6

10

TRANSACTIONS

OF XHK

ROYAL SOCIETY OF EDINBURGH.

VOL. X.

EDINBURGH :

PRINTED FOR WILLIAM TAIT, 78, PRINCE'S STREET ;

AND CHARLES TAIT, 63, FLEET STREET,

LONDON.

1826.

rv

CONTENTS

OF

VOLUME TENTH.

I KslUj f-'L
PART FIRST.

Page

I. On the Existence of Two New Fluids in the Cavities of

Minerals, which are immiscible, and possess remark-
able Physical Properties. By DAVID BREWSTER,
LL.D. F. R. S. Lond. & Sec. R. S. Edin. 1

II. Observations on the Comparative Anatomy of the Eye.

By ROBERT KNOX, M. D. Member of the Werne-
rian Society, and of the Medico-Chirurgical So-
ciety of Edinburgh, - 43

III. Notice of an undescribed Vitrified Fort, in the Burnt

Isles, in the Kyles of Bute. By JAMES SMITH, Esq.

of Jordanhill, F.R.S. Edin., - 79

IV. On the Formation of Chalcedony. By Sir G. S. MAC-

KENZIE, Baronet, F. R. S. Lond. & Edin., 82

V. Notice respecting the Vertebra of a Whale, found in a

Bed of bluish Clay, near Dingwall. By Sir G. S.
MACKENZIE, F. R. S. Lond. & Edin. In a Letter to
Dr Brewster, Sec. R. S. E. &c. - 105

VI. Description of Hopeite, a New Mineral from Alten-

berg, near Aiae-la-Chapelle. By DAVID BREWSTER,
LL.D. F. R. S. Lond. & Sec. R. S. Edin., - 107

TO CONTENTS.

Page

VII. Astronomical Observations made at Paramatta and
Sydney. By his Excellency Sir THOMAS BRISBANE,
K. C. B. F. R. S. Lond. & Edin., & M. RUMKER.
In a Letter to Dr BREWSTER, Sec. R. S. Edin., 112

VIII. On a Remarkable Case of Magnetic Intensity of a
Chronometer. By GEORGE HARVEY, Esq. M. G. S.
M.A.S. &c. 117

IX. Remarks concerning the Natural-Historical Deter-
mination of Diallage. By W. HAIDINGER, Esq. 127
X. Investigation of Formula, for finding the Logarithms
of Trigonometrical Quantities from one another.
By WILLIAM WALLACE, F.R.S. Edin., and Profes-
sor of Mathematics in the University of Edinburgh, 1 48

XI. A proposed Improvement in the Solution of a Case in
Plane Trigonometry. By WILLIAM WALLACE,
F.R.S. Edin. and Professor of Mathematics in the
University of Edinburgh, 1 68

XII. Some Notices concerning the Plants of various Parts

of India, and concerning the Sanscrita Names of
those Regions. By FRANCIS HAMILTON, M.D.
F.R.S. & F. A. S. Lond. & Edin. 171

XIII. On a New Species of Double Refraction, accompany-

ing a remarkable Structure in the Mineral called
Analcime. By DAVID BREWSTER, LL.D. F. R. S.
Lond. & Sec. R. S. Edin. .187

XIV. On the Specific Heat of the Gases. By W. T. HAY-

CRAFT, Esq., 195

XV. On the Forms of Crystallisation of the Mineral called
the Sulphato-tri-Carbonate of Lead. By W. HAI-
DINGER, Esq. F. R. S. E. 217

•

CONTENTS.

?«* • ' " -• r

PART SECOND.

Page

XVI. Inquiry into the Structure and probable Functions
of the Capsules forming the Canal of PETIT, and
of the Marsupium Nigrum, or the peculiar Vas-
cular Tissue traversing the Vitreous Humour in
the Eyes of Birds, Reptiles, and Fishes. By
ROBERT KNOX, M. D. F. R. S. ED., and Con-
servator of the Museum of the Royal College of
Surgeons, - - 231

XVII. On an Anomalous Case of Vision with regard to

Colours. By GEORGE HARVEY, Esq. F. R. S. E. 253
XVIII. Observations on the Germination of the Filices.
By the Reverend JOHN MACVICAR, Dundee.
Communicated by the Reverend JOHN FLEM-
ING, D. D. F. R. S. E. &c. - 263
XIX. Description of FERGUSONITE, a New Mineral

Species. By W. HAIDINGER, Esq. F. R. S. E. 271
XX. Biographical Account of ALEXANDER WILSON,
M. D. late Professor of Practical Astronomy
in Glasgow. By the late PATRICK WILSON,
A. M. Professor of Practical Astronomy in the
University of Glasgow, - 279

XXI. On the Determination of the Species, in Minera-
logy, according to the Principles of Professor
MOHS. By WILLIAM HAIDINGER, Esq.F.R.S.E. 298
XXII. On the Consolidation of the Strata of the Earth.
By SIR JAMES HALL, Bart. F. R. S. Lond. &
Edin.

XXIII. Observations before and after the Superior Conjunc-
tion of Venus and the Sun, with the Mural

CONTENTS.

»

Page

Circle at Paramatta, 1824. By His Excellency
SIR THOMAS BRISBANE, K. C. B. F. R. S. Lond.
& Edin. 330

XXIV. Observations on Two Comets discovered at Para-
matta in 1824, by Mr RUMKER and Mr DUN-
LOP. Communicated by his Excellency Sir TH o-
MAS BRISBANE, K. C. B. F. R. S. Lond. & Edin.
in a Letter to Dr BREWSTER, Sec. R. S. Edin.
To which are added the Elements of their
Orbits, calculated by Mr GEORGE INNES, and
Mr JAMES GORDON, A. M. Aberdeen, - 332

XXV. On the Construction of Meteorological Instruments,
so as exactly to determine their Indications dur-
ing Absence, at any given instant, or at successive
intervals of Time. By HENRY HOME BLACK -
ADDER, Esq. Surgeon, MED. STAFF H. p. - 337

XXVI. An Examination of Dr PARR'S Observations on
the Etymology of the word Sublimis. By GEORGE
DUNBAR, A. M. F. R. S. E. Professor of Greek in
the University of Edinburgh, - 349

XXVII. Results of the Thzrmometrical Observations made
at Leith Fort, every Hour of the Day and Night,
during the whole of the Years 1824 and 1825.
By DAVID BREWSTER, LL.D. F. R. S. Lond. &
Sec. R. S. Ed. Corresponding Member of the
Academy of Sciences of Paris, &c. 362

XXVIII. A Historical and Critical Introduction to an In-
quiry into the Revival of the Greek Literature in
Italy, after the Dark Ages. By PATRICK
FRASER TYTLER, Esq. F. R. S. E. & Sec. Lit.
Class, 389

CONTENTS. IX

Page

XXIX. On the Refractive Power of the Two New Fluids in
Minerals, with Additional Observations on the
Nature and Properties of these Substances. By
DAVID BREWSTER, LL.D. F. R. S. Lend., Sec.
Ri 8^ Edin.;, and Corresponding Member of the
Academy of Sciences of Paris, - 407

XXX. Observations on Two Species of Pholas, found on

the Sea coast in the neighbourhood of Edinburgh,
By JOHN STARK, Esq. M. W. S. Communica-
ted by Dr BREWSTER, - 433

XXXI. Description of a new Register Thermometer, with-

out any Index >• the principle being applicable to
the most delicate Mercurial Thermometers. By
H. H. BLACKADDER, Esq. F. R. S. E. , 440

XXXII. On a new Photometer, founded on the Principles
of Bouguer. By WILLIAM RITCHIE, A. M.
Rector of Tain Academy. Communicated by
Dr BREWSTER, - 443

HISTORY OF THE SOCIETY, - 447

Laws of the Society, enacted 23d May 1811, and altered
6n the 26th February 1820, 24th January 1823, 13th
January 1824, and 9th January 1826, _ 449

List of the Office-Bearers and Members elected since
March 3. 1823, - _ _ 457

List of the present Ordinary Members of the Society in
the order of their election, - r> _

CONTENTS.

Page

List of Non-resident and Foreign Members, elected under
the old Laws, 475

List of Honorary and Foreign Members, elected under
the new Laws, 476

List of deceased Members, and of Members resigned, from

1823 to 1826, 478

PRESENTS received by the Society since 1822, 479

I. On the Existence of Two New Fluids in the Cavities of Mine-
rals, which are immiscible, and possess remarkable Physical
Properties. By DAVID BREWSTER^ LL.D. F. R. S. Lond. &

Sec. R. S. Edin.

TER.

' '

(Read March 3. and 17. 182SJ

JLN the year 1818, my attention was accidentally directed to the
subject of water in crystallised bodies, by the explosion of a crys-
tal of Topaz, which I had exposed to a red heat, for the pur-
pose of expelling its colouring matter. This violent disruption
of the specimen, which was shivered into a thousand films, of ex-
treme tenuity, arose from the expansion of the imprisoned fluid,
and induced me to institute a series of experiments, for the pur-
pose of determining the nature of the fluid, the form of the cavi-
ties which contained it, and the arrangement of these cavities in
reference to the crystalline form of the mineral *.

Small portions of fluid had been long ago observed by mine-
ralogists in Topaz, Rock-Crystal, and Fluor-Spar. Mr SIVRIGHT
found them also in Calcareous Spar, Sulphate ofBarytes, and Sul-
phate of Lime; and I detected them in the Emerald, in Beryl,

* An account of these experiments was announced for publication in 1819, in
the 1st Number of the Edinburgh Philosophical Journal; but the desire of ob-
taining more general results prevented me from publishing it at that time.

VOL. X. P. I.

2 DR BREWSTER on the Existence of Two New Fluids

Cymophane, Peridot, Feldspar, and in the following crystals form-
ed by aqueous solution.

Sulphate of Iron. Sulphate of Ammonia and Magnesia.

Sulphate of Zinc. Nitrate of Silver.

Sulphate of Copper. Nitrate of Strontian.

Sulphate of Nickel. Muriate of Barytes.

Sulphate of Soda. Acetate of Lead.

Sulphate of Magnesia. Oxymuriate of Potash.

Sulphate of Ammonia. Muriate of Barytes.

Sulphate of Magnesia and Iron. Oxalic Acid.

Sulphate of Soda and Magnesia. Tartrate of Potash and Soda.

Sulphate of Alumine and Ammonia. Carbonate of Potash.

Being persuaded, from these results, .that water will be found
in every crystal deposited from a solution, I was next desirous of
finding it in crystals formed by heat, or by sublimation ; but in
no case have I been able to discover the slightest trace of its ex-
istence ; and, in the absence of all other information on the sub-
ject, I considered this result as highly favourable to the aqueous
origin of those minerals in which water has been discovered.

Sir HUMPHRY DAVY was, we believe, the first philosopher
who conceived the idea of opening the cavities of crystals, and of
examining chemically the nature of the fluid which they contain,
and of the gas by which it is sometimes accompanied ; and the
experiments which he undertook for this purpose, were con-
ducted with that sagacity and address which characterise all his
labours. Upon opening the cavities in a variety of rock-crystals
of different localities, and collecting the fluids in fine capillary
tubes, he discovered, that, in every case, except one, the fluid
was Water nearly pure ; — that, in this single case, it seemed to
be Naphtha ; — that the gas was in two cases Azote, and was about
65 times more rare than that of the atmosphere ;— that, in one
case, the gas (the nature of which is not mentioned) was compres-

in the Cavities of Minerals. 3

sed about 10 times more than atmospheric air ; and that in the
naphtha cavity there was almost a perfect vacuum *,

Such was the state of the subject, when my attention was
again turned to the examination of these cavities.

In resuming this enquiry, I have been fortunate, not only in
possessing many excellent specimens of my own, but in having
the free use of an interesting collection, belonging to Mr Siv-
RIGHT of Meggetland ; and though I have employed only the
microscope, and the agency of heat and of light, I have been led
to results of considerable generality and interest. This physical
method of determining the properties of minute quantities of
matter, though often very difficult, and sometimes perplexing in
its manipulations, carries with it a degree of evidence not infe-
rior to that of chemical analysis ; while it possesses the advantage
of examining the substance in its original and unchanged condi-
tion, and may be applied, in many cases, where the chemist can-
not avail himself of any of the resources of his art.

When the cavities in crystals are very large, which seems to
be the case principally when they contain water, the elegant me-
thod pursued by the distinguished President of the Royal Socie-
ty of London will afford precise results, and may be expected to
add greatly to our knowledge of this mysterious subject. Lea-
ving, therefore, this branch of the enquiry in the skilful hands of
Sir HUMPHRY DAVY, I have pursued the subject under a more
general form, and have studied the phenomena in their various
relations to the principles and methods of general physics.

Philosophical Transactions, 1822, p. 367.
A 2

4 Da BREWSTER on the Existence of Two New Fluids

SECT. I. On the Existence of a New Fluid in the Cavities of

Minerals.

In examining the cavities of crystallised bodies, I observed
the most striking difference in the phenomena presented by the
fluids which they enclosed. Impressed with the opinion that
the fluid was water, I tried every method of explaining, upon or-
dinary principles, the phenomena which were thus presented to
me, but the results of a more minute examination were incom-
patible with such a supposition, and rendered it necessary to
ascribe them to new fluids, possessing new physical properties.
In order to convey to the Society a correct idea of the methods
of observation, and the train of reasoning by which I was led to
this conclusion, I shall give a detailed account of the pheno-
mena, as exhibited in different minerals.

1. Topazes from New Holland, Scotland, and Brazil

As the cavities in the New Holland topazes are frequently
arranged in strata parallel or slightly inclined to its most eminent
cleavage, or the one perpendicular to the axis of the prism, they
are peculiarly fitted for carrying on this enquiry. The facility
with which this mineral may be split, allows us to dispense with
the aid of the lapidary, and to study the phenomena through
perfectly flat and highly polished surfaces.

In examining these specimens with the microscope, we ob-
serve the cavities arranged in strata. These cavities are some-
times beautifully crystallised, and sometimes amorphous, some-
times extremely shallow, and at other times deep. They have
often the shape of long canals, with parallel sides and round

in the Cavities (/Minerals. 5

terminations, and at other times their form is not far from that
of a circle.

The cavities now described, are filled with a colourless and
transparent fluid, as shewn at ABCD, Fig, 1. Plate I., and have
almost always a vacuity V, of a circular form, which moves by an
inclination of the plate to different parts of the cavity. The
depth of the cavity may be easily estimated, by the breadth of
its bounding line ABCD, which, in the flat cavities, is generally
the same as that of the circle V. In very shallow cavities, this
boundary is a narrow line, scarcely visible, and in deep ones it is
broad, with a penumbral termination inwards, arising from the
deviation of the light at the separating surfaces of the fluid and
the topaz, and at that of the fluid and the vacuity.

When the hand is applied to the crystal, the heat of it gra-
dually expands the fluid. The vacuity V consequently dimi-
nishes, and being in a short time reduced to a physical point, it
entirely disappears. When the fluid again cools, by withdraw-
ing the hand, it of course contracts, and quits the sides of the
cavity. The vacuity V reappears, increasing till it resumes its
former magnitude ; and it deserves particular notice, that the
evanescence and reappearance of the vacuity takes place simul-
taneously in many hundred cavities, of the same general form,
which may be seen in the field of view.

In order to obtain an accurate measure of the temperature
at which the vacuity reappears, which is almost the same as that
at which it vanishes, I plunged the topaz in heated water, and
by means of an accurate thermometer, I obtained the following
results :

\r A fAi n •*• Temperature at which the

Nature of the Cavities.

Vacuity reappeared.

1. Topaz from New Holland, with shallow cavities, 74 |° Fahr.

{74
77
78 \
82

6 DR BREWSTER on the Existence of Two New Fluids

\r 4 ffi. n '4- Temperature at which the

Nature of the Cavities.

Vacuity reappeared.

8. Colourless Topaz from Brazil, with only one
cavity j^th of an inch long, 5]gd of an inch
broad, and ?\th of an inch wide, 79 §

4. Topaz from New Holland, with large and

rugged cavities, 79 £

5. Topaz from New Holland, with a very flat

cavity, 81 |
A very long and very irregular cavity in the

same crystal, 82 i

6. Another colourless Topaz from Brazil, 83 j

7. Another colourless Topaz from Brazil with a deep cavity, 83 f

The reappearance of the vacuity at different temperatures in dif-
ferent cavities of the same crystal, admits of an easy explana-
tion. In those which are of the same size and form, and equi-
distant from the cooling surface, the vacuities disappear at the
same time ; but in those which are deep, and in those which,
though shallow, are near the cooling surface, the vacuities reap-
pear at a lower temperature. In very shallow cavities, the ad-
hesion of the fluid to the sides of the cavity prevents the va-
cuity from reappearing so soon as it would otherwise do ; while
in cavities that have a rough or irregular bottom, they reappear
earlier.

When the cavities are very small and narrow, only one va-
cuity reappears ; but when they are large, several small circular
vacuities make their appearance, and gradually unite into one,
though sometimes they remain permanently separate. When
the cavities are deep, a very remarkable phenomenon accompa-
nies the reappearance of the vacuity. At the instant that the
fluid has acquired the temperature at which it quits the sides of
the cavity, a rapid ebullition takes place, and the transparent ca-
vity is for a moment opaque, with an infinite number of minute

In the Cavities of Minerals. 7

vacuities, which instantly unite into one vacuity, that gradually
goes on enlarging as the temperature diminishes.

In order to determine the expansion which takes place by a
given increment of temperature, I measured the relative size of
the vacuity, and the cavity at the temperature of 50° and 80°,
the temperature at which the fluid had expanded so as wholly
to fill the cavity. In many cases this could be estimated with
tolerable accuracy, and it may be stated in general, from the esti-
mates and measures taken by myself, and by others, to whom I
shewed the cavities, that the fluid expands fully one-fourth of its
size, by an increment of 30° of heat.

Hence, since water expands ^Vd °f its Dulk in passing from
41°, its state of maximum density, to 212°, it will expand -fi^th
of its bulk for 30°, and T£T -r- £ = 31£ ; that is, the fluid con-
tained in the cavities is above 30 times more expansible than
water, by an increment of 30° of heat at the temperature of 50°.

This extraordinary result proved beyond a doubt, that the
substance contained in the cavity was a new fluid, differing from
all known fluids in its high expansibility, and resembling in this
respect a gaseous more than a fluid body.

In order to confirm this result, I was desirous of examining
the other physical properties of this remarkable substance. I
could not fail to notice, in the deep cavities especially, the singu-
lar volubility of the fluid, and its slight adherence to the sides of
the cavity, as indicated by the motion of the vacuity V. In
small cavities containing water, the adhesion of the fluid to the
stone is so strong, that the air-bubble moves with extreme diffi-
culty, and even when very large, it often changes its place by
starts, or remains stationary at the bottom or in the middle of
the cavity. In the present case, however, the vacuity moved
about with great facili ty, and in the cavity, ^th of an inch long,
by TaTth and TVd of an inch wide and deep, the slightest tap of the

8 DR BREWSTER on the Existence of Two New Fluids

finger on the microscope caused the air-bubble to tremble and
oscillate in this miscroscopic level. Hence the new fluid is dis-
tinguished by a second physical property, no less remarkable than
the first.

Although I now entertained no doubt of the accuracy of the
conclusion, that the fluid was a new one, yet I conceived it
might be possible to obtain at least an approximate measure
of its refractive power, and thus to put its novelty beyond the
reach of a doubt. In order to do this, it became necessary to
observe the manner in which the total reflexion of the upper
surface of the cavity was modified by the contact of the fluid,
and, if possible, to measure the angle at which total reflexion was
effected, by the separating surface of the fluid and the solid. For
this purpose I took a plate of topaz AB, Fig. 2., with a stratum
of cavities m ri, perfectly parallel to the natural surface of the
plate. I then placed upon each surface the rectangular prisms
ABC, ABD, and introduced between them a thin film of oil of
cassia. Rays of light RS, RS were then allowed to fall upon the
stratum of cavities m n, so that the rays reflected from the upper
surface of the cavity could be examined by a microscope whose
object lens is LL. Upon making this arrangement, the stratum
of cavities was seen in the most beautiful manner. The vacuity
V, Fig. 3. of a cavity seen in this way, shone with all the bril-
liancy of total reflexion, the separating surface of the new fluid
ABCD, and the cavity, exhibited a faint grey tint, while the sur-
rounding portions of the solid topaz were comparatively black.
The variations which the vacuity V undergoes by heat are now
finely seen, and at a temperature of 80° it vanishes in a brilliant
speck, leaving the whole of the cavity ABCD of the same uni-
form tint as in Fig. 4.

The phenomena now described are not so distinctly seen
when the stratum m n is deeply seated beneath the surface of

m tlie Cavities of Minerals. 9

the topaz, in consequence of the duplication and overlapping of
the images formed by double refraction.

This inconvenience, however, may be nearly removed, by ma-
king the plate of topaz very thin ; or it may be entirely reme-
died, in plates of any size, by causing the incident rays RS RS,
Fig. 2., to pass along one of the resultant axes of the topaz, while
the reflected rays SL SL pass along the other resultant axis.

In order to compare the angle at which. total reflexion took
place at the upper surfaces of the fluid and the cavity, with that
which would have taken place had the fluid been water, I placed
a drop of water on part of the lower surface of the plate AB,
and I found that the light reflected at the same angle of inci-
dence, was much more brilliant from the separating surface of
the new fluid and the cavity, than from the separating surface of
the topaz and the water, a result which indicated, in the most
unequivocal manner, that the new fluid had a refractive power
inferior to water, and that it differed in this respect from every
other known fluid.

Although, in this estimate, I attended carefully to the cir-
cumstance, that, in the one case, the light reflected from the
bottom of the cavity was combined with that reflected from its
surface, and therefore used deep cavities, where the two re-
flexions could to a certain degree be separated ; yet, in order to
remove any doubt that might remain on the subject, I took a
plate of topaz that contained water, or, to speak more correctly,
a fluid which did not expand by heat, and upon comparing the
reflexions from the cavities, the difference was most palpable.

In one specimen I measured the difference between the
angles of incidence at which total reflexion took place, at the
separating surface of the new fluid and topaz, and at the separa-
ting surface of water and topaz, and I estimated that the re-
fractive power of the new fluid was below 1.300, that of water
being 1.336.

VOL. X. P. I. B

10 DR BREWSTER on the Existence of Two New Fluids

In one specimen of Amethyst I was enabled to determine,
that the angle of total reflexion took place at 51° 26', and, con-
sequently, that the refractive power of the Fluid, or m, was —
m' + sin 51° 26' — 1.21066, m' being taken equal to 1.5484, the
ordinary refractive power of Amethyst.

Many other details might have been added under the present
head, in support of these conclusions ; but they are necessarily
reserved for the next section, with which they have a more im-
mediate connection.

2. Cymophane or Chrysoberylfrom Brazil.

In several specimens of this mineral I have discovered strata
of cavities, which contain the new fluid. One of these is re-
markable for having two strata parallel to one another ; one of
which, about yth of an inch square, contains no fewer than 30,000
cavities, filled with the new fluid, which expands and fills the
cavity with the heat of the hand. The cavities are in general
very small ; but I succeeded in determining that the vacuities all
reappear simultaneously, at a temperature of

3. Quartz-Crystals from Quebec.

In examining the crystals of quartz from Quebec, I have
found that almost every specimen of it contains cavities with the
new fluid.

In one crystal the vacuity reappeared at 76°. Another va-
cuity in the same crystal reappeared at 80° ; while another, al-
most in contact with this, required a temperature of 125° to
make the fluid fill the cavity.

: In another specimen of the crystals there are cavities where
the new fluid expands fully ^d of its bulk, by an additional tem-
perature of 30° ; and though they are very shallow, the vacuities
reappear in the form of several smaller vacuities, and exhibit an
appearance as if the fluid were thick and viscid.

in the Cavities of Minerals, 11

While I was applying a heat not above 170° to some of these
specimens, they frequently leapt from the plate of glass on which
they lay, and at other times threw off, with an explosion, consi-
derable fragments. In one of these experiments, I was fortunate
enough to observe a phenomenon which will be considered a
very remarkable one. When the compound microscope was ad-
justed to a distinct view of a stratum of globules containing the
new fluid, but particularly to a vast number of minute specks,
which the microscope had not power to resolve, a heat of about
150°, which happened to be applied to the specimen, produced
a sort of crackling noise, which arose from the bursting of the
cavities near the surface. Upon looking into the microscope, I
was astonished to observe a great number of darkish brown glo-
bules rising through the solid quartz, like globules of air in wa-
ter. In examining them more minutely, I observed, as shewn
in Fig. 5., that they took their origin from the minute specks or
cavities, which gradually enlarged and went off in the form of a
globule. This phenomenon lasted fully five minutes, when the
specimen burst into two or three pieces. While examining the
cavities of one of the fragments, I found that several of the large
ones, with flat faces, had been emptied of their contents, through
a fissure parallel to their flat faces, and that the faces of the fis-
sure had closed up, so as to transmit a brownish light, while a
bright light was freely transmitted through the polished faces of
the cavities as shewn in Fig. 6 *.

Had only one of the cavities shewn in Fig. 6. existed, the
fluids which it contained might have escaped through a narrow
fissure, not wider than its own breadth ; and this narrow fissure

' In a specimen of Topaz which split in the fire, I found that a quantity
of the new fluid had got into a fissure, where it has been permanently detained
without reaching the surface. It exhibits the same brown tint as the globules, at

particular inclinations.

*

12 DR BREWSTER on the Existence of Two New Fluids

might, in virtue of the elasticity of the stone, have closed up
completely, so as to transmit the light as freely as if it had never
existed. This process is by no means a hypothetical one. I
have repeatedly formed these fissures in glass, and have some-
times seen them close up in a few minutes, without leaving a
trace of their existence behind. When they are wide, a day, a
week, and sometimes a month was necessary, to effect the re-
union of their sides *.

These circumstances enable us to give a satisfactory expla-
nation of the remarkable phenomenon represented in Fig. 5.
When the expansive force of the imprisoned fluid was sufficient
to make it penetrate the stone, it would probably escape at the
weakest point of the cavity, and pass to the surface through a
narrow channel, which the elasticity of the stone would imme-
diately close up. These fissures would probably he in the di-
rection of the cleavage, and this seemed to be the path which
the globules took in their oblique ascent, as represented in
Fig. 5,

4. Amethyst from Siberia.

The greatest quantity of the new fluid which I have yet
seen, exists in a specimen of Amethyst belonging to THOMAS
ALLAN, Esq. This very interesting specimen is represented in
Fig. 7., where a, b, c, d, e, represent five cavities parallel to each
other. The largest of these is |f of an inch in length, and ^yth
of an inch in breadth ; and the vacuity is about one-fourth part
of the whole cavity. By the heat of the hand the fluid swells,
and fills all the cavities, and when the vacuity has been consi-
derably reduced by heat, it moves from one end of the cavity to
the other, with a degree of volubility truly surprising. By a

* A full account of these experiments will be found in the Philosophical Trmt-
sactwns for 1816, p. 73.

in the Cavities of Minerals. 18

careful experiment, I found that the vacuity disappeared at a
temperature of 83^° ; and when it was made to reappear by ra-
pid cooling, an ebullition took place, as in the deep cavities of
topaz.

As the cavities in this specimen were terminated with cry-
stallised summits at a, b, c, d, I was enabled to observe a curious
optical phenomenon, which accompanied the expansion of the
fluid. Whenever the vacuity was so much reduced by the ex-
pansion of the fluid, that it could be made to occupy one of the
crystallised summits, and afterwards to vanish, it left behind it,
on that summit, a system of beautiful concentric coloured rings,
which were constantly varying in tint, in diameter, and in num-
ber. These rings had the highest order of colours in their cen-
tre, and continued while the fluid preserved its expanded state ;
but they invariably disappeared when the fluid was allowed to
contract by cold, as if the substance which formed them had as-
sumed a gaseous form, and entered into the vacuity.

SECT. II. On the coexistence of two Immiscible Fluids, of different
Physical Properties, in the Cavities of Minerals, and accom-
panied with a vacuity.

Although many of the cavities which have been described in
the preceding section, contain only the new fluid, yet in a very
great number, particularly in Topaz, another phenomenon pre-
sents itself, which requires a very minute examination. This
phenomenon, as exhibited in Topaz, is represented in Figures 8,
9, and 10, where V is the vacuity, NNN the new fluid, and
WWW another fluid, which we shall distinguish by the name
of the Second Fluid. This second fluid WW commonly occupies
the angles of triangular cavities, as in Fig. 8., or the terminations
of longitudinal ones. It is always separated from the new fluid
by a curved surface m n, m n, &c. It never expands perceptibly

14 DR BREWSTER on the Existence of Two New Fluids

with heat, and never mixes with the new fluid NN. By a little
management, the vacuity V may be made to come in contact
with the bounding lines mn,mn, &c. ; but it never affects its
curvature, and seldom enters the fluid W. When the vacuity
V has been made to vanish by heat, these bounding lines remain
exactly the same.

Having at first observed this second fluid only in the angles
of cavities, as in Fig. 8., I experienced considerable difficulty in
establishing its fluidity. The improbability of two fluids exist-
ing in a transparent state, in absolute contact, without mixing
in the slightest degree, induced some of my scientific friends
to refer it to an optical illusion, and to consider the line which
separated it from the new fluid as a septum or partition in the.
cavity. The beautiful curvature of the bounding line, and its
perfect similarity to that of two contiguous fluids, rendered
this conjecture untenable. It was next supposed to be a va-
cuity into which the new fluid could not expand itself; but
though this idea explained the curvature of the bounding line,
it was inconsistent with other facts, and especially with the im-
portant one, that the second fluid acted upon light neither like
topaz nor a vacuum, but like water.

These difficulties were gradually overcome by more numerous
observations.

Although the cavities were generally like those in Fig. 8.,
where V is the vacuity, NN the new fluid, and WW the sup-
posed second fluid; yet I found several in which the second
fluid filled a great part of the cavity, as in Fig. 9., where NN is
the new fluid, and W the second fluid, or as in Fig. 10., where a
vacuity V also appeared within the globule N of the new fluid.

This great enlargement in the quantity of the second fluid,
removed most of the difficulties which had formerly presented
themselves ; but something was still wanting to prove its fluidity.
This desideratum was fortunately obtained in a specimen of to-

in the Cavities of Minerals. 15

paz belonging to Mr SIVRIGHT. In examining this specimen, I
observed a very remarkable cavity, of the form shewn in Fig. 11.,
where A, B and C are three separate portions of the new fluid,
insulated by the interposition of the second fluid DEF. The
first portion A of the new fluid had four vacuities V, X, Y, Z,
while the other two portions B, C, had no vacuity. Having of-
ten succeeded in making the vacuities pass from one branch of a
cavity to another branch, I did not doubt that the vacuities of
the portions B and C had passed over the second fluid into the
portion A. In order to determine this, I took an accurate draw-
ing of all the phenomena at a temperature of 50°, as represented
in Fig. 11., and I carefully watched the changes which took place,
by raising the temperature to 83°. The new fluid at A gra-
dually expanded itself, till it filled up ah* the four cavities V, X,
Y, Z ; but as the portions B, C, had no cavities for this purpose,
they could only expand themselves, by pushing back the sup-
posed second fluid DEF. This actually happened. The second
fluid quitted entirely the edge of the cavity at F. The two
portions of new fluid B, C, were immediately united into one ;
and the second fluid having retreated to its new limit mnn'o, and
being itself but slightly expansible, h'ke common fluids, its other
limit necessarily advanced to p q r. This experiment, which I
have often repeated, and shewn to others, involves one of those
rare combinations of circumstances, which Nature sometimes pre-
sents to us, in order to lay open some of the most mysterious of
her operations. Had the portions B, C, of the new fluid been
accompanied, as is usual, with their vacuities, the interposed se-
cond fluid would have remained immoveable between the two
equal and opposite expansions : but from the accidental circum-
stance of these vacuities having passed over into the other branch
A of the cavity, the second fluid is placed in a sort of unstable
equilibrium, and, h'ke the arms of a lever, it yields to every varia-
tion of the power and of the resistance.

16 DR BREWSTER on the Existence of Two New Fluids

If any additional evidence were wanted on this subject, we
have only to examine the mode in which the two portions of the
new fluid B, C, are united into one by a disunion of the second
fluid at g h, arid again separated by its reunion. Upon the ap-
plication of heat, the summits g, h, become more acute, and gra-
dually approach to each other, till they suddenly unite, and
force back the surface of the second fluid into the line m n n' o.
A portion of the second fluid, however, is retained by capillary
attraction, in the angular meeting of the planes, between c and
F, and between d and F, and also a small portion at^ a pheno-
menon which affords an ocular explanation of the immobility of
the second fluid in the terminations and angles of cavities.
When the fluids again cool, the surface n n' approaches to c d,
and when n is near c, the surface n n' of the second fluid and
that of the same fluid in c d, suddenly start into union, in virtue
of their mutual attraction, and the portions B and C are again
separated.

By allowing the specimen to rest in particular positions, I
have often driven part of the vacuity V towards X, so as to unite
all the three vacuities X, Y and Z into one ; and in like manner
I have caused the vacuities Y, Z and part of X to disappear and
unite with the vacuity V.

In order to examine the refractive power of the second fluid,
I made the arrangement represented in Fig. 2., and found that
the second fluid W always reflected less light than the new fluid,
and consequently that its refractive power approached nearer to
topaz than the new fluid. By the same means I determined,
that the angle at which total reflection took place at the separat-
ing surface from the topaz, was very nearly the same as if the se-
cond fluid were water.

The fortunate circumstance of the cavities B, C, being without
a vacuity, and the consequent mobility of their bounding lines
a b c, d ef, enabled me to compare the optical properties of the

in the Cavities of Minerals. 17

two fluids, by means of transmitted light. The sides of the ca-
vity being inclined to one another, like those of a prism, it is
manifest, that if a b c is the boundary of two fluids of equal re-
fractive power, the image of a luminous object will have the
same deviation, by the refraction of both. As the cavity, how-
ever, is too minute to permit an image to be distinctly seen
through it, it becomes necessary to look with a microscope at
the illumination of the surface of the cavity, and if the two re-
fractive powers are equal, the portion above a b c will be dark,
when the portion below it is dark, and vice versa. I found, how-
ever, that the portion of fluid B a b c was often dark, when the
second fluid below a be was light, and I therefore concluded that
this arose from their unequal refraction. To this conclusion it
may be objected, that the inclination of the refracting faces
might accidentally be different behind B a b c, although it is not
likely that the portion possessing this difference of inclination
would be bounded by a curve line a b c. I therefore applied heat
to the specimen, and, by expanding the new fluid at B and C,
the bounding lines were made to move from a be, def, to mnn'o,
and I remarked, that, during this change of position, the boun-
dary of the two fluids was always the boundary of the unequal
shades produced by unequal refraction.

As the arrangement of the fluids which enabled me to make
these experiments, possesses a peculiar interest, I have carefuUy
looked for similar cavities, but I have not succeeded in finding
more than a few examples, one of which is represented in
Fig. 12., as it appears at the temperature of 32°. This cavity
consists of two wide portions, separated by a narrow channel.
The new fluid occupies the portion between cc, dd, and also that
between a a and b b, these two portions being separated by the
second fluid dd, a a. The whole vacuity exists at V. If we now
apply heat, the new fluid at N and N expands, and the bounda-
ries dd, a a and b b, advance towards B. The vacuity V becomes
VOJL. x. P. i. c

18 DR BREWSTER on the Existence of Two New Fluids

an elliptical bubble, and finally vanishes. When this takes place,
the boundary b b has of course disappeared, and d d and a a
have advanced to d'd' and a! a', and c c is invisible, in conse-
quence of the new fluid having spread over it, as it were, in the
manner described in the following section.

Another cavity, consisting of three separate portions, AB,
CDE, FGHK, is shewn in Fig. 13., and is remarkable, in conse-
quence of each of these masses being connected with the ad-
jacent one, by a portion of the second fluid, which moves be-
tween them like a piston through the extremely narrow chan-
nels BC, EF. As the portion of new fluid between a b and ef
expands without having an air-bubble, it pushes the portion of
the second fluid B a b through BC into C a' b'. In like manner,
the second fluid c c? EF c' d varies its position with the expan-
sion of the fluids on each side of it. When the vacuity V dis-
appears, a portion of the second fluid shews itself in the space
D k h, and it again withdraws itself when the vacuity V touches
the sides of the triangular cavity.

In some cavities where there is a large proportion of the se-
cond fluid, the vacuities sometimes form two-thirds and even
three-fourths of the space occupied by the expansible fluid when
the cavity is full, and yet these vacuities are filled at the usual
temperature of 83°. In these cases, the circular vacuity did not
contract by heat, but extended itself till it disappeared. This
effect admitted of an easy solution, by supposing the surface of
the fluid to rise gradually by expansion ; but I found, by opti-
cal observations, that the vacuity occupied the whole thickness
of the cavity, and that it vanished by extension, when it was
held in a vertical direction. This remarkable fact will be fully
explained in the 5th section.

In some specimens, the faces of the cavities are accidentally
inclined to the surfaces, nearly at the angles of total reflection
from the surface of the new fluid, so that all the part of the ca-

in the Cavities of Minerals. 19

vity which it occupied appears of a brownish-blue colour, while
the part occupied by the second fluid is perfectly transparent.
This phenomenon explains, in many cases, the apparent opacity
of the cavities, which become perfectly transparent by inclining
the specimen. When the stratum of cavities is very much in-
clined, all of them appear like black specks, and hence they have
been generally considered by lapidaries as opaque particles.

Two immiscible fluids, possessing the properties now descri-
bed, exist also in Quartz, Amethyst, and Cymophane, and I have
reason to conclude that the one never occurs without the other,
as I have in almost every case discovered the second fluid in ca-
vities, where the difficulties of observation had at first prevented
me from detecting it.

SECT. III. On the Phenomena of Two Immiscible Fluids without
a Vacuity in the Cavities of Minerals.

The preceding results conduct us gradually to the develop-
ment and explanation of phenomena, which, had they been ob-
served alone, would have occasioned no inconsiderable per-
plexity.

In the same specimen of topaz, I have noticed the two classes
of cavities which form the subject of the two preceding sections ;
and, along with them, I have likewise found a third class, such
as AB, Fig. 13., which differs in no respect from those of the
first class, shewn in Fig. 1., when examined by the microscope
alone. Their difference, however, becomes very manifest by the
agency of heat and light.

When heat is applied to these cavities, the circular space N,
Fig. 14., in place of diminishing, as it does in Fig. 1., actually
increases, as in Fig. 15., as if the fluid WW had contracted with

c 2

20 DR BREWSTKR on the Existence of Two AVw Fluids

heat. This perplexing fact induced me to examine the cavity
under the circumstances of total reflexion, and it was then ap-
parent, that N was neither a vacuity nor a space filled with gas,
but a portion of the new fluid floating as it were on the second
fluid WW.

This phenomenon was analogous to what takes place in
the right hand portion of the cavity in Fig. 11.; but, as there
were here no vacuities into which the expansion of the new
fluid could push the second fluid, the difficulty remained un-
solved.

It may be proper to mention, that the cavities which present
this phenomenon are most frequently connected by a dark line
with other cavities, accompanied with vacuities, as shewn at N,
in Fig. 16, and 17. In Fig. 16., by a considerable cold, I have
caused a small vacuity to appear at V ; but it sometimes remains,
and sometimes disappears.

As there are cavities, however, such as that in Fig. 14., where
no connection can be traced with other cavities, and where the
fluid N seems to expand, and WW to contract, it is necessary to
seek for some explanation of this singular anomaly. That the
expansions and contractions are here only apparent, cannot, we
think, be doubted. Let AB, therefore, Plate II. Fig. 18. be a
section of the cavity in Fig. 14., where the new fluid NN floats
as it were on the other. When NN is heated, the effect of the
heat will tend to diminish the cohesive force of the fluid WW,
and to make the fluid WW spread itself into a thinner film, as
shewn in Fig. 19., so that it seems to occupy a greater space, as
shewn in Fig. 15.

In support of this explanation, I may adduce the case of other
cavities in topaz, such as those shewn in Figs. 20. and 21., where
the globule N of the new fluid never expands with heat, — an
effect which is probably owing to its occupying the whole thick-

in the Cavities of Minerals. 21

ness of the cavity, and not a portion of that thickness, as in

Fig. 18 *.

With the view of confirming this explanation, I took a cavity
AB, Fig. 22., in which the new fluid N occupied the whole 01
one side of the cavity, and the second fluid W the whole of the
other side. Having made the vacuity vanish, and increased the
heat to about 200°, the effect of this was to expand N, and make
the boundary a b move very slowly towards A ; but in a short
time, a portion of the fluid W, which had thus been pressed out
along the bottom of the cavity, made its appearance at the end
B, and gradually increased in quantity as a b moved towards A.
The new fluid then occupied the space between the dotted lines
c d and ef, which contained a greater area than the space be-
tween a b and B. The portion efB of the second fluid remained
for two hours in the position shewn in the figure ; but being
connected below N with the other portion cdA, it was drawn
over to the other side, and occupied its original position, as
shewn by A a b.

In one of the Quebec crystals of Quartz, where the cavities
are filled with a slightly yellowish fluid, I observed a very deep
cavity, such as that shewn in Fig. 23., where the globule N ex-
panded very considerably to the width of n n by a considerable
heat. I sought in vain for a vacuity, which, however, might
have been concealed in a cavity of such a depth, and of such ir-
regularity of surface ; but, upon plunging the crystal in hot wa-
ter, and applying the microscope, I observed two very minute
globules, either of vacuity or something else, floating within N,
which gradually diminished and disappeared. During another

* In Figs. 20. and 21. there are small squares, such as S, S, within the cavities,
which seem to be filled up with crystallized matter. These squares being sometimes
united only by contact with the surface of the cavity, exhibit very brilliantly the
colours of thin plates.

22 Du BREWSTER on the Existence of Two New Fluids

experiment with this crystal, one of the cavities burst, with a
heat not above 150°, and the fracture round the cavity was co-
vered with specks of an inspissated fluid *.

The formation of cavities with two fluids, and without any
vacuity, admits of an easy explanation, when they are connected
with other cavities, as in Figs. 15. 16., as there can be no doubt,
from the phenomena already described, that part of the fluid W
has passed through the narrow channel which connects the cavi-
ties. When the cavities, however, are entirely insulated, the ex-
planation is more difficult.

SECT. IV. On the Changes which these Fluids have undergone in

particular Crystals.

In the absence of all information respecting the nature and
constitution of these fluids, it becomes interesting to ascertain,
whether time, or accidental causes, have produced any per-
ceptible changes in their physical properties. With this view, I
have examined an immense variety of specimens, and have been
led to results of considerable interest.

In some specimens of topaz containing the two fluids, I have
observed several cavities in which the new fluid N is quite
opaque, as at a, Fig. 24., and others in which it has the appear-
ance shewn at b.

There are some cavities, such as that shewn at c, where
the fluid seems to have left a crust, lining the interior of it,
and there are others where a sort of black farinaceous matter
appears, both within and around the cavities, that appear to
have been burst by some accidental cause.

This crystal is the one referred to in page II.

In the Cavities of Minerals. 23

? The most unequivocal proofs, however, of a change in the
fluid, are obtained from various topazes, where the induration of
the fluid is perfectly obvious to the eye. It resembles a resinous
substance, and has a sort of cellular structure, like that shewn
at d, Fig. 24., where the vacuity retains its circular form. No
change whatever is produced upon these appearances by heat.
In the figure at e, the fluid N, with its vacuity V, still exists,
and the latter vanishing with heat ; but the induration is dis-
tinctly seen at the lower end of the cavity.

In other specimens the same cellular structure appears, but
the vacuity has lost, in different degrees, its circular form, as
shewn atf. ,•?

Similar phenomena occur in cymophane and felspar, in the
last of which the induration of the fluid is most distinct

SECT. V. On the Vaporisation and Decomposition of the New
Fluid at low Temperatures, when enclosed in the Cavities of
Minerals.

Let ABCD, Plate II. Fig. 30. be the summit of a crystallised
cavity in topaz, and let the length of the cavity be in a vertical
direction, so that SS is the second fluid, NN the new fluid,
bounded by a circular line abed, and V the vacuity in the new
fluid, bounded by the circle efgh. Let the face ABCD be
placed under a compound microscope, so that the rays of a lumi-
nous body incident upon it, may be reflected at an angle less than
that of total reflexion. When the observer now looks through
the microscope, the temperature of the room being 50°, he will
see the second fluid SS shining with a very feeble reflected light,
the new fluid NN with a light perceptibly brighter, and the va-
cuity V V with a light of considerable brilliancy. The boundaries
abed, efgh, are marked by a well defined outline, and also by

24 DR BREWSTER on the Existence of Two New Fluids

concentric coloured rings of thin plates, produced by the extreme
thinness of each of the fluids at the edges.

If we now raise the temperature of the room gradually to
58°, we shall observe a brown spot appear in the centre of the
vacuity V. This spot marks the visible commencement of eva-
poration from the new fluid below, and arises from the attenuated
vapour which attaches itself to the roof of the cavity. As the
heat increases, the brown spot enlarges, and becomes very dark.
It is then succeeded by white, and one or more rings rise in the
centre of the vacuity. The vapour then seems to form a drop,
and all the rings disappear, by retiring to the centre, but only to
reappear with new lustre. During the application of heat, the
circle efgh is in a state of constant contraction and dilatation,
like the pupil of the eye when exposed to light, being always
greatest when the rings disappear, and contracting its dimensions
when they are again formed.

When the vaporisation is so feeble as to shew itself only by
a single ring of one or two tints of the second order, they may
be made to disappear instantly by the slight degree of heat
produced by a single breath upon the crystal ; aud the same ef-
fect is produced by the approximation of a heated body. When
the heat reaches the fluid, however, it makes it throw off fresh
vapour, and the rings again appear.

If we put a drop of ether upon the crystal when the rings
are in a state of rapid play, the cold occasioned by its evapora-
tion immediately causes them to disappear, till the temperature
again rises.

When the temperature is perfectly uniform, the rings remain
stationary, and it is interesting to observe the first ring produced
by the vapour swelling out to meet the first ring at the margin
of the fluid, and sometimes coming so near it, that the darkest
parts of both form a broad black band.

in the Cavities of Minerals. 25

As the heat increases, the vacuity V advances to the summit
AB, and disappears at 79i°, exhibiting several curious pheno-
mena, which we have not room to describe. One of these, how-
ever, is so singular that it deserves to be particularly noticed.
After V has disappeared entirely, a brown spot comes from the
summit AB, and takes its station in the centre of the ring of the
new fluid abed. This brown tint sometimes rises to higher or-
ders of colours ; but disappears by the application of heat. That
the coloured rings formed within VV are vapour, and not a film
of the fluid itself, may be inferred from its never mixing with
the fluid with which it is in immediate contact. It might, how-
ever, be a fluid substance, arising either from the decomposition
of the fluid itself, or from the condensation of gaseous matter
within the vacuity ; though this is not very probable, from its
constant disappearance when it has accumulated to a certain de-
gree, and its constant reproduction while the temperature re-
mains the same.

These views respecting the vaporisation of the expansible
fluid, have been fully confirmed by the discovery of the cavities
already noticed, in which the expansible fluid occupies only one-
third or one-fourth of the cavity. Cavities of this kind are repre-
sented in Fig. 26., where AB is the cavity, V the vacuity in the
expansible fluid m n op, and A.mn, Bpo the second fluid. When
heat is applied to this cavity, the vacuity V does not contract, as
in ordinary cases, but expands, till its circumference coincides
with the boundary mnop. This unexpected effect might have
arisen from the expansible fluid occupying the lower part of the
cavity below V, as in the section, Fig. 27. In this case cefd
might have been the vacuity, and the surface of the fluid ef
might have risen by heat, and gradually filled the vacuity V, while
its boundary cd retired to m and n as the surface ef ascended.
In order to determine if this supposition was true, I placed AB

VOL. x. P. i. D

26 DR BREWSTER on the Existence of Two New Fluids

vertically between two rectangular prisms of glass ; and having
examined in succession the light reflected from the surfaces mp
and no, I found that it had suffered total reflexion, both from
the side cd and the side gh of the vacuity, and consequently
that the vacuity occupied the whole thickness of the cavity.
After the heat was applied, the sides c d and gh continued equal-
ly luminous, and when eg and dh had retreated to mn and po,
as shewn in Fig. 28., it became quite manifest, that the space
mnop was not filled with the expanded fluid, but with the fluid
in the state of vapour. The coloured rings at first appeared both
on the faces cd and gh, and when the whole was converted into
vapour they disappeared, and the light reflected from both the
surfaces mp, no, which was now uniform, was not that of total
reflexion, nor yet that of the expanded fluid, but of an interme-
diate intensity, corresponding to that of a dense vapour, with a
refractive power much lower than 1.21066.

There is another set of phenomena of exquisite beauty to an
optical observer, which seem to arise either from the decompo-
sition of the fluid, or the condensation of gaseous matter in the
vacuity.

When heat is applied to the cavity, the new fluid has its sur-
face in a state of constant agitation, resembling in the closest
manner a surface into which a fluid is discharging itself by drops.
When the vacuity is just filled up, one or more drops quit the
point where the vacuity disappeared, and pass along the surface
of the cavity, like a drop of oil adhering to it in close con-
tact, and never mixing with the fluid. Each of these drops be-
gins in a short time to spread circularly, and to exhibit within
its disc an immense number of close coloured rings. By slow
cooling the drops become thinner, and the rings less numerous,
and more completely displayed, till they entirely disappear at a
particular temperature. When the cooling is effected quickly, the

in the Cavities of Minerals. 27

matter which composes the thin plate that exhibits the rings,
discharges itself rapidly in gaseous bubbles.

When the drops quit the point where the vacuity vanishes,
and pass over one of the summits of the cavity, they often leave
an irregular streak, which also gives the colours of thin plates ;
and sometimes the circular expansion of the drops extends with-
in the circular vacuity, and thus displays two intersecting sys-
tems of coloured rings, which proves, in the most incontrover-
tible manner, that the vapour within the vacuity will not mix
with the fluid which composes the drops. The drops now de-
scribed often quit the vacuity before it is filled up by the ex-
pansion of the fluid, and one of them will sometimes remain on
the margin of the vacuity, which can be easily seen through it.

SECT. VI. On the Phenomena of the two New Fluids when taken
out of the Cavities.

From the extreme minuteness of the cavities in topaz, my
first attempts to extract the fluid were not attended with much
success ; but I at last fell upon a method by which I have open-
ed more than a hundred cavities.

When the most expansible of the new fluids first runs from
the cavity upon the surface of the topaz, it neither remains still,
like the fixed oils, nor disappears, like evaporable fluids. Under
the influence, no doubt, of heat and moisture, it is in a state of
constant motion, now spreading itself in a thin plate over a large
surface, and now contracting itself into a deeper and much less
extended drop *. These contractions and extensions are mark-

• A round hemispherical drop often stretches itself into a plane of more than
twelve times its original area.

D 2

28 DR BREWSTER on the Existence of Two New Fluids

ed by a very beautiful optical phenomenon. When the fluid has
extended itself into a thin plate, it ceases to reflect light, like
the most attenuated part of the soap-bubble, and when it is again
accumulated into a thicker drop, it is covered with all the co-
loured rings of thin plates. When one of the drops of fluid is
very minute and perfectly circular, it resembles, in the most ac-
curate manner, the small drops which pass from the vacuity, and
which have been described in the preceding section.

After performing these motions, which sometimes last for ten
or twelve minutes, the fluid suddenly disappears, and leaves be-
hind it a residue of minute and separate particles, which are
opaque by reflected, but transparent by transmitted light.
Upon examining this residue with a single microscope held
in the hand, I was surprised to see it again start into a
fluid state, and to extend and contract itself as before. This
was owing to the moisture of the hand ; and I can at any time
revive the indurated substance, by the approach of a moist body.
A portion of the fluid, which I took out of a cavity twenty days
ago, is still capable of being restored to a fluid state by mois-
ture. This portion was shewn to an eminent naturalist, the
Reverend Dr FLEMING of Flisk, who remarked, that, had he ob-
served it accidentally, he would have ascribed its apparent vi-
tality to the movements of some of the animals of the genus
Planaria.

After the cavity has remained open for one or two days, the
second fluid comes out of it, and hardens very speedily into a
yellowish resinous-looking substance, which is perfectly transpa-
rent. This substance absorbs moisture, but with less avidity
than the other. It is not volatilized by heat. It is not soluble
in water or alcohol ; but it is rapidly dissolved with efferves-
cence by the sulphuric acid. The nitric and muriatic acids also
dissolve it.

m the Cavities of Minerals, 29

*-

The residue of the first fluid is volatilized by heat ; and it
is also dissolved, but without effervescence, by the sulphuric, the
nitric, and the muriatic acids. After standing some time, both
these substances acquire a brilliant lustre, as if some metallic
body entered into their composition *.

SECT. VII. On the Existence of Moveable Crystals in a Fluid
•Cavity of Quartz.

Although particles of opaque solid matter have been observed
in the cavities of crystals containing fluid, as will be described
in the next section, yet, so far as I can find, no crystallized
body, and, indeed, no matter capable of crystallization, has ever
been discovered in them. The quantities of saline impregna-
tion, indicated by a scarcely perceptible cloudiness in solutions
of silver and muriate of barytes, were so minute in Sir HUMPHRY
DAVY'S experiments, that he considered the water as nearly pure.
I was, therefore, in no small degree surprised, when I discover-
ed, in a cavity of a quartz crystal from Quebec, from the cabinet
of Mr ALLAN, not only insulated crystals, but a tolerably large
group, which were moveable through the fluid upon turning the
specimen f . The crystal was perfectly sound round the cavity,

* In opened specimens, which had stood more than a month exposed to the air,
I observed small green spheres resting on the surface. They were soft and semi-
transparent, like green wax, and varied from j^th to 3Jr,th of an inch in dia-
meter. They were not acted upon by any of the above mentioned acids, and were
therefore a distinct substance from that of the two new fluids. They occurred in no
fewer than 25 out of 40 crystals, three being sometimes found in one specimen ;
and there can he no doubt that they consisted of fluid matter which had oozed out
«>f the crevices of the mineral.

-f- There were also numerous opaque particles in the cavity, which descended
slowly in the fluid.

30 DR BREWSTER on the Existence of Two New Fluids

which had a sort of triangular form, one of the sides of the tri-
angle being about one-tenth of an inch long. The fluid was
quite transparent ; and, as the air-bubble was not perceptibly di-
minished by heat, there is every reason to think that the fluid is
water. The crystals were transparent to a considerable degree,
and had a white milky tint, when seen by reflected light.

In considering the. circumstan es of this singular phenome-
non, we are led to suppose, that the included crystals had been
dissolved in the fluid at the time of its being shut up in
the quartz, and had afterwards been deposited from the solution.
The ingenious supposition of Sir HUMPHRY DAVY, that a liquid
hydrate of silica may exist at high temperatures, and may con-
tain small quantities of atmospheric air, will no doubt explain
the phenomena of water in rock-crystals ; but it is not easy to
comprehend how the formation of a group of crystals could ei-
ther have accompanied or followed the separation of the water
and the silex.

As the specimen now alluded to is too valuable to be destroy-
ed, for the purpose of analysing the minute crystals, it is pro-
bable, that our information respecting them would have been
very limited, had not a circumstance of an accidental nature en-
abled me to throw some farther light on the subject. Several
years ago, when I was examining, along with Earl COMPTON, a
large collection of quartz crystals from Quebec, for the purpose
of obtaining remarkable crystallizations, I was much struck with
the appearance of several spherical groups of whitish crystals,
within some of the specimens. Upon pointing out to Lord
COMPTON this peculiarity, his Lordship agreed with me in think-
ing that they belonged to the Zeolite Family. Having pur-
chased all the specimens that could be found, I have since re-
peatedly examined the included crystals, with the view of deter-
mining their nature. I found that they did not belong to the
zeolites, but consisted principally of carbonate of lime ; and, as

In the Cavities of Minerals. 31

every mineralogist who saw them considered them as something
new in appearance, I expected that a greater quantity of them
might be found for the purposes of analysis. Familiarised, there-
fore, with the aspect of these groups, I was convinced that the
crystals in the fluid cavity were the same substance ; and a more
accurate examination has established their perfect identity.

These white crystals sometimes occur in minute insulated
spiculae within the solid mass, but most frequently in spherical
groups of extreme beauty, surrounded with the most transparent
quartz. Many of the open hollows and crevices of the quartz
crystals are filled with them, and numerous aggregated groups
adhere to their external surface. These crystals, though very
minute, I have found to have a powerful double refraction ;
and as they are wholly dissolved with effervescence, excepting a
little adhering silex, in diluted nitric acid, there can be no doubt
that the external crystals and consequently those in the fluid ca-
vity, are carbonate of lime *.

SECT. VIII. On the Phenomena of a single Fluid in the Cavities
of Minerals and Artificial Crystals.

The phenomena which I propose now to describe, are essen-
tially different from those which form the subject of the preced-
ing sections. The fluid which occupies this class of cavities ex-
hibits no properties different from water or mineral oil, which
have long ago been detected by mineralogists, and the vacuity
which often accompanies these fluids, is either a perfect vacuum,
or filled with a gaseous body.

* Since these observations were made, Mr NOUDENSKJOU> has confirmed this
result by experiments made with the blowpipe.

32 DR BREWSTEU on t/te Existence of Two New Fluids

This class of cavities might, with propriety, have been divided
into three subdivisions : 1. Those where the cavities are entire-
ly filled with fluid ; 2. Those which have a perfect vacuum along
with the fluid ; and, 5. Those where the fluid is accompanied
with a gaseous body ; but, as several crystals seem to possess ca-
vities with all these characters, I shall describe the different
crystals in their order.

1. AMETHYST from CEYLON. — This fine specimen, in the ca-
binet of Mr THOMSON of Forth Street, originally belonged to
the King of Candy. It is about 3 inches long and If broad,
and has a large cavity, of the size and form shewn in Fig. 29-
The bubble V, which I have ascertained to be gaseous, by the
reflexion of light, moves by starts from one end of the cavity to
the other. It is not sensibly altered by heat. Another cavity
C, near the large one, has a small air-bubble in the middle,
which refuses to move from its place. There are several pieces
of opaque solid mater, which, with a little management, may be
seen within the cavity AB, and which may be made to fall from
one side of it to the other. This is the largest cavity that I have
ever seen in a solid crystal.

2. ROCK CRYSTAL. — This mineral abounds with cavities, con-
taining water and mineral oil, which is sometimes black, some-
times of a faint yellow, and sometimes of a rich orange red co-
lour.

The largest cavities are generally amorphous ; but there are
many crystals with thousands of cavities all regularly crystallized,
and of the exact form of the secondary crystal.

The quartz crystals from Quebec contain great quantities of
mineral oil, which does not perceptibly expand by the applica-
tion of heat. There are frequently within the cavities dark
little fragments, which are carried about by the motion of the

in the Cavities of Minerals. 33

fluid. In a crystal of quartz belonging to Mr ALLAN, and con-
taining a large cavity, with water and an air-bubble, he observed
a little black globule which adhered to the air-bubble. Upon
looking at it afterwards, he remarked that the black globule had
separated into a great number of minute black particles. This
opaque matter is likely to have had the same origin as that
which is described in page 23.

One of the most remarkable specimens of quartz which I
have ever met with, was shewn to me by Mr SIVRIGHT. The
cavities are of the most singular shape, and are almost all nearly
filled with a fluid, accompanied with a small air-bubble, which
does not perceptibly expand with heat. Some of the cavities
contain a yellow fluid, with various air-bubbles, which seem to
be naphtha apparently in a very viscid state. This specimen is
shewn, though very imperfectly, in Fig. 30.

3. TOPAZ. — There are many topazes from Brazil, New Hol-
land, and Scotland, which contain a single fluid, with an air-bub-
ble. In these the fluid does not perceptibly expand with heat ;
and I have ascertained that it is aqueous, and that the vacuity is
filled with a gas.

In several topazes, both from Aberdeenshire and Brazil, the
form of the cavities is extremely curious, resembling the writ-
ing in Eastern MSS. These grotesque forms generally contain
the new fluid ; but many of them have no vacuity at all, while
some of them contain a fluid of a decided yellow colour, which I
have never found accompanied with a vacuity. These cavities
are shewn in Fig. 31. The cavities in topaz containing the two
new fluids are shewn in Fig. 40.

In a particular specimen of topaz, I observed a regular rhom-
boidal space apparently filled with particles of dust suspended
in it. This rhomboidal space appeared green by reflected, and
red by transmitted, light.

VOL. x. P. i. E

34 DR BREWSTER on the Existence of Two New Fluids

4. CYMOPHANE. — In several specimens of cymophane, there
are strata of cavities apparently containing one fluid, but without
any perceptible vacuity. In the crystal containing the stratum
with the new fluids, there is another stratum parallel to it, of a
very remarkable kind, where the cavities have the form shewn
in Fig. 32. The nature of the fluid, however, I have not been
able to determine.

5. PERIDOT. — The largest and finest crystals of this mineral
are often intersected, in various directions, with strata of fluid
cavities having globules of air. In a set of unusually large crystals
a kind of resinous indurated matter seems to have been diffused,
sometimes in strata and sometimes throughout the mass of the
crystal. These peridots, which are very magnificent, belong to
the COUNTESS of WEMYSS ; but in consequence of their being
cut and set in gold, it was impossible to subject them to an ac-
curate examination.

6. FELSPAR. — The cavities in this mineral are very flat, and
irregularly formed. They contain a single fluid and an air-bub-
ble, which neither vanishes nor diminishes with heat.

7. EMERALD and BERYL. — The great degree of foulness
which is so common in these gems, arises generally from strata
of cavities containing a single fluid, and an air-bubble, which do
not perceptibly decrease with a temperature of 150°.

8 FLUOR-SPAR. — The crystals of green fluor-spar from Als-
ton Moor frequently contain cavities with water. I have seen
several about half an inch long, and of the form of a triangular
pyramid. The air-bubble moves sluggishly even in these large
ones, and with great difficulty in the small ones. The apparent
air-bubble is gaseous, and the fluid does not perceptibly expand

»/. in the Cavities of Minerals. 35

with heat. These crystals frequently burst with a heat not
above 150°. In several cavities I have observed solid fragments
falling through the fluid, by the inversion of the crystal.

9. SULPHATE OF LIME. — In this mineral the cavities have of-
ten a very singular form ; and in all the specimens which I have
examined, the fluid is aqueous, and is accompanied with a gas or
a perfect vacuum.

In Fig. 33. I have represented one of the most singular ar-
rangements of cavities that I have met with. In order to deter-
mine the thickness of the cavity, I reduced the specimen, so as
to give the polarized colours of the second order of Newton's
Scale, and, by carefully observing the difference of tint in the
cavities, and in the solid parts, I obtained a measure of the thick-
ness of crystalline matter abstracted in these parts. The differ-
ence of tint was very obvious, and proved that the thickness of
the cavity did not exceed the T oVo th part of an inch.

In many specimens, these very shallow cavities occur in long
canals. In others they resemble some foreign crystalline matter,
shooting out into the most singular forms, as at a, b, Fig. 34. and
sometimes the cavities appear to the eye like tufts of white silk
compressed between the laminae, though they are, in reality,
strata of rhomboidal cavities, occurring in thousands, and ar-
ranged in the direction of their longest diagonals, while the stra-
ta themselves are highly inclined to the surfaces of the laminae.
In other specimens, the cavities have the most singular forms, as
represented in Fig. 34. One of the canals in sulphate of lime is
shewn at AB, in Fig. 35., where abed, efgk are two air-
bubbles or vacuities. By applying heat to the side B, these
air-bubbles shift their places. All the lines a b, cd, ef, gh,
advance to B, but c d and ef approach to one another, and the
moment they come in contact, the two vacuities are converted
into one, which has the position a' If g' h'.

36 DR BREYVSTER on the Existence of Two New Fluids

10. SULPHATE OF BARYTES. — The cavities in sulphate of ba-
rytes were first pointed out to me by Mr SIVRIGHT. I have
since found them in various specimens. They are generally of a
very irregular shape, though sometimes they have regular crys-
talline forms.

Many of these cavities are entirely filled with fluid, but in
several a very small apparent air-bubble may be seen. This va-
cuity does not vanish by the heat of the hand, but it disappears
entirely at a temperature of about 150°, and again returns when
the specimen has cooled. It is therefore a vacuum.

11. CALCAREOUS SPAR. — Cavities filled with water are fre-
quently found in calcareous spar. The apparent air-bubbles,
which are very small, occur only in some of the cavities. To
some of the cavities I applied a heat of about 1 50°. The appa-
rent air-bubbles entirely vanished, and, what is very remarkable,
they have never again reappeared. This singular fact may be
ascribed to the strong cohesion between the fluid and the sides
of the cavity, which can only be overcome by a greater degree of
cold producing a greater degree of contraction than that of the
cabinet in which the specimen has been kept.

12. ROCK-SALT FROM CHESHIRE. — In this mineral the cavi-
ties assume the most beautiful forms. In one specimen, shewn
in Fig. 36., they have the form of regular cubes of various sizes,
and with numerous truncations on their sides and angles. In
other specimens the cavities have the form of octohedrons ; while
in others they have numerous varieties of forms. The cubical
hollows above mentioned are in general perfectly filled with
fluid ; but some of them have small apparent air-bubbles, which
contract to fully one-third of their size by a heat of 120°.

in the Cavities of Mimrals. 37

13. SULPHATE OF IRON. — The cavities in this salt are some-
times finely crystallized in the form of prisms, with double py-
ramids, and the sharpest truncations. In the same specimen
they are frequently oval, or imperfectly spherical. They some-
times contain apparent air-bubbles, and are often quite filled
with fluid. By the application of heat, these vacuities disappear
entirely, and reappear by cooling.

14. SULPHATE or NICKEL. — In this salt the cavities are
sometimes amorphous, and sometimes beautifully crystallized.
These vacuities frequently disappear by heat, and reappear by
the application of cold.

15. SULPHATE OF COPPER. — The air-bubbles move about in
this salt by the application of heat, but never vanish. By in-
creasing the heat, they diminish a little in size.

16. ALUM. — The air-bubbles in alum do not perceptibly
change their magnitude by heat. I have opened several cavi-
ties in this salt, but have never found the air to be either in a
state of dilatation or compression. The fluid seems to be pure
water.

17. TARTRATE OF POTASH AND SODA. — The cavities in this
salt are both crystallized and amorphous. A considerable vacui-
ty in a large cavity vanished completely with heat ; and in others,
where the vacuity was very large, it became extremely small
when heated. Two separate cavities, with separate vacuities,
became one, and united their vacuities. These phenomena, no
doubt, arose from the fluid having its dissolving power increased
by heat ; and it is probable that the disappearance of the large
vacuity arose from the dissolved salt occupying more space in its
fluid than in its solid state.

38 DR BREWSTER on the Existence of Two New Fluids

It is unnecessary to extend these details to all the artificial
crystals enumerated at the beginning of this paper, as I have
not observed in them any phenomena different from those which
have already been described.

There is another class of cavities which require to be studied
with some attention, namely, those which are entirely full of
fluid, or entirely empty. Mr SIVRIGHT first observed cavities in
the diamond *, and in garnet ; but, though I have examined
them in various specimens, I have not been able to determine
whether they are entirely filled with fluid, or are entirely emp-
ty. I have found cavities of a similar kind in cinnamon-stone,
where they are beautifully crystallized, in sulphate of Strontian,
in sulphur, in analcime, and in chabasie ; but I observed no ap-
pearance of air-bubbles, and have no certain evidence that they
contain a fluid f .

It would be improper to conclude this paper, without noti-
cing the relations which are supposed to subsist between this class
of phenomena and the two contending Geological Theories.
The existence of highly rarified gas in the cavities of crystals,
has been regarded by the distinguished President of the Royal
Society of London, as " seeming to afford a decisive argument in
favour of the igneous origin of crystalline rocks ;" and the " fact
of almost a perfect vacuum existing in a cavity containing an ex-
pansible but difficultly volatile substance," (as naphtha), he like-
wise considers as highly favourable to the same theory. The
discovery of compressed gas in similar cavities might have been
regarded as neutralizing, in some degree, the first of these argu-

« See the Edinburgh Philosophical Journal, vol. iii. p. 98., for an account of
the polarising structure which sometimes exists round the cavities in diamond.

+ This point may be easily determined by grinding the specimens, and exa-
mining the light reflected at the surfaces of the cavities.

in the Cavities of Minerals. 39

merits : but Sir HUMPHRY DAVY remarks, that it may be ex-
plained by supposing the crystal to have been formed under a
compression much more than adequate to compensate for the ex-
pansive effects of heat *.

Without presuming to combat these deductions, or to suggest
any of the numerous explanations by which the Neptunist might
reconcile with his own system the compressed and dilated condi-
tion of the included air, I shall content myself with stating, that
the facts described in the preceding paper appear to me de-
cidedly hostile to the igneous origin of crystals, and, in some
points of view, favourable to their aqueous formation. The exist-
ence of a fluid which entirely fills the cavities of crystals, at a
temperature varying from 74° to 84°, may, upon the principles
assumed in the opposite argument, be held as a proof that these
crystals were formed at the ordinary temperature of the atmo-
sphere, while the fact of a perfect vacuity existing in sulphate of
barytes, and capable of being filled up by the expansion of the
aqueous fluid, at a temperature not exceeding 150°, authorises
the analogous conclusion, that the crystal could not have been
formed at a higher temperature. On the other hand, the filling
up of the vacuities in sulphate of iron, and sulphate of nickel, at a
temperature much above that at wluch they were formed, may
lead geologists to renounce a species of argument which appeals
only to our ignorance, and to withdraw from the defence even of
their outworks, those faithless auxiliaries, which are so ready to
enlist themselves in the service of either power.

There is one geological relation, however, of the preceding
facts, which may deserve some attention. Hitherto the contend-

•I'v.v

* As the effects of heat and compression might exactly balance each other,
the gas would in this case be atmospheric air, in a common state of density ; so
that the volcanists are here sheltered against experimental hostilities, amid lh*>
generalities of their hypothesis.

40 DR BREWSTER on the Existence of Two Netv Fluids

ing theorists have limited their idolatry to two of the elements ;
but the existence of two new substances in minerals, one of
which combines a great degree of fluidity with the high expan-
sive power of the gases, renders it probable, either that these
substances existed at the formation of the globe, or that they are
the result of laws of crystallographic combination which have
escaped the notice of the philosophical geologist. Were such
fluids the product of the ordinary processes of crystallization,
they would occur in artificial as well as in natural crystals :
and, consequently, while they remain undiscovered in the cavities
of the first of these classes of bodies, we are entitled to attach a
new difficulty to the aqueous hypothesis.

Had the two new fluids occurred only in one mineral, or in
minerals of a particular composition, they might have been sup-
posed to have some relation to the elementary principles of the
body, and to have arisen either from some accidental irregulari-
ty, which prevented them from crystallizing, or from the decom-
position of the matter subsequently to its crystallization. The
perfect identity, however, of the two fluids, as found in pure
Quartz, in Amethyst, in Topaz, and in Cymophane, — minerals
brought from the most opposite parts of the globe, — from Scot-
land, Siberia, New Holland, Canada, and Brasil, — establishes the
universality of their existence, and adds to the probability of the
supposition, that they have performed some important function
in the organization of the mineral world.

While the preceding facts thus obviously connect themselves
with our geological theories, they promise also to be of some use
in the practical branches of Physics. A fluid possessing such a
high expansive power would be invaluable in the construction of
delicate Thermometers, and various other philosophical instru-
ments ; while its extreme fluidity would enable us to construct
levels of singular delicacy. If the resources of the chemist shall

in the Cavities of Minerals. 41

not enable him to form such a substance, a plate of topaz, with
particular longitudinal cavities, might be used, as a delicate ther-
mometer, for certain ranges of temperature ; and where slight
variations require to be observed, several such plates might be of
essential service in many researches, both of a chemical and a
physical nature.

VOL. x. P. i.

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II. Observations on the Comparative Anatomy of the Eye. By
ROBERT KNOX, M. D. Member of the Wernerian Society,
and of the Medical Chirurgical Society of Edinburgh.

(Read June 17. 1823.;

THE following observations, which I have the honour to pre-
sent to the Society, have arisen out of an inquiry into the struc-
ture and distribution of the nervous system throughout the ani-
mal creation. It will readily be imagined, that the nerves sup-
plied to the organs of sense, did not fail strongly to attract my
attention, and that those belonging to so important an organ as
the eye, were considered by me as worthy of the most minute
investigation. It was impossible to proceed in this inquiry with-
out submitting the organ itself to a very careful examination, in
executing which, several important facts presented themselves,
which I believed to be novel, or, at least, to lead to views respect-
ing the physiology of the eye, different from those generally
adopted. It became my duty to search into authors of the pre-
sent and of the past age, and to collect into view whatever had
been previously written on the subject ; but leisure being alto-
gether wanting for such an undertaking, I have thought it best
to describe what I have myself seen.

44 DR KNOX on the Comparative Anatomy of the Eye.

I. General Idea of Vision.

It has been said by a distinguished physiologist, that we can-
not obtain an immediate knowledge of real distance by sight
alone. Our countryman, Dr PORTERFIELD, however, demon-
strated that, within certain limits, perhaps within the range of
distinct vision, our knowledge of distance is perfect, and that it
depends on the organ being double and symmetrical. Beyond
this point, the mode by which we judge of distance becomes
complex, for we have to avail ourselves of other senses, and more
particularly of that of feeling. We reason also respecting the
distance of objects, from their degrees of illumination, from their
obscuring each other, from their magnitude, &c. With all these
aids, many individuals judge very erroneously of distance, whilst
others decide upon it with the utmost precision. This faculty
depends, therefore, on a peculiarly organised brain, conjoined
with much experience. The superiority of one military genius
over another is in no small degree attributable to this talent.
History is filled with the errors of those, who, miscalculating dis-
tance, have either crowded their troops into a space unable to
contain them, or, by too great an extension of their lines, have
presented a feeble front, incapable of resisting the enemy. Such
errors must necessarily lead to serious disasters.

A particular eye sees distinctly objects placed at only a cer-
tain distance, hence men are either short or long sighted ; but
we know that experience exerts great influence over this. Even
the vulture, whose eye is beyond all doubt the most keen and
piercing, is conducted by experience to a knowledge of the prey

DR KNOX on the Comparative Anatomy of the Eye. 45

suited to him *. I have repeatedly seen this bird deceived, and
have ascertained on many occasions, that though birds possess
the power of very distant vision, such vision is not distinct. By
the point of distinct vision, I understand the distance at which
a moderately small object may be clearly and distinctly made
out, independently of all experience. It must be obvious to
every one, that this distance is very limited, and depends, to a
certain extent, on the size of the object. Instead, therefore, of
talking of the limits of distinct vision, we shall consider the fa-
culty which the eye possesses, of adapting itself to the general
perception of objects placed at a variety of distances. We shah1
return to this subject, when describing the means employed in
effecting the changes supposed to take place within the eye-
ball.

There is still one other faculty possessed in various degrees
of excellence by different individuals ; I allude to rapidity of vi-
sion, or the power of instantaneously changing the focus of the
eye, and adapting it to objects placed at various distances. This,
no doubt, depends on the irritability of the organ, or, perhaps,
of the nervous system ; it is connected, as shah1 be shewn, with
the distribution of the ciliary nerves, and is of the same nature
with muscular motion in other parts of the body ; it is not pecu-
liar to any complexion, and hence will be found to be as com-
monly possessed by the blue as by the dark eye. The exercise
of this faculty to its greatest extent, is what constitutes the
sportsman ; but most men possess it to a considerable extent
when roused by danger, or excited by the unexpected appear-
ance of an extraordinary object. I have observed remarkable
differences amongst individuals in this respect, and shall cite an

* I have demonstrated, in a brief notice, which, I believe, was inserted in some
of the French journals, that it is by sight only that the vulture is led to discover his
prey, and not by the sense of smelling.

46 DR KNOX on the Comparative Anatomy of the Eye.

instance, which occurred in the person of a friend, whose powers
of vision were uncommonly strong, but whose eye, which was
dark, was so ill adapted to effect a sudden alteration of the fo-
cus, that, on hunting parties, he was always the last to discover
the game. It is extremely probable, that a principal part of the
phenomena depends on the rapidity of motion in the iris. I
think that I have noticed it oftenest in those in whom the iris
was of a blue colour.

The same individual may, with some- attention, distinguish
the same object at different distances, the limits of which may
be assigned, with respect to each individual. The eye, there-
fore, must have the power of changing the position of its parts,
by some means or other, and these must be placed, either within
it, or exteriorly to it. So far as I am aware, no satisfactory theo-
ry has been offered concerning this accommodating power of the
eye, nor has any one fixed on the parts by which the internal
changes are effected. It is true, that in viewing near objects,
the pupil admits only the rays which are nearest to the axis, and
which are consequently the least diverging. This has been sup-
posed by some to be capable of accounting for the phenomena ;
but we shall, in the sequel, endeavour to shew, that this mode of
accounting for our power of viewing very near objects, though it
be essentially requisite to an accurate and complete theory of
vision, is yet totally inadequate to account for the whole of the
phenomena. This was the opinion of the late JOHN HUNTER,
very few of whose assertions have ever been confuted.

It has been suggested by the celebrated Baron CUVIER, that
perhaps the limits of distinct vision are much more confined
than we imagine them to be ; and, it is probable, that, in many
cases, it only appears distinct, because it is assisted by the recol-
lection which we have of the object. Now, this should be con-
stantly borne in mind, for it prevents us from entertaining ex-
aggerated notions of the power of vision possessed by a variety
of animals.

DR KNOX on the Comparative Anatomy of the Eye. 47

Of the Figure of the Globe of the Eye; of the Form and Propor-
tions of its Chambers, and of the Density of its Transparent
Parts.

I have but little to add from personal observation, to the la-
bours of preceding writers on this subject. Indeed I suspect
that little remains to be done relative to the matter announced
in the section. So important an organ is that of sight, that it has
at all times attracted the attention of the profoundest philoso-
phers, and the examination of its various parts has been deemed
not unworthy the labours of the greatest mathematicians of the
present age. To the splendid works of these gentlemen I beg
to refer the Society.

The anterior part of the eye in fishes, and in the cetacea, is
flat. In the cuttle-fish, the cornea and aqueous humour are
wanting. In man, and in quadrupeds, it is almost spherical.
The cornea makes a slight projection anteriorly, because its con-
vexity is a portion of a sphere smaller than that of the rest of
the eye. In the porcupine and the opossum, this is said not to
be apparent, and it seems to me that the same remark is nearly
applicable to the ornithorinchus paradoxus. In birds, the cornea
is exceedingly convex, and is sometimes completely hemispheri-
cal. Thus we see, that the difference in the eyes of these ani-
mals is connected with the proportional density of the media in
which they live. It is true that the ostrich and cassowary ne-
ver rise from the ground, and yet have their eyes formed like
those of other birds; but as Nature has formed the various
classes of animals agreeably to certain determinate laws, and as
in none of these classes has she adhered so strictly to these laws
as in birds, so we can see no good reason why the eye of the os-
trich should differ much from that of other birds ; or perhaps it

48 DR KNOX on the Comparative Anatomy of the Eye.

might be better stated, that as the eyes of the ostrich and casso-
wary have a strictly ornithological character, this fact may be of-
fered as an instance of the close observance which Nature pays
to her general laws. I have thought that the vitreous humour
in birds was less dense than in the mammalia, but I have no di-
rect experiments to prove this.

Of the Sclerotic and Transparent Cornea.

The sclerotic, or external covering of the eye-ball, is so inti-
mately connected with the dura mater, forming the sheath of
the optic nerve, that it may be considered, as in some measure,
an analogous membrane. Anteriorly, its connection with the
cornea presents a variety of forms, but there is this uniformity
in all the animals which I have examined, namely, that the in-
ternal layer of the cornea, that to which the name of the Tunic
of the aqueous humour has been given, does not unite with the
sclerotic, but with the iris. The mode in which this union takes
place is simply this : the whole external layer of the sclerotic
passes forwards beyond the circulus niger, and is inserted into
the edge of the cornea. The inner membrane of the sclerotic,
of the origin of which I shall presently speak, in its passage for-
wards, is interrupted by that portion of the annulus albas which
is left adhering to the sclerotic, when the choroid has been for-
cibly removed from it, but may be readily detected between this
portion of the annulus albus, and the posterior edge of the mem-
brane of the aqueous humour, to which, it seems to me, to at-
tach itself. Whether this inner membrane of the sclerotic, and
that of the aqueous humour, be really the one a continuation of
the other or not, I have, as yet, been unable satisfactorily to
make out. I am inclined to think that they are attached and
not continuous membranes, though an appearance supporting the

DR KNOX on the Comparative Anatomy of the Eye. 49

latter opinion has been observed in the eye of the lion. In
birds and fishes, a reflected portion of the membrane of the
aqueous humour seems to cover the whole anterior surface of the
iris, and is the cause of that peculiar elasticity observable in the
iris of birds *, by which the relation of the iris to the cornea is
changed, when life is extinct, from a right angle to a very acute
one. In the eye of the deer, the ox, &c. the anterior layer of
the iris is connected to the inner membrane of the cornea, by
numerous short and seemingly tendinous fibres, and these mem-
branes are evidently distinct.

The inner membrane of the sclerotic is simply a reflected
membrane of the choroid. Near to the origin of the retina, or
at least to its point of union with the optic nerve, the inner
membrane of the sclerotic can hardly be distinguished from the
choroid, which may here be divided into as many layers as the
anatomist chuses. It is curious enough to trace the use which
anatomists, from preconceived notions, have been induced to
make of the pia mater. The celebrated ZINN and WRISBERG
considered the inner layer of the sclerotic to be a continuation
of the pia mater ; others, equally celebrated, imagined the outer
layer of the choroid to be the true continuation of the cerebral
membrane. It was soon transferred to the inner layer of the
choroid ; and, lastly, to the membrane immediately in contact
with the retina, and which has lately been described by Dr JA-
COB in the Philosophical Transactions. This latter opinion was
held by the late Dr MONRO. I do not consider the inquiry as
being of the least importance.

From the flexible nature of the sclerotic coat in man and
quadrupeds, and even in birds, it has been supposed that com-
pression exercised upon it by the muscles of the eye-ball, may

'

* This is not present in the eye of the cassowary.
VOL. X. P. I. 0

50 DR KNOX on the Comparative Anatomy of the Eye.

swell the cornea, by pushing the humours forward, and thus
enable the eye to distinguish very near objects. But this theory,
though supported by so distinguished an anatomist as BLUMEN-
BACH, is by most deemed inadmissible. It appears to me truly
wonderful, that such a theory could have stood its ground for
any length of time ; for, if it was intended by it to explain the
great power of vision in birds, it was unnecessary, since the na-
tural form of the eye-ball, and of its contained parts, is in them
sufficient to explain the phenomenon ; or, if proposed as a theo-
ry, by which to explain the accommodating powers of the eye, it
was not less in fault, since, in man, the changes produced in the
cornea, at whatever distance an object be placed, are altogether
trifling, and nearly inappreciable ; nor have I observed the least
alteration in the cornea of birds, whatever might be the distance
of the object they viewed. Lastly, Compression of the eye-ball
does not cause a protrusion of the cornea, though this experi-
ment be made with the eye of the horse, whose sclerotic is com-
paratively thin and flexible. During life, the cornea is perpe-
tually tense, clear, and, as it were, sparkling, especially in the
young and healthy. This is owing to the contraction of the ex-
ternal muscles of the eye-ball, an action which persists with life,
and is named by physiologists the tonic power of the muscles, in
contradistinction to the action caused by volition. After death
these muscles relax, the eye-ball is left to itself, and the cornea
becomes flat and dim. These appearances have generally been
attributed to the escape of the aqueous humour through the
cornea, now deprived of life ; but this is a gratuitous and unne-
cessary supposition. It was long ago remarked by Dr WHYTT *,
that, in apoplexies, whilst the patient still li ved, the eyes lost
their lustre, and, in some cases, put on the appearance of those

See his Physiological Essays.

Da KNOX on the Comparative Anatomy of the Eye. 51

of a person actually dead. We have, moreover, seen many in-
stances, in which the cornea retained its fullness and lustre for
some time after death had taken place. These various effects
are attributable to the different degrees of energy remaining in
the external muscles of the eye-ball. After a time, a film forms
on the surface of the cornea. I have already stated, that the an-
terior layer of the iris is inserted into the inner membrane of the
cornea, and that this forms a principal attachment. If the ana-
tomy of the eye in fishes be considered as affording a fair analo-
gy, we are warranted in asserting, that the inner membrane of
the cornea covers the whole anterior surface of the iris, though
the ox, the deer, and some other animals, present the modifica-
tion before described. On this depends the elasticity of the iris
in birds ; and, in fishes, we are compelled to admit this continui-
ty of the membranes ; for, between the coloured portion of the
iris, which, in them, we know to be the external layer of the
choroid, and the aqueous humour of the anterior chamber, there
exists no other membrane, than a thin, transparent, elastic tunic,
continuous with, and exactly resembling, the inner layer of the
cornea. We cannot well doubt that the action of the iris on this
membrane must alter, to a certain degree, the form of the cor-
nea internally, and, consequently, that of the aqueous humour,
which opinion was long ago maintained by JURIN, and admits al-
most of demonstration.

II. Of the Choroides, and its Appendages ; of the Iris and its
Motions ; of the entry of the Optic Nerve into the Eye ; and
of the Distribution of the Ciliary Nerves.

WE give the name of Choroides to that dark coloured mem-
brane found immediately within the Sclerotic. By Comparative
Anatomy, we best learn the nature of this membrane, the num-

52 DR KNOX on the Comparative Anatomy of the Eye.

ber of its component tunics, &c. Near its commencement in
the bottom of the eye-ball, it adheres very intimately to the in-
ner layer of the sclerotic, the one being simply a reflexion from
the other. Advancing forwards this union ceases, and they ad-
here only at those points where vessels and nerves pass from
without to the choroides. In some animals, these pass directly
through towards the choroid, but in birds and the deer tribe
their course is oblique. We shall return to this whilst descri-
bing the peculiarities in the anatomy of the eye of the deer.
Still further forward, they are more intimately united by the
annulus albus, and here the external layer of the choroid is sup-
posed to terminate. I have reason to think, that, in general, it
does not terminate, but passes forward with the inner layers of
the choroid, to form the ciliary processes and uvea. In fishes,
where the annulus albus is quite rudimentary, and does not im-
pede the passage of the choroid, or render its termination ob-
scure and complex, the external membrane of the choroid is ob-
served to pass onward to the edge of the pupil, nor can the most
careful dissection, aided by good glasses, demonstrate any addi-
tional tunic to exist between it and the transparent covering it
receives from the cornea. In some of the mammalia, and in birds,
it has appeared to me, that the external layer of the choroid in-
includes the annulus albus in part, or perhaps rather that it be-
comes looser in texture, and unites with the inner layer of the
sclerotic, and so passes forward towards the cornea : in general,
however, it seems to unite with the inner layer of the choroid,
and to pass forward towards the uvea internal to the annulus
albus. When the sclerotic and cornea are carefully removed in
the eye of any of the mammalia, the parts seen, and which we
may mention in succession, are, the exterior surface of the iris ; the
line by which this exterior surface of the iris, near its base, is na-
turally connected with the cornea, and which anatomists have
called the Circulus niger ; a dark coloured membrane, connecting

PLATE 10.

/Com/ .for- Trtui l',i/.f.finr,eS3.

f—

V . J .

fy . 4

DR KNOX on the Comparative Anatomy of the Eye. 53

the base of the iris with the anterior edge of the annulus albus,
and which may either be considered as a peculiar body, or a por-
tion of the choroid tunic immediately subjacent : this dark colour-
ed body forms the inner surface of a cavity, which will be more
minutely described afterwards : lastly, the annulus albus itself con-
nected posteriorly with the outer layer of the choroid coat. The
anatomy of these parts shall be described more minutely whilst
speaking of the various classes of Animals. -

As it is in birds that some of these parts are most distinctly
and readily made out, I shall here briefly describe the general
anatomy, drawn from very numerous specimens, of almost all the
natural families of that class ; but I shall dwell more particular-
ly on the eye of the cassowary, not because there is in it any pe-
culiarity, but because the magnitude of the eye-ball permits the
minutest parts to be satisfactorily demonstrated. Near the pos-
terior edge of the annulus albus, the choroid is firmly fixed all
round the eye-ball to the inner layer of the sclerotic. At this
point, the external layer of the choroid may be considered either
as terminating, or what, in favourable specimens, may be partly
demonstrated, as passing forward united to the inner layer, to
form the ciliary body. Anterior to this is another adhesion, be-
tween the anterior expansion of the annulus albus and the scle-
rotic ; this adhesion may be supposed to proceed onwards, and
to terminate in the cornea by a thin broad membrane, gene-
rally of a dark colour.

Anterior to the principal insertion of the annulus albus into
the sclerotic, and lying on a strong membranous expansion,
stretching between the annulus albus and cornea, are found the
ciliary nerves, which here resemble a plexus, being broad, large,
and ribbon-like ; they completely surround the eye-ball, and
send numerous distinct branches to the iris and to the annulus
albus *. I had already remarked, during the course of my dissec-

* See Plate III.Fig. 1.

54 DR KNOX on the Comparative Anatomy of the Eye.

tions, that the annulus albus assumed a variety of appearances,
but that it resembled a ligament in a very few animals only :
that in still fewer did it bear any resemblance to a nervous
ganglion ; which resemblance, I speedily satisfied myself, was a
complete deception. At last, having discovered, that in birds, and
in the deer, the so named ligament received numerous nerves,
that its texture bore no resemblance whatever to ligament, that
it became rudimentary in those animals whose sight was feeble,
which would not necessarily happen were it simply a ligament
for the suspension of the tunics and humours of the eye ; the
conclusion was irresistible ; that the annulus albus is a muscle,
that it is the muscle by which the eye adapts itself to the percep-
tion of distant objects, and that by it, in conjunction with the
iris, all the changes which take place in the interior of the eye-
ball are effected *.

In compliance with the wish of some of my friends, small
sections of the annulus albus were submitted to the microscope.
The result of this investigation was, that it had no resemblance
to a ligament ; that it contained comparatively large branches of
nerves ; that it did not resemble any of the textures of the eye-
ball except the iris, but that here the resemblance was so close
that they could with difficulty be distinguished.

It were desirable that I should bring forward ample collate-
ral proofs of the presence of this great central muscle of the
eye-ball, and which I shall henceforward call the Ciliary Muscle;
but I am by no means prepared for so extended an inquiry :
many, however, will readily suggest themselves to those who
have investigated the eye anatomically in a variety of animals.
Birds, for example, that have a strong ciliary muscle, amply sup-
plied with nerves, have powerful vision ; their perception of ob-

* The opinion that the annulus albus is muscular, has been often maintained, but,
so tar as I know, no proofs, derived from anatomy, of its muscularity, have ever been
laid before the public.

DR KNOX on the Comparative Anatomy of the Eye. 55

jects placed at a vast distance is tolerably distinct. It is strong
in man, and in the quadrumana ; weak in the ox and sheep, but
still weaker in the horse ; very powerful in the deer tribe, and
no doubt in the antelope. I had often remarked, without being
able to assign a reason, how greatly the antelope and deer trust-
ed to the organ of vision, and how inferior their organs of smell
were to those of the horse and ox. Whoever will carefully at-
tend to the habits of these animals when allowed to roam about
at large, may observe, that the horse and ox fearlessly enter
thickets, trusting to the acuteness of their smell for the disco-
very of wild ferocious animals, whilst the antelope prefers the
open plains, and seldom resorts to the bushy country, unless ur-
ged to it by a want of herbage and water *. Horned cattle,
with most ruminating animals, graze generally towards the quar-
ter whence the wind blows ; and, though I am aware that other

* I observed a very singular fact in Africa, which first awakened my suspicions
relative to the defective vision of the horse. In that country we were forced, from a
deficiency of pasturage, to allow our horses to graze at perfect liberty on the open de-
serts, and they, so situated, seemed to acquire many of the habits which the animal would
probably possess in a perfectly wild state. They grazed generally in small troops, to
which an entire horse, or one of the boldest of the geldings, seemed to serve as pro-
tector ; on the approach of strangers, the troop immediately collected into a circle, and
remained so until the horse appointed to watch over the general safety had ascertain-
ed whether or not danger was to be apprehended, by a nearer approach of the object
suspected. On one occasion, having gone into the fields with a few friends, of whom
one was dressed in a morning gown, and, coming unexpectedly on the troop of horses,
they were observed to collect immediately into a circle, and to detach one of their
number, with a view to ascertain the nature of the very unusual appearance, which
they evidently saw but indistinctly, though scarcely three quarters of a mile removed
from the place we stood. It was now I remarked, with some surprise, that the horse did
not, during the very long and circuitous course, approach much nearer to us, but made
hastily for that situation in which we should be placed between him and the quarter
from whence the wind blew ; thus evidently employing the organ of smell in prefe-
rence to that of sight.

56 DR KNOX on the Comparative Anatomy of the Eye.

reasons have been assigned for this, yet it evidently serves td
give them timely warning of the approach of their enemies. In
fishes, which have neither ciliary muscle nor nerves, nor true
moveable iris, the powers of vision are extremely limited. It
may also be readily imagined why, in those persons from whose
eyes the lens has been extracted in the operation for cataract,
the customary powers of the eye should remain nearly as strong
as previous to the operation, and that, on the adaptation of a
compensating lens for that which has been removed, the person
should feel no difficulty in adjusting the eye as before.

But I do not suppose that the whole of the phenomena of
the adjustment of the eye to the perception of objects placed at
various distances, depend entirely on the ciliary muscle. I have
every reason to believe, that the perception of objects placed at
very short distances, depends altogether, or nearly so, on the
contractions of the pupil or iris. I am quite aware of several
objections which might be offered to this theory, to obviate some
of which, I shall remark, that the eye, when not particularly
employed, remains in a middle state, i. e. we of preference re-
gard objects situated at moderate distances from us ; or, it may
be said, that we continually alter the focus from distant to near
objects, and vice versa. Now, when these changes go on rapid-
ly, there is little or no sense of fatigue, just as happens when the
various muscles of the body are put in action alternately, so that
gentle walking is always less fatiguing than standing still in pre-
cisely the same position. If an individual be directed to regard
a distant object, the most obvious change perceivable to the by-
stander is a sudden dilatation of the pupil, which dilatation is
necessarily in the ratio of the distance of the object, and the co-
lour of the iris. If the person be requested to examine the
same object with very great attention, the pupil will be seen
gently and slowly to contract, no doubt to throw out, as much

DR KNOX on the Comparative Anatomy of the Eye. 57

as possible, all the unnecessary rays of light ; this exertion may
be continued for some time, but every one knows, that it at last
becomes so irksome, that the eye involuntarily returns to a
middle state. We might suppose this sense of fatigue to arise
from our attempts to contract the iris, but this is by no means
probable ; it seems, to me, to arise from the exertions of the ci-
liary muscle, for it is extremely difficult to imagine why fatigue
should arise from a moderate contraction of the iris in viewing
distant objects, when we know that the same membrane is ge-
nerally much more contracted in its ordinary state. Moreover,
the eye cannot long regard distant objects without fatigue, even
though the attention be not particularly fixed thereon ; now it
cannot be the iris in this case. Lastly, Distant objects are seen
with tolerable precision when the pupil has been dilated by the
action of belladona ; now, here, the iris can scarcely be supposed
capable of much action. If a person who has been for some time
regarding distant objects, be now requested to examine one very
near, the pupil instantly contracts, and continues to do so in
proportion as the object is made to approach the eye. At last
the pupil reaches its maximum of contraction, and if the object
still approach the eye, the fatigue of distinct perception becomes
insupportable ; the iris suddenly returns to a middle state of con-
traction, and the object is no longer perceived. When bellado-
na has been applied to the eye, near objects cannot be perceived,
and the eye is said to have changed its focus, and to have be-
come long-sighted. These expressions are incorrect, the eye has
lost its power of viewing very near objects, because the iris can
no longer contract. It is also stated, that distant objects are
perceived as well after as before the use of the belladona, of the
accuracy of which assertion we may reasonably entertain doubts.
The inner membrane of the choroid has been well investigated
by anatomists ; there can be little doubt of its forming the cili-
VOL. x. p. i. H'

58 DR KNOX on the Comparative Anatomy of the Eye.

ary body and uvea *. It appears, at first sight, a very mechani-
cal notion, that the ciliary folds and processes are in a great mea-
sure formed, by a membrane being made to occupy a circle na-
turally too small for it in its expanded state ; but the way in
which these folds commence on the inner surface of the choroid,
actually bears out this idea, for the membrane may be unfolded
to a very great extent, and thus made to cover a much larger
surface. The same remark is applicable to the internal ciliary
folds or processes f. The external, or true ciliary processes,
have been admirably described and pourtrayed by ZINN, and
are, indeed, too well known to all anatomists, to require any par-
ticular notice here. Near their base, and between their inter-
vals, they are firmly fixed to the capsule, covering the canal of
Petit by a mechanism which I shall now endeavour to describe.
It has always been asserted, that when the ciliary processes are
removed from the humours, their impressions only remain ; but
this is incorrect. I at first thought that a portion of their sub-
stance was left adhering to the capsule over the canal of Petit ;
but further, and a more careful examination, proved this opinion
to be erroneous. When the iris is drawn backwards, after ha-
ving removed the cornea, and allowed the aqueous humour to
escape, the anterior edge of the ciliary processes may be seen
projecting into the posterior chamber of the aqueous humour ;
and on drawing these also backwards, a number of parallel fibres
are seen proceeding from the marginal or equatorial edge of the
capsule of the lens, to be inserted between each of the ciliary
processes. These fibres lie immediately over the canal of Petit,
and contribute with the perfectly transparent membrane lying

* Some anatomists have confined their description of the uvea to the coating of
the pigmentum nigrum, found on the posterior surface of the iris ; but this is not ge-
nerally received.

•f These are described a little below.

DR KNOX on the Comparative Anatomy of the Eye. 59

immediately beneath them, to form a portion of the parietes of
this canal. If we now examine the eye in the opposite direc-
tion, f. e. by dissecting off the sclerotic and choroid tunics, and
the retina, we may perceive a similar range of fibres proceeding
from the anterior edge of the vitreous humour, and from the
point where the retina terminates, forwards and upwards, to be
in like manner connected with the ciliary processes, by passing
in between each. If a lateral view be taken *, by making a very
delicate section of the eye, and gently raising the cut edges of
the ciliary body, there is still the same appearance, viz. of ante-
rior and posterior fibres, which have a common insertion be-
tween the ciliary processes near their base, and which form, in
conjunction with a transparent membrane, the external paries of
the canal of Petit. When we attempt to remove the ciliary pro-
cesses, and to detach them from the lens, some force is required,
and it not unfrequently happens, that the processes themselves
are torn, and a vast quantity of the pigmentum nigrum effused ;
at other times they may be detached, leaving the whole of the
semitransparent fibres lying over the outer paries of the canal of
Petit, and the canal itself perfectly untouched. The same re-
sult may be obtained by maceration ; but as it was evident that,
in separating the transparent humours from the dark tunic of
the choroid, a connection had been destroyed essential towards
understanding the anatomy of one of the most important parts
of the eye-ball, I re-examined the whole with great attention, in
numerous specimens, macerated for a long tune in spirits.

In order fully to describe the anatomy of these parts, we
ought to commence with the retina, or, perhaps, with the mem-
brane sometimes found between the retina and choroid coat.
This membrane appears to have been known, and partly de-
scribed, by the late Dr MONRO ; its existence has been often de-
nied and re-asserted ; on referring to my Notes, taken during

* See Plate III. Fig. 2.

H 2

60 Da KNOX on the Comparative Anatomy of the Eye.

the dissections, I find it stated, that the membrane is sometimes
partially absent, but, perhaps, never entirely ; that it seems to be
destined for the conveyance of bloodvessels, and, possibly, lym-
phatics *, and is apparently connected with the secretion of the
pigmentum nigrum ; for, in those animals in which the pigment
is very fluid and abundant, the membrane seemed most distinct ;
and, on the contrary, was altogether deficient, in those in which
the pigment seemed to form a part of the choroid itself. It is
difficult to say precisely where the membrane terminates ; but
there is little doubt of its being expanded over the membranes
forming the canal of Petit, and that it may even extend to the
edge of the pupil.

We may now proceed to examine the retina, because the
anatomy of its termination is intimately connected with a very
beautiful and very singular structure, not yet sufficiently de-
scribed. On its external aspect the retina is apparently inclosed
by a membrane, adhering to it so closely, that it cannot be de-
monstrated apart. From some successful dissections, I am in-
clined to consider the numerous bloodvessels seen on the inter-
nal surface of the retina, as expanded on an excessively deli-
cate tunic. These fix down the terminating edge of the retina
all round the anterior edge of the vitreous humour, and adhere
firmly to the capsules forming the external paries of the canal of
Petit. Whether or not the external parietes of the canal of Pe-
tit be a mere continuation of these membranes, conjoined with
the hyaloid, is a matter of little importance ; it is sufficient for
our purpose, that they seem continuous, and are firmly connect-
ed to each other. In whatever way formed, the membrane, or
assemblage of membranes, proceeds forwards, to be inserted into

* Dr PORTAL, in one case, found hydatids situate between the choroid and re-
tina. Unfortunately, he does not describe the pathology of the case with sufficient mi-
nuteness ; the fact, however, is valuable.

DR KNOX on the Comparative Anatomy of the Eye. 61

the circumference of the capsule of the lens, forming in its pas-
sage numerous longitudinal folds, and small projecting fimbri-
ated bodies, by which, in a natural state, the transparent hu-
mours are connected with the superjacent ciliary body. When
examined with a good glass, these folds are remarkably distinct,
and the whole bears the closest resemblance, in its distribution,
to the true ciliary body and processes. I have, therefore, ven-
tured to call them the Internal or Transparent Ciliary Body,
(or the ciliary body of the hyaloid membrane), in contradistinc-
tion to that of the choroid.

From the internal surface of the transparent ciliary body just
described, is detached a membrane, which being inserted into
the capsule of the lens, somewhat more posteriorly or central,
thus contributes to complete the triangular shaped canal of
Petit*. A number of appearances will immediately suggest
themselves, which the above details readily explain ; such, for
example, as the continuity of all the parietes of the canal of Pe-
tit, after the removal of the transparent humours from the eye-
ball, and the irregularities which the external paries of the ca-
nal presents, when distended with air, which induced the French
to call it " godronnee," and is owing to the bulging out of the
delicate tunic occupying the intermediate spaces of the folds or
processes, which being strengthened, and more firmly bound
down, do not expand like the other parts of the membrane.

* This may be considered as the hyaloid itself. Had I been aware at the time
these dissections were performed, that an excellent continental anatomist (M. RISES),
had formed similar opinions regarding these internal ciliary processes, I should, per-
haps, not have repeated my dissections so often as I did ; but I was forcibly struck
with the evident incorrectness of the descriptions given in some of the latest and best
elementary works on the Anatomy of Man ; and I was, moreover, anxious to disprove
the idea lately adopted, that these folds or processes are fibrous or muscular bodies.
M. RIBES' work has not yet reached this country ; and I allude simply to a brief
notice contained in an early number of the " Bulletin de Sc. Med?

62 DR KNOX on the Comparative Anatomy of the Eye.

By means of these transparent membranes, which I have called
the Internal Ciliary Processes, (or the ciliary processes of the
hyaloid membrane), the vitreous humour and lens are intimately
united together ; but it is also, as I have already shewn, by
means of the same membrane and processes that the humours of
the eye are affixed to the tunics immediately connected with
them, viz. the external ciliary processes, ciliary muscle, sclerotic,
&c. ; for the internal ciliary processes pass in between the folds
of the great or external ones, throughout a great part of their
course, and anteriorly near their termination in the capsule of
the lens, they send up numerous processes, to be inserted into
the superincumbent ciliary body between each of the ciliary pro-
cesses. Some have supposed these reduplications of the mem-
brane to be muscular fibres, an opinion against which we have
both ocular inspection and analogy. I am not prepared to as-
sert that microscopic fibres do not exist, but these, from their
very nature, must be exceedingly unimportant.

Of the Pigmentum Nigrum and its Membrane.

The late Dr MONRO observed, in two cases, a membrane
shutting up the pupil, the result of inflammation ; and in both
the posterior surface of the membrane was coated with pigmen-
tum nigrum. From this, and some other observations, I am in-
clined to think, that the pigmentum nigrum, in many animals, is
inclosed in a peculiar membrane, and that this membrane may
be continuous with that lying immediately external to the reti-
na, and betwixt it and the choroid coat, and generally known by
the name of the Membrane of Jacob. It is true, that through-
out a great part of its course, this membrane, when present, is
semitransparent, and that which sometimes incloses the pigmen-
tum nigrum is dark and opaque ; but I hare already demon-

DR KKOX on the Comparative Anatomy of the Eye. 63

trated, that this happens with the reflected membranes of the
choroid, and with several other membranous tissues of the eye.
In this case we should consider the membrana Jacobi as extend-
ing to the very edge of the pupil. The appearances, in the eye
of the cassowary, and in fishes, prove that there does exist a
membrane in the situation described.

The anatomy of the fishes' eye, which I shall now very brief-
ly describe, supports these opinions. Though a few striae may be
observed on the inner surface of the choroid in fishes, yet they
cannot be considered as constituting a ciliary body, whilst it is
very evident that there are no ciliary processes. The attach-
ment between the choroid and humours is by no means firm, but
still it exists, and the mode is as follows : On tearing off the scle-
rotic and cornea, a greyish-white line or chord, of considerable
thickness, is left. The choroid evidently passes under it, to in-
vest the internal surface of the transparent iris * ; but they can-
not be easily separated from each other. The proper choroid,
and innermost layer of this compound membrane, which had
been separated from each other posteriorly by the choroid gland,
unite intimately where the retina terminates, to pass forward
beneath the iris. A dark coloured fluid pigment covers the
whole surface of the retina, separated from it, however, by a thin
membrane ; but from the termination of the retina forwards, to
the very edge of the pupil, this pigment assumes the form of a
striated close membrane, perfectly black, and much resembling
the ciliary folds in the mammalia, and even possessing, as in the
cod, a beautiful fringed border, by which it adheres to the cap-
sule of the vitreous humour. In other words, the pigmentum
nigrum is no longer deposited on the surface of the choroid, but

* i. e. Supposing an iris to exist betwixt the prolongation of the choroid and
the reflected membrane of the cornea, which I do not believe to be the case.

64 DR KNOX on the Comparative Anatomy of the Eye.

becomes incorporated with a membrane. This takes place im-
mediately anterior to the termination of the retina. Though
the iris, and all the choroid coats, be removed, it is evident, that
there is still a very thin transparent membrane betwixt you and
the retina, connecting this latter with the membranous pigmen-
tum nigrum, and extending forwards to the edge of the pupil.
When the retina is pulled towards the optic nerve, this mem-
brane is drawn along with it ; when detached, the dark coloured
membrane assumes a fimbriated edge. The termination of the
retina is very precise and determinate ; the dark coloured mem-
brane adheres firmly to the subjacent hyaloid, but may be rea-
lily separated, for a certain distance, by commencing at the in-
ner edge of the pupil ; but on approaching the terminating
edge of the retina, the union becomes very intimate, and a
junction of all these membranes is very evident, by means of a
circular firm line, visible even to the naked eye. I have not ob-
served any adhesion of this dark coloured membrane to the
crystalline, and am, indeed, certain of the contrary. At its an-
terior edge, it quits the hyaloid, and proceeds to form that dark
membrane lining the iris, whilst the hyaloid, clear and transpa-
rent, advances forwards to inclose the lens.

The ease with which the retina may be separated from the
black membrane, shews that it lies external to the process of the
membrane connected with the hyaloid ; and this becomes evi-
dent, by observing the retina preserve, on being detached, its
anterior formal outline, or termination, and by the black mem-
brane still adhering to the hyaloid, which appears quite smooth
and continuous ; the anterior part of the retina is then, as it
were, inclosed between two folds of the membrane of the pig-
mentum nigrum, the exterior of which, no doubt, was described
long ago ; vessels unite it with the internal part of the iris, to
which, at these points, it becomes firmly attached.

I>R KNOX on the Comparative Anatomy of the Eye. 65

Perhaps the most remarkable appendage of the choroid is the
marsupium, supposed to exist only in the eyes of birds, but which
may be demonstrated in a great many fishes, and, I may add,
reptiles. The marsupium is a membranous expansion, sufficient-
ly firm, extending from the point at which the optic nerve ex-
pands, into the retina, and advancing generally through the
centre of the vitreous humour, to be fixed into the posterior and
lateral surface of the capsule of the lens, or, more correctly, into
that portion of the hyaloid membrane covering the posterior sur-
face of the lens. The marsupium is coated inside with a kind
of pigmentum nigrum, in some birds for about two-thirds of its
course ; in others much more ; the remaining portion, or that by
which it is attached to the choroid, is in many birds quite trans-
parent, and thus has escaped the notice of the anatomist. This
portion is, moreover, exceedingly delicate, and, unless the eye-
ball be opened with the greatest caution) is seldom seen. In the
eye of the cassowary it is of a brownish colour; In proportion
as the true anatomy of the marsupium was unknown, so were its
functions deemed mysterious and important ; its presence was
supposed confined to the feathered creation, and it thus became
associated with the superior vision of birds. But anatomy de-
monstrates, that it is simply a continuation of the choroid, that
portion being generally transparent by which they are con-
nected *.

I have already observed* that the portion of the choroid
which passes over the termination of the optic nerve, is trans-
parent, whilst, in those animals in which there is no considerable
artery passing through the vitreous humour, but where the ves-
sels proceed to the lens immediately under the retina, their
vessels will be found to be supported by a delicate transparent

* Plate III. Fig. 4.
VOL. X. P. I. I

66 DR KNOX on the Comparative Anatomy of the Eye.

membrane, which may be considered as an expanded transparent
marsupium *. Viewing the anatomy of these parts in the com-
parative range of animals, we observe, that, in the cat's eye, the
retina passes onwards to its destination unaided by any very dis-
tinct membrane ; the vitreous humour is eminently transparent,
and the circular point by which the optic nerve penetrates the
sclerotic is translucent. If the choroid transmit any membrane
across the termination of the optic nerve, it must be excessively
thin, and, to common glasses, altogether inappreciable. But, al-
ready in the horse, the passage of the choroid over the optic
nerve, and the escape of the medullary substance, to form or be
connected with the retina by innumerable small foramina, is vi-
sible to the naked eye. In the eye of some fishes, as the cod,
the principle is the same, though somewhat varied ; the retina
is divided into two portions, betwixt which a prolongation of the
choroid passes, to form a distinct, though partly colourless
marsupium. Lastly, In birds, we find a true coloured marsu-
pium f.

I have found it more difficult to decide on the functions of
the marsupium than on its true anatomy ; but if we cannot shew
what it is, we can at least demonstrate what it is not. As it is
in no way muscular, it cannot serve to alter the relation of the
internal parts of the eye to each other, but it may assist in re-
taining the lens in its situation, and give support to the numer-
ous vessels proceeding to it. It has no nerves.

* May not this membrane be the same with the dark coloured tunic, formed be-
tween the retina and vitreous humour, in the larger varieties of the cephdlopodous
mollusca ?

•f- It has appeared to me, that, in many animals, and even in some of the rumi-
nantia, the central artery of the retina does not send any branch through the centre
of the vitreous humour.

DB KNOX on the Comparative Anatomy of the Eye. 67

I ought now to speak of the mode in which the optic nerve
enters the eye-ball, which could not have been done previous to
describing the anatomy of the choroid and marsupium. It will
be unnecessary to detail the more usual facts, as they must be al-
ready well known to those whom I have the honour of address-
ing. I shall merely observe, that, in the mammalia generally, the
optic nerve passes through the choroid by innumerable little fo-
ramina, or, perhaps, by short canals, to expand into the pulpy
membrane of the retina, always supposing that the retina is an
expansion of the optic nerve *. The change relative to the en-
trance of the optic nerve commences in the ruminantia, for we
may observe, that, even in the sheep, the point at which the op-
tic nerve expands into the retina is not circular, but somewhat
semicircular. In the eye of the American deer f, the circular
mode of entrance has entirely disappeared, and the nerve pre-
sents, on entering the eye-ball, a small segment of a very large
arch. In the eye of the fallow deer, the line by which the nerve
enters the eye is nearly straight, and greatly lengthened. Last-
ly, In that of the bird, it is completely so. In the latter class of
animals, the nerve escapes on all sides through the reflected cho-
roid ; in others, it merely passes through the choroid, stretched
over the entrance of the nerve, when such happens to be the
case £. I have, throughout this paper, alluded often to the ana-
tomy of the eye of the deer ; it approaches very nearly that of

• Some anatomists think that the optic nerve is merely distributed on the reti-
na. There are several analogies in favour of this opinion, and even direct ocular in-
spection in the eyes of some fishes.

•j- The animal was said to have been sent to this country by his Excellency the
Governor-General of Canada.

* It is probable, that, in all animals, the choroid passes directly over the entrance
of the optic nerve ; but it would be extremely difficult to demonstrate this, owing to
the excessive tenuity and transparency of the membranous expansion.

i 2

68 DR KNOX on the Comparative Anatomy of the Eye.

the bird, and forms, as it were, the intermediate link, by which
the classes Mammalia and Aves are, so far as regards vision,
united together. I have already explained, why, in the deer,
though the mode by which the optic nerve enters the eye be the
same as in birds, there is still no distinct marsupium formed,
because the chief vessels do not pass through the vitreous hu-
mour, but accompany the retina. As the optic nerve passes
through the sclerotic in birds, this latter membrane forms, as it
were, a lengthened sheath (by a separation of its tunics) in which
the nerve proceeds for some way, before it penetrates into the
interior of the eye. In consequence of this peculiar form of the
sclerotic, the termination of the nerve which regards the vitre-
ous humour, is bounded by two strong, tendinous, straight lines ;
these are, of course, formed by the edges of the sclerotic. The
same distribution of the sclerotic and nerve takes place in the
deer, and extends even to the passage of the vessels, from the
exterior to the interior parts of the eye, mid-way between the
optic nerve and cornea. At these points (four or five in num-
ber), the choroid, by the transmission of prolongations, evidently
communicates with the exterior of the eye-ball *. The vessels
do not pass directly through the sclerotic, but between its layers ;
one edge of the sclerotic overhangs the other, and the more pro-
jecting line is strong, tendinous, and fixed down to the inner
surface of the sclerotic. But it is not in these points only that
the strong resemblance of the deer's eye to that of the bird holds
good ; the great ciliary muscle is remarkably broad and distinct,

* In the number of the Philosophical Transactions for 1810, (I quote from me-
mory), four distinct muscles are described within the sclerotic, in the eye of the rhi-
noceros. The situation of these muscles corresponds exactly with the prolongation of
the choroid membrane described in the text. I have examined the eye of the Afri-
can or two-horned rhinoceros, but do not remember to have observed any such
cles in it.

DR KNOX on the Comparative Anatomy of the Eye. 69

and the ciliary nerves are numerous, and send branches round
the iris, in the same way as in birds *.

In most fishes there is no true or moveable iris. In the
mammalia its relations appear complex ; but they may be unra-
velled, by comparing the structure with birds. I shall here de-
scribe very briefly its anatomy in the latter animals, and the
mode in which it may be best displayed. If we select the eye of
the larger birds, we may, unaided by glasses, perceive that the
pigmentum nigrum, covering the uvea, is inclosed in a delicate
and distinct membrane, and that this membrane proceeds from
the anterior part of the ciliary processes. The expansion of the
inner membrane of the choroid into the ciliary bodies, and then
into the uvea, is also most distinctly observed ; the formal termi-
nation of the middle layer, or true iris, in a brownish cellular
membrane, shewing clearly that it is a peculiar body, and not
a continuation of any other membrane ; and the connection this
cellular membrane has with the cornea, and with the tendinous
expansion of the ciliary muscle.

* I ought to have inserted, in this part of the observations, the result of my in-
quiries into the retina, its distribution, nature, &c. ; but at the time this memoir was
presented, I did not deem the researches sufficiently complete, or fitting to be sub-
mitted to the Royal Society of Edinburgh. But having repeated some of the dissec-
tions, and (the opportunity having presented itself) extended the researches, I made
the important, and most unexpected discovery, that Onejbramen centrale of the re-
tina, generally called the Foramen of S<EMM BEING, is not confined to the eye of Man,
and of some Quadrumanous Animals, whose organisation somewhat approaches him,
but is extended to the class Reptiles, contrary to the opinion of all comparative anato-
mists. The details of this very singular discovery are reserved for the Memoirs
of the Wernerian Society, and the fact is simply announced in this place, to make my
other observations more complete. " The foramen centrale of the retina exists in
many lizards, as the superciliosa, scutata, striata, and Calotes, and is in them compa-
ratively much more developed than in Man ; but it is wanting in the lizards called
gecko, mabuya," &c. See Memoirs of the Wernerian Society, Vol. v. Part 1.

70 Da KNOX on the Comparative Anatomy of the Eye.

There is still another mode of displaying the structure of the
eye in birds, equally advantageous with that described. Make
an incision through the ciliary body, immediately anterior to the
ciliary muscle, and a cavity will be opened into, lying imme-
diately over the ciliary plexus. This cavity is bounded internally
by the ciliary body ; externally by the ciliary muscle and nerves,
and their investing membrane ; posteriorly, by the connection of
the ciliary muscle with the choroid ; anteriorly by the membra-
nous expansion connecting the iris, ciliary body, cornea, and an-
terior termination of the ciliary muscle, to each other. This ca-
vity may, for short distances, be filled with air by the blowpipe.
It has never been described, though it exists in the eyes of the
mammalia. Where the ciliary nerves assume the ribbon form,
or become a plexus, the canal is interrupted by the passage of
the nerve across it, and by cellular membrane ; but it is to be
observed, that, in most of the mammalia, in which there is no true
plexus of ciliary nerves, the canal is small, and partly filled with
a very rare cellular tissue. The anatomy of this cavity displays
the whole anatomy of the anterior part of the eye-ball ; it shews
that the anatomist has confounded the ciliary nerves with the ci-
liary muscle, and it demonstrates the influence which the mo-
tions of the ciliary muscle and iris must have over the internal
configuration of the eye-ball. Numerous branches of nerves pro-
ceed to the ciliary muscle and iris, corresponding to the exer-
tions they are required to make in this class of animals.

The anatomical distribution of these parts differs but little
in the mammalia from that just described, and the analogy
may be deemed correct. The triangular cavity immediately
anterior to the insertion of the ciliary muscle into the sclero-
tic, is not so capacious, and the muscle is but indirectly connect-
ed with the internal layer of the cornea. It may be readily
imagined, that certain physiological differences will arise out of
the anatomical deviations just described. It has been often as-

DK KNOX on the Comparative Anatomy of the Eye. 71

serted, that the base of the iris is fixed immediately into the ci-
liary muscle, but this is incorrect ; for, though it seems to be so
in some mammalia, yet in birds, and even in most of the mamma-
lia, we find a considerable space intervening betwixt the base of
the iris and the anterior edge of the ciliary muscle, which space
is filled up by a dark coloured loose cellular tissue.

In the commencement of this Memoir, I have made a few
remarks on the Functions of the Iris, and, that I may not
seem to have overlooked the subject, I may observe, that many *
have ascribed muscular fibres to the iris, and, recently, Dr MAU-
NOIR has endeavoured to shew two sets of fibres, the one exter-
nal, radiated, the dilator of the pupil ; the other internal, nar-
rower, composed of circular fibres, the constrictor or sphincter
of the pupil. I have examined the iris very carefully in a great
variety of animals, but have never been able to detect any mus-
cular fibres as forming a part of its structure ; yet it is evi-
dently of a peculiar nature, and possesses in a high degree the
power of motion. It is most abundantly supplied with nerves
and bloodvessels, and, like other muscles, contracts under the
influence of galvanism f .

* I have not been able to procure a copy of M. MAUNOIE'S little treatise on the
subject, so that I quote the passage from the " Traite D'Anatomie Descriptive," by
Dr CLOQUET. Neither have I been able to obtain a sight of some observations which
I find announced by the Journals, as having been made on the same subject by Dr
EDWARDS of Paris. I regret this the more, because, from the known accuracy of
that excellent physiologist, I feel well assured, that, on the points investigated by him,
he would leave little to be done by future observers.

f Mr JOHN HCNTKE, whose physiological opinions scarcely admit of question,
seemed to think, a short time previous to his lamented death, that a fibrous structure
was not the sine qua non of muscularity. The application of this to the textures of
the iris and ciliary muscle is obvious.

72 DR KNOX on the Comparative Anatomy of the Eye.

We shall discuss, whilst considering the ciliary nerves, the
long agitated question, Whether the iris be a voluntary or invo-
luntary muscle. On the death of an animal, the pupil is in ge-
neral much dilated, but it again contracts whilst the other
muscles of the body are becoming rigid, these phenomena being
analogous. I have fancied that, in the horse, some time after
death, the pupil is more contracted than in most animals, which
may be attributed to the superiority of the sphincter over the
dilating part of the iris, and this is probably connected with the
peculiar fringe in which the superior margin of the pupil termi-
nates, compared not unaptly by SWAMMERDAM to the fringed
curtain-like body in which a part of the pupillary margin in the
eye of the skate terminates. There is a similar appearance,
though not fringed, nor yet so distinct, in the eye of the com-
mon dolphin.

III. Of the Ciliary Nerves, their Nature, and Distribution.

I regret that it will not be in my power to enter into any very
lengthened details relative to the ciliary nerves, and that I shall
be necessitated (by other avocations) to limit myself to a mere
outline, drawn up hastily, and even carelessly, though from nu-
merous dissections.

The nerves supplying the iris and ciliary muscle are derived
from the third and fifth pairs of cerebral nerves. They generally
form a ganglion, previous to giving off the true ciliary nerves ;
which ganglion is sometimes wanting, and would seem to have
but little influence over the action of the nerves. It resembles
anatomically, and perhaps physiologically, the gangh'on formed

DB KNOX on the Comparative Anatomy of the Eye. 73

by the superior and inferior maxillary branches of the fifth, and
is probably intended to subdivide the nervous filaments, and af-
ford a nucleus for the origin of a greater number of nerves than
could otherwise have happened, had they arisen from a single
trunk. That this is nearly the sole use of these gangh'a, we may
infer, by observing that they are often wanting in animals, with-
out giving rise to any difference in the functions of the nerves.
There is no lenticular ganglion in the horse, and this explains
the scarcity of ciliary nerves in that animal, the little develop-
ment of the ciliary muscle, and his very limited powers of vi-
sion. The submaxillary ganglion, and that so well described by
MECKEL, are wanting in a great number of animals ; and the
latter is not unfrequently absent in man himself. There is no-
thing, therefore, important in these gangh'a ; nothing affecting
directly the functions of the parts to which the ciliary nerves are
distributed. The connexion of the great sympathetic nerve with
the lenticular ganglion is very indirect, for the supposed con-
necting branch cannot be traced to the ganglion, and seems ra-
ther to join the ophthalmic branch of the fifth, in the same way
as the superior maxillary is connected with the superior cervical
ganglion, by means of the vidian.

The iris has been long considered an involuntary muscle, and
undoubtedly it is not so immediately under the power of volition
as many other muscles, and more particularly those of the extre-
mities ; but the assertion that the iris is altogether an involun-
tary muscle, and dependent for its motions on the stimulus of
light acting on the retina, may, I think, be disproved by the
simplest experiments. The iris dilates or contracts according
as the attention is more or less energetically fixed on an object,
though the quantity of light transmitted to the retina remain pre-
cisely the same. The cat and owl have the most complete command
over the motions of their iris, — a fact well known to every one ;

VOL. x. P. i. K

74 DR*KNOX on the Comparative Anatomy of the Eye.

and such is the power possessed by the parrot over this mem-
brane, that some have supposed the iris to be in this bird a vo-
luntary muscle. But there is no necessity for resorting to such
a supposition, for it is nearly as voluntary in man as in the par-
rot*.

The ciliary nerves are remarkable for their size and number
in birds, in the quadrumana, and in man ; they are very consi-
derable in the deer, remarkably distinct, readily traced into the
ciliary muscle, and send branches round the iris at about an
equal distance between the margin of the pupil and base. This
distribution is very remarkable in the hawk and owl, and may be
easily seen without dissection. A similar distribution prevails
in all the birds I have dissected, and even in many quadrupeds ;
in the former, the ciliary nerves pass through the ciliary muscle
in large trunks, and having reached the space or cavity existing
between the ciliary muscle and base of the iris, there form, or
are connected with, an extensive plexus of nerves, which passes
all round the eye-ball, and has been mistaken for the ciliary
nerves themselves. From this plexus arise a vast number of
very delicate nerves, which are distributed chiefly to the ciliary
muscle, and form partly on its inner surface, and partly within
its substance, a complete net-work of nerves. The meshes of this
net are large, and, at the junction of some of the nervous
branches composing it, delicate ganglia or swellings are perceiva-
ble. The iris seemed to me to receive but a few nerves from
the great plexus, and that by far the greater proportion of those
almost innumerable fibres which are distributed to it, pro-
ceeded from a few large trunks of nerves which pass immediate-

* Were we to suppose, that, in the cat, owl, and parrot, the movements of the
iris are dependent on volition, it would prove an unsurmountable objection to the
doctrines which teach that the nerves of volition never pass through ganglia.

Du KNOX on the Comparative Anatomy of the Eye. 75

ly to the base of the iris, and are not so intimately connected
with the plexus itself, except by communicating branches.
Where very distinct, as in birds and in deer, they send large
branches round the iris, imbedded in its substance, and from
these arise numerous nervous fibrils, supplying every part of the
iris. In those mammiferous animals in which the dissection can
be clearly made out, either from the magnitude of the nerves,
and the structure of the parts to which these are distributed, as
in the deer, or from structure only, as in the horse, we find, that
the ciliary nerves may be divided into two distinct sets, viz. one
passing to the ciliary muscle, and the other to the iris. The
former seem the least numerous, and are in some animals very
small ; the latter, with a few exceptions, are tolerably abundant
in all the mammalia.

In the horse, the nerves of the iris do not pass through the
ciliary muscle, but under it, *. e. between it and the choroid coat,
whilst the nerves supplying the ciliary muscle pass in long chords
along the inner surface of the ciliary muscle itself, constantly di-
minishing in size, by reason of the numerous fibrils sent to the
muscle. We thus discover the cause of the error lately commit-
ted by those very excellent anatomists, who fancied the ciliary
muscle to be a ganglion, or at least a nervous plexus ; for they
saw the ciliary nerves suddenly entering the muscle on their way
to the iris, and as it were disappearing ; they perceived, more-
over, that other branches seemed to arise from the ciliary muscle,
and they hastily concluded, that the intervening substance must
be a ganglion or nervous plexus at the least ; but I have shewn
this to be a great error ; for the smaller branches of those nerves
which enter the ciliary muscle are distributed to it, whilst the
larger ones pass directly through, to be expanded in numerous
fibrils on the true iris. We may now readily explain the mis-
take of those who fancied they discovered nerves proceeding to

K 2

76 DR KNOX on the Comparative Anatomy of the Eye.

the cornea. They found nerves going towards the ciliary muscle,
which were lost at the point where the muscle is inserted into
the sclerotic : they imagined, therefore, that these nerves must
be distributed to the cornea, as it was difficult to conceive how
any should be sent to the sclerotic.

I am fully convinced, from numerous dissections, that the so
named ciliary ganglion in man, and in the mammalia, is a pure
fiction, and imagined with a view to support the hypothesis of
the iris being altogether an involuntary muscle. As it is my in-
tention to resume the subject shortly, I shall here merely ob-
serve, that nervous plexuses, as those with which the nerves of
the extremities are connected in the mammalia, and the iridian
nerves in birds, are placed there by nature, not to impede the
influence of the brain, exercised during volition, over the muscles
to which these nerves are respectively distributed, but to afford
a more extensive point of connection to a much greater number
of nervous trunks than could have been the case, had the
branches connecting the plexus with the brain and spinal mar-
row, proceeded uninterruptedly to their termination in the re-
spective organs. The same observation is applicable, slightly
modified, to the ganglia found in the course of the cerebral
nerves, and in those of the vertebral column ; it is to the sym-
pathetic system of nerves, and their ganglia only, that the disco-
very of our celebrated countryman JOHNSON is applicable. It
must be evident to the Society, that to enter further into the
discussion of these doctrines, would lead me quite from the sub-
ject of the Memoir.

The nerve proceeding towards the choroid gland in fishes, is
a branch of the third, and not of the fifth ; moreover, it cannot
be traced to the gland. The remaining branches of the third are
distributed to the external muscles of the eye-ball. The sixth
pair of cerebral nerves in fishes join the fifth within the cranium.

Da KNOX on the Comparative Anatomy of the Eye. 77

i

There are no ciliary nerves, and consequently no true iris nor
ciliary muscle, in the specimens I have dissected ; but, as the
species I have had an opportunity of examining have been but
few, it is not intended that these observations should apply to
the whole class of fishes.

EXPLANATION OF PLATE III.

FIG. 1.

DISTRIBUTION of the ciliary nerves to the ciliary muscle and iris, in the eye of
the Cassowary.

The choroid tunic has been cut through, where it lies over the plexus of nerves,
and the cavity described at page 28 of the Memoir.

a The posterior surface of the Iris, generally called Uvea. On it may be seen the

remains of the membrane of the Pigmentum nigrum.
b The Ciliary Muscle.
c The posterior surface of the Cornea.
d The cut edges of the Sclerotic and Choroid.
e The Ciliary Processes and Striae.

f The external surface of the Ciliary Body removed from its situation to shew
the cavity containing the Ciliary Nerves.

FIG. 2.

The Anatomy of the internal Ciliary Processes, as seen in the Eye of the com-
mon Ox.

a The Iris cut up and reflected ; the cornea has been removed.

b The Lens in situ, inclosed in its capsule.

c The internal Ciliary Processes seen anteriorly.

d The same seen posteriorly ; the choroid has been removed. These different
portions of the internal ciliary processes are quite continuous, but are firmly
attached to the external ciliary processes immediately beneath the point f.
At c the external ciliary processes have been entirely removed, and an open-
ing made into the Canal of Petit.

78 DR KNOX on the Comparative Anatomy of the Eye.

FIG. 3.

A section of the Eye of the Heron.

a The internal Ciliary Processes surrounding the margin of the Lens,
a a The Lens covered by its capsule.
b A portion of the Vitreous Humour and its capsule,
c The Marsupium ; p, the very delicate and sometimes transparent portion by

which it is united to the choroid.
f The Choroid.
e The Sclerotic.

i The Ciliary Plicae, (their internal surface).
g One of the sheaths, transmitted by the choroid through the sclerotic, inclosing

blood-vessels. These sheaths are very remarkable and distinct in the eye of

the fallow-deer, American deer, &c.

FIG. 4.

A section of the Eye-ball of the Cassowary, to shew the mode in which the Mar-
supium is formed.

a The Marsupium. The lens has been removed.

b A portion of the Marsupium, (where this membrane meets the choroid, and is

continuous with it), removed, to shew the strong white medullary line of the

Optic Nerve,
c The Choroid.

d The Ciliary Body and Plicae.
e The posterior surface of the Iris, covered by the membrane of the Pigmentum

nigrum.
/ The Sclerotic.

( 79 )

III. Notice of an undescribed Vitrified Fort, in the Burnt Isles, in
the Kyks of Bute. By JAMES SMITH, Esq. of Jordanhill,
F. R S. Edin.

(Read March 17. 1823. J

IN the month of September last (1822), when becalmed in my
cutter in the Kyles of Bute, I accidently landed on the most
northerly of the Burnt Isles, a small group that stretches across
the Kyle or narrow channel between Bute and Argyleshire.

From the appearance of a ridge nearly covered with turf, I
imagined at first that kelp had been formerly burnt here, but on
examining it more narrowly I discovered that it was caused by
the remains of a vitrified fort.

The island on which it is placed is a flat gneiss rock, with
about half an acre of vegetable soil on its summit. The fort is
placed at the southern and most elevated extremity, but is not
more than twelve or fifteen feet above high-water mark. The
walls form a circle, or rather an irregular polygon, about sixty-
five feet in diameter, occupying nearly the whole of the highest
end of the island. I could trace the vitrified matter all round,
and should imagine, from what remains of the walls, that they
were originally about five feet in thickness. They seem to be
entirely composed of the gneiss which forms the rock of this and
the surrounding islands. Many of the stones have decayed by
the action of the atmosphere, previous to vitrification, and most of
them have been acted upon by the intense heat of the fire, although
in very different degrees. Some of them are but slightly glazed,
whilst in others the felspar appears to be converted into a dark

80 MB SMITH on an undescribed Vitrified Fort,

brown glass, either run into considerable masses, or into veins
alternating with the strata of quartz, which has become granular
like freestone : occasionally the vitrified matter forms a white
enamel.

I know not whether any more easily fusible substance has
been used as a flux, but I could not observe any appearance of
breccia, which Dr MACCULLOCH, in his paper on Vitrified Forts, in
the second volume of the Transactions of the Geological Society,
states to have been generally used for that purpose.

Within the walls the flat surface of the rock is exposed at
A (Plate IV). Near it, at B, there is a small hollow, which was per-
haps a well or cistern : at C there is an appearance of a ditch,
which, if artificial, was probably intended to strengthen the de-
fence on that side.

There are some peculiarities in the situation of this fort
which appear to me decisive of the question which is still agi-
tated whether the vitrification is the effect of accident or design.
Those who advocate the former opinion have supposed that they
were produced by ancient volcanoes, — by destruction by fire, — or
more recently, by the repeated action of signal fires. It is quite
unnecessary to say any thing here as to their volcanic origin ; *
and I think it proved by the experiments of Dr MACCULLOCH,
that, from the intensity of heat required to melt the most fusible

* Since this paper was written, the theory of their volcanic origin has been revived
by Dr HIBBERT, in consequence of an examination of the Fort of Finhaven, in the
county of Forfar. I have not seen that fort, but I cannot imagine that it will ap-
ply to the one in question, which is of a regular form, and placed on the flat surface
of a primitive rock. Neither can it be accounted for by supposing that volcanic pro-
ductions have been brought from a distance for the purpose of building, because
both from the size of the vitrified masses, and from the downward direction in which
the fused matter has run, we must conclude that the vitrification has taken place af-
ter the walls were built.

PLATE IV.

•

, «•'. — •. •»— «*r- t *. ..

in the Burnt Isles, in the Kyles of Bute. 81

of the rocks, it is impossible that any single conflagration could
have produced such eiFects.

In an article in the ninth volume of the Edinburgh Ency-
clopaedia, written, I believe, by Sir GEORGE MACKENZIE, these
effects are attributed " to making signals by fires," chiefly be-
cause those hitherto known have been placed in commanding si-
tuations. I apprehend, however, that this will not account for
the fort in question, because, in the first place, the situation, in
a flat, surrounded on all sides by hills of considerable elevation,
does not appear at all calculated for such a purpose ; and, in the
next place, the regularity of its form seems still more inconsist-
ent with the effects of any accidental cause.

We must, therefore, I think, conclude, that, in whatever man-
ner these singular buildings were constructed, or for whatever
purpose, they are the effects of design. They were probably
constructed at a period before the country was cleared of its ori-
ginal forests, when abundance of fuel, and ignorance of other
modes of cementing stone, had induced the inhabitants to resort
to the expedient of joining them by fusion.

VOL. x. P. i.

IV. On the Formation of Chalcedony. By SIR G. S. MACKENZIE,
Baronet, F. R. S. LOND. & Edin.

(Read January 21. 1822 J

ALTHOUGH I possess a collection of specimens of Chalcedony,
made expressly with the view to enable me to form some plau-
sible theory of its formation ; and, although my cabinet contains
a variety of forms, perhaps unequalled in any other collection,
I have, for many years, refrained from describing them, because
the oftener I contemplated my specimens, the less able I found
myself to apply any single agent, so that its operations alone
could account for their forms. It is, indeed, very long since I
entertained the opinion, that no hypothesis founded on the se-
parate agency of heat or of water, could be satisfactory to spe-
culative minds ; and that geologists could never account for the
formation of individual minerals, or of the rocks containing them,
without combining the power of heat with that of water. But
even this combination, though it can be easily conceived capable
of forming many of the productions of the mineral kingdom,
leaves numerous phenomena unexplained.

While we endeavour to account for the forms of Chalcedony,
we are not fettered by the appearance of animal remains, as in
the case of flint. It has indeed been supposed by some very
ingenious philosophers, that Chalcedony incloses some very deli-
cate vegetable forms ; but, while we know that various substan-
ces belonging to the mineral kingdoms, some of which are found
connected with Chalcedony, assume arborescent forms, we may

SIR G. S. MACKENZIE on the Formation of Chalcedony. 83

be permitted to hesitate to fix our belief, until we are admitted
farther into the secrets of Nature.

It will be allowed, that all attempts to account for what we
see in the material world, however unsuccessful they may be, are
so many steps 'towards discovery. The failure of one leads to
another. The naturalist is situate as if he were standing on a
spot whence numerous roads diverge, but of which only one leads
directly to Truth. He travels over many of them without ha-
ving struck into the right one ; but he gains at least the satis-
faction of having reduced the number yet to be examined, and
to have increased the chance of success to future adventurers.

The means by which Silica may be reduced into a condition,
from which it may assume the forms of chalcedony, of flint, of
crystals, or in which it may be introduced into the minute pores
of animal and vegetable bodies, may long continue to be a mys-
tery. We may hope, however, that the discovery of these means
may yet exalt the name of some fortunate philosopher, who, with
talent, observation, judgment, and perseverance, such as have
displayed to an admiring world the nature of the alkalies and
earths, will reduce the opacity of the veil that conceals some of
the most important and most wonderful operations of Nature.

Geological theorists have, in their anxiety to generalise, been
too prone to attribute all appearances to one proximate cause.
WERNER looked only to one cause, the solvent power of water ;
but water refuses to perform what has been ascribed to its power.
HUTTON regarded fluidity, caused by heat, and modified by com-
pression, as sufficient to account for every thing, while it is
speedily obvious to a careful observer, that the number of the
phenomena which can be best explained by the agency of heat,
is limited. The absurdities which have been published, for the
purpose of accommodating the theory of aqueous solution to
facts which bear the impress of a different process, are now ra-

L 2

84 SIR G. S. MACKENZIE on the Formation of Chalcedony.

pidly vanishing before the independence and candour of the pu-
pils of the Wernerian School itself. Many of them have gained
much credit to themselves, not merely for their careful examina-
tion of foreign countries, but from their having appealed to
the very scenes of their education, and acknowledged that they
now consider the views formerly impressed upon them to
have been erroneous. There is yet, however, a farther stretch
of candour to be expected from them ; and that is an acknow-
ledgment, that they had been anticipated in their views of
the origin of Trap-rocks, by the result of volcanic and trap coun-
tries having been examined by geologists of the Huttonian School.
The proofs of the igneous origin of such rocks, that were deposi-
ted in the cabinet of this Society more than eleven years ago,
will now be regarded as of more importance than what was then
conceded to them.

The idea of HUTTON, that the materials of all rocks have been
so affected by heat, as to have become in some cases soft, and in
most cases fluid, is, as a general proposition, manifestly contra-
dicted by facts. His theory, however, as illustrated by PLAY-
FAIR, I have always considered as better fitted to explain a great
mass of facts than any that has yet been promulgated. But it
does not explain every thing ; nor can I see any reason for ap-
pealing either to heat or to water exclusively, for the consolida-
tion of the globe, while both agents may be called to our aid,
and while the power of gravitation is in continual action. I
have it in my power to satisfy the Society, that there is another
power sufficient to convert loose materials into solid masses. I
refer to the power usually denominated the Attraction of Cohe-
sion. I had occasion, a considerable number of years ago, to fill
a medicine-chest, that was to be sent into the country. Into
one of the drawers I pressed some magnesia ; but I cannot now
recollect whether it was or was not then, as it is now, in the state

SIR G. S. MACKENZIE on the Formation of Chalcedony. 85

of carbonate. Some years afterwards I opened this drawer, and,
to my great surprise, I found the magnesia as hard as chalk. I
sent pieces of it from the country to my friends ; but, from my
having neglected at the time to commit the fact to writing, it
has been forgotten, and the specimens have been lost.

I have, however, the satisfaction to find that a quantity yet
remains in the drawer, which, though small, will be sufficient to
demonstrate the fact, that the mere juxta-position of the par-
ticles of magnesia is sufficient for consolidating them. Gravita-
tion, the attraction of cohesion, and the percolation of cold wa-
ter, containing such substances as it is capable of dissolving, may
account for the consolidation of many stratified rocks, though
certainly not for that of all. Water greatly heated may affect
much more as a solvent, and also by communicating heat. No-
thing, however, in my opinion, can account for many other phe-
nomena, but that the materials forming the rocks had been in a
state of actual fusion. While we suppose actual fusion to have
taken place, we may, without any risk of being considered fanci-
ful, believe that water may have been present in greater or less
quantity ; and that, when strongly heated, it has the property
of forming combinations, which it refuses to form when cold. Let
geologists, therefore, as they are at liberty to do, call to their aid all
the powers which nature presents, and cease to divide themselves
into parties. They have but one object in view, the discovery
of Truth. At present, geological theorists may be compared to
an army advancing against a fortress, with nothing but balls on
the right, nothing but guns in the centre, and nothing but pow-
der on the left. The three bodies make separate and indepen-
dent attacks ; but the arm of each is useless singly. They must
unite all the arms together before any impression can be made.

It is not my intention, in this memoir, to enter much into the
consideration of causes. I propose to iUustrate, as far as it may

86 SIR G. S. MACKENZIE on the Formation of Chalcedony.

be possible, by means of a few of the specimens I possess, the
condition in which Chalcedony must have been, previous to its
assuming the forms it now presents. This may appear to some
a superfluous labour, as it is acknowledged on all hands that
Chalcedony has been fluid. But the kind of fluidity has not
been agreed upon. Besides, I trust that what I have to remark
will not be altogether uninteresting. I have on all occasions
stated my conviction, founded on proofs which I have seen, and
examined over a large extent, and several of which are in the
cabinet of this Society, that the rocks in which Chalcedony is most
commonly found, are of igneous origin ; that is, that the whole
materials of which these rocks are composed have been placed
as we see them, by volcanic power acting under the influence of
particular circumstances, and especially of pressure. I shall now
endeavour, by an impartial examination of specimens, to ascer-
tain whether the condition of Chalcedony, before its consolida-
tion, was compatible with that conviction.

The various forms of Chalcedony may be comprehended, per-
haps, in four general varieties, to which I may give names, with-
out any other object than to facilitate description. I will there-
fore distinguish them by the appellations, Massive, Parallel, Bo-
tryoidal, and Pendulous. In the term Massive, I include the
agate structure, and I use it merely, because, though all solid
masses (with a very few exceptions *) have the agate form, that
form is not always visible, till the eye is assisted by cutting and
polishing the stone. By Parallel, I understand that variety
which is combined with varieties of opal, &c. in straight layers,
and which proves that these substances have had a common origin.

* I have but one specimen in which I cannot distinguish the agate forms even
with the help of polishing.

SIR G. S. MACKENZIE on the Formation of Chalcedony. 87

The term Botryoidal is often applied to mineral forms, and is
sufficiently understood. Pendulous I use in preference to Sta-
lactitic, because the latter term implies a peculiar mode of for-
mation already ascertained *.

No. 1. — The first specimen I exhibit is one in which the agate
structure is not visible ; it has a small cavity, lined with minute
crystals of quartz, and in its general appearance resembles flint.

No. 2. — This specimen is also massive ; and in its ordinary
fracture the agate structure is not seen ; but on the side from
which a slice has been taken, that structure displays itself.
This specimen is valuable on account of its exhibiting a peculiar
fracture, which cannot be described by words. It also shows an
exterior shell, such as I have succeeded in separating from ano-
ther specimen of the same sort.

No. 3. — This shell has the botryoidal form, and has given the
impression of this to the Chalcedony which has filled the cavity
formed by it, and which, therefore, is of posterior formation.1

No. 4. — In this specimen the parallel form is very slight, but
sufficiently visible.

No. 5. — This shows the parallel and massive forms combined ;
and there is a minute cavity, lined with quartz-crystals, in the

* This Memoir is printed nearly as it was read to the Society ; and there is un-
questionably some awkwardness in the references to the specimens, while neither spe-
cimens nor drawings of them can be examined. With respect to drawings, it is ex-
ceedingly difficult to represent mineral bodies well, without great labour and expence;
and the forms of the specimens referred to in this Memoir, as well as their general ap-
pearance, are such as render an attempt to represent them by engraving almost hope-
less. Indeed it would be useless, as many of the specimens referred to can be viewed
only by turning them in different directions, and placing them in different lights.
The facts are stated in such a manner, as, it is hoped, will leave nothing equivocal in
the mind of the reader.

88 SIR G. S. MACKENZIE on the Formation of Chalcedony.

centre. This specimen proves that both forms have had the same
origin.

I possess a number of specimens which shew considerable variety
in the parallel form, and some of which will be exhibited in con-
nection with other forms. In some specimens, the lines appear
as if the matter forming them had collected, or secreted into this
form while the whole was fluid. I remember having observed
some beds of trap in the Faroe Islands, which, when viewed at a
little distance, had the same appearance in respect to the nodules
of zeolite which they contained. The nodules appeared exactly as
if they had been arrested in their progress towards forming lines,
like flint in chalk, by the consolidation of the bed containing
them.

I have exhibited a specimen of the massive Chalcedony, from
which I had detached the exterior shell, which, impressing its
form on the included mass, proves that the shell had been first
formed, and had become solid, before the hollow, which it sur-
rounded, had been filled up.

No. 6. — I now produce a specimen of a shell which has the
botryoidal form, and which, from some remains of quartz-crys-
tals, appears to have been lined with them. But on the Chalce-
dony we observe the impressions of crystals, which prove that
the former was not, as in the other case, solid before other matter
was introduced.

No. 7. — Sometimes the shell, and the Chalcedony filling the
interior, are different both in colour and texture. In this spe-
cimen the shell is opaline and bluish white, and the interior mas-
sive Chalcedony is blackish grey.

The botryoidal form occurs in considerable variety of shape,
colour and size. Its origin is to be attributed partly to the sur-
face of the cavity containing it, but chiefly, I believe, to the
Chalcedony having, in its progress into the cavity, assumed the
spherical form, and to a number of such forms, while soft,

SIR G. S. MACKENZIE on the Formation of Chakedony. 89

uniting. The pendulous form seems to be only an enlargement,
or rather a prolongation, of the botryoidal ; and, to illustrate
this, I exhibit a beautiful specimen, having a pearly lustre. This
lustre is given by zeolite, or the substance called Cachalong,
forming the nucleus, or the thread, on which the Chalcedony has
been formed. The connection of the botryoidal with the pen-
dulous form is apparent.

No. 8. — I now exhibit a specimen, in which the massive and
pendulous forms are united ; and there are other specimens now
on the table, which show all the forms in a small space. Hence,
we may refer all the forms to one and the same previous condi-
tion of the substance of which they consist. That condition has
evidently been fluid ; but the kind and degree of fluidity is yet
to be investigated. Before proceeding farther, I may exhibit
the diversity of appearances which we meet with in the cavities,
which are formed by an exterior shell of Chalcedony.

It often happens that we find nothing within the shell,
which varies much in thickness ; being sometimes scarcely thicker
than paper, and in other cases several inches in thickness, of
which several specimens are on the table.

No. 9. — In the next specimen there is imperfectly crystal-
Used quartz within the cavity ; and we observe the impressions
of other crystals deeply inserted, but not penetrating to the
Chalcedony. The crystals that have made their impressions
were probably of calcareous spar.

No. 10. — Another specimen, although connected with the
pendulous form (which is always contained in cavities) serves to
shew a remarkable series of -depositions. We observe, first, that
a dark-coloured mass, probably a portion of the rock in which
the Chalcedony was contained, has assumed the pendulous form.
Around this, the Chalcedony forming the exterior shell of the
cavity, has formed a pendulous mass. The next coating is
formed of quartz, which, as it recedes from the Chalcedony, as-

VOL,. x. P. i. M

90 SIR G. S. MACKENZIE on the Formation of Chalcedony.

sumes the crystalline form. The Chalcedony and Quartz are dis-
tinctly separated by a thin film of a pale-bluish colour. Over
the quartz has been formed a layer of a white substance, proba-
bly opal or zeolite. Lastly, over this has formed a coating of
quartz, which shoots its crystals into the cavity.

These successive, and varied formations may be supposed by
some to have been produced by different fluids, introduced into
the cavity at different times ; and by others as a modification of
crystallisation from one fluid. We have already seen the prac-
ticability of separating an exterior shell from the matter that has
filled up the cavity. In the present case, the shell has assumed,
as is usual, the botryoidal form ; and there appears nothing to
lead to the supposition that it had not become solid before the
next layer, which is of quartz, had been formed. The quartz of
the second layer appears, evidently, to have formed its crystalline
points ; and these points have caused the third layer of opal or
zeolite to assume the botryoidal form. Now, it is not, perhaps,
possible that, during the crystallisation of different substances
from one fluid, any layer with the points of the crystals formed,
except the last one (that in the interior of the cavity), could ex-
ist. On the other hand, it may be argued with equal plausibi-
lity, that, when once a hard shell is formed, covering every part
of a cavity, it is impossible to conceive how any fluid could enter
to form a second layer ; and the difficulty of conceiving this be-
comes always greater, the more numerous and varied the layers
become. Other arguments, on both sides, might be stated, and
illustrated by specimens ; but as these do not appear to prepon-
derate more to one side than to another, I will not at present
pursue the subject. I have said enough to prove, that it is no
easy matter for us to comprehend the operations of Nature. As
it is impossible for us to define the difference between that which
is material and that which is immaterial, or to know any thing
at all of the nature of matter, without knowing the essence of

SIR G. S. MACKENZIE on the Formation of Chalcedony. 91

things ; so I believe it to be impossible for us to penetrate into
the modifications which have obtained in producing the appear-'
ances we are now considering. We are satisfied of the existence
of a certain order of succession, and we may live to see the
cause which rendered the objects of our investigation fluid ; but
I apprehend we shall never understand the mode of action by
which the properties and characters of mineral bodies are kept
distinct, in situations and circumstances in which we might ex-
pect them to be blended together, so as to produce an anoma-
lous mass *.

No. 11. — In order, however, to illustrate this subject still far-
ther, I exhibit a specimen, in which the evidence of the quartz-
crystals having assumed their proper form, before the substance
deposited over them had become solid, is distinct. This sub-
stance appears to be opal or zeolite, as in the former specimen ;
and over it is a coating of very minute quartz-crystals ; thus pre-
senting an alternation similar, in order, to the other case, but
having the crystallisation of the quartz more perfect.

No. 12. — Another specimen of this alternation, to which I re-
quest the attention of the Society, is a very remarkable one. The
quartz-crystals are distinctly formed, and a slight coating of Chal-
cedony appears over them. But above this is deposited a white
dust, some of which adheres firmly to the crystals, while the rest
is loose. This suggests the idea, that the cavity had been filled
with vapour, which had condensed into the form of this dust.

No. 13. — In the next specimen the shell is thick, and is lined
with a soft white substance. On looking at these specimens, the
advocates of the igneous theory may probably perceive something
not unlike the process of Sublimation.

* Among numerous examples, well known to mineralogists, I may mention one
specimen in my possession, not much larger than a man's fist, which is formed pf dis-
tinct crystals of brown quartz, white topaz, and beryl.

M 2

92 SIB G. S. MACKENZIE on the Formation of Chalcedony.

The last specimen of this kind which I submit to the inspec-
tion of the Society, is that described by Mr ALLAN, in his ac-
count of the minerals of the Faroe Islands, and which is publish-
ed in the Transactions. The peculiarity which this specimen
presents is, that the coating of Chalcedony over the quartzy crys-
tals appears to become thicker, as well as the crystals themselves
larger, and the mass of quartz greater, as we examine from one
end of the specimen to the other. The coating of Chalcedony
has assumed the botryoidal form, and this gradually becomes
more enlarged and distinct as the coating becomes thicker. The
idea of the formation of this specimen, which may probably na-
turally occur on the first inspection, is, that the cavity, at the
time when the quartz was introduced into it, was in a position
having the larger end downwards ; and that in consequence of
this, the accumulation of quartz became greatest at that end.
But let us remark, in the first place, that the outer shell of
Chalcedony preserves a uniform thickness all round, except at
the very extremity of the smallest end. It becomes, therefore,
as necessary to account for there being no accumulation of Chal-
cedony at the lower end, as for there being an accumulation of
quartz. This last is not such an accumulation as we should ex-
pect either from the entrance of a solution, or of a substance-
fluid per se. In the first case, if the entrance of the fluid had
been gradual, we should have observed successive coats, or suc-
cessive crystallisations ; but here we have no succession of coats,
nor of crystallisations ; the crystals extend all the way from the
shell to their points without interruption. I am aware that crys-
tals are common, which show that they have been enlarged by
successive depositions of matter ; but it is not easy to conceive
how such an enlargement could proceed, while the fluid was
moving from one part of a cavity to another. As the accumula-
tion of Chalcedony over the quartz appears, if I may so express
myself, to have the same local ratio as to quantity with the

SIR G. S. MACKENZIE on the Formation of Chalcedony. 93

quartz, we may appeal to it for illustration. Let us suppose,
then, the cavity placed with its two ends in the direction of the
plummet, and fluid Chalcedony entering by the upper end, and
obeying the law of gravity. In these circumstances, I cannot
conceive how the fluid was conducted, so as to coat each crystal
uniformly on all sides, and at the same time so that no more
Chalcedony should rest on the lower than on the upper faces and
angles of the quartz-crystals ; nor can I account for there not ha-
ving been a mass at the bottom with a horizontal surface. Thus,
when we examine a specimen with minute attention, we find our
first notions respecting it incorrect. With these remarks, I leave
this remarkable specimen, as a proof of the danger of maintain-
ing sweeping theories, that pretend to explain every thing. It
has been asserted, that a philosopher sitting in his closet, with a
specimen before him, cannot reason correctly on the mode in
which a mineral has been formed ; but the specimen we have
been considering proves the contrary ; and also defies him who
may boast of having traversed every mineral mass that is exposed
to view anywhere on the surface of the globe. We may be
enabled accurately to ascertain general circumstances ; but par-
ticular modes of action, and formation among mineral substances,
under such circumstances, we can explain but seldom.

I now come to consider the Pendulous form of Chalcedony,
which affords an ample field for the exercise of theoretical inge-
nuity ; and at the same tune proves the utter hopelessness of the
task, when any one undertakes to find in it a demonstration of
his theory, and attempts to discover the minute circumstances,
and laws of action, which produced the forms which he studies.
The forms we have already considered, do not afford sufficient
data for assuming either the kind or degree of fluidity to which
Chalcedony may have been subjected ; but we shall find them in
the pendulous form.

94 SIR G. S. MACKENZIE on the Formation of Chakedony.

With respect to the size of the pendulous masses, I possess
one in which it does not exceed the fiftieth part of an inch in dia-
meter ; and another in which the diameter is one inch and three-
tenths; and I have seen some larger. In contemplating this
great difference in size, we naturally recur to the state in which
the substance was before it assumed its present form. We know
that, from a small quantity of a very weak solution of a salt, very
minute crystals will be formed ; while, from an equal quantity
of fluid more highly charged, larger crystals will shoot. But
there is a h'mit to this j for after passing a certain extent in add-
ing soluble matter, the resulting mass becomes confused. To pre-
vent this, when we wish to procure large crystals, we use a large
quantity of a rather weak solution, and allow it to evaporate
slowly. But supposing, as some have done, that pendulous Chal-
cedony is a crystalline shoot, we cannot, I suspect, accommodate
ourselves by supposing solutions of different strengths ; and if
we could, we see no means of carrying on a steady evaporation.
But as we know of no such thing as a cylindrical crystal, we may
at once set aside the idea of such a thing as chimerical. But it
is not, perhaps, easier to account for this form of Chalcedony,
with respect to difference of form in the pendulous specimens, by
means of a state of fluidity from heat. From an inspection of
the two specimens I have presented, a person, desirous of ac-
counting for the difference of size, by an appeal to heat, as the
sole cause of fluidity, would assert that the mass had been more
fluid in one case than in the other ; and that the minute forms
owed their origin to a great degree of fluidity, while the Chalce-
dony forming the larger specimen had not been subjected to a
greater degree of heat than was necessary to render it viscid.
This would be very plausible, were these the only specimens we
had to appeal to. But when we look farther, we find, in a small
specimen, such as that which I now submit to the inspection of
the Society, the pendulous masses varying very much in size,

SIR G. S. MACKENZIE on the Formation of Chalcedony. &5

and, which is most remarkable, the size increasing gradually
from one end of the specimen to the other. We cannot imagine
that the heat varied so much in intensity within the space of a
few inches, as to render the Chalcedony in one part exceedingly
thin, and in another viscid.

There is another supposition, with respect to this form, which
may be considered, while the former is before us in its most simple
shape. It has been suggested, that the pendulous form has been
produced in the same manner as a stalactite, by the successive
deposition of layers from a solution. This idea appears exceed-
ingly plausible, when we find, for the most part, this form pre-
senting concentric layers. But we know that such layers may
be produced by simple fusion in particular circumstances. For
instance, when a wax-candle is about to be made, the wick is
suspended in the centre of the mould, and the melted wax is
poured in at once. From such an operation we should not ex-
pect to find the candle formed of layers. Nevertheless, it is so ;
and by exhibiting such a candle, I can satisfy the Society of the
fact. This appearance of concentric layers or coats, is evidently
caused by the wick operating in some peculiar manner, so as to
give a particular direction to the process of crystallisation. In
almost all the cases in which the layers in Chalcedony are per-
ceptible, we find something analogous to the wick of the candle ;
either a hollow tube, or a thread of chlorite, zeolite, or some other
substance. In the only large specimen of pendulous Chalcedony
which I possess that has not such a thread within it, no layers
are perceptible, even with the assistance of cutting and polish-
ing.

The strict parallelism of the layers of Chalcedony, in its dif-
ferent forms, cannot, I should think, be attributed to any other
cause than crystallisation, under the influence of some modifying
power ; and such facts as I have stated, seem to favour the idea
of a state of fusion, and to afford ground of triumph to its sup-

96 SIR G. S. MACKENZIE on the Formation of Chalcedony.

porters. But, the advocates of solution may say, unluckily for
our opponents, we find cases in which threads of foreign matter
have not only not produced a concentric arrangement around
them, but have not interfered with the assumption of the paral-
lel form. As it is my purpose to do justice to both sides of the
question, I am bound to state that there is a most important dif-
ference between these two cases. — In that of pendulous Chalce-
dony, there is nothing to influence the crystallisation but the
tube or thread, consequently all its tendencies are towards the
centre. In the case of parallel Chalcedony, the matter has been
acted on by the bottom and sides of the cavity in which it is
contained, and this, together with its own gravity, seems to have
exerted an influence superior to that of the foreign matter sus-
pended in the fluid mass. In many specimens, the parallel Chal-
cedony seems to have been formed by the fluid matter rising
from the bottom, as* it gradually filled the cavity, and to have
surrounded the pendulous matter previously formed. But, in
the example before the Society, it is evident that the shape of the
cavity has not exerted any influence in disturbing the production
of the parallel form, as it appears to have done in the case of
agates. Accident, however, has led me to the real structure of
the Chalcedony in such cases. The specimen which I now sub-
mit for examination, was cut from a mass which seemed, as in
the former specimen, to have surrounded the pendulous. The
lapidary's oil having insinuated itself between the layers (a proof
that the layers are not contemporaneous), when I heated the re-
maining portion of the specimen red-hot, the Chalcedony becom-
ing opaque and white, the charred oil afforded a display of the
actual structure ; and it is certainly not such as might have been
expected. On looking at a specimen in its natural state, we can-
not predicate any other connection between the pendulous and
parallel Chalcedony, than simple adhesion ; yet we see how a
mere accident can prove the uncertainty of our speculations.

SIR G. S. MACKENZIE on the Formation of Chalcedony. 97

The result of this accident shews a much more intimate connec-
tion than our eyes could before discover. It exhibits a process,
the steps of which are so distinct, as to lead immediately to a
mode of formation similar to the stalactitic. It appears that the
first formed portion of the pendulous mass had reached lower
than the subsequent coatings ; and that the matter, in its liquid
form, after depositing a coat on the pendulous mass, had spread
out horizontally to form parallel layers. The extreme thinness of
some of the coats indicates an extreme degree of fluidity ; while
the accuracy with which the right angle is preserved between
the descending coat and the horizontal layers is very striking ;
and hence we may conclude (as well as from the uniform thick-
ness of each layer), that the passage from fluidity to a state of
solidity must have been rapid. This conclusion leads us to ano-
ther, I think irresistibly, that Chalcedony has been fluid per se,
and that it has become solid in the same manner as tallow, wax,
or water when it passes into the state of ice. But before pro-
ducing specimens to confirm that conclusion, I must point out
another fact which the specimen now before us has brought to
light. It appears distinctly, that the fluid matter has not only
enlarged the pendulous mass, and thickened the mass at the bot-
tom by successive descending coats, but that each coat or layer
may be traced round the sides of the cavity ; and, as might have
been expected, there is a greater accumulation at the bottom
than on the pendulous mass and sides of the cavity. Thus, no
doubt is left of the mode of formation.

In the next specimen which I exhibit, we have some other
curious facts displayed, besides a remarkable example of what I
have been illustrating. In this we see the successive descent of
the coats along the sides of the cavity. But it appears that a
considerable quantity of Chalcedony had been previously intro-
duced in some other manner, and which has assumed the parallel
form at the bottom. The regular formation of the parallel form,

VOL. x. P. i. N

98 SIR G. S. MACKENZIE on the Formation of Chalcedony.

by the descent of successive coats along the sides, and their
spreading over the bottom, appears in this specimen to have
been interrupted, by the introduction of another substance in a
fluid state, between which and the Chalcedony there seems to
have been a repugnance, analogous to that manifested between
oil and water. It has evidently not entered by the sides, nor
along with the Chalcedony (at least so far as we can judge while
we do not possess the whole geode), but it appears to have mixed
with the Chalcedony after it had been introduced, and to have
interrupted the regular formation of the parallel form, in a man-
ner which cannot be explained.

Each successive layer of Chalcedony has insulated a portion
of the white substance, and at the bottom we see a layer of
quartz thus insulated. Though the regularity of the parallel
form is interrupted, the connection of the successive coats is not
prevented.

Before quitting this specimen, I have to remark, that at one
side there appears some threads of foreign matter, around which
the Chalcedony had formed in the pendulous shape, before that
forming the interior mass had been introduced ; and from the po-
sition of these, it seems as if that of the cavity had been changed.
Another curious thing to be observed is, that the accumu-
lation of matter from one of the side coats, immediately below
the white matter (which is to all appearance zeolite), has in-
cluded in it a number of white hemispherical bodies, which seem
to indicate the incipient secretion, or rather separation of the
substance which usually forms some of the layers of the parallel
form. In another specimen, bodies similar to them appear to be
formed of a number of concentric hemispheres. Such facts, how-
ever, though curious, do not lead to the principal object I have
in view, which is, if possible, to demonstrate the kind of fluidity
to which the matter forming Chalcedony has been subjected.

IM.ATR V.

»r f,,,:,f ,)Vy rnuu. IW. .V . /,.,./, .1.1 .

SIR G. S. MACKENZIE on the Formation of Chalcedony. 99

I will now exhibit a few specimens of the parallel form,
which present facts altogether anomalous with respect to the
laws which fluids in general obey. In the first, we see that the
surface of the Chalcedony forming the undermost layer is not
parallel with that of the uppermost, and the intermediate layer ,
of opal consequently takes the form of a wedge. In the next,
this kind of anomaly is still more remarkable, and cannot be ex-
plained by any effects which come under our ordinary observa-
tion *.

We observe in this specimen, that the upper part of the pa-
rallel form has been depressed in a singular manner by the mat-
ter forming a pendulous mass. It seems as if the depressed mat-
ter had disappeared ; for, on the other side of the cavity, the
coats follow the usual course. I confess that I am quite puzzled
by this specimen. One thing, however, seems evident, that the
matter had not been in a state of great fluidity.

I am now to shew a specimen which appears to indicate a
state of viscid fluidity ; or that state in which we observe glass
when under the hands of the blower. In this we have the pen-
dulous form thickened at the end, so as to resemble a drum-
stick. As the pendulous mass has come into contact with the
matter below, we may either suppose that this has caused the
thickening at the end, or that this shape had been assumed, as
glass assumes it when dropt, and also thick honey. I cannot
imagine this specimen to have been in any other state ; and I
have longed to possess another similar one, that I might exa-
mine the internal structure ; for I cannot reconcile myself to the
risk of losing that now before the Society, by attempting to cut

* Though in most cases it is exceedingly difficult to make intelligible drawings
of the minute appearances which Chalcedony presents, a delineation of the fact now
under consideration is easy, and it is given in Plate V. Fig. 1.

N 2

100 SIR G. S. MACKENZIE on the Formation of Chalcedony.

it, as it is interesting in another particular besides that on ac-
count of which I now exhibit it.

It is obvious that, if any change in the position of the pen-
dulous form has taken place, the fluidity of the mass could not
have been very great. I possess a great many specimens, the
forms of which cannot be accounted for in any other way than
by supposing that the cavities were in motion previously to the
Chalcedony becoming solid. In one of these the pendulous
masses have taken three directions. In another they appear as
if radiating from a centre ; and, in this one particularly, the form
of a dropping mass of viscid glass is very striking. In a third
we see the pendulous masses twisted in a variety of ways ; some
into the form of a cork-screw. In another cavity we have a few
twisted, but the greatest number are all bent in one direction.
The most beautiful specimen of this which I possess, shews the
pendulous form, after being fairly bent round, attached at both
ends to the side of the cavity. This has no appearance of two
pendulous masses having met and joined. The curve is quite
regular, and not in any degree altered by thickening, which
would have happened had two masses met ; nor is there the
slightest indication of the matter having made farther progress
downwards. Such a form as this could not possibly have been
produced from a state of extreme fluidity ; and hence there may
be drawn a strong argument for fluidity by heat ; and for pen-
dulous masses having, in some instances, been formed at once,
and not by a deposition of successive coats. But we are by no
means allowed to rest satisfied with such a conclusion as a general
one. I now present specimens which prove, most distinctly, the
matter of which they are formed to have been as thin, perhaps,
as water. Whoever has seen water trickling from above, amongst
grass or trailing plants, during frost, will have observed a forma-
tion of ice precisely of the form which Chalcedony has assumed
in this specimen ; which also proves that Chalcedony has been

SIR G. S. MACKENZIE on the Formation of Chalcedony. 101

formed, not from a solution, but from matter fluid per se,—a
fluid that has become solid as it advanced, in the same manner as
water during frost ; or, in other words, which has become solid
by the deprivation of heat, and not by the evaporation of a fluid.
Arriving at this conclusion we must examine the effects of heat
on other substances, in order to obtain an analogy which may
reconcile all the forms in which we find the very interesting sub-
stance I have been considering.

I have already pointed out the fact, that wax, when poured
into a candle-mould, arranges itself around the wick in the same
manner as Chalcedony appears to do around the matter which
we find in the centre of the concentric pendulous form. But
what we have now to observe of wax is, that when it arrives at a
certain temperature, it passes suddenly from a state of solidity,
(I should say cohesion perhaps) to that of extreme fluidity ; and
its transition from fluidity to the solid state is equally rapid.
To this substance, therefore, we may compare some forms of
Chalcedony, in respect to their previous condition and forma-
tion.

Glass passes very slowly from the fluid to the solid state ;
and to this we may compare other forms of Chalcedony in the
same manner. But the same thing cannot be similar in its pro-
perties to two dissimilar things ; and we must, therefore, imagine,
that some adventitious circumstances in the composition of Chal-
cedony, have had the power of altering its properties ; and that
these circumstances are too minute for us to discover. That
very minute additions to earthy compounds greatly alter their
figure and properties, we know by the facts brought to light by
the labours of analysts ; and we may hope that Chalcedony may
yet attract their notice more than it has hitherto done.

No chemist, so far as I know, has observed water in Chalce-
dony, except KLAPROTH, who found in the green variety (He-
liotrope) 2.5 per cent, of water. BERGMANN obtained 16 per

102 SIR G. S. MACKENZIE on the Formation of Chalcedony.

cent, of alumina in one specimen, and 2 per cent, in another, to-
gether with 1 1 per cent, of lime. May not such variations in
composition cause variations in the effects of heat applied to
Chalcedony ?

It is evident that the degree of heat necessary for the fusion
of Chalcedony, is not so high as we might be apt to imagine :
for in the specimens I now present, we find that Chalcedony has
covered calcareous crystals without altering their form. We
know, from the experiments of Sir JAMES HALL, the degree of
heat necessary for the fusion of carbonate of lime ; and from the
specimens it is clear, that the temperature required for the fu-
sion of Chalcedony, had not the power to melt carbonate of lime.
If, on the other hand, we are to call in the aid of a solvent, these
specimens prove that the solvent of Chalcedony could not act on
carbonate of lime. But it is useless to enter inte» a maze of sup-
position. I shall only observe, that I am rather puzzled, when
I see in one specimen Chalcedony covering calcareous spar, and
also calcareous spar covering Chalcedony. This is an anomaly
which, in the present state of our knowledge, cannot well be re-
conciled to contemporaneous formation, whether we suppose heat
or a solvent, or both together, to have been in action. Never-
theless, I am disposed to consider the formation to be contem-
poraneous ; and possibly when we come to be better acquainted
with the power of water greatly heated, the mystery may not ap-
pear so great.

There is yet another mode of formation to which some forms
of Chalcedony appear to have considerable analogy. I refer to
the formation of pendulous masses from vapour, of which the
best illustration is to be seen in the singular substance sometimes
found 'in the retorts of gas manufactories. That substance pre-
sents to us the botryoidal as well as the pendulous form; a
combination very common in Chalcedony. I have already pro-
duced a specimen in which the cavity is sprinkled with a sub-

SIR G. S. MACKENZIE on the Formation of Chalcedony. 108

stance in the form of dust or flocculi, which most probably had
condensed from a state of vapour.

When Chalcedony is heated, splinters are thrown off with ex-
plosion ; a fact that indicates the conversion of some ingredient
of its composition into vapour. The escape of a component part
is indicated also by the chalcedony becoming opaque. It is most
likely that the matter which escapes is water ; and, indeed, I
have no doubt that water has had a chief concern in the forma-
tion of Chalcedony, and also of opal, and of all the varieties of
zeolite. That heat has operated along with it cannot be doubt-
ed, since we possess unequivocal proofs of its having affected the
masses of rock in which Chalcedony is for the most part found
I possess one specimen of the rock through which the Chalcedo-
ny appears to have become solid, while it was collecting and pas-
sing through the rock, having taken the branching form of blood-
vessels. This proves, that both the matter of the rock, and the
Chalcedony, had been soft and fluid at the same time ; and this
precludes the idea of the formation of cavities, in the first place,
and the subsequent gradual infiltration of a solution, if a thou-
sand other facts did not contradict it. The exclusion of heat as
an agent in the formation of the crust of the Earth, while so
many phenomena warranted its assumption, has greatly contri-
buted to multiply absurdities in the aqueous theories of the
Earth, while the exclusion of water has hindered HUTTON and
his illustrator from rendering the igneous theory the most per-
fect that has appeared. It is probable that water heated under
a powerful compressing force, will be found sufficient to explain
many anomalies both of the aqueous and igneous theories. But,
as I stated at the beginning of this memoir, geologists ought not
now to limit themselves to any one of the numerous agencies of
Nature. When geology was beginning to assume the form of a
science, it was of advantage, in the excitement of research, that
there should be theoretical parties, however absurd the word

104 SIR G. S. MACKENZIE on the Formation of Chalcedony.

party sounds in matters of science, in which its origin can only
be found in ignorance. Our knowledge of the structure of the
crust of the globe is now so extensive, that, in endeavouring to
account for the mode of its formation, we should feel ashamed to
limit our views to any single agent or process. With respect to
minute modes of formation in regard to individual minerals, the
description I have given in this memoir will, I trust, prove the
inutility of considering them, until experiments shall have enti-
tled us to speak freely. If it does so, one object I have had in
view will have been accomplished.

( 105 )

V. Notice respecting the Vertebra of a Whale, found in a Bed of
bluish Clay, near Ding-wall. By Sir G. S. MACKENZIE,
Baronet, F. R. S. Lond. & Edin. In a Letter to Dr
BREWSTER, Sec. R. S. Edin., &c.

(Read March 17. 1828J

MY DEAR SIR,

A HE Vertebra which I now send to you, was found about two
years ago, on the property of Mr MACKENZIE of Hilton, in
Strathpeffer, county of Ross ; and that gentleman desires me to
present this interesting relic of some cetaceous animal to the
Royal Society of Edinburgh.

Some years ago, a navigable canal was cut from the mouth of
the River Conan to the Town of Dingwall, and the operation
displayed a bed of dark bluish clay, containing sea-shells in great
numbers. The thickness of this bed I have not been able to as-
certain. A successful attempt having been made to drain the
lower part of Strathpeffer, which is now in a high state of culti-
vation, this bed of clay was found to extend several miles up the
valley ; and it was in clearing out the drain that the bone was
found in the clay. It is probable that more of the skeleton
might have been found, had search been made for it.

This bed of clay has evidently been formed at the same pe-
riod with that which is seen along the south shore of the Forth,
as it is about the same height from the present level of the wa-
ter. The bone was found at a distance from high-water mark
of about three miles ; and the height above the sea, at Dingwall,
of the spot from which it was dug, is about 12 feet. The date
VOL. x. P. i. o

106 SIR G. S. MACKENZIE on the Vertebra of a Whale.

of its deposition must be very remote ; for the great mass of
gravel, which you saw the rivers of this county cutting through,
is a deposition subsequent to the clay which it covers ; and in
many places peat-mosses have been formed above the gravel.
You may remember my pointing out to you two distinct alluvial
deposites ; one consisting chiefly of clay, covering the sides of
the hills, and including enormous blocks of stone ; and the other,
consisting of gravel, which fills the valleys, and has been cut
through at different periods, as the succession of terraces tes-
tifies. I have seen nothing that certifies the comparative ages
of the marine clay and the oldest alluvion ; but the latter I con-
sider to be the oldest. It appears, therefore, that many centu-
ries must have passed since the sea retired from StrathpefFer, or
since the land was elevated. Whether the ocean be again ad-
vancing, I will not pretend to decide ; but I have not yet sub-
scribed to Mr STEVENSON'S theory.

I am sure that the Society will be glad to preserve the bone,
as its having been discovered in circumstances nearly similar to
those under which the skeleton was found at Airthrie, and on
the same side of the island, render it extremely interesting.

I am,

My Dear Sir,

Truly Yours,

G. S. MACKENZIE.
COUL, \

21st January 1823. )

( 107 )

VI. Description of Hopeite, a New Mineral, from Altenberg
near Aix-la-Chapelle. By DAVID BREWSTER, LL.D. F.R.S.
Lond. & Sec. R. S. Edin.

(Read June 17. 1823.;

ABOUT the end of the year 1821, when I was engaged in the
examination of the Family of the Zeolites, Mr HEULAND was so
obliging as to send me a variety of Stilbite from a Calamine mine
at Altenberg near Aix-la-Chapelle. Upon comparing its optical
structure with that of the Stilbites, it was manifest that it had
no connection with this class of crystals, and that it constituted
a new mineral species. Upon mentioning this result to Mr
BROOKE, this acute mineralogist was of opinion that it was the
Silicate of Zinc. Mr HEULAND had been led to regard this sub-
stance as a Stilbite, in consequence of having re-
ceived it as such from Major PETERSEN ; but, par-
ticularly, from finding in the collection of Mr C.
H. TURNER, a single crystal of the same sub-
stance attached to Carbonate of Zinc, and bear-
ing the annexed figure, with an inscription in
the handwriting of the Abbe HAUY, stating it to
be a new variety of Stilbite, to which he gave the
name of Stilbite Duovigesimale *.

* Attached to this figure is the following memorandum in HAUY'S handwrit-
ing : La position de cette figure est en rapport avec celle du noyau dans les planches
du Traite.

o 2

108 DR BREWSTER on Hopeite, a New Mineral,

Having determined, by many physical experiments, that it was
not Silicate of Zinc, I was anxious to obtain as much as would be
sufficient for the purposes of analysis. Mr HEULAND exerted
himself with his usual zeal for science, to obtain additional speci-
mens ; but Major PETERSEN, to whom he applied for this pur-
pose, informed him, that there was reason to believe that no spe-
cimens had been found excepting those which Mr HEULAND had
already received.

As those specimens were insufficient for chemical analysis, it
became necessary to examine the mineral by means of other
methods of observation, by which its existence as a New mineral
species was completely established.

Description of the Mineral.

Physical Character. — The specific gravity of a perfect crystal
was 2.76, and that of a larger specimen, with some black metal-
he particles adhering to it, was 2.91. It is scratched by calcare-
ous-spar, and its hardness is consequently below 3.0 of MOHS'S
scale. It is neither phosphorescent nor electric by heat.

The mineral must therefore be placed beside Anhydrite and
Cryolite, in the 1st order, or that of Haloide of the 2d class of
MOHS'S System.

Optical Character. — It has two axes of double refraction, the
principal one of which is perpendicular to the axis of the prism,
and also to the planes of most eminent cleavage. The action of
this principal axis is negative, like that of calcareous spar ; and
the inclination of the resultant axes of double refraction, mea-
sured with as much accuracy as the specimen would permit, is
about 48°. The index of the ordinary refraction, through one
of the summit planes, and one of the faces of the prism, was
nearly 1.601.

Jrom Altenberg, near Aix-la-Chapelte.

109

Crystallographic Structure *. — The perfect
crystal of this mineral is shewn in the an-
nexed figure. The angles taken by the re-
flecting goniometer were,

a upon a
b upon b

= 78° 36'
= 81 34

If we suppose the faces c, c, c, c enlarged
till all the others disappear, the crystal will
assume the form of a scalene four-sided pyramid (as shewn in
the annexed figure) whose edges have the following values :

SB - 107° 2'
y — 139 41
z — 86 49

Hence the ratio of
the axes will be

a : b : c = 1 : s/4.443 : ^1.493.

As the form resulting from the enlargement of the faces
c, c, c, c is the fundamental one according to MOHS'S System,
and designated by P, we obtain, by taking the angle of the ho-
rizontal prism at the apex of the pyramid, a — Pr — 101° 24',
and b — (Pr + oo)3 = 81° 34', the angle of the vertical prism
corresponding to the obtuse angle of the base of P. The mi-
neral has two cleavages perpendicular to each other ; the one pa-
rallel to d, which is easily obtained, and distinguished by its
pearly lustre ; and the other parallel to e, which is less distinct.

* I have been indebted for this crystallographic description of the mineral to Mr
HAIDINGEU.

110 DR BREWSTER on Hopeite, a New Mineral,

Hence the specific character of the mineral, in relation to its
form, will be

Prismatic, P = 139° 41' ; 107° 2' ; 86° 49'
Pr = 101° 24' (Pr + oo )3 - 81° 34'

w

Cleavage, Pr + co perfect, eminent. Pr + oo imperfect.

Chemical Character. — It is entirely soluble without any resi-
due, and without swelling or effervescence, in the muriatic and
the nitric acids ; but more rapidly in the former than in the lat-
ter. It is acted upon very slowly by sulphuric acid, whether
strong or diluted ; but is finally dissolved by it.

When exposed to the blowpipe * alone in the matras, it gives
off a great quantity of water, without any trace of carbonic acid.
It becomes first milk-white, and melts afterwards very readily
into a clear colourless globule, which, in melting, gives the flame
a greenish tint. With salt of phosphorus it melts in all propor-
tions very readily into a clear colourless glass, no skeleton of si-
lica being observed. If the mineral is in great proportion to the
salt of phosphorus, it turns opaque in cooling, but no fumes of
zinc are condensed on the charcoal f. With borax it fuses into
a clear colourless glass, which does not turn opaque in cooling.
It gives with soda a scoria, which, when hot, is of a yellowish co-
lour. The oxide of zinc is condensed round it in great quantity
upon the charcoal, and nearest to the scoria is a reddish-yellow
tint, which does not vanish in cooling, and indicates the presence
of Cadmium. When melted with soda, and moistened, it exhales
no hepatic odour. A solution of cobalt communicates a fine
bluish tint to the melted fossil.

* This examination of the mineral with the blowpipe was made for me by
M. NORDENSKJOLD, an able chemist from Abo, during his visit to Edinburgh.

•f- With all the siliceo-carbonates of zinc, when melted with salt of phosphorus, in
such a quantity that the glass turns opaque in cooling, a very perceptible ring of
oxide of zinc is condensed on the charcoal.

from Altenberg, near Aix-la-Chapelle. Ill

This mineral seems, therefore, to be a compound of some of
the stronger acids, such as phosphoric or boracic acid with zinc,
mixed with an earthy base and a little cadmium.

Having thus established the existence of this rare and inter-
esting substance, as a new mineral species, I avail myself of the
privilege of giving it the name of HOPEITE, in compliment to our
learned Vice-President Dr HOPE, who, to many general claims
of having his name associated with mineralogical science, adds
one more particularly memorable in the annals of this Society,
namely, the discovery and examination of the New Earth of
Strontites.

VII. Astronomical Observations made at Paramatta and Sydney.
By his Excellency Sir THOMAS BRISBANE, K. C. B. F. R. S.
Lond. & Edin. & M. RUMKER. In a Letter to Dr
BREWSTER, Sec. R. S. Edin.

(Read November 3. 1823J

MY DEAR SIR,

I REQUEST you will do me the favour of submitting to the
Royal Society the accompanying observations made at Para-
matta and Sydney. Those of the Comet, together with the
elements inferred from them, are exclusively Mr RUMKER'S, to
whom it is impossible for me to give adequate praise, either
for zeal, assiduity, or intelligence. In order to have a better
chance of observing the transit of Mercury over the Sun's disk,
I proceeded to Sydney, about 15 miles from hence, and I am
happy to say that we had a most propitious day throughout
for the observations, and that the near agreement of them
at both places tends to confirm their accuracy, as well as to
increase their value. Respecting the observations of the Sol-
stice, I have bestowed my utmost pains, and I trust they may be
considered as worthy of a place in the Transactions, as among
the first fruits of the Founder of an Australian Observatory to
his countrymen ; and when I acquaint you, that nearly ten thou-
sand stars of LA CAILLE'S Catalogue have been observed here,
and compared with his catalogue, by Mr RUMKER, in which ar-
duous work I have contributed but a very small share, I flatter
myself that such information will be received with more than
common interest by the Members of the Society, and that the

Observations made at Paramatta and Sydney. 113

Observatory will be considered in a tolerable state of activity,
when so much has been accomplished in eight months. You
are aware, however, that the necessary reductions will occupy
some months, as every clear day augments the catalogue. I think
I may most safely pronounce this to be a very favourable climate
for the astronomer.

I remain,

Most faithfully and truly yours,

THOS. BRISBANE.

P. S. — I omitted to mention in its place, in justice to Mr
JAMES DUNLOP, with whose merits you are well acquainted,
that it was he who first discovered the Comet of ENCKE with a
sweeper, at which occupation, besides many others, I find him
most valuable and useful.

Government House, Paramatta,
N. S. Wales, 17 tk January 1823.

VOL. X. P. I.

114 SIR THOMAS BRISBANE and MR RUMKER'S Astronomical

Elliptic Elements of the Comet in September 1822.

Time of passing the Perihelion,
Long, of Perihelion upon the Orbit,
Long, of descending Node,
Inclination,
Logarithm e,
Logarithm ^ Parameter,
Sidereal Revolution,

Oct. 24°.221201. Mean Time at Paramatta.

271° 36' 18.3"
272 42 23

52 40 41

9.9966440

0.3585731
663554.3 Days:

from mean Equinox.
1822.

= 82° 53' 11".

The agreement between the elements and the observations
will be seen from the following Table :

1822.

Mean Time at
Paramatta.

Mean
Longitude.

Errors of
Elements.

Mean Latitude.

Errors of
Elements.

Sept. 23.

8h 9 0"5

241° 53' 30"

0"

24° 10- 43" N.

0"

24.

8 0 47.4

241 55 4

— 27

23 2 20

— 6

26.

7 50 20.3

241 57 1

+ 45

20 50 45

— 11

27.

9 15 4.1

241 59 41

+ 16

19 43 38

— 2

29.

8 42 0.1

242 4 0

+ 17

17 43 29

+ 8

30.

7 43 28.2

242 6 48

— 4

16 47 42

+ 1

Oct. 12.

7 44 51.1

242 47 8

+ 5

6 54 45

+ 7

16.

7 44 17-5

243 1 57

+ 86

4 12 3

+ 12

17.

7 49 35.6

243 7 49

+ 86

3 33 47

+ 151

21.

8 11 13.3

243 24 56

— 12

1 6 18.6

+ 6

22.

7 28 28.0

243 28 57-6

0

0 32 29.5

0

26.

7 48 14.3

243 47 4

— 5

1 42 36.7 S.

— 48

27.

7 46 6.8

243 51 17

— 43

2 14 57

— 68

28.

7 23 7.5

243 55 52

— 7

2 44 59

__ -t

29.

7 24 1.1

244 0 59-8

— 39.8

3 15 57.2

+ 9

30.

7 30 20.2

244 4 56-0

0

3 46 47.5

+ 9

Nov. 2.

7 54 38.2

244 19 7

— 10

5 17 6.5

— 8

4.

7 43 21.7

244 28 26

— 6

6 14 36

— 4

7.

7 41 41.9

244 42 52

— 10

7 38 51.5

— 8

8.

7 45 59.1

244 47 58

— 25

868

+ 9

10.

7 47 49.5

244 57 12

'+ 8

9 0 58

— 27

11.

7 45 54.0

245 1 56

+ 18

9 27 18

— 6

Transit of Mercury over the Sun's Disc, November 3. 1822.

Immersion of preceding limb,
Complete Immersion,
Emersion of preceding limb,
Complete Emersion,

23h 20" 53".95 Apparent Time at Paramatta.
23 23 34 .53

2 5 93 .03

2 8 21 .55

Observations made at Paramatta and Sydney. 115

Immersion of preceding limb,
Complete Immersion,
Emersion of preceding limb,
Complete Emersion,

Immersion of preceding limb,
Total Immersion,
Emersion of preceding limb,
Total Emersion,

23" 5' 23".32 Mean Time at Sydney.
23 8 6.38

1 50 1 .78

1 53 0 .29

23" 21' 37".97 Apparent Time at Sydney.

24 21 .03
2 6 16 .43
2 9 14 .94

Winter Solstice 1822.

1822.

Dec. 14.
15.
17.
18.
19.
20.
21.

24.
25.
27.
28.

Q's true Zenith
Distance.

10°36'54".25
33 19.50
27

25
23

21
20
21
21
22
26
28

23.51
3.12
32.54
7.98
14.92
54.46
4.46
33.61
35.51
12.28
40.41

Reduction to
the Solstice.

16 4. 8
12 26.09
32.31
17.63
31.07
12.75

1.01
7.63
42.56
45.78
17.02
44.98

Solar Nutation,

Reduction to January 1. 1823,

Correction for
Q's Latitude.

+ 0.22
+ 0.10

— O.J8

— 0.33

— 0.49

— 0.61

— 0.74

— 0.85

— 0.93

— 0.94

— 0.94

— 0.82

— 0.68

Mean,

True Zenith Dist,
of Tropic of V^

10° 20* 49".67
53.51
51.02
45.16
60.98
54.62
51.46
52.60
55.90
50.11
48.79
54.44
54.75

10 20 52.54
+ 5.67

10 20 58.21
101

Mean zenith distance of Trop. of ft Jan. 1. 1823, 10 20 58.22
Ditto of Trop. of 52 Jan. 1. 1823, by summer

solstice, - - 57 16 25.697

Half Difference = obliquity 1823,
Half Sum = latitude of Observatory,

23 27 43.738
OS 48 41.958

116 SIR THOMAS BRISBANE and MR RUMKER'S Observations.

We add here the observations of the Comet of ENCKE, al-
ready transmitted in a former letter *.

1822.

Sidereal Time at
Paramatta.

Mean Right Aseen-
sion.

Mean Declination.

June 2.

J0h 39' 25"

92°43'51".3

17°39'46".3 N.

3.

11

93 46 20.7

16 53 7.5

4.

11 3 0

94 46 0.0

16 4 36.7

6.

11 7 38

96 42 11.6

14 22 42

7.

11 3 10

97 38 15.0

13 26 5

8.

11 17 25

98 33 47.7

12 31 18.6

10.

11 20 0

100 24 43.8

10 29 49.5

11.

11 24 39

101 19 44.5

9 26 46

12.

11 40 2

102 17 52.0

8 18 30

13.

11 42 1

103 15 2.0

7 6 30

14.

11 55 0

104 15 40.0

5 52 27

15.

11 40 48

105 17 0.5

4 33 40

19.

12 13 38

109 54 36.4

1 29 43.7 S.

20.

12 16 53

111 14 26.9

3 14 29.1

22.

13 18 46

114 12 20.5

7 8

23.

12 53 55

115 47 41.7

9 9 48.4

* The Letter here referred to never reached the Secretary, otherwise it would
have accompanied the present communication.

( 117 )

VIII. On a Remarkable Case of Magnetic Intensity of a Chrono-
meter. By GEORGE HARVEY, Esq. M. G. S. M. A. S. &c.

(Read November 17. 1823. )

A. BOX Chronometer having lately come into my possession, ex-
hibiting remarkable proofs of strong and active Magnetism, I
was induced to examine it particularly, and to ascertain the in-
tensities of its different parts, by means of an apparatus resem-
bling that employed by COULOMB, and which was capable, from
its very delicate construction, of indicating the existence of the
minutest traces of attraction.

By denoting the power of the terrestrial magnetism by 100,
the intensity of the Chronometer, one inch above the centre of
its crystal, was only 90.79, when the hour of xn pointed to the
north ; but, on turning the time-keeper, so as to bring ix into
the same direction, the intensity was augmented to 102.29, the
position of the oscillating cylinder remaining unchanged ; and by
again turning it another quadrant, so as to bring vi to the north,
the intensity again declined to 90.69, corresponding very nearly
with the result determined in the first position ; and, lastly, when
in was brought into the same situation, the measure of the in-
tensity farther declined to 78.89 : So that the attraction was a
maximum when ix was directed to the north, and a minimum
when in was brought into the same situation ; and what is farther
remarkable, the nearly equal intensities corresponding to the
positions of xn and vi, approach very closely to a state of equa-
lity, with the mean of the maximum and minimum intensities.

118 MR HARVEY on a Remarkable Case of Magnetic Intensity

The results, however, may be more conveniently examined in a
Table.

North.

Intensity.

XII
IX
VI

III

90.79
102.29
90.69
78.89

Mean

90.66

When these conclusions were obtained, the Chronometer had
not been in motion for some months. The time at which it stop-
ped being 9h 7m 50s, will of course determine the respective posi-
tions of the hour, minute, and seconds hands, with respect to the
oscillating bar, or the magnetic meridian. These particulars be-
came necessary to be attended to, in consequence of the strong
polarities of the three hands.

In two subsequent experiments, xu being directed to the
north, the intensity at three inches above the crystal was 94.70,
and at five inches 97.42.

Finding that such remarkable changes of intensity resulted
from merely turning the Chronometer, similar experiments were
performed at the same distance above the middle of the bottom
of the box, and the results of which are recorded in the follow-
ing Table,

North.

Intensity.

XII
IX
VI

III

77.17
91.34
101.26
94.94

Mean

91.18

and from which it appears, that the maximum intensity was
found when vi pointed to the north, and the minimum when xu

of a Chronometer.

119

was in the same situation ; and that the mean of the four inten-
sities approaches very nearly to an equality with that entered in
the former Table.

The top and bottom of the Chronometer presenting so many
varieties of attraction, it was conceived that similar anomalies
might result from an examination of its sides. Accordingly,
when xn was uppermost, and the oscillating cylinder one inch
above the middle of the side, the intensity amounted to 105.61 ;
but when the time-keeper was turned, so as to bring ix .below
the cylinder, the measure of the attraction rapidly declined to
89.61 ; and when vi was examined, it increased to 91.78 ; and,
lastly, when in pointed upwards, it again declined to 84.05.
These results may be conveniently arranged in a Table.

Side of the Chronometer
uppermost.

Intensity.

XII
IX
VI

III

105.61
89.61
91.78
84.05

Mean

92.76

The preceding observations having been made on the exter-
nal parts of the Chronometer, the intensity of its internal works
was next determined ; and, first, by placing the centre of the os-
cillating cylinder one inch above the extremity of the steel ar-
bor of the fusee, which possessed magnetism in a very high de-
gree, when the intensity was found to be 109.09 ; but when the
measure of the attraction was ascertained, in the line of a com-
mon tangent, proceeding from between the barrel and fusee, xn
being uppermost, it declined to 107.82. A still greater declen-
sion was, however, remarked, when the Chronometer was turned
another quadrant, so as to bring the middle of the side of the

120 MR HARVEY on a Remarkable Case of Magnetic Intensity

spring box an inch below the centre of the oscillating bar, ix be-
ing upwards, the intensity amounting only to 92.22 ; the north
pole, at the same time, dipping three degrees. Three coils of
the steel-chain were wound round the box. The time-keeper
being afterwards moved through a third quadrant, so as to bring
the cylinder over the spring of the balance, vi being uppermost,
the north pole dipped two degrees, and the intensity amounted
to 101.26. And, lastly, by turning the Chronometer through a
similar portion of a circle, bringing in upwards, and by this
means placing the centre of the oscillating cylinder over the small
interval between the balance and the fusee, the intensity fell to
79.51. Below the cylinder, in this case, were the arbor of the
fusee, and a ratchet and pivot for the same, all of steel, and pos-
sessing considerable magnetic power. These results are arranged
in the following Table :

Side of the Chronometer
uppermost.

Intensity.

XII
IX
VI

in

107.82
92.22
101.26
79.51

Mean \ 95.20

These conclusions bear some analogy, as, indeed, they ought,
to those recorded in the preceding Table, the maximum inten-
sity corresponding in each case to the position xn, and the mi-
nimum to that of in. The positions denoted by vi and ix are
also in both cases next to the maximum in point of magnitude.

The magnetism of the balance and its spring were also power-
fully displayed, by raising the Chronometer when vi was upper-
most, so as to bring the circumference of the latter within an
inch and a quarter of the oscillating cylinder ; the dip being in-

of a Chronometer. 121

creased from two to five degrees, and the intensity diminished
from 101.26 to 95.99.

On examining the balance, the inner rims of the arcs of com-
pensation were found to be of steel, and so likewise were the
time-screws, which connected them with the transverse arm.
These parts were in a state of active magnetism, particularly the
time-screws, one having strong northern polarity, and the other
southern. The small wormed cylinders also, on which the ther-
mometer pieces moved, presented equal proofs of polarity, one
being a north pole, and the other a south. The time-screw and
thermometer piece having northern polarity, were on one side
of the balance, and those having southern on the other. The
balance-spring likewise exhibited vigorous polarity.

When the north pole of a small bar magnet was placed near
the extremity of the wormed cylinder which possessed northern
polarity, the balance immediately receded a small quantity ; but
when the south pole was applied, the power was sufficient to
cause it to advance through a minute but sensible arc ; and simi-
lar effects were produced when the proper poles of the magnet
were presented to the extremity of the wormed cylinder having
southern polarity. On presenting a more powerful magnet, the
balance was drawn more than a quadrant from its quiescent po-
sition, and motion communicated to the Chronometer.

By placing the time-screws in the direction of the magnetic
meridian, and bringing the north pole of a pocket-compass near
that which possessed southern polarity, no deviation was of
course perceptible in the compass-needle ; but when the balance
was moved through the arcs recorded in the first column of the
following Table, the deviation in the direction of the compass
amounted to the quantities entered in the second ; the inertia
of the needle being too considerable to admit of its inversion.
By employing a needle of a more delicate construction, an in-
version of its poles took place, the moment the time-screw had
VOL. x. P. i. Q

122 Ma HARVEY on a Remarkable Case of Magnetic Intensity

passed through an arc of 90° ; when a deviation of the south
pole immediately followed.

Degrees of the
Arc of Com-
pensation.

Deviation of
the Compass
Needle.

0°

0°

10

41

20

8J

SO

12

40

15i

50

19

60

25

70

30

80

36|

90

43 £

100

49^

110

54|

When the Chronometer was so placed that the transverse
arm, which bears the time-screws of the balance, became east and
west, a fine compass-needle, having its centre over the middle of
the balance, immediately disposed itself in the same direction,
its north pole reposing over the screw which possessed southern
polarity. When also the balance was turned through an arc of
90°, the needle turned with it, the north pole in consequence
pointing to the south. The moment, however, the balance was
allowed to vibrate, the needle commenced its oscillations, vibra-
ting in progressively decreasing arcs, from the first semicircle de-
scribed by it, to zero in the magnetic meridian, where it main-
tained a small tremulous motion. In another experiment, when
the balance was turned through a greater arc than a quadrant,
before motion was communicated to the Chronometer, the needle
was nearly inverted, the north pole pointing west ; and on mo-
tion being given to the balance, the needle ranged for many se-
conds through the complete circumference, until the directive
power of the earth, by gaining the ascendancy, caused the arcs
of vibration successively to diminish, the needle ultimately ob-

of a Chronometer. 123

taining a position coincident with the meridian, where it conti-
nued in a state of tremulous motion as before.

The quantity of steel contained in this Chronometer was
truly remarkable, and no part of it was destitute of vigorous po-
larity. Every screw displayed its influence, and of which there
were ten large, and several small ones, in the frame alone. The
chain also, the axles of the different wheels and pinions, the ar-
bor of the fusee, the balance and its spring, exhibited the same
intense and active power *. Nor did this polarity partake of the
transient character of that imparted by induction from the earth
to soft iron, but was permanent, undergoing no sensible altera-
tion from change of position.

From the short time the Chronometer has been in my pos-
session, no satisfactory account has been obtained of its rate.
During the three preceding years it was constantly on ship-
board, and its general character is said to have been good ; al-
though, at times, it appears to hare been subject to rather
more than ordinary aberrations. It would be interesting if a few
facts connected with its previous history could be obtained, as
they might probably throw some light on the source from whence
it derived its active magnetic powers. At a future time, I hope
to be able to communicate something on this head.

On a subsequent occasion, another Chronometer was exa-
mined by means of the same apparatus. The balance evinced
no proofs of polarity when small magnets were presented to it ;
but the apparatus of COULOMB detected some minute varieties
of attraction in different parts.

* Mr Cox, the agent for AKNOLD'S Chronometers at this place, and whose ac-
curate knowledge of the principles and action of time-keepers is so well known to
many of the most distinguished officers of his Majesty's Navy, remarked, when the
Chronometer under consideration was shewn to him, that it appeared nothing less
than a Magazine of Magnets,

Q y

124 MR HARVEY on a Remarkable Case of Magnetic Intensity

By placing the oscillating bar three quarters of an inch above
the centre of the glass-crystal, the magnetic intensity was found
to be 94.36 ; and at the same distance above the centre of the
bottom of the brass-case, it amounted to 100.63. When the
Chronometer was turned so as to bring its side below the bar,
in being upwards, the intensity was 98.51 ; and on determining
it on the opposite side, or when ix was uppermost, it amounted
to 94.02. When the cover of the Chronometer box was closed,
and the intensity determined at the before-mentioned distance
above its middle, the measure of the attraction became 99.13.
The intensity therefore was the greatest near the bottom of the
brass-case.

This chronometer appeared to have been constructed with
every possible care, to avoid the introduction of magnetism. The
handles of the box, the hinges and screws, the lock, staples and
key, were all of brass; still, from the anomalous results above pre-
sented, the variations of intensity were more considerable than
could have been anticipated, considering the very small quantity
of steel that appeared in it. These variations are indeed incon-
siderable when compared with the changes of intensity exhibited
in the former instance ; but are sufficient to prove that magne-
tism exists in Chronometers, when, from the precautions em-
ployed in their construction, we should have imagined it alto-
gether removed.

That the application of magnets to Chronometers does not
in all cases communicate magnetic qualities of a very powerful
kind, may be inferred from the example of another Chronometer,
which had been frequently employed in inquiries connected with
magnetism, for many months, and which was subsequently exa-
mined by the apparatus of COULOMB. The oscillating cylinder
was placed one inch above the crystal, and the intensity deter-
mined in four positions of the time-keeper, namely, when its xn
o'clock mark was directed successively to the four cardinal points

of a Chronometer.

125

of the horizon ; the experiment agreeing in this particular with
one determined for the first Chronometer. The following Table
contains the results :

North.

Intensity.

XII
IX
VI

III

100.13
99-75
97.54
98.03

Mean

98.86

and from which it appears, that the mean of the four intensities
approach very nearly to the assumed terrestrial intensity, and
that, moreover, a much greater uniformity exists among the re-
sults than in those determined for the first Chronometer.

The examples that have been furnished by Messrs VARLEY,
FISHER, BARLOW and Captain SCORESBY, relative to the magne-
tism of Chronometers, and from many experiments I have had
an opportunity of performing, and a detailed account of which
I hope soon to draw up, induce me to believe, that nothing short
of the absolute removal of every thing capable of retaining the
magnetic influence in the balance, will prove an effectual remedy
for the errors to which the rates of Chronometers are liable from
this cause. Captain SCORESBY, in an excellent paper published
in the 9th volume of the Edinburgh Transactions, proposes, with
his usual ingenuity, to free the balance from any magnetism it
may have acquired, by causing it to be ground and polished in
the plane of the magnetic equator ; or, as they are now gene-
rally constructed of soft steel, to have them turned in that plane.
This method of obviating their anomalous action, would in all
probability be effectual, if similar precautions could be taken
with the steel employed in the other parts of a Chronometer.
But the chain alone would be capable of imparting, in a short

126 MR HARVEY on a Remarkable Case of Magnetic Intensity.

time, any magnetic qualities it might possess to the balance, and
thus to restore to it that power of derangement which had been
previously removed. Suppose, for example, that the balance of
the first Chronometer alluded to in this paper were to have its
magnetism removed by the ingenious method recommended by
Captain SCORESBY, or by any other, is it not probable that the
same property would be again acquired, from the active magne-
tism possessed by the numerous screws, the arbor of the fusee, the
chain, &c. in consequence of the balance either remaining quies-
cent, or incessantly performing its vibrations in the neighbour-
hood of that which may, without impropriety, be denominated a
System of Magnets ? On the whole, therefore, the employment
of a substance in the construction of the balance, not only with-
out magnetism, but without the capabili ty of acquiring it, will be
the only effectual and perfect remedy for the anomaly in ques-
tion. Platina, or an alloy of platina, has been mentioned by the
intelligent and active philosopher last alluded to ; and it is not
improbable, but that it may be ultimately found as well adapted
to the purposes of compensation as steel. Similar precautions
are necessary in the formation of the balance-spring. Gold, it is
said, is very well adapted for this purpose.

PLYMOUTH, August 12. 1823-

( 127 )

IX. Remarks concerning the Natural-Historical Determination
of Diallage. By W. HAIDINGER, Esq.

(Read November 3. 1823.;

JL HE following paper contains the results of a series of inquiries,
which lead to the conclusion, that the mineral called Smaragdite
by SAUSSURE, does not form a species of its own ; but that this
name has been given to a compound of certain varieties of two
distinct species, Augite and Hornblende, the natural-historical
species ofparatomous and hemiprismatic Augite-spar.

Owing in part to the slight degree of resemblance prevailing
among its varieties, the authors who have described them differ
so essentially in opinion, that I am obliged to go into va-
rious details, both respecting the external appearance of the mi-
neral itself, and of the opinions of mineralogists, in order to
afford a correct view of the natural-historical species, to which
these varieties belong, since this is the basis upon which every
system, and, indeed, all accurate information in natural history,
is founded, and the fixed point to which the one and the other
must be referred.

The more particular objects of these examinations are the
grass-green, and such other green and greenish-grey varieties as
are found to be in immediate connexion with them in the same
identical specimens. A connexion between the real Smaragdite
and the foliated Anthophyllite of WERNER, or the Schiller-spar
of the Hartz, does not exist, and has been gratuitously assumed
by the Abbe HAUY, and by other mineralogists.

There is scarcely any thing which tends more evidently to
prove the homogeneity of individual bodies, than the transi-
tions between them, if correctly ascertained ; but we must not

128 MR HAIDINGER on the Natural-Historical

take for granted as a genuine transition, whatever appears to be
so to the unassisted senses, or, indeed, what is considered as such
in many mineralogical works. A real transition should not be
considered to take place, till the differences in each of the single
characters, taken separately, have been collected into as many
continuous series * ; and before this has been accurately effected,
it will in every respect be found more useful for natural history,
to consider as particular, although doubtful, species, such varieties
as are but imperfectly known, than to unite them with other
species, respecting which our information is more complete : for
the uncertain existence of a particular species, will always be
more apt to induce naturalists to examine more closely the varie-
ty in question, than the admitted or supposed want of distinct-
ness of some varieties of another species, which has already been
correctly described.

Although HAUY may have traced the connexion between his
Diallage verte and some greenish-grey, and blackish varieties, yet
a similar passage is entirely wanting among these, and the two
subdivisions of his Diallage metallo'ide, the natural-historical spe-
cies of diatomous and hemiprismatic Schiller-spar. In the first of
these, the Diatomous Schiller-spar, the regular forms are as yet
unknown ; but, besides the difference in the hardness of that sub-
stance and Green Diallage, it is impossible to join into one
continuous series the degrees of their specific gravity. As to the
second, or Hemiprismatic Schiller-spar, that identity in the se-
ries of crystallisation, which is requisite to establish a transition,
is entirely wanting, at least in so far as we are yet acquainted
with the forms which it presents.

The first naturalist who considered Smaragdite as a spe-
cies of its own, was the elder SAUSSURE, by whom it was first ac-
curately described, and provided with the above-mentioned

* MoHs1 Grund-Riss der Mineralogie, Th. i. F. 408.

Determination of Diallage. 129

name *. Modern mineralogy itself can scarcely be said to go be-
yond that period. Smaragdite was joined to Felspar by ROME' DE
I/ISLE, and to Schorl by DE BORN. On account of the difference in
the perfection of its lamina?, HAUY gave it the name of Diallage f ,
and thus introduced it into the mineralogical systems. When
HAUY was publishing the first edition of his Traite, he was not yet
acquainted with those substances which in the second he calls Dial-
lage metattoide ; but he exhibits among his Diallage, under the
very same denomination, the varieties of Hypersthene (prismatoi-
dal Schiller-spar), which he afterwards established as a par-
ticular species. WERNER ^ does not acknowledge Diallage as
a particular species, but considers it as a variety of granular Acti-
nolite. Very little, at that period, had yet been prepared for a
more accurate examination of the natural properties of minerals,
and in determining new varieties, any principle upon which it was
possible to rely, was almost entirely wanting. Destitute of
the means now afforded to the mineralogist, WERNER has, in the
present instance, displayed that remarkable acuteness, by which
he often discovered the close natural-historical relation of certain
minerals of a very different aspect, whilst, on the other hand, he
pointed out a difference between substances, very much resem-
bling each other, which it required a long period of time to de-
monstrate by examining their properties with the greatest accu-
racy. But even WERNER has often been deceived, by founding
his determinations upon mere ocular inspection ; and we shall be
the more disposed to abandon so deceitful a method of obser-
vation, the more we are able to ascertain those properties of mi-

* Voyages dans les Alpes, t. v. § 1318.
f Traite, t. iii. p. 125.

{ HOFFMANN, " Handbuch der Mineralogie,'" continued by BHEITHAUPT,
Th. ii. 2. s. 800.

VOI« X. P. I. R

130 MR HAIDINGER on the Natural-Historical

nerals, which are capable of being expressed by numbers, for
they must uniformly appear the same, to all who examine them
with the necessary accuracy. WERNER'S collection at Freyberg,
contains as granular Actinolite the varieties from Corsica, those
from the valley of Saass, at the foot of Monte Rosa, and those
from the Bacher in Stiria. It is to the last of these that the epi-
thet of " granular" more particularly refers. KARSTEN * assumes
the varieties from Corsica as a particular species he calls Schma-
ragdite, which, however, he mentions as including only a part of
the Smaragdite of SAUSSURE, the other belonging to chatoyant
Hornblende (diatomous Schiller-spar). He was thus forced to
acknowledge the high degree of resemblance among the less
distinct varieties of Smaragdite and common Hornblende. In
the same manner STEFFENS f enumerates in his system a
particular species, of which the Smaragdite of SAUSSURE forms
the most distinct variety ; yet this author confesses himself un-
certain with respect to an exact natural classification, in regard
to that species, and to those of the genus Schiller-spar in ge-
neral, and therefore gives his determination merely as a tem-
porary one, till further researches should decide its correct-
ness. An opinion widely different from the preceding is en-
tertained by HAUSMANN. His system £ joins in the substance
Heterotype, the formations of Hornblende (hemiprismatic Au-
gite-spar), — Diallage, — Bronzite (hemiprismatic Schiller-spar),
— Hypersthene (prismatoidal Schiller-spar), — Anthophyllite (pris-
matic Schiller-spar), — together with several others that be-
long to the natural-historical species of hemiprismatic Augite-
spar. As farther subdivisions, Diallage contains the follow-

» Tabellen, 1800, p. 70. ; 1808, p. 40.
f Handbuch, Th. i. s. 326.
* Handbuch, Th. ii. p. 712.

Determination of Diallage. 131

ing kinds, viz. 1st, The real Smaragdite, of a grass-green colour ;
2d, The less distinct varieties of the same, as common; and, 3d, The
diatomous Schiller-spar from the Hartz, as falcons Diallage ; part
of the latter forms probably also the 4tth kind, or Schiller-stein.
HAUSMANN endeavours to explain the single or monotomous
cleavage of the different species of Schiller-spar, and the splen-
dent laminae of Diallage, as produced out of the two faces that
occur in Hornblende, by supposing one of them to become more
perfect at the expence of the other, whereby, in most cases also,
" the angle of inclination is changed, and approaches more or
" less to a right angle." A supposition of that kind, if granted,
would be sufficient to overthrow the whole of crystallography,
and that which has just now been quoted, has, for this reason,
been very strongly objected to by HAUY*. The substances
and formations, in fact, of HAUSMANN'S system, do not aUow
of any strict comparison with either genus and species, or with
species and subspecies ; hence it will be impossible to assert, whe-
ther or not HAUSMANN means to comprehend Smaragdite un-
der the species of Hornblende.

This latter opinion, very often quoted, indeed, but more com-
monly with the view of refuting it, seems in general to have
gradually disappeared ; and the most recent systematical mine-
ralogists agree in considering the perfectly foliated green varie-
ties of the Smaragdite of SAUSSURE as a particular species, which
they place accordingly in their systems. Yet among the vast
number of works that more especially treat of the present sub-
ject, there is none which does not attempt to reproach the rest
with the uncertainty of their determinations, and the want of
distinctness in their descriptions, though its own assertions can

* Journal des Mines, xxxviu. p. 161.
R 2

132 MR HAIDINGER on the Natural-Historical

only serve farther to increase the embarrassment, for it is not un-
der such circumstances that a complete h'st of quotations, or a
thorough knowledge of the authors consulted, can be of any use.
We must, therefore, recur to Nature herself, and conform our opi-
nions to her dictates.

The principal properties in which Diallage, in its most dis-
tinct varieties, is said to differ from other minerals, more or less
resembling it, consist in the grass-green colour, and in the facili-
ty of being reduced by fracture into thin laminae, of a bright
pearly lustre. All the works hitherto published on the subject,
state these to be produced by cleavage, and yet they are not
owing to cleavage, but merely to composition.

It has been reserved to the most recent period, to ascertain
the real and important difference between faces of cleavage and
faces of composition, which, indeed, are sometimes hardly distin-
guishable, if the latter possess a regular disposition in the inte-
rior of massive or crystallised varieties that seem to consist of a
single individual. As far as I know, Professor MOHS is the first
author who succeeded in giving an accurate definition of the phe-
nomenon of cleavage in crystallised bodies. He confined it to the
property of a simple mineral, of allowing its particles to be sepa-
rated in more or less regular faces, in various yet determined di-
rections. Only this property, and not the faces themselves, ex-
ist before the cleavage had been rendered visible by the assist-
ance of mechanical force *. It is quite another tiling with those
faces of composition, which preserve constant directions within re-
gularly formed crystals of certain minerals. They really exist be-
fore the mechanical division of the particles has been effected.
This can be proved by many examples, and, among others, with
a peculiar degree of evidence, by one of the most common in na-

* MOHS' Grund-Riss. Th. i. p. 264., &c.

Determination of Diallage. 133

ture, taken from Calcareous-spar. Here the faces of composition
are parallel to those of R — 1, the rhombohedron truncating the
terminal edges of R, or the fundamental form ; they are always
the consequence of thin laminae, or films of the same substance,
engaged in the mass in an opposite sense, whose exact di-
rections we can geometrically construct, by supposing one part
of the mass contained between two faces parallel with each other,
and with one of the faces of R — 1, to be revolved 180° round
a line perpendicular to these faces, considered as their axis
of revolution. Not even the perfectly transparent varieties from
Iceland are free from such laminae; their action upon light
has led Dr BREWSTER to ascertain their existence. If they
occur in greater number parallel to only one of the faces of
R — 1, they give rise to a variety, in which only one of the faces
of cleavage, parallel to R, is very deeply striated in the direction
of its horizontal diagonal. The seeming difference in the angles,
owing to that composition, has induced BERNHARDI to consi-
der these varieties as belonging to a particular species, which he
calls Streifenspath, or Striated-spar. It is necessary, therefore,
to be very careful, in ascertaining whether an observed face in
the interior of a crystal or of a cleaveable mass, be really produced
by cleavage, or whether it owe its existence to regular composi-
tion.

Certain faces of cleavage, not parallel to the primitive form,
have been said by HAUY to pass alongside of the molecules, with-
out touching or intersecting them, which faces, for that reason,
he called des joints surnumeraires. This explanation applies re-
markably well to the above mentioned faces of composition,
which have been so accurately described by HAUY * in a variety
of green Diallage, where their pearly lustre is peculiarly bright.

* Traite, 2de Ed. v. ii. p. 462.

134 MR HAIDINGER on the Natural-Historical

But this variety, likewise, contains real faces of cleavage situated
in other directions, which intersect the former in oblique angles.
They are but slightly marked, and rather incohering, wherever
the brightest green colour is joined to a more perfect appearance
of the laminae ; whereas they assume a higher degree of distinct-
ness in the darker blackish-green varieties, into which the former
pass without in the least changing their parallel position, exact-
ly as is mentioned by HAUY. There are two such faces of clea-
vage, intersecting the faces of composition at an angle of 152°,
while they intersect each other at an angle of 1 24°. Accurate mea-
surements, taken by means of Dr WOLLASTON'S goniometer, have
yielded the angle formed by the two faces of cleavage in hemi-
prismatic Augite-spar — 124° 13', very little different from
124° 1-5', the result of NORDENSKIOLD'S observations, both of
these being different from 124° 34', the angle indicated by HAUY.
If, according to the crystallographic method of Professor MOHS,
we designate this prism by (Pr + 00 )\ which sign it receives by
being considered in connection with the rest of the simple forms
in the same species, the face of composition, parallel to the
greater diagonal of this prism, or to the lesser one of P -f- oo ,
will be expressed by the sign P r + °° •

The regular composition of the twin-crystals of the present
species, is parallel to the very same face Pr-f- °os of which,
among many well known examples, I shall only mention the va-
rieties found in the basalt of Bohemia. Several varieties of com-
mon Hornblende present a similar composition, as, for instance,
that contained in the zircon-syenite from Friedrichsvarn in Nor-
way ; but none of the varieties, not even those of green Diallage,
exhibit these faces of composition so perfectly smooth and even,
as the greenish-black Hornblende from the Kiennerud mine near
Kongsberg in Norway ; and yet this has never been considered
as a variety of Diallage.

Determination of Diallage. 135

HAUY quotes among the peculiarities of certain joints surnu-
tnerctires, that they contain films of heterogeneous minerals, a
property in which they likewise agree with the above-mentioned
faces of composition. Thus the black Hornblende from the Kien-
nerud mine, contains lamina? of Talc (prismatic Talc-mica) ; many
varieties of the green contain laminae of paratomous Augite-
spar.

If we try to determine the specific gravity of two varieties of
Diallage of a different colour, the grass-green and those of a dark-
er shade, which, at the same time, are found to occur in one iden-
tical specimen, we meet very often with a difference amounting
to, or even exceeding, one-tenth. Thus, irr one instance, where
both the varieties were remarkably distinct, I found the specific
gravity of the green, at a temperature of 15° centigr. (59° Fahr.) to
be — 3.129 (agreeing with SAUSSURE'S statement of 3.140), whilst
that of the greenish-black was only zi 3.007, — a difference, the
cause of which I was naturally led to inquire into more close-
ly. When examining the darker parts, and comparing them
with the green, I found that in the latter there were thin la-
minae of another mineral, interposed between the particles
of hornblende, the face in which they meet being that of
P r -j- oo . These lamina? are not at all cleavable in the direction
of the faces of (Pr -f oo )3 = 124° 13', but they may be cleaved
in other directions, intersecting the axis of that prism under ob-
lique angles, the latter faces of cleavage being much inferior to
the former, both in lustre and continuity. In several of the va-
rieties of this mineral from the Bacher, the interposed lamina?
have increased in thickness, so far that the hemiprismatic Au-
gite-spar, entirely disappears from the composition, and we are
led to a mineral, which, with all its peculiarities, except the co-
lour of grass-green, we must acknowledge to be a variety of pa-
ratomous Augite-spar. Now, we find the specific gravity of this

186 Mr HAIDINGER on the Natural-Historical

— 3.232, and its cleavage, exactly like that of all other varieties
of paratomous Augite-spar, to take place in the directions of
(Pr -f oo )5 = 87° 33' (according to NORDENSKIOLD, = 87° 42' ac-
cording to HAUY), and in those of its diagonals Pr-f- GO and
Pr + °° • There is a face of composition still conspicuous in

•p *»

these varieties, but this face is parallel to -- — 73° 54' (ac-
cording to HAUY) in paratomous Augite-spar, as in the varieties
called Salite, some of the Mussite and common Actinolite of WER-
NER ; whereas in the hemiprismatic, we have found it parallel to
Pr -f- oo . Yet there exist varieties of paratomous Augite-spar,
which are likewise compound, parallel to the face of P f -f- co ;
this is the case in several Mussites, common Actinolite, &c.
The specific gravity of 3.350, mentioned by BREITHAUPT in
HOFFMANN'S Handbuch, after the authority of WERNER, for his
granular actinolite, refers to granular varieties of paratomous Au-
gite-spar, since it is comprehended between the limits of the spe-
cific gravity of paratomous, but not between those of hemipris-
matic Augite-spar.

From these observations we may conclude, that green Diallage,
even in the most distinct varieties, is not a species of its own,
but that it consists of the varieties of two other species, of para-
tomous and hemiprismatic Augite-spar, into each of which it in-
sensibly passes, when the relative proportion of the other by
continual diminutions finally disappears. Yet a passage of this
kind never can entitle us to consider Smaragdite as the link which
would join the two species, and consequently prove them to be
but a single one ; it proves nothing else but that Smaragdite is a
mixture of both. This mixture of the two species in the per-
fectly foliated varieties of Diallage has been excellently described
by HAUY, in giving its geometrical character in the first edition
of his Traite, where he mentions that the single laminae are very

Determination of Diallage. 137

often cracked in other directions than those of the less distinct
faces of cleavage, the latter of which correspond to P r + oo of
hemiprismatic Augite-spar, and that they shew a tendency of sepa-
rating into rhombs, — a property owing to the real faces of the clea-
vage of paratomous Augite-spar, which is spread in thin laminae
throughout the mass of the hemiprismatic. As long as it is
within the powers of our senses to distinguish, and to separate
these heterogeneous substances, the application of the Character-
istic will clearly lead to their respective species ; and no doubt in
regard to their determination can ever remain, as long as their
natural-historical properties can be ascertained with a sufficient
degree of exactness.

Professor MOHS, very long ago, and even during his residence at
Gratz, in consequence of accurate investigations, had recognised
the granular varieties from the Saualpe and the Bacher, as belong-
ing to paratomous, the latter also in part to hemiprismatic Augite-
spar, and united them accordingly with these species. The only
varieties still doubtful were those from other countries, so very
much distinguished by the perfection and high pearly lustre of
their laminae. The establishment of Smaragdite into the species
of axotomous Schiller-spar in the Characteristic of MOHS, was al-
most entirely founded upon foreign authority. It disappears
now from the series of particular mineral species, all its varieties
having been referred to those of hemiprismatic and paratomous
Augite-spar, in the properties of which they partake.

Although whatever belongs to the determination of the spe-
cies has thus been completed, and therefore the more peculiar
object of this paper attained ; yet I shall conform to the usage
hitherto received in mineralogy, not to pass over entirely the
instruction derived from other sciences foreign to natural his-
tory, in respect to the species under consideration, and shall
therefore give a brief account of the chemical constitution of

VOL. x. p. i. s

138

Mr HAIDINGEH on the Natural-Historical

Smaragdite, of its geognostic position, and concomitant mine-
rals. Fortunately the labours of some of the most celebrated
chemists and geologists afford the means of doing so.

The following analyses of the Smaragdite have been published
for some years.

1. Green Sma-
ragdite, accord-
ing to Lelievre.

9. Green Sma-
ragdite, accord-
ing to Vauque-
lin.

3. Grey Smarag-
dite, according
to Lelievre.

4. Granular Acti-
nolite from Stiria,
according to Kla-
proth.

Silica, - - -

51.0

50.0

50.0

56.0

Alumina, - -

13.5

11.0

7.0

3.25

Magnesia, - -

5.0

6.0

8.0

18.5

Lime, - - -

14.5

13.0

17.0

15.5

Oxide of Iron,

8.0

5.3

14.5

4.75

Oxide of Copper,
Oxide of Chrome,

0.5
4.0

1.5

7.5

0.0
0.0

96.5

( A trace of
•J Oxide of
( Manganese.

1.0

96.5

94.3

99.0

The agreement between the three first of these analyses, and the
results obtained by analyzing the several varieties of Hornblende,
is as obvious as the coincidence of that by KLAPROTH with the
components of certain varieties of Augite, although, in general,
these two species themselves do not present any striking diffe-
rence in the proportions of their constituent parts.

The geognostic relations of what has been called Smaragdite
and Diallage, seem to present more peculiarity. It is principal-
ly to VON BUCK that we are indebted for having ascertain-
ed its geognostic position, and a great number of its locali-
ties, of which he has published the accounts in several of his
works, and especially in two papers on Gabbro, inserted in the
Memoirs of the Berlin Society. Throughout these papers he

Determination of Diallage. 139

has adopted HAUY'S opinion, that Green Diallage is different from
either Hornblende or Augite, and that it constitutes but one and
the same species with Diallage metalloids ; and, in many instan-
ces, even the determination of the rocks is founded upon this
supposition.

The mineral most commonly accompanying green Diallage, is
Saussurite or Jade, a species considered as a variety of compact
Felspar, by both WERNER * and HAUY f , although it had long
before been pointed out as a particular species, and acknowledged
as such by a great number of mineralogists. HAUY takes for
granted that the forms are identical, but even these deviate in
Saussurite from the forms of the different species of Felspar : for
it is possible to obtain its forms of cleavage, out of certain granu-
lar varieties, in the shape of oblique-angular four-sided prisms,
of nearly 124° and 56°, which can very easily be cleaved, parallel
to their faces, and with a less degree of distinctness, also paral-
lel to their short diagonal. The difference between the specific
gravity of Saussurite, and that of the Felspars, is as remarkable,
and still more easy to be ascertained; the limits of the former be-
ing 3.2 and 3.4, whereas the latter never exceeds 2.8. The spe-
cific gravity of a compact Saussurite from Corsica, I found =3.206;
that of two specimens of the granular variety, one from Piedmont,
and another from Bayreuth, — 3.253 ; of a compact one from
the shores of the Lake of Geneva, •=. 3.343. The hardness of
Saussurite, is by many authors said to be superior to that of
rhombohedral Quartz ; yet it is no higher than 5.5 of the scale
of MOHS, (between Apatite and Felspar), if taken with the neces-
sary precautions by the assistance of a file. On account of its
remarkable toughness, it nevertheless very often scratches rhom-

* HOFFMANN'S Handbuch, Th. ii. a. s. 339-
t Traite, 2de Ed. T. iii. p. 95.

S 2

140 Mr HAIDINGER on the Natural-Historical

bohedral Quartz, and emits lively sparks, if struck with steel.
Of the rest of the minerals generally occurring along with Dial-
lage, the most frequent are ; Garnet, of a reddish colour, inclining
to grey, lustre resinous, hardness — 7.5, specific gravity — 3.647 ;
likewise Talc and Kyanite. These species, if intermixed with
each other, constitute that rock which has been called Gabbro by
VON BUCH ; but the relative quantities of the ingredients not
being every where the same, 1 shall shortly mention those in
some of the most generally known varieties.

The beautiful Verde di Corsica duro, almost entirely consists
of compact Saussurite, of different shades of bluish-grey, in
clouded delineations, containing small imbedded masses of green
Smaragdite, which is very nearly pure hemiprismatic Augite-spar.
Its specific gravity is — 3.000 ; the face of composition is not
very distinct, and rather incohering, while the real cleavage, pa-
rallel to the faces of the prism, is more distinct, from the co-ex-
istence of which and the former the silky lustre is derived,
particularly if its varieties be cut and polished. It contains,
moreover, small masses of Talc, with delicate acicular crystals of
that variety of hemiprismatic Augite-spar, which has received the
name of Actinolite.

The Saussurite, forming the paste of the Gabbro, from the Val-
ley of Saass, is greenish-grey, and nearly compact ; the Smarag-
dite which it includes, sometimes in masses of considerable di-
mensions, is mountain-green ; it presents very little lustre upon
the faces of composition, and almost no traces of cleavage. Yet
these varieties of hemiprismatic Augite-spar, seem to contain but
little heterogeneous matter, their specific gravity being — 3.056.
The faces of cleavage, appear more distinctly, in certain veins of
perfectly pure varieties of the same species, which traverse in all
directions the larger masses of Smaragdite, with which, however,
they always remain in a parallel position. In this variety of
Gabbro, we likewise meet with particles of Garnet and Talc, con-

Determination of Diallage. 141

taining crystals of Kyanite. Several other varieties from the same
locality, and from Piedmont, are composed of a coarser grained
greyish-white Saussurite ; they contain a greater proportion of
Garnet ; their Smaragdite is accompanied and intermixed with
Augite (paratomous Augite-spar), gradually increasing, so that the
laminae, in many instances, entirely pass into the latter species.
Sometimes it is accompanied by a dark-green granular mixture
of Saussurite and hemiprismatic Augite-spar.

The gabbro from Bayreuth consists of greyish-white Saussu-
rite, and paratomous Augite-spar, of nearly the same variations
of colour, slightly inclining to green. The specific gravity of the
latter is — 3.255.

The varieties from the Bacher mountain, in Lower Stiria,
are among the most remarkable. In comparison with those de-
scribed above, they contain only a small quantity of Saussurite,
but a great deal of Garnet, and also Kyanite, in beautiful blue
crystals and grains. The large foliated masses of Smaragdite are
seldom to be met with among them ; more commonly their con-
stituent parts separate into granular aggregates of the two spe-
cies, paratomous and hemiprismatic Augite-spar, the colours of
the former being more lively grass-green or greenish-grey, whilst
those of the latter incline to brown, since they are, in general,
either leek- or pistachio-green. They also differ in point of
transparency, the hemiprismatic presenting a higher degree than
the paratomous Augite-spar. The most instructive specimens in
this respect can be gathered from the stone heaps prepared for
the improvement of the road between Windisch-Feistritz and
Gonnewitz, in Lower Stiria.

I have not found an opportunity of examining the composi-
tion of the Norway varieties of Gabbro. To Dr NAUMANN of
Jena, I am indebted for several very distinct specimens of the
Diallage contained in the varieties from Vaage and Gulfield.
They are pure hemiprismatic Augite-spar, perfectly cleavable pa-

142 Mr HAIDINGER on the Natural-Historical

rallel to the prism (Pr + oo)3 = 124° 13'; and although com-
pound, in the direction of the faces of Pr+ oo, they neverthe-
less present but a very inferior degree of lustre, upon these
faces of composition, if compared with those of cleavage. The
colour is a dark greenish-grey, and the specific gravity — 3.043.

Besides the rocks described, there are still a great many whose
characteristic ingredient is said to be DiaUage, which, however,
do not contain any hemiprismatic Augite-spar at all, but only the
varieties of the paratomous. Thus, the Eclogite of HAUY, found
in the Saualpe in Carinthia, is a mixture of red Garnet and leek-
green, paratomous Augite-spar, of the variety called Omphazite
by WERNER. The rocks from Austria and Bayreuth, which con-
tain Omphazite, though smaller grained, are exactly of the same
composition. The variety from the Saualpe occasionally con-
tains small greenish-white prisms of Zoisite (prismatoidal Augite-
spar).

VON BUCK has sufficiently ascertained the remarkable geo-
gnostic relation between Gabbro and Serpentine, in many places
which he visited during his travels. The Bacher in Lower
Stiria, gives another proof of this fact. Here the Gabbro rock
appears to constitute considerable masses in the Serpentine, near-
ly in the same way in which the masses of ore usually occur in
beds, or still more distinctly in metalliferous veins, if we may in-
dulge ourselves in considering the latter as points of comparison.
Yet it has not been possible to strengthen this opinion, by ob-
serving the immediate contact of the two rocks ; it is rather the
consequence of their distribution over the surface of the coun-
try.

It is attended with less difficulty to determine the position of
the rock from the Saualpe. It constitutes a subordinate bed in the
gneiss, and mica-slate formation of the Alps, and has been opened
by a quarry situate at the southern extremity of the Saualpe, in

Determination of Diallage. 142

the neighbourhood of a spring called the Kupplerbrann, from
which quarry the country around is supplied with a coarse kind
of very hard mill-stones. The rock contains in this quarry thin
layers of Quartz, filled with a great number of beautiful varieties
of the Carinthine of WERNER (hemiprismatic Augite-spar),of Kya-
nite, of Zoisite, of crystallised varieties of Rutile (peritomous
Titanium-ore), and of many other minerals we admire in collec-
tions. The same rock is also met with in the north part of
the same mountain ; and Professor MOHS has found it in his
travels through the Stirian and Carinthian mountains, to extend
to the Koralpe, and the more western parts of the Bacher, the
east end of which is occupied by the Gabbro described above.

It would too far exceed the limits of the present paper to en-
ter into similar details upon another class of rocks, likewise called
Gabbro, or Euphotide, the chief ingredients of which are, not the
green, but the metalloidal Diallage (hemiprismatic Schiller-spar),
Labrador-felspar, and partly also Serpentine ; as, for instance, in
that from the Monte Ferrato, near Florence *. I only venture
to add a few remarks as to the last of these species.

Serpentine has been pronounced by VON BUCK to be no-
thing else but a fine-grained mixture of Gabbro and Talc, an

opinion rather too much the result of mere speculation, than
should ever be the case in a science connected with nature ; yet
the doubts respecting the existence of a particular species of Ser-
pentine, which he derives from this opinion, are strongly supported

* According to the descriptions given by Drs HIBBEET and MAcCuLLocn, the
Diallage-rock from Shetland belongs likewise to this class. I cannot pass entirely
unnoticed their labours in ascertaining the geological positions of these rocks ; but
not yet having had an opportunity of examining the rocks themselves, and having
only recently become acquainted with the accounts published by Dr HIBBERT in lu's
Description of the Shetland Islands, p. 372., and by Dr MACCULLOCH, in the Quar-
terly Journal of Science, Literature and the Arts, vol. x. p. 103., I cannot at present
dwell any longer upon this subject,

144

Mr HAIDINGER on the Natural-Historical

by the highest authorities. Among all the proofs for the pecu-
liarity of a species, there is none more evident than that found-
ed upon the existence of crystalline varieties. It seems that the
rarity of crystals of Serpentine, has been the reason of their not
sooner having been noticed by mineralogists ; although, perhaps,
they have long ago been observed, but not sufficiently distin-
guished from other substances.

The forms of Serpentine are combinations of the Prismatic
System of MOHS. One of its most common
varieties is that represented in the annexed
figure. According to the method of desig-
nation of Professor MOHS, its crystallogra-
phic sign is,

P*. P. (Pr+oo)3. Pr+oo. Pf + oo.
o P d b s

The measures of the angles of P, the fundamental pyramid, are :
189° 34', in the place of its more obtuse terminal edges ; 105° 26'
in that of the more acute ones, replaced in the represented variety
by the planes o of the horizontal prism Pr ; 88° 26' at the basis.
The ratio of the axis, and the diagonals « : b : c is — 1 : V 4.3 : V 1 .4,
which, however, must not be taken for any thing more than an ap-
proximation, the dulness of the faces being prejudicial to the em-
ployment of the reflecting goniometer. The angles of the prisms
are the following: Przz 128° 31', the angle contiguous to the ter-
minal edge ; (Pr + oo)3 = 97° 33' in the place of b, — 82° 27' in
that of s, the faces b and * forming truncations upon the respec-
tive obtuse and acute lateral edges of the prism d. Several of
these crystals have one-fourth of an inch, or even more, in their
greatest extension : they adhere to the sides of small cavities in
the interior of a massive Serpentine, which moreover contains
particles of Calcareous-spar.

Determination of Diullage. 145

1 could get no information respecting their locality ; but there
exists a variety of the same species in roughly terminated im-
bedded crystals in the Weiss-stein of Chursdorf, near Penig in
Saxony, where they occur in small irregular veins, composed of
Felspar, Quartz and Tourmaline. The crystals of Serpentine are
not pseudomorphous ; for, besides the peculiarity of their series
of crystallisation, they present very distinctly, faces of cleavage in
the direction of the prism (Pr + <x)3 = 82° 27', and of Pr+ oo,
its greater diagonal, exactly agreeing with their external form.
The imbedded crystals, too, distinctly exhibit these faces of clea-
vage, even if the external form should be entirely obliterated by
their contact with other minerals.

Yet an exact knowledge of the forms was not required ; and
even without it, the specific gravity, if properly attended to,
would have been an argument not to be refuted, against the opi-
nion that Serpentine is identical with a mixture of Gabbro and
Talc. The component parts of Gabbro are the following species :

Saussurite, the specific gravity of which is - above 3.2

Hemiprismatic Augite-spar, . . above 2.9

Paratomous Augite-spar, . . above 3.2

Labrador, above 2g9

Talc> above 2.7 .

Now, the specific gravity of Serpentine being — 2.507, in the
above-mentioned crystallised variety, and = 2.488 in the clea-
vable one from Saxony ; it appears not only below a mean term
of all the specific gravities of the above-mentioned minerals, but
far less than the lowest limit of any one of those species taken
separately, which are said to produce the mixture.

Yet there exist some varieties of Serpentine, which, to a some-
what higher degree of specific gravity, join distinct traces of a
crystalline formation. Thus the variety from Monteferrato gives
2.716 ; it contains no magnetic (octahedral) Iron-ore, as it does
not affect the magnetic needle, which is the case with other va-

VOL. X. P. I. T

146 MR HAIDINGER oil the Natural-Historical

rieties that shew a higher specific gravity, namely, the Serpen-
tine from Matrey in the Tyrol, G. — 2.700, from the Hartz,
G. = 2.684, from Lower Stiria, G. = 2.667. The difference
of the latter can easily be explained by an admixture of Iron-
ore, for 8 per cent, of this mineral mixed with 92 per cent, of a
Serpentine, whose specific gravity is — 2.5, will suffice for raising
that of the compound to 2.72 ; but the same explanation cannot
apply to the Serpentine from Monteferrato, and a difference of
that kind, not yet accounted for, must, of itself, be sufficient for
directing the attention of mineralogists towards a more accurate
examination in future, of the different varieties of Serpentine.

Thus, mineralogy being the natural history of the mineral
kingdom, must correctly determine the different varieties, and
collect them within well defined species ; but in this, it has ful-
filled its duty, at least as far as respects the establishment of the
species, and it must leave a great deal of valuable information to
be obtained from other sciences, which likewise refer to the mi-
neral productions, as, for instance, from natural philosophy, geo-
logy, chemistry, the art of working and smelting ores, &c. The
first determination of a mineral, if incorrect, is very often preju-
dicial to all the subsequent inquiries, and it would not be diffi-
cult, from more than one example, to support this observation.
An accurate investigation of the rocks, can alone enable the geo-
logist to ascertain the nature of the materials of which mountains
are composed, the grand object of his researches ; and hence the
fundamental knowledge of the mineral species which natural his-
tory affords, is as necessary to him, as it is to the chemist, who
intends to subject them to his analysis.

G. ROSE has given us a beautiful example of the latter, in
his memoir on the different substances hitherto indiscriminately
comprised under the name of Felspar *. The difference among

* GILBEET, Annalen der Physik, &c. 1823.

Determination of Diallage. 147

these minerals is so obvious, that it will be easily found in nature,
even by those mineralogists, who have not been aware of it, pre-
vious to the publication of that paper ; and no doubt but the
resolution of what has been taken for only one species into several,
must prove of great influence upon the former, namely, the deter-
mination of the rocks. In this respect, besides its pure natural-
historical purpose, the above examination of Smaragdite will, I
believe, not be found entirely devoid of interest.

T 2

( 148 )

X. Investigation of Formula, for finding the Logarithms of Tri-
gonometrical Quantities from one another. By WILLIAM
WALLACE, F. R. S. Edin. and Professor of Mathematics in
the University of Edinburgh.

(Read November 3.

-I.HE most simple and obvious use of the Trigonometrical
Tables, is to find the logarithmic sine, tangent, &c. correspond-
ing to a given angle ; and, reversely, the angle corresponding to
a given sine or tangent. However, in their more general appli-
cation, we have often to find a logarithmic cosine, having given
the corresponding sine, or the contrary ; also the sine or cosine
from a given tangent, and, in these cases, it may be of no conse-
quence to know the exact angle.

Supposing a logarithmic cosine to be given, to find the sine,
it is usual, first, to find the angle from the cosine, and then the
sine from the angle *. In this way, as the given cosine may not
be found exactly in the Table, the differences must be taken, and
two proportions made to find a correction, to be added to the ta-
bular sine next less to that which is required. Indeed the two
proportions may be brought into one, by leaving out the ratio of
the angles, which is common to both, and introduced unnecessa-
rily ; but, in either way, the result is an approximation, only of
the first degree, near enough, indeed, for most purposes, but
which, in certain cases, may not be sufficiently correct.

* CAGNOLI Trigonometric, Art. 428. 2de Edition.

MR WALLACE'S Formula. 149

For example, let the sine be required, corresponding to the
cosine 9.9450915962. Using VLACQ'S Arithmetica Logarithmica,
it appears that the given number is between the cosines of
28° 12' and 28° 13'. The differences between the cosines and
between the sines of these angles are now to be taken, and also
the difference between the given cosine and the next greater in
the Table, as follows ;

cos 28° 12' 9.9451254712 sin 9.6744484704 cos 28° 12' 9.9451254712

cos 28 18 9.9450577094 sin 9-6746839948 given cos 9-9450915962

Differences, 677618 2355244 338750

and this proportion stated :

677618 : 2355244 : : 338750 : correction.

The fourth term, or correction, comes out 1177417, which, added
to the sine of 28° 12', gives 9.6745662121 for the sine required.
This, however, is only accurate in the first seven figures, the
true value being 9.6745662532, and the error .0000000411. We
have therefore lost the advantage which may be derived from
the logarithms in these Tables being carried to ten figures in-
stead of seven, the common number.

Having been led to this subject, by what I consider an im-
provement in the mode of resolving a case in Plane Trigonome-
try, which will form the subject of a separate paper, I have inves-
tigated rules for deducing the logarithms of Trigonometrical func-
tions from one another. The formulas are indeed only approxima-
tions, but they are of the second degree, and therefore sufficient-
ly accurate ; and from their nature, they are well adapted to lo-
garithmic calculation. As they appear to me to be new, and
to possess considerable analytic elegance by their simplicity and
compactness, I have ventured to lay them before the Royal So-
ciety.

150 MR WALLACE'S Formula for finding the Logarithms

1. Let A# be the finite increment of any angle #, (the letter
A being employed as the characteristic of a finite difference) and
let m = . 4342945, the modulus of the common system of lo-
gariths. By TAYLOR'S theorem,

1 (A a/)2 sin a? (A a/)3 „ -.
logcos(;r+A;r) = logcosa; — m{ tan x-*x+ -^^ —$— + -^^ — ^- + &e. },

1 (A a-)2 , cos a? (A rf
log sin (a:+Atf) = log sin ^ + m { cot a? • A a; — ^g^ — ^— + -^^ ^ -- Stc, },

Employing now the notation of the theory of differences, and
expressing,

log cos (a- + A x) — log cos a? by A log cos x,
log sin (x + A x) — log sin a? by A log sin x ;

we get these two formula,

1 (Aa?)* cosir (A a?)3
?¥i-f2. + slnrj-^L-&c. }. (2),

Again, by TAYLOR'S theorem, we have

(A*)* + &c.

cos* x cos*

/-. \t n
- - A ar + ^^ (A *) -

1 t cos x

\x T- **• j — — " gi

and hence

m-A» f (A a;)*

•

1 (A a?)* sin a? (Aa?)3

-^-g- ***

COS^CA^

,-- c.

But by the calculus of sines,

sin (2 a?+ A,r)

sin (2 x + A a.')
cot (x + Aar) + cot a? - sin ^ 9in (a; + A a^) "'

Therefore,

of Trigonometrical Quantities from one another. 151

By adding the corresponding sides of equations (1), (3), and sub-
tracting those of (2), (4), we find

sin (2 .r + Ax) wAa? sin x m (A a?)* .. ,„
*l°g«>s* + cos * cos (a- + A*) W = co¥'^ " 6"

sin (2 a: + A a1) m • A a? cos a? m(Aa?)3 „ ,fiv

A lug sin x - smarsin(,r + A.r) — g— -^ —9—

And, again, by multiplying both sides of equation (5) by
cos x cos (x -f- A a?), and both sides of equation (6) by
sin x sin (<r + A a?), and adding the results, there is obtained

x. s sin x cos (a,1 + A x) -^

cos a- cos (x + A a?). A log cos x \ i cos^ I m(Aa,)*

V — -< > 2 «C.

. , -> i • ( ) cos x sin (a? + A x)
+ sin ,r sin (x + A x) • A log sin x 1 ( — . , ^

sin' a?

The expression which forms the coefficient of - 6 , is, by
the calculus of sines, equivalent to

sin A x + cos 2 x sin (2 x + A x)
2 cos1 x sin2 a;

But in the applications to be made of the formulae, the angle A a?
is always small ; we may therefore reject the term sin A x, and
assume sin (2<a?+ A#) =. sin 2# ; the expression will then become

cos 2 a? sin 2 x cos 2 « sin x cos x

5 — =-5 — = 3 =-» = — 2 cot 2 .r.

2 cos' a? sin2 x cosz x sin* x

Thus we have

cos * cos (x + A a;) • A log cos x ) w» (A a?)*

\ = — cot 2 x Q ' nearly. (7)
4- sin x sin (.r + A x) • A log sin x )

The second member of this equation vanishes when x is half
a right angle ; and supposing the angle A a? to be one minute ;
when x=l°, or when #=89°, the function

__ cot 2 x "»(AJ?)* _ — -0000000002,

the sign being — in the former case, and + in the latter;
therefore in any Trigonometrical Tables hitherto constructed,

152 MR WALLACE'S Formula for finding the Logarithms

if x and x + A x be any two adjoining angles, we have in
general

cos x cos (x + A x) • A log cos x + sin # sin (# + A .r) A log sin x = 0 nearly.

And consequently

(A)

sin x sin (x + A #) • A log sin * = cos x cos (a? + A x) ( — A log cos x) *.

This formula may be expressed independently of logarithms, by
considering that

sin (x + A x) , cos (x + A x)

A log 3in x = log *-i , A log cos x = log 5 — • -;

sin x cos a1

Hence we have, nearly,

(A')

sin x sin (x + A j) /- -| — cos * cos (* + A ,r)

• r*r\a I ™ I A /v>\ I v '

{1 sin x sin U + A j) /- -v _

sm (x + A .r) f _ I cos (a- + A a?) f

sin x f cos «• f

2. The object I have in view being the determination of the
logarithmic sine and cosine of an angle, the one from the other,
to adapt the formula to that purpose, I express it in these two
ways.

(B)

A log sin x = cot x cosec x cos (#-f Aa1) -: — ; - r- ( — A log cos x) ;

sin (x + A x)

,M V- • •"•»*• (C) ^ •

- , COS X

— A log cos x = tan x sec x sin (x 4- A *) - -, - r • A log sin x .

' cos (x + A x)

The same formulae, expressed in logarithms, will stand ready
for use thus :

(B')

Log (A log sin x) = log {cot x cosec x cos (x + &x)( — A log COS.T)} — A log sin/r;

Log ( — A log cos x) = log { tan x sec x sin (x + A#) • A log sin a: } + ( — A log cos x) ;

* The symbol — A log cos"* here indicates, that the sign of log x — log (x + A x)^
(which is a negative quantity), is to be changed to +.

of Trigonometrical Quantities from one another. 153

3. In applying the formulae, let it first be supposed that a
log. cosine is given, to find the corresponding sine : Then, putting
# + A# for the angle corresponding to the given cosine, the
next greater in the table will be cos x ; this, therefore, as well as
A log cos x (— log cos (x + A*) — log cos x), cot x, cosec x, and
sin x, will be given. Let us for a moment put

y = A log sin x, p = co\.x cosec x cos (x + A#) ( — A log cos #),

then formula (B') will stand thus,

here p is a known quantity, and we must find such a value of y
as satisfies the equation.

Now, y is always small, because it is the logarithm of a quan-
tity differing but little from an unit ; therefore, as a first ap-
proximation,

Log y = log p, and y = p nearly ;

and hence

Log y = \ogp—p nearly.

If the value of y, found from this last equation, be not suffi-
ciently exact, it is at least a nearer approximation than the first
assumption y =p ; therefore, denoting it by y', we shall have still
more correctly,

Thus, it appears, that to approximate to the value of y in the
equation

~Logy — \ogp- p,

we have only to form a series of quantities y', y", y", &c. from the
function p, such, that

y=p, iogy=iogp— y, iogy = iog^— y, &c.
and these will be successive approximations to the value ofy.

Next, let us suppose that a log. sine is given to find the cor-
responding cosine ; let x -f- A# be the angle to the given sine ;
the next less in the table will be log sin x, and their difference,
(viz. A log sin x) will be given, as well as tan x, sec x, and cos x.

VOL. x- P. i. u

154 ME WALLACE'S Formula! for finding the Logarithms
Let us now put

z = — A log cos ;r, q = tan x sec # sin (a- + A a1) • A log sin a1,

and instead of formula (C') we have this :

To resolve this equation, we must form a series of approxi-
mations,

z' = q, log tf' = log q + 2 log 2"' = log q + z", &c.

and the quantities z', z", z", &c. will quickly approximate to the
correct value of z.

4. To make the mode of proceeding perfectly clear, I shall
now give some examples.

(1.) To find the log. sine of an angle whose cosine —
9.9450803019 by VLACQ'S Arithmetica Logarithmica, which con-
tains a table of log. sines, &c. to every minute of the quadrant,
and to ten places of figures :

Given cosihe, log cos (x + Aa-) — 9'9450803019

Next greater in Tab. log cos #(28° 12') - g-9451254712

— A log cos x - -0000451693

Log.

cot x 10-2706770

cosecx - 10-3255515

cos(a- + Aa-) 9-9450803

— A log cos x - 5-6548434

=4-1961522 y =-0001571.... First approx.
y = £1959951 y = -0001570345 = A log sin a-

9-6744484704 = log sin x

The sine required, 9'67 46055049 = log sin (x +

The sine required is that of 28° 12' 40", and its correct value,
as given in VLACQ'S Trigonometria Artificialis, is 9'6746055050,
with which our approximation agrees almost exactly.

Of Trigonometrical Quantities from one another. 155

(2.) The log. cosine corresponding to log. sin 9'99835 15861
is required ?

Given sine,

Next less in Table,

tan^r

S6C.T

sin (x +

A log sin x

logq
log q + tf
log q + z"

=9-9983515861
= 9'9983442260

- 0-0000073601

logsin(.r
log sin x (85°)

A log sin x

Log.

11-0580482

11-0597040

9-9983516

6-8668887

= 4-9829875 sf = -0009616... First approx.
4-9839491 *' = -0009637... Second.
4-9839512 ^" - -0009637210 = — A log cos x
8-9402960083 = log cos x

The cosine required 8'9393322873 = log cos (x +

The cosine required is that of 85 ° 0' 40" ; its correct value is
8'9393322838, which differs from its value computed by our for-
mulae in the last two of the ten figures. A more correct result
would have been obtained, if the given sine and the next less in
the table had been continued to more decimal places, a small
change in the sine of so large an angle as 85°, producing a con-
siderable change in the cosine. This is an inconvenience in cal-
culation which can only be obviated by more extensive tables.

(3.) Let it now be required to determine, by BRIGGS'S
Table ( Trigonometria Britannica), the cosine corresponding to
sin (ac + A a?) = 9*99993516626353, which is known to be the sine
of 89° 0' 36'.

u 2

156 MR WALLACE'S Formula for finding the Logarithms

Given sine, log sin (x + A#) = 9'99993516626353
Next less, log sin x (89°) = 9'99993384980922

A log sin x =1

•00000131645431

Log.

tan or

11-7580785313

seed?

11-7581446816

sin (x + &x]

I 9-9999351663

A log sin x

61194057907

l°g?

3-6355641699

X =-0043208000..

.First approx.

log q + tf

3-6398849699

z" = -0043640000..

.Second.

log q + z"

3-6399281699

z"' = -0043644364..

— — A log cos x

8-2418553184..

.= logCOSd7

The approx. value of cosine, 8-2374908820
Its true value is, - 8-28749095...

Error of Approx. -00000007

From this example it appears, that, supposing the sine of an
angle about 89°, or the cosine of an angle about 1° to be known
with sufficient accuracy, the formula may be trusted to give the
cosine or sine true to seven decimal places. Towards the middle
of the quadrant its accuracy is much greater.

In these examples, the logarithmic differences to be found
have been expressed by seven or more significant figures : it was
therefore necessary in the calculation to take out the logarithms
to at least as many places ; but when the given sine or cosine
consists of only seven figures, besides the index, the logarithms
need not be carried so far ; as in this example.

(4.) To find the sine corresponding to log cos (x + *x) = 9 9409872
In BUTTON'S Tables, next greater, log cos #(60° 49/)= 9-9410461

cot * 10-25298

cosec* 10-31193

cos(,r + A.r) - 9-94098

log (_ A log cos x) 5-7701 2

— A log cos x 0000589

logp

— y

1-27601 i/ = -0001888... First approx.
-27582 t/' = -0001885 = A log sin*
9-6880688 = log sin a;

Sine required, 9'6882573

of Trigonometrical Quantities from one another. 157

The operations have been all put down at length ; but in
practice, the trouble of writing down so many cyphers, and the
repetition of the same figures, may be spared, just as in the com-
mon operations of multiplication and division.

5. Before leaving the consideration of formula (B'), (C'),
(art. 2), I may just observe, that they may otherwise be elegantly
expressed thus :

sin(*+A;r) — tan x sec x cos (x + A x)

sinQr + Aa?)) sUTT~ (cos (# + A.r)| . (JJ"^

~~ sin x \ ~\ cos a? )

cos (* + A *) cot x cosec x sin (x + A *)

cos(.r ~

cosx

Here we see immediately, that the determination of the sine
from the cosine, or the cosine from the sine, by the method we
have followed, requires the resolution of the exponential equa-
tions,

yy-p, zz = q,

p and q being known, and y and z unknown quantities, and each
having the value which it denotes in art. 3. The facility with
which they have been found is the consequence of their being
nearly — 1. The general solution of such an equation, how-
ever, is attended with more difficulty.

6. The determination of the sine from the cosine, or the
cosine from the sine, enables us to determine the tangent from

either the sine or cosine, (because tan x — ^-^ ) also the sine of

COS X J

twice the arc, which is equal 2sin<r cos x, and hence, again, the
cosine and tangent of double the arc.

7. I now proceed to investigate formulas by which the loga-
rithmic sine and cosine may be deduced from the tangent. By
the calculus of sines,

158 MR WALLACE'S Formula for finding the Logarithms

Log cos x = log tan x — log sin x,

therefore

— A log cos x = A log tan a: — A log sin x,

and hence, again,

( — cosx cos (x+ Ax) 'A log sin x.
But from formula (A) art. 1 . we have also

cos x cos (x + Ax) • ( — A log cos x) = sin x sin (x + AX) • A log sin x,

Hence, by putting the second members of these equations equal
to one another, and transposing, we find,

{cos x cos (x + A x) + sin x sin (x + A x) } -A log sin x = cos xcos (x + Ax) • A log tan x.

The expression which forms the coefficient of A log sin x is
by the calculus of sines equivalent to cos A x, therefore

cos A x (A log sin x) — cos x cos (x + AX) -A log tan x . (8)

By a mode of proceeding in all respects similar to the above,
we easily find

cos A x ( — A log cos x) = sin x sin (x + A x) • A log tan x .' (9)

As the omission of the factor cos A x will not affect the first
two terms of the series, which express the values of A log sin #,
and A log cos x, we may leave it out, and have more simply

A log sin x = cos x cos (x + A x) A log tan x ;

• V- ' ' ; ' "'<E)

— A log cos x = sin x sin (x + A x) A log tan x ;

8. The degree of accuracy of these approximations may be
estimated by comparing the series which express the exact va-
lues of A log sin x, A log cos #, and A log tan oc .

We have already found, art. 1, that

1 (A*1)2 cos x (AX)*
Alogsm* = m ^ .Aj-j^-g- + ^- SBjt _ &c.

( sin x 1 (A x)* sin x A xs 1

— A log cos x = m i - . A x + —z -- •—- + — 3 -- — - + &c. }• ;
(. cos x cos1 x 2 cos3 x 3 j

of Trigonometrical Quantities from one another. 159

Therefore, because A log tan x = A log sin x — A log cos x,

8 x — sin2 x (A a?)2 , cos4 a- + sin4 x (A a-) s „ )

— ~H 2 Q ' 3 '' — 3 — H

This last series being multiplied by

cos x cos (a? + A a?) = cos* x — cos x sin x • A a- — cos2 a|V^^- + &c.

and the same series also by

(A a1)2

sin x sin (a? + A a?) = sin* x + cos x sin x • A a: — sin2 a' , ' + &c.

the results, continued as far as three terms, will be

(cos a: 1 (A a?)2 2 cos4 x — sin4 a? (A a?)3 )

cos a- cos (.r + A x) A log tan x =. m \ -. -A a? ^- v '• H — -^ h «c, \ ;

(sin a? sm2 cos a? sin3 a?

f sin x 1 (Aa:)2 2 sin4 a? — cos* x (A a1) 3

sin a- sin (a? + A a?) A log tan x =. m\ • A x 4- - — =- - — — -\ 5 = rr" + »c.

(cosa? cos2 a- 2 cos3 a? sin a? 6

By comparing these series with the series for A log sin x, and
— A log cos x, it will appear that

A log sin x = cos x cos (x + A a:) A log tan x + m (2 cot x + tan x) „ , &c. (10)
— A log cos x = sin a? sin (x + A a?) A log tan .r + m (2 tan a- + cot a-) —5^-, &c. (11)

Hence we may infer the following properties of formulas (D) (E) :

(1.) The two formula? are least correct towards the extremities
of the quadrant.

(2.) The first is most correct when tan # = v/f , that is, when
x =r 54 1 :° nearly, and the second when tan x = \/%, in which
case x — 35^° nearly, because, in these cases, the functions
2 cot x -f- tan x, and 2 tan x -j- cot x are the least possible.

(3.) When x is a small angle, the error of the expression for
A log sin x is nearly double that for A log cos x. The reverse
is true when x is nearly a right angle.

9. Supposing the increment A x to be one minute, the er-
ror of the formula for A log sin x, when x — 2°, will be

160 MR WALLACE'S Formula for finding the Logarithms

.0000000001. Hence we may infer, that with a table of logar-
ithmic sines and tangents to every minute, and to ten decimal
places, such as that in VLACQ'S Arithmetica Logarithmica, the
log sine and cosine may be found from any log tangent correct
to at least 10 decimals between a> = 2° and x — 88°. Beyond
these limits the accuracy will diminish, but still they will be true
to seven figures, when ae — 10', and when x — 89° 50'. With
VLACQ'S Trigonometria Artificialis, which gives the sines and
tangents to every ten seconds and to ten figures, the formulae
will be accurate throughout the whole table.

10. The formulas (D), (E) when properly adapted to calcula-
tion, will stand thus,

. sin (x + A .r)

A log sin x •=. sin x cos x cot (x + Aa? ) ^ '- • A log tan x ;

sin x

V, :,:• - :;J •:!..,, r;.:. ..,-.• (E') fi ,' .:•:••'—:"

. COS (# 4- A #)

— A log cos x — sin # cos x tan (# + A x) ' *• • A log tan x ;

COS 3C

And in logarithms

(D")

log (A log sin x) = log (sin x cos a- cot (x + A a?) • A log tan x} + A log sin #,
log (—A log cos x) — log {sin x cos a? tan (x + A a?) -A log tan x} — ( — Ale

11. The mode of deducing A log sin x and A log cos x from
these formulae, is exactly the same as we have already employed
in art. 3. That is, putting

y = A log sin a?, z = — A log cos a; ,

r

tan (x + A x) '

= sin * cos * tan (a- + A*),

of Trigonometrical Quantities from one another. 161

if we find y' — r, logy" = log r + y', log y'" = log r + y", &c.

Then y', y", y'", &c. will be a series of successive approxi-
mations to y or A log sin x.

Also if z' — s, log z" r: log * — z', log z"' — log * — z", &c.
then shall z', z", z'", &c. be a series of approximations to the
value of z,

.1 in .iv,iu, i'h \L Jnonrmiii ^fL -vAuia '.>•//

12. Our formulae, although only approximations, are yet more
accurate than is necessary with the ordinary tables. Others
somewhat more simple, and sufficiently correct, may be deduced
from them, as follows : H>}

The two formulae (D) (E) may evidently be written thus,

cos (x + A x) A ,
A loe sin x — cos* x — • — A log tan x ;

* rns ,T

COAX

sin (x + A x) ,

A log cos x — sin2 x — - A log tan x .

sin oc

cos (x + A oc\
Near the beginning of the quadrant, ; - ' = 1 nearly,

COS 00

and towards the end Sm „. "V = 1 nearly. Therefore, in

Sill 00

these cases,

A log tan x = cos8 x A log tan x nearly ; ) .p.

— A log cos x •=. sin a? A log tan x nearly. )

13. That we may estimate the degree of approximation, let
us multiply the series for A log tan x by cos2 at, and by sin2 x ;
the results are,

cos x A cos* x — sin2 x (A a?)2 . )

~~ + &c-

cos'* A log tan * =

sin x cos*a? — sin2 d? (A x)*

A.r --- - -- 4- &c.

sin

By comparing these formulge with the series for A log sin x, and
A log cos x (art. 1.) we shall find
VOL. x. P. i. x

162 MR WALLACE'S Formula for finding the Logarithms

A log sin x = cos* x A log tan x — m (A xf + &c.
— A log cos x = sin2 x A log tan x + m (A .r)z + &c.

Hence it appears, that our two formulae F are only approxima-
tions of the first order ; but that the error, as far as it depends
on the square of A x, is independent of the angle #, or is a
constant quantity for a given value of A x.

If we make the increment A x an angle of one minute, we
have m (A #)* = .0000000367. Thus they appear to be correct
in the first seven decimal places ; we may therefore safely em-
ploy them with HUTTON'S or SHERWIN'S Tables, reserving the
others for Tables of greater extent.

14. Let it be required to find the logarithmic sine and co-
sine corresponding to the tangent 10*0763404 10548.

The given tan (x + A x) — 10-076340410548
The next less (Bmccs's Trig. Brit.) tan x (50°) — 10-076186469801

A log tan x = -000153940747
To find log sin (,r + A x)
sin x 9-8842539666

cos x 9-8080674968

cot (x + A x) 9-9236595895
A log tan x 4-1873535895

logr =5-8033346424 z' = -000063583 First Ap.

log r + .?'=: -8033982254 z" = 0000635914 Second Ap.

logr + .s" ~ -8033982338 %'" - -000063591378 = A log sin x

sin^r = 9.884253966554

sin (x + A x) = 9.884317557932

To find log cos (,r + A x)

sin x 9-8842539666

COS.T 9-8080674968

tan (x + A x) 10^0763404105

A log tan x 4-1873535895

log* = 5-9560154634 tf = -000090368 First Ap

log* — * = -9559250954 z" = -0000903494 Second Ap.

logs— 2" = -9559251140 z"' = -000090349367 = — A log cos j-

COS.T = 9-808067496752

cos (x + A x) = 9-8079771 47385

of Trigonometrical Quantities from one another. 163

Both results, viz. the sine and cosine of 50° 0' 36", may be
considered as correct in all the figures ; the cosine differing from
the true value only by an unit in the twelfth place of decimals.

2. As an example of formulae (F) art. 12., the logarithmic
sines and cosines corresponding to tan (x + A ac) :r 9'5632889
are required.

tan (x + A of) — 9.5632889
Next less (HuT-ro^s Tables) tan x (20° 5') = 9'5630278

A log tan x = 2611

. ' f 9-97276 f 9-53578

Rfe I 9-97276 sm'* | 9-53578

A log tan x 3-41664 Alogtana7 341664

A log sin x = 2302 3.36216 — A log cos. r = 308 2-48820

sin x = 9.5357832 cos x = 9.727554

sin (x + A a?) = 9-5360134 cos (x + &x) = 9'727246

;yjq«r« tyinitr -.iuifnad 7t*il) tluuiia hi -i.^ rfrj.lv/ -iir.fi ,.

15. I shall next, from the approximate values of the incre-
ments of the logarithmic sine and cosine of an angle, deduce
analytic formulae, which shall express their relations to the incre-
ments of the like functions of half the angle. In art. 1. it has
been shewn, that if we neglect the third and higher powers of

x. then

\.A,MM . | . -/v < •'••.,••»)

sin (2 x + A x) m • A x

A log sm x = -. ^ — ~ '-— — x ; Q 2)

sin x sin (x + A x)

sin (2 x + A x) m • A x

— A log cos x = H '— — -: — . H 3^

cos x cos (x + A x 2

From these expressions, by substituting \ x for &>, and ~ A x
for A an, we obtain

A , . sin (x + 4 A x) m- A x

A log sin A x = - — ; ii — rv *• — :- ; — ; H 41

sm \ x sin i (x + A x) 4

sin (x + I A x) m • A x

-AlogCOSi*:=cos|igcos|^+'A;r) -3- (15)

x 2

164 MR WALLACE'S Formula for finding the Logarithms

By comparing the latter two expressions with the former, and
observing that A being an angle, sin 2 A — 2 sin A cos A, we get
these formulae,

cos i x sin (x + A x) ,

A log sin A x = TT - -, - —. - r^ — . , ' - r A log sin x ; (G)

2 cos (x + | A x) sin \ (x + A x)

cos x cos (x + A x) ,

A log sin \ x = -. - ; — — - r— -. — : - : — f-f — — - — - ( — A log cos x) ; (H)
4 cos (x + £ A x) sin ^ x sin ^ (•*• + A ;r) v

sin i # sin (# + A a?)
-Alogcosi-r == g^i Acosx/Ag * log sing; (K)

cos a; cos (x + A a?)

A lo£T COS i a? == -: — - 7 - ; — r~, : - r -- ; - TT - ; - r A log COS X . (L.)

4 cos (x + ^ A a-) cos £ a? cos £ (x + A a-)

16. These expressions exhibit elegant analytic formulae, but
they cannot so readily be applied to calculation as the other for-
mulas, on account of the factor cos (ac + 1- A x), which enters
into them all. If we assume that

cos (x + I A x) = V cos x cos (x + A x) ,

which is nearly true when A an is small, they become more simple ;
however, they are less accurate. When put under the same
form as the expressions for A log sin so, and A log cos x, they will
stand thus,

( cot I x sin (x + A x) A I0g sin x\ sin I a;

' - "V -

(coti x Vcosd? cos (x + A*') — A log cos x) sini;r

log sin 4 £ = •< — - - . - - --- 5 - f— — . , , - r-; (ti)
( sin a? x, ) sin £ (x + A x)

( tan £ x sin (x + A x) A log sin x ) cos 1 x

- - —

CO.

f Vcos # cos ( ^ + A #) A log cos x) cos i a?

A log cos 1 x = < ~ - i — — - 1 . - &-. - >- - — ^-S - . (L ')

( cos2 \x 4 j cos i (* + A x)

Of these, formula? (H7) and (L'), which give the increments of
log sin £ x, and log cos ^ x, from that of log cos x are quite ana-
logous to those investigated in the beginning of this paper, and

of Trigonometrical Quantities from one another. 165

may be applied in the same way. The other two, which give
the same things by that of log sin or, require that cos (x -\- A x),
or at least the logarithm of v/cos at cos (ac + A x) be known : now

log x/cos x cos (x + A x) = log cos x + £ A log cos x ; (16)

therefore, when A log cos x is determined by formula (E') art. 10.
these may also be applied like the others.

17. Because A log tan x = A log sin x — A log cos ae, from
equations (14) and (15) art. 15, we find (omitting a factor
cos A x — 1 nearly).

4 sin (2 x + A x)

A log tan x = -T-TT — ' 0/ , . — o — ; (17)

sin 2 x sin 2 (x + A x) 2

Hence, again, putting | a? for a?,

A sin (a? -f A A x) m b. x

4> log tan i * = ^— - . (18)

sin x sin (.r + A x) 4

This last expression, compared with (12) (13) art. 15. and (18)
gives

A log tan | x — ' A log sin x ; (M)

vcos x cos (x + A x)

\/cos x cos (a? + A x) , . ,

A log tan 1 # = - — ^ — ,v , — H^ ( — A log cos #) ; (N)

sin x sin (x + A a?)

A log tan j a? = \/cos a,* cos (x + A a?) A log tan a- . (O)

18. The first and last of these are very simple, and they de-
serve attention, because the finding the tangent of the half of
an angle from the sine, or from the tangent of the whole angle,
occurs in the resolution of quadratic equations by the Trigono-
metrical Tables. Their application, however, again requires, that
we have the logarithm of /cos x cos (ac -f- A oc) .

When tan |- (x + A ac) is to be found from sin (ac + A x),
we may first find A log cos x by formula (C') ; this gives

166 MR WALLACE'S Formula for finding the Logarithms

log s/cos x cos (a> + A x} (16) ; then A log tan \ x may be found
by formula (M) .

When tan |- (x -f- A x} is to be found from tan (x + A x),
we have, in the first place, - - A log cos x — sin2 x . A log tan x ,
by formula F, art. 12., then,

log Vcos .r cos (X + AX)— log cos # — £ sin* .r • A log tan x,

so that we may express fomula (O) in logarithms thus,

log (A log tan | x) — log {cos * • A log tan x} — £ sin2 A log tan x. (P)

In like manner, if we make A x negative, we may find

tan 4- (x — A x) from tan (x — A x) by this formula,

log ( — A log tan x 4) =: log {cos AT ( — A log tan x)} + \ sin* .»• ( — A log tan x) (P')

the two, (P) (P') enable us to take for x the angle expressed
by the nearest even number of minutes, whether greater or less
than the angle corresponding to the given tangent.

As an example of the application of both formula?, I shall
take an unfavourable case, and suppose the tangent of
89° 1'= 1176587928 to be given, to find the tangent of
44° 30' 30".

Employing the first formula, we have

Tan (a- + A a-) = 11-76537923

tan o-(89°) = 11-75807853

A log tan a; = -00730070

sin2^ 19-9998676 COS.T 8-2418553

A log tan x 3-8633645 A log tan x 3-8633645

3-8632321 4^10521 98

sin* x • A log tan x — -0072985 £ sin* x A log tan x = -0036492

A log tan £ x — -00012635 4-1015706
tan | x (44° 30') = 9 99241975

tan J (* + A *•) = 9-99254610

of Trigonometrical Quantities from one another. 167

By the second formula,

Tan (a- — A *) = 11-70537923
tan x (89° 2') =11-77280468

— A log tan. r = -00742545

sin2 .*• Isi 1 19-9998764 cos x 8-2271335

— A log tan. r 3-8707229 —A log tan x 3-8707229

3.8705993 4-0978564

sin* x(— A log .7') = -0074233 4 sin* a- (—A log tana-) = -0037116

— A log tan » x = ' -00012635 4-1015680

tan k x (44° 3V) = 9'99267245

tan \(x — ±x) - 9-99254610

By either formula, the result is obtained true to eight places o*
decimals ; if x were a less angle, the accuracy would be greater ;
we may therefore safely employ the formula? with MUTTON'S or
SHERWIN'S Tables : with VLACQ'S Trigonometria Artificialis, the
tangent of half the angle may be found true to ten decimal
places.

THE short paper which follows this was originally intended
to have formed a part of it ; as, however, their objects are differ-

ent, they are given separate from one another.

'

'W O'K

.11 fflOIOOII J
: A •—»:: (fl -K A)- 1, irie : («

( 168 )

XI. A proposed Improvement in the Solution of a Case in Plane
Trigonometry. By WILLIAM WALLACE, F. R. S. Edin.
Professor of Mathematics in the University of Edinburgh.

(Read Nov. 23. 1823J

4 '

1. IN the present state of mathematical science, cultivated as
it has been, with assiduity, during the two preceding centuries,
it can hardly be expected that any considerable improvement re-
mains to be made in Plane Trigonometry, one of its most ele-
mentary theories. There is, however, one case in the resolution
of oblique-angled triangles, which appears to me to admit of a
solution somewhat more simple and convenient than those which
are commonly known ; it is that in which two sides and the in-
cluded angle are given to find the third side.

2. The usual way of proceeding, is to find half the sum and
half the difference of the angles opposite the given sides, and
from these the angles themselves ; the third side may then be
found in two ways, from the principle, that the sides are to one
another as the sines of the opposite angles. Instead of this, I
propose, that having found half the sum and half the difference
of the angles in the usual way, the remaining side shall be found
by either of these two formulae :

Let the sides of a triangle be a, b, c,
and the opposite angles A, B, C,

Theorem I.

cos i (A — B) : cos i (A + B) : : a + b : c.

Theorem II.

sin £ (A — B) : sin HA + B) : : a — b : c .

in Plane Trigonometry. 169

By applying both formulae, the same result will be obtained in
two different ways, a thing always desirable, and better than a
verification, obtained by a mere repetition of the calculation.

3. These formulae (which are not given as new) may be
briefly demonstrated as follows :

Because sin A : sin C : : a : c,
and sin B : sin C : : b : c;
Therefore sin A + sin B : sin C : : a + b : c;
also sin A — sin B : sin C : : a — b : c.
But because sin A + sin B = 2 sin ^ (A + B) cos £ (A — B) ,
and sin A — sin B = 2 cos ^ (A + B) sin ^ (A — B) ,
and sin C = sin (A + B) = 2 sin £ (A + B) cos ^ (A + B) ,
Therefore, sin A + sin B : sin C : : cos i (A — B) : cos ^ (A + B) ;
in like manner, sin A — sin B : sin C : : sin £ (A — B) : sin 4 (A + B) ;
Hence, cos £ (A — B) : cos $(A + B) : : a + b : c;
Also, sin HA — B) : sin | (A + B) : : a— b : c.

4. An example will serve to shew the distinction between the
common method and that proposed in this paper.

The sides of a triangle being a, b, c ;
and the opposite angles A, B, C .

(side a = 169584 feet ) . . , _, .

There are given \ side b = 119613 I to find the Slde C in two

1 angle C = 60° 43' 36" j ways'

a + b 289197 5-4611938

a — b 49971 4-6987180

tan i (A + B) 59° 38' 12" 10-2322235

14-9309415

tan HA — B) 16 26 0-23 9 -4697477

A = 76 4 12-23
B = 43 12 11-77

VOL. X- P. I.

170 MR WALLACE'S Improved Solution of a Case, 8fc.

To find side c by the common method.

sin A 9.9870362 sin B 9-8354297

sin C
side a

side c 152409-8

9-9406644
5-2293848

sin C
side b

side c

9-9406644

5-0777784

15-1700492

15-0184428

5-1830130

5-1830131

To find the side c by the method here proposed.

cos i (A — B) 9-9818861 sin £ (A — B) 94516338

cos i (A + B) 9-7037054 sin $ (A + B) 9'9359289

a + b 5-4611938 a — b 4-6987180

15-1648992 14-6346469

c 152409-8 5-1830131 c 5-1830131

5. By comparing the two solutions and their verifications, it
appears that by the common method, the Trigonometrical Tables
must be opened in ten different places, and that by the new me-
thod, only five different openings are necessary, because in this
last, the logarithms of a + b and a — b occur twice, and the
cosines and sines of the angles ^ ( A -f B) and ^ ( A — B) are
found in the same lines with their tangents. Even if we are sa-
tisfied with a single solution, omitting the verification, the me-
thod I have here proposed still appears td deserve the preference,
because, in the common way, the tables must be opened in eight
places, but in the other way, only in five. Of course I do not take
into account the operations necessary to find the sine and cosine
from the tangent. If they be found by formula (F) art. 12., of
the preceding paper, only one opening more will be required, viz.
that for the logarithm of the difference of the log. tangent ; and
it is presumed that they may be found more readily than the
correct values of ^ (A — B), (which, in general, is only a sub-
sidiary angle, and not wanted in the solution), and the log sines
of the angles A and B.

PLATE VI.

- accortLLnc" to

Anrtntt Tiib isions

used in /In-

LANGUA OK

( 171 )

••>:• '!(.' i»4 liiif[« 1

XII. Some Notices concerning the Plants of various Parts of India,
and concerning the Sanscrita Names of those Regions. By
FRANCIS HAMILTON, M. D. F. R. S. & F. A. S. Lond. &
Edin.

(Read June 18 1821.;

xVs it is my intention soon to publish, in various works on Na-
tural History, the observations on the Botany of India which I
made during my residence there, I wish to place on record an
account of the opportunities which I enjoyed of making such
observations, with the view of explaining to the Botanist where
he may find the various collections which I made in different
parts. I also wish to explain the geographical terms that I shall
employ, in giving an account of the places where I found each
species. For this purpose I prefer using the ancient Sanscrita
names *, both as being more scientific, and as being more likely to
remain permanent ; for, after a lapse of many ages, they continue
to be known to ah1 Hindus of learning, while each new invasion
or revolution sinks into immediate oblivion the mushroom appel-
lations imposed by modern rulers, whether Muhammedans or
Christians.

Immediately after my appointment to the Company's Service
on the Bengal Establishment, I was sent with Captain SYMES to
the Court of Ava, and, during the year 1795, I had an opportu-
nity of seeing somewhat of the Andaman Islands, with a good
deal of the kingdoms of Pegu and Ava. The plants of the An-
daman Islands are nearly similar to those of Chatigang, of which

. — .. -. _...—•. ..... i i. . .* — — .. — . i . .1 — •-•• ... , ,..,,

* A Map of India, according to the ancient divisions used in the Sanscrita
language, is given in Plate VI.

Y 2

172 DR FRANCIS HAMILTON on the Plants of India,

I shall give a more full account. Those of Pegu nearly resemble
those of the southern and eastern parts of Bengal, while those of
Ava bear a stronger resemblance to the productions of Mysore.
The reason of this seems to be, that the territory of Pegu enjoys
much more copious rains than Ava, which, like the southern
parts of what we call Hindustan, is a parched country, and, in
order to bring rice to maturity, requires artificial irrigation by
means of reservoirs or canals. On the way, however, between
Pegu and Ava, where we approached the mountains bordering
Arakan on the east, we had a vegetation much resembling that
of Chatigang, and of the mountains extending from thence along
the eastern frontier of Bengal, which will be afterwards de-
scribed. The plants, which I collected during this journey, were
transmitted, together with a good many .drawings, to the Court
of Directors, and were given to Sir JOSEPH BANKS, in whose col-
lection they probably remain ; but copies of most of the draw-
ings, partly coloured, were preserved by me, and deposited in
the Company's Library. I also preserved a copy of the Notes,
which I took on the spot, and this will be found in the same
collection.

In 1796, 1797, and part of 1798, I was stationed at Lukhi-
pur, in the south-eastern part of Bengal, and in the ancient king-
dom of Tripura. My time was there much occupied in describ-
ing the fishes of the country ; but I took many descriptions of
plants, which are also deposited in the Company's Library ; but
I did not preserve specimens. I corresponded, however, very
frequently with Dr ROXBURGH, and transmitted to him what-
ever he thought would be acceptable, learning, at the same time,
what both he and KCENIG called various plants.

In spring 1798, by the desire of the Board of Trade at Cal-
cutta, I visited the district of Chatigang, which, together with
that of Komila, formed the chief part of the ancient kingdom of
Tripura, and I afterwards skirted the hills of Komila, where the

and on the Sanscrita Names of that Country. 1 73

tribe of Tripura still maintains a kind of independence. Here"
I had a full opportunity of examining the splendid vegetation of
the well watered districts of Farther India (extra Gangem) which
bounds the extensive Gangetic plain on the east, and extends
south from what we call China to the Ocean. It must be obser-
ved, however, that this Farther India, as it has been called, is the
proper China of the Hindus, from whom we derived the word,
while, what we name the Chinese Empire, the Hindus call Maha
China, or the Great China.

The largest portion of this Farther India, or Southern China,
is mountainous and well watered ; but its mountains nowhere
rise to an alpine elevation, and, owing to a copious supply of
moisture, and a deep soil, are, in general, covered to the summit
with lofty forests. I have already mentioned, that a great part
of the proper kingdoms of Pegu and Ava differs a good deal from
the general appearance of the neighbouring countries, the former
resembling more the southern plains of Bengal, and the latter
the southern peninsula of India ; but by far the greater portion of
this Farther India, in its vegetable productions, resembles Chati-
gang ; and what RUMPHIUS called India aquosa, or the immense
Eastern Archipelago, including the Andaman and Nicobar
islands, may be considered as belonging to the same vegetable
arrangement. Of this the most prominent feature is a tenden-
cy in trees of considerable size to twine round others, forming
thus forests almost totally impervious. These twining trees, the
Funes sylvestris of RUMPHIUS, are often thicker than the human
body, and extend to great distances, overwhelming the most lof-
ty and vigorous woods ; and so strong is the tendency to this
kind of vegetation, that some even of the Palmae (Calamus, L.) a
tribe in general remarkable for erect stiffness, are here climbers,
and, after overtoping the highest trees, again drop branches to
the earth, which take root, and climb up the trees that are adja-
cent ; and thus, with other thicker, though less powerfully armed

174 DR FRANCIS HAMILTON on the Plants of India,

climbers, form a mat which becomes almost impenetrable. This
thick vegetation produces a delightful coolness, and preserves a
moisture that encourages the growth of numerous and beautiful
parasitical plants, Filices, Aroideae and Orchideae ; but renders the
climate rather sickly to constitutions unaccustomed to such a
moisture. In this fine region, the valleys between the hills are
uncommonly fertile, and, being well watered, produce abundant
crops of rice, the grand source of nourishment for the inhabi-
tants, although the tuberous Aroideas and Dioscoreas, both very
nutritious, may be considered as the proper offspring of this ter-
ritory, where they thrive with an uncommon vigour and variety.
In this country, even the unoccupied wastes have a luxuriance
of vegetation, that renders them almost equally impervious with
the forests ; and grasses, mostly of the genus Saccharum, shoot up
with a prodigious luxuriance and thickness. They generally
exceed six feet in height, and often reach to twice that ele-
vation.

The trees that are most common in this territory, are of the
orders of Urticae, Euphorbias, Terebinthaceag, Magnolias, Meliae,
Guttiferae, Sapotee, Vitices, and Eleagni, and, together with the
Palmae, Bambusae and climbers, form the great features of vege-
tation, which are of a totally exotic appearance to the European,
having scarcely any thing to recall the memory of his native
scenery ; yet still highly pleasing, not only from their novelty, but
also from their beauty and grandeur. Notwithstanding this great
difference of general appearance, several of the trees have an affi-
nity with those of Europe, and the woods contain an JEsculus,
and several Querci and Coniferi.

The specimens which I collected during this journey were
transmitted to Sir JOSEPH BANKS, in whose collection I saw
them in the year 1806, and there they no doubt will still be
found.

and on the Sanscrita Names of that Country. 175

Soon after my return from Chatigang, I was removed to Ba-
ruipur, a station near Calcutta, where I chiefly employed my
leisure in describing fishes. Still, however, I continued to col-
lect whatever appeared rare for Dr ROXBURGH, especially during
several journeys which I made through the great forests that oc-
cupy the islands formed by the estuaries of the Ganges. These
dreary woods, half inundated by the tides, and skreened by banks
of offensive mud, afford but little scope to the botanist. The
variety of vegetables which they contain is by no means great ;
and the danger in attempting to collect them, by landing where
tigers are so numerous and ravenous, is very great. I believe,
however, that in the various journies which I made between Cal-
cutta and Lukhipur, and from Baruipur, through these woods
and islands forming part of the ancient kingdoms of Vanga, Upa-
vanga, and Angga, I had an opportunity of describing most of
their vegetable productions. Mangroves of various kinds, includ-
ing Rhizophora, vEgiceras, Avicennia, Sonneratia, and Heritiera,
especially the latter, form the predominant feature of these
woods ; but they are ornamented with curious Convolvulaceae
and Apocineee, with many parasitical Filices, and some elegant
Lycopodiums and Lichens, not remarkable, indeed, for variety,
but of great size and beauty.

The cultivated parts of this Delta of the Ganges, as it has
been called, are not more favourable to the botanist than the
wastes. The plough or hoe occupies almost every spot, one rice-
field succeeds another, and the houses are buried among groves
of Mangifera, Artocarpus, and Bambusa, intermixed with Palmae,
and are only kept above water, by being raised on the banks
thrown up by digging ponds. In this territory the wastes are
generally covered with reedy grasses, almost as lofty as those of
Tripura. The whole aspect, indeed, of the country, and of its
vegetation, is strange and foreign to an European, unless to a

176 DR FRANCIS HAMILTON on the Plants of India,

Hollander. For four months in the year every field swarms with
fish, and at all times the only conveyance is by boats.

During my stay in this part of the country I made few bota-
nical observations, except by communications with Dr ROX-
BURGH. I, however, transmitted a few descriptions and drawings
to Sir J. E. SMITH, with whom they still remain.

During the year 1800, I was employed by the Marquis WEL-
LESLEY to examine the state of the country which he had lately
taken from TIPPOO SULTAN, and of the province which Europeans
call Malabar. I landed at Madras (Chinapatana of the natives),
and travelled through the territory belonging then to the Na-
bob of Arcot, which Europeans call the Carnatic, but it is the
Draveda of the Hindus, bounded on the south, at the mouth of
the Kaveri, by Chola, which Europeans call Tanjore, and to the
north by Andhra, the sea-coast of which by Europeans is usually
called the Circars, as having once been divided into five districts
(Circar), which were early ceded to Europeans by the Muham-
medan princes of Andhra or Tailingana. The coasts of Chola,
Draveda, and Andhra are usually included by Europeans under
the denomination of Coromandel, a name totally unknown to the
natives, who consider it as English, and from which we have se-
veral plants named Coromandeliana, as from the English word
Madras, with the addition of Patana (City) we have Maderaspa-
tana, as if plants grew in the streets. Both names should be
avoided as inconveniently long, as well as devoid of meaning in
any language.

On leaving Draveda, and ascending to the elevated region,
lately under the dominion of TIPPOO SULTAN, I entered the an-
cient Hindoo territory, called by them Karnata (Latine, Carna-
ta), but usually known to Europeans by the name of Mysore,
from the town where its princes for some generations resided.
Having examined this and the skirts of the interior of Andhra,
I descended again to the low country by the south, and exa-

and on the Sanscrita Names of that Country. 177

mined the country west from Chola, which the natives call Chera
or Cheda, but which Europeans, from a town in it, call Coimbe-
tore (Coiamatura). Chera as well as Chola is bounded on the
south by the country which the natives call Pandiya, extending
from near the Kaveri to the Southern Ocean. The northern
parts of this, towards Chera, I had an opportunity of examining.
The vegetation of all these countries is nearly similar. The
elevation of Mysore above the others, although probably about
3000 feet of perpendicular height, produces no great change.
The temperature is no doubt somewhat lower, and more agree-
able to European feelings ; but the aspect of the upper country
is not materially different from that of the lower. Both labour
under a scarcity of rain, so that artificial irrigation from reser-
voirs or canals is necessary for the production of rice, which, in
the low country especially, is the staple article of food, although
both there and in the higher country the rainy season produces
crops of miserable small grains, such as Eleusine Corocanus, Pa-
nicum Italicum, and Panicum miliaceum, that are used by the
natives as a succedaneum for rice. These crops have little of
an European appearance ; nor do the orchards and gardens
heighten the resemblance. The fruit trees round the villages
consist chiefly of the Mangifera, Citrus, Bassia, Artocarpus, Eu-
genia, Elate, and Borassus, while the kitchen gardens require to
be watered by machinery from wells. The general appearance
of the country is sterile, the rock projecting in a great many
places, while, during the greater part of the year, the grass is en-
tirely parched up from want of moisture ; and even in the rainy
season the grass is not longer than is usual in Europe. In the
woods, the trees are still more stinted than those of Europe,
and consist in a large proportion of wild prickly dates (Elate syl-
vestris) and Bambusae, with trees of the Leguminosae, especially
such as have prickles, and of the Rhamni. Even the thickets
consist chiefly of bushes of the Leguminosaa, and of the Rhamni
VOL. x. P. i. z

178 DR FRANCIS HAMILTON on the Plants of India,

and Caparides, almost all armed with prickles or thorns, while
the fences are chiefly of naked Euphorbias (Antiquorum and
TirucaUi). The most common trees besides the Leguminosae
and Rhamni, belong to the tribe of Eleagni and the genus
Grewia : and the most common herbage consists of small Cyperus,
Scirpus, Andropogon, Convolvulaceae, Acanthaceae, and Legumi-
nosae, especiaUy Hedysarum, Crotolaria, and Indigofera, so that
the vegetables have little in common with those of Europe, espe-
cially of its northern parts. With the more barren parts of
southern Europe there is more resemblance, the Rhamni and
Caparides being common to both.

After examining these countries of rigid vegetation, as it may
be called, I passed through the gap in the Animaliya or Elephant
Mountains, and entered the province called Malabar by Euro-
peans, but Kaerula and Malayala by the natives. These, indeed,
consider Malabar as an English word, meaning the whole sea-
coast between Cape Comorin andSurat, which seems to be the fact.
We ought, therefore, to call the province of Malabar by one or
other of the native appellations. The territory called Kaerula
by the natives, extends from the southern extremity of India to
almost the latitude of 12^ degrees North; but this includes a
portion of the English province of Canara ; and it extends from
the summits of the mountains to the sea. In its vegetable pro-
ductions and appearance, it more resembles Chatigang and the
mountains of Farther India than the adjacent territory of rigid
vegetation ; but it is better cultivated, contains more plantations,
especiaUy of Palmas, and, the rock projecting more, the vegeta-
tion is not quite so luxuriant. It has, however, perhaps still less
of an European appearance, none of the Amentaceae nor Coni-
ferae being found in its woods. The Dutch, however, have in-
troduced many fine trees from the Eastern Islands, and the Por-
tuguese some from the West Indies ; both of which give a consi-
derable variety to its plantations, and few countries possess a ve-

and on the Sanscrita Names of that Country. 179

getation so elegant, prospects more grand and beautiful, and a
climate more genial. Its highest mountains, although of consi-
derable height, perhaps 6000 feet perpendicular, have nothing of
an alpine appearance, but produce a moisture and coolness that
extends a more vigorous vegetation to the adjacent country
above.

Nearly connected with Kaerula, and little different from it in
vegetable productions, is Ceylon, the Taprobana of the Romans,
and the Lanka of the ancient Hindus. In 1815, I had an op-
portunity of a cursory examination of its southern end, and saw
sufficient to indicate, that, in general aspect at least, it does not
materially differ from Malayala.

North from Kaerula, and, as I have said, including a portion
of it, is the extensive Engh'sh province of Canara, a word of
doubtful origin, and supposed by the natives to be English. The
Hindus divide it into four territories : 1st, Part of Kaerula or Ma-
layala, extending to about 12° 28' North latitude; 2d, Tulava,
extending from thence to about 13° 35' N. ; 3d, Haiva or Haiga,
extending to about 14° 38' N. and Kankana (Latine Cancana) ex-
tending to the Portuguese territory of Goa ; but this, as well as
all the sea coast to near Bombay, are included in the territory
which the Hindus call Kankana. These countries, like Mala-
yala, extend from the summit of the mountains to the sea, and
scarcely differ in appearance or vegetable productions from that
territory ; but they are rather hotter and drier, and their vege-
tation is rather less vigorous, approaching more nearly to the ri-
gid thorny nature of that prevailing towards the East.

The specimens of plants which I procured during this jour-
ney, suffered much by the carelessness of those who were en-
trusted in conveying them from the ship to Calcutta ; but such
as they were, they were given to Sir J. E. SMITH, together with
a good many drawings, and both remain in his collection. The
notes which I took have been deposited in the Company's Li-

z 2

180 DR FRANCIS HAMILTON on the Plants of India,

brary. Some duplicate specimens were given to A. B. LAMBERT,
Esq. and I think that Sir J. E. SMITH has a copy of the notes : of
this, however, I am not certain.

Soon after my return from the south of India, 1 was sent to
Nepal along with the embassy conducted by Captain KNOX.
Having proceeded by water to Patna. I passed, by easy stages,
and with many halts, through the ancient territory of Besala,
now called Sarun ; and through a portion of Mithila now called
Tirhut. There I carefully examined and collected such plants
as were in flower ; and, on the 1st of April 1802, I ascended into
Nepal, where I remained nearly twelve months, delighted with
the variety, beauty, and grandeur of its vegetable productions, of
which I procured many specimens, descriptions and drawings, all
of which I gave to Sir J. E. SMITH, only reserving specimens,
where there were duplicates, for Mr LAMBERT. I afterwards
had an opportunity of procuring many specimens from the same
quarter, and of making many observations on these plants, which
I may have occasion to use under the disagreeable circumstance,
that I may have described the same plant under different names,
among those given to Sir J. E. SMITH, and among those which
I afterwards procured ; but under the circumstances already men-
tioned, this was unavoidable. For an account of the appearance
of the vegetables in this interesting region, I may refer to the
Account of Nepal which I have published.

Soon after my return to Calcutta in 1803, I was appointed
Surgeon to the Governor-General ; and the leisure I then had for
the study of Natural History, was chiefly employed in superin-
tending the Menagerie founded by the Marquis WELLESLEY, and
in describing the animals there collected. I returned to Eng-
land with this distinguished Nobleman in the end of 1805, and
in 1806 was appointed by the Court of Directors to make a sta-
tistical survey of the territory under the Presidency of Fort Wil-
liam, usually in Europe called Bengal ; but containing many ex-

and on the Samcrita Names of that Country. 181

tensive regions besides Bengal, taking that even in the most ex-
tended sense of the Mogul province of the name ; for in Hindu
geography, Vanga, [from whence Bengal is a corruption, is ap-
plied to only the eastern portion of the Delta of the Ganges, as
Upavanga is to the centre of this territory, and Angga to its wes-
tern hmits.

I commenced this survey after the rainy season of 1807, with
the English district of Dinagepore (Dinajpura), forming part of
the ancient kingdom of Matsiya, bounded by the Mahananda on
the west, by the Korataiya (Latine Coratasa) on the east, by the
mountains on the north, and by the Padma or eastern branch of
the Ganges on the south. This district is not very favourable
for the botanist, being in general highly cultivated; but its
southern parts, especially round the ancient city of Purua, are
woody, and yielded a considerable increase to my collection.

In spring 1 808, having finished the survey of Dinagepore, I
passed through the English district of Rungpur (Ranggapur),
the Kamrupa of the ancient Hindus, and having examined the
north-eastern wastes of that territory, where I added much to
my botanical stores, I halted for the rainy season at Goyalpara
(Latine Goalpara). This place, situated at the northern extre-
mity of the mountainous district, which bounds the Gangetic
Plain on the east, afforded me most ample employment as a bo-
tanist, producing a variety of beautiful and rare plants, almost
equal to that of Nepal ; and, with my journeys to Ava and Cha-
tigang, enabled me to form a proper estimate of the vegetable
productions of Farther India (ultra Gangem), the China of the
Hindus, and which I have already described.

With the fair weather of 1808 I recommenced the survey of
the Rungpur district, where I found an excellent field for a bo-
tanist, as it contains many wastes. As the rainy season of 1809
approached, I retired to a house near the town of Rungpur, and
there continued, in a situation not very favourable for a botanist,

18£ DR FRANCIS HAMILTON on the Plants of India,

until I had time left only to convey me to Purneah (Puraniya),
before the fair weather of 1 809 should commence.

The English jurisdiction of Purneah (Latine Purania) forms a
part of the ancient Hindu kingdom of Mithila, with a small por-
tion of Angga around the ruins of Gaur ; but my journey, during
the dry season, added little to my botanical stores. This, how-
ever, was amply recompensed by my stay, during the rainy sea-
son 1810, at Nathpur, on the frontier of the Kiratas or Ciratas,
subject to Nepal, from whence, as well as from the forests in the
northern parts of Mithila, I procured a great variety of rare and
curious plants.

In autumn 1810, so soon as the weather cleared, I proceeded
to the district of Boglipore (Bhagulpur), the eastern part of
which is included in the ancient Hindu kingdom of Angga, while
its western portion is in Magadha, and the portion on the north-
ern banks of the Ganges is partly in Angga, partly in Mithila.
The greater portion of this district being waste, was very favour-
able to me as a botanist, and I had here an opportunity of ex-
tending my knowledge of the rigid vegetation of the Vindhiyan
Mountains, which the Hindus consider as bounding the Gangetic
plains on the south, and as extending from the southern banks
of the Ganges to the Southern Ocean. These hills are here much
lower than the parts of the same mass which I examined in the
south ; but their vegetable productions are nearly the same, and
have a similar rigid thorny appearance ; but, the rains being more
copious, the vegetation is not quite so much stinted, although it
is very far from being so luxuriant as that towards the east or
north.

The rainy season 1811 I passed at Mungger, where the vici-
nity of the hills gave me a considerable increase to my stock of
plants, and I employed a Hindu physician, not deficient in learn-
ing, to point out the plants which he considered officinal, and to
give me both their Sanskrita and Hindu names, which I compa-

and on the Sanscrita Names of that Country.

red with those given to the same plants by the ignorant people
who collect and vend drugs.

In the following dry season 1811-12, I examined the ju-
risdictions subject to the magistrates of the cities of Patna and
Gaya, both included in the ancient kingdom of Magadha, which
for many centuries before the Muhammedan invasion, was consi-
dered the chief seat of Hindu power and glory, so that its princes
were indifferently called Kings of Magadha and of Bharatkanda,
or the Land of Virtue, the name by which the Hindus fondly call
the territory occupied by their race, the descendants of Brahma.
In these districts I had a farther opportunity of making myself
acquainted with the rigid vegetation of the Vindhiyan Moun-
tains, and, during my stay at Patna, in the rainy season 1812, I
extended my knowledge of the officinal plants of India, by con-
sulting the same physician and the druggists of Patna.

In the dry season 1812—13, I examined the jurisdiction
under the magistrate of Shahabad, forming a great part of the
ancient Hindu kingdom of Kikata (Latine Cicata) ; and here I com-
pleted my knowledge of the vegetation of the Vindhiyan Moun-
tains, which, the farther west I proceeded, rose to a greater ele-
vation, were more rocky, and communicated to their vegetation
more and more of the rigid and thorny nature of that produced
on the arid hills and mountains of Draveda, Karnata, and Chera.
Soon after the rainy season of 1813 commenced, I embarked
at Chunar, and proceeded up the Ganges and Yamuna (Jomanes
PLINII) or Jumna to Agra, and thus had an opportunity of examin-
ing the plants on the banks of these rivers, passing along a por-
tion of the ancient kingdom of Malava (Malwa) on the east of
the Yamuna river, near the Ken (Cainas PLINII) and Chumbul
rivers, and then proceeding through the centre of the ancient
kingdom of Kuru, which, in the earlier part of the Hindu govern-
ment, was the chief seat of power and glory, restored to it after-
wards by the Muhammedan conquest, and only lately restored to

184 DR FRANCIS HAMILTON on the Plants of India,

Angga by British valour and prudence ; for, in the time of ALEX-
ANDER, Angga was no doubt the chief seat of Hindu power, as
Palibothra seems to have been seated opposite to Rajamahal in
Angga, although on the skirts of Magadha, which in latter times
was the great seat of authority.

Before the end of the rainy season I returned down the ri-
vers, and ascending the Gagra, entered the district of Gorakhpur,
forming a considerable portion of Cosala, the territory of the
powerful Family of the Sun, who reigned at Oude (Ayudhiya).
During the dry season 1813-14, I remained in the district of
Gorakhpur, where I made large additions to my botanical obser-
vations, both from the forests of the country, and from the neigh-
bouring parts of Nepal, from whence I procured many plants.

When the rainy season commenced I again embarked, and
proceeded up the Ganges to Futehgar, where I had again an op-
portunity of examining the vegetable productions of the ancient
kingdom of Kuru, through the centre of which the Ganges
passes ; for it includes both banks of the Ganges and Yamuna,
being bounded on the east by Kosala, and on the west by Pang-
chala, now called the Punjab, or the country watered by the five
rivers joining the Indus from the north-east.

Having thus examined a considerable portion of the Gange-
tic plain, always considered the proper seat of the Hindu race,
descended from a colony of civilized persons calling themselves
sons of BRAHMA, who in the earliest ages settled at Vithora (Be-
toor Rennell), and gradually extended their power over what is
now called Hindustan, I shall proceed to give some general ac-
count of the vegetation of this fertile tract, which, without any
thing that can be called a hill, extends from the Indus to the
Eastern Ocean, and from the Vindhiyan to the Himaliya moun-
tains.

This plain, extending in length about fourteen degrees of
longitude, in the middle latitude of 25°, and in breadth from two

and on the Sanscrita Names of those Regions. 185

to four degrees of latitude, seems to derive a large proportion of
its vegetation from the neighbouring hills ; but grasses, especially
Bambusa, Saccharum, Andropogon, Apluda, and Panicum, toge-
ther with the allied tribes of Cyperoideae, form a larger and more
marked feature than trees or shrubs. On the whole, the rigid
and thorny vegetation of the Vindhyan mountains seems more
suited for the plain than the more ornamental vegetation of
either the Eastern or Himaliya mountains. Near both these,
however, their plants have made considerable encroachments, and
communicate a change of appearance to the adjacent plains, espe-
cially towards the east, where the air is vastly cooler and moister
than farther west.

I have already mentioned the appearance of the Gangetic
Delta, which, on the whole, has a strange and exotic appearance
to the European traveller. As we advance, however, to the
north, and still more as we proceed west, notwithstanding the
intense heats of the summer, the vegetation appears more of an
accustomed form. Wheat, Barley, Pease, and Rape-seed form
by far the largest proportion of the crops, and we observe fields
of Potatoes and Carrots, while the Palmae and Bambusae disap-
pear from the plantations, and the gardens produce the Vine,_ the
Fig, the Apple, and the Plum, with many flowers common in
Europe, and the thickets contain much of the wild Rose. Still,
however, even in Kuru, the Mangifera, the Eugenia, the Calyp-
tranthes, the Fici (religiosa and bengalensis) the Rhamni, and
the exotic crops produced in the rainy season (Oryza, Holcus,
Panicum, Paspalum, Dolichos) with the want of the Coniferse
and Amentaceae in the plantations, remind us sufficiently that we
are not in Europe.

I now was exhausted by a. long continued exertion ; the ob-
servation of plants making but a small part of my duty, and I re-
quired to pass the remainder of my days at peace in my native

VOL. x. P. i. A a

186 Da FRANCIS HAMILTON on the Plants of India, 8fc.

climate. I accordingly returned to Calcutta, to prepare for my
journey ; and, in the mean time, on the death of Dr ROXBURGH,
took charge of the Botanical Garden, having been appointed his
successor by the Court of Directors. While preparing for the
journey, I was deprived by the Marquis of HASTINGS of all the
botanical drawings which had been made under my inspection
during my last stay in India, otherwise they would have been de-
posited, with my other collections, in the Library at the India
House. By this ill-judged act of authority, unworthy of this
Nobleman's character, the drawings will probably be totally lost
to the public. To me, as an individual, they were of no value,
as I preserve no collection, and as I have no occasion to convert
them into money.

In February 1815 I embarked for Europe, and in September
presented my whole collections to the Court of Directors, with
an order from the Lords of the Treasury for their being deli vered
free from duty, — an order which was granted with the utmost li-
berality and urbanity.

( 187 )

XIII. On a New Species of Double Refraction, accompanying a
remarkable Structure in the Mineral called Analcime. By
DAVID BREWSTER. LL.D. F.R.S. Lond. & Sec. R. S. Ed.

(Read Jan. 7- 1822J

HE Mineral called Analcime or Cubizite has been ranked by
HAUY among those crystals which have the Cube for their primi-
tive form ; an opinion which has been adopted by all succeeding
mineralogists. No distinct cleavage-planes, however, so far as
I can learn, have been observed in it*. Crystallographers
presumed that such planes must exist, and, allowing conjec-
ture to supply the place of observation, they considered Anal-
cime as differing in no respect from other crystals of the same
series. This opinion was first rendered doubtful by the obser-
vation, that at thicknesses of -/^th of an inch, it displayed
a considerable action upon polarised light f ; but though,
from the tessular form of the mineral, this fact indicated some-
thing singular in its organization, yet, owing to the great diffi-
culty of obtaining proper specimens, I have been baffled in re-
peated attempts to investigate its structure.

* Mr PHILLIPS observes, " that there have been occasional appearances of
cleavage-planes parallel to the faces of the cube."— Mineralogy, 1823, p. 129. M.
MOHS describes the cleavage as hexaJtedral, but imperfect. HAUY does not seem to
have observed any cleavage. In the first edition of his Traits, published in 1801, he
says, Les cristaux diaphanes offrent seuls quelques indices de lames paraUeles aux
faces du aibe, torn. iii. p. 181 ; but in the second edition, published in 1822, he has
struck out this observation. See torn. iii. p. 170. In the transparent and perfectly
crystallised specimens, I cannot find any cleavages. I consider Analcime, therefore,
as a mineral without cleavage ; and if cleavage-planes are discovered, they will no
doubt be found in the direction of the planes of no polarisation.

f Philosophical Transactions, 1818, p. 255.

A a 2

188 DR BREWSTER on a New Species of Double Refraction,

Having lately received from the Reverend Dr FLEMING
of Flisk, some very transparent crystals of Analcime from the
Macdonalds' Cave in the Island of Eigg, and having also been
favoured with a very fine specimen from Montecchio Mag-
giore in the Vicentine, through the liberality of Mr HEULAND,
I have been enabled to resume the inquiry, and have obtained
the results which it is the object of this paper to describe.

The most common form of the Analcime is the Icositetrahe-
dron, a solid contained by twenty-four equal and similar trape-
ziums, and formed by three truncations on the eight solid angles
of the circumscribing cube, inclined 144° 44' 8" vto each of its
faces, and 146° 26' 33" to one another, (See Fig. 1. Plate VII.).
If we suppose this cube to be dissected, as in Fig. 2., by planes
passing through all the twelve diagonals of its six faces, it will
be reduced into twenty-four irregular tetrahedrons. The same
planes divide the icositetrahedron into twenty-four similar pen-
tahedrons, two of whose planes are placed at right angles to each
other, having for their common section one of the axes of the
solid, while a third, equally inclined to these two, and forming an
angle of 45° with their common section, passes through the
centre of the icositetrahedron. The other two planes are halves
of two of the adjoining trapezia, which form the surface of the
general solid.

If we transmit polarised light in a direction perpendicular
to any of the faces of the cube, we shall find that all the divi-
ding planes now mentioned, are planes of no double refraction
or polarisation, that is, that they consist of an infinite number of
axes parallel to the four axes of the solid *.

When any of the axes of the cube are in the plane of primi-
tive polarisation, the tints will disappear, and continue invisible

* These planes correspond \vitli the double set of cleavage-planes which, accord-
ing to HAUY, are found in Amphigene.

PLATE VII.
KB. 7.

Kavul .Inr.n-afi Val.X.P IS8.

Fzy 10.

and a remarkable Structure in Analcirne. 189

while the crystal is made to revolve round that axis ; but when
the axis is inclined 45° to that plane, or when the diagonals of
any of the cubical faces are in the plane, we observe a black cross
in the directions AB, CD, Fig. 1., separating four luminous sec-
tors covered with the tints of polarised light.

If ACBD, Fig. 3., representing a piece cut off the summit of
the icositetrahedron by a plane perpendicular to one of the axes,
is exposed to polarised light, it will exhibit, of course, the black
cross AB, CD, and the four sectors of polarised light. If the
crystal is now turned round CD as an axis, so that the part A
is brought near the eye, and B retires from it, the black cross
opens at the centre, and assumes the form of two curves A a C,
B d D ; but when B is brought near the eye, and A retires, these
curves have the position B b C, D c A.

When a slice is cut from the summit with three planes, or that
which corresponds to one of the diagonals of the cube, as shewn in
Fig. 4., the three planes of no polarisation a d, bd, cd, are dis-
tinctly seen. If the line c d is placed in the plane of primitive po-
larisation, the sector Sadb, opposite to it, becomes dark, and the
same is true of the other lines ad, bd. If, instead of a slice of
the crystal, we use a complete icositetrahedron, and look along
the diagonal of the cube, we observe six sectors, as in Fig. 5.
The reason of this is, that the three planes at the opposite end
of the diagonal have an inverse position, the three edges of the
one, corresponding with the diagonals of the three trapezia in
the other, as shewn in Fig. 6. If the analysing plate has its
plane exactly perpendicular to that of primitive polarisation, all
the six sectors are equally whitish in minute crystals ; but by
turning the plate to the left, three of the alternate sectors be-
come dark, and by turning it to the right, the other three be-
come dark. The polarisation is a minimum along this and all
the other diagonals. When the plane T a d c of the slice shewn
in Fig. 4. is inclined, so that d is brought nearer the eye, and

190 DR BREWSTER on a New Species of Double Refraction,

T retires, the tints rise in the scale, and vice versa. When the
light is transmitted obliquely, the lines c d, &c. disappear.

When a slice is cut off a summit with four planes, corres-
ponding to the edges of the cube, as in Fig. 7., the lines of no
polarisation a d, c d, bd, bf, ef, gf, are visible. The lines
a d, cd, and ef, gf, become sharper and narrower the more
the incident ray approaches to parallelism with the diameters
passing through d and/ When S s or df are in the plane of
primitive polarisation, the tints all vanish, because one of the
axes is then in that plane. When S s is inclined, so that S re-
cedes from the eye, the tints in S a b e rise, and those in sdbf
fall, and vice versa.

In order to determine the character of the tints, we have
only to cross them with the axis of a plate of any crystal the
character of whose action is determined. When the polarised
tints shewn in Fig. 3. are crossed by a plate of sulphate of lime,
having its axis inclined 45° to the arms of the black cross AB,
CD, the tints all descend in the scale, and consequently the po-
larising action of the crystal is negative in relation to each of the
four axes of the icositetrahedron. In like manner, when the axis
of the sulphate of lime crosses any of the three sectors in di-
rections passing through d, Fig. 4., the tints in the sector thus
crossed descend in the scale. When the axis of the sulphate of
lime is placed in the direction S s, Fig. 7., the tints likewise
fall.

In all these different directions, the tints polarised by the
crystal are exactly those of NEWTON'S scale, and have all the
properties of the tints of moveable polarisation.

From an attentive consideration of the preceding experiments,
it is obvious that the phenomena of the tints exhibited in any
individual sector COB, Fig. 8., have no relation to the axis of the
icositetrahedron passing through O, considered as an axis of
double refraction. The axis of polarisation of every portion in

and a remarkable Structure in Analcime. 191

«ach sector, as COB, is, on the contrary, perpendicular to the
line CB, or parallel to one of the rectangular axes of the icosi-
tetrahedron, which is perpendicular to the axis passing through
O. The tint of any point p, for example, does not depend upon
its distance pO from O, but upon its distance p q from the nearest
plane of no polarisation, taken in a direction perpendicular to CB.
Calling T, then the tint, as determined by experiment, of any
point P, whose distance Pr, taken in the manner now men-
tioned, is D, we shall have the tint t at any other point p whose
distance p q is d,

_
D2

the thickness of the crystal being supposed equal at both these
points. The polarising structure, therefore, of any two opposite
sectors, is the same as if it were produced by compression, the
axis of pressure coinciding with the axis of the icositetrahe-
dron perpendicular to CB, and to the axis passing through O.

This remarkable structure produces a distinct separation of
the ordinary and extraordinary images of a minute luminous ob-
ject, when the incident ray passes through any pair of the four
planes which are adjacent to any of the three axes of the solid.
The least refracted image is the extraordinary one, and conse-
quently the doubly refracting force is negative, like that of Cal-
careous Spar, in relation to the axis to which the refracted ray
is perpendicular.

In order to convey some idea of the remarkable structure of
Analcime, I have represented the Planes of no Double Refraction
and Polarisation, and the tints of the intermediate solids, in
Figures 9, 10, 11, and 12. The dark shaded lines are the planes
of no double Refraction, and the faint shaded lines represent
the tints. The appearances, however, shewn in these figures,
can never be seen by the observer at once, but they will assist
the reader in following the experimental details, and in forming

192 DR BREWSTER on a New Species of Double Refraction,

a correct notion of the phenomena. In Fig. 10. I have repre-
sented the Cube, seen in perspective; and in Figure 11. the
Cube, projected on a plane perpendicular to one of its diagonals.
Figure 9. represents the Icositetrahedron in perspective ; and
Figure 12. the same solid projected on a plane perpendicular to
one of its axes.

One of the most important results of these experiments, is
the singular distribution of the doubly refracting force, not mere-
ly in the crystal considered as a whole, but in each of the sepa-
rate pentahedrons which compose it. In all other crystals in
which the laws of double refraction have been studied, the axis to
which the doubly refracting force is related has no fixed locality
in the mineral. It is a line parallel to a given line in the pri-
mitive form, and every fragment of a crystal, however minute,
possesses this axis, and all the optical properties of the original
crystal, however large. The property of double refraction, in
short, in regularly crystallised substances, resides in the ulti-
mate particles of the body, and does not depend upon the mode
in which they are aggregated to form an individual crystal.

In Analcime, on the contrary, we have planes of no double
refraction, having a definite and invariable position, and we may
even extract a portion of each separate pentahedron which has
no axis at all.

Nor has the doubly refracting structure of Analcime any re-
lation to that of composite crystals, such as the Bipyramidal Sul-
phate of Potash*, which consists of several individual rhomboidal
prisms, beautifully combined to form a regular geometrical solid,
or that still more complicated mineral Apophyllite, where an in-
dividual crystal with one axis is symmetrically united with se-
veral individual crystals with two axes, so as to constitute a re-
gular crystal f . In these, and other cases, each individual crystal

* See Edinburgh Philosophical Journal, vol. i. p. 6.

+ See Edinburgh Philosophical Journal, vol. i. p, 1. ; and Edinburgh Tranz-
i vol. ix. p. 317.

and a remarkable Structure in Analcime. 193

that enters into the combination, retains its own character, and,
considered by itself, possesses the ordinary properties of double
refraction.

The Analcime partakes of the character of other composite
minerals, in so far as it is made up of twenty-four individual
pentahedrons ; but each pentahedron possesses a new species of
double refraction, which has been found in no other crystal. This
structure resembles, to a certain degree, that of rectangular plates
of glass, while in the act of being heated, in having the pheno-
mena related to planes of no double refraction ; but the resem-
blance goes no farther, as the structure of the glass depends
upon its external form, and the planes of no polarisation change
their position with the outline of the plate. In Analcime, on
the other hand, the structure is permanently fixed, and has no
relation whatever to the external shape of the fragment.

In the absence of more striking analogies, we may consider
this structure as resembling that which is produced by harden-
ing isinglass, when in a state of compression or dilatation. In
this case the isinglass retains a fixed doubly refracting struc-
ture, related to the axis of compression or dilatation ; and if it
were cut into pentahedrons, similar to those of the Analcime, we
might combine them together, so as to imitate, at least in the
direction of one of the axes, the phenomena exhibited by the
mineral.

The property which has now been described becomes an in-
falh'ble and easily applied mineralogical character for Analcime.
However shapeless be the fragment, and however much obliter-
ated be its external faces, its action upon polarised light will in-
stantly determine whether or not it belongs to this species.

HAUY first observed in Analcime the singular circumstance of
its yielding no electricity by friction, and he even derived its spe-
cific name from its want of this property. If we consider that

VOL. x. P. i. B b

194 DR BREWSTER on a New Species of Double Refraction.

the crystal is a combination of solids of variable density, and se-
parated from one another by numerous intersecting planes or
nodes, where the variations of density change their direction,
we may ascribe to this cause the difficulty with which friction
decomposes the natural quantity of electricity which resides
in the mineral.

( 195 )

XIV. On the Specific Heat of the Gases. By W. T. HAYCRA FT,

ESQ.

(Read November 3. 1823J

run* -,ilf 'io-ouLb «?Tjv7 .-fotyv/ -^/l.' : •vufii-ioqir,^ 7<v«of K ,"if> ml
THE experiments which I now submit to the Royal Society are
repetitions of those I made- many months ago, for the purpose of
ascertaining the Specific Heats of the Gases. The importance of
the subject so impressed my mind, that I determined to spare
no pains in the prosecution of the inquiry, and therefore I will-
ingly withheld my first experiments from the public eye, until,
by a fresh series, I might present them with the greater confi-
dence. The apparatus employed in these experiments was cal-
culated to operate upon greater quantities of the Gases than the
former one, and as every precaution which had been suggested
was adopted, they have, perhaps, given even more decisive re-
sults than the last. The results themselves, however, are in
every important particular exactly the same. It is also but jus-
tice to myself to state, that the conclusions which the former ex-
periments led to, were exactly the reverse of what I had antici-
pated, and that they seemed at the time totally opposed to the
doctrines of BLACK and CRAWFORD, which I am still disposed to
credit to a limited degree.

j i • • j

Before I enter into the detail, it will be necessary to take no-
tice of the modes in which former experimenters have proceeded
in these inquiries, and to point out what I conceive to have been
the sources of fallacy in some of their conclusions. Of all these
modes, none were more elegant than that adopted by Professor
LESLIE ; but as he himself states, that their results were discor-
dant with each other, it seems unnecessary to enter into a de-

• b £

196 MR HAYCRAFT on the Specific Heat of the Gases.

scription of it. Dr CRAWFORD'S method consisted of inclosing
two different Gases (previously exposed to muriate of lime,
for the purpose of depriving them of their watery vapour) in two
close vessels of equal size and weight ; these being heated to ex-
actly the same temperature, by a very ingenious contrivance,
were at the same time plunged into two vessels, containing wa-
ter of a lower temperature : these vessels were also of the same
size, form, and weight : then, by means of accurately adjusted
thermometers, he ascertained the comparative rise of tempera-
ture occasioned by the two Gases, and hence he determined
their specific heats.

I know of no imperfection in this mode, excepting that the
quantities of the Gases were so small, that the results could not
be obtained with sufficient accuracy.

This defect is entirely obviated by the method adopted by
Messrs DE LA ROCHE and BERARD : their apparatus consisted of
a column of water, so adjusted as to act with a constant and equal
pressure in a close vessel containing air ; which being gradually
expelled by the superincumbent water, pressed on the outward
surface of a bladder containing the Gas whose capacity was to be
examined. From this bladder the Gas was propelled through
the calorimeter : this consisted of a vessel containing water of a
low temperature, through which a spiral tube passed to conduct
the Gas. Previous, however, to its entering the calorimeter, the
Gas was heated, by a particular contrivance, to the boiling tem-
perature. After leaving the calorimeter, it was conducted, by
means of turn-cocks, into another bladder ; the latter was acted
upon in the same way as the former. By means of this recipro-
cating action, Messrs DE LA ROCHE and BERARD could cause
225.2 cubic inches of Gas, heated to the boiling temperature, to
pass through the calorimeter every minute. The temperature
communicated was ascertained by a thermometer, and from com-
parative trials, the capacity of the different Gases was inferred.

PLATE VET.

MR HAYCRAFT on the Specific Heat of the Gases. 197

This last method was superior to that of Dr CRAWFORD, inas-
much as greater quantities of Gas could be employed. In other
respects it was far inferior, because the experiments were not,
strictly speaking, comparative. Atmospheric air, whose capacity
was their standard of comparison, was subjected to trial, and the
results were remarked. The other Gases, at different periods,
with the surrounding media of different temperatures, and
under different barometrical pressures, were examined ; this plan
involved endless and very difficult calculations, in order to adjust
those differences. But the greatest imperfection in those expe-
riments, was the neglect of depriving the Gases of their watery
vapours previous to their examination. The apparatus itself
would not admit of this, because the water employed in the pro-
cess would necessarily keep the gas and the whole apparatus in
a state of moisture. Besides, this very great source of error was
materially increased by the high temperature to which the
Gases were exposed, being a condition in which they are disposed
to unite with a greater quantity of watery vapour than at ordi-
nary temperatures. Considering the subject in this point of
view, therefore, the experiments of Messrs DE LA ROCHE and
BERARD may be supposed to determine the capacities of the dif-
ferent Gases united with watery vapour at the boiling point, but
by no means of those Gases in their dry state, and at ordinary
temperatures.

The apparatus now to be described, will perhaps be found to
unite the advantages, and avoid the defects of both methods.

It consisted of two hollow brass-cylinders, (see Plate VIII.),
in each of which was a piston attached to a spindle by means of
two levers of equal length ; to the spindle was attached another
lever, terminating in a handle, to be moved by an assistant. Each
cylinder was closed at each end, excepting where the tubes were
attached, which served to conduct the Gases. By means of four
valves to each cylinder, fixed in such a way as, though difficult to

198 MR HAYCRAFT on the Specific Heat of the Gases.

describe in writing, may be easily understood by reference to
Plate VIII. Each action of the piston forced a quantity of air
through the tubes; thus, by means of one additional valve,
the apparatus would act upon exactly twice the quantity of air
that could be acted upon in a pump of the ordinary construc-
tion.

The pipes immediately connected with the four valves, ter-
minated in two tubes ; through one of which the air, during the
action of the apparatus, was propelled with a constant, and almost
uniform current, while, through the other, the same air having
passed through the heating apparatus and the calorimeter, re-
turned to the cylinder, to be acted upon again in the same way.
The heating apparatus just mentioned, consisted of a metallic
vessel, about 16 inches long, containing hot water, through which
the tubes passed, containing the air propelled from the cylinders :
those tubes traversed the heating vessel three times before their
exit, more effectually to secure the Gases arriving at the tem-
perature of the water contained in the vessel. By means of a
lamp placed under this vessel, I could raise the temperature
of the water to any point required. This last arrangement, how-
ever, was rather a matter of convenience than necessity, as it will
be easily perceived that, from the mode of conducting the expe-
riments, a fixed point of temperature was not required.

There were also two calorimeters, similar in construction to
those of Messrs DE LA ROCHE and BERARD before described.
Each of these was connected with the tube containing the Gas,
propelled by its cylinders through the heating apparatus, and
likewise with that through which the air flowed to the cylinder;
these tubes were all of metal, and air-tight.

The apparatus, then, must be considered as consisting of two
distinct parts, exactly the counter parts of each other, each con-
veying an equal quantity of Gas through the same heating me-
dium, but through separate calorimeters.

MR HAYCRAFT on the Specific Heat of the Gases. 199

The tubes communicating between the heating vessel and
the calorimeters were one inch in length. In these tubes there
was an opening, through which could be introduced a delicate
thermometer, for the purpose of ascertaining the temperature
of the Gases as they entered the calorimeters

Each of the calorimeters was inclosed in a polished metallic
case, for the purpose of preventing, as much as possible, the ab-
sorption or escape of caloric during the process. These latter
were also placed in a box containing water, which was repeated-
ly agitated, that the calorimeters might not be affected by the
unequal temperatures of the walls of the apartment.

For the purpose of facilitating the operation of filling the ap-
paratus with the Gas operated upon, there was a turn-cock fixed
in the course of each returning tube, by which the current of
Gas through the tube was interrupted. Two smaller turn-cocks
also were fixed in the same tube, one on each side of the larger
turn-cocks : these, when open, communicated with the external
atmosphere. When, therefore, the large turn-cock was closed,
and the small ones open, the air would necessarily, during the
action of the machine, rush in at one of the small turn-cocks, and
be forced out of the other, so that the air contained in the ap-
paratus would be constantly renewed. In order, then, to fill the
machine with the Gas, nothing more was necessary than to form
a connection between the gasometer or receiver containing the
gas and the apparatus, by means of a tube connected to the small
turn-cock first mentioned, through which the air rushed in. In
performing this operation, however, I usually made use of an air-
pump to exhaust the apparatus, and then opening the turn-cock
communicating to the gasometer, filled it with the Gas required :
after this operation had been several times repeated, I found
the gas contained in the machine to be nearly as pure as that
contained in the gasometer.

200 MR HAYCRAFT on the Specific Heat of the Gases.

By a slight consideration of this description of the apparatus,
which may be deemed rather prolix, and by an inspection of the
plate, it will be perceived that two Gases, contained in the two
parts of the machine, will be under circumstances precisely similar ;
the quantities of Gas transmitted through the calorimeters in a
given time will be the same ; the temperature of the surround-
ing media and the barometrical pressure will be equal ; the tem-
perature also of the Gases themselves must be the same, because
they passed through the same heating medium. In fine, the
size of the tubes, cylinders, calorimeters and valves, were the same
in the two parts of the machine.

Therefore, the temperature communicated by the two Gases
submitted to a comparative trial, will be the direct ratio of their
comparative capacities for caloric, provided there be no dispro-
portionate escape by absorption in the calorimeters, arising from
the different temperatures of surrounding bodies.

This source of fallacy was obviated by the arrangement of
Count RUMFORD, who contrived that the temperature of the sur-
rounding medium should be as much above that of the calorime-
ter at the beginning, as it was lower at the end of the experi-
ments.

The quantity of Gas propelled through the calorimeter was
12 cubic inches during the action of the piston. Those actions, as
regulated by a second pendulum, which was suspended in the
apartment, being 120 every minute, the whole quantity would be
1440 cubic inches of Gas propelled through the calorimeter every
minute. There was no occasion, however, to take these quanti-
ties into the account, because they were precisely the same of
each Gas subjected to trial.

My thermometers were adjusted by Mr AD IE of Edinburgh.
Each degree was divided into 5 parts, which were sufficiently
large to be divided by the eye into 4 parts ; so that the tempera-
ture could be ascertained to a 20th part of a degree, making al-

MR HAYCRAFT on the Specific Heat of the Gases. 201

lowance for the imperfection of all instruments. Each calorime-
ter was furnished with its thermometer, the bulb of which was
placed equidistant from its four sides : two smaller ones were
placed so as to ascertain the temperature of the Gases before
entering into, or coming out, of the calorimeter. One was at-
tached to the heating vessel, and another to the vessel of water
which served as the surrounding medium of the calorimeters.

Having filled both the calorimeters with water of the tem-
perature of 42°, and the heating vessel with it at a temperature
of about 1 80°, I admitted atmospheric air into each part of the
apparatus. The pistons were put into motion, and continued till
each of the calorimeters arrived at a temperature of 84°, with a
variation of little more than one-twentieth part of a degree.
Thus the temperature of the calorimeters was raised 42° each,
with a correction of T£7th part of the whole. Much greater al-
lowances may very properly be made for the imperfections of the
instruments. This experiment was designed to prove the accu-
racy of the apparatus, and was often repeated, at different periods*
with the same event. I was assisted in the following experi-
ments by my friend Dr CLENDINNING, to whom I am much in-
debted for their success.

Experiments on Carbonic Acid.
No. 1.

The part of the apparatus which I call A was filled with car-
bonic acid, obtained from carbonate of lime ; the part B with
common air. In each of the cylinders was placed, in a proper
receptacle, a quantity of very dry muriate of lime, for the pur-
pose of perfectly freeing the Gases from watery vapour. The ca-
lorimeters being filled with water at a temperature of 42°, and
the heating vessels with water at 149°^|, the following results
were obtained.

VOL. x. P» ij e e

202 MR HAYCKAFT on the Specific Heat of the Gases.

Temperature of Calori- Temperature of Calori- The comparative spe-

At the beginning \
of experiment, j
After 15 minutes,

At the beginning )
of experiment, )
After 15 minutes,

At the beginning)
of experiment, )
After 40 minutes,

At the beginning \
of experiment, 3
After 35 minutes,

At the beginning \
of experiment, )
After 25 minutes,

meter A, through
which the Carbonic
Acid passed.

42° Fahr.
68/0

No. 2.

42^0
6644

No. 3.

42
71M

meter B, through
which Atmospheric
Air passed.

42° Fahr.
68*5

42

71 8

a o

No. 4.

45 45

KO s RQ

UO-g-Q UO-

No. 5.

cific Heat of Car-
bonic Acid inferred
from the compa.
rative rise of the
Temperature of Hie
Air being 10000.

9730

9919

10035

10021

10000

MR HAYCRAFT on the Specific Heat of the Gases. 203

In these experiments it will be perceived, that the two first
indicate that carbonic acid has a less capacity for caloric than
common air. The three last, however, which do not differ ma-
terially from each other, will indicate an equal capacity, if we
take the average of their results. The cause of the two first
experiments indicating a lesser capacity, I suppose to arise
from the gas not being perfectly freed from watery vapours. In
the experiments I made last year, I observed that it was neces-
sary to expose this Gas to the drying influence of muriate of
lime, for 35 minutes at least, before it indicated the same speci-
fic heat as atmospheric air. This is not the case with all the
other Gases : from hence I would infer, that it has a greater af-
finity with watery vapour.

The Gas contained in the gasometer, as indicated by lime-
water, contained 99 per cent, of carbonic acid ; that taken from
the apparatus after the experiments were concluded, by the same
test, contained 90 per cent. The temperatures of the Gases while
entering the calorimeters were equal, as indicated by the thermo-
meters. It is worthy of remark, however, that these tempera-
tures appeared several degrees lower than that of the water con-
tained in the heating apparatus through which they passed.
This will be easily explained, when we consider that a thermo-
meter can never indicate the true temperature of any gas or
vapour, which is itself pervious to the radiation of heat or cold
from surrounding bodies. On this account the thermometers
indicated a temperature of the Gases much lower than the true
one, they being necessarily placed so near the calorimeters,
which usually contained water of a temperature nearly 100°
lower than that of the gases. In the same manner, the gases
issuing from the calorimeters appeared to have a temperature
something lower than that of the calorimeters themselves, being
surrounded with objects of a lower temperature than that of the
calorimeter!

c e 2

204 MR HAYCRAFT on the Specific Heat of the Gases.

Experiments on Oxygen Gas,

No. 1.

Having filled the part A with Oxyen Gas procured from
the Black Oxide of Manganese, and every arrangement being
made as before, the following results were observed :

At the beginning
of experiment,
After 5 minutes,
After 10 minutes,
After 15 minutes,
After 20 minutes,

Temperature of
Calorimeter A,
containing
Oxygen Gas,

o

67-2-

U< 2 0

71

Of Calorimeter B,
containing At-
mospheric Air.

1 A.
"20

70—

' U2 0

Inferred capacities.

10000

10000

10019

9982

No. 2.

At the beginning ~)
of experiment, )
In 10 minutes,
In 15 minutes,
In 20 minutes,

A

56.6°

66.16
71

74-*-

'^2 0

B

56.4°

66.14
70.18

10000

10000
10000
10000

The temperature of the Gases entering the calorimeters were
equal, being each 137°. The Gas contained in the gasometer
before the apparatus was filled, indicated 98° per cent, of Oxy-
gen, by the test of sulphuret of lime. After the experiment was
concluded, that contained in the apparatus indicated 91° per
cent-

MR HAYCRAFT on the Specific Heat of the Gases. 205

Experiments on Hydrogen.

Hydrogen Gas was procured from the decomposition of wa-
ter by means of sulphuric acid and zinc. The part B was filled
with the same, and the following experiments were made.

No. 1.

In this experiment the calorimeters were filled with water of
the same temperature, and the process was conducted on rather
a different principle than the former, namely, it was continued
until the calorimeters ceased to rise in temperature, or rather,
till the temperature began to fall. This latter circumstance
would take place when the heat communicated by the Gas was
exactly equal to that abstracted by the colder surrounding me-
dium. The number of degrees of temperature, then, which
each Gas would sustain in its calorimeter, will be the ratio of its
power for giving out heat, and consequently of its capacity for
caloric.

The temperature of calorimeter A, at the beginning of the
experiment, was about 50°, and after 105 minutes, the tempera-
ture of calorimeter A was 82° |-f, and that of B, containing Hy-
drogen Gas, was 82° |£, and the surrounding medium 60%°^, in-
dicating the comparative capacity of Hydrogen to be 98.64, be-
ing a difference so trifling, that it may be regarded as the same
as that of atmospheric air ; if we make allowance for the evident
greater ratio in its heating, and the smaller ratio of its rate of
cooling at the end of the experiment. This will be seen by the
following Table.

206 MR HAYCRAFT on the Specific Heat of the Gases.

At the beginning ~)
of experiment, }
In 5 minutes,
In 10 minutes,
In 15 minutes,
In 20 minutes,
In 25 minutes,
In 30 minutes,
In 31 minutes,
In 40 minutes,
In 45 minutes,
In 50 minutes,
In 55 minutes,
In 60 minutes,
In 65 minutes,
In 70 minutes,

Temperature of A,
containing At.
mospheric Air,

50°
59

"' 2"6

n] 6
2~0

75

771 6
• ' 2"0

79

80||

81*4

83
83

0

l 6

-"

Temperature of B,
containing Hy.
drogen Gas.

50°
58.6

70/

2"o"

76

7811

80/0

81

8

2"0
l 2

3T

l 6

No. 2.

At the beginning 1 . ,

of experiment, J

After 5 minutes, 55/o

After 10 minutes, 60

After 15 minutes, 64 J^

After 20 minutes, 67 A

After 25 minutes, 69/7

Inferred capacity*

55——

10500

60/7

10424

64/0

9950

67/o

10002

69/o

10000

This last experiment was conducted as the former ones.

MR HAYCRAFT on the Specific Heat of the Gases. 207

The air appeared, after the experiments, to contain 88 per
cent, of Hydrogen Gas, as indicated by explosion with Oxygen
Gas*.

In these two experiments it may be observed, that the wa-
tery vapour which may be presumed to be in the Hydrogen Gas,
before it had been sufficiently exposed to the drying influence of
the muriate of lime, seemed to decrease in specific heat, exactly
contrary to what might be expected. In the first experiment, at
the expiration of the first five minutes, it had a capacity of 9222,
pretty nearly the same as indicated in the experiments of Messrs
DE LA ROCHE and BERARD ; but in proportion as the experiment
had advanced, and the hydrogen had been exposed longer to the
muriate of lime, its specific heat approached to that of atmo-
spheric air, till, at the end of the experiment, they were quite
equal.

No. 2. was performed upon the same hydrogen, in its driest
state ; and throughout the whole experiment it indicated also a
capacity equal to the standard. In this experiment I know of
no source of fallacy, as the Gases, while entering into the calo-
rimeters, were of exactly the same temperature, and care \vas ta-
ken to ensure accuracy.

* The apparatus which I found most convenient for exploding gases, is a modi-
fication of Dr UHE'S syphon eudiometer. It consists of a hole bored in the solid bot-
tom of a mercurial trough, representing an inverted syphon ; one end of which opens
into the part" containing mercury, and the other through the edge of the trough to
the open air. To the latter opening is cemented an open glass tube ; and to the for-
mer a common graduated eudiometer is made to fit accurately. When this appara-
tus is used, the graduated tube is filled in the usual way, and applied to the opening
communicating with the trough. Mercury is poured into the other tube, to the same
height as that contained in the graduated one. The finger is then applied to the open
tube, and the electric spark passed. After the explosion, more mercury is poured into
the open tube, to the same height that it had risen in the eudiometer, after which the
degrees are read off.

208 MR HAYCRAFT on the Specific Heat of the Gases.

Azote.

Of Azote I shall merely state, that, last year, I performed si-
milar experiments upon this Gas, the results of which were per-
fectly analogous with those now detailed ; and as aU the experi-
ments agree that it has by volume the same specific heat as at-
mospheric air, namely 1000, I thought it needless to repeat
them.

Carburetted Hydrogen.

In my former experiments on Carburetted Hydrogen, pro-
cured from the decomposition of sea-coal, I concluded that it also
had the same capacity as atmospheric air ; but I have since found
that the capacity of this Gas varies extremely, according to the
modes in which it is procured. That produced from sea-coal seems
to have a capacity nearly equal to the standard ; that from the
decomposition by heat of animal fat, has a much greater capacity.
From the following experiments, however, it will appear that
olefiant Gas owes its increased capacity to the empyreumatic or
ethereal vapour with which it is usually combined.

No. 1.

This experiment I conducted in the same way as No. 1 . on
Hydrogen Gas. The part B was filled with olefiant Gas, obtained
from the gas-pipes of a public company. The calorimeters at
the beginning of the experiment contained water of the tem-
perature of 50°. At the end of 50 minutes the calorimeter A
had acquired its utmost temperature of 92° /0, and of B that
of 93° io 5 the surrounding medium being 66° -fc.

MR HAYCRAFT on the Specific Heat of the Gases. 209

No. 2.

The calorimeters were of a temperature of 52° -/^ at the be-
ginning of the experiment : after 55 minutes, the calorimeter A
had acquired a temperature of 92° ^ , and B that of 94° fa ; the sur-
rounding medium being 65°. The average result of these experi-
ments, Nos. 1. and 2., indicates the specific heat of olefiant gas to
be 10559. Though the results of these two experiments do not
quite agree with those I formerly made, yet the difference is very
trifling, and may be supposed to arise from the greater freedom
of the gas I formerly made use of, from empyreumatic va-
pour. This will appear probable from the following experi-

No. 3.

The part of the apparatus B was filled with carburetted hy-
drogen, procured by the destructive distillation of mutton-suet.
The calorimeters were filled with water of the temperature of
50° £ g. At the end of 40 minutes, the calorimeter, through which
the olefiant gas passed, had acquired its extreme temperature of
95°, the other that of 88° £g ; the surrounding medium being
65° /o ; indicating the specific heat of olefiant gas to be 12777.

That the gas procured from animal fat contains more em-
pyreumatic vapour, is evident from its sensible qualities, which
may account for its greater specific heat, compared with that pro-
cured from sea-coal. The gases, at the end of the experiment,
were exactly of the same temperature as when entering into
the calorimeters.

No. 4.

>"j.J<vi!.ry. . 1 ; ...i; '^, .

The last experiment was repeated, except that the olefiant
gas was procured from alcohol and sulphuric acid. After 25
VOL. x. P. i. D d

210 MB HAYCRAFT on the Specific Heat of the Gases.

minutes, the calorimeter A had assumed the temperature of
74/0°, and calorimeter B that of 75°.10; the surrounding me-
dium being 54° ; indicating the capacity of olefiant Gas to be
10643.

No. 5.

The last experiment was repeated, and gave a result of
10674 ; the medium result of experiments Nos 4. and 5. being
10658, indicating the capacity of olefiant Gas procured from al-
cohol and from sea-coal to be almost exactly the same.

XT ^

No. 6.

Wishing to ascertain if the ethereal or empyreumatic vapour
in olefiant Gas affected its specific heat, I poured a few drops of
sulphuric ether into the part of the apparatus containing atmo-
spheric air, that the latter, as well as the olefiant Gas, being
equally saturated with the vapours of ether, it might be ascer-
tained what effect that condition might have on the capacities of
the Gases. The part B contained the olefiant Gas as before.
After 40 minutes, both the calorimeters had acquired a tempera-
ture of 85^V, the surrounding medium being 61^. The in-
ference, then, may fairly be made, that it is the combined vapour
that increases the specific heat of olefiant Gas.

Experiments on the Air of Respiration.

Having last year made more than ten experiments which
prove that the mixtures of carbonic acid with atmospheric air
exposed freely to water, and at a temperature of about 100°, had
a much less capacity for heat than atmospheric air had, under
ordinary circumstances, and this curious fact seeming to throw-
some light upon the physiology of animal respiration, I filled the

Mil HAYCRAFT on the Specific Heat of the Gases. 211

part B with air from the lungs, and the part A with atmosphe-
rical air.

The heating apparatus was kept, by means of a lamp, at the
temperature of between 97° £g and 100° ££. After the end of 35
minutes, the calorimeter, through which the air of respiration
passed, attained the temperature of 59° /-Q, and the other that of
61° g-*0 ; the surrounding medium being 5 4°. 16, indicating the air
of respiration to be 6875.

eau oo

JNo. .

The last experiment was repeated, when the calorimeter arose
from 56Vo to 58° £J, and B from 56<VV to 57° if, indicating the
capacity of the air of respiration to be, as in the last experiment,
6875.

It may not be improper in this place to state, that, in my for-
mer experiments, mixtures of carbonic acid and atmospheric air,
under different conditions of temperature, and combination with
watery vapour, had relative capacities of 3333,66666.9999, and
13333. It was my intention to have repeated those experiments
in such a way as to ascertain the precise conditions under which
these changes of capacities took place ; but, from various engage-
ments, I am unable to do so. I may remark, however, that the
last two experiments seem to indicate, that the air of respiration
enters into the second of this series, making allowance for the
difference of the standard of comparison ; this being, in my for-
iner experiments, common undried atmospherical air, while the
standard of the latter was the same air carefully dried.

There is also a curious coincidence between this last-men-
tioned series of capacities of gas in different states of combina-
tion with water, and the expansive forces of air combined also
with different proportions of watery vapours. Having procured
a glass globe, to which a small stem was connected, in such a way

D d 2

212 MR HAYCRAFT on the Specific Heat of the Gases.

that mercury contained in the hollow ball would rise into the
stem upon any increase of the expansive force of the air contained
in the ball, I filled the latter with air at a temperature of 60° ; af-
ter which the ball was immersed into boiling water. In a short
time the mercury rose into the stem to the height of 7 inches.
The experiment was repeated, excepting that a few drops of wa-
ter were put, together with the air, into the ball. The mercury,
after the immersion of the ball in boiling water, rose to 21 inches.
Afterwards, on passing a quantity of water into the ball, the
mercury, after its immersion, rose to 28 inches. Some months
afterwards, on repeating the experiment, the mercury rose in one
instance to 14 inches. Thus we have a series of expansive forces
of air united to watery vapour of 7, 14, 21 and 28 inches : it was
upon this principle that I contrived an air thermometer. The
form of it is similar to that of the differential thermometer invent-
ed by Professor LESLIE. One ball contained atmospherical air
dried by means of muriate of lime ; the other contained air in its
usual state. Interposed between the balls was a column of the
volatile spirit of turpentine. Upon any rise of the temperature
of the atmosphere, the column immediately rose at the side
of the dry ball. After some time, however, the instrument
seemed to have lost its power; and after a still longer pe-
riod, the ball containing dry air had the greater expansive force.
This I accounted for by supposing, that the vapour of turpen-
tine had in process of time combined with the dry air, and had
given it its greater expansive power. This thermometer is now
a remarkably delicate one, though its degrees are of very une-
qual length, and appear to vary by lapse of time. Probably hy-
drogen gas contained in two platina balls, in ope of which a
h'ttle mercury might be placed, connected together in the same
way, would make an accurate pyrometer, indicating tempera-
tures as high as the melting point of platina.

MR HAYCRAFT on the Specific Heat of the Gases. 213

There is another condition under which air is capable of a
great variety of specific heats, namely, when it exists in different
degrees of density, whether arising from pressure or other causes.
The increased capacity of air, when under lesser degrees of atmo-
spheric pressure, has been properly made use of to explain the
extreme cold which exists in high regions ; and its decreased ca-
pacity under mechanical pressure, also satisfactorily accounts for
the heat evolved under that condition. This principle, so far as
I know, has not been used to explain one cause of the intense
heat produced during the combustion of gunpowder and other
explosive mixtures. If we reflect a moment, however, we shall
perceive that the resistance of the pressure of the atmosphere to
the expansion of the nascent gases produced by the combustion,
will cause them to exist in a state of greater density than when
the resistance of the atmosphere has been finally overcome. It
is during this state of potential compression, if I may use teh
term, that the intense heat is produced. After the first explo-
sion, however, the gaseous products will expand, and then there
will necessarily be an absorption of caloric, and consequently
comparative coldness, produced. In order to ascertain whether
there is a permanent evolution of caloric, occasioned by the com-
bustion of gunpowder, I made the following experiment.

Having a receiver containing 528 cubic inches, filled with wa-
ter of a temperature of 52°, placed in a pneumatic trough, the sur-r
rounding atmosphere being also 52°, I introduced 240 inches of
the aeriform fluids, produced during the combustion of that com-
position of gunpowder which is used for pyrotechnical purposes.
After the explosion, the gas in the upper part of the receiver
had acquired a temperature of nearly 54°, and the water not so
much. This experiment shews, that though heat is evolved in
the combustion of gunpowder, its quantity is not nearly so great
as has been imagined. Again, if we consider that the products
pf the combustion of gunpowder have not, by direct experiment^

214 MR HAYCRAFT on the Specific Heat of the Gases.

been proved to have a greater specific heat than the ingredients
of that composition, the phenomenon of heat being produced
during that combustion should not be urged as an objection to
the hypothesis of BLACK and CRAWFORD. Indeed it appears
very probable, from the inspection of the Table of Specific Heats
of Different Bodies, that those elastic products have a less capa-
city than the ingredients of gunpowder, from which they are
produced. For example, azote, which composes two-thirds of
the elastic products, has a capacity of 2669, and carbonic acid,
comprising one-third of the products, if my experiments are to
be trusted to, has a capacity of only 1751, water being 10000.
Nitric acid of a specific gravity of 1,1854, has a capacity of
5760. The azote, therefore, and oxygen, which is produced from
the decomposition of one of the ingredients forming the elastic
products of not half the specific heat of that ingredient, should,
according to the hypothesis of BLACK* evolve heat. This might
take place even if we make allowance for the lesser capacity which
nitric acid has in its state of one of the ingredients of the nitrate
of potash.

The same condition of potential compression may also con-
tribute to the intense heat which takes place in a blast-furnace.
This heat is known by all conversant with the phenomenon to
be, not in a ratio of the fuel consumed, but of some compound
ratio. This may be explained in the following manner : 1st, A
quantity of air is forced into contact with the coals in a state of
ignition, and its temperature is suddenly raised extremely high.
2d, In this condition, were it not for the pressure of the atmo-
sphere, it would become as suddenly expanded. 3d, Had this
expansion taken place, it would have acquired an increased ca-
pacity, and would consequently have absorbed a considerable
portion of the caloric evolved by the combustion, tending there-
by to lessen the capacity of the heat. 4th, But the heated air
being prevented by the pressure of the atmosphere from expand-

MR HAYCRAFT on the Specific Heat of the Gases. 215

ing in a ratio equal to the temperature acquired, the absorption
of caloric is lessened, and a greater proportion of the heat of com-
bustion is rendered free. Thus, although the total quantity of
caloric evolved at, and consequently to combustion, may be in a
direct ratio of the quantity of fuel consumed ; yet the intensity
of the thermometrical heat at the moment, and at the place of
combustion, will be greater in a compound ratio, directly as the
pressure of the atmosphere, and inversely as the times of expan-
sion of the air employed in the blast. These times are, of course,
inversely as the intensity of the blast. The thermometrical heat,
then, at the moment and place of combustion, will be in a com-
pound ratio of the quantities of fuel consumed, the weight of the
atmosphere, and the quantity of air employed in the blast in a
given time. The same rule will hold even in what are called
Chimney Furnaces ; and it is ascertained by experience, that
those furnaces of steam-engines through which a greater quan-
tity of air passes in a given time, consume a proportionally less
quantity of fuel to produce the same effect. Probably blast-
furnaces might be advantageously employed in lessening the
quantity of fuel used for those valuable machines.

Although, according to the foregoing experiment, it appears
contrary to my original expectation, that, by volume, oxygen gas
has the same specific heat as carbonic acid, it by no means follows
that caloric should not be evolved during the formation of the
latter by combustion. This formation does not consist of a con-
version of oxygen into carbonic acid, but of a union of two in-
gredients into a compound, having an absolute capacity for calo-
ric equal to one of the ingredients only, namely, the oxygen gas ;
consequently the whole absolute heat of the carbon is rendered
free.

The direct results of these experiments shew, that the speci-
fic heats of all the Gases experimented upon, are to each other

216 MR HAYCRAFT on the Specific Heat of the Gases.

inversely as their specific gravities; and, 2dly, That different
states of combinations of the Gases with aqueous and other va-
pours, affect the capacities of the Gases, and that probably, in
some instances, in a regular arithmetical progression, correspond-
ing with the arithmetical rate of expansive force of the Gases in
different states of combination with vapour. The most interest-
ing result to the physiologist is, that the air of respiration, at a
temperature of between 100^° and 95°, has a less specific heat
than atmospherical air. Many experiments were made which are
not here detailed, which shewed that the air of respiration, at the
temperature of 102° and upwards, and of 91° and downwards, had
a capacity the same as that of atmospherical air. I should feel
a hesitation in stating these results, had not experiments, very
often repeated, during a course of several months, warranted me
in my conclusions.

PLATE IX.

ftnml .«„• .fi-un.,. I': I X. l\t

/><•/. I.

Fig.

. 3.

fiy.

fig. .5.

217 )

.

XV. On the Forms of Crystallisation of the Mineral called the
Sulphato-tri-Carbonate of Lead. By W, HAIDINGER,
Esq. F. R. S, E.

'(Read February 16. 18H.)

JL HE history of the progress of discovery in the Natural Sci-
ences, records innumerable instances, where the different ways
of considering the same subject have created apparent contra-
dictions, which have subsequently been reconciled by more accu-
rate examination. The first observation of facts is very often far
from being accurate ; and, in most cases, this inaccuracy cannot be
corrected, till the science itself has attained a higher degree of
perfection. The optical and crystallographic inquiries into the na-
ture of mineral substances, refer equally to the regular forms
which these bodies present. The object of Crystallography is
to ascertain this regular form from direct observations ; and that
of the department of Optics, which relates to this subject, is to
determine the action of regularly crystallised bodies upon light.
According to certain general laws, it has been found possible to
argue from the optical phenomena to the external forms of mi-
nerals, and inversely from these forms to the actions dependent
upon them, which affect light in its passage through crystallised
substances.

It may be considered as a general law, as has been shewn by
Dr BREWSTER, that the external form of a crystallised body, ex<-
hibiting two axes of no polarisation uniformly throughout its
whole substance, cannot belong to the tessular, to the rhombo^
hedral, or to the pyramidal system. The observations of crystal-
lographers upon a few species, seem still to stand in opposition

VOL. x. P, i. E e

218 MR HAIDINGER on the Forms of Crystallisation

to this law, and to indicate certain exceptions to its generality ;
but as the existence of two polarising axes in a mineral, when-
ever it is capable of being observed at all, can always be ascer-
tained in the most unequivocal manner, and as several of the cry-
stallographic observations date from an early period of the sci-
ence, these exceptions are less likely to arise from the want of cor-
rectness or generality in the law, than from a want of precision
in observing the properties of minerals ; and hence a careful re-
examination of them is a subject deserving the particular atten-
tion of crystallographers. The Sulphato-tri-Carbonate of Lead
from Leadhills, as hitherto described, constitutes one of these
exceptions. It is the object of the present paper to remove the
difficulties in respect to this species, by a more accurate inves-
tigation of its crystalline forms.

Count BOURNON seems to have been the first author who
erected this substance into a separate species, under the name of
Plomb Carbonate Rhomboidal, which he describes * as presenting
the form of a regular six-sided prism, or that of an acute rhom-
bohedron of 70° 32' (the plane angles being given — 60° and
120°), variously modified by planes perpendicular and parallel
to its axis. He considers the acute rhombohedron as the primi-
tive form of the species. Mr BROOKE f, who calls this substance
the Sulphato-tri-Carbonate of Lead, likewise states the form of
the crystals most commonly occurring, to be a regular six-sided
prism, or an acute rhombohedron of 72° 30', terminated by a
plane perpendicular to its axis ; the latter being parallel to the
perfect planes of cleavage. He mentions, besides, a consider-
able number of secondary faces, and he has given the drawing
of a variety, which contains them, in the third edition of PIIIL-
LIPS'S Mineralogy, page 342., where he likewise assumes the
acute rhombohedron as the primary form of the mineral. Sup-
posing the angles given by Mr BROOKE to be exact, Professor

* Catalogue de la Collection Mineralogique, p. 343.
•j- Edinburgh Philosophical Journal, vol. iii- p. 118,

of the Suiphato-tri-Carbonate of Lead, 219

MOHS also considered it as rhombohedral, and arranged it in the
genus Lead-baryte, under the denomination of the Axotomous
Lead-baryte, being most distinctly cleavable in a single direction
intersecting the principal axis. Contrary to the general obser-
vation, that rhombohedral substances possess only one axis of no
polarisation, Dr BREWSTER * found that the mineral in question
exhibited two systems of coloured rings, more distant from each
other than those of Carbonate of Lead ; and from the existence
of the two axes, he inferred that its forms belonged to the pris-
matic system. He also remarked, that many crystals contain films
oppositely crystallised, as is the case in Arragonite.

I had at various times attempted to examine the forms of
Axotomous Lead-baryte, without, however, attaining a sufficiently
correct result ; but having lately resumed this examination,
the beautiful specimens in Mr ALLAN'S collection, and several
others, equally interesting, with which I had been favoured by
Dr BREWSTER, Mr IRVING, and Mr T. DOWLER, have enabled me
to ascertain the forms of this species with a considerable degree of
accuracy. The results of this examination are very remarkable.
They exclude the rhombohedron and the regular six-sided prism
from the range of forms, which the individuals of the species
may assume, and thus perfectly confirm the inference drawn
by Dr BREWSTER from his optical observations, while theyrtare at
variance with the crystallographic statements both of Count
BOURNON and of Mr BROOKE.

The crystals of Axotomous Lead-baryte have been described
as regular six-sided prisms, having angles of 120°, and termi-
nated by planes perpendicular to their axis. Upon examining
them, however, by the reflective goniometer, I found that neither
of these statements was correct, but that the six-sided prism is
a combination of three different simple forms, «, b, and c, Fig. 1 .
Plate IX., whose angles of intersection differ more or less from

* Edinburgh Philosophical Journal, vols. iii. p. 188. ; vi. p. 183. ; ix. p. 367;

E e 2

220 MR HAIDINGER on the Forms of Crystallisation

120° and 90°. The inclination of a upon b I found to be
= 90° 29' ; that of c upon c = 120° 20' ; and that of b upon c
= 119° 50'. Though slight, these differences are easily ascer-
tained, and their consequences, in the disposition of the crystal-
line faces, are so obvious, that they would certainly not have
escaped the practised eye of the crystallographers who described
them, had not a particular mode of regular composition seemed
to establish a kind of symmetry round a rhombohedral axis sup-
posed to be perpendicular to the faces of cleavage.

The system of crystallisation to which the forms of Axoto-
mous Lead-baryte belong, is not, therefore, the rhombohedral sys-
tem, nor do these forms enter into that class of prismatic forms
which exhibit the full number of faces of every simple form in
the combinations, but they must be considered as hemiprismatic,
the axis of crystallisation which is parallel to* the edges of the
prism c, being inclined to the base at an angle of 90° 29'.

There are two observations which can be very easily insti-
tuted on almost every group of well-pronounced crystals of the
species, and which evidently prove that the forms of these are
really hemiprismatic. The first of them refers to oblique trunca-
tions of the lateral edges, between b and c, as d,d, in Fig. 2., which
are inclined to b at an angle of 156° 27', and to c at an angle of
143° 22'. The other refers to the slightly, but very distinctly
marked planes of junction, between two individuals in the regu-
lar compositions, in a direction joining alternating angles, like A
and B, Fig. 1., in the supposed regular six-sided prism. The re-
mainder, ABA', of the terminal face of one of the individuals, is in-
clined to the similarly situated face of the other, at an angle of
179° 10', to which, on the opposite side, corresponds a re-enter-
ing angle of 180° 50'. Both these facts I had observed separate-
ly in numerous specimens, but the smallness of well-pronounced
crystals, and the impossibility of distinguishing by the eye an
angle of 119° 50', from one of 120° 20', rendered it very diffi-
cult to combine these different observations into one representa-

of the Sulphato-tri-Carbonate of Lead. 221

tion of its forms. The observation, that the plane of the result-
ant optical axes passes through a line parallel to A' A, Fig. 1.,
led me to inquire whether the face b, which I had before sup-
posed to be one of the faces of an oblique-angular four-sided
prism, might not be parallel to the short diagonal of the prism
produced by the enlargement of the faces c, c, &c. The exami-
nation of a small, but beautiful, and very regularly formed twin-
crystal, in the coUection of Mr ALLAN, carried on upon this
supposition, gave at last the results which form the substance of
this paper. One of the individuals of that regular composition
is represented in Fig. 3. ; and Fig. 4. is its projection, on a
plane parallel to the face a, the whole of the crystal having been
duly completed.

The number of faces which constitute this crystalline form is
so great, and the form itself is, on that account, so complicated
at first sight, that it will be more convenient to begin with con-
sidering some simple varieties of the substance, in order tq afford
a more distinct idea of its Series of Crystallisation.

One of these varieties is represented in Fig. 5. Beside the
faces of Fig. 1., all those edges which are not parallel to the axis
are replaced by the inclined faces e, e', P, and P'. If enlarged to
their mutual intersection, P and P' produce the fundamental
form of the species, Fig. 6., a scalene four-sided pyramid, in which
AX, the real axis of the form, is inclined to AP, a line perpendi-
cular to the base BCB'C', at an angle of 0° 29'. In the method
of Professor MOHS the angle MAP is called the Inclination of the
Axis. This method of considering hemiprismatic forms, is best
calculated to render more striking those analogies which exist be-
tween the series of crystallisation of the species in which the axis
is perpendicular, and of those in which it is inclined to the base
of the fundamental form. The development of the formulae ex-
pressing the angles of this kind of pyramids, depends upon the
comparison between the lines AP, MB, MC, and MP.

222 MB HAIDINGER on the Forms of Crystallisation

If we designate AP by a, MB by b, MC by c, MP by d, and,
moreover, call y and y the terminal edges AB and AB' conti-
guous to b, x the terminal edge AC, contiguous to c, and z the
lateral edge BC, which joins the two diagonals of the base, b and
c with each other, we obtain the following formula; :

COS «/ =

cos y =

COS X =

COS Z =

tang MAP =
tang BAP =
tang B'AP =
cos CAC' =

a2 (62 + c2) + c2 (6 —

^^^ + (& + d)*O(«*(&* + cs) + (& — <

v'L («* (62 -f c2) + (6 + d)* c2) (a2 (62 + c2) + (6 —

d -

a?

6 + rf
~^~~;

S — d

cos CBC' -

A* +

The ratio of the lines a:b:c:d, which gave a result agree-
ing nearest with observation, was that of 120 : 95 : 54.5 : 1. The
values of a •= 120, b •=. 95, c = 54.5, and d= 1, being substituted
in the above-mentioned formulae, give the dimensions of the fun-
damental form as follows :

p=

QR> \

10 };

7; 137°

72 10

Moreover, we have the angle of inclination MAP — 0° 29' ;
BAP = 38° 40' ; B'AP = 38° 4' ; CAC' = 49° 51' ; CBC; =
59° 40'.

of the Sulphato-tri-Carbonate of Lead. 223

According to the method of crystallographic designation of

MOHS, the faces P, P, next the observer, and contiguous to

P
the upper apex of the fundamental form, are denoted by g,

and the other faces P' P', contiguous to the same apex, are

T>

denoted by — ¥ . If we suppose the axis of a series of

such pyramids of equal bases, to increase and decrease according
to the powers of the number 2, the limits at which this series will
arrive are, on one side, a plane figure parallel to the base, on the
other a four-sided prism parallel to the axis of the fundamental
form. The face a, in the combination Fig. 5, corresponds to the
first, and the faces cc to the second of these limits ; while their
crystallographic signs will be P — co and P + GO . The inclina-
tion of the axis being so slight, the difference between the angles
of the base of P and those of the transverse section of P + oo
does not amount to 0° 1' ; P + oo is therefore = 59° 40'.

Supposing the faces a and b to disappear from the combina-

tions, the faces e will assume the figure of a rhomb NOQP,

P
Fig. 7, at the solid angle of combination between ^ and P -f oo .

As the diagonals of any rhomb bisect each other ; NR will be
- RQ. Draw NT parallel to BQ, and QT parallel to BM. Since
the angle NRS is = BRQ, and RSN — RBQ, and the line
NR — RQ, the triangles NRS and QRB will be equal and similar;
therefore NS = BQ, and also = ST, which will make NT— 2.NS.
If a tangent plane, laid on the terminal edge AB of the fundamen-
tal pyramid produces the horizontal prism P r , that plane, the
corresponding axis of which is double the axis of the former, will
produce a prism belonging to P -f- 1> and e, therefore, receives

the crystallographic sign - T^ . The inclination of e to a is

= 112° 0'. As the situation of e' is analogous to that of e, its crys-
tallographic sign is — r<^ , and the inclination of e' to a
ll'. Since the edges of combination between e and b are

224 MR HAIDINGER on the Forms of Crystallisation

horizontal, the form to which the latter faces belong is the limit
of the series of horizontal prisms, contiguous to the long dia-
gonal, and is consequently designated by Pf + oo . The sign
of the whole combination is

a P e P <> c b

Another combination is represented in Fig. 2. Besides those
of the preceding variety, it contains the faces d,f, g, g', and h.
The faces d form oblique truncations of the edges between b and
c, and they are inclined to the former at an angle of 156° 27' ; if
enlarged to their intersection above these faces, they will meet
under an angle of 132° 54', while that of the faces c and c is — 59°
40'. The diagonal c being supposed equal in both prisms, b' of
the prism d will be % b of the prism c. The edges of combina-
tion between a and h are paraUel to those between h and d; the
transverse section of the scalene four-sided pyramid produced by
the enlargement of the faces h, is therefore similar to that of the
prism produced by the faces d. But the edges of combination
between P and h are parallel to those between k andf,f and h,
and h and P, and consequently to the acute terminal edges of P ;
the ratio of «' and b', or of the axis, and that diagonal of the base
which corresponds to the long diagonal of P, will be in the de-
rived pyramid the same as that of a and b in the fundamental
form. The ratio of the three lines a' : b' : c' of the pyramid A

may be expressed by a : b : 4 c, which is equal to - ? : b : 4 c.
In the method of crystallographic designation of MOHS, the sign
(p")m is given to a derived pyramid, one of the diagonals of
which is equal to the similarly situated long diagonal of the
fundamental pyramid P', while the other diagonal and the axis
are equal to m times the analogous lines in that form. In the case

of the Sulphato-tri-Carbonate of Lead' 223

undef consideration m is n 4 ; but the axis of P' is equal to one-
fourth of the axis of P; the former pyramid consequently

— P — 2, and the sign of the derived form becomes — ~^-)
the divisor 2 being added, because the pyramid occurs in the
crystal only at that side of the axis which corresponds to |. The
angle formed by the intersection of h and h is = 142° 26'. The
prism d being the limit on one side of that series to which

•

(p~2)- belongs, will be represented by ( p -f- oo ) 4 . It is evi-
dent that/ which appears with parallel edges of combination in
the place of the terminal edge AB of P, must on that account be

o

— _ . The inclination of this face to P — co or « is

= 128° 40'. From immediate measurement, and from their
situation between a and P or P', the faces g and g belong to

p — i p — i

— £- , and g' and g' to ^ — • The edge produced by the in-
tersection of g and g is — 94° 18' ; and that produced by gr
and g' - 93° 52'.

The inclination of c to a is = 90° 14' ;

Pa— 111° 42V

P' a = 111° 18';

g a — 128° 23';

g' a - 128° 5'.

The representation of the whole form by crystallographic
signs is :

p_00 PJ . Pr + 1 Pj-1 (P — «)* P , Pr+j. P — 1 _ P

« f e g h P ef £ P

P + oo . (P + oo)* . Pr + co .
c d b

VOL. X. P. I. F f

226 MR HAIDINGER on the Forms of Crystallisation

It will now be easy to determine the relation of the simple
forms which enter into the combination Fig. 3. ; those under
which it is principally contained, being known from the pre-
ceding varieties.

The face i is determined, by immediate measurement, to be-
long to the horizontal prism, which truncates the terminal edge
of the pyramid P — 1 (g) ; and those faces which appear in the

II

combination, will therefore be designated by Fr~1. The incli-

IB

nation of i to a is 147° 52'. For the development of the pyra-
mid k, we have two data in the situation of the edges produced in
intersecting the faces of other forms. From the parallelism of the
edges between P and k, k and h, h and f, &c. it follows, that the
terminal edge of k, corresponding to the long diagonal of P, has
exactly the same inclination to the axis as the analogous edge of
that form. From the parallelism between k and g, and g and m,
it appears, that the other terminal edge of k, which corresponds
to the short diagonal of P, has the same inclination to the axis as
the analogous edge of P — 1 ; and the result of both these obser-
vations is, that the ratio between the lines a' : b' : c' in the pyra-
mid k, expressed by functions of the analogous lines in the funda-
mental form, will be a : b : 2c ; or ^ : b : 2c, which corresponds to

the crystallographic sign ^Fr~1^ • The edge in which two faces

k and k intersect each other, is = 111° 32'. Of the three hori-
zontal prisms /, m, and n, contiguous to the short diagonal of P,
only m can be determined from the situation of the edges of com-
bination between m and g ; it is Pr — 1 = 84° 30'. Immediate
measurement was resorted to, for ascertaining the dimensions of
the other prisms, which were found to be / = Pf — 2 = 122° 20',
and n = f Pr = 62° 24'. The inclination of / to a is = 151° 10';
of m to a = 132° 15'; of n to a — 121° 12'. The scalene four-
sided pyramid, to which belong the faces o, o, is perfectly deter-

of the Sulphato-tri-Carbonate of Lead.

mined by the parallelism between o, e and o, and by that be-
tween h, o and b. From the first of these data, it appears, that
the terminal edge of the pyramid o, contiguous to the long
diagonal of the fundamental form, is inclined to the axis under
the same quantity as the analogous edge of P+l, and that,
consequently, a' : b' will be in the ratio of 2 a : b. But, from the
second datum, it is evident, that the terminal edge of the same
pyramid, contiguous to the short diagonal of the fundamental form,

u

will be situated like the analogous line of h, which is ^ "^ ;- ;
and this makes the ratio of a' : c' — a : 4c •=. 2 a : 8c. The ratio be-
tween the three lines a' : b' : c' ~ ~ : b : 8c, in the derived pyra-
mid, is expressed by the crystallographic sign (p — 2)8. There
are some slight indications of faces between f and o, and between
o and d ; but they are too imperfect to allow of any accurate de-
termination. The rest of the faces which appear in the combi-
nation, are easily referred to those forms to which they belong,
because they possess on the opposite side of the axis a situation
perfectly analogous to that of the forms developed in the pre-
ceding observations. Thus, g' is analogous to g, and therefore

o

= — ^-^5 h' analogous to h — — ^ '~2^ ; k' analogous to k
— — (Pr—l)3 . Of analogous to o — — (P — ^)8. The designation
of the whole form is,

Pr — 1 Pr
P-co. — 2_' -.

a i f

u
I p O\ 8

lr- *> pr o pZ i

0 * i ~ ~ •*. Jrr— i.

o I m
(Pr 1\3 P fp 2,\*

- sj - r - *3p»' p+»- (£+»)4- pr+».

V P o' c d b

Vf2

Pr + 1.

P— 1

(P — 2)*.

(Pr

—

I)3 P

2

e

f Pr.

n

2
£

Pr + 1
2

/

2

h

p

~2~
^

1
— • .

g

k

2"
P

(P — 2)*

2
K

MR HAIDINGER on the Forms of Crystallisation

The perfectly hemiprismatic appearance of a crystal similar
to the last of these figures, would be alone sufficient for ex-
cluding the forms of Axotomous Lead-baryte from the rhom-
bohedral system, even though the measures of the angles should
have been found to approach still nearer to 120° and 90°. But
one and the same individual seldom presents more than one or
two of its six sides to the observer, being in most cases joined to
other individuals, according to the law of regular composition
mentioned in the beginning of this paper.

The planes of composition pass through a line nearly per-
jtendicular to two sides of the six-sided tabular crystals, like AB,
Fig. 8. They are parallel to one face of (p-f- co )3, rr 119° 40', a
prism which is likewise found in the crystals of this species.
Upon this supposition, the angles are = 90° 20', and 89° 40'. Of
the individuals AA'BCDE, and AA"BC'D'E', which meet in
the plane of composition passing through A B, nothing will re-
main but the rhomb-like trapezium AA'BA", the angles of which
are A = 60° 20' ; A' and A" each = 119° 50', and B = 60°. If
a third individual A'A"CGFC' joins the regular composition of
the preceding .two, being applied to BMA', the remainder of
BAA', Fig. 8. in the line A'M, there will also arise a face of
composition between A'MA" and BMA", and the angles of the
remaining triangular figure A'A"B will be exactly =. 60°. In
the compound crystals of Axotomous Lead-baryte, each of the
edges A'M, A"M, and BM is = 179° 10'.

The regular composition of three individuals of the variety
Fig. 5., if they terminate at the faces of composition, wiU produce
a form like Fig. 10., but the compound takes the appearance of
Fie. 11. whenever the substance of the individuals reaches to the
opposite side of the compound crystalline group, and thus pro-
duces faces of crystallisation on the other side, similarly situated,
and parallel to those considered above. If, in the compound

of the Sulphato-tri-Carbonate of Lead. 229

masses, the faces of Pi? -f- 1 or e are considerably increased, while

Tp

those of g or P disappear, the whole will assume, very near-

*

ly, the form of an acute rhombohedron, whose apices and lateral
solid angles are truncated. The incidence of e upon e' is
:= 72° 39', almost the same as the angle given by Mr BROOKE
for the terminal edge of his acute rhombohedron. Even
in crystals most perfectly formed,, it is very easy to overlook
-the small salient angle of 179° 10' upon the faces RST, sup-
posed perpendicular to the axis of the rhombohedron ; but this
composition is often so intricate, particularly in larger crystals,
that it sometimes becomes difficult to point out the direction
and extent of each separate individual, though the existence of
the composition is indicated by small, salient and re-entering
angles, and proves, with the highest degree of evidence, that the
forms of Axotomous Lead-baryte are not Rhombohedral but He-
miprismatic.

Although the observation of the optical properties of mine-
rals can never supersede the study of their regular forms, yet
the preceding examination of the forms of Axotomous Lead-
baryte, affords an ample proof that they may be highly useful in
guiding us through the latter, particularly if these regular forms
nearly coincide with certain limits. The crystallographic re-
searches relative to this species are attended with considerable
difficulties, since the angles approach in every instance within
one degree to the limits of 120° and 90°, and the regular com-
position very often hinders the crystals from being observed on
all sides, while the inclination of the optical axes of no polarisa-
tion upon each other is very considerable, and easily ascertained.

The inferences drawn from Dr BREWSTER'S general law,
respecting the existence of two polarising axes in crystallised sub-

230 MR HAIDINGEB on the Sulphato-tri-Carbonate of Lead.

stances, had excluded the forms of Axotomous Lead-bary te from
the Rhombohedral System, previous to their correct determina^
tion, and even in contradiction to the opinions entertained by
crystallographers. The preceding demonstration, that they are
Hemiprismatic, reconciles the results of both sciences.

( 231 )

XVI. Inquiry into the Structure and probable Functions of the
Capsules forming the Canal of PETIT, and of the Marsupium
Nigrum, or the peculiar Vascular Tissue traversing the Vitre-
ous Humor in the Eyes of Birds, Reptiles, and Fishes. By
ROBERT KNOX, M. D. F. R. S. ED., and Conservator of the
Museum of Ihe Royal College of Surgeons.

(Read March 15. 1824J

THE following additional observations on the comparative
structure of the eye-ball, are intended chiefly to illustrate the
philosophical anatomy and physiology of the capsules forming the
Canal of PETIT, and of the Marsupium Nigrum ; yet as I have
here taken notice of several other points in the comparative ana-
tomy of the eye, the memoir may be considered as supplemen-
tary to those formerly read to this learned Society, and which it
did me the honour to insert in its Transactions *. I have stated
in the first of those essays, that I had been led to inquire into
the structure of the Eye, partly as connected with researches
into the comparative anatomy of all the organs of sense, but
more particularly with a view to elucidate the nature and distri-
bution of the nervous system. I did not presume to think that
any remarkable peculiarities in the structure of this most inter-
esting organ, had escaped preceding anatomists ; but though I
found this to be true, in so far as regards the structure of the
eye in most of the mammalia, it yet appeared that the same or-
gan in other vertebral animals had by no means been investiga-
ted, or at least described, with the same care.

* Vol. x. Part i. p. 43.
VOL. X. P. II. G g

232 DR KNOX on the Philosophical Anatomy

Since that period I have repeated, with as much exactness as
possible, most of the dissections on which my former essay was
founded, and by employing very delicate coloured injections,
with which the bloodvessels of the eye were filled in several ani-
mals, I have thought it might not be uninteresting to state
briefly the result of these investigations to the Society, avoiding
as much as possible all tediously minute anatomical details.

I. Of the Retina.

I regret that it has not been in my power to extend my re-
searches into the structure of this most important membrane of
the e.ye in the human subject ; the obstacles in this country to
such dissections being considerable, and not to be overcome by
any individual not a teacher of anatomy : but I have seen
enough to convince me, that the first views adopted by me, re-
lative to the two most important points for investigation, viz.
the foramen centrale of the retina, and the mode in which the
membrane terminates anteriorly, are correct. Many of the mem-
bers of this Society are no doubt aware, that two distinct
opinions have been held relative to the nature of the discovery
of SCEMMERING ; some anatomists viewing the transparent point
in the axis of vision, (which he supposed peculiar to the hu-
man subject), as a distinct foramen, or absolute perforation of
the retina ; others, as the immortal CUVIER, considering it mere-
ly as a transparent point, and that there is no real deficiency of
the retina, but that the nervous membrane at this point merely
remains transparent after the death of the animal, whilst the sur-
rounding portions of the retina become opaque. They argue,
therefore, that the foramen centrale, or transparent point of
SCEMMERING, does not exist till some time after the death of the
animal.

of the Canal of PETIT. 233

1 hold this opinion to be altogether incorrect *, as applied to
the pulpy or true retina, but readily admit that the perforation
does not extend to the whole of the membrane usually called
Retina. The retina is composed, in most animals, of at least two
membranes f, viz. an external or pulpy layer, and an internal, (ge-
nerally vascular), described improperly under the name of tunica
vasculosa Retina. Air blown in betwixt the retina and choroid in
the situation of the Membrane of Jacob, cannot pass into the
chamber of the eye containing the vitreous humour, because it
is arrested in its passage through the foramen centrale by the in-
ternal tunic of the retina. When I discovered that the foramen
centrale of the retina was not peculiar to man and the quadru-
mana, as all anatomists before me believed ; but that, on the con-
trary, it was extremely developed in the cameleon, and in certain
lizards £ somewhat allied to the cameleon, I judged it a favour-
able opportunity for re-examining the subject with great atten-
tion. The structure was viewed under a good microscope, aided
by a strong light, and submitted to a number of gentlemen well
qualified to judge of such matters. Now, on this subject, there
was but one opinion, viz. that the pulpy part of the retina in the
situation of the foramen of SCEMMERING is absent, but that the

* See the facts stated in my " Account of the Discovery of the Foramen Cen-
trale of the Retina, in the eyes of certain Reptiles,'" published in the Memoirs of
the Wernerian Society, vol. 5. p. 1.

•f I conclude that even when the retina has no longer a tunica vasculosa, as we
find to be the case in birds, there still exist two layers, vascularity not being the essen-
tial character of either. Dissections by HALLER seem to confirm this idea; his words
are, " Lamina ergo hie in retina interior fibrosa est (in piscibus), et alia exterior
pulposa."" But he allows that it is exceedingly difficult (he might have added impos-
sible) to demonstrate this structure in birds ; it must therefore be simply inferred by
analogy .

I The Lacerta superciliosa, scutata, &c.

Gg 2

234 DR KNOX on the Philosophical Anatomy

inner membrane passes on uninterruptedly *. So far, then, it
would appear, that the transparent point of SOEMMERING is occa-
sioned by a deficiency of the pulpy portion of the retina.

We thus get rid of a war of words, which probably would
have arisen from the fact of the internal tunic being continuous,
which was never questioned.

The opacity assumed by the retina after immersion in spirits,
is chiefly owing to its pulpy layer ; and as this is wanting at the
foramen centrale, or directly in the axis of vision, we readily
perceive why the appearance should become more distinct after
the eye has been immersed in spirits.

In answer to those who argue, that, as the retina is perfectly
transparent during life, so the foramen centrale can be said to
exist only some time after death, when the nervous membrane,
becoming everywhere opaque, excepting in the line of the axis
of vision, permits our seeing the choroid at this particular spot ;
I would reply, That such might be the case were it only a trans-
parent point ; but it has been already shewn, that the pulpy por-
tion of the membrane is absent. I have, moreover, examined the
eye-ball in a great number of animals immediately after death,
and never found the retina to be absolutely transparent (except-
ing when dried), but uniformly of a bluish colour, and very
slightly, though in general visibly opaque. The bluish cast I
attribute to the subjacent choroid. This remark I have made
on the eyes of several of the domestic animals, as oxen, sheep,
horses, dogs, &e ; on many birds, and particularly on fishes ;
and, lately, on man himself. For this I am indebted to Dr
MONRO, who, with his accustomed liberality, permitted me
to examine the eyes of a man who was executed in this

* As I am assured that vascularity is not the essential character of this mem-
brane, I shall prefer calling it by the name of the inner membrane of the retina : the
reasons for so doing will be given afterwards.

of the Canal of PETIT. 235

place. The eye was opened in about eight hours after the
death of the criminal : the foramen of SCEMMERING was remark-
ably distinct, and of a deep yellow tinge ; there was no fold, a
fact which proves this appearance to be a post mortem one, and
that SCEMMERING has on this point misled all anatomists since
his discovery. The retina was semitransparent. There were
several vessels on the surface of the retina, apparently veins
filled with dark blood ; none could be discovered traversing the
vitreous humour, for the reason, no doubt, that the branch which
is found to do so in the foetus of the mammalia, disappears in
very early life, and perhaps soon after the structure of the lens
is completed.

The uses of this most mysterious part of the eye-ball, and
why it should exist only in certain classes of animals, and these,
too, differing widely from each other, are physiological problems
which seem to me of extremely difficult solution.

Several pellucid vessels or fibres seem to connect the retina
and vitreous humor around, and near to, the entrance of the op-
tic nerve. They are spoken of by HALLER in the following
passage : " Vitrea membrana, simplex, intra retinam ex seipsa
oritur, nusquam observabili aliquo vinculo connexa, nisi Albinia-
nam arteriolam velis, aut vasa vitrea? membranee pellucida, quae
in ove et bove ad eamdem retinam parallela sublinit, non ob-
scura veniunt."

The pulpy portion of the retina is not of uniform density, nor
is the membrane equally affected by the action of spirits : these
render the greater portion of it perfectly opaque, and of a slight
yellowish colour. But in the eye of the cat a large triangular
space, whose apex is at the entrance of the optic nerve, and base
externally and anteriorly, remains semitransparent, and compa-
ratively much thinner, than any other portion of the retina.

With regard to the anterior termination of the retina, I may
remark, that I have not found any reason to alter the opinions

236 DR KNOX on the Philosophical Anatomy

expressed in my former paper on the Comparative Anatomy of
the Eye. I therein state, that the pulpy layer of the retina
terminates by a well-defined margin near to the place where the
internal ciliary processes (Zonula Ciliaris of ZINN) commence ;
but that the inner layer of the retina may be considered as ad-
vancing forwards towards the lens, and uniting with the other
transparent tunics to form the internal ciliary processes *, and
the internal parietes of the Canal of Petit. I still admit, that this
opinion rests partly on analogy, but on analogy of the strongest
nature. We see the inner tunic advance forwards to the point
where the internal ciliary processes commence ; from this point
forwards to the capsule of the lens, the structure has changed
considerably ; the membrane has become much more vascular,
and it is folded into numerous plaits : but the difference in struc-
ture is not greater than what takes place in the corresponding
coloured membranes ; viz. the choroid and true ciliary processes ;
and I hold the analogy as to form, structure, and relation to
their respective membranes, as complete. The fact that the
retina separates very readily (after a little maceration) from the
portion of the vascular tunic, which we may suppose as contri-
buting to form the internal ciliary processes, merely shews, that,
at this part, the membrane is very delicate, and easily torn, but
perhaps not more so than at any other point of the retina.

This question was much disputed in HALLER'S time : he
adopted the opinion, that the inner or vascular tunic of the reti-
na extends as far as the capsule of the lens ; he even shewed

* These internal ciliary processes were called Fibres by ZINN, Lymphatic Vessels
by BERTRANDI, and Tendinous Fibres by CAMPER. They are composed chiefly of
arteries and veins. TENON well understood their anatomy, and describes their mode
of union with the true ciliary processes, and the important fact of their receiving
bloodvessels from the latter organs.

•

of the Canal of PETIT. 237

the membrane to ZINN; but that distinguished anatomist argued,
that this was the corona ciliaris, which he considered as distinct
from the membrane of the retina. M. DE BLAINVILLE adopts
the opinion of HALLER. But whether or not we suppose the
inner membrane of the retina to be continued as far as the
crystalline, it is always to be remembered, that after it has
quitted the pulpy layer of the retina, it assumes a new form,
becoming exceedingly vascular, and has the same title to be
considered as a structure distinct from the tunica vasculosa
retinae, as the true ciliary processes are from the choroid. I
view both as merely appendages, and continuations of the re-
spective membranes to which they belong. The intimate depen-
dence of the internal ciliary processes on the vascular portion
of the retina in the mammalia, may be judged of by the fact
stated, that these processes cease to be vascular in birds, where-
ever the former no longer has distinct bloodvessels. Finally, I
do not think that this continuation of the inner membrane of
the retina contributes so essentially towards the formation of the
Canal of Petit as does the continuation of the hyaloid mem-
brane.

By the employment of delicate vermilion injections, I find
that the ciliary processes of the vitreous humor (the Corona cili-
aris of ZINN) abound with bloodvessels. I beg leave to present
to the Society numerous preparations illustrative of so interest-
ing a point in the anatomy of the eye *. The union be-

—

* The preparations illustrative of this and numerous other important points in
the structure of the eye, amount to forty-seven. A far greater number was destroyed,,
in order to perfect the researches connected with this and the preceding papers. Of
those preserved, thirty-six have been deposited in the Anatomical Museum of the
Royal College of Surgeons of Edinburgh ; and the remainder, a distinguished ocu-
list of this place did me the honour of placing in his own collection. These
preparations are intended to illustrate every important fact in the Comparative
tomy and Physiology of the Eye.

238 DR KNOX on the Philosophical Anatomy

tween the true ciliary processes, and the ciliary processes of the
vitreous humor, is chiefly vascular. Branches of the central
artery and veins of the retina likewise anastomose with those re-
ceived from the external ciliary processes : but such anastomo-
sing vessels are comparatively few.

These dissections have explained to me a number of inter-
esting facts in the philosophical anatomy of the eye, which pre-
viously I could not understand, as they seemed totally uncon-
nected one with another.

The Canal of Petit, as has been stated, is formed by two
layers or membranes quite distinct from each other. It is not
of much importance whether we view these as merely a conti-
nuation of the hyaloid and of the inner membrane of the retina,
(as I consider them really to be), or as being of a totally different
nature from these membranes.

I have said in my former paper on the Comparative Anato-
my of the Eye (p. 19.), that, " from the internal surface of the
transparent ciliary body just described (the Zonule of ZINN) is de-
tached a membrane, which being inserted into the capsule of the
lens, somewhat more posteriorly or central, thus contributes to
complete the triangular-shaped Canal of Petit." But the pre-
parations I have now the honour to shew to the Society, de-
monstrate that the membranes forming the internal and external
parietes of the Canal of Petit, unite anteriorly with the capsule
of the lens, and ivith each other, occasionally by a very acute angle ;
and that it is from this point that a membrane seems to be trans-
mitted over the whole posterior surface of the capsule of the lens ;
but this membrane has nothing to do with the canal itself*.

* We shall return to this fact more particularly in a future part of the memoir.
The descriptions usually given of the structure and formation of the Canal of Petit, by
anatomical writers and lecturers, are frequently quite unintelligible.

of the Canal of PETIT. 239

Both layers are vascular ; the external one remarkably so, re-
ceiving innumerable branches, perhaps chiefly veins, from the co-
loured ciliary processes which are immediately superincumbent
to them, and they anastomose, as has been already stated, with
those branches, whether arteries or veins, which we find distri-
buted to the inner membrane of the retina in the eyes of most
mammiferous animals. But what purpose can this excessive vas-
cularity in these internal ciliary processes serve ? I was unable
to answer this question satisfactorily to myself, until I ascertain-
ed that, in the eyes of birds, the most delicate injections cannot
demonstrate any vessels either on the retina or on the internal
ciliary processes, and that the canal of Petit can hardly be said
to exist in these animals ; that, in short, the whole structure is
in them rudimentary ; the vascular or active, and really essential
part, being transferred to another organ.

I need scarcely recal to the remembrance of this learned So-
ciety, that it is principally by means of arteries that the various
parts of the body are nourished, and that it is through the me-
dium of veins and lymphatics that the superfluous parts are re-
moved : hence, anatomists have at all times been anxious to de-
monstrate the presence of these organs in the various textures
of the body, and numerous valuable physiological and pathologi-
cal facts, have arisen out of such inquiries. There exist, how-
ever, even at present, great differences of opinion as to the
source whence the humors of the eye are derived : the mem-
brane which some have called the secreting membrane of the
aqueous humor, seems to possess no such function * ; whilst to

* I have shewn in my former paper, that, in the eyes of certain animals, the inner
membrane of the cornea may be traced over the anterior surface of the iris, whilst in
others we merely infer its presence by analogy. In fishes, in which the first arrange-
ment is most distinct, the aqueous humor is very small in quantity. I readily con-
fess, that I have not been able satisfactorily to make up my mind as to the source of
VOL. X. P. II. H h

240 DR KNOX on the Philosophical Anatomy

one very delicate branch of a small artery has been consigned
the task of secreting and nourishing the lens, and perhaps even
the vitreous humor ; though, relative to this last, anatomists and

the aqueous humor ; and the assertion, of its not being present in the anterior cham-
ber of the aqueous humor in the foetus, appears to me extremely doubtful.

In examining the eyes of the foetus in the mammalia, with a view to the determi-
nation of the vascular structure of the pupillary membrane, several appearances
have presented themselves to me, which I shall here briefly state, since they may
be useful to those who may not have opportunities for making very minute vascular
preparations of the eye. It has always appeared to me (and I have sacrificed a great
number of very delicate preparations, in order to determine the anatomy of the pu-
pillary membrane), that, by means of this membrane, the anterior and posterior
chambers of the aqueous humor, form in the foetus two distinct shut sacs, each
enclosed in a proper capsule. With regard to the anterior of these, it is very evi-
dent from several preparations now lying before me, that it is formed by the inner
membrane of the cornea, (or at least of a membrane covering the inner surface of the
cornea) ; which is reflected over the whole anterior surface of the iris and pupillary
foramen ; but I cannot speak so decisively of the formation of the posterior sac, or
that situated behind the iris, i. e. I am unable to say, whether it terminates at the
equatorial margin of the lens, after investing, though loosely, the floating termina-
tions of the ciliary processes, or whether it invests the anterior surface of the lens. It
is very evidently connected with the membrane forming the canal of Petit. Betwixt
the portion of membrane extending from the equatorial margin of the lens to the
pupillary edge of the iris, (in the foetus), and which being continued forward, con-
stitutes one layer of the pupillary membrane, and the iris itself; there is a trian-
gular space, very distinct in several preparations I have now before me. This space
is occasioned by the membrane proceeding from the lens to the iris, in a straight
line, like the string of a bow; whereas the iris is arched or concave. It is pro-
bable that the (diagrammatic figure (Plate X.) may explain, much better than any
words could do, the distribution of these membranes in the foetus or very young
animal.

The great share the hyaloid membrane of the vitreous humor has in the forma-
tion of these membranes, as well by its intimate connection with the capsule of the
lens, as by its most evident and distinct connection with the posterior layer of the pu-
pillary membrane, is very remarkable, when contrasted with the extreme delicacy of
the vascular membrane of the retina, which scarcely contributes any thing towards
the formation of this admirable and very singular structure. Viewing the interior of

PLATE X.

or thf lioiftit. Soc.Trarv. Vol^p. 2,40

</-• T/ie /stiff t/tffo.ft'e/ in /Ay c.vy/.w/// • .

A _7Xfc- vitrw?*+v htittHHH-.

c Th&Jtpalvt&metn&nzrie «/«///*/ with

d. //if ifit/tv nicrtthttwc of tfie retitin at

I //v/« which. point is- &ent off the ?<ttnitui <*f lh<> \-ilr*'<>ifs- 7tutn<mr

« ijicltwirw it tuUer-iot-lif ; the tttcrribfurir' /• /> ulwttiff? w, contact with

t... ... whi.<-hJ&itj.ynw /f> he ft very <it?lt*.\ttc tntwihttinc incJft&uif/ i/tt* (vjt>,rft&* of 'the leti+v

but tfun f'tifitifti'en/ wtuliJij be dettuJti^rtr'ntect-.
in ttt 'Hie cutMfl ofTt'tit.
II +1 cuvijif t/mt Lititi be farrntxi bi/ blt*wiu<t t/if into it tittet* ru/>(nr/mf flic inemhrifit<\f

f'w/nuH/ tiii-canuJofJ*t'tit; ti~doe& not cttmitiuiiirtUe with unif ofher
C-- The fmlptf portion of (he retitia temutia&jttj ui iil/,<utinitiin where the intermit

cilififif ///v^wvtvj* <•/////////•///>*.
J:. .... 27ie 7nentbi\uie of Jacob.

// The sclerodc.

ft .The ///////////. i- //////M-.

of the Canal of PE TIT. 24 1

physiologists, with the exception of HALLER, have preserved the
profoundest silence.

When we consider the vast comparative size of the vitreous
humor, we may feel assured, that one small branch of an ar-

the eye-ball philosophically, we might say, that it is composed originally of a
or suite, of colourless capsules, forming generally shut sacs, in which are deposited
perfectly transparent substances, having various refractive powers. Posteriorly we
have the hyaloid sac, and the contained vitreous body : %dly, The crystalline capsule
and lens : 3dly, The posterior chamber of the aqueous humour, formed in the fetus
by its own capsule : lastly, The anterior chamber, like the rest, a shut sac. The
membranes forming these various capsules appear in the foetus to be continuous.

In the foetus, or very young animal, the quantity of fluid in either of the aqueous
chambers of the eye, must be very trifling, if it actually exist ; for the pupillary mem-
brane is in contact with the anterior surface of the capsule of the lens. On the
other hand, the crystalline humor in the foetus is very large, and has the posterior
segment of its capsule entirely covered with bloodvessels. The branch of the cen-
tral artery of the retina which passes through the vitreous humor in a young animal,
apparently quite disproportionate to the other branches of the arteria centralis, is for
the purpose, undoubtedly, of furnishing the lens with the means of rapid growth.
In the adult animal it is altogether obliterated, seemingly because no longer required,
the lens having, at an early period of life, acquired its full growth, and being, like
the enamel of the teeth, subject neither to decay nor renovation.

The vessels of the pupillary membrane come to it chiefly from those of the iris :
it may receive a few from the terminating branches of the artery distributed to the
capsule of the lens, but assuredly these must be very few. They were demon-
strated by Dr W. HUNTER, who also describes, very accurately, the distribution
of the posterior layer of the pupillary membrane : " Where the membrana pupillse
exists, there is a fine vascular membrane all around, which passes in the posterior
aqueous chamber, from near the edge of the lens to the edge of the pupilla *." Now,
it is extremely easy to demonstrate, that the membrana pupillaris consists of two
layers ; the posterior of which is a continuation of the one just described by Dr W.
HUKTEB. From the peculiar form of this membrane, (I mean the portion proceed-
ing from the margin of the lens and hyaloid membranes to the pupillary margin of
the iris), I should imagine it to be immediately ruptured and destroyed by the con-
traction of the iris, on the first admission of light through the pupil.

* Medical Commentaries, p. 63.

nh 2

242 DR KNOX on the Philosophical Anatomy

tery, (which artery is obliterated very early in life), is totally
inadequate for its growth and support, even supposing that
this vessel should entirely belong to it. But anatomists, anxious
to ascertain the secreting vessels of the lens, and of its capsule,
have pushed their researches relative to the branch of the cen-
tral artery of the retina, which passes through the vitreous hu-
mor in the young of mammiferous animals, so far as nearly to
have proved, that this vessel is ramified chiefly on the capsule of
the crystalline. It is nevertheless true, that a few excessively
delicate branches from the artery, seem to belong exclusively to
the vitreous humor ; but these are totally inadequate to the se-
cretion of so large a mass, proceeding even on the supposition
(in all probability incorrect), that the vitreous humor once se-
creted, becomes, as it were, a dead body, placed without the
circle of the circulation, and no longer subject to decay or re-
novation.

There is still another source whence the fluid composing the
vitreous humor might be derived. The branches of the central
artery of the retina, which are distributed in a beautiful net-
work over the inner tunic of the retina, proceed as far as the
zonule of ZINN, and are then lost upon the external parietes
of the canal of PETIT, and more particularly on those reduplica-
tions of this membranous body which I have called the Internal
Ciliary Processes. Still these anastomosing vessels are few, com-
pared with the almost innumerable branches the same processes
receive from the true or coloured ciliary processes, of which fact
I have already spoken.

Although these researches have as yet been, in a great mea-
sure, confined to the eyes of quadrupeds, and animals nearly ap-
proaching them in structure, I yet feel assured that the inferences
are strictly applicable to the human eye. WALTER, as early as
1778, partly describes them in the following words: " Interna
superficies membranas choroideae has conducit ad venas capsulse

of the Canal of PETIT. 243

lentis et corporis vitrei quae elegantissimum spectaculum quod
nunquam satis verbis efferri potest, oculis exhibent."

Again, speaking of the veins of the choroid, he says, " Pau-
latim magis parallels fiunt, minutissimae hae venulaa si accesse-
rint ad posteriorem terminum processuura ciliarium, ubi retina
crassiori sua parte, ad limbum posteriorem corporis ciliaris adhae-
rescit, et ubi retina subtilissimam lamellam emittit, quae ut sub-
tilissimum velamentum annulo mucoso, subjectam ad ambitum
capsulae , lentis advenit, et ubi ea in convexitatem anteriorem
transire incipit, huic adhasret." And a few pages further on he
says, " Ex hoc reti admirabili ciliari, ubi illud apicem processu-
ura ciliarium operit, exeunt minutissimi surcuh' qui subtilissimam
productionem retinae antea descriptam perforant, et paululum re-
flectendo, adeunt membranam corporis vitrei annulo mucoso
tinctam, plurimi horum surculorum se immergunt in capsulam
lentis, ubi ea, ope laminae anterioris zonula? ciliaris ZINNII, fir-
miter cum hyaloidea cohaeret, qui profundius delati in posteriore
convexitate capsulae lentis terminantur."

I do not hesitate in ascribing to these processes, or at least
to the vessels distributed to them, the office of secreting the vi-
treous humor, — of restoring it when partially lost, a process
we know to be very limited, — and of absorbing, by means of pro-
per vessels, the superfluous parts *. In birds, we find that the
inner membrane of the retina is no longer vascular, and, in-
deed, is with difficulty demonstrated. I have not been able to

* It seems unnecessary to remark, that the secretion must ultimately be effected
by means of vessels carrying colourless fluids, proceeding from those of a larger ca-
liber, and distributed on the parietes of the canal of Petit. Vessels carrying co-
lourless fluids no doubt penetrate into every part of the vitreous humor. Physiolo-
gists are as yet but little acquainted with the nature of the vessels carrying colourless
fluids only.

244 DR KNOX on the Philosophical Anatomy

satisfy myself of its existence. The most delicate arterial injec-
tions fail in shewing a single branch of a vessel carrying coloured
fluids in the zonule of Zinn, or capsule of the lens of birds ;
but the marsupium or pecten, passing through the centre of the
vitreous humor towards the lens, receives from the central arte-
ry a most abundant supply of bloodvessels : a few of them,
though they must be very delicate, are seen to pass to the cap-
sule of the crystalline *. Hence, it would seem, that the dif-
ferent arrangement of the vessels which occurs in the mammalia,
and in birds, occasions a difference in structure ; but that the
analogies are closely observed. In man, and in some other ani-
mals, the vessels intended to nourish the vitreous humor are
supplied to it chiefly by those sent from the ciliary processes,
from the branches of the central artery of the retina which are
distributed to its inner tunic ; and, lastly, though I believe only
in the young animal, from that branch of the central artery of
the retina which passes through the centre of the vitreous hu-
mor. In birds, all these vessels are collected into one large
group, and, as it were, projected through the mass of the vitre-
ous humor ; the vascularity of the inner membrane of the retina
has disappeared, and the zonule of Zinn, so conspicuous for its
vascularity and for the complexity of its structure in the mam-
malia, is reduced to a mere rudiment, destitute of bloodvessels.
We are forced, then, to consider the marsupium as analogous to
these organs ; as being in fact their substitute ; its principal, if
not its sole function, being to support, nourish and absorb the

* I am not sure if I rightly understand a passage in M. DE BLAINVILLE'S work
entitled, " Principes de 1'Anatomie Comparee." He there states, that he has seen a
bloodvessel entering the marsupium in the eye of the casuary ; but several of the
preparations exhibited to the Society, shew that sixteen or seventeen distinct vascu-
lar trunks may be counted in the marsupium of the common domestic fowl.

of the Canal of PETIT. 245

vitreous humor. Hence we see the reason why the marsupium
does not extend in general as far as the capsule of the lens, an
extent which its functions do not in the least necessitate. The
same structure exists in certain fishes, and apparently for the
same reason ; but, on account of the extreme difficulty of inject-
ing the bloodvessels in these animals, I am unable to speak from
so great a number of observations as I could have wished *.
The colour of the marsupium does not seem to be of so great
moment as one would at first suppose. It is very generally
dark-coloured throughout in birds, whilst in fishes it is most ge-
nerally coloured only in a small portion, and is quite transparent
near its base :jl.

I suppose the internal ciliary processes to be comparatively
less vascular in man than in many other animals ; stiU we know
that the canal of Petit is very distinct, and no doubt has its pa-
rietes well supplied with bloodvessels. The appearances pre-
sented by these parts impressed on my mind the great superiori-

* It would seem that in some fishes the vitreous humor is supplied by vessels in
both ways +, i. e. a branch of the central artery of the retina passes directly into the
centre of the vitreous humor, whilst the remaining branches pass into the same,
but more anteriorly through the medium of the marsupium. They anastomose about
the centre of the vitreous humor. We owe this fact to HALLER. It seems to
me quite conclusive as to the real functions of the marsupium in fishes ; yet this
great anatomist calls the marsupium the sustentaculum of the lens, and says that in
birds it carries the blood to the crystalline humor.

J The coloration of the iris, in itself a curious subject, is rendered more so by
several facts, which do not very readily admit of explanation ; such as the iris being
differently coloured in the two eyes of the same individual, an appearance I have
seen not unfrequently. QUINTUS CUKTIUS relates, that the eyes of ALEXANDER
the Great presented this appearance. TENON gives a very good engraving of an iris
on which there may be seen the letter T very distinctly,
•f- Element. Physiol. t. v. p. 391.

246 DR KNOX on the Philosophical Anatomy

ty, which simply extracting the cataract through an opening in
the cornea, must have over couching, or, indeed, over any other
operation for the destruction of the cataract, where the needle
or knife comes in contact with the canal of Petit and the inter-
nal ciliary processes. I recommend this consideration strongly
to the attention of the practical surgeon ; for if my memory fails
not, the surgeon, in performing the operation of couching, en-
deavours to pass his couching-needle just anterior to the termi-
nation of the retina. Now, this is precisely the spot which ana-
tomy teaches us to avoid, because it is here that the texture is
most complex, the vascularity greatest, and on the integrity of
which the vitreous body depends for its support.

In my former paper on this subject, I ventured to suggest
that the marsupium in the eyes of birds, is actually the tunica
vasculosa observed in the retina of man and other animals, or at
least the vascular part of that tunic ; that in place of being ex-
panded over the inner surface of the retina, the vessels were col-
lected into a group or bundle, and in this manner pierced the
vitreous humor, on their way towards its anterior part. I was
ignorant, at that time, of the extreme vascularity of the inter-
nal ciliary processes. This fact places the subject in a new light,
and proves that the marsupium in birds and fishes is the substitute
for the internal ciliary processes *.

The preparations which I have the honour to submit to the
consideration of the Society, prove the mode of formation of
the Canal of Petit to be different from what has been ge-
nerally described. I have found, that near the point where the

* I do not mean that there are no branches proceeding to the retina in birds, but
merely that they are so small as entirely to escape notice, and no longer constitute a
network on the inner surface of the retina, as in the mammalia.

of the Canal of PE TI T. 247

internal ciliary processes commence, and where the pulpy por-
tion of the retina ceases, there is detached a delicate colourless
membrane over the whole anterior concave surface of the vitre-
ous humor, and which, as is very correctly stated in anatomical
works, is merely contiguous to the posterior surface of the cap-
sule of the lens, but is not in any way connected with it. This
contiguity I perceived to be constant, by reason, probably, of the
elasticity of the membranes I am next to describe, viz. those im-
mediately forming the canal of Petit.

After the layer of the hyaloid membrane which invests the
anterior aspect of the vitreous humor has been detached, the
remaining structure passes on towards the equatorial margin of
the lens; but, previous to being fixed into its capsule, it al-
ters very much in appearance, and assumes a structure I have
already often described. It divides into two distinct layers ; the
external or outer, constituting the internal ciliary processes, and
an inner membrane, also vascular, separating the canal of Petit
from a cavity, which may be formed artificially, by blowing in air
betwixt the posterior surface of the capsule of the lens, and the
hyaloid membrane on which this rests *. Just as the membranes
forming the canal of Petit are about to reunite, they adhere
firmly to the capsule of the lens, and seem to transmit another
very delicate membrane, closely investing the posterior surface
of that capsule. This is the whole mechanism of the canal f .

* Marked h on the accompanying figure.

f 1 should think Mr JACOBSON in error, with regard to the openings he supposed
he discovered in the canal of Petit. The membrane passing betwixt the internal cilia-
ry processes, or its outer paries, is excessively delicate, and may possibly have been
ruptured. On this subject HALLEE expresses himself very positively, and with
much accuracy and brevity : " Flatu enim immisso adparet circulum Petit solum
inflari, neque aerem aut in lentem subire, aut in vitreum corpus, eum ergo circulum
VOL. X. P. II. I i

248 DR KNOX on the Philosophical Anatomy

II. Of the Membrane of JACOB.

WE owe to the excellent anatomist whose name this mem-
brane bears, the first correct description of a most interesting
texture of the eye-ball, which had been talked of before his day

versus lentem capsula claudi. Deinde sola lentis capsula facile inflatur, neque aer
aut in circulum, aut in vitreum transit. Denique etiam vitreum corpus aerem reci-
pit, qui neque in lentem transit, neque in Petit annulum."

HALLER'S description of the canal of Petit is obviously incorrect ; and Mr CLO-
QUET, by copying this description, but superadding to it the well ascertained fact,
that the layer of the hyaloid membrane covering the anterior aspect of the vitreous
humor, that, viz. upon which the lens with its capsule reposes, does not adhere to
the capsule, has become thereby quite unintelligible. I here quote both passages.

" Lamina posterior vitreae membranse discedit ad originem processuum ciliorium,
et ad lentem introrsum etiam, sed paulo posterius advenit, recta protensa, et earn
porro postquam attigit, tenaciter satis conjuncta, posterius includit.

" Inter has duas teneras laminas flatus potest immitti, qui circularem canalem, fre-
nulis subinde adstrictum, efficit," &c. But I have shewn, that if a delicate mem-
brane be actually stretched over the posterior surface of the capsule of the lens, nei-
ther this lamina, nor that placed immediately behind it, inclosing the vitreous humor
have any thing to do with the formation of the canal of Petit.

The passage alluded to in Mr CLOQUET'S work is as follows : " Au niveau des
proces ciliaires, vers le contour du crystallin, cette membrane (hyaloide) se divise
en deux lames ; Tune passe devant la capsule de ce corps, et Tautre tapisse la conca-
vite qui le re9oit en arriere. II result de leur ecartement un espace de la forme d'un
prisme circulaire a trois pans, complete par le circonference du crystallin. C'est cet
espace vide qu'on appele Canal Godronne ou Goudronna, ou Canal de Petit."

HAULER says that the canal of Petit is present in all quadrupeds ; an observa-
tion which agrees with the almost innumerable dissections I have made of that
organ. He thinks it totally wanting in birds : I have proved that the only important
part entering into its composition, viz. its vascular part, is wanting in these animals
for this very obvious reason, that its place is supplied by the marsupium ; but it
seems to me that there still exists, as it were, a rudiment of the part, though by no
means distinct.

of the Canal of PETIT. 249

as a structure of little moment, and had, indeed, been seen only
in detached portions, and had, moreover, been entirely misun-
derstood *. The value of the discovery may be best understood
by reflecting, that it immediately encloses the retina or sensitive
membrane of the eye, and hence becomes of the greatest inter-
xest to the physiologist. In my former paper, I was inclined to
view it as being perhaps the source of a portion at least of the
pigmentum nigrum, in which opinion I was strengthened by
viewing the membrane as extending in many animals as far as
the edge of the pupil, (a view which I still adopt relative to it) ;
but this opinion (in itself merely speculative, and connected
chiefly with the development of the membrane in the eyes of
fishes) a more deliberate and careful examination of the organ
compels me to abandon. It is not improbable that the gentle-
man to whom we owe the discovery, and our most correct views
of the subject, will himself resume the inquiry : in the mean
time, I shall take the liberty of stating a few observations I have
made relative to it, which seem hitherto to have escaped notice.
The membrane of Jacob is generally of a brownish colour,
and sufficiently opaque to arrest the rays of light, supposing
them to have passed through the semitransparent retina ; hence
we perceive that a part of the functions heretofore assigned by
physiologists to the choroid must belong to the membrane of Ja~

I am still inclined to think, that a very delicate membrane is detached from the
anterior termination of the canal of Petit, at the point where its parietes reunite, and
incloses the whole of the posterior surface of the capsule of the lens, closely adhering
to this capsule : it is very obvious that this membrane must be quite transparent, as
it is in the immediate line of the pupil. It would be extremely interesting to know,
whether it is this membrane, or the capsule itself of the lens, which, in certain dis-
eased states of the organ, becomes vascular, thickened, and opaque.

* HALLEE saw portions of this membrane, which he describes as a sort of inor-
ganic mucus. His words are : " Ut magnas maculas nigras saepe retina tunicse ad

i i 2

250 DR KNOX on the Philosophical Anatomy

cob. In those animals in whose eyes there exists a tapetum, the
membrane of Jacob is not absent, as I supposed *, but has the
same degree of transparency as the retina. Lastly, In most ani-
mals it is of a deeper colour than in man. If to these we add
the fact, that it does not possess any bloodvessels, and that the
colouring matter is absent in albino animals -j-, most compara-
tive anatomists will agree with me in thinking, that in the mem-
brane of Jacob, we may perceive a structure, the product of or-
ganisation, itself inorganic, and quite analogous to the coloured por-
tion of the rete mucosum of the skin.

III. Of the Annulus albus.

IN confirmation of a former conjecture as to the importance
of this part of the eye-ball, I find that it is sufficiently vascular
(perhaps nearly as much so as the iris J), in every portion ex-

hserentes viderim, in homine, ave, quadrupede. E<e macula In pisce in membrance
speciem cmifluunt totamque retinam tegunt."" It is very evident, however, from
several passages in the Ekmenta, that, with many others, he confounded, in most
instances, the membrane of Jacob with the pigmentum nigrum.

* Such was also the opinion of HALLER : " In animalibus quadrupedibus ab ea
parte abest, in qua tapetum illud lucidum conspicitur.1"

•f- " In cuniculo albo pupillis rubris, niger iste mucus desideretur, eaque ipsa est
ratio, quare per corneam membranam vasa retinae et choroideae percipias."

J The hypothesis that the iris is composed entirely of bloodvessels, chiefly ar-
teries, is founded on the supposed correctness of some preparations said to be in the
possession of PROCHASKA : those I have made, with very delicate injections, nega-
tively disprove the hypothesis.

The mode usually adopted to demonstrate the circular and radiating fibres of the
iris merits particular notice. If we hold the iris of man betwixt us and the light,
there may be seen, near to its pupillary margin, a portion of its texture of a de-
finite breadth, much more opaque than any other portion of the moveable iris.

of the Canal of PETIT. 251

cepting its base or point of insertion into the sclerotic : this seems
(as we would expect) to be of a cartilaginous nature. I have
found the annulus albus to be very lully developed in the dol-
phin, and repeated dissections have left no doubt in my mind of
the extreme inaccuracy there is in viewing this body as a nervous
ganglion *.

Now, this opaque circular stripe, which may be seen in the iris of man, of the
quadrumana, and many other mammiferous animals, (very remarkably in the otter),
and in almost all birds, is pompously called the Sphincter Muscle of the iris.
But to demonstrate the radiating fibres, a little artifice is resorted to, violating
at the same time, all the rules of philosophic anatomy. The iris of the ox, or
of some other large quadruped, is selected, in which the parallel membranous striae,
so abundant on the choroidean portion of the iris, are remarkably striking, and
these are called the Radiating Muscles of the Iris. These striae are not distinct
in man, and in several other animals, in whom the iris is extremely irritable ; its
choroidean portion becoming proportionally delicate •(•.

* WALTER says, that, in the human eye, the retina does not receive any arteries
from the central artery of the retina : " Retinam nullas accipere arterias a centrale
arteria." He proves, that, by filling the ophthalmic artery with coloured injection,
nearly the whole veins of the eye-ball are also filled ; and it was by comparing such
vascular preparations with those in which the veins only were injected, that he final-
ly adopted the above opinion. Succeeding anatomists do not seem to me to agree
with him relative to the distribution of the central artery of the retina.

I have made relative to these matters very considerable researches, but not on the
human subject. I find that when the eye of a quadruped, as the ox, sheep, deer, &c. is
removed from the head, and injected by the branch of the ophthalmic artery, pro-
ceeding to the eye-ball, the injection very readily fills, not only the arterial system,
but also the whole of the vasa vorticosa, the vessels of the capsule of Petit, and a
great portion of those supplying the iris ; but to succeed perfectly, the injection must
be thrown in with considerable force, and some of the vessels are generally ruptured.
I have not succeeded so well as I could have wished in those preparations intended
to exhibit the veins only. Hence I am not able to speak positively as to the relative
development of the veins, compared with the arteries, in the capsule of Petit ; it is not
improbable, however, that they observe the same proportion as in the other parts of

f See Memoir read before the Royal Society of Edinburgh , entitled, " On the Comparative Anatomy of
the Eye." Page *a et seq. of thi« volume.

DR KNOX on the Philosophical Anatomy, 8fc.

the eye. I have not remarked in any adult quadrupeds, whose eyes were pre-
pared by me for dissection, any vessel, or branch of a vessel, passing through the
centre of the vitreous humor ; the whole of the arteria centrcdis retina being ap-
parently distributed, in the first instance, to the inner membrane of the retina. In
birds, as I have observed, it is quite the reverse.

It is in the eye of the cat that most of the facts may be best observed ; for, in the
eyes of oxen, sheep, &c. the vessels are very apt to give way, and the injected fluid
becomes effused into the canal of Petit and betwixt the membranes. The principal
vascular union betwixt the two sorts of ciliary processes is close to the edge of
the lens.

( 253 )

XVII. On an Anomalous Case of Vision with regard to Colours.
By GEORGE HARVEY, ESQ. F. R. S. E.

(Read January 19.

As the following anomalous case relating to the vision of co-
lours, appears to possess some remarkable peculiarities, I have
considered it of sufficient importance to be submitted to the
Royal Society of Edinburgh.

J. B., aged 60 years, served in early life an apprenticeship
to a farmer ; but, disliking agricultural pursuits, became a tailor,
and afterwards entered into the Navy, and served in several ge-
neral actions. After quitting the sea-service, he resumed his
trade, and in the employment of which he now continues. From
his childhood, it appears, he was unable to point out colours by
their proper names ; or, excepting in a few cases, to distinguish
one colour from another. From the nature of his avocation, this
circumstance must have often been to him the source of much
inconvenience ; and during his whole life, he has found the ut-
most embarrassment from it. He has remarked, that his inabi-
lity of distinguishing colours, has cut him off from the enjoy-
ment of many innocent and harmless pleasures. If a painting
were placed before him, abounding with the most beautiful va-
rieties of colour, it would only present a dull and cloudy
appearance ; and hence he has never made a practice of stop-
ping at print-shops, or of visiting any scenic representations.
In early life, he once visited a panoramic exhibition, and he re-
marked, that his mortification was extreme, when he found every
one around him delighted with the splendour of the scenes;

254 MB HARVEY on an Anomalous Case of Vision

whereas, to him, to adopt his own words, the whole presented
nothing but " a smoky appearance." The face of Nature also,
which, to the perfectly organised eye, presents so many exquisite
varieties of colour, and so many beautiful diversities of light and
shade, has always appeared to him under a dark and murky as-
pect. While others have contemplated, with high gratification,
the splendour of the setting sun, or the glory of the rainbow,
he has seen but little to admire ; and, when led by the chances
of a seaman's life, into the Mediterranean, where a bright sun,
and a pure and cloudless sky, lend to the glowing tints and the
vivid colouring of Nature, charms unknown to the climates of
the North, the contrast produced no peculiar effect on him : nor
has this arisen from a morbid constitution of mind ; for, on the
contrary, he is remarkably happy and cheerful ; and, from all
the information I have been able to obtain respecting him, has
always been distinguished for his steadiness, cheerfulness, and
good conduct.

From several opportunities that I have had of examining
into the peculiarities of his case, I have drawn up the following
brief observations.

Of Whites, he appears to have a very good idea, and so also of
Greys ; — he having selected five pieces of cloth of the latter co-
lour, and arranged them according to their varieties of shade,
with perfect ease. By candle-light, however, he mistook a thread
of pink silk for grey, and, under the same circumstances, con-
founded flax-flower blue (No. 29. WERNER'S Nomenclature of
Colours by SYME) with the same colour.

On SYME'S page of Blacks being presented to him, he thought
the whole to be dark-green. At first he pointed out the speci-
men which had the darkest tone ; but after a few minutes, he re-
marked, that they all appeared the same. When specimens of
basalt and hornblende were placed before him, he could perceive

with regard to Colours. 255

no difference, although the former had a greyish, and the latter
a greenish hue. Between raven and fine velvet black he could
perceive no difference. His master furnished me with the fol-
lowing fact. Being desired to repair an article of dress that re-
quired black silk, he employed crimson ; and a similar mistake
occurred on two other occasions.

Both indigo and Prussian Blue (24. and 25. of SYME) he re-
garded as black. China and azure blue (26, 27. ibid.) he con-
sidered to be blue, but thought them good matches for carmine-
red (90.), when placed by its side. Ultramarine blue (28.), he
thought to be the same as lake-red ; and when a light lake-co-
loured wafer was laid on a piece of azure-blue cloth, he thought
the resemblance very perfect. Flax-flower blue (29.), he could
distinguish as blue. His master informed me, that he once con-
founded sky-blue with green when repairing some article of
dress ; and on another occasion, when a young gentleman's dark-
blue coat was brought to him for immediate repair ; the mother
of the lad was surprised to find the elbow of the coat repaired
with crimson *.

SYME'S Purples he regarded in general as blues ; the only one
to which he could perfectly adapt his notion of that colour, be-
ing the imperial purple (39.) of a specimen of fluor-spar. To
the pale blackish purple, the colour of the porcelain jasper, he
would only give the name of dark colour. A blue lilac he called
a lead colour ; nor could he trace a shade of purple in the sweet-
scented violet, or in a plum. From all the information I could
obtain, he regarded purple as a slight modification of blue.

Greens were to him a source of much embarrassment. On a
particular occasion, I requested him to bring me eight or ten

* In one of Dr NICHOLLS' cases, published in the Medico-Chirurgical Transac-
tions, the following anomalous circumstance is recorded. " CHARLES was in the
" Navy, and, several years ago, he purchased a blue uniform coat and waistcoat,.
"• with red breeches to match the blue."

VOL. X. P. II, K k

256 MR HARVEY on an Anomalous Case of Vision

specimens of cloth, of different shades of that colour. This, I
found from his master, was the occasion of much uneasiness to
him ; and he at last was compelled to ask one of his fellow- work-
men to point out the green bundle to him, although they had
been charged not to assist him in his difficulty. His master hav-
ing discovered this circumstance, substituted some pieces of black
and brown for some of the greens ; and he, unaware of the
change, furnished the following as varieties of green.

Four specimens of dark bottle-green.

One reddish-black, (21)")

One raven-black, (22) (

One liver-brown, (104) C

One blackish-brown, (108)3

When SYME'S specimen of verdigris-green was placed before
him, he declined giving any name to it, but remarked that it was
certainly not green. The beautiful green of the emerald (52.),
he called pale orange ; and to grass-green he applied the same
remark as to verdigris. Duck-green, which forms so interesting a
feature in the neck of the mallard, he named brown or green,
displaying much uncertainty ; and the same ambiguity was ma-
nifested, when olive-green was shown him. On another occasion,
being requested to point out two colours in the page, that re-
sembled each other, he immediately fixed on the two last-men-
tioned, and again called them brown.

All his ideas of green appeared to be extremely confused.
On being told that SYME'S specimens were varieties of that co-
lour, and requested to point out one that bore a resemblance to
the green fields, he expressed his surprise at the remark, and
contended that they bore no resemblance to it. The darker
kinds of green he considered to be brown ; those of a middle
tone ambiguous ; and the lighter kinds, as in the case of emerald-
green, of a pale orange colour.

with regard to Colours. 257

He experienced no difficulty with any of the brighter varie-
ties of Yellow. From a number of pieces of different coloured
cloth, he immediately selected a specimen of this colour ; and a
fragment of high-coloured sulphur he thought a beautiful ex-
ample of the same. Gallstone-yellow he conceived to be orange.
Wax-yellow (13.), which, in the Vegetable Kingdom, exists in the
greenish parts of the nonpareil apple, he supposed might be a
green. His ideas of yellow were, however, on the whole very
correct.

His notions of Orange were very imperfect. The common
marigold, he called Yellow ; and a sample of fine orpiment,
Orange ; and likewise equally choice specimens of reddish and
deep reddish orange he termed Brown.

Of the Reds, he considered carmine, lake, and crimson to be
blues;— the latter, indeed, a dark-blue, agreeing with the in-
stance of the coat before alluded to. When a great snapdra-
gon was placed before him, he called the margin of its upper lip,
which was purplish-red, a dark colour, and thought it a very
good match for my black coat. The part also near the throat
of the corolla, and which was of a light bluish-red, he called
light sky-blue. The yellow palate he distinguished perfectly ;
but as that colour gradually lost itself in the purplish-red, he
gave it the name of black. He remarked, that, when a boy, the
ruddy cheeks and arms of the milk-maidens, always appeared to
him of a bluish tone ; and, on being shown a rosy child, he per-
sisted in the same remark. The carnation, pink, and the cock's-
comb presented also the same appearance. Scarlet-red he dis-
tinguished readily by its proper name. Veinous blood * he as-
similated to brown or black ; and the brown disk of the common

* Mr DALTON, in. vol. v. p. 33. of the Manchester Transactions, remarks, that,
in his own case, blood appears not unlike bottle-green ; and, it is worthy of notice,
that, in the present case, it was termed, " not a black, but nearly so."

K k 2

258 MR HARVEY on an Anomalous Case of Vision

marigold, and the iron-flint, although presenting so marked a
difference to the perfectly formed eye, appeared to display no
variety to him. To the latter, indeed, he gave the name of olive.
The colours of the common garden rose and peach blossom,
were both designated lead-colour. To him, therefore, some of
the sweetest and most delicate colours of creation presented but
little beauty.

In the case of Browns, there was much uncertainty ; in the
greater variety of cases assimilating them to green. Mineral pitch,
although clearly a variety of brown, he considered to be black ;
and liver-brown he designated in the same manner. Chesnut-
brown he could not distinguish. An article of dress, indeed, of
the latter colour, he repaired with silk of an olive-green ; and, on
another occasion, he considered covered buttons of a bottle-green,
as a perfect match for a dress of a blackish-brown. Two frag-
ments of cloth, one a duck-green, and the other a liver-brown,
were placed before him, and he was unable to point out the dif-
ference.

From his having regarded crimson-red both as dark-blue and
black, it was anticipated that he would confound the two latter.
This accordingly took place, when the indigo and Prussian blues
of SYME'S Nomenclature of Colours were shown him, calling
them both black, notwithstanding they exhibited a marked dis-
tinction in that excellent work.

From the preceding observations it appears, that the only
colours he was capable of distinguishing with certainty (by day),
were White, Yellow, and Grey ; and that in the proper percep-
tion of the following colours, there appeared to be varied degrees
of uncertainty.

with regard to Colours.

259

Colours proposed for
Observation.

Perceptions of the proposed Colours.

BLACK.
BLUE.

PURPLE.
GREEN.

ORANGE.

RED.

BROWN.

Generally Green, in particular cases Crimson.

Darker kinds, Crimson and Black. Those of a middle
tone Carmine and Lake. Those of a lighter kind
able in general to distinguish.

Appeared to be Blue, excepting in the case of a very
bright Purple.

Confounded in general with Black and Brown. Greens
of a darker kind appeared Brown. Those of a middle
tone uncertain as to name. Greens of a lighter kind
Dark-Yellow.

Darker kinds Brown. Lighter kinds Yellow.
Carmine, Lake, and Crimson appeared Blue.
Green.

Since the above was written, the following circumstance oc-
curred. He was sent to obtain some patterns of green baize, and
having procured five varieties, placed them on his return in the
shop-window. In the course of the day, his master caUed on
him, to state the prices of the patterns he had obtained, at the
same time placing before him two pieces of crimson cloth, and
three of the green baize, and he, unconscious of the difference,
fixed prices on each.

On being informed of the circumstance, I prepared two ex-
cellent specimens of the above colours, and placed them before
him, first on a white ground, secondly on a yellow ground, and,
lastly, on one of a green colour, and, in each case, he regarded
the two colours, to use his own words, " as well matched." *

* A philosophical friend who was present, placed the colours under several dif-
ferent circumstances, but with the same uniformity of effect.

260 MR HARVEY on an Anomalous Case of Vision

The day being favourable on which the last experiment was
performed, a vivid and well-formed solar spectrum was thrown on
the wall. He pronounced it to be composed of two colours, yel-
low and light blue ; and which, in a former conversation, he de-
scribed as the ordinary appearance of the rainbow. The vivid
and brilliant red of the spectrum he could by no means distin-
guish. Its general appearance he regarded as in some degree
beautiful ; but the bursts of pleasure which escaped from my
children, as they contemplated the brilliant colours in succes-
sion, appeared to excite in him the greatest surprise. I after-
wards found, that he considered the prism as a thing moderate-
ly interesting, but as by no means meriting the praises which
had been bestowed on it.

His eyes appear to be exceedingly Well formed, and time has
but slightly impaired their powers. According to the opinion of
my friend Mr TRACEY, surgeon, they appear to possess all the
essentials necessary to good sight, namely, perfect transparency
of the several humours, a proper degree of convexity of the cor-
nea and ball of the eye, and to which may be added, the perfect-
ly healthy functions of its appendages ; the proofs of which are
discovered in the just adaptation of the eye to distance. In
his communication to me on the subject, Mr TRACEY observes,
" If I might adduce any one point (which, under common circum-
" stances, I should not be disposed to notice) I should say the
" grey colour of the irides is much fainter than usual ; and that
" the pupilla? are extremely small." The cause of the last-men-
tioned fact, is no doubt to be attributed to the constant exer-
cise of the eyes by candle-light, it being known, that, persons
similarly occupied, are of necessity obliged to bring the object
very near, and thus, from long habit, produce artificially a per-
manent diminution in the magnitude of the pupillae.

In the present limited state of our information on this very
interesting and curious subject, and with so few cases that have

with regard to Colours. 261

been hitherto presented to the philosopher, it may be premature
to offer any very decided observations on the cause. The ob-
jects of a true and legitimate philosophy are perhaps best ful-
filled, by diligently collecting facts, and, by cautiously deducing
inferences from them, to form gradually the successive links of a
chain, which shall ultimately lead to the true cause.

Of the hypotheses that have been proposed to account for the
phenomena in question, that which refers it to an insensibility of
the retina to certain impressions of light, appears at once the
most simple and philosophical. Some eyes, it is well known, are
capable of performing the general functions of vision, and are yet
unable to perceive those minute impressions of light, which to
other eyes are readily perceptible. A retina may be perfectly
adapted to receive the due and proper effect of a beam of light,
and yet, from some peculiarity in its organization, incapable of
perceiving all its component parts. In the present case, the ge-
neral objects of vision, as relate to form, distance, and magnitude,
were perfectly fulfilled, and the sensations arising from white,
yellow, grey, and the lighter varieties of blue, appeared in gene-
ral to be correct ; and it would therefore appear probable, that
the retina was sufficiently sensible to receive correct impressions
from pure white, up to colour of a certain intensity ; and, be-
yond which, 'sits power being enfeebled, it communicated only
imperfect and confused ideas *.

In the cases published by Dr NICHOLLS, in the Medico-
Chirurgical Transactions, the anomaly appeared in some measure
hereditary ; in one instance being derived through the father, and

* The point where this change appeared to take place, with respect to blue, was
between ultramarine and flax-flower blue, corresponding to 28. and 29- of SYME.

MR HARVEY on an Anomalous Case of Vision.

in the other through the mother. In some families, this pecu-
liarity of vision appears to be transmitted through a son, with-
out affecting in the smallest degree a daughter ; and in other
cases precisely the reverse. In the present instance, however,
the anomaly appears to have originated with the individual, no
member of his family being similarly circumstanced, — he having
always regarded himself as a singular and unfortunate exception
to the whole.

PLYMOUTH, July 20. 1823.

( 263 )

XVIII. Observations on the Germination of the Filices. By the
Reverend JOHN MACVICAR, Dundee. Communicated by
the Reverend JOHN FLEMING, D. D. F. R. S. E. &c.

(Read June 6. 1824.;

SINCE the perfecting of a Natural Arrangement has become the
grand object of scientific pursuit, it has been found necessary to
enter more minutely than was required by an artificial system,
into modifications of structure and function. Botanists have no
longer rested satisfied with observing plants in their fully de-
veloped forms, but have also had recourse to several other periods
in the existence of vegetable life, the observance of which gives
much insight into the organisation of the individual. Of these
there is none more important than germination, which is often
the only means afforded for ascertaining the structure of the
seed. This is the case with all the cryptogamic tribes, the seeds
of which are generally so minute, that many of them must be
brought together before they be distinctly visible. With such
subjects dissection is hopeless, and a knowledge of their struc-
ture can only be derived, during their formation and evolution.
The observations on this subject are as yet few, and those that
have been made do not accord well with each other. Such at
least is thought to be the case with the evolution of the Ferns.
It appears, however, by a repetition of the experiments, and an
uninterrupted series of observations on the evolution of the spo-
rule from first to last, that the discrepance of observation arises,
not from any inaccuracy on the part of any observer, but by each
looking at periods of evolution different from the other ; by do-
VOL. x. P. ii. L 1

264 MR MACVICAR on the Germination of the Filices.

ing which, each saw forms apparently irreconcileable, and by a
law of our nature, which requires us to believe the testimony of
our own senses in preference to that of another, late observers
have been led to attach doubts as to the accuracy of preceding
observations, which nothing but a different result, obtained by
the same process, could vindicate.

It has been the fate of LINDSAY, the first observer of im-
portance, according to the opinion of late and far more enlight-
ened naturalists, to see " several whimsical shapes *," which suc-
ceeding observers have not been able to recognise f. His obser-
vations £ were made at Jamaica some time previous to the year
1789, and the engravings were executed in England, where he
had no opportunity of superintending, so as to correct errors.
Notwithstanding, the figures are tolerably accurate, and certain-
ly entitle the author to more merit than has of late been awarded
to him. They commence with the sporule soon after germination,
and he gives several representations of the plantule in successive
stages, as seen by a high magnifier. These correspond to the
first seven figures in the accompanying drawing ; and, except
that he has represented the radicles in all of them as proceeding
from the sporule alone, — an error, it must be confessed, which of
itself shews that he did not understand the peculiarity of the
evolution, — they are not very unlike what the author has ob-
served. He then permits some weeks to pass without observa-
tions, until the little plants begin to appear to the eye as small
heart-shaped scales. His observations then correspond to the
accompanying Figures 10, 11, 12, 13, 14, Plate XL; they are
represented of the natural size, and are tolerably just. The

* Sup. to Encyc. Brit. Art. Anat. Veg.
+ Edin. Encyc. Art. Filices.
J Lin. Trans, vol. ii. p. 95.

MR MACVICAR on the Germination of the Filices. 265

greatest fault in his observations is, that he neglected to observe
a most interesting process in the evolution, and by proceeding
per saltum from the period at which a high magnifier was ne-
cessary to render his early forms visible, to the time when
these appeared to the eye as small scales, he has represented
forms nowise connected with each other, which has led late
observers to doubt their accuracy. Of these, the most distin-
guished is the author of the article Filices in the Edinburgh
Encyclopaedia, published in 1815. The experiments which he
there describes commence soon after what he terms the " seed-
lobes" become visible to the naked eye. Of course they corres-
pond to the second sets of LINDSAY'S observations, and, though
much more perfect, are on a general view pretty similar. He
has remarked the temporary radicles, the true root, and the
elevation around the opening formed by the emission of the
true frond, on all of which LINDSAY is silent. Besides these,
several others have noticed ferns in the act of germinating.
EHRHART seems to have observed some of the earlier forms of
LINDSAY. SPRENGEL saw a single species in a state of sponta-
neous germination, in its farthest advanced states, forms in which
young ferns are to be seen in every shady moist crevice, or other
place where ferns grow. MIRBEL has also observed some of the
later stages, differing in some unimportant particulars, in the
form of what have been named the Seed-lobes.

Notwithstanding, however, that observers have been so nu-
merous, it does not appear that the true mode of the evolution
has as yet been understood. LINDSAY makes no attempt to re-
concile his -early with his later forms ; while the author of the ar-
ticle Filices, though he made experiments on various genera,
could never observe the first forms of LINDSAY. These circum-
stances are easily explained, however, if the appearances present-
ed during the evolution of Poly podium vulgare be similar to

L! 2

266 MR MAC VICAR on the Germination of the Filices.

those of the other individuals of this natural family ; and this
we may safely conclude of all those at least having prostrate
stems. The accompanying figures are representations of what
the author has observed in that species. In the explanation, no
dates are given, as the progress of germination depends entirely
on the age of the sporule, the supply of moisture, temperature,
&c. which are the measures of the progress of vegetation rather
than of equal spaces of time.

After seeing the observations in the Edinburgh Encyclopae-
dia, it occurred to me that the seed of the Filices must consist
chiefly of two cotyledons folded together, which, by the absorp-
tion of moisture, and the germinating power, resolved themselves
into the forms represented by the author of that article ; an idea
in which I was confirmed by observing the sporule of Polypo-
dium vulgare, which appeared under a high magnifier curiously
folded together like the surface of a brain. Whatever the sur-
face of a sporule may be, however, the idea that it consists of
two folded cotyledons is altogether erroneous. The opinion of
GARTNER, that the testa of the seed is in them as well as in the
Musci and Fuci, totally occupied by what he terms vitellus, seems
much nearer the truth. The evolution of the Musci, indeed, has
so many points in common with that of the Filices, as to indi-
cate a similar structure of the sporule. HEDWIG, and, after him,
Mr DRUMMOND of Cork *, when observing the young shoot from
the seed of Funaria hygrometrica, saw that it had ruptured the
integument, which, until more extensive experiments be made,
may be considered as an epidermis. But whether this coat be,
as in the higher vegetables, an integument of a different struc-
ture from the enclosed parts, and existing previously to the ac-
tion of atmospherical causes, or whether it be a natural change

* LIN. Trans. Vol. xiii. Part 1.

MR MACVICAR on the Germination of the Filices. 267

produced by their action upon the uniform substance of the spo-
rule, after the soft matter in the theca has resolved itself into
little concretions, conducing powerfully to the preservation or
the vital principle in the interior, and similar to a change observ-
ed to take place on the surface of Vorticella rotatoria, and other
aquatic animalcula, when, by some accident, they have been ex-
posed to the action of the air, and by which the principle of life
has been wrapt up for several years, is not determined. The
sporules of these two acotyledonous tribes seem to be small con-
cretions of matter produced in the reproductive organs of most
species, possessed of the vital principle of those species without
the action of sexual parts, and of the power of giving rise to forms
of germination peculiar to the family to which they belong;
which intermediate forms, in their turn, and after the action of
the sporule has ceased, have a similar power of evolving the ma-
ture forms of the species. The irregularity in size, form, and
surface, observable even from the same theca, seems to counte-
nance this idea of the simplicity of the sporule. In Polypodium
vulgare they are comparatively large ; they vary in surface, from
nearly echinated to nearly smooth, and in form from globose to
reniform. In Pteris crispa they are generally equilateral tri-
angular pyramids, more or less perfectly formed ; but they vary
from having plane sides and sharp angles to globose.

Still, however, though this simplicity of structure were granted
to the sporule of the Filices, it does not follow that this magnifi-
cent family must be ranked with the Acotyledones. After leaving
the Dicotyledones, we do not observe the same uniformity in the
structure of the embryo. BROWN, our illustrious country-
man, has shewn *, that certain Aroideae produce seeds which
have an appearance and economy much more nearly resembling
the tuber of a root ; for instead of being distinguishable into a

* LIN. Trans, vol. xii.

268 MR MACVICAR on the Germination of the Filices.

cotyledon, a plumule and radicle, and of germinating in a de-
terminate manner, and from a single point ; they are composed
of a mass, whose internal structure is uniform, and on the sur-
face of which frequently more than one germinating point are
visible. And, there is reason to believe, that there are other
families in this class, the structure of whose seeds is equally ano-
malous.

The author of the article alluded to was led to conclude,
from his observations, that the seed-lobes of ferns possess not
only an analogy with, but partake of the essential properties of
cotyledons, as far as these have been accurately denned ; and
though he mentions some respects in which the germination of
ferns is peculiar to this family, he gives particularly three in
which it agrees with other dicotyledonous plants. The first is,
that the seed-lobes constitute the body of the minute seed.
Should the general mode of germinating throughout the family
be uniform, of which, as that writer remarks, there can be little
doubt, this cannot be the case ; for in every instance where the
sporule has been seen, and as long as it has been observed, it re-
mained of nearly its original form and size, which could not have
happened, had not what have been considered as seed-lobes been
solely the result of germination. The other two are, that these
seed-lobes nourish the other organs of the embryo, which they
include within their substance ; and that these organs germinate
from a tuber situate in the centre of the lobes. They certainly
do nourish the true bud, after they have disposed of the nutri-
tious matter derived from the radicles for their own aggrandise-
ment, until the law of their life does not permit them to increase
in size, but not till then do they form a bud ; and their action in
doing so, is not by yielding any albuminous matter contained in
their substance, as in true cotyledons, for they are thin cellular
membranes, and their function seems to be to convert the fluids
received from the numerous radicles on their under surface, into
the forms of the species.

MR MACVICAR on the Germination of the Filices. 269

Were we to seek for analogies to these hepaticoidal forms of
ferns, in more highly organised bodies, we do not know where
to find them beyond the limits of this family. But there are
several circumstances which might lead us to view them as re-
presentatives of the prostrate stem. They originate from the
sporule, a minute tuber ; they soon after emit radicles, which pe-
netrate the soil, and contribute to their increase, and, when ar-
rived at sufficient strength, they form a bud. And perhaps it
may be found, by future observations, that the elongation of the
hepaticoidal form, and the successive emission of radicles farther
up, are confined to those species having prostrate stems.

It is not among the Dicotyledones that the Filices lay any
claims to rank. Some most eminent botanists, however, have
classed them among the Monocotyledones ; a place assigned them
chiefly from the structure of the stem, in which the occurrence
of vascular fasciculi, and certain modes of growth, indicate many
points common to them and to species decidedly monocotyledon-
ous. But the detection of vessels in the stems of Ferns, and in
other nearly related tribes, may have arisen from the circum-
stance, that they exist there in a state easily detected, while the
minuteness of some other families very much limits the success
of dissection. In this question habit gives little aid ; for the gi-
gantic arborescent species seem to approach as nearly to the
magnificent Palms on the one hand, as the humble Trichomanes
and Hymenophylla do to the Mosses on the other. But while
the whole reproductive system is truly cryptogamic, and the ob-
ject of the botanist to confine to one of three classes the almost
infinite modifications of structure in the vegetating world, it
seems preferable, at least, until the structure of several other
cryptogamic tribes be investigated, to attach that importance to
the fructification which has usually been given it, and to place
them, where they have generally stood, among the Acotyledones ;

270 MR MACVICAR on the Germination of the Filices.

although, if authority were sufficient to satisfy the doubts of all,
their station should be among the Monocotyledones, having been
placed there by the two greatest botanists of the age, BROWN and
DE CANDOLLE.

EXPLANATION OF PLATE XI.

Fig. 1. A sporule of Polypodium vulgare begun to germinate. The frondose por-
tion is somewhat advanced before any radicles are emitted. Figs. 2, 3,
4, 5, different stages of progress. Fig. 6., at this stage the cellular struc-
ture becomes distinct, and radicles are emitted from the lower portion of
the frond. Figs. 7, 8., the fronds now become emarginate, and curiously
apiculate. The radicles are emitted from the margin and under surface.
Those from the sporule and lowest part of the frond begin to shrink,
along with that portion of the frond, as in Fig. 9., until, as in Fig. 10.,
the sporule is separated.

Fig. 11. The true frond beginning to shoot out from the centre of the hepaticae-like
form (copied from the Edinburgh Encyclopaedia, Ait. Filices).

Fig. 12. Plantule of Aspidlum Filix jcEmina, (copied from SPRENGEL'S Introduc-
tion to the Study of Cryptogamic Plants).

Fig. 13. Plantule of Polypodium lycopodioides (copied from LINDSAY'S Observa-
tions, &c. LIN. Trans, vol. ii.).

Fig. 14. Aspidium aculeatum (LIGHTF.) in a state in which they are easily found
growing spontaneously.

The first ten figures are magnified.

PJ.ATK XI.

t:,,,,nm;l far ll« Rm,,,l Xaf.Tran I',,/ X~ ,„„,,• 270

PI, ATK

' 11 1/ d for the Royal Society Tran-Tol. X .?.2. P. 272.

Attarn'te

Fit? .2.

f'u/.. 3

Fig. 6.

Ka.f.

( 271 )

XIX. Description of FERGUSONITE, a New Mineral Species.
By W. HAIDINGER, ESQ. F. R. S. EDIN.

(Read January 17. 1825. J

FEW cabinets of minerals contain so many of the rare substan-
ces, which were discovered in Greenland, by Sir CHARLES GIE-
SECKE', and perhaps none in equally interesting varieties, as that
of Mr ALLAN. The most prominent of them have been examined
both in a mineralogical and chemical point of view, and some de-
scribed as particular species. Mineralogy is already indebted for
Allanite, Sodalite, Eudialyte, and Gieseckite, to the zeal of the
indefatigable explorer of Greenland, and the subsequent labours of
Dr THOMSON and Professor STROMEYER ; and it is probable that
the number of new species from this source will yet be increased
upon farther examination.

Allanite had first been noticed by Mr ALLAN, who described
it as crystallised Gadolinite *, — a variety of which it had been con-
sidered by CountBouRNON, resting, in part, upon some partial che-
mical experiments. Dr THOMSON-)- afterwards analysed it, found
it to be a species of its own, and gave to it the name of Allanite,
under which it has been since received in most of the treatises
on mineralogy. The description of the crystals, given by this
author, and the second figure which accompanies his paper, are
perfectly correct, and refer to that variety of the mineral which
he has analysed. It is well known at present, that the first fi-
gure represents a crystal of Zircon of a very dark colour. This

* Transactions of the Royal Society of Edinburgh, Vol. VI. p. 345.
f Ibid., p. 371.
VOL. X. P. II. M HI

272 Description of FERGUSONITE,

species occurs along with the Allanite, and sometimes imbed-
ded in it, in small but very distinct crystals, generally of the
form of a four-sided prism, terminated by a four-sided pyramid,
in parallel position, and having occasionally its lateral edges re-
placed. HAUY, and most of the other mineralogists, in the de-
scription of Allanite, have quoted the measurement of the prism
117°, as indicated by Dr THOMSON. Messrs PHILLIPS* and
BROOKE f ascribe to it a rectangular four-sided prism, which
is incompatible with the real form of the mineral. That sub-
stance, the form of which Mr PHILLIPS has described, and
which he calls Crystallised Allanite, does not belong to this spe-
cies : it is a species of its own, but, like the AUanite, it belongs
to the order Ore, of the system of Professor MOHS.

The more particular object of the present paper, is to de-
scribe this new species, for which, at the suggestion of Mr ALLAN,
I propose the name of Fergusonite, in honour of a gentleman
too well known to the mineralogical world at large, and to the
members of this Society in particular, to require, in the present
place, a more detailed acknowledgment. In order to produce a
more distinct idea of the differences existing between the two
species, I shall begin with giving a short description of the Al-
lanite, and then add the description of Fergusonite, as derived
from the specimens observed in the cabinet of Mr ALLAN.

I. ALLANITE.

Its form is tetarto-prismatic. Plate XII. Fig. 1. shews the
elevation of a crystal. Fig. 2. the projection of the same, upon
a plane perpendicular to the sides of the prism. It is the same
crystal which has been mentioned by Dr THOMSON, and presents

* Ekmentary Introduction to Mineralogy, p. 264.
•J- Familiar Introduction to Crystallography, p. 458.

a New Mineral Species. 273

a greater number of planes than any of those which have been
described by Count BOURNON. I have noted the faces, with the
letters received for Axinite by HAUY, and in the Treatise on Mi-
neralogy by Professor MOHS, for the sake of an easier compari-
son of the analogies among the crystalline forms of the two spe-
cies. I obtained the following measurements of the angles :

r on M = 129° y on r — 109°

r on P = 116 s on x = 156|

M on P = 115 x on t = 164^

s on r = 135^ x on y — 151

d on r — 124^ t on y =

These angles are given merely as rude approximations to the
true angles of the crystal, as, besides the use of the common
goniometer, I was obliged to take impressions from them in seal-
ing-wax, to make them at all fit to be measured with the assist-
ance of the reflective goniometer. The surface is far from pre-
senting a good polish, or high degree of lustre ; the inclined faces
s, x, t, and y, are more perfect in this respect than those which
are parallel to the axis. The face M in particular is very rough
and uneven. The inclination of r on P is more easily ascer-
tained. The edge between P and M is also sometimes replaced
by a rough face.

Faint traces of cleavage are observable parallel to P and r ;
but they are very indistinct and interrupted. Fracture is imper-
fect conchoidal.

The lustre is imperfect metallic, if any thing inclining to re-
sinous ; the colour black, verging upon green or brown : the co-
lour of the powder or streak is greenish-grey, also a little brown-
ish. It is opake, only the edges of very thin splinters are some-
what translucent, and of a dark yellowish-brown colour.

M m 2

274 Description of FERGUSONITE,

The substance of Allanite is brittle ; the hardness = 6.0 ;
some varieties a little higher, others a little lower, but the dif-
ference is scarcely perceptible. The specific gravity is different-
ly stated ; but the highest obtained by Count BOURNON, which
seems to be that of the pure mineral, is = 4.001. It does not
act upon the magnetic needle.

This description does not differ in any material point from
that which has been given by Mr ALLAN, except in respect to
the regular forms, which were obtained from specimens disco-
vered after the publication of his paper.

II. FERGUSONITE.

The regular form of this mineral is one of the most interesting
of those comprised within the pyramidal system. The fundamen-
tal form, as deduced from approximate measurements, is an isosce-
les four-sided pyramid, having its terminal edges = 100° 28', and
its lateral edges = 128° 27', Fig. 7. The character of its com-
binations is hemi-pyramidal, like that of Tungstate of Lime, the
pyramidal Scheelium-baryte of MOHS, with which it agrees also
very nearly in its angles. The character of its combinations is
evident from Fig. 3., where the fundamental pyramid is in com-
bination with an acute four-sided pyramid, with a rectangular
four-sided prism, and with the pyramid of infinitely small axis,
or P — oo . The angle a b c in Fig. 6., which is the horizontal
projection of Fig. 3., being about 11°, it follows that the prism r
itself consists of the alternating faces of that eight-sided prism,
whose transverse section is 112° 37' 12", and 157° 22' 48", and
whose crystallographic sign, according to the method of Profes-
sor MOHS, is g00^ • The faces of the pyramid are general-
ly curved, and yield on that account various measures with the
common goniometer, giving the inclination at its base from 158°

a New Mineral Species. 275

to 170°. The angle of 159° 2' corresponds to the pyramid

(P 1)*, exactly the same ratio as we find in the two forms

of pyramidal Tin-ore, noted * and z by HAUY. The angle of
169° 26' belongs to (P + I)5. There is no sharp edge between
these faces ; but wherever they are most distinctly pronoun-
ced, they seem rather to approach to the position of the first of
these pyramids. The acute four-sided pyramid z is often in
combination only with P — GO , as in Fig. 5.

No crystal has yet been observed terminated on both ends.
In the portion of one represented in Fig. 4., the faces of the four-
sided pyramid z are disposed in the opposite direction from that
in Fig. 3. This may be conceived to be the opposite apex of
the crystalline forms.

There are faint traces of a cleavage observable parallel to P,
the fundamental pyramid of the species ; but they are incoherent,
and much interrupted by conchoidal fracture, which is of a high
degree of perfection. The surface of all the forms is rather un-
even, often irregularly streaked and rough.

Fergusonite possesses an imperfect metallic lustre, inclining
to vitreous in the perfect conchoidal fracture. Its colour is dark
brownish-black ; but, in very thin scales, it appears of a pale li-
ver-brown or yellowish-brown colour, and is translucent ; in lar-
ger crystals it becomes opake. Its streak is a pale brown pow-
der, exactly the same as in peritomous Titanium-ore.

It is brittle, the hardness rr 5. 5... 6.0, nearer the latter ; it is
scarcely different from that of the prismatic Feldspar. The
specific gravity, taken with great care by Dr TURNER, was found
— 5.800, nearly agreeing with 5.838, the result obtained by Mr
ALLAN. It does not act upon the magnetic needle.

Both these species were discovered in Greenland by Sir
CHARLES GIESECKE'. Allanite occurs at Alluk near the south-

276 Description of FERGUSONITE,

ern extremity of East Greenland, and, besides Zircon, it is asso-
ciated with Mica and Albite, and imbedded in Quartz. The lo-
cality of Fergusonite is Kikertaursak, near Cape Farewell, where
it is found in imbedded groups and single crystals, in white
quartz. The specimens of this species were brought from
Greenland by Sir CHARLES himself, and were presented by him,
on his arrival in this country, to Mr ALLAN.

Fergusonite, under the name of Allanite, has been examined
by Mr CHILDREN before the blowpipe *. The results of his ex-
periments agree pretty well with those given by BERZELIUS of
the Black Yttro-tantalite from Ytterby. Its slow but perfect
solubility in salt of phosphorus, leaving a long time some par-
ticles undissolved, the property of this glass-globule to become
opake by flaming, when saturated to a certain degree, and, on
cooling, when still farther saturated, may indicate the presence
of tantalum and yttria ; and even the rose colour, which it as-
sumes under certain circumstances, accords with the re-action of
a small quantity of wolfram, as quoted by BEIIZELIUS. It will
depend upon future examination of its physical properties, whe-
ther the black Yttro-tantalite can be arranged among the varie-
ties of Fergusonite. They agree in some respects, but their
differences in others are such, as, if ascertained with sufficient
exactness, would alone prove the two substances to be dif-
ferent species ; while the circumstance, that we know nothing of
the regular forms of the black Yttro-tantalite, renders every con-
jecture doubtful.

It is the more necessary to leave the decision of this point to
future observations, as there are some crystallised specimens in
Mr ALLAN'S collection, evidently belonging to a different species

* BERZELIUS on the Blowpipe, translated by J. G. CHILDREN, p. 291.

a New Mineral Species. 277

from Fergusonite, and: which Mr NORDENSKIOLD ascertained to
be an yttro-tantalite. This substance is crystallised in regular
octahedrons, the largest of them half a line in diameter, present-
ing no cleavage, but rather perfect conchoidal fracture. Its
lustre is resinous, almost imperfect metallic, at least in the frac-
ture ; for the surface of the crystals, though very even, possesses
but little lustre, the colour is pale yellowish-brown, the streak
still lighter, almost of the same colour as that of Fergusonite,
and it is translucent on the edges. It is brittle, but the hard-
ness inferior to that of Fergusonite, being only between 4.5 and
5.0.

The locality of this species is Godhavn in Greenland, where
it is found imbedded in Albite, with cleavable octahedral Iron-ore
and Fluor. It resembles the yellow Yttro-tantalite of BERZE-
LIUS ; but the forms of this substance not being known, it is as
impossible to say whether they belong to one species, as it is
with other varieties of Yttro-tantalites and the Fergusonite.

Several of the properties of Fergusonite have been quoted by
Mr PHILLIPS among the characters of Yttro-columbite, and some-
thing analogous to its form is represented as a crystal of Allanite.
The chief difference of this figure from the real crystals of Fer-
gusonite is, that the faces *, which appear on their extremities,
are inclined either to the right or to the left of each face of the
four-sided prism, while in the figure quoted above, they are re-
placed by an eight-sided pyramid, appearing with the full num-
ber of its faces.

The mineral from Bastnaes, called Cerite by HISINGER and
BERZELIUS, possesses many properties in common with Allanite.
On account of its agreement in regard to chemical composition,
it has been supposed by many mineralogists to constitute with
it but one and the same species. It would be too precipitate to
form at present a decided opinion on this question, as long as the

278 Description of FERGUSONITE.

regular forms of Cerite are unknown, or, at least, as long as
they have not been compared with those of Allanite. Professor
MITSCHERLICH, however, informed me, that he had a crystal of
Cerite in his possession, which the crystal of Allanite, described
above, immediately recalled to his memory, when he was looking
over that department of Mr ALLAN'S collection which contains
the minerals belonging to the order Ore.

*

( 279 )

-
Biographical Account of ALEXANDER WILSON, M. D. fate

Professor of Practical Astronomy in Glasgow. By the
late PATRICK WILSON, A. M. Professor of Practical Astro-
nomy in the University of Glasgow

(Read February 2. 1189.)

ALEXANDER WILSON, M. D., late Professor of Practical Astro-
nomy in Glasgow College, was a younger son of PATRICK WIL-
SON, town-clerk of St Andrew's, and was born there in 1714. He
was very young when his father died, and was afterwards brought
up by the care of his mother, CLARA FAIRFOUL;, a person much
respected for her prudence, virtue, and piety.

Having received the usual education at the different schools,
he entered to the College of St Andrew's, where he made great
proficiency in literature and the sciences, and, after completing a
regular course of studies, was admitted to the degree of Master
of Arts in his 19th year.

Before the expiration of his academical course, his inclina-
tion led him to prefer the study of Natural Philosophy, and par-
ticularly those branches of it which relate to Optics and Astro-
nomy. From his earliest years he discovered a strong propensity
to several ingenious arts, among which may be mentioned draw-
ing, modelling of figures, and engraving upon copperplate. Even
when a boy, he often devoted his leisure to such employments,

* This Memoir of Dr WILSON, after being read at the Royal Society, was with-
drawn by its author, for the purpose of making some alterations upon it ; and was
never returned for publication. It was found, however, among the papers of Mr
PATRICK WILSON, and is now printed with the consent of his family.
VOL. X. P. II. N n

280 Biographical Account of DR WILSON,

and though in all of them he was almost entirely self-directed
and self-taught, yet, from time to time, he produced specimens
of ingenuity which drew upon him a general attention, and
which, by real judges, were considered as indications of uncom-
mon natural talents.

Upon his leaving the College, he was put as an apprentice to
a surgeon and apothecary in his native city, with a view of fol-
lowing that profession. At this period he became more particu-
larly known to Dr THOMAS SIMSON, Professor of Medicine in the
University, who ever after treated him with much kindness and
friendship. About the same time he had also the good fortune
to find a patron in Dr GEOKGE MART INK, a physician in the
town. In those days the construction and graduation of ther-
mometers was little attended to or understood in Britain, and
Dr MARTINE, from a just conception of the importance of this
instrument, in many philosophical pursuits, was then employed
in composing those Essays on the subject of Heat which have
rendered his name so justly celebrated. The author, besides il-
lustrating so well the theory of the thermometer, was farther
very desirous of bringing accurate thermometers into general
use ; and, with this view, he turned the attention of his friend
Mr WILSON to the art of working in glass. Though this was to
him entirely a new attempt, depending upon many trials, and
much mechanical address, yet he very soon acquired an admi-
rable dexterity in forming the different parts of the instrument
by the lamp and blowpipe, and in constructing and graduating
the scales with accuracy and elegance ; an employment which,
for a long time, Mr WILSON continued to be fond of at conve-
nient seasons, and in which it is well known he greatly excel-
led.

Possessing naturally much activity of mind, and employing
most of his leisure in some ingenious attempt or other, it was
about this time that, in making certain optical experiments, he

late Professor of Practical Astronomy in Glasgow. 281

discovered the principles of the Solar Microscope, so far as to
exhibit to several of his friends, in a dark chamber, the images
of small objects enormously magnified, by the sun's rays enter-
ing at a hole in the window-shutter, and after several refractions
falling upon a white ground within. But Mr WILSON as yet was
too far separated from the great world, and had too little expe-
rience, for bringing forward to the notice of the public any no-
velty of this kind ; and, soon after, a similar combination of
glasses, with additional improvements, occurred to Mr LIEBER-
KUHN, and was at length received as a very curious enlargement
of the optical apparatus.

It was also, whilst employing himself in such researches, that
Mr WILSON proposed to many of his philosophical friends the
idea of burning at a great distance, by means of plain mirrors,
so situated as to throw the rays of the sun upon the same area,
without the smallest knowledge of such a thing ever having been
imagined by any person before him. But wanting the means of
providing himself with any costly apparatus, the matter was pur-
sued no farther ; and it is well known that M. DE BUFFON, some
years afterwards, when equally uninformed of what KIRCHER had
thought of, hit upon the same conception. In 1747, by a mag-
nificent construction far beyond the reach of Mr WILSON'S fi-
nances, the French philosopher shewed what might be done in
this way, and with such effect, as to render the famous secret
imputed to ARCHIMEDES, of setting on fire the Roman galleys,
much less apocryphal than it had ever been considered before
his time.

In 1737 Mr WILSON departed from St Andrew's, and, by the
advice of his friends, went to London, in order to seek for em-
ployment as a young person who had been bred to the medical
profession. Soon after his arrival there, he engaged himself with
a French refugee, a surgeon and apothecary of good character,
who received him into his family, giving him the charge of his shop.

H n 2

282 Biographical Account of DR WILSON,

and of some of his patients, with a small annual salary. About
twelve months after he had been fixed in this new situation, Mr
DAVID GREGORY, Professor of Mathematics at St Andrew's, co-
ming to London, introduced him to Dr CHARLES STEWART, phy-
sician to ARCHIBALD Duke of Argyle, then Lord Isla. Dr STEW-
ART received him with great kindness, and, not long after, made
him known to Lord Isla, who, very soon, was pleased to bestow
upon him marks of his attention and favour. In his interviews
with this nobleman, Mr WILSON had his curiosity much gratified
by some valuable astronomical and physical apparatus which his
Lordship had got constructed for himself, and had placed in his
library. On the other hand, Mr WILSON was happy in being
able to contribute in some degree to the amusement of his pa-
tron, by constructing thermometers of different kinds for him
and his friends, with more perfection and elegance than had been
hitherto done at London.

Near eighteen months elapsed in this way, during which
time he conciliated the good- will and esteem of his master, by a
faithful and regular discharge of whatever business was commit-
ted to his care ; and, in return, he found himself now and then
indulged in opportunities of keeping up his connections with
persons of a philosophical cast, when his attendance upon the
shop or patients could be conveniently dispensed with. Mr
WILSON has been often heard to speak of the satisfaction he en-
joyed even at this period, and of his perfect contentment with
every thing which had then fallen ta his- lot. But a serenity of
temper, and a felicity of disposition, were qualities which emi-
nently distinguished him throughout his whole life.

While he thus passed his time in what he considered as a
comfortable settlement at his first entering upon the world, a cir-
cumstance of a very accidental nature occurred, which gave a
new direction to his genius, and which, in the end, led him to an
entire change of his profession. This was a transient visit which

late Professor of Practical Astronomy in Glasgow. 283

he happened one day to make to a letter-foundery, along with a
friend who wanted to purchase some printing- types. In the
course of seeing the common operations of the workmen usually
shewn to strangers, he was much captivated with the curious
contrivances made use of in that business. Some short while af-
terwards, when reflecting upon what had been shewn in the letter-
foundery, he was led to imagine that a certain great improve-
ment of the art might possibly be effected, and of a kind, too,
that, if successfully accomplished, promised to reward the inven-
tor with considerable emolument. His ideas upon that subject
he presently imparted to a friend a little older than himself, who
had also come from St Andrew's, and who was possessed of a
considerable share of ingenuity, constancy, and enterprise. The
consequence of this was, a resolution on the part of both these
young adventurers to relinquish, as soon as it could be done
with propriety, all other pursuits, and unite their exertions in
prosecuting the business of letter-founding upon an improved
plan.

It was not long ere they were enabled to carry into effect
this resolution, and they first established a small type-foundery
at St Andrew's, and one on a larger scale, two years afterwards,
at Camlachie, a village near Glasgow.

In this situation, Mr WILSON had contracted habits of inti-
macy and friendship with several persons of the most respectable
character, particularly with the Professors belonging to the Uni-
versity of Glasgow, and with Messrs ROBERT and ANDREW Fou-
us, University printers, The growing reputation of the Uni-
versity Press, conducted by these gentlemen, gave additional
scope to Mr WILSON to exert his abilities in constructing their
types, and being now left entirely to follow his own judgment
and tagte, his talents as an artist became every year more con-
spicuous. When the design was formed by the gentlemen of

284 Biographical Account of DR WILSON y

the University, together with Messrs FOULIS, to print splendid
editions of the Greek classics, he, with great alacrity, undertook
to execute new types, upon a model highly improved. This he
accomplished, at an expence of time and labour which could not
be recompensed by any profits arising from the sale of the types
themselves. Such disinterested zeal for the honour of the Uni-
versity Press, was, however, upon this occasion, so well under-
stood, as to induce the University, in the preface to the folio HO-
MER, to mention Mr WILSON in terms as honourable to him as
they were just.

Though he thus continued to prosecute letter-founding as
his chief business, yet, from his great temperance, domestic ha-
bits, and activity, he was enabled now and then to command in-
tervals of leisure, which he never failed to fill up by some useful
or ingenious employment. One of these, in which he took great
delight, was the constructing of reflecting telescopes, an art
which he cultivated with unwearied attention, and in the end
with much success.

Among the more advanced students, who, in the years 1748
and 1749, attended the lectures on Divinity in the University,
was Mr THOMAS MELVILL, so well knwn by his mathematical ta-
lents, and by those fine specimens of genius which are to be
found in his posthumous papers, published in the second volume
of the Edinburgh Essays, Physical and Literary. With this
young person Mr WILSON then lived in the closest intimacy.
Of several philosophical schemes which occurred to them in their
social hours, Mr WILSON proposed one, which was to explore the
temperature of the atmosphere hi the higher regions, by raising
a number of paper kites, one above another, upon the same line,
with thermometers appended to those that were to be most
elevated. Though they expected, in general, that kites thus
connected might be raised to an unusual height, still they were

late Professor of Practical Astronomy in Glasgow. 285

somewhat uncertain how far the thing might succeed upon trial.
But the thought being quite new to them, and the purpose to
be gained of some importance, they began to prepare for the
experiment in the spring of 1749 *.

Mr WILSON'S house at Camlachie was the scene of all the
little bustle which now became necessary ; and both Mr MEL-
VILL and he, alike dexterous in the use of their hands, found
much amusement in going through the preliminary work, till, at
last, they finished half-a-dozen large paper-kites, from four to se-
ven feet in height, upon the strongest, and, at the same time,
upon the slightest construction the materials would admit of.
They had also been careful, in giving orders, early, for a very
considerable quantity of line, to be spun of such different sizes
and strength, as they judged would best answer their purpose ;
so that one fine day, about the middle of July, when favoured
by a gentle steady breeze, they brought out their whole appara-
tus into an adjoining field, amidst a numerous company, consist-
ing of their friends and others, whom the rumour of this new
and ingenious project had drawn from the town.

They began with raising the smallest kite, which, being ex-
actly balanced, soon mounted steadily to its utmost limit, carry-
ing up a line very slender, but of a strength sufficient to com-
mand it. In the mean time, the second kite was made ready.
Two assistants supported it between them in a sloping direc-
tion, with its breast to the wind, and with its tail laid out even-
ly upon the ground behind, whilst a third person, holding part
of its line tight in his hand, stood at a good distance directly in
front. Things being so ordered, the extremity of the line be-
longing to the kite already in the air, was hooked to a loop at

* As no public notice has hitherto been taken of this matter, though Mr WIL-
SON had always some thoughts of doing so, it is hoped the following detail will not
prove unacceptable or tedious to the reader.

286 Biographical Account of DR WILSON,

the back of the second, which being now let go, mounted very
superbly, and in a little time also took up as much line as could
be supported with advantage ; thereby allowing its companion to
soar to an elevation proportionally higher.

Upon launching these kites according to the method which
had been projected, and affording them abundance of proper
line, the uppermost one ascended to an amazing height, dis-
appearing at times among the white summer clouds, whilst
all the rest, in a series, formed with it, in the air below,
such a lofty scale, and that, too, affected by such regular and
conspiring motions, as at once changed a boyish pastime into a
spectacle which greatly interested every beholder. The pressure
of the breeze upon so many surfaces communicating with one
another, was found too powerful for a single person to withstand,
when contending with the undermost strong line, and it became
therefore necessary to keep the mastery over the kites by other
means.

This species of aerial machinery answering so well, Mr WIL-
SON and Mr MELVILL employed it several times during that and
the following summer, in pursuing those atmospherical experi-
ments for which the kites had been originally intended. To ob-
tain the information they wanted, they contrived that thermo-
meters, properly secured, and having bushy tossels of paper tied
to them, should be let fall at stated periods from some of the
higher kites j which was accomplished by the gradual singeing of
a match-line.

When engaged in these experiments, though now and then
they communicated immediately with the clouds, yet, as this hap-
pened always in fine dry weather, no symptoms whatever of an
electrical nature came under their observation. The sublime
analysis of the thunder-bolt, and of the electricity of the atmo-
sphere, lay yet entirely undiscovered, and was reserved two years
longer for the sagacity of the celebrated Dr FRANKLIN. In a

late Professor of Practical Astronomy in Glasgow. 287

letter from Mr MELVILL to Mr WILSON, dated at Geneva, 21st
April 1753, we find, among several other particulars, his curiosi-
ty highly excited by the fame of the Philadelphian experiment ;
and a great ardour expressed for prosecuting such researches by
the advantage of their combined kites. But, in the December
following, this beloved companion of Mr WILSON was removed
by death, — to the vast loss of science, and to the unspeakable
regret of all who knew him.

In the year 1752, Mr WILSON, who had married JEAN SHARP,
daughter of WILLIAM SHARP, a reputable merchant at St Andrew's,
brought his family to Glasgow. About five years afterwards he
invented the Hydrostatical Glass-bubbles, for determining the
strength of spiritous liquors of all kinds, which long experience,
especially among the distillers and merchants in the West Indies,
has now shewn to be more accurate and more commodious than
the instruments formerly used. From the minutes of a Philo-
sophical and Literary Society, composed of the Professors and
some of their friends, whose meetings were held weekly within
the College, it appears that these hydrostatical bubbles made the
subject of a discourse delivered by Mr WILSON in the winter of
1757. At this time he also shewed how a single glass bubble
may serve for estimating very small differences of specific gravi-
ty of fluids of the same kind, such as water taken from different
springs, or the like. This he did by varying the temperature of
such fluids, till the same bubble, when immersed, became sta-
tionary at every trial, and then expressing the differences of their
specific gravity, by degrees of the thermometer, the value of
which can be computed and stated in the usual manner.

In the year 1758 he read another discourse to the same so-
ciety, upon the motion of pendulums. On this occasion he ex-
hibited a spring-clock of a small compass, which beat seconds by
means of a new pendulum he had contrived, upon the principle
of the balance, whose centres of oscillation and motion were verv

•

VOL. X. P. II. O O

288 Biographical Account of DR WILSON,

near to one another. At one of the trials, it performed so well
as not to vary more than a second in about forty hours, when
compared with a very exact astronomical clock near to which it
was placed. It was some view of rendering much more simple
and cheap the machinery of ordinary movements, by the slow vi-
brations of such a pendulum, which induced Mr WILSON to pro-
secute these experiments.

Not long after this, he also put in execution a remarkable
improvement of the thermometer, which consists in having the
capillary bore drawn very much of an elliptical form, instead of
being round. By this means the thread of quicksilver upon the
scale presents itself broad, and much more visible than it does in
a cylindrical bore of the same capacity; The difficulty of con-
structing thermometers of this kind, had nearly hindered him
from completing his invention, as the thread of quicksilver was
found extremely liable to disunite when descending suddenly in
so strait a channel. But, by his long experience, joined to far-
ther investigation, and more trials, he at last discovered a method
of blowing and filling thermometers with flattened bores, which
freed them entirely from this defect.

About the same time, also, he conceived the design of con-
verting a thermometer graduated for the heat of boiling-water,
into a Marine Barometer, in consequence of the well-known dif-
ference of temperature which water, when boiling, acquires un-
der the variable pressure of the atmosphere. This he effected,
by making a boiling-water thermometer, about a foot in length,
with a pretty large ball, and having a thread of quicksilver as
broad and visible as was consistent with a very perceptible run
Aipon small alterations of temperature. The stem of this ther-
mometer he fortified, by inclosing it in a cylindrical case of white
iron, having soldered to it, at its lower end, a socket of brass for
receiving half of the ball, which afterwards became entirely de-

late Professor of Practical Astronomy in Glasgmv. 289

fended, by screwing to the socket a hemispherical cap. At the
other end of the case which environed the stem, there was sol-
dered a tube of brass, wide enough to admit a scale of proper di-
mensions, before which there was an opening in the tube, de-
fended by glass.

The utmost range of the scale he determined by the points,
where the thermometer was found to be stationary when the ball
and a certain part of the stem were immersed in water, boiling
under the greatest variations of pressure which the climate af-
forded. The interval so found, he subdivided by other observa-
tions into degrees, which corresponded to inches of the barome-
ter, and which were so denominated upon the scale.

In the year 1756, the College of Glasgow, upon the death of
Dr ALEXANDER MACFARLANE of Jamaica, a great lover of, and
proficient, in the sciences, received a legacy of a valuable collec-
tion of astronomical instruments, which that gentleman had got
constructed at London by the best artists, and had carried out
with him to Jamaica, with a view of cultivating astronomy in
that island. The College, upon this, soon built an observatory
for their reception, which, by medals placed under the founda-
tion, was called by the name of their generous benefactor ; and
Mr WILSON was immediately thought of by the members of the
Faculty, as a proper person for taking charge of it, and making
the astronomical observations. At this juncture his Grace AR-
CHIBALD, Duke of Argyle, who had all along continued his pa-
tronage to Mr WILSON, more especially since he had brought the
art of letter-founding into Scotland, used his influence with Go-
vernment, and procured his Majesty's presentation, nominating
and appointing him Professor of Practical Astronomy and Ob-
server in the College, with an annual salary of fifty pounds, pay-
able out of the Exchequer; and, accordingly, in 1760, he was
admitted to this new office by the unanimous and most cordial
welcome of all the members of the Faculty.

o o 2

290 Biographical Account of DR WILSON,

His two eldest sons, who had by this time entered upon a
course of liberal education, not long after took upon them the
further enlargement and improvement of the letter-foundery ; and,
before dismissing this topic, it deserves to be mentioned, that Mr
WILSON lived to such .an advanced age, as to enjoy in the most
feeling manner the reward of his early diligence and excellent
example, in seeing the business rising in their hands to the high-
est reputation, not only in these kingdoms, but in foreign coun-
tries.

In 1763, when upon a visit at St Andrew's, an honorary de-
gree in medicine was conferred upon him by his Alma Mater.

Among the objects which now occupied him in the Observa-
tory, his former labours towards improving the reflecting tele-
scope were resumed, and pursued for a considerable length of
time, with a view of obtaining some certain method of giving the
parabolic figure to the great speculum. These trials were made
upon a variety of metals, comparatively of a small diameter, and
focal distance ; but he regarded them only as preliminary ones,
and had always in contemplation to engage with apertures of
much greater dimensions. He was often heard to regret, that
no crowned head, or wealthy association, ever thought of patro-
nising an attempt to construct some vast telescope, to be em-
ployed in making discoveries in the Moon or Planets, or in ex-
ploring the Heavens ; and, it is more than probable, that if his
own means had been less circumscribed, he would of himself
have attempted something of this kind. The more recent la-
bours, and brilliant success, of the exceUent Dr HERSCHEL, have
fully shewn that such suggestions were by no means romantic ;
and the writer of this account, who has had the happiness of be-
ing well acquainted with both these men, has often remarked a
striking resemblance in their character and turn of mind.

In 1769, Dr WILSON made that discovery concerning the so-
lar spots, of which he has treated in the Philosophical Transac-

late Professor of Practical Astronomy in Glasgow. 29 1

tions of London for 1774. Not long after he entered upon this
new field, the nature of the solar spots was announced by the
Royal Society of Copenhagen as the subject of a prize essay.
This induced him to transmit thither a paper written in the La-
tin language, containing an account of his observations, and of
the conclusions drawn from them. In return, he obtained the
honourable distinction of a gold medal of near sixteen guineas
intrinsic value, having, on its reverse, the figure of Truth pen-
dent in the air, holding a wreath in one hand, and in the other
a perspective glass, and the motto, Veritati luciferce.

As an astronomical observer, he was remarkable for a sharp
and clear eye, devoid of all blemish, and which, too, without be-
ing liable to fatigue, had long been inured to examine and to
judge of small objects in their nicest proportions ; a circumstance
which must have proved of great advantage to him, when em-
ploying his sight upon celestial appearances by means of the te-
lescope ; and it required only to know him, to have the fullest
assurance of his fidelity in rendering an account of his observa-
tions.

His discovery in regard to the solar spots, though it be gain-
ing ground more and more among those most conversant in astro-
nomy, yet, like many other new discoveries, has not escaped its
share of opposition. This gave him occasion to publish, in the
Philosophical Transactions of London for 1783, the second pa-
per upon that subject, after a silence of near ten years, wherein,
upon the authority of many more observations made in that in-
terval, he obviates objections, and maintains the reality of his
discovery, with an entire conviction. The amount of it is, " That
the spots are cavities or depressions in that immensely resplen-
dent substance which invests the body of the sun to a certain
depth ; that the dark nucleus of the spot is at the bottom of this
excavation, which commonly extends downwards to a space equal
to the semidiameter of our globe ; that the shady or dusky zone

292 Biographical Account of DR WILSON,

which surrounds the nucleus, is nothing but the sloping sides of
the excavation reaching from the sun's general surface downward
to the nucleus or bottom." All this he has demonstrated by a
strict induction drawn from the following phases of the spots, as
they traverse the sun's disk.

When a large well-formed spot, consisting of a dark nucleus,
and its surrounding umbra or dusky zone, is seen upon the
middle of the sun's disk, the zone is generally equally broad all
around ; but when the same spot verges near to the limb, that
side of the dusky zone which lies nest to the centre of the disk,
begins much sooner than the side diametrically opposite to turn
narrower, and at last disappears, while the other still remains
dilated and visible. And, in like manner, when a spot enters the
disk, by the sun's rotation, we see first the nucleus, and the up-
per and under sides of the shady zone or umbra, together with
that side of it nearest to the limb, whilst the side opposite is still
wholly invisible. But as the spot advances farther upon the
disk, that side of its dusky zone which lately was invisible, now
shews itself, and continues to enlarge more and more, till it be-
comes as broad as any other part surrounding the nucleus.

These phases, which he found so very palpable when observ-
ing carefully the great solar spot in November 1769, and so very
frequent, though less obvious, in numberless other spots of a
smaller size, which for several years afterwards he examined,
prove in the clearest manner that the spots themselves are de-
pressions in the luminous matter of the sun, and lead to many
new and interesting ideas concerning the nature and constitution
of that stupendous body.

But though he was the first astronomer to whose lot it fell
to remark these phenomena of the solar spots which have been
just now described, and to draw such important conclusions from
them, it appears that the celebrated Mr FLAMSTEAD, so far back
as the year 1676, had very nearly anticipated this discovery.

late Professor of Practical Astronomy in Glasgow. 293

For, one day when observing a spot of considerable size near the
sun's limb, he actually beheld this appearance of the dusky zone
.which belongs to the nucleus, finding it almost wholly deficient
on that side which respected the centre of the disk ; and this, too,
when the distance of the spot from the limb corresponded very
nearly with that which Dr WILSON found to be so constant in
his observations. Mr FLAMSTEAD was then, indeed, viewing his
spot in peculiar circumstances, and the most favourable of all to
perfect vision of the sun, as, by the intervention of a mist, he was
enabled to use his telescope without the help of tinged glass put
before his eye. The following is his account of this remarkable
observation, in which, by the word macula, Mr FLAMSTEAD evi-
dently means the nucleus of the spot, and by nubicula the dusky
zone which surrounds it.

" 1676, Nov. 9. Deinde densi adeo vapores excepere solem, ut
per ipsos licuit ilium nudis oculis intueri. Adhibito turn lon-
giore tubo absque vitro rubro, (quo oculum ad versus ejus splen-
dorem munire soleo) maculum contemplatus sum : distincta valde
videbatur, ejusque figuree quae in schemate adpingitur : ' Nu-
' becula ipsi circumducta elliptica omnino ; sed, quod valde mi-
' ratus sum, admodum dilatata a parte limbum respiciente ; ab
' altera vero versus centrum, macuke fere cohserere videbatur.'

" Observavi dein macuke a limbo proximo distantium 1' 13"."
Hist. Cosiest. FLAMSTEEDII, vol. prim. p. 363.

When Dr WILSON saw the great spot on the 23d November
1769, it had nearly the same situation upon the disk, and the
same aspect as the one here described. But, at that time, like
Mr FLAMSTEAD, he had no conception of what was signified by
such an appearance. It was not till next day, after remarking
certain striking alterations of the form both of the nucleus and
umbra, that the suggestion first arose in his mind of the spot be-
ing an excavation or depression on the luminous matter of the

294 Biographical Account of DR WILSON,

sun ; which idea, the subsequent observations of the same spot
most evidently confirmed.

Not long before his death, in turning over at more leisure the .
pages of this admirable astronomer, Dr WILSON, for the first
time, met with the above passage, and was pleased at finding so
remarkable a coincidence as to the leading fact upon which his
discovery rests.

Among his papers there were found many letters he had re-
ceived from Dr MASKELYNE, upon whose correspondence Dr
WILSON set a very high value. All his papers, published in the
Philosophical Transactions of London, were communicated by
that friend. Among these, we find a short one in the volume
for 1774, wherein he proposes to diminish the diameter of the
finest wires, used in the focus of the astronomical telescope, by
flattening them according to a method there described ; an idea
which, though very simple, seems extremely worthy of atten-
tion.

In the month of January 1777, when conversing, as he often
did in the evenings, with his son, who had now made some pro-
ficiency in the sciences, their attention was somehow turned to
the following query, proposed by Sir ISAAC NEWTON, among
many others, at the end of his Optics, namely, " What hinders
the fixed stars from falling upon one another ?"

In reflecting upon this matter, they readily came to be of
opinion, that, if a similar question had been put in respect of the
component parts of the solar system, it would have admitted of
a very easy solution, on account of periodical motion appearing to
them as the great mean employed by nature for counteracting
the power of gravity, and for maintaining the sun and the whole
retinue of planets, primary as well as secondary, and of comets,
at commodious distances from one another.

In like manner, Dr WILSON thought it not unreasonable to
suppose, that the same principle might have assigned to it a do-

late Professor of Practical Astronomy in Glasgow. 295

minion incomparably wider in extent, and that the order and
stability, even of a universe, and of every individual system com-
prehended in it, might depend upon periodical motion round
some grand centre of general gravitation. This conception, be-
sides appearing to them warranted by every view they could take
of the nature of gravity, seemed moreover to receive some sup-
port from the discoveries which, since the time of the great HA-
LEY, have been made of what has been called the " Proper mo-
tions of the fixed stars," and particularly from the opinion enter-
tained by that excellent astronomer Dr MASKELYNE, " That,
probably, all the stars are continually changing their places
by some slow and peculiar motions throughout the mundane
space."

Soon after this view had arisen, out of the familiar conversa-
tion above mentioned, it was published in a very short anony-
mous tract, entitled, " Thoughts on general Gravitation, and
Views thence arising as to the state of the Universe." The
chief inducement to so early a publication, was the hope of draw-
ing immediate attention to so interesting a point, which might
possibly lead to the discovery of some way by which the matter
might be brought to the test of observation.

It is quite obvious, that the foregoing suggestions necessari-
ly imply a motion of the solar system, as one of that immense
host, which, for what we yet know, may be subjected to the laws
of periodical revolution. Accordingly, it early occurred, that,
perhaps the most advantageous way of advancing in this investi-
gation, might be to try to find out, if possible, symptoms of such
a law as affecting that system to which we ourselves belong.

It sometimes struck him, when looking over the progress of
philosophical discovery, that many things of high moment appear
to have lain long wrapped up in embryo, by our not employing
ourselves more frequently in what may be called " a direct search"
and in filling up with more attention and boldness the list of de-
VOL. x. P. ii. p p

296 Biographical Account of DR WILSON,

siderata. Between this last step, and the accomplishment of a
profound discovery, he conceived that the transition might some-
times be made with no great effort of invention, by only sifting
carefully such principles as are already known and familiar to us,
and availing ourselves of them in their full extent.

It was by proceeding in this way, and, when considering the
manner by which the motion of light would be affected by re-
flecting and refracting media, themselves moving with great ve-
locity, (a most interesting field in Optics, then wholly unculti-
vated), that two principles came into view, either of which may
possibly serve us in detecting a general motion belonging to the
solar system, relatively to the surrounding fixed stars, or in pro-
ving a negative with regard to it. Of these, a very summary ac-
count has been given in the historical part of the Edinburgh
Philosophical Transactions, vol. i. But, should they be success-
ful in discovering such a concealed motion, the same principles
cannot fail of determining the velocity and direction of it ; and,
in process of time, whether such a translation of the whole sys-
tem be in a straight line or a curve, and if in a curve, whether it
be of such a kind as may indicate a periodical revolution. And
it needs scarce be mentioned, that if such a thing should actu-
ally be made out, besides enriching astronomy with that know-
ledge which depends upon measurable parallaxes in the sphere
of the starry firmament ; it would also bestow a very high autho-
rity upon Dr WILSON'S suggestions, of what possibly may be the
plan of Nature in upholding the universe.

At the time of the last-mentioned publication, he was sixty-
three years old, but still continued to enjoy the blessings of an
uninterrupted state of good health. In the year 1784, at the
recommendation of the University, his Majesty was graciously
pleased to nominate and appoint PATRICK WILSON, A. M., Dr
WILSON'S second son, to be assistant and successor to his father,
as Professor of Practical Astronomy and Observer ; a circum-

late Professor of Practical Astronomy in Glasgow. 297

stance which heightened the consolations he enjoyed during the
evening of life.

In March and April 1786, when he had nearly completed his
seventy-second year, it became apparent to his family and friends
that his constitution and strength were fast declining. After a
gradual and easy decay, which lasted throughout the whole of
that summer and autumn, and which he bore with the utmost
composure and resignation, amidst the tender solicitudes of his
surrounding family, he at last expired in their arms, on the 16th
day of October.

THE private character of Dr WILSON was amiable to an un-
common degree. From his early youth to venerable age he was
actuated by a rational and stedfast piety, enlivened by those
gracious assurances which carry our hopes and prospects beyond
the grave, and sweeten the lot of human life. The cast of his
temper, though uniformly cheerful and serene, was yet meek and
humble, and his affections flowed in the warmest current imme-
diately from the heart. His looks, as well as his conversation
and demeanour, constantly indicated a soul full of innocence and
benignity, in harmony with itself, and aspiring to be so with all
around it.

p p 2

( 298 )

XXI. On the Determination of the Species, in Mineralogy, accord-
ing to the Principles of Professor MOHS, By WILLIAM
HAIDINGER, ESQ. F. R. S. EDIN.

( Read November 15. 1824 J

A. JUSTLY celebrated Naturalist * was of opinion, " that every
" distribution of mineral bodies, which is instituted before the
" determination of the species, must be mere confusion ; while,
" after having established it, according to fixed principles, no
" kind of distribution can be absolutely faulty." The distribu-
tion itself varies, along with the different principles of classifica-
tion, introduced for the purpose of obtaining a systematic ar-
rangement, conformable to the views of Natural History, of Che-
mistry, or of other sciences ; but the Species remains that unique
and unalterable point to which every system, and in fact every
inquiry, must be referred, if we wish to avail ourselves of the
prerogatives of the human mind, and preserve our information
in a scientific form.

The correct determination of the species is equally important
to every branch of our knowledge, in regard to the objects of
nature; since there does not exist another general idea applicable
to the same extent, or equally fertile in producing order and
stability, within the daily increasing mass of observations. It is

* DOLOMIEU, Sur la Philosophic Mineralogique, p. 113. Avant cPavoir prea-
lablement fonde Tespece, toute distribution n'est que confusion ; apres Tavoir etablie
sur des principes fixes, aucune distribution ne peut etre, jusqu' a un certain point, vi-
cieuse, parce qu'elle a toujours un fanal qui Teclaire^ un point de rappel d'ou partent
toutes les relations, et auquel toutes doivent concourir.

Mineralogy, according to the Principles of Professor MOHS. 299

the foundation of scientific Mineralogy, and it must, on that ac-
count, be reduced to constant and philosophical principles, and
not be left at the mercy of chance and empiricism.

If we consider the progress of mineralogical systems from
the first attempts of LINNJBKJS to the present day, it appears
that, while the general scientific form of the systems was insen-
sibly lost, — while essential degrees of classification were aban-
doned,— while even the characteristic marks between substances
resembling each other were deemed superfluous •* ; the determi-
nation of the species continued gradually to approach nearer to
perfection. The system of LINNAEUS, with its ternary distribu-
tion, containing three classes, each of which comprises three or-
ders, and the system of WALLERIUS, with its quaternary distri-
bution, each of his four classes comprehending four orders, gave
way to the systems of CRONSTEDT and WERNER, in which the
characteristic differences, and the order, as a unity of classifica-
tion, disappeared, and to the system of HAUY, in which distinc-
tive characters are introduced, not for discriminating a newly
observed individual from all the rest, but for producing a con-
trast between it and one or a few others, mentioned by name,
and which, moreover, at least in one, and the most numerous of
its classes, contains neither orders nor genera.

However valuable the labours of WERNER may have been in
clearing the mineral system of compound rocks formerly held, along
with the simple minerals, to be proper objects of mineralogy, yet
it is particularly to the accurate investigations of the forms by
HAUY, resting, in part, upon ROME' DE L'!SLE'S observations,
that we are indebted for a more correct determination of the
species contained in his system. This greater degree of correct-

* LINNAEUS, when speaking of the system and principles of CRONSTEDT, says
" J)efinit\ow8 characteristicas inutiles judicat : sufficere npsse." — Syst. Nat,

300 MR HAIDINGER on the Determination of the Species in

ness has been rather the consequence of a more intimate ac-
quaintance with nature, than the result of applying philoso-
phical principles to observation. The application of geometry
in the consideration of forms, imparted precision to a pro-
perty which had hitherto been as vague and uncertain as others
The striking contrasts offered by the forms of different species
being once recognised, it became almost impossible for HAUY,
and subsequent crystallographers, to fall into the same errors
which render the systems of an earlier period useless. The cry-
stallographic method of WERNER was far from affording preci-
sion and security, in its determinations ; and his species, there-
fore, are less correctly circumscribed than those of HAUY, who,
notwithstanding the great superiority of geometrical evidence to
that of mere inspection, considered the introduction of a chemi-
cal principle into the determination of the species as unavoid-
able. Although chemistry has always exercised a great influ-
ence upon the methods received in mineralogy, it cannot be said
that this was more particularly the case in respect to the esta-
blishment of the idea of the species, when it even required the
sagaeity of ROME' DE L'!SLE to demonstrate that there really
were such things as true species in the mineral kingdom, which
till then was denied by the chemists of the day. The Werne-
rian System demonstrates, in every one of its departments, that
it has in fact no principle upon which it might be said solely to
depend ; and the characteristic ingredient itself may be ambigu-
ously interpreted. This want of unity in the principle of the
Wernerian system, has perhaps nowhere been more plainly ex-
pressed than in the first edition of Professor JAMESON'S System
of Mineralogy, where we find the following passage : " The Wer-
" nerian oryctognostic system is founded solely on the natural
" alliances and differences observable among minerals. But on
" what do these depend? WERNER answers, on the quality,

Mineralogy, according to the Principles of Professor MOHS. 301

" quantity, and mode of combination of the constituent parts."
This is in fact tacitly supposing the results of mineralogy and
chemistry already to have been brought to a degree of coinci-
dence, which, though it may be rightly anticipated, has yet not
been established, even by the recent most rapid progress of the
two sciences. In this way the determination of the species of
WERNER, was almost entirely left to a certain tact which admits
of no definition, and must be more admired in the correct results
occasionally obtained, than praised for the certainty with which
the method could be pursued.

The definition of the species, as given by HAUY, that it com-
prises bodies having similar integral molecules, and being composed
of the same elements, in the same proportion *, consists of two he-
terogeneous parts, the first of which, taken alone, is insufficient,
though appertaining to the science, while the second is altoge-
ther foreign to mineralogy.

Natural Philosophy has been defined as " the science that
" unfolds those general principles which connect the events of
" the material world f ." As a branch of natural philosophy,
the science of Chemistry regards the events produced by the ac-
tion of bodies upon each other, in which the changes produced
are permanent, and, therefore, like the whole of natural philoso-
phy, it investigates phenomena in reference to their causes.

It is necessary to know what things those are, which act upon
one another; and definitions must therefore precede, before it is
possible to enter into the details of these sciences themselves.
One word may very often suffice for the definition of one object,
but if there be a great many, some of them, too, possessing very
similar properties, a degree of order must be introduced, even
in the enumeration of the above-mentioned definitions.

- j • - * t •• . '• * •; 1 1 : . . .

* Traitt, t. i. p. 162.

+ LESLIE, Elements of Natural Philosophy, p. 1.

302 MR HAIDINGER on the Determination of the Species in

Confining ourselves, in the present place, entirely to the pro-
ductions of Nature, there are in fact a great many bodies, which
more or less resemble each other. The problem to be resolved
here, as a first process to the introduction of other sciences, will
be to discriminate those which resemble each other most. This
discrimination is the object of Natural History ; a science, there-
fore,, which proceeds upon the principle of similarity.

Hence, it appears, that Chemistry and Mineralogy most
materially differ in regard to the point of view from which they
consider the productions of inorganic nature.

Mineralogy treats of those properties which minerals exhibit
in their natural state ; it collects the individuals within the ideas
of species, genera, &c., and, teaches us how to distinguish them
from one another. Chemistry refers to the substances of which
the natural-historical species consist ; it treats of the properties of
inorganic matter, manifested during the process of its forming
new combinations, and teaches us to recognise these substances,
not only in their pure state, but in all their various mixtures and
combinations ; and it enables us, by the comparison of its results
with the species previously determined, to form an opinion of the
chemical constitution of the latter.

The establishment of what may be with propriety considered
as a Species in Natural History, according to the pure principles
of that science, is its most important object, because its whole
scientific progress depends upon this idea. Mineralogists have
hitherto, almost uniformly, considered it as impracticable to at-
tempt the construction of systems, or the definition of the spe-
cies, without the assistance of chemistry : nay, professed minera-
logists have not hesitated to allow to the identity of chemical
substance, the first and most important place among the consi-
derations upon which they ground their species ; and, owing to
this preponderance, we see Arragonite and Calcareous-spar, and
the hexahedral and prismatic Iron-pyrites, in recently published

Mineralogy, according to the Principles of Professor MOHS. SOS

systems, degraded to subspecies or varieties of carbonate of lime,
and sulphuret of iron * .

These systems shew, that, in reality, they are not intended
for mineralogical purposes, but for exhibiting the present state
of our information respecting the chemical constitution of the
mineralogical species. They endeavour to exclude, in the for-
mation of the species, the influence of those properties which the
productions of inorganic nature possess in their natural state ;
but, it is evident, from the want of consistency in their different
parts, that they cannot arrive at their purpose, unless they ad-
mit, as their leading point of comparison, the species, determined
without the slightest influence of chemical properties or consi-
derations.

Professor MOHS has succeeded in producing a definition of
this idea, founded entirely upon the comparison of those proper-
ties which may be observed while the minerals continue in their
natural state ; and it is the object of the present paper to point
out the course, and to develope the principles, conformable to
which he has arrived at this important result.

There can be no doubt, that, in Mineralogy, as well as in Zoo-
logy and Botany, the species should comprehend the assemblage
of those individuals which are most closely allied to each other.
The exactness of the definition will therefore depend upon the
signification we attach to individuals, and to the degree of al-
liance necessary for joining them within one and the same spe-
cies.

Natural History requires that an individual be a single body,
and, as such, by itself, fit to be an object of natural-historical
consideration. It implies unity of form, and does not presup-
pose the existence of, or connection with, another individual.

* BECDANT, Traite elementaire de Mineraloffie, p. 406. 425.
VOL. X. 1'. II. Q Q

A

304 MR HAIDINGER on the Determination of the Species in

In Botany and Zoology, the determination of what constitutes
an individual, presents little difficulty, at least in the higher
classes of natural bodies. The branch of a tree is not an indi-
vidual itself, but part of one, and is considered in botany as be-
longing to it, on account of its connection with the individual. If
we draw inferences from portions of the fossil remains of animals,
it is likewise only in so far as we are conscious of having observed
parts only of individuals. It is more difficult to establish the
same idea in respect to the class of worms, and other inferior
productions of the animal, and also of the vegetable kingdom,
wherever the multiplication of individuals depends not only
upon the process of generation, but may be effected by dividing
a whole into several parts, which, after some time, may each of
them be again considered as a whole. The definition of the
species is here, in a great measure, dependent upon life, which,
during a certain variable period of time, places these bodies
beyond the reach of the powers that affect inanimate matter,
if removed from that condition. It is as essential to the organic
kingdoms, as the power of crystallisation is to the products of in-
organic nature. This power produces crystals which possess re-
gularity of form, and are evidently individuals. But although
this regularity should disappear, by the contact of several crystals
with each other, yet the continuity of the homogeneous matter
contained within them, and the unity of form, remain unimpair-
ed, and the portions of the compound mass, which may be traced
to the formation of one continuous crystallised product, stiU re-
main individuals. The individuals may be of various sizes, and
often are very small. We have frequently occasion to observe gra-
nular varieties of Calcareous-spar, in which the component indivi-
duals are large enough to be disengaged from their contact with
others, and their properties examined : in other varieties they are
of a smaller size, though still recognisable : but they are often so
small, that only a faint glimmer betrays their existence ; yet,

Mineralogy, according to the Principles of Professor MOHS. 305

from having observed the whole series of compound varieties,
we infer that the last is exactly the same thing as the first, and
only distinguished from it by the size of the individuals. It is
often the case that compound minerals again consist of com-
pound varieties, variously aggregated : thus Peastone is a granu-
lar composition of globular particles ; each of them consists of
concentric layers, parallel to their surface, and each of these on-
ly, if further examined, shews the disposition of delicate fibrous
individuals, in- a direction corresponding to that of the radii of a
sphere. Compound minerals are objects of a natural-historical
consideration, only in so far as they consist of individuals; in the
same way as herds of cattle or forests are considered in zoology
and botany, only because they consist of individuals, the more
peculiar object of these sciences.

Various opinions have been current among mineralogists as
to the exact meaning of the term individual in mineralogy.
Some extended the idea of individuality to every specimen or
fragment of a mineral whatever. Others maintained that per-
fect crystals only could be considered as individuals. According
to the opinion of some, there was only one individual, the spe-
cies itself; while others considered the mountain-mass from
which the specimen had been detached, as the only true indivi-
dual. Many denied the existence of individuals in mineralogy
altogether, or fixed this idea upon the ultimate particles of mat-
ter, in which the mechanical connection cannot be resolved,
without, at the same time, destroying the chemical mixture.

According to Professor MOHS, perfect crystals are individuals,
but not the only ones ; every product of the power of crystalli-
sation, consisting of continuous and homogeneous matter, of a
regular or irregular form, large or small, every component par-
ticle of granular limestone, every fibre of hematite, being like-
wise comprehended within that idea.

The connection among certain individuals, in preference to

Qq 2

306 MR HAIDINGER on the Determination of the Species in

others, in order to constitute a species, is produced by exa-
mining every property by itself, which minerals present, and join-
ing those individuals which either possess the same properties,
or in which the gradations of the differences in their characters
may be considered as producing continuous series. For ex-
ample, if it be impossible to unite two varieties of form, or two
degrees of specific gravity, within a single series, it is evident
that the individuals under consideration themselves cannot be
comprehended within the limits of the same series.

The fundamental proposition upon which, in natural history,
we ground this reasoning, is, that two individuals, which do not
differ in any of their properties, are identical, and may be sub-
stituted for one another, in every inquiry carried on according to
the principles of that science ; so that, if we have found one of
them to belong to a certain class, to a certain order, genus or
species, the other individuals also must belong to the same as-
semblage of natural productions. Two hexahedral crystals of
Fluor, possessing the same violet-blue tint of colour, the same
degree of transparency, and agreeing exactly in hardness
and specific gravity, may serve as examples of identical mi-
nerals.

But if, instead of one of these crystals, we compare the vio-
let-blue hexahedron with another individual of Fluor, possessing
the same form, but a honey-yellow colour, or the same colour,
but the form of a regular octahedron, the two individuals will
evidently be different, even though the rest of their properties
should be critically the same. A difference will also exist, if, in-
stead of the second individual, we take a hexahedron of Gold or
of Rock-salt ; and the difference between the latter individuals
and the individuals of Fluor is no doubt much greater than that
among the above-mentioned crystals of Fluor themselves. From
these considerations we infer, that the difference among several
individuals is not the same in every instance, but that various

Mineralogy, according to the Principles of Professor MOHS. 307

bodies may differ more or less from each other in regard to their
properties.

Experience shews, that, among the vast number of individuals
which may in this way be compared with each other, there are
some in which all the properties agree, except a single one.
Thus we find hexahedrons of Fluor agreeing in every respect, ex-
cept the colour, which is blue, or green, or yellow, or even some-
times perfectly white. This result of immediate observation may,
however, be obtained in a much more general and satisfactory
manner, by considering it in the regular forms of minerals. The
combination of the hexahedron and the octahedron, in an indivi-
dual of Fluor, may be considered as the product of the power
of crystallisation, which caused this individual to assume at
the same time the form of the hexahedron and that of the octa-
hedron. With each of these two forms, all the rest of the pro-
perties, to be observed in the individual, must be necessarily
connected. Every combination, however great the number of
simple forms which it contains, serves to demonstrate this pro-
position. We obtain thus a number of individuals, which belong
to the same series of crystallisation, and which, in regard to the
rest of their properties, are absolutely identical. The preceding
example shews, that if a number of individuals differ only in a
single one of their properties, the differences in this property
may be such as to allow them to be considered as the gradations
of a continuous series. This series may be the series of crystal-
lisation, as in the example ; but it may be every series that can
be possibly produced by gradations in the properties, as, for in-
stance, in colour, in lustre, in transparency, &c. ; nay, it may be
extended even to those properties which remain constant in
every instance, and which may be considered as producing a
series, all the members of which are equal.

Every individual, not excepting those which appear in com-
pound forms, must necessarily be identical with itself. If, in an

308 MR HAIDINGER on the Determination of the Species in

individual of this kind, we enlarge the faces of one of the simple
forms, after the other, we obtain a series of individuals, each of
which is in exactly the same relation to the idea of identity as the
fundamental individual, and though they are not absolutely iden-
tical, yet they agree in respect to this idea. It is evident that
the forms may be arbitrarily exchanged with each other, without
in the least producing any change in respect to the idea of iden-
tity. But two or more individuals become absolutely identical, if
we suppose them to possess one and the same form ; and this is the
process by which individuals, though not identical by themselves,
may yet be brought under the idea of identity. In the example
of Fluor quoted above, the hexahedron and the octahedron, both
possessing the same cleavage, the same refractive and dispersive
powers, the same colour, the same degree of transparency, the
same hardness and specific gravity, &c., may be taken in so far
for identical, as every thing that may be found to be true of the
one, in respect to a more general consideration of natural histo-
ry, will hold equally true in regard to the other : we are entitled
to exchange the hexahedron for the octahedron, or, in general,
any two members of one and the same series of crystallisation,
without destroying the idea of identity.

It is rare to find a number of individuals in nature which dif-
fer only in one of their properties. More generally we meet with
such as, at the same time, deviate more or less in one or several of
their other properties ; and, in order to be capable of drawing more
general inferences, it is necessary to join several series, like those
considered above, within one and the same idea. Let us suppose
a number of individuals of Fluor to be compared with each other,
all of them possessing the same colour, a dark violet-blue, but
various regular forms, as the octahedron (Aberdeenshire), the
dodecahedron (Ehrenfriedersdorf), the hexahedral trigonal-icosi-
tetrahedron (St Agnes), the second variety of tetragonal-icosi te-
trahedrons (Zinnwald), and various combinations of the same

Mineralogy, according to the Principles of Professor MOHS. 309

simple forms. With the same facility, we establish, from experi-
ence, a series of individuals, all of which appear under the form of
the hexahedron, but which present various colours, as honey-yellow
(Annaberg), wine-yellow (Freiberg), white (Alston), apple-green
(Beeralston), sky-blue (St Agnes), azure-blue (Alston). If now
we find an individual which possesses a dark violet-blue colour,
and whose form is the hexahedron, like some of those varieties
which have lately been found at Gourock, this individual may be
considered as a member of the first series, and also, at the same
time, as a member of the second series ; and all the individuals
constituting the one will thus be brought under the idea of iden-
tity with all the individuals of the other ; so that we are now en-
titled to consider as identical not only those combinations of
form and colour which we have really observed, but also those
which may be obtained by joining arbitrarily any form, or any
colour, of the two series with each other. The varieties thus
produced are in fact very frequently likewise observed in nature.
According to the same principle, we may extend our considera-
tions to all those properties of minerals whose gradations form
series, and include an assemblage of individuals, which, notwith-
standing their differences, may yet be brought under the idea of
identity. Those individuals to which the process is not appli-
cable, are, at the same time, distinctly and accurately excluded ;
and the assemblage produced does not only contain every
thing that can possibly be united with it, but, at the same time,
every thing is distinctly excluded, which must be considered to
be foreign to it, according to the principles of natural history, .-/u
These assemblages of individuals, connected by the gradations
of their properties, in the same series, are designated in minera-
logy by the name of Species. The individuals comprehend-
ed, are intimately connected, and, at the same time, distinct-
ly separated, by these series of characters from aU the others.
A species may therefore be defined to be the assemblage of indi-

810 MR HAIDINGER on the Determination of the Species in

viduals, whose natural-historical properties, that is to say, those
properties which may be observed while the mineral continues
to exist, are either absolutely the same, or present gradations
which form continuous series. These are either determinable a
priori, from one given member, or they are the result of accurate
and long continued observation. In the latter we are not per-
mitted to venture one step beyond the boundaries of actual ob-
servation, while, in regard to form, we are entitled to suppose,
according to analogy, that, whatever may be wanting for the
necessary completion of the representation, may still be supplied
in establishing the idea of the species.

We must not pass over unnoticed any of the characters or
natural-historical properties, otherwise the idea of the species it-
self would be incomplete ; the variety displayed in nature could
not be explained sufficiently, nor could it be demonstrated that
we are really entitled to consider certain bodies, under the required
circumstances, as belonging to one and the same species, although
they differ essentially in some of their properties. The properties
which are most useful, and must be particularly attended to, are
those which can be expressed by numbers or measurement ; in
fact, those which allow of the application of mathematics. The
properties referring to form and cleavage, simple and double re-
fraction, angle of maximum polarisation, and the dispersive power,
hardness and specific gravity, are therefore most minutely to be
examined, if we wish to arrive at a correct result. But it would
be contrary to the principles of natural history to determine the
idea of the species according to one single property, because, by
being thus confined, we would soon fancy ourselves under the
necessity of introducing considerations which are foreign to the

science *.

* C'est dans ces sortes de cas ou les caracteres geometriques se taisent, qu'il de-
vient necessaire d'avoir recours a la Chimie. HAOY, Traits, 2de Ed. t. iv. p. 179-

Mineralogy, according to the Principles of Professor MOHS. 311

The progress of the gradations in the single properties of the
individuals within one species, is what may be called with pro-
priety a transition or passage ; and individuals in which such
a progress is observable, are said to pass into each other. The
transitions arise from the series of characters ; and we may infer
from the existence of transitions between individuals, that they
belong to one and the same species. Transitions exist only
within the species, and no transition can take place from one
.species into another, because this very occurrence of a transition
between two supposed species, would unavoidably join them into
a single one. In regard to the numerous incorrect transitions
mentioned in mineralogical books, Professor MOHS says, " that,
" wherever the transition is correct, the determination of the spe-
" cies is erroneous, and vice versa ; that the transition is falsely
" stated, if the determination of the species be correct." *

The species, obtained by the process explained above, is the
object, not the product of classification, as some mineralogists
seem to believe, who begin and terminate classification with-
out previously digesting the idea of species. It has been a
common practice to take advantage of the constancy of the che-
mical composition within well defined natural-historical species,
and thus to exclude, as it were, the definition of the species from
the province of natural history, and to resign it entirely to the
ascendancy of chemical principles. Yet the inferences drawn
from chemical observations presuppose the existence of the spe-
cies, as produced by the comparison of the properties observable
in their natural state. One specimen of a species having been
analysed, we may conclude that other specimens of the same spe-
cies consist of the same principles, in the same proportion ; but,
we are entitled to draw this conclusion only, because the ana-

* MOHS' Treatise on Mineralogy, Transl. vol. i. p. 337.

VOL. x. P. ii. u r

312 MR HAIDINGER on the Determination of the Species in

lysed specimen, and all the rest, agree in their natural-historical
properties, not because they are acted upon by heat, or other
chemical re-agents, in a similar manner ; for this would only be a
repetition of the first process, — from the analysis of one specimen,
(however small), to infer the chemical constitution of the rest of
the individuals or varieties included in the species.

It has often been urged, that the method of Professor MOHS
tended to depreciate the merits of Chemistry, by excluding its
influence in the determination of the species, and in the con-
struction of mineralogical systems. This is by no means a just
observation. Every one is aware, and more particularly those
who have made minerals their study, that it is chemistry, in its
various departments, which gives their labours a manifold inte-
rest, in supplying the link between their abstract considerations
and the wants and comforts of mankind. The only thing ob-
jected to by Mr MOHS, is that unnecessary and improper union
of chemistry and mineralogy, in other words, chemical mineralo-
gy ; which, so far from producing the good consequences so fre-
quently boasted of, may actually be considered as having retard-
ed the researches directed towards the knowledge of the proper-
ties which minerals present in their natural state ; when it was
deemed more satisfactory to ascertain, however imperfectly, the
composition of a mineral, than to measure the angles of its crys-
talline forms, to determine its action upon light, or obtain from
experiment its hardness and specific gravity.

Fortunately for mineralogy, chemists have advanced so far in
their inquiries, that, besides obtaining new compounds, and dis-
covering new modes of producing them, they may now devote
their attention to a more accurate examination of those which
they have known long ago to exist. Professor MITSCHERLICH'S
doctrine of isomorphous bodies, is one of the most interesting
consequences already deduced from these comparisons. The
path entered upon by the artificial production of Pyroxene, of

Mineralogy, according to the Principles of Professor MOHS. 313

Chrysolite, and other species that have long ago been observed
in nature, will no doubt lead to brilliant discoveries. It is to be
expected that, the more we are capable of multiplying the points
of comparison between the natural-historical properties and the
chemical constitution of minerals, the more we shall find them
to tend towards harmony in their results ; but the correct deter-
mination of the mineral species, according to those properties
which it must always possess, in its unaltered and permanent
state, can alone guard us from stooping to empirical laws, when
it is practicable to arrive at results as direct as geometrical de-
monstrations, and not inferior in evidence.

( 314 )

XXII. On the Consolidation of the Strata of the Earth. By
SIR JAMES HALL, Bart. F. R. S. Lond. & Edin.

(Read April 4. 1825J

JL HE public attention, animated by scientific controversy, has
of late years been much directed to Geological subjects ; and
the certainty of many important facts, has in consequence been
ascertained beyond dispute, which were formerly unknown, or at
least involved in such obscurity, that no person could have ven-
tured to assert them, without being charged with extravagance.
But though, no doubt, many branches of this science still re-
main to be investigated, such inquiries may now be said to have
acquired a considerable degree of consistency and interest, from
the substantial basis upon which they have been found to rest.

Thus, in the present day, it is universally admitted, that a
great part, I believe, in point of bulk, by far the greatest part, of
the solid rock which constitutes the external mass of our globe,
is stratified : that these strata, or at least a considerable por-
tion of them, have at one period consisted of a loose assemblage
of sand and gravel, broken from rocks of still higher anti-
quity : that these fragments are infinitely various in quality, in
bulk, and in form ; some retaining their original sharpness,
others rounded and polished by agitation in the water : that
these beds alternate with others of limestone, composed, in a
great measure, of the shells of sea-fish, which shells are also oc-
casionally scattered through the other strata. So that on the
whole, it seems to be ascertained to the satisfaction of all par-

SIR JAMES HALL on the Consolidation of the Strata. 315

ties in geology, that the strata, — those, at least, of later forma-
tion, have once constituted collections of incoherent parts. And
it is further admitted, that these beds have undergone various
remarkable changes, some chemical, some mechanical.

The chemical changes consist in the consolidation of these
loose assemblages into their present state of rock, passing, in that
transition, through boundless varieties, in point of flexibility and
toughness, and occasional brittleness. The mechanical revolu-
tions are no less remarkable, principally in the change of the
strata to their present contorted shape, and elevated position, of-
ten many thousand feet above the surface of the sea ; though there
is full reason to believe that they all once lay in a horizontal
position at its bottom.

I have said that the greatest part of the crust of our habi-
table globe seems unquestionably to be stratified, and produced
from detritus or fragmented materials. The other portion,
though probably the least in bulk, is, generally, the most conspi-
cuous, owing to its durability, elevation, and picturesque beauty.
This kind of rock is contrasted with the former class, particular-
ly in its negative qualities ; in being, according to some geolo-
gists, altogether devoid of stratification in the general mass, and
entirely free from component fragments ; the whole being made
up of crystalline forms, moulded upon each other, in obedience
to certain chemical laws.

This crystalline rock, as the Society are well aware, abounds
in the neighbourhood of Edinburgh, in Arthur's Seat, Salisbury
Craigs, and in Corstorphine Hill. It is decidedly posterior to the
stratified class, of which it penetrates the crevices at all angles,
in the form of dykes or veins, like stucco cast in a mould ; fre-
quently also lodging between the strata in vast shapeless masses.

As the rock in question never fails to preserve this quality of
universal and perfect crystallisation, I heartily concur with Dr
HOPE in bestowing upon it the general name of Crystallite, un-

316 SIR JAMES HALL on the Consolidation of the Strata.

der which are comprehended all substances of this kind, includ-
ing not only Whinstone and Basalt, but also Porphyry, Granite,
and Sienite of every description.

The solid mass of our globe, then, in so far as it is naturally
exposed to our view, or has been penetrated by the labours of
the miner, would appear, (with the exception of some streams
which have flowed from Vesuvius, Lipari, and other volcanoes,
in which the rock possesses a glassy structure), to be compre-
hended under these two classes, Aggregates and Crystallites.

The whole of these rocks, of both classes, furnish, at every
turn, proofs of their having undergone revolutions of the utmost
magnitude ; and much ingenuity has been exerted, in endeavour-
ing to trace these changes to some consistent and rational sys-
tem. But of all the active powers of nature, one only has occur-
red to me as capable of affording a solution, in any degree satis-
factory of the phenomena, — I mean the power of internal heat,
which, in all ages, and in various countries, has made its appear-
ance at the surface of the earth, not unfrequently from under
the ocean, and which still, in our own days, gives occasional
proofs of its unabated activity.

To ascertain the reality and sufficiency of this agent, and to
trace the volcanic fire to its source, with tolerable probability, is,
doubtless, an object of great interest and curiosity ; but it has al-
ways appeared to me, that the progress of geology was retarded
by a premature anxiety to enter into such investigations.

Taking it for granted, however, as, indeed, no one can dis-
pute, that there frequently do arise violent exertions of heat from
under the bed of our ocean, Dr HUTTON held that this might
furnish a rational and sufficient theory of the earth, without en-
tering into any inquiry as to the origin of that heat ; and admit-
ting that there are many geological facts which cannot be ac-
counted for by such a fire as that of Vesuvius, now acting at the
surface, in free communication with the air, he contended that

SIR JAMES HALL on the Consolidation of the Strata. 317

the case may be very different, where that same cause acts at
the bottom of a deep sea, and under various modifying circum-
stances, by which its operation could not fail to be influenced.

This, indeed, constitutes the essence of the Huttonian Theo-
ry, which I learned principally in conversation with its illustrious
author ; and which, since his death, I have taken every means of
submitting to a variety of chemical tests ; being for ever on the
watch for such natural scenes as might illustrate these principles,
as well as for opportunities of making experiments, to deter-
mine whether such modifications on the action of heat were,
or were not, sufficient to justify the expectations of Dr HUT TON.

It was in prosecution of these views that I formerly under-
took a set of experiments, proving, I believe to the satisfac-
tion of the scientific world, the identity of Whinstone and
Lava, of which a fuh1 detail is given in your Transactions. In
farther illustration of the same topic, my experiments on Car-
bonate of Lime were formerly undertaken, by which it was
shewn, that calcareous matters, exposed to heat under pressure,
might be fused ; and, on cooling, would crystallise, so as in every
respect to resemble marble. To these I beg leave likewise to re-
fer the Society.

The immediate object of the paper I have now the honour of
submitting to the Society — the consolidation of the strata — has
been pursued in a similar spirit, and with similar views to those
formerly announced. In making efforts to trace the modifica-
tions which the action of heat would undergo, when compelled
to act under the influence of compression, or of other circum-
stances, all of which, in company, I have always been willing to
distinguish by the name of Plutonic, (although the term was ori-
ginally suggested, ironically, by one of our keenest antagonists,
the late celebrated Dr KIR WAN), I was led to the particular topic
of this paper, by an unexpected scene which presented itself in
my own neighbourhood, in the country.

318 SIR JAMES HALL on the Consolidation of the Strata.

It had often been urged, and apparently with good reason,
against this branch of the Huttonian Theory, that no amount of
heat applied to loose sand, gravel, or shingle, would occasion the
parts to consolidate into a compact stone. And as all my ex-
perience led to the same conclusion, I saw that, unless, along
with heat, some flux were introduced amongst the materials, no
agglutination of the particles would take place. The striking
circumstance above alluded to, as occurring near Dunglass, and
which will be particularly described presently, having suggested
to me the idea that the salt of the ocean might possibly have
been the agent in causing the requisite degree of fusion, I in-
stituted a series of experiments, the details of which I am about
to bring before the Society. By these, I conceive it will be
shown, that this material, under various modifications, is fully
adequate to explain the consolidation of the strata, and many
other effects which we see on the surface of the Earth.

My success, from the first, was such as to promise the most
satisfactory result, though it is only within the last year that I
have been able to command the repetition of the experiments in
a manner fit to be laid before this Society. This must be my
apology to those who hear me, and to such of my friends as take
an interest in these investigations, for having so long delayed
the publication of a set of facts, some of which had presented
themselves to my view many years ago.

Whoever, indeed, has had any experience in the prosecution
of new subjects of experimental inquiry, knows that, owing to
his ignorance of the requisite adjustment of the proportions of
the ingredients, and of other similar arrangements, he must de-
pend, in a great degree, upon chance for the success of his first
results, and that he must often submit to spend much time and
labour upon a subject, even after it has been made out to his
own satisfaction, before he has acquired sufficient command
over its details to answer for the result of any particular experi-

,v I '•

SIR JAMES HALL on the Consolidation of the Strata. 319

ment, so as to be able to produce it with confidence to the
public.

It may be interesting, in the first place, to describe, in a ge-
neral way, the geological structure of the country, in the neigh-
bourhood of the singular scene which gave rise to these specula-
tions,

On different occasions I have laid before this Society obser-
vations made on the rugged shore which occupies the southern
entrance of our estuary the Firth of Forth, which, from being
frequently washed by a very boisterous ocean, presents to view a
distinct exhibition of its internal structure. The eastern part is
occupied by the promontory of Fastcastle, composed entirely of
the elder quality of strata, called by the Germans Grey Wacke.
Further to the west it consists of cliffs formed of Sandstone,
nearly in a horizontal position. These two meeting in the crag
called the Siccar Point, afford the most distinct view we any
where have of the peculiar relation and mutual history of these
two rocks.

More inland, on the borders of Lammermuir, a set of hori-
zontal beds occur, consisting of a loose assemblage of rounded
stones, intermixed with sand and gravel, which bear every ap-
pearance of having been deposited by water, and which, as to
their general history, seem to have undergone no change since
the overwhelming, though transient, agitations of water, of which
I have frequently had occasion to speak in this Society.

In the summer of 1812, as I was returning from visiting the
granitic range which occurs in the water of Fasnet, in the hills
of Lammermuir, and riding down the little valley of Aikengaw,
which deeply indents this loose collection of gravel and shingle,
about two miles above the village of Oldhamstocks, and at the
distance of eight or ten miles from the sea, I was struck with
astonishment on seeing one of these gravel banks, formed, as

VOL. x. P. ii. s s

320 SIR JAMES HALL on the Consolidation of the Strata.

above described, of perfectly loose materials, traversed vertically
by a dyke, which, in its middle, consisted of whinstone, and was
flanked by solid conglomerate ; but this solidity abated gradually
till the conglutination of the rounded masses diminishing by de-
grees, the state of loose shingle and gravel was entirely restored
on both sides. The agglutinated mass adjacent to the dyke bore
no resemblance to the result of calcareous petrifaction ; scarcely
ever gave effervescence with acid ; and, by its gradual termina-
tion, differed from any whinstone-dyke I have seen to penetrate
the strata ; for, in the ordinary case, the termination of the cry-
stallite against the adjoining aggregate through which it passes,
is almost always quite abrupt.

About a hundred yards higher up the valley of Aikengaw,
there occurs an agglutination similar to the last, though without
any whin-dyke, and sufficiently strong to resist the elements, by
which the surrounding matters had been washed away, leaving
the pudding-stone, or agglutinated shingle, to stand up by itself,
in a manner remarkable enough to have attracted the notice of
the peasantry as something supernatural, since they have bestow-
ed upon it the name of the Fairy's Castle.

Farther up the stream, other agglutinations occur frequent-
ly, as we could see in little narrow glens cutting through the
mass ; and higher still, they are so numerous as to meet and con-
vert the whole into one unbroken mass of pudding-stone, occu-
pying all that is exposed to view.

These very remarkable, and, to me at least, novel appearances,
were the first which suggested the idea, that the consolidation
not only of this class of conglomerates, but of sandstone in ge-
neral, had been occasioned by the influence of some substance in
a gaseous or aeriform state, driven by heat into the interstices
between the loose particles of sand and gravel, where it had
acted as a flux on the contiguous parts. On considering what
this penetrating substance might be, and from whence it could

SIR JAMES HALL on the Consolidation of the Strata.

have come, the following circumstance presented itself to my re-
collection at the moment, and promised to afford some assistance
to these conjectures.

A few miles lower down the valley in which the above facts
were observed, at the distance of more than a mile from the sea,
and between two and three hundred feet perpendicularly above
it, there occurs a crag of sandstone, in which a numerous suc-
cession of strata are distinctly visible. Several of these beds
have yielded much to the action of the air, and, in dry weather*
exhibit a considerable white efflorescence, which has completely
the taste of common salt; and so remarkable is this circum-
stance, that the rock has acquired, in the country, the name of
Salt-Heugh.

Here, then, it immediately occurred to me, was probably the
source of an abundant supply of the elastic substance or fumiga-
tor, whose action as a flux had been pointed out by the aggluti-
nations in Aikengaw above described.

I conceived, that, if there were at the bottom of the sea a
bed of sand and gravel, drenched with brine of full saturation,
and that heat were applied to it from beneath according to
Dr HUT-TON'S hypothesis, the first effect would be, to drive the
water from the lowest portion of the sand, and to convert the
salt which remained amongst it, together with the sand, into a
dry cake. During this operation, or until the cake became
quite dry, the absorption of latent heat would prevent the tem-
perature from surpassing the boiling point of brine. But no
sooner was this dryness accomplished, than, I imagined, the tem-
perature of the mass would begin to rise above that pitch ; the
portion of it next the fire would gradually acquire a red-heat ;
that then the salt, being made by the heat in part to assume an
elastic form, would be sent in fumes through the dry cake just
described, and thus, by partially melting the contiguous parti-
cles, produce an agglutination.

Such being my theoretical views, no time was lost in submit-

8 S 2

322 SIR JAMES HALL on the Consolidation of the Strata.

ting them to the test of experiment. Taking it for granted that
a quantity of sea-salt must frequently be formed and deposited,
along with sand and gravel, at the bottom of the ocean (in the
manner I shall have occasion to describe at another stage of this

O

paper), where the water has been collected by its superior speci-
fic gravity, in the form of brine, I proceeded to make the follow-
ing experiments.

Dry salt was placed along with sand, sometimes in a separate
layer, at the bottom of the crucible, and sometimes mixed through-
out the experiment : the whole was then exposed to heat from be-
low. I found that the salt was invariably sent in fumes through
the loose mass, and by its action produced solid stone in a manner
completely satisfactory, as illustrative of the facts in Aikengaw ;
and so as to give a good explanation of the production of sand-
stone in general.

These artificial stones are of various degrees of durability and
hardness ; — some of them do not stand exposure to the elements,
and crumble when immersed in water ; — some resist exposure for
years ; — others are so soft as not to preserve their form for any
length of time ; — while some bear to be dressed by the chisel ;
and, it may be remarked generally, that, as far as the results of
my experiments have been compared with natural sandstone,
the same boundless variety exists in both cases. A striking in-
stance of tlu's resemblance occurs in the case of the Salt-Heugh,
the sandstone of which, when immersed in water, crumbles down,
exactly in the same manner as those results of my experiments
which taste much of salt.

The fumes of the salt, no doubt, act, in ah1 these cases, as a
flux on the siliceous matter, and thus cement the adjacent par-
ticles together. The Society are, doubtless, well aware of the
power of salt fumes in glazing pottery ; and the analogy, I con-
ceive, is complete. It is the application alone that is new.

So far the results were satisfactory. But it next occurred,
that it might be plausibly objected, that the presence of the su-
perincumbent cool ocean, would interfere with the process, on

SIR JAMES HALL on the Consolidation of the Strata. 323

the principles of latent heat. To put this to the test, I pro-
ceeded to expose a quantity of sand, covered to the depth of
several inches with common salt-water, to the heat of a furnace,
and, as the liquid boiled away, replenished it from time to time
by additions from the sea. Of course it gradually approach-
ed to a state of brine. But this proved a very tedious operation,
requiring a continued ebullition, during three weeks without
ceasing, before it became sufficiently saturated with salt by the
discharge of the fresh-water ; and I thought it much easier, and
no less satisfactory, to employ brine from the first, formed at
once by loading the water with as much salt as it could dissolve,
amounting to about one-third of its weight.

The vessels employed in these early experiments, were the
large black-lead crucibles used by the brass-founders. I filled
the vessel, which was 18 inches high and 10 broad, nearly to the
brim with brine of full saturation, the lower portion being occu-
pied, to the depth of about 15 inches, with loose sand from the
sea-shore, and thoroughly drenched with the brine. In order to
have a view of the progress of the experiment, I placed an
earthen-ware tube, about the size and shape of a gun-barrel,
closed at bottom, and open at the top, in a vertical position, ha-
ving its lower extremity immersed in the sand, and reaching to
within about an inch of the bottom of the pot, while the other
end rose a foot above the surface of the brine, and could be
looked into without inconvenience.

After a great number of experiments, furnishing an unbound-
ed variety of results, I at length obtained a confirmation of the
main object in view. I observed that the bottom of the porce-
lain barrel, and of course the sand in which it rested, became
red-hot, whilst the brine, which, during the experiment, had
been constantly replenished from a separate vessel, continued
merely in a state of ebullition : the upper portion of the sand,
drenched with the liquid, remained permanently quite loose,

324 SIR JAMES HALL on the Consolidation of the Strata.

but the lower portion of the sand had formed itself into a solid
cake.

On allowing the whole to cool, after it had been exposed to
a high heat for many hours, and breaking up the mass, I was
delighted to find the result, occupying the lower part of the
pot, possessed of all the qualities of a perfect sandstone, as may
be seen in the specimens now presented to the Society. When-
ever the heat was not maintained so long, the sandstone which
resulted was less perfect in its structure, tasted strongly of salt,
and sometimes crumbled to sand when placed in water.

Many of these early experiments were accomplished with to-
lerable success. But still the result was somewhat precarious,
and could not be announced with the confidence that I felt in
presenting my former experiments to this Society.

The cause of this uncertainty I traced to the chemical ope-
ration of the salt, acting as a flux upon the porcelain vessels em-
ployed. This very action, I was well aware, was the main agent
and cause of our success, when kept within proper bounds ; but,
on being allowed to pass those limits, and to act on the contain-
ing vessel as well as on the experiment, it destroyed the vessel,
and converted the whole into a confused mass of slag.

After numberless unsuccessful attempts, and after returning
again and again to the charge, with an interval sometimes of
years, I at last met with a quality in some of the materials to me
altogether unlocked for, by means of which may be obtained suc-
cessful results, with scarcely any risk of failure.

I found that the action of the salt upon the substances of the
crucibles of clay, did not exert itself in the same manner upon
iron; but that a large vessel of cast-iron, 18 inches deep by 10
wide, and a common gun-barrel welded up at the breech, and
open at the top, enabled me to work with the heat of melting
gold, without injuring the vessels, and at any time to produce a
perfect freestone ; thus satisfying our theoretical expectations.

SIR JAMES HALL on the Consolidation of the Strata. 325

Similar results, in all respects, were produced by exposing
pure pounded quartz to the action of the salt fumes, — and also
when gravel, or any other mass of loose materials, was used in-
stead of sand.

Having now shewn, in a satisfactory manner, that salt, whe-
ther in a dry state mixed along with loose materials, or driven
in fumes through them, or applied in the state of brine, and ex-
posed to heat, is a sufficient agent to produce a consolidation,
such as we see in natural sandstones and other stratified rocks,
it remains to be investigated, whether an adequate supply of
this flux may be reckoned upon in nature.

It is well known that great diversity exists in the degree of
saturation of the sea by salt, at different places ; and BUFFON has
been at much pains in collecting examples of this diversity in
his geological volumes, introductory to his Natural History. It
is known that, in many of the communications between sea and
sea, a constant current sets one way, indicating that the evapo-
ration from the sea, to which this stream flows, surpasses in
quantity its supply of fresh-water from the rivers, rains, and
springs. This is remarkably the case with the Mediterranean,
into which a perpetual stream sets from the ocean, at the Gut of
Gibraltar. We have reason, then, to conclude, both that the sur-
face of the Mediterranean is lower than that of the ocean, and
likewise that the quantity of salt in the former is perpetually on
the increase ; so that the specific gravity of the waters, and the
intensity of their saturation, must be perpetually advancing to a
state of brine. I am well aware, that an attempt has been made
to render such a conclusion unnecessary, by the supposition of a
counter-current flowing at the bottom, out of this great basin ;
but such suppositions are, in my opinion, altogether gratuitous.
. What is here said of the Mediterranean, will apply no less to
other seas, and even to the great oceans. And wherever a basin

326 SIR JAMES HALL on the Consolidation of the Strata.

occurs, in which a bottom of great depth is surrounded by a
ridge comparatively shallow, we may expect to find the lower
portion, at least, of the water in a state approaching to brine.

Without any such theoretical explanation of the manner in
which a supply of salt is supposed to be formed, it may perhaps
be considered sufficient for my purpose, to recal to the recollec-
tion of the Society, that there are in almost every part of the
world vast districts of rock-salt, and in some countries extensive
salt lakes and salt rivers ; and in our own country we have
many instances of brine springs, besides rock-salt in abundance.
Here then it seems to me, we are plentifully furnished with
the means of accounting, in the manner experimentally shewn,
for the agglutinations of such gravel as that of Aikengaw and
for the strata of the Salt-Heugh, which, by an easy analogy,
may be transferred to sandstone in general, and, perhaps, to
stratified rocks of every description.

A member of this Society, however, well known by his scien-
tific acuteness, alleged, first in his public lectures, and afterwards,
upon my requesting an explanation of his objection, again re-
peated, that I was not justified in such theoretical conclusions,
respecting the influence of heat at the bottom of the sea, since
the neighbourhood of the cool water would necessarily counter-
act that influence.

In answer to this difficulty, I must beg leave to remark, that,
in all my experiments above alluded to, the sand (viewed by means
of the gun-barrel) was seen to become red-hot during the process
of consolidation, while the superincumbent brine remained boil-
ing above ; and it was even found easy, by supplying cool brine
in sufficient quantity, to maintain the temperature of the fluid
permanently such, that the hand could be plunged into it at
top, without injury, the sandstone below remaining all the while
at a full red heat. But whenever I repeated this experiment*

SIR JAMES HALL on the Consolidation of the Strata. 327

with every circumstance the same, both as to duration and tem-
perature, as in the example above detailed, but in which, instead
of brine, fresh water was used, the result was very different. The
lower part of the gun-barrel, immersed in the sand, and in
which gold had melted in the brine experiment just mentioned,
now remained permanently black and cold; and the whole of
the sand in the pot, when removed from the furnace, fell out
loose by its own weight ; not the least trace of consolidation
having taken place.

We may thus, I trust, presume to have added one more new
and important modifying circumstance of heat, to those already
advanced in support of the Huttonian doctrines ; for, since it has
been experimentally shewn, that heat, under the modifications
produced by the presence of salt, as above described, is fully ade-
quate to the consolidation of loose materials, exposed to its ac-
tion, it may fairly be presumed, that salt has performed a part,
and a very important part, in the consolidation of the strata of
the globe.

I should be doing injustice to the subject, were I not to state,
that, besides the views developed in the foregoing paper, and
supported by actual experiment, many others have occurred to
me, respecting the agency of salt vinder various modifications,
and all bearing more or less directly upon the Huttonian
Theory of the Earth. Some of these views have been submitted
to the test of experiment, and the results, as far as they have
yet been carried, give me great hopes of ultimate success.
Others are still in the shape of mere conjecture ; and none of them
are yet in a state to lay before the Society in detail. A simple
allusion to one or two of the most important of these views may
probably be received with indulgence ; and I shall be very happy
if gentlemen possessed of adequate leisure, shall be induced to

VOL. x. P. ii. T t

328 SIR JAMES HALL on the Consolidation of the Strata,

follow up, by actual experiment, what I have thrown out as mere
matter of speculation.

I conceive that salt, in the state of fumes, and urged by a
powerful heat, possibly also modified by pressure, or perhaps
combined with other substances, may have penetrated a great
variety of rocks, acting as a flux on some, as in basalt, granite,
&c. ; agglutinating others, as in the case of sandstone, pudding-
stone, &c. ; softening others, as in the case of contorted strata
of greywacke. In many cases, too, I conceive that these fumes
may have had the power of carrying along with them various
other materials, such as metals in a sublimed state, which would
in this way be introduced into rents, veins, and cavities, or may
even have entered into the solid mass of the rocks, which I ima-
gine these fumes may have had power to penetrate. I have
already tried some experiments in pursuit of these ideas. Salt,
for instance, has been mixed with oxide of iron, reduced to fine
powder, and then exposed to heat along with quartzose sand
The iron, I found, was borne up along with the salt fumes.
The sandstone, formed in this way, was deeply stained with iron,
and other most curious appearances presented themselves.

Every one who has seen a sandstone quarry, must have no-
ticed evident traces of iron, the rock being stained in a great va-
riety of ways ; sometinfes in parallel layers, — sometimes in con-
centric circles, or rather in portions of concentric spheres, like
the coats of an onion,-*-and, generally speaking, disposed in a
way not accountable by deposition from water. All these ap-
pearances I would account for, by supposing the rock, either at
the moment of its agglutination into sandstone, or at some sub-
sequent period, to have been penetrated by the fumes of salt,
charged with iron, also in a state of vapour.

I may mention one very curious result of my experiments
with salt and iron, acting upon sand, namely, that, upon break-
ing up the specimen of artificial sandstone, an appearance often

SIR JAMES HALL on the Consolidation of the Strata. 329

presents itself of incipient crystallisation, if I may use this term ;
a number of large, shining, parallel faces pervade the whole mass,
and, by holding the specimen at the proper angle to the light,
this appearance becomes very obvious. What the nature of these
crystals is, I have not investigated ; but as they very much re-
semble what we see in different kinds of sandstone, I am of opi-
nion that they hold out a fair expectation, of our being able to
produce many of the crystalline appearances with which we are
familiar in nature.

Common sea-salt, such as I have used, as is well known, is
not pure muriate of soda ; and, in my experiments, I have mixed
various other substances with it. In Nature, we must suppose
that various contaminating substances would in like manner oc-
cur, to diversify the phenomena ; and, accordingly, we do find a
boundless variety, in the aspect not only of sandstone, but of al-
most every kind of rock ; and I am by no means without ex-
pectation, that, in the course of time, we shall be able to imitate
in our laboratory as many of these varieties as we choose to ex-
hibit.

I have long been engaged also in a series of experiments on
the formation of Crystallites, the name by which, as I have be-
fore stated, every crystallised rock might, perhaps, be usefully
distinguished in contradistinction to Aggregates, or those formed
of fragments. This great object in experimental geology, I hope
to accomplish by means of an instrument which I have long had
in use, for the regulation of high heats, a description of which
may probably soon be laid before the Society, together with
some further results in support of the Huttonian Theory of the
Earth.

x.t 2

( 330 )

XXIII. Observations before and after the Superior Conjunction of Venus
and the Sun, with the Mural Circle at Paramatta, 1824. By
His Excellency SIR THOMAS BRISBANE, K. C. B. F. R. S. Lond.
& Edin.

(Read May 16. 1824

iarome-

'hermometer

Transit over

Mean of the

ter.

the Meridian

4 Microscopes.

REMARKS.

out.

in.

wire.

1824.

h- / -,

o / //

0 July 17-

29-688

55.0

55.0

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4 26 34 .5

184 45 36.50

—

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-

57.8

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5 4 28 .5

214 21 14.22

—

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.

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-

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6 48 .5

160 12 51.73

—

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60.0

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7 36 45 .0

191 0 8.30

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18.

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60.2

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7 48 40 .1

189 26 31-62

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29-736

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6 47 .0

160 12 50.05

—

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9 Centre,

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8 12 25 .5

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AR of 0 following L.

J Aug. 1

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400

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4 26 15 .0

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^^~

SIR THOMAS BRISBANE'S Observations on Venus.

331

Barome-
ter.

Thermometer

Transit over
the Meridian
wire.

Mean of the
4 Microscopes.

REMARKS.

out.

in.

1824.

h.

J Aug. 1.

30.164

44.8

53.0

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/ H

5 4 9.0

214* 2l' 3.32

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1^

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8 47 39.2

186 11 57-90

0 1st L.

—

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8 53 58.3

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9 26 14.3

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8 53 45.2

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9 Centre,

8 58 59-3

187 1 6.28

,

h 4.

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183 45 58.37

>I -im "Jo

REMARKS.

.

24th July. The Sun's limb tremulous. The observations on ? good. Very cloudy, with high
wind, which prevented the observation being made on the 29th, 30th, and 31st July.

( 332 )

XXIV. Observations on Two Comets discovered at Paramatta in
1824, by Mr Rumker and Mr Dunlop. Communicated
by his Excellency Sir THOMAS BRISBANE, K. C. B. F. R. S.
Lond. & Edin. in a Letter to Dr BREWSTER, Sec. R. S.
Edin. To which are added the Elements of their Orbits,
calculated by Mr GEORGE INNES, and Mr JAMES GORDON^
A.M. Aberdeen.

(Read May 16. 1825. >

JL HE two Comets which are the subject of this communication
were discovered at Paramatta ; the first by Mr RUMKER, and the
second by our countryman Mr DUNLOP.

The elements of both have been calculated from the obser-
vations of Mr RUMKER and Mr DUNLOP, by Mr GEORGE INNES,
Aberdeen, and Mr JAMES GORDON, A. M.

COMET, August 1824.

1824.

Mean Time at
Paramatta.

Mean JB. of COMET.

North mean De-
clination.

No. of Ob-
servations.

August 21.

8 44 48"S4

245° 24 17,"47

36° 54 17^66

1

23.

7 11 13,70

244 18 58,30

37 65 14,85

11

24.

7 56 8,90

248 43 34,75

38 26 20,12

4

26.

8 1 0,39

242 38 44,46

39 25 24,65

6

27.

7 51 32,63

242 7 31,00

39 45 33,60

7

28.

7 26 36,32

241 37 14,30

40 22 49,24

4

29.

7 41 49,99

241 7 40,70

40 48 10,80

3

31.

7 24 19,26

240 11 32,85

41 42 20,01

5

SIR THOMAS BRISBANE on Two new Comets.

333

1824,

Aug. 21. Comet north, preceding anonymous star of the 7th magnitude, JR. of the
star = 246° 44' 2",47 ; declination 36° 49' 22",I8 ; diff. in M 1° 19' 45",0 ;
diff. in decl. 0° 4' 55",48.

23. Comet north, preceding 25 Hercules, FLAMSTEAD'S Catalogue, diff. in -51

29 9',60; in decl. = 7' 40",35.

24. Comet south, following anonymous star of 7th magnitude, JR of star =

241° 44* 3",30 ; declin. of star 38° 30' 33",32 ; diff. in M = 1° 59' 31",45 ;

diff. in decl. = 4f 13",20.
26. Comet south, following 31 Hercules, BODE'S Catalogue, diff. in JR =

1° 9' 37";70; diff. in decl. = 4' 40",35.
27- Comet south, preceding 49 Hercules, BODE'S Catalogue, diff. in JR =

1° 21' 16",30; diff. in decl. = 13' 31",70.
28. Comet north, preceding 49 Hercules, BODE'S Catalogue, diff. in M =

1° 51' 33",00; diff. in decl. = 1* 44",54.
29- Comet north, following 13 Hercules, BODE'S Catalogue, diff. in AH =

2" 8' 27",0; diff. in decl. =17' 19",20.
31. Comet north, preceding anonymous star of the 7th magnitude, Al of the

star = 240° 51' 25",25 ; declination of star = 41° 33' 28",47 ; diff. in JR

= 39- 52",40 ; diff. in decl.=: 8' 51",54.

Middle of Observations in Sidereal Time.

Aug. 21. at 18 43 35"70

23. ... 17 17 38,30

24. ... 18 6 37,43

26. ... 18 19 22,83

27. ... 18 13 50,05

28. . . 17 52 46,20

29. ... 18 11 56,00
81. -.18 2 18,50

Elements of Comet.

1824.

Mr INXKS.

Mr GORDON.

M. Time at Paramatta.

Time of the Perihelion passage,
Longitude of the Perihelion, . . .
Place of the Ascending Node,...
Inclination,

Sept. 29. 7 23' 26"
4° 23 12
279 17 56
54 22 14
1-048553

D. H. , „

Sept. 29. 7 25 10
4° 22 11
279 19 13
54 22 22
1-048739

Perihelion distance,

Motion direct.

334

SIR THOMAS BRISBANE on Two new Comets

This Comet is evidently the same as that which was first dis-
covered in Europe on the 23d of July by M. SCHEITHAMMER of
Chemnitz, and the elements of which, as computed by CAPOCCI,
CARLINI, and ENCKE, have been published in the Edinburgh
Journal of Science, vol. ii. p. 171, 172., and vol. iii., where the la-
test elements are given, upon the hypothesis of a hyperbolic or-
bit, which has been found by M. ENCKE to represent the obser-
vations better than a parabolic one. — D. B.

COMET of July and August 1824.

1824.

Mean Time at
Paramatta.

Mean M of Comet.

North mean Decli-
nation.

No. of Ob-
servations.

H. , „

July 28.

6 38 57,11

165 50 57,70

16 1 24,0

12

29.

6 49 24,29

166 43 15,30

16 41 4,72

8

31.

6 53 35,24

168 18 6,20

17 53 37,25

12

Aug. 1.

6 46 1,41

169 1 58,80

*18 27 14,56

10

3.

7 0 33,34

170 24 9,80

19 30 25,74

14

4.

6 50 17,73

171 0 52,85

19 59 40,65

9

6.

6 54 44,46

172 9 20,30

20 55 15,23

6

8.

6 40 28,72

173 11 34,6

21 44 41,35

1

11.

6 50 56,35

174 40 29,0

22 54 5,20

1

1824,
July 28. Comet south, preceding t Leonis, diff. in M = 24' 31 ",30 ; diff. in declin.

= 21' 57",61.
29. Comet north, following « Leonis, diff. in M = 27' 46",30; diff. in declin.

= 17' 43'x,12.

31. Comet south, preceding anonymous star of the 7th magnitude, Jl of the
star = 168° 35' 37",50, and the declination 18° 6' 6",30 North ; diff. in
M = 17' 31",30; diff. in declination = 1^ 29",05.

Aug. 1. Comet north, following another anonymous star of 7th magnitude, Jt of
the star = 168° 47' 40",80 ; declination = 18° 18' * 03",37 ; diff. in M
= 14' 18",0 ; diff. in decL = & 11",19.
3. Comet north, following 86 Leonis, diff. in M = 4f 0",80 ; diff. in decl.

• In the original it is inserted 18° 80' 03",37. It probably should have been 18° 18' 3",37.
gives 18° 27' 14",56 for the north declination, as in the Table.

This

discovered at Paramatta in J824.

335

1824,

Aug. 4. Comet north, preceding a small anonymous star, 8th magnitude, JR, of
small star = 171° 1' 9",0; declination = 19° 46' 59",20; diff. in A\ =
& 16",15 ; diff. in declin. = Iff 41",45.
6. Comet south, following 417 Leonis, BOOK'S Catalogue, diff. in JR =

W 46",20 ; diff. in declin. = 2& 44",17.
8. Comet north, following 417 Leonis, diff. in M = 1° 43' 0",5 ; declination

W 41",95.

11. Comet south, following 445 Leonis, BODE'S Catalogue, diff. in JR =
1° 27' 0" ; diff. in declin. = 17' 9",80.

Middle of Observations in Sidereal Time,

July
Aug.

D.

28.
29.
31.
1.
3.
4.
6.
8.

H.

at 15
... 15
... 15
... 15
... 15
... 15
... 15
... 15

2
17

29
25
48
45
54
47

46^06
11,46
16,17
37,91
5,14
40,95
4,91
40,0

11. ... 16 9 59,0

Elements of Comet.

1824.

Mr 1 \ M.S.

Mr GORDON.

M. Time at Paramatta.

Time of the perihelion passage,
Longitude of the Perihelion,

July 10. 10 17 30"
259° 45 32
330 29 8
57 0 36
0-5956114

D. H. , „

July 10. 10° 17 41
259 45 31
330 29 8
57 0 36
0-5956147

Place of the Ascending Node, . . .
Inclination,

Perihelion distance,

Motion retrograde.

This comet, which was not seen in Europe, is stated by Dr
OLBERS to have been discovered by Mr RUMKER, and to have
been observed by him from the 15th July to the 6th August.
The following are the elements given of it by Dr OLBERS, as
computed by Mr RUMKER :

VOL. x. P. ii.

u u

336 SIR THOMAS BRISBANE on Tivo new Comets.

H.

Time of Perihelion passage, Mean Time at Paris, July 11. 12 26 27

Longitude of the Perihelion, 260° 16 32

Longitude of the Ascending Node, 234 19 9

Angle between the Perihelion and the Node, 334 2 37

Inclination of Orbit, 54 34 19

Perihelion distance, 0-591263

Motion retrograde.

The difference between these elements and those obtained
by Mr GORDON and Mr INNES is very considerable. Dr OLBERS
remarks, that the observations might have been reduced with
greater accuracy ; and he adds, that we may perhaps expect ad-
ditional ones from Sir THOMAS BRISBANE or Mr DUNLOP. — D. B.

( 337 )

XXV. On the Construction of Meteorological Instruments, so as
exactly to determine their Indications during Absence, at
any given instant, or at successive intervals of Time. By
HENRY HOME BLACKADDER, Esq. Surgeon, MED. STAFF
H. P.

(Read May 2. 1825J

I T is universally admitted, that, in the present advanced stage
of Meteorological Science, nothing would be more desirable
than complete and accurate registers of the indications of Me-
teorological Instruments, — more especially of the Thermometer,
Barometer, and Hygrometer, such registers being cotempora-
neously kept at numerous places, and at various elevations on the
earth's surface. Many are the obstacles, however, which have
been found opposed to such an acquisition.

There are probably but few of those at all conversant with
meteorological pursuits, who have not been induced, at one time
or other, to commence keeping a register. But the necessary
regular inspection of instruments at certain fixed hours of the
day, and for many months or years in succession, has, in most in-
stances, been found to become so irksome, so liable to unavoid-
able interruptions, and so apt to interfere with other equally
important avocations, that few, indeed, have been able to perse-
vere for such a length of time as was necessary to arrive at any
very decided results. As to most of those registers to be found
in circulation, it is well understood, that little or no dependence
can be placed on their accuracy. But, even in those instances
in which accuracy may be expected, if we advert to the great di-

u u 2

338 MR BLACKADDER on Meteorological Instruments

versity of opinion as to the hours at which the indications of in-
struments ought to be noted ; and, consequently, the want of
correspondence between registers kept by different individuals,
the difficulty, or rather the utter impossibility, of deriving any
positive results from a comparison of these registers, must be
abundantly evident. The invention of a thermometer that re-
gisters accurately the highest and lowest temperatures that may
occur during a given period, was doubtless a great acquisition,
and such an instrument has been found of much use in many
highly interesting investigations. If, indeed, it were ascertained
that the mean of the highest and lowest temperatures of the day
was exactly equal, or bore a known and uniform relation to the
mean temperature of the whole day, then would such an instru-
ment be of great utility in determining the general and important
problem of mean temperature. This, however, has not yet been as-
certained, nor can such a problem be solved without much labour,
and an infinity of future observations. The result of some re-
cent observations would certainly lead to the conclusion, that the
mean of the extremes is not the mean of the daily temperature
in such countries as Britain, more especially at certain seasons of
the year, and in certain years, or series of years, less than in
others.

It has been acknowledged, that the only way by which the
mean daily temperature can be determined with accuracy, is by
taking the mean of observations made frequently, and at least
once every hour, during the whole period of the day and night ;
and nothing but the hitherto extreme difficulty of putting such
a method into execution, has prevented its adoption. Some few
individuals acting in concert, and by turns, have persevered se-
veral weeks in registering the hourly indications of the thermo-
meter. But, little is to be expected from such exuberant zeal ;
and, even those most likely to engage in such undertakings, are

which determine the Indications during Absence. 339

not such as would inspire that confidence in regard to accuracy,
that is so indispensably requisite in all such undertakings.

It has been considered possible, however, to procure an accu-
rate hourly register of the thermometer, by engaging a number
of individuals to act by turns, as registers, and for a pecuniary
compensation. But even this method (evincing, as it does, a
true devotion to science), there is reason to fear will prove but
too defective. It must be attended with great expence, and
hence can but rarely, and only in particular circumstances, be
put in practice. On the other hand, the accuracy, and even the
good faith of those who might agree to sell their time for such a
purpose, will by many be considered as questionable ; so that in
the end, and after no inconsiderable trouble and expence, a
lengthy register, of which, it is said, it may or may not be accu-
rate, is perhaps the only reward. That this would be the pro-
bable result in many instances, is the opinion of those who have
had an opportunity of forming a judgment in cases similar to the
one in question : and if I may be permitted to express my own
opinion, derived also from some little experience, I would say,
that, in general, on such occasions, some ingenious contrivance,
of the nature of a tell-tale, would be about as necessary to
insure accuracy, as a well-constructed thermometer.

It would be an ungracious task thus to enumerate so many
difficulties and deficiencies, had I no method to propose by
which these might be, in some measure at least, mitigated and
supplied. But it was to this end alone that the preceding-
remarks were directed. For many years my intention had been
directed to meteorological pursuits, having always in view, as
may be supposed, their connection with, or application to, phy-
siology and pathology, — a connection which has hitherto proved
so lamentably fruitless. I had, consequently, often with others
had occasion to experience and regret the obstacles and difficul-
ties to which I have adverted ; and I had often thought of a me-

340 MR BLACKADDER on Meteorological Instruments

thod by which it seemed probable that these might be overcome
or obviated. It was not, however, till within the last eighteen
months that circumstances permitted my bringing that method
to the test of experience.

For upwards of a year I have been in the daily habit of using
a thermometer, the indications of which may be registered at any
given instant, during absence, and so as to render the tenth of a
degree on Fahrenheit's scale readily distinguishable. Suppose,
then, a gentleman occupied in keeping a register of the varia-
tions of atmospheric temperature, — taking two observations in
the course of the day, — say 10 A. M, and 4 p. M., which, if not the
most proper, are about the most convenient hours. To carry on
his register, he must be at home and disengaged every day, and
exactly at these hours, which must be exceedingly irksome, if at
all possible, for any length of time ; or he must every now and
then trust to others, little skilled perhaps, or in no way interest-
ed in such pursuits, — circumstances sufficient to render the whole
register defective. By the method which I have to propose, this
obstacle is completely obviated. For the observer may be from
home many hours before and after the hour fixed upon for not-
ing his register ; and, on his return, he shall find the tempera-
ture of that hour exactly registered by the instrument.

If we can thus succeed in effecting a register of one observa-
tion at a given instant during absence, it is obvious that we may
so adapt matters as to have a register at successive intervals, —
say at the distance of one hour, half an hour, or two hours, be-
tween each ; and I shall presently have an opportunity of demon-
strating, that, with very little trouble, we can thus ascertain the
exact temperature every hour during the whole course of the day
and night.

If, again, a gentleman wished to carry on a set of ex-
periments at two or more places at the same time, such as by
the sea-shore, and at some inland situation, or at the foot and at

which determine the Indications during Absence. 341

the summit of a mountain, or tower, he would thus have his ope-
rations greatly facilitated, and insured of accuracy.

The principle of this contrivance applies either to the spirit
or mercurial thermometer, and consists in keeping a small index
suspended at, or in contact with, the extremity of the fluid in
the stem of the instrument ; so that the former shah1 accom-
pany the latter in all its movements, until the instant arrive
when we wish to determine the existing temperature. At this
instant the index is so acted upon as to remain fixed to its place,
while the fluid either passes beyond, or retires below it.

When a spirit thermometer is used, the bore of the tube, and
the weight and form of the index, require attention ; but the ad-
justment is not difficult. As to the spirit, there is a certain
strength which seems to answer best, and it must be colourless,
of some age, and carefully and repeatedly filtered. The colour-
ing matter usually added to spirit-thermometers, is in this in-
stance of no use, and would be injurious. For, after a time, the
colouring matter is partially deposited, and particles of this get-
ting into the stem of the instrument, would interrupt the move-
ments of the index. It is for the same reason that old spirit
and frequent filtration are requisite ; for if the spirit is new, and
if not frequently and carefully filtered, small whitish flocculi, or
minute fibres, may be seen suspended in the fluid, from which
interruption to the index is liable to take place. I had, on one
occasion, much trouble in adjusting an index, and, at length, dis-
covered, that the whole had arisen from a very minute particle of
colourless glass, which had by some accident got into the stem of
the instrument. With proper care and attention, however, no-
thing is more simple than the construction of a good and per-
fectly accurate spirit-thermometer, for meteorological purposes
Nothing, at the same time, is more rarely to be met with ; for

.

342 MR BLACKADDER on Meteorological Instruments

such instruments as are usually met with, are exceedingly in-
accurate, and altogether unfit for scientific purposes.

When a thermometer has been constructed in the way I have
described, all that is necessary to keep the index constantly and
exactly at the summit of the fluid, whatever change of tempera-
ture may take place, is to invert the instrument, and retain it
either in a perpendicular or somewhat inclined position ; the at-
traction of the fluid to the index being quite sufficient for the
suspension of the latter, and for overcoming its friction on the
sides of the tube. When, however, the instrument is placed in
a horizontal position, the index no longer accompanies the fluid
in all its motions ; for if the temperature rises, the fluid passes
the index as if no such body were present ; and if the tempera-
ture is diminished, the index is dragged along by the fluid.
Upon this latter property, the Psychrometer, or instrument for
registering the lowest temperature, was constructed. If, then,
we take such a thermometer as I have described, and suspend it
vertically, and in an inverted position, on a moveable axis, it is
obvious, that, by connecting with it a time-piece, we can have it
placed in a horizontal position at any given instant. And if we
also make provision, that the instant the instrument comes to its
horizontal position, its bulb is exposed to a higher temperature
than that of the air, it is evident that the index will point out
the exact temperature of the air at the tune the instrument was
changed from its vertical position, and that it will continue to do
so as long as the instrument retains its new position, and has its
bulb kept at a higher temperature than that of the air.

This, however, will be better understood from the inspection
of a model, than from description. The instrument is rudely
constructed ; but in other respects it is perfectly accurate, ha-
ving been in daily use for the last 15 months ; and, during the
coldest and most stormy, as well as during the hottest weather,
it has always given perfect satisfaction.

which determine the Indications during Absence. 343

After thus fully detailing the principle, it will not be neces-
sary to enter very particularly into the subsidiary details. The
particular form or construction of the instrument being immate-
rial ; it may be modified in many ways, agreeable to the particu-
lar views of each individual.

The means by which the bulb of the instrument is kept at a
higher temperature than that of the air, is the aqueous vapour
originating from the flame of a lamp ; and, in the coldest stormy
weather, the flame does not require to be larger than that pro-
duced by, at most, two small cotton threads immersed in oil.
When gas is at command, that is doubtless the most convenient
combustible, as a minute flame can be kept up almost intermi-
nably, and without requiring any attention. But it is not diffi-
cult to construct a lamp for burning oil, so as to answer every
desirable purpose, and not requiring inspection or adjustment
once in twenty-four or more hours.

I may here notice, that a lamp of very simple construction,
can be made to burn oil without any wick, giving out an intense-
ly white light, and furnishing so regular a supply of heat, that a
thermometer on the outside of a window, with which it may be
connected, shall not vary half a degree in the course of many
hours.

When a mercurial thermometer is used, the difference is,
that, in this case, the instrument is not placed in an inverted po-
sition ; and, when it is brought into a horizontal position, the
bulb, instead of being kept at a higher, must be kept at a lower
temperature than that of the air. This can readily be effected,
by providing the means for supporting a continual evaporation
from the surface of the bulb. When the instrument receives its
horizontal position, the bulb is made to come into contact with a
soft hair-pencil, of a hollow circular form, through which distils
guttatim, and slowly, from a reservoir, some evaporating fluid.
On some occasions, as in a very humid state of the atmosphere,

VOL. x. P. n* x x

344 MR BLACKADDER on Meteorological Instruments

ether may be requisite ; but, on most occasions, rain-water is
sufficient ; the use, however, of common ardent spirits for such
a purpose, is attended with but a trifling expence, and may be
found convenient.

Having thus shown how the temperature of the air and other
bodies may be determined, during absence, and at any given in-
stant, it may readily be conceived, how it may, in like manner,
be determined at successive intervals of time, by multiplication,
and fitting arrangement of the same means. Thus, omitting va-
rious less complete combinations, seven thermometers of the be-
fore-mentioned construction, connected by a very simple piece of
mechanism, will enable us to determine the exact temperature
every hour during the whole course of the day and night, and
that with very little trouble. For, to obtain this, it is neces-
sary to inspect the instrument only three times in the course
of the day, or during that period not usually appropriated to
sleep ; for example, at 7 A. M., 4 p. M., and 11 p. M.

It must be obvious, however, that there is nothing to pre-
vent the number of inspections being reduced to one in the
twenty-four hours, if there was a sufficient reason or motive for
doing so.

The instrument for registering the hourly atmospheric tem-
perature, and which is now exhibited to the Society, is intended
to be fixed on the outside of a window. It must be evident,
however, that the dimensions are much greater than are at all
necessary ; for if constructed by an expert workman, the mecha-
nism connected with the thermometers might be reduced to
about the size of a common musical snuff-box.

Having thus endeavoured to describe a method of register-
ing the indications of the thermometer at any given instant, and

which determine the Indications during Absence. 345

at successive intervals of time, the application of the same prin-
ciple to the registering of the hygrometer will not require much
illustration : For, if it be admitted that the atmizomic hygrome-
ter (that is, a hygrometer constructed on the Huttonian princi-
ple), may be depended upon, all that is requisite to procure an
accurate register is, to attach two thermometers to one slip of
metal, on which is engraved a scale for each, and to keep one of
the bulbs moist with water. When at any instant the instru-
ment thus constructed is brought into the horizontal position,
the index in the one tube will indicate the temperature of the
air, and that in the other the temperature produced by evapora-
tion. Nothing is more simple than this modification of the re-
gistering apparatus, for nothing can be more easily effected than
keeping one of the bulbs moist with water, and in this only does
it differ from that fitted to register the atmospheric temperature
alone. It therefore appears, that, with very little trouble, we
can ascertain the hourly variation of the temperature and humi-
dity of the atmosphere ; and we have the means of greatly facili-
tating other thermometric and hygrometric investigations.

Hitherto (I speak to the extent of my own information)
there has been no method devised for registering even the ex-
tremes of the barometric changes, which does not infer a very
considerable increase of mechanical friction ; and which, conse-
quently, does not include a degree of inaccuracy no way consist-
ent with the present advanced state of meteorological science.
For it is admitted, that, at the present day, a variation in the
elevation of the mercurial column to the five hundredth part of

an inch, must be attended to by those who aim at scientific ac-
curacy.

The principle of the method for registering the indications
of the barometer which I was led to adopt, consists in cutting
off, at a given instant, all communication between the atmos-

x x 2

346 MB BLACKADDER on Meteorological Instruments

phere and the mercury of the barometer, than which certainly,
nothing can be more simple. If, at a given instant, the com-
munication between the air and the mercury be cut off, the
height of the mercurial column must remain unaltered by any
change in the pressure of the atmosphere, until such time as the
communication is restored. And nothing is more simple than
the means by which this interruption of communication can be
effected, during absence, and at any given instant.

An accident, by which my instrument was broken, has put it
out of my power to exhibit a barometer constructed on this
principle. The principle, however, is so self-evident, and the
method of putting it into execution so simple, that little or no
illustration seems requisite. I have therefore made a section of
the cistern *, which will be quite sufficient for any explanation
that may be considered necessary. The cistern is made of iron,
and is about two inches in diameter — the depth of mercury in
the cistern, and the distance between the surface of the mercury
and the top of the cistern must be as small as the correct opera-
tion of the instrument will admit of. To the air-orifice is at-
tached an air-tight stop-cock, and by means of a lever, or other
piece of mechanism, connected with a timepiece, the stop-cock
may be shut at any given instant. In this way he can ascertain
the exact height of the mercurial column during absence, and at
any hour or minute that may be fixed upon.

As we found to be easily effected in the case of the Thermo-
meter and hygrometer, so also in this, by combining several such
instruments in one piece of mechanism, we can have the exact
height of the barometer every hour in the course of the day and
night. Thus f, seven barometers, arranged at equal distances
around a hollow column of wood, four inches in diameter, and

* See Fig. 1. Plate XIII. f See Fig. 2. Plate XIII.

PLATE XUf.

i'nqtfar the fayai Sar.Tran..VoiJ[.-p.3tS.

fy.t.

which determine the Indications during Absence. 347

about three feet in height, having a projection at the base, in
the form of a pedestal, would form not only an elegant but a
very complete and highly useful barometrical apparatus. The
column being hollow not only lessens the weight, but admits of
the timepiece and connecting mechanism being entirely conceal-
ed within it

The barometer, however, may also be arranged on a flat sur-
face * without producing any thing of an unwieldy appearance,
and the adaptation of the mechanism for shutting one of the
stop-cocks each hour in succession, is not thereby rendered more
difficult.

See Fig. 3. Plate XIII.

( 348 )

EXPLANATION OF PLATE XIII.

Fig. 1. Represents a section of an iron cistern for a barometer.

d. An orifice for the introduction of the mercury, afterwards shut up by

means of a screw.

e. The air-duct, having a screw formed on its outer surface.

f. An air-tight stop-cock, having a female screw, by which it is attached to

the air -duct.
g. A small orifice in the side of the stop-cock, to serve as a passage for the

air, and so as to exclude dust.
h. A lever connected with a timepiece, by means of which the stop-cock was

shut, and the communication of the air with the mercury cut off at any

given instant.

Fig. 2. Represents an instrument for determining the height of the barometer each
hour in succession, by three observations in the course of the day.

It consists of a hollow column of wood about 44 inches in diameter, and 84>
inches in height ; the base being about 2 inches in height, and 6J in dia-
meter.

It will be found convenient to have the column divided longitudinally into
two equal parts, and united by means of hinges.

At equal distances, on the circumference of the column, are arranged seven
barometers ; their cisterns being inclosed in the base, and so placed that
their stop-cocks shall form a circle in the interior. By means of a hori-
zontal wheel nearly on a level with the stop-cocks, and which, from its con-
nection with a time-piece, revolves once in seven hours. One of the stop-
cocks are shut each hour in succession. The adaptation of the mechanism
is so free of all complexity, as to render a more particular description un-
necessary.

Fig. 3. Represents the seven barometers arranged on a flat surface.

a. This circle points out the situation of a vertical wheel which revolves once
in seven hours. Levers are connected with each of the stop-cocks ; and
their central extremities, being placed at equal distances, and forming a
semicircle around the circumference of the upper half of the wheel,
one of the stop-cocks are shut each hour in succession.
A spiral or other spring for turning the stop-cocks, and operated upon by
the levers by means of a catch, both simplifies the operation, and secures
accuracy to any given instant.

( 349 )

XXVI. An Examination of Dr PARR'S Observations on the Ety-
mology of the word Sublimis. By GEORGE DUNBAR, A. M.
F. R. S. E. Professor of Greek in the University of Edin-
burgh.

( Read January 9- 1826.J

N the course of some inquiries into the affinity and structure
of the Greek and Latin languages, I was led to analyse the su-
perlative degree of both *, and to trace, as I thought, some con-
nection between it and the word Sublimis. While engaged in
the investigation, I was naturally led to examine the common
theories respecting the etymology of this remarkable word, and,
in particular, the origin assigned to it by the late Dr PARR, and
to weigh, with more attention than I had previously done, the
arguments and proofs he had advanced in support of his opi-
nions. All that I knew of them, till lately, was by verbal report,
as I had not seen the abridged statement of them in an Appen-
dix to the Notes of the 2d edition of Mr STEWART'S Essays.

Of the immense erudition of the late Dr PARR no one can
have a more profound admiration than myself. If I might, how-
ever, be allowed to express my opinion of his merits as a scholar,
I would say that the extent of his memory was prodigious ; that
his knowledge of classical literature was, perhaps, beyond that of
any man of his day ; but that his judgment was sometimes warp-
ed by prejudices and opinions, which he adopted with enthu-
siasm ; and upon which he brought the boundless stores of his

* On this subject I shall probably, in a short time, submit to the Society a few
observations.

350 An Examination of Dr PARR'S Observations

knowledge to bear in so many shapes, and in such a variety of
ways, as to confound and appal his opponents.

To Dr PARR'S notions respecting the origin of the word
Sublimis, Mr STEWART has given his assent more hastily, and in
more unqualified terms, than might have been expected from his
habitual caution, and the low estimate he had previously formed
of the common derivation of the word. " As for the etymology
of Sublime" (Sublimis), says he, " I leave it willingly to the con-
jectures of lexicographers. The common one, which we meet
with in our Latin dictionaries (q. Supra limum) is altogether un-
worthy of notice." This note, in the 1st edition of the Essays,
called forth, it is understood, a long and learned dissertation from
Dr PARK, the substance only of which Mr STEWART has given in
the Appendix above alluded to. In the 2d edition, he says, " I
have allowed the foregoing sentence to remain as it stood in the
former edition of this book, although I have since been satisfied,
by some observations kindly sent me by my very learned, philo-
sophical, and reverend friend Dr PARR, that the opinion which I
have here pronounced with so much confidence is unsound. The
mortification I feel in making this acknowledgment is to me
more than compensated, by the opportunity afforded me of gra-
tifying my readers with a short extract from his animadversions,"
&c. When two men of such celebrity, the one generally reckoned
the greatest classical scholar of his age, the other the most dis-
tinguished metaphysician of this or any other country, concur in
the same opinion respecting the etymology of a word, which has
been so long and so often disputed, it may seem to be presump-
tion of no ordinary kind, to attempt to call in question their de-
cisions. I derive, however, no small degree of encouragement,
from finding that I am supported in my opinions by one of the
most acute scholars of the present day, Dr HUNTER, the Pro-
fessor of Humanity in the University of St Andrew's, who, in
some notes, lately put into my hands by a common friend, to

on the Etymology of the word Sublimis. 351

whom I communicated my objections to Dr PARR'S theory, has
pointed out a few of its fundamental defects. With some of his
statements, however, I find I cannot agree ; but this is not the
place or the time to discuss them ; my present business is with
Dr PARR'S theory. The general remarks of that profound scholar
(contained in Article I. of the Appendix to the 2d edition of STEW-
ART'S Essays) on the power of custom and habit to communicate
grandeur and dignity to expressions, which, in their primary ac-
ceptation, suggest low, and sometimes disagreeable ideas, but
which, when compounded with other words, and applied meta-
phorically, convey more elevated notions, I shall pass over, as,
however true they may be in particular instances, they will not
hold in every other. His arguments and examples in support of
the derivation of Sublimis from Supra-limum, I shall examine
with as much care and attention as I can.

" In the formation (says the Doctor) of Sublimis, the process of
the mind seems to me to be this : Limus has the property of " ob-
structing." That to which the word Sublimis is applied, is " raised
above the obstructing cause." It can soar, — it does soar, — and thus
the notion of " soaring indefinitely" is familiarised to the mind.
The origin of the word, and its literal signification, did not pre-
sent themselves to the speaker or hearer." — It has too often hap-
pened in etymological speculations, that persons particularly con-
versant with them, are very apt to be led astray by a similarity
in the sound of words, and to task their ingenuity to the utmost
to discover some kind of association between them.

If we inquire into the meaning of the word limus in the best
Latin authors, we shall, I believe, scarcely find an instance where
the property of " obstructing" is attributed to it. It sometimes
denotes " tenacity," as in the following passage from VIRGIL —
Georg. iv. v. 45.

" Tu tamen e levi rimosa cubilia lima
Ungue fovens circum" -

VOL. X. P. II.

352 An Examination of Dr PARR'S Observations

In HORACE, Sat. i. v. 59. it conveys the idea of " muddiness"

" At qui tantulo eget, quanto est opus, is neque limo
Turbatam haurit aquam."

But suppose it even did convey the idea of " obstructing,"
should we thence infer that sublimis was employed to denote
" raised" above the " obstructing cause ;" and hence, as a conse-
quence, the notion of " soaring indefinitely ?" In tracing the
gradual and successive transitions in the meaning of words, every
link in the chain of the different relations should be distinctly
traced, otherwise, if we supply them by the mere effort of ima-
gination, we may rest assured there is something wrong in the
process. For every effect there must be an adequate cause ;
and the mind must have some object in its view to carry it from
the " obstructing clay" to the regions above. Has Dr PARR
mentioned a single instance of any object, remarkable by its fi-
gure, magnitude, or any extraordinary property, emerging from
tenacious clay, soaring to the regions of infinity, and drawing the
astonished gaze of the world to witness its sublime ascent ? or,
have any of the writers, who have attempted to explain the na-
ture of the sublime, produced an example that could in any
shape lend the least colour to his theory ? Not one. Nature
exhibits nothing of the kind ; and as the application of the terms
of language is chiefly borrowed from the appearance of natural
objects, we may thence conclude, that the Doctor's theory is fan-
ciful and unsatisfactory.

Dr PARR'S main argument, however, rests upon the meaning
he supposes the preposition sub conveys of elevation, when com-
pounded with another word ; for, " when standing alone," he al-
lows, it never has the sense of " up." " An objector," he re-
marks," might start up and say, How is u that, in the Latin
language, sub means " under," and " above" or " up ?" I admit
the fact (says he), but contend that the same letters, with the same

on the Etymology of the word Siiblimis. 353

sound, are of different extraction, and so different as to be adapt-
ed even to contrary significations. Let it be remarked that I am
going to speak of sub, when compounded with a verb, to express
" elevation."

Before entering upon an examination of the examples Dr
PARR has produced in support of his theory, I shall inquire
whether the derivation he has given of the preposition sub,
when compounded with verbs denoting " elevation," be cor-
rect. The Latin preposition sub has always been considered as
formed immediately from the Greek preposition vvo, and super
from vn% ; the Latin, as it is well known, substituting in several
instances an s for the Greek spiritus asper. Dr PARR, however,
says, that when sub signifies " elevation," it came from vvlg, and
that vvig, like VTO, lost the closing letters, and that p was changed
into b. He adds, " I never saw this stated in any book, directly
or indirectly, but no conjecture was ever more clear, or more sa-
tisfactory to my mind ; and it solves all difficulties." Notwith-
standing the high authority of the Reverend Doctor, I suspect
few Latin scholars would be inclined either to derive the prepo-
sition sub from UT^, or to allow that sub, in composition with any
verb, was ever used by any Latin author, with the force and
meaning of super. To me it appears, that he has entirely mis-
taken the precise meaning of sub in composition with some par-
ticular verbs : for in its general acceptation it cannot, by any
shew of reasoning, be confounded with super. I state it as my
decided opinion, and I am sure to be supported by every scho-
lar who knows any thing of the subject, that, whenever sub oc-
curs in composition, even when it may appear to denote " eleva-
tion," it is derived from vvo, and not from vvtg. The Greek pre-
position vvsg stands in the relation to vvro as comparative to
positive, as it is unquestionably the fragment of the compara-
tive vTTigog, by a syncope for virtg-urtgo/; ; as oVaros, the super-
lative, is for vvsg-curaro?. Let it be observed, that VTO denotes un-
der, but always in relation to a higher object ; and hence, where-

vy 2

354 An Examination of Dr PARR'S Observations

ever it is applied in the Greek language, either in a compound
or simple state, or its derivative sub in Latin, it expresses the re-
lations of a lower and a higher object. This I shall endeavour to
prove by examples. In HOMER'S description of the dove, struck
in mid-air by MERIONES, the preposition vvo occurs in two forms.
//. Y. 874.

£' viral vecptuv tide
cys divfuova-Kv VKO vrigwyog

In the first place, the adverb «4/< has no reference to a higher
object, but only denotes the elevation of something above the po-
sition of another. It is evidently the dative by abbreviation of
v^of. In the second place, uvui, which I take to be the old da-
tive feminine of the adjective i>vo?, is synonymous with vvo, and
both point out the relative situation of an object to another
above it. The dove was seen circling in air. Its situation might
have been pointed out in relation to MERIONES, who was stand-
ing on the ground ; and, if the Poet had resolved so to describe
it, he would have employed the preposition vvkg, not VKO. He
could not, however, by such a limited relation, convey an ade-
quate idea of the height of the dove above the spot where ME-
RIONES was standing ; he, therefore, employed a preposition
which expressed a kind of double relation, that of a lower to a
higher object, and, by inference, the relation of space between
MERIONES and the dove, ascertained by its height under the
clouds. These remarks will also apply to the expression VKO
Krigwyog £a'x* ptffffw. The wound was inflicted under the wing ;
i. e. the wing was higher than the wound ; or, vice versa, the
wound was in a part low in comparison to the situation of the
wing. As far as my experience goes, I know of no example in
the Greek language where wo, either in its simple or compound
state, has any other signification than under, relatively to a
higher object ; and even this idea may be traced in some words

on the Etymology of the word Sublimis. 355

whose general acceptation is very remote from the literal mean-
ing of their component parts.

But Dr PARR, aware that sub, derived from viro, would not
bend to his theory, by one of those stretches of imagination to
which etymologists usually have recourse when they are grie-
vously puzzled, derives it immediately from VTE^. I apprehend,
however, that, in no instance, is the Greek preposition wig ex-
pressed by any other Latin preposition than super in compound
words ; and the Roman writers never confounded super and sub
together. The learned Doctor, as I shall immediately shew, has
not attended to the relations which the preposition sub in com-
position frequently denotes. Let us examine some of his exam-
ples, and try whether the explanation given above of the Greek
preposition vvo, will not also apply to its Latin representative
sub :

" Quantum vere novo viridis se subjicit alnus." — VIRG. Ed. x. v. 74.

SERVIUS, " Subjicit, vel sursum jacit, vel subter jacit." Suppose
we were to substitute superjacit for subjicit, what would be the
meaning of the term ? It would be asked, " throws itself over
or above" what ? Could this be the meaning of the poet when
he employed the compound verb subjicit 9 Assuredly not. Is
it not evident, that he meant to express " the progress in growth
which the alder makes at the commencement of spring, compa
red with its former low state ?" It shoots up, i. e. from a low to a
higher state.

" Infraenant alii currus, aut corpora saltu
Subjiciunt in equos." VIRG. JEn. xn. v. 288.

SERVIUS, " Subjiciunt in equos, super equos jaciunt ; sed proprie
non est locutus, magisque contrarie, nam subjicere est illiquid
subter jacere." Dr PARR thinks, that although the scholiast was
puzzled with the word subjiclunt, " he is confident in his ability

356 An Examination of Dr PARR'S Observations

to solve the difficulty, even to the satisfaction of Mr STEWART ;"
and this he does by taking sub for super, or deriving it from the
Greek preposition vvig. I also am confident, that VIRGIL would
not have employed in this clause of the sentence superjaciunt as
synonymous with subjiciunt ; because the former would have sig-
nified, not that they threw themselves on horseback, but that they
threw themselves over the horses; and, besides, the preposition
in, which* with subjiciunt, signifies upon, could not have been em-
ployed with superjaciunt without a gross violation of the idiom
of the language * ; and no one knew this better than Dr PARR, if
he had not been blinded by his theory. The construction would
have been the same as the following :

" pontus

Nunc ruit ad tellus, scopulosque superjacit undam
Spumeus." VIKG. JEn. xi. 625.

Ille astu subit, at tremebunda supervolat hasta.

VIKG. Mn. x. 522.

The quivering spear flies over him. The same relation is to be
observed in the expression, Corpora subjiciunt in equos, as in the
former example. The preposition sub denotes the lower situa-
tion of the men relative to the higher position of the horses'
backs when they were going to throw themselves upon them :

Ter flamma ad summum tecti subjecta reluxit.1"

VIKG. Georg. iv. v. 385.

* I am quite aware that the preposition in was sometimes used in compound
verbs with super ; as, mperinjicere, superimpono, Sue. But when these two preposi-
tions are combined together, they imply a very different relation. Would VIKGIL,
or any other Latin author, have used the expression — aut corpora saltu superinjiciunt
equos ? I believe neither he nor any other. When he says, Georg. iv. v. 46. " et ra-
ras superinjice frondes,"he shews that the relative situation of the person to the hives
is just the reverse of the men to the horses1 backs, in the preceding example. Thus,
" and throw (from a higher situation) a few branches down upon them."

on the Etymology of the word Sublimis' 357

The flamma subjecta has a reference primarily to the low situa-
tion of the altar on which the fire was burning, compared with
the height of the roof to which the flame ascended. Sub, in this
example, in the sense of i>ing, would have conveyed an extraor-
dinary idea. It would have denoted, flamed above the roof, not
up to it ; and with the words ad summum would have violated
the construction of the language. The same compound fre-
quently denotes motion under : and, in such examples, sub must
evidently be derived from vvo. Thus, OVID, Trist. Eleg. i. 73.

" Canitiem galeae subjicioque meam."

In the two following instances, quoted by Dr PARR, the same
explanation must be given of the preposition.

Tibi suaves daedala tellus,

SummUtit floras." LUCEET. I. v. 9.

Tellus summittit flores, the earth sends up flowers ; sub, from her
bosom, which, relatively, is low compared with the flowers when
they have sprung up.

" Sic et averna loca alitibus summittere debent
Mortiferam vim, de terra quae surgit in auras."

LUCKET. vi. v. 818.

" De terra qua? surgit in auras" explains the whole relation of
summittere in the preceding line.

Having pointed out the relation indicated by sub in composi-
tion, in several examples from the poets, I shall now proceed to
examine some of the Doctor's examples from prose writers. " In
prose writers," says he, " we have sub for up. " Sublevare mentum
sinistra," CICERO. "Sublevare miseros," CJCERO. The same rela-
tion may be observed in both these examples. The chin is raised
from the breast to a higher situation by the left hand. It is raised
up, and prevented from sinking by the left hand placed under jk

3

358 An Examination of Dr PARR'S Observations

The wretched are raised from a low to a higher (better) condition :
z. e. a condition higher in the scale of existence. Nobody, I suppose,
ever heard of superlevare. The following quotations will shew the
relation which this verb points out. CICERO, Att. 1. x. c. 17. " Qui
nos sibi quondam ad pedes stratos, ne sublevabat quidem." PLI-
NY, 1. xi. c. 17. " Apes regem fessum humeris sublevant." LIVY,
1. XLV. c. 7. " Consul, introeunti regi dextram porrexit, submit-
tentemque se ad pedes sustulit."

" Upon sub, when standing alone," he says, " I speak doubtfully.
" There is a passage in LIVY where subire may have the sense of
" ascending, but I am not positive, and shall offer a different ex-
" planation." In the following passage, from the same author,
where a description is given of HANNIBAL'S passage over the Alps,
the verb subire can have no other signification than to ascend.
" Luce prima subiit tumulos, ut ex aperto et interdiu vim per
angustias facturus," 1. xxi. c. 32. So also, 1. xxvu. c. 18. " Ce-
terum, quamquam ascensus difficilis erat, et prope obruebantur
telis saxisque, assuetudine tamen succedendi muros, et pertinacia
animi, subierunt primi."

" Sub," says Dr PARR, " occurs under another form sus, which
hereafter will be explained. Sustineo, " I hold up. Suspicio, " I
look up." Mr STEWART will have the goodness particularly to
mark the form sus." After some other observations, which it is
not necessary to quote here, he proceeds : " Sub, then, signify-
ing " elevation," comes not from VKO, but from wrsg, and sus does
not immediately come from sub only, but by another process, as
we shall soon see." What immediately follows I shall omit, as
of little importance to the argument. He then goes on to say :
" Against SCALIGER'S third position I contend, that susum did
not come from sus, but versa vice, (as we ought to say instead of
vice versa), sus comes from susum, as retrovorsum was contracted
into rursum, so supervorsum was contracted into sursum, and
sursum was softened into susum, and susum when compounded,

on the Etymology of the word Sublimis. 359

shortened into sus." — Now, I contend that retrovorsum was ne-
ver contracted into rursum, but into retrorsum, backwards; as
being compounded of retro, and the perfect participle of verto
or vorto, which was originally versus, a, um ; and as for supervor-
sum, it is a word of the Doctor's own manufacturing, as it never
appears to have been used by any author ; at least I can find no
traces of it in the best Latin dictionaries. But, even though
it had existed, it would have given, by abbreviation, superorsum
(according to the analogy of retrorsum) and not sursum *.

The examples which Dr PARR gives of sus in composition are,
" suscipio," which, he says, is, Capio susum, " I take up ;" " sus-
pendo," is susum pendo, " I hang up ;" " sustineo" is susum teneo,
" I hold up." Suscito is, by SCALIGER'S own confession, susum
cito, " I stir up ;" and as specie begins with an s, the final letter
of sus contracted, (abbreviated, the Doctor should have said, for
it is not contracted,) from susum, is omitted upon the above men-
tioned principle of avoiding, as the old Romans avoided, the ge-
mination of the same letter." — It is surprising that Dr PARR did
not advert to the practice of the Greeks, in changing the final »
of the prepositions It and trvv into p and 7 before certain mutes ;
and also of converting it into whatever liquid the word with
which it was joined commenced with. They even omitted the
i of the preposition a-vv before <r and a mute ; as ffv-ffrg«,rsvopcu ;
(rv-ffvau, &c. In like manner, I imagine, the b of the preposition

* The venerable Dr HUNTER of St Andrew's has also shewn, in some notes upon
VIRGIL, that Dr PARR'S derivation of sub from i»T6£ is incorrect. After giving several
examples similar to those already quoted, he observes, " It may be further remarked,
that SURSUM, upward, is not, as Dr PARR supposes, superrwsum, but subrorsum.
Supervorsum would express, not in a direction FROM below or UPWARD, but in a di-
rection OVER." The coincidence of opinion between Dr HUNTER and myself, on se-
veral points in the present discussion, is to me the more gratifying, as his notes were
wholly unknown to me, till communicated by our common friend the Rector of the
High School of Edinburgh, after I had sent for his perusal the present examination.

VOL. X. P. II. Z Z

360 An Examination of Dr PARR'S Observations

sub was changed into other letters, and sometimes omitted in
compound words, euphonize causa. — Suscipio is sub and capio,
and so written as being more agreeable to the ear than subcipio,
or succipio, which SCALIGER says it originally was. Sustineo is
for sub and teneo. In this verb the preposition sub expresses
more nearly the force of the Greek preposition 0,1/0. than wro,
as sustineo is equivalent to a,t/i%u, " I hold up." Yet, in every
example where it occurs, the idea of supporting under may be
traced, sometimes very plainly, at other times more obscurely.
Hence it is often synonymous with tolero, patior. Thus OVID.
Metamorph. viu. v. 500. " Et quos sustinui bis mensium quin-
que labores." CICERO, Verr. 8. " Non tibi venit in mentem
quid negotii sit, causam publicam sustinere," which FACCIOLATI
explains by portar il peso. Suspicio is from sub and specio, the
6 being dropped as in the Greek verb ffv-<rvu.u. Its literal mean-
ing is, I \ookfrom under. Taken in a literal sense, it implies an
higher object. Thus CICERO, de Nat. Deor. n. c. 2. " Cum cce-
lum suspeanmus coelestiaque contemplati sumus." Metaphori-
cally, the sense of inferiority. " Translate est admirare," says
FACCIOLATI, " ammirare, quasi supra nos aspiciamus ilium esse
collocatum, quern admiramur." CICERO, Off. n. c. 10. " Itaque
eos viros suspiciunt, maximisque eiferunt laudibus."

From these, and many other examples which could be pro-
duced, it may be observed, that the genuine power of the pre-
position sub in composition, is always to mark the relation of in-
feriority to a higher object, and that it never can, consistently with
the usage of the language, be derived from v*\g. Had gramma-
rians and philologists been sufficiently attentive to observe the
relations which prepositions in particular denote, they would
not have committed such glaring mistakes as are frequently ob-
servable in their account of them. So far as my observation ex-
tends, I do not know a single work in which the Greek and La-

on the Etymology of the word Sublimis. 361

tin prepositions are treated of with any thing like philosophical
accuracy ; and hence the vague and uncertain ideas that are ge-
nerally entertained of their origin, nature and relations. The
classical literature of the day holds a very different course. It
contents itself with amassing authorities, investigating different"
readings, quoting parallel passages, and retailing opinions, without
once venturing from the beaten track, to take a view of the prin-
ciples of language. — The theory of language is no despicable
study ; for, if well and wisely conducted, it shews the progress
of the human mind from a rude state, when it was chiefly con-
versant with external objects, and ignorant in a great measure of
those associations which spring from the view of the living world,
and the comparison of its ideas, till it reach, through the me-
dium of relations, more and more refined and abstract in their
nature, the highest point of intellectual improvement. From the
failure of men of the deepest knowledge, and the greatest powers
in the science of philology, I consider it still in its infancy, and
likely to remain so, unless, with a thorough knowledge of the
primitive languages of Europe and Asia, there be combined more
of the study of nature, a better acquaintance with severe induc-
tive reasoning, and the philosophy of the human mind, than has
hitherto appeared in the speculations of the learned.

z z 2

( 362 )

XXVII. Results of the Thermometrical Observations made at
Leith Fort, every Hour of the Day and Night, during the
whole of the Years 1824 and 1825. By DAVID BREWSTER,
LL.D. F. R. S. Lond. & Sec. R. S. Ed. Corresponding Mem-
ber of the Academy of Sciences of Paris, &c.

(Read January 23. 1826J

J.N the year 1820, I had occasion to suggest to the Royal So-
ciety the propriety of establishing Registers of the Thermome-
ter in various parts of Scotland.

In a country embracing so many varieties of soil, climate and
elevation, and extending over nearly six degrees of latitude, it
was an object worthy of a public body to determine the Law of
the Distribution of Temperature, even if such a subject had not
possessed a separate interest in relation to the Horticulture and
Agriculture of the Country. The Society did not hesitate in
adopting this suggestion, and many intelligent individuals were
found, who undertook to observe the thermometer twice a-day,
and to measure occasionally the temperature of Springs and
Wells. During the first year, viz. 1821, nearly sixty Meteoro-
logical Journals were regularly kept in different parts of Scot-
land. The number diminished considerably in subsequent years ;
but, notwithstanding this diminution, there is now in our posses-
sion a rich series of observations during five complete years,
the results of which are nearly ready to be submitted to the
Society.

DR BREWSTER on the Register of the Thermometer. 363

In directing these observations, it became necessary to select
two hours of the day most convenient for marking the state of
the Thermometer, and the Mean Temperature of which ap-
proached nearest to the Mean Temperature of the day. The
hours adopted were 10 o'clock A. M. and 10 p. M., which had been
previously recommended by the Reverend Mr GORDON. The
observations were accordingly made at these hours, during
three years ; but it appeared to me, upon a more attentive consi-
deration of the subject, that the Thermometer should be obser-
ved at the two times of the day at which the Mean Tempera-
ture occurred ; for if one of the observations was omitted, the
other still possessed considerable value, as an approximation
to the Mean Temperature. Unfortunately, however, there were
almost no observations in existence from which the times of the
daily Mean Temperature could be deduced. Professor DEWEY
of New York had observed the Thermometer once every hour
during five days at a time, in the months of March, April,
July and October of the year 1816, and during eight days
of January, and two of February in the year 1817*; and
Mr COLDSTREAM of Leith registered the Temperature of 24
successive hours once every month, from July 1822 to July
1823. From this last series of observations the Mean Tem-
perature appeared to occur at \ past 7 o'clock in the morn-
ing, and \ past 8 in the evening ; and these hours were accord-
ingly used in most of the registers for 1824 and 1825. It was
very obvious, however, that these observations, though made
with great care, were too limited to afford any thing like an ac-
curate result ; and hence it became a desirable object to extend
the hourly observations of the Thermometer over a greater por-
tion of the seasons, or, if possible, to record its indications for
every hour of a complete year.

* Memoirs of the American Academy of Arts and Sciences, Vol. IV. Part II.
p. 392.

364 DR BREWSTER on the Register of the Thermometer kept

As such a plan could only be carried on with effect at a mi-
litary station, Leith Fort was considered the most eligible. Ap-
plication was therefore made to Colonel THACKERAY, command-
ing the Engineers, and to Colonel YOUNGHUSBAND and Mr
STREET of the Artillery ; and, as these gentlemen entered warm-
ly into the scheme, preparations were made to begin the register
on the 1st of January 1824. A large and accurate thermometer
was constructed by Mr ADIE for the purpose, and it was placed
in a situation as free as possible from all disturbing causes. Its
height above the level of the sea is 25 feet, and its distance from
the sea 200 yards.

The register commenced on the 1st day of January 1824,
and has been regularly and zealously carried on by the non-com-
missioned officers of the Fort for two complete years. The
observations themselves are recorded in the two Folio volumes
now submitted to the Society, and they may justly be regarded as
possessing a high value, not only from the scientific results
which they afford, but as being the only complete series of hourly
observations which have been made in any part of the world *.

In reducing these observations, Mr FOGGO junior of Leith
computed all the hourly, monthly, and annual means for the year
1824, and Mr CHRISTOPHER BELL made the same calculations
for 1825. These Mean Results are given in the following
Tables.

* Since this was written, we understand that similar observations, suggested by
the present series, are now carrying on at Toulon and at Montreal, the last of
which will possess a peculiar interest. The first example of this class of observa-
tions having been set in Scotland, we may be here allowed to express a hope, that
similar hourly registers will be established by learned Societies both in Europe and
America.

every Hour of the Day at Leith Foit, in 1824 and 1825. 365

HOURLY REGISTER FOR 1824,

o

The Mean Temperature of the Winter months, viz. Dec. Jan. Feb. is 40.67

of the Spring months, viz. March, April May, 45.38

of the Summer months, viz. June, July, Aug. 57.24

of the Autumn months, viz. Sept. Oct. Nov 47.91

The Mean Temperature of the Year 1824, from 8784 observations, is 47.81

TABLE I. — Containing the Daily and Monthly Mean Temperatures for 1824.

Day.

January.

Feb.

March.

April.

May.

June.

July.

Aug.

Sept.

Oct.

Nov.

Dec.

1

42.55

42.69

35.19

33.49

55.00

57.12

55.85

57.00

62.80

56.00

44.53

32.07

2

43.52

42.69

32.72

39.36

52.25

55.10

57.92

56.86

67.69

51.15

44.80

32.34

3

40.47

42.52

33.77

37.39

47.00

58.64

55.95

57.05

67.78

53.25

39.83

30.92

4

43.79

40.82

35.25

39.50

47.80

56.80

57.97

57.54

60.36

52.72

36.33

28.11

5

44.38

38.69

38.34

43.62

49.84

56.07

55.44

55.89

56.69

51.42

35.87

28.83

6

40.69

40.03

44.52

44.33

46.81

52.63

5829

55.70

54.10

52.90

35.63

38.54

7

36.50

49.63

43.29

45.06

50.67

60.98

58.75

57.38

58.18

53.79

49.30

38.39

8

45.30

46.40

38.83

44.58

51.98

55.83

63.64

61.37

50.00

54.09

45.76

35.39

9

50.08

41.76

36.50

4501

51.23

53.00

62.22

58.88

49.96

48.42

44.76

35.39

10

45.67

43.21

35.83

37.92

49.94

51.63

58.18

57.43

51.79

44.39

45.94

34.79

11

39.90

40.04

38.32

37.55

47.38

50.15

58.92

56.79

57.09

46.42

43.32

48.15

12

43.81

43.36

36.82

39.87

47.15

53.87

60.27

55.94

57.00

41.60

39.52

50.28

13

42.26

39.51

36.15

39.27

47.25

55.45

57.75

56.48

57.29

39.03

49.00

48.40

14

39.30

39.37

38.41

40.60

45.25

51.78

66.24

57.22

59.36

44.15

43.23

48.60

15

32.41

34.91

44.22

41.42

47.70

51.86

64.51

58.73

58.39

38.34

35.78

46.10

16

33.37

36.53

46.16

37.88

48.16

53.37

58.81

56.67

60.40

37.44

45.90

38.59

17

3826

37.65

46.02

41.68

51.34

53.01

58.35

55.58

61.61

37.56

52.15

37.79

18

44.01

38.07

48.00

46.35

47.64

54.45

57.23

54.39

61.78

44.22

42.49

44.09

19

40.56

41.30

45.05

51.62

43.63

53.12

58.13

57.07

54.30

49.98

41.12

49.24

20

41.93

41.07

50.03

54.93

42.50

52.87

61.29

56.03

51.81

48.48

41.52

36.91

21

39.33

41.07

45.34

55.47

44.77

54.03

60.99

53.79

51.06

49.00

41.39

37.53

22

39.32

42.01

38.95

52.27

48.09

55.38

65.73

52.82

56.66

54.50

40.06

35.45

23

38.60

41.51

38.67

48.90

52.77

54.09

63.35

56.10

54.44

53.53

42.64

34.11

24

40.31

41.36

41.37

51.46

54.54

54.57

56.92

58.35

53.44

52.97

45.27

40.33

25

48.04

40.72

42.29

52.64

57.18

56.57

58.72

56.63

50.51

53.96

4168

46.94

26

51.58

37.83

41.15

53.95

56.75

57.75

59.04

56.67

42.79

48.88

39-12

35.99

27

43.59

38.19

39.99

51.01

59.75

58.78

58.70

55.69

39.70

42.22

36.44

44.39

28

38.69

40.05

39.18

53.58

56.29

59.45

60.53

54.33

40.30

40.28

40.48

39.80

29

36.47

40.73

41.68

55.16

49.62

60.49

61.97

57.62

41.90

38.80

40.04

39.78

30

38.54

37.85

57.90

55.16

60.69

55.37

54.23

55.33

39.17

34.20

41.18

31

45.20

33.86

52.46

56.06

57.01

48.87

46.93

Means,

41.599

40.83

40.12

45.79

50.24

55.65

59.46

56.62

54.57

47.23

41.94

39.57

366 DR BREWSTER on the Register of the Thermometer kept

TABLE II. — Shewing the Mean Temperature of each Hour for each Month of 1824,

and for the whole Year.

Hour.

Jan.

Feb.

Mar.

April.

May.

June.

July.

Aug.

Sept.

Oct.

Nov.

Dec.

Mean Temp, of
each hour for
the whole year.

1 A.M.

2

41.19
408

39-9
4003

38.3
38 3

42.63
41 6

46.56
4603

52.6
523

55.4
55 2

53.3
532

52.3
52 1

46.17
4617

40.4
40 4

38.69
38 71

45.62

AK 4ft

3

40.8

39.95

3807

41 00

45.3

52.1

551

529

51 4

46.07

405

3902

4*5 is

4
5 ...

40.28
4007

39.68
3962

37.9
3765

40.08
398

44.7
44 9

51.8
51 8

54.9
55 2

52.5

527

51.1
51 2

46.2
45 6

40.47
40 45

38.9
388

44.93

44 so

6

40.1

3944

3745

39.9

45.7

52.7

558

533

51 6

44.8

4050

389

4500

7
8
9

40.23
40.3
4064

39.27
39.02
3993

37.77
383
39.13

42.2
43.1
45.9

46.9

48.3
49.8

58.1
54.3
55.2

56.9
58.2
59.7

54.5
55.5
56.8

52.1
53.4
550

45.3
45.9
46.6

40.7
40.8
41.3

38.8
38.8
390

45.64
46.32
4741

10

41.15

40.74

39.47

47.3

51.1

56.2

60.56

57.9

55.6

47.5

42.1

39.3

4824

11

41.54

41 35

41.13

48.2

52.3

57.3

61.5

58.7

565

48.5

43.1

404

49 21

12

423

4222

4223

489

533

578

632

595

575

49.3

43.9

4] 0

5009

1 P.M.

2

42.83
4315

42.7
427

42.7
428

49.3
498

54.2

54.7

58.0
589

63.2
632

59.8
600

58.5
587

499
49.9

44.2

44.7

41.2
40.9

50.45
5079

3
4

43.18
43.00

42.67
42.03

42.9
426

50.1
499

54.7
547

59.9
59 1

63.5
63.6

60.0
601

58.8
578

49.6
49.07

44.7
43.4

40.33
399

50.89
5043

5

4222

41 4

41 9

495

541

587

634

597

578

48.4

428

39.72

4997

6

41.98

40.9

41.07

49.1

53.2

57.7

62.6

59.1

57.0

47.9

42.4

39 52

49.38

7

41.7

40.53

402

47.8

52.4

56.9

61.7

58.0

55.8

47.2

42.1

39.19

4864

8

41.35

402

396

465

50.9

55.7

60.3

56.8

5507

46.73

41.7

39.00

47.90

9
10
11
12

41.3
41.26
41.12
40.92

40.2
40.03
39-9
39.9

39-2
38.8
38.3
38.3

45.3
44.6
43.1

42.7

49.4
48.9
47.8
47.1

54.5
53.8
53.2
52.7

58.9
57.6
56.9
56.03

55.9
55.0
54.3
53.8

54.3
53.7
53.4

52.7

46.7
46.0

45.8
45.7

41.3
40.8
40.4
40.3

39-09
39-09
39-1
39.29

47.17
46.64
46.20
45.79

The Mean Temperature obtained from the last column in the above Table, is 47°.588.
It occurred at 9h 13' A. M. and at 8h 26' P. M.

every Hour of the Day at Leith Fort in 1824 and 1825. 367

HOURLY REGISTER FOR 1825.

o

The Mean Temperature of the Winter months, viz. Dec. Jan. Feb. is 40.312

of the Spring months, viz. March, April, May, 46.121

of the Summer months, viz. June, July, Aug. 59.306

of the Autumn months, viz. Sept. Oct. Nov 49.907

The Mean Temperature of the year 1825, from 8760 observations, is 48.911

TABLE m.—Containiitg' the Daily and MonMy Mean Temperatures Jin- 1825.

Day.

Jan.

Feb.

March.

April.

May.

June.

July.

Aug.

Sept.

Oct.

Nov.

Dec.

1

45.15

41.31

39.78

42.38

44.71

56.88

55.50

63.77

60.40

53.63

4635

33.79

2

39.83

41.81

37.29

45.89

46.09

58.41

57.81

63.56

59.19

60.36

42.08

36.85

3

43.47

32.99

36.13

47.46

49.14

53.61

58.54

63.27

59.30

60.03

42.53

34.59

4

37.35

28.72

36.20

49.74

52.73

50.52

59.56

59.60

57.07

58.81

40.36

37.84

5

30.32

3308

36.50

54.18

48.69

49.43

58.66

59.71

55.39

58.38

43.04

37.09

6

39.26

34.99

38.24

47.26

52.59

52.35

59.24

58.21

55.99

57.57

41.52

40.72

7

44.17

38.51

39.55

49.80

53.19

58.30

58.09

59.06

58.79

53.79

36.04

43.21

8

39.80

38.81

44.20

52.11

54.63

57.46

57.05

59.88

55.45

54.48

36.82

44.71

9

38.11

42.78

52.46

47.04

54.27

55.24

56.05

57.71

58.30

55.49

35.73

42.95

10

35.55

47.11

52.48

48.55

50.77

59.59

55.25

59.37

60.26

56.79

32.37

43.35

11

41.48

46.28

44.97

50.13

48.32

65.67

56.26

57.34

58.21

54.00

36.22

44.12

12

39.91

46.06

44.18

41.03

48.75

62.71

61.09

56.41

60.55

57.80

33.78

43.90

13

42.03

46.98

43.41

40.79

47.50

59.09

65.45

59.74

56.27

54.09

42.32

42.45

14

44.75

41.82

37.83

48.62

48.91

60.14

69-94

56.78

56.30

53.57

40.82

38.56

15

46.73

41.48

36.40

5250

49.74

58.85

65.51

57.91

56.79

52.51

36.49

41.06

16

43.99

41.79

36.04

50.49

49-05

63.52

66.77

56.88

61.21

54.65

44.12

46.04

17

39.38

43.52

36.75

45.06

51.95

60.51

69.63

57.17

62.40

47.16

44.61

45.40

18

41.22

41.26

39.07

40.54

53.55

58.45

66.63

59.01

62.59

46.75

45.56

47.05

19

39-15

41.78

43.31

42.30

53.41

52.46

62.23

59.07

60.95

46.23

41.14

42.66

20

40.09

43.73

4058

50.49

50.41

52.70

60.02

65.40

59.87

40.24

45.56

42.44

.21

39.30

40.91

39.78

53.04

49.01

52.09

59.07

64.35

60.34

41.47

45.22

45.92

22

37.02

42.63

42.55

46.81

52.14

53.16

59.83

60.41

54.95

42.47

40.76

40.02

23

36.33

40.88

40.61

42.76

50.48

57.68

56.63

65.44

49.44

51.07

44.74

40.22

24

38.03

40.17

38.12

42.37

46.01

57.59

57.10

57.88

63.49

48.97

43.30

39.75

25

34.45

39.08

42.03

42.80

45.60

57.14

63.29

58.04

62.16

40.65

40.46

43.85

26

41.30

37.69

42.81

45.28

48.55

52.44

61.01

57.23

56.29

39.26

44.80

35.14

27

47.65

38.61

48.70

45.88

47.02

54.35

64.94

58.45

56.59

45.58

35.81

33.00

28

38.83

36.75

45.39

47.35

45.18

54.70

60.22

59.21

53.00

52.41

36.44

35.86

29

43.88

47.47

47.88

47.96

55.95

61.05

61.92

55.45

50.98

39.84

35.01

30

47.62

44.78

48.51

50.17

55.05

68.53

65.35

54.66

51.90

34.63

32.81

31

42.93

42.29

52.74

68.20

65.72

46.81

28.58

Mean ^
Temp, f
of each f
month,.!

40.583

40.412

41.610

46.968

49-785

56.531

61.262

60.125

58.055

51.223

40.443

39.940

VOL. X. P. II.

3 A

368 DR BREWSTER on the Register of the Thermometer kept

TABLE IV. — Shewing the Mean Temperature of each Hour for each Month in 1825,

and for the whole Year.

Hour.

1 A. M

3

4

5

6

7

8

9

10

11

12

1 P. M,

4

5

6

7

8

9

10

11

12...

Jan.

Feb.

39.073

39.968

39.823

39.855

39.814

39.774

39.831

39.927

40.121

40.508

41.161

41.748

42.000

42.032

42.009

41.371

41.153

40.920

40.475

40.404

40.258

40.3&

40.283

40.339

39.437

39-500

39.598

39.509

39-089

39.018

39.321

39-518

39.589

40.473

41.670

42.241

42.848

42.821

42.928

42.482

41.56!

41.089

40.70J

40.250

39.625

39.286

39.170

39.143

March.

39.604
39.162
38.516
38.355
38.275
38.404
38.718
39.524
40.661
41.605
42.701
44.404
44.661
45.226
45.259
45.484
45.210
44.630
43.556
42.711
41.718
41.083
40.523
40.24

April.

May.

43.350

42.742

42.050

41.500

41.317

41.542

43.050

44.725

46.842

48.892

49.992

51.142

51.617

51.817

52.275

51.858

51.175

50.767

49.275

47.300

46.117

45.425

44.733

44.133

47.016

46.750

46.460

46.161

46.210

46.944

47.476

48.597

49.653

50.702

51.363

51.863

52.186

52.540

52.686

53.315

53.645

53.493

52.484

51.137

49.637

49.097

48.508

47.927

June.

52.575
52.200
52.133
51.975
52.067
52.958
54.150
55.250
56.883
58.117
59.017
59.508
60.050

60.533
60.517
60.450
60.591
59-867
57.608
56.242
5.167
54.225
53.675

July.

56.935
56.798
56.087
55.403
56.121
57.637
58.855
60.032
61.298
62.693
63.500
64.484
64.670

60.500 65.468

65.798
65.807
66.250
66.742
65.975
62.807
60.742
59.492
58.581
57.605

Aug.

57.355

56.936

56.661

56.629

56.565

56.758

57.542

58.887

59-960

81.170

61.895

63.008

63.629

63.826

63.830

64.210

64.387

64.387

61.927

60.589

59.476

58.409

57.779

57.234

Sept.

55.358
55.058
54.792
54.333
53.992
54.117
55.192
56.442
58.050
59.842
60.667
61.500
62.100
62.575
62.258
62.075
62.042
60.333
58.875
58.008
57.283
56.575
56.042
55.517

Oct.

49.984

49.782

49.685

49.476

49.516

49.484

49.797

50.451

51.137

52.484

53.258

53.766

54.008

54.137

53.855

53.193

52.557

51.613

51.065

50.477

50.202

50.129

49.742

49.670

Nov.

39.325
38.800
38.975
38.858
39.050
39.183
39.417
39.383
39.825
40.825
41.833
42.258
42.667
42.708
42.808
42.250
41.517
41.192
40.667
40.442
40.350
39.867
39.492
39.117

Dec.

39.194
39.331
39.105
39.032
39.016
39.234
39.194
39.468
39.718
40.089
40.645
41.016
41.169
41.532
41.250
41.105
40.652
40.355
39.798
39.758
39.532
39.411
39.153
38.855

Mean Temp, of
each hour for
the whole year.

46.648
46.466
46.198
45.969
45.968
46.307
46.927
47.788
48.700
49.784
50.691
51.464
51.848
52.150
52.174
52.049
51.774
51.208
50.449
49.348
48.488
47.913
47.407
47.007

The Mean Temperature obtained from the last column of the above Table is 48°.944-
9" 13' A. M. and 8h 28 P. M.

It occurred, at

every Hour of the Day at Leith Fort in 1824 and 1825.

369

MEAN RESULTS OF THE HOURLY REGISTER FOR 1824 AND 1825.

O

The Mean Temperature of the Winter months, viz. Dec. Jan. Feb. is 40.491

of the Spring months, viz. March, April, May, 45.751

of the Summer months, viz. June, July, Aug. 58.273

of the Autumn months, viz. Sept. Oct. Nov 48.908

The Mean Temperature of the years 1824 and 1825, from 17,544 observations, is 48.360

TABLE V. — Containing the Average of the Daily and Monthly Temperatures of the

Years 1824 and 1825.

Day.

January

Feb.

March.

April.

May.

June.

July.

August

Sept.

October

Nov.

Dec.

1

43.85

42.00

37-48

37-93

49.85

57-00

55.67

60.38

61.60

54.82

45.44

32.93

2

41.67

42.25

35.01

42.62

49.17

56.75

57.86

60.21

63.44

55.75

43.44

34.59

3

41.47

3775

34.95

42.42

48.07

56.12

57.23

60.16

63.54

56.64

41.18

32.75

4

40.57

34.77

35.72

44.62

50.26

53.66

58.76

58.57

58.71

55.76

38.34

32.97

5

37.35

35.88

37-42

48.90

49.26

52.75

57.05

57-80

56.04

54.90

39.45

32.96

6

39.97

37.51

44.38

45.79

49.70

52.49

58.76

56.95

55.04

55.23

38.58

39.63

7

40.33

44.07

41.42

47-43

51.93

59.64

58.42

58.22

56.48

58.79

42.67

40.80

8

42.55

44.61

41.52

48.34

53.30

56.64

60.35

60.62

52.72

54.29

41.29

40.05

9

44.09

42.27

44.48

46.03

52.75

54.12

59.13

58.29

54.13

51.95

40.24

39.17

10

40.61

45.16

44.15

43.23

50.35

55.61

56.71

58.40

56.02

50.59

39.15

39.07

11

40.69

43.16

41.64

43.84

47.85

57.91

57.59

57.07

57.65

50.21

39-77

46.13

12

41.61

44.71

40.50

40.45

47-95

58.29

60.68

56.17

58.77

49.70

36.62

47-09

13

42.15

43.24

39.78

40.03

47-37

57.27

61.60

58.11

56.78

46.56

45.66

45.42

14

42.02

40.59

38.12

44.61

47.08

55.96

68.09

57.00

57-83

48.86

42.02

43.58

15

39.57

38.19

40.31

46.96

48.72

50.35

65.01

58.32

57.59

45.42

36.13

43.58

16

38.68

39.16

41.10

44.19

48.60

58.44

62.79

56.77

60.80

46.04

45.01

42.31

17

38.82

40.58

41.38

43.37

51.64

56.26

63.99

56.37

62.01

42.36

48.38

41.59

18

42.61

39.66

43.53

43.45

50.59

56.45

61.93

56.70

62.18

45.48

44.02

45.57

19

39.85

41.54

44.18

46.91

48.52

52.79

60.18

58.07

57.62

48.10

41.13

45.95

20

44.01

42.40

45.30

52.71

46.45

52.78

60.65

60.72

55.84

44.36

43.54

39.69

21

39.31

40.99

42.56

54.25

46.81

53.06

60.03

59.07

55.70

45.23

43.30

41.72

22

38.16

42.32

40.75

49.54

50.11

54.27

62.78

56.61

55.81

48.48

40.41

37-73

23

37.46

41.19

39.64

45.83

51.62

55.88

59.99

60.77

51.94

52.30

43.69

37-16

24

39.17

40.76

39.74

46.92

50.27

56.06

57.01

58.11

58.46

50.97

44.28

40.04

25

41.24

39.90

42.16

47.72

51.39

56.85

61.01

57.33

56.33

47.30

41.05

45.39

26

46.44

37-76

41.98

49.61

52.65

55.09

60.02

56.95

49.54

44.07

41.96

35.56

27

45.62

38.40

44.34

48.45

53.39

56.56

61.82

57-07

48.14

43.90

36.12

38.69

28

38.76

38.40

42.28

50.46

50.73

57.07

60.37

56.77

46.65

46.34

38.46

37.83

29

40.18

44.57

51.52

48.79

58.22

61.51

59.77

48.67

44.89

39.94

37-39

30

43.08

41.31

53.20

52.66

57.87

61.95

59.79

54.99

45.53

34.42

36.99

31

44.06

38.07

52.60

62.13

61.36

47.84

37-75

Means,

41.091

40.621

40.865

46.379

50.012

56.091

60.361

58.372

56312

49.226

41.191

39.775

3 A2

870 Dr BREWSTER on the Register of the Thermometer kept

TABLE VI. — Shewing the Average Mean Temperature of each Hour for each Month in
182,4s and 1825, and the average of these Two Years.

Hour.

Jan.

Feb.

March.

April.

May.

June.

July.

Aug.

Sept.

Oct.

Nov.

Dec.

Mean Temp, of
each hour for the
whole two years.

1 A.M.

2

40.131
40.384
40.311
40.067
39.942
39.932
40.030
40.113
40.381
40.829
41.350
42.024
42.415
42.591
42.594
42.185
41.686
41.450
41.082
40.877
40.792
40.827
40.702
40.629

39.668
39.751
39.774
39.594
39.354
39.229
39.295
39.269
39.759
40.606
41.510
42.230
42-774
42.761
42.709
42.256
41.481
40.994
40.617
40.225
39.913
39.658
39.535
39.521

38.952
38.731
38.293
38.127
37.962
37-927
38.244
38.912
39.895
40.537
42.915
43.317
43.680
44.013
44.079
44.042
43.555
42.850
41.878
41.155
40.459
39.941
39.411
39.271

42.990

42.171

41.525
40-794
40.558
40.721
42.625
43.912
46.371
48.096
49.096
50.021
50.458
50.808
51.187
50.879
50.337
49.933
48.537
46.900
45.708
45.012
43.916
43.416

46.788
46.390
45.880
45.430
45.550
46.322
47-188
48.449
49.726
50.901
51.830
52.581
53.193
53.620
53.693
54.007
53.872
53.346
52.442
51.019
49.518
48.998
48.154
47.513

52.587
52.250
52.116
51.887
51.933
52.829
53.625
54.775
56.041
57.158
58.158
58.654
59.025
59.700
60.216
59.808
59.575
59.145
58.383
56.654
55.371
54.483
53.712
53.187

56.167
55.999
55.593
55.152
55.660
56.718

57-877
59.116
60.499
61.626
62.500
63.842
63.935
64.334
64.649
64.703
64.825
64.671
63.837
61.553
59.821
58.546
57.740
56.817

55.327
55.068
54.780
54.564
54.632
55.029
56.021
57.193
58.380
59.535
60.297
61.254
61.714
61.913
61.915
62.155
02.043
61.743
59.963
58.694
57.688
56.704
56.039
55.51?

53.829
53.579
53.096
52.716
52.596
52.858
53.646
54.921
56.525
57.470
58.583
59.500
60.300
60.637
60.529
59.937
59.921
58.666
57.337
56.539
55.791
55.137
54.721
54.109

48.077
47.976

47-877
47.838
47.558
47.142
47.548
48.175
48.868
49.992
50.879
51.533
51.954
52.018
51.727
51.132
50.478
49.756
49.132
48.603
48.451
48.064

47-771
47635

39.862
39.600
39.737
39.664
39.750
39.841
40.058
40.092
40.562
41.462
42.466
43.079
43.433
43.704
43.754
42.825
42.158
41.796
41.383
41.071
40.825
40.333
39.941
39.708

38.942
39.020
39.062
38.966
38.908
39.062
38.997
39.134
39.359
39.694
40.522
41.008
41.184
41.216
40.790
40.502
40.186
39.937
39.494
39.379
39.311
39.250
39.126
39.072

46.134
45.933
45.689
45.449
45.394
45.653
46.2&J
47-029
48.055
49.012
49.950
50.777
51.149
51.470
51.532
51.239
50.872
50.294
49.544
48.624
47.829
47.276
46.803
46.398

3

4

5
6 ..

7 ..

8 ...

9

10

11 ......

12 ....

1 P.M.

2

3

4 .

.,.5

6

7 .

8
9
10

11

12

The Mean Temperature obtained from the last columns of the preceding Table is 48°.266.
occurred at 9h 13' A. M. and 8h 27' P. M.

It

every Hour of the Day at Leith Fort in 1824 and 1825. 371

HAVING given, in the preceding Tables, all the numerical re-
sults of the hourly Register for 1824 and 1825, I shall now
proceed to consider some of the most important conclusions
which may be deduced from them. These relate,

1. To the form and character of the annual and monthly

daily curve, or the daily progression of temperature.

2. To the determination of the two times of the day when

the mean temperature occurs.

3. To the relation between the mean temperature of the 24

hours, and that of any single hour, or pair of similar
hours, &c.

4. To the average daily range for each month.

5. To the Parabolic form of the branches of the Annual Daily

•/

, oni

1. On the Form and Character of the Annual and Monthly Daily
Curve, or the Daily Progression of Temperature.

The daily curve for 1824 is projected in Plate XIV., from
the numbers in the last column of Table II., and forms the low-
est curve. The point of the curve for each of the 24 hours is
the mean of 366 observations. The temperature is lowest be-
tween 4 and 5 o'clock in the morning ; it then increases with
great regularity till three o'clock in the afternoon, when it de-
scends till it reaches its minimum at 5 o'clock in the morning.
The period during which it performs its ascending motion is
9h 40', and the period of its descending motion is 14h 20' ; the
heat of the day, therefore, advances with more rapidity than the
cold of the night.

The daily curve of 1825 is projected in a similar manner in
Plate XIV. from the first column of Table IV., and forms the

372 Dr BREWSTER on the Register of the Thermometer kept

upper curve of the Plate. Each point of it is the mean of
365 observations. Its resemblance and general parallelism to
that of 1824, cannot fail to strike the reader, and proves how
nearly these observations have conducted us to the form of the
daily curve.

The intermediate curve, which is laid down from the last co-
lumn of Table VI., and is the mean of the two curves, is nearly
free from the very slight inequalities in the afternoon branch of
both curves, and may be considered as representing with great
accuracy the mean annual daily curve for the Latitude of Leith,
and at the level of the sea.

In order to observe the variation in the form of the daily
curves for different seasons, I have given in Plate XV. and XVI.
their projections for every month in 1824 and 1825; and in
Plate XVII. the mean of the monthly curves in 1824 and 1825.
These curves obviously divide themselves into three groupes or
classes, viz. 1. The Curves of High Temperature, such as those of
June, July, August and September ; 2. The Curves of Low Tem-
perature, such as those of November, December, January, February,
March ; and, 3. The Curves of Moderate Temperature, such as
those of April, May, and October.

But though the curves thus group themselves into three va-
rieties of temperature, yet it is obvious that those of April and
May have the same form as those of the summer months, while
the curve of October resembles the flat curves of the winter
months. In order, therefore, to obtain a type of the daily curves
of summer and winter, I have joined October to the winter
months, and April and May to the summer ones, as in the fol-
lowing Table for 1824 and 1825*.

* It is probable that the Royal Society of Edinburgh will publish a series of
Plates representing the daily curve for each day of 1824 and 1825.

at Leith Fort every Hour of the Day in 1824 and 1825. 373

TABLE, shewing the Mean Temperature of each Hour for Six Summer Months,
from April to September inclusive, and for Six Winter Months from October to
March inclusive.

Hours.
1 A.M.
2

3

4

5

6

7

8

9
10
11
12

1 P.M.

2

3

4

5

6

7

8

9
10
11
12

Mean, 54.59

40.63

By means of this Table I have projected the summer and
winter curves, as in Plate XVIII. These curves are beautifully
regular, and may be regarded as an accurate type of the daily
progression of temperature in summer and winter, each point of
each curve being the mean of about 180 observations.

374 DR BREWSTER on the Register of the Thermometer kept

The summer curve descends regularly from midnight till 4
o'clock in the morning, when the coldest time of the day occurs,
and it ascends with great regularity till 3 o'clock, when it
commences a very rapid descent to its minimum ; the total
mean range being about 8°. 61.

The winter curve, on the contrary, has a gentle rise from
1 A. M. till 2 A. M. It then descends till 6, when it commences
its ascent, reaches its maximum at 2, and again descends, but
more slowly than it rose, the greatest difference of temperature
being about 3°.86. By examining the individual curves which
compose the winter group, especially in the means of 1824 and
1825, the rise of temperature after midnight, and its subsequent
fall, will be very apparent, — an effect which never takes place in
the curves of summer.

The difference of character in the curves of April and Octo-
ber deserves to be noticed. Although these months are consi-
dered as giving nearly the mean of the year, and therefore as re-
sembling each other in temperature, yet there is a singular dif-
ference in the mode of its distribution. In October the mornings
and evenings are comparatively warm, while in April these
times of the day are remarkably cold. April, in short, unites
the low temperature of a winter month, with the great range of
a summer month ; while October unites the temperature of a
summer month, with the low range of a winter one.

II. On the Determination of the two times of the Day, when the
Mean Temperature occurs.

I am not aware of any observations made in our climate, by
which the hours, when the mean temperature of the day occurs,
could be determined. It has generally been believed that it oc-
curs at 8 o'clock in the morning ; and Professor PLAYFAIR not

at Leith Fort every Hour of the Day in 1824 and 1825. 375

only considers this as nearly the hour of mean temperature for
Edinburgh, but he regards the maximum as occurring " from 1
to half past 2, or even 3 o'clock * ;" and upon these principles he
has selected his three hours, viz. 8 A. M ., the time of maximum,
and 10 o'clock P. M.

It appears, however, from Tables II., IV. and VI. that the
mean temperature of the 24 hours occurs at the following times :
*» ,

Hours of Morning Hours of Evening

Mean Temperature. Mean Temperature.

1824, D' 13 8 26

1825, 9 13 8 28

Mean of two years, 913 8 27

This very extraordinary agreement between the results of
1824 and 1825, shews how nearly we have approximated to the
true form of the daily curve, and how much confidence may be
placed in the general result. The following may therefore be
regarded as the leading points of the annual daily curve.

M. •! ,3<

Time of Minimum Temperature, a little before 5 0 A. M.

Time of the Morning Mean Temperature, 9 13 A.M.
Time of Maximum Temperature, 2 40 P.M.

Time of Evening Mean Temperature, 8 27 P.M.

Interval between Minimum and following Maximum, 9 40

Interval between Maximum and following Minimum, 14 20

Interval between Morning and Evening Mean, 11 14

Interval between Minimum and Morning Mean, 4 13

Interval between Evening Mean and following Minimum, 8 33

* Edinburgh Transactions, vol. iv. p. 214, and vol. v. p. 293, 294. Mr PLAY-
FAIR also adds, that 10 o'clock p. M. is " as near as circumstances will allow to the
time of greatest cold.1" These opinions prove how little was then known of the form
of the daily curve. It will be seen from Plate XVIII. that, both in the winter and
the summer curve, the maximum temperature is never before 3 o'clock, and that
10 o'clock at night is nearer the mean than the minimum temperature of the day.

VOL,. X. P. II, 3 B

376 Dr BREWSTER on the Register of the Thermometer kept

The determination of the exact times of mean temperature
throughout the year, furnishes us with the two best times of the
day for recording the indications of the thermometer. These
times at Leith are obviously 9h 13' A. M. and 8h 27' P.M. ; for, if
any of the observations is accidentally omitted at one of the hours,
the mean of the remainder will approach nearer to the mean
temperature of the year, than if any other two hours had been
taken, and similar omissions made.

There is, however, another advantage of this determination,
namely, that the mean temperature of the year may be obtained
with great accuracy by a single observation made every day at
one of the times of mean temperature. Let us suppose that we
wished to determine the mean temperature of the year 1825 at
Leith, and that we had possessed no other observations than a
single daily one made at 9h 13', then the mean of these 365 daily
ones would have been 48°.944, the very same result that has been
obtained in 1825 from 24 observations every day.

If we examine the annual curve, and also the monthly curve,
it will be seen, that the ascending or morning branch is more re-
gular in its progression than the descending or evening branch.
On this account, we would prefer a single observation every day,
made at the time of the morning mean, to a single observation
made every day at the time of the evening mean.

It must be carefully observed, that the hours of mean tem-
perature which we have now been considering, are only mean
results for the whole year. If we wished to deduce the mean
monthly temperatures from an observation made once a-day, it
would not answer to take 9h 13' A. M. and 8h 27' P. M. ; for the
times of mean monthly temperature occur at different hours of
the day throughout the year, as will appear from the following
Table :

at Leith Fort every Hour of the Day in 1824 and 1825. 377

TABLE, shewing the Hours of the Morning and Evening when the Mean Monthly

Temperature occurs.

Mean

of

1824.

n

1825.

>

1824 &

1825.

A.M.

P.M.

A.M.

P.M.

A.M.

P. M.

H. ,

H. , .

H. ,

H. ,

H. .,

B. ,

January,

11 4

7 17

10 7

6 37

10 34

6 57

February,

10 9

6 11

9 56

7 40

10 2

6 56

March,

10 19

7 8

10 1

9 9

10 10

8 8

April,

8 58

8 35

9 4

8 17

9 1

8 26

May,

9 21

8 26

9 7

8 54

9 14

8 40

June,

9 27

8 2

8 47

8 47

9 7

8 24

July,

8 51

8 36

8 59

8 45

8 55

8 40

August,

8 51

8 13

9 8

8 25

i) 0

8 19

September,

8 44

8 39

9 0

7 57

8 52

8 18

October,

9 46

6 54

9 4

6 42

9 25

6 48

November,

9 56

7 21

9 23

8 0

9 39

7 41

December,

10 15

5 45

9 37

6 45

9 56

6 15

1824.

*

1825.

A

Mean of
1824 & 1825.

A

H. ,

9 2

10 12

H. ,

8 25
6 49

H. ,-

9 1
9 42

H. ,

8 31

7 29

H. ,

9 li
9 57

8 28
7 9

The following are the results for the six winter months, from
October to March inclusive, and for the six summer months,
from April to September inclusive :

Six Summer months,
Six Winter months,

III. On the relation between the Mean Temperature of the 24 Hours
and that of any single Hour, or any similar Pair of Hours,

'

It was long the practice of meteorologists to observe the ther-
mometer three times a-day, on the supposition that the mean of
these three observations gave the mean temperature of the 24
hours. Observations of this kind are still continued in many

3 B2

378 Dr BREWSTER on the Register of the Thermometer kept

parts of Europe. To the following short Table of some of
these, I have added the deviations from the mean temperature,
as computed from the results of the preceding Tables :

Morning.

Edinburgh, - 8h
Williamstown, 7
8

Deviation from
Afternoon. Night. Mean Temp, of day.

o

Maximum. 10h + 0.346 Professor Playfair.
2 9 +0.510 Professor Dewey.

1 6 +1.225 Proposed by the Phil.

Soc. of New York.

As three daily observations are not convenient for many me-
teorologists, who are engaged in professional pursuits, it became
desirable to select those two hours, the mean of whose tempe-
ratures approached nearest to that of the whole day. The fol-
lowing times have been used in this country, and many of them
give results that differ very considerably from the mean tempe-
rature of the 24 hours :

Hawkhill,

Gordon Castle,

Kinfauns,

Ditto,

Leadhills,

Isle of Man,

Royal Society, London,

Morning.

Afternoon.

8

2

8

2

8

10

10

10

6

1

9

11

9

34

9

3

9

24

8|

3

Royal Society, Edinburgh,

8
8
7
7
10

3
2
8
2
10

84

84

Deviation from Mean
Temp, of Day.

+ 0.982
+ 0.982

— 1.114

— 0.122

— 0.134

— 0.838
+ 1.453
+ 1.526
+ 1.511
+ 1.273
+ 1.258
+ 1.01S
+ 0.982
+ 0.641
+ 0.610

— 0.120

— 0.805
0-000

at Leith Fort every Hour of the Day in 1824 and 1825. 379

I have given these examples principally with the view of
shewing the application of the results of the hourly register, and
not with the design of contrasting the hours employed by diffe-
rent observers ; for it yet remains to be determined how far the
form and dimensions of the daily curve, as determined for Leith,
are applicable to places in different latitudes, and situated
at different heights above the sea. At Paris, for example, the
mean temperature of the day occurs before 9 o'clock in the morn-
ing ; and at Tweedsmuir * in Scotland, 1 300 feet above the sea,
it happens before 7^h A.M. ; but it must be remarked, that the ob-
servations at 9 o'clock in the one case, and at 7^h in the other,
are compared with a calculated mean temperature, and not with
the mean temperature of the whole 24 hours j- .

It is curious to remark, that, with the exception of the hours
of 10 A. M., and 10 p. M., no similar pair of hours has been used
by meteorologists. The following Table will shew how nearly
at Leith the mean of every similar pair of hours approaches to
the mean temperature of the day.

* At Salem, Massachussets, where a very accurate register has been kept by Dr
Holyoke for twenty-six years, the morning mean temperature always occurs before
8 o'clock in the morning.

f According to a very accurate register kept by Mr FAIHLIE, schoolmaster of

this parish, the results for 1825 are,

•j;;

Mean Temp, at Mean Temp, at Mean Temp, deduced

74k A. M. 8J11 P. M. from these.

45M67 4

880 Dr BREWSTER on the Register of the Thermometer kept

TABLE, showing the Deviations of the Mean Temperature of every similar Pair
of Hours from that of the Day.

Hours.

1824.

1825.

MEAN.

5

A.M. ... 5 P.M.

— 0°.193

— 0.073

— 0/133

6

... 6

— 0.398

—0.187

— 0.292

7

... 7

— 0.448

—0.256

— 0.352

8

... 8

— 0.478

— 0.401

— 0.440

9

... 9

— 0.298

— 0.350

— 0.324

10

... 10

— 0.148

— 0.096

— 0.122

11

... 11

+ 0.117

+ 0.105

+ 0.111

12

... 12

+ 0.352

+ 0.286

+ 0.319

1

... 1

+ 0.447

. + 0.301

+ 0.374

2

... 2

+ 0.507

+ 0.364

-f 0.435

3

... 3

+ 0.447

+ 0.242

+ 0.345

4

... 4

+ 0.092

+ 0.065

-f 0.079

From this Table it follows,

1. That of all the similar pair of hours, the mean of 4h

and 4h approaches nearer to the mean temperature of
the day than any other pair.

2. That the deviation of any pair is less than half a degree

of Fahrenheit's scale.

3. That the mean temperature of the pairs from 5b to llh

are less than the mean temperature of the day ; and
that the mean temperature of the pairs from llh to 5h
exceed the mean temperature of the day *.

* It now became interesting to compare with these results those deduced from
Mr COLDSTKEAM'S hourly register for one day in each month of the year, and also
those obtained by Professor DEWEY at Williamstown in North America.

at Leith Fort every Hour of the Day in 1824 and 1825. 381

In some instances, meteorological registers have been kept,
in which the thermometer has been observed only once a-day.
These registers may now be rendered useful, by means of the

Results deduced from Mr COLDSTREAM'S Observations in 1822 and 1823.

Deviations from the
Hours. Mean Temp, of the day.

5 and 5 + o!fl05

6 ... 6 —0.445

7 ... 7 —0.574

8 ... 8 —0.580

9 ... 9 —0.674

10 .. 10 —0.207

11 ... 11 —0.170

12 ... 12 —0.106

1 ... 1 +0.385

2 ... 2 + 0.385

3 ... 3 +0.840

4 ... 4 + 1.018

The law of the deviations in this table is very regular, particularly when we con-
sider that the observations were made only on twelve days in the year.

Results deducedfrom Professor DEWETI'S Observations.

MARCH 1816. APRIL. JULY. OCTOBER. JAN. 1817-

Hours.

o

o

o

o

o

5

and 5

+ 0.64

— 0.41

— 0.49

— 1.77

— 1.15

6

... 6

— 0.76

— 1.48

— 1.03

— 2.85

— 1.51

7

... 7

— 1.39

— 1.26

— 0.91

—3.81

— 1.91

8

... 8

— 1.44

— 0.87

— 0.92

— 2.95

— 1.55

9

... 9

— 1.96

— 0.44

— 0.60

— 0.64

— 0.35

10

... 10

— 1.38

— 0.28

— 0.89

+ 0.86

+ 1.44

11

... 11

— 0.62

+ 0.97 *

—0.15

+ 2.60

+ 3.47

12

... 12

+ 0.69

+ 0.07

+ 1,48

+ 1.82

+ 0.31

1

... 1

+ 1.35

+ 1.02

+ 1.48

+ 2.10

+ 0.67

2

... 2

+ 2.03

+ 1.23

+ 1.56

+ 2.45

+ 0.77

3

... 3

+ 1.68

+ 0.74

+ 1-47

+ 1.91

+ 0.44

4

.. 4

+ 1.02

+ 0.57

— 0.21

+ 0.28

— 0.12

There is an error in Professor Dewej's mean of 11 p. M. i it should be 34°.92, in place of 38'.ft2.

382 Dr BREWSTER on the Register of the Thermometer kept

following Table, which shews the relation between the mean
temperature of each hour and that of the whole day :

Hour.

1824.

1 A. M.

— 1.97

2

— 2.19

3

— 2.41

4

— 2.66

5

— 2.77

6

— 2.59

7

— 1.95

8

— 1.27

9

— 0.18

10

+ 0.65

11

+ 1.62

12

+ 2.50

1 P. M.

+ 2.86

2

+ 3.20

3

+ 3.30

4

+ 2.84

5

+ 2.38

6

+ 1.79

7

+ 1.05

8

+ 0.31

9

— 0.42

10

— 0.95

11

— 1.39

12

— 1.80

1825.

— 2.296

— 2.478

— 2.746

— 2.975

— 2.976

— 2.637

— 2.017

— 1.206

— 0.244
+ 0.840
+ 1.747
+ 2.520
+ 2.904
+ 3.206
+ 3.230
+ 3.105
•4- 2.830
+ 2.264
+ 1.505
+ 0.404

— 0.456

— 1.031
— 1.537

— 1.937

Mean of
1824 & 1825.

— 2.133

— 2.334

— 2.578

— 2.818

— 2.873

— 2.613

— 1.983

— 1.238

— 0.212
+ 0.745
+ 1.683
+ 2.510
+ 2.882
+ 3.203
+ 3.265
+ 2.972
+ 2.605
+ 2.027
+ 1.277
+ 0.357

— 0.438

— 0.990

— 1.463

— 1.868

From this table, it appears, that the mean annual tempera-
ture of any hour of the day never differs more than 3°| from the
mean temperature of the day for the whole year. It deserves
also to be noticed, that the deviations in the year 1825 are uni-
formly greater than those in 1824, which no doubt arises from
the former having been a much warmer year than the latter.

In order to obtain the mean temperature of the year from a
register which contains observations made only once every day,
we have only to correct the mean temperature which the regis-

at Leith Fort every Hour of the Day in 1824 and 1825. 383

ter gives, by applying, according to its sign, the correction oppo-
site to the given hour. In place of taking the mean of the two
years, it might be preferable to take the results for 1824 in cold
years, and those for 1825 in warm years.

Before concluding this part of the subject, it may be inte-
resting to ascertain, from the preceding results, the relation be-
tween the mean temperature of the day, and the results obtain-
ed from the hours used at Paris, Halle, and Abo, where the ther-
mometer is observed more than three times :

Hours used :

Deviation from the
Morning. Noon. Afternoon. Evening. Mean Temp.

Paris*, - 9 12 3 9 +1.282

Halle, 8 12 2 6 10 +1.103

Abo, aW. 8 11 2 510+ 1.053

These deviations are very great, and shew how little is gain-
ed by multiplying observations, as in the preceding journals.
Any two pair of similar hours would have given deviations less
than one-third of those in the preceding table. Indeed, it is ob-
vious, that any number of observations made during the day, can
never give a correct mean, without corresponding observations
made late at night and early in the morning. In the register at
Paris, Halle, and Abo, it would require the addition of the mi-
nimum to obtain the proper mean, as appears from the following
Table :

Deviation from th«>

Morning.

Noon. Afternoon.

Evening.

Mean Temp.

Paris,

Minimum,

9

12

3

9

+ 0?451

Halle,

Minimum,

8

12

2

6

10

+ 0.441

Abo,

Minimum,

8

11

2

5

10

+ 0.399

* The hours of 9 and 9 being nearly those that give the mean temperature of
the day, it is obvious, that the mean of 12 and 3, must give a result considerably
above the mean temperature of the day, and consequently, that the mean of ail
the^/owr observations must err considerably in excess.

VOL. X. P. II. 3 c

384 Dr BREWSTER on the Register of the Thermometer kept

Even with the addition of the minimum, it appears that the
mean temperature of these hours errs in excess.

IV. On the average Daily Range for each Month.

In a climate so variable as that of Scotland, the daily range
of the thermometer is often very great, both in winter and in
summer ; but the average daily range which we propose now to
notice, is the measure of the daily change of temperature for
each month, and will of course bear some relation to the sun's;
declination, as appears from the following Table :

TABLE, showing the average Daily Range of Temperature for each Month, anil

for the whole Year.

•

1824.

1825.

Mean of
1824& 1825*.

Hour of

Hour of Daily

Hour of

Hour of Daily Hour of

Hour

of Daily

Min.

Max.

liange.

Min.

Max.

liange.

Min.

Max.

Range.

H.

H.

H.

H.

•

H.

H.

January,

5

3

3.11

6

2

2.258

6

3

2.662

February,

8

u

3.68

6

3

3.910

6

3

3.570

March,

6

3

5.45

5

4

7.209

6

3

6.152

April,

5

3

10.3

5

3

10.958

5

3

10.629

May,

4

3

10.0

4

5

7.484

4

4

8.577

June,

44

3

8.1

4

3

8.558

4

3

8.263

July,

4

4

8.7

4

4

10.404

4

5

9.673

August,

4

4

7.5

5

54

7.822

4

4

7.591

September,

4

3

7.6

5

2

8.573

5

2

8.041

October,

6

H

5.1

4

2

4.661

6

2

4.876

November,

12

94

4.4

9.

8

4.008

2

3

4.154

December,

74

i

2.4

12

2

2.677

5

2

2.308

Whole year,

5

3

6°.07

5

3

6°.06

5

3

6°.138

This column is computed from Table VI. and is not the mean of the two preceding columns.

at Leith Fort every Hour of the Day in 1824 and 1825.

From the general character of the year 1825, these results,
as might have been expected, present greater uniformity in that
year than they do in 1824, or even in the mean of the two years.
The mean range is nearly at its maximum about the winter sol-
stice, and gradually increases till April, when it reaches its maxi-
mum. It then declines, and again rises to a second maximum
in July, after which it gradually diminishes till the end of the
season. The mean range for the year is 6°.065, and does not
vary above the 100th part of a degree in 1824 and 1825.

V. On the Parabolic form of the different branches of the Mean

annual Daily Curve.

Before concluding this Report, I was desirous of ascertaining
if the different branches of the daily curve had a resemblance to
any known curve. Their similarity to the parabola is very ob-
vious, from Fig. 2. of Plate XIV. where they are distinctly pro-
jected ; and I therefore calculated the following Table, upon the
supposition that AB, BC, CD, and DE, were parabolic branches
of the following dimensions :

-.

Branch

AB,

Ordinate,

AH

= 513

Abscissa,

BH

= 172

or 2°.873

Branch

BC,

Ordinate,

CH

= 253

'> +

Abscissa,

BH

= 172

or 2°.872

Branch

CD,

Ordinate,

CG

= 347

0-f

Abscissa,

DG

= 196

or 3°.266

Branch

DE,

Ordinate,

EG

= 327

Abscissa,

DG

= 196

or 3°.266

The ordinates 513 -f- 253 + 347 -f 327 are ~ 1440^ ~ 24
hours ; and the abscissa BH — 2°.872, and DG = 3°.266; when
reduced to the same scale as that of the ordinates, become 1 72

3 c 2

386 Dr BREWSTER on the Register of the Thermometer kept

and 196', as one degree of temperature on the projection is equal
to one hour. The abscissas which represent the temperature

were reconverted into degrees.

TABLE, shewing the Mean Annual Hourly Temperature for 1824 and 1825, as ob-
served, and calculated on the supposition of these being the abscisses of Parabolas >

Difference.

0.000
+ 0.075
+ 0.039
+ 0.003

— 0.024

— 0.113

— 0.186

— 0.138

— 0.016
0.000

— 0.098

— 0.244

— 0.184

— 0.082
0.000

+ 0.079
4-0.019
—0.124

— 0.008
—0.036

0.000
+ 0.183
+ 0.219
+ 0.250
+ 0.229
+ 0.159

0.000

The numbers in column 3. were calculated by the following
formulae. From the property of the parabola, we have

Hours.

Observed Temp.

Calculated.

H. • ,

e

8 27 P. M.

Mean, 48.266

Mean, 48.266

9

47.829

47.904

10

47.276

47.315

11

46.803

46.806

12

46.398

46.374

1 A. M.

46.134

.46.021

2

45.933

45.747

5

45.689

45.551

4

45.449

45.433

5

Min. 45.394

Min. 45.394

6

45.653

45.555

7

46.283

46.039

8

47.029

46.845

9

48.055

47.973

9 13

Mean, 48.266

Mean, 48.266

10

49.012

49.091

11

49.050

49-969

12

5Q.1TI

50.653

1 P. M,

51.149

51.141

2

51.470

51.434

3

Max. 51.532

Max. 51.532

4

51.239

51.422

5

50.872

51.091

6

50.294

50.544

7

49.544

49.773

8

48.624

48.783

8 27

48.266

48.266

at Leith Fort every Hour of the Day in 1824 and 1825. 387

BH : Bm = HA* : win* ; and
BH x mn?

Bm =

HA*

But since AE is the line of mean temperature, pn the depres-
sion of the temperature below the mean at the point of time p,
and pn = Hm = HB — Bm, then, calling p the mean tempe-
rature, and y the ordinate mw, we have the required tempera-
ture T at the time p, thus :

T HB j. HBx.V*-

= '•" l+ HA«

or if m is the minimum temperature of the daily curve, then, at
the point of time p, we have

For the semi-parabola BC, the formulae are as follows :

T HBx

I = m H pr

CH*

For the semi-parabola CD, in which the required tempera-
tures exceed the mean, we have at any point of time p,

or calling M the maximum temperature of the daily curve,

For the semi-parabola DE, we have the following formulae :

T L rr»

1 = (it + UD -- EG* '

EG*

Upon comparing the parabolic abscissae in column 3. with the
observed results in col. 2., it appears, that the greatest difference

388 Dr BREWS r F.I! on the Register of the Thermometer.

is a quarter of a degree of Fahrenheit, and that the differences
are most perceptible in the afternoon branch of the curve, be-
tween 4 p. M. and 8 P. M.

We have no hesitation, however, in saying, that the mean of
a greater number of years will produce a close approximation to
the parabola. In 1824, the afternoon branch is irregular. In
1825. which was a year of uniform character, the afternoon
branch becomes more convex, and approaches closely to the pa-
rabolic branch ; so that the mean of 1 824 and 1 825 whicli we
have given in col. 2. of the Table, and contrasted with the pa-
rabolic abscissae, partakes of the irregularities of 1824, and thus
occasions a flatness in the curve, and consequently the differences
observed between 3h P. M. and 8h 27' P. M.

JMjATK XIV.

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& >

. 1.M.

PL.ATK XV.

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f.Af.

ii in iv v vi vn vni ix x xt xn

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( 389 )

XXVIII. A Historical and Critical Introduction to an Enquiry
into the Revival of the Greek Literature in Italy, after
the Dark Ages. By PATRICK FRASER TYTLEK, Esq.
F. R. S. E. & Sec. Lit. Class.

(Bead 2\st Feb. 1826'.;

A HISTORY of the revival of literature in Europe, after its ex-
tinction in the middle ages, has been long a desideratum in the
annals of human knowledge ; and from the wide, and almost un-
travelled field, which such a history would embrace, and the re-
condite sources of information which rmist be consulted, it will
perhaps be long before any individual is found with sufficient
learning to estimate its difficulties, and yet hardy enough to at-
tempt to overcome them. Lord BACON * has presented us with
an eloquent and comprehensive sketch of the subjects which
ought to be included in a general history of learning. " The
task is none other (says he) than that of extracting, from every
possible source of information, a history of the sciences and the
arts, and marking the different a?ras, and the various regions in
which they have flourished. In this must be pointed out their
earliest origin, their progress to perfection, their travels through-
out different climes, and amid various tribes of people ; for we
know well that the sciences are migratory like nations. The
historian must mark them in their declension, in their somnolen-
cy, in their revival. In his attention to individual arts, he must

* De Augmen. Sclent. B. ii. c. ix.

390 Mr TYTLER'S Introduction to an Enquiry

explain not only their origin, but the causes to which they owe
their invention, the manner in which they have been transmit-
ted, the peculiar discipline, and the particular institutions under
which they have been improved and perfected. But the task is
not concluded. It is moreover the business of such a moral his-
torian, to note the most celebrated sects and controversies which
have sprung from the opinions of learned men, the persecutions
they have suffered, the glories and the honours they have won.
The most celebrated authors, the best books, the most learned
academies, schools, endowments, associations of philosophic spi-
rits, in short, every thing which regards the state and history of
literature, must be carefully described." Such is a feeble trans-
lation from the energetic latinity of the original, presenting us
with an outline, which, as has been remarked * by a later author,
is the most perfect which a scholar could devise, but which no
scholar can hope to complete. Dr JOHNSON, as we learn from
his delightful biographer BOSWELL, " would have a history of the
revival of learning contain an account of whatever contributed
to the restoration of literature, such as controversies, printing,
the destruction of the Greek empire, the encouragement of great
men, with the lives of the most eminent patrons and professors
of all kinds of learning in different countries." To the execu-
tion of this plan, which, although sufficiently vast, is but a cor-
ner of the mighty design of BACON, the works of TIRABOSCHI, of
BRUCKER, of MORHOFF, of BAILLET, and, latterly, of GUINGENE'
and SISMONDI, present us with materials, both of a philosophical
and of a critical nature, which are in the highest degree valuable.
The original volumes of the great restorers themselves, the now

* Preface to " An Introduction to the Literary History of the 14th and 15th
" Centuries," p. 5. ; an anonymous but able and elegant work, published by CADEU.
find DA VIES, 1798.

into the Revival of Greek Literature in Italy. 391

neglected folios of FICINUS, of ERASMUS, of POLITIAN, of Bu-
D^EUS, of the SCALIGEIIS, of CASAUBON, and their fellow-labourers
in the same field, compose a mine in the present day almost un-
worked, yet full of the richest ore. But it is out of this very
circumstance, the voluminousness and the value of the materials,
that the embarrassments of the undertaking arise ; and the mind
which had courageously sketched out the plan of the edifice, may
find, when it comes to struggle with the difficulties of execution,
how wide is the difference between the reveries of literary ambi-
tion, and the realities of literary labour.

When we glance over the various branches of this great sub-
ject, there is perhaps no one division which is more interesting
and important than the revival of the Greek language, and with
it the Greek literature in Italy, during the latter part of the
fourteenth century. For more than seven hundred years it had
been almost wholly lost ; and in the ages which elapsed between
the fall of the Western Empire, in the close of the fifth, and the
incursions of the Turks upon Europe in the fourteenth century,
not only Italy, but Greece itself had been covered by successive
swarms of barbarians. To trace the causes which led to the re-
vival of the language and literature of Greece, after the dark
ages, and to give some account of the lives and writings of
the eminent scholars to whom we owe their restoration, is the
object of the following historical enquiry ; But, before imme-
diately proceeding to this subject, there are two preliminary
questions, upon which it will be necessary to give a short intro-
ductory disquisition. These are, I. What was the brightest pe-
riod of the Grecian language and literature in its own soil, and
to what extent does it appear to have been cultivated in Italy,
after Greece had become a part of the Roman Empire ? II. What
were the effects produced by the inundation of the barbarous

VOL. x. P. ii. 3 D

392 Mr TYTLER'S Introduction to an Enquiry

nations ; and what was the period of the total extinction of the
Greek language and literature in Italy ?

The Grecian language appears to have reached its highest
perfection in that long and bright period, of almost six centu-
ries, which extended from the days of HOMER till the death of
ALEXANDER the Great. HESIOD, the great lyrists TYRT^EUS,
SAPPHO, ANACREON, and PINDAR, the dramatic giants
EURIPIDES, and SOPHOCLES, the historians HERODO-
TUS and THUCYDIDES, the orators LYSIAS, ISOCRATES and DE-
MOSTHENES, the fathers of philosophy PLATO and ARISTOTLE,
and the historian, soldier, philosopher, and accomplished man of
letters XENOPHON, — all these high and gifted spirits, whose
names and works have survived the calamities of more than two
thousand years, were born, and wrote and died in this brilliant
division of time.

This, says HARLES, was the aera of the youth and manhood
of the Greek language. " It was the aera of its .poetry, which at
first nourished in solitary excellence ; the aera of its eloquence,
which was created and encouraged by the constitution of the
Athenian Government, by the manners of that remarkable peo-
ple, their forms of judicial administration, the distribution of
public honours, and the liberty of thought and discussion which
was permitted in Athens. It was an aera full of talent in al-
most every branch of human knowledge, and fertile in minds
of the most splendid genius,— in poets, orators, philosophers and
historians, — and these all, or chiefly, belonging to that wonderful
little republic of Athens *.'

The decay of Grecian literature is to be dated from the de-
struction of Grecian liberty. In the three succeeding centuries
which intervened between the death of ALEXANDER and the

* HAELES, Literature Grsecae Notitia brevior, p. 25.

a 8

into the Revival of Greek Literature in Italy. 393

reign of AUGUSTUS, although the deterioration of the Grecian
language was at first scarcely discernible, yet the seeds of change
were but too surely sown. Greece itself was now occupied
by the Romans, that new and mighty nation which had already
acted so grand a part in the history of the world, and the Attic
muses, as if attracted and dazzled by the Roman triumphs, de-
serted their native valleys, and fixed their seats in the beautiful
fields of Italy. THEOCRITUS and MENANDER, the first in the
sweetness of his pastorals, and the second in the playful elegance
of dramatic poetry, shed, indeed, an auspicious ray over the com-
mencement of this period. POLYBIUS, too, published his ad-
mirable Commentaries ; and a crowd of philosophers, sophists,
and rhetoricians, preserved, in their works of controversy and cri-
ticism, some shadowy traces of the perfection of this noble lan-
guage. But, with metaphysical subtilties, there crept in new
forms of expression. A mixture of foreign nations, and a familia-
rity with less perfect and polished tongues, polluted gradually its
ancient purity ; and, to use the words of HARLES, those symptoms
of decay were visible, which told too surely that the freshness
and vigour of manhood were past, and the infirmities of age ap-
proaching *.

If such was the state of Grecian literature and philosophy
upon the death of AUGUSTUS, under whose reign the Roman
muses were destined to enjoy their highest triumph, it will rea-
dily be believed that the three succeeding centuries, which filled
up the interval from the accession of TIBERIUS to the reign of
CONSTANTINE the Great f, brought only increasing decay and
corruption to the pure and nervous language of DEMOSTHENES
and XENOPHON. Works of talent, and even of genius, were not
wanting. The geographical labours of STRABO J, PTOLEMY ||,

* HARLBS, p. 209. f From A. D. 14 to 806.

J STRABO died A. D. 25. || PTOLEMY, A. D. 161.

3 D 2

394 Mr TYTLER'S Introduction to an Enquiry

and PAUSANIAS ; the multifarious and amusing compilations of
PLUTARCH * , in philosophy, the amiable and original meditations
of the Emperor ANTONINUS f, are, of themselves, sufficient to
vindicate this age from any imputations as to deficiency in en-
terprise, or imbecility in thought and reasoning. Nor ought the
moral historian to forget, that the same era was illuminated by
the brilliant satyric wit of LUCIAN £, and instructed by the cri-
ticism of LONGINUS || . Some few historians also, yet of inferior
note, (^ELIAN, Dio CASSIUS, and HERODIAN), put forth their
feeble efforts ; but, with the single exception of the philosophic
soldier ARRIAN §, nothing was produced in history in any de-
gree worthy of the better days of Greece. If, however, even in
the most favourable instances, we turn from the works them-
selves to the language in which they are written, the change is at
once apparent and mortifying. The " undented well of Attic
purity," the clear, strong, various, yet simple language of Greece,
in its better days, had become insensibly but deeply polluted.
The Roman conquests, the mixture of strangers, the incursions
of the barbarians, the controversies between the Christians and
the supporters of the ancient philosophy, were the chief causes
which contributed to produce this deterioration ; and if, at the
conclusion of the second period, and in the days of AUGUSTUS,
the approach of age was distinctly visible upon the fabric of this
once noble language, in the days of CONSTANTINE these symp-
toms were not only confirmed, but increasing in strength, and
hastening to their consummation. " Flos Atticae elegantiae atque
eloquentiae (says HARLES) magis magisque deflorescere ccepit, et
sensim periit ^[."
Uu _ . _— — — —

* PLDTAUCH died A.D. 120. •}• ANTONINUS, A. D. 161.

\ LUCIAN, uncertain, probably in 170. || LONGINUS. slain A. D. 275.

§ ARRIAN lived under HAKUIAN, ^f HARLES, p. 303.
A. D. 147.

into the Revival of Greek Literature in Italy. 395

Such being a slight sketch of the revolutions of Grecian lite-
rature, from the age of HOMER till the era of CONSTANTINE, it
will not be unimportant to consider for a few moments the se-
cond part of our first preliminary question, namely, To what ex-
tent does Grecian literature appear to have been cultivated in Italy
after Greece itself was incorporated as a part of the Roman em-
pire ? And, in \hefirst place, It is evident that the Roman people
had no opportunities of becoming familiar with the poetry or li-
terature of Greece during its first and most brilliant period. At
the death of ALEXANDER the Great, the Romans were a brave
but yet an infant people, or rather tribe, engaged in an obsti-
nate struggle with the Samnites, obliged to defend their territo-
ries against the invasion of PYRRHUS, and, after the subjugation
of both these rivals, embroiled in a most fierce and lengthened
war with the Carthaginians. Immediately after the commence-
ment of the third Punic War *, their legions, for the first time,
entered Asia, and, with that overwhelming impetuosity which
characterizes the progress of their arms at this period, overturned
the ancient kingdom of Macedon, reduced the Achaeans, and
soon became masters of Greece. It is at this period of the third
Punic War, that the earliest traces of a literary spirit are to be
discerned in the history of the Republic, — that PLAUTUS, ENNIUS
and TERENCE began to imitate the masterpieces of Greece.
From this period of the dawn of Latin poetry, till the days
of AUGUSTUS, the literature and the language of Greece, if
not completely familiar td the nation in general, as some
writers have erroneously supposed, were certainly well known
to the poets, the orators, and the historians of Italy. It
may even be asserted, that, down to a much later period in

* An. C. 149.

396 Mr TYTLER'S Introduction to an Enquiry

the history of the Western Empire, the literature of the Ro-
man people, and the education of the Roman youth, evinced not,
indeed, an acquaintance with the purest Grecian writers, but at
least a knowledge of the language and philosophy of Greece,
such as they then existed, polluted indeed, and obscured, but
still retaining distinct traces of their original brightness. The
proofs of this assertion are certain and multifarious. The few
noble fragments which remain to us of ENNIUS, the father of the
Latin epic school, his study of the great Grecian models ; the
well-known popularity of MENANDER; the translations of many
parts of XENOPHON, PLATO and DEMOSTHENES, by CICERO ; the
fact that this great Orator could declaim in Greek* ; the asser-
tions of SUETONIUS concerning the profound knowledge of this
language, which had been attained by CLAUDIUS ; its cultivation
under some of the succeeding Emperors ; and the injunctions of
QUINCTILIAN, who recommends that his youthful pupils should
be introduced to an acquaintance with this noble language, even
prior to the study of their own ; all these facts very clearly show,
that the study of Greek letters was pursued not only by the
Poets and Orators, who there sought for their highest models of
imitation, but that it formed at Rome an important branch in
the education of its youth.

If such was the universality of the knowledge of the Grecian
language and literature in the days of AUGUSTUS and his succes-
sors, an acquaintance with these great sources of beauty and wis-
dom became still more prevalent in the reigns of HADRIAN, AN-
TONINUS Pius and MARCUS AURELIUS. In the commencement
of the second century, HADRIAN was an enthusiastic and unwea-
ried patron of the Greeks and their language. The temples of
Athens were rebuilt by his munificence, the public games re-

* Palaeoromaica, p. 26, 33.

into the Revival of Greek Literature in Italy. 397

stored, and a noble library, and new gymnasium, provided for
the instruction and exercise of youth. Education, says CHAND-
LER, now flourished in all its branches at Athens. The Roman
world resorted to the schools, and reputation and riches awaited
the able professor. At this period Athens abounded in philoso-
phers. It swarmed, according to Luc IAN, with cloaks, and staves
and satchels ; you beheld every where a long beard, a book in the
left hand, and the walks full of companies discoursing and rea-
soning. The enthusiasm of HADRIAN was seconded by the ef-
forts of his successors ANTONINUS and MARCUS AURELIUS, both
of them philosophic Emperors, and both deeply smit with the
love of Grecian literature. After the death of AURELIUS, for
more than a hundred years of crime and bloodshed, the Greek
language presents in its fate and fortunes a striking contrast to
the more melancholy destinies of its sister the Latin. It was pre-
served, certainly not in its original purity, yet in a state far re-
moved from decay, in the works of LUCIAN, Dio CASSIUS, HERO-
DIAN and LONGINUS. CONSTANTINE the Great, although him-
self little of a Grecian scholar, yet by the removal of the seat of
empire from Rome to Constantinople, promoted the more gene-
ral study of this language. It is well known, that to the Empe-
ror JULIAN, even from the days of his earliest youth, the religion A. D. 363
and philosophy of Greece were subjects of peculiar predilection,
and that this extraordinary man considered the Greek language
as his native tongue, and the language of Rome as a foreign and
less familiar dialect *.

Such is a slight sketch of the fate and fortune of Greek lite-
rature in Italy, down to the momentous period when the north-
ern nations, by partial inroads upon the frontiers, began to
threaten the empire, which they finally destroyed.

* Palaeoromaica, p. 40.

398 Mr TYTLER'S Introduction to an Enquiry

Towards the middle of the third century, some indications of
an irruption of the northern nations were discernible ; but these
formidable enemies may be said to have contained themselves
within their original settlements, until, in the fourth century, an
inundation of the Huns drove the northern tribes from the
countries where they had hitherto led a warlike and migratory
life, and compelled them to seek permission of the Emperor VA-
I,ENS to settle in Thrace. This was granted, probably it could
not have been prudently denied, and the historians of these
times affirm, that the whole of Thrace was almost instantly co-
vered by successive waves of this living flood of men. Macedo-
nia and Pannonia soon became entirely occupied by the multi-
tudes of stranger emigrants ; their tents were even pitched upon
the classic borders of Thessaly ; and war, as was to be expected
from the proximity of such formidable neighbours, was almost
instantly commenced with the Roman Empire. At the head of
his Goths ALAR ic penetrated to the borders of Italy, and the
pusillanimity of the Emperor ARC ADI us was content to purchase
an ignominious peace, by ceding to him the whole of Greece.
His next object was the conquest of Italy, which, after his army
had been reinforced by a new inundation of the Suevi, Alani and
Vandals, he concluded by the sack of Rome, in the commence-
ment of the fifth century. It is well known that he died when
meditating the conquest of Sicily and Africa. Every successive
year now more effectually confirmed the dominion of the
northern nations over the wide extent of the Western and
Eastern Empire.

Rome, as we see, was taken in the beginning of the fifth cen-
tury. In the same period the Vandals had established their
monarchy in Spain. Carthage soon after fell, and the Roman
provinces in Africa became subject to the same victorious people.
ATTILA, the scourge of the human race, next appeared, to act his
terrible part in the extermination of ancient nations ; and, lead-

into the Revival of Greek Literature in Italy. 399

ing his armies of Huns, overran and desolated the Roman pro-
vinces of Dacia, Thrace, Mysia, and Syria. It would be tedious
and unnecessary to enumerate all the triumphs of the north, and
all the defeats of the once illustrious Romans. Rome herself,
the mistress of the world, was successively taken by GENSERIC
king of the Vandals, ODOACER chief of the Heruli, and THEODO-
RIC prince of the Ostro-Goths, who, from this period acknow-
ledged by the eastern Emperor ZENO as king of the country
which he had subdued, commenced an able and glorious reign.
The brave and unfortunate BELISARIUS retrieved, for a while, by
his victories, the ebbing honours of the Western Empire, and
TOTILA the Goth, who, in the middle of the sixth century, had
again ravaged Italy, and twice become master of Rome, was de-
feated and put to death by the eunuch NARSES. But these tem-
porary triumphs only paved the way for the final and conclusive
victories of the Lombards, another swarm from the northern
hive, who, towards the conclusion of the sixth century, invited
into Italy by NARSES, to revenge his individual injuries, succeed-
ed in reducing to subjection the greatest part of the country.
Their empire continued to flourish from the end of the sixth till
the middle of the eighth century, when it was finally overturned
by CHARLEMAGNE, who, in the city of Pavia, was crowned King
of the Lombards, in the year 744. — Let us pause for a few mo-
ments, to consider the effects of these barbarian inundations
upon the literature of that great country in which they took
place.

The conquests of ALARIC, in the fifth century, did not ma-
terially affect Italy. It was evacuated by the barbarians, and,
although governed by ADOLPHUS, a relation of ALARIC, it was
governed by Roman laws, and the institutions and manners of
the Roman people remained unchanged till the second conquest
of the country by ODOACER, the first barbarian king of the West.
Yet although the Roman laws and language remained, the race

VOL. x. P. n. 3 E

400 Mr TYTLER'S Introduction to an Enquiry

of this ancient people was even at this period fast approach-
ing to extinction. Immense multitudes of Romans, who had
formerly enjoyed dignity and fortune, were reduced to the
state of captives in the barbarian armies, or slaves who culti-
vated their lands. Multitudes were driven, and multitudes vo-
luntarily retired, into exile, consenting to drag on a dependent
existence in the remotest provinces of the empire. Want and
famine, which, in the exhausted state of the provinces, were not
unfrequent visitants, carried off the victims which had been spa-
red by the ravages of war, many of those who remained, inter-
married with the barbarian families, and all these co-operating
circumstances began at this time to have a strong effect in pro-
ducing that physical and moral degradation of this once illustri-
ous people, which, in the course of the succeeding century, and
shortly after the settlement of the Lombard princes, concluded
in the total disappearance of the Roman race. For although still
the names of Roman families remained, nothing but the name
was left. All else was " second childishness and mere oblivion."
THEODOSIUS the Great * succeeded to the empire in the lat-
ter part of the fourth century ; and, during his reign, al-
though the highest qualities of a soldier were successfully and
brilliantly exerted, yet the accumulated difficulties which on eve-
ry side threatened the Western Empire, left little leisure for the
princely patronage of literature, or the peaceful acquisitions of
knowledge. The death of THEODOSIUS sealed the fate of the Ro-
man Empire, which, after lingering through the feeble reigns of
his unremembered successors, closed its mighty history of twelve
centuries, in the sack of Rome by ODOACER king of the Hem-

lif.

The Herulian dominion in Italy, which lasted only for seven-
teen years, was concluded, and the empire of the Ostrogoths

* A. D. 379. + A. D. 476.

f e

into the Revival of Greek Literature in Italy. 401

established, by the taking of Ravenna at the termination of the
fifth century. THEODOIUC, although of barbarian extraction, had
been educated at the Court of Constantinople, and not only him-
self, but his secretary CASSIODORUS, and his minister BOETIUS,
were famih'arly acquainted with the language and literature both
of Rome and of Greece, the cultivation of which appears to have
been a very general passion amongst the learned statesmen who
surrounded his Court. But Grecian literature, as we have al-
ready seen, had, at this period, fallen into a state of melancholy
weakness, even on its own soil, and the beautiful language of At-
tica was now no longer what it once had been.

In those dark ages, when beneath the loss of civil liberty, the
decay of ancient nations, and the inundation of barbarian hordes,
the cause of knowledge and of science was too speedily losing
ground ; the noble stand which was made for it by the Fathers
of the Christian Church ought not to be forgotten. Infinitely su-
perior to their pagan opponents, in the ardour with which they
devoted themselves to literary pursuits, and philosophical stu-
dies ; the sublimity of their doctrines, and the excellence of their
moral precepts, acquired additional strength from the classical
purity of their style. In the department of Grecian literature,
a lustre is thrown over the third century by the single name of
ORIGEN, the theologian *, the philosopher, the grammarian, the
adamantine pillar of the Church. Among the Latin Fathers,
and in the same century, names of no common eminence are to
be found. The dialogue of MINUCIUS FELIX f , a Roman lawyer
and Christian convert, is remarkable for the elegance of its La-
tinity, and for the interesting picture which it presents to us of

* OUIGKN was born at Alexandria in the year 186. ; HAIII.ES, p. 644. ; SPAN-
IIEIM, p. 248. ; CAVE, Historia Literaria Eccles. p. 112. vol. i.

•{• CAVE, Hist, Literaria, p. 101. vol. i.

3 E 12

402 Mr TYTLER'S Introduction to an Enquiry

the manners of the early Christians ; and there are few to whom
the history of their religion is a subject of interest, who have not
heard of CYPRIAN Bishop of Carthage, of his unwearied labours,
his unshaken piety, his eloquence, his misfortunes, and his mar-
tyrdom *.

If the cause of letters was so deeply indebted to the Chris-
tian Fathers in the third century, the exertions of the same en-
thusiastic and learned scholars become still more brilliant during
the fourth and fifth centuries, when contrasted with the increas-
ing darkness of paganism. GREGORY NANZIANSENE f, whose
mind, although engrossed in his labours as a Christian orator,
had imbibed in the schools of Athens the love of the ancient
philosophy ; and CHRYSOSTOM, whose studious and abstemious
youth, nursed for six years in the solitude of the desart £, ripen-
ed into a manhood of unremitting toil, and almost unrivalled
eloquence ; these two great men were sufficient of themselves to
oppose a very successful barrier against the inroads of ignorance
and barbarism. The compositions of CHRYSOSTOM are celebrated
not only by contemporary critics, but by the fastidious philolo-
gists of the sixteenth century, as admirable for their Attic puri-
ty of style || ; and, in the West, the writings of LACTANTJUS, HI-
LARY of Poitiers, JEROME and AUGUSTINE, were serviceable not
only in their zealous, though sometimes ill directed endeavours
for the protection of the infant Church from heresy, but in the
preservation of the purity of the Latin language.

1 may briefly advert to two remaining causes, which at this
period had a powerful effect in preserving from total extermina-
tion the relics of the learning of Greece and Rome ; and one of

* CYPRIAN was slain in the year 258. CAVE, Hist. Literar. p. 126. vol. i.
+ CAVE, Hist. Literar. p. 246- GREGORY flourished in the year 370.
\ CAVE, Histor. Literar. p. 300. || CHRYSOSTOM was born in 354.

into the Revival of Greek Literature in Italy. 403

which was destined to be eminently effectual in the restoration
of letters. The first of these is to be found in the writings of
the civilians ; the second in the rise of monastic establishments
in the fourth century. SALVUS JULIANUS, by order of the Em-
peror ADRIAN (says that learned author formerly quoted) framed
the perpetual edict, or a standing code to extract the essence of
preceding institutes, and exhibit an authentic body of salutary
laws. His successors distinguished themselves by industry and
learning. Proficients in philology, from the necessity of a close
application to the most ancient writers, they employed their
knowledge to correct and refine their language. Well versed in
the fashionable philosophy of Greece, they did not amuse them-
selves with the investigation of metaphysical subtleties, or the in-
volution of moral precepts, but devoted their acquirements to de-
fine the rights, and protect the property, of their fellow-citizens.
It need not be insisted how much such a body of writers have
done for the cause of learning, in counteracting the earlier affec-
tation, and the later barbarisms of cotemporary authors. Even
when the day of destruction came, they still furnished the most
essential services. It was the diffusion of their writings over the
provinces, and the use of the Roman jurisprudence in legal " de-
" cisions, that served to preserve the memory, and almost to em-
" balm the purity of the Latin tongue *."

In this passage the important effects ascribed to the plead-
ings and the writings of the Roman lawyers, throughout the pe-
riod of four hundred years, which elapsed from the reign of
ADRIAN till that of JUSTINIAN, in the beginning of the sixth cen-
tury, are not overrated ; and the three Emperors, to whose en-
couragement we mainly owe this preservation of the Latin lan-
guage, are ADRIAN, THEODOSIUS and JUSTINIAN.

* Introduction to the Literary History of the Fourteenth and Fifteenth Centu-
ries, p. 23, 24.

404 Mr TYTLER'S Introduction to an Enquiry

The obligations which the cause of letters owes to monastic
establishments, were different in their nature, but equal in their
importance. During the persecutions of the Christians in the
fourth century, which at this period were carried forward with
unremitting barbarity, a convert to the new religion, to escape
the terrors of death or torture, concealed himself in the desart of
Egypt. His life of abstinence and solitary piety caused many
devout persons to repair to the desart ; and, during the conti-
nuance of the persecution, the love of life, combined, with the ar-
dour of devotion, to increase the numbers who flocked to the
cave of this holy man ; and, either in emulation of his austeri-
ty, or perhaps under the idea of imitating the Divine Author of
their religion, betook themselves to prayer and seclusion in the
caves and mountains *.

The passion for the monastic life increased in an almost in-
calculable degree during the succeeding centuries. The differ-
ent orders established by these recluses, soon spread their rami-
fications not only throughout the East, but over the great-
est part of Europe, and, fortunately for the interests of human
knowledge, an eager love of learning, such as it then existed, in-
duced the monks to found libraries, to establish schools, to tran-
scribe ancient manuscripts, and to preserve at least, if they could
not appretiate, the invaluable volumes of antiquity.

But, upon the conquest of Italy by the Lombards, a darker
and more melancholy spectacle succeeds. Their dominion in
Italy continued for two centuries, and, under their iron yoke, the
literature both of Greece and of Rome became entirely extin-
guished. Hitherto the barbarian tribes had respected the con-
quered people. The Gothic race under THEODOBIC had become
amalgamated with the Roman. The luxury and enervating in-
fluence of Italian wealth, of the manners and the climate of this

* SPANHEIM, Epitom. ad Hist. Nov. Testara. p. 273.

into the Revival of Greek Literature in Italy. 405

voluptuous country, had tamed the pride, and softened the bar-
barity, of the northern invaders. But the Lombards were in
every respect a different people. They broke into Italy from
their native settlements in Pannonia, while all the vigour and sa-
vage freedom of barbarism was yet fresh and unworn upon them,
and in their conquest of that kingdom, they treated the degene-
rate Romans with cruelty and contempt.

" This ferocious nation," says St GREGORY, " is come upon us
" like a tempest, and, thundering on our defenceless heads, has
" ravaged our cities, levelled our fortresses, destroyed our mona-
" steries, and almost exterminated the inhabitants. Our fertile
" fields have no longer cultivators or proprietors, and places once
" populous are occupied and defiled by beasts, of prey *»*? f\:

Greece was now the only country where the light of science
and of literature still remained unextinguished, and where the
knowledge of the works of antiquity was still cultivated with en-
thusiasm ; but Italy could not profit by this circumstance ; for,
to fill up the cup of her misery, an almost perpetual war subsist-
ed between the Lombards and the Greeks, and all hopes of a se-
cond dawn from this wonderful country, in whose literary histo-
ry there seems to have been no middle age of darkness, were thus
completely extinguished.

The works of the philosophic BOETIUS, composed about the
beginning of the sixth century, independent of their own intrin-
sic beauty, acquire thus a reflected interest from the gloomy
period in which they were written, and, in their perusal, we truly
seem to listen to the latest sighs of the expiring literature of
Greece and Rome.

* St GREGORY in his Exposition of the Prophet EZEKIEL. See BARONIUS apiid
HOWKI.S, vol. 8. The Translation is by the author of the Dissertation.

406 Mr TYTLER'S Introduction to an Enquiry, Sfc.

This moral eclipse of all that was excellent in human know-
ledge, continued for nearly six centuries, during which period the
country of VIRGIL successively presents to the eye of the histo-
rian a confused assemblage of different races of men, Franks,
Normans and Saracens ; and when at length, after a long period
of war and bloodshed, the light of civilization breaks in upon the
scene, we find that out of this living chaos, there had arisen the
infant nations, and the unformed language of modern Italy.

The irruption of the Lombards into Italy, is the gloomy pe-
riod from which we may date the total extinction of the Greek
language and literature in the West * ; nor do we find any dis-
tinct traces of a spirit of revival until the middle of the four-
teenth century, the age of PETRARCH and BOCACCIO.

* BALDELLI Vita di BOCACCIO, p. 223.

( 407 )

XXIX. On the Refractive Power of the Two New Fluids in Mi-
nerals, with Additional Observations on the Nature and Pro-
perties of these Substances. By DAVID BREWSTER, LL.D. icdLJ
F. R. S. Lond., Sec. R. S. Edin., and Corresponding Mem-
ter of the Academy of Sciences of Paris.

(Read March 6. 1826.J

IN the Paper which I had the honour of submitting to the So-
ciety *, on the Two New Fluids in mineral bodies, I have given the
index of refraction for the most expansible of the two, as it exists
in the cavities of Amethyst ; but as I had not then ascertained
the refractive power of the second fluid, and as the principal
phenomena of the two fluids, especially those which related to
their properties when taken out of the cavities, were observed in
specimens of Topaz, it became desirable to have an approximate
measure of the refractive power of both of them, as they exist in
that mineral. As the fluid in Amethyst had never been exa-
mined in the open air, its identity with that in Topaz was in-
ferred solely from the equality of their expansion by heat, so that
the determination of the refractive power of the latter was ne-
cessary to establish either a difference between these two sub-
stances, or their perfect identity.

In the repetition of the experiments described in that paper,
and in extending my inquiries to different specimens of Topaz, I
sought diligently for a cavity whose shape and situation in the
crystal would enable me to obtain an accurate measure of the re-
fractive power of the two fluids. Such a specimen I have had

* See Page 1. of this Volume.

VOL. x. P. ii. 3 r

408 DR BREWSTER on the Refractive Powers, and other

the good fortune to meet with ; and one of the principal objects
of the present paper, is to give an account of the results which
it enabled me to obtain.

To those who are acquainted with the doctrines of refraction,
it is scarcely necessary to state, that if m is the index of refrac-
tion of any substance, such as Topaz, the sine of the angle at
which light incident on the second surface of it will suffer total re-

flexion, will be • - , and if any fluid is in contact with that sui-

m'

face, the sine of the angle of total reflexion will be — , the index

nv

of refraction of the fluid being mf. H ence

m' — m X Sin. Angle of Total Reflexion ;

so that the index of refraction of the fluid is easily deducible
from the angle of total reflexion.

When the surface of the cavity is parallel to a face of clea-
vage in the plate of Topaz which contains it, the angle of total
reflexion cannot be observed without cementing a prism upon one
of these faces ; but as this tended to make the experiment more
complicated, I sought for a cavity, the faces of which were in-
clined to the two parallel faces obtained by cleavage. This cavity,
shewn in Plate XIX. Fig. 1., consisted of a vacuity V; — of a large
portion NN of the highly expansible fluid, — and of a considerable
quantity MM of the second fluid, which suffered almost no
change by heat. The situation of this cavity in the specimen is
shewn in Fig. 2., where C is a section of the cavity perpendicu-
lar to its length MM, Fig. 1 ., and inclined to the parallel clea-
vage planes EF, GH of the Topaz.

In a room where the temperature was about 60° of Fahren-
heit, I fixed this specimen upon a goniometer, and I measured
the angle of incidence at the surface EF, when the light of a
candle RD, incident on the vacuity, began to suffer total re-

Properties of the Two New Fluids in Minerals. 409

flexion. This angle was 38° 42'. From the index of the ordi-
nary refraction of Topaz, which is 1.620, I computed the angle
of refraction CDB to be 22° 42' and the angle of total reflexion
DCP to be 37° 38' 35". Hence the angle ADC was 67° 18' ; the
angle ACD 52° 21', and DAC, the inclination of the face of the
cavity to the refracting surface EF, was therefore 60° 21'.

Calling x the inclination of AB to EF, or DAC and <p the
angle of refraction CDB, we shah1 have x~^ total reflexion + <p.
For in the similar triangles ADB, CPB right angled at D and
C, we have CAD = CPB. But CPB = DPQ = CDB + DCP,
that is x — ^ Total Reflexion -f- <p.

The goniometer remaining steady in its place, the divided circle
and the crystal were turned round, tiU the same ray RD began to
suffer total reflexion from the refracting surface of the expan-
sible fluid NN Fig. 1. and the Topaz ; and the new angle of in-
cidence KDR', at which this took place, was found to be 26° 39'.
The goniometer being turned still farther, the same ray suffered
total reflexion, from the separating surface of the second fluid
MM and the Topaz, when the angle of incidence KD was 11°
&.

These results obviously enable us to determine with accuracy
the refractive power of the Two New Fluids.

Calling 6 the angle of incidence, <p, <p' the angles of refrac-
tion, m m', m" the indices of refraction for Topaz, the expan-
sive fluid and the second fluid ; then we have sin 0 — -^— ;
, m

9 — oc— Angle of Total Reflexion, and

m' = m X Sin (tf — act)

m" =. m X Sin (<p" — a?)

Hence we have the indices of refraction as follows

m = 1.620 Topaz,

m" - 1.2946 Second Fluid.

m' — 1.1311 Expansible Fluid.

SF2

410 DR BREWSTER on the Refractive Powers, and other

The following Table will shew the relations of the indices of
refraction of these two new substances to those of other bodies
which I have found to possess a refractive power lower than
Water.

TABLE of Refractive Powers lower than Water.

Water, 1.3358

Cyanogen* rendered fluid by pressure, 1.316

Ice, 1.3085f

Second New Fluid in Topaz, in a cavity which
is filled by the other new fluid, at the tem-
perature of 83° 1.2946

New Fluid in Amethyst, which fills the cavity

at a temperature of 83*° of Fahrenheit, 1.2106

Tabasheer, whitish, from Nagpore, hard speci-
men, 1.1826

Tabasheer, transparent, from Nagpore, 1.1503

Do. do. another specimen, 1 .1454

New Expansible Fluid in Topaz, in the same •
cavity as the second fluid, whose index of re-
fraction is given above 1.1311

Transparent Tabasheer from Vellore, of a yel-
lowish tint, 1.1111

Ether e'xpanded into nearly thrice its original

bulk, 1.057

I have not made any attempt to measure the refractive power
of the new expansible fluid, after it has filled the cavity, having
satisfied myself with observing, that the angle of total reflexion
diminished when the fluid was in this expanded state J. In

* This Cyanogen was made by Dr TURNEB. Mr FAKADAY, who first rendered it
fluid, remarks " that its refractive power is rather less, perhaps, than that of water."
Phil. Trans. 1819, p. 286.

•f- This is a mean between Dr WOI.LASTON'S result and mine.

{ This experiment is a very interesting one to the spectator ; the new fluid, ap-
pearing quite transparent at a temperature of 60°, seems quite opaque when it is
made to fill the tube, by a slight increase of temperature, as if it had become black
by heat.

Properties of the Two New Fluids in Minerals. 411

those cavities where the vacuities are so large that the fluid its
converted into vapour before it fills them, the refractive power
of it, as measured when the cavities are full, will obviously be
much less than that which is obtained when the substance retains
its fluidity, and it will vary in different specimens, and even in dif-
ferent cavities of the same specimen, according to the proportions
which the vacuity bears to the quantity of the expansible fluid.

Additional Observations on the New Fluids in Minerals.

Having had occasion to shew the various phenomena of the
new fluids to several distinguished foreigners, and to others
who took an interest in the subject, I have thus been led to con-
tinue my examination of minerals in relation to these remark-
able substances. Some of my scientific friends, who were anxious
to repeat these experiments, have experienced great difficulty in
obtaining specimens of minerals containing the cavities of fluid.
This difficulty has no doubt arisen, from their examining the
well crystallised specimens which are generally found in the ca-
binets of mineralogists. If they had broken up with the ham-
mer only a few of the rounded or imperfectly crystallised white
topazes from Brazil or New Holland, they could scarcely have
failed to discover, with the compound microscope, innumerable
cavities fitted for the purposes of observation. After a little
practice in splitting and preparing the specimens, in which, from
the perfection of the cleavage planes, the aid of the lapidary is
almost never required, the patient observer will experience no
difficulty in detecting cavities of every variety of form, and in dis-
covering the fluid as it flows from the opened cavities over the
planes of cleavage. Mr SANDERSON, lapidary in Edinburgh, who
takes a great interest in every pursuit of a scientific nature, has
succeeded in obtaining some of the finest specimens of these new
fluids ; and by cutting and polishing the Topazes which contain

412 DR BREWSTER on the Refractive Powers, and other

them, so as to exhibit the cavities to the best advantage, he
has been enabled to shew most of the phenomena to those who
are interested in such pursuits. Several of these specimens are
of great value, as will appear from the drawings and descriptions
of some of the most remarkable, which will be given in the se-
quel of this paper.

In the additional observations which I have now to submit
to the Society on this subject, I shall confine myself to the fol-
lowing heads :

1. On the Number and Arrangement of the Fluid Cavities.

2. On the Form of the Cavities containing the New Fluids.

3. On the condition of the Fluids within the Cavities.

4. On the condition of the Fluids when taken out of the Ca-

vities ; and

5. On some miscellaneous phenomena connected with the

formation of Fluid Cavities.

1. On the Number and Arrangement of the Fluid Cavities.

In a former paper I had occasion to mention, that, in a spe-
cimen of Cymophane about yth of an inch square, I counted
30,000 cavities. Although this statement occasioned great sur-
prise, and some expressions of scepticism, yet it was too feeble to
convey any idea of their number. So minute are these cavities,
that the highest magnifying powers are often necessary to render
them visible ; and we might as well attempt to number the grains
of sand on the sea-shore, as to count these fluid cavities when
they appear in this minute state.

The strata in which these cavities are arranged, are not so
closely related to the primary and secondary planes of the cry-
stals as I formerly supposed. I have found them in almost every

PLATE XIX

JSmi^for tfit> Jiwut ,v*'.v'f/r 7>v.w . TW_X//. fj3.

.

Properties of the Two New Fluids in Minerals. 413

possible direction, and intersecting one another at angles which
cannot be referred to any of the crystalline forms of the mineral.
In a specimen of Quartz observed by Mr SOMERVILLE, and now
in the possession of Mr SIVRIGHT, they are arranged in hoUow
groupes somewhat like the cells of a honeycomb ; and when they
are viewed by reflected light, the corresponding faces of the ca-
vities are seen to be parallel, though the cavities have every pos-
sible variety of position with respect to each other. In other
specimens they form planes of variable curvature, and sometimes
curved surfaces of contrary flexure ; and in one specimen be-
longing to Mr SIVRIGHT the longitudinal cavities are grouped
and inflected, so as to resemble a curled lock of the finest hair,
as shewn in Plate XIX. Fig. 3. In a specimen of Blue Topaz
from Brazil, belonging to Mr SPADEN, lapidary in Edinburgh,
there are no fewer than four strata of cavities nearly parallel to
each other, and in the thickness of one-eighth of an inch. The
cavities have a different character in each stratum, and their num-
ber is such as almost to destroy the transparency of the plate.

In the distribution of most of these groupes, accident seems to
have had the principal share ; but there are certain modes of
distribution that appear to be the result of some general prin-
ciple ; and a more diligent examination of them, as well as of
others which may yet be discovered, will probably throw farther
light upon the origin of this class of phenomena. In a speci-
men, for example, belonging to Mr SANDERSON, and shewn in
Plate XXI. thirteen times its natural size, an immense number of
cavities are arranged in rectilineal groupes, radiating from a centre
A. Each rectilineal group consists of two, or in some places
three, rows of cavities, and several of the radiations are bent from
their original direction. The spaces between each pair of rows
are filled with curiously branching cavities, some of which are
half an inch long ; but the remarkable fact is, that these cavities
are connected with numerous slender branches, many of which

414 DR BREWSTER on the Refractive Powers, and other

communicate with a single cavity in the nearest rectilineal row
of the radiations between which the long cavities are placed.

They have a resemblance to lakes or rivers, whose branches
have been supplied from these rows of cavities ; though it is
more likely that the expansion of the fluid within the long cavi-
ties, and when the substance of the topaz was soft, forced out a
great number of globules, some of which continued to adhere to
the slender filamentous cavities from which they were discharged.

In all the cavities of this remarkable specimen capable of be-
ing examined, there are found both the new fluids, with the ex-
ception of the long branching cavity AB, from which they had
escaped, in consequence of the end A being cut by the lapidary.
The dense fluid always occupies the filamentous branches.

In some cases there is a breach of continuity in the branches,
a small part of the cavity being as it were filled up with solid
topaz. This fact favours very much the supposition that all the
rows of minute cavities had been thrown off from the great ones ;
though the rows of cavities on the left and lower side of the spe-
cimen are hostile to it.

The plane in which these cavities lie is perfectly flat, and is
nearly perpendicular to the axis of the prism, the line joining
the two resultant axes of double refraction being parallel to
MN.

2. On the Form of the Cavities containing the New Fluids.

In a former paper I have given drawings and descriptions of
some of the most remarkable shapes which these cavities assume ;
but in the prosecution of the subject, I have met with a variety
of new and remarkable forms. In a specimen belonging to Mr
SANDERSON, and which is one of the most valuable that I have
seen, each cavity (see Plate XIX. Fig. 6, 7, and 8), consists of

Properties of the Tivo New Fluids in Minerals. 415

a variety of cavities of different lengths and sizes, bounded by
parallel lines, and communicating by narrow channels, which al-
most escape the cognisance of the microscope. In these cavi-
ties thus curiously combined, the two new fluids are arranged
in the most remarkable manner, the dense fluid occupying
all the necks, and angles, and narrow channels, while the ex-
pansible one is left in the open and less capillary spaces. When
the heat of the hand is applied to the specimen, the fluids in
the cavities are all set in motion. The dense fluid quits its
corners, and assumes new localities ; and the different portions
of the expansible fluid either unite into one, or are subdivided
by the interposition of some portion of the dense fluid, which
has been expelled from its primitive situation, and drawn into
its new position by capillary action. When the specimen is
allowed to cool, the two fluids quit their new position ; and, as
if they were endowed with vitality, they invariably resume the
same positions which they occupied at the commencement of
the experiment.

Another form of the cavities still more remarkable occurs in
a very fine specimen belonging to Mr SIVRIGHT. These cavities
resemble a number of parallel cylinders, as shewn at AB in
Fig. 7. Plate XX ; but, owing to some cause which it is difficult
to conjecture, a number of them have been afterwards turned
aside towards C, so as to be open at one of their extremities.
From these extremities, which terminate in the surface ACB,
the fluids have made their escape, and have left the interior of
the cavities lined with a black and brown powdery residue, which
always remains after their evaporation. When the cavities thus
inflected and deprived of their fluids are submitted to the mi-
croscope, they exhibit the most extraordinary shapes ; some of
which are represented in Figs. 1, 2, 3, 4, 5, and 6, of Plate XX.
They have the appearance of having been formed by a turning

VOL. x. P. ii. 3 G

416 DR BREWSTER on the Refractive Powers and other

lathe ; and such is the symmetry and beauty of their outline,
that it is not easy to conceive that they are the result of any
mechanical cause. One of these cavities, which is unconnected
with the rest, resembles a finely ornamented sceptre, as shewn
in Fig. 2., in which the proportion and forms of the different
parts are executed in the finest taste. But what is most re-
markable, the different parts of this figure he in different planes,
so that, when it is seen in a direction at right angles to that of
symmetry, it appears merely a number of disjointed Hues, as in
Fig. 10.

The inflexion of the cavities AB into the directions bC, &c.
and the discharge of their fluid contents at the surface ACB,
could only have taken place when the whole mass ACB, though
crystallised, had not attained its permanent induration *. This
opinion derives great support from the fact, that the lines bC
are perpendicular to the axes of the prism, and consequently lie
in the planes of most eminent cleavage. The. direction, there-
fore, in which the fluids were discharged, was that of least resist-
ance,— a result which might have been expected.

In the specimen now under consideration, there is a stratum
of fluid cavities, composed of a great number of parallel rows of
cavities, and remarkable for their symmetry. One of these rows
is somewhat like AB, Fig. 9. If we now suppose that when this
specimen had not acquired its permanent state of induration, the
fluids in its cavities were expanded by a considerable heat, the
fluid in one cavity would force itself into the adjacent ones, so
that the row of cavities AB would form one cavity, somewhat
like that in Fig. 6. If the cavities lay in different planes, as
shewn in Fig. 10., then the expanded fluid would descend to the

* PATRIN, if we recollect rightly, speaks of crystals of Beryl in Siberia, which
were so soft that they broke like a piece of apple.

Properties of Two New Fluids in Minerals. 417

one immediately below it, and connect the whole together as in
Fig. 2. We do not mean to say, that the cavities bC in Fig. 7.
were actually formed in this manner, because this is rendered im-
probable by their connection with the rectilineal ones AB, but
merely to explain how cavities having the forms shewn in Figs.
1 — 7. may have their origin from the union of a great number
of cavities arranged as in Fig. 9.

When the cavities are regularly crystallised, which is frequently
the case in quartz and topaz, the homologous sides of the hollow
crystals are parallel to one another, and also to those of the pri-
mitive or secondary form which they resemble. In some very
curious but amorphous specimens of quartz from Brazil, belong-
ing to Mr SPADEN, the hollow crystals terminate in six-sided py-
ramids, with flat summits, and the axes of these pyramids is pa-
rallel to the axis of the system of polarised rings, and conse-
quently to the axis of the crystal.

3. On the Condition of the Fluids within the Cavities.

The phenomena of the expansible fluid have been so fully
described in my former paper, that I have only a few observa-
tions to add upon this part of the subject. In some specimens
of quartz, the expansible fluid seems to exert a very consider-
able elastic force, even at the ordinary temperature of the atmo-
sphere, and when a very small heat is applied, it sometimes has
sufficient force to burst the specimen. A very remarkable case
of this kind happened to a son of Mr SANDERSON, who put one
of the Quebec crystals of quartz into his mouth. Even with this
small accession of heat the specimen burst with great force, and
cut his mouth. The fluid which was discharged had a very dis-
agreeable taste.

The extreme volubility of the expansible fluid, and its power
of penetrating even the hard topaz in which it is inclosed, were

3 G 2

418 DR BKEWSTEH on the Refractive Powers and other

exhibited in a very remarkable manner, which I have described
and attempted to delineate in my former paper. Upon apply-
ing heat to a specimen of quartz, the elastic force of the impri-
soned fluid was such as to make it force its way through the so-
lid stone ; and when it had made its escape into the open air,
not a trace of its path was left behind. This phenomenon, which
was too extraordinary to present itself frequently, was afterwards
seen both by Mr SANDERSON and myself in a specimen of topaz,
when the fluid ascended through its substance with great rapidi-
ty, and resembled globules of quicksilver. This metallic ap-
pearance was owing to the total reflexion of light, which took
place at the refracting surface of the globule and the topaz.
That the fluid in this case forced its way through the clea-
vage planes of the mineral cannot be doubted, and I have in
another paper shewn, that fissures in glass may be closed up
without leaving the slightest trace of the two surfaces ever ha-
ving been separated *.

In the various cavities described in my former paper, the
whole of the expansible fluid, when exposed to heat, was either
driven into vapour f , or retained its fluidity after it had filled
the vacuity. Since that paper was published, however, I have
discovered cavities in which, after the application of heat, there
may be said to be three different substances, viz. 1. The expansi-
ble fluid in a state of fluidity ; 2. The dense fluid ; and, 3. The
vapour of the expansible fluid. This curious fact will be under-
stood from Fig 5. of Plate XIX, which represents a cavity in a
specimen belonging to Mr SPADEN. The cavity is one-tivelfth of
an inch long. The expansible fluid is lodged at N N and N' N',

* See Phil. Trans. 1816, p. 73.

•}• One of the largest vapour cavities that I have seen is one-twelfth of an inch
every way. It is less than half full of fluid, and hence it is driven into vapour by
heat. During the precipitation of the vapour it becomes perfectly opaque.

Properties of the Two New Fluids in Minerals. 419

where there are large vacuities V, V, and there is a globular por-
tion of it at n, without a vacuity. When heat is applied, the fluid
at N N and N' N' quickly goes off into vapour ; the portion at n
expands into an elliptical globule, but its force is not sufficient
to displace the mass of the second fluid between n and N, and n
and N' ; and being kept in equilibrio by the opposite and nearly
equal expansive forces of the vapour in N N, and N' N', it conse-
quently remains fluid at n *. In a plate of Topaz shewn to me
by Mr SIVRIGHT, where the expansible fluid consists of two por-
tions floating in a large quantity of the dense fluid, one of the
portions is a spherical drop which expands with heat, and con-
tracts with cold, exhibiting by transmitted light an effect similar
to the opening and shutting of the pupil.

In re-examining the phenomena of the second or denser
fluid, several very curious facts have come under my notice.

I had previously shewn, that, when several cavities communi-
cated with each other, the narrow necks, or lines which joined
them, were filled with the dense fluid, which shifted its position
when the equilibrium of the adjacent portions was destroyed by
heat ; but I have since had occasion to examine the phenomena
of the second fluid with more attention. The particles of this
fluid have a very powerful attraction for themselves, like those of
water, and they are also powerfully attracted by the mineral
which contains it. The particles of the expansible fluid have,
on the contrary, a very slight attraction for one another, and also
for the mineral which incloses them. Hence it follows, that, as
the two fluids never in the slightest degree mix with one ano-
ther, the dense fluid is either attracted to the angles of angular

* In Fig. 4>. of Plate XIX, I have represented another vapour cavity, which is
remarkable for having a very small portion of the expansible fluid, and also, for ha-
ving several crystalline forms within the dense fluid. 3

DR BREWSTER on the Refractive Powers and other

cavities, or occupies the bottom of round ones, or fills the nar-
row necks or channels by which two or more cavities communi-
cate with one another. The expansible fluid, on the other hand,
occupies all the wide parts of the cavities, and in those which are
deep and round it lies above the dense fluid.

If we now apply heat to a single deep cavity containing both
fluids, the elastic force exerted by the expansible one, after its
vacuity is filled up, will modify the form of the dense fluid, pres-
sing it out of some corners and into others, till the elastic force
of the one is in equilibrium with the capiUary attraction of the
other.

But if there are two cavities, A, B, communicating with each
other, as in Fig. 10. Plate XIX., where the dotted part represents
the expansible fluid, then the dense fluid will be found in the neck
at m, n, and at the angles o, p, r, s. Let us now suppose that there
is a vacuity V only in the smaller cavity B, and that heat is ap-
plied to the specimen. It is obvious that the greater expansion
of the dotted fluid in A, which has no vacuity to fill, will force
the dense fluid m n towards V, where it will take up a new posi-
tion about b m c when the expansive forces are in (equilibria. But
if the cavity A is very large compared with B, the fluid m n will
be driven out of the neck b n, and will find its way to some of the
corners o, or p, from which, upon cooling, it will again return to
its position m n.

Let us now suppose that the cavity A communicates with
other cavities which expand slowly into it, while it is expanding
into B ; then, at every expansion of A, the dense fluid m n will
be driven to a side, but it will immediately return, opening and
shutting like a valve. This effect is finely exhibited in an irre-
gular branching cavity of a specimen belonging to Mr SANDER-
SON ; but as the expansions and contractions are too numerous
and complicated, I shall describe them as existing in a cavity of a
more simple structure, represented in Fig. 9. Plate XIX, by A B

properties of the Two New Fluids in Minerals. 421

C D E. In ordinary temperatures, about 45°, there is a vacuity of
the size V, in the expansible or dotted fluid, and the dense, or
shaded fluid, occupies the necks b c, d e, DE, and also the extre-
mity F. By applying the heat of the hand to the specimen, the
expanding fluid in the branches V C, V D, finds space for itself,
by filling up the vacuity, but as there are no vacuities in the
portions of expanding fluid at A B, B, and E F, they must ne-
cessarily force out the dense fluid which confines them. The
dense fluid in the neck E D, is thus made to appear at D, and
the whole of the dense fluid at b c is driven off to d e, till, ac-
cumulating there, it is drawn by attraction to the nearest neck,
m n op. Here it first lines the circumference of the hollow neck,
from its powerful attraction for topaz ; and, as the lining becomes
thicker, it appears as a slight elevation between o and p, and be-
tween m and n. These elevations increase till they leap together
by their mutual attraction, and form a column of the dense fluid
mnpo. The column b c of dense fluid has now disappeared en-
tirely, and the space A B C D is filled with the expanding fluid.
The heat of the hand being continued, the expanding fluid A B
forces itself through the little cylinder of dense fluid d e, which re-
sumes its place the moment that a portion of the former has pas-
sed. But as the same heat has been expanding the fluid between
n p and C, which pushes out part of the dense fluid at m n o p,
this dense fluid, and the surplus of what was displaced from b c,
moves along the sides of the cavity till it occupies the portion
q r, of the branch V D. Sometimes the dense fluid is entirely
driven from m n o p, and part of it sent to the extremity C ;
though, in general, a very small portion remains at the very
neck m o.

As the specimen cools, the dense fluid quits m o and q r, and
is gradually transferred through the neck d e to the neck b c ;
every portion of it invariably resuming the very position which
it had before the application of heat.

422 DR BREWSTER on the Refractive Powers and other

A very curious modification of these actions is seen in a ca-
vity of the specimen shewn in Plate XXI., which I have repre-
sented separately in Fig. 1 1 . of Plate XIX. The branch b V has
always, at common temperatures, a vacuity V, and the cavity A,
connected with it by the filamentous channel o b, has no vacuity.
At the ordinary temperature, the dense fluid appears at a c, and
slightly at o and b, filling the narrow channel o b. By applying
heat, the expanding fluid in b V fills up the vacuity V ; and, as the
cavity A a o c has no vacuity, a portion of its fluid is necessarily
driven through the neck a b into b V in small globules ; but, ow-
ing to the narrowness of the neck at b, the phenomena are not
easily observed. Upon cooling, however, the retransference of the
fluid that had passed from A to b V, is finely seen. The con-
traction of the expanding fluid in A causes the dense fluid to
appear as at m n o, in Fig. 10., and, in a short time, the curved
surface m n becomes more flat ; and, at last, a straight line, as at
m' n', Fig. 12. This indicates a pressure along the canal b' o', in
the direction b' o', and a bubble of the expansible fluid instantly
issues from o', as in Fig. 12., and, passing through the dense
fluid, joins the expansible fluid in A'. After three or four of
these have passed, the equilibrium is restored. In this case, the
capillary force exerted by the channel o' b' upon the dense fluid
which it contains is too strong to permit the little globule of the
expansible fluid in b' V to displace it, as in Fig. 9., so that it
passes very slowly in separate globules.

The fluid valves, as they may with propriety be called, which
thus separate the different branches of cavities, afford ground
of curious speculation in reference to the functions of animal
and vegetable bodies. In the larger organisations of ordi-
nary animals, where gravity must in general overpower, or at
least modify, the influence of capillary attraction, such a me-
chanism is neither necessary nor appropriate ; but, in the lesser
functions of the same animals, and in almost all the microscopic

PLATE XXI

Properties of the Two New Fluids in Minerals. 423

structures of the lower world, where the force of gravity is en-
tirely subjected to the more powerful energy of capillary forces,
it is extremely probable that the mechanism of immiscible
fluids, and fluid valves, is generally adopted. We must leave it,
however, to the physiologist to determine the truth of this sup-
position.

In the second, or dense fluid, whose motions we have now de-
scribed, there exist frequently black spicular crystals, which may
be made to move to different parts of the cavity. Whether or
not these crystals are extraneous bodies, or indicate the com-
mencement of that induration of the fluids which I have describ-
ed in a former paper, is a point which can only be ascertained by
observing the progressive changes which the crystals may un-
dergo.

4. On the Condition of the Fluids when taken out of the Cavities.

I have already described so fully in a former paper the sin-
gular movements into which the expansible fluid is thrown, when
it first flows out of its cavity upon the surface of the plate of to-
paz which contains it, that I have nothing to add upon this sub-
ject *. It did not then occur to me that these movements might
be owing to electricity, till I read an account of the following expe-
riment made both by Professor ERMAN and Mr HERSCHEL. When
a globule of water, dropped on the surface of a flat dish of mer-
cury, is brought into connexion with the positive pole of a gal-
vanic battery, while the mercury is connected with the negative
pole, it instantly flattens and spreads to twice its diameter, re-
gaining its former sphericity when the circuit is broken. This
extension and subsequent re-aggregation of the globule of water,

* Some of the fluids in quartz seem to be entirely gaseous, while in sulphate of
barytes the fluid appears to be the mineral itself in a fluid state ; see p. 4525. and note'
on p. 427-

VOL. X. P. II, 3 H

424 Dr BREWSTER on the Refractive Powers and other

is precisely the same effect as that exhibited by the drop of ex-
pansible fluid ; and it is therefore very likely that the latter is
owing to an electrical cause. In separating the particles of bo-
dies, electricity is always produced ; and in the cleavage of To-
paz and Mica, even electric light is developed. But experiments
are still wanting to determine, whether, in the present case, the
electricity is derived from the separation of the cleavage planes,
or from the change of condition which the new fluid is under-
going during its rapid evaporation, and its partial conversion in-
to a powdery residue.

5. On some Miscellaneous Phenomena connected with the For-
mation of Fluid Cavities.

In my former paper, 1 have described the phenomena of a
single fluid in the cavities of various minerals and artificial crys-
tals *. Since that paper was written, I have seen many specimens
of this kind ; but as the fluid has always, when examined, been
found to be water, such specimens possess no peculiar interest, un-
less their cavities are opened, in the manner first adopted by
Sir HUMPHRY DAVY. One of these specimens, however, which
was kindly sent to me for examination by W. C. TREVELYAN,
Esq. is so peculiar as to deserve notice. In the drawing of it,
in Plate XX. Fig. 8., which is of the real size, A B is a cavity
in quartz, which is filled with a fluid, excepting the vacuity a It,
which may be made to move to different parts of the cavity. The

* Mr WILLIAM NICOL, Lecturer on Natural Philosophy and Chemistry, has
shewn me some fine specimens of Amber containing cavities. The inner surface of
these cavities is rough, like finely ground glass, and many of them contain a fluid
with a moveable globule of air. In a specimen of calcareous spar, in the possession
of Mr SANDEBSON, there is a fluid cavity about two inches long, an inch wide, and
one-eighth of an inch deep.

Properties of the Two New Fluids in Minerals. 425

fluid does not expand perceptibly by heat, and is in all probabi-
lity water. When the specimen is shaken, the fluid becomes tur-
bid, and of a whitish colour, arising from a fine white sediment,
which settles in the lower part of the cavity.

In a specimen of Quartz from Brazil belonging to Mr SPA-
DEN, there is a cavity with an air-bubble, about the tenth of an
inch long. It is nearly one-third full of a white powder, con-
sisting of crystalline particles, which, upon inverting the speci-
men, flow over the surface of the air-bubble like sand in a sand-
glass. In the specimens of quartz already mentioned in page 417.
as containing cavities with pyramidal summits, there is only one
fluid, in which there is generally an air-bubble. These cavities
often contain opaque spherical balls *, which are distinctly move-
able ; and in one cavity I have counted ten of these balls, seven
of which roll about the cavity when the specimen is turned
round f . In a second specimen, spherical balls of the same kind
are copiously disseminated in the quartz, and exist also in the ca-
vities. In a third specimen, the balls occur near the summits of
the pyramidal cavities, some of them being within and some of
them without the cavity.

In the crystallisations of ice several phenomena occur, which
are intimately connected with the preceding inquiry. When
water is frozen in a glass vessel, the ice is often intersected with
strata of cavities, which have the same general form and aspect

* These balls are of the same size as the seeds of Lycopodium, which amount to
32 parts of Dr YOUNG'S eriometrical scale. Their diameter is therefore 5555 B -r- 32
= j5Tth part of an inch.

•f- I have since opened several of these cavities by the blow of a hammer. In a
second or two the fluid was entirely gone, without leaving a trace of its existence be-
hind. The spherical balls remained in the cavities. They were not acted upon
either by the muriatic or the sulphuric acids.

3 H2

426 Da BREWSTER on the Refractive Powers and other

as those in minerals. I have sometimes observed frozen drops
of dew, containing a portion of water which remained unfrozen
even at low temperatures ; and I have recently had occasion to
examine some crystallisations of ice, which presented the same
fact, under more curious circumstances.

A very sharp frost occurred in Roxburghshire on the morning
of the 8th October 1825. The gravel- walks in the garden were
raised up about an inch above their natural level by the sudden
congelation of the water in the earth mixed with the gravel. All
the elevated portions consisted of vertical prismatic crystals of
ice of six-sided prisms, with summits which seemed to be tri-
edral. The leaves of plants, &c. were covered with granular crys-
tals, which were in general six-sided tables.

Upon examining with a microscope the prismatic crystals ag-
gregated in parallel directions, they presented some curious phe-
nomena. They had numerous cavities of the most minute kind,
arranged in rows parallel to the axis of the crystals, and at such
equal distances as to resemble a series of mathematically equi-
distant points. Some of the cavities were very long and flat, and
sometimes they were amorphous ; but in general they contained
water and air.

Upon submitting one of these cavities to a powerful micro-
scope, it appeared as shewn in Fig. 13. of Plate XIX, where
A B C is the piece of ice, having in it a long cavity m o, contain-
ing water and air. The ice gradually dissolved ; and when the
end n o of the cavity m n was near the edge of the ice C B, the
air, in a portion of it n o, detached itself, and went off at p,
through the solid ice, the cavity closing up again at n. This
phenomenon is analogous to the passage of the expansible fluid
through topaz and quartz, which has been already described; the
air in the one case, and the fluid in the other, finding its way in
the direction of easiest cleavage, and the fissure closing up again
in the manner already mentioned in a preceding part of this

PLATK XX.

-t'n,/:'t'ar thf £,imr Kayat Sacirtv Tr-aii U'l.X ./, .415 .p.t26

jty.S.

f'i-,,2.

J-'ui.S .

Properties of the two New Fluids in Minerals. 427

paper. The singular fact, however, is, that the portion no of the
cavity quitted by the globule of air, was immediately filled up
with ice, and the cavity reduced to the dimensions m n.

As the formation of ice from water is in every respect analo-
gous to the formation of crystals from a substance rendered fluid
by heat, the examination of its cavities is likely to throw some
light upon their formation in mineral bodies *.

In concluding tnese observations, I could have wished to en-
ter into some details respecting their geological relations ; but as
these would lead us too far into the regions of speculation I shall
not enter upon them on the present occasion. It may be proper,
however, to state, that the opinion which I hazarded in a former
paper, that the discovery of the two New Fluids in minerals at-
tached a new difficulty to the aqueous hypothesis, has been ren-
dered more probable by every subsequent inquiry ; and that I can
see no way of accounting for the phenomena, but by supposing
that the cavities were formed by highly elastic substances, when
the mineral itself had been either in a state of fusion, or ren-
dered soft by heat.

* Since this Paper was written, Mr WILLIAM NICOL has shewn me a very re-
markable specimen of Sulphate of Barytes, with fluid cavities of the same general
character with those which I described in my former paper (Trans, vol. x. p. 36.),
but much larger than any which I had seen. Upon grinding down on a dry stone,
one of the faces of this specimen, the largest cavity burst, and discharged its fluid
contents through the fissure upon the ground surface of the specimen. The fluid
lay in drops of different sizes along the line of the fissure, and in this condition Mr
NICOL put it into his cabinet. Upon looking at the specimen about twenty-four
hours afterwards, each drop of fluid had become a crystal of Sulphate of Barytes.
These crystals had the primitive form of the mineral.

This very curious fact is analogous to the uncrystallised water in the ice-cavities
mentioned above, the crystallisation in both cases being prevented by pressure.
When that pressure was removed, a portion of the water and the fluid sulphate of
barytes were immediately crystallised. Mr NICOL distinctly remarked, that the
crystals occupied as much space as the drops of the fluid ; so that the crystals of sul-,
phate of barytes were not deposited from an aqueous solution, but bore the same re,
lation to the fluid from which they were formed, as ice does to water,

4

( 428 )

XXX. Observations on Two Species of Pholas, found on the Sea-
coast in the neighbourhood of Edinburgh. By JOHN STARK,
Esq. M. W. S. Communicated by Dr BREWSTER.

*

(Read 9fith March 1826J

JL HE Natural History of the Pholades, so far as regards their
mode of burrowing in wood and stone, seems yet to be but im-
perfectly understood, though the Pholas was known to the an-
cients, and PLINY notices its phosphorescent quality *. RONDE-
LETiusf, JOHNSTON, and RUMPHIUS have figured several spe-
cies ; LISTER, among others, gives representations of three Bri-
tish species, the Pholas dactylus, Candida, and crispata £ ; and Sir
ROBERT SIBBALD, in his Prodromus, has three rude figures of
the dactylus or crispata, as Scottish shells. None of these au-
thors, however, attempted to explain how the Pholades exca-

* " His natura in tenebris, remoto luminc, alio fulgore clarere, et quanto magis
humorem habeant, ludere in ore mandentium, lucere in manibus, atque etiam in solo
et veste clecidentibus guttis." — PLIN. lib. ix. c. 61.

•f- " Hse in saxis latet, ut saxo undique contegatur, per foramen duntaxat exi-
guum et sensui vix patens aqua nutritus. Testis constat duabus longis, non in latum
extensis mytulorum modo, sed rotundis. Intus eadem fere est caro quae in mytulis."
— ROND. de Testaceis, lib. i. p. 49. I strongly suspect, that RONDELETIUS has fi-
gured the Mytilus lithophagus under the title of Pholas ; and that subsequent writers
have been misled from not having seen his figures. The species of Pholas which he
delineates is given under the name of Concha alter a longa. — Vide ROND. p. 23, 27.

| " Hse concha juxta Hartlepool frequenter reperiuntur, et in lapidis cujusdam
cretacei foraminibus latitant ab ipso eorum ortu ; nam ex his eximi non possunt, nisi
prius lapis frangatur."— LISTER, Anim. Ang. p. 172. 4

Mr STARK on Two Species of Pholas. 429

vated their habitations in the rock, or perforated the submerged
wood in which they seek protection. BONANNI, so far as I know,
was the first who turned his attention particularly to this in-
quiry. In his work, entitled " Recreatio Mentis et Oculi," the
first edition of which, in the Italian language, was published at
Rome in 1681, he has given figures of the Pholas dactylus, and
of pieces of the rock in which it was contained, shewing, with
considerable accuracy, the nature of the perforations, and dis-
tinctly marking the circular lines at the base of the cells. These
perforations are formed, in his opinion, by the action of the file-
like valves on the stone, the animal fixing itself, for this pur-
pose, by its callous foot to procure the necessary motion of its
shell *.

The celebrated M. de REAUMUR next took up the subject,
without, however, seeming to have been aware of the prior in-
vestigations of BONANNI, whose book is neither quoted nor allud-
ed to by the French naturalist. In the " Memoires de 1'Aca-
demie Roy ale des Sciences" for 1710, this intelligent observer
has a paper on the progressive movement of some species of Bi-
valves; and in the volume for 1712 he gives the sequel of his
observations on this curious subject. In this second memoir, af-
ter detailing the manner in which the Solenes burrow in the
sand, he is led to consider the means by which the Pholas per-
forates the softer rocks ; and this, he endeavours to prove, is done
merely by the action of its muscular foot. The hardness of the
substance perforated, however, induces M. de REAUMUR to form a
theory to account for an instrument, so apparently unsuitable, be-
ing able to perform what he ascribes to its action. The clay
rock from the coast of Poitou and Aunis, on which his observa-
tions seem to have been made, was too hard on the surface to
admit, in his mind, the supposition of its being bored by such

* BONANNI, Recreat. p. 36.

430 Mr Stark on Two Neiv Species of Photas

an implement ; and he therefore concludes, that the Pholades
must have entered the clay when it was in a soft state, and
that it had been subsequently hardened or petrified by some vis-
cous quality of the waters of the sea *. This theory, it may be
remarked, leaves no room for the multiplication of the species ;
for, on the supposition that the clay has been hardened on the
surface by some petrifying quality of the water, after the Pho-
lades had made their lodgment, the same cause would operate
to prevent the future races from commencing their cells f.

D'ARGENVILLE, with the knowledge, it appears, of what Bo-
NANNI and REAUMUR had written upon the subject before him,

* In opposition to this theory, it has been remarked, that, from the lodgment
which the Pholades have made in the pillars of the Temple of Serapis at Puteoli, it
must be concluded that they have bored their holes after the erection of the pillars.
Dr BOCHADSCH, who noticed these columns, observes, that the workmen would certain-
ly have rejected any stones that had been disfigured in this manner. The Pholades
must therefore have worked their way into them while they were buried by the influx
of the sea, which immediately succeeded the destruction of the city by an earthquake.
— BOCHADSCH, as quoted by Mr WOOD.

f As REAUMUR has been referred to as supporting a very different theory, I give
his own words :

" Apparemment qu?il n'y a guere dans la nature de mouvement progressif plus
lent que celui du Dail ; mure comme il est dans son trou, il n'avance qu'en s'approch-
ant du centre de la terre : le progres de ce mouvement est proportionne a celui de
1'accroissement de Tamma! ; a mesure qu'il augmente en etendue, il creuse son trou et
descend plus bas. La partie dont il se sert pour creuser ce trou est une partie charnue
situee pres du bout inferieur de la coquille ; elle est faite «n losange et assez grosse par
rapport au reste du corps. Quoiqu'elle soit d'une substance molle, il n'est pas eton-
nant qu'elle vienne a. bout de percer un trou assez profond dans une matiere dure : elle
y employe bien du temps. J'ai vu ces Dails se servir de cette partie a 1'usage que
je lui attribue, apres les avoir tires de leurs trous et les avoir poses sur un glaise aus-
si molle que de la boue ; en recourbant et. ouvrant ensuite cette partie, ils se creusoient
un trou, et en creusoient en peu d'heures un aussi profond que celui auquel ils tra-
vaillent pendant plusieurs annees, aussi y trouvoient-ils beaucoup moins de resistance,
et le besoin qu'ils avoient de se cacher leur faisoit apparemment accelerer leur travail,''
Mem- de TAcad. Roy. des Sciences, 1712, p. 127.

found on the Sea-coast near Edinburgh. 431

next professes to give an account of the manner in which the
Pholades perforate their dwellings ; but, from the contrariety
of his statements, and his completely misunderstanding one of
the authors quoted by himself, little reliance is to be placed upon
his authority as an observer. In one passage of his Zoomorphose,
when describing the shell of the Pholas dactylus, he says it resem-
bles a file, with elevated strias and asperities, dentated and crowd-
ed from the top of the shell to its base, -in such a manner that the
strongest points are towards the head. " It appears," says he, " that
with these arms it pierces the stones, and enlarges its tomb as it
increases in size." But, in a passage a little afterwards, he adds,
with a strange forgetfulness of what he had previously writ-
ten, " In proportion as this animal grows, it digs its hole with a
round and fleshy part like a tongue ; and it is not with its two
valves, nor with its teeth, that it performs this operation." Fur-
ther on he remarks upon another species, that it " is armed
at its extremity with two strong and cutting points, in form of
an auger, of which the dentated contour gives it the means of
turning upon itself, and of piercing the stone downwards. The
stria? and the teeth do the rest *."

Among the more modern writers, PENNANT mentions having
frequently taken the Pholades " out of the cells they had form-
ed in hard clay, below high water-mark, on many of our shores.
They also perforate the hardest oak-plank that is lodged in the
water. The bottoms of the cells," adds this acute observer, " are
round, and appear as if nicely turned with some instrument f ."
MONTAGU, speaking of the Mya Pholadia, says, " It is probable
this, as well as similar animals whose habits are to perforate
stone, are provided with an acid, or some other solvent men-

* L'Hist. Nat. eclaircie dans une de ses parties principales. — Zoomorphose, p. 69,
70. Paris, 1757.

t British Zoology, vol. iv. p. 158.

VOL. x. P. ii. 3 i

432 Mr STARK on Two Species of Pholas

struum capable of performing that office." And, in another pas-
sage, he observes, " The Pholades are performing similar works
assigned by nature on softer substances, such as chalk, indurated
clay, and wood, which, in like manner, are perforated by some
solvent power : — not by the thin fragile shells that cover such
animals, as some have erroneously asserted and is too generally
credited *."

A late writer, Mr WOOD, supports something like the same
theory ; at least he seems to think that the attrition of the shell is
insufficient for the effect produced ; " since," says he, " there are
some species, and particularly the P. orientalis, which are nearly
smooth at the anterior end, and, consequently, unfit for such a
purpose f ;" while Mr GRAY, in the Zoological Journal, gives it
as his opinion, that the Pholades " appear to bore by means of
rasping J."

Such are the discordant opinions that have been held regard-
ing the mode by which the Pholades perforate calcareous stones
and wood : one class of naturalists asserting that they do so by
the rotatory motion of their valves, or by means merely mecha-
nical ; while others suppose, from the apparent fragility of the

* Testacea Britannica, p. 560, 561 .

" It is well known (observes MONTAGU in another place) that animals as well as
vegetables prepare, by various occult processes, fluids powerfully corrosive : the viper
secretes a deadly poison, which is forced through the cavity of its fang ; the pismire,
and some other insects, eject a powerful acid, capable of dissolving calcareous stone.
Surely, then, it may most reasonably be admitted, that, by some such chemical means,
prepared in the great elaboratory of Nature, these testaceous Ascidia perform the part
assigned to them by the Creator of the Universe." — MONTAGU, Supplement, p. 15.

The Pholades, it is remarkable, bore the wood across the grain, while the Teredo
navalis perforates it in the direction of the fibres.

f General Conchology, vol. i. p. 74.

J Zoological Journal, No. 3. p. 406.

found on the Sea-coast near Edinburgh. 433

shell, that they must have the power of secreting some solvent
fluid, capable of decomposing the substances in which they bur-
row. That the first of these hypotheses is the one most confor-
mable to appearances, no one who has seen the living animals
can doubt, and accordingly, it has been adopted by most recent
observers ; while that supported by MONTAGU and others op-
poses .obstacles to its reception not easily to be got over. Any
acid or solvent fluid that would act with effect on the cal-
careous stones in which the Pholades lodge, would, it is evident,
act equally on the shell of the animal itself; and a solvent which
possessed the power of dissolving stone, would be little likely to
have the same effect on the fibres of submerged wood.

Some years ago, while residing at Portobello, I discovered, on
the coast at Joppa Salt-pans, where the rocks are uncovered at low
water, numerous perforations in the shale or clay-rock, which I
ascertained to be the work of Pholades. On breaking the stone
in different places two species of Pholas, P. crispata and candi-
da, were procured alive, in great numbers, and of all ages.
When the tide recedes, they withdraw their tube within the per-
forations, but when covered by the water, its rounded mouth is
visible above the upper surface of the rock. On striking the
rock with a hammer, near any of the holes, a spirt of water is
ejected, similar to what occurs when the Mya? and Solenes are
disturbed in their haunts. The Pholades are found at various
depths in the stone, corresponding to the age of the animal ; the
largest, and of course oldest, specimens being found at from four
to six inches, or even more, under the surface ; others at all in-
termediate distances, the youngest being merely covered by a
thin layer of the clay. The Pholas Candida, not a common spe-
cies on some coasts, occurs most plentifully ; but both species are
frequently found together.

The perforations in the rock at the surface are not much
larger in diameter than a quill ; many are much smaller, but they

434 Mr STARK on Two Species of Pholas

widen as they recede downwards, corresponding to the animal's
growth. The Pholas itself is found in an inverted pear-shaped
cavity at the bottom, the largest diameter of the shell being un-
dermost. Where the Pholades are crowded together, which is
generally the case, the divisions between the different cells are
often extremely thin, and in some this partition is completely
removed. The direction of the bore is not always vertical, though
nearly so ; but in some instances, where the rock had been bro-
ken down to an angle, or rounded, the Pholades were found at
various inclinations, corresponding to the surfaces of the stone.

From repeated examination of the recent animals, and their
perforations, I have no hesitation in asserting, that these two
species, at least, form their holes by the rotatory motion or rasp-
ing of the stone with their valves. Indeed, I am surprised how
any one who has seen these animals in their native rocks could
for a moment think otherwise ; for in the Joppa specimens, cir-
cular lines are distinctly visible in the cell of the animal, corres-
ponding to the elevated striae on the shell, and presenting the
appearance as of having been bored by an auger. PENNANT re-
marks the same circumstance in the cells of the Pholades found
by him on the English coast, as BON ANN i had formerly done in
the Italian specimens. These marks, indeed, disappear in the
upper part of the perforation, from the friction occasioned by
the expansion and contraction of the rugous tube ; but in the
cavity where the Pholas lodges it is always distinctly, and often,
especially when the animal is large, prominently marked.

Specimens of the shells, from the locality mentioned, are now
submitted to the Society, along with portions of the shale in
which they are found.

It has been held, as a presumption against the Pholades per-
forating rocks by a mechanical operation, that some of the spe-
cies have shells nearly smooth, and unfitted for such a purpose ;
and the Mya Pholadia and Mytilus lithophagus are produced as

found on the Sea-coast near Edinburgh. 435

instances where it is next to impossible that, without the aid of
a solvent fluid, such animals could form protecting cells in hard
substances. From not having seen the animals alluded to alive,
and in their native habitations, it would be presumption in me
to give a decided opinion on the subject. But, reasoning from
analogy in the structure of the animals, and the habits of such
as have been observed, it infers no impossibility to conceive that
they penetrate rocks in a similar manner. Little asperity in the
instrument is required where the operation is constant. In judg-
ing of the unseen or unobserved operations of nature, many are
guided in their opinion by what appears possible to be effected
by the limited powers which a preconceived theory prescribes
to the instrument employed. But little is known regarding
the time which these instinctive miners take to form their
deepening cells. A drop of water falling constantly on the
same spot soon leaves evidences of what time, with the smallest
force, can effect ; and the keys of musical instruments are, in no
long period, hollowed by the softest touch of the softest fingers.
There seems no impossibility, therefore, in conceiving that the
Pholades may perforate a substance less hard than their own
shell by mere attrition *, or even a harder substance, by the con-
stant action of their muscular foot.

LINNAEUS and LAMAKCK regard the Pholasas a Bivalve shell,
with accessory pieces ; while others, from the presence of these
auxiliary plates, have classed it among the Multivalves. The
animal is hermaphrodite and viviparous, hatching its young in
the little sacs of its branchiae. It has a membranous mantle, of

* Of the power of the Pholades to bore limestone, marble, or shale, it is easy to
satisfy one's self, by the simple experiment of rubbing the shell gently on a piece of
marble, which it cuts without rounding the asperities of the shell. Oak is likewise
scratched in the same manner ; but the action of the Pholades is always on submerged
wood or rocks partially covered by the tide, and the water, in both cases, must facili-
tate the process of boring.

3

436 Mr STARK on Two Species of Pholas

a tubular form, open at both extremities, like that of the Solen
or Mya *. From the superior opening of this tubular mantle
two united syphons arise, of which the anterior is the largest.
They are slightly dentated on the margin, and serve, the one for
the entrance of food, and the other for discharge. When cover-
ed by the tide, or in a basin, these tubes may be seen constant-
ly sucking in and ejecting the water. The foot is short and co-
nical, and, from its capacity of being projected and drawn in
within its circular covering, probably affixes itself by suction to
the bottom of the hole, and serves as a fulcrum for the rotatory
motion of the valves, or even may itself assist in deepening the
cell of the animal. Mr GRAY, in the third number of the Zoo-
logical Journal, has given some anatomical details regarding the
structure of the Pholades, particularly with regard to the singu-
lar falciform projections in the interior of the shell, which he
shews are nowise connected with the arrangement of the hinge ;
and POLI, in his " superb work " on the Testacea of the Two Si-
cilies, is said to have given the anatomy of the Pholas in de-
tail f-

* There are several striking points of similarity of habit between the Pholades and
the Myae. The Myae burrow in sand, gravel, or clay, and project their tube to the
surface in the same manner as the Pholades. The form of their syphon is nearly the
same, as is also the mantle which connects the two valves. Their mode of sucking in
the water, and expelling it in jets, is the same in both. I have kept the Mya arena-
ria alive in sea-water for several days, and witnessed repeatedly its wetting the room
to a considerable distance, from its often repeated and violent ejection of the water.
The Myae? however, at least the M. arenaria and truncata, though they easily pene-
trate soft clay or sand, do not seem to have the power of boring into hard substances ;
for in many specimens I have met with, in gravelly places, the shell was distorted,
from being placed between stones, which its force could neither remove nor form to
the contour of its shell.

•f- Since the foregoing remarks were written, I have seen POLI'S magnificent work,
and feel gratified by finding that the observations I have hazarded entirely coincide

found on the Sea-coast near Edinburgh 4S7

The Pholades being incapable of moving from their place,
the young are dropped from the tube of the parent on the sur-
face of their native rock. How they are enabled to penetrate
the rock, so as to secure themselves protection ; or how, previous-
ly to having formed a cell, they adhere to the surface, has not
hitherto been explained. RONDELETIUS, like others of the ol-
der naturalists, who believed in spontaneous generation, sup-
posed that the sea-water lodging in the pores of the rocks might
become, in process of time, Pholades * ; — a supposition not more
distant from truth than that which long afterwards prevailed as
to the Lepas anatifera being the young of a species of goose !
Perhaps some glutinous matter, such as fixes the byssus of the
M ytili, may keep the fry of the Pholades in their place till they
have excavated a hole sufficient to conceal themselves : but fu-
ture observation, by those who have the opportunity, will, there

UO 10 ' .'.:7r-Gf

with the opinions of that able observer. In Tab. VII. he has not only given beautiful
representations of the shell of the Photos dactylus, and its contained animal ; but has
displayed its anatomical structure in a series of figures which leaves nothing further
to be desired. M. POLI is clearly of opinion that the Pholades bore the rocks by me-
chanical action alone ; and he elsewhere adduces arguments to prove that even the
Mytilus lithophagits, the comparatively smooth shell of which seems unfitted for such
a purpose, forms its dwelling in a similar manner. The passage regarding the Pholas
is as follows :

" Cryptas hujusmodi conicam formam pras se ferunt, angustiore sui parte sursum
versa, per quam Molluscum Pholadem incolens tracheas pro lubitu exerit. Earum
amplitude Pholadum aetati, atque magnitudini respondere videtur : in adultis duos
circiter pedes in altitudinem patet, et hiatus diameter quinque lineas minus excedit.
In junioribus, mollusca turn pede exerto, ac in terebrae formam accommodate, turn
etiam conchas ministerio circa pedis apicem veluti circa axem revolutas, cryptam pro-
fundiorem, latioremque efficiunt quemadmodum adolescunt. Tanta est motus hu-
jusmodi efficacia, ut lapidibus simul perterebrandis par est."" — J. X. POLI, Testacea
utriusque Sictlite eorumque Historia et Anatome, vol. i. p. 40. Parma 1791.

* " Ego crediderim in saxorum cavernulis vel vi vel natura factis, aquas marina:
appulsu procreari atque in concham verti, qua? cavitatis sive foraminis figuram servat -"
— RONDELET. De Testaceis, lib. i. p. 49. Lugd. 1555.

438 Mr STARK on Two Species of Pholas

is little doubt, discover the arrangement by which these animals
are enabled to commence their cells.

The Pholades, it may be remarked, seem admirably con-
structed for the purposes of their existence, so far as these are
known. Possessing but a comparatively fragile shell, which the
least force would break, and, having no weapons of defence
against their aquatic enemies, Nature has furnished them with the
means of amply providing for this apparent deficiency, by giving
them an asylum in the solid rock. Having formed their destined
habitations, which they can never leave, the rock is honeycombed
by successive races till it falls in pieces, and a new surface is expos-
ed for new generations. The tribes of Pholades on the different
coasts are thus active and powerful instruments in the disinte-
gration of rocks. The shale in which they occur at Joppa runs
in parallel and alternating strata, with a coarse sandstone ; and
while the unconnected ridges of the sandstone still appear,
rounded by the weather, or hollowed into basins by the action
of the waves, the alternating beds of shale have nearly disappear-
ed, through the instrumentality of these powerful, though un-
seen agents *.

The Pholades are regularly used as an article of food on the
coasts of France and Italy, where they abound. In the neigh-
bourhood of Dieppe, bands of women and children, each armed

* The disposition of the strata on the coast at Joppa, and its present appearance,
strikingly illustrates the power of the instruments which Nature has employed in the
disintegration of certain classes of rocks. The beds of shale, which in some places
seem to have been from 12 to 20 feet thick, have in most instances wholly disappear-
ed ; parallel roads or spaces, deeply covered with sand, and on a level with the neigh-
bouring shore, being alone left to mark out the places formerly occupied by the shale.
Dead shells, of very large size, are also frequently found on various parts of the coast,
or dredged up by fishing-boats ; thus affording indications, in the places where they
are found, of the disappearance of strata effected by their agency. Encrinites are
found in the shale at Joppa inhabited by the Pholades.

Mr STARK on Two Species of Photos, Sfc. 439

with a pick-axe, break the rocks inhabited by them, for the pur-
pose of sending them to market, or as bait for fish. They are
found in every sea where the rocks are suitable for their burrow-
ing, and are met with fossil in many countries of Europe *.

* Bosc. in Nouv. Diet. cPHist. Nat. Vol.xxv. p. 539. M. G. P. DESHAYES has
recently described and figured four species of fossil Pholades, found by him, among
other perforating bivalves, at the village of Valmondois in France. — Mem. de la
Soe. PHist. Nat. torn. i. p. 245.

VOL. X. P. II. 3 K

fini ,lf{)« vvoatnwe Jiw^ r';r« unuhxi oj ar b^'iui^:

•

o a f,i

o iwooiiifi bnu Iwi>fvii> ai o«Lt oieaa arfj b«^ j/ifjfci, .J& b
•tod ,lyAs-->- on «i rft ;x}ui Twiio yj' T ijMntn) '.;u&ti

oi

440 Mr BLACK ADDER'S Description of a new

XXXI. Description of a new Register Thermometer, without any
Index ; the principle being applicable to the most deli-
cate Mercurial Thermometers. By H. H. BLACKADDER,
Esq. F. R. S. E.

(Read April 17. 1826.J

ON a former occasion, I had the honour of describing and ex-
hibiting to this Society a new Registering Thermometer, by
means of which the atmospheric temperature may be ascertained
at any given instant during absence. In the construction of
the instrument then described, a sliding index within the tube
is indispensable ; and, whenever such an index is employed, the
diameter of the tube, and consequently that of its bulb, must be
such as to render the instrument defective, when great accuracy
and attention to minute fractions is requisite, such as in barome-
trical measurements, and various delicate experiments. Besides,
though an instrument made with such an index may be so con-
structed as to perform with great accuracy, still, inasmuch as it
is a complication, it is defective, and is more or less liable to er-
ror, as its construction may have been more or less perfect.

The instrument which I now mean to describe, is free from
all such objections, as no index of any description is requisite,
and it may be made of two of the most delicate mercurial ther-
mometers, both tubes being attached to the same slip of ivory,
but with a separate scale for each.

One of the tubes, a, Plate XXII. Fig. 1. is hermetically seal-
ed as usual, and the scale also is divided and numbered in the
usual manner. The other tube d, is not hermetically sealed, but
left open at its upper extremity, which must be made flat and
smooth. This in general is easily and at once effected, by
making a small scratch with a sharp-edged file, previous to break-

PLATE XXIT.

e

J

/'

3

tf

,„.

4

0 |

'
'""

( &

i i : i 1 i i

-^TT

1 1 1

•*

d

4P»

•MMM

g

-4*^-

*

-

>

:

.'

'

I

^S

•f

^&^

-^^-

Kmi

frr^

"

i

!

~

\

\

a

Jiff. 3.

Register Thermometer without any Index. 441

ing off a small portion of the tube. The open extremity of the
tube d, is inserted into a portion of a larger thin glass-tube,
which exactly fits it, and which terminates in a hollow bulb,
containing a small quantity of mercury, c, Figs. 1, & 2. The
inner tube is carried forward until its extremity is about oppo-
site to that part of the outer tube where it begins to swell into
a bulb ; and the two tubes are then made to adhere permanent-
ly, by introducing a minute quantity of colourless varnish be-
tween them.

The scale of this tube commences from its upper open ex-
tremity, and is numbered downwards 1, 2, 3, &c. but marked as
in Fig. 1, 10, 20, 30, &c.

When an instrument thus formed is held upright, the glo-
bule of mercury in the bulb e, Fig. 1 . falls on the open extremity
of the tube d, as represented in Fig. 2. ; and if the bulb p be
now heated by the hand, the mercury will rise in the tube, and
unite with the globule c, with which it will remain connected as
long as the instrument is kept in the upright position. If the
instrument be now exposed in its upright position to the air,
which has, let it be supposed, the temperature of 60°, the upper
extremity of the mercury in the tube «, will be opposite that de-
gree of the scale ; but the mercury in the tube d, will still re-
main at the beginning of its scale, and continuous with the glo-
bule c. Let the instrument now be placed in a horizontal posi-
tion, and the entire globule of mercury will instantly quit the
open extremity of d, leaving the tube exactly filled with that
fluid, and the globule will then take the position c, Fig. 1. when
the instrument rests on the edge of its scale. If, from the in-
stant the globule is thus made to quit the open extremity of the
tube d, both of the bulbs n, and p, be kept moist with a rapidly
evaporating fluid, such as ether, alcohol, &c. the mercury in both
tubes will descend equally, and will remain permanently below
the elevation due to the temperature of the air, as long as the
* 3 R3

442 Mr BLACKADDER'S Description of a Register Thermometer.

evaporating fluid is kept applied to their bulbs. The existing
atmospheric temperature was supposed to be 60° ; let it now be
supposed that the loss of heat caused by evaporation is equal to
ten degrees. The mercury in the tube a will then point to 50,
and that in the tube d to 10 on their respective scales ; and then
10 + 50 — 60°, which was the temperature of the air at the in-
stant the globule quitted the open extremity of the tube d, when
the instrument received its horizontal position.

The way in which the instrument may be placed in a hori-
zontal position, at any given instant during absence, was former-
ly described, — a pocket time-piece, and a small additional but
simple piece of mechanism, being ah1 that is requisite. A vessel
for containing the evaporating fluid, fitted with a valve, and a
capillary tube terminating in one or more small and soft hair
brushes, Fig. 4. completes the apparatus, and which can obvious-
ly be made of such small dimensions as to be easily portable.

If the bulb at the upper extremity of the tube rf, Fig. 1, be
made of the bent form represented in Fig. 3, the instrument does
not require to be moved from a horizontal position. In this
case, the globule of mercury is made to quit the open extremity
of the tube </, and fall to the bottom of the bent bulb i, Fig. 3,
by the tube d, on a separate piece of ivory, being made to turn
half-way round on itself, the centre of motion being a line drawn
through the centre of the tube, and the extremity of the bent
portion being thus made to describe the half of a circle. Or,
both tubes may be attached to one slip of ivory, and the latter
be made to turn half-way round its own centre, being suspended
at each end, so as to admit of that motion.

This semirotation can readily be communicated at any given
instant, by the assistance of a time-piece, and a very little addi-
tional mechanism.

It is perhaps unnecessary to add, that this registering ther^
mometer may be used as an Atmizomic Hygrometer.

MR RITCHIE on a new Photometer. 443

f ' • <t -S. f

•

XXXII. On a new Photometer, founded on the Principles of
Bouguer. By WILLIAM RITCHIE, A. M. Rector of Tain
Academy. Communicated by Dr BREWSTER.

'

(Read May}. 1826.)
•

AHE celebrated BOUGUER was the first who discovered the
important fact, that the eye can detect a very small difference
between two similar illuminated surfaces, when viewed at the
same moment, — the only principle which has yet been applied
with any degree of success, in determining the relative illumi-
nating powers of artificial flames. The following is perhaps the
most commodious application of this principle, to determine the
relative illuminating powers of different artificial lights, particu-
larly of coal and oil gas. The instrument, or photometer, which
I employ for this purpose, is extremely simple. It consists of a
rectangular box, about an inch and a half, or two inches square,
open at both ends, and blackened within for the purpose of
absorbing the stray-light. Within the box are placed two rec-
tangular pieces of plane mirror, forming a right angle with each
other, and cutting the sides of the box at an angle of forty-five
degrees. In the upper side, or lid of the box, there is cut a
rectangular opening, about an inch long, and one-eighth of an
inch broad. This opening is covered with a slip of fine tissue
or oiled paper. In the annexed figure,
A B C D is the box ; C F, F D, the two
plane mirrors ; E G the rectangular open-
ing covered with a small disc of oiled or

fine paper. I need hardly mention, that c D

the two mirrors should be cut from the same plate, in order
that their reflective powers may be exactly equal. The rec-

444 Mr RITCHIE on a new Photometer,

.

tangular slit should have a small division of blackened card at
F, to prevent the possibility of the lights mingling with each
other, and thus affecting the accuracy of the result.

In using this instrument, place it in the same straight line
between two antagonist flames, at the distance of six or eight
feet from each other ; move it nearer the one or the other, till
the disc of paper appear equally illuminated on each side of the
middle division, and the illuminating powers of the flames will
be directly as the squares of their distances from the middle of
the photometer. In moving the instrument rapidly between the
two lights, we very soon discover a boundary, on each side of
which the difference between the illuminated discs becomes quite
apparent. By making the instrument move from one side of
this line to the other, and gradually diminishing the lengths
of the oscillations, we at last place it almost exactly in its proper
position. It is very convenient to have a board of the same
breadth with the instrument, divided into equal parts, for the
purpose of supporting it, and reading off with ease and accu-
racy the distances of the flames from the middle of the instru-
ment.

In viewing the illuminated disc of paper, I use a box, about
eight inches long, in the form of a prismoid, and blackened with-
in, in order to prevent any light entering the eye, except what
passes directly through the disc of paper.

Instead of the two mirrors, I sometimes use the same instru-
ment, with a piece of white paper pasted on the faces of the
mirrors, or on a piece of smooth wood, forming, as before, a right
angle. In this case, the illuminated discs are viewed directly
through the rectangular opening in the lid, without the inter-
vention of the tissue or oiled paper.

This instrument is still simpler than the preceding, and in
some experiments has decided advantages. But whatever form
of the instrument be employed, the following precautions should

founded on the Principles of Bouguer. 445

be employed, in order to insure a very close approximation to
the truth. Take any number of observations, turning the instru-
ment round at each time, and the mean of these will give a re-
sult, perhaps as accurate as the nature of the case admits ; at
least, it will be sufficiently accurate for all ordinary purposes.

When the colours of the flames are different, it is very diffi-
cult to ascertain the place of equal illumination. We can, how-
ever, as before, find the space over which the instrument moves,
before we discover an obvious difference between the illuminated
halves of the oiled or white paper. We must then take the
middle of this space, which will, even in that difficult case, give
us a very good approximation to the truth. The same method
was also used by M. BOUGUER, and found to be the best in simi-
lar cases. * But still this method is of very difficult application,
when one of the lights is of a fine white, and the other of a
dusky red or blue colour. In this case, I prefer the following
contrivance.

Procure a piece of fine white paper, and get it printed with a
small distinct type. Paste it on the rectangular opening in the
instrument, which, in this case, may be somewhat enlarged.
Brush over the paper with fine transparent oil, or, if the paper
be very fine, this will be unnecessary. Place the instrument be-
tween the flames, and cause two assistants move them in either
direction, till you can just read continuously along the paper
with the same ease, and the squares of the distances will then
afford a good approximation to the truth. If the second form
of the instrument be used, the printed slip of paper must be
pasted on the faces of the mirrors, or smooth wood, and read
directly through the opening in the lid.

* Traite d'Optique, page 50.

-

( 447 )

HISTORY OF THE SOCIETY.

VOL. x. p. ji.

( 449 )

LAWS

OF THE

ROYAL SOCIETY OF EDINBURGH,

ENACTED 23o MAY 1811, AND ALTERED ON THE 2&TH FEBRUARY 1820, 24TH
JANUAKY 1823, 13™ JANUARY 1824, AND QTH JANUARY 1826.

I.

JL HE ROYAL SOCIETY OF EDINBURGH shall consist of Ordinary, Fo-
reign, and Honorary Members.

II.

Every Ordinary Member, within three months after his election, shall
pay, as fees of admission, Five Guineas, and shall further be bound to pay
annually the snm of Three Guineas, into the hands of the Treasurer.

All Members who shall have paid Twenty-five years' annual subscrip-
tions, shall be exempted from future payments.

III.

Members shall be at liberty to compound for their annual subscription,
each paying according to the value of an annuity on his life, determined as
in the ordinary insurance on lives.

The power of raising the admission-fee and the annual subscription shall :
remain with the Society.

3L2

450 LAWS OF THE ROYAL SOCIETY

IV.

Ordinary Members, not residing in Edinburgh, and not compounding
for their annual subscription, shall appoint some person residing in Edin-
burgh, by whom the payment of the said subscription is to be made, and
shall signify the same to the Treasurer.

V.

Members failing to pay their subscription for three successive years,
due application having been made to them by the Treasurer, shall cease to
be Members of the Society, and the legal means for recovering such arrears
shall be employed.

VI.

None but Ordinary Members are to bear any office in the Society, or
to vote in the choice of Members or Office-bearers, or to interfere in the
patrimonial interests of the Society.

VII.
The number of Ordinary Members shall be unlimited.

VIII.

The Ordinary Members, upon producing an order from the Treasurer,
shall hereafter be entitled to receive from the publisher, gratis, the Parts
of the Society's Transactions which shall be published subsequent to their
admission.

IX.

The Society having formerly admitted as Non-resident Members,
gentlemen residing at such a distance from Edinburgh as to be unable re-
gularly to attend the Meetings of the Society, with power to such Non-
resident Members, when occasionally in Edinburgh, to be present at the
Society's Meetings, and to take a part in all their inquiries and proceed-
ings, without being subjected to any contribution for defraying the ex-
pences of the Society ; it is hereby provided, that the privileges of such

OF EDINBURGH. 451

Non-resident Members already elected shall remain as before; but no
Ordinary Members shall be chosen in future under the title and with the
privileges of Non-resident Members. The Members at present called
Non-resident shall have an option of becoming Ordinary Members ; if they
decline this, they shall continue Non-resident as formerly.

X.

The Foreign Members shall not be subject to the Annual Contribu-
tions, nor to any Fee on admission. They shall be limited to the number
of Thirty-six, and shall consist of Foreigners distinguished in Science and

Literature.

.-YX

XI.

The Honorary Members shall not be subject to the Annual Contri-
bution, nor to any Fee on admission. They shall be limited to the num-
ber of Twenty-one, and shall consist of Gentlemen eminently distinguished
in Science and Literature.

XII.

The Election of Members shall take place on the 1st Mondays of every
month during the Session, at the ordinary meetings of the Society, which
shall be considered as General Meetings for the Election of Members.
The election shall be by ballot, and shall be determined by a majority of
Two-thirds of the Members, provided Twenty-four Members are pre-
sent, and vote.

XIII.

No person shall be proposed as an Ordinary Member, without a recom-
mendation subscribed by One Ordinary Member, to the purport below *.

* " A. B. a gentleman well skilled in several branches of Science (or Polite Litera-
ture, as the case may be), being to my knowledge desirous of becoming a Member of the
Royal Society of Edinburgh, I hereby recommend him as deserving of that honour, and
as likely to prove an useful and valuable Member." <(

452 LAWS OF THE ROYAL SOCIETY

This recommendation shall be delivered to the Secretary, and by him laid
before the Council, and shall afterwards be read at each of three ordinary
meetings of the Society, previous to the day of the election, and shall lie
upon the table during that time.

XIV.

Any Three Members may transmit, through the Secretary to the
Council, recommendations of Foreign and Honorary Members. Foreign
and Honorary Members may also be proposed by the Council, and they
shall be elected in the same manner as the Ordinary Members.

XV.

The Classes shall meet alternately on the first and third Mondays of
every month, from November to June inclusive. It shall be competent,
however, to bring matters of a Physical or Literary kind, before either
Class of the Society indiscriminately. To facilitate this, one Minute-book
shall be kept for both Classes ; the Secretaries of the respective Classes
either doing the duty alternately, or according to such agreement as they
may find it convenient to make.

XVI.

The Society shall from time to time make a publication of its Trans-
actions and Proceedings. For this purpose the Council shall select and ar-
range the papers which they shall deem worthy of publication in the
Transactions of the Society, and shall superintend the printing of the
same.

The Transactions shall be published in Parts or Fasciculi, and the
expence shall be defrayed by the Society.

XVII.

There shall be elected annually, for conducting the publications and
regulating the private business of the Society, a Council, consisting of a
President ; Four Vice-Presidents, two of whom shall be resident ; a Pre-
sident for each Class of the Society ; Six Counsellors for each Class ; one

OF EDINBURGH. 453

Secretary for each ; a Treasurer ; a General Secretary ; and a Curator of
the Museum and Library.

XVIII.

The election of the Office-bearers shall be on the fourth Monday of
November.

XIX.

Four Counsellors, Two from each class, shall go out annually. They
are to be taken according to the order in which they at present stand on
the list of the Council.

XX.

The Treasurer shall receive and disburse the money belonging to the
Society, granting the necessary receipts, and collecting the money when
due.

•->* ,'j">dK iu ad ii.ju-.- ,

He shall keep regular accounts of all the cash received and expended,
which shall be made up and balanced annually ; and at a General Meeting,
to be held on the last Monday of January, he shall present the accounts
for the preceding year, duly audited. At this Meeting the Treasurer shall
also lay before the Society a list of all arrears due above twelve months,
and the Society shall thereupon give such directions as they may find ne-
cessary for recovery thereof.

XXL

At the General Meeting in November, a Committee of Three Mem-
bers shall be chosen to audit the Treasurer's accounts, and give the neces-
sary discharge of his intromissions.

The report of the examination and discharge shall be laid before the
Society at the General Meeting in January, and inserted in the records.

'

454 LAWS OF THE ROYAL SOCIETV

XXII.

A

The General Secretary shall take down minutes of the proceedings of
the General Meetings of the Society and of the Council, and shall enter
them in two separate books. He shall keep a list of the Donations made
to the Society, and take care that an account of such Donations be pub-
lished in the Transactions of the Society. He shall, as directed by the
Council, and with the assistance of the other Secretaries, superintend the
publications of the Society.

XXIII.

A Register shall be kept by the Secretary, in which copies shall be in-
serted of all the Papers read in the Society, or abstracts of those Papers, as
the Authors shall prefer ; no abstract or paper, however, to be published
without the consent of the Author. It shall be understood, nevertheless,
that a person choosing to read a paper, but not wishing to put it into the
hands of the Secretary, shall be at liberty to withdraw it, if he has before-
hand signified his intention of doing so.

For the above purpose, the Secretary shall be empowered to employ a
Clerk, to be paid by the Society.

XXIV.

Another register shall be kept, in which the names of the Members
shall be enrolled at their admission, with the date.

XXV.

A Seal shall be prepared and used, as the Seal of the Society.

XXVI.

The Curator of the Museum and Library shall have the custody and
charge of all the Books, Manuscripts, objects of Natural History, Scientific

'.*

* A

* * *'

OF EDINBURGH. 455

' * * *

Productions, and other articles of a similar description belonging to the
Society ; he shall take an account of these when received, and keep a re-
gular catalogue of the whole, which shall lie in the Hall, for the inspec-
tion of the Members.

XXVII.

All articles of the above description shall be open to the inspection of
the Members, at the Hall of the Society, at such times, and under such
regulations, as the Council from time to time shall appoint.

VOL. X. P. II. 3 M

( 457 )

> *

51 .fc&isdni

LIST

OF THE

OFFICE-BEAKERS AND MEMBERS ELECTED SINCE

MARCH 3. 1823.

May 5. 1823.

i;f> V

MEMBERS ELECTED.

ORDINARY.

Capt. THOMAS DAVID STEWART, Hon. E. I. Comp. Service.
ANDREW FYFE, M. D.
ROBERT BELL, Esq. Advocate.

June 2. 1823.
MEMBERS ELECTED.

ORDINARY.

Capt. NORWICH DUFF, R. N.

WARREN HASTINGS ANDERSON, Esq.

LISCOMBE JOHN CURTIS, Esq. Irigsdon House, Devonshire.

ALEXANDER THOMSON, Esq. of Banchory, Advocate.

4 3 M£

458 LIST OF OFFICE-BEARERS AND MEMBERS

November 24. 1823.

OFFICE-BEARERS.

Sir WALTER SCOTT, Bart. President.

d

VlCE-PnSSlDENTS.

Right Hon. LORD CHIEF BARON. Dr T. C. HOPE.

Lord GLENLEE. Professor RUSSELL.

Dr BREWSTER, General Secretary.

^t .

THOMAS ALLAN, Esq. Treasurer.

JAMES SKENE, Esq. Curator of the Museum.

PHYSICAL CLASS.

ALEXANDER IRVING, Esq. President.
JOHN ROBISON, Esq. Secretary.

Counsellors from the Physical Class.
Sir JAMES HALL, Bart. ROBERT STEVENSON, Esq.

Dr KENNEDY. Sir. W. ARBUTHNOT, Bart,

Rev, Dr MACKNIGHT. JAMES JARDINE, Esq.

LITERARY CLASS.

HENRY MACKENZIE, Esq President..
P. F. TYTLER, Esq. Secretary.

Counsellors from the Literary Class.
THOMAS THOMSON, Esq. Professor WILSON.

GEORGE FORBES, Esq. Sir W. HAMILTON, Bart,

Lord MEADOWBANK. Rev. Dr LEE.

ELECTED SINCE 1823. 459

r *

December 1. 1823.
MEMBERS ELECTED.

FOREIGN.

M. THENARD, Member of the Institute, and Professor of
Chemistry in the College of France.

ORDINARY.

. £
ROBERT KNOX, M. D.

ROBERT CHRISTISON, M. D. Professor of Medical Juris-

. j,
prudence.

GEORGE KELLIE, M. D. Leith.

January 19. 1824.

*• *•

MEMBERS ELECTED.

HONORARY.
«f

The Rev. JOHN BRINKLEY, D. D., F. R. S., and President

of the Royal Irish Academy.
W. H. WOLLASTON, M. D., F. R. S. &c. &c.

FOREIGN.

WILLIAM HAIDINGER, Esq. Vienna.

ORDINARY.

GEORGE HARVEY, Esq. Plymouth.
Dr LAWSQN WHALLEY, Lancaster v

46* LIST OF OFFICE-BEARERS AND MEMBERS

WILLIAM BELL, Esq. W. S. Edinburgh.

JAMES HAMILTON jun. M. D. Professor of Midwifery in the
University of Edinburgh.

ROBERT GROAT, M. D. Edinburgh.

ROBERT GRANT, M. D. Edinburgh.

CLAUD RUSSELL, Esq. W. S. Edinburgh.

H. W. WILLIAMS, Esq. Edinburgh.

Rev. WILLIAM MUIR, D. D. one of the Ministers of Edin-
burgh.

- February 2. 1824.
MEMBERS ELECTED.
ORDINARY.

ALEXANDER MUNRO, Esq. Edinburgh.

W. H. PLAYFAIR, Esq. Architect, Edinburgh.

March 1. 1824.

MEMBERS ELECTED.

ORDINARY.

JOHN ARGYLE ROBERTSON, Esq. Surgeon, Edinburgh.

JAMES PILLANS, Esq. Leith.

Dr MACWHIRTER, Edinburgh.

JAMES WALKER, Esq. Civil Engineer.

WILLIAM NEWBIGGING, Esq. Surgeon, Edinburgh.

ELECTED SINCE 1823. 461

May 3. 1824.
MEMBERS ELECTED.

ORDINARY.
WILLIAM WOOD, Esq. President of the Royal College of

Surgeons.
WILLIAM CROSBIE MAIR, M. D. Physician to the Embassy

to Mexico.

November 22. 1824.

OFFICE-BEARERS.

Sir WALTER SCOTT, Bart. President.

VICE-PRESIDENTS.

Right Hon. Lord CHIEF-BARON. Dr T. C. HOPE.

Lord GLENLEE. Professor RUSSELL.

Dr BREWSTER, General Secretary.

THOMAS ALLAN, Esq. Treasurer.

JAMES SKENE, Esq. Curator of the Museum.

PHYSICAL CLASS.

ALEXANDER IRVING, Esq. President.
JOHV PVOBISON, Esq. Secretary.

Counsellors from the Physical Class.
Rev. Dr MACKNIGHT. JAMES JARDINE, Esq.

ROBERT STEVENSON, Esq. Sir WILLIAM FORBES, Bart.

Sir WILLIAM ARBDTHNOT, Bart. Dr HOME.

462 LIST OF OFFICE-BEARERS AND MEMBERS

LITERARY CLASS.

HENRY MACKENZIE, Esq. President.
P. F. TYTLER, Esq. Secretary.

Lord M EADOWBANK. Rev. Dr LEE.

Professor WILSON. Right Hon. the Lord ADVOCATE.

Sir W. HAMILTON, Bart. Dr HOME.

*

December 6. 1824.
MEMBERS ELECTED.

ORDINARY.

JOHN CAMPBELL, M. D. Edinburgh.
GEORGE ANDERSON, Esq. Inverness.

January 3. 1825.
MEMBERS ELECTED.

HONORARY.
ROBERT BROWN, Esq. F. R. S. London.

February 7. 1825.

*

MEMBERS ELECTED.

ORDINARY.

Major LEITH HAY of Rannes.

Rev. JOHN WILLIAMS, Rector of the Edinburgh Academy.

JOHN HUGH MACLEAN, Esq. Advocate.

ELECTED SINCE 1«823. 463

March 7- 1825.
MEMBERS ELECTED.

FOREIGN.

M. MITSCHERLICH, Professor of Chemistry in the Univer-
sity of Berlin.

M. GUSTAVUS ROSE, Professor of Mineralogy in the Uni-
versity of Berlin.

ORDINARY.

WILLIAM PRESTON LAUDER, M. D. Edinburgh.
Right Honourable Lord RUTHVEN.

EDWARD TURNER, M. D. Lecturer on Chemistry, and Fel-
low of the Royal College of Physicians, Edinburgh.

April 4. 1825.

MEMBERS ELECTED.

ORDINARY.

Right Honourable Lord BELHAVEN.

Dr REID CLANNY, Physician, Sunderland.

November 28. 1825.

OFFICE-BEARERS.

Sir WALTER SCOTT, Bart. President.

VlCE-P»ESIDENTS.

Right Hon. Lord CHIEF-BARON. Dr T. C. HOPE.

Lord GLENLEE. Professor RUSSELL.

VOL. x. P. ii.

464 LIST OF OFFICE-BEARERS AND MEMBERS

Dr BREWSTER, General Secretary.

THOMAS ALLAN, Esq. Treasurer.

JAMES SKENE, Esq. Curator of the Museum.

PHYSICAL CLASS.

ALEXANDER IRVING, Esq. President.
JOHN ROBISON, Esq. Secretary.

Counsellors of the Physical Class.
Sir WILLIAM ARBUTHNOT, Bart. Dr HOME.
JAMES JARDINE, Esq. Professor WALLACE.

Sir WILLIAM FORBES, Bart. Dr EDWARD TURNER.

LITERARY CLASS.

HENRY MACKENZIE, Esq. President.
P. F. TYTLER, Esq. Secretary.

Sir W. HAMILTON, Bart. Sir HENRY JARDINE.

Rev. Dr LEE. Sir JOHN HAY, Bart.

Right Hon. the Lord ADVOCATE. Dr HIBBERT.

December 5. 1825.

MEMBERS ELECTED.

ORDINARY.

JOHN A. STEWART, Esq. younger of Grandtully.
JAMES HALL, Esq. Advocate.

ELECTED SIXCE 1823.

January 9. 1826.
MEMBERS ELECTED.

ORDINARY.
HENRY HOME BLACKADDER, Esq. Surgeon, Edinburgh.

At this Meeting it was agreed, " That Lair No. XII. be altered, so that
hereafter no Candidate, when WIVxt<^ for, shall be considered as admitted, un-
less there be a majority of at least Tiro-thirds of the Votes in his fimnr.~

February 6. 1826.

MEMBERS ELECTED.

ORDINARY.

— I *.*

ALEXANDER WOOD, Esq. Advocate.
Rev. DIONYSUS LARDNER, Fellow of Trinity College,
Dublin.

March 6. 1826.

MEMBERS ELECTED.

ORDDCARY.

GEORGE MACPHERSON GRANT, Esq. M. P. of BallindaHoch.
WILLIAM RENNT, Esq. W. S. Solicitor of Stamps.
ELIAS CATHCART, Esq. Advocate.

5x2

466 LIST OF OFFICE-BEARERS AND MEMBERS.

April 3. 1826.

MEMBERS ELECTED. .

ORDINARY.
ANDREW CLEPHANE, Esq. Advocate.

May 1. 1826.

MEMBERS ELECTED.

*

ORDINARY.

Rev. GEORGE COVENTRY.
Sir DAVID HUNTER BLAIR, Bart.

FOREIGN.

G. MOLL, Professor of Natural Philosophy in the Univer-
sity of Utrecht.

M. STROMEYER, Professor of Chemistry in the University
of Gottingen.

M. HAUSMANN, Professor of Mineralogy in the University
of Gottingen.

( -467 )

LIST of the Present ORDINARY MEMBERS of the
ROYAL SOCIETY OF EDINBURGH, in the order
of their Election.

His MAJESTY THE KING PATHOV

Date of
Election.

Andrew Duncan senior, M. D. Professor of the Theory of Physic.
Dr James Hamilton senior, Physician, Edinburgh.
Sir William Miller, Baronet, Lord Glenlee.
James Russell, Esq. Professor of Clinical Surgery.
Charles Stuart, M. D. of Dunearn, Physician, Edinburgh,
Dugald Stewart, Esq.

The above Gentlemen were Members of the Edinburgh Philoso-

phical Society.

1788. Honorable Lord Hermand.
Honorable Baron Hume.

» •*'*"* ^

Henry Mackenzie, Esq.

Honorable Lord Bannatyne.

Reverend William Trail, LL. D. Chancellor of St Saviour's, Connor.

The above Gentlemen were associated with the Members of the Philoso-
phical Society at the Institution of the Royal Society in 1783.

The following Members were regularly elected.

1784. Sir James Hall, Baronet, F. R. S. Lond.
• . Honorable Lord Eldin.

Reverend Archibald Alison, LL. B. Edinburgh.

1785. James Hare, M. D. late of Calcutta.

1786. Robert Blair, M. D. Professor of Practical Astronomy.

1787. James Home, M. D. Professor of the Practice of Physic.

OF ORDINARY MEMBERS.

Date of
Election.

1788. Thomas Charles Hope, M. D. F. R. S. Lond. Professor of Chemistry.

Right Honorable Charles Hope, Lord President of tlie Court of Session.

1792. Andrew Coventry, M. D. Professor of Agriculture.

1793. Sir Alexander Muir Mackenzie, Bart ofDelrin.

1795. The very Reverend Dr George Husband Baird, Principal of the University.
Robert Hamilton, Esq. Professor of Public Law.

1796. General Dirom, of Mount Annan, F. R. S. Lond.
Reverend Sir Henry Moncrieff Wellwood, Baronet.
The Honorable Baron Sir Patrick Murray, Baronet.
Andrew Berry, M. D. Edinburgh.

1797. Andrew Duncan junior, M. D. Professor ofMateria Medica.

1798. Alexander Monro, M. D. Professor of Anatomy, $c.
Right Honorable Sir John Sinclair, Bart.

1799. Reverend Thomas Macknight, D. D.
Honorable Lord Robertson.

Sir George S. Mackenzie, Baronet, F. R. S. Lond.
Robert Jameson, Esq. Professor, of Natural History.

1800. Sir William Arbuthnot, Bart.
Gilbert Innes, Esq. of Stow.

Sir Walter Scott, Baronet, of Abbotsford.
Colonel D. Robertson Macdonald.

1803. Reverend John Jamieson, D. D.
Thomas Telford, Esq. Civil Engineer.
James Bryce, Esq. Surgeon, Edinburgh.
Reverend Dr Andrew Brown, Professor of Rhetoric.

1804. William Wallace, Esq. Professor of Mathematics.
Sir William Forbes, Bart, of Pitsligo.
Alexander Irving, Esq. Professor of Civil Law.

1805. Thomas Allan, Esq. F. R. S. Lond.

Thomas Thomson, M. D. F. R. S. Lond. Professor of Chemistry, Glasgow.

1806. Robert Ferguson, Esq. of Raith, F. R. S. Lond.
George Bell, Esq. Surgeon, Edinburgh.
George Dunbar, Esq. Professor of Greek.

1807. Sir James Montgomery, Baronet, of Stanhope, M. P.
John Barclay, M. D. Lecturer on Anatomy, <Sfc.
John Leslie, Esq. Professor of Natural Philosophy.
John Campbell, Esq. ofCarbrook.

J.IST OF ORDINARY MEMBERS. 469

Date of
Election.

Thomas Thomson, Esq. Advocate.

William Fraser Tytler, Esq. Advocate.
1808. James Wardrop, Esq. Surgeon Extraordinary to his Majesty.

David Brewster, LL. D. F. R. S. Lond.

1810. Reverend Dr William Ritchie, Professor of Divinity.

1811. Charles Bell, Esq. Surgeon, London.
Alexander Nimmo, Esq. Civil Engineer.
Reverend Andrew Stewart, M. D. Erskine.
Reverend David Ritchie, D. D. Professor of Logic.
Major-General Sir Thomas Brisbane Makdougal, K. C. B.

1812. Right Honorable Lord Gray, F. R. S. Lond.
General Dyce.

John Thomson, M. D. Physician, Edinburgh.

James Jardine, Esq. Civil Engineer.

Captain Basil Hall, R. N. F. R. S. Lond.

J. G. Children, Esq. F. R. S. Lond.

Alexander Gillespie, Esq. Surgeon, Edinburgh.

W. A. Caddell, Esq. F. R. S. Lond.

Macvey Napier, Esq. F. R. S. Lond.

James Pillans, Esq. Professor of Humanity.

Sir George Clerk, Bart. M. P. and F. R. S. Lond.

Daniel Ellis, Esq. Edinburgh.

1813. William Somerville, M. D. F. R. S. London.
James Hare,jun, M. D. late of Calcutta.
Henry Davidson, M. D. Physician in Edinburgh.

1814. Sir Henry Jardine, King's Remembrancer in Exchequer.

Patrick Neill, Esq. Secretary to the Wernerian and Horticultural Societies.

Right Honorable Lord Viscount Arbuthnot.

Reverend John Thomson, Duddingston.

Reverend John Fleming, D. D. Elisk.

John Cheyne, M. D. Physician, Dublin.

Sir James Mackintosh, M. P. London.

Lieut-Colonel Tytler, Edinburgh.

Reverend Alexander Brunton, D. D. Professor of Oriental Languages.

Professor George Glennie, Marischall College, Aberdeen.

1815. Gilbert Laing Meason, Esq. of Lindertis.
Robert Stevenson, Esq. Civil Engineer.

Sir Thomas Dick Lander, Bart, of Fountain/Mil.
John Yule, M. D. Physician in Edinburgh.

A

470 LIST OF ORDINARY MEMBERS.

Date of
Klection.

Henry Home Drummond, Esq. of 'Blair- Drummond, M. P.

Charles Granville Stewart Menteath, Esq. ofCloseburn.

William Thomas Brande, Esq. Sec. R. S. Lond. and Professor of Chemistry
in the Royal Institution.

1816. Colonel Thomas Colby, F. R. S. Royal Engineers.
Leonard Horner, Esq. F. R. S. Lond.

Henry Colebrooke, Esq. Director of the Asiatic Society of Great Britain.

Reverend George Cook, D. D. LaurenceMrk.

Right Honorable William Adam, Lord Chief Commissioner.

John Fullerton, Esq. Advocate.

Thomas Jackson, LL. D. Professor of Natural Philosophy, St. Andrew's.

John Robison, Esq. Edinburgh.

Hugh Murray, Esq. Edinburgh.

1817. The Honorable Baron Clerk Rattray.

Right Honorable the Earl of Wemys and March.

Francis Hamilton, M. D. F. R. S. and F. A. S. Lond.

John Wilson, Esq. Professor of Moral Philosophy.

Honorable Lord Meadowbank.

John Fleming, M. D. late of Calcutta.

James Hamilton Dickson, M. D. Clifton.

William P. Alison, M. D. Professor of the Theory of Physic.

James Skene, Esq. pfRubislaw.

John Howell, M. D.

Reverend Robert Morehead, Edinburgh.

Robert Bald, Esq. Civil Engineer.

Thomas Sivright, Esq. of Meggetland.

1818. William Richardson, M. D. Physician, Harrowgate.
Right Honorable Lord Napier.

Harry William Carter, M. D. Oxford.
Patrick Miller, M. D. Exeter.
John Craig, Esq. Edinburgh.
John Watson, M. D.
Captain Thomas Brown, F. L. S.
John Hope, Esq. His Majesty's Solicitor-General.
Major James Alston of Auchenard.
William Ferguson, M. D. Windsor.
Sir William Hamilton, Bart. Professor of Civil History.
1819- Right Honorable Lord John Campbell, F. R. S. Lond. and M. R. I.
Sir John Hay, Bart. ofSmithfield and Hayston.

LIST OF ORDINARY MEMBERS. 471

Date of
Election.

Dr Shoolbred, Calcutta.

Patrick Fraser Tytler, Esq. Advocate.
Major-General David Stewart of Garth.
Patrick Murray, Esq. of Simprim.
James Muttlebury, M. D. Bath.
Thomas Stewart Trail!, M. D. Liverpool.
Alexander Kennedy, M. D. Physician, Edinburgh.
Mr Alexander Adie, Optician, Edinburgh.
William Couper, M. D. Glasgow.
John Hennen, M. D.
John Veitch, M. D.

Andrew Waddel, Esq. Hermitage Hill
Marshall Hall, M. D. Nottingham.
John Borthwick, Esq. Advocate.
Richard Phillips, Esq. F. R. S. London.
Rev. William Scoresby.
George Forbes, Esq. Edinburgh.
1820. James Hunter, Esq. of Thurston.

Right Honorable David Boyle, Lord Justice-Clerk.

James Keith, Esq. Surgeon, Edinburgh.

Right Honorable Sir Samuel Shepherd, Lord Chief-Baron.

James Nairne, Esq. W. S. Edinburgh.

John Colquhoun, Esq. Advocate.

Lieutenant-Colonel M. Stewart.

Charles Babbage, Esq. F. R. S. Lond.

Thomas Guthrie Wright, Esq. Auditor of the Court of Session.

John F. W. Herschel, Esq. Sec. R. S. Lond.

Adam Anderson, Esq. A. M. Sector of the Academy, Perth.

John Shank More, Esq. Advocate.

Dr George Augustus Borthwick, Surgeon, Edinburgh.

Robert Dundas, Esq. ofArniston.

Samuel Hibbert, M. D. and Sec. to the Society of Scottish Antiquaries, Edin.

Rev. Robert Haldane, D. D. Principal ofSt Mary's College, St Andrew's.

Sir John Meade, M. D. Weymouth.

Thomas Kinncar, Esq. Edinburgh.

Dr William Macdonald of BaUyshear.

John Hall, Esq. younger ofDunglass.

Admiral Adam.

VOL. X. P. II. 3 O

472 LIST OF ORDINARY MEMBERS.

Date of
Election.

John Hay, Esq. younger of 'Smithfield and Hayston.

George Ballingall, M. D. Professor of Military Surgery.
1821. Major-General Straton, C. JB. &c. &c.

Robert Graham, M. D. Professor of Botany.

A. N. Macleod, Esq. of Harris.

Sir James M. Riddell, Bart, of Ardnamurcfian.

Archibald Bell, Esq. Advocate.

John Clerk Maxwell, Esq. Advocate.

John H. Wishart, Esq. Surgeon, Edinburgh.

John Lizars, Esq. Surgeon, Edinburgh.

Edward Earl, Esq.

John Cay, Esq. Advocate.

Sir Charles Giesecke, Professor of Mineralogy to the Dublin Society.

Robert Kaye Greville, LL. D. Edinburgh.

Robert Hamilton, M. D. Edinburgh.

Robert Allan, Esq. Surgeon, Edinburgh.

Sir Archibald Campbell, Bart.

Sir David Milne, K. C. B.

Colonel Mair, Deputy-Governor of Fort-George.

A. R. Carson, Esq. Rector of the High School.

James Buchan, M. D, Physician, Edinburgh.

James Tytler, Esq. of Woodhouselee, W. S.
1822. Francis Chantry, Esq. F. R. S. London, &c.

Edward Troughton, Esq. F. R. S. London, &c.

James Smith, Esq. of Jordanhill.

William Bonar, Esq. Edinburgh.

Colin Mackenzie, Esq. Deputy Keeper of the Signet.

Rev. H. Parr Hamilton, Cambridge.

Captain J. D. Boswall, R. N. of Wardie.

Dr John Aitken, Physician, Edinburgh.

James Graham, Esq. Advocate.

George A. Walker Arnott, Esq. Advocate.

Rev. John Lee, M. D. Edinburgh.

John Ayton, Esq. of Inchdarnie.

Richard Saumarez, Esq.

James South, Esq. F. R. S. London.

Lieutenant-Colonel Martin Whyte, Edinburgh.

LIST OF ORDINARY MEMBERS. 473

Date of
Election.

Walter Frederick Campbell, Esq. of Shawfield, M. P.

George Joseph Bell, Esq. Professor of Scots Law.

Dr William Dyce, Aberdeen.

W. C. Trevelyan, Esq. Wattington.

Robert Abercromby, Esq. younger qfBirkenbog.

Dr Shortt, Edinburgh.

Dr Wallich, Calcutta.
1823. The Right Honorable Sir George Warrender, Bart. ofLochend.

John Russell, Esq. W. S. Edinburgh.

John Shaw Stewart, Esq. Advocate.

Alexander Hamilton, M. D. Physician, Edinburgh.

Thomas Harland, M. D. Physician, Scarborough*

John Dewar, Esq. Advocate, Edinburgh.

Right Honorable Sir William Rae, Bart, of St Catherines, Lord Advocate.

Sir Robert Dundas, Bart. ofBeechwood.

William Cadell, Esq. of Cockenzie.

Sir William Knighton, Bart.

Sir Edward French Bromhead, Bart. A. M. F. R. S. Lond., Thurlsby Hall.

Sir James Stuart, Bart. ofAllanbank.

Sir Andrew Halliday, Physician to His Royal Highness the Duke of Clarence.

John Bonar, Esq. younger of Kimmerghame.

Alexander Waddell, Esq. Hermitage Hill.

Captain Thomas David Stuart of the Hon. East India Company's Service.

Andrew Fyfe, M. D. lecturer on Chemistry, Edinburgh.

Robert Bell, Esq. Advocate.

Captain Norwich Duff, R. N.

Warren Hastings Anderson, Esq.

Alexander Thomson, Esq. of Banchoryj Advocate.

Liscombe John Curtis, Esq. Ingsdon House, Devonshire.

Robert Knox, M. D. Lecturer on Anatomy, Edinburgh.

xtobert Christison, M. D. Professor of Medical Jurisprudence.

John Gordon, Esq. ofCairnbulg.

George Kelly, M. D. Leith.
1824. George Harvey, Esq. F. R. S. Lond. Plymouth.

Dr Lawson Whalley, Lancaster.

William Bell, Esq. W. S. Edinburgh.
Dr Wilson Philip, Bristol.

3 02

474 LIST OF ORDINARY MEMBERS.

Date of
Election.

Dr James Hamiltoajwra., Professor of Midwifery in the University of Edinburgh.

Dr Robert Grant, Edinburgh.

Claud Russell, Esq. Accountant, Edinburgh.

H. W. Williams, Esq. Edinburgh.

Rev. Dr William Muir, one of the Ministers of Edinburgh.

Alexander Munro, Esq. Edinburgh.

W. H. Playfair, Esq. Architect, Edinburgh.

John Argyle Robertson, Esq. Surgeon, Edinburgh.

James Pillans, Esq. Leith.

Dr Macwhirter.

James Walker, Esq. civil engineer.

William Newbigging, Esq. surgeon.

William Wood, Esq. Surgeon, Edinburgh.

Dr William Crosbie Mair, Physician to the Embassy to Mexico.

John Campbell, M. D. Edinburgh.

George Anderson, Esq. Inverness.

1825. Major Leith Hay, ofRannes.

Rev. John Williams, Rector of the Edinburgh Academy.

John Hugh Maclean, Esq. Advocate.

Dr W. Preston Lauder.

Right Honorable Lord Ruthven.

Edward Turner, M. D. Lecturer on Chemistry, and Fellow of the Royal College

of Physicians..

Right Honorable Lord Belhaven.
Dr Reid Clanny, Sunderland.

John Archibald Stewart, Esq. younger of Grandtully.
James Hall, Esq. Advocate.
Sir William Jardine, Bart, of Applegarth.
H. H. Blackadder, Esq. Surgeon, Edinburgh.
Alexander Wood, Esq. Advocate.
Rev. Dionysius Lardner, Trinity College, Dublin.

1826. George Macpherson Grant, Esq. M. P. of BaUindalloch.
William Renny, Esq. W. S. Solicitor of Stamps.
Elias Cathcart, Esq. Advocate.

Andrew Clephane, Esq. Advocate.

Rev. George Coventry.

Sir David Hunter Blair, Bart. <

LIST OF NON-RESIDENT MEMBERS. 475

LIST of NON-RESIDENT and FOREIGN MEMBERS

elected under the Old Laws.

Sir Gilbert Blane, M. D. F. R. S. Lortdon.

John Hunter, LL. D. Professor of Humanity, St Andrew's.

George Jardine, A. M. Professor of Logic, Glasgow.

Right Honorable the Earl of Morton.

Right Honorable the Earl of Dundonald.

Right Honorable Sir Robert Listen, Bart.

Mr Jefferson.

M. Le Chevalier, Paris.

Dr S. L. Mitchell, New York.

Right Honorable Thomas Wallace, Esq. qfCarlton Hall.

Rev. Thomas Somerville, D. D. Jedburgh.

John Gillies, LL.D. Historiographer to his Majesty.

Robert Freer, M. D. Professor of the Theory and Practice of Physic, Glasgow.

M. P. Prevost, Geneva,

Rev. Walter Fisher, Cranston.

Rev. Bishop Gleig, Stirling.

Charles Hatchet, Esq. F. R. S. Lond.

Major Rennel, F. R. S. Lond.

Sir Henry Stuart, Bart. ofAUanton.

Sir William Blizzard, M. D. F. R. S. Lond.

Thomas Blizzard, Esq.

Sir William Ouseley, Bart.

The Right Honorable the Earl of Traquair.

Sir William Drummond, Bart, of Logic Almond.

Sir James Macgrigor, M. D.

Richard Chenevix, Esq. F. R. S. Lond.

Richard Griffiths, Esq. Civil Engineer.

' '

LIST OF HONORARY AND FOREIGN MEMBERS.

LIST of HONORARY and FOREIGN MEMBERS, elected
under the New Laws.

HONORARY.

The Marquis de Laplace, Member of the Institute of France,
Baron Cuvier, Secretary to the Institute of France.
M. Humboldt, Member of the Institute of France-
Sir Humphry Davy, Bart. P. R. S. Lond.
M. Gay Lussac, Member of the Institute of France.
M. Biot, Member of the Institute of France.
M. Arago, Member of the Institute of France.
His Royal Highness Prince Leopold.
His Royal Highness the Archduke Maximilian.

The above Members were elected before the new class of Foreign
Members was established.

His Imperial Highness the Archduke John of Austria.

M. Le Chevalier Joseph Hammer.

M. Goethe".

Rev. Dr Brinkley, F. R. S. Lond., and President of the Royal Irish Academy.

Dr W. H. Wollaston, F. R. S. Lond. &c. &c.

Robert Brown, Esq. F. R. S. Lond. &c. &c.

FOREIGN.

M. Le Chevalier Legendre, Member of the Institute of France.

M. Poisson, Member of the Institute of France.

M. Vauquelin, Member of the Institute of France.

M. Prony, Member of the Institute of France.

M. Brochant, Member of the Institute of France.

Baron Leopold Von Buch, Berlin.

M. Gauss, Professor of Mathematics, Gottingen.

M. Blumenbach, Professor of Natural History, Gottingen.

LIST OF FOREIGN MEMBERS. 477

Jacob Berzelius, M. D. F. R. S. Lend. Professor of Chemistry, Stockholm.

Count Volta, Como.

M. J. C. L. Simonde de Sismondi.

Baron Degerando.

Baron Krusenstern, Member of the Academy ofScknfes at St Petersburg.

M. Oersted, Secretary to the Royal Society of Denmark.

M. Ampere, Member of the Institute of France.

M. Shumaclier, Professor of Astronomy at Copenhagen.

M. Mohs, Professor of Mineralogy at Freyberg.

David Hosack, M. D. F. R. S. New York.

Nathaniel Bowditch, Esq. Salem, Massachussets.

Baron Larrey, Member of the Institute of France.

Sir Henry Bernstein, Professor of Oriental Literature in the University of' Berlin.

M. De Candolle, Geneva,.

Dr Olbers, Bremen.

M. Frederick Munter, Bishop of ZealQrtf.

M. Oriani, Milan. ',,fl

M. Dupin, Member of the Institute of France.

M. Brongniart, Member of the Institute of France.

The Chevalier Burg, Vienna.

M. Bessel, Konigsberg. •

M. Thenard, Member oftlte Institute of France.

M. Haidinger, Vienna.

M. Mitscherlich, Professor of Chemistry in the University of Berlin.

M. Gustavus Rose, Professor of Mineralogy in the University of Berlin.

G. Moll, Professor of Natural Philosophy in the University of Utrecht.

M. Stromeyer, Professor of Chemistry in the University ofGottingen.

M. Hausmann, Professor of Mineralogy in the University ofGottingen.

< 478 )

LIST of DECEASED MEMBERS, and of MEMBERS
RESIGNED,/rom 1823 to 1826.

1822.

Nov. 6. C. L. Berthollet, Member of the
Institute of France.

1823.
Mar. 9- M. Van Swinden, Amsterdam.

28. Sir Hay Campbell, Bart.
May 2. Right Honorable Lord Glen-

bervie.

July 8. Sir Henry Raeburn.
Sept. 23. Dr Matthew Baillie.

Right Honorable The Earl of
Hopetoun.

Dr Farquharson.
Dec. 81. Dr Rogerson.

Rev. Dr A. Bell.

1824.
Apr. 27. The Most Noble the Marquis

of Lothian-
Oct. 2. Dr Robert Groat.

Captain Robert Hay, R. N.

1825.

Apr. 19. Professor Pictet.
M. Breislak.
General Vyse.

Resignation.
April 7. 1823. Dr Borthwick Gilchrist,

( 479 )

LIST of PRESENTS received by the ROYAL SOCIETY OF
EDINBURGH. Continued from Vol. IX. p. 541.

PRESENTS.

The Door of the Bookcase of Sir Isaac New-
ton.

1823.

Mar. 17. The Vertebra of a Whale, found in the Blue

Clay near Dingwall. See Transactions, vol.

x. p. 105.
Apr. 7. Account of a Voyage to Greenland, by Cap-

tain Scoresby.

Account of Mr Clissold's ascent of Mont Blanc.
System of Practical Nosology, by Dr Hosack,

of New York.
May 19- Meteorological Journal kept at Lerwick for

1831, by Dr Scott.
July 1. Acts of the Parliament of Scotland, vol. x.

Nov. 3. Transactions of the Horticultural Society of

London, vol. v. part ii.
Asiatic Researches, vol. x.
Memoires de PAcademie Imperiale de Peters-

burg, vol. viii.
1824.
Jan. 12. Meteorological Register kept in Van Diemarrs

Land.

Transactions of the Horticultural Society,
vol. v. part 3.

VOL. X. P. II.

DONORS.

John Robison, Esq.

Sir George S. Mackenzie,
Bart.

Captain Scoresby.

Mr Clissold.
Dr Hosack.

W. C. Trevelyan, Esq.

The Commissioners of the

Public Records.
Horticultural Society.

Asiatic Society.
Imperial Academy of
Sciences of St Petersburg.

His Excellency Sir Thomas

Brisbane.
Horticultural Society.

480

LIST OF DONATIONS.

1824. PRESENTS.

Jan. 12. Antiquarian Annals of Copenhagen, 6 vols.

Transactions of the Royal Society of Stock-
holm for 1822. 3 vols.

Feb. 16. Transactions of the Batavian Society.
Flora Batava, No. 64.

Apr. 19. The Philosophy of Apparitions, by Dr Hib-

bert.
Flora Batava, No. 65.

May 3. Observations Medicales fails pendant les Cam-
pagnes de Russie 1812, par M. Le Cheva-
lier Kirchoff.
Memoirs of the Wernerian Society, vol. iv.

part ii.
June 7. Transactions of the Cambridge Philosophical

Society, vol. ii. part i.
Memoires de la Societe Naturelle de Geneve,

vol. i. part i. and ii ; and vol. ii. part i.
Nov. 15. Transactions of the Horticultural Society of

London, vol. v. part iv.
Report of the Garden Committee.
List of the Members of the Horticultural So-
ciety.

Transactions of the Royal Society of Corn-
wall, vols. i. & ii.
Catalogue of the Library of the American

Philosophical Society.

Dec. 6. History, of the Introduction of Christianity
into Norway, by M. Frederick Munter, Bi-
shop of Zealand.
Narratio de Lucio, Primo Episcopo Romano,

by M. Frederick Munter.
Account of the Bell-Rock Lighthouse, by
Robert Stevenson, Esq.

DONORS.

Mr Frederick Munter, Bi-
shop of Zealand.

From the Royal Society of
Stockholm.

From the Society.

His Majesty the King of
the Netherlands.

Dr Hibbert.

His Majesty the King of

the Netherlands.
M. Le Chevalier Kirchoff.

The Wernerian Society.

Cambridge Philosophical

Society.
Society of Natural History

of Geneva.
Horticultural Society.

Do.
Do.

Royal Geological Society

of Cornwall.
American Philosophical

Society.
M. Frederick Munter,

Bishop of Zealand.

Do.

The Commissioners for the
Northern Lighthouses.

LIST OF DONATIONS.

481

1824. PRESENTS.

Dec. 6. Acts of the Scottish Parliament, vol. xi.

Medical Essays, by Dr Hosack.
The following Works were presented by Dr
Zechinelli :

1. Alcune Riflessione Sanitario-Politiche
sulla Pelagra.

2. Narrazione dell' origine del Tiso conta-
gioso che ha regnata nella Citta di Padua.

3. Progetto per un Regolamento delle con-
dotte Mediche.

4. Memoria supra il Suspirium de Seneca.

5. Considerazione sulla Angina dell1 Petto, e
sulle Morte repentine.

6. Hiocrchc sul Indole, e sulla cura della
Febbro Gialla.

Dec. 20. Astronomical Observations of Professor Bes-

sel of Konigsberg.
1825.

Jan. 17. A Cast taken in Plaster of one of the Stones
on Corstorphine Hill, supposed to bear
traces of having been acted on by the at-
trition of stones carried along by a great
current of water.
Feb. 7. Memoirs of the Astronomical Society of

London, vol. i. part. ii.
Metnoire sur TAffinite des Corps pour la Ca-

lorique, par M. Le Chevalier Avogadro.
Dissertatio Inauguralis, by C. F. Bellingeri.
Memorie delle Reale Accademia delle Scienze

di Torino, Tom. 28.
American Journal of Science, by Professor

Silliman, Svols.

The Septenary System of generating Curves
by continued motion, with various specimens
of curves thus generated, by J. Jopling,
Esq. Architect.

DONOES.

The Commissioners of

Public Records.
Dr Hosack.

Dr Zechinelli.

Professor Bessel.

Sir James Hall, Bart.

Astronomical Society.

M. Le Chevalier Avoga-
dro.

Dr Bellingeri.

Royal Academy of Sciences
of Turin.

Professor Silliman.

J. Jopling, Esq.

482

LIST OF DONATIONS.

PRESENTS.

Transactions of the Society of Arts, vol. xlii.
Mar. 7. Discourse read at the Annual Election Meet-
ing of the Caledonian Horticultural Society,
by Dr Duncan senior,

Inaugural Discourse read before the New
York Horticultural Society, by Dr Hosack.

Description of a Breathing Pump, invented
by M. Van Houten, Amsterdam.

Elementary Treatise of Mineralogy and Geo-
logy, by Professor Cleaveland, 2 vols.

Meteorological Register kept in the Isle of
Man, by Robert Stewart, Esq. Receiver-
General.

The Snout of a Saw-Fish.

April 4. Memoirs of the Royal Academy of Sciences

of Berlin, 20 vols.
Flora Batava, No. 67.

Transactions of the Horticultural Society of
London, vol. v. part 5.

Traite General des Pese-Liqueurs, par M. N.
Benoit.

Memoires de F Academic Royale des Sciences
de Tlnstitut de France, 1819 and 1820.

American Journal of Science, vol. ix. part. i.
and ii. ; conducted by Professor Silliman.

Transactions of the Linnean Society, vol. xiv.
Dec. 5. The Edinburgh NewDispensatory, by Dr An-
drew Duncan jun.

Astronomical Observations, by Professor Bessel.

Observations on the apparent distance and po-
sition of 380, Double and Triple Stars, by
J. F. W. Herschel, Esq. and James South,
Esq.
Dec. 19. Astronomische Nachrichten, No. 64i-72.

DONORS.

The Society of Arts.
Dr Duncan sen.

Dr Hosack.
M. Van Houten.
Professor P. Cleaveland.
Robert Stewart, Esq.

The Marchioness of

Huntly.
The Royal Academy of

Sciences of Berlin.
His Majesty the King of

the Netherlands.
Horticultural Society.

M. Benoit.

The Royal Academy of

Sciences of Paris.
Professor Silliman.

Linnean Society.
Dr A. Duncan jun.

Professor Bessel.
The Authors.

Professor Shumacher.

LIST OF DONATIONS.

483

1825.

1826.

PRESENTS.

Observations made at the Heligoland Observa-
tory.

Feb. 20. Enumeratio Euphorbiarum quae in Germa-

nia et Pannonia gignuntur.
Disposition Methodique des Especes des

Mousses, par G. A. Walker Arnott.
Mar. 10. Transactions of the Horticultural Society of

London, vol. vi. p. i. and ii.
Cours de Medecine Pratique, par M. Leroux.
Description d'un Appareil Electro-Dynamique,

par M. Ampere.
PreVas de la Theorie des Phenomenes Electro-

dynamique, par M. Ampere.

April 3. Memoirs of the Astronomical Society of Lon-
don, vol. ii. part i.
Journal of the Academy of Natural Sciences

of Philadelphia, 4J vols.

Transactions of the American Philosophical

Society, vol. ii. New Series.
Transactions of the Society for the Encour.

agement of Arts, vol. xliii.
May 10. American Journal of Science, Vol. x. No. i.

by Professor Silliman.
Physicalische Beschreibung der Canarischen

Inseln, par Leopold Von Buch. Berlin,

1825.

Atlas for Do.
Memoirs of the Wernerian Society, vol. v.

part ii.
Memorie delle Rcale Accademia delle Scienze

di Torino, Tom. 29.
Memoire sur la Densite des Corps solides et

liquides comparees avec la Grosseur de

leurs Molecules, et avec leurs nombres

affinitaire, par le Chevalier Avogadro.

VOL. X. P. II.

DONORS.

Professor Shumacher.

Dr Roeper.

Mr Walker Arnott.

Horticultural Society.

M. Leroux.
M. Ampere.

M. Ampere.
Astronomical Society.

From the Academy of Na-
tural Sciences of Phila-
delphia.

American Philosophical
Society.

Society of Arts, London.

Professor Silliman.
Baron Von Buch.

Do.

Wernerian Society.

Royal Academy of
Sciences of Turin,

The Chevalier Avogadro,

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