore subdivided into no basins ; so that the whole may be con-
sidered as having resulted from a set of causes continuing in ac-
tivity throughout a long period.

Having procured a table of all our middle tertiary fossils at
present known to us, and with it an enumeration of the species,
recent and extinct, from the more important localities which
have been explored, I am enabled to attempt a determination of
the relative age of these beds, from the numerical relations of
the shells.

The total number of species from our tertiary beds, excluding
the eocene and the newer pleiocene, is about 195 ; of these, nearly
forty are known as recent shells, inhabiting principally our own
coast. This presents us with a proportion of rather more than
twenty-one in one hundred, or about the ratio of the living spe-
cies in the meiocene formations of Europe.

From New Jersey to North Carolina there is every reason to

42 ' FOURTH REPORT—1834.

suppose that the greater part of the tertiary tract will furnish
even a less proportion of living species than one fifth, while the
tertiary beds of North Carolina have contributed a group of shells
of which nearly two thirds are of recent species. The latter
territory would therefore most probably come within the plei-
ocene epoch, while the former districts are pretty clearly of the
American meiocene. It is an interesting fact, however, that our
meiocene shells, if we can at present call them such, resemble
most the species of the European older pleiocene.

The following brief details embrace the results of a compari-
son of the respective fossils of each principal locality of our
middle strata, according to present data.

New Jersey.—To begin with the locality in New Jersey, it
will be shown that we can at present enumerate only thirteen
species whose relations are established. Of these, twelve are
extinct, and one is supposed to be recent.

What is curious in this small list is its containing so small a
proportion of species recent on our coast, though the deposit
evidently does not belong to our older tertiary, or eocene. The
species are either the same as those found in the meiocene or
middle tertiary of Maryland, or where they differ they are mostly
analogous. It is certainly not fair to reason from such very
limited data as are furnished us by this small list of fossils. New
additions to our present rather small catalogue of recent shells
may materially lessen the proportion of the species regarded as
extinct : anticipating this, I feel the less hesitation in separating
the beds of New Jersey from the eocene period. I consider it,
nevertheless, possible that some of the middle tertiary forma-
tions of this country may ultimately exhibit very nearly eocene
proportions, while the character of a majority of their fossils
may mark them to be decidedly meiocene in their relations.

St. Mary’s, Maryland.—This place has furnished about fifty-
six species, thirteen of which are recent on our coast, while the
remaining forty-three are extinct. The proportion of recent
species here is 23 per cent.

Euston, Maryland.—The deposit upon the Choptank river,
near Easton, has presented, so far, about twenty-six species,
twenty-two of them extinct and four living. Among the extinct
species, the Perna mawillata is conspicuous, as it always is
wherever the deposit shows a large preponderance of species no
longer living. The recent species here are about 16 per cent.
of the whole, placing the bed, like that of New Jersey, perhaps
in the meiocene period.

Suffolk, Virginia.—Here the total number of species procured
is forty-five, about thirty-five of which are extinct and ten re-

a

ake

REPORT ON THE GEOLOGY OF NORTH AMERICA. 43

cent on our coast. It is evident that here the proportion of
living spécies is greater than in most of the preceding localities,
the proportion being something like 22 per cent. Should this
ratio not materially vary with new discoveries, the deposit must

- be ranked, like the preceding, with the meiocene period, notwith-
standing that its shells are rather the analogues of the European
older pleiocene.

York, Virginia.—About forty-four species are known from
this spot, thirty-six of which are extinct, and the remainder
recent. The living species here are nearly 18 per cent. of the
whole, which differs but little from the ratio at Suffolk. Fa sith

Smithfield, on the James River, Virginia.—The deposit at
this place has furnished sixty-four species, fifty-five extinct and
nine recent. This affords a proportion of about 14 per cent.,
which, if it be taken as the true expression of the relations of
the species, would place the locality in the meiocene, and per-
haps in an older division of the period than would belong to some
of the preceding deposits.

North Carolina.— Though the fossil shells of this State have
been very little examined, the present list indicates a group of
beds decidedly more modern than any detailed above. Of thirty-
seven species at present known, twenty-four, or nearly two
thirds, are recent: should this proportion remain nearly the
same, after the catalogue has been duly augmented, we must
rank some at least. of the interesting deposits of North Carolina
in our older pleiocene, placing them most probably late in the
period. A certain modern aspect about these shells lends coun-:
tenance to this prediction.

I shall terminate this account of our middle tertiary beds with
a list of the fossil shells of this period, which are common to
the strata of both America and Europe. They are:

. Lucina divaricata, Lam.

- Cerithium melanioideum, Sow. (In the London clay.)
. Ostrea virginiana, Gmel.

. Dentalium dentalis, Linn. (D, alternatum, Say.)

. Venus rustica? Sow. (Isocardia fraterna, Say.)

. Pectunculus subovatus, Say. (P.-variabilis, Sow.)

Older Tertiary, or Eocene.—The first notice of eocene de-
posits occurring in the United States, as characterized by organic
remains, was published by Mr. Conrad in the Journal of the
Academy of Natural Sciences in 1830, from observations he had
made in the vicinity of Fort Washington, in Maryland: he also
stated that such beds occurred at Vances Ferry, on the Santee
river, where it is since ascertained that they are covered by a su-
perficial deposit of the fossils of the pleiocene period. One cha-
racteristic fossil of the eocene of Claiborne (Ostrea selleformis,

Qor N=

44. ; FOURTH REPORT—1834.

Conrad,) occurs at the Eutaw springs and at Nelson’s Ferry on
the Santee river, but it lies in a white limestone, associated with
very different fossils from those which accompany this Ostrea at
Claiborne. This limestone is doubtless analogous to that on
which the tertiary of Claiborne is based, but its true character
is given by Dr. Morton, in his Synopsis, now in the press. Eocene
deposits commence in Maryland, and extending in a south-west
direction, crop out at intervals in the States of Virginia(?) and
North and South Carolina, and are always of very inconsiderable
breadth. They meet the Savannah river at Shell Bluff, fifteen
miles below Augusta, and appear at Silver Bluff and other
places, occupying a space of about forty miles, following the
course of the same river. According to Mr. Vanuxem, Shell
Bluff is about “ seventy feet high, formed of various beds of im-
pure carbonate of lime, of comminuted shells, and having at its
upper part the Ostrea gigantea? in a bed nearly six feet in
thickness.”

The eocene formation appears on the Oconee, below Mill-
edgeville, judging from a few fossils which have been sent from
that vicinity. The matrix is calcareous, whitish, and very fri-
able. We know nothing of its appearance on Ocmulgee and
Flint rivers, but it has been observed in various parts of Early
county, and it occurs at Fort Gaines on the Chattahooche, where
it constitutes a bluff from 150 to 200 feet in height, which has
a close resemblance to that at Claiborne. Its extent on the
river is about one mile.

In Georgia it is common to find the fossiliferous beds of the
eocene developed as a pure siliceous rock or Buhr stone. The
calcareous and other matter originally in the rock has all disap-
peared and been replaced by silica, preserving, however, the
casts of shells so perfectly that they may often be readily recog-
nised.

The eocene next appears in Wilcox county, Alabama, in the
state of a hard dark-coloured sandstone, containing the charac-
teristic shells, which are not mineralized at all, but are chalky
and imperfect. This formation only extends eight or nine miles
along the Alabama river. Claiborne Bluff is about one mile in
length : a similar bluff, of equal extent, occurs three miles below,
and about three or four miles south of this the deposit termi-
nates in a bluff of less elevation. Here the upper bed is charac-
terized by Scutella Lyelli (Conrad), the stratum being about
three feet in thickness, with a matrix of angular quartzose sand,
tinged by oxide of iron. Nearly the whole country in the vi-
cinity of Claiborne is secondary, the eocene having been traced
only about one mile east of the village, in the banks of a small

REPORT ON THE GEOLOGY OF NORTH AMERICA. 45

creek. The ridge dividing the waters of the Alabama and Tom-
beckbe, also secondary, is composed of cretaceous limestone, full
of Nummulites Mantelli (Morton). St. Stephens, on the
Tombeckbe, is situated on a bluff of the same, about one hundred
feet in height ; but the eocene appears a short distance north of
it, separated from the secondary by a strip of alluvial soil. Here,
however, the two upper strata only are visible, the superior bed
of limestone being but a few feet in thickness, whilst at Clai-
borne the corresponding one is about forty-five feet thick. The
arenaceous stratum is precisely similar to that of Claiborne, but
the fossils are not so well preserved, and are chalky and friable.
We know of no locality west of this, in Alabama or Mississippi,
where the eocene formation occurs; but on the Washita river,
near the town of Monroe, it is associated with the strata of the
cretaceous group, as Mr. Conrad ascertained by examination of
some fossils sent to the American Philosophical Society by Judge
Bry. The most abundant fossil beds of the eocene at this place
appears to be Corbula oniscus (Conrad), a shell very common
in the arenaceous strata at Claiborne.

No other information has been received of any other localities
of eocene deposits, but doubtless many will be discovered when
geology is pursued in a more systematic manner.

The following diagram will explain the order of succession
and the thickness of the strata in Claiborne Bluff, and to these
are added the two members of the cretaceous group, which oc-
cur in the vicinity. Those species are indicated which occur in
both formations ; they are highly interesting, as they furnish in-
dubitable evidence of the antiquity of these tertiary beds. Among
more than two hundred species of shells at Claiborne, there is
not one which is identical with a fossil of the pleiocene of this
county ; one only is even an analogue : not one can be referred
to any recent species, much less to a native of the coast of the
United States. One only, Lutraria papyrea (Conrad), is the
analogue to a species of our coast, LZ. canaliculata (Say), in its
general appearance, but is very remarkable in having the um-
bones turned in an opposite direction to those of the latter spe-
cies.

46 FOURTH REPORT—1834.

Diagram representing the Strata composing the Bluff at Claiborne.

Range of certain Spe-

Observations. Ges:

Thickness. |

1. Diluvium: 20 feet. |

Contains casts of a few species | Pecten calvatus.
occurring in the next stratum. | Scutella Lyelli.
The most characteristic fossil is
Scutella Lyelli. Some species
of Anthophyllum also occur.

' 2. Whitish friable | 45 feet.
limestone.

3. Ferruginous si- 6 feet.
liceous sand.

This portion is indurated, and the
fossils occur in casts,

14 feet. | Very friable, and contains about Cardita planicosta.
70 genera and 200 species of
shells: among them are Cardita
planicosta, Corbis lamellosa, Py-
ramidella terebellata, of the cal-
caire grossier; apparently no
species now existing, and none
identical with those of the plei-
ocene of Maryland.

4, Sand with acal- 3 feet.
careous cement.

Concretion of Ostrea selleformis.

eee . “ee eee

5. Softlead-colour-} 70 feet! Contain O. selleformis in abun- Plagiostoma dumo-
ed limestone. dance, but other fossils are rare; | sum. (Rare.)
some casts of univalves, a Pec-
ten, Anthophyllum, Flustra, Tur-
binolia, &c. Hardly a trace of
those species of the strata Nos.
3 and 6.

.
2
=
)
Ss

|

S
=

Ss

mQ
S
5
=]

Ss

3

=

o

6. Friable lead- | Thickness | Contains the same class of shells | Cardita planicosta.
coloured lime- | unknown. as stratum No. 3; the most cha-
stone. Level racteristic fossil Cardita plani-
of the river. costa, a shell very characteristic
of the eocene.

7. Very white fri- | Thickness |,Contains many casts of shells pe- | Scutella Lyelli.

able limestone. | unknown.

8. Blueish lime-
stone, alternat-
ing with friable
limestone, sili-
ceous sand, and
marl.

culiar to itself, and no other fos- | Plagiostoma dumo-

sil of the next deposit than
Gryphea Vomer. Characteristic
fossil, Nummulites Mantelli
(Morton).

The characteristic fossil is Ezxo-
gyra costata.

sum.
Pecten calvatus.
Ostrea selleformis.
Ostrea panda.
Ostrea cretacea.

Gryphea Vomer.

Ostrea panda.
Ostrea cretacea.
Gryphea Vomer,

near Claiborne.

C—O —O ee ee

Cretaceous Limestones,

REPORT ON THE GEOLOGY OF NORTH AMERICA. 47

“ If the deposit at Fort Washington, Maryland, be correctly
referred to the eocene, it must be a newer member of that for-
mation than Claiborne Bluff, in as much as the species are gene-
rally distinct, and no secondary fossil occurs amongst them.
The only recent species is Venus mercenaria (Lam.); and one
of the most characteristic shells, Ostrea compressirostra (Say),
is found in the middle tertiary on James river, Virginia. Per-
haps the deposit at Fort Washington will be found to class itself
in a more recent period than the eocene.”’

The total number of our eocene shells is about 210, nearly
all the species being from a single locality, namely, Claiborne,
Alabama. Other deposits, as that of St. Stephens on the Tom-
beckbe, present a large collection of species also, but they have
been found not to differ from the species at Claiborne.

It is remarkable enough that the older tertiary or eocene strata
of Alabama contain a profusion of specimens of four secondary
species, and yet possess not one species common with our
meiocene or middle tertiary. This is just the reverse of what
occurs among the corresponding formations in Europe, the eo-
cene and meiocene coalescing there by 42 common species
in 1238 of eocene, and the cretaceous and eocene strata having
nothing identical between them. From this, and the interesting
fact that our formations of this period contain not a single known
recent species, it seems pretty evident that our southern tertiary
strata assume an earlier place in the American eocene period
than the beds of the Paris basin occupy in the eocene period of
Kurope.

A fact equally as curious and unexpected is, that out of about
210 eocene fossils from Alabama, not more than six are disco-
vered to be common to the same period in Europe. They are,
- Corbis lamellosa, Zam.

. Cardita planicosta, Blainv.
. Bulimus terebellatus, Zam.
- Solarium patulum, Lam. (S. scrobiculatum, Conrad.)

canaliculatum, Lam. (S. ornatum, Lea.)
. Fistulana elongata, Desh.

& Crib oo to

It is not improbable, however, for reasons formerly advanced,
that the number of identical species will augment as our strata
and coast are more explored.

Several other species show a resemblance to fossils of. the
eocene beds of the Paris and London basins, though they are
obviously specifically different.

Connected with the foregoing comparisons among our tertiary
shells ought to be an inquiry into the number of shells which

frequent our coast, and their relations to the living species of

48 FOURTH REPORT—1834,

European seas. I have accordingly procured from my friend

Mr. Conrad a catalogue of the known marine shells inhabiting
our coast from Louisiana to Maine. This I should have been
glad to insert, as such a list has not before been made, but
for the length to which this Report has grown under my hands.
It is important to know, however, that the whole number of
marine species, excluding those of the West Indies and the
southern region of the Gulf of Mexico, does not much exceed
200. It is possible that by dredging our coast a large accession
to the list might accrue, yet it is apparent that the North Ame-
rican border of the Atlantic is not prolific in Testacea; and the
same seems to have been equally the fact during the several
tertiary periods.

Mr. Conrad and Dr. Morton have arranged with care the fol-
lowing useful table of recent species common to the European
and American coasts of the Atlantic.

1. Purpura Lapillus. 17. Thracia convexa.

2. Buccinum undatum. 18. Solecurtus fragilis.
3. Natica canrena. 19. Glycimeris siliqua.
4. Fusus islandicus. 20. Cardium islandicum.
5. Cyprina islandica. 21. — groenlandicum.
6. Saxicava rugosa. 22. Tellina punicea.

7. Lucina divaricata, 23. Venus mercenaria.
8. Pholas crispata. 24. Pecten islandicus.
9. — costata. 25. Strigilla carnaria.
10. Anomia Ephippium. 26. Balanus ovularis.
11. Solen ensis. 27. elongatus.
12. Mya arenaria. 28. Anatifera dentata.
13. Mytilus edulis. 29. ————— vitrea.
14. Modiola papuana. 30, ———— levis.
15. Mactra deaurata. 31. Teredo navalis.
16. Spirorbis nautiloides. 32. Serpula 3

The above list is likely to be sensibly augmented as fresh
species are discovered.

Here are 32 species in 200 (or one sixth) common to the two
sides of the Atlantic, while, as we have seen, in 195 fossils of
our middle tertiary there are but 6; and in 210 eocene fossils
also only 6 which inhabited both continents during those re-
moter eras. We shall presently see, that during a still earlier
period, that of the secondary cretaceous group, there was but a
single species in 102 described which had this wide dispersion
over both continents. Whether we shall discover a like dis-
similarity in the organic remains of yet older formations is a
question still to be solved, and it will require much preliminary
labour and research.

In concluding this survey of our tertiary formations, I ought

3

ee et ee oe

REPORT ON THE GEOLOGY OF NORTH AMERICA. 49

not te omit the curious and important fact, in harmony, I believe,
with all the views here advanced, that among the organic re-
mains of these deposits no traces of anything of freshwater or
terrestrial origin have ever been discovered.

Steps in the History of the Tertiary Formations of the United
States.—The whole of that large tract of the Atlantic plain and
the basin of the Mississippi now found to be occupied by the
tertiary and cretaceous formations, was originally laid down by
M’Clure as alluvial. The first approach to a just knowledge of
its geology commenced with the determination of about forty
species of fossil shells collected in Maryland by Mr. Finch.
Neither of these gentlemen, however, drew any geological in-
ferences from the organic remains they examined. Dr. Van
Ransaellar afterwards referred the deposits in question to the
age of the upper marine tertiary formation of England. Dr.
Morton supported the same opinion, pointing out several species
of fossil shells common to both sides of the Atlantic. After-
wards, in 1830, Mr. Conrad visited Maryland, discovered the
newer pleiocene at the mouth of the Potomac, which however he
did not pronounce to be tertiary, examined the fossils of the
formations which I have called middle tertiary or older pleiocene
and meiocene, and which he had previously named upper marine,
and also those of Fort Washington on the Potomac, which he
ventured to suggest were of the age of the London clay. In
1832, after a visit to Suffolk, James river, and York, to collect
tertiary shells, Mr. Conrad commenced his work on the fossil
shells of the tertiary formations of this country, retaining the
term ‘upper marine’ for the older pleiocene, using the title
‘middle tertiary’ for what he had shown to belong to the age
of the London clay, and which he now shows to be our eocene,
and applying the name ‘lower tertiary’ to a class of beds de-
scribed as the plastic clay formation, first by Mr. Finch, and
afterwards by Hitchcock.and Morton, and as subordinate to the
secondary by Vanuxem, but which I have recently shown, under
the appellation of ‘ ancient alluvium’, to be of much more recent
formation. Not long after, Mr. Conrad visited the eastern shore
of Maryland, where, on the Choptank, he procured many new
fossils, and made some interesting observations upon the beds
in which they occur. In 1833 he visited Alabama, where he
found the eocene very largely developed. His discoveries among
the organic remains of that quarter constitute the largest con~
tribution yet made to our tertiary geology. More recently, my
brother and myself have begun the development of the pleiocene
and meiocene in Virginia. In 1834, Mr. Lea published his
Contributions to American Geology, describing about twa

1834. E

50 FOURTH REPORT—1834.

hundred shells from the eocene of Alabama, the right of priority
to the discovery of many of which, however, Mr. Conrad and he
dispute.

Many scattered descriptions of parts of our tertiary field have
appeared from time to time in our Journals; but as they have
contained little or no scientific geology, I do not deem it neces-
sary here to mention them.

Cretaceous Formations.—The survey just given of our ter-
tiary formations is calculated, I think, to show how greatly
formations of the same or nearly the same period, occurring in
remote regions, may differ both in mineralogical characters and
in organic remains. The peculiarities which distinguish the
tertiary rocks of this country from those of Europe are clearly
traceable to the general dissimilarity in the physical structure
of the two continents, particularly in the almost total absence
of volcanic formations in the United States.

This country, for a long series of periods, seems to have suf-
fered less repeated and powerful convulsions than the opposite
shores of Europe; so that the same comparative exemption
from disturbances is as apparent in our secondary as I have al-
ready shown it to be in our tertiary periods. I have already
noticed the remarkably small number of species of fossils com-
mon to the tertiaries of the two continents, and I doubt if we
shall ultimately establish any closer identity in those of the
group now before us. While the cretaceous formations of EKu-
rope, from Ireland to Russia, are characterized throughout by
a numerous class of peculiar fossils, it is not a little simgular that
so few of the same species should present themselves in the
rocks of the corresponding period in America—not more than
two perhaps of the 108 which are known. This fact, in con-
junction with the no less striking one that we have yet disco-
vered no true chalk in North America, has made me hesitate to
apply without some qualification the received European names
to these formations. For our information regarding this group,
which embraces at present, perhaps, the most advanced portion
of our geology, we are mainly indebted to the writings and re-
searches of Dr. Samuel G. Morton, a new edition of whose work
having just appeared, I am enabled to present this branch of the
subject in its most complete state.

Dr. Merton entitles these newest of our secondary beds the
‘cretaceous group’, and regards them as divisible into two forma-
tions, the lowest of which he calls the ferruginous sand, and the
upper the calcareous strata. A very few years ago the group in
question was not known to extend beyond the peninsula of New
Jersey and a small part of Delaware. Subsequent discoveries,

REPORT ON THE GEOLOGY OF NORTH AMERICA. 51

however, mainly due to Mr. Conrad, have shown it to exist in
nearly all the Southern States ; and from specimens brought,
from time to time, from the interior of the continent, it would
appear to occur abundantly on the Missouri far across towards
the Rocky Mountains. From observations made by Professor
Hitchcock upon the clay and sand strata of Martha’s Vineyard,
there seems little reason to doubt its existence either beneath
that island or somewhere in the vicinity; and it is more than
probable, from appearances, that it underlies Long Island. “ It
is first unequivocally seen in New Jersey, whence it may be
traced locally through Delaware, Maryland, Virginia, North
and South Carolina, Georgia, Alabama, Mississippi, Tennessee,
Louisiana, Arkansas, and Missouri.” Dr. Morton remarks that
<‘ these various deposits, though seemingly insulated, are doubt-
less continuous, or nearly so, forming an irregular crescent nearly
three thousand miles in extent; and, what is very remarkable,
there is not only a generic accordance between the fossil shells
scattered through this vast tract, but, in by far the greater num-
ber of comparisons I have hitherto been able to make, the same
species of fossils are found throughout: thus, the Ammonites
placenta, Baculites ovatus, Gryphea Vomer, Ostrea_falcata,
Exogyra, &c., are found without a shadow of difference from
New Jersey to Louisiana, although some species have been found
in the latter state that have not been noticed in the former, and
vice versa.”

Calcareous Formations.—Beds of limestone and calcareous
sandstones form the upper strata of the secondary class through-
out the greater part of the marl region, as it is called, of New
Jersey. They always occur in thin, horizontal, and rubbly lay-
ers, either interstratified with blueish clay, or more commonly
resting immediately upon the friable sands and marls of the
formation beneath. The more calcareous beds are often highly
fossiliferous and partially crystalline, reminding me strongly in
their stratification and general appearance of some of the com-
pact and thin oolites of England. Dr. Morton describes these
calcareous strata as presenting the following varieties,—

An extremely friable mass, containing at least 37 per cent.
of lime, with a considerable proportion of iron, silex, &c. It
appears to be almost entirely composed of disintegrated zoo-
phytes—

«A yellowish or straw-coloured limestone, as hard as the car-
boniferous varieties, containing numerous organic remains,—

«A granular or subcrystalline limestone, intermediate in
structure between the former two, and including similar fos-
sils.

E 2

52 FOURTH REPORT—1834.

“¢ A white soft limestone, not harder than some coarse chalks,
which it much resembles, replete with fossils.

“ All these varieties occasionally contain infiltrations of sili-
ceous matter, and considerable masses of chert are sometimes
observed in them :. they also present some appearances of the
green grains so characteristic of the marls adjacent.”

These calcareous strata appear to be much less abundantly
distributed in New Jersey than the friable sands and marls upon
which they rest, for they have hitherto been found only at in-
terrupted intervals along the south-eastern border of the marl
region.

Limestone strata, however, seem to compose nearly the whole
of the cretaceous group in the Southern States, where they exist
on a scale of vast extent and thickness, rising into bold undu-
lating hills, which resemble in their features the surface of the
chalk in Europe, and seldom or never repose upon the sands
which form their substrata in New Jersey. In Alabama, Mr.
Conrad states this formation to constitute nearly the whole bed
of the country, the eocene occupying very limited patches in
the valleys of some of the rivers. Generally throughout Georgia
and the States south and west of it, these limestones are deve-
loped as two distinct strata. That which is universally superior
in position is a very white friable limestone, containing many
casts of shells peculiar to itself, while beneath this is a compact
blueish limestone, alternating with friable limestone and with
greenish siliceous sand, which is indurated into a rock, and con-
tains fossils and the peculiar green particles of silicate of iron.
The thickness of the lower deposit is stated to be about 300 feet
on the Alabama river. Its characteristic fossil is the Hxogyra
costata, the same shell which is so remarkably distinctive of the
marl beds in the ferruginous sand formation of New Jersey and
Delaware.

In some places, as in Wilcox county, Alabama, this lower
limestone is seen to rest upon a still inferior bed of a friable
greenish sandstone, containing fossils, especially the Ostrea fal-
cata, and also presenting, like the limestone above it, some of
the green grains everywhere characteristic of these cretaceous
formations.

Ferruginous Sands of New Jersey.—These arenaceous strata
compose tne chief mass of the secondary deposits in New Jersey,
being buc partially overlaid by the very thin calcareous strata
before mentioned. The mineralogical character of this deposit
is extremely variable, though the most usual constituents are
the following: Ist. Siliceous sand, mostly yellowish and ferru-
ginous, though sometimes of a green colour, answering to the

REPORT ON THE GEOLOGY OF NORTH AMERICA, 53

glauconie sableuse of Brongniart. These sands occasionally
occur in indurated strata containing fossils, when they form a
rock precisely the same in all respects as that which underlies
the limestone in Alabama. 2ndly. The peculiar greenish chlo-
ritic grains of the greensand formation of Europe. This mine-
ral exists generally in the shape of small grains of about the
size and form, and not unfrequently of the dark plumbago co-
lour, of gunpowder. Sometimes it has a rich warm green, but
more commonly an olive grey or dull blue, or even a very dark
chocolate colour.

The grains, although they contain about 50 per cent. of silica,
are not gritty, can be easily bruised between the teeth, and when
moistened some varieties can even be kneaded into a somewhat
plastic mass. A pile of this marl, as’ the granular mineral is
called by the inhabitants of New Jersey, after being somewhat
exposed to the air, frequently contracts a light grey hue, from
the exterior grains becoming coated with a white inflorescence,
which, from some observations I have made, is most probably
carbonate of lime. The following analysis by Mr. Seybert pre-
sents a fair average of the composition of the green grains :—
silica 49°83, alumina 6°00, magnesia 1°83, potash 10°12, prot-
oxide of iron 21°53, water 9°80; loss 0°89 = 100 grains. Other
analyses show occasionally as much as 5 per cent. of lime.

Mica in minute scales mingles not unfrequently in the less pure
varieties of the marl, which often contains more or less blue clay.

Once or twice, in examining a mass of these mineral grains,
I have detected numerous minute spicula of selenite. Almost
every large heap of the marl exhales a distinct odour, closely
resembling sulphur. These mineral grains occur in greater or
less proportion in-nearly all the strata, both arenaceous and
calcareous, of the formation ; but what is remarkable, they occur
alone, without any admixture of either sand or clay, in a homo-
geneous deposit, which seems to underlie nearly the whole secon-
dary tract of New Jersey, the stratum averaging ten or twelve
feet in thickness.

It is this stratum which is especially called the marl, rather
from its highly fertilizing action upon the soil than for any re-
semblance it has to marl strictly defined. I am not aware that
the green chloritic substance has been found composing any
extensive separate deposit, in such a state of entire purity, in any
other region. I have met with no description of any such stra-
tum out of New Jersey, either in Europe or among the creta-
ceous masses of our Southern States.

Beds of a dark blue tenacious clay, not unlike the gault of
England, occur sometimes associated with these beds of marl,

54. FOURTH REPORT —1834.

and sometimes the clay and marl are mingled. Beneath the
stratum of pure greensand or marl, a dark ferruginous sand-
stone, containing many of the same cretaceous fossils which
abound in the marl, has occasionally been reached. This, which
is the lowest bed of the group, exhibits a striking resemblance
to some of the ferruginous sandstone and conglomerate of the
lower greensand of England, and serves to indicate how similar
in general the chemical and mechanical circumstances appear to
have been during the same geological period on both sides of the
Atlantic.

Some localities in New Jersey present “beds of a siliceous
gravel, the pebbles varying in size from coarse sand to an inch
in diameter, and either loose, or cemented by brown oxide and
green phosphate of iron; the mass containing sometimes a pro-
fusion of fossils.” When it occurs, it usually rests above the
marl.

The last bed to be described is a sandstone deposit, resting
above all the deposits here enumerated. It occurs rarely 72 situ,
except as the top stratum on most of the detached ridges and out-
lying hills, but it is found, mingled with the general diluvium,
in worn and broken fragments over nearly all the denuded tracts.
It consists of sand and minute pebbles of quartz united by a
dark brown ferruginous cement, the whole rock having a very
perfect resemblance to the ferruginous conglomerate of the lower
greensand at Lockswell Heath in Wiltshire, England. It is
destitute, however, of fossiliferous impressions and casts. Some-
times it incloses a sensible quantity of the green grains, which,
however, have no effect in modifying its colour.

The sand composing the rock has often the character of a
coarse triturated beach sand; this is especially seen in the
quarries about four miles east of Burlington, where it occurs in
a regular horizontal bed many feet thick.

The diversified deposits of sand, marl, clay, sandstone, gravel,
&c., described above, assume a great variety of mineralogical
character, resulting from their various conditions of induration,
and their almost endless intermixture. The most fossiliferous
beds are the marl, and the marly sand which usually reposes im-
mediately upon it. In the marl the organic remains, consisting
of shells, zoophytes, and bones of Reptilia in great number, ap-
pear to have been preserved in a very perfect state from the
imperviousness of the greensand to water, which descends
with facility through the arenaceous beds above, but is invariably
arrested and thrown out along the upper surface of the marl.
The water percolating through the overlying marly sands has
effected a change upon the fossils, leaving them in this bed

REPORT ON THE GEOLOGY OF NORTH AMERICA. 55

either mere casts, or almost entirely obliterating them. In its
descent it is seen to become charged with ferruginous matter,
staining the fossils near the upper surface of the marl of a deep
brown colour, and coating whatever it overflows with a ferrugi-
nous incrustation.

I have nowhere seen a better example of the changes which
the infiltration of water can effect upon strata than may be wit-
nessed in these marl deposits of New Jersey, where every variety
of dissolving and cementing agency is in hourly operation upon
a large scale.

The mineral contents of these secondary strata of New Jersey
are, iron pyrites in profusion, lenzinite, peculiar spheroidal
masses of a dark green colour, carbonate and phosphate of lime
occasionally replacing the fossils in the form of casts. Lignite
is extremely abundant; it is found in the lower strata of the
Chesapeake and Delaware canal, in almost every variety from
charred wood to well-characterized jet.

The following appears to be the most usual order of the above-
described cretaceous strata in New Jersey :

1. Dark ferruginous sandstone and conglomerate, consisting
of limpid quartose sand, cemented by a dark brown ferruginous
paste; contains also some of the green grains.

_ 2. Rubbly calcareous stratum.

3. Arenaceous stratum, being chiefly a yellow sand, mingled
with a greater or less share of the green grains, or marl, and a
small quantity of clay. Sometimes thirty or forty feet thick.
Fossils usually in the state of casts.

4. Marl. A mass of little else than the chloritic grains, loose
and uncémented, 10 or 12 feet thick; full of fossils.

5. A red ferruginous sandstone, full of the impressions and
casts of shells ;—the particles being limpid quartz sand, and
some green grains.

With respect to the basis upon which the greensands of New
Jersey rest, nothing is known with certainty. Although a sec-
tion was made in cutting the Chesapeake and Delaware canal,
of nearly one hundred feet deep, the upper part through the
beds of the ancient alluvium, and the lower through those of the
cretaceous period, no older formation was reached. There seems
good’ reason to believe, however, from the nonappearance of
any formations along the Atlantic plain of an age correspond-
ing to the oolite and new red sandstone groups of Europe, that
the superior secondary beds repose, wherever they are developed
in the States north of Alabama, upon rocks of the primary class.
In Alabama, on the other hand, where the primary formations
do not extend, the probability is, that they rest upon rocks of

~

56 FOURTH REPORT—1834.

the age of the grauwacke and carboniferous formations, in as
much as the two have been seen by Mr. Conrad in the northern
part of that State almost in contact.

The whole of the above-described strata of North Jersey
might seem to merit the name of the greensand formation of
the United States, and I should propose applying this designa-
tion to the deposit, in lieu of that of ferruginous sand, which
was originally appropriated to it by Dr. Morten, were it not,
first, that the greensand being but little developed among the
beds of the same periods in the vast formations of the south,
the name would not be expressive of the prevailing character of
the group, except in the comparatively very limited area of
New Jersey; and secondly, that in the present early stage of
our discoveries, I am not entirely satisfied as to what are its
true relations to the European formations, and therefore hesitate
to appropriate to it the title of a formation with which there is
little prospect of its ever being shown to be strictly identical
either in mineral structure or organic contents.

The following more detailed description of these formations
in New Jersey is so well and succinctly given by Dr. Morton
in the recent edition of his Synopsis, that I shall extract the —
account almost entire.

“ Ferruginous Sand.—In New Jersey the tract which has
been known by the name of the marl district may be located as
follows: Draw two lines, one from Amboy to Trenton, the
other from Deal to Salem; let the Atlantic Ocean connect the
eastern, and the Delaware river the western points of these
lines: this irregular oblong tract incloses nearly the whole
marl deposits of New Jersey, so far, at least, as it has hitherto
been explored. There is reason, however, to suppose that it
occupies a much larger proportion of the peninsula, especially
in some places, overlaid by deep deposits of clay and sand, as
at Bordentown, White Hill, &c.

“Tn other localities, the older pleiocene (meiocene) overlies the
secondary, as is the case a few miles from Salem.

‘+ The fossils, as will hereafter be shown, are of a very strik-
ing character, occasionally grouped in vast numbers, and in
other instances almost wholly absent. The genera Gryphea,
Exogyra, and Belemnites are found abundantly throughout.”

“ Calcareous Strata.—The calcareous beds have been traced
as far south as Salem, and north to Vincent town, a tract of
nearly sixty miles in length, in a direction nearly parallel to the
Delaware river, and from seven to ten miles east of it. They
ave marked throughout by the several varieties of calcareous
rock already. described, and characterized by abundance of zo-

REPORT ON THE GEOLOGY OF NORTH AMERICA. 57

ophytes and Echini, and a few species of shells. These fossils,
with a few exceptions, have also been found in the arenaceous
bed; but many of the organic remains of the latter are not ob-
served in the limestone strata, which have not yielded any mul-
tilocular univalves, unless the doubtful fossil Belemnites? am-
biguus be of this character: neither do they contain Terebra-
tule nor Exogyre.”

Throughout the marl region of New Jersey, the traces of
an extensive denudation of the former surface are everywhere
conspicuous ; and, what is remarkable, the excavation has ex-
tended almost invariably down to the marl stratum, but hardly
in any case through it; the consequence of which is, that nearly
all the meadows and low grounds, which are very numerous,
expose this deposit immediately beneath the surface. These
depressions in the surface are always occupied by creeks and
streams, many of them receiving the tide, while the rest are
only a few feet above it. The uplifting force must therefore
have operated very equally over the whole region, as the strata
themselves sufficiently evince in their undisturbed features and
uniformly horizontal position, wherever they are seen, from
Salem to their termination on the shores of Amboy Bay. The
Neversink Hills, Mount Holly, and Mullica Hill, are low insu-
lated outlying hills, from 100 to 200 feet elevation, having,
like all the ridges in this region, their longer axes parallel with
the Delaware river, or in other words, with the longitudinal
diameter of the tract. These hills and ridges are almost inva-
tiably capped by a thin layer of the superficial ferruginous sand-
stone or conglomerate, which I have before stated to be the
general overlying rock of the marl deposits. The mineralogical
nature of this rock, its uniform parallelism to the other second-
ary beds wherever the surface has not sustained much denuda-
tion, its universal occurrence in scattered fragments throughout
all the intervening denuded tracts, and the quantity of the green
grains in it, are all reasons to induce me to think that this rock
is a true member, and the uppermost bed of the New Jersey
secondary group. The whole formation expands towards its
north-eastern extremity; in approaching which it seems like-
wise to increase regularly in elevation, attaining its greatest
height in the Neversink Hills. As to the various upheaving
and denuding actions which have brought this portion of New
Jersey to its present configuration, I am not: now prepared to
speculate, but shall merely in this place remark, that the valleys
adjoining the streams in this tract, like the valleys in the tertiary
districts further south, are never covered by the diluvium which
invests the general surface of the country. They are also of

58 FOURTH REPORT—1834.

such size and structure as to preclude the idea that the present
puny streams could have had any part in excavating them. They
must suggest to every geologist the conclusion that they have
been filled by the tide from one escarpment to the other, so
that each was a broad bay or short tidal river.

** Delaware. Ferruginous Sand.—In this State, the blue and
grey friable marls extend in the line of the Chesapeake and
Delaware canal, from St. George’s almost to the western lock.
St. George’s and its vicinity afford Gryphea and Exogyra in
great numbers, with Ostrea falcata, and some Belemnites.
The deep cut of the canal abounds in Ammonites, Baculites, and
Scaphites, without any of the fossils previously mentioned. This
locality consists of a series of pyritous sands and clays, of which
the shells are decomposed, leaving only the casts.”

** Maryland.—I am informed that the ferruginous sand oc-
curs below Annapolis in this state, at which place it is chiefly
characterized by dlcyonia. Mr. Conrad obtained at Fort Wash-
ington, on the Potomac, a solitary valve of Exogyra, indicating
the presence of this formation.”

* Virginia.—A writer in the dmerican Journal of Science
speaks of the occurrence of Belemnites and Gryphee on James
river, but gives no locality.”

** North Carolina. Ferruginous Sand.—This is well developed
at Ashwood, on Cape Fear river, where, according to the late
Mr. William Bertram, there are several beds of dark-coloured
marl containing Belemnites, shark’s teeth, pyritous lignite, &c.
&c. These strata are surmounted by the usual diluvial mass
to a depth of ten or twelve feet.’’ At Wilmington, North Caro-
lina, Mr. Conrad found the upper marine formation resting
immediately on secondary limestone precisely like that described
by Dr. Morton as occurring in New Jersey; it is in thin layers,
and reposes directly on a hard rock, which is the equivalent of
the ferruginous sand, as it abounds in Ewogyra costata and other
characteristic fossils. The calcareous strata are said by intel-
ligent persons here, to extend sixty miles up Cape Fear river,
and from its mouth coastwise as far north as Cape Hatteras.

* South Carolina.—The ferruginous sand formation occurs
near Effingham’s Mill, on Lynch’s Creek. The fossils are
chiefly Exogyra costata. Mar’s Bluff, on Pedee river, and Nel-
son’s Ferry on Santee river, afford the Belemnites americanus.

““Calcareous Strata.—The calcareous strata form an extensive
basin to the west of the city of Charleston: this limestone,
which is of the newest cretaceous formation, is mostly yellowish
white, friable, and replete with fossils, although the number
of species hitherto discovered is inconsiderable. Among these

REPORT ON THE GEOLOGY OF NORTH AMERICA. 59

the Ostrea cretacea and Ostrea panda occur also in the older
cretaceous deposits of Alabama.”’

“ Georgia.—The ferruginous sand appears to abound near
Sandersville in this State, whence I have received a number of
specimens of the Belemnites americanus.”

“ 4labama.—This State presents a vast deposit of both strata,
Mr. Conrad informs us that the counties of Pickens, Bibb,
Greene, Perry, Dallas, Marengo, Wilcox, Downes, Montgo-
mery, and parts of Clarke, Monroe,- and Conecute, are chiefly
composed of the older cretaceous strata. In Clarke county the
newer cretaceous rock predominates.

One of the localities most prolific of fossils is Prairie Bluff, in
Wilcox county. The following diagram will convey an idea of
its strata :

Feet 2. Loam.

2. Ferruginous sand, generally indurated, with Exogyra and Gryphea.
70. Same deposit, in a friable state, with abundance of Osirea falcata,
River bed.

<The older cretaceous rock constitutes the long and perpendi-
cular bluff at Demopolis, where it has been ascertained by boring
to be at least 500 feet thick. The more elevated bluff at Erie
is chiefly composed of the same rock, which is here very friable,
and weil characterized by fine specimens of Pecten quinque-
costatus, as well as abundance of Exogyra costata. A short di-
stance north of Erie, the cretaceous rocks terminate, following
the course of the Black Warrior ; and at Tuscaloosa the old red
sandstone with bituminous coal forms the bed of that river.
The Tombeckbe and most of its tributaries run entirely through
a region, the substratum of which is the cretaceous group, al-
though it is probable that their sources originate in the carbo-
niferous limestone, which may extend into the north-east section
of Mississippi. We learn from travellers that the cretaceous
rocks chiefly compose the countries of the Chickasaws and
Choctaws, and it is highly probable that nearly the whole State
of Mississippi is of the same formation. It is worthy of remark
that all the prairies of Alabama and Mississippi have a sub-
stratum of the older cretaceous rock. The newer cretaceous
strata prevail only in the southern portion of Alabama, are
never covered with a prairie soil, and have not been observed
north of the central parts of Clarke and Monroe counties.

<“ Nummulite Limestone.— After crossing the Alabama river
at Claiborne,’ says Mr. Conrad, ‘I travelled over a level allu-
vial country for two or three miles, when the surface became
broken by gravelly hills, covered by a pine forest. Near Suggs-

60 FOURTH REPORT—1834.

ville the hills are formed of the nummulite limestone, masses
of which are scattered in every direction: it is porous, and con-
tains spheroidal cavities, formed, no doubt, by the decomposi-
tion of organic remains, which leave loose casts that are easily
washed out by the rains. The most characteristic fossil at this
place is Ostrea panda.

‘ These limestone hills occur at intervals to the vicinity of
Jackson, on the Tombeckbe : on Basset’s Creek one of these hills
rises probably to a height of 300 feet above the water level. St.
Stephens is on a high bluff of this rock, which, wherever it
occurs, forms a very broken or undulating surface. A short
distance above the village, the bluff rises nearly perpen-
dicular from the river, and is about 100 feet high. Every-
where in the vicinity this limestone crops out on the summits
of the hills, and myriads of Nummulites Mantelli are scattered
over the surface of the decomposing rock. The Gryphea Vomer
is occasionally found among them, and the Ostrea panda is
abundant; but no other fossils occur excepting what are pe-
culiar to the limestone in question. On the hills the Pecten
Poulsoni is in abundance. Near low-water mark in the bluff
is a stratum of shells, consisting of Ostrea panda and Plagio-
stoma dumosum, both equally abundant. The surface of this
rock is in many places very hard and of a blueish colour, com-
pact and glittering when fractured, and is convertible into ex-
cellent lime.

“ Again it is often white and friable, and so much resembles
chalk that it is not surprising that it should have been mistaken
for the real chalk of commerce, from which it differs, in pos-
sessing a coarse and more granulated structure, and in contain-
ing a considerable proportion of argillaceous earth.”

“* Mississippi.—This State has an extensive marl tract in the
Chickasaw fields, near the borders of Tennessee.”

“© Tennessee.—The south-western portion of Tennessee re-
presents a continuation of the tract just mentioned, which takes
a westerly direction across the Mississippi River at the Chicka-
saw Bluffs.”

“ Louisiana.— Dr. Pitcher, in a recent letter, describes an
extensive deposit of ferruginous sand between Alexandria and
Natchitoches. Judge Bry has also noticed it near the township
of Wachita, on the Wachita River, where it is recognised by
Belemnites, Ammonites, and Gryphea.””

“ Arkansas.—Mr. Nuttall Jong ago found fossils of this for-
mation on the calcareous platform of Red River, above and
below the junction of the Kiameska; and Dr. Pitcher, of the

REPORT ON THE GEOLOGY OF NORTH AMERICA. 61

United States army, now at Fort Gibson, has obtained speci-
mens for my use, among which I readily identify the Gryphea
Vomer, Exogyra costata, &c.”

For the sake of exhibiting more fully the conditions of the
comparison between the formations of the superior secondary,
or cretaceous group of North America, and the equivalent group
in Europe, I shall present the following summary of the or-
ganic remains hitherto discovered in New Jersey, Delaware,
and Alabama.

SAURIA.

Mosasaurus.—Thought to be identical with the Mosasaurus of
Europe. New Jersey. (JMorton.)

Geosaurus.—Teeth and part of a jaw. New Jersey. (Dekay.)

Crocodile.—Teeth and other portions, indicating three species,
from the marl region. New Jersey.

Saurodon.—(Hays.) Portions of a jaw of an extinct animal,
the relations of which are not very clearly known. It is

_ thought to be analogous to the Saurians. (See dmerican
Philosophical Transactions.)

Great Saurian of Honfleur.?—1 have recently described two
vertebre from Jersey, and another from Alabama, which I
regard as either identical with, or very closely allied to, bones
figured by Cuvier from Honfleur, which he considers to ap-
proach nearer to the Plesiosauwrus than to any other genus.
(See Journ. of the Acad. Nat. Sci. of Philadelphia.)

TESTUDO.
Several bones from the marl deposit in New Jersey. (Morton.)
PIScEs.

Squalus.—Teeth and vertebre of several species of shark are
abundant in New Jersey and Alabama. (Morton.)
Sphyrena.—Some remains of this curious genus of fishes

occur in the blue marl of New Jersey. (Morton.)

AVES.
A solitary tibia of a bird of the genus Scolopax has been found
in the green marl in New Jersey. (Morton.)
TresTacena, &c.

The whole number of Testacea, Echinodermata, and Zo-
ophytes described by Dr. Morton in his Synopsis of the Organic
Remains of the Cretaceous Group of the United States, is 108
species. Of these, two belong to genera which are new, while
one species only, the Pecten quinquecostatus, is thought to be
common to the strata of both America and Europe.

This latter fact is certainly not a little remarkable, as it goes

62 FOURTH REPORT—1834.

to prove, contrary to general opinion, that the organic races of
remote regions differed as much during a part of the secondary
wera as during the more modern tertiary and recent periods.

It certainly seems difficult to explain, upon a distinction fre-
quently admitted between secondary and tertiary formations,—
namely, that the former are deep sea deposits, while the latter
have been formed in more confined and local basins,—why the
range of the species should have been actually less in the earlier
era than during the more modern dates of the tertiary. So far as
relates to the superior secondary formations of the United States,
I can perceive no evidence whatever that they were produced in
a deeper sea than the tertiary beds which succeeded them. The
secondary rocks have fully as much the appearance as the ter-
tiary of having been the bed of a shallow sea, like that which en-
circles our Atlantic coast with so wide a belt of soundings at the
present day. It must be borne in mind that all this portion of
North America is, and has been since the period of the coal forma-
tion, remarkably exempt from agitation by volcanic causes ; so
that the Atlantic plain offers no resemblance, in its universally
horizontal beds, to the broken, contorted, and denuded strata
which diversify the tertiary and secondary scenery of the western
regions of Europe. We are not likely ever to discover the
modern formations of this country resting among the Alleg-
hanies, as the cretaceous formations of Europe cap the Alps and
Apennines. For the same reason we may look in vain over
the whole of North America for a structure like that seen in
the Weald, or in other well-known disturbed districts along the
southern coast of. England. So many successive upheavings
and submersions as those shores have experienced, betoken the
long-continued activity of subterranean forces during a time
when the similar actions upon this side of North America were
almost dormant.

We are presented with no phenomena along the flat mono-
tonous coast of the United States, like those which lend so
high a charm to the geology and scenery of the cliff-lined coast
of the English Channel.

So small an amount of disturbing action ought to favour the
wide dispersion of the marine inhabitants of this region; and
we are therefore not to be astonished at seeing, as we do, many
of the New Jersey fossils in Alabama, or at finding, as we have
every reason to anticipate, the same group of species in the
strata upon the Missouri, 2000 miles west from the cretaceous
formations upon the Atlantic.

Similar reasons should lead us to look for a somewhat gra-
dual transition from the secondary to the tertiary series of

REPORT ON THE GEOLOGY OF NORTH AMERICA. 63

fossils ; and we do accordingly witness a manifest mingling of
the races of the two periods, as the following Table will make
apparent.

Tape showing the Species common to the Eocene and the
Upper Cretaceous Strata, and also the Species common to
the latter and the Lower Cretaceous Strata, in Alabama.

Formations. Range of Species.
Older tertiary, or Plagiostoma dumosum.
eocene. Ostrea selleeformis.

Pecten calvatus.
Scutella Lyelli.

Upper cretaceous Plagiostoma dumosum.
limestone. Ostrea sellzformis.

Pecten calvatus.

Scutella Lyelli.

Ostrea cretacea.

Ostrea panda.

Gryphza Vomer.

Lower cretaceous Ostrea cretacea.
limestone. Ostrea panda.
Gryphza Vomer.

oe RE OD

After carefully reviewing, in a tabular form, the relations
of the organic remains of our upper secondary group, I find
that if we adopt for our data the 102 known species of Testacea
and Echinodermata (rejecting the zoophytes), we perceive that
14 species are peculiar to the upper cretaceous formation of Ala-
bama, and that only two or three of its species are found in
the marl formation of New Jersey. We discover, however,
that a much larger number are common to the New Jersey
deposits, and the /ower limestone formation in Alabama.

Subtracting the above 14 species, in order to make the
comparison between the marl and this latter formation, we
have of the two classes mentioned 88 species. Out of these
88 species, 39 are peculiar to the marl formation of Jersey
and Delaware, 32 to the older calcareous strata, and 17
common to the two. These numbers show a want of identity
in the fossils of the two regions worthy of notice. The
two deposits, the ferruginous sand or marl of New Jersey, and
the inferior calcareous strata of the south, are regarded by
Dr. Morton as one formation. Though this opinion may
very possibly be correct, to establish it in the present state
of our data would be difficult. It is possible, indeed, that

64 FOURTH REPORT—1834.

while strata strictly synchronous are forming, as great a dif-
ference may prevail between two groups of species inhabit-
ing remote sections of the same coast as is observable in
comparing those of our two secondary deposits. But on the
Atlantic coast of North America such differences should be less
than upon almost any other, from the influence of the gulf-
stream, and other causes elsewhere stated.

We are therefore at present at a.loss to know how much of
this want of identity among the species we should ascribe to
disparity of age in the formations ; how much to difference in
the aqueous climate, and other circumstances controlling or-
ganic life.

Until a more extended list of fossils shall have been collected
for the comparison, and, above all, until our geologists shall
have examined more in detail the phenomena of the stratifi-
cation and structure of each region, I would recommend that
the question of their relative age be not anticipated by the ap-
plication of a common name, but that this point be left for a
season suh judice.

‘| think it not improbable that we shall ultimately regard the
upper limestone of our superior secondary group in Alabama as
a somewhat newer formation than the inferior calcareous strata
of the same state on the arenaceous marl deposit of New Jersey.
The occurrence of several of its fossils among the fossils of the
overlying eocene seems to indicate that its true position 7s near
the top of the secondary series.

Taken in their mineralogical relations, the marls and sands
of New Jersey would seem to occupy a place corresponding
nearest to the greensand formation of Europe ; and the lime-
stone strata of the south may be thought to harmonize imper-
fectly with the chalk, or a portion, perhaps, more truly with
the calcareous strata of Maestricht. Such certainly are their
rather obvious analogies mineralogically, but it is doubtful if
this ought to decide the question of their relative age. I would
not have it understood, therefore, that I view the American
upper secondary formations in any other light at present than
as the loose equivalents of the great cretaceous group of Kurope.
I have already mentioned the existence of but one, or at furthest
two species, to link the organic remains of these strata in the
two opposite continents.

Another striking peculiarity, which also marks the want of
that resemblance which we might expect, is the absence from
these formations of any true chalk deposit. There would ap-
pear to be no sufficient evidence of the existence of this remark-
able formation in any known region of North America. May

REPORT ON THE GEOLOGY OF NORTH AMERICA. 65

not this be another result of the long dormant state of the vol-
canic forces in this hemisphere? It has been a received doc-
trine, I believe, that igneous action has had much to do with
giving solubility to so vast a mass of silica and carbonate of
lime, which are regarded in the chalk formation as having been
produced rather in the state of a chemical precipitate than in
that of a mechanical sediment.

The following recapitulation of the leading facts and deduc-
tions brought forward in the foregoing survey of our superior
secondary formations, will assist in elucidating more clearly the
present state of this portion of our geology.

1. The deposits of New Jersey differ from those of the South-
ern States in being chiefly arenaceous, and in containing an
immense quantity of the pure chloritic mineral called green-
sand.

2. The organic remains hitherto discovered are nearly all,
with the exception of one or two species, peculiar to this con-
tinent.

3. The existence of great quantities of lignite, of the remains
of Scolopax,a shore bird, and the position of these beds in New
Jersey, contiguous to the primary boundary or ancient coast, all
indicate that they were deposited in a comparatively shallow
sea, analogous in position to the present extensive line of sound-
ings which skirts the coast.

The obvious shallowness of the portion of the secondary
ocean where these beds were formed, may perhaps help to ex-
plain the remarkable discordance alluded to between the Ame-
rican and European marine species of this period.

4. The calcareous masses of Alabama, at least the upper
beds, are probably different in age from the marls and arena-
ceous beds of New Jersey.

5. The marl formation of New Jersey is, perhaps, most nearly
represented by the European greensands. The limestone de-
posits of the South, on the other hand, resemble more the upper
members of the cretaceous group ; for example, the formation
of the plateau of Maestricht.

6. Thus far there is no evidence of the existence of true chalk
in North America. Genuine flints have not yet been found in
any bed.

7. Volcanic forces, during this period, seem to have been
nearly dormant, which may perhaps assist in accounting for
the absence of the chalk.

8. The want of accordance, both in organic remains and
mineral character, between these beds and the cretaceous group
of Europe; the difficulty of deciding their identity at present

1834. F

66 ‘FOURTH REPORT—1834.

for the want of a sufficient knowledge of the structure and su-
perposition of our formations; and, above all, the importance
of pursuing our geology free from the shackles of a nomencla~
ture originally adapted to another continent,—render it desi-
rable that we reject the terms in use, and appropriate to this
group of formations a name which shall be independent of old
associations, and yet express their position in the geological
series.

REPORT ON THE LAWS OF CONTAGION. 67.

Report on the State of our Knowledge of the Laws of Conta-
gion. By Wiitiam Henry, M.D., FR.S., &c., late Phy-
sician to the Manchester Royul Infirmary and Fever-Wards.

Tue subject of the following pages may perhaps appear, on first
view, not to fall within those boundaries, which have been as-
signed by the British Association to the field of its labours. I
hasten therefore to avow, at the outset, that it is no part of my
object to trespass upon the province of practical medicine, or to
treat the topic of contagion in any other light, than in that of a
purely philosophical question. Under this point of view, the in-
quiry is open to all, whose education has embraced the principles
of chemical and physical science, and who possess a general ac-
quaintance with the laws of the animal ceconomy. Much valu-
able information has indeed been already contributed to the
history of contagion by persons of this class ; among whom the
late John Howard, the enlightened and devoted philanthropist,
is an eminent example.

The establishment of sound conclusions on this subject is of
the highest importance, not only to individuals and to small
communities, but to the interests of whole nations. On such
principles alone can wise and salutary measures for obviating the
importation, and checking the spread, of contagious miladies,
be based ; and it is for want of them that legislators and execu-
tive governments have enforced regulations, some of which are
nugatory and absurd, and others positively mischievous. The
quarantine laws of every civilized country call, indeed, loudly
for revisal and remodelling ; and this can only be effected by
mutual agreement between different nations. In their present
state, those laws are both inadequate and oppressive. They lay
great stress upon observances that are of no value, and overlook
others that would be really efficacious. They impose grievous
restraints on personal freedom ; fetter our commerce; abridge
the demand for produce and manufactures ; and, by diminishing
employment over wide and populous districts, increase the suf-
ferings attendant on poverty, and give rise to inborn diseases,
even more formidable than those,} against which they are in-
tended to act as barriers.

An inquiry into the laws of contagion, it must however be ad-
mitted, is beset with many pressing difficulties. Our senses, the
great inlets of our knowledge of the material world, give us no
insight into the properties of this subtile agent ; nor do we ——

F2

68 FOURTH REPORT—1834.

any assistance from the most refined instruments, or from the
most delicate chemical tests. All that we perceive is a series of
events, often faintly marked, the connexion of which with each
other, even their order as to priority or sequence, can only be de-.
duced by processes of reasoning, that are open to more than usual
sources of fallacy. In no one instance is the effect of an external
agent upon living animals universally the same, but modified by
peculiarities of structure; by temperament, age, sex, and habit;
and above all, by those imperceptible changes to which the ner-
vous system is perpetually liable. Even our mental constitution
and habits,—the imagination, the affections, and the passions, —
exercise a powerful sway over our susceptibility to contagious
diseases ; and when such diseases do arise, often direct their
course and determine their issues. The phenomena of con-
tagion, moreover, are in many cases extremely complex, being
owing to a variety of causes which it is far from easy to ana-
lyse, and separately to weigh and appreciate. The omission, too,
of a single link in a chain of observations has frequently ren-
dered the whole series valueless, as data for accurate reasoning.

Difficult, however, as the investigation is in itself, it has been
rendered still more so by the manner and temper in which it has
been conducted. Every kind of error, that has obstructed the
progress of philosophy, may be exemplified from writers on this
subject. Observers have viewed phenomena with the desire of
establishing preconceived opinions. Facts have been described
in language so highly coloured, or so mingled with hypotheses,
that it is scarcely possible to discover its legitimate meaning.
All that favours one side of an argument has been strongly in-
sisted upon, while adverse evidence has been denied its due au-
thority; and the love of truth has been sacrificed to the anxiety
to baffle an adversary by ingenious sophistry. Such at least is
a faithful picture of the greater part of what has been written
on this subject in the spirit of controversy, excited, as it has
generally been, by intemperate discussions of the quarantine
laws. But it would be unjust not to except from this censure
a numerous class of writers on contagious diseases, who have
united an eminent capacity for observing and reasoning, with
perfect singleness of purpose in the pursuit of truth. The names
of Lind, Pringle, Cleghorn, Russell, Blane, Haygarth, Willan,
Currie, Ferriar, and of many others who might be enumerated,
are sufficient pledges for the accuracy of their reports of facts,
and for the soundness of their conclusions. It is to authorities of
this kind (in many instances confirmed, in a few corrected, by my
own observation,) that I am chiefly indebted for the materials of
the following pages, to which I have given the form of proposi-

alt

REPORT ON THE LAWS OF CONTAGION. 69

tions or ‘ general laws’; not that I consider them as entitled to
the weight of settled and invariable principles, but as open to be
modified and amended by the results of further experience.

Laws of Contagion.

I. The animal body, when the seat of certain morbid actions,
is known to elaborate within itself poisons, which are capable of
imparting to healthy individuals the same diseased condition,
and the power of generating similar poisons. These poisons
have been called conracions, from contingo, whence contactus ;
or INFECTIONS, from inficio. A distinction between these terms
has been attempted by some writers; but, avoiding etymolo-
gical discussions, I shall employ them in that general and po-
pular sense, which regards them as synonymous or nearly so.

_ II. It is consistent with the testimony of the best observers*,
that some contagions (chiefly those of typhus, and its congenera,)
may originate in the animal body when exposed to the action
of certain external causes. Among these causes are confinement
in overheated, close, and ill ventilated places; scanty or bad
food ; intemperance ; excessive fatigue; long exposure to cold
and moisture ; and, among mental influences, the whole train of
depressing passions and emotions. It was doubted, however,
by Mr. Howard+ whether any of these causes singly be ade-
quate to the production of contagious fever; but, though they
certainly operate more powerfully in conjunction, there is no
reason to disbelieve their separate efficiency. For, 1. The
crowding of numbers together without change of air has been
known: to occasion low fevers of the most formidable type. Out
of 146 persons, shut up during /a whole night of sultry weather
at Calcutta, in a wretched prison called the Black Hole, (a cube
with sides of only 18 feet,) not more than twenty-three survived,
of whom several were affected with low fevers of a typhoid cha-
racter, ending in carbuncular eruptions{. 2. Half a century has
scarcely elapsed since our prisons and hospitals were almost
constantly the seats of feversof the worst character§, generated
within their walls; and though banished from thence by an
improved system of construction and management, yet similar
fevers continue to originate in the crowded and squalid habita-
tions of the abject poor. 3. Even among the lower animals, si-
milar effects have been produced by the same causes. During a

- * Fordyce, Haygarth, Currie, Clark, Howard, Ferriar, Willan, &c.
+ On Lazarettos, 4to, p: 231.
t See Mr. Holwell’s interesting Narrative, Annual Register, 1758, p. 278.
§ Well described by Dr. Hunter, Medical Transactions, vol. iii, p. 345.

70 FOURTH REPORT—1834.

long voyage in a ship, the hold of which was densely crammed
with swine and sheep arranged on different sides of the vessel,
Dr. Fordyce observed that both those kinds of animals were at
different times attacked with contagious fevers, the symptoms
varying in the two species, and the disease not spreading from
the one species to the other, nor at all affecting the passengers
or crew*.

III. Independently of crowding and confinement, contagious
fevers do, however, occasionally arise without any immediate
prototype. The recollection of every medical practitioner must
furnish examples in which simple fevers, arising from cold and
other causes, in persons well fed and well clad, have by neglect
become contagious in their progress ; and if particular examples
of this kind are seldom recorded, it is because of the notoriety
of the general fact. An instance of typhus fever, thus origina-
ting spontaneously, is related to have happened to one of the
family of the late Dr. Jennery. z

1V. Diseases which break out in a scattered manner, where
the agency of contagion can neither be traced nor even suspected,
have been called sporadic (from cmopas, sparsus). This class
therefore includes all disorders that are not produced by conta-
gion; nor by accidents or obvious injuries; nor by any cause
affecting numbers of individuals in common.

V. There is an extensive class of acute diseases, which have
never yet been proved to arise sporadically. ‘These, from
the greater distinctness and more uniform succession of their
symptoms, have been considered as separate species. They
have therefore been termed SPECIFIC DISEASES, and their causes
SPECIFIC CONTAGIONS, OF SPECIFIC INFECTIONS. Such are
siphylis, measles, smallpox, cowpox, hooping-cough, scarla-
tina, and a few others.

VI. In a great proportion of instances, specific diseases may
be traced to communication, either by contact or near proxi-
mity, or intermediately, with some person suffering under the
same disease. But it frequently happens that the most search-
ing and diligent inquiry fails to trace a specific disease to its
source. Weare told that not one in twenty cases admitted imto
the Smallpox Hospital in London could be referred to any im-
mediate original{t. In a few instances, specific: diseases have
appeared within boundaries which might have been supposed to
have perfectly excluded them. In the Penitentiary at Millbank,
a prisoner was seized with smallpox, notwithstanding his ap-

* First Dissertation on Fever, p. 112.
| Baron’s Life of Jenner, p. 106,
t Dr. Gregory, Cholera Gazette, No. 2.

REPORT ON THE LAWS OF CONTAGION. 71

parently perfect insulation*. But in this and all similar cases,
the probability is much greater that a specific disease, like small-
pox, should have been received from a pre- existing source, than
that, contrary to all experience, the poison should have origin-
ated afresh. Many instances too are on record, in which the pene-
tration of contagious diseases, into situations supposed to be per-
fectly isolated, has been traced to intercourse, though forbidden
by the strictest rules, and even by menaced punishment. An-
other mode of conveying infection, beside that of direct commu-
nication, which will be pointed out in the sequel (§. xx11. e¢ seq.),
will account for a great part of the apparent exceptions.

VII. The conclusion that ‘ contagious diseases of a specific
kind never originate spontaneously,’ is strengthened by the fol-
lowing facts :—1. They have never been met with in any coun-
try, when visited for the first time, after having been previously
shut out from intercourse with the civilized world. 2. The hi-
storical eras may be fixed, when many of them first invaded the
countries where they now prevail, and the line of their march
may be distinctly traced outt. 3. Specific diseases have been
known to become extinct for a time in certain situations, and
their revival has been traced unequivocally to a foreign source.
Thus, the smallpox disappeared several times from the island
of Minorca, apparently from having already attacked all who
were liable to it. In one instance the interval extended to se-
venteen years; in another, after having been absent for three
years, its return was clearly traced to the crew of a ship of war
which had arrived from the Levant. Seven similar intermissions
of the same malady are recorded to have happened at Boston in
New England, in three only of which the channel of its reintro-
duction could be discovered. But these three instances render it
much more probable that the poison, causing the disease, should
in'the remaining four have been imported anew, than that it
should again have been generated. For though it cannot: be
denied that a poison may be again elaborated, by a concurrence
of the same circumstances which originally produced it, yet, in
assigning ‘causes, we must be guided by actual observations, and
= by possible contingencies f.

“+ F act communicated by Dr. Roget.

ve § Hawksworth’s Voyages, vol. iii. page 56. Siphylis was introduced by the
crews of Bougainville’s vessels into the Sandwich Islands, ii. 282. De Pauw,
Recherches Philosophiques sur les Américains, tom. i. Robertson’s History ‘y of
America, book iv. -
_-} The origin of new specific diseases is a topic too extensive to be entered
upon here. The reader is referred, therefore, to an excellent essay by Dr.
Ferriar, in the first volume of his Medical Histories and Reflections; to the
various publications of Dr. Jenner, J “as Hunter, Adams; &c.

2D

742 ‘FOURTH REPORT—1834.

VIII. It may be held as a general principle, that no specific
poison ever gives rise to any other contagious malady, than that
of which it is itself the product. The poison of smallpox never
occasions measles; nor that of measles smallpox. It must
however be acknowledged, that the sequent disease is seldom an
exact fac simile of the antecedent, but often differs from it, not
only in degree, but in the absence of one or more of the usual
phenomena, or in the addition of. others not commonly ob-
served. Scarlatina, it is well known, when communicated to
numbers from a common source, may affect some severely and
others slightly; and the general fever, the eruption, and the af-
rection of the fauces and throat, may exhibit almost infinite va-
rieties. In like manner, the mild and distinct smallpox has
often imparted a confluent and dangerous sorf; and the reverse.
It is needless to multiply examples, because inconstancy of
symptoms is. observable, not of contagious disorders only, but
of all others, whether acute or chronic. Our classifications and
nomenclatures of diseases are in fact founded, not on constant
and uniform characters, like those establishing the distinctions
of natural history, but on general features, which are liable to
be qualified by many exceptions, and which present almost in-
finite varieties of aspect.

IX. Of the nature of those processes, by which a simple fever
becomes contagious in its progress, we are totally ignorant. The
opinion that.a contagious poison is, in any case, generated bya
change in the animal fluids analogous to fermentation or to putre-
faction, (a change veiled by Sydenham under the phrase commo-
tio sanguinis), is inconsistent with general reasoning as well as
with observation. The tendency to putrescence in the solids or
fluids of the animal body, at temperatures favourable to that pro-~
cess in dead matter, is counteracted by the undefinable principle
of LIFE,so long as that principle retains sufficient energy. During
a contagious fever, none of those gases are necessarily evolved,
which are the constant products of animal putrefaction. A person
sick of typhus fever, enjoying all the advantages of cleanliness and
fresh air, and emitting no sensible odour, may yet impart a fatal
infection. An instance is on record, in which a person under such
circumstances was accompanied, for about half a mile, in a
coach, by four individuals, none of whom perceived the slightest
odour, but all caught the infection, and died in consequence*.
It may be remarked also, that the odours, which arise from per-
sons labouring under acute specific diseases, are not similar to
those of common putrefying matter, but are distinct and pe-

* Fordyce, Dissertation, p. 115.

REPORT ON THE LAWS OF CONTAGION. 73

euliar*. When we add to these arguments, that the perversion
of a vital process, such as that of secretion, occasions, in at
least one decided instance (rabies canina), the formation of a
poison, by an organ which commonly secerns a bland and harm-
less. fluid, the weight of evidence must be allowed greatly to
preponderate in favour of the opinion, that al/ morbid animal
poisons are the results of vital operations; and that chemical
changes, if concerned at all, are under the control of the vital
principle.

X. Among contagious poisons, there are some that exist in a
visible and tangible state, generally in that of liquids; others
are not at all perceptible by our senses, and are known to us
only by their effects. The liquid poisons are efficient, only when
applied beneath the cuticle, or to parts where the cuticle is very
thin, or to the surfaces of mucous membranes; and if imme-
diately and completely washed off, they inflict no injury. The
action of some of those poisons, “of siphylis for instance, does
not necessarily extend beyond the part to which they are ap-
plied. Other poisons, when inserted or inoculated, act locally
in the first instance, and afterwards give rise to general febrile
excitement, which is necessary to the formation of fresh poison
in the inoculated part, or in the system. After inoculation for
smallpox, the constitutional disturbance is generally well
marked ; in cowpox, often so faintly as to be scarcely distin-
guishable; yet even in the latter, some degree of general fever
seems: to be essential to the perfect state of the pustulet. It
is only at this period of full development (called the time of
maturation) that the fluid contents of the pustule, (which in
the cowpox is limpid, in smallpox purulent,) can be depended
upon for producing its appropriate effect. Before maturation,
the fluid is inert ; after that: period, it is sometimes effete, and
sometimes produces a modified diseaset. All attempts to ex-
cite smallpox or cowpox, by inoculating with the blood or

oo any other animal fluid, have been unsuccessful §.

XI. When the liquid animal poisons are kept in a moist state,
a temperatures not exceeding those of a warm atmosphere, they
undergo spontaneous changes which materially affect their spe-
cific properties. Variolous matter, thus negligently preserved,
has been known to produce a train of symptoms resembling
those of smallpox, but yet giving no security against the return of

> ‘The odours attending the plague, smallpox, and Asiatic cholera are in-
stances.

~ tJenner, Inquiry, &c:, 4to,, 1798, p. 71.

t Jenner’s Further: Oheroatann
_ § Darwin’s Zoonomia, § xxxiii. 2.

74 FOURTH REPORT—1834.

that disease*. But the liquid poisons, dried at the lowest tem-
perature adequate to that purpose, may be kept in close vessels
unimpaired for an indefinite time, and regain their infectious
properties when moistened with very little water. The mixture
of them, however, with a large proportion of water, renders them
inefficient. Dr. Darwin relates that, in some experiments by
Mr. Power, smallpox matter was found to be infectious after
diffusion through five times its quantity of water; but that its
dilution might be carried so far as to render it inertt.. This is
precisely analogous to what happens with common poisons,
the most virulent of which is disarmed of its noxious power,
when sufficiently diluted.

XII. Of the chemical constitution of the liquid contagious
poisons we are entirely ignorant; nor is it probable that the
knowledge, if we possessed it, would throw any light on their
mode of action. We are well acquainted with the composition
of many poisons (the prussic and arsenious acids, for example),
without at all understanding in what way they act so powerfully
upon the animal system.

XIII. Beside the liquid poisons, requiring contact for their
operation, there is another class which are independent of that
mode of communication, and are transmitted to small distances
through the atmosphere. Such are those of scarlatina, measles,
hooping-cough, chicken-poxt, &c. In a few instances diseases
imparted by contact are also caught by emanations or effluvia.
The smallpox, it is well known, may be propagated in both
ways; and the plague, certainly infectious at small distances,
has, of late years, been proved to be communicable by inocula-
tion with the matter of the glandular abscesses. Dr. White,
after two unsuccessful attempts to inoculate himself, caught the
plague by the third, and died in three days; and Dr. Valli, in
1803, fell a victim to a similarly rash experiment§.

* Jenner’s Further Observations, p. 19. + Zoonomia, u. s+

} Chicken-pox (varicella) is not inoculable. See Thomson’s History of
Smallpox, 8vo, p. 283.

§ See Sir Robert Wilson’s History of the Expedition to Egypt, p. 257;
Wittman’s Zravels in Turkey, pp. 516,518; and Granville in the Pamphleteer,
xxv. About the close of the sixteenth century a dispute arose, which has conti-
nued almost to the present day, whether the plague be a contagious disease or
not. Exclusion from that class has been extended also to typhus, yellow fever,
and searlatina. Indeed smallpox and measles are the only febrile maladies,
which are admitted by some of the opponents of contagion to be propagated by
‘aspecifie poison. All others, affecting numbers at one place and one time, have
been by them classed with epidemics. Itis needless to reply to the arguments
in favour of this doctrine, because they have been already refuted, in a man-
ner that should set the question at rest for ever, by Dr. Roget, in a Report
presented to Parliament in 1825. (See Parliamentary History and Review,

REPORT ON THE LAWS OF CONTAGION. 75

_ XIV. There is only one form in which ponderable matter is ca-
pable of being transmitted invisibly through the atmosphere, viz.
in that of elastic fluids, either permanent at common tempera-
tures, or existing as such within a certain range of temperature
and pressure. The former are called gases, the latter vapours ;
but the distinction is one of convenience only, and is not marked
by any weil defined boundaries. Contagious poisons, when dif-
fused through the atmosphere environing an animal body by
which they are generated, can exist only in the form of vapour.
Like all other vapours they must be governed, as respects their
degree of concentration in a given space, chiefly by the existing
atmospheric temperature.

XV. Of the chemical constitution of contagious emanations,
we are equally ignorant as of that of the liquid poisons. We
may conclude, however, that they consist of the commonly
known elements of animal matter, and that their diversities de-
pend, as in several well known instances of gaseous compounds,
on modifications of the proportions, or even of the molecular ar-
rangement of like proportions, of those elements. Thus, the very
same proportions of carbon and hydrogen are known to consti-
tute no less than three elastic fluids, each distinguished by pe-
culiar mechanical and chemical properties. From the little sta-
bility of composition of contagious poisons, evinced by their
being decomposed by temperatures not above 212° Fahr., as well
as, perhaps, by weak chemical agents, it appears that their ele-
ments are held together by very feeble affinities.

The notion, which appears to have originated with Kircher,
that contagious emanations are at all connected with the diffu-
sion of azmatcula or acari through the atmosphere, is purely
hypothetical. It has been defended, with a simgular want of
sound argument, by Nyander, in a dissertation which Linneus,
with equal want of judgment, has admitted into the fifth volume
of the Amenitates Academice. All that can be conceded in
favour of such an hypothesis, is, that the assigned cause is not
impossible; but not a single valid analogy has hitherto been
adyanced to confirm it. On the contrary, the opinion is at vari-
ance with all that is known of the diffusion of volatile contagions.
- XVI. We have no decisive evidence, through what channels
contagious emanations escape from the animal body. They may
issue from the whole of its surface ; but it is probable that they
transpire chiefly through that fine membrane, lining the air-
cells of the lungs, which the phenomena of respiration show to
8vo, published in 1826 by Longman and Co.) It is desirable that this valu-

able document should be made accessible to medical and general readers, by
republication in some less voluminous work. ;

76 FOURTH REPORT—15834.

be permeable, in both directions, by gaseous and vaporous fluids.
Through the same membrane, it is probable that contagious
emanations are chiefly admitted into the sanguiferous vessels.
Certain poisons (prussic acid, for instance,) have been traced by
their odour and chemical qualities into the blood*. But as we
have no tests of contagious poisons, it must remain conjectural
that they also are admitted into the blood-vessels, and circu-
late with that fluid. Even were that point established, it would
remain to be determined whether they act by producing che-
mical changes, or by at once affecting the nervous expansions,
and through them the great nervous centres.

XVII. The theory which has been framed to account for the
spread of contagious emanations, is founded on the same prin-
ciple as that assumed to explain the diffusion of aqueous and
other vapours, viz. that a chemical affinity exists between vapours
and atmospheric air, producing a kind of solaution analogous to
that of saline bodies in water. But this theory, though inge-
niously supportedt, is superseded by the more probable views of
Dr. Dalton, that in all mixtures of elastic fluids, whether gases
or vapours, with each other, chemical affinity has no share in
the effect, but that they maintain their state of equilibrium by
their respective elasticities alone{. In our atmosphere, for ex-
ample, the oxygen and nitrogen gases, which are its constant
ingredients, and the carbonic acid and aqueous vapour, which
vary a little in their proportions, are diffused through each other
by their respective elasticities, according to certain mechanical
laws. This is not the fit place for a detail of the evidences, on
which Dr. Dalton originally founded his opinion, nor of the ad-
ditional arguments deducible from the experiments of Mr. Gra-
ham§. It is sufficient to remark, that the probabilities are
greatly in favour of the new theory, which, by analogy, may be
extended to the contagious vapours. These effluvia, it is pro-
bable, are also diffused through the atmosphere, not by a pro-
cess of solution, but by the elasticities inherent in them as va-
pours; which elasticities are amenable only to variations of
temperature and pressure, and are totally independent of changes
in the proportions of the ingredients of the atmosphere.

XVIII. The activity of contagious emanations has been as-
certained to be confined within very moderate distances from

* Christison On Poisons, 8vo, 1829, p. 561. ‘‘ Poisons,” the same writer
observes, “‘ act on the mucous membrane of the pulmonary air-cells, with a ra-
pidity not surpassed by their direct introduction into a vein.” p. 22.

+ Chiefly by Dr. Haygarth. See his Inquiry, and also his Sketch.

+ Manchester Memoirs, vol. v. series i.

§ Transactions of the Ltoyal Society of Edinburgh, 1832.

REPORT ON THE LAWS OF CONTAGION, 77

their source. As respects the emanations of the plague, this
has been attested by several writers. 1. Dr. Russell, the author
of an excellent History of the Plague, preserved himself from
that disease, during a residence of several years at Aleppo, by
avoiding a nearer approach to the sick than four or five feet *.
Mr. Howard’s experience satisfied him that, in a still atmo-
sphere, twelve feet was a perfectly safe distancet. Assalini took
no other precaution, than to avoid inhaling the breath of persons
under that disease. 2. Smallpox infection was believed by Dr.
Haygarth, not only from his own experience but from a series
of experiments conducted by Dr. O’Ryan, of Lyons, not to ex-
tend beyond half a yard from the patient; and that of typhus
to be at least as limited{.. 3. Scarlatina, when introduced by
a new comer into a school, has generally been observed to spread
first to those associated in the same class, or otherwise, with the
infected person. On these facts is founded the salutary practice
of separating the sick from the healthy, on the first appearance
of a contagious malady; by which, in numberless instances, its
progress has been effectually stopped. It is a happy consequence,
also, of the limited extent of the infectious circle, that in a well
aired apartment, all those soothing and beneficial ministrations,
that do not require a very close approach to the sick, may be
performed with little if any danger to the attendants.

XIX. It is impossible, however, to assign, to any species of
contagious emanation, distinct and constant boundaries. Even in
each particular instance, these limits are necessarily liable to fre-
quent variation. For, 1. The more abundant the production of
contagious effluvia, the wider, ceteris paribus, will be the area
over which they will be diffused. 2. Imperfect ventilation ex-
tends the diameter of the infectious circle, and renders the poison
efficient at distances where, by due dilution with atmospheric
air, it would have been perfectly inert. Even the poisonous
gases prepared by chemical processes, it is well known, may, if
largely diluted with atmospheric air, be respired for a certain
time, without even the slightest injury. By availing ourselves
then of the law, which renders a certain state of concentration
essential to the activity of volatile contagions, it is easy to ob-
tain complete exemption from their deleterious effects. -4bun-
dant dilution, indeed, effected by well planned and assiduous
ventilation, is the most certain, if not the only, means of secu-
rity against contagious emanations, as they issue from the sick.

XX. The process.of spontaneous diffusion is too slow to ac-

* Russell On the Plague, 4to, 1791, p. 99.
+ On Lazarettos, p. 34; and Appendix to that work, p. 31.

t Inquiry, p. 97; and Sketch of a Plan to exterminate Smallpox, p. 237;
also Letter to Dr. Percival, p. 9.

78 FOURTH REPORT—1834.

count of itself for the spread of contagious emanations, and is ap-
plicable chiefly to a quiescent condition of the atmosphere. But
itis known that contagious poisons may be conveyed by the mo-
tion of masses of air, which mechanically sweep those effluvia
along with them, in a state consistent with their activity at mo-
derate distances. Of this it is sufficient to cite the following,
out of several similar examples :—1. At the Old Bailey Sessions
held in London in May 1750, the poison of jail-fever was wafted
by a current of air from a prisoner at the bar, in such a direc-
tion as to infect the lord mayor, two of the judges, several of the
barristers, and eight of the Middlesex jury, who all died in con-
sequence; but all the London jury, who sat out of the current,
escaped*. The black assizes at Exeter and Oxford were distin-
guished by similar catastrophes. 2. Even in the open atmo-
sphere, infection may be propagated to small distances. Dr.
Haygarth relates an instance, the circumstances of which were
strictly investigated, in which a child was infected with small-
pox, by passing another sick of that disease on the walls of the
city of Chester, where they are about a yard and a half broadf.
3. Howard and Russell agree, that, in the open air the contagion
of the plague lurks chiefiy to leeward; and they ascribe their own
exemption from its effects, when examining patients out of
doors, to the precaution of always standing to the windward of
the sick. Itis probable that currents of low degrees of force are
more dangerous vehicles of contagion than strong gales or
storms, since the latter must not only dilute the poisonous va-
pours below their point of activity, but rapidly carry them off,
so diluted, to a distance.

XXI. There is no reason to believe that the atmosphere of an
extensive district, or even of a city or open street, can be min-
gled with such a proportion of animal contagion, as to become
infectious tonumbers. The extreme mobility of the particles of
air among each other, and the almost unceasing variations of
temperature at the earth’s surface, occasion constant though
sometimes scarcely perceptible currents, which mingle any poi-
sonous vapours, that may be abroad, with the general atmospheric
mass. All experience, indeed, as well as general reasoning, is
against the wide diffusion of animal contagion in an active state.
The smallpox, we are assured by Dr. Haygarth, was never known
to spread from house to house, even in the most confined parts
of the city or suburbs of Chester, provided the rule of non-inter-
course with infected families was strictly observed {. The plague
does not cross the narrowest streets or alleys at Constantinople,

* Gentleman's Magazine, 1750. + Inquiry, pp. 97 and 100.
¢ Inquiry and Sketch of a Plan, &e. . .

REPORT ON THE LAWS OF CONTAGION. 79

though not ten feet wide ; and the English residents at that city
live in perfect security within the walls of the Pera, even while
the plague is raging around them*. Nor has it ever been known in
a single instance that fever hospitals, which were at first violently
opposed, and even indicted at law as dangerous nuisances, have
spread infection to a contiguous house. On the contrary, those
institutions have often cleared their immediate vicinity from
fever, by extinguishing solitary cases, which would otherwise
have multiplied rapidly in the midst of poverty and filth. It is
due to Dr. Haygarth to state, that in the year 1775, he first re-
commended the establishment of fever-wards as a practical in-
ference from the law of the limited sphere of contagion, of which
his inquiries had furnished many of the best illustrationst. His
proposal was soon afterwards sanctioned by Mr. Howard, who
had learned, by his own experience, the limited sphere of conta-
gion, and the great advantages of cleanliness and ventilation in
suppressing the fevers of jails and hospitals.

XXII. It has been long known that dry porous bodies, when
exposed to the atmosphere, increase in weight by absorbing
aqueous vapour. In like manner, there can be no doubt that
contagious vapours or emanations are absorbed by porous sub-
stances, and are again exhaled in an active state. Boyle remarked
that “‘ amber, musk, and civet perfume some bodies, though not
brought into contact with them, as the same determinate disease
is communicable to sound persons, not only by the immediate
contact of one who is infected, but without it{.’’ Contagious
emanations, thus imbibed by porous bodies, have received the
name of fomites§. They are capable of issuing forth with
unabated, and, it is even asserted on good authority, augmented
activity||. It is probable, therefore, that they are emitted in
a state of increased concentration, the porous body having
imbibed those vapours, in preference to the elastic fluids which
constitute the atmosphere. The propagation of contagious poi-
sons, in the state of fomites, is illustrated by the following among
numberless similar instances :—1. The contagion of the plague
of 1665 was conveyed in a box of clothes from London to Eyam,
a small village in Derbyshire, out of whose scanty population
it carried off two hundred and fifty persons**. 2. Smallpox
infection has been transmitted from London to Liverpool, by
means of new apparel made in a room where persons were sick

of that malady. 3. Dr. Hildebrant introduced the poison of scar-

* Clark’s Collection of Papers; and Macmichael, Pamphileteer, xxv.

+ Letter to Dr. Percival. t Boyle’s Works, by Shaw, 4to, vol. i.-

§ The plural of fomes, fuel. || Cullen, Lind, Campbell, Clark, &c.
** Mead, quoted by Howard On Lazarettos, p. 24.

80 FOURTH REPORT—1834.

latina into Podolia, a distance of several hundred miles, by a suit
of clothes, which he had worn at Vienna while attending persons
sick of that disease, and had laid by for several months*. 4. Of
the propagation of a fever of the typhoid character by fomites,
Sir John Pringle has recorded a striking example. A number
of old tents, which had been used as bedding by soldiers sick of
low fever, were, on the disembarkation of the troops at Ghent,
sent to be repaired. Twenty-three Flemish workmen were em-
ployed in the business, out of whom seventeen took the fever
and died, though they had no personal communication with
the troopst.

XXIII. It has not been ascertained how long fomites may
retain their activity; but there is reason to believe that in arti-
cles closely packed they may remain unaltered for several years.
Sennertus relates an instance in which, after a violent plague at
the city of Breslaw, in 1542, the pestilential contagion imbibed
by linen cloth which was kept folded up, issued forth fourteen
years afterwards in another city, and gave rise to a plague, which
caused great devastation{. In Dr. Parr’s Medical Dictionary
(art. ConTacron), a fact is stated, which, if well authenticated,
would indicate a much longer period for the durability of the con-
tagion of plague.

XXIV. The subject of fomites is well worthy of further in-
vestigation. Hitherto we have acquired no information respect-
ing the comparative powers of different porous bodies to absorb
contagion. Technical distinctions into ‘ more or less suscep-
tible articles”’ are, it is true, recognised by the quarantine laws ;
but they appear to be founded on loose analogies rather than on
careful observations. 1. It is extremely probable that different
porous bodies vary as to their powers of absorbing the same con-
tagious emanation, as we know that they differ in their powers
of imbibing a given elastic fluid. 2. In the same porous body,
it is quite conceivable also, that the power of absorbing different
contagions may vary with its states of dryness, temperature,
mechanical aggregation, and other circumstances. A _ light
and spongy material will probably be found a more active ab-
sorbent of contagion, than the same substance when rendered
dense by packing or by manufacturing operations. 3. A low
temperature of the porous body will probably cause it to ab-
sorb more contagion than an elevated one; the dryness of the
solid being supposed equal in both cases. When once im-
pregnated also, an increased temperature will probably act in

* Dict. de Médecine, Paris, 1822, art. Conracron.
+ Pringle On the Diseases of the Army, part I. ch. iii.
t Quoted by Boyle, Shaw's Abridgment, vol. i.

‘ Secte be

REPORT ON THE LAWS OF CONTAGION. 81

disengaging fomites, just as odours lurk unperceived in a garment
till the wearer enters a warm apartment. It is consistent with this
opinion, that clothes, which have been in contact with persons
suffering under typhus, sometimes infect those who wash them in
hot water. 4. The distance from the source of contagious effluvia,
at which porous bodies exert their absorbent power, is undeter-
mined. There is probably a distance at which their elasticity
may be so increased by dilution, as to be more than equivalent
to the absorbent power of the solid. The more highly the atmo-
sphere surrounding the sick is charged with contagious effluvia,
the more abundantly, may it be expected, that those effluvia will
be absorbed by solids. 5. The colours of porous bodies have been
shown, by the experiments of Dr. Stark, to exert a decided infiu-
ence over their absorption of odours, the dark colours being most
efficient. He has suggested, therefore, by a fair analogy, that
colour may modify also the absorption of contagious effluvia*.

XXV. Inseveral well authenticated instances, persons convey-
ing fomites with injurious and even fatal effects to others, havr
themselves escaped infection. Prisoners discharged in theie
usual health from Newgate, at the time when that jail was the
seat of a contagious fever, have infected the keepers of shops and

ublic-houses in the neighbourhood}. The same consequences
followed also the liberation of debtors from the jail at Gloucester.
In the memorable instance, too, already cited, the criminals who,
by the fomites lurking in their clothes, spread so fatal a pesti-
lence through the court of assize, were in their ordinary state
of health. Previous ablution of their bodies, and the putting on
clean and uninfected clothing, would doubtless have prevented
that extensive disaster.

XXVI.Of contagious diseases, some attack the same individual
repeatedly : such are siphilis, typhus, and the plague. The last-
mentioned, however, rarely attacks twice during one season ; for
out of 4400 cases, Dr. Russell observed reinfection to happen
within that interval in 28 only{. Other contagious maladis,
such as smallpox, cowpox, measles, hooping-cough, and scarla-
tina, especially the first four, occasion some change in the human
body, which, in a great majority of instances, secures it during
life from a return of the same disorder. Smallpox and cowpox
act as safeguards against each other; or when (failing this) the
one occurs in a person who has passed through the other, the

* Philosophical Transactions, 1832.

t Proceedings of the Board of Health at Manchester, p. 89——100. Clark’s
Collection of Papers, p. 10.

t Russell On the Plague, pp. 190, 305.

1834. G

82 FOURTH REPORT—1834.

second in order of sequence, whether smallpox or cowpox, as-
sumes a modified, and generally a much milder form*. There
can be little doubt, however, that those two diseases are essen-
tially the same. We have no evidence that any one specific dis-
ease affords a security against any other, which is distinguished
from it by marked characters and a different succession of sym-
ptoms. Neither smallpox nor cowpox gives a durable protection
against measles, hooping-cough, or scarlatina.

XXVII. It is in few instances only that two contagious poi-
sons act together upon the human body, producing simultane-
ously two distinct maladies. Scarlatina has been known to su-
pervene on typhus; and hence the precaution, in some fever
hospitals, of distinct wards for those two diseases. Smallpox
and cowpox may coexistt; so also may cowpox and measles{;
but smallpox and measles are incompatible at the same time.
Mr. Hunter inoculated for smallpox a child who, as afterwards
appeared, had been previously exposed to the infection of mea-
sles. The measles appeared and completed its course, before the
inoculation took effect, after which the smallpox began, and
passed through its usual stages§. Two similar instances are
related by Dr. Darwin, in both of which the smallpox, after
being suspended by the measles, exhibited an unusually mild
character ||.

XXVIII. A certain duration of exposure to contagious ema-
nations is essential to their full effect. This is precisely analo-
gous to what happens with respect to noxious gases, which may
be breathed in mixture with common air, for a few moments,
without injury. On this subject Dr. Haygarth’s observations
establish the conclusion, that air weakly impregnated with small-
pox or typhus contagion, may be breathed for a long time, and
air strongly charged with either, for a short time, with equal im-
punity§. Medical practitioners who have sustained no injury
from visits of ordinary dnration, have been infected after staying
unusually long in the apartments of persons suffering under con-
tagious fevers. A very dilute contagion, however, is known to
disorder the health, when it does not produce the whole of the
morbid phenomena in their usual degree and order of suc-
cession.

XXIX. We have no observations sufficiently correct to enable

* For the fact that cowpox is milder after smallpox, see Jenner’s Tract, 1798,

ws.
E + Adams On-Morbid Poisons, p. 398. t Jenner’s Tract, 1799, p. 63.
§ Hunter On the Blood, &c., Introduction. || Zoonomia, §. xxxiii.

§| Letter to Dr. Percival, p. 41.

REPORT ON THE LAWS OF CONTAGION. 83

us to pronounce, of any one disease, at what period it begins to
be infectious. Dr. Russell could not satisfy himself on this point
as to the plague*. The smallpox was believed by Dr. Hay-
garth not to be attended with contagious effluvia until after the
appearance of the eruption, and to diffuse its poison most abun-
dantly when the pustules had reached the period of maturationf.
Scarlatina is well known to spread by infection, before the cha-
racteristic eruption on the skin shows itself. It is probable
that the infectious period is not always the same for the same
disease, but bears some proportion to the violence of the fever,
and to other circumstances.

XXX. It has not yet been decided respecting any one disease,
when it ceases to be infectious. Dr. Russell could not determine
when convalescents from the plague ceased to infect others, nor
when the fluid contained in the glandular abscesses was no longer
dangerous. Persons, recovering from smallpox, infect others so
long as the smallest scab is visible on the skin. Convalescents
from scarlatina continue to impart that disease for ten days, or
longer, after all the symptoms have disappeared, and even after
the desquamation of the cuticle{. Hence, in part, the difficulty
of eradicating that malady from any situation where numbers are
subject to it. Asiatic cholera (a disease contagious under cer-
tain circumstances,) emits the most active poison in its advanced
stage, or rather in the state of consecutive fever. The infectious
property of the bodies of persons who have died of that disease,
though testified by several writers §, requires more accurate in-
vestigation. If the affirmative should be established, the effect
may still be imputed to a poison formed during life, and only
exhaled after death. Infection from bodies dead of plague is
denied by Howard, Desgenettes, and Wittman, and the infec-
tious power of yellow fever is said to terminate with life.

XXXI. It is seldom that the effects of contagious poisons, either
liquid or vaporous, manifest themselves immediately after being
received into the body. Well authenticated instances, however,
are not wanting of the speedy and decided operation of the effluvia
of plague, typhus, smallpox, &c., when in a concentrated form.
But in a great majority of cases, several days or weeks (in the
instance of hydrophobia, even months) have elapsed, before the
morbid phenomena have appeared. The period differs for dif-
ferent poisons, and is not always the same for the same poison.
It has been called the latent period of infection, the time of in-
cubation, &c. The following intervals, though collected from
the best sources, are to be considered merely as approximations,

* Russell, p. 304. + Inquiry, p. 53.

f Blackburn, pp. 5, 14, 36. § Becker On Cholera.
G 2

84 FOURTH REPORT—1834.

The plague, according to Dr. Russell, lies dormant about ten
days. Among those inhabitants of Aleppo, who shut themselves
up after having been previously in the way of being infected, no
instance occurred of the appearance of the malady after the ninth
or tenth day.

In anumber of cases of smallpox registered by Dr. Haygarth,
the eruptive fever began on some day between the sixth and
fourteenth after inoculation. Infection by emanations was not
apparent until about two days later*. The latent period of
chickenpox is, on an average, nine or ten dayst. The pustule
of cowpow is distinguishable about the third day after vaccina-
tion, and is perfected about the tenth{.

The contagion of measles lies dormant for ten or fourteen
days§. In scarlatina the interval does not exceed from two to
six days||. No attempts to inoculate either of those diseases
have yet succeeded].

Typhus makes its approaches in so gradual a manner, that it
is scarcely possible to mark distinctly its latent period. The ob-
servations of Dr. Haygarth indicate great latitude as to the time
during which typhus infection may remain dormant in the sy-
stem, viz. from less than ten days to even three or four weeks **.
The peculiar difficulty, however, of ascertaining the interval,
reduces greatly the value of the testimony of that careful ob-
server in this instance.

Asiatic cholera in Prussia, according to Dr. Becker, indicated
a latent period of from four to six days. Observations in this
country tend to establish a similar interval. Among all the ves-
sels that performed quaraniine at Standgate Creek, not one ex-
hibited an original case of cholera after the seventh daytt.

XXXII. When a number of persons are exposed, apparently
under precisely the same circumstances, to a contagious poison,
it seldom happens that all are affected by it. It is to individual
peculiarities influencing the state of the body at the time, that
we are to look for the causes of these varieties. The circum-
stances promoting the action of contagion have been classed to-
gether under the name of PREDISPOSING CAUSES, which agree
generally in lowering the strength of the body, or depressing
the energy of the mind. Among these may be reckoned fatigue,
want of sleep, extreme cold or heat, crowded or close places,
air tainted by putrefying substances, scanty or bad food, or oc-

* Inquiry. + Heberden, Comment. cap. 96. } Jenner.

§ Heberden, cap. 63. || Blackburn, p. 34

4] The experiments of Dr. Francis Home on the inoculation of measles, have
not, I believe, succeeded in other hands.

** Haygarth’s Letter to Dr. Percival. tt Cholera Gazette, No. 3.

Py

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et tS,

REPORT ON THE LAWS OF CONTAGION. 85

casional long fasts, excessive evacuations, and intemperate in-
dulgences of every sort. The depressing passions of fear, grief,
and anxiety are powerful auxiliaries of contagious poisons. So
also are religious creeds that lead to gloom or despondency, or
that inculcate observances requiring abstinence, or other prac-
tices unfavourable to health*. But of all predisposing causes,
poverty, with its attendant physical and moral evils, prepares
the greatest numbers of victims to contagious diseases, and most
widely spreads their destructive ravages.

It may be received, then, as a general conclusion, to be applied
to all our reasonings in special instances, that NO ONE MALADY
IS INVARIABLY AND UNDER ALL CIRCUMSTANCES CONTA-
Gious; in other words, that A CONTAGIOUS POISON IS SUCH
ONLY IN A LIMITED AND QUALIFIED SENSE.

XXXIII. Beside the general causes promoting or counteract-
ing the efficiency of contagious poisons, there are others of li-
mited operation, affecting chiefly certain individuals or classes of
men. 1. From peculiarities of structure or constitution not at
all understood, some persons enjoy an exemption from particu-
lar contagious diseases. Before the preventive powers of cow-
pox were known, it was not unusual to meet with instances in
which persons had entirely escaped the contagion of smallpox,
though repeatedly exposed to it, and even after being inoculated
with its virus. By diligent and careful inquiry, Dr. Haygarth
was led to estimate the proportion of persons who had reached
the middle age without taking the smallpox, at one in twenty-
three; and if it be admitted that in some instances the excep-
tions were only apparent, there will still remain a sufficient num-
ber to establish the general observation. During the prevalence
of typhus fever a similar proportion of persons has been esti-
mated to escapet. 2. Whole tribes and classes of men share in
liability to be infected by some diseases, and in the power of
resisting others. In hot climates the negro resists certain mor-
bid poisons which the European is unable to withstand. The
Bedouin Arabs, we are told, wear with impunity the cast-off
clothes of persons who have died of plague, without even at-
tempting to purify them{; but the soldiers of the French army
in Egypt fell victims to the same practice, which all the autho-
rity of the General-in-chief could not suppress§. 3. Different
periods of life modify the predisposition to infectious diseases.
Old persons enjoy an exemption from some contagions, but not

* Instance in Howard On Lazaretios, p. 25, and in the Doctrine of Fatalism.
. + Letter to Percival, pp. 32, 33. { Blane’s Medical Logic, p. 176, note.
§ Larry, Mémoires, p. 333.

86 FOURTH REPORT—1834.

from others; and infants at the breast show a remarkable in-
sensibility to some contagious maladies.

XXXIV. But of all the circumstances that impart the power of
resisting contagion, the most remarkable is the force of habit. In
this respect, as in many others, we find a close analogy hetween
ordinary and contagious poisons. Large doses of opium, any one
of which would be fatal to an uninitiated person, are habitually
swallowed several times daily, by those accustomed to its use.
In like manner, medical practitioners and the nurses of the sick
breathe, with impunity, contagious emanations to which they
are in the daily habit of being exposed. {[t was remarked by Dr.
Ferriar, that the keepers of lodging-houses in Manchester, of the
lowest and filthiest kind, from which typhus fever was seldom
absent, were untouched by the reeking poison, while the new-
comers kept up a constant succession of victims to its effects*.
To habit, also, the prisoners, who carried contagious poison in
their clothes into a court of justice, owed their own protection.

XXXV. The immunity acquired by habit is not, however, in
all cases either permanent or absolute. 1. Medical practitioners
and nurses, who have long discontinued their avocations, have
again become liable to be infected by febrile contagiont. 2. Per-
sons accustomed to breathe without injury atmospheres impreg-
nated to a certain extent with contagion, yield to the influence of
stronger doses. The late Dr. Clark, of Newcastle, though ren-
dered by constant habit proof against typhus contagion of com-
mon strength, caught that disease in a severe form by suddenly
undrawing the bed-curtains of a patient, and thus subjecting him-
self to a rush of air more than usually pestilentialf. 3. Persons,
who by habit are enabled to resist one kind of infection, do not
on that account enjoy a security against others. Of this, beside
many other instances, we have a striking illustration in the havoc,
which spread so rapidly among the medical practitioners in
Prussia, when Asiatic cholera first appeared in that country§.

XXXVI. There is reason to believe that contagious poisons
may be received into the system, and may remain in it some time
without manifesting their usual consequences, until some acci-
dental cause calls them into full action, and gives birth to the
usual train of symptoms. Circumstances of this kind have been
called CONCURRING or EXCITING CAUSES. Generally speaking,
they are identical with those which, acting upon the body before
exposure to contagion, are termed predisposing causes, the enu-

* Ferriar, Medical Histories, vol.i. p. 173.

+ Haygarth’s Letter, pp. 41, 44. ¢ Clark’s Collection of Papers.

§ Dr. Wagner's “Report of the Cholera in Prussia,” Bibl. Brit., No. 51.
p- 179; and Silliman’s American Journal, vol. xxy, p. 179,

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REPORT ON THE LAWS OF CONTAGION. 87

meration of which it is needless to repeat. Dr. Russell observed
the plague to “ hang ambiguously”’ for several days about per-
sons. In this state, and even when there was no such evidence
of being infected, an overheated bath or a sudden impression of
fear, especially when the disease itself was the object, has ex-
cited the lurking poison into activity*. The late Dr. Jenner,
after having been much exposed to typhus contagion, experi-
enced no ill effect until a long and fatiguing ride on horseback
in extremely cold weather proved an exciting cause of that ma-
lady, which he then underwent in its usual formt. Dr. Lind
relates, that out of a number of sailors, all of whom had been in
the way of febrile infection, a part only, who had been permit-
ted to go ashore, and while there had been engaged in a debauch,
fell sick of low fevers.

XXXVII. Among causes influencing the spread of contagious
diseases, climate has been reckoned, using that term in its en-
larged sense, and not merely as applied to geographical position.
There can be no doubt that climate modifies the predisposition
of the human body to receive infections. In addition to this ef-
fect, varieties of temperature, one of the principal elements
of climate, must necessarily affect the elasticity of vaporous con-
tagions, and consequently their diffusibilities. Certain poisons
(those perhaps which appear to have low vaporising points, as
smallpox, influenza, and Asiatic cholera,) exert their powers
alike in the hottest and coldest regions. Other poisons demand
a temperature not below 60° of Fahrenheit’s thermometer f.
Such is that of plague; while the yellow fever does not exist at
temperatures below 80°, and in North America has been checked
in its spread by a single frosty night. But an increase of tem-
perature above a certain point (90°) disarms the contagion of
plague of its power§; and typhus (or hospital) fever is unknown
in tropical regions||. Measles and scarlatina alsv are, in such
countries, of very rare occurrence. It is not improbable that
the highest temperatures observed in the atmosphere may ac-
tually destroy or decompose contagious poisons, as I have en-
deayoured to prove may be effected, so far as respects those of
cowpox and scarlatina, by temperatures not greatly exceeding
100° Fahr..

The influence of weather over the spread of contagion has not
been sufficiently examined. So far as respects predisposition, it

* Howard, p. 33 ; and Russell, p.303, + Baron’s Life of Jenner, p. 106,
t Blane, Med. Log., p. 178. § Russell, Antes, &c.

|| Dr. Hunter, Medical Transactions, vol. iii. p. 355.

] Phil. Mag. and Ann. of Philos., November 1831, and January 1832.

88 FOURTH REPORT—1834.

is probably considerable. Its direct effects upon contagious ef-
fluvia are perhaps resolvable into temperature alone.

XXXVIII. Such is a general outline of the facts that are
known respecting contagion, and of the conclusions to which
they lead. No one, however, who has inquired into this sub-
ject, can fail to be struck with the imperfections of our know-
ledge respecting it,—with the paucity of observations sufficiently
correct to serve as the foundations of general laws,—and with
the number of questions which still remain to be solved*. A long
course of diligent attention to phenomena, and a persevering
and rigid employment of the inductive logic, will doubtless sup-
ply many of these deficiencies. But there is another mode of in-
terrogating nature, hitherto little used in this department of phi-
losophical inquiry, that of EXPERIMENT, which, in the investi-
gations of physiology, has supplied materials for the happiest
generalizations. In exploring the nature and laws of contagion,
experiment has hitherto done very little; and extensive regions
of discovery remain to be entered upon, with the aid of that
powerful light. Difficulties and obstacles may be expected in
the research, but none that, either in number or amount, would
be insuperable by an ardent and inventive mind. Let it be re-
membered, as an incitement, that the inquiry has a higher ob-
ject than the gratification of speculative curiosity; that its ten-
dency to the advantage of mankind is direct and unquestion-
able ; and that its success would add another triumph to those,
which philosophy has already achieved over physical evil,—evil,
no doubt, permitted to exist, among other reasons, that it may be
overcome by the vigorous use of those intellectual powers and
faculties, with which man is so preeminently endowed.

XXXIX. This view of the subject of contagion would be in-
complete, without noticing a class of diseases, which have been
ascribed to causes of much more extensive operation, and are
generally contrasted with those of a contagious nature. They
are named ENDEMIC and EPIDEMIC DISEASESf. Both agree in
attacking a number of individuals; but the former are more li-
mited than the latter as to the extent of their diffusion, and may
often be traced to causes of local operation.

XL. 1. Acute or febrile ENDEMICs prevail, either constantly or
periodically, over tracts of country of considerable area; or they
may be confined to a province, a district, a city, or street, or a par-

* As these questions arise obviously out of the statements of what is already
known, it appears unnecessary to collect them into a series of ‘ gu@renda.’

+ Endemic, from ¢y in, and dyzos the people; Epidemic, from ews upon or
among, and the same substantive. The terms, therefore, differ only in the
greater comprehensiveness given by the latter preposition.

REPORT ON THE LAWS OF CONTAGION. 89

ticular part of a street ; or to a single building, as a house, a jail,
or a penitentiary. When spread over an extensive space, several
circumstances have been observed to be favourable to their pro-
duction. Such are, situation with respect to the level of the sea,
or that of the surrounding country; the form of the surface, as
inclined cr flat ; the nature of the soil or substrata; the quantity
and quality of the water; the state of drainage and cultivation ;
the vicinity of forests, and of swamps and marshes. From
marshy ground exhalations almost constantly ascend, which give
rise to fevers of a peculiar type, called remittents when they oc-
casionally abate, and intermittents when the symptoms are ab-
sent for distinct intervals. In no instance has a remittent or
intermittent been communicated from one individual to another;
but intermittents are apt to pass into remittents, and the latter
to assume a continued type, when they become decidedly con-
tagious.

2. Marshy exhalations, or miasms, as they may be exclusively
called (to distinguish them from animal contagions), are evolved
most abundantly in hot weather, from ground which is alter-
nately moist and dry, or barely covered with water; not if en-
tirely or constantly inundated. Either fresh or sea-water is ade-
quate to their production; but the alternation of the two has,
in certain situations, rendered miasms particularly virulent*.
Marshy ground, however, is not essential; for the half-dried
gravelly beds of rivers have been observed to occasion fevers of
a severe typet. In a few instances newly broken ground is re-
corded to have had the same effect{. In general, miasms occupy
low situations, insomuch that no greater an elevation than the
upper stories of a house has afforded protection against them.
But this is not universal, for they have been known to rise to
considerable heights§, though in such instances the form of the
ground indicates that they have been carried up inclined planes,
by winds blowing from the place of their production. The
sphere of the activity of marsh miasms surpasses beyond com-
parison that of animal contagions, obviously on account of the
infinitely greater quantity in which they are generated. The

* Giorgini (Mem. read to the Royal Academy of Sciences in July 1825)
gives a frightful picture of the disease called Malattie di Cattiva, caused by
marshes of this kind at the foot of the Ligurian Apennines.

+ Ferguson, Edinburgh Transactions, ix. 273.

+ A remarkable instance is related in one of the latter volumes of Silliman’s
American Journal.

_§ According to Monfalcon, (Hist. des Marais, Paris, 1824,) to 1400 or 1600
English feet. See also Ferguson, Joc. cit.

90 FOURTH REPORT—1834.

Pontine marshes, covering an area of eight leagues by two, have
spread their deleterious exhalations, in certain directions of the
wind, to the mouth of the Tiber. In the West Indies miasms
have affected the crews of vessels moored 1500 toises (3200
English yards) from the shore (Monfalcon) ; but this is pro-
bably much more than the usual distance.

3. The chemical properties of marsh miasms have been in-
vestigated by several writers, but with little other fruit than a
catalogue of negative qualities*. Miasms are not the mere pro-
ducts of putrefactiont, and have not necessarily a fetid odour.
Experiment has not demonstrated any departure, in the air over
marshes, from its usual proportions as to oxygen and azotic
gases. Neither carburetted, sulphuretted, or phosphuretted hy-
drogen, nor ammonia, has been detected in these exhalations.
The principle on which their peculiar agency depends, still re-
mains to be determined by experiment.

4. There are several points of analogy between the operation of
marsh miasms, and that of contagious poisons, upon the human
body. Both require a certain predisposition in the persons ex-
posed to them; and this susceptibility is imparted by the same
causes. The power of resisting miasms as well as contagions is
acquired by habit, at least to a certain extent. But no continu-
ance of usage ever protects persons, who are constantly exposed
to an atmosphere impregnated with exhalations constituting
malaria, from their pernicious effects. In some marshy coun-
tries, the perfect and vigorous human form is never seen; and
a race of men inhabit them who are alike destitute of physical
and mental energy, and who in middle life exhibit all the signs
of old age. Strangers arriving there are doomed to inevitable
destruction ; and all attempts to extend our geographical know-
ledge of such regions, however well concerted, have been baffled
by the overwhelming power of endemic pestilence.

XLI. Epipemics are much more widely diffused than ende-
mics ; so widely, indeed, that they have been imputed to certain
conditions of the atmosphere, called epidemic constitutions of the
air. 'To this term there can be no objection, provided it involve
no hypothesis as to causes. The only legitimate meaning of the
word epidemic is, an acute disease prevailing over the whole or
a large portion of a community, at seasons not in general

* The most elaborate and able work which I have seen on the subject, is the
Recherches Historiques, Chimiques, et Médicales sur l Air Marécageua, par
J. S. E. Julia. 8vo. Paris, 1823.

+ It has been suggested (Foreign Quarterly Review, No. XXI.) that miasms
are the products of plants of the genus Chara.

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REPORT ON THE LAWS OF CONTAGION. 91

marked by regular intervals, and not traced to local causes.
Though the works of writers on epidemics give us no insight
into their causes, yet they contain excellent descriptions of the
phenomena. Of these the following is a very general outline :

1. Epidemic diseases do not observe any fixed cycles, nor can
we at all anticipate the periods of their return. Some epidemics,
however, are disposed to prevail most at particular seasons of the
year, as in spring and autumn.

2. Epidemics seldom spread syddenly over very extensive re-
gions, but are observed to make a gradual, often a slow, progress
from one kingdom to another, from province to province, and
even from one locality to another not far remote. The influenza,
(a catarrh, accompanied with extreme debility,) which was epi-
demic in England in 1782, was noticed in the East Indies in
October and November 1781; at Moscow in December of the
same year; at St. Petersburgh in February 1782; in London it
was in full force in May; in France in June and July; and in
Italy in July and August. In the months of August and Sep-
tember it prevailed in Portugal and Spain*. The Asiatic cho-
lera, it is well known, made even a much more tardy progress
from the East westwards, and did not appear in England until
about fourteen years after it was known in British India.

3. On the first appearance of epidemics, they are not always
distinguished by those symptoms which mark them in subse-
quent periods. The plague, for instance, for the few weeks after
its first invasion, is frequently unaccompanied by bubos or car-
buncles, which are seldom wanting when it has raged long in any

lace.
: 4. When diseases of this kind attack any country, they con-
tinue to spread until they have reached the period of their most
general prevalence, called their acme, and then decline. These
periods of commencement, acme, and decline, seldom coincide for
the same epidemic at different places. Of three localities, for in-
stance, not far remote from each other, the plague, which visited_
England in 1666, was often observed at the same time to be first
showing itself in the one; to be at its height in another; and to
be on the wane in the third. The Asiatic cholera exhibited si-

_ -milar irregularities in this and other countries.

5. Epidemic diseases of the same name differ materially, both
as to degree and to symptoms, at different. visitations. The epi-
demic of one year may be almost universally a mild and tractable
disease, and that of another extremely severe and dangerous.

* See a general account of the Influenza, drawn up from the reports of me-

dical practitioners residing in various parts of England, in the Medical Com-
munications, vol. i.

92 FOURTH REPORT—1834.

6. All the predisposing causes enumerated as promoting the
spread of contagious diseases, contribute also to that of epidemics.
The latter, also, are propagated by some causes of general ope-
ration, such as a scanty harvest, or produce of bad quality; a
severe winter; a scarcity of fuel; an unusually crowded popu-
lation ; and, on some occasions, harassing and destructive wars.
In some instances, the path has been prepared for one epidemic
by the previous ravages of another: in other examples, the new
epidemic has acquired an ascendency over existing ones, and
has either modified or entirely extinguished them. In 1666 the
plague imparted much of its own form to a low petechial fe-
ver prevailing in London, but minor diseases for a while disap-
peared. Even the smallpox was superseded by the more power-
ful malady.

7- In what the influence of atmospheric changes in causing or
diffusing epidemics consists, it is impossible, in the present state
of our knowledge, toexplain. The most diligent observation has
not connected the prevalence of those maladies with any ascer-
tained condition, either physical or chemical, of the general atmo-
sphere. With respect to oxygen and nitrogen gases, which consti-
tute, at a mean of the barometer and thermometer, 984 in 100 of
its volume, an almost perfect uniformity is known to exist. In its
carbonic acid no variation has been discovered by experiment,
that can be supposed to affect the animal ceconomy. The varieties
of proportion in its aqueous vapour are, however, much greater ;
and when accompanied, as they often are, by sudden changes of
temperature, and by disturbances of the electrical equilibrium,
may interrupt the due performance of the bodily functions. But
other causes are necessary to account for those epidemics (cho-
lera, for instance,) which defy the influence of climate, seasons,
and of all changes that are objects of meteorological research. It
has been suggested that an ‘ epidemic constitution’ of the atmo-
sphere may depend on the presence of some substance alien to
its ordinary elements. No fact, however, confirms this suppo-
sition, if we except an observation of Dr. Prout, that at a period
coinciding with the appearance of cholera in London, the weight
of a given volume of air, making due corrections for differences
of pressure and temperature, seemed to rise to a small but sen-
sible amount above the usual standard, and continued above it
during six weeks*. This observation requires, however, to be
frequently and carefully repeated, and extended to other epide-
mics, as opportunities occur, before any sound conclusion can
be founded upon it.

8. Epidemics have been contrasted with contagious diseases,

* Bridgewater Treatise, p. 350.

ee ae

REPORT ON THE LAWS OF CONTAGION. 93

and supposed to form a distinct and separate class. But it must
not be forgotten that certain specific diseases, which by universal
consent are allowed to be contagious, at times prevail so gene-
rally as to be with propriety said to be epidemic. Such are the
smallpox, measles, scarlatina, and hooping-cough. But it is in-
conceivable that the specific poison, which in each of these in-
stances is the efficient cause of the disease, and which is the
undoubted product of vital operations, can be generated by any
€ corruption of air,’ or by any spontaneous changes in inanimate
matter. The only way in which a general condition of the atmo-
sphere can be supposed to influence the spread of specific dis-
eases is, either by rendering it a better vehicle of their respective
poisons, or by influencing the predisposition of the body to re-
ceive them. But if the view which has been taken (§. XVII.) of
the state in which contagions exist in the atmosphere be correct,
temperature alone, by modifying the elasticity of those vapours,
can affect their diffusion. It is well known, however, that ascer-
tainable conditions of the atmosphere, as to heat or cold, mois-
ture or dryness, and sudden transitions from the one state to its
opposite, produce in the animal body a predisposition to receive
contagion. ‘The same atmospheric variations may act also as
exciting causes, calling into action contagious poisons already
admitted into the system, but not yet manifested by the usual
phenomena; and when they operate on numbers, may occasion
those sudden and violent outbursts of epidemic diseases, of which
several examples are on record. Other general influences, in-
deed, may prove exciting causes of such outbursts. They have
followed closely, for example, upon seasons of riot and intem-
perance, and have spread rapidly in situations where those dis-
eases were previously confined to few and scattered individuals.

It is equally unfavourable to the progress of knowledge to over-
estimate what we know, as to shrink from the just appreciation
of difficulties opposed to its further advancement. On the sub-
ject of epidemics, they who have inquired the most will be most
ready to admit, that our actual knowledge is bounded by very

narrow limits. But we are not on that account to despair. The
_ genius of philosophers of our own age has unfolded the most

astonishing truths with respect to the subtile agents—light, heat,

electricity, and magnetism. Every new conquest, that science

achieves, enlarges our powers over nature ; and we are fully en-
titled by the past to hope, that the physical condition of man will
in future be progressively improved by his acquiring a command
over external agents, which have never yet been subjected to his
knowledge and control.

94:

FOURTH REPORT—1834.

INDEX TO THE SUBJECTS OF THE REPORT ON CONTAGION.

. The animal body generates morbid poisons.

. Causes which, acting on the body, produce those poisons.
. Originate independently of crowding and confinement.

. Sporapic diseases.

. Speciric diseases.

. Specific diseases not always traceable.

do not now originate.
produce only their own kind.

. Conversion of sporadic into specific diseases.
. Liquid contagious poisons.—INocuxation.

. Spontaneous changes in liquid poisons.

. Chemical nature of liquid poisons.

. Modes of communication of morbid poisons.

The volatile poisons are vapours, not gases.

. Their chemical constitution unknown.—Not animated.

Channels through which vaporous poisons issue.

. Emanations spread by pirrusion, not by affinity.
. Sphere of their activity limited.
. No constant boundaries assignable.

Emanations carried by currents.—Instances.

. The general atmosphere never infected.

. Porous bodies imbibe contagious vapours.—FomITEs.

. Fomites retain their properties durably.

. Modifications of the power of porous bodies to absorb fomites.
. Persons convey fomites without injury to themselves.

. Contagions acting once only, and oftener.

. Two contagions seldom act at once.

. Contagions require to be applied for a certain time.

. Period when diseases begin to be contagious. ~

cease to be contagious.

. Periods of latency or incnbation.
. Causes predisposing to the reception of contagion.

preventing infection.— Natural exemptions.

. Effect of naxit in protecting against infection.
. But habit not an invariable security.

. Exciting causes.

. Influence of climate and weather.

General Remarks.—Experimental inquiry proposed.

. Diseases commonly contrasted with the contagious.
. Enpemics; their production and causes; miasms.
. Eprpemics; their general phenomena, and dependence on atmo-

spheric changes.

=
he

=

A Spe eartiog

espe IAAL LEAR AEO

Report on Animal Physiology ; comprising a Review of the
Progress and Present State of Theory, and of our Informa-
tion respecting the Blood, and the Powers which circulate it.
By Witiram Crark, M.D., F.R.C. F.G.S. F.C.P.S.,
late Fellow of Trinity College, and Professor of Anatomy
in the University of Cambridge.

Tuat physiology should have been a science slow and uncertain
in its progress is scarcely surprising, when we consider how ex-
tensive are its objects. It pretends to nothing less than to explain
the phenomena of living nature,—the conditions upon which
they depend,—the laws by which they are governed. Hence, it
inquires not only into the relations of every component part of
an individual to each other and to the whole, but also, as far as

is possible, into the mutual relations of all living things to each

other, and to the rest of the world. In its useful application,
therefore, it is the foundation of agriculture, of husbandry, of
medicine. Intentions thus ample can only be fulfilled when all
particular sciences have gained their consummation. In earlier
geras it was included in those ideal assumptions, from which, as
from axioms, it was conceived that all the phenomena of nature
might be deduced ; whilst, in later times, the attempt to treat it
merely as a branch of the prevailing chemical or mechanical phi-
losophy of tke day favoured its advance in particular directions
only, and with very confined conceptions of its nature and extent;
as if any two of these sciences had yet ascertained, by means of
their own generalizations, a common proximate cause of their
phenomena ; or, as if particular sciences were something else
than constructions of the intellect to explain phenomena be-
tween which similarity has been established.

Physiology, as a positive science, can only be founded in obser-
vation and experiment; and the value of these depends, as in other
cases, not less upon the patience, the circumspection, the dispas-
sionate, and unprejudiced character of the observer than upon his
scientific and mental elevation. The multitude of physiological
experiments daily accumulated, tells us how easily they may be
made ; the facility with which one set of experiments so frequent-
ly supersedes a former, how difficult it is to make experiments of
real value. So numerous, indeed, are the conditions with which
every vital phenomenon is complicated, that the effect may really
be referrible to one or more of these entirely different from that
to which the experimenter has referred it. And, since it is im-

96 FOURTH REPORT—1834.

possible to abstract many of the conditions without destroying
life, innumerable modifications of the experiment can alone afford
an approximation to certainty. It is to experiments, in the hands
of able men, where the condition may be suppressed without de-
stroying life, that we owe a knowledge of various portions of the
nervous system which is no longer problematical*.

But we are not to expect too much from experiment. It may
point out the variety and the extent of vital reactions, but can
teach us (as Miller has pointed out,) nothing of the nature or
fundamental cause of these. For here the experiment is not like
one in chemistry, where, the known agent which excites reaction
in another unknown, entering as an element into the effect pro-
duced and ascertained, we are able to infer from what is known of
the nature of the one element that which was before unknown of
the nature of the other. But although we are thus necessarily re-
stricted to observation of the sequences of the phenomena, and
of the conditions under which they occur and are modified, yet we
cannot suppose that they are without some fundamental cause,
however it may be hidden from us. ‘“ Falso asseritur sensum
humanum esse mensuram rerum; quin contra omnes percep-
tiones, tam senstis, quam mentis, sunt ex analogid hominis, non
ex analogié universit.”’

When physiological facts have been accumulated by observa-
tion, extended through all living things, it is the object of the sci-
ence to determine the general relations which subsist amongst
them ; to ascertain what is common to these relations ; and thus,
ascending constantly to more comprehensive generalizations, to
arrive at that cause, least limited by conditions, which holds in-
ferior causes in subordination. And this is all that any experi-
mental science can pretend to.

On the contrary, however, the first philosophy of nature was
almost entirely deductive. The authors of it persuaded, as ra-
tional creatures, that all parts of the creation are but portions of
an harmonious whole—productions of the same intelligent first
eause—were led to speculate on the nature of that cause, and
thence deduced systems from assumed principles. The universal
appeared to express itself in particulars. It became the object of
philosophy to begin with the essence of things, and from it to de-
rive and explain all their phenomena. Such a philosophy, deal-
ing with abstractions, with primary essences of which the quali-
ties and their relations were necessarily hypothetical, could scarce-
ly have any application to a particular creation—to the world as it

_* Miiller, Introductory Essay to his Vergleichende Physiologie des Gesicht-
sinnes.
¢ Novum Organum, 41.

REPORT ON ANIMAL PHYSIOLOGY. 97

‘actually exists, however rigidly its conclusions might be de-

duced.
. A different procedure was forced upon physicians: their very of-
fice constrainedthem to observe the same vital phenomenon under
different circumstances,—to compare different phanomena,—to
separate what was common and essential from that which was
merely contingent and partial. Thus was established a new prin-
ciple of explanation, a principle little agreeing, perhaps, with
that deduced in the former way. As observation and experiment
extended the boundaries of this inductive knowledge of causes, it
continually encroached more and more upon the limits of hypo-
thetical belief. And the principles which were thus established,
being founded in realities, were really the expression of the phe-
nomena from which they were derived. It has been, however, by
slow and gradual steps that men have become willing to abstain
from assuming, as a privilege of the understanding, the power of
creating that spontaneously which can only be supplied by the long
and patient contemplation of nature. The two systems have been,
more or less, in conflict from the earliest to the present times.
Hippocrates was the first, whose writings have come down to
us, who made experience the interpreter of nature. He collected
a rich treasure of observations, the accumulated result of his own:
labours and of those of his family during 300 years. They relate
to the investigation of the effect of changes in the external con-
ditions of life,—viz. air, warmth, moisture, food,—upon its pha
nomena in man. On the other hand, his ideas of matter were
founded on the speculations of the Pythagorean school. He taught
that the four elements, variously combined, produced the four
eardinal humours, and these again the different organs of the body.
A vital principle, or principle of motion, $vo1s, or éevopydy, was:
superadded, depending upon innate heat, its manifestations
being excited by external things, &c. We see not how the theory;
has its application. Though Hippocrates did not, with many of
the ancients, suppose that the vital phenomena may be explained
by the properties of matter alone, but referred them to a prin-
ciple of life acting under external conditions ; yet his assumed.
properties of living matter are nowhere verified, nor the altera-.
tions asserted to be produced in such properties by alterations in,
the conditions of life in any way established.
- Aristotle far excelled his predecessors in extending natural sci-
ence by observation, and may be considered as the founder of com-
parative anatomy and zoology. His anatomical descriptions of
the elephant and the whale have merited the eulogy of Camper.,
Those portions of his works in which he records his observations
of the han faculties of animals, and compares.them with those
1834. H

98 FOURTH REPORT —1834.

of man, are particularly valuable. These faculties he connected
essentially with the organic body in which they are observed, and
referred them to a principle entirely different from what was then
considered elementary matter, which was the cause of all the phe-
nomena observed in living bodies, and which controlled the quali-
ties of matter to its own destined purposes. On observing the
modes in which this principle manifests itself, he distinguished
them logically as faculties : the nutritive, the sensitive, the cogi-
tative, the motive. He then reasons on these logical distinctions
as if they were real independent existences ; and inquires whether
they may not exist in different and in the same bodies as such.
His conclusion is, that three of these faculties are faculties of one
and the same real existence, wherever they are observed; but that
the fourth, the cogitative faculty, or rational soul, has a real and
independent existence. Thus he defined living bodies to be those
which contain within themselves the cause of their own motion.
But, far from supposing, as others have done, that this cause of
motion can move itself, he expressly states that the fundamental
causes of its motions are to be found elsewhere—in a supreme
animating principle, dois ; and asserted it to be the object of phi-
losophy to ascertain them. These delegated powers, he contends,
are four,—the material, the formal, the moving, the final causes.
The unknown cause of volition and the mental faculties he di-
stinguished as therational soul; theunknown cause that produces
and sustains the body, as the organic instrument of the former
to effect its manifestations, he called the sentient soul*. Thus,
primary matter (0a mpaty, an abstraction,) is utterly devoid of
properties; it receives from «ites all the shapes and powers
which it possesses: and so are formed the various bodies observ-
able in the universe with all their allotted qualities and energies.

If we reflect on this theory of Aristotle, and divest it of its
scholastic form, we shall find that its generalizations do not very
materially differ from those which have, after strict observation
in modern times, been presumed to be the most just, and are now
the axioms of physiological science : viz. peculiar vital properties
inherent in peculiar material textures :—a cause of living motions
operating, by means of these textures, according to fixed laws :
and phenomena so remarkably distinguished as to lead to their
division into those of animal and of organic life, and indicative of
powers directed to a purpose which, in the first instance, is the
preservation of the body in which they are manifested.

The Alexandrian school, founded by the Ptolemies, can scarcely
be considered as having made an adequate scientific return. What

* Barclay On Life and Organization.

h
&
&

REPORT ON ANIMAL PHYSIOLOGY. . 99

was valuable in the doctrines which they had adopted from the
philosophers of Greece and Ionia, became obscure and vitiated
by the additions of sophists ; and experiment and anatomy, which
had once been so highly cultivated by Erasistratus and Hero-
philus, fell nearly into disuse. I pass over, therefore, the vaunted
restoration of the Hippocratic method by Serapion, the pupil of
Herophilus, in the empiric school which rejected reasoning al-
together, and affected to rely upon experience. I pass over, also,
the methodic school of Asclepiades, which attributed, after De-
mocritus, all natural phenomena to the fortuitous concourse of
atoms, and the existence of bodies to the conjunction of these in
a certain form, and their functions to the mechanical aggregation
and separation of the same. Their doctrines have thrown no
light on our science. Each of these schools, and others like them,
had credit for a time; because, as they arose, men hoped to re-
pose in them, wearied with balancing theories which, being
founded on no extensive induction, and few just analogies, were
not unfrequently at the same time false generalizations of the
scanty instances upon which they were raised, and therefore ne-
cessarily contradictory.

~ The school founded by Galen has a just claim to the title of
eclectic, which had been assumed by another ; for its doctrines
were a mixture of the philosophy of Plato, of the physics and
logic of Aristotle, and of the practical knowledge of Hippocrates.
He perceived the objection to Aristotle’s theory, that it included
under a generic term the organic functions of plants and animals,
together with their manifestations of sense and intelligence*. He
therefore proposed another arrangement of the pheenomenaof life,
which deserves to be recorded, in as much as it contains the germ
of all those different classifications of the functions which have
prevailed in modern times. It is founded on the essential differ-
ence of the functions: first, that some are constantly necessary
for the support of life, and can never be suspended ; secondly,
that some are accompanied by consciousness, and are subject to
the will. The vital functions are those which cannot be inter-
rupted without inducing death; the animal, those which are
perceived, and for the most part voluntary; the natural, those
which proceed irresistibly, and without the consciousness of the
individual. These logical abstractions gave rise, unfortunately,
to the invention of corresponding imaginary principles as their
cause. Galen considered the heart, the liver, the brain to be re-
spectively the centres of these principles,—the occult powers dis-
tributing their influences in proportion to the elementary qualities
of those centres from which they emanated. He recognised, with

* Thompson's Life of Cullen.
H 2

100 FOURTH REPORT—1834.

Aristotle, four elements ; and deduced, from the various propor-
tions and mixtures of these, the elementary particles of the frame;
and secondary qualities, or cardinal humours founded on the
greater or less prevalence of one or other of the elementary princi-
ples, not greatly differing in this respect from Hippocrates. Ac-
cording to Galen, Nature presides over the vegetative, and the
soul over the voluntive faculties*.

The theory of Galen prevailed through many successive cen-
turies, its unestablished and mystical parts prevailing more or
less over those which were founded on experience and reason, ac-
cording to the degree of light and the character of the teachers
during that long lapse of time so much disfigured by ignorance
and barbarism.

At length, in the seventeenth century, Harvey’s great dis-
covery of the circulation of the blood gave an importance to ana-
tomical inquiry which the successive and valuable contributions
it had hitherto received had failed to bestow; whilst the dis-
coveries of Hooke and of Boyle in pneumatic chemistry turned
men’s minds to study with increased ardour the minute details
of every function, and to apply to the solution of the problem of
life all those analogies which the advance of science in every di-
rection so liberally afforded. Hence arose the chemical and the
mathematical schools of physiology to eminence. The first in-
cludes the names of Van Helmont, Sylvius, Willis, John Mayo,
Croone, Helvetius. Its insufficiency was exposed by Boerhaave,
Hoffmann, and Pitcairne, and in this country practically by Sy-
denham.

The mathematical school of physiology gained a better recep-
tion. Its doctrines, recommended by the prevalence of the atomic

theory of Descartes, gave the same direction to physiology and.

medicine with that in which science was principally advancing
under the auspices of the Florentine Academy. The philosophy
of Descartes appeared peculiarly applicable to such investiga-
tions, since no reason apparently could be assigned which should
render that law inapplicable to organic bodies which referred all
changes in matter generally to the figure and motion of the ulti-
mate particles of which they were composed+. Hence we find
the followers of Descartes representing in their works, the mathe-
matical forms of the ultimate particles, of which they supposed
the various organs to be composed, as figures for the application
of mathematical reasoning. The most distinguished disciple of
this school was Borelli. He united to all the anatomical infor-
mation of the day a depth of mathematical knowledge which
enabled him, in appearance, to apply its reasonings and its results

* Thompson’s Life of Cullen. + Ibid.

ENA heey ls

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a Bt gt ey ie

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Be SpN tary ere tet aed. ae

REPORT ON ANIMAL PHYSIOLOGY. 101

to explain the action of the organic machine. Thus, he submitted
muscular motion to calculation on the principle of the lever ; ex-
plained the action of the heart and the motion of the blood upon
hydraulic principles ; and accounted for the secretions from the
various diameters of the vessels. The proximate cause of mus-
cular motion he asserted to be the rush of nervous fluid from the
brain upon the muscular fibre. Bellini and Baglivi espoused the
same theory, and extended its application by their writings ; but,
as if internally aware of its insufficiency, and proving that they
merely reposed in it as that which was least objectionable, they
laboured to separate the theory from the practice of medicine.
Thus Baglivi was in practice a follower of Hippocrates and of
Sydenham. John Bernouilli was a celebrated disciple of this
school. He considered the elementary geometry of the Italians
insufficient in its application to the animal body, in as much as
this represents neither line nor plane either in itself or in the ulti-
mate particles into which it can be resolved. Hence he had re-
course to the calculus lately invented by Newton and Leibnitz
and the theory of curves. His theory of muscular motion gained
great celebrity, as well as his application of the analysis to de-
termine the decrement of the body in consequence of the various
transpirations and secretions. Another branch of the mathemati-
cal school was founded on the Newtonian theory of attraction,
and had for its supporters in this country Keill, the Robinsons,
Wintringham, and Meade.

These two schools, as may be well supposed, did not add very
much directly to the science as awhole. But they prepared the
way, each advancing it according to its own partial views. The
intimate structure of parts and their connexions were sedulously
ascertained by dissection, by the microscope, by chemical ana-
lysis, in order to ascertain the data upon which chemical or mathe-
matical constructions were to be founded. It is not unreasonable
to attribute to the hypothesis of Willis and of Vieussens, which
ascribed the cause of all the sympathies so remarkable in the
human body to the physical connexion of parts by means of
nerves, that great perfection which the anatomy of the nervous
system attained in their hands.

The followers of the chemical and mathematical schools either
overlooked the necessity of having recourse to a vital cause for
the operations they attempted to explain, or they had recourse to
an animating principle as presiding over them. Hence arose what
has been termed the dynamic school of physiology. In the sy-
stem of Stahl the soul not only produces and forms the body, but
maintains it in the performance of every voluntary and involun-
tary act. Those motions, even, which he allowed to exist exclu-

102 FOURTH REPORT—1834.

’ sive of muscular motion, which exemplify themselves by tension
and relaxation of parts,and which he called tonic motions,—those,
also, he considered as efiects of the soul’s power. He rejected
the laws of physics or of chemistry, and the discoveries of ana-
tomy, as throwing the least light upon the fundamental processes
by which the corporeal manifestations are effected. He considered
that the soul has no seat in any particular part, but that it is co-
extensive with the body itself; that it perceives in the organs of
sense, and operates in the muscles, independently of any con-
nexion with the brain*. Had not Stahl failed to distinguish be-
tween the manifestations of his vital principle, according as it ex-
emplifies itself by means of those organs which it has formed,—
had he not described it as the ‘ rational soul’,—his system, con-
firmed by subsequent observation as to the general principle
upon which it would then have been founded,—that of vital pro-
perties inherent in the several tissues,—could scarcely have been
justly censured. It was received in a modified form by many of
those whom I have instanced (from the mode in which they ap-
plied it,) as disciples of other schools. In England it was de-
fended by Bryan Robinson, and by Meade, and gained much ce-
lebrity from the writings of Hartley, whe assumed its principle
to explain the association of ideas. It was received also, ina
modified shape, by Sauvages in France, by Bonnet in Switzer-
land, by Whytt in Edinburgh. The latter taught that the soul
is the primary cause of all the motions observable in the body.
These he divided into three kinds : xatwral motions, depending
upona gentle and equable supply of nervous influence (of which
the tension of the sphincters and the general tone of parts are
instances), and proceeding without the interference of the will or
of stimuli; imvoluntary, excitable by stimuli affecting the
nerves (and he attempts to show that in all motions produced by
stimuli, whether in the muscles of the limbs or of the viscera,
the soul acts of necessity) ; voluntary motions, under the im-
mediate influence of the soult. James Johnstone greatly modi-
fied this theory in England, but his opinions were not received
by his own countrymen. He also assumed a vital principle to
effect that which mechanical or chemical powers were obviously
unable to perform. He placed its principal seat in the brain,
thence to be propagated by the nerves, and pointed out an office
of the ganglia, (which, indeed, had been hinted at by Winslow
and Le Cat,) viz., that those organs which are supplied with
nerves from the ganglia, performing their motions independently
of the will, the ganglia are to be considered as so many subsidiary
* Thompson, op. cit,
¢ Whytt On the Vital and Involuntary Motions, passim.

REPORT ON ANIMAL PHYSIOLOGY. 103

brains, which continually supply the parts to which they distri-
bute their nerves with new impulses and fresh activity, without
immediate dependence upon the brain; and that hence it is that
the vital functions are continued when the influence of the brain
is suspended, as in sleep or in paralysis. These opinions of
Johnstone respecting the ganglia were the foundation of that
hypothesis respecting the nerves of organic life which represents
them as a system distinct from the cerebral system, and which,
more fully developed by Bichat and by Reil, was pretty gene-
rally received from them by physiologists, until it was shaken by
the discoveries of Le Gallois and Wilson Philip.

In this way the physical and dynamic theories came to be vari-
ously combined. ‘Their union gained its greatest perfection under
Hoffmann and under Boerhaave, who insisted upon the primary
influence of the nervous system in modifying and regulating all
the organic functions, whether performed chemically or mechani-
cally. Thus nervous power came to be considered as nearly
equivalent to the anima of Stahl. But Stahl’s system was not
improved by the change; for nervous power, a manifestation of
the vital energy by means of the peculiar matter of the nervous
system which that energy has produced, and of which it is buta
partial effect, cannot properly represent the entire cause; and it
affords no explanation of the organic life of plants. For the vital
principle appears to manifest its several activities by means of
the organs which it has produced: and Stahl’s error seems to
have been that he connected its vegetative processes, which are
defined and necessitated, with those of consciousness and intel-
ligence, which are free, and are developed only with the develop-
ment of the brain*.

The age of Haller, at which we have at length arrived, is the
epoch from which modern physiology takes its date. The great.
object which that eminent person endeavoured to achieve, was
to discover, experimentally, the conditions and the laws which
govern those vital phenomena which the assumption neither of
mechanical nor of chemical forces had been able to explain, and
thus to render physiology as certain as other physical sciences.
For this purpose he excluded those metaphysical subtleties by
which his predecessors had so frequently veiled ignorance ; ex-
eluded also mathematical and chemical science in all cases in
which it was impossible to ascertain the elements upon which
their application could be founded. He was willing, as he him-
self says, to confess himself ignorant of the manner in which the
soul and body are united, and was content to proceed no further
than those discoverable laws which the Creator has himself pre-

* Miller, Physiologie.

104 FOURTH REPORT—1834.

scribed, without inventing others unwarranted by experience.
On this principle he instituted innumerable experiments to dis-
cover and illustrate the properties of the vital powers. He proved
the existence of a property in muscle, to which he restricted the
term irritability, which is only called into action by means of
stimuli, which affects a much greater vivacity of motion than
mere elasticity (a property of dead matter), the motions also con-
sisting in alternate oscillations, with contraction, swelling, and
wrinkling of the fibre, followed by extension, relaxation, and
elongation of the same. He further attributed to the muscles a
nervous power, distributed to them from the brain by means of
the nerves, as a necessary condition of their irritability *, but
which entirely differs from it. He concluded from his experi-
ments, as detailed in his earlier works, that the following parts
are destitute of irritability and nervous power : periosteum, peri~
toneum, pleura, ligament, tendon, articular capsules, the cornea,
pareuchyma of the viscera. In these tissues he admitted a force
analogous to elasticity, inherent in their organic texture, which
solicits them to contract slowly when divided, when exposed to
cold, &c., and which only abandons them when entirely disorgan-
ized. He proved that sensibility is inherent in the nerves, but
that they are destitute of irritability. He denied that irritability
could be imparted to the muscles by the nerves, because, seeing
that a nerve, on being stimulated, may excite motion in the muscle
to which it passes, but offers not the slightest motion itself, it is
impossible to suppose they should be the source of that to others
which they never possessed themselves ; and, more particularly,
because he perceived that the excitement of muscles through
nerves is a phenomenon not true of all, but only of certain,
muscles.

He proved, universally, that irritability resides in all parts
that have muscular fibre; that this power differs in intensity
and permanence in various parts; that these qualities are most
observable in the heart, more in the left ventricle than the
right ; that next in order come the intestines, the diaphragm,
the voluntary muscles. From reiterated experiments he concluded
that the heart and other involuntary muscles are not excited to
contract by stimulating the nerves with which they are supplied,
but that they require specific stimuli: thus, that the blood is to
the heart what the will is to the voluntary muscles.

* Si insita eorum organorum (cordis, intestinorum, &c.) vis est, cur accipiunt
nervos? Ii, nisi voluntatis imperia afferunt, quid agunt aliud? Primé sensum
afferunt, qui absque nervis nullus est. Adferunt etiam ex cerebro efficacia im-
peria non voluntatis, sed legum, corpori animato scriptarum, quz volunt, ad
certos stimulos certos nasci motus.— Lem. Phys., tom. iv. p. 516.

REPORT ON ANIMAL PHYSIOLOGY. 105

In this way Haller restricted the vital powers to {wo,—sensi-
bility and irritability ; the one exhibited in the brain and nerves,
the other in muscular fibre. His doctrine was vehemently op-
posed by Whytt, De Haen, Verschuir; and strenuously de-
fended by himself, by Bonnet, and by Fontana. It was seen that
many parts in the animal body to which neither irritability nor
sensibility, in Haller’s sense, could be extended, were not the
less alive. Thus during the numerous controversies which arose,
errors on each side were detected ; materials for more extended
views were accumulated ; experiments were infinitely multiplied
and eagerly criticised ; the excitability of various tissues, to which
Haller had denied that quality, because he had not called it into
action by an appropriate stimulus, was established on the one
hand, and on the other the mistake of confounding nervous in-
fluence with sensibility was made apparent. Thus the more pro-
bable it became that irritability and innervation are separate
powers, so didit follow the more necessarily that every different
part should have its own excitability and its own degree of ner-
vous power, and hence its own peculiar mode of life,—an opi-
nion announced by Bordeu, Barthez, Blumenbach *. Indepen-
dently of these expressions of vital energy in the various tissues,
these physiologists admitted a fundamental power, which they
termed vitality, or vis vite, of which the different degrees of
excitability and sensibility were considered merely as modes,
according to the organs in which the vital energy operated. But
the analogies thus assumed between the phenomena were not
established by any proof ; the modifications of the original power
were not accounted for ; and this theory, apparently philosophic,
has no firm foundation when its partisans would represent vitality,
or oxygen, or galvanism, as a proximate cause of all the pheno-
‘mena, residing in living matter as gravity does in dead +.

It might have been foreseen that this analytical mode of treat-
ing the living organism,—this isolation of powers which had

* They had all been anticipated by F. Glisson, who was President of the
College of Physicians in 1677: but the opinions of a man who was a century in
advance of the age in which he lived, and which were obscured by metaphysical
subtleties and scholastic language, had no great influence, upon those who were
engaged with mathematical or chemical theories of life. He proved the exist-
ence of a peculiar quality of living bodies, which he first named Inritability;
distinguished between perception and sensation, and adduced as instances of
perception without sensation, the contraction under stimulation of the heart and
muscles when separated from the body ; insisted that it was only through this
natural perception and sensation, and not immediately, that the animal appetite
on the one hand, and the mind on the other, puts the innate irritability in action,
and so produces all motions, which are either natural and vital, or sensitive.

¢ Thompson’s Life of Cullen.

106 FOURTH REPORT—1834.

been intended by their concurrent acts to produce the pheno-
mena of life, could scarcely lead to the detection of that control-
ing cause which forced the whole to conspire to a common pur-
pose. It became necessary, therefore, to consider the subject
under a different aspect; to contemplate living bodies in their
approach towards the possession of those powers which they ex-
hibit when their organs are formed. The means for this have
been supplied by the labours, extended through a long lapse of
time, of Harvey, of Malpighi, of the Hunters, of G. F. Wolff, of
Prevost and Dumas, of Meckel, of Tiedemann, of Serres, of G.
de St. Hilaire, of Von Baer. ‘The earliest examinations that
can be made of plants or of animals present them as consisting
of a minute globule of fluid, or a minute disc of slightly albumi-
nous matter, 7. e. under aspects not distinguishable in different
future genera or species, as to properties or forms of their matter,
by any tests which we possess. In the near neighbourhood of
the disc is placed, in animals, a quantity of nutritive substance,
by means of which it is destined to work. The effects, when
produced, are definite for each species ; but none occur except
under certain conditions. These conditions are, a due degree of
moisture, of air, and of, warmth. When they are supplied, the
disc is capable of being affected by the matter in its neighbour-
hood. It is excited, and it reacts. 'The consequence of the re-
action is a gradual expansion of the disc to surround the nutrient
matter; a separation of it into different superposed portions,
which come into view; and a gradual appropriation of the nutrient
matter. Upon the external portion of the disc, the first trace of
the nervous system is observed ; upon the internal portion, that
of the intestinal canal ; intermediate between them, that of the
vascular system. Though at first simple, these objects have still
a certain magnitude, and the later more complex formations are
seen to arise from them as if by vegetation. ‘‘ The first trace of
the nervous system is not merely that of the spinal cord or of
the ganglionic string, but is the potential whole of that system,
of the brain and all its appendages. The first trace of the ab-
dominal canal is not merely the rudiment of that canal, but of
the whole glandular apparatus also, which may be seen gradually
to spring from it*.’’ And thus is the observed process of de-
velopment altogether contradictory of the theory of Haller and
of Bonnet, which represents each organ as absolutely existing in
the germ, though in a miniature form. That the power which
effects these changes, and thus controls the disposition of or-
ganic molecules, resides in the disc, is ascertained from the facts,

* Miiller’s Physiology, vol. i. p. 20 et seq.

Ares Samy eT

vaindihhibeldaieiide ade d co

REPORT ON ANIMAL PHYSIOLOGY. 107

that ova belonging to species the most different, are all develop-
ed, according to their kinds, under similar external conditions,
and that ova of the same species are true to their kinds under
conditions which are not absolutely the same for any two indi-
viduals. If we call this power vitality with modern writers, or
the anima with Stahl, these words can teach us nothing physio-
logically, unless we ascertain the law by which it operates : how-
ever we may see that the final cause of its operation is plainly
in every case the production of those numerous bodies, definite
with respect to families, genera, and species, which it develops

- for its own manifestations in each. Our eyes inform us that

these bodies arise by means of the assimilative process, and
that the original power exhibits its faculties by means of the
organs which it has produced through this process. Our idea
then of the vital power is this,—that it is connected with the
matter of the germ in the act of its formation, and resides in it
as the potential whole, or sufficient cause, of the entire future
organism ; that in consequence of the excitability of the or-
ganic matter of the germ, imparted to it in the same act of its
formation, the expansion of the germ into portions or members
occurs by the visible process of assimilation or nutrition, each
portion thus acquiring its own excitability and its own reactive
energy, which are but partial manifestations of the original
power ; and that in proportion as each part is developed, new
internal conditions are introduced, in consequence of the new
formation, which affect all that previously existed, by modifying
the assimilative process in all. The phases of this process are
strictly defined for each species, and the subsidiary means neces-
sary for the purposed effect—as in the various forms of the re-
spiratory organ in the foetal state of the same individual to mode-
tate the condition of external air—are amongst the most beau-
tiful instances of provision for a definite end.

This formative act, this process of assimilation or nutrition,
which is thus performed by animals and plants, and has a rela-
tion not only to the present, but the future also, appears to be
the determination of a power acting according to Reason ; and
hence it must have been that Stahl referred it to the rational soul.
But, seeing that reason cannot exist without consciousness,—
a faculty which manifests itself only by means of the brain, a
late product of this very power by the act of assimilation,—seeing
also that the effect may be modified, within limits, (as in cases
of monstrosity,) when the conditions are altered, we rather con-
clude with Harvey that it proceeds from a power acting accord-
ing to fixed laws. ‘ Vegetative operationes potiis videntur

108 FOURTH REPORT—1834.

arte, electione et providentid institui, quam anime rationalis
mentisve actiones ; idque etiam in homine perfectissimo.”

A peculiar matter is necessary for the manifestation of vital
phenomena : this matter is called organic. It is not the cause
of life, but rather is its act; a production by means of the assi-
milative process, for the exemplification of the allotted faculties.
The faculty is imperfectly manifested if the organ be imper-
fectly formed: the organ ons its energy both vary with varia-
tions in the nutritive process *

Hence those subordinate expr essions of vital force, called ne7-
vous power, force of secretion, &c., cannot be considered as di-
stinct and independent powers. They are produced, or evidenced,
with their organs, by the force of assimilation, and are main-
tained by the same. They depend upon it for their manifesta-
tion and their due support f.

Vital power imparted to organic matter (which is itself the
product of the living power of the parents), and exemplifying
its faculties by means of the organs which it has developed
through the force of nutrition, seems to be the last step to which
observation and induction has hitherto led us. The induction is
verified by observation. Ifthe assimilative process be altered in
any organ, the expression of excitability and of vital reaction
peculiar to that organ is altered in the same degree.

There are then in living bodies as many species of excitability
and as many modes of reaction as there are tissues. Every one
of these has its own mode of both, which is called into action
by its own appropriate stimuli. ‘¢ Whatever these stimuli may
be,—whether external, as air, light, warmth, food; or internal
stimuli, the blood, nervous influence, the secreted humours,—
each organ reacts in its own peculiar manner; a manner which
supposes a peculiar organic power imparted to it in the act of
its formation by the process of nutrition, and sustained by the
samef.” ‘* The stimulus may be that of a chemical, or mechani-
eal, er organic substance ; the reaction, however, is always vital,
and indicates the existence of an organic force, of which it is the
effect. The physical properties of the one are in some sort in a
constant conflict with the vital properties of the other, and living
bodies only preserve their character of life so long as they are
able to resist the physical impression. When it is said that or-
ganic movements are occasioned by incitations, we do not admit

* Tiedemann, Physiologie. + Tiedemann.
t Tiedemann, Physiologie, vol. ii. In this excellent work, worthy of the
great name of its author, the theory, of which I have given this hasty notice,

is fully developed.

Se elas Rea OER Aa

Nae Begr mete

REPORT ON ANIMAL PHYSIOLOGY. 109

that they are the immediate effects of the mechanical or chemical
impressions, but assert that they are the effects of powers which
the external impression, be it mechanical or be it chemical, has
thus solicited to act.” .

Of these excitants some are necessary conditions of life,
and are therefore called vital stimuli. Plants cannot live any
considerable time without air, water, warmth, and light; nor
animals without the first three, and they become rickety when
deprived of the last. These being indispensable for the due
nutrition of parts, are necessary for the sustentation of those
powers which are developed with the parts by the act of nutri-
tion. But all animals are not dependent upon each of these
excitants in an equal degree. Thus, the new-born of warm-
blooded animals resist more easily the deprivation of air than of
warmth. They are drowned more readily in cold water than in
warm, within certain limits of warmth. They live longest
under water between 20—30° R., and if the heat be above or
below these limits die sooner. In general, the lower the place
of the animal in the zoological scale, the longer can it bear to
be deprived of these stimuli. Amphibia live from ten to thirty
hours, in distilled water, under the air-pump ; and frogs, whose
lungs have been extirpated, may survive thirty hours.

With respect to the stimulus of food the same general rule
prevails ; the intervals of supply may be greater without destroy-
ing life in animals, according as their organization is less com-
plicated, and their powers more limited. Thus, tortoises and
serpents may be deprived of food for months, and many mollusca
for yet longer periods.

Some also of the internal conditions of life may, in the lower
animals and in the imperfect states of the higher, be suppressed
or greatly altered, and yet life be supported for a longer or a
shorter period. The experiments of Legallois and others lead.
to the conclusion, that this period varies inversely as the per-
fection of the organ whose action is suppressed. The Batrachia
are found to live for many hours without the heart; a tortoise,
whose brain was removed by Redi, lived after the operation for,
several months ; in new-born rabbits, if the heart be extirpated,

‘sensibility persists for about fourteen minutes; when they are

fifteen days old, for only two and a half minutes ; thirty days old,

one minute* ; and the young of man may, at the time of birth,

be revived when the heart’s action has ceased for a period after
which, in the more adult state, it could not be restored.

_ In the more perfect forms of life there is a necessary depend-
ence of the whole organism upon each of its parts, and of the

* Essai, Legallois, p. 142,

110 FOURTH REPORT—1834.

parts upon the whole. Thus, for instance, respiration is neces-
sary to the heart’s action, the heart’s action to the respiratory
process ; neither can proceed after destruction of the nervous
system, and this requires for the production of its energy a due
supply of aerated blood. But this mutual relation of all and
each, alternately as cause and effect, has been improperly as-
sumed as a distinctive character of life. ‘The same is true of
an automaton, in which the moving power is part of the thing
moved: the same is also true of the planetary system as far as
we are acquainted with it*.”

Thus does the vital power, manifesting itself in the assimila-
tive process, occasion all the forms of life upon the earth.
Fach living thing, according to the nature of that original power
(of which we can know nothing but by its effects), requires its
own modifications of the common conditions of life, and presents
an organization (upon which classification is based,) adapted to
the region and the element in which it is destined to exist. Of
these creatures, all that are not microscopic are observed to
proceed from parents similar in structure to themselves by modes
of propagation peculiar to the kind; so that no one species,
under any modification of external condition, has ever been
known to assume the character or form which is distinctive of
another. The consideration of the stratification of the earth
assures us that all the families, genera, and species did not
commence their existence at one and the same epoch. On the
contrary, in the older strata are buried the remains of the sim-
pler forms of life alone ; in the more recent those of more com-
plex organization; whilst the remains of the most perfect and
of man have not been discovered in the most recent stratum.
Of the remains which have thus been brought to light, some
belong to species and genera which still exist, others to such as
are lost. Some physiologists, taking their stand upon the
general fact of this successive advance towards perfection of
development in correspondence with the successive changes of
the globe, have concluded that all the various modifications
of life may be but successive metamorphoses of the first most
simple form.

The undoubted fact that existing species have been perpe-
tuated unchanged for several thousands of years, would have
rendered such an opinion in the highest degree improbable, but
for the observations relative to the apparently spontaneous pro-
duction of animals and of plants from erganic matter in solution
—the apparent changes of species from simpler to more complex
under favourable external circumstances—and the interchange of

* Treviranus, Erscheinungen und Gesetze des organischen Lebens.

be (a

Kgalber

a a a ea

REPORT ON ANIMAL PHYSIOLOGY. 111

animal and vegetable form. If the facts were really thus, then
might the objection to the hypothesis of metamorphosis. founded
on the permanence of existing forms be encountered. It might
be averred that, notwithstanding our ignorance of the means,
the necessary conditions for such successive changes may have
been supplied in the earlier periods of the world, at epochs so
far removed, that the few thousands of years which have passed
away since the appearance of man upon the globe bear no pro-
portion to their immense distance, and only show that the rate
according to which the conditions of change are produced isa
very slow one.

Let us see to what conclusion the latest observations on In-
fusoria are tending.

It is well known that the experiments of Redi and of Vallis-
nieri were considered to have refuted the notions of the-ancients
concerning spontaneous generation, until those of Tuberville
Needham, of O. F. Miller and of Wrisberg, performed with the
most considerate exclusion (if that be possible) of circumstances
likely to throw a doubt upon the result, revived them. Miller,
repeating the experiments of Needham, concludes, that animal
and vegetable matter, by solution in water, is reduced to minute
membranous shreds, upon which, in a short time, are seen micro-
scopic globular points. These enter into a tremulous motion,
which gradually becomes more apparent; the globules are de-
tached, and Infusoria are produced from them. These first Infu-
Soria, he says, abound in all fluids, and are not to be confounded,
as is usually done, with other Infusoria, being, on the contrary,
elements which are the component molecules of all animals and

lants.
Poth conclusions Spallanzani drew from his experiments were
opposed to those of the above-named naturalists. He found the
structure of the infusory animals to vary with the nature of the

infusion, and explained their appearance upon the supposition

that ova had been introduced with the animal matter, or had
been suspended in the air, whose admission, at least in some
degree, is necessary for the success of the experiment.

‘The experiments of Priestley, of Ingenhouz, of Treviranus,
appeared to prove that the green matter of Priestley, produced
in organic infusions on exposure to light, is first a mass of ani-
malcules; then is resolved into green globules, which concrete
into conferve ; then, after the solution of these, again becomes
infusory animals and vegetables of a larger form. The organic
particles appeared indestructible, and common to each form of
life, passing from one to the other, and supplying the substance

112 FOURTH REPORT—1834.

from which each is formed, under the necessary external con-
ditions*.

The recent experiments and observations of Ehrenberg have,
however, tended to increase our doubts concerning the validity
of these conclusions. He has not succeeded, as Spallanzani con-
ceived he did, in producing definite forms of animalcules from
definite infusions. On the contrary, he has found the forms to
vary under circumstances the most similar. He has explained,
however, how it is that Spallanzani might be mistaken in his
conclusion. The species pass through many gradations of form
in their progress to maturity, each of which forms may have
been readily mistaken for a distinct species. These are not so
very numerous ; but the rate at which the individuals are multi-
plied is altogether extraordinary. For instance, the Hydatina
senta, which was observed for eighteen days, iscapable of afourfold
increase in twenty-four hours, which may give more than a million
of individuals from a single ancestor in ten days, and on the most
moderate computation may give nearly seventeen millions in
twenty-four days. According to Ehrenberg, infusories exist in
all waters, (except rain and dew, in which he could not discover
them,) and in some parts of plants, though here, probably, only
in a diseased state of the plant. Further, he has succeeded in
detecting a complex organization in those animalcules lately
considered of so simple a form. Even in the Monas, a creature
not more than the twenty-thousandth part of an inch in diame-
ter, the stomach is found to be of a compound structure, and
its motions are effected by cilia. In others he observed ova,
and propagation by means of them. If then, in the infusions
of Treviranus and Needham, no animalcules were produced
when the vessel was hermetically sealed, and the necessary
quantity of air exposed to a high heat—if they were produced
when fresh air was introduced after boiling—if the animalcules
have been shown to be capable of producing ova, which, indeed,
was never denied; it seems more reasonable to suppose, that
those observers who did not succeed in discovering the complex
structure of the creature so extremely minute, might fail also
in discovering the first ova, though they really existed in the
infusion, than that the animal should arise spontaneously.
Ehrenberg has not succeeded in detecting these first ova. No
very violent improbability is included in the supposition that
bodies so infinitely small have been conveyed by the air, like the

* Vide a full critique of the experiments of previous authors, and an account.
of his own, in Treviranus, Biologie, ii. 267, 403,

‘stinct and perfect animal of its kind+.

REPORT ON ANIMAL PHYSIOLOGY. 113

motes visible in the sunbeam. We now know how numerous
they must be*. .
. In the case of parasitical worms, (the Distoma hepaticum,
for instance,) the ova are too large to be either conveyed by the
air, or to be absorbed by vessels from the food and carried to their
nidus in the viscera. Such worms have even been found in the
viscera ofembryos. If we must have recourse to hypothesis to
account for the origin of these, let our hypothesis be supported
by analogy. It is not impossible that a portion of an ovum may
be able, as has been supposed by many, to germinate and pro-
duce a new individual, as a portion of a Polypus becomes a di-
The opinion of the gradual production of all creatures from
an original simple form has received confirmation, in the minds
of many, from their having observed that the embryo of the
highest forms of life passes by gradations through those which
are permanent in inferior animals. They have, however, sup-
posed this resemblance to be more complete than observation
allows us to believe it to be. We have seen that the first ob-
served embryo of all animals is extremely simple. With respect
to this simplicity, which but implies the imperfection of our tests,
a comparison may be allowed between embryos of a higher
order and the simplest forms of life, when the animal presents
no separation of distinct organs. As the development of the

* “ Although Dr. Ehrenberg, in refuting the notion of the extreme sim-
plicity of these animals, has overthrown one great argument in favour of their
spontaneous origin, yet he has offered no explanation of their production in
infusions which have been subjected to a heat sufficient to destroy any parent
animals, or even ova, supposed to be present. In these cases, as is well known,
the adversaries of the theory ascribe the origin of Infusoria to ova conveyed by
the air; an assumption which the supporters of the doctrine regard as highly
improbable, and which, if admitted as true, they consider inadequate to explain
the production of Infusoria in all the conditions under which it is reported to
have taken place by observers worthy of credit. It is true that Dr. Ehrenberg
neyer witnessed the spontaneous origin of Infusoria; but before denying the pos-
sibility of its occurrence, and discarding the theory of spontaneous generation
as unnecessary to account for the facts, it was incumbent on him to have sub-
jected anew to a rigid examination the observations of those who have arrived
at an opposite conclusion from himself, and either expose the fallacy of their
experiments, or show how they were to be explained on a different view from
that adopted by their authors. It is the more to be regretted that he has not
favoured us with such a critical examination, as, from his extensive knowledge
of the different species of the animals in question, his intimate acquaintance with
their mode of life, and his superior methods of observation, he is singularly well
fitted for thetask.”—Dr. Sharpey, Account of Professor Ehrenberg’s Researches
onthe Infusoria: Edinb. New Phil. Journal, Oct. 1833.

+ Entozoa have been found in embryos and in the eggs of birds: so also

have pins and small pieces of flint—Tiedemann’s 4nat. und Nat. Gesch. der
Vogel, b. ii. s. 128. quoted by Treviranus.

1834. I

114 FOURTH REPORT—1834.

embryo advances, we observe some organs superadded, though
still in a very simple form; so that here also a certain resem-
blance subsists between the embryo in this second stage and
animals a little more complex. As we continue to observe
the embryo of the higher family, we see organs come into
view, some of which are meant only for a transitory purpose
and disappear; some which have no purpose during feetal
life, but are meant for an ulterior use. Here the resemblance
between the embryo of the higher form, and the animal of the
lower form with which we may most favourably compare it, is
found to be less close. We find that the animal has organs suited
to the activities with which it is endowed, which are not to be
found in the embryo. Even if the two exist under similar ex-
ternal conditions of life, the organs adapted to these conditions
are not the same in both. To instance these several state-
ments : when no organs can be observed in the primitive streak
of the embryo, it resembles the zoophyte, in which nutrition
is performed by imbibition; but we observe in addition that
the primitive streak extends into a membrane which becomes
the vascular area. If we attempt the comparison when the
body resembles a worm, in as much as it is cylindrical and has
no limbs for motion, the resemblance scarcely extends further.
The worm has rings and contractile bands for its motions,
whilst the embryo has neither; and the simple tube, which re-
presents the heart in both, gives indications of a higher organiza-
tion in the embryo. If the worm resides in an aqueous medium
like the embryo, it respires by means of gills, the embryo by a
production of its abdominal tube—the umbilical vesicle (?),° or
the allantois, or the placenta. At another period remarkable
apertures are observed, at regular distances, towards the head,
between the imperfectly closed abdominal laminz in the higher
embryos, in which they resemble some of the cartilaginous fishes.
But with the former the vessels that follow the arches do not di-
vide for any respiratory purpose, whilst in the latter they are the
respiratory vessels of the gills. If, in a still further stage of ad-
vancement, we compare the higher embryo with the turtle, we find |
that in both the double heart is rendered virtually single, but for
very different purposes, and here the similarity is at an end*.
In these analogies, therefore, we look in vain for that precision
which can alone support the inference that has been deduced.
Far rather do we infer gradations of original power, which
manifest their different energies at-different epochs, under ex-
ternal conditions which may be similar according to a general
plan, the expression of each that is superadded modifying that
of all which preceded, and concurring with theirs to develop

* Weber in Hildebrandt’s Anatomy, vol. i. p. 125.

REPORT ON ANIMAL PHYSIOLOGY. 115

others which may be still latent. In the lower creature, a par-
ticular organ or set of organs attain their purpose and are com-

- plete; in the imperfect state of the higher, the corresponding

organs may in general resemble them, and may even perform a
similar office, yet still they are seen to be more than sufficient for
this lower purpose: in the midst even of this general similarity,
the indication of a higher destiny, yet unattained, is apparent.
We are disposed to conclude, then, generally, that all the
families, genera, and species of animated things were originally
created in such forms as we observe them in at present; and
that they continue to produce the organs which are the instru-
ments and the expression of their several powers by the process
of assimilation as a proximate cause. Amongst these different
organs the brain is peculiarly distinguished. We are sensible
in ourselves of ideas, of emotions, of desires—of powers which
present themselves to us as pure energies, without any interme-
dium: we have self-consciousness. These activities are excited
by our own will; we cannot contemplate them as observable
processes in any other person. On the contrary, the energies
of all the other organs are totally independent of our will; we

are aware of them only as their effects are matters of obser-

vation by means of our outward senses, and we observe them

better in other individuals than in ourselves. Life, thus pre-

senting such remarkable differences in these two respects, has
been distinguished as two forms. And this distinction is not
merely logical, for in the vegetable kingdom we have an instatice
in which the one form of life exists totally separate from the other.
But we find that even the higher form, the intellectual or purely
animal life, requires for its manifestation a body*. In living

‘creatures the two factors, though logically separable, exist as

one reality. The two spheres approach and intermingle in va~

“rious degrees in the different families of the earth, the animal

powers depending upon the vegetative for the formation of their
material organ. The life of the lowest animal scarcely appears
to differ from that of the vegetable. ‘“‘ From these animals,
which obtain food without any act of volition, we come to those
which can only obtain it by such an act, but who still, without
any act of this kind, obtain the influence of air, yet more imme-
diately necessary to their existence. We arrive at length at the
most perfect class, which can neither obtain food nor air except
y an act of the sensorium. In them the sensorial power is as
necessary for the inhalation of air, as the ingestion of foodt.”

st * Burdach, vol. iv. p.3. Burdach notices the impropriety of calling, with
Bichat, the animal life ‘ vie externe,’ and the organic ‘ interne.’
+ Wilson Philip, Phil. Trans. 1834.
12

116 FOURTH REPORT—1834.

And there enters, on the other hand, even into those organic mo-
tions which we call voluntary, much that is neither willed nor is
a matter of consciousness*.

The following, therefore, I would signalize as the great achieve-
ments of modern Physiology: viz.

The establishment of the general proposition, that peculiar
vital powers are connected with, or inherent in, peculiar animal
tissues ;—dating from Haller:

The establishment of the theory of development ;—dating from
G. F. Wolff:

The further generalization which derives all the vital powers
from modifications of the force of Assimilation ;— more fully pro-
pounded by Tiedemann.

Having thus presented a rapid outline of theoretical phy-
siology, in which I have purposely suppressed many details
which may be introduced more conveniently in other parts
of a review of the present state of physiology, I shall now
proceed in that direction in which the science must for a long
time attempt a progressive perfection, by endeavouring to as-
certain, as far as is possible, the inferior rules by which the prox-
imate cause operates. These include all the processes of vege-
tative life; and since they are all effected through a constant
interchange between external matter and the matter of the vari-
ous organs, I shall begin by pointing out the acquisitions added
in late years to our knowledge concerning the vehicle of the for-
mer—the blood.

Tue Biroop.—This fluid would be ill suited for its office, were
not its constituent molecules held together, in the living state,
by affinities so delicately balanced that they yield to every re-
active energy that the different organs to which it is presented,

can offer. Hence we account for the great discrepancies in the

results of chemical inquiry concerning it, from the ease with
which its components may be caused to combine in various pro-
portions, and from the different effects which different quanti-
ties of the same reagent are capable of producing.

In the body it exists as a colourless transparent fluid, in which
an infinite number of minute red bodies are equably diffused.

Out of the body it shortly coagulates, or separates into serum
and coagulum.

It was the opinion of Home and Bauer, that the coagulum is
formed by an aggregation of the corpuscles in the following way.

* Burdach, vol. iv. p. 3, &c.

REPORT ON ANIMAL PHYSIOLOGY. 117

The corpuscles consist of a nucleus inclosed in a membrane of
coloured matter, which membrane bursts, and the nuclei thus al-
lowed to escape attract each other and form the solid coagulum,
which is coloured by the broken membranes, and from which
the colouring matter may be washed out by water. This opinion,
which appeared to be confirmed by the observations of Prevost
and Dumas, of Dutrochet, and of H. M. Edwards, has been
very generally received. But it is certainly unfounded. For
the fibrin may be separated from the blood by stirring, whilst
the corpuscles remain in the serum unbroken and unchanged :
the serum, far from effecting their solution, supplies the best
medium in which they may be preserved for observation: if
in human blood the coagulation be retarded by adding a few
drops of solution of subcarb. potass., the corpuscles descend,
from their superior weight, before coagulation takes place: in
the course of half an hour a tender coagulum is formed, of which
the lower part (as far as the corpuscles reach) is red, the upper
pale and thready: operating on the blood of the frog, Muller
has succeeded in separating, by the filter*, the large corpuscles
of that animal from the clear liquor, which last afterwards sepa-
rates into fibrin and serum: fibrin is not soluble in water, the
corpuscles are so in part; and, in general, the two present some-
what different chemical reagencies.

The Corpuscles.—These bodies, called collectively cruor,
have been objects of much interest ever since they were first
observed by Malpighi. All that relates to them is even yet
matter of controversy,—their form, their size, their composition,
the cause of their colour. They have been too frequently ob-
served in water, rather than in serum, by which the two first
qualities are speedily altered.

Form.—They exist in all vertebral animals as round or oval

bodies, with well-defined edges. They are semi-transparent

_and pale when seen singly ; but present the colour of the

_ blood when seen by reflected light or in masses.

_ In all the Mammalia they are circular.
In the other Vertebrata they are oblong. De Blainville has
_ observed both these forms in Fishes, and Miiller in the
Frog, who thinks that the round corpuscles, one sixth of
___ the size of the others, belong to the lymph or the chyle.
_ Inall the Vertebrata they are flat. Rudolphi states, that they
ma a flattest in the Amphibia, less so in Birds, least of all in
an.
_ Hodgkin and Lister find the proportion of axes in Man to
be 1: 4°5.
_* Miiller, p. 106. The filter was composed of delicate animal membrane,
moistened bladder, and covered a glass tube from which the air was exhausted.

118 FOURTH REPORT—1834.

To the last-mentioned observers, as well as to Young, the i
corpuscles have not appeared uniformly flattened, but con-
cave on their surfaces. Muller, however, who believes in
the existence of a central nucleus, of which he finds the
thickness to equal the lesser diameter of the corpuscle, has,
if his observations admit not of another explanation, set

- that point at rest.

Size.—As a rule, the size is constant in the same individual,
and the same species; and their measurement assumes an
additional importance from the observation of Blundell, :
and of Prevost and Dumas, that death follows the transfu- |
sion of blood when its corpuscles differ in size from those
of the animal which is operated upon.

In Man the size of the corpuscle, according to
Rudolphi, Sprengel, Hodgkin,and Lister = 0°00033 in. 5455

Kater, Prevost, and Dumas ...... = 0:00025 atis
Wollaston, Weber ......-:.. -» = 0°00028 show
POU tal Me Me salah aR. elt eee atta te = 000016 sho

If we take the mean of these, we find the size of the human
corpuscle to be zg¢,dth part of an inch in diameter.
In different Mammalia, (Prevost and Dumas,)

the size of the corpuscle is the same as in
Man, inthe Dog, Hedgehog, Swine, Rab-

bit, Dolphin we TH AM OE eS = *00025 inch.
Larger in Simia Callithriv ......... = ‘00030
Smaller in Assi ier er is SA RE Soe OR ee 000g

Ro Te ORT RY Ve, de ae = °00020

SESS), OL NS ELIA HO RE QUE, = *00018

Chamois: oe Soa ais iS Ful. aa = ‘00017

GORGOOOT FBS: at Ov aSae he whith = :00014

Hodgkin and Lister have, however, found it smaller in the
Swine and Rabbit than in Man.

Diameter in Man : major axis in Frog:: 1: 4.

The corpuscles are of equal magnitude in arterial and venous
blood and similar in form.

Structure.— Hewson, from observing the mode in which the
fresh corpuscle appears to swell in water and to change, be-
coming gradually colourless, and appearing as a central nu-
cleus surrounded by an integument, concluded that it really
exists in the blood in this complex form. In this opinion he
has been followed by Home, Edwards, Dutrochet, Prevost,
and Dumas. The integument has been represented as the
colouring matter, and the nucleus as fibrin. Raspail, how-
ever, gives it as the result of his observation, that when the

REPORT ON ANIMAL PHYSIOLOGY. 119

homogeneous corpuscle comes in contact with water or an
acid, then first a change is effected; the density increas-
ing towards the centre, and the colour, at first diffused
through the whole mass, being then confined to the surface.
But however this may be, whether the nucleus have pre-
existed or be now first formed, it is not soluble either in
water or in dilute acetic acid, whilst the external portion
with the colour is gradually removed by this. This has
been pointed out by Miiller with great precision in his late
work : the subject of his examination, principally, was the
blood of the Frog.

Berzelius refers the insolubility of the corpuscles in serum to
the albumen which it contains: but this is not the only cause.
J. Miiller rather considers it to be an effect of the salts which
the serum holds in solution; for he found, that on adding to a
drop of Frog’s blood under the microscope a drop of a solution
of yolk of egg in water, the corpuscles lose their form and be-
come round as quickly as in water, whilst a drop of a solution
of such a salt as does not separate the blood (as subcarb. po-
tass.) causes no such change to be effected.

It has been stated by.some that iron does not exist in greater
quantity in the cruor of the blood than in its other essential com-
ponents. Engelhardt has discovered a remarkable property of
chlorine, confirmed by H. Rose, by which the incorrectness of
that opinion has been proved, and the conclusion of Berzelius
established, viz., that all the iron of the blood belongs to the
cruor. The chlorine precipitates the animal matter from its solu-
tion in water, and at the same time deprives it of the lime, soda,
phosphorus, iron, which may have been connected with it. The
liquor being strained, the oxide of iron may be precipitated by
ammonia: but that precaution is necessary, for otherwise, the
ammonia redissolves the organic matter, and the iron recom-
bines with it. Engelhardt could obtain no iron from similar
operations with serum and fibrin, though he did all the otter
salts ; and there was no ash left on combustion.

Berzelius’s estimate of the quantity of iron in the ash of the
eruor was confirmed by these experiments. Of the entire blood
metallic iron forms only one part in 1000.

It is yet undetermined whether the iron exists in the corpus-
cles of the blood in its reguline form or as an oxide, Engel-
hardt and Berzelius supporting the former opinion, and H. Rose
and Ginelin the latter. For the former opinion it has been con-
tended, that chlorine has a strong affinity for the metals, but
none for their oxides; and that the oxide of iron, if present,
would be dissolved by the mineral acids. But in Engelhardt’s

120 FOURTH REPORT—1834.

experiment, the affinity excited is between chlorine and animal
matter, not iron and chlorine. And if the mineral acids have
not the same effect, this does not prove the iron to be in a me-
tallic state; for if it were so, and unprotected by the animal
matter, it would be oxidized, and then dissolved by the acid.

' The labours of chemists to explain the mode in which the
elementary substances are united to produce the colour of the
cruor, however they may be unsatisfactory in this respect, have
thrown much light upon the reactions of these substances. Such
experiments, on the other hand, have introduced as constituents
of the blood, products which are perhaps merely the effects of
the chemical operations; or new combinations, not existing in
nature, of its elements. The iron seems to enter in too small a
quantity to form a metallic pigment for the cruor. Whatever
changes the constitution of the blood, as a living product, also
changes its colour. ‘‘ Since its chemical composition is only a
product of life, so are we unable by any aids derived from inor-
ganic nature to produce it. The colour has its cause in the con-
stitution of the blood as an organic whole; and each of its ele-
ments, iron amongst the rest, contributing to that constitution,
enters into the production of its colour*.”’

The Lymph, or liquor sanguinis.—The clear fluid in which
the cruor, or mass of corpuscles, is diffused. It separates spon-
taneously into two portions, fibrin and serum.

Fibrin.—I refer to Berzelius for all that is yet known con-
cerning this substance. Since Miller’s discovery, it is distin-
guished from the corpuscles; and De Blainville and Hodgkin
have shown that its fibres do not consist of strings of minute
globules.

Serum.—Lecanu has repeated the analysis of serum, and as-
serts, that certain oily substances exist as components, which
were unnoticed by Berzelius and Marcet. His mode was, after
desiccating a known quantity by moderate heat, and thus deter-
mining the quantity of water, to treat successively, with boiling
water and boiling alcohol at 40°, the residue of desiccation. The
water dissolved the soluble salts and extractive matters, the al-
cohol the fat matters. The watery solution was evaporated ; the
residue treated with alcohol to separate the extractive matters
soluble in it. What was insoluble was calcined, to determine the
proportion of organic matter it still contained ; the residue again
treated with boiling alcohol to separate the hydrochlorates.

The fatty matters taken up by the boiling alcohol were sepa- —
rated from each other by means of alcohol at 33°, which does
not dissolve when cold the crystallizable fat, but does the oily.

* Burdach, iv. 85.

ie

REPORT ON ANIMAL PHYSIOLOGY. 121

The albumen procured by means of boiling water and cold al-
cohol was dried, weighed, and calcined, and its salts determined.
Traces of iron were found in such minute quantity in serum,
that Lecanu presumes it would not furnish any if it were possi-
ble to procure it entirely separate from the colouring matter.
1000 parts of serum consist, according to this mode of ana-

lysis, of First Second
} Analysis. Analysis.
MUWARECE adh lore Ne cies Re. a hk EE, ens 90600 901-00
PED ELIE Pa Psi fod 5 ioc Kievlvtatataiat ile sta's ole ctetdieate uate e 78:00 81:20
Organic matters soluble in alcohol and water .. 1°69 2:05
Albumen combined with soda ..............6- 2:10 2°55
Crystallizable fatty matter...............+.... 1:20 2-10
irl MALE VASA RET ROS ba edt 1:00 ~ 1:30
Ghlofure:of sodium i Ste hg 1) LR a 6-00 5-32
——— potassium
Alkaline subcarbonate :
phosphate.... : aibinsootidse se bp suns oe 2°10 2:00
- sulphate......
Subcarbonate of lime ......
__-______. magnesia. .
hosphate of lime@s2.2...-. 2. ¢- see Safa 20 seiele == 0-91 0°87
- magnesia ......
AVON 7s. Yeeceeee:
PRS SR Sk RMT LS ate ch ots wi tltie eit orate 1-00 1-61

1000-00 1000-00

_ These fatty matters will be better understood by considering
Lecanu’s analysis of the entire blood. He poured alcohol in
excess on venous blood, separated the precipitate, and treated it
frequently with boiling alcohol, obtaining thus a mass insoluble
in alcohol, and a slightly rose-coloured liquor. This liquor,
subjected to evaporation, became turbid towards the end of the
operation, in consequence of the separation of a fat matter in-
soluble in the aqueous product. The residue of evaporation was
treated with «ther: a portion of it was dissolved. Hence an
ethereal solution A, and a residue B.

_ A, on spontaneous evaporation, gave a brownish residue, bit-
ter, of a consistence similar to that of turpentine, formed of two
distinct matters, one solid, the other liquid and like oil. The
residue was incompletely soluble in cold alcohol, the solid por-
tion remaining attached to the sides of the vessel. When this
solid portion had been separated, and dissolved in boiling alcohol,
it formed, on cooling, white nacreous laminz, similar to the fatty
matter of brain.

- On evaporating the alcohol with which this had been washed,
and in which the oily portion of the residue had been dissolved,
another residue, of a bitter taste and turpentine consistence, was
obtained ; insoluble in hot or cold water, soluble in alcohol or

-

122 FOURTH REPORT—1834.

ether, inalterable by hydrochloric and nitric acids, rendered
brown by sulphuric acid, soluble in potass with slight heat, and
precipitated from the solution by hydrochloric acid in white
flakes. If the excess of acid be washed off with water until the
latter no longer reddens the vegetable blues, it communicates to
alcohol, when essayed therewith, the property of reddening those
colours. Hence the oily part of the blood appears to be con-
vertible by potass into an acid substance, and is considered by
Lecanu as an immediate principle of the same.

From B treated with alcohol was obtained a brownish yellow
liquid and a residue C.

The liquid, on being evaporated, furnished an orange yellow
mass, insoluble in ether, but soluble in water and alcohol, which
then manifested alkaline properties. The watery solution af-
forded a precipitate with hydrochloric and nitric acids, and
with solution of galls ;—the same as that considered by Berze-
lius to be a mixture of animal matter and lactic acid; by other
chemists as resembling osmazome. It is considered by Lecanu
to differ from osmazome in as much as the latter is not precipi-
table from its solution by acids.

C was found insoluble in ether and alcohol at 40°: treated
frequently with boiling alcoho] at 33°, it gave the hydrochlo-
rates, and some extractive matter easily separable by alcohol at
40°. This new residue, treated with cold distilled water, was
nearly entirely dissolved, except a small quantity of a brown
matter insoluble in boiling water and alcohol, and considered
as a mixture of colouring matter, albumen, and fibrin.

From a portion of the saline solution, white flakes were abun-
dantly precipitated by acetic acid,—a gelatinous albumen, which
Lecanu considers, from the mode in which he obtained it, to
exist in this form in the blood. Another portion of the saline
solution was evaporated, the residue calcined, and the salts de-
termined *.

1000 parts of blood, according to the above, consist as fol-
lows :-—

First Second

Analysis. Analysis.
UR Ges SE ISS ieiciols Saal Siw atl Sis oot 780045 785°590
TN ee ee ee ee cane 2-100 3°565
PADI ONY 5. ase seictideias)<i0 Be pe Re 60-090 69°415
Colouring matter ........c0..seessscsesases 133-000 119-626
Crystallizable fatty matter................0- 2-430 4-300
Oily matter... . cee ccc e ce wee sess cces 1:310 2:270
Extractive matters soluble in alcohol andwater 1-790 1-920
Albumen combined with soda .........+.... 1:265 2-010

* Annales de Chimie et de Physique, tom. xlyiii. p. 310.

REPORT ON ANIMAL PHYSIOLOGY. 123
' First Second
Chlorure of sodium...... ee Analysis. Analysis.
-- potassium......
Subcarbonate, sealed ha ee bale ieiiat 8370 7304
Phosphate, ... palkaline..
Sulphate, .....
Subcarbonate of lime......
a See
Phosphate oflime ........
hii magnesia... f ‘10rttstt 00 2/100 1-414
IDO esiceaces
Peroxide of iron..........6+ J :
HUGHES sig cicteeve es ove Sieh neil cents a elatelle ae Oe ok 2:400 2°586

1000-000 1000-000

* Doubtless under various modes of applying heat, alcohol,
the subcarbonates, &c., to the blood, many substances may be
made to appear, which are but variations of its essential eompo-
nents— (albumen, fibrin, and cruor). The knowledge of these
may enrich animal chemistry, if the object were only to compre-
hend, comparatively and in the gross, the series of changes which
any matter may undergo under different agencies, and not to
discover new materials and declare them to be real components
of the organic body. Tiedemann reckons the peculiar matter
of saliva amongst the components of the blood; and lately urea
has been counted amongst the number, because it has been found
in the blood after extirpation of the kidneys. Incontestibly, in
certain cases of suppressed secretion or of increased resorption,
bile, the seminal fiuid, &c., have been found there ; but no special
product of secretion can yet, on sufficient grounds, be proved to
be a normal component of the blood, and from what we know of
it, such a result is not to be expected*.’’ Numerous colouring
matters have been classed amongst the components of the blood,
from the explanations of chemists respecting the causes of co-
lour—as globulin, erythragin, &c. Burdach thinks that they are
either the product of reagents acknowledged not to exist in the
blood, or are modifications of albumen. Boudet, by treating very

large quantities of blood, contends that all blood contains cho-
lesterint.

Gas.— Under the air-pump, air has been observed to escape

-from recent blood; its quantity has been variously computed.
Most observers, as Sir Humphry Davy, Brande, Scudamore, Vogel,
State that it is carbonic acid. The quantity is very variously esti-
‘mated. Brande obtained two cubic inches from eight ounces of

= Burdach, iv. 68. :
+ Annales de Chimie et de Physique, tom. lii. p. 342.

124: FOURTH REPORT—1834.

blood; Scudamore half acubicinch from six ounces; Sir Humphry
Davy ‘rather more than one cubic inch from twelve cubic inches
of blood. Dr. Clanny finds that the gas developed is principally
nitrogen. Dr. J. Davy asserts, from his experiments, that in no
case is carbonic acid ever developed from fresh-drawn blood ;
that, on the contrary, it absorbs one fourth of its bulk of carbo-
nic acid, which becomes combined. Miller has repeated the
analysis, both with fresh sheep’s blood and with that of man.
Even under a heat which amounted to 200° F., one pound of the
former gave off only 1°8 cubic inch of gas: of this quantity
not one fifth cubic inch was absorbed by lime water; and this
small quantity of carbonic acid he attributes to the action of the
air contained in the tube of his apparatus upon the blood. He
repeated the experiment in such a way as to exclude the air, and
obtained no trace of carbonic acid, nor any, except the merest
bubble, of any other gas. He further found, that blood artifi-
cially impregnated with carbonic acid did not yield it again un-
der the air-pump*, and thus has confirmed the same observation
of Dr. J. Davy. Mitscherlich, Gmelin, and Tiedemann have lately
performed another experiment with the same result. They in-
troduced small metallic tubes, provided with stop-cocks, into the
artery and vein of a Dog. After all air was evacuated from the
tubes, by allowing the blood to flow, they were brought under
glass cylinders inverted over mercury. The cylinders, half filled
with blood, were placed under the air-pump. On exhausting,
bubbles arose, so that the quicksilver, which had stood half an
inch above that in the cup, sunk about an inch. But when
the air was gradually readmitted to the bell of the pump, they
disappeared ; showing that they did not consist of gas, but of
watery vapour which had filled a vacuum. Both kinds of blood
comported themselves similarly. The authors found that the
blood contains carb. acid combined ; for blood mixed with vine-
gar gave bubbles under the air-pump, which, when venous blood
was employed, did not entirely disappear on readmission of the
air: hence the alkaline nature of the blood depends not upon
caustic alkalies, but upon their carbonatest.

The proportion of solid to fluid matter in the blood has been
determined by Prevost and Dumas, in a great number of animals.
They find that in Man the solid are to the fluid): : 1 : 9.

In carnivorous animals there are more cruor and fibrin together
than in graminivorous: in young animals less than in old of the
same speciest.

* Miiller, Physiologie, i. 313.
+ Archiv. fur Anat. und Phys., Miiller, 1834, 103. t J.Davy.

See ee ee eaten

REPORT ON ANIMAL PHYSIOLOGY. 125

In cold-blooded animals it is the quantity of cruor, not of
fibrin, which is diminished*.

Michaelis gives the following analysis of the components of
arterial and venous blood into the elementary gasest.

ALBUMEN.

Arterial. Venous.
Nitrogen........ ss seeeeees 15°562 157505
Carbonic acid............4 53-009 52°652
Hydrogen ..........00000- 6:993 7359

OXYgZeN Lv ceee cues sceeces 24-436 24-484
Frsrin.

Arterial. Venous.
Nitrogen......+.-+008 eee. 17587 17-267
Carbonic acid............0. 51:°374 50°440
Hydrogen .....-.+-- esses 7254 8-288
Oxygen .ssceecseeeecees ee 23-785 24-065

Cotourinc Matter.

Arterial. Venous.
Nitrogen. ..s.eeseesseeeees 17°253 17-392
Carbonic acid......eeseeses 51°382 53°2381
Hydrogen ...ssececesseaee 8:354 7711
Oxygen .eccesseeveeeree-- 20°011 21°666

Arterial blood contains more nitrogen and oxygen, but less
carbonic acid and hydrogen, than venous blood.

; Nit. C. Ac. Hyd. Oxyg.
Arterial blood ........16°800 51-920 7534 23-746
Venous blood ........ 16°720 52°107 7765 23408

- Lecanu has made some interesting comparative analyses of the
blood of individuals of different ages, sexes, and temperaments.
To determine the proportion of the essential principles, he dried
a portion of the serum after having weighed it, and thus deter-
mined its water, its extractive matter, and salts. He then divided
the clot into two portions, dried one of them; to determine, by
the loss, the quantity of water of the serum involved in it: and
washed the other, to obtain the quantity of fibrin. By the first
part of the process he ascertained that part of the weight due to

the extractive matter and salts left by the water of the serum

evaporated: subducting this he had the weight of fibrin and
colouring matter. By the second part of it he ascertained the
weight of the fibrin alone. The difference was the weight of the
colouring matter. In this way, examining the blood of twenty
healthy persons, ten males and ten females, he found the water

to vary in 1000 parts of blood—

* Miiller. + Poggendorf, dnnalen, 1832.

126 FOURTH REPORT—1834. j

In the females from 853°135 to 790°394:
Mean of the 10 cases 804°371.

In the males from 805:263 to 778625:
Mean of the 10 cases 789°320.

In different temperaments :
Females, lymphatic, mean of 5 cases 803-710.

, sanguineous, 4 792°984.

Males, lymphatic, 2 —— 800'566.

, Sanguineous, 5 —— 786'583.
Female, mean quantity of clot from 10 cases 115-963.
Male, ——_——_— 132:490.

Hence there is more water in the blood of females than of males.
The proportion of water was not found to depend upon age, at least
between the limits of. twenty and sixty years. In individuals of
the same age, it is less in the sanguineous than in the lymphatic.
The proportion of albumen is found to be sensibly the same
in the male and female, and not to be proportional to the age
between the same limits; and nearly the same in quantity in
sanguineous and lymphatic individuals of different sexes. The
proportion of colouring matter is found to vary in the blood of
individuals of different sex and age, in individuals of same sex and
different age: and to be greater in themale than in the female; and
greater in sanguineous than in lymphatic persons of same sex. —

Denis found from comparison of his analyses, that in the blood
of individuals ill nourished and accustomed to stimulant drinks,
the proportion of colouring matter increases, and is even more
abundant than in the blood of sanguineous subjects ; but that the
albumen, on the contrary, is in very small quantity*.

The principal change which J. Miiller found in the blood of
cholera patients, he states to be its propensity to coagulate even
during life. He therefore recommends the use of the subcar-
bonates of soda and potass, particularly the last, in large doses,
on the immediate accession of the disorder. Dr. O’Shaugh-
nessy, Dr. Clanny, and Mr. Bell found the salts and serum also
greatly defective in quantity in this disease.

There is no longer any question amongst physiologists as to
the life of the blood. That which enters into the composition
of all parts of the living body, from which they are produced,
and sustained, and restored, and upon which the body itself re-
acts, must possess life. Many have even supposed that its red
particles possess spontaneity of motion, as in the instances
quoted by Professor Alison in the Appendix to his Physiology 5
but the phenomena alluded to appear to be explicable partly from
acknowledged actions of the neighbouring living solids; and

* Majendie’s Journal, ix, 221.

ae

REPORT ON ANIMAL PHYSIOLOGY. 127

where they are not so, they are found to be not peculiar to mi-
nute organic products, but are observed also in unorganized mo-
lecules moving in fluids under the microscope*.

How quickly the body reacts upon the blood, is proved by the
direct experiments of Thackrah, Scudamore and J. Davy, who
found the quantity of fibrin to vary in different portions of the
blood during the same bleeding: generally diminishing.

That a due supply of arterial blood is necessary for support-
ing the functions of the more important organs of the body, is
seen from the singular anastomoses of the large arteries of the
brain; from the care taken to guard some of them from pres-
sure; from the imperfection observable in the muscular and ner-
vous powers of persons in whom the septum of the heart is im-
perfect, or the ductus arteriosus open ; and numerous other in-

* Thus, Dr. Czermack of Vienna observed a peculiar motion of the particles
of the blood when one of the vessels of the gills in the larva of the Salamandra
atra was cut through. The particles, under the microscope, of the effused blood
were seen to have an irregular motion backwards and forwards at some points,
but generally to move round in circles or ellipses. Dr. Sharpey has shown
(Edinburgh Medical Journal, 1830,) that in the larva of the Frog and Salamander
in the Mollusca and other inferior aquatic animals, the exterior covering of the
body generally, but especially of the respiratory organs, possesses the power of
impelling the water contiguous to it in a determinate direction along the sur-
face, by which a constant current is kept up, and successive portions of water
brought in contact with the gills, replacing the action of the respiratory muscles
in higher creatures. Drs. Purkinje and Valentin have lately published an in-
teresting paper in Miiller’s Archiven, Part V. 1834, in which are detailed ad-
ditional observations of the same kind. Whilst seeking for ovules in the tubes
of Rabbits which had been impregnated three days, they observed by the micro-

* scope that minute particles of the mucous membrane of the iubes presented a

lively motion under water, rolling round their axes, and recognised it as a mo-
tion similar to that of the cilia of Infusories (Flimmerbewegung). The mucous

membrane also of the entire uterus and generative passages exhibited similar

motions, though with different degrees of vivacity. ‘These distinguished observers
were thus induced to,inquire further. They found that in all Amphibia, as Ser-
pents, Lizards, &c., in Birds, andin Mammalia, the entire surface of the mucous
membrane of the oviduct presents this glittering motion (/limmert); also the
mucous membrane of the respiratory passages to theirmost minute subdivisions.
It could not be observed in the mucous membrane of the glottis, of the vocal
ligaments, of the mouth or gullet (Nasen-schleimhaut appears from the context
to be a misprint for Rachen-schleimhaut), of any part of the digestive tube or
its appendages. So much the more remarkable was the observation of it in the
nose, whilst the phenomenon ceased exactly on the limits of these parts. Its
presence serves as a sure criterion, where the membrane exactly begins to form
a part of the respiratory organ. In the Amphibia, as the Salamander, where the
mouth is not merely for swallowing, but is also a respiratory organ, the motion
is very lively. The phenomenon could not be perceived in any fishes which
were examined; but appeared to the authors, as far as their observations have

o extended, to be confined to the mucous surface of the respiratory organs,
and of the female generative organs in Amphibia, Birds, and Mammalia. Such

portions of the mucous membrane are provided with cilia, according to these
observations.

128 FOURTH REPORT—1834.

stances. But Blundell’s experiments prove, that diminution of
quantity is not so immediately hurtful to life as alteration of the
quality of the blood. Three fourths or more of all the blood in
the body may be removed, and the animal still live. Whena
’ Dog had been rendered apparently dead by the loss of ten ounces
of blood, it was recovered by transfusion of two ounces. This
vital influence of the blood is shown by Prevost and Dumas to
depend not so much upon the serum as upon the red particles.
An animal bled to insensibility, is not revived by serum of the
proper temperature, but is by blood from which the fibrin has
been removed by stirring. But with respect to quality, changes
of this, slight in appearance, produce important effects. Blundell
found, that when he had drawn blood from a Dog’s artery, and
reinjected it into a vein before coagulation had commenced, (per-
forming the operation until more blood had been thus transfused
than equalled the whole weight of the animal,) though it reco-
vered, it was ill for several days with oppressed respiration and
impeded action of the heart. When an animal, therefore, is re-
vived with blood of another of the same species, we may sup-
pose that the operation is not entirely without danger of ill con-
sequences. But when this is effected with blood from an animal
of a different genus, the consequence is generally fatal. Of dogs
revived with human blood, some died shortly after the operation,
some on the following, others on the sixth day. When Pre-
vost and Dumas transfused Calves’ blood into Kittens or Rabbits,
they seldom survived the sixth day: the pulse becoming quick,
the warmth diminished, the evacuations bloody. The transfusion
of the blood of an animal of another class, 7.e. with differently
shaped globules, almost always causes death. If blood with

round particles be injected into the veins of a bird, it dies with _

symptoms of poisoning from substances which act on the ner-
vous system*. ,

With respect to transfusion we cannot but assent to the fol-
lowing judicious observations of Burdach. The blood of every
creature is in as special a relation to it as are any, the most im-
portant, organs of its body, and is its own production as much
as they are. It is under the necessity of making its own blood
for its own purposes. When an animal, therefore, is saved from
death by means of transfusion, it is saved by a mode which in-
troduces into its system causes of derangement in all its func-
tions, and which it must throw off by its powers of secretion be-
fore healthy action can be restored.

Nysten’s experiments, and those lately detailed by Majendie
in his lecturest, seem to prove, that air injected into the veins

* Dieffenbach, quoted by Miiller. + Lancet, No. viii. 1834.

REPORT ON ANIMAL PHYSIOLOGY. 129

destroys life by mechanical interruption of the circulation. For
small quantities even of irrespirable gases (except nitrous, sul-
phuretted-hydrogen, and ammoniacal gases,) are not fatal.

The interesting and difficult inquiry into the causes which
produce coagulation of the blood has lately been ably resumed.
by Mr. Prater. His numerous comparative experiments show
how important an element is the quantity of the agent which
modifies that process: that the same agent which in a large
quantity altogether prevents coagulation, in a small quantity
favours it. He confirms also the fact, announced by Schroeder
Van der Kolk, that as the proportion of serum is relatively in-
creased, (as it is in blood last drawn,) so is the tendency to coagu-
lation also increased. The impression derived from his works
is one which strengthens our belief generally in the views of
Hunter; viz. that no theory can satisfactorily explain the phe-
nomena of coagulation which has not a regard to the vital pro-
perties of the blood; properties whose variations we are not yet
able to connect with those corresponding alterations in the com-
position and aggregation of its molecules which we cannot but
believe to accompany them. Mr. Prater attempts to infer from
his experiments what the vital properties of the blood are which

have hitherto been ascertained ; viz. vital elasticity (irritability),

ww

and contractility. See Essay on the Blood, and Experimental

Inquiries in Chemical Philosophy.
_ The Powers which circulatethe Blood—From the observa-
tions of Prevost and Dumas, of Baer, and of Baumgertner, we

find that many important organs of the body are traced out in

the primitive matter of the germ, before there is any indication

_ of blood or of vessel to contain it. According to Baumgertner*,
_ the motion of the blood is first perceptible in the Frog and Sala-

-mander seven or eight days after the rudiments of the brain and
cord are visible, and even twenty-five days after that time in the

Trout. In the same way rudimentary shapes, corresponding to
j _ skin and organs of sense, muscle and bone, digestive and respi-
_ tatory organs, are traced out in the original organic matter be-

fore they receive any blood. The vessels and the blood which

_ make up the first circulation between the vascular area and the
heart, are formed simultaneously from the granular mass which
__ has accumulated between the serous and mucous laminz of the
_ germinal membrane. The granules, gathering together into iso-
__ lated masses, present fissures between them:containing a yellow-
ish fluid which gradually becomes red. - The fissures increase in

number; the masses diminish in individual magnitude, whilst

- they extend the vascular area over a larger space. In these

* Beobachtungen tiber das Blut und die Nerven, quoted by Burdach.
1834. K

130 FOURTH REPORT—1834.

fissures, G. F. Wolff first traced the gradual formation of the
walls of the vessels, and the conversion of the fluid into blood
by the included masses. The formation of the heart is effected
similarly from the granular mass.

When, therefore, the junction between the vascular area and
heart has been effected, and the blood moves onwards by means
of the heart’s contractions, the direction which it takes is not in-
determinate as it would be if left to the influence of that power
alone. On the contrary, its course is determinate; it seeks the
different organs whose lineaments are perceptible, being soli-
cited thereto by the vital attraction which is now established be-
tween them, The streams which reach them vary in size, and sub-
divide through their masses in a way so peculiar for each organ,
that even in the adult and perfect form, each of them preserves
a mode of branching for its main vessels, and a figure for its
capillaries, which are found in no other. What, therefore, is es-
sential in the circulation of the blood, is an attraction subsisting
between the particles of each organ and the particles of the
blood, anda subsequent repulsion between the same, that which
is repelled by one set of organs being attracted by another. What
are the physical conditions of the organs and of the blood under
which the phenomena are effected, has not been determined.
Some have supposed that the particles of the organs and of the
arterial blood are in different states of electric polarity. Accord-
ing to them, the organ, as the more fixed, attracts the blood;
communicates to it its ownelectric state, and then repels it. It fol- .
lows, therefore, that arterial and venous blood are in opposite elec-
tric states. J. Miller, however, could discover no electric cur-
rent by the galvanometer, when one of its wires was placed in
an artery, the other in a vein of a living animal.

Though a negative experiment of this kind is not conclusive,—
for the electric organ of the Silurus does not affect the galvano-
meter,—yet Dutrochet’s opinion that the red particles in theblood
perform the office of galvanic plates, and his belief that he had
effected the formation of muscular fibre by galvanizing a drop of
serum, cannot be supported. His ingenious experiments are de-
tailed in the dnnales des Sciences Naturelles, 1831, p.400. They
have been repeated by Miiller, who has shown that the supposed
muscular fibre is merely a collection of granules of albumen, with-
out consistence, coagulated by the acid of the decomposed salts
of the serum; and that there is no sufficient reason for conclud-
ing that colouring matter and fibrin (the nuclei of the red par-
ticles according to Dutrochet,) are in opposite electric states *.
It is on this principle, however, of vital attraction, as I conceive,

* Miiller, Physiologie, p. 132.

REPORT ON ANIMAL PHYSIOLOGY. 131

that the phenomena of local inflammation, of determination of
. blood to particular regions, the emptiness of the arteries after
death, &c., are to be explained*. It may be abnormal, as in
many of these instances. It may also be suspended or destroyed.
Nervous influence seems to be a condition of its continuance,
where the animal hasnerves. It is stated that when the main
artery of a limb is tied, the circulation is not maintained by
_ anastomosing branches if the nerve be also tiedt. Many have
__ recorded that in persons bled to fainting, the blood which last
__ issues from the vein is arterial in colour.
__ The capillary vessels themselves seem to contribute nothing
_ to the motion of the blood : the diameter of the small threads of
blood in any of them is not seen to be in the least variable, whilst
the heart’s action continues the same and the muscles are at rest.
_ They are intermediate between the minute arteries and the minute
% veins, and continually anastomose. Dr. Marshall Hall states that
_he has in vain sought for instances of the immediate termination
_ of a minute artery in a minute vein: they all first pass into
capillaries. In this way it is that the blood is brought into near
mtact with the parenchyme of the various tissues, and the pro-
sses of nutrition effected. it was the opinion of the older
siologists that all the minute arteries did not thus terminate,
that some ended by open mouths, thus allowing the blood
to enter into the composition of the different organs of the
y. If, however, the transparent parts of living animals be ob-
ved, all the particles of blood are observed to pass from the
te arteries through the network of the capillaries, and by
e to enter into the veins. The minute anatomy of glands also
vs that the last divisions of their ducts are closed tubules ;
on these the capillary vessels are largely distributed, but
r pass into them. The smallest visible capillaries are those
ch convey red particles of the blood in single files ; their dia-
er therefore is about the ;55dth part of an inch. That there
e others so small as merely to convey the lymph of the blood
however the opinion of many physiologists. It was the opi-
of Haller, and Bichat, and Bleuland that there are such
els; the contrary that of Mascagni and Prochaska, and of
amerring in his later writings. The primitive fibres both of
cle and of nerve are smaller, considerably, than the least vi-
e capillaries.
the lowest animals, this vital attraction between the mole-
s of their body and the nutrient fluid which penetrates, by
ibition, their uniform mass, appears to be sufficient for the
urposes of their economy. But in higher creatures, a moving
_ * Kalken Brenner, Majendie’s Journal, viii. 81. t+ Baumgertner.
K 2

132 FOURTH REPORT—1834.

power, afforded by the contraction of living solids, is necessary to
bring the nutrient matter within the influence of this attraction.
For in them the organs are gradually collected into distinct
masses and individualized, and their life depends upon the reci-
procal action of these. That their activities may be maintained,
a common nutrient fluid is conveyed to them on the one hand,
and on the other, is brought into near contact with the air.
Wherever the heart exists, it is the principal moving power; but
it does not exist until there is a distinct apparatus for aerating
the fluid. In the Meduse and some Polypi, the nutrient fluid is
the immediate product of digestion ; the digestive cavity supplies
the place of a heart, and tubules proceed from it through their
substance. In insectsa single tube represents the heart : it pul-
sates from behind forwards, and absorbs at every diastole a por-
tion of a fluid mass which surrounds the intestine, and is the
product of digestion. Here the vessel scarcely ramifies, that
form being assumed by the respiratory apparatus which con-
ducts the air to every part of the body. In the Crustacea the
heart begins to be concentrated; there are arteries and veins : the
single cavity of the heart receives the blood from the gills and
distributes it to the body. In the Mollusca the heart consists
of an auricle and ventricle. In the highest of this class, there-
fore, it resembles the systemic heart of Mammalia; but in
some of the lowest it surrounds a part of the intestinal tube,
and in this respect they form a link between the others and those
animals in which the heart and digestive cavity are one and the
same organ. In the Vertebrata, wherever the heart is single it
belongs to the lungs; and here first the nutrient matter is ab-
sorbed from the digestive cavity by peculiar vessels, and then
conveyed to the circulating system. As the pulsating vessel is
gradually concentrated, so also is the nervous system. When
the heart has the form of an oblong sac, the nervous system pre-
sents a series of swellings connected by a single or double cord.
In the Mollusca the heart becomes more globose, whilst a cen-
tral mass of nervous matter represents the brain, and in many
instances surrounds the cesophagus as the heart does the intes-
tine in some. In vertebral animals the ganglionic chain becomes

a spinal cord, the ring a brain of a spheroidal shape, whilst the

heart is a more perfect central organ; and here first a peculiar

system of nerves is appropriated to the nutrient apparatus (the

sympathetic), whilst there is a peculiar set of vessels for absorp-

tion. Thus do the nervous and circulating systems appear to.

advance simultaneously towards perfection, the one being a con-
dition, but not a cause, of the other’s existence. In all the ver-
tebral animals the heart lies below the spinal cord and abdomi-

oe. 2) oe ss

*

_

REPORT ON ANIMAL PHYSIOLOGY. 133

nal canal. In all the invertebral it is placed above the gangli-
onic string, and above the abdominal canal*.

____-‘Treviranus has given a table in which the weight of the heart
__ is compared with that of the body, in the different classes of ver-
- tebral animals. In the Mammalia it varies from gq to zig 3 in
Birds, from 3, to z4z 3 in Amphibia, from 74; to 743 in Fishes,
from 51, to 74z- So that, assuming its power to circulate the
Dlood through the body to be in proportion to its weight rela-
_ tively to that of the body, he concludes that its influence de-
creases with the descent of the animal in the series.

__ Whether the arteries in any degree assist the heart in effecting
the circulation of the blood, is a question upon which physiolo-
" gists are by no meansagreed. That the heart is able to perform
__ this office alone, is proved by those cases where the circulation
in the limb was continued, though the main arteries were com-
pletely ossified and incapable of contraction; and that it does do

t
?

aries, whilst the blood is seen to flow more quickly in the
ns on contraction of the heart. Poisseuille{ has detailed ex-
eriments in which he has shown that the artery certainly dilates
d contracts under the heart’s action, which had been denied
Bichat and Parry, the cause of the pulse assigned by them
ng a motion of the entire artery in space, without alteration
diameter. By means of a metal cylinder capable of being
ened like a box, he surrounded a portion of the carotid artery
a horse with water. A small graduated glass tube projected
m the cylinder: the water rose and fell in the tube on expan-
m and contraction of the heart, thus evincing the varying vo-
eof the artery. With another apparatus he measured the
ecoil of the same artery, having detached a portion of it from
ebody. A glass tube was fixed to each extremity of the ar-
ry laid horizontally. Both tubes then turned perpendicularly
wnwards for a space; then one perpendicularly upwards, the
her upwards at an angle of 45°. The former had a stop-cock
the extremity near the artery, the other at the distant extre-
mity. The artery, filled with water, was submitted to a given
pressure by mercury and water, which filled the oblique tube,
mercury alone, which balanced it in the other. The artery
g thus distended, the stop-cocks were turned. When that
he extremity of the oblique tube was opened, the recoil of the
artery caused the mercury to rise in it, and to drive off a portion
_ * Vide Burdach, vol. iv. p. 451.
+ Erscheinungen und Gesetze des Organischen Lebens, p. 225. 1831.
a 4 - } Majendie’s Journal, vol. ix. p. 48.

taal

134 FOURTH REPORT—1834.

of the water. The perpendicular height of the remaining co-
lumn of water appeared to show that the contractile power’ of
the artery was greater than the power which dilated it by fifteen
millimetres of mercury. We suppose, however, that little can
be concluded from this experiment respecting the quantity of the
contractile force of the artery in the living body. It is placed
in the experiment in very different conditions. Being forcibly
dilated between fixed points, its coats represent in the longitu-
dinal direction a series of elastic cords, which are forced into
curves, and the whole effect is due in part to the recoil of these,
and in part to that of the circular fibres.

The elasticity of arteries, which lasts after death until decom-
position takes place, differs from that vital exertion of it called
tonicity, which is soon extinguished. By means of the two,
particularly the latter, the artery always adapts itself to its con-
tents. In consequence of the latter alone, the artery is smaller
shortly after death than after the lapse of several hours. I know
of no experiments which satisfactorily indicate any rapid con-
traction of arteries, which can be referred to muscularity. Their
middle coat, in which that property has been supposed to reside,
has been shown by Berzelius to differ from muscle, in being
more elastic, in having less combined fiuid, in being insoluble
in acetic acid, soluble in mineral acids, but not precipitable from
the solution by potass. Its fibre affords no trace of the trans-
verse strize which Hodgkin and Lister regard as a peculiar cha-
racteristic of muscle.

The pulse, depending upon dilatation of the arteries from the
force of the left ventricle, has until lately been by many supposed
to be synchronous throughout the body. KE. H. Weber, after
Scemmerring, Majendie, Stocks and Carlisle, has shown that it is
not exactly so; and for the reason that the arteries are not rigid
tubes. The blood driven by the heart into elastic tubes, distends
them by an undulation which is progressive. The pulse, which
is the distension of the vessel, is synchronous only at equal di-
stances from the heart, and in arteries at considerable distances
from the heart follows its beat by one sixth or one seventh ofa
second.

Heart.—Poisseuille, in order to ascertain the force with which
the heart drives the blood into the aorta, has repeated some of
Hales’s experiments in a more accurate manner. His appara-
tus consisted of a glass tube, bent into a semicircle, so that its
branches were parallel. The shorter of these was again bent at
right angles, and nearly to this level the parallel branches were
filled with mercury. What remained of the shorter still empty,
together with its horizontal portion, was filled with a solution of

REPORT ON ANIMAL PHYSIOLOGY. 135

subcarbonate of soda, in order to prevent coagulation of the blood
when the extremity of the horizontal portion was introduced into
an artery. The instrument being so introduced, the mercury
___- was found to oscillate in the parallel branches ; and the degree of
oscillation and altitude of the mean point was measured by means
__ of a graduated scale on the long limb, when the instrument was
held so that this should be perpendicular. The oscillation was
caused by the respiration of the animal, the mercury falling on
_ inspiration and rising on expiration. The mid point was found
(correction being made for the weight of the column of solution
of subcarb. sod. in the short branch,) to stand always at the
_ same place, whatever artery it might be into which the instru-
- ment was introduced, upon an average of many observations for
% each ; and gave the height of a column of mercury equal to the
om: "mean pressure of the heart, thus shown to exert the same force
_ throughout the whole arter ial system. ‘This mean pressure, mul-
_ tiplied by the area of the aorta, gives the statical force of the left
ventricle.
~The mean pressure was found to be in no degree proportional
o the weight of the heart, and to differ so little in animals of
ery unequal size that Poisseuille is disposed to attribute the
lations to individual circumstances of health, age, &c.; and
mks it not unreasonable to conclude that the blood is moved
great and small animals, and in different species, with the same
orce. From such principles it will follow, that the statical force
the heart in different animais will be proportional to the
uare of the diameter of their aortas. The mean pressure in
e Dog, the Horse, the Mare, was between the limits 140 and
0 millimetres. Taking the mean of these limits, and measur-
the aorta, the weight of a column of mercury equal to the
tical force of the heart (that with which the blood moves in
e aorta) is found in Man to equal 4lbs. 30z.; in the Horse,
Ibs. 100z. The statical force with which the blood moves in
radial artery in man under the same pressure equals half an
ace.
If the account which I have given of the beat of the pulse be
ect, that of the heart against the sides of the chest will de-
nd upon the contraction of the ventricles. I ought to men-
, however, that Corrigan, and Carson, and Burdach are op-

nsion of the ventricles, the contraction of the auricles imme-
‘diately preceding that of the ventricles. The last experiment
"y which I have found on this subject is that of Miiller*, per-
_ formed in conjunction with Prof. Albers. The chest of a Goat
a ‘ * Physiologie, p. 165.

136 FOURTH REPORT—1834.

was opened: whilst the animal lay on its back, the heart was vi-
sibly elevated during the contraction of the ventricles, and even
the apex turned upwards. When the hand was laid upon the
heart, the perceptible quivering was so powerful and so momen-
taneous, that it appeared impossible to assign the beat against
the ribs to any other cause than the systole of the ventricles, for
no agitation could be felt during the diastole.

This conclusion agrees with that which Mr. Carlisle derived
from his experiments. The dissections also of this gentleman
account for the tilting of the apex of the heart. The muscular
fibres, which pass from the basis to the apex, are found by him
to be considerably longer on the front than on the back part.
They contract therefore more: the apex is drawn towards the
basis, but at the same time forward*.

The causes of the two sounds which are perceptible by aus-
cultation, and which occur between two consecutive beats of
the heart, are scarcely yet determined to the satisfaction of phy-
siologists. The dull and more enduring sound is quickly followed
by one which is clearer and more brief, as was first well defined
by Laennec. They follow each other with a slight interval, and
then there is a pause. Laennec attributed the first to the con-
traction of the ventricles, the other to that of the auricles; but
the interval between the sounds does not correspond to the in-
terval between these contractions. All appear to be agreed that
the first sound is synchronous with the pulse at the heart, and
therefore they assign the cause of this as the cause also of the
first sound. Thus, Corrigan and others deduce the first sound
from the contraction of the auricles, the second from that of the
ventricles ; Williams, the first from the contraction of the ven-
tricles, the second from the action of the valves; Hope, the first
from the contraction of the ventricles, the second from the ex-
pansion of the ventricles by the bloodf.

Majendie, in a memoir read before the Academy of Sciences
of Paris, February 1834, has lately objected to all these explana-
tions. He could perceive no sounds when the heart was laid
bare; and therefore concludes that they cannot proceed from the
respective play of its different cavities, nor from the action of the
heart upon the blood, nor of the blood upon the heart. He then
institutes a set of experiments, in order to discover the true
cause of the phenomena in question. He found that though all
sound ceased when the sternum was removed, yet when elastic
bodies were brought in contact with the heart, sounds, variable
according to the nature of those bodies, were produced: when

* Vide Reports of the British Association, vol. ii. p. 456.
+ Compare Carlisle, loc. cit., p. 458.

REPORT ON ANIMAL PHYSIOLOGY. 137

the sternum of a Goose was raised and replaced, the sound was
annihilated and reproduced at pleasure; when air or water was
injected into the left pleura, so as to keep the heart at a distance
from the thorax, no sound could be perceived. Further, he found
_ that if he introduced a slip of metal, thin and fiat, into the thorax
_ of a Dog, so as to prevent the shock of the apex of the heart
against the parietes of the thorax, though the heart acted vio-
_ lently, the dull sound ceased ; if introduced so as to prevent the
right ventricle touching the thorax, the clear sound ceased.

-Majendie hence deduces the first sound from resonance of the
_ thorax, caused by the stroke of the apex; and the second from
_ resonance of the thorax, caused by the impulse afforded by the
heart, under sudden dilatation from the influx of blood, to the
anterior parietes of the right side of the chest.
% _ Bouilland, in a letter to the Academy of Sciences, has pro-
tested against Majendie’s explanation; asserting that it does
not satisfy the conditions, and raises a doubt concerning the va-
lidity of that theory alone which assigns the double sound to the
ay of the valves; (Romanet, in a recent inaugural dissertation,
ving maintained that the one sound arises from the shock given
the blood to the tricuspid and mitral valves, the other to the
ock on the sigmoid valves of the aorta and pulmonary artery ;
id E. L. Bryan the same in the Lancet.) Bouilland further
ges his own experiments. No sounds were heard when the
pulsated being emptied of its blood ; they were heard when
heart 72 sitw was laid bare, and had no connexion with the
is of the thorax. He further objects, that Majendie’s theory
yes not account for the varieties of sound produced by organic
ons of the valves ; nor for the fact, that sounds may be heard,
though distant, when fluid fills the pericardium and prevents
heart from reaching the thorax.
ere this subject rests for the present; but Majendie has un-
ken to examine, in a second part of his memoir, whether his
ation will account for all the particular circumstances con-
d with each of the sounds of the heart.
use of the Heart’s Action.—Haller, from observing that the
continues to beat for a considerable time even when re-
d from the body; and that its contractions, in the body,
y be affected by the direct application of mechanical and che-
stimuli to its fibres, whilst he could not influence them by
tion of the cardiac nerves, concluded that its power of con-
on is inherent, and totally independent of the nervous sy-
n. His theory was afterwards fortified by the dissections of
mmerring and Behrends, which appeared to show that the
ardiac nerves are distributed to the vessels of the heart alone.

188 FOURTH REPORT—1834.

And even after Fowler, Humboldt, and others had stated that the
heart may be stimulated by galvanizing its nerves, and Scarpa
had demonstrated that these are distributed to its substance as
in other muscles, Haller’s theory, though vehemently opposed
at first, came to be very generally received. It, however, met a
formidable opponent in Le Gallois, who published, in 1812, an
essay, containing results of numerous experiments, from which
it appeared that the heart’s power is altogether derived from the
spinal cord. He found, that if a Rabbit be decapitated, the heart’s
action is continued, artificial respiration being performed; that
if a portion of the cord be destroyed, as in the lumbar region,
the heart is unable to support the circulation, in a Rabbit twenty
days old, longer than four minutes, whilst it is continued in one
two days old; and that the destruction of the cervical and dor-
sal portions of the cord are still more suddenly fatal to the
heart’s action. He observed, on destroying successive portions
of the cord, that even when the circulation is suddenly arrested
life ceases, on the instant, only in those parts which derive their
nerves from that portion of the cord which has been destroyed,
continuing for a time in the rest of the body; that this time is
greater the nearer the animal is to the epoch of its birth, and is
determinate for each species. He concluded that those parts
which die last, on partial mutilation of the cord, die because the
power of the heart has been so much weakened that the circula-
tion through the entire arteries cannot be maintained. He hence
inferred, that if the work to be performed by the heart were
diminished in proportion as its power was lost, the circulation
might be supported. He found, accordingly, that if the aorta
was tied opposite to the part of the cord to be destroyed, the
circulation was continued through the remaining portion of the
trunk in connexion with the heart. His general conclusions
were, that the heart has no intrinsic power, but that it derives
its power from every part of the spinal cord; that each part of
the body is animated by that part of the cord from which its —
nerves arise; that the sympathetic system of nerves has its ori-
gin in the spinal cord, and not in the ganglia, its office being to
bring the parts to which it is distributed within the influence of
the whole nervous power of the cord; that the motions of the
heart which are visible after excision from the body, are similar —
to those which may be excited in other muscles after they have

been for some time dead, and are merely cadaveric phenomena. —

In 1818, Dr. Wilson Philip published his essay on the laws of |

the vital functions, and reviewed Le Gallois’ experiments and —
observations*. By unexceptionable experiments he showed,

* The first experiments of Dr. Philip are in the Phil. Trans. for 1815.

REPORT ON ANIMAL PHYSIOLOGY. 139

that if the sensibility of the Rabbit be destroyed by a blow on the
head, the brain and spinal cord may be entirely removed, the
heart still continuing to act, By other experiments he showed,
_ that (the sensibility of the animal being destroyed,) the heart may
be excited to act more powerfully by stimuli applied to any part
__ of the brain and cord; that if the stimulus be very powerful, as
_ erushing the central parts of the nervous system suddenly, the
action of the heart is suppressed. He infers from hence that
_ the mode in which Le Gallois destroyed the cord exhausted at
- once the excitability of the heart in those instances in which it
entirely ceased to act, and impaired it in others. He remarked
that the increased action of the heart could generally he observed
as long as the stimulus, whether chemical or mechanical, was
applied, unless it was of a nature to produce the sedative after the
stimulant effect; and inferred that the former isa direct opera-
tion of the agent, when it is observed, and not a consequence of
the latter. Dr. Philip therefore concludes, with Le Gallois, that
_ the functions of the cord are independent of the brain; and that
_ the heart is acted upon by every part of the cord. But he dis-
_ proves altogether Le Gallois’ opinion that the irritability of the
art is a quality derived from the cord. He proves that it re-
_ ceives no power from the central parts of the nervous system ;
_ but that nervous influence, like any other stimulant, is capable
of exhausting its excitability ; that it is acted upon not by the
cord alone, but by every part of the central masses, the brain
_and cord: obeying a much less powerful stimulus than the mus-
cles of voluntary motion, but that the stimulus must extend over
i large surface of the brain or cord to affect the heart.
_ Flourens*, from his experiments on fishes, concludes that the
wer of the heart is inherent, and is influenced only by destruc-
on of that part of the nervous system whose integrity is neces-
y for respiration, the medulla oblongata.
Dr. Marshall Hall}, making the Frog and Eel the subjects of
experiments, because the transparency of parts at different
ances from the heart (in the former the web and lungs,
the latter the caudal, dorsal, and pectoral fins,) allowed him
test the varying power of the heart to circulate the blood,
is deduced the following conclusions: that the heart’s action
enfeebled from the moment it is deprived, at once, of the in-
ence of the brain and cord; that it possesses an independent
ritability, which however, like that of the voluntary muscles,
lost after the organ has been separated from the central masses
the nervous system; that the circulation is first enfeebled,
n lost, in the most distant parts of the body from the heart,

* Mém. de l'Institut, tom. x. + Essay, 1831.

140 FOURTH REPORT—1834.

then in parts less and less remote; but that the power of cir-
culation in each part does not depend upon that portion of the
cord from which it derives its nerves. He has proved, by de-
cided experiments, that Flourens’ opinion of the dependence of
the power of the heart upon that. part of the central nervous
masses which supplies the nerves to the respiratory muscles is
unfounded, if that could be doubtful after Clift’s experiments on
the Carp, published in the PAil. Trans. 1815. Dr. Marshall Hall
could not observe that opium or spirit of wine, applied, to the
brain or cord, accelerated the circulation, as recorded by Dr.
Wilson Philip.

From these several experiments we conclude: that the heart’s
power is inherent, and not derived from the brain or cord ; that
it is under the influence of every part of the brain and cord;
that it endures for a time, even when the heart is separated from
the body.

The rhythmical contraction of the heart is an instance of that
periodicity which occurs in all involuntary motions, even in the
minute oscillations of the fibre on which the contractions of
those muscles depend which we call voluntary. The whole con-
tractionin the one case is periodical, for the stimulus is constantly
recurring; in the other the stimulus is dependent on the will.
Though the successive presence of the blood in the different ca-
vities of the heart may, as Haller explained, be the ordinary sti-
mulus to its activity, yet it cannot be the only one, for the rhyth-
mical contraction occurs when the heart is empty, and even when
placed in vacuo. Why then does the heart continue to act under
such circumstances, and what is the stimulus? We have seen,
from consideration of the growth of the embryo, that organic
activity depends upon the mode in which matter is compounded
under the assimilative process. Those organs which receive
more blood, are more active than those which receive less; and
such as are liable to be called into sudden and excessive action,
as the voluntary muscles, receive most blood of all: the blood
is there for assimilation as it is wanted; aerated blood, proper
temperature, and most probably nervous influence being neces-
sary conditions of the process by which each creature is enabled
to maintain that form and mixture of its parts which is neces-
sary to their life. Nutrition, then, or a constant interchange
between the particles of the organ and of the blood, being neces-
sary, it follows that something has occurred in the organ during
its active state, some alteration, which requires repair. Activity
has caused a change in that composition of its molecules which
nutrition must restore. If the restoration do not occur, the sub-
sequent reaction is different, or is impossible. The heart, when

REPORT ON ANIMAL PHYSIOLOGY. 141

removed from the body, responds to stimulation as long as the
composition of its tissue is such as to render it capable of doing
so. The stimulus may be the blood remaining in its vessels, if
its cavities be empty ; or may be the nervous influence which,
a there is reason to suppose, remains in its nerves for a time after
__ they have been cut off from communication with the brain and
cord. Underthese two conditions it is even possible that a low
j degree of assimilation may yet go on, which however can never
completely restore the state which the fibre possessed at the
time when any individual contraction was performed. The ex-
_ citability at length ceases. But even without this supposition,
1 stimuli which do not at the same time afford food for the nutri-
tive process, can, if food be not otherwise supplied, merely
_ exhaust. The final cause of this perdurance of a certain degree
_ of irritability in the heart, even when nutritive supply and ner-
“yous energy are suspended or imperfect, is obvious.
___Dr. Carson has pointed out the effect which the empty state
the auricles produces upon the circulation in the veins, im-
rting to the heart the power of a sucking instrument; and
_ also the effect of the resilient or elastic nature of the pulmonary
tissue in subjecting the heart to a less atmospheric pressure
than the rest of the body*.
Poisseuille, by means of his barometrical instrument, has
nfirmed Sir J. Barry’s conclusions respecting the effect of in-
ation on the venous circulation, as far as the large vessels
the heart are concerned. When the instrument was in-
uced into the vein of a Dog, towards the heart, the mercury
60 millimetres above the zero point during expiration, and
1 70 m. below it during inspiration ; the degree of rise and fall
ing with the struggles of the animal, but occurring syn-
nously with the respiratory movements. He did not find
; inspiration at all influenced the veins of the extremities ;
he confirmed Majendie’s observation, that expiration assists
not only the motion of the blood in the arteries, but that its
ffect extends through the capillaries to the veins; the blood
in them all during expiration, (the instrument being at-
ed to the peripheral portion in the case of the veins,) and
ing the systole of the heart..
rom all these experiments we conclude, that the heart sup-
s the power which effectually moves the blood in the higher
mals, not only through the arteries (to which Bichat con-
ned its effect), but also through the capillaries and the whole
ous system; that it is assisted by the elastic power of the
ries after they have been distended by the heart’s action upon
* Inquiry into the Causes of Respiration, §c.

5

142 FOURTH REPORT—1834.

the blood; assisted also by pressure, whether atmospheric or
otherwise, on account of the disposition of the valves in the ar-
teries and in the veins; that the vis a ¢ergo is more effectual
during expiration ; and that the return of the blood to the heart
is facilitated by the empty state of the auricles and by inspira-
tion ; that the vital attraction and repulsion between the mole-
cules of the organs and of the arterial and venous blood is a con-
current cause.

Hering has published some valuable experiments* made with
a view to determine the time in which the circulation is effected.
His method was to pour a solution of some harmless substance,
easy of detection by tests, as prussiate of potass, intoa vein; and
to determine, by observation of the blood taken from another
distant vessel at short intervals, how soon the presence of the
injected solution could be discovered in the latter. In Horses
it passed from one jugular vein through the lungs and great cir-
culation, and was detected in the opposite jugular vein in a time
varying from 20 to 25 and from 25 to 30 seconds; from the
jugular to the saphena, in 20°; from the jugular to the external
maxillary artery, in from 10% to 15°, and in another instance
from 20° to 25°; from the jugular to the metatarsal artery from
208 to 258, and from 255 to 30°; once it required 40°.

From other experimentst Hering has concluded that the ve-
locity of the blood is independent of the frequency of the heart’s
action. The prussiate of potass was not detected more quickly
than usual when the heart’s action had, in numerous instances,
been greatly quickened by infusion of tinct. of white hellebore,
camphorated spirit, &c. If, with Hales, we estimate the weight
of a horse at 800lbs., and his blood at 40lbs., which is certainly
not too high an estimate, and allow ten ounces to be thrown
from the heart at each systole, (the greatest possible quantity,)
then 1™ 37: will be the least time in which the whole mass of
the blood will go through the heart*. And though the circula-
tion consists not of one, but of many circles, the smallest being
that of which the course through the coronary vessels of the
heart forms part, and though each of these circles be performed
in a different time, yet it appears difficult to make any probable
supposition respecting the circuit taken by the substances in-
jected in the above instances which will satisfy the rapidity
with which they were detected. How then is their quick trans-
ference to be explained? Probably, as is suggested by Muller,
the foreign fluid diffuses itself through the mass of the blood
more rapidly than the latter circulates.

* Zeitschrift fiir Physiologie, vol. iii. | Zeitschrift, vol. y. part 1.

¥ Burdach.

143

Report on the Recent Progress and Present State of Zoology.
—By the Rev. Leonarp Jenyns, M.d., F.LS. F.Z.S.
e.P.S.

Tur following Report has been drawn up at the request of the
Section for Natural History of the British Association. I can-
not but express my regret that the task has not devolved upon
. Piet hands. The science of Zoology comprises such a wide
field, and so much has been effected in that field by the researches
_ of modern times, that it is difficult for any individual to obtain
a correct knowledge of all that is going on in different coun-
tries in its several particular departments. Still more difficult
is it to form in all cases a true estimate of the relative import-
se of the many facts and discoveries which are every day com-
to light,—to judge of their mutual bearing on each other,
nd their more or less immediate tendency to advance the pro-
gress of that science for the interests of which they are brought
orward. I must therefore hope for much indulgence from those
may discover in this attempt, what it is almost impossible
oid, many errors as well as omissions*. I have endeavoured
o avail myself of whatever sources were open to me, in order to
al the information requisite for the purpose ; but so numer-
s are the channels through which such information is now
blished, that I can hardly hope to have gleaned on this sub-
all which may be expected of me.
is right, however, that I should state in the outset, in what
int of view, and within what limits, I propose to consider this
ect. To follow it out in all its details would manifestly lead
beyond the bounds to which a Report of this nature must
arily be restricted. My intention, then, is principally to
tice those researches which of late years have tended to eluci-
te the characters and affinities of the larger groups of animals,
thereby to advance our knowledge of their natural arrange-
;. This will include the consideration of such systems as
been brought forwards in illustration of this part of the
t. With reference to this point, however, I do not pur-
ommencing from an earlier period than 1817, the year of
lication of the Régne Animal of Cuvier, whose general views
specting the classification of animals have been the basis of
t of those which have appeared subsequently. I propose,
rtheless, in the first instance, to make a few general remarks
I fear that these omissions will be found rather numerous, with respect to

erman works, some of which I have been unable to procure, whilst there are
_ probably others altogether unknown to me.

144 FOURTH REPORT—1834.

on the state of zoology in the early part of the present century,
and the circumstances which have led to the introduction of those
principles upon which it is now studied.

Il. Introduction.

It is now generally acknowledged, that the true and legitimate
object of zoology is the attainment of the Natural System; and
we may attribute it to this circumstance, and the consequent
close investigation of structure and affinity to which it has led
naturalists, that so striking a change has been effected of late
years in this science, causing it to assume an aspect at once cha~
racteristic of a distinct epoch in its history. Little else ap-
peared to be the aim of Linnzus and his followers beyond
that of distinguishing species, and classing them simply in
accordance with some law of arrangement arbitrarily assumed
in the first instance, and too often pertinaciously adhered to in
utter disregard of the general organization ; and although it may
have been their endeavour to group together those species a-
mongst which there appeared a certain resemblance, yet they
did not hesitate in numberless instances to associate in the same
class and order, and often in the same genus, beings of the most
discordant nature, rather than renounce the principle which they
had adopted for their guide. It is undoubtedly to Cuvier that
we are most indebted for the striking improvements which be-

an to be made upon the Linnzan system towards the close of
the last century*. This great master of modern zoology saw
the importance of studying the entire organization of animals.
He traced the connexion which subsists between their internal
and external structure, observed how these accorded with their
habits and ceconomy, and perceived that in grounding a classi-
fication of animals upon characters taken from these sources col-
lectively, we should make a near approach towards grouping
them according to their true and natural affinities. Daubenton
and Pallas had already furnished some materials for such an un-
dertaking, and by their exact descriptions, paved the way for a
more complete knowledge of animal structure; but it was re-
served for Cuvier to erect the building of which they may be
said to have only laid the foundation. Commencing with a re-
investigation of the invertebrate animals, which, according to the
statement of the French naturalist, Linnzus had left in a state

* It is not meant that there were none others besides Cuvier who had any
share in effecting this change, but only that he appears the most prominent.
Bruguiéres, Geoifroy St. Hilaire, Latreille, and Lamarck, especially the last, all
contributed to this end in their several departments. The labours of some of
these naturalists will be alluded to further on.

REPORT ON ZOOLOGY: 145

of worse arrangement than that of Aristotle, he afterwards passed
on to that of the higher classes*, carrying with him that reform
which the new principles he had adopted pointed out to be ne-
cessary. Cuvier’s first memoir on the Invertebrata was offered
to the notice of the Natural History Society of Paris in 1795,
and the time should be remarked as commencing the zra of a most
important revolution in zoological science. His Tableau Elémen-
taire de l Hist. Nat. des Animauz, containing a still further
development of his views, was only two years posterior to it.
This was followed by the Lecons d’ Anatomie Comparée, pub-
lished in 1800 and 1805 ; a rich series of memoirs on the mollus-
cous animals, which appeared in the earlier volumes of the dn-
nales du Muséum; the Recherches sur les Ossemens Fossiles, of as
great service to zoology as geology, and much of which was also
firstpublished in that collection; and lastly, in 1817,by the Régne
Animal, in which it was attempted to arrange all known animals
according to their natural affinities, as deduced from a compara-
tive view of their whole organization.

_ The above works, of some of which I shall have occasion to
speak further hereafter, were not only important in themselves,

_ but in the consequences to which they led.
In the first place, it is worthy of remark, that since these ad-

mirable endeavours on the part of Cuvier to elucidate the true
relations of animals by reference to their internal as well as ex-
ternal structure, and to the modifications, not of one or two ar-
bitrarily selected organs, but of all the organs considered jointly,
naturalists have everywhere felt the necessity of guiding their
researches after the same manner, and building upon a similar
foundation. If zoology has made much progress, as undoubtedly
it has, since the publication of the first edition of the Régne Ani-
mal; if more enlarged views have been acquired of the science
as a whole, and a more correct knowledge gained of some of its

‘Subordinate branches ; if new forms of structure have been dis-
_ covered, and affinities brought to light, which at that time were
_ not even suspected to exist by its illustrious author ; this is great-

ly due to the assistance which the science has derived from com-
parative anatomy: and it must never be forgotten, that it was
Cuvier principally who first taught us, in the works above alluded

_ to, how to bring this great and powerful instrument to bear

upon the researches of the naturalist. Yet it must not be sup-
posed from the intimate connexion which subsists between these

_ two sciences, that there is no line of distinction to be drawn

as

_ * In the arrangement of the Mammalia, Cuvier was much assisted by Geof-
roy. Their joint labours in this department form the subject of a memoir pub-
lished in the Magasin Encyclopédique, tom. ii. p. 164.

1834, L

146 FOURTH REPORT—1834.

between them. It is the object of the anatomist to investigate
the details of structure, and to record all facts connected with
the relative organization of animals. That of the zoologist is to
arrange these facts, and to make them subservient towards de-
termining the natural affinities of animals. Hence the latter is
but little concerned with any details which do not exercise a
marked influence upon the manner of life, or with those minute
differences of structure which are not accompanied by corre-
sponding differences in the rest of the organization*. What he
seeks for is a subordination of characters, selected in the order
of their importance, on which to build his system ; and to judge
of the value of any one in particular which anatomy presents to
him, he must trace by observation how far it is connected with
others, whether external or internal, or derived from the cecono-
my and mode of life, of which the value is known. On sucha
comparison, it may prove of too small importance to assist in
determining the affinities of a single species. Yet we can hardly
pronounce that it may not be found of some value hereafter ;
for although it may not in itself be sufficient to establish an affi-
nity, it may tend to corroborate our ideas respecting those which
would seem already indicated by other characters. And con-
sidered in this view, even the minutest anatomical details may
prove of service to zoology. As an instance in point, we may
refer to Mr, Owen’s recent discovery of a peculiar modification
of the stomach in the genus Semnopithecust. This genus had
been originally established by Geoffroy upon a slight difference

* It has been a complaint with some naturalists that zoology has of late
years been too much invaded by comparative anatomy, and that it has been in
danger of suffering from the encroachments of that allied science which was
originally called in to its assistance. For remarks on this subject the reader is
referred to the article Zootoeie in the Dict. Class. d’ Hist. Nat. (p.727), and the
Introduction to the Hist. Nat. des Mammiferes, (p. 2, &c.) by M. Fred. Cuvier.
Mr. Swainson would also seem to say as much in his Preliminary Discourse on
the Study of Nat. Hist. (pp. 84, 169, &c.), published since this Report was read.
To a certain extent there may perhaps be some ground for the complaint; but
it appears to me that it is only called for in those cases in which it has been
attempted to arrange animals solely from anatomical characters, no considera-
tion being paid either to external form or to the habits and manner of life. We
may fall into the error of attaching too much importance to differences of inter-
nal structure, as easily as we may in the case of those of external. The factis,
the whole must be considered collectively, and it is the relative value of the or-
gans, when viewed in their mutual dependencies, which alone should decide
on which of them we are to base our system. But after having determined our
groups in this manner, we may generally succeed in finding, at least amongst
the higher animals, some external character. by which they may be distin- ~
guished. And wherever this is the case, I fully agree with Mr. Swainson
(pp. 169 and 247), that for convenience sake such external characters should
be exclusively employed.

+ Zool. Trans., vol. i. p. 65.

wan

REPORT ON ZOOLOGY. 147

only in the dental system, and there were some doubts as to whe-
ther it should be retained. . Now, however, that we find it also
characterized by an accompanying difference in the internal or-
ganization, its claims to be admitted as a distinct group in the
system are considerably strengthened. In another communica-
tion this able anatomist has expressed an opinion*, that even
such details as tracing the convolutions of the brain “ may ad-
vance zoology, by bringing to light additional instances of affi-
nities between the different groups of Mammalia;’’ and he
grounds this opinion upon the fact of his having observed a re-
_markable uniformity of structure in this organ, in groups which
have been long since well established upon other characters.
At the present day, however, it is amongst the lower animals
that the researches of the anatomist will most assist zoology.
The structure of the higher classes is in general well understood,
and it is not likely that any future discoveries in anatomy will
much affect our present arrangement of the leading groups in
those classes, however they may contribute to the perfecting the
details of the system. But amongst the Invertebrata it is far
‘otherwise. There we not only find large groups of animals of
whose internal structure we know but little, but they are often
groups in which the external characters cannot be trusted, and
in which it becomes necessary to resort to the same organs for
distinguishing orders, families, and even genera, which in the
Vertebrata would only be employed in characterizing classes, or
groups of a still higher denomination. This arises from the much
more variable structure of the lower animals, with which there-
fore it becomes the more necessary for the zoologist to be ac-
-quainted.
_ Another circumstance which has in some measure resulted

a from Cuvier’s labours relates to the country in which these la-
_ bours were exerted, and their fruits made public. His works

have had a manifest influence over his countrymen. Those who
surrounded him quickly adopted his new views and principles ;

_and partly to this circumstance, partly to the magnificent esta~
blishment of the Jardin des Plantes, are we to attribute the
al rise of a school of zoology in France, which has ever
e maintained the highest reputation. It is only necessary

refer to some of the many valuable werks which appeared

ae

_ during the early part of the present century, in order to appre-
_ Giate the zeal and success with which zoology was cultivated in

_ that country. Lamarck’s Systeme des Animaux sans Vertébres

, _ and Philosophie Zoologique, Dumeril’s Zoologie Analytique,

8 Latreille’s Hist. Nat. des Crustacés et des Insectes, the Genera

* Zool. Trans., vol. i. p. 136.
L2

148 FOURTH REPORT—1834.

Crustaceorum et Insectorum by the same author, Brongniart’s
Essai @une Classification Naturelle des Reptiles, Savigny’s Mé-
moires sur les Animaux sans Vertébres, Lamouroux’s Histoire
des Polypiers Coralligenes Flexihles*, (not to dwell upon a rich
series of memoirs in the Annales du Muséum, Journal de Phy-
sique, &c., by Geoffroy, Fred. Cuvier, Blainville, Péron, Lessueur,
and others,) all appeared before the publication of the Régne
Animal, and not only contributed greatly to the further illustra-
tion of the natural system, but furnished many valuable hints to
Cuvier himself whilst engaged in that undertaking. England, we
fear, has but little to produce as the result of her labours in zoo-
logy during the same period. Our countrymen were too much
riveted to the principles of the Linnzan school to appreciate
the value of the natural system. Although there were some good
descriptive works in different departments, and a few excellent
observers, amongst whom Montagu will ever hold a distinguished
place, there was in general but little attention paid to structure
with a view to elucidate the natural affinities of animals. The
most remarkable, if not the only exception is undoubtedly to be
found in Kirby’s Monographia dpum Anglia, a work which,
though exclusively devoted to the illustration of a single Linnzan
genus of insects, presents a model for naturalists in all depart-
ments, from the profound views of its very illustrious author.
There were few, however, who followed up the path which was
thus opened to them. There was a general repugnance to every-
thing that appeared like an innovation on the system of Linnzus;
and for many years subsequently to the publication of the above
work, which appeared as far back as in 1802, zoology, which
was making rapid strides in France and other parts of the Con-
tinent, remained in this country nearly stationary. It is mainly
to Dr. Leach that we are indebted for having opened the eyes of
English zoologists to the importance of those principles which
had long guided the French naturalists. Whilst he greatly con-
tributed to the advancement of the natural system by his own
researches, he gave a turn to those of others, and made the first
step towards weaning his countrymen from the school they had so
long adhered to. The following are the principal works which re-
sulted from Dr. Leach’slaboursin zoology about the period of time
referred to. In 1813, he published the article CkusTacEOLOGY
in the Edinburgh Encyclopedia, in which he gave the system
of Latreille, with some slight modifications. In 1814, he gave,
in a paper to the Linnzan Society, “‘ A tabular View of the ex-

* In the above list I have not included the splendid volumes by Desmarest,

Vieillot, Audebert, &c., the object of which was more to illustrate species by
coloured plates than to treat of their systematic arrangement.

’ REPORT ON ZOOLOGY. 149

ternal Characters of the four Classes of Crustacea, Myriapoda,
Arachnida, and Insecta, with the Orders and other Subdivisions
of the three first of these Classes.’’ In the same year he com-
menced the Zoological Miscellany, which, though principally
intended for the illustration of new or little known species, con-
tains (the 3rd vol. especially, published in 1817,) an indication
of many new groups in different classes of zoology, with their
characters and natural affinities. In 1815, he published the article
Enromocoey in the Hdinburgh Encyclopedia; and in the same
year he commenced the Malacostraca Podophthalma Britannia,
which tended so much to our further knowledge of the Crustacea.
Besides the above, Dr. Leach also wrote the articles ANNULOSA
and Crrripepss in the Supplement to the Encyclopedia Britan-
nica, the latter containing an entirely new classification of these
animals. It is much to be regretted, that soon afterwards the la-
bours of this distinguished naturalist were interrupted by illness.
He had prepared and nearly completed a valuable work on the
British Mollusca, to the natural arrangement of which group he
had devoted great attention. Part of it was printed, though
never published. His other works, however, sufficiently testify
the obligations conferred by him on zoology. At the same time
they form a marked epoch in the history of this science, as con-
nected with our own country. Since the time of their publica-
tion many other excellent naturalists have arisen amongst us to
contribute to its advancement, to whom I need make no further
allusion at present, as of some I shall find occasion to speak

hereafter.

Il. Of the primary Types of Form, and other leading Divisions,

in the Animal Kingdom.

_ Cuvier considered the animal kingdom as exhibiting four pri-
mary types of form, to which he gave the names of Vertebrata,
Mollusca, Annulosa, and Radiata. The leading characters are
derived from the nervoussystem, which Virey was the first to point
Out* as the most important part of their organization, and there-

fore the most fit to be selected as the groundwork of the system.

Cuvier’s first enunciation of this arrangement was in a memoir
published in the 19th vol. of the dun. du Mus. in 1812, being five
years before the appearance of the Régne Animal. In it he ob-
serves, that he regards these four types or general plans as those

after which all animals appear to have been modelled, and of
_which the subordinate divisions are only comparatively slight mo-
_ difications, founded on the development or addition of certain

parts, which produce no essential change in the original plan,
* Nouv. Dict. d’ Hist. Nat., Art. ANIMAL. :

150 FOURTH REPORT—1834.

Before the date of this memoir, naturalists had generally a-
dopted Lamarck’s primary division of Vertebrate and Inverte-
brate animals. Cuvier objected to this, on the ground that there
were as great differences of structure amongst these last, as any
of those by which they were separated from the vertebrate divi-
sion. In his Hist. Nat. des An. sans Verteh. (the first volume of
which was published in 1815), Lamarck somewhat modified his
former views, by distributing animals under the three divisions
of Intelligent, Sensible, and Apathetic. As this arrangement,
however, is obviously objectionable, and has not met with much
reception, I do not consider it necessary to dwell further on it*.
I shall proceed, therefore, to noticesome modifications of Cuvier’s
system which have been proposed by different authors, as well
as some new systems and principles of arrangement which
have appeared since the publication of the Régne Animal, and.
which from their importance appear deserving of consideration.

The first in order of time, with which I am acquainted, is a
modification of Cuvier’s primary divisions proposed by Geoffroy
in 1820, and which arose from his peculiar views respecting the
unity of composition in animals. It is not necessary at the pre-
sent day to enter into any detailed analysis of these views, which
have been so long associated with the name of this distinguished
naturalist, and which belong more to the department of compa-
rative anatomy than zoology. It is sufficient to state that Geof-
froy, who had previously endeavoured to show that all vertebrate
animals were constructed so exactly upon the same plan as to
preserve the strictest analogy of parts in respect to their osteo-
logyt, thought to extend this unity of plan by demonstrating,
as It appeared to him, that the hard parts of Crustacea and In-
sects were still only modifications of the skeleton of higher ani-
mals, and that therefore the type of Vertebrata must be made to
include them also. It is impossible in this Report to follow up
the train of reasoning and anatomical] research which guided
Geoffroy in his attempt to establish this theory. The general
results at which he arrives are, that the segments of the dnnu-
losa are strictly analogous to the vertebre of the higher animals,

* Although Lamarck’s leading divisions are objectionable, there is much in
his system which is extremely valuable, particularly as respects the arrangement
of the Invertebrata. He was the first to point out that these last, if placed ac-
cording to their true affinities, must be considered as forming two distinet sub-
ramose series, one consisting of the articulated, and the other of the inarticu-
lated invertebrate animals.—See the Supplement to his first volume, p. 457.

+ Geoffroy’s principal memoirs relating to this subject were collected into one
volume, and published in 1818 under the title of Philosophie Anatomique. Se-
veral others however, more or less connected withit, are to be found in the Ann.
du Mus.

aa

Ps
*

_ demy at Toulouse, Jan. 1833. (L’Jnstitut, 1833, p. 3.) The other is a memoir

, sul
182:

¥

REPORT ON ZOOLOGY. 151

and that the former live within their vertebral column, in the
same manner as the latter do without. It is clear that, assum-
ing the correctness of these views, it becomes necessary to make
some alteration in the leading divisions of Cuvier’s system. The
following is the arrangement proposed by Geoffroy :

44)

Vertébré Hauts-Vertébrés. (Vertébrés, Cuv.)
S \ Dermo-Vertébrés. (Articulés, Cuv.)
aciz. § Mollusques. (MJollusques, Cuv.)
Hane a { Rayonnés. (Rayonnés, Cuv.)

Animanx

_ Thus we have a primary division into vertebrate and inverte-

rate animals, before arriving at Cuvier’s four types, taking
however the term vertebrate in a much more extended sense
than did Lamarck, or any other previous author, and likewise
that of invertebrate in a more restricted one. Geoffroy’s me-
moirs on this subject were published, as already stated, in 1820,
in the Journal Complémentaire*, &c. He subsequently fol-
lowed up the same views in some other publications, more
especially in a paper in the Mém. du Mus. for 1822+, in which
he entered into a strict analysis of the structure of the-vertebra,
first as it occurs in the higher animals, and afterwards as it ap-

ears, though modified, in the segments of the dnnulosat. His

heory, I believe, has been adopted by many of the French and
German naturalists, as well as by some in other countries.
Amongst the former, I may particularly mention Robineau-

lesvoidy, who in 1828 published a work§ in order to substan-
ate, by still further illustration, the vertebral structure of the
acea, Arachnida, and Insecta. Towards the conclusion, he

2 has pointed out the necessity (as it appears to him) of institut-
_ ing several new classes amongst the annulose animals. It may

be much doubted, however, whether these new classes will ever
be adopted generally, whatever may be the fate of those theore-
tical views which have alone suggested them ||.

%,

| “ Mémoires sur l’Organisation des Insectes,” Journ. Complém. du Dict.
8 Sci. Med., tom. vy. p. 340; and tom. vi. pp. 31 and 138.
tom. ix.
See also his Cours de I’ Hist. Nat. des Mammiféres, Leg. 5°, published in
§ Recherches sur l Organisation vertébrale des Crustacés, des Arachnides, et
d Insectes. Paris, 1828, 8vo. :
- || As connected with the subject of the differences and resemblances between
ebrate and invertebrate animals, I may refer to two recent memoirs, of
‘which abstracts will be found in L’Jnstitut. The first, entitled ‘* Recherches sur
les Parties dures des Animaux Invertébrés, par M. Dupny,”’ was read to the Aca-

tet “ Sur l’Opposition qui existe entre les Animaux Vertébrés et les
aux Invertébrés,” read to the Academy of Sciences at Paris in March
last. (See L'Jnstit. 1834, p. 90.)

152 FOURTH REPORY—1834.

A slight modification of Geoffroy’s views has been adopted by
M. Dumortier, and recently published in a memoir on the com-
parative structure of plants and animals, in the 16th vol. of
the Nov. dct. §c. Nat. Cur.*. Like Geoffroy, he considers
the hard parts of Crustacea and Insects as strictly analogous to
the osseous system of the Vertebrata ; but instead of the two pri-
mary groups into which he distributes animals, M. Dumortier
would adopt the three divisions of Endosceleta, Exosceleta, and
Asceleta, the second answering to Geoffroy’s Dermo-Vertéhrés,
and the third to his Jnvertébrés. These are given in a tabular
form, with the secondary groups into which he thinks the animal
kingdom should be divided, amounting to twelve in number, also
annexed. In a former part of his paper, M. Dumortier has
entered into considerable details on the subject of the analogies
which may be observed between the above three primary groups
of animals, and the corresponding primary groups in the vege-
table kingdom. It would, however, occupy too much room to
enter into any more extended analysis of his views.

In 1821, Mr. MacLeay published the second part of his Hore
Entomologice, in which he proposed a new arrangement of the
leading groups of the animal kingdom, and considered them as
referrible to five primary types, instead of four, the number
adopted by Cuvier. The new type, which he has called derita,
he intended should include the least organized of the Entozoa
of Rudolphi, as well as Cuvier’s classes of Polypi and Infusoria,
all which he considered as not sufficiently showing the true ra-
diated structure characteristic of the type to which Cuvier referred
them. Mr. MacLeay observed, that the necessity for this step had
been previously pointed out, though indirectly, by Lamarck and
Blainville. The establishing of this new group was not, however,
the most importantfeature in the Hore Entomologice. Mr.Mac-
Leay announced some new principles connected with the clas-
sification of animals, which, from the circumstance of their having
led to a peculiar school of zoologists in England, it will be ne-
cessary to consider a little more in detail. The most important
of these principlest are: lst, Zhat all natural groups, of what-
ever denomination, return into themselves, forming circles ;
2ndly, That eachof these circular groups isresolvable into exactly

five others; 3rdly, That these five groups always admit of a
hinary arrangement, two of them heing what he calls typical,
the other three aberrant; 4thly, That while proximate growps

*
p. 306.
+ It may be observed, that Mr. MacLeay has nowhere formally stated these
principles as above. They are only gathered from what he has written on the
subject.

|
|

al

ESI SRO GEL TES 5

REPORT ON ZOOLOGY. 153

in any circle ure connected hy relations of affinity, corre-
sponding groups in two contiguous circles are connected by
relations of analogy. Mr. MacLeay has also observed*, that,
in almost every group, one of the five minor groups, into
which it is resolvable, bears a resemblance to all the rest ; or,
more strictly speaking, consists of types which represent those
of each of the four other groups, together with a type peculiar
to itself. . These principles had been partly brought forward by
Mr. MacLeay, two years before, in the first part of the work
above mentioned. It was then, however, with exclusive refer-
ence to the natural arrangement of the Lamellicorn Insects, in
which group we are told it was that he was first led to detect
them. It was not till 1821 that he applied them more generally,
in showing that a tendency to circles prevailed throughout na-
ture, and that the same principles which he had observed to re-
gulate the natural arrangement of the above group, appeared to
regulate that of the entire animal kingdom. It is somewhat re-
markable, and certainly tending to confirm Mr. MacLeay’s views,
that in the same year, and apparently without any knowledge
of the first part of the Hore Entomologice, M. Fries, in Ger-

_ many, published his Systema Mycologicum, in which he an-
nounced principles somewhat similar to those above stated, as
_ regulating the natural distribution of Fungi. This gave rise to

apaper from Mr. MacLeay, read the following year to the Lin-
nean Society}, in which he commented on this identity (so far

as the identity prevailed,) of the principles which they had

respectively adopted. He also pointed out wherein they dif-
fered; one difference consisting in the determinate number, which

_ M. Fries considered as four, being the same as that formerly ad-

vanced by Oken. Mr. MacLeay’s arrangement of the Lamel-
licorn Insects in the first part of the Hore Entomologice was
the result of rigid analysis, and is therefore deserving of the

greatest attention; that however of the entire animal kingdom

in the second, was chiefly deduced from synthetical investigation,
and was moreover confined to the larger and more important

groups. It is not, therefore, surprising that many endeavours
should be made subsequently by himself, as well as by those
_ who had adopted more or less of his theory, to illustrate

his new principles by a more close application of them to
different departments of zoology. The first result was a paper
by Mr. Kirby, in 1822}, in which he described some insects that
‘appeared to exemplify Mr. MacLeay’s doctrine of affinity and

_ * Hor. Ent., p. 518. + Linn. Trans., vol. xiv. p. 46.
t Linn. Traus., vol. xiv. p. 93.

154 FOURTH REPORT— 1834.

analogy. In 1823*, Mr. Vigors made an application of Mr, Mae-
Leay’s principles to the class of Birds, pointed out the orders
and families, and endeavoured to show that the natural affinities
which connect the several groups in that class obeyed the same
laws as those laid down in the Hore Entomologice. The same
author subsequently followed up this inquiry in some particular
families of the same classt. In 1824¢, Mr. MacLeay applied his
own principles to the arrangement of the Mollusca Tunicata.
In the same year Mr. Swainson endeavoured§, with reference
to the circular and quinary system, to work out the natural
affinities of the family of Lanitide in ornithology. In 1825,
appeared the first number of the dnnulosa Javanica, in which
Mr. MacLeay again brought his views to the test by applying
them to the natural arrangement of the insects collected in Java
by Dr. Horsfield. Circumstances prevented Mr. MacLeay from
proceeding with this arrangement beyond that of a small portion
of the Coleoptera; but Dr. Horsfield himself subsequently pro-
ceeded to publish the Lepidoptera || classed according to the
same principles. In the same year, (1825,) Mr. Gray published an
attempt at the natural distribution of the Mammalia into tribes
and families{[, and likewise of the genera of the classes Reptilia
and Amphibia**. Both these, but the former more especially,
were intended to illustrate Mr. MacLeay’s principles. In 1826+,
Mr. MacLeay gave the result of some anatomical investigations,
which tended to confirm the accuracy of Mr.Vigors’s arrange-
ment of Birds. In the same paper he considered the affinities
which connect the various orders of Mammalia, the point of
transition from this class to dves, and he true analogies
existing between the respective orders of the two classes.
In 1827+t, Mr. Swainson gave a sketch of the natural affi-
nities of the Lepidoptera diurna of Latreille, being also an
applivation of Mr. MacLeay’s principles. Lastly, in 1831, ap-
peared the second part of the Fauna Boreali-Americana, in
which Mr. Swainson, still adopting Mr. MacLeay’s views in
part, but modifying them according to what (since his former

* Linn. Trans., vol. xiv. p. 395.

+ Zool. Journ., vol. i. p. 312. and vol. ii. p. 368.

{ Linn. Trans., vol. xiv. p. 527. § Zool. Journ., vol. i. p. 289.

|| Descriptive Catalogue of the Lepidopterous Insects contained in the Mu-
seum of the Hon. E. India Company, Sc., with introductory Observations on a
general Arrangement of this Order of Insects. 4to, 1828, &c.

q Ann. Phil., vol. xxvi. p. 337. *“*) Td., vol. xxvi. p. 193.

tt Linn. Trans., vol. xvi. p. 1.

tt Ann. Phil., vol. i. p. 180.

ey

Sip ee Ae Es
ESE J “ss

REPORT ON ZOOLOGY. 155

papers) he has conceived to make a nearer approach to the true
natural system, endeavoured to work out an amended arrange-
ment of some of the principal groups of birds. The modifica-
tions which Mr. Swainson has been led to make in this work of
Mr. MacLeay’s principles are these. He conceives, that although
every natural group is resolvable into five others, the primary
division is into three, each of which forms its own circle: he
thus rejects Mr. MacLeay’s binary distribution of his five groups
into typical and aberrant, which last not forming circles, would
seem to be rather at variance with his own principles. He has
also stated more precisely the law by which it appears to him
the relations of analogy are governed. It is thus given: The

contents of every circle or group are symbolically represented

hy the contents of all other circles in the same class of animals ;
this resemblance being strong or remote, in proportion to the
proximity or the distance of the groups compared*, This prin-
ciple, which Mr. Swainson terms the theory of representation,
he considers as affording the only certain test of a natural group.
Mr. MacLeay had considered such a test to be afforded by a
group returning into itself, which Mr. Swainson thinks not
sufficient, on the ground that there is not one group in three
which can be so tested; this arising partly from our superficial
acquaintance with forms, and partly, as he believes, from there
being many real gaps in the chain of continuity. It will be

_ observed that Mr. Swainson has been the first to bring forward

_ any new laws of arrangement at all analogous to those originally

developed in the Hore Entomologice ; and it is right to state,
that the above are not mere hypothetical deductions, but have

: resulted from eight years’ close analysis of the order Insessores
_ in the class of birds, with reference to which order principally
_ it is that he has illustrated them in the Fauna Boreali-Ame-

ricana,
It is evident that the necessary limits of this Report forbid any

further analysis of Mr. MacLeay’s theory, or of the several works

‘and memoirs above referred to; To some of these last I shall
have further occasion to allude afterwards. What has been ad-
vanced may tend, however, to point out the influence which this
‘theory has had over our own naturalists ; and if they have not
Deen all equally successful in their endeavours to apply it to

_* M. Isidore Geoffroy St. Hilaire, in France, has also attended to the subject
of analogies in zoology, and endeavoured to refer them to some general law. ‘Ihe

_ feader is referred to a note attached to a memoir published by him in the Nowv.

Ann. du Mus., tom. i. p. 380, in which he has given a slight sketch of his views

on this point. He proposes to make it the subject of a distinct paper at some
future opportunity. ?

156 FOURTH REPORT—1834.

different branches of zoology, these attempts have on the whole
certainly advanced our knowledge of natural groups, and deve-
loped many affinities before unsuspected. At the same time it
is difficult to believe that there is not some truth at the bottom
of this theory, however erroneous it may be in its details ; and
that some of its details are erroneous, as well as many of the
subordinate arrangements in the system which has been built
upon it, is almost certain, from many facts which have been
brought forwards of late years, as well as from that difference
of opinion* which exists with respect to these details amongst
those who admit the fundamental principles. Neither are these
fundamental principles entirely new. Mr. MacLeay has himself
shown} that his doctrines have all been in some measure ad-
vanced by authors prior to the publication of the Hore Ento-
mologice ; which circumstance, while it tends to strengthen our
conviction that they have more or less of truth in them, does not
detract from Mr. MacLeay’s merits in having developed them
far beyond what any of his predecessors had done. To him we
are certainly indebted for having pointed out the exact nature of
the difference between affinity and analogy in natural history,
however these two kinds of relation may have been observed by
former authorst. He was also the first to establish by proof
circular affinities. He has sufficiently demonstrated their exist-
ence in certain groups, to lead us to suspect that it is only our
as yet imperfect knowledge of forms, and the gaps necessarily
arising from the circumstance of many forms having become
extinct, which prevents us from tracing their existence gene-
rally. And these are by far the most important of Mr. MacLeay’s
principles. Whatever of error there may be in the rest of his
views, whatever modifications already have been, or may yet
further be made in them, by the help of the above principles he
appears to have approached nearer than any before him to the

* This difference of opinion more especially respects the determinate num-
ber. While Mr. MacLeay considers it as five, and Mr. Swainson as three, Mr.
Kirby is of opinion that it will turn out tobe seven. (Introd. to Ent.,vol. iii. p. 15.)
It must be stated that this gentleman has hitherto brought nothing forward in
support of this last number. It has, however, found an advocate in Mr. New-
man, who has also endeavoured to establish some other modifications of Mr.
MacLeay’s theory. See a small tract, called Sphina Vespiformis, published in
1832.

+ Linn. Trans., vol. xvi. p. 8.

{ I add this because, some time back, there was a controversy between M.
Virey and Mr. MacLeay on the question of priority with respect to the above
distinction. See a review, by the former, of some of Mr. MacLeay’s opinions in
Bull. des Sci. 1825. tom. iv. p. 275, in which M. Virey states having made this
distinction long before in the Nouv. Dict. d’ Hist. Nat., Art. Antmau. Mr. Mac-
Leay has replied to M. Virey in Zool. Journ., vol. iv. p. 47.

=<

REPORT ON ZOOLOGY. 157

true natural system, and (as has already been twice observed*)
been enabled to “ reconcile facts which upon no other plan can
be reconciled.”

_ It is necessary now to revert in point of time, for the purpose
of noticing some works which appeared on the Continent during
the above period. In 1821, Oken published his Esguisse de
Systeme d’ Anatomie, de Physiologie, et d Histoire Naturelle.
This celebrated German naturalist is well known to have im-
bibed some very original views connected with the classification
of animals, which have led to a peculiar school of zoology in
Germany, in like manner as those of MacLeay have in England.
T regret that I am unable to say much of his system, which how-
ever I believe to be only a modification of one which he had
before published in some of his earlier workst. It is based
upon a theory which supposes the animal kingdom to be deve-
loped after the same order as that in which the organs are in
the body. He considers that these organs form, characterize,
and represent the classes ; and that there are the same number
of classes as there are organs. He also attaches to them names

_ derived from the organs. Fanciful as this theory appears, it

has not only had many followers in Germany, but has given rise
to several attempts at a natural classification of animals founded
upon analogous principles. Such is the “‘ Synoptic Table of the
Animal Kingdom,”’ published at Dresden, in 1826, by Ficinus and
Carust{, in which the leading divisions are based upon views
somewhat similar to those of Oken. In 1827, Leuckhart also
eal at Heidelburg, “‘ An Attempt towards a Natural Clas-

ation of Intestinal Worms, followed by a Table of the
Affinities of Animals in general,’’ constructed upon the same
principles§. Iam unable to notice these works more particu-

h larly, but I conceive that it would be unnecessary, were it in
ge to do so.

n 1822, Blainville published his Principes d’ Anatomie Com-
parée, annexed to which are some Synoptic Tables of the Ani-

_ mal Kingdom, containing a slight modification of a new system
first brought forward in 1816 in the Journal de Physique|l.

In this system, the primary divisions, which are called sub-

v3 kingdoms, and are three in number, are established on characters

a. : ;
__ * Kirby, Zntrod. to Entom., vol. iv. p. 359; and Swains. Fn. Bor. Am., part2.

vi.
Br Philosophy of Nature, (in German,) Jena, 1809, 3 vols. 8vo. Also, 7rea-
tise on Natural History, (in German,) Jena, 1816. Oken is also the editor of

: Pepmble German periodical, called Jsis, containing many important papers in

Zoology. He was the first in Germany to abandon the Linnzean system.

tT Bull. des Sci. 1829, tom. xvii. p. 258. § Id., 1829, tom. xvii.
|| tom. Ixxxiii. p. 244,

158 FOURTH REPORT—1834.

taken from the general form, which Blainville finds in aecord-
ance with those derived from the nervous system when this is
present. The first of these subkingdoms he terms Artiomorphes
or Artiozoaires, being that in which the form is symmetri-
cal, or the parts disposed symmetrically on each side of the
body ; the second, dctinomorphes or Actinozoaires, in which
the parts radiate from a common centre; the third, Hétéro-
morphes or Hétérozoaires, in which the form is indeterminate.
The Artiomorphes are referred to three secondary types, cha-
racterized from the arrangement of the locomotive organs:
{1.) Osteozoaires, in which the body and limbs are composed of
several pieces articulated together, the articulations not being
visible from without; (2.) Hntomozoaires, in which the body
and limbs are likewise articulated, the articulations being exter-
nally visible; (3.) Malacozoaires, in which the body is of one
single piece, and not divided into several parts. The Osteo-
zoaires are the same as the Vertebrata of Cuvier. The Ento-
mozoaires answer nearly to his 4nnulosa, including, besides the
classes referred to that type in the #égne Animal, the Entozoa,
and likewise the Cirripeda and the genus Chiton. These two
last groups, however, form a subtype, which Blainville calls
Malentozoaires or Molluscarticulés. The Malacozoaires cor-
respond to the Mollusca of Cuvier, excluding the Cirripeda
and the genus Chiton just mentioned. -The second subking-
dom, 4ctinomorphes, comprises the Radiata of Cuvier, with the
exception of the Sponges, Infusoria, and Stony Corallines,
which compose the third subkingdom, or Hétéromorphes.
Blainville’s system, though different from Cuvier’s, deserves to
be studied, from its indicating many new affinities which had
not been before noticed. Its author however has adopted, and
in many instances very unnecessarily, an entirely new nomen-
clature, which alone has been sufficient to prevent it from having
been generally received by naturalists.

In 1825, Latreille published his Familles Naturelles du
Reéegne Animal, in which he considers the animal kingdom as
primarily divided into three great series: Vertebrata, the essen-
tial character of which group he does not derive however from
the vertebral column, so much as from the presence of a brain,

consisting always of a cerebrum and cerebellum, and the great —

sympathetic nerve, whereby it is particularly distinguished from
his second group, Cephalidia, in which the brain is only rudi-
mentary, and the third, 4cephala, in which it no longer exists.
His Cephalidia embrace the Annulosa and Mollusca of Cuvier,
with the exception of the Acéphales sans coquilles. These, with
the Zoophytes of the same author, constitute his Aeephala.

Pay cake

:
a vi

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REPORT ON ZOOLOGY. 159

Before arriving at the classes of the Vertebrata, Latreille adopts
a previous division of this series into Hamatherma (with warm
blood,) and Hemacryma (with cold blood). This last is again
divided into Pulmonea and Solibranchia, according as the re-
spiration is carried on by lungs or gills. In like manner we
d his second series, Cephalidia, divided into the three races
of Mollusca, Elminthoida (comprising the classes Cirripedes
and Annelides), and Condylopa (with articulated feet). The
Acephala also into Gastrica and Agastrica. Few will probably
_ prefer Latreille’s three primary divisions to Cuvier’s four types,
or judge his arrangement on the whole to be more natural than
that of the Régne Animal. His Cephalidia, in particular, bring
_ together under one head two very distinct groups which are well
separated by Cuvier.
i _. The above are some of the principal systems, or modifications
4. of that of Cuvier, which have been brought forwards since the
€, first. edition of the Régne Animal*. In 1829 appeared the
‘second edition of the work just mentioned, in which: however
there is no material alteration, at least as far as regards the dis-
_ tribution of the leading groups.
; pal may be thought by some that the subject is hardly deserving
> much notice; that the consideration of different systems,
e of which perhaps we feel sure are grounded upon errone-
ous principles, may be passed over as of not much importance
oon in Cuvier will teach us to judge otherwise. He ob-
_servest that the affinities of animals are so complicated, that
ught thankfully to receive every endeavour to set them be-
us in anew point of view. There are few systems which do
contribute something to our knowledge on this subject, and
ch do not thereby enable us to make some further advance
rds that which is the end and object of the science, the
wal system itselft.

| have been obliged to omit the notice of certain works which may per-
contain some new views respecting the arrangement of animals, but which
have been unable to get sight of. Such are the Elements of Zoology, (in Ita-
n,) by Ranzani, published at Bologna in 1819, &c.; and the Manual of Zo-
ogy: , (in German,) by Goldfuss, published at Nuremberg i in 1820. In 1828,
der Hoeven also published a Z'abular View of the Animal Kingdom, equally
wn to me except by title.
Hist. du Progrés des Sci. Nat., tom. iv, p. 182. 3
tr. MacLeay has well observed that « every discovery of an affinity is, in
rt, a discovery of natural arrangement.” (Hor. Ent., p. 324.) ,

160. FOURTH REPORT—1834.

mals, I may observe, that it is not my intention to do more than to
convey a general notion respecting the state of our knowledge
of the principal groups contained in them. At the same time
I shall notice any recent researches which appear to throw
light on their affinities, or to illustrate more clearly either their
external or internal characters. Of these last I confine myself
to such as are of immediate importance to zoology.

I. VerTEBRATA, Cuv.

1. Mammalia.—Cuvier and Geoffroy greatly contributed to
our knowledge of this class during the early part of the present
century. The former by his investigation of fossil species sup-
plied us with many new forms, serving in several cases as links
to connect groups which before were widely separated. He
also found it necessary, in order to determine the above with
accuracy, first to examine more closely the structure of such
species as are living at the present day. Owing to this circum-
stance his Ossemens Fossiles has conferred a lasting benefit on
this department of zoology. His researches served to elucidate
the history of numberless genera, and even led to the establish-
ment of one entire family*, of which the true affinities had pre-
viously been quite misunderstood. Geoffroy also laboured much,
and indeed has continued to do so to the present time, at the
natural arrangement of these animals. His various memoirs in
the Annales du Muséum and other French periodicals, more
particularly those on the Marsupialia, Cheiroptera, and Quad-
rumana ; his splendid work also, the Histoire des Mammiferes,
undertaken conjointly with M. Fred. Cuvier, are well known, and
deservedly celebrated. Yet notwithstanding the laborious re-
searches of these, and many other eminent zoologists, perhaps
it is not advancing too much to affirm, that we are still in many”
cases far from understanding the real affinities of the Mammalia,
and less agreed about the primary groups into which they ought
to be distributed, than in the instance of some other classes lower
down in the systemt. This will appear by referring to the
principal classifications which have been published since that of
the Régne Animal. Cuvier, in the work just mentioned, admits
the following eight orders: Bimana, Quadrumana, Fere (Car-
nassiers), Jtodentia, Edentata, Pachydermata, Ruminantia,

* The Herbivorous Cetacea.

+ This probably arises in a great measure from the paucity of forms which
this class presents compared with others. Mr. MacLeay has observed, (Annul.
Javan., p. Xi.) that we are more likely to detect the natural arrangement
amongst Insects, from the circumstance of their presenting such a multiplicity
of species, than in any other part of the system.

REPORT ON ZOOLOGY. 161

Cetacea. Desmarets, in his Mammalogie, published in 1820,
follows Cuvier. Blainville* distributes the Mammalia pri-
marily into the two subclasses of Monodelphes and Didelphes,
this last being instituted for the reception of the Marsu-
pialia, and Monotremata of Geoffroy. His subclass of JZono-
delphes includes seven orders; of these the first five are the
same as Cuvier’s, only the Rodentia and Edentata are trans-
posed, and the latter includes the Cetaceous animals, with the
exception of the Lamentines : these last, with the Proboscidiens
of Cuvier, form his sixth order, called Gravigrades: his se-
yenth order, Ongulogrades, comprises the rest of Cuvier’s
Pachydermata and his Ruminantia. Latreillet considers the
Monotremata as a distinct class altogether. His class Mam-
malia comprises Cuvier’s eight orders, besides the three ad-

ditional ones of Cheiroptera, Amphibia, and Marsupialia (in the

Régne Anim. only subordinate groups in the order Carnassierst.)
Mr. MacLeay, in a paper in the Linnean Transactions§ already
alluded.to in a former part of this Report, dated 1826~7, adopts
as primary divisions the old groups Primates, Fere, Glires,
Ungulata, and Cetacea, the first three, and last, being identical
with the four Linnzean orders bearing the same names, the fourth
(adopted from Aristotle and Ray) including the Linnean orders
Brute, Pecora, and Bellue. Mr. MacLeay has made some im-
portant and interesting remarks on the series of affinities con-
necting the above orders which deserve to be consulted, but which
would occupy too much room here. He attempts to show that
the chain returns into itself, forming a circle. He considers

My the whole class as passing off to the Birds by the Glires||, and
as also indicating an affinity to the Reptilia in the Monotre-

mata. In 1827, Temminck published the first part of his valu-

_ able Monographies de Mammalogie, at the end of which he
_ gives a systematic arrangement of the whole class. He adopts,
~ in addition to Cuvier’s orders, those of Chetroptera and Mono-

tremata: the former is inserted between the Quadrumana and
Carnivora; the latter is placed at the end of the whole series,
as serving to point out the transition to Reptiles and Birds.

Ont Bhat :

» * Principes, §c., tab. 3. t+ Fam. Nat.

¢ Latreille thinks that at the end of the Quadrumana, the Mammalia divide
themselves into two series: one composed of the Cheiroptera, Marsupialia,

_ Rodentia, and Edentata; the other of the Fere, Amphibia, Pachydermata,

Ruminantia, and Cetacea. See Fam. Nat., p. 59, note (+).
/ § vol. xvi. p. 1.
|| The analogy which exists between the organization of the Mammalia
Rodentia and that of Birds, was pointed out by Professor Otto of Breslau the
same year. See Bull. des Sci. 1827, tom. xii.
1834. M

162 FOURTH REPORT—1834.

The same year Lesson published his Manwel de Mammalogie :
his arrangement, however, is the same as that of Cuvier. In
1829, appeared the 2nd edition of the Régne Animal, in which
the Marsupialia are considered as a distinct order; in all other
respects the arrangement is the same as that of the first. The
same year Fischer published his Synopsis Mammalium. His
orders approach more in character to those of Linneus: he
adopts, however, two more than that author: one, Cheiroptera,
placed between the Primates and Fere; the other, which he
terms Bestia, and which includes the Insectivora and Marsupi-
alia of Cuvier, following the order last mentioned. Also in
1829, appeared a valuable treatise on the Mammalia by Fred.
Cuvier, in the 59th volume of the Dict. des Sci. Nat. His
arrangement differs in one respect from that of alf his prede-
cessors, in as much as he has thrown together in one order the
first two families of the Carnassiers of the Régne Anim. and the
Insectivorous Marsupialia, while of the Frugivorous Marsupi-
alia he has made a separate order. He has also made distinct
orders of the Amphibia and Monotremata.

In 1830, Wagler published his Matiirliches System der Am-
phihien, to which he has prefixed a classification of Mammalia
as well as of dves. His orders in the former of these classes,
amounting tu eighteen, are much more numerous than those of
any other author. It is hardly necessary to specify them, as few,
I conceive, will be disposed to adopt them all as primary divisions.
They more properly deserve the name of families. Wagler con-
siders the Monotremata as a distinct class, to which he gives the
name of Gryphi. It may be observed, that he also includes in it
the fossil Ichthyosauri and Plesiosauri, as well as the Ornitho-
cephalus of Sommerring*.

In 1831, Charles Lucien Bonaparte published an arrangement
of the Vertebrata+ differing in some respects from that of his pre-
decessors. The Mammalia are primarily divided into the two sub-
classes of Quadrupeda and Bipeda, the latter being intended to
receive theCetaceous animals. The Quadrupeda are again divided

into the two sections of Unguwiculata and Ungulata. His
orders resemble those of Fischer, excepting that he isolates the ~

Marsupialia, referring the Insectivora (with which they are
associated by this last author) to the order Fere. He also

* Mr. MacLeay has suggested in his Hore Entomologice, p. 267, that possibly
the Ornithocephalus may have been the connecting link between Mammalia and
Birds.

+ Saggio di una Distribuxione metodica degli Animali Vertebrati. 8vo, Rom.

831.

‘

y;

REPORT ON ZOOLOGY. 163:

makes a distinct order of the Amphibia. The Monotremata
he considers as a separate class*.

- Ona review of the above systems it will appear how much
difference of opinion exists respecting the value of certain groups,
more particularly the Cheiroptera, Marsupialia, and Monotre-
mata. 'To the number of those systematists who regard the
Cheiroptera as a distinct order, we may add Geoffroy, whose
opinion will have weight, when we remember the particular
study which for many years he is known to have made of these
animals. We may refer to the twelfth and thirteenth Lectures
in his Cowrs de |’ Histoire Naturelle des Mammifeéres, as pre-
senting considerable details respecting the general organization
of these animals and their several peculiarities. He regards
them as holding an intermediate place between the Quadrumana
and Fere, but requiring to be separated from both.

- The Marsupialia will continue to perplex us until we can
determine the true value of that peculiar character by which
they are so remarkably distinguished from all other Mammalia.
Is it to controul the characters derived from the organs of mas-
tication, digestion, and motion, which may be referred almost to
_ as many types as there exist genera amongst these animals ?
_ Even adopting that it ought, as most. naturalists seem disposed
to do, we have still to decide, whether the Marsuwpialia consti-
tute merely a peculiar order, or a group of any higher denomi-
nation as supposed by Blainville. Although Cuvier has only
_ admitted them to the former, he observes that they might alinost

_ be supposed to form a distinct class parallel to that of the or-

dinary Mammalia, and divisible into similar orders. The solu-

_ tion of these difficulties must probably be sought in a more pro-

- found study of the relative internal organization of these and

_ other Mammalia. This subject has, indeed, for some time al-

engaged the attention of Geoffroyt, and more recently it

has been taken up by Messrs. Morgant and Owen§. We may

reasonably hope that by the combined researches of these emi-

nent anatomists, some new light will before long be thrown
por the affinities of these singular animals.

a

_* ‘Since this Report was read, I have seen a sketch of a new arrangement of
e Mammalia recently proposed by M. Duvernoy. Like Blainville, he con-
fies the Marsupialia, (under which series he includes the Monotremata,) as
ip equivalent to the rest of the Mammalia taken together, for which last
retains Blainville’s name of Monodelphes. is orders are very numerous.
See L’ Institut, No. \xv. p.. 261.
"+ See the article Marsurtavx'in the Dict. des Sei. Nat., tom. xxix.
Linn. Trans., vol. xvi. pp. 61 and 455,
_§ Proceedings of the Zool, Soc. 1831, p. 159; 1833, p. 128.
M 2

164 FOURTH REPORT—1834.

The Monotremata, which are involved in quite as much
obscurity as the Marsupialia, have been for some time, but
particularly within the last two years, a subject of great contro-
versy amongst the first naturalists. Although belonging more
to the department of anatomy, it will be necessary to say some-
thing of this discussion, from its great importance to the science
we are considering. The controversy has chiefly turned upon
the existence or not of true mammary glands in these animals,
and their consequent claims to be admitted among the Mam-
malia.

Lamarck was the first to maintain, in 1809*, arguing from the
supposed absence of these glands, and the consequent probability
that the Monotrematat were oviparous, that they ought to form
a separate class. This opinion was subsequently adopted by
Geoffroy in the Bulletin de la Soc. Phil. 1822¢; and also by
Van der Hoeven in a memoir on the Ornithorhynchus, pub-
lished in 1823 in the Nov. Act. &c. Nat. Cur.§. In 1824,
Meckel announced, in Froriep’s Notizen, that he had dis-
covered these glands, and in 1826 he published his Anatomy
of the Ornithorhynchus||, in which their nature and situation
were more fully illustrated. In the course of the same year (1826)
Geoffroy endeavoured to show], that the supposed mammary
glands seen by Meckel were not truly lactiferous, but analogous
to certain glands which he had observed in the genus Sorea**,
In 1827+7 Meckel replied to Geoffroy, adducing further argu-
ments in support of his former opinion. The same year Geoff-
roy published a memoir on the structure of the genital and
urinary organs in the Ornithorhynchus{t, from an examination
of which he was still led to infer that it was certainly oviparous.
This belief was soon after much strengthened by the receipt of
information from Dr. Grant of the supposed discovery of ‘the
eggs of the Ornithorhynchus§§, which circumstance gave rise to

* Phil. Zool., tom. i. pp. 145 and 342.

+ The name of Monotremata dates from 1803, when Geoffroy, who first ap-
plied it in consideration of the peculiar structure of the genital organs, made
simply a new order of these animals. See Bull. de la Soc. Phil., tom. iii. p. 225.

+ p..95. § tom. xi. part ii. p. 351.
|| Ornithorhynchi Paradoui Descriptio Anatomica. fol. Lipsiz, 1826.

q Ann. des Sci. Nat., tom. ix. p..457. i

** These latter glands form the subject of a memoir published by Geoffroy,
in ate in the first volume of the Mémoires du Muséum; to which I refer the
reader.

tt Archiv. fiir Anat., band x. p. 23. tt Mém. du Mus., tom. xv. p. 1.

§§ See an account of the discovery, accompanied by.a description of these
eggs, in the Edinb. New Phil. Journ. for Jan. 1830, p. 149.

REPORT ON ZOOLOGY. 165

another memoir on the part of Geoffroy, published in the dnn.
des Sci. for 1829*. In 1832, the controversy respecting the
existence of the mammary glands again arose. In June of that
year, Mr. Owen read a paper to the Royal Society}, in which
ie entered into a close investigation of the structure of these
glands, and decided altogether in favour of Meckel’s opinion
that they were strictly lactiferous. This opinion was further
confirmed by a statement made the following September by
Dr. Weatherhead to the Zoological Society{, respecting the
itive discovery of milk in the instance of a female Ornitho-
rhynchus lately taken with its young in the interior of New South
Wales. In October of the same year, Mr. Owen laid before
the Zoological Society§ the results of an anatomical investigation
of the mammary glands of the Echidna Hystrix, in which ani-
mal he was also led to believe that they were really lactiferous.
In February 1833, Geoffroy published a memoir in the Gazette

_ Médicale||, in which he stated that the secretion of these sup-

. mammary glands was not really milk, but mucus, destined
for the nutriment of the newly hatched young. In the same
month, Blainville read a memoirf to the Academy of Sciences at
Paris in support of Mr. Owen’s opinion. In March, Geoffroy

_ made acommunication to the Zoological Society** on the subject

-

of his last memoir, to which Mr. Owen replied, alleging argu-
ments against the probability of the secretion being mucus as

_ Geoffroy supposed. In July the controversy between these two
_ individuals was resumed+{. Several other memoirstt have been

oe) tom. xviii. p. 157. _ + Phil. Trans. 1832, p. 517.
_ ¥ Proceedings of Zool. Soc., p. 145. § Proceedings of Zvol. Soc., p. 179.
_ || See Proceedings of Zool. Soc. 1833, p. 28.

~ § Nouv. Ann. du Mus., tom. ii. p- 369. In this memoir, although Blainville

‘considers the Monotremata as mammiferous, he retains his former opinion with

on from viviparous to oviparous animals. In the same subclass he suspects

ion to the propriety of instituting a subclass for them, as forming the trans-

a. e fossil Ichthyosaurus would claim a place. This, it will be observed, accords
_ with the views of Wagler already alluded to. j
_ ** Proceed., p. 28. tt Proceed. of Zool. Soc., p. 91.

tt For abstracts of these memoirs see L’Jnstitut, Nos. 4, 7, 9, 32, 33,40, 45,

_ and 46. From some of the later ones it will be seen that this controversy has

ot been confined to the subject of the Monotremata. Geoffroy endeavoured
to make it appear probable that the mammary glands of the Cetacea were of a

_ Similar nature with the Monotrematic glands (as he terms them) in the Orni-

thorhynchus ; and that if this were proved to be the case, the Cetacea also should

we been brought forward to demonstrate that these glands are certainly lac-

7 Tie be to constitute a distinct class. Several facts and statements!, however,

fiferous in the Cetacea, and I believe Geoffroy himself has since changed his
pinion on this head.

1 See an article by Dr. Traill in the Edinb. New Phil. Journ. for July of the
present year (1834), p. 177.

166 FOURTH REPORT—1834.

also read by Geoffroy to the Academy of Sciences at Paris, both
during the last and the present year, connected with this question.
Nothing, however, has as yet been brought forward serving to
prove the incorrectness of Mr. Owen’s views, which certainly
on the whole appear far more probable than those of Geoffroy.
We may add in conclusion, that Mr. Owen has recently dissected
a young Ornithorhynchus, the stomach of which was found filled
with coagulated milk*, which milk examined under a high mag-
nifying power, and compared with that of the cow, was found
strictly analogous to this last in respect to its ultimate globules.
‘This seems almost decisive of the matter. At the same time
the mode of generation in these animals, whether oviparous, or
ovoviviparous as appears more likely, remains yet to be ascer-
tained.

No one has paid so much attention to those organs.in the
Mammalia employed by zoologists in characterizing genera and
species as M. Fred. Cuvier. The teeth have been particularly
studied by him with reference to this point. His memoirs on
this subject in the dan. and JZém. du Mus.t formed the basis
of a complete work{, published in 1825, in which he has given
an accurate description of the dental system in each of the prin-
cipal genera throughout the Mammalia, illustrated by figures.
He has observed a remarkable uniformity of character in the
molares, in all those genera which are manifestly natural, and
generally admitted to be such by naturalists§. With reference
also to their zoological characters, he has more recently made a
study of the various productions of the cuticle. As yet he has
only treated of the structure of the spines of the Porcupine||,
which he selected in the first instance as most readily examined,
and likely to throw much light on the structure and development
of hair in general. His researches, as far as they have been
hitherto conducted, lead him to regard the hair as furnishing
the zoologist with characters of more importance than has been
usually supposed. He proposes, however, to follow up this sub-
ject on another occasion. In a memoir published in the same
volume with the one just alluded to, F. Cuvier has pointed out

* Proceed. &c. 1834, p. 43.

+ toms. x. xii. and xix. of the former, and tom. ix. of the latter.

t Dents des Mammiferes considérées comme Caractéres Zoologiques. 8vo, Par.
1825.

§ On the subject of the teeth of the Mammalia, their structure and zoological
characters, see a memoir recently published by Geoffroy. (Mém. de I’Institul,
tom. xii. p. 181.) His chief object is to prove that the long anterior teéth of
the Rodentia, usually considered as incisors, strictly represent the canine teeth.

|| Nouv. Ann. du Mus., tom. i. p. 409.

7

REPORT ON ZOOLOGY. 167

some valuable characters for distinguishing the species of Ves-
‘tilionide. These are derived from the form of the head,
which he refers to three distinct types; the form and direction
of the auricle, which he refers to seven types; and the form of
the tragus. He observes that in the restricted genus Vesper-
tilio, the organs of mastication and motion present but little
variation.
_» 2. Aves.—The structure of birds in general is perhaps quite
as well understood as that of Mammalia, and the leading groups
are on the whole better determined. It is also curious to observe
that the orders most generally adopted at the present day nearly
coincide with those of Linneus, thus evincing the tact with
which that great naturalist in some instances seized aflinities.
The only alterations which we find in the Régne Anim. consist
in the union of the two Linnzan orders Pice and Passeres, (be-
tween which it is certainly not easy to define,) and the separa-
tion of the Scansorial birds from the former to constitute a
distinct order by themselves. It will be well, however, to notice
the principal arrangements of this class which have appeared
‘since Cuvier’s, in some of which we shall find a desire to deviate
more widely from the system of Linnzus. This will also afford
an opportunity of pointing out those individuals who have most
contributed to the recent progress of this department of zoology.

_ The first is that of Vieillot, which appeared in 1818 in the 2nd

edition of the Nowy. Dict. d’ Hist. Wat. (Art. ORNITHOLOGIE).
Its author was previously well known for his many valuable
works’ on ornithology, in one of which* he had already given
a slight sketch of his arrangement. Vieillot’s orders are five in
number, and similar to those of Linneus, excepting that with

_ Cuvier he throws together the Pice and Passeres to form one,

which he calls Sylvicole. For the terms Gralle@ and dnseres,

_ healso substitutes Illiger’s names of Grallatores and Natatores.

In 1820, Temminck published the 2nd edition of his Manuel

_ @ Ornithologie, to which is prefixed a sketch of a general ar-
_ fangement of birds, professedly grounded on the habits and

ganization. Perhaps, however, this is the least valuable part
fa work, exceedingly rich in practical information relating to
his class, and indispensable to ornithologists on all other con-

siderations. Temminck’s system, which is a slight modifica-

tion of that given in the first edition of his Manual, cannot be
considered as natural. His orders, amounting to sixteen, are
greatly overmultiplied, and are far from being groups of equal
value. In fact, he has not distinguished between orders and

* Analyse d'une nouvelle Ornithologie élémentaire. 8vo, Par. 1816.

168 FOURTH REPORT—1834.

families. Blainville’s arrangement of this class* is grounded
upon the form of the sternwm and its appendages (clavicle and
os furcatorius), according to a plan first developed in a memoir
read to the Institute in 1812. At the same time, for the sake of
convenience, its author has had recourse to the usual external
characters for distinguishing the groups. As the sternum gives
attachment to the principal muscles of flight, and thereby ne-
cessarily exercises a certain influence over the ceconomy, it may
assist in determining many natural affinities which would other-
wise escape us. Hence Blainville’s system deserves to be re-
garded, although we may not be disposed to adopt it entirely.
One of its chief peculiarities consists in the forming a distinct
order of the Parrots, which stand first in the arrangement.
Blainville thinks that not only the form of the sternum, but the
whole organization and habits of these birds justify this step.
With the rest of the Scansores, which are separated from the
above by the intervention of the Birds of Prey, he associates the
Syndactyli and Caprimulgide, groups not referred by Cuvier
to this order. He has also made distinct orders of the Pigeons _
and Ostriches. His other orders nearly coincide with those of
the Regne Anim. Although not immediately following in point
of time, I may here notice an elaborate memoir on the sternum
of birds by M. L’Herminier, published, in 1827, in the dunn. de
la Soc. Linn. de Parist, in which he has endeavoured to draw
the attention of naturalists afresh to the great importance of this
part. He has studied its structure in a large number of species,
and founded upon it a new classification entirely different from
all former ones excepting that of Blainville. He divides birds
into two subclasses: the first comprises all those in which the
sternum is constantly furnished with a keel, and is distributed
into thirty-three families ; the second forms but a single family,
containing the Ostrich, Cassuary, and a few others, in which the
keel is always wanting. M. L’Herminier thinks that the birds
just mentioned conduct to the Reptiles, and not to the Mam-
malia as is generally supposed. In 1823 appeared Mr. Vigors’s
“Observations on the natural Affinities connecting the Orders
and Families of Birds{,”’ to which allusion has been already made,
as containing an application of Mr. MacLeay’s principles. His
primary divisions are the same as Cuvier’s, excepting that he
sinks the order Scansores, which he considers as only a subor-
dinate group of his order Insessores, which name he has sub-
stituted for that of Passeres. The names adopted for his other

* Principes, &c., tab. 4. 7 tom. v. p. 3—93.
+ Linn. Trans., vol. xiv. p. 395,

REPORT ON ZOOLOGY. 169

four orders are taken from Illiger*, viz. Raptores (Raptatores,
Ill.), Rasores, Grallatores, and Natatorest.. Mr. Vigors has
traced out the chain of affinities which connects the above
groups, and endeavoured to show that it returns into itself,
forming a circle. Latreille in his arrangementt{ follows Cuvier,
with some slight modifications. Thus, he has a primary divi-
sion of the whole class into the two sections of Terrestres
and Aquatici: he has also made a distinct order of the Co-
lumbe and Alectrides, Vieill., to which he gives the name
of Passerigalli. Wagler’s orders § are more numerous than
even those of Temminck, and deserve to be considered in ‘many
cases rather as natural families. He has annexed a synop-
sis of the genera of birds, arranged in the order of their affi-
nities||. In 1831, M. Lesson published his Traité d’ Ornitho-
logie, containing the result of a careful examination of the col-
lections at Paris, to which in some measure it serves as an
accompanying catalogue. In this arrangement, which professes
to be according to the natural system, we have a primary division
_ of birds into Anomalous and Normal, these groups being ana-
__ logous to M. L’Herminier’s subclasses, and characterized in like
_° manner from the sternum and its appendages. The former com-
_ prises the five genera of Struthio, Rhea, Casuarius, Dromaius
_ and Apteryx{. The latter is divided into orders, on the whole
_ similar to Cuvier’s, the Scansores, however, forming only a sub-
order among the Passeres. The Columbe and genus Penelope,

r.
a Merr., which Cuvier associates with his Gallinacés, are also
aD

x
-)

- referred to the Passeres, where they form a portion of another
suborder, called from Latreille Passerigalli. In the same year
(1831), Mr. Swainson published the second volume of the Faun.
_ Bor. Amer., in which he has stated his views with respect to the
natural arrangement of birds, although he has only illustrated

at length with reference to one order. Mr. Swainson’s
iples, which have been before alluded to, lead him to re-

Rees ~

a
Pighe Iiligert Prodromus Systematis Mammalium et Avium. Berol. 1811.

€
U

-

a work extremely useful even at the present day, on account of its containing
_ avery complete terminology with reference to the above two classes.
vo ot Mr. Vigors places the Struthionide among the Rasores. By Cuvier they
are associated with the wading birds.

4 Fan. Nat. § Natirliches System, §-c.

: Wagler had previously published, in 1827, a portion of a work entitled
ema Avium. It was not so much, however, a systematic arrangement of

™,

birds, as a collection of treatises on different genera, those being selected in the
first instance which he had studied most thoroughly. Jt was his intention to have
_ arranged them afterwards in a systematic table. ‘The work, however, was never
_ completed, and its talented author has recently met with a premature death.
Bete a paper by Mr. Yarrell on this anomalous genus in Zool. Zrans., vol. i.
p. i.

170 FOURTH REPORT—1834.

cognise three primary groups into which the class Aves is divisi-
ble. To these he does not affix names, but merely designates
them as the typical, the subtypical, and the aberrant. His
secondary divisions, at least those adopted in the above work,
which are equivalent to the orders of other authors, are the ©
same as those of Mr. Vigors. Inthe details of the arrangement
the systems of these two authors are in many respects different.
The latest arrangement of this class with which I am acquainted
is that of C. L. Bonaparte, in his Saggio di una Distribuzione, &e.
He divides it into the two subclasses of Insessores and Gralla-
tores ; the former containing the orders Accipitres and Passeres,
Cuv.; the latter those of Galline, Gralla, and Anseres.

The above are the principal authors who have treated of the
systematic arrangement of this class of late years. The general
leaning seems to be towards the adoption of the same orders as
those just mentioned*. The group which presents most diffi-
culties in the way of anatural classification is undoubtedly that
of Scansores, on the value of which naturalists are not agreed.
Latreille considers it as forming a parallel order to that of the
Passeres. It will probably, however, be allowed ultimately to be
only a subordinate group in this last order, as is already the
opinion of Vigors, Lesson, and others. In the details of the
system there is still much uncertainty, though more in some
groups than others. And this uncertainty can only be cleared
up by a more rigorous analysis of external characters, combined
with anatomical investigation. This last has already been suc-
cessfully resorted to in some families, for the determination of
true affinities. Thus, Mr. Yarrell, by studying the internal strue-
ture of the dnatide, has sketched out an arrangement of this
groupt, which Mr. Swainson finds in accordance with his own
views on the subject{ derived from the external characters and
habits. The same gentleman has recorded some important notes§
respecting the internal organization of Cereopsis and some allied
species, serving in like manner to confirm the notions previously
entertained respecting the affinities of these birds. There can
be no doubt also that we may derive much assistance from study-
ing the systems of those authors who, like Blainville and
L’ Herminier, have taken some one of the internal organs as the
basis of their arrangement. For however it may be true that
no such arrangement can be natural in itself, founded upon ‘cha-
racters derived from one organ exclusively, yet it affords an in-

* T speak of the groups themselves without reference to any particular names

for them. L
} Linn. Trans., vol. xv. p. 378. t Fn. Bor. Am., vol. ii. p. 486.

§ Proceed. of Zool. Soc. 1831, p. 25.

Se

ia
¢

t
¥

di

+

REPORT ON ZOOLOGY. 171

sight into the method of variation of that organ, teaches us in
consequence its exact value, and when viewed in connexion with
other systems previously established upon other characters, may
serve to correct and perfect many details in these last beyond
what we might be able to do by any other method. With re-
ference to this end, besides the above, I may refer to a system
of Dr. Ritgen, in the Transactions of the Cesarean Academy at
Bonn*, established upon the characters of the pelvis, as one,
not to be adopted entire, but capable perhaps of furnishing some
valuable hints which might otherwise be lostt.
_ The external characters of birds have recently received much
attention from M. Isidore Geoffroy St. Hilaire, who has published
amemoir on this subject in the Now. dnn. du Mus.{ which de-
serves to be consulted by all ornithologists. He has reviewed
those in most general use, and pointed out several of which he
thinks the proper value has not been correctly appreciated. He
particularly mentions the emargination of the bill, so much
trusted to in characterizing the Dentirostres, as one to which too
much importance has been attached. On the other hand, he
_ regards the disposition of the toes, in the Passeres more parti-
eularly, as not having been sufficiently studied in a general point
of view. His researches indeed on this point have led him to

_ propose a new arrangement of the order just mentioned, which

he divides into the three groups of Zygodactyles, Syndactyles,
and Deodactyles, this last comprising the great bulk of the

_ genera, which have the toes divided in the regular way. Hence

it will be seen that he does not side with those who regard the
Scansores as forming a distinct order. The feet of the Passeres,
and the characters which they furnish, have likewise been much

_ attended to by M. Dela Fresnaye, who has also proposed a new
a

arrangement of this order§, though not exactly upon the same
plan as Geoffroy’s. The year previously to that in which Isidore

an Geoffroy published the above memoir, he gave some new obser-
vations in the Annales des Sciences|| relating to the characters
of the Strigide in particular, to which however it would occupy

a
vs

too much room to allude more particularly.

__ The structure and mode of development of feathers, which has

_ been so ably illustrated by Fred. Cuvier{[, and subsequently by

wi

Bt na, xiv. p. 217.
+The pelvis of birds has been recently studied by M. Bourjot St. Hilaire,
and made the subject of a memoir, read to the Royal Academy of Sciences at
Paris in Augustlast. See L’Jnstitut, No. 66, p. 266. { tom. i. p. 857.
__§ See an abstract of M. De la Fresnaye’s memoir in the report of the French
Congress held at Caen in 1833, p. 69. See also other memoirs by him on the
Same subject in Guérin’s Magasin de Zoologie for 1832 and 1833.

} 1830, tom. xxi. p. 194. q Adem. du Mus. 1825, tom. xili. p, 327.

172 FOURTH REPORT—1834.

other observers*, is perhaps too much within the province of
pure animal physiology to require notice here. The laws, how-
ever, which regulate the assumption and changes of plumage are
of the utmost consequence for the exact discrimination of species.
These laws have received great attention from Mr. Yarrell, who
has lately added one to those previously establishedt, viz. that
“ Whenever adult birds assume a plumage during the breeding-
season decidedly different in colour from that which they bear in
the winter, the young have a plumage intermediate in the gene-
ral tone of its colour compared with the two periodical states of
the parent birds, and hearing also indications of the colours to he
afterwards attained at either period.” In the same paper Mr.
Yarrell has stated some experiments, the results of which fully
establish the point that in many cases a change of plumage is
certainly occasioned by a change of colour in the feather itselff,
quite independently of moulting.

The difficulty of finding specific characters for birds which
shall be applicable to both sexes and all ages, particularly in
those groups in which the changes of plumage above alluded to
are most prevalent, has been severely felt by ornithologists. Mr.
Macgillivray has considered this subject in a paper published in
the 4th volume of the Wernerian Memoirs§. He has pointed
out the insufficiency of some of those in common use, particu-
larly such as are derived from colour. He thinks it would be
possible to obtain others, from the situation, form, and position
of the feathers, which would be more preferable, as being of
general application and founded upon permanent and essential
organs. Mr. Macgillivray has annexed, as examples, the cha-
racters of several species drawn up in this manner. His sug-
gestions deserve to be considered, although it may be questioned
whether such characters will be found “ sufficiently diversified ”
to admit of being adopted in all cases.

3. Reptilia, Cuv.—The study of the animals belonging to
this division of the Vertebrata is difficult, and has received far
less attention from naturalists than that of either of the preced-
ing classes. Hence we are at present but little advanced in the
details of their natural arrangement. The propriety of separat-
ing off the Amphibia, and considering these last as a distinct
class, is becoming every day more generally acknowledged. This
separation was first proposed by Latreille || so long ago as in

* See more particularly Macgillivray in Ldinb. New Phil. Journ. 1827.

+ Zool. Trans., vol. i. p. 13.

} This had been often suspected to be the case, (see Whitear in Linn. Trans.,
vol. xii. p. 524, and Fleming in Edinb. Phil. Journ., vol. ii. p. 271,) but never

before ascertained by direct experiment.
§ p. 517. || Nouv. Dict. d’ Hist. Nat., 1st edition.

—

REPORT ON ZOOLOGY. 173

1804. It has not been adopted however by Cuvier, who divides
the whole group into four orders, Chéloniens, Sauriens, Ophi-
diens, and Batraciens, being the same arrangement as that of

.Brongniart*. Blainvillet follows Latreille in considering the

Reptilia and Amphibia as distinct classes, but differs from all
his predecessors in his subordinate groups. Attaching more im-
portance to the organs of generation than those of locomotion,
he has thought fit to unite the Saurians and Ophidians under
the name of Bispéniens; at the same time detaching the Croco-
diles to form a distinct order, which he calls Emydosauriens.
The class Amphibia he divides into four orders, Batraciens,
Pseudosauriens or Salamanders, Subichthyens (Proteus, Siren,
&e.), and Pseudophydiens (Cecilia). In 1820, Merrem pub-
lished his arrangement of the Amphibiat, under which name,
although he includes both the above classes, he considers these
as forming two divisions, which he calls Pholidota and Batra-
hia respectively. His Pholidota are distributed into three or-

ers, which correspond with those of Blainville, but are called
Testudinata, Loricata, and Squamata. The Batrachia include
the three subordinate groups of Apoda (Cecilia), Salientia

¥ ens, &c.), and Gradientia (Triton, Proteus, &c.). Mr. Mac-

Leay§, adopting the Amphibia as a distinct class, would divide
the true Reptilia into the five groups of Chelonians, Emydo-
saurians, Saurians, Dipod Ophidians, and. Apod Ophidians.

2 the considers the first and last of these groups as meeting in

e Emys longicollis, thus causing the five to unite and form a
circle. He looks upon the whole class as connected with that

; of Aves by means of the Chelonians. Latreille||, preserv-

1g the Reptilia and Amphibia as distinct classes, divides
former into the two sections of Cataphracta and Squamosa.

: ; His Cataphracta include Blainville’s two orders of Chelonians

wi Emydosaurians. The Squamosa, answering to the Bispé-
ms of Blainville, comprise, as two other orders, his Sauri-

ans and Ophidians. The Amphibia are divided into the two

ders of Caducibranchiaand Perennibranchia. In 1825, Mr.
Gray published in the dun. of Phil. an arrangement of the
classes Reptilia and Amphibia, in conformity with MacLeay’s
rinciples. As his primary groups are slightly modified in a
er treatise on these animals, to be alluded to presently, perhaps
it is unnecessary to specify them particularly. In 1826, Fitz-
Wi
aes dune Classification naturelle des Reptiles. Paris, 1805.
. - Seiten &e., tab. 5.
Tentamen Systematis Amphibiorum. Marpurg. 1820, 8vo. This work is,

strictly speaking, a second edition of one published by the same author in 1800.
Beer. Ent., p. 263. || Fam. Nat.

174 FOURTH REPORT—1834.

inger published a new classification of these animals* founded
upon their natural affinities. He considers the Reptilia and
Amphibia of Latreille in the light of orders only, to which he
affixes the names of Monopnoa (Reptiles breathing all their life
by lungs only), and Dipnoa (breathing by lungs and gills at
the same time). It will be seen that these two groups corre-
spond to the Pholidota and Batrachia of Merrem. The Mono-
pnoa he divides into four tribes, the first three being the same as
Merrem’s orders, with the same names; the fourth, called Nuda,
embracing the single family of Cecilie. The Dipnoa he sepa-
rates into the two tribes of Mutabilia and Immutahilia, the
former comprising those Amphibia which do, and the latter
those which do not, undergo metamorphosis. In the Nov. Act.
&c. Nat. Cur. for 1828, Dr. Ritgen has published an arrange-
ment of the Amphibia in which he admits but three orders, an-
swering to the Ophidia, Chelonia, and Sauria of other authors.
This last, however, is made to include the Batrachia as well as
the true Sawrians. He has selected for most of his groups new
terms, which from their great length will never be adopted gene-
rally. Waglert has very much augmented the orders of this
class, in like manner as he has done those of the Mammalia and
Birds. He adopts eight: Testudines, Crocodili, Lacerta, Ser-
pentes, Angues (comprising the genera Acontias, Chirotes, Chal-
cides, and Amphishena of the Régne Anim.), Cecilie, Rane,
and Ichthyodi (Subichthyens of Blainville). In 1831, Mr. Gray
published his Synopsis Reptilium, of which only the first part
has as yet appeared, comprising the Cataphracta of Latreille,
whose arrangement is for the most part adopted, with the ex-
ception of a new order instituted for the reception of the Ophio-
sauri, the second division of Latreille’s order Saurii. C.L.
Bonaparte, in his Saggio di una Distribuzione, &c., published
the same year, adopts the term Amphibia as a general name for
the whole group of which we are treating. These he divides
into the two subclasses of Reptilia and Batrachia, which are
again divided into sections, the former into four, and the latter
into two, before arriving at the orders. Thus we have Sect. 1.
Testudinata, comprising the single order of Chelonii; Sect. 2.
Loricata, comprising the two orders of Enaliosaurii (Ichthyo-
saurus and Plesiosaurus,) and Emydosaurii, Blainv.; Sect. 3.
Sgquamata, comprising the three orders of Saurii, Sawrophidii
(Amphishena), and Ophidii; Sect. 4. Nuda, comprising the
single order of Batrachophidii (Cecilia). Inthe subclass Ba-
trachia, we have Sect. 1. Mutabilia, comprising the order Ca-
* Neue Classificution der Reptilien, &c. 4to, Vienn. 1826.
+ Natiirliches System, &c.

REPORT ON ZOOLOGY. 175

ducibranchia; and Sect. 2. Amphipneusta (Immutabilia), com-
prising the two orders of Cryptobranchia and Perennibranchia.
The most recent work in this department is that by Duméril
and Bibron*, of which only the first volume has appeared hi-
therto, containing remarks on the organization of Reptiles in
general, and the Chelonians in particular.. There is also avery
complete Bibliography with reference to this branch of zoology.
The systematic portion of the work is not yet entered upon.
The authors, however, have it in view to adopt the same orders
as those of Cuvier.
_ The above are the principal authors who have treated of this
class as a whole, but some of its orders have received the par-
ticular attention of different naturalists, and derived much illus-
_ tration from their researches. No one has contributed so much
to our knowledge of the Chelonian Reptiles as Mr. Thomas Bell.
_ Several memoirs from him on these animals are to be found in
_ the Linnean Transactions and Zool. Journal, amongst which
_ Imay more particularly mention his “ Monograph of the Tor-
_ toises having a moveable Sternum’’ published in 1825+, and his
_ Characters of the Order, Families, and Generaofthe Testudinata’’
_ published in 1828. More recently (1833) Mr. Bell has com-
_ menced a splendid work § on this order, in which it is intended
_ to describe and figure all the known species, arranged according
_ to their affinities. Seven parts have already appeared, which
_ for beauty and accuracy of illustration it is impossible to surpass.
Before quitting this group I may just allude to a paper in the
_ Ann. des Sci. for 1828||, by MM. Isid. Geoffroy St. Hilaire and
_ J.G: Martin, on some parts of the internal organization of these
_ Reptiles. Being purely anatomical, I should not have noticed it,
did it not contain the statement of a curious fact respecting the
affinity well known to exist between the Chelonia and the Mo-
_ notremata. It is observed, that with regard to the urinary ap-
_ paratus, the analogy between the Ornithorhynchus and the Tes-
_ tudo Indica is even much greater than that. which is found be-
tween this last species and many other reptiles belonging to the
‘Same order.
1e Emydosauria were closely investigated by Cuvier and
}
|
|

Geoffroy, by the former more especially, in the early part of
the present century, and since their researches 4], I am not

Ei puaogie générale, ou Histoire Naturelle Complete des Reptiles, tom. i.

eae *

+ Zool. Journ., vol. ii. p. 299. t Zool. Journ., vol. iii. p. 513,
_ § Monograph of the Testudinata. fol. 1833, &c. || tom. xiii. p. 153.
4 See the earlier volumes of the dnn. du Mus., more particularly vol. x., con-
ial ing a valuable memoir by Cuvier on the different species of living Crocodiles,
and their distinctive characters. For the structure of these animals, see his
Ossemens Fossiles.

176 FOURTH REPORT—1834.

aware that much addition has been made to our knowledge of .
this group. Nevertheless there is great need of further exami-
nation in order to determine the value of those charaeters which
have been hitherto employed in distinguishing the species. It
may reasonably be questioned whether these have not been over-
multiplied, from placing too great reliance upon slight differences
in the form and number of the nuchal, cervical, and dorsal plates.
I may mention a memoir by Geoffroy on the Gavials, as more
recent than his others, published in 1825*, in which he has
treated largely of their organization and affinities. He consi-
ders the former as offering sufficient peculiarities to warrant the
establishing of a distinct genus of this group, which Cuvier re-
garded as merely a subgenus of Crocodilus. .
The Saurian Reptiles have been much attended to by. Mr.
Gray. Inthe Ann. of Phil. for 1827+, he has given a synopsis
of the genera belonging to this group. In a subsequent paper
published in the same volumeft he has made some additions
and corrections to his first communication. He has made it a par-
ticular object to revise the species of Chameleon. 'To M. Milne
Edwards we are indebted for a paper in the Ann. des Sci. for
1829§, which though relating only to the restricted genus La-
certa, may be found valuable in a general point of view from
the remarks which it contains on the zoological characters of
this group. Those who have studied these reptiles know what
difficulty attends the discrimination of species. Milne Edwards
has sought to remove this difficulty. He has ascertained that
in this genus the best distinguishing characters are derived from
the different kinds of scales, more especially the large squamous
plates which cover the upper part of the head. He particularly
dwells on the relative size of the occipital and parietal plates,
and the forms of the scales between the eye and the ear||. He
does not place much reliance on the character derived from the
number of femoral pores, which he finds often varying in the
same species, although considered as constant by Merrem and
Blainville. In the same volume with the above memoir is one
by M. Duges, treating partly of the same subject ; and it is sa-
tisfactory to find that he confirms what Edwards says respect-
ing the characters of the scales. It may be observed that Wagler
appears to have derived much assistance from the teeth in cha-
racterizing both the Emydosaurian and Saurian Reptiles. In
one portion of his work he has treated of this subject in great

* Mém. du Mus., tom. xii. + vol. ii. N.S. p. 54.

tp. 207. § tom. xvi. p. 50.

|| Merrem and others had previously availed themselves of these characters,
but according to Edwards, they have not made a judicious use of them, or se-
lected those scales on which any reliance can be placed.

detail, and given minute descriptions of the teeth as they occur
in all the different genera in the above two orders.
_ Among the Op/idia more perhaps remains to be done than
in any other order of Reptiles. Many new genera and species
have been discovered of late years, and described by different
authors; but of several the characters and synonyms are ill
determined, and their affinities still more so. Mayer has pro-
posed a new arrangement of this group*, founded on the pre-
sence or absence of rudimentary posterior extremities, which he
ks has succeeded in detecting in many genera in which they were
i not before known to exist. He would adopt as three subordi-

oo

REPORT ON ZOOLOGY. 17%

__ nate divisions: 1. Phenopoda, in which these extremities are
externally visible; 2. Cryptopoda, in which they are entirely
concealed beneath the skin; 3. Chondropoda, in which the ru-
_ dimental feet are reduced to mere cartilaginous slips, and Apoda,
> ih they are entirely wanting. M. Duvernoy, in the dun.
des Scien. for 1832+, has entered upon the consideration of the
4 mical characters which serve to distinguish the venomous
9m the innocuous serpents. As these groups are kept distinct
y Cuvier, as well as by some others, in their systematic ar-
agement of the Ophidia, such researches may prove service-
to the zoologist in helping him to the true situation of some
ra. In a later volume of the same work{, M. Duvernoy
ollowed up this inquiry, as well as treated of some other
of the internal organization of serpents in general. On
bject of the alimentary canal, he particularly observes that
ers sensible differences in different genera, and such as may
: to confirm or lessen the propriety of adopting some of those
h have been established by naturalists. In this last com-
cation, he has also made some remarks § on the forms and
igement of the scales on the head and body considered as
ogical characters. He thinks that such characters require
e compared afresh with those derived from the internal
ture, in order that their true value may be more correctly
tained. The genus Cecilia, which by some has been asso-
d with the true Reptiles, by others with the Amphibia, has
recently discovered by M. Miiller|| to possess gills in the
oung state, which fact seems to corroborate its claims to
> in the class last mentioned.
structure of the Amphibia has been much studied of late
and has given rise to many excellent memoirs on the part
ferent observers. As these, however, are for the most part
_* Nova Acta Acad. Nat. Cur., tom. xii. p. 819. + tom. xxvi. p. 113,
tom. xxx. pp. 5 and 118. § p. 25. Jo

|| Ann. des Scien. 1832, tom. xxv. p. 89.
1834. N

-

178 FOURTH REPORT—1834.

purely anatomical, it would be out of place to dwell on them in
this Report. Yet we may allude to one as of more importance
to zoology than some others. I refer to Dr. Davy’s discovery
of a second auricle in the heart of these animals, which will lead
us to correct what was always considered as one of their distin-
guishing characters, viz., their having a single heart like Fishes *.
The Perennibranchiate Amphibia received some time back much
illustration from Cuvier, whose researches on this subject will
be found in the first volume of Humboldt’s Comparative Anato-
myt He was led to regard the Siren and Proteus as adult
animals, bat suspected the 4rolotl to be a larva. In 1819,
MM. Configliachi and Rusconi published a valuable monograph f

on the Proteus anguinus, containing a full account of the struc-

ture and natural history of this singular animal. Dr. Rusconi is
the author of another work, published in 1821 §, in which he has
treated of the aquatic Salamanders, detailing some interesting
observations respecting the mode of development of these Rep-
tiles. This subject had not been previously followed up with
so much closeness of research. It may be stated that in this last
work Dr. Rusconi has doubted the accuracy of Cuvier’s views
respecting the Stren being an adult animal. Cuvier has recon-
sidered the subject in his Ossemens Fossiles|| ; but still adheres
to his former opinion on this point. From examining the os-
teology of this reptile, he feels satisfied that it never acquires
hind feet, as Rusconi supposes, and deems it very improbable
that it ever changes its form or loses its branchiz. ‘That the
Siren is not the larva state of the Amphiwna of Garden, as
some imagine, Cuvier has endeavoured to prove in a memoir
upon this last genus published in the Mém. du Mus.q for 1827.

* Edinb. New Phil. Journ. 1828, p. 160. Dr. Davy’s researches went no
further than to show the existence of a second auricle in several species of the
genus Rana; but reasoning from analogy, he thought it probable that the same
would be the case in all the other genera of this group. These suspicions have
been since partly confirmed by Mr. Owen, (Proceed. of Zool. Soc. 1834, p. 31,)
who has lately given the results of an examination of the hearts of several ge-
nera of the Perennibranchiate Amphibia, in all of which he finds it consisting
of three distinct cavities, as in the higher Reptilia.

+ ‘‘ Recherches anatomiques sur les Reptiles regardés encore comme douteux
par les Naturalistes; faites 4 l'occasion de l’Axolotl, par M. Cuvier.”—Humb.
Anat. Comp., tom. i. p. 93—126.

t Del Proteo Anguino di Laurenti Monografia. Pavia, 1819. An excellent
ae of this work will be found in the Edinb. Phil. Journ. for 1821, vols. iv.
and v.

§ Amours des Salamandres aquatiques, et Développement du Tetard de ces
Salamandres, depuis I’ Buf jusqu’a U Animal parfait. Milan, 1821. An analysis
of this work also will be found in the Edinb. Phil. Journ. for 1823, vol. ix.

|| tom. v. Pt. IT. p. 418, &c. { tom. xiv. p. 1.

x

REPORT ON ZOOLOGY. 179

_ 4, Pisces.—It is generally allowed that this class is connected
by close affinity with those Batrachian Reptiles which have
permanent gills. That it also leads back to the Mammalia by
means of the viviparous sharks, which approach the cetaceous
animals, will scarcely be doubted by any who have considered
the relative organizations of these last groups. Yet no one ap-
pears to have thought of placing the Fish between the Mamma-

_ tia and Amphibia before Mr. MacLeay, whose circular arrange-
‘ment of the classes of Vertebrata is certainly the only one yet
given that conforms itself to nature. As a class, the Fish have
received but comparatively fittle attention from naturalists; and

. from the time of the appearance of the first edition of the Regne
Animal of Cuvier, to that of the Hist. Nat. des Poissons by the
same illustrious author, but few attempts have been made by
other individuals to elucidate their true affinities. Several works
of great merit, descriptive of the fish of different countries have
appeared, and many detached memoirs on particular genera and
species, but no work of a regular systematic character since that

: of Lacépede.

_ Cuvier’s system, as developed in the first edition of the Regne
Animal, is very different from that of Lacépede, which he objects

_ to as having all the secondary groups established upon charac-

ters drawn from the presence or absence of the opercle and
branchiostegous rays, which Cuvier observes will often lead to
glaring violations of natural affinity, not to mention the circum-
_ stance thatin many instances Lacépede has assumed these parts

__ to be wanting where they are really present. Cuvier adopts as

-
2

+ al divisions the two groups of Cartilaginous and Osseous
_ Fishes, commencing with the former, which he divides into. the

two orders of Chondroptérygiens & branchies fixes and Chondro-
_ ptérygiens & branchies libres. The osseous fishes he divides into
_ sixorders. The first of these, Plectognathes, is characterized

by a peculiar mode of articulation of the jaws, and comprises
_ some of the genera before included in the old order of Branchi-
1 ah which is here abolished. The second, Lophobranches, is
founded upon a peculiar form of the gills, and includes but the
two genera Syngnathus and Pegasus of Linnzus. The remain-
‘ing orders comprise the Malacopterygii and Acanthopterygii of
Artedi, the former group being divided into three orders ac-
cording to the position of the ventrals, the latter kept entire as
one order.
_ Blainville’s arrangement of this class * does not differ materially
from that of Gmelin, excepting that the leading groups have
new names affixed to them, and new distinguishing characters.

* Principes, §c., tab. 6.
- 9

om

180 FOURTH REPORT—1834.

Thus, the osseous fishes he terms Poissons Gnathodontes, from
having their teeth implanted in the jaws, in contradistinction to
the cartilaginous fishes, which he calls Dermodontes, from the
teeth in this group adhering simply to the skin. In like man-
ner he calls the Branchiostegi of Gmelin by the name of Hété-
rodermes, or fish in which the structure of the skin is variable
in its nature, as opposed to the ordinary fish, which he terms
Squamodermes. The subordinate groups are established upon
the presence or absence, and on the position (either jugular,
thoracic, or abdominal,) of the ventrals, leading in too many
instances to unnatural combinations as well as separations.
Latreille in his Familles Naturelles considers the cartilagi-
nous and osseous fishes as forming two distinct classes in his
great division of Solibranchia, which he terms Ichthyodera and
Pisces respectively. He removes, however, the chondroptery-
gious fishes with free gills into the latter class, which is pri-
marily divided into the two groups of 4nomalia and Normalia.
The dAnomalia comprise, besides the Sturionii of Cuvier, his
two orders Plectognathes and Lophobranches. The Normalia
include the remaining orders of that naturalist, arranged how-
ever somewhat differently from what they are in the Régne
Animal. In the order Acanthoptérygiens, before arriving at

the families, he adopts a primary division into the two sections _

Kystophora and Akystica, characterized respectively by the
presence or absence of a swimming bladder.

Risso, in the 3rd volume of his Hist. Nat. del Eur. Mérid.,
published in 1826, has given an arrangement of this class ac-
cording to his own views. His orders, however, are nearly the
same as those of Gmelin. He only substitutes the orders
Plectognathes and Lophobranches of Cuvier for the Branchio-
stegi of the former author.

Besides the above, I am not acquainted with any systematic
arrangements of this class, deserving notice, prior to that of the

Hist. Nat. des Poissons by MM.Cuvier and Valenciennes. In this _

work, of which the first volume appeared in 1828, the leading
groups remain the same as in the Régne Animal. The details
of the arrangement are however slightly modified *. And un-

* One alteration consists in the commencing with the osseous, instead of the

cartilaginous fishes. Cuvier observes, however, with reference to this point, that,
strictly speaking, these groups form two parallel series, neither being superior
or inferior to the other. See Hist. Nat. des Poiss., tom. i. p. 419, and Régne
Animal (second edit.), tom. ii. p. 376.—Latreille seems to consider the Fish as
forming two series, which, after a time, unite and become one. His arrange-
ment of the groups in these parallel lines is, however, different from Cuvier’s.
See Fam. Nat. p. 115, note (1).

PER. og WS EAS

REPORT ON ZOOLOGY. 181

doubtedly much, very much remains still to be done before we
can. consider these details as not susceptible of any further im-
provement. Cuvier’s groups are on the whole natural and
well characterized; but the true position of many of them is
extremely doubtful *, and their relative value as yet undeter-
mined. He has done much, however, towards determining the
value of certain characters which had been considered in very
different points of view by former ichthyologists, especially that
derived from the structure of the dorsal rays. He states it to be his
firm opinion, deduced from a careful study of the entire organi-
zation in several hundred species, that the acanthopterygious
fishes ought to be kept quite distinct from the others, and that
whatever characters may be resorted to for the further subdivision
of the normal fishes, they must be held subordinate to the one
above mentioned. It is mainly in consequence of having attached

_ too little importance to this character, and set tov high a value

|
i

‘8
7

h

a

4

Re

upon that derived from the position of the ventrals, that Lin-
neus and several of the more recent authors have entirely failed
in their attempts at a natural arrangement of this class. No one
has made better use than Cuvier of the characters derived from
the structure of the jaws t, and the nature and position of the

_ teeth ; and perhaps in certain groups we can hardly select any
_ of more importance. For the teeth he has adopted a peculiar
set of terms, expressive of the different forms which they assume.
__ hese terms are, however, better adapted to the French than to

_ the English language. On the whole, it may be observed, that
although there may be some parts of his arrangement found de-
fective, Cuvier has done more for this department of zoology
) any one else. His Histoire des Poissons must ever be

: considered as forming a real epoch in ichthyology. If we look

- to the profound erudition it displays, the thorough knowledge
of its author with respect to all that had been done by previous
yriters on this class, the close and accurate researches which
he has made into every part of the internal as well as external
‘ganization of the subjects of which he treats, the minuteness
of detail which characterizes the description of species, at the

‘¥ . It is more than probable that Cuvier has in some instances mistaken re-
lations of analogy for those of affinity. One such instance has been pointed
out by Mr. Bennett (see Zool. Journ., vol. iii. p. 372,) in the case of the genus
t ius.

+ Cuvier first called the attention of naturalists to this part in a memoir
iblished in 1815, in the first volume of the Mém. du Muséum (p. 102.). One
the conclusions at which he arrives is, that the characters derived from the
ieces of the upper jaw and palatine arch, their various positions, proportions,
e., serve to indicate genera, but cannot be employed in distinguishing orders,
if we wish to preserve natural affinities.

182 FOURTH REPORT—1834.

same time that every attempt is made towards generalization, it
will be thought impossible to speak too highly of its merits. It
is almost a perfect model for works of this nature, and deserves
to be consulted by all naturalists engaged in similar undertak-
ings. It cannot but be a subject of deep regret that its talented
author has not lived to complete a work, for which he tells us he
had been forty years collecting materials. Let us hope, however,
that this may be yet effected by M. Valenciennes, whom, fortu-
nately for the scientific world, M. Cuvier had from the begin-
ning engaged as his coadjutor.

A slight modification of Cuvier’s arrangement appears in the
Saggio di una Distribuzione, &e., of C. L. Bonaparte, published
in 1831, principally as regards the value of some of the groups.
In the first place, the osseous and cartilaginous fishes are con-
sidered as two subelasses. The former are then primarily di-
vided into three sections: 1. PecrinIBRANCHII, comprising
the two orders deanthopterygit and Malacopterygii; 2. Lo-
PHOBRANCHH, including the single order of Osteudermi (Syn-
gnathus); and 3. PLECrOGNATHI, comprising the two orders
Gymnodontes and Sclerodermi. The Malacopterygii are sub-
divided into the three tribes of 4Abdominales, Subhbrachiani, and
Apodes. Thus we have two of Cuvier’s orders raised to a higher
rank than that which he assigned to them; while on the other
hand there are three lowered to a subordinate denomination.
In like manner we have the cartilaginous fishes divided into the
two sections of Cu1sMopNEI and TREMATOPNEI: the former
comprising the two orders of Eleutheropomi (Sturiones) and
Acanthorrhini (Chimere), the latter those of Plagiostomi and
Cyclostomé. A similar alteration in the value of some of Cuvier’s
groups will be found here.

The most recent work on ichthyology, and one of the most
important which has yet appeared, is that by M. Agassiz, now
in course of publication*. Although the object of its author is
more particularly to illustrate the fossil fishes, it is his intention
to bring forward an entirely new classification of fish in general.
The details of his arrangement are not yet published. He has,
however, put forth a slight sketch of his system, such as will
serve to show the striking changes which he contemplates in

* Recherches sur les Poissons Fossiles, par Louis Agassiz, 1833, &e. Only
two numbers have hitherto appeared.—M. Agassiz was before known to ich-
thyologists from having assisted Spix in the description of his Fishes of Brazil.
This work was published in 1829 under the following title: Selecta Genera et
Species Piscium quos in Itinere collegit Spix ; descripsit L. Agassiz. fol. In
1830, M. Agassiz had also announced the prospectus of a work on the Fresk-
water Fishes of Europe. This last has, however, not yet appeared.

REPORT ON ZOOLOGY. 183

this department of zoology. Thus, he adopts but four orders,
in each of which are to be found both osseous and cartilaginous
fishes,—both Acanthopterygians and Malacopterygians,—both
apod and abdominal genera,—and, in two out of the four, tho-
racic and jugular genera besides. Hence it will be seen that his
principal divisions are founded neither on the degree of ossifica-
tion of the skeleton, nor on the structure of the vertical fins, nor
on the position of the ventrals, as is the case in those systems
which have been hitherto most generally adopted. M. Agassiz
thinks he finds in the differences of the scales the most exact
indication of the natural affinities of all fish. Accordingly it
is from the scales that he has drawn the diagnostic characters
of his four orders, (which bear respectively the names of Pla-
coides, Ganoides, Cténoides, and Cycloides,) although in form-
ing them he has kept in view all the rest of the organization.
Ichthyologists will doubtless be impatient to see the full deve-
lopment of a system founded upon views so entirely opposed to
all those which they had previously entertained on the subject.
_. The science of ichthyology has been so little cultivated, that
_ there are but few individuals-to whom it is necessary to refer in
* a Report, besides those who have been already mentioned.
_ Many have made great contributions to the anatomy of fish,
amongst whom Geoffroy St. Hilaire stands preeminent; but I
allude to such only as have thrown light upon the affinities of
the larger groups, or helped us to a better knowledge of their
zoological characters. I must not, however, omit to mention
an important paper on the fishes of the Lake of Geneva by
_ M. Jurine, published in 1825, in the third volume of the Mém.
_ dela Soc. de Phys. et d Hist. Nat. de Geneve. It is not merely
_ valuable as a local catalogue, but as containing several new cha-
_ racters for distinguishing the species of Cyprinide, which is per-
_ haps one of the worst understood families in the whole class *.
_ This memoir is accompanied by remarkably accurate figures of
__ all the species fuund in the above locality. The scales of fish
_ were, some years back, particularly studied by M. Kuntzmann,
_ whose memoir+ on this subject will have acquired fresh interest
_ since naturalists have had their attention again directed to it by
_M. Agassiz. M. Kuntzmann has not only entered into consi-
_ derable details with respect to the structure of these organs in

__ least those of foreign countries, are much less known and understood than those
found on the coasts.
__ + Verhandlung der Gesell. Nat. Freunde in Berlin, vol. i. No.5, 1824, p. 269.
Tam, however, only acquainted with the analysis of it in Bull. des Sca, Nat.

Wa.

___ * Cuvier has somewhere observed that in general the freshwater fishes, at
1826, tom. vii. p. 118.

i

|

|

184 FOURTH REPORT—1834.

different groups, but considered their value as furnishing cha-
racters for distinguishing species. He seems to think, that in
general, if not in all cases, they are available for this purpose,
and advises that selection be made of those which are placed on
the middle of the sides of the body, and near the lateral line, not
only as being the largest, but as those in which the form is most
constant in a given species. M. Kuntzmann has instituted se-
veral divisions or classes amongst scales, in which they are ar-
ranged according to their form and structure. It would, how-
ever, occupy too much room to follow him in this part of his
subject. Before quitting this class, I may just allude to two
papers by Dr. Hancock, in the London Quarterly Journal of
Science for 1830*, in which he has made some remarks on the
composition of the fin rays in fishes. Dr. Hancock has dwelt
much upon the importance of the character derived from the
number of these rays, which he considers as offering the best
diagnostic marks for the discrimination of species. This cha-
racter, however, must be employed with some limitation, since
it will be found much more variable in some groups than others.

II. AnNuxosa, Cw.

Cuvier, in his Régne Animal, places this division below that
of the Mollusca, which last he appears to have regarded as
standing higher in the scale of organization on account of its
circulatory system. Geoffroy, guided by his peculiar views re-
specting the vertebral structure of the nnulosa, to which allu-
sion has been already made, has disputed the propriety of this
arrangement, and considers that the Mollusca should decidedly
give precedence. It is obvious, however, that these two groups
are formed upon such entirely different plans, that they scarcely
admit of direct comparison in this respect. Each has its own
peculiar marks of affinity with the higher animals ; and it is only
by supposing two points of departure from the Vertebrata, and
arranging the Invertebrata in a double series, that we shall pre-
sent a system at all conformable with nature. This double route,
indeed, was long since pointed out by Lamarck{, and subse-
quently by Latreille §, MacLeay||, and Blainville J. Latreille has
reconsidered the subject in his latest work, the Cours d’En-
tomologie, published in 1831. He there supposes ** the In-

* pp. 136, 287.

+ See his Cours de ’ Hist. Nat. des Mammif., Lecons 2 & 3.

{ Hist. Nat. des An. sans Vert., tom. i. p. 457.

§ Ina memoir published in 1820 under the title of Passage des Animaux
Invertébrés aux Vertébrés. 8vo.

|| Hore Entom. p. 206, and elsewhere, -

§| Princitpes d’ Anat. Comp., tab. 2. ** p, 15.

ma:
ay:
+

REPORT ON ZOOLOGY. - 185

vertebrata to be arranged on two lines, one occupied by the
Crustacea, Arachnida, and Insecta, the other by the Mollusca
and Zoophyta: he then supposes a lateral branch from the
Mollusca to the Crustacea, passing successively through the
Cirripeda, Annelida, and Entozoa, the connecting link at this
end of the ramification being found in the Lernee of Linneus,
That this arrangement is, however, not, quite correct, is rendered
probable by discoveries connected with the Cirripeda to be here-
after spoken of, and by the indisputable affinity between the
Annelida and Cyclostomous Fishes, which affinity points to the
former group as being necessarily at the head of one series, and
therefore not forming part of any lateral ramification *.
_ The following are the classes considered by Cuvier as belong-
‘ing to the Annulose type: Annelida, Crustacea, Arachnida,
and Insecta.
__ Mr. MacLeay adopts five classes + independently of the _dnne-
ts lida, which he regards as an osculant group connecting the ver-
" tebrate and annulose animals. Two of these are the Crustacea
“ and Arachnida of Cuvier. Two others are formed out of the
old class Insecta, and are the same as Clairville’s groups of
| Beeencebulate and Haustellata. The fifth, to which the name
of Ametabola i is given, includes the Myr iapoda and Thysanura

how: Latreille seems to consider, as he had done in his original memoir on this
a ‘subject, that the Crustacea are the most perfect of the articulated animals, and
that therefore they necessarily approach nearest to the Vertebrata. Mr.
& -MacLeay has controverted both these points. He maintains that Insects are
e highly organized than Crustacea. Furthermore he observes, that so far
Vien its being by the mos¢ perfect, it is by the least perfect group in the series
cso we might naturally expect to find a passage to the Vertebrata. Every
_ vertebrate animal would seem to “ have been constructed with reference to one
type, and every annulose with reference to another; and as the former is more
perfect i in its organization according as it approaches the annulose structure,
e latter is more imperfect in proportion as it possesses a distinct system of
sulation and other characteristics of the Vertebrata. It thus follows that the
« animals which connect them ought to be extremely imperfect in their organi-
_ zation.”” Such animals are the Cyclostomous Fishes on the one hand, and the
e rn on the other, the kiss perlty, between which } eo has been

Sides An, Artic., pp. 13, 15, a subliched : in 1828. yes phe
ees with Latreille in thinking that the Crustacea should follow immediately
after the Fish. See Mém. du Mus., tom. xvi. p. 2; also Cours del’ Hist. Nat. des
mif., Lec. 3, p. 18. Robineau Desv oidy ‘entertains the same opinion.
erches, §c., p - p. 78.
4] Hor. Ent., pp. 288 and 390.

186 FOURTH REPORT—1834.

of Latreille, the droplura of Dr. Leach, and a portion of the
Entozoa of Rudolphi. Mr. MacLeay has endeavoured to show
that these five groups unite to form a circle.

In Blainville’s Principes, &c., we find the 4Annulosa forming
his third type, Entomozoaires*, which he divides into eight
classes, characterized according to the presence or absence,
and when present the number or nature, of the appendages for
locomotion. The Annulosa with articulated feet he distributes
under the six classes Herapodes, Octopodes, Décapodes, Hété-
ropodes, Tétradécapodes, and Myriapodes ; the first including
the true Insects, the second the 4rachnida of Cuvier, the third,
fourth, and fifth the Crustacea of that author. The inarticulated
Annulosa, comprising the Annelida of Cuvier, form his seventh
and eighth classes, called Chétopodes (with setiform appendages,)
and Apodes (deprived of appendages altogether). The last of
these two includes also some of the Hntozoa. Few will pro-
bably be disposed to adopt this arrangement, which leads to di-
visions of very unequal value.

In the Familles Naturelles of Latreille, the Annulosa (or, as
they are there termed, Condylopa,) are primarily divided into
the two sections of Hyper hexapt and Hexapoda, according as
the feet are more than six, or six only, in the adult state, the
former term being adopted from Savigny. The Hyperhexapi
include the three classes Crustacea, Arachnida, and Myriapoda,
this last being adopted from Dr. Leach, who first instituted it in
a paper read to the Linmean Society in 1814 +. The Hexapoda
comprise the single class of Insecta. The Annelida are referred
by Latreille to a different branch of his arrangement of the
Animal Kingdom.

Straus-Durckheim, in his Consid. Génér. sur Anat. Comp.
des Anim. Artic. published in 1828, considers the articulated
animals as including the five classes -dnnelida, Myriapeda,
Insecta, Crustacea, and Arachnida. To the end of the Intro-
duction of his work he has annexed two synoptic tables, in
which he has represented what he conceives to be the true chain
of affinities connecting these classes, and the principal groups
contained in them. It would, however, occupy too much room
to follow him in these details.

In the Cours @ Entomologie, published in 1831, Latreille
has adopted the same divisions as in the Fam. Nat. He only
substitutes the name of Apiropoda for that of Hyperhexapt.

I shall now proceed to consider the progress and state of each

* Tab, 7. + Linn. Trans., vol. xi. p. 306.

REPORT ON ZOOLOGY. 187

of the classes referred by Cuvier to this type of structure sepa-
rately. To these I shall add Dr. Leach’s class of Myriapoda.
1. Annelida.—This class was established by Cuvier in 1802.
Lamarck, who adopted it from him, was, however, the first to
assign to it its presentname. The animals which it includes, al-
though possessing great interest from the circumstance of their
forming the passage from the Annulose to the Vertebrate type,
have been comparatively but little studied, and have received the
attention of only a few naturalists. It is principally to Cuvier,
Savigny, Blainville, and to the more recent researches of Au-
douin and Edwards, that we are indebted for what knowledge
we have respecting them as a class. Cuvier more especially ex-
- amined their internal organization. His arrangement, in both
editions of the 2égne Animal, is grounded upon the respiratory
‘organs, which furnish him with the characters of three groups,
which he terms orders: (1.) Zubicoles, in which the branchize
are in the form of tufts attached to the head or anterior part of
the body, generally inhabiting shelly tubes ; (2.) Dorstbranches,
in which they are arranged down the back or along the sides of

3 the body; and (3.) branches, in which there are no distinct
branchize visible. Savigny, whose valuable memoirs on these

_ animals * are inserted in the great French work on Egypt, paid

_ more attention to their external structure. He particularly
_ studied the conformation of those elastic and often brilliant
mwetallic-like sete, which in a great number of genera serve as

| _ organs of motion. He also entered intoa detailed examination of

:
b

_ the jaws, antenne, branchie, and the membranaceous append-
ages attached to the several articulations. His arrangement of
this class is very different from Cuvier’s. He divides it into
_ five orders: (1.) Néréidées, comprising such genera as have re-
_ tractile feet furnished with setz, a distinct head, and a mouth in
the form of a proboscis, generally armed with jaws; (2.) Ser-
yulées, in which there are also feet furnished with sete, some
_ of these being hooked, but no distinct head; (3.) Lombricines,
without feet or distinct head, but nevertheless furnished with
1all sete ; (4.) Hirudinées, without distinct head, feet, or setz,

t with a mouth in the form of a sucker; (5.) The last order,

‘of which he has not treated, he has left without a name. ‘The
result of Blainville’s researches into the structure of these ani-
i s, which form his class Chétopodes, will be found in the

* Recherches pour servir a@ la Classification des Annelides; and Tableau
systématique de la Classe des Annelides. The first of these memoirs was pre-
“Selited to the Royal Academy of Sciences in 1817. An analysis of them both
ott found in Latreille’s Report, published in the Mém. du Muséum, tom. vi.
p: 93.

188 FOURTH REPORT —1834.

Bull. de la Soc, Phil. for 1818. He divides them into three
orders, the characters of which are drawn from the similarity or
dissimilarity of the segments of the body with relation to the
appendages, and the more or less marked separation of these
segments into head, thorax, and abdomen. It is not necessary
to give the names of his orders, as he has changed them ina
more recent dissertation on these animals published in the
Dict. des Scien. Nat.*, and to which I refer the reader for
a full development of his views respecting their organization
and arrangement.

The memoirs of MM. Audouin and Edwards on the Annelida,
which are the most recent, and at the same time the most
valuable that have yet appeared, are contained in the 4nnales
des Sciences for 1832-33. These acute observers have not only
discovered a vast many new species, but found some exhibiting
such peculiar characters, as render it necessary to institute
several new groups, and to remodel entirely the classification of
former authors. They remark that the system of Cuvier, although
adapted to the small number of species then known, cannot be
employed for the arrangement of many which have been since
discovered, without entailing violations of natural affinity. In
fact, they find that the presence orabsence of the appendages
termed branchie does not by any means constantly coincide
with the true characteristic marks of the different types of
organization presented by these animals, and that more than
one instance might be adduced of species presenting these two
modifications of structure, yet identical in all other respects,
and indisputably belonging to the same family, if not to the
same genus. The systems of Savigny and Blainville they state
to be attended by similar difficulties. What they propose is,
instead of confining their attention to the branchi@é only as the
basis of their classification, to take into account the different —
membranaceous appendages in general, the consideration of
which will lead to more natural divisions. It would seem indeed
from their researches, that although the branchie are occa-
sionally much developed, so that it is impossible to mistake their
function, or to confound them with the cirri and tentacula, yet in
other cases respiration is carried on by some of the other mem-
branaceous appendages, all of which take up this function by
turns in different cases. Hence by considering these organs col-
lectively, and attaching the same value to all of them, we shall
obtain characters of the first importance for the classification of
the Annelida. It is accordingly from these organs, which the

* tom. lvii., Art. Vers. Also published separately under the title of Manuel
d' Helminthologie.

rL:

e

REPORT ON ZOOLOGY. 189

authors term the soft appendages of the body, that they derive
the characters of their four primary divisions or orders, to which
they attach the names of Annelides errantes, Annelides tubicoles
ou sedentaires, Annelides terricoles, and Annelides suceuses.
Audouin and Edwards have paid particular attention to the ex-
ternal organization of the 4nnelida, and have made some inter-
esting discoveries with respect to the structure and use of the
sete with which the feet are provided in the animals of their
first division, being those in which the organization is most com-
plex. They have observed that these sete are not mere orna-
ments or organs of motion, but offensive weapons of a very par-
ticular structure, and such as can only be compared to the stings
of bees or the spines of certain fish. Savigny had noticed that
they were in general capable of being exserted from the body

_ and retracted at pleasure, but does not appear to have entered

\
4

so deeply into the details of their structure as these authors.
MM. Audouin and Edwards have submitted them to a close
and microscopic examination, and have ascertained, that while

some are simple, assuming a great variety of different forms,

others are compound, always consisting of two parts, united by

__ an articulation, which gives way when the seta is employed for

_ Offensive purposes, leaving the apical portion in the body of the

~ animal attacked.

From giving a detailed account of the external organization of

the Annelida in general, MM. Audouin and Edwards proceed

_ to the subordinate groups. So far as they have hitherto ad-

_ vanced in the subject, they have described at length the charac-
ters of all the families and genera; but in regard to species, of

| those only found on the coasts of France. To give any further

4

analysis of their labours would, however, be inconsistent with
4 the limits to which this Report must be restricted. It is, more-
Over, necessary that we should proceed to notice several indi-
viduals who, though they have not written on this class as a
whole, have thrown great light upon some particular parts of it.

_ The Hirudinide especially have received more general atten-
tion than any other group, which is doubtless owing to the valu-
services of these animals in medicine. Dr. Rawlins Johnson

is the author of two memoirs in the Philosophical Transac-
tions for 1817, in one of which he has detailed some interesting
observations with respect to the habits and mode of propagation
of the Hirudo vulgaris; in the other he has instituted the ge-
nus Glossopora* for those species in which the mouth is fur-
nished with a projectile tubular tongue, including the H. com-

* The same as the genus Clepsine of Savigny.

190 FOURTH REPORT—1834.

planata and H. stagnalis of authors, and some others. Dr.
Johnson has also written two treatises on the Medicinal Leech,
to the last of which is appended a reprint of the memoirs above
alluded to. In the Turin Memoirs for 1820*, Professor Ca-
rena has published a complete monograph of the genus Hirudo,
in which, notwithstanding the labours of Savigny, who paid great
attention to this family, he has described several new species,
besides elucidating the history and synonyms of others known
before. A supplement to Carena’s monograph will be found in
the twenty-eighth volume of the same Memoirs. In the Ann.
des Scien. for 1825 t+, M. Rayer has published some interesting
observations with respect to the capsules and ova of several
species of Hirudo, and the gradual development of the young.
In 1827 appeared nearly at the same time two other valuable
monographs on this family, one by Moquin-Tandon f, the other
by Blainville §, this last being in part an extract from the Dict.
des Scien. Nat. In these works, which may serve as points of
departure to future observers, the history of these animals is
nearly complete up to the above time. In both will be found
considerable details with respect to their anatomy, physiology,
and habits, and likewise with respect to species. Of these last
Blainville enumerates thirty-six. Moquin-Tandon describes
thirty-seven, besides four which he considers as doubtful. It
may be stated that Derheims has also written upon this family ;
but Moquin-Tandon does not speak favourably of his work ||,
which I have not seen myself.

The Lumbrici, which received a large share of Savigny’s at-
tention, and of which he has described upwards of twenty
species 4 (as he considers them), before confounded under the
general name of L. terrestris, have been since much attended
to by Léon-Dufour, Dugés, and Morren. Léon-Dufour’s ob-
servations, contained in two memoirs in the Ann. des Scien.
for 1825 and 1828, chiefly respect the mode of reproduction,
which he asserts to be oviparous, and not viviparous as sup-
posed by Montégre** and Sir Everard Home;t. He has disco-
vered the capsules at the depth of five or six feet in the earth,
and found them analogous to those of the genus Hirudo.
M. Dugés is the author of an elaborate memoir in the Ann. des

* vol. xxv. p. 273. + tom. iv. p. 184.

t~ Monographie de la Famille des Hirudinées, par Alfred Moquin-Tandon.
Paris, 1827. 4to.

§ Essai d’une Monographie de la Famille des Hirudinées. Paris, 1827. 8yo.

|| Histoire Naturelle et Médicale des Sangsues. Paris, 1825. 8vo.

‘| The characters of these species will be found in Cuvier’s Analyse des Tra-
vaux for 1821,

** Mém. du Mus., tom. i. p. 242. t+ Phil. Trans. 1823, p. 143.

REPORT ON ZOOLOGY. 191

Scien. for 1828 *, which has principally for its object the
anatomy of Cuvier’s entire group of Annelides Abranches. So
far as respects the Hirudinide, he has added little to what
may be found in Moquin-Tandou’s work on this subject ; but he
has thrown much valuable light on the structure and physiology
of Cuvier’s first family. His researches, which relate to the
organs of circulation, respiration, and reproduction, have been
made on two species of Nazis and six of Lumbricus, which he
commences by characterizing. The latter he does not appear to
be able to identify in all cases with those of Savigny. Like
Léon-Dufour, he considers these animals as oviparous, and
thinks that what Montégre took for living young were only
intestinal worms. Morren’s work ¢, which was crowned by
the University of Ghent, was published in 1829, and is of the
most elaborate nature. Taken in connexion with the researches
of the Frenoh naturalists, it leaves scarcely anything to be de-
sired as far as regards the anatomy and physiology of the Lauwm-
brict. Its author seems in doubt, however, about the numerous
species described by Savigny and others. He is more inclined
to regard them as simple varieties. He in some measure recon-
ciles the conflicting testimonies of Montégre and Léon-Dufour
with respect to the mode of reproduction, by asserting it to be
both oviparous and ovoviviparous.

The structure of the genus Nais has been also investigated
by Dr. Gruithuisen. He has published two memoirs on the
anatomy of certain species belonging to this group in the Nova
Acta &c. Nat. Cur. t.

_ Before quitting this class, it may be remarked that the true
situation of the genus Dentaliwm, placed by Cuvier amongst
his Annelides tubicoles, is undetermined. M. Deshayes, who
has made it the subject of a monograph published in the Mém.
dela Soc. d Hist. Nat. de Paris§, and who has entered into much
detail with respect to its anatomy, seems to regard it as belong-
ing tothe Molluscous type. Further researches are, however,
' necessary in order to establish this opinion as correct.

2. Crustacea.—Until within these few years Latreille and
‘Dr. Leach were almost the only naturalists who had studied the
animals of this class collectively with any degree of care or
minuteness of detail. The latter gentleman is well known to
have devoted a great deal of his attention to their arrangement
and natural affinities. His treatises in this department, consisting

_ * tom. xv. p. 284.
+ De Lumbrici Terrestris Historia Naturali nec non Anatomia Tractatus.
Bruxell. 1829. 4to.

Tt tom. xi. p. 235, and tom. xiv. p. 397. § tom. ii. p. 321,

192 FOURTH REPORT—1834.

of the article Crustacro.oey in the Edinb. Encyclop., a pa=
per in the Linn. Trans. *, and the Malacostraca Podophthalma
Britannie, this last giving descriptions and coloured represen-
tations of a large portion of the British species, have been already
alluded to in aformer part of this Report. These works were
all published before the first edition of the Régne Animal of Cu-
vier. Nevertheless it may be well to give a slight sketch of Dr.
Leach’s arrangement, which, though founded upon Latreille’s +,
is somewhat different from that proposed subsequently by this
last author.

In the Linnean Transactions, above referred to, Dr. Leach
distributes the Crustacea primarily into the two large groups or
subclasses of Malacostraca and Entomostraca. The Malaco-
straca are then divided into two other groups, or legions as they
are called, bearing the names of Podophthalma and Edrioph-
thalma, according as the eyes are either pedunculated or sessile.
The Podophthalma include the two orders Brachyura and
Macroura, comprising, the former thirty-three, and the latter
twenty-two genera. The Edriophthalma are not divided into
orders, but merely distributed into thirty-eight genera, which
are grouped according to the form of the body, and other cha-
racters derived from the antenne and feet. In this division are
several new and curious genera, entirely unknown till Dr. Leach
first made them public. The Entomostraca had received so
little attention when Dr. Leach published his system, that he
did not attempt to arrange them according to their true affini-
ties, but merely gave an artificial distribution of the genera, to
serve till such time as we were made better acquainted with
their structure.

The arrangement of Latreille in the third volume of the first
edition of the Régne Animal t is different, as already alluded
to, from that adopted formerly by this author. In this work
the Crustacea are divided into five orders : Decapodes, Stoma-
podes, Amphipodes, Isopodes, and Branchipodes ; the charac-
ters of which are taken from tke situation and form of the
branchie, the mode of articulation of the head with the trunk,
and the organs of manducation. The Decapoda are divided into
the two families of Brachyures and Macroures, answering to
Dr. Leach’s two orders bearing the same names. The Stoma-
poda include one family, formed out of the Fabrician genus

* vol. xi. p. 306.

+ I allude to the system given by Latreille in his Genera Crustaceorum et
Insectorum. 4 vols. 8vo. Paris, 1806. !

+ Latreille undertook all that portion of the above work which treats of the

Annulose Animals with Articulated Feet, comprising the classes’ Crustacea,
Arachnida, and Insecta.

ee
en Se

“REPORT ON ZOOLOGY. 193

Squilla. The Amphipoda consist principally of such Crustacea
as were referred by Fabricius to his geuus Gammarus. 'The
Tsopoda answer to the Onisci of Linneus. The Amphipoda
and Jsopoda together constitute Dr. Leach’s second legion,
Edriophthalma. Latreille’s fifth order, Branchiopoda, includes
the Entomostraca of Miiller and Leach, referred by Linnzus
to his genus Monoculus *.

Since the appearance of the Régne Animal, other naturalists
have occupied themselves with this class. Latreille has also
modified his own arrangement in some subsequent publications,
availing himself of many valuable researches on the part of differ-
ent individuals, relating more particularly to the Entomostraca.

» In the Familles Naturelles, published in 1825, we find the
Crustacea divided primarily into the two sections of Mazxillosa
and Edentata. The former comprises, in addition to the old
orders Decapoda, Stomapoda, Amphipoda, and Isopoda, three
new orders,—one, Lemodipoda, for the reception of the Jsopodes
Cystibranches of the Régne Animal, placed between the Stoma-
poda and Amphipoda ; the other two, Lophyropoda and Phyllo-
poda,taken out of the old order Branchiopoda, and terminating the
first division. The second section contains the remainder of the
Branchiopoda arranged under the two new orders Xyphosura
and Siphonostoma. Thus we have the Hntomostraca, which
before constituted but one order, here forming four. Latreille
in his last work, Cows d’ Entomologie, has increased the orders
still further. He has adopted three other new ones, called Dicla-
dopa, Ostrapoda, and Trilobita. The first of these, inserted
between the Isopoda and Lophyropoda, includes the genera
Nehalia, Pontia, Condylura, and Cuma. The second, insti-
tuted by Straus, comprises the genera Cypris and Cytherea, and
is placed between the Lophyropoda and Phyllopoda. The third,
adopted for the fossil Trélobites, forms the last order in his first
division of Mazillosa. In other respects his system is the same
4s that in the Fumilles Naturelles.

_ The same year as that in which the /’am. Nat. of Latreille ap-
peared, Desmarest published his Considérations Générales sur
ta Classe des Crustacés. In this work, which is one of consider=
able merit as well as utility +, we have the systems of Latreille
and Leach in some measure combined. Thus, the Malacostraca
er ns

\ *® The above arrangement by Latreille was adopted, with some slight modi~
fications, by Lamarck in the 5th vol. of his Hist. Nat. des An. sans Vert.

* + M. Desmarest was the first to draw the attention of naturalists to the dif-
ferent regions marked out on the upper surface of the carapace in the Decapoda
Brachyura, and to show their exact accordance with the internal organs which
they respectively cover.

1834. o

194 FOURTH REPORT—1834.

and Entomostraca of this last author are retained as primary
divisions, and the former is still divided into the two secondary
groups of Podophthalma and Edriophthalma; but the groups
next in succession are the same as Latreille’s orders. At the
saine time there is a slight modification of these orders among
the Entomostraca. .

Risso, who has paid considerable attention to the Crustacea,
adopts, in his Hist. Nat. de ? Eur. Mérid., published in 1826*,
nearly the same arrangement as that of Desmarest.

The most important, as well as most recent, additions which
have been made to our knowledge of the Crustacea are due to
the researches of MM. Audouin and Edwards, who have for some
years back, the latter gentleman more especially, given particular
attention to this class of animals. Indeed-it is impossible to
speak too highly of their labours in this department. Bearing
in mind the close connexion which subsists between zoology
properly so called, and comparative anatomy and physiology,
they have commenced by studying closely the internal as well as
external organization of the Crustacea, before preceeding to in-
vestigate their natural affinities. The results of their researches
on this branch of the subject are contained in a series of me-
moirs published in the dnnales des Sciences, of which anylength-
ened analysis here would lead too much into anatomical details.
It may be just stated, that in their first two memoirs, published
in 1827+, they have treated of the circulation of the blood, con-
cerning the true course of which there prevailed before much
difference of opinion. They have determined with accuracy the
exact method in which the circulation is effected, and found it
to be in some respects analogous to that which is known to pre-
vail in the molluscous animals{. Inathird memoir, published
in 1828§, they-have entered into considerable details with respect

* The Crustacea are contained in the fifth volume. Risso had published
some years previously a work entitled, Histoire Naturelle des Crustacés des
Environs de Nice, 8vo, Paris, 1816.

+ Ann. des Scien., tom. xi.

} Two memoirs on the circulation of the Crustacea have been also published
in Germany by M. Lund, the one prior, the other subsequent, to those of Au-
douin and Edwards. In the first (Isis, 1825,) the author observes that he has
never been able to discover the slightest trace of veins in the Crustacea, which
he thinks are without them, and in consequence deprived of a complete cireu-
lation. In the second (Isis, 1829,) he confines himself to some remarks on the
researches of Audouin and Edwards, who have arrived at such different results
from himself.. He allows that they have discovered a system analogous to the
venous system of the Vertebrata and Mollusca, but does not agree with them as
toa near affinity between the Crustacea and Mollusca in regard to their cireula-
tory organs:

§ Ann., tom. xiv. p. 77,

————EE
——————

REPORT ON ZOOLOGY. 195

to the nervous system. Their particular object is to show that
in the Crustacea this system exhibits a-unity of composition, and
that all the different modifications which it presents in different
families may be easily referred to one type, these modifications
depending simply on a greater or less approximation, and ten-
dency towards centralization of the medullary ganglions. Ina
fourth memoir, read the same year to the Royal Academy of Sci-
ences*, they have considered the respiratory organs of these ani-
mals, their researches on which head have led them to discover the
true method of respiration in those Crustacea which are capable
of living for a considerable time out of water. They have as-
certained that it is not by any organ analogous to lungs, as was
formerly supposed, but by the help of a peculiar structure, ena-
bling them to retain the water within the respiratory cavity as in
a reservoir, from whence is supplied the necessary moisture for
a free exercise of the branchial lamine. In a subsequent me-
moir on this subject}, published in 1830, M. Edwards has ex-
pressed an opinion that the respiratory apparatus will be found
to afford some valuable characters for the determination of natural
_ groups.
The above memoirs on the anatomy of the Crustacea, with
the exception of the last, were undertaken by MM. Audouin
and Edwards jointly. During the present year (1834), M. Ed-
wards has published singly the first volume of a general work {
( yn the natural history of this class, in which he sepa ome pe

2 researches just alluded to, as well as treated of the classifica-
tion and systematic description of these animals. The following
is a sketch of his arrangement. He divides the Crustacea pri-
marily into the three subclasses of Crustacés Maxillés, Crust.
Suceurs, and Crust. Xyphosuriens. The first of these groups
commences with the legion Podophthalmiens, including the two
erders Décapodes and Stomapodes ; then follows the legion
Edriophthalmes, comprising the three orders Amphipodes, Iso-
podes, and Lemipodes; next in succession are the legions
Branchiopodes and Entomostracés, which he thinks form two

] series, the former containing the two orders of Phyllo-
podes and Cladocéres, the latter those of Ostrapodes and, Copé-
, this last being nearly the same as the, order Dicladopes

of Latreille. The legion J'rilobites is placed provisionally at
the end of the first subclass. The second subclass is divided
Hine -
oF Dizcport by Cuvier and Dumeril on this memoir wall be found in the dn,
des Sci. Nat., tom. xv. p. 85.
+ Ann. des Sci., tom. xix. p. 451.

t Histoire Naturelle des Crustacés, comprenant T Anatomie, la Physiologie, et,
la Classification de ces Animaux, par a Edwards, tom. i., Paris, 1834,,

oy)

196 _ FOURTH REPORT—1834.

into the two legions of Parasites Marcheurs and Parasites
Nageurs, the former comprising the single order Aranéiformes,
the latter the two orders Siphonostomes and Lernéens. The
third:subclass consists of the single order Xyphosures. It will
be seen that Edwards has adopted a large number of Latreille’s

principal groups. At the same time he has introduced some _

changes in the arrangement of this author. He has augmented
the number of orders, and likewise altered the limits of some of
these divisions. Two of the additional orders are for the recep-
tion of the Pycnogonida and Lernee, which Latreille does not
include in the present class. In the descriptive portion of his
work, M. Edwards has as yet proceeded but a little way. In
fact he has only got through the first two families of the Deca-
poda Brachyura. A few years back, however, he published a
monograph on the Crustacea Amphipoda, to which those may
be referred who want information on that particular order. An
extract from it will be found in the dun. des Scien. for 1830*.
Some researches on the Crustacea by a naturalist of this
country, of great importance, though leading to results which it
would be well to have confirmed by other observers, may be
noticed in this place. I allude to Mr. Thompson’s supposed
discovery of a metamorphosis in the animals of this class, an-
nounced in 1828, in the first number of his Zoological Re-
searches}. It is stated by this gentleman, that having examined
the newly hatched young of the common Crab (Cancer Pagurus),
he found them presenting exactly the appearance of the Zoea
Taurus, the Monoculus Taurus of Slabber, which animal he
conceives to be the first state of the species above mentioned.
From this circumstance he was led to conclude, that metamor-
phosis was general throughout the Decapod Crustacea; that in

the first stage of their existence they are essentially natatory, -

but that after a time the greater number of them lose the power
of swimming, acquire chele, and have their feet adapted for
crawling only. In a communication made by letter to the Zoo-
logical Society in 1830{, Mr. Thompson stated, in support of
the universality of this metamorphosis, that he had ascertained
the newly hatched animal to be a Zoea in eight genera of the
Decupoda Brachyura, viz. Cancer, Carcinus, Portunus, Eryphia,

' * tom. xx.
+ Zoological Researches, and Illustrations; or Natural History of Nondescript
or imperfectly known Animals. By J. V. ‘Thompson. Cork, 1828, &e.—Of this
work only five numbers have as yet appeared. In it will be found some other
valuable memoirs relating to the Crustacea besides that above alluded to, more
particularly one on the genus Mysis, and another on the Shizopoda.
t Proeeed. of Zool: Soc., p. 17.

’REPORT ON ZOOLOGY. 197

Gecarcinus, Thelphusa?, Pinnotheres, and Inachus; and in
seven genera of the Macroura, viz. Pagurus, Porcellana, Ga-
lathea, Crangon, Palemon, Homarus, and Astacus.

_ No direct observations have been as yet made by other natu-
ralists sufficient to establish the existence of any error in these
results at which Mr. Thompson has arrived. There is, how-
ever, enough on record to prove that this metamorphosis is not
universal ; and some excellent observers have been led by their
own inquiries to regard it as rather improbable altogether:
The researches of Rathke are decidedly opposed to it. This
profound anatomist is the author of an elaborate treatise on the
development of the young Cray-fish*, which he has traced
through all its stages from its earliest existence ; and so far from
observing any metamorphosis in this species, he particularly
states that the young at birth scarcely differ externally from the
adult except in size. M. Edwards has made some remarks upon
Mr. Thompson’s theory, which he does not consider as tenable,
without the support of further and more accurate observation.
At the same time he thinks it very possible that none of the in-
dividuals of the genus Zoea hitherto observed by naturalists had
reached their adult state;. We are informed by Latreillet, that
this gentleman had it in view to institute some particular re-
searches under the hope of throwing light on this matter. I
am not aware that any decisive results have been hitherto made
public. The subject, however, is undergoing investigation in
our own country, and will probably before long be satisfactorily
cleared up.

_ The above doubts respecting the metamorphosis of the Crus-
tacea relate only to its existence amongst the Decapoda. That
it takes place in some of the other orders in this class is quite
certain. Jurine long since detected it in the case of some of the
Entomostraca. More recently M. Edwards has observed strik-
ing changes of furm, almost, if not quite amounting to meta-
morphosis, taking place in several genera of the Crustacea Iso-
_ poda, in one genus (Cyamus, Latr.) of the L@modipoda, and in
one genus (Phronima, Latr.) of the dmphipoda§. At the same
time he has fully ascertained, that in other genera, more parti-
cularly Gammarus and Idotea, this kind of metamorphosis does

_ * See an analysis of this memoir in the Ann. des Sci. Nat. for 1830, tom. xx.
442,

a Ann. des Sci., tom. xix. p. 459. See also Hist. Nat. des Crust., tom. i.
p- 199; and Dict. Class. d’Hist. Nat., Art. Zor.

- $ Cours d’Entomol., p. 385.

_ § These researches are contained in a memoir, of which an analysis will be

found in the Ann. des Scien. for Dec. 1833, p. 360.

1S8 FOURTH REPORT—1834.

not occur. The genus in which the change of form is most con-
spicuous appears to be that of Cymothoa. In this instance he
has observed the young to be not only deficient in some parts
which are developed in the adult,—thus, having six instead of se-
ven thoracic segments, and consequently only twelve instead of
fourteen feet,—but possessed of others well developed, which in
the adult state are merely rudimentary. Thus, the adult has the
head extremely small, and the eyes scarcely perceptible exter-
nally. The young, on the contrary, have the head large, and the
eyes remarkably conspicuous. A similar difference occurs in
the segments of the abdomen, which in the adult are very short
and almost linear, whereas in the young they spread out almost
as much as those of the thorax*.

Naturalists who have studied this class have too frequently
confined their researches to the Malacostraca. The Entomo=
straca, although everywhere to be met with, like some other
equally neglected groups, have received, at least of late years,
but comparatively little attention. In this country they have
been scarcely noticed at all. The works of Miller} and Jurinet
still retain their value as the great storehouses of original ob-
servations relating to these animals, and are indispensable to
those who may feel induced to study them. The latter, which
is of recent date compared with Miiller’s, deserves especially to
be pointed out, as, though well known and duly appreciated on
the Continent, it does not appear to be familiar to our own na-
turalists. It embraces the history of Miiller’s genera Cyclops,
Daphnia, Polyphemus, Lynceus, and Cypris, including deserip=
tions of such species as are found in the neighbourhood of
Geneva. Jurine has paid the most scrupulous attention to the
habits and ceconomy of these minute animals. Many of them he
has traced through every stage of their existence; and, amongst
other valuable researches, has ascertained that the genera Amy-
mone and Nauplius of the Danish naturalist are only young
states of the genus Cyclops. This work is illustrated with beau-
tifully coloured figures of all the species. There is also ap-
pended to it a detailed and valuable memoir by Bénedict Prévost

* M. Edwards has sought to refer to some general principles these and other
similar facts which he has observed relating to change of form in the Crustacea.
He has arrived at the following generalization: That “ the different changes
of form which the Malacostraca (or higher Crustacea) may experience after
quitting the egg, tend always, whatever be their nature or importance, to alienate
the animal from the type common to the greater number of these beings, and in
some measure to individuate it more and more.” See Ann. des Scien., 1. ¢.

+ Entomostraca, seu Insecta Testacea, §c. 4to, Lips. et Haun. 1785.

t Histoire des Monocles qui se trouvent aux Environs de Geneve. 4to, Geneve,
1820.

REPORT ON ZOOLOGY. 159:

on the Branchipus of Latreille, or, as the author here calls it,
Chirocephalus*.
_ If to the above works we add a few separate memoirs devoted
to particular genera by different individuals,—that of the younger
Jurine on Argulus foliaceus published in 1806}, Straus’s two
memoirs on the genus Daphnia published in 1819 and 1820},
a third the year following by the same author on the genus Cy-
‘is§, and Brongniart’s memoir on the Limnadia Hermann
published in 1820||,—we shall have enumerated by far the most
valuable contributions which have been yet made to our know-
ledge of this portion of the Crustaceaf. Straus’s memoirs in
particular, which for patient research and close anatomical in-
vestigation, considering the minuteness of these animals, can
scarcely be equalled, deserve the highest commendation. It was
principally in consequence of the labours of this observer and
those of Jurine, which were subsequent to the appearance of
the first edition of the Régne Animal, that Latreille was led to
make such striking alterations in the arrangement of the Ento-
mostraca in his Familles Naturelles. 'These alterations have
_ been already pointed out ; and they clearly show what we may
yet expect from further researches into the structure of other
groups which have not hitherto received so close an examination.
‘The only recent contributions of any moment, at present known
to me, are, a memoir by Dr. Gruithuisen on the Anatomy of
Daphnia Sima published in 1828**, a second by Milne Kdwards
on the structure of the mouth in the Siphonostomous Entomo-
straca published in 1833{}, and a third published within these
few months by Mr. Thompson on the 4rtemis salinustt. The
principal object of M. Edwards’s essay is to show that notwith-
‘standing the apparent differences between the mouth of the
_ Sitphonostoma and that of the rest of the Crustacea, the parts
are strictly analogous in the two cases, and there is still kept up
__aunity of composition. Thompson’s memoir contains observa-
tions on the gradual development of the young of the4rtemis
salinus, and the metamorphoses which it undergoes before arriv-
‘Ing at an adult state. These metamorphoses are found to cor-

__ * This memoir had been previously published in the Journal de Physique for

1803, tom. lvii. + Ann. du Mus., tom. vii. p. 431.
¢ Mém. du Mus., tom. v. p. 380, and tom. vi. p. 149.
~ § Id., tom. vii. p. 33. || Zd., tom. vi. p. 83.

9] A treatise on the Monoculi was published at Halle, in 1805, by Ramd’hor,
who, according to Latreille, has anticipated Straus and Jurine in some of their
anatomical researches. I have not seen the work myself.

** Nov. Act. §c. Nat. Cur., tom. xiv. p. 368.

tt Ann. des Scien. Nat., tom. xxviii. p. 87.

Tf Zool. Researches, No.5, Mem. 6.

200 FOURTH REPORT—1834.

respond with those noticed in Branchipus, Apus, and other
genera of the Phyllopoda, to which the Artemis is allied. Mr.
Thompson has endeavoured to prove that there is a close affinity
between the drtemis salinus and the fossil Eyeless Trilobites.

I may also refer to a paper by Audouin and Edwards in the
Annales des Scien. for 1826*, containing an account of a very
singularly organized animal, forming a new genus (icothoe)
among the Siphonostoma of Latreille. It is of parasitic habits,
and was discovered firmly attached to the gills of the Lobster.
Perhaps there is no group in the Entomostraca in which we
may expect so many new forms yet to occur, and of whose
ceconomy in general we know so little, as that just mentioned.
With reference to this last point we may, however, except the
genus drgulus, Jurine’s memoir before spoken of leaving us
scarcely anything further to be desired in the history of that
animal.

3. Arachnida.—This class, which Lamarck was the first to
separate from that of Insects, has until very recently been much
neglected by naturalists. The consequence is that our know-
ledge of many of the groups contained in it is extremely imper-
fect. Even its limits are far from being determined ; and some
are of opinion that it ought to be resolved into two classes, on
account of the great differences which occur in the respiratory
organs. Dr. Leach was the first to entertain this last idea, in
the third volume of his Zoological Miscellany, published in
1817. In an article in this work} “ On the Characters of the
Arachnides,”’ he has restricted this class to the five families
of Scorpionide, Tarantulide, Phalangide, Solpugide, and
Araneide, in all of which respiration is effected by means of
pulmonary sacs. The Trachean Arachnida of Latreille, except-
ing the genera Pycnogonum, Phoxichilus, Ammothea, and
Nymphum, (whose situation he considers doubtful,) and the
genera Phalangium, Solpuga,and Trogulus, (and perhaps Siro,)_
he thinks constitute a peculiar class, which he proposes to name
Acari.

Although Latreille himself subsequently adopted this same
opinion respecting the propriety of forming two classes of the
Pulmonary and Trachean Arachnida}, he has not acted upon it in
any of his published works. In the Régne Animal these groups
simply stand as two orders, the first including the two families
of Fileuses (Adranea, Linn.) and Pédipalpes (Tarantula, Fab.,
and Scorpio, Linn.), the second those of Fauwz Scorpions, Pyc-

-

* tom. ix. p. 345. + p. 46.
t Fam. Nat., p. 317, note ('). Cours d’Entom., p. 161.

REPORT ON ZOOLOGY. 201

nogonides, and Holetre (Phalangium and Acarus, Linn.). In
the Familles Naturelles his arrangement is nearly the ‘same.
There is simply a change with respect to the order in which the
families stand, with the addition of some new ones amongst the
Trachean Arachnida: Butin the Cours d’ Entomologie we find a
third order, termed Aporobhranches, occupying a middle station
between the other two. This new group, which is characterized
by having gills without any external opening, Latreille intends
should include the Pycnogonida. It has been already mentioned
that these anomalous animals, which seem to form the passage
from the drachnida to the Crustacea, are considered by Kd-
wards as belonging to the class last mentioned.

It may be stated that Mr. Kirby appears likewise to be of

apiniion that the Pulmonary and Trachean drachnida should
not be included in the same class*.
_ Mr. MacLeay has, however, expressed himself differently. He
maintains ‘“‘ that the division of the organs of respiration and
circulation is not to be depended on in the classical arrangement
of the Annulosa;.”

. This last opinion, which will probably in the end be generally
assented to, has been adopted by Dugés in a valuable memoir on
the Acari, published during the present year{. In the intro-
duction to this memoir Dugés has made some observations on
the relation which subsists between the dcari and the rest of
the Arachnida. He remarks that there is nothing in the external
structure of these animals at all corresponding to those differ-
ences in the respiratory and circulatory organs which some au-
thors have made the basis of their arrangement. He thinks that

_ the value of the characters derived from these organs has been

overrated; and in proof of this, that it is only necessary to
observe the striking changes which such organs undergo (in the
case of the Batrachian Reptiles and aquatic insects) in the same

individual at different stages of its life.

Instead, then, of making the external form subordinate to the
organs of respiration and circulation, M. Dugés adopts the for-
mer as the groundwork upon which he establishes his principal
divisions. The following are what he considers as the true di-
stinguishing characters of the class Arachnida : Istly, the pre-
sence of eight feet adapted for walking; 2ndly, the absence of
antenn§ and reticulated eyes ; 3rdly, the constant union of one

_ * Introd. to Entom., vol. iii. p. 21. + Hor. Ent., p. 382.
~ t © Recherches sur l’Ordre des Acariens,”’ Ann. des Scien. Nat. for Jan. 1834,
p. 5.

§ Lamarck had observed, and formerly Latreille also, how strikingly the true
Arachnida were distinguished from the two classes of Crustacea and Insects by

202 FOURTH BEPORT—1834.

or more segments of the thorax with the head. The class thus
characterized, which, according to a new nomenclature of his
own*, he calls 4ranistes, he divides into the two subclasses of
Acarulistes and Aranulistes ; the former containing the single
order Acariens; the latter the three orders of Phalangiens,
Aranéens, and Scorpioniens. Each of these orders is again
divided into several families.

The rest of Dugés’s memoir is restricted to the investigation
of the Acari, and contains some novel and highly important re-
searches on this group of animals. These relate more espe-
cially to the gradual development of the young, and the meta-
morphoses which many of them undergo before arriving at the
adult state. M. Dugés has satisfactorily ascertained that many
of the hexapod genera constituting Latreille’s family of Micro-
phthira are only the larve of others, and he has sufficiently
multiplied his observations to lead him to suspect that this will
be found ultimately to be the case with all of them; that is to
say, that there will be found no instance of any of the 4rachnida
having only six feet in the adult state. He has proved Leptus
to be only the young of Trombidiwm, and he has strong reasons
for supposing Ocypete and Astoma to be so likewise. The genus
Achlysia of Audouin} he has shown to be the larva of Hy-
drachna: the genus Caris he suspects to be the larva of Argas.
Although these striking researches necessarily lead to the sup-
pression of many genera instituted by former naturalists, Dugés
has discovered or established others more than sufficient to make
compensation. In his arrangement of these animals we still
find twenty-four genera, distributed under seven families, the
former exceeding by five the number adopted by Latreille. It
is his intention to treat of each of these genera separately. As
yet, however, his valuable memoir remains unfinished.

But few individuals besides Dugés have hitherto devoted much
of their attention to the dcari. In 1826, Heyden published a
systematic arrangement of this groupt, in which he increased

the want of antennz. Liatreille, however, was led subsequently to take a dif-
ferent view of the subject, and to regard what are usually called the mandibles
or cheliform palpi in the drachnida as representing the intermediate pair of an-
tenne in the Crustacea Decapoda, only in the former class exercising a different
function and being always adapted for manducation. Thus the deficient parts he
considered to be the true mandibles, and not the antennze. See Fam. Nat., p.307.
See also some remarks on this hypothesis of Latreille, by MacLeay (Hor. Ent.,
p- 383,) and likewise by Dugés (J. c., p.9.):

* In this and some other instances Dugés has very unnecessarily changed
names which had long been consecrated by time, and adopted generally.

+ Mém. de la Soc. d’ Hist. Nat. de Paris, tom. i. p. 98.

t Isis, 1826, p. 608.

ee

REPORT ON ZOOLOGY. 203

the number of genera to sixty-nine, but in the opinion of Dugés
y of these rest on doubtful if not erroneous characters.
Léon-Dufour, Audouin, and De Théis have all contributed me-
moirs to the dnn. des Sci. Nat. on particular genera*. Accord-
ing to Latreille}, this last gentleman is engaged in a new work
on these animals, to be illustrated by plates.
The most important group among the Pulmonary Arachnida
' isthat of the 4rancide. Nevertheless, like all the others in this
class, it has been greatly neglected. Walckenaer, Latreille,
and Léon-Dufour in France, De Hahn in Germany, and Mr.
Blackwall in our own country, are almost the only individuals
who have given it any attention of late years. Walckenaer, who
has studied it most deeply, and whose Tableau des Aranéides,
published in 1805, has been hitherto the only guide for naturalists
in this department, has recently proposed a new arrangement of
these animals in a memoir read to the Entomological Society
of Francet. The principal groundwork of his system is the
same as in his Tableau, and he still adopts the two large divisions
of Théraphoses and Araignées, founded upon the position of the
jaws with respect to the rest of the body, and the articulation of
the mandibles. The number and position of the eyes serve
afterwards for characterizing some well-marked groups subordi-
nate to these two large tribes. Walckenaer observes that the
species of Spiders have been greatly overmultiplied, from suf-
ficient regard not having been paid to the changes incident to
different ages with respect to size and colour. Léon-Dufour
has more particularly occupied himself with the structure and
internal anatomy of the 4raneide. He is the author of some
important memoirs§ on this part of the subject, in one of which
he has instituted a new division of this group into the two sec-
tions of Tetrapneumones and Dipneumones, founded on the
number of pulmonary sacs, which he was the first to discover
are double oneach side of the abdomen in certain species, amount-
ing to four in all. The Zetrapnewmones, which comprise the
Théraphoses of Walckenaer, as well as a small portion of his
Araignées, form the subject of a memoir in the Nouv. dan. du
Mus.|| by Latreille, who speaks highly of this new principle of
arrangement. He thinks that it will serve as an immutable
aig 1

* Annedes Sci., tom. xxv., XXvi., and xxvii. _ + Cours d’Entom., p. 546.

t An extract from this memoir will be found in L’Jnstitute, 1833, No. 18.
i Malekenser has also lately commenced the publication of a work entitled,
ng a de France classées par leur Organisation, §c. (L’Instit. 1834,

0, 53. ,

§ Ann, des Scien. Physiques de Bruaelles, tom. v. and vi. || tom. i. p. 61.

204 FOURTH REPORT—1834.

foundation for a natural distribution of the genera in this exten
sive family. Latreille has adopted it in the second edition of the
Regne Animal, as he had previously done in his Familles Natu-
relles.. It must be observed, however, that Walckenaer does not
attach so much importance to this modification of the respira-
tory organs. He states that it is not accompanied by any cor-
responding differences in other parts of the structure, and that,
taken as the basis of a division, it leads to the separation of cer-
tain genera which, according to his views, are connected by the
closest affinity. Besides the above memoirs on the structure of
the dranee, Léon-Dufour has published several others descrip-
tive of new or ill-understood species*. He has particularly
attended to the species found in Spain, as well as to the species
of Phalangium met with in the same countryt. He has dis-
covered a new method of preserving the draneet, which it is
to be hoped may induce fresh labourers to enter upon this field.
It is greatly owing to the difficulty which has been hitherto
experienced in preventing the changes which occur after death
in these animals, that they have been so much neglected by
naturalists.

De Hahn is the author of a work now in course of publication,
the object of which is to illustrate by coloured plates the genera
and principal species of this family§.. Mr. Blackwall has pub-
lished some important memoirs on subjects connected with the
structure and ceconomy of the 4raneide||, as well as others de-
scriptive of some undescribed genera and species].

Before leaving this class it may be mentioned that in the third
volume of the Zoological Miscellany**, Dr. Leach has published
an article on the characters of the genera of the family Scorpi-
onide, accompanied by descriptions and coloured representations
of all the British species of Chelifer and Obisium. Some ad-
ditions to these genera by Théis will be found in the nn. des
Sci. for 1832++.

4. Myriapoda.—There can be no doubt that a certain affinity
exists between this class and the Annelida, as Latreille was the
first to point out in a memoir on the articulated animals pub-
lished in 1820¢{. The Myriapoda have not been much attended
to. In the third volume of the Zoolog. Miscell. is a valuable
paper by Dr. Leach on these animals, in which he has given the

* Ann. des Sci. Phys., tom.iv. Ann. des Sci. Nat., tomes ii. and!tom. xxii.

+ Ann. des Sci. Nat., tom. xxii. t Id.
§ Die Arachniden getreu nach der Natur abgebildet und beschrieben, von
C. W. Hahn, 1831, &c. || Linn. Trans., vols. xv. and xvi.

q Lond. and Edinb. Phil. Mag. and Journ., 1833, vol; iii.
a p. 48. t+ tom. xxvii. p. 57. tt Mem. du Mus., tom. vi. p. 116.

REPORT ON ZOOLOGY. 205.

characters of the genera which it comprises, as well as descrip-
tions of all the British species*. He divides the class into the
two orders of Chilognatha and Syngnatha, the former answering
_ to the Linnzan genus Julus, the latter to that of Scolopendra.
This arrangement is adopted by Latreille. Savi has made a
particular study of the Zu/z. In two memoirs, one published in
1817, the other in 1819+, he has recorded some valuable observa-
tions relating to the ceconomy of certain species of this family.
I am not aware of any recent contributions to our knowledge of
this class excepting a paper by Léon-Dufour on the internal
structure of the Lithobius forficatus and the Scutigera lineata.
This memoir is published in the dnn. des Sci. Nat. for 1824.
- 5. Insecta.—It is impossible to do more than to treat of this
class in the most general manner. Indeed from its great extent,
the immense additions which have been made to it of late years,
and the large number of individuals who have contributed to its
progress, it may well deserve to be made the subject of a separate
report. I shall simply state, Istly, the leading groups which
have been adopted or proposed in this class; 2ndly, the most
important works and memoirs which have appeared in illustra-
tion of its structure; 3rdly, the principal authors who have con-.
tributed to the advancement of particular parts of it. As the
chain of affinities connecting the several orders is far from being
determined with certainty, and much difference of opinion exists.
on this subject, to discuss which would lead to considerable
details, I shall be silent on this point altogether.
_ (1.) Inthe first edition of the Régne Animal the following orders
are adopted by Latreille, exclusively of the Myriapoda, which
he afterwards acknowledged as a distinct class. 1. Thysanura,
Latr.t; 2. Parasita, Latr.t; 3. Suctoria, De Geer; 4. Coleo-
_ ptera,Linn.; 5.Orthoptera, Oliv.; 6. Hemiptera, Linn. ; 7. Neu-
roptera, Linn.; 8. Hymenoptera, Linn.; 9. Lepidoptera, Linn.;
10. Rhipiptera, Latr. (Strepsiptera, Kirb.); 11. Diptera, Linn.
_» Inthe same year (1817), Dr. Leach published his amended
arrangement of the orders of the class Znsecta in the third volume
of his Zool. Miscellany. In this work we have a primary di-
vision into the two subclasses of Ametabolia and Metabolia.
The former includes the Thysanura and Parasita of Latreille,
the name of this last order being changed to Anoplura: the
latter, Latreille’s remaining orders, with the five additional or-
. ders of Dermaptera, De Geer, (gen. Forficula, Linn.) ; Dictyo-

peed. Leach has described several new species of Julus from the South of
Europe in the 7ransactions of the Plymouth Institution, 1830, p. 158.

+ See Bull. des Sci. Nat., 1823, tom. iv. p. 330. we a

t These two orders were established by Latreille in some of his earlier works,

206 FOURTH REPORT—1834.

ptera, (gen. Blatta, Linn.) ; Omoptera, (gen. Cicada, Thrips,

Aphis, &c., Linn.); Trichoptera, Kirb.(gen. Phryganea, Linn.) ;
and Omaloptera, (gen. Hippohosca, Linn.) ; amounting in all
to sixteen. Latreille’s name of Swetoria is changed to that of
Aptera.

Mr. MacLeay in his Hore Entom. (1821) has proposed Bom-
boptera, Megaloptera, and Rhaphioptera as three new oscu-
lant orders in his class Mandihulata, including the genera Sirex,
Linn., Sialis, Latr., and Boreus, Latr., respectively. The first he
considers as connecting the Hymenoptera and Trichoptera;
the second, this last and Neuroptera ; the third, this last and
Orthoptera. He regards Dermaptera and Strepsiptera like-
wise as osculant orders, the former connecting Orthoptera and
Coleoptera, the latter this last and Hymenoptera.

Blainville* divides the Insects (forming with him his class
Hexapoda) into three subclasses, Tetraptera, Diptera, and
Aptera. The first of these contains as subordinate groups the
orders Coleoptera, Orthoptera, Hemiptera, Lepidoptera, Neu-
xvoptera, and Hymenoptera.

In 1823, Duméril published his Considérations Générales sur
da Classe des Insectes. His work, however, which is of an ele-
mentary nature, offers nothing new on the subject of classifica-
tion. His orders, eight in number, are the same as those of
Linneus, with the addition of Orthoptera. M.Duméril adyo-
cates very strongly the dichotomous, or, as he terms it, the ana-
lytical method of arrangement, which he had adopted in his
former works.

In the Fam. Wat. (1825) Latreille adopts as a primary divi-
sion of this class the two sections of 4ptera and Alata. The
former comprises the orders Thysanura, Parasita, and Siphon-
aptera (name substituted for that of Swetoria) ; the latter, the
remaining orders of the Régne Animal.

In 1826 appeared the fourth volume of the Introduction to En-
tomology, in which Mr. Kirby proposes to adopt twelve orders.
Seven of these are the same as those of Linnzus; the remaining
five are Strepsiptera, Dermaptera, Orthoptera, Trichoptera,
and Aphaniptera (Siphonaptera, Latr.).

In the second edition of the Régne Animal, Latreille’s arrange-
ment is the same as in the first. But in his last work, the Cours
d’ Entomologie (1831), he has again taken that of the Familles
Naturelles, excepting that he has adopted one additional order,
the Dermaptera of Leach.

(2.) Our knowledge of the structure of Insects, both external
and internal, has been greatly advanced of late years by the re-

* Principes, §c., tab. 7.

‘REPORT ON ZOOLOGY. 207

searches of many excellent observers. Some of the most im-
portant contributions on the subject of their external anatomy
hayearisen out of an endeavour to trace analogies of structure
in the relative conformation of different groups in this class, as
well as in that of insects in general compared with the rest of
the Annulosa.. Savigny was the first to draw the attention of
naturalists to inquiries of this nature in two memoirs on the
structure of the mouth of the articulated animals, published in
1816*. In one he demonstrated that the same parts were to be
found, though modified, in this organ as it occurs both in the
Mandibulata and Haustellata, notwithstanding the apparent
dissimilarity of its structure in these two groups. In the other
he extended his researches, with the view of establishing similar
analogies, to the mouth of the drachnida, Crustacea, and En-
tomostraca. The year 1820 was rich in memoirs ofa similar
nature to those just alluded to. Liatreille first published one on
the structure of the wings of Insectst, in which he sought to re-
fer to some general law of conformation the organs of locomo-
tion in this class, as wellas in those of Arachnida and Crustacea.
Latreille’s memoir was followed by three from Geoffroy on the
Organization of Insects, already referred to in a former part of
this Report as containing the first. enunciation of his views re-
specting the vertebrate structure of Insects and Crustaceat.
The same year two memoirs were brought forwards by Audouin
on the same subject. The object of one was to point out ana-
logies of structure between the true. Insects and the Crustacea
and Arachnida, more particularly as regards the head and its
appendages, and the relative development of the segments of
the trunk§. That of the other was to generalize an extensive
series of observations with respect to the various parts which
enter into the composition of the thorax in the different orders
of Insects||.__ Latreille also published:two other memoirs besides

o* (Théorie des Organes de la Bouche des Crustacés et des Insectes,” Mém.
les An. sans Vert., Part I.

“+ De la Formation des Ailes des Insectes. 8vo.

‘t Journ. Comp. du Dict. des Sci. Méd., tomes v. and vi. It was in conse-

quence of Geoffroy’s first memoiron this subject, read tothe Academy of Sciences
an. 3, 1820, that Latreille was induced to write his memoir (before alluded to)

titled Passage des Animaux Invertébrés aux Vertébrés, which memoir of

Latreille was published, together with his former one, De la Formation des Ailes

des Insectes, as an 8vo pamphlet.

_-§ Lam ignorant as to where this memoir was published, or whether it was

ever published at all. I know it only from Cuvier’s Report in the Analyse des

Travaux, _

This memoir was subsequently published inthe Ann. des Sci. Nat. for 1824,

om. i. pp. 97 and 416. A short analysis of it had appeared previously in the »
Ub. de la Soc. Phil. for 1820,

908 FOURTH REPORT—1834.

that already alluded to; one on the supposed elytra of the Stre-
psiptera, and on the appendices of the trunk of Insects in gene-
ral* ; the other on the general relations of the external structure
of the articulated Invertebrata t. In 1821 Latreille published
a memoir containing further observations on the external struc-
ture of the Annulosa, principally with a view to fix the nomen-
clature of the principal partst. The same year appeared the
first of a series of elaborate memoirs by Chabrier on the organs
of flight in insects, with a detailed account of all the parts con-
tributing to the motion and articulation of the wings§. In 1825
an important memoir was brought forward by Mr. MacLeay on
the structure of the tarsus in the Tetramerous and Trimerous
Coleoptera of the French entomologists||. Its object was to
show the defects of an arrangement founded on this part, and to
prove that such arrangement must necessarily lead to the viola-
tion of natural affinities. In 1826 appeared an elaborate dis-
sertation on the external anatomy of Insects in the third volume
of the Introduction to Entomology by Kirby and Spence. In this
work there is given a collected view of the researches of previous
naturalists on this subject; at the same time there are some
material additions made to what had been already done by others.
In the Bull. des Sci. Nat. for 1828, is an abstract of a memoir
by Haan on the organs of manducation and motion in the arti-
culated animals]. It was during that year that Straus-Durck-
heim published his great work on the Comparative Anatomy of
the Articulated Animals**. This last is perhaps the most im-
portant and elaborate treatise of its kind that has hitherto ap-
peared. It is the first of a series of monographs which the au-
thor intends publishing on the structure of the different orders
of insects. It contains some general remarks on the organiza-
tion of the Annulosa, after which the author proceeds to the
investigation of that of the Coleoptera in particular, the Melo-
lontha vulgaris being taken asthe type. In the first part of his
subject, Straus-Durckheim has endeavoured to refer the different
modifications of structure which the organs undergo in passing
through different groups of articulated animals, to general laws.
In 1830 Straus-Durckheim read to the Royal Academy of Sciences
at Paris a portion of another work, treating in like manner of the
structure of the Hymenopterous Insects, the common Hornet

: * Mém. du Mus., tom. vii. p. 1. + Jd., tom. vi. p. 116.
» t Jd., tom. viii. p. 169. § Id., tomes vi., vii., and viii.
|| Linn. Trans., vol. xv. p. 63. { tom. xiii. p. 448.

» &* Considérations générales sur ! Anatomie Comparée des Animaux Articulés,
auxquelles on a joint l' Anatomie descriptive du Melolontha vulgaris (Hanneton),
donnée comme exemple de I’ Organisation des Coleoptéres. Paris, 1828, 4to.

REPORT ON ZOOLOGY. 209

(Vespa Crabro, Linn.) being selected as the type. I am not
aware that this second monograph has been yet published*.
During the same year an elaborate memoir appeared in this
country by Mr. MacLeay on the structure of the thorax in winged
insects, in which he has not only given the result of his own
inquiries, but reviewed the previous labours of Audouin and
Kirby on this subject, especially the nomenclature of the dif-
ferent parts of the thorax as assigned by these authors respec-
tivelyt. Inthe Annales des Scien. for 18321, is a memoir by
Dugés on the structure of the genus Pulex, with the particular
view of discovering its true affinities. This genus constituting in
itself an entire order of insects, the memoir is of considerable im-
portance. In the Entomological Magazine§, Mr.Westwood has
also made some remarkson these insects more particularly relating
to the structure of their antenne. Inthe Nouv. Ann. du Mus.
for the same year||, Latreille has published a valuable memoir
on the external structure and affinities of the Thysanura, which
his researches lead him to think form the transition from the
eg et to the true Insects. They are the only insects in
ch Latreille has not been able to discover stigmata; the ab-
sence of which he regards as one of the distinguishing charac-
ters of this order]. Lastly, I may refer to some papers by Mr.
Newman on the external anatomy of Insects in general, recently
published in the Entomol. Mag.** Latreille has also treated of
the whole subject in his Cours d’ Entomologiett.
- It would be out of place to dwell much on the internal ana-

tomy of insects in this Report. I shall do little more than ob-

serve that it is principally to the researches of Marcel de Serres,

Léon-Dufour, Dugés, and Straus-Durckheim in France, and to

those of Herold, Gaede, Carust{, Suckow, Meckel, and Miller

eo sous

* An analysis of it will be found in the Bull. des Sci. Nat. for 1830, (tom.

_ &xii. p. 347,) also in Cuvier’s Analyse des Travaua for the same year.
+ Zool. Journ., vol. v. p. 145. { tom. xxvii. p. 145.

_ § vol. i. p. 359. || tom. i. p. 161.
§ The Zhysanura have been sadly neglected by entomologists. Latreille
serves that with respect to the Podure there has appeared nothing new since

_ the time of De Geer. ** vols. i. and ii.

—_ - ——————

~ 4+ I may state in this place that two general introductory works on entomo-
logy have appeared recently which I have not:seen, both entering into details
le subject of the organization of insects. One of these is the Handbuch

_ der Entomologie, published by Burmeister at Berlin in 1832. The other is the

Introduction @ V Entomologie by Lacordaire, of which the first volume has only
just ay eared. See L’Insiit., No. 73, p. 324. é .

_ tt Carus has the particular merit of having discovered the circulation of the
bic a Insects. This remarkable fact, which was observed in the larve of
certain Newroptera, was first announced at the meeting of German naturalists
held at Dresden in 1826.

1834. P

210 FOURTH REPORT—1834.

in Germany, that we are indebted for the recent progress which
has been made in this department. Mr. Newport in our own
country has also lately entered upon this subject*. There can
be no doubt that our knowledge of the natural affinities of In-
sects will be ultimately much benefited by the laborious investi-
gations of such observers, although there may not have been
acquired hitherto a sufficient number of facts to warrant any
extensive generalizations. Those of Léon-Dufour may be more
particularly alluded to as throwing some light on this subject.
This patient anatomist, in one of a series of the most elaborate
memoirs on the internal structure of the Coleopterat, observes
that by dissecting insects he has been enabled to determine the
value of many purely entomological characters, to clear up doubts
with respect to the distinction of the sexes in certain cases,
and to add to the number of those characteristic marks which
had already been acquired from a study of the mouth, antenne,
and feet, and employed as the foundation of families and genera.
His researches have satisfied him that the system of Latreille is
for the most part in perfect harmony with anatomical facts.

(3.) Since the science of entomology has become so extensively
cultivated, and the field which it embraces been found to be so
extremely larget, naturalists have given up all attempt at a com-
plete Species Insectorum. They have even in many cases found
it impracticable to obtain a correct knowledge of any particular
order, regard being paid to al/ the included species. Hence they
have generally confined their researches to the more subordinate
groups, or to the insects of particular countries : and it is to such
works that we must have recourse, in order to learn the present
state of our knowledge of the different orders which are com-
prised in this class. It is not my intention, indeed it is not
practicable on the present occasion, to do more than indicate in
a general manner a few of the most valuable of such works which
have appeared of late years.

It is to the Count De Jean that we are indebted for the most
extensive work which has been published on the order of Celeo-
ptera§, although it has not extended as yet beyond the Cicinde-
lide and Carabide. Ina separate publication he has undertaken,
conjointly with M. Boisduval, the illustration of such species as
are found in Europe||. Several important monographs have,

* Phil. Trans, 1832. + Ann. des Sci. Nat. 1824, &e.

+ Messrs. Kirby and Spence have estimated the probable number of existing
species of Insects at not less than 400,000. See Introd. to Entom., vol. iv.
p- 477. See also_some remarks on this subject by Mr. Westwood in London’s
Magazine of Natural History, vol. vi. p. 116.

§ Species général des Coléoptéres. 8vo, Par., 1825, &c.

|| Iconog. et Hist. Nat. des Coléop., 1827, &c.

REPORT ON ZOOLOGY. 211

however, appeared upon particular families, some of which are
now in course of publication. ‘Thus, Zimmermann has made a
study of the Carahbide*; Erichson of the Dyticidet ; Gory and
Percheron of the Cetonice and some allied generat. Schon-
herr has published two valuable works on the Curculionide ;
one§ giving a general view of the subordinate groups in this
extensive family ; the other ||, which has been only recently
commenced, entering into the details of species. Lastly, I may
refer to an important monograph on the Staphylinide by Count
Mannerheim4.

The Orthoptera have been made the subject of particular
works by Zetterstedt** and Audinet Servillett. Toussaint de
Charpentier has also published a monograph on he European
species of this order in his Hore Entomologice.
~ Hahn has undertaken an illustrated work onthe Hemipteratt.
Schummel has written a monograph on the particular genera
Hydrometra, Velia, and Gerris, constituting Latreille’s family
Ploteres§§.

The Lepidoptera, at least the European species, have been
particularly treated of by Treitschke, Godart, and Duponchel.
The first has continued the valuable and well-known work of
Ochsenheimer||||. Godart is the author of a work on the Lepi-
doptera of France, which was commenced in 1822, but inter-
rupted in 1825 by his death. Duponchel has carried it on from
that time{[{]. Boisduval has published a valuable monograph on
the Zygenide***, He has als6 commenced two other works on
this order, one serving to illustrate the Lepidoptera of North
Americat+t, the other the caterpillars and metamorphosis of the
species found in Kuropet{{. In the former he is assisted by

-* Monographie der Carabiden. Berlin and Halle, 1831. See Entomolog. Mag.,
vol. i. p. 306; a work to which I am indebted for the only knowledge I have of
some of these monographs.

_ + Genera Dyticeorum. Berlin, 1832. (See Ent. Mag., vol. i. p, 501.)

_ -} Monog. des Cétoines, et Genres voisins, §c., 1833. (See Ent. Mag., vol. i,
p- 418. § Curculionidum Dispositio methodica, §c. Lips., 1826.
|| Genera et Species Curculionidum, §c., 1833, &c.
_ ¥ Précis d’un nouvel Arrangement de la Famille des Brachélytres, del Ordre des
_ Insectes Coléoptéres. St. Petersb. 1830. ** Orthoptera Suecie. Lund., 1821.
4+ Revue Méthodique des Insectes del Ordre des Orthoptéres. (See Ent.
Mag., vol. i. p. 304.)

tt Die Wanzenartigen Insecten, §c., Niirnberg, 1831, &c. (See Ent. Mag.,
vol. i. p. 308.) §§ See Ent. Mag., vol. i. p. 307.

||| Die Schmetterlinge Europ., mit Fortsetzung von F. Treitschke. 1825, &c.
4% Godart and Duponchel, Hist. Nut. des Lepidoptéres, ou Papillons de
France. 8vo, Par., 1822, &c.

_ *** Essai sur une Monographie des Zygénides. Par,, 1829, 8vo.

ttt Hist. Génér. et Iconograph. de tous les Lepidop. et Chenilles del’ Amér,
Septentrionale, 8vo. itt Sce Ent. Mag,, vol. ii. p. 110.

p2

212 FOURTH REPORT—1834.

Léconte, in the latter by Rambur and Graslin. Dr. Horsfield
has thrown much light upon the arrangement and affinities of
these insects in his Lepidoptera Javanica, already alluded to in
a former part of this Report.

The Neuroptera have been particularly attended to by Tous-
saint Charpentier and Vander Linden, who have each published
a monograph on the European Lihellule: that of the former
is contained in his Hore Entomologice. The Phryganee
(Trichoptera, Kirb.) form the subject of an elaborate and valu-
able work recently published by M. Pictet of Geneva*.

The only recent works devoted to the Hymenoptera, with
which I am acquainted, are those of Lepelletier de St. Fargeau,
Gravenhorst, and Nees ab Esenbeck. The first has published a
monograph on the Tenthredinide+. The second has treated at
great length of the European species of Ichneumonidet. 'The
third has written upon the more aberrant groups of the family
just mentioned§.

The Diptera have received great attention of late years from
several excellent entomologists. Fallen’s Diptera Suecie is
rather anterior to the period of time we are considering. Wiede-
mann’s Diptera Exotica ||, Meigen’s Diptera of Europe{], and
Macquart’s Diptera of the North of France**, are of more re-
cent date, and have greatly contributed, the last two especially,
to advance our knowledge of this order of insects. I may also
allude to a most elaborate work by Robineau-Desvoidy, which
though treating only of the Fabrician genus Musca, contains
descriptions of nearly 1800 species, referred to nearly 600
genera. This astonishing production, which is entitled Essai
sur les Myodaires, occupies the entire second volume of the
Mém. des Savans E'trang., published in 1830.

Besides the above works, I may mention Stephens’s J/dustra-
tions of British Entomology, now in course of publication in
our own country, as one which promises great additions to all
the orders. The Coleoptera and Lepidoptera have already,
appeared. Curtis’s British Entomology is confined to. the il-
lustration of the genera of British Insects, but as a work in the

* Recherches pour servir al Histoire et al’ Anatomie des Phryganides. >
Genéve, 1834. (For an analysis of this work, see L’Jnstit., No. 73.)

+ Monographia Tenthredinetarum Synonymia extricata. ’Par., 1823, 8vo.

} Ichneumonologia Europea. Vratislav., 1829, 3 vols. 8vo.

§ Hymenopterorum Ichneumonibus affinium, Monographie, Genera Europea
et Species illustrantes. vol. i. Stuttgart. et Tubing, 1834.

|| Aussereuropaische Zweiflugelige Insecten. Hamm, 1828—18380, 2 vols. 8vo.

¥ Systematische Beschreibung der bekannten Europaischen Zweiflugeligen
Insecten. Aachen, 1818—1830, 6 vols. 8vo.

** Published in ‘the Recueil des Travaucde la Société d’ Amat. des Sciences, &c.,
de Lille. 1826—1829.

nee

OO

,

REPORT ON ZOOLOGY. 215

illustrative department, is unrivalled in the beauty and accuracy
of its delineations. It is also extremely valuable from the num-
ber of dissections which it contains.

-. There are also many other valuable monographs, not published
separately like those already alluded to, to be found in Germar’s
Magazin der Entomologie, Guerin’s Magasin de Zoologie,
Silbermann’s Révue Entomologique, in the Entomological Ma-
gazine, and in the Annales de la Soc. Entomologique de France.

In concluding my remarks on this department of zoology,
I may observe that it has received a powerful impulse from the
recent establishment of two Entomological Societies, one in
France, and the other in our own country. ‘This last was only
instituted in 1833*.

; III. Mouxuusca, Cuv.

It is undoubtedly to the researches of Poli, Cuvier, Lamarck,
Férussac, and Blainville that we are to attribute the great advance
which has been made of late years in our knowledge of the ani-
mals belonging to this type. Poli’s work, consisting of two
volumes, on the anatomy of the Bivalve and Multivalve Testacea,
is well known. In 1826, a third volume was published by
Chiage, in which the anatomy of the Univalves was commenced
upon the same plan as that adopted in the two former volumes.
Cuvier’s Memoirs on the Mollusca, most of which had been pre-
viously inserted in the Annales du Muséum, were in 1816 col-
lected by himself into one volume and published separately.
They contributed greatly to our better knowledge of the natural
affinities of these animals, and furnished the basis of the system
developed the year following in the Régne Animal. In this
last work the Mollusca are divided into six classes+, Cephalo-
poda, Pteropoda, Gasteropoda, Acephala, Brachiopoda, and
Cirrhopoda, the characters being derived from the general form,
between which and the internal structure Cuvier observes there
is a pretty constant relation. The Cephalopoda are simply

livided into genera according to the nature of the shell. The

Pieropoda, a class instituted by himself in 1804 for the recep-
tion of the genera Clio, Pnewmoderma, and Hyale, are divided
into two sections, founded on the presence or absence of a di-
stinct head. The Gasteropoda are distributed under seven orders,
characterized according to the position and form of the respira-
tory organs. The Acephala comprise the two orders of Testa-
ceous and Naked Acephala. The Brachiopoda include the genera
_ * Since this Report was read, the Entomological Society of London has pub-
lished the first part of a volume of Transactions, containing several interesting
and important communications on this branch of Zoology.

- + Three of these classes, Cephalopoda, Gasteropoda, and Acephala, had been
established by Cuvier in. his Zabl. E'lém. de UV Hist. Nat. in 1798.

214 FOURTH REPORT—1834.

Lingula, Terebratula, and Orbicula, which had previously formed
a part of the class last mentioned. The Cirrhopoda comprise
the two genera Anatifa and Balanus, which Cuvier considers
as in some respects intermediate to the Molluscous and Articu-
lated Animals.

The benefits conferred upon this department of zoology by
Lamarck belong to a period of time somewhat anterior to the
publication of the Regne Animal. We may, however, make a
few remarks on the system adopted in the fifth and two suc- —
ceeding volumes of the second edition of the Animausx sans
Vertébres, which appeared in the years 1818—1822. Perhaps
it is in the details of the science, the grouping of genera, and the
characterizing an immense number of new species, that Lamarck’s
tact and penetration appear most conspicuous. His leading di-
visions present several peculiarities which are scarcely warranted
by the organization of these animals. Thus, he has separated
altogether from the Mollusca the Naked Acephala, and made
of them a distinct class under the name of Zwniciers, which he
refers to quite another place in his system, below the Articulated
Animals which intervene. Again, the rest of Cuvier’s Mollusca
he divides into only three classes, which we are naturally led to
infer he considers therefore as groups of equal value. The first is
that of Cirripédes. The second, or Conchiféres, answers to the
Testaceous Acephala of Cuvier, including also the Brachiopoda.
The third, to which Lamarck restricts the name of Mollusques,
comprises all the remaining classes of the Régne dnimal. The
ground of primary subdivision in Lamarck’s second class is more
entitled to our regard than that on which his higher groups are
established, although not particularly noticed by Cuvier. It is
the number of the muscles of attachment and the impressions
caused by them on the shell, points to which Lamarck was the
first to call the attention of naturalists in a memoir in the dnn.
du Mus. for 1807. These give rise to the two orders of Dimy-
aires and Monomyaires. The secondary groups in this class
are founded on the form and structure of the shell, the situation
of the ligament, and the form of the foot of the animal; the
families resulting from these principles of arrangement being on
the whole natural, though not in all cases distinguished by cha-
racters of the same importance. The third class, Mollusques,
is divided into five orders, one of which answers to the class
Pteropoda of Cuvier, and another to the Cephalopoda of the
same author: the remaining three are formed out of Cuvier’s
class Gasteropoda, and bear the names of Gastéropodes, Tra-
chélipodes, and Hétéropodes respectively. In this part of his
system Lamarck has not only altered the value of some of
Cuvier’s groups, but adopted peculiar views with regard to their

REPORT ON ZOOLOGY. 215

relative degrees of organization. Thus, he considers the Hete-
ropoda, comprising the genera Carinaria, Firola, &c., as de-
serving to be placed at the head of all the Mollusca, and as
forming the transition to the Fish, an opinion which few will
be inclined to adopt besides himself.

In 1819 appeared the first numbers of that splendid work
which M. de Férussac has devoted to the Land and Freshwater
Mollusca, a work which for beauty as well as accuracy of illus-
tration has perhaps never been surpassed. It is principally,
indeed, to this department of the subject that De Férussac’s
jabours have been directed, and no one has done more towards
elucidating the history of that immense assemblage of species
which belong to the Linnean genus Helix. In order, however,
to point out the relation between the land and freshwater genera
and the rest of the Mollusca, he has added a general arrange-
ment of all the Molluscous animals, which though nearly the
same as that of Cuvier, presents nevertheless two or three slight
modifications. Thus, before arriving at the classes, we have a
primary division into two sections, grounded on the presence or
absence of the head. The first section, or that of Cephalous
Mollusca, includes the first. three classes of Cuvier. The se-
cond, or Acephalous section, comprises the classes Cirripeda,
Brachiopoda, Lamellibranchia (name taken from Blainville),
and Tunicata, this last being admitted as a group of a higher
denomination than that assigned to it by Cuvier. There is also
a slight difference in the subordinate divisions. Thus, the Cepha-
lopoda are divided into the two orders of Decapoda and Octo-

oda*. Amongst the Gasteropoda, we find a new order esta-
blished for the reception of the Operculated Pulmonifera. It
may be stated that Férussac’s work, which for some time was
interrupted, has been recently recommenced, and it is much to
be desired that it may yet be completed according to the original
plan.

_ In 1820, Schweigger published in Germany a Manual of the
Inarticulate Invertebrate Animalst. In this work, which I have

not seen, the arrangement of the Mollusca is said to be on the
whole similar to that of the Regne Animal.

In 1821, Mr. Gray published in the London Medical Repo-
sitoryt anew systematic arrangement of the Mollusca, founded
upon the internal organization. In this system, one of the
principal features is an entirely new nomenclature for the pri-
mary divisions, which constitute seven classes, in other respects

* These groups are adopted from Dr. Leach. See his “‘ Synopsis of the Orders,
Families, and Genera of the Class Cephalopoda,” in his Zool Miscell., vol. iii.
p. 137. + Handbuch der Naturgeschichte, $c. 8vo, Leips. 1820,

t vol, xv. p. 229,

216 FOURTH REPORT—1834.

nearly the same as those of former authors. The Cirripeda,
however, are not included. The groups subordinate to the classes
are established principally upon the organs of respiration. The
arrangement of the families and genera of the Gasteropoda is
grounded upon the form of the opercle, which leads in many
cases to very natural relations. Mr. Gray has the merit of
having studied this part more profoundly than any of his pre-
decessors.

In 1824, M. Latreille published in the Ann. des Sci. Nat.*
a sketch of a new arrangement of the Mollusca, which was more
developed the following year in the Familles Naturelles. In this
last work, the primary division of these animals (from which the
Naked Acephala and Cirripeda are entirely excluded,) is into
Phanerogama and Agama, the former including all those in
which copulation is necessary in order to reproduction, the latter
such as impregnate themselves. The Phanerogama are further
divided into two large sections, the characters of which are de-
rived from the organs of motion. The first of these, which is
termed Pterygia, includes two classes, the Cephalopoda and
Pteropoda of Cuvier. The second, dpterygia, includes the
class Gasteropoda of the same author. In this last class, be-
fore arriving at the orders, which are characterized from the
organs of respiration, there is a subdivision according as the
sexes are Separate, or united in the same individual. In the se-
cond great division, or that of 4gamous Mollusca, we likewise
find two sections, grounded upon the presence or absence of an
apparent head. The first, Hxocephala, comprises a new class,
called Peltocochlides, established for the reception of the Gaste-
rop. Scutibranchia and Cyclobranchia of Cuvier. The second,
Endocephala, includes the Brachiopoda and Testaceous Ace-
phala of Cuvier, Lamarck’s name of Conchifera being adopted
for the class last mentioned.

In 1825 appeared the Malacologie + of Blainville, who had
already contributed many valuable memoirs to the Journ. de
Physique and Bull. de la Soc. Phil. on this department of
zoology. No one, after Poli and Cuvier, has done so much as
Blainville in illustration of the anatomy of the Mollusca. At
the same time his arrangement, which differs in several respects
from all preceding ones, can hardly be considered as preferable
to that of the Hégne dnimal. It has also the disadvantage, like
all the rest'of his system, of being attended by a peculiar nomen-
clature, embracing many names for the primary groups entirely

* tom. iii. p. 317.

+ Manuel de Malacologie et de Conchyliologie. 8vo, Paris, 1825. The greater
part of this work had previously appeared in the Dict. des Sci. Nat. under the
Art. Motuusaues.

,

REPORT ON ZOOLOGY. 217

different from those generally adopted. Blainville’s primary
subdivision of his type Malacozoaires is into three classes, esta-
blished upon the characters of the head. In the first class, Cé-

phalophores, which answers to the Cephalopoda of Cuvier, the
Toad 3 is well distinguished from the body. In the second, Para-
céphalophores, it is less strongly marked. In the third, Acé-
phalophores, it can be no longer observed. The Paracéphalo-
phores include the Gasteropoda and Pteropoda of Cuvier, though
arranged upon a very different plan, the characters of the sub-
ordinate groups being derived in the first instance from the re-
productive organs, and afterwards from the respiratory or-
gans. Thus we have the three subclasses of Paracéph. Dioiques,
P. Monoiques, and P. Hermaphrodites, each of which is divided
into two or more orders, according to the structure of the bran-
chie. The third class, 4céphalophores, is divided immediately
into four orders, which are likewise characterized from the re-
spiratory organs. The first of these orders, Palliobranches,
answers to the Brachiopoda of Cuvier ; the second, Rudistes,
comprises the Lamarckian family of bivalve JZollusca bearing
the same name; the third, Lamellibranches, includes the great

__ bulk of Cuvier’s Testaceous Acephala; and the fourth, Hétéro-

branches, his Naked Acephala. Blainville does not include

either the Cirripeda or the Chitones amongst his true Malaco-

soaires, but regards them as forming a subtype, Malentozoaires,

leading directly off to the Articulate Animals. In this group

they constitute the two orders of Mématopodes and qaleaeae

phores respectively.

The latest systematic work in this department with pres
Lam acquainted, is the excellent little Manuel des Mollusques*
by M. Rang, published in 1829. This gentleman is also the
author of a valuable monograph on the genus dplysiat, as well
as of some other important memoirs relating to the Mollusca.
His arrangement of these animals is nearly the same as that of
the Regne Animal. At the same time there are some alterations
with respect to the primary divisions. Thus, he sinks the class
Brachiopoda, regarding that group as only an order among the
Acephala, in which last class he admits as another additional

_ order the Rudistes of Blainville. He has also adopted some

new orders in the class Gasteropoda. Some of his families and
other subordinate ‘divisions he has borrowed from Lamarck and
Férussac. This work contains many new and original observa-
tions.

i: ec arrangement of the Mollusca in the pect edition of the

’ Manuel de’ Histoire Naturelle des Mollusques et de leurs Coquilles, Sc.
Paris, 1829. + Histoire Naturelle des Aply eHes Paris, 1829, fol.

218 FOURTH REPORT—1834.

Regne Animal, also published in the year 1829, does not differ
materially from that in the first. There are simply two additional
orders in the class Gasteropoda; one, named Tubulibranches,
including the genera Vermetus, Magilus, and Siliquaria; the
other, that of Hétéropodes, adopted from Lamarck.

From a review of the above systems, which have been briefly
sketched out in the preceding pages, it would seem that even the
primary groups in this branch of the animal kingdom are not
all determined with certainty. At the same time it is probable
that whatever alterations may be suggested by further researches,
they will not greatly interfere with those established by Cuvier,
and adopted with more or less modification by the generality of
naturalists. What we most want is a more exact determination
of their relative values. The.Cirripeda, however, probably do
not belong to the Molluscous type at all, as appears from re-
searches to be further alluded to hereafter. There is also great
uncertainty with respect to the exact situation, as well as limits,
of some of Cuvier’s smaller groups, such, for instance, as his
Gasteropoda Cyclobranchiaand Scutibranchia, of which Latreille
makes a distinct class. The genera Capulus, Crepidula, Navi-
cella, and Calyptrea, which are by most authors referred to the.
Scutibranchia, and which Cuvier himself placed in that order-in
the first edition of the Régne Animal, in the second hehas referred
to the Pectinthranchia, stating it as his opinion that they come
near the Zrochide. Indeed, in none of the classes has the chain
of affinities been hitherto worked out with any degree of cer-
tainty. We still require further anatomical investigations, both
in order to determine with more exactness the actual structure of
many entire families, and to learn the relative importance of those
organs from which naturalists have drawn their principal charac-
ters. Where we find the organs of motion, circulation, and re-
spiration, as well as the mode of reproduction, all varying to the
degree they do in these animals, it is clear that we must proceed
with great caution in endeavouring to ascertain the respective
degrees in which they are entitled to our confidence.

Before, however, quitting this division of the subject, it will be
right to notice several important memoirs which have appeared
of late years, connected with the structure and affinities of some
of the above classes in particular.

1. Cephalopoda.—All, except Lamarck, allow that this class
stands at the head of the Inarticulate Invertebrata, although it
is not decided to which of the Vertebrate classes it shows most
affinity. Cuvier, who was the first to make us acquainted with
the anatomical details of these animals, and who has particu-
larly noticed the striking development of some parts of their
organization, nevertheless does not allow that they conduct to

REPORT ON ZOOLOGY. 219

any other groups placed higher in the system *. Mr. MacLeay
has endeavoured to show that in their general structure they
make the nearest approach to the Chelonian Reptilest. He
allows, however, that the hiatus occurring between is very con-
siderable. M. Latreille, in a memoir published in 1823 f, has
pointed out several resemblances between them and Fish, and
thinks that they show considerable affinity to the Rays and other
Cartilaginous Fishes. These resemblances refer exclusively to
the external structure of the two classes. More recently the Ce-
phalopoda have been much investigated by MM. Laurencet and
Meyraux. In a memoir read to the Royal Academy of Sciences
at Paris in 1830§, these naturalists attempted to lessen the
gap that was supposed to exist between them and the Vertebrata,
in like manner as Geoffroy had previously done with respect to
_ the gap between these last and the dnnulosa. They would de-
monstrate that the plan upon which the Cephalopoda are con-
structed does not depart so widely as was imagined from that of
the structure of the Vertebrata; that the same organs appear
in both groups, though somewhat modified and transposed ; and
that in order to make the structures conformable, we are only
_ to suppose a vertebrate animal doubled back upon itself, when
_ the relative position of the several organs in this last will be
essentially the same as in a Cephalopod. Geoffroy, in his report
on this memoir to the French Academy, took occasion to ob-
serve how favourable the results at which these anatomists had
arrived were to his peculiar views respecting the wnity of com-
position in the animal kingdom. Cuvier, who was opposed to
these views, replied to Geoffroy; and for some time after a sharp
controversy was kept up between these two distinguished natu-
ralists on this subject. To state the several memoirs, and verbal
communications to the Royal Academy of Sciences, which
arose on both sides of this question, would lead us too far from
the present subject ||. We may mention, however, one memoir
by Cuvier, in which he states, with reference to the singular
_ Opinion advanced by Laurencet and Meyraux, the results of a
‘Tigid comparison which he actually made between a Cephalopod
and a Vertebrate Animal doubled back in the manner they di-

_ * Mém. sur les Céphalop., §c., p. 48. + Hor. Ent., p. 254 to 258.

} Mem. de la Soe. d’ Hist. Nat. de Paris, tom.i. p. 269.

~§ Quelques Considérations sur V Organisation des Mollusques. I am ignorant

as to whether this memoir has been hitherto published.

~ || Geoffroy’s memoirs were afterwards collected by himself into one volume,
and published under the following title: Principes de Philosophie Zoologique,
discutés en Mars 1830, au sein de’ Acad. Roy. des Sciences. Par. 1830, 8vo.
Cuvier also expressed a determination to publish his under the title of De la

Variété de Composition des Animaux. I am not aware, however, that these

last ever appeared.

220 FOURTH REPORT—1834.

rect. This memoir, which was published in the Ann. des Sei.
Nat. *, is illustrated by coloured sections of the two animals,
and its author shows that there are still many organs present in
each not found in the other, and that many of those common to
both are not, as was supposed would be the case, in the same
relative situation. In short, he attempts to demonstrate that,
pushed beyond a certain point, the analogy utterly fails. Du-
ring last year (1833) a second memoir appears to have been read
by M. Meyraux on these animals ¢, in which he still retains his
former theory, and, moreover, expresses an opinion that the
Cephalopoda ought to constitute an intermediate class between.
the Mollusca and the Vertebrata, their general organization de-
parting much from the type of the former division, at the same
time that it approaches that of the latter. This is in accordance
with the opinion formerly advanced by Mr. MacLeay, who in his
Hor. Entom. considered the Cephalopoda as constituting an
osculant group between the two large divisions just mentioned f.
Like Mr. MacLeay, M. Meyraux would seem also to consider
them as showing considerable affinity to the Chelonian Rep-
tiles. Perhaps, however, the final elucidation of this point must
wait for the discovery of some intermediate form, which it is
not too much to hope may yet occur at some future period.

- A few other memoirs require to be pointed out as valuable
contributions to our knowledge of this class, although not con-
nected with the subject particularly discussed in those just
alluded to. Foremost amongst these is amemoir by Mr. Owen
on the Pearly Nautilus, published in 1832§. This very valu-
able treatise contains a detailed account of the anatomy of the
animal inhabitant of the above shell, so often sought for since
the time of Rumphius, its original but imperfect describer. The
specimen dissected, which is the only one that has been
discovered in modern times||, notwithstanding the frequent
occurrence of the shell itself, was taken by Mr. George Bennett
off the New Hebrides in 1829. Mr. Owen has shown that its
organization, although exhibiting some differences, more par-

_ * tom. xix. p, 241.

¢ See L’Institut, No. 21, p. 180. Ionly know the memoir from the analysis
which is there given of it.

t Meckel is also stated to have proposed the making a distinct division of
the Cephalopoda, intermediate to the Vertebrata and Invertebrata. I am un-
able, however, to refer to the work in which he has advanced this proposal.

§ Memoir on the Pearly Nautilus (Nautilus Pompilius, Linn.), with illustra-

tions of its external form and internal structure. Lond. 1832, 4to,
' || A fragment of a Cephalopod animal, supposed to belong to the Nautilus
Pompilius, was brought from the Moluccas by MM. Quoy and Gaimard, and
described in the Ann. des Sci. Nat. (tom. xx. p. 470.), but there are great
doubts as to its identity with that species.

REPORT ON ZOOLOGY. 291

ticularly in the respiratory and circulatory systems, is on the
whole strictly conformable to that of the higher Cephalopoda,
between which and the Gasteropoda it constitutes an osculant
form*. At the conclusion of his memoir Mr. Owen has given
the characters of two orders, Dibranchiata and Tetrabran-
chiata, into which he proposes to divide the Cephalopoda, these
characters being founded on the details of the organization of
the Nautilus Pompilius.

_ Dr. Grant has also added considerably to our knowledge of
the structure of this class. In the New Edinb. Phil. Journ.:+
he has given the anatomy and external characters of an appa-

_ rently new species of Octopus t from the Frith of Forth. In

the Zool. Trans. § he has also published an account of the genus
Loligopsis of Lamarck, the very existence of which was before
disputed by some naturalists: he has examined its structure,
and found it to constitute a new form in this class, possessing
characters hitherto known only in the Testaceous Cephalopods,

with others common in the naked species. In the same volume}
_ is asecond paper by this distinguished naturalist on the anatomy

ofthe Sepiola vulgaris.

__. The controversy respecting the animal inhabitant of the 4rgo-
_ naut is not yet decided, at least not to the entire satisfaction
ofall parties. Future observation will, however, probably con~

firm the opinion of Poli {[ and Férussac**, that the animal

_ hitherto alone found in that shell (Ocythoé) strictly belongs to it.

The former authorexpresses himself decidedly with respect to this

§ point, asserting that he has traced the gradual development of

the shell from the egg. Mr. Broderip appears still to entertain
doubts on the subject, but the evidence which he has advanced

_ on the other side of the question is simply negative tt.

rit)

cepa cireumstance’seems to point out the impropriety of considering the

‘Cephalopoda as a distinct division of the animal kingdom, according to the

ews of Meckel, Laurencet, and Meyraux. - + 1827.
» f According to De Férussac, under the names of Octopus vulgaris, Loligo,
vulgaris, and Sepia officinalis, several very distinct species of Cephalopoda have

21 hitherto confounded. § 1833, vol. i. p. 21. || p. 77.

See Ann. des Sci. Nat. (1825), tom. iv. p. 495.
» ** Meém. de la Soc. d'Hist. Nat. de Paris, tom. ii. p, 160.
- +¢ See Zool. Journ. vol. iv. p. 57. Mr. Gray is also of opinion. that. the
Ocythoe is only parasitic in the shell of the Argonauta; and I may state, that
since'this Report was read he has brought forward what he considers as a new
argument in support of this side of the question. This argument is founded on
the size of what Mr. Gray terms the nucleus of the shell, or that original portion
of it which covered the animal within the egg, and which in some specimens of
young shells of Argonauta Argo and A. hians, lately exhibited to the Zoological

jociety; he has shown to be many times larger than the largest eggs of the
Ocythoé found within the Argonaut shells. From this Mr. Gray has inferred

222 FOURTH REPORT—1834.

Great additions have been made to our knowledge of the mi-
nute Polythalamous Cephalopoda by M. D’Orbigny, whose me-
moir on these animals, read to the French Academy of Sciences
in 1825, will be found in the seventh volume of the dun. des Sct.
Nat. He confirms the propriety of assigning them a place in
this class, to which they had been referred previously, more
from analogy than from any positive knowledge of their real cha-
racters. He has studied far more closely than any former ob-
server the structure and development of the shell in this group,
as well as in many cases the structure of the animal. He has
ascertained that the former is internal, or at least entirely
covered by a membrane, and destitute of a siphon; and that the
latter is possessed of true arms, or tentacula, analogous to those
of the larger Cephalopoda. He considers these animals as
forming a large and well-marked group in the present class, to
which he assigns the name of Foraminifera. He is acquainted
with upwards of six hundred species, nearly half of which have
been discovered by himself.

M. D’Orbigny has undertaken an arrangement of these shells,
which has led to a revision of that of the entire class of Cepha-
lopoda by himself and De Férussac jointly. It is the intention
of these authors to publish an extensive work * on this class,
which D’Orbigny divides into the three orders of Cryptodi-
branchia, Siphonifera, and Foraminifera. In the /farst, the
shell is either monothalamous, or internal and rudimentary,
never polythalamous: in the second, polythalamous, external,
or partially covered by the animal, which is capable of retiring
either wholly or in part within the chamber above the last sep-
tum; a siphon always continuous from one chamber to another:
in the third, the shell is polythalamous, and always internal;
the last septum terminal; no siphon, but only one or more
apertures causing a communication between the different cham-
berst. It may be observed that this arrangement by D’Or-
that it must have been produced by an animal whose eggs are of much greater
magnitude, and that therefore the Ocythoé cannot be the true artificer of the
shell in question. Mr. Gray’s communication on this subject, which is not yet
published, will shortly appear in the Proceedings of the Zoological Society. —

* Since this Report was read, I have seen the first three numbers of this
splendid work which have recently appeared under the following title: Mono-
graphie des Céphalopodes Cryptodibranches, par MM. De Férussac et D’Or-
bigny. Paris, 1834, fol. The plates are extremely beautiful. The Ceph.
Siphonifera and the C. Foraminifera are to form the subjects of two other
distinct monographs.

+ The same year in which D’Orbigny brought forward his memoir, De Haan
published at Leyden an important treatise, entitled, Monographie Ammonite-

orum et Goniatiteorum Specimen. In this work, which I have not seen, there
is said to be also a new arrangement of the Cephalopoda, and a similar division

i

————

v
¥

»
%

Rs)
.

’ REPORT ON ZOOLOGY. 223

bigny has been adopted by Rang in his Manuel des Mollusques
already alluded to.

2. Pteropoda.—De Férussac has given a systematic arrange-
ment of this class in the Bull. des Sci. Nat. for 1827*. Rang
has made several important additions to it, as well as recorded
many valuable observations respecting genera and species which
were already known. Nevertheless we have still but an imper-
fect knowledge of this group.

_ 3. Gasteropoda.—This being the typical and the most exten-
sive class among the Mollusca, it has received more general
attention than any of the others. Many of the families and ge-
nera contained in it have been made the subject of valuable
monographs by different individuals, which, however, it would
lead too much into detail to allude to more particularly. Na-
turalists do not appear to be agreed as to the exact value of cha-
-racters derived from the shell in distinguishing the genera of
this class. M. Deshayes, in a paper in the dan. des Sci.
Nat. for 1831+, has recorded some anatomical details, which
would seem to have been undertaken with the view of throwing
‘some light on this matter in the case of the Helices. His ob-
ject is to discover whether there may not be found some pecu-
liarity in the internal structure of the animal sufficient to war-

rant the adoption of many genera in this family, which hav-
% ead been established solely upon the characters of the shell, have

not hitherto been received by all naturalists. Tam not aware,

ever, that he has carried on this investigation beyond the
ease of Draparnaud’s genus Succinea, which is the only one
treated of in the above paper.

The opercle of shells, which, as already stated, has been much

employed by Mr. Gray in his arr angement of the Gasteropoda,
_ has been since studied with great care by Blainville, who in a
_ memoir in the Bull. de la Soc. Philom. for 1825 {, proposes

esdopt characters derived not merely from the presence or ab-

_ Bence of this part, but from its form and structure, its position,
mode of attachment to the animal. In the Ann. des Sci.
for 1829 §, Dugés has also a paper on this subject. His prin-
am object is to trace the analogies between this part and the
upper valve of the Inzequivalve dcephala, more particularly as
‘Tes P ects its mode of growth, and the production of the striz on

“of the ‘Pestaceous genera into two groups, characterized by the presence or
absence of a siphon. I believe De Haan was the first to make use of this cha-
_racter, although D’Orbigny is said to have had recourse to it without any know-
_ ledge of De Haan’s work. See Dict. Class. d’ Hist. Nat., — xi. p. 56. 9
* tom. xii. p- 345. + tom. xxii. p. 345. t pp. 91 and 108.

- § tom. xviii. p. 113, a

224 FOURTH REPORT—1834.

its surface. As these striae, however, have been used in some
cases for characterizing the genera of the Pectinibranchiate’
Gasteropoda, this memoir is not without its importance to the
systematist. During the last year Mr. Gray has again turned
his attention to this subject. In a paper in the PAil. Trans.
for 1833, he has detailed some observations on the structure of
the part in question, as well as on the structure and ceconomy
of shells in general. He considers that the mere fact of the pre-
sence or absence of the opercle is of small importance, but that
in its form and structure it offers some of the most constant
characters for the distinction and arrangement of families and
genera.

4. Brachiopoda.— Mr. Owen has recently published * an im-
portant memoir on the anatomy of this group, in which he has
offered some remarks with respect to its value and affinities.
‘He observes that in all essential points of structure these ani-
mals closely correspond with the Acephalous Mollusca, al-
though inferior to the Lamellibranchia as far as regards their
respiratory and vascvlar systems. He considers them as hold-
ing a middle place between these last and the Twnicata; not,
however, possessing characters of sufficient importance to justify
their being regarded as a distinct class, but forming a separate
group of equal value with those above mentioned.

5. Tunicata.—Whether we admit this group as a class or
only as an order, it is one which will always possess interest as
affording a natural passage to the Radiata of Cuvier. It is
especially to the researches of the naturalist just mentioned, and
to those of Savigny, that we are indebted for the first accurate
knowledge obtained respecting these animals. While the struc-
ture of the simple Zunicata was beautifully illustrated by the
dissections of the former t+, the latter had the merit of discover-
ing the true organization of those singular compound Ascidie
which until his time had always been confounded with the
zoophytes {. Péron, Desmarest, and Lesueur have all likewise
contributed to render this group better understood. What re-
cent additions have been made to our knowledge of it are
due principally to Mr. MacLeay, MM. Quoy and Gaimard,
MM. Audouin and Edwards, and Dr. Meyen. Mr. MacLeay is
the author of a paper, read to the Linnean Society in 1824 4, in
which he has given the anatomical details of some new forms
from the Northern seas, at the same time that he has thrown

* Zool. Trans. 1834, vol. i. p. 145.

¢ See Ann. du Mus., tom. iv., and Mém. du Mus.,. tom. ii. p. 10.
+ Mém. sur les An. sans Vertéb., Part 2.

§ See Linn. Trans., tom. xiv. p. 527.

REPORT ON ZOOLOGY. 225

out several remarks respecting the arrangement and affinities of
these animals in general. Quoy and Gaimard have communi-
cated some new observations relating tothe habits and anatomy of
the Salpe which they made during their voyage with Freycinet *.
Audouin and Edwards, who paid great attention to the Compound
Ascidie during their residence on the Chausey Islands, have
made some interesting discoveries respecting the mode of de-
velopment of these animals +. . They have ascertained that, al-
though in their adult state they are united to form one common
mass, and are immoveably fixed to some rock or other marine
substance, they enjoy at birth a separate individuality, and are,
moreover, endued with the power of swimming freely in the
water from place to place. It is not till after two days that this
__ locomotion ceases. They then seek a place favourable to their
further development ; and while some return to the parent mass
from which they first emanated, others attach themselves afar
off and found new colonies. These observations are of great
_ value. They not only throw light upon the history of these ani-
: mals, but serve to establish very important relations between
____ them and other groups in which similar facts have been noticed,
i connected with the early development of the young. Dr. Meyen’s
= researches are confined to the genus Salpu, which forms the sub-
a ject of a memoir by him in the Nov. Act. &c. Nat. Cur. for
Ef 1832}. He has revised the characters of more than thirty
eA imperies. 2
a 6. Cirripeda.—The doubtful situation of this class has been
Bo already alluded to. Indeed there are few groups whose true
__ affinities have been involved in so much uncertainty. The most
ag recent observations, however, seem decidedly in favour of the
opinion of those naturalists who regard it as partaking more of
=) ie Annulose than the Molluscous structure, and approaching,
_ onthe whole, nearest to the Branchiopod Crustacea. Straus
_ was the first to announce this affinity in his memoir on the genus
a published in 1819. He was led to observe it froma
: _ comparison of the relative structures of the genera Pentelasmis
oo) and Limnadia (Brong.). Two years afterwards, Mr.
Be MacLeay, apparently without knowledge of Straus’s memoir,
Xinted out the same relationship §, dwelling, however, more
ticularly on the affinity between Pentelasmis and Daphnia.
am not aware that anything further was written on this sub-
Jeet till 1830, in which year Mr. Thompson published the third

* Ann. des Sci. Nat. (1825), tom. vi. p. 28.; and Bull, de la Soc. Philom,
oe p. 123.

+ See Ann. des Sci. Nat., tom. xv. p. 6.
_ ¥ tom. xvi. p. 363. § Hor. Ent., p. 308,
1834, Q

SE —s—

226 FOURTH REPORT—1834.

number of his Zool. Researches, containing some observations
on the Cirripeda which appear to be quite decisive of their close
affinity to the dnnulosa in general, and the Branchiopod Crus-
tacea in particular. This gentleman asserts that he has ob-
served that these animals undergo a metamorphosis. He states
having discovered swimming freely in the sea a small crusta-
ceous animal furnished with a shell composed of two valves like
those of Daphnia; that being desirous of watching it further,
he kept it in water, and was much surprised, after a few days,
at seeing it throw off its bivalve shell, attach itself to the bottom
of the vessel, and become transformed into the Balanus pusillus
of Pennant*. For some time afterwards these alleged facts
were thought to require confirmation from other observers ;
more especially as in a communication made to the Zoological
Society last year+, Mr. Gray advanced some statements re-
specting the condition of the young of Balanus Cranchit (Leach)
observed iz ovo, as well as of the young of the genera Pentelas-
mis and Otion, which appeared to militate against the accuracy
of Mr. Thompson’s views. They have, however, been fully
established by Dr. Burmeister, who has recently published a
treatise on these animals announcing this circumstance; and
judging from his own observations, combined with those which
had been previously made by others, Dr. Burmeister infers that
the Cirripeda ought to be arranged with the Crustacea, forming
a particular tribe in that class f. ,

It may be stated that M. Martin-St.-Ange is said to be en-
gaged in a work on the organization and affinities of the Cirri-
peda. The results of his researches have been already given to the
public in a memoir read to the Royal Academy of Sciences at
Paris towards the end of last year§. They likewise favour the
opinion that these animals, at least the pedunculated genera, are
truly articulated, and allied to the lower forms of Crustacea.
M. Martin-St.-Ange thinks that they also show some points of
affinity to the dnnelida.

* It is a curious fact that, according to Mr. Thompson, the young animal
should not only possess the power of locomotion, which is denied to the adult,
but distinct organs of sight, which, after the transformation into Balani, gra-
dually become obliterated. This is analogous to Edwards’s observation (already
alluded to) in the case of the development of the Cymothogz. It is, however,
yet more striking.

+ See Proceed, of Zool. Soc. (1833), p. 115. :

+ The above statements are on the authority of De Férussac’s Introduction
to his recently published Monograph on the Cephalopoda. I have not seen
Burmeister’s work myself, which is said to be entitled Bettrage xur Naturge-
schichte der Rankenfiisser. 4to, Berlin, 1834, ’

§ See L’ Institut, No. 27. p. 226, and No. 62, p. 231.

set

REPORT ON ZOOLOGY. 927

_ The classification of the Cirripeda was greatly advanced by
the labours of Dr. Leach, who made a particular study of this
class, and instituted several new genera in it. His arrangement
is founded upon characters derived from the shelly covering of
these animals, which he submitted to a more minute and rigor-
ous analysis than any previous observer had done before him *.

_ Mr. Gray has also attended to this subject. In the 4nn. of
Phil. for 1825 +, he has published a synopsis of the genera
arranged in natural families.

IV. Raprata, Cuv.

_ As we descend the scale of organization we find the groups
defined with less and less certainty. In the present division,
our knowledge of their exact limits, we may even say of the
number of primary types of form which this division comprises,
is so imperfect, that it would be to little purpose to detail all
the different arrangements which have been proposed for these
animals, the classification of which is probably still destined to
undergo great and important revolutions. After all, it is doubt-
ful whether we must not admit with MacLeay that they form two
groups, each of equal value with that of the Vertebrute, Annu-

lose, and Molluscous divisions, instead of one only as Cuvier

supposes. In this state of uncertainty, I shall merely take
uvier’s classes in the order in which they stand in the Regne
Animal, and under each state some of the principal additions

_ which have been made of late years to our general knowledge of

these animals. This will naturally lead to the mention of several
important steps which have been gained towards an improved
classification of them.

_ The following are the classes into which Cuvier divides the

Raviata: Echinodermes, Intestinaux (Entozoa, Rudolp.),

Acaléphes, Polypes, and Infusoires.

1. Echinodermata.—To our knowledge of this class I am not

aware of many important additions that have been made recently.

Since the publication of Tiedemann’s work on the anatomy of
these animals, which gained the prize from the French Institute

1812, and which served to clear up many points in the details
their organization, no one appears to have studied their struc-

re more deeply than Delle Chiaje. Several memoirs have

_ appeared by this last author treating of the genera Echinus,

urn, (1825), vol. ii. p. 208.
t vol. xxvi. p. 97

~~ Memorie sulla ‘Storia e Notomid. degli Animali senza Vertebre. 4to, Nap.
1823, &c. P

Pin ‘
ys See the article Cirripepes in the Suppl. to the Encycl. Brit. Also Zool.

a2

228 FOURTH REPORT—1834.

sterias, Holothuria, and Siphunculus, «wll which he has sub-
mitted to a close investigation. His researches on the genus
Siphunculus lead him to think that this group has been wrongly
placed by Cuvier in the present class, and that it belongs more
properly to the dnnelida.

In 1827, Mr. Thompson published an account of a newly dis-
covered recent species of Pentacrinus*, a genus well known in
a fossil state, but one of which the true situation in the system
was before rather doubtful. From an examination of this spe-
cies, the structure of which in its several stages of development
he has given in full detail, Mr. Thompson fully proved that the
Crinoidea (so ably illustrated by the late Mr. Miller +) are closely
allied to the Asterie, and especially to the genus Comatula of
Lamarck. The only previously known recent species of this
tribe, the P. Caput Meduse, found in the West Indies, had not
been brought to Europe in a fit state to allow of any investiga-
tion of its structure.

Mr. Gray has lately submitted to the Zoological Society speci-
mens of the shelly covering of a new genus, which is interesting
as forming a distinct family, if not order, intermediate to the
Echinide and Asteriide. It is allied to the latter in having
only a single opening to the digestive canal; while it agrees
with the former in form and consistence, differing however from
it in not being composed of many plates. For this genus, which
Mr. Gray thinks bears a near affinity to the fossil Glenotremites
paradoxus of Goldfuss, he proposes the name of Ganymeda.

In the Ann. of Phil. for 1825§, Mr.Gray has published a
natural arrangement of the families of the Echinide||.

2. Entozoa.—In this group, as it stands in the Régne Animal,
we find an assemblage of animals which, though not much studied
in this country, have received great attention from several Ger-
man and French naturalists, from whose combined researches
it seems now quite certain that they can no longer be arranged
all in the same class. Cuvier divides the Entozoa into two

* Memoir on the Pentacrinus Europeus, §c. 4to, Cork, 1827.

+ Nat. Hist. of the Crinoidea, or Lily-shaped Animals, $c. 4to, Bristol, 1821.

t Proceedings of the Zool. Soc. (1834), p. 15. § vol. xxvi. p. 428.

|| Since this Report was read, a short but important communication on the
external structure of the Echinodermata and their mode of growth has been
published by M. Agassiz. His chief object is to show that the Echinodermata,
although usually considered as partaking of a radiated structure in which all
the parts of the body are similar, nevertheless exhibit a bilateral symmetry;
furthermore, that the addition of new plates, as the animal increases in size,
takes place ina spiral and not in a vertical succession, as would appear at first
sight to be the case. M. Agassiz announces it to be his intention to publish a
monograph on these animals, See Lond. and Edinb. Phil. Mag. and Journ. of
Sci. for Nov, 1834, p. 369,

laa

cn a Re OC cane

as

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a ~~ ads

’ REPORT ON ZOOLOGY: 999

otders, which he calls Intestinaux Cavitaires and Intest. Paren-
chymateux, the former answering to the Nematoidea of Rudol-
phi, the latter comprising the last four orders of this author.
Cuvier admits, however, that there is a great difference in the
respective organizations of these two groups. In fact, the Ne-
matoidea, raised so much above the other Entozoa by their di-
stinct nervous system, are now generally allowed to approach
closely the Annidose structure, if not to belong to that division
of the animal kingdom. Mr. MacLeay long since referred them
to that type, observing, that in a natural arrangement it seems
hardly possible to separate them far from Lumbricus and Gor-
dius*. With Blainville they also form a portion of his Hto-
mozoaires Apodest. Ina more recent publication{ this last
author has gone further into detail with respect to the arrange-
ment of the Hntozoa in general. He thinks they constitute
two classes at least ; the greater portion forming the last class
in his type Entomozoaires (in which class he includes the Hi-
rudinide); the remainder (comprising the third and fourth
families of Cuvier’s Intest. Parenchymateux) forming a sub-
type intermediate to the Entomozoaires and Actinozoaires (or
Zoophytes), though on the whole approaching nearest to the
former. Blainville does not admit that in the classification of
the Entozoa we should be at all more influenced by their pecu-
liar habitat than in that of other animals. He looks only to the
organization, which leads him to place in the same order (Oxy-
céphalés, Blain.) Filaria, Gordius, and Vibrio, genera certainly

_ not very dissimilar in structure, though residing in very differ-

ent situations. His other orders in the class Entomozoaires
_Apodes include in like manner both external and internal worms.
‘There can be no doubt that this principle is just to a certain
extent. Indeed it is supported by the opinions and researches
of others. Lamarck and Bory-St.-Vincent both suspected an
affinity between the Vibriones and the true Vermes. Dugés, in
the dnn. des Sci. for 1826§, has instituted a close comparison
between the Vibriones and the Oxyures of Rudolphi, and from
an examination of their digestive and reproductive systems,
‘seems decidedly to think that they belong to the same group.
_ Professor Baer of Konigsberg, whose researches have tended
greatly to elucidate the structure and affinities of the Entozoa,
has in a memoir (or rather one of a series of memoirs) on the
Tower animals, published in the 13th volume of the Nov. Act.
§c. Nat. Cur., endeavoured to show that neither the Entozoa nor
_* Hor. Ent., p. 224. + Principes d’ Anat. Comp., tab. 7.
bs t Art. Vers in the 57th volume of the Dict. des Sci. Nat., published in-1828.

This treatise also appeared separately under the title of Manuel d’Helmin-
thologie. § tom. ix. p. 225,

-_

230 FOURTH REPORT—1834.

Infusoria can be preserved as distinct classes. It should be
stated, however, that he has embraced some peculiar views re-
specting the systematic distribution of animals, of which it is
impossible to give any detailed account here. I may also allude
to a curious memoir by Dugés in the dun. des Sci. for 1832*,
as affording fresh suspicion that the Entozoa do not form a
natural class of themselves to the exclusion of other animals.
He describes a new and very singular genus found free in water
amongst duckweed, which appears to be closely allied to the
Tenie and Bothriocephali. It is small, but has its body di-
vided into segments like those animals, these segments being of
a similar form, and varying in number from four to eight. Dugés
thinks it not improbable that this may have been the supposed
Tenia which Linneus is said to have met with free in water.
He gives it the name of Catenula Lemne.

The Planaria, again, present us with a group of animals not
parasitic, which are now universally admitted amongst the Paren-
chymatous Worms, and considered as belonging tothe Zremadota
of Rudolphi. Cuvier indeed (as Lamarck and others had already
done) assigned them this place in the first edition of the Régne
Animal, but it was not without doubts as to their true situation.
These doubts are now quite removed by the researches of Dr.
Baer and M. Dugés, both of whom have investigated the struc-
ture of these animals, the former in the memoirs before alluded
to, the latter in the dn. des Sci. for 1828 and 1830}. |The
result is, that neither of these observers has been able to detect
any muscular, or ganglionic nervous system; and the latter thinks
that it is the absence of these systems principally which serves
to separate them from the Hirudinide, with which they have
been so often classed. At the same time, Dugés points out seve-
ral respects in which they clearly approach the group just men-
tioned. It may be added, that Dugés has proposed in his me=
moir to raise the Planarie to the rank of a family, in which
he particularizes three distinct genera. These he has charac-
terized from the structure of the digestive organs, and the situa-
tion as well as number of the orifices.

As there are some groups which, though of parasitic, require to
be associated with the Hntozoa, there are others which are para-
sitic, and which many have arranged with these animals, but of
which the true situation is extremely doubtful. Such are the Ler-
nee, presenting such evident affinities to the Siphonostomous En-

* tom, xxvi. p. 198.

+ I may also allude to two papers by Dr. Rawlins Johnson in the Phil.
Trans. for 1822 and 1825, containing the result of some inquiries into the power
of reproduction possessed by these animals. This subject, however, had been
previously investigated by Mr. Dalyell in his interesting memoir on the Plana-
viz, published at Edinburgh in 1814.

—— so

REPORT ON ZOOLOGY. 231

tomostraca, to which they are referred by Blainville, Straus-Durck-
heim, Edwards, and others, although placed by Cuvier at the end
of his Intestinaux Cavitaires. Blainville has made a particular
study of this family, in which he has characterized eight distinct

era*. Nevertheless, we stand much in need of further informa-
tion respecting their structure andceconomyt. On the other hand,
the dcephalocysti, and the Hydatids in general, appear so low in
the scale of organization, that it may be questioned whether
they can be placed in the same class with a// the other groups
included in Cuvier’s second order. Nitzsch and Leuckart, as
well as Dugez, think that the cephalocysti are allied to

the Volvoces and other vesicular Infusoriat. M. Kuhn, in ame-

moir lately published §, does not consider them as true animals,
but thinks that they should have a place assigned them amongst
those ambiguous beings which hold a middle rank between the
animal and vegetable kingdoms, and to which Bory St.Vincent
has given the name of Psychodiaires.

» From the above observations it will be seen how much re-
mains yet to be done towards a natural arrangement of these
animals.. Those who would enter into the details of their history,
will do well to consult,—besides the memoirs already alluded to,

__ and the works of Rudolphi, which are well known,—the works

of Bremser||, Cloquet{], Creplin**, and Leuckartt+. Bremser, in

~ * See Journ. de Phys. (1822), tom. xcv. pp. 872 and 437; also the 26th vol.
of the Dict. des Sci. Nat., art. Lerne'e.

» 4 According to the observations of Dr. Surrirey of Havre, the Lernee un-
dergo a metamorphosis, and are very different in their young state from what

they are in their adult. (See Blainville in Dict. des Sci. Nat., tom. xxvi. p. 115.)

Since this Report was read, I have learned that the above fact has been recently

confirmed by M. Nordmann, who is said to have published several very inter-

esting researches connected with the gradual development of these animals, and
such as leave no doubt of their forming part of the same group with the Sipho-
nostomous Crustacea. These observations are contained in a work entitled,

“ Mikrographische Beitrage zur Naturgeschichte der Wirbellosen Thiere,” Ber-

lin, 1832. “Not having seen it, I can make no further allusion to it in reference

to this subject. ¢ Ann. des Sci. Nat. 1832.

§ Mém. de la Soc. d’ Hist. Nat. de Strasbourgh, tom. i. part 2.
_ || Bremser published at Vienna, in 1819, a work on the human Ezéoxzoa,

which in 1824 was translated into French by Grundler and Blainville, and en-

ed with many valuable observations from this last author.

~~ § Author of Anatomie des Vers Intestinaux. Par. 1824, 4to. |
ial Creplin has published two treatises on the Intestinal Worms, one in 1825
under thename of Observationes de Entozois ; another, entitled Nove Observa-
tiones, §c. at Berlin in 1829. These works, which I have not seen, are said to
contain descriptions of a great many new species, along with dab detached
observations on these animals.

++ Leuckart is the author of a natural classification of Intestinal Worms, in
German, published at Heidelberg in 1827, This work has been before alluded
to as containing an arrangement in conformity with the principles of Oken.

232 FOURTH REPORT—1834.

addition to his treatise on the Entozoa of the human species, has
published a series of plates intended to illustrate Rudolphi’s ge-
nera, in which, by engraving on a dark ground, the white and
transparent parts of these animals are brought out in an admirable
manner. Van Lidth de Jeude has also published more recently
(1829) a collection of lithographed plates of these animals*.

3. Aculepha.—Our knowledge of this class must be considered
as very imperfect, notwithstanding it has engaged the attention of
many excellent observers. This is in a great measure to be at-
tributed to several difficulties connected with the study of these
animals, particularly those arising from their very delicate struc-
ture, which renders the preservation of specimens in many cases
almost impossible. Péron and Lesueur published some valuable
memoirs on the Meduse (taking this term in its full extent) in
the 14th and 15th volumes of the dn. du Mus., which contained
a far more detailed history of this tribe than any that had ap-
peared before, and contributed greatly towards an improved clas-
sification of it. These authors are, however, generally allowed to
have overmultiplied the species, and to have established several
genera upon insufficient observation. Many additions to this
class, and to our knowledge of its structure, were made subse=
quently by Chamisso and Eisenhardt in the 10th volume of the
Nova Acta &c. Nat. Cur., and a few in the 11th volume of the
same Transactions by Otto. Quoy and Gaimard also collected
much information with respect to the habits and organization of
these animals during their voyage with Freycinet. Some of their
observations were published in the dan. des Sci, for 1824+ and
1825. In this last volume, their remarks, so far as the 4ea-
lepha are concerned, relate only to the genus Berve. In the
Bull. de la Soc. Phil. for 18248, M. De Fréminville has pub-
lished some observations on the Physalia pelagica, to which are
annexed descriptions of three new species belonging to that ge-
nus. Some researches on the structure of the Physalie were
published about the same time in the 9th volume of the Peters-
burgh Memoirs by Kichwald. In 1825, Rosenthal published
some collections towards the anatomy of the Meduse||, the spe-
cies principally examined being the MZ. aurita, Linn. In 1827,
another memoir was published by Quoy and Gaimard in the
Ann. des Sci.§, containing an account of a vast number of new

* Besides the above works, I may mention that of Nordmann, already alluded
to, from which some valuable extracts will be found in the Ann. des Sci. Nat.
for 1833, tom, xxx.

+ tom. i. p. 245 { tom. vi. p. 28. §

|| Bull. des Sci. Nat. (1826), tom. ix. p. 253. {| tom. x.

aa

REPORT ON ZOOLOGY. 230

marine animals discovered by them the year before in the Straits
of Gibraltar, where they were detained some days by a calm
soon after the commencement of a second voyage with Captain
D’Urville. Amongst these are several new genera belonging to
the group of Diphyes, Cuv., which the authors consider as en-
titled to rank as a family. This memoir contains by far the
most valuable details respecting the organization of these re-

_markable animals which had appeared up to that time. In 1828,

Rang published in the Mém. de la Soc. d’ Hist. Nat. de Paris*
a memoir on the genus Beroe, which he considers as forming
another distinct family amongst the free 4calepha, in which he
describes two new genera. . Rang thinks that the free dca-

_lepha may be divided into three families, having for their re-

spective types Beroe, Medusa, and Diphyu. The characters of
these he proposes to take from the organs of locomotion. In
the first (Beroides, Rang,) they consist of a number (always an
even number) of longitudinal ribs formed by very numerous se-
ries of small cilize; in the second (Medusaires), these organs
are membranes, sometimes entire, sometimes fringed or cut into
leaflets, and ranged in a circle round an umbrella; in the third

_ (Diphides), these organs are found only in the margin of the
_ principal opening, and sometimes also in a membrane bordering

the circumference of it.

_ By far the most valuable work which has yet appeared in this
department of zoology is said to be the System der Acalephen,
§¢. of Dr. Eschsholtz, published at Berlin in 1829+. Its author
is well known as the naturalist who accompanied Captain Kotze-
bue in his voyage of discovery, and as having some time back
published valuable observations on the Physalie, Porpite, and
Velella, made by himself during that voyage{. In the present

work he has given a detailed account of the structure of the
_Acalepha in general, as well as presented a new arrangement of

these animals. Their organization, according to his researches,

_ would seem to be of a more complex nature than was formerly

supposed. He has discovered a very perfect vascular system in
the Beroe tribe, which has led him to place this group at the
head of the series. In his classification he adopts three orders,
Ctenophora, Discophora, and Siphonophora, the characters of
which are taken from the presence or absence of a central diges-

_ tive cavity, and from the form and structure of the organs of lo-

comotion.

* tom. iv. p. 166.

__ + Ihave not seen this work myself. The above notice of it is from the Bull.
des Sci. Nat. (1831), tom. xxiv.
Tt See Kotzebue's Voyage, vol. iii. Append.

234 FOURTH REPORT—1834.

- Since the appearance of Eschsholtz’s work, three or four valu-

able memoirs have been published by different observers in further
illustration of the dcalepha. One of these is a monograph on
the genus Diphya by Lesson*, containing several new remarks
onthese animals. He thinks that many of the genera instituted
by Quoy and Gaimard are only separate pieces, or articulations,
detached from the aggregate mass of the animal which forms his
genus Plethosoma. A second is a memoir by Tilesius, published .
in 1831+, in which are descriptions and figures of many species of
Meduse, more particularly belonging to the genus Cassiopea,
accompanied by general remarks on this group. A third is a
paper by Milne Edwards on the structure of Caryhda marsupialis,
in the Ann. des Sci. for 1833{; and a fourth, one by Dr. Grant
on that of the Beroe Pileus, published the same year§. These
last two memoirs, although treating only of single species, are
of importance as tending to raise our notions still further with
respect to the organization of these animals. The Carybda
marsupialis is a species belonging to that portion of the Je-
duse which have been hitherto considered as having no stomach,
and in this and other respects, as possessing a structure even far
more simple than the rest of this family. Edwards has found
this to be erroneous, by tracing the existence not only of a sto-
mach and mouth, but of biliary ducts, as well as ovaries. He
shows that its structure is quite as complicated as that of any
other of the Meduse. Dr. Grant, in dissecting Beroe Pileus, has
discovered an arrangement of filaments and ganglia which, from
their general appearance and mode of distribution, he considers
as constituting a nervous system. This is a great step gained
in our knowledge of the structure of the dealepha. Rosenthal
sought in vain for traces of a nervous system. Quoy and Gai-
mard, as well as many others, seem satisfied with respect to its
entire absence. Dr. Grant however observes, that although
nerves have not hitherto been shown in the Acalepha, he thinks
they will be found even in the simpler forms of J/eduse, which
he has shown elsewhere to be affected by light, as well as
Actinie, Hydre, and Furcocerce.

An important work was published by Blainville in 1830, in
which he has embodied a vast deal of information relating to the
structure, history, and classification, not only of the present
tribes, but of all the other animals belonging to Cuvier’s divi-

* Published in his Centurie Zoolog. Nov. 1830.
+ Nov. Act. §c. Nat. Cur., tom. xv. p. 247. { tom. xxviii. p. 249.
§ Zool. Trans., vol. i. p. 9.

REPORT ON ZOOLOGY. 235

sion of Radiata, with the exception of the Entozoa. I speak
of the 60th volume of the Dict. des Scien. Nat., the greater part
of which is taken up with the article Zoopuyrzs by the above
author*. Blainville, however, has exposed some peculiar views
respecting the affinities of certain families hitherto considered
as belonging to the Acalepha, to which it is necessary to make
some allusion}. These relate particularly to the Physalie, which,
he observes, are of a very anomalous character, and in some mea-
sure seem to depart from every known type. . He has, however,
ventured an opinion, grounded on an examination of specimens
of Physsophora and Stephanomia communicated to him by
Quoy and Gaimard, that the Physalie ought to be removed
from the place usually assigned them, and made to constitute a
distinct order among the Jollusca, near the orders called in his
system Polyhranches and Nucléobranches. Blainville appears
to have been led to this idea more from observing the arrange-
ment of the external parts of these animals, than from any close
investigation of their internal organization. Qn this ground,
Cuvier expresses himself as decidedly opposed to itt. He ob-
_ serves, that before we can admit them toa place in that division,
it, ought to be shown that. they possess a nervous, as well as
_yascular system, a heart, and liver, as well as male and female
_ organs of generation, all which he (Cuvier) has in vain sought
for, Blainville in like manner differs from other naturalists
with respect to the affinities of the Diphye, which he thinks
constitute a group intermediate to the Salpe and Physsophore,
_ Also the genus Beroe he thinks should be removed from the
_ great family of Meduse (.drachnodermaires, Blainv.), with which
_ it is so constantly associated. It must be obvious that many
speculations will arise with respect to the situation and affinities,
_ not of these groups only, but of several others amongst the lower
_ animals, until we are made better acquainted with their. organi-
_ gation and habits... These offer to us the only sure grounds upon
_ which we can proceed in the endeavour to determine their place
in the natural system; and very many researches relating to
_ these points remain yet to be made amongst the 4calepha...The
Diphye in particular astonish us by the singularity of their
_ form and structure. Composed of two polygonal, subcartilagi-
“WiKGO
_ * The Hniozoa are treated of in a former volume under the art. Vers, which
includes also the Annelida. To this article allusion has been already made in
a former part of this Report.
~ 4 A second edition of the above work has been published during the present
os) under the title of Manuel d’ Actinologie. The views of its author

emain, however, unchanged with respect to the above affinities.
t Analyse des Trav., 1828.

hate

st pays

wx ha

236 FOURTH REPORT—1834.

nous, transparent parts, found constantly in a state of union,
naturalists seem hardly to be agreed, whether these parts belong
to the same animal, or whether they constitute two distinct in-
dividuals, although in form always more or less dissimilar.
Blainville embraces the former opinion ; Quoy and Gaimard, as
well as Cuvier, seem inclined to the latter. It would not be
difficult to point out other instances in which we want further
information with respect to the dcalepha, The limits of this
Report forbid, however, our dwelling any longer upon this class.
It is one especially in which every new observation will have its
value; and it is only to be regretted that so few persons have it
in their power to study these animals in a recent state, in which
alone they admit of such an examination as is likely to conduct
to any important discoveries.

4. Polypi.—lIt is not advancing too much to affirm that natu-
ralists are only just beginning to get an insight into the natural
arrangement of that immense assemblage of beings which con-
stitutes Cuvier’s fourth class of Zoophytes, and that even this in-
sight extends but as yet to comparatively few families. Their
researches, however, are sufficiently advanced to prove clearly,
that the true situation and affinities of these animals are in many
cases very different from those which have been assigned to them
in the Régne Animal. Some have been shown to possess a struc-
ture entitling them to a higher place in the scale of organization ;
while in others the animal powers seem so reduced, the struc-
ture at the same time offering such peculiarities, that they appear
to constitute a distinct class, far below the generality of other
Zoophytes. One great drawback to our better knowledge of
these groups has arisen from the circumstance, that until lately,
naturalists, with some few exceptions, scarcely paid any attention
to the animals of the Incrusted Polypi*, which constitute so
large a portion of them. They looked only to the characters of
the calcareous covering ; and it is not surprising that with this
half-knowledge they should fall into many erroneous notions
with respect to affinities, in their attempts to arrange the species
systematically. It is this which at the present day detracts
somewhat from the value of the works of Lamouroux*, notwith-

standing their great merit in other respects, and the powerful in- _

fluence which they undoubtedly had over the progress of Zoophy-
tology at the time when they appeared. He has made us ac-

* The Polypes & Polypier of the French, for which we have no adequate

expression in our language.
+ Histoire des Polypiers Corallines Flexibles, §c. Caen, 1816, 8vo. And
Exposition Méthodique des Genres del Ordre des Polypiers, Paris, 1821, 4to,

sai

REPORT ON ZOOLOGY. 237

quainted with a vast number of new species, as well as established
several distinct genera which had not been before indicated, but
his classification is decidedly artificial. Adopting from the first
the artificial distinctions of Polypier flexible, Polypier pierreux,
and Polypier sarcoide, he has been necessarily led, as Blainville
observes, to a similarly artificial arrangement of all his subordi-
nate groups. <A better prospect has, however, opened upon us
in this respect. Naturalists are now guided in this department
of zoology by the same principles which have for some time
back directed their researches in the other branches of the sci-
ence. ‘They see the importance of studying the entire organiza-
tion. And while this has led them to a close investigation of
the Polypi themselves in those zoophytes in which they are
really present, it has also led them to distinguish, and to sepa-
rate from these last, others, in which it is now clearly ascertained
that no Polypi ever exist.
~ I can only make a brief allusion to a few important steps which
have been gained of late years in our knowledge of these animals.
One of these relates to the Madrepores, the animals of which have
been proved, bytheresearches of Lesueur*, Eysenhardt, and Cha-
_ misso, and more recently, as well as more decidedly, by those of
_ Quoy and Gaimard, to hold a much nearer affinity to the Actinie
than to the Hydre. Blainville, who has attempted to characterize
‘the genera} from a consideration of the hard and soft parts con-
jointly, considers them as true 4etinie, in the parenchyma of
_ which is deposited a considerable quantity of calcareous matter,
peiucing what the French call the Polypier. He observes,
_ that we may even find a gradual transition in this respect from
the softest of the 4ctinie tothe most solid and most calcareous
ofthe Madrepore. He accordingly throws them both together
‘in one class (Zoantharia, Blainv.), in which however they form
two distinct orders. Quoy and Gaimard paid particular atten-
tion to the Polypiferous Zoophytes during their voyage with
_ Freycinet}, and ascertained the nature of the animals in several
enera in which they had not been described before, or only in
imperfect manner. Amongst others may be mentioned the
Xs whipora of Linneus, which had been supposed by some to
Pete ii?

a
»
a

_ * Mem. du Mus., tom. vi. p. 271.
+ Dict. des Scien. Nat., art. Zoopuytes. "

t See the volume of Zoology annexed to that voyage; also dun. des Scien.
Nat., tom. vi. p. 273, and tom. xiv. p. 236. ‘The former of the two memoirs
just cited contains some remarks on the supposed rapid growth of Coral Islands,
and the power possessed by the Polypi of raising perpendicular walls from the
bottom of the ocean. According to their observations, the labours which have

een ascribed to these animals have been very much exaggerated, and the ac-
counts which have been sometimes given of them altogether erroneous.

238 FOURTH REPORT—1834.

be inhabited by an annelidous animal. MM. Quoy and Gai-
mard have shown it to be a true Polype. Delle Chiaje is said
also to have described the animals of certain species which had
previously been unnoticed. Dr. Fleming in our own country
has made many interesting researches connected with the genera
and species found on the British shores*. More important con-
tributions, however, to our knowledge of this class of animals
were made in 1825, and the two succeeding years by another of
our countrymen, whose labours in this department have acquired
for him the highest reputation. I allude to Dr. Grant, whose
series of papers on the Sponges and other zoophytes are replete
with new and valuable observations. Those on the Sponges es-
pecially, published in the Edinb. Phil. Journ. for the above
yearst, contain the results of a far closer investigation than had
been before made into the nature of these anomalous productions.
Indeed he was the first to discover their true organization and
functions. He clearly ascertained that they do not possess any
Polypi, nor even the power of contracting and dilating their
orifices, as had been formerly supposed. He was the first to
draw the exact distinction between the fecal orifices and the
pores; as well as to point out the nature and directions of the
currents which are constantly passing out from the former. He
also succeeded in determining the origin and mode of develop-
ment of the ova. The memoirs just alluded to relate to the
Marine Sponges. In a separate communication], he gave the
results of a similar investigation into the nature of the Spongilla
friabilis of Lamarck, found in fresh water, which he showed to
bear a close resemblance to the above in all essential respects,
although more simple in its structure, and occupying a still lower
place in the scale of organization. In 1827 Dr. Grant extended
his researches to the Flustr@, and published a detailed account
of the structure and ceconomy of this tribe of Polypi, which were
before but imperfectly understood. Several other equally valu-
able papers relating to the zoophytes appeared from him about
the same time, to which however I can only just allude. In one
of these§, he has described a new and highly interesting genus,
forming a connecting link between Alcyonium and Spongia ;
“« allied to the former by its contractile fleshy texture, and by
its distinct though microscopic Polypi; to the latter, by its

* See Edin. Phil. Journ., vol. ii. p. 82; and Wern. Mem., vol. iv. p. 485; also
his British Animals, published in 1828. . ,
+ vols. xiii. and xiv.; also vols. i. and ii. of the New Series.
t Edinb. Phil. Journ., vol. xiv. p. 270.
§ Edinb. Phil. Journ., N.S., vol. i. p. 78.

REPORT ON ZOOLOGY. 289

siliceous tubular spicula, ramified internal canals, tubul ar papille,
regular currents, and the distribution of its ova.’ In another,
published the same year in the same journal, he has detailed
some observations on the spontaneous motions of the ova of
several species of zoophytes, a motion which, though long since
observed by Ellis in the case of the Campanularia dichotoma,
Lam., scarcely seems to have attracted notice afterwards, not-
withstanding its importance as connected with the mode of
generation in these animals. In 1827, Dr. Grant also published
two papers in the Edinb. Journ. of Science, one* on the structure
and mode of generation of the Virgularia mirabilis and Penna-
tula phosphorea, the othert on the generation of the Lobularia
digitata. A supplement to his first. memoir appeared in the
same journal in 1829.

_ About the same time as that when Dr. Grant was engaged
with these researches, two or three observers in France were
_ busied in a similar investigation, as well of the Sponges as of
_ some of the freshwater gelatinous Polypi of Cuvier’s second
order. Raspail and Robineau-Desvoidy first read a memoir to the
Royal Academy of Sciences in 1827 § onthe Alcyonella of Lamarck.
Their object was to elucidate the structure of this ill-understood
; pzeephyte; and more eepecially to show that the supposed Polypi

“to the genus WVais, the tubes of the Polypier being naturally im-
perforate. This opinion was, however, retracted by Raspail in
/&econd and very elaborate memoir on this zoophyte read the
1e year||, in which he acknowledged the existence of the Po-
pi, but sought to prove by a course of detailed observations that
i eens was not distinct from Cristatedla or Plumatella; that

igdnd the sameanimal indifferent stages of development]. Ras-
ail ‘also made several observations on the structure of Sponges,
es respects analogous to those by Dr. Grant. In a me-
n0ir, likewise read in 1827 and published the year following**,
ave the results of a microscopic examination into the struc-
of the Spongilla friabilis, many of which results, however,
fiered very materially from those arrived at by our own coun-
tryman, Part of his object was to point out an analogy be-

Le

_ # vol. vii. p. 332. + vol. viii. p. 104. t vol. x. p. 850,

“at Cuv., Anal. des Trav., 1827. f

‘ae This. second memoir was subsequently published in the Mém. de la Soc.

V Hist. Nat. de Paris (tom. iv. p. 75).

4 Further researches seem necessary in order to establish beyond doubt the
entity of the above genera. The opinion of Raspail on this point has not

M universally adopted.

** Mém. dela Soc. d’Hist. Nat. de Par., tom. iv. p. 204.

240 FOURTH REPORT—1834.

tween the siliceous spicule found in this genus and in the other
Sponges, and the spiculz of oxalate of lime met with in certain
plants. In 1828, the Spongilla was again made the subject
of a memoir, by Dutrochet*. He confirmed Dr. Grant’s obser-
vations, particularly those relating to the existence of currents
(which Dutrochet attributed to endosmose) and the entire ab-
sence of Polypi. Dutrochet, however, considered the Spongilla
as a vegetable.

A series of valuable observations relating to the zoophytes
were also published in 1828 by Audouin and Edwards t, being
a portion of the researches of these indefatigable naturalists at
the Chausey Islands. They afford fresh confirmation of the
accuracy of Dr. Grant’s views respecting the Sponges and Flus-
tre. They also seem to lead to the important discovery that
many of the species in this last group possess an organization
more complex than has been hitherto supposed, and such as
brings them into near affinity with some of the compound As-
cidiet. The same complexity of structure is stated to have
been seen by them to a certain extent in many Vorticella.
These observers indeed have found such great differences in the
organization of the class of Polypi in general, so far as they
have had an opportunity of examining them, that they propose
a fresh division of this class into four sections, each of which
will constitute a natural family characterized by a peculiar type
of structure. The first of these groups will embrace the Sponges ;
the second, the fixed Polypi, whether naked or incrusted, in
which the digestive cavity is in the form of a cul de sac hollowed
out in the very substance of the body (Hydre, Sertularia,
many Vorticelle); the third will include those Polypi having
a cavity in the body, in the middle of which is suspended a
membranaceous digestive canal, communicating outwards by a
single opening, and bearing at its lower extremity appendices
in the form of small intestines, which appear to perform the
office of ovaries (Lobularie, Gorgonie, Pennatule, Veretille,
Cornularia, &c.); the fourth will include the Flustre and
other Polypi, in which the digestive canal communicates out-
wards by two distinct openings, and the organization of which
approaches that of the compound Ascidie. . i!

* Ann. des Sci. Nat., tom. xv. p. 205. + Id., tom. xv. p. 5.

¢ Cuvier states that similar observations had been made by Spallanzani, and
also more recently by Blainville. He adds, however, that according to Quoy
and Gaimard, there are certainly other species in which the animals are true
Polypi; and that hence it would be very desirable to ascertain which belong to
one type of structure, and which to the other. See Réegne Animal, tom. iil.
p- 3038. note (5).

a

REPORT ON ZOOLOGY. 241

. It is probably to this last group of zoophytes, containing the
- more perfectly organized genera, that the animal belongs which
Mr. Thompson has described under the name of Polyzoa in the
fourth number of his Zoological Researches. This name he
has applied as a general title for the animal inhabitants of seve-
ral zoophytes, which in their organization he considers as be-
longing to the Acephalous Mollusca, being possessed of a di-
stinct gullet, stomach, intestine, and ovarium. Such a structure
he has noticed in Sertularia imbricata, S. Cuscuta, 8. spinosa,
and §. pustulosa, and he thinks that it will probably be found.
imal] the other species of Sertularia ‘‘ not furnished with ovi-
_ ferous receptacles, distinct in size, shape, and situation from the
cells occupied by the animals, and consequently in all the Ser7-
_alaria of Lamarck.’’ Mr. Thompson has also observed the
‘game organization in the Flustre, thus confirming the observa-
tions of Audouin and Edwards, with which, however, he does
_ not appear to be acquainted*.
___. The memoirs which have been noticed above relate for the
__ most part to particular groups in the class under consideration.
_ The only work that has appeared of late years treating of this
entire department of zoology (I except Blainville’s, which is of a
__ more general nature,) is one published by Rapp in 1829+. This
__work is divided into two parts. The first treats of the classifi-
_ eation of the Polypi in general, presenting an arrangement in
which due consideration is had to the form of the animal. The
; pk I may take this opportunity of stating, that at the same meeting of the
‘y sh Association at which this Report was read, Mr. Graham Dalyell brought
ard a memoir containing some highly interesting observations connected
th the mode of propagation and development of the Sertwlarie, as well as of

_ some other zoophytes found on the coast of Scotland. An abstract of this
Memoir will be found in the Edinb. New Philos. Journ. for October last,

ncipal feature in this memoir is the discovery of the existence of currents
hin the stems of the Zubularia indivisa and of all the species of Sertularia
| were examined by the author. The circulating fluid, which appears to
‘be in some respects analogous to that observed in Chare, Mr. Lister is disposed
. "to regard as an important agent in the absorption and growth of the parts.
| + Ueber die Polypen im allgemeinen, und die Actinien ins besondere. Wei-
mar, 1829, 4to. I should state that a work appeared in 1819 by Schweigger,
entitled Anatomisch-physiologische Beobachtungen tiber Corallen, which is said
contain a great many valuable observations on the structure and ceconomy of
zoophytes : 1 have not, however, seen it myself. Some of his researches went
t to prove that the Coralline are only calcified plants. See an analysis of
his experiments on this subject by Dr. Grant in the Edinb, New Phil. Journ.,
vol. i. p. 220,
1834. R

242 FOURTH REPORT—1834.

primary division is grounded on the position of the ovaries or
germs, which are either external or internal, and give rise to two
groups accordingly. The former includes the genera Hydra,
Coryne, Sertularia, and Tuhbularia, united to form a small
family ; and the genus JJillepora. The latter comprises the
Alcyonia, or Polypi tubiferi of Lamarck ; the Twhipore ; the
Corals (Corallium, Gorgonia, Isis, and Antipathes) ; the Pen-
natule; the genera Zoanthus and Cornularia; and the Ma-
drepores. 'The second part of Rapp’s work is confined to the
Actinie, and may be regarded as a kind of monograph. on. that
difficult tribe, the species of which have been in general so ill-
determined.

The same year as. that in. which Rapp published. the above
work, he also published a paper, in the fourteenth volume of the
Nov. Act. &c., Nat. Cur., on the structure of some species. of
Polypi from the Mediterranean.

It is not pretended, in what has gone before, to point out all
the discoveries which have been made in this class of late years ;
and possibly there may be some of more importance than any
mentioned which I have omitted, through ignorance, to notice.
But whatever our knowledge may amount to, we may safely say
that it bears but a small proportion to what remains. to be ac-
quired. This is indeed true with respect to every department of
zoology, but it is most especially so with regard to the present.
As a proof, it is only necessary to mention that in Blainville’s
work (I speak of the second edition, which appeared during the
present year,) there are upwards of fifty genera (without includ-
ing those which have been hitherto only found fossil) the cha-
racters of which commence, with animaux inconnus*. I need
scarcely add what a field is here open to the naturalist, or how
far we must be removed from understanding the structure and
the true natural affinities of all the above groups.

5. Infusoria.—So complete a revolution has been effected in
this group by the recent brilliant discoveries of Professor Ehren-
berg, as entirely to sink the value of every arrangement that
had been previously brought forward of the animals which it in-
cludes. It is not, however, a department of zoology which had
before been much cultivated. Since the time of Muller, to
whom we are indebted for the first accurate researches into the
history of these minute beings, but little progress has been made
in our knowledge respecting them, till the period we are about
to speak of. The most important contributions were those of

* One of these genera is Antipathes, the animals of which, however, have

been discovered by Mr. Gray, who read a short notice respecting them to the:

Zoological Society in 1832. See Proceed. of Zool. Soc. for that year, p. 41.

REPORT ON ZOOLOGY. 243

Nitzsch in 1816, who illustrated the structure of the Cercarie
and Bacillarie, and with whom rests the merit of having first
ascertained the existence of eyes in several species belonging to
the former of these groups. Many other observers have pub-
lished descriptions of new species, as well as instituted new ge-
nera; but'not having had a sufficiently correct idea of the real
organization of these animals, they have in too inany instances
established their characters upon considerations which are found
at the present day to be of no importance whatever. This is
particularly the case with many new groups instituted by Bory
St. Vincent in the Dict. Class. d’ Hist. Nat., in 1826. In this
work, under the Art. Mrcroscopiaurs (which name he substi-
tutes for that of Infusoria), he has given a new systematic ar-
rangement of all the animals belonging to this class; but being
unfortunately based on the external forms, not only are his
genera and species’ greatly overmultiplied*, but his classifica-
tion’ is entirely artificial, and since the researches of Ehrenberg,
become perfectly useless. More important views on this sub-
ject were entertained by Professor Baer in a paper published in
the 13th volume of the Nov. Act. &c., Nat. Cur., to which al-
lusion has been already made in a former part of this Report.
He particularly noticed the great differences which appear in
the organization of these animals. Carried away, however, by
peculiar notions, which led’ him to consider them as only the
imperfect prototypes of other classes, he was for placing them
respectively in’ these classes, and suppressing that of Infusoria
altogether.

_ Ehrenberg’s researches, which form quite an epoch in this
department of zoology, were first made known in a memoir read
tothe Berlin Academy in 1830, and published in the Transac-
tions’ of that body for that year. So many excellent analyses of
them‘have already appeared, that it is not necessary, neither
would it be consistent with the length of this Report, to enter
here into any detailed account of them. I shall simply mention
some of the chief results ‘at which he has arrived with respect to
the structure’ of these animals, and which he has made the basis
of an improved classification of them. The principal feature is
the discovery that the Infusoria possess a much more complex
organization than naturalists before had any idea of. By sup-

dhe extent to which this has been carried, not only by Bory St. Vincent but

‘other writers on these animals, may be judged of from a statement by
nberg, who observes that Miiller has made of the Vorticella Convallaria
twelve ‘species, which’ form with Lamarck, Schrank, and Bory St. Vincent six
genera,

+ See the Edinb. New Phil. Journ. for 1831 and 1833. Also the Ann. des
Sci. Nat. for March, &c., of the present year.

R 2

244 FOURTH REPORT— 1834.

plying them with organic colouring matter as nutriment, he has
clearly ascertained that they are not mere homogeneous gela-
tinous masses supported by cutaneous absorption, as was for-
merly supposed, but organized bodies, provided in all cases with
at least a mouth and digestive system. This last indeed he

has found subject to great variation of structure, being some-.

times simply a round sac in the centre of the body, at other
times a long canal, often very much convoluted, and furnished
with a great number of cecal appendages, which he considers
as so many distinct stomachs. The mouth also varies in its
structure, and presents good characters for distinguishing the
subordinate groups. In the simpler Jnfusoria, it is a mere
unarmed opening, surrounded with a greater or less number of
cilie. In those of a higher order, however, it is much more
complicated, and in some cases even provided with a distinct
pair of serrated mandibles. Besides a digestive apparatus, Ehren-
berg has discovered a generative, and often a muscular system,
and has even in one or two instances observed traces of what
he considers as vascular and nervous systems. The existence
of these last, however, is at present somewhat problematical.
These striking discoveries have naturally led Ehrenberg to
reject entirely the principles upon which all former classifica-
tions of these animals had been grounded, and to construct a
new one after the internal organization. His arrangement is
based upon the structure of the digestive system, which gives
rise to the two natural classes of Polygastrica and Rotatoria ;
the former consisting of such as are provided with several sto-
machs or internal cavities ; the latter of such as have only one,
the mouth at the same time being surrounded by a peculiar
rotatory apparatus. Of these two classes the last is much more
complex in its structure than the former. It would even seem
to be more highly organized than some other classes in the
system, to which the animals included in it have been hitherto
always thought subordinate. With respect to the inferior groups,
those of the Polygastrica are characterized from the presence
or absence of an excretory orifice, the relative positions of the
mouth and anus when this last is present, and from the presence
and situation of the ciliz and other processes: in the Rotatoria,
the families are characterized from the mode of arrangement of
the cilize which form the rotatory organ. In each class the ge-
nera form two parallel series, one consisting of the naked Infu-
soria (Nuda, Khrenb.), the other of such as are protected by a
crustaceous or horny covering (Loricata, Ehrenb.), these two

series appearing to be intimately allied, and often presenting no -

other difference beyond that which has been just alluded to.

REPORT ON ZOOLOGY. 945

» Ehrenberg has rejected from the Infusoria several genera
which were formerly classed with these animals ; amongst others
the genus Vibrio, before spoken of as having been thought by
Dugés and Blainville to show an affinity to some of the Entozoa.
It also appears probable from some of his observations, that
the genus Monas and several allied genera are not distinct ani-
mal forms, but only the young state of some Kolpode, Para-
meca, &c. This idea has been subsequently adopted by
others*.

Ehrenberg has since’ published a second memoirt, in which
he has extended his researches to several points of great interest
in the history of these animals. He has endeavoured to ascer-
tain the duration of their existence, as well as the mode of their
development. He has also made some further discoveries with
respect to their structure. He has detected eyes (which before
he had only observed in some of the Rotatoria) in many of the
Polygastrica, and he has found them to furnish distinctive cha-
racters of great value in classification. He has fixed a nomen-
clature for all the principal external organs and appendages,
which he describes at much length. He has also made some
further remarks on the modifications of the alimentary canal, as
well as on those of the dental system. Since the date of his
first memoir he has found the teeth existing under several di-
stinct forms, and even ascertained their presence in some of the
Polygastrica. These discoveries have suggested some new
principles of arrangement.
~ The above is a condensed abstract of the striking researches
-made by this acute observer. We may judge what important
views they open to us, not only in respect to the structure of
these animals, but in respect to what may be the structure of
some other groups, in which also the organization has been con-
sidered hitherto as of the most simple kind. It is moreover not
improbable that they may ultimately help us in determining the
true limits of the animal and vegetable kingdoms, if between
them any fixed limits really exist. A complexity of structure,
of such a nature as is found in no vegetables, has been shown by
Ehrenberg to exist in those forms which were formerly regarded .
as very near the boundary; and although we now know of some
groups of a much more anomalous character than the Infusoria,
it is only extending our researches a little further, and we may
possibly be able to detect their real nature. There is one in-

__ * Seea paper entitled ‘‘ Observations upon the Structure and Development of
the Infusoria,” by Dr. Rudolph Wagner of Erlangen, in the Edinb. New Phil,
Journ. for October 1832,

+ Berlin Memoirs for 1831.

246 FOURTH REPORT—1834.

quiry in particular which forcibly suggests itself. Is there any
similar complexity of structure, anything approaching to an
alimentary sac or stomach, in those monads, which, it is asserted
by so many observers, become fixed after a time, and transformed
into Conferve? The determination of this point will go far
towards determining the true situation of a host of ambiguous
genera at present hovering between the two kingdoms, and hay-
ing almost equal claims upon the notice of the zoologist and
botanist*.

IV. Conclusion.

In the preceding pages I have endeavoured, though I fear
very imperfectly, to give a condensed view of the principal re-
searches which have been made of late years in Zoology, at least
such as haye tended to throw light upon the affinities of animals,
and thereby to adyance our knowledge of the natural system. It
was my original intention to have proceeded here to the con-
sideration of some other parts of the subject, such as the state
of our knowledge with respect to the actual number of species
in the several classes, and also with respect to the zoology of
particular countries. The former, howeyer, is rendered un-
necessary from the appearance of an article in the Hdinh. New
Philos. Journ. of last year ¢, expressly devoted to this branch
of inquiry. The latter would afford an opportunity of alluding
to several valuable works which have been recently published in
this and other countries, some containing many new and inter-
esting forms of importance to the science in general. But the
length to which this Report has already been extended precludes
my entering upon this subject. Considered also in connexion
with that of the geographical distribution of animals, it would
furnish ample materials for a separate communication. I shall
therefore, in conclusion, merely offer a few remarks connected
with the further progress of zoology, and its advancement in
this country in particular.

(1.) Its general progress, viewing the natural system as the
true object of the science, and considering the very imperfect
knowledge we haye of this system at present, must clearly de-
pend upon the discovery of new forms, and a more thorough in-
vestigation of those already known tous. If the former be ne-
cessary in order to supply some of the numerous links that are
yet wanting to complete the chain of affinities, the latter 1s not

* For further information respecting these anomalous productions, the reader
is referred to the article ArTHROIDEEs in the Dict. Class. d’Hist. Nat., and to the
articles Nemazoaires and Zoornytss in the Dict. des Sci. Nat.

+ No. 30, for July 1833, p. 221.

REPORT ON ZOOLOGY. 247

less so to determine the parts of the system to which these links
belong. But of these two, there can be no doubt the latter is
what we stand most in need of. I question whether we shall not
be rendering more service to zoology by paying closer attention
to the species we are already acquainted with, than by further
augmenting the immense collection of uninvestigated forms
which exists now in our cabinets. We have, perhaps, sufficient
materials on our hands, though not for discovering the whole
natural system, at least for solving many important problems in
zoology, were we only better instructed in the nature of these
materials. It has been shown in the course of this Report, that
there are large groups, even whole classes, of which the true
situation and affinities are either not determined at all, or in-
volved in much uncertainty, from the imperfect knowledge we
have of their structure and ceconomy ; and in the details of the
system, there is not one class which does not present many
genera, and a vast many more species in this predicament.
Here then is where the researches of naturalists should be di-
rected. Until we shall have more closely analyzed the charac-
ters of these groups, and learnt both the method of variation and
relative importance of all the organs, until we shall come to
understand their whole structure as compared with those struc-
tures we are already acquainted with, we can neither determine
the affinities of these groups, nor of any others allied to them
which we may hereafter discover.

Researches of the above nature are, perhaps, best embodied
in monographs. The value of such works has been every day
more and more appreciated since the science has become so
extensive, and since its legitimate object has been better under-
stood, especially when they refer to every point in the history
of the group treated of, and when due care is taken first to
ascertain what others have written on the same subject *. Many
excellent monographs fulfilling these conditions already exist,
some of which have been alluded to, and others might have
been had it been allowable to enter so much into the details of
the subject. Nevertheless it would be extremely desirable to
have them multiplied. By the help of such works we may
arrive step by step towards a more complete generalization of
the large number of facts embraced by zoology, at the same time
that we greatly facilitate the researches of other naturalists. But
allinquiries into the structure and ceconomy of animals presup-
pose an exact discrimination of species. Without this the most
detailed observations are rendered of little use, and it is the

t Seethe article Monocraruiz, by Decandolle, in the Dict. des Sci. Nat.

248 FOURTH REPORT—1834.

want of it which detracts from the value of much that has been
recorded by those who have not sufficiently attended to this
matter. Hence it should be one object of a monograph to in-
vestigate species with a view to their exact differences, and to
elaborate the synonyms of those which hayebeen noticed byother
authors. This is especially necessary in some groups, in which
great confusion exists on this head. Cuvier was particularly
sensible of the importance of this step. In his Histoire Naturelle
des Poissons it is impossible not to be struck with the care
which he has shown in endeavouring to trace every species to its
first describer, and to disentangle itssynonymy, before proceeding
to other points in its history. No researches have been spared
which could throw any light on this part of his subject. Every
author has been consulted; even the most ancient writers on
this branch of zoology he has had recourse to, under the hope of
being able to identify the species they have noticed. And he
has more than once observed in some other of his works, that
there is greater service done to natural history in thus extri-
cating from error and confusion the history of old species, than
in publishing and describing new ones.

But not all have it in their power, from the want of requisite
materials, to furnish a complete monograph of any entire group.
Such persons may, notwithstanding, still contribute greatly to
the advance of zoology by restricting their monograph to the
species in their own neighbourhood: only let such works be
conducted with the same care, the same original observation
and research, which are thought necessary in the productions
just alluded to. Faulty catalogues, or even works of a more
elaborate kind, if merely compiled from other authors, are
utterly worthless. Whereas good local Faunas, or portions of
a Fauna, however limited the district, may be rendered of the
greatest possible value. By studying with scrupulous exactness
the structure and habits, although only of a few species, we
may be able to throw much light upon their natural affinities *,
we may accumulate enough facts to make some approaches
to generalization ourselves; at any rate we are amassing the

est materials for enabling others to do so.

(2.) With reference to the further advancement of zoology
in this country in particular, I cannot forbear observing, that
while there are some branches of the science which are most
sedulously cultivated by us, there are others, and those too such
as, from our insular position, it might be thought would be
among the first to attract our notice, which have for a long

* Witness the researches of Thompson with respect to the Cirripeda.

REPORT ON ZOOLOGY. 249

time lain’ comparatively neglected. I allude to Ichthyology
and the study of the marine Invertebrata. I need scarcely say
how small is the number of individuals who have added any-
thing recently to our knowledge of the fish even of our own seas,
notwithstanding the opportunities for so doing which daily
present themselves to naturalists resident on the coast. The
fact has been repeatedly noticed. With regard to marine In-
vertebrata, I refer more particularly to the Radiata of Cuvier,
although there is reason to believe that our knowledge of the
Mollusca is far below what it might become by a more diligent
inquiry into these tribes. Excepting the important researches
of Dr. Grant and Mr. Thompson, excepting also a few detached
papers by Drs. Fleming and Coldstream, and more recently by
Dr. Johnston *, we have hardly any original observations with
respect to the radiated animals since the time of Montagu ft.
In the several classes of Echinodermata, Acalepha, and Polypi,
it is impossible to say what and how many species are to be
found on our own shores, or what important additions might
not be made to our general knowledge of these groups, as parts
of the natural system, by those whose situation and opportuni-
ties afford the means of studying them. As a striking illustra-
tion of what might be done, it is only necessary to look to the
results obtained by two French naturalists { (whose example
deserves to be imitated) during a series of annual excursions
to different parts of their own coast. There is no occasion to
specify these results in detail. Many, of the greatest possible
interest and importance to zoology, have been already alluded
to in former parts of this Report. I may, however, just state
the fact, that on their return from the Chausey Islands, which
were selected one season as the scene of their researches, they
enriched the Paris museum with upwards of 600 species of
marine Invertebrata, of which at least 400 were considered by
them as either entirely new, or before imperfectly understood §.
_ While it is thus in our power to do much for this science as
individuals, I conceive it is also in our power to do something
as a nation; and in no respect more than by encouraging and
promoting expeditions to foreign countries, deputing naturalists

_* This gentleman has lately published a useful paper on the recent Zoo-
Jhytes found on the coast of North Durham, in the 7’rans. of the Newcastle
Natural History Society.

+ I should also make an exception of Mr. Graham Dalyell, whose researches
on Scottish Zoophytes were brought forwards at the same meeting as when this
Report was read. These, however, have not yet been published in detail.
~ ¢ MM. Audouin and Edwards.

§ Cuvier’s Anal. des Travaux, 1828.

250 FOURTH REPORT—1834.

to those parts of the globe which have been least explored, and
affording the means of making known to the public the fruits of
their researches. France has long since set us an example in
undertakings of this nature. In the splendid volumes of zoology
annexed to the voyages of Captains Freycinet and Duperrey; in
the appropriation of a yearly sum for the support of travelling
naturalists for the benefit of the Royal Museum, which mainly
to this circumstance owes its unrivalled celebrity * ; we see
marks of an anxious endeavour on the part of that nation to up-
hold the interests of this science. I will not say that in no in-
stance has anything of the kind been done here. Within these
few years we have seen a work emanate from the British press,
the Fauna Boreali-Americana, under the immediate sanction
and patronage of our own government. I believe, however, it
is the first, wholly devoted to zoology, which ever appeared
under such auspices. And with respect to researches in foreign
lands, whatever may have been done for other sciences, or for
this science by private individuals, I apprehend we have effected
very little as a nation which will bear to stand in competition
with what has been done in this way by France, and some other
nations on the Continent which might be mentioned +.

Such are the hints which, with much diffidence, I would ven-

* M. D’Orbigny, who has been for these few years past exploring South Ame-
rica in the above capacity, has recently returned to Faris with rich and valuable
collections in all departments. He is said to have acquired no less than forty-six
new species of Mammalia alone, a surprising addition when we reflect that the
whole number before known scarcely exceeded 1200. (See L’Jnstit., No. 50.)
It was observed eight years ago, that “in the present advanced stage of informa-
tion, it cannot be expected that many new recent species of Mammalia should
be discovered.1” M. D’Orbigny, however, has shown that even in this class
novelties are far from at an end to reward those who will go in quest of them.

+ Perhaps it may not be without its use, to call the attention of the members
of the British Association to the following proposition which was made and
adopted at the congress of French savans held at Caen, July 1833. It was resolved
“ to encourage travels of discovery ; to recommend naturalists and all persons
interesting themselves in the progress of natural history, to organize these
kinds of travels by means of subscriptions, and to direct them towards those parts
of the globe which have been least explored.” See Congrés Scientif. de France,
1833, p. 261. I will not presume to say how far it would be practicable for
the British Association to set on foot any such project in this country.

Since this Report was read, Mr. Swainson has published his Preliminary
Diseourse on the Study of Natural History, in which he has treated, at some
length, of the Present State of Zoological Science in Britain as compared with
other countries. Without wishing it to be thought that I subscribe to every-
thing stated in that volume, I may refer to Part 4. as containing more ample
details in reference to this inquiry than it was possible for me to enter into.

1 Bicheno's Address io the Zoolog. Club, 1826, p. 5.

REPORT ON ZOOLOGY. 251

ture to throw out for the further promotion of zoology. I have
only to add, that with reference to the progress it is actually
making in our own country, and the promise which is held out
of uninterrupted advancement, comparing this country, not with
others, but with itself at former periods, there is ground for
much exultation. Looking to what has been effected of late
years, however more striking in some departments than others,
to the important works and memoirs which have appeared
amongst us, and to the channels which have been opened for the
more successful cultivation of this science, it is impossible not
to anticipate the most valuable results. There is one institution
in particular, of which I have hitherto not spoken, but which
more than anything has contributed to this impulse. I allude
to the Zoological Society, founded in 1826. The scale and plan
upon which this Society is conducted are calculated to obtain
for it the highest place amongst institutions of this nature. Its
Museum and Gardens, the latter for the reception of living
animals; its extensive correspondence with naturalists in foreign
countries, by which it has been enabled to acquire some of the
richest and most valuable collections ; are too well known to the
members of this Association to require being dwelt upon more
particularly. I may state, however, that it has recently com-
menced the publication of Transactions, of which two parts are
before the public, containing memoirs of the first importance to
zoology, and such as will bear competition with any of those
which have emanated from other quarters. ;
But it is not merely in the institution of the Zoological
Society that we trace a rising spirit of inquiry in this branch of
science. We see it in the establishment of Natural: History
Societies in almost all the principal towns of England. It is
unnecessary to specify these individually. It is enough to be
able to record the fact of their existence. This circumstance
alone speaks to a more generally diffused taste for zoology,
which is the first step towards the advancement of zoology it-
self. It is only necessary to give a proper direction to the re-
searches of these societies, to point out those departments which
need most cultivation, and we may reasonably hope that the time
is not far distant when England will no longer be considered
behind her continental neighbours in this, any more than in
other sciences.

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253

Report on the Theory of Capillary Attraction. By the Rev.
James Cuauuis, late Fellow of Trinity College, Cambridge.

In the Report which I had the honour of drawing up last year. on
the analytical theory of hydrostatics and hydrodynamics, a di-
stinction was made between problems on the common theory of
fluids, and those in which molecular attraction and the repulsion
of heat are explicitly taken account of, and the former kind alone
came under review. That distinction, it was said, depended on the
different bases of calculation, which in the former class of pro-
blems are observed facts ; in the other, certain hypotheses, which
can be verified only by a comparison of the results of calculation
with experience. The latter kind of questions are of the more
comprehensive nature, because frequently it is proposed in them
to account for the facts which serve for bases of calculation in
the other class, and an explanation of every such fact must in-
clude the explanation of all those that can be mathematically
shown to be dependent on it. The above distinction ought to
be kept in mind when we regard the part which calculation has
to perform in our inquiries into the nature and properties of
matter. It is not sufficient to say that analysis serves to classify
facts of observation, and to prove that several which are allied
to each other are consequences of some one observed fact; for
we have been taught by the labours of Newton, that there are
facts which are not phenomena, the existence of which can only
be proved by calculation. It may now be considered an esta-
blished fact that all bodies attract each other proportionally to
their masses, with forces varying inversely as the square of the
distances ; but the evidence for this truth is essentially mathe-
matical. So, if the existing theories respecting the internal
constitution of bodies, and the nature of the forces which ema-
nate from their molecules, should be established by the progres-
sive advance of science, the evidence on which they will rest
must be mathematical. For these reasons, this, the highest de-
partment of physical science, may be properly denominated
Mathematical Physics*. The great problem of universal gra-
vitation, which is the only one of this class that can be looked
upon as satisfactorily solved, relates to the large masses of the

“* In the former Report I have inadvertently written Physical Mathematics.
It might perhaps be questioned whether these terms be not equally proper;
but when, in addition to what is said above, the title of Newton’s Principia is
recollected, the other would seem to be preferable.

254 FOURTH REPORT—1834.

universe, to the dependence of their forms on their proper gra-
vitation, and the motions resulting from their actions on one
another. The progress of science seems to tend towards the
solution of another of a more comprehensive nature, regarding
the elementary constitution of bodies, and the forces by which
their constituent elements are arranged and held together. Va-
rious departments of science appear to be connected with each
other by the relation they have to this problem. The theories
of light, heat, electricity, chemistry, mineralogy, crystallogra-
phy, all bear upon it. A review, therefore, of the solutions that
have been proposed of all such questions as cannot be handled
without some hypotheses respecting the physical condition of
the constituent elements of bodies, would probably conduce, by
a comparison of the hypotheses, towards reaching that generali-
zation to which the known connexion of the sciences seems to
point. This end is kept in view in the following Report. It hap-
pens that with respect to fluids two problems have especially en-
gaged the attention of mathematicians, which in a very marked
manner lead to the consideration of molecular forces and the
repulsion of heat, viz. capillary attraction, and the propagation
of motion as affected by the development of heat. The one
refers to fluid in equilibrium, the latter to fluid in motion. It
was my intention originally to embrace both these in one Re-
port, but the time required for becoming acquainted with works
on these subjects which have not been very long before the
public, and contain new trains of thought and mathematical in-
vestigation, did not allow of preparing the Report, such as it
was intended to be, in time for the present meeting; and the
matter connected with capillary attraction alone will perhaps be
thought sufficient, and of sufficient interest, to form the subject
of a separate report.

The distinction above stated as applicable to two sorts of
hydromechanical questions, applies equally to statical and dyna-
mical questions respecting solids. Some may be treated on the
supposition of perfect rigidity, as is the case in most of the pro-
blems that occur in the common elementary treatises on mecha-
nics: in others the solids must. be supposed to be elastic; and
if the elasticity be regarded not as a datum of observation, but
as a result of molecular attraction and repulsion, then, to take
account of it, certain hypotheses-must be made respecting the
nature of these forces and the molecular arrangement, plainly
analogous and intimately related to the like hypotheses with re-
spect to fluids. Questions of this kind have of late largely en-
gaged the attention of some French mathematicians; and the
nature of their theories, and the results of the calculations

REPORT ON CAPILLARY ATTRACTION. 255

founded on them, deserve to be brought as much as possible
into notice.

_ Capillary Attraction.—The theory of capillary phenomena
will be best exhibited by tracing historically the principal steps
by which it has arrived at its present state.

Dr. Hooke is among the earliest speculators on the cause of

capillary attraction. He attributed the rise of the fluid to a di-
minution of the pressure of the atmosphere within the tube, by
reason of friction against its interior surface. This opinion was
shown to be erroneous when the fluid was found to rise as high
under the receiver of an air-pump as in the open air.
_ Hauksbee*, whose experiments on the capillary action of
tubes and glass plates have not even yet lost their value, made
the beginning of a true theory of the phenomena, by ascribing
them to the attraction of the tube or plate. Having ascertained
by experiment that the thickness of the matter of the tube made
no difference as to the height to which the fluid ascended, he
saw that the attractive force must. emanate entirely from the
particles of the tube situated at its interior surface. He does
not, however, pronounce a decided opinion whether the sphere
of their attraction extends: mediately or immediately to the par-
ticles of the fluid situated about the axis of the tube; and he is
in error in supposing that this’ attractive force, by pressing the
fluid particles perpendicularly against the capillary surface at all
the points with which the fluid is in contact, diminishes the
weight of the suspended column.

_In this last particular the explanation of Hauksbee was
shown to be untrue by Dr. Jurint, who found by experiment,
that the height to which water would rise in a tube, of which
ne, portion occupied by the fluid consisted of two cylinders of

BB ds

eed =e

_ * Physico-Mechanical Experiments. London, 1709. pp. 189—169. Also va-
rious papers in the Philosophical Transactions for the years 1711 and 1712.
_t Philosophical Transactions 1718, No. 355, p. 739. _ An additional paper
on the same subject, Phil. Trans. 1719, No. 363, p. 1083.

256. FOURTH REPORT—1834.

quantity of fluid raised being proportional to the raising peri-
phery, and consequently to the radius, and being proportional
also to the product of the height and the square of the radius,
it follows that the height is inversely proportional to the radius.
This reasoning is not incorrect, but defective, as we shall pre-
sently see. In a postscript to his paper, Dr. Jurin intimates
that the principle of his explanation was not unknown to New-
ton and Machin, who, however, do not appear to have sup-
ported their views by like experiments. He says also, that the
same two mathematicians suggested to him that what he calls
the periphery of the concave surface of the tube, is in reality
“a small surface whose base is that periphery, and whose height
is the distance to which the attractive power of the glass is
extended.’’ It is sufficiently evident that the theory of capil-
lary attraction had engaged the attention of Newton, from
the 31st query in the last edition of his Optics, which was pub-
lished a short while previously to the reading of Jurin’s paper.

In this 31st query, Newton is speculating respecting the na-
ture of molecular forces, to which he is of opinion that chemical
combinations are owing. In proof of the existence of such
forces, he appeals to several instances of attraction of the kind
which it has been agreed to call capillary attraction or cohesion.
One very singular instance is the suspension of a column of
mercury in a barometer tube, to more than double the height at
which it usually stands, by its adhesion to the top of the tube,
which it leaves only by being considerably shaken. Of the
same kind with this phenomenon, Newton considers the rise of
water between two parallel plates of glass held at a very small
distance from each other and dipped im the fluid. The height
to which the water rises, he says, ‘ will be reciprocally propor-
tional to the distance [between the plates] very nearly ; for the
attractive force of the glasses is the same, whether the distance
between them is greater or less, and the weight of the water
drawn up is the same, if the height of it be reciprocally propor-
tional to the distance of the glasses.”’ This explanation, though
true, does not prove that Newton had formed any very distinct
idea of the extent of action of the attractive force of the glass,
and the mode in which the water is influenced by it. He asserts,
moreover, that the height to which water rises in aslender glass
pipe, will be reciprocally proportional to the diameter of the
cavity of the pipe, and will equal the height to which it rises
between two planes of glass, if the semidiameter of the cayity
of the pipe be equal to the distance between the planes, or there-
abouts.” These are not, however, theoretical deductions, but
the results of experiments made before the Royal Society.

REPORT ON CAPILLARY ATTRACTION. Q57

Hauksbee records an experiment by which it appears that if

a large tube of glass be closely filled with ashes, and one end be
dipped in water, in the space of a week or fortnight the water
will rise within the tube to 30 or 40 inches above the level of
the water without. Newton, in noticing this experiment, says
correctly, that the rise is owing “to the action only of those
particles of the ashes which are upon the surface of the elevated
water, the particles which are within the water attracting or re-
pelling it as much downwards as upwards.”
- Another experiment by Hauksbee shows that a drop of wa-
ter inserted between two plates inclined to each other at a very
small angle, and touching at their edges, is attracted to the junc-
tion of the edges by a force varying inversely as the square of
the distance from it. Newton attempts to account for this phe-
nomenon, but unsuccessfully. The true explanation was reserved
for Dr. Young and Laplace.

When two planes inclined at a small angle are immersed in
water, with the line of. their junction vertical, the outline of the
water that rises between them is on each plane nearly an hyper-
bola, of which the asymptotes are the line of intersection of the
plane with the horizontal surface of the fluid, and the line of
junction of the two planes. Taylor first ascertained this by
measurement*. It isa simple consequence of the law accounted
for by Newton, of the rise of water between parallel planes to a
height inversely proportional to the interval between them ; for

‘the planes being inclined at a very small angle, opposite elements
of them may be considered parallel.

' The early theories of capillary attraction were defective in two
respects: they contained no calculation founded on the hypo-
thesis of an attraction sensible only at insensible distances from
the attracting centres, although the existence of such forces was
already recognised, and Newton had given an example of calcu-
lation made with reference to force of this nature in the instance
of the passage of light through a dense medium ; and they took
no account of the cohesive attraction of the parts of the fluid
for each other. The necessity of considering the mutual at-
traction of the particles of the fluid would seem to be very evi-
dent when once the law of attraction, sensible only at insensible
distances, was admitted; for supposing the capillary tube to
attract only the fluid particles at insensible distances from its
surface, a column of water of sensible breadth could not be
Suspended except by the intervention of a cohesive power resi-

* Philosophical Transactions, 1712, No, 336, p. 538.
1834. s ;

258 FOURTH REPORT—1I834.

dent in the fluid. Yet Clairaut was the first to see the ne-
cessity of taking account of the action of the fluid on itself;
and this addition to the theory of capillary attraction is the princi-
pal feature of the propositions on this subject i introduced, in rather
a cursory manner and beside his main purpose, into his cele-
brated treatise on the Figure of the Earth*. After stating the
insufficiency of the method of Jurin, he proceeds to a careful
consideration of all the forces concerned in raising the fluid,
both those due to the tube and those due to the fluid, as well at
the upper part of the column raised, as at the lower extremity
of the tube. His method of considering the forces, which is
stated clearly and illustrated by good diagrams, has been for
the most part followed in succeeding treatises on the same sub-
ject. But although Clairaut asserts that. the forces concerned in
this problem are sensible only at very small distances, he does
not seem to be aware that the distances must be considered alto-
gether insensible. This is not a necessary condition in his view
of the mode in which the forces act ; respecting the law of the
variation of which, as the distances increase, he makes no other
hypothesis than that the function which expresses it is the same
both for the tube and the fluid. He is consequently unable to
prove that the height at which the fluid stands in a capillary
tube is inversely proportional to the diameter.

By reasoning on the hypothesis just named, Clairaut arrives
at the following conclusion: “If the attraction of the capillary
tube should be of less intensity than that of the water, provided
it be not so small as half the other, the water will still rise.’’
This he confirms in another method, the principle-of which will
be exhibited by showing as follows, that if the attraction of the
fluid for itself were exactly double that of the tube for the fluid,
the surface of the fluid within the tube would be horizontal, and
consequently on a level with the surface without. Let us sup-
pose the fluid surface to be everywhere horizontal, and consider
the equilibrium of a particle in contact with the vertical surface
of the solid, which we will suppose to be plane.. Now as the
resultant of the forces acting on the particle must be perpendi-
cular to the fluid surface, and therefore vertical, the horizontal
attractions destroy each other. Therefore the horizontal attrac-
tion of the solid, which is its total action, is equal to the hori-
zontal attraction of the fluid, which is only half what it would
be if the fluid were continued above the particle as it is below,
and eahseqpently placed under the same circumstances of at-

* Théorie dela Figure dela Terre. Paris; 1 808, pp. 105—128.

REPORT ON CAPILLARY ATTRACTION. 259

traction as the solid. - Hence the truth of the proposition is
manifest. - We shall have occasion in a subsequent part of the
Report to allude to this demonstration.

~ In 1751, Segner*, aware that Clairaut had written some arti-
cles (“‘ articulos quasi episodicos’’) on capillary attraction, but
not having seen his work, attempted to determine theoretically
the form of the surface of a drop of water resting on a horizontal
plane, on the hypothesis of the attraction of the parts of a fluid
for each other. This is a problem of the same nature as that of
determining the form of the upper surface of the column of fluid
sustained in a capillary tube, neither of which had yet engaged
the attention of mathematicians. Segner begins with admitting
the tenacity of fluids, and ascribes it to the action of an attrac-
tive force resident in their constituent molecules, the law of
which he does not pretend to assign, but assumes only that: the
sphere of the activity of each particle is of insensible magnitudet.
Setting out with these correct principles, he is led to refer the
shape which the drop assumes to the action of its superficial
particles, which form, as it were, a sheet encompassing it, and by
their tenacity counteract the tendency of the drop to spread in
obedience to the force of gravity. The sequel of this essay is
not equally successful. In estimating the superficial tension
considered as depending on the curvature at each point of the
surface: of the drop, the author commits an error in taking ac-
count only of the curvature of the sections made by vertical
planes through its axis, and neglecting the effect of the curva-
ture in planes perpendicular to these. He intimates in a note
at the end of the essay that he became aware of some defect in
his theory.

© A considerable time after the theory of Segner was published,
Monge asserted, at the end of a memoirf on certain effects of the
apparent attraction and repulsion of small bodies floating on
fluids, that “by supposing the adherence of the particles of a
fluid to have a sensible effect only at the surface itself, and in
the direction of the surface, it would be easy to determine the
solid boundaries which contain them ; that these surfaces would
be lintearie, of which the tension, constant in all directions,

“* Comment. Soc. Reg. Gotting. tom. i. Ann. 1751, p. 301.
~+Generatim autem spatium illud sphericum, intra quod particule activitas
consistit, adeo exiguum est, ut nullo adhue sensu percipi potuerit.” (p. 303.)

Segner appears to have been the first to apply to capillary phenomena mathe-
matical calculation founded on this hypothesis.

{ Mémoires de Acad. des Sciences, An 1787, p. 506.
sz

260 FOURTH REPORT—1834.

would be everywhere equal to the adherence of two particles ;
and the phenomena of capillary tubes would then present no-
thing which could not be, determined by analysis.’’ The process
here indicated Monge did not follow up by mathematical caleu-
lations. The main purpose of the memoir, from which the above
sentence is extracted, is to give an explanation of the apparent
attraction and repulsion observed to take place between small
substances when they float near each other on the surfaces of
fluids. These phenomena are of three kinds. (1.) If two float-
ing bodies are each surrounded by a depression of the fluid sur-
face, and are separated at first by a small interval, they will
move towards each other as if mutually attracted. (2.) When
the fluid rises up around them, they will in this case also appear
to be attracted when brought near each other. (3.) When one
is surrounded by an elevation of the fluid, and the other by a
depression, they will appear to be mutually repelled. The motion
of the bodies towards each other in the first case, is owing to the
_circumstance that the depression of the fluid about one is in-
creased on their mutual approach by the depression about the
other, at those parts of each that are neighbouring ; which occa
sions an unequal hydrostatic pressure against each of the bodies
in the horizontal direction, the pressure being greatest where
the depression is least. This explanation was first given by
Mariotte. To explain the second phenomenon, Monge reasons
as follows. Ifa plate of any substance be dipped with its plane
vertical in fluid, the fluid will rise by capillary attraction on
each side of it. The surface of the raised water, being stretched
like a chain, will draw the plate in a horizontal as well as verti-
cal direction, but equally on both sides, so that it will remain in
its vertical position. If now another plate of the same matter,
and exactly alike circumstanced, be brought near the other, the
fluid, it is well known, will rise between them. The total quan-
tity of fluid raised above the ordinary level will remain the same
as if the actions of the two plates did not interfere with each
other, because the raising forces will be the same. But the
weight of water raised between the plates, being suspended from
a diminished quantity of fluid surface, the superficial tension
within will become greater than that without, and will more
than counterbalance the latter. The plates will consequently be
drawn together. The third phenomenon is explained by saying,
that when a body, surrounded by an elevation of the fluid, is
brought near one surrounded by a depression, there is occasioned
a diminution of depression on the side of the latter nearest the
other, and a consequent inequality of hydrostatic pressure, the
excess being on the side where the depression is least. This

REPORT ON CAPILLARY ATTRACTION. 261
body will consequently be repelled from the other. More ex-
act explanations of these phenomena have since been given by
Young, Laplace, and Poisson, but not materially differing in
principle from the above.

We ought now to notice the labours of Dr. Young in the theory
of capillary attraction, as being next in order of time ; but as his
paper on this subject was published only a short interval (some-
thing more than a year) before the “ Treatise on Capillary Ac-
tion”’ by Laplace, and as it contains an idea which is not in
Laplace’s theory, and which may be considered an additional
step towards the complete explanation of the phenomena, it
will be convenient to deviate from the historical order for the
purpose of exhibiting more clearly the progressive steps by which
the theory of capillary attraction has arrived at its existing state,
I will, therefore, now endeavour to give some notion of the prin-
ciples of Laplace’s theory, and of the extent to which they will
explain phenomena.

This essay was published in 1806, as a supplement to the
tenth book of the Mécanique Céleste. It contains explanations
more exact than had hitherto been given of the several facts we
have had occasion to mention in the foregoing part of the Report,
and of others in addition to these: and the explanations are sus-
tained throughout by mathematical calculations. The hypotheses
of the theory are, that the fluid is perfectly incompressible; that
there is as well an attraction of the particles of the fluid for each
other, as a mutual attraction between the particles of the fluid
and the particles of the tube, and that these forces are sensible
only at insensible distances from the attractive centres. From
these principles a fundamental equation relative to the upper
surface of fluid raised by capillary action, is derived bya process
of the following nature.

~ Conceive an infinitely slender canal, of uniform transverse
section, to be drawn from any point of the fluid surface, sup-
posed to be concave by reason of the capillary action, to a point
of the horizontal surface which is unaffected by the same cause.
Let the canal be everywhere beyond the sphere of the attraction
of the solid from which the capillary action proceeds. Suppose
its two ends to terminate perpendicularly to the surfaces, and to
be rectilinear for a distance from each of them not less than a
certain small quantity A, the extent of the sphere of activity of
the fluid’s attraction : it is proposed to determine the condition
of equilibrium of this canal. It is plain that any point of it
distant by more than a from its extremities will be attracted
equally in all directions. The case is different with all points
situated within the distance A from either of the extremities,

262 FOURTH REPORT—1834.

The attraction of the surrounding fluid on the points of the
canal so situated at the extremity which terminates in the hori-
zontal surface, will produce a pressure, which Laplace calls K,
on the canal downwards. Ifa tangent plane be drawn at the
other extremity, the fluid below this plane will produce an equal
pressure on the canal at this end, and similarly directed. These
two pressures acting in opposite directions along the canal, will
destroy each other by reason of the incompressibility of the
fluid. There will remain the attraction of the fluid between the
curve surface and the tangent plane. This produces a pressure
directed to the centres of curvature of the point where the canal
ends, and, as the calculation shows, proportional to the sum of
the greatest and least curvatures at that point; for, in fact, the
quantity of matter between the curve surface and tangent plane,
taken within the small distance 4 from the point of contact,
varies in the same proportion, and to. this quantity of matter
the total attracting force is proportional. Opposed to the pres-
sure thus arising is the effect of gravity on the whole canal in
producing pressure in the direction of its length, which effect,
it is known from the common principles of hydrostatics, is
equal to the weight of a column of the fluid of the same trans-
verse section as the canal, and whose height is the elevation of
one end of the canal above the horizontal plane in which the
other is situated. Calling this elevation z, the greatest and least
radii of curvature at the point of the curved surface under con-
sideration R and R’, and the density of the fluid e, we shall have

ee our
Ta ee a ie

This is the fundamental equation spoken of above. It does
not contain, as we perceive, the quantity K, which Laplace sup-
poses to be expressive of the force that causes the suspension
before mentioned (p. 256) of mercury in the tube of a barometer
to a height two or three times greater than that due to the at-
mospheric pressure. He thinks also that on this quantity de-
pends the forces which produce cohesion and chemical affinities.
The left side of the equation, expressing the pressure that arises
from the action of the small quantity of matter situated between
the curve surface and the tangent plane, and circumscribed by the
surface of the sphere of activity whose centre is the point of con-
tact and radius A, must be exceedingly small compared to K.

The above equation cannot be generally integrated; but in
the case in which it belongs to a surface of revolution the axis
of which is vertical, as, for instance, when the capillary tube is
cylindrical with a circular base, an integral is obtained which

REPORT ON CAPILLARY ATTRACTION, 265

conducts to the inference, that the surface of the fluid approaches
so much the nearer to that of a sphere as the diameter of the
tube is smaller. Hence it immediately follows that the surfaces
in tubes of different small diameters will be similar portions of
spherical surfaces, if at their juncture with the interior surfaces
of the tubes they make with them the same angle. This angle
will appear to be independent of the diameter of the tube, from
the consideration that the extent of the sphere of activity of the
attraction of the tube is altogether imperceptible ; so that even
in a tube of very small bore, we may regard the action of the
cylindrical surface on the superficial fiuid elements contiguous
to it, the same as if it werea plane*. Hence if / = the radius
of the fluid surface, and / its mean altitude above the horizon-

tal level of the exterior fluid, then R = R! = b, and - =goh.

But in different tubes the surfaces of the fluid being similar seg-
ments of spherical surfaces, b evidently varies as the diameter
of the tube. Therefore 4 varies inversely as this diameter.
Such is the explanation according to Laplace’s theory of what
may be looked upon as the principal phenomenon of capillary
attraction.

If the surface of the interior fluid were convex, as it is known
to be when a capillary glass tube is dipped in mercury, then if
we suppose for a moment all below the tangent plane at any
_ point to be fluid, the effect of the attraction on a canal terminat-

ing at this point perpendicularly to the surface, will only be
_ just equal to the action of the fluid on the other extremity,
where it terminates at the exterior horizontal level. If now we
- subtract the fluid between the tangent plane and the surface,
which tends to draw the canal wpwards, the resulting inequality
of action must be counterbalanced by the hydrostatic pressure
arising from a depression of the fluid in the tube. The mean
depth to which the fluid will be depressed may be shown, as in
the case of concavity, to vary inversely as the diameter of the
tube.
- From all this reasoning Laplace concludes that the attraction
of capillary tubes influences the elevation or depression of the
fluids they inclose, only by determining the inclination of the
- fluid surface to the contiguous surface of the tube, on which in-
clination the concavity or convexity ofthe fluid surface depends,
as well as the magnitude of its radius. He consequently speaks

_. * M. Gauss, who first remarked that the reason here assigned by Laplace
for the constancy of the angle of contact is vague and insufficient, has given a
More satisfactory demonstration, which we shall have occasion to speak of in a
subsequent part of the Report. se

264 FOURTH REPORT—1834.

of the concavity or convexity as the principal cause of the phee-
nomenon of elevation or depression, a mode of speaking to
which some have objected apparently because it does not expli-
citly point to the nature of the forces to which the observed ef-
fects are due. This manner, however, of referring capillary ef-
fects to the concavity or convexity of the fluid surface, is con-
venient in the explanation of phenomena; for we may say in
general, that wherever the fluid is bounded by a curve surface,
it is aeted upon at each point by a force tending from the surface
towards the centres of the curvature at that point.

In this way Laplace explains the well known fact, that a drop
of water put in a slender conical tube, having both ends open
and its axis horizontal, will move towards the smaller end. The
surface of the drop will be concave towards both ends of the
tube, but with a greater curvature on the side directed to the
smaller end than on the other. The drop will therefore be urged
by two forces in opposite directions ; but the forces being pro-
portional to the curvatures, the greater force will be that which
urges it towards the vertex of the cone. Ifa drop of mercury
were inserted, its surface would be convex towards both ends
of the tube, and the greater curvature would again be at that
part of the drop which is nearer the smaller end. Therefore, of
the two forces directed from the curved surfaces to the centres
of curvature, that will prevail which urges the drop towards the
base of the cone. It follows from the constancy of the angle of
contact, that the surfaces of the two ends of the drop, whether
it be of mercury or water, are similar segments of spherical sur-
faces. Their curvatures are therefore inversely as their distances
from the vertex of the cone; and the difference of the curvatures,
to which the difference of the forces which urges the drop is pro-
portional, will vary inversely as the product of these distances,
if the length of the column into which the drop is formed be
given, that is, this length being small, nearly as the square of
the distance inversely of the middle of the drop from the vertex
of the cone. ;

As the fundamental equation obtained above admits of being
successfully treated whenever the surface of the fluid contained
in a capillary space is one of revolution, it may be employed to
determine the capillary action which takes place between two

cylindrical surfaces having a common axis and distant from each

other by a small interval; for the surface of the inclosed fluid
will evidently be in this case a surface of revolution. The re-
sult of the analytical calculation is, that the fluid will be raised in
this space to the same height as in a tube of which the radius is
equal to the interval between the cylindrical surfaces. If the

REPORT ON CAPILLARY ATTRACTION. 265

radii of the two cylinders be supposed infinitely great, we have
the case of fluid inclosed between two vertical and parallel planes
very near each other. The same result still holds good ; and thus
the experimental fact cited by Newton in his 31st query re-
ceives a theoretical explanation. 3
The case in which the fluid is raised or depressed between
vertical parallel planes admits of being treated independently ;
and this Laplace has also done. The upper surface of the raised
or depressed fluid is that of a common cylinder when the interval
between the planes is small, and the elevation or depression is
directly proportional to the curvature.
These propositions being proved with respect to the action of
“parallel planes, we may apply to the case of a drop inserted be-
tween two planes inclined to each other at a very small angle,
reasoning analogous to that applied to a drop inserted into a
cone of small vertical angle. The force by which the drop is
urged, is shown, as before, to be inversely proportional to the
square of the distance from the juncture of the planes. We
have already mentioned that this law was obtained experimen+
tally by Hauksbee for the case in which a drop of water is in-
serted between planes. He arrived at it by observing the incli-
nation the planes must have to the horizon, that the effect of
gravity may just counteract the capillary action by which the
drop of water is drawn to the line of their junction. The sine
of the inclination, to which the resolved part of gravity is pro-
portional, was found to vary for the same drop when in equili-
brium, inversely as the square of the distance of its middle point
from the line of junction. Laplace’s calculation, besides verify-
ing this experimental result, further informs us, that if the two
planes form with each other an angle equal to half the vertical
angle of a cone which incloses a drop of the same fluid, the in-
clination to the horizon of the plane which bisects the angle
formed by the two planes ought to be the same as that of the
axis of the cone, in order that the drop may remain in equili-
brium ; and-that “ the sine of the inclination of the axis of the
cone to the horizon, is nearly equal to a fraction whose deno-
minator is the distance of the middle of the drop from the vertex
of the cone, and numerator is the height to which the fluid is
raised in a cylindrical tube, the diameter of which is equal to that
of the cone at the middle of the drop.”
If fluid be raised by capillary action between two vertical and
parallel planes, they will be drawn towards each other. The
Same thing will happen if the fluid be depressed between them.
These two facts, known by experience, were in a great measure
explained, as we have seen, by Monge. The theory of Laplace

266 FOURTH REPORT—1834.

not only accounts for the attraction of the planes towards each
other, but gives the measure also of the pressures which urge
them. By an exact consideration of all the forces concerned in
these phenomena, he finds that when the fluid is raised between
the planes, each plane experiences, from without to within, a
pressure equal to that of a column of the contained fluid, of
which the height is half the sum of the elevations above the or-
dinary level, of the points of contact of the interior and exterior
surfaces of the fluid with the plane, and whose base is the part
of the plane comprised between two horizontal lines drawn
through these points. The value of the pressure is similarly
stated when the fluid is depressed between the planes. Hence,
neglecting the small exterior elevation or depression, the pres-
sure varies as the sguare of the elevation or depression between
the planes, and consequently inversely as the square of the in-
terval between them. |

Laplace also enters into a consideration of the proposition
first announced by Clairaut, viz. that if the law of the attraction
of the matter of the tube upon the fluid, differs only by its in-
tensity from the law of the attraction of the fluid on itself, the
fluid will be raised so long as the intensity of the former of these
attractions surpasses the half of the intensity of the other. He
arrives at the following conclusions*. If the one intensity be
exactly half the other, there is neither elevation nor depression,
If the intensity of the attraction of the tube for the fluid be in-
sensible, the fluid will be depressed, and the depressed surface
will be convex and hemispherical. If the two intensities be
equal, the surface of the elevated fluid will be concave and hemi-
spherical. When the intensity of the attraction of the tube is
the greater of the two, the fluid, by attaching itself to the tube,
forms an interior tube to which alone the capillary elevation is
due, and which being of the same matter as the raised fluid, acts
with the same intensity, and causes the surface to be still con-
cave and that of a hemisphere. This appears to be the case with
water and oils in capillary glass tubes. M. Hauy found by ex-

* These conclusions appear to be correct, but the reasoning of Laplace in
this part*of his theory is liable to a serious objection, first pointed out by
Dr. Young. For in art. 12, he obtains the following equation,

Q cos (x — 6) = (2¢’—e) Ksin 4,

in which ¢ and ¢ are respectively proportional to the intensities of the attrac-
tion of the solid for the fluid, and the fluid for itself; 2 @ K is equal to the re-
sultant of the molecular attractions on a superficial particle of all the fluid
particles within the sphere of its activity; but ¢ the resultant of the attractions
of only a portion included between a tangent plane and surface passing through
the particle. This equation, therefore, could scarcely be true unless 2 9’ =e.
The source of the error that occurs here will be elucidated as we go on.

REPORT ON CAPILLARY ATTRACTION. 267

periment that the concave surface of these fluids differed little
from that of a hemisphere*. It would seem from this theory that
the intensity of the solid’s attraction for the fluid must exceed
that of the fluid for itself, in order that the fluid may wet the
solid. da :

The preceding are the principal facts which Laplace explains
in his first published Treatise on Capillary Action. The expla-
nations of some few others are added by way of corollaries at the
end of the Treatise. One of these, which serves to exhibit the
effect of the convexity of the fluid surfaces, may be mentioned
heres} 25
_ If acapillary tube be plunged to a small depth in water, and
then, with its lower extremity closed by the finger, be taken out,
on withdrawing the finger the fluid will be seen to sink in the
tube, and.to form a drop at the lower end. But when it has
ceased to descend, the height at which it rests above the extre-
mity of the tube is always greater than the elevation due to ca-
pillary action when the tube is just dipped in the fluid: The
reason of this excess is, that the effect of the convexity of the
drop, which takes place in the upward direction, is added to the

_ effect of the concave surface within the tube.

' Hence it follows that if a slender siphon with unequal arms
be filled with water, when the fluid is just on the point of run-
ning. from the longer arm it has to overcome the capillary
actions due to the concavity formed at the extremity of the
shorter arm and the convexity at that of the longer arm; and
unless the difference of the,lengths of the arms be greater than

_ the sum of the lengths of the finid columns which these two
_ actions will sustain at the respective extremities, the fluid will
_ The theory of Dr. Young respecting the phenomena of capil-
lary tubes is contained in an “‘ Essay on the Cohesion of Fluidst,”’
read before the Royal Society, December 20, 1804, and inserted
in the second. volume of his Lectwres on Natural Philosophy.

His views resemble those advanced by Segner and Monge,
Like these two mathematicians, he considers the phenomena to
be referable to the cohesive attraction of the superficial particles

_ of the fluids, in so far as it gives rise to a uniform tension of

- * Tt would be difficult to decide by experiment whether the surface be nearly
or exactly a hemisphere, because when the angle of contact is very small, the
Bpoeticantect is not readily discernible. The method of determining the angle
of contact by reflection, proposed by Dr. Young in his Lectures on Natural

“¢ ilosophy, (vol. ii. p. 666,) is preferable to measuring the sagitta of the sur-

face, which was the method adopted by Haiiy.
¢ Philosophical Transactions, 1805, p. 65.

268 FOURTH REPORT—1834.

the surface. He shows, moreover, how this uniformity of ten-
sion may be a consequence of ulterior principles.

The course of reasoning Dr. Young pursues in his essay is as
follows. He begins with making two assumptions: first, that
the tension of the fluid surface is uniform; secondly, that at the
juncture of a fluid surface with the surface of a solid, there is an
appropriate angle of contact between the two surfaces.“ This
angle,” he says, “‘ for glass and water, and in all cases where a
solid is perfectly wetted by a fluid, is evanescent: for glass and
mercury, it is about 140° for common temperatures, and when
the mercury is moderately clean.”” He shows next that a theory
founded on these two hypotheses will explain various capillary
phenomena. And lastly, at the end of the essay, derives the hy-
potheses from ulterior physical principles. It is in this last
part that Dr. Young’s theory contains views not to be found in
any previous theory. Following the order which the author
adopts, I will endeavour first to exhibit the way in which his
theory accounts for phenomena.

It is known from mechanical principles that if a curve line
be uniformly stretched, the normal force it exerts at any point
in a direction tending to the centre of curvature is directly as
the curvature. The same will be the case with a surface, if it
be cylindrical, and therefore curved only in one direction. If
the surface be spherical or like that about the vertex of an ellip-
tic paraboloid, the curvatures in directions at right angles to
each other will have independent effects. Consequently the
normal force in this case will vary as the sum of the curvatures:
and as, from a known property of curve surfaces, this sum is the
same for all perpendicular directions, the normal force will be pro-
portional to the sum of the greatest and least curvatures. Hence
because this force, applied at the surface, is employed in de-
pressing the fluid when the surface is convex, and elevating it
when concave, (for it is always directed to the centres of curva-
ture,) it may be shown in the usual manner, that by reason of
the action of gravity, the force at each point is proportional to
the distance of that point from the ordinary level of the fluid.
By reasoning of this kind, Dr. Young is conducted to the rela-
tion between the vertical ordinate and curvature of the surface,
which is expressed by the fundamental equation of Laplace’s
theory. As both theories also admit the constancy of the angle
made by the fluid surface with that of a given solid at the junc-
ture of the two, it is plain that the explanation of phenomena
must be virtually the same in both. In fact, before the publi-
cation of Laplace’s theory Dr. Young had accounted for most of

REPORT ON CAPILLARY ATFRACTION. 269

the facts whose explanations according to that theory have al-
ready been exhibited, and his mode of accounting for them dif-
fers not in any essential respect from that of Laplace, but chiefly
in a scrupulous avoidance of the use of mathematical symbols.
It will therefore be unnecessary to adduce the explanations of
any of these facts given by Dr. Young; we will only advert to
some applications contained in his treatise which do not occur
in the other.
_ Having first considered the rise of water in capillary tubes,
he proceeds to find the weight of water raised by the horizontal
surface of a solid elevated from the horizontal surface of a fluid,
and to determine the relation between the height of ascent in a
given tube to the height of adhesion; that is, the height of ele-
vation above the ordinary level just when the fluid detaches it-
self from the horizontal surface of the solid. The fluid is
supposed to wet the solid. Hence as the fluid surface, being
horizontal where it is in contact with the solid, has no tendency
by its tension to depress, the weight of water raised is very
nearly equal to the hydrostatic pressure of a column of water
standing on the raising surface and equal in height to the height
of adhesion. This pressure he finds to be 50} grains on a square
inch, agreeing very nearly with the result of experiments by
Taylor. If the raising surface be small, for instance a disc of
an inch in diameter, the curvature of the horizontal sections of
the raised fluid, which are convex outwards, will have a con-
trary effect to the curvature of the vertical sections which are
concave, and will consequently diminish the weight of fluid
raised. This also is confirmed by experiment. ‘ The height
of ascent in a tube of given bore varies in the duplicate ratio of
the height of adhesion.”
_ Thedepression of mercury in capillary tubes is next considered,
and the author does not confine himself to the case in which the
face of the mercury is spherical, which is true only when the
ameter of the tube is very small. In tubes less than half an
inch in diameter, the surface is very nearly that of an oblate
spheroid. The depressions for different tubes calculated theo-
pally, are compared with a table of experiments made by
Lord Charles Cavendish to ascertain the depression of mercury
in different barometer tubes. ssid 6b) 204
_ The height of adhesion of mercury to glass, and to substances
which it is capable of wetting, such as gold, silver, tin, &c., as
well as the thickness at which a portion of mercury will spread
out on glass and on substances wholly incapable of attracting it,
are quantities all determinable by this theory, and being cal-

270 FOURTH REPORT—1834.

culated are found to be sufficiently accordant with the same
quantities determined experimentally.

The theory conducts also to the following réesult : ‘The linear
dimensions of similar drops of different fluids depending from
a horizontal surface vary in the same ratio as the heights of
ascent of the respective fluids against a vertical surface, or as
the square roots of ascent in a given tube.”

In explaining the instances of apparent attractions ‘and re-
pulsions treated of by Monge, Dr. Young shows that in the two
cases of attraction, the force which urges the planes towards
each other varies inversely as the square of the interval between
them, because it varies once inversely as the distance on account
of the increase of curvature of the fluid surface as the interval
diminishes, and again inversely as the distance by reason of the
increase, proportional to the ascent of the fluid, of the surface on
which the capillary action is exerted. With respect to the
third case, that of repulsion, which is omitted in Laplace’s
treatise, he remarks, that ‘‘ the repulsion of a wet and dry body
does not appear to follow the same proportion, for it by no
means approaches to infinity on the supposition of perfect con-
tact : its maximum is measured by half the sum of the elevation
and depression on the remote sides of the substances, and as the
distance increases, this maximum is only diminished by a quan-
tity which is initially as the square of the distance.”

The strong cohesion of two solids produced by the interposi-
tion of a small quantity of a fluid, which wets them, between
their plane surfaces, is sufficiently accounted for by the great
curvature, arising from the proximity of the surfaces, of the
outer boundary of the interposed fluid, which is everywhere con-
cave like the rim of a pulley. This curvature corresponds to a
force which would be capable of sustaining a great elevation of
the fluid; but in this instance the force is not exerted in sup-
porting the fluid, but acts by reason of the mutual attraction
between the solid and fluid, on the plane surfaces of the’ solids,
drawing them together. If the solids were wholly immersed in
the fluid, no such cohesion would take place. On the same’prin=
ciple, if fluid be interposed between two solids which it is quite
incapable of wetting, so that its boundary is everywhere convex,
the force due to the convexity, being directed inwards, would
present a strong opposition to any force tending to make the
planes approach each other.

After showing, in the manner exhibited above, that a theory
founded on the two assumptions of a uniform tension of curved
fluid surfaces, and a constant angle of contact of the surface of

REPORT ON CAPILLARY ATTRACTION. 2a71

a given fluid with that of a given solid, will explain various ca-
pillary phenomena, Dr. Young proceeds to derive these laws
from ulterior physical principles. To account for the first he
reasons as follows. The repulsive force which appears to act
uncontrolled in aeriform bodies, exists also in fluids and solids.
In these it is counteracted by a cohesive force. These forces in
fluids are so balanced, that they allow the particles to move freely
in all directions. In solids the cohesion is accompanied by a
force opposed in greater or less degree to all lateral motion, and
independent, as he supposes, of the cohesive force. He considers
it simplest to regard the cohesive force as nearly or perfectly con-
stant in its magnitude throughout the minute distance to which
it extends, and its apparent variation to be owing to the variation
of the repulsive force, which diminishes with the increase of the
distance. In the internal parts of a fluid, the two forces hold
the particles in equilibrium ; but wherever ‘the surface is curved
or angular, it would be found by collecting the effect produced
on a given particle at the surface, by all the particles contiguous
to it and lying within the sphere of its proper activity, that on
the above hypothesis respecting the relative variation of these
forces, the cohesion must necessarily prevail over the repulsion.
The particle will consequently be urged in the normal direction
towards the centres of curvature of the point at which it is situ-
ated, whether the surface be concave or convex ; and reasons are
adduced by the author for concluding that the force which urges
itis proportional to the curvature, if single, or to the sum of
the curvatures in rectangular directions, and consequently indi-
cates, as is known from Mechanics, a uniform superficial ten-
sion. The reasoning by which he shows this need not be in-
_ troduced here. Suffice it to say, that this result might be obtained
_ by an analysis precisely the same as that which Laplace has
employed at the beginning of his capillary theory, in calculating
_ the attraction experienced by a superficial particle on the suppo-
- Sition of forces sensible only at insensible distances. Laplace
makes no hypothesis respecting the law of force, excepting that
it i is wholly attractive. The mathematical calculation would
remain the same, if the forcé were supposed partly attractive
_and partly repulsive, provided the attractive force decreased less
_Tapidly with the increase of distance than the repulsive, and be-
came the greater of the two before it ceased to be of sensible
_ magnitude. With this alteration* in Laplace’s theory, it would
re.
_ * This modification of the theory is pointed out by its author in a note at
' p. 122 of the Bulletin de la Société Philomatique, An 1819.

272 FOURTH REPORT—1834.

differ in no essential respect from that of Dr. Young, as far as
regards the principles on which the equation relative to the ca-
pillary fluid surface is obtained; and neither possesses an advan-
tage over the other in the explanation of phenomena. But the
way in which the latter mathematician accounts on physical
principles for the constancy of the angle of contact, (which is
the other hypothesis of his theory,) though incomplete, is more
satisfactory than anything we meet with on the same subject
in Laplace’s treatise. The following is his reasoning on this
oint.
. When the surface of a fluid is free, or exposed to a gas, the
superficial tension arising from the cohesive power of the par-
ticles acts with full force to produce pressure directed inwards,
from which, in fact, arises the tendency observable in small
fluid masses to assumeaglobular form. This contractile power
is altered by contact with a solid surface. For instance, if a
cube of water had one of its halves congealed, its other proper-
ties remaining the same, the other half would retain its form,
because the tendency to contract at the edges contiguous to the
solid, would be just counteracted by an equal and contrary action
of the solid; and at all other points of contact, the contractile
force would vanish for the same reason as at any point in the
interior of the fluid. If the solid were of smaller attractive
power than the fluid, the tendency to contract, and consequently
the tension of the surface in contact, would be proportional only
to the difference of the attractive forces, or to the difference of
the densities of the solid and fluid, if the law of the forces be the
same for both*. The portion of the solid surface which is con-
tiguous to, but not touched by, the fluid, will act on the fluid par-
ticles situated at the angle of contact, just as the fluid superficies
itself does, but in a different degree according to the difference
of density. Hence, the conditions of equilibrium are to be sought
of three forces acting on a particle at the angle of contact, one
in the direction of the surface of the fluid only, another in that
of the common surface of the fluid and solid, and the third in
the opposite direction along the exposed surface of the solid. If
ge and ¢! be the densities respectively of the fluid and solid, and
the first force be kg, the second will be & (g — ¢!), and the third
kg'. If then 6 be the angle of contact which the free surface of
the fluid makes with its surface of contact, the first force re-

-* Dr. Young adduces some facts relating to the spreading of the drops of oil
on water in support of the proportion here assigned. (Lectures on Nat. Phil.,
vol. ii. p. 659.) ;

REPORT ON CAPILLARY ATTRACTION. 273

solved in the direction of the solid surface, will give ke cos 6,
which is counteracted by ke’ — k(g —@’), the difference of the
other two forces. Hence is follows that

6
eS 8
ee COS

When 6 = 90°, 2¢!=e, as Clairaut found. The preceding
theory is deficient in not: informing us how the other resolved
portion of the tension of the fluid, viz. & y sin @, is counteracted.
The essay of Dr. Young, as it appears in the second volume
of his Natural Philosophy, contains by way of appendix some
remarks and strictures on Laplace’s theory, the results of which
are shown to be readily derivable from his own theory; but an
objection is raised against its principles on the ground that no
account is taken of a repulsive molecular force. We have al-
ready seen in what way this objection may be-obviated without
affecting the results of Laplace’s theory, or materially altering
the analysis. Another objection urged by him, to which allusion
has been made before (p. 266), lies against the reasoning, and. not
the principles, of Laplace’s theory. In determining the conditions
of equilibrium of a fluid particle situated at the angle of contact,
Laplace takes account only of the attractions of the solid and
fluid upon it, omitting the consideration of the variation of pres-
_ sure occasioned by these forces.as well near the free surface of
the fluid as near that in contact with the solid. The error to
which this omission leads will be understood by reverting to
the reasoning by which.it was shown (p. 258), according to Clai-
raut’s method, that when the attractive force of the fluid is double.
that of the solid, the capillary surface will be horizontal. The
same kind of reasoning as that employed to show that the hori-
zontal attractions in this case counterbalance each other, would
ilso prove that the. particle at the angle of contact is urged ver-
i cally downwards, by only half the force with which another
particle at the fluid surface situated beyond the sphere of the
ataction of the solid, is urged in the same direction. The
horizontality of the fluid surface may nevertheless be maintained
if we consider that the variation of pressure near the surface,
ae to the molecular attractions, will not be the same at the sur-
face in contact with the solid as at the free surface, by reason of
he solid’s attraction. Had Laplace taken account of this cir-
cumstance, as the principles of his theory required him to do,
notwithstanding the supposition of incompressibility, he would
pk obtained an equation equivalent to that which expresses
above the relation between 9g! and @, instead of the faulty equation
of art. 12 of his treatise. In fact, M. Gauss and M. Poisson, as
1834. T

Q74 FOURTH REPORT—1834.

we shall afterwards see, have obtained in different manners such
an equation on the supposition of absolute incompressibility.
The addition to Dr. Young’s essay contains also a more care-
ful investigation than he had given before of the depression of
mercury by capillarity in barometer tubes of diameters not ex-
ceeding half an inch. He obtains two formule, one for the
central depression, the other for the difference between the cen-
tral and marginal depressions. The diameter in inches being d,

> 015 d
and e beiug put for 416
the first formula is por = = e—14.5e,
5d + 100 d?

and the other, 15 6d + 100d) +18

The next work that we have to notice is Laplace’s Spple-
ment to the Theory of Capillary Action, in which the object
of the author is to perfect the theory and extend its applications,
to confirm it by additional comparisons with experiments, and
to present it under a new point of view. This work is prefaced
by a discussion relative to the fundamental equation of the
theory, which is shown to be derivable as well from the condi-
tion of the perpendicularity of the resultant of the forces to the
fluid surface as from that of the equilibrium of canals, the equa-
tion obtained by the former method being the differential of
that given by the other. Here also is deduced, from the funda-
mental equation, an expression for the weight cf fluid raised in
a cylindrical tube, the transverse section of which is any con-
tinuous and reentering curve. If ¢ be the contour of the ho-
rizontal section of the tube, H and g the same as in the fun-
damental equation, and § the angle of contact as before, the

H
weight of the fluid column is found to be = cos § It is to

be observed that this result is obtained by assuming the angle
of contact to be constant for the same solid and fluid, of which
law Laplace has failed to give a satisfactory proof.

After these preliminaries, the author proceeds to consider
capillary action in a manner different from that of his former
treatise *. It may be proper to remark that the subject admits
of this other method of treatment for the same reason that in

* In the observations with which the Supplement concludes, the author re-.
marks that this second method resembles that of Jurin, while the other may be
classed with the method of Segner and Young; and that the reasoning by
which Jurin proved the elevation in a capillary tube to be inversely as the dia-
meter, is correct when the tube is completely wetted by the fluid, and when in

REPORT ON CAPILLARY ATTRACTION. 275

common statical problems there are two kinds of equations of
equilibrium, those in which pressures and tensions are involved,
and those which result when forces of this kind are eliminated.
The force corresponding to the convexity or concavity of the
fluid surface in capillary tubes is of the nature of a tension, and
may be kept out of view in finding the conditions of the equi-
librium of the forces which suspend or depress the fluid column.
For this purpose it will be necessary to pay regard only to the
action of the tube on the parts of the fluid contiguous to it, and
to the action exerted on the raised or depressed column con-
tained within the tube by the rest of the fluid. The former, as
Laplace shows, resolves itself into the attraction of a ring of the
tube immediately above the extreme upper edge of the fluid,
and an equal attraction of a like ring at the lower extremity of
the tube; and the latter, into the attraction of the upper ex-
tremity of a tube of the fluid, supposed to be a continuation of
the solid tube, and attracting with the proper action of the fluid
on itself. . The first two forces tend to raise the fluid, the other
to depress it. If the total upward force be called 2q'gc, and the
downward force gec, both being proportional to c the contour,
it will hence appear that (2 q' — q) ec = the weight of fluid raised.
If 2q' = q, there is no elevation; a result which, as we know,
may be obtained in a very different manner.
The preceding expression for the weight of the elevated
column being equated to that previously obtained, gives

y 2q' — 4 = 500s 4.
- Now it is shown satisfactorilyin the former treatise*, that when
q =9q,4=0: so thatg = = This equality is also proved

by Laplace in an independent manner. It hence follows that
2

we

po >> which equation, if g' and qg be assumed to be in

i]

the proportion of the densities of the sold and fluid, is the same
as that first obtained by Dr. Young.

consequence the elevated column may be conceived to be contained in an
aqueous tube. Leslie, in a paper containing some original and ingenious views
on Capillary Attraction, (Phil. Mag., vol. xiv. 1802, p..193,) objects to the
principle of Jurin’s explanation, and attributes the rise of the fluid solely to its
perpendicular pressure against the surface of the tube occasioned by the tube’s
attraction. By this consideration he finds the height to be inversely as the dia-
meter. No doubt, as Leslie appears to have first observed, the rise is depen-
dent on a particular state of pressure at the surface of contact of the solid and
fluid, and according as this is greater or less than a certain pressure, there will
be a rise or depression.
* Art. 12. p. 48.
T 2

276 FOURTH REPORT—1834.

As it appears that the weight of the elevated column varies as
the periphery of the transverse section of the tube ; and as, for
tubes of like peripheries, the weights are as the products of the
heights and the squares of homologous lines, it follows that the
heights are inversely as homologous lines. This proportion,
says Laplace, is true also if the contour be not continuous, but
of the form, for instance, ofa rectilinear polygon ; for the error
that would be occasioned by the angles of the.polygon would
be of insensible magnitude, by reason of the small extent of
the sphere of activity of the particles. Gellert. has made some
experiments on the elevation of water in glass prismatic tubes,
with rectangular and triangular bases *. They confirm the law
according to which the heights are inversely as the homologous
lines of like bases. He thinks also that the elevation is the same
for a rectangular as for an equal triangular base ; but the experi-
ments do not appear to be decisive of this point. Laplace calcu-
lates theoretically that the difference would be one eighth be-
tween the elevations in a prism with a square base, and in one
whose base is an equilateral triangle of equal area.

One of the most interesting of the questions considered by
Laplace in the Supplement, relates to the capillary action
which takes place when two or more fluids are contained in the
same tube. Suppose a prismatic tube to be plunged vertically
in a vessel containing any number of fluids lying horizontally
one above another; then “ the excess of the weight of the
fluids contained in the tube above the weight it would have con-
tained without capillary action, is equal to the weight of fluid
which would have been raised above the exterior level, in case
the vessel contained only that fluid in which the lower extremity
of the tube is immersed.”’ For, in fact, the action of the prism
and of this fluid on the column of it in the tube, is plainly the
same asin this case, the action of the tube on each of the other
fluids being equal in opposite directions, and the mutual action
of the fluids being destroyed just as if they were supposed to
form a solid mass. The surface of the uppermost fluid is the
same as if that alone were in the tube.

When only two fluids are contained in a cylindrical tube, the
theory determines the common surface of their junction to be
spherical, and gives for the angle of contactt of this surface a

* Memoirs of the Academy of Petersburgh, vol. xii. p. 302. :

+ It ought to be observed that the angle which is here and elsewhere called
the angle of contact is, strictly speaking, not the angle which the fluid surface
makes with the surface of the solid at the points of their junction, but the angle
which a tangent plane to the surface of the fluid at the limit of the sphere of
activity of the solid’s attraction makes with the surface of the solid.

REPORT ON CAPILLARY ATTRACTION. a i |

formula involving the angles of contact proper to the fluids when
separately contained in the tube.

» When water and mercury are put in the same cylindrical glass
tube, and the water completely wets the tube, the mercury may
be considered to be contained in an aqueous tube, the action of
which on the mercury being small, the angle of contact is nearly
¥80° instead of 136°°8, which, according to Laplace, is that be-
tween glass and mercury. This result, which is also deduced
from the above-mentioned formula, is confirmed by the observa-
tions of Gay-Lussac. Another deduction from the theory also
receives confirmation from the same eminent experimenter, viz.
that mercury is less depressed in a capillary tube when its upper
surface is covered with a small portion of water, than when
covered by alcohol. For the capillary action of water on itself
exceeds that of alcohol on itself, and would therefore be likely
to have a greater action than alcohol on mercury.

Various other interesting results, which it would be long to
enumerate here, are readily deduced by the method of cousider-
ing capillary effects exhibited by the author in his Swpple-
ment. This method, in some applications, leads to results
more rapidly than that of the Zreatise; while at the same
time the latter has advantages peculiar to itself in all questions
relating tothe surfaces of fluid inclosed in capillary spaces, or
subject in any way to capillary action. Three such questions,
which had been either omitted or partially treated in the first
work, are handled at considerable length in the Supplement ;
and it will be proper now to advert to their solutions. These
problems, which for the most part had previously engaged the
attention of Dr. Young, are: (1.) The apparent attraction and
repulsion of small bodies swimming on the surfaces of fluids.
(2.) The adhesion of discs to the surfaces of fluids. (3.) The
gute of a large drop of mercury, and the depression of mercury

in a glass tube of a large diameter.

iY) By considering generally the capillary action between
fio vertical and parallel planes of different matters plunged with
the lower extremities in the same fluid, the following theorem
is obtained: Whatever be the substances of which the planes
are formed, the tendency of each towards the other is equal to
the weight of a fluid prism whose height is the difference of ele-
vation of the extreme points of contact of the fluid on the oppo-
site sides of the plane, whose depth is half the sum of these
elevations, and breadth, that of the planes. The elevation is to
be taken negatively when it changes into a depression; and if
the product of these three dimensions be negative, the apparent
attraction of the planes becomes a repulsion. These tendencies

278 FOURTH REPORT—1834. |

are shown to be the same for the two planes, and their actions
on each other by the intervention of the fluid to be equal and
opposite. The theory leads to the singular result that the re-
pulsion will change into attraction by making the planes ap-
proach very near each other, and experiments by M. Haiiy show
that such is the fact. ;

_ (2.) When a disc is applied to the surface of standing water,
on being raised it draws, by capillary action, a portion of the
fluid with it, which detaches itself when the disc is raised above
a certain elevation. At this limit the suspending force must
plainly be equal to the weight of the disc and of the portion of
fluid raised above the horizontal level of the water. As this force
may be accurately determined by experiment, we are furnished
with means of putting the theory to a test, because the surface,
and consequently the volume of the raised column, can be found
from the fundamental equation of the theory. When the calcu-
lation is made, the expression for the volume involves a quantity

which Laplace calls es , and which is, in fact, the same as as.
a

Now, as was said above, the weight of fluid raised in a capillary

tube is a © cos 6, or ihe © if the fluid perfectly wets the tube ;

-~ ~_

and this weight in a cylindrical tube is also equal to }. 7 c hg e, if r
be the radius of the cylinder, and / the mean elevation of the fluid ;

2H y j
so that —_ = 27 h = diameter of the tube x mean elevation of

the fluid * If, then, the diameter of a cylindrical capillary tube,
and the elevation in it of a fluid which perfectly wets it, be ob-

served, the value of : for that fluid is found experimentally. The

following numerical values of are deduced by Laplace from

the experiments of Gay-Lussac, after correcting for the tempe-
rature +, which was 8°°5 of the centigrade thermometer, and for
the difference of one sixth of the diameter between the mean
elevation, and the observed elevation of the lowest point of the

* This equality is also readily deduced from the fundamental equation.

+ ‘*‘ The elevation of a fluid which wets completely the sides of a capillary
tube is, at different temperatures, in the direct ratio of the density of the fluid,
and in the inverse ratio of the interior diameter of the tube.”” This is shown at
p- 388 of the Supplement. An increase of temperature diminishes the elevation
both by diminishing the density of the fluid and increasing the capacity of the
tube. Admitting that H varies as g, it will be seen from the equation above

that h varies as =

REPORT ON CAPILLARY ATTRACTION. 279

surface. The diameter of the tube was in each case 1™!*29441.*,
or in English measure, ‘05096 of an inch.

2 Mi.mi. Sq. Inch.

For water, .... . Z = 302621 = -0469

For alcohol, sp. she
ST dy alana ip
For oil of turpentine,| 2 ©
sp. gr. “86946, : 12 ee ee
By means of these values the weights of the columns of fluid
raised by a disc of white glass, 118™:366, or 4°66 inches
in diameter, just when the fluid detaches itself from the disc,
are determined by the theory to be respectively

= 121649 = ‘0188

Grammes. Grammes. Grammes.
J 59°5873 31°1435 34°350,
and the experimental determinations + are,
Grammes. Grammes. Grammes.
59°40 31°08 34°104.

- The nearness of these to the theoretical results not only con-
firms the theory, but shows also the correctness of the values

of sa deduced from the experiments on capillary tubes. Dif-
ferent experimenters { have determined differently the heights of

_* The ™- attached stands for millimetre, and ™i-™i- for square millimetre.

+ These weights expressed in English grains are respectively 917°14,
479°87, and 526:56, which being divided by the number of square inches in
the surface of the disc, give 532 grains corresponding to each square inch for
water, 28 grains for alcohol, and 31 grains for oil of turpentine. Achard obtains
for water 393 grains, for alcohol 23:4 grains: Dutour finds 441 grains, and
25°6 grains. In the experiment of Taylor (Phil. Trans. 1721) on the attrac-
tion of wood to water, the raising force was 50 grains to each square inch.

+ The following Table is given in the Art. Carituary Attraction of the Edinb.
Eneyel.: the heights are reduced to a tube whose diameter is 01 of an inch.

Height ofthe} Height x

x water. diameter. cerns.
Inches. Sq. Inch.

21 0:021 Haiiy and Tremery.

2°6 0:026 Hallstrom.

3:27 0:0327 Dr. Brewster.
a 3°92 0:0392 Musschenbroek.
1 4:0 0-04 Average assumed by Dr. Young.
i 4-2 0-042 Monge.
bil 4:28 0:0428 Weitbrecht.
ent 4:6 0°046 — From Morveau’s experiments.
a: 4:8 0:048 Martin.

5:3 0:053 Atwood.

The experiments of Sir David Brewster were made with much care, and em-

280 FOURTH REPORT—1834.

elevation in glass tubes, probably by reason of different degrées
of humidity of the interior of the tubes. When the tubes were
well wetted, Gay-Lussac found the elevations to be always very
nearly the same in different experiments. . As the weights re-
quired to detach discs from fluid surfaces can be measured with
considerable precision, the accordance of the preceding experi-
mental and theoretical values serves to verify the experimental

2
values of —.
a

Equal discs of different substances perfectly wetted by a fluid,
ought to raise columns of the same weight, because the resist-
ance to the separation of the disc is, in each case, produced by
the adhesion of the fluid to itself, that is, to the stratum of fluid
that lines the inferior surface of the disc.

As the angle of contact of mercury with glass under water is
nearly 180°, a glass disc applied under water to the surface of
mercury would not be capable of drawing up any portion of
mercury on being raised from the surface.

These two conclusions from the theory have been confirmed
experimentally by Gay-Lussac.

(3.) The analytical calculation for determining the form of a
large drop of mercury serves also to find the depression of ‘this
fluid in aglass tube of large diameter. Gay-Lussac ascertained
by experiment that the height at which a large drop of mercury
stands on a horizontal plane of glass is 3™':378 (= °133 of
an inch), agreeing very nearly with the result of a like experi-
ment by Segner. The drop was circular and one decimetre, or
3°937 inches in diameter, and the temperature at 12°°8 of the
centigrade thermometer. To calculate the height theoretically,

Sade 2 -
it is necessary to know the value of — for mercury in a glass
a

tube, and its angle of contact with glass. Laplace takes for
the former 13 ™-™i, (= -0201 square inch), and for the latter,
152° ( = 136°8). These values, he says, are mean results ob-
tained by comparing several observed capillary phenomena with
the theory, and may be further rectified by more numerous ex-
periments. The height of a large drop of mercury given by the
theory by means of these data is 3™!-39664.

brace a great variety of fluids; but the tube does not appear to have been
moistened in its whole extent. The results are tabulated in the article above
referred to, as well as those from the experiments of Mr. B. Martin, which, for
the same fluids, uniformly give a higher value of the constant. The values of
the constant for alcohol and oil of turpentine, as found by Gay-Lussac, do not
differ materially from the determinations of others. Sir David Brewster finds for
alcohol ‘0178, for oil of turpentine -0187; Martin, for the same fluids, ‘018
and °022; Musschenbroek for alcohol -021,

REPORT ON CAPILLARY ATTRACTION. 281

-0Gay-Lussac also observed in @ large glass vessel, containing
mercury and having its sides vertical, the differen de Between
the extreme elev ation of the fluid and the elevation at the points
of contact with the sides of the vessel, und found it to be
1™+455'(= -057 in.). The theory gives 1™-432.

Laplace concludes his work with some general observations
réspecting the interior constitution of bodies, and the nature of
molecular forces. The viscosity of fluids, he remarks, is a dis-
turbing cause in capillary phenomena, which can be strictly ex-
plamed by the theory only when the condition of perfect fluidity
is fulfilled. To that cause and the friction against the sides of
the tube, he considers the differences between the elevations of
water in capillary tubes as determined by different observers, to
be attributable. With respect to the variation of pressure from
nothing to the quantity K, which according to the calculations of
the theory ought to take. place withina space extending from
the free surface of the fluid to a small depth below, Laplace
observes that it may be attended with a sensible variation of
density, and have a perceptible effect on capillary phenomena.
The modification that his theory must undergo if this circum-
stance be taken into account, has been fully discussed, as we shall
a, see, by M. Poisson.

There is a good exposition of the leading propositions of
Laplace’ $ theory by M. Petit in the Journal of the te Ae
nic School*,

~The work of M. Gauss, entitled Principia generale: Theorie
Fis igure Fluidorum in statu Aiquilibrit +}, has for its main object
the correction of the — already pointed out in Laplace’s
theory, with regard to the proof of the constancy of the angle
of contact. To form the equations of equilibrium, M. Gauss
employs the principle of virtual velocities, which he applies to
the whole mass of the fluid, and not, as Lagrange has done, to
a differential element. This elegant method, which has the pe-
culiar advantage of evolving at once the equation of the free
surface of the fluid, and that relative to the contour, conducts
to a sextuple integral, which extends to the whole mass, and
is to be a minimum. By supposing the fluid to be homogeneous

and ‘Incompressible, the integral becomes quadruple. Byfurther

pliers of activity of these attractions to be insensible, the
“ysuaed (W) to be a minimum, is found to be expressed by

Jfids + 2U + (@ — 26°) T,

* tom. ix. eah, xvi. p. 1. + Gottingen, 1830.

282 FOURTH REPORT—1834,.

in which the first term is equivalent to the volume of the con-
tained fluid multiplied by the vertical ordinate of its centre of
gravity, U is the area of its free surface, and a** a constant de-
pending on the intensity of the attraction of the fluid particles
for each other, T is the area of the solid surface with which the
fluid is in contact, and 6° a constant depending on the intensity
of the attraction to which the fluid is subject from the particles-
of the solid. By making ?W = 0, and inthe variation suppos-
ing U constant, it is readily found that the mean elevation in a
capillary tube varies inversely as its diameter. By again put-
ting 8W = 0, and making the free surface subject to variation,
M. Gauss arrives at two equations, one of which, relating to the
free surface, is the fundamental equation of Laplace’s theory,
andthe other, relative to the angle of contact,is equivalent to that
which Dr. Young obtained. It is not the object of the author to
trace the consequences to be derived from these equations in ex-
plaining phenomena, as this was satisfactorily done by Laplace. -

The first published ideas of M. Poisson on the theory of ca-
pillary action are contained in a memoir on the Equilibrium of
Fluids, read before the Paris Academy November 24, 18287.:
His object in this memoir is to form the equations of the equi-
librium of fluids on physical principles, that is, by considering
them as composed of distinct molecules, separated from one
- another by spaces void of ponderable matter. He commences
with the following preliminary notions.

The dimensions of the molecules and of the spaces between
them are so small, that a line which may be supposed a great
multiple of them is of insensible magnitude. The molecules at-
tract each other; at the same time they mutually repel by their
proper heat. For each of these forces the action is equal to the
reaction: both decrease with great rapidity as the distances in-
crease, and are sensible only at insensible distances. The radii
of activity of these forces are nevertheless supposed to be ex-
tremely great compared with the intervals between the molecules,
and the rapid decrease to commence only at distances which
are great multiples of these small intervals. Without this sup-
position, in bodies whose molecules are not regularly distributed,
the resultant of the molecular forces, that is, the total force
which acts on each molecule, might be very different in magni-
tude and direction for two consecutive molecules, and conse-
quently would not be subject to the law of continuity. It seems
necessary therefore to make the above supposition.

: ’ . 2
* 4a%in M. Gauss’s work is the same as the — of Laplace.
a

+ Mémoires de V Académie des Sciences, tom. ix. Paris 1830.

REPORT ON CAPILLARY ATTRACTION. 283

By molecular action M. Poisson understands the excess of
the repulsion above the attraction betweenthe molecules. This
force he supposes to be different for different points of the two
molecules. Its mean value he calls the principal force, and the
variation from this normal value according as different points of
the molecules are directed towards each other, the secondary
force. This latter plays an important part in solids, giving rise
to. their rigidity and resistance to the lateral motion of their
molecules. Its absence from fluids is the occasion of the per-
fect mobility of their particles. The characteristic of fluids that
distinguishes them from solids isthus stated: If a point. be
taken anywhere in the interior of a fluid mass, and a straight
line of insensible length but a great multiple of the mean inter-.
val between the molecules, be drawn in any direction from that
point, the mean interval between the molecules that lie on the
line is constant, though the particles may be irregularly dis-
posed along it. The constancy of this mean interval is consi-
dered to be owing to the absence of the secondary force above
mentioned, by reason of which the molecules can readily take
positions that satisfy this condition*. —

Setting out with these principles M. Poisson arrives at equa-
tions relative to the pressure in the interior of a fluid mass,
which are the same as those usually obtained on the supposition
of equality of pressure in all directions from any given point.
The reasoning by which these equations are deduced is not
immediately founded on any observed fact, and as it conducts to
the same equations as those deducible from the known law of

~ equal pressure, it may be said to account theoretically for the
existence of this law. ‘This is an instance of mathematics ap-
plied in the manner spoken of at the commencement of the
Report. The bases of the reasoning are hypotheses; and it
leads to the explanation of a known fact. It would not be right
to conclude from this one explanation that the hypotheses must
necessarily be true. They can be considered to be satisfactorily
established, only when they have been successfully employed in
accounting for all the facts that are known to depend on the in-
timate constitution of fluids, and when they are found to require
for this purpose no modification.

After calculating, on the above-mentioned hypotheses, the

* Dr. Young has also speculated on the interesting subject of the immediate
cause of fluidity. He remarks in his Lecture on Cohesion, (Lectures, vol. i.
p- 620,) that ‘the apparent weakness of the cohesion of fluids is entirely owing
to the mobility of their particles.” It would be perhaps more correct to say,
that a weak cohesive power is a condition necessary to the existence of a great
degree of mobility.

284 FOURTH REPORT—1834.

pressures in the interior of a fluid, M. Poisson finds equations
of equilibrium relative to the surface of separation of two fluids
incumbent one on the other, and thence, by supposing one of the
fluids suppressed, the equation of the free surface of a single
fluid. The principal conclusion arrived at in the memoir is
thus stated in Art. 31: “ Capillary phenomena are due to the
molecular action resulting from the calorific repulsion and an
attractive force, and modified not only by the form of the sur-
faces as in Laplace’s theory, but moreover by a particular state
of compression* of the fluid at its superficies.”” The variation
of density near the surface, it is shown, must be extremely rapid.
Also, “ the molecular attraction in fluids as well as solids extends
further than the calorific repulsion.”’ (Art. 30.)

The above conclusion is confirmed in various ways, and the
consequences that flow from it with reference to capillary phe-
nomena are fully discussed in the work of M. Poisson entitled
Nouvelle Théorie de Action Capillairet. The object of this
treatise is to bring the theory of capillary phenomena to the
greatest degree of perfection that the power of analysis and the
existing knowledge of facts will permit. In the first chapter the
author proves that if the rapid variation of density near the
surface were neglected, the fluid within the tube would remain
horizontal, and there would be neither elevation nor depression.
He shows also the necessity of having regard to the variable
compression experienced by the fluid near the surface of the
tube, and reaching to the extent of the action due to the solid.
Whence it follows that the principles of Laplace’s theory are
defective, notwithstanding it is so successful in the explanation
of phenomena. In Arts. 18 and 19, M. Poisson obtains, on the
supposition of incompressibility, the equation of Dr. Young re-
lative to the angle of contact, which, as we have seen, was also

* It is not perhaps difficult to see, without the aid of analytical calculation,
that if bodies be assumed to be composed of isolated atoms held in places of
equilibrium by attractive and repulsive forces, the sphere of whose sensible in-
fluence is very small, there must be a rapid change of density at their surfaces.
If experiment should ever be able to detect such a change, this assumed con-
stitution of bodies would be rendered extremely probable.

+ Paris 1831. Extracts from this work, with Remarks by H.F. Link, will be
found in Poggendorff’s Annalen der Physik und Chemie, bd. xxv. 1832, p. 270,
and bd. xxvii. 1833, p. 198.

M. Poisson states in the preamble of his forthcoming treatise on “The Ma-
thematical Theory of Heat,” which appeared recently in a Paris weekly scien-
tific Journal (L’Jnstitut, No. for May 24, 1834,) that that theory forms the
second part of a “‘ Treatise on Mathematical Physics,” in which he proposes to
treat, without restriction to any predetermined order, different physical ques-
tions which admit of the application of analysis. The “ New Theory of Capil-
lary Action ” is the first part. ;

REPORT ON CAPILLARY ATTRACTION. 285

found by M. Gauss without deviating from the principles of La-
place’s theory. But this equation is no longer true if it be ne-
cessary to take account of the variation of density at the fluid
surface; nor in the same case can the argument hold good by
which Clairaut showed that the fluid surface is horizontal when
its attractive power is double that of the solid*.

In the next chapter, the equation of the free surface of fluid in
ee brian in acapillary space is obtained by an analysis which
takes into account any variation of density that may exist at the
fluid surface, although the exact law of variation be unknown.
This equation is of the same form as the fundamental equation
of Laplace, and involves an analogous quantity H. As M. Poisson

infers from it, by assuming an angle w, which is the supplement

of that we have hitherto called the angle contact, to be-constant,
that the weight of fluid raised in a capillary tube is — Hee COS w,

which is the expression for the same weight obtained by La-
place, it follows that H in the two theories is the same in mag-
nitude, though differently represented by the analytical for-
mule.

The third chapter is employed in finding on ‘the same princi-
ples the equation relative to the contour of the capillary surface.
The angle of contact, which is found as in preceding theories to
= constant, is assigned by the equation

F = H cos .

It may be useful to give some idea of the nature and compo-
sition of the constants F and H. The following formule will
serve to do this, when the significations of the letters they con-
tain have been explained :
it H EF
on gamit Ww cpr Le wc?

* pa it Ee ford
me ae ee eL°ff R, “ dudsds

BS. 3
‘ay pong shift fo RH dudsas
sf 9S 0 070 ’

Conceive the fluid mass to be divided by a curve surface pass-
ng through any point M into two parts A and B, and through
€ sides of a rectangular element of the surface at the point M,
let normal planes be erected inclosing a prismoidal element of

| *.M. Poisson’s theory cannot inform us how far that equation is erroneous,
nor whether it is, or not, very approximately true.

286 FOURTH REPORT —1834.

the portion A. Let m and m’ be two molecules of the fluid,
one in the prismoid, the other in some part of A. Then r is the
line joining them, w is its projection on the tangent plane at M,
and s s' are the perpendiculars from the molecules on the same
plane, so that 7? = wu? + (s—s!')2. R, R,, and R’ are functions
of r, which are insensible for every sensible value of this varia-
ble, and express the mutual action referred to the units of volume
of the fluid molecules at the distance r from each other. R re-
lates to the interior of the fluid, R, to its superficial stratum, and
R’ to the stratum adjoining the side of the tube. With respect
to R, the surface through M is parallel to the free surface of the
fluid at a distance / from it, and A answers to the fluid contained
between these two surfaces. So with respect to R’, the surface
through M is parallel to the surface of the tube at a distance
which may also be called /, and A answers to the fluid contained
between this surface and the tube. R, and R’ vary very rapidly
with s and s', and confound themselves with R so soon as
these variables exceed the radius of the molecular activity. The
quantity 7, which is the limit of the integrals with respect to s
and s', is greater than this radius, yet of insensible magnitude.
It is shown that g, and @ do not change sensibly with the mag-
nitude of @.

As the forms of the functions R, R,, and R’ are quite un-
known, the values of g, g,, and @ cannot be calculated a priori.
Neither are there any means known at present of determining
them experimentally. But experiment can assign the numeri-
cal values of H and », and consequently that of F. Hence if
the ratio of g, to g should become known, the three quan-
tities would be determined. The knowledge of this ratio is the
chief desideratum of the theory.. M. Poisson has shown that if
there be no variation of density near the surface of the tube,
which will happen when the molecular action of the tube is the
same as that of the solid, = 2q. Inthis case cos#= —

P is ra He shows also, according to what might be expected
from experience, that cos# = — 1, when the molecular attrac-
tion of the tube exceeds that of the fluid, but assigns no limit-
ing value of the excess at which this value of cosw begins. It
seems, therefore, reasonable to conclude that when the forces
are equal, cos w is nearly equal to —1, and consequently that
qg, is a small quantity compared tog. Also, as the density in the
thin superficial stratum of the fluid varies from 0 to the density
of the interior, the state of dilatation near the surface would
naturally lead us, as M. Poisson observes, to make this inference
with respect to the value of q,.

Sores

ay

REPORT ON CAPILLARY ATTRACTION. 287

Enough has perhaps been said to give an idea of the physical
part of M. Poisson’s theory; it remains to notice some of the
_ mathematical deductions obtained from the two principal equa-
tions in the succeeding chapters of the work. These equations
being the same in form as in Laplace’s theory lead to like results.
In several instances M. Poisson has carried the mathematical.
calculation to a greater degree of approximation, and by this
means obtained numerical results more nearly agreeing with
experiment. Thus, the elevation of the lowest point of the ca-
pillary surface in a tube 1™!-90381 (= ‘075 in.) in diameter, by
the experiments of Gay-Lussac is 15™1: 5861; by M. Poisson’s
calculations 15™*5829, by those of Laplace 15™1-5787.
_ After extending the analysis to the case in which the interior
surface of the tube instead of being cylindrical is any surface
of revolution with its axis vertical and its diameter small in the
whole extent, M. Poisson considers what will take place when
the fluid rises to the upper extremity of the tube, and finds, con-
trary to an opinion expressed by Laplace*, that the invariabi-
lity of the angle of contact is still maintained under these cir-
cumstances, because the radius of curvature of the edge which
terminates the interior surface of the tube is always exceedingly
greater than the radius of the molecular action. This circum-
stance ought to be taken into account in determining the weight
necessary to detach a solid disc from the surface of a fluid.
_ The weight of a drop of water suspended at the lower extre-
mity of a capillary tube and spreading to the exterior edge, is
calculated by the theory for the case in which it is just ready to
detach itself, and found to be something less than the mean
weight of drops falling in succession from the same tube, as in-
ferred from an experiment by Gay-Lussac.

In considering the case of two fluids superincumbent one on
the other in the same tube, M. Poisson obtains the same for-
mule as Laplace, and employs them to explain a singular phe=.
nomenon observed by Dr. Young, and supposed by him to pre-.
sent an objection to Laplace’s theory. Into a capillary tube.
containing water, Dr. Young inserted a small drop of oil, and
then saw the superior surface of the oil depress itself below the
original height of the water. This depression, no doubt, refers
to the centre of the capillary surface, where it cuts the axis of

the tube. If it may be supposed that the oil in descending
moistened the tube, and that the water did not wet it originally
in its whole extent, the-fact is accounted for by the theory.

___ The pressure of fluids as modified by capillary action is treated

* Supplement ala Théorie del’ Action Capillaire, p. 25.

288 FOURTH REPOR?T—1834.

at considerable length: both the vertical and the horizontal
pressures on a solid partly immersed in a fluid are determined,
and from the calculation of the latter it appears, that if a plate, -
the two parallel faces of which are of different substances, be the
solid immersed, the horizontal pressures on the opposite faces
exactly counterbalance, and consequently the solid can have no
motion of translation. It appears froma remark made by La-
place at the beginning of page 43 of the Supplement to his Ca-
pillary Theory, that his reasoning led him to suppose there would
be some difference of pressure, but so small that it might be
neglected. However small it might be, a motion of translation
would be the consequence, and this it seems difficult to admit.
Dr. Young advanced this objection to Laplace’s theory in a
letter to M. Poisson, against whose more exact theory, as we
see, the same objection does not hold good.

Various problems which had been handled by preceding
mathematicians, receive solutions in chapter vi. more exact
than had hitherto been given them, and more carefully com-
pared with experiments. The following are some of the re-
sults.

When two plates are immersed with parallel faces in a fluid
which rises against the surface of one andis depressed near that
of the other, it is found that the fluid surface between them may.
assume two different forms when the plates are near each other.
In one there is a point of inflection which is retained however
near the plates be brought to each other, and in this case they
constantly repel with a force independent of the interval between
them; the other is the form remarked by Laplace, whick con-
tains no inflection, and when it subsists the repulsion changes to
an attraction on making the plates approximate. M. Poisson
is of opinion, that the first of these forms obtains when the
plates, being originally at a great distance, are gradually brought
near each other, and the latter when, one plate being previously
immersed, the other is inserted into the curved portion. of the
fluid contiguous to it.

The values of the two constants of the theory, viz. 2.a*, the
product of the diameter of the capillary tube by the mean ele<
vation of the fluid in it, and: — , the angle of contact, are found
with. reference to mercury and glass, by comparing the theory
with the experiments of Gay-Lussac on the height of a large drop
of mercury on a horizontal glass plane, to be as follows :

2a? = 2 x 65262 sq. millimetres (= ‘02023 sq. in.)
the angle of contact = 154°-30! (= 138°52').

In Art. 116 the weights of fluid raised by circular discs are
calculated, and compared very satisfactorily with the experi-

REPORT ON CAPILLARY ATTRACTION. 289

ments of Gay-Lussac cited by Laplace for the same purpose. :
The heights of the disc above the horizontal level of the fiuid, at
the instants when the weights of the elevated columns are at a
maximum, are determined at the same time by the theory, but
these were not measured in the experiments.

_ Besides the usual problems in the capillary theory, M. Pois-
son has solved two others, not previously attempted, one relat-
ing to the form of fluid poured upon another fluid of greater
specific gravity; the other relative to the adhesion of the base of
a capillary solid cylinder to a fluid from which it is raised with

_its axis vertical. ‘This question is similar to that of the adhesion
‘of a disc, but requires to be treated by a different analytical

process.

_ The concluding chapter of the treatise contains notes and ad-
ditions, in which some points of the theory are further developed,
and new experiments compared. One section is devoted to a
full exposition of the author’s views respecting “ the interior
constitution of bodies, particularly of fluids, and the nature of
molecular forces ;’’ another treats of “ the general equations
of the equilibrium of fluids.’”’ It results from the complete
equation of the free surface of a fluid, obtained on the hypothesis
of disjoined molecules, held in equilibrium by attractive and re-
pulsive forces, that the resultant of the extraneous forces acting
on the fluid, is not exactly perpendicular to its surface, unless it
be perfectly plane. The views advanced in these sections are for
the most part those we have had occasion to adduce in speaking
of the Memoir on the Equilibrium of Fluids. Some of the
other subjects of this chapter ought not to be passed over with-
out notice.

. The depression of mercury in the barometer cannot be con-
veniently calculated by the theory except the ratio of the radius
of the tube to the constant a be either small or great. In
other cases it is necessary to recur to the method of quadratures.
A-table of depressions calculated in this way by M. Bouvard,

and inserted in the Connaissance des Tems for 1812, is cited by

M. Poisson, and placed in comparison with a like table from
Lord Charles Cavendish’s experiments, with which it is found
ie agree as nearly as could be expected from the nature of the
observations. It is desirable, he remarks, that the calculations
should be repeated with the more exact values of the constant a

_ and the angle of contact determined by himself.

__Casbois, Professor of Physic at Metz, pointed out a method

of constructing barometers with plane or even concave surfaces,

having observed that by boiling mercury the convexity of its

capillary surface is diminished, and by continuing the boiling
1834. U

290 FOURTH REPORT—1834.

a sufficient length of time, might be changed to concavity.
M. Poisson adduces a communication from M. Dulong containing
the following satisfactory explanation of this phenomenon. In
the operation of boiling, a thin layer of the mercury in contact
with the air is oxidized, and then mingling with the whole mass,
changes its properties in such a manner, that the action of the
mercury on its own particles and on those of the tube, or rather
on the particles of a thin coating of water which is always in-
terposed between the mercury and the tube, is not the same as
before, the change being greater in proportion to the greater
quantity of metal oxidized, that is, in proportion to the duration -
of the boiling.

A formula obtained in a previous part of the work (Art. 53,)
applicable to the rise in a capillary tube of a fluid consisting of
two fluids mixed in given proportions, is here compared with
experiments made along time since by Gay-Lussac, butnotbefore
published. This formula is founded on the supposition that the
loss of heat which takes place in mixing, has no influence,
when the temperature has become the same as before, on the
integral which determines the value of H, and on which the
phzenomena of capillarity depend, an hypothesis favoured by the
fact, that in the case of a single fluid, the decrement of elevation
at different temperatures is proportional to the augmentation of
density. The theoretical heights agree much less exactly with
the experimental for a mixture of water and alcohol, than for a
mixture of water and nitric acid; which shows that the above
hypothesis is more true for one mixture than the other.

M. Poisson lastly applies his theory to the explanation of the
remarkable phenomenon of endosmose. He conceives that the
two fluids meet without mixing in the capillary tubes which
permeate the membrane, and by the relation of the molecular
forces at their common surface of separation, one prevails over
the other, and so passes through to the opposite side of the
membrane. It has been objected to this theory that it does
not account for the phenomenon of exosmose*. An abstract
of Mr. Power’s views on this subject having been inserted in
the Third Report of the British Association, it will be only
necessary to state that in the paper on Residuo-Capillary
Attraction by the same author, subsequently published in the

* Admitting, as suggested by Professor Henslow, that each fluid tends to
spread into the other through the capillary communications, may not effects such
as are observed, be expected to result merely from the state of compression of
the fluid stratum in contact with the substance of the membrane? This will
vary with the varying density of the fluid from one point to another of the
surface of contact, being greatest where the density is least.

te
2
z

&
ia

_ REPORT ON CAPILLARY ATTRACTION. 291

Transactions of the Cambridge Philosophical Society*, his
theory has undergone some modification, the phenomena both
of endosmose and exosmose, and the variation of the maximum
difference of the heights of the fluids according to the difference
of their densities, being accounted for independently of any
particular mode of communication of the fluids in the capillary
spaces.

I beg leave to close this Report with proposing a query sug-
gested by the existing state of the theory of capillary attraction.
How does it happen that the principles with which Laplace’s
theory sets out conduct to two fundamental equations the same
in form as those of M. Poisson’s theory? Ought not the lat-
ter, seeing that the law of the molecular forces is quite ar-
bitrary, to embrace every possible method of arriving at these
equations ; and should we not expect that the method of Laplace

_ is not inconsistent with the other, but a particular case of it ?

The most probable supposition respecting the molecular forces
of fluids is, that the attractive force is comparatively small, de-
creases much more slowly with the distance than the repulsive,
and is sensible to a much greater distance from the centre to
which it is directed. The hypothesis of incompressibility cor-
responds to the limiting case, when the repulsive force being
infinitely great at first, deereases by very large gradations as
the distance from the centre increases, and within a very small
space becomes less than the attractive force. As the above law
of the forces as well as the limiting case of it are embraced by
M. Poisson’s theory, we may perhaps hence see why the sup-

_ position of incompressibility conducts to the same form of

the principal equations. In some objections that have been
made to the principles of Laplace’s theory, it does not appear
to have been sufficiently considered that by supposing the fluid
to be incompressible, he does in fact take account of a molecular

repulsion. It remains to be determined whether the variation

of density, which on the hypothesis of a disjoined molecular
constitution of bodies must obtain at their surfaces, be such as
to admit of the supposition of incompressibility as a near ap-

_ proximation to the truth. But this there are at present no

rimental means of determining. The experiments of Has-

senfratz+, from which he inferred that glass by being pounded
_ became specifically lighter, are not confirmed by those of Gay-
_ Lnssact. As no variation of density has been hitherto detected,
we. have a sort of negative evidence that the depth of the super-

st

| ® vol. v. part ii. + Ann. Ch. Gilb. I. p. 515.

t See Nouvelle Théorie de Action Capillaire, p. 6.
U2

292 FOURTH REPORT—1834.

ficial stratum in which there is any sensible variation must be
exceedingly minute. If that depth may be neglected in com~
parison of the radius of sensible activity of the attractive force,
Laplace’s principles suffice for a theory of Capillary Attraction,
without being inconsistent with those of M. Poisson. We may
add as a theoretical reason for the supposition of a rapidly
decreasing repulsive force united with a feeble and slowly de-
creasing attractive force, that we may thus understand how the
fluid particles will move readily among each other, retaining
the same mean interval ; for there will be a small obstacle to any
change of their relative positions by separation, but a great
obstacle to any approach within a certain limit*. Perhaps
experiments with light, which appears to be the most success-
ful instrument for searching into the intimate constitution
of bodies, offer the best chance of getting at something satis-
factory on the delicate point we have been speaking of. In the
mean time, while M. Poisson’s theory will engage the attention
of the speculative philosopher, there appears no reason why the
simpler theory of Laplace should not be made the vehicle for
conveying to the younger students of science, in an elementary
form, the explanations of a numerous and interesting class of
phenomena.

Various causes, which it would be useless to detail, prevented
me having a sight of the Number of Poggendorfi’s Annalen
containing the ‘‘ New Experiments on Capillarity,’’ by H. F.
Link+, (mentioned by Professor Moll at the Meeting of the
Association,) till within a short interval before the revision of
this Report for the press. I fear that, from want of time and
sufficient acquaintance with the German language, the following
notice of them will not be such as their importance demands.

The object of M. Link is to ascertain the comparative ascents
of different fluids by capillary attraction, in a manner that would
be free from the sources of error to which the methods of former
experiments had been liable. For this purpose he observes the
ascent between two glass plates inclined at a small angle with
the line of junction vertical, in which case, as we know, the
suspended fiuid takes the form of a rectangular hyperbola. The
instrument he made use of provided for the adjustment of the

~ #* Tt will readily be seen, that under these circumstances the fluid would be

susceptible of division by a thin plate by the application of a very small force,

and we might thus account for a characteristic property of fluids, which, as was

mentioned in my former Report (p. 133), has been employed as the basis of

their mathematical treatment. I was in error in supposing that this method

has only been recently proposed ; it appears to have been thought of by Pascal.
+ Annalen der Physik und Chemie, bd. xxix. 1833, p. 404.

et
tallow plates did not give quite so high a column. It would

_ seem, then, that the heights of ascent under similar circumstances
__are alike independent of the fluids and solids. It is remarkable

REPORT ON CAPILLARY ATTRACTION. 293

angle of inclination to any required magnitude, and was con-
venient for dipping the plates very frequently in the fluids.
The peculiar advantage of this method was, that the ascents
of different fluids could be observed under exactly the. same
circumstances: for all the observations could be taken at
the same parts of the plates and with the same interval of
separation; and after experiments made with one fluid, the
es, could be conveniently cleared of all remaining moisture,

before experiments were made with another. When the same

capillary twbe is used, it is difficult to get rid of the moisture
adhering to the interior; and when different tubes are used,
the experiments cannot well be under like circumstances by
reason of superficial inequalities in the glass surfaces, besides
that the exact proportion of the diameters is not readily ascer-
tained. The principal result that M. Link arrives at is, that all
the fluids rose to the same height. The fluids employed were,
distilled water, nitric acid, a solution of kali causticum (one oz.
to six of water), spirit of wine (very rectified), sulphuric zther,
and rectified sulphuric acid (sp. gr. 1°84). The ether stood
lower at first, but after repeated dippings rose to the same height
as the water. The sulphuric acid was at first higher than the
water, but afterwards sunk to the same level as the rest. Pre-
vious experiments have uniformly assigned a less ascent to ether
and spirit of wine than to water, and a greater ascent to sulphu-
ric acid. M. Link is of opinion, that the experiments were not
carried far enough, and that the different results of his own ex-
periments are attributable to the repeated wetting of the plates
by dipping them in the fluids. In another set of experiments
the plates were of various substances ; viz. glass, copper, zinc,
copper and zinc plates soldered together, first, with the zinc

‘surface opposed to the copper, next, the zine surfaces opposed

to each other, and then the copper surfaces opposed; lastly,
wooden surfaces smeared over with tallow. The heights of as-
cent were very nearly the same for all these, excepting that the

that this result might have been looked for from either Laplace’s

s or Poisson’s theory: for by either theory the height of ascent
_ in a given capillary tube, or between parallel plates separated by

@ given smal} interval, varies as —, when the fluid completely
wets the solid* ; and as H, in this case, depends only on the

* See p. 268.

294. FOURTH REPORT—1834.

molecular action of the parts of the fluid on each other*, the
simplest supposition respecting it is, that it varies as p; whence
it would follow that the height of ascent is the same for different
fluids.

In the applications of the theories of Laplace and Poisson to
Gay-Lussac’s experiments on the ascents of fluids in capillary
tubes, and the weights of the fluid columns raised by circular

F 2 ‘ i
discs, the values of the constant * for the different fluids, were

borrowed from the first class of experiments, and being em-
ployed in the theoretical formulz, gave results according with
the other class. If those values were incorrectly determined by
the experiments, this accordance can only be explained by sup-
posing the cause of error to be of the same kind and to act in
the same degree in the two classes of experiments.

M. Link remarks that there is,an essential difference between
the ascent of fluids against solid surfaces not previously wetted,
and the remaining height of suspension after the wetting. Tal-
low, for instance, will scarcely allow water to ascend at all in the
first instance; but after being moistened, will sustain a suspended
column, of nearly the same height, according to the experiment
mentioned above, as when other substances are employed. The
theory of the first ascents, must be of a very complicated nature,
on account of the difficulty of estimating the amount of various
retarding causes, such as greasiness, and the inequalities of the
solid surfaces. But the theory of the remaining suspensions
that result from wetting the surfaces, is of a more simple nature.
M. Link adduces an explanation of this fact, founded on a theory
of fluidity developed in the first part of his paper, in which, set-
ting out with Newton’s definition of a fluid, he is led to regard
it as composed of solid particles in an extreme state of pulveriza-
tion, and aggregated like the grains of a heap of sand. What-
ever in other respects may be the comparative merits of this
view of the nature of fluidity, and that adopted by Young and
Poisson, the latter has the advantage of being more readily made
a basis of calculation.

* pp. 275 and 285.

Report on the Progress and Present State of Physical Optics.
By the Rev. Humpurey Luoyp, 4.M,, M_2R.IA., Fellow
of Trinity College, and Professor of Natural and Experi-
mental Philosophy in the University of Dublin.

In the Report which I have the honour to submit to the Associa-
tion, I have attempted to consider in some detail the present
state of our knowledge with regard to the physical theory of
light, and the successive advances which have, in late years,
been made towards its establishment. The method which I
have thought it expedient to adopt in this review has been to
take, in the first instance, a rapid survey of the several leading
classes of optical phenomena, which the labours of experimental
philosophers have wrought out in such rich profusion, and after-
wards to examine how far they are reducible to one or other of
the two rival theories which have alone advanced any claim to
our consideration. This is, in fact, the only way in which the
truth of a physical theory can be established ; and the argument
in its favour is essentially cumulative.

- But in making this comparison it is not enough to rest in
vague explanations which may be moulded to suit any theory.
Whatever be the apparent simplicity of an hypothesis, —whatever
its analogy to known laws,—it is only when it admits of mathe-
matical expression, and when its mathematical consequences
can be numerically compared with established facts, that its
truth can be fully and finally ascertained *. Considered in this
point of view, the wave-theory of light seems now to have
reached a point almost, if not entirely, as advanced as that to
which the theory of universal gravitation was pushed by the
single-handed efforts of Newton. Varied and comprehensive
classes of phnomena have been embraced in its deductions ;
and where its progress has been arrested, it has been owing
in a great degree to the imperfections of that intricate branch of
analysis by which it was to be unfolded. The principles of the
theory of emission, on the other hand, have, in comparatively

_* C’est en tirant des formules les conséquences les plus subtiles et les plus
eloignées des principes, puis allant les vérifier par l’expérience, que l’on peut
réellement s’assurer si une théorie est vraie ou fausse, et si l’on doit s’y confier
comme a un guide fidéle, ou la rejeter comme un systéme trompeur.— Biol,
Traité de Physique, tom. i. p. xiv.

296 FOURTH REPORT—1834.

few instances, been mathematically expressed and developed ;
and accordingly this theory presents but rarely those points of
contact with experimental truth by which alone it can be judged.

This signal difference in the present state of the two theories
has been by some ascribed to a difference in the intellectual
power by which they have been worked; and it has been said
that had the Newtonian theory been cultivated with the same
zeal and talent as the Huygenian, it might have had equal
triumphs to boast of. This position, I confess, appears to me
altogether untenable. With respect to the implied fact, it may
be enough to observe that Newton and Laplace were both en-
gaged on one side of the question; and I believe I may add that
among the supporters of the wave-theory of light there are few
who have not had to encounter early predilections in favour of
the theory of emission. The nature and laws of projectile
movement are far more familiar to every lover of mechanical
philosophy than those of vibratory propagation ; and the tri-
umphant career of the former branch of this science, in its appli-
cation to the movements of the heavenly bodies, is in itself
sufficient to induce every one to lean to a theory which proposes
to account for the phenomena of light on similar principles.
As to the opinion itself, it seems highly improbable, to say the
least, that two theories so widely separated should run hand in
hand in their explanation of phenomena. There is indeed one
case, and that a striking one, of this kind :—The fundamental
laws of reflexion and refraction are exact and necessary conse-
quences of each of these theories; but I’ believe their history
affords no paraliel instance.

An unfruitful theory may, however, be fertilized by the addi-
tion of new hypotheses. By such subsidiary principles it may
be brought up to the level of experimental science, and appear
to meet the accumulating weight of evidence furnished by new
phenomena. But a theory thus overloaded does not merit the
name. It is a union of unconnected principles, which-can at
best be considered but as supplying the materials for a higher
generalization. Its very complexity furnishes a presumption
against its truth ; for the higher we are permitted to ascend in
the scale of physical induction, the more we perceive of that
harmony, and unity, and order, which must reign in the works
of One Supreme Author. The theory of emission, in its present
state, exhibits all these symptoms of unsoundness ; but there is
something stronger than mere presumption against it. It will
appear, I think, upon a fair review, that in almost every in-
stance in which it has been developed, its consequences are at

REPORT ON PHYSICAL OPTICS. 297

variance with facts; and the proof of its insufficiency seems
even stronger than the positive evidence in favour of the rival
‘ theory.

In proceeding to the consideration of these arguments, I have
foundit necessary to deviatefrom the arrangement which a strictly
theoretical view of the subject would naturally suggest. The
relation of theory to phenomena, which I propose to consider,
obliges me to examine the latter in the groups in which they
have been usually brought together, and under which their laws
have been investigated. I propose, therefore, to divide the fol-
lowing Report into two parts; of which the first will treat of
unpolarized, and the second of polarized, light. In the former
I shall consider separately, .

1. The propagation of light, and the principle of interference ;
2. The reflexion and refraction of light ;

3. Diffraction ;

4, The colours of thin and thick plates.

The second part will comprise,

1. The polarization of light, and the principle of transversal
vibrations ;
2. The reflexion and refraction of polarized light ;
3. Double refraction ;
_ 4. The colours of crystallized plates.

- Many subjects of high interest are omitted in this arrangement,
as being but remotely connected with the leading object of the
present Report. I have left wholly untouched, for this reason,
that branch of optical science which is sometimes denominated
“ mathematical optics,’ or the development of the fundamental
laws of reflexion and refraction. The phenomena of vision
have been in like manner omitted, as involving also the science
of physiology ; and the relations of light to other agents, as
heat, electricity, and magnetism, because these relations are as
yet little understood, and in the present state of the kindred
sciences, the science of light can hope to derive little aid from
their examination. These interesting subjects would, each of
them, well merit a separate consideration.

4%

Part I. Unrouarizep Lieut.

I. Propagation of Light. Principlé of Interference.

The first property of light which claims our notice is its pro-
gressive movement. Light, we know, travels from one point

298 FOURTH REPORT—1834.

of space to another in time, with a velocity of about 195,000
miles ina second. The inquiry concerning the mode of this
propagation involves that respecting the nature of light itself.

There are two distinct and intelligible ways of conceiving such
a motion. Either it is the self-same body which is found at
different times in distant points of space; or there are a mul-
titude of moving bodies, occupying the entire interval, each of
which vibrates continually within certain limits, while the vi-
bratory motion is communicated from one to another, and so
advances uniformly. Nature affords numerous examples of each
of these modes of propagated movement ; and in adopting one or
other to account for the phenomena of light, we fall upon one
or other of the two rival systems,—the theories of Newton and of
Huygens.

The Newtonian theory, in the shape in which it is usually
presented, is undoubtedly simpler in conception than its rival ;
but this simplicity is only apparent. Newton himself was
far too clear-sighted to suppose that the forces of attraction
and repulsion, by which the molecules of light were supposed to
be refracted and reflected, were adequate to account for all the
phenomena; and it is remarkable that, when he proceeds to
speculate on the physical theory of light, he has found it neces-
sary to admit all the apparatus required in the theory of waves.
In fact, Newton felt, and distinctly stated, that the vibrations
of an ethereal medium were necessary in his hypothesis*, al-
though he denied that these vibrations constituted light. He
has even gone further, and asserted that they were the chief
and essential parts of that hypothesis, the molecules emitted
from luminous bodies only performing the office of exciting these
vibrations, as stones flung into water produce waves ¢. On the
other hand, the molecules themselves are supposed to be emitted
by a vibratory motion of the parts of the luminous body { ;—the
same vibratory movement, though acting with a different energy,
in which he supposes heat to consist. It would appear, then,
that Newton assumed too much, and that he erred against his
own valuable rule: ‘* Causas rerum naturalium non plures ad-
mitti debere,”’ &c. Had he simply left out the molecular part of
his hypothesis, and supposed that the vibrations of his ethereal

* Phil. Trans. 1672.

+ “* Were I to assume an hypothesis, it should be this, if propounded more
generally,—-so as not to determine what light is, further than that it is something
or other capable of exciting vibrations in the ether ; for thus it will become so
general, and comprehensive of other hypotheses, as to leave little room for new
ones to be invented.” — Birch’s History of the Royal Society, vol. iii. p. 249.

t Optics, Query 8.

’
.

REORT ON PHYSICAL OPTICS. 299

medium were directly excited by those of the luminous body,
his theory would have resolved itself-into that of Huygens and
of Hooke. It may be observed, in connexion with this subject,
that Newton seems actually to have admitted the wave-theory
with respect to radiant heat; and that he supposed it to be pro-
pagated, not by the translation of material particles, but bythe
vibrations of an ethereal medium *.

The peculiar part of the theory of emission—the supposition
that the rays of light are bodies projected with a great velocity—
would seem to offer an easy criterion of its truth. If the weight
of a molecule of light amounted to one grain, its momentum
would equal that of a cannon ball 150 pounds in weight, and
moving with the velocity of 1000 feet in a second. The weight of
a single molecule may be supposed many millions of times less than
this ; but, on the other hand, millions of such molecules may be
made to act together, by concentrating them in the foci of lenses
or mirrors, and the effects of their impulse might, it was ex-
pected, be thus rendered sensible. This easy test of the materi-
ality of light was long since appealed to. The experiments of
Homberg seemed to have established the existence of a sensible
impulsive effect; but when these experiments were repeated
with more caution by Mairan and Dufay, they conducted to the
opposite conclusion. The results obtained by Michell at a later
period, and with the aid of a more sensible apparatus than any
before employed, seemed to be decisive in favour of the materi-
ality of light. The effects observed in these experiments,
however; have been with much probability referred to aerial
currents, produced by unequal temperature, or even to a differ-
ence in the elastic force of the air in contact with the opposite
surfaces of the body acted ont. ‘The subsequent experiments
of Mr. Bennet were made under circumstances far more favour-
able; and in particular, having been repeated in vacuum, they
are independent of the sources of error now alludedto. Their
result was conclusive as to the non-existence of a sensible
effect §.

_ The objection to the materiality of light, arising from its want
of sensible momentum, was first urged by Franklin. Horsley
attempted to remove the difficulty ||; but his laborious arithme-
tical calculations only go to prove that the particles of light, if
material, must be of extreme minuteness. It must at the same
time be confessed that objections of this nature are entitled to

* Optics, Query 18.

+ Priestley’s History of Optics, p. 387.

t Young “ On the Theory of Light and Colours,” Phil. Trans. 1801.

§ Phil. Trans. 1792. || 26. 1770. I.

300 FOURTH REPORT—1834.

little weight. It is easy to attribute to the molecules of light a
minuteness sufficient to evade any means that we possess of
detecting their inertia by their effects upon other bodies; and
in whatever point of view we regard the phenomena of optics,
we are forced to contemplate quantities immeasurably smaller
than any to which the imagination has been accustomed.

The aberration of the light of the fixed stars, resulting from the
motion of the earth and that of light, is an easy consequence
of the theory of emission, in which these motions are con-
ceived to subsist independently. In order to account for the
phenomenon in the theory of waves, it seems necessary to assume
that the ether which encompasses our globe does not participate
in its motion ; so that the ethereal current produced by this re-
lative motion must be supposed to have a free passage through
the solid mass of the earth ; or that, in the words of Young, “ the
luminiferous ether pervades the substance of all material bodies
with little or no resistance, as freely perhaps as the wind passes
through a grove of trees*. Fresnel has maintained the same opi-
nion, and, startling as the position seems at first, he has very
clearly shown that no fair argument can be advanced against it,
founded on the opacity of the mass which the ether is supposed
to permeate fT.

The discoveries of Bradley and Roemer, when compared to-
gether, have led to a further and most important conclusion re-
specting light,—namely, that its velocity is one and the same,
whatever be the luminous origin ; the light of the sun, the fixed
stars, the planets and their satellites, being all propagated with
the same swiftness. This conclusion must be allowed to present
a formidable difficulty in the theory of emission. Laplace has
shown that ifthe diameter of a fixed star were 250 times as great
as that of our sun, its density being the same, its attraction
would be sufficient to destroy the whole momentum of the
emitted molecules, and the star would be invisible at great di-
stances [. With a smaller mass there will be a corresponding
retardation ; so that the final velocities will be different, what-
ever be the initial. The suggestion of M. Arago seems to
offer the only means of avoiding this difficulty. It may be sup-
posed that the molecules of light are originally projected with
very different velocities; but that among these velocities there
is but one which is adapted to our organs of vision, and which

* “« Experiments and Calculations relative to Physical Optics,” Phil. Trans.
1803.

+ “ Sur l'Influence du Mouvement terrestre dans quelques Phénoménes
d'Optique,” Annales de Chimie, tom. ix.

t Gach, Ephem., iv. 1.

REPORT ON PHYSICAL OPTICS. 301

produces the sensation of light. This supposition seenis to be
supported by the discoveries of Herschel, Wollaston, and Ritter,
respecting the invisible rays of the spectrum; but it does not
appear to be easily reconciled with any hypothesis which we are

able to frame respecting the nature of vision. This uniformity

of velocity, on the other hand, is a necessary consequence of
the principles of the wave-theory. The velocity with which
vibratory movement is propagated in an elastic medium depends
solely on the elasticity of that medium and on its density ; and
if these be uniform in the vast spaces which intervene between
the material bodies of the universe, (and it is not easy to sup-
pose it otherwise,) the velocity must be the same, whatever be
the originating source.

_ The rectilinear motion of light has long been urged in favour
of the theory of emission, and against the theory of waves. If
light consists in the undulations of an elastic fluid, (it has been
said,) it should be propagated in all directions from every new
centre, and so bend round interposed obstacles. Thus luminous
objects should be visible, even when an opake body is between
them and the eye, just as sounding bodies are heard, though a
dense body intervene between them and the ear. To this ob-
jection, which was first insisted on by Newton*, a full answer
has been given. The phenomena of diffraction, and especially
the interior fringes in the shadow of narrow opake bodies, prove
that light does bend round obstacles, and deviate perceptibly
from the rectilinear course. When the obstacle is of consider-
able dimensions, the intensity of the light decreases, indeed,
very rapidly within the edge of the geometric shadow; so that

_ ata very small distance from that edge, it is no longer percep-

tible. But the darkness does not arise from the absence of
luminiferous waves, but from the mutual destruction of those
sent there. In fact, if the surface of the wave when it reaches

_the obstacle be divided into any number of small portions, the

motion of the ether at any point behind it is, by the principle of
Huygens, the sum of all the motions produced there by
these several portions, considered as separate centres of dis-
turbance; and it is easy to show, that, when the distance of
the point in question from the obstacle is a large multiple
of the length of a wave, the magnitude of this resultant must
diminish rapidly within the shadow, and the light become
insensible when the line drawn from that point to the edge of
the screen is inclined at a small angle to the normal to the frunt
of the wave. The accurate calculation of the intensity, in this

* Optics, Query 28.

302. FOURTH REPORT—1834.

and other similar cases, has been made by Fresnel by the aid
of the principle of interference, and the result is found to agree
in the most complete manner with observation *.

The same principles apply to the aerial waves which consti-
tute sound, and these too should present analogous phenomena.
But the scale is widely different. The length of an aerial wave

‘is more than 10,000 times greater than that of an ethereal un-
’ dulation ; and the distance of the ear from the obstacle must be
augmented in the same proportion, in order that the same con-
clusions may be applicable to the two cases.

. According to this account, then, the right-lined propagation
of the rays of light is a consequence of the principle of inter-
ference, combined with the principle of Huygens. A ver
different view of the subject, however, has been presented by
M. Poisson, in a memoir on the propagation of motion in elastic
fluids, read before the French Academy in the year 1823+. The
elasticity of the fluid being supposed the same in all directions,
the velocity of propagation will be also the same, and conse-
quently the waves spherical. The absolute velocities of the mo-
lecules themselves, however, will be very different. M. Poisson
finds that when the original disturbance takes place only in one
direction, the velocity of the molecules will be indefinitely small
in all directions inclined to it at finite angles, so that the motion
will not be sexsibly propagated except in that direction. This
diminution of intensity, he finds, will be greater the more rapid
the velocity of propagation ; and it is in this manner only, he
concludes, that we can account for the rectilinear motion of
light in the wave-theory. This conclusion however, M. Fresnel
has shown, is contradicted by the ordinary phenomena of dif-
fraction ; and he has adduced theoretical reasons, drawn from the
principle of the coexistence of small motions, to prove that it
cannot hold in any fluid whatever, but that the molecules are in
all cases disturbed in a sensible manner, in directions very much
inclined to that of the original vibrations {.

The principle of the superposition of small motions, which has
been more than once adverted to, is an immediate consequence of
the linearity of the original equation of partial differences which
determines the law of vibration of an ethereal particle. The
complete integral of this equation will contain, in general, a term
for every distinct original disturbance ; and the total disturbance
will be the sum of all the partial disturbances due to each cause
acting separately. The partial disturbances may, however, con-

* “ Mémoire sur la Diffraction,” AZémoires de I’ Institut, tom. v.
+ Annales de Chimie, tom. xxii. + Ibid., tom. xxiil.

————— es ee

REPORT ON PHYSICAL OPTICS. 303

spire, or be opposed ; so that in the case of two such disturb-
ances, for example, the second may have the effect either of aug-
menting or diminishing the first, and the absolute velocity of the
ethereal molecules may be increased, or lessened, or even wholly
destroyed by the union. In fact, if the form of the function
which expresses the wave-disturbance, be assumed to be that
by which the law of vibration of the cycloidal pendulum is re-
presented, the sum of two coexisting disturbances will be a sin-
gle disturbance of the same form, provided the component un-
dulations have the same length; and the effect of two such co-
existing undulations will be a single undulation of the same
length, but differing in the position and magnitude of the space
of greatest vibration from either of the components. The mag-
nitude of the resulting vibration may be the sum, or difference
of those of the component vibrations, or it may have any value
intermediate to these limits. When the component vibrations
are equal, the resultant may even vanish altogether; and two
lights of equal intensity when added together will produce
darkness, provided that the interval of retardation of one wave
on the other is an odd multiple of the length of half a wave.
This important consequence of the theory of waves—the princt-
ple of interference of the rays of light—was first distinctly stated
and established by Dr. Thomas Young, although some of the
facts by which its truth is experimentally confirmed were known
to Grimaldi*. The general calculation of the intensity of the
resulting light, for any relative position of the interfering waves,
is due to Fresnel ; and has been followed out and developed by
Sir John Herschel in his valuable Essay on Light. Whena
beam of homogeneous light is transmitted through two small
apertures in a card, or plate of metal, the light will diverge from
each as from a new centre. If the two apertures are close toge-
ther, and the diverging pencils received on a reflecting surface,
a series of parallel straight bands is observed, perpendicular to~
the line connecting the apertures, and separated by intervals
absolutely dark. That these alternations of light and darkness

a are produced by the mutual action of the two pencils, Young
__ proved by the fact, that when one of the beams is intercepted,

the whole system of fringes instantly disappears, and the dark
intervals recover their former brightness.

The experiment of Fresnel is still more satisfactory. In this
important and instructive experiment, the fact of interference is
placed beyond all question. The two pencils proceed from one

* This ingenious philosopher even stated explicitly that an illuminated body

may be rendered darker by the addition of light, and adduced a simple experi-
ment in proof of it. Physico-Mathesis de Lumine. Bologna, 1665.

304 FOURTH REPORT—1834.

common origin, and are separated simply by reflexion at plane
surfaces, without any attending circumstance which can, by
possibility, be supposed to influence the result. The pheno-
menon is thus divested of everything nonessential, and it
becomes impossible to hesitate about its nature. But the ac-
cordance of theory and experiment is maintained, not only in
the general features of the phenomenon, but even in its minu-
test details. The distances of the points of each fringe from the
two foci of reflected rays should, according to theory, differ by
a constant quantity,—that constant being an odd multiple of the
length of half a wave for the dark fringes, and an even multiple
of the same quantity for the bright ones. Hence the fringes.
should be propagated in hyperbolic lines, whose foci are the
foci of the reflected pencils ;—and the most accurate measure-
ments have shown that it is so. The constant differences jus;
alluded to are far too minute to be directly measured ; but they
can be calculated with great accuracy, when the distances of the
successive bands from the central one have been obtained. The
latter distances have been determined by Fresnel with much
nicety by micrometrical measurements ; and the lengths of the
waves of each species of simple light, thence computed, agree
in the most satisfactory manner with the values of the same quan-
tities as deduced from the observation of Newton’s rings.

The central fringe is formed at those points in arriving at
which the two pencils have traversed equal paths; and as its
position is therefore independent of the length of a wave, the
rays of all colours will be united there, and the fringe itself will
be white, or colourless. Such is the fact, as described by Fresnel
himself, and by most observers who have repeated the experi-
ment. Mr. Potter states, however, as the result of his obser-
vations, that the central fringe may be seen hoth black and white,
although more frequently the former; and he urges the fact in
opposition to the wave-theory*. But it seems premature to
draw any inference from such experiments, until the circum-
stances which have occasioned the variation in the results have
been fully investigated and understood.

The interference of the rays of light has, since the decisive ~
experiment of Fresnel, been admitted on all hands; and the
phenomena which were previously explained on the Newtonian
hypothesis of the “ fits of easy reflexion and transmission,”’ are
now, by most of the advocates of the Newtonian theory, referred
to this simpler and more fertile principle. This principle is,
it has been stated, an immediate and necessary consequence of
the wave-theory, and its experimental establishment must be

* Phil. Mag., (8rd Series,) vol. ii. p. 280.

REPORT ‘ON PHYSICAL OPTICS. 305

regarded as a weighty argument in favour of that theory. It now
remains to inquire whether any account can be given of it in the
theory of emission.

The molecules of light cannot be supposed to exert any
mutual influence; for the regularity of the laws of reflexion
and refraction compels us to consider them as independent,
and each, separately, the subject of those forces from which,
in the theory of emission, these laws are derived. The phe-
nomenon of interference may, however, be plausibly accounted
for by the vibrations of the optic nerve, produced by the
impulse of the rays of light upon the retina; and by the
accordance or discordance of these vibrations when caused by
two interfering pencils. On this supposition, which was sug-
gested by Dr. Young himself, the intensity of the light will de-
pend on the relation between the time of vibration of the optic
nerve, and the interval of the impulses of the succeeding parti-
eles. Ifthis interval be equal to the time of vibration, or to any
multiple of it, the second impulse will add its effect to that of
the first, and the motion be accumulated. It will, on the other
hand, be destroyed, if the second impulse follows the first at an
interval equal to half that time.

It is here assumed that the emitted particles succeed one
another at equal intervals, as will be the case if their emission:
be owing (as Newton supposed it to be) to a vibratory motion of
the parts of the luminous body. But we must assume further
that the intervals of emission vary with the nature of the par-
ticlés, in the light of different colours 3 or that all the red-
making particles (to use an expression of Newton) are emitted
at one certain interval, all the blué-making at another; and so for
each different species of simple light. Hence the vibratidns of
the parts of the luminous body must be of different periods for

é light of different colours. ‘This is, in truth, a part, and a
necessary part, of the theory of waves; but it has no connexion
whatever with the principles of the rival theory.

O 2: ;

><) IL. Reflexion and Refraction of Light.
_ To account for the phenomena of reflexion and refraction it
is supposed, in the Newtonian theory, that the particles of bodies
and those of light exert a mutual action ;—that, when they are
nearly in contact, this action is attractive,—that, at a distance
a little greater, the attractive force is changed into a repulsive
one,—and that these attractive and repulsive forces succeed one
another probably for many alternations. ‘The absolute values,

or intensities, of these forces are-different in - different bodies ;
1834. x ~

306 FOURTH REPORT—1834.

but the form of the law, or the function of the distance by which
they are expressed, is assumed to be the same for all*. From
these postulates Newton has rigorously deduced the laws of re-
flexion and refraction. The problem is the first in which the
effects of that important class of forces acting only at insensible
distances have been submitted to calculation ; and the solution
is regarded by M. Poisson as forming an era in the history of
science.

The reflexion of light at the exterior surface of dense media
is ascribed to the repulsive force; refraction and internal re-
flexion, to that inner attractive force which extends up to actual
contact. The outermost sphere of action of every body, in this
theory, is necessarily attractive, as well as the inmost ; for, were
it otherwise, no ray could enter, or emerge from, the medium at
an extreme incidence. Sir David Brewster has made an inge-
nious use of this principle to explain the remarkable fact noticed
by Bouguer, that water is more reflective than glass at oblique
incidences.

But though the theory of emission is perfectly successful in
explaining the laws of reflexion and refraction, considered as
distinct phenomena, yet it is by no means equally so in account-
ing for their connexion and mutual dependence. When a beam
of light is incident on the surface of any transparent medium,
part is, in all cases, transmitted, and part reflected. The in-
tensity of the reflexion is in general less, the less the difference
of the refractive indices of the two media; and accordingly the
reflective and refractive forces (if such be the cause of the phe-
nomena,) are related to one another in all media, so that one
increases or diminishes along with the other}. But how is it
that some of the molecules obey the influence of the repulsive
force, and are reflected ; while others yield to the attractive force,
and are refracted? To account for this, Newton was obliged
to have recourse to a new hypothesis. The molecules of light are
supposed to pass through certain periodical states, called ‘ fits
of easy reflexion and transmission,’ which modify the effects of
the attractive and repulsive forces, and in which they are dis-

* This assumption is tacitly made by Newton, when he takes the function
wl

as the measure of the refractive power. See Herschel’s “ Essay on

Light,” Encyc. Met. if

+ The reader will find much novel and interesting matter connected with
‘this subject in a paper by Sir David Brewster, ‘“‘ On the Reflexion and Decom-
position of Light at the separating surface of media of the same and of differ-
ent refractive powers,” Phal. Trans. 1829.

REPORT ON PHYSICAL OPTICS. 307

posed to yield alternately to one or the other. The actual deter-
mination of the particle will depend, partly on the phase of the
fit, and partly on the obliquity under which it meets the bound-
ing surface. Now the molecules composing a beam of light are
supposed to be in every possible phase of their fits, when they
reach the surface : some of them consequently will be reflected,
and others refracted; and the proportion of the former to the
latter will depend on the incidence.
As to the fits themselves, Newton thought they must be re-
‘ferred to a vibratory motion in the ether, excited by the rays
themselves ; just as a stone flung into water raises waves on its
surface. This vibratory motion is supposed to be propagated
faster than light itself, and thus to overtake the molecules, and
: impress upon them the disposition in question by conspiring
with or opposing their progressive motion. In one of his
queries Newton has even calculated the lesser limit of the elas-
ticity of the ether, as compared with that of air, in order that
___ it should have so great a velocity of propagation*. The hypo-
thesis of Mr. Melville and M. Biot is more in accordance with
the spirit of the theory of emission. The molecules of light are
supposed, in this hypothesis, to have a rotatory motion round
their centres of gravity which continues along with the progres-
sive motion, and in virtue of which they present attracting and
repelling poles alternately during their progress in space+.
Boscovich imagined a vibratory motion in the parts of the ray
itself, which it received at the moment of emission, and retained
in its progress{.
_ The theory of the fits has now lost much of its credit, since
the phenomena of the colours of thin plates, phenomena which
first suggested it to the mind of Newton, have been shown to be
irreconcileable with it. The explanation which it gives of the
facts now under consideration is, as was observed by Young and
Fresnel, inconsistent with the regularity of refraction. In fact,
the molecules which are transmitted, are not all in the maai-
mum of the fit of transmission, but are supposed to reach the
_ surface in very different phases of this, which may be denomi-
2 nated the positive fit. Now as a change of the fit from positive
to negative is, in general, sufficient to overcome altogether the
___ effect of the attractive force, and subject the molecule to the
: repulsive, it is obvious that the phase of the fit must modify the
effects of these forces in every intermediate degree ; and that the
molecules which do obey the attractive force must have their
velocities augmented in different degrees, depending on the
_* Optics, Query 21. + Phil. Trans. 1753. Traité de Physique, iv. p. 245.
{ Philosophie Naturalis Theoria.

ry

x 2

308 FOURTH REPORT—1834.

phase. Consequently, as the direction of the refracted ray de-
pends on its velocity, the transmitted beam will consist of rays
refracted in widely different angles, and will be scattered and
irregular. .

In some of his writings Newton attributes the reflexion and
refraction of light to a difference in the density of the ether
within and without bodies; or rather he refers the attractive
and repulsive forces to this, as toa more general principle. The
ether is supposed to be rarer within dense bodies than without,
and the rays of light, in crossing the bounding surface, are
pushed from the side of the denser ether; so that their motion
is accelerated if they pass from the rarer to the denser body,
and retarded in the opposite case. Reflexion at the surface of
the rarer medium is explained on the same suppositions; but,
to account for the ordinary reflexion by a denser medium,
Newton was obliged to introduce new and gratuitous hypotheses
respecting the constitution of the ether at the confines of two
media in which its density is different*.

The velocity of propagation, in the wave-theory of light, de-
pends solely on the elasticity of the vibrating medium as com-
pared with its density. If, then,:a plane wave be incident ob-
liquely on the bounding surface of two media, it is obvious that
its several portions will reach that surface at different moments
of time ; and each of these portions will become the centre of two
spherical waves, one of which will be propagated in the first me-
dium with the original velocity, while the other will be propa-
gated in the new medium, and with the velocity which belongs
to it. But, by the principle of the coexistence of small motions,
the agitation of any particle of either medium is the sum of the
agitations sent there at the same instant from these several cen-
tres of disturbance ; and the surfaces on which they are accumu-
lated at any instant will be the reflected and refracted waves.
These surfaces are those which touch all the small spherical
waves at anyinstant. It is easy to see that they are both plane;
and that the reflected wave is inclined to the surface at the same
angle as the incident wave, while the sine of the angle of incli-
nation of the refracted wave is to that of the incident in the con-
stant ratio of the velocities of propagation in the two media.

Such is the demonstration of the laws of reflexion and re-
fraction given by Huygens}. The composition of the grand, or
primary wave, by the union of the several secondary or partial
waves, in this demonstration, has been denominated the princi-
ple of Huygens ; and it is obviously a case of the more general

* Birch’s [History of the Royal Society, yol. iii. p. 247. Optics, Query 19.

} Traité de la Lumiére. . aa

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REPORT ON PHYSICAL OPTICS. 309

principle of the coexistence of small motions. It easily follows
from this mode of composition, that the surface of the primary
wave must mark the extreme limits to which the vibratory move-
ment is propagated in any direction, in:any given time; so that
light, according to this theory, is propagated from any one point
to another in the least possible time. This is) the well-known
Jaw of Fermat, the daw of swiftest propagation, and it will rea-
dily appear that it holds, whatever be the number of modifica-
tions which the course of the light may undergo by reflexion or
refraction ; as, likewise, whatever be the form of the elemen-
tary wave.

The demonstration of Huygens has heen thrown into an
analytical form by Lagrange*, but he has added nothing to its
rigour or perspicuity. An important supplement tothe demon-
‘stration was however given by Fresnel. From the reasoning of
Huygens it did not appear what became of those portions of
the secondary waves which did not conspire in the formation of
the grand wave. The crossing of these in all directions ought
to give rise to a weak diffused light, filling the entire space be-
tween the grand wave and the reflecting or refracting surface;
and, in fact, Huygens supposed that such a light did actually
exist, but was too feeble to affect the eye. Fresnel has shown,
however, that all those portions which do not conspire in the
formation of the grand wave,.are destroyed by interference + ;
so that the formation of one grand wave, by the union of an in-
a number of lesser waves, becomes a precise and definite
effect.

_ The total reflexion of light at the surface of a rarer medium
has been urged by Newton against the wave-theory, and the
apparent difficulty seems to have had much weight in inducing
him to reject that theory. It is, in fact, not easy to perceive at
first view why the disturbance of the ether within the denser
medium sho d not be communicated to the external ether, and
@ wave be thus propagated to the eye, whatever be the obliquity
of the incident wave. To this it may be enough to reply, that
the law of refraction itself, in all its generality, is a necessary
consequence of the wave-theory; and therefore that the phe-
nomenon of total reflexion, which is a particular case of that
Jaw, is likewise accounted for. But the principle of interfer-
ence furnishes a direct answer to the difficulty. It can be
shown that the elementary waves, which are propagated into the
rarer medium from the several points of the bounding surface,

* “Sur la Théovie de la Lumiére d’Huygens,” Annales de Chim., tom. xxi,

+ “Explication de la Réfvaction dans Ja Systéme des Ondes,” Annales de —
Chimie, tom. xxi.

310 FOURTH REPORT—1834.

destroy one another by interference, when the sine of the angle
of incidence is greater than the ratio of the velocities of propa-
gation in the two media, or the angle itself greater than the li-
miting angle of total reflexion*. It is here supposed that
the distance from the refracting surface is a large multiple
of the length of a wave. The conclusion does not apply
to points very near that surface; and for such points, there
is reason to think, the law of refraction is more complicated.
Experience shows, in fact, that light may issue from the
denser medium, to an appreciable distance, when the incidence
exceeds the limiting angle of total reflexion. If two prisms,
whose bases are slightly convex, be put together, and the
inclination of these bases gradually changed while we look
through them, it will be observed that, beyond the limiting
angle, the light will still be transmitted in the neighbourhood
of the parts in contact. By measuring the breadth of this space,
and comparing it to the diameters of the coloured rings, Fresnel
found that the interval of the glasses, through which this devia-
tion from the ordinary law of refraction occurred, exceeded the
length of a wave}. The analysis of M. Poisson points also to
the same result, and it is proved that the second medium will
be agitated in the part immediately in contact with the first, this
agitation decreasing rapidly and becoming insensible at a very
minute distance from the surface.

The laws of reflexion and refraction, then, follow from the
theory of waves, whether we suppose the vibrating medium, in
dense bodies, to be the body itself, the ether within it, or both
conjointly. Euler maintained the first of these opinions, and
believed that light was propagated through the gross particles
alone, in the same manner as sound. But this hypothesis is
contradicted by the most obvious facts; and according to it, as
Dr. Young has observed, the refraction of the rays of light in
our atmosphere should be a million times greater than it is. Of
the other two opinions, Young seems to have held the latter,
and to have thought that the molecules of the body formed, to-
gether with those of the ether within it, a compound vibrating
medium, which was denser than the ether alone, but not more
elastic. Others, lastly, attribute the propagation of light in
transparent bodies to the vibrations of the ether alone, that fluid
being retained by the attraction of the body ina state of greater
density within it than in free space.

A very different view of this subject has been recently main-

* See Fresnel ‘ Sur le Systeme des Vibrations lumineuses,”’ Bibliotheque
Universelle, tom. xxii.
+ Ibid.

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yy

REPORT ON PHYSICAL OPTICS. all

tained by Mr. Challis. Assuming that the density of the ether
is the same in solid media as in free space, (an assumption
which he seems to think required by the phenomenon of aberra-
tion,) this mathematician conceives that the reflexion of light,
and its retardation in the denser medium, may be both accounted
for by the reflexions which the ethereal waves undergo from
the solid particles of the medium which they encounter in their
progress *. He shows, in fact, that the absolute velocities
impressed upon the ethereal particles by such reflexion may be
resolved into two parts, one of which is propagated uniformly,
and is accompanied by a change of density ; while the other is
propagated instantaneously, without change of density +. The
former of these, he thinks, will account for the reflexion of light,
the latter for the diminished velocity of transmissiont. This
ingenious theory has the advantage of connecting the velocity of
propagation in dense bodies directly with their constitution, and
so of advancing a step in the process of physical induction. On
the other hand, it requires us to admit that the particles of ether
and those of gross bodies exert no mutual action of any kind.
We know too little of the ether, or of its properties, to deny this,
simply because it is unsupported by any of the properties of
matter hitherto revealed ; but it must at the same time be ad-
mitted that the violation of such analogies furnishes an argument
of some weight against the theory which demands them.

_ Whatever supposition we may frame respecting the constitu-
tion of bodies, or of the ether within them, in the wave-theory,
it must be such that the velocity of propagation is less in the
denser medium. In the theory of emission, on the other hand,
it is the reverse ; so that although it conducts to the same result,
it does so by an opposite route. Here, then, the rival theories are
at issue upon a matter of fact; and we have only to ascertain

»_ * This manner of conceiving the reflexion of light, in the wave-theory, was
that originally entertained by Fresnel, and was put forward in a memoir read
to the French Academy in 1819.

* + Phil. Mag., New Series, vol. xi.

- } The mean effect of these reflexions, Mr. Challis shows, is equivalent to
that of a retarding force; and, by a certain supposition respecting its value,

he has arrived at the following simple formula for the determination of the ratio

of the velocities of propagation in free space and in the medium

om —l= :
in which 9 denotes the density of the medium, and H a constant proportional
to the mean retarding effect of a given number of its molecules. For the gases,

pe

‘ —l1., :
then, the quantity 7 3 nearly constant, whatever be the compression.

This result is a very simple consequence of the theory of emission; its ex-
perimental truth has been established by MM. Biot and Arago. Phil. Mag., New

Series, vol. vii. :

312 FOURTH REPORT—1834.

this fact, in order to be able to decide between them: © This
seemed to be accomplished by the reasonings of Young. From
the laws of interference it appears that homogeneous light,
in its progress in space, passes through certain periodically re-
turning states, the intervals of which are constant in the same
medium ; while in different media they are proportional to the
velocities of propagation, since the member of such intervals in
a given quantity of light cannot be supposed to vary. Now it
followed from the experiments of Newton that the intervals,
by which he explained the phenomena of thin plates, were di- |
minished in the denser medium; and as these intervals have
been shown by Young to be identical with those deduced from
the law of interference, it followed that the velocity of light was
slower in the denser medium *. Newton had even found the
ratio of the magnitudes of the intervals to be the same with that
of the sines of incidence and refraction ; and this is precisely as
it should be on the principles of the wave-theory.

But the retardation of light in the denser medium has been
directly established by M. Arago. If two pencils be made to
interfere and produce fringes, as in the experiment of Fresnel,
and if a thin plate of a denser medium be interposed in the
path of one of them, the whole system of fringes will be shifted
to one side or the other, according as the light has been accele-
rated or retarded within the plate. The result of this import-
ant and decisive experiment was in favour of the theory of
waves ft.

The refractive index being equal to the ratio of the velocities
of light in the two media, direct or inverse, it follows, which-
ever theory we adopt, that any change in the velocity of the in-
cident ray must cause a variation in the amount of refraction,
unless the velocity of the refracted ray be altered proportionally.
Now the relative velocity of the light of a star is altered by the
earth’s motion; and the amount of the change is obviously the
resolved part of the earth’s velocity in the direction of the star.
It was therefore a matter of much interest to determine how,
and in what degree, this change affected the refraction. By the
observation of this effect, it was hoped, we should have an easy
and accurate method of determining the constant of aberration ;
we should be enabled to compare the light of different stars,
and detect any difference which might exist in their velocities ;
and lastly, we might compare these velocities with that of light

* « Experiments and Calculations relative to Physical Optics,” Phil. Trans.

1803.
+ Annales de Chimie, tom. i. See also the account of Mr. Potter’s repeti-

tion of this experiment, Phil. Mag., vol. iii. p. 333.

REPORT ON PHYSICAL OPTICS. 313

emanating from other sources, The experiment was undertaken
by M. Arago, at the request of Laplace*. An achromatic
prism was attached in front of the object-glass of the telescope
of a repeating circle, so as to cover only a portion of the lens,
The star being then observed directly through the uncovered
part of the lens, and afterwards in the direction in which its
light was. deviated by the prism, the difference of the angles
read off gave the deviation. The stars selected for observation
were those in the ecliptic, which passed the meridian nearly at
6 A.M. and 6 P.M., the velocity of the earth being added to
that of the star in the former case, and subtracted from it: in

‘the latter. No difference whatever was observed. in the devia-

tions ; and the result was the same whatever was the origin of
light +. Fraunhofer has likewise compared the light of several
of the fixed stars with respect to its refrangibility. No differ-
ence whatever was observed, although the method employed
was adequate to the detection of a difference so small as the
10,000th part of the whole refraction nearly {. .

This remarkable and unexpected result can be reconciled to
the theory of emission.§, as M. Arago has observed, only by
the hypothesis. already adverted to, namely, that the molecules
are emitted from the luminous body with various velocities ; but
that among these velocities there is but one which is adapted to
our organs of vision, and which produces the sensation of light.
The wave-theory has been more successful in its explanation. If
the ether which encompasses our globe were like its atmosphere,
and partook of its motion, the refraction would be precisely the
same as if the whole were at rest. This however, we have seen,
cannot be the case; and the. phenomena of aberration compel
us to. admit that. the ethereal medium which encompasses the
earth is not displaced by its motion. This being assumed, it
follows that the ether which is carried along by the refracting
mediam, is that which constitutes the excess of its density above

era ) : , ; i
* The idea of detecting a difference in the velocity of the light of the fixed
's,’ by its effect upon the amount of refraction, seems to have first occurred

_ te Mr, Michell. Such a difference of velocity, he conceived, must nécessarily

arise from the different attractions of the stars upon the emitted molecules ; and

he has computed the diminution of the original velocity of emission arising

from this cause. Phil. Trans. 1784.

' + Biot, Astronomie Physique, vol. iii.

_ Ldinb. Journ. of Science, viii. p. 7.

- § M. Prevost has endeavoured to reconcile the experimental result of M.
Avago with the ordinary suppositions of the theory of emission, and to show that
a change in the relative velocity of the light of the stars, caused by the motion
of the refracting plane, does not affect the refraction in the same manner as an
equal change of the absolute velocity,—“ De ]’Effet du Mouvement d’un plan
refringent sur la Refraction,” Geneva Memoirs, vol. i. His reasonings do not
appear to be conclusive.

314 FOURTH REPORT—1834.

that of the surrounding ether. On this supposition Fresnel has
caleulated the length of a wave in the moving medium, and
thence also the actual change in the direction of the refracted
ray produced by the earth’s motion*. This change is found to
be opposite, and exactly equal to that produced by the same
cause in the apparent direction of the ray ; so that the ray is
actually seen in the same direction as if the earth were at rest,
and the apparent refraction is unaltered by the earth’s motion.
These results, it may be observed, are precisely the same for
terrestrial objects, the velocity of wave-propagation being inde-
pendent of the motion of the luminous body.

Newton thought that the different refrangibility of the rays of
light could be explained by supposing simply that they were
bodies of different sizes, the red being greatest and the violet
least. It is obvious, however, that this supposition can have no
reference to the simple projectile hypothesis held by his followers,
or to the demonstration of the law of refraction given in the
Principia. It is connected with that more complex theory, in
which the molecules of light are supposed to excite the vibrations
of the ether in the bodies which they meet.

M. de Courtivron and Mr. Melville proposed to account
for the dispersion of light by a difference in the initial velocity
of the molecules, the red being swiftest and the violet slowest.
But were such the cause of the phenomenon, the dispersion
should be proportionate to the mean refraction. Indeed the
hypothesis was abandoned almost as soon as proposed. Its
authors had foreseen the consequence that, in the eclipses of
Jupiter’s satellites, the colour of the light should vary just before
immersion, and after emersion; and the existence of such an
effect, in the degree indicated by theory +, was completely dis-
proved by the observations of Mr. Shortt. Another conse-

quence of such a difference in the initial velocities of the light of ©

different colours is, that the aberration of the fixed stars should
also vary with the nature of the light, and each star appear as a

* The sine of the change isto the sine of the total deviation of the ray in the
ratio of the velocity of the earth to that of light. Fresnel’s result is much more
complicated, but it will be easily seen to reduce itself to this—‘ Sur 1’ Influence
du Mouvement terrestre dans quelques Phénoménes d’Optique,” Annales de
Chimie, tom. ix. y

+ The duration of this change, according to Mr. Melville, should amount
to thirty-two seconds, the velocity of the light of different colours being in-
versely as their refractive indices.—(Phil. Trans. 1758.) This principle, how-
ever, as M. Clairaut has shown (Phil. Trans. 1754), is obviously incorrect.
It will easily appear that the initial velocities must vary inversely as
the quantity 4/~* — 1, in order to account for dispersion ; and that the dura-
tion of the expected phenomenon must be even greater than that assigned
by Mr. Melville.

t Phil. Trans. 1753.

a

REPORT ON PHYSICAL OPTICS. 815

coloured spectrum, whose length is parallel to the direction of
the earth’s motion.

According to the modern advocates of the theory of emission,
the molecules of light are heterogeneous ; and the attractions
exerted on them by bodies vary with their nature, and are, in
this respect, analogous to chemical affinities. This supposition,
however, as Dr. Young has justly observed, is but veiling our
inability to assign a mechanical cause for the phenomenon.

It is remarkable that Newton himself was the first to suggest
that part of the wave-theory, in which the colour of the light is
supposed to be determined by the frequency of the ethereal vibra-
tions, or by the length of the wave *; and the addition has been
received by all its supporters. But observation proves that the
refractive index, or the ratio of the velocities of propagation,
in the two media, is different for the light of different colours.
The advocates of the wave-theory, therefore, are forced to con-
clude that the velocity of propagation in refracting media varies
with the length of the wave. Here, then, we encounter a diffi-
culty in this theory, which has been regarded as the most for-
midable obstacle to its reception. Theory indicates that the
velocity of wave-propagation is constant in the same medium,
depending solely on the elasticity of the medium as compared
with its density. That velocity, therefore, should be the same
for light of all colours, as it is found to be for sound of all notes:

Various attempts have been made to solve this difficulty +.
Euler thought that the successive waves underwent an increase
of velocity arising from their mutual action; and this increase
he supposed to vary with their length, the waves of greatest
length undergoing the least augmentation of velocity, and
being therefore most refracted {. But the phenomena of coloured
rings, as Kuler perceived, compel us, on the contrary, to sup-

<2

std that the lengths of the waves diminish as the refrangibility
ncreases ; and he seems himself to have abandoned his first
conjecture. 3

_ Dr. Young accounted for dispersion by the supposition that
the solid particles of the refracting substance vibrate, as well as

the particles of the ether within it ; and that the former vibra-

tions affect the latter, and affect them differently according to

* Phil. Trans. 1672.

+ It is scarcely necessary to advert here to the law proposed by M. Rudberg,
to connect the lengths of an undulation, or the velocities of propagation, in
different media ;—for this law is purely hypothetical, and its apparent consist-

ency with observation has arisen solely from the adaptation of the arbitrary

constants which enter the expression.— Annales de Chimie, tom. XXXvi. XXXVil.
t Opuscula varit Argumenti, tom. i.. p. 217.

316 FOURTH REPORT —1834.

their frequency. Mr. Challis has adopted and developed this
hypothesis. According to this author, it has been already ob-
served, the diminished velocity of transmission in the denser
medium may be explained by the obstacle which the solid
particles of the medium offer to the free movement of the
ethereal particles. If the former be supposed to be immoveable,
the ratio of the velocities of propagation, in free space and in
the medium, will be a simple function of the density of the
latter, and in a given medium its value will be constant; but
when the particles of the medium vibrate, the value of this
ratio will depend also on the length of the wave, and will there-
fore vary with the colour of the light *.

The solution suggested by Professor Airy is more closely
connected with received principles. It is now generally admitted
that part of the velocity of sound depends on a change of elas-
ticity, which the air undergoes during its vibrations, in conse-
quence of the development of latent heat by compression, | If
this heat required ¢ime for its development, the quantity de-
veloped, and therefore the elastic force, must vary with the time
of vibration. Consequently the velocity of propagation should
also vary with the time, and be different for waves of different
lengths. Professor Airy imagines something similar to this
in the case of light; and conceives that the elasticity of the
ether, in refracting media, may consequently undergo a change,
whose amount depends on the time of vibration.

But the explanation offered by Fresnel seems to be the
simplest and most natural. The conclusion of analysis—that
the velocity of wave-propagation is constant in the same homo-
geneous medium,—is deduced on the particular supposition that
the sphere of action of the molecules of the medium is inde-
finitely small compared with the length of a wave. If this re-
striction be removed, we have no longer any ground for con-
cluding that waves of different lengths will be propagated with
the same velocity. Fresnel states that he has demonstrated,
that when the mutual action of the ethereal molecules extends
to a sensible distance as compared with the length of a wave, the
waves of different lengths will be propagated with different
velocities ; the elasticity of the medium, and therefore also the
velocity, increasing with the length of the wavet. Here then

* “ An Attempt to explain theoretically the different Refrangibility of the
Rays of Light, according to the hypothesis of Undulations,” Phil. Mag., New
Series, vol. viii.

+ This demonstration is more than once referred_to by the author, as con-
tained in a note appended to his memoir on double refraction. ‘The note how-
ever, probably by some oversight, has never been printed.

ee

REPORT ON PHYSICAL OPTICS. ; 317

the constancy of the velocity of wave-propagation is regarded
but as the approximate result of an incomplete analysis. The
problem presented itself to M. Cauchy in a similar point of
view. In the profound researches of this mathematician relating.
to light, the ether is considered as a system of particles solicited
by mutual attractions or repulsions ; and from the partial diffe-
rential equations which represent their movement, he had de-
duced the laws of propagation in crystallized as well as homo-
geneous media. These equations however were but approximate,
and derived from others of greater generality by the omission of
the terms containing the higher powers of the displacements,
and of their derivatives with respect to the coordinates. Re-
suming the problem of the propagation of a plane wave, with
the aid of the more general equations, he has finally demon-
strated the existence of a relation between the velocity of pro-
pagation and the length of the wave*.

The opacity of bodies is ascribed by Newton to the discon-
tinuity of their parts, and to the multitude of internal reflexions
which the rays of light undergo within them+. We have many
reasons for believing this to be the case; but as yet we are far
from a complete account of the phenomenon. If the reflexions
and refractions, which thus arise at each new bounding surface,
be similar to those which take place at the outer surfaces of
bodies, the molecules of light will indeed be scattered in every
direction, but they should undergo no diminution of velocity.
How, then, is it that they do not emerge finally from the body as
readily as they entered it, and thus render it visible in all di-
rections,—not by a superficial reflexion, but by a secondary
emission? T'o account for the extinction of light, in the theory
of emission, we must suppose it united to the body which it
enters; and the simplest mode in which we can conceive this
union to be brought about, is by the direct impact of the mole-
cules of light on those of bodies, whereby they are brought within
the sphere of those interior attractive forces to which chemical
combinations are referred. This appears to have been the opinion
of Newton. ‘ Are not gross bodies and light,’’ says he, ‘* con-
vertible into one another, and may not bodies receive much of
their activity from the particles of light which enter their com-
position? For all fixed bodies being heated emit light, so long
as they continue sufficiently hot, and light mutually stops in
bodies as often as its rays strike upon their parts{ .”

* Mémoire sur la Dispersion de la Lumiére.—The attention of the Mathe-
matical Section of the British Association was drawn to this theory by Professor
Powell, at the last meeting, chiefly in reference to a limitation which seemed
to be required in the physical hypothesis. —See Report of Proceedings.

} Optics, book 2, part'3. + Optics, Query 30.

318 FOURTH REPORT—1834.

When from the simple fact of absorption we proceed to con-
sider its law, as depending on the nature of the light, the diffi-
culties increase at every step. -The intensity of the transmitted
light considered as a function of its refrangibility appears to be
subject to no law, or to a law so complicated as completely to
bafile all attempts to embrace it in an empirical rule. The max-
ima and minima are often actually numberless ; and the vari-
able does not reach them gradually, but by what seems to be an
abrupt violation of the law of continuity. These apparently ca-
pricious changes were observed long since by Dr. Young, in the
light transmitted through the common smalt-blue glass. Sir
David Brewster has recently directed his attention to the same
subject, and examined a great number of coloured bodies with
reference to their absorptive properties. He has found, in par-
ticular, that a very remarkable definite action is exercised upon
the rays of the spectrum by the green liquids obtained by extract-
ing the colouring-matter of the leaves of plants in alcohol; and
this action does not cease altogether even when the liquid has
become perfectly colourless *. But the absorbing properties of
nitrous acid gas, observed by the same author, are by far the
most remarkable ever noticed. When the light transmitted
through this gas is analysed by a prism, it is found that about
two thousand portions of the beam are stopped, and two
thousand dark spaces, or abrupt deficiencies of light, appear in
the spectrum. These increase in number and magnitude with
the temperature of the gas, until, by a sufficient elevation of
temperature, this rare body becomes perfectly opaque, and re-
fuses to transmit a single ray of the brightest sunshine +.
Prof. Miller and Prof. Daniell have found some analogous pro-
perties in other gases. In the spectrum produced by the light
transmitted through the vapours of bromine and iodine, more
than one hundred dark lines are visible, disposed at equal di-
stances f.

To account for the selection of certain classes of rays by
coloured media, in the theory of emission, it seems necessary
to suppose that an attractive force is exerted at a distance be-
tween the molecules of the body and those of light, and that
the absolute value of this force varies with the colour. It does
not seem easy to reconcile these suppositions to the Newtonian
account of refraction ; and the difficulty is still further increased
when we proceed to apply the same considerations to the ab-
sorption of definite rays; and introduce the hypothesis of

* ‘On the Colours of Natural Bodies,” Edin. Trans., vol. xii.
+ “ On the Lines of the Solar Spectrum,” &c., Edin. T'rans., vol. xii.
+ French translation of Herschel’s Zssay on Light, Supplement, p. 455.

ee

REPORT ON PHYSICAL OPTICS. 319

specific actions, varying in.the most abrupt and irregular man-
ner with the refrangibility of the ray *.

The absorption of light, and the opacity of bodies, were long
since urged by Halley as difficulties in the wave-theory. The
ether is supposed to penetrate all bodies freely, and why not
also the undulatory motion in which light consists? To this
difficulty we find a full and complete solution in the principle of
interference. When a wave enters a discontinuous substance,
it will be broken up, and its parts undergo continued subdivision
by internal reflexions; so that when these parts reach the
second surface of the body, they are found in every possible
phase, and must destroy one another by interference. The
phenomenon, as has been observed by Sir John Herschel, is
analogous to the impeded propagation of sound in a mixture of
gases differing much in elasticity as compared with their density.

_..The same writer has given an ingenious and natural account

of the absorption of specific rays on the principles of the wave-
theory, in a paper read before the Association last year+. He
considers the molecules of the body and those of the ether as
forming, conjointly, compound vibrating systems, which are
more disposed to transmit vibrations of some determinate period
than others. Other vibrations, however, not in unison with
these systems, may be propagated through them. These forced
vibrations, as he calls them, will be obstructed in their progress,
and. their amplitudes diminished by the mutual influence of the
motions of the parts of the systems ; and he shows that it is
possible to conceive systems, which will be wholly impervious
to a vibration of a particular period, while they freely transmit
others not differing from them materially in their frequency f{.
But these important and interesting speculations, it must be
remembered, are advanced by their author solely with the view
of removing an imagined inconsistency between the phenomena
of absorption and the mechanical laws of vibratory movement.

_ * See Sir David Brewster's Report on Optics.
~ +On the Absorption of Light by coloured Media, viewed in connexion with
the Undulatory Theory,” Phil. Mag., Third Series, vol. iii.
_ + An interesting interference experiment, similar in some respects to that
indicated by Sir John Herschel in this paper, has been recently made by Mr.
ane. _A compound tube, whose branches of 9 and 133 inches united at the
two extremities, was made to sound by the Janguette of an organ pipe. Each
of the tubes, separately, gave its own fundamental note, and all its harmonics;
and when a free communication was opened between them, the system gave all
the notes of the two series, with the exception of those whose waves were in
complete discordance. Thus the fundamental note of the short tube was stopped
altogether, while its octave was given with remarkable clearness; the two
waves being in complete discordance in the former case, and in complete ac-
cordance in the latter.

3820 FOURTH RELORT-~ 1984)

Weare still far from a precise theory of absorption. When
such a theory shall have been established, there seems reason to

believe that it will bring with it also an insight into the internal |

constitution of bodies even yet more close than that afforded by
the affections of polarized light; and that the laws of molecular
action may perhaps, at some future day, be studied in the phe-
nomena of transmitted light. .

The properties of solar phosphori, which attracted so much
of the attention of experimental philosophers of the last century,
“seem at first view to favour the account of absorption suggested
by the theory of emission, and to arise from the disengagement
of the light which had become united to the body. Canton ob-
served that light may remain in these bodies, as it were in a
latent state, for several months, until its re-emission is deter-
mined by the action of heat. But it must be observed, in the
first place, that the feeble light emitted from the phosphori
bears a very small proportion to that which they are supposed
to receive by absorption. Dessaignes has remarked that most
of these substances emit the same kind of light, whatever be
the species of light to which they have been exposed*. The
same fact has been observed by M. Grotthouss+ and other sub-
sequent inquirers; and in some of the diamonds. possessing
the property of phosphorescence, the most efficacious exciting
light is of a different colour from that excited. These facts
seem to be inexplicable in the theory of emission. In the wave-
theory, on the other hand, the phenomenon is easily compre-
hended. As the vibrations of the air excite those of sounding
bodies, and communicate to them a motion which continués for
some time after the exciting cause has ceased to act ; so it must
also be with the undulations of the ether. “When the body is
in unison with the incident light, their vibrations will continue
isochronous, and the undulations of the ether excited by the
body will be of the same length as those by which it is itself
excited. In the other case, the period of vibration, and conse-
quently the length of the wave, will be altered, and the excited
and exciting lights will be of different colours. The fact ob=
served by Canton is indeed not so easily explained. Young
supposed that the vibrations of the body may be abruptly sus-
pended by cold, and may proceed anew when released from this

* Mém. Inst. tom. xi.

+ Schweigger’s Journal, 1815.—The same observer discovered the curious
fact, that the electric current restored the property of phosphorescence, in
et cases where it appeared to have been destroyed by the action of violent
leat. :

REPORT ON PHYSICAL OPTICS. 321

restraint, like a string which has been stopped and detained in
any part of its vibration on either side of the centre.

The fixed lines in the solar spectrum first noticed by Wollaston,
and afterwards more minutely traced by Fraunhofer, have lately
been examined with great care, and with his usual success, by
Sir David Brewster ; and he has observed a remarkable coinci-
dence between these lines and the dark bands of the spectrum of
the nitrous acid gas*. Sir David Brewster has also studied, in
connexion with the same subject, the definite absorbing effects
of the earth’s atmosphere. This has been effected by examining
the solar spectrum, when the sun was near the horizon ; and it
has been found that most of the dark bands thus developed be-
longed to the fixed lines of Fraunhofer, which were thus, as it
were, widened, and brought out, by the absorptive action of the
atmosphere. A similar result has been arrived at in other cases,
and it has been found that the points of the spectrum on which
absorbing bodies exert the strongest specific actions are gene-
rally coincident with the deficient rays of solar lightt. This
singular connexion gives considerable weight to the speculations
of Sir David Brewster respecting the latter phenomena f.

The observation of the fixed lines in the solar spectrum led
Fraunhofer to examine the optical characters of the lights ema-
nating from other sources. He thus arrived at the interesting
discovery, that the system of bands in the different species of
light which he examined, varied with the source; while it was
constantly the same in the number of the bands, and their
relation to the coloured spaces, in the light of the same
source, however modified. In the light of Sirius there are three
bread bands which have no resemblance to those of solar light.
The light of the electric spark, on the other hand, when ana-
lysed by the prism is found to have several bright lines, of
which that in the green is remarkably brilliant. Similar phe-
nomena were observed in the light of artificial flames,—the flame
of an oil lamp, for example, exhibiting a well-defined bright
band between the red and yellow, and another not so distinct
in the green §. This however is not universally the case. In
the red flame of strontia, as was observed by Dr. Faraday and
Mr. Talbot, there are a number of red rays separated from each
other by dark bands; and in the flame of cyanogen, when .
similarly analysed, the violet is found to be divided into three
distinct portions with broad dark intervals §.

~* “ On the Lines of the Solar Spectrum,” din. Trans., vol. xii.
+ ‘ On the Colours of Natural Bodies,” Edin. Trans., vol. xii. °
t Report on Optics. § Munich Memoirs.
|| Phil. Mag., Third Series, vol. iv. p. 114. et
1834. Y

922 FOURTH REPORT—1834.

It is easy to account for the general fact of the deficiency of
certain classes of rays in certain lights. When a body violently
heated begins to shine, the phenomenon is simply accounted
for, in the wave-theory, by an increase in the frequency of its
vibrations. In the saine manner it seems natural to suppose,
generally, that the mechanical agencies at work during com-
bustion accelerate or retard, in various ways, the rate of vibra-
tion, and so alter the character of the emitted lights. The
light emitted in weak or incipient combustion is generally blue.
Sir John Herschel observed that when sulphur burns with a
feeble flame, its light contains all the rays of the spectrum,
and particularly the blue and violet ; while, in vivid combustion,
these disappear entirely, and the light is a yellow of almost
perfect homogeneity *. The various shades of colour in the
flame of a common candle,—from the deep blue of the lower
part (which is found by prismatic analysis to consist of five
distinct portions,) to the yellowish white in the centre, and
thence to the dusky red at the apex of the flame,—seem to be
referrible to the same principle. Fraunhofer and Sir David
Brewster have both remarked that the flame of oil; urged by
the blowpipe, consists chiefiy or wholly of yellow rays. The
same fact was long since observed by Mr. Melville with respect
to the flame of alcohol, into which nitre, muriate of soda and
other salts had been introduced + ; and Sir David Brewster has
found that the quantity of yellow light given out by burning
bodies increases with their humidity, the flame of alcohol diluted
with water being nearly a homogeneous yellow}. It is more im-
portant to remark however, in illustration of the undulatory
view of the phenomenon of emission, that the colowr of flames is
often found to depend on the presence of something which is it-
self unaltered in the process of combustion. Thus Mr. Talbot
has remarked that when a small quantity of muriate of lime was
placed on the wick of a spirit lamp, it gave out red and green
rays during an entire evening, though the salt was not sensibly
diminished §. The absence of definite rays in certain lights,
and the fixed lines of the solar spectrum, have been referred
by Sir John Herschel to the same principle by which he has
explained the absorption of specific rays ||.

In what has preceded we have assumed the truth of the re-
ceived theory with respect to the composition of solar light,
and the connexion between the colour of a ray and its refrangi-
bility. This theory however has been recently opposed by Sir

* “ On Absorption of Light in coloured Media,” Edin. Trans., vol. ix.
+ Edinb. Essays. t On a Monochromatic Lamp. Jbid.
§ Edinb. Journ. of Science, v.77. || Phil. Mag., Third Series, vol. iii. p. 407.

REPORT ON PHYSICAL OPTICS. 323

David Brewster. According to this philosopher, white light
consists of but three simple colours,—red, yellow, and blue ;
and the solar spectrum is composed of three overlapping spectra
of these colours, the intensity of each of which is greatest at
the point where that colour is strongest in the compound spec-
trum. According to this view, then, all the colours in the solar
spectrum are compound, and consist of red, yellow, and blue
light, in different proportions. 'These compound colours can-
not be analysed by the prism, in as much as the rays of which
they consist at any point of the spectrum have the same refran-
gibility; and it is only by the different action of absorbing
media on their constituent elements that their compound nature
can be detected. Each of them may be conceived to consist of
a certain quantity of white light, and of an excess of the light of
two of the simple colours; and if this excess be absorbed, a
white light will be the result, which will be indecomposable by
the prism. This result of his hypothesis has been experimentally
confirmed by Sir David Brewster *.

These views, if finally established, sever the connexion be-
tween the colour of a ray and its refrangibility, laid down by
Newton; and the former must be supposed to depend,—not on
the length of the wave,—but on some other element of the vi-
bratory movement.

ae Ill. Diffraction.

~ It has been already stated that Newton considered the undu-
lations of an ethereal medium to be a necessary part of his the-
ory, and that that theory as maintained by its author differed
from the theory of Huygens and of Hooke, only by the addition
of a new hypothesis. The necessity of something extraneous to
the undulations of the ether seems to have been admitted by
Newton mainly to account for the right-lined propagation of

; the rays of light ; and a careful consideration,of his optical

writings leaves the impression, that had the wave-theory alone
appeared to explain this fact, Newton would not have hesitated
to embrace it. This explanation has been spoken of in another
place, and it has been shown to follow from that theory, that
the light which encounters an obstacle must diminish rapidly
in intensity within the edge of the geometric shadow. It now
remains to consider the other phenomena which arise under these
circumstances ; and it will be found that the same theory affords
the most complete account, not only of their general characters,
but even of their numerical details.

In order to understand the theory of shadows, it is necessary

* “ On a New Analysis of Solar Light,” Edin. Trans. 1831.
Y2

B24 FOURTH REPORT—1834.

to investigate their laws in the simple case in which the mag-
nitude of the luminous body is reduced to a point. The effects
thus presented were first observed by Grimaldi, and they have
been since studied, as a separate branch of optical science, under
the title of diffraction or inflexion. Grimaldi found that when
a small opaque body was placed in the cone of light, admitted
into a dark chamber through a very small aperture, its shadow
was much larger than its geometric projection, so that the light
suffered some deviation from its rectilinear course in passing by
the edge. Observing these shadows more attentively, he found
that they were bordered with three iris-coloured fringes, which
decreased in breadth and intensity in the order of their distances
from the edge of the shadow, preserving the same distance from
the edge throughout its entire extent, unless where the body
terminated in a sharp angle. Similar fringes were observed
under favourable circumstances within the shadows of narrow
bodies*.

The phenomena of diffraction were subsequently examined
by Hooke and by Newton. The first observations of Newton
were but repetitions of those of Grimaldi; and it is remarkable
that he altogether overlooked the important phenomenon of the
interior fringes noticed by the Italian philosopher. But to
Newton we owe the analysis of the phenomena, so far as they
depended on the nature of the light. When the different species
of simple light into which the sun’s rays were divided by a prism
were cast in succession on the diffracting body, Newton observed
that the fringes formed were broadest in red light, narrowest in
the violet, and of intermediate magnitude in the light of mean
refrangibility, so that the iris-coloured fringes which are formed
in white light are but the fringes of different colours superposed.
But the observations of Newton most closely connected with his
physical theory are those in which the light is made to pass be-
tween two near knife-edges, whether parallel or inclined. From
these observations Newton concluded that the light of the first
fringe passed by the edge, at a distance greater than the 800th
of an inch, that of the second and third fringes passing at still
greater distances. These distances, however, were not the same
wherever the fringes were formed; and it appeared to follow
from the experiment, that the light of the same fringe was not
the same light at all distances, but that each fringe was, as it were,
a caustic formed by the intersection of the rays passing at dif-
ferent distances from the edge; the portion of the fringe near
the knives being formed of light which passed nearest to the
edge and was most bent f.

* Physico-Mathesis de Lumine, Bologna, 1665.
+ Optics, Book iii.

=

REPORT ON PHYSICAL OPTICS. 525
To account for these phenomena Newton supposed the rays
of light to be inflected in passing by the edges of bodies, by the
operation of the attractive and repulsive forces which the mole-
cules of bodies were conceived to exert on those of light at sen-
sible distances. Thus, the rays passing by the edges of a nar-

‘row opaque body are supposed to be turned aside by its repul-
sion ; and as this force decreases rapidly as the distance increases,
the rays which pass at a distance from the body will be less de-
flected than those which pass close to it. The caustic formed
by the intersection of these deflected rays will be concave in-
wards ; and as none of the rays pass within it, it will form the
boundary of the visible shadow. To explain the alternations of
darkness and light beyond this, Newton appears to have sup-

‘posed that the attractive and repulsive forces succeed one another

for some alternations ; and that the molecules composing each
ray, in their passage by the body, are bent to and fro by these
forces “‘ with a motion like that of an eel,” and are finally thrown
off at one or other of the points of contrary flexure. The sepa-
ration of white light into its elements is explained, by supposing
that the rays which differ in refrangibility differ also in inflexibi-
lity ; the body acting alike upon the less refrangible rays at a
greater distance, and upon the more refrangible at a less di-
stance*. In one of his letters to Oldenburgh ¢, Newton advances
a more refined theory of diffraction. The bending of the ray

' near the edge of the obstacle he conceived to arise from a varia-

tion in the density of the ether in the neighbourhood of the body ;
and, following the analogy of thin plates, he endeavoured to ac-

count for the coloured fringes by the vibrations of the ether

which are propagated faster than the rays themselves, and over-
take them at the middle of the curved portion of the trajectory
they describe. .
~ It isneedless to comment upon the vagueness of these expla-
‘nations. Newton himself was dissatisfied with them, and the
‘subject fell from his hands unfinished. Still, however, the mere
‘guesses of such a mind as that of Newton must possess a high
I terest, and we are not to wonder that among his followers more
‘weight should be attached to these explanations than he himself
“ever gave them. It seems necessary therefore to advert to some
of the circumstances of these phenomena, which are not only
unexplained by this theory, but which seem moreover irrecon -
cileably at variance with it.

If the phenomena of inflexion be the effects of attractive and

-Tepulsive forces emanating from the interposed body, and if

these forces are the same, or even analogous to those to which

- * Optics, Book iii. Queries 1, 2, 3, 4. :
t December 21, 1675.—Birch’s History of Royal Society, vol. iii.

326 FOURTH REPORT—1834.

the reflexion and refraction of light are ascribed in the theory of
emission, it will follow that they must exist in different bodies
in very different degrees ; so that the amount of bending of the
rays, and therefore the position of the diffracted fringes, should
vary with the mass, the nature and the form of the inflecting
body. Now it is clearly ascertained, on the contrary, that all
bodies, whatever be their nature or the form of their edge, pro-
duce under the same circumstances fringes identically the same ;
and in fact the partial interception of light, caused by the inter-
position of an obstacle of any kind, seems to be the only condi-
tion on which the character of the phenomenon depends.
Gravesende seems to have first observed that the nature or den-
sity of the body had no effect upon the magnitude of the diffracted
fringes ; and the fact has since been confirmed in the fullest
manner by almost every inquirer in this branch of experimental
science. One of the ablest supporters of the theory of emission
has admitted that the inflecting forces, if such exist, must be inde-
pendent of the chemical nature of the inflecting body, and altoge-
ther different in their nature from those to which, in the same
theory, the phenomena of reflexion and refraction are ascribed*.
To ascertain whether the form of the edge had any effect upon
the fringes, Fresnel took two plates of steel, the edge of each
of which was rounded in one half of its length and sharp in the
remaining half, and placed the rounded portion of one edge op-
posite the angular part of the other, and vice versd. If, then, the
position of the fringes depended on the form of the surface, the
effect would thus be doubled, and the fringes appear broken in
the middle. They were found, on the contrary. to be perfectly
straight throughout their entire length+.

Again, the inflecting forces (though they must be supposed
to vary in intensity, with the form and mass of the body, and
with the distance of the luminous molecule from the edge) can-
not be conceived to depend in any way upon the distance pre-
viously traversed by the molecule before it arrives in the neigh-
bourhood of that edge; so that the magnitude and position of

* Biot, Précis élémentaire, vol. ii. p. 473, 3"¢ Edit.

t Mémoire sur la Diffraction, p. 370. The Bulletin Universel for February
1828 contains some animadversions on this part of Fresnel’s optical labours, in
a paper signed by the secretary of the Academy of Sciences of St. Petersburgh,
and purporting to be an official reply to some remarks in a former number of
the Bulletin on the programme of the prize questions proposed by the Academy.
The writers have confounded two experiments of Fresnel which were instituted
with different views, and differently reasoned upon. Fresnel’s object in this
experiment was simply to show that the form of the edge produced no effect
upon the fringes, as it ought to do if diffraction arose from attractive or repul-
sive forces extending tosensible distances from bodies. Most of the objections
urged in the same paper against the wave-theory arise, in like manner, in mis-
conception.

'

br

REPORT ON PHYSICAL OPTICS. 327

the fringes, in this hypothesis, cannot vary in any way with
the distance of the inflecting edge from the luminous point.
But this conclusion is the reverse of fact: the fringes dilate in
breadth, and their mutual inclination is increased, as the screen
approaches the luminous origin. There seems to be but one
way of avoiding the inference drawn from this fact: against the
theory of emission. It may be supposed that the bands have
their origin at some sensible distance from the edge of the body,
and thus that the obliquity of the incident ray varies as the edge
approaches the luminous point. Such was the conjecture of

- Dutour, who noticed the fact. Fresnel has calculated the

breadth of the fringes according to this supposition, and found
that the computed and experimental results do not agree*. But,
in point of fact, the bands may be supposed without sensible
error to have their origin at the edge itself. Fresnel found by
direct measurement that the distance of the third band from the
edge of the shadow at its origin was less than the 100th part of
a millimetre. y

The objections just considered seem to apply equally to the
hypothesis of Mairan and Dutour, in which the phenomena of
diffraction are referred to the reflexions and refractions of an
atinosphere supposed to encompass all bodies. For if such an
atmosphere be retained around the body by its attraction, (and
this seems to be the only mode of accounting for its presence,)
its density and its form must vary with those of the body itself,
and consequently its effects upon the rays of light must vary
also. But the experiments of M. Haldat seem to leave no
tenable ground for these hypotheses. Every agent has been tried
which could be conceived capable of modifying the attractive
force of the body, or the density of the imagined atmosphere,
‘and without effect. The metallic wires and plates which pro--
duced the fringes were heated to redness, and cooled down be-
low the freezing-point ; they were traversed by voltaic currents,
and the charges of powerful batteries transmitted through them ;
“but in whatever manner the condition of the diffracting body
was varied, no change whatever was perceived either in the
intensity or dimensions of the diffracted fringest.
_ Although the phenomena of diffraction were studied by many
diligent observers { after the publication of the Optics, no ma-

_ *“ Mémoire sur laDiffraction de la Lumiére,” Mém. del’ Institut,tom. v. p.353.
+ “Sur les Causes de la Diffraction,” Annales de Chimie, tom. xli. Similar ex-
“periments had been made some time before by Mayer, and with the same result.
- Gottingen Memoirs, vol. iv.

$ Maraldi (Mém. Acad. Par, 1723.), Mairan (Ibid. 1738.), Dutour (Mé-
moires présentes, tom. v.), Mr. Brougham (Phil. T'rans., 1796—7.), and
Mr. Jordan (New Observations concerning the Inflewion of Light. London 1795).

328 FOURTH REPORT—1834.

terial accession was made to the knowledge of their laws until
the principles of the wave-theory were applied to their expla-
nation by Young. The exterior fringes, formed without the
shadows of bodies, were ascribed by Young to the interference
of two portions of light, one of which passed by the body and
was more or less inflected, while the other was obliquely re-
flected from its edge, the latter losing half an undulation at the
instant of reflexion*. The fringes formed by narrow apertures
were, in like manner, supposed to arise from the interference
of the two pencils reflected from the opposite edges ; while the
interior fringes, within the shadows of narrow bodies, were ac-
counted for by the interference of the pencils which passed on
either side of the body at an insensible distance, and were in-
flected into the shadow. The observed facts closely correspond
with the calculated results of this theory ; and in the case last
mentioned Young proved that the phenomena admitted of no
other explanation. Placing a small opaque screen on either
side of the diffracting body, so as to intercept the portion of
light which passed by one of its edges, the bands immediately
disappeared, although the light passing by the other edge was
unmodified. The same effect was produced, and by the same
means, upon the crested fringes of Grimaldi, formed within the
shadows of bodies having a rectangular terminationt. Thus the
phenomena of the fringes, or the alternations of light and dark-
ness, were shown to be cases of the more general principle of
interference ; and the connexion is now admitted by some of
the warmest advocates of the Newtonian theory{. The bending
of the light into the shadow, or the fact of inflexion itself, was
at first ascribed by Young to the refraction of an ethereal at-
mosphere encompassing bodies and decreasing in density with
the distance. He afterwards, however, adopted the simpler
doctrine of Huygens and Grimaldi, and referred the pheno-
menon to the fundamental property of waves.

But perhaps the most important of the labours of Young on
‘his subject is that in which he descends into numerical details,
and, taking the observations of Newton, as well as his own,
calculates the differences of the lengths of the paths traversed by
the two pencils, when they destroy or reinforce one another by
interference. These intervals he found to constitute an arith-
metical progression for the successive bands; the first term of
which was the same in the same species of light, whatever be

* “On the Theory of Light and Colours,” Phil. Trans. 1802. _

+ “Experiments and Calculations relative to Physical Optics,” Phil.
Trans. 1804.

{ Biot, Précis élémentaire, vol. ii. p. 472., 3° Edit.

REPORT ON PHYSICAL OPTICS. $29

the distance at which the fringes are received, or the other con-
ditions of the experiment. And, finally, comparing these con-
stants with the similar intervals of the two pencils reflected by
the surfaces of a thin plate, as deduced from the experiments
of Newton, he found that their difference was within the limits
of error to which such observations are liable, and that we are
warranted in concluding that the two classes of phenomena are
to be referred to one simple principle*. It is true, that in
these calculations, Young starts from an erroneous principle re-
specting the lights which form the diffracted fringes by their
interference, and he has remarked some discordances in his re-
sults which have, no doubt, their origin in that circumstance ;
but the results of the exact theory are not greatly different from
that which he adopted, and the more complete analysis of Fresnel
has only tended to confirm the conclusion obtained by Young.
The important experiment of Young, on the disappearance
of the fringes in the shadow of a narrow opaque body, when
the light passing by one of its edges was intercepted, was that
which first led him to the principle of interference. An in-
structive variation in this experiment was made by M. Arago.
The interior fringes were found to disappear likewise when the
light passing by one of the edges was transmitted through a
plate of some transparent substance; and by varying the
thickness of the interposed plate, M. Arago discovered that the
disappearance of the fringes in this case arose from their dis-
placement, the bands being always transferred to the side on
which the plate was interposed. From this it followed, that the
light was retarded in the denser medium+. M. Arago afterwards
produced the same modification in the interference bands formed

by two mirrors ; and the experiment, in this form, is a com-

plete crucial instance, as applied to the two theories of - light.
The amount of the displacement determines the velocity of
light in the medium, and therefore the refractive index, with an
accuracy unattainable by any other method. Professor Powell
has suggested a very elegant modification of this experiment,
which at once establishes the truth of the law, that the velocity
of light is inversely as the refractive index of the medium tra-
versed f.

_ The experimental laws of the diffracted fringes were next

_ examined by MM. Biot and Pouillet. In the case of a narrow

rectilinear aperture, (which was that chiefly studied,) they found

* “ Experiments and Calculations relative to Physical Optics,” Phil. Trans.
+ “ Sur un Phénoméne remarquable qui s’observe dans la Diffraction de la

Lumiére,” Annales de Chimie, tom. i.
} Phil. Mag., Second Series, vol. xi. p. 6.

330 FOURTH REPORT—1854.

that the deviations produced in the different species of simple
light, or the distances of the bands from the axis of the pencil,
were in all cases proportional to the lengths of the fits ; the mag-
nitude of the aperture remaining the same. The same analogy
was preserved in different media, the deviations varying in the
inverse ratio of the refractive indices of the media, or in the
direct ratio of the fits*. M. Pouillet adds, that they were un-
able to explain these laws, having adopted the theory of emissiont.
They are all simple consequences of the wave-theory. The in-
terval of the fits is exactly half the length of a wave, and the
true connexion between the place of the fringes and the latter
quantity had been already pointed out by Young.

Mayer afterwards studied the phenomena of diffraction, but
without adding any new facts to those already known. As to
the theory, he adopted that of Newton, with some modifications.
With Newton, he ascribed the inflexion of light into the shadow
to the operation of an attractive force; but, unwilling to admit
the existence of a repulsive force, he attempted to account for
deflexion by the impact of the molecules reflected from the edge
against those which passed by itt.

Fresnel at first adopted and developed Young’s theory of
diffraction, and found that the general laws of the fringes,—the
dependence of their magnitude upon the length of a wave, and
upon the distances of the luminous origin and of the screen,—
were thus fully explained. It was shown, that as the position
of the screen is varied, the successive points at which the same
fringe is formed are not in a right line, but constitute an hyper-
bola; and that when the distance of the luminous origin is les-
sened, the inclination of these hyperbolic branches considered
as coincident with their asymptots, augments, and the fringes
dilate in breadth§. Fresnel, however, was soon dissatisfied
with this theory. If the exterior bands had their origin in the
interference of the direct and reflected light, their intensity
should depend on the curvature of the edge; it is found, on
the contrary, that the fringes formed by the back and by the
edge of a razor are precisely alike in every respect. As to the
other cases of diffraction, there were many phenomena, and
especially those exhibited in Newton’s experiment with the two
knife-edges, which proved that the rays grazing the edges of the
body were not the only rays concerned in the production of

* Biot, Traité de Physique, tom. iv., Supplement a 1’Optique.
+ Elemens de Physique, tom. ii. p. 437.

t+ Comm. Soc. Gottingensis Recentiores, vol. iv. p. 49.

§ Annales de Chimie, tom. i. p. 239.

REPORT ON PHYSICAL OPTICS. Fo

the fringes, but that the light which passed by those edges at
sensible distances was also deviated, and concurred in their for-
mation*.

_ Fresnel was thus led to seek a broader foundation for his the-
ory, and the result of his investigations is given in the able
memoir which was crowned by the French Academy in 1819.
In this memoir the laws of diffraction are derived from the two
principles to which the laws of reflexion and refraction are them-
selves referred,—the principle of interference and the principle
of Huygens. To apply these principles to the present case,
Fresnel supposes the surface of the wave when it reaches the
obstacle to be subdivided into an indefinite number of equal
portions, and he applies the mathematical laws of interference,
unfolded in this memoir, to determine the resultant of all the

elementary waves sent by them at the same instant to any point.

This resultant is expressed by means of two integrals, which are
to be taken within limits determined by the particular nature of
the problem. Its square is the measure of the intensity of the
light; and it is found that its value has several maxima and
minima which correspond to the intensities of the light in the
bright and dark bands.

The problem of diffraction was thus completely solved, and
it only remained to apply the solution to the principal cases, and
to compare the results with those of observation. The cases of
diffraction selected by Fresnel are: 1st, The phenomena pro-
duced by a single straight edge ; 2nd, By an aperture terminated
by parallel straight edges; and 3rd, By a narrow opaque body
of the same form. The agreement of observation and theory is
so complete, that the computed places of the several bands sel-
dom differ from those observed by more than the 100th part of
a millimetre, the case of diffraction by narrow apertures alone
excepted. The small differences between observation and theory,
in this case, Fresnel ascribes to a false judgment of the eye as
to the position of the centre of the dark bands, occasioned by
the different intensities of the bright bands on either side; the
minimum always appearing nearer to the brighter light than it
really is. The computed places of the bands, in the first case
of diffraction, were found to differ from those deduced from the
hypothesis of Young by a small numerical quantity, the distance
of the first dark band being less in the former theory, in the
ratio of -936 to unity; but small as the difference is, the mea-
sures of Fresnel completely decide the questiont.

* Mémoire sur la Diffraction de la Lumiere, p. 368. t Lbid., p. 420,

3382 “FOURTH REPORT—1834.

M. Poisson applied Fresnel’s integral to the case of diffraction
by an opaque circular disc, and arrived at the singular result,
that the intensity of the light in the centre of the shadow is
precisely the same as if the disc were removed. This remark-
able anticipation of theory has been verified by the observation
of M. Arago*. Fresnel has himself solved the problem in the
analogous case of a circular aperture, and arrived at the result,
that the intensity of the light of any simple colour, at the cen-
tral spot, will be the same as that reflected by a plate of air,
whose thickness bears a certain simple relation to the radius of
the aperture, and its distances from the luminous origin and from
the eye. With homogeneous light, therefore, the illumination
of the central spot vanishes periodically, as the distance of the
eye from the aperture is varied; and in white light it assumes in
succession the most vivid and beautiful hues, coinciding with
those of the reflected rings of thin plates. These interesting
phenomena were observed about the same time by Sir John
Herschel, and their laws deduced, independently, from observa-
tiont. .

With the exception of the observations now referred to, no
attempt has been made to verify the theory, by comparing the
intensity of the light in the fringes with that deduced from the
formule ; and indeed it is obvious that a comparison of this
nature is ill calculated to afford any conclusive evidence on the
question. Fresnel thought, however, that the expression for the
intensity might be indirectly verified, by superposing two sets
of fringes (such as the interior and exterior fringes of a narrow
opaque body,) by means of double refraction, and then examin-
ing the position of the new maxima and minima. This ingeni-
ous suggestion does not appear to have been acted on.

The intensity of the light in the partial waves sent from each
point of the primary wave, considered as a distinct centre of
disturbance, will necessarily be different in different directions,
depending on the angle which these directions form with the
front of the original wave; and to solve the problem of diffrac-
tion in its most general form, it would be necessary to know the
law of this variation. Fresnel has shown, however, that the
rays whose directions are inclined at sensible angles to the nor-
mal to the front of the primary wave, destroy one another by
interference ; so that the actual effect is produced by rays inde-
finitely near that normal, and which therefore may be regarded
as of equal intensity. The truth of this assumption, however, is

« Mémoire sur la Diffraction, p. 460. t Essay on Light, Art. 729.

REPORT ON PHYSICAL OPTICS. Bue

disputed by M. Poisson. From his theory of the propagation
of motion in fluid media, this mathematician inferred that the
absolute velocities of the molecules are insensible in directions
making finite angles with the direction of the original vibra-
tions. He concludes, therefore, that these velocities, or the
intensity of the light in the partial waves, cannot be regarded
as sensibly equal in directions inclined to it at very small

angles*. Fresnel’s reply to this part of M. Poisson’s theory

has been already referredto. The principle of Huygens itself,
which forms the basis of Fresnel’s theory, though not denied
by M. Poisson, is yet objected to, as introducing a needless
complication. into the question ; and indeed it does not seem
easy to understand, at first view, why each point of the pri-
mary wave in this mode of composition should not give rise to
a retrograde as well as to a direct wave t. ;

An objection of a different nature has been raised against
Fresnel’s theory, derived from its supposed discordance with
phenomena. It is a consequence of that theory, when applied
to the case of diffraction by a narrow aperture bounded by pa-
rallel straight edges, that if a point be taken in the axis of the
pencil, whose distances measured from the centre and edge of
the aperture differ by half-a wave, that point will be the limit
within which all the interior fringes are confined; and beyond
that point the centre of the image will be always white. This
result is confirmed by the previous experiments of M. Biot, by
the observations of Fresnel himself, and by those of Professors
Airy and Powell, by whom they have been since repeated.
M. Biot found that the central band was dark and white alter-
nately, to a certain distance from the aperture; after which it
was always white. He remarks that when this limit is attained,
‘we may diminish the breadth of the aperture, and even bring its
sides into actual contact, without any change in the central
band except its enlargement and consequent diminution of in-

tensity t. ;
_ Newton’s celebrated experiment with the two knife-edges has

:
mee!

_* It may be necessary to state that it was part of M. Poisson’s theory, that
‘the vibrations are normal to the wave.
+ See Annales de Chimie, tom. xxii. p. 270, tom. xxiii.; and Airy’s Math.
Tracts, p. 267.
Traité de Physique, tom. iv. pp. 749, 760. The description of the pheno-
menon given by Mayer is very similar: “ Prout illa distantia acierum sem-
per magis magisque imminuitur, fascize adeo evanescunt, ita ut denique non
nisi fascia media remaneat ; sed ad dextram atque sinistram adeo in latitudinem
extensa, ut non nisi lumen languidunt, a medio spectri initialis utrinque instar
caude comet sese dilatans, representet.” Gottingen Memoirs, vol. iv. p. 61.

334 FOURTH REPORT—1834.

been adduced in opposition to these results. Newton found
that when the distance of these edges was the 400th part of an
inch, the light which passed between the knives parted in the
middle, and left a dark space in the centre*. The experiment
has been repeated by Mr. Barton, and with a similar resultt.
These experiments, however, were made with curved edges ; and
as Professor Powell has observed, we have no ground for sup-
posing that the phenomenon may not be modified by this change
in the conditions under which it is presented. The theory of
Fresnel has not been applied to the more complex problem of
an aperture with curvilinear edges, and the analytical difficul-
ties of the problem seem to be insuperable. There seems to be
some uncertainty, however, with respect to the phenomenon
itself. Professor Powell repeated the experiment with edges of
various curvatures, and always found that the centre was a point
of relative brightness, as compared with other points in the line
perpendicular to the length of the aperturet. As to Newton’s
experiment, it seems certain, as the same writer has observed,
that we are not acquainted with all its conditions; and it is
apparent from many passages that the illustrious observer him-
self was far from being assured with respect to the real nature
and circumstances of these phenomena.

But there is another essential circumstance to be taken into
account, in comparing the experiments of Newton with the re-
sults of Fresnel’s theory. In that theory the origin of light is
supposed to be a point, and this condition is practically fulfilled
by making the light to diverge from the focus of a lens of high
power ; the origin of the light in that case being (by the princi-
ples of the wave-theory) the minute image of the sun in the
focus. In Newton’s experiments, however, the sun’s light was
made to pass through a hole of sensible magnitude ; and in the
remarkable experiment now referred to, that hole was a quarter
of an inch in diameter. The problem of diffraction in this case
is one of much greater complexity. It is necessary to deter-
mine the joint effect produced at any point of the diffracting
aperture by the several indefinitely small portions of a wave

* Optics, Book iii., Obs. vi. and vii. 2

+ Phil. Maq., vol. ii. p. 268. + Ibid., p. 429, &e.

§ ‘ The subject of the third book I have also left imperfect, not having tried
all the experiments which I intended when I[ was about these matters, nor re-
peated some of those I did try until I had satisfied myself about all their cireum-
stances. To communicate what I have tried, and leave the rest to others for
further inquiry, is all my design in publishing these papers.” Optics, Adver-
tisement 1. See also latter part of Obs. 11. Book iii.

REPORT ON PHYSICAL OPTICS. 335

transmitted through the external hole; and, considering each of
these as a new centre of disturbance, to find their total resultant
at any point of the screen on which the fringes are received.
The method of solution has been pointed out by Professor Airy ;
and he has shown that when the external hole is a rectangular
parallelogram, and the diffracting aperture of the same form and
similarly placed, the law of illumination at any point of a screen
will be similar to that produced by a rhomboidal aperture, in
Fresnel’s method of observation ; the dimensions and distances
in the two cases being connected by certain relations*. From
these investigations Professor Airy concludes that the size of the
external hole could not account for the dark central shadow
mentioned by Newton in the sixth observation. He has con-
firmed this conclusion by experiment ; and employing holes of
various magnitudes, he found the central band in all cases bright.
The effect recorded by Newton is ascribed by Professor Airy to

the influence of contrast on the retina.

A remarkable class of phenomena arise when a lens is placed
close to an aperture of any form, and the light received ona
screen at its focus, or on an eyeglass at its own focal distance
from it. In fact, the phenomena of diffraction are in this manner
produced with holes of considerable dimensions, and were ob
served by Sir W. Herschel, with the undiminished apertures of
his great telescopes ; the stars being seen encompassed by seve-
ral dark and bright rings, succeeding one another at equal in-
tervals, when a high magnifying power was employed. But the
phenomena become more distinct when the aperture is limited
by a diaphragm of moderate size, the diameters of the rings
varying inversely as those of the apertures. The effects pro-
duced by diaphragms of different sizes and forms have been
examined in much detail by Sir John Herschel and M. Aragot.

_ The phenomena produced by minute apertures, when combined
with alens in the manner now spoken of, have been studied with
much zeal and success by Fraunhofer. The most remarkable of

these phenomena are those produced by a fine grating, such as

may be formed by stretching a fine wire between two parallel
Screws of equal thread. When such a grating is placed before
the object-glass of a telescope, and a narrow slit whose length
is parallel to the wires of the grating, viewed through it, the

direct image of the slit is bordered on either side by a succes-

* “ On the Calculation of Newton’s Experiments on Diffraction,” Cambridge
Trans., vol. v. part 2.

+ Professor Amici has also noticed some phenomena of the same class. See
Edin. Journal of Science, vol. iv. p. 306.

336 FOURTH REPORT—-1834.

sion of richly coloured diffracted images, which increase in
breadth and diminish in brightness, as they recede from the
centre. The first pair of spectra are separated from the central
image by a space absolutely black, and a similar interval occurs
between the first and second pair. Fraunhofer observed, under
favourable circumstances, 13 such spectra on either side of the
central image. He has measured with great accuracy the an-
gular deviations of the rays of each colour from the axis; and
he has found that the experimental laws thus deduced agree in
the most complete manner with the results of the principle of
interference*. The results are the same, both by theory and
experiment, in the case of reflexion from ruled surfaces}.

The optical phenomena of gratings are interesting in many
points of view. The appearance of lateral spectra, produced by
simply intercepting a part of the light, proves that the light
actually diverges in all directions from the front of the grand
wave where it meets the lens, and that it is to the interference
of this light with that intercepted by the grating that we are
to ascribe its want of sensible effect under ordinary circum-
stances t. Another very remarkable circumstance of these pheno-
mena is the purity of the light of each simple colour, which is
such that the fixed lines may be discerned in the spectra. The
distances of these lines, in the diffracted spectrum, are always
proportional, whatever be the diffracting substance; while the
ratio of their intervals, or the breadths of the coloured spaces,
in the spectra formed by refraction, vary with the nature of the

* The angular deviation, 6, of any ray from the axis is expressed by the

formula
sin , — ™*»
€ -

in which x denotes the order of the spectrum, a the length of an undulation,
and ¢ the interval of the axes of the wires. The value of ¢ is obtained with
great precision, so that the measurement of the angular deviations of the rays
of each simple colour affords the most exact data for the determination of the
length of their waves. Fraunhofer has in this manner computed the lengths of
the waves, corresponding to the seven principal fixed lines in the spectrum;
and the resulting values are perhaps the most exact optical constants we possess.
It.is a remarkable consequence of the expression above given, that whens is less
than a, the angle 4, will be imaginary. In this case, then, there can be no coloured
spectra; and it follows that scratches or inequalities on any polished surface,
whose interval is less than the length of a wave, do not disturb the regularity
of reflexion and refraction.

+ Fraunhofer’s researches on diffraction are published in the Memoirs of the
Bavarian Academy of Sciences, vol. viii. A very full analysis of them is given
in the Edinburgh Encyclopedia, art. Ortics; and in Sir J. Herschel’s “ Essay
on.Light,” Encyc. Metrop.

+ Airy’s Math. Tracts, p. 331.

REPORT ON PHYSICAL OPTICS. 307

prism. This fact appears to be decisive against the Newtonian
theory of inflexion, in which inflexion and refraction are referred
to the same cause.
The analytical investigation of the problem of diffraction in
the cases last alluded to,—those, namely, in which a lens is
combined with the aperture, and the intensity of the light is
sought at any point of a parallel plane passing through the focus,

. —is far more manageable than in most other cases. The gene-
Tal expression of the displacement is at once integrated with

respect to one of the variables, and the complete integral can,
in many cases, be exactly found. Professor Airy has given the
solution of this problem in his yaluable tract on the Undulatory
Theory*, and in applying it to the phenomenon last mentioned
has deduced all the appearances observed by Fraunhofer. The
remarkable appearance of the six-rayed star, observed by Sir
John Herschel, when a triangular diaphragm was placed before
the object-glass of a telescope, has been likewise deduced as
another case of the same problem.

The same effects, Fraunhofer observed, were produced by re-
flexion from grooved surfaces ; and their theory is to be referred

.to the same principles, the light reflected from the surfaces

between the grooves interfering in a manner precisely analogous
to that admitted through the apertures of the gratings. The
colours exhibited. by such surfaces under ordinary circumstances

_ were observed by Boyle and Grimaldi; Young showed that they

Were consequences of the principle of interference, and deter-
mined the law of their recurrence depending on the incidencet ;
and Sir David Brewster seems to have been the first to observe
that the spectra formed in these cases of multiplied diffraction
approached the solar spectrum in purity, far more nearly. than
the ordinary diffracted bands, or the coloured rings of Newton.
These phenomena indicate the superficial structure more uner-
ringly, perhaps, than the most powerful microscopes. Among
the most important and beautiful instances of this application
of optical science may be ranked the analysis of the colours of

mother-of-pearl}, and the investigation of the structure of the

_ Crystalline lenses of the eyes of fishes and other animals, by

Sir David Brewster§. The same author has also described a new
Series of periodical colours, which are exhibited by some of the

. plates of grooved steel constructed by Mr. Barton, and which suc-

“4 * Math. Tracts, p. 321, &c. .

+ “On the Theory of Light and Colours,” Phil. Trans. 1801.
t Phil. Trans. 1814. § Ibid. 1833.

1834. Z

3388 FOURTH REPORT—1834.

ceed one another in a plane at right angles to that in which the
usual spectra are developed*. The theory of this phenomenon
remains yet to be developed. In the solution of the analogous
problem, given by Professor Airy, a periodical variation in the
intensity of the light in the direction of the apertures of the
grating is indeed pointed out; but that variation, it is easily
seen, will not account for the facts last mentioned.

IV. Colours of thin Plates.

The earliest observations on record, in which the colours of
thin plates were made the subject of experimental research, are
those of Boylet+. This diligent observer remarked the fact, that
most transparent substances exhibit colour by reflected light
when sufficiently reduced in thickness; and that these tints
varied in the same substance, and therefore did not depend
essentially upon its chemical nature. The observations of Boyle
were made on the bubbles of various liquids, and he even suc-
ceeded in blowing glass sufficiently thin to exhibit similar phe-
nomena.

The vivid and varying colours of the soap bubble also engaged
the attention of Hooke t ; but the most important of the obser-
vations of this philosopher, connected with the subject of thin
plates, are those recorded in his Micrographia, which was pub-
lished in the year 1665. Inthis work he shows, that the colours
of lamine of mica are dependent on their thickness, and appear
only when that thickness is comprised within certain limits;
that when the tint exhibited by a given plate is uniform over its
entire surface, the plate is also uniformly thick; and that the
colour presented by two plates superposed is different from those
of either separately. Hooke has also the merit of producing the
phenomena of thin plates in the instructive form in which their
laws have since been studied, namely, by placing two object-
glasses in contact; and he found that any transparent fluid in-
troduced between the lenses furnished a succession of colours
as well as air ;—the colour, however, being more vivid, the more
the refractive power of the plate differed from that of the glasses
within which it was inclosed.

The attention of Newton was soon after directed to the same
subject ; and his investigations, which ended in the complete

* Phil. Trans. 1829.
+ Experiments and Observations upon Colours, 1663.
} Birch’s History of the Royal Society, vol. iii. p. 29.

REPORT ON PHYSICAL OPTICS. 339

discovery of the laws of the phenomena, will ever be considered
as a model of experimental inquiry. A convex lens of glass
being laid upon a plane surface of the same material, after the
manner of Hooke, the bands of the same colour are arranged
round the point of nearest approach in concentric circles; and
the diameters of these circles will be obviously as the square
roots of the thicknesses of the plate of air at the points at which
they are exhibited. In order to investigate the relation between
the colour and the thickness, then, it was only necessary to
measure the diameters of these rings in the different species of
simple light; and taking similar measurements when the other
circumstances of the phenomena were varied, Newton deduced
their laws, as they depended on the substance of the reflecting
plate, and on the obliquity of the incident pencil. Newton ob-
served, moreover, that there was a second system of rings formed
by transmission. 'The transmitted rings were found to observe
the same laws,—with this remarkable exception, that the colour
transmitted at any particular thickness of the plate was always
complementary to that reflected at the same thickness ; so that
in homogeneous light, the bright transmitted ring is always
found at the same distance from the centre as the corresponding
dark one of the reflected system.

The observations of Mariotte*, Mazeas+, and Dutourt have
added nothing essential to the laws discovered by Newton.
Most of these observations, in fact, related: to the colours ex-
hibited by the plate of air inclosed between two plane glasses ;
and in circumstances, therefore, much less favourable to the
analysis of the phenomenon than those selected by Newton.
Perhaps the most interesting of the facts noticed by Mazeas are
the effects produced on the coloured bands by the application

__ of heat to the glasses, the colours retreating to the edges of the

plates, and the bands diminishing in breadth as the temperature
was increased. The same author also found, that no. sensible
change took place in the phenomenon when the air was with-
drawn by the air-pump.

Inthe observations of Dutour, the reflected and the transmitted

tints were observed at the same time, the latter being reflected
from the second surface of the lower glass, and returning to the
eye through the entire system. This latter set of rings is ren-
dered more distinct, when the shadow of an opaque body is passed
over the upper surface. In this manner the phenomenon was
observed by Sir William Herschel ; and it was found that ad-

* Traité de la Lumiére et des Couleurs.
+ Mémoires présentés, tom. ii. + Tbid., tom. iv. v. vi.
z2

340 FOURTH REPORT—1834.

ditional sets of rings became visible by increasing the number of
reflecting faces. Sir William Herschel observed, likewise, that
the primary reflected system was produced when a lens was laid
upon a metallic reflector ; and he remarks, that in this case the
transmitted system must be conceived to be absorbed by the
metal. The same author has described a remarkable set of co-
loured bands adjacent to the iris, at the limit of total reflexion,
when a prism is in contact with aplane surface*. The analysis
of this phenomenon has been given by Sir John Herschel in his
Essay on Lightt.

The important observations of M. Arago are the next to de-
mand our notice}. Viewing the rings through a rhomboid of
Iceland spar, whose principal section was parallel or perpendicu-
lav to the plane of incidence, this philosopher observed that the
intensity of the light in one of the images varied with the inci-
dence, and that it vanished altogether when the rays made an
angle of 35° with the surface. It was further observed, that
the same image vanished, and at the same angle, whether the
rings were formed by reflexion or transmission. Thus, the light
of the transmitted, as well as of the reflected rings, was wholly
polarized in the plane of incidence, and at the usual angle for
glass. M. Arago has further shown, that the colours of the re-
flected and transmitted rings are not only complementary, but
that their intensities are also precisely the same ; for, when the
two systems are superposed, they completely neutralize each
other.

But the most remarkable of the results obtained by this author
relate to the rings formed by the plate of air inclosed between a
lens of glass and a metallic reflector. When these were ob-
served in the manner already alluded to, one of the images
vanished, as before, at the polarizing angle of glass; while its
appearance, at angles above and below the polarizing angle, pre-
sented a remarkable contrast. When the incidence was less
than this angle, the two images seen through the double refract-
ing crystal differed only in intensity ; the dimensions and colours
of the rings were the same in both. Beyond the polarizing
angle, however, the rings in the two images were of complemen-
tary colours; so that if the series in one commenced from a
black centre, in the other it began from a white one. The di-
mensions of the rings of the same order in the two images were
also different. Similar phenomena were produced when the thin

* « Experiments for investigating the Cause of the coloured Rings,” &c., Phil.
Trans. 1807, 1809, 1810.

+ Articles 641, 642.

} “ Sur les Couleurs des Lames minces,” Mémoires d’ Arcueil, tom. iii.

o

REPORT ON PHYSICAL OPTICS. 341

plate was of a density intermediate to those of the two sub-
stances between which it was contained. - I shall hereafter have
occasion to refer to the observations and deductions of Professor
Airy connected with these phenomena.

When the metallic reflector was slightly tarnished, a second
system of rings was visible to the naked eye. The formation
of these rings depended on the light irregularly dispersed at the
surface of the metal; and they were visible, in whatever manner
the eye was placed with respect to the incident light. Their
tints were complementary to those of the regular series.

It was soon felt that the phenomena of thin plates were closely
connected with some new and fundamental property of light*, and
that it wasin their application tothese phenomena that all theories
of light were to be judged. For their explanation, it has been
already stated, Newton invented his celebrated doctrine of the
‘* fits of easy reflexion and transmission,” a doctrine which will
always hold a prominent place in the page of philosophical hi-
story. Its application is obvious. The ray is in a fit of easy
transmission in its passage through the first surface; this is
succeeded by a fit of easy reflexion, and so alternately. On
arriving at the second surface, then, the ray will be in a fit of
easy transmission or easy reflexion, according as the interval of
the surfaces, or the thickness of the plate, is an even or an
odd multiple of the length of the fit. Thus the alternate suc-
cession of bright and dark rings in homogeneous light, and the
arithmetical progression of the thicknesses at which they are -
exhibited, are satisfactorily explained. To explain the variation
in the dimensions of the rings depending on the nature of the
light, it is necessary to suppose that the length of the fits
varies with the colour,—being greatest in red light, least in
violet, and of intermediate magnitude for the rays of interme-
diate refrangibility. Newton determined the absolute lengths
of these fits for the rays of each simple colour, and found that
they bore a remarkable numerical relation to the lengths of
the chords sounding the octave. These results are even yet
referred to as fundamental data in optical inquiries.
-’ To account for the remaining laws Newton was constrained to
make new suppositions, and to attribute properties to the fits
which seem inconsistent with every physical account which has
been given of them. Thus, to explain the dilatation of the rings

* It is unnecessary to refer to the theories of Sir William Herschel or of
M. Parrot, in both of which the laws of thin plates have been referred to those
of reflexion and refraction; or to that of Mayer, who attempted to reduce them
to inflexion. None of these theories have had supporters, and they are all of
them inconsistent with obvious facts.

342 FOURTH REPORT—1834.

-

with the increasing obliquity of the incident pencil, he assumed
that the length of the fits augmented with the incidence, and ac-
cording to a complicated law. This assumption is at entire vari-
ance with the physical theory. If the fits are produced by the
vibrations of the ether, which are propagated faster than the rays,
and which alternately conspire with and oppose their progres-
sive motion, their lengths should continue the same in the same
medium, whatever be the incidence. No attempt, that I am
aware of, has been made to reconcile this law with the physical
hypothesis of Mr. Melville and M. Biot.

The same may be said of the variation of the dimensions of
the rings with the substance of the reflecting plate. Newton
found that when a drop of water was introduced between the
glasses, the rings contracted ; and by comparing their diameters
in air and in water, he found that the corresponding thicknesses
of the plate were as 4 to 3, or in the inverse ratio of the refrac-
tive indices. It was necessary to suppose, therefore, that in
different media, the lengths of the fits varied in the same pro-
portion ; and, since in the Newtonian theory the refractive in-
dices are directly as the velocities of propagation, it followed that
as the velocity augmented, the spaces traversed by the ray in
the interval of its periodical states, must diminish, and in the
same ratio.

But the facts observec by M. Arago and Professor Airy seem
to overturn altogether this part of the theory of emission. The
rings formed by a plate of air, inclosed between a lens of glass
and a metallic reflector, vanish altogether when the light is po-
larized perpendicularly to the plane of incidence, and is incident
at the polarizing angle of glass. Under these circumstances,
no light is reflected from the upper surface of the plate; but as
it is abundantly reflected from the lower, the disappearance of
the rings proves that the light reflected from the wpper surface
is essential to their production. That the light reflected from
the lower surface also concurs in their formation, appears from
the effects observed by M. Arago, when the metallic plate was
tarnished ; and we are thus driven to the conclusion that the
phenomena arise from the union and mutual influence of the
pencils reflected from the two surfaces.

This mode of explaining the colours of thin plates was pointed
out by Hooke, in a remarkable passage in his Micrographia,
some years before the subject was taken up by Newton. In
this passage he very clearly describes the manner in which the
rings of successive orders depend on the interval of retardation
of the second “ pulse,’ or wave, on the first ; and therefore on
the thickness of the plate. But he does not seem to have had

REPORT ON PHYSICAL OPTICS. 343

any distinct idea of the principle of interference itself; and his
conception of the mode in which the colours resulted from this
** duplicated pulse ” is entirely erroneous. Euler was the next
who attempted to connect the phenomena of thin plates with
the wave-theory of light; but the attempt, like all the physical
speculations of this great mathematician, was signally unsuc-
cessful. Euler thought, in fact, that the colours of thin plates,
as well as those of natural bodies, arose from emitted, and not
from reflected light. The incident light was supposed to excite
the vibrations of the plate, the frequency of which depended on
its thickness, in the same manner as the frequency of the vibra-
tions of the column of air ina tube depends on its length. These
vibrations again were believed to excite those of the luminiferous
ether, and thus to produce the sensation of various colours, the
red corresponding to the less frequent vibrations, and the violet
to the most frequent*.

The subject remained in this unsatisfactory state until the
principle of interference was discovered by Young. When this
principle was combined with the suggestion of Hooke, the whole
mystery vanished. The application was made by Young him-
self, and all the principal laws of the reflected rings were readily
and simply explained by the interference of the two portions of
light which are reflected at the two surfaces of the plate}. In ap-
plying this principle, however, Young perceived that the interval
of retardation was not simply that due to the difference of the
‘paths traversed by the two pencils; but that one of them must
be supposed to undergo a change of phase, amounting to half
‘an undulation, at the instant of reflexion. Young clearly pointed
‘out the accordance of this effect with mechanical principles ;
and the connexion has been fully confirmed by the more com-
plete investigations of Fresnel. In fact, the two reflexions take
place under opposite circumstances, one of the portions being re-
flected at the surface of a rarer, and the other at that of a denser
medium; and the laws of impact of elastic bodies indicate that
the direction of the vibratory movement must be reversed by
reflexion in the one case, while in the other itis unchanged.
Young had the satisfaction of putting this principle to the test
in a remarkable manner. It followed from it that if the thin
plate were of a refractive density intermediate to those of the
two media within which it was inclosed, the laws of the phe-
nomenon would be determined by the difference of the paths
alone, the reflexion being of the same kind at the two surfaces.

* Mém. Acad. Berlin, 1752.
+ “On the Theory of Light and Colours,” Phil. Trans. 1802.
5 a

344 _ FOURTH REPORT —1834.

Young accordingly predicted that in this case the rings should
commence from a white centre, instead of a black one, and the
prediction was soon after verified on trial *. “4

The transmitted rings are accounted for, in the waye-theory,
by the interference of the direct light with that which has un-
dergone two reflexions within the plate; and it follows from the
preceding considerations that their colours must be comple-
mentary to those of the reflected system. This origin at once
shows the reason of the fact observed by M. Arago, that the
light of the transmitted rings is polarized in the plane of re-
flexion. M. Biot has laboured to reconcile this fact to the theory
of emission, with which it appears, at first view, at utter vari-,
ance. The account which he has given of the phenomenon will,
I think, be hardly deemed satisfactory t+. 16>)

The theory of thin plates, as it came from the hands of Young,
was however incomplete. It is obvious that the intensity of the
two portions of light reflected from the upper and under sur-
faces of the plate can never be the same, the light incident on
the second surface being already weakened by partial reflexion
at the first. These two portions therefore cannot wholly destroy
one another by interference; and the intensity of the light in the
dark rings.should never entirely vanish, as it appears to do when.
homogeneous light is employed. M. Poisson was the first to
point out and to remedy this defect of the theory. It is evident,
in fact, that there must be an infinite number of partial reflexions
within the plate, at each of which a portion is transmitted; and:
that it is the sum of all these portions, and not the two first
terms of the series only, which is to be considered in the caleu-
lation of the effect. Taking up the problem in this more gene-.
ral form, and employing the formula obtained by himself and
Young for the intensity of the light reflected and transmitted at
a perpendicular incidence, M. Poisson has proved that—at this
incidence, and at points for which the thickness of the plate is
an exact multiple-of the length of half a wave,—the intensity of
the reflected and transmitted lights will be the same as if the
plate were suppressed altogether, and the bounding media in ab-:
solute contact; so that when these media are of the same re-
fractive power, the reflected light must vanish altogether, and.
the transmitted light be equal to the incident t. Fresnel after-

* “ Account of some Cases of the Production of Colours,” Phil. Trans. 1802.

+ See Biot’s “ Zraité de Physique,” tom. iv. p. 308, et seq.

+ “ Sur le Phénoméne des Anneaux colorés,” Annales de Chimie, tom. xxii.
p- 337. M. Poisson has further shown that rings absolutely black will be formed
at points corresponding to the bright rings in the ordinary ease, when the velo-

REPORT ON PHYSICAL OPTICS. 345

wards showed that the result was independent of the expression of
the intensity of the reflected light ; and by the aid of the property
discovered by M. Arago, namely,—that the light is reflected in
the same proportion at the first and second surfaces of a trans-
parent plate,—he extended the conclusion to all incidences*.
The general expression of the intensity of the light in any part
of the reflected or transmitted rings has been given by Professor
Airy ft.

Here, then, we have reached a point with respect to which the
two theories are completely opposed. According to both, a cer-
tain portion of light is reflected from the first surface of the
plate. This in the Newtonian theory is left in all cases to pro-
duce its full effect; while in the wave-theory it is, at certain
intervals, wholly destroyed by the interference of the other pen-
cil; and the dark rings should be absolutely black in homoge-
neous light. The latter of these conclusions seems to accord
with phenomena, while the former is obviously at variance with
them. This is clearly shown by an experiment of Fresnel. A
prism was laid upon a lens having its lower surface blackened,
a portion of the base of the prism being suffered to extend be-
yond the lens. The light reflected from this portion, according
to the Newtonian theory, should not surpass in intensity that of
the dark rings. The roughest trial is sufficient to show that the
intensity of the light in the two cases is widely different, and
to prove that the dark rings cannot arise (as they are supposed
to do in the theory of fits,) from the suppression of the second
reflexion f.

‘Mr. Potter has applied a new method of “ photometry by com-
parison” to determine the relative intensities of the light in the
bright and dark rings of the transmitted system. In this method
the ratio of the intensities of the light reflected from two plane
glasses is varied, by varying the incidence, until it, is judged to
be equal to the ratio of the light in the bright and dark rings.
The former ratio is then deduced from the incidence by means
of an empirical formula. In this manner Mr. Potter concludes
that the ratio of the light in the rings, at a perpendicular inci-
dence, is 2°48 for green light, and 3-49 for red§. The ratio de-
duced from the principles of the wave-theory is about 1:20 in

city of propagation within the plate is a mean proportional to the velocities in
the bounding media.
* Annales de Chimie, tom. xxiii. p. 129.
. + Math. Tracts, p. 302, &c.
t Mémoire sur la Diffraction, p. 347.
§ Lond. § Edin. Phil. Mag., 3vd Series, vol. i. p. 174.

346 FOURTH REPORT—1834.

the case of crown glass. But, independently of the uncertainty
connected with the empirical law which is taken by Mr. Potter
as the basis of his computation in these deductions, the photo-
metrical method itself seems to be open to objection. It appears
to be assumed, in the application of that method, that where the
quantity of light incident upon an irregularly reflecting surface
is given, the quantity of reflected light will be the same in its
entire amount, and in all directions, whatever be the incidence.
This seems to be contradicted by obvious facts. There is yet
another difficulty in the application of this method which appears
to leave room for some uncertainty in the results. Where lu-
minous objects are so small that the eye cannot readily distin-
guish parts, the absolute quantity and the intensity of the light
are confounded. Iam not aware how far this may have been
the case in Mr. Potter’s instrument; but it is remarkable that
if we suppose the gzantities of light reflected from the two
glasses to have been taken as the terms of comparison, the cal-
culated results will accord very closely with theory *.

When a beam of light falls upon two plates superposed, some
of the many portions into which it is divided by partial reflexion
at the bounding surfaces are often in a condition to interfere
and exhibit colour. Thus, when light is transmitted through two
parallel plates, slightly differing in thickness, the colour pro-
duced will be that corresponding to the difference, and will be
independent of the interval of the plates. This phenomenon
was observed by Mr. Nicholson}, and was shown by Dr. Young
to arise from the interference of two pencils, one of which is
twice reflected within the first glass, and the other twice reflected
in the second. Sir David Brewster observed a similar case of
interference produced by two plates of equal thickness, slightly
inclined, the thickness traversed in the two plates being altered
by their inclination. In both these cases, however, the inter-
fering pencils are mixed up with, and overpowered by, the light
directly transmitted ; and some contrivance is necessary to make
the fringes visible. The phenomena are much more obvious in
the light reflected by both plates, and which, on account of their
inclination, is separated from the direct light. It is obvious, in
fact, that the direct image of a luminous object seen through the
glasses, will be accompanied by several lateral images, formed
by 2, 4, 6, etc. reflexions. These images Sir David Brewster
observed to be richly coloured. The bands are parallel to the
line of junction of the two glasses, and their breadth is greater

* See Phil. Mag. vol. vy. p. 441.
¢ Nicholson's Journal, vol. ii. p. 312.

REPORT ON PHYSICAL OPTICS. 347

the less the inclination of the plates *. The colours in the first
lateral image are produced by theinterference of the pencils which
have undergone two reflexions,—one of them being reflected
internally by the first plate, and externally by the second, while
the other is reflected internally by the second, and externally by
the first. ‘The routes of these portions differ only by reason of
the different inclinations at which they traverse the intervals of
the surfaces. M. Pouillet has observed a phenomenon of the
same kind, when a thick plate of glass is placed above a metallic
mirror, and in a direction nearly parallel to its surface +. The
interfering rays in this case appear to be those which have un-
dergone two reflexions within the plate, and one at the surface
of the mirror ; the reflexion from the mirror preceding the others
in the case of one pencil, and following them for the other.

The routes of two such pencils will slightly differ, owing to the
different obliquity under which they traverse the plate.

_ The remarkable phenomena observed by Mr. Knox when a
double-convex lens was combined with two plane glasses, one
adjacent to each surface, have been explained by Young on the
same principles. In addition to the rings exhibited by each
plate of air, a third system of concentric rings is formed in this
case, the dimensions of which are greater than those of either of
the primary systems. The diameters of these rings increase
indefinitelyas those of the primary systems approach to equality ;
until finally the circles become straight lines when these are
equal {. It is easily seen, in fact, that each ring is the locus
of the points for which the difference of the thicknesses of the
two plates of air is constant; and that this locus is a circle,
whose diameter will depend on the curvatures of the surfaces,
and on the interval of the centres of the two primary systems.
‘The fringes formed by “‘ double plates”’ have been observed un-
der another form by Mr. Talbot, when two films of thin blown
glass were superposed.

The “ colours of thick plates’’ are perhaps of too unusual
occurrence to entitle them to be studied as a separate class of
optical phenomena: the attention which they have received is
owing to the investigations of Newton. In the experiment of
Newton a beam of light is admitted through a small aperture,
and received on a concavo-convex mirror with parallel surfaces,
the second of which is silvered. When a screen of white paper
is then held at the centre of the mirror, having a hole in the
middle to allow the beam to pass and repass, a set of broad

* Edin: Trans., vol.vii. p. 435.
+ Elemens de Physique, tom. ii. p. 478.
t Phil. Trans, 1815, p. 161.

348 FOURTH REPORT—1834.

coloured rings will be depicted on it, similar to the transmitted’
rings of thin plates, the diameters of the rings varying inversely
as the square roots of the thicknesses of the mirrors. The Duke
de Chaulnes observed that similar phenomena were produced
when a metallic mirror was substituted for the glass one, and
the rays transmitted through a semi-transparent plate of any
kind, or even through a screen of gauze placed at a short
distance in front of the mirror*. Sir W. Herschel found
that the rings could be produced by scattering fine powder in
the air before the mirror} ; and M. Pouillet has ascertained that
similar rings are formed when the light incident on the mir-
ror is simply transmitted through an aperture of any form in
an opake screen t. More recently Mr. Whewell and M. Que-
telet have observed a set of coloured bands, which are formed
when the image of a candle is viewed in a plane glass mirror ;
the candle being held at a short distance in front of the eye, so
that the incident and reflected rays may make a small angle §.
M. Quetelet appears to think, however, that this phenomenon is
to be referred to a different class from those last considered.

Newton very ingeniously accounted for the colours observed
in his experiments by the fits of easy reflexion and transmission
of that portion of light which is scattered in all directions at the
first surface of the glass; and M. Biot has extended the expla-
nation to the analogous phenomena observed by the Duke de
Chaulnes. Young showed that they could be explained by the
interference of the two portions of light which are scattered in
the passing and repassing of the ray through the refracting sur-
face ||. . The complete investigation, as far as relates to the di-
mensions of the successive rings, is given by Sir John Herschel ;
and the formula obtained is found to agree precisely with New-
ton’s measures 4].

When the interval between two glasses is filled with different
substances, such as water and air, or water and oil, in a finely
subdivided state, the portions of light which have traversed them
are in a condition to interfere, the interval of retardation de-
pending on the difference of the velocities of light in the two
media. Accordingly, coloured rings will be seen when a Jumi-
nous object is viewed through the glasses; the rings being
similar to those usually seen by transmission, but much larger.

* Mém. Acad. Par. 1755. + Phil. Trans. 1807.

t Elemens de Physique, tom. ii. p. 476.

§ Correspondance Mathématique, tom. v. p. 6, et tom. vi. p. 1.

| “ On the Theory of Light and Colours,” Phil. Trans.; and Encyel. Brit.,
Art. CHRoMATICs.

q Essay on Light, Art. 679, et seq.

REPORT ON PHYSICAL OPTICS. 349

But when a dark object is behind the lenses, and the incident
light somewhat oblique, the rings immediately change their
character, and resemble those of the ordinary reflected system ;
one of the portions in this case being reflected, and therefore
suffering a loss of half an undulation. These phenomena were
observed and explained by Young *, and have been denominated
by him the “ colours of mixed plates.’’ Young also observed
some similar phenomena of colour in an unconfined medium.
Thus, when the dust of the lycoperdon is mixed with water,
the mixture exhibits a green tint by direct light, and a purple
tint when the light is indirect; and the colours rise in the
series when the difference of the refractive densities is lessened
by adding salt to the water. The interval of retardation in this
case depends also on the magnitude of the transparent particlet.
In closing the review of this part of the subject, I would ob-
serve that any well-imagined theory may be accommodated to
phenomena, and seem to explain them, if only we increase the
number of its postulates, so as still to embrace each new class
of phenomena as it arises. In a certain sense, and to a certain
extent, such a theory may be said to be true, so far as it is the
mere expression of known laws. But it is no longer a physical
theory, whose very essence it is to connect these laws together,
and to demonstrate their dependence on some higher principle :
—it is an aggregate of separate principles, whose mutual rela-
tions are unknown. Thus the cycles and epicycles of the
Ptolemaic system represented with fidelity the more obvious
movements of the planetary bodies; but when the refinements
of astronomical research laid bare new laws, new epicycles were
added to the system, until at length its complication rendered
it useless as a guide. Such appears to be the present state of
the theory of emission ; and so glaringly does this blemish show
itself in that part of the theory which has been last under con-
sideration, that one of its advocates says, ‘‘ Revera illz vices
reflexionis et transitus, cum omnibus additamentis fictitiis,
mirabiliores adhuc sunt quam phenomenon ipsum, ad cujus
explicationem in usum sunt vocate{}.’’ The same attribute
appears in the broader divisions of the science; and the several
classes of phenomena do not flow from the theory as from one
common source,—but each has its separate and independent
head, and its separate and independent data. In the wave-

* “© Account of some Cases of the Production of Colours,” Phil. Trans. 1802.
The Abbé Mazeas noticed many facts which appear to be referable to the same
principles,— Mémoires présentés, vol. ii.

+ Introduction to Medical Literature, p. 556.

t Mayer on Newton’s Rings,—Gdéttingen Memoirs, vol. v. p. 22.

350 FOURTH REPORT—1834.

theory, on the other hand, not only the individual laws, but the
classes of phenomena are related ; and to calculate, numerically,
the laws of refraction, the varied phenomena of diffraction, and
those of thin plates, we only need to borrow one result from
experience,—the length of a wave of light in each medium.
There is thus established that connexion and harmony in its
parts which is the never-failing attribute of truth. But power-
ful as is the weight of this intrinsic evidence in favour of the
wave-theory, it has yet stronger claims to our assent. These
claims are grounded on the vast body of new phenomena which
it explains,—and explains, (it is to be remembered,) not in a
vague and general manner, but in the precise language of
analysis, and with an accuracy which the refinements of modern
observation have not been able toimpugn. It may be confidently
said that it possesses characters which no false theory ever
possessed before.

Part Il.—Pouarizep Licnt.

(1) Polarization.— Transversal Vibrations.

In the various phenomena which have been hitherto de-
scribed as taking place when a ray of light encounters the sur-
face of a new medium, it has been assumed that the direction
and the intensity of the several portions into which it is sub-
divided are wholly independent of the manner in which the ray
is presented to the bounding surface, the direction of the ray
remaining unchanged. In other words, it was taken for granted
that a ray of light had »o relation to space, with the exception
of that dependent on its direction ;—that around that direction
its properties were on all sides alike ;—and that if the ray were
supposed to revolve round that line as an axis, the resulting
phenomena would be unaltered.

Huygens was the first to observe that this was not always
the case. In the course of his researches on the law of double
refraction, he foundthat when a ray of solar light is received upon
a rhomb of Iceland crystal in any but one direction, it is always
subdivided into two of equal intensity. But on transmitting
these rays through a second rhomb, he was surprised to observe
that the two portions into which each of them was subdivided
were no longer equally intense;— that their relative brightness
depended on the position of the second rhomb with regard to
the first ;—and that there were two such positions in which
one of the rays vanished altogether.

REPORT ON PHYSICAL OPTICS. 351

From this ‘ wonderful phenomenon,” as Huygens justly
called it, it appeared that each of the rays refracted by the first
rhomb had acquired properties which distinguished it altogether
from solar light. It had, in fact, acquired sides; and it was
evident that the phenomena of refraction depended, in some un-
known manner, on the relation of these sides to certain planes
within the crystal. Such was the conclusion of Newton : “ This
argues, ”’ says he, “ a virtue or disposition in those sides of the
rays, which answers to, and sympathizes with, that virtue or
disposition of the crystal, as the poles of two magnets answer
to one another.”’

This conception was followed out by Malus, whose varied
and important discoveries respecting the nature and laws of
polarized light have justly placed him in the rank of founder in
this most interesting branch of science. The molecules of a
polarized ray were supposed by him to have all their homolo-
gous sides turned in the same directions. He adopted the term
“* polarization”’ to express the phenomenon, and compared the
effect to that of a magnet which turns the poles of a series of
needles all to the same side. M. Biot has modified the hypo-
thesis of Malus in order to embrace the other phenomena of
light, and assumed that there was one line, or axis, similarly
placed in each molecule, and that these axes in a polarized ray
were all turned in the same direction. The molecules, however,
are at liberty to revolve round these axes, and thus to assume
different dispositions with respect to the attracting or repelling
forces to which they are exposed when they encounter the sur-
face of a new medium.

~The phenomenon of polarization seems to have had much
weight with Newton in forcing him to reject the theory proposed
by Huygens: “ It is difficult,’”’ he says, ‘to conceive how the
rays of light, unless they be bodies, can have a permanent vir-
tue in two of their sides, which is not in their other sides, and
this without any regard to their position to the space or medium
through which they pass*.”’ “* Are not all hypotheses errone-
ous,’’ he adds in another place, ‘‘in which light is supposed to
‘consist in pression or motion, propagated through a fluid me-
dium? .... Pressions or motions, propagated from a shining
body through an uniform medium, must be on all sides alike ;
whereas by those experiments it appears that the rays of light
-have different properties in their different sides f.’”’ In this ob- |
jection Newton seems to have fixed his thoughts upon that
species of undulatory propagation whose laws he himself had

* Optics, book iii. Query 29. + Query 28,

352 FOURTH REPORT—1834.

so sagaciously divined. When sound is propagated through air
or water, the vibrations of the particles of the fluid are per-
formed in the direction in which the wave advances; and if the
vibrations of the ether, which are supposed to constitute light,
were of the same kind, the objection would seem to be insuper-
able. But the case is altered, if, as is now assumed, the vi-
brations of the ethereal particles be transverse to that of the
ray’s progress. And though we were unable to render any ac-
count of this hypothesis, or even to show that it is consistent
with mechanical principles, yet the numerous classes of phe-
nomena which it has explained, and the striking and exact
manner in which its predictions have been verified on trial, com-
pel us to admit, that ifthe law to which we have thus reduced so
various and such complicated facts be not itself a law of nature,
it is at least coordinate with it, in such a sense that we may
take it as the representative of actual existence, and reason
from it as we would from an established physical law.

The hypothesis of transversal vibrations first occurred to Dr.
Thomas Young, who illustrated it by the propagation of undu-
lations along a stretched cord agitated at one of its extremities.
Young seems to have been led to this principle while consider-
ing the results arrived at by Sir David Brewster, in his re-
searches on the laws of double refraction in biaxal crystals.
The principle was soon after raised above the rank of a mere
hypothesis, and shown to be a necessary consequence of the
laws of interference of polarized light, if the theory of waves
be admitted at all. It follows, in fact, from the laws of com-
position of vibrations, that the intensity of the light resulting
from the union of two rays oppositely polarized will be con-
stant, and independent of the phase (as was proved to be the
case in the experimental researches of MM. Arago and Fresnel,)
only when the vibrations normal to the wave are evanescent.
It appears from the same investigation that the actual vibra-
tions are either parallel or perpendicular to the plane of polariza-
tion. As far as the phenomena of interference are concerned,
it is indifferent which of these results be assumed to be the fact.
But the theory of transversal vibrations itself, when applied to
the laws of double refraction, leads to the conclusion that the
vibrations which constitute the ordinary ray in uniaxal crystals
are perpendicular to the principal plane; and this being its
plane of polarization, Fresnel concluded that the vibrations of a
polarized ray are on the surface of the wave, and perpendicular
to the plane of polarization *.

* “ Mémoire sur la Double Refraction,’ Mém. Jnst., tom. vii.

REPORT ON PHYSICAL OPTICS. 353

- The principle of transversal vibrations, thus deduced from the
phenomena of interference of polarized light, is easily extended
to the case of common or unpolarized light. _ For when a ray of
such light falls perpendicularly upon a double-refracting crystal,
it is divided into two polarized pencils, neither of which, it ap-
pears from the preceding, can contain vibrations normal to the
surface of the wave. If, then, there were any such in the inci-
dent ray, they would be destroyed by refraction, and there
would ensue a loss of vis viva, and consequently a diminution in
the intensity of the light ; in other words, the sum of the in-
tensities of the two refracted pencils would be less than that of
the incident, which is contrary to observation. In unpolarized
light therefore, as in polarized, the vibrations are only on the
surface of the waves; and we must conceive such light to consist
of a rapid succession of systems of waves polarized in every pos-
sible plane passing through the normal to the front of the wave.
The phenomenon of polarization then, in this theory, consists
simply in the resolution of the vibrations into two sets, in two
rectangular directions, and the subsequent separation of the two
systems of waves thus produced.

The erroneous views of mathematicians on this subject, ac-
cording to oh pecan have arisen from the imperfect physical
conceptions which they have made the basis of their reasoning.
Elastic fluids have been represented as composed of particles in
contact, capable only of condensation and dilatation ; and ac-
cordingly the accelerating forces have been conceived to arise
solely from the difference of density of the consecutive shells of
the fluid. In this case, it is evident that if any row of particles
is displaced in the direction of the connecting line, this row will
slide upon the succeeding one, and the motion will be resisted
by no elastic force. But when we regard these bodies as they
really are, composed of molecules separated by intervals which
are probably considerable as compared with their magnitude,
and acting on one another according to some law varying with
the distance, the whole question is altered. When any row or
line of such molecules is similarly displaced, and through a
space which is small compared with the separating intervals, the

-molecules of the succeeding row will be moved in the same di-
rection by the forces which are thus developed with the change
of distance; so that the vibrations of the particles composing
the first row will be communicated to those of the second, and
thus the vibratory motion will be propagated in a direction per-
pendicular to that in which it takes place*. The rapidity of the

* The existence of transversal vibrations has been fully established in other -
cases of vibratory motion. M.Savart and Mr. Wheatstone have shown that in

1834. 2A

B54: FOURTH REPORT—1834.

propagation will depend on the magnitude of the force developed
by the displacement. ‘To account for the fact that there are no
sensible vibrations in a direction normal to the wave, we have
only to snppose the repulsive force between the mulecules to be
very great, or the resistance to.compression very considerable ;
for in this case, it will be seen, the force which resists the ap-
proach of two strata of the fluid is much greater than that which
opposes their sliding on one another. Fresnel’s views on this
subject are contained in a short paper, entitled, “‘ Considera-
tions Mécaniques sur la Polarisation de la Lumiére *,” and in
his celebrated memoir on double refraction t.

The principle of transversal vibrations, however, has not
been received without much discussion; and eyen to this hour,
the opinion of the mathematical world is not entirely at rest
upon the subject. In a memoir on the propagation of motion
in elastic fluids, read before the Academy of Sciences in the
year 1823, M. Poisson arrived at the conclusion that the vi-
bratory motions of the particles finally become normal to the
wave, whatever be the direction of the original disturbance f.
To this Fresnel replied that the equations of motion of elastic
fluids employed by M. Poisson are but a mathematical abstrac-
tion, which do not apply to anything actually existing. That
in fact these fluids are assumed to be composed of contiguous
elements, capable of compression in a degree proportionate to the
pressure exerted; that this hypothesis is untrue; and that al-
though it may accord with the statical properties of these fluids,
it can never lead to the discovery of their dynamical laws§.

M. Poisson seems to have felt the full force of this objection;
for in his memoirs on the same subject, read to the Academy in
the years 1828 and 1830, he has resumed the whole theory, and
reared it upon its firmer basis. In the former of these memoirs
he has formed the differential equations of equilibrium and
motion of elastic bodies, these bodies being supposed to consist
of molecules attracting or repelling one another according to
some function of the distance ||. In the latter he proceeds to
integrate these equations generally, and to deduce the laws of
propagation of waves at a considerable distance from the origin
of disturbance J. In the case of fluids he arrives at the con-

many instances the elementary motions of the molecules of bodies which trans-
mit sound are transverse to the direction of the propagation.
* Bulletin de la Soc. Philom. 1824. + Mémoires de l'Institut, tom. vii.
+ Annales de Chimie, tom. xxii. § Jbid., tom. xxiii.
| Mémoire sur l’Equilibre et le Mouvement des Corps Elastiques,” Mém.
Tnst., tom. viii.
q “ Mémoire sur la Propagation du Mouvement dans les Milieux Elastiques,”
Mém., Inst., tom. x.

REPORT ON PHYSICAL OPTICS. 355

clusion which he had before obtained, namely,—that when the
distance from the origin of disturbance is very great compared
with the length of a wave, the motion of the particles, in any
fluid, is normal to the surface of the wave, whatever be the
initial motions. He admits, however, that the fundamenial
equations of the motion of ‘fluids, and therefore also the conse-
quences deduced from them, will probably require modification
in the case of very rapid motions, such as those of the lumi-
niferous ether; there being a finite interval of time, whose
magnitude depends on the nature of the fluid, during which the
pressure is not the same in all directions. In the case of very
rapid motions this time must be taken into account, and the
equations of motion of fluids will no longer be those furnished
by the principle of D’Alembert *.

M. Poisson has shown also'that a disturbance produced in a
limited portion of a solid body will give rise to two waves,
which will be propagated with different velocities. He proves
further that whatever be the initial motions of the disturbed
particles, the vibrations in one of these waves will finally be
radial, or in the direction of the motion propagated ; while
those of the other are perpendicular to that.direction, or ¢rans-
versal. The first are attended with dilatations proportionate
to the absolute velocities of the molecules, and the waves thus
propagated are similar to those which take place in fluids. The
transversal vibrations, on the other hand, are unaccompanied
by any change of density in the medium. M. Poisson does not
seem to think that this result can justify the hypothesis of
transversal vibrations in the ethereal fluid; though he admits
thatthe properties attributed to the ether are in some respects
analogous to those of a solid’ body.

The propagation of transversal vibrations appears to be now
established as a necessary consequence of dynamical principles
by the able researches of M. Cauchy t. I shall shortly have
occasion to allude more particularly to the important conclu-
sions arrived at by this mathematician, on applying the general
laws of the propagation of motion in elastic media to the case of
light. For the present it will be sufficient to observe that the
form of the wave- surface, obtained in the course of these in-
vestigations,-is a curved surface of three sheets; and that con-
sequently a ray of light on entering any medium will be, in
general, subdivided into three rays, the directions of the vibra-
tions being determined in each. When the elasticity of the
ether, in this medium, is the same in all directions, these three

* Annales de Chimie; tom. xliv.

+ “Mémoire sur la'Théorie de la Lumiére,”’ Mém. Inst., tom. x.
oP aD

356 FOURTH REPORT—1834.

rays will have a common direction, and two of them a common
velocity. They are thus reduced to two, a single and a double
ray, coincident in direction ; the vibrations of the former being
parallel to that direction, and those of the latter perpendicular
to it. If the initial vibrations in the system in question are
contained in a plane perpendicular to the direction of the rays,
the single ray will vanish, and the vibrations of the molecules
of the double ray will be constantly parallel to the direction of
the initial displacements. This condition therefore reduces the
three rays to one, which is unpolarized; and as this is known
by experience to be the case in media in which the light is pro-
pagated in all directions with the same velocity, it follows that
the propagation of transversal vibrations is a necessary conse-
quence of the general theory.

Thus the theory of Young and Fresnel has received the
strongest possible confirmation; and when we consider the nu-
merous and important conclusions which have been reproduced
and confirmed by M. Cauchy in the development of his analysis,
it is scarcely possible to believe that there is anything defec-
tive in its principle. There is one important and fundamental
difference, however, between the theories of M. Cauchy and
Fresnel; a difference which seems to mark the limits to which
we have attained in this branch of mathematical physics. Ac-
cording to the latter author, it has been already stated, the vi-
brations are perpendicular to the plane of polarization, as it is
usually defined : according to M, Cauchy they are parallel to
that plane. I am inclined to think that the field on which this
question between the two theories must be decided, is their-ap-
plication to the laws of reflexion of polarized light; and if so,
there seems already reason for believing that the hypothesis of
Fresnel is the true one.

II. Reflexion and Refraction of Polarized Light.

Although the phenomenon discovered by Huygens was one
of the highest interest in itself, and in its bearings of such im-
portance, in the mind of Newton, as to force him to admit the
existence of properties in the rays of light which until then had
never been imagined ; yet the result remained for more than one
hundred years a wnigue fact in science, and the kindred pheno-
mena,—the properties which light acquires in a greater or less
degree in almost every modification which it undergoes,—re-
mained unnoticed until the beginning of the present century.
In the year 1808, while Malus was engaged in his experimental
researches on the Huygenian law of double refraction, he dis-

REPORT ON PHYSICAL OPTICS. 307

covered the important fact, that when a ray of light is reflected
from the surface of glass or water at certain angles, the reflected
ray acquires all the characters which had been found to belong
to one of the pencils produced by double refraction. When re-
ceived upon a rhomb of Iceland spar, one of the two pencils into
which it is generally divided vanished in two positions of the
principal section with respect to the plane of reflexion; while
in intermediate positions these pencils varied in intensity through
every possible gradation*. The same variations were observed
when it underwent a second reflexion at the same angle at
which the effect was produced by the first ; the twice reflected
light being a maximum when the plane of the second reflexion
coincided with that of the first, and vanishing altogether when
it was perpendicular to it,—the whole light in that case passing
into the refracted pencil. To represent the intensity of the re-
flected light, in any position of the plane of the second reflexion
with regard to the first, Malus assumed it to vary as the square
of the cosine of the angle which these planes formed with one
another +. The accuracy of this law has since been verified by
the observations of M. Arago and others.

From this law it follows that a beam of common light may be
represented as composed of two polarized beams of equal inten-
sity, whose planes of polarization are at right angles; for when
such a compound beam is received upon a reflecting surface at
the polarizing angle, the intensity of the reflected light will be
constant, and independent of the position of the plane of re-
flexion. But though this compound beam so far exhibits the
character of common or unpolarized light, it must not be re-
garded (as it seems to be by many writers,) as its physical re-
presentative. It appears, in fact, from the theory of the com-
position of vibrations, that two rays of equal intensity polarized
at right angles compound a single ray polarized in a single
plane, when the difference of their phases is nothing or equal
to any integer number of semiundulations; while in interme-
diate cases the polarization of the resulting light is either
circular or elliptic. These indications of theory have been
confirmed in the fullest manner by a beautiful experiment of
Fresnel.

On pursuing his inquiries Malus found that all other trans-
parent substances impressed upon the reflected light the same
modification ; and that the angle of incidence at which this effect’
was produced, and which he called the angle of polarization, was
in general different for every different substance. He ascer-
tained, moreover, the relation between the angles of polarization
at the first and second surfaces of the same transparent medium,

* Mémoires d’ Arcueil, tom. ii. p. 143. + Ibid., p. 254.

358 FOURTH REPORT—1834.

and found that their sines were in the ratio of the sines of inci-
dence and refraction ;—so that when the medium is bounded by
parallel surfaces, and the light incident on the first at its po-
larizing angle, the transmitted portion will meet the second
surface also at its polarizing angle, and the light reflected from
both be wholly polarized *. Malus was unable, however, to
discover any connexion between the polarizing angle and the
other properties of the substances; and he concluded that the
power of polarizing light by reflexion, which different bodies
possessed at different angles, was wholly independent of their
other modes of action upon light.

Sir David Brewster commenced, not long after, an extensive
series of experiments, with the view of determining the angles of
polarization of different media, and of connecting them by a law.
These researches terminated in the discovery of the law,—per-
haps the most beautiful in the whole range of this interesting
science,—that “the tangent of the angle of polarization is equal
to the refractive index.’’ This law, when translated into geo-
metrical language, declares, that. when the ray is wholly polar-
ized by reflexion, the angles of incidence and refraction are
complementary ; so that the reflected and refracted rays form a
right angle. The law applies to the case of reflexion from the
surface of the rarer as well as that of the denser medium; and
it follows from it that the two angles of polarization at the bound-
ing surface of the same two media are complementary +.

Malus obsetved that when the angle of incidence was either
greater or less than the polarizing angle, the properties already
described were only in part developed in the reflected pencil.
Neither of the two pencils into which it was divided by a rhomb
of Iceland spar ever wholly vanished’; but they varied in inten-
sity between certain. limits, these limits being closer the more
remote the incidence from the angle of complete polarization.
From this he naturally concluded that in these circumstances a
portion only of the reflected. pencil, had. received. the modifica-
tion to which he had given the name of polarization,—that por-
tion increasing as the incidence approached the polarizing an-
gle ;—and that the remaining portion was unmodified, or in the
state of common light. In this supposition Malus has been fol-
lowed, by most subsequent philosophers. A different view of

* Mémoires d’Arcueil, tom. ii. p. 152. M. Arago has extended the same
law to the case of’partial polarization, and has found that the sines of the angles
at which the first/and second surfaces of'a transparent medium polarize light by
reflexion in an equal degree, are to one another in the ratio of the sines of in-
cidenee and refraction ; so that the pencils reflected from the two surfaces of a
parallel plate, at any incidence, contain the same proportion of polarized light.

+‘ On the Laws which regulate the Polarization of Light by Reflexion from
transparent Bodies,” Phil. Trans. 1815.

REPORT ON PHYSICAL OPTICS. 359

the phenomenon of partial polarization has been taken by Sir
David Brewster, to which I shall have occasion presently to
allude; and he has employed his theory to explain a pheno-
menon which he seems to have been the first to observe,—
namely, that common light may be polarized by a sufficient
number of reflexions at any angle, the number of reflexions re-
quired to produce the effect being greater, the more remote the
incidence is from the polarizing angle *.

Examining the transmitted pencil, Malus found that it was
partially polarized; and that its plane of polarization was not,
like that of the reflected pencil, coincident with the plane of re-
flexion, but perpendicular to itt. The two portions of light
thus polarized in opposite planes he observed to be intimately
connected ; and in a subsequent memoir he announced the fact
that whenever we produce by any contrivance a ray polarized
in any plane, there is produced at the same time a second ray
polarized in the opposite plane. These two polarized rays
follow separate paths, and their quantities are always propor-
tionate. The connexion, however, is still more strict than was
supposed by Malus ; for the quantities of polarized light in the
reflected and transmitted pencils are not only proportionate, but
absolutely equal. This remarkable law was discovered by M.
Arago.

When a ray, which is partially polarized by transmission’
through a plate of glass, is received upon a second plate at the
same angle, the portion of common light which it contains
undergoes a new subdivision ; and so continually, whatever be
the number of plates. Hence when that number is sufficiently
great, the transmitted light will be, as to sense, completely
polarized; and the whole light is thus subdivided into two
pencils oppositely polarized,. one of which is reflected from, and
the other transmitted through, the pile. These facts were also
observed by Malus. The laws of the phenomena have since been
investigated, in much’ detail, by Sir David Brewster; and he
has arrived at the conclusion, that when a ray of light is trans-
mitted’ successively through any number of parallel plates, the
tangent of the angle at which the polarization of the refracted
pencil appears complete is inversely as their number tf.

_ I may now proceed to consider these phenomena in their re-
lation to the two theories of light.

ewton proved that the fundamental laws of reflexion and
refraction could be derived from the operation of attractive and

_* Phil. Trans. 1815. + Mém. Inst. 1810.
F; “On the Polarization of Light by oblique Transmission,” &c., Phil. Trans.
1814, -

360 _ FOURTH REPORT—1834,

repulsive forces exerted by the molecules of body on those of
light. The phenomena of polarization, however, show that
these forces are exerted in very different degrees, according to
the position of the sides of the ray with respect to the plane of
reflexion or refraction; and we are now to consider the additional
hypotheses which become necessary in the theory of emission
in order to render an account of these new facts.

It has been already mentioned that, in the theory of M. Biot,
a polarized ray was one in which certain axes (called the aves
of polarization) of all the molecules were turned in the same
direction. This effect is ascribed to the operation of certain
forces emanating from the molecules of the body. These forces
M. Biot denominates polarizing forces; and he considers them
as distinct from the reflecting and refracting forces, although
intimately connected with them. The effect of a polarizing force
is to give a rotation to the axes of the molecules; and that
which impresses the property of polarization upon the reflected
ray is assumed to act in the plane of reflexion. This being sup-
posed, since a ray of common light is polarized by reflexion
when incident at a certain angle, we are obliged to admit that,
at this angle, the polarizing force turns the axes of polarization
of all the molecules, and brings them into the plane of reflexion ;
and, ‘since this takes place for all the molecules of the reflected
ray, such an arrangement of the axes is conceived to be a ne-
cessary condition of reflexion at that incidence.

Now let such a polarized ray fall upon a second reflecting
surface at the polarizing angle, and let the plane of the second
reflexion be perpendicular to that of the first. Then the axes of
polarization of the molecules, in their incidence on the second
plate, are perpendicular to the plane of reflexion; consequently
the polarizing force acting in that plane affects equally the two
halves of the axis, and cannot therefore turn it into the plane
of reflexion,— a condition which is assumed to be necessary to,
reflexion at that angle. No light therefore is reflected. But
when the plane of the second reflexion is inclined to that of the
first at any angle less than 90°, the polarizing force of the
second plate no longer acts symmetrically on the two halves of
the axes of the molecules: it may therefore turn these axes so
as to make them coincide with the plane of reflexion, and thus’
subject the molecules to the action of the reflecting force. The-
effect of the polarizing force increases as the inclination of the
two planes of reflexion diminishes ; and consequently the num-_
ber of molecules reflected by the second plate increases likewise.

But here it is necessary to make another supposition. In
any position of the plane of the second reflexion with respect to.

REPORT ON PHYSICAL OPTICS. 361

the first, except the perpendicular one, experience proves that
a portion of the light is reflected and another portion refracted.
According to this theory, then, some of the molecules obey the
polarizing force and have their axes brought into the plane of
reflexion, while others donot. To account for this diversity of
effect there must be some diversity of condition in the molecules
themselves. The theory of M. Biot supplies this by attributing
to them an oscillatory movement round their axes of polariza-
tion, the molecules yielding to the polarizing force or not,
according to the phase of the oscillation in which they are
found at the moment they reach the surface.

The force which impresses the property of polarization upon
the refracted pencil is supposed by M. Biot to act also in the
plane ofincidence, its operation however being to turn the axes
of polarization of the luminous molecules in a direction perpen-
dicular to that plane. Thus, when a ray of light traverses the
surface of a plate of glass at the polarizing angle, it is subjected
to the action of two forces, one tending to bring the axes of
polarization of the molecules into the plane of incidence, the
other to turn them at right angles to it; and the molecules them-
selves yield to one or other of these forces according to the
phases of their fits. For the manner in which this may be
supposed to take place we must refer to the Zraité de Phy-
sique*. The whole quantities of light oppositely polarized by the
two forces, M. Biot supposes to be equal; but he conceives that
the force which polarizes the reflected pencil is exerted ona
much greater number of molecules than those which actually:
undergo reflexion. These molecules, thus polarized in, the
plane of incidence, enter into the transmitted beam,—neutralize
an equal number of molecules polarized by refraction in the.
Opposite plane,—and compound with them a beam of common
light. The whole quantities of light polarized by the two.
forces being then equal, the remaining portions effectively polar-
ized will still be equal, conformably to the law discovered by
M. Arago. .

I have endeavoured to present the theory of M. Biot as fully.
as the limits of the present paper will permit, because it appears.
to me that the nwmber and the nature of the hypotheses re-
quired, in order to render any account of the phenomena of
polarization in the theory of emission, furnish in themselves a.
sufficient argument against it. But let all these be admitted,
and how far can we be said to have advanced towards an expla-
nation of the phenomena? The assumed forces and the known
laws have not been connected, in any one instance, by the

: * Book vi. chap. i. vol. iv.

362 FOURTH REPORT—1834.

sure processes of mathematical deduction ; and we are there-
fore unable to state how far the explanation offered is com-
petent to express even the general facts,—far less can we
calculate them numerically, and compare the results with those
of observation.

The first attempt to connect the modifications of reflected
light with the theory of waves, was made by Dr. Thomas
Young. This sagacious philosopher succeeded in solving the
problem of reflexion in the case of perpendicular incidence,
and showed that the intensity of the reflected light in that case
was represented by a simple function of the refractive index *.
This formula was afterwards reproduced as the result of a more
refined analysis by M. Poisson, in a memoir on the simultane-
ous motions of two elastic fluids in contact, read to the French
Academy in 1817}. In that memoir, however, the author had
considered only the case of perpendicular incidence; or the law
of propagation of a plane wave parallel to the bounding surface
of the two media. In a subsequent memoir, to which I have
already alluded, and which was read to the Academy in the year
1823 {, he has resumed the problem generally, and examined
the modifications produced in the intensity as well as the direc-
tion of a wave, or series of waves, in passing from one fluid to
another of the same elasticity but of a different density. The
expressions obtained for the intensity of the reflected and re-
fracted waves, are functions of the angle of incidence and of the
ratio of the velocities of propagation in the two media. When
the wave is incident upon the surface of the denser medium,
the expression for the intensity of the reflected wave vanishes
at a certain angle, whose tangent is equal to the ratio of the
velocities of propagation. At this angle, which is the angle
of complete polarization, objects should therefore cease to be
visible by reflected light ;—a result which is contradicted by
all experience, and is only true when the light is polarized in a
plane perpendicular to the plane of reflexion. When the wave
is reflected at the surface of the rarer medium, there are two ex-
pressions for the intensity, for incidences above and below the
limiting angle of total reflexion respectively ; there are also in
this case two angles of evanescence. These conclusions, which’
apply to the case of sound as well as light, are sufficient to show
the physical inapplicability of the theory.

* Encyc. Brit., Supp., Art. Caromarics.

+ Mém. Inst., tom. ii.

t Only a portion of this memoir has‘ been printed in the Memoirs of the:
Institute, under the title ‘Mémoire sur le Mouvement de deux Fluides
elastiques superposés,” tom. X.

REPORT: ON PHYSICAL OPTICS. 368.

_ The theory of waves, however, when combined with the prin-
ciple of transversal vibrations, has afforded the complete solu-
tion of the problem we have been considering. In this develop-
ment of his theory the character of Fresnel’s genius is strongly
marked. Our imperfect knowledge of the precise physical con-
ditions of the question is supplied by bold, but highly probable
assumptions: the meaning of analysis is, as it were, intuitively
discerned, where its language has failed to guide; and the con-
clusions thus sagaciously reached are finally confirmed by ex-
periments chosen in such a manner as to force Nature to bear
testimony to the truth or falsehood of the theory *.

It:is evident that the strata of ether in the two media, which
are adjacent to the bounding surface, must undergo equal dis-
placements parallel to that surface, in as much as one of them
cannot slide on the other. Consequently the amplitude of the
vibration, resolved in a direction parallel to the surface, must
be the same in the two media. Fresnel assumes that this:
equality at the bounding surface is maintained at all distances ;.
and this furnishes him with one relation among the amplitudes
of vibration of the incident, reflected, and refracted waves. A
second relation among the same quantities is afforded by the law
of the’ vis viva; but to apply this it is necessary to know the:
relative densities of the ether in the two media. Here Fresnel
assumes that the elasticity of the ether in these media is the
samet, but the density different; and this being taken for
granted, it follows that the two densities are to one another
inversely as the squares of the velocities of propagation, and'that:
therefore their ratio:is given when the refractive index isknown,.,
The amplitudes of the reflected and refracted vibrations, and
therefore also the intensities of the light in the two pencils, are
obtained by simple elimination between the equations, just:
mentioned,

The expressions: for the intensity of the light in the reflected:
ray are different, according as:the incident light, is polarized! in.

* Fresnel’s' theory of’ reflexion is: contained’ im a: memoir read to’ the
Academy of:Sciences in the year 1823, entitled, ‘‘ Mémoire sur la Loi des:Modi-
fications que la Reflexion imprime 4 la Lumiére polarisée.” An incomplete ex-
tract of this memoir was published in the Annales de Chimie, 1825. ‘The ori-
ginal paper was mislaid, and for a time supposed to be lost ;’ it has lately, how-
ever, been recovered among the papers’ of M. Fourier, and: has been printed in.
the 11th vol. of the Memoirs of the Institute.

+ Fresnel states that he had solved the problem of reflexion in the general
supposition that the two media differ in elasticity. as. well as. density,— in the:
case of rays polarized in the plane of reflexion; and.that the resulting formula
was the same as that to which he had already arrived on'the more limited
hypothesis. dn. Chim., tom, xxiii.

364 FOURTH REPORT—1834.

the plane of reflexion or in the perpendicular plane*. The
intensity of the reflected light in the latter case vanishes when
the sum of the angles of incidence and refraction is a right
angle; and thus was solved the difficulty, which,—in the opinion
of Young, pronounced but three years before,—‘‘ would pro-
bably long remain, to mortify the vanity of an ambitious philo-
sophy, completely unresolved by any theory.”” When common,
or unpolarized light, therefore, is incident at an angle whose
tangent is equal to the refractive index, the reflected light will
be wholly polarized in the plane of reflexion ; and the beautiful
law of Brewster is among the first fruits of the theory of Fresnel.
The remarkable law obtained by M. Arago is also a necessary
consequence of the same formule ; and it is easily inferred that
the quantities of polarized light in the reflected and refracted
pencils are equal, whatever be the incidence.

In the case of perpendicular incidence, these formule are both

reduced to the simple expression obtained by Young and Poisson;
and when the incidence is 90°, or the ray grazes the surface,
the intensity of the reflected light is equal to that of the incident,
or the whole of the light is reflected, whatever be the reflecting
medium. The latter conclusion has been verified by the obser-
vation of the bands produced by the interference of direct light
with that which is reflected at an incidence of nearly 90°. The
first dark band appears to be perfectly black; and therefore the
two lights are, as to sense, of equal intensity +.
' We are thus furnished with the solution of a problem which
has long baffled the labours of experimentalists,—namely, the
determination of the law of intensity of reflected light as depend-
ent on the incidence. The formule obtained have not been
compared with experiment by Fresnel except in the case of two
observations of M. Arago; the observations of Bouguer and
Lambert being confessedly inaccurate. The result of the com-
parison alluded to has been given in the Annales de Chimie t,
and the agreement is as satisfactory as can be expected in obser-
vations of the kind.

Mr. Potter has recently examined the intensity of the light
reflected from diamond and glass of antimony, at various inci-
dences §. The photometrical method employed in these obser-
vations consistedin comparing the light reflected at any incidence
from the substance examined with that reflected from a piece of

* These two formule were first published in the Annales de Chimie, 1821 ;
the second without demonstration.

+ “ On a New Case of Interference,” Trans. Royal Irish Academy, vol. xvii.

+ tom. xvii. p. 190.

§ Phil. Mag., Third Series, vol. i. p.179; vol. iv. p. 6.

REPORT ON PHYSICAL OPTICS. 365

crown-glass, and then varying the incidence on the latter until
the intensities are observed to be equal. The intensity of the
light reflected from crown-glass at various incidences had been
already obtained from a detailed series of experiments ; and the
results were embodied in an empirical law, inwhichthe intensity is
represented by the ordinate of a rectangular hyperbola, the cor-
responding abscissa being the sine of incidence. This formula
then gives the intensity of the light reflected from crown-glass,
and therefore also from the substance examined, at the corre-
sponding incidences. Mr. Potter concludes in this manner, that
the intensity of the light reflected from diamond at a perpendicular
incidence is 9°3, and that from glass of antimony 8-2; the in-
tensity of the incident light being represented by 100. The
intensities calculated from the refractive indices, by the formulz
of Young, Poisson, and Fresnel, are 18°36, and 13°33, respec-
tively. This variance in the results of theory and experiment is
undoubtedly beyond the limits of the errors of observation ; and,
were it otherwise, the partial results obtained by Mr. Potter, in
these and other experiments of the same nature, agree too closely
to permit us to refer the discr@pancy to such a source. The
principle of the method however, appears, to say the least, un-.
certain ; and it cannot but be wished that some of the various
photometrical methods recently proposed should be applied to
the examination of this interesting question.

‘The formule of Fresnel supply the account of the re-
markable phenomenon observed by M. Arago;—namely, that
when Newton’s rings are formed between a lens of glass and a
metallic reflector, one of the two images into which they are
divided by a double-refracting crystal whose principal section
is parallel or perpendicular to the plane of reflexion, changes its
character as the incidence passes the polarizing angle of the
glass ; the colours being the same as in the other image when
the incidence is less than the polarizing angle, but comple-
mentary to them when it is greater. In fact, when the incident
light * is polarized perpendicularly to the plane of reflexion, the
amplitude of the reflected vibration (which vanishes at the angle
whose tangent is equal to the refractive index,) changes sign in
passing through zero; being negative when the incidence is
less than that angle, and positive when it is greater. Conse-
quently, if the wave reflected from the glass, at the central spot,
is in complete discordance with that reflected from the metal in
the former case, it will be in complete accordance with it in the
latter; and the centre, which before was black, will then be

r * The effect is the same whether the light be polarized before or after re-
exion. ;

566 FOURTH REPORT—1834.

white. For the same reason the whole system will be comple-
mentary to that which it was before. Professor Airy was led
to anticipate this result from the consideration of Fresnel’s ex-
pressions, and afterwards verified it on ‘trial*,—apparently
without any knowledge of the facts observed by M. Arago. A
similar confirmation of the same principles may be obtained by
combining, in Fresnel’s experiment, a metallic reflector with
one of glass. The light being polarized perpendicularly to the
plane of reflexion, the central band will be white when the
angle of incidence is below the polarizing angle of the glass ; at
the polarizing angle the interference bars will vanish altogether ;
and beyond that incidence they will reappear with a dark cen-
tre, instead of a whiteone. This method of observation would
seem to be peculiarly adapted to the investigation of the change
of phase produced by metallic reflexion at various incidences.
By the same considerations Professor Airy was led to expect
that when Newton’s rings were formed between two transparent
substances of different refractive powers,—the light being: polar-
ized perpendicularly to the plane of incidence,—the rings should
be black-centred, when the inéidence was less than the polarizing
angle of the low-refracting substance, or greater than that of
the high-refracting substance ; while they should appear with
a white centre, when it was intermediate to these angles ;—the
vibrations of the waves reflected from the two surfaces being of
opposite signs in the former case, and of the same sign in the
latter. All these expectations were fully confirmed by experi-
ment+. The substances selected by Professor Airy for these
observations were plate-glass and diamond,—-these substances
differing very widely in their refractive powers; and in ‘the
course of his experiments he has noticed certain peculiarities in
the phenomena, from which he has drawn some highly interest-
ing conclusions respecting the nature:of reflexion from diamond.
Had this been subjected to the ordinary laws, the reflexion
should cease, and the rings disappear, at the polarizing angle
of both substances. This however was not the case. The rings
did not vanish at the polarizing angle of the diamond; but the
first black ring contracted, as the incidence was gradually in-
creased, and finally usurped the place of the central white spot.
A portion of the light is therefore still reflected at the maxi-
mum polarizing angle of diamond ; and it is evident from the
phenomenon that the transition from a white to a black centre
is owing to a gradual change of phase of the reflected vibration,

* “ On a Remarkable Modification of Newton’s Rings,” Cambridge Trans.
1832.

+ * On the Phenomena of Newton’s Rings, when formed between two trans-
parent substances of different refractive powers,” Cambridge Trans, 1832.

REPORT ON PHYSICAL OPTICS. 367

‘amounting to nearly 180°, while the coefficient of the vibration
itself is not much altered. The diamond therefore has no angle
of complete polarization ; and Professor Airy concludes that the
nature of the reflexion from this singular substance, in the
neighbourhood of the angle of maximum polarization, is differ-
ent from any that has been hitherto described.

Fresnel’s theory of reflexion has received experimental confir-
mation of a different kind, and to an extent which leaves little
ground to doubt of its truth. When a ray polarized in any plane
falls upon a reflecting surface at any angle, the reflected ray is
still polarized, but its plane of polarization is changed,—the
amount of the change depending on the incidence. The law of
this change is at once furnished by the theory of Fresnel; for
the tangent of the inclination of the plane of polarization of the
reflected ray to the plane of incidence, is equal to the ratio of
the displacements in the plane of incidence and in the perpen-
dicular plane. The formula thus deduced has been verified in
the most complete manner by the observations of Fresnel him-
self, and more fully since by those of M. Arago and Sir David
Brewster*.

The views of the latter philosopher respecting the nature of
partially polarized light are founded upon the phenomenon of
the change of the plane of polarization by reflexion. If common
light be conceived:to consist of two pencils oppositely polarized,
in planes inclined 45° on either side of the plane of reflexion, the
effect of reflexion, it is obvious, will be to bring each of these
planes nearer to the plane of incidence ; so that the planes of
polarization of the two pencils will approach each other, and form
an acute angle after reflexion. Partially polarized light, then,

according to Sir D. Brewster, consists of two polarized pencils,
whose planes of polarization form an acute angle; and no por-
tion of it is in the condition of ordinary light}. This hypothesis
‘receives some support from the explanation which it affords
of ‘the effects of successive reflexions. When light thus con-
stituted is received upon a second reflecting surface in the same
plane of incidence, the planes of polarization of the two pencils
will be brought nearer, and so continually ; until by a sufficient
number of reflexions, these planes will, as to sense, coincide
with the plane of incidence, and the resulting light will appear
to be wholly polarized in that plane.

* Annales de Chimie, tom. xvii.; Phil. Trans. 1830.

+ Sir David Brewster has computed, on these principles, the quantity of
light apparently polarized in the plane of incidence, by a single reflexion at any
angle; adopting Fresnel’s expression for the intensity of the reflected ray. The
agreement of the formula with the observations of M. Arago is found to be

as near as can be expected in such comparisons. ‘ On the Law of Partial
Polarization of Light by Reflexion,” PAél. Trans. 1830.

368 FOURTH REPORT—1834.

This ingenious theory seems open to an objection already
noticed,—namely, that the light resulting from the union of
two oppositely polarized pencils cannot, in all respects, be
taken as the physical representative of common or unpolarized
light.. It also involves this further difficulty, that the positions
of the planes of polarization of the two oppositely polarized
portions are entirely arbitrary; and that if they be differently
assumed, the results will be physically different. Thus, for ex-
ample, if the two planes be taken, one coincident with the plane
of reflexion itself, and the other with the perpendicular plane,
neither of these planes will be changed by reflexion, although
the intensities of the corresponding pencils will.

Sir David Brewster has also investigated experimentally the
effect of refraction upon the plane of polarization of the refracted
ray; and he has found that the law of the change may be ex-
pressed by a very simple and elegant formula*. This formula
is anecessary consequence of Fresnel’s theory, although he does
not seem himself to have observed it. Its discovery by Sir
David Brewster adds one to the many instances of rare saga-
city by which this philosopher is guided in his experimental
inquiries. ‘The partial polarization of light by refraction has
been considered by Sir David Brewster inthe same memoir. In
the investigation of the quantity of polarized light in the refracted
pencil, he employs a principle similar to that which he had
already applied to the reflected ray ; and he arrives at the result
that the quantities of polarized light in the reflected and refracted
pencils are precisely equal, whatever be the incidence, con-
formably to the law of M.Arago. The effects produced by suc-
cessive refractions are accounted for on the same principles.

Sir David Brewster seems to have been the first who studied
the effects produced by total reflexion upon polarized light, and
he observed in particular the complementary colours which the
light thus reflected furnished when analysed with a rhomb of
Iceland spar t. At this time both he and Dr. Young concurred
in thinking that these phenomena arose from the interference of
two portions of light which were reflected at unequal depths ;
one portion, according to Dr. Young, beginning to be refracted,
and being then turned back by the continued exercise of the
same power f.

* qa anda’ being the azimuths of the planes of polarization of theincident and
refracted rays, estimated from the plane of reflexion, and 7 and #’ the angles of
incidence and refraction,

cot a! = cot a cos (i— 7).

“‘ Onthe Laws of the Polarization of Light by Refraction,” Phil. Trans. 1830.

+ Journ. Royal Inst., vol. iii.

t Suppl. Encyc. Brit., Art. Curomarics.

REPORT ON PHYSICAL OPTICS. 369

Fresnel had likewise observed, at an early period of his in-
quiries, that when a ray polarized in a plane inclined at an
angle of 45° to the plane of incidence undergoes total reflexion,
it is in part depolarized ; and that this depolarization is rendered
complete by two total reflexions at an incidence of about 50°.
The reflected light being then circularly polarized, is, according
to theory, composed of two equal pencils, one polarized in the
plane of incidence, and the other in the perpendicular plane, and
differing in their origin by a quarter of a wave. From this it
followed that the two pencils into which the incident light may
be resolved, polarized in these two planes, are not reflected at
the same depth; or that they have undergone unequal changes
of phase at the moment of reflexion, so that after reflexion one
of them is in advance of the other. After many ineffectual
attempts to discover in what manner this difference of phase de-
pended on the incidence, Fresnel was at length conducted to
the solution of the problem by the discussion of the formule
for the intensity of the reflected light already noticed.

When the angle of incidence exceeds the angle of total re-
flexion,—the light passing from. the denser into the rarer me-
dium,—these formule become imaginary. It is evident, how-
ever, from the law of the vis viva, that the intensity of the re-
flected light in this case is simply equal to that of the incident.
How, then, are the imaginary expressions to be interpreted >
They signify, according to Fresnel, that.the periods of vibration
of the incident and reflected waves, which had been assumed to
coincide at the reflecting surface, no longer coincide there when
the reflexion is.total; or in other words, that the ray undergoes
a change of phase at the moment of reflexion. The amount of
this change is deduced, by a train of the most ingenious reason-
ing, from the general expressions. Now when aray, polarized
in any azimuth, is incident upon the reflecting surface at an
angle greater than the angle of total reflexion, it may be resolved
into two: one polarized in the plane of incidence, and the
other in the perpendicular plane. The intensities of these two
portions will not be altered by reflexion ; but their phases will,
and each by a different amount. The reflected vibration, there-
fore, will be the resultant of two rectangular vibrations differing
in phase. This vibration, consequently, will be elliptic, and
the reflected light will be elliptically-polarized. When the
azimuth of the plane of polarization of the incident ray is 45°,
the intensities of the resolved portions are equal; and if, more-
over, their difference of phase, after reflexion, is equal to a
quarter of an undulation, the ellipse will become a circle, and
the light will be circularly-polarized.

1834. 2B

370 FOURTH REPORT—1834.

Reducing his formule to numbers, in the case of St. Gobain
glass, Fresnel found that the difference of phase of the two por-
tions of the reflected light amounted exactly to one eighth of an
undulation, when the angle of incidence was 54° 37’. Polishing,
therefore, a parallelopiped of this glass, whose faces of incidence
and emergence were inclined to the other sides at these angles,
it followed that a ray incident perpendicularly on one of these
faces, and once reflected at each of the sides, would emerge per-
pendicularly at the opposite face,—the difference of phase in the
two portions of the twice-reflected ray amounting to a quarter of
an undulation. If, then, the incident ray be polarized in a plane
inclined at an angle of 45° to the plane of reflexion, the emergent
light will be circularly-polarized. This was found to be the
case on trial ; and the parallelopiped thus constructed, and which
is known under the name of Fresnel’s rhomb, is of essential ser-
vice in experiments on circular and elliptic polarization. The
results of this remarkable theory have been confirmed by Fresnel
by other well-chosen experiments ; so that although the reason-
ing on which it is based is far from rigorous, there can remain
little doubt of its general truth. Fresnel was himself fully aware
of the incompleteness of his solution, considered in an analytical
point of view. In his memoir he has adverted to the method to
be adopted in order to obtain an exact solution of the problem,
unlimited by any arbitrary hypothesis ; and he proposed himself
to resume the question. But his brilliant career of discovery
was cut short by an untimely death. .

The problem of the reflexion and refraction of polarized light
has also engaged the attention of M. Cauchy*. The solution
given by this mathematician is derived from a consideration of
the conditions which must be fulfilled at the separating sur-
face of the two media; and it assumes that the density of the
ether is the same in both. The expressions obtained for the
amplitudes of the vibrations in the reflected wave agree with
those of Fresnel. The corresponding quantities for the refracted
wave differ from those deduced from Fresnel’s theory, by the
simple inversion of the ratio of the sines of incidence and re-
fraction, which occurs as a factor in both cases; and, thus,
though the formule are different, their consequences agree in
many instances,—as, for example, in the determination of the
plane of polarization of the refracted pencil. It is important to
observe, however, that according to the formule of M. Cauchy,
the velocities of the ethereal molecules in the refracted wave are
greater than in the incident; so that the law of the vis viva is

* Bulletin Uniwersel, tom. xiv. p. 6.

REPORT ON PHYSICAL OPTICS. 371

violated. This is not the case in Fresnel’s results, which are in
fact derived from that law.

The phenomena of metallic reflexion remain yet to be noticed
in connexion with this division of the science of light.

The effects produced upon light by reflexion at the surfaces of
metals did not escape the scrutiny of Malus. From his first
experiments upon the subject, Malus concluded that metals had
no effect in polarizing the light. He soon, however, modified this
opinion, and found that the phenomenon of polarization was
partially produced, the effect increasing to a maximum as the
incidence approached a certain angle. But the most instructive
mode of studying these phenomena, is to let fall upon the metal-
lic reflector a ray polarized in a plane inclined at an angle of
45° to the plane of reflexion, and to analyse the refiected pencil
by a double refracting prism. Proceeding in this manner Malus
found that when the incidence was very small or very great, the
reflected ray was still polarized ; while at moderate incidences
it was depolarized, and the pencil was divided into two in every
position of the rhomb. From these facts Malus concluded that
the difference between metals and transparent bodies consisted
in this, that the latter reflect all the light which is polarized in
one plane, and refract all the light polarized in the opposite
plane; while metals on the other hand reflect light which is
polarized in both planes.

The subject of metallic polarization was next examined by
Sir David Brewster; and his labours on this subject constitute
the most important addition which has been recently made to
our knowledge of the laws of polarized light*. When light re-
flected at a metallic surface is analysed by a double-refracting
crystal, it is observed to be partially polarized in the plane of
reflexion. The effect is greatest in galena, and least in silver ;
and the angle at which it is a maximum is about 74°, but varies
with the metal. By successive reflexions in the same plane Sir
David Brewster found that the proportion of polarized light was
increased ; and that bya sufficient number of reflexions the light
became, as to sense, wholly polarized in the plane of incidence.
The number of reflexions required to produce this effect varied
widely in the different metals.

In order to determine the nature and laws of this phenomenon,
it is necessary to examine the effect produced upon polarized
light. Adopting, then, the method of Malus, Sir David Brewster
found that when a ray of light polarized in the azimuth of 45°

* “On the Phenomena and Laws of Elliptic Polarization, as exhibited in the
Action of Metals upon Light,” Phil. Trans. 1830.

2B2

372 FOURTH REPORT—1834.

was received upon a metallic reflector at an incidence greater’
than 40° and less than 86°, the reflected light was partly depo-
larized. The effect produced was greatest at an angle of about
74°; and when the light underwent a second reflexion in the
same plane and at the same angle, it was restored to light po-
larized in a single plane. This new plane lies always on the
other side of the plane of reflexion; and its azimuth varies within
the limits 0° and 45°, being greatest for silver and least for
galena. It is evident, then, that the light produced by a single
reflexion cannot be common light. Neither is it plane-polarized
light, because it does not vanish in any position of the analysing
rhomb. Sir David Brewster concludes, that this light has re-
ceived a species of polarization hitherto unrecognised, interme-
diate between plane and circular polarization. He calls it elliptic
polarization, because the angles of reflexion at which this light
is restored to plane-polarized light, in any azimuth of the plane
of the second reflexion with regard to the first, may be repre-
sented by the variable radii of an ellipse; while these angles are
equal in all azimuths in the case of light circularly-polarized.

Sir David Brewster seems to have been led to employ the
term elliptic polarization” in this manner, in his desire to
avoid as much as possible all reference to theory. ‘The laws
which he has obtained, however, belong to elliptically-polarized
light, in the sense in which the term was introduced by Fresnel.
It appears, in fact, from the theory of the composition of vibra-
tions, as laid down by this author, that the vibration resulting
from the union of two rectilinear’ and rectangular vibrations,
will be in general elliptic; so that two oppositely polarized
pencils compound in general a pencil elliptically-polarized,—the
ellipse becoming a right line, when the difference of phase of the
two portions is an integer multiple of 180°. When, therefore,
by the effect of reflexion, two such pencils are made to differ 90°
in phase (as Sir David Brewster has shown to be the case when
a ray polarized in the azimuth 45° is incident at the maximum
polarizing angle of the metal), a second reflexion in the same
plane, and at the same angle, will raise the difference to 180°,
and the resulting light will be plane polarized. In other parts
of his memoir, however, Sir David Brewster seems to acknow-
ledge that theory; for he speaks of elliptic polarization as pro-
duced by the interference of two unequal portions of oppositely
polarized light, and even calculates their difference of phase for
any incidence.

The identity of the light produced by metallic reflexion, with
the elliptically-polarized light of the wave-theory, seems to be
placed beyond all doubt by an observation of Professor Airy.

REPORT ON PHYSICAL OPTICS. 373.

When Newton’s rings are formed between glass and metal,—
the incident light being polarized, and the angle of incidence
exceeding the polarizing angle of the glass,—it is found that the
rings dilate, as the azimuth of the plane of polarization with
respect to the plane of reflexion is increased; the dilatation
being a maximum when these two planes become perpendicular.
In order to account for this fact, Professor Airy has shown, that
if the vibrations of the incident pencil be resolved into two, one
in the plane of incidence, and the other in the perpendicular
plane, it is necessary to assume that their phases are unequally
changed by reflexion; the phases of the vibrations in the plane
of reflexion being more retarded than in the perpendicular plane.
The two oppositely polarized portions, therefore, will differ in
phase after reflexion, and will therefore compound a pencil ellip-
tically-polarized. Professor Airy has observed a similar pheno-
menon when Newton’s rings were formed between diamond and
plate-glass, the angle of incidence being a few degrees less than
the maximum polarizing angle of diamond; and he concludes
that, for such incidences, the nature of reflexion from diamond is
analogous to metallic reflexion.

Sir David Brewster has extended his researches on the subject
of metallic reflexion to a great variety of cases, and has traced the
effects of saccessive reflexions in the same, or in different planes ;
and at the same, or different angles. When the light which has
been restored to plane-polarized light, by two reflexions in the
same plane and at the maximum polarizing angle, undergoes a
third reflexion under the same circumstances, it becomes again
elliptically-polarized. By a fourth reflexion it is again restored to
plane-polarized light, the plane of polarization being, however,
brought nearer to the plane of reflexion. This continued ap-
proach of the plane of polarization to the plane of reflexion,
enables the author to explain, according to his peculiar views,
the effect of successive reflexions upon common light.

It remains, further, to extend the theory of Fresnel to reflexion
_at the surface of a medium in which the elasticity of the ether
is different in different directions. All that we know on this
interesting subject we owe to the unwearied zea] of Sir David
Brewster. It-had been supposed by Malus, and the opinion
seems to have passed current with succeeding philosophers, that
the exterior surfaces of crystallized substances acted upon the
reflected light exactly in the same manner as the surfaces of or-
dinary media; or, in the language of the theory of emission,
that the reflecting forces extended beyond the limits of the po-
larizing forces of the crystal. Sir David Brewster was led to
doubt this opinion; and in the year 1819 he undertook an ex-

874 FOURTH REPORT—1834.

tensive series of experiments on the subject of crystalline re-
flexion. One of the first results at which he arrived was, that
the angle of complete polarization on the same surface, varies
with the inclination of the plane of reflexion to the principal
section of the crystal; being least when the plane of reflexion
coincides with the principal section, and greatest when itis
perpendicular to it ;—and that with different surfaces the varia-
tion depended on the inclination of the surface to the axis of the
crystal. The difference of the greatest and least angles in the
case of Iceland spar, and on one of the cleavage planes of the
crystal, was found to amount to more than 2°.

But the effects produced upon the plane of polarization are
still more remarkable. On weakening the reflecting force, by
causing the reflexion to take place at the surface of contact of
the crystal and some fluid, such as oil of cassia, which had nearly
the same refractive power, Sir David Brewster found that the ray
was no longer polarized in the plane of reflexion ; and that the
deviation of the plane of polarization from the plane of re-
flexion depended on the angle which the incident ray formed
with the axis of the crystal. This relation Sir David Brewster
found to be expressed by the law,—that the sine of half the de-
viation varied as the square-root of the sine of the inclination of
the incident ray to the axis*.

It is much to be desired that the attention of analysts should
be directed to the problem of reflexion at the surface of extra-
ordinary media. It is one of the very few important provinces
of the science of light, which has not yet yielded its tribute to
the wave-theory ; and we can hardly conceive a finer subject for
the exercise of mathematical and physical skill +.

* “ On the action of Crystallized Surfaces upon Light,” Phil. Trans. 1819.

+ Since the preceding was written, Mr. M’Cullagh has arrived at an expres-
sion for the angle of polarization at the surface of crystallized media, in the
case in which the plane of reflexion coincides with one of the principal sections
of Fresnel’s ellipsoid; and he has found that the law, which he has extended
by analogy to all cases, represents with much exactness the observations of
Sir David Brewster. If a@ and 6 denote the semiaxes of the elliptic section
formed by the intersection of the plane of reflexion with the ellipsoid of indices,
(or the ellipsoid whose axes coincide in direction with the axes of elasticity of
the medium, and are equal to its three principal indices,) and r the radius of
the same section coinciding with the face of the crystal; the angle of polariza~
tion, , will be the same at whichsoever side of the perpendicular the ray is in-
cident, its value being given by the formula,
1%
Sin? = z

a b?

or.

REPORT ON PHYSICAL OPTICS. 37

III. Double Refraction.

The phenomenon of double refraction was first discovered by
Erasmus Bartholinus, in Iceland spar. After a long series of
observations, he found that one of the rays within the crystal
observed the known law of refraction discovered by Snellius,
while the other was bent according to a new and extraordinary
law. Anaccount of these experiments was published at Copen-
_ hagen in the year 1669, under the title “‘ Kaperimenta Crystalli

Islandict Disdiaclastici, quibus mira et insolita refractio de-
tegitur.”

The success of Huygens in deriving the laws of ordinary re-
fraction from the hypothesis of waves, naturally led him to
examine whether these new phenomena could be reconciled to
the same theory ; and in his desire to assimilate the two classes
of phenomena, he was happily led to assign the true law of
extraordinary refraction. Huygens had already shown that the
direction of the refracted ray, in glass and other uncrystallized
substances, could be deduced from the supposition, that the ethe-
real wave within the substance was a sphere ; or, in other words,
that the velocity of undulatory propagation was the same in all
directions. One of the rays in Iceland crystal, too, was found
to obey the same law; and judging that the law which governed
the other, though not so simple, was yet next in simplicity, he
assumed the form of its wave to be the spheroid of revolution,
the greater and lesser axis of the generating ellipse being in the
ratio of the greatest and least index of refraction. The form of
the wave being known, the law of refraction is derived from the
principle of the superposition of small motions. Conceive three
surfaces having their common centre at the point of incidence,
and representing respectively the simultaneous positions of three
waves diverging from that point,—the first in air, the other
two within the crystal. Let the incident ray be produced to
meet the air wave, and at the point of intersection let a tangent
plane be drawn: through the line of intersection of this plane
with the refracting surface, let planes be drawn touching the
two refracted waves ;—the lines connecting the centre with the
points of contact are the directions of the two refracted rays.
This beautiful construction, and the other speculations of Huy-
gens on the subject of extraordinary refraction, are contained
in the fifth chapter of his Zraité de la Lumiere.

Huygens was unable to reconcile the existence of a double
wave within the crystal with the supposition of a single vibrating
medium; and he was accordingly forced to assume the existence
of two such media, the spherical wave being propagated by the

376 FOURTH REPORT—1834.

vibrations of the ether alone, while the spheroidal wave arose
from the vibrations of the crystal and the ether jointly.

For the construction of Huygens, Newton substituted another,
without stating the theoretical grounds on which he formed it, or
even advancing a single experiment in its confirmation*. In
this unsatisfactory position the problem of double refraction
was suffered to rest for nearly a century; and it was not until
the period of the revival of physical optics in the hands of Young,
that any new light was thrown upon the question. This saga-
cious philosopher was led by the theory of waves to assume the
truth of the law of Huygens; and it was by his advice that Dr,
Wollaston undertook the experimental examination + which re-
called to it the attention of the scientific world, and ended in its
universal admission. The French Institute soon after proposed
the question of double refraction as the subject of their prize
essay, and the successful memoir of Malus left no doubt remain-
ing as to the accuracy of the Huygenian lawt.

The examination of Malus was chiefly directed to the case of
Iceland spar; but he made a few similar measurements, also,
in quartz, sulphate of barytes and arragonite. In the first of
these crystals he mistook the ordinary for the extraordinary ray ;
and the faces which he chose for examination in the two latter
not happening to be well adapted to the discovery of their pro-
perties, he was satisfied with a hasty generalization of the law
observed in Iceland spar, and concluded that it belonged to
all double refracting bodies. Malus entered largely, in the same
memoir, into several questions connected with the problem of
double refraction ; and he showed, in particular, that the laws
of extraordinary reflexion at the second surfaces of crystals are
deducible from the law of Huygens. In a memoir presented to
the Institute, in the following year §, he extended consider-
ably the list of bodies possessing the property of double refrac-
tion; and arrived at the conclusion that this property belonged
to all crystals, excepting those whose primitive form was
the cwhe or regular octohedron. Most organized substances,
whether vegetable or animal, were found to possess the same
properties.

In Iceland spar the extraordinary refractive index is less than
the ordinary. The extraordinary ray consequently is always
refracted from the axis of the crystal; and the same law had
been supposed to belong to all double-refracting substances.

* Optics, book iii., query 25.

+ “ On the Oblique Refraction of Iceland Crystal,” Phil. Trans. 1802.

+ “ Théorie de la Double Refraction,” Wém. Inst.

§ “ Sur l’Axe de Refraction des Cristaux et des Substances organisées,” Mém.
Inst. 1811. F

REPORT ON PHYSICAL OPTICS. 377

M. Biot made the important discovery that in many crystals
the extraordinary index was greater than the ordinary, and the
extraordinary ray therefore refracted towards the axis. Cry-
stals of the latter kind he called attractive, while those of the
former were called repulsive ; the extraordinary refraction being
ascribed, inthe theory of emission, to attractive or repulsive forces
which act as if they emanated from the axis*. These crystals
are now generally distinguished by the denominations positive
and negative. The Huygenian law applies to positive as wellas
to negative crystals; the spheroid being prolate in the former
case and oblate in the latter.

The construction given by Huygens for the direction of the
two refracted rays is, it has been stated, an immediate conse-
quence of the assumed form of the wave-surface. It easily
appears, from the principle of Huygens already adverted to,
that the same construction will apply in all cases, whatever be
the form of the wave or the law of the velocity of propagation
within the crystal ;—so that the law of direction is determined
when that of velocity is known. A similar connexion between
the velocity of the molecule and its path is established, in
the theory of emission, by the law of least action. This
principle, we know, holds generally in the motion of a point
subjected to the action of attracting or repelling forces; and in
applying it to the case of a luminous molecule acted on by
forces emanating from the particles of the body which it meets,
we may leave out of consideration the insensible curvilinear por-
tion of the trajectory described in the passage from one medium
into another of different density,—provided we assume, with
Newton, that the forces exerted by the molecules of body-on
those of light are sensible only at insensible distances. In this
simplification of the problem we have to deal only with straight
lines and uniform velocities ; and when the dependence of these
velocities on the directions is assumed or given, the principle in
question furnishes a relation between the directions of the two
portions of the trajectory. Such was the problem whose solu-
tion was given by Laplace, in his memoir on the motion of light
in transparent mediay; and he has arrived at two equations, in
which that solution is completely contained. Laplace applied
these results to two cases ;—one in which the difference of the
squares of the velocities of the incident and refracted rays is
constant,—and the other in which that difference is equal to a
constant quantity, plus another varying as the square of the
cosine of the inclination of the refracted ray to the optic axis.
In the former of these cases he obtained the known law of

* Meém. Inst. 1814. - + Ibid. 1809.

378 FOURTH REPORT—1834.

Snellius ; and the formule of refraction to which he arrived
in the latter were found to be identical with those furnished by
the construction of Huygens.

The velocity of the extraordinary ray, assumed by Laplace, is
the reciprocal of the radius-vector of the ellipsoid of Huygens,
and therefore the zverse of the assumed velocity in the wave-
theory. But Laplace himself has shown that the construction
suggested by that theory, and employed by Huygens for the
determination of the direction of the refracted ray, resolves it-
self into the principle of least time,—and that whatever be the
form of the wave-surface; and as the law of least action and
that of least time are identical, provided the assumed velocities
be reciprocal, it ceases to be strange that two such very different
methods should lead precisely to the same result. The difference
between Huygens and Laplace, as to the mode of deducing the
law of extraordinary refraction, is in fact precisely the same as
that which existed formerly between Fermat and Maupertuis
with regard to the ordinary law of the sines.

This identity of the results afforded by the two theories has
since been more distinctly pointed out by M. Ampére. By means
of the principle of least action he has arrived at the following
general conclusion, whatever be the assumed law of the veloci-
ties,—that if from the point of incidence on any extraordinary
medium, as centre, two surfaces be described whose radii-vec-
tores are inversely as the velocities of the incident and refracted
rays in their directions; and if the incident and refracted rays
be produced to meet these surfaces, and tangent planes be
drawn at the points of meeting, the line of intersection of these
planes will be 6n the separating surface of the two media*.
Hence the position of the refracted ray is determined when that
of the incident ray is known; and the construction thus sup-
plied for its determination is obviously the generalization of the
construction of Huygens already alluded to, if only the radii-
vectores be taken in the direct ratio of the velocities, instead of
the inverse.

It is obvious, then, that the problem of double refraction, con-
sidered as a physical question, resolves itself into the determina-
tion of the law of velocities. Newton showed that the constant
ratio of the velocities in ordinary media, and therefore the law
of the sines, could be explained on the supposition that the lu-
minous molecules are solicited by attracting forces emanating
from the molecules of the refracting body, and sensible only at
very small distances. The phenomenon of extraordinary re-
fraction, in like manner, was ascribed by Laplace to the operation

* Mém. Inst, 1815.

_ REPORT ON PHYSICAL OPTICs. 379

of similar forces emanating from the molecules of the crystal ;
but modified by the form of these molecules and those of light,
and by the manner in which they are presented to each other.
No attempt, however, has been made in the theory of emission to
advance beyond the point to which Newton arrived, and to de-
duce the velocity of the extraordinary ray in crystallized media
from any assumed constitution of the molecular forces* ; and,
indeed, when the condition of polarity is to be superadded to
the laws of such forces, the theory seems embarrassed in
inextricable difficulties. The refraction which a polarized ray
undergoes in a crystal depends upon its plane of polarization,
and, by a simple change of that plane, the refracted ray may be
converted from an extraordinary to an ordinary ray. The extra-
ordinary force then, it appears from the phenomena, exerts no
effect upon a ray polarized parallel to the principal plane; its
effect is greatest upon a ray polarized in the perpendicular plane ;
and it must be supposed to act in every intermediate degree
upon rays polarized in intermediate planes. Now aray of com~-
mon light, in the theory of emission, is composed of molecules
whose planes of polarization are turned in all azimuths; and
these molecules, consequently, should feel the influence of the
extraordinary force in every possible degree. Instead, therefore,
of two refracted rays, such a ray should be divided into an infinite
number, inclined in every possible angle between the limiting
directions of the ordinary and extraordinary rays.

It had been hitherto assumed, that no crystal had more than
one optic axis. While examining the rings which surround
these axes in polarized light, Sir David Brewster made the im-
portant discovery that the greater number of crystals possess
two optic axes; and he soon after discovered the connexion be-
tween these diversities of optical character and the crystalline
form.

‘The optic axes, however, as Sir David Brewster has shown,
cannot be regarded in general as the fundamental axes of the
double-refracting medium. He calls them apparent axes; and
considers them as the resultants of others, which he denominates

* Fresnel states, in the commencement of his memoir on double refraction,
that Laplace had derived the velocity of the extraordinary ray, in uniaxal cry-
stals, from the hypothesis of a resultant force acting in a direction perpendicular
to the optic axis, and varying as the square of the sine of the angle which the
ray makes with that line. Ihave not been able to discover, in any of La-

lace’s writings, the discussion thus adverted to.

+ The important relations here alluded to have been already brought under
the ppiention of the Association, in the able Report on Mineralogy, by Mr. Whe«
well.

880 FOURTH REPORT—1834.

true or polarizing axes, and from which the forces which pro-
duce the phenomena of polarization and double refraction are
conceived to emanate. The polarizing force proceeding from a
single axis, is measured by the difference of the squares of the
velocities of the ordinary and extraordinary rays, and is supposed
to vary as the square of the sine of the angle which the direction
of the ray within the crystal contains with it; and when two
such axes cooperate, it is assumed that the increment of the
square of the velocity, arising from their joint action, is equal to
the diagonal of a parallelogram whose sides are the increments
of the square of the velocity produced by each separately, and
whose angle is double of that formed by the two planes passing
through the ray and the axes*. From this hypothesis it followed
that two rectangular polarizing axes of equal intensity, and both
positive or both negative, compound a single resultant axis at
right angles to both. This axis is of the same intensity as the
component axes, but of an opposite character; and, accordingly,
three equal rectangular axes of the same character balance each
other’s effects, and have no resultant. 'Thus, then, the laws of
uniaxal crystals, as well as of singly-refracting media, are em-
braced in this hypothesis. The case of two resultant axes is
reducible to that of two unequal polarizing axes; and it has been
shown to be a consequence of the rule that the difference of the
squares of the velocities of the ordinary and extraordinary rays
within the crystal, is proportional to the product of the sines of
the angles which the latter makes with the resultant axes.
M. Biot was led to the discovery of this beautiful law by ana-
logyt, and he afterwards observed that it was implicitly contained
in the law proposed by Sir David Brewster.

The term ‘“ polarizing force’’ seems to have been adopted by
Sir David Brewster without any reference to the law which
governed the planes of polarization of the two pencils,—a law
which, in biaxal crystals, still remained unknown. In the ease
of uniaxal crystals, it could not fail to be observed, the plane of
polarization of one of the pencils contained the direction of the
ray and the axis; while that of the other was a plane passing
through the ray at right angles to the former. Conceiving that
these planes, in biaxal crystals, must be symmetrically placed .
with respect to the planes passing through the ray and the two
axes, M. Biot was led to the simple and elegant law—that the
plane of polarization of one of the pencils was that passing

* “ On the laws of Polarization and Double Refraction in regularly crystallized
Bodies,” Phil. Trans. 1818. ;

+ “ Mémoire sur les Lois générales de la Double Refraction, &c.,” Mém. Inst.,
tom, iii.

REPORT ON PHYSICAL OPTICS. 381

through the ray, and bisecting the dihedral angle contained by
these planes ; while that of the other was perpendicular to the
former, or bisected the supplemental dihedral angle *.

When a ray of light enters a crystal, the component molecules
are supposed, in the theory of M. Biot, to receive different mo-
tions round their centres of gravity, dependent on the nature of
the forces exerted upon them by the particles of the body.
Sometimes the molecules of the ray are turned by the operation
of these forces, so as to have certain lines in each, denominated
axes of polarization, all in the same direction ; and this arrange-
ment of the molecules is maintained throughout the whole of
their future progress. There are other cases, however, according
to this author, in which the molecules osci//ate round their cen-
tres of gravity in certain periods, during their entire progress
through the crystal; while in others, finally, they receive a
motion of continued rotation. To the two latter cases I shail
have occasion to advert hereafter.

_ The phenomena of fized polarization are ascribed by M. Biot
to the operation of certain forces, which he denominates polariz-
ing forces. In the case of uniaxal crystals these forces are sup-
posed to act in the planes containing the two rays and the axis
of the crystal,—the ordinary polarizing force tending to arrange
the axes of the molecules in the plane containing the ray and
the axis, while the extraordinary polarizing force draws them
towards the perpendicular plane. If the molecules were simi-
larly circumstanced in every respect, they would necessarily obey
the stronger of these forces, and there would be but one plane
of polarization. This, however, is supposed not to be the case.
Owing to the different phases of their fits, at their incidence upon
the crystal, the molecules are disposed to yield more readily to
one or other of these forces ; so that when a polarized ray meets
a double refracting medium, some of the molecules fall under
the influence of the ordinary polarizing force, and have their
axes of polarization turned into the plane containing the ray and
the axis of the crystal, while others are actuated by the extra-
ordinary force, and have their axes arranged in the perpendicular
plane. The number of molecules which yield to one or other
of these forces, or the intensity of the two polarized rays, is
supposed to depend on the angie which the plane of primitive
polarization makes with the two planes just mentioned. When
the plane of polarization coincides with the former, the extra-
ordinary force has no effect, and the ray receives only the ordi-
nary polarization ; the converse takes place when the plane of
polarization coincides with the perpendicular plane. Similar

* Ibid.

382 FOURTH REPORT—1834.

suppositions were made to account for the phenomena of polari-
zation in biaxal crystals.

Such was the state of the theory of double refraction when the
subject was taken up by Fresnel. The law of refraction, we
have seen, whether in the theory of emission or in that of waves,
was intimately connected with and dependent on the law of ve-
locities ; so that, considered as a physical question, the problem
resolved itself into the determination of the latter. With the
exception, however, of the reasonings of Young respecting the
form of the wave-surface in a medium compressed or dilated in
a given direction*, no attempt had been made to deduce the
velocity of the extraordinary ray from the principles of either
theory. Indeed, the general law of the velocities was itself un-
known, even as an experimental fact, although an important
relation between the velocities of the two pencils had been dis-
covered by the labours of Sir David Brewster and M. Biot. But
this was not all. It was evident that no physical theory of double
refraction could be regarded as complete, which did not at the
same time account for the attendant phenomenon of polarization.
In this branch of the subject, however, nothing had been accom-
plished ; and all that had been said in explanation of the pheno-
menon of polarization did not go further than some vague spe-
culations as to its cause. The theory of Fresnel to which I now
proceed,—and which not only embraces all the known pheno-
mena, but has even outstripped observation, and predicted con-
sequences which were afterwards fully verified,—will, I am per-
suaded, be regarded as the finest generalization in physical science
which has been made since the discovery of universal gravitation.

Fresnel} sets out from the supposition that the elastic force
of the vibrating medium is, in general, different in different
directions. This is, in fact, the most general supposition
that can be made; and whether we suppose that the vibrating
medium is the ether within the crystal, or that the molecules
of the body itself partake of the vibratory movement, there
will be obviously such a connexion and mutual dependence
of the parts of the solid and those of the medium in question,
that we cannot hesitate to admit for the one what has been al-
ready established on the clearest evidence for the othert. Now
if a disturbance be produced in a medium so constituted, and

* Quarterly Review, vol. ii.

+ “ Mémoire sur la Double Refraction,” MWém. Inst., tom. vii.

t M. Savart has shown that the elasticity of crystals, determined by means
of their sonorous vibrations, is, in general, different in different directions. The
optic axis of Iceland spar is the axis of least elasticity: that of rock crystal is
the axis of greatest elasticity. -

REPORT ON PHYSICAL OPTICS. 383

any particle displaced from its position of rest, the resultant of
the elastic forces which resist the displacement will not, in
general, act in the direction of that displacement (as in the case
of a medium uniformly elastic), and therefore will not drive the
displaced particle directly back to its position of equilibrium.
Fresnel has shown, however, that there are three directions at
right angles to each other, in any of which, if the particles are
displaced, the elastic forces do act in the direction of the dis-
placement whatever be the nature or laws of the molecular ac-
tion; and the only assumption which he makes is—that these
three directions are parallel all throughout the crystal*. These
directions Fresnel denominates aves of elasticity. He conceives
that they ought also to be axes of symmetry with respect to the
crystalline form ; but observes that M. Mitscherlich has noticed
some crystals in which this does not holdt. If on each of these
axes, and on every line diverging from the same origin, portions
be taken which are as the square roots of the elastic forces in
their direction, the locus of the extremities of these portions will
be a surface which Fresnel calls the surface of elasticity. This
surface determines the velocity of propagation of the wave, when
the direction of its vibrations is given.. For the velocity of un-
dulatory propagation in an elastic medium, being as the square
root of the elastic force, must be represented by the radius-vector
of the surface of elasticity in the direction of the vibrations.

. Now let us conceive a plane wave advancing within the crystal.
By the principle of transversal vibrations the movements of the
ethereal molecules are all parallel to the wave. But the motion
of each displaced particle is resisted by the elastic force of the -
-medium, and that force is, in general, oblique to the direction of
the displacement. Fresnel shows, however, that the displace-
ment may be resolved in two directions in the plane of the wave,
‘such that the elastic force called into action by each component
will be the resultant of two forces, one of which acts in the di-
rection of the displacement itself, while the other is normal to
the wave. The latter, by the principle of transversal vibrations,
can produce no effect ; and the former will give rise to a wave
propagated with a constant velocity. These two directions, he

* This will be the case, if the homologous lines of the groups of particles are
all parallel; an arrangement at once the simplest and most natural, and which
appears to be observed in most crystallized bodies. Fresnel admits, however,
the possibility of other regular arrangements; and he conceives that the pheno-
mena of circular polarization in rock crystal oblige us to suppose that its mole-
cules are arranged according to some less simple law.

+ See Bulletin de la Société Philomathique, March 1824.

384 FOURTH REPORT—1834.

finds, are those of the greatest and least diameters of the section
of the surface of elasticity made by the plane of the wave; and
if the original displacement be resolved into two, parallel to them,
each component will give rise to a plane wave whose velocity of
propagation is represented by that diameter, and the vibrations
in each wave will preserve constantly the same direction.

Thus it appears that a polarized plane wave will be resolved
into two within the crystal ; and these will be propagated with
different velocities, and consequently follow different paths. The
amplitudes of the component vibrations are as the cosines of the
angles which the direction of the original vibration contains with
the two fixed rectangular directions ; and, as the squares of these
amplitudes represent the intensities of the two pencils, the law
of Malus respecting these intensities follows as an immediate
consequence*. Again, the planes perpendicular to these two
directions are the planes of polarization of the two pencils.
And it is easily inferred that one of them must bisect the dihedral
angle contained by the two planes passing through the normal
to the wave, and the normals to the circular sections of the sur-
face of elasticity ; while the other is perpendicular to it. This
conclusion does not coincide mathematically with the experi-
mental law of M. Biot: but the differences are much within
the limits of the errors of observation, and the results of expe-
riment must be regarded as confirmatory of the theory.

The velocity of propagation of a plane wave in any direction
being known, the form of the wave-surface diverging from any
point within the crystal may be found. For if we conceive an
indefinite number of plane waves, which, at the commencement
of the time, all pass through the point which is considered as the
centre of disturbance, the wave-surface will be that touched by
all these planes at any instant. This surface is of the fourth
order. Fresnel has deduced its equation, although in an indirect
manner; and he has shown that it may be geometrically con-
structed by means of an ellipsoid whose semiaxes are the same
as those of the surface of elasticity. The form of the wave-
surface being known, the directions of the two refracted rays are
given by the construction of Huygens.

* Young seems to have been the first to observe that the law of the square
of the cosine could be derived from the hypothesis of transversal vibrations,
(Ency. Brit. Cunomatics, p. 161.) The subject of the experimental confirma-
tion of this important law has been recently brought before the French Academy
by M. Arago, and he has indicated the practical results which may be derived
from this law in its application to photometry.—Herschel’s Essay on Light :
French Translation, Suppl., p. 590.

REPORT ON PHYSICAL OPTICS. 385

From the construction now alluded to it appears that there
are two directions,—the normals, namely, to the two circular
sections of the ellipsoid,—in which the velocity of the two rays
is the same. These directions are called by Fresnel the optic
axes; although he sometimes applies this term to the normals
to the circular sections of the surface of elasticity, or the direc-
tions in which a plane wave is propagated witha single velocity.
It thus appears that crystals have in general two optic axes, and
can have no more. When two of the three principal elasticities
are equal, the two optic axes unite, and the wave-surface re-
solves itself into the sphere and spheroid of revolution... Thus
the form of the wave in wniaxal crystals, which Huygens assumed
as the most natural, comes out as a simple corollary from the
general theory of Fresnel. - When, lastly, the three elasticities
are all equal, the wave-surface becomes a sphere; the velocity
is accordingly the same in all directions, and the law of refrac-
tion is reduced to the known law of Snellius.

_ It was easily shown to follow from the general construction,
that the difference of the squares of the reciprocal velocities of
the two rays, in biawral crystals, is proportional to the product
of the sines of the angles which their common direction within
the crystal contains with the two axes; so that the remarkable

law of Sir David Brewster and M. Biot is brought under the
same theory. But it appeared further, from that theory, that the
velocity of neither of the rays is constant, and that the refraction
of both is performed according to a new law. This» conclusion
was at variance with all the received notions upon the subject ;
and indeed the experiments of M. Biot on limpid topaz* seemed
to warrant his assumption that the refraction of one of the rays
followed the ordinary law of the sines. It became, therefore, a
matter of much interest to decide this question by accurate ex-
periment. This has been done by Fresnel himself by the ordi-
nary method of prismatic refraction, as well as by the nicer
means afforded by the displacement of the diffracted fringes ;
and the result in both cases has been conclusive in favour of his
theory. The numerical data afforded by the observations of
M. Biot on topaz enabled Fresnel to compute, according to the
principles of that theory, the velocity of the ray in different
directions ; and the observed variation was found to agree with
that deduced.

The phenomenon of dispersion, in singly-refracting substances,
proves that the elasticity of the vibrating medium varies with
the length of the wave. The same thing must take place in

* Mém. Inst., tom. iii.

1834. 2€

386 FOURTH REPORT-—1834.

double-refracting media, in which the elasticity is different in dif-
ferent directions ; and as we haveno reason for supposing that the
elasticities should vary in the same proportion in the direction of
the three axes of elasticity, it will follow that in general each re-
fractive index will have its appropriate dispersive ratio. Sir
David Brewster first showed that this was actually the case, and
that Iceland spar and other double-refracting substances had two
dispersive powers*. M. Rudberg has recently examined the
laws of dispersion in double-refracting media with much care,
following the accurate method of Fraunhofer. He has in this
manner. determined the greatest and least refractive index cor-
responding to the seven principal dark lines of the spectrum in
Iceland spar and rock crystal, and the three principal indices in
arragonite and topaz; and has found, in accordance with the
discovery of Sir David Brewster, that the ratio of these indices
increased with the refrangibility of the light +. The experiments
of M. Rudberg confirm also the fundamental position of Fresnel's
theory, namely, that the velocity of'a ray in a given medium is
the same as long as its plane of polarization is unchanged.

The angle contained by the optic axes, in biaxal crystals, isa
simple function of the three principal elasticities ; and if their
ratio vary with the colour of the light, the inclination of the axes
must likewise vary. Such a variation has been established by
the observations of Sir John Herschel; and it has been found
that the inclination of the axes is greater in red than in violet light
for some crystals, while in others it is less{. In the case of Ro-
chelle salt, the angle between the optic axes of the red and violet
rays amounts to 10°. Generally the position of the three.axes
of elasticity is invariable, and the optic axes for all colours are
confined to one plane ;_ but Sir John Herschel has lately observed,
that in borax the optic axes belonging to different colours lie in
different planes; and we are compelled to conclude that the
direction of the axes of elasticity in this, and probably in many
other crystals, varies with the colour.

The first addition to the theory of Fresnel was made by

* Treatise on New Philosophical Instruments, Edin. 18138. Hs

+ Annales de Chimie, tom. xlviii. For the calculation of the phenomena of
double refraction in biaxal crystals, according to Fresnel’s theory, it is necessary
to know the three principal refractive indices, or the velocities of propagation of
rays whose vibrations are parallel to the three axes of elasticity. Beside the
researches of M. Rudberg, I do not know that we possess any other in which
all these data have been directly determined. It is true that if we know the
greatest and least index, and the angle contained by the optic axes, the mean
index can be deduced. But the inclination of the optic axes cannot be deter-
mined experimentally with the same precision as the other elements.

+ Phil. Trans. 1820.

REPORT ON PHYSICAL OPTICS, 387

M. Ampére.” The results alluded to are contained in two short
papers read to the French Academy in the year 1828, and since
embodied into one, and published in the Annales de Chimie*.
Fresnel had arrived at the eqtiation which’ belongs: to all the
tangent planes of the wave-surface, and had shown in what man-
ner the equation of -the surface’ itself might’ be thence deduced
by differentiation and elimination. This direct process, how-|
ever, he seemed to think would involve’complicated and embar-
rassing calculations. ° The method which he substituted for it
consisted in verifying the equation, to which he was led by rea~
sonings not altogether rigorous, and proving (by calculations
which he found too tedious to'transcribe), that it satisfied the
conditions already assigned. M.Ampére has supplied the direct
demonstration, and deduced the equation of the wave-surface in
the manner originally pointed out by Fresnel. From this equa~
tion he has derived also’ the beautiful geometrical construction
given by Fresnel, and which the latter had obtained indirectly: :
- A very concise demonstration of the same theorem, and of the
other principal points of Fresnel’s theory, was given not long
after by Mr. M’Cullaght. This writer has shown that both the:
magnitude and direction of the resultant elastic force, called into
action by any displacement, may be represented by means ‘of an
ellipsoid whose semiaxes are the three principal refractive in-=
‘dices of the medium ; and from this ellipsoid, by the ‘aid of a
few geometrical lemmas, he has deduced in a clear‘and simple
manner the leading results arrived at by Fresnel. The axes
of this ellipsoid coincide in direction with, and are inversely
proportional to, the axes of Fresnel’s generating ellipsoid; and
Mr. M’Cullagh has demonstrated the truth of Fresnel’s construc-
tion for the wave-surface, by means of a simple geometrical
relation between its tangent: planes and the sections of the two
ellipsoids. Rh <n
“Tn the third supplement to his “ Essay on the Theory of —
Systems of -Rays{,” Professor Hamilton has presented that
portion of: Fresnel’s theory, which relates to the fundamental
problem of the determination of the velocity and polarization of
a plane wave, in a very elegant analytical form; and from the

* Mémoire sur la Détermination de la Surface courbe des Ondes' lumineuses,”’
&c., tom. Xxxix. : :

+ “On the Double Refraction of Light in a crystallized medium according to
the principles of Fresnel,” Transactions of the Royal Irish Academy, vol. xvi.
A further development of the principles of this memoir has been recently given
by the author in the 17th vol. of the same Transactions, under the title “Geo-
metrical Propositions applied to the Wave-theory of Light.”

~ } Transactions of the Royal Irish Academy, vol. xvii.
2c2

388. FOURTH REPORT—1834.

velocity and direction of the wave he deduces those of the ray,
and therefore the form of the wave-surface, by means of the
general relations suggested by his view of mathematical optics. .

In this system, of which the author gave a brief sketch
at the late meeting of the Association, the laws of reflexion
and refraction, ordinary or extraordinary, are comprised in
two fundamental expressions, which state that the partial dif-
ferential coefficients of the first order of a certain function,;—
taken with respect to two final coordinates in the plane which
touches the reflecting or refracting surface at the point of inci-
dence,—are not altered by reflexion or refraction. The function
here considered is the characteristic function of the author,-
whose particular form may be considered as characterizing the
optical system, and on whose properties, he finds, all the pro-
blems of mathematical optics may be made to depend. On the
principles of the wave-theory, this function is equal to the undu-
latory time of propagation of light, from any one assumed point
to another, in the same or in a different medium; and the ex-
pressions just alluded to, signify simply that the components of
normal slowness of the wave parallel to the bounding surface,
or the reciprocal of the velocity of wave-propagation resolved in
the direction of that surface, are not changed by reflexion or
refraction. The normal slowness of wave-propagation is, then,
of fundamental importance in this theory; and if it be repre-
sented in magnitude by a line taken in its direction, there is
obtained for its expression a curved surface which, on the prin-
ciples of Fresnel, is found to be a surface of two sheets, connected
with the wave-surface by a remarkable relation of reciprocity.
When this relation is combined with the laws of reflexion and
refraction just alluded to, they lead to a very elegant construc-
tion for the reflected or refracted ray which is, in most cases,
more convenient than that of Huygens. Thus, when a ray pro-
ceeds from air into any crystal, we have only to construct the
surfaces of wave-slowness belonging to the two media, and having.
their common centre at the point of incidence. Let the incident
ray be then produced to meet the sphere, which represents the
normal slowness of the wave in air; and from the point of in-
tersection let a perpendicular be drawn to the reflecting or refract-
ing surface. This will cut the surface of slowness of the reflected
or refracted waves in general in two points. The lines connect-
ing these points with the centre, will represent the direction and
normal slowness of the waves; while the perpendiculars from
the centre on the tangent planes at the same points, will repre-
sent the direction and slowness of the 7ays themselves.

This important curved surface presented itself also to M. Cau-

REPORT ON PHYSICAL OPTICS. 389

‘chy in his able researches on the propagation of waves in elastic
media, although he does not seem to have been aware of all its
‘properties. The properties of the same surface, and its use in
‘constructing the direction of a reflected or a refracted ray, were
.also discovered, independently, by Mr. M’Cullagh, who has re-
‘cently applied them to the geometrical development of the theory
-of double refraction*.

The relations between the surface of wave-slowness and that
‘of the wave have led Professor Hamilton to the discovery of
some new geometrical properties of the latter. ‘These properties
‘are demonstrated by means of certain transformations of the
‘equation of the wave-surface; and it is shown that this surface
has four conoidal cusps, at the extremities of the lines of stnagle
ray-velocity, at each of which the wave is touched, not by two
planes as Fresnel supposed, but by an infinite number forming
‘a tangent cone of the second degree; while, at the extremities
‘of the lines of single wave-velocity, there are four circles of plane
contact, in every point of each of which the wave-surface is
‘touched by a single plane. These singular properties have led
Professor Hamilton to anticipate two new laws of refraction
called by him conical refraction, because in each case a single
tray is refracted into an infinite number forming a species of cone.
External conical refraction corresponds to the cusp on the wave-
‘surface; and takes place without, when a single internal ray
coincides with either of the lines of single ray-velocity. Internal
conical refraction, on the other hand, takes place within the
crystal, when a single ray is incident externally at an angle cor-
responding to the line of single wave-velocity within. In this
latter case, if the crystal be bounded by parallel planes, all the
‘rays of the cone will emerge at the second surface parallel to the
“ray incident on the first, so as to forma small elliptic cylinder,
‘whose magnitude will depend upon the angle of the cone and
the thickness of the crystal. All these remarkable conclusions
have been verified in the fullest manner by experimentt.

I shall now proceed to give a brief account of the labours
-of M. Cauchy in this interesting department of analysis. The
‘researches of this eminent mathematician, on the propaga-

tion of motion in elastic media, are scattered through various
livraisons of the Exercices de Mathematiques; and he has
given a valuable summary of the results of these investigations,

* “ Geometrical Propositions applied to the Wave-theory of Light,” Trans-
actions of the Royal Irish Academy, vol. xvii. SFr §

+ “ On the Phenomena presented by Light in its passage along the axes of
biaxal Crystals,” Zbid.

390 FOURTH REPORT—1834.

as applied to the wave-theory of light, in a memoir read to the
French Academy in the year 1830 *.

Having assigned the general equations of motion of a system
of molecules, acting on one another by attracting or repelling
forces which vary according to any function of the distance,
M. Cauchy observes that it is not necessary to have recourse to
their general integrals in order to determine the laws of undula-
tory propagation.. It is sufficient, in fact, to determine the law
of propagation of a plane wave. For if we consider a great
number of plane waves inclined to one another at small angles,
and which are at first superposed in the neighbourhood of the
point which is considered as the origin of the disturbance, the
vibrations in the elementary waves, to which each of these gives
rise, may be supposed too small to affect the sense separately,
and these waves become efficacious only by superposition. Con-
sequently the general wave-surface will be the locus of all the
points in which the elementary plane waves are superposed; and
will therefore be the surface touched by them all at any instant}.
Hence the problem is reduced to the determination of the law
of propagation of a plane wave. js

M. Cauchy then shows that a disturbance, confined originally
to a given plane, will in general give rise to three pairs of plane
waves parallel to the original plane, and propagated with uni-
form velocities,—the two waves of each pair moving with equal
velocities in opposite directions. The velocities of propagation
of the separate pairs, he proves, may be represented by the re-
ciprocals of the axes of a certain ellipsoid, whose form depends
upon the position of the plane wave and upon the nature of the
system ; and the absolute displacements of the molecules will be
parallel to the directions of these axes. Accordingly, a system
of plane waves, superposed at first at the point of original dis-
turbance, will be subdivided into three corresponding systems ;
and these, by their superposition, will generate a curved surface
of three sheets, each sheet being touched by all the plane waves
of the same system. From these principles it follows that a
‘single ray of light will be, in general, subdivided into three po-
larized rays ;—a ray being said, in this theory, to be polarized
parallel to a certain line or plane, when the vibrations of the
ethereal molecules are parallel to that line or plane. M. Cauchy

* “ Mémoire sur la Théorie de la Lumiére,” Mém. Jnst., tom. x.

+ M. Poisson does not admit the legitimacy of this conception of the wave-
surface; and he thinks that an assemblage of indefinite plane waves, having a
small part in common at the origin of the motion, cannot represent the initial
condition of a medium disturbed at that point.

REPORT ON PHYSICAL OPTICS. 391

does not state the precise physical condition on which the
existence of the third ray depends. It would seem, however,
that it must arise from the circumstance that the vibration
normal to the wave is not absolutely insensible, or that the
actual vibrations are not accurately in the plane of the wave.
He states that the intensity of this ray. will be in all cases very

- small, and that its observation therefore will be a matter of dif-

ficulty; but he promises in a future communication to point out
the means of manifesting its existence.

. The formule, on which the solution of the general problem
depends, may be reduced to contain nine constant coefficients
depending. on the law of distribution of the molecules in space.
Three. of them represent the pressures sustained in the natural
condition of the medium by any three planes parallel to those of
the three coordinates; and these, M. Cauchy afterwards con-
cludes, vanish of themselves. When the general theory is applied
to the case in which the elasticity is the same in all directions
round any line parallel to one of the axes of coordinates,
M. Cauchy finds that the nine coefficients are reduced to five 5
and that two sheets of the wave-surface become the sphere and
spheroid of the Huygenian law, provided that. the remaining
constants fulfill two assigned equations of condition. In the
general case, in which the elasticity is unequal in all directions,
hhe investigates the sections of the wave-surface made by the
planes of the three coordinates; and he finds that,—for two
sheets of that surface,—they are reduced to the circle and ellipse
of Fresnel’s theory, provided that the constants fulfill three

assigned equations of condition. ‘The wave-surface itself differs.

alittle from the surface of the fourth order obtained by Fresnel ;.
but is reducible to it when the excentricities of the ellipses just
mentioned are small,.as is the case in all known crystals.

. Thus the results obtained by M. Cauchy embrace and confirm
those of Fresnel; and the mathematical laws of the propagation
of light are shown to be particular cases of the more general laws
ofthe propagation of vibratory motion in any elastic medium
composed of attracting and repelling molecules. Considered,
‘however, simply with reference to the theory of light, the solu-
tion given by M. Cauchy cannot, I conceive, be considered as a
complete physical solution. In other words, the phenomena of
light are not connected directly with any given physical hypo-
thesis ; but are shown to be comprehended in the results of the
general theory, in virtue of certain assumed relations among
the constants which that theory involves., If, indeed, we were
able to assign the precise physical meaning of these equations
of condition, we should have nothing more to desire in the

392 FOURTH REPORT—1834.

general theory of light ; for these equations must necessarily
express the characteristic properties of the vibrating medium.
In this point of view their discussion becomes a subject of the
highest interest; and it is probable that the important conclu-
sions of which we have yet to speak may in this manner be
confirmed and extended. . he
These conclusions are contained in a memoir presented to the
French Academy by M. Lamé, in the spring of the present
year*; and in which the.author has proposed to determine the
laws according to which the molecules of bodies act on those of
the ether, and the molecules of the ether on one another. Set-
ting out from the existence of transversal vibrations, as esta-
blished by the fact of the non-interference of rays oppositely
polarized, the author supposes a disturbance of the ether to take
place in vacwwm,—that is, in a space devoid of all ponderable
matter,—and proceeds to consider what will be the result when
that disturbance reaches the ether contained in a transparent
body. Assuming the property of transversal vibrations noticed
by Fresnel, and more explicitly stated by M. Poisson,—namely,
that they are propagated without any attendant change of
density,—M. Lamé then seeks the conditions to be satisfied by
the function, which represents the mutual action of the mole-
cules of the ether and those of the solid body, in order that this
property may subsist. Introducing, accordingly, this principle
into the partial differential equations, which express the laws of
the vibratory movement generally, he arrives finally at an equa-
tion of condition, from which he concludes, that ‘ the action
of ponderable matter on the ether varies in the inverse ratio of
the square of the distance ; and that the elasticity of the ether
itself is proportional to its density.”’ .
In order to determine the sign of this action,—that is to say,
whether it is attractive or repulsive,—it is necessary to integrate
the differential equations. After certain transformations of these
equations tending to facilitate their examination, he obtains
their integral in the case of a single spherical and homogeneous
molecule of the body, around which the ether is distributed in
spherical shells. The conclusions deduced from this case being
combined with the established fact—that the velocity of light is
less in transparent bodies than in vacuum, he arrives at the re-
sult, that the mean density of the ether is /ess in the former ;
or that the action of the molecules of these bodies on those of

* “ Mémoire sur les Lois de l’Equilibre de l’Ether dans les Corps diaphanes.”
A full account of this paper is given in the Annales de Chimie for March. ‘The
memoir itself is not yet published.

REPORT ON PHYSICAL OPTICS. 393

the ether is repulsive. M. Lamé concludes also from the exa-
mination of the same case, that the retardation of the vibratory
motion, in penetrating into a dense body, will be greater, the less
the length of an undulation ; so that the refraction will be greater
for waves of shorter length. This he conceives to be the true
explanation of the phenomenon of dispersion.

» M. Lamé has likewise endeavoured to connect the phenomena
of double refraction with an assumed constitution of the ethereal
fluid. He takes the case in which the ether is supposed to be
distributed round the molecules of the body in confocal ellip-
soidal shells; and he concludes that a vibratory movement,
propagated from vacuum into a body so constituted, will be se-
parated at its eritrance into two component movements, which
will advance with different velocities. The two component
vibrations, he finds, will be at right angles, and parallel to the
lines of greatest and least curvature of the elementary ellipsoids.

Thus, the bifurcation of a ray of light on entering a crystallized
medium, and the opposite polarization of the two pencils, are
found to be consistent with a molecular constitution such as that
described.

. These results are of the highest interest ; and will, no doubt,
receive an early examination from those engaged in the same
department of analysis. Their author seems to be persuaded
that his methods will lead him to the mathematical laws of other
phenomena, which he conceives to depend, in like manner, on
the motions of the ethereal fluid*. .

» I cannot close this division of the present Report without
referring to the phenomena of absorption by crystallized media,
although the laws of these phenomena are as yet wholly without
the pale of theory. Dr. Wollaston seems to have been the first
who noticed any facts connected with this interesting subject.
The absorbing properties of crystals were found to vary with
the direction; certain crystals of palladium, for example, ap-
pearing of a deep red colour when viewed along the axis, and of
‘a yellowish green in a transverse direction. 'Tourmalines were
observed also to possess analogous properties}. Similar observa-

__ * Ina continuation of this memoir, recently read to the French Academy,
M. Lamé has considered particularly the mode of vibration of the particles of
the ether which are disposed round the ponderable particles of body in concentric
spherical shells of decreasing density. Transparent homogeneous bodies are
‘supposed to consist of a multitude of such particles distributed uniformly in
space, and at distances incomparably greater than their diameters; and he
conceives that the waves propagated from the particles adjoining to the surface
‘of emergence will, by their interference, give rise to phenomena resembling the
fixed lines in the spectrum. Ann. Chim., tom. lvii.
+ Phil. Trans. 1804.

594: FOURTH REPORT—1834.

tions were afterwards made by M. Cordier and the Count de
Bournon. sening
-The next step of any importance in this new field of research
was made by Sir David Brewster. _This philosopher observed
that in some double-refracting crystals, as carbonate of barytes,
the two pencils were differently coloured* ; while in others their
intensity was widely different}. The unequal absorption of the
two pencils is most remarkable in tourmaline, in which it was
observed, nearly at, the same time, by M. Biot and Dr. Seebeck ;
and the former philosopher inferred from the phenomena that
the more refrangible rays of the spectrum are more easily ab-«
sorbed by the mineral, when polarized parallel to its axis, than
when perpendicularly ft. hatvan
Sir David Brewster, to whom we owe the greater part of our
knowledge on this subject, has shown§ that similar properties be-
long, in a greater or less degree, to most coloured crystals which
possess double refraction; and that the absorption of light by
such media varies, in general, both with the colour of the light
and with the position of the plane of polarization. Whena ray
of common light therefore enters a plate of such a crystal, the
two pencils into which it is divided will be unequally absorbed,
and the emergent light will be partially polarized ;—the differ-
ence of the intensities of the oppositely polarized portions in-
creasing with the thickness of the medium traversed. But the
two pencils differ, in general, in colour as well as in intensity ;
and this difference, in uniaxal crystals, Sir David Brewster
found to depend on the inclination of the ray to the axis,—
vanishing when the ray coincided with the axis, and becoming
a maximum when it was perpendicular to it. A ray of common
light, therefore, transmitted perpendicularly through a plate of
such a crystal, will emerge coloured; and the resulting colour
will, in general, vary with the inclination of the surface to the
axis. Thus the phenomena of dichroism, observed by Wollas-
ton and others, are reduced to the more general laws of absorp-
tion. Analogous properties belong to biaxal crystals, and de-
pend in like manner on the planes of polarization of the two
pencils, or on the direction of the ray. These properties, Sir
David Brewster found, could be modified by heat; and were
even communicated by such influences to crystals in which they
did not naturally reside.

* Edin. Trans., vol. vii. + Phil. Trans. 1814.

t Traité de Physique, tom. iv. 313.

§ “ On the Laws which regulate the Absorption of Polarized Light by double-
refracting Crystals,” Phil. Z'rans. 1819.

REPORT ON PHYSICAL OPTICS. 595

. Notwithstanding the important labours of Sir David Brewster,
much remains to be done connected with this subject... Sir John
Herschel,has proposed empirical formule to represent. the in-
tensity ofthe transmitted light as dependent on its direction ;
andthe results of the formule present a general accordance
with observed facts*. It is much to be desired that these laws
should'be placed beyond doubt by an extensive series of experi-
ments directed to this specific. object.. Although the laws of
absorption by crystallized media are necessarily more compli-
cated than those of ordinary media, yet they bear an evident
‘and: close relation to the well-known Jaws of double-refraction,

-qwhich'seems to hold out a clue to their discovery; and I feel

persuaded that it is in the phenomena of dichroism that the
physical theory of absorption will first take its rise, and seek its
confirmation.

On i

IV. Colours of Crystalline Plates.

Ifa beam of light, polarized by reflexion, be received upon
a_second reflecting plate at the polarizing angle, it is wholly
transmitted when the second plane of incidence is perpendicular
‘to the first. But if between the polarizing and analysing
plates, as they are termed, there be interposed a plate of any
‘double-refracting crystal, a portion of the light is reflected,
whose quantity depends on the position of the interposed crystal.
In order to analyse the phenomenon, the crystalline plate may
be placed so as to receive the polarized beam perpendicularly,

‘that there are two positions of the plate in which the reflected
light totally disappears, just, as if no crystal had_ been inter-
posed. These two positions are those in which the principal
and the perpendicular sections of the crystal coincide with the
‘plane of the first reflexion, When the plate is turned round
from either of these positions, the light gradually increases ;
and it becomes a maximum when the principal section is in-
clined at an angle of 45° to the plane of the first reflexion. These

oh then turned round in its own plane. It is then, observed

_ .phenomena were observed by Malus.

_ The reflected light in these. experiments was in all cases
white. But M. Arago observed that when the interposed plate
is sufficiently thin,—such as the laminz into which mica or
sulphate of lime may be readily divided by cleavage,—the most
gorgeous colours appear, which vary with every change of incli-

* Essay on Light, p. 554, &e,

396 . FOURTH REPORT—1834.

nation of the plate to the polarized beam. When the plate is
_perpendicular to the transmitted pencil, and then turned round
in its own plane, the tint does not change, but only varies in
‘intensity,—being a maximum when the principal section of the
crystal is inclined at an angle of 45° to the plane of primitive
‘polarization, and vanishing altogether when it coincides with
that plane, or is perpendicular to it. On the other hand, when
the crystal is fixed, and the analysing plate turned so as to
vary the inclination of the plane of the second reflexion to that
of the first, the colours change in the most striking manner ;
and it is found that the colour reflected, in any one position of
the plane of the second reflexion, is always complementary to
‘that reflected in the perpendicular position. The colours dis-
appear altogether when the thickness of the crystalline plate is
reduced below a certain limit *. .

The experimental laws of these phenomena were investigated
with unwearied zeal by M. Biot t+. When the light was inci-
dent perpendicularly on plates of the same substance, of differ-
ent thicknesses, the tints were observed to follow the same law
‘as the colours of thin plates; the thicknesses of the crystal at
which each tint was developed in perfection being proportional
to the thicknesses of the plate of air which gave the same tint in
Newton’s scale. ‘These thicknesses vary with the nature of the
crystal; and are always much greater than the corresponding
thicknesses of the uncrystallized plate which exhibit the same
tint. Pursuing the same inquiry, afterwards, for oblique inci-
dences, M. Biot found that, in uniaxal crystals, the tint de-
veloped was determined by the length of the path traversed by
the light within the crystal, and by the square of the sine of
the angle which its direction made with the optic axis, jointly.
From this law it followed, that if a crystalline plate of moderate
thickness be cut perpendicularly to the axis, and a converging
or diverging pencil transmitted through it, the lines of equal
tint, —or the isochromatic lines, as they are sometimes called,—
will be disposed in concentric circles similar to Newton’s rings.
This phenomenon was observed, under different circumstances,
by Sir David Brewster, Dr. Wollaston, M. Biot, and M. See-
beck.

_ The researches of M. Biot were followed by those of Sir
‘David Brewster. In investigating the law of the tints in biaval
crystals, Sir David Brewster considers the optic axes as the re-
sultants of others which he denominates polarizing axes. The
tint developed by a single axis is taken as the measure of its

* Mém. Inst. 1811, + Lbid. 1812.

REPORT ON PHYSICAL OPTICS. 397

polarizing force, and is assumed to vary as the square of the
sine of the angle contained by the ray with it; and when two
such axes cooperate, the tint resulting from their joint action is
measured by the diagonal of a parallelogram whose sides repre-
sent the tints produced by each axis separately, and whose angle
is double the angle contained by the two planes passing through
_ them and the ray. This law Sir David Brewster has verified
by comparison with the observations of M. Biot on sulphate of
lime, and its agreement with phenomena was complete*. When
analytically developed by M. Biot, it was found to accord with
the beautiful law to which he was himself conducted by analogy ;
namely, that the tint is measured by the product of the sines of
the angles which the direction of the ray within the crystal
makes with the optic axes +. From this law it easily followed
that the isochromatic lines, in biaxal crystals, will be lemniscates,
whose poles are in the apparent direction of the optic axes. {.
This phenomenon was first discovered by Sir David Brewster in
topaz. The law has been established in the most complete.
manner by Sir John Herschel; and he has found that the con-
stant parameter, or the product of the radii-vectores drawn from:
any point to the two poles, varies inversely as the thickness of
the plate, for different plates of the same substance, and increases
from one curve to another in the same plate, in the ratio of the
numbers of the natural series.

To account for these varied phenomena in the hypothesis of
emission, M. Biot has imagined his ingenious and beautiful theory
of moveable polarization. When a polarized ray of any simple.
colour enters a crystalline plate, the component molecules are
supposed, in this theory, to penetrate at first to a certain depth
without losing their primitive polarization ; and then to com-
mence a series of regular oscillations round their centres of

= * “ On the Laws of Polarization and Double Refraction in regularly crystal-
lized Bodies,” Phil. Trans. 1818.

+ From the researches of M. Biot it appeared that the measure of the tint,
in uniaxal crystals, observed the same law as that attributed to the difference
of the squares of the velocities of the two rays in the theory of emission. The
same relation was assumed to hold generally; and thus from the law of the tints
in biaxal crystals the relation of the velocities of the two pencils, noticed in
the preceding section, was inferred.

t M. Biot has observed an apparent exception to this law in the diopside
of the Tyrol, in which the rings are in general unsymmetrical with respect to
the two axes. One of the axes presents the ordinary phenomena; but in the
neighbourhood of the other there is a remarkable distortion of the rings near
their centre, when the crystalline plate is turned in its own plane. ‘These dis-
tortions seemed to observe a regular law, and were the same in all the specimens
examined. It may be remarked that the optic axes of this crystal are unsym-
metrically placed with respect to the crystalline form, Mém. Inst., tom. x.

398 . FOURTH REPORT—1834,

gravity, the axes of polarization being carried alternately to one
side or other of the axis of the crystal, or of the perpen-
dicular line. These oscillations being isochronous, the thick-
ness traversed by the molecule in its motion of translation du-
ring each of them is constant, and is assumed to be equal to
double the depth to which it has penetrated before commencing
its vibrations. The oscillatory movement is supposed to stop,
when the molecules repass into air through the second face of
the crystal ; and the emergent ray has a fired polarization, the
same as if the last oscillation of the molecules had been actually.
completed at the instant of emergence. Thus a polarized ray
which has ‘traversed a thin crystalline plate is ultimately polar-
ized either in the primitive plane, or in a plane inclined to it at
an angle equal to double the angle which it forms with the prin
cipal section, according as the thickness of the crystal is an odd
or an even multiple of a certain length*. The formulz deduced
from these postulates is found to represent all the more obyious
laws of the tints with much fidelity.

This assumed difference between the effects produced by thick
and thin crystals has however been completely disproved by the
decisive experiments of Fresnel. When two mirrors, slightly in-
clined, are placed so as to receive the incident light at the polar-
izing angle, and two lamine of sulphate of lime of the same
thickness are interposed,—one in the path of each of the reflect-
ed pencils, and so that their principal sections are inclined at
angles of 45° on either side of the plane of primitive polarization,
—the phenomena of the interference bands prove in the clearest
manner that the light emergent from each consists of two pencils
polarized respectively in the principal section and in the per-
pendicular section of the crystals; and that the results differ
from those produced by thick crystals only in this, that the two
pencils are superposed t. The light resulting from the union of
these oppositely polarized pencils has, in certain cases, the
properties ascribed to it in the theory of M. Biot; but these
properties are immediate and necessary consequences of the
laws of interference of polarized light, and of the theory of
transversal vibrations.

* “Sur un nouveau genre d’Oscillation,” &c., Mém. Inst. 1812.

+ See Report made to the Academy of Sciences, in 1821, on the memoir of
Fresnel relative to the colours of crystallized plates, Annales de Chimie, tom. xvii-
Indeed, a more obvious objection to M. Biot’s theory may be drawn from the
fact which he has himself observed ;—namely, that the phenomena of colour
may be produced by crossing two thick plates of nearly the same thickness,
although the thickness in each was sufficient to furnish two images sensibly
separated, and therefore having a fixed polarization.

REPORT ON PHYSICAL OPTICS. 399

’

»Let-us now inquire what account the wave-theory furnishes
of the same phenomena.—A ray of light on entering a crystal-
line plate is divided into two, or, in the language of the wave-
theory, a series of waves incident upon the crystal is resolved
into. two within it, which traverse it in different directions and
with different velocities. One of these sets of waves, therefore,
will lag behind the other, and they will be in different phases of
vibration at emergence. When the plate is thin, the emergent
waves are superposed; and as the retardation will then amount
only to a few undulations and parts of an undulation, it would
appear that we have here all the conditions necessary for their
interference,.and the consequent production of colour. Such
was the sagacious conjecture of Young. And indeed, shortly
after the publication of the first researches of M. Biot on the
laws of the tints for different thicknesses, it was observed by
Young that these tints corresponded accurately to the interval
of retardation of the two pencils; so that they were manifestly
due to interference *. This correspondence is now made out
in the fullest manner.: It is an easy consequence of Fresnel’s
theory of double refraction, that the interval of retardation of
the. two pencils, in traversing:a crystalline plate, is nearly pro-
portional to the length of their path within the crystal multi-
plied by the product of the sines of the angles which its direction
makes with the two optic axes; and as this has been found to
be the general measure of the tint, it follows that the forms
of the isochromatic curves,-—the lemniscates and the circles,—
are all necessary consequences of the wave-theory.

~ But in the first application of the principle of interference to
the colours of crystalline plates there arose a difficulty to which
the known laws afforded no answer. So far as this explanation
went, the phenomena of interference and of colour should be
produced by the crystal:alone, and in common light, without
either polarizing plate or analysing plate. Such, however, is not
the fact; and the real difficulty seemed to be, not to explain
how the phenomena are produced, but to show why they are
not always produced. It occurred to MM. Arago and Fresnel
to inquire how far the state of polarization of the two pencils
might modify the known laws of interference; and the results
of this inquiry tf have happily furnished an account of the dif-
ficulty, and completed the solution of the problem. It was
found that two rays of light polarized in the same plane, inter-

_ * Quarterly Review, vol. xi.
+ “ Mémoire sur l’Action que les Rayons de la Lumiére polariseé exercent
les uns sur les autres,” Annales de Chimie, tom. x.

400 FOURTH REPORT—1834.

fere and produce fringes under the same circumstances as two
rays of common light ;—that, when the planes of polarization
are inclined, the interference is diminished and the fringes de-
crease in intensity ;—and that, finally, when the angle between
these planes is a right angle, the rays no longer interfere at all.
Hence the two rays which emerge from a crystalline plate, being
oppositely polarized, cannot interfere ; and, to produce the phe-
nomena of colour in perfection, their planes of polarization must
be brought to coincidence by the analyser.

The non-interference of rays oppositely polarized is a neces-
sary result of the mechanical theory of transversal vibrations.
Fresnel. has shown, on the principles of that theory, that the
intensity of the light resulting from the union of two such rays
is constant, and equal to the sum of the intensities of the com-.
ponents, whatever be the phases of vibration in which they meet.
But though the intensity of the light does not vary with the
phase of the component vibrations, the character of the result-
ing vibration will. It appears from theory that two rectilinear
and rectangular vibrations compound a single vibration, which
will be also rectilinear when the phases of the component vi-
brations differ by an exact number of semiundulations ; that, in
all other cases, the resulting vibration will be elliptic; and that
the ellipse will become a circle, when the component vibrations
have equal amplitudes, and the difference of their phases is an
odd multiple of a quarter of a wave. These results of theory
have been completely confirmed by experiment. When a polar-
ized beam diverging from a luminous origin is transmitted
through two rhomboids of Iceland spar of equal thickness, hav-
ing their principal sections inclined 45° on either side of the
plane of primitive polarization, the emergent light will diverge
as if from two near points, and the two portions will be oppo-
sitely polarized. It was found by Fresnel and Arago that the
light resulting from the union of these pencils was plane, cir-
cularly, or elliptically polarized, according to the difference of
the paths traversed when they met.

Here, then, we have an account of the facts which seem to
have suggested the theory of moveable polarization; and we
learn moreover that they are but particular cases of the general
result. The light arising from the union of the ordinary and
extraordinary pencils which emerge from the crystalline plate,
will be polarized in the primitive plane, or in a plane inclined
to it at an angle equal to double the angle which it makes
with the principal section, according as the interval of re-
tardation of the two pencils is an even or an odd multiple of
half a wave. In all other cases, the thickness of the crystal

REPORT ON PHYSICAL OPTICS. 401

having any other value than those which exactly answer to
these intervals, the resulting light will be elliptically-polarized.
The ellipse will become a circle, and the light will appear to be
completely depolarized, when the two pencils are of equal in-
tensity, and the interval of retardation is an odd multiple of a
quarter of a wave. Here, then, is suggested an easy method of
putting the theory of moveable polarization to the test. Ifa
plate of sulphate of lime, whose thickness corresponds to such
an interval, be placed in a beam of polarized light of some
simple colour, so that its principal section is inclined at an
angle of 45° to the plane of primitive polarization, the emergent
light should, according to the theory of waves, be circularly-
polarized; and the two pencils into which it is divided by the
analysing rhomb should not vary in intensity during its revolu-
tion. According to the theory of moveable polarization, on the
other hand, the light should be plane-polarized ; and one of the
images should vanish when the principal section of the rhomb co-
incided either with the primitive plane, or the plane perpendicu-
lar to it. This experimentum crucis was tried by MM. Fresnel
and Arago, and the result was just as had been predicted by the
wave-theory *.

In the prosecution of their researches on the laws of inter-
ference of polarized light, MM. Fresnel and Arago discovered
further that two oppositely polarized rays will not interfere,
even when their planes of polarization are brought to coinci-
dence, unless they belong to a pencil, the whole of which was
originally polarized in one plane ;—-and that, in the interference
_ of rays which have undergone double refraction, half an undula-
tion must be supposed’to be lost or gained, in passing from the
ordinary to the extraordinary system. The latter principle is a
beautiful and simple consequence of the theory of transversal
vibrations. When a vibration in any given direction is re-
solved into two at right angles, and each of these again into a
second pair, in two fixed directions which are also perpen-
dicular, it will easily appear that, of the four components into
which the original vibration is thus resolved, the two in one of
the final directions conspire, while those in the other are
opposed. 'The tint produced by the interference of the former,
therefore, corresponds to the actual difference of routes of the two
polarized rays in the plate; while that arising from the latter
is that due to the same difference augmented or diminished by
half an undulation.

The former of the two laws now mentioned explains the office

* Annales de Chimie, tom. xvii,

1834. 2D

402 FOURTH REPORT—1834.

of the polarizing plate in these phenomena. ‘To account me-
chanically for the fact of the non-interference of the two pencils,
when the light incident upon the crystal is wnpolarized, it is
necessary to consider such light as a rapid succession of systems
of waves polarized in all azimuths; so that if any two planes be
assumed at right angles, there will be an equal quantity of light
actually polarized in each. Each of these portions, when re-
solved into two within the crystal, and these afterwards reduced
to the same plane of polarization by the analysing plate, will ex-
hibit the phenomena of interference. But the interval of retard-
ation differs by half a wave in the two cases; the tints produced
therefore will be complementary, and the light resulting from
their union will be of a uniform whiteness.

We are obliged to admit, therefore, that common light con-
sists of a rapid succession of systems of waves, in each of which
the vibrations are different. But the phenomena of interference,
(which are exhibited by common light) compel us also to admit,
as Professor Airy has observed*, that the vibrations do not
change continually; and that in each system of waves there are
probably several hundred successive vibrations, which are all
similar,—although the vibrations of one system bear no relation
to those of another, and the different systems sueceed one
another with such rapidity as to obliterate all trace of polariza-
tion. This persaltwm transition from one system of waves, to
another in which the vibrations are wholly different, seems a
complication in the machinery of light, for which the elegant
simplicity of the parts better known has not prepared us; and
I cannot but indulge the hope that the hypothesis, which now
stands as the representative of experimental laws, may be found
to merge in some simpler physical principle.

The laws of interference of polarized light have thus supplied
the defective link in the explanation of the colours of crystallized
plates first suggested by Young. The magnitudes of the re-
solved vibrations are known, when the planes of polarization of
the two pencils are given with respect to the plane of primitive
polarization, and the plane of analysation; and as the laws of
double refraction enable us to find the interval of retardation of
these pencils, we have all the data necessary for the compu-
tation of the intensity and colour of the light resulting from
their interference. This computation has been given by Fresnel,
not only for a single plate, but likewise for two plates super-
posed}; and the theory has been since more fully developed by
Professor Airy{. The results are found to be, in all cases, in

* Mathematical Tracts, p. 407. + Annales de Chimie, tom. xvii.
t Cambridge Transactions 1831, and Math, Tracts.

_—— =

REPORT ON PHYSICAL OPTICS. 403

exact accordance with the observed facts; and all the circum-
stances of the coloured rings in uniaxal and biaxal crystals are
completely explained.

The form of the rings, or isochromatic curves, depends upon
the interval of retardation alone ; and the value of this interval
had been deduced but approximately. Mr. M’Cullagh has re-
cently given a general and exact method for its calculation, and
for the determination of the forms of the rings for any plate of
a double-refracting crystal bounded by parallel planes. This
method is made to depend upon the properties of the sawrfuce of
wave-slowness, of which I have spoken in another place ; and
it is found that if the incident ray be produced to meet the
sphere, (which is the surface of wave-slowness for air,) and
through the point of intersection a perpendicular drawn to the

‘refracting surface, meeting the two sheets of the surface of

wave-slowness for the crystal, the intervals of retardation of the
rays at emergence will be measured by the thickness of the cry-
stal multiplied by the difference of the corresponding ordinates *.
By the aid of an expressive notation for the path of a ray, the
author has extended his conclusions to the case of a ray which
has undergone any number of internal reflexions.

If the double-refracting energy of the crystal were the same
for the light of every colour, the colours of the rings should
follow exactly the Newtonian scale of tints, and their magnitudes
should observe the same laws as those of the rings formed between
two object-glasses. This is the case in carbonate of lime, beryl,
and some other crystals; and in these, therefore, the colours
are similar to those of thin plates. But many remarkable devi-
ations from this law have been observed by Sir John Herschel
and Sir David Brewster. Thus, in the common uniaxal apo-
phyllite, it was observed by the former writer, the diameters of
the rings are very nearly the same for all the colours of the
spectrum ; so that the rings of different colours are superposed,
and form a succession alternately black and white, which may
be traced through a great number of orders +. In this remark-
able case, then, the double-refracting energy of the crystal
varies very nearly in the subduplicate ratio of the lengths of the
waves for the rays of different colours. A very remarkable case

* Ify,y, y, represent the corresponding ordinates of the sphere, and of the

two sheets of the surface of wave-slowness for the medium, and 6 the thickness
of the crystal, 6 (y —y,), 4 (y,—y,) will be the retardations of the two refracted

waves at emergence, and 6 (y —y_) will be the interval between them.—
“ Geometrical Propositions applied to the Wave-theory of Light,” Trans. R. I.

‘Academy, vol. xvii.

+ Phil. Trans, 1820.
2n2

404 FOURTH REPORT—1834.

of the inversion of the Newtonian scale of tints was observed by
Sir John Herschel in some rare varieties of the same mineral.

The diameters of the rings, instead of contracting as the re-
frangibility increases, enlarge, and actually become infinite for
rays of mean refrangibility. Having passed through infinity,
they again acquire a finite value ; and diminish as the refrangi-
bility increases up to the extremity of the spectrum. Here, then,
for rays of a certain mean refrangibility the crystal is singly re-
fractive; and as the double refraction changes its character in
passing through zero, the crystal is positive for the rays of one
end of the spectrum, and negative for those of the other *. This
singular phenomenon is accounted for on the principles of Fres-
nel’s theory by supposing that the elasticity increases, with the
length ofthe wave, faster in the direction of the axis of the cry-
stal than in the perpendicular direction ; so that the difference
of these elasticities is positive for the rays ef one end of the
spectrum, negative for those of the other, ‘and vanishes at some
intermediate point.

In biaxal crystals similar deviations take place in the magni-
tude of the lemniscates corresponding to the different simple
colours. But there is here another source of irregularity which
is not found in uniaxal crystals. The optic axes vary, in general,
with the colour; so that the lemniscates differ also in the posi-
tion of their poles, and the colours are not the same in different
parts of the same ring. Where the optic axes belonging to
different colours are in different planes, as Sir John Herschel
has observed to be the case in borax, the irregularity ae
in the coloured curves is yet more striking.

In all the preceding cases, the laws of double-refraction are
dependent only on the direction, and are the same all throughout
the mass. It is otherwise, however, in many crystals,—such as
analcime and some varieties of apophyllite. The complicated
arrangement of the coloured bands which these substances dis-
play in polarized light, proves them to consist of several distinct
portions, possessing different optical properties ; and the phe-
nomena indicate relations among the molecular forces, and prin-
ciples of aggregation, of which it is difficult in some cases even
to form a conception. These remarkable phenomena, and their
laws, were discovered by Sir David Brewstert.

* Cambridge Trans. 1821. Similar properties have been observed by the
same author in other crystals, as hyposulphate of lime and vesuvian. From the
table of tints exhibited by the latter substance it appears that the most refracted
of the two images is the least dispersed.

} Edin. Trans., vol, ix. & x.

REPORT ON PHYSICAL OPTICS. 405

When a polarized ray traverses a plate of Iceland spar, beryl,
or almost any other uniaxal crystal, in the direction of its axis,
it suffers no change of any kind; so that when the emergent
ray is analysed by a double-refracting prism, the two pencils
into which it is divided are colourless, and one of them vanishes
when the principal section of the prism is parallel, or perpendi-
cular to the plane of primitive polarization. But when a ray
passes in the same manner through a plate of rock crystal, the
phenomena are very different. ‘Two images are given in every
position of the prism; these images are of complementary
colours ; and the colours change in the most beautiful manner
as the prism is turned round in its cell. These phenomena
indicate that the plane of polarization has been changed, and
differently for the different rays of the spectrum. They were
first observed by M. Arago; and he has given an account of his
observations in his: memoir on the colours of crystalline plates,
read to the Institute in the year 1811. ;

The subject was then taken up by M. Biot, in a paper pub-
lished in the Mémoires de l’ Institut, in the year 1812; and the
analysis of the phenomenon was completed in a second memoir
read in the year 1818*. When a polarized ray of any simple
colour passes through a plate of rock crystal in the direction of
the optic axis, it is still polarized after emergence; but its
plane of polarization is changed. The angle through which the
plane is made to revolve, varies with the colour of the light,
and with the thickness of the plate,—being proportional to that
thickness divided by the square of the length of the fit or wave.

In some crystals the plane of polarization revolves from left to

right, while in others it is turned in an opposite direction; and

the crystals themselves are denominated right-handed or left-
handed, according as they produce one or other of these effects.

When two plates are superposed, the effect produced is, very
nearly, the same as that due to a single plate whose thickness
is the swm or difference of the thicknesses of the two plates, ac-
cording as they are of the same or of opposite denominations.

_ This curious distinction between: plates cut from different
crystals has been connected by Sir John Herschel with a corre-
sponding diversity in the crystalline form. The ordinary form
of the crystal of quartz is the six-sided prism terminated by the
six-sided pyramid. The solid angles formed at the junction of
the pyramid and the prism are sometimes replaced by small
secondary planes, which in the same crystal lean all’ in the

__ * “ Mémoire sur les Rotations que certaines substances impriment aux axes

de polarisation des Rayons lumineux.”

406 FOURTH REPORT—1834,

same direction ; and it is found that when that direction is ¢o
the right, (the apex of the pyramid being uppermost,) the cry-
stal is right-handed ; and that on the contrary it is left-handed,
when the planes lean in the opposite way*. Sir David
Brewster has shown that the amethyst, or violet quartz, is
actually composed of alternate layers of right-handed and left-
handed quartz. It is to the cropping out of the edges of these
layers, that the undulating appearance peculiar to the fracture
of this mineral is owing. The structure itself is displayed in
the most beautiful manner in polarized light T.

Some liquids, and even gases, have been found by MM. Biot
and Seebeck to possess the same property as quartz, though in
a much feebler degree; and to impress a rotation on the plane
of polarization of the intromitted ray, which is proportional to
the thickness of the substance traversed. These liquids do not
lose their rotatory power by dilution with other liquids not pos-
sessing the property. They retain it even when raised to the
state of vapour; and, in general, the rotatory power is inde-
pendent of the mode of aggregation, provided the molecular
constitution is unchanged. Lastly, when two or more liquids
possessing this property are mixed together, the rotation pro-
duced by the mixture is the sum of the rotations produced by
the ingredients, in thicknesses proportional to the volumes in
which they are combined. From these and other facts M. Biot
concludes that the property of rotatory polarization is inherent
in the ultimate particles of bodies, and does not depend on their
mutual distance or arrangement {. On the other hand, quartz
is found to lose the property when deprived of its crystalline
structure. Thus Sir John Herschel observed that quartz held
in solution by potash did not possess the property; and the
same thing has been remarked by Sir David Brewster with
respect to fused quartz.

The phenomena of rotatory polarization in rock crystal, M.
Biot ascribed to a continued rotation of the molecules of light
round their centres of gravity, produced by the operation of
some unknown forces. Fresnel has proved that they arise from
the interference of two circularly-polarized pencils which are
propagated along the axis with unequal velocities, one revolving

* Cambridge Trans., vol. i. + Edin. Trans., vol. ix.

t M. Biot has recently extended his researches on this subject to a great
variety of substances, Annales du Museum d Histoire Naturelle, tom. ii. Ina
memoir read to the French Academy last year he has applied the laws of cir-
cular polarization to the analysis of the process of vegetation in the grasses ; and
he has shown, in general, the importance of the indications drawn from these
phenomena in the researches of organic chemistry. Institut, Nos. 1 & 9. ,

REPORT ON PHYSICAL OPTICS. 407

from left to right, and the other in the opposite direction. A’
plane-polarized ray, in fact, is equivalent to two circularly-
polarized rays of half the intensity, in one of which the vibra-
tions are from left to right, and in the other in the opposite di-
rection. When a plane-polarized ray, therefore, is incident
perpendicularly upon a plate of rock erystal, cut perpendicu-
larly to the axis, it may be resolved into two such circularly-
polarized rays. These are supposed to be transmitted with dif-
ferent velocities ; so that when they assume a common velocity
at emergence, one of them is in advance of the other. They
then compound a single ray polarized in a single plane; and
this plane, it can be shown, is removed from the plane of pri-
mitive polarization through an angle proportional to the interval
of retardation of the two pencils, and therefore measured by the
thickness of the crystal. But this interval varies also with the
colour of the light ; and we are obliged to suppose that it is the
same for a given number of waves, whatever be their length,—
so that, for a given thickness of the crystal, it varies inversely
as the length of a wave. From this supposition it will follow
that the deviation of the plane of polarization of the emergent
ray is inversely as the square of that length, agreeably to the
experimental results of M. Biot*. :

The laws of rotatory polarization are then completely ex-
plained ; and it only remained to prove the truth of the hypo-
thesis,—that two circularly-polarized pencils, whose vibrations
are in opposite directions, will actually be transmitted along the
axis of quartz with different velocities. This supposition is
easily put to the test of experiment ; since such a difference of
velocities must give rise to a difference of refraction, when the
surface of emergence is oblique to the direction of the ray. Ac-
cording to the hypothesis, therefore, a plane-polarized ray,
transmitted through a prism of rock crystal in the direction of
the optic axis, should undergo double refraction at emergence ;
and the two pencils into which it is divided should be circularly-
polarized. ‘This has been completely verified by Fresnel, by an
achromatic combination of right-handed and left-handed prisms
arranged so as to double the separation; and he has shown
that the two pencils are neither common nor plane-polarized
light, but possess all the characters which are impressed upon a
polarized ray by two total reflexions from glass at an angle of
about 50°.

The refraction of quartz, then, in the direction of its axis is
wholly different from that of every other known crystal. In

* Annales de Chimic, tom. xxviii. p. 147.

408 FOURTH REPORT—1834.

other directions, the two pencils into which a single ray is di-
vided, were supposed to obey the ordinary laws, and to be
plane-polarized in opposite planes. This supposition has been
overturned by Professor Airy *, and it has been shown that the
two pencils in quartz are, each of them, elliptically-polarized ;
the elliptical vibrations of the two rays being in opposite direc-
tions, and the greater axes of the ellipses being in the principal
plane, and perpendicular to it respectively. The ratio of the
axes, in these ellipses, is the same in the two rayst; but
varies with their inclination to the optic axis,—being a ratio of
equality when the direction of the ray coincides with the axis,
and increasing indefinitely with their inclination to that line ac-
cording to some unknown law. As to the course of the re-
fracted rays, Professor Airy finds that it is still determined by
the Huygenian law; but that the sphere and spheroid, which
determine the velocity and direction of the two rays, do not
touch, as in all other known uniaxal crystals, the latter surface
being contained entirely within the former. This position is
certainly a startling one. The two sheets of the wave-surface
being thus absolutely separated, there is a complete interruption
of continuity in passing from the velocity of one ray to that of
the other; a result which does not hold in any other case with
which we are acquainted. It is however necessary to the ex-
planation of the phenomena; for the interval of retardation does
not vanish with the inclination of the ray tothe axis. Professor
Airy has given an elaborate calculation founded on these hypo-
theses, of the forms of the rings, &c.—displayed by quartz in
plane-polarized, and circularly-polarized light, and in any posi-
tion of the analysing plate; and he has found the most strik-
ing agreement between the results of calculation and those of
observation. .
We yet want a mechanical theory which will account for th

peculiar form of the wave-surface just alluded to. Fresnel seems
to have thought that the difference of the velocities of the two
rays in the direction of the axis might be physically explained

* “ On the Nature of the Light in the two rays produced by the double re-
fraction of Quartz,”’ Cambridge Transactions 1831. As
+ In the Supplement to this paper Professor Airy has explained a highly in-
genious method of determining experimentally the relation between the ellip-
ticity and the direction of either of the rays. This method depends upon a
remarkable effect which he had been led to expect from theory ;—namely, a
sudden change of half an undulation in the interval of retardation, and there-
fore a change of half an order in the rings, when the incident light is elliptically
olarized. From the results of some experiments conducted in this method
vroheen Airy seems to think that the ratio of the axes in the ordinary ray ap-
proaches more nearly to one of equality, than in the extraordinary ray.

REPORT ON PHYSICAL OPTICS. 409

by an helicoidal arrangement of the molecules of the vibrating
medium, which will have different properties according as the
helices are right-handed or left-handed. But this hypothesis
can hardly be supposed to apply to the case of fluids, in which
the property of circular polarization is independent of direction ;
and we are driven to confess that, with respect to these import-
ant laws, physical theory is as yet wholly at fault. The singular
relation between the interval of retardation and the length of the
wave seems to afford the only clue to the unravelling of this

‘ difficulty.

The phenomena of depolarization and of colour, impressed
by double-refracting substances upon the transmitted light, are,
we have seen, the necessary results of the interference of the
two pencils into which the light is divided within them. These
properties, then, enable us to discover the existence, and to
trace the laws of double-refraction, even in substances in which
the separation of the two pencils is too minute to be directly
observed. By such means the important discovery has been
made, that a double-refracting structure may be communicated
to bodies which do not naturally possess it, by mechanical com-
pression and dilatation. Sir David Brewster observed that
when pressure was applied to the opposite faces of a parallelo-
piped of glass, it developed a tint in polarized light, like a
plate of a double-refracting crystal; and the tint descended in
the scale as the pressure was augmented. Singly-refracting
crystals, such as muriate of soda and fluor spar, acquired the
properties of double refraction by the same means*. All this
is in perfect accordance with the wave-theory. Owing to the
connexion of the vibrating medium with the solid in which it is
contained, its elasticity is rendered unequal in different direc-
tions by the effect of compression, the maximum and minimum
corresponding to the directions of greatest and least pressure.
Accordingly, the vibrations of the ray on entering the plate are
resolved into two in these rectangular directions, and these are
propagated with unequal velocities; the colour developed is
determined by the interval of retardation. These results of
theory were experimentally confirmed by Fresnel, by the me-
thod of interferences; and it was found that the velocity with
which a ray traversed the glass was greater or less, according
as it was polarized parallel or perpendicular to the axis of com-
pression. The bifurcation of the ray at oblique incidences is a
necessary consequence of this difference of velocities ; but this
was also shown by Fresnel by direct experiment. A series of

;

* Phil. Trans. 1815 and 1816.

410 FOURTH REPORT—1834.

glass prisms were placed together with their refracting angles
alternately in opposite directions, and the ends of the alternate
prisms powerfully pressed by screws. A ray transmitted
through the combination was found to be divided into two op-
positely polarized *.

The opposite effects of compression and dilatation may be
seen in a thick plate of glass which is bent by an external
force. When this body is interposed between the polarizing
and analysing plates,.so as to form an angle of 45° with the plane
of primitive polarization, two sets of coloured bands are seen
separated by a neutral line; and these vanish altogether when
the compressing force is withdrawn. By crossing the glass
with a plate of mica or sulphate of lime, Sir David Brewster
found that the parts towards the convex, or dilated side of the
neutral line, had acquired a positive double-refracting structure,
and those at the concave, or compressed side, a negative one t+.
The intimate connexion between the double-refracting property,
and the internal state of the body as to condensation or rarefac-
tion, is likewise proved by the curious observation of M. Biot,
—that glass, when in a state of sonorous vibration, possesses
the power of depolarizing the light. ’

In these cases of induced double refraction, the phenomena
are related to the form of the entire mass; and are essentially
different from those produced by regular crystals, in which the
law of elasticity and of double refraction depends solely on the
direction, and is the same in all parts of the substance. Sir
David Brewster has lately succeeded in communicating a regu-
lar double-refracting structure to a mixture of resin and white
wax, by pressing it into a thin film between two plates of glass.
This film had a single axis of double refraction at every point
in the direction of the axis of pressure ; and the tint developed
depended solely on the inclination of the ray to this line. Sir
David Brewster has drawn from this phenomenon some highly
interesting conclusions respecting the origin of double refraction
in regular crystals. He mentions several facts which seem to
prove that this property is not inherent in the molecules them-
selves ; and he conceives that it is developed by the unequal
pressure caused by the forces of aggregation, which are in gene-
ral different in the direction of three rectangular axes. Thus
the double-refracting properties and the crystalline form are
referred to the same agency f.

Sir David Brewster and Dr. Seebeck had before observed the

* Annales de Chimie, tom. xx. + Phil. Trans, 1816,
+ Phil. Trans. 1830.

REPORT ON PHYSICAL OPTICS. 411

phenomena arising from unequal condensation and rarefaction in
the case of uncrystallized bodies unequally heated. These phe-
nomena may be studied by applying a bar of hot iron to the edge
of a rectangular plate of glass, and placing it in the polarizing
apparatus, so that the heated edge may form an angle of 45°
with the plane of primitive polarization. At the end of some
time the whole surface of the plate is observed to be covered
with coloured bands, the parts near the opposite edges having
acquired a positive double-refracting structure, and those near
the centre a negative one. The effects are reversed when a plate
of glass uniformly heated is rapidly cooled at one of its edges ;
and all the appearances vanish when the glass acquires the same
temperature throughout*. These phenomena may be endlessly
varied by varying the form of the glass to which the heat is
applied. If now, by any means, the glass be arrested in one of
these transient states, it will have acquired a permanent double-
refracting structure. This has been accomplished by M. See-
beck by raising the glass to a red heat, and then cooling it
rapidly at the edges. As the outer parts, which are thus more
condensed, assume a fixed form in cooling, the interior parts
must accommodate themselves to that form, and therefore retain
a state of unequal density. The law of the change of density,
and therefore the double-refracting structure, will depend on the
external form; and M.Seebeck found, accordingly, that the
coloured bands and patches which such bodies display in po-
larized light, assume a regular arrangement which varies with
the shape of the masst. The laws of these phenomena have
been completely analysed by Sir David Brewster; and he has
shown that the colours are those of crystallized plates, the direc+
tion of the axes however being different in different parts of the
substance. .

As the double-refracting structure is communicated to bodies
which do not possess it naturally, by mechanical compression
or unequal temperature,—so, by the use of the same means, that
structure may be altered in the bodies in which it already resides.
Thus Sir David Brewster and M. Biot have found that the double
refraction of regular crystals may be altered, and the tints they
display made to rise or descend in the scale, by simple pressure.
But the changes induced by heat are yet more remarkable.
Professor Mitscherlich discovered the importaut fact, that, in

* Phil. Trans. 1816.

+ The experiments of M. Seebeck are recorded in Schweigger's Journal, 1814.
The depolarizing property of unannealed glass seems to have been first noticed
by M. Arago; and was afterwards studied by Sir David Brewster in glass which
had been melted and cooled in water.—Phil. Trans, 1814.

412 FOURTH REPORT—1834,

general, heat dilates crystals differently in different directions,
and so alters their form; and their double-refracting properties
have been found to undergo a corresponding change. Thus Ice-
land spar is dilated by heat in the direction of its axis; while it
actually contracts by a small amount in directions perpendicular
to it. The angles of the primitive form thus vary, the rhomboid
becoming less obtuse*, and approaching the form of the cube.
M. Mitscherlich, accordingly, conjectured that its double-refract-
ing energy must in these circumstances be diminished ; and the
conjecture was fully verified by experiment. This inquiry has
been followed up by M. Rudberg; and the effects of heat on the
refractive indices of double-refracting crystals examined by the
direct method of prismatic refraction. In confermity with the
observations of M. Mitscherlich, it was found that the extra-
ordinary index in Iceland spar increased considerably with the
temperature, while the ordinary index underwent little or no
change. In rock crystal, on the other hand, both indices dimi-
nished as the temperature augmented, and nearly by the same
amount. In arragonite a similar effect was produced on the
three principal refractive indices,—the least index, however,
undergoing the smallest proportionate diminution +.

The inclination of the optic axes, in biaxal crystals, is a simple
function of the elasticities of the vibrating medium in the direc-
tion of three rectangular axes ; and the plane of the optic axes is
that of the greatest and least elasticities. If, then, these three
principal elasticities he altered by heat in different proportions,
the inclination of the axes will likewise vary; and if, in the
course of this change, the difference between the greatest elasti-
city and the mean, or between the mean and the least, should
vanish and afterwards change sign, the two axes will collapse
into one, and finally open out in a plane perpendicular to their
former plane. All these variations have been actually observed.
Professor Mitscherlich found that, in sulphate of lime, the angle
between the axes (which is about 60° at the ordinary tempera-
ture) diminishes on the application of heat; that, as the tem- .
perature increases, these axes approach until they unite; and
that, ona still further augmentation of heat, they again separate
and open out in a perpendicular plane. The primitive form of
the crystal undergoes a corresponding change, the dilatation
being greater in one direction than in another at right angles to

* A change of temperature, from the freezing-to the boiling-point, produced
a change of 83’ in the dihedral angles at the extremity of the axis.—Bull. Soc.
Phil., March 1824.

+ Phil. Mag., Third Series, vol. i. 409.

REPORT ON PHYSICAL OPTICS. 413

it. Sir David Brewster has observed an analogous, and even yet
more remarkable property, in glauberite. At the freezing tem-
perature this crystal has two axes for all the rays of the spec-
trum, the inclination of the axes being greatest in red light and
least in violet. As the temperature rises the two axes approach,
and those of different colours unite im succession; and at the
ordinary temperature of the atmosphere, the crystal possesses
the singular property of being uniaxal for violet light and
hiaxal for red. When the heat is further increased, the axes
which have united open out in order, and in a plane at right
angles to that in which they formerly lay; and at a tempera-
ture much below that of boiling water, the planes of the axes
for all colours are perpendicular to their first position*. The
inclination of the optic axes in topaz, on the other hand, aug-
ments with the increase of temperature; and the variation,
M. Marx has observed, is much greater in the coloured than in
the colourless varieties of this mineralf.

* Edin. Trans., vol. xi.; and Phil. Mag., Third Series, vol. i. 417.
{| Jahrb. der Chemie, vol. ix.

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[ 415 ]

3 hi j

_ Report on the Progress and present State of our Knowledge

of Hydraulics as a Branch of Engineering. Part II. By
_ . Georce Renniz, Esg., F.R.S., Acad. Reg. Sc. Turin.

_ \$ Corresp., &c. &e.

__ My former paper was confined to a brief elucidation of the pro-
gress and present state of that branch of hydrodynamics which
relates to the motions of fluids through orifices, tubes, and arti-
ficial channels. My object was to combine together the expe-
_ riments which had been made by different philosophers (from
' Castelli and Galileo down to Lesbros and Poncelet,) to deter-
_ mine the effective expenditures from orifices of different kinds,
as well as the remarkable pheenomena exhibited by the motions
of fluid veins. In the first instance, with regard to orifices, it
was shown, That the law of Torricelli relative to bodies gravi-
tating in free space, (and which applies to all fluids,) requires
certain modifications which diminishes their expenditure as
compared with the areas of the orifices nearly one half, and the
_ diameter of the fluid vein after it issued from the orifice nearly
_ three fourths ;—That the*form of the orifice (with equal areas)
had little influence over the expenditure:
___-2ndly, That although an increase of expenditure (considerably
_ above the expenditures by simple orifices of equal magnitude, )
is found to take place through additional or cylindrical tubes,
_ equal in length to three times the diameter of the orifice, yet
_ very little variation exists in their coefficients ;—That the same
_ is true of conical or divergent ajutages, but with greater expen-

rdly, That the expenditures by incomplete orifices, i.e.
igh rectangular notches in dams, (and which form a particu-
se of simple orifices,) follow the parabolic law, with a co-
ient of two thirds of the orifice:
Athly, That the expenditures by rectilinear and curvilinear
pipes follow more complicated laws, which can only be re-
presented by a certain portion of the height or inclination of
the column ; and that the various formule which have been ap-
_ plied to the determination of ‘these questions approximate very
nearly.
__ The same may be said of the formule made applicable to the
‘motions of fluids in artificial and natural channels; and to other
_ €ases of orifices when influenced by variable pressures, as in

416 FOURTH REPORT—1834.

locks and sluices, &c.; or when the motions are rendered com-
plicated by a system of pipes, as in water-works. The influence
of friction* and adhesion was briefly alluded to. Friction was
stated to have been found to be nearly independent of pressure
and surface, being the same when the fluid was made to run over
different kinds of surfaces, such as glass, wood, and metals,
&c.; and with regard to the velocity, resistances were stated to
be as the squares of the velocities at moderate inclinations.
Lastly, as to adhesion, reference was made to the experiments
of Coulomb and others to determine the molecular action of
fluids,

The theory of the motions of canals and rivers is founded on
the following axioms :

Ist, That the fluidity of the water, which obliges it to main-
tain a perfectly level surface in any close vessel containing it,
allows it to move with the utmost facility in any direction,
under the influence of external impulse or gravity;

2ndly, That motion cannot take place in an artificial channel
without an inclination in the surface ;

* From the following experiments with which I have been favoured by
William Tierney Clarke, Esq. of the West Middlesex Water-works, the friction
and resistance of the pipes to the free motion of the water through them have
been found to be between one fourth and one fifth of the total height of the
column. .

Table showing the result of Experiments made at the West Middlesex Water-
works upon work performed by the 64-inch cylinder Engine by Messrs.
Boulton, Watt, and Co., working with coal as stated below, to Barrow Hill
Reservoir, being an elevation of 188 feet above low water of the river
Thames, and working through the 15-inch, 12-inch, and 9-inch Mains.

5 | tounds raised! Pounds raised 1| Pounds rais
prone raced {1 foot high a EY, high percwt.1 foot high pe
Ecol 2 pal sth edt. bushelofcoal con-jofcoal consumed, bushel of coalcon
Eecloaaeat ae ‘sumed, exclusive including all re- sumed, includin
tion and obstruc-0f friction andjsistance in pipes, all resistance i

Name of Coal. Sa obstructions incalculated at 42 pipes, calculat
ete =e pipes, calculated|feet—equal to 230 at 42 feet—equa'
ree “at 188 fect. feet head. to 230 feet head.

112 Ibs, 84 Ibs. 112 Ibs. 84 Ibs.

1833. Wylam Moor..| 41,406,202 | 31,054,651 | 50,656,523 | 37,992,391
1834. Hollywell Main| 44,625,373 | 33,469,029 | 54:594-871 | 40,946,153
— Ditto 45,094,274 | 33,820,705 | 55,169,560 | 41,377,170
— Ditto...........| 44,338,876 | 33,254,157 | 54,242,241 | 40,681,680
— Wylam Moor..| 41,046,265 | 30,784,698 | 50,213,782 | 37,660,33

_"

ee

REPORT ON HYDRAULICS.—PART II. 417

3rdly, That when the mean velocity of a current is uniform,
the accelerating force is equal to the retardations ;

Athly, That as the particles of the fluid fill up the cavities of
the surface and form their own fluid bed, the nature of the sur-
face makes very little difference in the retardation.

The inclination of the surface, or the force of gravity, being
the cause of motion in the whole mass, it follows that when the
motion has become uniform there pass equal quantities of water
through each section in equal times and velocities; hence the
depth of the water will be the same in every part of the sec-
tion, and the surface will be parallel to the bottom of the
channel. °

But the motion would never be uniform if the fluid were per-
fect and there were no resistance in the channel: on the con-
trary, it would follow the laws of acceleration. But experiment
proves, even with very great inclinations, that the motion soon
becomes uniform: hence the conclusion as a general principle,
that when water moves uniformly in any channel or conduit,
* the resistance which it experiences is equal to the force of acce-
leration*.”’

If we examine the motion of a stream of water running in an
open channel, we shall find that the instant the water enters
into the channel, it spreads along the bed in filaments, which
continue to precede the general mass until they are retarded by
the resistances of the bed and overtaken by the superior fila-
ments as they reach the termination of the channel, and being
no longer retarded by the friction of the bottom and sides, they
acquire a greater velocity, and thus produce inequalities in the
motions of different parts of the section of the stream ; and ex-
periment teaches us that every mass of water, whether it moves
in a pipe, open channel, or river, follows more or less the same
law ; and since the resistance is caused by the surface of the
channel, the greater the extent of surface, the greater will be.
the resistancef, and vice versd. WHence the effect of the re-
‘sistance will be in the inverse ratio of the section ; and as adhe-
sion forms a certain portion of the resistance, and has been
proved by Coulomb to be simply proportional to the velocity,
it follows that the resistance which water experiences in moving
in an artificial channel is proportional to the quantity of wetted

© Bossut found that when an artificial canal of wood 200 metres in length
‘was inclined in the proportion of one decimetre per metre, or one in ten, and
divided the length into 33 metres, each of the spaces, with the exception of the
first, was run over in the same number of seconds.

+ This has been found by me to be very partial.

1834. 25

418 FOURTH em 834.

surface, and the square of the velocity, plus a small fraction of
the velocity, and is in the inverse ratio of the section *.

In the preceding determinations we have supposed the water
to have an uniform motion; that is to say, that each section of
the fluid mass presents the same expenditure and velocity,
and consequently the same depth of water. M. Bélanger has
taken into consideration a motion in canals of a different kind ;
it is that in which the fluid mass gives the same expenditure
through its sections, but has not the same depth throughout, nor
with its surface parallel to the bottom. There are examples in
canals where the length is insufficient to produce uniformity of
motion at the commencement and extremity; likewise, where
the breadth and inclinations are unequal: but it is essential to
the theory of M. Bélanger that these variations should take
place insensibly.. By admitting the hypothesis of the paral-
lelism of filaments being perpendicular to the canal, this engi-

* Formula of Motion.

Let g p be the force of acceleration,
A and B the two constant coefficients,

A! the constant multiplier,

Bu the friction of the velocity assumed,
c the wetted perimeter of the section,
e

Fi the mean radius or relation of the area to the wetted perimeter
of the section ;

then A! < (v? + Bv) will be the expression of the resistance.

Then, adopting the principle of the resistance to be equal to the force of ac-
celeration gp, we shall have the following equation, viz. :

gp= AIS (8 + Bv),orp=A (+B),

by making A’ = Afore portion of the canal taken when the motion is uniform,

of which 7 = the length. P! being the absolute inclination, we shall have
1
Pp =F and |e x (v2 + Bv); or, taking the whole extent of the canal, L

being the length, P the total inclination, (from which inclination must be de-
ducted the height due to the velocity v of the uniform motion,) the equation

will then be P — o =A a (2 + Bv). Wemust now determine the two

constant coefficients A and B.
Then, taking Eytelwein’s results from 91 experiments made on different
canals and rivers, in which the velocity varies from 0°124 metre to 2°42 metres,
and the fluid section from 0:014 metre to 2°604 metres, it follows that ~
A! = 0:0035855, or
A = 0:00036554,
B = 0:06638,

So that, putting g for the numerical value, the fundamental equation of the mo-

REPORT ON HYDRAULICS.—PART II. 419

neer* arrives at an equation which expresses the relation of the
expenditure, the length, the section, and the depth of the water
in the canal under consideration; by a series of very com-
plicated calculations, M. Poncelet has arrived at similar re-
sults. But uniformity of motion cannot take place when
the surface of the water is not of the same inclination as the
bottom of the canal, as, for example, when the bottom is hori-
zontal, or the declivity is contrary to the current: it was there-
fore very important to establish the distinction between the two
kinds of regimen, and only to regard the uniform regimen as
a modification of the permanent regimen ; that is, it was neces-
sary to find a general formula which should represent all the

tion 4 water in canals becomes p = 0°00036554 - (vt + 0:0664v); that is, if
J» Q being the expenditure,
p 83 = 0:00036554 c (Q2 + 0:0664 QS);

for the expression of the velocity, v= — 0°0332 + V o7362" +0:011;
for the expenditure, Q@ = S (— 0:0332+ V 2736+ 0-0011) ;
€

or, what is sufficiently near, Q=S(4/ 2736%* — 0:0832).

In great velocities, where the resistance is simply proportional to their
squares, we have

yeaah sy gh he and Q=51 By ee;

c
These formule might be illustrated in practice in the method adopted by
Messrs: Prony, Girard, and d’Aubuisson. See Traité d Hydraulique, 8vo,
Paris, 1834, wherein several cases, such as the breadth, height and form of the
channel which gives the greatest expenditure, are determined ;—the circle, the
semicircle, and segment of a circle; afterwards the regular half-polygons, the
regular semi-hexagon, the semi-pentagon, and the semi-square.

But as many of these figures are inadmissible in practice for canals, we must
adopt a trapezium, with its smallest base for the bottom, and having its sides
inclined to angles of about 34°, but which form will be, however, obliterated in
the angles in time by deposits, and present a concave bottom.

By preserving the slope at 2 to 1, or x,
the mean velocity, 7+ nh—=2h; I being the length,
h = depth or height;
and consequently s =2/2 and c= 2h —nh+2hY¥n+1l=m,
by making 2—n+2</no+1=n'. These values will form the equation
ph& = 0:00004569 n! (Q 2h + 0°133 Q h®), from whence we can deduce h.
In the case of rectangular canals moving through an aqueduct or rock, the

breadth ought to be double the depth, and consequently / -

_ * Essai sur la Solution Numérique de quelques Problémes relatifs au Mouve-
ment permanent des Eaux Courantes: par M. Bélanger. '

2E2

420 FOURTH REPORT—1834.

circumstances of the permanent motion of running streams.
ee M. Bélanger has done, in adopting the following hypo-
eses.

He first supposes the current, when in a state of permanent
regimen, to be divided into plates perpendicular to the fluid
filaments, and the velocity of the particles of the water to be
constantly the same in the same and every plate :

Secondly, That each particle of water moves in a right line,
so that the centrifugal motion generated by the curvilinear mo-
tion (if there be any) may be neglected :

Thirdly, That, although the analysis which follows cannot ap-
ply but to cases where the dimensions of the section vary in very
small quantities in proportion to the length, the velocity of each
particle may be considered to be perpendicular to the plate it
traverses, neglecting the transversal velocities which exist as
soon as the section varies from one plate to the other.

Of these hypotheses, the first, namely, the motion of the cur-
rent by parallel plates, is never realized in nature, because the
resistance which the periphery of the canal opposes to the mo-
tion of the current is transmitted to the adjacent filaments, and
so on to the central filament, which moves the quickest ; but in
general the velocities of the different filaments differ very little,
and may be safely represented by a mean velocity, which is the
quotient, or the volume of water expended in a given time, di-
vided by the area of the section, as before stated. As soon as
this compensation is admitted, each fluid filament may be con-
sidered as retarded by a force equivalent to friction. M. Gi-
rard* has applied this idea to the formation of an equation to
represent the motion of the current, but with the supposition
that the two powers of the velocity are represented by the same
coefficients ; a supposition which cannot apply to every case.
M. Prony has shown that the function which expressed the re-
tarding force may be represented by

g = (av + bv*), in which the metre is taken for unity and

the second for the time :

g' = 9™ 8088 represents the accelerating force of gravity :

w = the area of the transverse section to which belongs the
particle under consideration :

x = the length of the wetted perimeter of the section:

v = the mean velocity supposed to be common to all the par-
ticles which traverse the section :

* Rapport sur le Projet général du Canal de l'Oureq: pay P. 8. Girard.
Paris, 1803.

. ae

a
5
.
;

REPORT ON HYDRAULICS.—PART II. 421

_aand b, two constant quantities to be determined by experi-
- ment*.
_ From these, and additional notations, M. Bélanger arrives at
a general expression for the permanent and uniform motion of
the current similar in some respects to that of M. Prony, whose
formula for canals is
By Loree
| av+bhbv= xa

The values of a and }, which represent the constant coefficient
of the first and second powers of the velocity, were determined
by M. Prony from thirty experiments deduced from the mean
and superficial velocities of the current :

thus a = 0:000444499
b = 0:0003093140F.

Eytelwein has exactly followed M. Prony, but from a greater

number of experiments.
a = 0°000242651
b = 0:0003655430.

The difference between these respective coefficients does not
much affect the results for calculations in the formule for the
relations between the velocity of the water in a canal, and its
length, inclination, and section, as they appear in M. Prony’s
Five Tables}.

If the form of the channel and the volume of water expended
remain the same, uniformity of motion can only take place when
the canal has one inclination and a proportionate depth through-
out its length.
~ The true principle, therefore, for regulating the inclination of
a canal, consists in establishing a relation between the ordinates
of the height and the horizontal distances, always considering

that for every volume of water contained in a given inclination,

there must be a depth corresponding to the uniform regimen.
M.Genieys§, who has investigated these principles with a view to

‘render them applicable to canals and aqueducts, has endeavoured
to find the velocity best suited to the nature of the soil, but al-

ways with reference to the velocity necessary to maintain the
salubrity of the water, which has been determined to be 35 centi-
metres, or about 13% English inches, per second for the minimum
velocity ; whereas M. Girard adopted a less velocity in the canal
deL’Ourcq. M. Girard at first proposed to lay out the inclination

_* Recherches Physiques et Mathématiques sur la Théorie des Eaux Courantes:
par M. de Prony. Paris, 1804.
+ Recueil de cing Tables : par M. Prony. Paris, 1825.
$ Mémoires de l’ Académie de Berlin (Années 1814 et 1815).
§ Essais sur les Moyens de conduire, d’élever et de distribuer les Eaux: par
M. Genieys.

422 FOURTH REPORT—1834.

according to the law represented by the coordinates of a funi-
cular curve, by which the upper part of the canal had an inclina-
tion of 0™-0000625 per metre, and the lower part of 0™:0001236
per metre ; but theseinclinations were found insufficient. M. Ge-
nieys prefers one decimetre per kilometre, or ;5455- Dubuat
is inclined to think that the smallest inclination capable of main-
taining the mobility of water is y5ggg55, but that at s5c555
it is barely perceptible ; and in an artificial channel set to 455
he found the mean velocity to be nearly 6 inches per second, and
7 inches per second in a drain near Condé, of which the inclina-
tion was 37355, and 10 inches per second in the river Hayne, with
an inclination of 3345,5*. M. Bossut found the motion to cease
entirely with pipes having less inclinations than those of Dubuat.
M. Dubuat has given the results of seventeen experiments on
the mean and superficial velocities and radius of a trapezium
canal set at inclinations of 54, to z4,, also the same results from
fifteen experiments made in a rectangular canal set at inclina-
tions of from 735 to g744g, also of four experiments on the
superficial and mean velocities of the river Hayne, all of which
he finds to accord with very nearly the theory laid down by him.
The Romans inclined their canals much more than the mo-
derns. Vitruvius fixed the inclination at 345, Scamozzi at 545.
From different observations made on the ancient aqueducts by
M. Rondelet}, he found the mean inclination to be 14 line per
French toise, or about 545, towards the lower part, 12 line, or
z7g» towards the upper part. More recent experiments have
made the inclination from 433 to gig.
According to M. Prony, the following are some of the inclina-
tions of the canals and rivers of the Pontine Marshes.

e r Low Water. High Water.
Canal of Pius VI., in two Met Metres. Metres.
lengths of ............ 17,677 | .4°811000 4°603000

Inclination in unity of the length, . . . > 0°000272 0-000260
Second length ........ . 9,112 | 0°619000 1°830000
Inclination in unity of surface... ._) 0°000068 0°000091

* The drains in Lincolnshire are inclined at 5 inches to a mile, or +42.
The slope of the New River is 3 inches per mile, or 3435. The slope of the
Eau Brink Cut in Norfolk is 5 inches per mile. The slope of the New Cut of
the Nene at Cross Keys Wash, in Lincolnshire, is about 4°9 inches per mile.
Of the inclinations of the Caer and Foss Dykes, originally constructed by the
Romans, we have no positive information ; but from +5355 to +ytaa seems to be
a fair average for the inclinations of the drains in low countries; and on straight
canals, such as the Thames and Medway, we have seen the effects of the wind
in raising the surface higher at one extremity than. the other equal to 13 inch

er mile.
: + See Commentaire de Frontinus sur les Aqueducs de Rome, par Rondelet :
Paris, 1820.

REPORT ON HYDRAULICS.—PART LI. 423.

The Ninfa, which runs into the above,
inclines from... ....... ++ +» 0°012466 to 0000090
; Saye 0:000095 0000049
The Uffente inclines from. .....% 0000410 0000420
Ist length ....... 0°001751 0°001305
The Amaseno 4 2nd ditto ..... - . 0°000636 0:001152
. 3rd ditto ........0°000665. 0°000905
Canalof Terracina, in a length of 3°728 ; ,
© ES NETTTS He aa ao a rear bo ers) /mOOOM I
Canal of Botte... . ditto ...... 0000187.

Similar examples might be quoted of the Pedicata, the Scara-
vazza, &c.

These inclinations vary according to circumstances, but in
general they may be taken from 5,45 to go55-

_M. Prony, in the 8th chapter of his Report, proposes to dis-
tribute the inclination of the rivers or drains so as not to
corrode their channels ; and this is effected by a series of planes
or falls, from 0°0005035 to 0°0002879 ; as an example he cites
the marshes of Bourgoin in France *.

M. Prony proposes to accommodate the high and low wa-

‘ters by forming the channel into a double set of trapeziums,

so that in times of flood the waters will have liberty to spread
above the lower banks ; and being confined between the higher
or external banks, the capacity but not the velocity will be in-
creased. This is precisely the mode adopted in the Eau Brink
and Nene Cuts by the late Mr. Rennie, and by the Italians in
the embankment of the Po and other rivers.

According to Deschalest, if the depth and quantity of water
in a river or canal be considerable, it will suffice in the part
nearest the mouth to allow a declivity of one foot perpendicular
in from 6000 to 10,000 feet in horizontal extent, above which the
declivity must be slowly and gradually increased, as far as the
current is made navigable, to 1 foot perpendicular in 4000 feet’
horizontal.

Riccioli partly confirms this statement with regard to the
mouth of the river Po. The mean declivity of several of the
canals and rivers in Flanders was found by the Abbé Mann to be
from 3355 to sgg5, and of the Lys, near Ghent, by M. Brisson,
one in 3z55- According to the observations of the Abbé Chappe
D’Auteroche, M. Nollet and MM. Cassini, the height of the

_* Description Hydrographique et Historique des Marais Pontins, &c.: par
M. Prony. Paris, 1818, de l’Imprimerie Royale.
+ De Fontibus et Fluviis, Prop. 49.
t Mémoires de ! Académie Royale des Sciences pour 1730.

424 FOURTH REPORT—1834.

Seine at Paris above the level of the sea is 127 French feet,
which divided over the length of that river to Havre is one in
4252. By similar observations made on the river Loire by
MM. Picard and Pitot, the declivity in proportion to its length
was found to be 3;"7z-

The Rhone gives the proportion 7,5, which is double the
mean declivity of the rivers in Flanders.

On the mean Velocity of Water running in artificial Canals.

We have seen, that the resistance of the sides of the channel
causes a diminution in the velocity of the water which is com-
municated to parts remote from the periphery; from which it
follows that when the section is a semicircle the greatest velocity
is in the middle of the surface; and that in a channel of any
other shape this maximum velocity is in the most distant point
from the periphery ; and that, vice versd, the velocity decreases
towards the periphery. A knowledge of this progression has
always been considered of great importance, and many experi-
ments have been made for that purpose.

Dubuat has perhaps made the most accurate experiments on
the subject ; and having performed them on a scale of consider-
able magnitude, he concluded that the relation between the velo-
city at the surface and the bottom was independent of the depth,
and greater in proportion as the velocity was smaller; he ob-
served also, that the mean velocity is a mean proportional be-
tween the superficial and bottom velocity, that is, calling

v the velocity at the bottom,

V_ the velocity at the surface,

wu the mean velocity,
the result of these observations may be represented by the
equations
y=(W V—0'165)?andu= 1 (V +2) =(W V—0:082)? +.0°00677.
M. Prony*, in discussing these observations of Dubuat, adopts
V+2°372 .

* Jaugeage des Eaux Courantes, 1802,

REPORT ON HYDRAULICS.—PART II. 425

but thinks that in practice « = 0°8V may be adopted, that is, that
the mean velocity of a current of water may be found by taking
4ths of the superficial velocity. In conclusion, we may say that
the resistance which water experiences in moving in a canal or
channel, is proportional to the wetted perimeter, and to the
square of the velocity plus a fraction of the velocity, and is in
the inverse ratio of the section. This is in accordance with
the experiments of Eytelwein, Funk, and Brunings, &c. And
with regard to the natural phenomena of water running in re-
gular channels, we have observed, that with the same inclina-
tion throughout the length, the water preserves the same breadth ;
that the section of its surface is composed of curved lines, result-
ing from the adhesion of the water to the sides of the channel,
and the mutual reaction of each half of the section, by which
a swell is produced in the middle; and, finally, that over the
whole surface a series of diagonal lines, crossing each other
from side to side like network, is formed, of which the obliquity
or resultant of the lateral impulsion is proportional to the velo-
city of the water in the channel.

On the Progress and present State of our Knowledge of Rivers.

- Hitherto we have confined our attention to the motions of a
fluid in pipes and artificial conduits: the motions of rivers follow
more complicated laws. So long as philosophers were contented
to reason from experiments made under given and determined
conditions, the problem was comparatively easy of solution ;
but the question was very much altered when they attempted to
apply the results to rivers. In the former case, they could regu-
late the inclination and velocity of the fluid, and, by comparing
the effective with the calculated expenditures, could analyse
the resistances with approximate accuracy. In the latter case,
they had to contend with an infinity of resistances, which were
augmented or diminished at every instant of time. i
_ These natural phenomena depend upon the physical constitu-
tion of the country and soil in which rivers derive their origin
and formation. For whether we trace them to their sources
among mountains, or follow their directions through the valleys,
to the plains, and thence into the sea, we shall find them (al-
though actually governed by well-defined laws,) subject to new
conditions from every inequality of soil and country. In ana-
lysing, therefore, the motions of rivers, it is necessary that we
should investigate not only the mechanical properties of the
fluid, but the elements of resistance with which these proper-
ties are combined ; that we should prove by comparison how the

426 FOURTH REPORT—1834.

sections of rivers assimilate in their inclination and magnitude,
and demonstrate the law of their augmentation in volume, but.
decrease of velocity, as they approach the sea. ¥ ie

It is the office of science to unravel these mysteries ; but al-
though the attention of philosophers has been directed to the
attainment of a true theory from the time of Galileo to the pre-
sent, our knowledge of the laws which govern the motion of
rivers is as yet very imperfect. The little success with which
they have been investigated may be attributed to the difficulty.
of making correct observations, and to the local obstructions
which generally exist in most rivers; and until we can ascertain.
these points correctly, by means of a series of careful experi--

‘ments, we can only arrive at approximate results. .

The application of the science of hydraulics to rivers may
be justly said to have arisen in Italy. The peculiar physical
structure of the surface of that country was well calculated to
produce such a result, as it is intersected in all directions by
mountains, and by numerous torrents and rivers, which carry
off the superfluous waters to the Mediterranean and Adriatic
seas, on either side of the Peninsula. But the lofty character
of these mountains, as compared with the small extent of the
country through which the rivers have to run, causes them to
descend with extreme rapidity into the plains, which are fre-
quently ravaged and desolated to an extent unknown in wider
expanses of country. The evils thus generated, independently
of the litigation and strife which they occasioned (and which
exist at the present day), could hardly fail to excite the atten=
tion of ingenious men at an early period; hence may be dated
the origin of that science which has since made such brilliant
progress in Italy.

The arts of irrigation and drainage had been long known and
practised by the ancients; but whatever science existed, seems to
have remained dormant until the eleventh and twelfth centuries,
when the Italians applied themselves to render several of their
rivers navigable, such as the Brenta, the Mincio, the Arno, the
Reno, the Tecino, the Adda, &c., also several canals for irriga-
tion and drainage, such as the Muzza and others. But it was
only after the invention of the lock * for transporting vessels

* Zendrini in his treatise, chap. 12, No. 20, speaking of the invention of the
lock says, ‘‘ Ho trovato dunque che Dionisio e Pietro Domenico, fratelli da Vi-
terbo de fu Maestro Francesco di detta citta, ingegnere della Signoria di Vene-
zia, acquistano del 14811i 8 di Settembre da Signori Contarini certo sito nella
Bastia di Stra, luogo ben noto verso Padova, per formare in esso un soratore del
Piovego, che é quel canale, che viene da Padova al detto luogo di Stra; ed in
certa supplica de’medesimi da Viterbo di detto anno resta espresso, ch’essi, che

REPORT ON HYDRAULICS.—PART II. 427

from one level of a river or canal to another, that a new career
was opened out to hydraulic architecture. By this beautiful
contrivance all the difficulties attending navigation were over-
come, rivers were rendered navigable, or avoided where too rapid
or too dangerous, whilst the irregularities of the surface of a
country were compensated.

The two canals which communicate to the Tecino and Adda
rivers, and which were afterwards united at Milan by the cele-
brated Leonardo da Vinci about the end of the 14th century,

_ were remarkable for the first. application of a series of locks to
any canal. The Naviglio Grande, made in the 13th century,
from the Tecino river to Milan, was undoubtedly the first canal
with a lock. In contemplating these works in the year 1827,
the words of that excellent writer on hydraulics, Paul Frisi,
naturally occurred to us, “ Io no getto mai gli occhi sopra questi
navigli senza un interno sentimento di stima verso que gl’ illustre
architetto chevi seppero vincere tante difficolta*.”’

From this epoch may be dated the progress of Italy generally
in the practice of hydraulic architecture. In the year 1516 a
commission of scientific men was appointed by Francis the First
to examine and consider the actual state of the canals then ex~-

si chiamano Maestri di Orologio, faranno che le barche e i burchi protranno
passare per la chiusa de Stra senza pericolo, operando in modo, che le acque
usciranno con facilita, senza esser obligate a scaricare, e senza essere tirate,” &c.

_ Antonio Lecchi, in his treatise on Navigable Canals, pronounces the inven-
tion of the lock to have taken place in the year 1420, because an early writer,
Pietro Candido Decembrio, in his Life of Duke P. M. Visconti, says, “ Meditatus
est et aque rivum, per quem ab Abbiate ad Viglevanum usque sursum veheretur;
aquis altiora scandentibus, machinarum arte, quas Conchas appellant.”

+ Antonio Lecchi further says, that about the year 1188, Pitentino, an archi-
tect of Mantua, had constructed a lock at Governolo, on the river Mincio, to
render it navigable, and that many remains of locks existed on several of the
Italian rivers anterior to the year 1188. « Paul Frisi, referring to the expression
of Visconti, says, it only meant a regulator of the surface of the water, and not
a lock. An anonymous Italian writer, in the year 1825, on the canal of Bologna,
gives the discovery to Alberti in the year 1452. In the ten books of Alberti’s
Architecture the following sentence occurs, “‘ Duplices facito clausuras, secto
duobus locis fiumine spatio intermedio quod navis longitudinem capiat, ut si
erit navis conscensura cum eo applicuerit inferior clausura occludatur, aperiatur
superior: sin autem erit descensura, contra claudatur superior aperiatur inferior,
navis eo pacto cum ista parte fluenti evehetur fluvio sécundo.” Lastly, Bru-
schetti, in his account of the progress of the internal navigation of the Milanese,
says, that the first lock (conca) was erected at the commencement of the 15th
century at Viarenna, and that the honour of this-invention was due to two
engineers of the Grand Duke Philip of Modena, named Orgagni and Fioravante,
and not Leonardo da Vinci, who did not flourish untila century after. The name
_ conea was given to the lock in consequence of its having been constructed for the
_ purpose of transporting the stonesintended for the Cathedral or Duomo of Milan.
* De’ Canali Navigabili, Tratiato del P. D. Paoli Frisi: Firenze, 1770,

428 FOURTH REPORT—1834.

isting in the Milanese, with a view to their further extension.
The result was a project to join the Lake of Como with Milan
by means of the river Adda and the canal of Martesana. This
project was finally executed, and the difficulties of the naviga-
tion of the river Adda were overcome by means of a small cut
with ten locks in it, called the canal of Paderno, which was
finished in the year 1520. The next idea was to open a direct
communication between Milan and the Po, but this project,
with many others, such as the junction of the lakes of Como
and Maggiore with the Po, the Tecino with the Po near Pavia,
and the Adda near Cremona*, were postponed on account of
political circumstances.
Hitherto the science of rivers had been greatly neglected,
and indeed had never made much progress until after the cele-
brated congress of scientific men in Tuscany in the year 1665.
This congress was appointed by the governments of Rome and
Florence with a view to put an end to the contests which had
taken place among the inhabitants bordering on the Val de
Chiana, (anciently called the Chesina Palus,) and now one of
the most fertile districts in Italy. It was precisely this river
which gave rise to the famous controversy in the Roman senate,
related by Tacitus, on the proposal for obviating the inundations
of the Tiber by diverting the Chiana into the Arno. The Chiana,
being situated between the Tiber and the Arno, had been alter-
nately forced backwards and forwards by the neighbouring popu-
lation until it had subsided into a noxious marsh, pouring out
its surplus waters wherever they could find a vent. The result
of the deliberation of the congress was a proposition by Cassini

* “Memoria sulla Navigazione interna del Milanese,” dell’ Ingegnere Parea,
Annal., lib. i. 79.

Almost the whole of the Val di Chiana has been raised by the process of
colmata, or warping, similarly to the practice adopted in the marshes border-
ing on the Humber in this country.

It takes from five to six years to raise the surface as many feet.

Torricelli alone recommended the system of Colmates in 1768. The Grand
Duke Leopold of Tuscany appointed a commission, at the head of which was
the learned Fossombroni, to direct the operations ; and on this occasion Fossom-
broni published a work, entitled, Memorie Idraulico Storiche sopra la Val di
Chiana, Firenze 1769, in which the whole system is detailed.

From experiments made on the depositions of the Ombrone (a small but
rapid river) at different periods, the deposits were found to be 35, s'x,
ais; sts of the height of the water. It is to be wished that this system were
practised over the whole of the marshes of the Tuscan Maremma, which are
alone computed to amount to 300 square miles: the most considerable are the
marshes of Viareggio, Grosseto, Piombino and the Pontine marshes. The
works which were executed by Ximenes in the year 1767, in the marshes of
Grosseto, although magnificent and effective for a time, were afterwards ruined
by neglect: several attempts have since been made to renew them,

REPORT ON HYDRAULICS.—PART II. 429

and Viviani to confine the Chiana by banks, and so conduct it
to the Arno. In a subsequent meeting, at which Torricelli was
present, the same system was recommended, on the ground that
the rivers Arno, Tiber, and Po were confined by the same means.

Although nothing important had arisen out of the proceed-
ings of the congress of Florence, the attention of philosophers
was excited to discover the true causes of these evils. Much
had been said and written on the rivers of Lombardy, Ferrara,
Bologna*, Tuscany, and other provinces of Italy; but no one
had undertaken to combine together the facts elicited, by a
careful observation on the rivers themselves, until the meeting
of a second congress at Bologna in the year 1681.

The Po and the Reno were the rivers that excited the greatest
interest, on account of the absorption of the river Primaro by
the Po, and the blocking up of the Reno by the depositions of
the Ferrara branch, by which the Reno was raised so high as to
cause the bursting of the banks, and the consequent inundation
of the most fertile provinces of the Bolognese. This evil was
greatly increased by the addition of five other torrents to the
mass. Such a scene was well calculated to increase the interest
upon this subject ; hence may be dated the rise of the science
of hydrometry in Italy.

The discovery of the law of falling bodies by Galileo, and the
subsequent misapplication of this law to the rivers Bisenzio and
Arnof in opposition to the opinion of Bartolotti, paved the way
to several very important investigations by Castelli, who in-
troduced the element of velocity, arising from pressure, into
the calculation of the quantities of water which flow in the beds
of rivers. Castelli proved,—

Ist, That in a river reduced to a state of permanence, the
quantity of water which passes through all its sections in equal
spaces of time will be equal :

2ndly, That the medium velocities in the different sections will
be reciprocally proportional to the amplitude of the sections ;

_ * Della Salveazione de’ Fiume del Bolognese e della Romagna, del M. R. P.
‘Leonardo Ximenes e del Pietro Paolo Conti: Roma,1776. Also, Zrattata de’
Canali Navigabili del Ab. Antonio Lecchi: Milano, 1776. Also, De’ Canali
Navigabili di P. D. Paoli Frisi, 1770.

+ Lettera di Galileo Galilei sopra il Fiume Bisenzio, a Raffaello Staccoli.

Bartolotti, an engineer, having projected to shorten the course of the river
Bisenzio by means of a cut or canal, Galileo opposed it for the following rea-
sons :—Ist, That in two canals of equal height, but of unequal lengths, the
velocity of the stream would be the same in both of them. 2ndly, That it is
not the inclination of the bed of the canal, but the surface, that regulates the mo-
tion of the water. 3rdly, That the velocities do not follow the ratio of inclination
as Bartolotti asserted, but differ in a variety of ways in similar inclinations.

430 FOURTH REPORT—1834.

3rdly, That if a river, flowing in a rectangular channel with a
certain velocity, be augmented by a flood to double its height,
the velocity of the water will be double; a principle sub-
sequently adopted by Genneté, and disputed so often by the
Italian philosophers. Castelli was well aware of the necessity
of removing the obstacles to the free flow of rivers; but he
was wrong in his supposition of the effect of sluices, and
in attributing the velocity of the water near the mouths of
rivers to the pressure of the superior waters. His opinions
relative to the effect of rivers in purifying the air, and in pre-
venting the increase of the sea-shore opposite Venice, were con-
tradicted by Montanari and Guglielmini, who advised the di-
version of the rivers from their ancient channels; and corrected
the evil for a time.

Torricelli was the first who endeavoured to prove the analogy
subsisting between spouting fluids and rivers, and their accelera-
tion on account of the slope of the surface.

The respect of Viviani for Galileo did not prevent him from
rejecting the ideas of his master as to the effect of shortening
the course of the Bisenzio*. WViviani added several useful ob-
servations on the subject.

Zendrini, in his experiments with the pendulum, discovered
that the velocities in the different parts of the section of the
river Po were nearly proportional to the square roots of the
heights, when the velocities were not very great +.

The truth of this law has been confirmed by all the experi-
ments which have been made with the hydrometrical flask
invented by the Bolognese in the year.1721, in which the quan-
tities of water entering in a given time by a small aperture left
open at the top, and collected by sinking the flask successively
to different depths in stagnant as well as running waters, were
at all times nearly in proportion to the square root of the
heights. Independently however of these experiments, the
parabolic law is sufficiently ascertained ; so that in a parabola,
of which the abscisses represent the depth of a river, and a cor-
responding semiordinate represents the velocity, all the other
semiordinates will express velocities corresponding with the
heights of their respective abscisses. Again, the space run

* Opinions are yet divided on the propriety of shortening the courses of
rivers; but in rivers carrying gravel there can be no doubt.

Viviani had several striking examples before him of the evil consequences
which had resulted from shortening the course of the Arno, both above and
below Florence ; and his observations upon the rising of the bed of that river
are applicable to all rivers similarly situated.

+ Leggi, Fenomeni, Regolazioni ed Usi delle Acque Correnti, di Bernardo
Zendrini, (Firenze, 1770,) eap. v. part. ii. pag. 100.

REPORT ON HYDRAULICS.—PART II. 431

through in one second, by a body floating on the surface of a
river, divided by the same parameter, will give the height due to
the velocity of the surface, which, added to the height of the
river, will give the whole effective or equivalent height: the
square root of the product of the equivalent height by the para-
meter will give the velocity at the bottom of the section.

- Two thirds of the product of the velocity at the bottom by
the whole equivalent height, minus two-thirds of the product of
the velocity at the surface by the height added to the actual
height, will give the mean velocity.

Finally, the product of the mean velocity by the actual breadth
and the actual height will give the quantity of water that passes
in one second through the rectangular section.

Zendrini’s observations on the continual rise of the Adriatic
Sea, in confirmation of the opinions of Sabbadini, Montanari, and
Manfredi, and on the prolongation of the whole shore of the Po,
as far as Ancona, and his Report on the diversion of the Ronco
and Montone, rivers near Ravenna, together with the extension
of the sandbanks at the mouths of the different rivers, are
extremely interesting. ¢ WOLMI ed Ti Set

His great experience on this subject led him to conclude that
a harbour ought not to have a turbid river either on its right or
left side within a distance of seven or eight miles.

_ As early as the commencement of the eleventh century the
opinions of philosophers coincided very nearly with the theory
that the surface of the Adriatic Sea was continually rising, and
certain indications along its shores seemed to confirm the cor-
rectness of these opinions. The cause was generally attributed to
the continual accumulation of the substances brought down by
the rivers and collected on the beach, and which, by prolonging
the shores and contracting the outline, caused an elevation of
the surface of the sea. This explanation, says Paul Frisi, would
be very plausible if the Baltic did not exhibit at one and the
same time an enlargement of its shores and a depression of its
superficial level ; and if it were not evident that as all seas must
have a common level with respect to each other, the absolute
height of the waters cannot be raised in one without being at the
_ Same time elevated in all the rest. In the Memoirs of the
Academy of Stockholm, Celsius, Dalin, Stembeek, and others
have given a long statement of facts, which prove very clearly
the extension of all the shores of the Baltic Sea*. But what-
Bi r

_* See Mr. Lyell’s Geology relative to the Delta of the Po, vol. i. pp. 236, 237 ;
‘also a paper recently presented by that gentleman to the Royal Society on the
rise of the shores of the Baltic Sea. The following examples in illustration of
Manfredi’s theory are mentioned by Col. Leake: Hafonisi, an island formerly

432 FOURTH REPORT—1834.

ever may have been the opinions of philosophers on this subject,
the fact was not known until Manfredi established it. Sabbadini
had given his opinion in his discourse on the Lagunes of Venice.

Montanari, in his essay entitled J/ Mare Adriatico e sua Cor-
rente esaminata, maintained that the rise of the bottom of the
Adriatic Sea was owing, not to the alluvion of the Po, as has
been asserted, but to the sands of the shores of the Mediter-
ranean brought by the current which runs from the Straits of
Gibraltar along the African coast, and through the Ionian Seas
into the Adriatic: his conclusions, however, are too fortuitous to
be quoted.

The observations of Manfredi on the levels of floors of several
ancient buildings at Ravenna, such as the Cathedral, Rotunda
and Church of St. Vital, as compared with the levels of the
neighbouring sea, and which Zendrini afterwards confirmed by
other observations of the same nature, are curious. Zendrini
observed that the rings formerly used to fasten boats to the
quays at St. Mark’s Place, are now below the level of the sea ;
that the subterranean church of St. Mark is no longer serviceable,
because it is below water; that the ground plot of the Piazza is
sometimes overflowed in moderately high tides, although it had
been raised a foot; that in the island of Capri the whole plat-
form of an ancient Roman edifice placed on the sea-shore was
inundated ; and he states that similar observations of Donati
along the coasts of Dalmatia gave the same results.

The observations of Zendrini on the embouchures of rivers in
the Mediterranean apply with equal correctness to all rivers
which empty themselves into inland seas and lakes.

Grandi repeated the experiments of Zendrini ; but although in
his treatise on the motion of running water he professes to fol-
low the principles of Galileo and Torricelli, his observations on
rivers indicate that he possessed very little knowledge on that
subject ; his dissertations on the river Era and other rivers have
merely a local interest, without adding anything to the science.
The same may be said of the treatises of Cassini and Michelini,
although the latter was the first to show the art of regulating
rivers.

But the treatises of Guglielmini on the measure of running
waters and on rivers are the greatest works of the Italian school
of hydrometry. The publication of these works originated with
the commissioners appointed in the year 1693 by Pope Innocent
XII. to investigate the state of the provinces of Bologna, Ferrara,

a peninsula; Monemvasia, an island formerly the promontory of Minerva; the
Cothon of Carthage, now a swamp separated by the port of Lecheum; Corinth,
the port of Patara, and the Catacombs of Alexandria.

Mh la al il eli is eee ea

REPORT ON HYDRAULICS.—PART II. 433

and Romagna, with a view to the regulation of the rivers and
the drainage of those districts. Guglielmini was included in the
Commission on the part of the city of Bologna ; and having in-
vestigated the whole of the circumstances connected with the
Po and Reno rivers, he published the result of his labours shortly
afterwards. In that Report he confines himself to the subject in
question, by detailing very fully the various projects which had
been proposed to ameliorate the condition of the country and
the rivers which flow through it, particularly the Po, the Reno,
and the Panaro, and he demonstrates the method by which the
difficulties could be overcome. His opinions were questioned
by several engineers of that period. In his work entitled La
Misura dell’ Acque Correnti, he adopts the theorems of Castelli
and Torricelli, and founds upon them asystem of hydraulics in-
consistent with experiment, in as much as he makes the velo-
city proportional to the square root of the height, and regards
every point in a mass of fluid as tending to move with the same
velocity with which it would issue from an orifice: and as
the velocities are as the square roots of the depths of the
orifices, the greatest velocity must be at the bottom of a stream
and the least at the surface, besides a continual acceleration of
the river as it moves. It was in vain that he attempted to
reconcile these principles to facts. But the great work of Gu-
glielmini is his Natwra de’ Fiumi, which was published with
notes by Manfredi in the year 1697, and followed by a second
part in the year 1712, after his death. The first three chapters
contain definitions and general notions on the equilibrium of
fluids, and the origin of fountains: the fourth and fifth chap-
ters relate to the motions of rivers down inclined planes,
with reference to friction and resistance, by which an equili-
brium is established between the force of the current and
the resistance of the bed. He states, that the inclination and
velocity of rivers continually diminish in proportion as the
rivers recede from their sources, and that consequently the
power of transporting materials and the magnitude of the
materials themselves diminish in a corresponding ratio ;—that if
there be two rivers of equal velocities, but of unequal masses, the
river which has the greatest mass will have the least inclination :
and from data not satisfactory he deduces that the greater the
ay of water in rivers, the less will be the inclination of their
S. .

_ Chapter the 6th relates to the direction of rivers, and to the
difficulty of restraining and regulating their courses; and in a
series of propositions and corollaries the author demonstrates,
That the direction of rivers is necessarily rectilinear # not in-

1834. 2F

434: FOURTH REPORT—1834.

fluenced by external causes ;—that the inequalities of the soil, to-
gether with artificial obstacles which rivers encounter in their
courses, are the causes of the bends, sinuosities, and irregulari-
ties which constantly exist in them ;—that rivers which carry
gravel preserve their direction with great difficulty, on account
of the alterations which continually take place in the time of
floods by partial depositions ;—that in consequence it is exceed-
ingly difficult to regulate such rivers by artificial works, but
much less so where rivers run through sand or other homoge-
neous beds.

Chapter the 8th contains several interesting observations re-
lative to the junctions of rivers with each other and with the sea.
In times of flood the elevation of the water is less sensible at
the embouchures than above them, but a few inches of elevation
at the embouchure occasions an elevation of several feet in the
river. The velocity also, although stated by Guglielmini to be
greater, is actually less at the embouchure than above it.

The author finishes this chapter by examining the cases_ of
rivers joining each other perpendicularly or obliquely, and when
they are subject to the flux and reflux of tides, and consequent
changes in the directions of the embouchures.

Chapter the 9th treats of the effects resulting from the union
of rivers with each other, and with the sea. In the 1st propo-
sition it is stated that if two rivers similar in section and volume
empty themselves separately into the sea, the sum of their sec-
tions will be greater than if they entered the sea in one united
bed. The author adduces the sections made of the Reno and
Tecino, afiluents of the Po, in the year 1719 as proofs of this
assertion. In proposition the 2nd he states, That two rivers
united in one bed have greater velocity and power of corrosion
of the bed than two rivers running in separate beds, and the
increased effect will not only take place below, but above the
confluence of the tworivers ;—that the breadth and section will
be less in the united than the disunited rivers ;—lastly, respect-
ing the effects of tides in keeping open the mouths of rivers, that
the water of the sea, which during the flood enters into the beds
of rivers, returning back with the ebb, helps to clean out the bed
and to sweep away the deposits. He has repeated this doctrine
elsewhere, expressing his opinion that so long as rivers could of
themselves keep their mouths open on a flat shore, the agitation
of the tides would prevent any shoals from forming in the trunk
lying above the mouth; and with regard to the entrance of rivers
into the sea, that the form of. the mouth will depend upon the
difference of velocity between the river and tide currents : that the
sediments of the river will settle along the eddy part of the shore

SS ee

REPORT ON HYDRAULICS.—PART II. 435

and form sand-banks, which will go on gradually increasing ;
and the river being opposed on one or other side, according to
the direction of the current of tide, will turn to the right or left
as may be. Proposition 3 :—Not only will the depth of the united
river be increased, but the depths of all the other affluents
likewise.

The remaining principles attempted to be established in this
chapter are :

Ist, That it is improper to unite rivers which shot gravel

“with rivers which carry sand ;

2ndly, That the courses of : gravelly rivers should not be short-
‘ened towards their embouchures ;

3rdly, That the corrosions of the borders of united rivers are
‘inevitable ;

4thly, That it is better to cause a river carrying gravel to de-
‘posit its gravel by lengthening its course than ‘to join it with
another river carrying sand: that the consequences’ of such.a
junction would be to oblige the greater river to change its direc- ,
tion or to raise its bed in the upper parts.

Chapter the 10th relates to the increase and diminution of
rivers, and the proportions in which they take place. Every
river is subject to variations in the volume of its waters and in
the capacity of its bed, from natural and artificial causes.

It is also affected by winds and tides. An affluent which
enters into a river when its waters are at the lowest state of
depression, will maintain a greater elevation of surface than
when the river is highest*. A small river may enter into
a larger. one without augmenting the section of the latter.
‘This apparent paradox is founded on the augmentation of
‘the velocity of the greater river, and Guglielmini quotes the
absorption of the Ferrara and Panaro branches of the Po by
‘that river, without. any:sensible augmentation of its channel:

this doctrine was first published by Castelli. The inutility of

‘diverting the waters of rivers by means of side cuts for the
purpose of lowering floods, is also insisted upon.

~ Chapter the 11th relates to natural and artificial streams, and
“the mode of conducting and distributing them for the purposes

-of drainage and irrigation. In the former case the author con-
‘cludes, from a variety of reasons, that it is better to unite all the
-waters of a region into one grand conduit, than to allow them
-to'run off by many separate conduits, and vice versd with respect
to irrigation.

_. * The truth of this observation seems to be generally allowed, although not
‘satisfactorily established,—That the water rushes quicker down rivers in their
high than in their low state.

or 2

436 FOURTH REPORT—1834.

Chapter the 12th treats of canals, and the precautions neces-
sary to supply them with water from rivers and reservoirs, such
as diminishing the force of the waters at their junction with the
canal, fortifying the points of junction, &c. The effects of sluices,
dams, regulators, aqueducts, siphons, and locks are all spoken
of in detail.

Chapter the 13th relates to the drainage and warping of
marshes. The first principle is to intercept and prevent tne ac-
cumulation of water, by diverting it from the borders of the
marsh, so that’by the cessation of the cause, the effect will also
cease. In this manner the whole of Lombardy was drained*.

The other principle is by raising the general surface of the
soil; by allowing the water to deposit its earthy materials in
times of floods: this was called colmata, or warping, a practice
often adopted in Italy, where the rivers have not been allowed to
raise their beds to an unnatural height above the general surface
of the adjacent country by means of embankments.

Chapter the 14th and last, is very important in an engineer-
ing point of view, as it treats of the effects of regulating and
shortening the courses of rivers. This operation ought never
to be undertaken without a perfect knowledge of the soil through
which it is proposed to carry the river. Cuts and shortening
rivers with gravelly bottoms are rarely attended with success,
but where the soil is muddy or sandy, such works are more du-
rable. The author adduces the Po, which has established itself
in the middle of its basin, as an example of the equilibrium
which its course has attained by the rivers which flow into it on
both sides. The work of Guglielmini contains much valuable
information, although, from its numerous contradictions and
errors, particularly on the formation and transportation of
stones and gravel, it requires to be consulted with caution.

The next author on rivers is Zanotti: this writer endeavours
to determine, by a series of observations, the position which the
beds of rivers should occupy near the sea, in proportion to the
superficies of their waters.

In considering the sections of the Po and Tiber, he was of
opinion that the acceleration of the waters occasioned by the
freeness of the outlet in these rivers, extended up the river to a
considerable distance, and reached to the spot which would be
struck by a horizontal line drawn from low-water mark. Finally,
on comparing these observations together in detail, he disco-

* This was always the principle adopted by the late Mr. Rennie in draining
the fens of Lincolnshire and Cambridgeshire, by means of catchwater drains at
the bases of the surrounding hills ; and by uniting the scattered waters by large
drains, they were conveyed to the sea.

a

a. 7s

roa.

REPORT ON HYDRAULICS.—PART II. 437

vered that the reduced slope of the surface in the highest floods,
reckoning from the point to which the surface of the sea at low
water reaches to the mouth, was equal to the reduced slope of
the bottom or of the lower superficies of the river, beginning
from the same point, and proceeding to the opposite direction.
His observations generally on rivers are valuable ; but the most
estimable writer, after Guglielmini, on rivers and torrents is Paul
Frisi.

The work of thisauthor is divided into three parts ; inthefirst the
author investigates the phenomena of rivers and. torrents which
flow over gravel; the origin of rivers; the substances brought
down by them; and the formation and rectification of their beds.
The 2nd chapter treats of the velocity of water from apertures
in vessels according to the theories of Torricelli, Newton, Michel-
lotti, &c.; and the velocities of rivers and artificial canals whe-
ther united or divided; their declivities, and the distribution of
them according to the principles of Galileo, Castelli, Grandi,
Guglielmini, Genneté and others: and the third part relates to
rivers which carry sands and mud; the states of the old and
new beds of rivers, with reference to the projects which had
been advanced for improving the Tiber, Arno, and other rivers
of the Bolognese; the resistances, whether natural or artificial,
opposed to the free flow of rivers; the doctrines of different
authors upon this subject; the effects of regurgitations oc-
casioned by dams, weirs, and other obstructions thrown across
rivers; and lastly, the phenomena attendant on rivers entering
into the sea. An interesting essay on navigable canals com-
pletes the work.

Frisi, after demonstrating that Guglielmini had been mistaken

in supposing that the formation of the smaller gravel and sand

in the beds of rivers was owing to the attrition of the larger
stones in the upper parts of the courses of rivers, maintained,

on the contrary, that gravel and sand are original bodies spread

over the earth through which the rivers traverse ; and, by expe-
riments, determined that the formation of sand in rivers is not

owing to the attrition of stones against each other, but to varia-

tions in the velocity of the current, which deposits the materials
according to the greater or less intensity of its force.

Viviani and Belgrado were of the same opinion. Belgrado ob-
served that stones torn from the mountains are precipitated
down their declivities, turning for the greater part of the time

on their own centres ; that they continue to roll along in the

same manner in the beds of torrents, until, the slopes becoming
less, they afterwards slide along the bottom, rubbing against it,
and are scattered to and fro by the impetuosity of the torrent ;

438 FOURTH REPORT—1834.

and that in consequence of the rolling and sliding motion they
acquire in their descent, there can be little or no abrasion of
the surface. Grandi, in considering the dam of Era, and com-
paring the specific gravities of the granite in the water, and of
the water itself, inferred that the transverse impetuosity of the:
waters was sometimes sufficient to raise the gravels from the
bottom, and to throw them on the edges of the dykes.

Besides his work on rivers and torrents, Frisi particularly
distinguished himself in the Bolognese and Ferrara controversy,
in which his plan for the rectification of the rivers of those
provinces in 1760 was approved of by all the mathematicians
then present. It was just at this period while Frisi was en-
gaged in the Bolognese controversy, that the work of M. Gen-
neté made its appearance ; and on comparing together the
observations made on rivers by both parties, it appeared to
Frisi that there was no sensible height even when there is a
considerable augmentation of water, and therefore, that the
velocity of the water increases sensibly in the same ratio as its
quantity.

The propositions of Genneté were,

lst, If two rivers be added to another during the time of its
flood, the river will experience no sensible rise in its surface;

2ndly, That if from the same river two branches be taken,
its surface will not be sensibly lowered.

These doctrines had been partly advanced with regard to ca-
nals by Castelli, Cassini, Guglielmini, and Corradi, but Gen-
neté was the first to apply them to rivers. It had been stated
by Frisi that the river Reno received the Samoggia without any
perceptible difference in the amplitude of its sections, and that
therefore it might receive other torrents without any sensible
augmentation. Doctrines so extraordinary, and at variance with
the received opinions on this subject, excited many discussions
in Italy. Genneté’s experiments were tried at Ferrara in the
year 1762, and at Rome in the year following, and again repeated
at Ferrara in the year 1766, but with results entirely different ;
he, however, clearly proved that the dissimilarity was principally
owing to the different modes of experimenting, although the
apparatus used at Ferrara resembled Genneté’s very nearly.
The recipient was 199 feet in length and 7 inches in width,
and the result was, that the first tributary stream (equal in sec-
tion to the recipient) occasioned an augmentation in height of
one half, and on introducing a second tributary of the same
section, the augmentation was double ; it was conceived, there-
fore, that Genneté had either erroneously stated his case, or
the effect was due to the increase of velocity occasioned by

REPORT ON HYDRAULICS.—PART II. 439

the pressure of the tributary waters against the water of the
recipient.

But, besides the law of acceleration, there remained other
elements to take into account, one of which related to the mo-
tion arising from the junction of two or more rivers.

In the Memoirs of the Academy of Sciences for the year 1738,
M. Pitot has used the same principle to determine the mean di-
rection which the waters of the two rivers will take when freely
united together, and this he does according to the resultant of
the collision of hard bodies, where the same quantity of motion
is invariably preserved; and from this hypothesis he draws as
its consequent that the common velocity of the united rivers is
equal to the quantities of motion in the two separate rivers di-
vided by the sum of those quantities of water. Grandi has en-
deavoured to decide by the same principles of the composition
and resolution of forces, not only the direction, but the absolute
velocity of the waters which either unite or divide. For this
purpose he constructed a float which gave the resultant of the
two confluences, from which he concluded that the course of
the river would naturally take an intermediate direction ; but, if
the banks of the recipient remained firm, its stream would pre-
serve the same direction as before, increasing, however, its for-
mer velocity by a part, in proportion to the velocity of the tri-
butary stream, as the cosine of inclination of the river is to the
radius: whence it would follow, that if the thread of water in
the tributary stream should second by its direction the thread
of water in the recipient, in making with it, as is generally the
case, a very acute angle, the velocity in the common bed would
be equal to the sum ofthe velocities of the recipient and affluent
streams. If this principle were admitted, it would follow, that
the sections of the receiving stream could not be considerably
augmented by the junction of the tributary, for this reason, that
the quantity of water augmenting, the velocities would be com-
pounded of this augmentation, and the flow of the current be
more rapid than it was before.

-Guglielmini, in the seventh chapter of his work, in consider-
ing the celebrated phenomenon of the Po (of Venice), which
receives the branch of the Ferrara and the Panaro without any
enlargement of its bed, has stated in general that a smaller river
might enter into a larger one without increasing either its
breadth or height; and he was of opinion that this might happen
without any lateral dispersion, because the whole of the in-
creased body continued in motion by following the direction of
the thread of the stream. On the hypothesis that all the-sections
were effective, and that the velocities before and after the con-

440 FOURTH REPORT—1834.

fluence of the two rivers were as the square roots of the actual
heights, the cubes of the heights would be as the squares of
the quantities of water which are discharged in an equal time
by the sections.

Manfredi deduced that the Reno, which added 5; part of the
whole quantity to the Po, could not raise the height of the Po
more than ;, part; but, reflecting afterwards that some expe-
riments made on adding or subtracting the water of a drain to
and from the Panaro, occasioned no difference in the elevation
ot the surface of that river, he concluded that the elevation of
the Po must be very small for any augmentation which the
waters of the Reno could cause in its stream*. The fatal conse-
quences which had arisen from dividing the Rhine into so many
branches from the frequent bursting of the embankments which
maintained them above the adjacent lands, and the continual
expenses entailed by them, necessarily excited great interest.

The great Rhine divides itself near Emmerik into twobranches,
nearly equal to each other, viz., the Waal and the Rhine: the
bed of each of these branches is nearly as large as that of the
whole river before its division, and when the waters rise they
are at an equal height in both. The second branch divides itself
again towards Arnheim to form the Issel, which has nearly the
same section as that of the Rhine. i

The first division of all the waters of the Rhine was begun
under the Roman generals Drusus and Corbulo: many subdivi-
sions were made in subsequent ages. This great multiplicity of
channels, although productive of advantages to Holland, occa-
sioned many fatal consequences: the waters, divided into so
many branches, lost the rapidity and strength necessary for
them to push forward the alluvial matter, occasioned a conti-
nual rising of the bottom, rendered the draining of the waters
from the adjacent lands more difficult, increased the expense of
the embankments, and augmented the damages over the exten-
sive lands when the dykes broke.

“ To secure that part of Holland which lies between Rotter-
dam, Utrecht, Amsterdam, and the ocean, it was proposed in
1754,” says Frisi, “ to form a cut, with sixteeen sluices, in the
Leck, which is another branch of the Rhine, by which part of
the waters would be discharged into the Meruva, which is the
junction between the Waal and the Meuse. M. Genneté op-
posed the project on the ground that it would not have dimi-
nished the height of the floods, but that it would have been pre-

* See Major-General Garstin’s Translation of Paul Frisi’s Work on Rivers
and Torrents.

REPORT ON HYDRAULICS.—PART II. 441

ferable to have united all the waters of the Great Rhine into the
ancient branch of the Issel, and thus have conducted them by
the shortest direetion to the sea, because by the union of the
waters their rapidity would have been increased, while the am-
plitude of the sections would have continued the same, and the
evils complained of would have been avoided: he supports his
opinion by several examples of the junction-of the Mayne and
Moselle rivers with the Rhine, without any sensible increase of
section in the Rhine before or after the junction; but, in order
to satisfy himself of this apparent anomaly, he caused an
artificial river to be constructed at Leyden, in the year 1755,
which was supplied with water by means of a vessel, five or six
feet in height, and connected by sluices with six other small
streams.

“The bottom of the recipient and of the tributaries had a
slope of 55; and he observed all the variations that occurred
either in adding the tributaries or in retrenching their streams.”

The results of these experiments were, that when a stream,
equal to half the water in the recipient, was added, and after-
wards another stream equal to another half, the quantities
of water in the recipient being successively as 1, 13, and 2,
the height of the water in the recipient was apparently the
same, while the velocities and quantities of the fluid in-
creased in the same proportion, viz., 1,13, 2. Again, when
the augmentations to the quantity in the recipient were in the
ratios of 3, 4, 5,6, and 7, the increase in the height of the water
in the recipient was only 75, oy, vs, ve». and 4, respectively.
By a contrary proceeding he let off the six tributary streams

_ successively, and found the diminution of the height of the wa-

ter in the recipient to prevail in the same proportion as the
augmentations.

Having witnessed these apparent anomalies in the junction of
rivers, it occurred to me to repeat the experiments of Genneté ;
and having provided a suitable apparatus, consisting of a wooden
trough ten feet in length, and six inches in width and eight inches
in depth, together with troughs of similar dimensions let into
the sides of the inner trough at angles of 30 degrees, and fur-
nished with suitable openings and valves, I caused one and two
streams respectively of water to be let into the main stream
from equal apertures and under equal and constant pressures,
from a cistern of two feet internal dimensions every way, and the
following Table shows the results :

442. FOURTH REPORT—1834.

Experiments made on Water, August 9th, 1834.

three

Position of
Trough in De-
grees of Inclina-

tion.

penings of 3 an
enings off an

pening of $ an
inch diameter.
inch diameter.
} 1
inch diameter each.

th of Water with
0}

Depth of Water with
Depth of Water with
Additional depth of
water with two open-
ings compared with
Additional depth of
Water with
openings compared
with one.

one oO
two o
Dep!

three

Y . Inches,

Trough level} 1-2 : 2°375

Inclined 1° : ° 1°375

1-125

1:

1:
‘937
*875
-812
“805
“7o
‘73

-_

. . 5
mas
AWE

b> b>
CO Or Or Or
nes

2
3
“3
5
6
7
8
i)
0

—_

The results were, Ist, That when the artificial river or re-
cipient was exactly level, it required two streams of equal
magnitude to raise the main stream to double of its original
height: 2ndly, That when the artificial river or recipient was
set at angles of inclination of from 1 to 10 degrees, a sensible
diminution took place in the altitude of the main stream, as
well as in the ratio of increase in the tributaries, corroborating
in some degree the experiments of Genneté.

In addition to the Italian collection, there appeared, at dif-
ferent intervals, a variety of works on the motions of rivers by
Mariotte, Hermanus, Michelini, Michelotti, Fontana, Poleni,
Statlerius, Ximenes, &c. In the year 1779 the Italian collection
was first made known in this country by the Abbé Mann, in a
valuable Treatise on Rivers and Canals, in the Philosophical
Transactions. The author recapitulates the different doctrines,
propounded by Torricelli and others, on the motions of rivers,
from the laws of their action, to the establishment of their beds.
He adopts the principles of Guglielmini in almost every instance
relative to the accelerations and retardations of rivers, and shows,
according to the principles laid down by Leibnitz and Euler,
that, in order to render the velocity of a current everywhere
equal, the bed should have the form of a curve, along which a
moving body should recede from a given point, and describe
spaces everywhere proportionate to the times.

EES ee ee
a

REPORT ON HYDRAULICS.—PART II. 443

The author gives ‘several practical rules relative to the junc-'

tion of and derivations from rivers, whether with each other or
with the sea; and, in the fourth section of his treatise, he de-
tails a series of experiments to determine the different velocities
of the same floating body, moved uniformly by an equal force
in different depths of water, the results of which are, that the
different velocities of the floating bodies are in an inverse ratio
of the respective depths of the water in which they float with an
equal impulsive force.

The author gives the declivities of several rivers in France and
in Flanders, such as

The Seine, from Paris to Havre, which he states tobe z)45-
PRE REN ce atta « Gbrad evcko fv efoheie gcdieus!¥ esr moe ——_
The Rhone, from Besancon to the Mediterranean,
stated to be one of the most rapid in the world, 4
or double of the mean declivity of the rivers in 2620"
Pianderis.. Povis aidhin sche uvak rund tists ois
The Ypres in Flanders to Newport ... .......:. 5230
CLE ROGET Stel 0a) 1} Re Bore
oe oie | ere oe ie a ae ae ete ros00"

444 FOURTH REPORT—1834.

The following Table is considered an approximation to the
actual state of Rivers.

Sy es .

) = | &

Distinctive Atiributes of the | 8* |@-2|ag_ [25 | dee |“25
various Kinds of Rivers. a. 28 SEE ae sue S88
abl | £25 | Gee | 224 | 28s | 23

aes | 858 | #32 | Eos | 288 | B58

Channels wherein the resist-}
ance from the bed, and other
obstacles, equal the quantity
of the current acquired from
the declivity; so that the wa- 1 0
ters would stagnate therein, |
were it not for the compression
and impulsion of the upper and
back waters.

Artificial canalsin the Dutch
and Austrian Netherlands.

Rivers in low flat countries,
full of turns and windings, and
of a very slow current, subject 3 1
to frequent and lasting inun-
dations.

ES EE eee

Rivers in most countries that
are a mean between flat and
hilly, which have good currents
butare subject to overflow; also
the upper parts of rivers in flat |
countries.

Rivers in hilly countries
with a strong current and sel-
5

dom subject to inundations ;
also all rivers near their sour-
ces have this declivity and ve-
locity, and ee ay much more.

tries having a rapid current
and straight course and very

Riversin ndubtaneedinod coun-
rarely overflowing.

Rivers in their descent from
among mountains down into
the plains below, in which
plains they run torrent-wise.

Absolute torrents among
mountains.

wera,

ee .

REPORT ON HYDRAULICS.—PART II. 445

In the year 1823 a new collection, or rather continuation, of
the Zrattato was published at Bologna, in six volumes, in which
the papers relating to rivers, are, first, An elegant dissertation
on the Natural Phenomena of Rivers, by Count Mengiotti; and
stcondly, An Exposition of the Experiments which have been
made by different authors to arrive at the true theory of running
waters, by means of various instruments, such as the float, the
pendulum, the wheel, &c. Thirdly, A confirmation of the doc-
trines of Castelli with regard to the ratio of Increase by Tribu-
taries : and remarks on the inutility of diversions in rivers, as ad-
duced by the diversions from the Po, the Rhine, and other rivers,
by Guglielmini and Genneté. The effects of regurgitations
in obstructing the free flow of rivers are quoted from different
authors and illustrated by experiment, more or less confirmatory
of the opinions of Guglielmini.

Volume the second, contains papers by De Lorgna on the In-
undation of the River ‘Adige ; the prolongation of Rivers into the
‘Sea, and the confining of their channels ; the effects of Affluents
nd Diversions.—A paper, by Zuliani, on the advantages and
disadvantages attending the expansion of rivers at their embou-
chures; the number and direction of the streams necessary to
‘maintain the water in its proper channel, and to resist the oppo-
sition of winds and waves. The author quotes many examples
in illustration of his theory, but concludes that the determination
jof the question in a mathematical point of view is beyond the
reach of science. .—Also, a learned paper on the motion and
‘measure of running water, by Tadini. The author adopts the
‘usually received theory of the velocity of running water, which
he reduces to expressions, and makes the relation of the velo-
‘city at the surface and bottom of a torrent to beas 1 : + 0:0016;
he states that in the case of a river such as the Po, of which the
‘inclination, when the experiment was made, was as 0:000214
metre per metre, the velocity at the surface and bottom is very
nearly alike, and that in similar cases the velocity is small and
the surface nearly par allel to the bed. The notion, therefore, that
the velocity of a river increases from the surface to the bottom
as the square roots of the depths, is erroneous.

_ The remaining chapters of Tadini’s treatise are devoted to an
-examination of the theory of the measurement of running water
‘through close and open channels according to the velocity and
amplitude of the sections, with due allowance for obstacles ; he
feos also the modes adopted by the different provinces in Italy,
in the measurement of running water, and the discrepancies
Tesulting therefrom, and concludes with a variety of experi-

“ments on the expenditures of orifices and rectangular channels,

446 FOURTH REPORT—1834.

but more particularly on the canal of Martesana, in which the
approximation to the parabolic theory is very close. In allusion
to the fluidity of water he states, that from accurate experiments
which had been made on the inclination of the Lake of Como
towards its outlet, the sensibility was found to be 7z;57+-

The treatise of Tadini is followed by a valuable practical pa-
per on the measurement of running water, reduced to the pro-
vincial measures of Italy and according to an extensive para-
bolical table appended.

Lastly, this volume contains papers by Masetti, on the Theory
and Practice of the different Instruments (tachimetri idraulict)
which have been invented for the purpose of measuring the
velocity of running water by Castelli, Guglielmini, Ceva, Grandi,
Pitot, Mann, Brouckner, Woltmann, Saverien, Ximenes, Lecchi,
Michelotti, Leslie, and Venturoli. He divides them into two
classes, floating and fixed instruments, and demonstrates, both
theoretically and practically, that the fixed instruments give
the surest results ; in general all of them indicated, in a greater
or less degree, the diminution of velocity towards the bottom.
Masetti’s conclusions are, that, for measuring the velocity of the
surface of rivers, the floating instrument or balls of Castelli. is
the simplest and best. Secondly, that of the fixed instruments,
‘the sliding rod of Bonati, and the pendulum of Guglielmini,
improved by Venturoli, are best.

A second paper, by Masetti, is devoted to the examination of
the different states of running water through orifices and rect-
tangular channels, according to the parabolic tables of Prony
and Eytelwein, calculated for different latitudes. The author
‘quotes the experiments of Newton, Borda, Bossut, Dubuat,
Mariotte, Michelotti, Navier, Hachette, Venturoli, &c.

Volume the third, contains a paper by Fossombroni on the
celebrated Val di Chiana, and the systems of Warping and
Drainage which have been practised in it at different periods.
This volume also contains papers by the same author on
‘the distribution of Alluvions, on the Draining the Pontine
Marshes, and on rendering the river Arno navigable by means
of Jetties and Contractions.

Volume the fourth, contains several valuable papers on Canals,
“by Lecchi, Ferrari, Bruschetti, and Parea, including the origi-
nal letters and reports concerning the early navigations and
canals of Italy.

Volume the fifth, is principally occupied by a translation from
the French of Borgnis Sur les Machines Hydrauliques, and two
“papers by Magistrini and Masetti on the action and reaction of
‘water on hydraulic machines.

EE

REPORT ON HYDRAULICS.—PART II. 447

The sixth and last volume, contains the experiments and con-
clusions of Bonati in opposition to those of Genneté, on the
Methods of Measuring the Expenditure of Rivers and of Canals
of Irrigation adopted bythe different provinces of Italy ; and in
which the author, after showing the discrepancies which exist
between them, gives the preference to the Milanese method.

A paper by Morri, on the Navigation of Faenza, and some
unsatisfactory experiments on the inclination, velocity, and pro-
duct of the river Po, together with several observations of minor
importance on the rivers Reno, Tiber, Brenta, and Velino, con-
clude the new collection. Such may be considered to be the
present state of hydraulic science in Italy. In rendering an
account of its progress it is impossible to withhold the just
tribute which is due to the Italians, namely, that of having been
the first to establish hydraulic science upon anything like true
principles.

Progress and Present State of Hydraulics in France,
Germany, and England.

The writers included under the above title may be considered
to consist of two classes, viz.. theoretical and practical.

The first have confined themselves to a purely speculative con-
sideration of the subject, in extending the chain of geometrical
truths without contributing anything to the real progress of

_the science.
The last have endeavoured by observation and experiment to
_arrive at practical inferences.
Mariotte belongs more properly to the latter class. His
treatise on the motion of water, accompanied by an immense
number of experiments, in the year 1728, has greatly contri-
buted to perfect the science.

Pitot demonstrated, that in open channels friction diminished

in proportion to the diminution of the surfaces in the inverse
ratio of the homologous sides; and that the friction of water
Moving in tubes at equal velocities, in relation to the volume of
water, is in the inverse ratio of the diameters.

Couplet illustrated this principle very clearly in his experi-
ments, although his deductions from them were incorrect.

Varignon contented himself with reducing the opinions of

-Guglielmini to geometrical forms.

_ Belidor followed the steps of Guglielmini in his great work
on Hydraulic Architecture.

_ Bossut was the first to follow the steps of the Italian school

‘by combining theoretical with experimental investigation. His

448 FOURTH REPORT—1834.

admirable work on Hydrodynamics shows abundant proofs of the
great sagacity with which he investigated every question relative
to the motions of waters through orifices and pipes; but his
experiments on artificial canals are unsatisfactory from his hav-
ing omitted the consideration of the depth.

The investigations of Bernoulli seem to have formed the
groundwork of the French school; for although he adopted
the opinion of Guglielmini, with regard to the analogy between
the motion of a river and the motion of a fluid escaping from a
vessel, yet his theory of the law of the velocity, however absurd
its application to the gradations of velocity in a river, is correct.
Although the science of hydrodynamics had acquired a high
degree of perfection at this period, it was nevertheless confined
to the hypothesis of the parallelism of filaments, in which all the
points of the same filament move in one and the same directiow.
It was desirable to express the motion from a given point in a
fluid in any direction. This problem was resolved by D’Alem-
bert, who discovered equations on two principles, namely,
that a rectangular canal, taken as a fluid mass, is in equilthrio,
and that a portion of a fluid, in changing its position, preserves
the same volume when the fluid is incompressible, or dilates
according to a given law when the fluid is elastic. This pro-
found and ingenious investigation was published in his Essai
sur la Résistance des Fluides in the year 1752, and afterwards
perfected in his Opuscules Mathématiques.

Euler, in his Mémoires des Académies de Berlin et de St. Pe-
tersbourg, and La Grange, in the year 1781, exhausted all the
resources of geometry for the same object, but without any ap-
plicable result. It was not untilthe year 1781, when M. Bossut
published his Traité Théorique et Expérimental, that the theory
of hydrodynamics was made subservient to experiment.

M. Bossut divides his work into two volumes, theoretical and
experimental : the first explains the general principles of hydro-
statics and hydraulics according to the previously established
theory ; the second contains a vast number of experiments on
practical hydraulics; on the motion of water through orifices,
pipes, and rectangular canals.

In the case of a rectangular canal of 105 feet in length, a con-
siderable difference between the natural and artificial expendi-
tures, arising from the friction of the sides of the canal and of
the atmosphere, was found to prevail: also a very considerable
swelling or rise of the water between the two extremities of the
canal; but without any diminution of the expenditure in a given
time, although the reverse is the case in pipes. He also found
that with the same initial velocity of the fluid, canals which are

$e

REPORT ON HYDRAULICS.—PART IT. 449

inclined pass off a greater quantity of water than horizontal
canals : this is illustrated by a great many experiments on the
velocities of water issuing from openings under variable and in-
variable pressures and inclinations of from three inches to eleven
feet.

. The experiments were repeated upon a larger scale in a canal
of 600 feet in length, and with nearly similar results, namely,
that the velocity augmented with the inclination. There were,
however, observed two distinct velocities, viz., the velocity of
projection as the fluid issued from the orifices, and the invariable
velocity which established itself in equilibrio with the resistances.
When the canal had scarcely any inclination below a tenth part
of its length, there existed little or no uniformity between the
primitive and permanent velocity. M. Bossut attempts to make
several applications of his experiments to rivers ; among others,
to the Beuvronne, which he found to have an inclination of
sg nearly, the same as the Seine at Paris*, although the
velocity of the Beuvronne, as compared with the velocity of the
Seine, was as 36 to 100, and the quantity of water passed
through the respective sections was as 1 to 278 ; from which he
deduced that with equal inclinations the greatest quantities of
water have the greatest velocities, but that the velocities do not
augment in the ratio of the quantities of water; hence the
reason, according to him, that when two rivers unite into one,
the capacity of the channel of the united river is always less than
the sum of the capacities of the minor rivers taken conjointly :
these minor rivers may also have different inclinations and velo-
cities than the united river. He differs in some respect from
the principles of Genneté, but agrees with him in the inutility
of derivations from rivers, and very properly refers to M. Du-
buat for more precise information on the subject.

__ Inspired by the perusal of Bossut’s work, Dubuat endeavoured
to investigate the subject de novo, by considering, that if water
was perfectly fluid, and received no impediment from the surface
over which it moved, it would be accelerated in the same man-
ner as bodies running down inclined planes; but as this effect
was found not to take place, he concluded that there existed a
certain. degree of retardation arising from the friction of the
channel or the viscosity of the water, and that when water ran
uniformly in any channel whatever, the accelerating force was
equal to the sum of the resistances. This principle, as we have

| seen, had been long known in Italy. Encouraged by this

th ' )
~ * According to later observations the inclination of the Seine varies from

1834, 26

450 FOURTH REPORT—1834,

apparent discovery, Dubuat endeavoured to render the experi-
ments of Bossut conformable to it, and in the year 1779 pub-
lished his Principes Hydrauliques.

Dubuat felt, however, that his theory required further elucida-
tion, and having undertaken a more extensive series of experi-
ments, published the result in three volumes in the year 1786*.

The first two volumes treat of the uniform and variable mo-
tions of water in rivers, canals, and pipes; the origin of rivers,
the establishment of the beds, and the effects of dams, sluices,
bridges, reservoirs, and fountains; the navigation of rivers and
canals, and the resistance of fluids.

The last volume treats of the mechanical properties of ztherial
fluids as affected by heat. Dubuat had been long sensible of
the unsatisfactory state of the theory of the motions of rivers
and the difficulty which surrounded the discovery of a true
theory, conceiving that.every river ran with an uniform velocity
peculiar to itself, and that the velocity in the middle was greatest.
He believed that the formation of bends in them was owing to
obstacles ; that the development of their curves was in propor-
tion to the mean radius: and having traced geometrically the cir-
cumstances of his hypothesis, he had recourse to analyses, out of
which he formed equations applicable to practice; and haying
observed frequent changes in rivers from floods and other causes,
he concluded, that it was easy to find the expenditure of a river in
any part of its course by calculating the annual produce of the
rains which fall upon the surface of the surrounding country,
deducting a certain proportion (4th) for filtration, evaporation,
&c. Hence the total expenditure of a river is deduced by the
product of its mean section and mean velocity. The author ap-
plied his principles to the river Seine; he examined different
cases of the expenditures of water, and added new expressions
for each to his formula of uniform motion; and in the case of
great rivers which are difficult to submit to experiment, he as-
similated their motions to the motions of fluids through conduit

ipes.
“~ commenting upon the experiments of Bossut, he says,
“‘ The experiments which occasioned the greatest ‘difficulties
were those on rectangular and trapezium canals, in as much as it
was found very difficult to render the motion of the current uni-
form ; but we have been amply recompensed by the experiment
which we had occasion to make on the diminution of the velocity

* Principes d Hydraulique vérifiés par un grand nombre d’ Expériences faites
par Ordre du Gouvernement; Ouvrage dans lequel on traite du Mouvement uni-
forme et varié del Eau dans les Rivieres, les Canaux, et les Tuyaua se Con-
duite, §c.: par M. le Chevalier Du Buat.

REPORT ON HYDRAULICS.—PART II. 451

of a uniform current, reckoning from the surface to the bottom,
and by very curious observations on the mode in which the
water corrodes the bottom, according to the kinds of soil, such
as gravel, sand, and clay, which constitute it.”

After recapitulating the various principles laid down in his
first edition relative to the effect of bridges, sluices, aque-
ducts, &c., he develops the fundamental principles of uni-
form motion, the causes which create, and the resistances which
affect it, which latter he makes proportional to the squares of the
velocities ; he gives a formula for uniform motion in any channel,
and then shows by experiment and by analyses the causes of va-
riation, what amount is due to friction, and what to adhesion or
viscosity. By this means the law of motion is developed from
infinite velocities to its total cessation. These elements deter-
mined, he examines the nature of the different beds over which
rivers run, whether natural or artificial; the effects of floods or
the affluents of rivers, shortenings, swellings, derivations ; the
forms most proper for canals, the piers of bridges ; and illustrates
the whole by a great variety of experiments, which are extended
to the resistance of fluids.

‘Dubuat values the effect of viscosity at 0-3 of an inch:
the mobility of water he limits to ane of the inclination, and

considers gg to be the smallest possible inclination that can
be given to a canal to produce sensible motion. He cites several
experiments made by him on an artificial canal with an inclina-
tion of 5,45, which gave only a velocity of 6 inches per second,
whilst in a drainage canal with an inclination of 57% the velocity
was only 7 inches per second, and in a part of the river Hayne
having an inclination of 55-000 the velocity was 10 inches per se-
cond, so that the velocity was greatest with the least inclination.
Dubuat adds, “it is impossible to reason against facts.” The
anomalies which prevail throughout the whole of Dubuat’s work
render many of his conclusions very doubtful. The principles
upon which Dubuat founds his theory of uniform motion are:
_ Astly, That water is composed of molecules perfectly spherical,
hard, and polished, but gifted with a certain degree of tenacity ;
_ 2ndly, That rivers cannot run without a certain degree of in-
clination in their surface ;
_ _ 3rdly, That when the mean velocity of a river is uniform, the
accelerating force is equal to the resistance of the bed ;
_ Athly, That it is the tendency of every mass of water to form
‘its own bed by filling up the inequalities of the bed itself ;
~ 5thly, That the surface of this bed consists of an assemblage
of molecules or globules, over which the other globules glide,
2G2

4.52 -FOURTH REPORT—1834.

and from which results a resistance proportional to the square
of the velocity with small velocities, and diminishing to nothing
in high velocities, the relation between the velocity and inclina-
/ mg
Vb—-LVvb+1°63
6thly, That the resistance which the whole mass experiences
from the friction of a part of it against the bed, is in the direct
ratio of the bed, and inversely as the section ;
7thly, That each molecule experiences a resistance in pro-
portion to its distance from the bed ;
8thly, That these velocities taken conjointly produce a mean
velocity, which leads to the following general expression :
gee 297 (Vr — 01)
V¥b—-LVh4+16
M. Dubuat considers that the amount of friction being pro-
portional to the extent of surface, and the circle containing the
least perimeter, that figure is preferable for pipes on account of
presenting less friction, but that rectangular figures are preferable
for aqueducts, and trapeziums for rivers, from the nature of the
channel and the velocity in all cases being sensibly proportional
to the square root of the mean radius of the bed: it follows that
a trapezium in which the breadth at the bottom is 3 of the
height of the water, and the slope of the sides 4 of the depth, will
give the least resistance.
The following are the results of his experiments :

tion being expressed by V =

—0°3(/7r—'01).

Inches.
Pine gravel ee ee eS, ees 4 per second.
Middling ditto. ........ oi) J ditte,
eangie wlsttes of) 0M Se dnc RT 12 ditto.

Gravel of the size of anegg. . . 36 ditto.

Hence the reason why in the channels of rivers there is necessarily
a relation between the tenacity of the soil and the velocity of their
currents ; and in general, if we call qg the relation to the breadth
: andr = —4 ‘
+2 ~ g +2’
or if the depth be undetermined and the breadth be finite, we

and depth of a ehannel, we shall have 7 =

shall have r = es and, vice versd, if the depth be finite and the

breadth undetermined, we shall have » = h. So that in rivers
in which the width is very great in proportion to the depth, we
may without any sensible error take the depth for the mean ra-
dius, and in this case their mean velocities for equal inclinations

REPORT ON HYDRAULICS.—PART II. 453

are as the square roots of their depths. We have, therefore,
formulz for calculating the different cases (two of the data
being given,) of the breadth, depth, mean radius, velocity, and
inclination, derived from a table of experiments on trapeziums
and rectangular canals, on the canal of Jard and the river
Hayne. In order to facilitate the use of these tables the late
Professor Robison reduced them for his Mechanical Philoso-
phy*: they have since been greatly enlarged by Mr. Laurie of
Glasgow, but are now ina great measure superseded by the
more accurate researches of Kytelwein.

Forthecurvesandsalientangles of rivers, and during permanent
and periodical floods, the author endeavours to establish theories
which have no relation to the actual state of things ; but it results
from his observations that an inclination of ;535, only produces
on account of bends a velocity due to z;4535- In applying his
formula of uniform motion to the course of rivers, he compared
the velocities: of the Seine and Loire in their mean state: he
found that the mean inclination of the Seine was 1 metre for
100 toises, or 7455; that its mean depth was 3 feet 7 inches, and
‘its mean velocity 25 inches per second ; and as the theoretical
velocity of an inclination of ;,55 gave 26 inches 10 lines instead
of 25 inches, the excess was occasioned by friction and the bend
of the river. In the Loire the inclination was 2 metres per 100
toises, or 4'55, the mean depth 34 inches ; but the velocity due to
the depth was 38 inches per second, consequently ;!, was lost
by friction and adhesion; the actual velocity being 35 in 6

ines.

In regard to the velocity, Dubuat may be said to have dis-
covered the following laws:

1st, In small velocities, the velocity in the axis is less than
that at the bottom ;
_ 2nd, This ratio diminishes as the velocity increases, and in
very great velocities approaches to the ratio of equality ;
_ 3rd, Neither the magnitude of the channel nor its slope has
any influence in changing this proportion while the mean velo-
city remains the same, whatever be the nature of the bed 5
. 4th, When the velocity in the axis is constant, the velocity
at the bottom is also constant, and is not affected by the bottom
of the river or the.magnitude of the stream. t

In some experiments the depth was thrice the width, and in
others the reverse, without any change in the ratio of the velo-
Cities. Another most important fact discovered by him is, that

_ * See an excellent article on Hydrodynamics in Brewster's Edinburgh En:
cyclopedia. 3 hi

4.54 FOURTH REPORT—1834.

the mean velocity in any pipe or open stream is an arithmetical
mean between the velocity in the axis and the velocity at the
sides of the pipe or bottom of the open channels.

Let V be the mean velocity, uv the velocity at the axis, wu the
velocity of the bottom :

u= VWvy—1 and V= "2",

also v= (“WV —i + }3)* and v= (Wu + 1)°
V=(Yu—4) +4) andV=(VWu+3)P4+4
u= (Vv —1)° and w= (WV — i — })*.

Also v —u=2 /%V—4 andv—V=V—u= VV —3;
that is, the difference between these velocities increases in the
ratio of the square roots of the mean velocities diminished by a
small constant quantity. The place of the mean velocity in mo-
derate velocities is about ith or 4th of the depth from the bottom ;
in very great velocities it is higher. (See Dubuat’s Table of Velo-
cities, also Robison’s Mechanical Philosophy and Theory of
Rivers.) There are, however, anomalies in these principles which
render their application extremely doubtful. It is unnecessary
to enter into detail of Dubuat’s method of rendering rivers na-
vigable by increasing their breadth or by diminishing their incli-
nations, nor of the different cases of the motions of canals for
irrigation or drainage, and the effect of obstruction, such as
bridges, sluices, dams, &c.; they have been investigated very
fully by Professor Robison and by M. Le Creulx*.

Such is a brief outline of Dubuat’s workt, ingenious in many
respects and abounding with new views and valuable suggestions ;
but whoever has had occasion to investigate the uncertain mo-
tions of rivers will find that the analogies attempted to be derived
from the motions of water in pipes and artificial channels are
extremely vague. His formula of the uniform motion of water,
modified as it is by contraction and resistances, approximates
very nearly to reality. In all cases his theory of the effects of
curves is quite contrary to nature, and this he acknowledges in
reference to several experiments in the Seine and Marne rivers.
His application of his theorem of the expenditure, velocity, and
inclination of the surface of a river being known, to determine
the dimensions of the bed, is necessarily incorrect.

* Examen Critique del Quvrage de M. Dubuat sur les Principes del’ Hydrau-
lique: par M. Le Creulx. Paris 1809.

+ Elements of Mechanical Philosophy, vol. ii., edited by Dr. Brewster; and
Theory of Rivers.

eat es.

REPORT ON HYDRAULICS,—PART II. 4.55

Neither do the results of his experiments on the amount of
expenditure correspond with those deducible from the rate of
inclination of the surface.

_ The uniform motion which he has supposed in rivers scarcely
exists in nature.

The article on rivers contained in the fourth volume of the
Architecture Hydraulique, by Belidor, published in 1759, is
compiled from the works of Guglielmini and Michelini.

The Nouveaux Principesd Hydraulique of Bernard, published
in the year 1787, contains much that is valuable relative to the
origin, formation, and establishment of rivers.

His theory of the efflux of water from the sides of a prismatic
vessel and along aninclined channel, and the pressure sustained
by adiaphragm placed at one of its extremities, is founded upon
the principles of Bernoulli, D’Alembert, Bossut, and Dubuat ;
the practical applications are derived from Guglielmini and other
writers. His observations on the inclinations and velocities of
several of the rivers in France, such as the Saone, the Durance,
the Rhone, led him to conclude, that there existed no precise
rules in these respects. In several, the mean velocity was found
to be ths of the depth.

According to Lalande, all rivers increase the height of their
waters as they approach their embouchures; the Saone was
observed to swell higher at its confluence with the Rhone, at
Lyons, than a league above it.

Bernard concludes with Frisi, that the gravels found in the
beds of rivers are not owing to the attrition of rocks and larger
stones in the upper parts of the beds of rivers, but that they
exhibit themselves accidentally, accordingly as they are traversed
by the rivers. The swell and consequent action of rivers are
greatest at their points of junction. Inundations are greater in
the superior than in the inferior parts of rivers, on account of
the pressure of the upper waters, although the velocity of the
lower waters be greatest. The same had been remarked by
Castelli and other writers.

_. The banks of the Po are 20 feet in height at 50 or 60 miles
Sastance from the sea, whereas at 10 or 12 miles distance from the
sea the banks are only 12 feet in height, whilst the breadth of
the river is the same in both places.

Amongst the subsequent writers of the French, German, and
Dutch schools, may be mentioned Fabre, Lecreulx, Sturm,
Leupold, Meyer, and Brunnings.

All of them merit attention, from the many valuable observa-
tions with which they abound relative to the natural phenomena
of rivers, but it is doubtful whether they have advanced the
science.

456 FOURTH REPORT— 1834.

In the years 1789 and 1790, Brunnings undertook an exten-
sive series of experiments for the purpose of determining the
relation between the superficial and mean velocities of the Rhine
and Waal rivers which traverse Holland. For this purpose he
constructed an ingenious tachometer upon the principle of ex-
posing a disc of wood or metal of any given magnitude to the
direct action of the current at different depths, so that by the
pressure of the disc against a lever placed above, the pressure
and consequent velocity was indicated very nearly.

The results are shown in the following Table :

Experiments
of
Ximenes
on the
Arno.

Velocity.

Rivers. | Depth.

Surface. Mean.

Waals) G44 1°57 0-670 0-627 0:934

tte) 3352, aR 1°57 0-708 0°664 0:938
Lower Rhine . 1:88 0°874 0-779 0°892
1 NS ee on 2°51 1-001 0:926 0:925 -
Higher Rhine . 2°51 1:097 1:058 0:965
Issel Apa 2°82 1-283 1-218 0-965
Dittor Fae eG 2°82 1-289 1-243 0-965
Lower Rhine . 2:82 1:307 1-259 0:963
Waals waded tix 3°45 1:025 0:938 0-915
Lower Rhine . 3:45 1-379 1-520 0-957
Higher Rhine . 3°76 1-307 1-220 0-936
Lower Rhine’ . 3°76 1:397 1-286 0-921
Ditto". uoa 3 3°76 1-416 1:361 0-962
Dittoretyyd seyess 3°76 1:433 1:369 0:954
LD ae oy 4-08 1:484 1:341 0:934
0 eS eee 4°39 1:184 1-068 0-902
Ditto-ete. 4°39 1°226 1-131 0-923
Higher Rhine . 4°39 1-467 1:332 0-908
ATOs ie Chior ceric 4:57 1:004 0°923 0:919

Admitting, however, the accuracy of these experiments, it is
difficult to come to any other conclusion than that of a gradual
though feeble diminution of the velocity (about 75th) between
the superficial and mean velocity.

Woltmann regarded the diminution according to the ordinates
of a parabola reversed.

Funk substituted the logarithmic scale, namely, whilst the
depth increases in an arithmetical progression, the velocity de-
creases in a geometrical progression.

Eytelwein, finding that no constant law could be discovered
by his experiments, finished by admitting, by way of approxima-
tion, a decrease of velocity in an arithmetical progression, and a

REPORT ON HYDRAULICS.—PART II. AST

diminution of jth of the superficial velocity for each metre in
depth, so that v being the velocity, dthe required depth, the
mean velocity of the particles will be v (1 — 0°0125 d).

But the experiments of Brunnings do not authorize such a
conclusion.

The tachometer of Woltmann, published inthe year 1790, was
constructed upon the principle of the common windmill, and
consisted of four small vanes, attached to an axle and connected
with wheel-work : the instrument, being exposed to the direct
action of the current at different depths, indicated by the number
of its revolutions the velocity of the stream.

The following Table gives the result of some of the experi-
ments made by Funk (amongst others on the Elbe and Weser,)
on the superficial and mean velocities of different parts of the
same section of the river contrasted with the experiments of
Dubuat.

Mean Velocity according

Partial Sections. Velocity Expense according to

of the pede’
Section | Depth. | Area. Surface. Experiment.| Dubuat. | Experiment.

Metres. |Sq. Mets,| Metres. Metres. Metres. Cub. Met.
0°55 {| 12°31) 0°403 0°403 0°315 4°96
0°91 | 16°75} 0°471 0-442 0:370 7-41
2-70 | 36°05) 0:431 0°267 0°337 9-62
6°28 | 40°78} 0°451 0:264 0°353 10°78
6°71. | 50°12} 0°412 0-248 0°322 12°44

Total |156:°01 45°21

_ The following experiments, by Brunnings, on the velocities of
the Rhine, Elbe, and Weser, were also made by Woltmann’s
machine. 3

State of | Mean

Rivers, Water. | Breadth.) Depth.

Inclination.

* .| Metres. | Millemetres. | Metres,
Rhine . . . . . | ordinary 3°63 | 0000115] 0-91

Ditto, at Nimuza . high 4:93 | 0:000115| 1°31
Weser. . +. + + low 1:98 | 0:000411] 1°58
Ditto, at Ktow . . high 4:12 | 0:000550| 2:41

ME Sos te ee ~ low 2°64 | 0°000254) 1°15
Ditto, at Magdebourg | high 4:07 | 0:000363| 1°63

‘It is somewhat remarkable, that the Nouvelle Architecture of
M. Prony, published in 1790, contains nothing relative-to rivers,

458 FOURTH REPORT—1834.

The section on Hydrodynamics is confined to the exposition of
the ordinary motion of fluids, and the resolution of the problem
of the efflux of a fluid from an orifice made in the side of a pris-
matic vessel on the principle of the parallelism of sections.

The discovery of the law of the resistances of a fluid in rela-
tion to the velocity, by Coulomb, paved the way to its success-
ful application to the case of a fluid moving in natural or artificial
channels by Girard; that distinguished mathematician and en-
gineer was then charged with the works of the Canal de L’Ouregq.
The researches made by him on that subject led to the publica-
tion of several memoirs on the theory of running water, in one
of which he proposed the adoption for the value of the resist-
ance, of the product of a constant quantity (determined from
twelve experiments of Chezy and Dubuat,) by the sum of the
first and second powers of the velocity, from which he obtained
a formula applicable to every case; that is, supposing the mass
of water to glide over a film of the same fluid adhering to the
periphery of the channel, the mass is at first retarded by the
viscosity of the rubbing surfaces in the proportion of the
velocity, a second resistance arising from the asperities of the
channel compounded of the number and force of the impulsions
in a given time, and hence proportional to the square of the
velocity.

The analogy supposed by M. Girard to exist between the
motion of water in an inclined channel, and a perfectly flexible
chain placed on a fixed or flexible surface, and his examination
of the best form for the transverse section of a channel, which
he finds to be the arc of a circle, are ingenious conceptions. His
theory of the resistances which influence the motions of water
was first published in the year 1804, and is remarkable for ex-
pressing them by a very simple function, compounded of the
two first powers of the mean velocity, and with more accuracy,
than the formula of Dubuat. Mons. Girard is also the author
of several interesting memoirs on the river and canal of Ourcq*,
the latter of which was laid out upon the funicular principle.

On the subject of locks for navigable canals, M. Girard devotes
three memoirs, for the purpose of developing the advantages
ebtained in point of economy, by reducing the height of locks.
The system is explained with that simplicity and elegance which
characterize the writings of this author. The conclusions, how-

* Mémoires sur le Canal de L’Ourcg et la Distribution de ses Eaux, le Deseche-
ment et U Assainissement de Paris et les divers Canaux navigables qui ont été mis
en Exécution ou projetés dans le Basin de la Seine pour l'extension du Commerce
de la Capitale. Tome 1. Paris 1830.

REPORT ON HYDRAULICS.—PART II. 459

ever, have been contested by several engineers, and by M. Mi-
nard in his Observations sur un Systeme @ petites Chutes.

_A fourth memoir*, published in the year 1826, examines the
question of the relative advantages and disadvantages which
belong to the conjoined or separate systems of locks. In this
memoir, M. Girard examines, under the different circumstances
of evaporation and filtration, the quantity of water necessary to
maintain a navigation of any given extent, the conditions of
which cannot always be fulfilled.

M. Girard refers the failure of all the schemes, hitherto pro-
jected, for the purpose of replacing the defects of the common
lock, to the impossibility of resolving the problem completely,
without an unnecessary expenditure of mechanical force, and
therefore reduces the maximum effect of the common lock to
questions of the comparative time and economy required by
boats for passing insulated or conjoint systems of locks. The
expression for the latter case is singularly modified in favour of
small rises of locks, when the boats pass in succession, and is
in favour of the conjoint system with regard to time.

2svan
In the formulat, number 4, T = = + boty = the

ovg g 2
time employed by the boat in passing through a number 7, of
simple or isolated locks, distributed over the total inclination o.
The author does not take into consideration the stoppage of the
boat, and consequent loss of time occasioned by the repeated
changes in the force of trackage required by the isolated system.
The value of the water lost can only be contrasted with the value
of time under certain circumstances; the question had already
been discussed, by Gauthey and others, with reference to the
locks of the canals of Briarie and Languedoc. An abstract of
M. Girard’s other hydraulic researches has already been given

; -* Quatriéme Mémoire sur les Canaux de Navigation considérés sous le rapport
de la Chute, et de la Distribution de leurs Ecluses. Pay M. Girard.
_ + The following are the formule:

a= the total height to overcome.

12¥%@ (n—1+ V/ vhs, s = the surface of the gate.
ov g Jn o = the orifice or sluice for filling
the lock.

9 iva Casati Oa g = gravity.
or bod bakes apa n n' = number of locks.
g ws L N= number of boats together.
4, 1 = section of canal.
3 Vnn! +2 i = space passed over the platform
“N= ore Vs ; in a second of time.
s = length of the lock.

460 FOURTH REPORT—1834.

in the first part of this paper. As we before stated, M. Prony
confined himself in his great work on Hydraulic Architecture to
the consideration of the dynamics of fluids; but in the year
1801, having been called upon by the Ecole des Ponts et Chaus-
sées to report on the produce of the streams which were re-
quired to supply the summit level of the canal that joins the
rivers Somme and Scheldt, M. Prony investigated the subject
with his usual sagacity, and the result was the publication of his
work, in the year 1802, on the measurement of streams*. His
method was to inclose a certain portion of the channel of the
stream by means of dams thrown across it at certain distances
from each other; and, by noting the time required to fill or empty
the space so inclosed, the volume of water which passed through
a given section in a given time was easily ascertained. M. Prony,
however, does not deny the superiority of the system (where
practicable) of ascertaining the expenditure of streams by means
of recipients of any given capacity; but it is in his Physico-
Mathematical researches + that he developes his general prin-
ciples of fluids. ;

The principal results are : .

lst, That a fluid, such as water, which runs through a pipe
or canal of a sufficient length to establish.an equilibrium, ex-
periences resistances which are equal to the force of gravity,
and produce uniformity in the motion of the stream;

2ndly, That although the experiments of Amontons and
Coulomb on the friction of solids give the results in the direct
ratio of the pressure, the experiments of Dubuat, Dobenheim
and Benezeck on the friction of fluids show that pressure has
little or no effect ;

3rdly, That in every transverse section the different molecules
taken perpendicularly to the section move with different velo-
cities; but that there is a point where the velocity is a maximum,
as in the centre of a pipe or at the surface of an open canal,
and that from these centres there is a progressive diminution of
velocity towards the periphery ;

Athly, That besides the maximum velocity, there exists a
minimum and mean velocity, by which the motion of the general
mass is regulated;

5thly, That when the fluid runs through a pipe or channel
capable of being wetted, a film or bed of fluid adheres to the
interior of the pipe or channel, which is the true bed of the fluid
mass in motion ;

th: Jaugeage des Eaux Courantes: par M. Prony. Paris 1802.

+ Recherches Physico-Mathématiques sur la Théorie des Eaux Courantes :
par M. Prony. Paris 1804.

— 2s +

Pas ee a ae eee ie ee

REPORT ON HYDRAULICS.—PART II. 461

6thly, That the experiments of Dubuat with pipes and chan-
nels composed of different substances are in accordance with
this doctrine ;

7thly, That the adhesion or cohesion of the particles of the
fluid to each other, and to the surface of the pipe, require to be
represented by different values, capable of being compared with
each other.
_ The remainder of M. Prony’s physico-mathematical researches
is devoted to the examination and determination of the general
relations which subsist between the longitudinal and transverse
sections to the perimeters, and the velocity of the water under
the influence of friction and viscosity ; the whole is illustrated
by tables and formule derived from numerous experiments by
Couplet, Bossut, Dubuat and Chezy. :

The corps of engineers of roads and bridges of France have
contributed largely to our knowledge of the theory of rivers, and
the numerous experiments which have been undertaken by dif-
ferent engineers of that body have confirmed in a great degree
the theories advanced by preceding writers. ‘The experiments
which merit the most attention are those of MM. Raucourt and
De Fontaine; the former on the river Neva at St. Petersburgh,
and the latter on the river Rhine.

The object of M. Raucourt’s experiments was to ascertain
how far the law of the velocities coincided with the theory of the
motions of water in pipes and open channels when the river was
frozen, and when free from ice.

_ Accordingly, he embraced the opportunity of the Neva being
frozen over in the year 1824; and having selected a place where
the width of the river is 900 feet, and the greatest depth 63 feet,
and the section very regular, and consequently assimilated to the
case of an immense pipe, he provided an instrument, constructed
on the principle of the common ship’s log, and ascertained the
velocities by sinking the instrument through several holes made
in the ice at proper intervals ; the maximum velocity was found
to be a little below the centre of each vertical, and diminished
as it approached either bank of the river. The ‘same relative
velocities, differing only 3th from each other, were found to
prevail after repeated trials. The results were, that the greatest
velocity was found to be a little below the centre of the deepest
vertical :
ft. ins.
viz. 2 7 per second.

1 11 ditto .... near the top. bet
1 8 ditto... . near the bottom. *

In the summer of the year 1826 M. Raucourt’ performed

462 FOURTH REPORT—1834.

similar experiments on the same river, both in calm and windy
weather: the maximum velocity was then found to be equal to
the velocity at the surface; but when the surface was affected se
winds, the acceleration was greater. or less.

M. Raucourt’s experiments have been partially tried by
Messrs. Detrem and Henry ; the latter made the relation be-
tween the mean and superficial velocities in the proportion of
0°715 to 0°903, and the product of the Neva 116,000 cubic feet
(English measure) per second: the maximum velocity diminished
from the upper to the lower part of the river from 1°79 metres
to 1015 metres. The inclination per thousand metres was found
to be 0°0267 *.

But the most important observations which have been made
on rivers in modern times are those of M. De Fontaine on the
river Rhine and its affluents.

Having been entrusted with the execution of certain works in
the year 1820, for the purpose of restraining and regulating the
course of that part of the river which adjoins the French territory,
M. De Fontaine felt it his duty to investigate the phenomena
exhibited by that river in different parts of its course, and the
result has been the publication (in the year 1833) of his obser-
vations in detail, in a work, entitled, Travaux du Rhine.
According to M. De Fontaine, the river Rhine derives its origin
from the glaciers of St. Gothard, in Switzerland, whence the
waters run by three principal affluents to Reichenau, where they
unite into one great river; after being increased by numerous
torrents from the Alps, it empties itself into the Lake of Con-
stance, out of which it passes to be precipitated over the falls of
Schaffhausen and Lauffen, and, after having received by means of
the river Aar #ths of the waters of Switzerland, passes through
the great valley which separates the mountains of the Vosges
from those of the Black Forest ; thence it passes through the
narrow defiles of Bingen, thence through Holland, after which
it divides itself into several branches (to one of which it gives
its name), and empties itself into the German Sea above Leyden.
In its course it receives many considerable affluents, such as the
Elser, the Kinzig, the Ill, the Moder, and the Murg on the
French boundary, and the Moselle, Mayne, Meuse, and others
as it approaches the sea; it communicates with the Zuyder Zee
by means of the Isel. The irregularity of its course and the

* Journal des Voies de Communication, 8vo, 1826, St. Petersburgh: “ Sur le
Jaugeages de la Neva et de ses differens bras.”

+ Des Travaux du Fleuve du Rhin: par A. J. C. De Fontaine, Ingénieur en
chef de premiere Classe des Ponts et Chaussées,

a le

eee ee

REPORT ON HYDRAULICS.—PART II. 463

ravages constantly committed on its shores, particularly those
of Alsace, one of the most fertile provinces of France, rendered
the construction of defensive works imperative, and it was to
counteract these evils that M. De Fontaine was selected to fulfill
this important task.

_ The length of the course of the Rhine from Reichenau to the
sea is stated to be 1342 myriametres, viz.

From Reichenau to the French frontier . . . 420

Along the French shore... .....44 « 222
Thence to theisea #3 dws en iediluls due ZOO
1342

_ From careful barometrical observations, the heights of the low
waters above the level of the sea at the following places are :

Metres,
' (At) Reichenaw sexes hele e ohs ind 94°00
i At the lake of Constance ....... 405°00
_ At the bridge of Basle ....... sey 25230
At the bridge of Kehl ........ . 138°96

At the confluence of the Lauter, which

is the limit of the French frontier .

At the bridge of Manheim ....... 93-00

At the entry of the defiles of Bingen . . 67-00

_ The general inclination, according to the three great sections
of the Rhine, is

"
¢

_ Total Fall. Per Metre. j

rom Reichenau to the French fron- Met.

NT eS ee ae a 941°71 0°002242
Along the French territory ...../ 145°30 | 0:000653
Thence to the sea ....-+..--+-{ 40°00 0.000057

a ee

1127-01

7 The part of the Rhine to which M. De Fontaine principally
directed his attention is comprised between Basle and Neubourg,
that being the political limit between France and the German
states. In this part the bed of the Rhine is situated in the
alluvium which forms the bottom of the valley, and through this
the Rhine forces its way by many channels, forming (in its
passage) islands and sandbanks, which render its motions very
irregular both in times of high and low water. Among the

>

464 . FOURTH REPORT—1834.

different channels there is generally one more considerable than
the others, and which forms the navigable channel, or thal-
weg, as it isthere termed. These branches are annually dimi-
nished by artificial works, and it seems probable that in a few
years hence, the whole of the waters of the Rhine will be forced
into one channel. In general, however, the Rhine may be com-
pared in the upper parts above Bavaria to an immense torrent.

The inclinations vary according to circumstances, but the
greatest inclination is near Basle, at low water, on account of
the rocks, which inclination decreases #ths in times of flood.

The inclination of the Upper Rhine, in its mean state, is
0964024 per 1000 metres ; while at the frontier below the con-
fluence of the Lauter, after a course of 222:460 metres along the
French shore, the inclination is only 0°395185 metres per 1000
metres, or a third only of the inclination of the upper part ; then
taking the total fall at 143-935 metres, the mean inclination
would be 0°647015 per 1000 metres, which is nearly the inclina-
tion of the river at Brisack and Sponeck, that is, about a third
of the total length of the river.

The velocities of the Rhine vary not only according. to the
differences in the inclinations, but according to the perpetual
changes which the river. undergoes in its motions from the irre-
gularities in its bed. The following are the velocities :

Velocities per Second.

Names of Places. Low WaterdNiean Wastes. aayauanriaeiale.
ESI S Soe Ad Low Water. | Mean Water. | High Water. —

Met. Met. Met.
1:65 2°25 4:16
Huningen 1-70 2°75
In the angle of Krembs.... 1-88 2°62
Schalampe.. 2°67 2°79
Opposite Vieux Brisach..... 11k) ie) ely”) 5 ll

At Sponeck 1:52 2°87
At Artolsheim 1:97
At Rhinau 2°51
At Guerstheim 2:19
At the bridge of Kehl...... 1:50
At Offendorff 1-40
At Drusenheim 1-49
At Beinheim 1:24
Limit of theBavarian frontier 0:97
At Manheim.........-. aki 0:70

The conclusions are, that the decrease of the velocities is
irregular, and that they do not follow the law of the square
roots of the inclinations, nor the cube roots of the wetted peri-
meters. '

iil a "I sce a a
ne se — o} 2

REPORT ON HYDRAULICS,—PART II. 465

Maximum and Minimum Depths under the mean level of the
Water.
The greatest depths of the Rhine do not exceed, on the ave-
rage, four or five metres, except in particular places, such as the
Rock of Istein, where the depth is. ...... 9°70 metres ;

et See FV EWIET ooh sou, blece eteeettae 700 —
At the Spur of Blodelsheim......... 12:00 —
At the foot of the volcanic rock of Sponeck. 11°50 —
Pat take SXtFEMILY OF CItTO! 6 she) ays epee One —
At the foot of the Glasserwoerth ...... 25:00 —

— Plitersdorff........ 13°60 —

From which it appears that the influence of corrosion is very
great where the current is obstructed, and hence the necessity of
the artificial works undertaken by M.de Fontaine.

Floods.—The floods of the Rhine occur periodically, namely,
from the end of May to the middle of September, during the
melting of the glaciers, after which the river returns to its
ordinary flow. The greatest floods generally happen about
March, after the first melting of the snows, but they occasionally
occur in other months. The rise of the waters at Basle seldom
commences until three days after the greatest rains and meltings
of the snow; the greatest rise in 24 hours never having ex-
ceeded 2°92 metres at Basle in 22 years ; and at Kehl, 1°38 metres
in 27 years. The floods of the affluents (between Basle and
Lauterbourg,) which descend from the Vosges and Black Forest
mountains, are generally over before the arrival of the floods
from Switzerland. This phenomenvn arises from the great
difference which prevails between the sections at Basle and Kehl :
for some time the Rhinometers at the two places indicate nearly
_ equal elevations; but as soon as the floods commence, the eleva-
“tions no longer maintain the same relation to each other; on the
contrary, when the Rhine has risen 0°01 metre at Kehl, it has risen
0°016 metre at Basle; and this relation occasionally ‘varies with
the changes in the two sections. The years 1801 and 1824 were
remarkable for the extreme rises of the waters, not only in the
Rhine but in all the rivers of France.

_ Tables are added in M. de Fontaine’s report showing the maxi-
mum Sh aaa oscillations of the waters at Basle, Kehl, and
Lauterbourg, for 22, 27, and 10 years respectively.

Expenditure of the Rhine.

(From a series of gauges taken at Basle, Vieux Brisach, and
_Kehl, according to the different states of the river at these
places. )

1834. 2H

466 FOURTH REPORT—1834.

The volume of water which passes,

At Basle,
Cub. Met.
During great floods. ..... isequalto 4624
During mean water...... do. 865
During very low water .... do. 330
At Vieux Brisach,
During great floods. ..... is equal to 4630
During mean water. ..... do. 885
During very low water .... do. 340
At Kehl,
During great floods. .... . isequalto 4685
During mean water. ..... do. 956
During low water. ......- do. 380
At Lauterbourg,
During great floods. ..... is equal to 5010
During mean water. ..... do. 1106
During low water. ...... do. 465

From which it results, that the volume of water which passes
per second during great floods, compared with the volume which
passes during the lowest waters, varies from 10 to 1, to 14 to 1;
and in comparison of the mean to the low water, from 43 to 1,
and 53 to 1.

The remaining and indeed principal part of M. de Fontaine’s
report is devoted to an account of the artificial works which have
been undertaken for the purpose of regulating the course of the
Rhine, in which the various kinds of fascines, embankments,
dams, jetties, counterforts, cuts, short channels, and the modes
of defending the banks are all spoken of in detail.

The principles which have guided him in the execution of
these works are,—

Ist, The union of the waters into one channel, and the closing
of the secondary branches ;

2ndly, The avoidance of all rectilinear cuts, and the adoption
of proper curves derived from observations on the rivers them-
selves ;

3rdly, The formation of proper channels corresponding to the
different volumes and velocities of the waters ;

In the first case, the practice of the engineer must be governed
by the volume and velocity of the waters and the nature of the
soil: ;

In the second, by the resistance of the soil :

REPORT ON HYDRAULICS.—PART II. 467

In the third, by the amount of the high, mean, and ordinary
volumes of water.

The velocity of the waters of the adjoining part of the river
must also be considered.

The advantage of the curvilinear directions is, that the force of
the centrifugal projection of the current on the concave side of
the river can be more easily counteracted.

The proper determination of the radii of curvature for the cuts
must depend on the inclination and force of the current ; and
from careful observations of the lengths of the curves in different
parts of the rivers, M. de Fontaine determined the maximum
lengths of the radii of curvature at 2200 metres where the depth
in the curved part of the river was 15°36 metres, and where the
_ corrosion did not exceed 11 metres in depth in the curve; he
fixed the minimum length of the radius at 1250 metres.

|

_ Declivities of the Rhine, from a series of experiments made

| with the Stromm Messer of Woltmann, on the velocities of
the Rhine in different sections, according to the following

Surface Mean
f Space of the Velocity
! st , sed | Velocity] Average Section of < deduced
| Velocities at different parts per | Velocity Motion after the
_of the Section. 5 of the : Formule
} i different * | of that of
Strata. the Surface.

Met.

sere

0-8347 ceo 1:0131117 | 0°84426 APLEPS

- tion of the two
divisions........
0-90 met. below.....

1:00

1:10 or
1-10 met. from the 44
, bottom....

BOttOM ...cccccccccsave cocleccoccsccecelece

—
acfy zi

rs
“_

Note.—These velocities have been taken from experiments made over an
extent of 60 metres, by means of a float, so suspended that its specific weight
did not exceed that of the water.

4

Qn 2

steers

468 FOURTH REPORT—1834.

The conclusions from the preceding observations, are,

Ist, That the greatest velocity is at the surface :

2ndly, That the velocity (which at first diminishes insensibly
downwards,) decreases rapidly towards the bottom, ina ratio de-
pendent on the nature of the bed:
. 3rdly, That supposing two right lines to pass through the
extremity of four ordinates, determined by experiment, and
conveniently chosen in the curve, which should pass through
all the points obtained, the ordinates of these right lines, cor-
responding to the velocities observed in the other points, will
differ little in the numerical expression of these velocities :

4thly, That the point of intersection of two right lines which
each partial surface of partial motion circumscribes, has for its
ordinate a numerical value which differs very little from the
mean velocity expressed by the quotient of the surface of mo-
tions divided by the depth of the water:

5thly, That the mean velocities resulting from the preceding
observations are greater than the mean velocities deduced from
the velocity of the surface by means of the formula adopted for
gauging streams :

6thly, That the position of the ordinates, which expresses
the mean velocity of each surface of partial motion, is nearer
the bottom than the surface, or 2rds of the depth, reckoning
from the surface, and } the depth when the bottom is very
regular.

Forms of the Surface of Rivers.

Opinions vary very much on this subject; some maintain
that the surface is convex, others concave, and others horizontal.
M. de Fontaine finds the form of the surface to vary accordingly
as the river is rising, falling, or slack.

After explaining in detail the principles which have guided him
in regulating the course of the Rhine between Basle and Lau-
terbourg, a distance of 194,490 metres, M. de Fontaine gives
the following Table as the probable results of the action of the
river when turned into the new course.

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469

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470 FOURTH REPORT—1834.

Although the lock had been long known in Italy, its introduc-
tion into France did not take place until the reign of Francis the
First, when a lock was erected on the river Ourcq, by Leonardo
da Vinci. The improvement of the navigation of the Seine, and
the junction of the Seine and Loire, were preludes to the execu-
tion of the canal of Briare under Henry the Fourth, in the year
1605, terminated in the year 1642 under Louis the Thirteenth,
and which was followed by the canals of Orleans, of Lourg, of
Beaucaire, and the junction of the Mediterranean and the Atlan-
tic seas by the celebrated canal of Languedoc, executed by Riquet
in the reign of Louis the Fourteenth, so well described by La-
lande, Andréossi, Gauthey, &c., and since made the subject of
the scientific researches of Navier, Prony, and Girard. The
works of Huerne de Pommeuse, of Becquey, of Brisson, and
Dutens show the advanced state of the canals of that country.

The following is a general statement of the canals of France,
according to M. Dutens.

Length. Estimated Cost.

Met. francs. ens.
Ist. Canals comprised in seven
lines of junction of the two 3°068°876-90* 306,429,601 50
s

sea
2ndly. Canals leading to Paris......} 1°020-022-64 143,935.916 0

Secondary or projected Canals.

1-955+200-00 114,682,870 00
6°511-200-00 578,297,863 50

1,138,346,251 0

On the subject of regurgitations, or the swelling of rivers, by
obstacles placed in them, such as dams, weirs, jetties, bridges,
or contractions of their channels, it only remains to notice the
experiments of Eytelwein, Bidone and Funk.

An abstract of Eytelwein’s experiments, by the late Dr. Young,
has already been given in the former part of my Report. When
the motion of a river is obstructed by a dam placed directly
across it, the surface of the river rises, and the water passes over

* The author of this paper is indebted to M. Le Grand, Directeur Général
des Ponts et Chaussées, &c., Conseiller d’Etat, for a detailed statement of the
canals of France, from which the total length of the seven great lines of junction
is 3,679,033 metres.

+ Rapport au Roi Louis XVIIT. pour l’'an 1820, sur la Navigation Intérieure
de la France: par M. Beequery, Conseiller d’Etat, Directeur Général des Ponts
et Chaussés.

rs
©

——————_ss se

eS)

REPORT ON HYDRAULICS.—PART II. 471.

the dam. The height of the river above the dam will be the
quantity designated by H in the formula, now adopted by
Messrs. Poncelet and Lesbros, for the expenditure through
notches in dams, where a = 1°80 HH, where 1°80 is the
value of m in the expression of 3m / 2g = 0°610; if therefore
bbe the height of the dam from the bottom of the river, and b’
the depth of the water before the erection of the dam, the height
of the swelling of the water will be H + b — b/, as we before
stated. The merit of having discovered the true law of the
expenditure of water through notches in dams belongs to
M. Bidone*, but he has carried his researches still further by
his valuable experiments on the effects of dams and other ob-
structions in raising the surface of running waters.
The following Table gives the results :

: Difference between
the two amplitudes|
afterwards.

Current without the Swelling.
Expendi- Dam. Height
ture per of the .
Second. Dam. Height

Ampli-

tude. Ob-

served.

on the
Dam

Hydrostatic

Met. Cub. 6 Met. | Met.
0°102 | 4°33
0:100 | 4:87
0-102 | 5-70
0°102 | 6°53
0-137 | 3°66
0-140 | 4:44
0:0351 0-148 | 5°22
0°144 | 5-87
0:143 | 6:69
0°167 | 3-36
0:0467 0-168 | 4:09
0-167 | 4:70

0:0208

a

Dubuat was the first who turned his attention to the forms
and extent of swellings. Observing that the depth of the water
towards the dam increased, whilst the velocity decreased in the
same proportion, he concluded that the surface was a concave,
similar to an arc of a circle, and calling H the height of the
swelling, » the inclination of the current before the erection of the
dam, and p! the inclination of the swelling immediately in front

of the culminating point, which he makes equal to ee -

* «« Expériences sur la Dépense des Réservoirs,” par George Bidone, 1824,
tom. xxviii. des Mémoires de ! Académie des Sciences de Turin.

72 FOURTH REPORT—1834.

is the hydrostatic amplitude; and as p! is very small in —
tion to p, the one amplitude ‘will be double the other. :

Funk, after having demonstrated that Dubuat’s method gave
too great an excess, admitted that the surface was a concave:
arc of a parabola, at a distance from the dam of twice the hydro-
static amplitude, of which the perimeter would be } H'p; con-
sequently at any distance from the dam, the height of the swell-

ing below the surface of the current is 2H’ —p a — / H!2 — 1H!
pa. When aaa this height is zero, from whence the point or
the surface of the swelling joins the current. The amplitude
will then be ae or 1} time the hydrostatic amplitude.

The following are the results :

Amplitudes.

By Observations. | By Calculations.

Metres. Metres.
7127 7007
5868 6984
1940 2128

785 900

This question has also been examined by Messrs. Bélanger
and D’Aubuisson*.

In like manner the contractions of rivers, by natural and ar-
tificial causes, occasion a rise in the surface of the water equal
to the difference between the heights of the water before and
after the contraction: the same applies to the piers of bridges
and to jetties ; both cases have been examined by Dubuat, Eytel-
wein, and Funk. Funk in particular made several experiments
on the swell occasioned in the river Weser by the bridge of
Minden. The mean breadth of the river was 180°71 metres, the
mean depth 5°37 metres; the produce of the water was 1318
cubic metres ; the height of the swelling was found to be 0°383 ;
the sum of the openings of the bridge was 96:03 metres ; the
velocity of the river before the swelling was 1°358 metres
(= ‘tay x os; ) ; but the velocity of the upper surface of the

* Page 162 of the Traité d Hydraulique & l'usage des Ingenieurs ; par J.T.
D'Aubuisson de Voisins: Paris 1834. See also Venturoli di Meccanicae d’ Idrau-
lica. Milan 1818.

REPORT ON HYDRAULICS.—PART II. 473

river is generally ,1,th greater than themean velocity v= 1-494 met.
As the current, however, was prevented from entering the arches
by fenders, placed to protect the piers from the ice, it was meces-
sary to adopt Eytelwein’s coefficient of contraction, or 0°855 ;
L, or breadth of the river, being 180°7 metres, and A, or depth
of the river, being 53°7 ; from which we get the numerical value
ltt 4: ie | (1°494)? 180°7 x 5°37 3
of x,which is equal to De S855 x 96 (537 +2) 1 }
7 5°37
Neglecting 537 ae
we have the first value of ......... = 0°437 metres.
eeeenCh Ta". Ue ree ne he SRN: . = 0358 —
SE ee LOPE. er ee ee ee ee RESTO ia
fourth and last, being the result of calculation, = 0°369 —
whilst that of the experiment is ....... =0°383 —
but such results must necessarily depend upon circumstances.

Progress of Hydraulic Engineering in England with reference
to Rivers, Canals, and Drainage.

Though practical works in hydraulic engineering of great mag-
nitude and extent have been carried on in England, the applica-
tion of this science to rivers has made little or no progress here
since its first introduction from the Continent. The demands of
of commerce have made us partially acquainted with some of the
common phznomena which they present; but the laws which
govern their motions, under all the variable circumstances to
which they are subject, are involved in mystery. The principles
upon which the earliest Acts of Parliament were framed for the
conservancy of our rivers consisted in deepening, straightening,
and embanking them where necessary, and, by means of sluices
and weirs, penning up or lowering the surface of the water for
the purpose of producing flashes and overcoming the obstruc-
tions to navigation. Experience had, however, shown that na-
vigations of this sort were liable to perpetual degradation, from
the alterations produced in the regimen of the rivers by such
artificial works, which frequently augmented instead of remedy-
ing the evil, whilst they obstructed the general drainage of the
country.

_ The circuitous navigation and the trackage against the stream
were at all times laborious and dilatory; these difficulties sug-
gested the propriety of deserting the natural bed of the river,

_* and led to the formation of separate cuts with the pound locks*,

_ * The first lock in England is supposed to haye been erected in the year 1675,
on the Exeter navigation. 7 :

A474 FOURTH REPORT—1834.

and the various contrivances which were subsequently invented
to supersede their use. Until the invention of the lock, therefore,
very little could be done in the way of inland navigation, ex-
cept in the fens, when connected with drainage; accordingly
the most ancient attempts of this kind are to be found in the
Carr and Foss Dykes * by the Romans,—the former skirting
the uplands and fens from the river Nene at Peterborough to the
river Witham near Lincoln, by a canal of forty miles in length,
and the latter, which connects the Witham at Lincoln with the
Trent above Gainsborough, by a level cut of eleven miles in
length.

The works also undertaken by the Church in the great level
of the fens, such as the cut from Peterborough to Guyhern by
Bishop Morton in the year 1478, and afterwards perfected by
Charles the First, conjointly with the Bedford Level adventurers,
may also be mentioned.

Superficial Content of the Fens adjoining the Wash.

Between the high lands on the south and south-east,

and the Great Ouse and Cam rivers, the superficial 138,880 acres
content is 217 square miles, or . .... .
Between Great Ouse and Cam rivers and river Nene,
394 square miles; ‘or + 4) Th CEO) a Poa GG we.
Between river Nene and Glen river, 389 square 248,960 do.

MaUasrors cit feue fare hre pekbcbuke \i's Pia enter oie wai cc ce hae

Between Glen river and Old Witham river, 414 264,960 do.
snare milegp Ot.) jepson! sre eiy Pee aipe ee eee ©

Between Old Witham river and Tetney drain, Bh 128,640 do.
Rqiare pales, OL / .i FAAl Pye PAV ASL, eis) pedis

Making a total of 1615 square miles, 1,033,360 acres.

The rivers that drain this immense district are,—

The Setch, or Nar, Holbeach river,
Great Ouse and its tributaries, Old Welland,
Little Ouse, or Brandon river, Glen river,

The Cam, Old Witham river,
Welney, Old river,

Nene and its tributaries, Louth river.

* The late Mr. Rennie, in his Report to the Commissioners of the First Di-
strict of the North Level of the Fens, dated 17th June, 1809, speaking of the
Caerr or Carr Dyke, says, ‘ The Carr Dyke acts as a catch-water drain to
the whole North Level; and if it were in good condition, and had a good
outlet, it would intercept the water falling on 12,000 acres of high land, and
would greatly relieve the whole level.

“‘ This great Roman work extended originally from the river Nene below
Peterborough to the city of Lincoln, and perhaps the river Trent at Torksey. I

]

REPORT ON HYDRAULICS.—PART II. 475

The general drainage act of Elizabeth in the year 1600, and
the failure of different attempts that had been made to drain
the fens by different engineers, combined with political cir-
cumstances, led to the employment of Dutch engineers *, then
the most celebrated hydraulicians in Europe; hence may be
dated the commencement of British engineering.

The established maxims of the Dutch engineers were to em-
bank the rivers, so as to prevent the land-floods and high tides
from overflowing the lands to be drained, to leave open the
rivers to the free action of the tides, to conduct the downfall
and soakage waters by separate drains to the sea, and to place
sluices at the outlets of the drains, which, while they prevented
the ingress of the sea during its influx, let off the land-waters
when the tides were sufficiently low. These operations, though
open to objection, especially as regards the separation of the
waters into cuts, and the consequent choking up of the natural
outlets of the rivers, gave, however, an impulse to. this depart-
ment of hydraulics, which, until then, had been practised without
principles or science.

With the reign of the Stuarts, therefore, may be said to have

commenced that system of practical engineering which has

flourished with such unparalleled success in this country, and
in which so much sagacity has been displayed by Elstobb,
Labyle, Kinderley, Dobson, Grundy, Kdwards, Smeaton,
Brindley, Watte, Whitworth, Page, and Golborn, and other en-
gineers in modern times.

From the Report of the late Mr. Rennie in the year 1800, and
according to the levels taken by his direction, it appears that the
fens of Lincolnshire, particularly the East, West, and Wildmore
fens are generally lower the more distant they are from the sea,
and this, on the supposition that they have been originally
covered by the sea, must always be the case; hence the great
collection of waters which are found in the interior parts of
these fens,—the difficulty therefore of draining them has always
been great. The great bay or estuary through which the dif-

have traced its course for the greatest part of the way, and a more judicious
and well-laidout work I have never seen.” In concluding his Report, he
says, ‘“ If the Carr Dyke be repaired and improved with a proper outfall to the
river Welland, there is no doubt that the first and fifth district of the Fens,
and indeed the whole level, will be greatly relieved.”

_ * Vermuyden, Westerdyke, and Van Scotten.

_ Westerdyke’s principles were to keep the waters in a body, and convey the
land-flood by the nearest and quickest way to the sea that may be.

See the valuable works of Coles and Wells on the Bedford Level. Kinderley

and Labyle found it the same, and itmay be particularly noticed in the Rother
Levels near Rye, in Sussex.

476 FOURTH REPORT—1834.

ferent rivers disembogue is very shallow and full of shifting sands
and silt. The rivers, which are constantly loaded with silt, par-
ticularly in times of flood, are met by the tide equally charged
with it; in the still water which is the result of the counter-
acting forces the sediment is deposited; banks are formed,
which are nearer to or more remote from the rivers in pro-
portion to the strength of the current; so that if the seasons
be wet, the rivers run to seaward with greater velocity and pro-
pel the silt further out; and vice versd, if the season be dry, the
outward power is lessened, and the silt deposited nearer to the
mouths of the rivers, where it prevents the free egress of the
waters from the fens. Such being the statement of the case,
the remedy is in a great measure pointed out.

The first object that merits consideration is the outfall.

The second, the discharging of the waters which fall on the
surface of the fens.

The third, the intercepting and carrying off the upper or
highland waters without allowing them to fall into and overflow
the fens.

To effect the first object, Mr. Rennie recommended that the
rivers should be conducted to the sea by as short a course as pos-
sible, and in this respect adopted the opinion of Kinderley, who
was well aware that none of the rivers which pass through the
fens are sufficiently powerful to force their way through the im-
mense extent of shallow flats which are left dry at every tide ;
and therefore proposed the scheme of joining the Nene, the Ouse,
the Welland, and Witham rivers. The above principles were
afterwards partly carried into effect, and the result has been the
most perfect system of drainage of all that district of country
eastward of the river Witham, called the East Fen, contaiming
upwards of 62,000 acres of valuable land *.

* The following is the abstract of the low lands paying drainage tax to the
gencral Commissioners for drainage by the river Witham:
Acres, Roods. Perches.
20

Ist district, containing ...... 24,544 3
2nd —————_——— 19,080 2 7
3rd 5p A669 std 7
27,743 O 26
sees iw aaa vee 0 0
tea en OE ETD 4,781 2 19
Oth, a ee 11565 2 5

2

Total, 126,768 4
But the total quantity of land drained by the river Witham is estimated to
amount to nearly half a million of acres.
The following is an abstract of a statement by the late Mr. Bower relative
to the improvements effected by Mr. Rennie’s drainage of the East Fens.
To show the advantage of this drainage it may be necessary to state the

SS

Se ee ee a

49) £
Wildmoor Fen . . 10,773 at 42s.peracre . . 22,623

REPORT ON HYDRAULICS.—PART IT, ATT

In 1810 the attempt was revived to effect a complete drain-
age of the Great Bedford Level, consisting of 300,000 acres.
The drainage here passes off by the rivers Ouse, Nene, and

their tributaries, which discharge their waters into the great

bay or wash, called the Metaris Mstuarium.

situation the fens were in every winter and spring prior to any works being
executed under the direction of Mr. Rennie. In the year 1799 the whole of
the three fens, which contain 40,482 acres, together with the low-lands and
commons adjoining, containing about 20,000 acres, were under water, except
a small part in Wildmoor and the West Fen; the whole of the East Fen, which
contains 12,664 acres; the lower part of the West Fen, containing about
17,052 acres ; and the lower part of Wildmoor Fen, containing about 7770 acres,
making together 37,484 acres, were every winter under water. The East Fen
deeps, containing about 2500 acres, and the part of Wildmoor Fen called No
Man’s Friend, containing about 1500 acres, were always under water during
the summer; the former upon an average, in the driest time, about two feet
deep. The quantity of high lands draining through these fens is not less than
12,000 acres, which, in ordinary wet seasons, send down upwards of 40,000
cubic feet of water per minute, which, added to the downfall water upon the
fens and the higher lands in the East Holland towns, amounting to about
25,000 acres, soon overflowed the said fens and low lands adjoining. This great
body of water had to find its way to the sea through three small gouts, or
sluices, viz. Austin’s Gout, which had an opening of fourteen feet; Maud
Foster, an opening of thirteen feet; and Tichloft, an opening of four feet: the
first were of little use, being so high up the river as to be overrode by the
most trifling flood. The whole drainage, therefore, of the fens and low-lands had
to depend upon the small sluice of Maud Foster, which sluice has three open-
ings of thirteen feet four inches each.

'_ From this it may fairly be said that what is now made of the fens since the

drainage is a total gain. The average value at which the fens are now let is
as follows :

Acres. s. d,
6 0
West Fen . . . 17,044 at 50s.peracre . . 42,610 0 0
- EastFen . . . 12,664 at 40s.peracre . . 25,328 0 0

.

40,481 acres. 90,561 6 0

_ Improved value
of low lands i 20,000 at 20s.peracre . . 20,000 0 0

60,481 Per annum 110,561 6 0

Money actually
_ paid for eb 433,905 at 5s. per foot 21,695 5 0
drainage
Ditto, upon the
division and 146,800 at 5 per cent. 7,340 0 0
roads Snes —_:-———
Interest per ANNUM. ..esecessseeeseesenee seoveere 29,085 5 O

Increased annual income,........:..0.. $1,526 1 0

478 FOURTH REPORT—1834.

The principles of drainage recommended by Mr. Rennie were,

1st, To shorten and deepen the courses of the existing rivers ;

2nd, To form new cuts or drains in different directions
through the fens, with inclinations in their beds of from three
to five inches ;

3rd, To form a catch-water drain round the bases of the hills
skirting the fens, and to conduct the upland waters by an in-
clined bed of six inches per mile, through a separate outlet, into
the head of the proposed Eau Brink Cut, into which all the drain-
age-waters were to be carried likewise.

The expense of completing this magnificent drainage was
estimated at £1,188,189.

The Eau Brink Cut was originally projected by Mr. Nathaniel
Kinderley in the year 1720: the object was to conduct the waters.
of the river Ouse by a direct cut across the marshes from Eau
Brink to Lynn, of about two miles and half in length, instead of
allowing them to flow by the old circuitous channel of upward
of five miles in length.

This Cut was completed, agreeably to Captain Huddart and
Mr. Mylne’s award, under the direction of Mr. Rennie, in the
year 1825.

In December, 1821, the tide rose on the average eleven feet
ten inches on the cill of Old Denver Sluice; while at low water
the average depth on the cill was 9°6 inches, and the average
height of the water in the river was 11°5 inches.

Since the completion of the Kau Brink Cut, in the year 1825,
the results have been,

That the low-water mark has fallen six feet lower than it
formerly stood at Denver Sluice, and from eight to nine feet at
Eau Brink.

That the spring tides now rise at Denver Sluice thirteen feet,
and neap tides eight feet.

That the river has deepened between Denver Sluice and Eau
Brink ten feet upon the average, and its general sectional area
has increased from one fourth to one third.

That the low-water mark in Lynn harbour has fallen four
feet, and the navigable channel in Lynn harbour has deepened
seven feet; and that where there were formerly twelve feet in
depth of water in the intercepted bed of the old Ouse between
Eau Brink and Lynn, there is now a tract of 900 acres of land
under cultivation, all of which has been effected by the process
of warping.

The tide in the Eau Brink flows three hours, and rises in that
time fifteen feet, thus leaving nine hours of ebb.

ae
2

eos ©

REPORT ON HYDRAULICS.—PART ITI. 479

The next and most important improvement in the Bedford
Level was the Nene Cut or Outfall. The river Nene, after
passing through Northamptonshire, enters the Level at Peter-
borough, whence it proceeds in an irregular direction through
Guyhern and Wisbeach to the sea near Gunthorpe Sluice, and
thence loses itself amongst the irregular channels and sands of
the Washway.

The defective state of this river and of the drainage have been
at all times complained of ; and the attempts which had been
made to remedy it, by Bishop Morton in 1478, by Sir Clement
Edmonds in 1618, by Kinderley in 1721, and by Smeaton in
1767, had in a great measure failed, not so much from a de-
ficiency of skill on the part of the engineers as from other causes.
The very successful drainage of the East Fens in Lincolnshire
by Mr. Rennie induced the Commissioners of the North Level
to apply to him in the year 1813, and the result was a very
elaborate Report from that gentleman in the following year,
detailing very fully the causes and effects of the evils, and the
measures necessary to remedy them. The following facts are
curious :

From accurate levels and sections of the river Nene, it ap-
peared that the fall at low water from Sutton Wash to Crab
Hole (below the sands of the Wash) was 12 feet in about
4 miles ;. from the surface of the water at Gunthorpe Sluice to
Crab Hole, a distance of 54 miles, the fall was 13 feet ; and from
Wisbeach Bridge to the same point, a distance of 114 miles,
the fall was 134 feet.

_ From Guyhern to Crab Hole, a distance of 17 miles, the fall
was 14 feet 6 inches; and from Peterborough Bridge to the
same point, a distance of 30} miles, the fall was only 18 feet
6 inches; whereas from Peterborough Bridge to Sutton Wash,
a distance of more than 26 miles, the fall was only 63 feet,
or 33 inches per mile; but at the intermediate distances, be-

_ tween Sutton Wash and South Holland and Gunthorpe Sluices,
_ the fall was nearly double the above average.

From these facts it appeared evident that the great bar to the

_ discharge of the waters of the Nene, and of course to the general

drainage of the fens, was the high and shifting sands which lay

_ between Gunthorpe Sluice and Crab Hole, independently of the

narrow and confined state of the river above ; Mr. Rennie there-

_ fore recommended the river to be carried by a new cut, of a
_ suitable capacity, across the marshes to Crab Hole, 5} miles in

aa l

- The Cut has been since carried into execution under the

480 FOURTH REPORT—1834.

direction of Messrs. Telford and Rennie, and the result has ex-
ceeded the most sanguine expectations.

The lands immediately drained by this Cut were estimated to
amount to 35,000 acres.

The improvements of the river were estimated at £373,713.

And the internal drainage at . . . . . . 263,604.

——

Making atotalof . . 637,317

According to Mr. Wing, the district drainage which would be
effected by the river Nene would amount to 116,900 acres.

“The effect which the works, when completed, will have on‘

the internal drainage of the fens connected with them may be
appreciated,’ says Mr. Wing, “ by the following facts: The
windmills used in the North Level are not permitted to throw
any water to the height of more than four feet above the lands
in Thorney North Fen, which are about four feet three inches
above the cill of Gunthorpe Sluice, making the greatest fall
which can be obtained from the drains only eight feet three
inches; but it seldom happens that the low-water mark is less
than two feet above the cill, so that the general fall may be
considered as not more than six feet three inches ; whereas the
low water at Crab Hole is nine feet nine inches below the cill of
Gunthorpe Sluice, and consequently below the lands in Thorney
Fen.”’ Another important object was that at least 10,C00 acres
would be gained from the sea by the improvements, and this
operation is now going on very rapidly. The expense of up-
wards of sixty windmills, costing on the average 4385/. per
annum, would be saved, independently of other advantages, all
of which are fully detailed in Mr. Wing’s pamphlet *.

A similar plan for a Cut has since been carried into execution
on a modified scale below Boston, in Lincolnshire, and with cor-
responding benefit both te the navigation and drainage.

Principles similar to the foregoing have been recommended by
Mr. Rennie in his various Reports on the drainage of the marshes
of Hatfield Chase, Congresbury, Romney, Holderness, &c.

The system of canal navigation in England has been carried
on for more than half a century on a scale no less extensivé
than the drainage. The completion of the Sankey Canal in the
year 1760, and of the Bridgewater Canal in the year 1761,
opened the eyes of the nation to the vast advantages that were
likely to be derived from artificial navigation, and led to the

* Considerations on the Principles of Mr. Rennie’s plan for the Drainage of
the North Level of South Holland. By Tycho Wing, Esq. Peterborough, 1820.

Se ncaa me

REPORT ON HYDRAULICS.—PART II. 481

system of direct and indirect communication, which has united

all the great rivers and ports of the kingdom.

ia Tn Sco tant the progress of inland navigation, althongh less

rapid, was proportionably successful; so early as the reign of
Charles II. the idea of joining the Forth and Clyde rivers ori-
ginated with the Duke of York. The subject was again resumed
in the year 1722; in 1762 a survey was made by Messrs. Mackell

and Watt; and in 1766 that great work was commenced by

Mr. Smeaton, and finally completed in 1790. Between the above

periods, also, Mr. Watt, the great improver of the steam-engine,

made many reports on the improvement of the river Clyde and
on the Monkland, Crinan*, and Caledonian Canals; and in the
year 1802 Mr. Telford was employed to make surveys of the
whole coast and interior of Scotland, with a view to improving
its harbours and rivers, and which led to the execution of the
great Caledonian Canal by that gentleman in the year 1821.
Several other canals have been since completed in Scotland by
different engineers.

_ The following is an approximate statement of the number of
miles and the cost of river- and canal-navigation in England,
Wales, and Scotland :
ante ‘ Miles Cost.

River-navigation in England and Wales. 2036 £5,000,000
eters ecollard ss ee, ee BUY 1,269,000

Total river-navigation 2236 £6,269,000

Canal- navigation in England and Wales. . 2277 19,793,065

Ditto in Scotland . . + ot ing 200,» 2,344,394

—_ oo

Grand total 4713 £28,406,389

Average cost of canal per mile :

2 In England . . £9,000

mite In Wales. . .... . ~=5,000 to 6,000

In Scotlandumdy iw. iouiey sodae<co:kl,000

_ The first idea of improving river-navigation in Ireland is due
to the enlightened administration of the unfortunate Earl of
Strafford, who had witnessed the effects of inland navigation
in the Low Countries. In the year 1703 the first act of par-
liament was passed for making the river Shannon navigable,

_ and many improvements were projected: nothing, however, was

effected, but an useless expenditure of 140,000/. of public money
on the rivers Shannon and Boyne in the year 1758.

* Executed by Mr. Rennie.
1834. 21

482 FOURTH REPORT—1834.

Various sums of money were granted by Parliament, and frit-
tered away in partial improvements of the Shannon, Boyne,
Barrow, and Newry rivers, besides the Grand, Royal, Kildare,
Naas, and Lough Earn navigations.

Up to the year 1790 there had been expended £587,537

And in 1800 a further sum Of ...sssecceseeeseceees 423,798

And from 1800 to 1831 an addition, for further
improvements, Of ...ccccrcecssseseeseecseesves 800,000

Making a grand total of 1,811,335

The total number of miles of inland nayigation which have
been completed in Ireland amounts to 483 miles,—i-e. of canal,
312; navigable rivers, 171 ;— exclusive of the river Shannon,
which is 234 miles from its source to the sea.

In the year 1809 an act of parliament was passed for the ap-
pointment of Commissioners to inquire and examine into the,
nature and extent of the bogs of Ireland, the practicability of
cultivating them, and the best means for effecting the same.

The result was a very detailed report by Mr. Griffith on the
origin, composition, and extent of the Bog of Allen, and of the
first district, or eastern division of that bog, amounting to 36,430
English acres. |

Mr. Griffith found that the average thickness of the Bog of
Allen was 25 feet; that it was nowhere less than 12 feet, nor
thicker than 42 feet; and that the height of the highest part
of the bog above high-water mark in Dublin Bay was 296 feet.
The cost of draining the whole of the eastern division was esti-
mated by Mr. Griffith at 70,000/., and to increase the annual
value of the land 20s. per acre.

The second Report of the Commissioners laid before Parlia-
ment stated, That they had received detailed reports from their
engineers on an extent of bog amounting to 197,000 acres ;

That the several districts.reported upon were intersected with
streams, the channels of which were found to be generally in
the under strata, usually consisting of gravel or clay ;

That on the surfaces of these bogs there appeared to be abun-
dant falls towards these streams to carry the surface-water into
them ;

That in respect to differences of opinion which seemed to
‘prevail among the engineers, whether deep or surface drainage
is best adapted to the reclamation of bogs, there were satisfac-
tory proofs that the surface or bog might be highly improved,
so as to bear crops without drawing off the water from the
lower strata.

REPORT ON HYDRAULICS.—PART II. 483

The Commissioners however conclude, that neither system
should be exclusively preferred ; the successful application of
either must depend on circumstances ;—that ‘‘ wherever exten-
sive bogs are to be drained, main and minor drains’ will be. re-
quired for the purpose to act as receiving drains for the water,
witha system of numerous small surface-drains, to collect the
water in considerable quantities.”’ 0 hh wd
-. Mr. Edgeworth’s report on the seventh district is compre-
hensive and ingenious; his instrument for sounding and taking
the sections of rivers was. capable of. giving correct. results.
Mr. Edgeworth advocated the system of surface-draining instead
of deep .cuts.; he:proposed portable wooden railways to be sup-
ported on the bogs by piles for the: purposes of conveying manure
to the surface, which he states to be similar to the plan adopted
by. Mr. Roscoe on Chat) Moss; His experiments.on the com-
pression of bogs:are, however, very contradictory *.

The third Report of the Commissioners is confined to a state-
ment of:former: proceedings ; and:to giving the reports. of their
engineers onthe surveys of 474,808 English acres of bog. ...

vy The:fourth and last Report:concludes the labours of the Com-
missioners, by giving the: reports: of the engineers, Messrs.
Nimmo, Edgeworth, and Griffith, on 305,012 acres of bog, .ex-
elusive of 500,000 acres of bog in the counties of Kerry and
\ > For.the improvement of mountain bog, Mr. Nimmo recom-
mends? irrigation, the advantage of which in reclaiming bogs,
he states, has been proved by experience in some few instances
in Ireland, but principally in Scotland. .

© Mr. Nimmo observes, that wherever a stream flows through a
bog it’ appears to: prevent the: growth of bog-plants, and the
vegetation of wholesome grass is rapid on its banks; but.as this
system can only be applied to bogs in elevated situations, he
recommends surface-draining for bogs in flat countries, adopting,

»°# The author of this paper, when making the survey of the present Liver-
pool and Manchester ; Railway in the year 1825, found that, a cubic foot of
‘moss, taken from Chat Moss, weighed 62:24 lbs; a heap.of moss'4 yards by
3 yards, and 23 yards in height, weighing about 223 tons, sunk 18% inches.
..A quantity of moss, 12 inches long and 6 inches square, was put into
‘a box with holes; its weight at first was 12 pounds; after being compressed
‘some time it ‘weighed only..34 pounds: the moss was found to be reduced to
43 inches in thickness. It was further reduced by a compression of 20 tons, and
an, evaporation by ,heat.to 13 inch; so that the total loss in weight was
‘10 pounds of water, being'in the proportion of five of water to one of yegetable
atter, and the compression in bulk of eight to one; and in taking accurate
levels of Chat Moss, its surface.was found to rise and fall two feet above its
average rise in wet weather. + fitorr be ‘ si dios ;
212

484 FOURTH REPORT—1834.

however, the system of catch-water drains to intercept the
waters from the higher grounds, and then a system of shallow
drains to deliver the surface-water of the bog into the natural
streams: these drains will of course vary in number and di-
mensions, but in no case ought they to exceed six feet in depth.
Mr. Griffith agrees with the principles of irrigation laid down
by Mr. Nimmo.

From the results of the reports it appears that the number of
English acres of bog which have been surveyed in the twenty-
five districts amounts to. . Jovet de) eendQha, 258
And that there remain upon the: three. mountain

districts of Wicklow, Erris, and Connemara. . 387,090
Exclusive of peat soil, which forms the general cover-

ing of these mountains. . . oobu pseet SiR 000
besides other lands, not examined ; Mrom! all of which it is in-
ferred that the extent of peat soil in Ireland exceeds 2,830,000
English acres,—whereof 1,576,000 are flat red bog,—which
might be converted to the general purposes of agriculture. '

As regards the Shannon river, which forms the most import-
ant feature in the internal navigation in Ireland, various
examinations and surveys have been made, from the year 1715
down to the present time: the most detailed reports have
been made by Mr. Rennie, Mr. Grantham, Captain Mudge,
Mr. Rhodes, and Col. Burgoyne. The result of these reports
may be stated in a few words, namely, That the Shannon may
be considered as a combination of lakes and rivers, from its
source in Lough Allen to the sea below Limerick :

The total distance from Limerick to Lough Allen is 144 miles:

The total height of the mean surface of the water in Lough
Allen above that of the surface at Limerick is 143 feet seven
inches, which gives an inclination of rather less than, mere
inches in a mile:

The natural fall is, however, reduced to a series of bow seo
planes of different lengths by locks:

The general direction of the river is extremely irregular, ai
broken by many streams, islands, and rocks:

The soundings vary in the same manner, and in some ples
are very deep, in others very shallow :

The river is liable to be overflowed to a great extent on both
banks, and the large expanse of the lakes renders the vessels
which navigate the river unfit for the lakes:

The works which have been constructed to overcome the
natural difficulties of the navigation are either insufficient or in
a state of decay ; and it seems to be generally admitted that.very
little real good can be effected until the natural obstructions are

REPORT ON HYDRAULICS.—PART II. 485

removed, the number of lakes reduced, and the channel deepened
and improved in various parts, notwithstanding which it is gene-
rally believed that the navigation would only be fit for steam-
boats.

- The difficulty experienced in preserving the channels of rivers
free from the changes which take place in times of flood by the
depositions of gravel and other obstacles, induced Col. Burgoyne
to make the following statement in his Report: “ It is a very
usual opinion among engineers, that side artificial canals are
eventually more judicious than the attempt to dredge channels
in the beds of the streams themselves; and that for the purposes
of navigation, rivers are only useful to supply canals with water.
It may therefore be important, in estimating the propriety of
excavating the required depth of this river according to the plan
now proposed, to take into consideration the nature of the shoals.
If they have been created by deposits collected by the action of
the current, it may be inferred that the same process will con-
tinually tend to the same results, and that an effort to preserve
the channel would require to be constant and laborious ; but if
the obstructions have been artificially made, or consist of a
natural and solid substratum, it may be reasonable to presume
that the openings once made will be permanent, or at all events
require but little attention to maintain. Appearances would
seem to indicate that the shoals in the Shannon come almost
all under the two latter descriptions.”

The Report of the Parliamentary Committee on this sub-
ject, in 1834, states, that “great detriment has arisen to the
navigation from the land-floods, so prevalent upon the river,
and over which there is no machinery for exercising any
control.”

The main question appears to be, whether the free and natural
flow of the floods is to be arrested by locks, dams, and other
works ?

Although the principles which have guided the operations of
our engineers have been various and contradictory, in general
the practice has been to confine the freshes by artificial works,

asin the Clyde, Witham, and other rivers, and to preserve the
receptacles for tidal waters to their full extent. A contrary
proceeding has tended to ruin many of our rivers and estuaries,
whereby the drainage and navigation have been greatly im-
peded, and the destruction of several of our harbours, such as
the Dee and Rye, occasioned.

The effects of embankments in Plymouth and Portsmouth
harbours, and particularly in the estuary of the Mersey, (one
third of the ancient capacity of which has been filled up by en-

486 FOURTH REPORT—1834,.-

croachments,) have materially diminished the depths of the sea-
channels, and a consequent deterioration of the harbours has
been the result.

On the Course, Dimensions, Inclinations, and Velocities of the
River Thames, and the Effects which have heen occasioned to
the River by the removal and. rebuilding of Old and» New
London Bridges, according to the Observations and Experi-
ments which have heen: made on the River during the Years
1832, 1833, and 1834, by Messrs. George and John Rennie.

The general course of the river Thames is from west to east.

Like other rivers, it forms the drainage of a very extensive
district of country by means of rivulets and streams, which con-
duct the waters of the uplands into one great artery, or trunk,
which conveys them to the sea. The total number of these
affluents so circumstanced may be about twenty.

It is difficult to estimate the superficial extent of country
drained by the river Thames, but it cannot be less than 5000
square miles.

The course of the river is very tortuous and winding, being
double of its distance by a straight line.

The navigable distance from London to Lechlade is about
1464 miles; but from Sheerness the total distance is 2043
miles. The total fall of the river, from Lechlade to low-water
mark, is 258 feet, or twe1ty-one inches per mile; and this fall
is nearly uniform, although there are places where the fall varies
from nineteen inches to thirty-two inches per mile, as shown in
the following Table; but in no instance is the law of the funi-
cular curve of M. Gerard established.

REPORT ON -HYDRAULICS.—PART II. 487

gaia ti Rivers Isis and Thames.

Fall in feet |Ratio of In-
Names of Places. ‘ 74 : per Mile. | clinations.

‘From Lechlade at St. John’s Bridge
to Oxford at Folly Bridge. ‘
From Oxford to Abingdon Bridge .
‘From. Abingdon to Wallingford
or LS ae Se
‘FromWallingford to Reading Bridge.
From Reading to Henley Bridge
From Henley to Marlow Bridge
From Marlow to Maidenhead Bridge.
From Maidenhead Bridge to Wind-
sor Bridge. . . . +. -
3 From Windsor to Staines Bridge
From Staines to Chertsey Bridge
| From Chertsey to Teddington Lock.
From Teddington-Lock to London
. pmridge (. set ele
From London to Yantlet Creek .

Byoin Lechlade to Yantlet Creek
oy Deduct

From Lechlade to London. .

The velocity of the Thames might be expected to fol-
low the law of variation of the inclinations; but the natural
obstructions which exist in all parts of the river upwards, from
bends, shoals, islands, weeds, &c., and the artificial obstacles.
from weirs, pound-locks, fishing-aytes, &c., render it impos-
sible to ascertain the velocity correctly. Much depends also
upon the volume of water passing down the river, and the use
of flashes. |
» In general the velocity may be estimated at from half a mile
to two miles and three quarters per hour, but the mean velocity,
may be reckoned at two miles per hour, . In the year 1794 the
late Mr. Rennie found the velocity of the Thames at Windsor
two miles and half per hour.
--The produce of the river varies also with the situation and
the seasons. .
The river when gauged in a very dry season in June, 1794,

at Windsor, produced 961 cubic feet per second ;

at Laleham,. ... . 1153 do.

at Kingston Bridge . 1600 do.
According to Messrs. Rennie’s experiments made on the 28th and
29th of May 1835, the produce was 1700 cubic feet per second ;
andon the 29th of May, after rain . 1800 do. do.

488 FOURTH REPORT—1834.

The surface of the river, however, stood about eighteen inches:
above the summer level. i
According to Dr. Halley’s computation, the quantity of water
which passes through Kingston Bridge, upon the average, per
second, amounts to 7920 cubic feet = 684,288,000 cubic feet
per day, and 239,765,120,000 cubic feet per annum : he calcu-
lated the surface of country drained by the Thames and its
tributary streams to be equal to an area of 50263 square
miles, or 140,129,776,600 superficial feet; and taking the
average depth of rain which falls over the above surface in the
course of a year to be twenty-four inches, amounting, conse-
quently, to 280,259,555,200 cubic feet, he found this to be
40,494,435,200 cubic feet more than the quantity carried down
by the river Thames to the sea; and he therefore concluded that
one seventh of the whole was absorbed and evaporated.
Mr. Anderson, of the Grand Junction Water-works, stated
in his evidence given before the House of Commons in 1834,
that he had on the 4th of December, 1830, ascertained that the
quantity of water flowing down the river Thames at Staines was
2050 cubic feet per second; but as the river was then about
four feet above its summer level, not more than about one third
of the above quantity would be carried down the river during the
dry season.

Mr. Anderson further stated, that he had ascertained that the
quantity of water flowing over the weir at Teddington Lock in
the month of June, 1834, amounted to 700 cubic feet per second
when there were eighteen inches of overfall, and 1260 cubic
feet per second when there were two feet of overfall; the
mean therefore of these three quantities being 1337 cubic feet
per second, gives 115,516,800 per diem, or 42,163,632,000
cubic feet per annum; leaving, therefore, agreeably to Dr.
Halley’s computation of the surface of country drained by the
river Thames, rather better than five sixths of the quantity of
rain which falls in the course of the year to be absorbed and
evaporated.

Below Teddington weir the river is under the combined in-
fluence of the freshes and tides, and the impediments which
they meet with from the different bridges.

Previously to the erection of the old London Bridge, im the
year 1209, there can be no doubt that the state of the river was
very different from what it now is, and that many of the low-
lands which are now embanked out, were formerly covered both
by the floods and tides. The old bridge, although it obstructed
the flow of the tides to their full height, operated reversely with
the land-waters, by penning them back; and in extreme cases

REPORT ON HYDRAULICS.—PART II. 489

the difference of level was found to be occasionally as much as

. fourteen inches between, the high water below and above bridge,

and five feet seven inches between low-water mark above and
below bridge, depending of course on the state of the freshes and
tides. The bridge was considered to act like a pound-lock, and,
by penning up the water, to tranquillize the motion of the cur-

rent, and deepen the navigation above. In consequence, how-

ever, of the danger and inconvenience arising from both the im-
peded navigation through the bridge and the floods, Mr. George
Dance was instructed by the Corporation of London, in the year
1746, to draw up aseries of queries, which were addressed to the
Royal Society.

The result was a Report from the Society requesting certain
information relative to the tides, which however did not elicit
anything positive upon the subject until the year 1754, when the
erection of Blackfriars Bridge was contemplated. The opinions
of Mr. Robertson, as detailed in Dr. Hutton’s Mathematical
Tracts, were given on the unfounded supposition that the pro-
posed bridge was to be built with piers and starlings like London
Bridge, and to produce a similar obstruction. The enlarge-
ment of the water-way in the year 1759, by lowering the
surface of the water several inches, caused a diminution both
in the depth of the water, and in the power of the water-works.
The area of the water-way was again contracted, and the river
restored to its former state, on the supposition that the naviga-
tion would have been otherwise injured, and the low lands over-
flowed. And when the question of rebuilding the bridge came
to be agitated, it was argued, That the old bridge acted as a bar
to check the velocity of the river both ways ;—that an increased

_ velocity in the river would impede rather than accelerate the

navigation, as wherries and small craft could not stem the
current ;—that the bed of the river would be laid dry during
the ebb tide ;—and, lastly, that the upper part of the river
would be choked with mud, and all the low grounds on either
side of the river would revert to marshes and be rendered un-

inhabitable.

- On the other hand it was contended, That the tides would not

_ rise more than a few inches higher than formerly, or fall lower

than three feet;—that the old bridge not only acted as a

- dam to check the flux and reflux of the tides, but tended

to pen back the land-waters, and to cause floods above; and

that the proof of the bridge causing such an effect was

the greater prevalence of floods before the enlargement of the
waterway of the old bridge in the year 1759, than afterwards ;—
that the decrease in the velocity of the river tended to assist

490 FOURTH REPORT— 1834.

the filling up and raising the bed by depositions of gravel and
mud;—that independently of the annual loss of lives and pro- |
perty, occasioned by the contracted waterways of the bridge;
the navigation was at times wholly impeded; whereas, by re-
moving the dam, the great increase in the velocity of the current
would clear the bed of the river, facilitate navigation, and effect
a more perfect drainage of the country by the quicker passing off
of the land-floods ;—that the river being more perfectly emptied
at each reflux, the flux would have less time to fill the increased
void ; and that, therefore, before it had attained its greatest sur-
face of elevation, the tide would have begun to run down ;—that
although many shoals would have undoubtedly been: exposed,
yet the increased velocity of the current, assisted by dredging
the hard places, would very soon reduce the channel to its ancient
depth. The latter assertions have been verified to their full ex-
tent, as will be seen hereafter.

The phznomena of the tides in the port of London have Ween
very ably discussed by Mr. Lubbock and by the Rev. Mr. Whewell
in the Philosophical Transactions for the years 1831, 1833, and
1834,—the former gentleman in his papers containing numerous
tables compiled from 13,073 observations made at the London
Docks in a period of nineteen years, viz. from January Ist,
1808 to the 31st of December, 1826, with the corrections for
the time of high water, as it is affected by the right ascensions,
declinatiuns, and parallaxes of the sun and moon ; and the latter
in his paper on the empirical laws of the tides in the port of
London, and in his essay towards a first approximation to a map
of cotidal lines.

In the case of the times of high water especially, says Mr.
Whewell, “ the general course of the variations of the quan-
tities is as regular as can be expected, and as is requisite for
my formule. The heights are much more anomalous ; pro-
bably they are more affected by winds, &c. than the times are :
and when we reflect that the tide at London may be affected by
the operation of causes in a remote part of the ocean, propa-
gating their effect by the progression of the tide-wave, we shall
not be surprised at considerable deviations from the rule. The
trade-winds and other winds of the tropical regions may be felt
in our tides, and may even affect the means of long series of
observations ; for it is to be recollected that the averages which
we obtain are not the averages of the effects of the sun and
moonalone, but the averages of their effects, together with that
of meteorological causes.

*“ It is moreover to be observed, that the peculiar circum-
stances of London in having a tide compounded of two tides

REPORT ON HYDRAULICS.—PART II. 49}

arriving by different roads, after journeys of different lengths,
may easily be supposed to give rise to additional chances of
irregularity.”

In reference to the causes of inaccuracy in tidal observations,
Mr. Whewell says,

* There is in fact no doubt that most or all the statements
of such discrepancies are founded in a mistake, arising from the
comparisons of two different phenomena, namely, the time of
high water, and the time of the change from the flow to the
ebb current. In some cases the one and in some the other
of these times has been observed as the time of the tide; and
in this manner have arisen such anomalies as have been men-
tioned.

“ The time of the change of current or the time of slack
water never coincides with the time of high water, except close
in ‘upon the shore, and within its influence; the interval of the
two times is generally considerable. Great confusion has been
produced by these two times not being properly distinguished ;
so great, ‘indeed, that almost all the tide observations which we

possess are of doubtful value.

_ © The persuasion ‘that in waters affected by tides the water
rises while it runs one way, and falls while it runs the opposite
er ‘though wholly érroneous, is very general.”

_ ~ “Mr: Whewell instances the case of the waters of the river
_ Dee at Aberdeen, which have almost a constant current to
_ seaward, notwithstanding the opposite direction of the flood-
tide of ‘the ‘ocean. Many instances could also be adduced of
—~ phenomena vaiginyacry occurring in our estuaries and
Tivers. ;

_ Inthe’river Thames the motion of the current continues for
some time’ after the tide has made‘its mark, which is undoubt-
; edly owing to the momentum. In general the tides of the river
_ Thames have been found to observe considerable regularity both
_ in‘their elevations and periodical times, except when influenced
_ by winds and floods. In comparing, however, the sea- with the
_ fiver-tides a considerable discrepancy is found to prevail in the
- elevations ; in’ some cases on account of the convergence or
_ swelling of the tidal wave, on the principle of the conservation
_ of mechanical force, as in the Severn, &c., and in other cases a
4 lowering of the surface by expansion, as in the Mersey, which
_ is very narrow at its mouth.

~ In the river Thames the height of the tidal’ wave diminishes

_ much less from the effect of friction and obstacles than might

be expected. From reference to Mr. Lloyd’s observations on

492 FOURTH REPORT—1834.

the rise of the tides at Sheerness, with the mean of Mr. Lub-
bocks at the London Docks, it appears that

The spring tide high water at the London Docks 2-0361
above the same at Sheerness, is 4 -

0:2068
The mean high water ditto ditto ditto 2°2429

0°1050
The neap tide ditto ditto ditto 2°3579

0:6900
The spring tide low water ditto ditto 1:6679

0°3680
The mean level of the tides ditto ditto 2°0359

spring high and low water at Sheerness, the

Or, taking more correctly the half difference between
1-7249
mean spring level is

It seems from the above summary, that as the water decreases
in height, so the height of the water’s surface at London Docks
above the same at Sheerness also decreases, with the exception
of spring tides at the London Docks and the neap tide. These are
the means, not of the highest tides, but of the tides at a parti-
cular time of the moon’s southing: at Trinity high-water mark
at London Bridge, it was found by Mr. Lloyd to be 1:9040
above mean spring tide high-water mark at Sheerness.

With respect to the influence of the winds on the tides in the
river Thames, Mr. Lubbock states, on the authority of Sir
John Hall, of the St. Katharine Docks, that “ during strong
north-westerly gales, the tide marks high water earlier than
otherwise, and does not give so much water, whilst the ebb-
tide runs out later and marks lower ; but upon the gales abating
and the weather moderating, the tides put in, and rise much
higher, whilst they also run long before high water is marked,
and with more velocity of current; nor do they run out so long
or so low, &c. A south-westerly gale has a contrary effect
generally, and an easterly one gives some water; but the tides
in all these cases always improve the moment the weather
moderates.”’

The very valuable tables of Mr. Lubbock, compiled with his
corrections from upwards of ten thousand observations, have
contributed very largely to our knowledge on this subject.

From a series of levels and observations made on the tides in
September and October 1820, between the entrance of London
Docks and Westminster Bridge, by Mr. Francis Giles, for the
Select Committee of the Bridge-house lands, the following were
found to be the facts :

Ist, The high water of spring tides at the entrance of the

REPORT ON HYDRAULICS.—PART II. 493

London Docks ayeraged a level of 1°5 inch higher, and ten
minutes earlier time, than at the lower side of London Bridge ;
2nd, The low water of spring tides at London Docks averaged

a level of three inches lower, and nine minutes earlier time, than
at London Bridge ;

3rd, The high water of neap tides at London Docks averaged
a level of one inch higher, and eight minutes earlier time, than at
London Bridge;

4th, The low water of neap tides at the London Docks aver-
aged a level of two inches lower, and fourteen minutes earlier
time, than at London Bridge.

It was found also, That high water of the highest spring tides
occurs at three or four o’clock, and high water of neap tides at
eight or nine o’clock :

The flow of the spring tides is from four to five hours; and
the ebb from seven to eight hours and half:

The high water of spring ‘tides produced an average fall
through London Bridge of eight inches, but the greatest fall up-
wards was 1°1 inch:

The low water of spring tides produced a fall of 4:4 inches
through the bridge; but the greatest fall was 5-7 inches: —

The high water of neap tides through London Bridge upwards
produced a fall of 5 inches :

At the low water of neap tides the fall upwards was 2°1 inches ;
but the least fall at low water was 1°1 inch.

It appeared also, That it took forty minutes after low-water
spring-tides to produce slack water under the bridge with a
flood tide; two hours with a flood of neap, and with an ebb
spring tide thirty minutes after high water, and fifteen minutes
after an ebb of neap tides :

That the time of high water was about ten minutes earlier at
London than at Westminster Bridge :

That the mean low-water line has a fall of—

4-0 in. from Westminster to Waterloo Bridge; 7 min. later at Westminster
than at Waterloo Bridge.
4:3 do. from Waterloo to Blackfriars Bridge; 6 ditto.

3-2 do. from Blackfriars to Southwark Bridge; 5 ditto.
0°5 do. from Southwark to London Bridge; 4 ditto.

S

34.

FOURTH REPORT—18

494.

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REPORT ON HYDRAULICS.—PART II. 495:

Gradation of the Ebbing and Flowing of the Tide at London
, Bridge, taken ahove-and-helow; on the 29th of July 1821,
_ being the day of the new moon; by Mr. Giuxs.

; a {J Above Bridge.

Low water at Pepper Alley 50 min. ; High water at Pepper Alley 35 min.
past 9 o’clock in the morning. __ past 2 o’clock in the afternoon.
Flood: Tide. Ebb Tide.

ft. in. ft. in,
Depth of water when flood 6 0 | lst hour, fall... eee Bode 21%
- commenced ...........005 Qrid ditto’ f.. Ss.d0c8s0. see eesst Sdect DAT
Ist hour rise............c.cceeeeeeee 21) Gudrditto.3s Ik Soe ewe 2 0
MEV IELO 4.0 vee chacsssad- sed ceauert 3 0 | 4th ditto .............. ous Beseadeas ae Blg
8rd ditto ....... BSC Cene vag B AREANC TE 2,10/( ath: ditto Ten us eee eee a dane Ys
pe CAMELOT. 5 «ss ght pas wade ens 5 Sans Der Srr MEO NLD) ©) Hebeebie. Ses sess sls oueee 1 2
_ 45 minutes .......... SE Boo SRR DL Uap MtsCUcl@’ "s.ceecteserancsvscecttccce 1 0
: SP minibes 4121, MGR teas 0 11
Depth at low water ................ 5 6

4 hours and 45 minutes. 18 5 | 7 hours and 55 minutes

Below Bridge.
Low water at Coxe’s Quay, 30 min. | High water at Coxe’s Quay, 18 min.
past 9 o’clock in the morning. past 2 o'clock in the afternoon.

Flood Tide. Ebb Tide.

reed bees EES, ft. in. ft. in
Depth of water when pee 1 3 | Ist hour, fall... ie C2i Set
commenced....... aah Eaddessp s 2nd ditto .....5.....c... Oh etdeh Al ad
BUSOU TISC.. o.-.scsssanqate conse. OS ie AEG CIUNS craps ttencinie.s sane es 31
® 2nd ditto ................. eee sonst 5-4‘) 4th ditto oo. iissr. cy S--- wecueselss sean? ail
3rd ditto ...... qa tete ans Bes. 8S. 2. 9 | Sth ditto wo... ees Wntee 2.13
AGh Gitte 6 wees! cessed decease Weoceses 24S | Gth: ditto siceececcecces a. SUSERSEOR 1.9
48 minutes...............066 Se de Sify AUD QIiL0 powson set crea Mpmci os weatesced Ly lG
pf UIMILES: oS dawtadanancaoananen Seaene3O LL

mt LFS RRP LCE, age « sanasans pen cto 0 4
4 hours and 48 minutes . 18 10 | 7 hours and 59 minutes......... 18 10

Difference between the Levels of high- and low-water Spring
Tides, between Rotherhithe and Battersea, in the year 1820.

ft. in.

_ Rotherhithe Old Horse Ferry . . . 21 10
Mondon Old Bridge: jasiie ic% tenho bSmdee
ilackitiars 17. 5-2 ae wins eee es ara
Westminster «- pen ie sy sree 0 atest mcr
Vampaiall 7. Seo. See a uit ES le

a Datered . eee ee ED bg
From Battersea Bridge to London Bridge . . 5 miles.

‘From London Bridge to Old Horse Ferry . . 1} ditto.

‘From London Bridge to the Nore... .. 44° ditto.

496 FOURTH REPORT—1834.

The following observations were made in March 1833:

March 6.| March 7,| March 8,

m. h. m.

The difference in time of high water at London 4 34 ‘ 42| 1 36
Bridge after that at Sheerness.........sssseeseeeeeeee

ft. in.| ft. in.| ft. in,
The rise of tide at Sheerness ..........sccceseeseseceseceees 18 3/18 11/18 7

=——WTESN, (WD ATE:. «.nslst'chssecs escent snomsclaeae tone 20 8{|19 10
————-— New London Bridge ...............6+ 18 1/18 6|18 3
The fall through the site of Old London Bridge ................. ae Zp Ig?

The difference of level of High-water mark at Lon-
don Bridge above that at Sheerness ..........s00+00

The difference of level of Low-water mark at Fresh
Wharf above that at Sheerness .............ss0eeeeee \

N.B.—The above levels are from the Trinity datum as transferred from Lon-
don Bridge to Sheerness by Captain Lloyd.

Observations and Experiments upon the Velocity of the Tides
of the River Thames.

The earliest experiments on this subject with which we are
acquainted are those of Mr. H. Saumarez, inserted in the PAi-
losophicul Transactions for the year 1720, ‘On the strength
and gradual increase and decrease of the Tides of flood and ebb in
the river Thames, as observed in Lambeth Reach, off Manches-
ter Stairs, and in the middle of the river, with a new instrument
called the Marine Surveyor, on the 9th and 18th of June 1790,
both with spring and neap tides.”

These experiments are interesting, as showing the effect of
Old London Bridge on the river previously to the alteration of
the bridge and enlargement of the waterway in the year 1754.

Mr. Saumarez’s tables indicate the depth and velocity of the
floods and ebb of spring and neap tides for every fifteen minutes,
and the following are the results :

hrs. min.
The time of flood spring tide was only .....- - 3 50
prea OPS? SEBS. “S ditto es Le es
Ditto. . . . flood neap ditto. ...... 2 ae
Ditto’ A5... ebBe . 4 sa GittO: sca noy s,s spect in 7. 35
miles per hour.
The greatest velocity in flood spring tides was . . . . 2°00
1b LAY Uni Sak aS a ebb’ “Uitip. 2. 02. “s--. « < vest ae
Total number of miles run by the flood spring tide . . 5°25
(nee ee eae ebb ¢)..st.rakam 10°50
The greatest velocity in neap tides was..... .- . ee
Ditto, with ebb of neap tides ....... , « ~ 1°30

The total distance run with a flood of neap .... . 4°75
Ditto, with an ebb of ditto .......4... 7°75

REPORT ON HYDRAULICS.—PART II. 497

According to the experiments of Mr. Giles in the year 1823,
: the velocities of the flood tide are,— .
. ‘From London Bridge to Putney Bridge, 24 miles per hour ;
Between London, Southwark, and Westminster Bridges, 2 do.
And with an ebb tide the velocities are,—
Between Westminster and Waterloo Bridges, 2 ae per hour; :
_ Between Waterloo and Blackfriars Bridges, 24 do. ;
Between Blackfriars and London Bridges, 22 do.

Experiments on the Flood Tide of the River Thames from London Bridge,
19th of June, 1834.* (Wind W.S.W. Fresh breeze and clear.)

Tide | Distance! mp. 5
Name of place. Time. Geet apes fest Iptt Me pent Remarks.
Bridge. | Bridge, | Vater. | place.
miles per
hrs. min.| ft. in. | miles. |hrs. min,| hour. .
London Bridge ....| 8 6 |17 3) 0-0 | 0 31 | 0-00 {Float putin at centre.
Southwark do...... 8 30 {14 11 | 0:28 | 0 55 | 0:70 |Centre of centre arch.
Blackfriars do...... 8 53 |13 O| 0-75 | 118 | 2:16 |4th City arch.
Waterloo do. ...... 914 }11 5 | 1:34 | 1 39 | 1:68 |2nd City arch.
Hungerford Market .| 9 23 |10 10 | 1:50 | 1 48 | 1:07
| Westminster Bridge .| 9 36 | 9 3 | 2:00 | 2 1 | 2:30 |6th Middlesex arch.
| Horse Ferry ...... 9 50) 8 10 | 2:42) 2 15 | 1°82 ,
| Vauxhall Bridge ...|10 83) 7 11 | 2°95 | 2 283) 2°33 |Centre arch.
| Chelsea Col. (Stairs) . 10 84 | 5 10 | 421 | 2 59} 2-48
_ | Chelsea Bridge ..../10 55 | 4 2) 5:04 | 3 20 | 2:36 |6th arch.
| 4 mile above do. ...J/11 9/3 2) 5°54 | 3 34 | 2-14
| ilmile do. do..... 11 20| 2 6| 6:04} 3 45 | 2°73
| 14 mile(Wandsworth)|11 31 | 2 0] 6:54 | 3 56 | 2-73
M2 miles.......... 1142/1 7| 704)4 7| 2°73
_ | Putney Bridge Biase 3 | 1 3 | 7-48) 415 | 3-30 |11th arch.
i 1 2) 7:54) 4 18 | 1:08
0 9 | 8:04) 4 31 | 2°40
0 8| 854 | 4 45 | 2:14
q 1 0 8} 9:04 | 4 55} 38:00
_ | HammersmithBridge. ts 010 | 9:20; 5 0! 2-00 |} from Middlesex
#43 miles 2s. 25... 1 2)| 954) 5 10} 2-00] pier.
5 miles (Chiswick) . 4 0 | 1 11 | 10-04 | 5 25 | 2-00
Bee annles:. we. 1 15 | 2 11 | 10°54 | 5 40 | 2:00
MO TUES....or.cerevie ' 135 | 4 5/11:04 | 6.0] 1:50
63 White Hart, Baws 14515 1411-29} 6 10 1-50 |Tide had fallen 4 in-
[Thirty yards. above ches.
4 5 5/11°30 |] 6 15

the White Hart.. .| 1 50

; 7 Lo a hrs, min. ft. in.
4 Bow water at bi a ridge ae = nig, = under Trinity high-water mark.

__* These experiments were tried with floats immersed at different depths; also with
-Massey’s patent log.

1834, o. ee

498 FOURTH REPORT—1834.

Experiments on the Ebb Tide of the River Thames to London Bridge,
19th of June, 1834. (Wind W.S,W. Fresh breeze and clear.)

Tide |Distance
Gauge at
Lo

Time | Velocity
mdr ‘om low} at each

Name of place. Time.
Bridge. | Bridge. | Water. | Place.

hrs. min.
Thirty yards
White Hart
64 White Hart, Barnes.
6 miles....,

er ot

5 miles (Chiswick) . .
Water Works

44 miles
HammersmithBridge.

—_
ton oo

3 miles from Chelsea
Bridge....

2% miles

Putney Bridge

2 miles

14 mile( Wandsworth)

1 mile

4 mile above

Chelsea Bridge ...

ChelseaBridge (Stairs)

Vauxhall Bridge. ...

Horse Ferry

Westminster Bridge .

Hungerford Market .

Waterloo Bridge ..,

Blackfriars do. ....

Southwark do. ....

London do,

Cl
ROOK DNANAFAOCUOS

Custom House(centre)
cae eee
| St. Katherine’s Doc
entrance
Miller’s Wharf ....

Cm of NOCD’

hrs, min. ft. in.

Rees aise FS B x My 3} under Trinity high-water mark.

REPORT ON HYDRAULICS.—PART II. 499

Comparative Average Velocities of the River Thames, as taken upon
the Flood and Ebb Tides, in 1831 and 1833.

Between Westminster and Waterloo Bridges.

First of Flood. | Last of Flood. | First of Ebb. Last of Ebb.

Feet Miles Feet Miles | Feet Miles Feet
per per per per per per
Second. Hour. | Second. . | Second, Hour; | Second.

sesseeee| 2°507 = 1-709 | 2-833 = 1-981 | 2-840 = 1-936 | 3-221 = 2-196
1831........| 2-384 = 1-591 | 2-599 = 1-772 | 2-730 = 1-861 | 2°834 = 1-932

Increase| “173 ‘118 | -284 °159| -1l 8 | ‘387-264

Between Waterloo and Blackfriars Bridges.

Feet Miles | Feet 7 Feet Miles | Feet
per _ _ per per per per per
Second. Hour, | Second. rian. Second, Hour. | Second.

370 710

Between on and Raley NES pecs.

7 Miles Feet Miles
per e er er
second. Hou ut. Seton: Hour. | Seca Bou.

So en 2-903 ~ 1-979 | 4-327 = 2-950 |
1831......| 2°685 = 1-796 | 4-468 = 3-046 |

Increase | -268 wo ‘141-096

Beit Miles | Feet Miles es Miles | Feet
Pp per per er er
Second. Hour. | Second. ts Bibi Second, poe Reais Bioan.

1833......| 2-610 = 1779 4-24) = = 2-891 5 293 = = 3°609 | 4:785 = 3-263
1831....,. hea S44 = I 938 | 4-89 = 3:334 | 6-050 = 4:124 | 5625 = 3-835

Decrease| 984 “159 | 649 448 | 757 515 | 840 -573

2K 2

500 FOURTH REPORT—1834.

Greatest Velocities.

Between Westminster and Waterloo Bridges.

Years. | Quickest Flood. Quickest Ebb.

Feet Miles Feet Miles

per er per per
Second. Hour. | Second. Hour.

1833 3505 = 2389 | 3:333 = 2-272
1831........| 3-230 = 2-200 | 2:990 = 2-038

Increase| °*275 “189

Between Waterloo and Blackfriars Bridges.

| Feet Miles Feet Miles
per per per per
| Second. Hour. | Second. Hour.

fia 4:279 = 2-917 | 4-186 = 2-854
1831......... 3°880 = 2-640 | 3-660 = 2-490

Increase , +399 277 | 526 364

Between Blackfriars and Southwark Bridges.

| Feet Miles | Feet | Miles

per per |. per per
Second, Hour. Second. Hour.
5217 = 3:556 | 5-428 = 3-700
4-990 — 3-400 | 4590 = 3129

Increase} °*227 “156 | +838 571

|

Between Southwark and New London Bridges.

Feet | Miles Feet Miles
per r per per
Second. | Hour. | Second. Hour.

1833. 4-788 = 3-264 | 5-725 = 3-903
1831........| 5540 = 3-777 | 8:160 = 5560

Decrease! °752 513 | 2-435 1-657

REPORT ON HYDRAULICS.—PART II. 501

The surveys which have been made under the direction of the
late Mr. Rennie, by order of the Lords Commissioners of the
Admiralty and of the Corporation of the City of London, both
above and below bridge, at different periods, and also by Mr. Tel-
ford previous to the building of New London Bridge, have left
ample data of the course and sections of the river Thames ; but
no measures seem to have been adopted to ascertain the effect
which the removal of the Old London Bridge- was likely to
occasion in the operation of the tides; and, as before stated,
opinions being. very contradictory, it occurred to Messrs. Rennie
to institute a series of observations for that purpose.

Accordingly, the new bridge having been opened to the public
in the year 1831, the demolition and total removal of the old
bridge commenced on 22nd November following; and on the
25th, Mr. Combe (Messrs. Rennie’s assistant) was instructed by
those gentlemen to proceed up the river to collect information,
and to make preparations for establishing a series of observations
at Putney, Kew, and Richmond Bridges, and at Teddington
Lock. 'Tide-gauges accurately adjusted by levelling to a tide-
gauge similarly fixed at New London Bridge, and at Fresh Wharf,
and a little below the bridge, were therefore fixed at these
places, and experienced persons were appointed to keep a daily
register of the high- and low-water marks as indicated by the
gauges. Accordingly, everything being ready by the 30th of
November, a simultaneous commencement was made at the dif-
ferent places on the 1st of December, and the observations were
daily recorded in a book kept by each person and forwarded to
London every ten days, until the first of June 1832; and in order
to prevent any mistakes, the gauges were frequently visited
and inspected, and upon every occasion Mr. Combe found them
undisturbed and each person attentive to his duty. Up to the
first of June, however, scarcely any part of the bridge which
obstructed the waterway had been removed, with the exception
of two piers which had been cleared away for the accommoda-
tion of the craft navigating upwards during the building of the
new bridge, the works of which nearly compensated for the en-
largement of the waterway under the old bridge. These alter-
ations had, however, lessened the fall at low water about one
foot.

The flood or low water in the early part of the year having
been found to interfere so much with the free action of the tides,
and as at the commencement of the year 1833 there was a consi-
derable fresh in the river, it was deemed unnecessary to resume
the observations until the beginning of the month of March; at
which period, however, both in the year 1833 and 1834, ‘the

502 FOURTH REPORT.—1834.

gauges were again correctly fixed, and recorded as before, and
the results of the three years have been separately and collec-
tively analysed and compiled for three months in each year, as
follows :

The prevailing winds in the months of March, April, and May
were,

In the year 1832, northerly in excess ;

1833, north and south equal ;
- — 1834, north 2, south 1.

The sectional areas at London Bridge :
Years. ‘ * i o Sup. feet.
1825, previous to any alteration, in Old London Bridge
=a 7360
below Trinity datum ...... Sa WE eee ,
1832, after two piers of the old bridge were removed. . 8700
1833, when nearly the whole of the masonry and 13800
starlings of the old bridge had been removed ;
1834, Old London Bridge entirely removed... ... . 17600

Summary for Three Years of High- and Low-water Mark
above and below Trinity datum, at Putney, Kew, and Rich-
mond Bridges, and Teddington Lock.

AT PUTNEY BRIDGE.
High Water.

Above T. dat. Below T. dat.
ft. i ft. i

Years. Tides, in. in. ft, in.

1832. 88 stood from 1 1 to5 93 mean of all the tides 1 11°17

1833. 84 12-44; 1. 5-769

1834. 89 ————— 1 4+47; —- 1 961°
Low Water.

1832. 88 stood from 10 0 to 12 7; mean of all the tides 11 8°08

1833. 84 ————-. 9 9- 12 5; 11 3°94°
1834. 89 11 9=13 0; — 12 3°64¢
Duration of the Day Flood Tides.

; hrs. min. hrs. min. é hrs. min. sec.
1832. 87 flowed from 2 45 to4 30; meanofallthetides 3 50 13
1833. 80 3 0-4 30; ———- 3 40 26°
1834. 89 3 0-4 30; 4 56 37‘
ft. in.

b a : Sag } which the high-water mark had risen.

: “1 aeas which the low-water mark had fallen.

© Or 9 min. 47 sec.

f Or 6 min. 24 ey decrease in the duration of flood tides.

REPORT ON HYDRAULICS.—PART II. 503

Conclusions.
_ The changes at Putney Bridge, situated 7 miles 3 furlongs
above London Bridge, have been as follow :
1. The high-water mark at the top | 3 ins. higher than in 1832.
_- of spring tides stood in 1834 f 2 ditto . . ditto . . 1833.
2. The high-water mark at extreme } 14 do. . . ditto. . 1832.

of neap tides... ... 1833 [3 ditto . . ditto. . 1833. —
3. The high-water mark on average | 1°56 higher than in 1832.
tides. ........ - 1834 f 3°85 lower than in 1833.

4. The low-water mark at the top | 21 ins. lower than in 1832..-
of spring tides stood in 1834 { 24 ditto . . ditto . 1833.
5. The low-water mark at the ex- | 5 ins. lower than in 1832.
treme of neap tides, in 1834 f 7 ditto . . ditto. . 1833.
6. The low-water mark upon the | 7°56ins. lowerthanin1832.
average stood in. . . . 1834 {11°70 ditto . ... 1833.
7. The range of the flood tide upon | 9°12 greater than in 1832.
the average was in . . 1834 { 7°85 ditto . ditto . 1833.
8. The range of the flocd tide, how- 15 ditto . . ditto . 1832.

ever, at the top of chee 17 ditto . . ditto . 1833.

WS WR. an vers le fe | SO
21 ditto . . ditto . 1832.
9. The range of the flood tide at the J 1 ditto less than in 1833.
extreme of neaps was in 1834 \ 6 min. 24 sec. longer
. L than in: ... . 1832.
10. The duration of the flood tide | 16 min. 11 sec. longer
upon the average was in 1834 than in ... 2. 1833.

AT KEW BRIDGE.
High Water.

Above T. So Below on dat.
ft. ft.

Years. Tides.

1832. 88 stood from 1 7 to4 8; mean of all the tides 1 3: 44
1833. 82 ————_ 1 10—- 3 8; O 9°61?
1834. 89 —————- 2 0-4 33 ——— 1 5°37°

Low Water.

1832. 88 stood from 4 6to8 11; mean ofall the tides 8 0°39
1833. 82 ————- 4 10 -- 8 10; 7 5°59°
1834. 89 8 2-911;— 9 0°88¢

ft. in.
a Or 0 5°83 which the high-water mark had risen.
b Or 0 1:93 which the high-water mark had fallen.
¢ Or 0 6°89 which the low-water mark had risen.
@ Or 1 0-49 which the low-water mark had fallen.

504 FOURTH REPORT—1834.

Duration of the Day Flood Tides.
hrs. min. hrs. min. hrs, min. sec,
1832. 88 stoodfrom 2 15 to4 0; meanofailthetides3 5 6
1833. 82 ————. 1 45-3 15; 250 542
1834. 89 —————. 2 30-3 30; 3., 1.47"

Conclusions.

The changes at Kew Bridge, situated 13 mil. 0 fur. 12 pol.
above London Bridge, have been as follow :

1. The high-water mark at the top |_5 ins. higher than in 1832.
of spring tides stood in1834f2 ditto ditto 1833.

2. The high-water mark at the ex- ' .
treme of neap tides stood in - pipes ditto’ 1832.
UGAdi tengradenssiodeteh ads: cies Sacks Sosneeak ane
. The high-water mark upon the |.1:93 ditto ditto 1832.
average stood in 1834 ...... { 7°76 ditto ditto 1833.
4. The low-water mark at the top| 44 ditto ditto 1832.
of spring tides stood in 1834 {40 ditto ditto 1833.
+ MMereme of neap tides stood in | 12 ditto ditto’ 1892.
nae P 13° ditto ditto 1833.
6. The low-water mark upon the |12°49ditto ditto 1832.
average stood in 1834........ f 19°29 ditto ditto 1833.
7. The range of the tide upon ae 56 greater thanin 1832.

oo

on

average was in 1834 ......... {11°53 ditto ditto 1833.
8. The range of the flood tide how- ditto ditto’ 1839.
ever at the top of spring tides ditto ditto 9esae.
was in 1834... sev eeeeerece
9. The range of the “flood tide at
the extreme of neaps was in

1834 eeeee eee eee eesteeeeseees eeeeee
min. 19 sec. longer

r 1 ditto ditto 1832.
10. The duration of the flood tide sf eee ay

2
4 ditto ditto 1833.
3

upon the average was in 1834 | 19 min. 53 sec. ditto 1833.

3°49 ins. less than in 1832.
3°94 ditto ditto 1833.

11. Theaverage of high-water mark
stood at Kew Bridge above
that at Putney in 1834.......+

21. The average declivity of low-

0°8707 ditto ditto 1832.
| 1°3405 ditto ditto 1833.

water line between Kew and
Putney Bridges, per mile, was
in 1834. eteeeee eet erteeereeeeeeee

hrs. min, sec.
aOro 14 12

b Ord 3 19 \ decrease in the duration of the flood tide.

REPORT ON HYDRAULICS.—PART II. 505

AT RICHMOND BRIDGE.

< High Water.
Above Trin. i are ie dat. :

Weare, Tides. " FE GH 8 are ts a
1832. 88 stood from 1 10 to 3 9; mean of all the tides O rs 3°67
1833.84 ——- 2 2-30; : 0 :2°762
1834. 89 ——- 1 11 - 3 ”; -———-———_ 1 1°70°

Low Water.
1832. 88 stood from 1 4 to 5 6; mean of all the tides 4 4°23
1833.°84 —————_ 0 9-5 2; Za7Al*
1834. 89 ————_ 4 7-64; ————. 5 5734

Duration of the Day Flood Tides.

hrs.min. hrs. min. hrs. min. sec.

1832. 84 flowed from 1 15 to 2 45; meanofallthetides159 3

rats. oe 15 8 30; — 152 37°
1834. 89 ———— 115-2 20; 1 50 108
Conclusions.

The changes at Richmond Bridge, situate 16 miles 0 fur. 6 pol
above London Bridge, have been as follow :

1. The high-water mark at the top | 1 in. higher than in . 1832

. | of spring tides stood in 1834 { 3 ins. lower than in . 1833
2. The high-water mark at the ex-

treme of neap tides stood : Hog ee ee =

Bias sense Bs oo 2 2 1834

3. The high-water mark upon the | 5°03. ditto ditto . 1832

vaverage stood in ... Lb pa ditto ditto . 1833

4. The low-water mark at the top of | 39. ditto ditto . 1832

spring tides stood in . 1834 {46 ditto ditto . 1833

§. The low-water mark athe ex] 19. ais ditto «1832

if 14. ditto ditto . 1833

Wily ont m) 4a ff. hehemheee 1834

6. The low-water mark auake the |. 13°50 ditto ditto . 1832

average stood in .. . 1834 f 22°32 ditto ditto . 1833

ft. in. :
@ Or 0 5-91 which the high-water mark had risen.
> Or 0 5:03 which the high-water mark had fallen.
© Or 0 8-82 which the low-water mark had risen.
4 Or 1 1:50 which the low-water line had fallen.
Me ‘ Pa FE ay ecrease in the duration of the flood tide.
1834. 2 K*

506 ; FOURTH REPORT—1834.

7. The range of the flood tide upon | 8°47 ins.greater thanin 1832
the average was in . . 1834 f 11°38 ditto ditto . 1833
8. The range of the flood tide how- : :
ever at the top of spring tides 7 cat oad : ts
mwas eS 1834) ~~ a eS eras
9. The range of the flood tide at ( f
the extreme of neaps was ditte ditto,” »:1833
bt ee raag|8p v4 Cite dittovg. 1839
10. The duration of the flood tide | 8m. 3s. less than in . 1832
upon the average was in 1834 { 2m.27s.less than in . 1833
11. The average high water mark) .,,,- é
stood at Richmond Bridge ate pas. dese oa yy aed
above that at Kew in. 1834 :
12. The average declivity of low-
water line between Rich-| °3388 ditto ditto . 1832
mond and Kew Bridges, per ( 4776 ditto ditto . 1833
mile, wasin ..... 1834

AT TEDDINGTON LOCK.

High Water.

Above Trin, gat. cpa ged dat.
Years. Tides, ft. it,

ft. in.
1832. 76 stood from 1 8 to 0 8; mean of all the tides 0 5°13

1833. 84 ——— 2 2- 08; ee O 9°51?
(eek oy PR Ag yo te ae Oe ae
Low Water.

1832. 76 stood from 0 7 tol 3; mean of all the tides 0 7°52
1833. 84 ———— 1 7 - 1 6;; — 0 0°35¢
4034, soos 9 g!igeye) adie poe sate gga ge
Duration of the Day Flood Tides.

hrs, min. hrs. min. hrs. min, sec.
1832. 55 flowed from0O 45 to2 45; igs es all the tides 1 32 10
1833.72 ———— 0 30- 3 15; 1 36 2°
1834. 71 ————. 0 30 -2 30; —-——_ 1 13 5f

ft. in,
4 Or 0 4:38 which the high-water mark had risen.
b Or 0 9:01 which the high-water mark had fallen.
e¢ Or 0 7:87 which the low-water line had risen.
ad Or 1 1:64 which the low water line had fallen.

e Or 3 min, 52 sec. é : ie Fa
PR Toman 8 ee decrease in the duration of the flood tide.

REPORT ON HYDRAULICS.—PART II. 507

Conclusions.

- The changes at Teddington Lock, situated 183 - miles above
Reseslon Bridge, have been as follow:

1. The high-water mark at the top : ~ lower than in 1832
of spring tide stood in 1834 ditto ditto . 1833
2. The high-water mark at extreme “F ditto ditto . 1832
of neap tide stood in ..1834f16 ditto ditto . 1833
3. The high-water mark upon the 19°91 ditto ditto . 1832
average stood in .. . 1834 f 13°39 ditto ditto . 1833
4. The low-water mark at the top|16 — ditto ditto . 1832
of spring tide stood in 1834 {28 ditto ditto . 1833
5. The low-water mark at extreme 1.16. ditto ditto . 1832
‘of neap tide stood in . 1834.f13 ditto ditto . 1833
6. The low-water mark upon the | 13°64 ditto ditto . 183
__ average stood in. ... . 1834 {21:51 ditto ditto . 1833
7. The range of the tide upon the | 4°63 in. greater than in 1832
average wasin .... 1834 f8:12 ditto ditto . 1833
8. The range of the tide at the top 8 ditto ditto . 1832
of spring tide was in . 1834 {15 ditto ditto . 1833
9. The range of the flood tide at the | 2 ins. less than in 1832
extreme of neaps was in 1834 f 2 ditto ditto . 1832
10. The duration of the flood tide | 19min.5sec. ditto . 1832
‘upon the average was in foil: 22 min.57 sec. ditto . 1833

11. The average high-water |)
stood at Teddington Lock es 98 ins. less than in 1832
’ ee that at Richmond {2°48 ditto ditto . 1832

SS ILI BBS elgeige 1834
12. The average declivity of low-

* water line between Tedding- | 0512 ins. less than in 1832
ton Lock and Richmond ( °5529 ditto ditto. . 1833
» Bridge, per mile, was in 1834 HES

512 FOURTH REPORT—1834.

Summary Table of the Day Tides,

Showing the greatest and the least tides in March, April, and
May, 1832, 1833, and 1834, at New London Bridge.

In the first year none of the lower portions of Old London
Bridge, (with the exception of two piers,) which prevented the
natural flow of the tidal waters, were removed ; and in the se-
cond year almost the whole of that structure was cleared away
as regarded the masonry and starlings, although the section of
the river was far from being completed ; many portions still re-
maining one or two feet above low-water mark, and which were
finally. removed in the year 1834.

Surface of Low

an + pet Duration of Surface of High Water Water Mark |

me Flood Tide. | above or below Trinity datum.| below Trinity
Bridge. datum.

New London Bridge.

Greatest of

Greatest of
Springs.

Greatest.
Springs.

Neaps.
Greatest of

Least of
Greatest of
Springs.
Springs.

in ft. in.| ft. in

ft. in./ft. in.| ft. in. ;
Obelow}15 5/15 8

1832.|3 6/1 10)16 9

B
5

° ft.
4 above} 5

SD
ae
>

0 10ditto| 1 9 ditto}17 11/15:

20 3

In conclusion, it may be stated,—That the drainage of the
districts bordering on the river Thames. has been greatly im-
proved ;—that barges, which used formerly to be towed up from
Putney to Richmond by horses, are now carried by the current
from London Bridge to Richmond in one tide ;—That the fall
of the low-water surface be/ow Bridge has been so considerable
as to cause ships, in many instances, to ground in their tiers at
low-water ;—and that from a register of the tides, kept by Capt.
Maugham of the London Docks, the average depth at low-water
on the cill of Shadwell Dock was 1 ft. 10 in. below the Old Tri-
nity datum ; and that where formerly there were 8 feet in depth
upon the Dock cill, there are now only 6 feet 2 inches on the
average: on the 5th of November, 1834, the tide fell as low as
4. feet 3 inches on the cill.

The accompanying Plate shows the section of the river Thames,
from actual survey, from the mouth of the river Kennet to the
Nore. The upper part could not be taken in time.

* During equinoctial gales in March, wind N.W., but the average rise barely
exceeded six inches above Trinity datum.

[ 513. ]

TRANSACTIONS OF THE SECTIONS.

1. MATHEMATICS AND PHYSICS.

MATHEMATICS.

On the Application to Dynamics of a General Mathematical
Method previously applied to Optics. By W.R. Hamixton,
M.R.I.A., Astronomer Royal for Ireland.

Tue method is founded on a combination of the principles of
variations with those of partial differentials, and may suggest
to analysts a separate branch of algebra, which may be called,
perhaps, the Calculus of Principal Functions ; because, in all
the chief applications of algebra to physics, and in a very ex-
tensive class of purely mathematical questions, it reduces the
determination of many mutually connected functions to the
search and study of one’ principal or central relation. In ap-
plying this method to Dynamics, (having previously applied it
to Optics,) Professor Hamilton has discovered the existence of
a principal function, which, if its form were fully known, would
give, by its partial differential coefficients, all the intermediate
and all the final integrals of the known equations of motion.
Professor Hamilton is of opinion that the mathematical ex-
planation of all the phznomena of matter distinct from the
phenomena of life, will ultimately be found to depend on the
properties of systems of attracting and repelling points. And
he thinks that those who do not adopt this opinion in all its
extent, must yet admit the properties of such systems to be
more highly important in the present state of science, than
any other part of the application of mathematics to physics.
He therefore accounts it the capital problem of Dynamics, ‘‘to

_ determine the 3 ” rectangular coordinates, or other marks of

position, of a free system of attracting or repelling points, as

functions of the time,” involving also 6” initial constants, which

depend on the initial circumstances of the motion, and in-
1834. 2.

514 FOURTH REPORT—1834.

volving, besides, x other constants called the masses, which
measure, for a standard distance, the attractive or repulsive
energies.

Denoting these m masses by m, m...m,, and their 3» rectan-
gular: coordinates by a Yj 2j++++++%n YnSn, and also the 3 2
component accelerations, or second differential coefficients of
these coordinates, taken with respect to the time, by 2”, y;
Bn yl ln Bn, he adopts Lacraner’s statement of this pro-
blem; namely, a formula of the following kind,

SMa! te py ty + 2! 82) = 30S Pale.)

in which U is the sum of the products of the masses, taken two
by two, and then multiplied by each other and by certain func-
tions of their mutual distances, such that their first derived
functions express the laws of their mutual repulsion, being
negative in the case of attraction. Thus, for the solar system,
each product of two masses is to be multiplied by the reci-
procal of their distance, and the results are to be added in
order to compose the function U. oat

Mr. Hamilton next multiplies this formula of Lagrange by
the element of the time dt, and integrates from the time o to
the time #, considering the time and its element as not subject
at present to the variation 8. He denotes the initial values,
or values at the time o, of the coordinates x y , and of their
first differential coefficients x! y'z', by abc and able; and
thus he obtains, from Lagrange’s formula (1.), this other im-
portant formula,

E.m (a dx—aldat ydy— b'db + a!bz — cdc) =8S, (2.)
S being the definite integral

) mn =f" {U +2 2 @? + 92+ 29} hi cdi. (3)

If the known equations of motion, of the forms

3U sU _8U,
ae 7 rm)

mx',= gf es Sos MG eg
had been completely integrated, they would give the 3 » coor-
dinates x y x, and therefore also S, as a function of the time ¢,
the masses 7,...%,, and the 62x initial constants db c¢ a’ be;
so that, by eliminating the 3 initial components of velocities
a' b! c' we should in general obtain a relation between the
7n + 2 quantities S, t, m, x,y, z, a, b,c, which would give S as
a function of the time, the masses, and the final and initial co-
ordinates.. We do not yet know the form of this last function,

als

TRANSACTIONS OF THE SECTIONS. 515

but we know its variation (2.), taken with respect to the 6 » co-
ordinates ; and on account of the independence of their 6 va-
riations, we can resolve this expression (2.) into two groups,
containing each 3 n equations: namely,

Manne Pacem i 5
Gay eo Pro tapen\, ay fa | ns Oe prey (5.)
and
lit alanine Thal. 8S = .py..fl. da. ee tanh dos
Pe Me le se m, O;, Fo mess . 6.)

the first members being partial differential coefficients of the
function §, which Mr. Hamilton calls the Principal Function
of motion of the attracting or repelling system. He thinks
that if analysts had perceived this principal function S, and
these groups of equations (5.) and (6.), they must have per-
ceived their importance. For the group (5.) expresses the 3 2
intermediate integrals of the known equations of motion (4.),
under the form of 3 7 relations between the time ¢, the masses
m, the varying coordinates x, y, x, the varying components of
velocities x! / z', and the 3 initial constants a bc; while the
group (6.) expresses the 3” final integrals of the same known
differential equations, as 3 relations, with 6 initial and ar-
bitrary constants abe a! b'c', between the time, the masses,
‘and the 3 varying coordinates. These 37 intermediate and
3 n final integrals, it was the problem of dynamics to discover.
Mathematicians had found seven intermediate, and none of the
final integrals.

Professor Hamilton’s solution of this long celebrated pro-
blem' contains, indeed, one unknown function, namely the
principal function 8, to the search and study of which he
has reduced mathematical dynamics. This function must not
be confounded with that so beautifully conceived by Lagrange,
for the more simple and elegant expression of the known dif-
ferential equations. Lagrange’s function states, Mr. Hamilton’s
function would solve the problem. The one serves to form the
differential equations of motion, the other would give their
integrals. 'To assist in pursuing this new track, and in dis-
covering the form of this new function, Mr. Hamilton remarks
that it must satisfy the following partial differential equation
of the first order and second degree, (the time being now made
to vary,)

8s 1 aS\?, (8S\2, (/88\2l _ 7
Mano am A Gado Mtg). (es) PVE

2)

516 FOURTH REPORT—18354.

which may rigorously be thus transformed, by the help of the
equations (5.),

sas. f"(u-8 = (G8) + G9) G2)

2
tf's.d {828s (518) 44 (FS 38) "J a
o . 2m Ox oa oy oY oz d2

S, being any arbitrary function of the same quantities, ¢, m, x,
Ys 8, a, b,c, supposed only to vanish (like $) at the origin of
time. If this arbitrary function S, be so chosen as to be an
approximate value of the sought function S, (and it is always
easy so to choose it,) then the two definite integrals in the for-
mula (8.) are small, but the second is in general much smaller
than the first; it may, therefore, be neglected in passing to a
second approximation, and in calculating the first definite in-
tegral, the following approximate forms of the equations (6.)
may be used,

')
A = — mai, *5s =—miJ, >a =—-me.. (.)

In this manner, a first approximation may be successively and
indefinitely corrected. And for the practical perfection of the
method, nothing further seems to be required, except to make
this process of correction more easy and rapid in its appli-
cations.

Professor Hamilton has written two Essays on this new
method in Dynamics, and one of them is already printed in
the second part of the Philosophical Ti 'ransactions (of London)
for 1834. ‘The method did not at first present itself to him
under quite so simple a form. He used at first a Character-
istic Function V, more closely analogous to that optical func-
tion which he had discovered, and had denoted by the same
letter, inhis Theory of Systems of Rays. In both optics and
dynamics, this function was the quantity called Action, consi-
dered as depending (chiefly) on the final and initial coordinates.
But when this Action-Function was employed in dynamics, it
involved an auxiliary quantity H, namely the known constant
part in the expression of half the living force of a system; and
many troublesome eliminations were required in consequence,
which are avoided by the new form of the method. “at

Mr. Hamilton thinks it worth while, however, to point out
briefly a new property of this constant H, which suggests a
new manner of expressing the differential and integral equa-
¢jons of motion of an attracting or repelling system. It is often

, 3s

TRANSACTIONS OF THE SECTIONS. 517

‘useful to express the 3 » rectangular coordinates x, y, 2+
Ln Yn Zn, as functions of 3 other marks of position, which may
be thus denoted, y, 19...%3n; and if 3m” other new variables,
‘@ Wo...@n, be introduced, and defined as follows,

Ox jy éa
ed Cee BE eh od va! CERO,

i in 7 On Oni )
it is, in general, possible to express, reciprocally, the 6 » va-
riables x y z x! y! 2! as functions of these 6 m new variables 4 @ ;
it is, therefore, possible to express, as such a function, the
quantity :

H= =. F@? + y%+2%)— Us... + (ly
under the form

Pea tet mh hein) ey U ae tents hee)

in which the part F is rational, integer, and homogeneous of
the second dimension with respect to the variables 7. Now
Mr. Hamilton has found that when the quantity H is expressed
in this last way, as a function of these 6 new variables, » a, its
variation may be put under this form,

SH=zD(y da—a sy), .. . . » (13.)

ya’ denoting the first differential coefficients of these new va-
riables » a, considered as functions of the time. The 3n dif-
ferential equations of motion of the second order, (4.), between
the rectangular coordinates and the time, for any attracting or
repelling system, may therefore be generally transformed into
twice that number of equations of the first order, between these
6 variables and the time, of the forms

SH 6H
Fa SOREL R Reg
ebay 54;

To integrate this system of equations, is to assign, from them,
6n relations between the time ¢, the 6 » variables y,; a; , and
their 6 » initial values which may be called e; p;. Mr. Hamilton
resolves the problem, under this more general form, by the
‘same principal function S as before, regarding it, however, as
depending now on the new marks e of final and initial posi-
tions of the various points of the system. For, putting, in this
new notation,

2 (14:.)

Aap ee? ,
S= f[" (05 -H) di... . (15)

518 FOURTH REPORT—1834.

and considering the time as given, he finds now the formula of
variation

$82 SS PPL yas Goenka.

and therefore the 6 » separate equations
és 8S
a,= Th, i — Se; owe . . . (17.)

which are forms for the sought relations.
Professor Hamilton thinks that these two formule of va-
riation, (13.) and (16.) namely

Odd c= Ei (ql Orie! By)y ashe 1 ee
and
oS ="E (a ty — pie), . 2).

are worthy of attention, as expressing, under concise and
simple forms, the one the differential and the other the inte-
gral equations of motion, of an attracting or repelling system.
They may be extended to other problems of dynamics, be-
sides this capital problem. The expression H can always
easily be found, and the function S can be determined with in-
definite accuracy by a method of successive approximation of
the kind already explained.

These properties of his Principal Function are treated of
more fully in his ‘‘ Second Essay on a General Method in Dy-
namics*”; in which he has introduced several forms of a cer-
tain Function of Elements, connected with the Principal Func-
tion, and with each other, and adapted to questions of per-
turbation; and has shown that for the perturbations of a
ternary or multiple system with any laws of attraction or re-
pulsion, and with one predominant mass, the differential equa-
tions of the varying elements of all the smaller masses may be
expressed together, and as simply as in the usual way, by the
coefficients of one disturbing function; (namely, the disturbing
part of the whole expression H,) and may be integrated. rigor-
ously by a corollary of his general method.

* This Essay will be found in the Philosophical Transactions for 1835.

TRANSACTIONS OF THE SECTIONS. 519

On Conjugate Functions, or Algebraic Couples, as tending to

illustrate generally the Doctrine of Imaginary. Quantities,
and as confirming the Results of Mr. Graves respecting the
Existence of Two independent Integers in the complete ex-
pression of an Imaginary. Logarithm. By W.R:Hami-
Ton, M.R.LA., Astronomer Royal for Ireland.

ApmIrTTING, at first, the usual things about imaginaries, let

uto/ —1 = diltitpy WW bad)ejas silt ty? laa)
in which w, y are one pair of real quantities, and wu, v are an-
other pair, depending on the former, and therefore capable of
being thus denoted, w,,, vzy. It is easy to prove that these
two functions, %,z,y, Vy, must satisfy the two following equations
between their partial differential coefficients.of the first order:

du __dv du_ _dv “(be
7 cnattalad Pin habeaeing L 3E SAID QTR i

Professor Hamilton calls these the Equations of Conjugation,
between the functions w, v, because they are the necessary and
sufficient conditions in order that the imaginary expression
wu +v+#%—1 should be a function of + ¥/—1. And he
thinks that without any introduction of imaginary symbols, the
two real relations (b.), between two real functions, might have
been suggested by analogies of algebra, as constituting be-
tween those two functions a connexion useful to study, and. as
leading to the same results which are usually obtained by ima-
ginaries. Dismissing, therefore, for the present, the concep-
tion and language of imaginaries, Mr. Hamilton proposes to
consider a few properties of such Conjugate Functions, or Al-
gebraic Couples; defining two functions to be conjugate when
they satisfy the two equations of conjugation, and calling, un-
der the same circumstances, the pair or couple (w, v) a,function
of the pair («, y). |

An easy extension of this view leads to the consideration of
relations between several pairs, and generally to reasonings
and operations upon pairs analogous to reasonings and opera-
tions on single quantities. For all such reasonings it is neces-
‘sary to establish definitions: the following definitions of sum
and product of pairs appear to Mr. Hamilton natural :

(ayy) (a0) = (EPG EO re ie a (c.)
(x, y) x (a,b) =(wa—yb,xb+ya),. .. (d)
‘and conduct to meanings of all integer powers and other ra-

520 FOURTH REPORT—1834.

tional functions of pairs, enabling us to generalize any ordinary
algebraic equation from single quantities to pairs, and so to in-
terpret the research of all its roots, without introducing imagi-
naries.

Without stopping to justify these definitions of sum and pro-
duct, which will probably be admitted without difficulty, Mr.
Hamilton inquires what analogous meaning should be attached
to an exponential pair, or to the notation (a, 6)*”); or, finally,
what forms ought to be assigned to the conjugate functions
Uzy) V2, in the exponential equation

(ie EPP esos 20 Tey ONO OTe Vat se (e.)

In the theory of quantities, the most fundamental properties
of the exponential function a” = ¢ («) are these:

o(x) ¢(—)=o(e4+ £),ando(I)=a; . . . (f)

Mr. Hamilton thinks it right, therefore, in the theory of pairs,
to establish by definition the analogous properties,

: (a, bY) (a, BSE” = (a, B/EFEYtM, LL, (g.)
an ‘
(2, bY) = (Ga Bid uA Desce bb STA ae

Combining these properties with the equation (e.) and with the
definition (d.) of product, and defining an equation between pairs
to involve two equations between quantities, Mr. Hamilton ob-
tains the following pair of ordinary functional equations, or
equations in differences, to be combined with the two equations
of conjugation :

Up,y Ue n tos ny "2 qe, +&yt "| (i )
is
Ms,y Ment May Men = Met by tn
and also the following pair of conditions,
Uo = 4, Yyoz=oa - . - 1 ee we (RK)

Solving the pair of equations (i.), he finds
Uzy=f (y+ Pix). cos(ay+Bx),| — )
Upny=f (aly t+ Bla). sin(ay+Bx2),} © @)

a 8 a! B! being any four constants, independent of 2 and y, and
the function f being such that

- 72 oe
SMSH1l+7+ rot fragt &es binow) ee)

TRANSACTIONS OF THE SECTIONS. 521

-and haying established the following, among many other gene-
_ral proper rties of conjugate functions, that if two such functions
be put under the forms

okiper 7 9 Up y =S (P2,y) - COS Os 95
si Pry =f (P., y- sin 6, fe)

Jf still retaining its late meaning, the functions p, , 9, , are also

‘conjugate, he concludes that the 4 constants of (I.) are con-
nected by these two relations,

C= + a, Se. le ae Wee acy eeu Cem (0.)

so that the general expressions for two conjugate exponential
functions are :

whales do gwen a

(n.)

2,4 =f («x — By).sin (ay + Ba); - (p-)

and it only remains to introduce the constants of the base-patr
(a, 6), by the conditions (k.). Those conditions give

a=f(a).cosB,b=f(a#).sinB,. 2... . (q)
and therefore, finally,

ua VE Fey
ss f =i Ce Seed ane et a unciccuet gate ae
B= Bo +Rin,

i being an arbitrary integer, and {, being a quantity which may
be assumed as > — 7, but not > 7, and may then be deter-
mined by the ee

: é (s.)
ve 24 Ve+e
The form of the direct Le pair (a, b)), (or of the
direct conjugate exponential functions w, v,) is now entirely de-
rmined ; but the process has introduced one arbitrary inte-
ger i.
Another arbitrary integer is introduced by reversing the
‘process, and seeking the inverse exponential or logarithmic

par,
fas! (ase y) =a iooe! eg erie seared EL)
ey (a,b) bs

cos By = ————,, sin By =

522 FOURTH REPORT—1834.

Professor Hamilton finds for this inverse problem the formule
Ae ad + B46

_ %)—Bp. . ;
ae in B?’ y = e i Be’ . . . . . . (u.)
in which « 6 are the constants deduced as before by (r.) from
the base-pair (a, 6), and involving the integer 2 in the expres-
sion of 6; while p and 4 are deduced from uw and v, with a new
arbitrary integer / in 4, by expressions analogous to (r.), namely,

Vit +0 dy
sic prick. weevialer ott essga eae ae Re
6= 0 + 2k,

in which 4 is supposed > — 7, but not > 7, and

u v
§ = ——— _, ] § = —__——.. = . Ww.
con Ny Vu? + x? rth Vue + v? (w)
By the definition of quotient, which the definition (d.) of pro-
duct suggests, the formulz (u.) may be briefly comprised in the
following expression of a logarithmic pair:

yeh Uae Me pans peg! Ne Cee ae
(x, y) (2, B)’ (x )

and, reciprocally, the direct exponential pair (u,v), as already
determined, may be concisely expressed by this other form of
the same equation,

(Pip Casi (eiBiy lnobed sees tke ReaeN

if we still suppose
(ayo) SF pe cose, fp bes
(a, b) = (fa.cosP, fa. sin B).

Thus all the foregoing results respecting exponential and loga-
rithmic pairs may be comprised in the equations (y.) and (z.)
When translated into the language of imaginaries, they
agree with the results respecting imaginary exponential func-
tions, direct and inverse, which were published by Mr. Graves
in the Philosophical Transactions for 1829, and it was in me-
ditating on those results of Mr. Graves that Mr. Hamilton was
led, several years ago, to this theory of conjugate functions*, as

* An Essay on this theory of Conjugate Functions was presented some years
ago by Professor Hamilton to the Royal Irish Academy, and will be published
in one of the next forthcoming volumes of its Transactions.

TRANSACTIONS OF THE SECTIONS. 523

tending to illustrate and confirm them. For example, Mr.
Graves had found, for the logarithm of unity to the Napierian
base, the expression .
2khrf—1

tee) > ie aie ee
which is more general than the.usual expression. This result
of Mr. Graves appeared erroneous to the author of the ex-
cellent Report on Aigebra, which was lately printed for the
Association; but it is confirmed by Mr. Hamilton’s theory,
which conducts to it under the form of a relation between real
pairs, namely,

Log . (1, 0) = 0, 2 kx),

Cy ue EZ)
and the connexion of this result with that Report was thought
to justify a greater fulness inthe present communication* than
would have been proper otherwise on a question so abstract
and mathematical.

On the Theory of Exponential Functions. By Joun Tuomas
Graves, of the Inner Temple, Esquire, A.M.

In October, 1826, the author of the Memoir, of which the
following pages contain an abstract, was engaged in researches,
and obtained results, which were communicated to the Royal

Society of London in the year 1828, and published in the

Philosophical Transactions for 1829, under the title “ An At-
tempt to Rectify the Inaccuracy of some Logarithmic For-
mule.”

Certain theorems of Newton, Euler, and Moivre were known
to establish a remarkable connexion between exponential and
trigonometrical functions; and the corrections made by M. Pois-
son and M. Poinsot in formule of the latter class, induced the
author to apply similar corrections to those of the former; more
generally than appeared to have been previously accomplished.
Accordingly, his original paper exhibited formule involving
arbitrary integers, by means of which he considered that. a
solution was afforded for various difficulties that had formerly

* Since this communication was prepared, Professor Hamilton has learned
that Professor Ohm of Berlin has been conducted by a-different method to re-
sults respecting Imaginary Logarithms, which agree with those of Mr. Graves:
as do also the results obtained in other ways, by Mons. Vincent and by Mr.
Warren. The partial differential equations (b.) have been noticed and em-
ployed, for a different purpose, by Mr. Murphy of Cambridge.

524 FOURTH REPORT—1834. —

perplexed mathematicians. In particular, he professed to elu-
cidate the subject of the logarithms of negative and imaginary
quantities, which, at different periods, had occasioned contro-
versies between Leibnitz and Jean Bernoulli, Euler and D’Alem-
bert. E

The researches of others have since confirmed the views of
the author, whose claim to independent discovery and priority
of printed publication is undisputed. In a paper of subse-
quent date, published in the same volume of the Phil. Trans.,
the Rev. John Warren of Cambridge, by original investiga-
tion, arrived at some of Mr. Graves’s results. In June, 1832,
M. Vincent published at Lille, results identical in effect with the
author’s principal formule. M. Vincent claims to have antici-
pated Mr. Graves in their discovery, and appeals, in corrobora-
tion of this statement, to unpublished documentary evidence in
the archives of the Société Philomatique, containing the Rapport
of MM. Ampére and Bourdon on a Mémoire read August 18,
1827, as appears by the procés-verbal of that day. This Mé-
moire is said by M. Vincent to have been substantially the
same as that of June, 1832, and to have been communicated to
M. Gergonne as early as April, 1825. Finally, Professor Ha-
milton, of Dublin, has deduced from his ingenious ‘‘ Theory of
Conjugate Functions or Algebraic Couples” a complete confir-
mation of the author’s system.

Mr. Peacock, in his ‘‘ Review of the recent progress of Analy-
sis,” (page 267 of the Transactions of the Association for 1833,)
noticed the researches of Mr. Graves, but did not acquiesce in
his conclusions, which he conceived to be difficult to reconcile
with received opinions, and to be founded on the untenable
assumption of a periodic logarithmic base. It was for the pur-
pose of removing the impression which the high authority of
Mr. Peacock is calculated to produce that the Author presented
to the Association a second paper on the subject, in order to
invite the attention of analysts to a condensed statement of his
reasoning and results, exhibited in a more systematic and po-
pular shape than in his former essay.

He is of opinion that the embarrassments and absurdities
which still encumber the doctrine of exponential functions have
chiefly arisen from calculating without fixed original principles;
from occasionally regarding disintegrated properties, of partial
and collateral application to such functions, as the foundations
of essential and unlimited theorems; from incautiously em-
ploying developments in unterminated series, without reference
to their complements and the limits of their accuracy; and,
above all, from applying algebraic rules, that are appropriate

TRANSACTIONS OF THE SECTIONS. 525

only to individualized values, to formule more or less indefi-
nite, containing those values among others. ‘This is in fact the
paralogism of applying to an equivocal term used in one sense,
a predication proved only with respect to a different sense. He
adopts the position of M.Crelle, (Journal fir die reine und
angewandte Mathematik, tom. vii. cah. 3 and 4,) that no equa-
tion is admissible, of which one side may not be proved to be,
by previous consistent postulates, an ‘‘ identical transformation”
of the other. He would not banish diverging series from ana-
lysis, but he agrees with M. Poisson and M. Cauchy in holding
that the remainder or complement of a series, even after an in-
finite number of terms, ought always to be taken into considera-
tion, since postponement, however long continued, cannot, of
itself, destroy. He goes so far as to maintain that, even in con-
verging series, this remainder, though an infinitely small quan-
tity, may, in certain cases, produce sensible effects. Thus, in
his opinion, we are not always at liberty to assume that the sum
of the series obtained by differentiating an infinite number of
terms of a converging development will approximate indefi-
nitely to the differential coefficient of the function, because (as
he shows by example) the differential coefficient of the infinitely
small remainder may be of finite magnitude. He assumes the re-
ceived symbolic rules of algebraic addition, subtraction, multipli-
cation, and division, (which are in accordance with certain lead-
ing and elect truths of numerical science,) and he proceeds in
like manner to define exponential quantities and logarithms by
means of properties which he supposes that mathematicians
would generally acknowledge to be characteristic and funda-
mental. He admits also the theorems of the integral and the
differential calculus as derived from the consideration of limits.
From these definitions and postulates, he contends that his
conclusions not only legitimately follow, but are consistent with
received notions, as far as the latter are consistent with them-
selves and with each other.
_. He explains a® (where a and « may be any quantities, real
or imaginary,) by means of the following functional definition,
viz. ‘‘a” comprises in succession every function (¢ x) of «, which,
independently of x and 2’, fulfils the following conditions :
de pean ie a tat . (1)
gl=a” 5 ‘
__ From this definition, (which Mr. Hamilton recommended him
to make, in explicit terms, the basis of his former Essay,) he

proceeds to evolve all the properties of a”. It embodies the
well-known characteristic which led to the extension of expo-

526 FOURTH REPORT—1834.

nential notation from integral to fractional, to incommensurable,
to negative, and to imaginary quantities. He contends that
there are no propositions connected with the theory more fun-
damental than that, first, “in any exponential system, the ex-
ponent of the product of similar exponential functions of any
quantities is equal to the sum of the exponents of the factors” ;
and that. secondly, ‘‘an exponential function of 1 is equal to
the base.”

If a* = y, the search of either symbol, (y the power, a@ the
base, x the logarithm,) as a function of the other two, fur-
nishes three principal problems.

First, To find y in terms of a and x.

The solution is a Sar FV ay ene rea)

In this formula the notation f 6 signifies cos # + /—1 sin$,
cos 6 and sin@ being functions of any real or imaginary quan-
tity , which, independently of @ and 4, fulfil the following con-
ditions :

(3)

cos 6 cos @ — sin@ sin = cos (6 + #)

sin 6 cos 6 + cos@sin& = sin (§ + &)

(cos $)? + (siné)? = 1
Leta =r+W0/-—lIs, r and s being real, then the notation
f 7} a signifies
8 us r eae 1

2 j —— ‘COs ae — ree GT) ae y
AFF age 3 Vee IVF +e (4.)
In this formula 7 denotes 0, or any integer positive or nega-

s
vs if
than 0. When s is positive or negative, s/ s” denotes the po-
sitive square root of s*, The author makes considerable use

tive ; denotes 1 or —1, according as s is not less or less

s
of the class of expressions of which va is anexample. They

are extremely convenient in general formulz, particularly on
account of their property of obviating the necessity of separate
cases. COS, ris represents the arc, when radius = 1, in the
first positive semicircle (including 0 and 7) whose cosine = 0.
In the statement of propositions having limits, he suggests the
peculiar importance in these investigations of expressing clearly
whether the limits, or either of them, are to be taken inclu-
sively or exclusively. /4 denotes the ordinary real Neperian
logarithm of 6.

TRANSACTIONS OF THE SECTIONS. 527

» The value of f-'a, corresponding to a particular 7 in (4.),
he denotes by f>'a. There is a discontinuity in fy; ‘a or
Jt, (r+ “—1s), as above defined. When r is negative,
tf; (r+ W —1s) is suddenly diminished by (quam proximé)
2 on the completion of the passage of s through 0 from po-
sitive to negative. For the purposes to which the author ap-
plies fs? a, it is not necessary that for all nascent and trans-

itive, as well as finite and quantitative states and values of
the r and s and the +r‘ and s* belonging respectively to a and

a, it should be predicable absolutely that f; ' a, as above de-
fined, is the same individual function of a and i, that f;'@ is
of @ and the same é. It is sufficient for him, that, in all ima-
ginable cases, f; ' a, when ¢ is supposed to be arbitrary, com-
prises ali the roots of the equation f@ = a, and, when ¢ is sup-
posed to be individualized, denotes awnique value. ‘These lat-
ter objects are attained by his notation, as above explained,

which arbitrarily defines ar to mean I, whenever s = 0.
s

_ That value of a* which is expressed by f(x f, ‘a), he de-
notes by the symbol a}, and terms the i value of a®: a; is
an individual solution of $x in equation (1.); a; and a? are
similar individual exponential functions of w and x’, in a ‘sy-
stem where a, is equal to a, and independent of 7. The theo-
rems contained in the author’s paper depend upon the original
definitions and principles assumed; and if different subsequent
definitions, subservient only to notation, were employed,—if

a value of a” different from his a} were arbitrarily assumed as

the primitive, the same theorems would still exist, though they
might require to be differently expressed. He gives sym-
metrical converging developments and easily calculable formule
for the real and imaginary parts of (r +V Plaines
x and 2* being real as well as r and_s.

Second. The second problem is to find a such that a? = Y>
x and y being given quantities, real or imaginary,
' The general solution is

; a=f(GhvRHet oe

for y will certainly be found among the values of a*, when'a

528 FOURTH REPORT—1834.

is equal to any quantity furnished by formula (5.), and con-
versely, if any value of a* = y, a cannot but be equal to
some one of those quantities.

If, however, the problem be to find a, such that the 7™ value
of a? may = y, 7 being given as well as a and y, it may be
impossible to solve the problem by any value of a@ represent-
able by admitted algebraic symbols, or reducible to the form
r+%—Il1s. The general result of the author's investigations
on this branch of the subject is, that being given the equation
apes ote =p + “—1q, we shall have, when r is not = 0,
at least 2 algebraically representable solutions, and may have
n + 1 solutions, if r?+ s? be greater than » V r?; and that we
can have at most but one such solution, and may have not even
one, when r? + s? is not greater than /7*. When / 7? is
equal to or greater than I, one representable a at least may
always be found to satisfy the equation. The “ chance of re-

presentability” of a, when a" 7-15 is given, when @ is for

the first time taken at random, and r is not = 0, may be de-
2 2

noted by , certainty being denoted by 1. Let r be = 0,

then the equation becomes av “Ms pt+W/—l1q. This equa-

tion, ¢ being given, as well as s, p, and gq, will have an infi-

: ae |
nite number of roots for a, if ~ L be greater than

WV p? ue g
(2% — 1), and not greater than (27 + 1) 7; otherwise, it will
have not one representable root.

Third, The third problem is to represent all the logarithms
of a given quantity in a given base. ,

Let a” = y, then every quantity which, being substituted for
x, allows any value of a’, as explained by (1.), to be equal to y,
is, according to the author’s definition, a “‘ LogariTHM” of y
in the base a.

The solution of this third problem is

ws? ee: tao so a ea

Any particular logarithm (2) will be of the form ; 4 i andi

being arbitrary independent integers.

i, in the denominator of the preceding formula, names, ac-
cording to the author’s nomenclature, the “‘orpER” of the lo-
garithm, and 7, in the numerator, its “RANK” in that order.

TRANSACTIONS OF THE SECTIONS. 529

._ If x be a logarithm of y of any rank in the é™ order in the
base a, we shall have a; = y.

When individualization is required, the author proposes to
denote the logarithm of y in the base a, of the ¢™ rank in the
é order by the symbol a-log; y, since the ordinary symbol
(log y) yields no information as to the base, the sayeth the

& in
| rank. Thus, e being the Neperian base, e-log, 1= Cy ey iar

Having solved these general problems, the author proceeds
to affix limits to some commonly received equations, to explain
some of the difficulties and paradoxes incident to the subject,—
to account for known facts, and to deduce novel facts relative to
the equation a? = y,—to apply his theory to other useful for-
mulz connected with exponential functions, and to show how
far it accords with ordinary notions in a variety of particular
cases; but the limits of an abstract preclude an enumeration of
his results. The following, however, may be noticed :

Let

1 gue? ed it
P= VaNV et Paha VM (9 4+ 8? 1)? Ar
then we shall have

cos, , (r+ V%—1s)

Lee (br p se V7 Ss
=2int4 cos, Wie nt A/S i( = vi=~) } aes (7.)

With reference to this formula, it is observable that Mee
ts ; P
2
+ Tats is the reciprocal of “ ~ are and _ that

when s = 0, p is equaltol, 7’, or either, according as / r?
exceeds, is less than, or is equal to, 1.

By showing that the commonly received equation (a”)” = a?”
requires to be thus modified (a”)” = 1” a*”, and by determin- —
ing the corresponding individual values of the modified equa-
tion, he points out the defect of the reasoning of M. Clausen,
_ of Altona, (noticed by Mr. Peacock, page 347 of his Report

for 1833,) which seems to prove that a. value of at ee

equal tol. He takes occasion to enforce the important distinc-

tion between the algebra of formule that are left more or less

indefinite and of individualized values. He remarks, for in-
1834. 2M

530 FOURTH REPORT—1834.

stance, that though f-'a + f-'a =f-' (aq@), yet, as f-'a
+ f—' a, in its indefinite form, admits the addition of any one
value to any other value of f—' a, it has twice as many values as
2f-'a: that f-' (a*?)=2in + 2f-‘a,and that f-'1+f-11,
or generally f—'1+.f—'a, considered as an indefinite formula,
is precisely equivalent to f—'1 or fa respectively.

a’°= 1" a; or generally a* = 1’ aj, é.e. all the values of a”
are given by multiplying any single value in succession by all
the values of i*. Now 1* has an infinite number of values,
unless x be a ‘‘ rational fraction” (positive or negative, inelu-
ding integers,) in which case the number of values is equal to
the denominator of the fraction in its lowest terms. :

If a* have among its values two quantities differing only in
sign, x is a rational fraction, with, in its lowest terms, an even
denominator. Let @ be positive and x a rational fraction,

which in its lowest terms = = the number of real values of

a* will be one or two, according as m is odd oreven. Let
a: = y, then x, if a be negative and y positive, must be a ra-
tional fraction, with, in its lowest terms, an even numerator
and odd denominator; if @ be positive and y negative, an odd
numerator and even denominator; if a and y be both nega-
tive, an odd numerator and odd denominator. When « is of
the form r + 4 —1s, a real, and r irrational, a* can have
only one real value. When a is real, r rational, and s not

= 0, at vs 5 if it have one real value, has an infinite num-
ber. When x is of the form —1s and a real, whenever
one value of a” is real, all the other values, of which there are
an infinite number, are also. real.

A quantity (p + “—14q) may have no real logarithm, and
can have no more than one in a given base (r+ “ —1s), un-
less the ‘‘ moduli” of the quantity (= / p*+ q°*, adopting the
phraseology of M. Cauchy,) and of the base are both = 1, in
which case the number of real logarithms is infinite. When
one real logarithm exists, and one only, it is = a a

8 , ys l/eet+ se
When an exponent is real and rational, and in such case only,
it will reappear at intervals with different ranks in different
orders, as a logarithm of the same quantity in a given base.

In conclusion, the author states, that, as all the values of |”
were before known (at least when x was real) to be comprised

in the formula cos (2ia7) + —1 sin(2ia7), the principal

TRANSACTIONS OF THE SECTIONS. 531

novelty of his theory consists, Ist, in always determining (and
that, in a form capable of approximate numerical computation)
some single value of a® (ex. gr.a,), which appeared not to
have been accomplished, for all real and ‘imaginary values of
a and x; and, 2ndly, in showing that the complete formula for
the logarithms of a given quantity in a given base involves Two
arbitrary independent integers, or that every quantity has an
infinite number of orders of logarithms in a given base, and an
infinite number of logarithms in each order. He suggests the
application of his results to the theory of numbers, of equations,
and of factorial functions.

P.S.—Mr. Graves has learned, since his paper was presented
to the Association, that Professor Ohm, in a volume, published
in 1829, of his highly valuable system of Algebra, gives some
formule for exponential functions which agree with the princi-
ples promulgated, probably about the same time, in the First
Part of the Phil. Trans. for 1829, but are confined to cases
where the given quantities are real. This distinguished Ger-
man analyst, however, was aware that expressions of a similar
kind might be obtained, which, like those of the preceding
Abstract, would include powers, where the root and the expo-
nent, and logarithms, where the number and the base, were
imaginary.

PHYSICS.

Notice of the Reduction of an anomalous Fact in Hydrody-
_ namics, and of a new Law of the Resistance of Fluids to the
Motion of Floating Bodies. By Joun S. Russe.i, M.A.

"The author has been induced to contribute this paper to
the Transactions of the Association, in consequence of a state-
ment made last year by Mr. Challis in his excellent Report on
Hydrodynamics, the first part of which is contained in the last
volume of the Proceedings. The paragraph containing the
statement referred to is the last of the Report, and is to be
found in page 150, beginning “ A singular fact,” &c. The au-
thor also refers to another passage in the Report of Mr. Chal-
lis, consisting of the two first sentences of the paragraph im-
mediately before the former quotation (p. 149).

From these statements, and many others that could readily
be quoted, it appears that the theory of the resistance op-
posed by fluids to the motion of floating bodies remains in.a
very imperfect state; that the resistance is generally stated to

2mMm2

5382 FOURTH REPORT—1834.

increase with the square of the velocity ; that this law is sub-
ject to a remarkable exception at some point where the re-
sistance suddenly ceases to increase in the former ratio, and
appears to follow a new and unknown law. To this subject
the author has been recently induced to pay considerable at-
tention, and he has enjoyed some facilities of observing these
phznomena on a large scale, as well as of making experiments
on a more limited one, which have induced him to take a view
of the subject considerably different from any with which he
has had the good fortune to meet.

In regard to the point of velocity at which the phenomenon
occurs, he states that it is in the transition from 8 to 9 miles
an hour; and that after passing that point, the force required
to propel the boat at the higher velocity is less than at the
lower. It is also consonant with his observations and with exact
measurement, that the vessel at this point rises out of the
water, so that a vessel drawing 12 inches of water when at
rest, rises 2 inches out of the water when brought up to a ve-
locity of 9 miles.

Such is the fact; and it is equally a fact, as Mr. Challis
remarks, that theory never predicted anything of the kind.
It appears to the author that the reason why theory has
hitherto been so ineffectually applied to this subject is that
the theory of immersed bodies has been confounded with the
theory of floating bodies. The immersed and the floating
body are in circumstances totally different. He has therefore
considered them apart from each other, and has arrived at the
following conclusions, which are entirely different from the
principles hitherto received, and which perfectly coincide with
the facts noticed, and readily account for them.

The following are the results of the investigation.

1. That in all cases and at all velocities the displacement of
water by a floating body is diminished by communicating ho-
rizontal rectilineal motion to it: that this effect is not con-
fined to velocities of 8 and 9 miles an hour, but extends from
the bottom of the scale of velocity to the top of it.

2. That this emersion is independent of the form of the
body, and will take place equally with the worst and best form
of vessel, the only difference being that the other elements of
resistance will render more force necessary to communicate
the required velocity in the former than in the latter case.

3. That for the velocity of one mile an hour, the section of
immersion when compared with that section when at rest, con-
sidered as unity, will be diminished by ‘0228, or 4-nearly; at
5 miles an hour, the emersion becomes ‘114 = jj nearly; and

a

TRANSACTIONS OF THE SECTIONS. 533°

by a further increase to 9 miles, ‘205 = 1 nearly. The im-
mersion goes on diminishing at superior velocities in a con-
tinuous ratio, the emersion becoming at 20 miles -456 = 4; at
30, °684 = 3; at 40 miles an hour, only ;1, of the whole section
will be immersed ; and at 43°859 miles the elevating force will
exactly balance the gravitation of the vessel, and she will rise
entirely on the top of the water, descending to skim its sur-
face and again rising above it at alternate intervals of equal
duration.

4. The law may be generally expressed thus: If any float-
ing body be put in motion with a given velocity, the pressure
which it exerts downwards upon the fluid in virtue of gravity
as diminished by a quantity proportional to the weight of a
column of the fluid having the height due to the velocity ;
and the ratio of the height of such a column to the velocity it
represents will express the ratio of the dynamical section o
immersion to the statical one, and the resistance will be that due
to this diminished section.

5. Although the author has not verified this law experi-
mentally to higher velocities than 20 miles an hour, yet from
its perfect coincidence with observation up to that point, he
has sufficient confidence in its correctness to predict that it
will hold rigorously in the higher velocities; and if either this
theory or a more accurate one substituted for it should be
found to hold, we may yet save our science from some imputa-
tion of sluggishness.

Let S = section of statical immersion.

v = velocity of motion.

& = measure of gravity.

s’ = dynamical section of immersion.
vs = displacement of statical section.

v seg i
Ze = height due to velocity.

of =8.(o- 2) vas {1-2}

_ When s = 0, v = 2g = 64 feet per sec.

Table showing the relation of the dynamical section of immer-
_ sion due to a given velocity, the statical section being consi-
dered as unity.

Miles per hour. Feet per second. Amount of Emersion,
TP ae ess BSEG? Ve ce weet eters *0228125
Diss rapt aah DR OANy wo i stiald evehore 0456250
tae aelaaiatala els SETS ie Oh Habana 0684375
x Habpatoiiir th ~ OL Ass eke ofss 0912500

534 FOURTH REPORT—1834.

Miles per Hour. Feet per Second. Amount of Emersion.
Dacca ec 7°30 eaprera tink *1140625
AW 361. ots SG. ees soe. -1368750
11) Te: MO ELD vm ca hers.'e wcclepale *1596875
8 Se aie aie TLGSr Akt ae Some “1825000
RIOT AE: WS TA Og. ond. *2053125

LO} fhepae cee L460 A ede *2281250
Bis. Se ees MGOGRS nto ke ee *2509375
42 Sieheetaiete 17°52 ea one *2737500
Wea, debedctecmccctets TSS ae ee mee *2965625
GR otitesc ik eid OA Sia'sceh cate *3193750
19) Peon Be AFORE eseee. f *3421875
ZONE ZOD AS wala. steratetars *4562500
PERM ee Oe DO OO) o. ciate ns *56703125
OP hapac terete sc FS OO ated cae cist ee “6843750
OTs is elaeke DEMO RA. staan “7984375
401 62. ess 3 58°40 EN Gavte.. *9125000
AWA Asp oats DOLSG tii. egies vue *9353125
BD tS ES GSB) OS Nee: *9581250
BOM Ph cil Mateos GUzi Sree eh izte tas *9809375
TD ae act cea. > Oa se) Ayan eve imiedere 1:0000000

On the Collision of imperfectly Elastic Bodies. By Eaton
Hopexinson, Salford, Manchester.

The theory of imperfect elasticity of which Newton gave
the elements, from experiments alluded to in the Principia
(scholium to the laws of motion), has not always been received
with that cordiality which attaches to scientific deductions
clearly proved; and among our neighbours the French, it is
seldom used. This circumstance, together with the remarks
in a work of great value by a member of the University of
Cambridge*, and a suggestion of its distinguished author,
made me desirous to repeat the experiments of Newton; and
to seek for data necessary to supply, amongst other things,
the laws that regulate the elasticities after collision in bodies
of the same, and of different natures.

In this research I have been, as on former occasions, gra-
tuitously supplied with every requisite, so-far as I found it ne-
cessary, by Mr. Fairbairn, engineer, of Manchester.

To obtain the results, the mode I usually adopted was nearly
that used by Sir Isaac Newton himself, in which two balls, A,
B, were suspended from points C, D, with equal radii, so as
just to be in contact when hanging vertically ; and the curves
AEH, BFG, were circular arcs round the centres C, D, in-
scribed on a wall contiguous. The arcs were divided accord-

* Mr. Whewell, in his Mechanics.

TRANSACTIONS OF THE SECTIONS. 535
ing to their chords, each way, starting from the lowest point,

the point. of junction of the balls when still; since the velo-
cities acquired by bodies falling down those arcs are as their

Cc

chords. In the experiments with the larger balls, two persons
usually supported the balls at any points, G, H, of equal height,
as directed, and let them fall at the instant that a sharp blow
was given on the wall for a signal, the author and another
person observing the points E, I, to which the balls returned
after having impinged at the lowest point. The chords of the
arc, fallen through and returned, were, as mentioned above,
considered as the measures of the velocities of impact and re-
coil. In some of the experiments one of the balls was at rest
at the lowest point, before impact. The resistance of the air,
in the lighter bodies especially, was generally allowed for. _

In the tabulated results of experiments accompanying this,
each number set down for the elasticity is the greatest from
about ten impacts; and in the smaller balls, especially in the
greater arcs, it is often from as many as twenty, on account of
the difficulty of obtaining, with large arcs, direct and central
impacts. Nf

Conclusions from the Experiments referring to the “‘Tabulated
Results” for proofs and illustrations.

Conclusion 1. All rigid bodies are possessed of some de-
gree of elasticity; and among bodies of the same nature, the
hardest are generally the most elastic.

This conclusion obtains a good illustration from metals.
Thus, the soft metal lead has an elasticity of :20, as exhibited
by its mean ratio; brass, which is harder than lead, has its
elasticity *36; bell-metal, which is harder than brass, has °59;
cast iron, still harder, has °66; and steel, the hardest metal of
all, has °79 for its elasticity. (Expts. 13, 10, 12, 1 to 3, 31.)
The same conclusions might be drawn from the elasticities of

536 FOURTH REPORT—1834.

other bodies increasing in hardness: thus, malleable clay, stone,
hard-baked clay, glass, give elasticities of about ‘17, 79, 89,
94, (Expts. 18, 27, 29, 24.)

Conclusion2. There are no perfectly hard inelastic bodies,
as assumed by the earlier, and some modern, writers on me-
chanics.

If Conclusion 1. be true, this will follow as a consequence,
the proofs of both being of the same nature.

Conclusion 3. The elasticity, as measured by the velocity
of recoil divided by the velocity of impact, is a ratio which
(though decreasing as the velocity increases,) is nearly constant,
when the same rigid bodies are struck together with consider-
ably different velocities.

The proofs of this are very numerous; they may be taken
(with some anomalies,) from almost every experiment. In ex-
periments 1 and 2, cast-iron balls striking together with ve-
locities as 4, 6, 8, 10, 12, gave, in the one case, elasticities
*69, ‘66, ‘66, ‘61, ‘59; and in the other case ‘70, *69, °66, °64,
“62. In experiments 10 and 11, balls of soft brass struck to-
gether with velocities varying from 4 to 20, gave for their elas-
ticities ‘38, *37, °36, ‘30, °33; and even lead, which permanently
changes its figure at every impact, preserves considerable ap-
proximation to equality in its elasticities, as may be seen from
Experiments 13 and 14. The same may be said of other bo-
dies besides metals, as will be evident by inspection of the
tables of results; the irregularity and decrease of elasticity
being greater in those bodies that least recover their forms
after impact. It is probable, too, that the decrease of elasticity,
in some bodies, from the larger impacts, is somewhat less than
as indicated in the table, on account of the great difficulty then
of obtaining perfectly central impacts.

Conclusion4. The elasticity, as defined in Conclusion 3, is
the same whether the impinging bodies be great or small.

This fact is proved by Experiments 1, 2, and 20, in which
the elasticities of cast iron are ‘64, ‘66, and °73; differing in
the first and second experiments only 3, though the weights of
the equal balls in experiment | are more than five times the
weight of those in experiment 2. In the Ist and 20th experi-
ment, the difference of elasticity is but 4th, though the balls
vary in weight as 74 to 1.

Conclusion 5. The elasticity is the same, whatever be the
relative weights of the impinging bodies.

This will be shown by comparing the results of experiments
5 and 58, in which the same stone ball was struck against two
balls of cast iron, one 33 times as heavy as the other; the elas-

TRANSACTIONS OF THE SECTIONS. 537

ticity in the two cases being *71 and 76, or nearly equal. In
experiments 6 and. 60, balls of brass, varying in weight as 30
to 1, were struck against the same stone ball, and their elas-
ticities varied only from ‘62 to ‘68.

Various other proofs, both of this and the preceding “ Con-
clusion,” may be obtained from the tabulated results; and
therefore the elasticities given in the tables will apply, what-
ever be the relative or absolute weights of the impinging
bodies.

Conclusion 6. In impacts between bodies differing very
much in hardness, the elasticity with which they separate is
nearly that of the softer body.

This may be shown by many examples: thus, lead, the elas-
ticity of which is ‘20 (Exp. 13.), is much harder than cork,
whose elasticity is 65 (Exp. 25.) ; but the elasticity of lead
struck against cork is ‘57, differing only 4 from that of cork
(Exp. 44.). The elasticities of steel, cast iron, stone, and
glass, are ‘67, °73, "79, ‘94, (Expts. 30, 20, 27, 24); and these
bodies are very hard, compared with lead, whose elasticity is
‘20; but if they be successively struck against lead, the re-
sulting elasticities will be °19, °17, °28, -25 (Expts. 50, 49, 56,
32); differing not widely from that of:lead. There is fre-
quently, however, a considerable loss of elasticity in impacts
between bodies differing much in hardness, arising from the
softer body being crushed with the blow, in the manner that a
soft body would be by a hammer.

Conclusion 7. In impacts between bodies whose hardness
differs in any degree, the resulting elasticity is made up of the
elasticities of both; each body contributing a part of its own
elasticity in proportion to its relative softness or compressibility.

From Conclusion 6 we see that if any body, as lead, be struck
successively by two other bodies, as cork and steel, one very
soft and the other very hard compared with itself, the lead in
the first case will contribute scarcely any of its elasticity, the
cork giving nearly the whole of its: and in the second case the
lead would contribute nearly all its elasticity, and the steel
searcely any. (Expts. 13, 25, 30, 43, 50.) Hence we may
conclude that if the lead had been struck against another body
of equal softness or compressibility with itself, the lead would
have contributed half of its own elasticity, and the other body

half of its own, to form the resulting elasticity.

- This reasoning seems to be borne out by experiment, as will
be seen further on. Admitting it therefore to be generally
correct, we see that in the two extreme cases of collisions, be-
tween bodies of equal hardness and of very different hardness,

538 FOURTH REPORT—1834. /

each. body contributes a portion of its own proper elasticity in
proportion to its relative compressibility.. Hence in collisions
between bodies whose hardness differs in any other degree, it
seems natural to conclude that the same law is preserved.

To exhibit this in a form capable of submitting it to the test
of experiment: Let a and represent the relative hardness of
two bodies, a’ and J! their respective elasticities, to find the
elasticity resulting from their collision.

Since in bodies considered as springs the compression of
each is inversely as the hardness, or resistance to compression,

calling a = the compression of the first body, we have
zs = the compression of the second.

Whence = ss a the compression from the two.

b
l
da lisgn bn, Uh att:
TOROS ig the compression from the first
— ay Ear
a b
body in terms of the whole compression.

1

fission ke Hee
Rofwk Faik aepeis the compression from the se-
a b

cond, in terms of the whole.
But by the 7th Conclusion,

x a = the elasticity contributed by the first

a+b
body;
3 - 5% b’ = the elasticity from the second.
! ! :
Whence their sum wets = the required elasticity from
both.

The modulus of elasticity seems to afford the best means of
judging of the relative powers of bodies to resist incipient com
pression. I have therefore selected that datum from Tredgold’s
Essay on Cast Iron, in the few cases that answered my purpose,

TRANSACTIONS OF THE SECTIONS. 539

and ‘supplied it in: some others from*my own ‘experiments ;
reckoning the modulus in lbs., and for a base of an inch square.

Cast iron...... ttisceeesessesesseeesesessseeesee 18,400,000 lbs. Tredgold.
White marble. cei ee aes eee 2,520,000
a ae A eee denrsns eae w. 1,340,000
Lead, cast......... wide ub oetely ay eee peaeeed oe 720,000

Best double shear steel*, not hardened... 31,165,000
‘Bell metal +, same as in our experiments 11,380,000
Soft brass, same as in our experiments 10,440,000

Glass, from window-glass .......ese00. eseee 8,980,000
ENGEY. ented edvervtce vaaeewed ade suena wasnce ss 1,630,000
COT cnt dss ohieu as Soa reels fies, asd: ts 2,369

Suppose it were required to find the elasticity of glass struck
against brass.

The modulus of a glass being 8,580,000, and that of brass
10,440,000, their relative hardness is as 86 to 105 nearly; and
the elasticity of glass is ‘94 and of brass -41 (Expts. 24, 22.):
hence in the formula, for the elasticity above, we have a = 86,
a = ‘94, b = 105, b' = -41,

. 40 +ba _ 86 x 414105 x 94 _. (i
ticity required (being ;;th less than that given by Exp. 34.).
In impacts between other bodies we have as follows:

Computed

Names of Bodies, with their Elasticities. pyomPuted Elasticities, Errors,
Glass (-94) against lead (-20) ..0c00-- "257 sescesvee °25 casece Sa =
Glass (-94) against bell-metal (-67)... “82 ......4 fe PEO TIN: Shc aes —y,
Ivory (-81) against cork (-65) .......0. RGA ceteacees 160 cecesenas ts

-* A bar of best double shear steel, not hardened, -99 inch deep, ‘96 inch
broad, and 6 feet 8 inches long, weighing 22% lbs. was laid on props 6 feet
asunder, and 196 Ibs. suspended from the middle bent it -63 inch without in-
juring its elasticity: other weights, as 252, 308, 364, 420, bent it “81, 1:00,
1:17, 1°35. The experiment was made with great care, and a long wedge of
wood was employed to measure the deflections.

t+ A bar 2 feet between the supports, -51 inch deep and 1-03 inch broad, bent
*27 inch with 1214 lbs. without injuring its elasticity : 304 Ibs. bent it 62, and
318 broke it. .

} A bar 2 feet between the supports, ‘52 inch deep, and 1-04 inch broad,
bent ‘15 inch by 663 lbs. without injuring the elasticity: other weights, as
944, 150%, 1714, 2194, bent it -22, -48, -70, 2°87, showing its great softness and
flexibility. Its modulus calculated for double the weight necessary to destroy
its elasticity was only 5,270,000 lbs., half that given above.

The modulus for glass was obtained from the mean between three experi-
ments made by bending slips of window-glass,giving 9,600,000lbs., 8,505,000lbs.,
and 7,634,000 lbs.

The modulus for ivory was obtained by bending two slips of ivory ; and for
cork by compressing a rectangular piece 16 inches long and 2-05 inches sec-
tion; the decrement with 127% lbs, being °42 inch,

540 - FOURTH REPORT—1834.

Names of Bodies, with their Elasticities. ,computed ae ne Errors.
Ivory (°81) against lead (-20) ....c.02. ‘3D ceseceeee “EE ceceereee — F
Ivory (*81) against brass (*41)...es0e0. °76 cececeeee °78 eeeeeeeee — ay
Ivory (‘81) against bell-metal (67)... *79 ....se000 SNe oxansenine as
Brass (41) against bell-metal (67)... °53 ......0- ANGE lets —3
Brass (‘41) against castiron ("73) ... ‘52 ....... sphgrrd ) hoeeeaccse 2s
Brass (‘41) against steel (*67)-......... "4 epeecenes *A( caseananen =
Brass (-41) against limestone* (*79). ‘71 — ..sse00e 273). ‘ssteunnae —
Lead (-20) against limestone (*79) ... °32 ccseceeee "28 ceseeenee =F
Lead (:20) against elm + (‘60)......... R00. cleseassuses Go| na nenenee eet
Brass (:41) against elm (‘60) ......... ‘OS stevosces, OO) steacenae meee

Other instances might be adduced, but the above may be
sufficient to show the consistency of the formula, and of the
7th Conclusion, from which it is deduced.

* T have supposed the modulus of limestone to be 2,520,000 Ibs., the same
which Mr. Tredgold found for white marble. The balls we used were some-
what softer than it; but Mr. Tredgold’s results being obtained from the flexure
at the time of fracture, must be too low, as he himself has observed.

+ I have assumed the modulus of elm, struck across the fibres, to be
1,000,000 lbs. ; its value in the direction of the fibres being 1,340,000 lbs., as
before given.

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544 FOURTH REPORT—1834.

Theoretical Explanations of some Facts relating to the Com-
position of the Colours of the Spectrum. By the Rev. James
CHALLIS. ;

A ray of homogeneous light, in the undulatory hypothesis,
consists of the isochronous undulations of an elastic medium; and
the velocity at a given instant, of the undulating particles situ-
ated on a straight line drawn in the direction in which the light

travels, is expressed by the function m sin ( <= + e), x being

the distance of any point on the line from a fixed point. The
condition of homogeneity is, that m and A be constant: the
colour depends on A.

If two rays be combined, for which m is the same and A dif-
ferent, the compound ray, by the principle of the coexistence
of small vibrations, is expressed by

. (* 2x a ae \.
m sin Se + msin a ea Meg 3

; 1 hifi 1 hes BAP oe. 1
or if teeta and Pigg pay ,» by

2m cos(** + 7) sin ( + ¢2))

In the spectrum the greatest and least values of A are to each other

nearly in the ratio of 3 to 2, so that ae == is at least equal

to a) and Z at least equal to 6 4. Hence in the periodic func-

tion cos (= + ) the periods recur much less frequently than

those of the other factor, sin (= oa my) ; in which L is an har-

monic mean between A and A. It does not appear that the eye
can appreciate periods of slower recurrence than those corre-
sponding to the rays of the spectrum. We may, therefore, con-

clude that the periodicity of cos i - ¢) would not be per-

ceived, and that the eye would be sensible only of that of the
other factor. The compound ray will therefore be of an inter-
mediate colour.

|
;
|

eee

TRANSACTIONS OF THE SECTIONS. 545

Newton asserts, in a letter to Oldenburg, that “ if any two
colours be mixed, which in the series of those generated by the
prism are not too far distant from one another, they, by their
mutual allay, compound that colour which in the said series
appeareth in the mid-way between them*.”

_ Dr. Young states that “ perfect sensations of yellow and of
blue are produced respectively by mixtures of red and green,
and of green and violet light +.”

According to the theory here proposed, the compound colour
is independent of the origins of the component rays, for ¢ and
e may be any arbitrary quantities; and this agrees with ex-
perience.

It follows, too, from this theory that the red and violet can-
not be produced by mixing two colours of the spectrum, but
every other prismatic colour may. Dr. Young takes red, green,
and violet as fundamental colours in his theory of composition.
In Mayer’s theory, red, yellow, and blue are the fundamental
colours, and violet is supposed to be a compound only because
it produces, without being mixed with any other colour, a sen-
rey impression of redness. See Herschel’s Treatise on Light,

rt. 515.

The difference between two rays expressed respectively by
the functions m sin _ + c) and 2 m cos = + )
sin sis + e), is exhibited in figures 1 and ¥. Since it is

known by experience that the eye is not sensible to a momen-
tary interruption of a ray (as exhibited in fig. 3.), there seems
to be no reason to expect that it would perceive any difference
between the rays of figures 1 and 2, Nothing in light corre-
sponds to discords in sound.

Fig.\. momma mtn
Fig. 2. perme
Fig.3. anon a ieee,
Fig. 5. ot RG AAR 5) NAS tg 8 Bg ST |

» Sir John Herschel is of opinion that the fact of the complete
unitation of the prismatic green by a mixture of adjacent colours

- et ie
be * Horsley’s Edition of Newton's Works, vol. iv. p.303.
+ Lectures on Natural Philosophy, vol. i. p.439.

1834, 2N

546 FOURTH REPORT—1834.

favours the idea of the possibility of an analysis of white light
distinct from that afforded by the prism. (Treatise on Light,
Art. 516.) The tendency of the preceding theory is to show,
that the possibility of decomposing one ray is no ground for
thinking that another exactly the same in appearance is also
decomposable.

If m were not the same in the two component rays, the com-
pound ray would not be so like a homogeneous ray, since the
intervals between the points of no velocity would not all be
equal. In mixing two simple rays there must consequently be
an adjustment of the quantity of light in each to bring out the
purest compound.

Composition of all the Colours of the Spectrum.—Let RQBV
(fig. 4.) be the curve line (as determined by the experiments
of Fraunhofer,) whose ordinates represent the intensity of
light from R, the red end, to V, the violet end of the spectrum.

Vv

R M A D

Draw AB, dividing the area into two equal parts, RAB, VAB.
Divide each of the parts into the same number of small equal
portions (m). Let RH and VK be taken in the proportion of
the values of A for the extreme red and violet rays, and let the
curve line HPK be such that an ordinate PM is as the value of
A corresponding to the intensity QM. Also let DE be an har-
monic mean between RH and VK. ‘Then, compounding the
small portions two and two, taking one in each of the areas
RAB, VAB, beginning with the extreme portions at R and
V, and proceeding with the others in succession to B, there will
be as many compound rays as there are portions, and each will
be expressed by such a function as

Tx oad © 26
2m cos CF + =) sin ( - es)
in which J is greater in proportion as the combined portions
are nearer each other, and L is always intermediate to the
values of A corresponding to AC and DE. The sum of all
these functions is the function expressing the result of com-
pounding the whole spectrum. Nothing can be anticipated
respecting the nature of the final expression, except that it in-

on

TRANSACTIONS OF THE SECTIONS. 547

dicates that the points of no velocity are at irregular intervals
from each other, as exhibited in fig. 5. ‘This would appear by
combining two or three of the functions by mechanical construc-
tion. It seems probable, then, that this condition is necessary
to produce white light, and that the whiteness is more perfect
in proportion as the intervals are more irregular. The colours
which are neither white nor those of the spectrum, may be con-
ceived to correspond to undulations in which there is an ap-
proach to regularity by the preponderance of two or more sets
of equal intervals.

Newton asserts that the sun’s light is not perfectly white, but
has a tincture of yellow. If there be a preponderance of any
colour, the preceding theory would lead us to expect it would
be of that which corresponds to the ordinate AC, which, as
may be judged from Fraunhofer’s curve, is situated in the yellow
part of the spectrum. (See the figures to Articles 419 and 496
of Herschel’s Treatise.) For the greater number of the com-
ponent portions have / very large, and L very nearly equal to
the value of A, corresponding to the ordinate AC*.

Ifa part of the spectrum towards the violet end be inter-
cepted, and the rest compounded as before, AC will be shifted
a little towards the red end, but DE considerably more so.
Thus DE and AC will be brought nearer each other, and the.
compound, if yellow before, will now be more decidedly yellow.
By stopping a still greater portion, these ordinates will approxi-
mate still more, till they coincide, and at length DE passes to
the other side of AC. In the mean while the resulting colour
will pass through orange till it becomes red.

If the spectrum he progressively stopped, beginning at the
other end, the resulting colours will be approximations to
those that lie towards the violet end. The ordinates AC, DE
will never in this case coincide, since the greater portion of
the light of the spectrum lies towards the red end.

If the middle part of the spectrum were stopped, the colour
which results by compounding the remainder may not be any
in the spectrum, though the two parts of which it is composed,
taken separately, give nearly spectrum colours; for by the union
of these two parts, the intervals between the points of no ve-
locity become more irregular than in either of them, the effect
of combination being in general to increase the irregularity.

_All this agrees very well with what is said in Art. 409 of
Herschel’s Treatise. “ If the violet light be intercepted, the

_* The residuum colour would be different for a different form of the curve,
May not the colours of the fixed stars be owing to a difference of this kind?

2n2

548 FOURTH REPORT—1834.

white will acquire a tinge of yellow; if the blue and green be
successively stopped, this yellow will grow more and moreruddy,
and pass through orange to scarlet and blood red. If, on the
other hand, the red end of the spectrum be stopped, and more
and more of the less refrangible portion thus successively abs-
tracted from the beam, the white will pass first into pale, and
then to vivid green, blue-green, blue, and finally into violet. If
the middle portion of the spectrum be intercepted, the remain-
ing rays, concentrated, produce various shades of purple, crim-
son, or plum-colour.”

The subject of this paper admits of more lengthened and ac-
curate treatment than is given to it here. The object of this
communication is merely to call attention to a circumstance
which appears to have been overlooked in the undulatory
theory of light, viz. an analogy existing between the composi-
tion of colours and the composition of small vibrations.

On the Achromatism of the Eye; in continuation of a Paper
in the last Volume of the British Association Reports. By
the Rev. BapEN Powe 1, M.A., F.R.S., Sav. Prof. of Geo-
metry, Oxford.

In the paper referred to the author inadvertently introduced
a formula which he did not observe was incorrect till the sheet
had been printed. The correct expression will be found by
taking the general formula for the principal focal length (F)
after refraction through two surfaces, at which the relative in-
dices (taking the sines in the order of transmission) are p #,
and the radii 7 r (remaining to be affected by their proper
signs), which is (see the author’s Optics, p. 23,)

i Tapa habe tae i: Le-l

Ps nr Pie

Adapting this to a double convex lens (when r becomes nega-
tive), and equating similar expressions for the red: and violet
rays, the condition of achromatism will be found to be

Per _ [(7 +7) tr — 7) By

Ho [ir +7) by — 71

When this is fulfilled, achromatism may be produced by the
nature of the medium in which the focus is formed. This prac-
tically differs little from what was given in the former paper.

TRANSACTIONS OF THE SECTIONS. 549

On the Theory of the Dispersion of Light by the Hypothesis
of Undulations. By the Rev. Bapren Powe 11, M.A., F.R.S.,
Sav. Prof. of Geometry, Oxford.

The object of this communication was principally to give
a brief view of the nature of the explanation afforded by
M. Cauchy’s analysis of the dispersion, which has hitherto pre-
sented so formidable a difficulty, whether to the undulatory or
to any other theory, and of some important suggestions which
have been made with respect to it. An attentive examination
of the quantities entering the analysis points out a limitation,
or condition, which must be annexed to M. Cauchy’s conclu-
sion, It is the object of his analysis to show that there exists
generally a relation between the length of a wave and the time
of its propagation. It appears from the nature of the expres-
sions employed, that, in order that this should hold good uni-
versally, we must add to his original hypothesis as to the con-
stitution of the ztherial medium this condition, that ‘‘ the di-
stance between two molecules must not be very small compared
with the length of an undulation.

On the Repulsion excited between Surfaces at minute Di-
stances by the Action of Heat. By the Rev. BapEN PowELt,
M.A., F.R.S., Sav. Prof. of Geometry, Oxford.

That bodies at very small but finite distances repel each
other when heated, seems probable from the analogy of expan-
sion by heat ;—was supposed to be proved from some very deli-
cate, but perhaps doubtful, experiments of Libri, Sargey, and
Fresnel;—and has been assumed by Professor Forbes as afford-
ing an explanation of the vibrations of heated metallic bars, first
observed by Mr. Trevelyan.

A simple mode of trying the experiment occurred to the au-
thor of this communication. 'Two lenses of very small curva-
ture are laid upon one another, without pressure, and form the
coloured rings. These afford an accurate test of the interval
between the glasses. Heat being applied, the rings always
contract, and the colours always descend on the scale; or the
glasses are separated, and consequently repel each other.

The curvature, or warping, of the glass, owing to the heat,
_will, upon consideration, be found to be such as ought, in the
first instance, to diminish the angle of contact, and conse-

quently to make the rings enlarge.

It should also be observed that the curvature must be suffi-

550 FOURTH REPORT—1834.

ciently small to produce rings of considerable diameter, other-
wise the surfaces in contact will not be sufliciently large to
allow sufficient effect to overcome the weight or inertia of the
glasses.

The author has made various other researches on the sub-
ject, which have been recently communicated to the Royal So-
ciety, and which will appear in the forthcoming volume of its
Transactions. In particular he has attempted to compare the
times ef communication of heat through two glasses in seve-
ral degrees of contact (as estimated by the tints), and has found
it rather more rapid with the higher degrees of contact. But
when the central black is produced, it requires a considerable
heat to overcome the powerful attraction which subsists at that
minute distance. Some singular illustrations of the intensity
of this force have been observed. It seems not improbable that
at this distance there may be a limit where attraction becomes
predominant. The contact between glass and liquids is proba-
bly within this limit, since no heat seems capable of overcoming
the attraction. Again, the repulsive power seems capable of
being excited by heat only within a certain limit the other way,
and between surfaces regularly opposed to each other. An
iron at a bright red heat could not be made to repel a delicately
suspended gilt card disc, though brought to about one tenth
of an inch distance.

Suggestions respecting Sir John Herschel’s Remarks on the
Theory of the Absorption of Light by coloured Media. By
the Rev. Witt1AM WuHEWELL, F.R.S. F.G.S.

At the meeting of the British Association last year, Sir John
Herschel made some remarks*, the object of which was, I con-
ceive, to show, that though it may not be easy to determine at
present in what way the dark lines of the spectrum and other
phenomena of absorption are produced by the undulations of
the luminiferous ether, it is not difficult to show that there are
ways in which those undulations may produce phenomena of
such a kind. I would beg leave to add one or two considera-
tions, which appear to me to bear upon what he then stated.
He observes that if undulations have to traverse canals which
ramify and meet again, there may be certain relations among
the lengths or other conditions of these canals which may pro-
duce a destruction of undulations for one particular rate of vi-
bration, and thus produce a.dark line for one particular colour
in the luminiferous vibrations. To this view might be objected,

* Since published in the Philosophical Magazine, December, 1833.

TRANSACTIONS OF THE SECTIONS. 551

(1.) the great number of the dark lines in many kinds of light,
which would appear to make a very complex structure of me-
dia necessary, (2.) the difficulty of conceiving that, on such an
hypothesis, the absorptive properties of media should be the
same in all directions. Both these objections seem to be much
diluted by the following considerations :

1. A combination of channels of vibration which would
destroy any rate of vibration, would also destroy all the har-
monics of that rate, if the vibrating body were aline. If the
fundamental rate were much slower than those which were no-
ticed by the senses, this consideration would give many more
vibrating rates near each other. Thus, if the fundamental
rate were a million undulations a second, we should have a
dark line for every multiple of this; and, therefore, since red
light makes 458,000,000,000,000 vibrations, and violet light
727,000,000,000,000 vibrations, per second, we should have
270,000,000 lines in the spectrum on this account only.

But it is to be observed that the vibrating masses of the
ether are not lines. The experiments on vibrating plates have
shown that the harmonics of plates are more numerous and va-
ried than those of lines, as theory also shows.. But the vibra-
ting masses of zther are solid spaces, and the way in which
they may be divided by nodal surfaces into portions vibrating
isochronously will be still more various ; so that in this way the
rates of vibration for which the vibration is extinguished may
become as numerous as any observations can require.

2. If we conceive with Sir John Herschel a medium which
will not transmit vibrations except through certain canals, these
canals must have a determinate direction; and therefore such
a constitution of diaphanous bodies would give different pro-
portions in different directions. But let a medium consist of
certain particles regularly distributed, the intervening space
being filled by a medium capable of vibration. Let it be sup-
posed, also, that each vibration, on reaching a medium so dis-
posed, proceeds in part directly, and in part by the indirect
routes which go round some of the particles and rejoin the di-
rect course. We have thus combinations of ramifying and re-
uniting paths, which, though very complex in éach direction,
are the same in different directions, in consequence of the re-
gular distribution of the particles. If the distribution, though
regular, have a reference to certain axes, as in many crystals,
the phenomena of absorption may be different in different di-
rections with regard to these axes.

In this way the theory of ramifying canals comes to coincide
with the theory of vibrations, of which parts are differently re-

552 FOURTH REPORT—1834.

tarded, and thus interfere with each other; a theory which has
been suggested by other authors. ' f

It is acknowledged that the above hypotheses are arbitrary.
The object is to show that there is no incongruity between the
undulatory theory and the phenomena of absorption. For it
may be observed, the above hypotheses do not at all interfere
with the laws hitherto assumed in the calculations of the undu-
latory theory. When the laws of the absorption here spoken
of are known, the undulatory theorist will have before him the
task of pointing out what és the constitution of transparent me-
dia. The object of the present remarks is to show that the
existence of a constitution which shall embrace the facts as far
as we know them, is not at all at variance with the undulatory
theory.

On the Visibility of the Moon in Total Eclipses. By the
Rev. T. R. Rosinson, D.D., §c.

Some years since, the late Sir John Leslie brought forward
an hypothesis, that the planets, and in particular the moon,
shine, not, as is commonly supposed, by reflected light, but by
a kind of phosphorescence; either absorbing solar light and
emitting it with some modification, or becoming luminous in
consequence of its action. He supported this opinion with his
usual ingenuity, and in particular availed himself of the argu-
ments afforded by the moon’s secondary light, and the red ap-
pearance of her disc in total eclipses. The first of these he
thought far too intense to be the result of ‘‘ earthshine,” and
the second still more disproportioned to that which is com-
monly reputed its cause, the refraction of rays transmitted
through the earth’s atmosphere. His reasoning on these facts
is, however, vitiated by defective data, for he certainly under-
rates the reflective force of unpolished surfaces, and exagge-
rates the moon’s light ; and the author would not have reverted
to it but for an appearance that presented itself during the
eclipse of December 26th, 1833. While the moon was enter-
ing the shadow, the eclipsed portion exhibited the usual yel-
lowish red glare, which in this case, from the great illuminating
power of the telescope, was very striking, giving the idea of an
immense globe of brass faintly ignited. ‘This was least bright
but most coloured at the eastern limb, and the division between
it and the portion still enlightened by the sun was made bya
zone of blueish grey light about 30" or 40" broad, which was
seen by several persons with this telescope. ‘This disappeared
when the moon was totally immersed. At the middle of the

%
ak
re

os

TRANSACTIONS OF THE SECTIONS. 553

bs
eclipse her surface was all red, but towards its close a kind of

twilight spread over that part towards the place of emersion,
which became at length so bright as to make the moment of its
occurrence inappreciable. As soon as a portion of illuminated
surface was decidedly seen, the above zone could again be traced,
and was seen till about one third of the disk had reappeared.
This zone the author supposes to be the effect of those rays
that pass through the atmosphere, their illumination being
greatest near the edge of the shadow and gradually decreasing
towards its axis, which, as he presently shows, it is improbable
that any of them ever reach except at a distance far beyond
the moon. The reddish light must proceed from some other
cause, which the author does not attempt to conjecture; it is
commonly ascribed to the absorption of the more refrangible
rays in their transmission, and illustrated by reference to the
setting sun and the clouds of evening. But if this absorption
be effected by the vapours diffused in the atmosphere rather
than by the air itself, we are forced to conclude that no light
can pass through the region where they occur bright enough
to be sensible when reflected from the moon.

The deviation of a ray of light passing through our atmo-
sphere will be twice the horizontal refraction of that stratum
of air which is at the vertex of its path. Considering this
stratum as an elementary zone ofa refracting sphere, it will form

: 5 :.
an image of the sun at the distance ——3=, when r = zone’s
sin 2H

radius and H the horizontal refraction. Jn this image all the
rays transmitted by the zone must be found; and the inverse
proportion of their areas would give the ratio of direct sunshine
to that of the refracted light were air perfectly transparent.
This ratio can easily be transferred from the image to the lunar
section; and summing the effect of any number of these zones,
we obtain the lunar illumination derived from the source.

Let, for instance, T I and T G be refracted rays coming from
the lower and upper points of the sun’s disc, and also RI and
RG. I Gwill be the image; after which the rays diverge and

554 FOURTH REPORT—1834.

all that have passed through the element T will be found in the
line N H at the distance of the moon; and going round the
zone, all its light in the circles described with N M, H M as
radii.
The cones T A R and K L C are dark, but in I A C and
I C G the intensity is doubled by the section overlapping. As
the refracting zone is taken higher in the atmosphere H dimi-
nishes, and the point A approaches M till they coincide, and
the point M, or that point of the moon which is central in the
shadow, receives no light from the higher zones.
Putting S = sun’s semidiameter,
and p = moon’s hor. parallax,

we have
ITAM=AEI+AIE=S+4+ 2H;
but when A coincides with M, IAM =a, and at the limit
H=? or at their mean values (Baily’s formule)
Edm) ore
scarcely less than that observed by the academicians at Quito.
The angle

(9)

~

NEM=S842H—-~p
MEH=S-—-2H-—p.
Hence, calling I the intensity of light in the pencil transmitted
through the element T’, we obtain for the zone’s addition to the
density of illumination in O H or N M, omitting the higher
powers of h, the height above the surface,
®*xIx dh
diastase See

r {S°4+ (2H — p)?}’

integrating which between the limits (H) = 35’ 6” and
H = 20! 29"-7, we obtain half the illumination of the point M.
If we take H = p — S — n for the latter limit, we obtain the
mean illumination of a space, whose diameter is 2n. For
this we require to know the relation between S and H, but it
depends on the law of density, of which we know little more
than this, that it must be between the decreasing geometrical
and arithmetical progressions when / increases in the latter.
For the present purpose it is sufficient to assume it such as will
represent the actual condition of the atmosphere between (H)
and H. This is afforded by the observations which Gay Lussac
made in his celebrated aéronautic expedition. The heights as
given in the account of it depend on Laplace’s hypothesis of the
decrease of temperature, being each derived from comparison
with the barometer of the observatory ; but we avoid this para-

TRANSACTIONS OF THE SECTIONS, 555

logism, if we break the total elevation into a sum of smaller
ones, as through a few hundred feet the average temperature
ean differ but little from the half-sum of the extremes. Deriving
the densities from the barometer heights and temperatures,
using the expansion of dry air, we find very nearly
. ax
hx ee
when a = 39534 feet and 2 is the decrease of density divided
by that at the surface.
_ As the horizontal refraction is proportional to the density of
air at the vertex of the ray’s trajectory,
ig i
The quantity I is given with sufficient accuracy for this in-
quiry (see Méc. Céi., iv. 283.) by the equation
—2¢H
I=e,
e being the base of Napier’s logarithms, and « a coefficient de- _
rived from the observed extinction of light in traversing the
atmosphere, which for H = (H) is supposed to give

1
T= 3746"
Substituting these expressions and putting
2 PRES Ne Aber be ad aon a
LS 8. Pee RL) Ss =¥Yy,
and developing dh, we obtain
See Ue a
ee — prac 2 A—Boy+ Cox? ~—, &e.
BR a otae Tae y Pg }
3
in which A = ie , and the others B, C, &c., its suc-

cessive differential coefficients divided by 1, 1:2, &c., which
are easily derived independently. This series is converging,
though but slowly, and 27 terms of it give for the integral be-

tween the limits y = + oe.

191,93368

D ae 1Q'e

{ 5:3437 mi o-o2635 }.

Thus we find that for a circle 7 minutes radius round the axis
of the shadow, the illumination derived from this source must

556 FOURTH REPORT—1834.

be the hundred and ten millionth of direct sunshine, which as-
suredly would illude all vision; and as the moon’s latitude at
the middle of the eclipse was only four minutes, a considerable
part of its disc ought to have been dark.

The only part of this reasoning which may be questioned is
the coefficient «. It was derived by Laplace from Bouguer’s
experiments, and we cannot but feel that we have a right to
demand something better from the improved powers of mo-
dern research. The actinometer, described at the last Meeting
of the Association, (see Reports of the Cambridge Meeting,
p: 379,) promises such a result, which, if possible, should be ob-
tained at different elevations, and accompanied with determina-
tions of the density and hygrometric state of the air. In the
ascent of Gay Lussac he did not pass the region of clouds ; but
even at heights much inferior, it is possible the quantity of ab-
sorption may be very different from what prevails at the sur-
face. We also want a comparison of moonlight with sunshine.
The author states that these remarks are submitted to the Sec-
tion in hopes that some of its members may be induced to turn
their attention to supply these desiderata. It is also probable
that, if carefully examined, traces of polarization would be found
in that blueish grey illumination which has been noticed at the
same time. If they were wanting in the red part of the lunar
disc, this would decide the difference of their causes. This,
however, the author could not try, as, independent of other rea-
sons, the first were too faint to be visible through a plate of
tourmaline, the only analyser which he possessed.

Account of some Observations made for the purpose of deter-
mining the Positions of the Axes of Optical Elasticity in ob-
lique prismatical Crystals. By Professor MILLER,

In crystals belonging to this system it is well known that
one of the axes of optical elasticity coincides with that crystal-
lographic axis which is perpendicular to the other two axes.
The object of the observations was to determine the position of
the remaining two axes of optical elasticity, and, if possible, to
discover some general law by which their position could be
made to depend upon the form of the crystal. After having
found the positions of the axes of elasticity in a variety of
oblique crystals, the hypothesis suggested by Neumann’s ob-
servations on gypsum, viz., that the faces of the crystal could
be referred to the axes of elasticity as crystallographic axes,
was tried, but, except in one instance, did not succeed. In many
crystals no other relation between the form and axes of elasti-

|
i

TRANSACTIONS OF THE SECTIONS. 557

city could be traced. But in felspar, epidote, and pyroxene,
according to the author's own observations, and in chromate of

lead according to the observations of Professor Nérrenberg,

one of the axes of elasticity in question coincides very accurately
with the axis of one of the principal zones of the crystal.

An Account of a new Phenomenon of sonorous Interference.
By R. Appams, Lecturer on Chemistry and Natural Philo-
sophy.

Two systems of sound waves, simultaneously generated by a
tuning-fork, in tubes, interfere and neutralize each other when
the axes, or lines of direction in which the two systems are
propagated, are at right angles to each other.

The apparatus which the author of this communication em-
ploys to demonstrate the foregoing case of interference, consists
of two glass tubes, one inch in diameter, each furnished with
a piston, in order to adjust the length of the included column
of air, so as to make it unisonant with a tuning-fork (according
to the method first devised by Mr. Wheatstone). These tubes
are placed rectangularly, one vertically, the other horizontally,
and with their mouths in contact, edge to edge.

When a tuning-fork is vibrated, and held so that the medial
line between its branches coincides with the intersecting point
of the axes of the tubes, there will be no sound heard; but
upon covering the mouth of either tube with a card, an audible
sound is reciprocated by the air in the open one.

Variations in the intensity of the sound occur by altering the
angle of position of the tubes.

Account of Magnetical Observations in Ireland, and of a New
Method of observing the Dip and the Force with the same
Instrument. By the Rev. Professor Luoyp, F.T.C.D.

In the last Report of the Transactions of the British Asso-

‘ciation for the Advancement of Science it was recommended,

“ that a series of observations upon the intensity of terrestrial
magnetism be executed in various parts of the kingdom, similar
to those which have been carried on in Scotland by Mr. Dun-
lop; and that observations should be made in various places
with the dipping-needle, in order to reduce the horizontal to
the true magnetic intensity.” After alluding to the time occu-
pied in the preliminary observations required in such a task,—
such as those made to ascertain the magnetic condition of the
needles used for the force, and the changes of this condition

558 FOURTH REPORT—1834. -

dependent on temperature,—Professor Lloyd proceeded to
give an account of a series of observations which had been
commenced in Ireland by Captain Sabine and himself, and of
the steps which had been taken to carry into effect the recom-
mendation of the Association in that country.

The first object of the observers was to compare, with accu-
racy, the direction and intensity of the magnetic force at Dub-
lin and Limerick, the two stations from which it was proposed
to set out. This was accomplished with much care, the mag-
netic intensity at the two stations having been compared by a
repeated interchange of needles; and in this manner a close
approximation was made to the direction of the magnetic lines
in Ireland, and thus the most favourable points of observation
ascertained. The latter of these two stations has recently
been compared with London, by an interchange of needles be-
tween Captain Sabine and Commander Ross; and a similar com-
parison of the total intensity in London and Dublin has been
made by Professor Lloyd, so that the series is thus connected
with observations taken elsewhere. ‘The series itself will, it is
hoped, be shortly completed, and a connected view of the re-
sults laid before the Association at its next meeting.

Besides the usual method of determining the terrestrial mag-
netic intensity suggested by Hansteen, Professor Lloyd adopted
another, in which the dip and the intensity are ascertained by
the same observation, and with one instrument. This method
consists in observing the direction assumed by an ordinary dip-
ping-needle under the combined influence of magnetism and
gravity. If two small weights be successively attached to the
southern arm of the needle, and if and 6 denote the inelina-
tions of the needle in the two cases, these angles will be con-
nected with the dip and the force by the equations

pw cos = oo sin (8—2)
vcos § = $o sin (0-4),

in which » and v denote the moments of the added weights, @
the dip, ¢ the force, and ¢ a constant depending on the distri-
bution of magnetism in the needle. . Hence, if the two moments,
» and v, be known, and if the angles, g and 9, be observed, the
two unknown quantities, § and 4, will be completely determined.

The friction of the axle, however, which is the main source
of error in the dipping-needle, will affect these quantities differ-
ently in different positions. Professor Lloyd has found from
theory that the limit of error in the determination of the dip
arising from this cause will be least when the position of the

TRANSACTIONS OF THE SECTIONS. 559

needle coincides with the line of the dip, while that of the force
is least when the needle is at right angles to that line. ‘These,
then, are the most advantageous positions for the determina-
tion of the two elements ; and accordingly the best mode of ap-
plying the preceding method consists in observing, Ist, the
position of the needle when unloaded ; and, 2ndly, when loaded
with a weight sufficient to render it nearly perpendicular to the
line of the dip. As the inclination of the needle in the first
position is nearly equal to the dip, and would be accurately so
if the centre of gravity of the needle perfectly coincided with
the axle, it is convenient to consider this first angle as the ap-
proximate value of the dip, and to seek the correction required
in order to reduce it to its true value. ‘ If « denote this correc-
pie it can be readily shown from the formule already given,
that

e b coi ROOB Gy & ag
d=C+e, sine= oa bee (¢ — 4),
p denoting the ratio of the moment of the needle itself to that of
the weight afterwards added. When the needle is well con-
structed, this ratio is very small, and the correction itself may
be disregarded. The force is deduced from the second posi-
tion of the needle when loaded, and is given by the formula

_ Bcosé
sin (8 — 4)’
B being a constant, which is determined from the values of 8
and § at the place where the force is taken as unit.

In the usual method the horizontal force is determined by
the rate of vibration of a horizontal needle, and the actual force
deduced by multiplying it by the secant of the dip. The in-
strumental errors, therefore, are of two kinds, and as these may
have the same sign, the limit of error is thereby increased. But
even supposing the determination of the horizontal force to be
perfect, the limit of error in the actual force, arising from the
error of the dipping-needle, is to that in the method now pro-
posed, in the ratio of the tangent of the dip to unity; so that
the latter method is more accurate whenever the dip exceeds
45°, and in our latitudes its accuracy is nearly three times
greater than that of the received method. This result has been
verified by observation, and it has been found that, with a small
circle 44 inches in diameter, the value of the force deduced from
the mean of two or three observations may be depended on
with certainty, to the third place of decimals inclusive.

560 FOURTH REPORT—1834.

On an apparent Anomaly in the Measure of Rain. By Sir
Tuomas M. Brissane, President of the Association.

~ Sir Thomas M. Brisbane has for some time observed a curious
fact with respect to the rain collected in his gauge, the receiver
of which is 7 feet from the ground, and about 210 feet above
the level of the sea. The rain always stands in the gauge some
hundredths of an inch higher an hour or two after it has fallen
than it does four or five hours after; and the author suggests
that the phenomenon may be owing to atmospheric air absorbed
by the drops in their descent, and afterwards slowly escaping
from the gauge.

Second Report of the Result of Twelve Months’ Experiments
on the Quantities of Rain falling at different Elevations above
the Surface of the Ground at York, undertaken at the request
of the Association by Wituiam Gray, Jun., and Professor
Puitures, F.R.S. F.G.S., Secretaries of the Yorkshire Philo-
sophical Society ; with Remarks on the Results of these Ex-
periments, by Professor Putuurrs.

I. Report of the Experiments.—The report presented to the
Cambridge Meeting of the Association* contained the register
for twelve months of the quantities of rain collected above the
top of York Minster, on the top of the Yorkshire Museum, and
on the ground adjacent; the elevations of the’ upper stations
being 212 feet 10} inches, and 43 feet 8 inches.

The present series of twelve months is continuous with the
former, and commences on February 1, 1833. The same gauges
were used with the same precautions as in the previous year;
but for particular objects the intervals of measuring the con-
tents of the gauges were purposely and considerably varied. It
will be recollected that the discharge-pipe of the gauges was
stated to have been kept stopped with a cork, and during the
whole of the first twelve months this was always observed ; but
for more than three months of the present series the cork of
one of the gauges (the middle one) was left out. Comparative
experiments were made to determine the probable increased
loss from evaporation arising from this cause and a compensa-
tion calculated. The corrected numbers are placed in the co-
lumn, and the original observations in smaller figures on the
side.

* See Reports of the British Association, vol. ii. p. 401.

_ee

r a

TRANSACTIONS OF THE SECTIONS, 561

1833-1834. Minster. Museum. Ground. Remarks,
Inches, Inches. Inches,

Feb. 1 to Feb, 28. | 1-509 | 2-108 2°834

March . . 13. 327 ‘560 (*539) 791
28, 546 “687 (663) | 1:018

April . .21.| +570] 745 (709) | 1-030

Chiefly snow and hail
and cold rain drift-
ing from N.N.W., &c.

Rain fell on the 2nd,
May. . .20.| -686| -787 (-785) | 1-015 3rd, 4th, and 2Uth of

May.
30. | 0: 0: 0: .:
June... 17.) 1525 1-942(1:902) | 2:386 ;
July . 1. | +559 | +649 791
August . . 3. 810 | 1-030 1-246 | {Small Hymenoptera

in the Minster gauge!
With Mr. Lubbock.
Small Hymenoptera
in the Minster gauge.

19. “391 “484 575

September . 16. | 2-175 | 3-000 3°835
{ This is the only obser-
| vation in which the
October. . 8.| -386| -473! Pag giigney aysaton. hed
nights were exces-
sively dewy.

oe 4 } With Major Emmett,
74 er ee dae just after the fall of
; 5 perpendicular rain.
} November . 12. | 1-216 | 1-574 | 1:894 | High winds.
aT 2 Most violent gales
December . 31. | 1:811 | 2:558 &| 3641 N.W. Snow onthe
5 11th of December.
‘February . 1. | 2-139 | 2-798 | 3°678
Totalof12months | 14-963 | 19-852 25-706 |

II. Remarks on the Results of the Experiments.—The quan-
tities of rain collected in other gauges at York and in the neigh-
‘bourhood agree nearly with those recorded for the ground

“gauge in these experiments. For 1833, from February 1 to
‘December 31, we have,

_J In the garden gauge ...... . . 22:028
‘af York Mr.J.Gray’s self-registering gauge 22:205

(=)

Moilai Dr, Wasse’s gauge, Moat Hall, on higher

ground, 12 miles N.W. ....,......-. 23488
Mr. Cholmeley’s, at Brandsby ; level with top
wt Minster; 12 *mmeeeN, her eee Re 24° +:
The quantities and ratios at the several stations for particular
periods of the year are as under:

1834. 20

=

562 FOURTH REPORT—1834.

M On On On
Periods. Tq; eal Minster. Museum. Ground, Ratios,
emp. | In. of Rain. | In. of Rain. | In. of Rain.

19°850 | 25-706 | 58°20 77-21
11:959 | 15:858 | 55:6 75-4
9-606 | 11:850 | 62:6 81-0
10-285 | 13856 | 546 74:2 | ,
7-932 | 9-848 | 62-4 80-5 mn
7-464 | 10°153 | 53:8 73-3
2-779 | 3:854 | 55-2 72-1
4105 | 4-998 | 65:7 821
5:503 | 6-701 | 61:0 821 J

Whole year.... | 48:2 | 14-963
7 colder months. | +40°8 8°817
7 warmer months | 55°5 7-415
5 colder months. | 39°3 7-548
5 warmermonths | 58:5 6:146
Winter quarter . | 36:3 5:459
Sprmg ......% 476 2°129
Summer...... | 60°8 3°285
Autumn...... i 4-090

On comparing these ratios with those obtained in 1832, it is
impossible not to be struck with their wintry character, which
agrees with the fact of the months of February, March, April,
October, November, and December, being almost diurnally
rainy. In 1832-3 the greatest part of the rain fell in the warm
months; but in 1833-4 the cold months were most rainy. In
1832-3 the mean diminution of rain was

on the Minster (d) ....... 33°9 per cent.
and on the Museum (d') ... 14°7
but in 1833-4 these numbers were,
41°8
22'8
In 1832-3 the mean annual value of the function of the height
was h*®*,—in 1833-4 it was h“*. By uniting the observa-
tions of thirty months, (to August 30, 1834,) h™*.

It is hence very apparent that a few years’ observations will
give this mean value very accurately, determine the limits of its
variation, and the dependence of this upon the monthly tem-
perature and other causes. I shall, however, purposely abstain
from discussing the subject any further at present, because the
experiments will be continued under the present arrangement
six months longer, and thus any conclusions which may be
offered rendered more trustworthy. Besides, I do not wholly
despair of being furnished with some aid from other observers
in different regions and under various circumstances, for I am
far from thinking that all the conditions of this curious problem
can be determined at one locality, however favourably situated*.

* My friend Mr. W. D. Littledale has established three gauges at Bolton-Hall,
in Craven, and Mr. A. Halliday has obliged me by undertaking a similar labour
at Manchester.

}

q
1

TRANSACTIONS OF THE SECTIONS. 563.

. The following table shows the sum of the diminutions per
cent. of quantity of rain at the two upper stations for two years,
with a column of numbers inversely proportional tothe tempera-
ture during the several parts of the year.

In 1832-3. | In 1833-4. Difference.

Whole year 486 | 64-6 : 21+

7 cold months 61-9 79:0 : 1:0— |

7 warm months 41:7 56:4 20+

5 cold months 74:8 (A, 1-0— ff

5 warm months se 47°1 57-1 37—
82-2 | 73-4 0-24
60°2 72:7 F 6:9—
30-4 | 522 . 534
57-5 | 56-9 144

Mean values of d+-d', whole year .. . 11:0+

7 cold and 7
warm months
5 cold and 5
warm months
3 cold and 3
warm months
SpringandAu-

59-75 12°6— },

-_ By comparing the last column with the mean values of d+d’,
their almost exact coincidence will be immediately evident ; and
therefore it appears that the conclusion advanced in the last
Report, p. 408, as to this value being an inverse function of the
temperature, is now strongly supported by additional observa-
tions, the whole nearly agreeing with the simple formula

Gadd.

On the Difference of the Quantity of Rain at different Heights
above the Surface of the neighbouring Ground. By Luxy
Howarnp, F.R.S., &c. ’

The author, referring to the experiments on this subject,
printed in the second volume of the Reports of the British As-
sociation, pp. 401, &c., proposes a different opinion as to the
cause of the augmentation of the quantity of.rain at the lower

stations.
202

564. FOURTH REPORT—1834.

- He allows that this effect of the coldness of the superior rain
enters for something into the aggregate of the causes of increase
by descent; but that it is considerable or appreciable he does
not admit.

- He observes (and refers for further particulars to his work on
the Climate of London), that rain falls principally in two ways:
1._By the condensation or collapsing of the mass of an elevated
cloud, (effected by the subtraction of the electrical atmosphere
of the cloud, or by the extension of the atmospheres of the
spherules of the cloud, through their mutual attraction, the
electrical charge now taking its seat upon the smaller surface
of a congeries of larger drops, as is manifest by the charge
these give to the insulated rod,) or, 2. By loss of heat in the
whole mass of air from which it is about to rain (this lowered
temperature being the actual cause of the rain), in which case
the separation of the water is effected precisely in the manner
of the precipitation of solids from a menstruum in which they
were held in solution. The nascent drops exist in every part
of the raining space, and find their way to the earth subject to
the small augmentation, by virtue of the lower temperature
found at greater heights above mentioned.

In the first case the rain at the top of a building and the rain
at the ground are equal in amount; in the second, there is an
augmentation in the lower strata, which so overbalances the
former case, both in frequency and amount, as to give the aver-
ages the character they exhibit.

An attempt to connect some of the best-known Phenomena of
Meteorology with established Physical Principles. By Pro-
fessor STEVELLY, A.M., of Belfast.

The author examines, in this point of view, the following
four points:

1. The nature and origin of clouds ;

2. The production of rain, and some of its consequences ;

. 8. The origin of wind from clouds or rain ;

4. The formation of hail.

1. Nature and Origin of Clouds.—The author adopts the
opinion, that the constituent particles of clouds are minute
spherules, but not vesicles; and refers the suspension of clouds
to two causes: the extreme slowness of descent through the air
of such exceedingly minute particles, and the repulsive action
of the electrical atmospheres of these particles upon the ambient
air.

Clouds are stated to owe their origin to the excess of vapour

————————orr eee ee

TRANSACTIONS OF THE SECTIONS. 565

which at any time happens to exist in the air, collected inte
drops by the capillary attraction of the elementary particles,
which now appear as spherules of water; the spaces around
them becoming drier than before, and the whole space occupied
by the cloud having its elastic tension reduced in proportion
to the quantity of vapour converted into water. In conse-
quence of this circumstance, a diminution of sensible tempera-
ture will be occasioned, and a secondary formation of clouds
may take place, notwithstanding some addition, on the other
hand, from the development of the heat latent in the vapour.

The atmospheric equilibrium being thus disturbed, wind will
blow from all points toward the cloud, and if this was previously
in motion, there will be a comparative calm before the cloud,
and a strong wind following it. Hence the appearance of the
edges of driving clouds varies; small portions detach themselves
from the ragged posterior part, and float away, while the an-
terior part is of smoother outline, and suffers little change.

Another consequence of the conversion of the vapour into
drops of water is an increase of electrical intensity in the
cloudy space. r

Clouds frequently divide into portions which have opposite
electrical states, when they come into contact with a hill, in
consequence of the effect of the ordinary laws of induction. .

2. Origin of Rain.—When two oppositely electrified clouds
rush together, and the spherules unite into drops, these descend
lower in the atmosphere, or fall in the form of rain, which is
more or less heavy, according to the densities of the. original
clouds or the degree of their electrical intensity. On the
principles of electrical induction may also be explained the
cessations and renewals of rain, and the intermitting peals of
thunder.

As the rain descends, a void space is occasioned in the place
lately occupied by the clouds, and a depression of temperature
in the superior regions, by the expansion of the air. An in-
crease of temperature, to a smaller extent, happens below, from
the condensation of the air.

3. Origin of Wind.—Breezes and gales are produced by the
secondary formation of clouds, particularly when the clouds are
formed fromamass that has, in appearance, attached itself to a hill.

Squalls are gusts of wind caused by heavy showers passing
over the country in vast and distinct patches. In the front of
the shower the wind is driven out by the rain most violently
in the direction in which the general current was previously
moving. . Towards the close of the shower, however, the wind
becomes moderate, or even reversed, the chief rush of the air

566 ' FOURTH REPORT—1834.

from behind being directed upwards, to supply the spaces
above. The author states that the phenomena of tropical and
other extraordinary rains and winds agree with the results
which may be deduced from the foregoing facts and consi-
derations. :

4. Origin of hail.—Referring to Sir J. Leslie’s experiments,
and to the well-known effects of the compressed air in the
engine at Chemnitz, the author explains the formation of hail
by stating, that when very sudden and violent falls of rain take
place, especially in summer, the air, expanding into the void
space left aloft, robs the succeeding rain so effectually of its
caloric as to freeze the drops. The author proposes to pub-
lish his views in an enlarged form, with adequate illustration
by statements of observed facts.

Extract of a Letter to Professor Forses from Professor
CurIsTIE.

The writer observed a very peculiar and well-defined light
proceeding, in the form of a ray, from the sun as it was setting,
having the sun for its base, and retaining the same position for
about half an hour. The ray was absolutely vertical, gradually
decreasing in splendour, until it was lost, at about the height
of 20° or 25° above the horizon, expanding but slightly from
its base to this point, and it was unaccompanied by any lateral
rays. Its expansion in breadth did not in any part exceed a
degree and a half on each side. These circumstances attracted
his attention on the occasion of his first witnessing the appear-
ance; and on a more particular examination he was persuaded
that it could not be of the ordinary description of rays, pro-
ceeding from an opening in amass of cloud. Independently of
its permanence in a very peculiar position, there were appear-
ances in the ray itself which precluded such an opinion. The
30th of June, the day on which he first observed the phzeno-
menon, had been clear and hot. At the time of the observa-
tion, above the sun there were faint streaks of haze, scarcely
to be denominated cloud, increasing in density towards the
horizon, and on these the ray was exhibited; but he does not
remember to have noticed any well-defined clouds, even in the
horizon. At sunset on the 17th of July he again witnessed this
phznomenon, but the ray was stronger and better defined than
on the former occasion, and although of much greater extent,
reminded him of the form and appearance of the- tail of the
comet of 1819. Its position was, as before, absolutely vertical,
andit continued visible for about half an hour. The sky had

se

TRANSACTIONS OF THE SECTIONS. 567-

been cloudless all day, and the sun intensely hot; a decided
change of temperature took place about sunset, at which time
a fine breeze from E.S.E. sprung up, gradually increasing,
rendering the evening and night cold. At sunset the sky was
clear, except towards the north and west, where dense masses
of cloud rose a few degrees above the horizon; and also in the
intermediate part above the sun, where streaks of thin haze
were rendered visible by its light: upon these a narrow but
slightly expanding vertical band of well-defined light, having
the sun for its base, was again exhibited.

It had occurred to Professor Christie, after he had first
observed this light on the 30th June, that it might be due to a
succession of images of the sun imperfectly reflected by strata
of thin vapour, and all the appearances which he observed on
this second occasion tended to impress this notion more strongly
on his mind; but he thinks repeated observation of the phzno-
menon will be required before it can be decided whether this be
the correct explanation. On both occasions, the position in
which Mr. Christie saw the light, was looking almost immediately
across some extent of sea, the sun setting behind the Hants
and Dorsetshire hills. The light was most brilliant very shortly
after sunset, and gradually declined in brightness till it wholly
disappeared, about half an hour afterwards; but its direction
was invariable, and its general character the same during. the
whole time of its continuance. Early on the morning of the
18th July there was thunder and lightning, with rain, which
continued more or less until the middle of the day.

_ Notes on mean Temperatures in India. By Lieut. Col.
5 ids . Sykes, F.R.S.

‘The author states the results of several observations of mean
temperature in India, at different elevations above the sea,
between 10° and 25° N. lat., and 70° and 82° E. long., for
comparison with the formule of Meyer, and the generalizations
of Humboldt and others.

Mhon, in Malwa, in lat. 22° 23! is 2000 ft.) ,
above the sea; the mean temperature ob- > 74-00
ts -coaserved iby Dri Crawit. saece eth) 2 cei havent ,
' Calculated by Meyer’s formula, and adopting 69-8
the correction of 1° Fahr. for 300 ft. ascent }
Calcutta is in nearly the same lat. (22° 35’) and
its mean temp. as determined in 1781, and $ 78°13
again after a lapse of 52 years .......
There is therefore a difference of 4°13’ between the mean

568. FOURTH REPORT—1834.

temperature of Calcutta and that of Mhon, giving 480 ft.
nearly to each 1° of temperature.

Ahmednuggur, in the Deccan, in lat. 19° 6', and 1900 feet
above the sea, has a mean temperature, as determined by Dr.
Walker, of 78° Fahr., while the calculated mean temperature at
the level of the sea is 78°°6, giving a difference of 0°°6 of a
degree, for a difference of level of 1900 ft. The mean tem-
perature at Col. Sykes’s residence in Poona, lat. 18° 30', eleva-
tion above the sea 1823 ft., was 77°°7. The calculated mean
temperature at the level of the sea is 78°-94, giving 1° for
1471 feet.

The mean temperature of a spring in the excavated caves in
the Hill-fort of Hurreechundurghur, lat. 19° 23', at 3900 ft.
above the sea, was 69°°5 Fahr. The calculated mean tempera-
ture at the level of the sea, 78°°45 ; giving 1° Fahr. for 435 ft.

The mean temperature of Seringapatam, at 2230 ft. above
the sea, is 77°:06, corresponding nearly to the mean of Poona
and Ahmednuggur, although the latter places are between
6° and 7° of lat. turther north, and their levels nearly the same.
The calculated mean temperature of Seringapatam, at the level
of the sea, is, by Meyer’s formula, 81°-77; by Brewster’s amended
formula, 79°°9, and by his general formula, including the con-
sideration of two poles of maximum cold, (see Trans. of the
Roy. Soc. Edinburgh, vol. ix.) 76°'55. In the first case the dif-
ference of temperature corresponding to 2230 ft.=4°°71, (or 1°
for 473 ft.); in the second, 2°°84 (or 1° for 785 ft.); in the third
the result is negative.

In an observation at a height of 8500 ft., the value due to
each degree of alteration of temperature corresponds very
closely with the general result (332 ft.) adopted by Professor
Forbes in his Report on Meteorology.

The mean temperature at the equator has been stated at
814°: the result of 21 years’ observations at the Observatory of
Madras, more than 10° from the equator, situated on an open
beach, has determined the mean temperature of that place to
be 81°69; and in general, Col. Sykes concludes that the ob-
served mean temperatures in India everywhere exceed those
given by calculation. By the result of several years’ observa-
tions, he has found that the mean temperature of the hour of
the maximum diurnal atmospheric tide (between 9 and 10 a.m.)
is equal to the mean temperature of the year in India. ‘The
heights of places mentioned in this communication were deter-
mined barometrically.

TRANSACTIONS OF THE SECTIONS. 569

=

On a peculiar Oscillation of the Barometer. By the Rev.
i J. HAILsTONE.

~ The author presented a table of observations on the height of
the barometer, at short intervals of time, between November 28,
1833, and January 10, 1834. The circumstance in these ob-
servations, which the author especially desires to point out for
the attention of meteorologists, is, a small and short oscillation
of the mercury, sending it up seldom above a few thousandths
of an inch, after which deviation it resumes its usual march
again.

On the use of Leshe's Hygrometer with anew Scale. By
H. H. Watson. .

In this communication, the author states the reasoning and
experiments by which he was induced to apply to Leslie’s
hygrometer a scale of equal parts, such that the cold produced
by evaporation of water, being measured upon this scale,, and
the parts considered to represent degrees of Fahrenheit’s ther-
mometer, the dew-point, or constituent temperature of the
vapour, should be immediately known. The author states, as
the consistent result of many experiments, that the difference
in degrees between the temperature of the air and the dew-
point, is to the degrees of cold produced in Leslie’s hygrometer,
by evaporation of water, as 20 to 13: this ratio is consequently
employed for the divisions of the new scale of the hygrometer,
which thus is supposed to give results sufficiently in accordance
with the direct experiment on the dew-point, to justify its use
in cases where rigorous accuracy is not demanded.

Account of Experiments on the Expansion of Stone by the ap-
_ plication of Heat. By Avrxanver J, Aviz, Civil Engineer.

The author laid this communication before the Association
principally to give the expansion of sandstone, taken from what
is called the Liver Rock of Craigleith Quarry. The subject
under experiment with the pyrometer, is placed in the interior
of a double metallic case, which is heated by means of a current
of steam, a method which is very convenient for keeping up a
steady temperature for any length of time, and affords great
facility in preserving the substance in the same hygrometric:

570. FOURTH REPORT—1834.

state. The length of the rods, of which the expansion was
determined, was 23 inches, and they varied in the cross section
from half an inch to three quarters of an inch square: the length
is laid off on the heads of small silver studs, sunk into the stone.
The micrometer microscope of the pyrometer measures the
thirty-thousandth part of an inch; and as a test to satisfy him-
self of the correctness of the instrument, and of the uniformity
of its results, the author determined the expansion of cast zinc,
selected, as a simple metal, having the greatest range, and his
determination of it agreed very nearly with that given by
Smeaton. He then procured a rod froma very equally-grained
block of sandstone, from what is called the Liver Rock of
Craigleith Quarry, from the same part of the bed from which
the large stone in the pillar of the mural circle in the Edinburgh
Observatory was: cut; it possessed a considerable degree of
flexibility when wet, but gradually stiffened as it became dry.
The expansion of this sandstone, as determined from a length of
twenty-three inches, with a range of temperature of 145° Fahr.,
gives ‘0270446 of an inch for 180° Fahr., or 0011758 in decimals
of its length, which is the same as the expansion of glass given
by Berthoud, and very nearly the same as the expansion of cast
iron as found by Lavoisier. Black marble, from Galway, in
Treland, has the least degree of expansibility of any substance
which Mr. Adie has tried, with the exception of wood. Hestates
it to be -00043855 of its length for 180° F., which is rather
more than one third part of the expansion assigned by Lavoi-
sier to steel, and nearly half that of platinum and glass for
the same number of degrees. He also measured the expansion
ef Carrara marble; but as the specimen used was only one foot
long, he does not state the result numerically: it was less, how-
ever, than that assigned to it by M. Destigny. A rod of oak,
split from the tree to insure the straightness of the fibre, ex-
panded ‘000062007 in decimals of its length, for 180° Fahr., which
is just one fifteenth part of the expansion of platinum for the
game number of degrees; an insensibility to the change of tem-
perature which arises very much from the wood being very
dry when the experiment was made. The number here given
is a mean of three trials, but the same rod of wood gave avery
different result when a very small quantity of steam was allowed
to blow into the case which contained it. It is Mr. Adie’s in-
tention to repeat these and other experiments during the
winter, when he hopes to be able to command a greater range
of temperature in his instrument. He will then give a full
account of them, and the manner in which they have been

ee

TRANSACTIONS OF THE SECTIONS. 571

performed, together with a drawing of the pyrometer, in order
that it may be the more easy to judge of what reliance may be
put in the accuracy of the results.

Il. CHEMISTRY.—MINERALOGY.

‘Table of the Proportions of anhydrous acid in acetic acid of
every degree of concentration between pure water and the
hydrated acetic acid, compared with the specific gravities,
water at 59° Fahr. being taken at unity. Founded on Ex-
periments, by ADAM VAN DER ToorRn.

Anhydrous Anhydrous Anhydrous
Acid in 100 | Density at59°.|| Acid in 100 | Density at 59°.}| Acid in 100 | Densityat 59°.
arts by weight. parts by weight. « |\partsby weight.|
0 1:0000 29 1:0472 58 1-0740
1 1:0019 30 1:0485 59 1:0745
2 1:0037 31 1:0498 60 _ 1:0749
3 1:0055 32 1:0510 61 ~1:0753
4 1:0072 33 1:0522 62 1:0756
5 1:0089 34 1:0534 63 1:0759
6 1:0107 35 10546 64 10762
me 1:0124 36 1:0558 65 1:0764
8 1:0141 37 1:0569 66 10765
9 1:0159 38 1:0580 67 1:0766
10 1:0177 39 1-0591 68* -1-0766
11 1:0194 40 1:0601 69 10766
12 1:0211 41 1:0611 70 . 1:0765
13 1:0228 42 1:0621 71 1:0763
14 1:0245 43 1:0631 72 »1:0759
15 1:0261 44 1:0640 73 1:0754
16 1:0277 45 1:0649 74 1:0748
17 1:0293 46 10658 75 1:0741
18 1:0310 47 1:0667 76 1:0732
19 1:0326 48 1:0675 77 1:0722
20 1:0342 49 1:0683 78 1:0710
21 1:0358 50 1:0691 79 1-0696
22. 1:0373 51 10698 80 1:0681
23 1:0389 52 1:0705 81 1-0664
24 1:0404 53 10711 82 1:0646
~ 25 1:0419 54 1:0717 83 1:0626
26 1:0433 = 65 1:0723 84 1:0603
27 1:0447 56 1:0729 85 1:0574
28 10460 57 1:0735 85°11 1:0570

B72 FOURTH REPORT— 1834.

Account of some Experiments on the Electricity of the Copper
Vein in Huel Jewel Mine. By Rosurt W. Fox.

The author transmitted a section of the deepest part of the

mine, with a description of the manner in which he conducted
the experiments on its electricity.

Huel Jewel. Deepest workings on South or Main Lode, which
underlies about 23° towards the North.

‘Black and vitreous Copper in the Vein, with some yellow Sulphuret intermixed.

East.

$8 fathoms from
the surface.

Yellow Sulphuret of | | Copperin the vein.

2
f
4
i]
2
e
ry
ry
ra
.
*
.
:
:
,
.
.
*

98 fathoms, BBs

Rene Ter Werte eee

108 fathoms.
Vitreous BS Copper.

Direction of Electricity from the Vein.

Positive. Negative. _ Distance.
Gap toy. B 19 fathoms.
Seal Rice: Te nS 37 ditto,
pany A roel ahh Ry. 8 34 ditto.
Gay GF 23 ditto.
| Sat ESS S|

The vein consists of black and vitreous copper above, and

below, the yellow sulphuret of copper. Their boundaries are
shown by the dotted lines.

ar se ee

TRANSACTIONS OF THE SECTIONS. 573:

A represents the observed station in a level 98 fathoms’
under the surface.
» B,C, D, E, and F, show the points of contact where the metallic
plates or copper wires were pressed against the vein, mostly
by means of a wooden prop; and the dotted lines represent
the copper wires employed.

Copper and zinc plates were alternately, or rather succes-
sively, used at each of the points of contact with the vein, except
at D; but these changes of metal did not affect the character
or direction of the electricity, nor did the contact of points only
with the ore do so. But in all cases the easterly wires were
positive with respect to the westerly ones. ‘These experiments
were made in order to prove that the electrical action is derived.
from the vein, and that it is not in any degree excited by the
mere contact of the metal with the ore, as some have sur-
mised.

» In order to obtain some idea of the electric energy of the vein,
the author placed a galvanic trough as in the circuit, at m, and
caused it to act with the electricity of the vein, and also against
it. In the former case, the deflections of the needle were con-
siderably increased; and in the latter, when the electricity pro-
duced by the galvanic apparatus was opposed to that of the
vein, the positive electricity from C was reversed, the gal-
vanometer giving evidence of a slight negative action in that
direction. ‘The electricity from D, however, was only just
neutralized, and that from E was merely diminished in intensity,
the deflection of the needle being in the same direction, and
equal to about 40°, from the magnetic meridian, instead of 100°
at least, produced by the vein alone.

' The galvanic apparatus consisted of a plate of copper, and
another of zinc, plunged into strong brine, to which some sul-
phuric acid was added, and each plate exposed about 180
square inches to the action of the liquid. The voltaic activity
was much diminished before the completion of the experiments ;
but even at the last, when the wires of the apparatus were
applied to the galvanometer without the intervention of the
vein, and the extensive circuit and comparatively imperfect
contacts which it involved, a violent agitation and rapid rota-
tion of the needle were produced.

These experiments afford strong evidence of the energy of
the electricity of the vein; and this method may become useful
to the practical miner, in helping him to appreciate the value of
his discoveries, and enabling him to ascertain whether the ores
in distant parts of a vein are connected or insulated, or whether
what appear to be parallel veins are really so, or ramifications

574 FOURTH REPORT—1834.

of the same vein. Galena, and copper, and iron pyrites are the
only substances usually met with in the Cornish mines which are’
eapable of conducting voltaic electricity; and as iron pyrites is
much more generally found in insulated masses than the other
two, the test here suggested may be employed with a consi-
derable degree of confidence on many occasions.

It was in Huel Jewel, and more than four years ago, that the
author first obtained electro-magnetic results. The workings
haye been so much extended since, that the last experiments
were made 60 fathoms deeper, and at least 80 fathoms further
towards the east, than the first; and it is satisfactory to find
that the direction of the electricity remains unchanged, viz.
positive from the east. The temperature at the bottom level
of the mine, 38 fathoms under the surface, was then 59°, and it is
now, at the depth of 108 fathoms, 70°. The author has observed
that when the sulphuret of copper or of lead is heated, or even.
slightly warmed, it becomes positively electrical, and yet the
deepest parts of the veins of those ores, although warmer than
nearer the surface, appear generally to be negative.

Notice respecting a remarkable Specimen of Amber. By Sir
Davip Brewster, F.R.S.

This specimen of amber was brought from India by Mr-
Swinton, and was found in the kingdom of Ava. Its size is
nearly equal to that ofa child’s head, and its general aspect arid
physical properties, seem to differ considerably from the ordi-
nary specimens of amber. The remarkable fact, however, which
distinguishes it from all specimens of amber which the author
has seen or read of, is that it is intersected in various directions
by thin veins of a crystallized mineral substance. ‘These veins,
which cross one another, are sometimes as thin as a sheet of
paper, and in other places about the twentieth of an inch thick.
In order to determine the nature of the mineral, he extracted
a portion of the thickest vein; and having obtained, by cleavage,
a small rhomb, succeeded in measuring the inclination of its
planes, and found it to be a carbonate of lime. The specimen,
however, did not enable him to ascertain whether the angle was
that of the pure carbonate of lime, or that of carbonate of
lime and magnesia.

At the next meeting of the Association, the author hoped to
be able to bring forward a detailed account of this curious
specimen, and to exhibit it to the Section; but he considered
the single fact which he had now mentioned as calculated to
throw so much light on the origin of amber, that he trusted it

TRANSACTIONS OF THE SECTIONS. 575

would induce those who are in possession of specimens to ex-
amine them with attention, and especially in reference to empty
or filled cavities, and to veins or portions of foreign matter
which may exist in the mass.

Remarks on the value of Optical Characters in the discrimina-
tion of Mineral Species. By Sir Davip BruwstTeER.

If minerals were all formed from solutions containing the
same ingredients, having the same temperature, and crystallizing
in perfect tranquillity, the differences recognised by the chemist,
the crystallographer, and the optical observer would have no
existence ; but as this hypothetical state of the mineral, when
inastate of fluidity or solution, is inadmissible, we must consider
minerals as having been formed under the influence of many
disturbing causes. In order to illustrate this remark, the author
takes the case of chabasie, which he regards as a congeries of
several substances, formed in succession round a central rhomb
of the same mineral in a perfect state. The central rhomb has
a certain degree of double refraction, which is equal in all
parallel directions; but there is another rhomb formed round
it which has a less double refraction, and each successive
rhomb has its double refraction successively diminishing till it
disappears altogether, at which period the form of the crystal
would be a cube. Beyond this neutral line an opposite kind
of double refraction appears, corresponding to a new series of
rhombs, deviating more and more from the cubical structure. °

Now it is very obvious that these changes may have, or rather
must have, taken place, either from some agitation in the fluid
which prevented its particles from assuming the perfect type
of the mineral, or from the addition or abstraction of some of
the ingredients of which the central rhomb was composed.

If a crystallographer, therefore, were to examine such a-
mineral, he would report to us only the condition of the outer
rhomb, while the chemist would detail to us the elements which
form the whole compound mass. The optical observer, how-
ever, is alone admitted into the secret, and his results are in-
fallible. The changes which take place in the optical characters
of minerals by heat, do not in the least affect their value, any
more than similar changes affect the ordinary characters which
are employed by mineralogists. The specific gravity of bodies
varies also with heat, and probably the hardness also of the
softer minerals; and it is well known that changes of tempera-
ture not very great may drive off the more valuable ingredients
of minerals, and thus prevent the chemist from obtaining their
actual composition.

576 FOURTH REPORT—1 834.

Experiments on the effects of long-continued Heat on Mineral
and Organic Substances. By the Rev. Wit11aM VERNON
Harcourt, F.R.S.

Mr. Harcourt gave an account of tle experiments on this sub-
ject, which the kindness of the proprietors of the Low Moor
and Elsecar iron works in Yorkshire, had enabled him to in-
stitute.

The blast furnaces at Low Moor are sometimes regularly
worked for twelve years or more; but the average time for
which they continue in action, is from six to seven years. The
furnace at Elsecar is usually blown out at the end of three
years. During these periods of time the fusion of the iron-
stone never ceases in the hearths; the bottom stone of the fur-
nace may be considered as constantly kept at the temperature
of melting iron, and the hearth-walls in some parts at a still
higher heat. When the furnace is blown out, the cooling of so
great a mass of masonry is extremely slow.

The bottom stone, which is about 16 inches thick, is worn
away and excavated by degrees, sometimes to more than half
its depth, by the aetion of the iron, so that a pool of metal lies
in the hollow, below the level at which the iron is from time to
time run off; this stone is cracked in various directions by the
heat to which it is subjected, and the cracks are filled with
veins of melted metal, which occasionally penetrate into the
sand on which the stone is laid, and fuse it.

It is in the metal thus detained within the bottom stone that
the segregation of metallic titanium takes place, disseminated
in general irregularly through the mass of iron, but where acci-
dental vacuities have admitted of its crystallization, forming
clusters of cubes.

On examining with attention the bottom stones of furnaces_

which had been worked out, Mr. Harcourt observed in them
several other species of crystals, some of which appeared to be
owing simply to the mutual reaction of the ingredients of
the stone itself. The stone is a felspathic grit, and if this ma-
terial alone is capable, under these circumstances, of supplying
instances of chemical and crystalline rearrangement, it seemed
not unreasonable to expect, that by multiplyimg the means of
such rearrangements scope might be afforded for the ap-
pearance of numerous interesting phenomena of a similar de-
scription.

For this purpose, and to forward an undertaking sanctioned by
the Association, the Yorkshire Philosophical Society, with great
liberality, furnished a supply of materials from its museum, and

—- — —e-

17

TRANSACTIONS OF THE SECTIONS. 57

with thé assistance of Professor Phillips, Mr. Harcourt selected a
variety of specimens of rocks and minerals from its collection,
which were arranged, some in mass and some in powder, ina
strong deal box, the capacity of which was five cubic feet. Some
synthetical compositions of minerals were added, and oppor-
tunities contrived for the formation of others, by placing differ-
ent substances in contact, and making provision for the passage
of volatile bodies through materials with which they enter into
union. Metallic substances were introduced at different points,
and among different materials, both to serve as measures of
heat, and to furnish illustrations of the phenomena of veins.
A second box of equal dimensions was chiefly devoted to the
purpose of placing organized substances, recent and fossil,
animal and vegetable, under a variety of conditions with re-
spect to the materials in which they were imbedded.

The boxes were conveyed to the foundries of Messrs. Hird
and Dawson, at Low Moor, on the 17th of July 1833. They
were placed immediately under the bottom stone of the furnace
in the sand which supports it, and built round with fire-brick ;
larger pieces of various rocks, metals, &c. were placed by their
side, and similarly inclosed by walls of fire-brick. t

The defect most to be apprehended in this arrangement is,
that the heat in the position above described may not suffice
to produce the fusion or semi-fusion of the rocks and minerals ;
it is presumed, however, that the cracks of the hearth-stone
and the shrinking of the materials will admit such an influx
among them of the melted metal as will secure this object ;
but lest such should not be the case, Mr. Harcourt was
anxious to effect a repetition of the experiments in a position
nearer to the source of heat. An opportunity of accomplishing
this was afforded by Ear! Fitzwilliam at his foundry at Elsecar,
near Wentworth House. Here, under the direction of the
Superintendant, Mr. Hartop, holes were worked in the bottom
stone itself, and in the back wall of the hearth, to contain the
subjects of experiment ; the number of holes was twenty-three,
those in the bottom stone being about a foot in diameter and in
depth, whilst those in the back wall were two feet in depth and
six inches in diameter, worked obliquely downwards. In some
of these were placed crucibles of six inches in diameter, and
eight inches in height ; in others similar cylinders of granite and
limestone, hollowed out, and containing various materials, the
spaces round, and the interstices within, being filled with
powders of different kinds of rocks: in the rest the minerals
and organized substances were imbedded in powders of the
same kind, without any other receptacle than the stone itself.

1834. 2P

578 FOURTH REPORT—1834.

The orifices of the holes were filled to the depth of three or four
inches by stoppers made of the gritstone of which the furnace
was built.

The danger in this disposition of the materials is, that
a portion of them may be obliterated by the intensity of
the heat and the wear of the furnace; but there is reason to
expect that enough will remain to show what light is likely to
be derived from such experiments, and in what manner they
may hereafter be most advantageously conducted.

The experiments themselves are nearly similar to those which
have been before described, the chief difference consisting ina
more liberal introduction of crystals, especially of that class
which includes water as a constituent part. As examples of the
intention with which these were added, it may suffice to notice
the selection of natrolite, a mineral which, if the water it con-
tains were expelled, might be expected to pass into sommite ;
and of apophyllite, which in the same case might perhaps re-
solve itself into tabular spar and quartz.

The time at which the Elsecar furnace commenced working,
was in October 1833; it is probable, therefore, that an exami-
nation of the hearth may become practicable before the end
of 1836.

Dr. CLark gave an account and an explanation of the suc-
cessful application of the Hot Blast to the production of Cast
Tron.

In the Clyde iron-works, near Glasgow, during the first six
months of the year 1829, every ton of cast iron required for
its production 8 tons 1} ewt. of splint coal, reduced to coke, at
a loss of 55 per cent.

During the first six months of the year 1830, after the appli-
cation of Mr. Neilson’s invention, when the air had been heated
to about 300° Fahr., every ton of cast iron required 5 tons 34
ewt. of splint coal, converted into coke. Adding 8 ewt. of coal
consumed in heating the air, the saving effected was 24 tons of
splint coal on every ton of cast iron produced. And the same
blast was found to be capable of making much more iron, the
diminished requisite of air being pretty nearly proportioned to
the diminished fuel required.

But during the first six months of the year 1833, when the
temperature of the blast had been raised to above 600°, and
when the process of coking the coal had been discovered to be
superfluous, and was accordingly omitted, a single ton of cast
iron was produced by only 2 tons 5} ewt. of splint coal. Even
when we add 8 ewt. of coal to heat the air, the quantity of

Ee St

TRANSACTIONS OF THE SECTIONS. 579

splint coal required in 1833, to make a ton of cast iron, was
only one third of what was used in 1829. The blast machinery
continued the same, but the same blast made twice as much
iron as in 1829,

_ The same coal produced thrice as much cast iron; the same
blast twice as much.

The iron-furnaces alluded to are worked 23 hours out of
the 24; a half-hour every evening, and another every morning,
being occupied with letting off the iron produced.

During every working-hour, the solid materials which feed
the furnace at the top amount to 2 tons almost exactly, while
the air forced in at the bottom, in the same time, amounts to
the surprising quantity of 6 tons.

Since a smelting-furnace must have a certain elevated tem-
perature, in order to work it favourably, when we consider
the cooling effect of 6 tons of air an hour,—2 cwt. a minute,
—supplied at the bottom of the furnace, and entering near the
hottest part, it is easy to account for the increased energy of
the furnace when this prodigious refrigeratory is removed, by
heating the air before it passes into the furnace.

On hydrated Salts and metallic Peroxides ; with Observations
on the doctrine of Isomerism. By Professor GRAHAM.

Various classes of salts, besides the arseniates and phos-
phates, contain water, which is essential to their constitution: of
this the sulphates of magnesia, and the protoxides of zinc,
manganese, iron, nickel, copper, and cobalt, are examples.

These salts crystallize from their aqueous solutions, either
with seven or five atoms of water, one of which is in a state of
much more intimate union than the other six or four. Thus,
crystallized sulphate of zinc loses six atoms of water, at a tem-
perature not exceeding 65°, when placed over sulphuric acid
in vacuo, but retains one atom of water at 410° and all inferior
temperatures. This salt may be viewed as a sulphate of oxide
of zinc and water, with six atoms of water of crystallization; a

constitution which may be expressed as follows, H ZnS +6H.
This sulphate may be made anhydrous, but when moistened
always regains one atom of water, slaking with the evolution
of heat. This last atom of water appears to discharge a basic
function in the constitution of the salt, and affords a clue to the
disposition of this sulphate to form double sulphates. Sulphate
of zinc combines with sulphate of potash, and forms a well-

known double salt, in which the basic water of the sulphate of
2P 2

580 FOURTH REPORT—1834.
\

zinc, is replaced by sulphate of potash, without any further

change. The formula of the double sulphate is (K $) ZnS6+H.
In the double salt, the whole six atoms of water are retained
with somewhat greater force than in the simple sulphate; but
even the double sulphate becomes anhydrous below 212° in
vacuo.

The sulphates of the other metallic oxides mentioned are
quite analogous to sulphate of zinc in their habitudes with
water, although the particular temperature at which they part
with their water of crystallization is different in each. The
analogy holds also in the double sulphates of those oxides.

Of hydrous sulphate of lime, or gypsum, the two atoms of
water which it contains appear to be essential, and are retained
at 212°, At a temperature not exceeding 270°, this salt becomes
anhydrous, but retains the power of recombining’ with two
atoms of water, or setting. The salt is then in a peculiar con-
dition. It is the debris of the hydrate, and not a neat chemical
compound. Heated above 300° the salt becomes properly
sulphate of lime, and has lost the disposition to combine with
water.

The protochlorides, and corresponding cyanides of zinc, man-
ganese, iron, &c., are disposed to combine with two atoms of
water. Hence the cyanide of iron combines with two atoms
of cyanide of potassium, to form the double cyanide of iron and
potassium, commonly called the ferroprussiate of potash.

Berzelius found the peroxide of tin formed by the action of
nitric acid on metallic tin, to differ in certain properties from
the same compound precipitated from a persalt of tin by an
alkali, and distinguished the first under the name of the nitric
acid peroxide of tin. Both peroxides combine with muriatic
acid, but the muriate of the nitric acid peroxide is peculiar in
being insoluble in water strongly acidulated with muriatic acid.
But the precipitated peroxide of tin assumes, I find, all the
properties of the other modification, when kept for some time
exposed to the heat of boiling water, or even when strongly
dried over sulphuric acid in vacuo, at the ordinary temperature
of the atmosphere. ‘The two modifications are merely differ-
ent hydrates of the peroxide of tin, but it is difficult to ascer-
tain what proportion of water is essential to each. The hy-
drates, combine with acids, and form two sets of compounds ;
but absolute peroxide of tin itself (which is obtained by heat-
ing the hydrated peroxide to redness,) has no disposition to
combine with acids. ‘The same is true of many other metallic
peroxides; they combine as hydrates only with acids. There

a, ae

TRANSACTIONS OF THE SECTIONS. 581

are at least two hydrates of peroxide of iron: the muriate of
that which contains least water is red in solution, and the muri-
ate ofthe other, yellow; but these muriates pass readily into
each other. Mr. R. Phillips observed of the red muriate,
that it is precipitated by an access of acid, which, it may be re-
marked, establishes an analogy between it and the muriate of
the nitric acid peroxide of tin, which possesses the same pro-
perty.

Metallic peroxides can in general be obtained by the appli-
cation of a moderate heat to their hydrates, in-a state in which
they are the debris of hydrates, and not neat chemical com-
pounds. Upon heating peroxides in this condition to redness,
they generally glow or become spontaneously incandescent at a
particular temperature, (a phenomenon to which the attention
of chemists has been particularly directed by Berzelius,) and
lose their solubility in acids at the same time. ‘Till they have
undergone this change, they are not absolute or proper perox-
ides. Various salts, such as phosphates, antimoniates, &c.,
exhibit the same phenomenon when heated ; but they all had
possessed water, which is essential to their first constitution,
but not to their second.

The doctrine of isomerism, or that two bodies may exist of
the same composition, but differing in properties, has been pro-
posed by Berzelius as a sequence from such facts as the pre-
ceding. But the propriety of the inference may be doubted.
Most, if not all cases of apparent isomerism may be explained

by reference to one or other of the following facts :

1. Water is essential to the constitution of many bodies.
Thus, what have been called metaphosphoric acid, pyrophos-
phoric acid, and common phosphoric acid, are three different
phosphates of water, or compounds of one absolute phosphoric
acid with three different proportions of water.

2. A particular condition of bodies must be recognised, in
which they are the debris of some compound, and not proper
chemical compounds of their constituents. Thus, on heating

‘a certain borate of water and magnesia to redness,, water. only

is expelled; but what remains is not a simple borate of magnesia,
but a mixture of boracic acid and magnesia, from which the
former may be dissolved out by water. Stucco in. a, state for
setting is in this particular condition, But this is a depart-
ment of corpuscular philosophy which stands much in want of
further development.

___ 3. The proximate constitution of many bodies may be widely

different, of which the ultimate composition is the same. Thus

the cyanic acid of Wohler is undoubtedly an oxide of cyanogen,
but we have no evidence that cyanogen exists in fulminic acid,

582 FOURTH REPORT—1834.

which consists of the same proportions of carbon, nitrogen,
and oxygen as cyanic acid. It is wrong, therefore, to speak
of the fulminic as a second cyanic acid, and useless to couple
them together as isomeric bodies. Tartaric and racemic acids
are of the same ultimate composition, but they certainly con-
tain different radicals, and probably have as little natural rela-
tion to each other as any two vegetable acids which could be
named. Why, then, associate them as isomeric bodies, and call
them the tartaric and paratartaric acids?

4. A minute trace of adventitious matter may sometimes aftect
the properties of a chemical body to a surprising degree.

Professor Rose, of Berlin, has shown that the two kinds of
phosphuretted hydrogen, one of which is spontaneously inflam-
mable in air, and the other not so, are of the same composition
and specific gravity. To account for their possessing different
properties, recourse is had to the doctrine of isomerism. But
my observations indicate the existence of a peculiar principle
in the spontaneously inflammable species, which principle may
be withdrawn, and leaves the gas not spontaneously inflamma-
ble. Phosphuretted hydrogen gas, which is not spontaneously
inflammable in air, may be made so, by the addition to it of one
ten-thousandth part of its volume of nitrous acid vapour. There
are grounds for supposing that the peculiar principle of the
ordinary gas is a volatile oxide of phosphorus analogous to
nitrous acid, and that it is present in a minute, almost infinite-
simal, proportion. Subsequently to the meeting of the Associa-
tion, an account of the author’s researches on phosphuretted
hydrogen has been published in the number for Dec. 1834, of
the London and Edinburgh Journal of Science.

On some new Chemical products obtained in the Gas-works
of the Metropolis. By Grorce Lows, F.G.S., M.R.L,
M. Art. Soc., Engineer to the Chartered Gas Company.

Mr. Lowe stated that in consequence of the recommendations
adopted at the last meeting of the Association, he was induced
to lay before the Section some specimens of the products of
heat, obtained at the Metropolitan Gas-works. He exhibited a
fine specimen of artificial pyrites, containing cubical and octa-
hedral crystals.

These are produced by a long-continued action of fire, at a
dull red heat, and are deposited on the aluminous interior coat-
ing of the cast iron pots, in which muriate of ammonia is sub-
limed into the sal ammoniac cakes of commerce.

The rough muriate contains also some sulphate of ammonia,
and the clay soon becomes saturated with muriate of iron.

——

es ttt

ss

TRANSACTIONS OF THE SECTIONS. 583

Mr. Lowe conceived that this artificial mode of producing
the bisulphuret of iron, in crystals, would be an interesting
fact to the geologist, as affording some confirmation of the
igneous origin of trap rocks, in reference especially to the
observation made by Professor Sedgwick and Mr. Murchison,
that rocks of an aluminous nature are often found at the point
of contact with basaltic matter, to be not only indurated, but
to contain crystals of pyrites. ;

He also showed upon a portion of a worn-out cast iron
retort numerous octahedral crystals of protoxide of iron,
the effect of long-continued heat. Good specimens of these
crystals are very rare, now that only the best iron, and
that of the second melting, is used in the gas-works to which
Mr. Lowe is attached. A wrought iron bolt, which had been
for many hours acted upon by steam, at a bright red heat,
presented a crystallized surface. ;

Mr. Lowe likewise laid before the Section specimens of pure
Prussian blue, and of blue and green pigment, obtained from
the refuse lime-water of gas-works. :

This refuse was for many years allowed to run to waste into
the river Thames; of late it has been evaporated under
the bars of the furnaces, and passed, partly decomposed, up the
chimney. It may now be rendered available for a more useful
purpose.

On the quantity of Carbonic Acid in the Atmosphere. By
Henry Hoven Watson. Communicated by Dr. Datton.

At the commencement of his undertaking, the author con-
fined his experiments principally to the quantity of carbonic
acid in the atmosphere of the town of Bolton; and then, to
arrive at the difference in quality between an atmosphere in
its natural purity and one like that of Bolton, which we know
to be artificially impregnated, he fixed upon Horrocks Moor,
a situation three miles north-west of the town of Bolton, and
elevated, as he had found by barometrical observation, about
584 feet above it; and made the remainder of his experiments
upon air received at this place, except that thrice during the
course of his investigation he operated upon air received on
the top of Winter Hill.

Winter Hill is situate from five to six miles north-west of
Bolton, and about a mile north-east of the well-known Rivington
Pike ; its height above Bolton is about 1211 feet.

The author gives his first experiment as an example of his
method of analysis. A bottle capable of holding 188-400 grains of

584. : FOURTH REPORT—1834.

water was filled with air, by repeated blasts of a pair of hand
bellows, and into it were poured 480 gr. measures of lime-water
such as requires 460 gr. measures of test sulphuric acid, for neu-
tralization, the test acid being such that sulphuric acid of specific
gravity 1°135 constitutes ;1,th part of it: 520 gr. measures of
pure water were added. ‘The mouth of the bottle was secured ;
and the liquor, after being frequently and well agitated, (which
was done inmost instances daily for a week or more,) was passed
through a paper filter with the washings of the bottle; it was
then found to be neutralized with only 270 gr. measures of
the 51, test acid; this being 190 gr. measures less than it
would have required previously to being put into the bottle.

_ Now if 100 gr. measures of sulphuric acid, sp. gr. 1°135, is
equal to 17} grains by weight of real dry sulphuric acid, 190 gr.
measures of the +35 test acid is equal to 0°3325 of a grain by
weight of real sulphuric acid. And taking the atomic weight of
sulphuric acid at 35, and that of carbonic acid at 19:4, the
0°3325 of a grain of sulphuric acid is equal to 0°1843 ofa grain
by weight of carbonic acid, or 0°3921 of a cubic inch.

And deducting 1000, the bulk of the liquor put into the bot-
tle, from 188400, the total capacity of the bottle, we have 187400,
the number of water grain measures of air operated upon,
= 742°3 cubic inches.

Then 742°3 : 0°3921 : : 10,000 : 5-282.

Therefore, in this instance, 10,000 volumes of air contained
5°282 volumes of carbonic acid.

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TRANSACTIONS OF THE SECTIONS. 587

On the Chemical Composition of the crystallized Oxichloride of
Antimony. By J.F.W.Jounston, F.R.S.E. F.G.S., Reader
in Chemistry and Mineralogy in the University of Durham.

When a solution of oxide of antimony in muriatic acid is
diluted with water, a white powder is precipitated, which has
been long known under the name of the powder of algaroth.
If the diluted solution be set aside, the precipitate assumes the
crystalline form, presenting the appearance either of a fine
sand with little lustre, of long transparent slightly yellowish
needles radiating from a centre, or of a congeries of micro-
scopic right oblique prisms having the acute terminal angle
_ about 84° 40’. These crystals are slightly yellowish, transpa-
rent, having occasionally a high degree of lustre, give off no
water when heated, but at an elevated temperature decrepitate
and emit fumes of chloride of antimony. Heated with dry, or
boiled with a solution of, carbonate of soda, they are decom-
posed, and oxide of antimony remains. Nitric acid also decom-
poses them by the aid of heat, leaving antimonic acid.

Several analyses of this substance have been published, but in
none of them, the author believes, was the compound employed in
a crystallized state; and as it is partially decomposed by washing
with water, it is obvious, that unless in this state the true con-
stitution of the compound cannot be obtained by analysis. In
four experiments, crystals prepared at different times gave the
author 11°32, 11°26, 11°22, 11215 per cent. of chlorine re-
spectively. Of these the highest is preferred, for the reason
above stated. In six experiments, by three different methods,
Mr. Johnston obtained: Ist, 76°82; 2nd, 75°93, 76°506, 75°98;
ord, 76°6, per cent. of metallic antimony. Of these he prefers the
last. 'The compound, therefore, consists of

' Chlorine, 11°32= 2°55 atoms.
Antimony, 76°6 = 9°498
Loss, Oxygen, 12°08=12:08
Atoms.
or the (C1+0) : Sb: : 14°247: 9-498 : : 3 : 2 nearly. It consists,
therefore, of oxide combined with chloride of antimony, and
they are in the proportion of one atom of chloride to 44 of oxide,

or of 2:9. This gives the formula 2 (3 Cl+2 SI)+9 SI. The
results of calculation compared with experiment are as follow:

Calculation. Experiment.
{£2 Cl 663 11-49 11°32
Ser. Weve nsBeutdane7 46
36:29 4-54 , 51368
30 675 11°79 12-08

S774 100- 100:

588 FOURTH REPORT—1834.

The chlorine and antimony found by experiment are, as was
to be expected, a little less than is indicated by theory, causing
the amount of oxygen to appear greater than it ought to be.*

On the phenomena and products of a low form of Combustion.
By Cuartes J. B. Wituiams, M.D.

It must have been often observed, that after a candle is ex-
tinguished in a dark room, if no spark be left on the surface,
the wick continues to be, for a few instants, faintly luminous.
This phenomenon attracted the author’s attention many years
ago, and on investigating the matter further, he found that
wax, tallow, oil, resin, sealing-wax, and many other compound
inflammables, are luminous in the dark, when heated to a point
considerably below redness. A bar or mass of iron, heated to
incandescence, and then allowed to cool till it ceases to give
out light in a dark place, affords the most convenient means of
exposing substances to the degree of heat required for this
phenomenon. If small portions of wax or tallow be thrown on
this iron, they give out a pale bluish light, which, if the heat
approaches to incandescence, assumes the form of a lambent
flame. Various animal and vegetable oils, resins, lac, caout-
chouc, cotton, hemp, linen, paper, flour, starch, gum, silk,
cloth, leather, hair, feathers, and almost all compound com-
bustibles, exhibit, in various degrees, the same phenomenon.
Sugar does so very slightly. Camphor and other velatile matters,
and olefiant gas, may be made to show the light by bringing
the vapour or gas into contact with a hot iron held over them.
A short statement of the most material of these facts was pub-
lished in the Annals of Philosophy for July 1823. ‘The author
has lately found that some of them were noticed by Mr. T.
Wedgwood, in the Phil. Transactions for 1798, and were by
him suspected to be ‘*‘ some kind of inflammation.” The lumi-
nous appearance has generally, however, been considered to be
of the nature of simple phosphorescence, like that of fluor
spar and other minerals when heated. These substances
give out light independently of access of air, and under water
or oil; and the cause of this singular property, to which the
term phosphorescence has been applied, is wholly unknown.
On comparing this phenomenon, however, with that of heated
inflammables, the author saw enough difference to induce the
belief that they are not similar, but that the latter is owing to
a kind of low combustion.

* For a fuller account of these experiments see Edinburgh Journal of
Science, January 1835.

TRANSACTIONS OF THE SECTIONS. 589

To bring this matter to the test of experiment, he tried
whether the light would continue to appear when the bodies in
question are heated without the contact of air. Wax, tallow,
and other inflammable matters were heated in different close
tubes in the dark; they were observed to give out no light
until they were opened, when it appeared as usual. On closing
them again, if the heat was kept up, the light gradually disap-
peared, butwas restored on again opening the tubes to the air.
A roll of paper, heated in a close tube till part was charred,
gave outno light, but a piece of paper applied externally to the
heated tube became immediately luminous. Some tallow heated
in a ladle till it became luminous, lost its light on being plunged
into carbonic acid gas.

It having thus been proved that the absence of oxygen pre-
vented the appearance of the light, it was natural to expect
that a free supply of this element would increase it. Some wax
was heated in a ladle till it became luminous in the dark, and
on being plunged into oxygen gas it became brighter, and if
the heating had been considerable, although there was no
spark, it burst out into an open flame. Wax, lac, cocoa oil,
tallow, sperm. oil, sulphur, and some other things could be
kindled into open combustion in this way; but with paper,
most vegetable oils, silk, &c. the pale light was only brightened

‘by contact of oxygen.

The author considers it, therefore, proved that the light ob-
served was not phosphorescence, but depended on chemical
action between the air and the subject of the experiment; that
it was, in short, a form of combustion. The bodies which give
out most light are wax, animal oils, hair, silk, wool, fine white
paper, cotton fabrics, ether vapour, olefiant gas, and sulphur.
Some of these, as paper, tallow, and cocoa oil, begin to give
out light ina dark room below 300°. Wax requires a tem-
perature of at least 400°; and this, the author remarks, isthe
reason why wax candles burn with little or no smell, whilst, in
those of tallow, portions near the wick are heated sufficiently
to undergo the imperfect combustion, which causes the odour
so disagreeable in an imperfectly extinguished candle. The

degree of heat necessary for low combustion may be estimated
by the fact, that as soon as oils or other compound inflamma-

bles begin to give out vapours, they will be found to be lumi-
nous in the dark. When, therefore, tallow or oil is heated to
ebullition in contact with the air, the surface is actually under-
going combustion. If the heat be further increased, the pale
luminosity elevates itself into a lambent flame, which, under
circumstances favourable for the accumulation of heat, will

590 FOURTH REPORT—1834.

burst out into open ignition. It is to be remarked, how-
ever, that this low combustion differs from ordinary inflamma-
tion in its products, and that the transition from one to the
other is not gradual, but abrupt, and attended with a slight
explosion.

Several of the metals exhibit the phenomenon of low com-
bustion. The action is limited in most cases by the speedy
formation of a coat of oxide on the surface of the metal ; but in
the case of arsenic, whose oxide is volatile, a pale flame sur-
rounds it at any temperature capable of raising it into vapour,
and continues until the metal is consumed. The fresh filings
of zinc, iron, cobalt, antimony, tungsten, and copper, become
momentarily luminous when thrown on an iron heated below
redness. Potassium presents the phenomena of low combus-
tion at ordinary temperatures; in fact, the rapid tarnishing of
its surface, after it is cut or rubbed, is accompanied by the
-evolution of a faint light, which becomes brighter if the tempe-
rature is raised.

The light of this low combustion is worthy of notice, which
varies somewhat in different shades of pallid or bluish white.
It becomes a question, what constitutes this light ? That of ordi-
nary flame is supposed to consist of minute particles of the com-
bustible, or of its product, in a state of incandescence. Sir H.
Davy extended this supposition even to the low combustion of
phosphorus, attributing its feebleness of heat to the extreme
paucity and tenuity of the particles of phosphoric acid thus
raised to a white heat. The author conceives that if this were
the cause, there would be a red tinge occasionally present, as
the result of the cooling of these particles to the red degree of
heat. In most ordinary flames such a red tinge occurs, and is
particularly apparent in daylight, but the author has never
seen it in low combustion. The lowest luminous degree of
heat has commonly been stated to be red, that called by arti-
sans cherry red being the first visible degree. If, however,
we examine the phanomena of incandescence in a room other-
wise perfectly dark, by watching a large piece of iron cool
from a red heat, we shall find that, before it ceases to be lumi-
nous, ét loses wholly its red light, and appears of a pale or
milky white. 'This, although fainter, is precisely the colour of
the lights of low combustion.

The author then drew a brief comparison between the pro-
ducts of low combustion, and those of fermentation and putri-
faction, in which he noticed a new process for the expeditious
manufacture of vinegar. In this case an infusion of malt, or
sweet-wort, is made to drop through a room full of faggots of

aa
'

TRANSACTIONS OF THE SECTIONS. 591

twigs, so as to be exposed freely to the air in their interstices ;
and what goes in at the top as cold-wort, comes out at the
bottom, in the course of an hour, hot vinegar.

Abstract of the Discoveries made by Dr. RetcHensacn, in his
examination of the products of destructive Distillation. By
Witiiam Grecory, M.D., F.R.S.E.

Dr. Reichenbach, in the course of a series of experiments,
of great extent and accuracy, on this subject, has shown that
the products of destructive distillation are of a very complex
nature, and contain, besides a variety of principles previously
known, not less than six new principles, all of which are sus-
ceptible of some practical application. These new principles
are:

1. Paraffin.—This is a solid body, white, without taste or
smell, soluble in hot alcohol and ether, which deposit the
greater part on cooling, insoluble in water, fusible at 100° F ahr.,
boiling at a very high temperature, and distilling unchanged.
It is not acted on by the strongest reagents, and from its per-
manence is susceptible of many useful applications. It burns
with a bright light and without smoke. Sp. gr. 0:870..

2. Eupion.—This is a very mobile and volatile liquid, boiling

at about 112° Fahr., and distilling unchanged. It is equally
permanent with paraffin, and, like it, burns brilliantly without
smoke. It has an extremely fragrant smell. It is more ex-
pansible by heat than any known liquid, and is the lightest
known liquid under ordinary pressure, having a sp. gr. of
0:655. Its expansibility recommends it for thermometers, and
it seems well adapted for burning, from the brightness and
purity of the light it produces. .
_ 8. Kreosote.—This is a liquid, sp. gr. 1-037, transparent and
colourless, said to combine a low refractive with a high disper-
sive power. It boils at 400° Fahr., and distils unchanged. It
possesses a strong smell of smoke, and is the antiseptic ingre-
dient of tar, smoke, and pyroligneous acid. It is sparingly
soluble in water, abundantly in alcohol and acetic acid. It
coagulates strongly the albumen of animal substances. It has
been applied with success to the cure of toothache, acts as a
powerful styptic, and is the active ingredient of tar, tar-water,
aqua binelli, and Dippel’s oil. It may be usefully employed
in the art of curing hams and other smoked meats.

4. Pittakall.—This is a solid body, resembling indigo, of a
splendid blue colour, passing on the polished surface into the

592 FOURTH REPORT—1834.

aspect of gold. It is not volatile when pure. It is easily fixed
on cloth, and forms a permanent dye of remarkable beauty.

5. Picamar.—This is the bitter principle produced in de-
structive distillation. It is an oily liquid, heavier than water,
boiling at a temperature above 500° Fahr. It is very perma-
nent. It has an intensely bitter taste. From its permanence
and fixity, it is well adapted for greasing machinery.

6. Kapnomor.—This is a liquid, sp. gr.0°977, boiling at 365°
Fahr. Its most important property is its power of dissolving
caoutchouc. It forms the chief part of the coal naphtha em-
ployed in the arts.

Besides these new substances, Dr. Reichenbach has recog-
nised acetic acid, pyroligneous and pyroacetic spirits, in the
products of destructive distillation. He considers, and appa-
rently with good reason, the pyroligneous spirit as a mixture
of alcohol with pyroacetic spirit. The alcohol is formed by the
fermentation of sugar in the sap of the wood, and distils over
when heat is applied to the wood. Naphthaline is not, accord-
ing to Dr. Reichenbach, a product of destructive distillation,
properly so called, but is always formed when any of the pro-
ducts above mentioned are exposed, in the state of vapour, to a
red heat. .

Dr. Reichenbach has also shown that the naphtha distilled
from the Italian and Persian petroleum, is not produced by
destructive distillation, but is oil of turpentine unaltered, the
origin of which he attributes to the pine-forests of which most
coal beds are composed. Some very fine naphtha, sent by
Mr. Swinton from the East Indies, was found by Dr. Christison
to have all the characters of oil of turpentine. Dr. Christison
supposed that this oil had been fraudulently substituted for the
naphtha, but Dr. Reichenbach has succeeded in obtaining a
similar oil from several species of coal, by distilling along with
water, in which case no destructive distillation could occur.

One naphtha, however, from Rangoon, appears to be a pro-
duct of destructive distillation. Dr. Christison discovered in
it paraffin, which he called petroline, Dr. Reichenbach’s expe-
riments not being at that time known in this country; and
Dr. Gregory has lately proved in it the presence both of
eupion and kapnomor. There is reason to think, therefore,
that this naphtha, and perhaps some others, have been pro-
duced at a high temperature.

lo te

TRANSACTIONS OF THE SECTIONS. 593

It. MATHEMATICAL INSTRUMENTS AND
MECHANICAL ARTS.

On a new Sympiesometer. By Professor Forses, F.R.S.

A BAROMETER acting by measuring the volume of a confined
portion of air, first recommended by Dr. Hooke, has been re-
cently constructed in a convenient form, under the name of the
Sympiesometer, by Mr. Adie of Edinburgh. The chief difficulty
found in operating with this instrument consists in ascertaining
the precise temperature of the inclosed air. This is proposed
to be accomplished by placing both the gaseous ball and that
of the attached thermometer in one common chamber, sur-
rounded with mercury; whilst the difference of temperature
which may exist between that mercury and the external air is
determined by means of a small differential thermometer.
The scale of the mercurial thermometer is read downwards, and
the volume of gas js indicated by a thermometric scale of its
expansions under a constant pressure of 30 inches.

On the construction of Achromatic Object-Glasses. By Davip
Dicx, Architect and Engineer, Edinburgh.

Having several years ago attempted the construction of a
triple object-glass of 4 inches diameter, of which the interior
surfaces were cemented together, as recommended by the late
Professor Robison, Mr. Dick found that, when the surfaces
were found to coincide, it was rather difficult to separate them
without scratching, and therefore preferred to proportion the
radii of curvature so as to leave a small interval of the meniscus
form, which was filled up with the cementing substance. This
mode of construction suggested to him the possibility of em-
ploying a cementing substance having such an action on the
green light, in relation to that of the two sorts of glass, that
the colours of the secondary spectrum might be diminished, if
not entirely removed. By referring to the discoveries of
Sir David Brewster regarding the action of the different re-
fracting media on gieen light, it was found that Canada bal-
sam, oil of turpentine, and in a very high degree the oil of
cassia, were all possessed of the quality sought for, and the
author has in fact succeeded in the construction of object-
glasses of considerable size, which produce images almost, or

1834. 2eQ

594: FOURTH REPORT—1834.

perhaps quite, as free from colour as the images produced
from reflection.

To prove the durability of a glass thus constructed, the
author mentions the fact of .a feur-inch object-glass, which was
put together three years ago with Canada balsam, and has been
exposed to heat, cold, and solar light, without injury. In order
to remove a doubt recently: started on this subject, the glass
has been subjected to a heat of 140° for more than half an hour,
and immediately afterwards tried on the moon, when it ap.
peared to have suffered no injury.

Considerable care must be observed in putting in the cement.

It should be poured upon the centre of the concave lens,
over which the centre of the convex lens being let down
should be brought into contact with the cement, so as to pre-
vent the introduction of air bubbles; the superfluous cement
is then to be gently pressed out, the pressure being applied at
the edges of the lenses. When this has been done, should
the lenses subsequently be shifted much, or turned round their
centres on each other, the distinctness of vision would almost
invariably be destroyed, and is not afterwards recovered.

On a new Klinometer and portable Surveying Instrument. By
Joun Dunn, Optician, Edinburgh.

[With a Plate.]

Fig. 1. represents this instrument drawn to half its real
size. On the brass plate A BC D, there is traced a semi-
circle, divided into half-degrees, and within it a series of
rectangular coordinates, commencing at the centre. Round
the centre of the: semicircle, an arm, E F, moves, carrying the
sights ef, and a spirit-level L, turning on two pivots; and at
one corner of the plate is placed a small compass-box, ¢’, re-
moveable at pleasure. The plate is attached to the tripod hs
fig. 2, by a universal joint, HS; and the clamping-screws,
S and N, enable the observer to secure it in any required
position.

To use this instrument as a klinometer, the edge A D is laid
on the dip of the stratum, and the arm E F is made horizontal,
by means of the level L, when the angle of the dip is indicated
on the semicircle by the edge I K, and the ratios of the base
to the altitude and slope of the inclined plane by the rectan-
gular coordinates, and the divisions on the straight edge I K.
For the more accurate purposes of the mining-engineer, and in
cases where the dip is to be determined over a considerable
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TRANSACTIONS OF THE SECTIONS. 595

tion on its stand, and the sights e f directed to the top of a
post of equal height with the instrument, at the other extremity
of the slope. .

The instrument, when placed in a horizontal position, serves
as a plane table; in this case the divisions onI K, and the
rectangular coordinates, offer peculiar facilities for the execution
ofa rough survey. The distance between two stations being
found on the scale I K, the readings on the rectangular lines
will at once give the easting and northing of the undetermined
station; these can at once be transferred to a skeleton, prepared
by tracing squares on a piece of paper, and each successive
step of the survey is thus completely indicated on the map.
The bearings of the different lines must, of course, be noted, in
order that, by setting back upon them, the observations may
be rendered independent of any changes in the magnetic direc-
tion.

On aChronometer with a Glass Balance-spring. By E.J.DeEnt.

Mr. Dent presented an account of the rate of this instru-
ment, kept at the Royal Observatory, Greenwich, since the last
meeting of the Association. He shewed a chronometer in
motion, with a pure palladium balance-spring; and produced
a table of the variations of gold, steel, palladium, and glass,
from 32° to 100° Fahr.; and another table of the quantities
respectively due to direct expansion, and to loss of elasticity,
in steel and palladium.

On the Polyzonal Lens. By Mr. Gorvon.

Mr. Alexander Gordon exhibited Moritz’s modification of
Fresnel’s polyzonal lens, which (with a common Argand flame)
is proposed as an ceconomical light for ports and harbours, and
to be adopted (when a more intense flame is used) for coast
lighthouses, in situations where the use of parabolic reflec-
tors is not absolutely necessary.

On an Instrument for taking up Water at great depths. By
Mr. REnnte.

Mr. G. Rennie described the principle of construction, and
the practical method of employing this instrument, which has
been tried by him at the estuary of the Tamar, near Plymouth,
and found to succeed completely. ;

2Q2

596 FOURTH REPOR1'—1834.

On the application of a Vernier to a Scale, not of equal, but
of variable parts, and particularly to Wollaston’s Scale of
Chemical Equivalents. By Professor STEvVELLY.

The form of this instrument is that of a pair of lazy tongs,
consisting of a series of parallelograms, placed in a line, angle
to angle, whose diagonals, when the series is drawn closer or
pushed further apart, diminish or increase, according to the
same law that connects the divisions of the portion of the
scale which is to be read off. An adjusting-screw passes along
the whole length of the vernier; ten divisions of which being
made by the adjusting-screw to equal eleven on the scale,
the vernier is set for marking decimally: the marking-points
are formed by thin metallic blades coinciding with the cross
diagonals of each parallelogram.

IV. NATURAL HISTORY, ANATOMY, AND
PHYSIOLOGY.

BOTANY.

On the plurality and development of Embryos in the Seeds of
Conifere. By Rosurt Brown, LL.D. §e.

Tue earliest observations of the author on this subject were
made in the summer of 1826, soon after the publication of his
remarks on the female flower of Cycadee and Conifere. He
then found that in several Conifere, namely, Pinus Strobus,
Abies excelsa, andthe common larch, the plurality of embryos in
the impregnated ovulum was equally constant, and their arrange-
ment in the albumen as regular as in Cycade@; and similar ob-
servations made during the present summer on several other
species, especially Pinus syivestris and P. pinaster, render it
highly probable that the same structure exists in the whole
family.

The first change which takes place in the impregnated
ovulum of the Conifere examined, is the production or separa-
tion of a solid body within the original nucleus.

In this inner body, or albumen, several subcylindrical corpus-
cula, of a somewhat different colour and consistence from the
mass of the albumen, seated near its apex and arranged in a
‘circular series, soon become visible. .

In each of these corpuscula, which are from three to six in
number, a single thread or funiculus, consisting of several,

lt ie ee! ee

TRANSACTIONS OF THE SECTIONS. 597

generally of four, elongated cells or vessels, with or without
transverse septa, originates. The funiculiare not unfrequently
ramified, each branch or division terminating in a minute rudi-
ment of an embryo. But as the lateral branches of the funiculi
usually consist of a single elongated cell or vessel, while the
principal or terminal branch is generally formed of more than
one, embryos in Conifere may originate either in one orin several
cells, even in the same funiculus.

A similar ramification in the funiculi of the Cycas circinalis
has been observed by the author.

Instances of the occasional introduction of more than one
embryo in the seeds of the several plants belonging to other
families have long been known, but their constant plurality
and regular arrangement have hitherto only been observed in
Cycadee and Conifere.

On the Cocculus Indicus of Commerce. By G. A. W. ARNoTT,
M.

In Wight and Arnott’s Prodromus Flore Peninsule Indie
Orientalis, vol.i. p. 446, the Menispermum Cocculus of Linnzus,
the Cocculus tuberosus of De Candolle, or the Cocculus indicus
of commerce, is removed from the genus Cocculus as consti-
tuted by De Candolle, altlhough-De Candolle considered it the
type of that genus, and placed in the Anamirta of Colebrooke.
(Linn. Soc. Trans. xiii. pp. 52 and 66.) No reasons for this
change are there given, and it is the object of this paper to
state them. The proof depends, Ist, On the general accuracy
of the figure of the fruit given by Gertner (De Fruct. et Sem. i.
t. 70. f. 7.), which is presumed to have been taken from a berry
obtained from a shop; 2nd, On the correspondence of that
figure with berries of the officinal plant procured from the
museum of the materia medica class in the University of Edin-
burgh; 3rd, On the correspondence of the above-mentioned
figure and berries with fruit in Arnott’s herbarium, and which
fruit still remains attached to a branch with its leaves ; 4th, On
a specimen of the male inflorescence, which comes from the
same district as that in fruit, and exactly resembles it in every
point, except having male flowers instead of berries ; 5th, On
a comparison of flowering male specimens from the botanic
garden of Calcutta, in the herbarium of the Linnzan Society of
London, and which specimens were derived from berries planted
in that garden by Dr. Roxburgh, and transmitted to him by

deyne, from Malabar, as the plant of commerce; 6th, On the

total dissimilarity of the male flowers from those of the genus

598 FOURTH REPORT—1834.

Cocculus as characterized by De Candolle, and their exact
coincidence with those described by Roxburgh under his
Menispermum heteroclitum (Fl. Ind. iii. p. 817.), and figured by
him among his drawings in the East India Company’s museum
(x. 130.) under the name of Men. monadelphum, and of which
Colebrooke has constituted his genus Anamirta. Mr.Colebrooke
has named this species An. paniculata, but Mr. Arnott con-
siders it better to resume the Linnean appellation, and call it
An. Cocculus. .

Mr. Arnott also remarked, in the course of the paper, that
although the order Menispermacee has been described by De
Candolle, Ach. Richard, Lindley, Hooker, and by himself, as
well as by most other writers on the subject, as having either
(and usually) no albumen, or in small quantity, it is in reality
almost always present, and of considerable thickness ; and,
indeed, in an examination of many species of the order, he has
only yet discovered one in which it does not exist.

On Excretions from the Roots of Vegetables. By C. DauBeny,
M.D., Professor of Botany, Oxford.

Dr. Daubeny described the experiments which he is now
carrying on, in compliance with the recommendation of the Bo-
tanical Committee of last year, (see Report of the Third
' Meeting, p. 484.) with the view of ascertaining in what manner
and to what extent particular plants deteriorate the soils on
which they grow. The results of the experiments will be laid
before a future meeting of the Association.

On the Distribution of the Phanogamous Plants of the Faroe
Islands. By W.C. Trevetyan, F.R.S.E. §e.

"Phe: author states that the number of species is 271, of
which 84 are monocotyledonous, and 187 dicotyledonous. (See
the Edinburgh Journal of Science.)

ZOOLOGY.

On the Propagation of certain Scottish Zoophytes. By Joun
Grauam DALYELL.

The author commenced his illustrations of this subject by
a few preliminary observations on the Actinie and the Hydra,
animals whose structure exhibits many analogies, though
standing far apart in the artificial Systema Nature.

————————————— rrr Srt™™~™™—SD
.

TRANSACTIONS OF THE SECTIONS. 599°

1. The Actinia equina is nearly cylindrical, the upper margin
begirt by a triple row of 70 or 80 tentacula, with 30 or 40
purple tubercles at their root. A purple ring encircles the
base, and there are two purple patches on the mouth. All the
remainder is brown, speckled with green. Food is seized and
conveyed to the mouth by the tentacula; smaller portions are
absorbed into the system without any visible residue: the
tubercles open to discharge purple flakes, after moderate sup-
plies; but larger quantities are rejected in the form of a ball,
digestion having probably operated on the surface only.

This animal is viviparous, though the fact is to be very
rarely witnessed. The embryos, one or more, appear first in the
tentacula, from whence they can be withdrawn, and transmitted
to others by the parent, and are at last produced by the mouth,
In the course of six years,a specimen, preserved by the author,
produced above 276 young; some pale, and like mere specks,
with only eight tentacula, others florid, and with twenty.
They are frequently disgorged along with the half-digested
food, 38 appearing thus at asingle litter. An embryo extracted
artificially from the amputated tip ofa tentaculum, began to breed
in fourteen months, and survived nearly five years. Mon-
strosities by excess are not uncommon among the young: one
produced naturally, consisting of two perfect bodies, and their
parts sustained by a single base, exhibited embryos in the
tentacula at ten months, bred in twelve, and lived above five
years. While one body was gorged with food, the other con-
tinued ravenous.

2. Hydra tuba, the trumpet polypus, thus denominated from
its form, inhabits the Frith of Forth, near Edinburgh, where
its natural abode seems the internal concavity of the upper

_ oyster-shell. Removed to an artificial site, it suspends itself by

its narrow base, while the long slender tentacula, above thirty
in number, descend two inches, to wave as a beautiful white ©
silken pencil in the water. Thus it is by much the largest. of
the Hydre proper.

This animal is alike voracious as the former. Its colour,
naturally a dingy white, is affected by the quality of the food,
and the fertility of both species is dependent on the quantity
of nutriment. The flesh of muscles seems that which is most
acceptable to many of the small aquatic animals.

The embryo originates in a rude organic mass, as an ex-
ternal bud, near the base of the parent. Prominences above
soon indicate incipient tentacula surrounding the mouth, while
the lower part remains united by a ligament, which gradually
decreases until itis ruptured, as the embryo withdraws to esta

600 FOURTH REPORT—1834.

blish itself independently. It never drops from the parent, but
often, when yet immature, buds are germinating from its
sides, while the opposite side of the parent enlarges also; the
whole presenting a shapeless and distorted congeries, which is
refined by time into separate, distinct, and perfect animals.
A single specimen had eighty-three descendants in thirteen
months, nor were its prolific powers then exhausted.

Some authors have maintained that the Hydre of fresh
water propagate by buds at one season, and by ova at another.
Nothing of this alternation occurred in the course of the au-
thor’s observations, protracted during five years, on an original
group, and the posterity of these marine Polypi.

The locomotive faculties of the Actinte and the Hydre@ are
exercised very seldom, and on the most limited scale.

3. Tubularia indivisa.—A splendid stem rooted below, and
rising thirteen inches high, is crowned by a scarlet head, bear-
ing some correspondence with the structure of the former
animals. The mouth is situated in the centre, amidst forty or
fifty less active filaments, and the margin is surrounded by
thirty or thirty-five tentacula, expanding fourteen or fifteen
lines between their opposite tips. A tenacious yellowish matter
fills the tubular stem, which is frequently discharged in con-
siderable quantities if the root be ruptured.

Splendid groups are formed by fifty or even a hundred spe-
cimens of this zoophyte, in immediate approximation.

An ample ovarium, resembling clusters of grapes, is borne
externally on the head, and weighing it down by its exuberance.
On approaching maturity the ovum drops from its cluster for
evolution below, where slight prominences soon denote incipient
tentacula, as in the Hydre, while incorporated with the parent.
But, as they extend, a knot enlarges their extremities, contrary
to their ultimate acute formation in adults. Next, the nascent
animal, reversing itself, enjoys the faculty of progression by
means of the inverted tentacula, as on so many feet, apparently
to select a site ; when, again resuming the natural direction with
the extremities upwards, the lower surface fixes itself below,
and roots there for ever: meantime elongation of the stalk
raises the head amidst its watery element.

It is evident, therefore, that the Tubularia indivisa, though
subsequently rooted as a plant, is originally of animal nature
exclusively.

The head is deciduous, generally falling from the stem a
short time after removal from the sea; but regeneration ensues
at intervals of from several days to several weeks, though the
successive heads are never equally luxuriant, nor bear a prolific

TRANSACTIONS OF THE SECTIONS. 601

ovarium like the first. The number of tentacula decreases pro-
gressively. Another smaller species, here denominated, provi-
sionally, Tubularia polyceps, sometimes occurring in groups of
five hundred heads, propagates after the same manner. The
head is regenerated also, and under a similar deficiency. A
specimen had originally twenty-one tentacula, but only sixteen
were renovated with the second head; and with the seventh
they had diminished to six. The head evidently rises as a bud
within the tube from below, and its origin seems dependent on
the subsistence of the internal tenacious matter.

Regeneration may be effected artificially, and even to re-
dundance, beyond the apparent provision of Nature. Thus,
twenty-two heads were obtained in five hundred and fifty days,
from three sections of a single specimen. An equal number
was never reproduced by any specimen preserved entire.

3. Sertularia.—The most luxuriant of this diversified genus
may be compared to leafless shrubs in miniature, composed of
stem, boughs, branches, and twigs, all clothed with variously
shaped prominent cells, the habitation of so many Hydre or
Polypi, capable of protruding from them. These are generally
white, or of a light grey or green colour; some more sluggish ;
others very vivacious, having from eight to twenty tentacula in
a single row, with the mouth dilating, as a cup, in the centre,
to absorb the prey. None exceed a line in diameter. The
whole product is tubular, and occupied by an internal pith or
animal substance, with which the polypi are connected, and on
the presence of which in their vicinity their survivance depends.
The largest hitherto obtained by the author from the Scottish
seas, ishere denominated, provisionally, Sertularia Uber; itrises
nearly three feet high, by the slenderest stem, thus exceeding
greatly the dimensions usually ascribed to these zoophytes.

. Besides a profusion of cells, many specimens, of various
species, bear an indefinite number of vascular substances, three
or four times their size, or even larger, and of greatly diver-
sified configuration and arrangement. ‘They are spherical,
ovoidal, formed as a vase or as a Florence flask, indented,
irregular, with an orifice at the summit or in the side. It does
not appear that all specimens of the same species bear uniformly
the same kind of vesicle. ‘They abound at every season, pro-
bably from the nearly equable temperature of the sea, sub-
sisting long if undisturbed; but their origin is never to be
witnessed. .

Each vesicle contains from one to thirty white, grey, reddish,
green, or yellow corpuscula, the number, and perhaps the
size, depending partly on the species of Sertularia. However,

602 FOURTH REPORT—1834.

white and yellow respectively occur on different specimens of
the same species, and they are the most common of all. '

Preceding naturalists have maintained that the vesicles are
the ovaria, and the corpuscula the ova, whereby Sertularie are
propagated. But the author’s experiments and observations
greatly multiplied during many years, on many specimens of
various species, have not led the author directly to the same
conclusion.

The contents of the vesicle are not distinguished originally
by any definite form. At a certain stage they are recognised
as spherical or ovoidal corpuscula, the former being their
earliest sensible shape. In advancing somewhat further, they
resolve into spherical triangular prisms, betraying evident ani-
mation by extension and contraction; and motion commencing,
places are interchanged among them. At length, attaining
maturity, they issue from the orifice of the vesicle, not as
young Sertularie, but as a race of perfect animals, bearing
many features of the Planaria, and which may constitute a new
genus, to be denominated Planula. ;

The vesicle now remains empty and transparent, nor is it
known to be replenished by another brood; but occasionally a
small portion appears in the centre, as of a slender twig haying
penetrated upwards. .

These creatures are produced in extraordinary profusion.
Above 1200 have issued from the vesicles of a portion of the
Sertularia Uber; and multitudes, in still greater proportion, |
from those of others. But only one was contained in the
vesicles of the Sertularia abietina examined, and in those of
several species which did not attain maturity.

Ordinarily the Planule are white or yellow, opake, smooth,
and flattened, somewhat triangular, tapering from the head
which is always obtuse, downwards to the lower extremity,
and extending from inferior dimensions to rather above a line.
Those of certain species are pyriform, and of others linear,
with obtuse extremities. Neither eyes nor any external or-
gans have been discovered.

The motion of the Planule is smooth and gliding; they crawl
actively over the bottom of the containing vessel or up its
sides ; they suspend themselves in the water by an invisible
thread, as the Planaria, and like them swim supine.

But in a few days their motion relaxes; they become sluggish |
and stationary; their figure alters, and they die, yet without
that speedy decomposition incident to Planaria.

Very soon afterwards a circular spot or low spherical segment
of the same colour, white or yellow, is observed in just about

TRANSACTIONS OF THE SECTIONS. 6035.

the identical place where the Planula perished. A short
spinous prolongation rising from the centre, becomes a stalk,
with an enlarging summit, which, forming into a cell, in a few
days more bursts, to display a living polypus in full activity.

While scarcely mature, other buds are germinating along
with further extension of the parts, and quickly perfected as
so many more cells with their polypi; and thus by progressive
multiplication is the entire specimen produced under its proper
aspect.

- Meantime the circular spot below, invariably white or yellow,

according to the Planula, is losing its opacity; it breaks into
divisions resembling radicles, still confined within its margin,
and at last disappears in tenuity.

Thus, with the precaution of selecting specimens bearing
prolific vesicles,—those exhibiting corpuscula to the eye,—a
whole forest of nascent zoophytes may be easily obtained.

The author cannot affirm that amidst a multitude of observa-

tions he has ever witnessed their origin, under other conditions
than the presence of the Planule, and these have been afford-
ed by eight or ten species of Sertularia, vegetating as para-
sites, or, independently, from solid foundations.
_ Nevertheless, as truth is the sole purpose of scientific re-
search, several difficult questions must be offered for solution.
1. When does the vesicle originate? 2. Is it deciduous and
regenerated? 3. Does it include some invisible pericarp or
true ovarium, containing the elements of the progeny of the
Sertularia? 4, Is their maturity indicated by the presence of
the Planula? 5. Does its escape by the orifice of the vesicle
promote their discharge? 6. Are these elements absorbed
by the Planula while in the vesicle, and their evolution after-
wards promoted by its death ?

4, Flustra carbasea.—The genus Flustra is of more simple
structure, and consists of fewer parts than Sertularia.

_ The Flustra carbasea rises from the root by a short flattened
stem, with a stout yellow margin, simply as a leaf consisting of
foliaceous subdivisions, free at the margin, as they are suscepti-
ble of enlargement. One surface is covered by cells of ashuttle,
or rather a slipper shape, the edges of the whole forming
that surface, level, not prominent. Each cell is composed of a
broad flattened top connected with the bottom by sides like
those connecting the back and belly of the violin, and there is
an aperture above towards one extremity for protrusion of the
polypus, which, affixed by the posterior part, reposes within,.
folded as the letter S, and when active extends to display:
about twenty-two tentacula. The leaf rises vertically, and the.

604: FOURTH REPORT—1834.

protrusion of the polypus is horizontal, or at right angles to
its surface.

Cells are occasionally occupied by a large, irregularly round,
solid, yellow, ciliated animalculum, afterwards quitting them
to swim heavily below. Its motion relaxes, it becomes sta-
tionary, and dies, like the Planule, without speedy decompo-
sition.

In just about the same spot also where the animalculum
became quiescent, a yellow nucleus is soon discovered, with a
pale diffusing margin. This enlarges as the nucleus declines ;
it gradually approximates the shuttle or slipper form ofa cell,
and, converted to such, it gives birth in nine or eleven days to
a polypus. The adult Flustra was vertical, but the new cell is
horizontal. One extremity, however, is already rising vertically,
which, extending after a similar fashion, proves the nidus of a
second polypus in nine or eleven days more. ‘The protrusion
of the two animals now shows them at right angles to each
other. But as if the existence of the first were only a sole or
foundation for securing the superstructure in its growth, it
perishes as a third cell with its polypus forms above the second
by enlargement of the leaf.

- Thus there seems to be some relation between the spherules
occupying the cells and the originating Flustra ; but equal diffi-
culties require solution here as with the preceding race.

5. Cristatella mirabilis —Naturalists, attracted by the sin-
gular diversity of structure in the genus Sertularia, and too
readily satisfied with mere external aspect, have devoted infi-
nitely more attention to the simple skeleton or tube than to
the animated parts. In as far as the author is aware, the tenta-
cula of all their polypi, together with those of the Flustra,
Tubularia, the Aleyonium, and Pennatula, are disposed in cir-
cular arrangement, the mouth being in the centre. Several
zoophytes of very different conformation habit the ponds, the
lakes, and the streams of Scotland; among these the propa-
gation of the Cristatella mirabilis is chiefly considered by the
author, as the product itself seems to have eluded the research
of previous observers.

Perfect specimens occur from six lines to twenty-four in
length, by two or three in breadth, of a flattened figure, fine
translucent green colour, and fleshy consistence. Some of the
shorter, tending to an elliptical form, may be compared to the
external section of an ellipsoid ; but those of the largest dimen-
sions are linear, that is, with parallel sides and curved extre-
mities.

-.The middle of the upper and the whole of the under surface

TRANSACTIONS OF THE SECTIONS. 605

are smooth; the former somewhat convex, occasioned by a
border of 70 or 80, or even of 350 individual polypi, disposed
in a triple row. Their number depends entirely on the size of
the specimen,—increasing as long as it grows.

This product is endowed with the faculty of locomotion,
either extremity indifferently being in advance ; but its progres-
sion, uncommonly slow, seldom exceeds an inch in twelve or
twenty-four hours.

Each of the numerous polypi, though an integral portion of
the common mass, is a distinct animal, endowed with separate
action and sensation. The body, rising about a line by a tubu-
lar fleshy stem, is crowned by a head, which may be circum-
scribed by a circle as much in diameter, formed as a horse-
shoe, and bordered by a hundred tentacula. Towards one
side the mouth, of singular mechanism, seems to have projecting
lips and to open as a valve; folds up within, conveying the
particles which are absorbed to the wide orifice of an intestinal
organ, which descends perhaps in a convolution, below, and
returns again to terminate in an excretory canal under the site
of the tentacula. Probably the whole race of Cristatelle is
distinguished by a similar conformation.

The polypus is a very vivacious animal, quickly retreating for
security when alarmed, and rising to expand in activity. 'T hough
each be endowed with independent life, sensation, and all the
motions that can be exercised without actual transition, the
whole are subjected to the volition of the sluggish mass in re-
spect to progression:—They are borne along with it.

A specimen having been cut transversely asunder, each por-
tion seemed to recede by common consent ; but both survived,
as if sustaining no injury. Neither is any polypus affected by
the violence offered in its vicinity.

Twenty, thirty, ormore lenticular substances, of considerable
size and in the most irregular arrangement, imbedded in the
flesh, are exposed through the translucent green of the animal.
Its death and decomposition towards the end of autumn liberate
them to float in the water. Subjected to the microscope, or,
indeed, to the naked eye, their convex surfaces prove brown,
the circumference yellow, and begirt with a row of spines,
terminating in double hooks. Each is an ovum of the Cris-
tatella, with a hard shell, and occupied by yellowish fluid con-
tents. ‘

In five or six months the ovum gapes at one side to allow the
protrusion of an originating polypus, which by a remarkable
provision of Nature now floats reversed, with the head down-
wards, to ensure absorption of the liquid element below. On

606 FOURTH REPORT—1834.,

quitting the ovum it attaches itself to some solid substance by
the base, then disproportionately large, from which a second
polypus quickly rises, then a third, and a fourth; and thus with
others. In earlier stages the Cristatella mirabilis seems to be
of a circular figure, and in its most mature state there is a mar-
gin projecting beyond the root of the polypi.

6. Cristatella paludosa.—The indistinct descriptions of au-
thors embarrass naturalists excessively in their endeavours to
recognise the lower animals; and this will be found one prin-
cipal source of multiplied synonyms, and of the errors some-
times unjustly charged on the framers of each systema nature.

That which is here designated the Cristatella paludosa ap-
pears generally as a grey gelatinous mass, overspreading the
surface of fresh or faded leaves in a single stratum, and pos-
sibly thickening into a blackish spongy substance with age. ©
During earlier stages, while merely superficial, it invests the
under surface of the growing leaf in an irregular stellate figure
with diverging points. When larger it extends into an area equal
to two or three square inches over one or both sides, especially
of the leaves which have fallen, and, unlike the Cristatella
mirabilis, it is affixed in firm and permanent adhesion.

The whole is studded with white specks, proving under the
microscope to be as many polypi, intimately resembling the
former in their general structure and nature; but they are in-
finitely smaller: more than one is incorporated with a common
portion; nor do the tentacula bordering the crescent exceed
forty-four or forty-eight. The arrangement of the intestinal
parts and their functions seem the same.

Numerous minute ova, resembling the former, but not ex-
ceeding a tenth part of their size, and destitute of cireumferen-
tial spines, are dispersed throughout the greyish mass, being
more accumulated towards the white bases of the polypi. They
seem to escape from the recent product by transmission through
the tubular body of the polypus, passing between the side and
the intestinal organ, to be discharged somewhere above. ‘The
ova escape from the recent Cristatella mirabilis also, but in
what manner has not been ascertained.

Multitudes, liberated as the Cristatella paludosa breaks up
in decay, are usually attracted to the side of the vessel by the
curve which is formed there by the water, besides some re~
maining at the surface. The ovum gapes as before, and the
two halves sunder to give birth to a single polypus, often in a
few days after discharge or liberation. The nascent animals
are affixed permanently to the first spot they reach, and in the
course. of increment their bodies seem incorporated together.

TRANSACTIONS OF THE SECTIONS. 607

7. It would require a separate dissertation to illustrate the
mode of increment peculiar to zoophytes in detail, and to de-
scribe their extraordinary reproductive properties.

The stem of the Tubularia indivisa elongates only during
the subsistence of the head. This having fallen, it remains
stationary. The elements of this important organ, the recep-
tacle of food and the source of the progeny, seem dispersed
throughout the stem, and it is regenerated from the residue left
by sections very near the root. The original ceil of the nascent
Sertularia polyzonias is accompanied by a diminutive twin in-
vested by a common membrane; and one is always forking off
in future increment as the other gains maturity. Sometimes
polypi are regenerated in the vacant cells of. Sertularie, pro»
vided the pith be entire ; but the reproductive powers succeeded
by violence are not displayed as in the Tubularie.

Wounds and lacerations, inevitably destructive to the large

animals, are suffered with impunity by those allied to the Hydra,
and in promoting the evolution of dormant parts denote that
the principle is there. In others of the lower tribes, such as
those now denominated Annulosa, it is doubtful whether the
elements of the entire animal do not even reside in every seg-
ment. The Amphitrite ventilabrum, which attains twelve or
fifteen inches in length in the Scottish seas, regenerates either
the higher or lower extremity indifferently when mutilated.
The author has found also that very small intermediate sec-
tions near the extremity of this and other species regenerated
the beautiful complicated anterior plume of branchiz, and the
posterior glandular parts, perhaps aiding the construction of
the tube. While the body remains a fragment, the former is
disproportionately large, nor can its singular mechanical pro-
perties be exercised when the redintegrated animal is dislodged
from its original dwelling.
. However luxuriant a zoophyte may appear in ultimate ma-
turity, though consisting of hundreds of naked animals as in
the Cristatella and Alcyonium, or of a thousand cells with their
polypi as in the Sertularia and Flustra, the origin of all is one
only. Perhaps the formation of the cell and the other inani-
mate parts undergoes some modification with the age of the
product: the animal with which it originates is equally large, if
- not larger than any of its successors.

. All the products described in this memoir, except the Cris-
tatelle, dwell in the sea, from whence their recovery is often’
as much the consequence of accident as design. Most of the-
preceding results have been verified only with years of obser-
vation. :

608 FOURTH REPORT—1834.

On the Transformations of the Crustacea. By J. O. West-
woop, F.L.S, &c.

The object of this communication having reference to one of
the three queries relative to the annulose animals, proposed by
the Association, was to endeavour to prove the correctness of
the views of Rathke, and the consequent want of foundation of
those of Thompson: egivsit

lst, By a summary of the recent authorities particularly
bearing upon the question; and 2ndly, by a statement of some
facts which had come under the notice of the author himself. :

In the former branch of the subject were mentioned the
dissertation of Rathke upon the development of the oya of
Asellus aquaticus; the memoir of Dr. Zencker upon the
Gammarus Pulex; and the more generalized memoir of M. H.
Milne Edwards, of which a report by M. St. Hilaire has been
published in the Annales des Sciences Naturelles, in which,
however, the nature of the transformations of the genera Cy-
mothoa, Cyamus, and Phronima is particularly noticed.

From these works, as well as from Mr. Thompson’s own
memoirs on Mysis and Artemia, and Mr. Coldstream’s paper
upon Limnoria terebrans, (Jameson's Edinburgh Journal,
April 1834,) it is evident that although the more typical Crus-
tacea (Malacostraca) undergo a series of moultings, whereby
an increase of size, and sometimes a slight increase in. the
number of locomotive organs are obtained, yet there is no
violent change of form similar to the metamorphoses of insects;
such, in fact, as it is asserted by Mr. Thompson that even the
more typical Crustacea undergo. :

With reference to the second branch of his notice, the
author stated that although the land crab of the West Indies
was that particular species upon whose habits Mr. Thompson
more especially dwelt, as indicating the necessity of metamor-
phosis in Crustacea, he had obtained from the collection of
the Rey. L. Guilding specimens of the ova and young, just
hatched, of that species, and which he had himself extracted
from beneath the abdomen of a female, where many hundred
others were deposited, the young having all the appearance of
the perfect animal, and not a single zoe being present. He had
also obtained from the same collection xoes nearly. an inch
long, rather too large to admit of the supposition that they
would subsequently be transformed into crabs, and dwindle
into the size of the young ones just noticed. 5 inn) de
_. Thus types of all the great divisions of the Malacostraca have
been ascertained to undergo no metamorphosis ;

TRANSACTIONS OF THE SECTIONS. 609

The Brachyura being represented by the Land Crab,

The Macrura ——. Cray-fish,

The Schizopoda Mysis,

Tid Aeihinoda Gammarus and Phro-
hit 4 nima,

The Lemodipoda ———-——— Cyamus,

Asellus, Cymothoa,
and Limnoria.

The Isopoda

The author, in conclusion, suggested that there might possibly
be some parasitic connexion between Zoé and the Crabs where-
by Mr. Thompson’s statements might be accounted for, adding
that precisely analogous case exists in the young of the Cole-
opterous genus Meloé and the Pediculus Melitte.

Observations on the Orbital Glands in certain tribes of Birds.
By P. J. Sevsy, F.R.S. §c.

In this paper, after adverting to the little attention hitherto
paid by naturalists to these glandular bodies, or their supposed
use in the ceconomy of the birds in which they are found, the
author proceeds to point out their situation, &c., and to show
that they secrete an oily fluid of a peculiar quality, which fluid
is distributed, by appropriate ducts, over the eyes, and serves to
defend them from the action of the water, in which the birds
possessing the glands usually reside, or at least are in the
frequent habit of procuring their food; that all birds. be-
longing to the order Natatores, hitherto examined, possess the
glands, developed toa greater or inferior extent as their habits
are more or less aquatic; that they are largest in the habitual
Divers, and in such as feed with the head submerged; that they
also exist in many species of the order Grallatores, but only in
such as are well known to submerge the head in search of
food, by probing the sand &c. beneath the surface of the
water. After instancing several examples belonging to both
orders, and contrasting the size of the organ with the known
habits of the birds, he further suggests that this oily fluid may
be more especially secreted to protect the eye from the effects
of saline or sea water, as the development of the gland appears
in a great degree to be regulated by the marine habits of the
birds, and that its mode of action is that of a thin and transparent
varnish spread over the globe of the eye. The structure and
form of the gland are then described, and the course of the ex-
cretory ducts pointed out.

1834. 2R

610 FOURTH REPORT—1834.

Notice of Birds observed in Sutherlandshire, June 1834.
. * By P. J. Seay, FL.RS. §e.

Ordo RAprTorEs.
Fam. Fatconipz.

- Aquila Chrysaétos. Common in the North and West of Su-
. Haliaétus albicillus. f therland; very destructive to sheep and

lambs. Premiums paid for their destruction: 171 full-grown
birds killed within the last three years.

. Pandion Haliaétus. Common on the north-west coast.
. Falco peregrinus.
. Fale. Tinnunculus. Abundant.

Milvus vulgaris.
Buteo vulgaris.

- Circus cyaneus. Only one individual seen.

(No Strigid@ seen.)

Ordo INSEssoREs.
Tribus FisstrostTrREs. Fam. Hirunpinipz.

9. Hirundo rustica.

. Hir. urbica. Smoo cave, and limestone rocks, Inch-na-damff:
. Hir. riparia.
. Cypselus murarius. Smoo cave.

Fam. Topipz.

. Muscicapa Grisola. Rose Bank, south of Sutherland.

Tribus DENTIROSTRES. Fam. Mervutipz.

. Merula musica. Abundant more to the northern extremity of

Sutherland, wherever birch coppice abounds. All of the com-
mon species, and no appearance of a smaller kind, called by
Mr. Laidler the little brown thrush.

. Mer. vulgaris. Rare.
. Mer. torquata. Abundant in all the mountainous parts.
. Cinclus aquaticus. Now becoming rare, as it is destroyed by

every device, from an idea that it feeds upon the salmon spawn.
This is not established.

. Fam. Syiviapz.

18. Sylvia phragmites. Met with throughout the greater part of

Sutherland.

19. Sylv. Trochilus. Ditto, wherever birch abounds.

. Curruca cinerea. In the South of Sutherland,

21. Erythrea Rubecula.
22, Phoenicura Rutacilla.

. Saxicola Ginanthe. Very abundant throughout the county.

24. Sax. Rubetra.

25. Sax. Rubicola.

> .
he

rc
2

52.

53.
54,
55.
56.

TRANSACTIONS OF THE SECTIONS. G11

- Motacilla alba. Common.
- Mot. Boarula. In various parts.
. Anthus pratensis. Very abundant.

Accentor communis.

. Parus ater.
-Par. ceeruleus.

Tribus ConrrostTREs. Fam. FrinetLLipz.

. Alauda arvensis. Abundant. -
. Emberiza miliaria.

Emb. citrinella.

Emb. Scheeniculus.

Fringilla ceelebs.

Passer communis. .

. Linaria cannabina. Rare.
. Lin. montium. Very common.

Lin. minor. In birch woods.

Fam. Corvipz.

- Corvus Corniz. Common.

Cor. frugilegus. On the southern border only.
Fam. STuRNip&.
Sturnus vulgaris. At Smoo Cave and Scourie.

Tribus ScansoreEs. Fam. CrertTHrIaDz.

. Troglodytes europeus.

Fam. Cucuuipz.

. Cuculus canorus. Very abundant.

Ordo Rasores.
Fam. Cotumsipz.
Columba Livia. Common; caves upon the coast.

. Col. Palumbus. Rare.

Fam. TETRAONIDA.

Tetrao Tetrix.
. Lagopus scoticus.

Lag. mutus.

Lag. rupestris, Killed upon the Benmore (Assynt) range.
Perdix cinerea.

Ordo GRALLATORES.
Fam. CuarapRiaDz.
Charadrius pluvialis. Very abundant. Breeding upon the heather.
Char. Hiaticula. Ditto. i
Vanellus cristatus. Ditto.
Hematopus Ostralegus.
2r2

612 >. FOURTH REPORT—1834.

Fam. ScoLopacip.

. Scolopax Gallinago. Abundant. Scolopax Gallinula is also said

to breed near Tongue, but we did not meet with it.

58. Totanus Calidris.

72.
73.

74,
75.

76.
7.
78.

19.

. Tot. Glottis. Breeds in Sutherlandshire. Breeding- station pre-

viously not known. Young procured.

- Tringa variabilis. . Abundant.
. Numenius arquatus. Ditto in particular districts.
. Num. Pheopus. Rare.

Fam. Ratzipez.

. Fulica atra. Rare.

Ordo NATATORES.

Fam. ANaTIDA.

. Anser Segetum. Discovered breeding on many of the lochs, viz:

Lochs Shin, Laighal, Barncuh Naver, &c. Young in the downy
state procured.

. Anas Boschas.
- Mareca Penelope. On many lochs. Breeding. Nest and eggs

found for the first time in Britain.

. Fuligula marila. Found breeding for the first time near to En-

boll, in a small freshwater loch.

- Mergus Serrator. Common upon all the lochs.
. Merg. Merganser. Rare.

Fam. Cotymeips.

» Colymbus glacialis. Pair in summer plumage: seen in Balna-

chiel Bay.

- Col. arcticus. This beautiful species was discovered for the first

time in Britain. Breeding in most of the freshwater lochs.
The eggs and young were procured and two old birds killed.
Plumage of both seaes alike. Eygs deep oil green with darker.
blotches.
Col. septentrionalis. Seéén in different lochs, but no nest found. —
Podiceps minor. Rare.

Fam. ALcApD&.
Uria Troile. iz
DadGrylie. \ Upon the southern coast.
Fam. PELECANIDE.

Phalacrocorax Carbo.
-Phal. cristatus.
Sula Bassana. Northern coast.

Fam. Larip2.
Larus marinus.

TRANSACTIONS OF THE SECTIONS. 613

80. Larus argentatus.

81. Lar. fuscus.

82. Lar. canus. 5 Merete in various places.
83. Lar. ridibundus.

84. Sterna arctica.

85. St. cantiaca.

Observations on the Salmonide which were met with during an
excursion to the North-west of Sutherlandshire in June 1834.
By Str WituiaM Jarvine, Bart. *

A short excursion was undertaken to Sutherlandshire in June
last for the purpose of examining the natural productions of the
county, for which object, including the examination of the fish-
eries, every facility, by permission, and direction to the tacks-
men, was afforded by the Duchess of Sutherland.

The county of Sutherland having a large range of sea-coast
indented with innumerable bays, its shores were a favourite
resort of the Salmon, and the fisheries were valuable and car-
ried on extensively. On account of the deterioration of them
of late years, the Duke of Sutherland took them entirely un-
der his own direction two years since. The close time was
regulated according to the season of running in the different
rivers. The fish were strictly preserved, and in several rivers
the Gilse were all permitted to run. This year (the second of
the improved management) the produce was in many streams
doubled. Experiments were also instituted (principally in the
Laxford by Mr. Baigrie) to ascertain whether the Gilse re-
turned to the river the same year in which they were spawned ;
and the fact that they did so was satisfactorily established.
The general weight of those that returned first was from three
to four pounds. It may be here remarked that the salmon is
often taken on the Sutherland shores, at the Haddock lines,
baited with sand-eels, and in the Durness Firth with lines set

on purpose with the same bait ; thereby disproving Dr. Knox’s
hypothesis that their only food in the sea consists of Entomo-
straca and the ova of star-fish.

Of the Migratory Salmonida, that of next importance to the
‘Salmon is what in all the North Highlands is called the Sea
‘Trout, distinguished by the tacksmen as the larger and smaller
kinds, the first entering the rivers about the commencement of
June, the second about the middle of July. The first or largest
fish was thought to be identical with the Tweed Whitling ; 300

__* The gentlemen composing the expedition were Mr. Selby, Mr. James
Wilson, Dr. Greville, Sir William Jardine, and Mr. Jobn Jardine. - - :

614 FOURTH REPORT—1834.

were sometimes taken at a sweep of the common salmon draught
net from the weight of one pound to about three. The second
or smaller fish upon comparison was found to be identical with
the Herling of the Solway Firth, the Salmo albus of Fleming’s
British Zoology. It occurs in numbers in proportion to the
first of about ten to one.

Non-migratory Salmonide.—The North-west of Sutherland-
shire is studded with an immense multitude of lochs, in which
Trout are almost the peculiar fish; they differ from each other
so much in the various districts as to warrant the suspicion that
more than one species is included under the common name of
Trout. The characters were constant in particular districts,
and four very marked varieties were exhibited, differing chiefly
inthe general form, proportion of the fins, andform ofthe scales
and of the intestines. By many ichthyologists the different ap-
pearances of trout are all referred to S. Fario, with a most
extensive range of variation; but the subject appears yet to
require investigation. Many of the trout in these lochs are of
very fine quality. ;

In most of the larger lochs, particularly in the district of
Assynt, the Greater Grey or Lake Trout, Salmo ferox, Jard.,
was found. This fish is noticed by several of the British writers,
but only as a variety of the common trout. It is distinct, and
possesses good specific characters. It reaches the weight of
twenty-five pounds. In Scotland it has been taken in Lochs
Awe, Shin, Loyal, Assynt, &c.; in the latter fourteen speci-
mens were procured. Its food is almost exclusively fish. The
flesh is very coarse, and of a yellowish pink colour.
~The Char, Salmo alpinus (8. Umbla, Agass.), is found in most
of the lochs; but, from the difficulty of tempting them with any
bait, few were procured. They are only seen and taken in num-
bers when approaching the mouths of the small rivulets to spawn,
and at that time are deteriorating in condition. They appear
in best condition in June and July, and might then be taken in
numbers with nets stretched across or into the lochs. They
feed on aquatic insects, but seem active chiefly during the
night.

The Parr, Salmo Salmulus, Penn., was found in many rivers
sparingly, nowhere abundant, and apparently decreasing in
number towards the north.

No other Salmonide were met with during the excursion;
but after the above remarks upon those mentioned, specimens
were exhibited of the Gillaroo Trout from Ireland apparently
only a variety of Salmo Fario. The food found in the stomach
consists exclusively of different species of freshwater shells,

TRANSACTIONS OF THE SECTIONS. 615

but the coats and sides of the stomach are not more muscular
than in the common trout.

The Whitling and Bull Trout of the Tweed are the young
and adult states of the same fish, which is the Salmo Eriox of
some authors, and reaches a large size.

TheLochmaben Vendace, Coregonus marenula(?).—Thelochs
in the neighbourhood of Lochmaben are the only known habitat
in Scotland for this fish, and the author is not sure that there
is any authentic station for it in England or Wales. The
stomachs were entirely filled with minute Entomostraca, which
certainly at times constitute the greater part of the nourish-
ment of this fish.

Note.—All these fish were shown to M. Agassiz. All the trout
he considered as varieties of Salmo Fario; S. ferow, an ad-
dition to the Salmonide of Europe, and new to him; the Whit-
ling and Bull Trout also new to him, and differing from any of
the fish he was acquainted with in the Continental rivers ; Parr,
the young of 8. Fario; and the Lochmaben Vendace distinct
from the Coregonus marenula of continental ichthyologists.

Notice regarding the Coleopterous Insects collected during a
Tour in Sutherland. By James Wiuson, F.RS.L. $e.

[The following extract from this memoir will show the views of the author,
who is engaged in preparing a report on the geographical distribution of in-
sects for the next Meeting of the Association. ]

In the total absence of any information regarding the entomo-~
logical productions of the North of Scotland, the following ca-
talogue of species was drawn up, as a commencement, however
defective, of those local lists, which, in a completed state, will
tend to illustrate an important department of natural history.
The value of such lists is in a great measure independent of
their presenting the names of new or rare species: it consists-
in their exhibiting a true picture of the prevailing entomologi-
cal character of countries. From an assemblage of such pic-
tures the general distribution of species and the laws by which
it is regulated and maintained are eventually to be deduced.
No apology need, therefore, be offered for the want of novelty.
in the following catalogue :

COLEOPTERA.

Cicindela campestris. - Carabus arvensis.
Cychrus rostratus. cancellatus.
Carabus catenulatus. violaceus,

616, _ FOURTH REPORT—1834.

Carabus hortensis. _
glabratus.
clathratus.

Helobia brevicollis.
Gyllenhalii.

Leistus rufescens.

Lamprias chlorocephalus.

Clivina fossor.

Dyschirius gibbus.

Broscus cephalotes.

Feronia nigrita.

melanaria.
nigra.
orinomum,

Abax striola.

Peecilus cupreus.

Argutor erythropus.
pullus.

Harpalus ruficornis.

limbatus.
zeneus.

Tarus basalis.

Curtonotus aulicus.

Bradytus apricarius.

Amara eurynota.

communis.
vulgaris.
familiaris.
similata.

Patrobus rufipes.

Calathus piceus.
cisteloides.
melanocephalus.
mollis.

Clisthopus rotundatus.

Agonum meestum.
viduum.
parumpunctatum.

Anchomenus albipes.

Loricera pilicornis.

Badister bipustulatus.

Trechus minutus.

Blemus paludosus.

Peryphus littoralis.

Notiophilus aquaticus.

biguttatus.

Elaphrus cupreus.

Blethisa multipunctata.

Dyticus marginalis.
Hydroporus trivialis.
Colymbetes bipustulatus.
agilis.
uliginosus.
Gyrinus marinus.
natator.
Helophorus aquaticus.
griseus.
granularis.
Hydrobius melanocephalus.
fuscipes.
orbicularis.
Spheridium 4-maculatum.
Necrophorus vespillo.
Oiceoptoma rugosa.
thoracica.
Silpha obscura, var.
Phosphuga atrata; and var.
Meligethes viridescens.
Byrrhus pilula.
fasciatus.
zeneus.
varius.
Hister carbonarius.
Onthophilus striatus.
Geotrupes stercorarius.
sylvaticus.
vernalis.
levis.
Aphodius rufipes.
fimetarius.
terrestris.
fossor.
rufescens.
Phyllopertha horticola.
Trichius fasciatus.
Ctenicerus tessellatus.
pectinicornis.
cupreus.
Elater minutus.
Anathrotus ruficaudis.
niger.
Campylis linearis.
Sclasatomus zeneus.
Hypnoidus riparius.
Cataphagus obscurus.
marginatus.

TRANSACTIONS OF THE SECTIONS. 617

Atopa cervina. |
Malthinus biguttatus.
Cyphon melanurus.
Telephorus bicolor.
rusticus.
dispar.
nigricans.
testaceus.
pallidus.
Anobium castaneum.
Hypera arator.
Hylobius abietis.
Barynotus mercurialis.
Merionus obscurus.
Otiorhynchus tenebricosus.
leevigatus.

atro-apterus.

ovalis.
Hylacites gemmatus.
Strophonomus coryli.
Sciaphilus muricatus.
Sitona lineata.
Phyllobius argentatus.
mali.
reniformis.
parvulus ?
mali, var. ?
Rhagium bifasciatum.
Donacia sericea.
cincta.

Donacia simplex. -
Galeruca tanaceti.
caprez.
Chrysomela staphylza.
fastuosa.
Phaedon vitellina.
Raphani.
Coccinella tredecimpunctata.
Helops caraboides.
Goerius olens.
Creophilus maxillosus.
Staphylinus murinus.
castanopterus.
stercorarius.
zeneocephalus.
Ocypus similis.
Quedius tristis.
picipennis.
Philonthus splendens.
politus.
varians.
Othius fulgidus.
Gyrohypnus longiceps.
linearis.
Lathrobium lineare.
Stenus ?
Tachinus rufipes.
marginellus.
Tachyporus chrysomelinus.
Aleochara concolor ?.

_ Remarks on the different Species of the Genus Salmo which
_ frequent the various Rivers and Lakes of Europe. By

__M. Aaassiz.

The genus Salmo, as it has been established by Linnzus and

Artedi, or rather by Rondeletius, has supplied Cuvier with the
type of a peculiar family, in which he has retained the generic
characters of Linnzus, viz. one dorsal fin with soft rays, and
a second one, which is rudimental and only adipose. Cuvier
places this family in his order Malacopterygit Abdominales,
between the Silurida and the Clupee ; and he subdivides it,
on just grounds, into a great number of generic sections, which
comprehend a vast variety of exotic species. In his work on
the fishes of Brazil the author added several new kinds to those
which Cuvier established; and is of opinion that, in the natural
classification, it is now absolutely necessary to unite the family

618 FOURTH REPORT— 1834.

of the Clupee to that of the Salmonide, since the only differ-
ence between them consists in the presence or absence of an
adipose fin, an organ assuredly too insignificant to constitute
the distinctive character betwixt two families, and the less
so as there are some genera of the family which possess it,
whilst in others it is completely wanting, as, for example, in the
Siluride. We may with equal truth affirm, that all the real
Salmones of Cuvier have not this adipose fin, for in many spe-
cies of the genera Sarrasalmus, Myletes, &c., it is composed
of rays which are truly osseous.

Restricted to the limits which.Cuvier has assigned to it, the
genus Salmo comprehends all the species of which the body is
somewhat lengthened, the mouth large, and supplied with teeth,
which are conical, pointed, and formidable, implanted into all
the bones of the mouth, that is to say, into the interior maxil-
lary bones, both superior and inferior, into the vomer and
palate bones, into the tongue itself, and into the branchial
arches. The margin of the upper jaw is formed by the interior
and superior maxillary bones, and constitutes only a single con-
tinuous arch, as in the higher classes of animals; a conforma-
tion which in the class of fishes is found only in the Clupee.

It is also singular that the number of branchial rays is seldom
exactly the same on the opposite sides of the head, the number
varying from ten to twelve. The pectoral and the ventral fins
are of a middling size; the latter placed about the middle of
the belly, opposite to the dorsal, at their base, and along their
insertion there is a fleshy fringe, somewhat similar to the long
scales which are found on the greater number of the Clupee.
The caudal fin is attached to a very fleshy root, and is moved
by. very powerful muscles.

This elastic tial is to these fishes a most powerful lever :
when wishing to leap to a great height, they strike the surface
of the water with a kind of double stroke. By this means they
overcome obstacles which appear insurmountable, and leap over
nets which are intended to confine them: the most formidable
waterfalls can scarcely arrest them. The several species of this
genus are found in the northern and temperate regions of Eu-
rope, Asia, and America. .

The fishes of this family are very ravenous, and feed princi-
pally upon the larvee of aquatic and other insects and of the
small crustacea; they also devour fishes of a smaller size.
Their alimentary canal is short, but the stomach is proportion-
ally long and strait. At its pyloric extremity may be observed
a great number of appendices, which are connected with the
pancreas, and to which is generally, but erroneously, applied

TRANSACTIONS OF THE SECTIONS. 619

the name of cecum. The swimming-bladder of all of them is
very large, and opens into the cesophagus near the bottom of
the gullet. Though unable here to enter into the subject
very fully, the author states his persuasion that this organ
ought to be regarded as the lungs of fishes; that the cir-
culation of the blood in these animals has been inaccurately
interpreted when it is supposed that in their heart there may
be traced a pulmonary course; also, when their branchie have
been identified with the lungs of other animals; and, finally,
when their great dorsal artery has been considered as analo-
gous to the aorta of the mammalia.

Most of the varieties of salmon reside in fresh waters ; in
summer they pay a visit to the sea, and do not mount up again
to the rivers, except for the purpose of there depositing their
spawn. It is sufficiently remarkable that most of our species
deposit their ova in November and December, and that the
young fry of course come into existence in the coldest season of
the year. From this circumstance we may suppose that it is
owing to this habit of enduring intense cold in the first days of
their existence, that they can subsequently support all that va-
riety of temperature to which they are soon to be exposed.

In proportion as the genus Salmo is now circumscribed within
its natural limits, so much the more is it difficult to characterize
the various species; and M. Agassiz affirms without hesita-
tion, that since no one has devoted himself to their history, so
no one has yet succeeded in determining, with any degree of
’ precision, their distinctive characters. The greatest obstacle to
the solution of this problem arises from our ignorance of the
accuracy of the characters hitherto employed to distinguisa the
several species the one from the other. .

Naturalists have especially attached themselves to the form
of the head and to the arrangement of the colours; but these
two particulars are much too variable to supply precise charac-
ters. As to the variation in the colour, we may say it is infinite.
There are, however, two circumstances which especially modify
the tints of the salmon tribes, namely, their age and the season of
the year. The younger fish are in general much more spotted
than the older ones, whose tints become more and more uni-
form. 'The Salmo Hucho, for example, with violet spots more
or less distinct, has, when young, large black transverse bands
upon the back down to the middle of its sides. In the second
and third years of its existence these bands break up into black
spots, less deep in colour, and they disappear more and more,
till in its latter years the fish acquires a colour which is almost
uniform. The Salmo lacustris of Linneus, when young, has

620 FOURTH REPORT—1834.

large black and ocellated spots upon all the superior parts of
its body; but from the third year they diminish, and ere long
they entirely disappear.

The Salmo Umbla, so long as it is young, is of a greenish
yellow colour, with the abdomen white ; and at a later period of
life these tints assume a deeper hue of a more lively green, and
finally pass into a blackish green. The abdomen soon becomes
silvery white, afterwards yellow and orange coloured, and then
of a golden lustre. Its flanks are very soon adorned with ocel-
lated yellow spots, more or less distinct ; but ere long there are
no spots at all. In the Salmo Fario the spots vary even more.
In the young they are found yellow, green, brown, and even
black and violet, also black and red; but at length they all
entirely disappear.

The author has also noticed that the seasons have an influ-
ence on the colours of the different kinds of Salmo.

It is during the autumn, and at the time of the greatest cold,

that is to say in October, November, December, and January,
that their tints are most brilliant, and the colours become more
vivid by the accumulation of a great quantity of coloured pig-
ments. We might almost say that these fishes bedeck them-
selves in a nuptial garb as birds do. The colour of their flesh
varies according to the nature of their aliment. This family of
fishes feeds, as we have said above, especially upon the larvee
of aquatic insects and of small crustacea. It is in the waters
which contain the most of these last that the most beautiful
salmon-trout are found. Direct experiments which were made
in lakes have proved, to the author’s satisfaction, that the in-
tensity of the colour of the flesh arises from the greater or smaller
quantity of Gammarine which they have devoured.
- As to the structure of the head, it offers, in the opercular
bones, in the surface of the cranium, and in its proportions re-
lative to the whole body, very excellent characters: but those,
on the other hand, which are taken from the proportional
length and size of the jaw-hones are of no value at all; the
lower jaw is longer or shorter than the upper according ‘as
the fish opens or shuts its mouth; and this consideration in-
troduced into the characteristics of the family has very con-
siderably contributed to multiply the institution of species.
The hook which forms the jaw of the Salmo Salar is not even
a peculiar characteristic of this species, since the full-grown
males of all the species of the genus present a crooked prolon-
gation of their lower jaw to a greater or less extent.

Possessed of these facts, which had been collected with the
most minute and jealous precautions, M. Agassiz tried to deter-

TRANSACTIONS OF THE SECTIONS. 621

mine the various species which are found in the fresh waters
of the Continent, grounding his examination upon the study of
the interior organization and upon the particulars already de-
termined which the integuments present concerning the struc-
ture of the scales. He has also introduced the shape of the
body and the proportional size of its internal parts as important
accessories to the description of the species. Of these in-
vestigations he proposes to give an account in his treatise upon
the fishes of the fresh waters of Central Europe, confining him-
self here to a short statement of the results which he has ob-
tained.

It is a very singular fact that those fishes which are the most
widely distributed, and those which are most highly prized,
are precisely those whose natural history is the most perplexed.
The opinions, too, which are most general concerning their
geographical distribution are not at all in unison with the real
state of things. . There scarcely exists a country to which some
peculiar species of salmon has not been assigned; and the
author adds that even in the Réegne Animal of Cuvier are many
nominal species, which are not even local varieties, as he pur-
poses ere long to demonstrate.

The cupidity of the fisherman, the rivalry of epicures, and
the fastidiousness of the palate of salmon-eaters, have, without
doubt, contributed to spread these opinions upon the narrow
limit assigned to the haunts of the species of the salmon. There
is especially a famous variety in the annals of epicurism, over
which the greatest possible obscurity has been cast, it is the
Ombre Chevalier, the Char, or Alpine Trout. >

After having attentively examined the Continental varieties,
M. Agassiz with eagerness availed himself of the opportunity
lately afforded him of examining near their native haunts seve-
ral species of this genus which are found in England. Through
the kindness of Sir William Jardine and of Mr. Selby, he has
also had an opportunity of examining all those which they have
collected from the Scottish lakes ; and the result has been that
he has succeeded in determining the perfect identity of many
of them with the species found in other countries in Europe,
while, on the other hand, he is convinced by the observations of
these naturalists that there are species peculiar to Scotland.
Nevertheless it is true that systematic authors, from having
allowed themselves to fall into error through the prevailing opi-
nions circulated concerning the vast multitude of species of this’
genus, have been investigating the characters of a great num-
ber of merely imaginary species. But to the philosophical
naturalist the distinctions upon which they support themselves

622 : FOURTH REPORT—1834.

in establishing the differences of species are quite insufficient,
and the comparative examination of these pseudo-species admits
of very different results. ,

M. Agassiz is convinced that all the fish belonging to this
family on the Continent may be reduced to the six following
species :

1. Salmo Umbla, Linn.; the Char of England; the Ombre
Chevalier of the Lake of Geneva; the Rétheli of Swiss
Germany ; and the Schwarz Reutel of Saltzburg.

Synonyms: Salmo Salvelinus, Linn.; Salmo alpinus,
Linn. ; Salmo salmarinus, Linn., (but not the Salmo
alpinus of Bloch).

This fish is found in England and Ireland, in Sweden and
Switzerland, and in all the southern parts of Germany.

2, The Salmo Fario, Linn.; the Trout of brooks ; Common-
Trout, Gillaroo-Trout, and Parr.

Synonyms: Salmo sylvaticus, Schrank ; Salmo alpinus,
Bloch; Salmo punctatus, Cuvier ; Salmo marmora-
tus, Cuvier; Salmo Erythrinus, Linn.

It is found as extensively as the first species.

3. Salmo Trutta, Linn.; Sea-trout, Salmon-trout. Tt is
the same as the Salmo Lemanus of Cuvier, and the Salmo
albus of Rondeletius.

4. Salmo lacustris, Linn. The same as the Salmo Illanea
and the Salmo Schiffermullert of Bloch.

Found in the lakes of Lower Austria, and in the Rhine above

Constance.

5. Salmo Salar, Linn.; the True Salmon. The Salmo
hamatus of Cuvier is the old fish, and the Salmo Gadeni
of Bloch the young fish.

Found in the northern seas, whence it ascends the rivers

even as far as the Swiss lakes.

6. Salmo Hucho, Linn.
Peculiar to the waters of the Danube.

It results, then, from these observations, that the different
species of the Salmon family, far from being confined within
the narrow limits of some small bodies of fresh water, are, on
the contrary, very widely distributed. They also thrive in all
climates, at least in all elevations above the surface of the
ocean, whether in fresh water or in salt. Nevertheless they
prefer those situations where the water is limpid.

The author concludes by stating that it is not upon vague
data that he has drawn these several conclusions, but upon the

TRANSACTIONS OF THE SECTIONS. 623

actual examination of living specimens of all the species that
have been named, and that he has himself studied them in the
localities where they were caught.

‘ Dr. Atten Tuomson exhibited some specimens of the fol-
lowing reptiles : |

Amphiuma means (didactylus of Cuvier), Menopoma (of Har-
lan), Menobranchus lateralis, and Proteus anguinus ; and made
some remarks upon the place which these animals and the Ce-
cilia hold among the other Batrachian reptiles.

Dr. Thomson then exhibited a few specimens and drawings
of the young of the common Thornback at the period when the
external branchial filaments exist. He described the connexion.
of these filaments with the internal gills, and the circulation of
the blood in the single vessel running through each of the
fifteen filaments that project from the side of the neck, which
he had observed in the animal, kept alive for some days.

On the Laryngeal Sac of the Reindeer. By J. 8S. Trat.t,
M.D., F.RSE. §c.

The curious pouch connected with the larynx of the rein-
deer was detected by Camper; but his figure does not convey
any correct idea of the form and position of that membranous
sac. Dr. Traill minutely described this sac, and exhibited
drawings of it when inflated in situ, from which it appears to
have an elongated form, with a blunt, bifid extremity towards the
angle of the jaw, and to taper to a point at the opposite end,
which reached to within 6 or 8 inches of the anterior part of the
sternum. Its length equals 18 inches; its greatest diameter
about 5: inches. Its blunt extremity is covered by a delicate
expansion of a pair of muscles, that derive their origin from the
transverse processes of the cervical vertebre, and from the
horns of the os hyoides. ‘These muscles appear to act as com-
pressors of the sac when the animal inclines to expel the air.
The only aperture of the sac communicates with the superior
angle of the thyroid cartilage by an orifice capable of easily
admitting the fore finger. The animal from which these draw-

ings were taken was a male, from Norwegian Lapland, dissected
by Dr. Traill in 1822.

On: the Ancient Inhabitants of the Andes. By J. B. PENTLAND.

: The author having offered some observations on the physical
configuration of the Andes of Peru and Bolivia, and on the
distribution of organic life at different elevations on the decli-

624: FOURTH REPORT—1834.

vity of these gigantic chains, stated the reasons which have led”
him to conclude that there existed there at a comparatively
recent period a race of men very different from any of those
now inhabiting our globe, characterized principally by the
anomalous form of the cranium, in which two thirds of the
entire weight of the cerebral mass is placed behind the occi-
pital foramen, and in which the bones of the face are very much
elongated. Mr. Pentland entered into details to prove that
this extraordinary form cannot be attributed to pressure or any.
external force similar to that still employed by many American
tribes, and adduced in confirmation of this view the opinion of
Cuvier, of Gall, and of many other celebrated naturalists and
anatomists.

The remains of this race are found in ancient tombs among
the mountains of Peru and Bolivia, and principally in the great
inter-alpine valley of Titicaca, and on the borders of the lake of
the same name. These tombs present very remarkable arehi-
tectural beauty, and appear not to date beyond seven or eight
centuries before the present period.

The race of men to which these extraordinary remains be-
long, appears to Mr. Pentland to have constituted the inhabi-
tants of the elevated regions situated between the 14th and
19th degrees of south latitude before the arrival of the present
Indian population, which, in its physical characters, its customs,
&c., offers many analogies with the Asiatic races of the Old
World.

GEOLOGY.

On the Geology of Berwickshire. By Davip MILNE, Advocate,
A.M., F.RS.E. F.G.S.

Mr. Milne commenced his paper by describing the bounda-
ries of the district he had examined, and for the better illus-
tration of which he exhibited a coloured map and sections. The
district in question comprehends the Lammermuir hills on the
north, the valley of the Tweed on the south, and a line drawn
north and south through Melrose on the west. He mentioned,
that there are at least four different formations or groups of
rocks to be found in this district. First, the grawwvacké rocks,
composing the greater part of the Lammermuir hills. Second,
the old red sandstone, which ranges along the base of these hills,
and is found filling up. their valleys and burn-courses. Third;
the coal-measures, which, to a certain extent, are distinctly de-
veloped, resting on the old red sandstone, and forming the lower
parts of Berwickshire ; and fourthly, the trap, which forms the

TRANSACTIONS OF THE SECTIONS. 625.

greater number of the isolated hills, that are outliers from the
mountain chain of the Lammermuirs.

Mr. Milne then described the external appearance or confi-
guration of the district as that of an oval-shaped. basin, cut
across at the east end by the German Ocean, and the northern
edges of which are the grauwacké hills, some of which rise
1800 feet above the level of the sea. The country then slopes
down to the valley of the Tweed, and is diversified by a number
of tributary streams, which easily cut and form deep ravines in
the soft clay strata, of which the lower parts of the country are
chiefly composed. Next to the grauwacké formation, in point
of level, is the old red sandstone group, which ranges along the
base of the Lammermuir, Galawater, and Cheviothills, and occu-
pies perhaps one fifth of the intervening space, between the hills
and the Tweed, but is never visible at a lower level than 200 or
300 feet above the sea, or higher than 900 or 1000 feet above
the sea. The coal-measures and marl strata occupy the west
and lowest parts of the surface of the basin, being cut through
by the Tweed, in its course from Kelso to the sea; the higher
parts of the river, above Kelso to Jedburgh, displaying sections
of the old red sandstone.

After this general sketch of the three several deposits of stra~
tified. rocks in this district, Mr. Milne proceeded to notice the
situation of the trap-rocks, the exact boundaries of which, he
said, it was more difficult to. describe; though it may be re-
marked that they occur most abundantly in the grauwacké and
the old red sandstone series. The traps in these two different
groups also possess very distinct characters, the grauwacké trap
being remarkable for its compactness, and the old red sandstone
trap being of a looser and more friable texture. Almost all the
isolated hills, which diversify the appearance of the upper parts
of Berwickshire, as Cowdenknowes, the Dirringtons, Cockburn
Law, Lamberton, Home Castle, Kyles’s Hill, and others of in-
ferior note, consist of this less compact trap, and all occur
within the limits of the old red sandstone.

Mr. Milne then entered into a more detailed account of these
different formations, pointing out some circumstances charac-
terizing each of them.

I. The Grauwacké Hills —These have been usually de-
scribed as running from St. Abb’s Head across the country to
the Irish Channel. Though this is true as a general remark,
yet, on an examination of these hills in detail, it is found that
a considerable portion of them, perhaps 1th or sth, consists of
trap-rocks intermixed. One-half of the promontory of St:
Abb’s Head consists of trap; and there are few sections in the

1834, 2s

626 FOURTH REPORT—1834.

ravines of the mountain torrents of these hills wherein masses
of trap may not be perceived insinuating themselves, even
among the grauwacké strata, and deriving from them a stratified
appearance. The grauwacké strata, from this cause, have been
dislocated and contorted in a thousand different ways, and there-
fore exhibit no uniformity in their dip and direction. But
there is still on the whole, and more particularly in those parts
which have not been disturbed by immediate contiguity to trap,
a tendency to a particular direction or run, viz. from east to
west. The texture of the rock is finely granular, and is gene-
rally of a greenish, or sometimes of a yellowish brown colour.
Occasionally it passes into a slate which is quarried for various
purposes.

No fossils have been found in the grauwacké rocks, nor any
mineral except copper. There are in several parts of the Lam-
mermuir range, veins of this metal, some of which have been
worked, as at Elmfond, Faseney, and Norton, and run in a di-
rection very nearly east and west.

II. The next series of rocks, in descending from the hills, is
the old red sandstone formation, which rests on the flanks of
the Lammermuirs. They consist of a coarse conglomerate at
their basis, of a slaty sandstone in their central parts, and of
soft beds of unconsolidated sand or clay in their upper parts.

This formation not only flanks the base of the grauwacké
range, but is found filling all the ravines and valleys of these
hills up to a certain level. The series is one apparently of in-
considerable thickness at the sides of the hills where it rests on
them ; but towards the plains, and at a distance from the hills,
it is found to be of great depth. In the upper parts of Lammer-
muir the conglomerate appears to have a thickness of no more
than 10 or 20 feet, whilst on the banks of the Tweed, between
Kelso and Melrose, there are cliffs of conglomerate 80 or 100
feet high. The same remark applies to the sandstones, which
have been deposited over the conglomerate, deep sections of them
being visible on the Tweed, whilst in the upper parts of Lau-
derdale they are much more shallow. This fact, Mr. Milne ob-
served, could be at once accounted for on the supposition that
these old red sandstone rocks had been deposited in an ocean or
sea which washed the sides of the Lammermuir hills, and in-
ereased in depth at a distance from them. The grauwacké
strata, on which the conglomerate of this formation has been
deposited, must have formed the bed of that ancient ocean ; and
accordingly, though the conglomerate presents great unevenness
and irregularities in its level, the upper part of the red sand~
stone series very nearly occupies one level throughout the whole

TRANSACTIONS OF THE SECTIONS. 627

district, but slopes gradually from the hills. Mr. Milne ob-
served that the conglomerate of the old red sandstone is com-
posed of fragments, varying in size from small gravel to boul-
ders of a foot or two in thickness; they consist of the same
rocks of which the neighbouring hills are composed, being either
grauwacké ‘or trap, though the grauwacké fragments greatly
predominate. All the fragments have been completely rounded,
‘as if they had been worn down by the action of water ; not that
they seem to have been transported from a great distance, for
the fragments are now generally either at the very base of the
parent rocks or are in the immediate vicinity of them; but that
they seem to have been acted on like shingle, or a bank of gra-
vel at the foot of a sea-cliff, the pebbles of which have been
worn and smoothed by the incessant motion of the waves.

The fragments are agglutinated together by a cement of small
gravel or sand, hardened by oxide of iron, which gives a red
tinge to the mass; and wherever the fragments are oblong or
flat, their flat sides are almost always parallel to the line of
stratification.

That these conglomerate rocks were deposited on the grau-
wacké, and from the debris which must have been collected at
the foot of them, is not only the only possible way of explaining
their present situation and appearance, but is proved by sections
at various points where the junction is seen. Mr. Milne then
referred to several drawings of these points of junction.

The conglomerate is overlaid by a deposit of sandstone, which,
as already observed, is thinner near the edge of the deposit than
at greater distances from the hiils. There is one character in
the mineralogical appearance of the rock, besides its red colour
and slaty structure, by which it is everywhere marked, viz. the
occurrence of white or greenish white spots or patches upon its
longitudinal fracture : these white spots do not generally exceed
two inches in diameter, being sometimes oval, but generally very
nearly circular.

‘The upper part of the old red sandstone formation consists of
beds of red sand and red clay, which are so little consolidated,
that in the part of the country where they are best seen, (viz. be-
tween Whiteburn, Greenlaw, and East Gondon,) numbers of
hillocks and rounded knolls have been formed by the effect of
the rains, and the rivulets which now encircle them. In many
places where the formation is less ferruginous, these upper beds
are worked for the sand they yield.

No fossil remains of any kind have been found in this forma-
tion.

Since the deposition of these rocks they have been subjected

282

628 FOURTH REPORT—1834.

to the most violent disturbance and dislocation. Through a great
many different parts of the red sandstone girdle, flanking the
hills, the trap is now seen protruding, and bearing, far above the
rest of the surface of the surrounding country, the red sandstone
strata on its top or sides. .

At Home Castle, which is built upon basalt, a large quantity
of the sandstone is seen enveloped in the trap. The whole mass
of trap here is very considerable, and may be perhaps altogether
two miles in circumference. Home Castle is about 200 or 250
feet above the red sandstone plains surrounding it; and very
near its walls the red sandstone above referred to may be seen
very highly inclined, leaning upon the basalt. There are various
other hills of trap, which occur among the old red sandstone
strata, such as the Dirringtons, Lamberton Hill, Kyles Hill,
Kildon Hill, &c. The protrusion of these immense masses of
trap (some of them forming hills 1000 or 1200 feet above the
level of the sea, and 300 or 400 feet above the surrounding coun-
try,) could not have failed to elevate the district immediately in
contact with them, and the effect of this elevation must neces-
sarily have been to produce great rents or fissures across the
strata so elevated and disturbed. Suppose that by the eleva-
tion of Home Castle rock, for example, the red sandstones,
which were originally horizontal, were pushed upwards so as to
raise one part several hundred feet above the surrounding coun-
try; the width of the cracks or rents caused by this elevation,
and their extent through the country, would, of course, depend
upon the height to which the strata were raised, and the di-
stance to which the disturbing force operated. But one thing is
evident, that these rents or fissures would generally run from
the point of highest elevation or greatest disturbance as a centre ;
and whilst there the rents would be of considerable width, they
would gradually diminish in width in proportion to their di-
stance from that centre. This observation is well illustrated by
what actually occurs in the neighbourhood of Home Castle ; for
two or three trap-dykes (to be afterwards more particularly de-
scribed) are found to run across the country for several miles from
that point as a nucleus, this nucleus having served as the source
or fountain-head to supply the different currents of trap which
now form the dykes that have filled up these extensive rents.

These trap-rocks seem to be generally confined to the old red
sandstone group, and occur more frequently next the edge of
the group contiguous to the hills than to the one more distant
from them.

There are several instances of the lower conglomerate having
been cut through and hardened by veins of trap; indeed, in one

TRANSACTIONS OF THE SECTIONS. 629

jocality, a mass of conglomerate, about 30 feet thick and 100
yards long, (the breadth unknown,) may be seen resting on the
top of a trap-hill, which has risen up between the grauwacké
and the old red sandstone. This is near the sea-coast, at asmall
village called Burnmouth.

- JII. Mr. Milne then proceeded to describe the lowest- parts
of the basin, viz. those occupied by rocks decidedly mem-
‘bers of the coal-deposit, from which extensive supplies are ob-
tained along the south bank of the Tweed, and also by those
other rocks, of more doubtful character, which some geologists
have considered as new red sandstones.

Mr. Milne here observed, that in speaking of the Berwick
coal-fields, or coal formation which occurs along the south
bank of the Tweed, he only meant to state the fact, that strata
are developed there, having one and all of the distinctive features
of the coal-measures, derived from the mineralogical characters,
as well as the organic remains found in them. These strata
have, however, been described as subordinate members of the
mountain limestone group, and to this opinion he cordially ac-
ceded. But his object was merely to state the fact of extensive
deposits of coal, and its usual concomitant rocks, being in that
neighbourhood, when he spoke of them under the convenient
appellation of coal-measures.

There are on the south bank of the Tweed altogether eight
workable seams of coal, and the collieries extend from near the
shore at Berwick to the river Till, which joins the Tweed about
20 miles from the sea. Those strata, with the rest of the coal-
measures, rise at Berwick, about north-north-west ; but further
inland they rise more and more decidedly to the westward ; and
near the Till, where they are not far from the Cheviot hills,
they rise nearly due west. In short, they appear to lie con-
formably to the belt of old red sandstone, which winds along
the foot of the Lammermuir and Cheviot ranges, and rise always
to the hills nearest to them.

These coal-seams vary in thickness from 23 feet to 53 feet,
and are worked so extensively as to supply with fuel not only
the district of Northumberland and Durham wherein they occur,
but also the greater part of Berwickshire and Roxburghshire.

It is from the same coal-deposit that all the lime used for
agricultural purposes is procured.

It is hardly necessary to add that the sandstones, limestones,
and shales, accompanying the coal which is worked south of
the Tweed, contain all the fossil remains usually characteristic of
a coal-deposit. Crinoidea with the Producta, Spirifera, Modi-
ola, and other marine shells are abundant, whilst the Equiseta-

630 FOURTH REPORT—1834.

cee, Filices, and similar plants, are easily distinguishable in the
impressions visible on the sandstones and shales. It is by these
limestones that the remarkable foldings are exhibited, which do
not occur in the strata of shale lying above and below them.
These foldings are seen at Berwick and at Scremerston on the
shore.

These coal-measures cross the Tweed, and are observable in
the lower parts of Berwickshire. But the only members of
them there indubitably belonging to the furmation are the
sandstones and a few shales. The rest of the formation, of more
doubtful character, consists of thick beds of argillaceous blue
clay, and strata of marl and sandstone, slightly impregnated with
calcareous matter.

The thick beds of sandstone of decidedly carboniferous cha-
racter are dark red, white, and yellowish, as usually occurs in
coal-fields, and the same beds or strata may be traced running
through the country for many miles. All the freestone quar-
ries in Berwickshire are worked in these carboniferous strata,
which are sometimes 50 or 80 feet in thickness. These sand-
stones are filled with all the impressions of vegetable remains
usual in coal-fields, and no difference of any sort can be ob-
served between them and the sandstones of the Mid Lothian
deposits.

On some of the beds of shale found on the banks of the Tweed,
not far below Coldstream, impressions of marine shells are
abundant, which seem to be of the genus Modiola.

Mr. Milne here also mentioned that on the north side of the
Tweed, along the sea-coast, these coal-measures are accompanied
not merely by the characteristic limestone, but also by three
seams of workable coal. These coal-seams may be traced along
the coast from Scremerston and Berwick, and are undoubtedly
a continuation of the seams which occur there. But they form
a narrow belt along the coast, and at length disappear under the
German Ocean, at a point where the trap of Lamberton Hill
projects into the sea, and throws up the coal-measures, not only
on their edges, but so as to form an obtuse angle with the hori-
zontal basis of the hill. About thirty years ago these three seams
of coal were worked on several parts of the Berwickshire coast,
and the proprietor has lately again advertized them to be let.

Mr. Milne then came to describe those other deposits of
doubtful character, which some have considered as of more re-
cent origin, and belonging to the new red sandstone series.
Mr. Milne described them as consisting generally of blue clay
beds, and their marl strata, the latter being generally of a
lightish brown, sometimes a yellowish colour. The ordinary

TRANSACTIONS OF THE SECTIONS. 631

dip and deviation of the strata are like those of all the other
strata towards the hills; and though, in particular localities, they
do not lie altogether conformably to the coal-measures, yet, on
the whole, they may be said to be conformable; and in some
places, as will immediately be seen, they are actually overlaid
by the coal-measures. In these beds of soft blue clay numer-
ous strata of sandstone are seen, but not of any great thickness
or running to any extent. They are commonly wedge-shaped,
and thin away to nothing. These imbedded masses of sand-
stone very commonly contain, nay, sometimes are entirely com-
posed of, accumulations of small conglomerate, containing num-
bers of pebbles, vegetable impressions, and even fossil remains,
in curious and interesting confusion. This conglomerate not
unfrequently is highly ferruginous. It was in the latter kind
that Lord Greenock discovered an entire tooth and the remains
of others. This tooth has been described in the Edinburgh
Philosophical Journal. 1t was sent to London, and submitted
to the inspection of Mr. Clift; but Dr. Grant has since more
minutely examined it, and particularly its internal parts, which
were not seen by Mr. Clift, and he is decidedly of opinion that
it is a tooth of the Lophius piscatorius, or sea devil, and further,
- touse his own words, that it “ has been preserved to us precisely
as it fell from the jaw upon the loose sand.”’

Besides these imbedded sandstones there is, in this marl for-
mation, a yellowish calcareous and cellular rock, which has all
the appearance and many of the properties of magnesian lime-
stone. This rock is seen on the banks of the Tweed, princi-
pally near Coldstream: the strata are thin, none of them exceed-
ing a foot in thickness. It is not, however, only on the banks
of the Tweed that this mineral has been found ; it is associated
in a beautifully crystallized state with the Scremerston seam
of coal worked near Berwick, and even in some parts is blended
with the coal so as to render the latter impure, and in a great
measure unfit for sale. This limestone has been analysed, and,
out of 100 parts, found to contain 50 of carbonate of lime, 44
of magnesia, 4 of silica, and 1-2 of peroxide of iron. The spe-
cimen analysed was from Birgham Haugh. In beds of dark
blue clay or shale, immediately in the vicinity of these strata of
magnesian limestone, nodules of iron ore occur, though far less
pure and genuine than generally occurs in the coal-fields.

Another mineral of occasional occurrence in the mar]-forma-
tion is gypsum. There are three kinds, red and white gypsum
in veins intersecting the clay beds of blue marl; and selenite,
which fills up the. cracks and interstices of the marl beds, where
they are exposed to the air.

632 FOURTH REPORT—1834.

The red gypsum occurs in irregular masses, from the size of
‘a walnut to 3 or 4 feet in diameter. The white isin thin veins,
not always, but generally in the same beds with the red gyp-
sum ; and whenever they come in contact, the thin white vein is
invariably cut off and intercepted by nodules of the red, which
thas therefore been the more recently formed. Although gyp-
sum occurs in abundance in this district, no rock-salt in a mi-
neral state has been found: but several springs are known in
it which contain a considerable quantity of salt; for example,
on an analysis of well-water at the Manse of Eccles, out of 87
parts, 57 were found to be sulphate of lime, and 30 of common
salt; and in the mineral water of Dunse Spa (also within the
limits of the marl group), as analysed a number of years ago by
Dr. F. Home, a large proportion of common salt was found.

Vegetable fossils have been found among the marl -beds form-
ing very extensive deposits. At three or four several localities
large trees have been discovered, in beds of blue clay, in a petri-
fied state. The trunks vary in size from a few inches to several
feet in diameter; but none have yet been discovered of any
length: indeed, none exceed 3 or 4 feet, and they have generally
the appearance of having been transported from some distance,
being rounded at the ends. These trees have been converted
into a hard calcareous rock, which does not always assume the
shape and size of the tree:enveloped in it, but is generally a
little larger, and on being broken presents an accumulation of
small twigs and branches of trees, which are found to be of the
same species as the imbedded trunks. These fossils have been
all ascertained to belong to the genus Conifere.

These fossil trees are always covered or skinned over by a
coaly matter, which seems to have been! the original bark, and
which has been occasionally found nearly one inch thick.

The internal parts of those fossils have not been so entirely
displaced by the intrusion of calcareous matter as to have lost
all their woody structure. On the contrary, specimens are con-
stantly met with in which the branch or trunk displays all the
concentric rings formed by the annual growths. The original
resinous matter of the tree has been seen oozing or exuding
from its interior fibres.

Many of the trees have been fiattened, and flattened so en-
tirely as to show that the whole of the interior parts have been,
as it were, squeezed out, whilst the bark above has been pre-
served, of course in a state of coal, and now appearing as thin
seams of lignite in the beds of clay.

Besides these deposits of trees in the beds of clay, there are
numberless impressions of vegetables in the marl-strata very

TRANSACTIONS OF THE SECTIONS. 633

similar to those found in coal-fields. The plants are entirely

_ flattened, some of the impressions being those of small branches,
and of very delicate structure. It is manifest that if these

plants have not actually grown in the places where they are now

. found, they could not have been transported far, from the small.
degree of injury which they appear to have sustained. In some
cases impressions of leaves have been found.

The animal remains found in a fossil state are very few. In
addition to the fish’s tooth already noticed as having been found
in the sandstone conglomerates of Tweed banks, there are a few
shells of a minute character which appear to be the Zeredo, the
Serpula, aud Modiola, and which occur not only in these con-

-glomerates but also in marl-strata, clearly contemporaneous
with it.

As to the position of these marl-strata, in respect to their
dipping under or overlying the coal-measures, Mr. Milne stated
that there are two or three localities where these are distinctly
seen to be covered by the coal-measures. In particular, one
locality on the sea-coast was mentioned where these marl-beds
and the coal-measures are found in contact, and where the
genuine character of these respective strata is placed beyond
all doubt by the occurrence of gypsum in the one and of seams
of coal in the other. A section is there well exposed, showing
the contact of the coal-measures and marl-strata, the latter ma-
nifestly lying beneath the coal-measures.

Mr. Milne alluded to the opinions of several distinguished
geologists, that the marl-rocks which he had just been descri-
bing belonged to an epoch more recent than the mountain lime-
stones or carboniferous group; and there was no doubt that
they have many of the characters of the true marls or new red
sandstone formation. But the nature of the fossils found in it, as
well as the fact of its being seen dipping under the coal-mea-
sures, Mr. Milne stated, had led him to consider the formations
as subordinate to them, and deposited nearly under the same
circumstances. These circumstances were, the prevalence of the
same sea and a similar climate, as proved by the occurrence of
the same marine shells in both kinds of strata. One distinction
between them might be the unconsolidated condition of the
calcareous deposits on the north of the Tweed, as compared
with the compact limestones on the south of the Tweed; and
also the absence of the larger marine shells and corallines from
these marl-beds, and the occurrence in them of deposits: of
trunks of fossil trees and branches, which have not been often
found in the same uncompressedstate in the coal-measures. Whe-
ther or not these data would justify the impression that the sea,

634: FOURTH REPORT—1834.

at the bottom of which these marl-strata were formed, was not of
the same depth as that part of the ocean where the thick beds
of limestone south of the Tweed have been deposited, he did not
venture to say. But Mr. Milne remarked that it was a confir-
mation of this view, that the same fossil trees which are found
in the marl-beds do not occur further south, as they would not
probably be drifted very far from the shores whereon they grew.
Besides, it is well known that currents and eddies at the bottom
of the sea are more frequent along the coast and the mouths of
large rivers than ata distance from land; so that the same
cause might serve to explain the formation of those wedge-
shaped sandstone strata in the thick beds of clay and marl fre-
quent on the banks of the Tweed, as well as the gravelly conglo-
merates, where are seen mixed up together not only fragments
of various rocks, but vegetables, small’shells, and fishes’ teeth.

Another deposit derived from the marl strata just described
consists of lacustrine deposits of shell-marl. There are several
of these worked on account of the calcareous matter which they
afford, to be spread over the land for agricultural purposes. On
the estate of Kimmergham near Dunse, (the property of James
Bonar, Esq.,) there is a mass of this nature about seven acres
in extent. There is at the surface a covering of peat, which,
in some places, is ten feet deep. Below this there are two beds
of white calcareous marl filled with minute shells, the beds
being separated by a stratum of blue clay. Each of the beds of
marl is about six feet in thickness. The shells found in them seem
to be of exactly the same genera as those found by Mr. Lyell
in the lacustrine deposits of Forfarshire, the Planorbis, Iyjm-
nea, &c. In addition to these shells, remains of the beaver,
and of a large species of deer, were some years ago discovered
in this bog. The remains of the beaver, it is believed, are now
in the museum. A specimen of the horns found in the moss
was exhibited, together with portions of the marl, containing
multitudes of minute shells.

In the parish of Merton, where a shell-marl moss of 100 acres
occurs, horns of the same species of deer were found, as well as
the remains of beavers. These horns were pronounced by Sir
Humphry Davy to belong to an extinct species.

IV. The only remaining formation in the district is the trap,
which in Berwickshire, as in most other districts, may be di-
vided into three kinds, according to the epochs at which it was
successively ejected.

1. The older trap occurs, as has been already mentioned, not
only in large amorphous masses among the grauwacké strata,
but also occasionally alternating with these rocks, and assuming

Fey

TRANSACTIONS OF THE SECTIONS. 635

their regular stratified appearance. An example of the strati+
fied trap may be seen at Fassney Water, (a locality described
by Professor Playfair,) and on the north face of Soutra, about
200 yards east from the London road. In these places it has
all the appearance of sienite, both from its hardness and the
intermixture of red felspar and hornblende. It is hardly neces-
sary to add that these sienitic and other trap strata, which ap-
pear in this stratified form, have acquired that condition from
the grauwacké strata, between which they have been pushed up
in a manner similar to what occurs in Salisbury Crags ; and the
like effect as is there seen has been produced upon the grau-
wacké rocks, which are greatly hardened, and even made to as-
sume so crystalline an appearance as to render it difficult to find
the exact line of division.

2. The trap of St. Abb’s Head belongs to a more recent pe-
riod. It may be traced, except for a very short interval, occu-
pied by grauwacké, southwards along the coast, to a point where
it is found enveloping the conglomerate of the old red sand2
stone. On this part of the coast the conglomerate may be seen
in vertical beds, and at another point, viz. at Eyemouth Har-
bour, in immense horizontal masses, resting on the trap, and
dipping, at a small angle, into the sea. Here copper is found
in the trap in great abundance, not in the form of veins, but
in small nodules, which, by oxidizing on exposure to the air,
give a curious appearance to the surface of the rock, which is
in consequence speckled over with green patches.

-To the same epoch may be referred the eruption of most of
the trap-hills of Berwickshire; those at least which have pros
truded through the old red sandstones, some of which, as, for
example, the Eildon Hills, are about 1300 feet above the level
of the sea.

There are trap-dykes which traverse the red clay beds and
sandstones of this formation, some of which run from Home
Castle, and in which numerous red crystals occur. Some of
these crystals are of that red colour and jasper appearance as
to lead to the opinion that the trap had occasionally taken up
some particles of the adjacent red strata and jaspidified them.
These dykes abound also with large crystals of glassy green
felspar. ;

This old red sandstone trap is of various textures, from the
crystalline basalt to the friable and almost vesicular tufa which
is seen on the outskirts of the trap-hills. It sometimes also
occurs as a soft breccia or conglomerate, the imbedded portions
being manifestly derived from the rocks or soil among which it
had flowed. In one locality the conglomerate consists of very

636 FOURTH REPORT—1834.

small pebbles or gravel, which are agglutinated together by a
tufaceous paste or mud, having exactly the appearance of a
stream of hardened lava. This occurs in the middle of the
old red sandstone formation, on the banks of the Whitadder,
north-west of Dunse.

3. There are a few examples of trap ejected after the deposi-
tion of the coal-measures, which in consequence are greatly
disturbed in its neighbourhood. The whole of Lamberton Hill -
(near the sea: coast) is an example of this, the coal-measures
which run along its base for about four miles on the shore being
now seen not only vertical, but even inverted to a considerable
extent. The trap here has risen up, and is so extensive as to
have upraised not merely the coal-measures on the one side,
but the grauwacké on the other, and completely obliterated the
old red sandstone group at this point, the only trace of it left
being a patch of conglomerate on the top of the hill.

A few miles to the south of Berwick there is another mass
of trap, which forms the Kyloe hills, and from which a dyke
runs fifteen miles in a straight line towards Home Castle rock.
In the Tweed below Coldstream it thins out to nothing. The
dyke is a light-coloured greenstone. It varies in width, though
generally speaking it is broader near the Kyloe hills than at
its further extremity.

The usual effects of trap in hardening the strata with which
it is in contact, are observable in this dyke and in those previ-
ously described.

In some places there has been a slight overflow of the trap-
dyke into the softer strata in contact with it, as, for example,
the shales and coal, which could less easily resist the lateral
pressure of the confined current.

There do not, however, appear, at any of the localities where
the dyke and the sedimentary rocks are seen in contact, to have
been any other changes effected on them. They are in no case
turned up on their edges, or altered in their general bearings.
But the case is widely different with the trap-Aills, all of which
have, wherever they are in contact with the trap, upraised the
adjoining rocks. This difference between the effect of trap-hills
and the effect of dykes may be explained by supposing that
they were merely currents of trap, which flowed into fractures
or rents previously existing across the country, caused, per-
haps, by the elevation of particular points by masses of trap
which have been pressed up from below. Such a rent was very
likely to be produced by the elevation of the Kyloe hills, and
the direction it took would naturally be towards some other
point where a similar disturbing and rending force existed.

TRANSACTIONS OF THE SECTIONS. 637

Kyloe dyke was traced by Mr. Milne for about fifteen miles in a
direct line, towards the trap-hills of Home Castle. May not the
consideration just stated account for the direction of this dyke ?

_ Another circumstance was noticed by Mr. Milne as a pro-
bable effect of the trap upon the incumbent strata, viz., the oc-
currence of indurated clay-beds, and even of chert, in the im-
mediate vicinity of it. At Carham there are thick beds of a
coarse gritty limestone, which contain abundance of quartz, of
a dusky brown and red colour. These beds of limestone are
themselves of a whitish cream colour ; and much indurated clay,
of the same colour, occasionally a little tinged with green or
red, accompanies them. ‘These strata rest upon a porphyry,
which is in some places amygdaloidal, containing small grains
of quartz tinged with green earth. ~

Near Dunse the same chert is again seen, but in strata of cal-
careous sandstone, which are of about the same thickness as
the limestone beds at Carham. They are here also immediately
incumbent on trap. At Newton Dony, at Marchmont, at Pres-
ton, and at Berwick the same indurated marls have been found,
which are sometimes so compact as to have been mistaken and
burned for limestone; but which proved to be only marls har-
dened by their contact with, or vicinity to trap.

The only other subject to which Mr. Milne adverted was the
changes which appear to have been produced on the surface
of the district, and on its elevation above the level of the sea,
at successive periods.

Mr. Milne described at least four apparent elevations of the
land at successive periods: Ist, The elevation by which the
grauwacké strata were upraised ; 2ndly, The elevation by which
the old red sandstones were made to emerge from the waters
wherein they were deposited; 3dly, The elevation which con-
verted the marine strata of the coal-measures, or mountain
limestone of Northumberland, into dry land ; and, 4thly, a still
more recent elevation, the precise epoch of which has not yet
been exactly determined. ;

It may, perhaps, throw light on the causes of these succes-
sive elevations to remember, that at the time when these for-
mations were respectively disturbed and elevated, trap-rocks
appear to have risen up, which at each successive outburst
most probably acted, not merely upon the particular group of
rocks among which they now protrude, but on the whole
district of country including the grauwacké range. These out-
bursts of ancient lava would most probably, like the cones on
the sides of a volcanic mountain, take place laterally, where the
resistance would be less than directly among and through the

638 FOURTH REPORT—1834.

grauwacké hills; and thus it is that after the ejection of the
old red sandstone trap, along the sides and base of the grau-
wacké range, the more recent eruptions are more distant from
the hills, and among the more modern deposits of coal-mea-
sures. But still, these succesive upheavings of trap, though
they have found an outlet among the softer rocks, may have
increased the elevation of the grauwacké at different periods,
without there being on these occasions any visible eruption
of trap among these hills. It is perhaps a confirmation of this
remark, that the old red sandstone conglomerate, which was of
course originally at the same general level along the base of
the grauwacké range, is now 800 and 900 feet higher in the
western parts of it, than at the sea-coast, and the rise is most
remarkably uniform and regular on proceeding inland from the
coast. At the sea-shore, as already stated, the conglomerate is
lifted upon the top of the trap, and dipping into the sea. About
two miles inland (at Foulden) it is about 150 feet above the sea;—
at old Melrose, in the valley of the Tweed, it is 300 feet above
the sea ;—at Greenlaw, nearer the hills, it is 480 feet ;—at Dod’s
Mill, near Spottiswoode, 500 feet above the sea ;—at Norton, in
Lauderdale, 540 feet ;—at Carfrae Mill, still nearer the central
range, 640 feet ;—and at the foot of Soutra Hill, on both sides of
the ridge, (which is probably about 28 miles from the sea,) be-
tween 820 and 890 feet above its level.

Since, however, the elevation of the country at these succes-
sive periods, corresponding to the three kinds of trap now visi-
ble in the district, there seems to have been a fourth, though it
is admitted that this fact is more problematical, and is sup-
ported by indications of a less decisive character. The vertical
coal-measures at the foot of Lamberton Hill, along the sea-coast,
have seen described. Immediately south of Burnmouth there
is a tract of table-land, now about 100 feet above the level of
the sea, which extends between the beach and the base of the
hill. It is in shape a triangle, the base of which runs along
the foot of Lamberton Hill for about 13 mile, and the two sides
form the present sea-cliffs for about 3} miles in extent. This
table-land consists of thevertical strata, which run parallel with
the base, and are seen at the two sides of the triangle, at the sea-
shore, running right across the table-land. It is not a little cu-
rious that these vertical strata should all have had their edges
worn down to a horizontal and level plain, just as would have
been the case if the rocks had been exposed to the action of
marine currents incessantly sweeping over their edges. When
the tide is far out, exactly the same appearance is presented
by the vertical rocks, which form the bottom of the shore,

es

TRANSACTIONS OF THE SECTIONS. 639

for a considerable distance out from the existing cliffs; and
were there to be an elevation of the coast, we should have
another table-land, formed of vertical strata, with their edges
worn down to a nearly horizontal level, like the table-land,
at present about 100 feet above the level of the sea.

Perhaps, connected with this very recent elevation of the
coast, may be some extensive rents and fissures in the land vi-
sible near St. Abb’s Head, and particularly on the north side of
it about Dunglass.

One of the most perceptible of these fissures runs for about
13 mile from the Siccar Point past the ruins of a church called
St. Helen’s, and towards the valley of the Pease bridge, where
the rent is nearly 150 feet deep. In the part of its course first
described, the valley is perfectly dry, and there are no symptoms
of any rivulet having ever run init. The strata of grauwacké
are here and there nearly vertical, and form a smooth unbroken
wall for several hundred yards, on both sides of the valley,
which has been formed by the sundering, or separating, or slip-
ping of the strata from off each other.

Similar rents are seen at Cockburnspath and at St. Abb’s
Head, some of which are about 180 feet deep, and have small
rivulets running at the bottom of them (which are too insigni-
ficant to have cut through these hard strata to such a depth);
but some of them are so shaped that they never could have had
rivulets running in them at all.

This district bears upon its front the well-marked symptoms
of diluvial action. Large boulders of mica-slate, and every va-
riety of trap are found buried in the alluvial strata on the
banks of the Tweed, as well as at the foot of the hills ; and the
hills are most generally devoid of vegetation, and bared to the
rock upon their south-western flanks. This is particularly the
case with Home Castle rock, Cowdenknowes, Stitchel, Bemer-
side, and others of less note.

A good deal of red soil is found scattered over localities, and
even among the grauwacké hills, where alone it could have
been brought and deposited by a flood, which swept the red
sandstones of Roxburghshire, and, as it were, painted the south
front of the Lammermuirs with a vermilion edge, to mark the
force and direction of its waters.

On the Coal-fields of Scotland. By Major-General Lord
Greenock, F.R.S.E. F.G.S.

[ With a Plate.]

_ It is more than forty years since Dr. Ure published his
History of the Parishes of Rutherglen and Kilbride, in which

640 FOURTH REPORT—1834.

he noticed the discovery of organic remains either of some
species of large fishes or of Saurian reptiles in the coal-fields of
the West of Scotland: since that period new facts of a similar
nature have been brought to light in the coal-districts of Clack-
mannanshire, Fifeshire, and the Lothians, as well as near Glas-
gow, showing that these remains are not confined to particular
localities, but that they are very generally distributed through-
out the whole extent of the coal-formation in the great valley of
the Scottish lowlands.

The specimens that accompany this paper were found in the
bituminous shale or blaes which lies immediately above, and in
contact with, what is called the Jewel coal, in Sir John Hope’s
coal-works at Stoney Hillnear Musselburgh. These organic re-
mains appear to abound in all the pits where the flat seams are
worked in the Mid Lothian coal-field ; they have also been ob-
served in the edge seams, at the Edmonstone Colliery, in the
same coal-field, and at Dguart in Fifeshire.

The Jewel coal is the lowest of what are usually termed the flat
seams, and that of Edmonstone the highest of the edge seams ;
but whether these remains may be most abundant in that part
of the series, or whether they are equally distributed through
the whole, is a question that must be determined by further in-
vestigation. The observations which the author has hitherto had
opportunities of making lead him at present to believe that this
will be found to become more rare, if they do not entirely dis-
appear, as they descend in the series, and approach the lime-
stone containing marine shells and Encrinites, although their
reappearance in such vast abundance in an inferior portion at
Burdie House is a circumstance not easily to be accounted for.

It may be necessary here to explain that the flat seams are
merely the upper beds, five in number, which, being nearer to
the surface, are comparatively more level than the edge seams,
or those which, occupying an inferior position in the series, dip
down to a greater depth in the basin, and are consequently seen,
at the places where they are worked, to stand at a much higher
angle; but it has now been ascertained that the flat seams,
where they have been met with in this coal-field, are in every
respect conformable to the edge seams.

The flat seams contain the most valuable coals in the district ;
but they occur only partially in the Mid Lothian coal-field, as
they are not to be found to the southward and westward of
the road from Edinburgh to Dalkeith, having, it is said, been
thrown off by a dyke near Sherriff Hall, beyond which some of
the edge seams appear to have been brought up and flattened.
These are worked as flat coals at the Dalhauria, Polton, and
Eldon collieries.

TRANSACTIONS OF THE SECTIONS. 641

Mr. Bald, in giving a Section of the edge seams, estimates the
total depth of the coal strata in the basin to be at least 500 fa-
thoms, and that the aggregate amount of the thickness of the
whole of the seams. of coal, twenty-six in number, is 109 feet
6 inches.

- Although the Firth of Forth is generally considered to be the
northern termination of the Edinburgh coal-fields, there appear
to be sufficient reasons to warrant the supposition that the coal-
district on the opposite coast of Fifeshire was originally a part
of the same deposit. That the coal strata do extend across the
water is evidently shown both by the circumstance of their be-
ing worked near Wemyss Castle, 300 yards beneath the bed of
the river, and their outcrop being seen on both sides of the
Forth beyond the low-water mark, as well as at Inchkeith,
which is situated in the middle of the channel ; at the same time
it must be confessed, that with the knowledge we possess re-
specting them it would be very difficult to prove their exact
correspondence, either by their lines of bearing or by the qua-
lity of the coals: but when all the disturbances by which they.
are known to have been affected on both sides of the Forth are
taken into consideration, it will not appear improbable that the
same Causes may have operated, even in a still greater degree,
to produce similar derangements and dislocations in those parts
that are now concealed beneath the water, which might suffi-
ciently account for any alteration that may be observed in their
appearance when they emerge from it on either shore.
The upburst of the trap hills that surround Edinburgh,
which, from the occurrence of glance coal, and other appearances
observable in them, we may with’ great probability suppose to
have taken place after the deposition and consolidation of the
coal series, may very possibly have obliterated many beds of
coal’ that might have previously existed where they now
stand, and have variously affected all the others within reach of
their influence. i
- On the other side of the water we see, by the plan accom-
panying Mr. Landale’s reports on that district, that the coal
strata meet with so much interruption from trap dykes, that’
instead of proceeding to any distance on their regular lines of:
bearing, the greater part of them have been deflected to the
eastward, and take directions nearly parallel to the line of the
coast.
- It appears also from the same authority that the number of
coal beds, and the total thickness of the coal’in them, in the’
Fife district, is very nearly the same as in the Edinburgh coal’
ee according to the accounts given of it by Mr. Eald, viz. <
34. 27

642 ' FOURTH REPORT—1834.

Fifeshire District. Edinburgh District.
29 beds of coal. 26 beds.
119 feet 6 inches. 109 feet.

The two seams of coal, the workings of which have lately been _
resumed on the estate of Captain Boswell at Wardie, have ap- -
parently been thrown out of their natural position by some dis-
turbance: they rise from the beach near that place in a saddle
form, having on the east side an inclination of one in seven, and
dipping to the west at an angle of one in fourteen. The coal is
said to be of caking quality, which is rarely met with in these
coal-fields: one of the Dunnshire seams, marked No. 25. in
Mr. Landale’s plan, appears to be the only coal of this description
in the Fifeshire district. It is a smith’s coal, and of the same
thickness as the upper bed at Wardie ; but it would not be easy
to trace any other connexion between them, although the coal
of Wardie evidently extends across the firth to the opposite
coast.

The nodules of ironstone, of which there is a great abundance
in the bituminous shale of Wardie, are very remarkable ; for
scarcely one is to be found that does not contain an organic
nucleus, either a coprolite or some portion of a fossil fish. Si-
milar nodules, containing the same remains, have been also ob-
served on the opposite shore and at Inchkeith.

_ The specimens of coprolites and fossil fishes which were ex-
hibited by Mr. Trevelyan at the Cambridge Meeting, were from
this locality, and additional specimens were now produced.

On the Ossiferous Beds contained in the Basins of the Forth,
the Clyde, and the Tay. By Dr. Hinserr.

The author pointed out, in a general manner, the order of sue-
cession observed by the beds which were deposited later than the
primary and transition schists. These were the peculiar grey mi-
caceous sandstone, principally to be found on the north of the
Tay, known by the name of the Arbroath pavement ; the red
sandstone, into which the Arbroath pavement passes; and the
stupendous masses of conglomerate materials, formed by rolled
fragments of primary and transition rocks, which repose at the
foot of the Grampians. It was incidently stated that, near
Cratown, the conglomerate strata were traversed by a trap rock,
containing large crystals of glassy felspar, which gave to it the
exact character of one of the modern trachytes of the Sieben-
gebirge. The conglomerate rocks were supposed to haye been
formed at two distinct epochs. The author expressed a sus-

TRANSACTIONS OF THE SECTIONS. 643

picion that certain patches of sandstone, occurring both on the
east and west coast of Scotland, might be considered as new red
sandstone.

That the grauwacké schist and its associate beds of limestone
contain organic remains, has not yet been shown. The author
exhibited a specimen of the Arbroath pavement containing ve-
getables, and he stated that Mr. Lindsay Carnegie of Kimbleth-
mont in Angus had presented to the College Museum some
striking specimens of remains inclosed in the Arbroath pave-
ment, one of which appeared to belong to a crustaceous animal.

But it was shown that organic remains had been most abun-
dantly found in the carboniferous group, characteristic of the
basins of the Forth and the Clyde, which the author had pre-
viously described at the meetings of the Royal Society of Edin-
burgh. Certain limestones for instance, namely those of Bur-
diehouse, East Calder, Burntisland, &c., which he conceived to
be of freshwater origin, and belonging to the lower members
of the carboniferous group, severally contain both vegetable and
animal remains.

The limestone of Kirkton, near Bathgate, is remarkable for
its mammillated and ribboned structure; which last peculiarity
is produced by thin layers of pure flinty matter alternating
with other distinct layers, which are severally calcareous, ar-
gillacous, or bituminous, This rock has a striking resemblance
to the tertiary limestones of Auvergne, which exhibit a similar
character where they come in contact with volcanic eruptions ;
and hence, as the limestone of Kirkton alternates with tufa,
and is in the immediate neighbourhood of trap-rocks, it pro-
bably owes its peculiar geological character to similar circum-
stances. ‘This limestone contains numerous plants, as well as
the remains of a most remarkable crustaceous animal, a nearly
complete specimen of which the author was enabled to exhibit
to the Meeting, through the kindness of Dr. Simpson of Bath-
gate, into whose possession the relic had fallen. The author
remarked, that a larger head of the same animal had been de-
scribed by Dr. Scholer; but as this naturalist had unfor-
tunately not seen the extremity of the animal, the description
was of necessity imperfect *.

* Incidental to this notice, Mr. Smith of Jordan-hill, near Glasgow, exhibited
to the Society the more perfect head of the animal described by Dr. Scholer.
And Mr. Jameson Torrie placed in Dr. Hibbert’s hands a memoir just published
by Dr. Harlan of America, in which fossil remains are figured of a similar
character, but of the diminutive size of five inches only. The generic name of
Lurypterus has been given to the American specimen. Dr. Hibbert announced
that drawings, accompanied by a description of this singular animal, would be
shortly published.

272

644 FOURTH REPORT—1834.

_ The limestone quarry of Burdiehouse was very briefly de-
scribed, as many details regarding it have already been published
by the author. This limestone is a very deep-seated bed in the
carboniferous series. Above it are alternating beds of sand-
stone, shale, and thin seams of coal. A limestone contain-
ing marine shells and corallines follows, while the whole is
surmounted by the coal-measures of Loanhead. The Burdie-
house limestone incloses a variety of plants, minute Hntomo-
straca (among which there appears to be a Cypris), various un-
described fish, the bones of gigantic animals, large scales, and
coprolites. Among the bones are pointed teeth of the extraor-
dinary length of three inches and three quarters, and of the width
of one inch anda half at their base, which resemble those of
Saurian reptiles. These teeth are adorned with a most beau-
tiful brown enamel, as well as the large scales which are so
plentifully found in the quarry. There were also exhibited some
bony rays of the extraordinary length of fifteen inches, which
must have belonged to an immense fish.

The author announced that all the relics of fish hitherto dis-
covered at Burdiehouse would be submitted to the inspection
of M. Agassiz, who, in the invaluable work on fossil ichthyology
which he was publishing, promised to fill up, with the success of
a Cuvier, this great blank in natural history *.

On the Geological Structure of the Orkney Islands. By
SCS. Tratui, .D.

The geological character of these islands is very simple ; the
whole group, with the exception of a small granitic district near
Stromness, consisting of rocks belonging to the old red sand-
stone formation. The prevailing rock is a species of sandstone
flag, much charged with argillaceous matter. It occurs in di-
stinct strata, usually slightly inclined, which form hills of but
small elevation, but often present very magnificent cliffs around
the coasts. It has a colour varying from pale greenish to
blackish grey. It has a slaty structure, and readily splits into
layers, the thickest of which form a very durable building-stone,
as the remains of very ancient Scandinavian edificies attest ;
while the thinnest form excellent flags, or even a tolerable roof-
ing-slate. It is in this slaty rock that the fossil fishes are found.
It occasionally contains bitumen, so as in a few places, espe-
cially in the islet of Rushholm, to approach to bituminous
shale.

* Dr. Hibbert likewise displayed the teeth and other relics of a large fish,
which he had recently discovered in the black limestone of Ashford,*in Derby-
shire. : :

TRANSACTIONS OF THE SECTIONS. 645

Connected with the sandstone flag we find thick beds of com-
mon sandstone, of a yellowish or tile-red colour. It forms the
chief part of the mountains of Hoy, the highest point in Ork-
ney; and also several headlands in Pomona and in Edey. In
the vicinity of the red sandstone we occasionally find the strati-
fied flag assuming a higher inclination.

Last year Dr. Traill discovered a thicker bed of basalt in the
sandstone of Hoy; and there are many veins of basalt and
greenstone traversing the slaty rocks, particularly in Shapin-
shey, and in that part of Pomona where the fossil fishes are
found. It may not be unworthy of notice, that the general di-
rection of these last trap veins is towards that part of Hoy in
which the bed of basalt occurs.

Granite exists in Orkney only in one district. It constitutes
a chain of moderate hills, running from the southern boundary
of the township of Yesnaby, in a south-east direction, to Strom-
ness; occupying a length of about six miles, with a breadth
varying from one to half a mile. The granite again appears on
the north side of the small island of Gremsey; but the slaty
rock is interposed between it and the mountains of Hoy. This
granite is close-grained, contains much felspar, and often ap-
proaches to gneiss in structure.

The granite is everywhere in immediate contact with a coarse
conglomerate, consisting of nodules of quartz, and fragments of
granite and sandstone, imbedded in an arenaceous base. The
junction of these rocks is well seen at the western end of
Gremsey, on the shore at Stromness, and in the burn of Cairs-
ton. The conglomerate is of small extent, almost immediately
passing into sandstone flag. Both the granite and the conglo-
merate bear a striking resemblance to the prevailing rocks on
the eastern side of Sutherland and the south of Caithness ;
and the sandstone flag of Orkney is so exactly similar to the
slaty rock of the latter county, which also contains fossil fishes,
that it is impossible to resist the conclusion, that these rocks
belong to the same geological epoch. The researches of Messrs.
Sedgwick and Murchison have proved that the Caithness flag
is a member of the old red sandstone; repeated observations,
and an examination of most of the Orkney Islands, have con-
vinced Dr. Traill that the sandstone and sandstone flag of that
group ought to be referred to the same formation. In no part
of these islands did he discover any traces of a coal formation,
unless, with some geologists, we are to consider the slaty rock
charged with bitumen as the lowest bed of that deposit; for
certainly no vestige of its other more important members exists
in Orkney.

646 FOURTH REPORT—1834.

Fossil Fishes.—Dr. Traill exhibited many specimens of the
fossil fishes discovered in the slaty flag of Orkney. They are
reported to occur in several parts of that group of islands ; but
Dr. Traill only saw them near Smaill in Pomona, about two
miles from the northern extremity of the granitic chain. They
occur in a quarry about 100 feet above the level of the sea. The
quarry is covered by 3 feet of soil and debris; then we find
from 9 to 11 feet of solid strata of flag: but no fish appear
until we reach the two lowest beds, which are together about
2 feet in thickness. The uppermost chiefly contains fishes, of ©
a flattened form, with a granular skin: which appear to be-
long to the family Raja. One of these measured 15 inches in
length, of which the tail was 6, and the greatest breadth of the
body 6 inches. Unfortunately the specimens of these, which
Dr. Traill had collected, never reached Edinburgh. The lowest
bed of the quarry abounds most with fishes, and from it almost
all the specimens exhibited were extracted. These fishes, in a
high state of preservation, were carefully examined by the distin-
guished naturalist M. Agassiz, who detected among them eight
distinct species, five of which were quite new to him, and even
belonged to three new genera. M. Agassiz considers the spe-
cies of the fish to indicate that the rock in which they occur is of
an era prior to the coal formation. The only trace of vegetable
remains observed in that quarry was a single leaf of some mono-
cotyledonous plant, resembling that of a reed or a Canna. Be-
low the fish slate a shining rock occurs, which contains no or-
ganic remains.

Professor JAMESON exhibited a fossil fish, the Cephalaspis of
Agassiz, which he had found in the old red sandstone (Forfar-
shire) several years ago, long after he had determined that the
sandstone of Caithness, Orkney, Shetland, and of the whole
tracts of country on the east and west of Scotland were of the
same geognostical age.—Mr. Bhack appER exhibited a fossil fish
from Glammis millstone quarry in the same district.

On the Fossil Fishes of Scotland. By M. Acassiz.

The high geological antiquity of the greater part of the stra-
tified mountains of Scotland gives a peculiar interest to the in-
vestigation of their organic remains; as they lead us to the
knowledge of the condition of our planet at a period in regard
to which we possess only a few insulated fragments of informa-
tion. The mollusca, zoophytes, &c. of these formations have
been examined by many, but the remains of vertebrate animals

TRANSACTIONS OF THE SECTIONS. 647

have been but little investigated ; and of fishes, we are acquainted
with those only which have been described and figured by
Messrs. Sedgwick and Murchison, and which have also been
noticed by Cuvier and Pentland. The occurrence of a large
number of these was known, but no particular information as to
their nature was communicated. For a long period M. Agassiz
has been anxious to have an opportunity of examining these in-
teresting fossils, and this has been afforded him by the meet-
ing of the British Association at Edinburgh.

The collections which have afforded him the most important
materials are the following : That of the Royal Society, which,
through the unwearied exertions of the Secretary, Mr. Robinson,
contains many remarkable remains from Burdiehouse; Dr.
Traill’s collection, containing many interesting fishes from Ork-
ney; Lord Greenock’s extensive series of ichthyolites from the
coal formation, and especially from Newhaven. In Professor
Jameson’s possession is a large head of a fish from the old red
sandstone of Forfarshire, of which Messrs. Murchison and Sedg~
wick have shown M. Agassiz a less perfect specimen, but one
which exhibits the other parts of the body. Mr. Torrie sub-
mitted to his examination an extensive collection of fossil fishes
from Caithness, similar to those described by Messrs. Sedgwick
and Murchison; and also some fishes from Gamrie, first noticed
by Mr. Murchison, who also described their geological position.

Of the fossil fishes not from Scotland which he has seen on
the present occasion, he will take another opportunity to speak.

As to the determination of the Scottish fishes he remarks
generally, that they all belong to two orders of the class, viz.
some to the order of Placoidian Fishes, Agass. (Cartilaginee,
Cuv.) ; but the larger number to the division Ganoidian Fishes,
Agass., and two to the section Heterocerci, in which the upper
lobe in the caudal fin is longer than the lower.

In the old red sandstone there are two species from Glammis,
Forfarshire, viz. one species of the genus Cephalaspis (Gano-
idian), which has hitherto been found in this formation only.
The most remarkable characters of this genus are the shield-
like covering of the head, which is prolonged backwards in the
form of two horns as in the Trilobites, and the manner in which
the eyes are placed near each other on the head. The other
species belongs probably to the genus Hybodus (Placoidian), but
of this only an ichthyodorulite has been seen.

The fishes from Caithness and Orkney approach one another
most nearly ; though amongst the latter there are several new
genera, and in all eight species. Those from Caithness seem to

648 FOURTH REPORT—1834.

belong to two species only. Amongst the Orkney fishes there
are two very remarkable genera, resembling the 4canthodes of
the coal formation, also having very small scales; but the new
Cheiracanthus is furnished with a spine in the pectoral fin only,
and the other, the Cheirolepis, instead of having the spine, is
provided with a row of small scales. M. Agassiz has been con-
vinced by the examination of many specimens that the genus
Dipterus has two dorsal fins and two anal fins, which sometimes
are opposite one another and sometimes alternate ; and these
are types of two genera, the Diplopterus and the Pleiopterus.

The fishes from Burdiehouse are also very numerous ; in their
characters they agree with those of the coal formation, but are
more removed from those of Saarbriick than are the remains
found at Newhaven.

The most remarkable amongst them is an animal which, from
the structure of its teeth, might be considered as a reptile, and
which must have been of very considerable dimensions ; but
which, from its skeleton and its scales, is decidedly a fish. This
animal forms a new genus under the name Megalichthys, and
confirms the opinion formerly expressed, that we observe in
older deposits organic remains which, with the usual characters
of their family, unite the characters of the types which have
made their appearance at a more recent period. Unfortunately,
no perfect specimen of the Megalichthys has been found, and
it has not been possible to bring together all the different parts
of the skeleton. Another new genus, related to the Amblypte-
yus, has a long dorsal fin extending beyond the ventral fin and
the anal fin, and may be named the Ewronotus. The other
species belong to the genera Pygopterus and Amblypterus.
Very large ichthyodorulites occur not unfrequently, and seem to
belong to the genus Hyhodus.*

At Newhaven eight species occur, of which some bear a con-
siderable resemblance to the fossil fishes of Saarbruck, though
still distinguished from them by some characters. They belong
to the genera Pygopterus, Amblypterus, and Paleoniscus ; and
there is one species which will in all probability form a new
genus, as it differs considerably from the genus <Acrolepis.
Placoidian fishes are also found, but only in fragments, so that
their specific characters have not been determined; and there

* M. Agassiz was led by the specimens which he subsequently examined at
Leeds, to consider the larger relics of Burdichouse as belonging to two large
animals instead of one. ‘he large scales and the long bones are referred by
him to Plammolipis, while the large teeth and round scales are supposed to be-
long to the animal he has named Megalichthys Hibberti.

TRANSACTIONS OF THE SECTIONS. 649

are two other species, of which small traces only have been ob-
tained.

In the coal formation of Fifeshire a new specimen of Palec-
niscus has been found.

M. Agassiz remarks that it may appear strange that he should
consider the Gamrie fossil fishes as belonging to the coal for-
mation, but they seem to be so nearly related to that deposit
that he cannot regard them as of much more recent origin. There
are three species, namely, one Cheiracanthus, one Paleoniscus,
and a third, of which perfect specimens have not yet been obtained.

From this short notice it must be evident how important the
study of the fossil fishes of Scotland is for advancing our know-
ledge of the beings which existed before the oolitic period,
and how much we may yet expect from future careful investi-
gations.

On the Geology of the Pentland Hills. By C. Mactaren.

These hills are about fifteen miles in length and from three to
six in breadth. The fundamental rock is transition slate, accom-
panied by grauwacké in vertical strata, which are covered un-
conformably by conglomerate and various felspar and claystone
porphyries, in beds dipping to the south-east, at angles varying
from 10° to 35°. Beds of conglomerate, alternating with grau-
wacké, abound in the western part; in the eastern, the grau-
wacké is accompanied chiefly by felspar, claystone porphyries,
and amygdaloids. A vast mass of sandstone forms the termi-
nation of the chain on the west, and rises to the height of nearly
1800 feet in the two Cairn Hills. The age of the hills, or the
period of their elevation, is indicated by the position of the secon-
dary rocks on their flanks. The sandstone of the Cairn Hills in-
clines against the transition rocks, at a considerable angle, on the
north side, and at Craigintarrie appears in beds almost vertical.
On the south side the older strata of the coal formation are found
at various places, in a position highly inclined or vertical, while
a newer portion of the same series is found in horizontal beds,
or dipping in towards the hills at a low angle, and in juxta-
position with the former. It follows that the elevation of the
transition rocks took place at a period subsequent to the depo-
sition of the older, but previous to the deposition of the newer,
part of the coal formation.

650 FOURTH REPORT—1834.

Account of the central Portion of the great Mountain Range
of the South of Scotland, in which arise the Sources of the
Tweed. By W. Maccituivray.

The mountains forming the most elevated part of this range are
situated in the parishes of Tweedsmuir, Megget, and Mannor,
which form the southern and south-eastern parts of the inland
county of Peebles, and are continuous with the high land form-
ing the celebrated pastoral districts of Yarrow and Ettrick in
Selkirkshire, and with the higher parts of the parish of Moffat in
Dumfries. The region is composed of uniform, smooth, round-
ed hills of grauwacké, scarcely ever precipitous or even abrupt,
clothed to the summits with Juncee, Cyperacee, grasses, heath,
and pasture plants, and separated into groups or ridges by long,
narrow, straight valleys, which, although generally green, sel-
dom present any natural wood, even along the clear streams that
flow into the valley of the Tweed. Whitecoon, Hartfell, and
other mountains, were described, and the alpine plants observed
on them enumerated, with the view of contrasting this region
with the Grampian range. An account was also given of the
vegetation of the clenchs or ravines. The Tweed was then fol-
lowed from its sources to Peebles, and finally to the mouths
of the Gala and Ettrick, in the whole of which space the rocks
are composed of grauwacké, grauwacké-slate, clay-slate, slate-
clay, and occasional small beds of limestone, none of which,
however, are wrought. The districts of Yarrow and Ettrick,
which are of precisely similar geological structure, were then
described, with reference to their scenery, vegetation, and ani-
mal productions.

Perhaps few districts in Scotland, of equal extent, present less
varied geological phenomena than that which contains the
sources of the Tweed. The general direction of the strata is
from south-west to north-east; they are usually highly inclined,
but present every degree of inclination: the general dip is to
the north-west. The composition of the grauwacké exhibits
considerable variety.

In form, the hills approximate in a considerable degree to
many of the granite masses of Aberdeenshire, but they never
present the precipices and corries, which characterize the more
elevated of the latter. The whole district, with its rounded,
smooth, sloped mountains, connected in elongated heaps, its
long, narrow, straight, or slightly tortuous valleys, its argilla-
ceous and pebbly soil, its clear and rapid streams, and its grassy
vegetation, with the absence of natural and the scarceness of

TRANSACTIONS OF THE SECTIONS. 651

planted wood, forms a strong contrast with the mountainous
districts of the middle and northern divisions of Scotland, in
which peaked and serrated and ridgy mountains, with precipices
and corries, rugged and winding valleys, slopes covered with
debris, and patched with heath and bracken, brown or limpid
streams fringed with birch and alder, rivers and lakes with ca-
taracts and islands, dark forests of pines and thickets of briars,
still give interest to the ancient land of the Gael.

The object of this paper was principally to show the pro-
priety of taking the geology, botany, and zoology of a district
in connexion with each other.

Notice of the Limestone of Closeburn, in reply to a Query of
the Geological Committee. By C.G.S. MENTEATH.

The limestone quarry at Closeburn is situated in a small valley,
surrounded by hills of transition rocks and under thick beds of
the old sandstone formation. There are two beds of limestone
in this deposit, separated by beds of stone eighteen feet thick,
chiefly argillaceous, with some calcareous matter in their com-
position. The upper bed of limestone is 14 feet thick, and
from the analysis made of it by the late Dr. Murray, contains 40

er cent. of magnesia, 57 of carbonate of lime, and 3 of iron.
The lower bed of limestone is 18 feet thick, and contains 88 per
cent. of carbonate of lime, the remainder being clay and sand,
with a few grains of iron. The upper part of this bed consists
of hard compact limestone, of a reddish colour, 9 feet thick ;
then 4 feet of thin beds not more than 6 inches thick, between
which are interspersed thin layers of a kind of stone marl, con-
taining 10 per cent. of carbonate of lime, with impressions of
shells; the remaining 5 feet consist of laminz of a more red
colour, and contain organic remains of Orthoceras, Ammonites,
and shells of the Producta of a larger size than are found in any
other quarry in Scotland.

The limestone deposit at Closeburn is situated in one of the
small valleys of the mountain chain running across the island
from the German Ocean to the Irish Sea; no similar deposit of
limestone has as yet been recognised elsewhere in this chain of
hills.

Notice of the Flints of Aberdeenshire. By Dr. Knieut.

Dr. Knight read a notice on the flints found in various parts
of Aberdeenshire, and more especially in the vicinity of Peter-
head. He particularized the fossils found in them, and exhibited
an interesting series of specimens.

652 FOURTH REPORT—1834.

On the Old Red Sandstone and the Formations beneathit. By
R. I. Murcuison, #.R.S. &c.

Mr. Murchison presented a tabular view of the order of suc-
cession of various undescribed formations of great thickness,
and distinct from each other in their organic remains and mi-
neralogical characters, which rise from beneath the old red
sandstone of England and Wales. He then dwelt upon certain
remains of fishes which he had traced through the central divi-
sion of the old red sandstone of England and Wales, over an area
exceeding 3000 square miles. The most striking of these fishes
(Cephalaspis, Agassiz,) it now appears is common to the central
portion of the old red sandstone of England and strata oc-
cupying the same geological position in Forfarshire and other
counties in Scotland. Mr. Murchison further expressed his
opinion that the Arbroath pavement is the equivalent of the tile-
stones or lower member of the old red sandstone of England.
Mr. Murchison stated that Dr. Lloyd of Ludlow was the person
who first called his attention to the fishes of the old red sand-
stone of Salop.

On the Change of Level of the Land and Sea in Scandinavia.
By C. Lyeuy, FR.

Mr. Lyell prefaced his statement with a brief sketch of the
state of the controversy touching the gradual rise of Scandinavia,
at the time of his visiting that country. It was more than a
hundred years since the Swedish naturalist Celsius had declared
his opinion that the level of the waters, both of the Baltic and
the ocean, was suffering a gradual depression.

In confirmation of this phenomenon, Celsius had appealed to
several distinct classes of proofs: 1st, The testimony of the in-
habitants on the northern shores of the Gulf of Bothnia, that
towns formerly sea-ports were then far inland, and that the sea
was still constantly leaving dry new tracts of land along its bor-
ders; 2ndly, The testimony of the same inhabitants, that various
insulated rocks in the Gulf of Bothnia, and on some parts of the
eastern shores of Sweden, then rose higher above the level of
the sea than they remembered them to have done in their youth;
3rdly, That marks had been cut on the fixed rocks on the shore
some thirty years or more before, to point out the level at which
the waters of the Baltic formerly stood when not raised by the
winds to an unusual height, and that these marks already indi-
cated a sinking of the waters. On the whole, Celsius concluded

TRANSACTIONS OF THE SECTIONS. 653

that the rate of depression amounted to three or four feet in a
hundred years. To this conclusion it was objected that there
were many parts of the Baltic where the level of the sea had not
fallen, as could be proved by ancient pines and castles standing.
close to the water’s edge, and other natural and artificial monu-
ments. It was remarked that the new accessions of land were
chiefly where rivers entered the sea, and where new sedimentary
deposits were forming; and that the marks were not to be de-
pended upon, because the level of the sea fluctuated in conse-
quence of the action of the wind.

Von Buch, in the course of his tour in Sweden and Norway,
about twenty-five years ago, found at several places on the
western shores of Scandinavia deposits of sand and mud con-
taining numerous shells referable to species now living in the
neighbouring ocean. From this circumstance, and from accounts
which he received from inhabitants of the coasts of the Both-
nian Gulf, he inferred that Celsius was correct in regard to a
gradual change of relative level. As the sea cannot sink in one
place without falling everywhere, Von Buch concluded that cer-
tain parts of Sweden and Finland were slowly and insensibly,
rising. Mr. Lyell, together with Von Hoff and others, still
continued to entertain doubts with regard to the reality of this
phenomenon, partly on grounds stated by former writers and
above enumerated, partly because Sweden and Norway have
been, within the times of history, very free from violent earth-
quakes, and because the elevation was said to take place not
suddenly and by starts, according to the analogy of the inter-
mittent action of earthquakes and volcanos, but slowly, con-,
stantly, and insensibly.

Mr. Lyell visited some part of the shores of the Bothnian
Gulf between Stockholm and Gefle, and of the western coast
of Sweden between Uddevala and Gothenburg, districts parti-
cularly alluded to by Celsius. He examined several of the marks
cut by the Swedish pilots under the direction of the Swedish
Academy of Beiencel in 1820, and found the level of the Baltic
in calm weather several inches below the marks. He also found
the level of the waters several feet below marks made seventy or
a hundred years before. He obtained similar results on the
side of the ocean ; and found in both districts that the testimony
of the inhabitants agreed exactly with that of their ancestors re-
corded by Celsius. After confirming the accounts given by Von
Buch of the occurrence on this side of the ocean, of elevated
beds of recent shells at various heights, from 10 to 200 feet,
Mr. Lyell added that he had also discovered deposits on the
side of the Bothnian Gulf, between Stockholm and Gefle, con-

654 FOURTH REPORT—1834.

taining fossil shells of the same species which now characterize
the brackish waters of that sea. These occur at various eleva-
tions of from 1 to 100 feet, and sometimes reach 50 miles inland.
The shells are partly marine and partly fluviatile: the marine
species are identical with those now living in the ocean, but are
dwarfish in size, and never attain the average dimensions of
those which live in waters sufficiently salt to enable them to
reach their full development. Mr. Lyell concluded by declar-
ing his belief that certain parts of Sweden are undergoing a gra-
dual rise to the amount of two or three feet in a century, while
other parts visited by him, further to the south, appear to ex-
perience no movement.

On Marine Shells of recent Species, at considerable elevations,
near Preston. By W. GILBERTSON.

The situation of these fossils is in the county of Lancaster,
betwixt the Lune and the Mersey: the greatest elevation at
which they have yet been found is 350 feet above the sea, in the
excavations made by the Preston Water Company at the foot of
Longridge Fell.

The shells are interesting, as being of the same species as
those now found on our shores; and showing, therefore, that
this elevation has taken place since the creation of existing
species : and the stations and roads of the Romans being upon
this deposit, prove that there has been no change in the form
of existing species during the period that has elapsed since they
occupied this country.

Notices in reply to a Question proposed hy the Geological
Committee at Cambridge, as to the Relations of Mineral
Veins and the Non-metalliferous Joints in Rocks. By Joun
Puituirs, F.R.S. G.S., Professor of Geology in King’s Col-
lege, London.

The author states that his attention was first drawn to the
special investigation of the direction and other characters of the
joints of rocks, during an examination of the upper slate system
of Westmoreland and Yorkshire in 1823*, and again excited by
observations on the magnesian limestone of the North of En-
gland in 1828+. Since that period he has at different times ga-
thered additional facts on the subject by investigations among

* Transactions of the Geological Society, vol. iii. p. 1.
+ Phil. Mag. and Annals, vol. iv. (1828.) p. 401.

TRANSACTIONS OF THE SECTIONS. 655

the oolitic, coal, and mountain limestone strata, in the latter of
which he has endeavoured to ascertain what relation of direc-
tion, intersection, width, and other characters there may be be-
tween joints and mineral veins.

Geologists have in general given little attention to the joints
in stratified and especially secondary rocks, though the structure
which they impart to these rocks is often quite as remarkable
and characteristic as that derived from the stratification. In
most instances they cause in rocks of a given mineralogical cha-
racter a definite figure of the separable blocks; as the prisms
of basalt, the tables of slate, the rhomboidal masses of shale,
the cuboidal blocks of limestone: they are often arranged with |
so much regularity as to assume some of the leading features of
symmetrical crystallization. There are several kinds of joints.

1. Cracks, which are usually confined within the substance
of one bed of stone, and appear to have been caused internally
by the process of condensation of the mass. Some of these,
called by the workmen dry cracks, though scarcely visible to
the eye, open with slight blows, and often display on their faces
dendritical oxide of iron, or oxide of manganese. The width of
the space left between the opposite faces of a crack varies in
some ratio to the nature of the rock; thus in some septariate
ironstone beds and nodules they are very wide, in certain lime-
stones almost evanescent. Some of them are empty, others
filled with carbonate of lime, quartz, and other substances,
and in particular places with sulphuret of lead, carbonate of
copper, &c.

. That the cracks have been produced since the deposition of
the rock is easily proved, for they divide imbedded shells, plants,
fishes, &c.; in conglomerate rocks also they are found to divide
the rolled masses, as at Oban and in the Righi, where veins of
quartz filling cracks traverse many different sorts of pebbles.

2. Joints which go through one bed of stone, or even through
several of the conformable beds of the same quality, in several
directions, dividing them into blocks of characteristic forms.

3. Fissures traverse a great variety of strata, though of very
different quality, as limestone, shale, sandstone, and coal ; these
are often termed backs, or slines; they, as well as the other
joints, are of great importance to quarrymen and miners; they
materially influence the lines of the escarpments of rocks along
hill-sides and valleys, the direction of streams, &c.

In some rocks, e. g. magnesian limestone, they are open for
great lengths and depths, or filled with clay and pebbles, intro-
duced from the surface : in the oolite and mountain limestone
they exhibit every gradation of sparry repletion from a few cry-

656 ROURTH REPORT—1834.

stals on the walls toa solid.mass of fibrous orlamellar carbonate
of lime occupying the whole cavity, and, occasionally instore pevaedl
with metallic. substances. f
In passing through different sorts of rocks, the: fissures. pre-
serye. nearly the same. inclination from the vertical, but their
breadth. and regularity ;are very, unequal. The same fissure’
which in limestone is open, or filled: with spar to some inches”
width, may be reduced to a mere divisional plane in the: alter-;
nating shales: the fissures in coarse sandstone are irregular,
those in fine shale possessed of almost crystalline symmetryy. »:
Viewed upon a horizontal plane, the fissures and joints almost
always, except in greatly deranged masses of rocks, appear -to)

follow. definite directions ; so as, by their mutual intersections:

to dissect the area into compartments, of which the figure varies;
according to the nature of the rock., This variation appears
principally due to the joints, for the great, lines of fissure hold,
nearly the same courses throughout. The joints usually ter-
minate in the fissures; these last are of unequal extent, some

being more persistent.than others, so as,to deserve the title of |
master fissures. ... i

In slate rocks of the North of England there are often several:

sets of joints, besides the cleayage, which are more or less.di-~.

stinct and continuous ; some of them vertical, others inclined at
considerable angles, and passing in different directions, remind-,

ing us of the various intersections of the Cornish veins. In the,
Crayen slates the most constant of all the divisional planes is...
that of cleavage which ranges. W.N.W. and _E.S.E., having a..

variable dip to the S.S.W. or N.N.E. ; it is crossed by vertical,
joints ranging nearly N. and S.

In the mountain limestone tracts also, the great fissures. ‘are.
in general parallel to one or other of two lines: they either,
range nearly EK. and W., or W. of N. and E. of S.; of these.
directions the latter is perhaps the most predominant. Fissures
in other directions are indeed often noticed, but they are of less,
importance.

In the magnesian limestone of Yorkshire the directions of ;

the principal and most continuous fissures are from E. to .W..

and from N. to S.: the same is the case with some parts of the.

oolitic ranges on the north of the Vale of Pickering.

The author concludes, from actual observation, that thr oughout™

the greatest part of Yorkshire north of the Aire and Wharfe,.

the most continuous fissures are nearly vertical, and range either _

E. and W. or nearly so, or a little W. of N. and K. of S.
The tract of country thus defined connects itself on the north
with the mountain limestone districts of Durham, Cumber-

_

TRANSACTIONS OF THE SECTIONS. 657

land, and Northumberland, as far as the valley of the South
Tyne; so as to constitute one great elevated geological area,
bounded on the north by a dislocation, varying in amount from
600 to 1200 and 2000 feet, which ranges in general E. and W.,;
on the west by the great Cross Fell fault, of at least 3000 or 4000
feet, ranging S. by E., from Brampton to near Kirby Lonsdale;
and on the south by the double Craven fault, of 1000 to 3000
feet, which goes to the E.S.E.

Within this area numerous mineral veins are found, princi-
pally running E. and W., or parallel to the northern boundary,
comparatively few productive veins being found passing N.and S.,
though dislocations and rock dykes of importance, anda great
proportion of the leading fissures, take the direction N.N.W.,
which is nearly parallel to the great Cross Fell fault.

This east and west tendency of the veins is conspicuous in all
the northern mining tracts of the Tyne, Wear, Tees, and Swale ;
it is less predominant in the southern mining fields in Wharf-
dale and Niddersdale, which are near to the E.S.E. fault in
Craven. That fault is remarkable for its double line of disloca-
tion ; and for the coincidence of its direction with the most con-
tinuous divisional planes of the slate, with one parallel dyke of
greenstone, and one or more bands (veins) of pyritous slate.

There is therefore in this great tract of country a clear gene-
ral analogy in direction between the lines of convulsive move-
ments, mineral veins, and open or sparry fissures. The fissures,
joints, and cracks often display in their contents, and circum-
stances of arrangement, a close affinity to metalliferous veins ;
and the whole investigation appears to indicate among them all
a common and fundamental relation. Professor Phillips is of
opinion that the definite direction of the joints and fissures is
one of the facts to be most attended to in a theoretical point of
view, since it appears extremely probable that this character
of joints is the primary phenomenon which, by presenting
lines of least resistance to the disturbing forces concerned, has
permitted the dislocations to follow certain principal parallels.
The agencies whereby not only the slip veins, but often the un-
disturbed fissures, joints, cracks, and hollows in rocks, and
insulated cavities in shells, have received their metallic or sparry
contents, constitute a really distinct branch of inquiry, though
it is already evident that the solution of either problem cannot
be effected without unfolding common principles of symmetrical
aggregation, and chemical and electrical action not yet familiar
to geologists.

1834.

LX)
q

658 FOURTH REPORT—1834.

On some Caverns containing Bones, near the Giant’s Causeway.
By James Bryce, Jun., W.A., F.G.S. &c.

The author was made acquainted with the existence of these
caves by Dr. M’Donnell of Belfast, in the beginning of August
last. As he was ignorant of comparative anatomy, he requested
Dr. Scouler, Professor of Mineralogy and Geology in the Royal
Dublin Society, to join him in an examination of the caves.
The following facts are the result of the joint observation of
Dr. Scouler and the author.

Only three caves on the north-east of Ireland have been yet
found to contain bones; they are situated in the immediate vi-
cinity of Ballintoy, about 5 miles from the Giant’s Causeway ;
one of them a few perches west of a small bay or creek called
the Port of Ballintoy, another about 50 perches further east,
and the third in Carrickarede Island. At the first-mentioned
place a trap dyke traverses a chalk cliff of about 40 feet in
height ; the entrance to the cave is in this dyke at the base of
the cliff: the direction of the dyke is soon crossed by the cave,
which is afterwards entirely in the chalk. The mouth of the
cave is about 10 feet above high water, and 4 perches distant
from the line to which it generally advances. A ridge of co-
lumnar basalt which runs along the coast protects this bay from
the fury of the waves, and it seems impossible in the present
state of the surface that the highest tides could flow into it.
Persons living in the neighbourhood assert that the tide has
not risen so high within their memory. The cave consists of
two chambers, separated from one another and from the entrance
by low and narrow passages, which admit the body of a man
with difficulty. Beyond the inner and larger chamber, which
is 7 feet high and 6 wide, one of these passages extends to an
unknown distance. The floor of the cave, particularly in the
two chambers, is covered with loose masses of chalk, chalk flints,
and trap, of various sizes, intermixed with sand and white gravel,
the latter consisting of chalk and flint. The sides and roof and
many parts of the floor are covered with incrustations of sta-
lactite and stalagmite, which in some cases meet and form co-
lumns. The bones occur loosely among these stones, or im-
bedded in the sand and gravel at the depth of 3 or 4 feet; they
are often cemented together by stalagmite, or along with other
substances form a conglomerate with a stalagmitic base. There
were found bones of the horse, ox, deer, sheep, and perhaps
goat; otter, water-rat, cod-fish, and of several birds. The
bones were always detached, and never lying together so as to
form an entire skeleton of an individual.

TRANSACTIONS OF THE SECTIONS. 659

The second cave is in a chalk cliff terminating a small bay
called Pait-Dhu, whose sides are so steep in all parts as to
prevent the descent of most quadrupeds. At the entrance the
cave is about 12 feet high and 9 wide, the floor being on the
level of the water. The tide has thrown up a shingle bank,
which nearly blocks up the mouth, and prevents the entrance of
the sea at present, though there are indications that it has not
been long excluded : there was no termination found to the cave,
but after 120 feet it is low and narrow. The bones met with
belonged to the horse, ox, sheep and goat, deer, dog, badger,
pigeon, cormorant, and gull; they were dispersed, as in the
former cave, over the floor, which was of similar composition,
A very interesting conglomerate, of recent origin,was found here
in loose masses ; it consisted of rolled pieces of chalk, flint,
trap, and bits of opal, and sometimes included bones.

_ The cave that remains to be noticed occurs on the north-
west side of Carrickarede Island, which consists entirely of
amygdaloid and greenstone. The high cliffs which form the
shore near the cave being constantly washed by the sea, the
cave is quite inaccessible from the land : from the sea it is only
to be entered at low water in calm weather. At other times
a heavy surf breaks into it, so that a visit to it is attended with
some danger, and the risk of being detained several days.
The floor ascends a little from the entrance, so that in ordinary
tides the water does not rise far into it. For nearly fifty yards
from the mouth it preserves a width of 70 feet, and a height of
40 or 50: beyond this its dimensions are very much con-
tracted. It probably goes nearly quite through the island. The
floor is of the same structure as before, except that chalk,
flint, and stalagmitic incrustations are less frequent than in the
other caves. A black mould, apparently of vegetable origin,
is in some places interstratified with the sand. Bones of the
following animals were found: horse, ox, deer, sheep, dog,
cod-fish, skate, wolf-fish. A white greasy substance, like de-
composed bone, was found in some places among the sand.

It is difficult to account for the formation of these bone de-
posits : few of the bones bear the marks of attrition, and none of
them marks of gnawing. All the caves are inaccessible to most
of the-animals named; it is therefore most probable that the
bones of the tame animals were introduced by man, who may
have made these caverns a place of refuge, while some of the
wild animals may have lived and died where we now find their
remains: in confirmation of which it will be recollected that
Carrickarede cave afforded no bones of wild animals. Some of
the bones may doubtless have been washed in by the waves.

2u02

660 - 9 FOURTH, REPORT—1834._ _.

It is worthy: of remark: that:no. bones, of the hog .were: found.;
which seems to:show that the animal-did not exist in the coun-
try when the remains were introduced, into the cayes.

On some Caves in the Island of Rathlin and the adjoining Coast

of the County of Antrim. By Taomas AnpDREws, of Tri-
_mity College, Dublin. - Wt ats 2

MILES

» Of these caves six were examined by the author, vize four in
Rathlin, one in the rock) called Carrick-a-rede, and:one inthe
mainland near Ballintoy.»' In‘a cave in: Rathlin, a thick layer
of sea sand containing marine shells was found beneath«the:sta-
lagmite, near the termination of the cave ; and in another eave
@ different variety of water-worn sandstones was discovered: in
‘a Similar| situation, but no trace:of shells could be:seen: ) In.an-
ther large caveat’ Rathlin, a rude piece of antiquity formed: of
iron and resembling the handle of asword,was found quite close
to the’skeleton of a'sheep. The length of the Rathlim caves varied
from ‘150 to: 250 feet’; the dimensions: in other respects: wete
wery different. -It/seems obvious from these'circumstances; from
the position of the entrances to some of the caves:and the nar-
-rowness of those ‘of others, Ist, that: many of the animals could
‘not have entered them in their present position and state; 2nd,
‘that the sea must have formerly entered them at a much higher
relative elevation than its present level. 1) od of lis nad;

48D BIS

On the Anatomical Structure.of recent and fossil Woods. .
RES ae By W.Nicou, ~ PRY SF
With a view to acquire some precise information on, this
subject, the author cut transverse sections of various trees,:and
soon perceived that the reticulated texture of; the recent; Coni-
fere was essentially the same,as that of the fossil specimens.
As soon as he was thoroughly convinced of the: similitude, »he
mentioned the circumstance to many of his friends, and-showed
them both the recent and fossil sections in the microscope.. The
-similitude was so:striking as:to be admitted by all;. but, as. the
fossil sections presented no appearance of regular annual-layers,
some were led to entertain doubts as to the actual identity... On
examining soon after some fossils which he had.found in the
vicinity of Whitby, and one. in particular which he had found
among the debris of the porphyritic pitchstone in, the, island
of Eigg, he observed the same>reticulated: structure associated
with the most regular, annual: layers. .These-left .no. doubt
on his:mind as to the Coniferous origin.of the whole; but it was

ie

TRANSACTIONS OF THE SECTIONS. 661

not until last year that he’ was enabled: satisfactorily to remove
the doubts that some ‘still entertained, by showing that the drat
caria Cunninghami, and a-species of: Callitris from Moreton
Bay in New Holland, were equally destitute of annual layers.
Since the author first began to direct his attention to the
structure of. fossil woods, he has examined some hundreds of
specimens from various countries widely separated from each
other. From the tertiary formations he has obtained monoco-
tyledons and dicotyledons, but, with one:exception, no Conifere.
Thevexception is in the/island of, Sheppy, from whence; in the
Edinburgh College museum, there are two, specimens ‘the| coni-
ferous origin of which cannot be doubted. ‘The: tertiary. forma-
tion of the island of Antigua is-well known to furnish many, spe-
‘cimens of fossil wood; and out of a hundred and fifty specimens
from: that squarter there was not,a ‘single; coniferous: plant; the
‘greater part being dicotyledons, the rest monocotyledons: From
*actertiary formation in the island of Java, the author. has lately
‘examined several specimens; but found no-Conifer@ among them.
Yet although coniferous:fossils would seem: to occur sparingly,
‘at least in: some tertiary formations, they -are: evidently widely
distributed:among the different rocks.of the carboniferous depe-
‘sits) -'The author has examined: many specimens of fossil wood
not only from the coal districts of this country; but also from
those of New Holland, and Nova Scotia-in America,, and;found
them all to be Conifer. Most. of them are siliceous, but some
are calcareous, and others partly siliceous and partly converted
into the bituminous state of jet. Of the last, Mr. Nicol has in
his possession a’ very illustrative specimen’ which he found in
the lias formation in the vicinity of Whitby. The siliceous
“portions of this specimen, which have been twisted round in
“different directions, display distinctly the coniferous reticulated
“structure, and: the. larger. portions’ of ‘the jet have the ‘same
“blackish zic-zac lines: which: occur in every transverse section
of that bitumen, but show no trace of’the original structure. In
“another ‘specimen, however, consisting partly of an earthy: mat-
“ter and’ ‘portions of jet, which he also found in the same locality,
“some of the: ‘portions of jet retainy: though much obscured; the
true coniferous! structure;iand this ‘is the eens wens of ‘the
“kind:he ‘has ever: observed.) 00 On
°\) Jet, as generally found in the vicinity of Whitby, coniintet of
S@etached masses resembling the trunks or branches of trees very
“wiuch compressed. When’ cut) into thin: slices’ it is’ perfectly
transparent, and’ of’ a deep’red? or pale yellow colour, according
‘othe thiekness ; but although the three principal: sections.ipre-
“Sent apeculiar and constant: structure, the author has mare

662 FOURTH REPORT—1834.

observed, except in the above specimen, the true coniferous
structure. The coniferous origin of jet will, in all probability,
be generally admitted ; and the analogy of the naphtha of coal to
the turpentine of the Conifer, as lately indicated by Dr. Reichen-
bach, gives room to surmise that coal in general has resulted
from the bituminization of coniferous plants.

The transverse section, though always sufficient to distinguish
the Conitfere from the monocotyledons and dicotyledons, does
not furnish any criterion by which to distinguish with certainty
one species from another. The longitudinal section, however,
parallel to the partitions extending from the centre to the sur-
face, enables us to divide the whole family of Conifere, whether
recent or fossil, into two distinct divisions. The discs or areole
to be seen in that section are so different in form and arrange-
ment in the two divisions,that there is no risk of mistaking any
species in the one for any species in the other.

The first divison, which may be called the Pine division, in-
cludes the true pines, the cypresses, the junipers, the thujas,
the callitrises, and Salishuria adiantifolia; the second divison,
which may be called the 4raucarian, includes the araucarias
and dammaras. The author first took notice of the discs in the
recent pine division, and then pointed out examples of similar
dises occurring in fossils of the same division. )

The discs or areolze to be seen in all the species do not occur
in every part of a section. They are generally distributed in
groups more or less extensive. Their form is for the most, part
circular ; but they are sometimes slightly elliptical, and when
that is the case the transverse diameters are perpendicular to
the longitudinal partitions. They are arranged in a vertical di-
rection, most frequently in single rows. Double rows, however,
are often to be seen; but more than that number the author has
never observed, although he has cut and examined many hun-
dreds of sections. The discs in a row are sometimes in contact
with one another, but often detached at very different distances ;
and wherever they occur in double rows, they are always placed
side by side in a horizontal direction. In many of the true pines
the discs have the largest dimensions towards the inner side of
each annual layer, and they are larger and better defined than
those in most of the other tribes of this division. When a section
of any of the larger true pines is properly cut, the discs often pre-
sent an apparently flat surface, consisting of a number of distinct
concentric rings, especially when illumined with artificial light,
as that of a candle, and viewed with a garnet lens of the fortieth
or fiftieth of an inch radius. It does not always happen that
the discs are wholy composed of concentric circles. In many

TRANSACTIONS OF THE SECTIONS. 663

of them four or five circles towards the circumference, and one
or two towards the centre, are all that is to be seen ; and it often
happens that the discs are cut so thin that scarcely a trace of
the circles remains.

Among the fossil Conifere a form and arrangement of discs
perfectly similar to what occurs in the recent true pines is often
to be seen. Ina specimen, for example, from the coal formation
of Nova Scotia in America, belonging to Professor Jamieson,
the discs are numierous and well defined. They are arranged
both in single and double rows. When in double rows, they
are placed side by side in a horizontal direction. Their size is
equal to that of the discs occurring in many of the larger true
pines, and some of them display distinct concentric circles. A
similar form and arrangement of discs the author has often seen in
other specimens, particularly in one from Australia, and in an-
other from the vicinity of Whitby. In the transverse section
these three fossils have regular annual layers, and present with
great distinctness the coniferous reticulated structure. Hence
it appears that in several widely distant regions fossil Coni-
fere occur perfectly resembling in anatomical structure the
recent true pines.

With regard to the other division of the Cunifere, namely,
that which includes the Araucarias and Dammaras, we find in
the longitudinal section, parallel to the partitions extending
from the centre to the surface, groups of discs differing widely
from those occurring in the Pine division, not only in size, but
also in form and arrangement. In this division, which we have
distinguished by the name of Araucarian, the discs occur in
single, double, and triple rows. They are in general arranged
in groups, but sometimes a row may be seen quite detached
from all others. The number of discs in a row varies from two
or three to sixty or seventy, and in any one row they are gene-
rally equidistant and near one another. In the double and triple
rows the discs are never placed side by side in a horizontal di-
rection, but always alternate with each other ; and this is a cha-
racter by which an Araucarian species may at once be distin-
guished from any one species of the pine division. When the
discs are placed at a certain distance from each other, they are cir-
cular ; when in contact, the approximating sides are compressed ;
and when at an intermediate distance, the approximating sides
become rectilinear. When the discs in the double rows are at
a particular distance from each other, they are partly polygonal
and partly circular. The contiguous boundary of each consists
of four straight lines, and that part of the periphery next the par-
tition is a segment of a circle. When the discs are arranged

664, ») FOURTH REPORT—1834.. |

in triple rows, those constituting. the middle. row: are: the anost
perfect equilateral hexagons; -and, those constituting the-side
rows are partly polygonal and partly circular, similar invevery
respect to those constituting the double rows... The: corre-
sponding sides of the: polygonal discs are- generally connected
-by,two fine lines or.fibres placed near-the ends of \each; and
when. the discs are well defined, they generally display concen-
tric circles in the interior, and two parallel straight lines: corre-
sponding with the.rectilinear boundaries of the polygonalkind.
‘The largest. Araucarian discs are scarcely a quarter’ of the side
of the, largest, of those. occurring jin'the, true Pines,:'They are
so minute that to see them with advantage they should be-mag-
nified four or five, hundred times, and: illumined by the-light of
a snow-white. cloud. itaocr ovods enoieivil +0
_ ,QOn,.cutting longitudinal _ sections, of: various: fossils ‘parallel
tothe partitions extending from the centre to the surface, discs
are often to be seen, resembling in every respect those oceurring
in the Araucarian division of recent Coniferce.. They occur in sin-
gle, double, triple, and sometimes even in quadruple rows.‘They
are, sometimes circular, sometimes polygonal, at least in the
double and triple series, but in general the polygonal form 'pre-
dominates, When the arrangement is in the triple or quadruple
series, the discs inthe middle row or rows are in general hexa-
gons, more.or less regular; but,in most specimens they are-very
much obscured, and in many parts even completely obliterated.
In respect. of size they are much smaller than those of the pine
division of coniferous fossils ; but they seldom or never display

rit} SF10 FO

more than the external bounding line, whether that: line be cir-—

cular or polygonal. y odd br
Many examples of fossil Conifere possessing discs similar to
those of the recent draucarie might here be adduced, but:at pre-
sent it may suffice to notice three... Of these the fossil tribe at
present laid bare in Cragleith quarry first claims ‘attention... In
that fossil the discs are in some parts entirely obliterated, but in
other parts, though much obscured, they are sufficiently obvious.
They are arranged in single, double, triple, and quadruple rows.
For the most part they are of a hexagonal form, and distinctly
alternate with each other. They merely retain the external
bounding line, and the vessels containing them are oftenivery
much distorted. Their size is smaller than that of those of the
fossils belonging to the Pine division, but it’ is difficult to: say
whether the double, triple, or quadruple series predominates.
One of the fossil Conifere from New Holland, contains dises
similar to those in the Cragleith tree, but muck bolder, and
better defined. They are chiefly-arranged in single and double

TRANSACTIONS’ OF THE SECTIONS, 665

‘rows ; “and:in’ the double rows ‘those in one-row alternate with
those ‘in the other row, andthe contiguous boundaries of each
are polygonal. In another from’ the’ vieinity ‘of’ Whitby, the
discs are distinctly seen in several! places: They occur in'sin-
‘gle, double, ‘and: triple rows, and: are in''some parts circular,
‘and -in»other ‘parts polygonal: Their form; however, is often
rather indefinite on account of their: boundaries" = very much
obscured: ls
»o After: having edadsiricth the structure ‘of iianly ‘fossil Conifere,
Mr. Nicol has not met/with even one'possessing characters essen-
tially different: from: thosé' to be seén in one or other of ‘the recetit
tribes. The'transverse'section ‘is analogous in both ; the discs,
‘wherever they are well defined; agree with those in one ‘or other
of the divisions above mentioned: In some instances, it is true,
‘even: where ‘the: reticulated texture ‘in’ the’ transverse section i is
tolerably ‘perfect, the discs in’ the longitudinal séction ‘are’ often
very muchobscured," and ’even totally obliterated ; but’ this'is
no: proof that they did not exist in the wood ‘before the ce
mencement of| the petrifactive process.’ In some'recent woods
the dis¢s are! very obscure, even nearly’as much so’ as in’ some
of the fossil kind ; and were such'to become petrified, it is highly
probable they. ‘would’ entirely disappear. The author has’ ‘seen
fossil ‘sections’ ‘which’ on a cursory ‘view seemed to have ‘no
dises;" but) which‘on sabe inspection’ showed traces of them
inseveral parts. 00 © ete
«The recent) attempts to establish new’ fossil genera’ soa
per oe to: have arisen from, considering ‘a single ‘section ‘of one’ or
two true piries as containing the: characters of all the Conifere’;
and yet the discs in the Araucarias and Dammaras are so strike
ingly different from those in the true Pines, that it is impossible
to mistake the former for the latter. Had even a single longi-
tudinal section: of an ‘Araucaria ‘been/examined,: it would have
been seen that» multiplicate rows of ‘discs’ of a” poly#o mal form
could not be admitted ‘as’ a'foundation for: anew’ fossil genus.
Hada few sections of some'of the common Pines been examiried,
it: would ‘have been seen that doubie rows of discs ‘existed in
recent:as well,.as in fossil:Conifere, and therefore could not be
‘adopted as the foundation: for: a new fossil genus.’ Had'even a
limited’ number of ' transverse sections of ‘recent. Conifere ‘been
examined; such’a diversity inthe size of the pith would ‘have
beemseén: as 'to preclude the idea of erecting’ into:a new genus
a single fossil, the distortedpith of which had a mean diameter
of about four tenths| of an inch. :'The-author has in his osses+
‘sion a portion of the stenr of an: Araucaria Brasiliensis the pith
of which is upwards of ‘three: tenths‘of an-inch in diameter. * Had

666 “FOURTH REPORT—1834.

a sufficient number of fossil sections been examined, it would
have been seen that in some of them the whole structure in the
longitudinal direction had been so much obscured that scarcely a
trace even of the longitudinal partitions remained, and that
therefore the absence of discs could not be admitted as the
foundation of a new fossil genus. The presence or absence of
discs must often depend on the thickness of a section. In proof
of this Mr. Nicol has prepared a section of the present Crag-
leith tree, which when of the proper thickness showed the discs
very distinctly, but which now shows not a trace of them, in
consequence of the thickness being a little diminished. A source
of deception too often arises from the water absorbed in the pro-
cess of grinding. In some fossil woods, particularly those of a
whitish colour, the translucency is such, when the substance is
penetrated with water, that discs may be seen; but when the
water is evaporated, a degree of opacity ensues which renders
them invisible.

Mr. W.C. TREvVELYAN exhibited slices of fossil wood, from a
specimen which he had brought from Faroe, with drawings by
Mr. MacGillivray, who considers it an undescribed species, and
proposes naming it Penuce Ferroensis.

It occurs in the island of Suderoe, in the bed of clay asso-
ciated with coal, (all the other strata in that island belonging to
the trap family,) of which Mr. Trevelyan has given a short ac-
count in the Transactions of the Royal Society of Edinburgh
vol. ix. p. 461. |

Captain MacConnocuig, Secretary to the Royal Geogra-
phical Society, gave an account of the origin and progress of
that Institution. He communicated some details relative to the
late expedition to the Niger, and to the expeditions which are
about to be sent out to the interior of Africa and to British
Guiana.

Mr. Hauv’s model of a part of Derbyshire was exhibited.

Mr. Saut exhibited drawings of the incisors and canine teeth
of the fossil Hippopotamus, from a gravel-pit near Huntingdon.

Dr. Buckuanp laid before the Section a drawing, by Mrs.
Turner of Liverpool, of a large fossil marine plant, found in the
new red sandstone of that neighbourhood in 1829.

TRANSACTIONS OF THE SECTIONS. ‘667

Iv. ANATOMY AND PHYSIOLOGY.

Observations on the proper method of studying the Nervous
System. By Sir Cuarves Beir, F.R.S. K.A., &e.

Sir Cuaryes BELL commenced by stating the remarkable simi-
larity in the ideas entertained on the nervous system from the
time of Galen to that of Monro and Baillie, which he attri-
buted to the anatomists and teachers rigidly following the same
mode of investigation, and having the subject presented ever in
the same aspect. After illustrating by different examples how
men placed in exactly similar circumstances have the same con-
ceptions elicited, he proceeded to show how inconsistent the
minute anatomy of the nervous system in the human body was
with the prevailing doctrine of one source of energy, and the
notion of the brain being the officina spirituum, and to prove
that to explain the meaning of the seeming intricacies of the
nervous system, it was necessary to consider the nerves as
possessed of different endowments. In prosecuting the inquiry
there were three distinct considerations to be attended to—

1. The minute distribution of the nerves,

2. The functions of the parts to which they go,

3. Their roots, or the distinctions in their origins.

_ With regard to the first, he observed that during the period
of his early teaching, and some time previously to that, the ana-
tomists of Europe had brought the knowledge of the branching
and distribution of the nerves to great perfection, but with no
commensurate improvement in the knowledge of their functions.

As to the second head, he said it had been most negligently

considered ; it was the investigation into the functions of the
art to which the nerves went which must be the ground of
all rational theory. .

His first illustration was taken from the eye. Six nerves
crowd towards this small organ; what purpose could this
‘serve ? But when we consider not only the capacity of vision,
but the exquisite and peculiar sensibilities of the surfaces of
the eye ; when we consider the sensibilities as putting in action
all the guardian motions of the eye; when we consider the
globe of the eye moved by four muscles subject to volition, and
others whose motions are instinctive; the motions of the eye-
lids ; the motions of the iris; and the motions of the eyeball ;
the conviction arises that there is a relation between the many

+i

668 FOURTH REPORT—1834. _

nerves going to. the-organ and the various functions it performs.
He then gaye a,view.of the many actions performed by the fea-
tures, and: especially. by,the mouth and lips, contending that
these different..motions, could not be performed by the opera-
tion of one uniform.source of energy in the brain, and one
mode-of communication between the brain and exterior organs,
and .that, these considerations laid open to us the reason why
different nerves came to the same part, and formed connexions
which, without seeing the necessity for such combination, would
appear to us. matter of accident, ns MERE y o¢0

Sir Charles Bell proceeded to show how the investigation, of
the roots of nerves. threw. further light upon this, interesting
subject. He spoke of, the columns of the spinal marrow, the
double roots of the spinal nerves, the ganglions on the posterior
root, and the.resemblance of the fifth nerve of the head to the
spinal _ neryes. Taking the great work of Monro upon the
nervous system, he presented in succession the plates of the
roots of the spinal.neryes, that of the ganglion of the fifth, and

that of two nerves going to one muscle, He called upon those
gentlemen who were of his own standing to remember the zeal
with which their old professor treated of these subjects, and
asked them if they thought his gratitude was due to any other
authority. ‘“Often,’’ said he, “have I hung over these plates
and. repeated. all the dissections.” These are the points of
anatomy that have suggested the experiments to ascertain
whether nerves were common nerves, or whether each was
endowed with powers differing from those of others, and re-
sulting from the column or part from which it took origin.’ “A
short history of his experiments on the spinal nerves and on
the fifth, terminated this discourse. .

In continuation of the preceding remarks, Sir Charles Bell re-
minded hisaudience of the extraordinary complication of nerves
presented in the human body after minute dissection. He laid
before the section the plates of the nerves given by some of our

best authors,.and asked if there could be found any clué to this
-remarkable intricacy. He then proceeded to show that there was
a method in addition to those he had pointed out before, a
. method of inquiry which enlarged the field of our observations,
and vastly increased the interest of the subject, This was com-
parative anatomy; the investigations of which, still following
the functions of the parts, shewed the nerves increasing” in
- number and in complication, in proportion as additional actions
. were required, in the parts constituting the system of the ani-
~ mal body. . . pastors is

He presumed it. would be granted that Nature wrought with

TRANSACTIONS OF THE SECTIONS. 669
GO o * - :"

ROUGH wWinuc

‘eat, uniformity, and that if it were proved in any one instance

that sensibility and motion réstilted from ‘iervous matter, Ht -must
be.admitted that whenever m fion and sensation were’ observ--
able in a creature, there there must be nervous matter: As ‘in
some of the lowest animals we perceive ‘motion to ‘result from
the influence of, heat and light, where yet’ ‘no nerves were visi-
“ble, it leads to the inquiry, what is the function’ of @ nerve? isa
“nerve of itself a source of energy, or is it only a track of nervous
-matter wrapped up in membrane for the purpose of ‘conveying
an influence ? : rece vue, 152 Svodiiw loisdy
_ He proceeded to observe that in’ the lowest links of the chain
_of animals there was ever attached to its nearer or eentralex-
‘tremity,a little mass of ‘nervous thattér, or gariglion 5 and that
this. central mass, it was reasonable to ‘suppose, was the| ‘real
organ, whilst the nerves were the appendages, the internwneti,
‘between the central organ and the’ external’ organ’ of 'sense;:or
_ between that central organ and the moving instrument of ‘the

animal. He proceeded to describe the ganglionic cord ‘of the
_ Annelides, to show that the system in’ these lower ‘animals was
-_essentially the same with that of man, although the’ extraor-
., dinary accumulation of the. central masses in the‘brain “and
_spinal marrow of the latter obscured the resemblance. He' here
_ introduced the name of Mr. Newport with high approbation ‘of
__his talents: he said, having observed the happy methods that

age ntlen an, employed in investigating the nervous’system ofthe
_ dinvertebral animals, he persuaded him to investigate their mie-
_dullary cord, and to ascertain whether or ‘not there was a di-
, stinction of an anterior and posterior portion ‘of that cord ;’ and
ina very few days afterwards that gentleman brought him a pre-
“paration of the nervous system of the ‘lobster, ‘in which it’ was
_.shown. that the anterior or lower portion of the cord passed ‘over
_.the ganglion, and that the posterior ‘portion merged in the gan-
_-glion. Here was a remarkable ‘confirmation of the strict “re-
~ semblance between the spinal narrow. of the higher animals and
the medullary cord of the Invertebrata! "ON 988 Shs i
'. Such then, Sir Charles “Bell contended, were’ the modes“ of
.. investigating the nervous system: Ist, By minute ‘dissection ‘of
_ the nerves of the human body ; " ond, By the study of functions,
“which requires both the finest hand and the highest capacity*for

re

19d

__ observation ; 3rd, The observation of the roots of the nerves

“and the different sources from which ‘they proceed ; “4th, Expe-

_riments upon the living animal by observing what functions: are

cut off by, the division of certain nerves, a mode of proceeding

“which for many reasons ought not to be lightly undertakenj and

. which could be suecessfully prosecuted only under thé gttidance
: . oh SETS 90 DOW hivireeates 3 |

670 FOURTH REPORT—1834.

of knowledge obtained by the former methods; 5th, By com-
parative anatomy, the most satisfactory of all the modes by
which the apparent confusion of the nerves of the human bod
were to be unravelled and systematized. Sir Charles Bell then
gave ashort account of his paper about to be published by the
Royal Society, in which he has followed out the relations be-
tween the cerebrum and the sensitive and motor nerves; and
where he has distinguished two portions of the crus cerebri, one
descending anteriorly to the transverse septum of the pons, the
other posteriorly to that septum; the anterior relating to the
nerves of motion, the posterior to the nerves of sensation: and
he proceeded in some detail to show that any attempt to explain
the most familiar symptoms of disease in the brain must be
imperfect without the knowledge of these facts.

On the interest and importance to the Medical Profession of
the study of Mental Philosophy. By Dr. ABERCROMBIE.

The remarks on this subject were delivered in a closing ad-
dress to the Medical Section. Dr. Abercrombie said he was
aware of the objections which had been brought against admit-
ting the philosophy of mind as one of the regular sections of
the Association; and to aconsiderable extent he admitted their
truth, as it might be difficult to preserve such discussions from
those hypothetical speculations by which this important science
had been so much obscured and retarded in its progress. But
by treating it as a branch of physiology, he trusted this might
be avoided, by rigidly restricting the investigation to a careful
observation of facts, and the purposes of high practical utility
to which they might be applied. Keeping in view the importance
of these rules, he earnestly recommended the subject to medical
inguirers, as capable of being cultivated on strict philosophical
principles as a science of observation, and as likely to yield
laws, principles, or universal facts, which might be ascertained
with the same precision as the laws of physical science. For
this purpose, however, inquirers must abstain from all vain
speculations respecting the nature and essence of mind, or the
mode of its communication with external things, and must con-
fine themselves toa simple and careful study of its operations. -

Respecting the means of cultivating the philosophy of mind
as a science of rigid observation, Dr. Abercrombie alluded to
the study of mental phenomena and mental habits in ourselves,
and in other men; the whole phenomena of dreaming, insa-
nity, and delirium; and the mental conditions which occur
in connexion with diseases and injuries of the brain, The sub-

TRANSACTIONS OF THE SECTIONS. 671

jects of dreaming and insanity, which have hitherto been little
cultivated with this view, he considered as capable of being pro-
secuted on sound philosophical principles, and as likely to yield
curious and important results respecting the laws of association
and various other processes of the mind.

_ The practical purposes to which mental science may be ap-
plied, Dr. Abercrombie considered briefly under the following
heads: 1. The education of the young, and the cultivation of a
sound mental discipline at any period of life. In all other de-
partments we distinctly recognise the truth, that every art must
be founded upon science, or upon a correct knowledge of the
uniform relations and sequences of the essences to which the art
refers; and it cannot be supposed that the only exception to
this rule should be the highest and most delicate of all human
pursuits, the science and the art of the mind. 2. The intel-
lectual and moral treatment of insanity, presenting a subject of
intellectual observation and experiment, in which little com-
paratively has been done, but which:seems to promise results
of the highest importance and interest. 3. The prevention of
insanity in individuals in whom there exists the hereditary pre-
disposition to it. He gave his reasons for being convinced that
in such cases much might be done by a careful mental culture;
and that irremediable injury might arise from the neglect of it:
4. Dr. Abercrombie alluded to the importance of mental science
as the basis of a philosophical logic; and concluded his address
by some observations on the dignity and importance of medi-
cine, characterizing it as one of the highest pursuits to which
the human mind can be directed, as it combines with the cul-
ture of a liberal science, the daily exercise of an extensive bene-
volence, and thus tends at once to cultivate the highest powers
of the understanding and the best feelings of the heart.

Notice of some Experiments on the connexion between the.
Nervous System and the Irritability of Muscles in Living
Animals. By Dr. J. Ret. With Observations by Dr.
ALISON.

_ Although physiologists are still divided in opinion as to the
question whether nerves furnish a condition necessary to the
irritation of muscles, (¢.e. whether every stimulus which excites.
a muscle to contraction acts on it through the intervention of
nervous filaments,) they have now very generally abandoned the
once prevalent theory, that the irritability of muscles is derived
from the brain or spinal cord, i.e. that muscles are continually
receiving, through their nerves, from those larger masses of the

672 FOURTH REPORT—1834.

nervous system, supplies of a certain influence or energy, which
enables them to contract; and that some of the statements of
Dr. Wilson Philip, in particular, are generally regarded as de-
cisive against this theory.

Dr. Wilson Philip found by experiment, that the irritability
of a muscle of which the nerves were entire, was exhausted by
applying a stimulus directly to the muscular fibres (sprinkling
salt on them) even more quickly than that of a muscle of which
the nerves had been cut, and where all communication with the
supposed source of nervous influence or energy had been cut
off; and he states generally that a muscle of voluntary motion,
if exhausted by stimulation, will recover its irritability by rest,
although all its nerves have been divided.

But in opposition to this statement, and in support of the old
theory of nervous influence continually flowing through certain
of the nerves into the muscles, it has lately been stated by
Mr. J. W. Earle, that when the nerves of the limb of a frog
were cut, the skin stripped off, and the muscles irritated by
sprinkling salt on their fibres, until they had lost their power
of contraction, although they did not lose their power much
more quickly than when the nerves were entire, yet they did
not regain their power, although left undisturbed for five weeks ;
while the muscles of the limbs of another frog, similarly treated,
but of which the nerves were left entire, completely recovered
their irritability.

It occurred as a fundamental objection to the experiment of
Mr. Earle, that in the case where the nerves had been divided,
the muscles had become inflamed ; being found at the end of
the five weeks “softer in their texture than natural, a good
deal injected with blood, and with some interstitial deposition
of fluid in them ;’’ while in the limb to which the salt had been
applied, but of which the nerves were left entire, and where the
irritability was recovered, ‘‘ although the colour of the muscles
was rather darkerthan natural, their texture remained unchanged,
and there was no interstitial deposition. of fluid in them.”

In these circumstances it might evidently be supposed that it
was the inflammation and disorganization of the muscles, not
the section of the nerves, which prevented the recovery of the
irritability in the case where the nerves had been cut; and it
became important to have the experiment repeated, with care to
avoid such injury of the limb of the animal as should cause
inflammation to succeed the section of the nerves.

With this view, Dr. Reid performed a number of experiments
on frogs, in which the irritability of the muscles of both hind-
legs was exhausted or greatly diminished by galvanism, after

TRANSACTIONS OF THE SECTIONS. 673

the nerves of oné leg had been divided and the lower part. of the
limb rendered perfectly insensible and incapable of voluntary,
motion, (but without stripping off the skin,) while the nerves
of the other had been left entire. The state of the muscles of
both limbs was examined after some days. The results of these
experiments were not uniform ; but in several, where every at-
tention to accuracy seemed to have been paid, the irritability.
of the muscles in the palsied limbs appeared to be restored as
perfectly as in the others; contractions ‘being excited in them,
in Several instances, by the galvanism from four or even two
plates, whereas they had formerly been irritated until they were
no longer excitable by that from fourteen plates. eaticue:
- That the muscles which thus recovered their irritability had’
lost all nervous connexion with the brain or spinal cord was.
proved, not only by their obvious insensibility, but by after-
wards cutting off the heads of the animals and forcing a probe
along the spinal canal, which excited forcible contractions in all

parts excepting the palsied limbs. ~*~ Bae La

» Dr. Alison’s paper contained the details of several of these

experiments ; and he stated in conclusion, that as, a positive

result'in such an inquiry must always outweigh a negative one,

(particularly where a source of fallacy attending the latter can”
be pointed out,) these experiments appear fully to justify the as-
sertion of Dr. Wilson Philip, that a muscle of voluntary, motion

may recover its irritability by rest, although all its nerves be

divided; and that they afford, perhaps, more direct evidence,
than any others in support of the doctrine of Haller, now gene-_
rally admitted in this country, that the property of irritability
in’ muscles is independent of any influence or energy continually

flowing from’ the nervous system, although, like every other.
endowment of living animals, it is subjected to the control of
causes which act primarily on that part of the living frame.

_ Dr. ALLEN, THoMson expressed:a doubt whether these expe-/
riments warranted the conclusion drawn from them,not because
he, acquiesced in the theory to which they are opposed, nor be-
cause he called in question the accuracy of the results described
to. have been obtained, but because he knew that former experi-.
menters had failed in producing such diminution. or exhaustion:
of, the irritability. of -museles.as had been found: by Dr. Reid ;:
and. conceived. it possible that:some of the numerous. fallacies: to.
which such experiments are liable might not ‘have been-suf='.
ficiently guarded against.* - @ bie# 30 tas dae 1

* A Committee, of which Dr. Thomson was a member, was appointed for the :
repetition of the experiments, which has performed the duty assigned to'it,

1834. 2x

674 FOURTH REPORT— 1834.

_ The accuracy of Dr. Reid’s statement as to the great diminu-
tion or apparent exhaustion of the irritability of the muscles
under the influence of the galvanism, and the subsequent reco-
very of the power, notwithstanding the division of all their
nerves, was satisfactorily established. It is to be remarked,
however, that in these experiments, as usual in such cases, the
limbs to which the galvanism was applied were kept moist by
the same saline solution with which the galvanic trough was
charged ; and Dr. Thomson has observed, that when they are
moistened with pure water, the diminution of the irritability
under the excitement by galvanism is much less obvious.
Hence he was led to suspect that the apparent loss of power in
the muscles under that process might depend, not on the cir-
cumstance of repeated excitement, but on a degree, however
slight, of injury to their texture by the action of the salt. This
inquiry he proposes to prosecute further; but in the mean time
it is certain that by the usual process of galvanizing a living mus-
cle moistened by a saline solution, a very great diminution of its
irritability may be effected, which may subsequently be regained,
notwithstanding the division of all its nerves ; and as the fact of
its recovery, not the cause of its diminution or exhaustion, is
the point on which the inference drawn from these experiments
rests, that inference may be held to be sufficiently justified.

Notice of some Observations on the vital properties of Arteries
leading to inflamed parts. By Dr. Avison.

These observations were made with. the able assistance of
Mr. Dick, veterinary surgeon, on the arteries of the limbs of
several horses, condemned on account of injury and inflamma-
tion there.

The immediate object of inquiry was, whether the tortuous
and strongly pulsating arteries leading to an inflamed part are
really endowed with a greater vital power of contraction than
sound arteries; and the method taken to ascertain this was,
to make a comparative examination of the condition of these
arteries, and of the corresponding arteries in the opposite
sound limbs, immediately on the animals being killed (by blow-
ing air into their veins) ; and again after the lapse of 16 or 24
hours, when it is known that the tonic contraction, which takes
place at the time of death, and is the indication of the only
vital power which experiments authorzie us to ascribe to arteries,
has relaxed.

The animals were killed, and the observations made, at dif-
ferent periods varying from twelve hours to twenty days after

TRANSACTIONS OF THE SECTIONS. 675

the commencement of the inflammation, in the five cases of
which an account was read. The extent of the inflammation
was various. In all the cases, the. artery leading to the in-
flamed part, when laid bare as high as the groin as soon as
possible after the death of the animal, was larger in its whole
length, 7. e. had contracted less at the moment of death, than
that of the sound limb. In two of the cases, where the inflam-
mation was of long standing, and the coats of the artery ap-
peared to have been affected by it, this vessel at the second ex-
amination appeared smaller than the artery of the sound limb,
having not only contracted less at the moment of death, but di-
lated less after death, than the artery in the natural state. In
the other cases the artery of the inflamed limb remained larger
than the other at the second examination; and it was further
obvious that its elasticity was impaired, for when slit open and
smoothed out, it had less power than the sound artery of reco-
vering the cylindrical form.

In all the cases, the artery of the inflamed limb retained after
death a considerable quantity of blood, while the other was al-
most empty; and that this was not owing to inflammatory
effusion, preventing the artery of the affected limb from empty-
ing itself at the time of death, was proved, in two of the cases,
by cutting across the vessel, immediately on the death of the
animal, a little above the inflamed part, whereby it had full op-
portunity to rid itself of its blood, if it had retained the power
to do so.

One of these observations was made in the presence of Dr.
Yelloly, Dr. Clark, Dr. Fletcher, Mr. Broughton, Mr. Clift,
and Mr. Bracy Clark; and it may be added here, that in a sub-
sequent experiment, in which Dr. Alison and Mr. Dick were
assisted by Dr. Fletcher, they obtained further proof of the loss
of elasticity in the artery of an inflamed limb, by finding that
after it had been distended by a given weight of mercury (in
the way practised by Poiseville,) it had less power than the
corresponding sound artery, 1o contract on itself and expel its
contents when the distending force was withdrawn. But this
last experiment was made too long after the death of the ani-
mal to justify an inference as to the strictly vital power of the
vessel.

Dr. Alison stated, that it seems now generally admitted by mi-
croscopical observers, that during by far the greatest part, and
during the highest intensity of inflammation, nothing but dila-
tation or relaxation of the small vessels of the inflamed part can
be perceived. If the present observations shall be confirmed
by others, they will show more distinctly than any statements

2x2

676 FOURTH REPORT—1834.

hitherto on record, that the same holds true of the larger vessels:
supplying an inflamed part. Now, there are two changes in the
movement of the blood through the vessels of an inflamed part
which seem well ascertained by many observations, viz. re-
tarded movement or absolute stagnation (stase du sang) in many
of the small vessels most affected, even during the height of
the inflammation ; and accelerated movement in the neighbour-
ing vessels, with greatly increased transmission, in a given time,
through the whole veins of the part. This last change may,
perhaps, be reasonably ascribed to the relaxation of the vessels
giving increased effect to the impulse from the heart; but it
seems impossible to ascribe likewise to that relaxation of ves-
sels, the former, which is just the opposite change in the move-
ment of the blood ; and yet no modification of the action of any
of the vessels, except simple relaxation, can be detected.

. The fair inference from these facts therefore seems to be, that
the phenomena of inflammation are truly inexplicable by any
ehanges which occur, during that state, in the contractile power
of the vessels containing the blood ; and that, instead of seeking
for an explanation of these phenomena in the state of contrac-
tions of any of the solids, we ought rather to look for it in the
state of the attractions subsisting during the living state among
the particles of the blood, and between them and the surround-
ing solids. And this inference the author thinks might be sup-
ported by reference both to other facts in the history of im-
flammation, and also to many other phenomena of the living
body both in health and disease.

Report of Progress made in an Experimental Inquiry regard-

ing the Sensibilities of the Cerebral Nerves, recommended
* at the last Meeting of the Association. By Dr. MarsHaui
- Hatt and Mr. Brovueuton.

Some disagreement appears to exist amongst the results of the
investigations regarding the sensibilities of the cerebral nerves,
which demands further experimental inquiry. A series of ex-
periments has therefore been instituted at the request of the
Committee of the Medical Section, and the establishment of
Messrs. Field in Oxford-street, London, was selected for the
purpose of carrying the inquiry into effect ; the horse and the
ass, from their large size, being considered. as the most favourable
subjects for the free exposure of the nerves.

_ The properties of some of the cerebral nerves being admitted
upon other grounds than experimental proof, this investigation
was exclusively directed to the facial branches of the fifth pair

TRANSACTIONS OF THE SECTIONS. 677

‘of nerves, the hard portion of the seventh, the vagus, the spinal
accessory, the glosso-pharyngeal, the lingual, and the sympa-
thetic nerves. Upon the properties of the first, second, third,
fourth, sixth, and the soft portion of the seventh pairs of nerves
no doubt or discrepancy exists.

- It has long been known that the properties of the cerebral
nerves are various. Thus, one nerve governs the function of
motion; another that of some specific sensation, as of light or
sound; and these properties are held independently of each
other. To understand clearly the properties of nerves, it is also
necessary to apply the test of experiment to their roots; for
branches from two or more roots unite to form one nerve ap-
parently, which may then assume two distinct properties, that
is, the peculiar property of each root. This is exemplified in
the origin and distribution of the nerves of the face.

--The apparent discrepancies in the results of experiments
probably depend much upon the indefinite manner in which cer-
tain physiological terms have been employed. Thus, sensation
has been coupled with consciousness in some instances, and in
others it has been supposed to exist without consciousness. In
the present report the term sensation implies consciousness. It
is considered as identical with feeling, and when violently excited
it becomes pain. And this is manifested by general and in-
stantaneous efforts or struggles. These are, therefore, the signs
of sensibility.

Three modes of judgement have appeared as necessary to be
kept in view in the present inquiry in reference to the above de-
finition : 1

1. It was observed that when a nerve of unequivocal sensibi-
lity was pricked or pinched, an immediate and general struggle
followed. The facial branches of the fifth nerve are examples. :

2. That when a nerve as unequivocally devoted to motion is
pinched, there is an immediate contraction of the muscles which
that nerve supplies, and of no other muscles.

3. That on pinching the par vagum, neither of the pheeno-
mena above noticed occurs; but by continuing the compression
for a few moments, an act of respiration and of deglutition fol-
lows, with a tendency to struggle and cough. f

Of these three phenomena the first only is considered as in-
dicating the property of sensation, or the power in the nerve:
subjected to experiment to transmit sensible impressions.

- The movements in the third instance appear to arise from
secondary causes, the mechanical irritation of the nerve not
being attended with immediate consciousness.

<1. Experiments upon the. Facial. Nerves.—These nerves go-:

678 FOURTH REPORT—1834.

vern the actions of the face, and preside over the sensibilities of
its different organs and surfaces. The first function is performed
by the facial portion of the seventh nerve and a portion of the
fifth. The second function is performed by the large portion of
the fifth pair of nerves. Thus the fifth nerve possesses two di-
stinct properties of transmission, one voluntary, the other sen-
tient, in consequence of its having two distinct roots. One of
these roots, the largest, has a ganglion attached to it, and is ex-
clusively a sentient nerve. The smaller root has no ganglion,
is insensible, and governs the motions of those muscles which it
supplies. The first fact is easily gained by experiment, but the
second is admitted upon other grounds, for the smaller root can-
not be experimented upon in the living animal. It is to be ob-
served that the larger root of the fifth nerve is divided into three
branches, spread and ramified over the face, and frequently con-
nected in its ramifications with branches of the seventh nerve ;
so that unless the experimental tests be applied to distinct
branches, no certain response can be obtained as to their several
properties.

Pricking or pinching the trifacial nerve was attended with
instantaneous indications of consciousness ; when its branches
were divided, all sensibility ceased in the parts which they supply.
The lower divided ends made no response when bruised, but the
upper indicated sensation. The motions of the face, however,
still remained unimpaired, until the seventh nerve was divided
as near its origin as possible, when the organs which it supplies
became permanently motionless. When this nerve was slightly
pinched in its entire state, those muscles exclusively which it
supplies were seen to be convulsed, without any general effort ;
when the compression was increased, and continued for a few
moments, signs of uneasy respiration occurred. Pricking this
nerve with a needle and cutting through it produced no struggle

whatever, as is the case with the trifacial nerve. When the:

lower end of the nerve, after division, was irritated, no movement
followed; but on compressing the upper end, the same signs
were exhibited as when the nerve was irritated in its entire state.

2. Experiments upon the Nervus Vagus.—In the year 1820
Mr. Broughton experimented upon this nerve; the results were
published in the Quarterly Journal of Science of the Royal In-
stitution. It was found to be insensible when slightly pinched,
pricked, or divided. The present experimental investigation
confirmed this remark. It was also on the former, as well as
upon the recent occasion, clearly shown that, when a forcible
compression was continued a few momentsupon thenervus vagus,
arespiratory effort followed, and an act of deglutition, with a

TRANSACTIONS OF THE SECTIONS. 679

cough anda struggle. In the recent investigation it was observ-
able that when the nervus vagus was divided, mechanicalirritation
applied to the upper end of the divided nerve produced the same
signs as when the nerve was entire. Every repeated compres-
sion of this nerve (as was also the case with the seventh) pro-
duced corresponding respiratory struggles ; whilst a uniform,
uninterrupted compression caused no repetition of the pheno-
mena. An additional argument in support of the opinion that
these effects are independent of any sensible property in the
nerve itself is furnished by the fact that Dr. Marshall Hall has
found precisely similar effects to occur in the turtle after its de-
capitation, on pricking the jateral spinal nerves, whether of the
sentient or motory class.

3. Experiments upon the Spinal Accessory Nerve.—This
nerve having been pricked without any response, was then
slightly pinched and scraped ; when the sterno-maxillaris mus-
cle, the levator humeri, and other muscles of the neck exclu-
sively were seen to contract at each application of this mecha~
nical irritation. But when the forceps was applied firmly, and
continued a few moments, similar effects were produced as with
the vagus and the seventh. The branches of this nerve appeared
to be equally destitute of sensibility with the root. The com-
pression of the upper end, after dividing this nerve below its
bifurcation, was followed by no effects, unless the pressure was
made opposite the giving off of the anterior branch, when the
same phenomena occurred as were exhibited in the entire nerve.

4. Experiments upon the Glosso-Pharyngeal Nerve.—When
this nerve was pricked, scraped, or divided, no response was ob-
served. The muscles of the root of the tongue were most pro-
bably set in motion by the compression of this nerve at inter-
vals; but no opportunity occurred of bringing this part of the
tongue into view. Neither in its entire nor divided state did any
struggle arise from the continued compression of this nerve,
which is therefore regarded as one simply of muscular motion. .

5. Experiments upon the Ninth Nerve.—The sensible sur-
face of the tongue is supplied by the ganglionic portion of the
fifth nerve, whilst the muscles of its fore part are furnished with
branches from the ninth nerve. No sign of sensation was
evinced by mechanically irritating the trunk’ of this nerve, and
its division was unattended with any sign of feeling or pain.
But upon pinching it slightly at intervals, those muscles which
it supplies, on the same side of the tongue, were convulsed. If
the nerve was forcibly compressed, a slight gulp followed. When
the nerve was divided, pinching the upper end of it was not fol-
lowed by any muscular contractions.

680. FOURTH REPORT—1834, |

6. Experiments upon the Sympathetic Nerve,—No experi-
ments upon this nerve have hitherto exhibited any signs of sen-
sation or muscular motion of any kind whatever. Its division
is never followed by any visible effect.

Remarks.—By these observations some researches of other ex-
perimenters stand confirmed, whilst others are contradicted; the
necessary consequence of discrepancies, often arising from the
different modes of applying certain terms. Although the my-
sterious properties and actions of the nerves may never be com-
pletely unravelled, yet much has been effected by the successive
and combined efforts of physiologists of different ages and
countries.

The present investigation leads to theassumption, that one only
of those nerves which derive their roots from the brain itself
is, according to the definition laid down, a nerve of sensa-
tion. This is the larger and ganglionic division of the fifth
nerve, whereby animals are enabled to examine by touch and to
feel.

With regard to the other nerves subjected to experiment in
this inquiry, none of them appear to possess in themselves any,
power to excite consciousness or feeling directly. Some of them
are simply nerves of motion, and they transmit no other impres-
sions but such as excite local muscular motion, limited to the
muscles which they supply. Others, again, seem to possess a
property of a different description from either of the two former
kinds. One of these, the eighth for example, appears to be so
intimately connected with the respiratory function as to be capa-
ble of influencing it in a most remarkable degree, without ex+
hibiting any sign of sensation in itself, or of simple and direct
muscular contraction.

It is a most remarkable fact, that when a nerve which ae
ences respiration is divided, and the upper division is bruised or
compressed for a few seconds, the same effects occur as when
the irritation is applied to the entire nerve. This phenomenon
affords matter of curious and interesting speculation with regard
to the relations which subsist between the nervous and the re-
spiratory functions.

The further pursuit of this inquiry may lead to some further
development of facts hitherto exposed in some instances to doubt
and controversial discussion.

Dr. Hall was necessarily absent at one of the experiments,
that on the ninth nerve; but he feels perfectly satisfied with,
the joint testimony of Mr. Field and Mr, Broughton.

TRANSACTIONS OF THE SECTIONS. 681

On the Effects of Poisons on the Animal Ciconomy.
By Dr. Hopexin and Dr. Riiprett.

Dr. Hodgkin and Dr. Riippell, who were appointed at the
Cambridge Meeting of the Association to draw up a report for
the Medical Section respecting some points connected with the
effect of poisons, stated that they were not as yet prepared. to
present the results of their inquiries ; but Dr. Hodgkin informed
the Section that his colleague had paid very considerable atten-
tion to the subject, although his extensive materials were not put
together in a form to be offered to the Association. Dr. Hodgkin
also laid before the Section the Fasciculi published by Dr. Rup-
pell, and read a preliminary paper reporting the progress which
he had himself independently made, illustrated by various draw-
ings by C. J. Canton, and wax models by Joseph Towne.

The points alluded to in this preliminary essay were the na;
tural structure of the lining membrane of the stomach ; the
differences which it presents in its normal and abnormal state
in respect of colour, consistence, and equality of surface ; the
condition of the mucous membrane of the stomach with respect
to follicular appendages ; some. indications which may be drawn
from the situation of that part of the stomach which has been
most injured by ingesta; and the different extent to which various
noxious agents and their effects may be traced along the course
of the alimentary canal.

The drawings and models exhibited the appearances observed
in numerous human stomachs, occasioned by disease, congestion,
arsenic, hot water, sulphuric and prussic acids ; and the effects
of hot water, alcohol, arsenic, corrosive sublimate, and oxalic
acid on dogs or horses.

Inquiries into the Varieties of Mechanism by which the Bloog
may be accelerated or retarded in the Arterial and Venous
Systems of Mammalia. By Dr. T. J. AIrKin.

The attention of the Section was particularly directed to four
modifications of arterial distribution, as indicated, (1.) by the an-
gle at which a branch comes off from its trunk; (2.) the direc-
tion of the vessel; (3.) the subdivision; and (4.) the formation
of plexus. ;

In illustration of the first, or angle of origin, Dr. Aitkin ex-
hibited a preparation of the aorta of the tiger, in which the supe-
rior intercostals arose at an acute, the middle at a right, and the
lower. at an obtuse angle; from which he inferred that the force

682 FOURTH REPORT—1834.

and velocity of the blood are rendered equal through the whole
series. In speaking of the direction of the vessel, he adverted
to the tortuous entrance of the internal carotid and vertebral
arteries into the skull in the human subject, and showed that
it is still more remarkable in the horse, which in feeding requires
to have the head for a considerable time in the dependent pos-
ture. But the best examples of the tortuous, or serpentine,
course are to be seen in the spermatic arteries of the Mammalia.
This mechanism, the author contends, adapts the circulation to
the various positions in which organs may be placed, and to
their states of action and repose. In speaking of the third mo-
dification, or the subdivision into numerous long branches, he
particularly alluded to the observations of Sir A. Carlisle with
respect to the arteries of the sloth, and showed that a similar
ramification is found in the hedgehog, both in the arteries of
the panniculus carnosus and of the mesentery. Of the last mo-
dification, the plexus, he showed examples in the rete mirabile
of Galen in the internal carotid, and of Hovius in the ophthal-
mic artery, of the Hwminantia. He inferred that this structure
prevents valvular turgescence, which would otherwise occur
during the long period these animals keep their head in the de-
pendent position while browsing. He also showed that a rete
mirabile exists in the ophthalmic artery of the seal and goose,
and considered it probable that in them it is conducive to the
alternate adaptation of the eye to vision in air and water. He
described the remarkable plexiform arrangement which exists
in the mesenteric arteries and veins of the hog; and instituted
a comparison between those vessels in carnivorous and herbivo-
rous Mammalia, concluding that these modifications are in con-
formity with the transmission of blood through the liver, the
rapidity of the peristaltic motion, and the power of nutrition.

Observations on the Anatomy of the Blood-vessels of the Por-
poise. By Dr. SHARPEY.

1. The artery of the anterior extremity or fin of the porpoise,
corresponding to the brachial in man, presents a peculiarity of
distribution similar to that observed in the arteries of the limbs
of slow-moving animals. The vessel, after crossing the first
rib, divides into a great many long and small arteries, which
run nearly parallel, but repeatedly anastomose, so as to form an
elongated plexus, consisting at its thickest part of at least forty
vessels. This plexus continues as far as the distal end of the
humerus, where its component vessels again unite into five or
more larger arteries, which run along the radius and ulna.

TRANSACTIONS OF THE SECTIONS. 683

2. Convoluted arterial plexuses, similar to those in the thorax
and vertebral canal of this and other cetaceous animals, (in
which situation they were particularly described by Mr. Hunter
in the Philosophical Transactions for 1787,) are formed also by
several arteries of the neck and head.

- 3. Several arteries show a tendency to divide into long parallel
branches, of which the arteries of the bladder, vagina, and ute-
rus offer a striking example.

4. The mode of division of the posterior or caudal portion of
the aorta differ somewhat from the description given by Cuvier,
in as much as that vessel is not wholly resolved into small
branches, which unite to form it anew, but is only diminished
in size, and concealed in the midst of a plexus formed by its
branches, from which, after becoming larger, it again emerges.

5. The veins as well as the arteries present in several regions
of the body a plexiform arrangement, and in some situations
plexuses of both kinds of vessels are associated or mixed with
one another.

6. The artery corresponding to the internal carotid, which at
its origin is as large as in man, diminishes in a tapering manner,
and without giving off branches, till it enters the skull, where it
is scarcely thicker than a pin.

On the Use of the Omentum. By Mr. Dick.

From a comparison of the structure of this organ in the horse
and in the sheep,—in the former the omentum being small,
the intestines are fixed, and undergo comparatively little change
of place,—the author inferred that the omentum might serve,
by interposition between the intestines and abdominal parietes,
to facilitate motion.

On the Infiltration of the Lungs with hlack Matter, and on
hlack Expectoration. By Dr. W.'THomson.

The author particularly noticed the cases of this singular in-
filtration, occurring in coal-miners, iron-founders, and other
workmen exposed by their employment to the inhalation of
carbonaceous gases and powders. He referred to a variety of
published and unpublished communications on the subject, and
exhibited a number of preparations and drawings illustrative of
the appearances, nature, and seat of the disease.

684 , FOURTH REPORT—1834, »

~

On Excision of diseased Joints. By Professor Symp.

‘The author explained that his object was not to discuss the
merits of the operation, to institute a comparison between it
and amputation, to establish the principles which seem most
conducive te its safe and effectual performance, or to enter into
any more particular details concerning the different modes of
procedure which are requisite for the different joints, but merely
to prove by actual demonstration that the two great objections
which have been urged against the operation, however specious
in theory, are not supported by experience. These objections
he stated to be, 1st, that the diseased bone could not be com-
pletely removed by excision, so as to afford a perfect and per-
manent cure ; and, 2ndly, that the limb preserved by the opera-
tion must be nearly or altogether useless to the patient. In reply
to the first of these objections, he produced a woman, 44 years
of age, who eight years ago had the shoulder-joint removed,
on account of caries in the head of the os humeri which had
existed for six or seven years, and reduced her to an extreme
degree of weakness. The head of the bone, completely hollowed
out by disease, was exhibited, and the woman showed that while
her general health and strength were quite restored, there was
hardly any perceptible difference in the utility of her arms. He
also placed before the meeting a boy who had his elbow-joint
excised between five and six years ago, on account of caries
which had existed twelve months. The articulating extremities
of all the bones entering into the formation of the joint were
exhibited ; and the boy proved, by free and varied movements
of his arm, that he retained completely the power of flexion, ex-
tension, and rotation of the elbow, without any diminution of
strength. In reply to the second objection, he stated that it
seemed to be grounded on the difficulty of conceiving how the
tendons, after being cut away from their attachments, could
again adhere to the bones so as to move them in obedience to
the action of the muscles, and on the erroneous idea which ge-
nerally existed as to the changes that occur between the osseous
surfaces subsequently to the operation. In order to show that
when tendons have their attachments divided they readily ac-
quire new ones, so as to perform their usual offices, he brought
forward a patient who had suffered Chopart’s amputation of the
foot for caries of the tarsus and metatarsus, and who conse-

uently, having only the os calcis and astragalus remaining, had
had all the tendons opposing the extensors of the ankle divided,
but who nevertheless retained completely the power of bending

TRANSACTIONS OF THE SECTIONS. 685

and extending the joint. In respect to. the changes which take
place between the osseous surfaces after the operation of exci-
sion, he stated that anchylosis could not be induced unless the
limb was kept perfectly motionless ; and that the bones almost
invariably became united, not by any structure analogous to a
joint, but by means of a fibrous substance possessing such
thickness, strength, and flexibility as to preserve the shape and
firmness of the limb, and allow a proper degree of motion in
the seat of the joint. A specimen of this structure was exhi-
bited in the case of an elbow-joint which had been dissected
about twelve months after the performance of excision. Having
made these remarks, he submitted to the meeting the positive
evidence afforded by several persons in addition to those already
exhibited, in all of whom the operation of excision had pre=
served limbs hardly if at all less useful than they were before
suffering from the disease. :

Abstract of a Registry kept in the Lying-in Hospital of Great
- Britain-street, Dublin, from the year 1758 to the end of
1833. By the late Dr. Joseru CuarKke, of Dublin.

. This communication illustrated in a very striking manner the
importance of thorough ventilation, and the great diminution of
mortality among the children in this hospital since that object
has been attended to. It appears that during the 75 years men-
tioned, relief has been afforded to upwards of 129,000 poor wo-
mén; that in 1781 every sixth child died within nine days after
birth, of convulsive disease ; and that after means of thorough
ventilation had been adopted, the mortality of infants, in five
successive years, was reduced to nearly one in twenty.

STATISTICS.

aa .
._ Statistics of Glasgow. By Jamzs CievAnD, LL.D.

r™\

~The parochial register of births in Glasgow being so defective
that no reliance could be placed on it, Dr. Cleland obtained the
necessary information in the following manner :

Concerning Births. —On 6th December 1829, he addressed a
letter to each of the seventy-five clergymen and lay pastors in the
city and suburbs who baptize children, requesting to be favoured
with the number they might baptize from 14th December 1829, to
15th December 1830, both days inclusive, being the year previous

686 FOURTH REPORT—1834.

to the last Government census. The letter was accompanied by a

book, in which the sexes and the particular parishes in which the

parents resided were to be inserted. He also requested the
various Societies of Baptists, the Society of Friends, and Jews,
and others, who do not dispense the ordinance of baptism of
infants, to favour him with the above particulars relative to
children born to members of their societies, and at maturity. He
had the satisfaction of receiving returns from the whole; asalso
an account of the children of parents who, while disapproving
of infant baptism, did not belong to any religious society; when

it appeared that in the city and suburbs there were 6397 children

baptized or born to Baptists, &c., and that of that number there

were only 3225 inserted in the parochial registers, leaving un-

registered 3172.

Concerning Marriages.—Although in Scotland there is no

marriage act as in England, restricting the solemnization of
marriages to clergymen of the Established Church, this ordinance
can only be regularly celebrated by persons duly called to the
pastoral office, and not until a certificate of the proclamation of
banns has been produced. "
Persons irregularly married are deprived of the privileges of
the Church till they appear before the Session, acknowledge their
fault, and are reponed. From this circumstance, in connexion
with the solicitude of the female and her friends to have the mar-
riage registered, the marriage register of Glasgow and its suburbs
may be held as correct for all statistical purposes. )
Concerning Deaths.—The deaths are ascertained by the
number of burials. The burying-grounds in the city and
suburbs are placed under the management of fourteen wardens.
These officers, who attend every funeral, enter in amemorandum
book, at the grave, the name, age, and designation of the person
buried, along with the amount of fee received, and the name of
the undertaker. Having taken these and other particulars, the
wardens afterwards enter the whole in a book, classified con-
formably to a printed schedule drawn up by Dr. Cleland. At
the end of the year they furnish him with an abstract from their
books; and it is from a combination of these abstracts that he
ascertains the number of deaths at the various ages. The abs-
tract includes still-born children, and the deaths of Jews and
members of the Society of Friends, who have separate burying-
laces.
: Concerning the Population of Glasgow and its Suburbs.—
Having been appointed to take the sole charge of conducting
the enumeration and classifying the population of the city of
Glasgow and suburbs for the Government census of 1831, the

—

TRANSACTIONS OF THE SECTIONS. 687

author employed twelve parochial beadles, nineteen mercantile
clerks, and one superintendent of police to take up the lists. Be-
fore the books were prepared, an advertisement was put in the
ten Glasgow newspapers, requesting theinhabitants to favour him
with their suggestions as to classification ; and before the list-
takers commenced their operations, bills were posted on the
public places and dwelling-houses of the city, informing the in-
habitants of the nature of the inquiries, and that they had no
reference to taxes; and, moreover, that noncompliance, or
giving a false return, subjected them toafine. When the books
were returned, the public, through the medium of the press,
were requested to call at an office, appointed for the purpose,
and to correct any omission or error which might have been
made in their returns.

The list-takers having made oath before the Lord Provost
that the name of every householder in the district assigned to
them had, with the other particulars, been faithfully entered in
a book, the author proceeded to classification, and to the forma-
tion of tables and abstracts for each parish, containing numerous
details not required for the Government digest.

Bill of Mortality from 14th Dec. 1829, to 15th Dee. 1830.

A General List of Births, Baptisms, Marriages, and Burials, within the ten
Parishes of Glasgow, and the Suburban Parishes of Barony and Gorbals.

Births and Baptisms detailed thus: Of whom have died. ©

‘ i Males. Females. Total- ae Males.Females.Total.
Returns from Clergymen tiL-DOrN .easeseeeee vee 246. 225 1
and Lay Pastors. } 3281 31166397 Under one year...... 463 414 e
Add still-born, from do. » 246 225 471 L and under 2, ae 307 623
3 —_ —— ___ — 5. 2 500
Total 3527. 3341 6868 Srey EA, 7k oa! 253
Of this number there were 1678 1547 3995 10 —— 20, 144 132 276
registered only 20 —— 30, 189 145.334
Suh te ids, === ES a _ a 169 144 313
‘umber unregiste ex- iS —_— 50, 184 164 348
Aare uta bom... 5 1603 15693172 50 — » 177 175 352
” — — 60 —— 70, 168 171 9339
The children were baptized as follows, viz. CO arm Fh ie 109 «102s 211
By Clergymen of the Church of Scotland ......... 3123 a" "SD, 55 58 113

By do. ofthe Secession Church wwe. 664 BD iy Hite B55, 48 48
By do. of the Relief Church ........... 671 8 —— 90, 24 26 50
By do. of the Roman Catholic Church... 915 Ds > 9 10 19
By do. of the Scotch Episcopal Church, 9 —— 100, 3 6 9
Independents, Methodists and other denomi- 1024 100 0 1 1
nations, including births among Baptists, So- —_—_— —_ —
ciety of Friends, Jews, &c. Total2701 2484 5185

Total 6397

Marriages engrossed in the registers of the City, Barony, and Gorbals.

In the City.>........000.008) (857
Barony saccccceseecacccssese 691
Ser Te a SE RRS

Total 1919

688. FOURTH REPORT—1834.

Burials engrossed in the registers of the City, Barony, and Gorbals
Burying-grounds.

Males. Females. Total.

January .:...s6 273 268 541
February ......... 226 223 449
Marelt 22.35. nee. 218 207 425
Apes 208 184 392
May sass tls 185 175 360
fh ph ae a 200 178 378
DULY Fada tdes a paeerrrt 194 182 376
TRUSTING so nena <5 ds ot 232 206 438
September ...... 240 229 469
October ........... 236 184 420
November........ 234 189 423
December......... 255 259 514

—[—

Total 2701 2484 5185

Total Burials within the City...... 1951
Tota! Burials in Barony Parish... 1831
In Gorbals Burying Ground...... 1403

Total Burials in City and Suburbs 5185

Classified List: of the Ages of Persons in Glasgow and the
Suburban Parishes of Barony and Gorbals.

Ages of persons in Glasgow and in the suburban parishes of
Barony and. Gorbals, for the census of 1831.

15 20 | 30 40 | 50 | 60 | 70 | 80 | 90} 100
Under 5. to | to to’ | to | to | to | to | and} Total.
20. | 30. 10. | 50. | 60. | 70. | 80. | 90. | 100./upw.

ome a | | i

|
Males, 15422 8489/15177 12179] 8685) 5549|3228/1090| 260} 26) 1
Females, 14855 12256 ware 9329] 6099|3692|1502) 385

Total 30277 |25707|21211 20745/38185 5 | 202426
“|

Concerning the probability of Human Life in Glasgow.—
The author states that he endeavoured to obtain from the
medical gentlemen-a note of the diseases of which their patients
died during the period in which he had requested the clergy to
give a note of the baptisms, but succeeded only with a small
portion of the members of the faculty, and suggests that every
attempt to accomplish this object, so interesting in a medical
point of view, will fail, till a compulsory act regarding parochial
registers be obtained.

That Glasgow is a place of average health for statistical pur-
poses may be inferred from the daily state of the weather, which
the author published in 1831, by which it appeared that the

TRANSACTIONS OF THE SECTIONS. 689

average quantity of rain which fell yearly during thirty years
preceding that period, amounted to rather less than twenty-three
inches. But more particularly, the degree of health may be
known, and tables formed for ascertaining the probability of
human life, from a series of the Mortality Bills, where the age
of the living and that of persons who have died are narrated in
connexion with the population, and a table of longevity for Scot-
land which the author prepared in 1821; by which it appeared
that, on an average of all the counties of Scotland, there was
one person eighty years of age for every 143% of the popu-
lation; while in the county of Lanark, with a population of
3163790, including 263,046 who live in towns, viz. in Glasgow
202,426, and in other towns 60,620, there was one such person
for every 169;21,, showing a degree of health in the population
of Glasgow nearly equal to that of the whole of Scotland.

- The following results have reference to Glasgow and its sub-
urbs, which partake of a mercantile and manufacturing popula-
tion, or something between Liverpool and Manchester, the town
population being 198,518, and the rural 3908.

In 1831 the population was found to be 202,426, the burials
5185, and the rate of mortality consequently 39;4,. The births
being 6868, there is one birth for every 29747, persons. The num-
ber of marriages being 1919, there are 3,47, births to each

100

marriage, and one marriage for every 10543, persons, The num-

ber of families being 41,965, there are 4,82, persons to each
family. It is very satisfactory to know that with the same
machinery in 1821, the population being 147,043, the burials
3686, the rate of mortality was ascertained to be 39-83%, or in
other words as near as may be to the mortality in 1831. By
reference to the Bills of Mortality between the years 1821 and
1831, similar results will be found.

It appears from all the authentic Bills of Mortality the author
has ever seen, that there are more males born than females, but
taking the population above fifteen years the number of females
preponderates. The following results for Glasgow are derived
from the census of 1831 :

Births—Males, 3527 Females, 8341 excess of Males, 186
Males under 5 years, 15422 Females, 14855 excess of Males, 567
Males under 10 years, 28549 Females, 27435 excess of Males, 1114
Males under 15 years, 39040 Females, 38155 excess of Males, 885
Males under 20 years, 47529 Females, 50411 excess of Females, 2882
“Males under 30 years, 62706 Females, 73419 excess of Females, 10713,
Males—entire Population, 93724 Females, 108702 excess of Females, 14978
Burials—Males, 2701 Females, 2484 excess of Males, 217

ADDENDA FOR 1831. Z

Description of Householders.—Married men 30,032.Widowers
1790. Bachelors 1437. Male householders 33,259. Widows

1834. 2¥

690 FOURTH REPORT—1834.

wee

6824. Spinsters 1882. Female householders 8706. Total
families 41,965.

Countries to which the Population helongs.—Scotch 163,600.
English 2919. Irish 35,554. Foreigners 353. Total 202,426.

Religion of thePopulation.— Established 104,162. Dissenters,
Episcopalians and Jews 71,299. Roman Catholics 26,965.
Total 202,426.

Number of Paupers and expense of maintaining them.—The
number of paupers in the city and suburbs being 5006, and the
population 202,426, there is one pauper for every 40;4%,.

The number of paupers being 5006, and the sum expended
for their maintenance or relief 17,2817. 18s. 04}d., shows the cost
of each pauper to be 3/.9s.0}d. If the sum for the relief of
paupers were equally paid by the whole non-recipient population,
the proportion to each would be one shilling and ninepence and
a small fraction. The sum of 17,281/.18s.03d. includes the
entire expenditure of the out- and in-door paupers, surgeon’s
salaries, medicines, clothing and educating children, maintaining
lunatics, funeral charges, &c.

The cost of each pauper in St. John’s parish is 3/. 8s. 10$d.
The poor in that parish are maintained or relieved on the paro-
chial system introduced by Dr. Chalmers in 1820, 7.e. by the
Kirk Session from its own resources, without receiving any part
of the general assessment for the poor, although the inhabitants
of St. John’s parish are assessed for the maintenance of the poor
generally in the same manner as other citizens.

Analysis of the Report of an Agent employed hy the Manchester
- Statistical Society in 1834, to visit the Dwellings and ascertain
the condition of the Working Population in Police Division
No. 2, and in the first Subdivision of Police Division No. 1,
of the Town of Manchester*. Communicated by the Society.
The agent having been refused admittance into some houses,
and the occupiers of others being absent and their dwellings
closed, his report only extends to 4102 families, but which num-
ber comprises all the labouring population within this district
into whose houses he obtained access. ”

The Report on the condition of the dwellings must be consi-
dered merely as the general impression of the agent, an intelli-
gent Irishman, who was himself a hand-loom weaver, and who
in this classification has been principally guided by the appear-
ance of cleanliness or otherwise in the dwellings.

All the other entries are stated from the answers given by the
parties themselves.

* The population of this portion of the town is (according to the census of
1831) 42,135 or 8932 families. Itis a district inhabited more than any other

in the town by the working classes and by those of the poorest description. It
was on that account determined to commence the investigation in this quarter.

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692 FOURTH REPORT—1834.

Notice of the ‘ New Statistical Account of Scotland.’ By Mr.
Gorpon, Secretary to the Committee.

There is now in progress and in the course of publication a
periodical work descriptive of the parochial statistics of Scot-
land at the present time, under the title of Zhe New Statisti-
cal Account of Scotland.

A similar work was produced upwards of forty years ago by
the exertions of Sir John Sinclair, Bart., to whose enlightened
enterprise so many of the most useful institutions in this country
owe their existence or their improvement.

The two works resemble each other in the important circum-
stance that every parish has been treated by itself, and that the
parochial accounts have been furnished by the ministers of the
respective parishes. They resemble each other, also, in incor-
porating, as a relief to matters more strictly statistical, detached
notices of the chief historical events, of the eminent characters,
and of the remains of antiquity connected with the parishes.
They differ from each other, 1st, in the arrangement, which in
the new work presents the parishes placed together under their
respective counties, while the matter of each parochial account
is treated under the same heads in uniform succession ; 2nd, in
the greater expansion which the whole department of natural
history, under the several branches of meteorology, hydrogra-
phy, geology, zoology, and botany, has received in the new
work; and, 3rd, in the statistical details themselves, which,
from the changes that have taken place within the last forty
years, are found to be so different from those of the former work
as to render the present almost entirely new.

It may be added, that each parochial account in the new work
observes the following general divisions: 1. Geography and Na-
tural History; 2. Civil History; 3. Population; 4. Industry ;
5. Parochial GEconomy. That the first and second. of these
divisions have the advantage of elucidation from county maps ;
that to each county there is appended a tabular summary of
whatever particulars belonging to the several parishes are capa-
ble of being exhibited in a tabular form, together with some
general observations applicable to the whole county, and not an-
ticipated under individual parishes.

To this useful labour the clergy of the Church of Scotland
have on this occasion been invited, not, as formerly, by an in-
dividual, but by the Society instituted to promote the interests
of their sons and daughters ; and it is honourable to the clergy
that they have not only been cordially disposed to return to the

TRANSACTIONS OF THE SECTIONS. 693

task, but that they have returned to it with a manifest increase
of accomplishment for every part of its performance.

Three numbers of the work already published are now pre-
sented to the Association. Without specifying any portion of
the statistical results which they have established, it may be
noticed generally that the accounts are so uniformly complete
on certain essential points, as to have furnished a set of tables,
representing in every parish the quantity of cultivated and un-
cultivated land ; the amount of agricultural produce ; the dif-
ferent descriptions of the population ; the ecclesiastical state of
the parishes, as indicated by the various numbers of the several
religious denominations, with the provisions for their respective
clergy; the state of education, as shown by the number of
teachers, and of the young in the course of receiving instruction ;
the number of the poor, and the amount of the provision made
for them from the different sources of voluntary contribution,
endowment, and assessment. At the same time, these are but
the items which admit of being presented in a tabular form, and
there is besides in each account a great variety of interesting
notices on the several branches of natural and civil history.

Remarks on the Statistical Reports regarding Agriculture.
By Earl Fitzwiuram, F.R.S.

The expediency of furnishing more minute details with respect
to the agricultural part of statistical reports was suggested in
these remarks. The statements ought to show not only the
total amount of land in cultivation, but also the quantities allotted
at the time of the inquiry to the various kinds of produce, the
number and value of agricultural implements, the number of
draught and other cattle, and similar details. Lord Fitzwilliam
stated that he had succeeded in obtaining such returns for some
parishes in his own neighbourhood, and observed, that accurate
and minutely detailed information for only a small number of
places would furnish more safe grounds for correct inferences
than could be obtained from a more widely extended, but less
precise inquiry. ;

The Rey. E. Sran.ey undertook to prosecute such an inquiry
in his own parish (in Cheshire), and to furnish the results at the
next meeting of the Association.

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INDEX.

?

Proceepines of the General Meeting,

oti

General Committee, xxvi.

Proceedings of the Committee of Re-
commendations, xxx.

of the Committees of Science,

Xxxii.

of the Sectional Meetings, xli.

Appropriation of Funds, x].

Abercrombie (Dr. ), address at gene-
ral meeting, xxiii; on the import-
ance to the medical profession of
the study of mental philosophy, 670.

Acetic acid, proportions of anhydrous
acid in, 871.

Achromatic object-glasses, on the con-

_ struction of, 593.

Achromatism of the eye, 548.

Addams (R.) on a new phenomenon
of sonorous interference, 557.

Adie (A. J.) on the expansion of stone
by the application of heat, 569.

Agassiz (M.) on the different species
of the genus Salmo, 617.

on thefossil fishes of Scotland, 646.

Agriculture, on statistical reports re-
garding, 693.

Aitkin (Dr.) on the mechanism by
which the blood may be accelerated
or retarded, 681.

Alison (Dr.) on the vital properties of
arteries leading to inflamed parts,
674.

on the irritability of muscles in
living animals, 673.

Alluvial deposits, 8; alluvial terraces,
10; ancient alluvium, 18.

Amber, on a remarkable specimen of,
574.

America (North), on the geology of, 1.

, physical geography of, 1

Anatomy, 667.

Andes, on the ancient inhabitants of
the, 628.

\

—~+>—_

Andrews (T.) on some caves in Rath-
lin and adjoining coast of Antrim,
660.

Anhydrous acid, proportions of in
acetic acid, 571

Animal Kingdom, on the primary
types of form and other leading di-
visions in the, 149; on the several
classes in the, 159.

Annulose animals, present state of
knowledge respecting, 185, 608.

Antimony, chemical composition of
the crystallized oxichloride of, 587.

Arnott (G. A. W.) on the Coceulus
- Indicus of commerce, 597.

Arteries leading to inflamed parts,
vital properties of, 674.

Atmosphere, on the quantity of car-
bonic acid in the, 583.

Attraction, capillary, on’ the theory
of, 253.

Barometer, on a peculiar oscillation of
the, 569.

Bell (Sir C.) on the proper method
of studying the nervous system,
667.

Berwickshire, geology of, 624.

Blood, on the state of our information
respecting the, 116.

, on the powers which circulate it,
129.

——, on the mechanism by whieh it
may be accelerated or retarded, 681.

Blood-vessels of the porpoise, anatomy
of the, 682.

Botany, 596.

Brewster (Sir D.) on a remarkable
specimen of amber, 574.

on the value of optical charac-
ters in the discrimination of mineral
species, 575.

Brisbane (Sir ‘T. M.) on an apparent
anomaly in the measure of rain, 560.

Broughton (Mr.) on the sensibilities
of the cerebral nerves, 676.

696

Brown (Dr. R.) on the plurality and
development of embryos in the
seeds of Conifere, 596.

Bryce (J.) on some caverns containing
bones, near the Giant's Causeway,
658.

Canals, on the mean velocity of water
running in, 424.

Capillary attraction, on the theory of,
258.

Carbonic acid in the atmosphere, on
the quantity of, 583,

Caverns containing bones, near the
Giant’s Causeway, 658.

in the island of Rathlin and ad-
joining coast of Antrim, 660.

Challis (Rev. J.) on the theory of ca-
pillary attraction, 253.

on some facts relating to the
composition of the colours of the
spectrum, 544.

Chemical equivalents, application of a
vernier to Wollaston’s scale of, 596.

Chemical products, new, 582.

Chemistry, 571.

Christie (Prof.) on a peculiar and well-
defined light, in the form of aray,
from the sun, 566.

Chronometer, with a glass balance-
spring, 595.

Clark (Dr.) on the application of the
hot blast to the production of cast

iron, 578.

Clark (Dr. W.) on animal physiology,
9

5.

Clarke (Dr. J.), abstract of a registry
kept inthe Lying-in Hospital, Dub-
lin, 685.

Cleland (Dr.), statistics of Glasgow,
686.

Clouds, nature and origin of, 564.

Coal-fields of Scotland, on. the, 640.

Cocculus Indicus of commerce, 597.

Coleopterous insects of Sutherland,
615.

Colours of the spectrum, on some facts
relating to the composition of, 544.

Combustion, pheenomena and products
of a low form of, 588.

Conifere, plurality and development

- of embryos in the seeds of, 596.

Contagion, on the laws of, 67.

Copper vein, on the electricity of a,
572.

INDEX.

Crustacea, state of our knowledge of
the, 191.

, on the transformations of the,
608.

Crystals, oblique prismatical, on the
positions of the axes of optical elas-
ticity in, 556.

>

Dalyell (G.) on the propagation of
certain Scottish zoophytes, 598.

Daubeny (Dr.) on excretions from the
roots of vegetables, 598. “i

Dent (E. J.) on a chronometer with a
glass balance-spring, 595.

Dick (D.)on the construction of achro-
matic object-glasses, 593.

Dick (Mr.) on the use of the omentum,
683.

Diluvial action over North America,
14. 2

Dipping-needle, method of observing
the dip and the force by the same
observation, 557.

Distillation, destructive, examination
of the products of, 591.

Dunn (J.) on a new klinometer and
portable | surveying . instrument,
594,

Dynamics, application to, ofa, general
mathematical method previously.ap-
plied to optics, 513. i

Elastic bodies, imperfect, on the, col-
lision of, 534. , ’

Electricity of the copper vein in Hnel
Jewel mine, on the, 572. —,

Embryos, on their plurality and. de-
velopment in the seeds of Conifere,
596. :

Endemics, their production and causes,
88

Entomology, 205, 615.

Epidemics, their general, phenomena,
and dependence on atmospheric
changes, 90. ;

Expansion of stone by the application
of heat, 569.

Eye, on the achromatism of the, 548.

Fitzwilliam (Earl) on. statistical re-
ports regarding agriculture, 693.
Fomites, 79. are
Forbes (Prof.), address at General

Meeting, xi.
—— on a new sympiesometer, 593.

‘INDEX.

Fossils, 23, 41, 61, 646, 652, 65+, 660,

- 666. fj

Fox (R. W.) on the electricity of the
copper vein in Huel Jewel mine,
572.

Functions, calculus of principal, 513 ;
-conjugate, 519; exponential, 523.

Geography, physical, of North Ame-
rica, 1.

Geology of Berwickshire, 624.

of North America, 1.

of the

the South of Scotland, 650.

of the Orkneys, 644.
of the Pentland Hills, 649. -

, on the change of level of the

land and sea in Scandinavia, 652.

,on marine shells of recent spe-

cies, at considerable elevations, 655.

, on some caverns near the Giant’s

Causeway, in the island of Rathlin,

and the adjoining coast of Antrim,

659, 661.

, on the coal-fields of Scotland,

639.

, on the limestone of Closeburn,

651.

, on the old red sandstone and the

formations beneath it, 652.

, on the ossiferous beds of the

Forth, Clyde, and Tay, 642.

, on the relations of mineral veins
andthe non-metalliferous joints’ in
rocks, 655.

Gilbertson (W.) on marine shells of
recent species, at considerable ele-
vations, near Preston, 654.

Glands, orbital, in birds, 609.

Glasgow, statistics of, 685.

Gordon (A.) on the polyzonal lens,
595.

Gordon (Mr.) on the ‘ New Statistical
Account of Scotland’, 692.

Graham (Prof.) on hydrated salts and
metallic peroxides, and on the doc-
trine of isomerism, 579.

Graves (J. T.) on the theory of expo-
nential functions, 523.

Gray (W. jun.) on the quantities of
rain falling at different elevations
above the surface of the ground at
York, 560.

Greenock (Lord) on the coal-fields of

- Scotland, 639.

great mountain’ range of |

697

Gregory (Dr.), abstract of Dr. Reich-
enbach’s discoveries in destructive

- distillation, 591.

Gulf of Mexico, raised estuary forma-

‘ ‘tions of the, 13.

Hail, origin of, 566.

Hailstone (Rev. J.) on a peculiar os-
cillation of the barometer, 569.

Hall (Dr.) on the sensibilities of the
cerebral nerves, 676:

Hamilton (Prof.) on the application
to dynamics of’ a general mathe-
matical method previously applied
to optics, 513. i

on conjugate functions, or alge-
braic couples, as tending to illus-
trate the doctrine of imaginary
quantities, 519.°

Harcourt (Rev. W. V.) on the effects
of long-continued heat on mineral
and organic substances, 576.:

Heart’s action, cause of the, 137. _.

Heat, expansion of stone by, 569.

, long-continued, its effects on mi-

neral and organic substances, 576.

, on the repulsion excited between
surfaces at minute distances by the
action of, 549.

Henry (Dr. W.) on the laws of con-
tagion, 67. "y
Hibbert (Dr.) on the ossiferous beds
of the Forth, the Clyde, and the

Tay, 642. ; \

Hodgkin (Dr.) on the effects of poi-
sons on the animal ceconomy, 682.

Hodgkinson (E.) on the collision of
imperfectly elastic bodies, 534. —

Howard (L.) on the difference of the
quantity of rain at different heights,
563: ' , : :

Hydraulic engineering, its progress in
England with reference to rivers,
canals, and drainage, 473. e

Hydraulics as a branch of engineer-
ing, state of our knowledge of, 415.

in France, Germany, and En-
gland, present state of, 447. _

Hydrodynamics, on the reduction of
an anomalous factiin, 531.

esses Leslie’s, on the use of,
569.

Ichthyology, 179, 613, 617.
Imaginary quantities, on conjugate

698

functions, or algebraic couples, as il-

. lustrating the doctrine of, 519.

India, on mean temperatures in, 567.

Inoculation, 73.

Interference, sonorous, new pheeno-
menon of, 557.

Iron, cast, application of the hot blast

-. to the production of, 578.

Isomerism, on the doctrine of, 579.

-L.

“meson (Prof.) on the fossil fish Ce-

« phalaspis, 646.

Jardine (Sir W.) on the Salmonide
of the North-west of Sutherland-
shire, 613.

Jenyns (Rev. L.) on the recent pro-
are and present state of zoology,

143.

Johnston (J. F. W.) on the chemical
composition of the crystallized oxi-
chloride of antimony, 587.

Joints, on excision of diseased, 684.

Klinometer, new, 594.
Knight (Dr.) notice of the flints of
Aberdeenshire, 651.

Lens, polyzonal, 595.
Leslie’s hygrometer, on the use of, 569.
Light, on the theory of its absorption
by coloured media, 550.
, on the theory of its dispersion by
the hypothesis of undulations, 549.
, state of our knowledge of the
physical theory of, 295.
(unpolarized), propagation of,
297; principle of interference, 303 ;
reflexion and refraction of, 305 ; dif.
fraction, 323 ; colours of thin plates,
338.

(polarized), polarization, 350;
transversal vibrations, 352; lesion
and refraction of, 356; double re-
fraction, 375; colours of crystalline
plates, 395.

Lighthouses, an ceconomical light for,
595.

Limestone of Closeburn, on the, 651.
Lloyd (Prof.) on the progress and pre-
sent state of physical optics, 295.

, account of magmnetical observa-

tions in Ireland, and of a new me-

thod of observing the dip and the
force with the same instrument,

557.

INDEX.

Lowe (G.) on some new chemical
products obtained in gas-works,
582,

Lungs, on their infiltration with black
matter, 683.

Lyell (C. ) on the change of level of the
land and sea in Scandinavia, 652.

Macgillivray (W.) on the central por-
tion of the great mountain range of
the South of Scotland, 650.

Maclaren (Mr.) on the geology of
the Pentland Hills, 649.

Magnetical observations in Ireland,
account of, 557. -

Manchester, ‘statistics of, 690.

Mathematical instruments, 593.

Mathematics, 513.

Mechanical arts, 593.

Mental philosophy, its importance to
the medical pee eens 670.

Menteath (C. G. S.) on the limestone

ison Closeburn, 651.
eteorology, 560.

Miasms, ie atte exh?™ ‘ical+y “ofa

Miller (Prof.) on the § 2 veruter fre
axes of optical elastigy’ a ‘oblique
ptismatical crystals, 5

Milne (D.) on the geology of Berwick-
shire, 624.

Mineral species, on the value of opti-
cal characters in the discrimination
of, 575,

Mineral substances, effects of long
continued heat on, 576.

Mineral veins and the non-metallifer-
ous joints in rocks, on the relations
of, 654.

Mineralogy, 571.

pereerest river, on the recent changes
in the, 9

Molluscous animals, present state of
knowledge respecting, 213.

Moon, on her visibility in total eclipses,
552.

Murchison (R. J.) on the old red
sandstone and the formations be-
neath it, 652.

Natural history, 596.

Nerves, cerebral, on the sensibilities
of, 676.

Nervous system, on the proper method
of studying the, 667.

Nervous system and the irritability of

INDEX.

muscles in living animals, on the
connexion between, 671.
Nicol (W.) on the anatomical struc-
ture of recent and fossil woods,
. 660.

Object-glasses, achromatic, 593.

Omentum, on the use of the, 683.

Optical elasticity in oblique prismati-
cal crystals, on the positions of the
axes of, 556.

Optical characters, their value in the
discrimination of mineral species,
575.

Optics, physical, on, 295.

Organic substances, effects of long-
continued heat on, 576.

Orkney Islands, geology of, 644.

Ornithology, 167, 610.

Oxichloride of antimony, crystallized,
chemical composition of, 587.

Pentland (J. B.) on the ancient inha-
heonts of the Andes, 623.

‘gy dlie, 579.

, 4 lants of the Faroe Is-
lanas,

Phillips (1 .of.) on the quantities of
rain failing at different elevations
above the surface of the ground at
York, 560.

on the relations of mineral veins
and the non-metalliferous joints in
rocks, 654.

Physics, 531.

Physiology, 95, 667.

Poisons, contagious, on, 73.

, morbid, generated by the animal

body, 69.

, their effects on the animal ceco-
nomy, 681.

Porpoise, anatomy of the blood-ves-
sels of the, 682.

Powell (Prof.) on the achromatism of
the eye, 548.

on the dispersion of light by the

hypothesis of undulations, 549.

, on the repulsion excited between

surfaces at minute distances by the,

‘action of heat, 549.

Radiate animals, state of our know-

ledge respecting the, 227.
Rain, on an apparent anomaly in the
measure of, 560.

699

Rain, on the quantities falling at dif-
ferent elevations, at York, 560.

, on the difference of the quaniaty
at different heights, 563. :

, origin of, 565.

Reichenbach (Dr.) on the products of
destructive distillation, 591. cS

Reid (Dr. J.) on the connexion be-
tween the nervous system and the
irritability of muscles in living an‘
mals, 671.

Reindeer, on the laryngeal sac of the,
623.

Rennie (G.) on the state of our know-

* ledge of, hydraulics as a branch of
engineering, 415.

on an instrument for taking up
water at great depths, 595.

Reptiles, on the natural arrangement
of, 172.

Repulsion, excited, between surfaces
at minute distances by the action of
heat, 549.

Resistance of fluids, on a new law of,
531.

Rivers, application of the science, of
hydraulics to, 425.

, forms of the surface of, 468. ,
Robinson (Rev. Dr.) on the ‘visibility
of the moon in total eclipses, 552.
Rogers (H. D.) on the geology of North

America, 1.

Riippell (Dr.) on the effects of poisons
on the animal ceconomy, 681.

Russell (J. S.) on the reduction of an
anomalous fact in hydrodynamics,
and on a new law of the resistance
of fluids, 531.

,

Salmonide of the North-west of Suther-
landshire, on the, 613; on the dif-
ferent species which frequent the
rivers and lakes of Europe, 617.

Salts, hydrated, 579.

Sedgwick (Prof.), address at general
meeting, ix.

Selby (P. J.) on the orbital glands in
birds, 609.

Sharpey (Dr.) on the anatomy of the
blood-vessels of the:porpoise, 682.
Shells, marine, at considerable eleva-

tions near Preston, 655.

Statistics of Glasgow, 685.

of Manchester, 690.
, regarding agriculture, 693.

700 -

Statistics, on the ‘ New Statistical Ac-
count of Scotland’, 692.

Stevelly (Prof.), attempt to connect
the best known phenomena of me-
teorology with established physical
principles, 564.

on the application of a vernier to
a scale not of equal, but of variable
parts, 596. ;

Stone, on its expansion by the appli-
cation of heat, 569.

Surveying instrument, portable, 594.

Sykes (Lt.-Col.) on mean tempera-
tures in India, 567.

Syme (Prof.) on excision of diseased
joints, 684.

Sympiesometer, new, 593.

Temperature, mean, in India, 567.

Tertiary formations, 29, 49.

Thames, on the course, dimensions,
inclinations, and velocities of the,
486.

Thomson (Dr. A.) remarks on some
specimens of reptiles, 623.

Thomson (Dr. W.) on the infiltration
of the lungs with black matter, and
on black expectoration, 683.

Toorn (A. van der), table of the pro-
portions of anhydrous acid in acetic
acid, 571.

Traill (Dr.) on the laryngeal sae of
the reindeer, 623.

on the geological structure of
the Orkney Islands, 644.

Trevelyan (W. C.) on the phenoga-
mous plants of the Firoe Islands,
598.

INDEX.

United States, geology of the, 6.
——-, fossil mammalia of the, 28.

Veins, mineral, 572, 654.
Vertebrate animals, state of our know-
ledge respecting, 160.

Water at great depths, an instrument
for taking up, 595.

Watson (H. H.) on the use of Leslie’s
hygrometer with a new scale, 569.

on the quantity of carbonic acid
in the atmosphere, 583.

Westwood (J. O.) on the transforma-
tions of the Crustacea, 608.
Whewell (Rev. W.) on the theory of
the absorption of light by coloured

media, 550.

Williams (Dr.-C. J. B.) on the phe-
nomena and products of a low form
of combustion, 588.

Wilson (J.) on the coleopterous in-
sects of Sutherland, 615.

Wind, origin of, 565. wv

Wollaston’s scale of chemical*x~ .s¥a-
lents, application of a veruter to,
596.

Wood, recent and fossil, anatomical
structure of, 660.

Zoology, 598.

, on the recent progress and pre-
sent state of, 143. ’
Zoophytes, state of our knowledge of,

236.
, Scottish, on the propagation of,

598.

Printed by Richard Taylor, Red Lion Court, Fleet Street.

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