fi7.
REPORT
EIGHTH MEETING
BRITISH ASSOCIATION
ADVANCEMENT OF SCIENCE;
HELD AT NEWCASTLE IN AUGUST 1838.
VOL. VII.
LONDON:
JOHN MURRAY, ALBEMARLE STREET.
1839.
PRINTED BY RICHARD AND JOHN E. TAYLOR,
RED LION COURT, FLEET STREET.
CONTENTS.
Objects and Rules of the Association v
Officers and Council, 1838-9 viii
Table of Places of Meeting and Officers from commencement. ... is
Table of Members of Council from commencement x
Officers of Sectional Committees xii
Corresponding Members xiii
Treasurer's Account x iv
Reports, Researches, Desiderata, &c xv — xxvi
Synopsis of Sums appropriated to Scientific Objects xxvii
Arrangements of the General Evening Meetings xxx
Address by Mr. Murchison xxxi
REPORTS OF RESEARCHES IN SCIENCE.
Account of «k Level Line, measured from the Bristol Channel to
the English Channel, during the Year 1837-8, by Mr. Bunt,
under the Direction of a Committee of the British Association.
Drawn up by the Rev. W. Whevi^ell, F.R.S., one of the
Committee 1
Report on the Discussions of Tides prepared under the direction
of the Rev. W. Whewell, F.R.S., by means of the grant of
money made for that purpose by the Association 19
Account of the Progress and State of the Meteorological Obser-
vations at Plymouth, made at the request of the British Asso-
ciation, under the direction of Mr. W. Snow Harris, F.R.S.
(Drawn up by Mr. Harris.) 21
A 2
\y CONTENTS.
rage
A Memoir on the Magnetic Isoclinal and Isodynamic Lines in the
British Islands, from Observations by Professors Humphrey
Lloyd and John Phillips, Robert Were Fox, Esq., Captain
James Clark Ross, R.N., and Major Edward Sabine, R.A. By
Major Edwakd Sabine, R.A., F.R.S 49
First Report on the Determination of the Mean Numerical Values
of Raihvay Constants. ByDioNYSiusLARDNER,LL.D.F.R.S.,&c. 197
First Report upon Experiments, instituted at the request of the
British Association, upon the Action of Sea and River Water,
■whether clear or foul, and at various temperatures, upon Cast
and Wrought Iron. ByRoBERTMALLET,M.R.l.A. Ass.Ins.C.E. 253
Notice of Experiments in Progress, at the desire of the British
Association, on the Action of a Heat of 212° Fahr., when long
continued, on Inorganic and Organic Substances, By Robert
Mallet, M.R.I.A.. 313
Provisional Reports and Notices of Progress in Special Re-
searches entrusted to Committees and Individuals 31.5
Report of the Committee for the Liverpool Observatory 316
Notice of Apparatus for the Detection and Measurement of Gases
present in minute quantity in Atmospheric Air. By Wm. West. 316
Notices of Progress in Special Researches 317
Appendix to a Report on the Variations of the Magnetic Intensity
(printed in Vol. VI.). By Major Edward Sabine, F.R.S. ,
&c 318
For Contents of the Notices and Abstracts of Communications to the
British Association for the Advancement of Science, at the New-
castle Meeting, August, 1838, see pp. iii — viii. of the second portion
of this Volume.
Indices I. and II 179, 180
For Catalogue of the Philosophical Instruments, Models of Inventions,
Products of National Industry, &c., &c., contained in the First Ex-
hibition of the British Association for the Advancement of Science,
see the end of this volume.
Plates I.— XVII.
OBJECTS AND RULES
THE ASSOCIATION.
OBJECTS.
The Association contemplates no interference with the ground
occupied by other Institutions. Its objects are, — To give a
stronger impulse and a more systematic direction to scientific
inquiry, — to promote the intercourse of those w.ho cultivate Sci-
ence in different parts of the British Empire, with one another,
and with foreign philosophers, — to obtain a more general atten-
tion to the objects of Science, and a removal of any disadvan-
tages 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 subscri-
bing an obligation to conform to its Rules.
The Fellows and Members of Chartered Literary and Philo-
sophical Societies publishing Transactions, in the British Em-
pire, shall be entitled, in like manner, to become Members of
the Association.
The Officers and Members of the Councils, or Managing
Committees, 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.
RULES OF THE ASSOCIATION.
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 Secre-
taries.
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.
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 week of the
Meeting, or longer, to transact the business of the Association.
It shall consist of the following persons : —
1. Presidents and Officers for the present and preceding years,
with authors of Reports in the Transactions of the Association.
2. Members who have communicated any Paper to a Philo-
sophical Society, which has been printed in its Transactions,
and which relates to such subjects as are taken into considera-
tion at the Sectional Meetings of the Association.
3. Office-bearers for the time being, or Delegates, altogether
not exceeding three in number, from any Philosophical Society
publishing Transactions.
4. Office-bearers for the time being, or Delegates, not ex-
ceeding three, from Philosophical Institutions established in
the place of Meeting, or in any place where the Association
has formerly met.
5. Foreigners and other individuals whose assistance is de-
sired, and who are specially nominated in writing for the meet-
ing of the year by the President and General Secretaries.
6. The Presidents, Vice-Presidents, and Secretaries of the
Sections are ex officio members of the General Committee for
the time being.
SECTIONAL COMMITTEES.
The General Committee shall appoint, at each Meeting,
Committees, consisting severally of the Members most conver-
RULES OF THE ASSOCIATION'. VU
sant 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.
The Committees shall recommend 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.
COMMITTEE OF RECOMMENDATIONS.
The General Committee shall appoint at each Meeting a Com-
mittee, which shall receive and consider the Recommendations
of the Sectional Committees, and report to the General Com-
mittee the measures which they would advise to be adopted for
the advancement of Science.
LOCAL COMMITTEES.
Local Committees shall be formed by the Officers of the Asso-
ciation to assist in making arrangements for the Meetings.
Committees shall have the power of adding to their numbers
those Members of the Association whose assistance they may
desire.
OFFICERS.
A President, two or more Vice-Presidents, one or more Se-
cretaries, and a Treasurer, shall be annually appointed by the
General Committee.
COUNCIL.
In the intervals of the Meetings, the affairs of the Association
shall be managed by a Council appointed by the General Com-
mittee. The Council may also assemble for the despatch of
business during the week of the Meeting.
PAPERS AND COMMUNICATIONS.
The Author of any paper or communication shall be at liberty
to reserve his right of property therein.
ACCOUNTS.
The Accounts of the Association shall be audited annually, by
Auditors appointed by the Meeting,
EIGHTH REPORT 1838.
OFFICERS AND COUNCIL, 1838-9.
Trustees {permanent.) — R. I. Murchison, Esq. John Tay-
lor, Esq.
President. — His Grace the Duke of Northumberland.
Vice-Presidents.— The Bishop of Durham, F.R.S., F.A.S.
Rev. W. Vernon Harcourt. Prideaux John Selby, Esq., F.R.S.E.
President elect. — The Rev. William Vernon Harcourt, F.R.S.
Ptce- Presidents elect. — Marquis Northampton, Pres. Royal
Soc. Earl of Dartmouth. Rev. T. Robinson, D.D. John
Corrie, Esq., F.R.S.
General Secretaries. — R. I. Murchison, Esq., F.R.S. Rev.
G. Peacock, D.D., F.R.S.
Assistant General Secretary. — Professor Phillips, York.
Secretaries for Birmingham. — George Barker, Esq. Joseph
Hodgson, Esq. Follett Osier, Esq. Peyton Blakiston, M.D.
General Treasurer. — John Taylor, Esq., 2, Duke Street,
Adelphi.
Treasurers to the Birmingham Meeting. — J. L. Moilliet,
Esq. James Russell, Esq.
Council. — Dr. Arnott. F. Baily, Esq. Rev. Dr. Buckland.
R. Brown, Esq. The Earl of Burlington. Professor Clark.
Dr. Daubeny. G. B. Greenough, Esq. Professor Graham.
J. E. Gra}% Esq. Robert Hutton, Esq. Rev. L. Jenyns.
Sir Charles Lemon, Bart. Charles Lyell, Esq. J. W. Lubbock,
Esq. Dr. Lardner. Professor Owen. SirJ. Rennie. Major
Sabine. Colonel Sykes. Rev. Professor Whewell. Professor
Wheatstone. Captain Washington.
Secretary to the Council. — James Yates, Esq., 49, Upper
Bedford Place, London.
Local Treasurers. — Dr. Daubeny, Oxford. Professor Hens-
lov,', Cambridge. Dr. Orpen, Dublin. Charles Forbes, Esq.,
Edinburgh. William Gray, jun., Esq., York. William Sanders,
Esq., Bristol. Samuel Turner, Esq., Liverpool. Rev, John
James Tayler, Manchester. James Russell, Esq., Birmingham.
William Hutton, Esq., Newcastle-on-Tyne. Henry Wool-
combe, Esq., Plymouth.
.2 S
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ca -
X EIGHTH REPORT — 1838.
II. Table showing the Members of Council of the British Association
from its Commencement, in addition to Presidents, Vice-Presidents,
and Local Secretaries.
r Rev. \Vm. Vernon Havcourt, F.R.S., &c. 1832—1836.
. Francis Baily, V.P. and Treas. R.S 183.^.
General Secretaries. < ^ j Murchison, F.R.S., F.G.S 1836—1838.
I Rev. G. Peacock, F.R.S., F.G.S., &c. ...1837, 1838.
General Treasurer. John Taylor, F. R.S. , Treas. G.S., &c. ...1832—1838.
C Charles Babbage, F.R.SS.L. & E., &c. (Resigned.)
Trustees(w\mzx\ent).< R. I. Murchison, F.R.S., &c.
L John Taylor, F.R.S., &c.
Assistant General f professor Phillips, F.R.S., &c 1832—1838.
Secretary. J
Members of Council.
G. B. Ah-y, F.R.S., Astronomer Royal 1834, 1835.
Neill Arnott, M.D 1838.
Francis Baily, V.P. and Treas. R.S 1837, 1838.
Georffe Bentham, F.L.S 1834, 1835.
Robert Brown, D.C.L., F.R.S 1832, 1834, 1835, 1838.
Sir David Brewster, F.R.S., &c 1832.
M.I.Brunei, F.R.S., &c 1832.
Rev. Professor Buckland, D.D., F.R.S., &c. 1833, 1835, 1838.
The Earl of Burlington 1838.
Rev. T. Chalmers, D.D., Prof, of Divinity,
Edinbm-gh 1833.
Professor Clark, Cambridge 1838.
Professor Christie, F.R.S.,&c 1833—1837.
William Clift, F.R.S., F.G.S 1832—1835.
JohnCorrie, F.R.S., &c 1832.
Professor Daniell, F.R.S 1836.
Dr. Daubeny 1 838.
J. E. Drinkwater 1834, 1835.
The Earl Fitzwilham, D.C.L., F.R.S., &C....1833.
Professor Forbes, F.R.SS.L. & E., &c 1832.
Davies Gilbert, D.C.L., V.P.R.S., &c 1832.
Professor Graham, M.D., F.R.S.E 1837.
Professor Thomas Graham, F.R.S 1838.
John Edward Gray, F.R.S., F.L.S., &c 1837, 1838.
Professor Green, F.R.S., F.G.S 1832.
G. B. Greenough, F.R.S., F.G.S 1832—1838.
Henry Hallam, F.R.S., F.S.A., &c 1836.
Sir William R. Hamilton, Astron. Royal of
Ireland 1832, 1833, 1836.
Rev. Prof. Henslow, M.A., F.L.S., F.G.S.. ..1837.
Sir John F. W. Herschel, F.R.SS. L. & E.,
F.R.A.S., F.G.S., &c 1832.
Thomas Hodgkin, M.D 1833—1837.
Prof Sir W. J. Hooker, LL.D., F.R.S., &c. 1832.
Rev. F. W. Hope, M.A., F.L.S 1837.
Robert Hutton, M.P., F.G.S., &c 1836, 1838.
Professor R. Jameson, F.R.SS. L. &E 1833.
Rev. Leonard Jenvns 1838.
MEMBERS OF COUNCIL. XI
Sir C. Lemon, Bart, M.P 1838.
Rev. Dr. Lardner 1838.
Professor Lindley, F.R.S., F.L.S., &c 1833, 1836.
Rev. Provost Lloyd, D.D 1832, 1833.
J. W. Lubbock, F.R.S., F.L.S., &c., Vice-
Chancellor of the University of London 1833—1836, 1838.
Rev. Tliomas Luby 1832.
Charles Lyell, jun.. Esq 1838.
William Sharp MacLeay, F.L.S 1837.
Patrick Neil), LL.D., F.R.S.E 1833.
Richard Owen, F.R.S., F.L.S 1836, 1838.
Rev. George Peacock, M.A., F.R.S., &c 1832, 1834, 1835.
Rev. Professor Powell, M.A., F.R.S., &c 1836, 1837.
J. C. Prichard, M.D., F.R.S., &c 1832.
George Rennie, F.R.S 1833—1835.
Sir John Rennie 1838.
Rev. Professor Ritchie, F.R.S 1833.
Sir John Robison, Sec. R.S.E 1832, 1836.
P. M. Roget, M.D., Sec. R.S., F.G.S., &c. ...1834—1837.
Major Sabine 1838.
Rev. William Scoresby, B.D., F.R.SS. L. & E. 1 832.
Lieut.-Col. W. H. Sykes, F.R.S., F.L.S., &C....1837, 1838.
Rev. J. J. Tayler, B.A., Manchester 1832.
Professor Traill, M.D 1832, 1833.
N. A. Vigors, M.P., D.C.L., F.S.A., F.L.S.. ..1832, 1836.
Captain Washington, R.N 1838.
Professor Wheatstone 1838.
Rev. W. Whewell 1838.
William Yarrell, F.L.S 1833—1836.
Secretaries to the f Edward Tm-ner, M.D., F.R.SS. L. & E... 1832— 1836.
Council. \ James Yates, F.R.S., F.L.S., F.G.S 1832—1838.
EIGHTH REPORT — 1838.
OFFICERS OF SECTIONAL COMMITTEES AT THE
NEWCASTLE MEETING.
SECTION A. MATHEMATICAL AND PHYSICAL SCIENCE.
Preside)it.— Sir J. F. W. Herschel, Bart., F.R.S.
Pice- Presidents. — Frauds Baily, Esq., F.R.S. Sir D. Brew-
ster, Knt. Sir W. R. Hamilton, Knt. Rev. D. Robinson.
Secretaries. — Rev. Professor Chevalier. Major Sabine, F.R.S.
Professor Stevelly.
SECTION B. — CHEMISTRY AND MINERALOGY.
President.— Rev. W. Whewell, F.R.S., P.G.S.
Vice-Presidents. — Dr. T. Thomson. Dr. Daubeny. Professor
Graham.
Secretaries. — Professor Miller. H. L. Pattinson, Esq.
Thomas Richardson, Esq.
SECTION C. — GEOLOGY AND GEOGRAPHY*.
President for Geology.— C. Ljell, Esq., F.R.S., V.P.G.S.,&c.
President for Geography . — Lord Prudhoe.
Vice-Presidents.— V\\ Biickland, D.D., F.R.S., V.P.G.S.
John Buddie, Esq., F.G.S.
Secretaries for Geology. — W. C. Trevelyan, Esq., F.R S.E.,
F.G.S. Captain Portlock, R.E., F.R.S., F.G.S.
Secretaries for Geography. — Captain Washington, R.N.
SECTION D. — ZOOLOGY AND BOTANY.
President. — Sir W. Jardine, Bart.
Vice-Presidents. — R. K. Greville, LL.D. Rev. L. Jcnyns,
F.L.S. Rev. F. W. Hope, F.R.S.
Secretaries. — John E. Gray, Esq., F.R.S. Professor Jones,
F.R.S. R. Owen, Esq., F.R.S. John Richardson, M.D., F.R.S.
SECTION E. — MEDICAL SCIENCE.
President.— T. E. Headlam, M.D.
Vice-Presidents. — Professor William Clark, M.D., F.G.S.
John Yelloly, M.D., F.R.S. John Fife, Esq.
Secretaries. — T. M. Greenhow, Esq. J. R. W. Vose, M.D.
* By a resolution of the General Committee at the Newcastle Meeting, the
title of this Section will in future be Geology and Physical Geography.
OFFICERS OF SECTIONAL COMMI'ITEES. XIU
SECTION F. STATISTICS.
President. — Col. Sykes, F.R.S., V.P. Statistical Society of
London.
Vice-Presidents. — Sir Charles Lemon, Bart., M.P., F.R.S.
G. R. Porter, Esq. Charles W. Bigge, Esq.
Secretaries. — James Heywood, Esq. W. R. Wood, Esq.
Win. Cargill, Esq.
SECTION G. MECHANICAL SCIENCE.
President. — Charles Babbage, Esq., F.R.S., &c. &c.
Vice-Presidents. — Bryan Donkin, Esq., V.P. Inst. C,E., &c.
Sir John Robison, Sec. R.S.E. G. Stephenson, Esq. Pro-
fessor Willis.
Secretaries. — R. Hawthorn, Esq. T. Webster, Esq., Sec.
Inst. C.E. C. VignoUes, Esq.
CORRESPONDING MEMBERS.
Professor Agassiz, Neufchatel. M. Arago, Secretary of the
Institute, Paris. A. Bache, Principal of Girard College, Phi-
ladelphia. Professor Berzelius, Stockholm. Professor De la
Rive, Geneva. Professor Dumas, Paris. Professor Ehrenberg,
Berlin. Baron Alexander von Humboldt, Berlin. Professor
Liebig, Giessen. Professor (Ersted, Copenhagen. Jean Plana,
Astronomer Royal, Turin. M. Quetelet, Brussels. Professor
Schumacher, Altona.
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DESIDERATA, ETC.
The following Reports on the Progress and Desiderata of dif-
ferent branches of Science have been drawn up at the request
of the Association, and printed in its Transactions.
Vol. I.
On the progress of Astronomy during the present century,
by G. B. Airy, M.A., Astronomer Royal.
On the state of our knowledge respecting Tides, by J. W.
Lubbock, M.A., Vice-President of the Royal Society.
On the recent progress and present state of Meteorology,
by James D. Forbes, F.R.S., Professor of Natural Philosophy,
Edinburgh.
On the present state of our knowledge of the Science of Ra-
diant Heat, by the Rev. Baden Powell, M.A., F.R.S., Savilian
Professor of Geometry, Oxford.
On Thermo-electricity, by the Rev. James Gumming, M.A.,
F.R.S., Professor of Chemistry, Cambridge.
On the recent progress of Optics, by Sir David Brewster,
K.C.G., LL.D., F.R.S., &c.
On the recent progress and present state of Mineralogy, by
the Rev. WiUiam Whewell, M.A., F.R.S.
On the progress, actual state, and ulterior prospects of
Geology, by the Rev. ^Villiam Conybeare, M.A., F.R.S. ,
V.P.G.S., &c.
On the recent progress and present state of Chemical Science,
by J. F. W. Johnston, A.M., Professor of Chemistry, Durham.
On the application of Philological and Physical researches to
the History of the Human Species, by J. C. Prichard, M.D.,
F.R.S., &c.
Vol. n.
On the advances which have recently been made in certain
branches ofAnalysis,by theRev. G. Peacock, M.A.,F.R.S.,&c.
On the present state of the Analytical Theory of Hydrostatics
and Hydrodynamics, by theRev. John Challis,M. A., F.R.S., &c.
On the state of our knowledge of Hydraulics, considered as a
branch of Engineering, by George Rennie, F.R.S., &c. (Parts
I. and II.)
On the state of our knowledge respecting the Magnetism of
the Earth, by S. H. Christie, M.A., F.R.S., Professor of Mathe-
matics, Woolwich.
On the state of our knowledge of the Strength of Materials,
by Peter Barlow, F.R.S.
On the state of our knowledge respecting Mineral Veins, by
John Taylor, F.R.S., Treasurer G.S,, &c.
Xvi EIGHTH REPORT — 1838.
On the state of the Physiology of the Nervous System, by
William Charles Henry, M.D.
On the recent progressof PhysiologicalBotany,byJohnLind-
ley, F.R.S., Professor of Botany in the University of London.
Vol. III.
On the Geology of North America, by H. D. Rogers, F.G.S. '
On the philosophy of Contagion, by W. Henry, M.D.,F.R.S.
On the state of Physiological Knowledge, by the Rev. Wm.
Clark, M.D., F.G.S. , Professor of Anatomy, Cambridge.
On the state and progress of Zoology, by the Rev. Leonard
Jenyns, M.A., F.L.S., &c.
On the theories of Capillary Attraction, and of the Propaga-
tion of Sound as affected by the Development of Heat, by the
Rev. John Chalhs, M.A., F.R.S., &c.
On the state of the science of Physical Optics, by the Rev.
H. Lloyd, M.A., Professor of Natural Philosophy, Dublin.
Vol. IV.
On the state of our knowledge respecting the application of
Mathematical and Dynamical principles to Magnetism, Electri-
city, Heat, &c., by the Rev. Wm. Whewell, M.A., F.R.S.
On Hansteen's researches in Magnetism, by Captain Sabine,
F.R.S.
On the state of Mathematical and Physical Science in. Bel-
gium, by M. Quetelet, Director of the Observatory, Brussels.
Vol. V.
On the present state of our knowledge with respect to Mine-
ral and Thermal Waters, by Charles Daubeny, M.D., F.R.S.,
M.R.I. A., &c., Professor of Chemistry and of Botany, Oxford.
On North American Zoology, by John Richardson, M.D.,
F.R.S., &c.
Supplementary report on the Mathematical Theory of Fluids,
by the Rev. J. Challis, Plumian Professor of Astronomy in the
University of Cambridge.
Vol. VI.
On the variations of the Magnetic Intensity observed at dif-
ferent points of the Earth's Surface, by Major Edward Sabine,
R.A., F.R.S.
On the various modes of Printing for the use of the Blind,
by the Rev. William Taylor, F.R.S.
On the present state of our knowledge in regard to Dimor-
phous Bodies, by Professor Johnston, F.R.S.
On the Statistics of the Four CoUectorates of Dukhun, under
the British Government, by Col. Sykes, F.R.S.
DESIDERATA, ETC. XVU
The following Reports of Researches undertaken at the re-
quest of the Association have been published, viz.
Vol. IV.
On the comparative measurement of the Aberdeen Standard
Scale, by Francis Baily, Treasurer R.S., &c.
On Impact upon Beams, by Eaton Hodgkinson.
Observations on the Direction and Intensity of the Terrestrial
Magnetic Force in Ireland, by the Rev. H. Lloyd, Capt. Sabine,
and Capt. J. C. Ross.
On the Phaenomena usually referred to the Radiation of Heat,
by H. Hudson, M.D.
Experiments on Rain at different elevations, by Wm. Gray,
jun., and Professor Phillips.
Hourly observations of the Thermometer at Plymouth, by
W. S. Harris.
On the Infra-orbital Cavities in Deers and Antelopes, by A.
Jacob, M.D.
On the Effects of Acrid Poisons, by T. Hodgkin, M.D.
On the Motions and Sounds of the Heart, by the Dublin Sub-
Committee.
On the Registration of Deaths, by the Edinburgh Sub-Com-
mittee.
Vol. V.
Observations on the Dii'ection and Intensity of the Terres-
trial Magnetic Force in Scotland, by Major Edward Sabine,
R.A.,. F.R.S., &c.
Comparative vievp of the more remarkable Plants vrhich cha-
racterize the Neighbourhood of Dublin, the Neighbourhood of
Edinburgh, and the South-vpest of Scotland, &c.; drawn up for
the British Association, by J. T. Mackay, M.R.I.A,, A.L.S.,
&c., assisted by Robert Graham, Esq., M.D., Professor of
Botany in the University of Edinburgh.
Report of the London Sub-Committee of the Medical Section
of the British Association on the Motions and Sound's of the
Heart.
Second Report of the Dublin Sub-Committee on the Motions
and Sounds of the Heart. (See Vol. iv. p. 243.)
Report of the Dublin Committee on the Pathology of the
Brain and Nervous System.
Account of the recent Discussions of Observations of the
Tides which have been obtained by means of the grant of money
which was placed at the disposal of the Author for that purpose
at the last Meeting of the Association, by J. W. Lubbock, Esq.
b
xviii EIGHTH report — 1838.
Observations for determining the Refractive Indices for the
Standard Rays of the Solar Spectrum in various media, by the
Rev. Baden Powell, M.A., F-R.S., Savilian Professor of Geome-
try in the University of Oxford.
Provisional Report on the Communication between the Arte-
ries and Absorbents on the part of the London Committee, by
Dr. Hodgkin.
Report of Experiments on Subterranean Temperature, under
the direction of a Committee, consisting of Professor Forbes,
Mr. W. S. Harris, Professor Powell, Lieut.-Colonel Sykes, and
Professor Phillips (Reporter).
Inquiry into the validity of a method recently proposed by
George B. Jerrard, Esq., for Transforming and Resolving
Equations of Elevated Degrees : undertaken at the request of
the Association by Professor Sir W. R. Hamilton.
Vol. VI.
Account of the Discussions of Observations of the Tides
which have been obtained by means of the grant of money which
was placed at the disposal of the Author for that purpose at the
last Meeting of the Association, by J. W, Lubbock, Esq.,
F.R.S.
On the difference between the Composition of Cast Iron
produced by the Cold and the Hot Blast, by Thomas
Thomson, M.D., F.R.SS. L. & E.,&c., Professor of Chemistry,
Glasgow.
On the Determination of the Constant of Nutation by the
Greenwich Observations, made as commanded by the British
Association, by the Rev. T. R. Robinson, D.D.
On some Experiments on the Electricity of Metallic Veins,
and the Temperature of Mines, by Robert Were Fox.
Provisional Report of the Committee of the Medical Section
of the British Association, appointed to investigate the Com-
position of Secretions, and the Organs producing them.
Report from the Committee for inquiring into the Analysis of
the Glands, &c. of the Human Body, by G. O. Rees, M.D.,
F.G.S.
Second Report of the London Sub-Committee of the British
Association Medical Section, on the Motions and Sounds of
the Heart.
Report from the Committee for making experiments on the
Growth of Plants under Glass, and without any free communi-
cation with the outward air, on the plan of Mr. N, I. Ward,
of London.
Report of the Committee on Waves, appointed by the British
DESIDERATA, ETC.
Association at Bristol in 1836, and consisting of Sir John Robi-
son, K.H., Secretary of the Royal Society of Edinburgh, and
John Scott Russell, Esq., M.A., F.R.S. Edin. (Reporter).
On the relative Strength and other mechanical Properties of
Cast Iron obtained by Hot and Cold Blast, by Eaton Hodgkinson.
On the Strength and other Properties of Iron obtained from
the Hot and Cold Blast, by W. Fairbairn.
Vol. VII.
Account of a Level Line, measured from the Bristol Channel
to the English Channel, during the Year 18<37-8, by Mr.
Bunt, under the Direction of a Committee of the British As-
sociation. Drawn up by the Rev. W. Whewell, F.R.S. , one
of the Committee.
A Memoir on the Magnetic Isoclinal and Isodynamic Lines
in the British Islands, from Observations by Professors Hum-
phrey Lloyd and John PhiUips, Robert Were Fox, Esq., Cap-
tain James Clark Ross, R.N,, and Major Edward Sabine,
R.A., by Major Edward Sabine, R.A., F.R.S.
First Report on the Determination of the Mean Numerical
Values of Railway Constants, by Dionysius Lardner, LL.D.,
F.R.S., &c.
First Report upon Experiments, instituted at the request of
the British Association, upon the Action of Sea and River
Water, whether clear or foul, and at various temperatui'es,
upon Cast and Wrought Iron, by Robert Mallet, M.R.I.A.,
Ass. Ins. C.E.
Notice of Experiments in progress, at the desire of the
British Association, on the Action of a Heat of 212° Fahr.,
when long continued, on Inorganic and Organic Substances,
by Robert Mallet, M.R.I. A.
Experiments on the ultimate Transverse Strength of Cast
Iron made at Arigna Works, Co. Leitrim, Ireland, at Messrs.
Bramah and Robinson's, 29th May, 1837.
Provisional Reports and Notices of Progress in Special Re-
searches entrusted to Committees and Individuals.
The following Reports and Continuations of Reports have been
undertaken to he drawn up at the request of the Association.
On the Connexion of Electricity and Magnetism, by S. H.
Christie, Sec. R.S.
b2
XX EIGHTH REPORT — 1838.
On the state of knowledge of the Phaenomena of Sound, by
Rev. Robert Willis, M.A., F.R.S., &c.
On the state of our knowledge respecting the relative level
of Land and Sea, and the waste and extension of the land on
the east coast of England, by R. Stevenson, Engineer to the
Northern Lighthouses, Edinburgh.
On circumstances in Vegetation influencing the Medicinal
Virtues of Plants, by R. Christison, M.D.
On Salts, by Professor Graham, F.R.S.
On the Differential and Integral Calculus, by Rev. Professor
Peacock, M.A., F.R.S. , &c.
On the Geology of North America, by H.D.Rogers, F.G.S.,
Professor of Geology, Philadelphia.
On the Mineral riches of Great Britain, by John Taylor,
F.R.S., F.G.S.
On Vision, by Professor C. Wheatstone, F.R.S.
On the application of a General Principle in Dynamics to
the Theory of the Moon, by Professor Sir W. Hamilton.
On Isomeric Bodies, by Professor Liebig.
On Organic Chemistry, by Professor Liebig.
On Inorganic Chemistry, by Professor Johnston, F.R.S.
On Fossil Reptiles, by Professor Owen, F.R.S.
On the Salmonidie of Scotland, by Sir J. W. Jardine.
On the Caprimulgida?, by N. Gould, F.L.S.
On the state of Meteorology in the United States of Nbrth
America', by A. Bache.
On the state of Chemistry as bearing on Geology, by Pro-
fessor Johnston.
On Molluscous Animals and their Shells, by J. E. Gray,
F.R.S.
On Ornithology, by P. J. Selby, F.R.S.E.
On the Specific Gravity of Steam, by a Committee, of which
Mr. B. Donkin is Secretary.
On the Geographical Distribution of Pulmoniferous Mol-
lusca, by E. Forbes, F.L.S.
Reports requested, Researches recommended, and Desiderata
noticed by the Committees of Science at the Neivcastle
Meeting.
REPORTS ON THE STATE OF SCIENCE.
Prof. Bache, of Philadelphia, was requested to furnish a
Report on the state of Meteorology in the United States, for
the next meetinsr of the Association.
DESIDERATA, BTC. XXI
Pi'of. Johnston was requested to prepare a Report on the
present state of Chemistry as bearing upon Geology.
Mr. J. E. Gray, F.R.S., was requested to prepare a Report
on the present state of our knowledge of Molluscous Animals
and their Shells.
Mr. Selby was requested to draw up a Report on the present
state of knowledge of Ornithology, for an early meeting.
Mr. Bryan Donkin (Secretary), Dr. Ure, Dr. Faraday, and
Mr. Cooper were requested to Repoi-t as to the state of our
knowledge on the Specific Gravity of Steam generated at differ-
ent Temperatures ; Mr. Donkin to act as Secretary.
Mr. E. Forbes was requested to Report on the present state
of the knowledge of the Geographical Distribution of Pulmo-
niferous MoUusca in Britain, and the circumstances which influ-
ence this distribution.
The Council Avere requested to apply for a Report on the
present state and recent discoveries in Geology.
Specific Researches in Science involving applications to
Government or public bodies.
MAGNETICAL OBSERVATIONS.
Resolved, — 1. That the British Association views with high in-
terest the system of Simultaneous Magnetic Observations which
have been for some time carrying on in Germany and in various
parts of Europe, and the important results towards which they
have already led ; and that they consider it highly desirable
that similar series of observations, to be regularly continued in
correspondence with and in extension of these, should be insti-
tuted in various parts of the British dominions.
2. That this Association considers the following localities as
particularly important :
Canada, Van Diemen's Land,
Ceylon, Mauritius, or the
St. Helena, Cape of Good Hope ;
and that they are willing to supply Instruments for the purpose
of observation.
3. That in these series of observations, the three elements of
horizontal direction, dip, and intensity, or their theoretical
equivalents, be insisted on, as also their hourly changes, and on
appointed days their momentary fluctuations.
4. That this Association views it as highly important that the
Xxii EIGHTH REPORT 1838.
deficiency yet existing in our knowledge of Terrestrial Magnet-
ism in the Southern Hemisphere should be supplied by obser-
vations of the magnetic direction and intensity, especially in the
higher latitudes, between the meridians of New Holland and
Cape Horn ; and they desire strongly to recommend to Her
Majesty's Government the appointment of a naval expedition
directed expressly to that object.
5. That in the event of such expedition being undertaken, it
would be desirable that the officer charged with its conduct should
prosecute both branches of observations alluded to in Resolu-
tion 3, so far as circumstances will permit.
6. That it would be most desirable that the observations so
performed, both in the fixed stations and in the course of the
expedition, should be communicated to Prof. Lloyd.
7. That Sir John Herschel, Mr. Whewell, Mr. Peacock, and
Prof. Lloyd be appointed a Committee to represent to Govern-
ment these recommendations.
8. That the same gentlemen be empowered to act as a Com-
mittee, with power to add to their numbei', for the purpose of
drawing up plans of Scientific cooperation, &c. &c., relating to
the subject, and reporting to the Association.
9. That the sum of 400/. be placed at the disposal of the
above-named Committee, for the purposes above mentioned*.
ASTRONOMY.
Sir J. Herschel and Mr. Baily were requested to make
application to Government for increase in the instrumental
power of the Royal Observatory at the Cape of Good Hope, and
the addition of at least one assistant to that establishment.
SCIENTIFIC RESEARCHES IN INDIA.
Resolved, — 1. That the British Association regard the mea-
surement of an arc of longitude in India comparable in extent
to the meridional arc ah'eady measured in that country, as a
most important contribution to other facts illustrative of the
earth's true figure, and, by a necessary con sequence, jto the pro-
gress of astronomy.
2. That the verification and comparison of the standards of the
Indian and English surveys, as compared with the proposed
Parliamentary standard, is indispensable to the correct know-
ledge of the meridional and parallel arcs.
• The application to Government on this subject has been successful, the
command of an expedition to the Antarctic regions being entrtisted to Capt.
J. C. Ross.
DESIDBRATA, KTC -^^i"
3. That pendulum observations at the principal elevations, or
contiguous plains, and on the sea-coast, if possible, on the same
parallels of latitude, will afford results of great value to physical
^"r That observations for the determination of the Laws of Re-
fraction in the elevated regions of the Himalayas, and at the
Observatories of Madras and Bombay, will be a most important
service to science. . , , ^^
5 That it is highly desirable also that magnetical observations
should be made in India similar to those which are carrying on
in other parts of the world, and which are justly regarded with
so much interest. ,
6 That a topographical map of India, upon a large scale, ac-
companied by statistical and geological information, would be
highly desirable*.
ORBNANCE SURVEY.
Resolved,— That a Committee be appointed to inquire how
far in the future progress of the Ordnance Survey, the several
metalliferous and coal-mining districts could be represented on
a larger scale. The Committee to consist of Mr. Greenough,
Mr. Griffith, Mr. De la Beche, and Major Portlock.
MINING RECORDS.
Resolved,— 1. That it is the opinion of this Meeting, that,
with a view to prevent the loss of life and of property which
must inevitably ensue from the want of accurate mining records,
it is a matter of national importance that a depository should
be established for preserving such records of subterranean ope-
rations in collieries and other mining districts.
2. That a Committee be appointed to draw up a Memorial
and to communicate with the Government in the name of the
British Association, respecting the most effectual method of
carrying the above resolution into effect.
3. That the Committee consist of the following gentlemen,
with power to add to their number : The Marquis of Northamp-
ton Sir Charles Lemon, Sir Philip Egerton, John Vivian, Esq.,
Davies G. Gilbert, Esq., J. S. Enys, Esq., W. L. DiUwyn, the
President of the Geological Section of theBritish Association, the
President for the time being of the Geological Society of Lon-
» These Resolutions have been submitted to the consideration of the Di-
rectors of the East India Company ; and, in particular, the recommendation
for magnetical observations has been promptly acceded to.
Xxiv EIGHTH REPORT — 1838.
don, the Professors of Geology at Oxford, Cambridge, London,
and Durham, H. T. De hi Beche, Esq., John Taylor, Esq., John
Buddie, Esq., Thomas Sop«ith, Esq.
Specific Researches in Science involving Grants of Money.
The following new Recommendations were adopted by the
General Committee*.
That it is desirable that the meteorological observations made
at the equinoxes and solstices, agreeablj" to the recommenda-
tions of Sir John Herschel, Bart., should be collected together,
as far as is practicable, and reduced to an uniform mode of ex-
pression, so that comparisons may be made of the same, with a
view of deducing results that may lead to the improvement and
elucidation of meteorology.
That Sir John Herschel be requested to superintend the same,
and that the sum of 100/. be placed at his disposal for that
purpose.
That it is desirable that the whole of the stars observed by
Lacaille at the Cape of Good Hope, the observations of w hich
are recorded in his Caelum Australe Stelliferum, should be re-
duced.
That Sir J. Herschel, Mr. Airy, and Mr. Henderson be a
Committee for carrying the same into effect.
That the sum of 200/. be appropriated to that purpose.
That it is desirable that a Revision of the Nomenclature of
the Stars should be made, with a view to ascertain whether or
not a more correct distribution of them amongst the present
constellations, or such other constellations as it may be con-
sidered advisable to adopt, may be formed.
That Sir J. Herschel, Mr. Whewell, and Mr. Baily be a
Committee for that purpose, and to report on the same at the
next meeting of the Association.
That the sum of 50/. be appropriated to defray the expenses
that may be incurred in this inquiry.
That 100/. be placed at the disposal of Sir D. Brewster
and Professor Forbes, for the purpose of procuring Hourly
Meteorological Observations, to be made at two parts in Scot-
land, one at Fort George, on the coast, and the other at some
central part, at a great elevation above the sea.
That it appears to the Committee desirable to diffuse in this
• For a general synopsis of money grants sanctioned at the Newcastle
Meeting, see p. xxvii.
DESIDERATA, ETC. XXV
country the knowledge of the Scientific Memoirs published on
the Continent, and that, for this object, 100/. be placed at the
disposal of a Committee, consisting of Dr. Robinson, Sir John
Herschel,SirD. Brewster, and Professor Wheatstone, with power
to add to their number, towards procuring the translation and
publication of such memoirs as they may approve.
That Mr. Pattinson and Mr. Richardson be requested to un-
dertake experiments to ascertain whether any perceptible Gal-
vanic influence is exerted by the Stratified Rocks of the neigh-
bourhood of Newcastle, and that 201. be placed at their disposal
to meet the expenses of such experiments.
That Dr. Arnott and Dr. Yelloly be a Committee for the
purpose of improving Acoustic Instruments (in reference to dis-
eases of the ear), with 25/. at their disposal.
That Mr. Cargill, Mr. Wharton, Mr. Buddie, Mr. Forster,
Professor Johnston, and Mr. Wilson be a Committee for in-
quiries into the Statistics of the Collieries of the Tyne and Wear,
with 50/. at their disposal.
That Sir John Robison (Secretary), and Mr. J. S. Russell,
and Mr. James Smith be a Committee for instituting Experi-
ments on the Forms of Vessels, with 200/. at their disposal.
Researches not mvolving Grants of Money or application
to Government.
The Meteorological Committee was requested to furnish a
System of Meteorological Instructions for the next meeting of
the Association.
A Committee was formed, consisting of Mr. Greenough,
Mr. De la Beche, Mr. Buddie, and Mr. Grifl&th, to draw up a
proper form and scale of the Sections to be sent to the Geolo-
gical Society by the engineers and proprietors of railways.
The following gentlemen were appointed a Committee to in-
vestigate the Salmonidfe of Scotland, and directed to place them-
selves in communication with Mr. Shaw, who has offered to
submit his experiments on that subject to their inspection :
Mr. Selby, Dr. Parnell, Mr. J. S. Menteith, Professor R. Jones,
Dr. Neill, Sir W. Jardine, Bart., Secretary.
The following gentlemen were appointed members of a Com-
mittee constituted for the purpose of investigating the Insects
of the genera Eriosoma and Aphis, which attack the Pines of
this country : Mr. Spence, F.R.S., R. K. Greville, LL.D., Sir
W. Jardine, Bart., Mr. Selby, Secretary.
XXVi EIGHTH REPORT — 1838.
The Committee on Diseases of the Lungs in Animals was
reappointed.
The Committee for obtaining a complete account of the
Fauna of Ireland was altered so as to consist of Capt. Portlock,
Mr. R. Ball, Mr. W. Thompson, Mr. Vigors, Mr. Halliday, and
Dr. Coulter, who Mas requested to act as Secretary.
The following Resolutions relaWig to the Conduct of the
3Ieetings, <^c. luere adopted by the General Committee.
That Section C. be styled henceforth the Section of Geology
and Physical Geography.
That the several Sections be empowered, at the desire of
their respective Committees, to divide themselves into sub-
sections as often as the number and importance of the commu-
nications delivered in may render such divisions desirable.
That with a view to facilitate and extend the intercourse of
persons engaged in investigating the same departments of
science, the rooms in which the Sections are appointed to be
held be open in future at 10 o'clock, vice 11, so that an hour
may be allowed for conversation before the Chair is taken and
the reading of papers is commenced.
That Members of the Association, when subscribing- their
name and address, be invited or enabled to enter also in a se-
parate column the Section to which they wish to attach them-
selves.
SYNOPSIS.
Synopsis of Sums appropriated to Scientific Objects hy the
General Committee at the Newcastle Meeting.
Section A.
* 1. For the Reduction of Meteorological Observa-
tions, under the superintendence of Sir J.
Herschel £100
* 2. For the Reduction of Lacaille's Stars, under the
superintendence of Sir J. Herschel, Mr. Airy,
and Mr. Henderson 200
* 3. For the Revision of the Nomenclature of the
Stars : Sir John Herschel, Mr. Whewell, and
Mr. Baily 50
4. For a Level Line from the Bristol to the English
Channel, (an additional grant) : Mr. Whewell,
Col. Colby, Mr. Greenough, and Mr. Griffith 100
5. For Tide Discussions : Mr. Whewell .... 100
6. For the Reduction of Stars in the Histoire Ce-
leste : Mr. Baily, Mr. Airy, and Dr. Robinson 500
7. To extend theRoyal Astronomical Society's Cata-
logue: Mr. Baily, Mr. Airy, and Dr. Robinson 500
* 8. For Magnetical Observations, (Instruments,
&c.) : Sir J. Herschel, Mr. Whewell, Mr.
Peacock, and Mr. Lloyd 400
9. To the Committee on Waves : Sir J. Robison
and Mr. J. S. Russell 50
*10. For the Translation of Foreign Scientific Me-
moirs : Dr. Robinson, Sir J. Herschel, Sir
D. Brewster, and Prof. Wheatstone .... 100
11. For Tabulating Meteorological Observations:
Mr. Harris and Mr. Osier 15
12. To complete the Repair of an Anemometer at
Plymouth : Mr. Osier . . • 8 10
13. For the Expenses of the Meteorological Obser-
vations at Plymouth (additional grant) : Mr.
W, S. Harris .... 40
*14. Hourly Meteorological Observations : Sir D.
Brewster and Mr. Forbes 100
£2263 10
XXviii EIGHTH REPORT — 1838.
Section B.
15. For Researches on Atmospheric Air : Mr. W.
West £ 40
16. For Experiments on the Action of Sea Water on
Cast and Wrouifht Iron : Mr. Mallet and Prof,
Davy 50
17. For Experiments on the Action of Water of 212°
on Organic Matter : Mr. Mallet 10
18. For Chemical Constants : Prof. Johnston . . 30
*19. For Galvanic Experiments on Rocks in vicinity
of Nevccastle : Mr. Pattinson and Mr. Ri-
chardson 20
£150
Section C.
20. For the Promotion of Fossil Ichthyology : Dr.
Buckland, Mr. Murchison, and Prof. Sedg-
wick £105
21. For Researches on the Mud of Rivers : Mr.
Bryce and Mr. De la Beche 20
•f22. For the Promotion of our Knowledge of British
Fossil Reptiles, by a Report on that subject :
Mr. Greenough, Mr. Lyell, and Mr. Clift . 200
£325
Section D.
23. For Experiments on the Preservation of Animal
and Vegetable Substances, Prof. Henslow, Mr.
Jenyns, Dr. Clark, and Prof. Camming ..£60
Section E.
24. For Experiments on the Sounds of the Heart :
Dr. Roget, Dr. Williams, and Dr. Dodd, &c.
&c £50
25. For Experiments on the Lungs and Bronchi:
Dr. Williams 25
*26. For Experiments on Medico-Acoustic Instru-
ments : Dr. Arnott and Dr. Yelloly ... 25
£100
synopsis. x3
Section F.
27. Inquiries into the State of Education in Schools
in England : Col. Sykes, Sir C. Lemon, and
Mr. G. R. Porter £150
28. Inquiries as to the State of the Working Popu-
lation : Sir C. Lemon, Col. Sykes, and Mr.
G. R. Porter 100
*'29. Inquiries into the Statistics of the Collieries of
the Tyne and Wear : Mr. Cargill, Mr. Wharton,
Mr. Buddie, Mr. Forster, Prof. Johnston, and
Mr. Wilson 50
Skction G. £300
30. Researches in the duty performed by the Cornish
Engines : Mr. John Taylor and Mr. Rennie . £50
31. For Inquiries into the Speed of American
Steamers : Mr. W. Fairbairn, Dr. Lardner,
Mr. J. S. Russell, and Mr. John Taylor . . 50
32. For a Report on the Duty and Engines not in
Cornwall : Mr. W. Bryan Donkin, Mr. James
Simpson, Mr. G. H. Palmer, and Mr. T.
Webster, Sec 50
*33. For Experiments on the Forms of Vessels : Sir
J. Robison, Mr. J. S. Russell, and Mr. James
Smith 200
34. For Experiments on the Hot-blast Iron as com-
pared with Cold-blast Iron : Mr Hodgkinson,
Mr. W. Fairbairn, and Mr. P. Clare, Sec. . 100
35. For Railway Constants: Mr. H. Earle, Dr.
Lardner, Mr. Locke, Mr. Rennie, and Mr.
MacNeil 20
36. For Apparatus used in Researches regarding Ma-
rine Steam Engines : Mr. J. Scott Russell . 17
37. For completing an Instrument for Investigating
the Duty of Marine Steam Engines : Dr. Lard-
ner, £50, Mr. Russell, £28, and Mr. W. Fair-
bairn, £33 Ill
Section A £2263 10
— B 150
— C 325
— D 6
— E 100
— F 300
— G. . . . • . . 598
£3742 10
XXX EIGHTH REPORT — 1838.
The above grants expire at the Meeting in 1839, unless the
Recommendations shall have been acted on, or,a continuance of
the grant applied for by the Sectional Committees, and ordered
by the General Committee. Those marked thus *, relate to
subjects on which no previous resolution has been adopted :
the grounds for such new grants will be found in the previous
pages. The mark t is affixed to grants for objects previously
recommended by the Association, but without grants of money.
The others are renewals or continuations of former grants for
objects which have been detailed in previous volumes.
In grants of money to Committees for purposes of Science,
the member first named is empowered to draw on the Treasurer
for such sums as may from time to time be required. The
General Committee does not contemplate, in the grants, the
payment of personal expenses to the members.
Arrangement of the General JEvenmg Meetings.
On Monday evening, August 20, the President, His Grace
the Duke of Northumberland, having taken the Chair in the
Central Exchange, the Address of the General Secretaries
was read by R. I. Murchison, Esq.
On Tuesday evening, in the same room, the attention of the
Meeting was called to the collection of Models in the Exhibition
Room, and addresses, explanatory of particular Inventions or
Processes, were delivered by C. Babbage, Esq., the Rev. Dr.
Robinson, and Professor Willis.
On Wednesday evening, the Green Market, fitted up for the
purpose, was opened for Promenade and Conversation, and
Mr. Addams explained and exemplified the process by which
the Solidification of Carbonic Acid Gas is effected.
On Thursday evening. Abstracts of the Proceedings which
had taken place in the Sections were read by the Presidents of
the Sections in the Central Exchange.
On Friday evening, the Assembly Rooms, enlarged for the
occasion, were opened for Promenade and Conversation.
On Saturday evening, the Concluding General Meeting
of the Association took place in the Central Exchange, when
an account of the Proceedings of the General Committee
was read by the Rev. Professor Peacock.
ADDRESS
BY
MR. MURCHISOK
CxENTLEMEN, — At the conclusion of the first Septenary which has
elapsed since the establishment of the British Association, the Council
have deemed it expedient to direct us to prepare a general and com-
prehensive view of its past progress and future prospects. In virtue,
therefore, of the commission thus entrusted to us, we shall endeavour
to perform a task which we cannot approach without a feeling of ap-
prehension and anxiety, impressed as we are with the difficulty of duly
appreciating the prominent labours of our associates, and of estimating
their bearing and probable influence on the advancement of science.
The space of time, however, which is allotted to this address, will not
allow us to attempt an analysis of all the past proceedings of the As-
sociation. We are therefore compelled to confine ourselves to a few
allusions to the reports of former meetings, (dwelling more particularly
on the last,) and to a statement of the great principles which form the
basis of our constitution, and which have directed and regulated its
practical operations. And if, in thus stating the aims of the Asso-
ciation, and the principles on Avhich it proceeds, we should be guilty of
repeating some things which have been better said before, we trust it
will be borne in mind, that from the migratory character of our meet-
ings, and the change which that character implies in the body of mem-
bers present at each, a probability arises, that those principles may
not be sufficiently understood, if they are not from time to time re-
stated and re-explained.
It would be superfluous for us to speak of those objects of the As-
sociation which are the most obvious, and which undoubtedly con-
stitute the highest enjoyment these meetings afford us — the union of
congenial minds — the mutual communication, without let or hindrance,
of the knowledge we have acquired in our respective pursuits — the
scintillations of new ideas struck out in private conversation and pub-
lic discussion. " This feast of reason and this flow of soul," agreeable
and instructive as it is, requires no comment ; and though it contri-
butes most essentially to all the purposes for which we are assembled,
and gives life to all our proceedings, it is however on no account to be
regarded as the chief aim and business of our meetings. That which
XXxii EIGHTH REPORT 1838.
has, from the first, gentlemen, been laid down as the highest object for
which we meet, is to supply the great defect under-which science has
formerly laboured, of depending solely on individual and insulated
efforts, by combining its cultivators into a body politic, calculated to
give force and consistence to those efforts, and exercise a powerful
influence both on its own members and on the public mind ; thus
marshalling a scattered militia into an organized and effective army,
and converting desultory incui'sions into a regular and progressive
march. The want of some such public authority in matters of science
as belongs to an union like the present, could not be more strikingly
shown than by the service which, on two occasions, the British Asso-
ciation has rendered to astronomy, in obtaining from Government the
means of effecting the laborious and expensive reductions of the obser-
vations, first of the planets, and lastly of the moon, which had been
made by Bradley, Maskelyne, and Pond. The existence and liberal
support of the noble establishment at which these observations were
made, bore evidence that our rulers have not been insensible to the
immense importance of astronomical inquiries to a great maritime
nation ; but that so much of the precious ore which had been accu-
mulated during the greater part of a century, by the successive labours
of the greatest practical astronomers of any age or nation, should have
remained unwrought and nearly useless for the highest applications of
science, amidst the vain and oft-repeated regrets of those who were
the most competent judges of its value, — what does this prove, but that
there were no councillors of sufficient weight, number, or influence,
not only to offer advice to the Government, but also to secure attention
to it when offered ?
In whatever degree the practical value of science may be beginning
to be understood and appreciated among us, business of more proxi-
mate interest and more obvious urgency engrosses the attention of our
public functionaries and legislators : numerous projects are presented
to them rarely reduced to a practical form, among which they know
not how to distinguish which are, and which are not deserving of na-
tional encouragement; and the consequence has been, with few ex-
ceptions, the general discouragement of all, — a consequence neither
conducive to the reputation, nor serviceable to the interests of so great
a country. But a representation on subjects of science proceeding from
such an Association as this bears a public character, and carries with it
a degree of weight which does not, and ought not, to attach to indivi-
dual applications; and as long as the same judgement and forbeai-ance
M'hich have hitherto characterized its course in this respect shall con-
tinue to be exercised, — as long as special care is taken to ask nothing
of Government but ic/iat it belongs to the national interests or honour
to effect, and irhat cannot be effected 'but bij national means, — so long
ADDRESS BY MR. MURCHISON. XXxiU
doubtless that attention will be 2)aid to our recommendations which they
have already begun to receive. Wisely cautious and reserved in exertino-
its influence, tlie Association has hitherto made but few applications to
the government. Besides those to which we have before referred, and
which were immediately complied with, another was made regarding
the slow progi-ess of the ti'igonometrical surveys of England and Scot-
land : the latter probably owes its recent acceleration to the attention
thus first drawn to the subject, subsequently reinforced by a deputation
from the Royal Society of Scotland ; but the survey of England,
which, having commenced nearly half a century ago, has not yet
reached the Trent, is still in abeyance ; and these northern districts in
which we are assembled, and which comprise so large a part of the
staple riches of the country, continue without their due share of the
advantages which would attend its execution. There have been like-
wise two other national objects on which the Association has expressed
its opinion ; the one being the establishment of a magnetical observa-
tory in Great Britain, the other an expedition for the purpose of making
magnetical observations in the Antarctic seas. For the attainment of
the former of these objects no interference was found necessary, an
arrangement every way satisfactory being determined upon for con-
necting it with the Royal Observatory at Greenwich, on the recommen-
dation of the Board of Visitors. The iJublication, in the present volume
of our Transactions, of an elaborate report on the variations of the mag-
netic intensity of the earth, (unquestionably one of the most valuable
which has hitherto appeared in them, whether we consider the labo-
rious reductions it has required, or the important conclusions to which
they lead,) recals our attention to the latter point. The subject is one
of such deep interest, that we hope we shall not be thought to trespass
too much on the time of the meeting, if we repeat some of Major
Sabine's remarks upon it in his own words : —
" I have already adverted to what the influence of the Association
may effect, in causing the spaces yet vacant on the map, in the British
possessions in India and Canada, to be filled. But beyond all compa-
rison, the most important service of this kind, which this or any other
country could render to this branch of science, would be by filling the
void still existing in the southern hemisphere, and particularly in the
vicinity of those parts of that hemisphere which are of principal mag-
netic interest. This can only be accomplished by a naval voyage ; for
which it is natural that other countries should look to England. That
the nations that have made exertions in the same cause do look to
England for it, cannot be better shown than by the following extract
of a letter of M. Hansteen's, which I take the liberty of introducing
here, both for this purpose, and because it expresses in so pleasing a
manner the praise that is so justly due to his own country, and which
c
XXxiv EIGHTH REPORT — 1838.
I am sure will be cordially responded to by all who cultivate science
in this country, and particularly by those who know the kindly feeling
with which Englishmen are ever welcomed in Norway.
" C'est le Storthing (la Chambre des Deputes) de la Norvege, qui a
donne les frais a I'expedition en Siberie. On a fait cela dans un terns
ou on a refuse les depenses pour un chateau de residence pour sa
Majeste a Christiania. Dans un terns, ou une telle economic a ete'
necessaire, il est tres honorable, qu'une Chambre, composee de toutes
les classes du peuple, meme d'un grand nombre de paysans, a tina-
nimemerit resolu de donner les frais pour une expedition purement
scientifique, dont les resultats n'auront jamais aucune utilite econo-
niique pour la patrie, et dont on ne comprenait pas la haute valeur
scientifique. Regarde les ressources tres-bornes de notre pays, c'est
une generosite presque sans exemple.
" Comme la petite Norvege a fourni toutes les observations entre les
meridiens de Greenwich et de Ochozk, et entre les paralleles de 40° et
75° de latitude boreale, il ne me semble pas une demande trop grande
ou immodeste a I'Angleterre, si grande, si riche, si puissante, qui a
necessairement un plus grand interet dans toutes les sciences combinees
avec la navigation, de fournir toute la partie meridionale de la carte.
Une telle entreprise doit reflechir une splendeur a la nation, et payera
a la fin les frais par des resultats aussi utiles pour les sciences que pour
la navigation. II ne faut plus dans notre tems laisser I'avancement des
sciences au hasard. Par des observations fragmentaires et discontinues
on a tache avec grande peine d'etudier les phenomenes magnetiqucs de
la terre pendant deux ou trois siecles. Par deux ou trois expeditions
arrangees expres pour ce hut, on pourrait en peu d'annees avoir une
collection plus complete, et d'une plus grande utilite pour la theorie."
The subject has in every Avay a claim on this country. The existence
of four governing centres, and the system of the phenomena in corre-
spondence therewith, was originally a British discovery. The sagacity
of our countryman Halley was the first to penetrate through the com-
plexity of the phenomena, and to discern what is now becoming gene-
rally recognised. England was also the first country which sent an
expedition expressly for magnetic observation, namely, that of Halley
in 1698 and 1699. Whilst approving and cordially co-operating in
magnetic inquiries of other kinds which have their origin in other
countries, it is right that we should feel a peculiar interest in that in
which we have ourselves led the way, especially when its object is
subordinate to none. As the research would require to be prosecuted
in the high latitudes, a familiarity with the navigation of such latitudes
would be important in the person who should undertake this service ;
and a strong individual interest in the subject itself would be of course
a most valuable qualification. I need scarcely say, that the country
ADDRESS BY MR. MURCHISON. XXXV
possesses a naval officer* in whom these qualifications unite in a
remarkable degree with all others that are requisite ; and if fitting in-
struments make fitting times, none surely can be better than the pre-
sent. Viewed in itself and in its various relations, the magnetism of
the earth cannot be counted less than one of the most important
branches of the physical history of the planet we inhabit; and we may
feel quite assured, that the completion of our knowledge of its distri-
bution on the surface of the earth would be regarded by our contem-
poraries and by posterity as a fitting enterprise of a maritime people,
and a worthy achievement of a nation which has ever sought to rank
foremost in every arduous and honourable undertaking.
The course pursued by the Association in reference to this object is
well calculated to show the system of its operations, and the active but
yet unintrusive and guarded spirit in which it prosecutes its aims. It
was proposed at one of our meetings by the Committee of the Physical
Section, that a repi-esentation should be made to government of the
advantage which would accrue to science from an expedition to the
Southern Ocean, devoted to the purpose chiefly of instituting mag-
netical observations. This proposal first underwent the revision of the
Committee of Recommendations, and then obtained the sanction of
the General Committee of scientific members; subsequent circum-
stances, however, being considered by the Council as unfavourable to
the success of the application, it was not urged at that time upon the
government, yet the object was not lost sight of. The Association
next procured reports to be drawn up, (from one of which we have
quoted the foregoing paragraph,) presenting a luminous exposition,
both from published and unpublished sources, of the present state of
our knowledge of the magnetism of the earth, and of the reasons which
there are for wishing to extend to the Southern hemisphere those re-
searches which in the Northern have led to such important conclu-
sions ; and thus has the way been prepared through information thus
communicated to the public for pursuing the intended course with
advantage, and making a more efiectual application to the government.
There may be, once in an age, or in many ages, an individual ani-
mated by so lofty an ardour for the advancement of a favourite branch
of knowledge, as to engage, at his own cost, in an enterprise (like a
recent survey of the southern skies) which it might have become a
nation to take upon itself; and there may be au individual whose dis-
interested munificence may extend to the point of rendering labours of
this magnitude as available to the public as if the state itself had con-
tributed its aid ; but such sacrifices to science are not only uncommon,
they are in general impracticable ; and there are numerous most im-
portant data and elements for philosophical reasoning, with all its
* Capt. James Ross, R. N.
c2
XXXVi EIGHTH REPORT — 1838.
train of practical utilities, wiiicli individuals cannot be expected to
undertake, unless provided with pecuniary assistance. We have al-
ready said, that one of the principles on which the Association pro-
ceeds, is not to look to government for anything which can be other-
wise attained; but when this Institution was established, the founders
of it foresaw that it might itself be made applicable, in a great degree,
to the object of supplying funds for such undertakings. The resources-
of other societies are emjiloyed on their publications or collections ;
and it is one of the rules of the German scientific " Reunions," that
they shall possess no propertj^ Our objects were more extensive than
theirs, and, therefore, our plan was different. We have accumulated
property and expended it, to give wings to investigation, partly by
providing instruments and materials for carrying on certain determi-
nate inquiries, and partly in defraying the expense of labour, especially
labour of that kind, which, whilst it is of the highest value in its re-
sults, possesses no attractions in its execution, and would meet with no
adequate remuneration.
The present volume of our Transactions contains many proofs of
the service which the Association has rendered by such applications of
its pecuniary means. In the account there rendered of the discussion
of observations of the Tides, Mr. Lubbock (the Reporter) thus ex-
plains the manner in which the last grant of money placed at his dis-
posal has been employed. He reports that two gentlemen had been
engaged by him to discuss the observations which had been accumu-
lated at Liverpool and the London Docks, — the one series continued
during nineteen years, and consisting of 13,391 observations, the
other carried on for thirty-five years, and including 24-,592 obser-
vations, — and also to examine carefully the esiahlishment and average
height of high loater in order to ascertain the fluctuation to which these
quantities are subject ; and after bearing testimony to the pains and
accuracy with which the work has been executed, and stating the
conclusions which result from these laborious calculations, adds, that
" they never could have been undertaken but for the interest winch
lias been felt on the subject by some of the most distinguished mem-
bers of the Association, and but for the pecuniary grants which have
at different times been devoted to this object," expressing, at the same
time, a well-grounded hope " that when these results (which have since
been published in the Philosophical Transactions) are carefully ex-
amined, they will not be found disproportionate in value to the great
labour and expense m hich liave been required for their attainment."
A service of a similar description has been rendered to astronomy in
the determination, by Dr. Robinson, of the disputed Constant of Nu'
tation from the Gi'eenwich Observations. Of this work, which in-
volves much labour of reduction, and which, to use the words of the
ADDRESS BY MR. MURCHISON. XXXVU
eminent astronomer who executed it, the powerful aid of the Asso-
ciation has enabled him to perform, a brief statement only, comprising
the method employed and the general results, is given in our Trans-
actions the fuller details requiring, as the author mentions, a different
mode of publication. And this, Gentlemen, leads us to remark how
unfounded were the apprehensions of those who feared that this In-
stitution would divert the springs from which other societies are sup-
plied ; whei'eas the instances before us prove that their Transactions
have been enriched instead of being impoverished by our operations.
There is a further remark which we are prompted to make on the
work accomplished under Mr. Lubbock's superintendence, by a re-
ference which his report contains to a subject of great interest to the
science of Geology. " I conceive (he says) that the best, if not the
only method of investigating alterations in the height of the land above
the water, in any given locality where the water is influenced by tlie
tides, will be to examine carefully whether any alteration has taken
place in the value of the (tide) constants D and E for that place, the
height of high water being, of course, always reckoned from some
fixed mark in the land." The meeting will here perceive one of those
connexions between departments of inquiry apparently remote, which
show how much each is concerned in the advancement of another,
and ought to prevent any jealousy respecting the distribution and
allotment of our funds. There is, indeed, no part of the proceedings
of the Association which requires to be regarded with more care than
the disposal of its grants, and our constitution has been framed with a
joarticular regard to this point. In the first place, every section of
science has its own committee, from whose deliberations every pro-
posal of a grant must emanate. Secondly, these proposals are all
submitted to a central committee, which recommends such of them as
it deems unobjectionable to the General Committee for final adoption
or rejection. By these means the best provision has been made for
preserving the administration of our pecuniary resources pure, judi-
cious, and consistent. So far as any rule of allotment has been fol-
lowed, it seems to have been only to assign the largest grants to the
most determinate, and at the same time expensive investigations ; but
the Association has not deemed it expedient to restrict itself to these.
Whenever the committee of any section lias been desirous of confiding
any inquiry involving an outlay of money to a competent person, the
committees of revision and approval have always been anxious to
comply with the recommendation. The meeting will observe with satis-
faction that the first step towards the solution of tlie geological question
alluded to by Mr. Lubbock, has been taken under tlie superintendence
of the committee appointed for the purpose. Mr. Whewell, to whose
more special superintendence the conduct of this work was intrusted,
XXXviii EIGHTH KEPORT 1838.
reports that a line has been leveled by Mr. Bunt from Bridgewater to
Axmouth, to be thence continued to the Bristol Channel ; and such
marks have been left as will allow of repeating or extending the levels,
and comparing at a future period the height of the several fixed points.
We are thus led to say a few words about Geology, a science which
is rapidly advancing to take its permanent station among the more ac-.
curate natural sciences. It is now six years since Mr. Conybeare laid
before us his eloquent general view of its then existing state ; but the
lapse of a much shorter period in a science which is making such vi-
gorous shoots, would present sufficient materials for a report which
should enumerate and define the latest conquests it has achieved. The
fact is, that the very literature of this subject is so vast, that none but
the most practised and laborious geologists can keep pace with its pro-
gress ; and though the anniversary discourses of the successive Presidents
of the Geological Society generally contain a sketch of the works and
memoirs which have appeared in the course of the preceding year, still
we are convinced, that a condensed retrospect of the progress of geo-
logy, which should embrace a somewhat larger period and a wider
range, executed from time to time at the request of the Association,
would not only be grateful to geologists, but would also tend to com-
bine the discoveries and promote the advancement of this science. But
besides general rejiorts on geology, this Association will, it is hoped,
encourage a continued attention to the consideration of mineral veins,
since there is no branch of geology of such direct public interest as
the results of the miner's discoveries. In a clear and instructive re-
port formerly read by our Treasurer, Mr. John Taylor (himself a most
experienced and able miner), he expressed a wish, which we trust to
see accomplished, that miners would hereafter not rest satisfied with
such observations and knowledge as the mere practice of their art re-
quired, but would extend and combine their inquiries in such manner
as to make them the foundation of more general and comprehensive
views, and would tend to connect more intimately than heretofore the
science of geology with practical mining. This subject, so important
in its bearing upon the production of our mineral wealth, cannot be
too strongly recommended to the attention of the Geological and Me-
chanical Sections of the Association. We venture, indeed, to hope
that the Newcastle meeting will be pre-eminently marked by the dif-
fusion of much sound mining knowledge, flowing as it must from the
meeting together of the most experienced Cornish miners with those
of Durham and Northumberland. We are further encouraged to in-
dulge in this expectation from knowing that this meeting is honoured
by the presence of an Austrian nobleman, long valued by English geo-
logists, and whose thorough acquaintance with mineral veins, and all
their complicated faults and changes, well entitle him to occupy the
ADDRESS BY MR. MURCHISON. XXXIX
high station confided to him by his sovereign *. And here we cannot
but obsei-ve, that as, with all its mineral wealth, Great Britain is the
only country in Europe without a national school of mines, so much
the stronger is the call upon the British Association to promote the
analysis of every natural phenomenon and useful invention connected
with the art of mining. But while we make this appeal, we cannot
assemble in this neighbourhood without congratulating the University
of Durham on having led the way to the establishment of a school of
mines and engineering, in which the principles and knowledge of this
branch of science are regularly taught ; and we further feel gratified,
that so important a charge has been intrusted to men distinguished for
their scientific attainments, including in their numbers one of the earliest
promoters of the British Association, and one of its local secretaries at
this meeting f.
In the arrangements of the Association, the sciences of Mineralogy
and Chemistry have been united. Such an union may be justified, not
merely by its convenience in the distribution of our labours, but by
the close alliance which subsists between those sciences, in all that
concerns the connexion of chemical composition with crystalline forms,
presenting so many remarkable relations of very recent discovery, and
leading so rapidly, as Mr. Whewell has, on more than one occasion,
so clearly shown, to enlarged views of the true principles of minera-
logical qualification. But whilst we fully recognise the connecting
links which unite those sciences, we trust that this partial and tempo-
rary separation, which the active and somewhat absorbing study of
palaBontology has almost necessarily occasioned, will not be of long
continuance, and that the laws of crystallization, which constitute its
alliance with another science, will in the progress of our knowledge
give as much importance to its connexion with the study of the cry-
stalline structure of vast masses of the surface of the globe, as in the
most searching analysis of its minutest particles. Let not, however,
the exclusive advocates of any one theory of the proper relation of
those sciences induce us to abandon inquiries so pregnant with re-
markable conclusions, and which truly constitute the great basis and
framework of modern geology : for the more minute and laborious our
investigations, the more certainly do we make out that many rocks
which were once supposed to be made up of inorganic matter, are in
truth composed of animal remains. And do we not look for the
presence among us of a distinguished philosopher of Berlin, who,
above all others, has eliminated this discovery, and who, by the
powers of the microscope, has revealed to us the skeletons of millions
* Count Breunner, Director of the Imperial Mines, Foreign Member of the Geo-
logical Society.
t Professor Johnston.
xl EIGHTH REPORT — 1838.
of once living and perfect animalcules inclosed in a single cubic inch
of solid stone. Well, indeed, may we quote the reoent work of Lyell,
who, rejoicing in this great discovery, exclaims with the poet, —
" The dust we tread upon was once alive."
In noticing the labours of the Section of Geology and Geography, we
have to observe, with regret, that the latter science has not hitherto
received at our meetings that amount of attention to Avhich it is justly
entitled. When we consider the advances which the science has re-
cently made under the auspices of the Royal Geographical Society of
London, we cannot but lament that the British Association did not, at
an earlier period, request a report from some one of its members upon
the present state of our geographical knowledge, and upon those de-
partments of it in which our researches might be most advantageously
prosecuted. The annual reports of the Secretary of the Geographical
Society, — particularly the last report of Capt. Washington, and the
admirable discourse recently delivered by its President, Mr. W. R.
Hamilton, — have in great measure supplied this deficiency, making the
public acquainted both with much that has been done, and much that
remains to be worked out in this very important branch of knowledge.
But though we have thus been partially anticipated, we feel satisfied
that such a report, by bringing into prominent notice, before the whole
body of the Association, a statement of those great geographical pro-
blems, whose solution is most specially desired or most easily effected,
may serve to secure for the promotion of geography the application of
some portion of those funds which have been hitherto exclusively
appropriated to other sciences.
The merits of the Statistical Section have been already made mani-
fest, by the collection of a great variety of very important data. On
this occasion we have to notice a very perspicuous and well-arranged
report, which appears in our Transactions, upon the statistics of a
large province of Hindostan, which sufliciently proves that a statist,
who would really contribute to the advancement of statistical science
by collecting facts in distant regions, must possess no slight qualifi-
cations. In vain, in the absence of other essential branches of know-
ledge, may he accumulate half-digested and ill-assorted observations ;
he must also combine, as in the person of Colonel Sykes, the ac-
quirements of the naturalist and geologist with those of an accom-
plished soldier and of a man of general information.
The accumulation of such facts is obviously a very fit part of the
labours of this Association, for they prove statistics to be truly a
science of method. This science occupies the same relation to politi-
cal economy in its most comprehensive sense, which astronomical ob-
servations held relatively to astronomy before the discoveries of me-
ADDRESS BY MR. MURCHISON. xll
chanical philosophy enabled recent philosophers to make those early-
observations perform a mighty part in testifying the great primal
truths of physical philosophy, and applying them to explain, and even
to predict, the varied motions and phenomena of the earth and hea-
vens. Such a stage there must be in every inductive science, — one in
which immediate straining after comprehensive truths would be rash,
while the marshalling and classing phenomena is a task full of use-
fulness and hope. Those only who mistake the stage of discovery in
which statistical observers are now placed, — who do not see that at
present observation without premature speculation is the one and
necessary step towards wide truths, — will either be impatient to weave
rash theories from our present imperfect materials, or to scoff at the
unscientific character of those Avho labour patiently to increase and
arrange them. The analogy between the early stages of astronomy
and the actual position of statistics might be made more complete.
The secular character of many classes of statistical observations neces-
sary to elucidate difficulties and disentangle truth might be easily de-
monstrated, but enough has been said for the purpose of indicating the
really scientific character of this useful branch of our Institution.
It has fallen to our precursors to comment on the advances in Natu-
ral History which have been made by the Section of Zoology and Bo-
tany; and although, on this occasion, we are not presented with any
report upon these sciences, you all know how ably they have been
elucidated at former meetings, by a Lindlej% a Jenyns, and a Richard-
son ; and also with what vigour that section has prosecuted its inqui-
ries under the auspices of a Henslow and a Macleay. We must, how-
ever, here allude to the distinguished Northumbrian naturalist who
occupies one of our vice-chairs, and express our hopes that Mr. Pri-
deaux Selby may soon be called upon to contribute what is yet a de-
sideratum — a report upon the present state of the science of Orni-
thology.
We have hardly ventured to allude to the separate proceedings of
the Sections, for any discourse which should attempt to analyze their
labours or to do justice to their usefulness would occupy too large a
portion of your time. And besides this consideration, you, Gentlemen,
are all aware, that these Sectional Meetings give rise to the Reports
we have been considering, and also to the various practical researches
which are carried out by the employment of your own funds, or by
demands upon the country. If, therefore, the Reports constitute our
high claim upon the literature of science, the proceedings of the Sec-
tions must be viewed as the fresh current of scientific enterprise, which
continually vivifies and renovates the whole body of the Association.
Among the investigations which are proceeding under the auspices
of the Association, those which originated in the Committee of the
xlii EIGHTH REPORT — 1838.
Medical Section, including several subjects of physiological interest
reported upon in the present volume, are remarkable for that spirit of
co-operative labour which has not been common in this country, and
which it is one of the liappiest effects of these meetings to facilitate
and encourage. In like manner, a question of great interest as re-
gards one of the most important products of our mineral wealth and
national industry, which had been discussed with more than common
warmth and earnestness at former meetings of the Association, has
been examined by an analysis, performed by one of the most distin-
guished chemists of the present day, of the iron produced by the ap-
plication of the hot and cold blast respectively ; which was undertaken
at the request of the Chemical Committee, combined likewise with
experiments, on an extensive scale, upon its relative strength and other
properties, which were commenced at the desire of the Mechanical
Section, by Messrs. Hodgkinson and Fairbairn, whose profound and
extensive knowledge of practical mechanics so well qualified them for
a task which they have executed with singular ability, enterprise, and
skill. The experiments on Waves, which are detailed in Mr. Russell's
report in our present volume, were likewise undertaken at the request,
and carried on by the aid of the funds of the Association. The accu-
rate conception of a wave, its origin, propagation, and laws, is one of
the most difficult and fundamental of those which are required in
many of the delicate and embarassing inquiries of natural philosophy ;
and the experiments of Mr. Russell are well calculated to illustrate
and confirm many of the results which the mathematician has deduced
from the theory of fluid motion. Adhering, therefore, to our design
of mainly noticing those parts of our recent transactions winch illus-
trate the prominent points in our system of operations, we shall con-
clude our remarks by noticing a report by Prof. Johnston, on a new
and curious subject of chemical inquirj^, as aflfbi'ding a good example
of the execution of an object which the Association has had much in
view. The discovery that there exist definite chemical substances,
which are capable, under certain conditions, of assuming more than
one crystalline form, not deducible from nor referable to each other,
and accompanied with different physical properties ; and furthermore,
that there are instances of substances which are capable (independently
of any change of composition) of undergoing some internal transmu-
tation sufl[icient to vary even their chemical aflinities : these are dis-
coveries which, pointing out a new road to the investigation of the
hidden mysteries of molecular attractions, peculiarly deserve to be
verified and extended. But it so happens that they have been little
studied or prosecuted in our country ; and, therefore, the Chemical
Committee, in accordance with one of the prominent designs of the
Association, selected this particular point as the subject of the Report
ADDRESS BY MR. MURCHISON. xliu
on Dimorphism, printed in this volume, which gives a fuller statement
than we before possessed, of the facts arrived at by foreign experi-
menters, the reasonings founded upon them, and the questions which
are left for future inquirers to solve. This is the precise point at
which the Association aims in the reports on the state of our know-
ledge, which occupy the chief space in its publications ; they are not
intended, like the articles in an encyclopaedia, to teach and diffuse
science, but to advance it — to show what has been done, with a specific
view to what there remains to do — to look forward to conquests to
come, rather than backward on those which are past — to survey the
border territory, and reconnoitre the debateable land. We have in
this, as in other respects, followed in the steps of him who gave the
original sketch of .an Institution like the present. The great teacher
of inductive science and experimental philosophy, who first showed
the importance of knowing the lines which divide knowledge from
ignorance, and in the memorable list of desiderata which he drew
up, did more for "the progression of the sciences" than Would have
been done by anj' discoveries he could have made.
Having thus endeavoured to elucidate, by reference to some portions
of its recent transactions, the comjarehensive system of this Association,
and to mark the real value of its corporate influence, its pecuniary re-
sources, and its concentrated intelligence, I would lastly notice that
part of the system which has given occasion to our present muster in
this prosperous and splendid city — the migratory character of our
meetings. In these migrations there is a double advantage ; the As-
sociation gains much by them, and perhaps the places it visits do not
gain less ; for its visits may sometimes have the effect of drawing
genius from obscuritj', and giving an impulse to powers which might
never have been exerted, and a direction to labours which might
otherwise have been misapplied. To our own body two great advan-
tages are derived : one is, that the wave, in rolling along, gathers to it
all the scattered science of the land, and that a more general and
powerful union is thus formed than could ever be collected by an
Institution resting on a fixed point : the second is, that varied objects
of interest and different opportunities of utility are offered by circum-
stances proper to the different places which the Association visits;
thus the lofty tower of York furnished means for the best experiments
that have been made on the phenomena of rain ; Liverpool contributed
its contingent to our knowledge of the tides ; whilst Bristol carried a
line from sea to sea, to ascertain the permanence or the mutations of
the level of the land and water. And does not this city and vicinity,
Gentlemen, also present its own peculiar objects of speculation and
opportunities of research? Is not the optical philosopher interested
in its celebrated glass-works? Can the chemist contemplate with
Xliv EIGHTH REPORT — 1838.
indifference those conspicuous and truly magnificent establishments
which exhibit, on so grand a scale, the application of those processes,
which have been deduced and perfected in his laboratorj', to pro-
ductions so important in our manufactures and arts? Can the geo-
logical or physical inquirer stand near its mines — those vast store-
houses of nature for the uses of art, the theatre of the most beautiful
of all the applications of science to the purposes of humanity — without
having his curiosity awakened ? or contemplate those deep excavations,
the most accessible of any that have been carried into the bowels of
the earth, without being tempted to investigations which may lead
perhaps to a better understanding of the internal condition and struc-
ture of our globe? Or can we survey the architectural creations
which surround us in the place in which we are assembled, where
order and magnificence have replaced confusion and meanness, with a
rapidity more resembling the illusions of an Arabian tale than the
sober anticipations of experience, Avithout being encouraged in our
own efforts by witnessing such noble results of individual enterprise,
genius, and arrangement, which have associated the triumphs of art
with tliose of manufactures and commerce, and combined the refine-
ments of wealth with the most varied productions of industry?
" Hic portus alii effodiunt ; liic alta theatris
Fundameuta locant alii, imnianesque columnas
Rupibus excidunt, scenis decora alta futuris."
Finally, Gentlemen, there is another reason for these migrations,
which it would be highly ungrateful in us to overlook, Mhich is equally
felt by the Association and by the place which it visits — the warmth of
hospitality which we see these visits call forth, the union of hearts and
the excitement of kind and friendly feeling acting on all our objects,
like oil on the wheels of a vast and powerful machine, without which
its every movement would be retarded, and its whole power brought
to a stand. Never, indeed, can the vitality of this Association be Ira-
paired, so long as the leaders who have borne the bark of science along
the waves shall lay stoutly to their oars. Assembling for a common
cause, and confiding in each other, may they ever glory In having
knit together all classes in the love of science ; and whether presided
over, as on this occasion, by a noble duke, alike illustrious for his just
appreciation and generous encouragement of our pursuits, or in the
ensuing year by some one eminent in their cultivation, we shall, we
trust, go o!T waxing in strength, and holding out the cheering example
of a great and triumphant commonwealth of science !
REPORTS
ON
THE STATE OF SCIENCE.
Account of a Level Line, measured from the Bristol Channel
to the English Channel, during the Year 1837-8, by Mr.
Bunt, imder the Direction of a Committee of the British
Association. Drawn up by the Rev. W. Whkwell, F.R.o.
one of the Co?nmittee.
1 . At several of the meetings of the British Association it
was suggested, that the exact determination of the relative level
of three points considerably distant from each other on the coasts
of this island might throw Tight upon several important questions.
Such a determination, it was represented, might especially be
made subservient to the solution of the two important problems,
— how far the position of the earth's surface is permanent — and
what ought to be understood by " the level of the sea." For if,
as some geologists think, many parts of the earth's surface are
slowly changing their position, such a change is extremely dif-
ficult to prove or disprove by observations made at any one point.
But if three points were at one time determined to be in one
horizontal surface, and were at a subsequent period found to be
at different heights, their relative elevations at the second epoch
would not only establish the fact of a change in the position of
the earth's surface, but M'ould enable us to determine, by an easy
calculation, the angle through which this part of the surface had
been elevated, and the axis about which the elevation had taken
place. And with regard to the level of the sea, it is well known
that surveyors and naval men are in the habit of assuming the
surface of low water of spring tides to I'epresent this level.
Now not only is such a surface extremely indefinite (varying
very considerably with the parallax and declination of the moon
and sun) but it is not in fact, not even approximately, a level
surface at all. The level of the sea, thus determined, would be
VOL. YII. 1838. J5
2 EIGHTH REPORT — 1838.
twenty feet lower on some parts of the coast of England than
on oUiers. And although men of science hav£ very generally
seen the pi'opriety of taking mean ivaler, (the mean of low and
high water,) for the level of the sea, this selection, till confirmed
by some actual observations of facts, might appear arbitrary and
insecure. But if it be found that the mean water is at the same
level at different and distant points of the coast, where the low'
water is at different levels, the propriety of taking mean water
for the level of the sea will probably be generally acknow-
ledged.
It may be observed, moreover, that the question of the per-
manence or change of the height of any point of the coast (un-
connected with a system of interior leveling) cannot be de-
cided by observation, except by reference to the level of the sea ;
and therefore to determine what is the level of the sea is im-
portant also to the geologist. On coasts where there are tides,
the question of the stability of the land involves the question of
the laws of change of the water.
2. For these reasons it was considered desirable to ascertain
by careful and exact levelling the relative heights of certain
points of the coast of England, and to refer these points to the
sea by adequate tide observations. The British Association at
its meeting in 1834, voted a sum of money (500/.) to be em-
ployed upon this object, and appointed a Committee to decide
upon and direct the requisite operations. The same thing was
done at the subsequent meeting in 1835. But the difficulty of
fixing upon a plan of operations and of selecting the means of
carrying it into effect by a joint deliberation of a large Com-
mittee scattered over thewhole empire, prevented anyactive steps
being taken towards the attainment of the object. At the meet-
ing at Bristol in 1836, in order to remedy this inconvenience,
those members of the Committee who had the opportunity of
conferring with each other after the separation of the Association
took upon themselves the task of directing the execution of the
plan. And it appeared to them desirable that a person should
be selected to perform the leveling operation for the Associa-
tion, independently of any other surveys which might be going
on ; for no materials collected for the purpose of any other sur-
vey could, in accuracy and other conditions, answer the purposes
contemplated by the Committee. They considered themselves
fortunate in being able to engage Mr. Bunt oi Bristol in this ser-
i^ice, having entirely satisfied themselves of his accuracy and
scrupulousness in observing, and of his clear apprehension of
the nature of the operation. They also took the precaution of
directing Mr. Bunt to execute a preparatory level from Bristol
J
REPORT ON A LEVISL LINE. 3
to Portishead, (a distance of eleven miles) and back to Bristol,
in order to ascertain the degree of accuracy which could be at-
tained in this operation. The total amount of error resulting
from this operation was 1*07 inches ; but there appeared grounds
for believing that the uncertainty of the result was very much
smaller than this quantity ; and this belief has been confirmed
by the general course of the subsequent operations.
3. An excellent telescope level was constructed by Mr. Simms
for the Association, to be used on this service, and also a level-
ing staff, for which however Mr. Bunt afterwards found it con-
venient to substitute one of his own construction. This is de-
scribed in the Appendix to this account.
4. The extremities of the line selected were on the north coast
of Somerset and the south coast of Devon, as affording the case
where coasts belonging to separate seas could most easily be
brought into connexion. A north and south line being thu3
obtained, it was proposed to extend the operation to the east-
ward, so as to obtain a third point under suitable conditions.
The first line selected for leveling*, on a careful inspection of
the country, was one proceeding from Bridgewater up the river
Parret byLangport to Ilminster, Chard, Axminster, and thence
to the mouth of the river Axe, which was fixed upon as one of the
terminal points where tide observations were to be made. Bridge-
water was connected with the sea at the other extremity by a
line, which, skirting the Quantocks, reached the shore in the
first instance at Stolford opposite the Wick rocks ; but was after-
wards carried further to the west in order to reach a more solid
rock, and terminated at East Quantocks head near Watchett.
5. The leveling from Bridgewater to Axmouth was begun
May 16, and ended July 8, 1S37. From Bridgewater to Wick
rocks the operations of leveling and preparing for tide observa-
tions were carried on in October 1837- Tide observations were
made at Axmouth from January 4, to February 2, 1838, and at
Wick rocks from November 9, to December 9, 1837 j and again
at Axmouth, simultaneously with Portishead, July 14 to 21,
1838.
The line thus leveled crossed no very great elevations, and
was for the most part very conveniently even. The highest
point was at Whites House near Chard, where it attained a
height of 280 feet.
6. The extension of the leveling process to any considerable
distance east or west of this line was a matter of difficulty ; the
ground in both directions consisting of a series of hills and val-
• See Plate I., (the map).
B 2
4 Eir.HITI REPORT — 1S38.
leys of considerable magnitude. Such a couiitiy would require
to be leveled by a series of very short distance^ ; and this cir-
cumstance would not only add greatly to the labour and expense
o: the operation, but would render doubtful, in a very material
degree, the accuracy of the result. It was therefore judged ad-
visable to be content with extending the level rorth-eastward
to Portishead and Bristol. By this means the east and west-
extent of the surface surveyed became nearly equal to the ori-
ginal north and south line ; and the level line which rests upon
the Qiuuitocks at one extremity, crosses the Mendips and the
Leigh Down Hills, connecting a great number of different geo-
logical formations.
7. This line from Bridgewater to Portishead was leveled
between May 15, and July 6, 18.3S; and tide observations were
made at the latter place in May 18.3/, and July 1838.
8. Both in the leveling and in the tide observations, every
precaution Avas taken to avoid mistakes and to ensure accuracy.
As leveling operations of a very delicate kind have rarely been
performed, and are nowhere sufficiently described, it is con-
sidered worth Awhile to record the raetliod employed in this in-
stance, and an Appendix is added containing this description.
It may here be observed, that the most important precaution,
that of making the distances of the staff from the telescope
equal in the fore observation and the back observation, was
throughout attended to ; and that all the lines were leveled in
both directions, proceeding from the beginning to the end of the
line, and then returning back fron\ the end to the beginning.
9. By employing this method of verification, an apparent
error in the process is brought into view, for which it is difficult
to account, but which is so constant in its occurrence that we
caimot help supposing it to depend on some general cause. The
error consists in this ; — that in proceeding \Aith the leveling
opei'ation along a line which is really level, the further end con-
stantly appears, from the observation, to be the lower end ; and
the amount of this depression appears to increase with the di-
stance. Hence, when v.e go to the end of a line and then return
I0 the starting point, we find the resulting elevation of the point
lower than its real elevation. The difference arising from this
cause is never considerable, but is always in the same direction,
and generally (in the same series of operations) greater in pro-
portion as the distance is greater. Thus in the line from Bristol
to Portishead (11 miles) it was 1*07 inches; from Bridgewater
to Axmouth (40 miles) it was 4*11 inches; from Bridgewater to
East Quantockshead (16 miles) it was 1*94 inches; from Bridge-
water to Portishead (^9 miles) it was 7'6 inches.
- REPORT ON A LEVEL LINE. •>
10. It is very difficult to explain the cause from which this
seeming error arises, or even to conceive any cause from which
it can arise. The errors arising from the curvature of the earth,
and from any permanent refraction, are eliminated by the con-
dition of equal distances in the fore and back observations. The
difference does not seem to arise from the effect of the sun's rays
on the instrument, for it is not removed by shading theinstrument
Avith white paper ; nor fi'om any rise of the peg between the fore
and back observation, for it is not confined to soft ground. It
appears to go on increasing with the time during which the ob-
servations are continued, and is such an error as would result,
if we suppose that in every interval of time between the back and
the fore observation, something takes place by which the staff
is apparently (by refraction or otherwise) less elevated (or more
depressed) at the fore observation than it had been at the pre-
ceding back observation. For these elevations are supposed to
be equal in the process ; and if the elevation of the fore point by
refraction or any other cause be the smaller, the point will ap-
pear to be lower when it is really on the same level. This state-
ment, however, is made rather with a view of explaining the
nature of this error than of assigning its cause.
1 1 . But since it is thus probable that this apparent error arises
from some constant and general cause, it is clear that we shall
get rid of its effects in each case by taking the mean of the first
and last results. We may therefore suppose the mean difi:erence
of levels obtained by leveling between two points, first in one
direction and then in the other, to be accurate within limits very
much smaller than the errors above mentioned. We may venture
to confide in this result to a fraction of an inch.
12. The relative heights of the parts of the lines surveyed
being determined by the operations of which we have been speak-
ing, marks were fixed at various points, by means of which the
position of the line now measured may hereafter be again dis-
covered. These mai'ks are the following. A place was selected
in the solid rock on the shore just below tlie fort at Portishead ;
and in this was inserted horizontally a cylinder of iron, two
inches diameter and fifteen inches long, containing in its centre
a brass wire one eighth of an inch in diameter, which marks
the position of the standard point, about eight feet above the
highest high Avater. This mark is on the property of James
Adam Gordon, Esq., of Naish House, who kindly gave per-
mission for its being placed there. Tiie mark at East Quan-
tockshead is on a farm called Perry Farm, the property of J.
F. Luttrell, Esq., of Dunster Castle. It consists in a block
of granite, a ton and half weight (the gift of the corporation of
6 EIGHTH lllCI'ORT — 1838.
BridgewHter) in which is inserted horizontally, without lead, a
copper cylinder an inch and a half diameter and fourteen inches
long. In order to prevent this bolt being drawn, it is fastened
with a copper key passing through a transverse hole into a
notch in the bolt, and the transverse hole is filled with lead. A
similar block of granite, (also presented by the corpoi'ation of
Bridgewater) with a similar copper bolt, is the mark at Wick'
rocks, in the parish of Stogursey near Bridgewater, which stands
on the property of Sir Peregrine P. Acland, Bart. The mark
at Axmouth is a similar block of granite, procured by J. H.
Hallett, Esq., of that place, on wliose property the mark
stands, and who has manifested a great disposition to forward
the operations in every way. The kindness and liberality of the
gentlemen who have been mentioned, on whose ground the marks
have been inserted, have much forwarded the undertaking, and
deserve the best acknowledgement the British Association can
make. These gentlemen are also willing to perpetuate the obli-
gation which science thus owes them, by allowing themselves to
be considered the guardians of the permanent level marks thus
existing on their property ; and this is a kindness the more
valuable, since the British Association neither has nor can have
any valid right to such services. The marks of which this
statement contains the record, may hereafter be of great conse-
quence in settling important questions of a scientific nature, if
their pi*eservation be, as we do not doubt it will be, kept in mind
by the proprietors of the estates above mentioned.
There is also a bolt inserted in the Avail of the church at Ax-
mouth ; and it is intended to place a similar mark in the church at
Uphill, a village situated where the level line crosses the western
extremity of the Mendips.
With the permanent level points at Axmouth, Wick rocks,
and Portishead, the surface of the sea was compared by means of
tide observations made at first for a month at each of those places.
In pursuance of the views already stated, the mean of high and
low water was taken as representing the level of the sea. In
fact, this level of " mean water" is so nearly constant, that even
a few days will give its position with tolerable accuracy ; and
observations continued for a fortnight, which of course includes
spring tides and neap tides, give the result with great precision.
The first result was, that while the level of mean water at Ax-
mouth and at Wick rocks did not differ by more than a small
fraction of an inch, the level of mean water at Portishead was
four inches and a half lower than at the other places. As how-
ever it appeared possible that this difference might result from
the observations being made at different times of the year, further
REPORT ON A LEVEL LINE. 7
observations were made shnidtaneously at Axmouth and at Por-
tishead, from July 16 to 30, 1838 ; the result of which was that
the level at Portishead is nine inches higher than that at Axmouth.
13. The difference between the result of the first and second set
of tide observations at Axmouth (1"29 feet in the mean level,)
was such as to require examination. It appeared possible that
this difference might arise from some of the inequalities which
affect the tide, and depend upon the time of year ; one set of
observations having been made in January 1838, and the other
set in July. I therefore requested Mr. Bunt to examine the Ply-
mouth observations of high and low water for the same period
(with which observations I was supplied by the Admiralty). The
result of this examination was that the mean sea levelat Plymouth
was only one fiftieth of a foot higher in January than in July
last : and it therefore appears certain that no annual inequality
of the tides is the cause of the difference. T am led to ascribe
it to the circumstance, that in the observations of January, the
low water at Axmouth was taken within the bar at tiie mouth of
the river. In Julj'^, the low water, within this bar, was certainly
higher by a foot or two than it was on the outside ; and though the
bar had altered its position in the intermediate time, I have little
doubt that it was in such a condition in January as to vitiate
the observations of low water. The observations of low water
made in July last, simultaneously with those at Portishead, were
made entirely outside the bar.
14. Taking the simultaneous observations made at Axmouth
and Portishead in July, 1S38, as the most free from obvious objec-
tions, we obtain the following results respecting the comparative
level of the sea at the two extremities of our line. The measures
of level were all referred to a certain zero point, assumed 100
feet below the point where the operations began. The level of
the mean tide above this zero was
at Axmouth . . . 71*96
at Portishead . . . 72-69
difference . . '73 foot;
or something less than nine inches. But the range of spring tides
at Axmouth was 5 feet above and below this level ; at Portis-
head 17"87 feet above and below. Hence we have for the relative
levels of high and low water at spring tides
High Water. Low Water.
at Axmouth . . 76-96 . . . 66-96
at Portishead . . 90*56 . . . 54-82
differences . . 13-60 . . .12-14
8 EIGHTH RErORT — 1838.
Thus the sea ;it Portishead is at high water 13*6 feet higher and
at low water 12-14 feet lower than at Axmouth. ' And if we take
the extreme tides whicli occurred during the observations, the
differences are still greater ; for the greatest range of tides at
Axmouth was 10*8 feet, and at Portishead 41*1 feet. And the
difference of the halves of this is 15-1 feet, which is greater by.
2-23 feet than the difference of the ranges just employed. Also
these elevations of the ocean are nearly contemporaneous ; for
the high water at Axmouth occurs (at a mean) forty-four minutes
earlier than at Bristol, and at Portishead two minutes and three
quarters later than at Bristol.
We have in these results a very strong indication that the
mean tide is what we must take as the level of the sea, for it
would be difficult to believe that the level of the sea is fourteen
feet higher at Portishead than at Axmouth, or sixteen feet lower,
which are the consequences of taking for the level high water
or low water at spring tides*.
We may add, that at another of our stations, the Wick rocks,
by a month's observations in November, 1837, the mean level
was 73*11, or 3*8 inches higher than at Portishead. Perhaps a
portion of this difference may be due to the inevitable errors of
the operations. The range of the tides at this place is nearly
the same as at Portishead, and the time of high water (at the
mean) about thirty-seven minutes earlier than Bristol, and there-
fore about seven minutes later than Axmouth.
15. The general result to which we are led is that the mean tide
must he taken as the level of the sea. This result had already
been arrived at by various persons. Capt. Denhani had asserted
it as the consequence of his observations at Liverpool ; and Mr.
Walker had been led to the same conclusion by the tides of Ply-
mouth. I had also pointed it out as the result of the Plymouth
observations in the Philosophical Transactions for 1837-
] 6. But these conclusions were supported only by observations
made at a single place ; namely, by its appearing that the height
of mean tide was nearly constant, (varying at most only a few
inches) while both high and low water varied by many feet.
And so far as I have yet seen the evidence, it seems probable that
though the change of the level of mean tide during a fortnight
be small, there really is some regular change of this level tide,
produced by the effects of the moon and sun. But the small-
ness of the "changes of this level, as it is now announced, rests
upon quite different evidence, and appears to indicate a perma-
• In Plate II. I have lepfcsenled the relative range of the tides at these
places as observed.
tlErORT ON A LEVEL LINE. 9
iience of a more rigorous nature. The mean level of mean water
at one point of the coast of the island, taken for a semilmiation
(and probably still more if taken for several lunations), may be
asserted to agree with the mean level at another point taken
in the same manner, within a very few inches. Perhaps the
agreement, if places situate on the open sea were taken, is still
nearer; for Portishead, and even Wick rocks, may be affected
by the narrowness of the Bi'istol Channel, which may elevate
the low water there, as it certainly does in a river. It appears
very probable that the level of mean tide at different places on
the open coast agrees as nearly as the operation of leveling can
determine.
17. This result is not only very curious in itself, but pregnant
with important practical consequences. It is very clear, from the
slightest consideration of our results, that nothing but error and
confusion can result from processes, such as have often been em-
ployed up to the present time, in which heights are determined
from " the level of the sea," this level being understood to be
that of low water spring tides. Such heights are not measured
from a level at all, but from a surface of which some parts are
sixteen feet lower than others within the limits of our operations,
and probably above twenty feet, if we take the extreme cases on
the shores of our island. The only method of stating heights
which can have any pretensions to accuracy, is that of reckoning
them from a conventional fixed datum upon the solid land ; to
which datum the sea as well as the land must be referred by
proper leveling operations.
18. As a specimen of the doubt and confusion which have
hitherto prevailed on this subject, I may quote a passage from
Mr. Telford's report on the project of a ship canal, intended
to connect the Bristol Channel with the English Channel, and
following nearly the same course as our level line. He says
" the total distance from Beer Harbour [near Axmouth] to
Bridgewater Bay [in which are Wick rocks] is forty-four miles
five furlongs. The fall from the summit to high water at an or-
dinary tide in Bridgewater Bay is 23 1 feet ; but by taking an-
other tide at Beer, the fall was found to be 233 feet."
The vague mode in which this result is expressed, an '^ordinary
tide " being taken in Bridgewater Bay, and " another tide " at
Beer, without any indication whether any correction was re-
quired for the difference of tides, and whether the result could
pretend to any accuracy, is, I conceive, an instance of the impos-
sibility of referring any elevations to the sea in a satisfactory man-
ner, till it is determined how we are to allow, not only for the
difference of high and low water, but for the different heights of
10 EIGHTH RKPOKT — 1838.
different high watei-s ; that is, till a proper discussion of tide
observations is combined with a system of leveling operations.
I may add that this result is certainly erroneous ; for it gives
the high water in Bridgewater Bay only two feet higher than on
the south coast of Devon ; whereas by our observations, which
certainly cannot err a foot, the former level is at least fourteen feet
higher than the latter. The difference, which is perhaps not to
be wondered at in rough leveling such as that performed in a
preparatory survey for a canal, is twentyfold greater than our
operations, carried backwards and forwards, and only differing
one or two inches in the result, allow us to consider as possible.
19. We may observe, in conclusion, that the result of our
operations, namely, that the mean tide in different points of the
coast is at the same level within a few inches, is of no small
practical value. For this being so, the level of any place within
a moderate distance of the coast may be determined, for the
purposes of canals or railroads, or any similar undertakings,
with reference to the level of places hundreds of miles distant,
by taking a fortnight's observations of high and low water, and
then leveling a few miles into the interior of the country.
20. It may perhaps be said that the conclusions thus stated de-
pend upon a single comparison ; that of the south shore of the
Bristol Channel, with the north shore of the English Channel.
When itis recollected that there are, omitting thesmaller flexures,
some hundreds of miles of coast between the two extremities of
our line, and that the tides at the extremities differ as forty feet
and twelve feet, I think it is impossible not to allow great value
to the result ; the operations being, as I conceive, of unim-
peachable accuracj'. But I am at the same time quite ready to
admit that it would be highly desirable to have the result corro-
borated by other comparisons of the same kind, especially by a
comparison of the east and west shores of England. For this
purpose it might be desirable to carry a level line from Bristol,
which is already connected with our operations, to London. The
expense of this, if performed in the same manner as that which I
have described, would be great ; but it appears to be worth con-
sideration, whether this expense might not be much reduced by
observing the waters of existing canals.
21. I will add, that such an extension of our level to London,
and in like manner to Plymouth, Liverpool, and other principal
ports of the empire, would be desirable in another view. As I
have already said, we cannot speak with accuracy of any level
except a conventional one ; and as each of these ports has its
own tide scales to which the rise and fall of the sea's surface is
referred, it would be desirable to compare the absolute position
RETOllT ON A LJEVKL LINE. 11
of these scales with regard to a level surface. We may in this
manner, and in no other, learn the true form of the ocean at any
time ; besides the practical advantages, which, as I have said,
would flow from having standard levels in various parts of the
island. I may mention, that the kingdom of the Netherlands
already possesses such a system of levels, by which all points of
its surface are referred to a certain zero at Amsterdam.
Whether such an extension of the level line measured for the
Association be desirable, may best be determined by the Com-
mittee of the Physical Section. In the mean time I trust that what
has already been done possesses no small value, being, so far as I
am aware, the first attempt of the kind, executed with great care,
and I see every reason to think, with great accuracy.
22. The following are the heights of the marks above the zero
point.
Feet.
Iron bar at Portishead Fort 102-5795
Temporary mark at Wick rocks (Station N° 810) . . 99*4833
Copper bar in granite block, Axmouth 83*6513
Copper bar in Axmouth church 89*53 18
Copper bar in Uphill church. (This is not yet insert-
ed. The + cut on the east end of the church is at
the height) 205*8305
Copper bar at Perry Farm, East Quantockshead . . 244*4365
Copper bar at Stolford 125*1114
Level of mean water at Portishead 72*69
Wick rocks ...... 73'11
Axmouth 71*96
Account of the Leveling Operations between the Bristol
Channel and the English Channel, hy Thomas G. Bunt.
Previously to my commencing the leveling which I had re-
ceived instructions from Professor Whewell to undertake on
account of the British Association, I was desirous of deriving
such assistance as might be obtained from any published account
of a similar enterprise, in which due attention had been paid to
the niceties which the operation requires, and the best means
for ensuring accuracy ascertained and pointed out. All the or-
dinary treatises on leveling are of the most elementary and su-
perficial kind ; and the only account I have met with which could
at all assist me is that given by Captain Lloyd in the Philoso-
phical Transactions for 1831, which details with clearness, and
12 EIGHTH UEPORT — 1838.
at considerable length, every particular connected with his kyel-
ino- from Sheerness to London ; a scientific enterprise of similar
character to that in which I was about to engage. This memoir
of Captain Llo5'd I regard as one of considerable value, and
have derived from it much information and assistance. Most
of his arrangements appear to me to be very judicious, and se-
veral of them I have either adopted or imitated. On one im-
portant point, however, I am obliged to differ from him, to
which I shall have occasion to advert presently.
The instruments made for this undertaking were a spirit-level,
and brass leveling- staff, by Simms, London. The telescope,
though only 14 inches in length, was found to bear the high
nia"'nifying* power of 26 so well under all circumstances, that
the other eye-piece with which it is furnished was never em-
ployed. The glass spirit-tube is so nicely ground, that the
position*of the air-bubble is sensibly altered by raising or lower-
ing either end of the tube jo^th part of an inch. In the focus
of the telescope are a horizontal and two vertical hairs, which
latter afford a very convenient means of measuring the distance
of a station, within about the y^pth part of the truth, by count-
ino- the number of intercepted divisions of a scale made for the
purpose, and held horizontally over the station by an assistant.
The legs which were made to support the level, although very
strong, were found to vibrate so much from the action of the
wind, as to render it difficult to take a correct observation, ex-
cept in perfectly calm weather. It was also next to impossible
to level the spirit-tube, unless by accident, for want of a slower
and more delicate motion than that afforded by the parallel
plate screws. I therefore ordered a very strong stool to be made
by a carpenter, the top of which was a thick board 12 inches
in diameter. The level was then detached from its former sup-
port, and fastened to a circular piece of mahogany, which rested
by three foot-screws on the top of the stool, and was firmly se-
cured to it by a stout wooden screw, with a nut at bottom,
passing through both the circular boards. On trying this appa-
ratus, I found that a more delicate vertical motion was still
wanted, which was at length perfectly attained by causing one
of the three foot-screws to rest on a small brass lever at a very
short distance from the fulcrum, while tiie farther end, furnished
with a fine screw and milled head, communicated about j^ th of its
own vertical motion to the foot-screw of the level, affording a
very simple and delicate means of adjustment.
The level, although now incomparably steadier than before,
was still found liable to disturbance from the wind, when it blew
with any considerable force ; to protect it from Avhich we car-
REPORT OX A LEVEL LINE. 13
ricd with us a piece of canvas, 6 feet square, nailed to two poles,
^vhich were sharpened at the bottom, to enter the ground. This
screen being held firmly by two men on the windward side of
the instrument, sheltered it so completely, that T was able to
proceed in windy weather, with but little interruption.
The brass leveling staff was employed in leveling between
Bristol and Portishead ; but being found inconvenient, and liable
to get out of repair, was obliged to be laid aside. The staff
which I subsequently constructed and used, is of wood, 9 feet
long, and 2 inches wide, a single piece of straight- grained oak.
On the face are two different scales of equal parts. One is the
common scale of feet and hundredths of a foot ; the other has
larger divisions, in the proportion of 19 to 16 nearly, or more
exactly, as 1*18702 to 1 : an aliquot ratio of the scales having
been purposely avoided. Both of these are reckoned upwards
from a common zero at the bottom of the staff. The centesimal
divisions of the foot are produced in strong black lines towards
the left, and large figures denoting feet and tenths placed against
them, so that the height may be read off at the telescope to the
j-igth part of a foot at a distance of 150 or 200 yards. These
marks are also useful for directing the assistant where to fix the
vane, by calling the division to him, especially when the reading
was near the top of the staff. A stud of wire, about half an
inch long, projects from the bottom of the staff, and a hole is
bored to receive it in the top of the peg which is driven into the
ground at every station, and on which the staff rests during the
observation. A small spirit-cup with a glass cover, screwed to
the lower part of the staff, serves to adjust it to a vertical posi-
tion, in which it is held fast by a clamp attached to three strong
legs, jointed and folding together, in the usual manner.
The vane is a small mahogany box, about 3 inches in each
dimension, open at the. ends to admit the staff, which slides
through it. Two large wooden screws at the back of the vane
clamp it very firmly to the staff, and preclude all danger of
shifting. In front is a frame of brass, about 2 inches square,
sliding within an outer frame of brass screwed to the vane, with
a range of motion of about half an inch, either upwards or down-
wards, being moved by a large vertical screw with a milled head
working through the lower part of the outer frame. A square
aperture, corresponding with the inside of this frame, is cut
through the mahogany, in order that the divisions of the staff
may be seen. A small ivory door moving on a hinge, is fitted
into the sliding frame, on which are drawn two thick black lines,
crossing each other at a small angle, and a black ring with a
white circular spot within, at the centre, or intersection. At-
14 KIGIITH REPORT 1833.
tached to the inside of the sliding frame, and exactly behind the
centre of the white circle, is a vernier, nea'tly in contact with
the face of the staff, which divides the hundredth of a foot into
five parts, of 20 ten-thousandths each, so that the observation is
read off and recorded to four decimal places. The white circular
spot, and the angular spaces between the lines, may be bisected. by
the horizontal wire of the telescope, with great exactness. In
favourable weather, I have usually found the average error, or
the difference of a single reading from the mean of the number
taken to be about ^ ju'^'^ ^^ ^^^ inch, on a distance of 88 yards,
or about a quarter of a second of angle. (See Wood-cut at the
end of this paper.)
When the vane was raised so near the top of the staff as to be
out of the reach of the hand, the adjusting screw was worked by
a long fork of stout wire thrust into holes made in the milled
head to receive it. A groove made in the upper part of the
staff receives the fork when it is not in use.
In leveling, I proceeded regularly in the following manner.
Two equal distances, usually of 4 chains or 88 yards each, ha-
ving been measured forwards from the last station, the level was
placed at the end of the first distance, and, at the second, a
strong wooden peg driven firmly into the ground, for the fore
station, the level being exactly midway between the stations.
When, (as happened in a very few instances,) I was prevented
from making the fore and back distances equal, compensating
unequal distances were immediately afterwards taken, so that
the sums of the two sets of distances were kept equal through-
out. The staff being held vertically on the back station peg, by
the means before described, and the first observation taken, the
height was read off and written down by the assistant in a rough
minute-book wliich he carried for the purpose. The vane was
then purposely thrown out, by turning back the screw, the level
re-adjusted, and a second reading taken. If these readings
agreed within 20 lO.OOOths (about ^^th of an inch), the staff
was brought forward to me, when 1 read off and inserted the
last reading, according to both scales, in separate columns of my
book ; the mean of both readings was also inserted in a third
column, after my assistant and myself had called over and com-
pared the last reading. The assistant then read off and called
to me the last reading from the large scale, as a check on what
I had entered in my book. The needle bearing and distance in
links, being also inserted in their respective columns, completed
the back observation. The process in taking the fore observation
was the same, except that instead of having the staff brought to
me to be read, 1 had then to carrv forward mv level to the staff.
REPORT ON A LEVEL LINK. 15
A rigid adherence to this sj'stem rendered it improbable that
a wrong reading could be written down, without immediate de-
tection : — in fact, such an instance does not appear to have oc-
curred. Had it even been so, a discrepancy must have existed
between the columns of different scales, which would have been
readily detected on casting up and compai-ing the totals, at the
end of the day. From erroneous readings, therefore, it is evi-
dent, there was little or nothing to fear ; but these are far from
being the only, or the principal sources of error. On one or
two occasions, we were very near committing a mistake, in be-
ginning at a different station from the one on which we had
previously closed. This would have occasioned an error, per-
haps of large amount, which could only have been detected by
the second and independe3it series of levels, taken over the
ground in an opposite direction. For this i-eason alone, I should
not consider it safe to depend on one course of levels only,
whatever may have been the precautions used to guard against
error.
The total length of my line of leveling between Portishead
and Axmouth, besides the branch lines to Bristol and East
Quantockshead, is about 74 miles. This distance was divided
into separate stages ; each of which, averaging about 10 miles
in length, was twice leveled over, first in one direction, and
then in the opposite, before the next stage was commenced. It
is very remarkable, that with a few partial exceptions, the heights
of all the points touched upon by both series, came out less by
the levels returning, than by the levels going : so that the first
station,or starting-point, always appearedlower when Ireturned,
than it was at my setting out. But as the height of this point
is the same in both cases, the error must, of course, be thrown
on the distant point, or station at which the returning levels
commenced, which reverses the first apparent differences, and
makes all the heights in the second series progressively greater
than those in the first, the most distant point having the greatest
error. The following table gives the differences thus found at
20 points along the line between Portishead and Axmouth, the
height, in every instance, coming out greater from the series of
levels returning towards Portishead.
No. of Station
in Minute-book.
1683 . .
Miles from
Portishead.
. .
Height greater by
2nd than 1st Levels.
Feet.
. . 0-0000
1631 . .
3 . .
. . 0-0633
159.S . .
. . 6 . .
. . 0-1557
1562 . .
. . 9 . .
. . 0-2703
16 KU.HTH RKPORT — IS.^8.
No. of Station Miles from Height greater by
in Minute book. Portishead. 2iul tiiau 1st Levels.
Feet.
1527 .... 12 ... . 0-3501
1278 .... 15 ... . 0-.3796
1229 .... 18 ... . 0-4591
1178 .... 23 ... . 0-5339
1128 .... 27 ... . 0-5734
759 .... 30 ... . 0^352
1 .... 33 ... . 0-6888
45 .... 37 ... . 0-6956
63 .... 39 ... . 0-7170
114 .... 43 ... . 0-7532
177 .... 49 ... . 0-8237
210 .... 52 ... . 0-8622
246 .... 56 ... . 0-9021
248 .... 59 ... . 0-9208
402 .... 63 ... . 0-9373
462 .... 68 ... . 0-9714
656 .... 74 ... . 1-0294
After the most careful examination of every circumstance
which could possibly tend to occasion these curious differences,
I am inclined to believe that they arise principally from rapid
variations in the amount of atmospheric refraction which occur
durin(( the time that elapses in a single observation, and that
the progression of the error is in some way or other connected
with the progressive changes of the average temperature during
the course of the day, from about eight in the morning till six
or seven in the evening, — the usual limits of my working hours.
These variations in the refraction are much greater and more
sudden in summer than in winter, especially during the forenoon
of a hot and sultry day, when there are frequent alternations of
cloud and sunshine, and copious exhalations of moisture from
the ground. On such occasions I have sometimes known the
sudden clearing away of a cloud from the sun followed almost
in an instant, by a change in the apparent height of the vane
amounting to y^^^^ ^^ ^" inch, or more, on a distance of only 88
yards. At other times the change has been more gradual, so
that several successive readings, taken at intervals of two or
three minutes, have all either increased or diminished progress-
ively. Different seasons or states of the weather may therefore
fully account for the more rapid increase of these differences at
certain times than at others, such as the above table presents, in
which the errors are fovmd proportionablygreaterbetvveen Portis-
head and Bridgewater, than between Bridgewatt>r and Axmouth ;
REPORT ON A LEVEL LINK.
17
thelatterdistancehavingbeen levelled over in the suinnierof 1837,
and the former in that of 1838. For the same reason it appears
much better to divide the distance into stages and finish them
one at a time, than to go over the whole in one direction, before
returning upon any part of it ; it being much more probable
that errors depending on the state of the atmosphere will balance
each other in the former than in the latter case.
My own experience, therefore, leads to the conclusion, that
no levelling can be expected to give a correct result, unless it
be performed in opposite directions, and the mean of both re-
sults be taken ; instead of depending, as Captain Lloyd appears
to have done, on the consistency of separate sets of successive
readings. I have myself invariably found (as that gentleman
also did.) the agreement of these to be almost identical, both in
the going and in the returning series, notwithstanding the great
progressive difference of these two series of levels from each
other ; of which progression not the smallest trace is discover-
able in the separate columns of the same series, I have entered
the more minutely hito this subject, because I am not aware
that any one has described, or even noticed the existence of
such differences before ; and should feel much interest in reading
the statements of any experienced person who had been engaged
in a similar undertaking, and had conducted it with sufficient
care to render the law of the errors in any degree discernible.
VOL. VII.— 1838.
i
jg EIGHTH REPORT — 1838.
SKETCH OF THE NEW LEVELLING STAFF AND VANE.
19
Report on the Discussions of Tides, prepared under the direc-
tion of the Rev. W. Whewell, F.R.S., by means of the grant
of money made for that purpose by the Association.
The grant of money made at the last meeting of the Associa-
tion, has enabled me to continue the discussions of tide observa-
tions which I had already carried on for some time, and to ob-
tain some results which I hope will be considered as valuable.
I engaged Mr. Bunt to proceed with those discussions, accord-
ing to methods which I had previously framed, and instructed
him in the execution of j and at present, his skill in the appli-
cation of these methods being improved by practice, and stimu-
lated by a great zeal and love for the subject, I believe his work
(which I produce to the meeting,) will be found of extraordi-
nary accuracj' and clearness. I am fully persuaded that in con-
sequence of the advantage of the plan pursued, and of the ex-
cellent manner in which Mr. Bunt has executed it, the exact-
ness of the results is of a most unexpected kind : for example,
it is quite clear that the tables for semimenstrual inequality and
for lunar parallax, (if not for declination,) obtained by our me-
thods from a year's observations, are as good as those previously
obtained from the discussion of nineteen years' observations.
And the proof of this is found, not only in the regularity which
the curves expressing the corrections exhibit without any arbi-
trary impi'ovement whatever, but also in the complete symme-
try of the curves above and below the mean ; the parallax cor-
rection curves for 60' and for 54' (3' above and below the mean
570 '^^^ t)f exactly the same form.
I have given an account of the results of these discussions in
a memoir read before the Royal Society, and printed in their
Transactions, entitled "On the Determination of the Laws of the
Tides from short series of Observations," being the ninth series
of my tide researches. An account is also there given of the
method pursued by Mr. Bunt in these discussions. I may men-
tion here the questions of which I have in that paper attempted
the solution.
1 . To which transit of the moon ought we to refer the tide ?
2. How does a change of the epoch affect the semimenstrual
inequalities ?
•S. How does a change of the epoch affect the (lunar) parallax
correction of the times ?
4. How does a change of the epoch affect the (lunar) declina-
tion correction of the times ?
c 2
20 EIGHTH REPORT — 1838.
5. How does a change of the epoch affect the parallax correc-
tion of the heights ?
6. How does a change of the epoch affect the declination
correction of the heights ?
7. Does the parallax correction of the heights vary as the pa-
rallax ?
8. Does the parallax correction of the times vary as the pa-
rallax ?
9. Does the declination correction of the heights vary as
the square of the declination ?
10. Does the declination correction of the times vary as the
square of the declination ?
11. Can the laws of the corrections be deduced from a single year?
12. Are there any regular differences between the corrections
of successive years ?
13- Do the corrections of different places agree in laws and
amount ?
The epoch here spoken of is that transit of the moon, anterior
to the tide, and to which the tide is referred. The question ex-
amined is, whether we obtain the closest accordance with the
observations by taking a transit one day, one and a half day, or
two days anterior to the tide which we consider.
Although I have given the answers to these questions in the
memoir in the P/iilosopkical Transactions already referred to, I
here lay before the Association the curves*, the comparison of
which exhibits these answers, and exhibits indeed the result of
my discussions more clearly and exactly than words can do.
The careful examination to which we have subjected the Bristol
tides, has shown us that there are scarcely any irregularities in
these phsenomena which m'c have not reduced, or may not hope to
reduce, to empirical laws, which laws constitute the first step to
the solution of our great tidological problem, the explanation of
the phfenomena on hydrodynamical principles. I may add that
the Report on Waves by Sir John Robison and Mr. Russell, inclu-
ded in the reports of the seventh meeting of the Association, con-
tains highly valuable materials, likely to assist us in the further
prosecution of this subject. The unexplained residue, which, in
our method of discussion, exhibits the difference between obser-
vation and our tables as hitherto corrected, although it is small
(upon the average two or three minutes in time, and as many
inches in height in a tide of forty feet), is so far seemingly subject
to some rule as to offer a promise of additional laws of cor-
rection, and I should be desirous of discussing this residual
quantity with such an object.
* These curves are given in Plates 3, 4, 5, 6, 7, 8.
21
Account of the Progress and State of the Meteorological Ob-
servations at Plymouth, made at the request of the Bi'itish
Association, under the direction of Mr. W. Snow Harris,
F.R.S. {Di-awn up by Mr. Harris.)
The Meteorological Instruments, now in operation, are as
follow :
1. A Wind Gauge invented by the Rev. W. Whewell.
2. A Wind Gauge invented by Mr. Osier, of Birmingham.
3. The Barometer.
4. The Wet-Bulb Thermometer.
5. The common Thermometer.
Professor Whewell's instrument has been carefully attended to
by Mr. Southwood, of Devonport. The results of the register
accompany this communication. In consequence of Mr. South-
wood's removal from Devonport, the instrument, together with
the wood work employed in its erection on his house, have been
preserved : it will be again set up as soon as possible.
Ten pounds, voted to defray the expense incurred in the erec-
tion, repair, &c., of this instrument, since its employment after
the Meeting at Bristol, have been paid to Mr. Southwood.
The Wind Gauge lately invented by Mr. Osier, and exhibited
to the Physical Section at the last Meeting at Liverpool, has at
length been set up in a very excellent situation, at the house of
Mr. Cox, Optician, Devonport. I am sorry that many unavoid-
able delays in the manufacture, &c. &c. of this machine have in-
terfered so much with its final completion, that I am unable to
send any well digested result of its action. It is, however, now
at work, and the Association will, I have little doubt, be amply
rewarded for the trouble and expense incurred on account of it.
Forty pounds was voted for this instrument ; of this 30/. has
been paid to Mr. Osier. The attendant expenses on it have
amounted to 201. This includes the erection of an apartment
of wood in which the instrument works, carriage from Bir-
mingham, clock for the register, and sundry other expenses
of a minor kind.
As the daily register must be carefully attended to it will be
necessary to provide some slight remuneration for the person
employed for this purpose. I should therefore feel obliged if
the Committee would recommend the sum of 10/. for the ge-
neral current expenses of the next year, should they so think
fit. The machine appears an extremely valuable one, and when
its register is taken in connexion with that of the barometer and
22 EIGHTH REPORT — 1838.
the tides, &c., will I have no doubt aflford very valuable infor-
mation, since it registers the force and direction of wind, with
the amount of rain for every instant in twenty-four hours.
The observations with the barometer are complete up to June
last, all the observations having been reduced. I have not,
however, been enabled to arrange in Tables more than those ■
of the year ending January 1, 1838. These observations being
for one year only, I have thought it undesirable to write any
detailed report of them. I may, however, be permitted to lay
before the Section, as an approximative result, the march of the
atmospheric pressure through one mean day, as shown in Table
A, Plate 9, and deduced from 8760 observations ; from which
some idea may be formed of the probable horary oscillation in
this place, a subject of singular interest in meteorology. It
appears by the result of the hourly observations for the year
1837; that the horary oscillation amounts to 0*0144 of an inch.
The hours of max. being 11 a.m. and 9 p.m.
The hours of min. being 5 a.m. and 3 p.m.
The line of mean pressure appears to be crossed 4 times in
the 24 hours, viz. between 2 and 3 a.m., and between 7 and 8
A.M. ; between 12 and 1 p.m., and between 6 and 7 p-m-
The deviations being .rjrvor , }-for the max. and min. a.m.
and .Qnqf-, >ior the max. and min. p.m.
The neg. sign indicates the depression below the line of mean
pressui'e, the pos. sign the elevation above it.
The mean pressure by these observations, at 60 feet above the
level of the sea, and at a temperature of 55° of Fahrenheit, is
29-9532*.
On the 1st of January, 1839, we shall have completed 2 years
of these hourly observations, when general results, entitled to
more confidence than those deduced from a single year, will
probably be arrived at. It seems therefore desirable, in order
to avoid too hasty generalization, not to enter further at present
into this question. I avoid for a similar reason any further
notice of the register of the hygrometric thermometer, the ob-
servations being in a state of progress only.
The register of the ordinary thermometer, first contemplated
by the Association at York in 1831, is, I am happy to say,
complete for 5 years, and the observations are novv' reduced up to
January last.
* A general type of the daily march of the barometer is given in Table A,
Plate 9.
METEOROLOGICAL OBSERVATIONS AT PLYMOUTH. 23
The general results^ which accompany this comniunicationj
and which are exhibited in Plates 10, 11, 12, must be consi-
dered merely as corrections of similar statements exhibited in
my fix'st report ; the former being arrived at by a more exten-
sive series of observations. It will be seen by an examination
of Table III., Plate 12, that the approximations in calculating
the hourl)' temperatures, on tiie supposition that they may be
represented by parabolic abscissfe, are much nearer than in the
similar table and plate before given.
Of £50 voted for these observations, £35 has been spent in
defraying the expenses attendant on them up to June last,
leaving a balance of £15 ; part of this has been expended in aid
of Mr. Osier's wind-gauge.
The labour attendant on the reduction and discussion of the
observations made hourly with these last-named instruments
being now very considerable, it becomes necessary to employ
competent persons to assist in working out tlie ordinary ai'ith-
metical operations, &c. I would therefore suggest to the Com-
mittee the propriety of recommending a sum not exceeding £40
for this and other attendant expenses until the next meeting of
the Association, when I hope to have the pleasure of submitting
to the Section a full report of the results obtained from the
respective registers.
W. Snow Harris.
32, Union Street, Plynioutb,
August 20, 1838.
Table I.
24
EIGHTH REPORT — 1838.
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METEOROLOGICAL OBSERVATIONS AT PLYMOUTH.
25
See Plate 11.
Table II. Showing the Mean Hourly Temperature for each of
the Seasons, viz. Spring, Summer, Autumn, and Winter,
for the Years 1838, 1834, 1835, 1836, 1837-
I
Hour.
Spring.
Summer.
Autumn.
Winter.
1
45-709
56-369
50-348
43-875
2
45-353
55-982
50-056
43-749
3
45-018
55-648
49-926
43-539
4
44-827
55-493
49-817
49-427
5
44-857
55-774
49-677
43-262
6
45-613
57-240
49-908
43-179
7
47-399
59-418
50-428
43-217
8
49-534
61-714
51-693
43-563
9
51-743
63-487
53-703
44-290
10
53-264
64-777
55-513
45-562
11
54-334
65-676
56-836
46-873
12
55-185
66-323
57-575
47-697
I
55-535
66-479
57-810
47-888
2
55-308
66-624
57-253
47-649
3
54-757
65-818
56-613
47-127
4
53-919
65-193
55-524
46-417
5
52-659
64-108
54-287
15-458
6
51-239
62-815
53-359
44-992
7
49-765
61-313
52-571
44-689
8
48-671
59-779
52-075
44-420
9
47-812
58-625
51-607
44-227
10
47-109
57-929
51-207
44-084
11
46-649
57-448
50-882
43-989
12
46-166
56-773
50-620
43-903
Means
49-684
60-867
52-912
44-878
Mean 52-085.
26
EIGHTH REPORT — 1838.
See Plate 12.
Table III. Showing the Mean Annual Hourly Temperatures
for 1833, 1834, 1835, 1836, 1837 at Plymouth, as ob-
served and calculated on the supposition that they may be
represented by Parabolic Abscissae.
Hours.
Obs. Temp.
Cal. Temp. I Diff.
Morn. Branch A B.
4 30
5
6
7
8
8 16
48-391 m
48-391
48-985
50110
51-626
/J 52-078
48-391
48-456
48-976
50-015
51-559
52-078
0000
- -065
+ -009
+ -095
+ -067
-000
Id
o
o
;2;
9
10
11
12 r.M.
1
53-306
54-779
55-929
56-695
M 56-928
53-468
54-982
56062
56-712
56-928
- 162
- -203
- -133
- -017
-000
Q
2
3
4
5
6
7
56-708
56-079
55-263
54-128
53-101
/It 52-093
56-794
56-369
55-716
54-773
53-560
52-093
- -086
- -290
- -453
- -645
- -459
•000
Night Branch E A.
8
9
10
11
12
1 A.M.
2
3
4
51-236
50-567
50-082
49-742
49-355
49-075
48-785
48-533
m 48-391
51-342
50-689
50-117
49-627
49-218
48-891
48-646
48-483
48-401
- -106
- 112
- -035
+ -115
+ -137
+ -184
+ -139
+ -050
- 010
METEOROLOGflCAL OBSERVATIONS AT TLYMOUTH. 27
Table IV.
See Plate 10.
Hour.
Summer
Months.
Winter
Months.
Hour.
Summer
Months.
Winter
Months.
1
52-898
45-251
I
63-218
50-638
2
52-526
45044
2
63-176
50-240
3
52-208
44-857
3
62-475
49-684
4
52-051
44-730
4
61-711
48-815
5
52-196
44-589
5
60-491
47-764
6
53-364
44-607
6
59-068
47-134
7
55-406
44-815
7
57-536
46-632
8
57-742
45-510
8
56-161
46-311
9
59-817
46-794
9
55-117
46-018
10
61-243
48-315
10
54-431
45-733
11
62-282
49-577
11
53-917
45-567
12P.M
62-994
50-395
12
53-324
45-386
Means
57-306
46-850
Mean 52-078.
Table A, Plate 9. Showing the Mean Pressure of each Hour
for the Year 1837-
Hour.
Pressure.
Hour.
Pressure.
1 A.M.
29-9558
1 P.M.
29-9492
2 ...
29-9556
2 ...
29-9467
3 ...
29-9492
3 ...
29-9440
4 ...
29-9474
4 ...
29-9442
5 ...
29-9467
5 ...
29-9463
6 ...
29-9497
6 ...
29-9484
7 ...
29-9519
7 ...
29-9547
8 ...
29-9555
8 ...
29-9596
9 ...
29-9572
9 ...
29-9627
10 ...
29-9567
10 ...
29-9628
11 ...
29-9580
11 ...
29-9621
12 ...
29-9545
12 ...
29-9590
1
Mean
29-9532
28 EIGHTH REPORT — 1838.
Tables, fyc, of Observations made with Professor Whewell's
Anemometer at Mount Tfise, Devonport. From November
1837 to June 1838, inclusive.
These Tables comprise: — 1. The observations as daily re-
corded. 2. The reduction of these observations. 3. A sum-
mary Table, in which the general result is condensed. Lastly,
The charts and general type of the wind, as shown by the re-
spective reductions and summary.
Plate 13, contains the general summary : the month of No-
vember 1837 is coloured blue, and marked 11 ; December is red,
and marked 12 ; January 1838 is again blue, and marked 1. The
remaining months continue to be marked 2, 3, &c. The breaks
in the continuation of the lines show when the instrument was
under repair. The direction of the wind is here only recorded
and indicated by dotted lines.
The black dotted lines show the resultant magnitude and di-
rection for each month ; the five black lines are continued re-
sultants, viz., that marked 1, 2, is the resultant of 11 and 12,
that marked 1, 2, 3, of 11 and 12, and so on to the last marked
1 to 8 ; which is the resultant of 8 months. The scale of this
Plate is that of the 400 equal parts to the inch.
MBTEOROLOGICAL OBSERVATIONS AT PLYMOUTH.
Indications of Whewell's Anemometer at Mount Wise,
Devonport, 1837, 1838.
November, 1837.
29
4
W. N.W.
12 3
15
18
E.
4
4
5
N.W. W.S.W.
11 5
16
19
W.S.W.
14
14
6
W.N.W.
3
3
20
W.S.W.
25
25
7
W.N.W.
21
W.S.W. W.
15 13
28
8
S.S.E. S.
11 26
37
22
W.S.W. S.W.
10 28
38
9
S.
42
42
23
S.W. S.S.W.
21 33
54
10
S.S.W. W.S.W.
2 10
12
24
S.W.
Under repair.
■
11
S.W. W.
9 6
15
25
W. N.W.
Under repair.
12
W. S.W.
5 5
10
26
S.W.
13
W.
2
2
27
W.S.W. N.W.
33 5
38
14
W.S.W.
15
15
28
W.S.W.
8
8
15
W. N.N.W. N.N.E.
9 9 12
30
29
W.N.W. N.N.W.
5 7
12
16
N.N.E.
3
3
30
S.W.
12
12
17
E.
11
11
EIGHTH REPORT — 1838.
December, 1837.
1
W.S.W. S.W.
3 24
27
16
Under repair.
2
S.W.
1
17
Do.
3
E.S.E.
18
Do.
4
E.
4
4
19
Do.
5
E.
15
15
20
Do.
6
E.N.E.
6
1
6
21
Under repair.
7
N.E.
5
5
8
N.E.
.
9
N.W.
2
2
10
N.E.
11
N.E.
2
^
12
N.E.
13
E.
S.E.
14
15
S.
65
65
31
S.
88
88
meteorological observation8 at plymouth.
January, 1838.
31
1
S.
112
112
17
E.
2
2
2
S.
59
18
E.
10
10
59
3
S.
180
S.W.
40
220
19
E.
20
20
4
W.S.W.
21
20
N.E.
5
5
21
5
W.
N.W.
21
E.N.E.
5
5
6
N.
22
S.E.
18
18
7
E.
23
E.S.E. S.E. E.S.E.
96 33 105
234
8
E.
12
12
24
S.E.
Under repair.
9
E.
31
E.N.E. E.
7 18
56
25
E.
10
E.
1
26
E.
1
: 11
i ■
N.E.
1
27
S.E.
1
12
N.E.
2
S.E.
2
28
»
13
E.
29
E.
ll4
E.
5
5
30
E.
15
E.
12
12
31
E.
16
E.
2
32
EIGHTH REPORT — 1838.
February, 1838.
1
E.
Under repair.
15
E.S.E.
240
240
2
N.E.
16
E.S.E.
210
210
3
N.E.
>5
17
E.S.E.
103
S.W.
19
122
4
N.E.
)5
18
W.N.W.
22
22
5
E.
19
E.S.E.
9
9
6
S.E. S.
20
S.E.
75
75
7
s. s.w.
21
S.E.
34
34
8
s.w.
>5
22
S.E.
25
25
9
w.
23
S.E.
83
83
10
w.
Repaired and replaced.
24
S.E.
83
83
11
E.
49
49
25
S.E.
40
W.S.W. S.
65 45
150
12
E.N.E. N.
25 17
42
26
S.
63
S.E.
26
89
13
E.
25
25
27
S.E.
65
65
14
E.N.E. E.S.E.
14 49
63
28
S.E.
5
5
j
MBTEOROLOGrCAL OSSKtlVATlO>fS AT PLYMOUrFl
March, 1838.
33
1
S.S.E. S.
8 15
23
17
W.N.W.
33
33
2
S.E.
5
5
18
W.N.W.
22
22
5
3
S.E.
5
5
19
W.N.W.
5
4
S.E. W.S.W.
30 5
35
20
W,
53
53
5
W.S.W. N.W.
18 6
24
21
W.
23
23
6
N.W. W.
22 31
53
22
W. N.N.W.
7 5
12
7
W.S.W.
14
14
23
N.N.W.
16
16
8
N.W.
14
14
24
N.N.W.
3
3
9
W.N.W.
6
6
25
N.N.W. W.N.W.
5 16
2]
10
S.
29
29
26
W.N.W. E.S.E.
2 5
7
11
S. S.E.
10 21
31
27
E.
5
5
12
E.S.E.
2
2
28
E.
13
14
W.S.W.
23
23
29
S.E.
W.S.W.
10
10
30
S.E.
3
3
15
16
w.
15
15
31
N.W.
W.N.W.
5
5
VOL. vii. — 1838.
34
EIGHTH REPORT — 1838.
April
, 1838.
1
E.S.E.
22
22
16
W.N.W.
18
18
2
E.S.E.
5
5
17
W.N.W.
Under repair.
3
N.
8
8
18
N.W.
4
N.W.
19
N.W.
5
W.N.W.
20
N.
6
W.N.W. W.S.W.
5 15
20
21
N.
Under repair.
7
W.S.W.
33
33
22
N.
8
W.S.W.
22
22
23
N.E.
>5
9
W.S.W.
8
8
24
N.E.
55
10
s.
6
6
25
N.N.E.
Replaced.
11
S.S.W.
3
3
26
N.N.E. N.E.
6 10
N.N.E.
2
18
12
N.
3
3
27
N.N.E. E.N.E.
8 4
12
13
S.
5
5
28
N.E. E.
3 3
E.N.E.
9
15
14
W.S.W.
16
16
29
N.N.E. N.
27 8
N.N.W.
5
40
15
N.W.
6
6
30
W.S.W.
40
40
meteorological observations at plymouth, 35
May, 1838.
1
w.s.w.
10
W.
45
55
17
E.S.E.
7
7
3
2
s.w.
18
S.S.W.
43
61
18
E.S.E.
3
w.
S.
3
S.W.
69
69
19
S.S.W.
25
s.
40
65
4
s.s.w.
15
28
43
20
S.E.
30
S.s.w.
46
76
5
N.E.
78
78
21
S.S.W.
1
s. w.
19
N.W.
20
4
6
W.S.W.
21
S.S.W. E.S.E.
13 2
36
22
s.
1
S.W.
2
N.N.AV.
1
7
E.S.E.
6
6
23
w.
2
W.N.W.
15
17
8
E.S.E.
28
28
24
N.N.W.
6
6
9
S.E.
81
81
25
W.N.W.
2
E.
3
S.E.
5
10
10
S.E.
51
51
26
S.E.
26
26
• 11
S.E.
110
110
27
S.E.
87
87
12
S.E.
19
W.S.W.
2
21
28
E.
55
E.N.E.
111
166
33
13
E.N.E.
41
41
29
E. S.S.E. S.
6 8 4
S.S.W.
15
14
N.N.E.
30
30
30
S.W.
31
-
31
N.N.E.
8
S.E.
39
47
31
S.W.
16
E.S.E.
21
21
1
D
2
36
EIGHTH RKPORT— 183S.
June, 1838.
1
S.W.
15
S.
39
39
2
s.
4
S.W.
15
19
16
S.
14
14
3
S.W.
20
20
17
S. S.E. S.
12 3 4
19
4
S.W.
7
W.S.W. S.
14 16
37
18
S. S.E.
4 4
8
5
S.W.
9
E.S.F.
9
19
S. W.
21 19
40
6
S.W.
5
N.
10
15
20
S.W.
56
56
7
N.
18
18
21
S.W. W. S.W. W.
51 10 15 1
77
8
N.N.W.
10
10
22
W.S.W. S.W.
40 13
53
9
N.N.W.
1
S.W.
2
3
23
W.S.W.
29
29
4
10
S.
35
35
24
E.S.E.
4
11
S.
9
S.W. N.
21
30
25
E.S.E. S. N.
12
N.W.
5
5
26
This day I left my house
and removed the anemometer
to Mr. Cox's, Fore Street.
13
S.S.W.
3
3
27
14
s.
8
8
28
J. A. SOUTHVVOOD.
METEOROLOGICAL OBSERVATIONS At PLYMOUTH. 3/
The following calculations with the accompanying Plates re-
present the result of observations made at Plymouth, with an
Anemometer of Mr. Whewell's construction. This instrument
gives what Mr. Whewell calls the integral effect of the wind,
namely, a space proportional to that which a particle of air would
pass over in each day in consequence of the wind, taking into
account both the strength of the wind and the time during which
it blows. These integral effects being put together according to
their directions, each day beginning at the end of the preceding so
as to form a continuous line, as is done in the Plates, we obtain
the path of the wind for each month, or for a longer time. The
annual path of the wind at each place will have, it may be ex-
pected, a general similarity in different years ; and the mean
form to which the annual path thus approximates is called the
ti/pe of the wind for each place.
A description of the Anemometer, of the mode of using it,
and of the process of i-educing the observations is given in the
Transactions of the Cambridge Philosophical Society for 1837 j
vol. vi. Part II.
38
EIGHTH REPORT — 1838.
;s
O ^
^
"
^
*
^
^
»
Z
OS ;
o»
'i^
;2;
;?
^
M r-^
rf
'A
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EIGHTH REPORT — 1838.
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METEOROLOGICAL OBSERVATIONS AT PLYMOUTH.
41
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METBOROLOGICAL OBSJS
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EIGHTH REPORT — 1838.
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Meteorological observations at Plymouth.
45
46
KIGHTH REPOHT 1838.
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METEOROLOGICAL OBSERVATIONS AT PLYMOUTH.
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15 4
48
EIGHTH REPORT — 1838.
SUMMARY TABLE.
N.
S.
E.
W.
1837. Nov.
4 to Nov. 7, 1837.
9
25
8 „ 15.
99
51
15 „ 18.
22
21
19 „ 23.
89
119
Nov.
27 „ Dec. 1.
39
50
Dec.
4 „ 11.
15.
31 „ Jan. 4, 1838.
8
65
540
28
47
1838. Jan.
8 „ 23.
105
349
Feb.
11 „ Mar. 4.
705
917
Mar.
4 „ 9.
10 „ 12.
13 „ 26.
26 „ April 2.
17
46
53
13
15
36
99
215
April
3 „ 16.
26 „ 29.
30 „ May 4.
65
26
134
39
112
203
May
5 „ 18.
19 „ 25.
25 „ 29.
29 „ June 24.
152
136
49
351
352
251
28
283
1
167
2558
2003
1232
South 2391.
East
776.
J
C 49 ]
A Memoir on the Magnetic Isoclinal and Isodynamic Lines
in the British Islands, from Observations by Professors
Humphrey. Lloyd and John Phillips, Robert fFere Fox,
Esq., Captain James Clark Ross, R.N., and Major Ed-
ward Sabine, R.A. By Major Edward Sabine, R.A.,
F.R.S.
At the meeting of the British Association, held at Cambridge
in the year 1833, a resolution was passed, recommending that a
series of determinations of the magnetic dip and intensitj^ should
be executed in various parts of the United Kingdom.
Early in 1834 Professor Lloyd, who had attended the meet-
ing at Cambridge, proposed to me to unite with him in carrying
the recommendation of the Association into effect as far as re-
garded Ireland. I was at that time employed on the staff of
the Army in the south-west district of Ireland, and found
it not incompatible with other duties to undertake that portion
of the island. Our observations were continued at intervals
throughout that year, and until the autumn of 1835, in the sum-
mer of which year we were joined by Captain James Clark Ross.
A report of our operations, drawn up by Professor Lloyd, was
made to the British Association, assembled in that year in Dub-
lin, and was printed in 1836 in the fourth volume of the Asso-
ciation Reports. A re-calculation of the Irisli results, incorpo-
rating the observations which have been made since in that part
of the United Kingdom, has been furnished by Mr. Lloyd, and
occupies its appropriate place in this i-eport.
Mr. Robert Were Fox, who was present at the Dublin meet-
ing in 1835, brought with him an apparatus for magnetic ob-
servations on a new construction of his own invention, with
which, after the meeting, he made several observations of the
dip in the course of a tour in the west and north of Ireland.
These observations, with others made on his return through
Wales, were published in 1836, in the report of the Royal Po-
lytechnic Society of Cornwall for 1835. Several of these ob-
servations were made in houses, and were consequently liable
to disturbing influences. Mr. Fox has selected eight deter-
minations of the dip in Ireland, and nine in AVales, as free from
objection on this account; and with his permission they are
now incorporated in the present report.
Having obtained two months leave of absence from military
duty in the summer of 1836, 1 employed them in extending the
survey to Scotland, by observations at twenty-seven stations dis-
VOL. VII. — 1838. E
50 KIGHTH REPORT — 1838.
tributed over that country ; forming the basis of a memoir on
the Scottish Isoclinal and Isodynamic lines, which was printed
in the fifth volume of the Association Reports, and published in
1837.
In the same summer Professor Lloyd commenced the mag-
netic survey of England by a series of observations at fourteen
stations, principally in the midland and southern districts ; these-
observations have not been hitherto published, and will be found
in their place in the present memoir.
The interest which had been excited at the meetings of the
British Association by the Irish and Scotch Magnetic Reports,
induced Professor Phillips to provide himself with an apparatus
for the dip and intensity ; having particularly in view the inves-
tigation of the influence which he deemed it possible the con-
figuration of the surface, or the geological character of the di-
strict, might have on the position or on the inflexions of the lines
representing these phagnomena. In the summer of 1837 Mr.
Phillips visited and observed at twenty-four stations in England,
chiefly in the northern district ; these observations arc now first
published.
In the same summer Mr. Fox determined the dip at twenty
stations in the north of England and south of Scotland ; and in
the summer of 1838 at eight stations in the south of England,
extending from London to the Scilly islands ; at some of the
latter stations he also observed the intensity : these observa-
tions form part of the present memoir.
In August 1837 Captain James Ross commenced a series of
magnetic observations, which he continued almost uninterrupt-
edly until the close of 1838; they extend over England, Ire-
land and Scotland generally, and comprehend fifty-eight sta-
tions. His observations of the dip and of the intensity are in-
cluded in the present memoir.
Lastly, between August 1837 f»id October 1838, 1 have taken
advantage of an interval between military duties, to observe the
dip and intensity at twenty-two stations, distributed for the
most part round the coasts of England and Wales, and extended
into Ireland and Scotland for the purpose of accomplishing a
more complete connexion of the different series.
It has been the wish of the four gentlemen connected with
me in this undertaking, that I should draw up the memoir of
what our joint labours have accomplished. Our observations
have been now carried over the whole extent of England, Ire-
land and Scotland ; and may be considered in their combination,
and by their extent, to obtain, in some measure, the character
of a national work ; presenting to the immediate requisitions of
MAGNETIC SURVEY OF GREAT BRITAIN. 51
science, the actual state of the phaenoniena of the magnetic dip
and intensity in the British islands ; and furnishing for distant
times the means of a comparison, whereby the secular changes
of these elements may be correctly judged of.
It has been found convenient to divide the report into two
parts, the first comprising the observations of the Dip, the se-
cond those of the Intensity.
Division I. — Dip.
In the memoir on the magnetical observations in Ireland
(British Association Reports, vol. v.), Mr. Lloyd has noticed
the discrepancies which have been occasionally found in the re-
sults of observations of the dip made at the same station with
different instruments. The observations of Captain Ross at
Westbourne Green, which are there related, place these discre-
pancies in the strongest light. Captain Ross employed eight
needles, making from eight to ten observations with each, each
observation consisting of eighty readings; i. e. of ten in each
of the eight usual positions. The dip at Westbourne Green,
resulting from each of these needles considered separately, va-
ried from 69° 01'-5 to 69° 42'-6. On these discordances Mr.
Lloyd remarks as follows : "Thus it appears that there is a dif-
ference amounting to 41' in the results of two of the needles
used; and that the diffei-ence is very far beyond the limits of the
errors of observation, will appear from the fact, that the extreme
difference in the partial results with one of these needles, B (1),
does not amount to 4'^, while with the other, (P), the extreme
difference is only 2'. In fact, it so happens, that these very
needles which differ most widely in their vnecm results are those
in which the accordance of the partial results is most complete.
Of the eight results obtained with needle P, there is one only
which differs from the mean of the eight by a single minute;
and yet the mean of all the observations with this needle differs
by more than 20' from the mean of any of the others, while its
excess above the mean of tlie entire series amounts to 25'.
" These differences cannot be ascribed to any partial mag-
netism in the apparatus, for three of the needles (I, P and R)
were of the same dimensions, and were used with the same cir-
cle, and yet their results, as we see, are widely discordant. We
must seek then in the needles themselves the cause of these
perplexing discrepancies; and we are forced to conclude that
there may exist, even in the best needles, some source of con-
stant error which remains uncorrected by the various reversals
usually made ; and that accordingly no repetition of observa-
£ 2
52 EIGHTH REPORT— 1838.
tions with a needle so circumstanced can furnish even an ap-
proximation to the absohite dip."
I may add to the preceding remarks, that the discordances
thus noticed far exceeded the limit of either diurnal or irregular
fluctuations of the dip in England, as far at least as these phae-
nomena have hitherto been the subject of observation.
An attentive consideration of the various sources of error to
which dip observations might be liable, — of those which were
already guarded against, and of those which still remained un-
provided for, — induced the belief, that a considerable part at least
of the discrepancies in question, and of similar discordances ex-
perienced elsewhere, were occasioned by the axle, on which the
needle rests on the agate planes, not being perfectly cylindrical.
Careful observers on the continent had already noticed' defects of
workmanship in this respect ; and had been led thereby to have
needles made, in which the axle, instead of being permanently
fixed to the needle, was secured in its place merely by strong
friction, and could be taken out, turned a portion of a circle on
its own centre of rotation, and replaced; thus enabling the
points of the circumference of the axle in contact with the sup-
porting planes to be varied in successive trials. At Captain
Ross's desire, Mr. Robinson undertook to have four needles of
this description made, for one of which Mr. Frodsham, whose
chronometers are so well known for their excellence, undertook
to make the axle. On these needles being completed, they were
tried each in four different positions of the axle, — that is to say,
the axle being secured, an observation of the dip was made in
the usual manner, and with the usual reversals : — the axle was
then removed, turned on its own centre a portion of a circle,
replaced, and the dip again observed : — in like manner, a third
and fourth change was made in the position of the axle, and the
dip observed at each. The process thus described was twice
repeated with each needle. Of the four, Mr. Frodsham's axle
proved the best ; but the trial clearly manifested in all the im-
perfection which had been apprehended. The results with the
needle furnished with Mr. Frodsham's axle are given in the
subjoined table, where that needle is designated as No. 1.
With this experience Mr. Robinson undertook to replace the
axles of the other three needles with three which should be the
workmanship of his own hands. On these being tried, the dis-
crepancies of each in the four positions were less than of any of
the four axles in the former trial, but still amounted to several
minutes. The results of the best of Mr. Robinson's axles have
been selected for illustration, and are those of No. 2. in the sub-
joined table,
i
MAGNETIC SURVEY OF GREAT BRITAIN.
53
Table I.
Trials of the Axles of the under-mentioned Dipping Needles.
Needle 1 . Frodsham's axle.
Needle 2. Robinson's axle.
Position of
the Axle.
Poles :
a direct.
/3 reversed.
Mean Dip.
Position of
the Axle.
Poles :
«■ direct,
j3 reversed.
Mean Dip.
a. 6°9 34-5
/3 68 48-2
a, 70 01-2
/3 69 44
« 68 34
/3 69 52-6
« 70 06-8
y3 69 43-1
69 11 -4
69 52-6
69 13-3
69 54-9
a. 6°8 42-3
/3 70 02-9
a. 70 15-6
/3 68 40-1
a. 69 13-5
/3 69 39- 1
u 69 49-8
/3 69 08-6
6°9 22-6
69 27-8
69 26-3
69 29-2
Mean of four positions 1 ^„ oo nc
of the Axle / 69 33-05
Mean of four positions 1 e(\ aa a
of the Axle. / 69 26-5
Experiment
a. 69 43-2
/3 68 54-6
« 70 11-2
/3 69 51-9
« 69 05-4
/3 69 47-1
a. 69 42-9
/3 69 54-9
repeated.
69 18-9
70 01-5
69 26-3
69 48-9
Experiment
« 69 54
/3 68 43
« 68 53-1
/3 70 05-8
« 69 50-8
/3 68 55-2
a, 69 02-6
/3 69 566
repeated.
69 18-5
69 295
69 23
69 29-6
Mean of four positions 1 69 38-9
of the Axle /
Mean of four positions \ 69 25"]5
of the Axle J |
The observations having been made in a house, the dip ob-
served is not the true dip in London. This is immaterial, as the
object of the experiment was solely the agreement or otherwise
of the results in the diffei'ent positions of the axle.
Had the axles been perfect, the same dip should of course
have been given in all positions of the axle : we perceive, how-
ever, that the differences in the one needle amount to above 40',
and in the other from 7' to 11'. The results of these experiments
fully impressed Mr. Robinson with the necessity of employing
more effectual means for ensuring a true figvu-e to the axles of
dipping needles ; and in several which he has since made, and
which have been carefully examined, he has proved successful.
Having exhibited the discrepancies of the earlier needles, it
may be satisfactory to show the improvement in some of the later
ones ; and for that purpose the following observations are given
with needles which were afterwards employed in the general ob-
servations of this report. The axles of these needles, being made
54
EIGHTH RBPORT 1838.
to revolve, were successively tried in four positions, which were, as
nearly as could be guessed, a quarter of the circumference apart ;
had they been precisely so, the needle must have rested on the
same points of the axle, in the 1st and 3rd positions, and in the
2d and 4th, (as the poles are reversed in each observation), and
the results in those positions should have been the same ; but
as this can have been only approximately done, each position may
be considered as bringing a different set of bearings into play.
The observations were made as before, in Mr. Robinson's house,
and have therefore no reference to the true dip.
Table II.
Trials of the Axles of the undermentioned Dipping Needles.
London, June and July, 1838.
Positions
of the
Axle.
1st Pair.
2nd Pair.
3rd Pair.
R. 4.
R.5.
R. e.
R.7.
W. 1.
W. 2.
1
2
3
4
6°9 44-9
69 43-8
69 381
69 43-4
69 43-5
69 39-9
69 46-2
69 44-8
6°9 39-8
69 40-4
, 69 41-4
69 36-8
6°9 4'3-l
69 40-8
69 47-0
69 38-8
6°9 48-4
69 50-4
69 49-5
69 53-5
6°9 48-9
69 46-0
69 46-7
69 47-8
Mean...
69 42-5
69 43-6
69 400
69 42-4
69 50-5
69 47-4
In all these six needles a great improvement was manifested.
The greatest difference occurring in any tvvo positions of the
axle of any one of the six needles is 8', including of course ac-
cidental errors of all kinds.
The imperfection of the axle is a source of error, from the
effects of which, if it exists, the results can scarcely be freed
by any mode of conducting the observation ; at least, without
going through the very tedious operation of observing round
the circumference of the axle on every occasion. When accu-
racy is desii'ed, therefore, only such needles should be employed,
as have been ascertained by preliminary trial to be nearly
free from this defect. Needles with revolving axles are easily
tried. Those of the ordinary description, in which the axle is
permanently fixed, may be examined by observing the angle of
inclination shown by the needle when the circle is turned in
different azimuths from that of the magnetic meridian, and by
computing the dip by means of appropriate formulae, from the
angles shown in the different azimuths. If the axle is perfect the
dips so computed should all accord. In the azimuths intermediate
between the magnetic mei-idian and its normal plane, the needle
rests successively on all points of the axle comprised in a por-
tion of the quadrant equivalent to the complement of the dip ;
MAGNETIC SURVJEY OP GREAT BRITAIN. 55
and the corresponding points of the other three quadrants be-
come in turns the points of support in the customary processes
of the reversals of the poles and circle. If this operation is
gone through at any part of the earth on or near the line of no
dip, the whole of the quadrant is thereby subjected to exami-
nation. In such situations, consequently, this method affords
the means of examining the whole circumference of the axle ;
and in all other localities, as much of the circumference as
amounts to four times the complement of the dip. Whatever
portion in the latter cases remains unprovided for, may be tested
by converting the needle, temporarily, into one on Mayer's
principle. This can easily be done by the application of a little
wax ; the quantity of which may be varied at pleasure, so as to
correspond with the weights of different sizes, by which, in
Mayer's method, the angles of inclination, from which the dip
is computed, are varied in successive observations. By one or
other of these processes the true dip at any station can be
obtained from any and every inclination of the needle; and every
part of the circumference of the axle can consequently be tested.
In what has been said, it has been presumed that there
is no magnetism in the circle itself, as, should such exist, it
would certainly become the source of discordance in the results
derived from different azimuths, or from different weights, in-
dependently of any defect in the axle ; and so far, therefore,
the agreement of the results in such trials (should they be found
to agree) indicates with great probability the freedom of the
circle from magnetism as well as the goodness of the axle. But
Mr. Lloyd has employed and has described in a subsequent
part of this report an independent and much more delicate mode
of examination for magnetism in the circle.
The customary provision of ttvo needles for each apparatus
does not alone afford security against the errors which may be
occasioned by either of the defects to which I have now al-
luded. In respect to the axle, if the results of the two needles
are accordant, it is thus far satisfactory, that it certainly is not
probable that both needles should have accidentally exactly the
same imperfection ; but if they differ, the observer has no guide
as to which is to be preferred ; whilst their mean result cannot
usually be more than an approximation to the true dip, for it is
also improbable that the two needles should have an exactly
equal amount of error in opposite directions. As a means of
detecting magnetism in the limb, two needles are of no more
avail than one ; because both are directed to the same point of
the circle when observed with at the same station, and, if a dis-
turbing influence exists, both will be subjected to the same error.
If, howevei', one of the needles is temporarily fitted on Mayer's
plan, — and the dip is obtained in successive experiments from
56 EIGHTH RKPORT — 1838.
ai'cs differing very widely from each other, and distributed ge-
nerally round the whole circle, — and if the results in such case
accord well with each other, and with those of the unweighted
needle, — it may be concluded that tliere is no disturbing influ-
ence in the limb.
Those who are desirous of making accurate observations,
should regard the preliminary examination of the axle and limb
of the apparatus they employ as an indispensable precaution.
When these points have been satisfactorily examined, and the
instrument is found correct, the natural magnetic direction,
both in regard to azimuth and inclination, is the most advan-
tageous for the observation of the dip. It is in the preliminarj^
examination, that the method devised by Mayer, and that of
varied azimuths, are chiefly valuable*.
It may now be satisfactory to exhibit the observations that
have been made at Westbourne Green in the years 1837 ^"d
1838 with different circles and approved needles. (Table III.)
The greater part of these instruments were made by Mr. Robin-
son since his attention has been particularly directed to the cir-
cumstances above noticed; and those who will take the trouble
to compare their performance with that of the several needles
employed by Captain Ross at the same station in 1835,
will have an opportunity of judging how great an improve-
ment has been effected in our English dipping needles since
that period. Of the two other instruments not made by Robin-
son, one was made by Gambey for Captain Fitz Roy, of the
Royal Navy, and kindly placed by that officer at my disposal, to
be employed in the observations in this report. The excellence
of the dipping needles of this artist is too well known to need
any comment in this place. The other instrument was made by
Mr. Thomas Jordan of Falmouth, the artist employed by Mr.
Fox to make the dip apparatus on the construction which he
has devised, and which is described in a paper in the 3rd vol.
of the "Annals of Electricity, &c." Mr. Fox's needles donoti-est
on a C5'lindrical axle supported by planes, but the axle is ter-
minated by exceedingly fine and short cylindrical pivots, which
* The needle employed by Sir Everard Home in the observations published
in the last volume of the Phil. Trans. 1838, Part 2, appears, by its results at
the Athenaeum at Plymouth, and at Ham, near London, to have given dips ex-
ceeding the truth by about half a degree. It is probable that a careful examina-
tion would trace this error to imperfection in the axle; and in such case errors
of a contrary character would exist when the axle should rest on some other
points of its circumference, and may have influenced the determinations at
some of Sir Everard's foreign stations. By the methods pointed out in this
report, a table of errors at diflerent dips might be formed for this needle, by
which its results might be' corrected. This additional trouble would be well
bestowed in perfecting this extensive series, on which so much pains have
already been expended.
MAGNETIC SURVEY OF GREAT BRITAIN.
57
work in jeweled holes. By means of the " deflectors " which
make a part of Mr. Fox's apparatus, the dip may be deduced
from readings at various parts of the circle, and there is there-
fore the same opportunity of discovering errors caused by mag-
netism of the circle, or by imperfection in the bearings of the
axle, as the azimuthal and Mayer's methods furnish in needles
of the ordinaiy construction : the jewel-plate itself is also made
to revolve, so that the resting-places of the axle in the jewels
may be changed at pleasure. The performance of these needles
sufficiently indicates the great care bestowed on their workman-
ship. As the different observations in Table III. include an in-
terval of eighteen months, they have been rendered more strictly
comparable by the addition of a column, in which they are re-
duced to the common epoch of the 1st January, 1838, by ap-
plying a proportional part of the annual rate of decrease of the
dip in London at this time, which, from reasons that will be
assigned hereafter, is considered to be 2'*4.
Table III.
Observations of Dip at Westbourne Green in 1837 and 1838,
with approved Needles.
Artist.
Needle.
Observer.
Date.
Observed Dip.
Deduced Dip,
Jan. 1. 1838.
Robinson . .
PI.
Phillips
May 30, 1837
69° 22-5'
69°21-1'
P2.
69 17-9
69 16-5
Gambey . . .
Gl.
Ross.
Aug. 10, 1837
69 20-6
69 19-7
G2.
69 19-8
69 18-9
Robinson . .
PI.
Phillips
March 28, 1838
69 19-5
69 20-1
P2.
69 17-0
69 17-6
Jordan ....
Fox
June 8, 1838
69 17-0
69 18-0
Robinson . .
Wl.
Ross
June 16, 1838
69 16-2
69 17-3
W2.
69 12-9
69 14-0
R4.
July 6, 1838
69 13-7
69 14-9
R5.
69 12-8
69 140
R6.
July 7, 1838
69 14-0
69 15-2
R7.
69 16-4
69 17-6
R4.
Dec. 4, 1838
69 15-5
69 17-7
R5.
69 12-8
69 150
R6.
Dec. io, 1838
69 15-9
69 18-2
R7.
69 14-4
Mean
69 16-7
69 17-2
The subjoined tables, IV., V., VI., VII., VIII., exhibit in de-
tail the azimuthal examinations which have been made of some
of the instruments employed in the observations contained in this
report ; it has appeared the more desirable to give these tables,
because the practice of this method is new in this country.
58
EIGHTH REPORT — 1838.
Table IV. contains observations made at Tortington on the
17th of October, 1837, with Captain Fitz Roy's Gambey, and
its needle No. 2. The dip is here successively deduced from
the angles of inclination observed in azimuths 90° apart from
each other. In such case, cot^ B = cot^ i + cot^ i', S being the
true dip, and i and i' the angles of inclination in any azimuths
90° apart. In the first example in the table, i is the angleof
inclination shown by the needle when the plane of the circle is
removed 10° from the magnetic meridian ; that is, when it is in
the direction of N. 10° E., and S. 10° W; therefore includes,
and is the mean of observation with the poles direct and re-
versed, and with the index of the azimuth circle at 10° and 190°;
e" is in like manner a mean of the angles of inclination with the
poles direct and reversed, when the index of the circle is at
(10 + 90^=) 100°, and at (100 + 180° = ) 280°: here cot2^■ + cot2
l'=cot^69° 13'-5 + cot-86° 15'-2 = cot28; whence 8 = 68°56''64.
In the next deduction, the values of i and i' are obtained with
the index of the azimuth circle at 20° and 200°, (20 + 90°=) 1 10°
and 290°, and so forth.
Table IV.
Tortington, Oct. 17, 1837, with Captain Fitz Roy's Gambey,
Needle 2. Observer, Major Sabine.
10
190
100
280
20
200
110
290
30
210
120
300
40
220
130
310
Poles
direct.
69 15
69 07
12
86 25
70 04-5
70 00-2
82 36-2
82 45-5
7139
71 26-2
79 09-7
79 20-5
73 37-7
73 23-8
76 07
76 16-5
Poles re-
versed
69 03
69 29
86 28-7
85 5.5
69 50
70 16
82 50-7
82 23-5
71 16-2
7140-3
79 26
78 56
73 18-3
73 40-2
76 23-2
75 55
^6913-5
I 86 15-2
70 02-7
82 39
}
}
1 71 30-4
170 13
73 30
76 10-4
Dip
deduced.
68 56-64
68 55-64
68 56-96
68 56-26
50
230
140
320
60
240
150
330
70
250
160
340
80
260
170
350
180
Poles
direct.
Poles re
versed.
76 06-5 75 50-7
75 53-2,76 13
73 34-2 73 49-2
73 44-3 73 24-3
79 08-7
78 52-8
7134
71 39-2
82 31-7
8218-8
70 05-7
70 07-5
86 11
85 56
69 09-2
69 13
55-5
68 52
78 48
79 16-5
71 50-2
71 19-5
8214
82 36-5
70 22-5
69 52-5
85 44
86 14-7
69 30-5
69 02-3
68 46
69 12-2
V 76 00-9
1 73 38
1 79 01-6
} 71 35-7
1 82 25-2
I7OO7
-86 01-5
.6913-9
• 68 55-4
Dip
deduced.
.68 56-40
68 56-05
6855-55
68 54-90
58 56-4
MAGNETIC SURVEY OF GREAT BRITAIN.
59
The mean of the nine results in the preceding table is 68° 56'* 1 .
Each angle is a mean of four readings. Total number of read-
ings, 272.
Table V. (In two parts) contains observations made by Cap-
tain Edward Johnson, R.N., F.R.S., and myself, with the same
circle and needle, in the Regent's Park, London, on the 15 th
and 16th November, 1837- In this case, the reversal of the
needle on its supports was made a part of the sei'ies, in addition
to the reversals in the last table ; thus the values of i and i' are
each the mean of eight angles instead of four.
Table V.
Observations with Capt. Fitz Roy's Gambey, Regent's Park, London.
Observer, Captain Johnson. 1837.
Nov.
Azimuth.
Poles Direct.
Poles Reversed.
Means.
Dip Deduced.
Ne<
Direct.
^le.
Reversed.
Needle.
Direct, i Reversed
15.
t 180
69 !9'25
69 19-75
6°9 14-25
69 24-25
6°9 16-75
69 43-75
6°9 35-25 6°9 21-371 rq o/os
69 28-75 69 29-13/ ^^ ^^'^^
69 25-25
r 15
195
105
285
70
69 58
84 15-5
84 28
69 49-5
70 07-5
84 36
84 15
69 50
70 15-5
84 37-5
84 13-5
70 04-5
69 59
84 28-5
84 30-5
69 56 I -f. „,
70 05 / '" ^^
84 29-4 -1ft. OR R
84 21-7 1 ^* ^^'^
169 22-08
30
210
120
300
72 04
71 54
79 15
79 26
71 45-5
72 05
79 34-5
79 09-5
71 48-5
72 14-5
79 33-5
79 06
72 08
72 00
79 14-5
79 27
n 034 } 71 59-95
1 69 25-30
15&16
45
225
■ 135
315
75 12-5
75 07
75 03-5
75 05
74 58-5
75 16
75 11
75 00-5
74 57
75 19-5
75 17-5
74 52-5
75 16-25
75 03
75 OS-5
75 07
?^S}75 08-7
.69 24-30
60
240
150
330
79 29
79 2S
71 55
71 56-5
79 10
79 34
72 04
71 45
79 13
79 37
7-2 12-5
71 46-5
79 38
79 15-5
71 52-5
71 58-5
79 22-5 -1 y
79 28-1 1 7J ^a ^
n?;-6 } 71 56-3
169 24-20
75
255
165
_ 345
84 33-5
84 28
69 56-5
70 03-5
84 21-5
84 31
70 04-5
69 51-5
84 18
84 41-5
70 17
69 48
84 36-5
84 21
69 57
70 06-5
8l SI} 84 28-9
SS:r}70 00-6
169 22-50
16.
r 180
1
69 17-5
69 20-5
69 29-7
69 13-5
69 41-5
69 10
69 07-75
69 38
^?2r}«^^-
69 22-30
General Mean. |
69 23- 7
60
EIGHTH REPORT — 1838.
Table V.
Observations with Captain Fitz Roy's Gambey, in the Regent's Park,
London.
Observer, Major Sabine. 1837.
Nov. i
Poles Direct.
Poles Reversed. |
Lzimuth.
Nee
Direct.
die. Nee
Reversed. Direct.
die.
Reversed.
15,
[ ^
[ 180
69 20-8
69 17-5
6°9 14-5
69 25-2
69 15-7
69 43
6°9 35
69 26-3
r 15
195
105
285
70 03
69 59-5
84 18
84 32
69 49
70 10
84 40-5
84 15-5
69 45
70 19
84 38-5
84 16
70 05-5
69 59
84 23
84 33
30
210
120
300
72 02
71 54
79 13
79 24-5
71 45
72 06
79 35-5
79 12-5
71 46-5
72 12-5
79 32-5
79 02-5
72 11
72 07
79 23
79 23
15&16
45
225
i 135
315
75 07-5
75 06
75 04-5
75 07-5
74 59-5
75 14
75 10
74 57-5
74 58-5
75 15
75 20
74 54
75 21-25
75 04-5
75 08-5
75 08
60
240
150
330
79 24
79 24-5
71 50-5
71 57-5
79 13-5
79 36
72 03-5
71 44
79 16
79 37-5
72 14-5
71 45
79 42
79 16
71 54-5
71 56-5
75
255
165
345
84 37
84 28-5
69 55-5
70 06-5
84 225
84 32
70 05-5
69 49
84 19-7
84 36
70 18
69 50-5
84 37-5
84 29
69 57
70 05
16.
r 180
1
69 17
69 21
69 33
69 13-2
69 42-7
69 12-5
69 09
69 43-5
Dip Deduced
69 21-5
69 28
:»}
69 24-75
69 55-6
70 06-9
84 30
84 24-1
71 561
72 04-9
79 26
79 15-6
75 06-7
75 09-9
75 10-75 \ ,
75 01-75/
I 70 01-2
I 84 27
I 72 00-5
}
}
79 20-8
75 08-3
75 06-25
79 23-9 "1
79 28-5 J
72 00-75"
71 50-75
79 26-2
};.
55-75
84 30-3
84 29-2 \
84 31-4 /
70 04^.} 70 00-9
69 57-;
69 25-44"
69 22-56
69 24
69 24-75
.69 22-61
.69 25-72
69 24-47
.69 24-17
69 23-08
69 24
General Mean.
69 24-11
Each of the numbers, both in Captain Johnson's and Major
Sabine's observations, is a mean of the readings of the two ends
of the needle. In the azimuths and 180° each niunber is also
a mean of two distinct observations, between which the needle
was raised from its support.s, and lowered afresh. At all the
other azimuths one such observation by each of the observers
was considered sufficient. The total number of readings is 224
by each observer.
MAGNETIC SURVEY OP GREAT BRITAIN.
61
Table VI.
Observations with Gambey's Circle and Needle 2 at Dover ;
by Major Sabine. 1837.
Azimuth.
Face of Needle to face of Circle.
Remarks.
Poles
Direct.
Poles
Reversed.
Mean.
Dip.
30 and 2°10
120 and 300
60 and 240
150 and 330
and 180
/
71 311
79 04-5
79 07- 1
71 26-4
68 48-8
7°i h
78 59-1
79 09-8
71 29-6
68 54-8
7°1 3'2 1
79 01-8 ]■
79 08-5 "1
71 28 1
68 51-8
68 53-2
68 52-9
68 51-8
On the side of the
hill above Arch-
cliff Fort on the
2nd November.
Beneath Shak-
speare's Cliff on
the 7ih November.
68 52-6
30 and 210
120 and 300
60 and 240
150 and 330
and 180
Face of Needle Reversed.
71 30-5
79 02-2
79 14-5
75 21-7
68 52-7
71 32-5
78 54-5
79 13
71 27
68 54-6
71 31-5 1
78 58-4 /
79 13-7 "1
71 24-4 /
68 53-6
68 51-3
68 52-2
68 53-6
68 52-4
Table VII. contains observations by Professor Phillips, with
a six-inch circle by Robinson, and its needle 1. The inclination
of the needle (i) was observed with the circle in different azi-
muths {6), and the dip computed from the inclination found in
each azimuth by the formula cot 8 = cot i sec 0.
Table VII.
Observations of the Dip with Mr. Phillips's Circle and Needle 1.
York, Sept. 13, 1838.
Helmsley, Sept. 14, 1838. 1
Malton, Sept. 15, 1838. |
Azimuth. Inclination
Dip.
Azimuth.
Inclination
Dip.
Azimuth.
Inclination
Dip.
e
I
5
e
I
5
6»
I
i
o^
O 1
O /
o
o /
00
70 50-6
70 50-6
00
70 57-4
70 57-4
00
70 51-7
70 51-7
10
71 08-2
70 51-5
10
71 14-2
70 58-0
10
71 08-1
70 52
20
71 53-7
70 491
20
72 01-7
70 560
20
71 54
70 49-3
30
73 16-9
70 52-5
30
73 21-5
70 57-5
30
73 15-5
70 50-6
40
75 04-6
70 48-5
40
75 13
70 59-5
40
75 03
70 47
50
77 22-5
70 47-3
50
n 31-4
71 000
50
77 26-1
70 52-5
60
80 07-9
70 49-9
60
80 16
71 040
60
Mc
80 05-9
an Dip...
70 45-4
M«
an Dip...
70 48-6
M<
an Dip...
70 58-9
70 49-8
63
EIGHTH REPORT 1838.
Table VIII. contains observations by Captain James Ross,
with a six-inch circle by Robinson, and its -needles R. 4. and
R. 6., at Jordan Hill, in September 1838. The dip is here com-
puted by the formula, cot -B = cot - i + cot ^ i' ; and in the
linal column the dip observed in the ordinary manner, i. e. in
the azimuths and 180°, is inserted for comparison.
Table VIII.
Observations with Robinson's Needles R. 4. and R. 6., Jordan
Hill, September 1838.
Observer, Captain James C. Ross,
Needle U. 4.
Aximuth.
Poles a.
Poles 13.
Means.
Dip
Deduced.
Azimuth.
Needle
Direct.
Needle
Reveised.
Needle
Direct.
Needle
Reversed.
60
240
150
330
8°1 '4-6
81 4-2
74 31-6
74 47-2
81 10-4
81 3-6
74 27-8
74 29-9
§1 3d
81 3-3
74 19-8
74 40-8
81 18-3
80 44-5
74 32-3
74 28
|81 4-1
1 74 32-1
o
1.72 21-6
,
72 22-2
Needle R. 6.
45
225
135
315
77 10-7
75 5-8
77 18-5
77 15-7
77 5-5
77 24
77 5
77 23-3
77 26
77 22-8
77 251
77 21-7
77 26
77 13
77 21-2
77 22-9
}77 167
1 77 19-5
1 72 19-4
72 17-7
Annual Alteration of the Dtp.
The observations of dip included in this report, extend over
an interval of four years and upwards. To reduce these to a
common epoch, we require to know the amount of the change
which the dip undergoes from year to year. In the Reports on
the Magnetic Observations in Ireland and Scotland, an annual
decrease of three minutes was provisionally assumed ; but we
must now endeavour to assign the amount with somewhat
greater precision.
In the 2Ist volume of the Annalen der Physik, M. Hansteen
has assembled all the most trustworthy observations of the dip
in London, Paris, Berlin, and Geneva during the present cen-
tury, and the latter part of the last ; and has computed from
them the most probable amount of the annual decrease of the
dip at each of those stations, corresponding to every tenth year,
from 1780 to 1830. As the results of this investigation have
not been published, I believe, in this country, I have subjoined
a table in which they are exhibited.
MAGNETIC SURVEY OF GREAT BRITAIN.
68
Table IX.
Annual Decrease of Dip.
Year,
Paris.
London.
Berlin.
Geneva.
Mean.
1780
6-75
4-90
5-26
504
5-49
1790
5-92
4-57
4-71
4-71
4-98
1800
511
4-21
4-15
4-38
4-46
1810
4-29
3-88
3-r)8
4-05
3-95
1820
3-47
3-55
302
3-72
3-44
1830
2-64
3-22
2-46
3-39
2-93
The differences whicli appear in the progression and rate of
the annual decrease at the four stations in this table, are proba-
bly attributable in far greater proportion to incidental errors in
the observations, than to the actual existence of such differences.
We may consequently regard the final column, or the mean of
the results at the four stations, as affording, in all probability,
a more satisfactory conclusion in regard to the rate of change at
any one of the stations than is drawn from the observations at
that station only.
We may proceed to examine how far this rate of decrease cor-
responds with the most recent observations made in Britain. In
August 1821, I made a series of more than usually careful ob-
servations on the amount of the dip in the Regent's Park in
London ; employing for that purpose a needle on Mayer's
principle, with weights of different magnitudes to obviate the
liability to any constant instrumental error, and continuing the
observations during several days in order that the general re-
sult might approximate the more nearly to the true mean dip
at the period. These observations were published in the Phil.
Trans, for 1822, Art. I. ; their final result being a dip of 70°
02'''9, corresponding to the middle of the month of August
1821. To compare with this, we have the observations made
in London, at different times and in different localities, by
the contributors to this report. It is proper that we should
employ for the present purpose only those observations which
give entirely independent determinations ; viz. those only which
are complete in all the requisite positions of the needle and
circle, including the reversal of the poles, and which need no
correction for instrumental defects. Of such observations we
have those at Westbourne Green, already given in Table III. j
those in the Regent's Park, ccmtained in Table V. ; an obser-
vation by Mr. Fox, in May 1838, in a field west of Maiden
64
EIGHTH REPORT — 1838.
Lane, ."xnd one of mine, on the 13th of October, 1838, in the
gardens of the Palace at Kew. These are collected in the fol-
lowing table.
Table X.
Observations of the Dip in London in 1837 a^nd 1838,
with approved Needles.
Date.
Observer.
Dip observed.
Place of Observation.
1837.
May 30
Aug. 10
Nov. 15. & 17
1838.
March 28
Phillips
Ross
Johnson & Sabine
Phillips
Fox
Fox
Ross
Ross
Ross
Sabine
Ross
Ross
69 20-2
69 20-2
69 23-9*
69 18-2
69 190
69 170
69 14-5
69 13-3
69 15-2
69 16-5
69 141
69 15-2
Westbourne Green.
Westbourne Green.
Regent's Park.
Westbourne Green.
Maiden Lane.
Westbourne Green.
Westbourne Green.
Westbourne Green.
Westbourne Green.
Kew Gardens.
Westbourne Green.
Westbourne Green.
May 22
July 6
July 7
Oct. 13
Dec. 4
Dec. 10
T.f r corresponding to the beginning "1
*^^*" t of May 1838. /
69 17-3
We have therefore 70°02'-9 in August 1821, and 69° 17*3 in
May 1838 J or a diminution of 45''6 in 16*7 years, equivalent
to a mean annual decrease of 2'* 73, corresponding to the middle
of the interval, or to the beginning of the year 1830. The
* This is the mean of fourteen results, extremely accordant with each other,
obtained in difTerent azimuths ; (see Table V.). It will be remarked that it is
decidedly the highest of the results from which the mean dip in London has
been derived. The observations with the same instrument at Kew, as well as
every comparison between this and other instruments, give reason to believe
that the high dip in the Regent's Park, in November 1837, is not attributable
to any instrumental error. It may then have arisen either from the dip on
those days being actually greater by three or four minutes than its general
average, or from some local disturbing influence. The locality is the same in
which the observations in 1821 were made, and the result in question may
on that account appear more strictly comparable with them; but though
the locality is the same, it is not one in which we can feel confident that no
change may have occurred in regard to magnetic influence. The Regent's Park
is certainly not so eligible a situation 9iow for magnetic experiments as it was
in 1821. These considerations have induced me to derive the London Dip in
1838 for the purpose in the text, from the mean of the observations and local-
ities in Table X, rather than from those in the Regent's Park alone ; and not
to give to the latter result that additional weight in comparison with the
others to which it would seem entitled as derived from observations in so many
azimuths.
MAGNETIC SURVEY OP GREAT BRITAIN. 65
mean rate for the same year in M. Hansteeii's table is 2'* 93,
which must be regarded as a satisfactory accordance, the dif-
ference being less than exists between the rate for that year at
any one of the stations in M. Hansteen's table, and the mean
of the four stations. We may infer from the accordance, there-
fore, that both these numbers, 2'*93 and 2'* 73, are extremely
near the truth ; and I have employed that which results from
our own observations, namely, 2'"73 corresponding to 1830.
Following the progression in M. Hansteen's table, the rate of
decrease would become 2'*4 in 1836, which is the middle pe-
riod of the observations contained in this report. In the re-
ductions to a common epoch, 2'*4 has consequently been em-
ployed as the mean annual decrease of the dip in the British
Islands between 1834 and 1838. In the absence of any certain
knowledge in regard to the unequal distribution of the yearly
decrease in the different months of the year, I have regarded it
as taking place in the uniform proportion of 0'*2 per month.
In a recent communication to the Royal Irish Academy, Mr.
Lloyd has stated the result of thirty-nine observations of the dip
in Dublin between October 1833 and August 1836, which, cona-
bined by the method of least squares, give 2''38 for the most
probable rate of the annual diminution of the dip in Dublin
during that period. This result, though drawn from so limited
a period, is in remarkable accordance with the deduction from
the observations in London, and furnishes a strong presumption
that the rate thus found is applicable both to England and Ire-
land. In regard to Scotland, no observations have as yet been
made, I believe, witli this particular object. The general
aspect of the observations in Scotland, at different dates, con-
tained in this report, would certainly indicate a less annual
change than has been deduced from the observations in England
and Ireland; and in every instance in Scotland where obser-
vations have been made at the same station and at different
periods, either by the same or different observers, the evidence
is of the same nature, — the results would be brought into better
accord if a smaller rate of decrease were adopted. In the case
of the Shetland Islands, the dip observed by Captain Ross at
Lerwick in August 1838, 73° 45', compared with that observed
by Sir Edward Parry and myself in June and November 1818,
74° 22', makes a decrease of 37' in twenty years, or a yearly
diminution of l'*85, corresponding to the mean epoch of 1828.
The observations of 1818 and of 1838 were made in the same
garden. The identity of the spot, — the length of the interval, —
and the repetition of the observations on different days on both
occasions, — all give weight to this comparison ; and strengthen
VOL. VII. 1838. p
66 EIGHTH REPORT— 1838.
the inference, that the rate of annual decrease is less in Scot-
land than in England. Still, in the absence of more positive
data, I have not chosen to make any assmTiption ; and have
employed the one rate for the whole of the British Islands.
The general result in Scotland, /. e. the mass of observations
taken collectively, is independent of the amount of this re-
duction, the sum of the + and — reductions to the mean epoch
of the 1st of January, 1837, being very nearly the same: the
effect of a less rate of diminution than that adopted would be
to increase the dips deduced from the observations in 1836, and
to decrease those deduced from the observations in 1837 and
1838 ; and thus to give a rather more consistent aspect to the
whole, without sensibly altering the resulting isoclinal lines.
No correction has been applied for the different hours of the
day at which the several observations were made ; but the hour
is in almost all instances recorded. Professor Phillips had
devoted several days of observation to the investigation of the
regular horary variations of the dip, and had obtained results
remarkably consistent, considering that they were derived from
observations with the ordinary dipping needle*; but the recent
invention of instruments specially adapted to this object, renders
it probable that the phenomena of the periodical changes will be
shortly determined with an accuracy hitherto unattainable : in
the mean time, it has appeared preferable to apply no correc-
tion on this account. It may be proper to remind the reader,
that the most perfect correction in this respect would still leave
unremedied the influence of the irregular fluctuations, which
there is great reason to believe frequently exceed in amount, and
occasionally counteract the ordinary periodical movements.
I proceed now to give in detail the observations which com-
prise the first division of this report ; namely, those of the Dip
in England, Scotland, and Ireland. It will be convenient to
separate these into three sections, commencing with those of
England ; and it may here be remarked generally, that all the
latitudes and longitudes in this Report are taken from the maps
published by the Society for Diffusing Useful Knowledge. The
longitudes east of Greenwich are distinguished by the negative
sign prefixed.
* Mr. Phillips's observations at St. Clairs and York, in the summer of 1837,
from 7 a.m. to 11 p.m., appear to indicate a morning maximum of dip at 9 or
10 a.m., an evening minimum about 8, with a difference of above 5 minutes,
the mean dip recurring about 3 p.m., and the line passing through the three
points nearly parabolic.
MAGNETIC SURVEY OF GREAT BRITAIN.
67
Section I. — England.
Mr. Fox's observations. — I have arranged in the following
table the observations of the dip in England with which I have
been furnished by Mr. Fox^ and have added thereto the columns
containing the latitudes and longitudes^ and the dips reduced
to the mean epoch of the 1st January, 1837. The results in
1835 were obtained with a six-inch apparatus; those in 1837
with a seven-inch, and those in 1838 with a four-inch appa-
ratus ; all the instruments being those of Mr. Fox's construc-
tion, and made by Mr. Thomas Jordan of Falmouth.
Table XI.
Mr. Fox's Observations of the Dip in England.
Dip de.
Lat.
Long.
Dip
observed.
duced,
1 Jan.
1837.
53 19
1 37
7°1 04
71 00-8
53 14
4 06
71 02
70 58-8
53 09
4 14
70 58
70 54-8
53 07
4 03
70 57
70 53-8
53 06
3 53
70 48
70 44-8
52 07
2 19
70 11
7007-8
51 55
2 35
70 00
69 56-8
51 40
3 46
69 57
69 53-9
51 38
2 40
69 48
69 44-8
55 07
1 53
71 17
71 18-6
54 40
3 09
71 15
71 16-6
54 32
3 09
71 14
71 15-6
54 43
2 00
71 14
71 15-5
54 27
3 01
71 13
71 14-6
54 32
1 33
71 07
71 08-5
53 54
2 47
70 59
7100-7
54 08
1 34
70 56
70 57-5
53 39
2 50
70 45
70 46-7
53 25
2 55
70 44
70 45-7
53 25
2 58
70 39
70 40-7
53 08
1 32
70 19
70 20-5
51 32
11
r69 19l
16917/
69 21-4
51 26
10
69 14-5
69 17
50 09
5 06
69 13-5
69 17-3
51 17
19
69 08
6911-5
50 47
-0 16
68 45
68 48-5
51 31
2 34
69 32
69 35-6
49 55
6 17
69 26
69 30
49 57
6 18
69 27
69 31
Place of
Observation.
Holyhead
Bangor
Carnarvon
Llanberris
Capelcrig
Malvern
Ross
Neath
Chepstow
Belsay
Skiddaw
Keswick
Shull
Grassmere
Darlington
Garstang
Studley Park ...
Bussco Bridge
Near Liverpool
Liverpool
Matlock
London i
Tooting
Falmouth
Eastwick Park
Eastbourne
Combe-House .
St. Mary's, Scilly
Trescow, Scilly
Sept. 1,
Sept. 1,
Sept. 1,
Sept. 1,
Sept. 3,
Sept. 5, -35 -
Sept. 8,
Sept. 11,
Sept. 9,
Aug. 25,
Sept. 7,
Sept. 7,
Aug. 19,
Sept. 9,
Aug.21,
Sept. 12,
Aufif. 14,
Sept. 12,
Sept. 23,
Sept. 19,
Aug. 9,
May 22,
June 8,
June 14,
July 31,
June 16,
June 20,
July 2,
Aug.31,
Aug.31,
5f A.M.
10 A.M.
3 P.M
6^ P.M.
7| A.M.
8§ A.M.
10# A.M.
5 l-.M.
9§ A.M.
4 P.M.
2 P.M.
8 A.M.
11 A.M.
Hp.m.
8 a.m.
7i A.M.
83 a.m.
7l AM.
11§ AM.
1 P.M.
4 P.M.
8 A.M.
05 P.M.
10 A.M.
5 P.M. 1
1 P.M. J
8 A.M
6 P.M.
8^ A.M.
3 P.M.
8-5 A.M.
8 A.M.
1 P.M.
Hotel Garden.
Hotel Garden.
Hotel Garden.
Foot of Snowdon.
Hotel Garden.
Mean of 3 Stations.
Glenvellyn Cottage.
Hotel Garden.
The Summit.
Near the Lake.
Behind the Inn,
Polham Hill.
Inn Garden.
At the Dingle.
IBotanic Gardes.
Balh Hotel Garden.
f Near Maiden Lane,
(. Wesiboirne Green,
The Grove.
Mr, Fox's Garden.
/Grounds of
I D. Gilberl, Esq.
f2
68 EIGHTH REPORT — 1838.
We have in this table the dip observed at twenty-nine sta-
tions, of which the central geographical position is 52° 45' N.
and 2° 49' W. If we desire to express the general result of
this series of observations, as to the position of the isoclinal
lines, their mean direction, and their mean distance apart in
the district of country which the observations comprise, in the
manner proposed by Mr. Lloyd in the discussion of the Irish
Magnetic lines (British Association Reports, vol. iv. pages
151 — 156);— and if we call B the dip at the central posi-
tion ; u the angle which the isoclinal line, passing through the
central position, makes with the meridian ; r a co-efficient de-
termining the rate of increase of the dip in the normal direction ;
a and h co-ordinates of distance in longitude and latitude of
the several stations from the central position, expressed in geo-
graphical miles : and if we make r cos «=.r, and r sin ic = i/ -, —
we may proceed to form equations of condition of the form de-
scribed in the report on the magnetical observations in Scot-
land (British Association Reports, vol. v. pages 4 and 5), and
to combine them by the method of least squares. It is unne-
cessary to encumber this report with the details of calculation ;
and it is sufficient to state, that from the three final equations
we obtain .r=+ -2633; ?/=--5154; ?<= — 62"'41 (the direc-
tion being from N. 62° '41 E. to S. 62° '41 W.) ; ?- = 0'-580,
being the rate of increase of dip in each geographical mile mea-
sured in the direction perpendicular to the isoclinal line ; and
g = 70° '22*9 the dip at the central position at the mean epoch
of the observations, namely, January 1, 1837.
Mr. Lloyd's Observations. — These observations were made
with a 4^ inch circle by Robinson, and two needles, designated
as L 3 and L 4, employed also for determinations of the inten-
sity. These needles consequently had not their poles reversed ;
and the dips observed with them require corrections to produce
the true dip. These corrections have been ascertained by Mr.
Lloyd, as stated in a subsequent part of this Report, to be as
follows :
Needle L 3. + 5^-3
Needle L 4. +13''4
These corrections have been applied in the following table^ in
the column entitled Corrected Dip.
Table XII.
station.
1836.
Hour.
Needle
Observed
Dip.
Corrected
Dip.
Place of Observation.
London ..
Apr. 19.
1 P.5I.
L 3
69 25-0
69 30-3
Westbourne Green.
Apr. 19.
1 28 P.M.
L 4
69 07-8
69 21-2
Apr. 21.
2 37 P.M.
L 4
69 13-8
69 27-2
Apr, 21.
2 58 P.M.
L 3
69 21-3
69 26-6
Shrewsbury
Apr. 25.
2 45 P.M.
L 4
70 05-1
70 18-5
3 10 P.M.
L 3
70 31-4
70 36-7
Holyhead .
Apr. 27.
11 15 A.M.
L 4
70 55-6
71 09
Rocky Height near
1 1 30 A.M.
L 3
71 030
71 08-3
the Town.
40 P.M.
L 4
70 53-4
71 06-8
1 7 P.M.
L 3
71 04-0
71 09-3
1 20 P.M.
L 3
71 04-7
71 10
Birkenhead
Aug. 8
9 a.m.
L 4
70 36-2
70 49-6
Garden of the Hotel.
9 35 A.M.
L 3
70 43-6
70 48-9
10 a.m.
L 3
70 43-0
70 48-3
10 20 A.M.
li 4
70 36-2
70 49-6
Shrewsbury
Aug. 9
II 15 A.M.
L 4
70 17-1
70 30-5
Fields near the River.
11 40 A.M.
L 3
70 22-1
70 27-4
7 P.M.
L 3
70 19-4
70 24-7
20 P.M.
L 4
10 14-6
70 28
Hereford...
Aug. 10
10 50 A.M.
L 4
69 52-0
70 05-4
In a Plantation one
11 20 a.m.
L 3
70 02-6
70 07-9
mile from the
11 45 a.m.
L 4
69 53-2
70 06-6
Town.
5 p.m.
L 3
70 03-2
70 08-5
Chepstow..
Aug. 12
11 40 a.m.
L 4
69 32-6
69 46
Near the Castle.
10 P.M.
L3
69 44-5
69 49-8
Salisbury...
Aug. 13
10 45 A.M.
L 4
69 09-0
69 22-4
Field near the Town.
11 10 a.m.
L 3
69 18-5
69 23-8
Ryde
Aug. 15
11 30 a.m.
L 4
68 571
69 10-5
Near the Sea.
L 3
69 01-6
69 06-9
f of a mile East of
Aug. 16
20 P.M.
L4
68 40-5
68 53-9
the Town.
45 P.M.
L3
68 53-8
68 59-1
Clifton
Aug. 29
11 15 A.M.
L 4
69 27-0
69 40-4
Durdon Downs.
11 40 a.m.
L3
69 39-8
69 45-1
5 P.M.
L 4
69 30-8
69 44-2
O 30 P.M.
L 3
69 35-4
68 40-7
Ryde
Sept. 24
11 45 a.m.
L 4
68 49-4
69 02-8
15 P.M.
L3
68 50-5
68 55-8
40 P.M.
L 4
68 47-8
69 01-2
1 10 p.m.
L 3
68 55-4
69 00-7
Brighton...
Sept. 27
11 15 a.m.
L 3
68 43-8
68 49-1
Downs N. E. of the
11 40 a.m.
L 4
68 36-9
68 50-3
Town.
L3
68 44-0
68 49-3
O 30 P.M.
L 4
68 36-8
68 50-2
London ...
Oct. 4
45 P.M.
L 3
69 17-4
69 22-7
1 20 P.M.
L 4
69 02-6
69 16
1 40 P.M.
L 3
69 120
69 17-3
2 P.M.
L 4
69 06-8
69 20-2
[Cambridge
Oct. 8
20 P.M.
L 3
69 37-0
69 42-3
Grounds of Trinity
40 P.M.
L 4
69 31-0
69 44-4
College.
1 10 P.M.
L 3
69 30-5
69 35-8
1 35 P.M.
L 4
69 30-1
69 43-5
L.ynn
Oct. 10
55 P.M.
L3
69 51-0
69 56-3
Pleasure-ground
1 25 P.M.
L 4
69 38-6
69 52
near the Town.
2 P.M.
L3
69 48-5
69 53-8
2 20 P.M.
L 4
69 37-5
69 50-9
Matlock ...
Oct. 12
15 P.M.
L3
70 27-2
70 32-5
Field N.of the Town.
25 P.M.
L 3
70 25-5
70 30-8
35 P.M.
L 4
70 13-4
70 2G-8
50 P.M.
L 4
70 13-4
70 26-8
Manchester
Oct. 14
10 50 a.m.
L 3
70 43-5
70 48-8
Field near the Town.
11 05 A.M.
L 3
70 44-2
70 49-5
11 20 A.M.
L I
70 34-4
70 47-8
11 35 A.M.
L 4
70 31-4
70 44-8
70
EIGHTH REPORT 1838.
Table XII. contains the latitudes and longitudes of Mr.
Lloyd's stations, and the mean dip at each station : the number
of distinct comparisons are, at London *2, Shrewsbury 2,
Ryde 2 ; at each of the other places, 1 : in the subsequent
calculation, these numbers are taken as the weights.
Table XII.
station.
Lat.
Long.
Dip.
Station.
Lat.
Long.
Dip.
Holyhead ...
Birkenhead .
Manchester.
Matlock ...
Shrewsbury.
Hereford ...
Lynn
53 19
53 24
53 28
53 08
52 42
52 04
52 45
/
4 37
3 00
2 14
1 35
2 46
2 44
-0 25
7°1 08-5
70 49-1
70 47-7
70 29-2
70 27-6
70 07-1
69 53-2
Chepstow ...
Clifton
5°1 38
51 27
52 13
51 04
51 32
50 44
50 50
/
2 41
2 36
-0 07
1 47
11
1 10
08
69 47-9
69 42-6
69 41-5
69 23-1
69 22-7
69 01-3
68 49-7
Cambridge ...
Salisbury
London
Ryde
Brighton
If we combine these fourteen results by the method of least
squares, we obtain the following values : a; — + -2899 •
y=--5753; «=-63°15'; ?- = 0-644 ; and S = 69° 54' at the
mean geographical position, of which the latitude is 52° 4', and
the longitude 1° 43' W.
Professor Phillips's Observations.— These were made with a
six-inch circle and two needles, by Robinson. At some of the
stations marked f, the reversal of the poles was intentionally
omitted, from a desire to determine small local differences, under
circumstances as similar as possible, the needles being very
nearly equilibrated. The table shows which of the observations
were thus incomplete ; and the comparison of the results at the
other stations, before and after the reversal of the poles, shows
the probable small limit of error which may have been involved
by the omission. With the poles direct, and also with the poles
reversed, the mean of four positions was taken, being eight in all ;
the needle was always inverted on its supports, as well as the
circle turned in azimuth : four readings of each end of the
needle were generally taken in each position.
MAGNETIC SURVEY OF GREAT BRITAIN.
Table XIII.
Professor Phillips's Observations of the Dip.
71
station.
Date.
Hour.
'3
1
Poles,
« direct,
/3 reversed.
Mean.
Mean Dip.
Place of
Observation.
1837.
o /
/
London
May 30
2 P.M. 1
a 69 22.9
/3 69 22-1
69 22-5
1 /
2
a 69 16-6
/3 69 19-1
69 17-8
U9 20-2
Westbourne
Green,
■)■ Doncaster . . .
June 2
6J P.M.
1
« 70 25-6
70 25-6
"1
— 3
7 A.M.
2
1
2
cc 70 27-6
a 70 34-3
cc 70 33-1
70 27-6
70 34-3
70 33-1
70 301
Garden of the
New Angel
Inn.
York
— 3
2,§ P.M.
1
a 70 48-6
/3 70 47-3
70 47-9
-V
2
cc 70 52-1
iS 70 45-3
70 48-7
7 P.M.
1
2
cc 70 48-4
/3 70 44-5
a 70 45-3
/3 70 45-3
70 46-4
70 45-3
— 5
9 A.M.
1
« 70 50-3
|3 70 51-6
70 50-9
2
« 70 50-7
fi 70 51-9
70 51-3
■ 70 48-6
Stone in Pro-
fessor Phil-
11 A.M.
1
2
« 70 51-2
/2 70 50-5
« 70 51
/S 70 51-5
70 50-8
70 51-2
lips's garden,
and stone in
the grounds
of the Philo-
7i P.M.
1
« 70 45-1
sophical So-
2
/3 70 46
« 70 47-5
/3 70 49
70 45-5
70 48-2
ciety.
Thirsk
— 6
3 P.M.
1
a 71 00
/3 70 59-1
70 59-5
"1
2
« 71 00-2
/3 70 57-5
70 58-8
1 70 59-2
Garden of the
Fleece Inn.
Osmotherley. .
— 6
8 P.M.
1
cc 71 1-6
/3 71 2-3
71 1-9
I
2
a 71 5-7
Ul 3-2
Garden of the
Hawibleton
H 71 3-3
71 4-5
J
Inn.
End
— 7
9 A.M.
1
a 71 3-6
/3 71 7-4
71 5-5
1
2
« 71 21
fi 71 3-1
71 2-6
Ul 4-0
Top of the
mountain.
Whitby
— 9
7i A.M.
1
« 70 59-4
|3 70 57-4
70 58-4
"
2
a 70 56-7
|S 70 57-9
70 57-3
■ 70 57-9
In Mr. Rip-
ley's garden.
Flamborough.
— 11
8 P.M.
1
«■ 70 33-8
/3 70 40-7
70 37-2
-,
2
« 70 36
P 70 37
70 36-5
• 70 36-9
Garden of the
Seabird'sInn
Scarborough. .
— 13
1 P.M.
1
a 70 40-4
/3 70 42-5
70 41-4
1
2
«. 70 42-3
[70 41-9
In Dr. Mur-
1
/3 70 41-9
70 421
J
ray's garden.
72
EIGHTH REPORl' — 1838.
Station.
Date.
Hour.
1
roles.
a direct,
fl reversed.
Mean.
Mean Dip.
Place of
Observation.
1837.
o /
o /
York
June 14
— 14
Hi A.M.
Hi A.M.
1
« 70 47-4
/3 70 47-5
70 47-4 ■
2
«, 70 47-5
/3 70 48-6
70 48-0
— 15
4 P.M.
1
« 70 46-1
^ 70 45-2
70 45-6
o /
2
« 70 46-5
H 70 49-3
70 47-9
i-70 46-5
Stone in Pro-
fessor Phil-
8 P.M.
1
2
a 70 44-9
/3 70 44
« 70 41-5
70 44-4
lips's garden,
and stone in
the grounds
a 70 49
70 45-2
of the Philo-
Sheffield
— 17
7 P.M.
1
a 70 27-5
/3 70 31-3
70 29-4
sophical So-
ciety.
2
« 70 27-2
/3 70 32-6
70 29-9
70 29-6
Botanic Gar-
den.
Birmingham. .
July 3
2§ P.M.
1
2
» 70 9-5
/J 70 9-1
« 70 77
H 70 13-5
70 9-3 ■
70 10-6
— 8
6^ P.M.
1
2
a 70 4-5
/5 70 6-6
« 70 1-5
70 5-6
70 5-5
70 3-5
-70 07-2
Mr. Wreford's
garden at
Edgbaston.
St. Clairs near
— 19
8^ A.M.
1
a 68 59-1
Ryde.
2
/3 68 58-3
a 68 55-3
/3 69 07
68 587
68 58
— 20
11 A.M.
1
2
a 69 1-2
a 69 1-2
« 68 56-8
/3 69 37
69 1-2
69 0-2
— 21
2J P.M.
1
2
X 68 597
/3 68 557
« 68 58-8
/3 68 59-5
68 577
68 59-1
■ 69 1-2
In the garden.
— 22
8i A.M.
1
2
« 69 6-6
/3 69 97
a 69 3-5
/3 69 9-9
69 8-1
69 67
York*
Aug. 1
7 A.M.
1
« 70 48-3
/3 70 53-6
70 50-9
2
« 70 32-5
/3 71 5-3
70 48-9
9J A.M.
1
2
« 70 53-5
/S 70 54-5
« 70 35
/3 71 7-1
70 54
70 510
3 P.M.
1
2
« 70 52-3
/3 70 517
a 70 33-2
/3 71 7-6
70 52
70 50-4
•70 51-1
Stone in Pro-
fessor Phil-
lips's garden,
and stone in
— 3
7| A.M.
1
2
« 70 49-1
/3 70 53-2
« 70 497
70 51-1
the grounds
of the Philo-
sophical So-
/3 70 5M
70 50-4
ciety.
Needle 2 was subjected to an alteration by Robinson, after the observations of
MAGNETIC SURVEY OF GREAT BRITAIN.
73
station.
Date.
Hour.
1
Poles.
a direct,
S reversed.
Mean.
Mean Dip.
Place of
Observation.
1837.
/
o /
Calderstone,..
Aug. 12
lOfA.M.
1
2
« 70 44-6
j3 70 45-6
a. 70 42-6
|3 70 49-5
70 45-1
70 46-0
o /
1^ r.M.
1
2
a. 70 37-6
/3 70 42-2
a 70 44
70 39-9
-70 43-5
In thegrounds
ofj. N.Wal-
ker, Esq.
Douglas, Isle
H 70 41-6
70 42-8
_
of Man
— 17
3 P.M.
1
« 71 20-5
/3 71 22-7
71 21-6
"1
tCastleton ...
— 18
8§ A.M.
2
1
« 71 23
/S 71 22-5
/3 71 23-3
71 22-7
71 23-3
^71 22-2
}71 22-55
Castle Mona
Inn garden.
2
/3 71 21-8
71 21-8
In a field ad-
fPeel Town ..
— 18
2 P.M.
1
/3 71 22-6
71 22-6
"1
joining the
2
/3 71 24-7
71 24-7
1
Inn yard.
3J P.M.
1
/3 71 24
71 24
■71 24-0
Near the Inn
2
/3 71 24-6
71 24-6
and on the
f Birkenhead..
— 26
I P.M.
1
2
/3 70 40-6
/3 70 39-8
70 40-6
70 39-8
1
Castle Hill,
2^ P.M.
1
2
« 70 38-8
« 70 38-6
70 38-8
70 38-6
•70 39-4
Inn garden.
Coed Dhu....
Sept. 20
Noon
1
« 70 40-7
/3 70 40-2
70 40-4
,
2
* 70 41-3
■70 40-9
Grounds of J.
fBowncss ...
— 25
9 A.M.
1
/3 70 41-5
/3 71 18-9
70 41-4
71 18-9
}71 18-4
|71 19-5
}71 19-6
Taylor, Esq.
2
,8 71 17-9
71 17-9
Ullocks Inn,
fConiston ...
— 25
1 P.M.
1
/3 71 19-1
71 19-1
the terrace.
2
/3 71 20
71 20
Field near the
fPalterdale...
— 27
li P.M.
1
/3 71 19-9
71 19-9
Inn garden.
2
/3 71 19-4
71 19-4
Inn garden.
fPenrith
— 28110} A.M.
1
/3 71 23-7
71 23-7
|71 23-4
2
A 71 23-2
71 23-2
In the Castle.
fCarlisle
— 29
lO^A.M
1
/S 71 27-5
71 27-5
}71 28-5
J71 18-1
2
/3 71 29-5
71 29-5
In the Castle.
fNewcastle...
— 30
7 A.M
1
/3 71 18-2
71 18-2
2
/3 71 18
71 18
Fields west of
1838.
the town.
London
Mar. 28
4| P.M
1
a 69 20-4
/3 69 18-6
69 19-5
]
2
« 69 16-1
^ 69 17-9
69 17
^9 18-2
Westbourne
Green.
Table XIV. contains the latitudes and longitudes of Mr. Phil-
lips's stations, and the mean dip at each station reduced to the
middle period of his observations, viz. the 1st of August, 1837-
the 22nd July, one of its arms having been originally longer than the other, so as
sometimes to touch the circle. By shortening this arm the centre of gravity was
slightly displaced, as is shown by the observation of Aug. ] . This was remedied
by Mr. Phillips, the same evening, by grinding the other arm.
74
EIGHTH REPORT — 1838.
Table XIV.
station.
Lat.
Long.
Dip,
1 Aug. 1937.
Station.
Lat.
Long.
Dip,
lAug. 1837.
Carlisle
54 54
54 13
54 40
54 04
54 10
54 32
54 22
54 22
54 58
54 20
54 22
54 14
2 54
4 43
2 45
4 40
4 27
2 56
3 05
2 55
1 38
1 15
1 18
1 21
71 28-5
71 24
71 23-4
71 22-5
71 22-2
71 19-6
71 19-5
71 18-4
71 181
71 04
71 03-2
70 59-2
Whitby
54 29
53 58
53 23
54 17
53 11
53 24
54 08
53 31
53 22
52 28
51 32
50 44
O /
37
1 05
2 53
24
3 12
3 00
08
1 07
1 31
1 53
11
1 08
70 5*7-9
70 48-4
70 43-5
70 41-8
70 40-9
70 39-4
70 36-9
70 30-2
70 29-6
70 07-2
69 19-2
69 01-2
Peel Town.......
Penrith
York
Calderstone
Scarborough
Coed Dhu
Birkenhead
Flamborough....
Doncaster
Sheffield
Patlerdale
Newcastle
HambletonEnd.
Osmotherly
Thirsk
Birmingham. ...
St. Clairs
If we combine these twenty-four results by the method of
least squares, we obtain the following values : .r= + "2658
^=-•5270; z<=-63° 14'; r = 0'-590 ; and S =70° 50'-l on
the 1st of August, 1837j at the mean geographical position of
which the Latitude is 53" 49', and the Longitude 2° 08'.
Captain Ross's Observations. — In this extensive series no less
than fifteen needles were employed. Those designated as R L 1
and R L 2, J, C, C 2, and C 3, were four-inch needles made by
Robinson, and used in a circle made by Jones ; the remainder
R L 3, R L 4, R 3, R 4, R 5, R 6, R 7, W 1, and W 2, were six-
inch needles, also by Robinson, and used in a circle by the same
artist : R 4, R 5, R 6, R 7, W 1, and W 2, were fitted with revol-
ving axles, and were found on trial to give accordant dips in
dififerent positions of the axle : each observation with them re-
corded in the following tables is a mean of the usual eight
positions. For these needles, consequently, no corrections
are applied, and it will be seen by the observations at West-
bourne Green in June, July, and December, 1838, that all
these needles gave very nearly the same dip when used under
like circumstances of time and place. Their mean result at
Westbourne Green has been employed by Captain Ross as a
standard to furnish corrections for the other needles which he
had employed previously, and on which he could not rely with
equal confidence. Of these, RL 1, R L 2, R L 3, and R L 4, were
used for the intensity as well as for the dip, and their poles,
therefore, were not reversed. They were always used in pairs,
and the correction determined for the mean result of R L 1 and
R L 2 was + 3, and that for R L 3 and R L 4, + 1 6.
MAGNETIC SURVEY OF GREAT BRITAIN.
75
The remaining five needles were observed in the usual eight
positions, but in consequence of imperfect workmanship re-
quired corrections, which, by comparison with the standard
needles, were assigned as follows :
J=+7 C2=+5 R3=-8
C=+2 C3=+8
Wherever these needles are employed, the proper corrections
are applied in a column in the table headed " corrected dip."
Table XV.
Captain J. C. Ross's Observations of the Dip.
g Poles.
g a direct,
^ & reversed.
Corrected
Dip.
Mean Dip.
Place of
Observation.
mdon .
iishey .
'irtington.
iventry.
1837. h m
Aug. 9 10 p.M,
3 p.M
:rminghatn..
Iifford.
— 10
July 31
— 30
Aug. 27
— 28
— 15
Sept. 1
— 4
— 7
1 10 p.M
A.M,
P.M
5 30 P.M,
10 30a.m,
5 30a.m,
8 A.M,
Noon
5 15 p.m.
5 30 p.M,
Noon
3 40 p.M
Noon
30 p.M
1 40
4
1 p.M,
2 20
4
4 30 p.M,
RL 1
RL 2
C 1
RL
RL 2
RL 2
RL
RL
RL
a 69 31-8
li 68 46
« 69 01
/3 69 28
69 27-3
68 59-1
69 4-2
/5 69 17-8
a. 68 58-4
/3 69 41-3
69 35-1
69 101
69 7-6
69 38-5
a. 69 9-2
/3 68 25-6
a. 68 39-8
/3 69 IM
69 8-2
68 37-6
RL 1 69 46-8
RL 2 69 26-8
a. 69 26-5
j3 69 49-6
«, 69 57-5
/3 69 15-6
RL 2
RL 1
C
RL 1
RL 2
C
69 8-9
69 14-1
69 13-2
69 11
69 19-9
69 22-6
69 23
68 47-4
68 55-4
68 52-9
69 36-8
69 38-1
69 52
70 16
a, 69 45-3
|3 70 3-9
a. 69 26
/3 70 16
70 19-8
69 57-6
a. 69 54-6
/5 70 21-6
a 70 24-2
/3 69 36 -4
69 36-5
70
4
69 54-6
69 51
70
8-7
70
8-1
70
0-3
69 15-9
69 161
69 16-2
69 16
69 21-9
69 25-6
69 26
68 54-4
68 57-4
68 55-9
69 39-8
69 40-1
69 43-5
70 7
69 56-6
69 58
70 11-7
70 10-1
70 7-3
69 16-05
69 24-5
68 55-9
69 4M
■70 0-5
70 Q-7
Westbourne
Green, Har-
row Road.
In the garden
of Bushey
Lodge.
In the garden
of Tortington
House, near
Arundel.
In the garden
of the Wheat-
sheaf Inn.
In a field half
a mile south
ofSt.Mar tin's
Church.
In the garden
of the New
Inn. Old
Church, N,
34° W. (true)
half a mile.
1^
EIGHTH REPORT 1838.
Station.
Date.
Hour.
S
^
Poles.
a direct,
;8 reversed.
Jlean.
Corrected
Dip.
Mean Dip.
Place of.
Observatio
1837.
h
m
o /
1
Birkenhead...
Sept. 18
3
30 P.M.
RL 2
70 29
o /
O /
4
45
RL 1
70 45-2
70 37-1
70 40-1
■
— 19
9
50.\.M.
C
a 70 20-2
r.
p, 70 45-1
70 32-6
70 34-6
1 70 3'6-2
In the gan
Noon
J
«. 70 52-9
/3 70 0-7
70 26-8
70 33-8
of the Ho
Douglas, (Isle
— 21
11
A.M.
RL 1
71 22-9
of Man).
2
30 P.M.
P.M.
RL 2
C
71 207
« 71 2
71 21-8
71 24-8
^
/3 71 30-2
71 161
71 181
-71 203
Inthegroui
4
P.M.
J
« 71 35-7
/3 70 46-3
71 11
71 18
of Castle A
na.
Birkenhead...
Oct. 11
Noon
C
« 70 16-3
/3 70 46-9
70 31-6
70 33-6
■»
1
30 P.M.
J
a 70 51-4
^ 69 58-6
70 25
70 32
1 70 35-3
In the gard
2
15 P.M.
RL 2
70 29
of the hot*
2
45 P.M.
RL 1
70 45-8
70 37-4
70 40-4
J
Pwllheli
— 1410
45 a.m.
C
« 70 22-1
/3 70 38-7
70 30-4
70 32-4
-\
1
P.M.
J
a 70 44-1
/3 69 56-9
70 20-5
70 27-5
1 70 32-5
In the gard
2
10 p.m.
RL 1
70 40
of the Fi
2
50 p.m.
RL 2
70 29
70 34-5
70 37-5
J
Crosses In
Marlborough.
- 17
1
2
P.M.
30 P.M.
C
J
« 69 9
/3 69 33
«. 69 40-7
69 21
69 23
^
/3 68 57-3
69 19
69 26
. 69 25-4
In the wo
3
50 P.M.
RL 2
69 12-2
S. W. of t
4
30
RL 1
69 36
69 24-2
69 271
.
Castle Inn
Clifton
— 21
3
50 P.M.
C
«. 69 17-7
/3 69 43-9
69 30-8
69 32-8
..
_ 2210
45 a.m.
J
«. 69 50-3
/3 69 1-3
69 25-8
69 32-8
-69 34
In the gard
1
P.M.
RL 1
69 47-2
of the Roj
2
10 P.M.
RL 2
69 19-6
69 33-4
69 36-4
J
Gloucester
Hotel.
Pembroke ....
— 25
2
30 P.M.
C 2
« 69 38-1
g, 69 59-4
69 48-7
m 53-7
-V
— 26
10
A.M.
J
« 70 9-6
(3 69 26-8
69 48-2
69 55-2
► 69 55-9
In the gard
11
30a.m.
RL 1
70 4-7
of the Drag!
30 p.m.
RL 2
69 46-9
69 55-8
69 58-8
■^
Inn. Pel
broke Chun
Swansea
— 27
10
20a.m.
30 P.M.
C 2
J
«. 69 5-3
/3 70 9-9
« 70 2-8
69 37-6
69 42-6
^
North (mag
half a mile.
/3 69 20-4
69 41-6
69 48-6
- 69 46-7
On the sane
1
40 P.M.
RL 1
69 56-4
about half
2
20 P.M.
RL 2
69 35-2
69 45-8
69 48-8
^
mile west
the Pier.
MAGNETIC SURVEY OP GREAT BRITAIN.
n
1827.
Nov. 2
— 3
— 14
— 15
— 18
— 21
Poles.
a, direct,
j3 reversed.
h in
2 40 P.M.
10 A.M.
11 50
1 20 p.m.
2 30
4 15 p.M
8 15a.m
10 A.M
Noon
10 A.M.
Noon
1 45 P.M.
2 30
30 P.M.
3 P.M.
C 2
C
J
RL 1
RL 2
C 2
RL 2
RL 1
J
« 68 59-5
f. 70 4-1
a 69 4
)3 70 4-6
«. 69 51-2
|3 69 7
69 50-9
69 19-9
a. 68 43-8
/5 69 56
69 14-5
69 36-7
a. 69 45-8
g. 68 45
— 22
— 28
— 29
— 30
Dec. 2
10 50a.m.
Noon
2 10 p.m.
3 50 p.m.
11 30 A.M
11 50a.m.
1 40 p.M
3 P.M.
3 45 p.M
2 20 p.M
4 p.M
— 4
— 5
C 2 a 68 35
/J 69 39-8
a. 69 34-8
/3 68 46-4
69 2-4
69 28-2
RL 2
RL 1
1 45 p.M,
3 20
20 p.M,
1 45
3 20
C 2
J
RL 1
RL 2
C 2
J
RL 1
RL 2
C 2
J
RL 1
RL 2
C 2
J
RL 1
RL 2
C 2
J
RL 2
RL 1
a 68 42-9
/3 69 37-5
a. 69 37
(3 68 48
69 28-9
69 7
a 68 24-3
/3 69 27-3
a. 69 20
g, 68 36-8
69 22-2
68 56-8
a. 68 37-1
69 45-7
a. 69 29-2
/3 68 46-8
69 30-3
69 4-6
a. 68 25-1
/J 69 29-8
«. 69 22-8
/3 68 35-2
69 22-3
68 54-7
a 68 30-7
/3 69 40-8
a 69 31-3
p 68 44-8
69 1-5
69 27-7
Corrected
Dip.
Mean Dip.
69 31-8
69 34-3
69 29-1
69 35-4
69 19-3
69 25-6
69 15-4
69 7-4
69 10-6
69 15-3
69 10-2
69 12-5
69 17-9
68 55-8
68 58-4
69 9-5
69 11-4
69 8
69 17-4
68 57-5
68 59
69 8-5
69 5-8
69 8
69 14-6
69 36-8
69 36-3
69 361
69 38-4
69 24-3
69 28-6
69 22-4
69 12-4
69 17-6
69 18-3
69 15-2
69 19-5
69 20-9
69 0-8
69 5-4
69 12-5
69 16-4
69 15
69 20-4
69 2-5
69 6
69 11-5
69 10-8
69 15
69 17-6
\ 69 36-9
• 69 25-1
■69 161
■ 69 18-5
■ 69 6-2
■69 17-3
■69 6-7
■ 69 14-5
Place of
Observation.
In the garden
of Rock Cot-
tage, the resi-
dence of B
L. Coxhcad,
Esq.
On the sands
opposite to
the town.
Pendennis Cas-
tle, bearing S 69°
17' E 2 or 3 miles.
Near the granite
pillar at thenorth
end of the raeri.
dian line.
In a field East
of the First &
Last Inn in
England.
In the g.irden
of the Athe
In a field, Ex
eter Cathe
dral, S.E. \\
mile.
New Church S.
W. by S. i of a
mile.
In the garden
of the Bush
Hotel.
In a field,
Salisbury Ca
thedralw.s.w.
(niag.)l|mile
78
EIGHTH REPORT — 1838.
Station.
Date.
Hour.
1
Z
Poles.
as direct,
(5 reversed.
Mean.
Corrected
- Dip.
Mean Dip.
Place-
Observ£in|
1838.
h
m
O /
Southsea
Dec. 8
11
20 A.M.
C 2
« 08 21-4
H 09 25-8
6°8 53-6
6°8 58-6
-,
1
20 p.m.
J
«. 09 17
O y
fi 68 30-6
68 53-8
09 0-8
>09 0-4
Til the o
2
40
RL 2
68 49-2
of the 1
3
30
RL 1
69 8-4
68 58-8
69 1-8
J
Hotel.
Guildford.....
— 12
2
3
P.M.
30 p.m.
C 2
J
« 68 20-9
/3 69 33-7
a 69 20-1
68 57-3
69 23
^
1
/3 68 36-9
68 58-5
69 5-5
-69 5-1
In a fieldl
— 13
11
A.M.
RL 2
68 54
mile eastfl
RL 1
69 14-8
69 4-4
69 7-4 .
)
Town tli
London
Mar. 6
1
P.M.
C 3
« 68 33-6
a 69 40-7
69 7-2
69 15-2
— 8
3
P.M.
C 3
« 68 33-3
li 69 41-6
69 7-5
69 15-5
April 10
1
50 p.m.
C 3
a 68 36-2
p, 69 41-2
69 8-7
69 16-7
.
4
P.M.
« 68 36
/3 69 29
69 2-5
69 10-5
■ 69 14-7
Westbou €
Green, a
— 25
11
9
20a.m.
A.M.
R 3
RL 3
RL 4
« 69 561
/3 68 49-8
69 3-7
68 54-5
69 22-9
68 59-1
69 14-9
69 151
row Ro .
1
Margate
— 17
2
4
P.M.
20 P.M.
RL 3
RL 4
R 3
68 48
68 37-8
a 69 32-8
68 42-9
68 58-9
-|
1
iS 68 32-2
69 2-5
68 54-5
- 68 57-2
In the g '
C 3
a. 68 18
/3 09 226
68 50-3
68 58-3
,
of the H
Anchor 11
York
— 27
2
30 P.M.
RL 3
RL 4
70 33-7
70 23-5
70 28-6
70 44-0
-.
4
10 P.M.
R 3
a 71 19-7
H 70 17
70 48-3
70 40-3
— 28
10
A.M.
R 3
« 71 27-8
/3 70 25-2
70 50-5
70 48-5
• 70 45-2
In the gii
of the Id
Keys lie
Noon
RL 3
70 34-5
RL 4
70 28-2
70 31-4
70 47-4
Scarborough. .
May 1
1
40 P.M.
RL 3
RL 4
70 32-5
70 21-6
70 271
70 43-1
..
3
P.M.
R 3
« 71 28-3
/3 70 13-2
70 50-8
70 42-8
70 43
In the g
of the
Inn, &
Bridlington...
— 3
9
15 a.m.
RL 3
70 27-4
to the «
RL 4
70 21-3
70 24-4
70 40-4
•\
Church.
11
10
R 3
a. 71 24-8
jS 70 5-4
70 451
70 37-1
. 70 38-8
In the g; e
7
P.M.
RL 3
70 27-3
of the t<
RL 4
70 18-7
70 23
70 39
,
Inn.
MAGNETIC SURVEY OF GREAT BRITAIN.
79
>tation.
Date. 1 Hour.
1
Poles.
a direct,
Mean.
Corrected
Mea^i T^in
Place of
(
!§
/3 reversed.
Dip.
Observation.
1838.
h m
Worth ...
May 9
8 15a.m
R ;
i a 71 12-3
/3 69 58-9
70 35-6
70 ■2'7-6
-.
1 30p.m
RL J
70 15-6
■ 70 27-5
In the grounds of
1
RL 4
70 7-2
70 11-4
70 27-4
WadworthHall,
the seat of R. J.
Ingham...
— 12
Noon
R 3
« 71 3-9
H 69 45-7
70 24-7
70 16-7
^
Coulman, Esq.
1 20 p.m.
RL 3
70 4-4
. 69
16-3
Nottingham
RL 4
69 55-4
69 59-9
69 15-9
Church, S.S.E.
I^ mile.
1.
— 16
7 15 a.m.
R 3
« 71 12-2
,8 69 46-2
70 29-2
70 21-2
"1
In a garden at
Callington.
9 30a.m.
RL 3
70 4-9
> 70
19-5
Louth Church,
RL 4
69 58-5
70 1-7
70 17-7
J
S.W. 1 mile.
In the garden of
the Wool-pack
cier
— 21
8 A.M.
R 3
a 70 34-8
/3 69 18-7
69 56-8
69 48-8
"1
Inn, River-head.
4 50 p.m.
RL 3
69 31-8
)■ 69 46-1
In the garden of
RL 4
69 22-8
69 27-3
69 43-3
J
the Post-office,
close to the
stoffe ...
— 24
5 p.m.
R 3
a. 70 14-4
/S 68 57-4
69 35-9
69 27-9
1
Church.
6 30 p.m.
RL 3
69 16-7
y 69 29-2
In the grounds
RL 4
69 12-1
69 14-4
69 30-4
J
oftheSuflfblk
Hotel.
rich
— 28
3 20p.m.
R 3
« 70 2
/3 68 41-9
69 21-9
69 13-9
■\
5 P.M.
RL 3
68 56-3
RL 4
69 3-5
68 59-9
69 15-9
► 69
15-4
In the grounds
— 29
3 P.M.
RL 3
69 3-6
of the AVhite
RL 4
68 57-2
69 0-4
69 16-4
J
Horse Inn,
2 miles west
r
June 16
July 6
1 15 p.m.
3 10
3 40p.m.
W 1
W 2
R 4
« 69 11-7
/3 69 20-7
a. 69 13-2
/3 69 12-6
« 69 16-1
H 69 11-5
69 16-2
69 12-9
69 13-7
of Harwich.
7 P.M.
R 5
a 69 11
/3 69 14-6
69 12-8
■ 69 14-3
Westbourne
Green, Har-
— 7
Noon
2 10p.m.
R 6
R 7
«. 69 101
/3 69 17-9
« 69 15-8
/3 69 17
69 14
69 16-4
row Road.
— 7
5 p.m.
RL 3
69 3-25
1
— 10
5 p.m.
RL 4
68 51-6
68 57-4
69 13-4
lastle
Aug. 28
2 p.m.
R 6
« 71 10-4
4 p.m.
R 4
j3 71 16-7
« 71 13-4
71 13-6
l^'
13
'n Mr. New-
/3 71 11-4
71 12-4
J
ton's nursery
M-
grounds.
80
EIGHTH REPORT — 1838.
>laceJ
ervtM
Stonehouse.
London.
1838.
Sept. 1
Dec. 4
— 10
h m
2 45 p. M,
4 15 p.m.
10 45a.m.
30 p.m.
Noon
2 P.M.
Poles.
u direct,
/3 reversed.
R 6 a 71 17-3
/3 71 27-3
a 71 25-5
/3 71 26-4
R 4
R 4
R 5
R 6
R 7
* 69 19-3
/3 69 11-7
a 69 8-3
/3 69 17-4
«. 69 12-3
H 69 19-6
a 69 13-9
j3 69 14-9
71 22-3
71 25-9
69 15-4
69 12-8
69 15-9
69 14-4
Corrected
Dip.
Mean Dip.
}
71 241
69 14-67
In the gro
pf Stoneb
theseatol
Sir Hew
rymple I
K.C.B.
Westboun
Green,
row Ro«
Table XVI. contains the latitudes and longitudes of Captain
Ross's stations, with the mean dip at each station reduced to the
1st January, 18.38, being the middle period of his observations.
Table XVI.
I-^g- IJanll'a
Lat.
Long.
Dip,
i Jan. 1838.
o /
o /
o /
51 12
4 06
69 36-5
51 27
2 35
69 33-5
52 28
-1 50
69 30-2
51 25
1 43
69 24-9
50 33
4 56
69 24-8
51 38
22
69 23-6
50 05
5 40
69 18-3
50 43
3 31
69 17-1
51 56
-1 13
69 16-4
50 09
5 06
69 15-8
51 32
11
69 15-4
51 04
1 48
69 14-3
50 37
2 27
69 06-5
50 23
4 07
69 06-0
51 14
34
69 05-0
50 48
58
69 00-2
51 23
-1 23
68 57-9
50 50
34
68 55-0
Berwick ...
Stonehouse .
Douglas ...
Newcastle . . .
York
Scarborough
Bridlington .
Birkenhead .
Pwllheli ...
Wadworth...
Louth
Nottingham
Stafford
Birmingham
Pembroke...
Cromer
Swansea ...
Daventry ...
55 45
54 55
54 10
54 58
53 57
54 18
54 08
53 24
52 55
53 28
53 19
52 57
52 48
52 28
51 39
52 56
51 36
52 16
2 00
2 44
4 28
1 36
1 06
26
14
1 08
71 43-6
71 25-7
71 19-6
71 14-6
70 460
70 43-8
70 39-6
70 35-1
70 320
70 26-6
70 18-6
70 15-4
70 090
69 59-7
69 55-5
69 47-0
69 46-3
69 40-3
Ilfracombe ...
Clifton
Lowestoffe ..,
Marlborough ,
Padstow
Bushy
Land's End..,
Exeter
Harwich
Falmouth ...
London
Salisbury
Weymouth ..,
Plymouth ...
Guildford ...
Southsea
Margate
Tortington ...
If we combine the results at these thirty- six stations by the
method of least squares, we obtain the following values :
a:= + -1974; ?/=--5114; i« = — 68°54'; r = 0'-548; and
8=69° 53'"4 at the mean geographical position of 52" 16' N.,
and 1° 55' W.
Major Sahine's Observations. — These observations were
made at fifteen stations, with a 9-^-inch circle, and two needles
by Gambey, (Table XVII.); and at twelve stations with a circle
of Nairne and Blunt of 11 inches in diameter, and a needle by
Robinson, designated as S 2, (Table XVIII.)
MAGNETIC SURVEY OF GREAT BRITAIN.
81
Table XVII.
Major Sabine's Observations of the Dip with Captain
Fitz Roy's Gambey.
Poles.
a direct,
/I reversed.
Mean at the
Station.
Place of
Observation.
Tortington ..
Birkenhead .
Aberyslhwith
Dunraven
Castle ....
Tortington
Dover
Margate
Regent's Park
London ..,
Lew Trencliard
1837.
Aug. 15
— 15
Sept. 17
— 18
— 21
— 21
— 26
_ 26
— 28
Oct. 16
— 17&19
Nov. 2
— 7
— 6
— 9
— 9
— 11
— 15&16
— 16
1838,
July 19
— 21
1 V.M,
2 P.M.
35 P.M.
1§ P.M.
3 P.M,
Sj P.M.
« 69 05-1 1
H 6S 54-8 ]■
68 56-4 1
j3 69 02-1 /
a. 70 30-6 1
/3 70 40-0 /
a. 70 33-0 \
/3 70 36-7 /
« 70 20-6 1
H 70 26-1 /
a 70 29-3 \
li 70 17-9 /
« 69 52-1 1
/3 69 39-9 /
a 69 42-7 \
A 69 48-6 /
« 69 42-6
H 69 48
« 68 51-8
/3 68 56-6
68 55-8
li 68 56-4
«68 51-n
/3 68 54-1 /
« 68 51-6 1
(3 68 53-0 /
68 54-0-1
/3 68 49-8 1
« 68 59-4 \
/3 69 04-1 /
« 69 09-9 1
/3 69 00-8 /
« 69 04-1 1
iS 69 03-7/
2-61
3-2/
« 69 20-7
/3 69 25
■1}
Noon
11 A.M
«69 13-61
/3 69 22-2 /
«69 17-91
/3 69 22-5 /
68 59-95
68 59-3
70 35-3
70 34-85
7023-35
70 23-60
69 460
69 45-65
6945-4 *
68 54-2
6854-9 t
68 52-6 t
6852-3 f
68 51-9 t
69 01-75
69 05-3
69 02-54 1
6923-9 §
69 23-1 II
69 17-9
69 20-2
-68 59-6
.70 35-1
• 70 23-5
(.69 45-7
-68 54-8
.68 52-3
.69 02-9
► 69 23-8
69 19-0
In the grounds
of William
Leaves, Esq.
Garden of the
Hotel,
On a hill north
of the town.
In the grounds
of the Earl of
Dunraven
In the grounds
of William
Leeves, Esq,
On, and be.
neath the
CliflFs.
Field behind
Marine Ter-
race.
In Mr. Jen-
kins's nur-
sery grounds.
In the grounds
of W. Ea-
ring Gould,
Esq.
* Observed by Viscount Adare. f Observed in various azimuths.
J Observed in various azimuths.
§ In various azimuths. Observers, Capt. Johnson, R.N., and Major Sabine.
II Observed by Capt. Johnson and Major Sabine,
VOL. VII. 1838. Q
82
EIGHTH REPORT — 1838.
Station.
Date.
Hour.
1
Poles.
a direct,
Mean.
Mean at the
Place of
K
fi reversed.
Stations.
Observation.
1838.
Falmouth ..
July -25
9 A.M
2
« 6°9 09-1 1
/3 69 14-7/
6°9 11-9
69 n-9
Inthegrounds
of Robert
Were Fox,
Whitehaven..
Aug. 16
3 P.M
2
« 71 06-81
/3 71 15 /
« 7105-81
/3 71 12-2/
Esq.
71 10-9
71 10-9
Fields south of
Newcastle ..
— 28
H P.M
2
the town.
71 09-0
71 09-0
In Mr. New.
ton's nursery
Alnwick Castle
- 31
3 P.M.
2
« 71 22-9 1
fi 71 22-2 /
grounds.
71 22-6
71 22-6
Inthegrounds
of the Duke
of Northum-
Stonehouse ...
Sept. 2
5 P.M.
2
a 71 18-91
/3 71 20-2/
berland.
71 19-5
71 19-5
Inthegrounds
of Colonel Sir
Hew Dal-
rymple Ross,
Helensburg...
— 10
8§ A.M.
2
a 72 14-81
/3 72 19-2/
u 72 12-6 1
/S 72 15-0 f
K.C.B.
72 170
72 170
Fields nearthe
Jordan Hill . .
— 11
4^ P.M.
2
72 13-8
^
Baths Hotel.
— 13
2
J }
^ 1
J }
X 69 03-91
8 69 09-6/
7216-4*
— 13
i
2
72 IM*
>72 14-3
fn the grounds
of James
— 14
2
72 15-8»
Smith, Esq.
Worcester
Oct. 8
3 P.M.
2
Park
59 06-7
69 06-75
n the grounds
Kew
— 13
4i P.M.
2
* 69 14-71 ,
3 69 18-2 f '
39 16-4
69 16-45 1
n the garden
1 |- - 1
ofthePalace.
Observed by Archibald Smith, Esq.
MAaNBTIC SURVEY OP GREAT BRITAIN.
83
Table XVIII.
Major Sabine's
Observation
s of Dip.
Needle, S 2.
station.
Date.
Hour.
Obser-
fed Dip
Mean.
Corrected
Dip.
Place of
Observation.
1837.
o /
Tortington
May 17
69 05-8
— 29
Aue. 5
69 04-8
69 15-7
•6°9 68-25
6°8 58-65
In the grounds
of William
- 5
69 06-7
Leeves, Esq.
July 27
69 26-3
1 69 28-15
69 18-55
Cloister Gar-
Westminster
- 27
69 29-8
dens.
Shrewsbury
Sept. 19
— 19
4 P.M.
5 P.M.
7034-2
7034-7
|70 34-45
79 24-85
Fields near the
House of Industry.
Aberysthwith ...
— 21
— 21
1 If A.M.
Noon
7035-6
7035-4
|70 35-5
70 25-9
Hill north of the
town.
Garden of the
Hotel.
Mr. Thompson's
grounds.
Brecon
— 22
— 22
6 A.M.
6f A.M.
70 12-6
70 12-9
J70 12-75
70 03-15
Merthyr
— 23
— 23
2 P.M.
2J P.M.
70 15-2
7011-8
|70 13-5
70 03-9
Dunraven Castle
— 25
2§ P.M.
6958-8
7
— 25
3* P.M.
69 57-9
U9 57-4
69 47-8
In the Castle-
Oct. 3
0| P.M.
69 55-5
J
grounds.
Tortington
Dover
— 15
— 19
Nov. 2
— 3
4 P.M.
11^ A.M.
2 P.M.
3 P.M.
69 07-9
69 04-3
69 01-0
6903-8
|69 06-1
169 02-2
68 56-5
69 52-6
In thegroundsof
W. Leeves, Esq.
On and beneath
— 6
2 P.M.
69 01-8
J
the Cliffs.
Margate
— 9
— 10
— 14
11 A.M.
1^ P.M.
69 08-2
69 12-6
69 26-9
|69 10-4
69 00-8
Field behind Ma-
rine Terrace.
Regent's Park,
London
— 14
— 14
2|P.M.
3 P.M.
69 27-2
69 34-2
[69 29-72
r
69 20-12
Mr. Jenkins'
nursery-
— 16
22 P.M.
69 30-6 J
grounds.
1838.
Jordan Hill
Sept. 13
— 13
1 P.M.
2 P.M.
72 22-0-1-2 2,,
72 20-8/'^ ^^*
72 11-8
In the grounds of
J. Smith, Esq.
Kew
Oct. 13
H P.M
69 24-0 69 24-0
69 14-4
In the gardens of
the Palace.
1
Note on the correction applied in Tables XVIII. to the Dips
observed with S 2. This needle being employed for the statical
measurement of the variations of the intensity, the poles were not
reversed in the dips obtained with it. The "observed dips" in
Table XVIII. are consequently a mean of four positions only of
the needle and circle ; namely, of the circle in the azimuths 0° and
180°, and the same repeated with the needle reversed on its sup-
ports; both ends of the needle being read, and ten readings taken
in each position. There are twelve stations at which the dip was
thus observed with S 2 ; at eight of these it was also observed
with Gambey's instrument, in which the poles of the needle were
g2
84
EIGHTH REPORT — 1838.
reversed, and the observation was consequently complete. At
the other four stations Gambey's circle was not employed, and
we have to deduce from the observations with S 2 th^ dips that
would have been shown by a needle with the poles reversed. In
the report of the Magnetic Observations in Scotland, (B. A. re-
ports, vol. vi. page 98,) a correction for this purpose was de-
rived from a comparison of results obtained at Limerick with
S 2, and with a needle on Mayer's principle, used in a ciixle
of Nairne and Blunt's ; and we have here observations at eight
other stations, furnishing materials for a similar comparison
between the results of S 2, and of Gambey's instrument.
Table XIX.
Dips observed.
Error of
S2.
No. of
Sets.
Weight
n+n'.
= N.
eXN-
station.
82.
Mayer or
Gambey.
= c
S2.
= n.
Mayer or
Gambey.
= n'.
71 14-63
69 11-2
70 35-45
69 57-4
69 06-1
69 02-2
69 10-4
69 29-7
72 21-4
69 24-0
7°1 03-27
68 59-6
70 23-5
69 45-7
68 54-8
68 52-3
69 02-9
69 23-8
72 14-3
69 16-45
+li-36
+ 11-6
+ 11-95
+ 11-7
+ 11-3
+ 9-9
+ 7-5
+ 5-9
+ 7-1
+ 7-55
10
2
2
3
2
3
2
4
2
1
5
2
2
3
10
5
5
8
4
1
3-3
10
1-0
1-5
1-7
1-9
1-4
2-5
1-3
0-5
37-49
11-60
11-95
17-55
19-21
18-81
10-50
14-75
9-23
3-78
Tortington (Aug.)
Aberysthwith
Dunraven Castle
Tortington (Oct.) ,
Regent's Park ...
Jordan Hill
Kew Gardens
16-1
154-87
Mean error of S 2 when the poles were not reversed -f-9-6
* The observations at Limerick with S 2 and Mayer's needle have been already
detailed in the 6th Report of the British Association, page 98. As the comparison
of their results is slightly affected by employing a different rate of annual decrease
for the purpose of reducing the observations to a common epoch, they are stated
afresh.
Needle.
Date.
No. of
Sets.
Observed Dip.
January 1836.
Mean, allowing
weight for the
number of Sets.
S2
Mayer
July 1835
Dec. 1835
Feb. 1836
May 1836
Nov. 1833
May & June
4
3
1
2
2
3
7°1 16-93
71 14-6
71 13-4
71 12-0
71 11-7
71 0005
7°1 l'5-83
71 14-5
71 13-7
71 12-9
71 06-6
71 01 05
•7°1 14-63
J71 03-27
JIOOO
MAGNETIC SURVEY OP GRKAT BRITAIN.
85
A correction is therefore required of— 9' 6 to all the dips
observed with S 2. The application of this correction pro-
duces the final column in Table XVIII., entitled " Corrected
Dips."
In Tables XVIII. and XIX., we have, then, the dip observed
at fifteen stations with Gambey, and at four additional stations
with S 2, making in all nineteen stations, which are inserted
in the following table with their geographical positions, and the
dips reduced to the mean epoch of the observations themselves,
viz. the 1st January, 1838.
Table XX.
station.
Lat.
Long.
Dip,
Jan. 1.1838.
Station.
Lat.
Long.
Dip.
Jan. 1.1838.
Alnwick
Castle
Stonehouse ...
Whitehaven ...
Newcastle
Birkenhead ...
Shrewsbury ...
Aberysthwith
Merthyr
/
55 25
54 55
54 33
54 58
53 24
52 43
52 24
51 43
51 57
1
1 42
2 44
3 33
1 36
3 00
2 45
4 05
3 21
3 21
o /
71 24-2
71 21-1
71 12-4
71 10-6
70 34-4
70 24-2
70 22-8
70 03-2
70 02-5
Dunraven Castle
Regent's Park
Lew Trenchard
Kew Gardens...
Westminster ...
Falmouth
Worcester Park
5°1 2'8
51 34
50 40
51 29
51 31
50 09
51 23
51 23
50 50
51 08
3 3'7
10
4 10
18
07
5 06
17
-1 23
34
-1 19
6°9 45-0
69 23-5
69 20-3
69 18-3
69 17-5
69 13-3
69 08-6
69 02-6
68 55-5
68 51-9
Tortington
Combining these by the method of least squares, we
obtain the following values: .r=-f2305; y=— '498;
M=— 65° OS'; r = -548; and 8 = 69° 56'-6 at the mean geogra-
phical position, of which the latitude is 52° 18', and the longi-
tude 1° 59'.
If now we collect in one view the several values of u and r
which have been thus obtained from the observations in Eng-
land, we havd as follows :
Table XXI.
Observer.
No. of
Stations.
Mean Geographical
Position.
Values of
Lat.
Long.
u.
r.
Fox
29
14
24
36
19
52 45
52 04
53 49
52 16
52 18
/
2 49
1 43
2 08
1 55
1 59
-6°2 41
-63 15
-63 14
-68 54
-65 08
0-580
0-644
0-590
0-548
0-548
Lloyd
Phillips
Ross
Sabine
86
EIGHTH REPORT — 1338.
If we regard the several values of u and r as entitled to
weight proportioned to the number of stations of which each is
the representative, we obtain —65° 05' and (V'Sys as the mean
values of u and r derived from the English series, corresponding
to the central geographical position 52° 38' N., and 2° 07' W.
Section II. — Scotland.
Ohservatio7is of Captain J. C. Ross. — These observations
were made with Robinson's six-inch circle, and the needles
R 4, R 5, R 6, and R 7? which have been already described.
Table XXII.
Captain J. C. Ross's Observations of the Dip, Scotland.
station.
D.ite.
Hour.
1
Poles.
« direct,
S reversed.
Mean.
Mean
Dip.
Place of
Observation.
1838.
Aberdeen ...
July 18.
4 P.M. R 4
a 72 28-7
/S 72 25-7
72 27-2
1
In a field
1 P.M.
R 5
« 72 30
;3 72 25-8
72 27-9
172 27-6
one mile
south of the
city.
Lerwick
— 24
Noon
2-15 P.M.
R 4
R 5
« 73 50-3
/3 73 46-9
« 73 43
/3 73 41-6
73 48-6
7342-3
— 25
Noon
R 6
«. 73 41-8
li 73 46-4
73 441
Gardie-
— 27
Noon
R 6
cc 73 44-8
/3 73 47-8 |73 46-3
73 44-9
House, Bras.
sa Island.
1-40 P.M.
R 4
a 73 48-9
/3 73 43-3
73 461
3 P.M.
R 5
a 73 43-2
/3 73 41 J73 42-1J
J
MAGNETIC SURVEY OP GREAT BRITAIN.
87
Place of
Observation.
In the garden
of the Cale-
donian Ho.
tel.
In the garden
of Rose-
bank, the
seat of Mr
M'Leay.
Dunrobin
Castle, E. |
of a mile. —
In the wood.
In the garden
of the Cale-
donian Ho-
tel.
In the grounds
ofCuIgruff.the
seat of George
Clark Ross,
In the grounds
of Jordan Hill,
the seat of J.
Smith, Esq
In a garden half
a mile north of
the Scotch
Gate.
In a planta-
tion of larch,
Craigie
Barns,S.W,
byW. three
or four
miles.
88
EIGHTH REPORT — 1838.
Table XXIII. contains the latitudes and longitudes of Captain
Ross's Scottish stations, and the mean dip at. each station at
the dates slionn in the preceding table. The whole interval
in which they are comprised is so short, that no reduction
to a common epoch has been applied.
Table XXIII.
station.
Lat.
Long.
Dip.
station.
Lat.
Long.
Dip.
Lerwick . .
Kirkwall ...
Wick
o /
60 09
59 00
58 24
57 58
57 28
/
1 07
2 58
3 05
3 57
4 11
73 44-9
73 20-4
73 J 9-9
73 04-3
72 46-2
Aberdeen ...
Dunkeld
Jordan Hill...
Berwick
CulgruflF
57 09
56 35
55 54
55 45
54 58
/
2 05
3 33
4 21
2 00
4 00
o /
72 27-6
72 23- 1
72 20-0
71 41-9
71 35-7
Golspie
Inverness ...
If we combine these ten results by the method of least
squares, we obtain the following values : x = + "250 ;
^=-•484; n=-62°39'; r=0'-545; and 8=72°40'-8 at the
mean geographical position 57° 20' N., and 3° 08' W., and at
the mean epoch August 18, 1838.
Major Sahines Observations. — These observations were
made at twenty- seven stations in the summer of 1836, with a
circle by Nairne and Blunt, and the needle S 2 of Robinson.
The details have been already published in the 5th vol. of the
Reports of the British Association, and need not therefore be
repeated in this place. When that Report was published, the
correction of S 2 was provisionally taken as —12'; it has since
been more correctly ascertained to be — 9'*5 bj?^ a much more
extensive series of comparative observations; (Table XIX.) The
subjoined table (XXIV.) contains the latitudes and longitudes of
the twenty-seven stations, and the dips, to which the new correc-
tion of — 9''5 has been applied. As the whole of these obser-
vations were comprised within an interval of six weeks, no
reduction to a mean epoch has been thought necessary.
MAGNETIC SURVEY OP GREAT BRITAIN.
89
Table XXTV.
Long.
Dip.
o /
o /
6 01
73 07-6
6 07
73 05-2
6 02
73 02- 1
3 57
72 55-5
4 11
72 46-4
5 48
72 42-8
3 09
72 40-8
4 40
72 40-3
2 50
72 25-6
5 17
72 22-9
2 45
72 21-9
2 55
72 17-4
5 07
72 17-1
4 41
72 16-7
Long.
Dip.
56 38
57 14
57 14
57 58
57 27
50 33
Toberniorie ..
Loch Scavig..
Loch Slapin..
Golspie
Inverness
Artornish
Gordon Castle 57 37
Fort Augustus' 57 08
Rhynie
Loch Ranza...
Alford
Newport
Glencoe
Helensburg ...
57 20
55 42
57 13
56 25
56 39
56
Loch Kidan ..
Castle Duart ..
Braemar
Kirkaldy
Loch Gilphead
Glasgow
Great Cumbray
Campbeltown ..
Blairgowrie
Edinburgh
Loch Ryan
Melrose
Dryburgh
55 57
56 31
57 01
56 07
56 04
55 51
55 48
55 23
56 36
55 57
54 55
55 35
55 34
5 10
5 45
3 25
72 16-6
72 15-2
72 14-1
72 10-9
72 07-6
72 01-6
72 Oil
71 55-9
71 54-7
71 50-3
71 43-3
71 36-8
71 33-6
If we combine these twenty-seven results by the method of
least squares, we obtain the following values : .r= + '337 J
^=-•461; u=-53° 4'J' ; r=0-57l ; 8 = 72° ]8'-7 at the
mean geographical position 56° 28' N., and 4° 19' W., and
at the mean epoch September 1, 1836.
Mr. Fox's Observations. — ^These observations were made
with Mr. Jordan's 7-inch circle and needle, and are as follows :
Table XXV.
Mr. Fox's Observations of the Dip in Scotland.
station.
Date.
Hour.
Lat.
Long.
Dip.
Place of Observation.
1837.
Melrose
Aug. 26
IH A.M.
55 35
2 44
71 38
East of the Abbey.
Edinburgh ...
— 28
8 A.M.
55 57
3 11
71 47
Gard. opposite Princes St.
Edinburgh ...
— 28
6 P.M.
55 57
3 11
71 53
Botanic Garden.
Linlithgow ...
— 30
U P.M.
55 59
3 37
71 59
Near ruins of the Palace.
Inverary
— 31
6 P.M.
56 15
5 04
72 7
In the Park.
Loch Lomond
Sept. 1
5 P.M.
56 13
4 40
72 15
Lakeside near Tarbet.
Glasgow
— 4
4^ P.M.
55 51
4 14
72 5
Botanic Garden.
Moffat
— 6
— 6
8 A.M.
2 P.M.
55 20
55 01
3 27
3 04
71 40
71 29
Near the Inn.
Behind the Inn.
Gretna Green
90
EIGHTH REPORT — 1838.
The portion of country over which these observations extend
is too limited to afford an advantageous combination for the
deduction of the vahies of u and r; I have therefore combined
them with my own twenty-seven results in Table XXIV.,
forming an united series of thirty-six stations towards the final
deduction of the values of u and r in Scotland, Mr. Fox's ob-
servations having been previously reduced to September 1836.
From this combination we obtain the following values; x=s
-t--320; r/=--447; «=-54°20'j )- = 0-550 ; 5=72° 13'2 at
the mean geographical position 56° 18' N., and 4° 10' W.
If we collect in one view the values of u and r which have
been thus obtained from the observations in Scotland, we have
as follows :
Table XXVI.
Observer.
No. of
SMtion.
Mean Geographical
Position.
Values of
Lat.
Long.
u.
r.
Ross
Sabine and Fox
10
36
57 2'0
56 18
3 08
4 10
-62 3'9
-54 20
0-545
0-550
Regarding the values of u and r as entitled to weight propor-
tioned to the number of stations of which each is the represent-
ative, we obtain u= —56° 06', and r = 0-549, as the mean va-
lues derived from the observations in Scotland, and corre-
sponding to the central geographical position of 56° 49' N., and
3° 39' W.
MAGNETIC SURVEY OF GREAT BRITAIN. 91
Section III.— Ireland.
{This Section is by the Rev. H. Lloyd.)
Before entering into the details connected with this division
of our memoir, it will be necessary to make a few remarks upon
the principles of the calculation which has been employed in
deducing the position of the isoclinal lines from the scattered
observations.
If z denote the dip (or intensity) at any station of observa-
tion ; s!q that at some near station, which is taken as the origin
of co-ordinates ; and x and 1/ the actual distances (in geogra-
phical miles) between the stations, estimated on the parallel of
latitude and on the meridian, respectively, — or the co-ordinates
of position of the first station referred to the latter as an origin ;
then I have shown*, (Fifth Report, p. 151) that the relation
of these quantities is expressed approximately by the equation
SI- Zo = Mx + l<li/; (1)
in which M and N represent the increase of the dip (or inten-
sity), corresponding to each geographical mile of distance in
the two directions.
In employing this equation in the calculation of the isoclinal
and isodynamic lines, I had taken one of the stations of ob-
servation — namely, Dublin — as the origin of co-ordinates : ob-
servation, therefore, gave the values of z and Zq, and the equa-
tions of condition thus obtained were combined, by the method
of least squares, so as to give the most probable values of M
and N. In a subsequent application of this method, (Sixth
Report, p. 99) Major Sabine adopted a better course, and
took an arbitrary station, with an unknown dip and intensity,
as the origin. Zq was thus unknown, as well as M and N ; and
the resulting equations gave not only the most probable values
of the increase of the dip (or intensity) in the two directions,
but likewise that of its absolute amount at some one station.
Let this latter quantity be denoted by L, i. e. let ^g = L in
the preceding equation ; then each observation will furnish an
equation of concfition of the form
L + Mx + Ny = s. (2)
Combining these equations by the method of least squares, we
have the three following final equations :
* The notation here used is somewhat different from that employed in the
Report. The variation can cause no embaiTassment to the reader.
92 EIGHTH REPORT — 1838.
L S {w) + Mt{2vx) +^'E (to y) = S {w ^),
L S {w x) + M S (mj a:^) + N 2 (w x >/) = X{w x s:), (3)
L 2 (m) y) + M 2 (^« a; y) + N S {iv ?f) =^{wys:);
in which w denotes the loeight of the determination, and the
symhol S the sum of the n values of the quantities within the
brackets, n being the number of separate determinations. From
these equations, the most probable values of the three unknown
quantities, L, M, N, are obtained by elimination.
If the point taken for the origin of the co-ordinates be that
for which
2 (w x) =0, ^{loy) =0;
or be, as it were, the centre of gravity of the stations, the final
equations are reduced to
L 2 {iv) = 2 {w s),
M 2 {iv x^) + I^t{tvx7/)=t (wx;:;),
M.t{tvxy) + N2 (w if) = 2 (toy:^).
The values of L, M, N being obtained, we may apply
the equation (2) either to determine the value of z, when x
and y are given, i. e., to deduce the most 2^robable value of the
dip for a given place, — or, conversely, to infer the relation of
X and y when s is given, i. e. to determine the eqtiation of the
line passing through all the points of given dip. In this latter
application let ;:; — L = K ; the equation of the line then is
M a,' + N 2/ = K, (4)
X and y being the co-ordinates, measured along the parallel of
latitude and the meridian respectively. On this supposition,
then, the isoclinal line is a right line ; the angle which it makes
with the meridian is
ang (tan = — ^j J ; (5)
and the increase of the dip corresponding to each geographi-
cal mile of distance, in a direction perpendicular to the line, is
VM? + W. (6)
In this mode of computation it is assumed, not only that the
portion of the earth over which the observations extend
may be treated as a plane surface, but also that the differ-
ences of dip (or intensity) are linear f\xnct.\o\\s of the differences
of latitude and longitude,— in other words, that the isoclinal
and isodynamic lines are straight. This supposition may be
safely made, where the district of observation, itself inconsider-
able in extent, is remote from the poles of dip or of intensity ;
MAGNETIC SURVEY OF GREATT BRITAIN. 93
for in such cases the curvature of the hues not being rapid, the
curve itself may, for a small portion of its extent, be confound-
ed with its tangent. It suggests perhaps the best mode of de-
termining with precision the empirical laws of the distribution
of terrestrial magnetism ; namely, by means of small groups of
observations, each of which will give, by this method, not a point
in the curve merely, but a portion of its tangent.
The extent of the district in which this method is available
will, of course, vary with the curvature of the lines on the
earth's surface, becoming more and more limited as we approach
the poles. Where the flexure of the lines is rapid, and we
seek, nevertheless, to combine the observations scattered over
a moderately extensive tract of country, it becomes necessary
to obtain some means of pushing the approximation further.
Such means I'eadily present themselves. Whatever be the
laws of distribution of magnetism on the surface of the earth,
it is manifest that the dip (or intensity) at any station is a func-
tion of its co-ordinates of position ; or that
^ = F(a,^),
a and /3 denoting the co-ordinates of the station (in parts of
radius) referred to some neighbouring station as an origin.
Accordingly,
+ I (^) 13' + &c.
2 \ci i3y ^
the brackets denoting the particular values of the derived
functions, when a = 0, yS = 0. The quantities u and /3, in the
preceding equation, being small, we may push the approxima-
tion as far as we please, by including a greater number of terms
in the development.
Let the co-ordinates of linear distance be denoted, as before,
by X and y,
*' a y
r r
r being the radius of the earth. Substituting these values in
the preceding equation, and making
we have
s; = L + M ^ -h N 2/ -1- P A'M- Q ^ 2/ + R 2/^ + &c. (7)
94 EIGHTH REPORT 1838.
If we retain only the terms of this equation in which x and y
are of the first dimension, we have the equation (2) already
obtained.
To advance another step in the approximation, we should in-
clude the terms in which x and y are of the second dimension ;
and we shall thus have six unknown coefficients L, M, N, P, Q,
R, to be determined. For this purpose, the equations (in number
the same as the stations of observation) are to be combined by
the method of least squares ; and the six resulting equations
will give, by elimination, the quantities sought.
The coefficients L, M, N, &c. being known, the Hne oi given
dip is
R y^ + Q a: y + P a;2 + N y + M ^ = K, (8)
in which K denotes, as before, the particular value of ^ — {z).
Here, then, the isoclinal hne is of the second order ; and its
species is determined by the relation of the first three coeffi-
cients, P, Q, R. The equation of the curve being found, it is
easy to construct it graphically by points.
The preceding solution of the problem is probably suffi-
cient for all purposes ; but the determination of six unknown
quantities by the method of least squares, when the equations
of condition are numerous, is a formidable labour ; and it is
therefore important to consider whether we can safely stop
short at any step of less generality. Now it is easily seen that
in most cases to which we have to apply this method, the iso-
clinal line may be represented by the equation
p ^2 ^ N y + M ^ = K, (9)
in which there are only four coefficients to be determined*.
This equation (considered as belonging to a plane curve) is that
of a parabola.
The equation, being linear m. one of the co-ordinates, is very
easily constructed by points.
* This is evident from geometrical considerations.
Let L M be a portion of the cm-ve, re-
ferred to the axes of co-ordinates O P, O L ;
and let L Q be its tangent at the point L,
making with the axis of abscissiE an angle
whose tangent is u. The ordinate of the
curve P M, is equal to P Q + Q M. But
P Q, the ordinate of the tangent, is equal to
ax + h,b denoting the ordinate at the ori-
gin, O L. And the sagitta Q M, is pro-
portional to Q L^ the arc being small in
proportion to the radius of curvature ; i. e.
Q M = A X Q L2 = /f (1 -i- a2) .x2 = ca!^
MAGNETIC SURVEY OF GREAT BRITAIN. 9&
The object proposed in the preceding method has been at-
tained by Major Sabine by a different process, which will be
applied by him in the sequel. It is therefore unnecessary to
make any application of that here laid down.
In combining the equations of condition by the method of
least squares, it is manifest that we cannot, in general, allow
equal weight to all. The result obtained at one station may be
derived from a single observation only ; while, at another, it
may be the mean of several observations, made at different
times, and with different instruments. In a former discussion
of the observations in Ireland, weights were assigned to the
results at each station, but on arbitrary and uncertain princi-
ples. I now proceed to remedy this defect ; and I do so the
more willingly, both on account of the great importance of
this branch of the theory of probabilities in Physical science,
and because the results to be referred to are connected wath
researches not as well known as they deserve.
Let x^, a-g, x.^, &c., x^, be n values of the quantity x, ob-
tained by separate and independent observations ; and let a
denote their arithmetical mean, so that
a— -(^1 + or. + 0^3 + &c. -f- x^ ;
then the probable error of this mean, i. e. the limit on either
side of which there are equal chances of the actual error lying,
is given by the formula
n{n-l) ' ^^^
in which S (j: — «)^ denotes the sum of the squares of the dif-
ferences of the several partial results and the mean, or the va-
lue of
{x, - af + {x^ - af + &c. + (07,^ - af ;
and in which, also, p is the number which satisfies the equa-
tion
'' e ''dt^i ^-
Numerically, p = 0"4769 ; and substituting in (10)
E« = -iS^lifl^' (11)
n [n — 1)
The pi'obable error of a single result, as deduced from com-
parison with the rest, is in like manner given by the formula
96 EIGHTH REPORT 1838.
„ -4549 S (* - aY
(12)
n-1
so that e* = « E*. The weights, in both cases, are measured by
the inverse of the squares of the probable errors ; that is
WE2 = ], we^= 1, (13)
tv and W denoting the weights of the single result, and of the
mean, respectively*.
When the quantity sought is a linear function of two or
more unknown quantities, which latter are obtained imme-
diately by observation, its probable error is connected with
those of the quantities on which it depends by a very simple
relation.
Let X and y be the quantities sought by immediate observa-
tion, and let the quantity actually sought, ^, be a linear func-
tion of these, expressed by the equation
z=px + qy.
Let a denote the ai-ithmetical mean of m observations of the
unknown quantity x \ h the mean of n observations of y ; and
let E and E be their probable errors, or the limits on either
side of which there ai'e equal chances o{ the actual errors, x—a,
y — b, being found. Then the probable error of .?, E^, is ex-
pressed by the formula f
E^=^^E^ + ^,E^. (14)
The case of a linear function includes every case in which
the quantities sought are already approximately known. We
have only to substitute for these quantities their approximate
y?L\\ies plus the unknown corrections, and to neglect the squares
and higher powers of the latter.
To apply these principles to an important case, — let it be re-
quired to determine the probable error (or the weight) of the
mean dip at a given station, as deduced from n^ observations,
with n. instruments.
The true dip being equal to the observed dip p/M« the in-
strumental correction, it is manifest that, in this case,
E^ = E^„+EV
* For the demonstration of these theorems, the reader is referred to a paper
by Prof. Encke, in the Aslronomisches Jahrhuch for the year 1834. See also a
paper by M. Poisson on the same subject in the Connohsance des Temps, 1827.
I See a paper by M. Poisson in the Btdletin Universel des Sciences, tome xiii,
p. 266, See also the Memoir by Prof. Encke, already referred to.
MAGNETIC SURVEY OF GREAT BRITAIN.
97
E denoting the error of observation, and E that due to the
°
imperfection of instruments. But
E^ = ^, E, =-i,
€ denoting the probable error of a single observation, and e^that
of a single instrument. Hence
4 ^
E^ = - + — .
(15)
We have here taken no separate account of the error arising
from the variations of the dip, that error being inseparably
combined with the error of observation ; the symbol e^, there-
fore, in the -preceding, denotes the probable error resulting
from the two conjoint sources.
In order to estimate the value of e^, I have taken the follow-
ing series of observations, made with the needles, L. 1, L. 4,
in Dublin, the longest series of observations made with the
same instrument at a single station in Ireland. The 1st column
of the table contains the dates of observation ; the 2nd the ob-
served dips (uncorrected) ; the 3nd the reduced dips, referred
to the 1st of January, 1836. In the 4th column are the differ-
ences between the partial results and the mean ; and in the oth,
the squares of these differences.
Table XXVII.
Needle L. 1.
Date.
Observed Dip.
Reduced Dip.
x-a
ia,-af
Oct. 21, 1833
7b 5'6-4
7°0 51-2
- 0-4
0-16
Aug. 7, 1834
70 51-6
70 48-2
- 3-4
11-56
— 8.
70 57-6
70 54-2
+ 2-6
6-76
— 9,
70 54-3
70 50-9
- 0-7
•49
— 19.
70 49-5
70 46-1
- 5-5
3025
Sept. 22,
70 56-0
70 530
+ 1-4
1-96
— 23,
70 53-8
70 50-8
- 0-8
•64
Sept. 4, 1835
70 46-7
70 45-9
- 5-7
32-49
- 5,
70 55-6
70 54-8
+ 3-2
10^24
— 7,
70 54-2
70 53-4
+ 1-8
324
- 9,
70 54-4
70 53-6
+ 2-0
4-00
— 14,
70 56-7
70 55-9
+ 4-3
18-49
— 15,
70 53-3
70 52-5
+ 0-9
-81
VOL. vn.
1838.
98
EIGHTH REPORT. — 1838.
Table XXVIII. Needle L. 4.
Date.
Observed Dip.
Reduced Dip.
x — a
(^-«)2
Sept. 22, 1834.
71 2-2
70 59-2
+ 9-1
82-81
— 23,
70 53-8
70 50-8
+ 0-7
0-49
— 29,
70 44-8
70 41-8
- 8-3
68-89
Oct. 25,
70 541
70 513
+ 1-2
1-44
Aug. 19, 1835.
70 51-6
70 50-8
+ 0-7
0-49
Sept. 4,
70 43-6
70 42-8
- 7-3
53-29
— 5,
70 52-8
70 52-0
+ 1-9
3-61
— 7,
70 52-2
70 51-4
+ 1-3
1-69
— 9,
70 46-2
70 45-4
- 4-7
22-09
— 14.
70 53-4
70 52-6
+ 2-5
6-25
— 15,
70 55-0
70 54-2
+ 4-1
16-81
Nov. 5,
70 49-6
70 49-2
- 0-9
0-81
— 5,
70 45-8
70 45-4
- 4-7
22-09
— 6,
70 53-9
70 53-5
+ 3-4
11-56
Apr. 11, 1836.
70 48-1
70 48-9
- 1-2
1-44
— 15,
70 471
70 47-9
- 2-2
4-84
May 7,
70 50-9
70 51-7
+ 1-6
2-56
— 9.
70 56-4
70 57-2
+ 7-1
50-41
Aug. 5,
70 431
70 44-5
- 5-6
31-36
- 6,
70 51-3
70 52-7
+ 2-6
6-76
From the former of these tables we find
w = 13, a = 70° 51'-6, S (^ - df = 121-09 ;
and from the latter
« = 20, a = 70° 50'- 1, %{x - of = 389-69.
Substituting these numbers in (12), the probable error of ob-
servation in the former series is found to be 2''1 ; and in the
latter 3'-0.
It is remarkable that the squares of these errors (the inverse
of which are the measures of the weights) are, almost exactly,
in the ratio of 1 to 2 ; that is, in the inverse ratio of the num-
ber of readings with each needle. This is a curious confirma-
tion of the accuracy of the conclusion.
From the preceding it follows, that in combining the results
of the two needles, L. 1 and L. 4, (when used together) double
weight must be allowed to the former. It appears from (14)
that the probable error of the mean, thus deduced, is l'*8. We
may therefore consider two minutes as the probable error of
observation in the present series, whether the result be that
of a single needle with the usual number of readings, or the
mean of the two needles L. 1 and L. 4.
The probable instrumental error, e,, varies, of course, within
very wide limits, depending on the perfection of workmanship.
In a former part of this memoir. Major Sabine has pointed out
the very great improvement which our English dipping needles
MAGNETIC SURVEY OF GREAT BRITAIN".
99
have undergone in this respect, subsequently to the year
1835*. The mean error, for any set of needles, may be ob-
tained from (15), when we have made a series of observations
with these needles at any one station. Let e denote the pro-
bable error of the result given by any set of observations with
a single needle, as inferred from comparison with the others ;
Then e* = n. E% and substituting in (15), we have
eU = e
n.
-el
n„
in which the value of e^ is deduced from the observations by
means of (12).
To deduce, according to these principles, the value of e^ for
the needles employed in the Irish survey, we must compare
the results obtained at Limerick, — that being the only station
where all the needles were employed. These results are con-
tained in the following table. The first column contains the
names of the needles employed; the second, the dips obtained,
reduced to the 1st of January, 1837, of which the mean value
is 71° 0''5 ; in the 3rd column are the differences of the par-
tial results and the mean; and in the 4th, the squares of these
differences.
Table XXIX.
Needle.
Dip = X.
X -a
(* - a)'
S.2
71 2-6
+ 2-1
4-41
M
71 1-4
+ 0-9
0-81
S. It
70 57-6
-2-9
8-41
S. If
70 59-1
- 1-4
1-96
L. 1
71 4-7
+ 4-2
17-64
L. 4
70 57-7
-2-8
7-84
From the last column of the preceding table we find
t {a; — aY = 41-07; and substituting in (12), e^ = 3-70.
n.
Again, w,- = 6, n = 26, and, assuming e^ = 2, — i e^ = 0*92.
o
* The probable instrumental error of the needles employed at Westbourne
Green in 1835, as deduced from the observations recorded in the Irish Report
(Fifth Report, p. 142), amounts to 8'-3. The mean probable error of the
needles employed at the same place in 1837 and 1838, as deduced from the
observations contained in Table III. of the present memoir, is ahout one minute
only.
t_The needle S. 1 had undergone a change in the disposition of its axle in
the interval between the two observations recorded in this table. These obser-
vations must therefore (as far at least as the axle is concerned) be regarded as
the results of different instruments.
h2
100 EIGHTH REPORT — 1838.
We have, therefore, from the preceding formula, e^^ = 2"78, and
e.= l'-7.
>
It appears, then, that the instrumental error is somewhat less
than the error of observation. The difference, however, is
probably less than the error of our result ; and we shall as-
sume, in round numbers, two minutes as the amount of each
error in the Irish series.
Taking, then, e . = e^ = 2, we have (15) (13)
E2 = l = 4(- + -V (16)
From this formula we learn how useless it is to multiply obser-
vations with the same instrument, in order to obtain the dip at
a given station : When ??,• = 1, we have
i-=4(- -f l), - = 4x2;
W \n / w
tv denoting the weight of a single observation ; so that
W _ ^% _
w ~" «„ + 1 '
and, however the observations be multiplied, the weight of the
result can never amount to double the weight of a single ob-
servation.
In what precedes, we have considered only the actual dip at
a given station. But in deducing the position of the isoclinal
lines from observations of dip made at several stations, it is
necessary to consider likewise the probable difference between
this dip and that due to the geographical position of the sta-
tion : or, in other words, the probable mean local error.
Let €i denote this error ; then it is manifest, from what has
been already said, that the actual resulting error will be ex-
pressed by the formula
«„ n, '•
(17)
The mean local eri'or will, of course, be very different in dif-
ferent countries, the differences depending chiefly on the re-
lative proportion of the igneous and sedimentary rocks. In
Scotland, as appears from Major Sabine's excellent report (Sixth
Report, p. 102), the local error is considerable ; in England it
is probably small. We may estimate its amount in any district,
by computing the dip due to the geographical position of each
station, by the formula (2), and taking the sum of the squares
MAGNETIC SURVEY OF GREAT BRITAIN.
101
©f the differences between the computed and observed results.
This, substituted in (12), will give the total mean probable
error, or the value of e in the equation (17) {rig and w,- now
denoting the mean number of observations, and of instruments,
at each station) ; and, e and e. being already known, we de-
duce the value of e^.
In addition to the observations of dip already printed in the
Irish Magnetic Report, the following pages contain, 1st, a se-
ries of observations made by Robert W. Fox, Esq., at nine
stations, chiefly in the West of Ireland ; 2nd, observations
made by Major Sabine, chiefly in Limerick; 3rd, my own ob-
servations in Dublin ; and 4th, a series of observations made
by Captain James Ross, at twelve stations, distributed uni-
formly over the whole island.
Mr Fox's observations are contained in Table XXX. They
were made in the autumn of the year 1835, at a tinie when the
other parts of the Irish survey were in progress ; but, Mr. Fox
not being at that time associated in our labours, his results were
separately published*. They are now, with his permission,
republished in the present memoir. The instrument employed
in these observations has been already described f.
Table XXX.
Mr. Fox's Observations in 1835.
station.
Date.
Hour.
Dip.
Place of Observation.
Dublin
Aug. 17
— 19
— 19
— 22
— 24
— 24
— 25
— 27
— 28
11 A.M.
9i A.M.
3i P.M.
2p. M.
11| A.M.
6 P.M.
10 A.M.
4^ P.M.
91a.m.
70 59
71 26
71 41
71 52
72 3
72 8
72 7
73 15
72
Garden of Trinity College.
Hotel Garden.
Island in Lough Corrib.
Hotel Garden.
Garden of Hotel (Sligo Arms).
West side of Lough Conn.
Hotel Garden.
East side.
Hotel Garden.
Galway
Clifden
Ballina
Giant's Causeway
Cushendall
Major Sabine's additional observations, contained in Table
XXXI, were made at Limerick, Dubhn, and Bangor, in the
year 1836 %. These observations have been already printed
• Proceedings of the Cornwall Polytechnic Society.
t Page 3.
X With the exception of one set of ohservations made with Mayer's needle
in the year 1833. These observations, though referred to in the Irish Report,
were overlooked in the compilation of the tables.
102
EIGHTH REPORT. — 1838.
in the Scotch Magnetic Report, and are reprinted here, so
as to have all the data connected with Ireland present in one
view. The needles employed, (Mayer's needle and needles
S. 1, S. 2,) have been already described.
Table XXXI.
Major Sabine's Observations.
station.
Date.
Hour.
Needle.
Dip.
Limerick...
Nov. 1,
1833.
1 P.M.
Mayer's.
7°1 11-0
— 2&4
1833.
1 P.M.
71 11-9
Mean...
71 11-5
Limerick...
May
1836.
Mayer's.
June
Mean...
71 0-0
May
1836.
SI
71 0-6
Limerick...
Feb. 20,
1836.
1 P.M.
S2
71 13-4
Limeriek...
May 5
11 A.M.
71 130
— 5
1 P.M.
71 11-0
Mean...
71 120
Dublin ...
July 22,
1836.
Noon
71 141
— 22
1 P.M.
71 11-6
— 23
Noon
71 13-7
Mean...
7i
71 131
Bangor ...
Sept. 21,
1836.
10 A.M.
71 48-7
Dublin ...
Oct. 4
I P.M.
71 12-7
My own additional observations were confined to Dublin, and
were made in the years 1836 and 1838. The observations of
the former year, contained in Table XXXIII, were made with
the statical needles, L. 3 and L. 4, already described. Those
of the latter, (Table XXXII), with the dip circle, and needle
G. 2 made by Gambey * ; and with another circle of the same
size, and two needles, made by the same distinguished artist
for the Dublin Observatory. All these latter observations
were made according to the method of arbitrary/ assimuths. In
conjunction with the observations of Captain Ross in Dublin,
they are taken as the basis on which the determination of the
corrections of my other needles, L. 1, L. 3 and L. 4, is made
to rest.
Page 50.
MAGNETIC SURVEY OF GREAT BRITAIN.
103
Table XXXII.
Mr Lloyd's Observations in Dublin in 1838.
Gambey's Needles.-Method of Arbitrary Azimuths.
Needle.
Date.
90
10
100
20
110
30
120
40
130
50
140
60
150
70
160
80
170
0*f
90
30
120
60
150
Angle.
70 49'8
89 43-4
71 41
86 42-2
71 540
83 33-0
73 11-4
80 27-4
75 0-9
77 40-2
77 20-4
75 17-9
80 1-0
73 280
83 4-4
72 6-4
86 16-5
71 14-8
90
30
120
60
150
70 59-1
89 53-5
73 111
80 16-2
80 9-6
73 20-7
70 55-9
89 51-2
73 16-1
80 22-0
80 16-0
73 26-7
o
Lit
71 26-0
105
85 19-4
45
75 53-9
135
76 33-6
75
84 28-3
165
71 46-7
180
270
190
280
200
290
210
300
220
310
230
320
240
330
250
340
260
350
180
270
210
300
240
330
180
270
210
300
240
330
195
285
225
315
255
345
Angle.
7°0 56'0
89 49-4
71 11-6
86 37-2
71 59-1
83 21-9
73 19-4
80 13-9
75 4-0
77 32-4
77 240
75 11-1
80 8-6
73 20-0
83 8-5
71 59-1
86 23-0
71 71
Mean Angle.
71 1-9
89 52-3
73 19-5
80 110
80 16-9
73 171
71 1-7
89 530
73 29-1
80 6-8
80 24-9
73 19-5
71 32-6
85 13-4
75 59-4
76 30-4
84 31-1
71 38-1
70 52-9
89 46-4
71 7-8
86 39-7
71 56-5
83 27-5
73 15-4
80 20-6
75 2-5
77 30-3
77 22-2
75 14-5
80 4-8
73 24-0
83 6-5
72 2-8
86 19-8
71 110
Dip.
71 0-5
89 52-9
73 15-3
80 13-6
80 13-3
73 18-9
70 58-8
89 5
73 22-6
80
80 20-5 \
73 231 /
58-8 -1
52-1 /
22-6 1
14-4 J
70 52-8
70 52-6
70 560
70 56-0
70 551
70 55-3
70 560
70 55-4
70 52-6
71 0-5
70 52-7
70 55-6
71 29-3 "1
85 16-4 J
75 56-6 \
76 32-0 J
84 29-7 1
71 42-4 J
70 58-8
70 59-3
71 2-5
70 58-3
70 53-5
70 59-9
* The Azimuth O' is the magnetic meridian, the face of the instrument being to
the east. The azimuths increase in the order N., t.., h., VV. „„„,,„r of dc-
t The azimuths in this last observ..tion are set down in a round number ot
grees. They were (exactly) 14° 15', 44° 15', 74° 15', &c.
104
KIGHTH REPORT 1838.
Table XXXIII.
Mr. Lloyd's Observations in Dublin in 1836.
Date.
Needle h. 3.
Needle L. 4. 1
Hour.
Dip.
Hour.
Dip.
April, 11.
— 15.
Mean...
h
12
12
12
m
18
30
24
70 53'4
71 0-0
70 56-7
h
12
12
12
m
43
8
25
7°0 48'-l
70 471
70 47-6
May 7.
— 9.
Mean...
1
1
1
32
25
28
70 56-5
71 0-9
70 58-7
1
12
1
10
50
70 50-9
70 56-4
70 53-6
Aug. 5.
— 6.
Mean. .
3
2
3
50
35
12
70 54-7
70 58-4
70 56-5
3
2
2
28
10
49
70 431
70 51-3
70 47-2
The observations of Captain Ross were made in October and
November, 1838, with the needles designated as R, 4, R. 5,
R. 6, R. 7, L. 3, L. 4, in the preceding pages. The stations
of observation being sufficiently numerous, as well as uniformly
distributed, it has been thought advisable to combine them in a
separate determination. The observations are contained in
Tables XXXIX. and XL.
We have now to consider the actual errors of the instru-
ments employed in the preceding observations.
The errors of dipping needles may be ascribed to one or
other of the three following causes: namely, 1, the friction of
the axle on its supports ; 2, the imperfect curvature of the
axle itself; 3, magiietism in the limb.
It is owing to the first-mentioned cause that a dipping nee-
dle assumes, in general, a new position of equilibrium after it
has been disturbed, the limit of error being the angle at which
the directive force, increasing as the sine of the deviation,
becomes equal to the friction. This limit varies, for a given
state of polish of the axle and of its supports, with the radius
of the cylindrical axle, the weight of the needle, and its direct-
ive fores'^. In all the earlier dipping needles constructed in
this country, this limit of error is considerable, owing to the
unnecessary size of the axle.
The errors arising from the two latter causes are, however,
of a very different nature. The positive and negative errors
due to friction are equally probable, and the effect of the dis-
• Trans. Royal Irish Academy. Vol. xrii. p. 1 66.
MAGNETIC SURVEY OF GREAT BRITAIN. 105
turbing cause is merely to widen the limits of probable error.
The imperfect curvature of the axle, and the magnetism of the
limb, act however very differently. Either of these sources of
error must, at a given place, affect all the results in the same
manner; and, consequently, no repetition of observation, with
an instrument so circumstanced, can afford even an approxi-
mation to the true dip. At different places the error will be
different, and will vary according to no assignable law.
The course to be pursued by the observer with reference
to these errors is manifest. Their existence or non-existence
should be ascertained at the outset by one or other of the means
pointed out by Major Sabine in the commencement of this me-
moir ; and if found to surpass certain limits, the instrument
should be rejected. The case is different, however, when the
instrument has been actually employed for some time pre-
viously to the detection of the error. Here we must seek, if
possible, to determine the probable amount of the error, and
apply it, with an opposite sign, as a correction to the results.
Where the district of observation is limited, this is practicable.
It will be easily understood, that the imperfect curvature of the
axle, or the disturbing action of the limb, must, within a moderate
range of dip, affect all the results in the same manner, so that
they will all require a correction having the same sign ; and that
when the range of dip is very small, the amount of the dis-
turbance will be nearly the same throughout, and consequently
the correction required will be nearly constant. In such a case
then we have only to determine the amount of the error at some
one station, by a comparison of the results with those of proved
needles obtained at the same place, and, if possible, at the same
time.
Again, in needles whose poles are unchanged, gravity acts
with a certain moment with or against the directive force ; the
coincidence of the centre of gravity with the axle being rarely
attained. The observed inclination, therefore, deviates from
the true dip, and the amount of this deviation varies in different
places, according to a known law*. To obtain its actual
value, however, at any station, it must be known at some one ;
and this knowledge is to be obtained, as before, by a com-
parison of the results with those of other needles at that sta-
• Fifth Report, p. 144. With needles whose poles are inverted in each
observation, the true dip may be inferred from the observed angles of incli-
nation, however considerably they may deviate from it. In such needles,
therefore, the non- coincidence of the centre of gravity with the axle cannot
properly be ranked among the sources of error.
106 EIGHTH REPORT 1838.
tion. When the district of observation is limited, the vari-
ation of this quantity may be disregarded.'
The importance of an exact determination of these needle-
corrections is very great in the present instance. When, in-
deed, the same needle is employed throughout an entire series
of observations (as was done by Major Sabine in Scotland), it
is manifest that any error in the amount of its correction will
have the effect only of displacing the isoclinal lines in absolute
position, leaving their direction and interval unaltered. For
the dii'ection and interval of the lines depend solely on the dif-
ferences of dip ; and these are manifestly independent of the
correction, which alters all the dips by the same amount. The
case is different, however, when (as in the present instance)
different needles requiring correction are employed in the same
series. Here the differences of dip cannot be known, unless
we know the differences of the corrections of the needles em-
ployed ; and it is manifest that any error in the amount of that
difference will displace one entire group of results relatively to
the rest, and thus (when the mean geographical position of
these groups is different) induce a grave error in the direction
of the lines.
Before we proceed to determine the amount of these errors
in the needles employed in the Irish survey, it may be desirable
to make a few remarks on their particular causes.
Of the two sources of error above mentioned, the imperfec-
tion of axle appears to be the most common ; and it is to it we
are to ascribe (as Major Sabine has already remarked*) the
chief part of the discordances in the results obtained at West-
bourne Green in 1835. The same series, however, affords like-
wise a remarkable instance of the other error. Having pur-
posely destroyed the balance in two of my dipping needles, so
that they rested nearly in the horizontal position in Dublin, I
proceeded to use them exclusively for observations of intensity.
The results thus obtained were, however, so anomalous, that I
was compelled to reject them altogether. After some tedious
and vain attempts to discover the source of the anomaly, I was
at length satisfied, by a careful inspection of the results, that the
needles were under the influence of some other force besides
the earth's magnetism and gravity, and I concluded that this
disturbing force covild be no other than magnetism in the dip
circle itself. Trial soon verified this conjecture, and I had the
mortification to find that the apparatus which I had been so
long using was throughout magnetic, and that the magnetismf
* Page 46.
t Magnetism induced in ferruginous matter, not permanent.
MAGNETIC SURVEY OF GREAT BRITAIN. 107
was greatest in the graduated limb, the very part in which, from
its proximity to the needle, it must operate most powerfully.
I had next to consider the painful question, — How far the nu-
merous results obtained with this instrument were vitiated by
this newly-discovered source of error? Whether they were
entitled to any confidence ; and if so, what were the probable
limits of error ? It is manifest that if the ferruginous matter
were uniformly distributed throughout the limb, it could pro-
duce no disturbance in the position of a needle which (Uke the
dipping needle) divides the hmb symmetrically. It is only by
an irregularity in its distribution that the magnetic matter of
the Hmb can operate as a disturbing cause ; and then it is ma-
nifestly only by the difference of the attractions, on the two
sides of each pole, that the needle is actually disturbed. Hence,
though the magnetism of the limb may produce very decided
effects upon a test needle, in a position at right angles to its
plane, the effect upon a dipping needle may be comparatively
trifling.
In order to estimate the amount of these effects, I separated
the divided circle from the apparatus, and placed it on a hori-
zontal support of wood. Three strong pins in contact with the
inner edge of the limb, and dividing it equally, were then driven
into the support, so as to prevent the limb from having any
motion, except one of rotation in its own plane. A magnetic
bar, wh9se length was nearly equal to the diameter of the circle,
was then supported delicately within it, and the deviation of
the bar from its undisturbed position was observed in the
different positions of the limb with respect to it. It was thus
found that most parts of the limb exerted a sensible disturbing
effect upon the needle ; and that this effect was not only con-
siderable in the neighbourhood of the two zero points of the limb
(the part where the anomalies had been first observed), but that
it also varied there very rapidly. A detailed examination of
the effects in this position showed that there was a disturbing
centre of ferruginous matter in the neighbourhood of each of
these points, and that it was to the action of these centres
that the anomalies in the observations above alluded to were
owing.
In the neighbourhood of the divisions of 70° the disturbance
of the needle was likewise considerable, and its direction was
such as to diminish the apparent dip. Here, then, we have the
cause of the large negative error of the results obtained with
this instrument. But this deflection did not vary rapidly on
either side of these positions, so that for small changes of dip
108
EIGHTH REPORT — 1838.
the error may be regarded as nearly constant*. Defective,
therefore, as the apparatus is in this respect, there is reason to
conclude that the differences of dip obtained with it in Ireland
may be relied on within the usual limits of probable error, and
that to obtain the true dip from the observed results, we have
only to apply a positive correction, which may be regarded as
constant throughout the series.
The instrument referred to in the preceding pages having
been much employed in Dublin, and with very consistent re-
sults, we shall take, as the basis of its correction, the dip in
Dublin as deduced from the observations with Gambey's nee-
dles, Table XXXII. In these observations, made according
to the method of arbitrary azimuths, the bearing points of the
axle^ and the position of the needle with respect to the limb,
are different in each azimuth ; so that the results may be re-
garded as, virtually, the results of different instruments.
Their accordance is sufficient to show that the errors of axle
and of limb are inconsiderable. For the convenience of refe-
rence, the observations are put together in the following Table ;
the dips being reduced to the 1 st of January, 1 838.
Table XXXIV.
Needle.
Azimuth.
Dip.
Needle.
Azimuth.
Dip.
of
,
(i e
o o ^
o, /
t%
0& 90
70 54-2
J^-A
^ r
0& 90
71 2-3
10 & 100
70 54-0
A
30 & 120
70 54-5
O Q
20 & 110
70 57-4
=S°o
60 & 150
70 57-4
1i°
30 & 120
70 57-4
r
0& 90
71 0-6
^^^
40 & 130
70 56-5
_i
15 & 105
71 01
.■" "Sb.S
50 & 140
70 56-7
i\
30 & 120
71 11
l?§f^
60 & 150
70 57-4
*-i„°
45 & 135
70 55-3
%.1
70 & 160
70 56-8
It
" 1
60 & 150
71 4-3
09
O
80 & 170
70 54-0
o^
L
75 & 165
71 1-7
The mean of these results is 70° 57''9. If we combine with
this the mean result obtained by Captain Ross at the same
place, as deduced from six observations with four needles, and
reduced to the same epoch, (namely, 71° 1''7,) we have, for
the mean dip in Dublin, on the 1st of January, 1838,
70° 58'-8.
* A comparison of the results with those of other instruments seems to point
to the conclusion that this error diminishes with the dip, and is somewhat less
in England than in Ireland.
MAGNETIC SURVEY OP GREAT BRITAIN.
109
To compare with this, we have the following observations
with the needles L. 1, L. 3, L. 4, in Dublin.
Table XXXV.
Needle.
No.
Date.
Observed Dip.
Reduced Dip.
Mean Dip.
L 1
1
Oct. 21, 1833
7°0 56-4
70 46-4 1
—
6
Aug. 25, 1834
70 53-8
70 45-8 I
7°0 46-8
—
6
Sept. 9, 1835
70 53-5
70 47-9 J
L 3
4
Apr. 25, 1836
70 57-7
70 53-7 1
70 53-1 /
70 53-5
—
2
Aug. 5, 1836
70 56-5
L4
4
Oct. 2, 1834
70 53-7
70 45-9 ^
—
7
Sept. 6, 1835
70 50-7
70 451
—
3
Nov. 5, 1835
70 49-8
70 44-6 y
70 45-4
4
Apr. 25, 1836
70 50-6
70 46-6
—
2
Aug. 5, 1836
70 47-2
70 43-8 J
Hence we obtain the following corrections :
Needle L. 1, correction = + 12'*0
„ L. 3 „ = + 5'-3
„ L. 4 „ = + 13'-4
In L. 3 and L. 4, needles whose poles are unchanged, the
errors here deduced are, of course, those which result from
the moment of the needles' weight, combined with that arising
from the disturbing action of the limb.
The weights due to these corrections are at once deduced
from the principles of the preceding pages. When the results
of one needle, at a given station, are compared with those of
others, and that we seek their difference, it is manifest that
/» = 1,5'= 1, (14), and that, consequently,
W = Ei^ + Eg^ ;
Ej denoting the probable error of the mean result of the
given needle, and Eg that of those with which it is compared.
When we look no further than the actual difference of the re-
sults at the one station, it is manifest that
E,
fi_ E2 — ii.
> ■'-'9 — >
n^ ^ Tic
c, and €3 denoting the probable errors of a single observation,
in the needles compared, and Wj and Wg the number of obser-
110 EIGHTH REPORT — 1838.
vations. Hence, if e^ = Cg, that is, if the reading power be
the same in the two cases, and the same pains be bestowed on
the observations,
l=i+i, (18)
n denoting the value of the ratio ^f^, or the equivalent num-
ber of observations of the difference sought, supposing it to be
the immediate subject of observation.
But when we desire to compare the result of the uncor-
rected needle with the actual dip, we must also take into ac-
count the probable instrumental error of the results with
which it has been compared ; and we have (15)
And in place of equation (18), we have the following:
11 1 eM
-= - + - + -J_-. (19)
n «i n^ e% n.
To apply this, we shall assume, as before, the instrumental
error to be equal to the error of observation, the latter inclu-
ding the error of epoch ; and we obtain
Needle L. 1, n^ = 13, n = 6-1,
— L. 3, 6, 3-9,
— L. 4, 20, - - 7-3.
We shall adopt the nearest whole numbers, 6, 4, 7.
The correction of needle S. 2 has been determined with
great care by Major Sabine *, by a comparison, at various sta-
tions, of its results with those of the needles M and G. 2,
needles which may be regarded as almost free from all instru-
mental error. The amount of this correction is — 9'*6 ; and
its weight 16. This amount is almost identical with that pre-
viously employed in the calculation of the Irish observations.
The other needle employed by Major Sabine in Ireland, S. 1,
is constructed on a plan suggested by Mr. Dollond. The
middle of the needle has the form of a cube, and is perforated
so as to receive the axle in different directions, the intention
being, that the position of the axle should be varied in the
• Table XIX,
MAGNETIC SURVEY OF GREAT BRITAIN. Ill
course of every observation. From some defect of workman-
ship, however, the balance of the needle was much deranged
in some positions of the axle ; and it was accordingly employed
by Major Sabine as an ordinary dipping needle, the axle being
permanently fixed in one position in which the needle was to-
lerably balanced. This was the case during the observations
made with it in August, September, and October, 1834 (Fifth
Report, p. 139) ; the axle being undisturbed during the whole
of the series. In 1835, when Captain Ross used this needle
at Westbourne Green, the axle had been repolished, and was,
moreover, fixed by the artist in a different position from that
which it had occupied during the observations of the preceding
year. So far, therefore, as axle error is concerned, the needle
must, then and thenceforward, be regarded as a different nee-
dle.
In order to deduce the amount of the axle error, previously
to the alteration just alluded to, we may compare the result
obtained with this needle at Limerick, in August 1834, with
the mean dip of the place as given by other needles. The dif-
ference (4''2) is probably not greater than the probable error
of observation, which, owing to the imperfect polish of the
axle, was in this needle considerable. Under these circum-
stances, we are not justified in assigning to it any correction.
The needles employed by Mr. Fox appear to give results
extremely consistent with one another, and with those of other
needles. In their case, therefore, no correction is required.
We are now prepared to exhibit in one view the mean*
values of the dip, as deduced from these various needles. The
following table contains the results of observations arranged
chronologically, and corrected as has been above explained.
* Where the needles L. 1 and L. 4 have been employed together, double
weight has been allowed to the results of the former in taking the mean, in
accordance with the conclusion of page 98.
112
EIGHTH REPORT 1838.
Table XXXVI.
Corrected Dip.
station.
Needle.
Dip.
Mean Dip,
Dublin
Limerick
Limerick
Dublin
Limerick
Glengariflf
Killamey
Tulla
Carlingford
Armagh
Colerain
Cam
Strabane
Enniskillen
Fermoy
Limerick
Dublin
Galway
Gallhorick
Clifden
Westport
Puntoon
Ballina
Giants Causeway
Cushendall
Markree
Ballina
Belmullet
Achill
Galway
Oct, 21,
Nov.
July,
Aug. Sept.
Sept, Oct,
Aug. 1, 16
Sept. 27, 28
Oct. 4
— 12
— 13
— 13
— 14,15
— 14, 15
— 20
— 20
— 21
— 21
— 23
— 23
Oct. 24
Dec. 2
July,
Aug. 17
— 19
— 19
— 22
— 24
— 25
— 27
— 28
— 21
— 21
— 22
— 22
— 24
— 24
— 25
— 25
— 28
— 28
1833
1833
1834
1834
1835
L. 1
M
L.l
L. 1
L-4
S. 1
S. 1
S. 1
S. 1
L.l
L.4
L.l
L.4
L.l
L.4
L.l
L.4
L, 1
L.4
L.l
L.4
8-4
11-7
11-5
5-8 1
7-U
3-5
1-5
4-5
15-8
28-3 \
34-0/
43-5 1
39-7 J
27-6 1
25-6 /
59-81
3-0 /
3-61
52-8 ]■
00
48-3
7-3
590
260
410
52-0
30
8-0
70
150
0-0
5-61
9-0/
13-9 1
5-2/
14-7 1
10-9 J
6-4 1
6-6/
33-9 1
30-8/
71 8-4
71 11-7
71 11-5
71 61
3-5
1-5
4-5
71 15-8
71 30-2
71 42-2
71 26-9
72 0-9
72 0-0
72 00
70 48-3
71 7-3
70 590
71 260
71 410
71 520
72 30
72 80
72 70
73 150
72 00
72 6-3
72 110
72 13-4
72 6-5
71 32-9
MAGNETIC SURVEY OF GREAT BRITAIN.
113
Needle.
No.
L.l
1
L.4
1
L.l
1
L.4
1
L.l
1
L.4
1
L.l
1
L.4
1
L.l
1
L.4
1
L.l
1
L.4
1
L.l
1
L.4
1
L.l
6
L.4
7
L.4
3
S. 2
1
S. 2
1
S. 2
1
S. 2
1
S. 2
3
S. 2
2
S. 2
1
S. 2
2
S. 1
1
M
2
L.3
4
L.4
4
S. 2
3
L.3
2
L.4
2
S. 2
1
S.2
1
G. 2
9
D. 1
3
D.2
6
Dip.
Mean Dip.
Aug. 28
— 28
— 29
— 29
— 31
— 31
Sept. 1
— 1
— 3
— 3
— 3
— 3
Sept. 4—15
Aug. Sept.
Nov. 5, 6
— 8
— 12
— 18
Dec. 10
— 26, 27
— 29
Feb.
May
May
May, June
April, May
April, May
July 22, 23
Aug. 5, 6
Aug. 5, 6
Sept. 21
Oct. 4
Aug. 3 — 7,
Sept. 25, 26
Sept. 27— Oct. 2
1836
1838
13-51
12-5/
3-91
0-9 /
41-3 \
46-6;
49-6 V
52-2/
31 -41
45-0/
55-41
56-5/
53-11
54-2/
5-5 "1
4-1 1
3-2
19-5
5-4
8-1
26-9
5-0
39-4
3-8
2-4
■0-6
00
3-01
4-0/
3-5
1-81
0-6/
391
31
54-6
56-3
58
71 13-2
71 2-9
70 431
70 50-5
70 35-9
70 55-8
70 53-5
71 5-0
71 3-2
71 19-5
71 5-4
71 8-1
71 26-9
71 5-0
70 39-4
71 3-8
71 11
3-5
3-5
1-2
•3-1
■71
71 391
71 31
70 54-6
79 57-9
VOL. VII. 18.38.
114
EIGHTH REPORT 1838.
The following table contains the final mean dip at each sta-
tion, reduced to a common epoch, (the 1st Janliary, 1837,) ; and
the latitudes and longitudes of the stations :
Table XXXVII.
station.
Lat.
Long.
Dip.
Causeway .
5% 15
o /
6 31
7°3 11-8
BelmuUet .
54 13
9 57
72 10-2
Ballina ...
54 7
9 7
72 5-8
Puntoon ...
53 58
9 10
72 4-8
Markree ...
54 12
8 26
72 3-1
Achill
53 56
9 52
72 3-3
Westport . . .
53 48
9 29
71 59-8
Cushendall
55 4
6 5
71 56-8
Cam
55 15
7 15
71 55-6
Enniskillen
54 21
7 38
71 54-8
Strabane ...
54 49
7 28
71 54-8
Clifden ...
53 29
9 59
71 48-8
Bangor ...
54 39
5 42
71 38-5
Gallhorich .
53 25
9 5
71 37-8
Armagh ...
54 21
6 39
71 36-9
Galway ...
53 17
9 4
71 26-3
Carlingford
54 2
6 11
71 250
Station.
Lat.
Long.
Dip.
Colerain ...
5% 8
6 40
7°I 21-6
TuUa
52 52
8 43
71 17-5
Ballybunan
52 30
9 41
71 16-8
Ennis
52 51
8 58
71 10-0
Dingle
52 8
10 17
71 5-4
Valentia ...
51 56
10 17
71 2-7
Limerick...
52 40
8 35
71 1-8
Dublin ...
53 21
6 16
71 1-2
Killarney .
52 3
9 31
70 591
GlengarifF .
51 45
9 31
70 561
Gorey
52 40
6 17
70 52-6
Ratlidrum .
52 55
6 14
70 50-3
Waterford .
52 16
7 8
70 47-3
Ferraoy ...
52 7
8 16
70 43-3
Cork
51 54
8 26
70 39-9
Youghal ...
51 57
7 50
70 37-0
Broadway .
52 13
6 24
70 32-7
Of the foregoing results, those obtained at the Giants' Cause-
way and at Colerain are manifestly aflPected, to a very consider-
able extent, by the disturbing action of the basaltic rocks. The
effect of the basaltic pillars of the Causeway upon the magnetic
needle has been long since observed ; and on comparing the dip
recorded in the preceding table, with that due to the geogra-
phical position of the station, we find it in excess to the amount
of 50'. At Colerain, on the other hand, the effect of the
disturbing action has been to diminish the dip, but in a less
amount. The cause of these irregularities being apparent, we
have no hesitation in rejecting the results, in the computation
of the the isoclinal lines.
Before we proceed to this computation, we must estimate the
weights of the observed results ; and for this purpose it is ne-
cessary to know the amount of the probable error of station.
This is obtained by computing (with assumed approximate
values of L,M,N,) the probable dip at each station, due to its
geographical position, and comparing it with that observed.
The sum of the squares of the diflferences of the computed and
observed results, substituted in (12), will give the total mean
probable error ; from which (the errors of observation and of
instrument being already known) the local error is deduced
by means of the equation (17).
MAGNETIC SURVEY OF GREAT BRITAIN. 11«^
Now assuming the approximate values
L = 71° 22'-5, M = +-30, N = +'51 ;
the probable dip at each station will be given by the formula
s! = 7l°22''5 +-30 X +-51y;
and the computation gives for the sum of the squares of the
differences of the computed and observed results, at the 32
stations,
t{x-ay'= 119209;
from which we find (12)
E2 = 17-48, E = 4-2,
E denoting the total probable error at any one station. But if
E and E. denote the mean probable errors of observation and
of instrument at each station, and E^ the probable local error,
E' = E^ + E? + Ef.
I I
For the observations of this series, E^= ^i~ ^'^* 5 "wherefore
E,= 3'-L
To deduce the weight of the result of n^ observations, with «,•
instruments, at any station, we substitute the values thus ob-
tained in (17), and we obtain
w \n n . I
When the local error, therefoi-e, bears so great a proportion to
the errors of observation and of instrument, as it does in the pre-
sent instance, it is manifestly waste of labour (as far as regards
the determination of the position of the isoclinal lines) to mul-
tiply observations at any one station. In the case under con-
sideration, the weight due to the result at any station (however
the observations be multiplied, and whatever the number of in-
struments employed) can never amount to double the weight of
a single observation.
Substituting the values of n^ and n^ in the preceding formula,
we find the weight of the mean dip, in Dublin and Limerick,
equal to 1 '8, the weight of a single observation being unity : in
no other case throughout this series does the weight amount
to more than \'3. Taking the nearest whole numbers for the
value of this ratio, we shall assign a weight of 2 to Dublin and
* Throughout a considerable portion of the series, two needles, T>. 1 and L. 4,
were used together. The probable error of observation of the mean is nearly
2'; the instrumental error is little less than that of a single needle, being, in this
case, due chiefly to the magnetism of the limb.
I 2
116
EIGHTH REPORT — 1838.
to Limerick, the weight of each of the other stations being unity.
The results of the calculation are the foUoviihg:
L = 71° 22'-74, M = +-300, N = +-505.
u= -59^ 16^ r=-587.
Accordingly, the clip at the central station (latitude = 53° 2V,
longitude = 8° 0') is 71° 22'-7 ; the epoch being the 1st Ja-
nuary, 1837.
Captain Ross's Observations of Dip in Ireland.
These observations were made at 12 stations, with the needles
already designated as R. 4, R. 5, R. 6, R. 7. They are con-
tained in the following table.
Tabj.e XXXVIII.
station.
Date.
Hour.
1
/^ct. Observea
^ reversed. ^'P-
VIean Dip.
Place of
Oljservation.
1838.
Waterford ....
Oct. 4
1-0 P.M.
R 6 a 70 43-41
^
/3 70 50-4
7°0 46-9
] o .
3-15 P.M.
R 4
a 70 44-3
V 70 45-8 In an Orchard,
H 70 45-1
70 44-7
j
^ mile mag. S.
Cork
— G
1-45 P.M.
R 6 a 70 36-61
70 39-3
of the Church.
p, 70 42
3-20 P.M.
R 4
« 70 34-5
fi 70 38-3
70 36-4
— 7
2-15 P.M.
3-30 P.M.
R 7
R 5
«. 70 41-7
p, 70 41-7
cc 70 36-6
/3 70 43-4
70 41-7
70 40
■ 70 39-4
In Mr. Jones's
nursery grounds.
Valontia Is-
— 12
2-30 P.M.
R 6
« 70 50-2
land.
j3 70 54-4
70 52-3
■\
— 13
1-0 P.M.
R 4
a 70 51-5
/3 70 52-1
70 51-8
► 70 52
Near tbe N. W.
2-30P.M.
R 5
« 70 50-2
/3 70 53-6
70 51-9
point of the
Island.
Killarney
— 17
1-30 P.M.
R 6
a 70 49-3
a 70 55-9
70 52-6
>
_ 19
11-20.A.M.
R 4
«. 70 49-6
;3 70 49-6
70 49-6
-70 51-1
In the grounds
30 p.M
R 5
OS. 70 50-2
/3 70 53-6
70 51-9
ofMucruss,near
the Abbey, the
Limerick
— 22
2-30 p.M
R 6
a 70 58-2
demesne of H.
(3 71 1-8
71
"
ArthurHerbert,
40 r.M
R 4
a 70 58-4
,3 70 58-4
70 58-4
Esq.
— 23
1-0 p.M
R 5
« 71 1
^ 70 59-6 In the garden of"
/3 70 59-J
71 0-4
Somerville, the
2-45 P.M
R 7
a 70 59-J
seat of James
1
|S 70 59-(i
70 59-6
Hervey, Esq.
Shannon Har
- _ 26|ll-20.i.M.iR 61 a 71 19
hour.
H 71 25-4
71 22-2
■
1-0 P.M. R 4 a 71 25S
I 71 23-2
In the garden of
fi 71 22-J
71 24-1
■
Faulkner's Inn.
MAGNETIC SURVEY OF GREAT BRITAIN.
117
1
Poles.
station.
Date.
Hour.
« direct,
!5
P reversed.
1838.
Dublin
Oct. 29
1-0 P.M.
R 6
« 7°0 58-2
a 71 4-2
2-0 P.M.
R 7
« 70 59-4
a 71 1-4
2-45 P.M.
R 4
« 70 59-8
H 71 0-2
4-0 P.M.
R 5
a 70 56-6
j3 71 0-8
— 30
Noon
R 6
« 70 57
a 71 1-3
1-30 P.M.
R 4
a 70 57-8
/3 71 0-6
Armagh
Nov. 2
11-0 A.M.
R 6
« 71 38-4
/3 71 42-4
0-30 P.M.
R 4
a 71 39-7
(3 71 40-3
2-20 P.M.
R 5
a 71 41-]
/3 71 41
Londonderry .
— 5
1-30 P.M.
R 4
« 72 4-7
/3 72 0-5
4-0 P.M.
R 6
a 72 2-6
/3 72 3-7
— 6
2-30P.M.
R 5
« 72 1-7
/3 72 0-7
Sligo
— 10
0-40 P.M.
R 6
a 72
/3 72 0-6
2-30 P.M.
R 4
« 72 2-2
/3 71 58-2
Westport
— 13
1-30P.M.
R 6
« 71 57-8
/3 71 58-8
3-lOp.M.
R 4
a 72 1-0
/3 71 58-4
Edgeworths-
— 19
115 p.m.
R 6
« 71 27-6
town.
/3 71 32-6
3-15 P.M.
R 4
« 71 29-2
/3 71 29-9
Mean Dip.
Place of
Observation.
59-8
40-5
2-3
72 0-2
Near the Mag-
netic Observa
tory in the Gar-
dens of Trinity
College.
In the garden
North of the
Observatory
In an orchard,
S.W. by S. true
1^ a mile from
the Cathedral
In the grounds of
Markree Castle,
the demesne of E.
J. Cooper, Esq.,
M.P.
In the garden of
the Hotel.
In the garden of
the residence of
the Edgeworth
family.
The next table contains the latitudes an^ longitudes of
Captain Ross's Irish stations, and the mean dip at each station.
The observations were made in such quick succession that the
reduction to a mean epoch is unnecessary.
Table XXXIX.
Station.
Lat.
Long, j Dip.
Station.
Lat.
Long.
Dip.
Londonderry
55 'O
54 12
53 48
54 21
53 42
53 14
°7 20 7°2 ()2-3
8 26 72 00-2
9 29i 71 59
6 39 71 40-5
7 331 71 29-8
7 52 71 23-2
Dublin
53 21
52 40
51 56
52 03
52 16
51 54
6 16
8 35
10 17
9 31
7 08
8 28
70 59-8
70 59-6
70 52
70 511
70 45-8
70 39-4
Armagh
Edgeworth's-town
Shannon Harbour
Cork
118 KIGHTH REPORT — 1838.
The foregoing observations having been made with different
needles in the same circle, it becomes necessary, in estimating
tlie probable error, to separate those due to the limb from those
which arise from irregularities in the axle. From the mode in
which the observations were taken, — namely (in all but one in-
stance) a single observation with each needle, — the axle error
and the error of observation are combined ; and the beautiful
accordance of the partial observations shows that their com-
bined result is inconsiderable. There seems reason, however,
for believing that the circle itself is not free from error. The
mean result obtained with these needles, in this circle, at West-
bourne Green, is S'^O less than the mean of the other needles
employed at the same place (see Table III.) ; while on the other
hand, they give a result 3''8 in excess of the mean dip, as shown
by Gambey's needles in Dublin, — the latter being observed by
the method of ai'bitrary azimuths.
Now the total probable error at each station, in this series,
(as deduced from a comparison of the computed and observed
results) is found to be 4'"0, — a result scarcely differing from
that of the former series. Of this, the part which is reduced
by repetition is (as has been already stated) exceedingly small ;
and, consequently, the remainder (the combined result of the
station and circle errors) is considerable. Under these cir-
cumstances, it will be readily seen, no disproportion in the
number of observations can materially alter the weights ; and
as, in addition to this, the observations have been distributed
with some attention to uniformity, it is manifest that we must
regard the weights of all the stations as equal.
The results of calculation are
L = 710 22''0, M = +-270, N = + -550
M = -63^ 49', r='QlS.
Hence the dip at the central station, on the 1st November,
1838, was 71° 2^''0, the central station being the same as
before ; consequently, the probable dip at that station, on the
1st January, 1837, was 71° 26''4.
Finally, if we combine these results with those of the former
series, allowing weights in proportion to the number of stations,
we find
L = 71° 23'-7, M = +-292, N = + -517
u= -60° 32', r =-594;
L denoting the mean dip at the central station, on the 1st
January, 1837.
MAGNETIC SURVKY OF GREAT BRITAIN.
119
Report resumed hy Major Sabine.
To the observations in Ireland I have to add a very careful
determination of the dip at Lissadel in the county of Sligo,
the seat of Sir Robert Gore Booth, Bart., made at my request
with Captain Fitz Roy's Gambey by Archibald Smith, Esq., of
Jordan Hill.
Table XL.
Poles.
Lat.
I-ong.
Date.
Hour.
u
^
a. direct,
S reversed.
Mean.
Mean Dip.
5°4 23
8 33
1838.
Sept. 19
Noon
2
«. 7°1 57-5
/3 71 57-6
O /
71 57-6
o ,
— 22
2 P.M.
2
« 71 54-4
71 55-3
71 55
— 24
9J A.M.
2
CC 71 54-5
/3 71 56
71 55-2
■71 56
— 25
9* A.M.
2
CC 71 54-5
/3 71 57-8
71 56-2
Collecting in one view the values of u and r obtained from the
observations in Ireland, we have as foUoAvs : —
Table XLI.
Observer.
No.
Stations.
Cent. Geog. Posit.
Values of
Lat.
Long.
u
r
Lloyd, Fox, and Sabine
34
12
5°3 21
53 21
8 6
8
—59 16
—63 49
0-578
0-613
Regarding the values of m and r as entitled to weight, propor-
tioned to the number of stations, of which each is the represent-
ative, we obtain — 60° 32' and 0'-594 as the mean values derived
from the Irish series, and corresponding to the mean geogra-
phical position, 53° 21' N. and 8° 00' W.
120 KIGHTH REPORT 1838.
Collecting in one view the values of ii ajid r at the central
geographical positions in England, Scotland and Ireland, as
they have been derived from the several series in each country,
we have as follows :
England, Lat. 52° 38'. Long. 2° 07'; ^<=-65°05'; r=0-S75'
Scotland, — 56° 49'. — 3° 39'; m=— 56°06'; r = 0-549'
Ireland, — 53° 21'. — 8° 00' ; z<=-60°32'; r=0-594'
Whence it appears that the isoclinal lines do not intersect the
geographical meridian at the same angle in the three countries;
that they form a greater angle with the meridians in England
than in either of the other two countries ; and that the angle
is also greater in Ireland than in Scotland.
It also appears that the distance between the lines is greatest
in Scotland, less in England, and least in Ireland ; the number
of geographical miles, measured on the perpendicular, corres-
ponding to differences of a degree of dip, — being
109-2 in Scotland;
104*4 in England;
101-0 in Ireland.
It follows, from the different values of r, that the assumption,
upon which we have hitherto proceeded in these combinations,
of parallelism of the lines and their equidistance apart, does not
hold good when applied to an area of the extent of the British
islands, and not strictly so for any of its three portions ; and
that it is desirable to find a method of more exactly represent-
ing the observations, by tracing each isoclinal line separately
from observations nearly of its own value, and consequently but
little removed from it in geographical distance. If we have
the approximate values of u and r at any station where the dip
has been observed, we may readily compute the latitude and
longitude of a point furnished by that observation for the po,-
sition of the next adjacent isoclinal line. If the isoclinal lines
sought are those of complete degrees {i.e. the lines of 69° 00',
70° 00', 71° 00', &c.), and if the observation be also without
fractional minutes — say, for example, 69° 00' — the point fur-
nished by that observation for the line of 69° 00' is at the
station itself. If the observation exceeds or falls short of
69° 00' by a few minutes, the point furnished by it for the
isoclinal line must be distant from the station a geographical
space, equivalent to the value in distance of the fractional mi-
nutes, as computed by the value of r, and in the direction of
u + 90^. Thus, if D be the degree of dip represented by the iso-
MAGNETIC SURVEY OF GREAT BRITAIN. 121
clinal line, B the dip observed at a station, of which the latitude
is \, then is (D — 8) the difference of latitude, and (D — 8)
r
^^^ sec X the difference of longitude, between the station and
r
the point which it furnishes for the isoclinal line.
We have the values of u and r at the central geographical po-
sitions in England, Ireland, and Scotland, as derived from obser-
vation. If, for a general central station in the British Islands,
we take the mean of the central stations in the three countries,
viz. lat. 54° 16' N., long. 4° S5' W., we may deduce the values
of u and r for that station from equations of the form
iij = u + a^x + b/i/
r, = r + a,a; + i^y,
where u, is the angle and r, the rate of increase at one of the
three central geographical positions ; a, and b, co-ordinates of
distance in longitude and latitude from the general central sta-
tion, expressed in geographical miles ; and a; and y coefficients
of the change in the values of u and r in each geographical mile,
y in the direction of the meridian, and .r in that of the perpen-
dicular thereto. The mean results in the three countries will
then furnish respectively the three following equations for the
value of u ;
England, 3905' = u — 89 a;- — 98 y
Scotland, 3366' = u — 34 ^ + 153 y
Ireland, 3632' = u + 123 x ~ 55 y
The number of stations from which the mean results were ob-
tained was,
In England, 122 1 i • x. f 3
In Scotland, 46 I o'" nearly m the I
In Ireland, 39 J P^^P^^-^ion of ^ ^
In combining these equations therefore by the method of
least squares, to obtain the most probable values of u, x, and y,
we may give the weight of 3 to the English result, and that of
unity to each of the two others.
Pursuing the usual process, we derive u = — 60° 42' ; x =
+ 0'6 ; y = 4- 2-0 : and we may compute the approximate value
of u at any geographical position in the British Islands, by the
formula
« = — 60° 42' + 0-6 a + 2 b,
122 EIGHTH REPORT — 1838.
the origin of the coordinates, a and h heing the general central
station in 4° 35' W. longitude, and 54° 16' N. latitude.
Proceeding in the same manner for r, we have the 3 equations :
England, + 0*575 = r -- 89 *^ — 98 y ;
Scotland, + 0-549 = r — 34 x + 153 y ;
Ireland, + 0*594 = r + 123 a? — 55 y.
Giving the English result the vs^eight of 3, and each of the
others that of unity, and deducing by the method of least squares
the most probable values of r, x, andy, we obtain x= + '00007;
y = —-00013 ; and r = 0-571. at the central general station
in lat. 54° 16' and long. 4° 35' W.
Whence the approximate value of r is found at any other geo-
graphical position in the British Islands by the formula
r = + 0-571 +-00007 a —-00013 b ;
the longitude and latitude of the general central station being the
origin of the coordinates a and b.
The points furnished by the several observations for the near-
est adjacent isoclinal line, computed in the manner above de-
scribed, are inserted in the general table which closes this divi-
sion of the report. The table is in two parts ; the one con-
taining the observations, the other the deductions. In the first
part are shown the observed dip, the latitude and longitude of the
station, the date, the observer, and a reference to the particular
table in which all the details connected with the observations
may be examined. In the division which contains the deduc-
tions, are shown the dip reduced to the mean epoch of the 1st
January, 1837 ; the differences of latitude and longitude between
the station and the point furnished by it for the nearest isoclinal
line ; the latitude and longitude of the points, and the values of
u and r, employed in their deduction.
By the method thus described, the transfer of the observation
to the isoclinal line involves no other material inaccuracy than
such as may be occasioned by incorrectness in the employed
values of u and r. We may, therefore, examine the probable
limit of the inaccuracy which may be thus incurred : — 30 mi-
nutes of dip is the extreme fractional amount in any case for
which a deduction is required : if we suppose an error in the
assumed value of r equal to O'Ol, which is nearly a fovu-th of
the extreme difference found for England, Ireland and Scot-
land, — the corresponding error in the geographical distance of
the point from the station will be less than one mile. An error
of 1° in the value of u, in the same extreme case of a fractional
amount of 30' of dip, would cause an error in the position as-
MAGNETIC SUBVKY OF GREAT BRITAIN. 123
sio-ned to the point of less than one mile in latitude, and half a
mile in longitude. We may hence estimate the probable limits
of inaccuracy in the extreme cases alluded to. It is obvious that
^^•hen the fractional minutes in the observation are less than
thirty, these limits are proportionally reduced ; and it is further
plain that errors thus occasioned will be of a contrary nature to
each other, according as the fractional minutes are in excess or
in defect of the degree which the line represents. When, there-
fore, the observations are numerous, and fall on both sides of
the lines, as is the case in this survey, a mutual compensation is
afforded, and whatever small inaccuracies there may be in the
values of u and r, their ultimate eifect on the lines may be re-
garded as wholly insensible.
If the observations at each station were free from instru-
mental defect and local influence, — and if they were continued
sufficiently long at each station to furnish its mean dip inde-
pendent of diurnal and irregular fluctuations, — the points com-
puted from them and transferred to a map would require merely
to be connected in order to form the isoclinal line. As might
be expected, however, the results of the observations are far
from presenting this perfect accordance, especially in Scotland,
where the prevalence of igneous rocks produces much disturb-
ing action. An examination of the map, however, in which the
points, and the stations they are derived from, are inserted, will
show that, notwithstanding the disturbing causes referred to,
they do arrange themselves in such manner as to leave very
little uncertainty in any quarter in tracing the position and
direction of each isoclinal line. Each line thus becomes an
independent determination, derived from observations which be-
long to itself alone, and unhifluenced by those which differ more
than thirty minutes from the degree which the line represents*.
By this method of combination, any departure from system-
atic arrangement which might exist in any one of the lines
passing across the British Islands, would become manifest at
once to the eye. Individual stations there are, particularly in
Scotland and the north of Ireland, which throw their points to
some distance from their respective lines. In some very few
cases, a group of neighbouring stations appears to be similarly
affected. The most prominent instance of this is in North Wales,
where there appears a decided disposition of the majority of the
* This has been strictly adhered to in the table everywhere ; and in the map
everywhere over the surface of the land. The lines are extended in the map a
short distance heyond the land ; and as the observations which justify this ex-
tension are few in comparison with those in other parts of the map, the determi-
nations which fall nearly midway between two lines have, in these few cases,
been given a bearing on the lines on either side of them.
124 EIGHTH REPORT 1838.
points to fall to the south of the line of 71°, contrasted with and
counterbalanced by an opposite tendency of the points furnished
for the same line on the east of Ireland*. A more extensive
research is necessary to determine whether, by multiplying the
number of stations in these localities, this apparent irregularity
would disappear, or whether the observations referred to truly
represent what may be termed a district anomaly. Whilst,
however, on minute examination the eye may rest on single
stations, or on groups, which present examples of the slight
irregularities here referred to, it cannot fail, on the general
aspect of the map, to be struck by the absence of any important
unsymmetrical inflections, and by the obvious general systematic
arrangement of the terrestrial magnetism indicated by the lines.
Here, as elsewhere, they present the features of the general
magnetic system ; the effects of local and partial disturbance
being indeed discernible on close examination, but not being
found of sufficient comparative magnitude to influence the
general representation.
The lines of dip as they appear on the map are slightly
curved, being convex towards the S.E. If the extreme points
of each line were connected by an arc of a great circle, the cur-
vature of the arc, on the projection which is here employed,
would be in the opposite direction to that of the isoclinal lines,
or the convexity would be towards the N.W. Their departure
from such a straight line on the surface of the globe (or their
difference from great circles) is greater therefore than appears
in this projection.
• This apparent dislocation of the line of 71° between England and Ireland
was noticed by Mr. Fox in the Report of the Royal Cornwall Polytechnic So-
ciety for 1835. No trace of a corresponding irregularity occurs in the conti-
nuity of the line 72° in crossing the Irish Channel.
I
MAGNETIC SURVEY OF GREAT BRITAIN.
125
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EIGHTH REPORT — 1838.
DIVISION II.— INTENSITY.
The observations of the Intensity are arranged in three
sections, in the same manner as those of the Dip.
Section I. — England.
§ 1 . Statical Method.
Mr. Lloyd's Observations. These were made with the needles
L. 3, L. 4, (page 82), in a 4^ inch circle, made by Robinson.
Table XLII contains the detailed statement of the obser-
vations.
Table XLII.
[6 is the angle which the needle makes with the horizon, the
southern arm being loaded with a weight. The negation sign
indicates that the north pole of the needle is above the hori-
zontal line.
SUtion.
Date.
Needle L. 3. 1
Needle L. 4.
Hour.
Ther.
e
Hour.
Ther.
e
Dublin ...
London ...
Shrewsbury
Holyhead .
Dublin ...
1836.
April 11
— 15
— 19
— 21
— 22
— 25
— 27
May 7
— 9
h m
18 P.M.
30
1
2 58
30
3 10 .
1 20
1 32
1 25
57-5
53-
55-8
58-5
59-2
55-2
53-
57-2
60-
- 15 23'-4
- 15 3-6
- 18 43-5
- 18 47-6
- 19 60
- 17 31-1
- 16 19-4
- 15 52-5
- 15 52-5
h m
43 P.M.
08
1 28
2 37
14
2 45
40
1 10
50
57°8
53-5
56-8
58-5
60-5
550
54-0
56-5
60-5
- 1°3 26-4
- 13 210
- 16 31-9
- 16 59-9
- 16 57-6
- 14 56-8
- 13 65-6
- 13 22-5
- 13 18-4
Dublin ...
Birkenhead
Shrewsbury
Hereford...
Chepstow ..
Salisbury...
Ryde
Clifton
Aug. 5
— 6
— 8
— 9
— 10
— 12
— 13
— 15
— 16
— 29
3 50
2 35
10 A.M.
10 50
11 40
07 P.M.
11 20 a.m.
05 P.M.
10
11 10 a.m.
Noon.
45 P.M.
11 40 A.M.
30 P.M.
61-8
67-8
68-9
66-8
67-2
66-5
64-5
66-4
63-2
71-2
71-5
72-2
62-5
63-5
- 15 53-8
-16 9-2
- 18 14-9
- 18 07-5
- 19 4-8
- 19 2-5
- 19 13-5
- 19 11-2
- 19 14-0
- 19 58-8
- 20 33-2
- 20 361
- 19 27-3
- 19 21-9
3 28
2 10
9 A.M.
10 20
11 15
20 P.M.
10 50 a.m.
11 45
11 40
10 45
11 30
20 P.M.
11 15 a.m.
5 P.M.
61-8
66-5
68-8
67-5
65-5
66-4
64-5
66-2
61-8
69-5
72-5
70-0
62-5
63-0
- 13 43-6
- 13 34-4
- 15 07-2
- 14 58-4
- 15 56-8
- 16 20-8
- 16 24-5
- 16 14-9
- 16 47-2
- 17 360
- 18 24-2
- 18 20-8
- 16 44-2
- 17 09-6
Ryde
Brighton...
London ...
Cambridge
Lynn
Sept. 24
— 27
Oct. 4
— 8
— 10
15
1 10
11 15 a.m.
Noon.
45 P.M.
1 40
20
1 10
55
66-4
64-6
61-5
610
56-0
57-0
59-5
56-2
57-8
- 20 22-6
- 20 16-6
- 20 41-4
- 20 21-9
- 19 45-0
- 19 42-4
- 19 49-0
- 19 390
- 19 16-5
11 45 a.m.
40 p.m.
11 40 A.M.
30 P.M.
1 20
2
40
1 35
1 25
65-8
650
61-5
61-2
57-0
56-4
58-5
55-8
57-5
- 22 53-5
- 22 45-8
- 23 25-8
-23 11-8
- 22 54-3
- 22 32-8
- 22 34-8
- 22 291
- 21 48-6
MAGNETIC SURVEY OF GREAT BRITAIN.
139
Tabular view of the variations of the angle 6, for the purpose
of ascertaining the loss of force undergone by the needles,
and the period of the change. The angles are reduced to
the standard temperature, 60°*.
Table XLIII.
station.
Date.
Needle L. 3.
Needle L. 4.
Dublin
April 11 &c.
— 19 &c.
— 25
— 27
May 7 &c.
August 5 &c.
— 8
— 9
— 10
— 12
— 13
— 15 &c.
— 29
Sept. 24
— 27
Oct. 4
— 8
— 10
-f5 21-2
-18 55-9
-17 38-8
-16 30-6
-15 547
-15 53-8
-13 307
-16 520
-15 4-8
-14 5-2
-13 22-9
-13 32-3
-14 497
-15 59-2
-16 111
-16 44-3
-17 20-8
-18 4-6
-16 52-4
Shrewsbury
Holyhead
Dublin
Dublin
Birkenhead
Shrewsbury
-17 581
-18 527
-19 3-6
-19 8-9
-19 40-9
-20 157
-19 19-8
-20 10-8
-20 297
-19 49-3
-19 50-1
-19 19-9
Chepstow
Ryde
Clifton
Ryde
-22 410
-23 16-6
-22 48-8
-22 36-5
-21 521
London
Cambridge
Lynn
Note hy Mr. Lloyd. — It appears from this table that Needle
L. 3 sustained a loss of force in the interval of time which elapsed
between the two observations at Shrewsbury. Now the obser-
vations at Dublin in April and May prove that the loss sus-
tained by the needle during the series of observations in spring
was comparatively trifling ; while, from the results obtained at
the same place in May and August, it appears that the mag-
netism of the needle remained perfectly steady in the interval
between the two series. We are consequently conducted to
the conclusion, that the change occurred in the short interval
between the observations at Dublin on the 5th of August and
those at Shrewsbury on the 9th ; and we have every reason to
believe that it was previous to the observation at Birkenhead,
and probably due to some accident in the passage across the
channel. The magnetism of the needle appears to have been
steady during the remainder of the autumn series. This, we
think, will appear from the difference of the angles at Shrews-
• For the mode of effecting this reduction see Fifth Report British Associ-
ation, page 147.
140
EIGHTH REPORT — 1838.
bury and London (near the commencement and end of the se-
ries, respectively), as compared with the difference observed at
the same places in spring.
With respect to Needle L. 4, the observations at Dublin in
April and May show that its magnetism was perfectly steady
during the spring series. This needle, however, sustained a
very great loss of force between the two sets of observations
with it at Ryde ; and this loss appears to have been, in a great
measure, a sudden one. But that the magnetism of the needle
was not stationary during the remainder of the autumn series,
will appear at once from a comparison of the observations at
Shrewsbury in April and August. As we have no satisfactory
means of determining the amount of this loss, and of interpo-
lating a correction, we are forced to reject all the results ob-
tained with this needle in autumn.
Table XLIV.
Computed Intensity.
station.
Date.
Needle.
Dip.
London = 1-0000.
1836.
London ....
r
•i
April 19
— 21,22
L. 3
L. 4
- 69 26-4 1
1-0000
10000
Shrewsbury.
■{
— 25
L. 3
L. 4
1 70 27-6 1
10076
1-0099
Holyhead....
•{
- 27
L. 3
L. 4
1 71 08-5 1
10140
10149
Birkenhead .
August 8
L. 3
70 49-1
10112
Shrewsbury .
_ 9
L. 3
70 27-7
1-0056
— 10
— 12
— 13
L. 3
L. 3
L. 3
70 07- 1
69 47-9
69 231
10046
10041
10006
Ryde
— 15,16
— 29
Sept. 24
— 27
October 4
— 8
L. 3
L. 3
L. 3
69 02-6
69 42-6
69 00-1
0-9969
10030
0-9975
Clifton
Ryde
L. 3
L. 3
L. 3
68 49-7
69 190
69 41-5
0-9955
1-0000
1-0001
Cambridge .
— 10
L. 3
69 53-2
1-00.30
Means.
Shrewsbury 1-0077
Holyhead 10144
Ryde 0-9972
We have here eighteen results at the twelve stations, which
being combined by the method of least squares, give the following
values : a: = + -000047 ; y = — '000067 ; ?< = - 54° 49' ; r =
•000082 ; the mean geographical position being lat. 52° 0', and
long. 1° 50' W., at which the probable value of the intensity is
1-0048.
MAGNETIC SURVEY OF GREAT BRITAIN. 141
Major Sabine s Observations. — The needle S 2 with which
these observations were made, has been already described in
the Reports of the British Association, vol. v. pages 141 — 149.
It is 11^ inches long, on Professor Lloyd's statical principle, and
is used in a circle made by Nairne and Blunt. The observa-
tions, together with the deduced values of the intensity, are
contained in the subjoined table, No. XLV. Each observation
is a mean of forty readings, taken in four positions of the needle.
The thermometer by which the temperature was registered was
always enclosed with the needle in the dip circle. The values of
-: — 77; TT are reduced to a standard temperature of 60°, in the
sm (b — ff)
manner described by Mr. Lloyd in the Transactions of the
Royal Irish Academy for 1836 ; the coefficient of t — t' in the
reduction, or the value of M a experimentally determined, is
•000024. (See 6th Report, British Association, pp. 11, 12.)
The observations with this needle at Tortington, in Sussex,
in the summer of 1837, repeated in the autumn of 1837 and
summer of 1838, and lastly in the autumn of 1838, produced
on each occasion an almost identical result, and afford most
satisfactory evidence of the unaltered state of its magnetism
cos
during the whole of the present series : the values of -: — 75 rr,
*' '^ sm (0 — a)
resulting from the observations at Tortington at the three
epochs alluded to are as follows :
Mean.
May to September, 1837 . . . 0-95390
October 1837 to July 1838 . . 0-95361
October 1838 0-95375
cos u
To obtain the value of -r — p; rr- in London, to serve as
sm (6 — 6)
the unity of the series, observations were made on three several
occasions, and in three different localities ; namely, in the gar-
dens of the Little Cloisters, Westminster ; in the nursery gar-
den in the Regent's Park ; and in the gardens of the palace at
Kew. The results were as follows :
Little Cloisters . . . 0-95245
Regent's Park . . . . 0-95684
Kew Gardens .... 0-95479
Mean. . . 0-95469
142
EIGHTH REPORT 1838.
The mean of these values, 0*95469, has therefore been taken as
the equivalent to unity, and the relative values of the intensity
at the other stations have been computed thei'eby, and are in-
serted in the final column of the table.
Table XLV.
g
6
J
cosfl
Intensity.
London
=10000.
station.
Date.
Hour.
I
sin (S - fl)
1837.
o
O /
June 1
58
-17 521 •
Little Cloisters,
Westminster . '
— 1
July 25
9JA.M.
58
70
-17 56-6
-18 07-4
■ 69 18-5
•95245
09977
— 25
lO^A.M.
73
-18 00-3
''
May 17
— 29
55
56
-17 38 "
-17 41-4
June 5
11Ja!m.
65
-17 55-6
— 5
§ P.M.
65
-17 50-2
July 20
4^ P.M.
69
-17 29-5
Tortington •
- 20
Aug. 5
5^ P.M.
2 P.M.
69
70
-17 371
-17 51-2
' 68 59-6
•95390
09992
_ 5
21 P.M.
70
-17 49-7
— 31
Noon.
60
-18 03-1
— 31
1 P.M.
60
-18 04-6
Sept. 1
1* P.M.
57
-17 421
— 1
2§ P.M.
57
-17 38-5
Shrewsbury ■
— 19
— 19
3j P.M.
4§ P.M.
68-5
68-5
-16 34-8
-16 37-0
1 70 24-9
•96009
10057
— 21
10 A.M.
66-5
-16 01-8
Aberystwith ...-
— 21
— 21
lOj A.M.
3i P.M.
66-5
66
-16 01-8
-15 41-5
■ 70 25-9
•96430
10100
— 21
4^ P.M.
66
-15 408
J
Brecon ■
— 22
— 22
5| A.M.
6i A.M.
54
54
-16 26-3
-16 30-3
1 70 03-2
•96041
10060
Merthyr j
— 22
— 22
\h P.M.
2* P.M.
62
62
-16 09-8
-16 130
1 70 04-0
•96346
1^0081
■ — 25
4§ P.M.
59
-16 30-5
— 25
5| P.M.
59
-16 30-3
Oct. 2
5 P.M.
62
-16 13-9
— 2
6 P.M.
62
-16 220
— 3
11 A.M.
65
-16 26-5
Dunraven Castle -
— 3
— 5
Noon.
11 J A.M.
65
65
-16 25-9
-16 27-6
. 69 45-7
•96215
1^0078
— 5
Noon.
65
-16 26-9
— 5
5 P.M.
60
-16 311
— 5
5 j P.M.
60
-16 31-7
— 6
11^ A.M.
62
-16 40-6
1
— 6
Noon.
62
-16 390
' Nov. 2
J P.M.
48
-18 24-7
._
— 2
1^ P.M.
52
-18 29-2
Dover
— 3
— 3
2§ P.M.
3 P.M.
50
50
-18 18-8
-18 25-0
. 68 52-3
•94948
0-9945
— 6
\ P.M.
50
-18 21-7
— 6
1* P.M. 1 50
-18 21-4
-
MAGNETIC SURVEY OF GREAT BRITAIN.
Table XLV. — {continued).
143
s
COS0
Intensity.
station.
Date.
Hour.
u
H
e
i
sin (J - fl;
London
=1-0000.
1837.
o
o
■
Nov. 9
114 a.m.
50
-17 58
]Vf&r<^te
— 9
— 10
ir.M.
11 A.M.
50
48
-17 56-6
-18 01-6
■ 69 02-9
•95180
0^9970
— 10
Noon.
48
-J8 01-9
5-
— 14
Noon.
50
-17 12-8 ■
— 14
1 P.M.
50
-17 14-7
London (Re-
gent's Park) /
— 16
3 P.M.
37
-16 53-7
-69 23-8
•95684
1-0022
— 16
4 P.M.
37
-16 52-6
— 16
4§ P.M.
37
-17 00-6
-
Oct. 15
2i P.M.
56-5
-17 20-8 '
— 15
3 P.M.
56-5
-17 24-2
— 19
11 A.M.
58
-17 47-3
— 19
12
58
-17 58-4
— 19
5 P.M.
54-5
-17 51-3
Nov. 24
Ill A.M.
60
-17 27-5
— 24
f P.M.
60
-17 25-2
1838.
Tortington
June 18
— 18
3f P.M.
4,i P.M.
63
63
-17 46-2
-17 45-7
■ 68 54-0
•95361
0-9989
— 19
8^ A.M.
61
-17 48-9
— 19
9 A.M.
61
-17 48-8
— 19
IJ P.M.
,66
-17 39-7
— 19
2 P.M.
66
-17 37-5
— 23
4 P.M.
64
-17 53-9
— 23
5 P.M.
64
-17 49-6
July 9
3 P.M.
71
-18 12-9
— 9
3J P.M.
71
-18 11-8
r
— 19
7iA.M.
64
-17 02-5
1
— 19
9 A.M.
64
-16 59-7
— 19
Noon.
72
-16 56-8
Lew Trenchard . -
— 19
2J P.M.
72
-16 52-2
- 69 190
•95901
10045
— 20
7^ A.M.
58-5
-16 42-8
— 21
8 A.M.
58-5
-16 57-1
— 21
i p.jt.
65
-16 57-6
■ — 24
4 P.M.
58-5
-17 36-6
"\
— 25
7§ A.M.
59
-17 07-5
Falmouth .<
— 25
8 A.M.
59
-17 06-6
-69 11-9
•95607
10015
— 25
1 t.M.
63
-17 30-8
— 26
4 P.M.
65
-17 18-8
- — 31
If P.M.
65
-14 291
"■
— 31
2i P.M.
65
-14 29-7
Dublin <
Aug. 2
— 3
2i P.M.
3 P.M.
66
— 14 19-8
- 70 54-6
•97200
1^0182
67
-14 29-5
— 3
4 P.M.
67
-14 26-0
Whitehaven \
— 16
— 16
lO^A.M.
IUa.m.
56
56
-14 24-8
-14 19-5
1 71 10-9
•97144
1-0176
Newcastle ^
— 28
— 29
4, J P.M.
7i A.M.
69
53
-15 00-8
-14 48
1 71 09
■96870
10147
Alnwick Castle .
— 31
4j P.M.
62-5
-14 39-9
71 22-6
•96987
1^0159
(
" Sept. 2
1§ P.M.
59
-14 24-9
1
Stonehouse ■<
— 2
2f P.M.
59
-14 22-9
\ 71 19-6
•97150
10176
1
— 4
10^ A.M. 60
-14 19-1
J
144
EIGHTH REPORT — 1838.
Table XLV. — (cotitinueil).
station.
Hour.
g
»
f
cos 8
Intensity.
London
=1-0000,
Daic.
1
sin ^J - S)
1838,
o
o /
'Sept
8
8 A.M.
53-5
-12 541
■>
—
9
7i A.M.
48
-12 33-6
o /
Helensburgh ...-■
—
9
8 A,M,
48
-12 35-2
^72 170
•97870
10252
9
6 P.M,
53
-12 43-4
—
9
6 P.M,
53
-12 40-8
—
11
3i P.M,
60
-12 540 '
Jordan Hill •
—
11
13
3^ P.M,
114 A.M,
60
61
-12 530
-13 19-3
- 72 14-3
•97722
10236
—
13
Noon.
61
-13 18-4
'Oct,
8
11 A.M,
55
-17 33-6 -
—
8
i P.M.
55
-17 361
Worcester Park.-
—
9
9
IHa.m,
i P.M,
57
57
-17 19-8
-17 19-5
69 06-7
•95524
i^oooe
—
10
lliA,M.
54-5
-17 33-2
—
10
^ P.M,
54-5
-17 31-5
—
12
2J P.M,
48
-17 321
London (Kew
Gardens)
—
12
13
3f P.M,
lOi A,M,
48
46-5
-17 33-9
-17 18-3
69 16-4
•95479
10001
13
1Ha,m.
46-5
-17 26-8
—
17
11^ A.M.
61
-17 45-9
Torttngton ■
—
17
18
i P.M.
2^ P.M,
61
54-6
-17 45-8
-17 49-5
■ 68 52-4
•95375
09990
—
18
3 P.M,
54-6
-17 45-8
Omitting Dublin, which has been transferred to the Irish
section, and taking a mean of the three resuks at Tortington
for the intensity at tliat station, we have here twenty sta-
tions in Britain to be combined by the method of least
squares : whence x= + -000048 ; y = - -000062 ; ti = — 5^
27'; r = -000078; and/= 1-0075, the probable value of the
intensity at the mean geographical position, of which the lati-
tude is 52° 36', and the longitude 2° 1 1'.
Professor Phillips's observations. — ^These were made with
a needle on Mr. Lloyd's statical principle, employed in Mr.
Phillips's six-inch circle. The needle had been recently re-
ceived from the maker (Robinson), when it was first used at
York in June 1837; and the results obtained with it on the
3rd and 5th June, compared with those on the 15th June, indi-
cated that its magnetism had not become steady. To obviate
this inconvenience as far as might be possible, Mr. Phillips re-
peatedly, during the series of his detei-minations, brought the
needle back to York, and re-examined its magnetic state.
We are thus furnished with observations at that station in
June, August, September, October, 1837, and in February,
1838, which are arranged in Table XLVI., and show the pro-
MAGNiSTfC SURVEY OF GRBAT BRITAIN.
145
portion of magnetic force lost by the needle in the several in-
tervals. It will be seen that the loss, on the daily average,
progressively diminished ; and, excepting in the first interval,
namely, between the 4th and 15th June, was not of sufficient
amount to create much uncertainty in the results, after the ap-
plication of a correction assigned in the usual manner, viz. a
daily rate for each interval, obtained by dividing the whole loss
in an interval by the number of days which it contains. In re-
gard to the first interval, when the loss was considerable, and
where a correction applied on the above principle can scarcely
be supposed an exact representation of the facts, it fortunately
happens that the six included stations are all in Yorkshire ;
and thus, though an equable correction in this interval may
make the values of the intensity at these stations appear more
discrepant with each other than they otherwise would do, yet
their collective bearing on the position and direction of the
isodynamic lines is scarcely affected.
By experiments with this needle in different temperatures,
Mr. PhiUips found -000090 the coefficient (a) of (t^t') in the
reduction for temperature ; which has been employed in re-
ducing the values in the column g.^g_g to a mean temperature
of 60°.
Table XLVI.
Observations at York, collected in one view, to show the loss of
magnetism sustained by Mr. Phillips's needle. 8 =:= 70° 48''8.
cos 9
sin (5-0)
Interval,
Days.
Average
daily loss.
June 3 & 5, 1837
June 15
Aug. 1
Sept. 7
Oct. 2
Feb. 19 & 20, 1838...
62-2
68-2
67-5
65-0
63-5
35-5
15 24-9
16 100
16 46-2
17 000
17 06-9
16 550
0-96632
0-96254
0-95897
0-95747
0-95665
0-95530
I 46
j 38
I 25
1 140
•00378
•00357
•00150
-00082
•00135
00034
00008
00004
00003
00001
Mr. Phillips's observations at twenty-four stations in England
are comprised in Table XL VII. : the values of ''"^.^ „ are re-
' ' sine— y
146
EIGHTH REPORT — 1838.
duced to a mean temperature of 60° : the two last columns con-
tain the relative values of the intensity, in the first column to
York, and in the second to London. The frequent repetition
of the observations at York, at different dates, renders that
station the proper base of Mr. Phillips's series. The obser-
vations at York and London in February and March 1838,
furnish a direct comparison of the force at those stations, and
by means of that comparison, a determination of its value at all
the other stations relatively to the London unity.
Table XLVIL
cos 9
sin (6-«;
Intensity.
York
=1-0000.
London
= 1'0000.
Doncaster .
York
York
York
York
York
Thirsk
Osmotherley
Hambletonend
Whitby
Flamborough
Scarborough. .
Sheffield
Birmingham.
Birmingham.
St. Clair's
St. Clair's
St. Clair's
York
Calderstone..
Douglas
Castletown ..
Peel Castle Inn
Peel Castle Inn
Birkenhead ...
York
Coed
Bowness .
Coniston .
Patterdale.
Penrith. ..
Carlisle. . .
Newcastle.
York
York
7
2§
9i
12
4
1837.
June 3
June 3
June 5
June 5
June 15
June 15
June 6
June 6
June 7
June 9
Jtine 11
June 13 1§
June 17 6§
July 3 3
July 8 6§
July 19 9
July 22 3
July 25 6|
Aug,
Aug. 12
Aug. 17
Aug. 18
Aug. 18
Aug. 18
Aug. 26
Sept. 7
Sept. 20
Sept. 25
Sept. 27
Sept. 27
Sept. 28
Sept. 29
Sept. 30
Oct,
Oct.
London ,
York. ...
York. ...
2
1838.
Mar. 28
Feb. 19
Feb. 20
4
12
3
9
2
3|
H
H
12
9^
8^
u
m
m
7k
210
A.M.
P.M.
A.M.
P.M.
P.M.
P.M.
P.M.
A.M.
A.M.
P.M.
P.M.
P.M.
P.M.
P.M.
ik.M.
P.M.
P.M
P.M.
P.M.
A.M.
P.M.
P.M.
P.M.
P.M.
A.M.
A.M.
P.M.
A.M.
A.M.
A.M.
A.M.
P.M.
P.M.
A.M.
P.M.
580
56-7
60
70
73
63-5
53
42-5
56
52
57
71
70
73
70
68
76
66-5
67-5
69-5
68-5
66-2
70
69
62
65
68
54
51-5
52
50
56-5
53
63
64
58
33
38
-15 501
-15 17-3
-15 32-3
-15 25-2
-16 18-7
-16 01-3
-14 51-3
-15 08-7
-15 191
-15 220
-16 291
-16 28-3
-16 18-0
-17 04-6
-16 47-1
-18 52-7
-19 01
- 18 42-1
-16 46-2
-17 27-7
-15 271
.15 29-8
-15 490
.15 39-7
.16 33-8
.17 00
.17 22-8
.15 54-7
.15 39-4
.15 55-5
.15 510
.15 421
.16 06-9
.17 10-4
.17 3-5
• 19 22-2
■ 16 54-8
16 55-2
70 30-2
►70 48-8
70 59-2
71 03-2
71 04-0
70 57-9
70 36-9
70 41-8
70 29-6
\ 70 07-2
[.69 01-2
70 48-8
70 43-5
71 22-2
71 22-5
|-71 24-0
70 39-4
70 48-8
70 40-9
71 18-4
71 19-5
71 19-6
71 23-4
71 28-5
71 18-1
• 70 48-8
69 19-(
-70 48-1
•96383
•96632
•96848
•96583
•96606
•96553
•95988
•96111
•96220
•95897
•94786
•95897
•95668
•96610
•96564
•96454
•95980
•95747
•95560
•96229
•96346
•96202
•96222
•96357
•96120
•95665
•94346
•95530
0-9971
10000
1^0029
10002
10008
1-0009
0-9958
0-9978
0-9998
0-9980
0-9878
1-0000
0-9981
1-0081
1-0077
1-0065
1-0019
1-0000
0-9985
1-0056
1-0070
1-0054
1-0057
1-0072
1-0047
1-0000
0-9876
1-0000
1-0096
10126
1-0155
1-0128
1-0134
1-0135
1-0083
10103
1-0124.
1-0105
1-0002
1-0126
1-0106
1-0208
1-0203
1-0192
10145
1-0126
1-0110
1-0182
1-0196
1-0181
10184
1-0198
1-0173
1-012G
1-0000
1-0120
MAGNETIC SURVEY OF GREAT BRITAIN.
147
If we combine the mean results at the twenty-four stations
in this table by the method of least squares, we obtain the fol-
lowing values : a: =+ -000061 ; ^=--000066; M=-47° 37';
r='000090; andy= 1*0136, at the mean geographical position
in lat. 53° 49', and long. 2° 08'.
Mr. Fox's observations. — These were made with a 4| inch
needle, on the principle described by its maker, Mr. T. B.
Jordan, of Falmouth, in the third volume of the " Annals of
Electricity," &c. The needle has a small grooved wheel on its
axle, which receives a thread of unspun silk, furnished with
hooks, to which weights may be attached. The weights em-
ployed were successively 2*0 grains, 2' 1 grains, 2'2 grains ; and
with each weight the intensities are in the inverse ratio of the
angle of deflection produced, corrections being applied for
differences of temperature at the different stations. The fol-
lowing table exhibits the angles of deflection occasioned by
the respective weights, and the values of the intensity deduced
therefrom. The angles are reduced to a common temperature ;
1° of the centigrade scale having been found by experiment to
be equivalent to 2', or 2'*4 in the angle.
Table XLVIII.
Weight.
Angle of
Deflection
Intensity.
Place of
Observation.
I London
Eastbourne
Eastwick Park ...
Combe House ...,
Falmouth
1838.
May 22
June 4 & 8
June 20
June 16
July 2
July 5 & 7
Grains.
f2-0
\2-l
[2-2
20
21
2-2
'20
21
2-2
20
21
22
■20
21
2-2
48 367
51 55-3
55 330
48 57
52 19
55 57
48 35
51 57
55 40
48 25
51 45
55 18
48 29
51 48
55 20
1-0000
1-0000
1-0000
0-9938
0-9921
0-9952
0-9997
0-9996
0-9986
1-0023
1-0024
I-003I
10013
1-0017
1-0026
1.0000
.0-9937
}
0-9993
1-0026
-1-0018
f Mean of results in
a field N. of Mai.
J den Lane ; in the
"S Regent's Park ;
and at West-
I t)ourne Green.
{In the grounds
of Davies Gil-
bert, Esq.
In the grounds.
In the grounds.
In Mr. Fox'i
grounds.
148 EIGHTH REPORT — 1838.
§ 2. By the Method of Vibrations.
The observations by this method include twenty- seven sta*
tions ; i. e. 18 by Captain Ross ; 7 by Major Sabine ; and 2 by
Mr. Lloyd.
1st. Captain Ross's determinations were made with a cylin-
der (X) vibrated in an apparatus on the well-known plan of -M.
Hansteen. The loss of magnetism sustained by the cylinder
during the time of its employment, from July 1837 to June 1838,
was very considerable, and was occasionally so irregular as
to prevent any satisfactory conclusion whatsoever being drawn
from the observations. On a careful examination, there ap-
peared two intervals, viz. from the middle of September to the
middle of November 1837, — and from April 24 to June 5, 1838,
— during which there was reason to infer that the loss of mag-
netism, though considerable, had been tolerably uniform and
regular. During the second interval, viz. from April 24 to
June 5, 1838, on both which days the cylinder was vibrated in
London, the increase in the time of vibration at the same sta-
tion affords a direct measure of the diminution in its magnetic
intensity ; and being divided by the number of days comprised
in the interval, furnishes the amount of the daily correction.
But in the first interval we have the additional disadvantages
of having no direct observation showing the amount of the loss
of magnetism, and no direct comparison with the force in
London : and it is necessary, consequently, to have recourse to
indirect means for the purpose of determining these particulars.
On the 19th of September, 1837, Captain Ross vibrated cylin-
der X at Birkenhead ; and on the 21st of September, at Dou-
glas, in the Isle of Man. In Table XLVII. we have the
value of the intensity at both these stations relatively to the
London unity, determined by Mr. Phillips ; and in Table
XLIV. we have Mr. Lloyd's determination of the force at
Birkenhead. We may employ these determinations to supply
the time of vibration in London corresponding to the observa-
tions with the cylinder at Douglas and Birkenhead. In like
manner we may accomplish a second indirect comparison with
London by means of Captain Ross's observations at Falmouth
on the 18th of November, 1837, combined with the values of
the intensity at that station determined by Mr. Fox, (Table
XLVIIL), and Major Sabine, (Table XLV.). The several
observations and processes by which the times of vibration
of the cylinder in London have been derived at different epochs,
are comprised in Table XLIX. ; and in its final column is
MAGNETIC SURVEY OF GREAT BRITAIN.
149
shown the average daily loss of magnetism experienced in each
of the two intervals ; which is subsequently applied in Table
L,, in assigning the corresponding times of vibration in Lon-
don, on days when the cylinder was employed elsewhere.
Table XLIX.
station.
Date.
Time of
vibrational
60°.
Observed
dip.
Intensity of
London = 1-0000
Corresponding
times of vibration
of Cylinder X in
London.
Daily loss
of force in
the respec-
tive interr
vals.
Birkenhead...
Douglas
Falmouth
London
London
1837.
Sept. 19
Sept. 22
Nov. 18
1838.
April 24
June2&5
275-22
279-27
271-48
275-84
28006
7°0 35-0
71 20-3
69 16-1
69 15-0
69 15-0
r 1-0145 Phillips 1
t 1-0112 Lloyd J
1-0208 Phillips
r 1-0015 Sabine "1
\ 1-0018 Fox ;
1-0000
268-45 1
^68-37
268-30 J
271-70
1-0-06
I 0-015
275-84
1-0000
280-06
Table L. contains the observations made by Captain Ross
with cylinder X, and the values of the intensity derived from
them. The coefficient in the formula for the reduction to a
mean temperature, is "00017 : the reduction has been applied
in the column entitled " corrected time."
Table L.
station.
Date.
Hour.
Temp.
Time of
100
vibrations.
Corrected
Time.
Observed
Dip.
Correspond.
ing time of
vibration in
London.
Intensity.
London
= roooo.
Birkenhead...
Douglas, (Isle
of Man).
Pwllheli
Marlbro'
Clifton
1837.
Sept. 19
Sept. 22
Oct. 14
— 15
— 18
— 22
— 26
h m
1 48 r.M.
2 17
9 47 A.M.
10 36
5 11 P.M.
8 55 A.M.
10 57
10 50
11 14
2 30 P.M.
2 55
1 17
1 48
70
70
60
60
47
47
60
58
60
56
56
56
56
s
275-81 "1
275-58 /
279-2 I
279-35 /
274-62 1
275-30 I
275-98 J
270-53 -)
270-75 1
271-4 X
271-57/
272-75 1
272-80 /
S
275-22
279-27
275-71
270-68
271-66
272-95
/
70 35-0
71 20-3
70 32-5
69 25-4
69 34-0
69 55-9
s
268-45
268-30
269-81
270-00
270-24
270-48
1-0128
1-0208
1-0173
1-0018
1-0031
1-0128
Pembroke
VOL. VII.
1838.
L
150
EIGHTH REPORT — 1838.
Table L. (contimied.)
station.
Date.
Hour.
Temp.
Time of
100
vibrations.
Corrected
Time.
Observed
Dip.
Correspond.
ingtimeof
vibration in
London.
Intensity.
London.
= 1-0000.
1837.
m
s
s
s
Swansea
Oct.
27
5 1 P.M.
45
273-381
—
28
11 46 A.M.
54
273-12 I
273-66
69
46-7
270-60
1-0010
—
29
6 59
54
273-23 J
Ilfracombe....
Nov.
3
5 2 P.M.
46
271-42
27206
69
36-9
270-80
1-0071
Padstow
—
14
1 12
1 35
56
56
270-85 1
271-00 ■
27110
69
25-1
271-49
1-0096
Falmouth
—
18
3 42
50
271-02
271-48
69
16-1
271-70
1-0017
Land's End...
—
23
11 6 A.M.
11 29
56
56
270-98-1
270-93 /
271-14
69
18-5
272-00
1-0082
1838.
London
April
24
3 41 P.M.
53
53
275-52 •)
275-51 /
275-84
69
15-0
275-84
1-0000
York
—
28
1 40
2 7
48
50
284-431
284-85 j"
285-16
70
45-2
276-24
10094
Scarbro'
May
1
10 56 A.M.
47
285-7 '
11 23
48
286-43 .
286-85
70
43-0
276-54
0-9975
11 49
49
286-68
Bridlington...
—
2
3 44 P.M.
60
285-82 "
5 50
56
285-0
285-46
70
38-8
276-66
1-0048
6 35
54
285-08
Wadworlh ....
—
10
3 39
60
284-07
284-07
70
27-5
277-50
1-0117
Nottingham . .
—
12
7 46 A.M.
58
283-02
283-12
70
16-3
277-70
1-0104
Louth
—
16
11 40
I 7 P.M.
57
58
283-7 1
283-67 /
283-81
70
19-5
278-10
1-0111
Cromer
z
21
22
7
6 r
60
60
281-051
281-38/
281-21
69
46-1
278-65
1-0065
Lowestoffe....
23
24
11 31 A.M.
16 P.M.
10 14 A.M.
61
62
61
279-90'
279-73
280-30
10 58
1 51 P.M.
64
60
280-68
280-65 ■
280-66
69
29-2
278-90
0-9990
25
10 28 A.M.
37 P.M.
1 12
52
53
54
281-0
281-10
281-17
Harwich
—
29
11 46 A.M.
1 40 P.M.
63
66
26013^
279-93
30
10 23 A.M.
3 P.M.
11 14 A.M.
65
66
66
280-20
280-43
280-53
280-00
69
15-4
279-50
0-9974
London
June
2
11 52
65
280-27'
-
5
21 p.M
10 58 A.M.
5 p.M
65
65
68
280-32
280-25
280-53
280-06
69
15-0
280-06
1-0000
MAGNETIC SURVEY OF GREAT BRITAIN.
151
2. Mr. Lloyd's observations were made with two cylinders,
L (a) and L {b), vibrated in Hansteen's apparatus. The
agreement of their times of vibration in Dublin, in April and
May 1836, is an evidence that their magnetic state I'emained
unaltered in the interval. The values of the intensity at
Shrewsbury and Holyhead are deduced, in relation to the Lon-
don unity, by means of the force in Dublin ; which, in a sub-
sequent part of this Report, will be shown to be 1'0195. The
coefficient in the formula of reduction to a mean temperature,
is -00025 for both cylinders. (5th Report, B. A., pp. 119 and
120.)
Table LI.
station.
Date.
Cyl.
Temp.
Time of
100
vibrations.
Corrected Time.
Observed
Dip.
Intensity.
London = 1-0000.
1836.
s
s
/
Dublin ...
April
11
L(a)
56-2
243-56
243-76 ]
—
12
610
243-96
243-88 1243-78 l
1-01951
April
15
11
L(6)
56-6
56-5
243-50
292-93
243-69 J
293-161
71 03-5
■1-0195
—
12
59-2
293-50
293-53 U93-33 J
1-0195.
15
56-8
293-09
293-29 J
Shrews- -1
bury...'
April
25
L(a)
62-0
62-0
241-64
241-68
290-83 /
70 27-6
10095 1
1 1-0080
1-0066/
25
L(6)
70-0
291-58
Holy- .
head... J
April
27
L(a)
54-2
53-2
244-08
244-02
244-421 0^^ ^0
244-42} 244-42 1
293-92 /
71 08-5
1-0192-1
1 1-0195
1-0198/
27
L(6)
59-0
293-87
Dublin ...
May
May
7
9
7
9
L(a)
L(6)
57-6
610
58-0
61-0
243-96
243-90
292-95
293-43
71 03-5
1-0195 1
[ 1-0195
1-0195 J
3. Major Sabine's observations were made with Mr. Lloyd's
cylinders L (a) and L (b), and with a pair, in all respects simi-
lar, designated as L (3) and L (4). The results are comprised
in the two following Tables, LII. and LIII. Table LII. con-
tains observations made to determine the value of the intensity
at Tortington, in Sussex ; and Table LIII. the values at six other
stations in Great Britain : in Table LIII. the value of the force
in Dubhn =1'0195, has supplied the means of checking the
magnetism of the cylioders.
l2
152
EIGHTH REPORT — 1838.
Table LIT.
Deduction of the Intensity at Tortington.
i
1. By comparison with Dublin. The observations at Dublin are by Professor
Lloyd; those at Tortington by Major Sabine. The intensity at Dublin
= 1'0195. The co-efRcient in the formula for the reduction to a mean
temperature of L (3) = -00027 ; of L (4) = -00022.
Cyl.
Time of
100
Vibrations,
Corrected
Time.
Dip.
Intensity.
London
= I'OOOO.
L (3),
Tortington
Dublin
Tortington
1838
Feb. 9
— 10
March 3
— 3
— 5
March 10
— 10
h m
4 40 P.M.
1 31
1 37
2 02
3 03
1 44
2 38
42
36
46-2
47
46-5
46
45-5
295-67 1
295-09 ]■
307-79 1
308-00 J.
307-35 J
296-74 1
296-53 /
s.
297-05
308-81
297-75
68 55-1
70 58-4
68 55-1
0-99C3
L(4).
Tortington
Dublin
Tortington
Feb. 9
— 10
March 3
— 3
— 5
March 10
— 10
5 09 p.m.
34
2 46
3 08
2 40
10 43 a.m.
41
36
46-8
44-2
47-2
49
46
271-22
270-78
282-58
282-58
282-57
272-53
271-98
272-28
283-40
272-99
68 55-1
70 58-4
68 55-1
0-9985
2, By direct comparison with London. The London observations were made in
the Palace Gardens at Kew.
Cyl.
Time of 100
■Vibrations.
Dip.
Intensity,
London
= 1-0000
L («).
L(6).
("London
L Tortington
TLondon
LTortin
gton
1838.
Oct. 13
— 13
Oct. 18
— 18
Oct. 13
— 13
Oct. 17
— 18
— 18
h m
3
3 16
08
27
11 45
15
1 28
10 17
11 07
39
40
52
53
44
44
58-5
48-0
50-5
I?'
238-98
237-77
237-81
236-651 0Q7.i/>
236-80 1 '''*' ^^
303-92 \
304-06 ;
303-26]
302-18 y 303-20
302-46 J
-305-21
69 16-4
69 53-5
69 16-4
68 53-5
0-9986
'0-99G5
The values of the intensity at Tortington, relatively to unity in London thus de-
duced, are as follows :
L (3), 0-9963 ; L (a), 0-9986 ;
L (4), 0-9985 ; L (6), 0-9965 ;
Mean, 0-9975.
MAGNETIC SURVEY OF GREAT BRITAIN.
Table LIII.
Deduction of the Intensity at Six Stations in Britain.
153
L(b).
Station.
Date.
Hour.
Therm.
Time of 100
Vibrations.
Corrected
Time.
Observed
Dip.
Correspond-
ing Time of
Vibration in
Intensity.
London
— 1-0000.
London.
1838.
h m
lOndon
June
1
10 21 A.M.
62
284-17 1
284-17 /
283-73* ■)
283-66 f
292-88 1
292-48 /
294-46
o /
1
11 04
62
284-01
69 17-4
284-01
1-0000
alraouth
July
7
1 10 P.M.
67
—
25
18 p.m.
62
283-40
69 12-0
283-94
0-9997
>ubl!n
Aug.
6
3 42
67
8
I 42
63
292-32
70 54-6
283-87
1-0195
/hiteliaven...
Aug.
16
4 25
57-5
294-64
71 10-7
283-94
1-0180
fewcastle . . .
Aug.
28
2 28
71-5
295-22
294-38
71 09-0
283-94
1-0183
L (a).
lublin
Aug.
6
4 12 p.m.
66
246-30 T
245-81 /
247-81
8
3 44
63
245-77
70 54-6
238-60
1-0195
r^hitehaven...
Aug.
16
4 55
57
248-00
71 10-7
238-80
1-0169
Newcastle ...
Aug.
28
2 57
73-5
248-40 1
248-07t J
—
30
I 00
63-0
247-72
71 09-0
238-80
1-0177
tonehouse ...
Sept.
3
11 30
59
248-86
248-92
71 19-6
238-80
1-0171
[elensburgli..
Sept.
9
2 50
55
253-22 1
253-45 /
253-66
—
9
3 20
57
253-58
72 17
238-80
1-0310
ardan Hill...
Sept.
13
3 24
59
253-72
72 14
238-80
1-0273
ondon
Oct.
13
3 00
39
237-77 1
237-81 /
—
13
3 16
40
238-98
69 16-4
238-98
1-0000
The results in Table LIII., collected in one view, are as
follows :
station.
Intensity, London = l-OOOO.
Station.
Intensity, Lon-
don = 1-0000.
L CO.
L(a).
Mean.
L(a).
Whitehaven
1-0180
1-0183
0-9997
10169
10177
1-0175
1-0180
0-9997
Helensburgh
10310
1-0273
1-0171
Newcastle
Falmouth
If we combine, by the method of least squares, the results at
the twenty-seven stations at which the intensity was thus de-
* Observed by Mr. Fox.
t Observed by Captain Ross.
154
.EIGHTH REPORT — 1838.
termined by horizontal vibrations, — namely, eighteen stations
by Captain Ross, exclusive of those which have served to ex-
amine the magnetism of the cylinder; two stations by Mr.
Lloyd; and seven by Major Sabine, — we obtain the follow-
ing values : 0;= +'000064; y = --000069; M = -47°14^;
r =-000094. The mean geographical position is 52° 43' N.,
and ^^ 18' W.
If we now collect in one view the several values of u and r
which have been obtained from the intensity observations in
England, we have as follows :
Table LIV.
Observer.
Method.
No. of
Stations.
Mean Geogra.
phical Position.
Values of
Lat.
Long.
u
r
Lloyd
Statical
Statical
Statical
Horizontal "1
vibrations j
12
24
20
27
52° 01
53 49
52 36
52 43
1°56
2 08
2 11
2 18
-54 49
-47 37
-52 27
-47 14
•000082
•000090
•000078
•000094
Phillips
Ross "1
Sabine \
Lloyd J
If we regarded the several values of u and r in Table
LIV., as entitled to weight proportioned to the number of
stations of which each is the representative, we should assign
a prepondei'ance to the values obtained by the horizontal vi-
brations, which the circumstances of the observations from
which they are derived would scarcely justify. To give them
exactly their just weight, would require a lengthened investiga-
tion of the respective probable errors, not only of the two me-
thods, but of the horizontal method under some disadvantages,
as shown in page 143. The occasion would not justify the ex-
penditure of the necessary time and labour ; and I have assign-
ed the arbitrary value of 18 to the horizontal deductions from
the twenty-seven stations ; making, in this particular instance,
three horizontal determinations equivalent to two statical. Thus
weighted, we obtain — 50° 48' and -000086 as the mean values
of u and r derived from the English series, corresponding to
the central geographical position in 52° 48' N. lat., and 2° 07
W. long.
MAGNETIC SURVEY OF GREAT BRITAIN. J55
Section II. — Scotland.
§ 1 . Observations by the Statical Method..
Major Sabine s Observations. — These were made in the
summer of 1836, with the statical needle S (2) ; an account of
them is contained in the report on the Scotch Magnetical
Lines, in the 6tli vol. of the Reports of the British Association.
Between the 30th of July and the 4th of October, in which in-
terval the magnetism of the needle was shown to have sustained
no change, twenty-two stations were observed at, including two
in Ireland, viz. Bangor and Dublin. These are now transferred
to the Irish Series, and being thus included in their more appro-
priate place, will be omitted here. At the time of the publica-
tion of the Scotch report, no direct comparison had been made
of the intensity in Scotland with that in London ; but its values
at the several Scottish stations relatively to London were given
provisionally, by means of the observations in Dublin, and by
adopting 1'0208 as the ratio of the force in Dublin to unity in
London, according to a determination of Mr. Lloyd's, published
in the Transactions of the Royal Irish Academy, in 1836. The
values at the Scottish stations were consequently subject to
be altered by any modification which Mr. Lloyd's determina-
tion in Dublin might subsequently receive. In the present
report Mr. Lloyd lias given a corrected value for the force in
Dublin, resulting from a much larger number of determinations.
The corrected value is 1*0195. With this value, therefore,
and the comparative observations at Dublin and Helensburgh,
published in the Sjxth Report of the British Association, we
may now derive a more correct expression, relatively to London
for the intensity at Helensburgh as the base of the Scottish
determinations.
The observations contained in the Scotch report presented
a double comparison between DubHn and Helensbui'gh : one
by the observations of the 22nd July, in Dublin, and the 27th
July, at Helensburgh ; the otlier by those of August 2, and
September 13 and 14, at Helensburgh, and October 4, at Dub-
lin. They are presented in the following tal)le.
Note. — Between the first and second comparisons the needle
sustained an accident, which is related in the Scottish Report,
and which accounts for the angles of deflection being diflerent
in the two comparisons.
156
eighth report — 1838.
Table LV.
Station.
Date.
Ther.
e
S
cos 6
Intensity.
sin (J - 6)
Dublin=l
London =
Dublin
1836.
July 22
July 27
56
60
-18 27-2
-17 17-9
7°1 03-6
72 16-8
•94843
•95478
1-0000
1-0067
roi95
r02G3
Helensburgh ...
Helensburgh ...
Helensburgh ...
Dublin
Aug. 2
Sept.l3&14
Oct. 4
65
64
49
-18 59-7
-19 06-1
-19 53-3
72 16-81
72 16-8/
71 03-2
•94572
■93993
1-0062
roooo
10258
vol 95
Whence it results that ( — - — "^ ) = 1*0261 expresses
the force at Helensburgh relatively to unity in London, as de-
rived through the medium of Dublin.
In 1838 I visited Helensburgh for the purpose of obtaining a
direct comparison with London. The observations vifhich I then
made are included with the series already given in Table XLV;
their result is 1 '0252. The near agreement of this result, with
that obtained in 1836 through the medium of Dublin, is satis-
factory, both in confirming the relation of the Scottish inten.^i-
ties to London, and in showing the confidence to which this
mode of experiment is entitled. I have taken 1*0258 as the
force at Helensburgh, considering the determination through
Dublin as entitled to rather the most weight ; and have com-
puted from it the value of the intensity at the other stations,
as inserted in the final column of Table LVL
Table
LVL
station.
Date.
Ther.
e
5
cos 6
Intensity.
sin (S - 6)
Temp. 60°
Helensburgh
= 1-0000
London
= 1-0000.
Helensburgh -j
Cumbray
Tobermorie ...
Loch Slapin ...
1836.
Aug. 2
Sept. 13&14
July 30
Aug. 10
— 14
— 17
— 20
— 24
— 23
— 25
— 27
— 30
— 31
Sept. 1
— 3
— 6
— 7
— 8
— 9
— 16
— 16
— 18
65
64
64
70
56
57
59
58
51
60
57
44
59
60
60
51
56
55
56
57
53
52
-l°8 59-7
-19 061
-18 31-9
-15 29-3
-15 59
-17 50-8
-16 44-2
-16 53-7
-17 08^4
-16 52-4
-18 22
-18 40-1
-18 06-1
-18 40^8
-18 37-7
-19 43-7
-19 561
-19 24
-19 24
-18 55-9
-18 16-1
-19 31-8
|72 16-8
72 01-2
73 07-7
73 02-2
72 17-2
|72 46-5
72 55-6
72 40-9
72 22
72 14-2
71 54-7
72 17-5
72 11
71 37
71 33-7
71 49-4
72 01-7
72 23-0
71 56
71 43-5
-94572
•94839
•96452
•96130
•95173
•95718
•95510
•95693
•94900
•94668
•95052
•94745
•94769
•94111
•94023
-94320
-94330
•94600
•94925
•94230
1-0000
1-0028
1-0199
1-0165
1-0064
1-0121
1-0099
10119
10035
1-0010
1-0051
1-0018
1-0021
0-9951
0-9942
0-9973
0-9974
1-0003
1-0037
0-9964
1-0258
1-0287
1-0462
1-0427
1-0324
1-0382
10360
1-0380
1-0290
1-0269
1-0310
1-0277
1-0279
1-0208
1-0199
1-0231
1-0232
10261
1-0296
I 0221
Inverness ... ■<
Gordon Castle
Alford
Blairgowrie ...
Kirkaldy
Dryburgh
Edinburgh
Loch Ranza ...
Cainbleton
Loch Ryan ...
MAGNETIC SURVEY OF GREAT BRITAIN.
157
In the discussion of these observations in the 6th Report of
the British Association, I have adverted to the frequent in-
fluence of the igneous rocks in Scotland in producing vi^hat
may be termed statioti error. In the table in page 20 of that
Report, the intensities observed at Tobermorie, both by the
statical and horizontal methods, are shown to have been af-
fected, apparently by an error of this nature, to a degree much
exceeding that of the results at any other station. In com-
bining the results of both methods, therefore, for the values
of X, y, &c., I have thought it right to omit altogether the inten-
sities at Tobermorie. We have, therefore, the statical results
at nineteen stations to combine by the method of least squares,
vi'hence we obtain the following values : a; = + •000083 ;
y = - -000107 ; e^ = - 52° 15'; r^= '000136. The mean geo-
graphical position is in latitude 56° 22' N. and longitude
4° 01' W.
Captain Ross's Observations. — These were made "with two
needles, RL (3) and RL (4), on Professor Lloyd's principle, used
in Captain Ross's six-inch circle. One of these needles (R L 3)
appears to possess the peculiar property of preserving its mag-
netism unchanged in different temperatures, requiring no re-
duction to a mean temperature. Table LVII. contains a series
of experiments with it, made by Captain Ross, by which it will
be seen that in differences of temperature, including the whole
range of natural temperatures to which it is likely to be exposed,
the time of vibration of the needle remained unaltered.
Table LVII.
Observations to investigate the influence of differences of tem-
perature on the time of vibration of Captain Ross's statical
needle R L (3).
Time of 100
Time of 100
Date.
Hour,
Ther.
Horizontal
Vibrations.
Pate.
Hour.
Ther.
Horizontal
Vibrations.
1839.
h m
s
1839.
h m
s
Jan. 17.
10 39 A.M.
32
428-4
Jan. 17.
2 29 P.M.
60
428-0
10 54
32
428-4
2 45
56
428-2
11 42
98
428-8
3 01
53
428-2
11 58
92
428-4
3 16
51
428-0
17 P.M.
83
428-2
3 32
50
428-4
56
92
428-4
Jan. 18.
10 32 a.m.
28
428-4
1 U
87
428-4
10 47
29
427-8
1 27
81
428-8
11 08
30
428-4
I 44
75
428-6
11 34
30
428-4
1 58
70
428-2
11 49
30
428-6
2 14
64
428-4
05 P.M.
30
428-5
The following table. No. LVIII. contains two series of ex-
periments of a similar nature, with R L (4), one made by Major
158
EIGHTH REPORT— 1838.
Sabine, and the other by Captain Ross, the results according
extremely well in the value of the coefficient deduced.
Table LVIII.
Observations to ascertain the coeflScient in the formula for reduction to a mean
temperature of Captain Ross's statical needle R L (4).
Major Sabine, Tortington, December 18, 1838.
Hour.
Temp.
Time of 100
Vibrations.
Bleans.
h m
S
10 38 A.M.
11 34
47
46-5
480-4 •)
480-4 ;
480-4 at 46-75
ri • .u f 1 2(T-T'),
Here, in the formula, a = —r, ; ,
' T'(r-r')
1 57 P.M.
109
480-8 ■
T = 480-25 ; T - T' = 0-75 ;
2 22
103
481-4 y
481-0 at 103-3
r — r' = 55°-8 : whence a —
2 42
98
480-8 J
-000056.
5 02
49
479-4 1
G 43
48
480-8 i
480-1 at 48-3
7 44
48
480-0 J
Captain Ross, London, February 21, 1839.
Hour.
Temp.
Time of 100
Vibrations.
Means.
h m
s
1 14 p.m.
1 45
38
38
474-2 ■)
474-23 J
474-22 at 38°
2 19
104
474-96 1
2 41
3 7
103
103
474-93 1
474-61 f
474-90 at 102-5
Here T = 474-2 ; T - T'= P16
3 30
100
475-01 J
r — r' = 45°-l ; whence, a =
-000054.
3 51
88
474-36 "
4 34
4 53
77
71
474-72 1
474-66 f
474-51 at 75-7
5 15
67
474-30 J
8 7
8 32
50
50
473-98 \
474-08 J
474-03 at 50
By the mean of the two determinations a = -000055 ; which being multiplied by
-43429, the modulus of the common system of logarithms =-000024, the coeffi-
cient of (t— t') in the correction for temperature.
MAGNETIC SURVEY OF GREAT BRITAIN.
159
In the following table are collected the observations made
with these needles in London, in July 1838, and in December
of the same year, for the double purpose of examining the
steadiness of their magnetism in the interval, — during which
they had been employed in the observations in Scotland now
under notice, find in a similar series in Ireland, — and of deter-
mining the angle of deflection in London as the base station of
both series.
Table LIX.
Needle.
Date.
Hour.
Ther.
9
S
CO8
Intensity.
sin (8 - ».)
co"
1838.
July 7
July 12
Dec. 5
h m
5 30 P.M.
30
1 30
3
3 40
fo
70
70
45
45
-2°6 38-4
-27 1-9
-27 48-3
-26 32-9
-26 30-3
1 69 14-2
|69 14-7
•89683
•89932
0-9986 -j
• 10000
1-0014 J
Mean.
•89807
July 10
July 12
Dec. 4
5
4
5
3
4 30
68
72
72
47
47
-13 33-2
-13 32-7
-13 30-7
-13 28-8
-13 28-0
1 69 14-2
|69 147
•98061
•97970
rooos 1
• i^oooo
0-9995 J
Mean.
•98015
On comparing the observations with both needles in July
and in December, we may conclude that the magnetism of
both had remained unchanged during the interval ; the small
differences are only such as frequently occur on different days ;
they are, moreover, in different directions, and so far will com-
pensate each other in the final deduction.
In Table LX. are comprised Captain Ross's observations
with these needles at nine stations in Scotland and the north
of England.
160
EIGHTH REPORT — 1838.
Table LX. Needle, R L (3) .
Hour.
Ther.
h m
3 P.M.
63
3 r.M.
30
1 10
54
53
53
11 30 A.M.
30 p.si.
60
60
2 30 P.M.
3 15
59
59
4 P.M.
5
60
60
sin (J - fl)
Aberdeen ...
Lerwick
Kirkwall
Inverness ..
Newcastle ..
1838.
July 19
— 25
— 26
Aug. 1
— 14
— 29
- 23 32-3
- 22 291
- 22 33-1
- 22 21-8
22
22
21 49-6
21 531
24 55-9
24 57-1
72 27-6
73 44-9
73 20-4
72 46-2
130
}"
Therm. eo°
92185
•92947
•93081
•93118
•91202
Needle, RL (4).
Aberdeen ...
July 19
Lerwick
— 25
— 26
Kirkwall
Aug. 1
Inverness ...
— 14
Newcastle ...
— 29
Stonehousc...
Sept. 3
Jordan Hill..
— 11
— 13
Berwick
— 17
Dunkeld
— 20
4 P.M.
3 30 P.M.
3
3
1 30 p.m.
2 10
3 30 P.M.
4 30
3 00 p.m.
3 30
10 40 a.m.
Noon.
2 O P.M.
3
10 A.M.
11
11 30 a.m.
Noon.
O 15 P.M.
2
- 7 352
- 4 522
- 4 sro
- 5 00
- 4 55^6
- 5 0^
- 5 14^7
- 5 141
- 9 51-9
- 9 52-9
- 9 48-5
- 9 50-7
- 7 36^7
- 7 415
- 8 2-8
- 8 3-5
- 8 19^9
- 8 12-0
- 7 37-2
- 7 37^4
72 276
r0056
1 73 44^9
10159
|73 20^4
1-0175
1 72 46^2
1-0180
■71 13^0
•99727
|71 24^1
•99713
■ 72 20-0
1-0055
|71 41-9
10050
■ 72 231
10063
MAGNETIC SURVEY OF GREAT BRITAIN.
161
Collecting the results in one view, we have as follows
Table LXI.
station.
R L (3.)
RL(4).
Mean.
Station.
R L (3).
Aberdeen ...
1-0266
1-0270
1-0268
Dunkeld
1-0267
Lerwick
10351
10365
10358
Jordan Hill..
10259
Kirkwall ...
1-0366
1-0381
1-0373
Berwick
1-0254
Inverness ...
1-0370
1-0386
1-0378
Stonehouse...
1-0173
Newcastle ...
1-0156
1-0175
I0I65
If we combine the results at these nine stations by the
method of least squares, we obtain the following values :
x=+ -000080 ; 2/ = - '000069 ; m = - 40° 38' ; r = -000106.
The mean geographical position is in latitude 56° 52' and lon-
gitude 2° 45' W.
§ 2. By the Method of Vibrations.
Major Sabine's Observations. — These observations were
made in the summer of 1836; a detailed account of them is
given in the Sixth Report of the British Association. Two
cylinders, L a and L b, were vibrated at twenty-two stations in
Scotland, between the 28th July and 18th September, during
which interval the magnetism of the cylinders was proved to
have been steady. The times of vibration at the several stations,
reduced to a temperature of 60°, are inserted in Table LXII.,
being taken from the Sixth Report of the Association. The
values of the horizontal intensity are given in the table in re-
lation to unity at Helensburgh ; and those of the total force to
unity in London : the intensity at Helensburgh having been
already shown to be as 1 -0258 to 1 '0000 in London.
162
EIGHTH REPORT 1838.
Table LXII.
Helensburgh ....
Great Cunibray
Loch Gilphead. ,
Tobermorie
Loch Slapin
Artornish
Glencoe
Fort Augustus...
Inverness
Golspie
Gordon Castle..
Rhynie
Alford
Braemer ,
Blairgowrie ,
Newport
Kirkaldy
Melrose
Dryburgh
LochRanza
Campbelton
Loch Ryan
1836
{July 28— Aug. 21 L a
Sept. 13-14 L a
July 28— Aug. 2 L 6
Sept. 13-14 L b
r July 30 IL a
L b
rAu^7..,
r Aug. 10
/Aug. 14
/Aug. 16
/Aug. 17
r Aug. 19
[Aug. 21 ....
I Aug. 24 ....
1 Aug. 21 ....
[Aug. 24 ....
/Aug. 23 ....
/Aug. 25 '.'.'.'.
/Aug. 26 ....
/Aug. 28-29"
1—28 ....
f Aug. 30 ....
fAu^si :;;;
/Sept. 1
/Sept. 3 ......
/Sept. 6
I — 6 and 7 ,
Sept. 7
/Sept. 16
/Sept. 17
/Sept. 18 '.'.'.'.'.'.
L a
L b
L a
L b
L a
L b
L a
L b
L a
L b
L a
L b
L a
L a
L a
L b
L a
L b
L a
L b
L a
L b
L a
L b
L a
L 6
L o
L 6
L a
L 4
L a
L b
L a
L a
L *
L a
L b
L a
L 6
Time of
Vibration,
Therm. 60,
)51
i7]
08 1
33/
25105
251-27
302-08
301-33
249-82
300-71
249-75
300-22
254-34
305-46
254-50
305 04
252-57
303-75
250-32
301-17
253-34
304-00
253-111
253-53/
303-161
304-25 /
254-48
305-87
252-72
303-29
251-09
301-24
252-23
302-67
250-96
300-88
248-10
297-69
251-26
301-72
250-79
300-87
247-56
296-85
247-20
252-57
303-15
249-33
29905
247-68
297-06
Horizontal Inten-
sity. Helensburgh
= 1-0000.
i. 1-0000
■1-0087
1-0106
1-OOOOT
1-0000
1-0108
1-0066
10113\
1-0099/
2S} 0-9753
0-9782 1'^^^^l
S:S}0-9878
1-00351 , „„ri
1-0067/^^^^^
0-9849 I ^'^^^^
0-9831 1
|«.
0-9869
0-9741 lo
0-9729/"
0-9877
0-9895
1-0006
1-0031
0-9916
ly
!}»
1-0031 / ^
0-9936/*^
1-00161 ,
1-0055 /
1-02491,
1-0272/^
0-9992
0-9998
1-00301 ,
1-0055/'
1-02931 ,
1-0330/'
1-0323
0-9889 1 „
0-9905 / "
1-01481 ,
1-0178/'
1-02831 ,
10315/'
9850
9735
■9886
0018
9926
0035
0260
9995
0042
0311
9897
0163
0299
Observed
Dip,
72 16-8
01-2
07-7
07-7
02-2
42-9
17-2
40-4
72 46-5
55-6
40-9
25-7
220
14-2
54-8
17-5
110
37
33-7
23
56-0
43-4
MAGNETIC SURVEY OF GREAT BRITAIN.
163
Omitting Tobermorie, for the reasons assigned in page 157,
and combining the results at the other twenty-one stations by
the method of least squares, we obtain the following values :
ar = + -000080; ?/ = --000118; u =-55° 46'; r = '000143.
The mean geographical position is latitude 56° o5', and longi-
tude 4° 15' W.
Captain Ross's Observations. — These were made in the sum-
mer of 1838 with a cylinder (X) described in page 148. It was
vibrated at Westbourne Green, near London, in June and
July 1838, and again in December of the same year, having
been used in the interval both in Scotland and in Ireland. The
observations at Westbourne Green, showing that its magnet-
ism underwent no change in this interval, are contained in the
following table.
Table LXIII.
Time of
Mean Time of 100
Observed
Date.
Hour.
Therm.
Vibrations.
Vibrations at 6o°.
Dip.
1838.
h m
s
June 2...
11 52 a.m.
65
280-27.
_
21 P.M.
65
280-32
June 5.,.
10 59 A.M.
65
280-25
279-99"
—
4 P.M.
68
280-63 f
June 8...
11 49 a.m.
67
279-78
— ,
12 P.M.
57
279-63-^
July 6...
11 05a.m.
11 27a.m.
68
70
280-38-
280-40
280-24
■ 280-06
69° 14-5
July 12...
10 50a.m.
68
280-83 ■
11 12a.m.
68
280-98
Nov. 30...
11 O A.M.
11 27a.m.
50
51
279-48 \
279-52 /
279-95.
The coefficient in
the fori
■nula for the reduction to a
mean
tempera
ture is -00017.
Table LXIV. contains the observations with cylinder (X) at
ten stations in Scotland, and at two stations in the north of
England, viz. Newcastle and Stonehouse. The values of the
total intensity in the final column, relatively to unity in London,
have been computed by means of the time of vibration of this
cylinder in London shown in the preceding table.
164
EIGHTH REPORT— 1838.
Table LXIV.
Hour. Therm.
Time of
100
Vibrations.
Corrected
Time.
Observed
Dip.
Intensity.
London
= I'OOOO.
Aberdeen
Lerwick ..
Kirkwall.
Wick ..
Golspie
Inverness ..,
Newcastle .
Stonehouse ,
Culgruff...,
Jordan Hill.
Berwick ,
Dunkeld ,
1838.
July 18
July 23
24
26
27
28
July 31
Aug.
Aug,
Aug,
1
3
4
C
8
10
11
12
Aug. 13
14
29
30
Aug.
Sept.
Sept.
9
Sept. 11
12
13
Sept. 1 7
18
Sept. 20
21
h m
2 10 P.M.
3 1
2 52 P.M.
11 12 a.m.
11
11 12
40 P.M.
11 50 a.m.
10 50
11 44
11 21
11 28
11 12 A.M.
11 42 a.m.
11 27
10 28
1 32 p.m.
Noon,
8 3 A.M.
10 40
11 15
46 P.M.
11 11a.m.
45 P.M.
10 18 a.m.
43 P.M.
9 47a.m,
5 27 P.M.
11 A.M.
8 54
9 4 A.M,
9 2
10 22 A.M
10 19
64
61
50
54
52
60
54
56
59
58
60
57
58
66
63
62
58
59
52
59
60
57
60
58
47
52
51
60
56
60
56
52
58
48
299-37
309-27
305-31
305-43
303-26
300-51
291-41
292-86
293-50
298-39
294-02
298-92
72 27-6
73 44-9
73 20-4
73 19-9
73 04-4
72 46-0
71 130
71 24-0
71 35-7
72 20-3
71 41-9
72 23-1
1-0292
1-0386
1-0403
1-0390
10382
10395
10167
1-0163
1-0219
1-0289
I 0241
10281
If we combine these twelve results by the method of least
squares, we obtain the following values, viz. : x= + '000091 ;
2/ = --000086; « = -43°32'; r = -000125. The mean geo-
graphical position is 5G° 56' N. lat., and 2° 58' W. long.
MAGNETIC SURVEY OP GREAT BRITAIN.
165
If we collect in one view the values of u and r which have
been obtained from the several series in Scotland, we have as
as follows :
Table LXV.
Observer.
Method.
No. of.
Stations.
Mean Geographical
Tosilion.
Values of
Lat.
Long.
u
»■
Sabine ...
Ross
Sabine ...
Ross
Statical
19
9
21
12
56 22
56 52
56 35
56 56
4° 01
2 45
4 15
2 58
-52 15
-40 38
-55 46
-43 32
•000136
•000106
•000143
•000125
Statical
Hor. Vibrations....
Hor. Vibrations....
Regarding the values of u and r as entitled to weight pro-
portioned to the number of stations of which each is the re-
presentative, and giving equal weight to a result by each me-
tlj|d, we obtain —50° 02' and -000132 as the mean values of
u and r derived from the Scottish series, and corresponding to
the central geographical position in bQ° 40' N. lat., and 3° 30'
W. lonffitude.
Section III. — Ireland.
{By the Rev. H. Lloyd.)
1. Method of Vibration.
The body of results obtained by this method in Ireland has
received some valuable accessions, and undei'gone other impor-
tant alterations, since the publication of the Irish Magnetic
Report. We shall consider these under the following heads.
1. Additional observations ; 2. Corrections of the results pre-
viously obtained ; 3. New determinations of the intensity at the
base stations.
Additional Observations. — These consist in a comparison of
the intensity at London and Dublin, made by myself in the year
1836; a comparison of Dublin and Bangor, made by Major
Sabine in the latter part of the same year; a comparison of
London and Dublin, by the same observer, in the year 1838;
and a complete series of observations made by Captain James
VOL. VII. 1838. M
166
EIGHTH REPORT 1838.
Boss, in the year 1838, at twelve distinct 'stations throughout
the island. This latter series, forming in themselves a complete
body of results, will he considered separately. The additional
observations made by Major Sabine and myself are contained in
the following table*.
Table LXVI.
Cyl
mder L
(«)•
station.
Date.
Hour.
Time.
Temp.
Corr. Time.
April 11, 1836.
h
11
14
243-56
o /
56-2
s
243-76
Dublin •
— 12
11
8
243-96
61-0
243-88
— 15
11
14
243-50
56-5
243-69
Mean.
243-67
57-9
243-78
April 19
12
11
236-02
59-5
23604
London ■
— 21
2
3
235-94
600
235-93
— 22
11
51
236-23
61-5
236-13
Mean.
236-06
60-3
23603
May 7
12
30
234-96
57-6
244-10
Dublin ■
— 9
12
6
243-90
61-0
243-83
1-
Mean.
243-93
59-3
243-96
July 24,1836.
9
243-47
59-0
243-53
Dublin <
— 25
7
30
24311
55-0
243-41
I
Mean.
243-29
57-0
243-47
Sept. 21
9
45
246-53
48-6
247-20
Bangor •<
— 21
10
15
246-72
49-0
247-39
Mean.
246-62
48-8
247-30
r
Oct. 3
10
10
243-25
45-0
244-16
— 3
2
8
243-22
47-0
244-01
Dublin •}
— 3
2
30
243-09
48-0
243-82
— 4
1
45
243-18
51-5
243-70
I
Mean.
243-18
47-9
243-92
June 1, 1838.
11
37
236-27
62-0
236-15
London -;
— 1
11
56
236-15
620
23603
Mean.
236-21
62-0
23609
Aug. 6
4
12
246-30
66-0
245-93
Dublin ■
- 8
3
44
245-81
63-0
245-63
Mean.
246-05
C4-5
245-78
Oct. 13
3
237-77
390
239-01
London ■
— 13
3
16
237-81
400
238-99
l-
Mean.
237-79
39-5
239-00
* The details of the comparison of Bangor and Dublin have been already
printed in the Scotch Magnetic Report; they are reprinted here, so that all the
results obtained in Ireland may be seen in connexion.
MAGNETIC SURVEY OF GREAT BRITAIN.
167
Table LXVII.
Cylinder L (Z») .
station.
Date.
Hour.
Time.
Temp.
Corr. Time.
1836.
h
m
s
o /
»
April 11
10
48
292-93
56-5
29316
— 12
10
44
293-50
59-2
293-53
Dublin -
— 15
10
48
293-09
56-8
293-29
Mean.
29317
57-5
293-33
r
April 19
11
36
284-17
61-0
284-08
— 21
1
38
284-44
60-5
284-38
London ■
— 22
11
22
284-27
60-5
284-21
Mean.
284-29
60-7
284-22
■
May 7
12
5
292-95
58-0
293-08
Dublin \
— 9
11
40
293-43
61-0
293-34
L
Mean.
293-19
59-5
293-21
r
July 24
8
30
293-22
59-0
293-29
Dublin ■
— 25
8
292-25
54-0
292-69
— 25
8
40
292-57
55-5
292-90
Mean.
292-68
56-2
292-96
Bangor
Sept. 21
11
10
295-28
49-6
296-04
'
Oct. 3
9
25
291-02
44-5
292-15
— 3
9
45
291-24
44-5
292-37
Dublin -<
— 3
2
55
291-37
49-6
29213
— 4
1
15
291-73
53-5
292-20
Mean.
291-34
48-0
292-21
r
Junel,1838
10
21
284-17
62-0
284-00
London <
11
4
284-17
62-0
284-00
I
Mean.
284-17
62-0
284-00
f
Aug. 6
3
42
292-88
67-0
292-37
Dublin <
- 8
1
42
292-48
63-0
292-26
I
Mean.
292-68
65-0
292-31
Correction of the Results. — ^The first correction that seems
to be required is in the series of results obtained in the North
of Ireland, in the autumn of the year 1834. On a comparison
of the times of vibration of cylinder L (Jj) in Dublin, at the com-
mencement and end of that series, it will be seen that the mag-
net sustained a loss of force ; and an attentive examination of
the other parts of the series shows that this loss occurred im-
mediately previous to the final observation in Dublin. This
fact will be seen very evidently by means of the following table,
which contains the corrected rates of the two cylinders, and the
deduced values of the intensity compared with the intensity in
Dublin at the time of the initial observation. Tlie results ob-
tained with the two cylinders present a very close agreement,
except in the final observation.
M 2
168
EIGHTH REPORT — 1838.
Table LXVIII.
station.
L(a).
L(6).
Time.
Intensity.
Time.
Intensity.
243-90
1-000
-976
•966
•963
-964
1-000
292-74
296-40
297-71
298-22
297-83
293-62
1-000
•975
•967
•964
-966
-994
Armagh..
Cam
246-88
248-10
248-51
Enniskillen
Dublin
248-42
243-92
Hence, instead of comparing the other results of C3lincier L (A)
with the mean of the initial and final observations in Dublin,
they are to be compared with the initial observations alone ; the
final observations not being comparative with the rest of the
series. The loss of force sustained by the cjdinder L {b) being
•006, the amount of the correction is
5/, = --003 X A;
h denoting the horizontal intensitj'^, as originally deduced, and
Z h its correction.
A correction of a similar kind (that is, depending on the rate
of vibration at the base station) seems to be required also in the
series of results obtained in the west and south of Ireland in
the summer of 1835. In reducing the observations of this series,
I had taken as the Dublin time, the mean of the initial and final
times, without regarding the number of separate observations ;
but, if we suppose the difference between these times to be owing
to errors of observation, or to ?i\\y fluctuating source, it is ma-
nifest that we should take, as the Dublin time, the mean of the
separate results themselves. This seems to be the proper course
in the present instance. The initial time is the result of a sin-
gle observation only, and that taken under the disadvantage of
an uiuisually high temperature ; so that the difference bet^^een
it and the final time (which difference is nearly the same for the
two cj'linders) is probably due either to the irregular fluctuations
of the horizontal intensity, or to error in the coefficient of the
temperature correction.
It is easy to determine the amount of the required correction.
If T denote the time of vibration at any station, 'l^ tliat at the
base station, and h the ratio of the horizontal intensities,
h-Tl
MAGNETIC SURVEY OF GREAT BRITAIN. 169
Hence if ST' denote the small correction in the value of T', and
8 h the corresponding correction of //,
h ~ T'
To apply this in the present instance, we have
I. («) L (b)
s s
Mean of separate observations . . . 243*43 293*18
Mean of initial and final results . . 243-29 293-06
Correction of T', or ST' +0-14 +0-12
Resulting value of -r* + -0011 + -0008
n
The corrections here obtained are applied to all the results
of the series (Aug. 19, to Sept. 15, 1835) in Table LXVIII.
Values of the Intensity at the Base stations. — The following
is a summary of the comparisons of the horizontal intensity in
London, Dublin, and Limerick, as contained in Table LXIX.
Horizontal intensity in Dublin, referred to London :
July, August, 1835. Cyl. R c
Int. = -9456
— — — — RfZ
— = -9421
Sept. Oct. Nov. 1835. — L «
— = -9354
J. _ _ _ _ LZ.
— = -9348
April, May, 1836. — L«
— = -9367
— — — — LZ»
— = -9392
June, Aug. Oct. 1838. — La
— = -9340
_ _ _ _ —Lb
— = -9440
Mean
. . . = '9390
Horizontal intensity in Limerick, referred to London :
July, Aug. Sept. 1S34. Cyl. S h Int. = -9396
July, 1835. — S /j — = -9470
Jxily, August, 1835. — Re — =-9461
July, August, 1835. — Rrf —=-9513
Mean = -9460
170 EIGHTH REPORT 1838.
Horizontal intensity in Limerick, referre'd to Dublin
October, 1834. Cyl. L a Int. = 1 -0075
— — — LA — = 1-0015
July, Aug. 1835. —Re — = 1-0005
— — — — Rrf — =1-0098
Aug. Sept. 1835. — L« — = 1-0039
— — — — lib — = 1-0055
Nov. Dec. 1835. — L« — =1-0001
— — — — LZ»— = 1-0021
Mean = 1*0039
Now, the comparison of Dublin with London and with Li-
merick being each the mean of eight separate comparisons,
while that of Limerick and London is deduced from four only,
we have (see Fifth Report, p. 133.)
A = 2B = C.
Hence the formulae of page 134 become
4(a^+c,2)+l' ^ ^{a^ + c^) + i>
but a=-9390, Z» = -9460, c=l-0039j
c, = -=l-0075, e,— c=:-0036:
and, substituting these values,
8.r=+'0009, 8y=-'00l7}
.r=a + Sa^ = -9399;
j/ = b + ht/ = '944S.
The numbers in the 6th column of the following table are
deduced from those of the 5th, by multiplying by one or other
of these numbers, according as the station has been compared,
in the first instance, with Dublin or with Limerick.
It will readily appear, from the principles laid down in pages
95 et seq., that the iveights of these determinations are ex-
pressed by the formulae
X=A + #C£;, Y=B + . ^C
Ba^+C ^ ^Aa^ + Cc^'
MAGNETIC SURVEY OF GREAT BRITAIN.
171
Now, A=C = 8, B—4; substituting these values, and those of
a, b, c, given above, we have
X«10-8, Y = 8-2;
the weight of a single comparison being unity.
Table LXIX.
Intensity of the Horizontal Force.
station.
Date.
Cyl.
No.
Hor. Int.
Hor. Int.
( London =1.)
1834.
July, Sept.
Aug. 20-27
86
Sb
5
20
•9396
1^0000
London
Sept. Oct.
— 9, Oct. 8
— 9,-8
— 16
— 17
— 17
— 27
— 27
— 27
Oct. 4
— 4
— 4
— 12
— 17
— 19
86
La
L6
86
La
L6
S6
La
L6
S6
La
L6
S6
86
86
3
2
3
1
1
1
1
1
1
1
1
1
1
1
1
rooooi
roooo L
rooooj
1-0010 1
•9954 I
1-0029]
1-01101
1-0110 I
•9997
1-0039
1-0086 L
1-0066 J
-9983
10404
1-0092
•9443
-9441
-9511
•9503
•9427
•9824
•9530
Dec. 2
— 10
86
S6
1
1
1-0157
1-0000
-9591
•9443
Dublin
Oct. 10-28
— 11
— 8
— 8
— 13
— 14, 15
— 14, 15
— 18, 20
— 21
— 21
— 23
— 23
— 24
— 24
La
L6
La
L6
L6
La
L6
L6
La
L6
La
Lb
La
Lb
6
2
1
2
1
2
2
2
1
1
1
1
1
1
1-00001
1-0000/
1-0075 1
1-0015/
-9868
-9761 1
-9754/
-9870
•9665 "1
•9669/
•9633 1
•9636 /
-9640 1
•9661 /
-9399
-9441
-9275
-9172
-9277
-9086
-9056
•9070
Cam
172
EIGHTH REPORT 1838.
Station.
Date.
Cyl.
No.
' Hor. Int.
Hor. Int.
London=l.
1835.
July 4-7
July 8-201
Aug.28-31 /
July 27, 28
— 27-29
— 29-31
Aug. 16
— 14
— 19
— 19,20
S&
lie
Rd
Sb
Re
Rd
Re
Rd
Re
Rd
12
25
14
2
10
11
3
3
3
3
1-0005
1-0098
1-0000
1-0000
•9531
•9558
1-0000
1-0000
1-0000
•9470
•9461
•9513
•9456
•9421
•9012
•9005
Dublin
Dublin
Aug. 19 1
Sept. 12-15/
Aug.21
— 21
— 22
— 22
— 24
— 24
— 25
— 25
— 26
— 26
— 27
— 27
— 28
— 28
— 29
— 29
— 31
— 31
Sept. 1
— 1
— 2
— 2
— 3
— 3
La
L6
L«
L6
Ln
L6
La
L6
La
L6
La
L6
La
L6
La
Lb
La
Lb
La
Lb
La
Lb
La
Lb
La
Lb
5
1 •00001
roooo/
•9580 1
•9566/
•9545 1
•9517/
•9497 1
•9454/
•9576 1
•9552 f
•9621 1
•9636/
•9777 1
•9781 /
•9995 1
•9977 /
1^0039 \
r0055/
1-0211
1-0294*
1-0125 1
1-0115/
1-0215 1
1-0246/
1-00131
10035 /
•9399
•8998
•8959
•8906
•8990
•9051
•919]
•9386
•9443
•9597
•9512
•9615
•9422
BelmuUot
Achill
Cork
Sept. 19-221
Oct. 23,24/
Sept. 12-151
Nov. 5, 6/
La
Lb
La
Lb
6
roooo
l^OOOO
•9354
•9348
Dublin
Dublin
Nov. Dec. Jan.
Nov. Dee. Jan.
Dec. 19-23
— 19-23
La
Lb
La
Lb
8
7
3
3
1-0000
1-0000
10001
1-0021
Apr. 19-221
1836. /
Apr. 11-151
May 7-9 /
La
Lb
La
Lb
3
3
5
5
10000
1^0000
•9367
•9392
Dublin
* Disturbing influence suspected in this observation : the result has been ac-
cordingly omitied in deducing the number in the last column.
MAGNETIC SURVEY OF GREAT BRITAIN.
173
Station.
Date.
Cyi.
No.
Hor. Int.
Hor. Int.
(London=l.)
Dublin
1836.
July 24, 25 1
Oct. 3, 4 /
Sept. 21
— 21
La
Lb
La
Lb
6
7
2
1
1-00001
10000/
-97101
•9768 /
•9399
•9154
London
Dublin
June 1, Oct. 13,1838
— 1
Aug. 6-8
• - 6-8
La
Lb
La
Lb
4
2
2
2
1-0000
1-0000
•9340
•9440
The following table contains the resulting values of the hori-
zontal intensity, those of the total intensity thence deduced,
and the latitudes and longitudes of the stations. The values of
the dip employed, in deducing the total from the horizontal
intensities, will be found in Table XXXVI.
Table LXX.
Dublin
Limerick ...
Ballybuuian
GlengarifF...
Killarney ...
Kiltanon ...
Templemore
Clonmel ...
Fennoy
Carlingford
Armagh
Colerain ...
Cam
Strabane ...
Enniskillen
Markree ...
Ballina
BelmuHet ...
Achill
Leenan
Oughterard
£nnis
Cork
Waterford...
Broadway ...
Rathdrum...
Bangor
53 21
52 40
52 30
51 45
52 3
52 52
32 47
52 20
52 7
54 2
54 21
55 8
55 15
54 49
54 21
54 12
54 7
54 13
53 56
53 36
53 26
52 51
51 54
52 16
52 13
52 55
54 39
Long. Hor. Int. Total Int.
6 16
8 35
9 41
9 31
9 31
8 43
7 48
7 41
8 16
6 11
6 39
6 40
7 15
7 28
7 38
8 26
9 7
9 57
9 52
9 40
9 18
8 58
8 26
7 8
6 24
6 14
5 42
•9399
•9443
•9441
•9511
•9503
•9427
•9824
•9530
•9591
•9275
•9172
■9277
•9086
•9056
•9070
•8998
•8959
•8906
•8990
•9051
•9191
•9386
•9597
•9512
•9615
•9422
•9154
r0203
1^0260
r0283
1-0300
1-0318
r0259
1-0279
1-0272
10250
1-0346
1-0303
1-0321
1-0316
1-0313
1-0274
1-0308
1-0270
1-0236
1-0209
10194
1^0137
1-0266
Of these results, those obtained at Templemore, Carlingford,
and Colerain, are not included in the computation of the lines.
174 EIGHTH REPORT 1838.
being manifestly affected by disturbing action. The disturb-
ance at the two latter stations is obviously due to the presence
of trap rocks.
In deducing the lines of total intensity, I have been guided
by the principles laid down in page 95 and seq.., and have ac-
cordingly assigned double weight to the results in Dublin and
Limerick, the weight of each of the other comparisons being
taken as unity. The results of the computation are as follows :
L = l-0268, M= + -0000748, N= +'0000501;
M=-33°48', r = -0000900;
L denoting the intensity at the central station (Lat. = 53° 21',
Long. = 8° 0'), the intensity at London being unity; M and N
the increase of the intensitj^, corresponding to each geographical
mile of distance in the direction of the two coordinates ; n the
angle which the isodynamic line, passing through the central
station, makes with the meridian ; and r the increase of the
intensity in the direction perpendicular to that line.
The lines of horizo)ital intensiti/ rest upon a somewhat
broader basis, there being four stations where the horizontal
force was observed without the dip. In deducing them, I have
given a weight of two to the results obtained at Dublin, Lime-
rick, and Markree, the weight of each of the other determinations
being unity. We find, accordinglj^,
L = '9290, M=— -000190, N= — -000368;
M=— 62°40', r=-000414.
Captain Ross's observations are contained in the following
table. They were made in the autumn of the year 1838, with
a single cylinder, designated as R (X) in the following pages.
The stations are twelve in number, and are distributed uniformly
over the island. The permanency of the magnetism of the
cylinder during this series, and its time of vibration at West-
bourn Green, near London, have been already shown in
Table LXIII.
MAGNETIC SURVEY OP GREAT BRITAIN.
175
Table LXXI.
Time of 100
Vibrations,
Mean
reduced to
Temperature
Waterford .
Cork
Valencia Island
Killarney
Limerick
Shannon Harbour
Dublin
Armagh
Londonderry
Markree
Westport
Edgeworth's Town
1838.
Oct. 3
— 4
— 6
— 7
— 8
— 12
— 13
— 17
— 18
— 19
— 22
— 23
— 26
— 29
Nov.
h. m.
42 3 P.M.
10 17 A.M.
5 32 P.M.
11 40 a.m.
38 P.M.
11 26 a.m.
10 26 A.M.
11 2 a.m.
11 40 a.m.
2 3 A.M.
10 22 A.M.
11 8 A.M.
Noon
8 41 a.m.
11 6 a.m.
9 35 a.m.
10 14 a.m.
11 28 A.M.
11 51 A.M.
7 59 A.M.
8 30 A.M.
4 32 P.M.
8 44 A.M.
11 41 A.M.
11 13 A.M.
11 17 A.M.
4 13 P.M.
32 P.M.
11 15 A.M.
15 P.M.
10 59 A.M.
56
56
54
63
54
54
53
52
52
52
58
60
62
54
57
50
52
50
50
40
41
42
43
52
51
44
43
45
42
45
44
287-18 "I
287-35 J
285-43
286-47
286-08
286-83 \
286-68 /
286-75"
286-96
286-65
286-87
288-33
288-47
287-98
288-18 j
290-35 1
290-52 /
288-82^
288-78 I
287-95 f
288-13 J
292- \
292-17/
295-181
295-07/
294-33 \
294-33 /
293-97 1
293-70 /
291-00/
291-28/
287-45
286-20
287-07
287-17
288-33
290-88
289-12
292-95
295-55
295-16
294-66
292-04
The following table contains the resulting values of the hori-
zontal intensity; those of the total intensity thence deduced,
and the latitudes and longitudes of the stations. The dips
employed in deducing the total from the horizontal intensities,
are given in Table XXXIX; the London dip used in the com-
putation is the mean dip at Westbourn Green (Table III.)j
reduced to the mean epoch of the present series.
176
EIGHTH REPORT 1838.
Table LXXII.
Waterford
Cork
Valencia
Killarney
Limerick
Shannon Harbour
Dublin
Armagh
Londonderry
Markree
Westport
Edgeworth's Town
52 16
51 54
51 56
52 3
52 40
53 14
53 21
54 21
55
54 12
53 48
53 42
Long.
7 8
8 26
10 17
9 31
8 35
7 52
6 16
6 39
7 20
8 26
9 29
7 33
Hor. Int. Total Int,
•9493
•9576
•9517
•9511
•94.35
•9270
•9383
•9140
•8979
•9003
•9034
•9196
b0205
1^0239
r0285
10271
10262
1-0287
1-0205
1-0296
10314
1-Q321
1^0345
r0264
In deducing the values of L, M, N, equal weights have been
assigned to all the results. The following are the values ob-
tained for the lines of total intensity.
L = 1-0276, M = +-0000858, N=- '0000671;
u=—38°(y, ?• = -000109.
For the lines of horizontal intensity, we find
L = -9269, M=--000138, N=— -000379;
'?<=:-70°0', r = -000403.
2. Satical Method.
Additional Observations. — The observations made according
to the statical method since the printing of the Irish Magnetic
Report, consist of my own observations in London and Dublin,
in the year 1836; Major Sabine's obsei-vations in Limerick,
Dublin, and Bangor, in the autumn of the same year ; a com-
parison of London and Dublin, by the same observer, in the
year 1838; and a series of observations, at eight distinct sta-
tions, made by Captain James Ross, towards the close of the
latter year. The details of my own observations, and of those
of Major Sabine, are given in the following tables. Captain
Ross's observations, as before, will be considered separately.
MAGNETIC SURVEY OP GREAT BRITAIN.
177
Table LXXIIT.
Mr. Lloyd's Observations, Needles L 3 and L 4.
Needle.
Station.
Date.
Hour.
Temp.
Angle.
April 11,1836.
h
12
18
o
57-5
/
-15 23-4
Dublin ■
- 15
12
30
530
-15 3-6
Mean.
12
24
55-2
-15 13-5
■
April 19
1
55-8
-18 43-5
05
_ 21
2
58
58-5
-18 47-6
1-^
London ■
— 22
12
30
59-2
-19 6-0
.2
Mean.
1
29
57-8
-IS 52-4
fu
■ May 7
1
32
57-2
-15 52-5
^
— 9
1
25
600
-15 52-5
Mean.
1
28
58-6
-15 52-5
Dublin <
Aug. 5
3
50
61-8 ■
-15 53-8
1
- 6
2
35
67-8
-16 9-2
1
I
Mean.
3
12
64-8
-16 1-5
April 11, 1836.
12
43
57-8
-13 26-4
D«bliii •
- 15
12
8
53-5
-13 21-0
Mean.
12
25
55-6
-13 23-7
April 19
1
28
56-8
-16 319
•V
— 21
2
37
58-5
-16 59-9
h-]
London •
— 22
12
14
60-5
-16 57-6
Ji
Mean.
1
26
58-6
-16 49-8
- May 7
1
10
56-5
-13 22-5
/?
_ 9
12
50
60-5
-13 18-4
Mean.
1
58-5
-13 20-5
Dublin ■
Aug. 5
3
28
61-8
-13 43-6
- 6
2
10
66-5
-13 34-4
Mean.
2
49
64-2
-13 390
178
EIGHTH REPORT 1838.
Table LXXIV.
Major Sabine's Observations, Needle S 2.
station. Date.
Temp.
Angle.
July 15, 1836.
o /
58-0
-1°7 32-8
— 15
57-0
- 17 25-9
Limerick
— 16
59-8
-17 21-5
Mean.
58-3
-17 26-7
r
July 22
54-0
-18 31-6
— 22
56-0
-18 28-1
Dublin
— 23
57-5
-18 22-7
Mean.
55-8
-18 27-5
Bangor
Sept. 21
500
-18 55-9
Dublin
Oct. 4
June 1, 1837.
490
58-0
-19 53-3
-17 521
r
— 1
58-0
-17 56-6
July 25
70-0
-18 7-4
— 25
73-0
-18 0-5
Mean.
64-8
-17 59-2
London -
Nov. 14
50-0
-17 12-8
— 14
50-0
-17 14-7
— 16
37-0
-16 53-7
— 16
37-0
-16 52-6
— 16
370
-17 0-6
Mean.
42-2
-17 2-9
■ July 31, 1838.
65-0
-14 29-1
— 31
650
-14 29-7
Dublin ■
Aug. 2
— 3
660
670
-14 19-8
-14 29-5
— 3
67-0
-14 260
\
Mean.
66-0
-14 26-8
' Oct. 12, 1838.
48-0
-17 321
— 12
48-0
-17 33-9
London -.
— 13
46-5
-17 18-3
— 13
46-5
-17 26-8
Mean.
47-2
-17 27-8
Correction of the Results. — The only correction which seems
necessary in the results already recorded is that due to the ef-
fect of temperature upon the needle S 2, the temperature-cor-
rection of that needle having been obtained by Major Sabine
subsequently to the publication of the Irish Magnetic Report.
This correction is small, the coefficient in the logarithmic for-
mula being only -000024*. The corrected results are given in
Table LXXV.
As the expression of the uitensity deduced by the statical
method is a function of the dip, as well as of the inclination of
the needle when loaded, it may be necessary to show that the
changes in the dip-corrections of the needles (page 104 and seq.)
• Sixth Report, p. 108. I
MAGNETIC SURVEY OF GREAT BRITAIN. 179
can have no sensible effect upon the deduced values of the in-
tensity.
The ratio of the intensity at any station to that at the base-
station being denoted by (f), we have (Fifth Report, p. 147,)
_ cos sin {Si ~ 6^
^ ~ cos 6, sin [h — 6)'
Hence, supposing S and S, to vary by any small and equal amount,
A h, the corresponding variation of <^ will be expressed by the
formula
^ = { cotan (S, ^ e;) - cotan {8-d)} AS.
Now the quantity, A S, is very small, and (where the stations
are not widely separate) the coefficient by which it is multi-
plied is likewise small; for such, stations, then, the result-
ing value of —^ is inconsiderable. On substituting the nume-
rical values of S, S^, 6, 6i, for the extreme stations of the present
series, it will be seen that the correction does not affect the fourth
place of decimals.
Values of the Intensity at the Base stations. — The following
is a summary of the comparisons of the intensity at London,
Dublin, and Limerick, as contained in Table LXXV.
Intensity at Dublin, referred to London :
Aug. Sept. 1834 . . . Needle L 4 Int. = 1-0194
Sept. Oct. Nov. 1835
April, May, 1836 . .
April, May, 1836 . .
June 1837, Oct. 1838
— L 4 — = 1-0212
— L 3 — = 1-0194
— L 4 — = 1-0189
— S 2 — = 1-0183
Mean . . =1-0194
Intensity at Limerick, referred to London :
June, July, Aug. 1834 . Needle L 4 Int. = 1-0262
Intensity at Limerick, referred to Dublin :
Aug. Sept. 1835 .. . — L 4 Int. = 1-0030
July 1836 — S 2 — = 1-0062
Mean . . = 1-0046
We have therefore (Fifth Report, p. 148),
a = 1-0194, h = 1-0262, c = 1-0046;
c^ = — = 1-0067, 0,-0= -0021 ;
A = 5, B = 1, C = 2.
180
EIGHTH REPORT — 1 838.
Substituting these values in the formulae of page 1.34 (Fifth Re-
port), we find
S.^■ = + -0003, Sy = - -0012 ;
.v = a + Sx = 1'0197;
1/ = h + Sy = 1-0250.
The results in the 6th column of the following table are deduced
from those of the 5th, by multiplying by one or other of these
numbers, according as the station has been originally compared
with Dublin or with Limerick.
The iveights due to the preceding determinations are given
by the formulae of page 170. Substituting the numerical values
of A, B, C, &c., we find
X = 5-7, Y = 2-4 ;
the weight of a single comparison being unity. Adopting the near -
est whole numbers, we may consider the deduced value of the in -
tensity inDublin as equivalent to the result of *<> separate compa-
risons j and that of the intensity in Limerick as equivalent to two.
Table LXXV.
Intensity of the Total Force.
station.
Date.
Needle.
No.
Intensity.
Intensity.
( London =1.)
August, 1834.
June, July.
S:^pt. 22—29.
L 4
3
3
4
10000
1-0262
1-0194
Dublin
Dublin
Sept. Oct.
Oct. 13.
— 14, 15.
— 20.
— 21.
— 23.
L4
5
1
2
1
1
1
1-0000
1-0166
1-0044
-9997
1-0151
l-OIOO
10197
1-0366
1-0242
1-0194
1-0351
1-0299
*Carlingford
Dublin
Aug. Sept. 1835.
Aug. 21.
— 22.
— 24.
— 25.
— 28.
— 28.
— 29.
— 31.
Sept. 1.
— s!
— 3.
L 4
5
1
1
1
1
1
1
1
1
1
1
1
1
1-0000
1-0197
Markree
10091 1 1-0290 1
Ballina
1-0077
10093
10096
1-0086
1-0055
1-0030
•9992
-9966
•9976
•9933
-9944
1-0276
1-0292
1-0295
1-0285
1-0253
1-0229
1-0189
1-0162
10173
1-0129
1-0140
Belmullet
Achill
Galway
Ennis
Limerick
Cork
VVaterford
Broadway
Gorey
Sept. Oct. 1835.
Sept. Nov.
L. 4
6
7
1-0000
1-0212
Bublin
* Evident local distuvbance at these two stations. The district about Cav-
lingfovd is intersected \Yitli trap djkcs ; Colevain lies within the basaltic field
of the North East gf Ireland.
MAGNETIC SURVEY OF GREAT BRITAIN*
181
station.
Date.
Needle.
No.
Intensity.
Intensity.
(I.ondon=l.')
July, Dec. 1835.
Nov, 8.
— 12.
— 18.
Dec. 10.
S. 2
5
1
1
1
1
1-0000
1-0083
1-0013
1-0091
1-0031
1-0250
10335
1-0294
1-0343
1-0282
Ballybunian
Dec. Jan. 1835.
Dec. 29.
S. 2
3
2
1-0000
■9970
1-0250
1-0219
Youghal
April, 1836.
April, May.
April, May.
L.3
L.4
L.3
L.4
3
3
4
4
1-0000
1-0000
1-0194
1-0189
Dublin
July 15, IG.
— 22, 23.
S. 2
3
3
1-0062
1-0000
Dublin
Dublin
Oct. 4.
Sept. 21.
S. 2
1
1
1-0000
1-0059
1-0197
10257
Junel837,Oct.l838
July, Aug. 1838.
S. 2
13
5
1-0000
1-0183
Dublin
The following Table contains tlie resulting values of the in-
tensity at each station, with the latitudes and longitudes of the
stations.
Table LXXVI.
station.
Lat.
Long.
Intensity.
Station.
Lat.
Long, 'intensity.
Dublin
53 21
52 40
54 2
54 21
55 8
55 15
54 49
54 12
54 7
54 13
53 56
53 17
6 16
8 35
6 11
6 39
6 40
7 15
7 28
8 26
9 7
9 57
9 52
9 4
1-0197
1-0250
1-0366
1-0242
1-0194
1-0351
1-0299
1-0290
1-0276
1-0292
1-0295
1-0285
52 51
51 54
52 16
52 13
52 40
52 55
52 30
51 56
52 8
52 52
51 57
54 39
8 58 ; 1-0253
8 26 1 1-0189
7 8 i 10162
6 24 1-0173
6 17 1 l-OlifS
liimerick
Carlingford...
Armagh
Colerain
Cam
Strabane
Markree
Ballina
Belmullet
Achill
Cork
Waterford ...
Broadway ...
Rathdrum ...
Ballybunian ..
Valentia
Dingle i...
Kiltanon
Youghal
Bangor
6 14
9 41
10 17
10 17
8 43
7 50
5 42
1-0140
1-0335
1-0294
1-0343
1-0282
1-0219
1-0257
Gal way
Of the foregoing results, those obtained at Carlingford and
Colerain are not included in the deduction of the isodynamic
lines, on the grounds already stated. To all the others equal
weights have been assigned ; the local en*or bearing* so large a
VOL. VII. 1838. N
182
EIGHTH REPORT — 1838.
proportion to the error of observation, that the resulting pro-
bable error is but slightly diminished by the multiplication of
the observations.
The following are the results of the calculation :
L = 1-0252, M = + -000095, N = + -000058 ;
?/= - 31° 20', r = -000111;
tlie central station being the same as before.
Captain Ross's observations of intensity (according to the
statical method) were made in the autumn of the year 1838,
with two needles designated as R L 3 and R L 4. They are
contained in the following Table.
Table LXXVII.
1
station.
Date.
Hour.
Temp.
Angle.
July 10 1838
— 12
— 12
Mean...
Oct. 4
h m
5
4
5
4 40
11
12
11 30
4 20
.5 40
15
1 35
2 58
30
1 20
11
12
15
2
1 8
40
2
1 20
10 10
11
10 35
45
2
1 22
3
4 30
3 45
68°
72
72
70-7
57
57
57-0
58
56
60
60
58-5
53
53
51
51
520
59
59
59-0
61
61
61-0
52
52
520
49
49
49-0
47
47
47-0
- 13 33-2
- 13 32-7
- 13 30-7
- 13 32-2
- 9 42-2
- 9 390
- 9 40-6
- 9 22-9
- 9 24-9
- 9 360
- 9 39-1
- 9 30-7
- 8 36-2
- 8 21-0
- 8 121
- 8 13-8
- 8 20-8
- 8 44-4
- 8 44-0
- 8 44-2
- 8 48-5
- 8 51-4
- 8 50-0
- 9 34-3
- 9 33-7
- 9 34-0
- 5 27-6
- 5 34-0
- 5 30-8
- 13 28-8
- 13 28-0
- 13 28-4
Waterford
Cork
Mean...
Oct. 6
_ 6
_ 7
_ 7
Mean...
Oct. 12
Killarncy
_ 12
_ 13
_ 13
Mean...
Oct. 19
_ 19
Mean...
Oct. 22
Dublin
_ 22
Mean...
Oct. 30
Londonderry ...
30
Mean...
_ 6
Mean...
Dec. 4
— 4
Mean...
MAGNETIC SURVEY OF GREAT BRITAIN.
183
Pi
9)
Station.
Date.
Hour.
Temp.
Angle.
July 7
h m
5 30
30
1 30
2 30
11 30
11 45
11 20
40
40
2
1 20
3
3 40
3 20
70°
70
70
70-0
52
52
520
51
51
51-0
45
45
45-0
45
45
45-0
- 2°6 38-4
- 27 1-9
-27 4-8
- 26 550
- 24 27-3
- 24 22-3
- 24 24-8
- 22 47-6
- 22 49-8
- 22 48-7
- 22 19-7
- 22 20-9
- 22 20-3
- 26 32-9
- 26 30-3
- 26 31-6
Dublin
12
_ 12
Mean...
Oct. 30
Londonderry ...
_ 30
Mean...
Nov. 6
— 6
Mean...
Nov. 14
— 14
Mean...
Dec. 5
_ 5
Mean...
With respect to these observations. Captain Ross observes :
"The I'eadings of R, L 4 at Dublin, with the letters on the needle
to the face of the instrument, gave 5° greater when facing the
east, and .5° less when facing the west, than the mean of similar
facings with the needle reversed on its axle. I therefore thought
that the axle had got some bend, and was totally ruined; and
accordingly used R L 3 always in future. But at Londonderry
I had some spare time, and thought I would try and find out the
cause of this error, for I was sure it had sustained an injury.
"At Londonderry the mean of the readings E. and W., with
the letters to the face of the instrument, was 2| degrees less
than the mean of similar readings with the needle reversed on
its axle. I therefore believe that some considerable irregularity
of the axle, about the point where the needle (with its letters
to face of instrument) should rest at about —7°; has occasioned
this error; and the circumstance of the Dublin observation
coming out right, is merely aftiidental. In all other parts of the
axle that I have tried, its readings agree very nearly with each
other."
Under the circumstances above detailed, it seems necessary
to reject the observations with RL 4 at Dublin and Londonderry.
The following Table contains the compxited results of the
foregoing observations, and the latitudes and longitudes of the
stations. Li making the computation, no correction for tempe-
rature has been applied to the results of R L 3 ; the logarithmic
correction of R L 4 is -000024.*
See pages 157 and 158.
N 2
184
EIGHTH REPORT — 1838.
Table LXXVIII.
station.
Lat.
Long.
Intensity.
Station.
Lat.
Long.
Intensity.
Waterford ...
Cork .
52 16
51 54
51 56
52 3
o /
7 8
8 26
10 17
9 31
10197
10211
10272
r0253
Limerick
Dublin
5°2 40
53 21
55
53 48
§ 35
6 16
7 20
9 29
r0243
1^0186
l^OSOl
10329
Valentia
Killarney
jLondonderry..
Westport
In deducing the position of the isodyiiamic lines from these re-
sults, equal weights have been assigned to all, for the reason al-
ready given. The following are the results of the computation :
L = 1-0256, M = -t- -000091, N = + -000067 ;
u= — 36° 29', r = -000113.
The results which have been above obtained respecting the
position of the isodynamic lines in Ireland, are combined in the
following Table :
Table LXXIX.
Observers.
Method.
No. of
Stations.
L.
M.
N.
Lloyd, Sabine, Ross..
Hor. Vibr. ...
Statical
20
22
12
8
r0268
r0252
r0276
r0256
•000075
•000095
•000086
•000091
•000050
•000058
•000067
•000067
Ross
Hor. Vibr. ...
Ross
In deducing the mean values from the preceding results,
we cannot, consistently with the character of the observations,
assign to each a weight in proportion to the number of stations
from which it is derived. If we compute the probable value
of the intensity at each station, and compare it with that ob-
served, we shall find that the differences are in general smaller
in Captain Ross's observations than in those of the two earlier
series ; so that the individual results are entitled to a greater
weight. This superiority is due, in great measure, to the cir-
cumstance that, in the latter series, all the observations were
taken by the same observer, with the same instrument, and
about the same time. On instituting a similar comparison
between the results of the two methods, it will be found that,
in Captain Ross's two series, the weight due to the results of
the statical method is very nearly double of that in the method
of vibration ; the probable errors being, nearly, in the ratio of
1 to V2. The same disparity between the methods is not
found in the results of the two earlier series, a fact wiiich
MAGNETIC SURVEY OF GREAT BUITAIN. 185
seems to be fully accounted for by the imperfection of the
instrument used by me in the statical observations, the eifect
of the magnetism of the limb (page 106 et seq.) being in this
case uncorrected.
The equations of condition afford the means of deducing
the weights of the preceding results, on the supposition that
there is no constant error. But as this cannot be supposed,
we are left to a certain extent unguided. On the whole, we
shall probably be not far from the truth in assigning equal
weights to each of the former results, notwithstanding the
disparity in the number of stations. The following are the
mean values thus deduced :
L = 1-0263, M = + -000087, N = + -000061.
Accordingly, the probable value of the intensity at the central
station (lat. = 53° 21', long. = 8° C) is
1 -05^63.
And from the mean values of M and N we obtain, for the di-
rection of the isodynamic line passing through that station,
M = - 35° C;
and for the rate of increase of the intensity in the direction
perpendicular to that line, _
r = -000106.
In order to reduce the intensity results of the present survey
to absolute measures, it is only necessary to determine the ab-
solute intensity of the magnetic force at some one of the base
stations, according to the method of Professor Gauss. This
will be done, ere long, in Dublin; and it is therefore important
that the ratio of the intensities in Dublin and London (with
which latter station all the others are compared) should be ac-
curately known.
For the determination of this ratio we have abundant mate-
rials in the present memoir. The ratio of the horizontal inten-
sities in Dublin and London, as deduced from the first series,
was found to be -9399 ; the result being equivalent to the mean
of eleven distinct comparisons. If we combine with this the
result obtained by Captain James Ross, namely, -9383, the
mean value of the horizontal intensity in Dublin is found to be
-9398;
the horizontal intensity in London being vmity. But the dip in
London corresponding to the mean epoch of these observations
(the 1st of January, 1837) is 69° 19'-6; and that in Dublin is
'71° 1''2 ; wherefore the total intensity in Dublin is
' 1-0201,
the total intensity in London being vmity.
Again, we have found that the intensity in Dublin, as de-
duced by the statical method from the observations made by
Major Sabine and myself, is expressed by the number 1-0197,
186
TAGtiTH REPORT — 1838.
the intensity in London being unity. The value of this ratio
obtained by Captain Ross in 1838 is 1-0186 ; and the former
result being equivalent to the mean of six distinct comparisons,
the final mean is 1-0195.
Of these results, deduced by the two methods, the difference
is only -0006 ; and we should therefore err very little from the
truth in taking their arithmetical mean. But the probable error
of a single comparison in the latter method is so much less than
in the former, that we shall certainly be nearer to the truth in
adopting the latter result. We shall accordingly consider the
number 1*0195 as expressing the ratio of the intensities of the
magnetic force in Dublin and London.
Report resumed by Major Sabine.
Collecting in one view the values of u and r resulting from
the several series of intensity observations, we have as follows :
Table LXXX.
Method.
Observer.
No. of
Stations.
Vfean Geog.Vosit.
«.
r.
Lat.
Long.
England .<
Scotland.-!
r
Ireland . . \
Statical ...
Statical ...
Statical ...
Hor. Vibr.
Statical ...
Statical ...
Hor. Vibr.
Hor. Vibr.
Statical ...
Statical ...
Hor. Vibr.
Hor. Vibr.
Lloyd
Phillips ...
Sabine
fRoss T
\ Sabine... \
[Lloyd ...J
Mean...
Sabine
Ross
Sabine
Ross
Mean...
r Lloyd....'
\ Sabine ... J
Ross
f Lloyd ...I
\ Sabine... \
[Ross J
12
24
20
27
52° 01
53 49
52 36
52 43
i 5'0
2 08
2 11
2 18
-54 49
-47 37
-52 27
-47 14
•000082
•000090
•000079
•000094
74
52 48
2 07
-50 48
•000086
19
9
21
12
56 22
56 52
56 30
56 56
4 01
2 45
4 10
2 58
-52 15
-40 38
-55 46
-43 32
•000136
•000106
•000143
•000125
61
56 40
3 30
-50 02
•000132
22
8
20
12
53 21
8 00
-31 20
-36 29
-33 48
-38 00
•0001 11
•000113
•000090
•000109
Mean...
62
53 21
8 00
-34 06
•000104
The values of u in England and Scotland, or the angle whicli
the isodynamic lines in those countries make with the meridian,
appear to be very nearly the same ; the difference in the mean
values is much within the order of the differences of the partial
MAGNETIC SURVEY OF GREAT BRITAIN. 187
results. But the values of r, or the rate of increase of the in-
tensity corresponding to equal geographical spaces, differ con-
siderably, and give a decided indication that the spaces between
the isodynamic lines are less in Scotland than in England. If
we examine the partial results obtained in the two countries by
the different observers, and by the different methods of obser-
vation, we perceive that all the series are consistent in this in-
dication. The lines which are selected for representation in the
map are those of unity (passing through London), of I'Ol, 1"02,
and 1-03 : the mean distance between the lines, which thus differ
•01 \i\ the values of the intensity they represent, is in England
116, and in Scotland 75 geographical miles ; the partial results
vary in England from 106 to 1^6 miles, and in Scotland from
69 to 94 miles.
Whatever may be the cause of this difference in the value of
r in the northern and southern portions of the island, it is obvi-
ously much too great to be taken as a regular part of a general
progression; as in its extension towards the N.W. and S.E., the
separation between the lines would in the one case be soon ren-
dered extravagantly small, and in the other extravagantly great.
In order to deduce the position of the several isodynamic
lines in best conformity with the observations, it is particularly
necessary, under such circumstances, to derive each line from
those observations only which are in its immediate vicinity ;
and thus to reduce within very small limits the effect on each
of the rapidly-changing and somewhat uncertain values of r.
We require, for this purpose, only its approximate values
in the vicinities of the respective lines ; and without entering
into nice calculations where we have not a sufficiently satisfac-
tory basis, we may provisionally assume these values as follows ;
always remembering, that any inaccuracy in the assumption will
produce an opposite effect on the deductions from the observa-
tions which are on either side of each isodynamic line, and that
such opposite effects will counterbalance each other in the mean
position assigned to the line.
Approximate values of r in England and Scotland, in the vici-
nity of the several isodynamic lines :
Line of 1-0 , r= -00008
.... 1-01 ; r = -00009
.... 1-02; r = -00011
.... 1-03; ?• = -000135
The mean value of r in Ireland, derived from the several
series in that country, is -000104 or -000106, (page 185,) which
corresponds so nearly with the value which might be interpo-
lated from the results in England and Scotland for the latitude of
the central geographical position in Ireland, that we may safely
take "00010 as a general value for the Irish deductions.
188 EIGHTH REPORT — 1838.
If we compare the mean value of u derived from the Irish
series, — 34° 6' (varying in the several partial results from
- 31° 20' to -38° 00'), with its mean values in England and
Scotland — 50°, (the partial results varying from — 40° 38' to
— 55° 46'), we find, notwithstanding the amount of the partial
differences, a general and consistent indication that the isody-
namic lines are less inclined to the meridian in Ireland than in
Great Britain, The two Irish series which give the least values
for this angle, are those which were the earliest obtained, —
which had consequently the disadvantages of less experience in
the observers, and less perfection in the instruments ; and of
combining in one series observations at different epochs, and
results by different observers, and with different instruments.
The two series of Captain Ross were, on the other hand, ob-
tained by one observer with the same instruments ; were well
distributed over the country ; and were made in immediate
and rapid succession. We may therefore safely infer, as Mr.
Lloyd has done (pages 184, 185), that the values of u derived
from Captain Ross's series are entitled to weight beyond the
proportion which the number of the stations wliich they repre-
sent bears to the number of stations in the other Irish series.
Still the difference in the angle with the meridian in Ireland and
in Great Britain cannot, in any consistency Avith the observa-
tions, be less than several degrees. I have employed — 35°,
the value deduced by Mr. Lloyd, pages 184 and 185, as the
general mean value of u in the Irish deductions.
If we compare generally the mean results of the horizontal
with those of the statical series, we are not able to discover any
ap])arent systematic differences whatever in regard to the values
of u and r. The individual observations by the horizontal me-
thod do indeed exhibit much greater discordances with each
other than is the case in the statical method. This has been
already shown in detail in the analysis of the observations by
the two methods in Scotland, in pages 20, 21, of the Sixth
Report of the British Association : and Mr. Lloyd has else-
where pointed out the causes of the advantage in this re-
spect of the method for which we are indebted to him. Al-
though, therefore, the accordance of the two methods, when
the observations are grouped, is a satisfactory confirmation of
the conclusions which they unite in estabhshing, the horizontal
observations are less fitted than the statical to be employed in
a graphical representation of the particular nature adopted in
this report, in which the discordances of individual observa-
tions are brought strongly into notice, and if exceeding a cer-
tain limit might produce inconvenience, by in some degree
perplexing the judgment. In extreme cases they might entirely
mislead it; as, for example, if the point furnished by an obser-
vation for a particular line should fall nearer to an adjacent
MAGNETIC SURVEY OF GREAT BRITAIN.
i8d
line than to the one to which it really belongs ; and this will
occur whenever, from accidental causes of any kind, the dis-
cordance exceeds in amount half the interval between the lines
which are represented. Such extreme cases are frequent in the
horizontal observations ; but are of very rare occurrence in the
statical. Of the 114 statical results, there are only five which
have been omitted in the graphical representation; (though of
course included in the table). Four of these are, Ballybunian,
Dingle, Gorey, and Rathdrum, all in the south of Ireland, and
amongst our earliest observations. The two first named were
my stations, and the intensity is in excess ; — the two others
were Mr. Lloyd's stations, and the intensity is in defect of the
general body of the results ; the omission of the four should
consequently have no effect on the position of the lines.
The fifth observation omitted in the map is Captain Ross's
at Berwick, which would furnish a point for the line of 1 'Oo in a
geographical position which is nearer the line of 1'02.
The evidence supplied by the collective horizontal observa-
tions is, however, too valuable to be dispensed with in the
representation. I have collected in the following Table the
values of the intensity derived, for the respective mean geogra-
phical positions, from the combined observations of each series,
both horizontal and statical. In the map the central stations
are designated thus, +, with the initial of the observer an-
nexed ; and the points furnished by the respective intensities
for the nearest adjacent line thus, ^, with H or S', according
as the series was horizontal or statical, and a figure is added
expressing the number of stations contributing to the result.
In Ireland the ope central station has been taken by Mr.
Lloyd as common to all the series, and the initials of the ob-
server, therefore, are transferred to the points.
Table LXXXL
statical.
Horizontal.
s
Mean Geogra-
V
Mean Geogra-
u
phical Position.
Intensity.
1
phical Position.
Intensity.
Lat.
Long.
Lat.
Long.
p
53 49
o /
2 08
1-0136
R^
o /
o
s
52 3fi
2 11
1-0075
s i-
52 43
2 18
10087
L
52 01
1 50
1-0048
I^ 1
s
56 2-2
4 01
10390
s-
56 30
4 10
1-0285
R
.56 52
2 45
1-0277
R
50 56
2 58
1-0302
U
53 21
8 00
10252
n
53 21
8 00
1-0268
K
53 21
8 00
1-0256
R I
I
R
53 21
8 00
1-0276
190
EIGHTH BEPORT 1838.
The General Table of the intensity results by the statical
method is analogous to the General Table of the Dip observa-
tions : it appears, therefore, to require no separate explanation.
The intensities which exceed 1 "035 belong to the line of 1*04,
of which no representation has been attempted, because the
results on which it would rest are all, with a single exception,
on one side of the line. The stations to which these results
belong are, however, retained in the map, and are accom-
panied in each case by the numerical value of the observed
intensity.
General Table.
Intensity. Statical Method.
OBSERVATIONS.
DEDUCTIONS.
Long.
Intensity. ' h]
Isodynamic Line
of 1-03 in
Long.
Lerwick '60 09
Kirkwall '59 00
Gordon Castle... 57 37
Golspie ...
Inverness
Loch Slapin 57 14
Carn 55 15
57 58
57 28
1 07
2 58
3 09
3 57
4 11
6 02
7 15
1-0358 n
10373 '
1-0380 ,i
10360 I
1-0382 "I ;
] -0378 /
10427 j;
1-0351 1
These stations belong
to the isodynamic line of
1-04, which is not drawn
in the map.
Berwick 55 45
Aberdeen 57 09
Alford 57 13
Newport 56 25
Kirkaldy j 56 07
Blairgowrie 56 36
Braemar
Dunkeld
Helensburgh.
Cumbray
Glencoe
Loch Ranza .
CampLelton .
Bangor ,
Londonderry.
Strabane
Markree
Kiltanon
Ennis
Galway ,
Ballina
Westport
Killarney .....
Ballybunian ..
BelmuUet
Achill
Valencia
57 01
56 35
56 00
55 48
56 39
55 42
55 23
54 40
54 59
54 49
54 12
52 52
52 51
53 17
54 07
53 48
52 02
52 30
54 13
53 56
51 56
Dingle 52 08
00
05
45
55
09
18
25
33
41
52
5 07
5 17
5 38
5 40
7 19
7 28
8 26
8 43
8 57
9 04
07
29
.30
41
57
52
10 17
10 17
R
R
S
S
s
s
s
R
s
s
s
s
s
s
R
L
L
s
L
L
L
R
R
S
L
L
{«
1-0254
10268
10294
1-0277
1-0279
1-0310
1-0269
1-0267
1-0258
1-0287
1-0324
1-0261
10296
1-0257
1-0301
1-0299
1-0290
1-0282
10253
1-0285
1-0276
10329
1-0253
1-0335
10292
10295
1-02941
1-0272/
1-0343
'+25I+39I56 10
+ 181+28 57 27
+ 4+ 5' 57 17
+13+20|56 38
1+11+17 56 18
- 6|- 9 56 30
+ 171+26 57 18
+ 19+28,56 54
+23 +36] 56 23
+ 8+12:55 56
-13|-20 56 26
+22+33 56 04
+ 2+ 3 55 25
+25 +57I 55 05
- 1:54 58
+ 1 54 50
+ 13 54 18
2 39
2 33
2 50
15
26
09
51
01
17
04
- 1
1+ 1
'+ 6
1+10
■+28
1+ 9
+ 13
-17
1+28
1-21
53 02
53 19
53 26
54 20
53 31
52 30
52 09
54 18
53 59
52 05
-251-58 51 43
+23
+64
+20
+32
-39
+64
-48
+ 5+11
!+ 3!+ 7
i+ 9|+22
4 47
5 50
5 41
6 37
7 18
7 29
8 39
9 06
10 01
9 24
9 39
8 50
10 34
8 53
10 08
9 59
10 39
9 19
MAGNKTIC SURVEY OF GREAT BRITAIN.
i9i
General Table — {continued).
OBSERVATIONS.
Thirsk
Newcastle
Alnwick Castle...
Dryburgh
Melrose
Stonehouse
Penrith
Carlisle
Bowness
Patterdale
Coniston
Edinburgh
Whitehaven
Glasgow
Jordan Hill
Douglas
Castleton
Peelton
Loch Ryan
Dublin
Broadway
Armagh
Waterford
Yougbal
Cork
Limerick
54 14
54 58
55 25
55 34
55 35
54 55
54 40
54 54
54 22
54 32
54 22
55 57
54 33
55 51
55 54
54 10
54 04
54 13
54 55
53 21
52 13
54 21
52 16
51 57
51 54
52 40
Long.
1 21
1 37
1 42
2 39
2 44
2 44
45
54
55
56
05
II
33
14
4 21
6 16
6 24
6 39
7 08
7 50
8 26
8 36
P
{t
S
s
{t}
p
p
p
p
p
s
s
s
p
k
L
L
s
Intensity.
0155
01731
0165 I
0147 1
0159
0199
0208
0173-1
0176/
0184
0198
0182
0181
0196
0231
0176
0232
0236 \
0259 J
0208
0203
0192
0221
0195
0173
0242
0162 1
0197/
0219
0189 1
0211 J
0250 \
0243/
DEDUCTIONS.
+31
+26
+28
+ 1
- 6
+17
+11
+ 1
+13
+14
+ 3
-22
+ 16
-23
-34
- 6
- 2
+ 6
-15
+ 3
+15
-24
+ 12
-11
-27
+45
+38
+41
+ 1
+25
+16
+ 2
+18
+19
+ 4
-31
+24
-32
-48
- 3
+ 8
-21
+ 7
+36
-57
+26
-25
-63
Isodynamic line
of 1-02 in
Lat. Long.
54 45
55 24
55 53
55 35
55 29
55 12
54 51
54 55
54 35
54 46
54 25
55 35
54 49
55 28
55 20
54 04
54 02
54 19
54 40
53 24
52 28
53 55
52 28
51 46
51 54
52 13
2 06
2 15
2 23
2 40
2 36
3 09
3 01
2 56
3 13
3 15
3 09
2 40
3 57
3 42
3 33
4 19
4 37
4 51
4 37
6 23
7 00
5 42
7 34
7 25
8 26
7 33
It
192
ICIGHTH REPORT — 1838.
General. Table — {continued).
OBSERVATIONS.
Flamborough
Scarborough
Whitby
York
Doncaster
Hambleton
Osmotherley
Sheffield
Birmingham .. ..
Shrewsbury
Calderstone
Birkenhead
Coed
Brecon
Merthyr
Dunraven Castle
Aberysthwith
Holyhead
Rathdrum
Gorey
54 08
54 17
54 29
53 58
53 31
54 20
54 22
53 22
52 28
52 43
53 23
53 24
53 11
51 57
51 43
51 28
52 24
53 19
52 55
52 41
Long.
08
24
37
1 05
1 07
1 15
1 18
1 31
53
12
21
21
37
05
37
6 12
6 15
Intensity.
1-0083
10103
10135
10126
1-0096
10134
1-0128
10124
1-0105
1-00771
1-0057/
1-0106
1-0112-1
1-0145 ]■
1-0110
1-0060
1-0081
1-0078
1-0100
1-0144
1-0140
1-0129
DEDUCTIONS.
+14
- 3
-29
-22
+ 3
-28
-24
-20
- 4
+27
- 5
-24
- 8
+35
+ 17
+20
-38
-34
-25
+19
- 4
-43
-31
+ 5
-41
-34
-28
- 6
+38
- 7
-33
-12
+46
+23
+26
-53
-48
-34
Isodynamic line
of 1-01 in -
Lat. Long,
54 22
54 14
54 00
53 36
53 34
53 52
53 58
53 02
52 24
53 10
53 18
53 00
53 03
52 32
52 00
51 48
52 24
52 41
52 21
52 16
27
20
-0 04
34
12
34
44
1 03
1 47
3 23
2 46
2 27
TH
Margate
Dover
Lynn
Eastbourne ...
Cambridge
Brighton
Worcester Park
Eastwick Park
Tortington ....
St. Clair's
Ryde
Salisbury
Combe House
Clifton
Chepstow
Hereford
Lew Trenchard
Falmouth
51 23
51 08
52 47
50 47
52 13
50 50
51 23
51 17
50 50
50 44
50 44
51 04
51 31
51 27
51 38
52 04
50 40
50 09
Long.
-1 23
-1 19
-0 25
-0 16
-0 07
08
17
19
34
5 06
S
S
L
F
L
L
S
F
S
P
L
L
F
L
L
L
S
{I
Intensity.
0-9970
0-9945
1-0030
0-9937
1-0001
0-9955
1-0006
0-9993
0-9990
1-0002
0-9972
1-0006
1-0026
1-0030
10041
1-0046
1-0045
1-0018 1
1-0015/
Isodynamic line
of I 00 in
Lat. Long.
+29+39
+53+70
-29-39
+5r+68
- 1 - 1
+ 44'+58
-6-7
+ 7; +
+10+13
-2-2
+27+35
- 6- 7
-26-34
-29-39
-40-53
-44-59
-43;-56
-17-22
51 52
52 01
52 18
51 38
52 12
51 34
51 17
51 24
51 00
50 42
51 11
50 58
51 05
50 58
50 58
51 20
49 57
49 52
-0 44
-0 09
-1 04
52
-0 08
1 06
10
27
47
1 06
1 45
4 44
MAGNETIC SURVEY OF GREAT BRITAIN.
193
Extension of the Isoclinal and Isodynamic Lines into Meri-
dians East and West of the British Islands.
Having thus completed the representation of the principal
lines of dip and intensity passing across the British Islands, it
appears desirable to trace their prolongation on either side,
until they are brought in connexion with the lines of the same
value in adjacent meridians to the east and west, as determined
by recent and satisfactory observations. As a single line of
each of the phenomena will suffice to exhibit this connexion, I
have selected for that purpose the isoclinal line of 70°, and the
isodynamic line of 1 "03.
In Plate III. the portion of the isoclinal line, which is repre-
sented by an unbroken line, has been determined by the ob-
servations contained in this report. In its eastern prolongation
it passes through countries where its position is well assured
by observations of higher amount on the one side, and of lower
amount on the other, too numerous for insertion in a map on
so small a scale, and too well known to need a recapitulation
here. Towards the north-eastern extremity of the map, the
position of Gros Novgorod is marked in lat. 58° 31' and long.
31° 19', where M. Erman observed the dip 70° 26'-l on the
13th of July, 1828. This observation, reduced to January
1837, by allowing an annual diminution of 3', becomes 70° O0'"6:
the line of 70° is therefore made to pass through this station.
To the west of the British Islands, the line is prolonged until
it is brought in connexion with M. Erman's observations on
his homeward passage, in August 1830. For this purpose I
have formed M. Erman's observations into two groups, each
of three stations, as follows :
1830.
Lat.
Long.
Dip.
Aug. 19
o /
41 27
/
.327 25
/O 03-6 1 o ;
69 47-6 \ 70 19-4
— 20
42 29
328 34
— 21
44 22
330 55
71 07-1 J
— 22
4G 46
335 42
70 18-3]
— 24
47 47
343 58
69 460 \ 70 06-3
— 23
47 46
344 25
70 14 9 J
Allowing, as in Britain, an annual decrease of £'-4, the dips in
January 1837, corresponding to the mean positions of these
groups, are as follows :
194
EIGHTH REPORT— 1838.
Lat.
Long.
Dip.
o /
42 46
47 26
328 58
341 2,2
70 04
69 51
These positions are marked in the Map, and the isoclinal line
of 70° is prolonged to the westward in correspondence with
the mean of M. Erman's observations thus corrected for
epoch.
To connect the isodynamic line of TOS with intensities of
the same value in the adjacent meridians, it is necessary to ex-
press the value of this line in terms of the arbitrary scale em-
ployed by Continental observers, in which the force in Lon-
don = 1*372. In this scale the line of 1'03 corresponds in value
to (1-03 X 1-372 = ) 1-413. The portion of this line which is
represented in the Map by an unbroken line has been deter-
mined by the observations contained in this report. Its pro-
longation to the eastward is traced in conformity with M.
Hansteen's observations in Norway, and with MM. Han-
steen's and Erman's in Russia. The station mai'ked in lat.
60° 11' and long. 10° 20' is the mean geographical position of
a group of six stations in Norway, not far removed from each
other, for which M. Hansteen's observations in 1821, 1823,
and 1825, gave a mean intensity of 1*414 (7th Report, British
Association, page 49). At Gros Novgorod (lat. 58° 31', long.
31° 19') the determinations of MM. Hansteen and Erman ac-
corded in assigning 1*412 as the value of the force (7th Report,
British Association, page 51), and the line has been still fur-
ther extended, in conformity with the observations of the same
gentlemen at Moscow, in lat. 55° 46', and long. 37° 36', their
mean determination being 1*405. The position of the line in
its western prolongation has been drawn in conformity with the
values of the intensity at the islands of Terceira and Madeira,
contained in the general table of the memoir on the magnetic
intensity already referred to, viz.
Terceira . Fitz Roy . . 1836 . . . 1*457
,- , . rSabine ... 1822 .. . 1-373"! , ^^^
Maden-a j^j^^ ^ _ ^ IS^g ^ ^ ^ i.3.^|l*3/5.
Both stations are included in the Map. The values of the
force at M. Erman's dip stations in the same quarter, deter-
mined by the same excellent observer, are also inserted in the
map, as affording corroborative evidence of the correct position
of the isodynamic line in this its western extension.
MAGNETIC SURVEY OF GREAT BRITAIN.
195
In order to render the view in this Map of the magnetic
phenomena in the British Islands more complete, I have added
the direction, shown by arrows, of the horizontal or compass
needle at three extreme stations, determined by Captain James
Clark Ross, viz. Lerwick, in the Shetland Islands ; Valencia,
at the S.W. extremity of Ireland ; and Bushey, near London.
The geographical positions of these stations, and the variations
observed at them, are as follows, the latter being the mean va-
riation at the epoch named, obtained by observations repeated
every fifteen minutes from 7 a.m. to 7 p.m. for several succes-
sive days.
Station.
Date.
Lat.
Long.
Variation.
Lerwick .
Valencia .
Bushey .
July 26, 1838
Oct. 13, —
April 3, —
60 09
51 56
51 38
1 07 W.
10 17 W.
22 W.
2°7 08 35 W.
28 41 52 W.
23 59 24 W.
196
REPORT ON THE MAGNETIC ISOCLINAL AND ISODY-
NAMIC LINES IN THE BRITISH ISLANDS.
TABLE OF CONTENTS.
Introduction page 49
Division I. Dip.
Errors of dipping needles, and recent improvements 51
Annual alteration of the Dip 62
Dip in London, May 1S3S 64
Sect. L Observations in England 67
Sect. 2. Observations in Scotland 86
Sect. 3. Observations in Ireland. (This section is by Mr. Lloyd.) 91
Summary, and deduction of the Isoclinal lines 120
General table of the Dip observations 125
Division II. Intensity,
Sect. 1. Observations in f § 1. Statical method 138
{
England. ... 1§ 2. Method of horizontal vibrations . . 148
Sect. 2. Observations in f § 1. Statical method 155
Scotland . . \§ 2. Method of horizontal vibrations . . 161
Sect. 3. Observations in f § 1. Method of horizontal vibrations . . 165
Ireland .... \ § 2. Statical method , 176
(Section 3 is by Mr. Lloyd.)
Summary, and deduction of the Isodynamic lines 186
General table of the Intensity observations, by the statical method 190
Conclusion.
Extension of the Isoclinal and Isodynamic lines into meridians east
and west of the British Islands 193
RAILWAY CONSTANTS. 19/
Mrsi Report on the Determination of the Mean N'umer'ical
Values of Railway Constants. By Dionysius Lardnbr,
LL.D. F.R.S., 8}c.
It will be in the recollection of the Members of the Mechani-
cal Section of the British Association, that the circumstance out
of which this inquiry arose, was the discordance of opinion
which prevailed ainong the members of the Section, including
several engineers and other practical men, on the subject of the
amovmt of the resistance to the tractive power offered by trains
on railways ; this resistance being variously estimated at six,
seven, eight, nine, and even ten or twelve pounds per ton of the
gross load.
The resistance to the motion of a train of wagons or coaches
on a level and stx-aight line of rails arises from the following
causes :
1°. The friction of the axles with their bearings.
2°. The resistance to the rolling motion of tlie tires on the rails.
3°. The friction of the flanges with the rails bi'ought into oc-
casional contact with the latter by the lateral oscillation of the
carriages.
4°. The resistance of the air.
If the line of rails be curved, another source of resistance arises
from the pressure and consequent friction of the flanges of the
outer wheels on the rails, which combined with the effects of
the conical form of the tires, is in fact the force by which the
direction of the motion of the train is continually changed.
If the line be inclined at any given angle to the horizon, the
resistance will be modified by the gravitation of the load in a
manner which is easily inferred from the elementary principles
of mechanics.
The practical importance of ascertaining the proportion in
which the whole resistance is distributed among these several
sources is evident. It is only by determining this that the en-
gineer can be guided in the selection of means for reducing
that resistance ; and the importance of reducing it will be un-
derstood, when it is considered how large an item in the expen-
diture of railway companies is locomotive povver, and that the
amount of this power is, ceteris paribus, in the exact proportion
of the resistance of the loads which it draws.
The first question to which the present inquiry has been di-
rected was, to determine what the total resistance which is pro-
VOL. vii. 1838.
198 EIGHTH REPORT — 1838.
duced on a straight and level railway by the combination of all
the above-mentioned causes. It is a matter of regret that the
obstacles to experiment which are produced by the great amount
of traffic on the principal railways are sucli that, notwithstanding
the lapse of time wliich has taken place since the commencement
of this inquiry, means have not been obtained for making such
an extensive and various course of experiments as would be sufli-
cient to solve this question. Besides the obstacles produced by
the traffic on the different lines of railway, difficulties also arose
in obtaining the means of experimenting, owing in some cases
to the inability of railway companies to spare the necessary en-
gines, carriages, and wagons. It is nevertheless due to these
companies to state their general willingness to facilitate the in-
vestigation, and this acknowledgement is especially due to the
Boards of Directors of the Grajid Junction and the Liverpool
and Manchester Railway Companies.
Three methods for discovering the amount of resistance op-
posed by a train to the tractive power have been proposed :
1". By a djmamometer, interposed between the tractive power
and the load, which should measure and record the force exerted
by the tractive power in drawing the load along a level and
straight line of railway.
2°. By observing the motion of a load down an inclined plane
sufficiently steep to give it accelerated motion, and comparing
the rate of its acceleration with that which it ought to receive
from gravity, if it were subject to no resistance.
3°. By putting a load in motion on a straight and level line
of railway, so as to impart to it a certain known velocity, and
then permitting it to run until it is brought to rest by the re-
sistance gradually destroying the velocity imparted to it.
Each of these methods of experimenting was attended with
difficulties and objections. In practice, a line of rails is never
truly level. That which is commonly called level is a line
which, being examined from point to point at intervals — say of
quarter miles, is found neither to rise nor fall upon the whole.
But the surface of the rails along the intermediate parts is sub-
ject to considerable departures from an uniform level. How-
ever accurately they may have been laid when the line is first
constructed, the traffic upon them soon impairs their evenness,
and the inequalities of level become so considerable, that it fre-
quently happens that a wagon will not rest in certain positions
upon them, but will roll until its wheels get at the lowest point
of a part of the rail which has sunk. In the use of any form
of a dynamometer this circumstance produces extreme variations
in the index, so much so that in most of those which have been
RAILWAY CONSTANTS. 199
tried, the index oscillates between zero and the extreme limit of
its play.
Besides this difficulty, which, from the nature of the resist-
ance, would appear to be inseparable from every form of dyna-
mometer, another will arise if it be admitted that the atmo-
sphere have any considerable share in producing the resistance
which the tractive power has to overcome. The dynamometer
must be interposed between the engine and tender, or between
the latter and the first coach or wagon in the train ; or, to speak
more generally, it must be immediately before the coach or
wagon whose resistance it is used to measure, and must be
behind the engine, tender, or carriage which precedes that load.
It is evident that, under such circumstances, the atmospheric
resistance will produce only a modified and partial effect on the
dynamometer; nor will this instrument, under such circum-
stances, exhibit a true estimate of the resistance arising from
friction alone, independently of the atmosphere, since the effect
of the atmosphere is only partially intercepted by the preceding
part of the train.
The only manner in which the dynamometer could be used
with any prospect of obtaining a tolerably correct and satisfac-
tory result, would be to construct it in such a manner as to re-
gister its own indications, by describing a curve on paper with
a pencil moved by the index of the instrument, so that the ordi-
nate of this curve would represent the resistance, and the cor-
responding abscissa the point of the road where that resistance
was produced. If the instrument thus constructed were applied
with so very slow a motion as to render the atmospheric resist-
ance so small that it might be practically disregarded, then the
mean value of the ordinate of the curve, or, what is the same,
the area of the curve divided by its abscissa, would express the
mean amount of the resistance.
The second and third methods of experimenting are those
which have been hitherto generally used for the practical deter-
mination of the resistance of railway trains to the tractive power.
The combination of both has been resorted to by M. de Pam-
bour in the following manner : — He placed the cai-riages whose
resistance was to be determined upon a steep inclined plane,
having a line nearly level at its foot, and allowing them to move
by gravitation from a state of rest, they attained a certain velocity
at the foot of the plane ; with this velocity the carriages moved
along the level until they were reduced to a state of rest. It
was then assumed that the resistance was represented by the
ratio of the difference of absolute levels of the point from which
they started and the point at which they stopped, to the di-
o 2
200 EfGHTH RElPOttT 1838.
stance, measured along the rails, between thfe same points. This
method would be unobjectionable if the resistance was, as M. de
Pambour and most others at that time supposed it to be, inde-
pendent of the velocity. But we shall show presently that, so
far from this being the case, it has a dependence on the velocity
which renders this method of experimenting altogether falla-
cious.
The foUowuig method of experimenting, with a view to the
determination of the amount of the resistance due to friction,
occurred to the reporter as being subject to fewer objections than
any of the methods above mentioned.
Let two inclined planes of diflferent acclivities be selected.
Let h = the gradient of the steeper plane, expressed by the sine
of its inclination, or the numerical ratio of its height to its
length.
Let /i' = the gradient of the other plane, similarly expressed.
Let L = a load which an engine, with an observed pressure of
steam in the boiler, and the regulator open to an observed
point, is capable of moving up the steeper plane at a slow uni-
form rate ; and let L' = the load which the same engine, in pre-
cisely the same state, is capable of moving up the other plane
at a slow uniform rate.
The resistance on each plane will be the sum of the gravity
of the load down the plane and the friction. Now if F repre-
sent the friction on the former, and F' on the latter, the resist-
ance on the former will be
L A + F,
and the resistance on the latter will be
L' h< + F.
Since these two resistances are balanced respectively by the
tractive power of the same engine in the same state, they must
be equal. Hence we have
LA + F = L'/i' + F
•.• F'-F = LA-L'A'
F-F _ LA -L 7t
'•" L' - L ~ L' - L *
But F' — F l)eing the difference between the friction of L' and
L, tlie first member of this equality will be the ratio of the fric
tion to the lead. If this be expressed by/, we shall therefore';
have
•^ ~ L'-L > ''^
RAILWAY CONSTANTS. 201
To reduce this to experiment it is onlj' necessary to attach to
an engine a train of loaded wagons, and so to adjust the load
and the engine that the latter shall be just capable of drawing
the former up the less steep plane with a slow uniform motion.
Let it then be taken to the steeper plane, and let such a number
of wagons be detached as will enable the engine, all things being
as before, to draw the remainder slowly and uniformly up the
steeper plane. If then for L' in (1) be substituted the former
load, for L the latter, and for h and A' the gradients of the two
planes, the numerical value of/ will be obtained by the fomnula
(1), and this will be the ratio of the friction to the load for the
wagons or carriages, which were detached to enable the engine
to draw the load up the steeper plane.
It is evident that this experiment may be varied by altering
the tractive power of the engine, which may be done within
practical limits, by vaiying the pressure of steam in the boiler,
and the extent to which the regulator is opened. This will
produce a corresponding variety in the values of L and L', and
in this way various experiments may be made on the same pair
of planes.
In this mode of experimenting it is not necessary that the ac-
tual pressure of steam on the pistons be known. All that is
indispensable is, that on both planes the tractive power of the
engine be the same.
The equality of the tractive power would be more satisfac-
torily insured if the pressure of steam in the cylinders could be
measured and recorded, but no means have yet been contrived
for accomplishing this in locomotive engines. The pressure of
steam in the cylinders, however, depends on, 1°, the pressure
of steam in the boiler; 2°, the extent of the opening of the
regulator or steam valve; 3°, on the velocity of the piston.
These will be the same, if in both cases the motion of the engine
be slow and uniform, the regulator be equally open, and the
steam-guage show the same pressure.
The limits of error depend on the practicability of trimming
the load so as to accommodate it to the same tractive power of
the engine. If the train on the less steep plane consist of a
great number of wagons, this may be done very nearly by
casting off a certain number of them on the steeper plane ; but,
if necessary, the load of the wagons remaining may be trimmed
by the addition or subtraction of weights.
On the Grand Junction Railway, between Madeleyand Crewe,
there is a succession of three planes which are well adapted for
this method of experimenting : proceeding from Crewe, the first
ascends at the mean inclination of 1 in 330, the second at 1 in
260, and the third 1 in 178.
202 EIGHTH REPORT — 1838.
As it is necessary to observe with some precision the pressure
of steam in the boiler, during experiments made according to
this method, the writer of this report constructed a self regis-
tei'ing steam-guage for the purpose.
A smaller cylinder in which a piston is accurately fitted, simi-
lar to the cylinder and piston of common " indicators," is let
into the boiler at a place near the position of the engineer. The
piston-rod is carried through a tube outside the boiler, in which
it is made to act on a spiral spring, the force of which is op-
posed to the motion of the piston, when driven upwards by the
pressure of the steam. The position of the piston being deter-
mined by this spring becomes an indication of the pressure of
steam, and so far the instrument is a mere steam-guage.
Attached to a part of the piston-rod is a pencil, the point of
which is lightly pressed against the surface of a drum or cylin-
der which stands over the boiler and near the steam-guage.
This drum is covered with paper rolled repeatedly round it, and
gradually discharged from it to a small roller placed beside it, and
pressed by a spring against it. On the axis of the drum is fixed
a worm-wheel, which is driven by an endless screw. The latter
receives its motion from a ratchet-wheel, in which a claw or
catch acts. This claw is alternately raised and drawn down by
some part of the machinery which has a reciprocating motion,
so that for each stroke of either piston the ratchet-wheel is
pulled through a space equal to one, two, three, or more of its
teeth, according to adjustments which are provided in the appa-
ratus. In this manner the drum receives a slow motion of ro-
tation, bearing a known relation to the revolution of the driving-
wheel, and therefore to the speed of the engine. By such means
the drum may be made to revolve once in a quarter of a mile, or
any other given distance.
If the pressure of steam in the boiler remain unvaried, the
pencil will continue in the same position, and the paper moving
under it will receive the mark of a straight and horizontal line
at a certain height, which, by a scale previously adjusted, will
express the pi*essure of steam in lbs. per square inch. If, how-
ever, the pressure of the steam vary, the pencil will have a cor-
responding variation of height, and a curve will be traced the
ordinate of which will express the pressure ; and since the
absciss will represent the motion of the pistons, it will repre-
sent according to a known scale the motion of the engine along
the road, and therefore the absciss corresponding to any ordi-
nate will register the exact part of the road where the pressure
of the steam was expressed by that ordinate.
The method of investigating the amount of resistance from
friction above explained is attended with the further advan-
RAILWAY CONSTANTS. 203
tage, that the result is very slightly, perhaps insensibly, affected
by the resistance of air. The wagons whose friction is here ob-
served, being those thrown off in passing from the less to the
more steep plane, are preceded by others, before which the air
is driven. Besides, the motion being slow, the resistance of
the air to the motion of the wheels must be quite insensible,
and the motion on both plains being at nearly the same rate,
the same resistance, or nearly so, from the air is encountered.
For all these reasons the quantity F — F' in the formula (1.) may
be taken to represent the actual resistance from friction of the
wagons detached.
In the course of the limited number of experiments which
this Committee have been enabled to make, however, they have
not yet obtained an opportunity of instituting any by this me-
thod, the provisions for which are not easily obtained in the
midst of the busy traffic constantly carried on upon the railways ;
and this difficulty has been increased by the circumstance that
there are vei*y few gradients on railways which fulfil the con-
ditions here required, and these few not always accessible.
The method of determining the resistance by observing the
accelerated motion of carriages down inclined planes, and by ob-
serving the gradual retardation of their motion on a line where
the inclination is not such as to render gravity greater than the
friction, next demands attention.
An extensive series of experiments having been formerly
made by M. de Pambour by this method, it will be convenient,
in the first instance, to notice the principles adopted by him and
the chief results at which he arrived.
Let ^-^the accelerating force of gravity.
Q = the angle which the plane makes with the horizon.
<^ = the accelerating force of the load moving down the
plane.
T = the time of the motion counted from the moment
at which the load commences to move by gravity
from a state of rest.
V = the velocity it has acquired in the time T.
d V
Then we shall have <p = -ryf, •
M. de Pambour then infers that if the load which descends
the plane were free from friction, we should have
^^sinfi = |^ (2.)
and that if x express the space moved over in the time T,
20i< EIGHTH REPORT— 1838.
\ = 'L^'.'YdY = g sin 9 d x,
which being integrated, supposing that when a- = o, V = o, gives
V^ = 2 ^' X sin 9.
But if the load be subject, as it always is in practice, to fric-
tion, then let the retarding force of friction be/, and the above
equation will become
Y2 = 2 (^ sin 6 -/) x ;
and if the load descend a succession of planes of different gra-
dients, passing from one to the other without any shock by
which it M'ill lose velocity, let a,', x", &c. represent the spaces
over which it moves on each plane. Its motion will be then
represented by the equation,
V2 = 2 (^ sin 6 -/) X + 2 {g sin 5' -/) x' + 2{g sin fl" -/") x" + &c.,
or, V^ = 2S{(5-sin9-/).r} (3.)
Siich is the equation obtained by M. de Pambour for the mo-
tion of a train down one or more inclined planes.
But this is manifestly erroneous and does not really express
that which it professes to express :
1st. Because the condition (2.), from which all the others are
deduced, would be only true on the supposition that all the par-
ticles of the load moved in lines parallel to the inclined plane
■wdth a common velocity V, M'hich in fact is not the case, since
the wheels and axles of the wagons or carriages have a motion
compounded of a progressive and rotatory motion ; and the mass
of these bears a considerable proportion to the whole weight of
the load.
2nd. Admitting that the error just mentioned were corrected,
it is assumed that the excess of the gravity down the plane over
the resistance opposed to the motion is independent of the velo-
city. Now, if any resistance be produced by the aii", that re-
sistance will increase, according to some law, with the velocity.
It is therefore implicitly assumed in the reasoning of M. de
Pambour, either that the resistance of the air in his experiments,
or any other resistance depending on the velocity, is so incon-
siderable that it may be disregarded, or that even at the greatest
velocity it bears so small a ratio to the friction, that it may be
confounded with the friction, and that the result will exhibit the
mean resistance with sufficient accuracy for practical purposes.
Let usj in tl)e first place, see to what extent the error arising
from the omission of the consideration of the wheels operated
on the result of M. de Pambour's experiments. To accomplish
RAILWAY CONSTANTS. 205
this we must obtain the correct solution of the problem of a
train of wheeled carriages moving down an inclined plane, sub-
ject only to a resistance which is independent of the velocity,
that being the condition on which M. de Pambour's investiga-
tion proceeds.
Let M = the gross load in tons.
g = the velocity produced by gravity in a fall-
ing body in one second.
/ = the ratio of friction to gravity.
'.' f g = the velocity destroyed by friction in one
second.
Let h = the gradient or the ratio of the height of
the plane to its length.
•.• g h = the velocity which would be imparted to
a body in one second moving down the
plane without the friction.
'.' g (h — f) = the velocity which would be imparted to
a body descending the plane by the ex-
cess of the gravity over friction.
Let T = the time in seconds.
••• Mg{h—f)dT = the moving force which would be impart-
ed to the descending load in the time
dT.
Let V = the velocity of the train when started down
the plane in feet per second.
V = its velocity after T seconds.
'•• rf V = the velocity it acquires in dT.
Let m = the weight of a pair of wheels and their
axles.
dm = a, particle of this mass.
z = the distance of that particle from the
centre of the wheel.
r = the semi-diameter of the wheel,
ft) = its angular velocity round its centre.
•.' Z(o = the linear velocity of dm.
z dm = the increment of its velocity in fZT.
zdm d m = the increment of its moving force in d T.
= this increment i-educed to the point of
^ contact of the wheel with the rail.
/z^ dw dm , , . . c • r • J 1
= the increment or moving force received by
*' the entire mass of the wheels and axle
in the time T; and this being applied
to each pair of wheels in the train.
206 EIGHTH REPORT 1838.
S ( / ) — the increment of moving foi'ce received
^*^ *" ' by the mass of all the wheels and axles.
But since r dco =. clY, if day be eliminated we have
By the principle of D'Alembert the moving forces which act
upon the train must be in equilibrium with the moving forces
received by it. Therefore the forces M^ (/'—/) (^T must fulfil
the conditions of equilibrium with M <i V, the progressive mo-
mentum of the whole train, and f/ V S I / - — § — ) the re-
volving momentum of all the wheels and axles.
Hence we have
M^ {h-f) rfT- j^M + S (y£!^)J. dY = 0,
which being integrated gives
M^o. (h -/) T = {m + 2 (y ^)} (V - V) . . . (4.)
The quantity / z'^ d m being the moment of inertia of the
wheels round their centres is equal to m k"-, where k is the di-
stance of the principal centre of gyration from the centre of
gravity; and this quantity m k" may be determined by observing
the vibration of the wheels on any point of suspension, and
thence determining the corresponding centre of oscillation.
Let d = the distance of the point of suspension from the centre
of gravity.
I = the distance of the centre of oscillation from the pohit
of suspension.
Then by known principles we have
d{l-d) = k^,
and hence m k^ may be found for each pair of wheels.
We shall therefore consider the quantity
as thus determined, and for brevity shall call it M', so that the
equation (4.) shall be reduced to the form
Mg (h-f) T={M + M') {Y -\') . . . (5.)
If S express the space over which the train moves in the time
T, then \ dT = dS, and we obtain the relation between V and
RAILWAY CONSTANTS. 20/
S by eliminating T. Hence we have
2Mg{h-f)dS -2 (M + M') V(^V = 0.
2 M^ {h -/) S = (M + M') (V^ - V'2) (6.)
2 (M + M') S = M^ (A -/) T2 + 2 V (M + M') T . (7.)
It is evident that from the formulae (5.), (6.), and (7.)j the value
of / may be found if the initial velocity V' of the train and the
time of passing the posts by which the plane is staked out be
observed.
If the train be allowed to move from a state of rest by gravity
alone^ the formulae will be simplified by the condition V' = 0.
They then become
Mg{h-f)T = {M + M')Y .... (8.)
2Mglh -f) S = (M + M') V^ . . . . (9.)
2 (M + M') S = M^- {h -f) T2 . . . . (10.)
In the preceding formulae the load is considered as descend-
ing the gradient. If it ascend^ gravity will become a retarding
force, and the sign of h must be changed ; also the sign oi dY
will become negative. The formulae (5.), (6.), and (7.)? will then
become
M^{/+/OT = (M + M')(V'-V) ..... (11.)
2M^(/+ A) S = (M + M') (V'2- V2) .... (12.)
2 (M + M') 8=-Mg{f+ h) T^ + 2V'(M + M')T (13.)
If in this case the load having the initial velocity V be allowed
to run until it stop, we shall have V = •.* (11.), and (12.) be-
come
Mg{f+h)T = {M + M')Y> . . . . (14.)
2M^(/ + A)S = (M + M')V'2 . . . . (16.)
In the case of retarded motion in descending a gradient less
steep than the angle of friction, h in these formulae must be
taken negatively.
If, therefore, the train move down an inclined plane from a
state of rest, we shall have (9.)
instead of
Y^ = 2g{h-f)S,
according to M. de Pambour. The value of V^, therefore, ob-
tainetl by him (neglecting all resistances which depend on the
velocity) is greater than the truth in the ratio of M + M'
toM.
208 EIGHTH REPORT — 1838.
If the train move successively on two planes whose gradients
are li and A', we shall have
If we suppose that on the second plane /> A' the motion
will be retarded, and still more if A' be negative, or, which
is the same, if the second plane be an ascending gradient. If
the train in such case be allowed to move until it come to rest,
we should have V^ = 0, which would give
(A~/)S + (//-/)S' = 0. . . . (17.)
Now, it is remarkable that this conclusion will follow equally
from the correct formulae which include the effect of the wheels,
and from the erroneous formulae in which that effect is omitted.
This takes place by a compensation of two contrary errors. So
long as the motion of the train is accelerated, the error pro-
duced on V^ by neglecting the wheels is in excess, and while it
is retarded, the error produced on V^ is in defect; and in M. de
Pambour's formulas this excess and defect are equal. They
therefore neutralize each other, and the final result, so far as
respects the effect of the wheels, is thus accidentally correct.
From the condition (17.) we obtain
The quantities AS and A'S' are the dift'erences between the
levels of the extremities of the spaces S and S', and if A' be
taken negatively when the gradient rises, the quantity A S + A' S'
will be the actual difference between the level of the point from
which the train commences its motion and that of the point
where it stops. Thus the resistance would, according to this
reasoning, be found by dividing the difference of levels of these
two points by the entire space run over by the train.
The Sutton inclined plane on the Liverpool and Manchester
Railway, falling toward Manchester, was staked out in distances
of 110 yards, commencing from a point 1100 yards from the
foot of the plane. The level of the tenth stake, which marked
the foot of the plane, is stated by M. de Pambour to be 34-61
feet below the level of tlie first stake. The line extending from
the foot of the plane towards Manchester, which continued to
fall, but in a very slight degree, was also staked out through a
distance of more than a mile from the foot of the plane.
Five wagons loaded with bricks, and weighing gross .81-31
tons, were allowed to descend by gravity from the point 1100
yards from the foot of the plane ; and they continued to move
ttAILWAY CONSTANTS.
209
along the gradient at the foot of the plane until they had traversed
9933 feet and had attained a level 38*55 feet below the point
from which they started. Hence, by the formulae already given,
O Q C C 1
the ratio of the friction to the load would be — = , beina:
993300 258 ^
at the rate of 8'69 lbs. per ton of the gross load.
By throwing off a quantity of the bricks the load was then
reduced to 25*58 tons, and the experiment was repeated in the
same manner, when the proportion of the resistance to the load
was found to be — — or 9' 17 lbs. per ton.
244 *^
Three loaded wagons and an empty one were next allowed
to run separately down the plane, and the following were the
results.
Difference
Ratio of Fric-
Friction in
Gross Load.
Distance run.
of Level.
tion to Load.
lbs. per Ton.
Tons.
Feet.
Feet.
One to
4-65
7326
37-16
197
11-36
515
6663
36-95
180
12-42
5-20
7455
37-19
200
11-17
1-85
6204
36-78
169
13-28
Without pursuing the experiments of M. de Pambour further,
it will be easily perceived that the atmosphere must have exei*-
cised upon them an influence much greater than he suspected,
and certainly greater than he has taken any account of in the
computations which he has founded on them.
When the five wagons were chai'ged with a load amounting
to 31*31 tons gross, the resistance computed by the formula
(18.) was 8*69 lbs. per ton, and the total resistance was conse-
quently 272 lbs. When the gross load of the same wagons was
reduced to 25*58 tons, the resistance per ton, computed in the
same way, was 9*17 lbs., and the total resistance was 235 lbs.
If the resistance were, like friction, proportional only to the
load, the resistance ^^er ton would have been the same in both
cases. But we find, on the contrary, that by diminishing the
gross load, the gross resistance is not diminished in so great a
proportion and the resistance per ton is increased*.
• All the experiments which have been made to develope the laws of friction,
go to prove that, except in extreme cases, friction bears an invariable ratio to
the pressrue on the rubbing surfaces. When pressures, however, bearing a
very high ratio to one another are compared, the corresponding quantities of
fiiction are not found to be in this ratio, the friction corresponding to the greater
pressure bearing a ratio to that corresponding to the lesser pressure, less than
that of the pressures. This exception to the law of the constant ratio between
the friction and pressure has, however, no application in a case like the above.
210 EIGHTH REPORT — 1838.
This is just the effect which the resistance of the air would
produce. If the velocity were the same in both experiments,
that part of the total resistance due to the air would be the same,
because the same wagons being used in each case, the same
surfaces were exposed to the air. In that case, therefore, the
same amount of atmospheric resistance being divided amongst
a less number of tons, there would necessarily be a greater re-
sistance per ton in the second experiment, and the gross re-
sistance of the train would be diminished in a less proportion
than the load.
But it is evident that the mean velocity must have been less
with the lesser than with the greater load, because a less amount
of atmospheric resistance would be sufficient, combined with
friction, to balance the diminished effect of gravitation. M. de
Pambour, however, did not observe, or at least has not recorded,
the time which the train took in any case to move down the
plane, or to come to rest, and has not, therefore, supplied any
data by which the mean speed can be computed.
If it be admitted that the resistance due to friction is inde-
pendent of the velocity, it will follow that the difference between
the resistance per ton in the one experiment and the other must
be altogether ascribed to the air. Now, if A express the whole
resistance due to the air in the first experiment, and A' in the
second, we shall therefore have
25-58 31-31
equal to the difference of the resistance per ton in the one case
and the other. Hence we shall have
^ ^ = 9-17 - 8-69 = 0-48.
25-58
25-58 31-31
Let A' = A — A . Hence we obtain
^(2^-3r3T) = «'^^ +
Whence we find
A = 67 + 5-5 A.
In the absence of the necessary data for determining A , we can
only infer from this that A > G*]. Now let/' be the resistance
due to friction, properly so called, in lbs. per ton. We have
then
31-31/ + A = 272,
.•.31-31/ = 272 -A.
RAILWAY CONSTANTS.
211
But since A > 67,
31-31/' < 272 - 67 = 205,
•••/' < 6-6.
Thus it follows that the resistance from friction, properly so
called, in these experiments was less than Gj^jjlbs. per ton, and
the angle of friction would therefore be less than 1 in 340.
These results are not as definite as could be desired, but they
seem to be the only ones to which the data supplied by the ex-
periments are sufficient to conduct us. Had the moment of the
train commencing to move, and the moment it came to rest,
been observed, its mean velocity M'ould in each case have been
known ; and although that would not have been sufficient to
establish the amount of resistance at any given speed, it would
at least have supplied the means of better approximation. Had
the experiment, however, been satisfactorily conducted with a
view to develop the effect of the resistance of the air, the time
of passing each successive stake should have been observed, and
thus tlie rate of the variation of the speed woiild have been dis-
coverable, as we shall presently perceive.
Since the preceding paragraphs were set in type, the writer of
this report has been favoured by Mr. Edward Woods, engineer
to the Liverpool and Manchester Railway Company, (to whose
intelligent aid the Committee has been throughout its proceed-
ings much indebted,) with an account of the times of passing the
successive stakes in the experiment made with the five wagons
loaded with the reduced weight of 25*58 tons. Mr. Woods,
however, wishes it to be understood that for this observation of
the times M. de Pambour is not responsible, it having been taken
on the occasion by Mr. Woods himself for his individual satis-
faction.
s
OJ
«
jj
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C
tf
u
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Time.
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Levels.
Q
Time.
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Levels.
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Time.
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-
a
s
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6
(5
yards.
h m s
in.
yards.
h m s
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ft.
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h m s
s
ft. in.
29
7 5
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1210
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2420
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1430
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2640
26
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330
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440
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2860
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37 iri
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550
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1870
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880
32 10
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07
The foot of the inclined plane corresponded with the stake
No. 19; and it will be observed, that the time of descejiding
212 EIGHTH REPORT — 1838.
1100 yards was 172 seconds, and that therefore the mean ve-
locity of the descent was 19* 18 feet per second. But by com-
paring the times of descending each successive interval of 110
yards, it will be observed that the rate of acceleration, instead
of being uniform, as it would be independently of the resistance
of the air, is gradually less ; and the last 330 yards of the plane
was descended at an uniform velocity of 33 feet per second.
Mr. Woods has computed the value of /. determined by the
formula 10, page 207, for the first 110 yards, the first 220 yards,
the first 330 yards, and the first 440 yards, and the following
are the results.
1. From to 110 yards /= -00228 = 5'107 pounds per ton.
2. FromO to 220 yards/ = '00255 = 5*712 pounds per ton.
3. FromO to 330 yards/= -00265 = 5-936 pounds per ton.
4. From to 440 yards/ = -00293 = 6-563 pounds per ton.
The increasing value of/ shows the increase of the resistance
with the velocity. In the first 110 yards, the mean velocity
being only 6-34 feet per second, the resistance of the atmosphere
was trifling, and the value of/ may be considered as a close ap-
proximation to the friction, properly so called.
Since in the first 110 yards there must have been some atmo-
spheric resistance, however small, it follows that the friction,
properly so called, must have been less than the value of / ob-
tained by Mr. Woods' calculation. We shall therefore assume
that /was in this case less than 5-11 pounds per ton. The total
amount of friction, therefore, for the load of 25-58 tons would
be less than 130-7 pounds. If we take the mean resistance of
this load at 9-17 pounds per ton, as determined by M. de Pam--
hour's method, we shall find the total mean resistance to be
234-55 pounds. The mean atmospheric resistance would there-
fore be greater than 104 pounds.
It will be observed that this result is in accordance with that
already obtained for the load of 31-31 tons, by a different process
of reasoning. The determination of the limit of /, by the for-
mula (10.), may, however, be regarded as a closer approximation.
The angle of friction corresponding to 5-11 pounds per ton,
would be 1 in 438. Therefore /< — -•
438
We shall not pursue these experiments of M. de Pambour
further than to observe, that the computed resistances of the
single wagons, as given in p. 209, rendered the eff"ects of the
resistance of the air still more apparent. While the mean
computed resistance of the train of five wagons was only 8*69
lbs. per ton, their gross weight being 31-31 tons, that of the
RAILWAY CONSTANTS. 213
single wagons was abont 11 '3 lbs. per ton. This difference
M. de Panibour ascribed to the atmosphere, yet it does not ap-
pear to have occurred to him to direct his experiments or cal-
cuhitions to the determination of the share which friction and
the air had respectively in resisting the motion. Having disre-
garded in all cases the effect of the velocity in modifying the
resistance, and having based all his calculations on suppositions
which are only applicable to friction, we must conclude, that
he regarded the effects of the air as so inconsidei-able, that,
without any error of practical importance, the mean retardation
due to them might be considered as part of the friction.
It has been thought right to bestow some attention on the ex-
periments and calculations of M. de Pambour in this place, be-
cause they are not only the most extensive series of which we
have any knowledge, but because much stress is usually laid on
them by engineers and others who are interested in these ques-
tions. We shall, however, presently demonstrate that the re-
sistance of railway trains has so important a dependence on the
velocit}'^, that no principle of calculation can be admitted which
proceeds, like those of M. de Pambour, upon the supposition
of a constant amount of resistance. But we shall also be enabled
to give a conclusive proof, founded on direct experiments, that
the method of determining the resistance by the formula (18.)
adopted by M. de Pambour is altogether fallacious, and that by
such a method any value, however great, of the resistance might
have been obtained.
Having noticed these erroneous conclusions to which M. de
Pambour has arrived, it is but justice to that gentleman at the
same time to acknowledge the activity and zeal with which he
pursued his inquiries, and the quantity of valuable results of his
extensive experiments by which he has enriched the practical
science of this country. That M. de Pambour should have over-
looked or underrated a source of resistance to locomotive power,
which, however obvious, had eluded the attention of the whole
engineering profession in Great Britain, as well as of his own
country, will not, we are sure, be felt by him to be any serious
disparagement to his sagacity.
In commencing this inquiry, it was not suspected that that
part of the resistance which increases with the velocity, the
chief part of which, if not the whole, is probably due to the
atmosphere, formed so important an agent in opposition to the
moving power on railways worked at high speeds as the results
of experiments which were subsequently made have proved it
to be ; and in the acknowledgment of this oversight tlie writer
of this report very willingly joins. This source of resistance
VOL. VII. 183S. p
214 EIGHTH REPORT 1838.
had been however to an equal extent neglecfed, so far as we are
informed, by engineers generally, and indeed by all who had
directed their attention to the practical working of railways and
to the experimental investigation of their effects. Some scien-
tific men had called the attention of engineers to the subject,
and Mr. Herapath more especially insisted on its importance,
made various calculations of its probable effects, and predicted
that on railways worked at higl\ speeds it would prove to be the
chief source of resistance to the moving power. As, how-
ever, no direct experiments had been made to demonstrate its
amount, and as it was known that the theory of the resistance
of elastic fluids had not been based on experiments with suf-
ficient certainty and precision to render its principles capable
of being applied for practical purposes in operations of the kind
now considered, these suggestions were disregarded, and the
effects of the resistance of the air continued to be considered
as sufficiently allowed for by estimating them in combination
with friction at mean speeds, no attempt whatever having been
made to ascertain experimentally the variation of resistance of
the same loads at different speeds.
It was determined, in the first instance, to repeat and vary
the experiments on the accelerated motion of trains down in-
clined planes, and their retarded motion in running to rest
where the resistance exceeded the moving power.
The first experiments made with this view were tried on the
same inclined plane on which the experiments of M. de Pam-
bour were made, viz. the Sutton plane on the Liverpool and
Manchester Railway. This plane and the level at its foot were
staked out as in M. de Pambour's experiments, but in the pre-
sent case the tiine of passing each successive stake was observed
and recorded, so that the variation of speed, during the motion,
might be rendered apparent.
In these experiments it became manifest, that the rate of ac-
celeration in the descent and the subsequent retardation could
not be represented by the formulae for uniformly accelerating
and retarding forces, and that therefore some force was in ope-
ration which, milike friction, had a dependence on the velocity.
To decide this, it was determined to try the effect of gravity
on a train of loaded wagons descending an inclined plane less
steep than those which occur upon the Liverpool and Man-
chester Railway, and for that purpose the Madeley plane on the
Grand Junction Railway, already mentioned, was selected, and,
as a first trial, a train of wagons loaded with iron rails and
chairs was prepared. This train was placed near the summit
of the plane, and was allowed to move down by gravity. The
RAILWAY CONSTANTS. 215
plane was staked out in distances of a hundred yards by 58
stakes, commencing from the lowest point and numbered up-
wards, and the inclination was ascertained to be at the rate of
1 in 178, with great uniformity, throughout the whole length of
5800 yards.
The time of passing the stakes successively being observed, it
was found that the motion of the wagons was accelerated rapidly
at first, but gradually less and less, until at length all acceleration
ceased and a perfectly uniform motion was maintained to the
foot of the plane.
The unfavourable state of the weather prevented the circum-
stances of these earlier experiments from being observed and
recorded with sufficient accuracy to render them fit to be taken
as the basis of any exact calculation of resistance, but more
than svifficient evidence was obtained from them that no prin-
ciples of calculation could be applied to the motion of trains on
railways with any view to accurate results, or even to a rough
approximation in which the increase of resistance due to the
increase of velocity is not allowed for.
The problem which now presented itself for solution was the
motion of a train of wheeled carriages subject to resistances
which have some dependence on the velocity. All the investi-
gations which have been hitherto made respecting friction are
in accordance in showing that the amount of this resistance is
independent of the velocity; and unless it be maintained that
the friction of carriages on railways differs from all the varieties
of friction to which experimental inquiry has been directed, it
must be admitted that the part of the resistance to railway car-
riages which depends on friction is independent of the velocity
of the motion.
The problem of the resistance opposed by fluids to solids
moving through them has been investigated by Newton, and by
the most eminent of his successors, Bernoulli, Euler, and the
principal mathematicians of the last century. Their researches,
however, so far as regards the resistance of elastic fluids, are
more remarkable for profound mathematical skill than for prac-
tical usefulness, most of them being founded on conditions in-
applicable to the actual motion of bodies through the air, and
I leading to results more or less in discordance with expei'ience.
I The earliest experiments on the resistance of the air to bodies
1 moving through it which are entitled to attention, are those of
i Robins, made about the middle of the last century. These were
[subsequently repeated and to some extent varied by Borda,
jwho published the results of his inquiry in the Memoirs of the
lAcademy of Sciences of Paris, in 1763.
I p2
216 EIGHTH REPORT 1838.
The object of the experiments of Robins was to obtain grounds
for a practical treatise on gunnery, and they were accordingly
limited for the most part to the motion of cannon balls at high
velocities. The result of these experiments was to prove, that
the law of the resistance being proportional to the square of- the
velocity was not true in comparing slow with very high speeds.
It was found, for example, to give a resistance in some cases
three times less than the actual resistance, showing, that when
extended to such limits, the resistance must vary in a much
higher proportion.
Dr. Hutton was, so far as we are informed, the latest inquirer
who undertook a course of experiments with the view of de-
termining the amouint and the law of the atmospheric resistance.
Besides directing his inquiries to more varied velocities, he also
endeavoured to investigate the effects which the form of the
moving body produces upon the resistance. The experiments
were made with hemisphei*es moved alternately with the con-
vex and flat sides foremost, with cones moved alternately with
the point and base foremost, with cylinders moved with the end
foremost, and with spheres.
It was found that at moderate velocities the resistance did not
sensibly vary from tlie law of the squares of the velocities ; but
in comparing slow speeds with high speeds, a gradual departure
from that law took place, the resistance increasing in a higher
ratio. '
In comparing together bodies exposing a frontage of different
magnitudes with the same speed, it was fovmd that the resist-
ance was not proportional to the magnitude of the frontage, but
in some higher unascertained ratio.
It was also found that the resistance did not depend alone on
the magnitude of the transverse section, for that with the saiiie
transverse section different resistances were encountered accord-
ing to the form of the body. Thus, in general, a flat front pro-
duced more resistance than a round or pointed one. But on the
other hand, the resistance was not found to diminish in propor-
tion to the sharpness of the foremost end of the moving body;
but that, on the contrar}-, a body presenting a hemispherical
end was less resisted than one presenting a conical end, the
transverse section of both being the same.
It was also found that the resistance did not depend alone on
the magnitude or form of the foremost end, but had some de-
pendence on the hinder part. Thus, a cone, hemisphere, and
cylinder, having equal bases, moved base foremost, with the same
velocity, suffered different resistances.
No law was obtained from these experiments by which the-
RAILWAV CONSTANTS. 21/
resistance of a body could be calculated from its form and mag-
nitude. The results obtained were merely negative^, showing
that the resistance could not be calculated on such or such data,
but that it depended on some principle not yet discovered, and
which the experiments themselves of Dr. Hutton did not de-
velop.
These experiments also were made on bodies of very limited
magnitude : the bases of the cones, cylinders and hemispheres
were less than a quarter of a square foot. It will therefore be
apparent, that they furnish no just grounds by which the resist-
ance to bodies of the form and magnitude of railway trains can
be computed independently of experiment. How strongly Dr.
Hutton himself was impressed with the imperfect nature of his
results, and with the necessity for further experimental inquiry
before any i-eal or satisfactory determination of the atmospheric
resistance could be obtained, will be collected from the fol-
lowing observations, with which he closes this part of the in-
quiry :
'' On a review of the whole of the premises, we find that the
resistance of the air, as determined fi'om the foregoing experi-
ments, differs very widely, both in respect to its quantity on all
figures, and in regard to the proportion of its action on oblique
surfaces, from the same actions and resistances, as assigned by
the most plausible and imposing theories which have been hitherto
delivered and confided in by philosophers. Hence it may be con-
cluded that all the speculative theories on the resistance of the
air hitherto laid down are very erroneous, and that it is from
experiments only, carefully and skilfully executed, that a rational
hope can be grounded of deducing and establishing a true and
useful theory of the action of forces so intimately connected with
the numerous and important concerns of human life."
Since the only two sources of resistance to moving bodies
with which we are acquainted, are the friction of the parts mo-
ving upon and against one another, and the resistance of the at-
mosphere through which the body moves ; and since all scientific
experiments which have been directed to ascertain the law of
the former agree in showing it to be proportional to the weight
or pressure and independent of the velocity, and that the latter,
within moderate limits of speed, varies in a proportion, cceteris
paribus, not much departing from that of the square of the velo-
city ; the form which may with most probability be assigned to
the expression for the resistance of a railway train will be one
consisting of two terms, one of which is proportional to the load
and the same at all velocities, while the other for the same train
will vary as the square of the velocity. If, then, R express the
218; EIGHTH REPORT — 1838.
whole resistance of a train moving with a velocity V, we shall
have
R = rtV2 + B.
Now, since B is proportional to the load, if M express the load
in tons, and /the resistance for a load of one ton with an inde-
finitely slow motion, we shall have
B = M/,
and therefore
R = « V2 + /M.
The coefficient a being the constant number which, being
multiplied by the square of the velocity, gives that portion of
the resistance which varies with the velocity, will depend on
the form and magnitude of the train, on the number, form, and
magnitude of the wheels, and in general on any circumstances
by which the resistance of the air to the moving parts of the
train may be affected. But it should be observed, also, that
there is nothing in the mere mathematical formula which limits
the term a V^ to represent the effect of the air ; that term in
fact represents any effect which would be attended with a resist-
ance proportional to the square of the velocity.
If any means were devised by which the total resistance of
the same train at two different velocities could be found, the
value of the coefficient a might then be determined ; for let R
and R' be the two resistances of the same train at the velocities
V and V, then we have
R =«V2 + M/
R' = aV'2 + M/
' ^ V^ — V'*'
Hence it appeal's that the difference between the two observed
resistances, divided by the difference of the squares of the cor-
responding velocities, woukl be the value of a.
But as the estimation of the resistance of trains by any direct
means is attended with difficult}^, it may be useful to seek in
the circumstances of accelerated and retarded motion on inclined
planes which are straight, other means for the solution of this
problem.
If R, as already explained, express the ratio of the retarding
force produced by the whole resistance to the retarding force
of gravity, expressed as usual by g, then the velocity which
gravity would destroy in the time d T being g d T, the velocity
which the resistance would detroy in the same time will be
KgdH.
RAILWAY CONSTANTS. 219
If we suppose the train to move down an inclined plane whose
gradient is h, the effective moving force will then be the excess
of the gravitation of the train down the plane above this resist-
ing force : this excess will be
and the moving force which that will impart in the time d T
will be
(MA-R)^(/T.
This, by the principle of D'Alembert, must be in equilibrium
with the moving force which in the same time shall be received
by the train ; and since this moving force, including as before
that which is absorbed by the revolution of the wheels, will be
(M + M')f^V,
we shall have
(MA-R)^cZT = (M + M')(/V; ■
and substituting for R its value already found, this will become
{M (A -/) -aY'}gdi:=: (M + M)dY.
To integrate this, let
M(/i-/) ' ''^ V a •'^•*-
Hence we have
V M «(A-/)(1 - A-2) ^ rfT = (M + M') dx
.. ^^Ma{h-f) dx
M + M' i' " ^ - 1 - ;j;2'
which being integrated gives
VM a{h-f) _ 1 1 +x
M + M' ^ ^ - 2 ^ T^r^ + ^'
the logarithm being hyperbolic.
If x' be the value of x, which corresponds to T = 0, the above
integral will become
VMa{h-f) _l {i+x){l-x')
M + M' ^ ^ - 2 ' (l-a;)(l +0;')' * ' ^^^''
The relation between V and S may be found by eliminating T
by V rf T = rf S, by which we obtain
{M (A -/) - a V^} ^ c/S = (M + M') V(/V
• ytZS _ NdY
* * M + M' ~ M (A -/) - a V^'
220 EIGHTH REPORT — 1838.
which being integrated gives
M + M'~ M(/i-/)- «V^'
where V is the value of V corresponding to S = and T = 0,
and is therefore the initial velocity.
Hitherto the train has been assumed to move with accelerated
motion down an inclined plane. If it ascend, having received
any initial velocity, V, the motion will be retarded, and the
equation will be
{M {h -vf) + « V'^} gdi:= - (M + M) rf V.
Substituting as before, let
..- «v' ..,v = */^5±Z).rf..
V a
•* -M(/i+/)
Hence we have
VUa {h +/) (1 + x'-)gdT = - (M + M') dx
•.• '/Ma (A + /) jrp dx
which being integrated between the limits x and x', the value x'
corresponding to T = 0, we have
^ jWMa (A + ,n ,p\ x' - X
And substituting for x and x' their values, we find
^ ^Ma(A+/) „^_ >/M«(A+/).(V^-V) .^, v
*""' M + M' ^^~ M(A+/) + «VV' •• ^"'-^
The relation between V and S will be found as before :
2agS _ ( Mik+f) +a\>^' \
M + M'~ VM(A f /) + aVV' • • • V— ;
If the train move down a plane, of which the gradient is such
that h < /, the motion will be retarded, and in that case the
equations may be put under the forms
^-•^"1 M + M^ ^^J- M{f-h) + a\\' (-^-^
2as-S
/ M(/-A) + aV^ \
M +M'~ VM(/-/0
Such are, then, the equations of the motion of a train of wheeled
carriages which are submitted to the action of accelerating and
x-etarding forces, or retarding forces only which are independent
RAILWAY CONSTANTS. 221
of the velocitj'', combined with a retarding force which is propoi*-
tional to the square of the velocity ; and such will be the actual
equations of the motion of a train of railway carriages if the
friction be independent of the speed, and the resistance of the
air, and any other retarding forces which act upon it, be as the
square of the speed.
It will now be a matter for consideration, in what manner ex-
periments may be devised so as to enable us to determine the
values of the constants / and a.
If a train descend an inclined plane by gravity with accelerated
motion, that part of the I'esistance which increases with the
speed will be continually augmented, while the accelerating
force of gravity will remain unaltered. At length, therefore, a
velocity will be attained which will render the resistance so
great that it will be equal to the accelerating force of gravity,
and then all acceleration will cease, and the train will move with
an uniform velocity. The condition under which this will take
place will be expressed by putting the value of rf V = 0, whicli
gives
M(/a-/) -aV2 =
•.•M/+«V^ = MA (25.)
where V is the vmiform velocity attained in moving down the
gradient h.
If the same train be moved down another gradient, h\ another
uniform velocity, V, will be attained, and we shall have the con-
dition
From these two equations the values of a and / may be ob-
tained.
M {h - h')
"= V^-V'^ (26.)
J — ya __ y/2 •••... (27.)
If, therefore, two inclined planes be selected sufficiently steep to
produce accelerated motion in the train, and if the same train
be allowed to descend them until it acquire an uniform velocity,
this will give values for V and V ; the inclinations of the planes
will determine h and h', and the weight of the train will deter-
mine M. The values of a and / may then be computed by the
above formulfe.
In the practical application of this method there are some cir-
cumstances which will demand attention. It may happen that
222 EIGHTH REPORT. — 1838.
the inclined plane selected for the experiment may not have suf-
ficient length to allow the acceleration of the train by gravity to
continue till the velocity become uniform. It will therefore be
more convenient to dismiss the train with a considerable speed
from the top of the plane, which may be done by impelling it
by means of a locomotive engine towards the top of the plane,
and detaching the engine so that the train shall be started down
the plane with the velocity given to it by the engine. If this
velocity be less than that which balances the accelerating force
down the plane, the train will be accelerated until it attain the
limiting speed. If it be greater, then it will be retarded by the
air until it be reduced to the limiting speed.
In the preceding investigation M^e have proceeded upon the
supposition that the air through which the train is moved is
quiescent. The effects of a wind of any considerable force would
generally be so complicated, that it would be difficult indeed to
introduce them into the calculation in such a manner as to give
results of any practical value. If the wind blow in the direction
of the motion, the velocity of the train through the air will be
the difference between the velocity of the train and the velocity
of the wind ; and if this was all the effect to be considered, the
investigation woidd not be attended with much difficulty ; for it
would only be necessary to consider in that case the velocities
expressed by Vand V in the preceding formula to, be the excess
of the velocity of the train above that of the air. But it should
be remembered, that besides the progressive motion of the train,
a part of the resistance which is assumed to vary in proportion
to the square of the velocity, is produced by the revolution of
the wheels. Now this part of the resistance is not affected by
the wind, and will be the same whatever be the state of the
atmosphere. Thus it is possible to suppose the velocity of the
train equal to the velocity of the wind, and therefore no resist-
ance whatever to be produced by the progressive motion of the
train. Nevertheless, in such a case, it is evident that the i-evo-
lution of the wheels would produce by the action of their spokes
the same resistance as if the atmosphere were calm. These con-
siderations appear to lead to the conclusion, that the diminution
of resistance to be expected from a wind blowing in favour of a
train, and the increase of resistance from a wind blowing against
it, will not be so great as it might be expected to be, if no effect
but the progressive motion were taken into account.
But if a correct investigation of the effects of a wind either
directly favourable or directly adverse to the motion of a train
be attended with doubt and difficulty, the effects of every side
or oblique wind are still more so. An oblique wind would be
RAILWAY CONSTANTS. 223
resolved into components parallel and perpendicular to the mo-
tion of the train. The component parallel to the motion would
then be treated as a wind directly favourable or adverse. The
lateral component acting against the extensive surface usually-
presented by the side of the train, would have the effect of press-
ing the flanges of the opposite wheels against the rails. This,
combined with the effect of the conical form of the tires, would
have a tendency to impart to the carriages an oscillating motion
between the rails, causing the flanges alternately to strike the
i*ails, and thereby to produce a resistance the amount of which
it would be diffiicult indeed to reduce to general methods of cal-
culation.
It appears, therefore, most desirable that experiments for the
exact determination of the mean amount of resistance to railway
trains should be made when the atmosphere is calm, but it is
rarely that this condition can be obtained. In its absence, the
results of the experiments can only be regarded as approxima-
tions, more or less precise as the disturbing causes exist in a
less or greater degree.
It was not easy to find on the railways which have been com-
pleted inclined planes in convenient situations in all respects
suited for the plan of investigation which was contemplated. On
the whole, however, it seemed that the most eligible were the
Whiston and Sutton inclines on the Liverpool and Manchester
Railway, and a series of inclines between Madeley and Crewe
on the Grand Junction Railway.
The summit of the Whiston plane is at about nine miles from
Liverpool, and the plane falls at nearly an uniform rate of 1 in
96 towards Liverpool for a distance of 2700 yards. From the
foot of the plane the line rises at the average rate of 1 in 936 for
a distance exceeding the range of the experiments.
A stake marked was placed at the summit of the plane, and
twenty- seven other stakes, marked successively 1, 2, 3, &c., di-
vided the whole length of the plane into spaces of 100 yards.
The distance from the 27th stake, which marked the foot of the
plane, to the 24th mile post was 150 yards, and the line from
that point towards Liverpool was divided by quarter-mile posts,
the levels of which were taken.
The inclined plane thus divided by the twenty-seven stakes
was perfectly straight from the summit to the 24th stake. At
that stake curves having a radius of 3300 yards commenced,
which terminated at the 24^ mile post, a point about 900 yards
from the foot of the plane. From that point to a point 220
yards beyond the 24f mile post from Manchester the line was
sg from the
stake 0, the remainder of the line to Crewe being divided by
quarter-mile-posts.
Five merchandise wagons were loaded with iron chairs, so as
to weigh precisely six tons each gross. The empty wagons
weighed two tons each.
These wagons were constructed with high sides and ends,
capable of being removed and laid flat upon the platforms of the
wagons, so as to expose a greater or less bulk of carriage alter*-
q2
232
EIGHTH REPORT — 1838.
nately to the air. The transverse section of these wagons is
represented in the annexed figure. The rectangle A B F E re-
presents the moveable end, which, when the fi-ontage of thewagon
is required to be diminished, is laid flat upon the platform. The
whole frontage, composed of the rectangle A B D C, and the
transverse section of the framing, wheels, springs, and axle,
amounts to 47'8 square feet, which, when the high sides are
lowered, is diminished by the magnitude of the rectangle ABFE.
This latter being twenty-four square feet, it follows that the
transverse section with the high sides has very nearly double
the magnitude of the transverse section when the sides were
lowered.
Immediately before the experiments, the wagons had been
taken a distance of thirty miles, from Warrington to the Made-
ley summit,, so that the axles might be expected to be in good
running order, and the grease properly melted and supplied.
The weather was fair and quite dry,' with a breeze from the
north blowing almost directly up the planes, and therefore in-
RAILWAY CONSTANTS.
233
creasing the resistance of the air. The rails were clean, and
the line had previously been accurately levelled from stake to
stake.
The other members of the Committee being absent, the fol-
lowing experiments were made by Mr. Hardman Earle, Mr.
Edward Woods, engineer of the Liverpool and Manchester Rail-
way, and Mr. Alfred King.
The line changes its direction by curves, all of which have a
radius of a mile at the parts marked in the following table with
an asterisk.
In conducting the experiments, the train of wagons was al-
lowed, in each case, to pass without interruption from gradient
to gradient, tlie time of passing each successive stake being ob-
served and recorded. But as the motion on the different gradi-
ents are essentially distinct experiments, they have been sepa-
rately tabulated and reduced. In experiment I. the train was
brought to the stake No. 33 on the plane falling 1 in 178, and
allowed to descend by gravity fron\ a state of rest. It was al-
lowed to move on the next gradient until it reached the seven-
teenth stake, where it was stopped by the brake.
In experiment II. the same train, in the same state, was
jjlaced at the fifty-seventh stake, at the summit of the plane,
falling 1 in 178, and was allowed, as befoi'e, to descend by gra-
vity from a state of rest. It moved along the successive gradi-
ents, and finally stopped 364 yards beyond the 51^ mile-post,
on the gradient falling 1 in 330,
In experiment III. the high sides of the wagons were taken
down, and laid on the platforms of the wagons, so as to reduce
the surface exposed to the air without altering the gross weight
of the train. The train was then started again, as in the second
experiment, from the fifty-seventh post, and it descended the
successive gradients, and finallj'^ came to rest on the level at
three yards beyond the fifty-fourth mile-post.
In the second and third experiments the train was started
from the same point ; in the one case it came to rest at 10,019
yards from the point of its departure, and descended 139 feet,
and in the other case it came to rest at 14,058 yards from the
point of its departure, and descended 175 feet.
In the following table the results of the three experiments on
the gradient of 1 in 178 are exhibited in the same manner as in
the table of the experiments on the Whiston plane already given.
234
EIGHTH REPORT — 1838.
o =
Experiment I. Experiment 11.
Experiment III.
Time of
Passing.
Diff.
Mean.
Time of
Passing.
Diff.
Mean,
Time of
Passing.
Diff.
Mean.
feet.
feet.
m S
S
S
m S
s
S
m s
s
s
57
49
37
56*
1-63
1-63
50 37-5
97-5
39 7-5
127-5
55*
3-36
1-73
51 19
41-5
40 5
57-5
54*
5-06
1-70
52
32
51
46
53*
6-68
1-62
52 19-5
28-5
41 32
41
52*
8-48
1-80
45
25-5
42 10-5
38-5
51*
10-21
1-73
53 8-5
23-5
45
34-5
50*
1206
1-75
31
22-5
43 17
32
49*
13-57
1-51
52
21
48
31
48*
15-30
1-73
54 12
20
44 17-5
29-5
47*
16-98
1-68
31
19
46
28-5
46*
18-70
1-72
49
18
45 13
26
45*
20-38
1-68
55 6-5
17-5
40-5
27-5
44*
22-04
1-66
23-5
17
46 6
25-5
43*
23-49
1-65
40
16-5
31
25
42*
25-40
1-91
56
16
54-5
22-5
41*
27-14
1-64
56 11
15
47 17
22-5
40*
28-79
1-65
26
15
38
21
39*
30-53
1-74
41
15
58
20
38*
32-11
1-58
55
14
48 17
19
37*
33-78
1-67
57 9
14
35-5
18-5
36*
35-50
1-72
23
14
53
17-5
35
37-09
1-59
36-5
13-5
49 10-5
17-5
34
38-82
1-73
50
13-5
27-5
17
33
40-54
1-72
53
58 3
13
43
15-5
32
42-24
1-70
55 2
122-
16
13
58
15
31
43-87
1-63
t 47-5
45-5
29
13
13
50 13
15
30
45-81
1-94
56 22
34-5
41-5
125
27-5
14-5
29
47-49
1-68
51
29
54
12-5
41
13-5
28
49-23
1-74
57 17-5
26-5
59 6
12
1203
54
13
27
50-87
1-64
1 42-5
25
18-5
12-5
51 7
13
26
52-51
1-64
58 6
23-5
31
12-5
20
13
25
54-12
1-61
28-5
21-5
43-5
12-5
32-5
12-5
24
55-89
1-77
49-5
21
56
12-5
12-5
44-5
12
23
57-58
1-69
59 10
20-5
8
12
56
11-5
22
59-25
1-67
1 30-5
20-5
20
12
52 8
12
21
60-93
1-67
! 50-5
20
32-5
12-5
19-5
11-5
20
62-76
1-83
8-5
18-5
44-5
12
30-5
10-5
19
64-28
1-52
27
18-5
57
12-5
12-02
42
11-5
18
66-01
1-73
44-5
17-5
1 9
12
52-5
10-5
17*
67-61
1-60
21
12
53 3-5
11
16*
69-31
1-70
1 18
33-5
33
12
14
10-5
15*
71-03
1-72
34
16
45
12
24-5
10-5
10-66
14*
72-71
1-68
50
16
57
12
34-5
10
13*
74-41
1-70
2 5-5
15-5
2 9
12
12
44-5
10
12*
75-98
1-57
! 21
15-5
21-5
12-5
55
10-5
10-16
11*
77-67
1-69
36
15
34
12-5
54 5
10
10*
79-31
1-64
50-5
13-5
14-25
45
11
15
10
9*
80-94
1-63
' 3 4-5
14
57
12
25
10
8*
82-92
1-98
18-5
14
14
3 9
12
35
10
7*
84-68
1-76
33
14-5
21
12
44-5
9-5
6*
86-21
1-53
46-5
13-5
14-25
33
12
54
9-5
9-83
5*
87-89
1-68
1 4
13-5
45
12
12
55 4
10
4
89-50
1-61
14
14
57
12
13
9
3
91-13
1-63
27
13
13-5
4 9
12
12
23
10
2
92-83
1-70
1 41
14
20
11
32-5
9-5
1
94-48
1-65
54
13
13-5
32-5
12-5
42
9-5
95-96
1-48
5 7
13
44
11-5
12
51
9
9-5
* The divisions marked with an asterisk are curved with a radius of a mile.
RAILWAY CONSTANTS. 235
In the first experiment the motion was continually accele-
rated, until the train passed to the succeeding gradient. The
acceleration was rapid at first, but gradually lessened as the
speed increased, proving a continual augmentation of the re-
sistance. For the last thousand yards of the plane, the accele-
ration became very small in amount, showing a tendency to an
uniform speed, and therefore to an equality between the moving
force and the resistance.
In the second experiment, the train being started from the
fifty-seventh stake, a more extensive space was allowed for the
action of the gravity of the inclined plane. Throughout the
first 3300 yards the motion, as nearly as possible, corresponded
with tlie motion of the train in the first experiment, the velo-
city at corresponding posts being neai'ly the same. The rate
of acceleration, as before, gradually diminished, until the train
arrived at the twenty-eighth stake, from which to the foot of
the plane the motion was sensibly uniform. From the twenty-
eighth to the eighteenth, the rate of motion is 100 yards in a
small fraction above 12 seconds, and from the eighteenth stake
to the foot of the plane the motion is uniformly 100 yards in 12
seconds, being at the rate of 25 feet per second, or 17 miles an
hour.
Hence it follows, that with this train of five wagons, weigh-
ing 30 tons gross, with high sides, and presenting a frontage of
47" 8 square feet, the whole resistance, at a speed of 17 miles an
hour, was equal to yfiyth part of its weight, or 377 lbs., being
at the rate of 12*6 lbs. per ton.
In the third experiment, in which the high sides of the wa-
gons were taken down so as to reduce the frontage or end sur-
face of the train to 23*8 square feet, the motion continued to be
accelerated to the foot of the plane ; but for the last 1000 yards
the acceleration is so little as to be barely sensible. There is
a tendency to an imiform velocity of 100 yards in 9 seconds, or
33*3 feet per second, being at the rate of 22| miles per hour.
If this be assumed as ti>e uniform velocity which the train
would have attained had the plane preserved an uniform incli-
nation for a sufficient distance, it will follow that its resistance
at this speed, with the reduced frontage, was equal to its resist-
ance at 17 miles an hour with the larger frontage.
Thus, with the same expenditure of tractive power, a dimi-
nution of frontage in the ratio of 2 to 1 nearly gives, in this case,
an increase of speed in the ratio of only 25 to 33*3.
After descending the plane of 1 in 178, the train in each ex-
periment moved along the next plane, the average descent of
which is 1 in 266. The first 1700 yards of this inclination was
236
KIGHTH EEPOET 1838.
staked at intervals of 100 yards, and the 50|^ mile-post from
Birmingham M'as 55 yards beyond the l7th stake. The re-
mainder of the plane was divided by quarter-mile posts. In the
following table the times of passing the successive posts in each
experiment and their differences are given. In the column of
mean differences the mean time of traversing a hundred yards
is given, the means being taken at intervals as in the former
tables.
II
1
IP
Experiment I.
Experiment II.
Experiment III.
Time of
Passing.
Diff.
Mean.
Time of
Passing.
Diff.
Mean.
Time of
Passing.
Diff.
Mean.
feet.
feet.
m s
s
S
m s
s
S
ra s
S
s
4 44
55 51
1
1-37
1-37
5 20-5
55
11
56
9
2
2-59
1-22
34-5
14
5 7
12
9
9
9
3
3-64
1-05
47
12-5
19
12
11-7
18-5
9-5
4
4-72
1-08
6 1
14
13-5
32
13
28-5
10
9-75
5
5-79
1-07
15
14
44
12
38
9-5
6
6-89
1-10
30
15
56-5
12-5
12-5
48
10
9-75
7
7-95
1-06
45
15
14-7
6 9
12-5
58
10
8
9-00
1-05
7
15
23
14
12-2
57 7-5
9-5
9-75
9
1014
1-14
15-5
15-5
37
14
18
10-5
10
11-24
1-10
31-5
16
15-5
51
14
28
10
10-25
11
12-38
1-14
47
15-5
7 4-5
13-5
13-7
38-5
10-5
12
13-40
1-02
8 3-5
16-5
18-5
14
49
10-5
10-5
13
14-65
1-25
20
16-5
16-2
33
14-5
59-5
10-5
14
15-79
1-14
36-5
16-5
47-5
14-5
14-3
95
10
105
15
16-95
1-16
52-5
16
8 2
14-5
20
10-5
16
18-25
1-30
9 9
16-5
16-6
17
15
31
11
17
19-22
0-97
27
18
32
15
14-8
41
10
10-5
50i
19-28
0-06
44
17
40
8
47
6
i*
24-36
5-08
9 50-5
70-5
16
59 34
47
10-6
3*
29-44
5-08
11 6
75-5
17-2
22
58
13-2
51
34-52
5-08
12 45
99
22-6
1 17
55
i-
39-60 5-08
14 31
10-6
24-1
2
43
11-8
In the first experiment there is a gradual retardation, which
continues until the train is stopped by the brake. At all the
velocities, therefore, which it attained, the resistance to its mo-
tion was greater than its gravity down the plane.
In the second experiment, where a greater extent of the plane
is given for the motion, the retardation is also continued until
the train passes to the succeeding gradient. The average speed
of the train for the last quarter of a mile is 100 yards in 24* 1
seconds, or 12*4: feet per second, being at the rate of S^ miles
an hour. Hence we infer that the resistance to the train at tliis
speed vvas greater than its gravity down, 1 in 266, wliich is
equivalent to 8'5 lbs. per ton. The total resistance of this train
of 30 tons, was therefore greater than 255 lbs. at 8^ miles an
hour.
RAILWAY CONSTANTS.
237
In the third experiment, in whicli the end surface was dimi-
nished, the train attained an uniform velocity at the 10th
stake of 100 yards in 10^ seconds, or 28-6 feet per second,
or 19^ miles an hour, whicii it preserved to the foot of the
plane. The resistance, therefore, at this speed with the dimi-
nished end surface was 8*5 lbs. per ton, and the total resistance
was 255 lbs.
It appears, therefore, that with the frontage of 47' 8 square
feet this train suffered a greater resistance at 8^ miles an hour,
than that which it sustained with the lesser frontage of 23-8
square feet at 19^ miles an hour.
In the second and third experiments the train continued to
move on the succeeding gradients, and the circumstances of its
motion are exhibited in the following table. The gradient of
1 in 330 and the succeeding level are straight.
Average
Experiment II.
Experiment III.
No. of Posts.
Gradient,
one in
Time of
Passing.
Diff.
Time of
Passing.
Diff.
)U S
s
m s
S
51}
330
14 31
2
§
330
17 9
15-8
2 50
50
1
330
21 24
25-5
3 40
50
52
330
4 31-5
515
'4
330
5 24
52-5
"o
330
6 18
54
f
330
7 15
57
53
330
8 16
61
i
330
9 22-5
66-5
i
330
10 35
72-5
f
level.
11 52
77
54
level.
14 40
16-8
-|- 3 yards.
level.
11 55
15
It appears, therefore, that with the greater frontage the train
came to rest after having proceeded half a mile on the gradient
of 1 in 330. With the diminished surface the motion was gradu-
ally reduced to the foot of the gradient of 1 in 330, the average
epeed on the last quarter of a mile of that gradient being 109
yards in 72'5, or 4*14 feet per second, being nearly three miles
an hour. It may therefore be inferred that with the lesser sur-
face, at very slow rates of motion, the resistance was somewhat
gi'eater than the gravity down an inclination of 1 in 330. This
resistance is at the rate of 6*8 lbs per ton, and the total resist-
ance for the train of 30 tons was therefore greater than 204 lbs.
It may be observed that this result is quite in accordance
with those already obtained in p. 21 1 and p. 231, from the ex-
238 EIGHTH REPORT — 1838.
periments down the Whiston plane, and from those of M. de
Pambour on the Sutton plane.
In considering these experiments, and in deducing from them
any inferences of a genei-al nature, it is of importance to re-
member that in all of them a wind of unascertained force blew
up the planes, and therefore against the motion of the train.
It may be observed that in these experiments no perceptible
effect is produced by the curves. The uniform velocity of the
train in the second experiment is the same before entering on
the curve which commences at the I7th stake on the gradient of
1 in 178, and after passing the 5tli stake, where the line becomes
straight.
From all these experiments it is apparent that a train of rail-
way cai-riages in descending an inclined plane is subject to a re-
sistance which is continually augmented as its motion is acce-
lerated, and that if the plane have sufficient length, this resist-
ance will at some certain speed become equal to the gravitation
down the plane, and then all further acceleration must cease.
This conclusion will be corroborated, and indeed put beyond all
doubt by other experiments which are still to be reported. It
will be evident, therefore, that if the train on Avhich the experi-
ments were made be started from a point at a sufficient distance
from the foot of the plane, the velocity which it will have when
it leaves the foot of the plane and commences to move along the
next gradient will be the same, whatever maybe the point from
which it may have been started.
Let A B be the inclined plane down which the train is moved,
and let B C be the succeeding gradient. Let S be a point
from which the train being started it will acquire the uniform
speed before it arrives at B. Then, if it be successively started
from S', S", or any other point still more distant from B, it will
have, on arriving at B, the same velocity. It will, therefore, in
all cases move on B C to the same point before it be brought to
rest. Let this point be R.
According, then, to the method of determining the resistance
adopted by M. de Pambour (p. 199.), the amount of resistance
obtained when the train is started from S would be equal to the
gravity on the inclination S R ; if started from S', it would be
equal to the gravity on the steeper plane S' R ; if started from
i
RAILWAY CONSTANTS. 239
S", it would be equal to the gravity on the plane S" R ; and, in a
word, the value of the resistance according to this method might
be found to be of any amount whatever.
The experiments were next directed to the trial of the move-
ment of trains of coaches down the series of planes extending
from Madeley to Crewe, already described, and were conducted
by Dr. Lardner. A train consisting of one first-class and three
second-class close coaches, were loaded in the same manner as
the train of first-class coaches used in the experiments already
described upon the Whiston plane, the gross weight being 18
tons. The second-class coaches differed in nothing but the
structure of their body from the first chiss, their transverse sec-
tion being nearly the same. In addition to the fifty-seven stakes
by which the plane falling 1 in 178 had been divided, a fifty-
eighth stake was placed at the top of the plane, the inclination
being found to extend 100 yards higher than fifty-seventh stake.
The direction of the line was nearly due north and south, and
the wind was from the south, and therefore blowing directly
down the plane. No means of ascertaining its velocity could
be procured at the time. The train was in each case pushed by
an engine to the fifty-eighth stake, and there dismissed to de-
scend the plane by gravity. The time of passing the successive
stakes was observed as in the former experiments. In the first
two experiments, given in the following table, the entire train
was dismissed down the plane, the carriages being coupled
by Mr. Booth's patent couplings. In the third experiment the
first-class carriage and one of the second-class carriages, coupled,
were used ; and in the fourth experiment the other two second-
class carriages. The entire transverse section of the carriages,
including the frame, wheels, and axles, was 61 square feet, and
the distance between carriage and carriage, when coupled by the
patent couplings, was 3 feet 10 inches.
240
EIGHTH EEPORT — 1838.
Total
Fall.
S5
Is
c
c
c
Experiment I.
Experiment
11.
Experiment lit.
Experiment IV.
Time of
J
§2'
= 1
Time of
ll
1
rom
Stake.
Time
yards.
Time of
ll
« 01
2
Passing
i^
_ c
Passing
*
g§
Passing '— 1 „
Passing
■^o
.-
o
'^l
Stakes.
u
P '='
Stakes.
So
Stakes.
So S"l
Stakes.
So
5 ®
c
si
l|
'i^s
^l
H|
l|
S
tn
K
CO
"^
feet.
feet.
m 8
m s
m s
m s
58
49 58
11 36
30 10
57
50 20
22
50
14
22
12
56*
1-63
1-63
36
16
37 13
12 4
11
35
13
55*
3-36
1-73
48
13
31
18
18
14
48
13
54*
5-06
1-70
51 1
12
44
13
33
15
31 4
16
63*
6-68
1-62
12
11
54
10
48
15
20
16
52*
8-48
1-80
176-9
22
10
38 4
10
13 3
15
34
14
51*
10-21
1-73
32
10
12
8
18
15
49
15
50*
12-06
1-85
41
9
10-4
22
10
10-2
31
16
15-2
32 4
15
15-2
49*
13-57
1-51
50
9
31
9
49
15
19
15
48*
15-30
1-73
59
9
40
9
U 3
14
33
14
47*
16-98
1-68
1-6-5
52 7
3
50
10
13
15
49
16
46*
18-70
1-72
12
5
59
9
34
16
33 4
15
45*
20-38
1-B8
26
14
9
39 7
8
9
50
16
15-2
19
15
IS
44*
22-04
1-66
36
10
17
10
15 4
14
37
18
43*
23-49
1-45
45
9
27
10
20
16
54
17
42*
25-40
1-91
178-1
54
9
37
10
36
16
34 10
■6
41*
27-14
1-74
53 3-5
9-5
45
8
51
15
28
18
40*
28-79
1-65
13
9-5
9-4
55
10
9-6
16 5
14
15
43
15
16-8
39*
30-53
1-74
23
10
40 4
9
21
16
58
15
38*
32-11
1-58
33
10
13-5
95
38
17
35 14
16
37*
33-78
1-67
179-0
43
10
23
9-5
53
15
29
15
36*
35-50
1-72
53
10
33
10
17 8
15
44
15
35
37-09
1-59
54 3
10
10
43
10
9-6
24
16
15-3
36 3
19
16
34
38-82
1-73
13
10
53
9
40
16
23
20
33
40-54
1-72
23
10
41 1
9
56
16
40
17
32
42-24
170
177-3
33
10
10
9
18 12
16
58
13
31
43-87
1-63
43
10
20
10
28
16
37 15
17
30
45-81
1-94
53
10
10
30
10
9-4
34
16
16
31
16
17-6
29
47-49
1-68
55 3
10
40
10
19
16
47
16
28
49-23
1-74
13
10
50
10
14
14
38 2
15
27
50-87
1-64
173-8
23
10
42
10
30
16
17
15
26
52-51
1-64
34
11
9
9
45
15
32
15
25
54-12
1-61
44
10
10-2
19
10
9-8
20
15
15-2
47
15
15-2
24
55-89
1-77
54
10
29
10
15
15
39 5
18
23
57-58
1-69
56 4
10
39
10
- 30
15
18
13
22
69-25
1-67
179-0
24
10
48
9
45
15
32
14
21
60-93
1-68
24
10
58
10
21
15
48
16
20
62-76
1-83
34
10
10
43 7
9
9-6
15
15
15
40
12
14-6
19
64-28
1-52
44
10
16
9
30
15
15
15
18
66-ni
173
54
10
26
10
45
15
30
15
17*
67-6I
1-60
179-4
57 3
9
36
10
22
15
30
14
16«
69-31
1-70
13
10
43
9
14
14
58
14
15*
71-03
1-72
23
10
9-8
55
10
9-6
28
14
14-6
41 10
12
14
14*
72-71
1-68
33
10
44 4
9
42
14
26
16
13*
74-41
1-70
42
9
13
9
56
14
40
14
12*
75-98
1-57
179-2
52
10
23
10
23 10
14
53
13
11*
77-67
1-69
58 2
10
33
10
24
14
42 3
15
10*
79-31
1-61
11
9
9-6
43
10
9-6
38
14
14
20
12
14
9*
8O-94
1-63
21
10
52
9
51
13
34
14
8*
82-92
1-98
31
10
45 1
9
24 4
13
47
13
7*
84-68
1-76
172-4
40
9
10
9
17
13
43
13
6*
86-21
1-53
50
10
20
10
30
13
14
14
5*
87-89
1-68
59
10
9-8
30
10
9-4
43
13
13
26
12
15-2
4
89-50
1-61
9
9
39
9
43
38
12
3
91-13
1-63
19
10
49
10
43
52
14
2
92-83
1-70
184-0
29
10
58
9
43
44 4
12
1
94-48
1-65
39
10
46 7
9
43
18
14
95-96 1-48
191-7
48
9
9-6
17
10
9-4
25 49
66
13-2
32
14
13-2
111 the first and second experiments made with the train of
four coaches, it will be observed that after having descended
800 yards, a velocity of 100 yards in nine seconds was acquired,
which underwent a very slight diminution througlioutthe middle
* The divisions thus marked ai-e curves having a radius of a mile.
RAILWAY CONSTANTS. 241
of the plane, and subsequently a very slight increase. These
fluctuations were, however, so small that they may fairly be
attributed to the varying effects of the wind arising from the
different exposm-e of the train in cuttings and on embankments.
The velocity, therefore, may be regarded for nearly 5000 yards
as practically uniform, the mean rate in the first experiment
being 100 yards in 9'74 seconds, or 30*8 feet per second, which
is equivalent to twenty-one miles per hour ; and in the second
experiment 100 yards in 9"95 seconds, or 31'6 feet per second,
being 21| miles per hour. The mean of the two will give a ve-
locity of 51*2 feet per second, or 21;^ miles per hour. Hence it
appears that the resistance of this coach train, at a velocity of
21| miles an hour, is the l78th part of its weight, or 226*8
pounds, being at the rate of 12*6 pounds per ton of the gross
weight.
In the third experiment made with the first-class carriage
and one second-class carriage coupled, the speed commencing
from the summit was 100 yards in fourteen seconds, which was
gradually diminished to a point beyond the middle of the plane,
where it was reduced to 100 yards in sixteen seconds. It then
slightly increased to 100 yards in thirteen seconds, which was
maintained uniform for the last 1000 yards. In the fourth ex-
periment with the second-class carriages, the initial velocity
at the top of the plane was 100 yards in twelve seconds, which
was gradually diminished,till at the middle of the plane the ve-
locity was 100 yards in 172 seconds, after which it was gradually
but slightly increased to the foot of the plane, where the final
velocity was the same as in the third experiment. Considering
the lightness of the trains and the consequently increased efl"ect
of the wind, these fluctuations of speed probably arose from the
varying shelter and exposure of cuttings and embankments in
the descent. In the third experiment the mean velocity through
5000 yards was 100 yards in 14'7 seconds, or 20*4 feet per se-
cond, being at the rate of 13-91 miles per hour. In the fourth
experiment it was at the rate of 100 yards in 15*16 seconds, or
] 9'8 feet per second, being at the rate of 13*5 miles per hour. The
mean of these two is 20" 1 feet per second, or 13-7 miles per hour,
Now it follows that, the wind being with it, this train of two
coaches suffered a resistance, the total amount of which, at 13'7
miles per hour, amounted to the l7Sth part of their gross weight,
or to 113-4 pounds.
The train of four coaches after having descended the plane
falling 1 in 178, as described in the first two of the preceding
experiments, was allowed to continue its motion on the succeed-
ing plane, falling at the mean rate of 1 in 266, and extending to
a distance of 5360 yards from the foot of the former plane.
The particulars of these experiments are given in the following
table.
242
EIGHTH REPORT — 1838.
Sis
©OJOOCOO-H©— <,-lr-l(N-Ht-((N-H*J
0<l U5 05 t-» in «0
gs
Si
35S50©©0«©-<IN©-^0<
S M
QOt>.?OtOtO«O«O«O5Ot»O5O5©©"eO>nt^a0GOa000ir5©CC«OQOe0pH?5»^
3 05 © — 5<l M Tj( ic ?0 «^ 00 ® 1-c
a c5
s«
e<5m©aomK5 — ^©©-J'SC'-io^i-ioo
OIOIOSO©©®®©©©©'-!— -^■-1'-
iC^'»(Mu)^u;u;'n":>noo
RAILWAY CONSTANTS. 243
In the first experiment the train moved over this gradient
with a gradual retarded motion, commencing with the velocity
with which it left the former plane, and gradually diminishing
in speed until it attained the rate of 100 yards in 16*36 seconds,
with which speed it passed on to the succeeding gradient. In
the second experiment the train, in like manner, was retarded
till it attained the velocity of 100 yards in 14-32 seconds, with
which it passed to the succeeding gradient. The difference be-
tween the final velocities in descending this gradient in the two
experiments must be ascribed to the varying force of the wind,
since the train in both was the same, and the initial velocity
was not materially different. The mean of the two final velo-
cities is 100 yards in 15*34 seconds, or 19*55 feet per second,
being at the rate of 13*3 miles per hour.
Since, then, this train in descending the gradient 1 in 266 had
not yet ceased to be retarded, having attained the velocity of
19*55 feet per second, it follows that at this velocity the resist-
ance to the train must have exceeded its gravity down that
gradient.
It was now determined to try the effects of four carriages
moved separately down the inclined plane falling 1 in 178. The
carriages were therefore separately puslied to the summit of the
plane and dismissed from it at a higli speed, the times of pass-
ing the successive posts being observed as in the former case.
The results of these four experiments are exhibited in the follow-
ing table.
244
EIGHTH REPOUT — 1838.
.5
Experiment I.
Experiment II.
Experiment III.
Experiment IV.
i
Total
Fall.
-0
c
1
s-i
Time of 0^
!t
£-1
Time of £ .2
Time of
Stake,
rime
yards.
Time of
rom
Stake.
Time
yards.
Si^
Passing "-
-0
Passing
*- _
eg
Passing 'r 1
Passing
*- Q
=
ll
Stakes, c"
3
Stakes.
3 0!
Stakes.
sr
-
Stakes.
s'Z
M
i
h
^i
^i
^11
ss
4^ P.
s
X
ai
in
Si
feet.
feet.
m s
m s
m s
m s
58
29 54
40 3
21 43
31 50
57
30 3
9
11
8
50
7
57
7
56*
1-6.1
1-63
13
10
19
8
32 3-5
6-5
55*
3-36
1-73
21
9
29
10
22 7
17
U
7-5
54*
5-06
1-70
30
9
37-5
8-5
9-0
16
9
19
8
53*
6-68
1-62
41
11
46
8-5
25
9
28
9
52*
8-43
1-80
176-9
50
9
55
9
33
8
36-5
8-5
51*
10-21
1-73
31 1
11
41 4
9
42
9
45
8-5
50*
12-06
1-85
12
11
10-2
14
10
52
10
9-0
53-5
8-5
8-5
49*
13-57
1-51
24
I2
25
11
23 3
11
33 3
9-5
48*
15-30
1-73
35
11
36
11
13
10
12
9
47*
16-98
1-68
176-5
48
13
47
11
24
u
23
11
46*
18-70
1-72
32 1
13
58
11
34
11
34
11
45*
20-38
1-68
15
14
12-6
42 10
12
11-2
45
12
10-6
45
11
10-3
44*
22-04
1-66
28
13
22
12
57
12
55
10
43*
23-49
1-45
42
14
35
13
24 10
13
34 7
12
42*
25-40
1-91
178-1
57
15
47
12
21
11
18
11
41*
27-14
1-74
33 12
15
59
12
34
13
30
12
40*
28-79
1-60
26
14
14-2
43 11-5
12-5
12-3
46
12
12-2
43
13
11-6
39*
30-53
1-74
41
15
25
13-5
25
14
55
12
38*
32-11
1-58
58
17
39
14
14
14
35 10
15
37*
33-78
1-67
179'0
34 13
15
52
13
26
12
23
13
36*
35-50
1-72
30
17
44 5
13
41
15
38-5
15-5
35
37-09
1-59
45
15
15-8
19-5
14-5
13-6
no
53
14-5
14-0
34
38-82
1-73
35 2
17
33-5
14
26 8
27
36 6-5
13-5
33
40-54
1-72
18
16
46
12-5
21
13
22
15-5
32
42-24
1-70
177-3
34
16
45
14
35
14
37-5
15-5
31
43-87
1-63
49
15
13
13
48
13
52
14-5
30
45-81
1-94
36 6
17
16-2
27
14
13-5
27 1
13
15-8
11-8
29
47-49
1-68
22
16
41
14
37 23
31
23
49-23
1-74
39
17
55
14
27
26
39
16
27
50-87
1-64
173*8
55
16
46 8
13
41
14
55
16
26
52-51
1-64
37 12
17
22
14
38 10
IS
25
54-12
1-61
29
'Z
16-2
36
14
13-8
28 5
24
12-8
25
IS
18-6
24
55-89
1-77
45
16
50
14
17
12
40
15
23
57-58
1-69
38 3
18
47 3
13
25
8
55
15
22
59-25
1-67
179-0
19
16
17
14
40
15
39 20
15
21
60-93
1-68
35
16
31
14
50
10
25
15
20
62-76
1-83
52
17
16-6
45
14
13-8
29 4
14
U-8
40
15
15-0
19
64-28
1-52
39 10
18
59
14
16
12
55
15
18
66-01
1-73
27
17
48 13-5
14-5
28
12
40 10
15
17*
67-61
1-60
i79--»
45
18
29
15-5
42
14
25
IS
16*
69-31
1-70
40 3
18
44-5
15-5
54
12
40
15
15*
71-03
1-72
21
18
17-8
14-76
30 7
13
12-6
55
IS
15-0
14»
72-71
1-68
40
19
49 13
28-5
20
13
41 10
IS
13«
74-41
1-70
41
20
29
16
33
13
27
17
12»
75-98
1-57
179-2
18
18
44
15
46
13
43
16
11*
77-67
1-69
37
19
59
15
59
13
59
16
10"
79-31
1-64
57
20
19-2
50 14
15
15-05
31 12
13
13-0
42 14
15
15-8
9"
8O-94
1-63
42 17
20
23
9
25
13
29
15
8"
82-92
1-98
36
19
47
14
38
13
45
16
7"
84-68
1-76
172-4
57
21
51 3
16
SO
12
43
15
6"
86-21
1-53
43 17
20
20
17
32 4
14
16
16
5^
87-89
1-68
37
20
18-0
36
16
14-4
16
12
12-8
33
17
15-8
4
89-50
1-61
44
23
52
16
29
13
SO
^l
3
91-13
1-63
23
23
52 8-5
15-5
42
13
44 6
16
2
92-83
1-70
184-0
4S
23
25
16-5
54
12
23
17
1
94-48
1-65
45 11
25
41
16
33 8
14
41
18
95-96
1-48
191-7
36
25 123-8
57
16
16-0
21
13
13-0
59
18
17-2
The divisions thus marked are curves having a radius of a mile.
RAILWAY CONSTANTS. 245
In the first experiment the velocity, commencing with 100
yards in nine seconds, was continually diminished to the foot of
the plane, where it was reduced to 100 yards in 238 seconds,
being at the rate of 12*6 feet per second, or 8*6 miles per hour.
At this speed, therefore, with a favourable wind, the resistance of
the carriage used in this experiment was greater than its gravity
down 1 in 178. In the second experiment the speed, com-
mencing at 100 yards in eight seconds, was gradually retarded
to the bottom of the plane, where it was reduced to 100 yards in
sixteen seconds, or 12*75 feet per second, being at the rate of
12*8 miles per hour. Since the retardation had not ceased, the
resistance of this carriage at the velocity of 18*8 miles per hour
must be greater than its gravity down 1 in 178. In the fourth
experiment, likewise, there is a continual retardation, com-
mencing at 100 yards in seven seconds. The velocity was gra-
dually diminished until, at the foot of the plane, it was reduced
to 100 yards in 17*2 seconds, being at the rate of 17'44 feet per
second, or 11'9 miles per hour, at which speed, therefore, the
resistance of the carriage used in this experiment was greater
than its gravity down 1 in 178. In the third experiment the
speed, commencing at 100 yards in seven seconds, was gradually
reduced, about the middle of the plane, to 100 yards in 12*8
seconds. Throughout the last 3000 yards the speed varied be-
tween 100 yards in 11*8 seconds, and 100 yards in thirteen
seconds, alternately increasing and decreasing, probably from
variations of the wind and the varying exposure on cuttings and
embankments, accompanied probably with slight changes in the
gradient. The speed may therefore be regarded as practically
imiform throughout this distance of 3000 yards, and its mean
value was 100 yards in 12*7 seconds, or 23*62 feet per second,
being at the rate of 16*6 miles per hour.
The coach used for this third experiment was now taken to
the top of the plane and there dismissed with the speed of 100
yards in seven seconds, and it was determined to allow it to
move along the successive gradients until it should come to rest.
To observe the motion, the gradients were staked out in intervals
of 100 yards to a distance of 7200 yards beyond the foot of the
plane falling 1 in 178. The seventy-second stake was 275
yards short of the 53^ mile post, and the line beyond that was
divided by quarter- mile posts. The particulars of this experi-
ment are given in the following table.
VOL. VII. 1838.
246
EIGHTH REPORT — 1838.
c
S
_c
1 I 1
■•*
c
ijt.
g
al
iA
1
efrom
to Stake.
uTime
10 yards.
i
c
Time of
Sm
c2
c
Time of
c 2
c
Time of
•5
Passing
aS
M
"t3
Passing
i> °
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The coach being dismissed from the summit with a velocity f
of 100 yards in seven seconds, was gradually i-etarded until it
reached the twentieth stake, when it attained a speed of 100 '
yards in 13^ seconds. It fluctuated between 100 yards in 13*2
seconds and fourteen seconds to the foot of the plane. The
velocity, therefore, for the last 2000 yards may be considered
as uniform, its mean amount being 100 yards in 13^ seconds,
being the same with the result of the former experiment. At
this speed, therefore, with a favourable Mind, the resistance of
• Distance from this stake to h'i\ mile post =: 275 yards.
RAILWAY CONSTANTS. 247
the coach was equal to the gravity on the plane. As the coach
descended the next gradient its motion was again gradually re-
tarded until the speed became 100 yards in seventeen seconds,
but was again accelerated until it became 100 yai'ds in fourteen
seconds, these fluctuations being probably due to the varying
exposure to the wind. The uniform motion down this gradient
may therefore, perhaps, be taken as a mean of the varying mo-
tion of the train in descending it. This mean would be 100
yards in sixteen seconds, or 12-8 miles per hour.
If it be assumed that the train of four coaches used in the ex-
periments down the Madeley plane, falling 1 in 178, had the same
friction as the train of four first-class coaches used in the ex-
periments down the Whiston plane (page 224), the proportion
in which the whole resistance is in each case due to friction and
the air, may be obtained by an easy calculation derived from
the formulae 26 and 27 ; making in these the following substi-
tutions,
M = 18, A = — , h' = -L, V = 49-45, V = 31-2,
' 96 178 '
we shall find
/• 1 1
409 17043
In both these experiments the wind was favourable, but its
force unascertained, and in the formula from which these values
of/ and a have been deduced no allowance has been made for
its effect. By comparing the value of/ thus obtained with the
value of/ in page 231, it will be seen that the present value is
less in amount, as might be expected, from the effect of the wind.
The resistance per ton due to friction according to this cal-
culation would be 5-48 pounds, and the total resistance from
friction for the load of eighteen tons would therefore be 98*64
pounds.
Since the entire resistance of this load at twenty-one miles
per hour was found by the experiments to be 226'8 pounds per
ton, it follows that the total resistance due to the atmosphere
was 128" 16 pounds.
Two objections have been advanced against the method of
determining the resistance by moving down inclined planes
until a velocity be obtained which renders the resistance equal
to the gravitation on the plane. The first is, that the engine
not being in front of the train, the flat surface of the foremost
carriage is exposed to the air, and that a greater atmospheric
resistance is thereby produced than would be produced if the
engine were in front of the carriage inasmuch as the engine
R 2
248 EIGHTH REPORT — 1838.
would have, in a greater or less degree, the same effect upon the
air as the bow of a ship has upon the water through which it
is carried.
The second is, that under such circumstances the moving
power acts from behind against the resistance, in the same man-
ner as an engine acts when used to push the train from behind
instead of drawing it ; that thereby the coaches composing- the
train are thrown out of square, and tlie resistance from flange
friction, and other causes consequent on such derangement, is
increased, and is the main cause of the excessive amount of re-
sistance whicli has been found in these experiments.
To the first of these objections it may be answered, that the
engine and tender placed in front of the train increase the
amount of the transverse section by which the air is displaced
in the motion of the train ; the tire-box and ash-pit extend
nearly to the ground, and fill a space which is left almost open
in the absence of the engine ; the chimney rises above the roof
of the carriage and produces a resistance which has no existence
in the absence of the engine ; the head of the engine is usually
flat, and so far as it is concerned produces as much resistance
as an equal extent of flat surface upon the foremost end of
the coach. The tender which follows the enghie presents a
concave form to the air, a form considerably more adapted to
produce a resistance than the flat end of the carriage which it
intercepts.
Up to the period of writing this report no opportunity has
been presented to the committee of ascertaining the force due
to this objection by direct experiment ; but it is intended to
place an engine and tender in front of a train, disconnecting
the working machinery, -so that the engine shall have no other
resistance than a coach of equal weight and similar construction,
and to repeat the experiment with the engine and tender so
placed. It will then appear how far the resistance will be mo-
dified by the form of the engine dividing the air in front.
To the second objection it may be ansvvered, that the case of
the train moving by gravity down an inclined plane is not analo-
gous to that of an engine pushing a train behind. In the latter
case the whole power of the impelling force acts against the end
of the last carriage, Avhile the resistances which it has to overcome
have their position in the moving parts of each individual car-
riage, and in the frontage exposed to the resistance of the air.
But in the case of a train descending an inclined plane by gravity
neither the whole moving force nor any part of it acts against
the back of the hindmost carriage : the moving force, being the
gravitation of the matter composing the several carriages, will
1
RAILWAY CONSTANTS. 249
necessarily act at their respective centres of gravity. Thus the
force which moves the first carriage will act at its centre, and
that portion of it which is expended on the friction of that par-
ticular carriage will act in a manner as favourable as a drawing
force would act. The same may be said of the force of gravi-
tation of the several carriages ; but that portion of the force of
gravitation which balances the resistance of the air is subject in
a modified sense to the objection. Thus, that part of the gra-
vitation of the second coach which is over and above the resist-
ance from friction, is transmitted to the first coach, and through
it to the air which it drives before it ; and the like may be said
of the gravitation of each succeeding coach. But it should also
be remembered that the resistance of the air to a train of coaches
does not act exclusively on the front of the first coach. The
coaches of the train are nearly four feet asunder, and the air
probably acts more or less on the foremost end of each coach.
This portion of the resistance is not acted upon with the same
disadvantage by the gravitation of the coaches as that resistance
which is produced by the end of the first coach.
It is intended to test the force of this objection by moving a
train of coaches with an engine along a level, or up an inclina-
tion, first placing the engine in front and afterwards behind, and
comparing the time taken by the engine to drive the train
a given distance under both circumstances : but at the time of
making this report the committee had not had an opportunity
of making such an experiment.
Whatever importance may be attached to this objection, it is
presumed that it cannot for a moment be supposed that the dif-
ference between the resistance in pushing a train from behind
and drawing it in front can account for the enormous dispropor-
tion between the common estimate of resistance, and that which
results from the experiments here given, the common estimate
being about nine pounds per ton, while that which the trains
exhibited moved down the Whiston plane at thirty-two miles
an hour, amounted to more than twenty-three pounds a ton,
and that even with the advantage of a favourable wind.
A further objection, however, has been made to the effect,
that the trains on which the various experiments have been
made, especially those with which the greatest velocities were
attained, were lighter than trains generally are in railway prac-
tice, and that therefore the proportion which the atmosphei'ic
resistance would bear to the whole resistance would be greater
than in practice it is, for that if the magnitude of the train were
increased the resistance from the air would not be proportion-
ately increased.
250 EIGHTH REPORT 1838.
To a certain extent the force of this objection may be admitted.
The fastest trains, however, on the Liverpool and Manchester
railway, viz. the 11 o'clock first-class train consists invariably of
four coaches and no more. The trains of passengers, however,
generally consist of from seven to nine coaches, and it is in-
tended before the next meeting of the Association to extend the
experiments to trains of this magnitude. It will then be seen
whether the lightness of the train increases the proportionate
resistance at a given speed, and if so, to what extent.
A summary of the results of the experiments contained in
this Report is exhibited in the annexed table. It is, however,
to be regretted that the effects of the wind were such as to
render these results not so exact as could be wished. Still
they may be regarded as tolerable approximations, all circum-
stances considered. The experiments which appear to be en-
titled to most attention and likely to give the most accurate re-
sults, were those made with the train of four first-class coaches
on the Whiston plane.
In reviewing the results of these experiments, the near agree-
ment of the several values obtained for the friction proper from
different experiments by different principles and processes of
calculation, is sufficiently striking, and affords a presumption
of truth. Before, however, conclusions apparently so much in
discordance with all previous estimates of resistance on railways
can be accepted with confidence, it will be necessary to multiply
and vary the experiments, and more especially to do so with a
view to meet the objections which have been brought against
some of those detailed in the present Report. Meanwhile,
whatever be the source of the resistance to the tractive power,
and whatever may be its exact amount, it does appear to be
established by tolerably conclusive evidence that the resistance
of railway trains at high speeds is considerably greater than the
common estimate : and, on the other hand, that at low speeds
it is probably less. Should it appear upon further investigation
that the motive power necessary on railways has a material de-
pendence on the speed, and that at high speeds, such as velo-
cities from thirty to forty miles an hour, its amount is as con-
siderable as the experiments here detailed would indicate, some
important changes must be admitted in the principles which have
hitherto guided those who have projected and constructed rail-
ways.
If it be admitted that the power engaged in opposing friction
forms but a small part of the whole power used in working rail-
ways at high speeds, it will become a matter of comparatively
small importance to contrive means of diminishing an obstruc-
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252 KIGHTH REPORT 1838.
tion already of such trifling amount. The adoption, therefore,
of hirge wheels, of expensive lubrication, of friction i-ollers,
and of other similar contrivances for reducing the amount of
friction, Mill be clearly unadvisable, since such expedients wou^d
be attended with much more expense and inconvenience than
M'ould be adequate to any effects they could prodilce in dimi-
nishing a resistance already so small.
The importance of low gradients will be diminished. The
advantages supposed to attend these are founded on the suppo-
sition that the tractive power upon a level requires so great an
increase when a moderate gradient is ascended, that either a
superfluous moving power must be provided on the level, or that
the moving power adapted to the level will be overstrained in
ascending the gradient. So long as the resistance on a level is
estimated at eight or nine pounds a ton, a gradient rising at the
rate of eighteen or twenty feet a mile will require the power
to be doubled ; but if the whole resistance on the level be con-
siderably greater, and the proportion of it due to friction be small,
then a much steeper inclination would be necessary to double
the resistance to the tractive power ; and, on the other hand, a
small diminution in the velocity of the train would compensate
for the increased efi"ect from gravitation. In laying out lines of
railway, therefore, intended exclusively or chiefly for rapid pas-
senger-traffic, instead of obtaining by a large outlay of capital a
road nearly level, steeper gradients would be adopted, and the
resistance to the moving power rendered sufficiently uniform by
variation of speed. That this has been in fact practically ac-
complished on some of the more extensive railways now in
operation in this countrj', is within the knowledge of some of
the Members of this Committee ; and it is hoped that in a
subsequent Report they will be enabled to prove it by pro-
ducing the actual results of such experience.
If it shall appear, as now seems at least probable, that in
railway traffic conducted at high speeds the cliief part of tlie
moving power is engrossed by the atmospheric resistance, it
Mill be a matter for serious consideration how this resistance can
be diminished ; and it is evident that, ceteris ])ai'ibus, wide
frontage, and therefore increased gauge is disadvantageous.
These are points to the investigation of M^iich the Committee
will hereafter devote attention, and it is hoped they will be
enabled to lay before the Association such experiments and such
results of the practical traffic on railways, as will justify distinct
and satisfactory conclusions upon them.
ACTION OF WATER ON IRON. 253
lurst Report upon Experiments, instituted at the request of
the British Association, ujjon the Action of Sea and River
Water, ivhether clear or foul, and at various temperatures,
upon Cast and Wrought Iron. By Robert Mallkt,
M.R.I.A. Ass. Ins. C.E.
1. Thk subject of the present report, for the furtherance of
which the Association, at its last meeting, made a grant of
money, is one of great interest in a scientific point of view, and
of paramount importance as an inquiry of civil engineering.
Scarcely half a century has elapsed since the adaptation of iron
in its various forms to the many purposes of the engineer, upon
a scale before unknown, and as forming parts of public struc-
tures whose limit of duration was to be measured, not by years,
but by centuries, first made it necessary to inquire — What was
the durability of the apparently hard and intractable material
employed ? What were the forces likely to occasion its destruc-
tion ? How would they act ? What would be their results ?
And what were the means of arresting their progress ?
Yet important as a full answer to these inquiries would be,
and though the application of iron in construction to harbours
and ships, bridges and railways, and the innumerable other con-
trivances by which the engineer subdues and administers the
forces supplied by the Creator to the social wants of man, yet
our information upon this fundamental subject is scarcely more
advanced than it was twenty years ago ; and while the chemist
is not precisely informed as to the nature of the changes which
air and water (our most universal elements), separate or toge-
ther, produce on iron, the engineer is without data to determine
what limit their corroding action sets to the duration of his as-
piring and apparently unyielding structures. The investigation,
therefore, is one full of importance to science and to the arts ;
and although the commands of the British Association, as re-
spects it, have not been neglected, yet the conditions of the
subject were such, and the difficulties and delays in procuring
the requisite specimens of iron so great, that the following re-
port consists chiefly of a general survey of the present aspect
of this field of knowledge, and of the operations commenced or
intended by us for extending its boundaries, than of acquisi-
tions already made.
2. It comprises, therefore, — 1st, a very brief "precis" of the
actual state of chemical knowledge of the subject at large, viz.
254 EIGHTH REPORT — 1838.
of the chemical actions, under vai-ious modifications, of air and
water upon iron ; 2nd, a statement of the experiments upon
the large scale which have already been instituted at the re-
quest of the British Association ; 3rd, a refutation of some fal-
lacies as to supposed methods of protection of iron from the
action of air and water ; 4th, the suggestion of a proposed new
method of protection of cast and wrought iron from tliese ac-
tions, now in progress of experiment ; and, lastly, the state-
ment and consideration of such questions upon this subject as
still stand in need of experimental answers, and are desiderata
to chemical science and to civil engineering.
3. There has been much discussion as to the number and
composition of the oxides of iron, arising partly from the diffi-
culty of procuring iron free from foreign matter for experiment,
and partly from its oxides combining with each other. They
are now reduced to two, viz.
The Protoxide = F e O
The Sesqui-oxide = F Cg O3.
The hydrate of the first is not permanent, and its water has not
been precisely determined ; it is highly probable from analogy
that it has the composition F e O + 2 H O.
There are two hydrates of the sesqui-oxide, one of which
occurs native = 2 F Cg O3 + 3 H O, and the other formed arti-
ficially = F Cg O3 4- 3 H O, and others probably exist. These
two oxides are capable of combining and forming
Magnetic oxide (native) = F Cg O3 -j- F e O,
Forge scales (battitures) = Fe^O^ + 6FeO.
Other less distinctly ascertained combinations have been de-
scribed. It is dubious whether forge scales are a chemical com-
bination at all, but I'ather a mixture of the protoxide and sesqui-
oxide in progress of cliange by cementation into the latter.
4. And first of our chemical knowledge of the action of air
and water upon iron.
Of the Action of Pure Water upon Iron.
" Pure water deprived of air does not act on iron at any tem-
perature below 80° Reaum. = 212° Fahr., and at that but slowly.
The water was freed from any air bj^ Hall, by boiling, and by
the action of the iron itself." — (Marshall Hall, Phil. Trans.
1818; Karsten, Chim. du Fer.)
." At a red heat, and above it, iron is instantly oxidized by
decomposition of vapour of water, producing, according to Ro-
biquet and othei's, (Fe^Og + FeO)." — {Journal de Pliarm.
1818.)
ACTION OF WATER ON IRON. 255
The resulting combination, the oxidum, ferroso-ferrique of
Berzelius, is, according to him, by long continued watering,
converted all into a h3^drated peroxide (FcgOg + 2 HO). Gay
Lussac, however, states, that it is impossible to oxidate iron to
its maximum by the action of water, which seems most proba-
ble. He states the composition of the oxide produced at 37*8
per cent, of oxygen, which approaches that of the native mag-
netic oxide. Neither iron nor its oxides are at all soluble in
pure water according to Westrumb.
Of the Action of Dry Air upon Iron.
5. Perfectly dry air has no action whatever on iron, nor has
dry oxygen below ignition, unless we consider the " blueing "
of steel as a state of oxidation. Both air and oxygen rapidly
decompose iron at and above the temperature of ignition, pro-
ducing, according to Berthier, sesqui-oxide of iron, quadri-pro-
toxidated = F Cg O3 + 4 F e O.
Mosander's results, however, do not agree with these j he
found, that iron oxidated by dry air, at a red heat, produced an
outer coat of sesqui- or peroxide, and beneath this, one having
the composition (F Cg O3 + 6 F e O).
The extreme slowness with which moderately dry air acts on
iron is evidenced by an experiment of M. Zumstein, who fixed
a polished iron cross on the summit of Monte Rosa, in the Alps,
in August in 1820: on visiting it again, in August, 1821, it
was found neither rusted nor corroded, but had merely acquired
a tarnish the colour of bronze. The temperature of the air was
21" Fahr. Barometer, 16 inches 42 lines, and height above the
level of the sea, 14,086 feet. — [Bib, Univer. xxxiii. p. 65.)
6. Of the Action of Air and Water combined on Iron.
While at common temperatures, both air and water are sepa-
rately strictly neutral bodies in respect of iron ; yet when acting
conjointly, the case is widely different. In general it may be
stated that any neutral body, however slight its own electro-
positive or negative relations may be in presence of iron and
oxygen, will modify the action of these bodies on each other
in proportion as it tends to render the oxygen more negative
and the metal more positive.
7. It must be confessed that there are many points in the ac-
tion ef air and water combined still in need of being experi-
mentally cleared up. We are enabled, however, to discern the
general nature of the phenomena. We are to be understood as
speaking, in the first instance, of wrought and malleable iron,
256 EIGHTH REPORT — 1838.
or iron as nearly pure as possible. Air or oxygen dissolved in
water is in a condensed state, and hence in a condition pecu-
liarly appropriate to combination. Rain water- frequently con-
tains, when fresh fallen, one-fifth of its volume of oxygen.
8. When a piece of iron is immersed in such water, the whole
becomes electrically excited. The water, rendered more nega-
tive by contact with the iron, repels its dissolved oxygen, while
the iron, become more positive by the contact of Avater, exer-
cises an unusual affinity for the oxygen. Supposing the surface
of the metal everywhere uniform, a film of oxide is soon pro-
duced over it, and this once efi^ected, decomposition proceeds
with increased rapidity ; for as every metal is positive with re-
gard to its own oxides, it follows that the film of rust and the
iron beneath now form a voltaic couple of greater energy than
the last ; and whereas the electric energies were before only
sufficient to bring the dissolved oxj'gen of the water into com-
bination Avith the iron, they now become sufficient to decompose
the water itself, and hydrogen commences to be evolved. At this
epoch, if the volume of water be not too great in proportion to
the iron, and the latter present a large surface, as in the pre-
paration of ^thiop's Martial, considerable heat even is evolved,
but the water is previously decomposed in the cold. (Guibourt,
Jour, de Pharm. 1818.) It is a most remarkable JFact, how-
ever, that while iron has this vigorous action on water holding
air in solution, neither the metal nor its peroxide have any on
the eau oxygen^ of Thenard. — (Thenard, Triiit^.)
9. Should the surface of the iron not be uniform in the first
instance, as when patches of rust pre-exist upon it, or when
one part is much harder or denser than another, these form
voltaic elements from the beginning and aid the progress of
oxidation. In nearly all specimens of wrought iron, when ex-
posed to the action of water holding air in solution, in addition
to the first coat of rust, one of carbon and sometimes, in mi-
nute quantity, of oxides higher in the electro-negative scale, are
deposited upon its surface, which still further exalt the condi-
tions favouring corrosion.
10. When iron is freely exposed to air and water in a shallow
vessel, the result of their reaction is a hydrated peroxide ; if,
howevei*, the surfaces of the iron are placed near, but not in
contact with neutral solids, as glass or porcelain, or the depth
of water be considerable, there is also formed a large proportion
of magnetic oxide. Becquerel considers this difference to be
owing to the increased slowness of action in the latter case,
from the greater depth to which the water has to carry the
oxygen.
ACTION OF WATER ON IRON. 25/
11. It has been doubted by Marshall Hall and others, who
assert that nothing but nitrogen is evolved, whether water is
ever decomposed by iron at common temperatures, though in
presence of air ; but independent of the conclusive and simple
experiment of Guibourt, of mixing in large bulk iron turnings
and water, and collecting the hydrogen, Becquerel is of opi-
nion, that the existence of ammonia in the oxides produced,
which was first detected by Vauquelin, is corroborative of the fact,
inasmuch asthe water must suffer decomposition as well as the
air, in order that the hydrogen and nitrogen may combine to
form ammonia. Chevallier and Bousingault also found ammonia
in the native oxides of iron ; and Austin states, that it is always
present when iron is oxidated by air and water. {Ann. de Chim.
vol. xxxiv. p. 109.) Too much stress, however, cannot be laid
upon this argument, as it has been found that rust, in common
with other porous bodies, greedily absorbs ammonia and many
other gaseous substances.
12. When the action of air and water on iron has taken place
with sufficient slowness, the resulting oxides are found crystal-
lized in the form of the native octohedral iron ore. Becquerel
describes a case of crystals, of both hydrated and anhydrous
peroxides, found united in one specimen of corroded wrought
iron from an old chateau of the ninth century. The hydrated
oxide would seem here to have been formed first, and after-
wards decomposed by the action of the still unchanged iron
upon its water.
13. When water contains foreign admixture, the composition
of the rust resulting from its action varies accordingly, together
with the rapidity of its corrosion ; thus, when it contains car-
bonic acid, the rust contains water and subcarbonate of iron,
according to Dr. Thomson ; and Soubeiran found rust under
such circumstances, formed of the sesquioxide, combined
with 3 atoms of water, and containing variable quantities of the
sesqui-basic carbonate of iron, and occasionally the carbonate of
the protoxide. Carbon is always, silica occasionally, deposited
from the iron dissolved.
14. With the exception of those bodies which are occasionally
met with in mineralized waters, and of carbonic acid, and the
constituents of sea water, that rendered foul by decaying organic
matter, and that from mines, all others are rather beside our
present object, as modifying the action of air and water on iron.
We proceed, then, to consider the nature and results
Of the Action of Sea Water on Iron
at ordinary temperatures ; and although the results of the careful
258 EIGHTH REPORT — 1838.
observations of Marcet, Scoresby, and others, show that the water
of the ocean is rather denser, or contains more saline matter in
torrid and temperate zones than in high latitudes, yet from 3^
to 4 per cent, of solid salts may be taken as the general average.
And as these have a complex constitution, so the results of their
action on iron and water containing air are complex; and expe-
riments are yet wanting to enable a perfect rationale of the pro-
cess to be given and its results precisely stated.
15. In the first instance the actions already described, in the
case of air and pure water at low temperatures, take place and
give rise to the oxides of iron ; and as the sea water almost
always contains carbonic acid, a portion of these is resolved into
carbonate of iron.
16. As in pure so in sea water, when iron is deeply immersed
the oxide produced is the magnetic in the first instance, the
iron becomes covered with a light buff coat of rust; but if the
vessel be shallow, the sesqui-oxide is formed gradually from it.
In each case, the first appearance of action which the fluid pre-
sents is the formation of numerous slight green streaks in it.
These form usually in about thirty minutes from immersion of
the metal, and appear to be protoxide in progress of transition
into magnetic oxide and sesqui-oxide, of which latter oxides a
large precipitate soon forms at the bottom of the vessel.
17. But as sea water likewise contains chlorides of sodium
and magnesium, the carbonate of iron is, in part at least, de-
composed, and a subchloride of iron is formed which unites
with a part of the sesqui-oxide of ii'on, having previously as-
sumed the slate of sesquichloride, and forms with it an inso-
luble compound.
18. It happens hence, after a mass of iron has lain for a con-
siderable time in a limited quantity of sea water, that the latter
holds carbonate of soda in solution, and the further action be-
comes very slow, and that a hydrated carbonate of magnesia
has deposited on the iron.
19. It would appear also, that the sulphates are in part de-
composed, the sulphuric acid passing to the iron and forming
a basic insoluble sulphate, and the lime an insoluble carbonate,
with the carbonic acid of the water. But sulphiu'ic acid is by
no means uniformly to be detected in the ochreous deposit
formed by the action of sea water on iron, nor indeed chlorine
either. But besides chlorides, sea water contains bromides and
iodides, and of the part which these play in the decompositions
conseqvient on the action of iron, it must be confessed we are as
yet wholly ignorant. Analogy, however, gives reason to pre-
sume they play similar parts to the chlorides.
ACTION OF WATER ON IRON. 259
20. If malleable iron or steel have been snbjected to the sol-
vency of sea water, carbon and sometimes silicon are deposited
in small quantities ; but when cast iron is acted on more re-
markable results follow. After it has remained for a length of
time immersed, the metal is found wholly removed, and in its
place a pseudomorph of its original size remains, as first observed
by Priestley, consisting of a carbonaceous substance, analogous
to plumbago, mixed with oxides of iron, and which frequently,
but not invariably, possesses the property of heating or in-
flaming spontaneously when exposed to air. There have been
unfortunately, as yet, but few cases of this remarkable change,
which requires the lapse of time to take place, carefully ob-
served ; and it is as yet by no means clear how it is produced,
what is its precise composition, or to what is owing the rise in
its temperature on exposure to air.
21. It is remarkable, that not cast iron alone is subject to
this change ; under circumstances but little understood as yet,
the purest malleable iron is alike converted into what we shall
for brevity call phnnhago.
Karsten mentions, that when iron, whether wrought or cast,
has been long exposed to water holding in solution alkaline or
earthy salts, it is at length dissolved ; that when hard bar iron
had remained some centuries in sea water it was altogether dis-
solved, and a mass of carbonaceous matter remained, as though
it had been submitted to the prolonged action of a diluted acid.
This change, he says, is generally attributed to the decomposi-
tion of the carbonic acid contained in the sea water; but it is
much more likely that, in the long run, the sulphates and chlo-
rides contained in the sea water are decomposed likevdse by
the iron.
The writer possesses a portion of an ancient anchor taken up
in the port of Liverpool, the iron that remained of which was
of remarkable purity, and which was converted into plumbago
of unusual hardness and brilliancy to the depth of half an inch.
This plumbago did not heat on exposure. Its specific gravity is
1'773- This fact militates against anobservation made by Hatchet,
and repeated by Becquerel, that anchors and other objects of
forged iron sustain no alteration in sea water but oxidation,
from which we must suppose that the contact of iron and plum-
bago in the cast iron produces a voltaic current, which accele-
rates the action of the latter.
Berzelius' opinion is, that the carbonic acid contained in the
water dissolves and removes the iron. He quotes an instance
of the guns of a vessel which had foundered off Carlscrona,
which, when taken up fifty years afterwards, were found nearly
260 EIGHTH RKPORT 1838.
wholly converted into plumbago, and whicli heated to such an
extent in a quarter of an hour after exposure as to evaporate the
water contained in its pores. He adds, "W-e know not pre-
cisely what passes under these circumstances." — {Traitd de
Chim. vol. iii.) Dr. M^CuUoch states, that plumbago thus
formed always possesses the property of spontaneous heating.
This, however, from the writer's own observation, is certainly
erroneous. — {Edin. Phil. Jour. No. 14.)
Hatchet examined a specimen of plumbago which remained
long immersed in sea water at Plymouth : he found it contained
a little chloride of iron, and that it was composed of
Oxide of iron . . 0*81
Plumbasro . . . 0-16
0-97
Dr. M*Culloch made several experiments upon the artificial
formation of this phunbago by the action of diluted acids ; he
found it bore in quantity no definite relation to the species of
cast iron from which it was obtained.
Pig iron produced more than that cast into guns or shot ; of
the latter the blackest varieties, as might be expected, produced
the most.
This author mentions a case of its production from the action
of London porter on iron, and also of the recovering of some of
the iron guns of the Armada off the coast of Mull, which be-
came so hot on being weighed, that they could not be touched.
He found that the produce of plumbago from the blackest cast
iron, dissolved in dilute acetic acid, equalled the bulk of the
iron, and was not pulverulent, but coherent, so as to be cut
with a knife.
In some cases the plumbago heated, and in some it did not ;
in the latter he presumes oxygenation to have taken place du-
ring solution.
From his experiments Dr. M'CuUoch drew the rather singu-
lar conclusion, that the plumbago was the oxide of a peculiar
metal, the oxygenation of which produced the heating.
Dr. Thompson, in commenting upon this paper, observes,
that M'CuUoch appears ignorant of the existence of silicon in
cast iron,,an,d of Daniell's experiments upon the subject.
22. Mr. Daniell has given some interesting experiments on
this subject in a paper, on the structure of iron developed by
solution, in the Journal of the Royal Institution. In this, after
describing the formation of this plumbago by the action of di-
lute acids, and its properties, he gives an analysis of the sub*
ACTION OP WATER ON IRON. 261
Stance, and a theory of the cause of its heating on exposure
to air.
Hydrochloric and sulphuric acids both produced it. Nitric
acid produced it, but in a state incapable of beating in air. It
did not lose this property by long exposure in a solution of a
salt of iron, or in water. It absorbed oxygen from the air with
evolution of heat. In pure oxygen or chlorine it became much
hotter, absorbing either : the residue, after absorption of oxy-
gen, was found to contain silex; and Mr. Daniell considers
that the plumbaginous cDmpound consists of carburet of iron
and silicon, and that, by absorption of oxygen, these became
protoxides without separation from the carbon.
The experiments of Berzelius and Stromeyer, however, ad-
duced by Mr. Daniell in support of this view, appear rather to
militate against its truth ; and however it may be a " vera
causa " that the presence of silicon may occasionally produce
the spontaneous heating of this plumbago, the result of my
own experiments prove that it can be produced from many
specimens of cast iron which do not contain a particle of si-
licon.
23. Dr. William Henry has given, in Thomson's Annals for
January 1815, an interesting account of his examination of this
substance produced from cast iron in a coal-pit shaft near New-
castle-on-Tyne. The cast iron was part of a pipe used to con-
vey the water, and evolved gases from a bed of quick sand ; its
external characters were the same as those previously described.
The specific gravity of the specimen was from 2-008 to 2-155.
He states its composition "as iron, plumbago, and the other
impurities usually present in cast iron ; " his examination, how-
ever, was cursory and rather imperfect. The water from the
shaft contained 64 grains in a wine-pint of chlorides of sodium,
calcium, and magnesium, and of the sulphate and carbonate of
lime. He ascribes the i-emoval of the metal to decomposition
of the chlorides, and instances their capability of removing the
iron from ink. He also adds a case of conversion of cast iron
into plumbago by the action of steam and powdered charcoal
on it.
24. Dr. Thomson gives in his Annals for 1817 a case of like
change, produced, with un\isual rapidity, by the action of sour
paste, or weavers' "dressing" to cast-iron rollers. The change
was so rapid as to oblige the substitution of wood for iron. It
is not stated whether the rollers were heated by steam or
otherwise, or were at the atmospheric temperature. In the
Annals for 1825, a very interesting case is -given in a letter
VOL. vxi. 1838. s
h
262 EIGHTH REPORT — 1838.
from Charles Horsfall, Esq. to Dr. Traill, in which bars of cast
iron of 3 inches broad by 1 inch thick, which formed protectors
to the copper of a vessel, to the amount of abo'ut ^no ^^ its sur-
face, were, in a voyage of not quite five months, to Jamaica and
back, converted into plumbago to the depth of half an inch ; it
heated on being scraped and exposed to the air when the ship
first went into dock. Mr. Brande, in the Quarterly Journal,
vol. xii., describes an iron gun which had long lain in water as
converted into plumbago to the depth of an inch. I have also
been favoured by my friend, Mr. Firmston of Glasgow, with a
piece of similarly changed cast iron from the false keel of the
John Bull, East Indiaman. In four years this piece of 1| inch
by 4 inches was completely altered through. Its specific gra-
vity is 1*259. I have not yet been enabled to determine the
composition of this specimen, or that from the wrought iron
before alluded to.
25. Mr. Pepys found cast iron similarly changed by the ac-
tion of pyroligneous acid (Gill's Tech. Rep., vol. iii.) ; and I
have myself obtained specimens so produced by this acid in a
state of vapour. The same change is produced by the vapour
disengaged in the roasting of coffee ; and a curious case of simi-
lar action of sherry wine on wrought iron and steel is to be
found in Thomson's Annals. It is also well known that the
cast-iron plates at first used in the interior of Coffey's Patent
Still, were I'apidly converted into plumbago by the action of
the low wines and proof spirits. Much more lately cannon
shot have been found immersed in the sea, near the site of the
battle of La Hogue, converted to the depth of an inch into plum-
bago, or, according to another statement, all through. The
battle of La Hogue took place in May 1 692 ; hence these shots
have lain in the sea for a period of about 145 years; it is pro-
bable they were thirty- two pound shot, and, if converted into
plumbago all through, this fact shows that some cast irons may
be wholly destroyed in the above period by sea water, to the
depth of 3^ inches, — a 32 lb. shot being about 6j in. in diameter.
26. I have thus collected and given at a tedious length nearly
all the cases of this singular change published ; they serve as an
index for future experiments, and they show how very little we
know of the real nature of the phenomena. It is equally ob-
vious that, from the want of precision and of data as to time
and surface, &c. in most of the statements, no information is
afforded of any use to the engineer.
It strikes one at once, that every author hitherto who has
studied this subject has wholly omitted any consideration of a
ACTION OF WATER ON IRON. JsOO
most important I'esult which the carbon in iron, especially cast
iron, plays during its solution.
It is established that carbon exists in cast iron, steel, &c.
in two states : as graphite or crystallized carbon, disseminated
in its mass, giving it brilliancy of fracture, softness, porosity,
and fluidity in fusion ; and as a definite carburet, combined with
a portion of the iron chemically, and mixed mechanically with
the remainder.
Now, in the decomposition of iron so circumstanced by air
and water, whether in presence of an acid or not, besides the
combination of oxygen furnished both by the air and water with
the metal, other reactions take place. Nitrogen and hydrogen
are both set free, but they may or may not be both evolved. The
nitrogen combines with part of the hydrogen to form ammonia,
which, according to circumstances, is evolved, or combines with
the oxides of iron produced.
But it is probable, from the experiments of Thenard and
Despretz, that an azoturet of the undissolved metal may also be
formed. Iron at a higher temperature is unquestionably capable
of decomposing ammonia and combining with azote, so as to aug-
ment its weight by 0'12. But in addition, as the combined car-
bon is set free from the iron in a nascent state, it seizes upon
a portion of the evolved hydrogen, and forms a highly volatile
and odorous oily hydrocarbon, while some of the uncombined
or suspended graphite, also set free in a highly divided state,
combines with another portion of the hydrogen and with oxy-
gen, and produces an extractive mattei- — apotheme of Berzelius,
and which differs little from ulmic acid in its reactions. This
latter deposits as a brown substance, soluble in alkalis, &c.,
and combmed ivith all the magnesia and silica due to the
amount of their bases, which the iron may have contained, if
any. The volatile oily hydrocarbon is partly dissipated with the
hydrogen evolved, partly swims upon the surface of the fluid,
rendering it irridescent, and is partly held absorbed by the
porous mass of oxides, carbon, and ulmic acid resulting from
the whole reaction. Hence we see that the simple decomposi-
tion of cast iron by air and water may give rise to no less com-
plex a result than the following formula indicates : —
(FeC^ + C + %i + M^g) + (HO -f- N^O) = {¥e^O^+YeO)
+ (F.,03 + 3HO) + (H + C,.H,.) + (CeoHgoOjs? + SfOg f M^-O)
+ C.
And here several of the substances commonly present in cast
iron are omitted ; if these be included, or an acid present, the
result will of course be still further complicated.
s 2
264 EIGHTH REPORT — 1838.
27. Now to the presence of these hydrocarbons I conceive we
are to look for the phenomenon of the spontaneous heating of
the phunbaginous matter, so many cases of the production of
which have been adduced. It appears to be owing to their fur-
ther oxidation, on exposure to air, presenting a great sui'face to
absorption as existing in the porous mass of plumbago, and to
be a strict analogue of the cases of spontaneous combustion-
produced by various fat oils, &c. exposed to air, in contact with
cotton, linen, &c. &c., or other carbonaceous bodies exposing
a large surface to absorption. The fact that cast iron, which
will produce spontaneously-heatingplumbago, when decomposed
by air and water, or by hydrochloric acid, when dissolved in
riitric acid, gives a plumbago which will not heat spontaneously,
favours this view of the subject; the nitric acid supplying the
oxygen in the first instance.
This is at present but an hypothesis used in directing experi-
ments now in progress to determine the ultimate constitution of
these hydrocarbonous compounds, which have not yet been ana-
lyzed, or collected even in sufficient quantity to admit of ana-
lysis by others, and to discover the nature of the changes which
they suffer in presence of air or oxygen.
28. The analogy of this substance with the carburets pro-
duced by the destructive distillation of the iron salts of the or-
ganic oxacids and cyanogene compounds, is obvious. These,
Berzelius is of opinion, are true carburets, while other chemists
conclude them to be mere mixtures of finely-divided carbon
with the base of the salt.
I cannot, howevei', but coincide in the view of Boucharlat,
whose experiments lead him to believe them mixtures of car-
bon, with one or more definite carburets of iron whose pro-
perties he has described. If thus, they are analogous to the
conditions in which carbon exists in cast iron itself.
29. It also bears a striking resemblance to the powders de-
scribed by Messrs. Stodart and Faraday, as obtained by the so-
lution of some of their alloys of steel in sulphuric and hydro-
chloric acids : these were not acted on by water, but oxidated in
air, and burnt like pyrophorus when heated to 300° or 400°
Fahr., leaving protoxide of iron and the alloying metal. They
conclude, that during the action of the acid, hydrogen entered
into combination with the metal and charcoal, and formed an
inflammable compound, as they found these powders sometimes
burnt with flame. By the action of nitric acid on these powders
they obtained some fulminating compounds.
I have found that when borate of lead is decomposed by the
joint action of charcoal and platina with heat, a boruret of pla-
ACTION OF WATER ON IRON. 265
tina is formed, which, on subsequent digestion in nitric acid,
becomes powerfully explosive ; boron here apparently playing
the part of the carbon in Mr. Faraday's compounds.
30. The inflammable powders produced by Magnus, by reduc-
tion of the difficultly fusible metals by hydrogen, also connect
themselves with the subject. To complete our knowledge of all
these remarkable substances, with reference to the immediate
subject of this report, will need a careful and extensive series of
experiments.
31. There have been but few observations made as to the
variations in composition of cast and wrought iron as regards
their acceleration or retardation of the action of solvent agents
upon it. It is not known at this moment with certainty what
properties'" should be chosen, in either cast or wrought iron,
that its corrosion may be the least possible, under given cir-
cumstances, when used in construction.
32. Faraday found the alloys of most of the metals he tried
with steel much less acted on by moist air than steel unalloyed;
but he also discovered the remarkable circumstance, that a very
minute quantity of an alloying metal produced an increased ac-
tion of sulphuric acid on steel, within certain limits ; thus, ^i^
of platina greatly increased the action of the acid on the steel
with which it was alloj^ed ; with from ^^^ to ^i^ it was power-
ful; with 10 per cent, of platina there was a feeble action;
with 50 per cent, of platina the action was the same as with
unalloyed steel ; and an alloy of 90 platina and 20 steel was not
touched by the acid. In these cases even acids of very weak
combining power, as oxalic, tartaric, and acetic, rapidly dis-
solved the steel. Of three possible modes of accounting for
this suggested by Sir H. Davy, Mr. Faraday justly chooses
that which supposes the platina in part forming a definite alloy,
and the remainder diffused through the substance of the steel ;
thus forming an indefinite number of voltaic elements. On the
first action of the acid some of the particles of platina are de-
nuded, and being strongly negative with respect to the rest of
the compound, aid its solution. Upon this ground the action of
the excess of platina, in reducing the action, is obviously de-
pendent upon the whole alloy becoming definite again. Solu-
tions of chloride of sodium did not act more rapidly on these
alloys than on steel alone.
33. It has been long observed how little liable to tarnish or
rust native and meteoric iron are, which contain often as much
as 9*5 per cent, of nickel, and variable proportions of chrome
and cobalt. The following tables embody perhaps the whole of
266
EIGHTH REPORT — 1838.
our present knowledge on this interesting point, in which the
alloying metals are grouped according to their producing an
alloy more or less corrodible by oxidizing agents than iron
alone.
Alloys more Cor-
rodible than Iron.
Authorities.
Alloys less Corrodible
than Iron.
Authorities.
Potassium. . . .
Sodium
Barium
Glucinum. . . .
Aluminum . . .
Manganese . . .
Silver
Platina
Silicium
Antimony ....
Arsenic
SeruUas
Lampadius
Davy
Berthier
Berzelius
Faraday
Berthier
SeruUas
Berthier
Nickel
Cobalt
Tin
Copper
Copper and Zinc
Mercury
Iridium
Osmium ,
Columbium ....
Chrome
Berzelius
Rinmann
Karsten
Vazie
Berzelius
Karsten
Berthier
The metals are here arranged according to their electrical
order, beginning with the most positive. In the first column
all above silver are positive to iron, and all below it, inclusive,
and in the second column, negative to it. It is obvious, how-
ever, that this gives us very defective information, as Faraday's
case of the platina alloy shows that mere difference in propor-
tion may wholly change the properties of the alloy in this re-
spect. An analogue to the peculiar action of the platina in this
case is found in the epigene crystals of native oxide of iron,
which are generally auriferous, and have the form of the bisul-
phuret of iron, whosa decomposition the electric agency of the
noble metal seems to have facilitated, though present in such
minute quantity in an uncombined state.
34. Dr. Faraday also found that the alloys of pure iron vvere
less acted on by moist air than those of steel. It is also ex-
ceedingly remarkable, that in respect of corrodibility, the alloys
of steel follow a totally different order to those of wrought iron.
In the following table the first column shows the order of cor-
rodibility of various alloys with steel, compared with steel alone,
commencing with the less corrodible ; and the second column
shows the electric order of the metals with reference to iron,
beginning with the most positive.
ACTION OF WATER ON IRON.
267
Order of Corrodibility.
Electric Order.
E+.
Unalloyed Steel.
Iron or Steel.
Steel and Chrome
Nickel
. . Silver
Silver
. . . . Gold
Palladium
. , Nickel
Platina
. . Rhodium
Rhodium
. . Iridium
Iridium
. . Osmium
Gold
. . Palladium
Osmium
. . . . Platina
Chrome
E
It is obvious that each of these must be considered, not as a
binary alloy, but as a ternary compound of two metals with
carbon, or of one metal with a carburet of iron. These tables
point out a wide field for experiment of great interest.
We may from these results conclude, that the alloy of iron
with any metal in a negative relation to it, unless the alloy be
definite, will probably be attended with an increased corrosion
of the metal; and that its alloy with a metal positive to it, though
it may possibly initially protect the iron from action, will, by
its own removal, be likely to render its texture open and porous,
and hence more fitted for subsequent solution and removal.
85. M. Vazie has recommended an alloy of brass and cast
iron, in other words, a quadruple compound of carbon, copper,
iron, and zinc, as a suitable metal for various large works where
capability of resisting rusting or corrosion is important. It is
stated that experiments made with it on a large scale, at Glei-
witz, in Silesia, were attended with satisfactory results. These
require repetition, and much may possibly yet be done in im-
proving the durability of cast iron by minutely alloying it. It
will be recollected, that a minute quantity of iridium alloyed
with iron confers on it the same power of being hardened by
rapid cooling that carbon, boron, and silicon do.
36. The porousness of the ci'ystalline grain of cast iron is
frequently very remarkable, and is such as to permit many fluids
to enter its pores, and actually saturate the metal like a sponge.
A very remarkable case of this is recorded in the Quarterly
Journal of Science, vol. ii. p. 385. M. Clement formed a
large cylinder of coppei', within which he placed a turned cylin-
der of cast-iron, also bored out ; a space intervened between
the two, into which he poured melted tin. To his surprise, on
becoming cold, much of the tin was squeezed through the cast-
iron cylinder, and appeared as a fine filamentous wool, lining
268 EIGHTH REPORT — 1638.
the internal part of the cast-iron cylinder. It was of such
tenuity as to take fire and burn at a candle like tinder. It is
here obvious that the iron and copper cylinders were heated
alike, but the latter expanded much more than the former, and
hence, on cooling, compressed the tin (still fluid, probably, about
the centre of the length of the cylinder, althougli cold at its
ends), and forced it out through the pores of the iron. The
limit of force here was only that of the cohesion of the copper'
cylinder.
37. It is usually considered an ignorant prejudice of workmen,
that a " hard shin," as it is technically called, is given to cast
iron, after planing or turning, by coating it with oil, and, until
a short time since, I was myself of that opinion ; but, on exa-
mining some broken castings, whose surfaces had been turned
and exposed to oil for several years, I found that the oil had
penetrated the pores of the iron to a considerable depth.
38. I also possess a piece of cast iron, of considerable thick-
ness, which formed, I believe, part of a furnace for decomposi-
tion of sea salt ; it contains throughout its mass a minute
quantity of chloride of sodium, and a great deal of sulphur.
This has been produced by cementation, in the same way as
Herapath describes an alloy of
Zinc 92-6
Iron 7-4= 100-0
as being produced in the Bristol Zinc Works ; and as alloys of
cast iron with arsenic, antimony, and lead have been formed.
These observations are intended to show the importance of se-
lecting close-grained cast irons for works designed to resist
longest the action of air and water.
39. Of the relative rates of corrosion of the various com-
mercial "makes," or specimens of wrought and cast iron,
scarcely anything is known, and that of a very general cha-
racter. It is certain that the blackest cast irons, viz. those
which contain the largest quantity of uncombined carbon or
graphite in a mere state of mixture, are acted on by air and
water the most rapidly. This has probably partly an electro-
chemical cause, and partly a mechanical one, from defects of
hardness, and open and porous grain. There can be little doubt
but that the suspended graphite in this kind of iron forms the
negative element of innumerable voltaic couples which aid the
process of oxidation.
The gray or mottled iron most used for castings of ma-
chinery and engineering purposes in general, as containing a
less quantity of uncombined carbon, and having a denser
ACTION OF WATER ON IRON. 269
structure, is less acted upon ; and the varieties of iron which
present scarcely any symptoms of a crystalline texture at all,
but still are grained or mottled, and can barely be touched by
the file, turned, or bored, are those which, while they are still
capable of being used for almost every purpose to which cast
ii'on is applicable, are the least susceptible of alteration or decay.
40. The officers of the French artillery, amongst whom M.
Born has been most conspicuous, have made a number of expe-
riments on this branch of our subject. They have found that
the corrosion of iron by air and water is greater in proportion
to the purity or goodness of the coke with which the iron is
made, and that it is altered less when made with charcoal than
with coke. In the former case, it is probable this arises from
the iron containing the largest dose of uncombined carbon or
graphite ; and in the latter, namely, in that made with charcoal,
it seems to arise from the less quantity of silicium contained in
this cast iron. Various careful analyses made by Berzelius,
Karsten, Berthier, and others, show that, while coke-made iron
contains from 0*025 to 0*045 of silicium, that made with char-
coal only contains from 0*002 to 0*013 ; and it is certain that
the presence of silicium disposes iron to corrode, although in
dissolving in menstrua it may sometimes act as a mechanical
protector, covering it with a coat of silex.
41. M. Born has also observed that iron cast in "dry sand,"
or "in loam" moulds faced with charcoal, oxidates much less
speedily than when cast in green sand ; and that "chilled" cast
iron, or that cast in iron moulds, is the least of all susceptible
of this change. — {Comptes Rendus, 1837.)
42. Becquerel, in remarking upon these statements, observes,
that cannon which are cast of close gray iron, and in "dry sand,"
sustain little alteration further than a single coat of rust, or
browning like a gun-barrel, which seems to suspend further
action. This he attributes to the charcoal facing of the mouldy
and adds, that if it were possible to carburate the surfaces of ob-
jects cast in iron in the operation of moulding, this alone would
preserve them from further oxidation. There appears, how-
ever, here to be a serious mistake ; the presence of a carbona-
ceous coat on the surface of cast iron, unless impervious to air
and water, cannot preserve it from rust, however uniformly
spread. That it should do so, would be at variance not only
with the observed facts, and with the circumstance that the coat
of plumbago formed by the action of sea-water on iron does not
'preserve the remainder, but is at variance with an experiment
of Becquerel himself, in which he shows that the application of
a piece of common charcoal to the surface of iron in a solution
270 EIGHTH REPORT — 1838.
of sea salt and sub-carbonate of soda greatly promotes its
oxidation. Unless, then, it were impervious to the fluid agent,
it could never prevent the oxidation, however uftiform.
43. It cannot have escaped the notice of any one who has had
an opportunity of observing castings, with what rapidity the
Avater of a fresh-fallen shower of rain, which is highly charged
with oxygen, attacks fresh-made castings of iron ; and this,,
according to my observation, more rapidly in "dry sand" or
"loam" castings than those made in damp or "green sand,"
contrary to the opinion of the French engineers : which I at-
tribute to the circumstance, that in "loam" or "dry sand"
moulds, moisture not being present, but little hydrogen is
generated by the fluid metal to burn off the " facing" of char-
coal, which remains "parseme" on the surface of the casting,
producing innumerable voltaic couples in contact Avith water ;
while, in the case of "green sand " castings, most of the char-
coal facing is removed in a gaseous form from the casting before
it leaves the sand.
44. "Chilled" cast iron, or that whose substance, to a greater
or less depth, has suffered an alteration of cr3'stalline arrange-
ment by having been cast in a cold iron mould, is unquestionably
that which suffers least change, in a given time, in water
charged with air, whether fresh or salt ; and this from two di-
stinct causes : first, from its greatly increased density and hard-
ness ; and, secondly, from the fact that a very large portion of
luicombined carbon is pressed or squeezed out by the expansion
of the crystals of iron at the moment of consolidation.
45. I have presented to the Chemical Section two specimens
of chilled cast iron, in which, by a little management, this phe-
nomenon has been rendered very apparent. On these the sus-
pended or uncombined carbon is seen exuded in the form of a
metalline dew, and adherent to the surface in drops of various
sizes.
These specimens are interesting in another point of view, as
affording decisive instances of the expansion of iron in con-
solidating.
I have also in my possession a piece of an unusually dense and
white "chilled" iron, of large dimensions, whose entire substance
is filled with interspersed octohedral crystals of apparently
pure carbon. They are nearly all of equal size, the principal
axis of the crystal being about one twentieth of an inch in
length. They are hard enough to scratch quartz, and are ex-
ceedingly obvious and striking from their dark colour, compared
with the iron in which they are imbedded, the grain of which
also is brilliaiit and highly crystalline.
ACTION OF WATER ON IRON. 271
46. It has been considered by most authors that ^'chilled" or
white cast iron contains less combined carbon than the black
or gray varieties ; this, however, appears to be a mistake ; yet
it is undoubtedly true that it does contain much less carbon or
graphite in a suspended or uncombined state, and that the latter
is mechanically expressed and locally deposited in much the
same way, as the author has endeavoured to show in another
place, — that the contemporaneous quartz veins in granite have
been formed from the residual quartz existing in that rock, over
and above that which was necessary to the atomic composition
of its constituent minerals. It is also analogous to the ob-
servation made by Pelletier respecting the combination of
phosphorus and silver, viz. that this metal holds more phos-
phorus in combination, or rather in suspension, while in fusion
than when solid, for at the moment of congelation of fused
phosphuret of silver it exudes a quantity of phosphorus, which
takes fire, unless the whole be suddenly cooled in water. —
[Ami. de Chun. vol. xiii. p. 110.)
47. By two remarkable properties may the whole of the
metals be divided into as many classes, namely, those which
pass from the fluid state of fusion instantaneously to the solid ;
and those which assume the latter state by passing through an
intermediate condition of pastiness.
The former property is exemplified in all the metals which
crystallize best, as bismuth, zinc, arsenic, &c.; and the latter in
potassium, sodium, iron, platina, &c. The power of being
welded is entirely due to this latter condition of intermediate
pastiness between fluidity and solidity, and hence it is properly
not confined merely to metals, for wax, tallow, resins, camphor,
caoutchouc, glass, and most vitrifactions, have strictly the
welding property.
But it results from this that those bodies which can be
welded can scarcely ever be crystallized by fusion and slow
cooling, because that pasty and viscid condition they assume
before solidification forbids the freedom of motion to their
molecules, which is essential to their crystalline arrangement.
But in "chilling" cast iron bj^ sudden cooling, time is not
given it to assume the viscid or pasty state; its particles are
compelled to pass ])er saltiim from a liquid to a crystalline solid,
and, e converso, by continued cementation at a temperature ap-
proaching its fusing point, "chilled" cast iron may be brought
back again to the ordinary grain of common cast iron. By this
instantaneous change, the crystals of iron in forming, in obe-
dience to the general law, reject and throw out the uncombined
carbon as heterogeneous, which itself also assumes the cry-
272 KIGHTH REPORT 1838.
stalline form. We see here, also, the close analogy to the pheno-
mena and properties of unannealed glass, that is, of silicates
which have been compelled suddenly to pass from the semi-fluid
state to that of solidity, without passing through the pasty con-
dition. In these the crystalline arrangement is distinctly pro-
duced, as Sir David Brewster has determined by the optical
examination of Prince Rupert's Drops, and yet these, by being
annealed, are brought back to the state of ordinary glass.
48. Hence, then, the superior hardness and greater specific
gravity of chilled cast iron. But while it accrues, from the
chilling of cast iron, that it corrodes less rapidly, a singular
and in some cases disadvantageous circumstance occurs in the
manner of its corrosion, which needs further consideration, as it
may sometimes happen to be of much greater practical im-
portance than any amount of mere decay of substance.
49. When a piece of cast iron moulded in sand is exposed to
corrosion, this takes place with somewhat variable, but yet with
very considerable uiiiformity over its entire exposed surface.
Not so, however, with chilled castings ; in these, each nucleus
of exudation of its uncombined carbon forms with the iron in its
immediate vicinity a voltaic couple ; and its results are, that,
in place of the uniform action as before, the largest portion of
the surface remains unchanged, and corrosion is nearly wholly
confined to these spots, as so many local centres of action. The
oxides of iron are formed as usual ; but, from the texture of the
casting, and its constitutional carbon being all in a state of
combination, little or no carbonaceous or plumbaginous matter
is produced ; hence, as the spots of carbon form, with the rest
of the casting, so many voltaic couples, the oxides formed are
rapidly transferred to these points, and gradually produce large
tubercular concretions, which, M. Payen states, alu'ays consist
of (F e O) + (F e^ O3 + F e O) + (F Ca O3), and which in course of
time contain crystals of the octohedral iron ore thus artificially
produced.
50. M. Payen has presented several memoirs to the Academy
of Sciences on the sulDJect of these local actions on iron, and has
applied to their explanation the facts he had previously disco-
vered, as to the effects of alkaline and saline solutions in retard-
ing or accelerating the corrosive action of water on iron. The
principal facts he has established are the following, as given by
the Commission of the Institute, in reporting on his memoir. —
{Coj)iptes Rendus, Feb. 1837, No. VI.)
" He has found solutions, containing an alkali and sea salt in
such proportions, that, in place of being at all preserved, iron
placed therein was rapidly attacked.
ACTION OF WATER ON IRON. 273
" A cylinder of iron, filed bright, is preserved for a long time
from all alteration when plunged into a solution of pure potass
diluted with one thousand times its weight of water ; but if the
solution be left in contact with the air, the alkali, absorbing
carbonic acid, by degrees loses its preservative power.
" When the water contains yf^ of its volume of a saturated
solution of carbonate of soda, it forms conical concretions of
oxide," &c.
What is more remarkable in this mode of alteration is, that
all points of the surface of the metal are not equally attacked ;
the action commences where there are breaks of continuity, or
where foreign bodies are deposited, which constitute, by their
contact with the iron and the liquid, a voltaic couple : all the
rest of the surface pi-eserves its metallic lustre.
"A saturated solution of sea salt preserved from contact of
air only produces some excrescences of oxide of iron ; while, if
exposed to air, oxidation goes on as usual.
"When this solution is saturated with carbonate of soda it
possesses the property of preserving iron from all alteration,
even though exposed to air, but it loses it when the solution is
diluted.
" It might be presumed that this difference arose from the
saturated solutions containing less air than the dilute, but this
cannot be so, since M. Payen has proved that the proportions
of alkaline bases capable of arresting all oxidation elimhiate but
a very small portion of the air contained in the water.
" M. Payen has determined the proportions of sea salt and
sub-cai'bonate of soda which accelerate the formation of tuber-
cles (or local corrosion) most. A solution of these two salts,
diluted with 75 times its volume of Seine water, produced,
in less than a minute, on cast and wrought iron, a commence-
ment of oxidation, indicated by light green points, which, in
less than ten minutes, formed visible projections."
The effect is increased by applying to the surface a fragment
of charcoal, in which case a voltaic circle is formed ; — " Hence,"
says the Report, " in similar circumstances, cast iron will alter
more rapidly than pure iron."
We see, then, that solutions which have a feeble alkaline re-
action possess the property, in presence of air and sea salt, of
producing on cast and wrought iron, which they moisten, local
concretions which preserve the remainder of the surface from all
change ; and that these effects vary according to the proportion
of the different salts, breaks of continuity, and the foreign bodies
adherent to the surface of the metals.
" M. Payen thinks that the concretions formed in the pipes
274 KIGHTH REPORT 1838.
which supply Grenoble with water (presently to be described)
are formed in tliis way, the waters which pass in them having a
feeble alkaline reaction, owing to the presence of carbonate of
lime, and being slightly saline.
"At the suggestion of the Commission, M. Payen incrusted
pieces of wrouglit iron in cast iron, and fragments of cast iron
in plates of cast iron of another sort : in all these cases he found-
the tubercular oxidations adhered to the points of contact.
" It may be concluded (they continue), from the observed
facts, that whenever there is a want of homogeneity in cast-iron
pipes, which convey water slightly alkaline and saline, tubercles
will be formed at the points where heterogeneity exists. M.
Payen has studied the circumstances in which, as regards the
formation of tubercles, white cast iron produces the same effect
as gray or black;" having diluted one volume of a solution of
carbonate of soda and of chloride of sodium, saturated at a
temperature of 15° Cent., with from 100 to 200 volumes of
distilled water, he has found that all the solutions between
these limits produce on white cast iron oxidations evidentlj'-
more tubercular and better localized than on the other kinds of
cast iron. These last afford more points of easy attack, and
produce more numerous tubercles, and hence less distinct.
" We see, then, that white cast iron, as being less oxidizable
by certain mineral waters, appears to merit the preference over
gray iron for water-pipes."
The reporters further add, " We are not obliged to say that
the constitution and composition of the artificial tubercles are
the same as those of the pipes at Grenoble, which would tend to
prove that both depend on like causes."
51. This local action, in many cases, is of small importance,
and indeed might be more advantageous than that deep removal
of metal which takes place in softer irons ; but in the case of
pipes or similar receptacles for the containing or conveying of
water, the accumulation of these tubercular excrescences gradu-
ally chokes the passages at numberless places, and obliges the
removal of the whole conduit. Nor does this evil solely apply
to chilled cast iron ; all hard cast iron which has been rapidly
or unequally cooled is pro iatifo liable to the same.
52. M. Vicat, in the Comptes Rendiis, vol. iii. 1836, p. 181,
gives an account of the formation of these tubercles on the pipes
which supply Grenoble with water, in which they had increased
to such an extent as seriously to reduce the delivery of water,
and engaged the attention of the authorities. He proposed as
a remedy the coating of the pipes inside with hydraulic mortar
to the thickness of 2i millimeters, — in fact, to brush them over
ACTION OF WATER ON IRON. 27&
inside with Roman cement. Tills mode would no doubt for a
time diminish corrosive action, but it is much to be feared that
it could have but little permanence when the current was rapid ;
and, should the water contain much earthy matter, the tendency
of this to deposit and adhere to the pipes must be fatally
increased.
53. The Academy appends a note to M. Vicat's communi-
cation, in which an opinion is expressed, that the tubercles of
Grenoble have attained their lai'gest size, and are stationary ;
and it is questioned, Will they always remain so ? It must be
obvious, indeed, that the rate of increment of these must be a
decreasing one ; but I do not perceive anything to set a limit to
their accretion, except the stoppage of corrosive action.
54. In the same volume of the Comptes Rendus, p. 462, a
letter is published, from M. Prunelle, stating a case in which
tubercles had formed in conduit pipes where the water passing
was found not to contain a trace of iron. He did not chemically
examine the tubercles, which were friable, and as large as eggs.
From this it would seem to be the author's view that these
masses originate from iron contained in the water ; that this,
however, is not the nature of their formation, has been already
shown, and is evidenced by the fact, that no tubercles are found
in any of the pipes conveying the waters of Grenoble except
those made of iron. — (Payen, Ann de Chim. vol. Ixiii. p. 409.)
55. The explanation of the phenomena of tubercular cor-
rosion given by M. Payen and the reporters to the Academy,
seems to lose clearness in proving too much. Mere want of
homogeneity of structure or of surface is alone sufficient ground
to explain the results ; and that the peculiar preservative action
of alkaline solutions is not a necessary adjunct, I have lately
had an opportunity of proving. In experimenting on the action
of very dilute hydrochloric acid, on wrought and cast iron par-
tially coated with zinc, I found that, after a time, local con-
cretions or tubercles were formed at the points of contact of the
zinc and iron ; thus the effect is produced indifferently in acid
and in alkaline solutions. And I have since found tubercles
formed in iron pipes at Curraghmore, the seat of the Marquis of
Waterford, by water, which appears free from alkaline or earthy
matter. The peculiar effect, too, is confined to chilled or un-
equally-cooled cast iron, to mottled cast iron, and to damasked
wrought iron, or that of mixed constitution, and in all appears
to result from heterogeneity of composition ; it is therefore un-
necessary to call in to the aid of the explanation the distinct
and curious phenomena of the preservative action of alkaline
solutions.
276 KIGHTH REPORT — 1838.
In further corroboration of which may be again noticed M.
Payen's own experiment, — that wrought iron locally encrusted
with cast iron, by dipping into the hitter while fluid, or pieces of
cast iron cast into and surrounded by plates of a different sort
of cast iron, are liable to like tubercles, which attach them-
selves to the points of contact; reasoning from which, Becquerel
rightly concludes, that luant of homogeneity is the cause of this •
peculiar action.
56. M. Payen, as we have seen from his experiments to de-
termine the conditions in which white or chilled cast iron would
be acted on like the darker- coloured varieties, concludes very
erroneously on the practical maxim, that it is much " better to
make conduit pipes of white cast iron than any other, as various
mineral waters will oxidate it less" — and truly they will so ;
but as the peculiar nature of the oxidation in this case stops up
the i)ipes at intervals, any amount of uniform corrosion which
merely sets a limit to their duration is to be preferred to this,
which renders their entire object nugatory.
57- A letter is found in the Comptes Rendus for 1836, p. 506,
from Sir John Herschel, stating that the pipes supplying Cape
Town with water had become tubercular ; and that, at his re-
commendation, the engineer, Mr. Chisholm, had remedied this
by coating the pipes internally with Roman cement. The
ancient pipes in the streets of Dublin are likewise much affected
in this way ; and some fragments of tlie tubercles, and a piece
of the cast iron, which is of the white variety, were presented
to the chemical section at Newcastle.
58. Another method for preventing tubercular cSncretions
has been employed successfully by M. Juncker, at Huelgoat
mine, in France, viz. that of impregnating the cast iron of
which the pipes are made with linseed oil, rendered drying by
litharge, and caused to penetrate the pores of the iron l)y great
pressure. This fact is confirmatory of a preceding observation
I have made, as to the permeability of cast iron to many sub-
stances, and seems to offer a new field of investigation, as ii
method of protecting cast iron from the action of corroding
agents. We know that it has been long usefully applied to
other hard and crystallized substances, as stone, marble, &c.
59. Another method, wholly mechanical, is described in the
Mining Review as in use in Cornv/all for the preservation of
iron pipes, and must be eminently useful in many cases.
Each length of pipe is lined with a thin tube of wood, con-
sisting of staves of pine, of equal length with the pipe, driven
in from the end, and to which the iron pipe forms, as it were,
one elongated hoop. The pine staves are driven in when very
ACTION OP WATER ON IRON. 277
dry. On being wet, they expand^ and force themselves up so
close to the interior of the pipe, and at their joints, that the
whole cast-iron pipe becomes staunchly lined with a casing of
wood, which cuts off all communication with the corroding
agents.
60. The diffei'ence in the rate of action of air and water, but
still more of acids, on different specimens of cast iron, contain-
ing variable minute quantities of foreign matter, is very remark-
able. The iron obtained by the remelting of old coal-gas
retorts is of a quality closely approaching what is called " Re-
finery Pig, or No. 4 '," in fact, by a little management, it may
be forged at once on the anvil into a bar. It is found to contain
a large quantity of sulphur, and an unusual amount of silex, in
some cases as much as 18 per cent., with very little carbon.
A fragment of this iron placed in hydrochloric acid, diluted
with 15 volumes of water, will not be dissolved for months, a
coat of silex being apparently formed ; while a fragment of the
iron before mentioned as containing chloride of sodium in mi-
nute quantity, with a large proportion of sulphur and carbon,
will dissolve in the same acid almost as readily as sugar in
water.
Sulphur, also, which acts on wrought iron with such intensity
at a bright red heat, acts on black cast iron, according to
Colonel Evans, at the same temperature with comparative
feebleness.— r^y^nn. de Chim. vol. xxv. p. 107.)
61. Both these highly sulphuretted irons seem to coordinate
with the highly carburetted ones, or black cast irons, the sulphur
appearing to form a definite compound, intermixed with the rest
of the substance mechanically.
62. Of the relations in respect of corrodibility subsisting be-
tween the different known varieties or " makes" of bar iron and
of steel, but very little is established with any certainty. The
hardest kinds of malleable iron generally appear to oxidize
slowest, but this is not universally true, as Swedish iron is acted
on by air and water with great rapidity.
63. Karsten states that cold short iron is rapidly corroded.
Steel appears less corrodible than any variety of wrought iron ;
but of none of these is there any precise knowledge on our sub-
ject, or that approaches numerical results, which alone are of
practical use in directing the engineer, or indeed the jihysicien.
Neither is our actual knowledge more advanced as to the variable
effects of corrosive action on the same iron, of different waters,
su9h as are commonly met with, containing their usual mineral
ingredients in solution. We know not whether foul water, or
VOL. VII. 1838. T
278 EIGHTH REPORT — 1838.
clear water, strongly saline, or merely brackish, calcareous, al-
kaline, or chalybeate, holding much or little cai-bonic acid, acts
most powerfully in producing rust, that is, produces the largest
quantity in a given time from any one specimen, or in what re-
lative degree. This statement is made exclusively, of course, of
the better-understood cases of mine-waters, such as solutions of
sulphate of copper, &c., whose action on iron belongs to another
branch of our subject.
64. There are some cases of local action on wrought iron,
however, which appear remarkable, and need investigation.
The very purest and finest specimens of wrought iron, when ex-
posed, with turned or boi'ed surfaces, to fresh water, frequently
corrode entirely locally, by deep and destructive jntting. A
portion of a turned wrought iron valve was presented, acted on
in this way, in about two months, by a remarkably pure stream
of fresh water, holding nothing but air and a trace of carbonate
of lime and iron in solution. This sort of reaction appears the
converse of M. Payen's tubercles, and its explanation would
seem to lie in the iron so affected possessing a damasked
structure, that is, in fact, being composed of two sorts of iron
chemically different, and united by welding. This is unavoidably
the case with all "scrapped" wrought iron, or that forged or
rolled from scraps of various sorts. Now these differently- con-
stituted irons, being in different electrical relations, give rise to
a voltaic circuit, in which the most positive is corroded fastest ;
but as all the surface is in some degree affected, the oxides
formed cannot adhere, and hence, while pitting goes on in some
places, tubercles are formed in none. This view suggests the
importance of having large bars, which require to be formed
by rolling several smaller ones together, formed from iron all
of the same " make," if for any important purpose as regards
durability.
It shows that rolled bars, as being more uniform, are pre-
ferable, for the same reason, to "scrapped" or hammered iron;
and it points out that the practice adopted in some cases of
making railway bars by rolling together two bars of different
sorts of iron, the one hard and rigid, to give a durable upper or
working face to the bar, and the other tough and soft, to resist
extension, is highly objectionable as regards the duration of the
rail, under the influence of air and moisture — eminently so, be-
cause the lower segment of the rail, viz. the extended part, will
corrode the fastest, thus losing strength where it is most wanted.
65. There were also presented the two extremities of a bar of
wrought iron found at the bottom of a very deep well in a
ACTION OF WATER ON IRON. 2^9
brewery in Dublin*, where it was supposed to have lain in about
20 feet of water for nearly eleven years.
The bar lay approximately due north and south, horizontally.
When taken up it was found powerfully magnetic, with polarityj
and though the bar was throughout equally exposed, corrosion
had alone taken place at its two extremities. The ends were
injudiciously cut off, by which its magnetism was almost de-
stroyed. This curious subject needs further elucidation. It is
doubtful if any authentic instance has yet been given in which
magnetism appeared directly to play a chemical part. And the
question is one of considerable importance as regards our sub-
ject ; for, as it is well known that bars of iron, by long standing
in the vertical or certain other positions, acquire magnetic pro-
perties ; if it should be found that magnetic polarity exercises
any direct effect upon chemical agencies, then it may result
that the duration of a structure in iron may in some degree de-
pend upon the position of its parts with respect to the magnetic
poles of the earth.
Long since. Professor Maschmann, of Christiana, published
some curious experiments, which were confirmed by Hansteen,
on the effects of a magnet on the crystallization of the Arbor
Dianfe, in a U-shaped tube of glass, beneath or above which it
was placed. (Quarterly Journal of Science, vol. xvii. p. 158.)
His results, howevei', were denied by some British chemists at
the time.
66. Since that time, the investigation of this influence, which
has been repeatedly asserted and denied, has been undertaken in
a very careful and particular manner by Professor Erdmann.
He first points out the number of delicate perturbing causes
which may, and have occasionally led to mistakes, pointing out
the effects produced by irregularity in the wires, handling them
with the uncovered fingers, &c. &c.; and especially states that
many repetitions of each experiment should be made. The bars
and magnets which he had occasion to use were very powerful,
some of them competent to lift 80 pounds.
I. By experiments made to ascertain the oxidation of the
iron wire, when under the influence of terrestrial magnetism, it
was ultimately proved, — 1st. That the oxidation of iron placed
under water is not at all influenced by terrestrial magnetism.
There is no point of the horizon towards which it is more
strongly or more quickly produced than towards another. 2nd.
The oxidation arising from imequal contexture of the iron
always begins at the point where the wire is in contact tvith
* Messrs. Guinness, James' Gate,
T 2
280 EIGHTH REPORT — 1838.
other bodies, not only metals, but even wax or baked earth.
3rd. Diffuse daylight, or the weakened rays of a winter sun,
neither retard nor assist oxidation, provided they are accom-
panied by no change of temperature.
II. In experiments made with magnetized wires, the results
were the same ; no difference of oxidation occurred at the poles
or other parts.
III. In experiments on the reduction of metals by the humid
process, as in the Arbor Dianae, no influence of terrestrial mag-
netism could be observed. The crystallization took place in
both branches of the syphon tube, and without reference to
their direction.
IV. In repeating the experiments with the additional power
of a very large magnet, its poles proved not to have the slightest
power over the formation or disposition of the crystal within.
V. Numerous salts were made to crystallize slowly in vessels
placed over the poles of magnets, with every care that their
power as conductors of heat should not interfere. The mag-
netism exerted not the slightest influence over the crystal-
lization. In chemical actions, where gas was evolved, no
difference in the rapidity of evolution, or quantity of gas pro-
duced, occurred, when magnets were present or absent.
VI. No evidence of the influence of the magnetic poles over
the colours of vegetable solutions could be obtained. — {Bib.
Univ., xlii. p. 96.)
67. These apparently satisfactory experiments of Professor
Erdmann are, however, again laid open to discussion by some
curious results stated by M. Levol {Annal. de Chim. vol. Ixv.
p. 285), in a paper " On the phenomena which accompany the
precipitation of a metal in the metallic state by another, in
presence of a third metal, exercising no chemical action ; and
on the circumstances which may modify the results." In this
the following statement occurs : —
" I found a circumstance which appeared to me very curious.
It is, that the position of the iron, during the precipitation (all
other things being equal), is by no means indifferent as regards
the separation of the copper (viz. from its solution).
" In varying in different ways the experiments which were
requisite, I have observed that the results, which were accordant
when I plunged the iron horizontally, ceased to be so when
(making a double experiment) I placed in one the iron hori-
zontally, and vertically, or nearly so, in the other.
" In the first case I have constantly moi-e copper on the
platina {i. e. the passive metal), less iron dissolved, and delay
of the complete precipitation.
ACTION OP WATER ON IRON. 281
" Insulation, or free communication with the substance of
one of the two metals, having scarcely any influence on these
sorts of reactions, as I have assured myself, and which also
conforms to the pi'operties (proprietes) of electric currents, I
have thought that these variations might result from magnetism,
acquired by the iron placed vertically ; and, to try if in fact it
had any influence on the decomposition of the salt, I plunged,
in this position (viz. vertically), a bar of soft iron in a tube of
glass containing a neutral solution of sulphate of copper, and
corked it. As scarcely any disengagement of gas agitated the
liquid, I saw that decomposition began towards the two ex-
tremities of the bar, advancing progressively towards its middle
point ; the two extremities and this point acting meanwhile on
a magnetic needle, as the two poles and the neutral point of a
magnet, and the poles changing by reversal in the usual manner.
The efi"ect of this magnetization appeared then to augment che-
mical action, and hence to diminish the quantity of copper de-
posited on the platina."
Are we to conclude from this that magnetism modifies che-
mical action, or that chemical action is capable, under certain
conditions, of conferring magnetism on iron ?
The subject is obviously in need of much further experiment,
and is one of interest in a general, as also in our particular view.
68. It will be now necessary to state the nature and extent of
the experiments upon the large scale which have been instituted
at the desire of the Association, and aided by its funds. On the
very first consideration, it appeared important that those expe-
riments in which time was an element should be first of all put
in progress ; and of these the most important seemed to be,
1st. To obtain experimentally a set of numerical results of
the relative rates of corrosion of all the difi'erent most im-
portant makes of British cast iron, exposed under the same
circumstances to sea water, and unprotected, except from
mechanical abrasion ; and a like set for fresh water, va-
rying the conditions in both cases as far as might occur in
practice.
With this view coiiiplete sets of authenticated specimens of
cast iron from most of the principal iron-works in Britain have
been written for and obtained. A very considerable delay ne-
cessarily occurred in procuring these, and it was not until
about two months since that it was found practicable to com-
plete the collection, which numbers between eighty and ninety
specimens.
These specimens were then all fused, at the works with
which the writer is connected, separately in crucibles, to avoid
282 EIGHTH REPORT 1838.
change of composition bj' contact with the fuel, and cast in
green-sand moulds into the form of parallelopip.eds, of 5 inches
by 5 inches x 1 inch thick, and of 5 inches by 5 inches x |
inch thick, respectively ; and at the same time a bar of 1 inch
square and 12 inches long was cast of each description of iron.
The whole of these specimens, whose surfaces are as nearly
equal as possible, were then weighed each to a single grain, or-
within about :f o Vo o °^ ^^^ weight of the piece, and inclosed in the
external frame of the box (fig. 1, as shown in Plate XVII.), No. .
This box is so contrived as to permit free access of air and sea
water at all sides, and while the specimens of iron are held fast
at four of their angles, they are freely exposed to the action of
these agents ; but each in a separate cell, for a reason to be here-
after mentioned. As any mode of numbering these specimens
would be inadmissible, if not impracticable, they are to be re-
cognised when reexamined solely by their place in the box.
The series commences at A. fig. 1, and reads from left to right,
going upwards, as more particularly described in the notes at-
tached to the tables. No iron used in the construction of the
box enters its interior, and the specimens, with the frame in
which they are arranged, can be lifted out at any time for in-
spection, without disturbance of their position or touching their
surfaces. This box, like the others to be described, is of stout
oak kyanized, which, although the researches of Lassaigne upon
this subject, showing that the combination of albumine and bi-
chloride of mercury is soluble in alkaline chlorides, renders it
probably of less service in sea water, yet is not likely to inter-
fere in any ^vay with the results of these experiments.
69. The object of casting the parallelopipeds of two thick-
nesses, viz. 1 inch and j inch, is, that the " grain " or crj'stalline
arrangement, and proportion to the metal of " skin," as it is
technically called, varies with the scantling of the casting :
hence these thin castings will give residts discovering what
variety of British metal produces a skin best calculated to re-
sist corrosion, and what amount of variation of skin each sus-
tains by difference of thickness in casting.
70. The castings were all poured, as nearly as possible, at
the same temperature, (the crucibles having been heated in
draught furnaces,) and all permitted to cool at the same rate.
Their forms being all regular, and their dimension and weight
known on again weighing after taking up and cleansing from
adherent matter, a set of numerical results will be obtained,
giving the relative rates of degradation in sea and fresh water,
of most of the British cast irons per unit of surface ; thus ena-
bling the engineer to choose that which will be most durable in
ACTION OF WATER ON IRON. 283
his structures, and enabling us, by analysis of the least and
most corrodible, to see on what these properties depend. Hot
and cold blast iron are included in this box, and also specinaens
of the same cast iron chilled, and cast in loam, dry sand and
green sand, cooled rapidly and slowly, and some with protected
surfaces, (not electro-chemically protected however.) as will be
again alluded to. This box was sunk and moored in Kings-
town harbour in 3\ fathom water, at half tide, at the second
mooring buoy in from the western pier head, at one o'clock, on
the 3rd of August (1838), on a bottom of clean sharp sand;
temperature of the water, 58° Fahr. It is proposed being
weighed and examined once every six months if possible, and
at the expiration of a year the specimens weighed accurately
and again put down, and so weighed year by year for at least
four years. By this, not only the actual amount, but the rate
of progress of corrosion on every specimen will be determined,
71. The object of casting the inch-square bars 12 in. long, of
each sort of iron, at the same time with those exposed to the
sea and fresh water, is in order to have specimens, comparable
in all respects with these as to constitution and texture, whose
specific gravities have been, or are in progress of being, taken,
and whose chemical or physical properties can be in future de-
termined, should the progress of the experiments on the exposed
pieces render such desirable.
There is the utmost variability of structure and composition
amongst these specimens, as will be observed by referring to
the column of observations in the table, but can only be fully
perceived by inspection of the castings, when fresh broken.
As an accurate knowledge of the specific gravities of these spe-
cimens was of some importance in several respects, and chiefly
as being a check upon the weighings, and upon the soundness
and dimension of the rectangular pieces of iron, submitted to
experiment, some pains were taken in arriving at the best and
most expeditious mode of proceeding.
The common mode of taking the specific gravity of solids by
weighing in air, and then suspending from a silk fibre or hair in
water, is subject to many inconveniences and sources of error,
as the variable quantity of the suspending thread wetted and
immersed, its capillarity and the resistance of the fluid to free
vibration of the beam, &c. &c., a modification was therefore
adopted of the plan of weighing the solid in air and immersed
in a given volume of water, which is weighed along with it.
But as the cast irons, if broken into fragments sufficiently
small to go into a common specific-gravity bottle, would be
likely to involve air bubbles hard to be extricated, each speci-
284 EIGHTH REPORT — 1838.
men of cast iron whose specific gravity was required was filed
accurately by a steel gauge to a cube of 0*75 of an inch; this
cube was weighed in air at a temperature of GO^Tahr. A small
glass cylinder Avas provided capable of being closed air tight at
its open end by a circular disk of thin Bohemian plate glass,
equal in diameter to its exterior. The size of the cylinder was
such as just to admit, without contact at the angles, a cube of.
the above size, and its weight with the plate-glass cover, was
under 100 grains when empty. Its weight was then accurately
determined from the mean of a number of weighings, when
quite full of distilled water, free from air, at 60° Fahr. The
filling is easily accomplished by pouring in the water after
having been boiled in vacuo and cooled, until its surface rose a
little above the edge or top of the cylinder, and then sliding on
the glass plate. A number of the iron cubes having now been
weighed in air were thrown into a considerable volume of di-
stilled water at 60°, and placed under the exhausted receiver
of the air pump, and agitated until all air bubbles had escaped.
The glass cylinder being filled as before, each cube was taken
out of the water by forceps and placed in the cylinder, from
which it of course expelled its own bulk of water ; the cylinder
was now closed, dried rapidly in bibulous paper with gloved
hands, and weighed, the temperature of the apartment being
preserved carefully at 60° Fahr.
It is sufficiently obvious from these data that we get the spe-
cific gravity from the formula
s = ^,
W
— where S is the specific gravity of cast iron, tt; = the weight of
a cube of distilled water = 0'75 of an inch, s = the specific gra-
vity of water, and W the weight of the cube of cast iron,
equal in volume to the cube of water.
This method possesses several advantages in rapidity and ease
of execution, and in precision of result, besides involving a check
upon any serious error of experiment in every instance ; for as
each cube is weighed in air, and the weight of a cubic inch of
distilled water at 60° Fahr. is well determined, the specific gra-
vity of each ciibe is at once known within the limit of error in
the gauged dimensions to which the cast iron cube is filed.
There was found to be no difficulty in drying the outside of the
cylinder, so that it did not change its weight in the balance, i. e.
perfectly, and no sensible evaporation took place from under
the plate-glass disk, after remaining in the balance for forty-
eight hours.
ACTION OF WATER ON IRON. 285
I have entered rather at length upon the mode of taking these
specific gravities, because the method in its details will be found
useful in other researches, as in taking the specific gravity of
small mineral specimens, &c., and because the precise determi-
nation of the maximum and minimum specific gravity of cast and
wroiight iron is of importance to the iron founder and engineer,
as giving the data upon which the weight of castings are esti-
mated, and which, as usually stated by authors, are an unsafe
guide, inasmuch as the specific gravity of cast iron varies with
its composition, the way in which it is cast, the rate of its cool-
ing, and the depth of the mould, to an extent not generally
known.
72. I was favoured by my friend Mr. William Fairbairn, of
Manchester, with a few specimens of the same hot and cold-
blast irons, on which he and Mr. E. Hodgkinson experimented
as to their cohesion, so that not only the physical properties of
these will be known from the experiments of these, gentlemen,
but their durability from the present.
73. Some specimens of Irish iron from the Arigna works,
county Leitrim, are also included, and some experiments, made
by Messrs. Bramah, of London, upon its strength are given, on
the authority of the agent of the works, as an appendix to the
tables, by which it will appear, that in point of cohesion this
iron ranks with almost any in Britain, while its fluidity in
easting recommends it as equal to the best Scotch iron. It is
sold on the terms of the latter in the market. — This iron being
scarcely known out of Ireland, these experiments and remarks
will not be deemed irrelevant.
74. Four other similar boxes have been prepared, which all
contain a selection of specimens coordinating with those in
No. 1. The second box, No. 2, is sunk and moored in the
foul and putrid sea water at the mouth of the Kingstown town
sewer, where it debouches into the sea.
The water here is 2 feet deep at ebb, and from 8 to 12 feet at
flood tide, and a constant succession of bubbles of sulphuretted
hydrogen and marsh gas pass thro\igh it from the deep deposit
of mud which forms the bottom.
Precautions have been taken to prevent the box of specimens
sinking in the mud. The temperature of the water is 58° Fahr.;
it contains as much saline matter, except during heavy rains, as
the clear water of the harbour — its specific gravity, when filtered,
being the same.
The results of this experiment will determine the relative
actions of clear and foul sea water, when examined in the same
way and at the same periods as No. 1.
286 EIGHTH REPORT 1838.
75. The box, No. 3, containing a similar set of specimens
with No. 2, has been deposited, by permission of the Dublin
and Kingstown Railway Company, in the hot-Avater cistern of
their baths at Salt Hill, in clear sea water, maintained con-
stantly at a temperature varying from 110° to 125° Fahr. The
object of this experiment is to determine the change of cor-
rosive action produced by increased temperature in sea water
containing but little combined air, and the differences of this
action on various kinds of iron.
76. Van Beek and Dr. John Davy appear to be of opinion,
that sea water, after it has been boiled, is incapable of decom-
posing iron from containing no air 5 at the temperature of 125°
Fahr. decomposition is however most rapid, as the action of the
sea water on the iron cisterns of these baths demonstrate ; and
yet the water contains little air at that temperature.
The results of my own experiments also show me, that after
all the air is expelled that can be from sea water by boiling, it
is still capable, at its boiling temperature, of decomposing iron,
and that with a rapidity as great as at ordinary temperatures,
however highly charged with air. In addition to which, there
is no longer any reason to doubt the fact, that under such cir-
cumstances the alkaline chlorides are in part decomposed by
the iron as M'ell as the other salts contained in sea water.
77' Indeed Scoresby's experiments appear to prove that it is
impossible to deprive water, Avhether salt or fresh, of all its air,
by any amount of even alternate boiling and freezing. He found
that, on boiling briskly some sea water in a phial, and then
corking the latter and exposing it to cold, as the water froze
air bubbles began to appear moving upwards in the fluid, and
the ice produced was full of microscopic air bubbles. Hence
he concludes it probable, either that water is not entirely freed
from air by boiling, or that some of the water is decomposed
during the progress of the freezing process : of the latter there
is no likelihood.
Boussingault also states that he found 16 per cent, of oxy-
gen in snow collected from the summit of Chimborazo in South
America. — {Annul, de Chi:n.) It is to be remarked, howevei",
that, as has been observed to be the case with lead and some
other metals, so iron seems to be corroded nmcli more rapidly
by air and distilled water at a high temperature, than by water
holding any alkaline or earthy salts in solution. The destruc-
tive effects of a small leakage of steam producing a trickle of
distilled water to steam boilers have often been observed by
engineers.
78. The experiments of Dr. Faraday on the order of deposi-
ACTION OF WATKR ON IRON. 287
tion by boiling of the saline contents of sea water, and the re-
spective temperatures at which each salt deposits, sliowing that
they fall in the order of their respective insolubilities, indicate
that important differences in the corrosive action of sea water,
when boiling, may result from its degree of saline concentra-
tion, and to this, the resulting boiling point, the electro-con-
ducting power of the fluid, as well as the nature of the salts
deposited and remaining in solution, are conditions. And, fur-
ther, as means have been devised (although with increased ex-
penditure of fuel) of preserving sea water in marine steam
boilers, (or others using salt water,) at a constant degree of sa-
turation, it becomes important to discover when this is such as
to produce a minimum corrosion, whether before or after the
deposition of the sulphate lime, or of the chloride, sodium or
magnesium.
79. The next box, No. 4, has been moored by permission and
assistance of the Ballast Corporation of the port of Dublin, in
the foulest water of the river Liffey, in the mid stream, opposite
the mouth of the Poddle river, at this place a tributary of cor-
rupted water. It lies in water 4 feet deep at ebb, and from 15
to 20 feet at flood tides. The water is very brackish at full
tide, and at the other periods fi-esh ; its temperature, when the
box was sunk, was 61° Fahr. The specimens in this are the
same as in Nos. 2 and 3, as may be seen by the tables. Its ob-
ject will be to determine the relative effects of foul river water,
alternately brackish and fresh, and this will again compare with
the results to be obtained from the last box, No. 5.
80. It has been sunk in the clear, unpolluted fresh water of
the Liffey above Island-bridge, and within the premises of the
Royal Military Hospital. It lies in water varying at times from
3 feet to 6 feet in depth ; its temperature varies with the season.
Specimens of water have been taken from these five localities
for examination, and vvill be again taken and examined from
time to time. The highest and lowest temperatures of each
will also be observed.
81. In each of these boxes have been included a number of
specimens, coated with various protecting varnishes and paints.
— This was originally suggested by a fact of importance commu-
nicated to the writer by Thomas Rhodes, Esq., civil engineer,
whose experience in the construction of great works in iron is
well known. He mentioned, that when engaged on the locks
of the Caledonian canal, certain cast-iron sluices were put down
and exposed to the ocean water, having been coated over with
common Swedish tar, with the exception of their faces,
which were ground together, and were removed in about four
288 EIGHTH REPORT — 1838.
years afterwards : every part of the iron still covered with the
tar was found sound and untouched as when put down ; but the
ground faces, which had not been tarred, were softened and con-
verted into plumbago to the depth of | of an inch.
This interesting and important observation shows that, where
abrasion does not interfere, if Ave could get any coating to ad-
here to the iron which would be impervious to air and water, •
the preservation of the metal would be effected in the best and
simplest manner. Unfortunately, many difficulties oppose this,
and few, if any, varnishes can be obtained which will spread
over the iron withovit leaving uncovered spaces or microscopic
pores .
Professor Lampadius long ago directed his attention to this
point, and, in the Annales des Arts et Manufactures, published
the composition of a paint or varnish for the preservation of
iron from rust, the basis of which is sulphate of lead and sul-
phate of zinc ground M'ith plumbago and oil. It is difficult,
however, to see the precise point aimed at by this composition.
82. The paints and varnishes which have been placed in pro-
cess of experiment in the above five various conditions are seve-
ral of those most ordinarily in use, with the view, that as no-
thing certain is known upon this branch of the subject, the fate
of these coverings, many of whose other properties are well
known, may afford leading indications as to the direction in
which improvement may be sought.
83. As yet it has been impossible to arrange any experiments
upon a large scale upon wrought iron, nor indeed to collect suf-
ficient specimens ; but there has been included in each of those
five boxes a single parallelopiped, all of equal size, and cut from
the same bar ; it is of what is called common Welsh bar iron,
or No. 1, and was made at Dowlais Iron-works, South Wales.
This bar I have called " The Standard," and the remainder
of it, which is some feet in length, is proposed being deposited
with some learned body to be appointed by the British Asso-
ciation.
Now this standard being placed in each box in circumstances
precisely similar to the rest of the specimens, it is intended to
take the action of the sea and fresh water upon it as unity, and
refer their action upon all the other specimens to this, by which
means not only will this whole series of present and projected
experiments on wrought and cast irons be numerically compa-
rable most conveniently by the engineer, but any future experi-
menters upon novel makes of iron, or upon foreign ones, can,
by reference to the standard bar in possession of the Associa-
tion, make their experiments comparable with these.
ACTION OF WATER ON IRON. 289
Without this precaution the present experiments, although
correct, would stand isolated, and be scarcely capable of being
even brought into comparison with future ones. Nor could it
be hereafter determined what change as to corrodibility, future,
and now perhaps unthought of, revolutions in the manufacture
of iron may produce in the metal to be made in years yet to
come.
84. The writer's experiments also lead to the expectation,
that with the same bar of iron, or the same casting, a simple and
closely approximate estimate may be formed of its destructi-
bility in water or in solutions of the alkaline or earthy chlorides ;
by the rate of its solution in other agents ; and with this view
experiments are in progress upon the standard bar and other
iron, and in the event of their results being found as here stated,
it is obvious that upon the basis of the present prolonged ex-
periments in sea water, the durability, under similar circum-
stances, of all other or future irons may be determined in a few
hours by the aid of this new method of examination.
85. The subject now leads us to consider briefly the various
modes of protection which have been proposed for the purpose
of preventing, as far as possible, those actions of water and air
on iron, the rate and nature of which our experiments have been
directed to determine ; and these, with the exception of mere
superficial coverings, as already alluded to, have all been of the
electro-chemical class, and more or less directly derived from
Sir Humphry Davy's original discovery and proposal of the
protection of the copper sheathing of vessels. In that paper the
great principle was developed of counteracting chemical by
electrical forces ; his successors have only, with greater or less
perfection, developed and applied his brilliant idea to particular
cases, while in doing so, it must be confessed, they have cor-
rected some small errors into which this great philosopher fell.
In Sir H. Davy's original papers on the preservation of copper
sheathing, he distinctly states, that it follows from his principles
then developed, that cast or wrought iron may be preserved
from chemical action by suitable protectors of zinc or tin.
But my friend Professor Edmund Davy has unquestionably
the merit of having been the first to conduct a series of well-
devised and careful experiments upon the subject on the large
scale, which he did partly in connexion with the preservation
of the iron work of the mooring chains and buoys in Kingstown
harbour, under the auspices of the Board of Public Works.
The results of these have been already communicated by him to
the Association, at its meeting in Dublin, and published in its
reports.
290 EIGHTH REPORT 1838.
The results of these investigations show that zinc is fully ca-
pable of protecting cast or wrought iron in sea or fresh water,
when applied in a massive form, at least for a time. They also
put in a forcible point of view the important part which the
contact of air plays in the corrosion of iron.
86. It would seem, however, to be doubtful how far this pro-
tecting power even of zinc is completely permanent, for as a •
portion of the oxide of zinc is transferi'ed to the surface of the
iron, as Professor Edmund Davy has observed, it would seem
that the preserving power of the zinc is diminished.
A forelock key, now presented, with which I have been fa-
voured by Professor Davy, and which has been immersed in sea
water for about three years, though protected by zinc in form
of a ring loosely connected with it, is yet somewhat acted on, a
crust of magnetic oxide being formed all over it, spotted over
with the oxide of zinc ; yet the action is incomparably less than
it would have been in the same time and circumstances if wholly
unprotected. My attention has also been drawn by Professor
Miller, of Cambridge, to the curious fact, that the surface of the
iron is covered in places with microscopic crystals of calc spar;
these he was kind enough to examine for me with the gonio-
meter, and although under vex'y disadvantageous circumstances,
succeeded in verifying their form as that of the common calc
spar rhomb. This fact is interesting, as a new instance of the
production of an insoluble crystallized minei'al by galvanic cur-
rents of low tension,
87. Pepys long since proposed to preserve polished instru-
ments of iron and steel from rust in air by zinc protectors. This
seems to have been unsuccessful, and was found to be so by
Professor Edmund Davy.
88. Very lately a company has arisen in London, under the
name of the "British Galvanization of Metals Company," based
upon a patent for the protection of iron by coating its surface
with fluid zinc, obtained by a French engineer, M. Sorel. I
lately wrote to the secretary of this company, and have obtained
specimens of the so-called galvanized iron, which are now pre-
sented. I also wrote to another company, styled the " Zincked
or Galvanized Iron Company" : my letter was returned un-
opened by the secretary. Having only received the specimens
a very few days before the present meeting, I have been unable
as yet to make many experiments upon them ; some, however, are
detailed in the prospectus of the company, of Professor Graham,
Mr. Children, Mr. Garden, and Mr. Brand, which amount to
this, that, as was to be expected, the zinc preserved the iron, in
dilute acids, vintil the whole of it was dissolved. In the speci-
ACTION OF WATER ON IRON. 291
mens furnished us, the iron, which is all wrought, (and its ap-
plication to the more carbonaceous cast irons must be more
difficult,) is zincked or, if the expression may be used, tinned
with zinc ; the coating is excessively thin, and from its peculiar
greasy feel, leads to the presumption that it has been slightly
amalgamated also.
89. I was enabled to detach from one spot a few grains of
zinc, which, on examination, appeared to be as pure as it is
usually found in commerce. I expected to have found it alloyed
with lead ; of this it contains a trace, and a good deal of iron,
probably taken up in part from the bar. No mercury could be
detected in it.
90. A very few minutes are sufficient to dissolve oif the whole
of the zinc from the surface of the iron when immersed in hy-
drochloric acid, diluted with 40 volumes of water.
91. Oxide of zinc is rapidly deposited in sea water or a solu-
tion of common salt, when acting on it.
92. When a bar of the zincked iron is placed in hydrochloric
acid, diluted with 20 volumes of water, the zinc having been
completely removed by the file from one half of its surface, hy-
di'ogen is given off both from the zinc and iron surfaces from
the first moment ; and after the whole of the zinc is dissolved,
this gas is much more copiously evolved from the surface that
had been zincked, than from that from which it was filed off.
This circumstance appears to be connected with the strength of
the acid ; it does not occur in that which is very dilute.
93. There can be no doubt of the power of this combination
to protect iron for a time, or while the thin coat of zinc lasts
perhaps, and in some practical points of view it would seem to
offer advantages over zinc protectors, as proposed being ap-
plied by Edmund Davy. But it seems to be forgotten by the
advocates of this attenuated application of the preserving metal,
that for every particle of iron protected, an equivalent of zinc
must be destroyed, and that hence, unless a sufficient mass of
the electro- positive metal is provided to allow for degradation,
its efficacy must soon be null.
94. It is not intended, however, to pronounce any decisive
opinion as to the advantages or disadvantages of this peculiar
mode of applying zinc protectors until we have had time to make
other and careful experiments upon it; meanwhile, in justice
to my friend Professor Edmund Davj^, I must remark upon
the arrogation of original discovery to M. Sorel, the patentee
of this process, which some of the French scientific journals
make. It does seem strange how any pretension to originality
of discovery can be now set up on this score, after the previous
292 EIGHTH REPORT — 1838.
publications of Sir H. Davy, Pepys, and Edmund Davy ; and still
more, how a French patent is to be maintained for a process
which, although its principle was doubtless then not under-
stood, was, with little variation, before patented on the 26th of
September, 1791, by Madame Leroi de Jaucourt, for preserving
metals from rust by covering with an alloy of zinc, bismuth,
and tin. I may add, that Professor Davy informs me he used
the method of zincking over the surface of iron as a preserver
so far back as 1834.
95. M. Sorel's patent is described as capable of being ap-
plied in three ways, viz. 1st, by covering the surface with fluid
zinc ; 2nd, by the application of a paint made from zinc ; 3rd,
by covering with a powder made from zinc. Unless the second
mean a paint made from ground metallic zinc, it is similar to
Lapadius' varnish, before described ; and if the former, then it
does not differ from the third mode described, appai'ently. We
have, however, not been furnished with specimens of either of
these modes, which would seem beforehand not likely to answer
their intended purpose, from a want of that continuity of me-
tallic connexion which appears essential to preservation in this
way.
96. Sir H. Davy erroneously supposed that tin also possessed
the property of preserving iron in sea water. -This opinitm has
been controverted by the experiments of M. Van Beck, of Utrecht,
and of M. Mulder, of Rotterdam, and more recently by Profes-
sor E. Davj'^, in a paper communicated to this Association, in
which he shows that iron, on the contrary, will preserve tin, but
that zinc will preserve both.
Sir H. Davy, and his brother Dr. John Davy, who has
defended his opinion, appear both to have been led astray by
merely considering and experimenting upon the galvanometri-
cal relations of tin to iron when first ]ilaced in contact. But
Van Beek, in the paper alluded to [Edin. New Phil. Journal
for October 1837,) has cleared this up by the discovery of the
remarkable and anomalous fact, that although it is certain that
tin is to iron in a positive relation in atmospheric air, yet when
both are plunged into sea water, after a period, never greater
than half an hour, has elapsed, the astatic needles of the galva-
nometer, which had before indicated the above relation, gradu-
ally return to zero, and pass through it to the opposite side,
and indicate that the iron has become positive with respect to
the tin, thus showing the singular fact apparently, that metals
retain for a longer or shorter time the electrical condition they
have once acquired.
97. By decisive and direct experiments also, M. Mulder, of
ACTION OF WATER ON IRON. 293
Rotterdam, determines the corrosion of iron in presence of tin,
and its amount : — 1st. A plate of iron weighing 32-907 grains
was placed in a glass vessel containing one litre (= 61 -028 cub.
in.) of sea water, during 20 days, at the temperature of the
month of November 1836 (at Rotterdam namely). After the
experiment the weight of the iron was found to be = 32-72G
grains, loss by oxidation = 0*1 81 grain.
2nd. A similar plate of iron, exactly of the same weight of
32-907 grains, but on whose surface was fixed a small piece of
tin weighing 8-140 grains, was in the same manner exposed for
20 days in one litre of sea water : the weight of the iron, after
the experiment, was found to be = 32'674, that of the tin
8-139 grains J hence loss by oxidation of the iron = 0-233
grain, and loss by oxidation of the tin = 0-001 grain. These
results show that the iron, when exposed to sea water as above,
alone lost by oxidation 0-052 grain less than when in contact
with the tin.
Van Beek, in recording these experiments, observes, that the
action on the tin must have taken place at the first moment of
immersion of the metals, and before it had become negative
with respect to the iron. — {Netv Edin. Phil. Journ., Oci. 1837.)
98. De la Rive has observed an analogous change of electri-
cal state in these metals in a different research, and the fact is
a very important one as regards our subject : it may possibly be
hereafter found that the diminished preservative power of zinc
to iron, after a length of time, has an analogous cause, as may
the following like phenomenon. It sometimes happens that
when one of Schoenbein's inactive wires, and another rendered
inactive by it, have remained together in a tube of nitric acid
for a very considei-able time perfectly passive, they at length
suddenly, and without any assignable cause, both become active,
and the reaction on the iron is so miusually violent, that most of
the acid is instantly driven out of the tube with a sort of ex-
plosion.
99. We have now to consider the subject of a communication
made at the last meeting of this Association, at Liverpool, by
Mr. John B. Hartley of that town, upon the power of brass to
preserve cast and wrought iron in sea water. Mr. Hartley is
reported to have stated in the Chemical Section, that certain
iron sluices having brass in connexion with some of their parts,
had on examination been found perfectly sound and uncorroded
in the neighbourhood of the brass, after an exposure of twenty-
five years, but were corroded elsewhere; and that in conse-
quence of this discovery, all the iron work below the tidal level
employed in the Liverpool Docks had been placed in connexion
VOL. VII. 1838. U
294 EIGHTH REPORT 1838.
with brass in some way, and that its preservation had fol-
lowed.
100. The statement created considerable discussion and atten -
tion at the time, and at first seemed to Professor Davy and myself
an important element in the subject of investigation with which
we had been entrusted by the Association. Accordingly, very
soon after the meeting, Professor Davy addressed Mr, Hartley-
upon the subject, detailing the results of his previous experi-
ments, and expressing his conviction of the non-protective pow-
er of iDrass to iron, and assigning another and sufficient cause
wholly unconnected with electro-chemical protection to the phe-
nomena described by Mr. Hartley. A copy of his letter is an-
nexed, as published in Saunders' News-letter of Oct. 24, 1837.
"To John B. Hartley, Esq., Liverpool.
" Royal Dublin Society's Laboratory.
" Sir,
" You will I am sure excuse the liberty I take in addressing
you, on an interesting and important subject on which you have
recently been engaged, namely, preventing the corrosion of cast
and wrought iron in salt water : I also have made many experi-
ments with a view to the same object. I have to express my
regret that the state of my health prevented me from taking an
active part in the proceedings of the Chemical Section at the
late meeting of the British Association for the Advancement of
Science in Liverpool. I was not present when your paper " On
preventing the corrosion of cast and wrought iron in salt water"
was read and discussed. The object of it, as reported in the
only two public prints I have seen, namely, Saunders' News-
letter of 15th Sept., and the AthenaBum of the same date (the
former of which I only saw yesterday), was to prove that brass
protects cast and wrought iron from corrosion in salt water,
without being itself corroded. It was also stated, that the iron
so protected remained in excellent preservation after a period of
twenty-five years. I must confess that these statements appear-
ed to me to be not only anomalous, but in direct opposition to my
own experiments. I have no hesitation in stating, as the result
of my experience, that brass will not protect cast or \vrought
iron or steel from corrosion, either in salt or fresh water ; but,
on the contrary, these metals will protect brass from corrosion
under 6'uch circumstances, at least for a limited time.
" I need not tell you that if brass were found to protect cast
and wrought iron in salt water, suppose for ten days, the pre-
sumption would be, that it would do so for twenty-five years ;
but if, on the contrary, brass will not protect iron for ten days,
ACTION OF WATER ON IRON. 295
nor for a single day, which is the fact, then it would seem ab-
surd to expect that it will protect them for twenty-five j^ears !
" If I mistake not there is little difficulty in accounting for
the preservation of the iron under the circumstances noticed by
you, without having recourse to any fancied power of protection
in brass, which it really does not possess.
" In Saunders' News-letter already referred to, which con-
tains the fullest report of your paper which I have seen, the
iron is stated to be ^an iron pin working in a brass socket,
which was again inclosed in an iron case ; all the iron in con-
nexion with the brass was in excellent preservation, whilst that
removed from it was corroded.'
" Now it seems clear to me that the preservation of the ii'on,
under the circumstances here enumerated, was an effect due to
the mere condition in which the metal was placed, which was
such as precluded (almost entirely) the access of air, on which
its corrosion, both in salt and fresh water, depends. Under
similar conditions I entertain no doubt but that iron will pre-
serve iron, and brass, brass, and each of these metals the other
respectively; and glass, porcelain, &c., will equally preserve
both brass and iron from corrosion in salt and fresh water.
But the preservation of metals under such circumstances is not
protection in the sense in which it has been commonly under-
stood, since the first just views on the subject were advanced by
the late Sir Humphry Davy.
" As the protection of cast and wrought iron in salt water by
brass is not only spoken of as a discovery, but has already been
acted upon as such in some of the great public works in Liver-
pool, and may soon be extended to other seaports, to our ship-
ping, and to innumerable cases where iron is exposed to salt
water, I lose no time in making you acquainted with my expe-
rience and views on the subject.
" I beg, in conclusion, to remark, that my statements pro-
ceed on the ground that the brass spoken of, without any qua-
lification, is no other than the common brass of commerce. If
you haee used a different alloy containing more zinc or other
material, allow me to suggest to you the propriety of setting
the public right on such a matter, as well as your humble ser-
vant,
" Edmund Davy."
Professor Davy has since favoured me with the following ad-
ditional note containing the results of his more recent experi-
ments on the subject. He proceeds : —
101. "As the protection of cast and wrought iron in salt
u 2
296 EIGHTH REPORT— 1838.
water by brass was not only spoken of as a discovery, but also
acted upon as such in some of the great public \vorks in Liver-
pool," Professor Davy (who was not present when Mr. Hart-
ley's paper was read and discussed) lost no time in making Mr.
Hartley acquainted with Iiis experiments and views on the sub-
ject, which he did in a letter inserted iu " Saunders' News-letter,
24th October, 1837." In this communication Professor Davy
stated, as the result of his experience, " that brass will not pro-
tect cast or wrought iron either in salt or fresh water, 1)ut that,
on the contrary, these metals will protect brass from corrosion
imder such circumstances at least for a limited time.
" Professor Davy refers the preservation of the iron under the
circumstances enumerated to the mere condition in which it was
placed, being such as almost entirely precluded the access of air,
on which its corrosion, both in salt and fresh water, depends.
" Professor Davy was at first led to suppose that Mr. Hart-
ley's brass, which was spoken of without any qualification, was
the common brass of commerce ; but on learning that its com-
position was different, he instituted experiments with Mr. Hart-
ley's brass, for specimens of which he was indebted to Mr.
Robert Mallet. On trying the eff"ects of this brass on iron in
salt water, it had no more ])rotecti)ig power than the glass ves-
sel in which the experiments were made. When the two metals
were in close contact, the iron presei'ved its original brightness,
as was also the case where the iron was in contact with the
bottom of the glass vessel ; but all the other exposed surfaces
of the iron were cori-oded just as readily as if common brass
were used Avith the iron."
102. In April last I wrote to Mr. Hartley requesting speci-
mens of his brass, and of the iron preserved by it. I received a
very minute portion of brass, and a piece of iron stated to have
been in contact with it, together with a piece of plumbaginated
iron, part of a sluice or paddle, through Mr. Gilbert Cummins,
with the following letter : —
"Dock Yard, Liverpool, 23rd April, 1838.
" Sir, — In Mr. J. B. Hartley's absence from England (he
being at present on the continent, and not expected back for
some lime) I have to acknowledge the receipt of your letter of
the 21st instant, and in accordance A^ith your request have for-
warded to your address, by the City of Dublin Company's packet,
a small parcel, containing a specimen of the brass composition
referred to, and also of the cast iron preserved by it ; the latter
is part of the hinge of a large cylinder used as a valve to admit
the ingress of sea water into a mill-dam or reservoir ; the brass
is a part of the bu?h with which the interior surface of the hinge
ACTION OF WATER OX IRON. 297
was lined. The bolt or pin for connecting the valve to the cy-
linder is of wrought iron, which, as well as the cast iron, was
found in a perfect state. I have also sent a piece of a cast-iron
clough paddle, taken out of one of the dock sluices. When
first taken up it was quite in a soft state, capable of being easily-
cut with a knife] but by exposure to the atmosphere has again
become hard.
" I am, Sir, your obedient servant,
" Gilbert Cummins.
" To Mr. Rohert Mallet."
With this fragment, weighing only about 500 grains, we made
a few experiments, and shortly vi'rote again to Mr. Cummins,
requesting a larger supply of the brass, and replies to certain
questions respecting its influence, as in annexed copy: —
''Mr. Gilbert Cummins,
"Sir, — In reply to yours of the 23rd instant, Professor Davy
and myself return you our thanks for your attention, and for
the specimens of altered cast iron and the brass, &c. just re-
ceived. The specimen of brass is quite sufficient to enable us
to determine its composition, but insufficient to enable us to
institute some comparative experiments as to the precise condi-
tions of its preservative power. For this purpose it would be
necessary to have five or six pomids of the brass, the value of
which, should that stand in the way, we are quite ready to pay;
we therefore hope to receive it by the same conveyance which
brought the former specimens. We M'ould also desire replies
to the following questions in yoiu* next —
" 1st. Is the brass — brass proper or gun metal, viz. — made
with zinc or tin, and what, about, are its proportions ?
" 2nd. How long has it been in use as a preserver of cast
iron, and to what purposes chiefly applied ?
" 3rd. How has the brass been chiefly applied ? has it been
cast into or round the cast iron preserved, at a temperature of
fusion, or merely placed in contact at a common temperature ?
" 4tli . Have its preservative effects been uniform, or have thei'e
been exceptions, and if so, under what conditions ?
" 5th. Has its preservative influence been found as effective
when the iron Avas exposed to 'wet and dry,' or about the level
of ordinary spring tides, as when ahvays immersed in sea \vater?
" 6th. Has cast iron in the neighbourhood of the brass, but
not actually shielded or covered up from the sea water, been as
well protected as when covered ; for instance, would the pin of
a hinge in a brass socket be better protected than the parts of
the iron hinge outside the socket ?
298 EIGHTH REPORT— 1838.
^' 7th. Are cast and wrought iron equally well protected ?
" 8th. Has it been tried in fresh water ?
** The favour of your replies as early as convenient to these
queries will be esteemed by us."
To which we received the following reply :- —
" Dock Yard, Liverpool, 27th April, 1838.
" Sir, — I am in receipt of yours of the 25th instant, the con-
tents of which I have communicated to Mr. Hartley, sen., who
has directed me to inform you, that he has only a small portion
of the brass left that was attached to the cylinder that first
caused his attention to the preservative properties of that metal ;
and with regard to the series of questions put by you, I am de-
sired to say, that daring his son's absence his other avocations
are such as not to afford time or opportunity of properly attend-
ing thereto.
" I am. Sir, your obedient servant,
" Gilbert Cummins.
"To Mr. Robert Mallet."
We hence were precluded from any information or assistance
from Mr. Hartley, and were about giving up all hope of expe-
rimenting on the identical brass stated to have been used at
Liverpool for protection, when we were unexpectedly favoured
by Professor Kane with a piece of this brass weighing about
tvvo pounds, which he stated had been personally handed to him
by Mr. Jesse Hartley ; with these the following selection of
experiments made by the writer, from amongst many others
made by Professor Davy and himself, may be stated with their
results.
103. When a piece of cast iron was placed in a glass vessel
of sea water with a piece of this brass laid in close contact with
its upper side, the iron was rapidly attacked, the brass remain-
ing bright, and rust soon deposited in large quantity.
104. An equal sized piece broken from the same specimen of
cast iron, and exposed in similar circumstances to sea water
alone, was much less acted upon by it.
105. Two pieces of wrought iron similarly treated produced
similar results.
106. Specimens of cast iron and of wrought iron similarly
treated, with and without the presence of the brass, produced
similar results, as above, in fresh ivater, but more slowly.
107. Where the surfaces of the brass and iron were in close
contact, the iron remained nearly bright ; but it did so likewise
when a piece of plate-glass was substituted for the brass, or
ACTION OF WATER ON IRON. 299
when wood, mica, paper, or another piece of the same iron took
its place.
108. The larger was the proportion of the bi-ass present to
the quantity of iron exposed, the faster the latter corroded.
109. When the brass was attached by solder to the iron,
whether cast or wrought, the action was the same, with in-
creased energy, provided the solder (composed of lead and tin)
was not immersed in the fluid. When it was, so the results
were anomalous, corrosion being retarded at first, and after-
wards accelerated, apparently from a change of electric relation
between the metals, as in Van Beek's experiments before
noticed.
110. When a cylinder of brass, in composition the same as
Mr. Hartley's, was cast round a turned cylinder of wrought iron
at its fusing temperature, the iron on exposure to sea water was
rapidly acted upon, and carbonates of lime and magnesia were
deposited upon the brass, which remained bright.
111. Corrosion in all cases commenced at the moment of
immersion, and continued without change for periods of nearly
two months.
112. When cast or wrought iron was exposed to sea water or
fresh in the same vessel with a surface of this brass, but without
contact, but each communicating by a gold-soldered platina wire
outside the fluid, corrosion took place of the iron more rapidly
than when similar pieces were exposed without the presence of
the brass.
113. No modification of alloy in the brass within the limits
of brass or gun metal seemed to produce any very remarkable
change in the increased rate of corrosion of iron by its presence,
nor did the results dififer materially whether brass proper, viz.
zinc and copper, were used, or Mr. Hartley's brass, which is,
in fact, impure gun metal, or copper and tin.
114. As the proportion of zinc, however, in the brass in-
creased, a tendency to preservation should be manifested, and
conversely as the copper predominated, increased corrosion
would be expected. This view has suggested a very curious
branch of investigation now in progress, as to the changes of
electrical relations to a third metal of definite atomic alloys of
two other metals, whereof one is in a positive, and the other in
a negative electrical relation to the former.
115. These results are sufficient to prove incontestably, that
brass or gun metal have no protective power over iron what-
ever, but, on the contrary, greatly promote its corrosion in sea
or fresh water, and, as we also found, in diluted acids.
116. But as practical instances often come more home to the
300 EIGHTH REPORT 1838.
practical man than any experiments made on a small scale, it
so happens that I am enabled to present an actual instance from
the Dublin Docks of cast iron deeply acted on and corroded in
a period of eighteen years, though in close contact with brass.
This is a portion of a sluice, situated between high and low
water, made eighteen years since by the firm to which I belong,
and lately obliged to be removed and replaced with a new one, .
in company with several others, from the deep corrosion and
softening it had undergone.
The brass was here a facing riveted to the cast-iron sluice all
round, to make it water tight. The composition of this brass
differs from Mr. Hartley's only in containing some more zinc,
of which his contains but a very small quantity, which by ana-
logy and according to Mr. Hartley's own view is ail in its fa-
vour. Here, then, is an experiment of eighteen years' duration,
which results in showing that brass has had no protective power
in the tidal water of the River Liffey.
117. It appeared worth while to make a quantitative analysis
of Mr. Hartley's brass and of this from the Dublin Docks, both
for the purpose of comparison, and to see if they were atomic
compounds or mere accidental mixtures with approximations to
atomic constitution, as is generally the case in brass used for
engineering purposes, whicli is produced by remelting. I ac-
cordingly analyzed a fragment of tlie first specimen of Mr. Hart-
ley's brass, sent us direct fi-om Liverpool, and also of the Dub-
lin Dock brass, and lastly, that given us by Dr. Kane. The
method adopted with all was the following, which differs in
some respects from the modes usually recommended for the
analysis of brass, and which are incapable of giving results ap-
proaching correctness.
1st. A given weight of brass was dissolved with heat, con-
tinually agitating in strong nitric acid, which was boiled nearly
to dryness, diluted with water, and the stannic acid separated,
washed, ignited, and weighed.
2nd. Tiie solution and washings evaporated nearly to dryness,
sulphuric acid added, evaporation continued to dryness, water
added, and sulphate lead, separated, ignited, and weighed.
3rd. The solution being acid, treated with sulphuretted hy-
drogen, and precipitate washed in water impregnated with the
same; the CuS — redissolved in aqua rcgia, with heat, again
precipitated hot with caustic potass washed with hot water, ig-
nited, burning filter and weighed.
4th. The solution and W'ashings concentrated, and pure am-
monia added in excess, and the Fe^Og separated and weighed.
5th, Bicarbonate potass added to the filtered solution, boiled
I
ACTION OP WATER ON IRON. 301
briskly to dryness, avoiding spattering, redissolved in water,
and precipitate of ZnO. separated, ignited, and weighed warm.
6th. The sohition tested for remains of zinc by bihydro-sul-
phuret ammonia.
118. 24*80 grains of the brass received from Liverpool through
Mr. Gilbert Cummins, analyzed in this way, gave the following
results, reduced to per cent. :
Tin = 12-012
Lead = 0*266
Copper = 79*750
Iron = 3*137
Zinc = 4*786
Loss = 0*049
100-000
119. 42*085 grains of the brass from the Dublin Docks gave
the following composition, also reduced to per cent. :
Tin = 0-807
Lead = 4*062
Iron = 0-879
Copper = 65-890 = 2 atoms Cu
Ziiic = 28-288 = 1 atom Z'n
Loss = 00-074
100-000
120. I analyzed 41-705 grains of tie specimen of Mr. Hart-
ley's brass given us by Dr. Kane, with the following results,
Miiich present a larger amount of loss than I could have wished,
arising from my having been several times delayed in comple-
ting the process by unavoidable business. — It gave, reduced to
per cent..
Tin = 4-524
Lead = 13 051
Iron =1-743
Zinc = 8-639
Copper = 67-233
Loss = 4-810
100-000
It is hence obvious that all these brasses are chance mixtures,
and that the Dublin Dock brass contains the most zinc, and
comes nearest to atomic constitution 5 and hence might have
been expected, on Mr. Hartley's hypothesis, to have most ef-
302 EIGHTH REPORT 1838.
fectually preserved the iron it was in contact with. It is still
more remarkable, however, how great the discrepancy in consti-
tution of the two specimens of Liverpool brass is, the latter
containing an enormous proportion of lead.
121. It is not difficult to imagine that the mistake of Mr.
Hartley has arisen from neglect in observing that which Pro-
fessor E. Davy has first pointed out, namely, that iron, or other
metals, in its relation to water are preserved from corrosion by
covering surfaces, although the water insinuates itself between.
Nor does it appear difficult to account for this result. It would
appear to be a case of slow or retarded chemical action by the
opposition of capillary forces of the same class as slow action,
through Becquerel's clay plugs or diaphragms, in which, when
once the first portion of air, combined with the fluid between
the surfaces in contact, is decomposed and taken up, the chemi-
cal affinity of the iron, or similar metals, for it, is counteracted
by the capillarity of the flat tube formed by the opposed sur-
faces which it is unable to overcome, so as to draw in fresh air
to the fluid within, already exhausted of it,
122. Indeed, if Mr. Hartley be reported rightly, he is stated
to have mentioned that '^soil," mud I suppose, lay on the sluices
said to have been preserved, and which had to be removed prior
to their examination ; if so, there is little wonder they should
7iot have sustained corrosion. — Liverpool Journal.
123. Another, and an extremely probable reason for the mis-
take, may have been the supposed preservative surfaces being
often smeared with oil or grease, which, for a considerable time,
resists the action of sea or fresh water, and protects the metal
on which it lies. Indeed, if we could get an air and water-tight
covering which would remain so, no further protect(n' for im-
mersed or moistened metals need be sought for.
124. Accordingly, Mr. Arthur Aikin suggested the applica-
tion of melted caoutchouc, with or without admixture of oil of
turpentine, as a varnish to preserve iron and steel, &c., from
corrosion, so far back as 1821. — Gill's Tech. Rep. vol. i. p. 55.
And Dumas has proposed the employment of caoutchouc in so-
lution as a varnish to the shot and shells in the French arsenals
{Comptes Rendus, 1836. p. 373) ; but Payen states that this had
been tried by the nmnicipality of Grenoble in the year 1834, and
found useless after a short period.
125. During the experiments already detailed it seemed just
possible that Mr. Hartley's might be yet a concealed case of
Professor Schoenbein's anomaly of passive iron, or of Dr. An-
drew's inactive bismuth, and the writer was just about com-
mencing some experiments with a view of elucidating this, when
ACTION OF WATEK ON IRON. 303
he received the BibUotheque Universelle, published in February
last, containing an article by Professor Schoenbein on the very
subject. In this he shows^ as indeed he had previously done in a
letter to Dr. Faraday in the Lond. & Edinb. Philosophical Maga-
zine for December last, that he, Schoenbein, "had already demon-
strated, 1st. That iron only comports itself passively as the anode
in relation to the oxygen disengaged by the current in aqueous
solutions, which contain alone oxygenized compounds, as oxacids,
oxide, oxysalts, &c.; 2nd. That the state of chemical indifference
of iron can only be obtained with respect to oxygen ; and, 3rd.
That this metal acts in its ordinary way when it is plunged as an
anode into aqueous solutions of the hydracids of the chlorides,
bromides, iodides, fluorides, or sulphurets ; in fact, in solutions
of combinations whose negative element has a great affinity to
iron. In these cases the oxygen resulting from the electro- che-
mical decomposition of the water combines with the ix'on in the
same way as the chlorine or iodine disengaged under like cir-
cumstances. Hence," continues Schoenbein, " as the substances
which are in solution in sea water are for the most part electro-
lytes which do not contain oxygen as a constituent, it is impos-
sible, after the facts above stated, that iron as an anode can be
indifferent chemically, in relation to sea water; but, on the con-
trary, this metal must combine with the oxygen, chlorine, &c.
disengaged by the current."
Scheenbein then states the result of an experiment he made
directly with sea water, by plunging an iron wire connected with
the positive pole of a pile into it, thereby closing the circuit ; no
oxygen was evolved at the iron, which was oxidized, in strict
accordance with his general principle. He then proceeds to
show, that assuming Mr. Hartley's view to be right, it involves
an initial absurdity or contradiction in principle ; and finally
concludes, that the observation of Mr. Hartley must be con-
sidered as doubly anomalous, namely, in relation to common
and acknowledged electro-chemical laws, and also to those spe-
cial ones developed by himself.
126. The anomaly, however, may now be considered simply
as an error, but one of a very serious character, apparently from
the extent to which its consequences seem to have been wrought
out in the application stated to have been made of brass as pro-
tectors to all the work of the Liverpool Docks, which, unless
removed, must be attended with the rapid decay and destruc-
tion of all the iron it is connected with. I have also understood
that, acting on this presumptive protection, the Liverpool chain-
cable makers now supply gun-metal pins to their cable shackles,
at intervals of a few fathoins, by way and under the name of
304 EIGHTH REPORT — 1838.
"preservers ;" a more destructive practice can scarcely be con-
ceived, or one more fatally applied. From these circumstances,
and lest these mischievous results should be extended elsewhere,
it lias been deemed right thus at length to refute it, which I
conceive is fully done by Schcenbein's, Professor Davy's, and
my own experiments.
127. To recur again for a moment to the subject of the boxes •
of specimens of cast iron sunk for experiment, it was stated
that they were divided into separate cells for each kind of iron
by veneers of varnished oak. The reason of this arrangement,
and a deduction which has grown out of it, and is likely to prove
important as affording a mode of protecting cast and wrought
iron, remain to be stated. It having been early remarked that
the harder irons, whether cast or wrought, were acted on much
more slowly than the softer and more carbonaceous ones, it
appeared not impossible that if several different sorts were in-
closed in electrical continuity in the same box, grave errors
might be introduced into our results by the iron least acted on
standing in a negative relation to those more rapidly corroded,
and increasing the action of the sea or other M'ater upon them,
and at the same time being themselves preserved to a certain
extent.
128. By a few preliminary experiments with the galvano-
meter, this was found to be a correct view, — it was found that
of any two different irons, the harder was always in a negative
relation to the softer, which was positive to it, and hence the
separation of every specimen became necessary in order to eli-
minate this source of error.
129. This at once suggested to the writer the possibility of
preserving the hard gray cast iron and the wrought iron, &c.,
in common use, by the application of protectors formed of the
softest and most highly carburetted cast iron attainable ; and as
the conversion of this latter into plumbago, to a great extent,
did not seem materially to alter its electrical relation to gray or
A^hite cast iron, or to wrought iron, it seemed probable that it
might afford an electro-chemical protector superior in many re-
spects even to zinc. With this view experiments are now in
progress, and so far are decisively in favour of the method.
130. The intensity of current produced by soft and hard cast
iron is much greater than would have been anticipated. When
two small bars, each 4 in. long, by 0*5 in. wide, by 0"25 thick,
one of soft black and the other of hard gray cast iron, were both
broken in two, and an iron wire soldered to each half, on im-
mersing the two halves of either one piece in common water
the needle of a Melloni's galvanometer was scarcely disturbed ;
ACTIOX OF WATKR ON IRON. 305
it oscillated about 2° ; but when one half of each of the two
original pieces, i e. the black and the gray, were immersed, the
needles deviated at once from 78° to 80°, and on adding a sino-le
drop of hydrochloric acid, flew round.
13 1 . This action in common water or sea water always showed
the softer iron positive to the other, and continued constant and
unchanged in an experinaent continued for some days.
132. When two pieces of cast iron, such as the above, were
immersed in dilute hydrochloric acid, tied together and in con-
tact, the harder one remained quite bright and untouched be-
fore and after the acid was saturated, while the softer was rapidly
blackened and dissolved ; neither was any gas evolved from the
negative piece, unless the acid was concentrated.
133. The subject is not in a state to do more now than state
the principle in view, and that so far as experiments have yet
gone, it is likely to add a new if not a better mode of protecting
iron to those already known ; if successful, its application to
engineering structures will afford many facilities of execution,
and be attended with much greater economy than any process
in which zinc is used possibly can.
134. It already suggests to the engineer the importance of
preserving uniformity of texture and of chemical composition
in all parts of his structures of iron, in order that one part may
not accelerate the destruction of the other. It also shows the
necessity, when wrought iron (which is negative to all but chilled
cast iron) is applied in contact with cast iron, of allowing extra
substance in the latter to meet the increased corrosion produced
by the wrought iron at the points of contact, and it explains
why the vital injury is so often sustained in works in cast iron
of this metal being first eaten away round the bolt holes, as for
instance, in the air-pumps and condensers of marine engines,
where the parts of the work are secured together ; and it further
suggests, that where the sides of these bolt holes in the cast
iron can be chilled or cast on an iron core, as is often practica-
ble in such cases, while the bolt will slightly suffer, the cast
iron round it will be preserved. On a future occasion I hope
to lay the results of this branch of the investigation before the
Association.
135. M. Payen's observations as to the power of alkaline
waters to protect iron from rust, though seldom applicable, are
worthy of further investigation, and an'attempt to discover their
rationale. It has very long been known that lime in powder, or
limewater, possesses a decided power of this sort, and both are
in use amongst workmen.
Cases may be found in practice where solutions of an alkali
306 EIGHTH REPORT — 1838.
or alkaline earth would be admissible and valuable if found
effective preservers of iron; for instance, lime-water might
readily replace the bilge-water in steamers, whose action is at
present so destructive to the holding-down bolts, blow-off pipes
and cocks, boiler bottoms, coal bunkers, &c., and to the de-
composition of which in a great degree the peculiarly offensive
smell of the bilge- water of steamers is owing. There is no rea- "
son to assume that dilute lime-water would have any injurious
action on the timbers of the ship.
136. Dr. Andrews' and Schoenbein's experiments, however,
in which a metal becomes capable of rendering passive or of
protecting in certain cases another, alt/tough itself not acted
on, give hope that protectors of this kind may yet be found and
practically applied to iron ; and hence it is in this direction that
our efforts should be bent with most energy in seeking to pre-
serve metals from oxidation, namely, to obtain a mode of elec-
tro-chemical protection, such that, ichile the metal shall be
preserved, the protector shall not be chemically acted on, and
whose protection shall be invariable.
137, In illustration of this I may adduce a very interesting
experiment of Becquerel and 'Dunms {Comptes Rendus, 6th Feb.
1837) : " Having taken a flask half filled with distilled water, in
which was dissolved -j-Ao ^f potass, they plunged into it a slip
of perfectly polished iron, and another of gold ; to each was fixed
a wire of the same metal passing through the cork. The flask
was sealed with all possible care to prevent the access of air.
Seventeen months afterwards the iron preserved all its bril-
liancy, no tubercles had formed on it, and every thing indicated
that it had undergone no appreciable alteration."
When the gold and iron wires were placed in communication
with a multiplier with a short coil, an immediate deviation of
35° was produced, and the magnetic needle having oscillated
awhile, came to rest again at zero. On interrupting and again
re-establishing the communications it remained motionless, but
on leaving the circuit open for a quarter of an hour, and again
closing it, the needle deviated 25°, and after remaining inter-
rupted for half an hour, the deviation amounted to 35° again.
The experiment was repeated, and always with accordant re-
sults. The current produced is then the result of a discharge
like that of a Leyden phial.
Thus, when the iron is in contact with the alkaline water, the
metal takes by degrees a charge of negative electricity, and the
water a charge of positive electricity, as if there had been a
chemical reaction between them. (De la Rive in fact considers
that it is due to a chemical action, though excessively slow.)
ACTION OF WATER ON IRON. .307
These two electricities, notwithstanding their reciprocal attrac-
tion, remain in equilibrium at the surface of contact, which they
are not able to break, and they only recombine when we esta-
blish the communication between the iron and the solution by
means of a wire of gold or platina. Hence it results that the
iron rendered constantly negative is found in the least favoura-
ble state for combining with the oxygen of the air present in
the solution.
It is unnecessary here to pursue the extract into the rationale
and objections thereto discussed by the authors, as I merely wish
to indicate the class of experiments which are the most valua-
ble as regards our subject. Others very analogous, in which
anthracite, plumbago, and sesquioxide of manganese are the
agents, are to be found in Becquerel's fifth volume of his Traits
de I' Elechncit^.
138. The subject, of which I have thus given I fear a very
imperfect sketch, is a wide and important one, and many care-
ful experiments are wanting to complete our knowledge of it.
The following especially are desiderata immediately applicable
to the engineer and also to the chemist.
1st. A series of experiments to determine the rate of pro-
gression of corrosion in sea water and fresh, at increasing
depths, from to say 10 fathoms.
2nd. A comparative series for this reaction at the various
temperatures of the sea and of rivers, &c. known to be found
within the the range of our inhabited climates.
3rd. A determination of the nature and amount of air con-
tained in sea Avater at various depths, as recommended by M.
Biot to the officers of the "Bonite."
4th. A set of comparative experiments on the action of sea
water, diluted with various known proportions of fresh, as at
the mouths of tidal rivers.
5th, Experiments are wanting as to the effects of the pre-
sence of animal matters in a state of putrid fermentation in sea
and river water, in modifying their action on iron, as in rivers,
&c. receiving the sewerage of cities.
6th. Determinations of the amount and nature of the plum-
bago produced from various makes of iron, its precise compo-
sition, and the conditions of its heating or not spontaneously,
with the results of this action.
A careful repetition of many of the experiments on the action
of pure water, and of air and water on iron, is also needed, the
results of former experiments being neither satisfactory nor
uniform.
A paper of some novelty on this subject has just appeared in
308 EIGHTH REPORT 1838.
the Bihliotheqiie Universelle for June and July, 1838, by Profes-
sor Bonsdorf of Helsingfors. In this the author studies in ge-
neral the action of various metals on air and water, under the
following conditions : —
1st. In air perfectly dry and free from carbonic acid.
2nd. In air saturated with vapour of water, but free from
cai'bonic acid.
3rd. In air containing both the latter.
4th. In contact with liquid water and air, both free from, and
also containing carbonic acid.
He states that in the first condition no metal oxidates but po-
tassium and sodium. That in the second case no metal oxidates
but arsenic and lead ; in particular, that zinc, iron, and bismuth
do not oxidate, and that a gentle heat increases the action on
the first two. The author also brings forward some new views
on the subject of the deposit of moisture on metallic surfaces in
certain conditions, which, however, do not seem quite correct.
7th. Experiments would also be desirable as to whether mag-
netism affects the rate or form of corrosion of iron, and hence,
whether position as to meridian has any thing to do with the
durability of engineering works in iron.
8tli. Experiments vipon the suitability of various protecting
paints and varnishes, and the modes of their application to works
exposed to air and moisture, would be verj^ vahiable, giving pre-
ference to those which, with other obvious properties, dry soon-
est after rain, and, imder given circumstances, cause the least
deposit of dew. Upon this point Bonsdorf 's paper above alluded
to may be consulted.
9th. A comparative set of experiments would be useful also
showing, under like circumstances, the effect of corrosion of sea
water, and of its mechanical abrasion by this fluid in motion, or
of the difference of action on iron in still sea water and in a tide-
way.
10th. It would be exceedingly important also, as an element
of this investigation, as well as useful to the mechanic, to obtain
a correct measvu-e of the resistance to abrasion of various makes
of iron. This has been attempted by Mr. Fairbairn, unsuccess-
fully, by means of grinding on a stone a piece of weighed iron,
of given surface and under a given pressure, for a known time,
and noting the loss of weight. The most likely means of ar-
riving at this will probably be by making wheels of the various
irons to be tried, turned on the face and fitted on to steel axles,
suspending these in a swinging frame, and causing them to re-
volve for a length of time against the faces of other turned
wheels, all of one sort of iron, say tyred with No. 1 Welsh bar
ACTION OF WATER ON IRON.
309
iron (our standard), and pressed together by known weights.
The loss of weight sustained by the wheels would then indicate
their respective ratios of abrasion, the loose axles being, pre-
viously to weighing, taken out so as to eliminate their wear from
that of the face of the wheel.
This method and the probability of its giving correct results
have been suggested to me by the uniformity with which the
wheels of railway carriages wear when tyred with the same iron.
Railway experience also shows that the resistance to abrasion
in rails of wrought iron is to that of cast iron as 15:4.
(Wood on Railways. )
139. In conclusion, I have to regret that my friend Professor
Davy's public avocations have hitherto prevented his devoting
more of his attention and great experimental skill to this sub-
ject, which, while it has been entrusted to us conjointly, would,
I am certain, in his hands have found an abler reporter.
Our thanks also are due to the several public bodies and pri-
vate individuals to whose assistance we are indebted in making
our experiments. — To the Board of Public Works and the Bal-
last Corporation of the Port of Dublin we are under obligation,
not only for personal assistance, but for freely placing their
stores in Kingstown Harbour and the Port of Dublin at our
disposal.
Note.
Since the foregoing report was sent to press it has been con-
sidered unnecessary to print the tables of experiments on the
great scale referred to therein at length in this volume, in as
much as at present they necessarily consist more of data than
of results, the latter demanding the lapse of time for their col-
lection. It has been therefore determined at present merely
to give a synoptic view of those tables of experiments in
progress.
These experimental tables at present contain the following
data respecting the specimens of iron submitted to trial, viz.
'1
t ■
•E CO
O
. c
If
"sis
.s?go
1"
il
if
3£
1
11
Hi
o J2 c
> S o
M ° i
The whole series of experiments in progress on the great
scale is contained in five separate boxes, each containing seve-
voL.vn. 1838. x
310 EIGHTH REPORT — 1838.
ral classes, each of which again consists of numerous individual
specimens of iron, and are arranged as follows :^
Box, No. I. — Sunk in the clear sea water of Kingstown
Harbour, and containing: —
Class, No. 1. — Welsh cast iron. Experiments, No. 1 to 13
inclusive, i. e. 13 specimens, different.
Class, No. 2. — Irish cast irons. Experiments, 14 to 17.
Class, No. 3. — Staffordshire and Shropshire cast irons.
Experiments, 18 to 25.
Class, No. 4. — Scotch cast irons. Experiments, 26 to 57.
Class, No. 5. — The standard bar of wrought iron.
Class, No. 6. — Scotch cast iron, cast in green sand, and also
chilled.
Class, No. 7. — Welsh cast iron, cast in green sand, and also
chilled.
Class, No. 8. — Staffordshire cast iron, cast in green sand,
and also chilled.
Class, No. 9. — Irish cast iron, cast in green sand, and also
chilled.
Class, No. 10. — Mixed cast irons, various — Scotch and
Welsh, Irish and Welsh, &c. &c. &c.
Class, No. 11. — Cast iron used by Messrs. Hodgkinson and
Fairbairn in their experiments, viz. Scotch, Welsh, Derby-
shire, Yorkshire, &c. &c. &c.
Class, No. 12. — Mixed cast iron, suitable for fine finishing
in machinery, with the " skin" removed entirely by the planing
machine.
Class, No. 13. — Hard gray mixed irons, protected by various
known paints and varnishes, viz. caoutchouc varnish, copal,
mastic, turpentine, asphaltum, white-lead paint, soft cement
(wax and tallow), Swedish tar, coal tar laid on hot, drying oil.
Box, No. II. — Sunk in the foul sea water at the mouth of
the Kingstown sewer.
Box, No. III. — Sunk in clear sea water, at temperatures
varying from 115° to 125° Fahr., in the Dublin and Kingstown
Railway Company's hot baths at Salt Hill.
Box, No. IV. — Sunk in the foul water of the river Liffey,
within the tidal limits, opposite the Poddle river.
Box, No. v.— Sunk in the fresh water of the river Liffey,
within the premises of the Royal Hospital, Kilmainham.
All these boxes, viz. II., III., IV., and V., contain classes
of specimens co-ordinating with those before stated as con-
tained in No. I., consisting in all of about one hundred and
sixty separate and different specimens.
It is intended to take up these boxes at determinate intervals
ACTION OF WATER ON IRON. 311
and examine the reaction which may have taken place ; when
this has been done, it is purposed to give, in addition to the
foregoing data, the following information, with such other in
addition as may hereafter appear desirable.
1st. The weight of each specimen when taken up after an
interval of twelve months, again after two years, and again,
perhaps, after a longer period.
2nd. Loss of weight when cleared from adherent plumbago,
and weight of the latter when dry.
3rd. Loss of weight per unit of surface.
4th. Loss of weight per unit of surface as referred to the
standard bar as unity.
5th. Uniformity or otherwise of corrosion and its depth.
6th. Amount of water absorbed by the iron, if any.
7th. Chemical properties of the plumbago, e. g. if it ignite
spontaneously, &c. &c.
8th. Physical properties of the iron if altered.
9th. Relative preservative effects of the various varnishes or
coverings, if any.
As the giving the information under the second head above
will obviously render it possible that the reaction on the speci-
mens may be greater the second and subsequent years than it
would have been if the plumbago were not removed, means are
taken to compare the eflPects of water, &c. on iron in the same
times and circumstances as above, when the coat of plumbago
is periodically removed, and when it remains untouched for the
whole period of experiment.
x2
312
EIGHTH REPORT. — 1838.
The following Notice of Experiments on the ultimate Trans-
verse Strength of Cast Iron made at Arigna Works, Co.
Leitrim, Ireland, at Messrs. Bramah and Robinsons, ^th
May, 1837, is appended to the preceding Report.
.£ '^
No. of
Mark or Mixture of
Deflection
as ..H
Exper,
Iron used.
in ins. 1000.
g g
o t.
on
Observations.
1
No.l, Arigna pig
0-472
220
2
No. 2, ditto ....
0-555
240
Maximum strength.
3 1
1 of No. 1, pig. .
\ of No. 2, pig. .
1 0-460
164
4 1
1 of No.l, pig..
1 of old scraps. .
1 0-5605
236
5 1
^ of No. 2, pig. .
5 of old scraps. .
\ 0-617
236
6 1
^ of No. 1, pig. ,
f of old scraps. .
1 0-4767
252
M
^ of No. 2, pig. .
§ of old scraps. .
j 0-547
256
M
i of No. 1, pig. .
f of old scraps. .
1 0-384
172
M
i of No. 2, pig. .
^ of old scraps. .
j 0-440
192
Note. — The size of the bars used was 1-5 inch square by
3 ft. 6 in. long. The distance between the supports was 3 ft.
1 inch.
The comparative breaking weights in column the fourth,
multiplied by 12, will give the absolute weight in pounds which
broke the bars.
ON INORGANIC AND ORGANIC SUBSTANCES. 313
Notice of Experiments in Progress, at the desire of the British
Association, on the Action of a Heat of 212° Fahr. when
long continued, on Inorganic and Organic Substances. By
Robert Mallet, M.R.I.A.
The original object of these experiments has been to try how
far it is possible to form many mineral substances which we
either have not formed in the laboratory, or which have only
hitherto been produced by the dry method.
Many circumstances concur with the few scattered experi-
ments which have been made on this subject in causing us to
suppose that this may frequently be effected by the long-con-
tinued action of boiling water or steam, or both, on the consti-
tuents of the mineral to be formed.
These may be presented to the action of these agents either
in a nascent state, as in silex and earths, or oxides recently pre-
cipitated, without being dried and mixed in the atomic propor-
tions required to constitute a given mineral if combined ; or
the mineral may be formed by the mutual decomposition and
recombination of other bodies, more or less difficultly soluble
in boiling water. Attention has been directed to both methods,
and indications are not wanting to give hopes of success in
both. It has been, for instance, some time known, that chal-
cedony may be formed by the prolonged action of a boiling
temperature upon gelatinized silica ; while, on the other hand,
it can be equally well formed by the decomposition of certain
kinds of glass by the same means as remarked by the late Dr.
Turner. Indeed, the extreme facility with which almost every
kind of glass decomposes, under the continued action of boil-
ing water, has greatly retarded these experiments. None has
been found to answer the purpose but the hard Bohemian
glass, (which is objectionable in point of expense,) and green
bottle glass ; the latter imperfectly.
The minerals as yet chosen for experiment have been chiefly
hydrates, of which the following may serve as a type ; the
production of these has been attempted by direct combination
of their constituents with excess of water.
Formula adopted.
Chalcedony or Opal . . . . Sg + H O
Lenzinite . A + S + HO ,
Triklasite A + S^ + HO
CymoUte A + Sg + HO
Terre de Reigate A + S4 + 3HO
314 EIGHTH REPORT 1838.
Formula adopted.
Mesotype SAS + NaSa + SHO
Prehnite 3 AS + Co^Sg + 2HO
Steatite A S2 + 2 Ma Sg + 4 H O
Chabasie 3 A S2 + Ca S3 + 6 H O
Analcime 3 A Sg + Na 83 + 2 H O
Harmotome 4 A Sg + B« S4 + 6 H O
Killinite 8AS2+KS4 + 3HO
Various uniaxaland biaxal micas, and some metallic sulphurets
and sulpho-salts, have also been attempted by way of double
decomposition.
The substances to be tried, when mixed and covered with
water, are sealed in Bohemian glass tubes, numbered and ex-
posed to steam in a box between two low-pressure boilers, in
one or the other of which steam is always up.
Specimens of peat, of lignin, of coal, and other analogous
organic bodies, have also been exposed in various ways, in the
expectation that some light may be thrown upon the formation
of coal and bitumens ; and various supposed insoluble crystal-
lized native minerals have also been exposed immersed in boiling
water, in order to determine what its action, if any, may be on
their crystals, and what effect may result from the dissolved mat-
ter. Various woods have been placed in contact with gelatinized
silex and its solutions, in the hope of slowly forming silicifica-
tions similar to those from Antigua, &c.
These experiments, it is conceived, will connect themselves
in a very interesting point of view with those in progress under
Mr. Vernon Harcourt's superintendence upon the action of a
much higher but indefinite temperature upon mineral bodies.
There is every probability that very many of the minerals in
the crust of the earth, especially the crystalHzed ones, have
been formed at a comparatively low temperature. Quartz is
daily deposited from the water of the Geysers, and has been
found in a soft and pasty state elsewhere. — {Betidant Traiie.)
Malachite has been found in a similar state. Vauquelin found
stalactitic quartz, {Ann. de CJmn. xxi.). Crystals of quartz have
been found in the United States, containing anthracite, and
one containing a liquid with a piece of coal floating in it ; and
Mr. Haig found hard crystals of quartz in a bottle of Saratoga
water, which had stood many years, [Quart. Jour. xv.). The
globules of fluid found in amethyst, chrysoberyl, topaz, fluor
spar, &c. &c., a fluid found by Dr. Brewster to be volatile at
75° Fahr., {Edin. PJnl. Jour.) ; the existence of bitumen in
I
PROGRESS IN SPECIAL RESEARCHES. 315
basalt, serpentine, greenstone, mica, and many other minerals
discovered by Mr. Knox [Phil. Jour.), and of fire damp in the
vesicles of sal gem by Dumas ; all these indicate the compa-
rative low temperature at which the formation of many mine-
rals has probably proceeded.
Coal too has been found in Scotland converted into plumbago
by the proximity of a dyke, yet at such a distance that its com-
municated heat must have been extremely low. On the other
hand, facts are not wanting to indicate the powerful effects of
water and a moderate heat in decomposing and changing or-
ganic or organized bodies, as, for instance, the changes re-
marked by Perkins in the oil of his high-pi'essure steam engine,
and very many similar known to the organic chemist.
Again the analytical chemist is familiar with abundant cases
of the direct combination under favourable circumstances — of
oxides with oxides, earths with earths, salts with salts, &c., to
prove the likelihood of minerals being formed by synthesis
■without further decomposition resulting, than loss of consti-
tutional water; as the combination of alumina and magnesia
when precipitated together, giving a compound when ignited
of A^g + M^, or colourless spinell, as remarked by Chenevix.
These scattered facts are sufficient to show that the experi-
ments here indicated, while they belong to chemistry and mi-
neralogy, abound in interest to the geologist. The experiments
have not been sufficiently long in operation to yield definite re-
sults.
Provisional Reports and Notices of Progress in Special Re-
searches, entrusted to Committees and Individuals.
Physical Section.
Professor Forbes contributed a notice of the experiments he
has been some time prosecuting into the Temperature of the
Earth at different depths, and in different sorts of rock. The
results will be laid before a future meeting of the Association.
Sir J. Robison and Mr. J. S. Russell reported the progress
of their investigations on Waves. As this subject has been
again entrusted to the further examination of the Committee,
it is thought proper to defer the publication of the results already
obtained till the Committee shall present their complete report.
Mr. Baily reported that the Committee appointed to repre-
sent to government the importance of reducing the Greenwich
observations of the moon, had vraited on the Chancellor of the
Exchequer, and that the sum of 2000/. had been appropriated
316 EIGHTH REPORT — 1838.
for that purpose, which was placed at the disposal of the As-
tronomer Royal, who had undertaken to superintend the re-
ductions.
Mr. Baily reported that the reduction of the stars intended to
form the enlarged Catalogue of the Royal Astronomical Society
was in progress ; that a small portion only of the original sum
appropriated had been expended ; but that, in all probability,
the whole would be I'equired in the course of the ensuing year.
Mr. Baily reported that the reduction of the stars in the His-
toire Celeste, &c., was in progress ; that a small portion only of
the sum appropriated had at present been expended ; but that
about half the amount would be required.
Mr. Baily added, that he had made repeated application to
the Secretary of the Bureau des Longitudes for the corrected
copy of the Histoire Celeste gratuitously offered by that Board
for the use of the computers ; but that he had not yet received
any answer to such applications.
Report of the Committee for the Liverpool Observatory.
The Committee, after carefully examining the local circum-
stances of the port of Liverpool, and arranging the plan which
seemed most expedient for the establishment of an Observatory
at Liverpool, laid it before the local authorities, who approved
of the proposed arrangement, and expressed their readiness to
carry it into effect as soon as the necessary powers could be
obtained from Parliament.
Chemical Section.
Apparatus for the Detection and Measurement of Gases pre-
sent in minute quantity in Atmospheric Air. By Wm. West.
Mr. West produced and reported verbally upon his apparatus
for the above purpose, for the construction of which the Asso-
ciation had, in a former year, voted the sum of 20/. By the ac-
tion of a spiral spring in front of the drum or cylinder of Cros-
ley's gasometer, a partial vacuum is produced, to fill which the
air presses from without, and in its passage is conducted through
several two-necked bottles filled with liquids fitted to combine
with and detain the gases sought, as lime-water for carbonic
acid, &c. The same gasometer registers the quantity of air
thus deprived of the accidental and variable gas, while the
quantity of gas separated is found by calculation from the pre-
cipitate formed in the bottles. The apparatus had been con-
PROGRESS IN SPECIAL RESEARCHES. 317
structed too recently to admit of any results being obtained
beyond preliminary trials, which promised well, both as to effi-
ciency and accuracy.
Information was furnished of the progress made by Professor
Liebig in the preparation of his report on Organic Analysis.
Professor Johnston read a preliminary report on Inorganic
Analysis.
Geology and Geography.
The progress made by M. Agassiz in developing the Fossil
Ichthyology of Great Britain was stated.
Natural History.
Sir W. Jardine, Bart., presented a report on the Salmonidge of
Scotland, and expressed his desire to continue the investiga-
tion. The full report will consequently appear hereafter.
Mr. Gray communicated a preliminary notice on the subject
of the Perforation of Rocks by Mollusca.
Mr. Jenyns stated, that the Committee on preserving animal
and vegetable substances in a moist state were in operation.
_ The commencement of Mr. Gould's Essay on the Caprimul-
gidse was communicated.
Mr. Vigors stated, that considerable progress had been made
by the Committee on the Irish Fauna.
Medical Science.
The London Committee on the Sounds of the Heart stated
the circumstances which prevented the preparation of their re^
port, and announced that it will be ready at the meeting in 1839.
" The Committee have been engaged almost daily for several
hours during the months of June and July, in prosecuting the
researches for which they were appointed, and have obtained
many interesting results, particularly in relation to the sounds
of the heart and arteries as signs of disease. These results were
to be presented at the present Meeting of the Association; but
the death of a colleague having prevented the member who was
to draw up the report from completing it, the Committee are
obliged to postpone it to the next meeting, when they trust
that it will be made still more worthy of the attention of the
Medical Section of the British Association."
Dr. WilUams expressed his hope of being able to present a
report on the Physiology of the Lungs and Bronchi m 1839.
vol. VII. 1838. Y
318 EIGHTH REPORT — 1838.
Dr. Carson stated, that owing to the small number of cases
of lung disease in animals which had occurred in-the Zoological
Gardens of Liverpool in the winter of 1837-8, the Committee
on that subject had not been enabled to make a report to the
Newcastle Meeting, but intended to do so at the Birmingham
Meeting.
Appendix to a Report on the Variatioiis of the Magnetic In-
tensity (printed in vol. vi.). By Major E. Sabine, F.R.S.,
In reference to the report on the Variations of the Magnetic
Intensity, wliich the British Association have done me the ho-
nour to print in their last volume, I wish to communicate tiie
results of the observations made by Captain Duperrey in his
voyage of circumnavigation in the Coquille, in 1822 — 1825,
which I have received in a private communication from that
distinguished officer and magnetic observer. The Section will
learn with pleasure the satisfactory accord of these observa-
tions with those of Captains De Freycinet and Fitz Roy, pub-
lished in my report. When in compliance with the wishes of
the Association, I first entertained the purpose of collecting in
one body the observations of intensity made by different ob-
servers in all parts of the globe, so far as they are comparable
with each other, one of my first steps was to write to Captain
Duperrey to solicit the communication of any intensity results
which he might have obtained. I find, by the letter which I
have received, that Captain Duperrey did kindly comply with
my request ; but, unfortunately, the packet which must have
contained the particulars of his observations has never reached,
me. The letter which I have received contains a notice, both
of the results he obtained, and of the mode in which they were
observed. Had I possessed this information at the time my
report was printed, I should on every account have rejoiced to
have embodied it in the report : and I am anxious to avail my-
self of this opportunity of doing what may yet be done to sup-
ply the omission. Captain Duperrey's observations were made
with a horizontal needle, which, from accidental circumstances,
was not observed with prior to his departure from France.
The usual test of the permanency of the magnetism of the
needle, viz. its vibration at the same station, at the commence-
ment and at the close of the series, was, therefore, omitted in
this case. In the absence of this, which is the most conclusive
test, Captain Duperrey has estimated the loss which his needle
278-50 E. .
. 1-024
130-44 .
. 1-079
151-1^ .
. 1-617
57-31 .
. 1-181
VARIATIONS OF THE MAGNETIC INTENSITY. 319
may have sustained, by comparing its rate of vibration at Paris
on his return, vi'ith its rate at a station in Peru, in the line of
no dip, in which comparison he has assumed the relation of the
force at that station to the force at Paris to be as 1 to 1-3482.
The loss of magnetism sustained by the needle on this estima-
tion was altogether inconsiderable. The times of vibration at
four other stations at which this needle was employed, cor-
rected for temperature and arc, give the following values of
the total intensity.
Payta 5° 6'S. .
OfFak 2 ,
Port Jackson .. 33 52
Isle of France . . 29 9
These determinations are inserted in a map engraved in 1832,
referred to in a paper read by M. Duperrey to the Academy
of Sciences at Paris in 1833, entitled, " Considerations sur le
Magnetisme Terrestre." Captain Duperrey notices, that at two
other stations, viz. Talcahuano and St. Catherine's, he observed
the times of vibration of a dipping needle, the poles of which
were reversed at each station, in the usual manner, for the ob-
servation of the dip ; and that the results derived from the vi-
bration of this needle, presuming it to have received, on every
occasion when the poles were changed, an equal magnetic
charge, correspond in a remarkable manner — as indeed they
do, — with the subsequent observations of Captains King and
Lutke ; but Captain Duperrey, of course, attaches to these
determinations no independent value, and therefore I need not
notice them further. Captain Duperrey has also communicated
to me three results obtained at stations in France in 1834, with
one of M. Hansteen's needles, made, as it appears, with very
great care, and with every necessary jirecaution. These re-
sults are, for
Lat. Long. W. Paris.
Brest 48-24 .. 6-50 ., 1-365
Landevence . . 48-18 . . 6'o5 . . 1-363
Orleans 47-54 .. 0-26 .. 1-.341
I may take this opportunity also of adverting to the observa-
tions of Professor Bache and other gentlemen of the United
States, which were not included in my report. These obser-
vations were made at New York, and in the adjoining states ;
and Mr. Bache is now engaged in connecting them with Eu-
rope, and, consequently, with the general body of the intensity
observations. Until this comparison is complete, which it will
not be until Mr. Bache returns to the United States, the ob-
320 EIGHTH REPORT — 1838.
servations referred to serve to determine the value of the mag-
netic force at the stations at which they are made relatively to
each other, but not relatively to other parts ofthegme.^nA
they were not. therefore, avadable for my report The Ame-
rican observations were made with magnetic needles inclosed
"a vacuu;; apparatus, which Mr. Bache had devised, with the
view of avoiding some of the anomalies occasionally experienced
by other observers. They were made with extreme care, and
were remarkable for minute attention to all those circumstances
which conduce to the accuracy of the results.
END OF THE REPORTS.
NOTICES
AND
ABSTRACTS OF COMMUNICATIONS
TO THE
BRITISH ASSOCIATION
FOR THE
ADVANCEMENT OF SCIENCE,
AT THE
NEWCASTLE MEETING, AUGUST, 1838.
ADVERTISEMENT.
The Editors of the following Notices consider themselves responsible
only for the fidelity with which the views of the Authors are abs-
tracted.
CONTENTS.
NOTICES AND ABSTRACTS OF MISCELLANEOUS
COMMUNICATIONS TO THE SECTIONS.
MATHEMATICS AND PHYSICS.
Page
Mr. Charles Graves on a General Geometric Method I
Sir W. R. Hamilton on the Propagation of Light in vacuo 2
Sir W. R. Hamilton on the Propagation of Light in Crystals 6
Professor Powell on some Points connected with the Theory of Light .... 6
Sir D. Brewster on an Ocular Parallax in Vision, and on the Law of Vi-
sible Direction 7
Sir D. Brewster on a New Phenomenon of Colour in certain specimens
of Fkior Spar 10
Sir D. Brewster's Account of certain New Phenomena of Diffraction .... 12
Sir D. Brewster's Account of an Analogous Series of New Phenomena of
Diffraction when produced by a Transparent Diffracting Body 12
Sir D. Brewster on the Combined Action of Grooved Metallic and Trans-
parent Surfaces upon Light 13
Sir D. Brewster on a new kind of Polarity in Homogeneous Light 13
Sir D. Brewster on some Preparations of the Eye by Mr. Clay Wallace,
of New York 14
Sir J. F. W. Herschel on the Structure of the Vitreous Humour of the
Eye of a Shark 15
Professor Wheatstone on Binocular Vision ; and on the Stereoscope, an
instrument for illustrating its phenomena 16
Sir John F. W. Herschel's Observations on Stars and Nebulse at the Cape
of Good Hope 17
Sir John F. W. Herschel on Halley's Comet 19
Sir Thomas M. Brisbane on the Difference of Longitude between London
and Edinburgh 20
Mr. G. B. Airy on the means adopted for correcting the Local Magnetic
Action of the Compass in Iron Steam-ships ^ 21
Lieut.-Colonel Reid's Statement of the Progress made towards developing
the Law of Storms ; and of what seems further desirable to be done, to
advance our knowledge of the subject 21
Professor A. D. Bache's Note on the Effect of Deflected Currents of Air
on the Quantity of Rain collected by a Rain-gauge 25
Dr. William Smith on the Variations in the Quantity of Rain which falls
in different Parts of the Earth 27
Professor Forbes's Notice of a Brine Spring emitting Carbonic Acid Gas.. 28
Dr. Daobeny on the Climate of North America 29
Rev. J. Watson on the Helm Wind of Crossfell 33
Mr.HoDGKiNsoN on the Temperatures observed in certain Mines in Cheshire 34
Mr. Dent's Facts relating to the Effects of Temperature on the Regulators
of Time-keepers ; and description of some recent improvements in Pen-
dulums, with Observations, and Tabulated Experiments 35
Sir John Robison's Notice of a cheap and portable Barometrical Instru-
ment proposed for the use of Travellers in Mountainous Districts 37
The Rev. Professor Temple Chevallier's Tables intended to facilitate the
computation of Heights by the Barometer 38
a2
CONTENTS.
CHEMISTRY.
Page
Extracts from a Letter addressed by Dr. Hare to the Chemical Section
of the British Association for the Advancement of Science 39
Dr. Thomas Thomson's Observations on the Foreign Substances in Iron. . 41
Dr. Thomas Thomson on the Sugar in Urine of Diabetes 43 .
Dr. Thomas Thomson on Galaetin 46
Dr. Thomas Thomson's Notice respecting the native Diarseniate of Lead... 46
Dr. T.Thomson and Mr. T. Richardson on Emulsin 48
Mr. Thomas Richardson's Examination of Sphene 49
Mr. H. L.Pattinson on a New Process for the Extraction of Silver from
Lead 50
Dr. GoLDiNG Bird's Observations on some of the Products obtained by the
Action of Nitric Acid on Alcohol 55
Dr. GoLDiNG Bird's Notice respecting the Artificial Formation of a Basic
Chloride of Copper by Voltaic Influence 56
Dr. GoLDiNG Bird's Notice respecting the Deposition of Metallic Copper
from its Solutions by slow Voltaic Action at a point equidistant from
the Metallic Surfaces 57
Professor Johnston on a new Compound of Sulphate of Lime with Water 59
Professor Johnston on a new Compound of Bicyanide with Binoxide of
Mercury ••■• 59
Prof. Johnston on some supposed Exceptions to the Law of Isomorphism 59
Professor Johnston on the Origin of Petroleum, and on the Nature of
the Petroleum from Whitehaven 60
Professor Johnston on Middletonite and some other Mineral Substances
of Organic Origin 60
Professor Johnston on the Resin of Gamboge (Gambodic Acid) and its
Compounds 60
Mr. R. Phillips on a Blue Pigment 60
Mr. C. T. Coathupe on the Blue Pigment of Dr. Traill 61
Mr. R. Mallet on a new case of the Chemical Action of Light in the Deco-
loration of Recent Solutions of Caustic Potass of Commerce 61
Mr. Scanlan's Observations on the Constitution of the Commercial Carbo-
nate of Ammonia 63
Mr. Scanlan on the Blackening of Nitrate of Silver by Light 63
Rev. T. ExLEY on the Specific Gravities of Nitrogen, Oxygen, Hydrogen,
and Chlorine ; and also of the Vapours of Carbon, Sulphur, Arsenic,
and Phosphorus 64
Rev. T. ExLEY on Chemical Combinations produced in virtue of the pre-
sence of other bodies which still remain 68
Mr. John Samuel Dawes on an Improvement in the Manufacture of Iron,
by the Application of Gas obtained from the decomposition of Water... 68
Dr. Andrews on the Influence of Voltaic Combination on Chemical Action 69
Mr. Robert Addams on the Construction of Apparatus for solidifying Car-
bonic Acid, and on the elastic Force of Carbonic Acid Gas in contact
with the liquid form of the Acid, at different Temperatures 70
Mr. William Herapath on a New Process for Tanning 71
Mr. William West on some New Salts of Mercury 72
Mr. William Maugham on a New Compound of Carbon and Hydrogen. . 72
Mr. William Maugham on a Mode of obtaining an Increase of Atmo-
spheric Pressure, and on an Attempt to liquefy Hydrogen and Oxygen
Gases, with accompanying Apparatus 73
Mr. John Murray on the Water of the Dead Sea ' 73
CONTENTS. V
Page
Lieut. Morrison's Observations and Experiments made upon an Instru-
ment termed a Magnet-Electrometer 74
Mr. Thos. E. Blackwall on the Production of Crystals of Silver 74
GEOLOGY.
Mr. John Buddle's Observations on the Newcastle Coal-field 74
Mr. D. Milne on the Berwick and North Durham Coal Fields 76
Mr. Nicholas Wood on the Red Sandstone of the Tweed and Carlisle 78
Mr. H. T. M. Witham's Account of Rolled Stones found in the main Coal
Seam of Cockfield Fell Colliery 79
Mr. T. SopwiTH on Sections of the Mountain Limestone Formation in
Alston Moor, exhibiting the general uniformity of the several beds 79
Mr. J. B. Jukes on the Position of the Rocks along the South Boundary of
the Penine Chain ;... 79
Mr. R.I. MuRCHisoN on the Silurian System of Strata 80
Mr. R. Griffith on the Geological Structure of the South of Ireland . ... 81
Capt. PoRTLOCK on a small Tract of Silurian Rocks in the County of Tyrone 84
Account of the Footsteps of the Cheirotherium and five or six smaller Ani-
mals in the Stone Quarries of Storeton Hill, near Liverpool, communi-
cated by the Natural History of Liverpool 85
Mr. Oram on a Plan of cementing together Small Coal and Coal Dust for
Fuel 85
Mr. Long's Description of a Cave at Cheddar, Somersetshire, in which Hu-
man as well as Animal Bones have been lately found 85
Mr. Joshua Trimmer on the Discovery of the Northern or Diluvial Drift
containing Fragments of Marine Shells covering the remains of Terres-
trial Mammalia in Cefn Cave 86
Mr. James Smith on the Shells of the Newer Pleiocene Deposits 87
Mr. C. Lyell on Vertical Lines of Flint, traversing Horizontal Strata of
Chalk, near Norwich 87
Mr. John Leithart on the Stratification of Rocks 88
Mr. John Leithart on Faults, and Anticlinal and Synclinal Axes 89
Mr. Robert Were Fox on the Production of a Horizontal Vein of Carbo-
nate of Zinc by means of Voltaic Agency 90
Sir D. Brewster on the Structure of the Fossil Teeth of the Sauroid Fishes 90
Dr. Daubeny on the Geology and Thermal Springs of North America ... 91
Mr. Austen's Considerations on Geological Evidence and Inferences 93
Mr. T. W. Webb on Lunar Volcanos 93
Mr. Thomas Sopwith on the Construction of Geological Models 94
Rev. G. Young on the Antiquity of Organic Remains 9.5
Dr. G. H. Adams on Peat Bogs 95
GEOGRAPHY.
Professor Von Baer's Recent Intelligence on the Frozen Soil of Siberia... £6
Prof. Baer's Sketch of the recent Russian I'^xpeditions to Novaia Zemlia.. 96
Captain Washington's brief Account of a Mandingo, native of Nyani-
Marii, on the River Gambia, in Western Africa 97
Captain Washington on the recent Expeditions to the Antarctic Seas ... 97
Captain Washington's Summary Account of the various Government
Surveys in Europe, illustrated by specimens of the Maps of England,
France, Austria, Saxony, Tuscany, &c. &c 98
Lieut.-Col. Velasquez de Leon on the recent Government Map of Mexico 98
Major Jervis's Sketch of the Progress and Present State of the Trigono-
metrical Survey in India 98
VI CONTEXTS.
Page
Captain W. Allen on the Construction of a Map of the Western portion
of Central Africa, showing the probability of the River Tchadda being
the outlet of the Lake Tchad '. 99
Mr. J. B. Pentland on the recently-determined Position of the City of
Cuzco in Peru 99
Lieutenant Lynch on the recent Ascent of the River Euphrates 99
ZOOLOGY.
Mr. J. HiNDMARSH on the Wild Cattle of Chillingham Park 100
Lieut.-Colonel Sykes on a rave Animal from South America 104
Rev. L. Jenyns on certain Species of Sovex 104
Professor Owen on Marsupiata 105
Dr. J. Richardson on Pouched Rats 105
Mr. John Hancock's Remarks on the Greenland and Iceland Falcons ... 106
Mr. Arthur Strickland on the Ardea Alba 106
Mr. A. Strickland on a species of Scyllium taken on the Yorkshire Coast 107
Mr. T. Allis on the Toes of the African Ostrich, and the Number of Pha-
langes in the Toes of other Birds 107
Dr. Edward Charlton on Tetrao Rakelhahn 107
Mr. Edward Backhouse, Notice of the Annual Appearance on the Durham
Coast of some of the Lestris tribe 108
Mr. W. Yarrell on a New Species of Smelt from the Isle of Bute lOS
Dr. Richard Parnell on some new and rare British Fishes 109
Dr. P. D. Handyside on the Sternoptixiiiese, a family of Osseous Fishes... 110
Messrs. W. H. Clarke and John Mortimer on a Fish with Four Eyes ... 110
Mr. J. E. Gray on a new British Shell 110
Mr. J. E. Gray on the Formation of Angular Lines on the Shells of cer-
tain Mollusca Ill
Mr. J. E. Gray's Notice of the Wombat Ill
Mr. J. E. Gray on the Boring of Pholades Ill
Mr. E. Forbes on the Distribution of Terrestrial Pulmonifera in Europe... 1 12
Rev. F. W. Hope's Remarks on the Modern Classification of Insects 11.3
Rev. F. W. Hope on the Noxious Insects which have this year (1838) se-
riously injured the Apple Trees and Hops ,, 113
Mr. J. A. Turner on a new Species of Goliathus and some Lucani, from
the Coast of Africa 113
Mr. T. P. Teale on the Gemmiferous Bodies and Vermiform Filaments of
Actinese • 113
Mr. G. B. SowERBY on certain Monstrosities of the Genus Encrinus 115
Professor Ehrenberg's Notice of Microscopical Discoveries 116
BOTANY.
Professor Morren on the Production of Vanilla in Europe 116
Mr. Charles C. Babington on the Botany of the Channel Islands 117
Capt. J. C. Cook on the Genera Pinus and Abies 117
Mr. G. B. SowERBY on Lycopodium Lepidophyllum 119
Rev. W. HiNCKs on Vegetable Monstrosities 120
Mr. Wallace's Account of an Inosculation observed in two Trees 120
MEDICAL SCIENCE.
Dr. BowEiNo's Observations on Plague and Quarantine, made during a
residence in the East 120
Mr. GooDsiR on the Origin and subsequent Development of the Human
Teeth 121
I
CONTENTS. Vii
Page
Dr. Spittal's Experiments and Observations on the Cause of the Sounds of
Respiration 2 22
Dr. A. T. Thomson on the Medicinal and Poisonous Properties of .some of
the Iodides 223
Dr. Adams on the Placenta Souffle 123
Dr. J. Reid's Experimental Investigation into the Functions of the Eighth
Pair of Nerves 1 24
Mr. T. M. Greenhow on the Beneficial Effects of Mercurial Action rapidly
induced, more especially in certain forms of Neuralgic Disease 124
Mr. R. M. Glover on the Functions of the Rete Mucosum and Pigmen-
tum Nigrum, in the Dark Races of Mankind 125
Dr. Inglis's Remarks on the Skull of Eugene Aram 125
Dr. G. O. Rees on the Chemical Analysis of the Liquor Amnii 126
Dr. R.D.Thomson on Mr. Farr's Law of Recovery and Mortality in Cholera 126
Dr. Dalziel on Sleep, and an Apparatus for promoting Artificial Respiration 127
Dr. Yelloly on an Improved Acoustic Instrument 129
Mr. J. Blake on the Action of various Substances on the Animal Economy,
when injected into the Veins 129
Dr. A. B. Granville on an Improved Stethoscope 129
Mr. T. M. Greenhow on Fractures 130
Dr. Crawford on a Case of Anthracosis in a Lead Miner 130
Dr. D. B. Reid on the Amount of Air required for Respiration 131
Dr. Robert D. Thomson on the Modus Operandi of Nitrate of Silver as a
Caustic and Therapeutic Agent 132
Mr. R. Torbock's Observations upon Uterine Haemorrhage, and Practical
Hints on the best mode of arresting it 133
Dr. Bellingham on the occurrence of Crystals in the Human Intestines... 134
Dr. Thomas Barnes on Abscess of the Lungs 134
Professor Owen on the Structure of Teeth, and the resemblance of Ivory
to Bone, as illustrated by microscopical examination of the Teeth of
Man, and of various existing and extinct Animals 135
MECHANICAL SCIENCE.
Count Augustus Breunner on the Use of Wire Ropes in Deep Mines ... 150
Mr. B. Green on the Timber Viaducts now in progress on the Newcastle
and North Shields Railway 150
Mr. Peter Nicholson's Outline of the Principles of the Oblique Arch ... 152
Mr. W_. H. Miller on an Alteration in the Construction of Wollaston's
Goniometer, by which its Portability is increased 153
Mr. C. Babbage's short Account of a Method by which Engravings on
Wood may be rendered more useful for the Illustration and Description
of Machinery j^a
Professor Willis on the Odontograph ' 154
Mr. Thomas Sopwith's Description of an Improved Leveling Stave for
Subterranean as well as Surface Leveling I54
Mr. Thomas Sopwith's Description of Instruments to facilitate the Draw-
ing of Objects in Isometrical Projection I55
Mr. Thomas Sopwith on an Improved Method of constructing large Tables
or Writing-Cabinets, adapted to save much time, and to secure a sy-
stematic arrangement of a great number and variety of Papers 156
Mr. Thomas Sopwith's Suggestions on the practicability and importance
of preserving National Mining Records 156
Mr. Lang on Improvements in Ship Building \ I57
Mr. T. Motley on the Construction of a Railway with Cast-Iron Sleepers]
as a Substitute for Stone Blocks, and with continuous Timber Bearing. . 157
Vlll CONTENTS.
Page
Mr. T. Motley on a Suspension Bridge over the Avon, TivM-ton l/)7
Mr. J. Price on an Improved Method of constructing Railways l.'iS
Mr. Hall's Machine for raising Water by an Hydraulic Belt 158
Mr. Samuda on Cliff's Dry Gas Meter 158
Mr. Joseph Garnett on anew Day and Night Telegraph 159
Mr. Hawthorn on an Improved Method of working the Valves of a Loco-
motive Engine 160-
Mr. W. Fairbairn on the Application of Machinery to the Manufacture of
Steam-Engine Boilers, and other Vessels of Wrought Iron or Copper,
subject to Pressure 160
Mr. J. Price on a Steam-engine Boiler 162
Mr. S. Rowley's New Rotatory Steam-Engine 162
Mr. W. Greener's Remarks on the Construction of Steam-Boilers 162
Mr. Maule on a Substitute for the Forcing Pump in supplying Steam-
Boilers, &c 1 63
Mr. John Scott Russell's Notices on the Resistance of Water 163
Mr. J. T. Hawkins on Methods of Filtering Water 163
Mr. DoBsoN on a Method of making Bricks of any required Colour 163
Mr. Poorness on Coal-Mine Ventilation 163
Mr. Joseph Glynn on the Water- works of Newcastle-on-Tyne 164
STATISTICS.
Mr. Cargill on Educational Statistics of Newcastle 165
Mr. D. H. Wilson on the Church and Chapel-room in All Saints' Parish,
Newcastle 166
Mr. John Stephens's Return of Prisoners coming under the cognizance
of the Police in Newcastle, from the 2nd of October, 1837, to the 2nd
of August, 1838 166
Rev. J. M'Alister's Statistical Notices of the Asylum for the Blind lately
established at Newcastle-upon-Tyne 167
Mr. Hindmarsh on the State of Agriculture and the condition of the Agri-
cultural Labourers of the Northern Division of Northumberland.. 167
Mr. W. H. Charlton's Statistical Report of the Parish of Bellingham in
Northumberland 168
Mr. P. M'DowAL on the Statistics of Ramsbottom 168
Mr. W. L. Wharton's Statistical Tables of the Engines, Ventilation,
Screens, Sales, &c. ; and Pitmen ; and the Strata of Nine principal
Collieries in the County of Durham : the first eight being situated on the
East or "Dip" Side of the great Durham Coal-field 169
Rev. H. L. Jones's Series of Statistical Illustrations of the principal Uni-
versities of Great Britain and Ireland 170
Mr. W. R. Rawson's Description of the " London Fire Engine Establish-
ment," and of the Number, Extent, and Causes of the Fires in the Me-
tropolis and its Vicinity, during the Five Years from 1833 to 1837 170
Mr. Rawson's Abstract of Report of the Railway Commissioners of Ireland 171
Mr. W. Felkin's Abstract of Statistics respecting the Working Classes in
Hyde, Cheshire 172
Mr. T. Wilson's Short Account of the Darton Collieries' Club 173
Mr. G. R. Porter's Statistical View of the recent Progress and present
Amount of Mining Industry in P'rance, drawn from the Official Reports
of the" Direction Generale des Fonts et Chaussees et des Mines" 174
Colonel Sykes on the Statistics of Vitahty in Cadiz 174
Mr. Hare on an Outline for Subjects for Statistical Inquiries 177
Mr. Jeffries Kingsley's Criminal Returns of the Empire 177
NOTICES AND ABSTRACTS
OF
MISCELLANEOUS COMMUNICATIONS
TO THE SECTIONS.
MATHEMATICS AND PHYSICS.
On a General Geometric Method. By Charles Graves, F.T.C.D.
Mr. Graves was led to the views he was about to explain, from ob-
serving the use in the doctrine of Conic Sections of a theorem given
by M. Chasles, in his "Histoire de la Geometric," viz., that ''the en-
harmonic relation of four lines drawn from four fixed points in a conic
section, to any fifth point in the curve, will remain invariable" Mr.
Graves explained the term "enharmonic relation," as employed by
M. Chasles, to mean the ratio of Sin. (a, d). Sin. {h, c) to Sin. (a, b)
Sin. (c, d) ; a, b, c, and d, being right lines diverging from the same point.
He insisted on the importance of M. Chasles's theorem, as a kind of
geometrical characteristic of the conic sections, defining them like an
equation ; and showed how it might be advantageously applied in the
determination of loci, and also in the invention, proof, and generaliza-
tion of theorems relating to the conic sections. In ascertaining whether
the plane curve described by a point, subject to a certain condition, is
a curve of the second degree or not, the general method that suggests
itself is, to find four particular positions of the point, and to draw from
these points right lines to any fifth point in the locus. If the enhar-
monic relation of these four lines be invariable, the curve will be a
conic section, and not otherwise. Among several exemplifications of
this method, Mr. Graves discussed the problem of finding the locus of
the centres of all the conic sections passing through four given points.
The middle points of the sides of the quadrilateral, at whose angles ar^
the given points, being evidently situated on the locus, it was sufficient
to show that the enharmonic relation of lines drawn from them to any
VOL. VII. 1838. B
2 EIGHTH REPORT — 18.38.
other point in it was constant ; and this follows immediately from a
theorem announced by Mr. Graves, viz., that '^Uhe enlmrmonic relation
of four diameters of a central conic section, is the same as that of their
four conjugates." In order to connect this mode of investigation with
the ordinary algebraic method, Mr. Graves formed the equation of a
conic section passing through the four points (x\ o), {—x", o), {o,y'),
(o,— y"), (the axes of the co-ordinates being made to pass through the .
points,) and finding only the co-efficient of xy to remain indeterminate,
he establishes the following equation between this co-efficient B, and (r)
the enharmonic relation of four lines drawn from any point in the locus
to the four given points, r = —^, — . From this Mr. Graves
yy -^x y' -\- B
deduced some elegant consequences, and pointed out the readiness with
which M. Chasles's theorem serves to group together, and to prove
other very general ones ; such, for instance, as that of Pascal, relating
to irregular hexagons, inscribed in conic sections, of which it furnishes
by far the shortest and most elegant proof yet obtained. He concluded
with the expression of a wish, that mathematicians would not disdain
to employ the resources of geometry combined with analytic methods
in the treatment of conic sections, many valuable properties of which
have been lost sight of by those who seem to consider the study use-
ful only as an exercise in the application of algebra to geometry.
A paper was read by Charles Ball, Esq., of Christ's College, Cam-
bridge, "On the meaning of the Arithmetical Symbols for Zero and
Unity, when used in General Symbolical Algebra."
On the Propagation of Light in vacuo. By Professor Sir W. R.
Hamilton, F.R.S.
The object of this communication was to advance the state of our
knowledge respecting the law which regulates the attractions or repul-
sions of the particles of the ether on each other. The general differential
equations of motion of any system of attracting or repelling points
being reducible to the form
£jE = S. «i A x/(r), (1.)
the equations of minute vibration are of the form
^ = S. m, {Mx.fir) + ^x. Sf(r)), (2.)
in which
lf(r)=f'(r)W, (3.)
and
Zr= ^A2.r + ^ A^y + ^ A oz. (4.)
TRANSACTIOXS OF THE SECTIOXS. .j
A mode of satisfying the differential equations (2), and at tlie same
time of representing a large class of the phenomena of light, is to as-
sume,
in which r, v\ C are constants, depending on the extent and direction
of vibration : a, b, c, are the cosines of the inclinations of the direction
of propagation of a plane wave to the positive semi-axes of x, ?/, z ; v
is the velocity of propagation of that wave, and \ is the length of an
undulation ; and tt is the semicircumference of a circle, of which the
radius is unity. With this assumption (5.), and with a natural and
obvious supposition respecting a certain symmetry of arrangement in
the ether, causing the sums of odd powers to vanish, it is permitted to
substitute in (2.) the expressions
d- ox /2 ir 7;\„ „
ITF - -(-X-)"*^"' (6-)
A (J,r = — vers. A d. Sx, /y.)
in which A = — (aAaj+AAy-fcAz); (§,)
and thus arises a system of conditions of the form
r (^^y = ^> ^ S. {/(.) 4- ^V (r) } vers. A
+ n mS ^/' (r) vers. A d
+ CmS. /' (r) vers. A 9 (9.)
the masses m^ of the etherial particles, being supposed each = ,«,
Three conditions of this form (9.) exist for every particle, and deter-
mine, in general, for any given values of a, b, c, X, that is, for any
given direction of propagation, and any given length of wave, the value
ot V, and the ratios of C, v\ C, that is, the velocity of propagation of
the wave, and the direction of vibration of the particle. Accordin^^Iv
with some slight differences of notation, they have been proposed for
this purpose by Cauchy, and adopted by other mathematicians. Sup-
pose now, for simplicity, that the plane wave is vertical, so thatc = o •
and let, at first, the direction of its propagation coincide with the posi-
tive semi-axis of x, so that b also vanishes, and a is = 1. Then for
transversal vibrations, tlie expression for the square of the velocity of
propagation is ^
'' = (2^.)^ - S {/(O + ''^^f (r) } vers. ^^ , ^,0.)
which appears to extend not only to the interplanetary spaces, but also
to all ordinary transparent media, and contains, for them, the theore-
B 2
4 EIGHTH REPORT — 1838.
tical law of dispersion, which was first discovered by Cauchy, namely,
the expression
v' = Ao- A,X-2+ A.jX-*&c. ' (11.)
in which
' 1.2.3.4..... (2e + 2) Y ^ ■> ^ 2r ^ ^ '' J ^ ^
But, in order that this law may agree with the phenomena, it is es--
sential that tlie series (11.) should be convergent, even in its earliest
terms ; and this consideration enables us to exclude the supposition
which has occurred to some mathematicians, that the particles of the
ether attract each other with forces which are inversely as the squares
of the distances between them. For if we suppose rf(r) — r'^, and
therefore/(r) = r-^,f' (r) = — 3 r-^ we shall have
A.= i
(2.y
J — r-^+Sr-s Aa.'2J
^ 1. 2.3 A.... (2 i + 2)
Aa;2' + 2; (13.)
and by extending the summation to particles, distant by several times
the length of an undulation from the particle which they are supposed
to attract, these sums (13.) become extremely large, and the terms of
the series' (11.) diverge very rapidly at first, though they always finish
by convergino-. In fact, if we conceive a sphere, whose radius = « \
= n times the length of an undulation (n being a large multiplier),
and whose centre is at the attracted particle ; and if we consider only
the combined effect of the actions of all the particles within this sphere,
we may, as a good approximation, convert each sum (13.) into a triple
definite' integral, and thus obtain, for the general term of the series
(11.), the expression
(—l)'4!7rmn"-\'^ (2-n-nY* /, , -,
(- ly A.-X— = ^— (,^ ^ ,) ,3 • ,,^,L (2i + 3 ) ' ^''-^
€ being the mean interval between any two adjacent particles of
the ether, so that the number of such particles contained in any
sphere of radius r, is nearly = -^, if r be a large multiple of e.
And hence we find, by taking the sum of all these terms (14.), the ex-
pression .
o X''"* r 1 . cos.2 7r?^ sm. 2 tt yt \ _ . .
^ =-^ |3 + 727^ - 12^^ I • ^'^•>
so that, by taking the limit to which v'^ tends, when n is taken greater
and greater, we get at last as a near approximation
t'^=^. (16.)
3 rrc'
and
^ = a/— ""• (17.)
t> V m
TRANSACTIONS OF THE SECTIONS. 5
But - expresses the time of oscillation of any one vibrating particle ;
this time would therefore be nearly constant, if the particles attracted
each other according to the law of the inverse square of the distance ;
and consequently this law is inadmissible, as being incompatible with
the law of dispersion. It had appeared to Sir William Hamilton im-
portant to reproduce these results, though he remarked that they
agree substantially with those of Cauchy, because the law of the in-
verse square was one which naturally offered itself to the mind, and
had, in fact, been proposed by at least one mathematician of high
talent. There was, laowever, another law which had great claims on
the attention of mathematicians, as having been proposed by Cauchy
to represent the phenomena of the propagation of the light in vacuo,
namely, the law of a repiilsive action, proportional inversely to the
fourth power, or to the square of the square of the distance. M.
Cauchy had, indeed, supposed that this law might hold good only for
small distances, but in examining into its admissibility, it appeared
fair to treat it as extending to all the neighbouring particles which act
on any one. But against this law also. Sir William Hamilton brought
forward objections, which were founded partly on algebraical, and
partly on numerical calculations, and which appeared to him decisive.
The spirit of these objections consisted in showing that the law in
question would give too great a preponderance to the effect of the
immediately adjacent particles, and would thereby produce irregu-
larities which are not observed to exist. In particular, if it be supposed
that
S. r' A ar 2 = S. r '■ A y« = S. r '■ A z%
S.r' Ax*= S. r' At/* = S.7-iAz*,
S.r'Ax'^Ai/' = S.r'Ai/^Az" = S.r' Az^ Ax\
and also, in (5.), that c = o, a =^ b, and that X is much greater than e,
it is found that the two values v'^ and v/^ of the square of the velocity
V, corresponding to vertical and to horizontal but transversal vibra-
tions, are connected by the relation
t;« = — - ,
31;%
being expressed as follows :
r«=^S(^5r Ax*-r \
v« = — S(r -5r Ax*);
In conclusion, he offered reasons for believing that the law of
action of the particles of the ether on each other resembles more the
law which Poisson has in one of his memoirs proposed as likely to
a EIGHTH REPORT — 1838.
express the mutual action of the particles of ordinary and solid bodies,
being perhaps of some such form as the following : —
_C r\'' — ( ^ ^*'
rf(r)=-a.b ^' + a,b, ^'' ' (18.)
h and bf being each greater than unity, and ff, ff,, h, h, being some large
jjositive numbers, while a and a^ are constant and positive multipliers,
and e is, as before, the mean or average interval between two adjacent
particles. With such a law there would be a nearly constant repulsion,
if a be greater than a^, and if ff be less than ff,, as long as — is sensi-
bly less than unity; but the force would rapidly change, as the distance
r approached to p e, and would then become a nearly constant attraction,
until r became nearly = g^e ; it would then diminish rapidly, and soon
become insensible. Sir William Hamilton did not, however, intend to
exclude the hypothesis, that the function r f(r) may contain several
alternations of such repulsive and attractive terms, — much less did he
deny that at great distances it may reduce itself to the law of the in-
verse square.
On the Propagation of Light in Crystals. By Prof. Sir W. R.
Hamilton, F.R.S.
By continuing to modify the analysis of M. Cauchy in the manner
already explained, he had succeeded in deducing, more satisfactorily
than had in his opinion been done before, from dynamical principles,
a large and important class of the phenomena of light in crystals ;
though much still remained to be done before it could be said that a
perfect theory of light was obtained. He had employed, for the pur-
poses of calculation, the supposition that the arrangement of the parti-
cles of the ether in a crystal differs from an exactly cubical arrangement
only by very small displacements, caused by the action of the particles of
the crystalline body ; and had attended only to those indirect or reflex
iiffects of the latter particles which are owing to the disturbances which
they produce in the arrangement of the former particles : but he did
not mean to assert that he had established any strong physical pro-
bability for this being the true modus operandi in crystals, though
he thought the hypothesis had explained so much already that it de-
served to be still further developed.
On some Points connected with the Theory of Light. By Professor
Powell, F.K.S.
At the last meeting, the author dwelt on the importance of extending
.observations on the refractive indices for the standard rays to more
highly dispersive media. In prosecuting these inquiries, he has to re-
TRANSACTIONS OF THE SECTIONS. 7
port that a prism of chromate of lead, owing to the nature of the sub-
stance, will not enable him to determine the indices, as the whole spec-
trum is confused, no lines visible, and the violet end totally absorbed.
In the identification of certain of the standard raj's of Fraunhofer
some discrepancy appeared to exist between different representations.
The author's attention is now directed to this point, among others
connected with a more accurate repetition of his former approximate
determinations of refractive indices, on which he is now engaged.
He wishes also to draw attention to questions connected with the
application of photometry to the theory ; especially to that referring to
the power of the eye to judge of the equalization of lights, and the in-
fluence which the illumination of one space has upon that of another in
juxtaposition. To show how great the uncertainty Ls, the following
very simple experiment may be referred to. On receiving the rays of
a candle on a white screen, and intercepting a portion of them by a
clear plate of glass, the eye can recognise no difference in the illumi-
nation of the covered part. Yet, from both the first and second sur-
faces of the glass, there is a copious reflection.
With regard to the mathematical theory, he alludes to the important
researches of Mr. Tovey, especially those on elliptic polarization. All
the preceding investigations for integrating the differential equations for
waves, including the dispersion, have proceeded on the supposition that
certain terms vanish. This appears essential to the general solution.
Mr. Tovey has, however, shown, that if those terms do not vanish, we
have still a particular solution : and this applies to the case of light
elliptically polarized. This case is absolutely excluded in the former
investigations, which are therefore imperfect. The author has endea-
voured to clear up some points connected with this inquiry. Upon the
evanescence or non-evanescence of these terms simply depends the el-
liptic, circular, or rectilinear character of the vibrations. Corresponding
to these mathematical conditions, are those of the arrangement of the
aetherial molecules in the medium, or part of the medium, where the
polarization is communicated. He has pointed out the connexion be-
tween these views and the investigations of Prof. MaccuUagh, in which
that gentleman connects with certain equations of motion the elliptic
polarization in quartz, by which Mr. Airy had explained the results
and laws of M. Biot.
On an Ocular Parallax in Vision, and on the Law of Visible Direc-
tion. By Sir D. Brewster, K.H., F.R.S.
The honour of suggesting or illustrating the law of visible direction
belongs, said Sir David Brewster, to Dechales, Porterfield, and Reid.
D'Alembert, in his " Doutes sur dift'erentes questions d'Optique*,"
maintains that the action of light upon the retina is conformable to the
* Opuscules Mathcmatiques, torn. i. p. 266, 268.
"8 EIGHTH REPORT 1838.
laws of mechanics ; and he adds, that it is difficult to conceive how the
object could be seen in any other direction than that of a line perpen-
dicular to the curvature of the retina, at the point where it is really ex-
cited. He then proceeds to investigate mathematically how the ap-
parent magnitudes of objects would be affected, on the two suppositions,
that the line of visible direction coincided with the refracted ray, or
with a line perpendicular to the retina, at the point where the refracted
ray fell upon it. On the fii*st supposition, he finds that the apparent
magnitude of small objects would be increased about l-13th or l-16th,
if the anterior surface of the crystalline is supposed to have a radius of
six lines in place of four. On the second supposition, namely, that
of Porterfield and Reid, he finds that the apparent magnitude of objects
would be increased nearly one-third, which, as he remarks, being con-
trary to experience, we cannot suppose that vision is thus performed,
however natni-al the supposition may appear. " According to what
line then," he continues, " do we perceive objects or visible points,
which are not placed in the optic axis ? This is a point which it ap-
pears very difficult to determine exactly and rigorously. However, as
experience proves that objects of small extent, which are within the
range of our eyes, do not appear sensibly greater than they are in
reality, it follows, that the visible point, which sends a ray to the cornea,
is seen sensibly in its place, and, consequently, this visible point is seen
sensibly in the direction of a line joining the point itself and its image
on the retina. But why is this the case ? It is a fact which I will not
undertake to explain*." This abandonment of the inquiry will appear
the more remarkable, when we consider the assumptions from which
D'Alembert has deduced the preceding results. He takes for granted
the dimensions of the eye as given by Petit and Jurin ; and he assumes
Jurin's Index of Refraction for the human crystalline lens, though it is
almost exactly the same as that of an ox, as given by Hawksbee, These,
indeed, were the best data he could procure ; but he should have inquired
if the most probable law of visible direction was compatible with any
other dimensions of the eye, and any other refractive powers of the hu-
mours, which were within the limits of probability; and, above all, he
ought to have examined experimentally the truth of his fundamental
assumption, that visible points are really seen in their true places when
thev are not in the axis of vision. In submitting this assumption to
experiment, I had no difficulty in ascertaining that there exists an ocular
parallax, and that this parallax is the measure of the deviation of the
visible from the real direction of objects. It is nothing in the axis of
the eye, and increases as the visible point is more and more distant from
that axis ; and hence it follows, that during the motion of the eye, when
the head is immoveable, visible objects do not appear absolutely fixed,
and have an apparent magnitude greater than their real magnitude.
We are, consequently, not entitled to reject any law of visible direction,
on the ground of its giving a position to visible points, and a magnitude
* Opuscules Matlicmatiqucs, toni. i. p. 2".
TKANSACTIONS OF THE SECTIONS. 9
to visible objects, different from their true position and magnitude.
Having removed this difficulty, I proceeded to examine the other data
upon which D'Alcmbert reasoned. According to the anatomy of the
eye which he adopted, the centre of curvature of the retina, which he
supposes to be spherical, (as he does the eye-ball,) is equidistant from
the extremity of the axis, or the foramen ovale, and the centre of the
crystalline lens. This, however, is far from being the case. M. Dutour,
M. Maurice, a recent and able writer on vision, and, which is of more
consequence, Dr. Thomas Young, have all made the centre of curva-
ture of the retina, at the bottom of the eye, coincident with the centre
of the spherical surface of the cornea ; and this centre, in place of being
almost half way between the apex of the posterior surface of the lens
and \kiQ, foramen ovale, is actually almost in contact with that apex. The
dissections of Dr. Knox, and of Mr. Clay Wallace, of New York, give
results conformable with those of Dr. Young ; and almost all these
authors regard the human eye as a spheroid. When we add to these
considerations the fact that the refractive power of the crystalline lens
assumed by D'Alembert is nearly triple of what it really is, we have no
scruple in concluding that the results of his calculations are inadmissible.
Assuming, then, the most correct anatomy of the eye, namely, that
according to which the cornea and the bottom of the retina have the
same centre of curvature, it is veiy clear that if there was no crystalline
lens, pencils incident perpendicularly upon the cornea will pass through
this common centre, and fall perpendicularly upon the retina. Hence,
in this case, the line of visible direction will coincide with the line of
real direction, and also with the incident and refracted ray, and will
likewise pass through the centre of curvature of the retina. Now, the
refractions at the surfaces of the crj^stalline are exceedingly small, and
at moderate inclinations to the axis the deviations from the preceding
law are very minute. At an inclination of 30°, a line perpendicular to
the point of impression on the retina passes through the common centre
already referred to, and does not deviate from the line of real visible
direction more than half a degree, a quantity too small to interfere with
the purposes of vision. At greater inclinations to the axis of the eye,
the deviation of course increases ; but as there is no such thing as di-
stinct vision out of the axis, and as the indistinctness increases with the
inclination of the incident ray, it is impossible to ascertain by ordinary
observation that such a deviation exists. Hence, the mechanical prin-
ciple of D'Alembert, and the law of Dr. Reid, are substantially true.
If the retina is spheroidal, the centre of visible direction will shift its
place along the axis of vision, and will correspond to the points where
lines perpendicular to the surface of the spheroid cut its lesser axis.
As the Almighty has not made the eye achromatic, because it was un-
necessary, so he has, in the same wise economy of his power, not given
it the property of seeing visible points in their real directions.
10 EIGHTH REPORT — 1838.
On a New Phenomenon of Colour in certain specimens of Fluor Spar.
By Sir D. Brewster.
Mineralogists have long ago observed, in certain varieties of fluor
spar, a beautiful blue colour, different from that which is seen by trans-
mitted light. Haiiy noticed this property in some of the fluor spars
from Derbyshire. Succeeding mineralogists, however, have confounded
this colour with the ordinary tints of the spar, and, so far as the author
knows, its nature and origin have not been successfully investigated. In
describing a species of dichroism, noticed by Dr. Prout * in the purpu-
rates of ammonia and potash. Sir John Herschel f ascribes the reflected
green light to " some peculiar conformation of the green surfaces, pro-
ducing what may be best termed a superficial colour, or one analogous
to the colour of thin plates, and striated or dotted surfaces." And he
adds — " A remarkable example of such superficial colour, differing
from the transmitted tints, is met with in the green fluor of Alston
Moor, which on its surfaces, whether natural or artificial, exhibits, in
certain lights, a deep blue tint, not to be removed by any polishing."
As the phenomenon which Sir D. Brewster had studied in the Derby-
shire fluors was clearly one of internal structure, he was led to sup-
pose that the superficial colour seen by Sir John Herschel on the
Alston Moor specimens, belonged to another class of phenomena; but
having attempted in vain to communicate the blue colour of the Alston
Moor crystals to wax or isinglass, he is disposed to believe that the
two phenomena are identical. In the fluors from Derbyshire, which
consist of differently coloured strata parallel to the faces of the cube,
the blue colour is most powerfully developed in the purplish brown or
bluish brown strata, in a less degree in the greenish strata, and scarcely,
if at all, in those layers which are colourless by transmitted light. In
the first of these cases, the blue colour may be distinctly seen emanating
from the interior of the crystal, when it is held in the common light of
day. In the sun's light the colour is still more brilliant; but the effect
may be greatly increased by covering the greater part of the crystal
with black wax, or by immersing it in a trough of glass covered ex-
ternally with wax, and containing an oil of nearly the same refractive
power as the spar. If there are fissures within the crj stal, they M'ill
greatly influence the effect of the experiment, by reflecting to the eye
the transmitted light. In order, however, to witness this experiment
in all its beauty, and to have ocular evidence of its nature and charac-
ter, a beam of condensed solar light should be transmitted through the
crystal, as shown in the annexed figure, where l l is the condensing
lens, F its focus, and m n the system of diffierently coloured layers, tra-
versed by the cone of refracted rays. The first layer of spar reflects
in all directions an intensely blue light; the two adjacent layers (sepa-
rated by a thin layer which reflects blue light) reflect a light nearly
white ; the next layer gives a blue of exceeding brilliancy ; and so on
with the other layers, till the cone reaches tiie brown central nucleus,
which also reflects a rich blue tint, though inferior to that of one of
• Phil. Trans. ISIS, p. 424. t Treatise on Light, sec. 1076.
TRANSACTIONS OP THE SECTIONS.
11
the preceding layers. In the green fluor of Alston Moor there are
also different layers, some of which are pirik, and some of different
shades of green ; but the different shades of bine which they give out
under exposure to strong light, are not so strikingly contrasted as in
the Derbyshire specimens. As the blue colour now described is re-
flected from surfaces within the spar, and as it does not occur in all
specimens, nor in every part of the same crystal, it must be produced
by extraneous matter of a different refractive power from the spar, in-
troduced between the molecules of the crystal during its formation.
That the blue colour is not produced by shallow cavities or minute
pores, as in some of the opals, is inferred from the perfect transparency
of the specimens in which it occurs, and from the fact that the same
reflected tints are found in fluids, particularly the juices of plants ex-
tracted by alcohol, and in several artificial glasses, particularly in those
of a, pink and orange colour, the former of which give a blue and the
latter a green colour. Having found that some of the dichroitic colours
in doubly refracting crystals were discharged by heat, it occurred to the
author that the blue tints in fluor spar might suffer a similar change,
and might even be connected with the phosphorescence of the mineral.
He therefore exposed two jiieces, one of the Derbyshire and one of the
Alston Moor fluor, to a considerable heat. Both of them gave out a
blue phosphorescence, similar to that of the reflected tint, and much of
the natural colour of the fragments was discharged by the heat. In
both specimens tlie blue reflected tint was greatly diminished. In an-
other specimen of the Alston Moor fluor, it appeared to be wholly re-
moved ; but in a third, taken from the solid angle of the cube, the
blue tint still appeared, though with an impaired brilliancy. It is pos-
12 EIGHTH REPORT — 1838.
sible, that a very intense heat might discharge the blue tint altogether,
but it is difficult to obtain satisfactory results with a mineral which de-
crepitates by the action of heat, and thus prevents the observer from
comparing the tints under circumstances exactly the same.
An Account of certain New Phenomena of Diffraction.
By Sir D. Brewster.
The phenomena of the inflexion or the diffraction of light observed
by Sir Isaac Newton, Fresnel, and others, were those which are visible
at a greater or less distance behind the diffracting body, and according
to the undulatory theory they are produced by the secondary waves
which fall converging on the points where the fringes appear within and
without the geometrical shadow. These fringes are all calculable by a
formula given by Fresnel, depending on the relation of the two quan-
tities a and b, a being the distance of the place where the fringes are
formed from the diffracting body, and b the distance of the diffracting
body from the point from which the beam of light diverges. In the
phenomena hitherto studied, the quantity a is always positive. The
new phenomena discovered and described by Sir David Brewster are
those in which a is negative ; and they may be represented by a formula
differing from Fresnel's only in the sign of a. These new phenomena
are rendered visible by bringing lenses of different foci in contact with
the diffracting body, and the fringes seen in any case are those belong-
ing to a value of — a equal to the focal distance of the lens. The fringes
are in this case produced by the secondary waves, which proceed
diverging from the main wave, from a point between the diffracting body
and the luminous centre, whose distance from the former is a. When
— a is equal to b, the fringes are formed in parallel rays ; and when the
diffracting body is placed between the lens and the eye, they are formed
in converging rays. Hence, in studying these phenomena, we may use
a telescope with a micrometer, and obtain accurate measures. These
phenomena were illustrated by diagrams.
An Account of an Analogous Series of Neio Phenomena of Diffrac-
tion lohen produced by a Transparent Diffracting Body. By Sir
D. Brewster.
These phenomena, when carefully produced by the various methods
which he explained, exhibited a series of splendidly coloured bands of
light, sometimes perfectly symmetrical and sometimes unsymmetrical,
accordingly as the diffracting body was regular or irregular in its section ;
and the author remarked, that an instrument could thus be constructed
for giving new patterns of ribands of all forms and colours. The theory
of the phenomena he considered quite simple and obvious, but he stated
that a comparison of the results of theory and experiment would be
difficult, from the difficulty of ascertaining the exact form of the dif-
fracting body.
I
TRANSACTIONS OF THE SECTIONS. IS
On the Combined Action of Grooved Metallic and Transparent Sur-
faces upon Light. By Sir D. Brewster.
The phenomena described in this paper, discovered by the author,
were altogether new and of a very remarkable description. The spectra,
produced by the methods which were explained to the meeting, were
covered with bands liiie those produced by the action of nitrous gas
upon the spectrum, and the phenomena varied with the distance of tlie
grooves, with the relation of the dark and luminous intervals, and with
the inclination of the incident ray. Sir David Brewster described
analogous phenomena and others of a remarkable character when the
grooves were made in transparent surfaces ; and he explained to the
Section the manner in which he conceived the phenomena were pro-
duced, on the principles of interference.
On a New Kind of Polarity in Homogeneous Light.
By Sir D. Brewster.
At the last meeting of the Association Sir D. Brewster communi-
cated an account of a new property of light, which did not admit of
any explanation. Since that time he has had occasion to repeat and
vary the experiments; and having found the same property exhibited
in a series of analogous though diiferent phenomena, he has no hesi-
tation in considering this property of light as indicating a new species
oi polarity in the simple elements of light, whether polarized or unpo-
larized. In the original experiment, two pencils of perfectly ho-
mogeneous light, emanating from the same part of a well-formed
spectrum, interfered after one of them had been retarded by trans-
mission through a thin plate of glass. The fringes were exceedingly
black, but no phenomena of colour were visible. He was anxious to
observe what would take place when the retarded pencil passed through
the edges of various plates differing very little in thickness, so that dif-
ferent parts of it suffered different degrees of retardation, for the pre-
ceding experiment entitled him to expect a series of overlapping bands
and lines of different sizes. In making such an experiment, however,
he encountered great difficulties, and he failed in every attempt to com-
bine such a series of thin edges. He had recourse therefore to lami-
nated crystals, and in an accidental cleavage of sulphate of lime he ob-
tained the desired combination of edges. " Upon looking through this
plate at a perfect spectrum, in the manner described in my former com-
munication, I was surprised to observe a splendid series of bands and
lines crossing the whole spectrum, and shifting their place and changing
their character by the slightest inclinations of the plate. But what sur-
prised me most was to perceive that the spectrum exhibited the same
phenomena as if it had been acted upon by absorbing media, so that
we have here dark lines and the effects of local absorptions produced
by the interference of an unretarded pencil with other pencils, proceed-
ing in the same path with different degrees of retardation. The bear-
ing of this unexpected result upon some of the most obscure questions
14 EIGHTH REPORT — 1838.
in ph3'sical optics, I may have another opportunity of explaining. At
present, I beg the attention of the meeting to another part of the ex-
periment. We have seen that the effects of interference are distinctly
developed in a certain position of the retarding plates. This position,
when the effects are most distinct, is that in which the edges of the
plates are turned towards the red end of the spectrum and are parallel
to its fixed lines. If we give the plates a motion of rotation in their
own plane, the bands and lines and the phenomena of absorption be-
come less and less distinct as the angle between the edges of the plates
and the lines of the spectrum increases. When this angle is 90° the
bands disappear altogether, and during the next 90° of rotation they
continue invisible. At 270° of azimuth they begin to reappear, and
attain their maximum distinctness at 360°, when they have returned to
their original position. Here then we have certain phenomena of in-
terference, and also of absorption, distinctly exhibited when the least
refrangible side of the retarded ray is towards the most refrangible
side of the spectrum, or towards the most refrangible side of the unre-
tarded ray ; while the same phenomena disappear altogether when the
most refrangible side of the retarded ray is towards the least refrangible
side of the unretarded ray ; and between these two opposite positions
we have phenomena of an intermediate character. Hence I conclude,
that the different sides of the rays of homogeneous light have different
properties when they are separated by prismatic refraction or by the
diffraction of grooved surfaces or gratings, — that is, these rays have po-
larity. W^hen light is rendered as homogeneous as possible by absorp-
tion, or when it is emitted in the most homogeneous state by certain
coloured flames, it exhibits none of the indications of polarity above
mentioned. The reason of this is, that the more or less refrangible
sides of the rays lie in every direction, but as soon as these sides are
arranged in the same direction by prismatic refraction or by diffraction,
the light displays the same properties as if it had originally formed part
of a spectrum."
On some Preparations of the Eye by Mr. Clay Wallace, of New
York. By Sir D. Brewster.
Sir David Brewster laid before the Section a series of beautiful pre-
parations of the eye made by Mr. Clay Wallace, an able oculist in
New York, calculated to establish some important points in the theory
of vision. Mr. Clay Wallace, he stated, considers that he has discovered
the apparatus by which the eye is adjusted to different distances. This
adjustment is, he conceives, effected in two ways. In eyes which have
spherical lenses it is produced by 2i falciform, or hook-shaped muscle,
attached only to one side of the lens, which by its contraction brings
the crystalline lens nearer the retina. In this case, it is obvious that
the lens will have a slight motion of rotation, and that the diameter,
which was in the axis of vision previous to the contraction of the mus-
cle, will be moved out of that axis after the adjustment, so that at difr
TRAXSACTIOXS OF THE SECTIONS. 15
ferent distances of the lens from the retina different diameters of it will
be placed in the axis of vision. As the diameters of a sphere are all
equal and similar, Mr. Clay Wallace considered that vision would be
equally perfect along the different diameters of the lens, brought by
rotation into the axis of vision. Sir David Brewster, however, remarked
that he had never found among his numerous examinations of the lenses
of fishes any which are perfectly spherical, as they were all either
oblate ov prolate spheroids, so that along the different diameters of the
solid lens the vision would not be similarly performed. But, inde-
pendent of this circumstance, he stated that in every solid lens there
was only one line or axis in which vision could be perfectly distinct,
namely, the axis of the optical figure, or series o^ positive and negative
luminous sectors, which are seen by the analysis of polarized light.
Along every other diameter the optical action of the lens is not sym-
metrical. When the lens is not a sphere, but lenticular, as in the
human eye or in the eyes of most quadrupeds, Mr. Clay Wallace con-
siders that the apparatus for adjustment is the ciliary processes, to
which this office had been previously ascribed, though not on the same
scientific grounds as those discovered by Mr. Wallace. One of the
most important results of Mr. Wallace's dissections is the discovery of
Jibres in the retina. These fibres may be rendered distinctly visible.
They diverge from the base of the optic nerve, and surround the^ra-
men ovale of Soemmerring at the extremity of the eye. Sir John Her-
schel had supposed such fibres to be requisite in the explanation of
the theory of vision, and it is therefore doubly interesting to find that
they have been actually discovered.
On the Structure of the Vitreous Humour of the Eye of a Shark.
By Sir J. W. F. Herschel, Bart.
Sir J. Herschel states, that while crossing the Atlantic on his return
from the Cape, a shark was caught in lat. 2° N. and long, about 20° W.
Having procured the eyes, which were very large, and extracted the
crystalline lenses, the vitreous humour of each, in its capsule, presented
the usual appearance of a very clear, transparent, gelatinous mass, of
little consistency, but yet forming, very distinctly, a connected and
continuous body, easily separable from every other part. Wishing to
examine it more narrowly, it was laid to drain on blotting-paper ; and,
as this grew saturated, more was applied, till it became apparent that
the supply of watery liquid was much too great to be accounted for by
adhering water or aqueous humour. " Becoming curious to know to
what extent the drainage might go, and expecting to find that, by car-
rying it to its limit, a gelatinous principle of much higher consistency
might be insulated, I pierced it in various directions with a pointed in-
strument. At every thrust a flow of liquid, somewhat ropy, but de-
cidedly not gelatinous, emanated ; and, by suspending it on a fork, and
stabbing it in all directions with another, this liquid flowed so abun-
16 EIGHTH REPORT — 1838.
dantly, as to lead me to conclude that the gelatinous appearance of this
liumour, in its natural state, is a mere illusion, and that, in fact, it con-
sisted of a liquid no way gelatinous, inclosed in a sTructurie of trans-
parent and, consequently, invisible cells. The vitreous humour of the
other eye, insulated as far as possible, was therefore placed in a saucer,
and beaten up with a fork, in the manner of an egg beaten up for culi-
nary purposes. By this operation, the whole was resolved into a clear
watery liquid, in which delicate membranous flocks could be perceived,"
and drawn out from the water in thready filaments, on the end of the
fork. From this experiment, it is clear that the vitreous humour (so
called) of this fish is no jelly, but simply a clear liquid, inclosed in some
close cellular structure of transparent membranous bags, which, by
their obstruction to the free movements of the contained liquid, imitate
the gelatinous state."
On Binocular Vision ; and on the Stereoscope, an instrument for illus-
trating its 2)henomena. By Professor Wheatstone.
Professor Wheatstone stated that, at the last meeting of the Royal
Society, he had pi'esented the first of a series of papers on the phe-
nomena of vision, in the investigation of which subject he had been
for some years engaged. On the present occasion he proposed merely
to state so much as would enable him to explain the experiments which
the appaiatus on the table was intended to exhibit. This apparatus he
called a Stereoscope, from its property of presenting to the mind the
perfect resemblances of solid objects. To understand the principles on
which it was constructed, he explained the circumstances which enable
us to distinguish an object in relief from its representation on a plane
surface ; he showed that when a solid object, a cube for instance, was
placed at a short distance before the eyes, its projections on the two
retinae fonn two dissimilar pictures, which in some cases are so different,
that even the eye of an artist would with difficulty recognise them as
representations of the same object ; notwithstanding this dissimilarity
of the two pictures, the object is seen single ; and hence it is evident
that the mind perceives the object in relief, in consequence of the
simultaneous perception of the two monocular pictures. He next
showed, that if the object were thus drawn, first as it appears to the
right eye, and then as it appears to the left eye, and those two pictures
be presented one to each retina, in such manner that they fall on the
parts as the projections from the object itself would, the mind perceives
a form in relief', which is the perfect counterpart of the object from
which the drawings have been taken : the illusion is so perfect, that no
effort of the imagination can induce the observer to suppose it to be a
picture on a plane surface. Professor Wheatstone described various
modes by which the two monocular pictures might be made to fall on
similar parts of the two retinas ; but he gave the preference to a method
which may be understood by the annexed diagram.
TRANSACTIONS OF THE SECTIONS. 17
e e are the two eyes of the observer placed before two
plane mirrors, incluied to each other at an angle of
90°; the axes of the eyes converge to a point c; the
pictures p p are so placed on sliding panels, that
their reflected images may be adjusted to appear at
the place of convergence of the optic axis ; it is ob-
p' vious, then, that the pictures on the retinae will be
precisely the same as if they proceeded from a real object placed at c.
In this manner may solid geometrical forms, crystals, flowers, busts,
architectural models, &c. be represented with perfect fidelity, as if the
objects themselves were before the eyes. The law of visible direction,
which is universally true, for all cases of monocular vision, may. Pro-
fessor Wheatstone stated, be extended to binocular vision, by the
following rule : That every point of an object of three dimensions is
seen at the intersection of the two lines of visible direction, in which
that point is seen by each eye singly.
Observations on Stars and Nebulce at the Cape of Good Hope.
By Sir John F. W. Herschel, Bart. F.R.S., ^c.
The notice of these observations laid before the Section reduced
itself to the following heads :
Reduced Observations of 1232 Nebulae and clusters of Stars, made
in the years 1834, 5, 6, 7, 8, at the Cape of Good Hope, with the
twenty-feet Reflector.
Reduced Observations of 1192 Double Stars of the Southern He-
misphere.
Micrometrical Measures of 407 principal Double Stars of the South-
ern Hemisphere, made at the Cape of Good Hope, with a seven-feet
Achromatic Equatorial Telescope.
A List of the Approximate Places of fifteen Planetary and Annular
Nebulae of the Southern Hemisphere, discovered with the twenty-feet
Reflector.
Drawings illustrative of the Appearance and Structure of three
principal Nebulae in the Southern Hemisphere.
The observations in the first two of these communications form parts
of two catalogues of southern nebulae and double stars respectively,
which comprehend the chief results of the author's astronomical obser-
vations at the Cape. They are complete only as far as the first nine
hours in right ascension. In ths other hours, only a few of the objects
which occur are added, being the results of a partial and very incom-
plete reduction of the observations in those hours. Sir John Herschel
considered it probable, that when the reduction of his observations
shall enable him to complete these catalogues, the total number of ob-
jects contained in them will be nearly doubled. The first catalogue
contains all the nebulae and clusters comprised in the two Magellanic
clouds, which are very . numerous. Each reduced observation ex-
presses the mean right ascension and north polar distance of the
VOL. vn. 1838. c
18 EIGHTH REPORT 1838.
object for the beginning of 1830, together with a description (in ab-
breviated language), more or less detailed, of its appearance and phy-
sical peculiarities — as to size, degree of brightness, condensation, &c.
The observations of double stars in the second catalogue express the
mean place for the epoch above named — the angle of position of the
stars witli the meridian, as micrometrically measured at the time of
observation — the estimated distance, and the magnitude assigned to
each star, together with a column of remarks, in which peculiai'ities of
colour or other phenomena are noted. The micrometrical measures in
the third paper were taken with the same achromatic and micrometer,
and are arranged in precisely the same manner as the former similar
observations made by the author, which have been printed in the Trans-
actions of the Astronomical Society. Among the principal double
stars in this work occur, a Centauri, a Crucis, y Centauri, y Lupi,
fi Lupi, TT Lupi, /3 Hydrse, e Chameleontis, y Piscis Volantis, y Coronas
Australis, &c. Of these, the measures therein stated afford unequi-
vocal evidence of rotation in several of the double stars, among which
may be particularized o Centauri, /3 Hydrse, y Coronas, and tt Lupi.
In the case of a Centauri, the diminution of distance, even within the
comparatively short period of observation, is remarkable ; and the
author stated verbally, that on examining the catalogue of the Astro-
nomical Society, that of Captain Johnson, and the Paramatta Cata-
logue, in all which the places of the two stars are given separately,
he finds this diminution of distance fully borne out, and regularly pro-
gressive ; from which he is led to conclude, that in no great nimiber
of years from the present time (fifteen or twenty), the stars may be
expected to appear in contact, or to be actually occulted one by the
other, as has recently been obsei-ved to happen to y Virginis. The
fourth of these communications is a list of the planetary and annular
nebulae of the Southern Hemisphere, which have been detected by Sir
J. Herschel in his sweeps. They are arranged in order of R.A., and
numbered. Among these, several are somewhat elongated, and ofier
the appearance of being double. One of them (No. 7) is of a fine
blue colour, and being particularly well defined, has exactly the aspect
of a blue planet. No. 4 is a very bright and considerably large elliptic
disc of uniform light, on which, but excentric, is placed a pretty large
star. Several are very small; No. 15, in particular, is not more than
3" or 4" in diameter. Many of them occur in crowded parts of the
Milky Way, with not fewer than 80 or 100 stars in the field of view at
the same time. — The drawings above mentioned were copies of much
more elaborate originals, and were produced merely as specimens se-
lected from a greater collection, illustrative of three of the most singu-
larly constituted nebulae in the Southern Hemisphere, viz. 6 Orionis,
r/ Argus, and 30 Doradus. Sir John Herschel gave several examples
from the voluminous tables of the manner of registering the observa-
tions respecting each star, double star, clusters, and nebulae ; he also
explained how, by the contrivance of a small achromatic collimator
placed inside of his great sweeping telescope, he was able to obtain
nearly the same precision in his observations as was to be had in fixed
TRAXSACTIONS OP THE SECTIONS. 19
observatories : although, from the ropes and wooden frame M^ith which
it was mounted, it was subjected to great hygrometic and pyrometric
changes of form and position. These changes, however, by equally
affecting the cross of the collimator, and the object itself, were readily
detected and corrected.
On Halley's Comet. By Sir John F. W. Herschel, Bart.
F.R.S., ^c.
" One of the most interesting series of observations of a miscella-
neous kind I had to make at the Cape of Good Hope, was that of
Halley's comet. — I saw the comet for the first time after its perihelion
passage on the night of the 25th of January. Mr. Maclear saw it on
the 24th. From this time we both observed it regularly. Its appear-
ance was that of a round, well-defined disk, having near its centre a
very small bright object exactly like a small comet, and surrounded by
a faint nebula. This nebula in two or three more' nights was absorbed
into the disc, and disappeared entirelj% Meanwhile, the disc itself di-
lated M'ith extraordinary rapidity ; and by examining its diameter at
every favourable opportunity, and laying down the measures by a pro-
jected curve, I found the curve to be very nearly a straight line, indi-
cating a uniform rate of increase ; and by tracing back this line to its
intersection with the axis, I was led, at the time, to this very singular
conclusion, viz. that on the 21st of January, at 2h. p.m., the disc must
have been a point — or ought to have had no magnitude at all ! in other
words, at that precise epoch some very remarkable change in the phj'-
sical condition of the comet must have commenced. So far all was
speculation. But in entire harmony with it is the following fact
communicated to me no longer ago than last month by the venerable
Olbers, whom I visited in my passage through Bremen, and who was
so good as to show me a letter he had just received from M. Bogus-
lawski, Professor of Astronomy at Breslau, in which he states that he
had actually procured an observation of that comet on the night of the
21st of January. In that observation it appeared as a star of the sixth
magnitude — a bright concentrated point, which showed no disc, with
a magnifying power of 140 ! And that it actually ivas the comet, and
no star, he satisfied himself, by turning his telescope the next night on
that point where he had seen it. It was gone ! Moreover, he had
taken care to secure, by actual observation, the place of the star he
observed ; that place agreed to exact precision with his computation ;
that star teas the comet, in short. Now, I think this observation every
way remarkable. First, it is remarkable for the fact, that M. Bogus-
lawski was able to observe it at all on the 21st. This could not have
been done, had he not been able to direct his telescope point blank on
the spot, by calculation, since it would have been impossible in any
other way to have known it from a star. And, in fact, it was this
very thing which caused Mr. Maclear and myself to miss procuring
earlier observations. I am sure that I must often have swept, with a
night-glass, over the very spot whore it stood in the mornings before
c 2
20
EIGHTH REPORT — 1838.
sunrise ; and never was astonishment greater than mine at seeing it
riding high in the sky, broadly visible to the naked" eye, when pointed
out to me by a notice from Mr. Maclear, who saw it with no less
amazement on the 24-th. The next remarkable feature is the enor-
mously rapid rate of dilatation of the disc and the absorption into it of
all trace of the surrounding nebula. Another, is the interior cometic
nucleus. All these phenomena, while they contradict every other hy-
pothesis that has ever been advanced, so far as I can see, are quite in
accordance with a theory on the subject which I suggested on the oc-
casion of some obser\'ations of Biela's comet, — a theory which sets out
from the analogy of the precipitation of mists and dews from a state of
transparent vapour on the abstraction of heat. It appears to me that
the nucleus and grosser parts of the comet must have been entirely
evaporated during its perihelion, and reprecipitated during its recess
from the sun, as it came into a colder region ; and that the first mo-
ment of this precipitation was precisely that which I have pointed out
as the limit of the existence of the disc, viz. on the 21st of January, at
2h. P.M., or perhaps an hour or two later."
On the Difference of Longitude between London and Edinburgh. By
Sir Thomas M. Brisbane, F.R.S.
Having observed the surprising accuracy with which the diiFerence
of longitudes of London and Paris had been obtained by Mr. Dent's
chronometers. Sir Thomas Brisbane applied to that gentleman, who,
with great liberality, furnished for the purpose of the experiments
twelve of his valuable chronometers. With these, the differences of
longitude of London, Edinburgh, and Mukerstoun were taken ; and by
a mean of all the obsei-vations taken in going to the latter station and
in returning, they were found to differ only by five one-hundredths of
a second. He exhibited to the Section the following table.
Chrono.
meters.
Difference of Longitudes.
— 0.16 Minimum difference.
-|-0.34 Maximum difference.
Going.
Returning.
Mean of
Going and
Returning.
A
B
C
D
m. s.
2 40.14
... 39.68
... 39.85
... 39.68
m. s.
2 39.10
... 39.66
... 39.52
... 39.96
m. S.
2 39.62
... 39.67
... 39.68
... 39.82
E
F
G
H
... 39.66
... 40.33
... 39.48
... 39.79
... 39.89
... 39.92
... 39.95
... 40.13
... 39.78
... 40.12
... 39.72
... 39.96
I
K
L
M
... 39.99
... 40.03
... 39.76
... 39.52
... 39.59
... 39.68
... 39.73
... 39.75
... 39.79
... 39.86
... 39.74
... 39.64
Means
2 39.83
2 39.74
2 39.78
TRANSACTIONS OF THE SECTIONS. 21
On the ineans adopted for correcting the Local Magnetic Action of the
Compass in Iron Steam-ships By G. B. Airy, F.R.S., Astrono-
mer Royal. {In a letter to Rev. Prof. Whewell.)
In this communication, the author states some of the principal results
of a series of observations and experiments (made at the request of the
Admiralty) for correcting the local magnetic action on the compass in
the steam -ship the Rainbow.
" The compass was placed in four different stations near the deck,
and in four stations about IS feet above the deck ; and for each of these
the ship was turned round, and the disturbance observed in many posi-
tions. The disturbances even at the upper stations were great, but at
all the lower stations they were very great, and at the station next the
stern they were enormous. The whole amount there was 100° (from
— 50° to + 50°) ; and on one occasion, in turning the vessel about
24°, the needle moved 74° in the opposite direction. I should have
perhaps found some difficulty in reducing these to laws if I had not
made some observations of the horizontal intensity at the four lower
stations in different positions of the ship. From these I was able to
infer the separate amounts of disturbance due to the permanent mag-
netism of the ship and to the induced magnetism, and to construct cor»
rectors. These correctors I tried yesterday, completely at the sternmost
station, and imperfectly at two others. The correction at the sternmost
station was (speaking generally) complete ; the extreme of deviation,
which formerly exceeded 100°, did not, with the corrector, exceed 1°,
At the other stations I had not leisure to adjust the apparatus : but I
fully expect to-morrow to produce the same accordance at them. This
result is, I should think, important in a practical sense. Some theo-
retical results which I did not anticipate are also obtained. At the stern
position, the disturbance is produced almost entirely by the permanent
magnetism, the inductive magnetism producing only gV of the whole
effect. Going towards the head, the effect of the permanent magnetism
diminishes, and that of the inductive magnetism increases, till the latter
produces about ^ of the whole effect. The resolved part of the per-
manent magnetism transverse to the ship varies little (increasing
somewhat towards the head): the part longitudinal to the ship decreases
rapidly from the stern to the head (where it is less than the transverse
part)."* « G. B. AiBY,"
A Statement of the Progress made towards developing the Law of
Storms ; and of what seeins further desirable to he done, to ad-
vance our hnotoledge of the subject. By Lieut.- Colonel Reid, Royal
Engineers.
Having been ordered, in the course of military duty, to the West
Indies in 1831, the author arrived at Barbadoes immediately after the
* A memoir containing the full investigatim of this subject has been presented to
the Royal Society, and is expected to appear in the forthcoming volume of the Philo-
sophical Transactions.
22 EIGHTH REPORT 1838.
great hurricane of that year, which, in the sliort space of seven hours,
killed upwards of 1400 persons on that island alone. He Avas for two
years and a half daily employed as an engineer officer, amidst the
ruined buildings, and was thus naturally led to the consideration of the
phenomena of hurricanes, and earnestly sought for every species of
information which could give a clue to explain them.
The first reasonable explanation met with was given in a small
pamphlet, extracted from the American Journal of Science, written by
VV. C. lledfield, of New York.
The gradual progress made in our acquaintance with the subject of
storms is not uninteresting. The north-east storms on the coast of
America had attracted the attention of Franklin. One of these storms
preventing his observing an eclipse of the moon in Philadelphia, he
Avas much surprised to find that the eclipse had been visible at Boston,
which town is noitli-east of Philadelphia : this was a circumstance not
to be lost on such an inquiring mind as Franklin's. By examination
he ascertained that this north-east storm came from the south-west ; but
he died before he had made the next step in this investigation.
Colonel Capper, of the East India Company's Service, after having
studied meteorological subjects for twenty years in the Madras terri-
tory, wrote a work on the winds and monsoons in 1801. He states his
belief that hurricanes will be found to be great whirlwinds, and that
the place of a ship in these whirlwinds may be ascertained ; for, the
nearer to the vortex, the faster will the wind veer ; and subsequent
inquiries prove that Colonel Capper was right in this opinion.
Mr. lledfield, following up the observations of Franklin, probably
without knowing those of Colonel Capper, ascertained that whilst the
north-east storms were blowing on the shore of America, the wind,
with equal violence, was blowing a south-west storm in the Atlantic.
Tracking Franklin's storms from the southward, he found throughout
their course that the wind on opposite sides blew in opposite directions ;
and that, in fact, they were progressive whirlwinds, their manner of re-
volving being always in the same direction. By combining observations
on the barometer with the progressive movement of storms, Mr. Red-
field appears to have given the first satisfactoi-y explanation of its rise
and fall in stormy weather, and Colonel Reid's observations confirm his
views.
The first step taken by the author, in furtherance of this inquiry,
was to project maps on a large scale, in order to lay down Mr. Red-
field's observations, and thus to be better able to form a judgment on
the mode of action of the atmosphere.
These maps, which have now been engraved for publication in a
separate work, were laid before the Association. The M'ind is marked
on them by arrow's. On the right-hand side of the circles the arrows
will be observed to be flying from the souih ; on the left-hand, coming
back from the north.
Tlie field of inquiry which this opens can be but mei'ely indicated
here ; to proceed in a satisfactoiy manner with the inquiry, the study
being a new one, requires that tlic proofs be exhibited step by step.
TRANSACTIONS OF THE SECTIONS. 23
The inferences drawn from the facts appear very important, and the
further pursuit of the investigation well deserving attention.
The manner in which Colonel Reid has followed it up has been by-
procuring the actual log-books of ships, and combining their inform-
ation with what could be obtained on land, so as to compare simulta-
neous observations over extended tracts. On Chart VII. were repre-
sented thirty-five ships in the same storm, the tracks of several cross-
ing the storm's path, and the wind as reported by the ships corroborated
by the reports from the land.
The observations of ships possess this great advantage for meteoro-
logical research, that merchant log-books report the weather every two
hours, and ships of war have hourly observations always kept up.
After tracing a variety of storms in north latitudes, the author was
struck with the apparent regularity with which they appear to pass to
the North Pole ; and was thence led to suppose, from analogy, that
storms in south latitude would be found to revolve in a precisely con-
trary direction to that which they take in the northern hemisphere.
Earnestly seeking for facts to ascertain if this were really the case, he
had obtained much information to confirm the truth of the opinion
before he was at all aware that Mr. Redfield had conjectured the same
thing, without, however, having himself traced any storms in soutli
latitude. Chart VIII. represents the course of a storm productive of
very disastrous consequences, encountered by the East India fleet, under
convoy, in 1 809, and it is strikingly illustrative of this important fact.
If storms obey fixed laws, and we can ascertain Avhat those laws are,
the knowledge of them must be highly useful to navigation ; but to
apply the principles practically, requires that seamen should study and
understand them. The problem so long desired to be solved, viz. on
which side to lay to a ship in a storm, Colonel Reid trusts h now ex-
plained. •
By watching the mode of veering of the wind, the portion of a storm
into which a ship is falling may be ascertained. The object required
is, that the wind, in veering, shall veer afi instead of ahead ; and that
a vessel shall come up instead of having to break off. To accomplish
this the ship must be laid on opposite tacks, on opposite sides of a
storm ; but the limits of this notice render it impossible to attempt an
explanation in detail.
The researches which have been carried into the southern hemi-
sphere afford a very interesting explanation of the observations of
Capt. King, in his sailing directions for the southern extremity of Ame-
rica, namely, that the rise and fall of the barometer in storms corre-
spond with the rise and fall in high nortliern latitudes ; east and west
remaining the same, but north and south changing places.
Five connected storms which occurred in 1837, and followed each
other in close succession, possess an interest altogether new, for they
give us a clue to explain the variable winds. Since these Avhirlwinds
revolve by an invariable law, and always in the same direction, every
new storm changes the wind. Thus the hurricane of the middle of
August 1837, traced on Chart VII., had hardly passed towards the
24 EIGHTH REPORT — 1838.
Azores, with the wind in the southern portion of it blowing violently
at the west, when another storm, coming from the south, and bringing
up the ship Castries witli it, at the rate of seven or ei^ht knots an hour,
reversed the wind to east.
The storms expanding in size, and diminishing in force, as they pro-
ceed towards the poles, and the meridians at the same time approaching
each other, gales become huddled together; and hence, apparently,
the true cause of the very complicated nature of the winds in the lati-
tude of our own country.
Since great storms in high latitudes often extend over a circular
space of 1000 miles, the length and breadth of the British Islands aiford
far too limited a sphere for their study. Nations should unite to study
the laws of atmospheric changes. By exchanging the observations
made at the light-houses of dili'erent countries, reports would be ob-
tained along the coasts of the whole civilized world. If the merchant
log-books, instead of being destroyed, which is often the case at pre-
sent, were preserved in depots, each great commercial port keeping
its own, they would greatly assist in giving information, by simulta-
neous observations on the sea and along the coast. The meteorolo-
gical reports within the interior of different countries should, after the
same manner, be exchanged, and we should then soon be enabled to
trace the tracks of storms over almost the entire surface of the globe.
(The author then alluded to certain electro-magnetic phenomena,
which offer close analogies to the phenomena of revolving storms.)
During his investigation of the law of storms Colonel Reid endea-
voured also to ascertain the laws by which water-spouts revolve. After
many fruitless researches, he obtained at length two satisfactory in-
stances, one of which is from Captain Beechey. It is remarkable, that
in these two instances, which occur in opposite hemispheres, the revo-
lutions are in opposite directions, but both in the contrary direction
to great storms. The double cones in water-spouts, one pointing up-
wards from the sea, the other downwards from the clouds, peculiarly
mark these phenomena, and we ought to observe whether the cloud
alcove, and the sea below, revolve in the same directions with each other.
To ascertain their electrical state would be also highly interesting, and
this perhaps may not be impracticable, for the great hydrographer and
navigator Horsburgh actually put his ship through small phenomena of
this description, in order to examine them.
Colonel Keid notices the apparent accordance of the force of storms
with the law of magnetic intensity, as exhibited by Major Sabine's re-
port to the Association. It is frequently remarked, with astonishment,
that no storms occur at St. Helena ; the degree of magnetic intensity
there is nearly the lowest yet ascertained on the globe. Major Sabine's
isodynamic lines to express less than unity are only marked there, and
they appear, as it were, to mark the true Pacific Ocean of the world.
The lines of greatest intensity, on the contrary, seem to correspond
with the localities of typhoons and hurricanes, for we find the meridian
of the American Magnetic Pole passing not far from tiie Caribbean
Sea, and that of the Siberian pole tlirough the China Sea.
TRANSACTIONS OF THE SECTIONS. 25
The author then notices the performance of Mr. Whewell's and Mr.
Osier's anemometers, and observes, " It is very desirable that these
beautiful instruments should be placed beyond the limits of our own
island, particularly in the West Indies and at the Cape of Good Hope,
where they may measure the force of such a gale as no canvass can
withstand ; tliat which forces a ship to bare poles.
" It is not only to measure the wind's greatest force that it is desi-
rable these anemometers should be multiplied and placed in different
localities, but that we may try, through their means, to learn something
more of the gusts and squalls which always occur during storms."
Note on the Effect of Deflected Currents of Air on the Quantity of
Rain collected by a Rain-gauge. By Professor A. D. Bache, of
Philadelphia.
The experiments referred to grew out of a report made at the request
of the British Association, on the quantity of rain collected at different
heights, whicli was presented at the Cambridge meeting of the Associa-
tion by Professor Phillips and Mr. William Gray, jun. Professor Rogers
was then present, and at his instance the author commenced a series of
observations about the close of the year 1833. Philadelphia, from the
extent of the plain on which it stands, is a good locality for such a pur-
pose. The observations were at first made by gauges placed at three
different heights. One of these stations was the top of a tower for-
merly used for making shot. The height of the tower is 162 feet. A
second was near the ground within the inclosure about the tower, and
the intermediate one was the roof of the university. The author's at-
tention was ultimately fixed upon the fact that the effect of eddy winds
upon the phenomena observed, Avas by no means a secondary one in
amount, and that he could not hope to deduce a law, nor to throw any
light on the nature of the phenomena, until this disturbing action was
got rid of. He has therefore thought that it might be useful to those
who may undertake similar experiments, to submit some of the evi-
dence of the effects which he attributes to deflected currents of air.
The observations on this point were chiefly made at the upper station,
on the top of the tower. The tower is square in its section, and the
alternate sides are nearly parallel and perpendicular to the meridian.
At the roof the horizontal section is about twelve feet on a side, and a
parapet wall, cut like a battlement, surroimds it. At first, one gauge
was placed at the N.W. angle of the tower, rising about six inches
above the parapet wall ; subsequently, a gauge for collecting snow was
placed at the S.W. angle ; and ultimately, four gauges, besides the ori-
ginal one, were placed at the four corners of the toMer, upon the para-
pet wall, above which they rose about ten inches. The rain gauges
consisted of an inverted cone, with a cylindrical rim, about five inches
in diameter, attached to the base, and a small aperture near the vertex ;
this fastened tightly upon a vessel serving as a reservoir. The snow
gauges were frustums of upright cones, the upi^er section being nearly
26
EIGHTH REPORT — 1838.
four inches in diameter. The water was measured in a glass tube, in
which one-thousandth of an inch of rain fallen was measurable. When
the snow gauges became useless, they were used as rain gauges, by at-
taching a funnel to them, or were finally replaced by rain gauges simi-
lar to those described. The quantity of water collected was measured
after each rain, and the direction of the wind during the rain was fre-
quently noted. To illustrate the effects which are attributed to cur-
rents of air deflected by the tower, Professor Bache has taken from the
journal of the latter months of observation the records of the quanti-
ties of rain collected by four similar gauges, placed at the four angles
of the tower, under different circumstances as to the direction of the
wind. These are selected so as to present, as far as possible, a case of
rain with each principal direction of the wind.
Angle of the Tower at which the
Relative Quantities at
Date.
Wind.
Gauge was placed.
different Angles.
N.E.
S.E.
.S.W.
N.W.
N.E.
S.E.
S.W.
N.W.
July 20
N.
Kain in Inches.
1-00
1-37
1-35
1-05
0-552
0-760
0-749
0-583
Aug. 6
N.E.
0-311
0-378
0-607
0-491
1-00
1-21
208
1-58
Julv 15
E. & N. bv E.
0-912
1-398
1-868
1-715
1-00
1-53
2-04
1-88
April 13
N.E., S.E., S.W.
1-316
1-180
1-568
1-670
1-10
1-00
1-31
1-40
Aug. 20
S. & S.S.E.
0-407
0-253
0-241
0-391
1-68
1 04
1-00
102
June 19
W.S.W. cSc S.S.W.
0-389
0-285
0-252
0-198
1-96
1-43
1-20
100
Sept. 1
W.
0-302
0-328
0-202
0-141
2-14
2-32
1-43
1-00
Sept. 5
W.N.W., N.
0-638
0-731
0-429
0679
1-48
1-70
1-00
1-58
On this table the author remarks, — 1. Tliat it illustrates the very
great differences between the quantities of rain collected at the different
angles of the tower. In one extreme case the quantity collected at the
S.E. angle was 2^ times that at ^he N.W. angle. 2. That, in general,
the gauges to leeward received more rain than those to windward.
Thus, with a north wind, the gauges at the S.E. and S.W. angles re-
ceived more rain than those at the N.E. and N.W. angles. With a
N.E. wind the gauge at the S.W. corner of the tower received the most
rain. In the case given in the table, the ratio of the quantities is nearly
2*1 to 1. With an easterly wind the N.E. and S.E. gauges received
less than the N.W. and S.W. With a south-easterly wind the S.E.
gauge received the least, and the N.W. the greatest quantity of rain,
and so on, nearly in the order stated in the general remark. 3. As the
more considerable rains accompany certain winds, it is not to be ex-
pected that averages of any number of observations exposed to such
errors Avill lead to an accurate result of the quantity of rain falling at
a certain height above the surface. In fact, tiie averages from a period
of nine months do not agree nearly so well as those from the selected
specimens in the table. These give ratios of 1, 1*19, r24', and 1*20,
TRANSACTIONS OF THE SECTIONS. 27
for the quantities at the different angles ; while the former-mentioned
averages at the N.E. and S. W. angles are nearly as one to one and a half.
4. The connexion between the direction of the wind and these effects
is easily made out ; but without an anemometer this is not possible for
that of the force. " I have found, however," observes the author,
" in the case of the N.E. wind, which most frequently attends our
greatest rains, considerable differences, even Avith a moderate wind
amounting, for example, as high as a ratio of one and a half to one.
Having seen that I could not hope for accurate results by these ar-
rangements, I next tried the effect of elevating the gauge upon a high
pole, as was done by Professor Phillips and Mr. Gray with the gauge
on the top of York Minster. The differences that appeared in this case
were very trifling indeed : thus, on the 26th of August, when the N.E.
and S.W. gauges upon the parapet wall gave quantities in the ratio of
1 to 1*68, those six feet above the parapet gave 1 to 1*08 ; with a more
moderate wind the quanties were more nearly the same."
The author proposes to resume this inquiry with reference to the ge-
neral question on his return to America. (See Reports of the Asso-
ciation, Vols. II. III. IV. for the researches conducted dui:ing three years
at York.)
On the Variations in the Quantity of Rain lohich falls in different
Parts of the Earth. By William Smith, LL.D.
Effects so very local, as shown by rain-gauges, at short distances
apart in our own island, must arise. Dr. Smith imagines, from local
causes. The general remark, that much less rain falls on the eastern
than on the western side of England, stands confirmed by the tables ;
and as at Edinburgh there fall only 22 inches, and in Dublin 22*2, it
seems likely to hold in other parts. The local variations in the qusm-
tities of rain in England are, however, very great ; and in a short table
of sixteen local averages, from 67 inches at Keswick, down to 22*7
at South Lambeth, the half of them on the western side of England
are by far the highest ; but the comparatively small quantities of rain
at Bristol and Chatsworth not according with this generalization, and one
place on the eastern coast being even higher than these, and higher than
Liverpool, this generalization. Dr. Smith conceived, required to be
modified. More local causes seemed requisite to account for the ob-
served facts ; and Dr. Smith imagined that they are to be found in the
nature of the surrounding country, that is, in the physical differences of
the vicinity of each place, and not altogether in the track of the most
rainy winds.
In confirmation of this opinion, meteorological registers were quoted
to show that, although westerly and southerly winds blow at London
101 days more than the drier easterly or northerly winds, yet London
is the least rainy place in Britain, except Edinburgh, which averages
seven tenths lower than South Lambeth. The cause of much rain de-
pends not, therefore, he conceived, wholly on the prevalence of westerly
28 EIGHTH REPORT — 1838.
winds ; but, in part at least, on the humidity of the neighbouring re-
gions. The westerly winds, before they reach London, pass over a great
extent of high and dry land ; and, consequently, there'is, at the level of
the chalk hills (600 to 800 feet high), a dry atmosphere over London.
Bristol, having 5"2 inches less rain than Liverpool, and nearly seven
inches less than Manchester, is surrounded by high and dry hills of
limestone ; and Chatsworth, having 4 inches less than Bristol, is also,
except on the eastern side, surrounded by very high and dry hills. Dr.
Smith illustrated this part of his argument by reference to other places.
Manchester, having S6*l inches, is not far west of the high and damp
hills of millstone grit, which here form the summit ridge of England ;
but about Lancaster, the width of wet-topped hills increases, so that
vapour from these, the southern swampy shore, and of the tides and
sands of Morecambe bay, may account for 39*7 at Lancaster. Townly,
high, and in the vicinity of bog-topped hills, has 41 "5; Grisdale, West-
morland, 5'-2'3 ; and Kendal 5?>'9 ; the latter, perhaps, partly from the
hills, and partly from Lancaster sands and adjacent marshes ; but Kes-
wick averages 67 inches. This, perhaps, is the greatest quantity of rain
which falls at any one place in England, and is perhaps to be accounted
for by the peculiar situation of Keswick, at the meeting of four valleys,
which intei'sect a group of very high mountains, and near to swampy
ground, and large pieces of water, on whicli the winds have great in-
fluence in raising vapour, which the cold sides of the mountains rapidly
condense. Tliese hill tops, as well as those of millstone gi-it, have a
covering of peat, which holds water like a sponge.
Notice of a Brine Sj)ring emitting Carhonic Acid Gas. By Professor
Forbes, F.R.S. (In a Letter to Prof . Phillips.)
The letter of Prof. Forbes noticed a rem-arkable spring, about a mile
from Kissingen, Bavaria, Avhich had occupied much of his attention, and
of which he will proljably at a future time draw up a more detailed ac-
count *. It is a hrine spring, having 3 per cent, of salt, rising in a bore,
325 Bavarian feet deep, in red sandstone ; but the author understands
that the water flows at about 200 feet in depth. Its temperature is never
less than 65° ; the mean temperature of springs near being only 50° to
52°. It discharges carbonic acid gas in volumes almost unexampled,
keeping the water, in a shaft eight feet diameter, in a state resembling
. turbulent ebullition. The enormous supply of gas has led to its use in
gas baths, for which purpose it is carried off by a tube connected with
a huge inverted funnel, which rests upon the Avater. It contains scarcely
a trace of nitrogen. It is conducted into chambers properly prepared,
and thence into baths, in which it lies by its weight, and is used as water
would be. But the most remarkable feature still remains to be noticed.
About five or six times a day the discharge of gas suddenly stops ; in a
few seconds the surface of the well is calm. The flow of water, amount-
* This account lias been publislied in the Edinburgh Philosophical Journal, 1839.
TRANSACTIONS OP THE SECTIONS.
29
iug to forty cubic feet per minute, also stops, or rather becomes negative,
for the water recedes in the shaft even when the pumps commonly used
to extract the brine do not work, and the water subsides during fifteen
or twenty minutes. It then Hows again, the water appearing first and
suddenly, the gas gradually increasing in quantity, till, after three quar-
ters of an hour, the shaft is full as at first. The state of greatest dis-
charge continues with little variation for three or four hours, but by no
means with absolute regularity. It is also affected by various circum-
stances, apparently extraneous ; this has gone on with little variation
since the bore was made in 1822. Within a short distance is a bore 554
Bavarian feet deep, which exhibits somewhat similar phenomena. Alto-
gether, Prof. Forbes considers that the salt spring at Kissingen is the
most singular phenomenon of its kind in Europe except the Geysers,
On the Climate of North America. By Dr. Daubeny, Professor of
Chemistry and Botany, Oxford.
The principal object of this communication was to invite the atten-
tion of meteorologists to the present state of our knowledge with
respect to the climate of the North American continent. With this
view the professor laid before the Section the following general table
which comprehends all the observations on this subject that he had been
able to collect during his late visit to the United States and Canada.
The best observations made in Canada are those of Mr. M'Cord of
Montreal, who has procured from England excellent instruments, and
has spared no pains in arriving at accurate results.
From his statement, it would seem as if there had been a sensible
deterioration in the climate of that part of Canada since 1830, for the
mean of that year was 47"8
of 1831 46-8
1832 44-7
1833 44-8
1834 45-0
1835 42-9
1836 40-43
1837 41-22
And a tendency in the same direction may perhaps be detected in the
observations recorded at Fort Diamond, above Quebec.
Temp.
For in 1830 41-00 Fahr.
1831 39-00
1832 35-50
1833 36-91
1834 36-87
1835 33-41
1836 35-82
30 EIGHTH REPORT 1838.
It would be interesting to find out, whetlier this reduction of tem-
perature indicated a permanent change in the climate of Canada, or
whether the years noticed constitute the coldest portion of a cycle of
longer duration, and consquently give a result below the actual mean.
Dr. Daubeny remarks, that the position selected for meteorological
observations at Quebec is so elevated and exposed that it does not
fairly represent the mean temperature of the neighbourhood. In the
United States the best observations made are those carried on at the
several academies in the state of New York, under the direction of the
state government. The author has quoted a sufficient number of
these to convey a notion of the climate of that portion of the Union,
and the " Annual Report of the Regents of the University of the State
of New York" for the remainder. The mean temperature of Phila-
delphia cannot yet be regarded as settled, though good observations
have been carried on for the last three years by Captain Mordecai.
These have been quoted in preference to others of longer date
reported by Mr. J. Young, stated by him to have been deduced from
twenty years observations, as the mean obtained by the latter (58*4) is
so much above that of places lying to the south (Washington and
Richmond for instance), that we are driven to suppose that the spot
selected must have been an unsuitable one.
TRANSACTIONS OF THE SECTIONS,
31
Table of the comparative Temperature of various places in the continent of
North America, from N. Lat. 46° to 24°, compiled from various sources.
3.S<;s
46th ^
45th
44th
43rd
42nd-
41st
E.
W.
E.
W.
W.
E,
E.
E.
E.
E.
W.
W.
W.
E.
W.
E.
W.
Locality and
Geographical situation.
Cape Diamond, Que-
bec, Lower Canada
Fort Brady, near the
Falls of St. Mary
Michigan State
Montreal, Lower Ca
nada
Fort Howard, S. extre-
mity of Green Bay,
Michigan
Fort Snelling, near the
junction of the St.
Peter's and Missis-
sippi rivers
Fort Sullivan, East-
port, Maine
Dartmouth Coll. Ha
nover. New Hamp-
shire
Dover, New Hamp
shire
Concord, New Hamp
shire
Portsmouth, New
Hampshire
Rochester, New York
State
Le wiston near Buffalo,
New York State
Albany, New York
State
Cambridge, near Bos
ton. State of Mas
sachusetts
Detroit, State of Mi-
chigan
Newport Harbour,
Rhode Island
Council Bluffs', above
the mouths of Platte
River, Missouri
46-50
46-39
45-30
44-40
44-53
44-44
43-45
43-20
43-20
43- 5
43-08
42-50
42-39
42-25
42-30
41-30
41-25
71-10
84- 5
73-35
87- 2
93-15
67-11
72-22
H
&5
37-66
41-3;
69-12
70-22
70-46
77-10
79-20
73-20
71-
82-50
71-25
95-50
44-20
44-50
45-
8 years, viz.
1829tol836
Not stated
Authority for
the annexed
statement.
506
42-44
40- 6
42* 8
42- 4
45- 8
47-26
48-35
48-56
52-36
47- 4
51-02
50-82
8 years, viz.
1830toI837
Not stated
Not stated
Mr. Watt.
Lovell's Re-
gister, quoted
by Darby
(View of the
Unit. States).
Mr. M'Cord.
Lovell's Re-
gister, quoted
by Darby.
Ditto.
Not stated
2 years, viz.
1835 & 1836
1 year, viz.
1836
1 year, viz.
1836
Not stated
Ditto.
Vermont Chro.
nicle.
A. Tufts.
J. Farmer.
5 years, viz.
1830, 33,
34, 35, 36
6 years, viz.
1831 to 1836
11 years, viz.
1826tol836
2 years
1 year, viz.
1818
Not stated
Not stated
Mellish's de-
scription.
Regents of
the Univer-
sity of New
York.
Ditto.
Ditto.
Humboldt on
Isothermal
lines.
MeUish's de-
scription.
Lovell.
Ditto.
32
EIGHTH REPORT 1838.
S o c =
6
C «
' t^'i
1
|s§f§
locality and
Geographical situation.
3
3
C J=
t3^
Authority for
the annexed
statement.
fk
Ifs
^
1
S2
<
'
E.
New York Harbour...
4°0-42
7°3-2'o
52-82
Not stated
Ditto.
w.
Fort Columbus, near
40-82
80-20
54- 2
1 year, 1820
MeUish.
40th.
Pittsburgh, Pensyl-
vania
E.
Gerniantown, near
Philadelphia
40-03
75-
52-37
10 vears,viz.
1819tol828
R. Haines.
E.
Philadelaphia
Ditto
39-56
75-10
52-52
50-67
Not stated
1836-7-8
Humboldt, fr.
comparing
the observa-
tions of Rush
and Legare.
Captain Mor-
39th-
decai, journal
of the Fi-ank-
lin Institute.
E.
Baltimore
39-17
77-
53-
8 years, viz.
L. Bruntz.
1817tol824
W.
Cincinnati
3907
84-50
500
54-
8 years, \iz.
1806tol813
Drake, View of
Cincinnati.
f
E.
WasMngton Citj'
38-50
77- 2
57-09
8 years, viz.
1821 to 1827
Rev. R. Little.
38th<
W.
St. Louis, State of
Missouri
38-36
90-40
550
55- 2
7 years, viz.
1829 to 1836
Dr. Drake.
■
W.
N. Harmony, Indiana
38-11
86-50
340
56-69
3 years, viz.
1826-7-8
Dr. Tront.
37th
E.
Richmond, Virginia...
37-04
77-50
56-81
14 years, viz.
1824tol837
ChevaUier.
34th
E.
Smithville, mouth of
Cape Fear River,
North Carolina
34-
78-
58-88
Not stated
D. LoveU.
■
E.
Charleston, South Ca-
32-44
80-20
58-80
18 years, \iz.
Drayton, View
roUna
1750tol759
of South Ca-
32nd-
rolina.
>
W.
Ditto
60-18
64-76
Not stated
4 years
Dr. Lovell.
Dunbar.
Natchez, State of Mis-
31-28
91-45
180
sissippi
31st -<
W.
Jessup Cantonment,
near Sabine River,
Louisiana
31-30
94-
150
68-31
Not stated
Dr. LoveU.
r
W.
Baton Rouge, Louis-
30-26
91-40
68-07
Not stated
Ditto.
30th .{
iana
1
W.
Pensacola, W. Florida
30-24
87-40
68-77
Not stated
Ditto.
W.
New Orleans, Louis-
29-57
90- 8
66-
1 vear, viz.
Professor
29th-
iana
'1836
Barton.
E.
St. Augustine, E. coast
29-50
81-50
72-23
Not stated
Dr. Lovell.
I
of Florida
24th
E.
Key, West Florida...
24-33
82-20
76- 6
6 years, viz.
1830 to 1835
WTiitehead,
collector of
customs.
TRANSACTIONS OF THE SECTION'S. 33
On the Helm Wind of Crossfcll. Bij the Rev. J. Watson.
Helm Wind is a local name of uncertain origin, but generally sup-
posed to be derived from the cloud that, like a cap or helmet, is often
seen on the tops of the mountains. It is specially applied to a very violent
wind, blowing frequently from some easterly point of the compass, but
mostly due east, at the west side of the mountains known by the name
of the Crossfell range, and confined both in length and breadth to the
space contained between the Helm and Helm Bar, hereafter described.
Along the top ridge of the mountains, and extending from three or
four to sixteen or eighteen miles each way, north and south, from the
highest point, is often seen a large long roll of clouds ; the western
front clearly defined and quite separated from any other cloud on that
side ; it is at times above the mountain, sometimes rests on its toji, but
most frequently descends a considerable way down its side ; this is called
the Helm. In opposition to this, and at a variable distance towards
the west, is another cloud v.'ith its eastern edge as clearly defined as
the Helm, and at the same height : this is called the Bar ov Burr; the
space between the Helm and the Bar is the limit of the wind. The
distance between the Helm and Bar varies as the Bar advances or
recedes from the Helm; this is sometimes not more than half a mile,
sometimes three or four miles, and occasionally the Bar seems to
coincide with the horizon, or it disperses and there is no Bar, and then
there is a general east \vind extending over all the country westward.
However violent the wind be between the Helm and the Bar, it extends
no farther ; on the west side of the Bar there is either no wind or it
blows in a contrary direction, that is, from the west, or from various
points in sudden and strong gusts, when the Bar advances so far as to
unite with the Helm ; if the Bar disperses, the wind ceases. Neither the
Ilelm nor Bar are separate or detached clouds, but may be rather said
to be the bold, clearly defined fronts of bodies of clouds extending east-
ward behind the Helm, and westward from the Bar. The clouds forming
the Helm and Bar cannot perhaps strictly be said to be parallel ; the
ope^' space between them may rather be called a very flat ellipse,
in which the transverse diameter varies from eight or ten to twenty-five
or thirty miles, and the conjugate from half a mile to four or five miles :
they appear always united at the ends.
This wind is very irregular, but most frequent from the end of Sep-
tember to the month of May; it seldom occurs in the summer months ;
there was one this year, 1838, on the 2nd of July, and there have been
more in the last two years than in the preceding six. Sometimes,
when the atmosphere is quite settled, not a breath of wind stirring,
and hardly a cloud to be seen, a small but well-known cloud appears
on the summit, extends itself to the north and south — the " Helm is
on," and in a few minutes blowing furiously, suflScient to break trees,
overthrow stacks of grain, throw a person from his horse, or overturn
a horse and cart. The Helm at times seems violently agitated, and on
ascending the fell and entering it there is little wind, and this some-
times not in the direction of the M'ind below : one may, in fact, be in
VOL. VII. 1838. D
34 EIGHTH REPORT — 1838.
the Helm for a whole day without being aware of the wind on the west.
The Helm appears sometimes to run or pour off from the highest
part, each way towai'ds the north and south points of the junction of
the Helm and Bar, and there to be piled up in great masses ; occa-
sionally a Helm forms and goes off without a blast. The open space
between the Helm and Bar is clear of clouds, with the exception of small
pieces breaking off now and tlicn from the Helm and driving rapidly
over to the Bar ; through this open space is often seen a higher stratum
of clouds quite at rest.
Most mountainous countries, particularly where the mountains ter-
minate abruptly, seem liable to sudden gusts of wind, such as occur at
the Cape of Good Hope, in Switzerland, and among the lakes in our
own country; but the Helm wind differs from all in respect to the Bar,
and that within the space described it blows continually ; it has been
known to blow for nine days together, the Bar advancing or receding,
or continuing stationary for a day. When heard and felt for the first
time it does not seem so very extraordinary ; but when we find it
blowing and roaring morning, noon, and night, for days together, it
makes a strong impression on the mind, and we are compelled to ac-
knowledge that it is one of the most singular phenomena of meteorology.
Its sound is peculiar, and when once known is easily distinguished from
that of ordinary winds ; it cannot be heard more than three or four
miles beyond its limit, but by persons who have stood within the wind
or near it, it has been compared to the noise made by the sea in a vio-
lent storm, or that of a large cotton mill when all the machinery is
going. It is seldom accompanied by rain within the open space, and
never continues long after it begins to rain heavily; in spring, it is
most frequent after rain. The countrj' subject to it is very health}',
but the wind does great injury to vegetation, as it batters the grain,
grass, and the leaves of trees till they are quite black. Various hypo-
theses have been suggested to account for this phenomenon ; one of
the most plausible assumes that the air is cooled by its gradual ascent
from the east coast, and on reaching the summit of the mountains,
rushes with great force down the Avestern escarpment into a lower and
warmer region. In opposition to this it is stated, that the valley of the
Tyne, a\ here the Helm Avind is not felt, is not much higher than that
of the Eden ; and secondly, the wind does not extend farther west than
where the Bar is vertical, and this is not very often so far as the Eden.
The cause, Mr. Watson thinks, must be sought for in that region of
the atmosphere, extending from 800 to about 5000 feet above the
earth's surface.
On the Temperatures observed in certain Mines in Cheshire. By
Eaton Hodgkinson, Esq.
(The results will be given hereafter in combination with the account
of other experiments.)
TRANSACTIOXS OP THE SECTIONS, 35
Facts relating to the Effects of Temperature on the Regulators of Time-
keepers ; and. description of some recent improvements in Pendulums,
with Observations, and Tabulated Experiments. By Edward John
Dent, F.E.A.S.
The subjects contained in Mr. Dent's pajier may be arranged under
three heads.
1st. The continuation of an inquiry into the compound effect of
, variable temperature upon the regulating machinery of Time-
keepers, the commencement of Avhich had been laid before the
Association some years before.
2nd. A description of improvements in mercurial pendulums, princi-
pally with a view of making them portable.
3rd. Improvements in the suspension of pendulums in general ; and
incidental remarks connected with the subject.
In all estimates of the eifect of variable temperature upon the regu-
lating part of timekeepers, made for the purpose of ascertaining the
necessary amount of compensation, it had generally been assumed
that the effect was confined to an alteration of length in a part of the
regulator. Mr. Dent, having long felt that this view of the subject was
insufficient to account for facts which his daily practice brought be-
fore him, at length commenced a series of experiments with a view to
a more complete and consistent explanation of them; and, in 1833, at
the meeting of the Association in Cambridge, he endeavoured to show
that the effect of variable temperature upon the balance-springs of
chronometers might be resolved into two distinct portions : viz. the
one, long known, which produces the variation of length ; and an-
other, which had hitherto escaped attention, affecting the elasticity of the
spring.
Mr. Dent afterwards extended the inquiry to the pendulums of clocks,
and succeeded in separating and determining the respective amounts of
effect which changes of temperature produce upon the elasticity of the
spring and the length of the rod. The details of this subsequent in-
quiry, with descriptions of the apparatus invented and used for the pur-
pose, were described at length. As an illustration, the following ex-
periment is taken from amongst many others : —
A clock provided with a spring-pendulum, and adjusted to keep cor-
rect time at an ordinary temperature, was found, when the temperature
was maintained at 48° Fahr. higher, to lose twelve seconds in twenty-
four hours.
Mr. Dent attempts to demonstrate by experiment that eight parts
and a half only of this difference belong to the effect of elongation in
the rod, and the remaining one and a half are produced by a decrease
of elasticity in the spring.
From the epoch of the introduction of the mercurial cistern to the
present time, this admirable modification of the pendulum has remained
nearly in the state in which it was left by its inventor.
The mercurial pendulum cannot even now be filled and transported
in a state proper to be immediately attached to a timekeeper ; conse-
d2
36 EIGHTH REPORT — 1838.
quently in the case of the transport of clocks with this description of
penduhim to great distances, either this part of the lyachine {which re-
gulates the tohole) must be placed in inexperienced hands, to be filled
with mercury and to have the column adjusted to the exact length re-
quired for compensation, or a workm.an must accompany the clock and
set it in action. The expense of the latter process constitutes, gene-
rally, a very serious objection.
The pendulum cistern being made of glass, is liable to fracture, and,
on account of the risk which attends the boiling the mercury within
it, to drive off the air, this process is never attempted. It is very pos-
sible to give to a glass vessel, externally, a form matliematically coi'rect,
but the case is very different when similar accuracy is required for the
interior. The glass cistern, therefore, never receives a perfect figure,
and the mercurial column it contains cannot be a regular cylinder. This
condition, combined with the irregularity of expansion which glass is pe-
culiarly liable to from its compound nature, renders measurement and
calculation with regard to the column, so vague and deceptive that they
are ne^'er employed.
In order to meet these serious obstacles to the satisfactory and ex-
tensive use of this valuable instrument Mr. Dent has recommended the
substitution oi cast-ii'on iov glass in the cistern.
Mercury and cast-iron are quite as little disposed to amalgamate as
mercury and glass ; and iron is a material, compared with glass, which
is more simple in its nature, and more obedient to the workman. It is
susceptible of the most perfect forms, which it will maintain with very
little liability to alteration, and is quite proof against numerous acci-
dents that would be fatal to glass. The expansion of ii'on by heat being
also uniform and well known, it is evident that, in tlie cast-iron cistern,
we may have a vessel of a known, regular, and permanent figure, or, if
not strictly permanent, one whose changes and their laws we are acquaint-
ed with. Calculation may, therefore, be used in anticipating results, with-
out any fear of its widely differing from experiment.
Further, — in a cistern of cast-iron, the mercury may be boiled at any
time. The clockmaker may do it himself when he first puts the machine
together, — he may adjust the column, — he may then hermetically seal
it, and despatch the pendulum to the most distant countries with the ad-
justment so perfect that it maybe instantly attached to the wheel-work
by any workman capable of setting the clock upon its supports. If, at
a subsequent period, minute portions of air have, from any cause, again
mingled with the mercury, and rendered the pendulum susceptible of
barometric changes, the air may be again driven off with the greatest
facility, by repeating the process of boiling, without removing the mer-
cury from the cistern.
Mr. Dent has accompanied the introduction of cast-iron in the cistern
with several other alterations which have all the same intention of im-
proving this kind of pendulum. Among others, he has removed en-
tirely the metal stirrup, or frame, Avhich carried the cistern, and has at-
tached the latter to the rod ; — he has prolonged the rod, and plunged
jt into the mercury, nearly to the bottom of the cistern ;— a condition evi-
TRANSACTIONS OF THE SECTIONS. 37
dently favourable to uniformity of temperature in the rod and mercury,
&c. &c.
All strain or warp of the spring, in the final suspension of the pendu-
lum, can be avoided. The pendulum being first suspended freely, is
left until, by the cessation of its action, it arrives at its own line of rest
in every direction, particularly in that which passes through the plane of
the spring. The fixing-piece is then brought to it and the whole per-
manently attached togethei".
The line of the flexure of the spring can be determined and preserved.
Usually, the exact position of this line is, within certain limits, left to
accident, and is, from several causes, continually changing its position ;
consequently, the pendulum is simultaneously varying in length. Er-
rors in rate, often attributed to other causes, are the necessary conse-
quence.
Notice of a cheap and portable Barometrical Instrument proposed for
the use of Travellers in Mountainous Districts. By Sir John
RoBisoN, Sec. R.S.E., ^c.
The instrument is a glass tube about 0*25 of an inch in diameter,
and about 14 inches long, with a small bulb like that of a thermometer
blown on the upper end. The stem of the tube has been graduated by
divisions made experimentally by the instrument-maker in the follow-
ing manner. On a day when the barometer stood at 30 inches, and
the temperature of the air was 62°, it was placed in the receiver of an
air-pump, and when the rai-efaction allowed the barometer of the
pump to fall to 29 inches, the instrument v/as lowered until the open
end of the tube became immersed in a cup of water, over which it had
been suspended by a thread and wire passing through a stuffing-box.
On allowing the atmosphere to enter the receiver, the water was jDressed
up the tube until the density of the air corresponding to 30 inches
was restored, and the height of the fluid was carefully marked. The
instrument was a second time suspended in the air-pump receiver, and
the exhaustion was repeated until the barometer gauge indicated 28
inches, the immersion in the cup having been made as formerly ; the
air rushed in, and the graduation of the tube corresponding to 28
inches was accomplished. By continuing this process, the graduation
of the stem was carried on as far as was thought requisite, (the inter-
mediate divisions having been made in a similar manner,) when the in-
strument became ready for use.
It is obvious, that in this manner a traveller arriving at a station in
the midst of mountains, and having with him a number of such tubes,
would only require to send messengers to their summits with one or
more of these tubes and a tin case containing water, for the purpose of
giving him the means of determining their heights with considerable
accuracy. Each messenger, carrying with him the empty glass tubes,
is to be instructed to insert their open ends in his flask of water when
he shall liave i-eached the summit, and to bring them down again.
38 EIGHTH REPORT — 1838.
Having done so, tlie air in the bulb and tube having become rarilied
to the tension of that on the top of the mountain, is compressed by the
water which the increased pressure of tlie atmosphere as he descends
forces into the tube, so that when he returns to the place where the
barometer is at 30 inches, the height of the fluid will indicate the
height at which the barometer would have stood on the summit of the
elevation. If the barometer be not exactly at that height, a correction
may be applied.
If the temperatm-e and degree of moisture of the air in the tube on
the mountain and at the lower station were alike, no further correction
would be requisite : but just as in the case of the barometer so with
this instrument ; for minute accuracy, a thermometer and hygrometer
should accompany it, and be simultaneously observed, so as to permit
the application of the usual corrections.
In many cases precisely equal temperatures may be obtained at the
upper and lower stations by keeping the tin case supplied with water,
melting snow, or ice.
In a general and i-apid survey of a country, such instruments would
possess value from their portability and cheapness.
Tables intended to faciUtate the computation of HeigJtts by the Barometer.
By the Rev. Temple Chevallier, B.D., Professor of Mathematics
in the University of Durham.
In these tables, the correction for the temperature for the air is
computed, so that the difference of elevation of two stations, in feet,
is at once found by taking the difference of two numbers correspond-
ing with the heights of the column of mercury at the two stations, and
the mean temperatui'es of the air. The table is constructed for differ-
ences of one tenth of an inch in the barometer, the proportionate varia-
tion for hundredths and thousandths of an inch being readily found
by an accompanying table of proportional parts.
A table is given for the correction for the difference of temperature
of the mercury.
Mr. J. S. Russell described a magnetic instrument invented by Mr.
Watt, of Lasswade, which, according to the experience of the inventor,
appeared to take positions corresponding to the direction of the wind.
TRANSACTIONS OK THE SECTIONS.. 33
CHEMISTRY.
Extracts from a Letter addressed hy Dr. Hare, of Philadelphia, to the-
Chemical Section of the British Association for the Advancement of
Science.
" Since July last, when I had the honour of addressing you through
your venerable and distinguished president Dr. Dalton, I have made
some additional observations and attained some farther results, of
which a brief notice may, I trust, be deemed worthy of attention.
" I have, by improvements in my process for fusing platina, suc-
ceeded in reducing twenty-five ounces of that metal to a state so liquid,
that the containing cavity not being sufficiently capacious, about two
ounces overflowed it, leaving a mass of twenty three ounces. I repeat,
that I see no difficulty in extending the power of my apparatus to the
fusion of much larger masses.
" When nitric acid (or sulphuric acid and a nitrate) is employed tO'
generate ether by reaction with alcohol, there must be an excess of
two atoms of oxygen for each atom of the hyponitrous acid which en-
ters into combination. This excess involves not only the consumption
of a large proportion of alcohol, but also gives rise to several acids and
to some volatile and acrid liquids.
" It occurred to me, that for the production of pure hyponitrous
ether, a hyponitrite should be used. The result has fully realized my
expectations.
" By subjecting hyponitrite of potash or soda to alcohol and diluted
sulphuric acid, I have obtained a species of ether which differs from
that usually known as nitrous, or nitric ether, in being sweeter to the
taste, more bland to the smell, and in being more volatile. It boils
below 65° F., and produces by its spontaneous evaporation a tempera-
ture of 15". On contact with the finger or tongue, it hisses as water
does with red-hot iron. After being made to boil, if allowed to stand
for some time at a temperature below its boiling point, ebullition may
be renewed in it apparently at a temperature lower than that at which
it had ceased. Possibly this apparent ebullition arises from the partial
resolution of the liquid into an aeriform etherial fluid, which escapes
both during the distillation of the liquid ether and after it has ceased,
even at a temperature below freezing. This aeriform product has been
found partially condensible by pressure into a yellow liquid, which
when allowed to escape into the mouth or nose, pi'oduced an impression
like that of the liquid ether. I conjecture that it consists of nitric ox-
ide, so directed to a portion of the liquid ether as to prevent the wonted
reaction of this gas with atmospheric oxygen. Hence it does not pro-
duce red fumes on being mingled with air.
" Towards the close of the ordinary process for the evolution of
sweet spirits of nitre, a volatile acrid liquid is ci'eated, which affects
the eyes and nose like mustard or horse-radish. It is probable, however.
40 EIGHTH REPORT — 1838.
tliat this is in part due to the presence of chloride of sodium, as I have
reason to suspect the acrid liquid to be chlorocyanic^ ether.
" Quick, lime, when the new ether, as it first comes over, is distilled
from it, becomes imbued with an essential oil, which it yields to hydric
ether. This oil may be afterwards isolated by the spontaneous evapo-
ration of its solvent. It has a mixed odour, partly agreeable, partly
unpleasant. From the affinity between its odour and that of common
nitrous ether, I suspect that it is one of the impurities which exist in
that compound.
" The new ether is obtained in the highest degree of purity, though
in quantity less, by introducing the materials refrigerated by snow and
salt into a strong, well-ground, stoppered bottle. After some time the
ether will form a supernatant stratum, which may be separated by de-
cantation. Any acid having a stronger affinity for the alkaline base
than the hyponitrous acid, will of course answer to generate this ether.
Acetic acid not only extricates, but appears to combine with it, form-
ing apparently a hyponitro-acetic ether.
" I observed some years ago, that when defiant gas is inflamed with
an inadequate supply of oxygen, carbon is deposited, and the resulting
gas occupies double the space of the mixture before explosion. Of
this I conceive I have discovered the explanation. By a great number
of experiments performed with the aid of my barometer-gauge, eudio-
meter, and other instrunients, I have ascertained, that if, during the
explosion of the gaseous elements of water, any gaseous or volatile in-
flammatory matter be present, instead of condensing there will be a
permanent gas, formed by the union of the nascent water with the in-
flammable matter. Thus, two volumes of oxygen with four of hydro-
gen and one of olefiant gas, give six volumes of permanent gas, which
burns like light carburetted hydrogen. The same (|uantity of the pure
liydrogen and oxygen with half a volume of hydric ether, give on the
average the same residue. One volume of the naw ether, under like
circumstances, produced five volumes of gas.
" An analogous product is obtained when the same aqueous elements
are inflamed in the presence of an essential oik With oil of turpentine,
a gas was obtained weighing per hundred cubic inches I6j\^ grains,
which is nearly half the gravity of light carburetted hydrogen. The
gas obtained from olefiant gas, or from ether, on the average weighed,
for the same bulk, ISf^y grains: this leaves no doubt of its being
chiefly constituted of the water, as the olefiant gas which 1 used
weighed per hundred cubic inches only SO^V gi'ains ; if per se expanded
into six volumes, it could have weighed only one sixth of that weight,
or little over five grains per hundred cubic inches.
" With a volume of the new ether, six volumes of the mixture of
hydrogen and oxygen gave on the average about five residual volumes.
" The gases thus created do not contain carbonic acid, and, when ge-
nerated from olefiant gas, appear to yield the same quantity of carbon
and hydrogen as the gas affords before expansion.
" These facts point out a source of error in experiments for ana-
TRANSACTIONS OF THE SECTIONS. 41
lyzing gaseous mixtures by ignition with oxygen or liydrogen, in wliich
the consequent condensation is appealed to as a basis for an estimate.
It appears that the resulting water maj- form gaseous products with any
volatile matter which may be present. It is in this way, as I conceive,
that olefiant gas, when inflamed as above mentioned with a quantity of
oxygen inadequate to saturate it, is expanded into a residual gas larger
than that of the mixture before ignition.
" I remain, gentlemen, with high esteem, your co-labourer,
" RoBEUT Hare."
Some Observatio7is on the Foreign Substances in Iron. By Thomas
Thomson, M.D. F.R.S., ^-c. Prof, of Chemistry, Glasgow.
The great difference which exists between different specimens of
iron is generally known. The best Swedish iron when compared with
British iron, even of the best quality, in point of strength is as 4 to 3.
A Swedish wire of a diameter of about y'jth of an inch supports a
weight of 450 lbs. without breaking, while the utmost weight that a
wire of British iron of the same diameter can bear is 350 lbs. Iron
from the mine of Dannemora in Sweden makes excellent steel; Avhile
British iron is so ill adapted for the purpose that it is hardly ever con-
verted into steel, and never into good steel. Dr. Thomson thought it
likely that their differences were owing to something in the British
iron which injured its quality and which Mas v.'anting in SM'edish iron.
The results of some analyses made by Dr. Thomson do not entirely
clear up the question ; but they present some important information
on the peculiarities of iron. The following is the statement of the ex-
periments.
" I selected, as best suited to the object which I had in view, the
best Dannemora iron, Avliich is all used for conversion into steel, com-
mon Welsh iron, which is hardly capable of being converted into steel,
and Lowmoor iron from Yorkshire*. Mr. Buthray, a very intelligent
steel-maker and iron- smelter in the neighbourhood of Glasgow, was
kind enough to supply the specimens, so as to ensure their coming
from the places stated.
" The first remarkable difference in these three specimens is their
specific gravity. It was as foUoM's :
Best Dannemora iron .... 7*9125
Lowmoor iron 7*3519
Welsh iron 7*4059
These differences are much greater than I expected to find : perhaps it
will be more intelligible if I state them as follows :
" If the specific gravity of Dannemora iron be reckoned . 1000
the Lowmoor iron will be . 929
the Welsh iron .... 939*7
* Dr. Thomson was informed tLat tliis iron from Lowmoor was smelted with char-
coal.
42 EIGHTH REPORT 1838.
or Lowmoor iron is about 7 per cent, and Welsh iron 6 per cent, lighter
than the best Danneniora iron.
" To analyze Dannemora iron I dissolved 100 grains of it in muriatic
acid, evaporated the solution to dryness in a gentle heat, and redis-
solved the residue in water slightly acidulated witli muriatic acid.
There remained undissolved a gray-coloured matter, which was tho-
roughly washed, and dried at a temperature of 300°. It weighed 0*32.
gr. or very nearly one-third of a grain. Being ignited in a platinum cru-
cible, the weight was reduced to 0"06 gr. of a gray matter, which,
examined before the blow-pipe, proved to be silica very slightly tinged
with iron. The 0'26 gr. lost by ignition was probably carbon ; for a
temperature of 300° was doubtless sufficient to drive off all the water
which might at first have been present.
" The muriatic acid solution Avas mixed with nitric acid and boiled for
several hours in a flask, to peroxidize the iron. When cold, the excess of
acid was neutralized as exactly as possible by carbonate of soda, taking
care that no precipitate fell. It M^as then raised to the boiling point
and thrown upon a filter. The whole peroxide of iron which it con-
tains is retained upon the filter, and must be well washed with hot wa-
ter. At first the water passes through the filter quite coloui'less ; but
when most of the common salt is washed out the oxide of iron begins
to pass also. To prevent this we must wash it with water containing
sal ammoniac dissolved in it : this salt not only prevents the oxide of
iron from passing, but the solution of it speedily replaces the conmion
salt in the oxide, and thus enables us to wash it much more speedily
and completely than we otherwise could do. The oxide being washed,
di'ied, and ignited, weighed 142'23 grains, equivalent to 99*56 grains
of iron.
" The solution thus freed from iron was evaporated to dryness by a
gentle heat: the residue redissolved completely in water, showing the
absence of phosphate or arseniate of iron. The solution being mixed
with carbonate of soda, a white powder fell, weighing after ignition
0'07 grains. It was brownish red, and being fused with carbonate of
soda it exhibited the well-known characters of red oxide of manganese.
It was equivalent to 05 grain of manganese. According to this
analysis, the constituents of Dannemora iron are
Iron 99-56
Carbon 0-26
Manganese .... 0'05
Silicon 0-03
99-90
"Thus almost the only foreign matter in Dannemora iron is carbon,
which cannot be injurious as far as steel-making is concerned ; for the
manganese and silicon together amount only to 8 parts in the ten
thousand, or not so much as the -j-ynu^'^ part, which could not affect
the quality to any great amount.
" In tiu' Lowmoor iron I found no carbon ; the only foreign bodies
TRANSACTIOXS OF THE SECTIONS. 43.
were manganese and silicon ; the f'onnei' to the extent of nearly 2 per
cent., and the latter almost to that of fo'^ioth part : the analj'sis gave
Iron 98-060
Manganese .... 1-868
Silicon 0-090
100.018
" In the Welsh iron the quantity of manganese was small, but, owing
to an accident, I did not separate it from the iron. The silicon was
sensibly the same as in the Lowmoor iron. But in the Welsh iron I
found another substance, phosphorus, to the amount of nearly a half
per cent. ; this substance is entirely wanting in the Dannemora and
Lowmoor irons. The constituents of Welsh iron were
Iron, with some manganese . 99*498
Phosphorus 0-417
Silicon 0085
100-000
The presence of phosphorus is probably the reason why Welsh iron is
too brittle to be converted into steel.
" I hardly think that these analyses enable us to account for the
striking difference in the specific gravity of these three irons. I rather
ascribe this difference to a luechanical cause ; the Dannemora iron has
probably been exposed to longer hammering or rolling than either of
the British specimens. If this be so, it will in some measure explain
its greater strength, for the strength of iron, cceteris paribus, is well
known to increase with the degree of hammering to which it has been
subjected."
On (he Sugar in Urine of Diabetes. By Thomas Thomson, M.D.
F.R.S., Professor of Chemistry, Glasgoiv,
" Though the existence of sugar in the urine of persons labouring
under the disease called diabetes rnellitus, has been known for more
than a century aud a half, having been discovered by Dr. Willis, who
died in the year 1678, and though it has been frequei.tly extracted
from such urine and exhibited in a state of purity, the author was not
aware that experiments requisite to determine its nature had been
made. After noticing the statement of Dr. Prout (Phil. Trans. 1827),
that such sugar contained gr. 36 to 40 per cent, of carbon, and gr. 60
to 64 per cent, water ; Dr. Thomson described the results of some ex-
periments which he had recently undertaken to remove the imcertainty
which appeared to involve the subject."
By evaporation, and subsequent digestion in alcohol, the sugar was
obtained white, and by i-e-solution in boiling alcohol and slow cooling,
acicular crystals were obtained. Specific gravity, when simply dried
in air, 1378; heated to fusion (which takes place at 239°) the specific
gravity becomes 1*423, while that of common sugar is 1-56, and that
44 EIGHTH REPORT 1838.
of sugar of grapes is stated by Prout at 1*5. Diabetic sugar dissolves
without limit in boiling water, and at 62° in its owq bulk of water.
By analysis with oxide of copper, the constitution of this sugar was
found to be
Carbon 37-23 or 12 atoms = 9-00 or per cent. 38-09
Hydrogen.... 7*07 13 .. 1*625 .. 6-88
Oxygen 55-70 13 . . 13 .. 55-03 •
100-00 23-625 100-00
Starch sugar, according to Dr. Prout, is composed of
Carbon 12 atoms 9-
Hydrogen.... 14 .. 1*75
Oxygen 14 . . 14-0
24-75
differing from diabetic sugar by an additional atom of water.
Pure crystallized sugar, according to the analysis of Liebig in 1834,
is composed of
Carbon 12 atoms 9-
Hydrogen .... 1 1 . . 1 "375
Oxygen 11 11-
21-375
By uniting the diabetic sugar with oxide of lead, it was found to
have combined with three atoms of oxide of lead, and to have lost three
atoms of water, constituting a trisaccharate of lead, composed of
Carbon .... 12 atoms = 9-
Hydrogen.. 10 .. = 1-25
Oxygen 10 .. =10-
20-25
Oxide of lead 3 . . = 42-00
In this combination the diabetic sugar is therefore exactly isomeric
with common sugar, in its combination with two atoms of oxide of lead,
as determined by Berzelius.
From the yellowish-brown solution which had yielded the trisaccha-
rate of lead the addition of alcohol caused a Hocky precipitate to fall,
which appeared, on analysis of a saiidl quantity, to be disaccharate of
lead, containing
Sugar 0-56"|
Oxide of lead. . ^0^ Lrnearlytwo atoms of lead to one of sugar;
l-2oJ
and Dr. Thomson supposes from some trials he made that the sugar in
this combination had lost two atoms of Mater, so as to be composed of
TRANSACTIONS OF THE SECTIONS. 45
Carbon, 12 atoms = 9*
Hydrogen, 11 .. = 1'375
Oxygen 11 .. =11-
21-375
but the analysis requires repetition on a larger scale before any definite
conclusion on this particular subject can be drawn.
It appears from the facts stated in this paper that there are three
species of sugar distinguished from each other by the quantity of wa-
ter which they retain when heated to as high a temperature as they
can bear without decomposition ; viz. common sugar, which may be
deprived of one atom of water by combining with oxide of lead ; dia-
betic sugar, which may in like manner be deprived of three atoms of
water ; and starch sugar, which by analogy may be presumed to be
capable of losing four atoms : so that all the species would, under
these conditions, become isomeric with anhydi'ous common sugar.
If tliese views have any solidity, it would appear that sugar, like
pliosphoric acid^ has in all cases the same constitution, and that the
three states of it depend upon the quantity of water and probably of
other bases with which it is disposed to combine.
Common sugar combines with one atom of water, diabetic sugar
with three, and starch sugar with four. There is doubtless a fourth
variety of sugar, not yet discovered, capable of uniting with two atoms
of water.
All the three species are capable of undergoing fermentation and of
being resolved into 4 atoms carbonic acid and two atoms alcohol.
4 atoms carbonic acid .... C^ O^
2 atoms alcohol C* H'^ O*
C12 Hi2 O''^
Starch sugar has an excess of 2 atoms of water and diabetes sugar
of 1 atom ; while common sugar requires an atom of water to undergo
the decomposition.
Dr. Thomson had previously mentioned that 39 65 grains of diabetes
sugar dried in vacuo over sulphuric acid, when exposed for 24 hours
to the heat of a steam-bath, lost 3*35 grains of moisture, and were of
course reduced to 36*3 grains.
But 36-3 : 3-35 : : 23-625 : 2-18.
It follows from this, that diabetes sugar dried over sulphuric acid is
deprived of two atoms of water when exposed to the heat of a steam-
bath or to 212°. The diabetes sugar, therefore, when in crystals, is
composed of
12 atoms carbon ■=. 9*
15 atoms hydrogen = 1-8Y5
15 atoms oxygen = 15-
25-875
4() EIGHTH REPORT — 1838.
So that the atomic weiglit of tlie crystals of this sugar is 2.'j-875, and
it can be deprived of 5 atoms of water by combiniTig it Avilli oxide of
lead.
Dr. Thomson then noticed & crystallized sugar obtamed from diabetic
urine by Mr. Macgregor of Glasgow, by Ambrosiane and Maitland
from the serum of blood in diabetes, and by himself in urine in a case
of diabetes, 1827. This sugar was in 4-sided prisms of 110° and 70*
white, translucent, sweetish, soluble in alcohol. This is believed by
Dr. Thomson to be a fourth kind of sugar, but having been interrupted
in his experiments upon it he recommends the subject to the attention
of chemists.
On Galactin. By Thomas Thomson, M.D., F.R.S., Professor of
Chemistry, Glasgow.
This is a substance which constitutes the principal ingredient in the
sap of the Cow-tree, or Galaclodendron utile of South America, which
is used as a substitute for cream. The sap, on standing, throws up a
white matter, soluble in boiling alcohol, but deposited as that liquid
cools. When well washed and dried, in vacuo, over sulphuric acid, it
constitutes galactin. It is yellow, translucent, brittle, has a resinous
aspect, and is tasteless. It is insoluble in water, but becomes white
and soft by imbibing that liquid. It is soluble in alcohol and ether.
This white compound becomes soft and ductile at 60°; at 117° it is
still solid, but at 137° it is liquid. Abundance of aqueous vapour is
driven off, but the galactin does not become translucent and yellow till
kept some time at 170°. The specific gravity of pure galactin is 0-969.
It dissolves readily in oil of turpentine and olive oil. It does not com-
bine with potash, nor form a soap. Its con.^tituents are —
6 atoms carbon = 4*5, or per cent. 72
6 hydrogen = 0'75 12
1 oxygen = 1 16
6-25 100
being isomeric with Brazil wax, which does not, according to Mr.
Brande, form a soap with potash.
Notice respecting the native Diarseniate of Lead. By Thomas Thom-
son, M.D., F.R.S., Professor of Chemistry, Glasgow.
During the last meeting of the British Association at Liverpool, a
mineral dealer from Cumberland exposed a collection of North of
England minerals for sale. Among others there was one labeled vana-
diate of lead, from Caldbeck fell. On examining it. Dr. Thomson
thought that it differed too much, both in its colour and lustre, from
the true vanadiate of lead, of which he had been in possession for
some years, to be that mineral ; and, upon comparing it with the vana-
diate in his cabinet, this siispicion was confirmed.
TRANSACTIONS OF THE SECTIONS. 47
The Caldbeck fell mineral was in botryoidal concretions, upon
quartz. When examined by the microscope many of the nodules had
the aspect of cylinders.
Colour honey yellow, similar to that of the Cornish arseniate of lead,
first described and analyzed by Mr. Gregor, but lighter, and much less
translucent.
The lustre is resinous, and it has much greater brilliancy than speci-
mens of vanadiate of lead.
The hardness is not easily determined, from the shape of the no-
dules. Calcareous spar v.as not sci'atched by rubbing them against it
while selenite was scratched by them with great facility. The specific
gravity by two diiferent trials was 7*272. This specific gravity is
decisive that the mineral is not vanadiate of lead, for the specific gra-
vity of native crystals of vanadiate is only 6"663. The specific gravity
of Cornish arseniate of lead is still lower, being 6*41.
When exposed to a red heat on platinum foil it undergoes no altei'a-
tion, except becoming a shade lighter in colour. Before the blow-pipe
on platinum it melts into a transparent globvde, which assumes nearly
its original appearance on cooling, and does not crystallize like phos-
phate of lead. On charcoal it gives out abundance of arsenical fumes,
when acted on by the blow-pipe, and a globule of metallic lead is ob-
tained.
It was analyzed twice in Dr. Thomson's laboratory, with every at-
tention to accuracy, by Mr. Stenhouse. During the first analysis he
suspected the presence of a minute quantity of phosphoric acid ; but
he did not succeed in separating it from the arsenic, and of course the
actual existence of this acid in the mineral is still problematical. The
quantity is certainly very minute, and cannot amount to so much as
half per cent., otherwise it would have been separable from the arsenic
acid.
The two analyses were very similar : the following are the consti-
tuents as determined by the second analysis, which Mr. Stenhouse
considers as most to be depended on :
Chlorine .... 2*46
Lead .... 7-10
Arsenic acid . . . 18*20
Protoxide of lead . . 70*14
Peroxide of iron • . 1*20
Volatile matter . . . 1*00
100*1
The moisture and peroxide of iron are obviously accidental impuri-
ties. The chloride of lead in 100 grains of the mineral amounts to
about half an atom, the arsenic acid to 24- atoms, and the oxide of lead
to 5 atoms. If we abstract the chloride of lead, which exists in nearly
the same proportion in phosphate of lead, vanadiate of lead, and arse-
niate of lead, as in this mineral, the constituents are 1 atom arsenic acid,
and 2 atoms protoxide of lead. It is therefore a diarseniate of lead,
constituting a new species of lead ore, which has bepn met with
48 EIGHTH REPORT — 1838.
the first time in Cumberland at Caldbeck fell. The author's spe-
cimen of this mineral exhibits a deposit of yellow.phosphate of lead
upon another side of the mass of quartz, upon which the diarseniate
has been deposited.
On Emulsin. By Dr. T. Thomson and T. Richardson.
Some years ago Robiquet and Boutron CharlaM showed that volatile
oils of bitter almonds and prussic acid, which are obtained by the di-
stillation of bitter almonds, do not exist naturally in almonds but re-
sult from the pi'ocess. They further ascertained that when milk of
bitter almonds, formed by triturating almonds with water in a mortar,
is treated with strong boiling alcohol, white crystals are deposited, on
cooling, which separate in larger quantity by concentration. To this
substance they gave the name of Amygdalin. Liebig and Wiihler have
determined this body to be an amide of amygdalic acid, represented
by the following formula :
Subsequently, the investigation was continued by Wohler and Liebig,
who observed that when a solution of amygdalin is brought in contact
with a milk of sweet almonds, a most remarkable and peculiar action
takes place ; prussic acid and oil of bitter almonds are foi'med, as in
the instance already mentioned. When milk of bitter almonds is distilled
without the artificial addition of amygdalin, besides prussic acid and
oil of bitter almonds, there is also formed sugar, which may be de-
composed by fermentation. The solution after the termination of the
fermenting process affords a strong acid reaction which is not produced
by acetic acid or any other volatile acid. When alcohol is added and
the solution concentrated, thick white flocks are precipitated which
obviously contain no emulsin, because when dissolved in water they
have no action upon amygdalin. From these properties the flocks
would appear to be gum.
The phenomena exhibited in the reaction described, which have
been termed Catalytic by Berzelius, resemble in a great measure those
which take place in fermentation ; and their investigation promises to
throw great light upon some of the most important processes of the
vegetable and animal ceconomy. With the view of assisting in the
elucidation of the subject, the authors have commenced with the ex-
amination of the essential ingredient of the milk of sweet almonds which
has been termed emidsin.
The process by which this substance was obtained was as follows.
Sweet almonds were triturated in a mortar and small portions of water
were gradually added until a milky fluid was obtained. This fluid wa5
mixed with four times its volume of ether and frequently agitated so
as to eff"ect an intimate mixture. A clear fluid gradually separated at
the bottom of the stoppered bottle in which the experiment was made,
which in the course of three weeks was drawn off by means of a syphon.
This fluid was passed through a filter, and to one-half of the clear so-
TRANSACTIONS OP THE SECTIONS. 49
lution a large quantity of alcohol was added ; a copious precipitation
of white flocks ensued ; these were emulsin. From the other half the
emulsin was separated by bringing the solution to tlie boiling point,
when it precipitated in flocky coagula. The emulsin precipitated by
alcohol was carefully washed with alcohol, and then diied over sulphu-
ric acid in the vacuum of an air-pump, to avoid the effects of heat. In
this state it possessed the following characters : it is a white powder,
destitute of taste and smell, soluble in water, insoluble in alcohol and
ether. When submitted to analysis in the usual way, the following
results were obtained :
I. -Si'SSgrns. gave •6180grns. CO2 and -S^i^grns. H-2 O.
II. •3625grns. gave -6365 grns. CO2 and -2505 grns. I-I2 O.
The relation of the carbon and azote, as determined by experiment,
was 6 00.2 : 1 N or 3C : IN. From these data, which the authors
would desire to state only with diffidence till better confirmed, the
following composition may be deduced :
I. II.
48-555
18-74.2
7-677
25-026
c.
49-025
N.
18-910
H.
7-788
0.
24-277
100-000 100-000
The fact of tlie existence of the substance operated on in the almonds
appears to be established by its acting on amygdalin in the same man-
ner as the milk of almonds in the case alluded to in the commencement
of the paper. After numerous trials with various re-agents, its most
distinguished character was elicited by the phenomena exhibited when
boiled with barytes. During the whole of the boiling, which was con-
tinued for above six hours, ammonia was slowly and continuously dis-
engaged. Through the solution a current of carbonic acid was passed
and the whole filtered ; the clear solution was evaporated to dryness,
and the residual salt, which contained a large quantity of barytes, pos-
sessed a strongly bitter taste, leading to the conclusion that emulsin
is an amide, and that the salt formed by the action of barytes is a com-
pound of barytes with an acid which it is proposed to term emulsic
acid. From this fact the authors are inclined to infer that fibrin, ge-
latin, casein, &c., are all amides.
Examination of Spkene, By Thomas Richardsok.
The author having been supjilied with two specimens of sphene by
Mr. Hutton, of Newcastle, submitted them to analysis. One of these,
from Arendahl, in Norway, possessed a specific gravity of 3-425 : — co-
lour, light brownish yellow; — translucent; — brittle ; — fracture uneven;
— lustre vitreous, inclining to resinous. The mineral was fused with
carbonate of soda, and the fused mass digested in the cold with dilute
VQL. VII. 1838. E
50 EIGHTH REPORT — 1838.
muriatic acid. Caustic ammonia was added, and the precipitate
separated by filtration. Tlie precipitate was washed M'ith cold di-
stilled water, and in this state was exposed to the air for about six weeks
without the application of heat, when it appeai'ed quite dry. The
solution and washings from the precipitate were carefully evaporated
to dryness, but on digesting the same with water everything redissolved,
showing that all the silica had been precipitated by the ammonia.
The solution, after being gently heated, was mixed with oxalate of am-
monia, and the precipitated salt of lime thrown on a filter. The dry
precipitate obtained by ammonia was digested in the cold with con-
centrated muriatic acid, and the insoluble portion, after the ordinary
washing and ignition, Aveighed. The titanic acid was precipitated from
the filtered solution after being gently warmed by caustic ammonia, of
which reagent an excess was carefully avoided. The specific gravity
of the second specimen was 3'5128 ; hardness, G'75; — lustre, resinous;
— colour, cinnamon brown ; — cross fracture, granular and uneven; —
opaque, but translucent in thin plates. Before the blowpipe alone on
charcoal, it became white, but did not fuse. With carbonate of soda
in the oxidizing flame it fused into an orange bead. Its locality is not
known. The following is the composition of the two specimens : —
Silica 31-05 29-35
Titanic Acid 43-90 4-2-60
Lime 24-80 24-90
Water I'OO 1-15
100-75 98-00
and the formula,
3 (Ca O, 2 Ti Oj + 2 (Ca O, 2 Si O3).
On a Neto Process for the Extraction of Silver from Lead.
Sy H. L. Pattinson,
The object of this communication was to lay before the Association
an account of a discovery made by the author some time ago, the ap-
plication of which to practice constitutes a new process in the arts, and
forms an important improvement in the extraction of silver from lead.
Adopting the estimate of Mr. J. Taylor, in 1 828*, that the quantity
of lead raised annually in England and Wales amounts to 45,5C0 tons,
the author states that it all contains silver, in variable proportions, but
with so much of constancy in the proportion of silver in the lead ore of
each vein, that it is easy to arrive at a tolerably accurate knowledge of
the quantity of silver contained in the lead of each district.
Of 22,000 tons of lead yielded in the district of Alston Moor, it is
believed that 16,000 tons contain silver at the rate of from 6 to 12 oz.
per ton, and 6000 from 3| to 6 oz. per ton — the average being about 5.
* See Records of Mining for tliat year ; also Reports of the British Association,
vol. v., for an estimate, by Mr. J. Taylor, of the quantity of lead raised in Great Bri-
tain iu 1835.
TRANSACTIONS OP THE SECTIONS. 51
4700 tons from Swaledale, and Wharfdale, Pateley Bridge, &c. yield
on an average only 2 oz. per ton. The lead of Derbyshire and Shrop-
shire, 4800 tons, from 1 oz. to li oz. only. The lead of Cornwall and
Devon, 2000 tons, is rich in silver, so as to yield on an average 20 to
30 oz. per ton ; half of that from Flintshire and Denbighshire, contains
from 4i to 6A oz., and the other half 9 or 10 oz.
The ordinary process of cupellation or refining*, consists in the
oxidation of the lead, kept at a red heat, and traversed by a current of
air ; the silver remains nearly pure ; the oxide of lead is either re-
duced, or sold as litharge. The cost of this process and the waste of
lead are so considerable, that with lead at the price of 20/. the ton
from 6 to 8 oz. of silver are required to barely cover the whole charge
against the operation. About 18,000 tons of the whole quantity raised
in England and Wales are supposed to undergo the refining process ;
and the waste of lead upon the ^vhole quantity would amount to 1 000
tons. Where the lead before refining was impure, with admixture of
other metals, its quality is improved by the process, sometimes to the
value of 10s. a ton ; but this is only the case in small quantities.
The desirableness of some more economical mode of extracting silver
from lead has been long obvious to those conversant with that branch
of our national industry ; and Mr. Pattinson had for some years been
engaged in occasional experiments on the subject. Among these, he
describes the attempts which he vainly made to separate the lead from
the silver by distillation and long-continued fusion.
Various other experiments were tried by the author, both in the dry
way and by the application of liquid menstrua, all of which were un-
successful ; but during their prosecution in the month of January 1 829,
he required lead in a state of powder, and to obtain it, adopted the
mode of stirring a portion of melted lead in a crucible, until it cooled
below its point of fusion, by which the metal is obtained in a state of
minute subdivision. In doing this he was struck with the circumstance,
that as the lead cooled down to nearly its fusing point, little particles
of solid lead made their appearance, like small crystals, among the li-
quid lead, gradually increasing in quantity as the temperature fell.
After observing this phenomenon once or twice, he began to conceive
that possibly some difference might be found in the proportions of sil-
ver held by the part that crystallized, and the part that remained liquid.
Accordingly, he divided a small quantity of lead into two portions,
by melting it in a crucible, and allowing it to cool very slowly with con-
stant stirring until a considerable quantity crystallized, as already men-
tioned; from which the remainder, while still fluid, was poured off: an
equal weight of each was then submitted to cupellation, when the button
of silver from the liquid lead was found to be very riiuch larger than
that from the crystallized lead ; proving that argentiferous fluid lead
suffers a portion of silver to escape from it, under certain circumstances,
in the act of becoming solid.
* See Mr. Sadler's Essay in Nicholson's Journal, vol. xv,, and Mr. Pattinson's paper
in Newcastle Transactions, vol. xi. pt. I,
e2
52 EIGltTIl REPORT — 1838.
The lead used in the original experiment was what is considered rich
in silver; it contained 10 oz. 15 dwts. 8 grs. per ton, and was divided
into a crystallized portion, found to contain 25 oz. 4 dwts. 21 grs., and a
fluid portion, holding 79 oz. 1 1 dwts. 12 grs. per ton ; the latter being ne-
cessarily much smaller than the former in quantity. The experiment
was repeated a great number of times upon lead of every variety as to
proportion of silver, with the same general result ; but being always pef-
formed in a crucible upon small quantities of lead, which of necessity
cooled quickly, the crystallized portion was never entirely deprived of
its silver, nor indeed reduced below two or three ounces per ton.
It was not until the spring of the year 1833 that the author was con-
veniently circumstanced to proceed in applying to practice the principle
he had developed; but at that time his attention was again directed to
the subject, and he began by providing large pots of cast iron, in each
of which he could melt together and crystallize several tons of lead. All
the phenomena of crystallization in the large way were speedily observed,
Avhich, with the mode of conducting the operation adopted then and since
continued without alteration, may be thus briefly described. Four or
five tons of lead being melted in one of the pots, the metal was carefully
freed, by skimming, from all dirt or oxide, and its surface made quite
clean ; it was then suffered to cool very slowly, care being taken to
break off and mix with the fluid mass, from time to time, any portion
that might congeal on the sides of the pot : when the temperature had
fallen suflficiently, small solid particles or crystals began to form, princi-
pally upon the surface of the melted mass. These, if suffered to remain,
would have cohered together and formed a solid crust ; but being con-
tinually struck, and the whole body of metal kept in motion by constant
stirring, they sunk doM'ii to the bottom of the pan, and soon appeared
in considerable quantity. By means of a perforated iron ladle, the cry-
stals were taken out of the pan from time to time as they formed, and
placed in another pot, the liquid lead being drained out of them as much
as possible, and suffered to flow back into the original pot. In this way
the operation was conducted until two-thirds or three-fourths of the ori-
ginal lead was crystallized and withdrawn from the pot. The author
now found, as before, that the crystals always contained much less silver
than the lead from which they were formed ; but still he did not succeed
by one or even by two crystallizations, when operating with lead con-
taining eight ounces of silver per ton, in making them sufficiently poor:
for instance, a pot filled M'ith 8 ounce lead would yield at first crystals
holding from 1 to 2 ounces of silver ; in a little time, as the lead in
tlie pot became richer by receiving silver from the previously formed
crystals, it yielded crystals of 2 to 3 ounces ; and the crystals became
jH'ogressively richer, until, in the end, the original lead was divided into
three parts of crystalized lead holding about 4 ounces, and one part li-
quid lead holding about 20 ounces per ton. Upon the lead of 4 ounces,
as well as upon tTie lead of 20 ouuces, the operation miglit evidently be
repeated without limit, until the crystals became nearly free from silver
on the one hand, and tiie liquid lead exceedingly rich on the other ; but
this seemed to involve so much labour and delay, that the author wa^
TRANSACTIONS OF THE SECTIONS. 53
most desirous of finding a mode by wliicli the object could be accom-
plished at once. Conceiving tliat tlie crystals would be rendered poorer
if more thoroughly drained from the liquid lead, he adopted the plan of
exposing them, after removal from tlie pot to a cautiously regulated
heat in the chamber of a reverberatory furnace, so as to melt out from
among them a further portion of liquid lead ; and in this way he suc-
ceeded in obtaining at one operation from original lead holding 12
ounces of silver per ton, four parts of poor lead containing not more than
^ of an ounce per ton, and one part of rich lead containing 50 ounces
per ton, or thereabouts. This was effected at a moderate expense, and
with a very inconsiderable loss of lead ; and the new process thus ar-
rived at, which he called the process of separation, was immediately
adopted and carried on in this way for some time at different lead- works
in the kingdom.
The exposure of the crystals a second time to heat, required, how-
ever, a peculiar and rather expensive apparatus, and Avas found somewhat
difficult to get managed properly, for the workmen could not always keep
the furnace in which it was performed at the exact temperature neces-
sary for the operation ; and it often happened that, by the application
of too much heat, the crystals were melted entirely without being drained
of their richer lead ; besides, the lead exposed to heat in its crystallized
state was oxidized rapidly, and the subsequent reduction of the oxide
occasioned some loss of metal. These objections to the draining pro-
cess induced the author to recommend in preference the simple plan of
repeated crystallization, which has been everywhere adopted, and now
constitutes the process of separation ; experience and practice have gra-
dually rendered it easy and perfect, and it has become an established
operation among the arts of this country.
The apparatus required for the separating process is exceedingly sim-
ple, and consists merely of a number of nearly hemispherical iron pots,
each capable of holding about five tons of lead, the size for which is about
4" ft. diameter and 2 ft. 3 in. deep ; one or two smaller pots, 18 in. diameter
by 2 ft. deep, are required for the purpose of holding melted lead, in
which the perforated iron ladles ai'e to be occasionally dipped to keep
them hot; and another pot, about 2 ft. 10 in. diameter by 1 ft. 10 in.
deep, for melting the ultimate poor lead to be cast into pieces. These,
with a few perforated iron ladles 15 in. diameter, and 5 in. deep, and
one or two whole ladles of lesser size for casting the melted lead
into pigs, are the principal articles required. The large pots are to be
placed side by side in a line, each with a separate fire-place, (upon
which there must be an ash-pit door as well as a fire door,) and also with
a separate flue and damper, so that the draught imder each pot can be
entirely stopped by closing the flue with its damper, and the heat of the
fire-place in some measure retained by shutting the ash-pit door. Above
the centre of this line of pots, at the height of six or eight feet, it is con-
venient to have a small iron railway, with a frame or carriage on four
wheels to move backwards and forwards the whole length of the range
of pots, from which is to depend a chain, terminated by a hook at the
bottom, and reaching to nearly the top of the pots. This is for the
54 EIGHTH REPORT — 1838.
purpose of more easily conveying the ladles filled with crystals from
pot to pot.
AH this being provided, one of the large pots is filled with lead, con-
taining silver, say 10 oz. per ton, and after it is melted and skimmed,
the fire is withdrawn, the damper put down, and the ash-pit door
closed, when it cools and crystallizes as already described. Crystals,
as they are formed, are laded out into the second pot until about three-
quarters of the whole have been removed, which will contain about 5
ounces of silver per ton : upon this the operation is repeated, giving lead
2 ounces ; and by a third crystallization, there is obtained from this,
poor lead, holding not more than 10 to 15 dwts. of silver per ton,
which is cast into pieces for sale as separated lead. The rich lead, on
the other hand, is collected and repeatedly crystallized, until it is made
to contain 200 or 300 ounces per ton, after which the silver is extracted
by cupellation. In working, the different pots at each stage are filled
up always with lead of the same content of silver before beginning to
crystallize, and a greater or less amount of crystals taken out, as the
operator may think fit, in which respect the practice differs almost at
every establishment ; but the process is so very simple and the mode
of proceeding so obvious, that it is unnecessary to give a more minute
detail.
By operating in the way described, it is evident that but a very small
portion of lead is made to undergo the process of cupellation, not more
than one twentieth part, when 10 ounces of lead is enriched to 200
ounces by repeated crystallization ; and as the loss by separation has
not been found to exceed a 250th part of the whole lead, the loss by
the joint processes becomes -^^^ of g^j + zio' '^^' a^iout one part in
120. The expense of separation is something less than that of cupel-
lation, so that by the reduction of expense and the reduction of loss of
lead, the extraction of silver is so far economized that 3 ounces per
ton will now fully cover the whole charge.
By this reduction of the cost of extracting the silver, all the lead of
Alston Moor (22,000 tons), Devon, Cornwall, and West Cumberland
(2000), and the lead of North Wales (12,000), making a total of
36,000 tons per annum, can now be made to yield up its silver with ad-
vantage, so that on the very low average of 6 ounces per ton, at least
54,000 ounces of silver per annum are gained by the arts. There may
also be safely estimated a reduction of the loss of lead on the 18,000
tons generally I'efined by cupellation of at least 300 tons. The lead
obtained by separation is much improved in quality, being more soft
and ductile than ordinary lead.
It only remains to consider, how it happens that lead in the act of
consolidation gives up a portion of its silver to the suiTounding and
still fluid lead ; and the most simple view of the matter is, undoubtedly,
that it is an instance of true crystallization, in which the homogeneous
particles of lead arc dra\vn together by virtue of their molecular at-
traction, to the exclusion of the foreign body, silver. On examining
the crystals, it is true, no trace of regular form can be perceived ; but
this could scarcely be expected, from their being so much agitated and
TRANSACTIONS OF THE SECTIONS. 55
broken at the instant of their production : if, however, a pot in the act
of crystallizing is suffered to remain at rest a few moments until a
crust forms on its surface, on carefully withdrawing a portion of this
crust, it is found on its under side to exhibit a distinctly crystalline ap-
pearance, proving that the solid particles, which are merely this crust
broken to pieces, are the result of a rapid crystallization.
This reasoning the author endeavoured to confirm by illustrations
drawn from other chemical processes, and mentioned experiment to
ascertain the degree in which, by a cautiously regulated heat, silver
may be separated from lead by the process of eliquation. Pieces of
lead were most cautiously heated till a few drops of fused metal oozed
out from their pores ; this was found to be slightly richer in silver than
the original mass. In these experiments, as in the draining of the cry-
stals, the separation is effected by the difference of fusibility between
pure lead and lead containing silver, aided, no doubt, by the tendency
of pure lead, in that state of semi-fluidity, to assume a crystalline form.
Observations on some of the Products obtained by the Action of Nitric
Acid on Alcohol. By Golding Bird, M.I).-, F.L.S., G.S., ^c.
Lecturer on Natural Philosophy at Guys Hospital, London, ^c.
In this paper the author alluded more particularly to the nature of
the substances produced simultaneously with hyponitrous ether during
the preparation of the spiritus etheris nitrici of the London Pharma-
copeia, which products have been usually stated to be malic, oxalic,
acetic, and carbonic acids, together with a substance mentioned by
Thenard as " tres facile a charbonner," in addition to the hyponitrous
ether (4 C, 5 H, O + N, 3 O). Taking advantage of the residue left
after preparing a large quantity of sp. eth. nit. in the pharmaceutical
laboratory of Guy's Hospital, Dr. Bird instituted a series of experi-
ments enumerated in his paper, from which he was induced to believe
that oxalic acid was by no means a necessary product, and that it is
not generated until aldehyd begins to ajjpear in the distilled fluid. As
the paper is published entire in the Philosophical Magazine for this
year, it is unnecessary to do more than give the result of Dr. Bird's
investigations :
1 . That in the preparation of sp. etheris nitrici, as long as the latter,
with alcohol only, distils over, no oxalic acid is produced ; an acid ap-
parently identical with the oxalhydric alone appearing in the retort.
2. That on continuing the distillation beyond this point, the free
nitric acid in the retort acting on the oxalhydi-ic acid, generates oxalic
acid.
3. That during the action of nitric acid on alcohol in the cold, as in
Dr. Black's process for the preparation of hyponitrous ether, acetic
acid is produced, instead of, or in addition to, oxalhydric acid.
4. That aldehyd is, as has been long known, produced by the action
of nitric acid on alcohol, but that it is not formed in any quantity, or at
56 EIGHTH REPORT — 1838.
least does not appear in the distilled fluid until the formation of hypo-
nitrous ether has nearly or altogether ceased.
5. That the production of aldehyd and oxalic acids are nearly si-
multaneous ; and that both these ap]:)ear to result from the secondary
action of nitric acid upon products formed in the eai-lier stages of the
operation.
6. That the crystals long known as " les cristaux de Hierne" formed
when the distillation is protracted until red fumes appear, are oxalic
acid, notwithstanding their remarkable micaceous form ; and that the
" substance tres facile a charbonner" of Thenard is probably aldehyd,
which, from its behaviour witli alkalies, might apparently merit that
character.
Notice respecting the Arlijicial Formation of a Bcmc Chloride of Cop-
per hj Voltaic Influence. By Golding Bird, M.D., S)-c.
Becquerel has proved that a homogeneous metallic surface exposed
to the action of a given fluid will assume a state of electric tension,
provided that the fluid in Avhich it is immersed is of different degrees
of concentration in two different layers, so that the plate may become
unequally acted upon at two different points. The crystallization of
protoxide of copper by the immersion of a plate of that metal in a so-
lution of its nitrate, some of the black oxide being placed in the lower
part of the vessel, affords a familiar example of this circumstance. But
if the fluid remains homogeneous, quoad its degree of concentration,
no action, so far as electricity is concerned, ensues, unless one portion
of the metallic surface immersed is in a condition which enables it to be
more readily acted on than the other. This may be effected by partial
and superficial oxidation, by roughening or burnishing part of the me-
tallic surface, or by the induction of that peculiar passive state which
Schonbein has shown to exist in some metals under certain circum-
stances.
If a plate of metallic copper is made the negative electrode of a single
pair, acting on a solution of copper, crystallization of the latter metal,
often in delicate, rosette-like patches, if the current is weak, ensues.
This deposition generally takes place at the lower part of the metallic
plate, leaving the upper one smooth and free from crystals. A plate
thus prepared is in a condition to assume two different electric states
on immersion in a homogeneous fluid, in consequence of the delicate
crystals of metallic copper undergoing oxidation more readily than the
smooth part of the plate. Such a piece of metal was immersed in a so-
lution of common salt during three months in a dark closet ; on ex-
amining the plate at the end of that time, the smooth portion, on which
no metallic crystals had been deposited, was found tarnished and covered
with blackish patches, without any perceptible roughening of the sur-
face. The lower portion of the same plate on whicli the copper had
crystallized had undergone a very interesting change, the metallic
crystals having become replaced by an infinite number of hemispheri-
TRANSACTIONS OF THE SECTIONS. 57
cal patches from a mere point to the size of a large pin's head, of a rich
green colour, of a somewhat velvety or satiny lustre. On breaking
some of the crystals they were found to be radiated like zoolito, without
any metallic nucleus, and firmly adhering to the copper on which they
were deposited. The crystals were insoluble in water, did not effervesce
with sulphuric or nitric acids, in which they Avere with difficulty solu-
ble, the solution being at first brownish, and readily becoming green by
exposure to the air : their solution, in dilute nitric acid, precipitated
nitrate of silver. These hemispheric radiated crystals are therefore re-
garded by Dr. Bird as a basic chloride, probably resembling the native
tribasic chloride. This, however, he has not yet had an opportunity of
proving by direct analysis.
The theory of the formation of these crystals appears to be very
simple. On immersing the copper plate into the brine, its electricity
became disturbed, and two states of electric tension were assumed, the
smooth and polished part becoming the negative, and the rough and
crystalline portion the positive electrode of a simple voltaic circle. The
chloride of sodium becoming decomposed, the chlorine uniting with
the crystalline surface of the positive electrode, the soda being at first
set free, although probably almost immediately after re-acting on the
newly-formed copper salt, and thus reducing it to the state of basic
chloride, the crystalline deposition resulted from the slowness of the
action, as in Becquerel's experiments.
Notice respecting the Deposition of Metallic Copper from its Soltitio?is hy
slow Voltaic Action at a poi?it equidistant from the Metallic Surfaces.
By GoLDiNG Bird, M.D., ^c. ^e.
At the last meeting of the Association Dr. Bird presented some re-
marks on the possibility of reducing metallic bases on surfaces not in
contact with the electrode*. During the past year he has varied his
experiments, chiefly with a view to the prevention of any source of
fallacy connected with accidental metallic contact; and, although
he has repeatedly succeeded in reducing metals on, or in the cen-
tre of masses of earthy substances, as plaster of Paris or clay, he
has never yet obtained metallic deposits in a fluid intermediate be-
tween electrodes when these substances were absent. An interesting
modification of the apparatus, described at Liverpool, has been con-
trived by Mr. Sandall, chemical assistant at St. Thomas's hospital,
whilst engaged in constructing a voltaic battery on Prof. Daniell's ar-
rangement, but in which the membranes should be replaced by cylin-
ders of sulphate of lime. This gentleman carried on his experiments
during this summer, and Dr. Golding Bird requested him to break up
the masses of plaster that had been used in his arrangement, for the
purpose of ascertaining whether any deposition of metallic copper had
taken place at any part not in connexion Avith the metallic surfaces, as
* See vol. vi., p. 45.
58
EIGHTH REPORT — 1838.
he considered these results would go far to support or refute the opi-
nions he had hazarded on this subject.
The results of these experiments were uniform ; they differed from
Dr. Bird's in one remarkable circumstance, viz. that the copper, instead
of being deposited in a crystalline form, was in nodular or tubercular
masses (a specimen was exhibited to the Section). When the plaster of
Paris diaphragm, which of course was vertical, was carefully made, and
one side of ajar thus divided was filled with water, and the other with
a solution of sulphate of copper, no intermixture of fluids was evident
even at the end of a month. On placing in the solution of sulphate
of copper, at a certain distance from the vertical partition, a mass of
copper pyrites, connected by a copper ribbon with a piece of zinc im?
mersed in the water in the other cell, voltaic action slowly commenced.
At the end of a few days the water in the zinc cell became acid, bub-
bles of hydrogen gradually appeared, and were slowly evolved, whilst
the copper pyrites slowly assumed the iridescent appearance of peacock-
ore described by Mr. Fox : in a month the apparatus was dismounted ;
no trace of sulphate of copper was found in the water cell, and neither
the zinc nor the mass of pyrites had touched the plaster diaphragm.
On removing the latter, a copious deposition of firmly adherent me-
tallic copper, in a nodular or almost stalagmitic form, was found on that
surface Avhich had been exposed to the metallic solution ; and, on
breaking the mass of plaster transversely, numerous delicate veins of
copper appeared permeating it in every direction. This experiment is
considered by Dr. Bird to be less liable to sources of fallacy, and
much less exceptionable than those described by him last year ; for,
not only is all metallic contact with the plaster diaphragm carefully
avoided, but the very form of the reduced copper would afford an ar-
gument against its being furnished by portions shooting off from the
negative electrode, on the beautifully iridescent surface of which,
moreover, no trace of reduced copper liad appeared.
Arrangement of the Apparatus.
A is a conical earthen vessel, in which the
plaster diaphragm B is carefully fitted.
C. The cell filled with water, and contain-
ing a piece of zinc metallically connected with
a mass of native copper pyrites, placed in the
cell D, which is filled with a solution of sul-
phate of copper. On the surface of B, where
the irregularities E are sketched, is the cop-
per deposited in a nodular form, and con-
nected apparently with delicate metallic veins
traversing B in every direction.
TRANSACTIONS OF THE SECTIONS. 59
On a new Compound of Sulphate of Lime with Water.
By Prof. Johnston, F.R.S.
This compound is represented by 2Ca S + H, and occurs in masses
of a minute radiated structure, in minute cj'lindrical crystals, and in
large six-sided prisms. It is formed as a sediment in the boiler of a
steam engine at the Team Colliery, near Newcastle. The boiler is
worked under an average pressure of about two atmospheres. {See the
Loud, and Ed. Phil. Mag. for Nov. 1838.)
On a new Compound of Bicyanide with Binoxide of Mercury.
By Prof. Johnston, .F.Ii.S.
When dilute hydrocyanic acid is digested on red oxide of mercury
in excess, a white nearly insoluble compound is formed, which may be
separated from any soluble bicyanide which may be present in the su-
pernatant liquid by collecting it on the filter. Boiling water dissolves
the new compound, and leaves the excess of oxide of mercury. On
cooling, the salt is, in a great measuie, deposited on the sides and bot-
tom of the vessel in minute, pure, white, transparent, prismatic needles.
This salt is anhydrous, its solution has an alkaline reaction, and it con-
sists of equal atoms of the two mercurial compounds, or it is (HyCyc,
+ HyOj). When heated in a tube, it decomposes with a slight deto-
nation, giving off carbonic acid, nitrogen, cyanogen, and metallic mer-
cury, leaving a black residue (para-cyanoge?t). Neutralized by nitric
acid, it gives a beautiful salt in long, delicate, quadrangular prisms,
which are represented by HyCyo + (HyO^ + | NO^), and are very
soluble in water. It gives also with acetic acid, a crystalline compound,
in which the quantity of acid appears to exist in a still smaller propor-
tion. With acid nitrate of silver, it gives Wohler's salt (HgCyg +
AgN + 4H), nitrate of mercury remaining in solution. With neutral
nitrate of silver and various other salts, it gives crystalline compounds.
On some supposed Exceptions to the Law of Isomorphism.
By Prof Johnston, F.R.S.
In this paper the author endeavoured to show, that if the chemical
analyses and crystalline measurements of certain groups of substances
are to be depended on, the law indicated by previous researches, that like
forms indicate like formulce, is not universally true. The paper does
not admit of abridgement, but may be consulted in the Loiid. and Ed.
Phil. Mag. for Dec, 1 838. See also Reports of the British Association,
Vol. VL,p. 173, etseg.
60 EIGHTH REPORT — 1838.
On the Origin of Petroleum, and on the Natin-e of the Petroleum from
Whitehaven. By Prof. JoiiifSTON,'P.Ii.S.
The author stated that petroleum was obtained in considerable quan-
tity from the mass overlying the three several seams of coal Avhich
are worked in the neighbourhood of Whitehaven. This petroleum he
found to agree in nearly all its characters with that of Rangoon. -In
thickness, colour, smell, and especially in the products of distillation
alone, and with water, the two varieties agreed ; and as there can be
no doubt of the origin of the one variety — that it has been volatilized
from the coal into the bed which covers it, and from which it now ex-
udes — the author of the paper considered it to be almost certain that
the wells of Rangoon must derive their supplies from subjacent beds of
coal, and that deposits of combustible matter are to be looked for
wherever similar sources of petroleum are met with.
On Middletonite and some other Mineral Substances of Organic
Origin. By Prof. Johnston, F.R.S.
The name Middletonite is given by the author to a yellow resinous
substance found in the body of the coal at the Middleton Collieries,
near Leeds, and in other parts of the Yorkshire and the Staffordshire
coal fields. It is represented by the formula C.20 H , , O, and is chiefly
interesting as being in all probability the resin of certain trees of the
carboniferous epoch, more or less altered.
Of the Resin of Gamboge (^Gambodic Acid) and its Compounds.
By Prof. Johnston, F.R.S.
Prof. Johnston stated that this acid resin is represented approximately
by the formula C=, H3 O, and that it forms three classes of salts, repre-
sented respectively by
RO 4- 5 (C5 H3 O)
RO + 10 (C5 H3 O)
RO + 15 (C5 H3 O)
This resin he also stated to be distinguished from all other known
resins by dissolving in dilute caustic ammonia, forming a solution
which may be diluted with any quantity of vater, and which throws
down gambodiates from ammoniacal solutions of magnesia, of the oxides
of copper, zinc, siher, manganese, and the other metallic oxides which
dissolve in dilute ammonia. No other resin is known to be capable of
giving salts from aqueous solutions.
On a Blue Pigment. By R. Phillips, F.R.S., ^c.
During the meeting of the Association at Liverpool, Professor Traill
exhibited to the chemical section a fine blue pigment prepared by add-
TRANSACTIONS OF THE SECTIONS. 61
ing a solution of ferrocyanide of potassium to one of chloride of anti-
mony ; at the request of the Professor, Mr. R. Phillips undertook to
examine the pigment in question, and has communicated the following
observations.
" Having by me some chloride of antimony, which I employ on or-
dinary occasions, I added to it some ferrocyanide of potassium, and im-
mediately produced the blue precipitate. This solution had, however,
a very slight yellow tint, and remembering that Professor Clarke had
shown me that hydrochloric acid very much deepens the colour of
perchloride of iron, I suspected its presence ; I therefore prepared some
chloride of antimony from hydrochloric acid, and a protoxide which I
believed to be pure. I obtained a perfect colourless solution, and in
this no blue precipitate was formed by ferrocyanide of potassium.
" To show that the chloride of antimony, which I first employed,
contained peroxide of iron, I decomposed a portion of it by the addi-
tion of water; the solution gave a much deeper blue precipitate than
before, while the oxychloride of antimony, re-dissolved in hydrochloric
acid, gave scarcely any blue tint whatever ; and the slight one which
it did yield was evidently owing to the adhesion of a small portion of
peroxide of iron precipitated with it ; for, again precipitating with water
and dissolving in hydrochloric acid, this minute portion of peroxide of
iron was almost entirely removed.
" It is therefore evident, that the blue pigment is merely Prussian
blue, largely diluted and rendered pale by ferrocyanide of antimony."
The author again adverts to the curious fact, already alluded to as
pointed out to him by Professor Clarke, of the colour imparted to hy-
drochloric acid by perchloride of iron. A few drops of the perchloride
were rendered perfectly colourless by half an ounce of water, while
three ounces of colourless hydrochloric acid acquired a considerable
yellow tint by the addition of a similar quantity of the perchloride.
Oh tlie Blue Pigment of Dr. Traill. By C. T. Coathupe.
Mr. Coathupe stated other experiments which confirm the conclusion
of Mr. R. Phillips, that the colour in question could not be produced
from pure chloride of antimony.
A new case of the Chemical Action of Light in the Decoloration of
Recent Solutions of Caustic Potass of Commerce. By R. Mallet.
The author of this paper has examined chemically a large number
of specimens of commercial caustic potass, with a view to determine
the reality of the cause usually assigned to the deep green colour
of its aqueous solutions, namely, the presence of manganese, in the
state of manganesiate of potdss. The colour of these solutions gra-
dually fades in close or open vessels, and in light or darkness, an effect
which has been ascribed, as above, to their containing mineral ca-
62 EIGHTH REPORT — 1838.
meleon. On careful analysis, however, the author has assured himself
that manganese does not occur as a constituent of caustic potass, and
that its aqueous solutions own their colour, and the change of their
colour, to the presence of protoxide and proto-chloride of iron in solu-
tion ; the former being held so by the presence of chloride of potas-
sium. These, by taking up oxygen (probably from the air combined
with the water), become further oxydized and gradually precipitate in
combination, leaving the solution colourless, and giving rise to a new
compound of sesquioxide and sesquichloride of iron, consisting, by the
author's analysis, of 10 atoms of the former and one of the latter body,
or
(Fe, CI,) + 10 (Fe, O^).
It is anhydrous. Having observed that these changes took place
at very different rates in bottles of variously coloured glass, the
author commenced a series of experiments on the relative effects of
light transmitted to the solution through various media, and has found
and recorded in ruled sheets, by curves, the results of observations
made every two hours. In these curves, the ordinates represent time,
and the abscissae the rate of chemical change, as marked by certain
changes of colour.
Means were taken to prevent inequality of temperature, or of inten-
sity of light, in each solution exposed to a coloured ray, and some of
the results arrived at are given in the subjoined table.
Mode of exposure to light. ^SoratiS!*
Violet glass, exposed to air 30 hours.
Violet glass, closed 50
Flint glass, colourless, exposed to air 80
closed 115
. . yellow „ 170
. . blue „ 185
. . orange „ 190
, . red „ 200
Green glass, by oxide copper ] wholly unchanged in
Do. Bristol bright metal j colour in 200 hours.
The rate of progressive decoloration for different rays at different pe-
riods is very various.
The result as to grcon glass agrees with Mrs. Somerville's experi-
ments. Ink, which Sir John Herchel found transmitted white light
unaltered, was used to reduce all the coloured media to the same illu-
minating power, and immersion in water to preserve the temperature
constant.
The author conceives that this is the first attempt that has been
made to reduce the phenomena of the chemical action of light to nu-
merical registration, and suggested the importance of the subject,
upon which so little was known, and in which the observed cases were
so few.
TRANSACTIONS OP THE SECTIONS. 63
Ohservations on the Co?istitution of the Commercial Carbonate of Am-
monia. By Mr. Scanlan.
Having occasion some months ago to make a quantity of the " So-
lution of Sesquicarbonate of Ammonia," of the London Pharmacopoeia,
the author found, (without knowing that Dr. Dalton had done so be-
fore,) by pouring successively small portions of pure water on large
quantities of the salt, that saturated solutions were obtained, success-
ively decreasing in specific gravity, and smelling less and less of
ammonia, till all the salt was dissolved. He agrees with Dr. Dalton
in opinion, that the commercial carbonate of ammonia is not a homo-
geneous salt, not a sesquicarbonate of ammonia, but a mixture of car-
bonate and bicarbonate, of which the former is first dissolved by the
water. The irregular masses of salt which remain still retain, almost
exactly, their original form and dimensions — they are, in point of fact,
skeletons of the original mass, but consist solely of a congeries of cry-
stals of bicarbonate of ammonia, from the interstices of which carbo-
nate of ammonia has been removed by the solvent power of the water,
if we do not proceed so far as to dissolve all. What takes place here,
may be likened, in some measure, to the case in which the gelatin is
removed from bone by water, leaving the phosphate of lime. Inde-
pendently of showing the true nature of the salt, this is of some im-
portance, as it affords us a very ready mode of preparing bicarbonate
of ammonia without the waste, which occurs by exposure of the com-
mercial salt in powder to the air, or without the trouble of transmitting
a current of carbonic acid gas through its solution, as directed by the
Dublin Pharmacopoeia. Indeed, the latter method is both troublesome
and wasteful, for it is difficult to evaporate a solution of bicarbonate of
ammonia without decomposition. Mr. Scanlan has found that water at
90° or 100° decomposes bicarbonate of ammonia, setting carbonic acid
at liberty.
On the Blackening of Nitrate of Silver by Light. By Mr. Scanlan.
Nitrate of silver was recommended many years ago, by Dr. John
Davy, as a test of the presence of organic matter in distilled waters.
He showed, that if nitrate of silver in solution be added to perfectly
pure water, it is not altered by exposure to direct sunshine ; but if the
water contain a trace of organic matter, it will become blackened.
Mr. Fergusson, some years ago, when he had the management of the
chemical laboratory belonging to the Dublin Apothecaries Company,
informed Mr. Scanlan, that perfectly pure nitrate of silver is not
blackened by long exposure to direct sunlight, but it is believed that
he never gave further publicity to this fact than mentioning it to his
chemical friends in Dublin at the time. In consequence of some
observations upon the blackening of this salt, made by Dr. Aldridge,
of Dublin, in his review of Mr. Phillips's translation of the London
Pharmacopoeia, Mr. Scanlan was led to make the following experiment
upon the subject : — He took two cylinders of perfectly pure fused
64 EIGHTH REPORT — 1838.
nitrate of silver, immediately tliey were cast, from the mould, and
wrapped one of them in paper, in the usual way -that this substance is
found in tlie sliops ; the other cylinder was transferred to a glass tube,
and sealed up hermetically, by means of the blow-pipe, without being
suffered to come in contact with organic bodies: it was pushed from
tlie mould into the tube by means of a glass rod. After a lapse of
three days, the paper was removed from the first, and it was then
sealed up in a tube, in a similar manner to the other. The two tubes
were now exposed to the direct rays of the sun, and in half an hour the
nitrateof silver that had lain in contact with paper was blackened, while
that in the other tube was not altered by six weeks constant exposure.
The whole amount of blackening of the cylinder that had been papered
was produced in the lialf hour. Nitrate of silver, free from oi'ganized
matter, is sometimes blackened by exposure to the air; but this may be
owing to the presence perhaps of sulphuretted hydrogen, accidentally
present. Atmospheric air too is, perhaps, seldom free fi'om organic
matter.
On the Specific Gravities of Nitrogen, Oxygen, Hydrogen, and Chlo'
rine ; and also of the Vapours of Carbon, Sulphur, Arsetiic, and
Phosphorns. By the Rev. T. Exley, M.A.
The author of this communication first shows the bearing of his new
theory of physics on questions relating to the combination of atoms,
which he classes according to their supposed absolute forces and rela-
tive spheres of repulsion. Among the consequences of this theory the
author mentions the deduction, that " equal volumes contain equal
numbers of atoms," and proceeds to show the application of this to the
construction of a general table of specific gravities for chemical com-
pounds in the gaseous form. Taking the specific gravity of air as
unity, he shows, from comparison of the best experimental results, that
the following specific gravities may be depended on within minute
errors : — •
Carbon* . . . 10-12ths.
Sulphur t . . . 60-9ths.
Arsenic J . . . 10^.
Phosphorus § . . 4^.
Now these numbers, being compared with the atomic weights of the
substances, lead to the following simple rule for determining specific
gravities in all gaseous bodies : — Multiply the sum of the atomic
Aveights of the atoms of a single group by -^-^^ (the specific gravity of
hydrogen), the product is the specific gravity required. By this rule
the following table was calculated : —
* The number for carbon is inferred from its gaseous combinations.
t It is by calculation only 1°, but the author explains this difference by supposing
the sulphur vapour to exist in single groups of three atoms each, a)id gives reasons
for thinking this probable.
X By calculation 5^- ; supposed to consist of single gi'oups of hpo atoms each.
§ By calculation 2| ; supposccl to consist of single groups of two atoms each.
Nitrogen
35-3Cths.
Oxygen
10-9ths.
Hydrogan
10-144th3
Chlorine
. 2i.
TRANSACTION'S OP THE SECTIOXS. 65
A Table of Chemical Compounds in the Gaseous Form.
Composition.
fell
Sp. gr.
By Cal.
Air= 1.
By Expt.
Autliority,
I. COHESIVE COMBINA-
TION.
1. Carbonic Oxide
2. Nitric Oxide
3i Muriatic Acid
4. Hj'drobromic Acid ....
5. Hydriodic Acid
C. Fluoric Acid
7. Sulplmret of Mercury.
8. Common Air
C
N
CI I H
Br I H
I|H
F I H
"g I Hg .,
I N I N I N
N.
Cyanogen
Chloride of Sulphur
Chloride of Mercury
Bromide of Mercury
Iodide of Mercui'y
Fluoboric Acid
Nitrous Acid
Peroxide of Hydrogen ...
Persulphuret of Hydrogen
E. Davy's Carb. of Hydro.
Faraday's Carb. of Hydro.
Olefiant Gas
Etherine
Faraday's Oil Gas
Naphtha
Naphthaline
Petrolene
Camphene
Oil of Turpentine
Hydrocarb. of Chlorine
Arsenious Acid
Chloride of Silicon ,
Fluosilicic Acid ,
Aikarsin ,
33. Water
II. SINGLE GROUPS.
NCorN(Co)N
CI S or CI (So) CI ,
CI Hg or CI (Hga) CI
Br Hg or Br (Hgj) Br
IHg, or I (Hga) I
FBorF(B2)F ,
O2 N or N (O4) N ,
HO, or H (O2) H
HS, or H (S2) H
HC, or H (C2) H
H3C3
HsCorH, C, H
H4C2
Hj C3 or H2 C, H2 C, H2 C
H5 C3 or Ho C, HC, H2 C
H4C5
H3 C]o
Hg Cj
Hs Cg
H2CIC, orH, CIC, H ...
As2 O3 or 0, OAso, ...
CI2 Si, or CI, Si, CI
Fo Si, or F, Si, F
Ha Co As, or Ho C, H„ As,
H,'C .". .'.....
III. DOUBLE GROUPS.
H (O) H .
14
15
18
40J
63 J
n
m
14i
26
68
136
180
226
34
46
17
33
13
39
14
28
42
41
64
128
68
80
50
200
88
52
106
•9722
1-0426
1-2847
2-8125
4-4097
•6597
5-3703
1
1-8055
4-7222
9-4444
12-5
15-6944
2-3611
3-1944
1-1805
2-2916
•9027
2-7083
•9722
1-9444
2-9166
2-8472
4-4444
8-8888
4-7222
5-5555
3-4722
13-8888
6-1111
3-6111
7-3611
•9727
1-0409
1-2814
2-731
4-443
5-384
1
1-8064
4-70
9-439
12-362
15-67
2-3622
3-1764
Berzelius.
Davy ; Thomson.
Thomson.
Turner.
Gay Lussac.
Dumas.
The unit.
Gay Lussac.
Dumas.
Mitscherlich.
Ditto.
Ditto.
Thomson.
Gay Lussac.
these are decomposed by a
■ degree of heat below the
boiling point.
6-25
-9027
2-776
-9709
1-91
3-0555
2-833
4-528
9-415
4-767
5-0130
3-4434
13-6695
5-939
3-600
6-516
-0235
E. Davy.
Faraday.
Thomson.
Faraday.
Ditto.
Saussure.
Dumas.
Boussingault.
Dumas.
Gay Lussac.
Ditto.
Mitscherlich.
Dumas.
Thomson.
Bunsen.
Gay Lussac.
VOL. VII. 1838.
G6
EIGHTH REPORT 1838.
Table continued.
Composition.
5 II Sp-gr.
,T3 By Cal.
Air= 1.
By Expt,
Authority.
34. Sulphuretted Hydrogen..
35. Carburetted Hydrogen ..
36. Telluretted Hydrogen
Seleuuretted Hydrogen ..
38. Inflble. Phosphtted. Hyd.
39. Carbonic Acid
40. Sulphurous Acid
41. Deutoxide of Chlorine ..
42. Protoxide of Chlorine ..
43. Bichloride of Sulphur ..
44. Bichloride of Carbon
45. Chloride of Manganese ..
46. Chloride of Selenium
47. Borochloric Acid
48. Chlorocyanic Acid
49. Hydrocyanic Acid
50. Bisulphuret of Carbon ...
51. Nitrous Oxide
52. Protochloride of Mercury
53. Pi-otobroniide of Mercury
54. Bromide of Sulphur
55. Sulphuric Acid
56. Selenic Acid
57. Phosphiuretted Hydrogen
58. Arsenuretted Hydrogen ..
59. Ammonia
60. Chloride of Phosphorus ..
61. Chloiide of Arsenic
62. Sesquichloride of Carbon
63. Chlorocarbonic Acid
64. Light Carburetted Hydr.
65. Perchloride of Tin
66. Perchloride of Titanium..
67. Chloral
68. Infl. Gas of Dr. Thomson
69. Chloroform
70. Muriatic Methyline
71. Sesquiodide of Arsenic ..
H(S) H
H (C) H
H(Te)H
H (Se) H
H (P)H
0(C)
(S)0
(C1)0
C1(0)CI
C1(S)C1
C1(C)C1
Cl(Mn) CI ,
CI (Se) CI
Cl(B)Cl
N(C)C1
N(C)H
S(C) S
N (0)N
Hg(Cl)Hg
Hg(Br)Hg
B (S)B
0(S0)0
0(SeO)0
H (PH) H
H (AsII) H
H (NH) H
CI (PCI) CI
CI (As CI) CI
CI (CCl) CI
CI (CO) CI
H (CHa) H
Cl(SnCl2)Cl
Cl(TiClo)Cl
CI (CI Ca HO) CL ,
C1(C1CH2)C1 ....
CI (CI CH) CI
H (CICH)H
I (AS3) I
17
7
33
41
17
22
32
34
44
52
42
64
76
44
31
m
38
22
118
140
96
40
64
39i
8^
70
92
60
50
8
130
98
7M
61
60i
25^
240
1-1805
•4861
2-2916
2-8472
1-1805
1-5277
2-2222
2-3611
3-0555
3-6111
2-9166
4-4444
5-2777
3-0555
2-1527
•9375
2-6388
1-5277
8-1944
9-7222
6-6666
2-7777
4-4444
1-2152
2-7430
•5902
4-8611
6-3888
4-1666
3-4722
-5555
9-0277
6-8055
5-1736
4-2361
4-2013
1-7708
16-666
1-1912
•490
2-292
1-1935
1-523
2-221
2-346
3-0
3-67
3^942
2-153
-9385
2-6447
1-5269
8-204
9-665
3-0
1*214
2-695
-5967
4-875
6-295
3-472
•5550
9-1997
6-836
5-0
4-1757
4-2
1-736
15-64
Thenard.
Dumas.
Brande.
Rose.
Thenard.
Thomson.
Thenard.
Gay Lussac.
Dumas.
Dumas.
Ditto.
Thenard.
Gay Lussac.
Thomson.
Mitscherlich.
Ditto.
Mitscherlich.
Dumas.
Ditto.
Biot & Arago.
Dumas.
Ditto.
Henry.
Thomson.
Dumas.
Ditto.
Ditto.
Thomson.
Dumas.
Ditto.
Mitscherlich.
ill
TRANSACTIONS OP THE SECTIONS.
Table continued.
67
Composition.
Sp. gr.
By Gal.
Air= 1.
Bj' Expt,
Authority.
Nitric Acid
Hyponitrous Acid
N (O5) N
N (O3) N
Pyroxylic Spirit
PjToacetic Spirit
Protohydrate of Metliyline
Sugar Anhydrous .,
Alcohol
Mercaptan
Oil Gas
Muriatic Ether
Hydriodic Ether
Aldehyd
Acetic Acid
Ether
Citrene
Oxalic Ether
Carbonic Ether
CEnanthic Ether
Benzoic Acid
91. Benzoic Acid, concentrat.
Paranaphthaline .
Camphor
Acetic Ether ....
Benzoic Ether.
Nitric Ether .
Sulphur Vapour
Phosphorus Vapour
Arsenic Vapour
H (HoOC)H
H, C (H2 OC) Ho C
H2C (HjC) H2O
HjC (0„C) HgC
HsCCHgO) HjC
H2C(H2S)H2C
H2C(H2C)H2C
HgC (01 H) H2C
HjC (IH) HoC
H2C(0) H2C
H2 C (C2 O3) H2 C
H4 C2 (H, 0) H4 Cs
H4C2(C)H4C2
H4 C2 (Ho O4 C2) H4 C2
H4C2(H2 03C) H4C2...
H4 C2 (H2S O3 C,4) H4 C2
H4C5(OC2)H4Cs|H2C
(C02) H2C
H4 C5 (H4 C5 O3) H4 c,
H,
H4 C5 (H4 Cj) H4 c,
H8C5(0)HsC5 ...
H4 C„ (H2 0) H4 C,
c (C2 03) H2 c ..:
H4 C„ (H2 O) H4 C2— H4
C2(H4 03C„)H4C2...
H4 C2 (H2 0) H4 C2 I N
(03)N
S3
P2
|As,
54
38
16
29
23
36
23
31
21
32i
m
22
50
37
34
73
59
150
60
120
96
76
43J
96
64
152
3-75
2-6388
1-1111
2-0138
1-5972
2-5
1-5972
2-1527
1-4583
2-2569
5-3819
1-5277
3-4722
2-5694
2-3611
5-0964
4-0972
10-4166
4-1666
8-3333
6-6666
5-2777
3-0208
5-4513
2-6041
6-6666
4-4444
10-5555
3-75
2-6388
1-115
2-019
1-60
1-6133
2-326
1-458
2-219
5-4749
1-532
3067
2-5860
2-385
5-087
4-243
10-4769
4-27
8-352
6-741
5-29
3-067
5-419
2-627
6-648
4-327
10-362
Henry.
Inferred from No.
96.
Brande.
Dumas.
Dumas.
Sohd.
Gay Lussac.
Bunsen.
Henry.
Gay Lussac.
Ditto.
Liebig.
Dumas.
Gay Lussac.
Dumas.
Ditto.
Etthng.
Delachamps.
Dumas.
Inferred from 85
and 95.
Dumas.
Ditto.
Ditto.
Ditto.
Ditto.
Mitscherlich.
Ditto.
Ditto.
p2
6S felGHTIl REPORT — 1838.
On Chemical Combitialions produced in virtue of tfie presence of oilier
bodies vjhich still remain. By Rev. T. Exi.e^, M.A.
Mr. Exley points out in this paper the application of his theory to
the explanation of those cases in chemistry where powerful affinities
between bodies are brought into activity by means of other substances
which are present and continue to exercise the same energies. Berze-
lius attributes this to a peculiar force, which he calls catalytic, and Mr.
Exley taiies four examples to show how these phenomena receive an ex-
planation in conformity with his general view of atomic centres of force.
The first case is that of the combination of hydrogen and oxygen,
effected by the presence of clean platinum. " Since metals are simple
bodies and dense solids, the theory recognises their atoms as having
small spheres of repulsion, and those of ])latinum must be very small
because of the great density of the metal: hence, the atmosphere of
ethereal matter belonging to this metal is very dense, being more dense
as the square of the radius of the sphere of repulsion is less and as the
atomic weiglit is greater. For this reason the oxygen can approach ex-
tremely near to the atoms of platinum, and yet not combine with them
by reason of that dense atmosphere ; and the hydrogen being drawn
close on them the reunion in question occurs, the generated steam
escapes, heat is evolved, and the process advances till ignition is pro-
duced."
The author examines in succession three other oases of supposed
peculiar actions, and explains them on the j^rinciples of his theory :
The conversion of starch into sugar by the action of a weak solu-
tion of sulphuric acid.
The conversion of sugar into alcohol by the action of barm.
The conversion of alcoliol into ether by the action of sulphuric
acid.
On an Improvement in the Manufacture of Iron, hy the AjypUcation of
Gas obtained from the decompositio)i of' Water. By John Samuel
Dawes, of Bromford cmd Oldhtry l7-onworks, near Birmingham.
Mr. Dawes has attempted to obtain a heating effect approaching in
intensity to that which is produced by the oxy-hydrogen blow-pipe, but
upon a scale sufficiently large to be available in the smelting of iron.
Hydrogen gas, in addition to its great inflammability, exhibits, when
applied to the above purpose, a purifying property in a high degi'ee, so
that the most sulphurous materials may be used with advantage, and
metal of good quality be produced. There can be little doubt (Mr.
Dawes thinks) as to the value of hydrogen thus applied ; the question
would rather be. Can the gas be obtained at a sufficiently cheap rate so
as to make the use of it profitable ? This, he thinks, may now be con-
fidently answei-ed in the affirmative. The method of proceeding is as
follows. Jets of steam are made to pass through red-hot cast-iron
pipes filled with small coke or charcoal ; (the riddlings from the coke
hearth answer the purpose, and are of little value ;) decomposition
TRANSACTIONS OF THE SECTIONS. 69
immediately takes place. The carbon of the coke combines with the
oxygen of the steam, forming, in the first instance, carbonic acid,
■which, by passing on through a further portion of the red-hot carbon,
is converted into carbonic oxide ; the hydrogen gas, together with the
oxide before-mentioned, is applied to the furnace by means of a jet
inserted within the blast-pipe tongue ; the pressure upon the gas, of
course, being equal to that upon the blast. The pipes require to be
replenished with the brays about every twelve hours, which is con-
veniently effected by means of a plug fitted to the top of each of them.
At first some difflSculty arose from destruction of the pipes ; but as
the melting point of cast-iron is so much higher than the temperature
required to decompose water, it was evident that the cause of the mis-
chief lay in the construction of the heating furnace. This haS been
remedied, and the apparatus seems now to be very durable. The pre-
sent one at Oldbury has been in operation for some months, and the
pipes are apparently little the Avorse for wear. The quantity of fuel
required to keep them hot is from twelve to fifteen cwt. of small coal
for twelve hours ; and as the steam is obtained from the engine-boilers,
and the fireman of the hot-air apparatus has time enough to attend to
it, the expense, with the exception of wear and tear, is a mere trifle.
The wear and tear, in every probability, Avill be very moderate, and
Mr. Dawes has sufficient reason to conclude that the cost will not be
more than three or four shillings for every hundred thousand feet of
gas, every foot of Avhich is, of course, equivalent to a certain quantity
of fuel. Various experiments have now shown not only that the qua-
lity of the iron is very much improved by this process, but that the
producing power of the furnace, at the same time, has greatly increased.
In conclusion, Mr. Dawes observes, that any advantages it may be
found to possess in the smelting of iron must be equally valuable in
the reduction of other metals.
On the Influence of Voltaic Combiyiation on Chemical Action.
By Dr. Andrews.
In dilute sulphuric acid, composed of one atom of the dry acid and
eight atoms of water, the solution of distilled zinc is permanently acce-
lerated, by connecting it with a plate of platina, immersed in the same
liquid, so as to form a voltaic combination. In acid, containing seven
atoms of water, the ordinary action is at first increased, and afterwards
rather diminished by contact with platina. But when zinc is heated in
acid, containing less than this quantity of water, the connexion with
platina transfers the evolution of gas, from the surface of the positive
to that of the negative metal, and at the same time diminishes its
quantity, and consequently retards the rate of solution of the zinc.
The formation of a galvanic circle exerts, therefore, a reverse effect on
the solution of zinc in sulphuric acid containing more or less than
seven atoms of water. The principal circumstances which influence
these results are the adhesion of the hydrogen gas to the surface of the
70 EIGHTH REPORT — 1838.
zinc ; the formation of sulphate of zinc, which is greatly facilitated by
the presence of seven atoms of water in union with each atom of acid
(that being the number of atoms of water of crystallization contained
in it); and, lastly, the proper action of the voltaic circle, which tends
to diminish the solution of the zinc. In dilute acid, the first circum-
stance retards the action on the zinc alone, and the second facilitate^
its solution ; then the platina surface enables the hydrogen to escape.
But in the stronger acid, the voltaic association impedes the solution
of the zinc, partly from the evolution of gas being transferred to the
platina, and thus the saturated liquid being allowed to accumulate
around the zinc plate, and partly from the real effect of the galvanic
combination. That the proper tejidency of a voltaic circle is, to dimi-
nish the chemical action of the solution on the electro-positive metal,
the author endeavoured to show, from the consideration, that in or-
dinary solution the electricities thus developed have only an indefi-
nitely small portion of liquid to traverse, while in voltaic solution their
reunion can only be effected by passing across a column of variable ex-
tent, and composed of an imperfectly conducting substance. And, as
the action is greater the nearer the plates are to each other, that action
ought to attain a maximum when the distance between the plates
vanishes, provided this condition could actually be realized.
On the Construction of Apparatus for solidifying Carbonic Acid, and
on the Elastic Force of Carbonic Acid Gas in contact loith the liquid
form of the Acid, at different Temperatures. By Robert Addams.
Mr. Addams prefaced the communication by adverting to the ori-
ginal production of liquid carbonic acid by Dr. Faraday, in 1823, and
also to the solidification of the acid by M. Thilorier, and then exhibited
three kinds of instruments which he (Mr. Addams) had employed for
the reduction of the gas into the liquid and solid forms. The first
mode was mechanical, in which powerful hydraulic pumps were used
to force gas from one vessel into a second, by filling the first with
water, saline solutions, oil, or mercury ; and in this apparatus a
" gauge of observation" was attached, in order to see when the vessel
was filled. The second kind of apparatus is a modification of that in-
vented and used by Thilorier. The third includes the mechanical and
the chemical methods, and by which, as stated, a saving of a large
quantity of acid formed in the generator is effected ; whereas by the
arrangements of Thilorier's plan, two parts in three are suffered to rush
into the atmosphere, and are lost. With this set of instruments are
used two gauges of observation, — one to show when the generator is
filled with water by the pumps, and consequently all the free carbonic
acid forced into the receiver ; and the other to determine the quantity
of li(|uid acid in the receiver. Mr. Addams likewise exhibited other in-
struments for drawing off and distilling liquid carbonic acid from one
vessel into another, and mentioned some experiments which were in
progress, and especially the action of potassium on liquid carbonic
TRANSACTIONS OF THE SECTIONS.
71
acid, — an action which indicated no decomposition of the real acid,
but such as implied the presence of water, or a hydrous acid. A table
of the elastic force or tension of the gas, over the liquid carbonic acid,
was shown, for each ten degrees of the thermometer, beginning at
zero, and terminating with 150 degrees. The following are some of
the results : —
Degrees.
lb. per sq. inch.
Atmospheres of
151b. each.
279-9
18-06
10
300-
20-
30
398-1
26-54
32
413-4
2;-56
50
520-05
34-67
100
934-8
62-32
150
1495-65
99-71
_ Mr. Addams announced his intention of examining the pressure at
higher temperatures, up to that of boiling water, and above ; and as-
serted his belief that carbonic acid may be profitably employed as an
agent of motion — a substitute for steam, — not directly, as had been
already tried by Mr. Brunei, but indirectly, and as a means to circulate
or reciprocate other fluids. The solidification of the acid Avas shown,
and the freezing of pounds of mercury in a few minutes, by the cooling
influence which the solid acid exercises in passing again to the gaseous
state.
On a New Process for Tanning. By William Herapath.
The author, after noticing the impediments to a perfect accomplish-
ment of the three great objects of the tanner, viz. to make the skins of
animals iiisoluble, imputrescible, and impermeable to water, describes a
new process, by which these objects are accomplished at a less cost
than that of the old methods. In the ordinary process, the harder
fibres of the skin are perfectly tanned ; but the gelatine, which, if re-
tained, would be of the greatest value in rendering leather imperme-
able to water, disappears from the product, or is seen as an injurious
yellow coat on the surface. In reasoning on the difficulties experienced
by tanners, Mr. Herapath was brought to the conclusion that they were
occasioned by the force of capillary attraction ; and finding that the or-
dinary modes of 3i]ip\png pressure, handliuff, &c. were expensive and in-
sufficieut, he determined to try the effect of rolling the hides, connected
together as an endless band.
" If I wish to tan one hundred hides a week, I should have eight pits,
over each of which would be affixed a pair of rollers ; the upper ones
to be loaded by weights fixed on their levers. For each pit fifty hides
or butts would be made into an endless band by ligatures of twine ;
upon introducing each band between a pair of rollers, each hide would
be in succession pulled from the bottom of the pit, squeezed by the
72 EIGHTH REPORT — 1838.
rollers, and then returned again into the pit for a fresh supply
of tanning liquor ; such liquor becomes exhausted, about tAvo degrees
of the barktrometer, in twenty-four hours, when it is pumped to
the next pit backwards of the series ; and, by the time it arrives at the
last pit, (eight days,) it will have lost from 16 to 20 degrees by the
same instrument. The eight pairs of rollers require one-horse powe;r
to work them, and two boys of 2s. 6d. a week each to superintend
them ; when two bands or one hundred hides will be taken off weekly,
as one month is sufficient for them to be on the rollers. They are now
laid by in strong solutions for another month, when they are found to be
completely tunned; weighing 10 per cent, more than if they had been
operated upon in the old way, while the leather has more soft elasti-
city, and is ten times more impervious to water.
" The levers are loaded according to the state of tannage, and the
liquors are changed once a day, making twenty-four changes in the
whole, which is about one-fourth of the number formerly used."
The author entered into a minute statement of facts to prove the
practical advantages of the process thus briefly describfd, in respect of
cheapness, expedition, quick return of capital, and quality of the pro-
duct.
On some Neiv Salts of Mercury. JBy William West, Leeds.
This paper describes the composition and properties of some salts,
composed of bicyanide of mercury, with the haloid salts of potassium.
As these salts had, without Mr. West's knoAvledge, been previously
formed by other chemists, it is unnecessarj^ to detail his experiments,
which confirm former researches as to their composition. The author
observed that the pearly lustre of some of these crystals, especially those
from the bromide, was such that they might probably be employed in
place of the scales of the Bleak, for the manufacture of artificial pearls.
On a Nciv Compound of Carbon and Hydrogen. By William
Maugham, Lecturer on Chemistry at the Royal Gallery of Practi-
cal Science, London.
The compound in question is produced when, the electrodes of a vol-
taic battery are amied with charcoal points, and these points introduced
into a vessel of distilled water. The points should be attached to the
copper-wire electrodes by means of platinum wires. On bringing the
charcoal points together under 
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