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TRANSACTIONS

OF THE

ROYAL SOCIETY OF EDINBURGH.

TRANSACTIONS

OF THX

ROYAL SOCIETY

OF

EDINBURGH.

VOL. XL

EDINBURGH,

PUBLISHED BY CHARLES TAIT, AND BELL & BRADFUTE ;

AND T. CADELL, LONDON.

MDCCCXXXI.

PBIKTBD BY NBlLL & CO.

Old Ffchntfrket, Edinburgh.

CONTENTS

OF

VOLUME ELEVENTH.

PART FIRST.

Page

I. Description of Sternbergite, a New Mineral Species.

By W. Haidingee, Esq. F. R. S. Ed. 1

II. A Description of some Remarkable Effects of Unequal
Refraction, observed at Bridlington Quay in the sum-
mer of 1826. By the Reverend William Scoresby,
F. R. SS. Lond. & Edin., M. W. S.9 and Corresponding
Member of the Institute of France, - ■ - 8

III. On a New Combustible Gas. By Thomas Thomson,

M. D., F. R. SS. Lond. & Edin., Professor of Chemistry

in the University of Glasgow, - - - - - 15

IV. Some Experiments on Gold. By Thomas Thomson,

M. D., F. R. SS. Lond. & Edin., Professor of Chemistry
in the University of Glasgow, - - - - - 28
V. On the Construction of Polyzonal Lenses, and their Com-
bination with Plain Mirrors, for the purposes of Illu-
mination in Lighthouses. By David Brewster, LL.D.
F. R. SS. Ltad. & Edin. 33

VI CONTENTS.

Page

VI. On the Parasitic Formation qf Mineral Species, depend-
ing upon Gradual Changes which take place in the In-
terior of Minerals, while their External Form remains
the same. By William Haidingee, Esq. F. R, S. Ed. 78
VII. On the Influence of the Air in determining the Crystalli-
zation of Saline Solutions. By Thomas Graham, Esq.

A.M. 114

VIII. Mineralogical Account of the Ores of Manganese. By

William Haidingee, Esq. F. R. S. Ed. - - - 119
IX. Chemical Examination of the Oxides of Manganese. By
Edward Turner, M. D., F. R. S. Ed., Professor of
Chemistry in the University of London, Fellow of the
Royal College of Physicians of Edinburgh, - - - 143
X. An Account of the Formation of Alcoatbs, Definite Com-
pounds of Salts and Alcohol, analogous to the Hydrates.
By Thomas Graham, Esq. A. M. - - - 175

XI. An Account of the Tracks and Footmarks of Animals

found impressed on Sandstone in the Quarry of Corn-
cockle Muir in Dumfriesshire. By the Rev. Henry
Duncan, D. D. Minister of Ruthwell, - 194

XII. On the Combination of Chlorine with the Prussiate qfPo-

» ■ •

task, and the presence qf such a compound as an impu-
rity in Prussian Blue. By James F. W. Johnston,
A.M. 210

XIII. On, a Mass qf Native Iron from the Desert of Atacama

in Peru. By Thomas Allan, Esq. F. R. S. Ed. - 223

XIV. Observations on the Structure qf the Fruit in the Order

* • . •

of Cucurbitacece. By Francis Hamilton, M. D.,

F. R, S. & F. A. S. Lond. & Ed. - - - - 229

3

CONTENTS. VU

PART SECOND.

Page

XV. Some Experiments on the Milk of the Cow-Tree. By
Thomas Thomson, M. D., F. R. SS. Lond. & Edin.,
Professor of Chemistry in the University of Glasgow, - 285
XVI. Account of the Constituents qf various Minerals. By
Thomas Thomson, M. D., F. R. SS. Lond. & Bdin.,
Professor of Chemistry in the University of Glasgow, - 244

XVII. Account qf a remarkable peculiarity in the Structure of

Glauberitef which has one Axis qf Double Refraction
for Violet, and two Axes for Bed Light. By David
Brewster, LL.D., F. R. SS. Lond. & Edin. - - 273

XVIII. Experimental Inquiries concerning the Laws of Magne-

tic Forces. By William Snow Harris, Esq. - 277

XIX. On certain new Phenomena of Colour in Labrador Fel-
spar, with Observations on the nature and cause of its
Changeable Tints. By David Brewster, LL.D.,

F. R. SS. Lond. k Edin. 322

XX. On the Composition qf Blende. By Thomas Thomson,
M. D., F. R. SS. Lond. & Edin., Professor of Chemistry,
Glasgow, 332

XXI. Notice regarding a Time-Keeper in the Hall qf the Royal

Society of Edinburgh. By John Robison, Esq. Sec.

R. S. Ed. ,_------ 345

XXII. On Asbestus, Chlorite, and Talc. By Thomas Thom-

son, M. D., F. R. SS. Lond. & Edin. &c., Regius Profes-
sor of Chemistry in the University of Glasgow, - - 352
XXIII. Observations to determine the Dentition qf the Dugong ;

to which are added Observations illustrating the Ana-
tomical Structure and Natural History qf certain qf

• •*

V1U CONTENTS.

Page

the Cetaeea. By Robert Knox; M. D., F. R. S. Ed.,

and Lecturer on Anatomy, ..... 389

XXIV. Remarks explanatory, and lobular Results of a Meteoro-
logical Journal kept at Carlisle by the late Mr Wil-
liam Pitt during twenty-four years. By Thomas
Barnes, M. D., Physician to the Fever Hospital and
Public Dispensary at Carlisle, &c. .... 418

XXV. On Mudarine, the Active Principle of the Bark of the
Root of the Calotropis Mudarii, Buch. ; and the singular
influence of Temperature upon its solubility in Water.
By Andrew Duncan, M. D., F. R. S. Ed., Professor
of Materia Medica in the University of Edinburgh, - 433

XXVI. Description and Analysis of some Minerals. By Thomas
Thomson, M. D., F. R. SS. Lond. & Edin., Professor
of Chemistry in the University of Glasgow, - - 441
XXVII. Observations on the Structure of the Stomach of the Pe-
ruvian Lama ; to which are prefixed Remarks on the
Analogical Reasoning of Anatomists, in the Determi-
nation a priori of Unknown Species and Unknown Struc-
tures. By Robert Knox, M. D., F. R. S. Ed., and
Lecturer on Anatomy, 479

Proceedings xf the Extraordinary General Meetings, and
list of Members elected at Ordinary Meetings, since
May 1. 1826, 499

List of the present Ordinary Members in the order of their

election, - - 521

List of Deceased Members, and of Members Resigned, from

1826 to 1830, 533

List of Presents, continued from Vol. X.p. 483. - - 535

3

I. Description of Stern bergite, a New Mineral Species. By
W. Haidinger, Esq, F. R. S. E.

(Read December 4. 1826.)

X he mines of Joachimsthal in Bohemia, have long been cele-
brated for their riches. They were successfully worked at an
early period, and though their produce has been exceedingly
fluctuating, yet the mining district, in which they occur, con-
tinues one of the most important of that country. They seem to
have been particularly lucrative and important while they be-
longed to the house of the Counts Schlick, and when, in the
beginning of the sixteenth century, a larger kind of silver coin
was introduced into Germany, it took the name, of Joaehimsthaler,
from the place of its coinage, a name* which was afterwards
changed into thaler, talaro, and dollar *

These mines are not less remarkable for the variety of the
species, and for the beauty of the specimens which they have
produced. The ancient collections of minerals at Vienna, the
Imperial cabinet, that of Von der Null, that of Von Morgen-
besser, and others, contain magnificent suites of sulphuret of sil-
ver, of red silver, &c. chiefly crystallised. The finest specimens,
however, of the red silver, and perhaps the finest that ever were

* These Thalers bear the head and the name of the then reigning Count Schlick,
and the earliest of them the date of 1517. There are some coins, however, of the
same value, with the head of the Emperor Maximilian I., as far back as 1493.
They used to be called KlUpplinge, an antiquated German word, which means some-
thing ponderous, giving a sound when struck against a hard body.

VOL. XI. PART I. A

2 Description of Sternbergite,

known in the species, were dug up so late as 1817 and 1822.
The National Museum at Prague possesses one of them, consist-
ing of a group of crystals several inches long, without having
any rock attached to it, and weighing about twelve marks, or up-
wards of six pounds Avoirdupois, the value of the silver of which
is more than L. 16 Sterling.

It was in the same collection that I first observed a variety
of the species of Sternbergite, which it is the object of the pre-
sent paper to describe- Professor Zippe, the keeper of the mu-
seum of natural history, directed my attention towards it, as be-
ing something he could not bring under any of the species al-
ready known ; and as it appeared an interesting mineral, I re-
quested his permission to take it with me to Edinburgh, in or-
der to examine its forms, and other properties, a request which
was readily granted. Gubernialrath Neumann of Prague, late
Professor of Chemistry there, was not less liberal in allowing
me to take with me the only specimen of it contained in his
collection, where it had been designated by Mr Zippe as a pinch-
beck-broum problematical fossil, crystallised in six-sided tables. The
crystals in this specimen are very distinct ; they are aggregated
along with crystals of red silver in drusy cavities in quartz, which
protected their edges from being rounded off by rubbing, like
the specimen from the collection of the National Museum.
Here, too, the Sternbergite is associated with red silver, and with
brittle silver, making the whole highly valuable as an ore of sil-
ver. It is likely that most of the specimens have long ago been
melted down ; perhaps some of them may yet be discovered in
the Imperial cabinet in Vienna, which contains a great number
of specimens from Joachimsthal. Professor Zippe informs me,
that he has found another specimen of the substance in the Mu-
seum at Prague, once I had the pleasure of inspecting it in his
company.

STE K."? B EEIJJTJ;

^^^^

a new Mineral Species. 3

The following account contains the characters ascertained in
the two specimens.

The forms of Sternbergite belong to the prismatic system.
Its fundamental form (Plate I. Fig 8.) is a scalene four-sided
pyramid, having edges of 128° 49', 84° 28', and 1 18° C The ra-
tio of its axis and diagonals a : b : c, is — 1 : ^1.422 : v/0.484.

The specimens contained the following secondary forms,
P— oo (a); P(/); P+ 1 ig) = 122° 17', 68° 22', 146° 34';
(P?)3 (d) = 92° 28', 107° 17', 131° 17' ; P? +1(6) = 61° 35' ;
| p; + 3(c) = 13° 36'; P? + oo (•) ; -*? 7— 3(h) = 153° 2'.

The combinations observed are,
1. P_ oo.(P?)3. P + l.£P? + 8.Pr°+ oo. Fig. 1.

S. P—oo.'IP^— 3.P.(Pr)3.P? + l. P? + oo. Fig.2r

There were traces of planes taking off the edges between d and
d\ which I could measure. The measurement gave for the base
of the pyramid d9 by approximation 81° 12'.

S.P— oo.±Pr — 3-Pr-f l.(Pr)3. P + 1 • i Pr + 3. Fig. 3.

The edges between b and two adjacent faces of d are pa-
rallel.

4. p_ oo.P.Pr + l.(P?)3.P+l. |Pr + 3. Fig. 4.

The crystals are very much compressed between a and a. They
assume the aspect of Fig. 5., or of a six-sided table with two
angles of 119£°, and four of 120i°. The faces * are usually
smaller than those marked m, which in fact are nothing but a
succession of planes, having the inclination of/ and g.

Cleavage is highly perfect, and easily obtained, parallel to the
face a ; in other directions the laminae may be torn asunder, like

a 2

4 Description of Sternberg/ te,

thin sheet-lead, but they do not present any traces of clea-
vage.

The broad faces a are delicately streaked parallel to the
edges of combustion with A, or in the direction of the long die-
gonals of the rhombic plates. They possess high degrees of
lustre. The lustre upon the other faces is not so bright, and they
are streaked parallel to their intersections with a ; the faces d
less than the rest. A difference of tarnish is likewise often ob-
servable. The faces a retain their original colour, while all
the rest assume a superficial violet-blue tint.

The lustre is metallic ; colour dark pinchbeck-brown, nearly
resembling the colour of magnetic pyrites, only it inclines more
to black.

It affords a black streak. It is very sectile. The lamina?
are perfectly flexible, and after having been bent, they may be
smoothed down again with the nail, like tin-foil or platina leaf.

The hardness is = 1.0 ... 1.5, little superior to talc. On ac-
count of this low degree of hardness, the mineral leaves traces
on paper like black lead, which may be removed by a piece
of caoutchouc. The specific gravity of several fragments, amount-
ing to 598 milligrammes, I found = 4.215.

Two individuals often join in a regular composition, and pro-
duce a twin-crystal ; the axis of revolution being perpendicular,
the face of composition parallel, to a face of P + oo% Fig. 6.

Fig. 7. shews a projection of such a twin upon a plane parallel
to the face a. The appearance of the twins is, however, not al-
ways very regular. Sometimes they are joined by their sides, in
a manner somewhat analogous to the twins of felspar found near
Carlsbad in Bohemia.

Generally several crystals are joined in an irregular manner,
and implanted together, being fixed to their support with one of
their sides, so as to produce rose-like aggregations, and globules

a new Mineral Species.

with a drusy surface. Massive varieties usually present the ap-
pearance of certain kinds of mica.

The crystals subjected to measurement were taken from Mr
Neumann's specimen. Owing to the striae upon the crystalline
faces, parallel to the intersections of these faces with the face a,
and to the great flexibility of the laminae, the angles could not
be ascertained with the utmost degree of exactness. The di-
mensions of the forms were calculated from the admeasurement
of the angle at the base of P = 118°, and of the angle abc in
Fig. 7., shewing the inclination of two faces parallel to its short
diagonal in a twin-crystal, the latter of which was found to be
equal to 119?°. The remaining measurements which were taken,
agreed with the angles obtained by calculation, as well as could
be anticipated from the nature of the substance. There is no
mineral, however, which could be confounded with it among
those of a similar aspect, if we except, perhaps, the flexible sul-
phuret of silver, first described by Count Bournon *, a sub-,
stance which I never had an opportunity of examining. The
angles given by Mr Brooke f being 125° instead of 119£°, and
the character of symmetry itself, since he considers a rhomboidal
prism, and not a rhombic one, as the type of the forms of
the species, sufficiently establish a crystallographic difference
between the two substances. The difference among them is
strengthened even by the difference in the shade of colour,
said to be black in the flexible sulphuret of silver, where-
as Stembergite is decidedly brown, although the characters of
flexibility and hardness pretty nearly agree. The remaining
properties, particularly the specific gravity, which would be of
great importance, have not been ascertained in the flexible sul-
phuret of silver.

* Catalogue, p. 209. t PhMpf Mineralogy, p. S8&

6 Description of Sternbergite,

The flexible sulphuret of silver was found by Dr Wollaston
to contain silver, sulphur, and some traces of iron. In this re-
$pect Sternbergite is very nearly allied to it, only the iron forms
a much more considerable part of the composition, as appears from
the experiments with the blowpipe.

In the glass-tube it gives off a strong odour of sulphurous
acid, loses its lustre, and becomes dark-grey and friable. Alone
on charcoal, it burns with a blue flame, and sulphurous odour,
and melts into a globule, generally hollow, with a crystalline sur-
face, and covered with metallic silver. The globule acts strong-
ly on the magnetic needle, and before the blowpipe it has all the
properties of sulphuret of iron. It communicates to fluxes the
ordinary colours produced by iron, red while hot, and yellow on
cooling, in the oxidating flame, greenish in the reducing flame.
Borax very readily takes away the iron, and leaves a button of
metallic silver.

The characters observable in Sternbergite, and its great re-
semblance to the black tellurium, to the flexible sulphuret of sil-
ver, to the rhombohedral molybdena-glance, unequivocally as-
sign it a place in the order Glance of the system of Professor
Mohs, Whether it should form a genus of its own, or be com-
prised within one genus, with one or several of the above-men-
tioned species, remains doubtful, as long as those species them-
selves are so imperfectly described. No systematic name, there-
fore, can at present be applied to it.

In proposing a single name for this mineral, I cannot find a
more appropriate one than that of Sternbergite, in honour of
Count Caspar Sternberg ; and I know, that, in doing this, I
concur with the feelings of my friends Neumann and Zippe, who
so liberally furnished me with the specimens examined. I could
not forego the pleasure of thus paying a just tribute to a man
in his exalted station in life, equally high in scientific attain-

a new Mineral Species. 7

ments and in patriotic zeal, who has been most forward in esta-
blishing the National Museum at Prague, an establishment emi-
nently calculated to be useful to travellers, who thus find
means to examine at once the productions of the country ; but
still more important for the inhabitants, to whom it affords an
opportunity of acquiring information in various brandies of
knowledge, and among whom, in particular, it diffuses a taste for
the natural sciences.

( 8 )

II. A Description of some Remarkable Ejects of Unequal Re-
fraction, observed at Bridlington Quay, in the Summer of
1826. By the Reverend W. Scoresby, F. R. S. S. Lond.
" & Edin. M. W; S., and Corresponding Member of the In-
stitute of France.

(Read January 22. 1827J

Jn the session of 1820-21, 1 had the honour of communicating
to the Royal Society, a description of some remarkable atmo-
spheric refractions observed in the Greenland Sea. Sirice that
period, additional opportunities for observation, under circum-
stances peculiarly favourable, afforded a great number of other
examples of a similar kind, along with some still more sin-
gular. Among these, the most extraordinary was the invert-
ed image of a ship, which appeared in the lower part of the at-
mosphere, so distinctly and beautifully defined, that I could
venture to pronounce it to be the representation of my father's
ship, as, indeed, it proved to be, though we were then distant from
each other about 28 miles, and some leagues beyond the limit of
direct vision. But an account of the principal* of these extraor-
dinary appearances is already before the puplic, and I merely al-
lude to them, in consequence of their similarity to the refrac-
tions I have now to describe, that occurred upon our own

m

coasts.

These phenomena occurred during the last summer about
Bridlington Bay, and were seen from my residence at Bridling-
ton Quay.

I shall first describe the appearance of the shipping in the
Bay, as represented in Plate II. Fig. 5.

* Voyage to Greenland in the Summer of 1822.

i I

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' Mi '

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fa

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Sl-.ii'.i

■5.

On the Effects of Unequal Refraction at Bridlington Quay. 9

In the afternoon of the 12th of June, about five o'clock, after
a clear hot day, the phenomena were first observed. All the
shipping, at a sufficient distance, began to loom, and were va-
riously distorted, and many vessels, when examined by the tele-
scope, exhibited inverted images immediately above them. A
portion of the extreme verge of the sea seemed to separate, as
by a transparent fog-bank, and, between the real horizon and
L r,.fj,«l horiJon, all the distortions and inverted images
occurred. Some of the ships were of their natural proportions,
with an inverted facsimile above. Others, at distances, or in si-
tuations such, that the top of the masts reached more than one-
half the height of the refracting interval, were abridged of their
upper sails. One brig, nearer than the rest, only exhibited its
hull and courses, with an inverted resemblance of the same over
the top ; and what gave it a still more curious appearance, was,
a narrow clear space between the vessel and the image, as if there
were in that place (in the line of the top-sails of the brig) a per-
fect void. In one or two cases, besides the inverted image, there
was also an imperfect erect image, placed upon the upper line of
the horizon. Most of the vessels figured, though they appear
situated upon the true horizon, were, in reality, greatly more dis-
tant, and many of them altogether beyond the limit of ordinary
vision. Hence, whilst the eye was fixed upon them, owing to
the perpetual changes of the atmosphere, one or other of them
would frequently disappear, and remain for some time invisible,
and then suddenly start into sight as before. Objects within
the horizon (about six miles distant) were scarcely, if at all, af-
fected by the refraction. The upper or refracted horizon was of-
ten irregular in its outline, and sometimes broken. It was general-
ly dark, and well defined ; but the interval between it and the
real horizon was frequently more faint in its shade, as if by atte-
nuation. Sometimes there was a treble horizon exhibiting pa-
rallel streaks. The low coast of Holderness (forming the south-

VOL. XI. PART I. B

10 The Rev. W, Scores* y an some remarkable

ern part of Bridlington Bay) was slightly influenced by the same
refraction. The air on this occasion was clear and calm, — occa-
sionally there was a gentle sea-breeze.

Twelve days after this (June 24th), the phenomena were re-
peated with several new peculiarities, especially in regard to the
land, as hereafter noticed. The interval between the true and
refracted horizons (measuring between one and two minutes of a
degree) was, as before, of a bluish-grey colour, and resembled a
thin mist. But, besides the usual appearances of the ships, there
were many erect images perched, as it were, upon the upper line
of the horizon, and belonging to vessels that were evidently far
out of sight ! This, occurred at noon, when the temperature was
80° in the shade. In the afternoon, the temperature becoming
more equable, most of the phenomena disappeared ; but in the
evening, with the change of temperature, they were renewed in
their principal varieties. On this day the sky was again cloud-
less, with a slight breeze from the eastward, though occasionally
it was quite calm.

The. following day there were very beautiful repetitions of
the phenomena The upper horizon was occasionally double and
broken. A second erect image, of some of the ships, appeared
between the two upper lines.

Again, there was a renewal of these interesting appearances
on the 26th of June. The day was, as before, clear and hot ;
but with a smart sea-breeze. The horizon began to separate
about 10 a. m., and between 11 and 12, every object at sea, be-
yond the distance of six miles, became influenced by the une-
qual refraction. There were, on this occasion, several instances
of a single inverted image of a ship, clearly defined, though the
ship to which it referred was altogether out of sight !

Two or three days after this I left the coast, and had no
other opportunity of looking out for these phenomena until the
middle of August ; and after that time I could never perceive
any recurrence of them.

EjffecU of Unequal Effraction at Bridlington Quay. 1 1

All the representations of ships in Plate II. (Fig 5.), it should
be observed, are telescopic, being taken from a view obtained with
an ordinary spy-glass. With the naked eye, the looming of the
vessels could be readily perceived ; but it required a magnifying
power to resolve the apparently confused and enlarged outline
into the ship and its images. The images were, in most respects,
very similar to what I have formerly observed in the Arctic Re-
gions, though scarcely so distinct and well defined. In high la-
titudes, indeed, I have seen them as sharp and definite as if cut
with a graver.

On June the 24th, a day already referred to as one distin-
guished by unequal refractions, the Holdetness Coast was most
singularly affected by the state of the atmosphere. The ordina-
ry appearance of this coast, as seen from the window of my
sitting-room, which commands a view of all the southern part of
Bridlington Bay, is that represented in Plate II. Fig. 4. But in
the forenoon of this day, the sun having intense power, this low
and uninteresting part of the promontory, terminating at the
Spurn, assumed the appearance of Fig. 2. to the naked eye. Slight
hummocks and knolls, on the ridge of the land, weire raised into
parallel vertical pillars, resembling immense detached columns of
basalt ; and the whole range, for a considerable extent, seemed to
be surmounted by a horizontal and almost continuous platform !
This platform or causeway, which it resembled, seemed in many
places entirely unsupported ; the clear view of the sky being ob-
tained beneath it. But this apparent platform was in reality the
refracted image of the stratum of land beneath, forming conti-
nuous columns, where the land was highest and the image joined
the protuberances ; but leaving vacant interstices, where the land
was low and the resemblances more remote.

Having made a sketch (Fig. 2.) of the appearance of the
coast from my window, which is at the height of about 40 feet
above the level of the sea at low-water, (the state of the tide at

b2

12 The Rev. W. Scoresby on some remarkable

the time), it occurred to me that there might possibly be a dif-
ference of appearance at another level. And, on ascending to
the attic story (about 60 feet above the sea), I was surprised to
find the phenomena altogether changed (see Fig. 1.), and the
natural form of the land almost restored. Having made a sketch
of this appearance, I returned to the sitting-room, and found the
refracted state before observed from thence remaining unchanged.

I next descended to the cellar-flat (about twenty feet above
the sea), where, on a level platform, by the side of the house,
there was a clear view of the same coast. Here, again, I expe-
rienced another surprise, in finding the appearance almost per-
fectly what it ought to be at that level (see Fig. 3.), scarcely
any remains of the refractive influence being observable; yet at the
middle position, in the sitting-room, the phenomena continued
unaltered ! No material change, indeed, occurred in the general
character of any of the views, whilst I was making the three
first sketches given herewith. The last view (Fig. 4.) was taken
on a subsequent day, and all the four were arranged in the same
vertical plane, and adjusted to the same proportions, by marking
on the sketches the position of a regular series of posts on the
side of a wooden pier, which fortunately lay extended beneath
the whole line of coast. This renders the comparison between
the effects attributable to the refraction, and the natural state of
the view, quite certain.

On this occasion, objects within four miles of the observer,
were slightly influenced by the refraction, though the greatest
effects occurred, in respect to objects six to ten miles distant.
The phenomena continued to preserve their character, as seen
from the three different levels, for above an hour, and then the
appearance of Fig. 2. began to descend ; so that eventually, as
the heat of the day increased, or rather became more general and
uniform, the view from the sitting-room became nearly that of
Fig. 1., whilst Fig. 2. was seen from a level ten or fifteen feet

Effects of Unequal Refraction at Bridlington Quay. IS

lower. Shortly after mid-day, it appeared so striking from the
level of the street, (ten feet below the sitting-room), that it be-
gan to attract the notice of all the inhabitants in the neighbour-
hood.

From 2 until 5 p. m., the phenomena were more indistinct, and
less interesting ; but as the heat began to abate (towards 6 p. m.),
the appearances observed in the morning were in a great mea-
sure repeated.

On several other occasions, the coast of Holderness was seen
through unequally refractive media ; but there was no appear-
ance so interesting as the one above described.

No other cause requires to be sought for, in explanation of
the phenomena, than that of different parallel strata of air, of un-
equal density, so ably demonstrated and illustrated by. Dr Wol-
l aston (Phil. Trans, for 1810) ; and so strikingly exemplified
by Dr Brewster, in bis experiments resembling the very effect
in nature, with hot and cold strata of water or glass.

Nor is the striking peculiarity observed on the Holderness
Coast, of the phenomena being confined to a particular level in
the position of the observer, of difficult explanation. In this
case, it is perhaps only necessary to suppose, (I speak doubtful-
ly, however), that the distant coast, observed from the upper al-
titude, was seen altogether through an upper stratum of air, of
pretty uniform density ; and also observed from the lower sta-
tion, that it was either seen chiefly through a lower stratum, or
through different strata, amid which the rays of light passed from
the distant coast converging, but not having arrived at a focus ;
but that from the middle altitude, the rays from the land passed
so obliquely out of one medium into the other, that a part was
refracted back again into the former medium, so as to double the
object, by presenting an inverted image.

The occasion of the frequency of these phenomena, during
the last summer, and of their extraordinary character, may, per-

14 On the Effects of Unequal Refraction at Bridlington Quay.

haps, be accounted for, from a remarkable and sudden change in
the temperature of the air. The cool weather of the preceding
spring had continued down till the beginning of June. The sea,
even near the coast, was, in consequence, at its winter tempera-
ture, whilst the air became quickly heated, by the fervent glare
of an unclouded sun. When, therefore, the air near the surface
of the earth became greatly warmed, the stratum immediately
in contact with the sea was chilled by its coldness, whereby me-
dia of unequal density and refracting power were produced.
And through these unequal media, the rays of light both from
the shipping and the Uolderness Coast, had to pass to the eye of
Hie observer, — an uninterrupted surface of water, in all cases, ly-
ing between the objects and myself. The passing of the rays of
light, at an extremely small angle, through these different stra-
ta of different refracting powers, would sufficiently account, on
the principles already referred to, for most of the phenomena
observed.

Beldlington Quay, )
December 1. 1826. J

( 15 )

III. On a New Combustible Gas. By Thomas Thomson, M. D.
F JR. S. Lond. & Edin. Professor of Chemistry in the
University of Glasgow.

(Read April 16. 1887;;

It has been generally known for several years, that, when the
acetic acid formed by the distillation of wood is rectified, there
is obtained a transparent spirituous liquor, analogous in many re* -/

spects to alcohol, though very different in others. This liquid
has received the name of pyroxylic spirit. It is manufactured
by Messrs Turnbull and Ramsay of Glasgow. I have been in
the habit for several years of employing it for combustion in
lamps instead of alcohol It is a good deal cheaper, and raises
just as good a heat as alcohol ; for I can make the small plati-
num crucible, which I use for drying the products of analysis,
red-hot by means of a pyroxylic spirit lamp inafew minutes.

Pyroxylic spirit is as limpid and colourless as alcohol. Its
specific gravity, when well rectified, is 0812. It has an agree-
able smell, not, however, quite free from that of naphtha. Its
taste is very disagreeable, owing, I believe, to a small portion of
naphtha, or empyreumatic oil, which it hold* m solution, and
from which we cannot free it by any known process. A set of
experiments on pyroxylic spirit, by Messrs Macaibe and Mar-
cet was published, in the Bibiiotheque Universelle for October
1823. These gentlemen have described several of its properties,
and. subjected it to an analysis, from which it appears that, like
alcohol* it is composed of hydrogen, carbon and oxygen* though
the atomic proportions are different.

My object, in this short paper, is to give an account of a new
gaseous substance which I accidentally obtained about a year

16 Dr Thomas Thomson on a New Combustible Gas.

ago, when I attempted to substitute pyroxylic spirit for alcohol
in some processes which I had occasion to perform during a set
of experiments on protoxide of chromium, in which I was at that
time engaged. The gas in question may be easily procured by
the following process.

Put into a flask a mixture of 1^ ounce of muriatic acid, half
an ounce of the nitric acid of commerce, and half an ounce of py-
roxylic spirit, all by measure. By means of a perforated cork in-
sert a bent glass-tube into the mouth of the flask. The cork
must fit so tight, that nothing can escape from the flask ex-
cept through the tube. Heat the mixture over a spirit lamp
till it begin to effervesce, and till the colour of the liquid changes
to red. The flask must then be withdrawn from the lamp, and
the extremity of the bent tube plunged into a mercurial trough.
The gas issues in torrents for five or six minutes, and may be
collected in any quantity, in glass jars, previously filled with
mercury, and inverted on the trough. From the quantity of
materials stated above, I think at least 200 cubic inches of the
gas are extricated.

The gas, as it comes over, acts with considerable energy on
the mercury ; both calomel and corrosive sublimate being form-
ed in abundance. But this is owing to the presence of some
chlorine, with which the gas, as it issues from the flask, is mixed.
For when we transfer the gas into a clean jar, it may be left for
any length of time on the trough, without acting in the least on
the mercury, or changing its volume.

The gas thus obtained possesses the following characters :

1 . It is transparent and colourless, and possesses the media*
nical properties of common air.

2. Its smell is exceedingly pungent and disagreeable ; but so
peculiar, that I can compare it to nothing eke. It acts with

Dr Thomas Thomson an a New Combustible Gas. 17

considerable energy upon the eyes and nose, occasioning a flow
of tears, and exciting considerable pain in the eyes.

3. It is combustible, and burns with a lively bluish-white
flame*

4. Water absorbs it pretty rapidly : one volume of water, in
my trials, absorbed five volumes of the gas. The water acquires
a pungent taste, and the peculiar smell of the gas. But it does
not alter the colour of litmus or cudbear paper.

5. One volume of oil of turpentine absorbs thirty volumes of
the gas ; the oil assumes a light-green colour, and resembles caje-
put ; but still retains its peculiar odour.

6. The gas is neither absorbed by acids nor alkalies. Hence
it possesses neither acid nor alkaline properties.

7. When common air or oxygen. gas is mixed with this gas,
the usual red fumes of nitrous acid appear, and the volume of
the mixture is diminished. It is not, therefore, a homogeneous
substance, but contains mixed with it a considerable proportion
of nitrous gas. I endeavoured to determine the proportion of
nitrous gas in 100 volumes, by mixing it with determinate quan-
tities of oxygen gas over mercury. The diminution of vo-
lume was noted, and two-thirds of that diminution reckoned
as nitrous gas. This method of proceeding is not susceptible of
perfect accuracy, because the nitrous acid formed acts upon the
mercury. But as the action is not rapid, and the time of each
experiment short, I do not think that the error thence arising-
could amount to so much as 5 per cent. Five experiments made
in this way did not absolutely agree with each other. But the
discordancy did not exceed 4 per cent. A mean of the whole
gave the amount of nitrous gas in 100 volumes of the new gas,
68 volumes, or rather more than three-fifths of the whole.

I tried to determine the proportion of nitrous gas over wa-
ter, by causing the water to absorb the new inflammable gas, and
then agitating the residual gas in a solution of protosulphate of
iron. But this method yields no good results. The new in-

VOL. XI. part i. c

16 Dr Tbqmas Thomson on a New Combustible Gas.

flammable gas has the property of greatly increasing the absor-
bability of the nitrous gas in water ; so much so, that a gas,
which, when analysed over mercury, was fforand to contain 63 per
cent, of nitrous gas, if it was agitated in water, as long as that
liquid continued to absorb it, left no more than 7*5 per cent, of
nitrous gas. I abide, therefore, by the analysis over mercury,
which, from numerous comparative experiments, cannot deviate
very far from the truth.

100 volumes of the gas, after being washed in water, and in
a solution of protosulphate of iron, left 8 per cent, of azotic gas.

Thus it appears, that the gas extricated from a mixture of
aqua regia and pyroxylic spirit, is a mixture of

New inflammable gas, 29

Nitrous gas, 63

Azotic gas, 8

100

Whether these proportions be constant, I cannot venture to de-
termine. But I analysed gas obtained in ten different processes,
without finding any deviation in the proportions of its constitu-
ents. I found the specific gravity the same in gas from two dif-
ferent processes.

8. The specific gravity of the gas was taken in a flask which
had been twice exhausted, and filled each time with hydrogen
gas. It was 1.945, the specific gravity of common air being reck-
oned unity.

It is easy to calculate the specific gravity of the pure inflam-
mable gas in this mixture.

Let A = volume of nitrous and aeotic gas ;

u r: specific gravity of a mixture of 63 volumes nitrons

and 8 azotic gas ;
B = volume of inflammable gas ;
w = specific gravity of inflammable gas ;
c = specific gravity of the mixed gas.

Dr Thomas Thomson on a New CombmtMe Gm. 19
We have, from a well-known hydrostatics! property of gases,

(A + B)c-A«

*- s

In the present case,

A = 71 ; a = 1.08884 ;
B = 29 ; c = 1945.
Consequently, m = (100)1-945-71x108884 = 4.1757;

4*1757 considerably exceeds the specific gravity of chloro-carbo-
nic acid, or the phosgene gas of Dr Davy, which is 8*47*2.

9. I found by repeated trials, that the new inflammable gas,
(the nitrous gas being removed by means of oxygen gas and pot-
ash), requires for complete combustion twice its volume of oxy-
gen gas. The mean of five experiments gave 12 volumes in-
flammable gas, and 24.38 volumes of oxygen gas consumed, when
an electric spark was passed through the mixture over mercury.
The only products after the combustion were calomel and carbo-
nic acid gas.

When the detonation of the mixture of the inflammable
gas and oxygen was made over a little water, holding nitrate of
silver in solution, the liquid became milky, owing to the forma-
tion of chloride of silver. It is obvious from these facts, that two
of the constituents of the gas are chlorine and carbon.

A mixture of 12 volumes of gas, and 24*38 volumes of oxy-
gen, left, after detonation over mercury, 15#43 volumes of car-
bonic acid gas. This is a mean of four experiments, which did
not agree very well with each other ; two of them giving only
13*89 volumes of carbonic acid, and the other two 15.98 volumes.
I made twelve additional experiments, with a view of getting re-
sults more to be depended on. But the mean of the whole
scarcely differed from 15.43, and the same discordancy appeared
in the new as in the old experiments.

c2

L

20 Dr Thomas Thomson on a New Combustible Gas.

The result of the analysis seems to be, that IS volumes of
the gas consume 24 volumes of oxygen, and form 16 volumes of
carbonic acid gas.

The 16 volumes of carbon would require 16 volumes of oxy-
gen to convert them into carbonic acid gas. The 8 remaining
volumes of oxygen, must have united to hydrogen ; and they
would require 16 volumes of hydrogen gas to convert them into
water.

Thus it appears, that the gas contains equal volumes of car-
bon vapour and hydrogen gas ; 1 volume of the gas requires for
complete combustion 2 volumes of oxygen, and it forms 1£ vo-
lume of carbonic acid gas. The remaining 0*66 volume of oxy-
gen must have combined with 1£ volume of hydrogen, and form-
ed water. Hence a volume of the gas contains

1 i volume of carbon vapour, 7 eaadamd into one volume
1£ volume of hydrogen gas, J

*
Specific gravity of 1^ volume of carbon vapour, 0*5555

1£ volume of hydrogen gas, 0*0926

Total, - - 0-6482

This subtracted from 4*1757, (the specific gravity of the gas),
leaves 8*5275 ; which must be the weight of chlorine gas con-
tained in a volume of the combustible gas. Now the specific

gravity of 1£ volume of chlorine gas is 8*8338.
The gas seems to be a compound of

1£ volume carbon vapour, -\ condensed into one volume.
1£ volume hydrogen gas, L These added together make
1£ volume chlorine gas, j a specific gravity of 8*9814.

This is lighter than the gas was found by experiment by
about ^st part But there is some uncertainty about the actual

Dr Thomas Thomson on a New Combustible Gas. 21

-:<i.~.mii

gravity, as it depends upon the proportion of nitrous gas,
a proportion not determined with perfect accuracy.

I am disposed to consider it as not unlikely, that the propor-
tion of nitrous gas may have been rather underrated. On that
supposition, I think it very probable, that the true constituents
of a volume of the gas are,

1 volume carbon vapour, 0*4166
1 volume hydrogen gas, 0*0694
1£ volume chlorine gas, 8*7500

4*2S6i

This would make the specific gravity of the gas 4.2361 ; which
only exceeds the specific gravity found by about T',th part. A
difference certainly not greater than might be looked for in de-
termining the quantity of nitrous gas mixed with it.
The gas, then, is a compound of

1 atom hydrogen, 0*125
1 atom carbon, 0*750

1£ atom chlorine, 6*750

7-625
and its atomic weight is 7.625.

It contains only half the carbon and hydrogen, but 1£ times
the chlorine which exists in a volume of chloro-carbonic acid.

As it will be requisite to distinguish this new inflammable
gas by a name, perhaps the term sesqui-chloride of car bo-hydrogen,
may be employed as giving an accurate idea of its composition.

The discovery of this gas was gratifying to me, for a reason
which it may be worth while to explain. In the " First Prin-
" ciples of Chemistry" vol. i. p. 249, I pointed out a remarkable
property of the compound of one atom carbon and one atom hydro-
gen. This compound we may distinguish by the name carbo-hydro-
gen, since the appropriate term carburetted hydrogen has been un-

82 D* Thomas Thomson on a New Combustible Gas.

luckily applied to a different cottbmatioB. Carfao>»hydrogen
has the property of forming a variety of gratis and vapours, dif-
fering from each other in the number of integrant particles of
carbo-hy drogen, which a angle volume of the gas or vapour con-
tains. The gas described in this paper (abstracting the chk*-
rine), contains only one integrant particle of carbo-hydrogen in
a volume ; olefiant gas contains two integrant particles. One of
the oleaginous liquids obtained by condensing oil-gas, which has
been examined by Mr Faraday in an insulated state, but which
had been previously detected in oil gas, in the state of vapour,
by Mr Dalton, contains three integrant particles. Sulphuric
ether vapour (abstracting the water) contains four integrant par-
ticles ; while the vapour of naphtha contains six integrant par-
ticles. The following table exhibits the atomic weights, and spe-
cific gravities^ of these gases and vapours.

Atomic Specific

Weight. Grtvity.

Simple carbo-hydr ogen gas, - 0-875 0*486 1

Olefiant gas, or deuto-carbo-hydrogen, 1 .75 0*9722

Oil-gas vapour, or trito-carbo-hydrogen, 2*625 1 -4588

Ether vapour, or tetarto-carbo-hydrogen, 8*5 1 9444

Naphtha vapour of hexa-carbo-hydrogen, 5-25 2*9 1 66

The existence of the simple carbo-hydrogen was merely hy-
pothetic, till the discovery of sesqui-carbo-hydrogen has given us
an example of its actual existence. Thus the only doubtful part
of this reasoning has been shewn to be actually correct. This
circumstance gives an importance to the discovery of sesqui-car-
bo-hydrogen, to which it would not otherwise be entitled.

s

( *» )

IV. Some Experiments on Gold. By Thomas Thomson, M. D.
F. R. S. Lond. & Edin. Professor of Chemistry in the Uni-
versity of Glasgow.

(Read April 16. 1887.J

In the first volume of ray M Attempt to establish the First Prvu
" eiples <if Chemistry by Experiment" p. 442, I give the analy-
sis of the sodium chloride of gold, and find the constituents to

be

2 atoms chlorine, - 9

1 atom gold, - - 25

1 atom common salt, - 75

8 atoms water, - 9

50-5

But I state at the same time, my uncertainty whether the
gold in the salt was in the state of a chloride or muriate. This
uncertainty raising a doubt, whether the peroxide of gold con-
tained two or three atoms of oxygen, I thought it highly neces-
sary to clear it up. In this paper, I shall state the experiments
Which 1 have made with that object in view.

The whole weight of evidence is in favour of peroxide of
gold containing 8 atoms of oxygen. We have the analyses of
Berzelius repeated at two different times, and at a considerable
interval, and, in both, that most skilful and accurate chemist
found gold in the peroxide united with three atoms of oxygen.
This analysis has been confirmed by M. Javal, who informs us,
that he obtained the very same results as Berzelius had done.

24 Dr Thomas Thomson on some Experiments on Gold.

The authority of these philosophers is deservedly of the greatest
weight, and has, I believe, induced chemists, so far as I have had
an opportunity of judging of their opinions, to consider the per-
oxide of gold as a ter-oxide.

1. In order to determine the quantity of oxygen combined
with gold, when in the state of peroxide, I dissolved a known
quantity of pure gold in nitro-muriatic acid, and rendered the
solution as neutral as I could, by evaporating it to dryness in a
very moderate heat, and then dissolving the crystallised salt in
distilled water.

It has been long known, that proto-sulphate of iron has the
property of precipitating gold from its solution in muriatic acid,
in the metallic state, and that the salt is at the same time con-
verted into persulphate of iron, obviously by uniting with the
oxygen previously in combination with the gold.

I have shewn in my " Attempt" vol. i. p. 343, that an atom
of iron weighs 3*5, and that the oxides of this metal are compo-
sed as follows :

Protoxide of 1 atom iron, + 1 atom oxygen,
Peroxide of 1 + H

If the atomic weight of gold be 25, as I have shewn it to be,
and if peroxide of gold contain 3 atoms of oxygen, then, in or-
der to reduce 1 atom of peroxide of gold to the metallic state, it
is obvious that we must employ 6 atoms of protoxide of iron ; so
that to reduce 28 grains of peroxide of gold, we must employ
27 grains of protoxide of iron. To see how far this supposition
was well-founded, 50 grains of gold were dissolved in nitro-mu-
riatic acid ; 208'5 grains of newly crystallised protosulphate of
iron were dissolved in warm distilled water, and the two solu-
tions were mixed.

Dr Thomas Thomson on some Experiments on Gold. 25

To understand the reason for taking 208*5 grains of proto-
sulphate of iron, the reader has only to call to mind, that this
salt is composed of

1 atom sulphuric acid, 5
1 atom protoxide of iron, 4*5
7 atoms water, - 7'875

1 7-375

so that 17'375 grains of this salt contain the equivalent of 1
atom of protoxide of iron. As 2 atoms of peroxide of gold were
to be reduced, it was necessary to employ 12 atoms of protoxide
of iron. Now, 17375 X 12 = 2085. So that 208-5 grains of
protosulphate of iron, contain the equivalent of 12 atoms of pro-
toxide of iron.

The gold, precipitated by 208*5 grains of protosulphate of
iron, was collected on a filter, washed and dried, and exposed to
a red heat. It weighed 48*04 grains, or 1 *96 grain less than the
quantity originally dissolved. An additional dose of protosul-
phate of iron being poured into the original gold solution, a far-
ther precipitate of gold was obtained, which weighed 1*67 grains.
Thus all the gold was recovered, with the exception of 0'29
grain, which I believe was lost, in consequence of the improper
method taken to wash the gold. This was done by decantation.
Now the films of gold were so extremely fine, that they were
very apt to swim on the surface of the liquid. And though I
was at great pains to avoid throwing any of the gold away, a few
of these flocks might have escaped my observation. And as the
decantation was repeated a good many times, I think a loss of
0*29 grain might have been sustained.

The gold precipitated by 208a5 grains of protosulphate of
iron was almost 2 grains less than it ought to have been. I was
prepared to expect this diminution of weight before I weighed

VOL. XI. PART i. d

26 Dr Thomas Thomson an some Experiments on Gold.

the gold. For I had tried the iron solution before mixing it
with the muriate of gold, by weans of prussiate of potash,
which had struck with it a pretty strong blue, shewing, that the
iron was not at all in the state of protoxide, but had been at least
partially peroxidized ; for protoxide of iron is precipitated
white, and not blue, by prussiate of potash. This partial oxy-
dizement had been induced by the air existing in the distilled
water, and partly also by the air adhering to the crystals, when
they were put into the water. For when I let fall a small crystal
of protosulphate of iron into prussiate of potash, the precipitate
was not quite white ; but had a very sensible blue tinge.

2. The preceding experiment was repeated with additional
precautions, to prevent the peroxydizement of the iron in the
protosulphate. 25 grains of gold were employed in the experi-
ment, and 104.25 grains of protosulphate of iron ; the distilled
water was bailed for half an hour before it was used, and the
protosulphate of iron crystals were thrown into the boiling-hot
liquid, which was added to the solution of gold as quickly as
possible. The gold solution in this second experiment was not
neutral, but had an excess of acid, from a notion that this excess
might have a tendency to prevent so much air from being con-
tained in the liquid as seemed to have been the case in the pre-
ceding experiment. The gold obtained weighed 24*9 grains ; so
that the loss was only O'l grain, which is little more than one-
tenth of the loss sustained in the first experiment

Even in this experiment, the iron was not absolutely in the
state of protoxide ; for the solution gave a whitish blue preci-
pitate with prussiate of potash.

This last experiment coming within *i~oth of the theoretic
quantity, I was satisfied with it We see that the 25 grains of
gold, dissolved in the muriatic acid, had been combined with 3
grains of oxygen. For six times 4*5 grains of protoxide of iron

Dr Thomas Thomson on some Experiments on Gold* 27

had been converted into peroxide, and had, therefore, united
with 8 grains of oxygen. I consider it demonstrated, therefore,
that peroxide of gold is composed of

1 atom of gold, - 25

3 atoms of oxygen, 3

28

3. I was curious to know the composition of muriate of gold.
It was exceedingly probable, from the facts stated in the " At-
" tempt" vol. i. p. 440, that muriate of gold is a compound of
two atoms muriatic acid, and one atom peroxide of gold. But
a direct analysis seemed more satisfactory. It was executed in
the following manner.

Twenty-five grains of pure gold were dissolved in nitro-mu-
riatic acid ; the solution was cautiously evaporated, till it as-
sumed a brownish-red colour. It was then allowed to cool
When cold, it was solid, had a most disagreeable, astringent,
and metallic taste, and possessed the usual corrosive qualities
which characterize muriate of gold. It weighed 42*8 grains.
When this salt was dissolved in water, a small quantity of mat-
ter remained, which had a dirty-greenish colour, was easily re-
duced to metallic gold, by the application of the heat of a spi-
rit lamp, and weighed, when thus reduced, 0*8 grain. Thus a
quantity of muriate of gold, containing 24.2 grains of gold,
weighed 42 grains.

To determine the quantity of muriatic acid in this salt, it
was necessary, in the first place, to get rid of the gold. For,
when nitrate of silver is dropt into the undecomposed salt, both
the gold and the muriatic acid precipitate along with the silver.
I therefore put a clear plate of copper into the solution, and left
it till the whole gold had been precipitated in the metallic state.
The copper was then precipitated by caustic potash, and after

d3

28 Dr Thomas Thomson on some Experiments an Gold.

the excess of potash had been neutralized by nitric acid, nitrate
of silver was added to the solution, till it ceased to produce any
farther precipitate. The chloride of silver being collected on a
filter, washed, dried, and fused, weighed 34 -65 grains, equiva-
lent to 8*543 grains of chlorine, or 8*78 grains of muriatic acid.
Thus it appears, that 24*2 grains of gold, in the state of per-
oxide, had been combined with 8*78 grains of muriatic acid.
Consequently, 25 grains of gold in the state of peroxide, must be
united with 911 grains of muriatic acid. This is only 0.14
grain less than 925, the equivalent for 2 atoms of muriatic acid.
From this result it is obvious, that muriate of gold is a com-
ppund of 2 atoms muriatic acid, and 1 atom peroxide of gold.
The weight of the dry salt having been 42*8 grains, it is clear
that it must have contained 5 atoms of water, and that muriate
of gold is composed as follows :

2 atoms muriatic acid, 9*25

1 atom peroxide of gold, 28
5 atoms water, - 5*625

42-875

The precipitation of the gold by protosulphate of iron, seems
to show, that the gold in this salt is in the state of oxide, and
consequently combined, not with chlorine, but muriatic acid. It
is equally clear, that, in the sodium chloride of gold, that metal is
not oxydized, but in the metallic state, and united to chlorine.
Hence the reason why it is so difficult to reduce the gold from
the sodium chloride by heat, while it is so easy, by a very mode-
rate heat, to reduce the gold from the muriate.

4. Gold furnishes a striking example of the want of coinci-
dence in the proportions of oxygen and chlorine, which unite
with bodies, and of the danger of being misled, when we infer the

Dr Thomas Thomson on some Experiments on Gold. 29

composition of a chloride from that of an oxide. The peroxide
of gold, containing 3 atoms of oxygen, one would have been dis-
posed to infer, that the chloride would also contain three atoms
of chlorine. Yet it contains only two atoms. This want of
coincidence between the peroxide and chloride of gold, is pro-
bably the reason why the muriate of gold cannot be converted
into a chloride by heat ; at least all my attempts to obtain a
chloride by that process, have ended in disappointment. In what
manner the change takes place in the atomic proportions, when
common salt is added to the muriate, it is not easy to conceive ;
but the experiments which I have related in this paper, and in
my u Attempt" leave, I conceive, no doubt that the conversion
from muriate to chloride actually takes place.

5. There is an analogy visible between the muriate of gold
and the hydrocyanate of potash. Both of these salts are very
easily decomposed in their isolated state ; but when we combine
the former with an alkaline muriate, or the latter with a metal-
lic hydrocyanate, they become both very permanent and diffi-
cultly decomposed salts.

6. It has been lately maintained by Berzelius, that muriatic
acid is incapable of combining with metallic oxides ; that no mu-
riates exist, but merely chlorides, or compounds of chlorine and
the metal, united to a certain quantity of water. With regard to
the greater number of these compounds, it is a matter of indiffer-
ence which of the two views we take. Thus we may either
consider what is usually called muriate of bary tes, as a chloride
or a muriate. In the first case, the crystals of it will be com-
posed of

1 atom chloride of barium, 13-25

2 atoms water, - - 2*25

15.50

30 Dr Thomas Thomson on some Experiments on Gold.

In the second case, the salt will be a compound of

1 atom muriate of barytes, 14*375
1 atom water, - - 1*125

15-500

The atomic weight and the ultimate elements are the same in
both views. The only difference is, that, if the salt be a muriate,
one of the atoms of water is decomposed, its oxygen being united
to the barium, and its hydrogen to the chlorine. While, accord-
ing to the first view, all the oxygen and hydrogen present are unit-
ed together, and constitute water.

But considerable difficulty will be experienced in applying this
reasoning to the muriate of gold. If this salt be a chloride, it is
obvious, from the experiments stated in this paper, that it is a com-
pound of

2 atoms chlorine, 9

1 atom gold, - 25

34

The salt contains besides, 5 atoms of water, = 5*625

2 atoms hydrogen, = 0*250

3 atoms oxygen, = 3*000

8-875

Making a total of 8*875, which, added to 34, make 42*875, the
atomic weight of the solid salt. But 2 atoms hydrogen, and 3
atoms oxygen, cannot unite together, so as to constitute water.
Nor, on the supposition that the salt in question is a chloride, can
we easily explain the reason why six integrant particles of pro-
toxide of iron are necessary to precipitate one atom of gold, nor
why the protoxide of iron, when employed to precipitate gold from
its solution in muriatic acid, is converted into peroxide.

Dr Thomas Thomson an same Experiments oh Gold. 81

I may mention another example of a muriate, which cannot,
without great violence, be viewed as a chloride, — I mean the per-
muriate of tin.

I have shown, in u The First Principles of Chemistry," that
the atomic weight of tin is 7*25, and that it forms two oxides, the
protoxide, which is black, and the peroxide, which is yellowish-
white. Protoxide of tin is composed of 1 atom tin -f 1 atom oxy-
gen, and its atomic weight is 8*25 ; while . peroxide of tin is a
compound of 1 atom tin + 2 atoms oxygen, and its atomic weight
is 9*25. Muriatic acid combines with each of these oxides, and
forms with each crystallisable salts. Both of these salts may be
formed by dissolving tin in muriatic acid. And I have got diem
both in Mr Monteath's Turkey-red work near Glasgow, where tin
is dissolved in muriatic acid in large quantities, to prepare the
usual mordant for dyeing. Permuriate of tin is the mordant
used ; but, occasionally, protomuriate of tin crystallises likewise ;
and as it does not answer as a mordant, they were in the habit of
throwing it away, till I ascertained its nature.

The protomuriate of tin is a white salt, which crystallizes in
large oblique four-sided prisms, having usually one of the acute
edges of the prism replaced by a tangent plane. It strongly red-
dens vegetable blues, probably because the crystals always shoot in
a solution containing a large excess of acid. Lustre rather silky ;
but the salt is transparent. The taste is acid, and very acrid and
disagreeable. Specific gravity 2*656.

When put into water, the crystals dissolve, with the exception
of a few white flocks of hydrated tin. When heated, it melts,
and flows like nitrate of silver, quite transparent and colourless ;
then it becomes dry, and a white matter remains, which is soluble
in water. It dissolves in alcohol with the same opalescence as in
water. In oil of turpentine it does not dissolve, but becomes yel-
lowish and opaque, and increases in volume. Its constituents were
found to be

82 Dr Thomas Thomson on some Experiments on Gold.

1 atom muriatic acid, 4'625 + 0*209

1 atom protoxide of tin, 8*25

1 atom water, - 1.125 + 0'77

14000

The excess of acid and water was doubtless derived from the
acid solution in which the salt crystallized, and was mechanically
lodged between the plates and the salt.

This salt might be viewed as a compound of 1 atom chloride of
tin, and 2 atoms of water.

The permuriate of tin has been long known, being prepared on
a large scale as the mordant in the scarlet dye. Its crystals are
long white needles, seemingly four-sided prisms. The taste is
acrid, and slightly acid. It reddens vegetable blues. When put
into water, the liquid becomes quite milky. When the salt is
heated, it melts, boils, loses its water, becomes yellow, fuses, and is
volatilized in a white smoke. When analysed, it yielded

1 atom muriatic acid, 4'625 — 0*034

1 atom peroxide of tin, 9.25

f atom water, - 075 — 0'04

It contained also a small trace of protoxide of tin, amounting at
most to aVth °f *he oxide present. Probably the water was only
mechanically lodged in the salt, as it did not amount to an atom.
Were we to view this salt as a chloride, it would consist of

1 atom chloride of tin, 1 1 #75

2 atoms oxygen, - 2*00

1 atom hydrogen, - 0.125

Here the oxygen and hydrogen could not form water. Nor, sup-
posing the salt a chloride, could any reason be assigned why the
tin is thrown down by an alkali in the state of peroxide rather than
protoxide. On these accounts, I am induced to consider this salt,
like that of gold, as a muriate, and not a chloride.

P I. A T e in.

( as )

V. On the Construction of Polyzonal Lenses, and their Combination
with plain Mirrors, for the purposes of Illumination in Light-
Houses. By David Brewster, LL. D. F. R. S. Lond. &
Sec, R. S. Edin.

(Bead May 7. 1827J

In the year 1811, when I was occupied in drawing up an ar-
ticle on Burning Instruments for the Edinburgh Encyclopedia,
my attention was in a particular manner directed to the con-
struction of Large Lenses, and to the different methods by which
they could be combined with plane and spherical mirrors, for
the purpose of obtaining an intense heat from the concentration
of the solar rays. I was thus led to examine the inventions and
contrivances which had been previously proposed by others, for
accomplishing the same object ; and after giving a historical ac-
count of them, I proceeded to describe the improvements and
constructions which had occurred to myself.

In this inquiry, my attention was particularly arrested by an
ingenious speculation of the celebrated Buffon, for augmenting
the power of Burning Lenses, by grinding out a portion of the
glass, and thus diminishing their thickness, without altering
their focal length. This idea will be understood by referring to
Plate III. Fig. 1., which is Buffon's own perspective representa-
tion of it, and which he has described in the following words :

u This method consists in working my piece of glass by steps.
To make myself better understood, let us suppose that I wish

VOL. XI. PART I. E

34 Dr Brewster on the Construction of Polyzonal Lenses,

to diminish, by two inches, the thickness of a lens of glass 26
inches in diameter, 5 feet in focal length, and S inches thick
at the centre. I divide the arc of this lens into three parts,
and I make each of these portions of the arc approach to
each other concentrically, so that there remains only an inch
of thickness at the centre ; and I form on each side a step of
half an inch, to bring together the corresponding parts. By
this means, in making a second step, I arrive at the extremity
of the diameter, and I have a lens with steps, which is nearly
of the same focus, and which has the same diameter, and near-
ly two times less thickness than the first, which is a great ad-

»

vantage.

" If we wish, in short, to cast a piece of ghssjburfeet in dia-
meter, by two and a hawfinches in thickness, and to work it by
steps to a focus of eight feet, I have computed, that, by leaving
one and a half inch of thickness at the centre of this lens, and
at the exterior ring of the steps, the heat of this lens will be
to that of the lens of the Palais Royal as 28 to 6/ without ta-
king into account the difference of thickness, which is very
considerable, and which I cannot estimate before hand.

" This last kind of refracting mirror is the most- perfect
which can be made of its kind ; and even if we should reduce
it to three feet in diameter, by fifteen lines in thickness at the
centre, six feet in focal length, which would render the execu-
tion of it less difficult, we should always have a degree of heat
at least ,/our times greater than that of the most powerful len-
ses that we know of. I venture to say that this mirror with
steps will be one of the most useful instruments in physics. I
have contrived it more than twenty years ago, and all the phi-
losophers to whom I have spoken of it, are anxious that it should
be executed. It might be made highly useful in the promo-
tion of science, and by adapting to it a Heliostate, we might

for the purposes of Illumination in Lighthouses. 85

perform in its focus all the operations of chemistry, as conve-
niently'as could be done in a furnace *•"

There can be no doubt that the lens thus described by Buf-
fon, would have produced the effect which he ascribes to it, had
it been possible to execute it ; but though he invented it twenty-
five years before he described it, — though all the philosophers to
whom he mentioned it anxiously desired to see it made, — and
though sixty years have elapsed since the publication of his
work, such a lens has neither been attempted nor executed.
The fact, indeed, recorded on the authority of M. Rochon and
M. Charles, that Buffon had constructed a lens with steps
made of one piece qf glass, and only 12 or IS inches in diameter,
may be regarded as a proof that the principle was not practical-
ly applicable to lenses of a large size. So visionary, indeed, did
the scheme appear to me, when I read Buffon's Memoir, of
grinding down a solid lens, five, or even three feet diameter, in-
to three spherical surfaces on each face, the one felling below the
other, that I never hesitated to suppose that he proposed his
lens to consist of three separate rings ; and under the influence
of this mistake, I drew up my description of Buffon's invention.
But though the formation of the lens by means of three sepa-
rate rings, would remove in a great measure the difficulty of
grinding and polishing the successively descending surfaces, yet,
even with this improvement, the scheme is just as visionary as
before, since the difficulty and expence of casting, grinding, and
polishing a ring of glass, five or even three feet diameter, is as
great as to execute a solid lens of the same size.

But, however this maybe, the lens actually proposed by Buf-
fon, ingenious as it is, must be ranked among those visionary
contrivances which never find a practical application.

Supplement I FHUtoire Naturdky torn. ii. IS*" Paris 1774.

e 2

36 Dr Brewster on the Construction of Polyzonal Lenses,

Perceiving, therefore, that a limit was necessarily set to the
construction of lenses of one piece, by the difficulty of procuring
colourless homogeneous glass, and by the trouble and expence of
casting and grinding it into its proper form, without flaws and
impurities, I conceived the idea of building a lens with a num-
ber of separate pieces, and, in 1811, 1 printed in the Edinburgh
Encyclopedia the following method of carrying it into effect.

" In order to remove these evils, and at the same time to di-
minish the expence, and simplify the construction of dioptric
burning instruments, the following construction has been pro-
posed by Dr Brewster. If it be required, for example, to con-
struct a burning lens 4 feet in diameter, it should be composed
of different pieces, as represented in Plate III. Fig. 2.,f where
ABCD is a lens of flint-glass, 1 8 inches in diameter. This lens
is surrounded by several segments, AGID, AGEB, BELC,
CLID, ground in the same tool with ABCD, but so formed with
respect to their thickness at AB and GE, &c. that they may ex-
actly resemble the corresponding pprtions of a solid lens. These
different thicknesses can be easily calculated, and there is no dif-
ficulty in giving the segments their proper form. This zone,
consisting of separate segments, is again surrounded with other
segments, GNOF, FOEP, PEMQ, QMLR, RLKS, SKIT,
TIHV, VHGN, each of which is six inches broad in the direc-
tion of the radius. The section of this lens is represented in
Fig. 3. where DE is the central portion, DC 72, E o F the second
zone, and CA m, FB p the external zone. One of the segments
is shewn separately in Fig. 4. By this combination of segments,
a lens four feet in diameter will be formed, and will obviously
possess the same properties as if it consisted of solid glass.
The advantages of this construction may be very shortly enu-
merated.

for the purposes qf Illumination in Lighthouses. 37

" 1. The difficulty of procuring a mass of flint-glass proper
for a solid lens, is in this construction completely removed.

" 2. If impurities exist in the glass of any of the spherical
segments, or if an accident happens to any of them, it can be
easily replaced at a very trifling expence. Hence the spherical
segments may be made of glass much more pure and free from
flaws and veins than the corresponding portions of a solid lens.

" 3. From the spherical aberration of a convex lens, the focus
of the outer portion is nearer the lens than the focus of the cen-
tral parts, and therefore the solar light is not concentrated in the
same point of the axis. This evil may, in a great measure, be
removed in the present construction, by placing the different
zones in such a manner that their foci may coincide *.

" 4. A lens of this construction may be formed by degrees,
according to the convenience and means of the artist. One zone,
or even one segment, may be added after another, and, at every
step, the instrument may be used as if it were complete. Thus,
in Fig. 3. the segment NV v n may be added to the lens, without
the re3t of the zone to which it belongs, and it will contribute, in
the proportion of its area, to increase the general effect.

" 5. If it should be thought advisable to grind the segments
separately, or two by two, a much smaller tool will be necessary,
than if they formed one continuous lens. But, if it should be
reckoned more accurate to grind each zone by itself, then the va-
rious segments may be easily held together by a firm cement.

" 6. Each zone may have a different focal length, and may
therefore be placed at different distances from the focal point, if
it is thought proper."

Although the method now described enables us to construct
lenses without any other limit to their magnitude, but that

* " The burning focus lies a little beyond the red rays, and is therefore at a great-
er distance from the lens than the luminous focus.7"

38 Dr Brewster on the Construction qf Polyzonal Lenses,

which arises from the difficulty of keeping the segments in their
place, yet, when used for lighthouses or Winu^-imtnimente, the
very purpose to which they are applied, we are confined to dia-
meters of a moderate size. Under these circumstances, it may
be desirable to introduce into the parallel or convergent beam
a greater quantity of light than what passes through the lens.
This may be effected by a catadioptric combination of lenses
and mirrors, which I described in 1811, and which, when applied
to lighthouses, possesses the advantage of throwing into one pa-
rallel beam almost every ray of light which diverges from the
luminous source.

For the purpose of applying these, or lenses of any form,
to produce powerful effects as burning instruments, I proposed
the subsequent combination, under the name of a Burning
Sphere. The following is the passage from the Encyclopaedia :

" In order to construct a burning instrument which shall, in
a great measure, be unlimited in its power, we must combine the
principles both of reflection and refraction. We are not aware
that any instrument of this kind has ever been proposed ; and
we are the more surprised at this, as the proper combination of
lenses and mirrors must naturally suggest itself to any one who
considers the limits which are set to the construction of single
lenses, and the disadvantages, either of a theoretical or a practi-
cal nature, to which they are liable.

« The lenses A, B, C, D, E, Plate III. Fig. 5., which may be of
any diameter and focal length, are so placed in the spherical sur-
face AMN, that their principal foci exactly coincide in the point
F. If any of the lenses have a different focal length from the
rest, the coincidence of its focus with that of the other may be
easily effected, by varying its distance from F. The whole sphe-
rical surface, whose section is AMN, except a small opening for
admitting the objects to be fused, may be covered with lenses,

for the purpose* of Illumination in Lighthouses. 39

having all their foci coincident at F ; though it will, perhaps, be
more convenient to have the posterior part MN without lenses,
and occupied by a mirror of nearly the same radius FA as the
sphere. The object of this mirror, is to throw back upon the
object at F the light that passes by it without producing any ef-
fect Each of the lenses, except the lens A, is furnished with a
plane glass mirror, which may be either fixed to the general
frame of the sphere, or placed upon a separate stand. When
this combination is completed, the sphere is exposed to the sun,
so that its rays may fall at right angles upon the lens A, which
will, of course, concentrate them at F, and produce a pretty in-
tense heat The plane mirror PQ, when properly adjusted, will
reflect the sun's light perpendicularly upon the lens B, by which
it will be refracted accurately to the focus F, and produce a de-
gree of heat fully one-half of what was produced by the direct
refracted rays of the sun through the lens A. A similar effect
will be produced by the mirror RS and lens D, the mirror TU
and lens C, the mirror VW and lens E, and all the other mirrors
and lenses which are not seen in the section* The effect may be
still farther increased by the addition of a large lens at XX. As
the angle which the. surface of each mirror forms with the axis
of its corresponding lens, is a constant quantity, the mirrors may
be all fixed to the general frame of the sphere, and therefore the
only adjustment which the instrument will require, is to keep
the axis of the lens A parallel to the direction of the solar rays.

" In order to estimate the advantages of this construction, let
us compare its effects with those of a solid lens, which exposes
the same area of glass to the incident rays.

" 1. In the burning sphere, almost the only diminution of
light is that which, arises from reflection by the plane mirrors,
and which may be estimated pretty accurately at one-half of the
incident light ; but this loss can be amply compensated by add-
ing a few more lenses. *

40 Dr Baewster on the Construction qf Polyzonal Lenses,

u 2. In the solid lens, a great diminution of light arises from
the thickness of the central portions, and from the obliquity of

the parts at the circumference ; which, we conceive, will be fully
equal to the light lost by reflection in the burning sphere.

" 3. In the burning sphere, the lenses may be obtained of
much purer glass than can be got for a solid lens ; and therefore,
ceteris paribus, they will transmit more light.

" 4. Owing to the small size of each lens in the burning
sphere, the diminution of effect arising both from spherical aber-
ration, and from the aberration of colour, will be very much less
than in the solid lens.

" 5. In the burning sphere, the effect is greatly increased, in
consequence of the shortness of the focal length of each lens,
and the greater concentration of the incident light.

" 6. In the burning sphere, all kinds of lenses may be com-
bined. They may be made of any kind of glass, of any diame-
ter, and of any focal length ; and the lenses belonging to different
individuals may be combined for any occasional experiments in
which a great intensity of heat is requisite"

To those who are acquainted with the laws of the distribution
of light which passes through lenses, or which falls upon reflec-
tors, it is scarcely necessary to say, that the very same appara-
tus which is best fitted for producing combustion from the solar
rays, is also best fitted for producing the column of illumina-
tion in lighthouses. The only difference between the two ope-
rations is, that, in the one case, the parallel rays of the sun pass
through the lens, and are refracted to its focus ; while, in the
other case, the rays pass from the focus, and are refracted by the
lens into a parallel beam. Hence, the Polyzonal Lens, and the
Burning Sphere above described, are peculiarly applicable for
the illuminating apparatus of lighthouses. This application of
these contrivances early presented itself to me ; and some time
between 1818 and 1820, 1 was in communication with Mr Ste-

Jor the purposes of Illumination in Lighthouses. 41

venson, the Engineer to the Scottish Lighthouse Board, on the
subject of introducing the lenses into the Northern Lighthouses.
The origin and history of this communication is as follows.
Between the years 1818 and 1820, some experiments had

«

been made in France, with the view of fitting up lighthouses with
Lenses, a method which had been in use in England in the
Lower Lighthouse of the Island of Portland since 1789 *. The
French had proposed to use Lenses in connection with a very
powerful lamp, the particulars of which were communicated in
a letter from Major Colby to Mr Stevenson. On the receipt
of this letter, Mr Stevenson stated to me his intention of inves-
tigating the subject, in reference to the use of lenses in light-
houses. I immediately pointed out to him the improvements in
the construction of lenses, and the method of arranging them
for the purposes of illumination, which I had suggested in the
Edinburgh Encyclopaedia ; and he proposed that we should make
some experiments, with the view of introducing them into the
Northern Lighthouses. Before proceeding, however, to this in-
quiry, Mr Stevenson was anxious to obtain an account of what
had been done in France; and having afterwards understood
that the Cordouan Lighthouse on the French coast was to be
fitted up with lenses, he stated it to be his intention to make per-
sonal observations upon it, whenever the alteration on that light-
house should be completed.

Unfortunately, however, the years 1820, 1821 and 1822 pass-
ed away, without any thing being done to ascertain the merit
of my invention for lighthouse illumination. In the beginning of
November 1 822, Mr Stevenson and I received copies of a memoir
by M. Fresnel, entitled, Memoir e sur un Nouveaux Systeme (FEclai-
rage des Phwres. This memoir was read at the Academy of

* The lenses in this lighthouse, which are two in number, are twenty-two inches
in diameter.

*

VOL. XI. PART I. F

42 Dr Brewster on the Construction of Polyzonal Lenses

Sciences on the*20tk July 1822 ; and the New System of Illumi-
nation/or Lighthouses which it describes, is, with the exception of
the lamp * (which is a combination of the inventions of Count
RmurGEin and M. Oarcel), the very same as mine* The com-
pound lens which M. Fresnel gives as an invention of his own,
is the same as that which I had invented eleven years before ;
and the combination of lenses and lateral reflectors for widening
the main column of light, is exactly the same as mine. In
1815, 1 had transmitted to the Library of the Institute of France,
and also to M. Biot, one of its most, distinguished members, a
copy of the -Edinburgh Encyclopedia, containing the article
Bunting Instruments, in which these inventions ware not only de-
scribed, but distinctly engraven ; and it certainly seems strange,
that, during the seven years which preceded the publication of
M. Fresnel's memoir, the eyes of none of his colleagues in the
Institute, should ever have fallen upon the above article, or up-
on the engravings by which it is illustrated. M. Fresnel, how-
ever, has the honour of being the first who actually applied the
built up lenses to lighthouse illumination ; and M. Becquet, Rear-
Admiral Halgan, Baron Rossell, M. Pftotf y, M. Akago, and the
other Commissioners for French lighthouses, are entitled to no
slight praise for the liberality with which they seconded his views,
and the promptitude with which they have adopted the valu-
able improvements which he submitted to their consideration.
• -* •

Under these circumstances, I lost no time in calling the pub-
lic attention to the history of these lenses, and to their great
utility for lighthouses f ; but although this appeal was made in
December 1822, it excited no notice, and the compound1 lenses

* This lamp" has been brought to a high degree of perfection by MM. Arago
and Fbesnel, and is a most valuable addition to the apparatus for lighthouses.

f See Edin. Phil Journ. vol. viii. p. 165.

for the purposes qfliiummatum in Lighthouses. 43

seemed destined tot shire that fate which too frequently befalls
British inventions that are beyond the sphere of individual - en-
terprise.

In the year 1825, the Engineer of the Northern lighthouse
Board went to Paris, and brought over to Edinburgh one of the
compound lenses as manufactured by M. Soleii,, Although, this
invention had been aaeribed to another, it was no alight satisfaction
to find that it had been distinguished by the approbation of the
most eminent French philosophers. It had occupied the attend
tion of the Institute itself; and after repeated trials, and a careful
comparison with the large parabolic reflectors of. M. Lenoir,
thirty-one inches in diameter, and certainly not inferior to any ma-
nufactured in this country, the Commissioners of Lighthouses lor
France, consisting of mathematicians, civil engineers, and offi-
cers of the navy, have adopted the compound lens, and the com-
bination of lenses and mirrors, as a new system of illumination ;
and a definitive arrangement has been made for bringing it into
immediate operation on the English Channel, the Bay of Bis-
cay, and the Mediterranean Sea.

But notwithstanding all this testimony in its favour, the com*
pound lens has never yet been put to a public trial in Scot-
land. In the course of last winter, it was carried to the Tower
of London, and exhibited to a number of gentleipen distinguish-
ed by their rank and talents ; but it was exhibited as a foreign
invention, and some of those who witnessed its effects transmit-
ted descriptions of it as such to the newspapers of Edinburgh,
where it had long before been described, in two widely circu-
lated works. Another of these lenses was brought from France
as a Burning Instrument ;. and both it and the Compound Lens
purchased by the Engineer to the Lighthouse Board, have been
exhibited as a French contrivance in our own University.

Under these circumstances, I resolved to address myself direct-
ly to the Commissioners of the Northern Lighthouses ; and the

f2

44 Dr Brewster on the Construction of Polyzonal Lenses

reception I have experienced from that liberal and enlightened
body, has convinced me, that if I had made this application in the
year 1819, 1 should now have had the satisfaction of seeing the
new method of illumination introduced into our own lighthouses.
The Commissioners have allowed me opportunities of explaining
to them, both personally and in writing, the construction and
advantages of the new apparatus ; and I have been authorized
to have one of the Polyzonal Lenses constructed under my own
superintendence. This work has been entrusted to Messrs Gil-
bert of London, who are now executing one of the lenses in
flint-glass, with a diameter and a focal length of three feet. I
have no doubt that the Trinity-House of London, and the Corpo-
ration for Improving the Port of Dublin, the two bodies who have
the superintendence of the English and Irish Lighthouses, will
also concur in putting the new method to the test of direct ex-
periment ; and I do not hesitate in expressing my conviction,
that, in a few years, it will be established in every maritime
country where the preservation of life and property has become
an object of public concern.

Having thus given a brief account of the origin and history
of the new system of illumination, I shall now proceed to point
out its superiority to that which is at present in use. In doing
this, I shall adopt the following arrangement.

I. On the imperfection of the present system of illumination
by Hammered Reflectors.
II. On the construction and properties of the Polyzonal Lenses.

III. On the combination of Lenses with Plain and Spherical

Mirrors, for Fixed and Revolving Lights.

IV . On the Construction of Distinguishing Lights.

V. On the occasional exhibition of Powerful Lights in Light-*
houses.
VI, On the introduction of Gas into Lighthouses.

far the purposes of Illumination in lighthouses. 45

I. On the Imperfection of the present system of Illumination by

Hammered Reflectors.

The best constructed lighthouses in Great Britain are fitted
up with parabolic reflectors, like that represented in Plate III.
Fig. 6. The dimensions of these reflectors are

Diameter AB, 24 inches.

Depth CD, - - - - 10£

Centre of wick from apex, or LC, - 4
Circumference of wick from apex C, 3f

Circumference of glass-chimney from
apex C, ----- 3

The reflecting material, before it is hammered, is a flat disc
of copper plated with silver, which, by repeated hammering up-
on a polished steel anvil, is beaten into the form of a paraboloid,
by the assistance of a gauge, which the workman constantly ap-
plies to the hammered surface. When the reflector is brought
as nearly to the concavity required as the gauge and the eye of
the workman can determine, it is then polished with the hand,
by rubbing it with a piece of leather and the usual polishing
material *. It is then fitted up, as shewn in the figure, with
an argand-burner placed in the focus of the paraboloidal sur-
face, and supplied with oil by the lamp behind.

• " The reflectors," says Mr Stevenson, " consist of a circular sheet of copper,
measuring, when, flat 96{ inches in diameter ; weighing Hi lb. on an average, and
plated with silver in the proportion of 6 oz. to each pound avoirdupois of copper.
These plates are formed into the parabolic curve by a very nice process of hammer,
ing, and afterwards set into a bezil or ring of brass."— Account of the Bell Rock
Lighthouse, p. 527.

46

Lenses

The apparatus now described, is executed in a very admir-
able manner for the Northern Lighthouses ; but no excellence
in its execution, and no care in its application, can compensate
for its numerous imperfections and disadvantages, which we shall
now particularly explain.

. *

1. On the Imperfection of the Material employed. — Of all re-
flecting substances, a silver surface, not produced by hammer*
ing, is the best. The effect of hammering is to give different
densities to different parts of the hammered Surface ; and as it
is proved *, that part of the light reflected from metals pene-
trates the reflecting surface, and that surface* polished by ham-
mering act upon the light in a different manner from a surface
not hammered, and ground and polished upon pitch, it is mani-
fest, that the light which enters a reflecting surface of unequal
density, or upon which that surface produces a physical change,
will not be reflected in lines determined by the form of the re-
flecting surface itself, but will be to a certain degree scattered
in all directions. This effect will be understood by examining
Fig. 7., where ABDC is the silver-plate highly magnified, and
CDFE the copper, the intersecting arches shewing the eflect
produced by hammering.

2. On the Imperfections of the Surface. — The imperfections of
the external surface of the present reflectors, arises from two
causes : 1st, From its being a surface produced by hammering ;
and, 2<%, From its being covered with innumerable scratches
and circular lines. From the first of these causes, the surface
cannot possibly reflect a diverging pencil of light into a parallel
pencil, even if the general surface were mathematically exact*

* See Art. Optics, Edinburgh Encyclopaedia, vol. xv. p. 607. ; and Biot's
Traiti de Physique, torn. iv. p. 579.

for the purposes t^ IlAwdnation in Lighthouse*. . 47

Sir Isaac Newton has himself remarked, " That every irreguku-
ritg m a reflecting superficies, makes the rays stray five or six times
mare outr of their due course, Han the like irregularities in a refract*
jng*me ;" and we may therefore easily conceive what a scattering
and 'dispersion of the rays must take place from a surface ham*
mered into a parabolic curve. This dispersion may not appear so
conspicuous, when we examine the reflected beam near the reflec-
tor itself; but at moderate distances even, it miist exercise an
enormous influence, in weakening the intensity, disturbing the pa-
rallelism, and consequently destroying the uniform density of the
reflected column of light. The second source of imperfection of
surface, namely, the scratches and striae, will be easily under-
stood by those who have examined the beautiful Iris ornaments
of Mr Barton. All the light which falls upon the scratches
on a metallic surface, is reflected in coloured pencils to a distance
from the direction of the rest of the light ; and this distance in-
creases with the number and closeness of the scratches. Not
a single ray of this coloured light can ever enter the main beam
of a lighthouse reflector, so that it is entirely lost. By standing
in front of One of these reflectors, it will be seen, that these
scratches are so numerous, that the surface has the appearance
of being covered with the finest hair. If the surface had been
regularly ground and polished upon pitch, like the specula of te-
lescopes, no such effect would be produced; but this cannot, be
done with parabolic reflectors. <

3. On the Imperfection of the Parabolic figure. — The practical
execution of a parabolic surface for optical purposes, has long
been regarded as a very difficult operation, even when effected
by the nicest machinery. Hence, the operation of forming a
parabolic surface by a gauge and a hammer, directed solely by
the eye of a' workman, is not likely to be successful. Had
such a surface been intended for that of a solid for ornamen-

48 Dr Brewster on the Construction of Polyzonal Lenses

tal purposes, where the eye alone is to be the judge, the ope*
rater's eye would be sufficiently accurate for directing such a
process ; but when we consider, that the object is to reflect di-
vergent rays into a beam of light, which is required to preserve
its parallelism and its density for 30 or 40 miles, we cannot but
wonder that such inadequate means should have been so long
employed to produce this effect.

Even if the light in the focus of the hammered reflector were
a mathematical point, the most favourable of all suppositions, it
would, after reflection, be thrown into divergent pencils a short
way beyond the mouth of the reflector, and the resulting column
would soon cease to preserve its density and its parallelism.

4. On the Disadvantages arising from the size of the Argand*
burner. — As the argand-burner now in use cannot admit of di-
minution, it may seem strange that its magnitude should be
ranked among the disadvantages of the present system. Tf a
burner an inch in diameter were placed in the focus Qf a lens, or
even in the focus of a large spherical mirror, it would not produce
the same imperfections in the reflected column as it does in the
focus of the hammered paraboloid. In a reflector 2 feet in dia-
meter, the circumference of the wick is only 3£- inches from the
apex C of the curve ; but as the glass-chimney which surrounds
the flame is nearly 2 inches in diameter, and as the rays from
the wick are refracted by the irregularities of this glass, we may
safely assume that the virtual diameter of the mass of light,
which is the source of illumination, is nearly 2 inches. Now, as
the nearest point of the luminous body is only three inches from
the apex C, while the most remote is Jive inches, it is manifest,
that no parabolic curve can reflect such pencils into a parallel
beam ; nay, it is quite clear, that these two pencils must quit the
reflector in a divergent state, and must, at no great distance^ be
thrown into the sea, or scattered upwards in the atmosphere.

for the purposes of Illumination in Lighthouses. 49

This remark applies particularly to the back portion MCN, Fig. 6.
Plate III. of the reflector, which includes a whole hemisphere of
the rays which radiate from KL ; and as all the rays included
between LA and LB are not incident upon the reflector, its
main effect must be produced by the action of the zone corre-
sponding to the rays between MLA and LNB, which will ren-
der the column most luminous near its circumference, and least
luminous along its axis.

The reader who has followed us in these observations, must
have anticipated the conclusion, that a parabolic reflector shaped
by the hammer, and furnished with an argand-burner, whose
flame is only three or four inches from the back of the reflector, •
cannot possibly afford a parallel and dense beam of light, capable
of penetrating space, and forcing its way through the haze even
of an ordinary atmosphere. That this conclusion is well found-
ed, may be readily proved by examining the distribution and in-
tensity of the light in different sections of the reflected beam,
taken at considerable distances. In one of the best reflectors
which I have seen, I observed, even at the distance of twenty
feet from it, a large dark spot on its surface. This opening, or
space destitute of light, must have been so enormously great at
the distance of five or six miles, as to diminish very considerably
its penetrating power.

But, independent of the dispersion of the light by imperfect
reflexion, and its deviation from the axis of the parallel beam,
there is a great portion of the light lost by the use of hammered
reflectors. The loss of light arises from two causes, namely, the
absorption of the light by the metallic surface, and the loss of
light by the collision of the rays at their points of intersection.
All metallic surfaces, even when highly polished and perfectly
smooth, absorb on an average one-half of the light which falls
upon them ; but while the hammered reflectors are peculiarly
liable to that imperfection, the convergency of the pencils which
they reflect, occasions a loss of light almost equally great. Cap*-

VOL. XI. PART I. G

50 Dr Brewster on the Construction of Polyzonal Lenses

tain Kater has shewn, that the intensity of a pencil of light, af-
ter its rays have crossed one another in a focus, is reduced
nearly one-half* ; and though the cause of this is not fully as-
certained, yet it is obvious, that a beam of light, composed of
rays imperfectly reflected, crossing one another in every part of
its section, must, from this cause, undergo a great diminution of
intensity.

In addition to the disadvantages now explained, we may
mention two others, which merit particular notice.

1 . The 'Parabolic Reflectors do not admit of amy augmentation of
the light in cases of emergency . — In dark and hazy weather, when
the mariner requires to be warned of his danger by the ringing
of bells, it would be most desirable to double, or even quadruple,
the intensity of the light. One reflector, however, cannot, in
such cases, be made to augment the effect of another, and the
introduction of a larger burner, in place of producing an increase
of light, would actually occasion a diminution of it f . It will
be seen, however, in the sequel of this paper, that the polyzonal
lenses possess this advantage in a peculiar manner.

2. The Parabolic Reflectors are peculiarly unfit for the pro-
duction of distinguishing lights. — In order to form a distinguish-
ing light, by difference of colour, it is necessary to interpose a
plate of red glass, two feet in diameter, in front of the reflector.
This mfethod is not only an expensive one^ but it is very limited
in its resources. In the case of a lens, a piece of glass a few
inches square is sufficient, and from this cause we can avail our-
selves of various coloured media, which could not be used in the
present system.

* See Edinburgh Encyclopedia, Art. Optics, vol. xv. p. 67.

f A burner with two concentric wicks should be immediately introduced into
the lamps now in use.

for the purposes of Ilhminatian in Lighthouses. 51

In consequence of the weakness of the column of light, Red
is the only colour which has been used for distinguishing
lights ; but when the column of light is rendered strong by an
improved system of illumination, several other colours may be
used with great effect, and the power of varying the lights may
be thus widely extended.

The only advantage which parabolic reflectors possess, as a
compensation for their numerous defects, is, that they receive a
very large part of the sphere of light which radiates from the
burner ; but this advantage is more nominal than real, for we
shall afterwards see that a smaller portion of the sphere well
reflected, or well refracted, into a parallel beam, will produce
a much more useful effect.

If any partiality for reflectors should still exist, they ought to
be made much larger, and should be built up of separate zones
and segments, like the polyzonal lenses *. The material should
be speculum metal, ground and polished upon pitch. The cen-
tral portion should be a spherical mirror of considerable radius,
and the other zones might be ground with annular surfaces, so ad-
justed as to afford a parallel beam of light. As such reflectors,
however, would still possess several of the inconveniences of the
present system, we shall content ourselves with merely allud-
ing to them, and shall proceed to the description of the New
Lenses.

* That the reflectors for lighthouses are considered by competent judges to re-
quire improvement, appears from the following passages : " It is greatly to be de-
sired," says the Editor of the Bibliotheque UniverseOe for July 1826, " that the
perfection to which optical instruments have been brought, should be extended to
that branch of the science which has for its object the illumination of lighthouses."

" From certain experiments now in progress," says Mr Stevenson, " the
writer ia in expectation that considerable improvements may be introduced in the
construction of reflectors ; and that additional modes of distinguishing the lighthouses
on the coast will be obtained*— -Account of the Bell Rock Lighthouse, p. 527-

G2

52 Dr Brewster on the Construction of Polyzonal Lenses

II. On the Construction and Properties of the Polyzonal Lenses.

As the construction and properties of common lenses are well
known, I shall merely give a section of a common plano-convex
lens, and of a double convex lens, made of one solid piece of
glass, in order that they may be more readily compared with
the new lens shewn in Plate IV.

Fig. 1 . Is the section of a plano-convex lens of solid glass.

Fig* 2. Represents a section of one of the new plano-convex
polyzonal lenses, in which the continuous surface is con-
vex. It consists of a single lens in the centre, surround-
ed with five zones, each of which zones is composed of se-
parate segments, as shewn in the plan, Fig. 7.

Fig. 3. Represents a section of another plano-convex poly-
zonal lens, in which the continuous surface is plane.

Fig. 4. Is the section of a double convex lens of solid glass.

Fig. 5. Is the section of a double convex polyzonal lens.

Fig. 6. Represents another form of the double convex poly-
zonal lens.

Fig. SK of Plate III. is a perspective view of a portion of the
five zones of a Double Convex Polyzonal Lens.

Fig. 7. Represents a plan of the polyzonal lens, three feet
in diameter, in which the central lens is fourteen inches in
diameter *.

In examining these figures, it will be seen, that the polyzo-
nal lenses differ from the common lens, in having, as it were,

* A central lens of this size may be easily executed in flint-glass, free from any
considerable imperfections, for the late M. Fraunhofeb undertook to execute a
flint lens for achromatic telescopes, eighteen inches in diameter ; and M. Guinand
actually made one of that size.

PLATE fV.

fy 3

for the purposes oflttumnation in Lighthouses. 53

removed from them a great portion of the solid glass, and that,
as the surfaces of the glass which is left, are parallel to the sur-
faces of the glass which is removed, the rays of light will suffer
nearly the same refractions in the one lens as in the other. Let
AC B b m A, Plate IV. Fig. 8., for example, be the section of a
large solid lens, from which the great mass of glass efg act hi
kCe has been removed, the polyzonal lens which is left, will re-
fract light nearly in the same manner as the solid lens, in con-
sequence of the surfaces^ and acb being parallel to e C k. A
ray of light FC falling on the solid lens at C will be refracted into
the line C n, and will emerge in the direction n R. In the poly-
zonal lens, the ray F c will be refracted at c into a line c m, nearly
parallel to C a, and will consequently emerge at m9 in a direction
R m, nearly parallel to n R. I have said nearly, because there
is a slight difference between the refraction in the two cases, but
this difference, as will afterwards be seen, is in favour of the po-
lyzonal lens, which is actually a more perfect lens than the so-
lid one. The following are the advantages of the hew lenses,
compared with those of the common form.

1. The polyzonal lenses are much more transparent than
common ones made of the same glass. As the finest glass
has a decided colour above certain thicknesses, and as the tran-
sparency of different masses is inversely proportional to their re-
spective thicknesses, the polyzonal lenses must, from their very
nature, have a superior transparency to common ones made of •
the same glass.

2. As it has been hitherto found impracticable to cast large
lenses free of veins, flaws and impurities, which scatter and ob-
struct the refracted light, the formation of them, in separate
zones and pieces, enables us not only to construct them of pure
and homogeneous glass, but to make them of a size which has
been hitherto deemed impracticable. When it is impossible to
obtain 300 lb. of good homogeneous glass for a solid lens, it may

54 Dr Brewster on the Construction of Polyzonal Lenses

be quite easy to obtain 50 or 100 lb. for a polyzonal one. It is not,
however, necessary that the lens be made of one kind of glass.
Let us suppose that we have six different kinds of glass, with
six different refractive powers, we have only to form the central
lens of the least refractive glass, and the other zones of the other
kinds of glass, so that the refractive power of the glass of any
one zone is greater than that of the zone within it. Nay, it is
not necessary even that each zone be made of the same kind of
glass. If the glass of any segment has a different refractive
power from the rest of it, we can make its focus coincident with
the rest in three ways, 1. By a slight variation of its distance
from the burner ; 2. By a change in the curvature of its sur-
face, or imperfectly by a slight variation from its proper posi-
tion. It can seldom be neeessary to have recourse to such ex-
pedients; and they are mentioned here chiefly to shew the
number of resources which are within our reach.

If any segment, when finished, is imperfect, we may, without
replacing it, remove the imperfection in the following manner :
Let ABC, Plate III. Fig. 9.9 be a section of the segment, having
an air-bubble, or other impurity, as tn n, then we have only to
cut out the portion d efgy as shewn at ATJ'C, taking care to
make the surface ef concentric with AC, and to give the lines
e d9f<j9 the same convergency as the rays which pass through
that part of the segment.

3. The construction of lenses in separate zones, enables us to
diminish the spherical aberration, which, as I shewed in 1811,
may be done by various means. 1 . Each zone may be made of
different kinds of glass, so as to refract the rays which they re-
ceive to the same focus, the radius of curvature of each zone
being the same. 2. Each zone, though made of the same glass,
and having the same curvature, may be so placed relatively to
each other, as to have one common focus. In Fig. 2. and 6. of
Plate IV., for example, if the radiating point is on the left

far the purposes of Illumination in Lighthouses. 55

band side of the lenses, the aberration will be greatly less than
it is in the solid lenses, Fig. I . and Fig. 4. 3, When the zones
are placed, as in Fig. 1 ~ and Fig. 4., the aberration may be cor-
rected by dirtiiniflfring the curvature of the zones, as they recede
from the central lens, or by varying the inclination of their sur-
faces to the axis of the lens, till the middle line of each zone is
nearly in the surface of a hyperboloid. By any of these ar-
rangements, it is easy to construct the lens, so that parallel rays
shall be collected within a space not exceeding the magnitude
of the flame from which the parallel beam of light is to be ob-
tained, which is all that is required for the purposes of light-
houses. But, when the lens is to be used as a burning instru-
ment, the accurate correction of the spherical aberration is, as
Mr Herschel has found, a matter of the first importance.

Having thus described a method of constructing lenses su-
perior in transparency, in homogeneity of substance, in size, and
in their action upon light to solid lenses, we shall now point out
their superiority to hammered parabolic reflectors for the pur-
poses of lighthouses.

Let AB, Plate III. Fig. 10.,. be a lens which forms a parallel
beam of light AR, BR, by means of a lamp at L placed in its
focus. By comparing Fig. 6. with Fig. 10., it will be seen that
the reflector ACB, Fig. 6., throws into the parallel beam A m
B n, all the light which radiates from L, excepting what is con-
tained between LA and LB ; whereas the lens AB, Fig. 10.,
throws into its parallel beam only what is contained between
LA and LB. The lose of light, however, in the reflector is
more than one-half of what falls upon it, while in the lens it is
only about one~ten£h. This circumstance alone compensates, to
a certain extent, for the smaller portion of the sphere of rays
which faUsi upon the lens ; and it will be afterwards seen that we
can actually avail ourselves of the rest of the sphere of light

1

56 Dr Brewster on the Construction of Polyzonal Lenses

in Fig. 10., in strengthening and widening the. main beam AH,
BR. But, though the reflector throws much light into the
beam, it reflects it in a very imperfect manner, from the causes
which we have already explained. In the lens, on the contrary,
the light is refracted into the beam by a highly polished and
regular surface ; and when we consider, that, in a lens, three feet
in diameter, the distance JLC is three feet, while in the reflector,
the distance LC is little more than three inches, we must see at
once how peculiarly the lens is adapted to collect the cone of
rays LAB into a dense and regular beam, capable of penetrat-
ing space, and forcing its way through the fogs and mists of the
ocean.

From the nature of a parabolic reflector, we are prevented
from using a very powerful lamp, and hence a common argand
burner is the only light which has been hitherto used in Great
Britain. The proximity of the focus to the back part of the
mirror, renders it impracticable to increase the flame, without
at the same time diminishing the parallelism and density of the
reflected column. In the case of the lens, however, we may
use the powerful lamp recommended by Count Rumford with
2, 3, 4, or even 5 and 6 concentric wicks ; and we can thus
throw a much greater quantity of light into the refracted beam,
than we can possibly throw into the beam formed by reflection.
In the present system of illumination, it is out of our power to
increase the light in cases of emergency, when the lighthouse
ceases to be visible at short distances ; but, in the system of il-
lumination by lenses, we may increase the light tenfold of what
is necessary in a favourable state of the atmosphere.

In this comparison, we have supposed, that all the rays which
flow from L, Fig. 10. are lost, excepting those between LA and
LB ; but while we retain the lens AB, we can enlarge the cone
of rays LAB, by placing a small lens between L and C, and
we can increase its intensity, either by throwing back through L

fy-tl S<*. Tw tWSl,,.T,

far the purposes of Illumination in Lighthouses. 57

a similar cone L a b9 by a mirror a ft, or by obtaining a conver-
ging cone of much greater size, by means of a contrivance which
will afterwards be described.

IV. On the Combination of Lenses with Plain and Spherical Mir-

rors$for Fixed and Revolving Lights.

From the comparison which has now been made of lenses
and parabolic reflectors, it appears that, when the lens is used
singly, a very large proportion of the light of the flame is not
rendered available. In revolving lights, where two or more lenses
are combined, this light may be very advantageously employed ;
but in fixed lights, or in lights where only one lens is to be used,
it requires to be combined with smaller lenses, and with plain and
spherical mirrors, in order to enable us to throw into the paral-
lel beam all or most of the rays which flow from the lamp.

The contrivance which occurred to me for this purpose, and
which I published in 1812, has been recently adopted in the new
system of illumination introduced into the French lighthouses.
It is represented in section, in Plate V. Fig. 1., where F is
the lamp or source of light, whose rays it is required to throw
into one parallel beam. More than one-half of the sphere of
light which radiates from this lamp, viz. GCABDE, is intercept-
ed by lenses AB, AC, CG, BD, DE. The cone of rays inci-
dent upon the lens AB, which is larger, and has a greater focal
length than the rest, fall diverging upon the large lens LL, and
are refracted into a parallel beam of light LRLRJ*. This beam
of light is rendered more intense by the cone FMN, which, fall-
ing on the concave mirror GMNF, whose centre is F, is made
to converge again to F, from which, diverging a second time, it

* By the interposition of the second lens AB, a much larger cone of rays is
thrown into the main beam by the lens LL than could have been done without AB.

VOL. XI. PART I. H

I

58 Dr Brewster on the Construction of Potyxonal Lenses,

is refracted by the lenses AB and L3U, and thus strengthens
every part of the main column of light LRLR.

The cone of rays FAC, and FBD fall upon the lenses AC,
and BD, and are refracted into parallel beams, which are thrown
into horizontal directions a R b R, f R e R, by the plane mirrors
ab, ef. In like manner, the cones FCG, FDE are thrown into
the parallel beams iR rfR, ARg-R, The eonetf rays FGM be-
ing reflected back to F by the mirror GM, will pass through the
leas BD, aad strengthen the beam/R e R, as if it had radiated
from F, and in the same way, the cone FNE, reflected by NE, will
add to the intensity of the beam a R b R* All the other mirrors
and lenses not seen in the section, will, in like manner, refract
and reflect the light which falls upon them into horizontal beams,
so that the main column LRLR will be surrounded on all sides
with a concentric cylinder of light. The beam might be still
farther widened by another zone of lenses, and another set of
mirrors, which would throw the cones FGM, FEN into a hori •
zontal line, but it is decidedly preferable to throw that light into
the beams cRiR, and/R e R.

By the construction now described, we have obviously the
power of throwing into one horizontal beam all the sphere of light
which radiates from a luminous source, with the exception of
what falls between the lenses, which cannot amount to two-tenths
of the sphere. In parabolic reflectors only six-tenths of the
sphere of light falls upon the reflecting surface, so that the com-
bination of lenses and mirrors, has, in this respect, a remarkable
superiority, arising from the luminous focus being actually en*
veloped by the refracting and reflecting surfaces.

The allowance of two-tenths of the whole sphere of light for
what is lost between the lenses, is sufficiently large ; but it may
' be reduced even to one-tenth, if, instead of making* the lenses
circular, we form them into a real zone, each lens, placed on the
surface of the sphere, being comprehended between two paral-
lels of longitude and two parallels of latitude. In this way the

for the pufpmes of Illumination m Lightlmnes^ 59

first zone of tenses will be close to the eirfcumferencfe of the lens
ABt Plate V. Fig. 1. ; and the second zone of lenses Will be
close to the first zone, without any space whatever between them.

The preceding apparatus is intended to be a substitute for a
single parabolie reflector ; but when the light is to be seen in se-
veral directions, or is required to revolve, then two er more pa-
rabolic reflectors are united^ back to back. Each of the reflec-
tors thus united has necessarily a separate lamp ; but if two or
more lenses are used, the sariie lamp will serve for them all, —
an advantage of no slight consideration.

The ftiethod of uniting two or more lenses will be understood
from Plate IV. Fig. 2.f which, if the number of large lenses i*
only two, will be a horizontal section of the apparatus ; but if
the large lenses axe Jour f six, or eight in number, it will be a ver-
tical section of the apparatus, room being left at D for admitting
the lamp, and at C for the chimney. The parallel beam of light
formed by the small lens AB, and the large one LL, is widened
by means of the lenses AC, BI>, and the mirrors ab9 eff while the
opposite parallel beam, formed by the small lens GF, and the
large one UL, is widened by means of the lenses CG, DF, and
the mirrors cd> g h. In this manner, by increasing the number
of large tenses, we may, by means* of ofte powerful lamp at F,
throw any number of parallel columns of light into a horizontal
plane, and increase the width of these beams, by employing small
lenses and mirrors to reflect horizontally the light that would
otherwise be east into the sea, or thrown up into the atmosphere.

IV. On the Construction of Distinguishing Lights.

" The methods resorted to for distinguishing one light from
another, on the coast, in cases where the distance and bearings
by the compass may be so trifling as to render some method of
distinguishing them necessary, till of late, was only effected by

h2

60 Dr Brewster on the Construction of Polyzonal Lenses,

shewing double and single stationary lights, exhibited from se-
parate lighthouse towers. This description of lighthouse is suf-
ficiently characteristic : it is, however, not only expensive, but,
from the frequent repetition, such lights have at length become
so general, as to be no longer a distinguishing guide to the ma-
riner. The next idea which suggested itself, was the revolving
light, exhibiting the alternate effect of light and darkness, by
the periodical revolution of a frame or chandelier with reflectors,
kept in motion by machinery. The revolving light has also
been constructed as single and double ; and even treble revolv-
ing lights, as at the Casket Rocks, in the British Channel.
But this mode, from the increasing number of lighthouses, it
has also been found necessary to vary ; and revolving lights are
now distinguished from each other by shades of glass stained of
a red colour, which are interposed between the eye of the spec-
tator and the reflector. Upon the first suggestion of this plan,
it was expected that a great range of colours might be made use
of; but after many trials with glasses coloured red, green and
blue, and also by means of coloured fluids, introduced between
plates of white glass, it has been found that red shades only were
calculated to answer the purpose effectually, of distinguishing
and characterising sea lights *. To complete the lighting of the
coasts of Great Britain and Ireland, however, many lighthouses
must still be erected ; and the distinguishing of the new light-
houses from those already in use, becomes an object of the first
consideration with persons engaged in these useful and import*
ant works/'

* In his Account of the Bell Rock Lighthouse, p. 322., Mr Stevenson adds,
" that, after the most full and satisfactory trials, the red colour was found to be the
only one applicable to this purpose. In tolerably clear weather, the light of one re-
flector tinged red was easily distinguishable, at the distance of eight or nine miles ;
while the other colours rendered the light opaque, being hardly distinguishable to
the naked eye at more than two or three miles."

for the purposes of Illumination in Lighthouses. 61

description of distinguishing lights, which we have ta-
ken from -Mr Stevenson's excellent article on Lighthouses, in
the Edinburgh Encyclopedia, indicates very distinctly the defects
of the present methods, the great importance of resuming the
subject, and the particular points which demand the attention
of the scientific inquirer. In the construction of distinguish-
ing lights, three methods may be adopted :

1. The first method consists in making one or more lights

disappear and reappear in regular succession, by their
revolution round a vertical axis.

2. The second consists in tinging the columns of light with

the different colours of the spectrum.

3. And the third consists in the combination of these two

methods.

If the lighting apparatus consists of two large lenses, of
which Fig. 2. Plate V. is a section, and if it is made to revolve
round a vertical axis thirty times in an hour, the brilliant co-
lumn of light LRLR will be seen every minute, and it will be
preceded and followed by the other columns which surround it.
If the large lenses are four in number, the same effect will be
produced by a rotation of fifteen times in the hour ; or, by ma-
king the velocity of rotation the same as before, the disappear-
ance and reappearance of the lights will follow each other with
greater rapidity. If a zone of eight equal lenses is used, an
eclipse and a brilliant light will be seen eight times during every
revolution ; and this may be varied, by making each alternate
lens of inferior power, so that there will be a transition to total
darkness by two different intensities of brilliancy.

In constructing a distinguishing light on this principle, I
propose that the lenses shall have the form of a parallelogram,
and shall be arranged so as to form the faces of an eight-sided

62 Dr Brewster on the Construction of Potysmal Lenses,

prism, as shewn in Plate VI. Fig. 1 . (of which Fig. 2. is a sec-
tion) where AB B'A', CD D'C, EF F'E', GH WQ'9 are the
larger lenses, having the form shewn irt Fig. 3. Plate II., and
having equal segments on each side of the centre, eat off by
vertical lines A A', BB', &c. The other lenses BC, DEy FG, and
HA, have the same height, but less width, and consequently
must be ground to a longer foeal length thai* the others, in order
to be placed on the faces of the same prism.

When the lamp Li, Fig. 2., is placed in the centre of this octohe-
dral prism, the whole zone of light which is contained between the
upper and under edges of the prismatic faces, will be concentrat-
ed into eight parallel and horizontal columns of light, every alter-
nate column having a different intensity. If the whole now revolves
in Jour minutes, we shall have a bright Same from the large
lenses recurring every minute, and a fainter one from die small-
er lenses every minute, so that there will be a reappearance of
the light every thirty seconds, and an eclipse every thirty se-
conds. By removing one or mere of the lenses, variations in
the character of the light may be introduced to a considerable
extent.

The advantages of the preceding construction may be thud
enumerated.

1 . The whole zone of light which flows from the lamp be-

tween the terminal edges of the prism is rendered
available.

2. The lenses may be much more easily, and accurately fit-

ted up, in the form shewn at AB B'A', Fig. 1. Plate VI.
than if they had a circular or a square form, as die edges
of the segments may be fitted into grooves in the ver-
tical bars A A', B B', and easily adjusted.

3. Though, for a burning instrument the horizontal sides* of

a lens, which are cut off in Fig. 1., are as* useful as

PLATE VI.

Kejfal Shu Tra*. F0I ~ZTp .6*1.

Ar./.

Hm2.

Fif.6.

/V 3.

nrjf

for tie purposes of lUunasuUion in Lighthouse*. 63

the vertical ones which remain, jet- in lighthouses,
they are of less use, as the width of the column, in a
vertical plane, is necessary to embrace a wider extent
of sea.
4. From the very mode of fitting up the lens AB B'A', it is
obvious that we can give it a much greater diameter in
a vertical direction, and at less expenee, than could be
done while it has either a square or a circular form.

In lighthouses when it may be convenient to employ the
reflectors, and Argand burners of the old system, the following
arrangement of them with lenses will be found to constitute
a cheap and effective apparatus for distinguishing lights. In
Fig. 3. AB, AC, A'B', A'C, are the sections of two truncated
polyzonal lenses, the elevation of which is shewn in Fig. 4. Ar-
gand burners F, F', are placed in the foci of the four lenses,
and each of the two burners is surrounded with a parabolic re-
flector P m rf Q, F' op' Q', having openings mn, tn' ri, op, o' p\
sufficiently large to afford a passage for the cones of rays to the
lenses AB, AC ; A'B', A'C'. By this arrangement we shall
have eight beams of light, namely two powerful columns BRRC,
B'R'R'C, produced by the lenses, two columns PQRR,
F'Q'R'R', produced by the reflectors, and four of much inferior
intensity AB rr, AC r r, A'BW, A'C'rV, produced by the
oblique passage of the cones F'AC,. F'A'C, FATB', FAB,
through the lenses. These last columns, will have a slight
convergency, as the burners which produce them are placed
a little without the principal focus of the lenses ; but this evil
may be remedied, by bringing the burners F, F' as near as pos-
sible, and placing the lenses AB, AC, A'B', A'C, at an angle.
The effect of this will be to divide the columns BCRR,
B'C'R'R', into four, so that we shall thus have ten columns of

64 Dr Brewster on the Construction of Polyzonal Lenses,

light, and ten eclipses, during each revolution of the appara-
tus *.

2. In order to produce distinguishing lights, by altering the
colour of the rays, it is necessary, under the present system, to
cover the whole mouth of the reflector with a plate of coloured
glass mn9 Plate III. Fig. 6. two feet in diameter ; and in the
passage already quoted, we are informed by Mr Stevenson, that
no other colour but red has been found to answer. This colour,
however, is the worst that can be employed, as it is the very co-
lour which white light assumes in passing through a dry hazy
atmosphere, or through a long tract of even clear air. Hence
occasions will often occur, when such a colour will cease to be
a distinctive mark of any individual lighthouse.

When it is admitted that red shades only have been found to
answer the purpose of characterising sea-lights, it is a virtual
admission of the total incompetency of the present system of il-
lumination, for nothing can be more certain, than that other co-
lours may be introduced as characteristic of sea-lights, provided
the intensity of the illuminating columns is sufficiently strong
to allow of that additional loss by absorption, which takes place
in passing through various coloured media.

. * In order to render available the reflectors of the old system, the following com-
binations may be adopted with advantage in many cases.

As the back part of the reflector is almost useless, an aperture two or three inches
in diameter may be cut away at D, Fig. 5., so as to give free passage to the cone of
rays FAB, which, falling upon the lens AB, will be reflected into a parallel beam
ARBR.

Two reflectors CDEE , C'EKEE' may be coupled together, as in Fig. 6., so that
the lamp F may be exactly in the focus of each, and in this manner we shall have two
beams of light in place of one.

Or we may give additional power to the reflector, as in Fig. 7. by using another
lamp F, and surrounding the reflector with the external zones of a lens AB, in whose
focus the lamp F is placed. The column of light CDRR, thrown out by the reflector,
will be widened on all sides by a hollow cylinder of light, whose section is ACRR,
DBRR.

far the purposes of Illumination in Lighthouses. 65

The system of illumination by lenses, may therefore be con-
sidered as absolutely necessary to the proper construction of co-
loured distinguishing lights, in so far as this system will alone
enable us to dispense with the use of red light, the very colour
which the atmosphere itself can produce. But there is another
most important consideration, which renders the lenticular system
peculiarly adapted to coloured lights* While a large sheet of co-
loured glass is necessary for colouring the column reflected from
a parabolic reflector, we may accomplish the same purpose in len-
ses, by means of a small plate of coloured glass three or four inches
square, placed as close as can be conveniently done, to the illu-
minating flame, which will colour the whole column of light as
effectually as if it had been of the same diameter as the lens.
This facility of applying coloured media, will enable us to avail
ourselves of natural and artificial substances, which could not
possibly be procured in large plates *. Yellow orpiment, for ex-
ample, or sulphate of copper, and various other substances,
might be placed, in thin pieces, between two plates of glass, so
as to form a square-coloured plate, sufficiently large to receive

* This advantage is strikingly pointed out by the following fact stated by Mr Ste-
venson : " After having corresponded with all parts of the kingdom in endeavouring
to procure red glass of the finest quality, by having it coloured in the furnace, it was
mortifying to find, that its manufacture was wholly impracticable, excepting in the pro-
duction of small pieces not more than three or Jour square inches, similar to those in
the compartments of cathedral windows, which, in the process of shading a reflector,
must have induced a number of minute divisions, and necessarily obstructed much
of the light The writer at length resolved on confining his attention to plates of
crown-glass stained by repeated application of the litharge of gold, laid on after the
manner of gum or paint, which was afterwards subjected to a strong heat in a muffled
furnace of a peculiar construction, forming altogether a very nice and difficult pro*
oes& * • • * • Although the effect produced in this way cannot be so perfect as
if the glass were uniformly coloured in the pot, yet, when applied to the purposes of
a distinguishing light, its effects are highly characteristic and beautiful." — Account
of the Bell Rock Lighthouse, p. 39&

VOL. XI. PART I. I

66 Dr Bbewster en the Construction of Polyzonal Lenses,

the cone of rays near the lamp, and colour the whole of the illu-
minating column.

3. The two methods of forming distinguishing lights, which
have now been described, might in some cases be advantageous-
ly combined, so that in places where lighthouses are numerous,
we may, at little additional expence, produce many well-marked
variations in revolving lights.

In particular cases, where the lighthouses are exposed only
on one side to the ocean, a motion of the apparatus through the
arch of a circle is all that is necessary, and there are situations
where a slight angular motion of the illuminating column in a
vertical plane might be desirable.

V. On the occasional exhibition of powerful Lights in Light-
houses.

In the present system of illumination, no provision whatever
has been made for the occasional exhibition of intense lights,
when the atmosphere is so hazy and foggy as to absorb entire-
ly, at moderate distances, all the rays which proceed from
the reflectors. At the Bell-Rock Light-house, two large bells,
each weighing twelve hundred weight, are tolled night and day
during foggy weather, so as to warn the mariner of his approach
to the rock. This contrivance is certainly better than none,
though there are cases in which it may mislead the mariner to
his ruin.

No fact in physics is better established, than the inability of
the ear to judge of the direction of sound ; and, indeed, the
whole deception of the ventriloquist is founded upon this fact.
In some conditions of the atmosphere, the sailor may err in his
judgment of the direction of the sound several points of the com-
pass, and he may thus be cast on the very rock which, under
the guidance of other data, he might have avoided.

for the purposes of Illumination in Lighthouses* 67

Admitting, however, as must be done, the absolute necessi-
ty of improvement in this point, it may be asked, How are
strong lights to be procured ? The answer to this is by no means
difficult. In using reflectors, we cannot by any union of a num-
ber, enable them to penetrate a fog, for twenty Argand burners,
placed separately, will disappear nearly at the same distance as
one ; but by the introduction of lenses, we can adopt various me**
thods of obtaining ten times the light in hazy weather. Some of
these methods have been already described ; but another may be
mentioned, which is suited only to short distances. In place of
having only one large lamp in the focus of the lens, we may sur-
round it with five or six of the same size. All of them, but one,
will be out of the focus, and they will therefore form slightly di-
verging, and slightly converging, columns of light ; but as the
distance through which they are required to penetrate is neces-
sarily small, they will all add powerfully to the intensity of the
main beam, and cause it to penetrate through a considerable
tract of hazy atmosphere *.

The circumstances of the case, however, seem to demand even
a more powerful light than can be obtained from oil or gas. Many
years ago, Sir William .Herschel suggested the idea of using
in lighthouses the powerful, and almost unsupportable, light de-
veloped during the deflagration of charcoal by galvanic action.
The suggestion scarcely excited notice, from the enormous expence
of maintaining such a light, and from the difficulty of applying
it to reflectors ; but though it would be extravagant and unne-
cessary to maintain such a light for common occasions, there
would be no absurdity in its occasional exhibition, when all other
means of illumination fail.

* If gas were used, we might, on such occasions, employ a burner ten inches in
diameter, and having many concentric flames.

i2

_ ^^^ •

68 Dr Brewster on the Construction of Polyzonal Lenses,

In the year 1820, I prepared a very thin slice of chalk, and
having exposed it to the heat of the blowpipe, I found that it
emitted a white and brilliant dazzling light, not much, if at all,
inferior to that which arises from the deflagration of charcoal by
the action of galvanism *. The idea afterwards occurred to Lieu-
tenant Drummond of obtaining this intense light from a ball of
chalk a quarter of an inch in diameter, by directing upon it
three alcohol flames, by means of a stream of oxygen. The
light thus produced he found to be eighty-three times more in-
tense than the brightest part of the flame of an Argand burner.
Dr Hope produced the same effect, by directing upon a ball of
lime the flames of oxygen and hydrogen proceeding from sepa-
rate vessels ; and Dr Turner has accomplished the same object
by oxygen and compressed oil gas.

In certain lighthouses, therefore, we would strongly recom-
mend such a light to be used, on great emergencies, when the
risk of human life, and of valuable property, would authorise
such an additional expenditure.

VI. On the Introduction of Gas into Lighthouses.

Ever since the introduction of gas-light, its application to
the purposes of a lighthouse has been often suggested ; but
though the suggestion has been in some cases taken into conside-
ration, it has been invariably rejected, and there is not a light-
house under the superintendence of the English, the Scottish,
or the Irish boards, in which gas has been used, or in which
there is at present the slightest intention of using it f .

* See Edinburgh Journal of Science, No. X. p. 139.

f Since writing the above, I have learned that gap has been used in one or more
lighthouses.

for the put poses of Illumination in Lighthouses. 69

Although, therefore, I cannot claim the merit of first re*
commending its introduction, I am desirous of having the
greater honour, of being the means of bringing it into general
use, by placing before the public eye its numerous and palpable
advantages.

There can be no doubt that oil-gas is preferable to coal-gas ;
but the methods of manufacturing and purifying the latter have
been brought to such perfection, that its cheapness far more
than compensates its inferior illumination. I shall therefore
suppose, that the gas to be used is made from cannel coal, pu-
rified by the most approved methods.

Mr Stevenson informs us, that, about 1810, it was proposed
to alter the lighthouse of Inchkeith, from an oil to a gas light :
" But upon inquiring into the state of the expence of the appa-
ratus, and other circumstances connected with this plan, it was
found that the adoption of the proposed alteration would not be
an object in point of economy. The gas-light, in this instance,
was disapproved of by the Scotch Board, chiefly from the appa-
rent uncertainty which seemed to attend the regular and con-
stant exhibition of those lights." Whatever may have been the
character of these objections in 1810, they have now no force, as
the economy and regularity of gas-lights have been established
by the experience of thousands. A single lighthouse-keeper is
perfectly able, in the time that he would spend in cleaning his
lamps, to manufacture the best coal-gas from cannel-coal, at the
expence of less than Jive shillings for every 1000 cubic feet, where-
as the same quantity of oil-gas is now sold from the pipe at fifty
shillings, and compressed oil-gas at eighty shillings #. Economi-

* The economy in oil, in wicks and in lamps, must be very considerable, and,
were it necessary, might be easily valued. In lighthouses which are near towns where
gas is compressed, and to which it could be sent by sea-carriage, portable gas might
be introduced with the most obvious advantage.

70 Dr Brewster on the Construction of Polyzonal Lenses

cal as coal-gas must necessarily be, it is not in this respect that
I wish at present to consider it. It is to its power of produ-
cing a more intense light, and a more effective system of illu-
mination, that I am anxious to direct the attention of the Socie-
ty. The advantages arising from the use of this gas may be
thus enumerated.

1. By the use of Gas, we may in many situations dispense en-
tirely with the use of Reflectors and of Lenses. — It has been found
by the French Commission, that the oil-lamp with four concen-
tric wicks gives a light fully equal to 22 good Argand burners.
I have constructed a gas-burner with four concentric flames,
which I consider equal to that number of Argand burners ; but if
it should be inferior, we have only to add another flame to the
four. In 1759, when the Eddystone Lighthouse came out of the
hands of the celebrated Smeaton till the year 1803, and proba-
bly later, it was lighted with 24 large tallow candles, without any
reflectors or concentrating apparatus. Now, it cannot be doubt-
ed that 22 Argand burners are fully equal to 24 large tallow
candles ; so that a single gas burner, with four or six concentric
flames, is sufficient to produce the same light which was exhi-
bited for 35 years at the Eddystone lighthouse, and which Mr
Stevenson informs us *, was seen at the flag-staff of the fort near
Plymouth. If this single burner, however, should not be found
sufficient, we have only to place beside it a second, a third, and
even a fourth, and we may convert it into a distinguishing light
by the revolution of coloured, opaque, and lenticular screens.

The expence of this flood of gas-light, emanating from four
burners, with from four to six concentric flames, or from one
burner with from 12 to 15, will, from the cheapness of coal-gas,
be not much, if at all, greater than that of 24 tallow candles.

* Edinburgh Encyclopaedia, Art. Lighthouse, Vol. XIII. p. 10.

far the purposes of llUanmatumc in Lighthouses. 71,

2. By the use of Gas, we may greatly improve the present sys-
tem of Illumination by means of Reflectors. — In all our lights
houses, an Argand b&rher with one wick is used,, because an en-
largement of ite size would cause a great divergency of the re-
flected light, and consequently, a greater diminution of its inten-
sity, than there would be an increase from the augmentation of
the flame. By the use of. gas, however, we can introduce a
burner with two or even three concentric flames, which will not
occupy, more space than a single Argand burner, and which
will, therefore, greatly improve the present system of illumina-
tion.

3. The use of Gas is peculiarly adapted to the new system of 11+
Imrination by. means of Lenses*— As the lenses employed in light*
houses will, in general vary from two to three feet in diameter*
the distance jo£ the lamp will also vary frota two to three feet,
which allows us to use a flame from two to foiir inches in dia-
meter! In oil lamps with concentric wicks, it is necessary to
supply the flame with supier abundant oil, by means of a piece of
clock-work ; and the lamp and machinery for this purpose cost
d§ 45. A gas burner, producing the same intensity of light,
may be executed for £ 3 or £ 4, and has, besides, the great ad*
vantage of never going out of repair ; whereas the French lamp
would require to be under the superintendence of a person well
acquainted with mechanism. Independent, therefore, of the
great saving of expence, the substitution of a gas burner is pe-
culiarly applicable in lighthouses, where the machinery is not
only liable to go wrong, but where it cannot easily be repaired

ly as possible,
Discouraging

72 Dr Brewster on tie Construction of Polyzonal Lenses.

as its first reception has been, it requires no prophetic spirit to
anticipate its early and complete triumph. I am aware of the
prejudices, and, I grieve to add, the sordid interests with which
it must contend ; but these are not the days in which the tide of
knowledge and improvement can be thus stemmed. The force of
reason will gradually dispel the one, and before the frown of pu-
blic opinion the other will disappear.

It is in Great Britain, if any where, that the lighting of her
shores ought to be an object of national concern. Her naval and
commercial pre-eminence, the sum of human life, and the a-
mount of valuable property which are risked at sea, call loudly
for every aid which science can confer. The ingenuity which
has been already exhausted, the humanity which has been al-
ready roused, and the national liberality which has been already
freely dispensed, in devising and promoting every scheme for
saving the shipwrecked mariner, cannot now receive a nobler
direction, than in rendering more effective those beacons of mer-
cy which light the seafaring stranger to our coasts, and warn
him of the wild shelves with which it is defended.

( 73 )

VI. On the Parasitic Formation qf Mineral Species, depending
upon Gradual Changes, which take place in the Interior of
Minerals, while their External Form remains the same.
By William Haidinger, Esq. F. R. S. Edin.

(Read 19M March 1827. J

JJjVERY mineralogist is conversant with some of the facts rela-
tive to the subject of this paper. Some of the observations enu-
merated, are comparatively new, as the attention of naturalists
has been only of late more particularly directed towards these
facts. Others, which I have had an opportunity of collecting
myself, I trust will not be considered uninteresting, as they tend
materially to rectify certain ideas connected with the determi-
nation of the mineralogical species, the most important branch
of natural-historical research.

The mutual attraction of the elements of mineral bodies, can-
not at present enter into play on so extensive a scale, as during
the period of the formation of those enormous masses of rocks,
particularly those having a crystalline character, which form a
great portion of our globe ; for these bodies are the result of the
very action of the elements on each other, by which they have
arrived at a settled state. There are some agents, however,
which we every day observe to affect, more or less considerably,
the constitution of certain minerals, more prone than others to
decomposition. Many species of the class of salts are continu-
ally destroyed by their solution in water, and regenerated by its
evaporation. Iron-pyrites, exposed to the alternating influence
of water, the oxygen of thex atmosphere, and the changes of tem-
perature produced in the natural course of the seasons, or by the

vol. XI. part i. x

74 Mr Haidinger on the Parasitic Formation

decomposition of the substances themselves, will effloresce, and
yield sulphate of iron. Heat, and the disengagement of power-
ful acids, in the neighbourhood of active volcanoes, and burning
coal-seams, give rise to the formation of a number of new sub-
stances, while those which existed before are destroyed. Usually
even the last trace which could lead us to discover, from what
source the new substances draw their origin is lost ; but there
are examples in which the form, peculiar to the crystals of the
decomposed substances, is entirely preserved, while the rest of
their properties undergo more or less notable changes. The
consideration of these constitutes the especial object of this
communication.

Mineral productions of the description alluded to, have been
comprised by most authors under the idea of pseudomorpAoses, a
name expressive of their nature, if we attend only to the etymo-
logy of that word, since, indeed, the form is not the one be-
longing to the substance ; but not agreeing with the definition
given of them, which requires that they should be produced by
the deposition of crystals in an empty mould, left in the sur-
rounding mass, by a decomposed crystal of another species.
The names proposed by Haut, 4piginiesr and by Breithaupt,
metamorphous crystals, are more objectionable than the usual
denomination, if we regard etymology ; and as they were nei-
ther circumscribed by accurate definitions, nor applied exclu-
sively to this kind of formation of substances, we need not be
over careful in making use of any of them, by preference,
particularly since difficulties might arise from the circum-
stance, that the effect of the decomposition is not always the
same, and that only some cases will be found, in which the en-
tire form is preserved, while it is considerably impaired, though
still recognizable hi others, and frequently altogether lost. If
we were to select a particular word for this kind of formation,
the most appropriate expression would be parasitic, to denote the

of Mineral Species. 75

intrusive nature of the new compounds, in prejudice of those
which existed before.

The facts met with in nature, are at all events highly in-
teresting, and deserve the particular attention of naturalists,
who should have an opportunity of ascertaining the circum-
stances under which they take place ; this may eventually com-
plete the series in which they are here considered, beginning
with the simplest case, when the substance formed has the
same chemical composition as the one destroyed, and termi-
nating in those where the composition of the two is so different,
that even the analogies of the cases will not suffice for removing
every doubt concerning their formation in the manner described.
One remarkable result, however, we obtain by this comparison,
that a new species is always produced, though its individuals be so
small, that they are beyond the reach of natural-historical exa-
mination.

I. Changes in substances having the same composition.

The chemical mixture, essential to the common vitriol of
zinc, is a dimorphous one, or one of those which are capable
of crystallizing in two different kinds of forms, incompatible
with each other. The most common of them is derived from
a scalene four-sided pyramid, which has its three axes per-
pendicular to each other, and is comprised in the prismatic
system. It is deposited from solutions not sufficiently concen-
trated to form a crystalline skin on their surface, and at tern*
peratures below 126° Fahrenheit. Above that temperature,
a highly concentrated liquid yields crystals of another spe-
cies, whose forms are derived from a scalene four-sided pyra-
mid, having its axis inclined on the base, and belonging to
the hemi-prismatic system. The chemical composition of both

k2

76 Mr Haidinger on the Parasitic Formation

2

substances is expressed in the formula by Berzelius, of Zn S
+ 14 Aq, which is derived from Mitscherlich's analysis of the
prismatic species, giving oxide of zinc 27.67, sulphuric acid
27,57, and water 44.76.

To Professor Mitscherlich we are likewise indebted for the
following curious fact *. When a crystal of the salt, with a
form belonging to the prismatic system, is heated above a tem-
perature of 126°, we may observe certain points at its surface
become opaque, and then bunches of crystals shoot out from these
points in the interior of the original specimen. Since this is
transparent, and the newly formed crystals almost opaque, or of
a milky whiteness, they are easily distinguished from the sur-
rounding 'mass, while they continue to grow. In a short time,
the whole is converted into an aggregate of those crystals, di-
verging from several centres, that are situated on the surface
of the original crystal. No water escapes during this process,
except what may have been accidentally included in the lamel-
lae of the specimen. This circumstance proves the identity of
the chemical composition of the two species, one of which is
formed within that space, which is occupied by the other up to
the very moment of the decomposition of the latter, which gives
rise to the new substance.

I have obtained crystals of the hemi-prismatic species, more
transparent than usual, by exposing, on a warm stove, a highly
concentrated solution of the salt, well covered and wrapt up,
to crystallization. The remaining liquid having been decant-
ed, the crystals obtained were dried and slowly cooled in the
same manner. If they are taken out of the solution singly,
and cooled rapidly, they soon lose their transparency, and, when
broken, frequently present an aggregate of crystals of the pris-
matic species, which is likewise immediately produced by drops

* Edinburgh Journal of Science, vol. iv. p. 301.

of Mineral Species. 77

of the solution remaining on the surface of the hemi-prismatic
crystals. Change of temperature is the only agent upon which,
in both cases, .the change of the position of particles within the
solid mass depends.

The isomorphism of zinc and magnium, is remarkably dis-
tinct in the regular forms, with all their peculiarities, and in the
cleavage, of their sulphates. But it extends even to the pheno-
mena, described above of sulphate of zinc. They both give
exactly the same results.

The specific gravity of the hemi-prismatic species has not
been ascertained. It is very probable that it does not mate-
rially differ from that of the prismatic species, as the change
from one to the other takes place without producing a consider-
able change in the appearance of the shape of the crystals.
When arragonite is exposed to heat, it becomes opaque, and
splits violently into multitudes of small particles, previous to its
giving off any of its carbonic acid. It is highly probable that
it is thus transformed into common calcareous spar, which re-
quires more space to exist in than arragonite, nearly in the ratio
of 29 to 27, their contents of carbonate of lime being equal, and
no attention given to the accidental and variable contents of
carbonate of strontia. Perhaps the separation of the particles is
assisted by the unequal expansion of the rhombohedral indivi-
duals in the direction of their axis, and perpendicular upon it.

I must mention here another example of the formation of
crystals in the place of a solid mass, consisting of the same che-
mical ingredients, as a product of the power of crystallization,
though the substance in which it occurs, is not comprised within
the generally received idea of a mineral. M. Beudant, I be-
lieve, first called the attention of naturalists to the fact, that the
whitish coat with which barley-sugar is covered, when it is kept
for some time, shews a fibrous structure, the direction of the

78 Mr Haidikger on the Parasitic Formation

fibres being perpendicular to the surface of the specimens. When
the decomposition, which here only affects the form and ar-
rangement of particles, is allowed to proceed farther, crystals of
sugar-candy are formed in the space forfnerly occupied by a ho-
mogeneous mass which presented the most perfect conchoidal
fracture, and not a trace of crystalline structure.

II. Changes dependent upon the presence of Water.

Haut's Chaux sulfatee epigene, is a substance familiar to
every mineralogist, as it is found in great quantities, and is to
be met with in almost every collection. His view of it is per-
fectly correct : it was anhydrite, and is changed into gypsum,
by combining with a portion of water. The original cleavage
planes, still discoverable in the white, opake, and faintly glim-
mering masses, would give no argument of weight for uniting
the two species into one ; and yet considerations of this kind
have induced some mineralogists to join blue copper and mala-
chite into one species. These traces are not, however, produced
by cleavage, which is the mere tendency of the particles of anhy-
drite to separate more easily in certain directions than in others ;
but they are owing to actual fissures in the direction of the planes
of cleavage, visible in every fresh or not decomposed variety of
the species. On these fissures, and still more distinctly on some
larger irregular ones traversing the masses, distinct crystals of
gypsum are formed. Of the latter, I have seen several speci-
mens from Aussee in Stiria, in the collection of Gratz. The
decomposed individuals are much smaller in these than in the
varieties from Pesay in Savoy, described by HaAy.

The absorption of water from the atmosphere, in saline sub-
stances, is usually attended with a solution of the latter in the
water so attracted ; that is to say, they deliquesce, and change

of Mineral Species. 79

their form, in passing from one state of aggregation into another.
The reverse also very frequently takes place. Crystals efflo-
resce by losing their water, and are converted into a loose mass
of a pulverulent consistency, which retains the original shape,
but readily gives way to the pressure of the finger, and falls
into powder. Prismatic glauber-salt, prismatic natron-salt and
others, are familiar examples of this change. Many more
might be quoted of the numerous cases of what chemists call
spontaneous decompositions, depending upon loss of water, oxi-
dation, &c. Among a great many facts of a similar nature, ob-
served by Professor Mitscherlich, during my stay in Berlin in
the winter of 1825, 1 shall mention here a very interesting one,
in which a crystallized substance was formed within another, by
the application of heat, and a loss of water thereby occasioned.
He exposed crystals of hemi-prismatic vitriol-salt, the ordinary
hydrous protosulphate of iron, immersed in alcohol, to a degree
of temperature equal to the boiling point of that liquid. De-
composition ensued, though the external shape of the crystals
remained unchanged. On being taken out of the liquid, and
broken, each of them was found hollow, and presented a geode
of bright crystals, deposited on the planes of the original ones.
The crystals had the form of low eight-sided prisms, belonging
to the prismatic system, and were proved by analysis to contain
exactly half the quantity of water which is required in the mix-
ture of the original species.

III. Changes in Minerals containing Copper.

Mineralogists are very generally acquainted with the crystals
from Chessy in France, having the form of blue copper, but con-
sisting of fibrous masses of malachite. Such varieties are found
in that locality, as well as perfect homogeneous crystals > but

80 Mr Haidinger on the Parasitic Formation

only extensive collections, or the large quantity gathered and
preserved on the spot, both of which I had the good fortune to
examine, will allow of observing perfect and continuous passages
from one extreme to the other. The series begins with such
crystals as not only possess the shape of the blue copper, but
likewise consist of that substance, with the exception of small
particles of the green fibrous malachite, which appear like some-
thing foreign, accidentally imbedded in the otherwise homoge-
neous mass. It terminates in such varieties as scarcely betray
the original shape of the hemi-prismatic crystals, the last blue
particles having disappeared, and the fibres grown out even be-
yond the original surface of them, and shewing disengaged crys-
talline terminations. The intermediate members distinctly pos-
sess the shape of crystals of the blue copper, nay, they have oc-
casionally even particles of the original substance here and
there distributed over their surface, which, to the last, preserve
a parallel position. These particles are not displaced by an in-
crease of bulk of the newly formed species. The chemical diffe-
rence between the two species is not considerable. Several ana-
lyses published by Klaproth, Vauquelin and Phillips, agree
very nearly with the formulae proposed by Berzelius, which are,

Cu Aq* + 2 Cu Cf, for the blue copper, and Cu C + Aq
for the malachite. The proportions of the ingredients are,

Blue Copper. Malachite.

Oxide of Copper, - 69-16 71-89

Carbonic Acid, - 2561 1996

Water, - - 523 8- 15

»

The change effected during the process of decomposition is
the loss of a portion of carbonic acid, which is compensated by
an additional quantity of water. If the formulae above men-
tioned are resolved into their constituent parts, as given sepa-
rately in the analysis, the blue copper is composed of three

of Mineral Species. 81

atoms of oxide of copper, two of water, and four of carbonic acid,
while malachite contains three atoms of each. One atom of
carbonic acid is therefore exactly replaced by one of water.

Haut does not consider the crystals formed by aggregated
masses of the green filamentous malachite as 6<pigenies of the
blue copper, as he unites the two species into one, and rejects
the slight difference in the results of the chemical analysis as ir-
relevant. Beddant seems to be the first naturalist who viewed
this process of decomposition in a proper light *.

Not only the blue copper, but also the imbedded octahedrons
and dodecahedrons of octahedral copper-ore, are found in that
locality in a state of incipient decomposition, resembling it in so
far as the form of the crystals is not altered. There is one cu-
rious difference, however, in the progress of this decomposition.
In the octahedral copper-ore, the surface first turns green by
the absorption of oxygen and water, since the protoxide is con-
verted into a hydrate of the peroxide, and then the decomposi-
tion penetrates deeper into the mass, whereby a more or less
considerable coating of compact malachite is formed ; whereas
the reverse takes place in blue copper, the surface of the crystals
being the last portion which is converted into malachite, since
the decomposition begins from the point of support. There are
crystals of an octahedral form, which consist, near the surface, of
fibrous malachite, of the same kind as that which often consti-
tutes the body of crystals, having the shape of blue copper ; they
generally contain a nucleus of octahedral copper-ore, not decom-
posed. A dodecahedral crystal of octahedral copper-ore, changed
into blue copper on the surface, is preserved in Mr Allan's ca-
binet ; but such examples are rare.

The cuivre hydrosiltceux of Hauy, comprehending chry-
socolla, is a species not yet well established, as the crystals

* Traiii de Mintralogie, p. 158.
VOL. XJU PART I. L

82 Mr Haidinger on the Parasitic Formation

usually observed in collections are not in a . determinable
state. They are for the greater part converted into malar
chite, but their angles shew, that, in their original state,
they have not beep blue copper. I haye seen crystals in
Mr Allan's cabinet, pretty distinctly pronounced, in the shape
of compressed six-sided prisms, the narrow faces meeting at
angles of about 1 12° ; and the narrow with the broad faces at
angles of about 122° and 126° ; from which it appears that the
original substance, as to form, belongs to the hemiprismatic or
tetartoprismatic systems. There is an angle in Haiti's description
of 122° 19', situated like the one of 122° ; but the fundamental
prism being supposed to be a right rhombic one, the other two
angles of the derived six-sided prism follow to be 115° 22/, and
122° 197. Besides, Hauy gives a specific gravity of 2.73d to his
crystals, while the varieties of chrysocolla never go beyond 2.2.
I know only of one specimen, with crystals apparently homoge-
neous, and resembling chrysocolla, engaged in a pale-brown
clayey substance. It forms part of the magnificent collection
of Mr Behgemann of Berlin, who intended to subject it to a
chemical analysis, while Professor Gustavus Rose was to exa-
mine its mineralogical, and particularly its crystallographic cha-
racters. We haye therefore to look to the ability and zeal of
the Berlin mineralogists and chemists, for more accurate infor-
mation regarding this remarkable substance.

The blue oap)pet9 ground to an impalpable~powder, is employ-
ed as a blue painty of a very bright tint, paler than the mineral
itself. It is not, however, highly valued, because it 'is apt to
lose its original colour, and to turn green* This is mentioned
by Hauy, who quotes authorities, as old as Wallerius and Bora-
tius be Boot, for the colou? obtained from the Armenian stone
of the ancients #. ' The decomposition of the blue pigment is a

* Traiii, &* edit. t. Hi. p. 608.

of Mineral Species. 83

ease exactly similar to that of the blue crystals, as presented by
the specimens found in mines.

Copper, in its pure metallic state, when exposed to the action
of the atmosphere, variously combines with the elements contain-
ed in that fluid. I have seen remains of Egyptian vessels, in the
possession of Major Steuart of the Hon. E. I; C. service, which
had formerly consisted of copper or bronze, and still presented the
exact outline of their original shape, with a pretty smooth sur-
face. Some of the fragments were nearly one-fourth of an inch
thick, but so complete was their disintegration, that they could
be easily broken across with the hands, presenting on their frac-
ture a compound mass full of small drusy cavities. In these the
octahedral crystals of the copper-ore, of which the whole mass
consisted, were distinctly visible. The curved surface of most of
the vessels was covered with atacamite, sometimes crystallised,
particularly on the concave sides. There were some white
patches also, which I did not then examine. During his resi-
dence in the Ionian Isles, Dr John Davt * paid much atten-
tion to similar changes, which have taken place in antique
Greek tumour and coins. He found that the substances forming
green, red and white spots on the surface of these articles, which
consisted of alloys of copper and tin, were carbonate and submu-
riate of copper, octahedrons of protoxide of copper, and of pure
metallic oopper, and oxide of tin. In several instances, there was
no metallic copper formed, and the protoxide was blackened by
an admixture of peroxide. Since it cafinot be supposed that the
substances formed on the surface of these bronze articles, were
deposited from any solution, Dr Davt infers, that an internal
movement of the particles must have taken place, caused by the
influence of electro-chemical powers. Dr Davy's opinion, that
such considerations will explain many phenomena, occurring in

+ Philosophical Transactions for 1826, p. 55.

L2

84 Mr H aiding er on the Parasitic Formation

the mineral kingdom, is shewn to be perfectly correct, by the
facts collected in this paper. In the native copper, I never
could observe any such changes, though I have examined a
great number of specimens with the view of discovering them ;
probably we have to attribute to the admixture of tin, and the
electro-chemical action dependent upon the contact of the two
metals, the greater disposition of bronze, to form new compounds
with the elements contained in the atmosphere, and in water.

There are several species into the composition of which sul-
phuret of copper enters as one of the most important ingredients,
such as the prismatic copper-glance, or vitreous copper, and the
octahedral and pyramidal copper-pyrites, or the variegated cop-
per and copper-pyrites. All of them are more or less subject to
successive changes in their chemical constitution, while the form
in some cases remains, and in others is entirely lost. Mr Allan
is in possession of a very interesting and numerous series of
copper ores, which he collected chiefly in the summer of 1824,
on a journey in Cornwall, in which I had the pleasure of accom-
panying him. This series has given me an opportunity of noti-
cing several peculiarities, which had not been mentioned before
by mineralogists.

Dark-grey crystals of copper-glance, with a bright metallic
lustre, are often deposited on low six-sided prisms, which have a
tarnished surface. These, in respect to form, entirely agree with
the crystals of the other species ; their surface; however, is never
perfectly smooth, and on breaking them, they do not present
throughout a uniform appearance. Generally the portions near-
est the surface consist of the reddish metallic substance of varie-
gated copper, having an uneven fracture, while the rest possess
the grey colour, and perfect conchoidal fracture of the copper-
glance. Often, and particularly in thin plates, the whole shews
the appearance of variegated copper, whereas in large crystals,
the two species are more or less irregularly mixed up with each

of Mineral Species. 85

other. These prisms are sometimes more than an inch in
diameter, but are usually smaller. The copper-glance, which
originally occupied the regularly limited space, has been suc-
ceeded by variegated copper. The arrangement of the por-
tions of both species in successive coats, shfews that the decom-
position has proceeded from the surface.

On breaking some of the six-sided prisms here alluded to, I
found a stratum of copper-pyrites, of its usual bright yellow co-
lour, contiguous to their surface, while the rest consisted of va-
riegated copper. The original form had here still been preserv-
ed ; but a new change in the chemical constitution had con-
verted the variegated copper into copper-pyrites. The peculiar
twin-crystals, discernible in groups of six-sided plates, crossing
each other at nearly right angles, and the distinct form of the
six-sided plates themselves, leave no doubt that two of Mr Al-
lan's specimens, consisting entirely of copper-pyrites, owe their
origin to the decomposition of copper-glance. One of them is
covered with a black pulverulent oxide ; but the surface of the
other is perfectly bright, and of a fine brass-yellow colour. It
presents to the observer the deceitful and puzzling appearance
of copper-pyrites crystallized in nearly regular six-sided plates.
No cleavage can be traced ; but this being not easily obtained
in any of the species, it cannot form, in the present instance, a
sufficient distinctive character between the simple and com-
pound minerals.

The variegated copper itself occurs in distinct crystals, mostly
small, which are hexahedrons. Some larger ones, but with curved
and irregularly formed faces, occur in regular compositions, si-
milar to those of fluor, twins being produced by two individuals,
which may be supposed in transverse position to each other, in re-
ference to one of the rhombohedral axes of the hexahedron. Each
of these groupes contains in its interior a six-sided prism, whose
smooth surfaces may be relieved from the surrounding homoge-

86 Mr Haidinger on the Parotitic Formation

neous mass* merely by breaking off the latter. The Jx>sition of
this prism is such, that its planes, within the angles different
from 120% agree in position with the prism R+oo , which is the
limit of the series of rhombohedrons, the hexahedron shewing
here the properties of this form in regard to the principal axis of
the enveloping twin-crystals of variegated copper. There is a
face of the hexahedron contiguous to every lateral face of the
six-sided prisms ; nay, it is possible that the existence of the
twins depends upon that of the prisms, which might exercise a
considerable influence in the deposition of the particles of the
species of variegated copper. The substance of the prisms
themselves is likewise variegated copper ; they are divided into
thin laminae parallel to the base of the prisms, having external-
ly a black colour, and scarce any lustre, but presenting the
usual appearance of variegated copper, when broken across.

The. original form is generally lost, when the decomposition
proceeds farther. In this case, what is usually called black
copper will remain, a more or less pure peroxide of copper,
in pulverulent masses. A specimen in the collection in Grate,
from the Bannat, with crystals of the form of copper-glance,
changed into this substance, is the only one I remember ever
to have met with, in which the change has proceeded so far,
without at the same time altering the form. It is probable
that it has taken place immediately, and not proceeded through
the stages of variegated copper, and copper-pyrites* though both
of them, when decomposed, will likewise yield a black powdery
residue.

The prismatic copper-glance is a pure sulphuret of eopper,
whose composition is expressed in Beneeuus's chemical formu-
la Cu S, the two ingredients copper and sulphur being in the
ratio of 7973 and 20*27. Most analyses give a slight quantity
of iron.

According to the analysis by Mr Richard Phillips, of a

of Mineral Species. 87

specimen of variegated copper from Ireland, this species is com-
posed of one atom of protosulphuret of iron, and four atoms of
sulphuret of copper, or Fe S* + 4 Cu S. The three ingredients,
copper, iron, and sulphur, are in the ratio of 62*67, 13*44, and
23-89.

The composition of copper-pyrites, from the analysis of Pro-
lessor Henry Ross, might be considered as being essentially one
atom of protosulphuret of iron, and one atom of a sulphuret of
copper, containing twice as much sulphur as the native sulphu-
ret, which forms the species of prismatic copper-rglance. Fro-
fessor Rose is of opinion, however, that the copper contained in
the mineral is in combination only with one atbm of sulphur,
as in other species, and that the whole mixture should, be consi-
dered as a compound of one atom of protosulphuret of iron, one
of persulphuret of iron, and two of the suiphuret of copper.
The chemical formula ie Fe 3* + Fe S4 +2 CuS, and the ra-
tio among the ingredients, capper, ijjon and sulphur, is 34.80,
29.83, and 35.37.

The changes, therefore^ can be explained, upon* the supposi-
tion that the copper contained in the original species has been
replaced by iron, i» a smaller quantity, however, as every par-
ticle of iron required twice the qgantity.of sulphur to be convert-
ed into, protosulphuret, in; the variegated: coppef , and: four times
the quantity for that portion of it in the copper-pyrites, which is
in the state of persulphuret. The compound of protosulphuret
and persulphuret of iron, which, in the last species, is joined to
the sulphuret of copper, is one of .those forming the chemical con-
stitution of magnetic pyrites- .

When1 the. sulphur is entirely driven qJ£ «od the copper at-
tracts so much oxygen as . to be: converted into the peroxide,
black copper bemaind; ••• iRurmg this process, also, some of the
carbonate is frequently formed.

88 Mr Hai dinger on the Parasitic Formation

IV. Changes in Minerals containing Iron.

Through the exertions of the late travellers in Brazil, we
have become acquainted with octahedral crystals, often of consi-
derable magnitude, of a particular ore of iron. They afford a
red streak, and should seem, therefore, together with other in-
stances of the same kind that had been observed, to form a con-
tradiction to the character given for the species of octahedral
iron-ore in the Characteristic of Mohs #, namely, that it should
have a black streak. On a more close inspection, however, the
octahedral masses are found to be composed of a great number of
small crystals, resembling those of the rhombohedral iron-ore, a
species, one of whose characters is in fact the red streak ob-
served. A specimen from Siberia, given to Mr Allan by Sir
Alexander Crichxon, presents the same change, excepting
that in this specimen the individuals of the rhombohedral iron-
ore are so minute, that they form a compact mass, contained
within smooth planes, having the situation of the faces of a re-
gular octahedron. As in the decomposed anhydrite, these planes
are not the remains of cleavage, but they existed in the octa-
hedral iron-ore previous to its decomposition, as fissures parallel
to its octahedral cleavage. The chemical change necessary for
transforming the mixture of octahedral iron-ore into that of
rhombohedral iron-ore, is a very slight one, the former being
a compound of one atom of protoxide and two of peroxide

of iron, expressed by Berzelius's formula Fe + 2 Fe, while the

• ••

latter is the pure peroxide, or Fe. The relative contents of oxy-
gen are 28.215 and 30.66 per cent. There is a group of crys-
tals from Vesuvius in Mr Allan's cabinet, elucidating, by their

* Treatise on Mineralogy, Transl. vol. i. p. 439.

of Mineral Species. 89

coarser texture, the explanation given of the Brazilian octahe-
drons. The rough form of an octahedron is produced by very
distinct flat crystals, united in various positions, of the rhom-
bohedral species, the face perpendicular to the axis of the fun-
damental rhombohedrons being much enlarged. Some of them
have their broad faces in the direction of the faces of the oc-
tahedron ; and in some of the octahedral groupes, this circum-
stance has produced a kind of raised reticulated appearance on
the adjoining faces of the original octahedron, which the newly
formed crystals intersect, and project beyond them.

The changes which affect the brachytypous parachrose-ba-
ryte, or sparry iron, deserve our particular notice, as they are
not only highly interesting in themselves, but have been well
attended to at all those places where this species forms the pre-
dominant ore of iron. The characteristic chemical ingredient
of it is the carbonate of iron, Fe C*, in which the protoxide
of iron and the carbonic acid are in the ratio of 61.47 and 38.53.
It contains occasionally an admixture of the carbonates of lime,
magnesia and manganese. The colour of the original varieties
is usually a pale yellow, inclining to grey : the lustre and trans-
parency are considerable. When left exposed to the action of
the atmosphere, the surface soon assumes a brown tint, which
by degrees penetrates deeper into the substance of the crys-
tals. Some lustre even then remains, and cleavage is still obser-
vable. Specimens bounded by fissures on all sides, or broken out
of a solid mass, when examined in this stage of their decompo-
sition, often still contain a nucleus of the yellowish-grey undecom-
posed substance. When the decomposition has arrived at its end,
every trace of cleavage has disappeared, the fracture of perfectly
well pronounced crystalline shapes is uneven, or earthy, and the
colour a dark brown, which is likewise visible in its streak. The
substance now consists of a compact variety of the hydrate of per-
oxide of iron, whose chemical composition is expressed in the

VOL. XI. PART I. M

90 Mr Haidinger on the Parasitic Formation

• • •
formula 2 Fe + 3 Aq, and which contains 14.7 per cent of wa-
ter. One atom of the carbon contained in the original com-
pound will therefore go away in the state of carbonic acid, while
the other must be transformed into oxide of carbon, in order to
convert the protoxide of iron into a peroxide. The change in
those masses has taken place so insensibly, that the action of
the power of crystallization was prevented, and the interior pre-
sents a pretty uniform texture ; but, at the same time, some par-
ticles of the hydrate of iron commonly also follow their own innate
attraction, and form geodes of brown hematite, that is, of prisma-
tic iron-ore. Hiittenberg in Carinthia has perhaps no equal in
illustrating the exactness of this explanation, for the distinct-
ness of the specimens which it affords. The geodes occucring at
that place, of various sizes, are very frequently adorned with
crystals of arragonite, of calcareous spar, of prismatic manganese-
ore, or with the silvery flakes of another manganesian mineral,
whose exact chemical composition has not yet been ascertained.
With the decomposition of the sparry iron is also intimately con-
nected the formation of those beautiful coralloidal varieties of
arragonite known by the name of flos ferri, which are found in
caverns near the surface of the rocks, as at Eisenerz in Stiria.

The ankerite, or paratomous lime-haloide of Mohs, is al-
so apt to be decomposed in a similar manner. But as it is a
compound of the carbonates of lime and iron, in which the for-
mer amounts to more than half the weight, only what might be
termed a skeleton of the hydrate of iron remains, while the rest
of the ingredients disappear by the action of chemical agents.
The texture of the remaining mass is much less compact than
that of the residue left by the decomposition of the sparry iron.

The product of the decomposition of the two species last
mentioned, is exactly the same as the substance which remains,
when iron-pyrites suffers a decomposition, without changing its
form. Both species, the hexahedral and the prismatic iron-py-

of Mineral Species. 91

rites, having the same mixture, are also subject to the same
change : the sulphur goes away, and the iron takes up oxygen
and water ; the decomposition proceeds from the surface. We
often see crystals covered on the surface with a brown tarnish,
and this is the first 'stage of the change. There are specimens
with a thin coat of the hydrate of iron ; there are others consist-
ing almost entirely of the latter, with only a nucleus left of the
original bisulphuret of iron. Such are found at Wochein in Car-
niola, where this hydrate of peroxide of iron, produced from the
decomposition of the bisulphuret, occurs in such abundance and
pureness, that it is melted as a very valuable ore of iron. The
iron extracted from it is particularly remarkable for its softness.

V. Changes in Minerals containing Lead.

The mineral called Native Minium is probably, in every in-
stance in which it has yet been observed, the product of decom-
position of some other substance containing lead. Such is the
variety which M. Bergemann of Berlin found in the lead mines
of Kail, in the Eiffel in Germany, where the ore, chiefly the sul-
phuret and carbonate of lead, is dug out in irregular masses,
from the loose earth, to the inconsiderable depth of a few fa-
thoms. To him I have been indebted for several distinct crys-
tals, possessing the regular forms of the di-prismatic lead-bary te,
not only in regard to the simple prisms and pyramids of which
the combinations consist, and the striae on the surface of some
of them, but also in regard to the identical mode of being joined
in twin-crystals. The beautiful red colour, which, in these com-
pact masses, much more nearly approaches the colour of vermi-
lion, than in the best varieties of the usual minium in the state
of powder, and the apparent homogeneity of the mass in the

m 2

92 Mr Haidinger on the Parasitic Formation

conchoidal fracture, together with the external crystalline ap-
pearance of it, at first rendered it extremely probable that this
was actually a species of original formation ; a supposition which
proved to be erroneous, on the substance being more accurately
examined. In the present case, it is carbonate of lead, or Pb C%
according to Berzelius's formula, corresponding to 83.52 oxide

of lead, and 16.48 carbonic acid, which is changed into the red

in

oxide of lead, or Pb, containing 10.38 per cent, of oxygen. In
order to explain this change, we must suppose, that of the two
atoms of carbon contained in the original compound, one goes
away in the state of carbonic acid, and the other in that of oxide
of carbon, one of the atoms of oxygen being employed to convert
the yellow oxide contained in the carbonate of lead into red oxide.
The best artificial minium is obtained by a change exactly ana-
logous to what we find in nature. Carbonate of lead, in the state
of an impalpable powder, is exposed to heat, care being taken to
stir it continually, in order to renew the surface exposed to the
air. If crystals of the di-prismatic lead-baryte be heated in a
glass tube, the first application of heat changes them into a red
mass, which, however, at a higher temperature, loses an addition-
al portion of oxygen, and becomes yellow on cooling. It then
contains lead 92.83, and oxygen 7.17, and is Pb, or protoxide of
lead.

The hexahedral lead-glance, consisting of one atom of lead
and two of sulphur, Pb S*, in the proportions of 86.55 and
1 3.45, is very liable to decomposition by means of the natural
agents. There are examples of compact varieties of prismatic
lead-baryte formed by its decomposition, and still presenting the
traces of fissures parallel to the hexahedral cleavage planes of the

original species. The prismatic lead-baryte consists entirely of

« » • • •

sulphate of lead (Pb S*), in which the two ingredients, lead and
sulphur, are in the same ratio as in the lead-glance : the two species
are chemically distinguished from each other only by the presence

of Mineral Species. 93

of the oxygen in the sulphate. The form of the hexahedral lead-
glance, however, is not always recognizable in the products of its
decomposition, though there can be no doubt, that, in many cases,
the numerous crystalline species of the genus lead-baryte are form-
ed in this way in the veins. Those who might be still inclined to
doubt, should visit the repositories of these species at Lead-hills,
a place conspicuous in the annals of the mineral collector for the
beauty of the specimens with which his cabinet is adorned. They
occur there in a vein in grey wacke, filled with a clayey mass, in
which nodules of the minerals containing the lead are imbedded.
On their outside, they are almost uniformly covered with crystals
of the carbonate, more rarely of the phosphate, of lead. In the
drusy cavities which they include, are deposited the rarer species
of the sulphato-carbonate, the sulphato-tri-carbonate, the cupreous
sulphate, and the cupreous sulphato-carbonate, and likewise the
phosphates and sulphates of lead. These cavities also are fre-
quently lined with fine crystals of the carbonate itself. A piece
of the sulphuret, with bright cleavage planes, is often discovered,
engaged among all these species, whose formation so much de-
pends upon its previous existence. In such cases, we find the
sulphuret corroded and rounded, presenting a surface nearly si-
milar to that of hexahedral rock-salt, or gypsum that have been
exposed to the dripping of water. The space between it and
the external coating is often filled with water, when the nodules
are found in the mine. Mr B aires then surgeon at Lead-hills,
gave a pretty complete account of the changes by which the oxi-
dized species are formed from the sulphuret *.

Miners pretty generally have an opinion, that the contents of
metallic veins are not always the same, and that they are often
working such as are not yet ripe, or would have been more pro-
ductive, if attacked at a later period. This opinion is founded

* Memoirs of the Wernerian Natural History Society, vol. iv. p. 508.

94 Mr Haidinger on the Parasitic Formation

chiefly on a belief, that blende is changed into lead-glance. We
are not entitled by observation to admit of such a change ; and
though in this manner it does not appear that we can come too
soon with our mining operations, we see plainly that at least, as
at Lead-hills, we may come too late ; for that vein which now
contains the carbonates, and sulphates, and phosphates, must have
been once replete with the much more valuable sulphuret of
lead. Evidently, also, those among the Freiberg veins have been
opened too late, which now are found to contain the large six-
sided prisms of iron-pyrites, produced by the decomposition of
that valuable ore, the brittle silver, or prismatic melane-glance of
M ohs ; this, at least, is the only species to which we can attri-
bute the shape of those prisms, although they themselves remain
in some measure problematical.

The changes are not at an end, even with the complete
destruction of the sulphuret. I must in particular mention
three cases, all of them in specimens from Lead-hills, in the
cabinet of Mr Allan, in support of this observation. One
of them has distinctly the form of large, perfectly recogniz-
able crystals, with a rough surface, however, of die prisma-
tic lead-baryte. The whole of the substance of the crystals

is a granular tissue of minute crystals of the di-prismatic

• • • ••

lead-baryte. The sulphate, Pb S8, containing 73.56 per cent,
oxide of lead, has been here converted into carbonate, PbC*,
which contains 83.52 per cent, of the same ingredient. The
form in the second case is that of the low six-sided prisms of the
axotomous lead-baryte, with pretty smooth surfaces. Its sub-
stance is an aggregated mass of crystals, likewise of the di-pris-
matic lead-baryte, but presenting in their distribution much re-
semblance to the mode in which the individuals of malachite are
arranged, which replace the crystals of the blue copper. The sul-
phato-tri-carbonate has here given way to the carbonate of lead.
The third specimen, like the preceding one, has the form of the

qf Mineral Species. . 95

axotomous lead-bary te ; but, beside white crystals of the di-pris-
matic, also yellow ones of the rhombohedral lead-baryteare found
to occupy the space originally taken up by the axotomous lead-
baryte. Here the carbonate and the phosphate have replaced
the sulphato-tri-carbonate of lead.

A very interesting change of the sulphuret of lead into a gra-
nular mixture of carbonate and phosphate, was mentioned to me
by M. Von Weissenbach of Freyberg, who had first observed
it, and who likewise shewed me the specimens he had collected
on the spot, at the mine called Unverhofft Gliick an der Achte,
near Schwarzenberg in Saxony. The original forms of the lead-
glance, regular octahedrons, were still distinctly visible ; but they
consisted of a tissue of white and green crystals of the di-pris-
matic and rhombohedral lead-baryte. There was a black friable
residue left, which was considered as friable lead-glance. Such
a substance is often left on the surface of decomposing lead-
glance, where, even in the portions that yield to the pressure of
the nail, and soil the fingers, some traces of cleavage continue.
Very good examples of it occur at Mies in Bohemia, along with
the well known large crystals of carbonate of lead. Selb also
observed black di-prismatic lead-baryte in the shape of cubes,
originating from, and containing particles of, lead-glance, from
the Michael mine in the territory of Geroldsegg in Swabia *

The changes described above are not of a rare occurrence in
the various mining districts, not only in such where the works
are carrying on in actual veins, but also in those which are si-
tuated in metalliferous beds. It has been very generally ob-
served, that such mineral repositories yield crystals chiefly in
4heir upper levels, and that they are found more compact when
the works are carried to a greater depth. They follow in gene-

• Leonhard's Handbuch der Oryktognosie, 2d edit. p. 293.

96 Mr Haidixger on the Parasitic Formation

ral from the oxidation of the original substance, t have seen
only one example of the contrary, which was shewn to me by
Professor Hausmann, in the museum at Goettingen. Impres-
sions, of a hexahedral form, produced by lead-glance, contained
a residue, of a very loose texture, of native sulphur. This spe-
cimen was found in Siberia. '

The mineral usually designated by the name of Blue Lead,
is in some respects the converse of the changes considered above.
Its forms are those of the rhombohedral lead-baryte, namely, re-
gular six-sided prisms. The compound of phosphate of lead and
chloride of lead, of which their substance originally consisted,
has given way to the sulphuret, which usually appears in granu-
lar compositions, filling the crystals. The first varieties that
were noticed by mineralogists, were those from Tschopau in
Saxony. I remember having seen specimens of it, entirely con-
sisting of compact galena, but I have not had an opportunity of
comparing any again, after having examined some of the other
varieties of the same substance. At Huelgoet in Brittany, six-
sided and twelve-sided prisms are found, often upwards of an
inch in length, and nearly half an inch in thickness, which con-
sist of a coarse-grained compound variety of lead-glance, the
component individuals being so large that it is very easy to
ascertain their hexahedral cleavage. Sometimes these indivi-
duals have one of their hexahedral faces of crystallization co-
incident with the original surface of the hexagonal prism. The
stratum of lead-glance contiguous to the surface of the origi-
nal crystal, is usually separated from the body of it by an empty
space, so that it may be very easily broken off. Sometimes only
this stratum is in the state of lead-glance, while remains of the
original species are still visible in the interior, or part of the crys-
tal only has begun to have a portion contiguous to the surface
converted into lead-glance, while the rest presents the ada-
mantine lustre and brown colour of the rhombohedral lead-ba-

of Mineral Species. 97

ryte. In the six-sided prisms of the same kind of formation
met with at Wheal Hope in Cornwall, generally a film of lead-
glance is also observed near the surface; but the crystals of
the suphuret in their interior are often much more curiously ar-
ranged. Partly they are simply composed of a mass of very com-
pact galena, partly also they present, when broken, the appear-
ance of being cleavable with great facility perpendicular to then-
axis, and at the same time also parallel to the sides of the six-
sided prisms, and parallel also to the planes replacing their edges.
The smooth planes obtained in this manner, are actually the
faces of cleavage of the hexahedron peculiar to lead-glance. The
individuals of the sulphuret namely, gradually formed in the
crystal of the phosphate, assume such positions, that two of their
feces are parallel to the sides, and two to the terminations of
the six-sided prism ; the two remaining ones will be perpen-
dicular to the lateral and the terminal faces. The direc-
tion of them appears distinctly in the annexed sketch of the
transverse section of a crystal, as indicated by the lines parallel
and perpendicular to the sides of the hexagon.
On breaking the prisms, we obtain fractures
situated like the line abed, which I have
sometimes observed, giving a clear demon-
stration of the actual composition of the
crystal in the manner described. Generally
the portion adjoining the centre, as it were
the axis of the prism, consists of perfectly
compact lead-glance, provided the original species has entirely dis-
appeared ; then comes a more or less considerable stratum of the
cleavable mass, which, however, is often wanting ; and then a coat-
ing of a coarser texture. From the mere arrangement of the par-
ticles, it is placed beyond a doubt, that the crystals of the sulphuret
have not been formed in moulds from the phosphate. They are
probably the product of the gradual decomposition of the latter

VOL. XI. PART I. n

98 Mr Haidingeh on the Parasitic Formation

by sulphuretted hydrogen, an explanation which was first pro-
posed by Rome' de l'Isle, even though the *pal chegiiflfcl com-
position of the rhombohedrai lead-baryte was thenupkitown, to
account for the appearances which he so well describes *. Such *
decomposition easily takes place even at the common temperature
of the atmosphere, if a stream of sulphuretted hydrogen i# allow-
ed to paw over the brown variety from Huelgoet, reduced to
powder. Both the phosphate and the chloride of lead are de-
composed, sulphuret of lead is formed, while the oxygen, phos-
phorus and chlorine are carried off, forming hydrophosphoric and
hydrochloric acid and water.

VI. Changes in Minerals containing Manganese.

m

The ores of manganese have not yet been sufficiently exa-
mined, in regard to their chemical composition, to allow us
clearly to establish the changes that take place in what may be
rightly supposed the decomposition of the prismatoidal manga-
nese-ore. I have shewn on another occasion f , that the tegular
forms belonging to that species, are properly found in specimens
having a brown streak, a degree of hardness equal or superior to
that of fluor, and a specific gravity contained between the limits
of 4.3 and 4.4, but that the same form is often united to the cha*

s *

racter of a black streak, a degree of hardness lower than that of
calcareous spar, and a specific gravity often approaching to 4.7.
These latter varieties frequently form a coat round the former ;
and a crystal whose internal particles afford a brown streak, may
give a black streak when the experiment is tried with the out-
ward layers. The form remains the same, and even cleavage con-

«

* CristaOographie, vol. iii. p. 400.

f Edinburgh Journal of Science, vol. iv. p, 41.

of Mineral Species. 99

iiftties, in thtt&e £art* whose streak is black ; nay, it deems to be
more easily obtained, particularly the faces parallel to tile short
diagonal of the prism of 99° 4C. From chemical considerations,
Professor Leopold Gmelin had formed nearly the same opi-
nion in regard to a change of composition within the crystals or
crystalline masses of one of the species. One of them is a hy-
drate of the oxide of manganese, and that is the prismatoidal
manganese-ore, giving a brown streak;/ the other is the hyper-
oxide, formed by loss of water and absorption of oxygen, and it
gives a black streak. Hitherto ho crystals of the latter substance
have been described, that did not depend upon the previous ex-
istence of the prismatoidal manganese-ore. Professor Gustavus
Rose of Berlin shewed me small crystals, having the form of right
rhombic prisms, with their acute lateral edges replaced, and mea-
suring 86° 9Xf and 93° 4C, a prism not to be found in any of the
known varieties of the former species. But the faces not being
very bright, and the measurements therefore not quite decisive,
inferences drawn from the observed difference in the angles might
prove erroneous.

The pyramidal manganese-ore, too, sometimes appears to be
a product of the decomposition of the prismatoidal species. In
a specimen in Mr Allan's cabinet, the pyramidal species forms
very distinctly the substance of elongated crystals, resembling
those of the latter ; but unfortunately the decomposition has
proceeded so far, that the surface of the original crystals no
longer exists, in a manner similar to what occurs in several in-
stances of malachite in the shape of blue copper. We cannot
guess at the chemical change taking place here, as the composi-
tion of the pyramidal manganese-ore is entirely unknown. From
the preference given to the varieties with a black streak above
the pyramidal species by the miners of Ihlefeld, where Phrfessor
Gustavus Rose last summer found the pyramidal species to oc-
cur in a particular vein in porphyry, it would appear that this

n 2

100 Mr Haidinger on the Parasitic Formation

species contains less oxygen than the product of the other kind
of the decomposed hydrate. The pyramidal manganese-ore con-
tains no water, at least not to a considerable extent.

VII. Changes in Minerals containing Baryta.

A change analogous to some of those described in the genus
lead-baryte, is that which affects baryto-calcite, or the hemi-pris-
matic hal-baryte, a mineral consisting of one atom of carbonate
of lime and one of carbonate of baryta. It occurs not only in
perfectly formed crystals, with bright surfaces, but also in such as
have lost their original brightness, and are covered with a coating
of crystals of sulphate of baryta, constituting the chemical compo-
sition of the prismatic hal-baryte. There are varieties, also, which
still shew the exact hemi-prismatic form of the baryto-calcite, but,
when broken, do not exhibit a trace of the original foliated tex-
ture, being altogether composed of a granular tissue of small
crystals of heavy-spar. Sulphuric acid and water must have act-
ed jointly to effect this change, but the decomposition must have
proceeded slowly. The carbonic acid is expelled by the former,
and the latter will carry away the sulphate of lime which is thus
formed, leaving only the sulphate of baryta.

The pure carbonate of baryta, also, which constitutes the
chemical substance of the species of witherite, is found in all
stages of a decomposition of the same kind; that is, from the
state of a carbonate, the base enters that of a sulphate. The
decomposition proceeds from the surface. Perfectly bright crys-
tals of the substance are rare, and almost entirely confined to
some small drusy cavities in the interior of those large globular
shapes occurring at Alston-moor, which are white and opake on the
outside, and more translucent and yellowish within. The white
coating is not, however, carbonate, but it consists of a number of

of Mineral Species. 101

minute crystals of sulphate, and is of variable thickness, in some
specimens more considerable than in others. Often, too, nothing
but the general outline of the original form is left, and large six-
sided pyramids or tabular prisms, as we are accustomed to find
them in witherite, shewing on their outside a drusy surface of nu-
merous crystals of heavy-spar, are found, when broken across, to
consist of the same species in aggregated crystals, generally in-
cluding cavities, from which the original species has disappeared,
and which have not been completely filled up. One of the spe-
cimens from Dufton, in Mr Allan's cabinet, deserves a particu-
lar description. On a support of crystallized calcareous spar and
heavy-spar, the latter in rectangular tables of three inches in
length and upwards, are deposited the shapes of isosceles six-
sided pyramids, some of them two inches long, with a propor-
tional diameter, which were formerly witherite, but now pre-
sent a surface rough with crystals of heavy-spar, many of them
more than a line in length, and of course easily recognizable.
While the process of the transformation of carbonate into sul-
phate was going on, crystallized portions of the latter were like-
wise deposited on the surface, and particularly along the edges
of the original large tabular crystals of heavy-spar, where they
assume a position dependent upon the latter, and may be consi-
dered only as continuations of the same individuals. The se-
condary deposit, being of an opake milky whiteness, may be
readily distinguished from the transparent substance, of the. ori-
ginal crystals. These crystals themselves do not shew a homo-
geneous texture throughout. There are cavities inside of them,
often in such multitudes, that the remaining mass of heavy-spar
assumes a carious aspect, though still, by its cleavage, shewing
that it is part of the individual within whose external form it is
found. Many of the cavities are filled with small brown crystals
of calcareous, spar. The crystallization of the calcareous spar,
begun in the form of the fundamental rhombohedron R, with

102 Mr Hai dinger an the Parotitic Formation

yellowish-white faintly translucent matter, as appears from the
delineation of colours^ wa» completed by a brownish opake mat-
ter, in the shape of the Combination R — 1 . R+ oo, the form
dodecaedre of Mauy. These brown portion* have also: a cdribus
aspect, as from decomposition, and are studded With small crys-
tals of heavy-spar, of the same kind as that which replaces the"
crystals of witherite.

VIII. Change* in Minerals containing Antimony.

The

have not been sufficiently attended to. It is certain that the na-
tive antimony takes up oxygen, and then presents a white opake
mass, shewing every peculiarity, in respect of form, of the original
substance, as I have seen in a specimen in the museum at York.
This is probably the oxide of antimony. The prismatxridal anti-
mony-glance consists of sulphuret of antimony, a mixture of one
atom of the metal and three atoms of sulphur, Sb S5, the ratio of
antimony and sulphur being 72.77 and 27.28. It is converted by
decomposition into a yellowish opake mass, of an earthy aspect,
which is proved by experiments with the blowpipe still to eon-
tain a notable quantity of sulphur, beside water and antimony.
In this ease the form is preserved. Sometiriaes, however, as at
Braeunsdorf in Saxony, the decomposition is complete, and at-
tended with change of form, in the same manner as the lead-
glance. The decomposition begins from the surface, which is
corroded, and becomes perfectly smooth. In the cavities thus
produced, crystals of the antimony-baryte are deposited, which
consist of pure oxide of antimony, one atom of the metal com-
bined with three atoms of oxygen, or Sb, the two ingredients be-
ing in the ratio of 84.32 to 15,68. Each atom of sulphur is ex-
actly replaced by an atom of oxygen.

qf Mineral Species. X 03

IX. Changes in some of the so-called Earthy Minerals, and others.

The explanation of m#ny of the cases enumerated above, de-
pends upon the ordinary laws, active in our chemical laborato-
ries. Carbonates are changed into sulphates, metallic substances
are oxidized, copper is replaced by iron : in general weaker affi-
nities give way to stronger ones. The conversion of sulphates

4

into carbonates, and other cases, may perhaps depend upon some
process of mutual decomposition, in which one of the products
has been subsequently removed ; but the specimens preserved in
collections do not usually present any explanations of the facts
which they furnish. We must endeavour to ascertain the causes
which have contributed towards successive alterations in the
chemical composition of minerals, by observing their natural re-
positories, veins and beds, and mountain masses, exposed to the
action of the atmosphere and of water, and to the mutual re-
action of the mineral species of which they are constituted.

One of these examples, where the cause of a change in ap-
pearance is not so palpable, is the well-known one of the substance
usually named the Grey Andalusite. Its specific gravity alone,
being above 3.5, while that of the real andalusite never exceeds
8.2, would be sufficient to prove them to belong to different
species. But Professor Mohs has found the grey crystals actual-
ly to consist of a great number of small individuals of disthene,
with an easy cleavage, whenever they are large enough to be dis-
tinguished from others, and lying in different directions through-
out the mass. Both minerals are found in nodules of quartz en-
gaged in mica-slate. Frojn the analysis by Arfvedson, it ap-
pears that disthene is a compound of one atom of silica and two
of alumina, or Al* Si. Andalusite contains about 83 per cent

104 Mr Haidingee on the Parasitic Formation

of the same mixture, the rest being a trisilicate of potassa *
The loss of this ingredient sufficiently accounts for the chemi-
cal difference between the two bodies ; but we are at a loss to
conjecture in what manner such a change may have taken place.
Mr Allan has in his cabinet several specimens from the trap
district near Dumbarton, exhibiting the shape of analcime, but
entirely composed of aggregated crystals of prehnite. Mr Wil-
liam Gibson Thomson is likewise in the possession of seve-
ral exceedingly distinct and instructive specimens of the same
description. There is one, among the former, where prehnite,
aggregated in globular shapes, is implanted on icositetrahedral
masses, once of analcime, but now likewise converted into preh-
nite. The implanted varieties are green and translucent ; I
found their specific gravity equal to 2.885 : the portions within
the faces of the icosi tetrahedrons are white and opake, and give
2.842, both of them rather lower than the usual results obtained,
which are a little above 2.9, at least in simple crystals. But the
arrangement of the divergent individuals in the reniform shapes,
is highly remarkable, and throws some light also on the gradual
formation of the new species within the space occupied by the
crystals of analcime. The centres of the single globular groups,
aggregated in a reniform manner, are situated on the surface of
the icositetrahedrons. From these, the fibres diverge, not only
towards the surface of the globules, but also on the other side,
in the direction of what formerly was analcime. The original
surface of the icositetrahedrons may be laid bare, by breaking
off the exterior coat of prehnite. Even in those places where
there was no coating of prehnite, the decomposition of the anal-
cime has taken place in the neighbourhood of other decomposed
crystals. The ingredients of prehnite are silica, alumina, lime, and
water ; those of analcime, silica, alumina, soda and water. There

* Beudant's Mineralogy, p. 838. & 363.

of Mineral Species. 105

is no similarity between the two in the mode of combination of
their ingredients, analcime being considered as a compound of
bisilicates of soda and alumina with water, while prehnite is con-
sidered as a compound of simple silicates of lime and alumina,
with a hydrate of silica.

On another occasion *, I have described a very curious in-
stance of pyramidal forms, agreeing as near as possible with those
of the pyramidal scheelium-baryte, which consisted in their in-
terior of multitudes of columnar crystals of the prismatic scheel-
ium-ore. They were found at Wheal Maudlin in Cornwall, and
are partly implanted on quartz, arsenical pyrites, chlorite, &c. and
partly imbedded in cleavable blende. The chemical composition
of the two species is almost identically the same, at least not
more different than in the varieties of pyroxene, or other similar

• • • • • _

substances. The chemical formula of the first is Ca W* ; that

«• «•• » » ...

of the second Mn W2 -f 8 Fe W*, different only in the isomor-
phous bases of calcium in the one, and manganese and iron
in the other, one atom of the protoxide of each of them be-
ing united with two atoms of tungstic acid. This curious re-
semblance of the chemical mixture was then pointed out to
me by Professor Mitscherlich, who supposed, that, from the
isomorphism of the bases, the varieties observed might be ge-
nuine crystals, of the same ingredients as wolfram, but with the
form of the scheelium-baryte : this was disproved, however, by
the observation of the mechanical composition of the masses. Of
itself, the hypothesis is plausible enough that such was origi-
nally the case, and that the cohesion among the particles was
so slight, as to be afterwards overpowered by the greater crys-
talline attraction of the same particles in hemi-prismatic crystals,
subsequently formed, and as they now appear ; in a manner ana-
logous to the decomposition of the common hydrous sulphates

* Edinburgh Journal of Science, vol. i. p. 380.
VOL. XI. PART I. O

106 Mr Haidinge* oh the Parasitic Formation

of zinc or magnesia by heat, as described above. The other hy-
pothesis, that the lime in the original species has been subse-
quently replaced by the oxides of iron and manganese, is ren-
dered more likely by the fact, that there are crystals which in
part consist of the scheelium-baryte, while near the surface, bat
within the planes of the original crystals, and where portions of
them seem to be wanting, we observe an aggregate of crystals of
the scheehum-ore. A specimen of this kind I saw at Schlaggen-
wald, its native place.

Hare we must also consider Haytorite, a substance newly
discovered, but which has already given rise to various and con-
tradictory hypotheses, and in connection with it some of the
pseudomorphoses of vhombohedral quartz in general. Haytorite
has been ascertained by Mr Levy to have the shape of the spe-
cies to which he gives the name of Humboldtite. All those mi-
neralogists who have examined it, agree in pronouncing the sub-
stance of it to be caleedony, which is itself a granular compound of
exceedingly minute individuals of rhombohedral quartz : so much
appears from its physical characters. Dr Brewster obtained
the same result, by ascertaining its action on light He has also
directed the attention of naturalists to the circumstance, that
the planes of composition between the different individuals, and
which are always so very distinct in datolite, axe as distinct as
possible in haytorite ; and hence he draws the correct inference,
that they cannot have been formed in a mould, like the pseu-
domorphoses. Datolite contains a notable quantity of silica,
36.5 per cent, according to Klaproth's analysis. The succes-
sive exchange of its contents, of lime and boracic acid for an ad-
ditional, quantity of silica, if it goes so* far as completely to de-
stroy the original species, will transform the substance of the
crystals intaa mass of caleedony. There » no prooft however,
that such a process has actually taken, place, so. long as. we do
not discover the remains of the former species included in the

of Mineral Species. 1 07

other, testifying the progress of the change ; and we must be
the mere careful in establishing hypotheses, i£ as in the present
case, we are not led by analogous occurrences in other varieties
of the same species.

Calcareous spar is one of those species which are very easily
acted upon by atmospheric agents. The hollow scalene six-
sided pyramids of brown-spar, the macrotypous lime-haloide of
Mohs, consisting of imbricated rhombohedrons with parallel axes,
form a remarkable instance in this species of the replacement of
one substance by another, not sufficiently explained by any of
the authors which treat of it, though some of the observations on
which the actual explanation of the appearances is founded, may
be traced in several of their writings. A specimen of a pale yel-
lowish-grey colour in Mr Allan's cabinet, of the nature alluded
to above, and broken across, in order to shew the inside, presents
a cavity, the sides of which are lined with small rhombohedrons
of brown-spar, forming a surface analogous to the external one
of the six-sided pyramid. But it shews, besides, also the remains
of what formerly filled up the space altogether, of a crystal of the
rhombohedral lime-haloide. The planes of cleavage of this crys-
tal are still visibly in the same position in which they originally
existed, as appears from the contemporaneous reflection of the
image of a luminous object from the portions of it, now no longer
cohering. The surface of these portions has the same appear-
ance as fragments of calcareous spar which have been exposed to
the corroding action of acids. Crystals of the brown-spar are
likewise deposited on some of those portions disengaged from
the rest, and, as it were, pushed off from their original position,
by the gradual increase of the crystals of brown-spar. The mass
of this latter species forms a coating of pretty uniform thick-
ness over the whole surface of the original six-sided pyramid.
Nearly in the middle of the stratum, wherever it is broken across,
may be observed a whitish, or only rather more opake line, of

o 2

108 Mr Haidinger on the Parasitic Formation

the same colour as the rest, dividing it into two, without pro-
ducing the least deviation in the faces of cleavage upon which it
is seen. This line is evidently the section of the original sur-
face of the pyramid of calcareous spar, upon which one por-
tion of the brown-spar was deposited, while another portion
was formed within the space previously occupied by the calca-
reous spar, and destroyed in the progress of decomposition.
The chemical change is here very distinctly indicated ; part
of the carbonate of lime is replaced by carbonate of magnesia,
so as to form in the new species a compound of one atom of
each. How this change was brought about, is a difficult ques-
tion to resolve, though the fact cannot be doubted, as we have
in the specimen described a demonstration of it, approaching in
certainty almost to ocular evidence. It is scarcely surprising
that such appearances should be visible in metallic veins, like
some of those near Schemnitz in Hungary, the whole nature of
which shews that they must have been gradually changed by
successive revolutions, the uppermost part being often almost
entirely composed of cellular quartz, which is formed in fis-
sures contained in other species or compound masses, subse-
quently decomposed, and leaving the quartz alone. I shall not
enter into an inquiry respecting the probability of such changes
in mountain masses, of such an enormous bulk as the dolomite of
the Tyrol, to which Von Buch ascribed a similar origin. The
facts observed on a small scale, do not exclude the possibility of
such changes, though we are certainly less prepared to expect
them, where powerful and momentary revolutions are supposed
to have taken place at the same time, than where any period of
time, even the most protracted, may be granted for the succes-
sive replacement of one particle of matter by another.

Crystals of calcareous spar, previously coated with small indi-
viduals of quartz, often entirely disappear, and leave an empty
shell. We sometimes observe particles of the calcareous spar

of Mineral Species. 1 09

with a corroded surface, still contained within the covering, but
much diminished in size. A large pseudomorphosis in the shape
of a scalene six-sided pyramid, from the zinc mines in Somerset-
shire, in Mr Allan's cabinet, from which the original species of
calcareous spar has entirely disappeared, is of a particularly inte-
resting nature. Beside the superficial coating, the quartzy matter
has introduced itself into the fissures of the crystal, parallel to its
planes of cleavage, and the interior of it is now not quite empty,
but divided into cells by lamellae of quartz, the cells having the
shape of the fundamental rhombohedron of calcareous spar. The
formation of what now remains must have begun, therefore, when
the original crystal was still perfect, and have proceeded during
the decomposition of it. The change was gradual, and so we
must conceive these processes to go on in every instance. It is
highly- probable that the formation of another species, so near,
or even within the boundaries of a crystal previously existing,
will greatly influence, by its electro-chemical action, upon the ar-
rangement and composition of the particles of that body.

Quartz, more than any other species, is known to fill up the
vacuities formerly occupied by crystals of calcareous spar, of fluor,
and of gypsum. Such masses of secondary formation are called
peeudamarphoses9 and are usually conceived to have been formed
in moulds, arising from a substance which surrounded the original
crystals, and was left unchanged, while the latter was destroyed
by decomposition, in a manner similar to the process of making
first the mould of a bust or statue, and then filling it with plaster
of Paris. The cast obtained, from a mineralogical point of view,
is a pseudomorphosis of gypsum. We have but rarely an oppor-
tunity of observing entire series of specimens illustrative of such
a process. Even in extensive collections, it is difficult to bring
together a sufficient number of them, in order to give an ex-
ample of each stage of the gradual formation and decomposition
of one species after the other. The moulds in which many of

110 Mr Hai dinger on the Parasitic Formation

the pseudomorphoses are supposed to have been formed, never
were seen or described by any mineralogist ; for instance those of
quartz in the shape of fluor from Beeralston ; those of hornstone
in the shape of calcareous spar from Schneeberg ; those of calce-
dony, in the shape probably of fluor, from Tresztyan in Transyl-
vania. We might be inclined to think, that actually there have
never been any, but that the new substance was formed while
the old one was disappearing. A film of quartz, deposited on
the surface of a crystal, would be the support of any new matter,
subsequently added, as we see in many instances, particularly
the pseudomorphous hornstortr from Schneeberg, that, like the
inside, wherever it is not entirely filled up, the outside also of-
ten shews the reniform and botryoidal shapes depending upon
the undisturbed formation of the component individuals. Wa-
ter, charged with carbonic acid, and by that means holding si-
lica in solution, may have dissolved the original species, and de-
posited the siliceous matter in its stead.

In the varieties from Schneeberg, which consist of perfectly
compact rhombohedral quartz or hornstone, the original outline
of the decomposed crystals of calcareous spar cannot any longer
be descried. There are varieties, however, also in the shape of
the same species, and consisting likewise of quartz, where this
is still possible ; and among them I know of none that are
more distinct than those from Bristol The quartz, in well
defined individuals, is deposited partly inside the space for-
merly occupied by calcareous spar, producing as many geodes
or drusy cavities, and partly on the outside of the same space,
the two sets of deposits being separated by the surface of the
original crystal, the only thing still remaining of it. They do
not cohere firmly, but the outer deposit may be removed, leaving
the inner one in the shape of perfectly formed crystals of calca-
reous spar, the surface of which is stained brown by oxide of
iron. Mr Allan has one in his cabinet, which he disengaged in

of Mineral Species. Ill

this way from the surrounding mass, terminated on both ends,
and altogether shewing only a small portion of its surface, where
it might have been attached to an original support.

In the example just now described, the crystals of quartz are
deposited pretty regularly, at least m so far as their axes are
nearly perpendicular to the surface of the crystals of calcareous
spar. This is not the case in the prismatoidal manganese-ore
from Ihlefeld, which fills up, and at the same time surrounds,
the space formerly containing crystals of calcareous spar, and
where likewise nothing but the surface of the original crystals
has remained. Both masses, however, are perfectly alike, and
consist of granular individuals, still easily recognizable. Such
component individuals are sufficiently small to withdraw them-
selves from observation, in the varieties of compact rhombohe-
dral iron-ore from Johanngeorgenstadt in Saxony, and other
places, which exactly, like the manganese-ore, include shapes, or
rather surfaces of crystals only, of calcareous spar.

A similar explanation no1 doubt appMes also to the steatite
from Gcepfersgrftn 2h Bayreuth, well known to collectors, but as
to the causes which have produced it, stiff unknown to minera-
logists. Their perfectly homogeneous appearance excludes every
idea of their being formed by a mixture, however intimate, of
steatite, and the spefcies whose forms' the crystalline shapes af-
fect ; for, oti thfe supposition, they still1 must retain some of the
properties peculiar tiv those species. The feet that several forms
are found, not only incompatible with each other, but evidently
belonging to other twoi or more well known species, as quartz,
calcareous5 spar, and pearl-spar, likewise distinctly proves them not
to" be actual1 crystals, belbnging to the internal* nature of steatite.
Btet if* we compare* the analogy of such bodies as those described
above, which, like the steatite, include only the form of another
species, we can have no doubt that all of them must have been
formed in the same way. The chemical composition of steatite

112 Mr Haidinger on the Parasitic Formation

is not well ascertained : it is probably a compound of some sili-
cate and of a hydrate of magnesia. Quartz is entirely composed
of one of its ingredients ; but the other species, calcareous spar,
for instance, whose crystals have been replaced by steatite, do
not contain so much as a trace of these substances, so that we
must suppose them to have been entirely destroyed, even with-
out giving up part of their ingredients to the new mixture, while
the latter was forming within and without the space which these
crystals occupied.

Earthy and friable masses are often the result of decomposi-
tion, that is to say, of a change in the arrangement of particles,
which then are so minute, that none of their natural-historical
properties can be ascertained. The pale green friable masses,
in the form of crystals of pyroxene, from Tyrol and Transylva-
nia, considered by Werner as crystallized green-earth, by Hauy
as a variety of steatite ; the red masses sometimes shewing the
forms of olivine, and dependent upon the decomposition of that
species, included in some of the rocks of Arthur's Seat, near
Edinburgh ; porcelain-earth, probably owing to the decompo-
sition of the porcelain-spar of Fuchs * ; various kinds of stea-
tite, quoted by authors, some in the form of garnet, others
in the form of trigonal-dodecahedrons of an unknown mineral,
engaged in the serpentine from Siberia, others in the form of fel-
spar, &c. yield examples of such bodies. They have not yet been
examined with that degree of attention which they deserve, not
so much perhaps on their own account, as rather for the infe-
rences to which researches of this kind might lead. But it must
be allowed, that many of them cannot be instituted in those
fragments of the entire series, which, for their more apparent
distinctness, are preserved in our mineralogical cabinets. Beside

* Denkschrtfien der Akademie der Wissenschaflen zu Munchen f&r 1818 und
1819.

of Mineral Species. 113

extensive series of the minerals in question, they require the
joint efforts of mineralogical inquiry, for ascertaining the species
which have been destroyed, and those which have been formed ;
of chemical examination, for ascertaining the difference in the
ingredients of the two ; and of geological observation of the spe-
cimens in their natural repositories, in order to establish the
causes by which the chemical affinities, balanced by the forma,
tion of the original compounds, have again entered into action.

From the preceding enumeration, it is but too evident, that
our knowledge of the facts, as well as of their causes, up to this
moment is scanty and imperfect. A wide field of research is
still open, promising a fair return for the labour, naturalists may
bestow upon its cultivation. 1 have endeavoured to collect on-
ly some of the most remarkable and familiar instances of the
changes which may take place in the solid body of a crystal, the
ulterior study of which, while it illustrates the idea of species,
will throw some light also on the causes of such alterations as
do not appear conformable to the known laws of chemical affi-
nity, for which we cannot account at least in the present state of
our information.

VOL. XI. PART I.

( 114 )

VII. On the Influence qf the Air in determining the Crystallization
of Saline Solutions. By Thomas Graham, Esq. A.M.

(Read December 17. 1827.J

The phenomenon referred to has long been known, and pbpu-
lairfy exhibited in the case of Glauber's salt, without any ade-
quate explanation. A phial or flask is filled with a.bcriling satu-
rated solution of sulphate of soda or Glauber's salt, and its mouth
immediately stopped by a cork, or a piece of bladder is tied tightly
over it, while still hot. The solution, thus protected from the
atmosphere, generally cools without crystallizing, although it con-
tains a great excess of salt, and continues entirely liquid for hours
and even days. But upon withdrawing the stopper, or punc-
turing the bladdfcr, and admitting air to the solution, it is iron
mediately resolved into a spongy crystalline mass, with thfe eyo*
lution of much heat. The crystallization was attributed to the
pressure of the atmosphere suddenly admitted, till it was shewn
that the same phenomenon occurred, when air was admitted to
a solution already subject to the atmospheric pressure. Re-
course was likewise had to the supposed agency of solid particles
floating in the air, and brought by means of it into contact with
the solution ; or it was supposed that the contact of gaseous mo-
lecules themselves might determine crystallization, as well as so-
lid particles. But although the phenomenon has been the sub-
ject of much speculation among chemists, it is generally allowed
that no satisfactory explanation of it has yet been proposed.

In experimenting upon this subject, it wag found, that hot
concentrated solutions, in phials or other receivers, might be in-

Mr Graham on the Crystallization of Saline Solutions. 115

verted over mercury in the pneumatic trough, and still remain
liquid on cooling ; and thus the causes which determine crystal-
lization were more readily examined For this purpose, it was
absolutely necessary that the mercury in the trough should be
previously heated to 110° or 120° ; for otherwise that part of the
solution in contact with the mercury cooled so rapidly, as to deter-
mine crystallization in the lower part of the receiver long before
the upper part had Mien to the temperature of the atmosphere*
In such cases, crystallization beginning on the surface of the
mercury, advanced slowly and regularly through the solution.
Above, there always remained a portion of the solution too weak
to crystallize, being impoverished by the dense formation of crys-
tals below. It was also necessary to clean the lower and exter-
nal part of the receivers, when placed in the trough, from any
adhering solution, as a communication of saline matter was some*
times formed between the solution in the receiver and the atmo-
sphere without. When these precautions were attended to, sa-
line solutions over mercury remained as long without crystallizing
as when separated from the atmosphere in the usual mode.

. Solutions which oompletely filled the receivers when placed
in the trough, allowed, a portion of mercury to enter, by con*-
tracting materially as they cooled. A. bubble of air could thus
be thrown up, without expelling any of the solution from the
receiver, and the crystallization determined, without exposing
the solution directly to the atmosphere.

The first observation made was, that solutions of sulphate of
soda sometimes did not crystallize at all upon the introduction
of a bubble of air, or at least for a considerable time. This irre-
gularity was chiefly observed in solutions formed at temperatures
not exceeding 150° or 170°, although water dissolves more of the
sulphate of soda at these inferior temperatures than at a boiling
heat* Brisk ebullition for a. few seconds, however, rendered the
solution upon cooling amenable to the usual influence of the air

p 2

116 Mr Graham on the Influence of the Air in determining

In all successful cases, crystallization commenced in the upper
part of the receiver around the bubble of air, but pervaded the
whole solution in a very few seconds. A light glass bead was
thrown up into a solution without disturbing it.

It occurred to me, that, since the effect of air could not be
accounted for on mechanical principles, it might arise from a
certain 'chemical action upon the solution. Water always holds
in solution a certain portion of air, at the temperature of the at-
mosphere, which it parts with upon boiling. Cooled in a close
vessel after boiling, and then exposed to the atmosphere, it re-
absorbs its usual proportion of air with great avidity. Now, this
absorbed air appears to affect in a minute degree the power of
water to dissolve other bodies, at least a considerable part of it
is extricated upon the solution of salts. When a bubble of air is
thrown up into a solution of sulphate of soda, which has pre-
viously been boiled and deprived of all its air, a small quantity of
air will certainly be absorbed by the solution around the bubble.
A slight reduction in the solvent power of the menstruum will en-
sue at the spot where the air is dissolved. But the menstruum is
greatly overloaded with saline matter, and ready to deposit ; the
slightest diminution of its solvent power may therefore decide
the precipitation or crystallization of the unnatural excess of sa-
line matter. The absorption of air may in this way commence
and determine the precipitation of the excess of sulphate of soda

in solution.

Here, too, we have an explanation of the fact just mentioned,
that solutions of sulphate of soda which have not been boiled,
are less affected by exposure to the air than well boiled solu-
tions ; for the former still retain the most of their air, and do
not absorb air so eagerly on exposure as solutions which have
been boiled.

But the theory was most powerfully confirmed by an expe-

the Crystallization qf Saline Solutions. 117

rimental examination of the influence of other gases, besides at-
mospheric air, in determining crystallization. Their influence
was found to be precisely proportionate to the degree in which they'
are absorbed or dissolved by water and the saline solutions.

To a solution of sulphate of soda over mercury, which had
not been affected by a bubble of atmospheric air, a bubble of car-
bonic acid gas was added. Crystallization was instantly deter-
mined around the bubble, and thence through the whole mass.
Water is capable of dissolving its own volume of carbonic acid
gas, and a solution of sulphate of soda as strong as could be em-
ployed was found by Saussure to absorb more than half its vo-
lume.

In a solution of sulphate of soda, which was rather weak,
both common air and carbonic acid gas failed to destroy the
equilibrium ; but a small bubble of ammoniacal gas instantly de-
termined crystallization.

When gases are employed which water dissolves abundantly,
such as ammoniacal and sulphurous acid gases, the crystallization
proceeds most vigorously. It is not deferred till the bubble of
gas reaches the top of the receiver, as always happens with com-
mon air, and frequently with carbonic acid gas, but the track of
the bubble becomes the common axis of innumerable crystalline
planes, upon which it appears to be borne upwards ; and some-
times before the ascent is completed, the bubble is entangled and
arrested by crystalline arrangements which precede it.

The number of gases which are less soluble in water than at-
mospheric air is not considerable, but of these hydrogen gas was
found to be decidedly less influential in determining crystalliza-
tion.

Minute quantities of foreign liquids soluble in water likewise
disposed the saline solution to immediate crystallization, as might
be expected, and none with greater effect than alcohol. It is
known that alcohol can precipitate sulphate of soda from its

118 Mr Graham on the Crystallization of Saline Solutions.

aqueous solutions. The soluble gases I suppose to possess a si-
milar property.

These fects appear to warrant the conclusion, that air deter-
mines the crystallization of supersaturated saline solutions, by
dissolving in the water, and thereby giving a ahock to the feeble
power by which the excess of salt is held in solution.

Before concluding, I may be allowed to make a remark, on
the usual description of the sudden congelation of the solution
of sulphate of soda upon the admission of air. It is said that the
solution expands in solidifying, in the same way as water does
in becoming ice. But the expansion which takes place is mere-
ly temporary, and not due to such a cause, but entirely to a mo-
mentary dilatation of the whole contents of the phial, both liquid
and solid, by the evolution of heat, which occurs on the instant
of crystallizing, and which always amounts to 20° or 30°. That
the salt does not permanently expand on crystallizing is easily
proved, by the sinking of a crystal in the densest solution of the
salt which can be formed.

( 119 )

VIII. Mineralogical Account of the Ores of Manganese. By

W. Haidinger, Esq. F. R. S. E.

{Read December 17. 1827.)

A he mineralogical determination of those species, the chief
constituent of which is Manganese, has been for a long time des-
titute of that precision at which other species had long arrived,
whose chemical constitution was better known. Two years ago I
published, in a memoir " On the Crystalline Forms and Properties
of the Manganese-Ores*" the most accurate information I could
then collect, partly from some works on mineralogy, partly from
my own observations. In the general descriptions which I propose
giving here for the mineralogical illustration of Dr Turner's
account of their chemical properties, I have availed myself of
the corrections given in the translation of the same paper in
Poggendorff's Annals by Professor Gustavus Rose, who has
corrected or verified the angles given, and compared them again
with nature ; so that the statements have gained a considerable
accession of authority. I have added the description of that
species, which consists of the anhydrous peroxide of manganese,
and which, from the difference of its properties from all the rest,
whatever may be the mode of its formation, should be consi-
dered as a species of its own.

It is attended with considerable difficulty, and offers but
little advantage, to collect the synonyms used by the older mi-
neralogical authors, the two names Grey Manganese and Black
Manganese, and other ones of a similar cast, having been almost

; *

♦ Edinburgh Journal cf Science, vol. It. p. 41.

120 Mr Haidinger's Mineralogical Account of

indiscriminately applied to every one of the species, or at
least to those which most commonly occur in nature. I have
again compared, in this respect, some of the treatises on mine-
ralogy, and given the synonyms as nearly exact as I could.
Those of Hauy I have left out, because this author, though of
the greatest importance where regular forms can be made out,
is remarkably deficient in the particular point of the ores of
manganese. The undeterminable varieties, such as black-wad
and others, I have thought best to omit altogether from the ge-
neral descriptions, as their connection with the rest is not quite
clear ; and I have done so the more willingly, as Dr Turner
has not subjected them to any chemical examination. The
authors and works quoted are the following :

Handbuch der Mineralogie. By J. F. L. Hatjsmann.

System of Mineralogy ; 3d edition. By R. Jameson.

Elementary Introduction to the Knowledge of Mineralogy. * By W. Phillips.

Grundriss der Mineralogie. By F. Mohs.

Treatise on Mineralogy. By F. Mohs. Translated by W. Haidingeb.

On the Crystalline Forms and Properties of the Manganese-ores. By W.

Haidinger, in the Edinburgh Journal of Science.
Handbuch der Oryctognosie. By E. C. von Leonhard.

Four of the species belong to the genus Manganese-ore of the
system of Mohs, and they are accordingly provided with syste-
matic denominations. The fifth species differs so materially
from the rest, particularly in regard to hardness, that I hesitate
to assign it a place in the same genus, or even order, and there-
fore shall not at present propose a systematic denomination for
it. None of them are as yet provided with good trivial names;
those phrases and definitions which were used, in general con-
veying nothing but an imperfect, and often erroneous allusion
to the chemical constitution of the species. Those which I here
venture to propose, have at least the property, essential to all
good trivial names, that they consist 9f one single word ; and,

the Ores of Manganese. VX1

though I am aware that to give names of this kind to old spe-
cies is arrogating to one's self a great portion of authority, yet
I believe this to be the only consistent plan, the advantages of
which will no doubt overbalance every consideration of difficul-
ty. Their explanation will be given with the description of
each of the species.

When I began to collect the information contained in works
on mineralogy relative to the localities of the different species,
the result was scanty, and on account of the erroneous determi-
nation, generally uncertain. I resolved therefore, in enumerating
the localities, to mention those only which I knew to be correct
either from personal knowledge, or by comparing the localities^
attached to specimens in the various collections, with the verbal
information of several of my mineralogical friends. With this
view, I have examined the mineralogical cabinets of Mr Allan
and Mr W. G. Thomson in Edinburgh, of Mr Von Struve and
Mr Hertz in Hamburgh, of the Royal Museum and of Mr Tam-
nau in Berlin, of the National Museum in Prague, and of Mr
Von Pittoni in Vienna, and of the public museums in that city,
the Imperial Cabinet, the Brazilian collection, and that of the
Polytechnic Institution. I have been indebted to the proprie-
tors of the private collections, and the gentlemen attached to
the public ones, for much kindness and many interesting notices
of such localities as they had visited themselves, or were other-
wise acquainted with ; especially to Professor Gustavus Rose,
Professor Ziffe, Professor Mohs, Mr Partsch, Dr Pohl, and
Professor Riepl. From Mr Von Leonhard, Professor Ber-
thier, and Mr Leman, I also obtained some interesting speci-
mens, and much valuable information.

VOL. XL FART I. Q

122 Mr Haidinger's Mincralogical Account of

I. Prismatoidal Manganese-ore.

Manganite.

Grau-Braunstein, in part, Hausmann, p. 288.

Grey Manganese-ore, in part, Jameson, vol. iii. p. 262.

Grey Oxide of Manganese, in part, Phillips, p. 248.

Prismatoidisches Manganerz, Mdhs, vol ii p. 488.

Prismatoidal Manganese-ore, Mcihs, Translation, vol. ii. p. 419.— Id. HaUHn-

ger, Edin. Journ. of Science, vol. iv. p. 41.
Gewaessertes Mangan-Hvperoxidul, Leonhard, p. 239-

Fundamental Form. * Scalene four-sided pyramid. Ps ISO0
49*, 120° 54', 80° 9,9!. Plate, Fig. 1.

a:b:a = 1 : • S.S7 : • 2.4. «

Simple forms. 1. P — oo (o).

2. P (P) = 130° 49', 120° 54', 80° 22'.

8. P + 1 (ro) =112° 85', 97° 85', 1 1 8° 45'.

4. P+oo (M) = 99° 40'.

5. (f £r)8 (c) = 117° 16', 144° 5', 74° 28'.

6. (W)3 (n) = 95° 4', 182° St/, 103° 24'.

7. (£r + oo)» (/) = 61° 18'.

8. (Pr — l)8 (h) = 154° 18', 116° lO', 70° 2'.

9. (Pr + oo) * (r) = 134° 14'.

10. ($ P — 2) « (#) = 162° 39^, 1 1 5° Ji 0', 67° 42'.

11. (£r + oo)5 (s) = 76° 37'.

12. Pr(d) =114° 19'.
13.^(0) =122° SO'.

Character of combinations hemi-prismatic, with inclined faces.

Combinations. 1. P— oo. P + oo- Fig. 2.

2. P— oo. P + oo. (£r + oo)<. Fig. 3.
8. Pr. P+oo. (£r+oo)'. Fig. 4.

PIiiLTE vn.

Edu*rir+yml S+c. 7Hw* Voi. M. J».122.

r?.J.

Fif 2.

M

M

Fig.*.

V ,

M

M

Fig. 3.

Fig. J.

Fi,.*.

h J?

Fig. 9.

JTJfir M

Fig.W.

Fig, 6.

FigJ9.

Kg. II.

FigJS^

M

M

Fu?2*.

Ftg.SS.

WJU

the Ores of Manganese. 128

These are the most common, and at the same time the least
complicated of the varieties of the present species.

,4. (£pr_2)*. (|.Pr)». (Pr)5. P+l. P + oo. (£r+oo)».

(Pr + oo)*. Fig. 5.

The 6th Figure represents the projection upon P — oo, the
7th Figure the elevation upon a plane parallel to the short dia-
gonal of the prism P+oo. The hemi-prismatic character of the
species appears only in the disposition of the feces marked c.

They form horizontal edges of combination with (Pr) 9 . These
crystals are from two to three lines in thickness, and some of
them nearly an inch long.

5. Pr. (Pr — l)3. Pr. P. P + l. P+oo. (£r + oo)<.
(£r+oo)5. (Pr+oo).*. Fig. 8.

Small but very well pronounced crystals of this variety were
disengaged from the same specimen which contains the variety 4.
They were found in small drusy cavities, which were discovered
when the whole was broken up for analysis. The edges between
(Pr — I)5 and P + 1 are parallel to those between P+l and
(P r + oo)5. The faces of Pr, marked e in the figure, are rarely
observed in the crystals of this species.

Cleavage, Pr + oo highly perfect and easily obtained ; P + oo
also perfect, but less easily obtained; traces of Pr+ oo, and of
P — oo. Fracture uneven ; surface of the vertical prisms streaked
parallel to their common edges of intersection ; Pr streaked pa-
rallel to the edges of combination with P ; P — oo parallel to
those with Pr. In general, the faces are smooth, and possess
pretty high degrees of lustre.

Lustre, imperfect metallic. Colour, dark brownish-black, in-
clining to iron-black. Streak, reddish-brown. Opaque, in larger

q2

184* Mr Haidiw ger's Minerahgical Account of

masses. When broken or cleaved in the direction of Pr + xx,
and exposed to. the light of the sun, minute splinters axe often
observed, which, by transmitted light, appear of a bright brown
colour, so that the mineral cannot be said to be absolutely
opaque.

Brittle. Hardness = 4.0... 4.25, a little higher than fluor.
Specific gravity = 4.328, of a number of fragments of crystals;
= 4.312) in another experiment, of a single crystal of consider-
able size.

Compound Varieties. — Twin-crystals, formed in two different
manners. In the first of them, the axes of the two individuals
are parallel, dependant on the hemi-prismatic character of the
combinations of the species ; in the second, they are inclined.
1 . Face of composition parallel to Pr + oo ; axis of revolution
perpendicular to it. Fig. 9. If we did not give attention to the
compound state of this variety, shewn in the present instance by
the groove along the place of junction, which is not always vi-
sible, we might be induced to believe that it possesses a hemi-
prismatic character, referred to an axis inclined upon the base
of the fundamental pyramid, which is not the case. One can
generally trace the peculiar disposition of the crystalline faces
upon each of the individuals. A repetition of this law pro-
duces thick prisms, terminating perpendicularly upon their axis
by a rough face, which consists of the apices of numerous indi-
viduals, or rather of numerous particles of two individuals, alter-
nating with each other. Such faces are not uncommon in the
prismatoidal manganese-ore. &. Axis of revolution perpendicu-
lar, face of composition parallel to a plane of Pr. Fig. 10. The
disposition of the faces marked e, upon which the hemi-prisma-
tic character of the species depends, is such, that a mere revo-
lution of 180° is not sufficient to bring the two individuals into
the position required for joining in a regular twin ; though the
general disposition takes place also in the present instance, the

the Ores of Manganese. 125

portions of the two crystals similarly situated being 180° distant
irom each other, compared to the plane of composition. This
peculiarity of the twin-crystals, as Professor Gustavus Rose re-
marks, may be shortly explained, by considering that of the he-
form c ; — the inverse of what is found in one of the in-

dividuals, occurs in the other.

Irregular composition is very common in this species : it is
either granular or columnar. The latter occurs much more fre-
quently.

Observations.

The name of Manganite, proposed for this species, is formed
m allusion to the metal which it contains, in preference to others,
as it is the one which occurs most frequently in nature. In
most mineralogical works, the characters of manganite. and of
pyrolusite have been confounded with each other, or rather a
medley of the two, neither of them exactly ascertained, was given
as the description of a single species. The insufficiency of the
descriptions of Hauy and older authors was felt by many mine-
ralogists, and several of them endeavoured to substitute better
ones in their place. The result, obtained by Mr Von Leon-
hard, in the first edition of his system, is by no means more
satisfactory than that of Hauy ; Mr Phillips, with his usual
skill in crystallographic observations, has succeeded much better.
The description of the forms given by Mohs agrees very nearly
with the latter, at least much more so than any two other de-
scriptions. There ace some differences, however, in regard to
the absolute measurement of the angles, and in the statement
that, according to Mohs, the cleavage parallel to the short dia-
gonal of the prism P + oo = 99° 4C is more distinct, and more
easily obtained than any other cleavage of the species ; whereas,
according to Phillips, the crystals " cleave readily, and with
txrilliant surfaces parallel to the lateral planes of a rhombic prism

1$6 Mr Haidinger's Mineralogical Account qf

of 100° and 80°, and both its diagonals." Though, in many va-
rieties, the cleavage parallel to the long diagonal of that prism
may in fact be obtained, it is always less distinct than that pa-
rallel to the short diagonal, and often not at all observable. It
is important to attend to this difference in the perfection of
cleavage ; the more so, because the cleavage parallel to the short
diagonal of P + oo = 99° 40', is at the same time parallel to the
long diagonal of another prism (Pr + oo)' = 76° 86' (the sup-
plement of which is 108° 24'), which occurs very frequently in
the same mineral, and might be, or has actually been, mistaken
for it, in a more superficial examination of the crystalline forms
of the species.

The most remarkable peculiarity in the series of crystalliza-
tion of this species, is its hemi-prismatic character, the faces of
those forms which assume it being inclined to each other. I
have much pleasure in adding here, that the observation of this
peculiar character, which I gave an account of from a rather li-
mited number of crystals, has since been repeated, and perfect-
ly confirmed, by Dr Charles Hartmann of Blankenburg. The
faces marked c, if sufficiently enlarged, would give rise to a form
resembling a tetrahedron, like Fig. 11, the planes of which are
equal and similar scalene triangles. Among the remaining spe-
cies whose forms belong to the prismatic system, only the sul-
phates of zinc, of magnesia, and of nickel, are known to possess
an analogous formation. This was first placed beyond a doubt
by Professor Mitscherlich, who observed the fact, that the
faces s and t> Fig. 12, appear only contiguous to the alternating
faces of / ; although the alternating enlargement of these same
faces, represented in Fig. IS, had been previously noticed in the
sulphate of magnesia by mineralogists, so far bade as the time of
Rome' de L'Isle and Linnjeus. Large crystals of this salt ge-
nerally shew the hemi-prismatic character much more distinctly
than small ones.

the Ores qfManganes 127

Manganite occurs in very few places. It is found in great
abundance, often beautifully crystallized, in the manganese mines
of lhlefeld in the Hartz, occurring in veins traversing porphyry.
Thin crystals and masses consisting of columnar individuals, when
rubbed down on a plate of porcelain biscuit, in order to ascertain
the colour of their streak, frequently yield a black powder at
first, the characteristic brown tint appearing only when a consi-
derable portion of the whole has been rubbed off. At lhlefeld
Manganite is associated with calcareous spar, and heavy-spar,
particularly with the latter. The specimens analyzed, which
Eri* JTC yielded Figs. 5, to 10, dSed .Wefwe* found
at lhlefeld, and were brought by Dr Turner from Germany.
The same species occurs in gneiss, occasionally traversing it in
small irregular veins and mixed with quartz, at Granam in Aber-
deenshire. It is found likewise at Christiansand in Norway, and
Undenaes in Westrogothia in Sweden. A massive variety of
manganite, consisting of small spicular crystals with many drusy
interstices, is found in Nova Scotia.

II. Pyramidal Manganese-ore.

Hausmannite.

Blaettricher Schwarz-Braunstein, Hausmann, p. 293.

Foliated Black Manganese-ore, Jameson, vol. iii. p. 263.

Black Manganese, Philtips, p. 881.

Pyramidales Mangan-erz, Jfafo, vol. ii* p. 484.

Pyramidal Manganese-ore, Afohs, Trans, vol. ii. p. 416. Id. Haidinqer, Edin,

Journ. of Science, vol. iv. p. 46.
Schwarz-Manganerz, Leonhard, p. 760.

Fundamental form. Isosceles four-sided pyramid,
P = 105° 25', 117° 54'. Fig. 14.

a = s/Z76,

*28 Mr Haidinger's Minerahgicai Account of

Simple forms. £ P — 4 (a) = 189° 56V 57° 57'; P— 1 =r
114° 51', 99° 11'; P(P).

Char, of comb, pyramidal.

Combinations. 1. \Y — 4. P. Fig. 15.

2. -JP— 4. P_ .1. P.

Cleavage, P — oo rather perfect ; P — 1 and P less distinct, and
interrupted. Fracture uneven. Surface, \ P — 4, very smooth and
shining, P horizontally streaked, and often dull.

Lustre, imperfect metallic. Colour, brownish-black. Streak,
dark-reddish, or chesnut-brown. Opaque.

Hardness = 5.0, 5.5, a little higher than apatite. Sp. gr. =
4.722, of a crystallized variety.

Compound Varieties. — Twin crystals : axis of revolution per-
pendicular, face of composition parallel to a face of P— -1, Fig. 16.
The composition is often repeated parallel to all the faces of the
pyramid, Fig. 17. Generally small particles only of the surround-
ing individuals are joined to the central one. Massive : compo-
sition granular, firmly connected.

Observations.

Professor Hausmann, in compliment to whom Dr Turner and
myself propose to call the present species '" Hausmannite," ranks
so high among the professors of his science, that it must appear
much more extraordinary, no species should as yet commemorate
his name, than that we should pay this tribute of friendship and
respect to that distinguished individual He has been accustomed
in his lectures, subsequent to the publication of his work, to point
out the present species as a peculiarly remarkable substance, of a
nature not yet exactly ascertained. %

It would be superfluous to enlarge here on the propriety of
considering it as a species of its own, since, besides Mr Mohs, it

the Ores of Manganese. 129

has likewise been established as such by Messrs Brooke and
Phillips, and by the Abb6 Hatty. Even in the works of the
Wemerian school, the pyramidal forms had been long ago de-
scribed, in reference to the identical specimen from which the
above description was derived. Count Bournon * mentions an
ore of manganese crystallized in regular octahedrons, having
their solid angles replaced by low four-sided pyramids ; a form
which might be explained upon the supposition, that the variety,
Fig. 12* appears in the regular composition represented Fig. 14. ;
at least it would be necessary to have these varieties compared
again with each other, for the purpose of fixing the species to
which they belong.

Hausmannite is hitherto confined to the porphyry formation
near Ihlefeld in the Hartz. It is found in a vein by itself) as
was observed by Professor Gustavus Rose.

III. Uncleavable Manganese-ore*

Psilomelane.

Dichter Schwarz-Braunstein, Hausmann, p. 295.

Compact and Fibrous Black Manganese-ore, or Black Hematite, Jameson, vol. iii.

p. 361, 262.
Black Iron-ore, Philiips, p. 2S2.
Untheilbares Mangan-erz, Mohs9 vol. ii. p. 486.
Uncleavable Manganese-ore, Jfi bhs9 Trans, vol. ii. p. 418. Id. HcAdinger, Edin.

Journ. of Science, vol. iv. p. 47*
Schwarz-JEisenstein, I^eonhardy p. 734.

Regular forms and cleavage unknown. Fracture not observ-
able.

* Catalogue, p. 396.

VOL. XI. FART I. R

ISO Mr Hai dingers Mmeraiogical Account of

Lustre, imperfect metallic Colour, bluish-black and greyish
black, passing into dark steel-grey. Streak, brownish-black, shin-
ing. Opaque.

Brittle. Hardness zz 6.0... 6.0, between apatite and felspar,
Sp. gr. n 4.145, a botryoidal variety.

Compound Varieties.*— Ileniform, botryoidal, fruticose : compo-

sition columnar, impalpable ; fracture flat oonchoidal, even ; in a
second composition it is curved lamellar, the faces of composi-
tion bang smooth, rough or granulated. Massive : composition
granular, impalpable, strongly connected ; fracture, flat oonchoi-
dal, even.

Observations.

The name " Psilomekme," from ^iXoc, smooth or naked, and j*t-
Aac, black, is formed in allusion to the black colour and smooth
hematitic shapes of this mineral It is an almost literal transla-
tion into Greek, of one of the names applied to this species, in
German, " Schwarzer Glaskogf;" the latter, though the ortho-
graphy should seem to say the contrary, being surely much more
expressive of a u bald head," than of a " vitreous head."

This k a pretty common species, among those containing
manganese. The specimen analyzed is from the neighbourhood
of Schneeberg in Saxony, and agrees perfectly with the preced-
ing description. It consists of alternating layers, having more or
less lustre, disposed in reniform coats. The specific gravity of
- those portions, which possess a rather stronger lustre, and a con-
choidal fracture, is == 4.004, while the specific gravity of those
without histae, and an uneven fracture, was found to be
= 4.079.

Psilomelane is one of the most widely diffused ores of man-
ganese. It is usually associated with the prismatic manganese-
ore, sometimes in a very curious manner. Both of them occur

the Ores qf Manganese. 181

in botryoidal, reniform, and stalactitic shapes, frequently alter*
nating with each other in layers of different thickness. Speci-
mens of this kind are found at Knorrenberg in the district of
Kirchen, county of Sayn, and other localities of the Westerwald
in Prussia, at Schwarzenthal in Bohemia, and at Arzberg in Bay-
reuth. It happens still more frequently that the two species are
less regularly intermingled ; or that they are disposed longitudi-
nally, the slender crystalline portions of pyrolusite forming rami-
fications within the botryoidal and stalactitic masses of psilome-
lane. Particularly fine examples of this kind occur in the mines
of Siebenbriider and St Johannes, near Langenberg in the mining
district of Annaberg in Saxony, also at Conradswaldau and Neu-
kirchen in Silesia. Various places in the western provinces of
Prussia are productive of most beautiful claviform, stalactitic and
botryoidal specimens of psilomelane, as in the Hollert iron-mines ;
also in the county of Hanau in Hessia, particularly at Pfaffen-
seifer and Bieber. It is a very common mineral in the Saxon
Erzgeburge, chiefly in the veins of red ironstone, which traverse
gneiss ; and occurs at Schimmel, and other mines near Johann-
georgenstadt, at Raschau, at Vater Abraham near Scheibenberg,
at Spitzgleite near Schneeberg, and others. From one of them,
I could not learn which, there are pseudomorphous crystals in
the shape of the octahedrons of fluor ; they are now in the Royal
Museum at Berlin, and were brought there in 1813 by Mr Strom.
Psilomelane is also found at Reinwege in Gotha and Ilmenau in
Weimar, as also in the territory formerly belonging to the Elec-
tor of Treves, and in the Upper Palatinate. It occurs at Busau,
m the manor of Jessenitz in Moravia, in nodules of limestone,
and these varieties in particular have a very strong lustre. It
was brought by Mr Partsch from Arshitza near Jakobeni in the
Bukovina. At Rhoniz in Hungary it is met with in brown he-
matite. At Vondernberg in Stiria psilomelane was found by Pro-
fessor Riepl in a vein traversing the decomposed sparry iron.

r2

182 Mr Haidinger's Mineralogical Account qf

At Artaberg in Bayreuth also, it appears as the product of the
decomposition of the same substance, covering the surface of the
cavities left in quartz by the original rhombohedrons of the spe-
cies.

The English localities of psilomeiane are Restormel and Up-
ton Pine near Exeter in Devonshire, and Cornwall.

IV. Brachytypous Manganese-ore.

Braunite.

Brachytypous Manganese-ore, Haidinger, Edin. Journ. of Science, vol. iv. p. 48.
Brachytypous Manganerz, Leonhard, p. 759.

Fundamental form. Isosceles four-sided pyramid. P = 109°
53', 108° 89'. Fig. 18.

a = Vl.94.

Simple forms. P — oo (o) ; P (P), Wunsiedel, Bayreuth ;
P + 2 (s) = 96° 38', 140° Stf, Fig. 17., Elgersburg, Thuringia;
(P+ l)3 (z) = 144° 4', 128° 17', 154° 25'.

Char, of comb, pyramidal.

Combinations. 1. P — oo. P. Fig. 20., Wunsiedel.

2. P. P + 2. Fig. 21., Elgersburg.

3. P. (P-H)5. Fig. 22., 'St Marcel, Piedmont.

4. P— oo. P. P+2. Fig. 23., Wunsiedel.

Cleavage, very distinct in the direction of the faces of P ; en-
tire forms of cleavage may be obtained from larger individuals.
Fracture uneven. Surface, P — oo, possessing less lustre than P,
but even, and sometimes faintly streaked parallel to the edges of
combination with P ; P often a little rounded ; P + 2 uneven,
rough and horizontally streaked; the eight-sided pyramid
(P+ l)s smooth and even.

the Ores qf Manganese. 183

Lustre, imperfect metallic. Colour, dark brownish - black.
Streak, of the same colour.

Brittle. Hardness = 6.0 . , . 6.5, higher than felspar. Sp. gr,
= 4.818, large cleavable individuals from Elgersburg.

Compound Varieties. — Massive; composition granular, indivi-
duals strongly coherent

Observations.
The present specie3 is proposed to be named " Braunite" by
Dr Turner and myself, in compliment to our mutual friend
Cammerath Braun of Gotha, a gentleman who has pursued the
study of mineralogy with much zeal and success, and to whom
Dr Turner and myself are particularly indebted for a number
of specimens of this substance, upon which its mineralogical and
chemical examination was founded. From him Dr Turner ob-
tained,, when in Germany, the first variety of the species of
brachy typous manganese-ore, which I afterwards had the good
fortune to examine. Being struck with the facility with which
this mineral yields to cleavage in the direction of the faces of a
four-sided pyramid, and supposing it to belong to the species of
the pyramidal manganese-ore of Mohs, I requested Dr Turner's
permission to extract the form of cleavage from it, but was much
surprised when I could not discover the single cleavage perpen-
dicular to the axis, which is so very distinct in that mineral, and
has been likewise indicated by Messrs Brooke and Phillips.
Though the mineral cleaves very readily, yet its great hardness,
being superior to that of felspar, and a strong connection among
the particles, render it extremely difficult to obtain the faces
sufficiently smooth and even, to reflect a good image even of a
single very luminous spot. I was therefore led to suppose, by
several approximate measurements, that the regular octahedron
should be considered as the fundamental form of the species,

1 34 Mr Haidixgeil's Mineraiegical Account of

In some of the cavities of the same specimen there were, how-
ever, crystals in the form of acute four-sided pyramids, similar
to Fig. 19, which did not agree with the symmetry of tessular
forms. They were rough, and possessed tittle lustre, so that
they afforded only indistinct measurements of about 1 40° for the
base of the pyramid. Certain varieties from Wunsiedel, in Bay-
reuth, in the cabinet of Mr Allan, engaged in heavy-spar, and
associated with pyrolusite in very delicate columnar composition,
possess the form of Figs. 18, £0. and 28. The two first of these
I also observed in a specimen, procured from Mr Heuland, in
the collection of Mr Ferguson of Raith, having the following
ticket : " Hydrous ootids of manganese* in the form qf an octahe-
dron, with a square basis. Thuringia — is extinct." As Hauy's
works contain the pyramidal manganese-ore of Mohs, under the
denomination of Manganese oxide hydrate*, this specimen is pro-
bably intended far a variety of that species, which, however, is
very inaccurately described by Hauy, who united under one
head the physical properties of one species with the physical and
chemical properties of two or three others, to form a general
description, to which no object in nature corresponds. I had
long ago observed crystals of the form Fig. 22. engaged in a spe-
cimen of the tpidote manganesifere of Hauy, in the cabinet of
Mr Allan, but which I believed likewise to be a variety of Haus~
mannite. Upon measurement, however, for which the small
but beautifully formed and bright crystals of this variety are
better suited than any of the rest, these also turned out to be-
long to a species different from the pyramidal one formerly de-
scribed. The angles which these crystals afforded are given above
as the dimensions of the species. The results obtained from the
remaining varieties are not sufficiently consistent to be consi-
dered different from these, and as, moreover, the colour of their

^-^»

* TrmUj 8de ed. t. iv. p. 264.

the Ores of Manganese. 135

streak and their hardness coincide, we may safely consider them
as belonging to the same species. Some of the octahedral crys-
tals, quoted by Count Bournon * for which he* proposes the de-
nomination of Fer owydule manganesien, must also very likely be
referred to the brachytypous manganese-ore. He supposes their
form to be derived from the regular octahedron, but does not
quote in favour of this opinion any decisive proofs, which are
rendered necessary, when a species, nearly resembling the varie-
ties alluded to, is found to have for its fundamental form a four-
sided pyramid so little different from the regular octahedron.
Those individuals which have their solid angles replaced by four
feces, may perhaps belong to Hausmannite, as k mentioned in
the observations annexed to that species, which was likewise not
distinguished as a species of its own at the period of publication
of Count Bournox's Catalogue.

Braunite is found, both crystalline and massive, at Oehrenstock
near Ilmenau, at Elgersburg, Friedrichsroda, and other places
in Thuiingia, in veins in porphyry, along with pyrolusite and
psilomelane. At Leimbach in the county of MansfekL it was dis-
covered in octahedral crystals by Professor Hoffmann of Halle,
in cavities of white quarts, which appear to have been filled ori-
ginally with some other substance. The specimens were collect-
ed from the masses which were broken for repairing the roads.
It occurs also at St Marcel in Piedmont. The locality of Wun~
siedel in Bayreuth, given in Mr Allan's cabinet for the varieties
of braunite, Figs. 19, and 21, appears to me exceedingly proble-
matical ; since, among a vast number of specimens in various col-
lections, I have not seen any from that place, while the specimens
in the cabinet possess the aspect of those derived from the mines
of Thuiingia.
- - -■■■-- rl — _^ i^— ■ ■■■■ . . ■■■.. — ^^_____^_____^___

* Catalogue, p. 895.

186 Mr Haidinger's Minerafogkal Account of

V. Prismatic Manganese-ore.

Pyrolusite.

Grau Braunstein, in part, Hausmann, p. 288. Fasriger Schwarz . Braunstein,

Id. p. 293.
Grey Manganese-ore, in part, Jameson, vol. iii. p. 252.
Grey Oxide of Manganese, in part, Phillips, p. 243.
Mangan-Hyperoxid, Leonhard, p. 240.

Form and cleavage probably belonging to the prismatic sys-
tem ; the cleavage taking place in several directions.

Lustre metallic. Colour iron-black ; in very delicate columnar
compositions the colour becomes bluish, and the lustre imperfect
metallic. Streak black. Opaque.

Rather sectile. Hardness = 2.0 . . . 2.5. Sp. gr. = 4.94, a
specimen from Elgersburg, and another, locality unknown, =
4.819, according to Dr Turner.

Compound Varieties.— f^emform coats. Both columnar and
granular composition is often met with, particularly the former ;
the individuals often radiating from common centres. If the in-
dividuals are very delicate, the masses will soil the fingers, and
write on paper.

Observations.

The name of Pyrolusite alludes to a property, for which this
mineral is reckoned the most valuable one among the preceding
species. It is derived from tJ^, fire> and Xov», I washy being em-
ployed, in consequence of the large quantity of oxygen which it
emits at a red heat, to free glass from the brown and green tints
produced by carbonaceous matter and protoxide of iron. The

the Ores qf Manganese. 137

manganese of commerce has been for this reason facetiously called
by the French le savon des verriers> or le savon du verre.

There can be no doubt that pyrolusite should form a species
of its own, if we only attend to the marked differences in its
hardness, strength, &c. from all the rest. As yet, however, its regu-
lar forms are unknown. For some time past I have endeavoured
to collect specimens either of crystals or cleavable masses of this
substance, but have not succeeded in getting any fit for measure-
ment. Mr Von Leonh abd kindly communicated to me some crys-
tals from Tiefe Kohlenbach, near.Eiserfeld, in the province of Sie-
gen, possessing the form Fig. 24., with uneven surfaces, and yield-
ing a black streak. They form a coating on the reniform shapes of
the uncleavable manganese-ore. Professor Gustavus Rose had
obtained a similar specimen from the same source ; and by some
approximate measurements, but which were far from decisive, we
found the inclination of a on a, over the small face 6, to be
= 86° 20'. The faces of the horizontal prism d9 did not admit
of measurement at all. There exists cleavage parallel to a and 6,
but not very perfect. Among the forms of manganite, there is no
prism, parallel to the axis, which even comes near the one here
mentioned, though the approximation at the angles be ever so
rude ; and the crystals may be therefore considered as the actual
type of the species of pyrolusite, which is likewise the opinion of
Mr Rose. I have observed crystals of the form of manganite,
yielding the characteristic brown streak only in the interior por-
tions of the crystals, while that of the exterior strata is black.
This may be the result of one of those changes of substance, the
form remaining the same, which are recorded in a preceding part
of this volume ; it may, however, be also one of those curious in-
stances, where two species, of different forms, enter, as it were,
into a regular composition with each other, as in felspar and ai-
bite, disthene and staurolite, and others ; many of which 1 have

VOL. XI. part i. s

138 Mr Hai dinger's Mineralogical Account qf

observed, and propose to give an account of, on some future oc-
casion.

Pyrolusite was found by M. Gmelin to be a superoxide of
manganese. In most mineralogical works, the descriptions given
of the only species that they contain, is made up of the forms
and colour of manganite ; and the hardness, streak and colour of
pyrolusite.

This is at once the most common species, and the most useful
one, on account of the large quantity of oxygen which it contains.
It is the ore of manganese properly so called, in an economical
point of view, and is extensively, though not exclusively, worked
for in many countries. The principal mines are the ancient ones
of Ilmenau, Friedricksroda, Reinwege, Elgersburg and other
places in Thuringia. Almost every one of the varieties, particu-
larly the compound ones, granular and columnar, are found there,
consisting of individuals of all sizes. Here, at Oehrenstock, near
Ilmenau, are also found the curious shapes of a parasitic forma-
tion, which present even the slightest peculiarities of the crystal-
lizations of calcareous spar as to regular form, but consist of a
tissue of crystals of pyrolusite, and engaged in a mass of the same
description. From the mines of Ehrensdorf near Maehrisch Trie-
bau in Moravia, since their discovery in 1798, many thousand
hundred weights of excellent ore are annually procured. At
Ehrensdorf the pyrolusite occurs in large nodules or masses, I
could not learn in what rock. It resembles the Thuringian va-
rieties. In Thuringia it forms veins in porphyry, and is often
accompanied with heavy spar. It is remarkable that no pyro-
lusite should have been found at Ihlefeld in the Hartz ; at least
there was no trace of it in all those collections which I examined,
if we except some thin masses in porphyry, and slender crystals,
evidently of the form of manganite, the superficial layers of
which yield a black streak, a circumstance which has not yet
received a satisfactory explanation.

the Ores of Manganese. 139

Pyrolusite is very often the product of decomposition of the
brachytypous parachrose-baryte, the carbonate of iron of the
latter being converted by the natural agents into the hydrate of
the peroxide, while the lime which it occasionally contains is de-
posited in the shape of calcareous spar or arragonite, and the
manganese is often found covering the surface of decomposed
rhombohedrons of the original species, in the shape of minute
crystals. In this manner it occurs in the mines of decomposed
sparry iron in beds in gneiss at Hiittenberg in Carinthia, at
Schmalkalden in Hessia, and other places. It is likewise found
in this manner in the counties of Sayn, Siegen, Salm and Hamm
in Prussia, in the veins of sparry iron traversing clay-slate,
which are decomposed in the upper levels, and then contain
much brown hematite. The localities are chiefly Friedewald
and Knorrenberg in the district of Kirchen, Sayn ; Streitberg
near the town of Siegen, and Horhausen and Herdorf, Siegen ;
Berge, Salm ; the mine Huth, near Hamm. One of the varie-
ties from Horhausen is particularly remarkable for the delicacy
of the fibres, which are disposed in small tufts within the geodes
of brown hematite, and which greatly resemble the fibrous varie-
ties of prismatoidal antimony-glance. There are specimens of it
in the imperial cabinet in Vienna, and in that of Mr Yon Strcve
in Hamburgh. Weyer in the county Wied-Runkel, Hirschberg
near Ahrensberg, and Bendorf on the Lower Rhine, are like-
wise named as the localities of superb specimens of pyrolusite.
Krettnich on the Blies, west of the Rhine, is likewise one of its
localities. Similar varieties occur in the iron mines of Bayreuth,
as at Armenhiilfe near Schnarchenreuth, and at Arzberg, in
those of Flatten, for instance Hilfe Gottes, and of Schwarzen-
thal in Bohemia, in those of Johanngeorgenstadt, Eubenstock,
Langenberg and others in Saxony, also at Reinerz in the county
of Glatz, and at Conradswaldau in Silesia.

The finest crystals of pyrolusite occur at Schimmel and Oster-

s2

140 Mr Haidinger's Minerahgkal Account of

freude near Johanngeorgenstadt, and at Hirschberg in West-
phalia. - These are chiefly short thick prisms, often resembling
Fig. 3. or nearly so, terminating on their extremities in nume-
rous fibres. Large flattish crystals of great beauty, terminating
in sharp elongated pyramids, with curved faces, occur at Maes-
kamezo, near Maggar Lapos, south of Kapnik in Transylvania,
in geodes of brown hematite, and associated with crystals of
quartz. This variety is found in a thick bed, of no great extent,
of brown iron-ore in gneiss. A similar one occurs also in a simi-
lar position at Gyalar near Vayda Hunyad in the same country.
Cleavable individuals of considerable size are found near Goslar
in the Hartz, in a mountain called Gingelsberg near the Ram-
melsberg. They are imbedded in small veins of quartz and
calcareous spar in clay-slate, particularly where they cross each
other. Distinct though small crystals are met with in many of
the mines in the west of Germany, for instance at Tiefe Kohlen-
bach in Siegen ; still smaller ones were found many years ago
in the Palffy iron-mines of Haerethof near Frohstorf in Austria,
associated with grey quartz. Very small crystals are found im-
bedded in and alternating with layers of black wad in Bay reuth.
A variety much resembling the German ones, found in similar
repositories, occurs at the mine of Antonio Pereira near Villa
Ricca in Brazil, along with brown hematite and psilomelane, in
beds in clay-slate, produced according to Dr Pohl's account,
from the decomposition of sparry iron.

Small granular pyrolusite occurs at Skidberget in the parish
of Lepand in Dalecarlia, Sweden. But the individuals are often
much smaller, and appear in the form of a black sooty substance.
Such are frequently found in the iron-mines of Raschau and
other places in Saxony, also at Platten and other similar reposi-
tories in the north of Bohemia; sometimes they include small
globules and reniform masses of red hematite, or red iron-ochre.
The same pulverulent oxide occurs also at Schladming in Sti-

the Ores of Manganese. 141

ria, at Felsobanya in Hungary, and at Piitten in Austria. Dr
Pohl observed several localities of it in Brazil, as at St Toao
d'el Bey, with brown hematite ; on the road between Anta and
Su Rita, in the capitania of Goy az, and at Banderinha do
Caelho in Minas Geraes. In the latter place it includes nume-
rous reddish nodules, or cylindrical and ramified concretions of
indurated clay.

The pyrolusite, as was observed above, is very generally found
along with psilomelane. In fact, it is seldom found without it.
Another species frequently accompanying it, is the brown hema-
tite, and these two species, like the pyrolusite and psilomelane,
are often very curiously associated with each other. At Arz-
berg in Bayreuth crystals of quartz are found, covered with a
stratum of brown hematite, upon which is deposited another dis-
tinct stratum of pyrolusite. In some varieties from Berge in the
county of Sahn, thin stalactites of brown hematite are uniformly
covered with a stratum of pyrolusite. The same is found also *
in masses of larger dimensions at Friedewalde in the county of
Sayn, and in these the concentric disposition of the brown and
black layers of the two species, visible in the cross fracture,
gives the whole a particularly elegant appearance. Pyrolusite
occurs in England at Upton Pine, near Exeter, in Devonshire,
and in Cornwall.

The manganese oxide noir barytifere of Hauy, from Bomaneche,
near Macon, does not appear to be a simple homogeneous mine-
ral. When examined with the magnifying lens, it exhibits dis-
tinctly a compact and a fibrous substance mixed up with each
other. The latter, as far as the minuteness of the particles will
allow, shews the properties of pyrolusite, its colour and general
aspect, and its hardness ; for even on the fracture newly obtained,
this compound soils the fingers, though on the file the hardness
appears as high as 5.0 . . . 5.5, that is, superior to apatite. The

142 Mr Ha i dinger on the Ores of Manganese.

compact mass is aggregated into reniform shapes, which leaves
numerous interstices between them. The colour is nearly the
same as that of the uncleavable manganese-ore, a bluish or grey-
ish black passing into dark steel-grey. The streak is black, with
a slight tinge of brown ; the place on the mineral, where it has
been examined, becomes shining.

( 143 )

IX. Chemical Examination qf the Oxides qf Manganese. By
Edward Turner, M . D. F. R. S. E. Professor of Chemis-
try in the University of London, and Fellow of the Royal
College of Physicians of Edinburgh.

(Read 3d and nth December 1827 J

1 * was originally my intention, in entering on this inquiry, mere-
ly to ascertain the composition of the ores, the mineralogical cha-
racters of which have been so ably delineated by Mr Haidinger
in the preceding paper. I had advanced however but a short way
in tJi.ve.tiSwhen my p*^ „. arreted by d*ta
both as to the manner of conducting the analyses, and as to the
mode of calculating their results. In this uncertainty I found
it necessary to extend my original plan, with the view of supply-
ing by my own researches what appeared to be not sufficiently
established by the labours of other chemists. I have accordingly
divided the essay into two parts ; attempting in the first division
to ascertain the atomic weight of manganese, and the composi-
tion of the artificial oxides of that metal ; and in the second, ap-
plying the facts thus established to illustrate the chemical con-
stitution of the native oxides described by Mr Haidinger.

PART L

ON THE ATOMIC WEIGHT OF MANGANESE.— ANAL Y8IS OF THE

CARBONATE OF MANGANE8E.

A pure carbonate of the protoxide of manganese was prepared
in the following manner. The dark brown mass left in the pro-
cess for procuring oxygen gas from the common peroxide of

144 Dr Turner's Chemical Examination

manganese by heat, was mixed with a sixth of its weight of
powdered charcoal, and exposed to a white heat for half an hour.
The protoxide thus formed was dissolved by muriatic acid, the
solution evaporated to dryness, and the residue kept for some
time in a state of fusion at a red heat. The resulting chloride
of manganese was re-dissolved by distilled water ; and after be-
ing filtered, was found to contain no impurity except a little
lime, which was separated by the oxalate of potash. The man-
ganese was then precipitated by a solution of the bi-carbonate
of potash, and the carbonate of manganese was carefully edul-
corated and collected on a filter. After removing the upper
layer which had become rather brown by exposure to the air,
the white carbonate was kept in a vacuum along with a ves-
sel of sulphuric acid until it became quite dry. The salt thus
prepared yielded a colourless solution, without any residue, when
put into dilute sulphuric acid, and was therefore free from the
red oxide of manganese.

Of this carbonate 8a805 grains were heated to redness in a
green glass tube, and the water collected in a tube filled with
fragments of the chloride of calcium. The quantity of water
procured in this way amounted to 0742 of a grain, equivalent to
8-427 per cent.

The proportion of carbonic acid was estimated by noting the
loss of weight which the carbonate of manganese experiences
when dissolved in dilute sulphuric acid. This mode of analysis,
as commonly performed, is inaccurate ; because the liquid retains
carbonic acid in solution, while the gas during effervescence car-
ries off with it an appreciable quantity of watery vapour. But
when performed with the precautions which I adopted, it yields
uniform results, and is susceptible of great precision. A known
quantity of the carbonate is placed in a small glass phial fitted
with a tight cork, in which two tubes are inserted. One of these
tubes descends to near the bottom of the phial and then bends

<f the Oxides qf Manganese. 145

slightly upwards, so as to admit of the acid being gradually intro-
duced without affording an exit to the gas. The other commu-
nicates with a tube filled with chloride of calcium, over which all
the carbonic acid gas passes before escaping into the air. As
soon as the effervescence has ceased, the carbonic acid retained
by the solution is driven off by causing it to boil during the
space of a few minutes ; and the gas is by the same means ex-
pelled from the interior of the phial, into which on cooling the
atmospheric air is admitted by the tube for introducing the sul-
furic acid. The carbonic acid gas remaining with the chloride
of calcium is replaced by atmospheric air, which is introduced by
inhaling at one extremity of the tube while the other is open.
The upper part of the tube for introducing the dilute sulphuric
acid, when not required to be open, is of course closed with a
cork in order to avoid loss by evaporation.

It was found by means of the preceding process that 20-68
grains of the carbonate, when dissolved in dilute sulphuric acid,
lose precisely 7*18 grains, or 84*72 per cent of carbonic acid. It
is accordingly composed, in 100 parts, of

Protoxide of Manganese 56*853

Carbonic Acid 84*720

Water 8427

100*000

Regarding 22 as the equivalent of carbonic acid, we have the fol-
lowing proportions :— As 34*72 : 56*853 : : 22 : 36*024.

According to this analysis, 36 may be safely adopted as the
combining proportion of the protoxide of manganese ; and pre-
suming the elements of this compound to be in the ratio of one
equivalent of oxygen to one equivalent of metallic manganese,
28 will be the equivalent of the latter. This result, with respect

VOL. XI. part i. x

146 Dr Turner's Chemical Examination

to the acid and base, corresponds exactly with the analysis of
Dr Thomson as mentioned in his First Principles of Chemistry.
(vol. ii. p. 350.) It differs considerably from the proportions
stated by Dr Forchhammer. (Annals of Philosophy, N. S. vol. i.
p. 54) According to this chemist 9305 parts of carbonic acid
combine with 51755 parte of the protoxide of manganese, a pro-
portion which would fix 34*45 instead of 86 as the equivalent of
the protoxide. This estimate is certainly erroneous ; and- Dr
Forchhammer appears to have fallen into the mistake by sup-
posing that the carbonate of manganese is converted by a red
heal into the deutoxide, whereas according to my experiments

the red arid* chiefly is then generated

It appears doubtful whether the water found by analysis in
the carbonate, after being .dried in vacua with sulphuric acid, is
mechanically retained by it or is in a state of chemical union. As
the proportion is not atomic, it is probable that the carbonate is
really anhydrous. If the ratio were as 58 to 45 instead of 5887,
the salt might be regarded as a compound of . two equivalents of
the carbonate of manganese and one equivalent of water.

Composition of the Sulphate of Manganese.

The most recent analyses of the sulphate of manganese are
by Dr Forchhammer and Dr Thomson, described in the works
already quoted. Dr Forchhammer precipitated the acid of a
known quantity of the neutral sulphate of manganese by the ni-
trate of baryta, and inferred from the weight of the precipitate,
that 100 parts of the sulphate of manganese are composed of
54378 parts of sulphuric acid and 45*622 of the protoxide. Ac-
cording to this analysis, the atomic weight of the protoxide is
3356, a number which is surely very far from the truth, and is
inconsistent with the equivalent of that oxide derived from Dr
Forchhammer's own analysis of the carbonate.

Dr Thomson analyzed the sulphate of manganese by mixing

of the Oxide* qf Manganese. 147

•■•

uri

it in atomic proportion with the muriate of baryta and
that,*fter the insoluble precipitate had subsided, retrace
of -sulphuric acid or baryta could be found in the solution. 'From
this experiment he infers- that 86 is the equivalent of the prot-
oxide. I am of opinion that the number assigned by -Dr Thom-
son is correct* bat I am not so certain that the means by which
he arrived at this conclusion are altogether free from objection.
The principle of his method is unexceptionable, especially if the
quantity of the precipitated sulphate be carefully observed at the
same time ; but it is essential to accuracy that the atomic Weight
of baryta be perfectly established. Dr Thomson supplied this
element in the inquiry in the following manner. He dissolved
88 parts or one equivalent of sulphate of potash, and 106 parts,
or what he considered one equivalent, of the chloride of barium
in separate portions of distilled water, and then mixed the solu-
tions together. After the precipitate had subsided, the super-
natant liquid was found to contain no trace either of sulphu-
ric acid or baryta. It hence follows, if no error is committed,
that 70 is the true equivalent of barium. But in a recent
number of Poggendobff's Annakn der Physik and Chemie
(vol. viii p. 5.), Berzelius denies the accuracy of the experi-
ment. He declares that after mixing together the sulphate of
potash and chloride of barium in the proportions mentioned
by Dr Thomson, ££ per eent of the chloride of barium remain-
ed in the residual liquid ; and on repeating this experiment
for jhv own information* I certainly -found that the whole of the

baryta was not precipitated. I wish it to be distinctly under-
stood, however, that I do not confidently rely on the accu-
racy of my result, having been hitherto unable, from want of
leisure, to examine the subject with that care which I deem
necessary before attempting to decide a point in dispute be-
tween chemists, for whose analytical attainments I entertain
such high respect Dr Thomson will doubtless fed the ne-
cessity of verifying his conclusions without delay ; since as er-

x 2

148 Dr Turner's Chemical Examination

ror in the atomic weight of barium will at once vitiate an ex-
tensive series of his most elaborate analyses. My own observa-
tion, however, combined with the remark of Berzelius, has in-
duced me in the mean time to secure my own researches as
much as possible from any uncertainty respecting the atomic
weight of barium, and I have been therefore induced to ascer-
tain the composition of the sulphate of manganese synthetically
rather than by analysis.

Nine pJL of pun protoxide of muquese, prepared from
the red oxide by means of hydrogen gas, were dissolved in dilute
sulphuric acid, the solution was slowly evaporated to perfect dry*
ness in a platinum crucible, and the dry salt exposed for half an
hour to a red heat. It then weighed 1901 grains ; and regard-
ing the increase in weight as owing to the acid combined with
the protoxide, the resulting sulphate must consist of 9 grains of
the protoxide of manganese and 10*01 grains of sulphuric acid.
The atomic weight of the protoxide indicated by this process, is
35*96. The experiment was repeated with 4*855 grains, and the
resulting sulphate weighed 10*26 grains, indicating 35.98 as the
equivalent of the protoxide of manganese.

As some chemists may doubt the accuracy of this process, I
shall attempt to show the grounds on which its merits are to be
estimated. Dr Thomson says it is scarcely possible to expel all
the water from the sulphate by means of heat, without at the
same time driving off some of its acid. It is indeed very easy
to effect the decomposition alluded to by Dr Thomson ; but I
found no difficulty, by slow evaporation and raising the fire gra-
dually, to keep the salt at a red heat for an hour or longer with*
out decomposing a particle of it. If the heat should accidentally
become so intense as to decompose a little of the salt, the defect
is easily remedied by adding a drop or two of acid, and replacing
the crucible in the fire.

Dr Forchhammer has judiciously remarked, that in expell-
ing an excess of sulphuric acid, a portion of the salt is very apt

\

\

of the Oxides of Manganese. 149

to be carried off mechanically by the acid vapour and lost. This
accident has occurred to myself, and always happens when a large
quantity of free acid is rapidly expelled. By employing a slight
excess of acid, and raising the heat slowly, all loss from this cause
may easily be avoided.

The dry salt obtained in my experiments was white, and dis-
^ed «£% .1 completely inZkd water.

Like many other neutral metallic solutions it reddened deli-
cate litmus paper. It was nevertheless quite neutral ; for a single
drop of a dilute solution of potash occasioned a precipitate which
was not in the slightest degree re-dissolved by agitation.

Analysis qfthe Chloride of Manganese.

In an excellent paper published in the Philosophical Trans-
actions for the year 1812, Dr John Davy states the chloride of
manganese to be composed of 54 parts of chlorine and 46 of me-
tallic manganese. The atomic weight of manganese calculated
from these data is 80*67, a number which is considerably be-
yond the truth. Dr Davy prepared the chloride by heating the
muriate in a glass tube communicating with the atmosphere by
a very small aperture. I have never failed by this method to
decompose some of the chloride, a circumstance which compli-
cates the analysis, and probably gave rise to Dr Davy's error.

According to the analysis of M. Arfwedson {Annals of Phi-
losophy, N. S. vol. vii. p. 274.), the elements of the chloride of
manganese are in the ratio of 8403 parts of chlorine to 6677 of
manganese. This result, in the accuracy of which M. Arfwed-
son does not place implicit confidence, would fix the equivalent
of manganese at 28*61. He prepared the chloride by placing
the carbonate of manganese in a spherical cavity blown in a ba-
rometer tube, transmitted over it a current of muriatic acid gas,
and heated the carbonate by means of a spirit-lamp as sopn 93

i

150 Dr TtrBmgft'ft Chemical Etcmmmation

the atmospheric «r was expelled from the tube. As it is diffi-
cult byTJiis,' aft weil as by Dr Dayy'b proctess, to preetirfe a3 per-
fectlypure chloride 6f manganese, I tad reeowse i6*he^lh>w-*
hig method. A solution iff the ratuifcte of manganese ^pias eva-
porated to dryness, the heat being carefulljrlregulatfd Se^as not
to decompose any of the salt, and the dry cotnpotind was placed
in a spherical cavity in the middle of a barometer tube about six
indies long. Muriatic acid gas was their transmitted through
the tube, and heat applied by the flame or a spirit-lamp. The
ctilbride entered into perfect fiision at a low red ifeat, and on
cooling yielded a highly crystalline lamellated mass of a beaatt-
ful pink colour. Every trace of acid and moisture was expelled
by heat ; and while the tube was still hot, its extremities were
closed by corks, so that the chloride might be weighed without
attracting moisture from the air. In the sense above explain-
ed it was quite neutral. Of this chloride 12*47 grains were dis-
solved in distilled water, and formed a colourless rotation with-
out any residue. Hie muriatic acid was thrown down by the
nitrate of silver, and yielded 28-42 grains of the timed chloride
of silver, equivalent to 7*008 grains of chlorine. Consequently
the chloride of manganese consists of

Manganese .... 5*462 28*06

Chlorine 7008 86

It follows from the preceding researches, that 26 ss the true
atomic weight of metallic manganese, and 86 the equivalent of
that oxide of manganese which forms definite coanpounds with
acids, and which I regard as the real protoxide of the metal It is
consequently composed of US parte of manganese and 8 parts of
oxygen. These numbers agree with the atottid weight of man-
ganese as stated by Dr Thomson, but not with that given by
Berzelius, who fixes it at 98*463. This estimate is made from
an analysis of M. Abfwedson, who finds that the dtotoxide «*f

of the Oxide* qfMcmganest. 151

manganese is composed of 100 part§of the metal an&4#J6 part*
of oxygen; feut at will appear firom the sequel of tbia paper that
the real quantity, of oxygen united, with, 100 parte of manganese
to constitute the deutoxide is 42*857 and not 42*16 as Abfwed-
son supposes.

On the Protoxide of Manganese.

• • * - • - . . lit .« .

By this te*m. imean. tfre salifiable base of manganese, the
only oxide of tl^ metal which appears .to me capable of forming
regular salts with acids. I am of opinion that in this compound
manganese is in its lowest degree of oxidation.. The existence
of the sub-oxides described by Berzelius and Dr Jo^n of Ber-
lin has never been, satisfactorily demonstrated ; and I have rea-
son to suspect that. 9PGP* °$l$r o£ them would in some of my
experiments have been generated, did there exist any tendency
to theiriorma^pn. ....

The protoxide, may be formed, as was shewn by M. Berthier
in th^ 20th volume of the Annates de Chimie et de Physique, by
exposing tjie peroxide, deutoxide, or red oxide of manganese to
the combined agency, of charcoal and a white heat ; and Dr
FoRCHEtAMMER has in the Annals of Philosophy described an ele-
gant method of preparing it by means of hydrogen gas at a red
heat. Arfwedson has likewise had recourse to tins method*
and I have employed it very extensively during the course of
the present investigation. The mode of performing the experi-
ment is as follows. The material for yielding the protoxide
was either the red oxide, deutoxide, or peroxide of manganese ;
and, occasionally, the carbonate was used When it was wished
to employ a red heat only, the material was placed in a small tray
of platinum foil, which was introduced into a tube of green glass,
through which the hydrogen gas was transmitted. The heat
was applied by means of a pan of burning charcoal. To pre-

152 Dr Turner's Chemical Examination

vent the tube from bending while softened by the heat, two or
three pieces of tobacco-pipe were tied to it longitudinally by
means of iron-wire. But when it was wished to prepare the
oxide at a very high temperature, the material was put into a
small tube of porcelain, and then introduced into a gun-barrel
which was exposed to a full white heat in a common wind-fur-
nace. A supply of hydrogen gas was procured in the usual
manner from zinc and dilute sulphuric acid ; but before coming
in contact with the oxide of manganese, it was purified by being
transmitted through a strong solution of potash, and then dried
by the chloride of calcium. At the close of the process, the prot-
oxide was of course preserved in an atmosphere of hydrogen gas
until it was quite cold.

The abstraction of oxygen commences at a temperature be-
low that of redness ; and when the peroxide is employed, it be-
comes red hot by the caloric evolved during the formation of wa-
ter, considerably before the tray which supports it is rendered
luminous by the heat of the fire. It appears nevertheless from
all my experiments that a strong heat is requisite in order to
convert all the red oxide into the protoxide. When the process
is conducted at a low red heat, I uniformly found that on putting
the product into dilute sulphuric acid, which instantly dissolved
all the protoxide, a portion of the red oxide came into view.
This affords a sure criterion of the operation being complete ;
for the pure protoxide dissolves without residue in dilute sul-
phuric acid, and yields with it a perfectly colourless solution.
There seems to be no risk of decomposing the protoxide by the
employment of a high temperature. I have exposed the recently
prepared protoxide a second time to the action of hydrogen gas
and a long continued bright red heat without the weight being
changed in the slightest degree ; and after exposure to the same
gas and a full white heat for an hour, it dissolves in dilute sul-
phuric acid without the slightest effervescence.

of the Oxides of Manganese. 153

The protoxide of manganese is described by Forchhammer as
being of a beautiful light-green, and by Arf wedson as of a pis-
tachio-green colour. I have seen specimens with a tint very
near the pistachio-green, but these always contained an admix-
ture of red oxide. The colour of the pure protoxide is very near
the mountain-green.

With respect to the action of air, my observations differ from
those of Forchhammer who found that recently prepared prot-
oxide attracted oxygen from the atmosphere before he could
weigh it. The protoxide procured in my experiments is far
more permanent. I exposed fifteen grains of recently prepared
protoxide to the free action of the air during the space of nine-
teen days, when it was found to have undergone no change ei-
ther in appearance or weight. If, therefore, it does attract oxy-
gen at all from the air, the operation must proceed very tardily.
It absorbs oxygen very slowly even at a temperature of 400° F. ;
for 7.269 grains of the protoxide, after an hour's exposure to that
degree of heat, did not gain in weight more than 0.021 of a grain.
At a temperature of 600° F. it absorbs oxygen much more rapid-
ly ; and at a low red heat it loses its green tint, and becomes al-
most black in an instant. I have repeated this process frequent-
ly, but in no case did the protoxide take fire, as occurred in the
experiments of Forchhammer and Arfwedson. I entirely
agree with M. Arfwedson, however, in the statement, that the
protoxide is converted, by simultaneous exposure to heat and air,
into the red oxide. This is the uniform result at whatever tem-
perature the oxidation is effected.

I have already mentioned my opinion, that, of the oxides of
manganese, the protoxide is the only one which forms definite
compounds with acids. It unites readily with this class of bo-
dies, without effervescence, producing with them the same salt
which is formed when the same acids act on the carbonate of
manganese. When it comes in contact with concentrated sul-

VOL. XI. part i. u

154 Dr Turner's Chemical Examination

phuric acid, an intense heat is instantly evolved ; and the same
phenomenon is produced, though in a less degree, by strong
muriatic acid. This oxide is likewise the base of the salts which
are formed when sulphuric or muriatic acid is heated with the
peroxide, deutoxide, or red oxide of manganese. As the accuracy
of this statement, as respects sulphuric acid, has been denied by
an acute chemist and good observer, I have been induced to ex-
amine the question with considerable care. I mentioned in my
Elements of Chemistry, in explaining the process for procuring
oxygen gas by means of sulphuric acid and the black oxide of
manganese, that the peroxide loses a whole proportion of oxygen,
and is converted into the protoxide, which unites with the acid,
forming a sulphate of the protoxide of manganese. The gentle-
man who has done me the honour to review that work in the
Annals of Philosophy, I apprehend Mr Richard Phillips, has

*

made the following remark on the preceding passage. " This
statement is at variance with both Dr Thomson's and also with
the results of our experiments ; for we find that 44 or one atom
of peroxide of manganese yield 4.2 of oxygen, which is so much
nearer 4 than 8, that there is no question but that the deutoxide,
and not the protoxide is obtained by the action of sulphuric acid ;
that this is the case is farther proved by the deep red colour of
the solution of the sulphate, and by its losing that colour, as
stated by Dr Thomson, when mixed with sulphurous or nitrous
acid."

To decide this point between the reviewer and myself, it is
only necessary to heat the peroxide of manganese with concen-
trated sulphuric acid, so as to form a solution highly charged
with the oxide of manganese, and decant off the solution while
hot from the undecomposed peroxide. The liquid on cooling
deposits a perfectly white salt, which possesses every property of
the protosulphate of manganese. If the acid, which retains ah
amethyst-tint even when cold, be again heated, the red colour

of the Qxides of Manganese. 155

speedily disappears ; because the red oxide, which is dissolved in
small quantity by the sulphuric acid, is then also converted into
the protoxide with the evolution of oxygen gas. The red colour
disappears gradually even without the aid of heat ; for the solu-
tion will be found after a few days to be almost and sometimes
quite colourless, while a minute quantity of red oxide has sub-
sided to the bottom. On applying a very gentle heat, the red
oxide is redissolved, and the acid acquires a lively amethyst-red
colour. It is easy, by operating in this way, to obtain satisfactory
proo£ that a minute portion of red oxide suffices to communicate
a rich colour to a considerable quantity of sulphuric acid. The
acid may be made to retain its red colour, either by diluting it
with water, or by keeping it in contact with undissolved oxide.

On the Bed Oxide.

I have followed the usage of 'most chemists in applying the
term Red Oxide to that compound which Arfwedson has de-
scribed under the name of Oxidum Mmganoso-mangamcum, (An-
nals of Philosophy, N. S. vii. 267), and which is uniformly pro-
duced when the nitrate, peroxide, or deutoxide of manganese is
exposed to a white heat. In my early experiments on this oxide,
I entertained considerable doubt as to the uniformity of its com-
position. This opinion originated in the remark, that, on ex-
posing the peroxide of manganese to a white heat, the quantity
of oxygen lost by different portions of it, though agreeing per-
fectly in some experiments, differed widely in others ; and that,
on one occasion, I procured the green oxide almost in a state of
purity. I subsequently discovered, however, that the disagree-
ment in the results was occasioned by the want of a free current
of air within the furnace. In some of the experiments the draft
was unguardedly cut off, and consequently an atmosphere of

u 2

156 Dr Turner's Chemical Examination

carbonic oxide gas, collecting around the heated manganese,
reduced it more or less nearly to the state of protoxide. On
avoiding this source of fallacy, the results were no longer dis-
cordant ; and I am now quite satisfied that the red oxide formed
at a white heat and with free exposure to atmospheric air, is
uniform in its composition. The accuracy of this inference is
established by the occurrence of the red oxide in nature, as will
appear in the sequel of the present communication.

The red oxide, when formed at a white heat and rubbed in a
mortal* to the same degree of fineness, is always of a brownish-
red colour when cold, and nearly black while warm. The pow-
der of the native red oxide has a reddish-brown tint, and the
colour of the red oxide prepared by exposing the precipitated
protoxide or the carbonate to a moderate red heat, has most
commonly an admixture of yellow, something like rhubarb,
though of a deeper hue ; but both of these acquire the red co-
lour when heated to whiteness.

The red oxide manifests little tendency to pass into a higher
degree of oxidation by abstracting oxygen from the atmosphere,
even by the aid of heat. Thus a portion of the red oxide, pre-
served for an hour at a low red heat, and freely exposed to the
air at the same time, did not acquire any appreciable addition
to its weight The protoxide of manganese precipitated from
the sulphate by an excess of pure potash, collected on a filter
and washed, fully exposed to the air in its moist state for twenty-
four hours, and then heated in an open vessel to a moderate red
heat, which was insufficient to decompose the deutoxide, lost
only 0.218 per cent by subsequent exposure to a white heat.
The quantity of deutoxide present, therefore, must have been
very minute. The anhydrous protoxide, as already mentioned,
always yields the pure red oxide when heated to redness in the
open air. The carbonate, also, in similar circumstances, is con-

of the Oxides qf Manganese. 157

verted into a Ted oxide containing but a very small proportion of
the deutoxide. It will appear from'these experiments that it is
unsafe in analyses to heat the precipitated protoxide or carbo-
nate to redness, and consider the product as the deutoxide ; a
practice which is calculated to lead analytical chemists into
considerable errors, and indeed- has actually done so. If it is
wished to procure the deutoxide, the precipitate should be moist-
ened with nitric acid, and then exposed to heat.

I have endeavoured to ascertain the composition of the red
oxide by several methods. The first is by the combined agency
of heat and hydrogen gas. In the first experiments 100 parts
of pure red oxide, in being thus converted into the protoxide,
lost 6.802 and 6.817 parts of oxygen ; but as the resulting green
oxide, when put into dilute sulphuric acid, was found to contain
a little red oxide, the loss in oxygen must be rather below the
truth. To avoid this error I exposed 44.256 grains of red oxide
to hydrogen gas and a white heat for the space of one hour,
when the loss amounted to 3.153 grains on 7.125 per cent.

Judging by the increase in weight which the protoxide ac-
quires when heated in the open air, 100 parts of the red oxide
consist of 93.05 parts of protoxide and 6.95 of oxygen. Accord-
ing to a similar experiment made by Arfwedson, the red oxide
is composed of 93.153 protoxide and 6.847 parts of oxygen.

In an analysis already described, the carbonate of manganese
was found to contain 56.853 per cent of the protoxide of man-
ganese. When 100 parts of the same carbonate are exposed to
air and a white heat, 61.18 parts of red oxide are obtained.
From these data it may easily be calculated that the red oxide
consists of 92.927 parts of protoxide, and 7.073 of oxygen.

As a mean of the numbers afforded by these three methods,
it follows that the red oxide is composed of 92.951 parts of the
green oxide and 7.049 of oxygen, or of 72.291 parts of metallic

158 Dr Turner's Chemical Examination

manganese and 27.709 of oxygen. According to M. Berthier,*
who reduced the red oxide to the metallic state by means of
charcoal and a long continued intense heat, the oxygen is only
26.6 per cent. But this estimate, as M. Berthier himself
suspects, certainly renders the quantity of oxygen too small;
for though, guided by theoretical views, I am disposed to con-
sider my own number not rigidly exact, yet from the care with
which the experiments were made, I am satisfied their result
cannot be far from the truth.

From this proportion of manganese and oxygen, we may con-
sider the red oxide a compound either of 80 parts or two equi-
valents of the deutoxide and 36 or one equivalent of the prot-
oxide, as M. Arfwedson supposes, or of 44 parts or one equi-
valent of the peroxide and 72 or two equivalents of the protoxide
of manganese. If, on either of these suppositions, the composi-
tion of the red oxide in 100 parts be calculated, it will be found
to consist of 93.104 parts of the protoxide and 6.896 of oxygen,
or of 72.414 parts of metallic manganese and 27.586 of oxygen.
These numbers approximate closely to those furnished by my
experiments, and may serve perhaps to correct them.

The red oxide of manganese, when agitated with strong sul-
phuric acid, is dissolved in minute quantity, without appreciable
disengagement of oxygen gas, and the solution is promoted by
a slight increase of temperature. If the resulting liquid be se-
parated from undissolved oxide, and exposed to heat, its ame-
thyst-red tint quickly disappears, and the protosulphate of man*
ganese is generated. When the red oxide is briskly heated with
sulphuric acid, the protosulphate is formed, and oxygen gas
evolved with effervescence.

On boiling the red oxide with an excess of very dilute sul-
phuric acid (in the proportion, for example, of two measured

* Annates de Chimie et de Physique, vol. xx.

qf Ike Oxides of Manganese. 1 59

drachms of strong acid to five ounces of water), a colourless so-
lution of the protosulphate is obtained ; while a portion of per*
oxide is left, the quantity of 4rhich corresponds to the atomic
view just given; that is, 1 16 parts of the red oxide yield 44 parts
of the peroxide of manganese.

When the red oxide is mixed with strong muriatic acid, a
portion of it is almost instantly dissolved, and communicates a
deep red colour to the liquid. But the solution is not perma-
nent. The odour of chlorine is perceptible from the beginning,
even at a temperature of zero of Fahrenheit ; the disengage-
ment of that gas continues slowly, though without distinct effer-
vescence, until in a few days the solution, if separated from un-
dissolved oxide, becomes quite colourless. The red oxide dis-
solves in hot muriatic acid with effervescence, owing to the evo-
lution of chlorine.

On the Deutoxide*

This oxide is prepared by exposing the nitrate or peroxide of
manganese for a considerable time to a rather low red heat. I
have found great difficulty in procuring it artificially in a pure
state. After exposing the peroxide for an hour or longer to a
moderate red heat, the residue frequently contains too much
oxygen for constituting the deutoxide ; and on augmenting the
temperature slightly, the loss in oxygen is very apt to become
excessive. The result is so much influenced by slight differ-
ences of temperature, that I do not feel confident in infer-
ring the existence of the deutoxide from such researches. That
there is such a compound, however, is demonstrated by its occur-
ring in two different states in the mineral kingdom. My expe-
riments as to its composition, as will afterwards appear, agree
with the statement of Berzelius, Arfwedson, and Thomson.

160 Dr Turner's Chemical Examination

It is intermediate between the protoxide and peroxide, consist-
ing of 28 parts or one equivalent of manganese, and 12 parts or
one equivalent and a half of oxygen ; or rather, to be consistent
with the atomic theory, of two equivalents of the former to three
of the latter. Its elements, it is obvious, are in such proportion,
that it may be regarded as a compound of 44 parts or one equi-
valent of the peroxide, and 36 parts or one equivalent of the
protoxide of manganese ; and into these it may be resolved by
being boiled in dilute sulphuric acid.

The colour of the deutoxide of manganese varies with the
source from which it is derived. That which is procured by
heat from the native peroxide or the hydrated deutoxide, has a
brown tint ; but when prepared from the nitrate of manganese
it is almost as black as the peroxide itself, and the native deut-
oxide is of the same colour.

On heating a mixture of the deutoxide of manganese and con-
centrated sulphuric acid, oxygen gas is evolved with efferves-
cence, and the protosulphate is generated. In the cold the acid
acts upon it slowly, and acquires an amethyst-red colour ; but
this efiect does not take place so readily as with the red oxide.
The solution is attended with the disengagement of a little oxy-
gen, a circumstance from which it may be inferred that a por-
tion of deutoxide is resolved into oxygen and the red oxide, and
that the latter, on being dissolved, -is the cause of the red colour.
Arfwedson represents the deutoxide as yielding a deep grass-
green coloured solution with sulphuric acid ; but I have never
been able to observe this phenomenon.

Strong muriatic acid acts upon the deutoxide in the same
manner as on the red oxide of manganese, excepting that the
acid acquires the deep red tint more rapidly with the latter than
when the former is employed. It is hence probable that the red
colour is really communicated by the red oxide.

of the Oxides of Manganese. 161

• Peroxide of Manganese.

To procure a pure peroxide of manganese, a solution of the
protonitrate was evaporated to dryness, and the heat continued
until the whole of the salt was converted into a uniform black
mass. It was then reduced to fine powder, carefully washed with
distilled water, and dried by exposure for several hours to a tem-
perature of 600° F. On heating a portion of this peroxide to
redness in a glass tube, a little moisture was expelled, which red-
dened litmus paper powerfully. Consequently the peroxide still
retained a little nitric or nitrous acid, which I found it impos-
sible to expel entirely, except by the employment of a tempera-
ture bordering on a commencing red heat. The peroxide, after
exposure to that degree of heat, was quite free from acid, but
still retained a trace of moisture. On exposure to a white heat
it lost only 10.82 per cent of oxygen, whereas had the peroxide
been pure, it should have yielded 12.122 per cent. It appears
therefore that the heat required to expel the last portions of the
nitric acid, decomposes some of the oxide itself; and this cir-
cumstance induced me not to rely on the analysis of the artifi-
cial peroxide of manganese.

From my examination of the native peroxide of manganese, I
conclude with all other chemists who have of late years studied
the oxides of manganese, that it contains twice as much oxygen
as the protoxide. It is accordingly composed of 28 parts or one
equivalent of manganese, and 16 parts or two equivalents of
oxygen ; and in being converted by a white heat into the red
oxide, it should yield 12.122 per cent of oxygen gas*

Sulphuric acid acts very feebly on the peroxide of manganese.
At first I could observe no action at all j but on employing a
considerable quantity of the oxide, and agitating the mixture
frequently, the acid after an interval of two or three days ac-

VOL. XI. PART I, X

162 Dr Turner's Chemical Examination

quired an amethyst-red tint, a minute quantity of oxygen gas
being at the same time disengaged. The nature of the change
which is produced when sulphuric acid is heated with the per-
oxide of manganese, has already been discussed.

Muriatic acid, as is well known, acts upon the peroxide of
manganese at common temperatures, chlorine gas being disen-
gaged with effervescence. If heat and an excess of acid be
employed, a colourless muriate of the protoxide is procured ;
but in the cold, or if the oxide be in excess, in addition to the
protomuiiate, a deep red coloured solution is formed, similar to
that already mentioned in the description of the red oxide.

PART II.

ON THE COMPOSITION OP THE ORES OF MANGANESE DESCRIBED

BT MR HAIDINGER.

Method qf Analysis.

Pure fragments of the ores were carefully selected, reduced
to fine powder in a mortar of agate, and washed with distilled
water. Some of the ores yielded nothing to the action of water ;
but from some of them, especially from those of Ihlefeld, minute
quantities of the muriate and sulphate of lime, and sometimes of
soda, were separated by the action of water. It is the accidental
presence of the muriates which gives rise to the disengagement
of chlorine when sulphuric acid is added to some of the native
oxides of manganese, and which induced Mr Macmdllin to re-
gard chloric acid as a constituent of these ores. For the cor-
rection of this error we are indebted to Mr Richard Phillips,*

* Philosophical Magazine and Annals, vol. L p. 818.

tfthe Oxides qf Manganese. 168

with whose observation my own experiments correspond ;— none
of the native oxides yield a trace of chlorine on the addition of
sulphuric acid, provided the muriates have been previously re*
moved by washing.

The ores, before being submitted to analysis, were dried at
212° FM by which means they were brought to the same degree
of dryness which they possessed before being washed. The water
naturally contained in them was ascertained in every instance
by heating a known quantity of the ore to redness, and collect-
ing the water in a tube filled with fragments of the chloride of
calcium.

The quantity of oxygen was in most cases ascertained both by
bringing the ore to the state of red oxide by exposure to a white
heat, and by converting it into the protoxide by means of heat
and hydrogen gas. When performed with the precautions stated
in the first part of this communication, either of these methods
may be relied on with confidence ; but the first is more conve-
nient in general practice, because it requires less time and a
more simple apparatus. The latter is sometimes very trouble-
some, owing to the difficulty with which some of the ores of
manganese, the native peroxide for example, are reduced by
hydrogen to the state of pure protoxide. I have in no instance
estimated the quantity of oxygen by means of the deutoxide, the
formation of this compound being in my opinion too uncertain
to adm& of any analytic process being founded upon it.

In searching for the presence of foreign matters I have em-
ployed the following processes. The water which was expelled
from the ores by heat, was examined with test paper, hut was
always found quite free from alkaline or acid reaction. The ab-
sence of carbonates was ascertained by the entire want of effer-
vescence on the addition of dilute nitric acid. Strong sulphuric
acid did not cause the evolution of chlorine or any acid fumes.

x 2

164 Dr Turner's Chemical Emminatum

On dissolving the ores in muriatic acid and evaporating the
solution to perfect dryness, the residue, with the exception of a
little siliceous matter and red oxide of manganese proceeding
from slight decomposition of the chloride, was always complete-
ly redissolved by water. This circumstance demonstrates the
absence of phosphoric and arsenic acids, which, if present, would
have been left as the insoluble phosphate or arseniate of manga-
nese. By well known methods I satisfied myself of the absence
of sulphuric acid, alumina, and magnesia. In several of the ores
the oxalate of ammonia detected a trace of lime. It is remark-
able that every species, with one exception, contains baryta. In
most of them, indeed, it is present only as an impurity ; but in
two of the ores, the uncleavable manganese-ore or black hema-
tite, and the manganese oxide nair barytifere of Hauy, it is an
essential ingredient of the mixture. In those species in which
this . earth exists as an impurity, it is not united with the sul-
phuric or carbonic acid; but is most probably combined with
the peroxide of manganese.

From the frequency with which iron has been found accom-
panying the ores of manganese, I was led to expect its presence,
and employed the ferrocyanate of potash and hydrosulphuret of
ammonia as re-agents for its detection. The muriatic solution
of the different species yielded a white precipitate with the ferro-
cyanate of potash, and the characteristic flesh-coloured sulphuret
of manganese with the hydrosulphuret of ammonia. It hence
follows that all the ores submitted to analysis, even the uncleav-
able manganese-ore, which has been placed among the ores of
iron, are perfectly free from iron, as well as from copper, lead,
and similar metallic substances.

of the Oxides of Manganese. 165

Analysis o/Manganite or the Prismatoidal Manganese-ore.

This ore, even when selected with the greatest care, yields
to distilled water traces of the muriates and sulphates of lime and
soda. It dissolves without residue in muriatic acid, and is free
from siliceous earth, lime, baryta, and every other impurity. It
is the purest native oxide of manganese which has fallen under
my notice. Its powder has a uniform brown tint, and . I have
been unable to observe in it any tendency to pass into the per-
oxide by absorbing oxygen from the air. After exposure to the
air for six months, during which it was frequently moistened
with distilled water, it underwent no change of weight. Cold
sulphuric acid acts very feebly on this oxide. M. Gmelin * o
Heidelberg states that it is not dissolved at all by this acid in
the cold, and I was at first of the same opinion ; but by employ-
ing a considerable quantity of the oxide, and agitating the mix-
ture frequently, the acid does acquire a red tint in the course of
two or three days. In this respect manganite agrees with the
peroxide ; but differs from all the other species, which commu-
nicate a red colour to cold sulphuric acid with much greater
facility.

When manganite is heated to redness it gives out 10.10 per
cent of water ; and the total loss from exposure to a white heat
is IS. 15 per cent Deducting from the last number the amount
of water, S.05 remain as the loss in oxygen. The result of this
Analysis is therefore,

* I regret that I have been unable to obtain a sight of that volume of the
Zeiischrifi der Mineralogie, which contains M. Gmelin's paper on the composition
of the oxides of manganese. My knowledge of his labours is solely derived from
M. Leonhard's Handbuch der Oryktognosie.

166 Dr Turner's Chemical Examination

Red oxide

, . 86.85

Oxygen . .

, . 8.05

Water . .

. . 10.10

100.00.

According to this analysis, manganite contains an oxide of
manganese, 89-9 parts of which yield 3.05 of oxygen, on being
converted into the red oxide. An equal quantity of pure deut-
oxide, in undergoing a similar change, should lose 2.997 of
oxygen.

Exposed to a strong red heat and a current of hydrogen gas,
100 parts of manganite lost 19.09 parts in one experiment, and
19.07 in another. The mean is 19.08, and subtracting 10.10 as
water, 8.98 remain as oxygen. According to this analysis the
raangamte is composed of

. . • 80.92
Oxygen . . . 8.98
Water . . . • 10.10

100.00

Now as 80.92 : 8.98 : : 36 : 8.995.

From the result of both analyses it is apparent that manganite,
in relation to manganese and oxygen, is a deutoxide.

Also as 89.90 : 10.10 : : 40 : 4.494.

The fourth number is so near 4.5, half an equivalent of water,
that we may safely regard manganite as a compound of 80 parts
or two equivalents of the deutoxide of manganese, and 9 parts
or one equivalent of water.

qf the Oxides of Manganese. 167

The material for the preceding analysis was taken from a very
fine crystallized specimen from Ihlefeld. The result of Gme-
lin's analysis of the same variety is as follows :-r— Red oxide
87*1, oxygen S#4, water 9'5. The water Js here certainly under-
rated.

The grey oxide from Undenaes in West Gothland, analyzed by
Arfwedson, is a similar compound.

Analysis qf the Brachytypous Manganese-ore or Braunite.

The colour of this ore, both in mass and in powder, is nearly
black. With sulphuric acid it yields no distinct odour of chlo-
rine. It dissolves in muriatic acid, leaving a trace of siliceous
matter. The solution gives a precipitate of sulphate of baryta
with sulphuric acid, but does not contain any other impurity. Of
all the native oxides this is the most easily reduced to the state
of protoxide by the action of hydrogen gas. The material for
analysis formed part of a specimen from Elgersburg.

As a mean of two closely corresponding experiments, this
oxide contains 0*949 per cent of water.

To ascertain the quantity of oxygen, 16*634 grains were ex-
posed for half an hour to the action of hydrogen gas at a red
heat. The residue weighed 14*837 grains, and had the light
green tint of the protoxide. The total loss was 1797 grains, or
10*80 per cent ; and subtracting 0*949 for water, there remains
9*851 per cent as the loss in oxygen.

The baryta was precipitated by sulphuric acid from a solu-
tion in muriatic acid of 42*09 grains of the mineral The preci-
pitate after being heated to redness amounted to 1*44 grains*
equivalent to 0*951 of a grain or 2-26 per cent of pure baryta.

*

168 Dr Turner's Chemical Examination

According to this analysis, 100 parts of the ore contain

Protoxide 86*94

Oxygen ..».., 9851

Water 0-949

Baryta 2260

Silica a trace.

100000

Now 86*94 : 9*851 : : 86 : 4079 ; and as the presence of water
and baryta, from the small quantity of these substances, must be
regarded rather as accidental than essential to the mixture, it fol-
lows that Braunite is an anhydrous deutoxide of manganese.
I apprehend the baryta must be in combination with deutoxide
of manganese ; since, were it united with peroxide, the loss in
oxygen would exceed the quantity above stated.

I am not acquainted with any analysis of this mineral by
other chemists.

Analysis of the Pyramidal Manganese-ore or Hausmannite.

Hausmannite, before being washed, yields a faint odour of
chlorine by the action of sulphuric acid. When heated to red-
ness it gives off 0*435 per cent of water ; and at a white heat the
loss is only 0*65 per cent, indicating 0215 of oxygen. When
dissolved in muriatic acid, a small quantity of silica is left,
amounting to 0887 per cent ; and on adding sulphuric acid to
the solution, a little sulphate of baryta subsides, indicating 0*1 1 1
per cent of the pure earth. Hausmannite is accordingly resolved
by this analysis into

■of the Oxides qf Manganese. 169

Red oxide 98.098

Oxygen 0*215

Water 0*435

Baryta 0111

Silica 0-337

100-000

This oxide is manifestly an anhydrous red oxide of manga-
nese. The small quantity of oxygen lost at a white heat is pro-
bably owing to die admixture of a little deutoxide or peroxide,
combined with the baryta.

From some preliminary experiments on Hausmannite M.
Gmelin of Heidelberg * inferred that it is a pretty pure red
oxide, an inference which entirely agrees with the result of the
preceding analysis. This is the only chemical examination of
Hausmannite by other chemists, which I have met with. The
material for my analysis was part of a specimen from Ihlefeld,
for which I am indebted to the kindness of Professor Stro-
meyer.

Analysis vf Pyrohmte, or the Prismatic Manganese-ore.

The following analysis was made with a compact columnar
variety from Elgersburg, which has a specific gravity of 4'94,
and the individuals of which have a parallel direction. With
sulphuric acid it does not yield a trace of chlorine ; and the only
impurities which I could discover in it are silica and baryta, the
former amounting to 0*5 IS, and the latter to 0-532 per cent

* Lkonhaed's Handbuch der Oryktognosie.
VOL. XI. PART I.

170 Dr TtMcmnto Chemical Examination

The quantity of* water was determined as usual by means of
the chloride of calcium, and amounted to l'l£per cent.

On exposing 23*746 grains of this oxide to a white heat, the
loss proved to be 8064 grains or 12*90 per cent Subtracting
1'12 for water, there remain 11*78 as the loss of oxygen.

Accordingly, T00~parts of the Pyrolusite were resolved into

Red oxide
Oxygen.
Water ...

Silica

. 84055
L. U>78

.. <fr5»&
. OrSia.

**i

100-000

Now; emitting the water, baryta** and silica as accidental! imp**,
rities, the reioaining 97*83$ parts lose 11*78 parts, op 18rQ4< per
ceHt' of oxygen in being' converted into the red oxide. . Oil the
supposition that Pyrolusite is composed of one equivalent of
manganese and two equivalents of oxygen, it should lose ut pass*
ing into the state of red oxide exactly 12*122 per cent of oxygen,
a quantity which corresponds closely with the result of analysis.
It is therefore an > anhydrous peroxide of manganese.

I have analysed another columnar variety of Pyrolusite, which
has a density of 4*819, and of which the individuals radiate from
a common centre. I brought it with me from Germany, and be-
lieved it to be from Ihlefeld, as the ticket indicated; but Mr
Haid wgek, after carefully inspecting several large cabinets in
Germany, has been unable to discover any similar specimen which
is known to have been found in that place. Its locality there*
fore is doubtful.

This variety is less pure than the foregoing. Before being
washed, it yields chlorine on the addition of sulphuric acid ; and

of the Qambs *f Mangtmese. 171

after the muriates have -been removed bydistilled tiwMteiy the neu-
teal- solution in amsriatic acid gives traces of lime with oxalate*^
potash. It contains silica and baryta nearly in. the same proper-*
tion as the first variety.

The following is the result of my analysis :

•Red Aside. 85*617

Oxygen 11599

Water 1-566

Silica 0-553

Baryta 0665

Lome a trace

•■*«■»■

100.000

Subtracting 2784 as impurities, there remain 97*214 parts, which
lose 11599, or 11931 per cent, of oxygen in being converted in-
to the red oxide. It is therefore an anhydrous peroxide, most
probably containing an admixture of some other oxide.

Analysis of Psilomelane, or the Uncleavable Manganese-ore.

This mineral when reduced. to powder has a brownish-black
colour. With sulphuric acid it does not emit any odour of chlo-
rine. It dissolves completely in muriatic acid, excepting a small
quantity of silica which amounts to 0*26 per cent ; and the only
substances which 1 could detect in the solution are baryta and
the oxide of manganese. Though this, .ore has. been placed by
mineralogists among the oxides of iron, under the names of Black
Hematite and Black Iron-ore, pure fragments of it do not con-
tain a trace of that metal

y 2

172 Dr Turner's Chemical Examination

When heated to redness Psilomelane gives out 6*216 per
cent of water. The diminution in weight occasioned by expo-
sure to a white heat is 13*58 per cent ; and on subtracting 6*216
for water, there remains 7*364 as the loss in oxygen.

To ascertain the quantity of baryta 80*028 grains of the mi-
neral were dissolved in muriatic acid, and the baryta precipitated
by means of the sulphate of soda, a considerable excess of mu-
riatic acid being allowed to remain in the liquid, to prevent any
manganese from adhering to the precipitate. The sulphate of
baryta, after exposure to a red heat, amounted to 7'434 grains,
equivalent, according to the atomic numbers of Dr Thomson, to
4*914 grains, or 16*365 per cent of pure baryta.

According to this analysis, 100 parts of Psilomelane have
yielded of

Red oxide 69795

Oxygen 7*364

Baryta 16*365

Silica 0*260

Water 6*216

100000

The precise atomic constitution of Psilomelane is not made
apparent by this analysis ; and, indeed, the result is of such a
nature as to leave no doubt of this mineral containing more
than one oxide of manganese. For it follows, from the quantity
of oxygen expelled by heat, that a considerable part of the man-
ganese must be in the form of peroxide ; but it is equally clear
that the whole of it cannot be in that state, because 69*795 parts
of red oxide require 9'627 instead of 7'364 parts of oxygen to
constitute the peroxide. On perceiving this deficiency of oxy-
gen, I at first suspected that the baryta might prevent the usual

of the Oxides of Manganese. 178

quantity of oxygen from being expelled from the peroxide by
beat. Accordingly I ascertained the quantity of pure red oxide
by the way of precipitation ; but its amount corresponded closely
with the number already stated. Psilomelane must therefore,
I conceive, be a mixed mineral. I was at first disposed to re-
gard it as a compound of baryta and peroxide of manganese,
accidentally containing an admixture of some other oxide in a
lower stage of oxidation ; but the fact noticed by Mr Haidin-
ger of Psilomelane being, frequently and intimately associated
with Pyrolusite in the mineral kingdom, appears to justify the
inference, that the uncleavable manganese-ore consists essentially

«

of some compound, in proportions not yet ascertained, of baryta
and the deutoxide of manganese, and that Pyrolusite is the ac-
cidental ingredient. The propriety of this view is further shown
by an analysis of the following ore from Romaneche, a mineral
which is analogous to Psilqmelane in the proportion of its ingre-
dients, and in which an admixture of Pyrolusite may be detected
by the eye.

Analysis qf the Maganese oxide noir Barytiffcre /rom Romaneche.

The observations of Mr Haidinger leave no doubt of this
ore being a mixed mineral ; and according to my analysis it is
very analogous to Psilomelane. The specific gravity of some of
the purest fragments which I cquld select, is 4*365 ; and the den-
sity of Psilomelane, according to Mr Haidinger, is 4' 145. The
colour of both minerals is similar.

The black oxide of Romaneche yields a very faint odour of
chlorine with sulphuric acid. When heated to redness it gives
out 4*13 per cent of water. At a white heat it loses 11*39 per
cent ; and after subtracting 4*13 for water, there remain 7*26 as
the loss in oxygen.

1 74 Dr TubnekHi CSmmcalyBdMmnatwt of Manganese.

In wcder to'ascertain the quantity of baryta, 3^13 igraJHW were
dissolved in- miadatic acid ; .and after separating aranaUL portkm
erf sBioa, which amounted to 0953 per cent,Ip^cipitated the
baryta by means of the sulphate of soda* The insoluble snl-
phate, after exposure to a Ted heat, weighed 8*118 grains, equiva-
lent to #863 grains, or 16^9 per cent of pare baryta.

100 parts of themide are accordingly reeled into

Re!d oxide 70HH57

Oxygen 7-860

Baryta 16690

Silica 0-958

Water 4130

100-000

This mineral was analyzed some years ago by Vauquixik
and Dolomieu ; but the numbers which they have mentioned,
owing to the insufficient mode of analysis employed at that time,
are not entitled to any confidence. — (Journal des Mines IX.
778.)

( 175 )

X* An Account qf the Formation qf Alcoates, Definite, Com*
pounds of Salt* and Alcohol anabgmts 1» the* Hydrate*. By
Thto*as^rahamv Esq. M;A.

*

(Read 17th December 1821.)

In determining the solubility of salts and other bodies in alco*
ho^ it is desirable to operate with a spirit wholly free from waten
But anhydrous or absolute alcohol is formed with difficulty, even
by the most improved proeess — that of Richter* In rectifying
aleehol from chloride of calcium, as recommended by Richtkr*
I have never obtained it under the specific gravity 0.798 at the
temperature of 60°, by a single distillation ; but upon rectifying
this product again from new chloride of calcium, I generally
succeeded in reducing it to 0.796, which is the specific gravity
of the standard alcohol of that chemist. The following experi-
ment illustrates this process.

Four measures of alcohol of the specific gravity 0.826 were
poured into a retort, and a quantity of well dried chlpride of
calcium, amounting to three-fourths of die weight of the alcohol,
gradually added with occasional agitation. Much of the salt was
dissolved* with the evolution of heat; and the combination: was
promoted by boiling the whole for a few minutes, the vapour
being condensed in the neck of the retort, and returned to the
solution. A receiver was then adjusted to the mouth of the re-
tort, and the distillation conducted so slowly that the alcohol
wa» condensed entirely in the neck of the retort, and fell drop*
by drop into the receiver, — nearly two seconds elapsing between
the fall of each drop. The first measure of alcohol which came

176 Mr Graham's Account of the Formation of Alcoates.

over was of the specific gravity 0.800, at 60° ; the second mea-
sure, 0.798 ; and the third measure, 0.801 : the distillation was
then discontinued. These three measures were mixed together,
and subjected to a second distillation, which was conducted in
the same manner ; and two measures of alcohol obtained of the
specific gravity 0.796. It was found that farther rectification did
not reduce the specific weight of the alcohol below 0.796. From
the analysis of alcohol by Saussure, and the determination of the
specific weight of its vapour by Gat Lussac, there can be little
doubt that the alcohol thus obtained is perfectly anhydrous. It
is true that such alcohol still contains oxygen and hydrogen to
the amount of an atomic proportion of water ; but this propor-
tion of oxygen and hydrogen is essential to the constitution of
alcohol,*— the partial abstraction of it converting alcohol into
ether, and its total abstraction converting alcohol into defiant
gas ; while the supposition that the oxygen and hydrogen exist
in the state of water, is altogether gratuitous.

The process of Richter is exceedingly tedious, from the ne-
cessity of conducting it so slowly, and the waste of alcohol is
considerable. I tried newly burnt quicklime instead of chloride
of calcium, and distilled by the heat of a saline water-bath. If
it is merely our object to obtain alcohol perfectly free from wa-
ter, no process could be more effectual. The product was of the
specific gravity 0.794 ; but it contained a trace of ether, to which
the extraordinary lowness of its specific gravity is -attributable ;
and had an empyreumatic odour, notwithstanding the moderate
temperature at which the distillation was conducted. This like-
wise is a very slow process.

The process which I preferred is founded on the principle of
Mr Leslie's frigorific apparatus. The alcohol is concentrated
by being placed under the receiver of an air-pump, with quick-
lime. A large shallow basin is covered to a small depth with
recently burnt lime in coarse powder, and a smaller basin con-

Mr Graham's Account of the Formation ofAlcoates. 177

taining three or four ounces of commercial alcohol is made to
rest upon the lime : the whole is placed upon the plate of an
air-pump, and covered over by a low receiver. Exhaustion is
continued till the alcohol evinces signs of ebullition, but no far-
ther. Of the mingled vapours of alcohol and water which now
fill the receiver, the quicklime i3 capable of combining with the
aqueous vapour only, which is therefore quickly withdrawn, while
the alcohol vapour is unaffected. But as water, unless it has an
atmosphere of its own vapour above it, cannot remain in the al-
cohol, more aqueous vapour rises. This vapour is likewise ab-
sorbed, and the process goes on till the whole water in the alco-
hol is withdrawn. Several days are always required for this pur-
pose, and in winter a longer time than in summer. The follow-
ing cases exhibit the rate, according to which the water is with-
drawn. The first experiment was made in summer. Four ounces
of alcohol of the specific gravity 0.827 were concentrated. The
specific gravity was taken every twenty-four hours, and the fol-
lowing series of results obtained :

0.827
0.817
0.808
0.802
0.798
0.796.

In this case the whole water was withdrawn in five days, but
occasionally a period somewhat longer is required, although it
rarely exceeds a week. In winter the alcohol generally requires
to be exposed to the lime for a day or two longer than in sum-
mer. The following rate of concentration was observed in one
case in winter, the quantity of alcohol and other circumstances
being the same as in the former experiment:

VOL. XI. PART I. Z

178 Mr Graham's Account of the Formation of Alcoates.

0.825
0.817

0.809
0.804

0.799
0.797
0.796.

Quicklime, as a porous substance, appears to be capable of
condensing a small portion of alcohol vapour. It is therefore
improper to use it in great excess. In one case, in which three
pounds of quicklime were employed with four ounces of alcohol,
about one-sixth of the alcohol was lost from this absorption.
The quicklime should never exceed three times the weight of
the alcohol, otherwise the quantity of alcohol absorbed becomes
sensible. It should be spread over as great a surface within the
receiver as possible.

In Richter's process it is improper to operate upon more
than a few ounces of alcohol at a time ; as when a large quan-
tity of materials is introduced into the retort, the heat necessary
to disengage the alcohol in the centre of the mass inevitably ex-
pels the water left in the chloride of lime, at the points where it
is more exposed to the heat. In the air-pump also, only a few
ounces can in general be concentrated at a time. But in a tall
receiver, two or three shallow basins of quicklime can be sup-
ported at a little height above each other, each of them contain-
ing a small basin of alcohol resting in it. Or the process might
be conducted with facility on the large scale, by means of a tight
box of any size, furnished with numerous shelves, which might
be covered with quicklime in powder, and support a large num-
ber of basins of alcohol The box might be sufficiently exhaust-
ed of air by means' of a syringe, for it is not necessary that the
exhaustion be nearly complete ; and indeed more inconvenience

Mr Graham's Account qf the Formation if Aicoates. 179

is to be apprehended from a complete than from ati imperfect
exhaustion. After producing the exhaustion, no farther atten-
tion would be necessary ; and upon opening the box at the ex-
piration of a week or ten days, the alcohol would be found an-
hydrous. It is evident that absolute alcohol, procured by this
process, could be sold at a price but little exceeding its original
cost. It would moreover be of much greater value for the pur-
poses for which it is employed in the arts and medicine. I be-
lieve, however, that, by the excise laws as they at present exist,
no rectifier of spirits is permitted to concentrate alcohol beyond
a certain strength. Licensed apothecaries alone are allowed to
prepare and sell absolute alcohol. *

Alcohol may be concentrated in a close vessel with quicklime,
without exhausting ; but the process goes on much more slowly,
at least at the temperature of the air. The experiment was
tried at a high temperature, by heating in a water-bath a large
bottle with a very wide mouth, containing a quantity of alcohol
at the bottom, and quicklime suspended over it in a linen-bag.
When the water-bath attained the temperature of 150°, the
bottle was corked, and the bath prevented from becoming hotter.
Much of the lime was very quickly converted into hydrate, and
the alcohol considerably concentrated. But the process is trou-
blesome, and much inferior to that in which the air-pump is
employed.

In the place of quicklime, sulphuric acid cannot be substituted
in the foregoing process as an absorbing liquid, from a remark-

* Care should be taken that the temperature be nearly equable during the expe-
riment ; otherwise, when the atmosphere becomes cold, a condensation of alcohol
vapour takes place upon the cooled bell-glass, which runs down upon the plate of
the pump. The experiment, therefore, should not be performed in a room with a
fire, or near a window, but in a dark closet or press. From the manner in which I
performed the experiment, this condensation had never been experienced by myself;
but Dr Duncan junior observed it, on repeating the process.

z2

180 Mr Graham's Account of the Formation of Alcdates.

able property which it possesses. It is capable of absorbing the
vapour of absolute alcohol, in the same manner as it absorbs the
vapour of water. I was led to make this observation from a con-
sideration of the phenomena which attend the mixing of alcohol
and sulphuric acid. Nearly as much heat is evolved as if water
had been. added to the acid, even although absolute alcohol be
employed. Alcohol is also retained by the acid when heated to
500° or 600°, or at a temperature when the alcohol would be
decidedly in the state of vapour, — which indicates the possibility
of the same relation between sulphuric acid and alcohol vapour,
that subsists between water and those gases which it detains in
the liquid state, such as ammoniacal gas, when they would na-
turally assume the elastic form. But besides merely detaining
such gases, water can condense and absorb them. Sulphuric
acid, besides merely detaining alcohol vapour, might therefore
condense and absorb it.

As alcohol, like water, occasions cold by its evaporation, it
may be substituted for water in Mr Leslie's frigorific appara-
tus, sulphuric acid being retained as the absorbing liquid. In
circumstances precisely similar, it was found that a thermometer,
the bulb of which was covered with cotton, fell to 7° when moist-
ened with water, but when moistened with absolute alcohol its
temperature fell to — 24°. Continuance of the pumping during
the experiment, as is done in the case of ether, had a prejudicial
effect. But alcohol diluted with a third of water was found to
have as great a cooling power as absolute alcohol. The advan-
tage to be derived from the great volatility of alcohol appears to
be counterbalanced in part by the small latent heat of its vapour.
Probably a mixture of alcohol and water, in certain proportions,
would produce the greatest degree of cold attainable by this
process. Sulphuric acid loses its power to absorb alcohol vapour
by being diluted with water. When impregnated with alcohol
vapour, the acid becomes of a pink colour ; but no appreciable

Mr Graham's Account of the Formation of Alcoates. 181

quantity of gas is emitted at the temperature of the atmosphere,
even in the vacuum of an air-pump.

From one experiment, water appears to have the power to in-
duce the evaporation of alcohol by absorbing its vapour, as sul-
phuric acid does, but much more feebly. Two cups, one con-
taining alcohol and the other pure water, were enclosed together
in a tin canister which was nearly air-tight, and set aside in a
quiet place for six weeks. The cups were not in contact, but a
little apart from each other. At the expiration of that period it
was found, on opening the canister, that the cup . which origi-
nally contained pure water, now contained a mixture of water and
alcohol, while the alcohol remaining in the other cup was of di-
minished strength. Professor Leslie informs me, that he per-
formed a similar experiment a considerable time ago, although
no account of it was published. But the absorption of alcohol-
vapour by water is so feeble as not to occasion a sensible reduc-
tion of temperature in the alcohol.

Chloride of calcium is disqualified as an absorbent of aqueous
vapour in the purification of alcohol, for the same reason as sul-
phuric acid. I find that chloride of calcium absorbs the vapour
of absolute alcohol, and runs into a liquid, or it deliquesces in
alcohol-vapour. A small quantity of this substance was sus-
pended in a little capsule, at the height of two inches above a
quantity of absolute alcohol, in a close vessel. In the course of
twenty-four hours it was entirely resolved into a liquid, just as
if it had been suspended over water. The liquid proved to be a
solution of chloride of calcium in absolute alcohol. The experi-
ment was frequently repeated. As salts which deliquesce from
the absorption of aqueous vapour are always capable of forming
hydrates, I was led from the observation of this fact to attempt
the formation of analogous compounds of alcohol and salts,— to
which I now proceed.

182 Mr Graham's Account of the Formation of Alcoates.

These solid compounds of salts and alcohol, which are definite
and imperfectly crystallizable, may be denominated Alco-ofe*> — a
designation which is not unexceptionable, but appeared to me
preferable to the name Vimte, as there is a sulpha-vinous acid,
or to any other name that might have been imposed upon them.

The alcoates which I succeeded in forming are not numerous.
They were formed simply by dissolving the salts, previously ren-
dered anhydrous, in absolute alcohol, with the assistance of heat.
On cooling, the alcoates were deposited in the solid state. The
crystallization was generally confused, but in some cases crystal-
line forms appeared of a singular description. The crystals are
transparent, decidedly soft, and easily fusible by heat in their
alcohol of crystallization, which is generally considerable, amount-
ing in one instance to nearly three-fourths of the weight of the
crystals.

1. AUmte of Chloride qf Cakium.

Pure muriate of lime was dried as much as possible on a sand-
bath of the temperature of 600° or 700°, and then slowly heated
to redness, and retained for some time at that temperature. The
dry chloride of calcium thus obtained dissolves in absolute alco-
hol at 60° with great facility, and with the production of much
heat, sometimes occasioning the boiling of the solution. The
quantity of chloride taken up increases with the temperature ;
and at 173°, the boiling point of alcohol, 10 parts alcohol dissolve
7 parts chloride of calcium. This solution is thick and viscid,
but perfectly transparent, provided the chloride be pure. It
boils at 195°, alcoholic as well as aqueous solutions boiling at
higher temperatures than the pure liquids. The viscidity of
the solution of chloride of calcium increases greatly as it cools.
Bright crystalline stars soon appear on the surface and on the

Mr Graham's Account of the Formation of Jkoatos. 1 85

r

sides of the vessel, which have been moistened by the solution.
The solution, however strong, never crystallizes instantaneously,
but gradually, in thin transparent and colourless plates, the
forms of which cannot be made out, except on the surface of the
solution and sides of the vessel. — To obtain the alcoate in a
state of absolute purity, it is necessary to form a solution so
weak, that, while hot, it will pass through thin filtering paper;
and afterwards to concentrate the filtered solution by heat. A
solution of one part chloride of calcium in five parts alcohol
passes through the filter. It is remarkable that the most distinct
crystalline forms are not obtained from the slow crystallization
of comparatively weak solutions ; but in solutions which have
been fully saturated, or nearly so, at the boiling temperature.
In the former case, the crystalline plates are large, but confused,
and nothing but angles can be made out ; while in the latter,
the forms, under which the plates appear on the surface of the
solution, and to the greater advantage, on the sides of the vessel,
are generally distinct These plates are always small, often beau-
tiful, and delicately striated ; and they always present the form
of isosceles triangles. In general, four of these triangular figures
are grouped with their apices together ; and if similar, they form
a square. But, as more frequently happens, the opposite pairs
of triangles only are similar ; and the figure presented is a rect-
angular parallelogram,. divided by two diagonal lines into four
triangles. The resolution of the rectangle into triangular figures
is rendered perceptible by the discontinuance of the striae, and
the formation of clear diagonal lines, which have a beautiful ef-
fect. These crystals cannot be removed from the phial in which
they are formed without injury, froth their softness. Exposed
to the air, they speedily deliquesce from the absorption of hy-
grometric moisture. The heat of the hand is sufficient to melt
them. The whole of the alcohol is expelled by a heat amount-

n

184 Mr Graham's Account of the Formation of Alcoates.

ing to 250°, and pure chloride of calcium remains, which emits
nothing else upon being heated to redness*

A quantity of this alcoate was dried, first by strong pressure
between many folds of linen, and then by pressure between folds
of blotting paper. The alcoate, carefully dried in this way, had
a white appearance much resembling bleached wax, and was soft,
but without tenacity.

Ten grains were heated in a glass capsule, till the whole alco-
hol was driven off. There remained 4.1 grains chloride of cal-
cium. The atomic weight of chloride of calcium is 7, and that
of alcohol 2.875. In the alcoate, 4.1 grains chloride of calcium
were combined with 5.9 grains alcohol

4.1 : 5.9 : : 7 : 10.0731.

In a second analysis, in which 20 grains of alcoate were em-
ployed, the result was precisely similar, as 8.2 grams chloride of
calcium remained, which is just double what was obtained in the
previous case from half the quantity of alcoate. If this alcoate
should be considered a compound of one equivalent proportion
of chloride of calcium, and three and a half proportions alcohol,
the alcohol would amount to 10.0625, which approaches very
nearly to the experimental results. But it would be better to
express the composition of the alcoate thus :

Two atoms chloride of calcium, ... 14.
Seven atoms alcohol, 20.125

84.125

In the solution of chloride of calcium, no crystallization takes
place at the temperature of 50°, when the alcohol exceeds the
proportion of 10 parts to 4 parts of the dry salt. But the solu-

Mr Graham's Account of the Formation of Alcoate*. 185

tion crystallizes readily when farther concentrated. A solution
saturated at 170°, and which consisted of 10 parts alcohol and 7
parts chloride of calcium, or nearly the atomic proportions of the
alcoate, crystallized slowly upon cooling, forming crystals upon
the surface of the liquid and sides of the phial, of great regularity
and beauty. The whole crystallized during a cold night, leaving
no mother liquor whatever.

The injurious effect of the presence of water, in the forma-
tion of this alcoate, was evident in alcohol of the specific gravity
0.798, in which the contaminating water did not amount to 1
per cent. A solution of chloride of calcium in alcohol of this
strength did not crystallize readily, and the crystals eventually
deposited were small and ill formed. Chloride of calcium does
not crystallize at all in alcohol of the specific gravity 0.827. The
same inconvenience arises from employing chloride of calcium
containing a little water.

Although the alcoate of chloride of calcium in a state of pu-
rity is entirely decomposed at a temperature not exceeding 250°,
yet, when water is present, alcohol can be retained by the chlo-
ride of calcium at a much higher temperature. - Thus I repeat-
edly found, that chloride of calcium, from which alcohol had
been rectified, and which afterwards had been washed out the
retort by water, gave indications of the presence of alcohol, after
being exposed on the sand-bath to a heat of 400° or 500° for
several hours. Transferred in a crucible to the fire, after it
ceased to lose weight on the sand-bath, alcohol-vapour was emit-
ted, which took fire and burned.

2. Alcoate of Nitrate of Magnesia.

It is difficult to expel the whole of the water with which ni-
ate of magnesia is combined, without driving off a portion of

VOL. XI. part i. a a

186 Mr Geabam's Account if the Formation qf Aleoates.

the acid, and decomposing the salt. For this salt may be wholly
reduced in a glass-tube by the heat of a spirit4amp, and yet a
sand-bath heat of 600° or 700° is not sufficient to drive off all
its water of crystallisation. But a partial decomposition of this
salt is of no great consequence, as alcohol dissolves the unde-
cootposed portion of the salt, while the magnesia resulting from
the decomposition precipitates, and may be separated by decant-
ing the solution, or by filtering.

Four parts alcohol at 60° dissolve one part nitrate of magne-
sia, and boiling alcohol dissolves more than half its weight of
this salt. From the great difference between the solubility of
this salt at high and low temperatures, the alcoate is obtained
with facility. A hot solution, containing a greater proportion of
nitrate than one part to three parts alcohol, became, upon cool-
ing, an irregular dry mass, which could he indented fay the point
of a glass-rod, but was much harder than the alcoate of chloride
of calcium, In solutions considerably weaker crystal? were de-
posited on cooling, which sometimes resembled the crystals of
the former alcoate, but were much smaller, and less distinct ;
but more frequently, the crystals were exceedingly minute, and
detached, without any regular form which could be discerned,
But the great mass of crystalline matter precipitated in scales of
a pearly lustre and whiteness, but apparently made up of the
small crystals.

Dried hy pressure, in blotting paper, this alcoate much resem-
bled the alcoate of chloride of calcium in external characters. It
sank in water, but floated on the surface of a saline solution of
the specific gravity 1.1. Heated, it melted readily ; boiled, and
muchlohol was given off. When boiled violently, red fame,
rise with the alcohol-vapour ; but when dried slowly, no loss of
acid takes place.

Upon cautiously heating 13.4 grains alcoate of nitrate of mag-
nesia to dryness, there remained &£6 grains nitrate of magnesia.

Mr Gbaham's Acoaunt qf the Formation qfJkoates. 187

Thi* gives 9.84 alcohol to 3.66 nitrate of magnesia But the
atomic weight erf anhydrous nitrate of magnesia is 9*25. Now,

8.56 : 9*84 : : 9.25 : 25.57.

In another case, 16 grains alcoate were reduced to 4.2 grains.
This gives 11.8 grams alcohol to 4.2 grains nitrate of magnesia.

4.2 : 11.8 : : 9.25 : 25.99.

On the supposition that this alcoate consists of one atom ni-
trate of magnesia united with nine atoms alcohol, the alcohol
should amount to 25.875, a number intermediate between the
two results. This alcoate will be thus represented :

One atom nitrate of magnesia, . 9.25
Nine atoms alcohol 25.875

85.125

8. Alcoate qf the Nitrate qf Lime.

Nitrate of lime may be obtained anhydrous with much greater
facility than nitrate of magnesia, as, after being dried on the
sand-bath, it may be heated in a glass-capsule by the spirit-lamp
without decomposition, although it partially fuses. Boiling al-
cohol saturated with thk salt formed a solution, which became
very viscid on cooling, and remained without crystallizing for a
whole day. But during a frosty night it was resolved into an
amorphous solid, slightly moist, but without airy appearance of
crystallization. Thk substance was careftdly dried in the usual
way. *

Aa2

188 Mr Graham's Account of the Formation qfAlcoatea.

14.8 grains were reduced by heat to 8.8 grains. This gives 6
grains alcohol to 8.8 grains nitrate of lime. The atomic weight
of anhydrous nitrate of lime is 10.25. Now,

8.8 : 6 : : 10.25 : 6.98.

In another case, 15.6 grains were reduced to 9*2, which gives
6.4 alcohol to 9.2 nitrate of lime. But,

9.2 : 6.4 : : 10.25 : 7.13.

This approaches 7.1875, or two and a half equivalent proportions
of alcohol. The composition of the alcoate of nitrate of Ume
would be represented on this view, by

Two atoms nitrate of lime, . 20.5
Five atoms alcohol, .... 14.375

84.875

In another strong alcoholic solution of nitrate of lime, a few
irregular crystals were deposited, but the quantity was not suffi-
cient to admit of examination, although they proved that this
alcoate is capable of crystallizing.

4. Alcoate of Protockloride qf Manganese.

The protochloride of manganese, dried in a glass-tube, at a
red heat, was light, friable, and of a reddish colour. Alcohol dis-
solved a very large quantity of it. When the solution was made
at a high temperature, the alcoate crystallized readily upon cool-

Mr Graham's Account of the Formation qfAlcoutes; 189

ing in (dates with ragged edges. 14.6 grains of this alcoate,
carefully dried by pressure in blotting paper, were reduced by
heat to T. grains. The alcoate, therefore, consisted of 7 grains
protochloride of manganese, and 7.6 grains alcohol. The atomic
weight of protochloride of manganese is 8. Now,

r

7 : 7.6 : : 8 : 8.686.

This slightly exceeds three atoms alcohol = 8:625, but the ap-
proximation to the theoretical number is as close as could be
expected. The composition of this alcoate may therefore be ex-
pressed by

One atom protochloride of manganese, 8.

Three atoms alcohol 8.625

16.625.

5. Alcoate qf Chloride qf Zinc.

Alcohol dissolves chloride of zinc with great facility, and the
solution when filtered is of a light amber colour. This solution
may be concentrated to a very great extent without injury, and
becomes so viscid when cold, that it maybe inverted without
flowing perceptibly. It is not till so concentrated that it begins
to deposit crystals, which are small and independent, but appa-
rently of no regular shape. A viscid solution, in which, crystals
formed, was found to be composed 20 parts chloride of zinc, and
7 parts alcohol. The small proportion of alcohol is astonishing ;
yet no more alcohol was given out when the chloride was heated
nearly to redness, and began to volatilize ; nor did a portion of
the chloride thus heated take fire when exposed directly to the
flame of a candle.

190 Mr Graham's Atemmt qf the Formation tf Alcoates.

The crystalline matter was dried with difficulty by pressure in
blotting paper. When dry, it possessed the usual waxy softnew
of the alcoates, and was of a yellowish colour* Heated, it entered
into a state of semifusion, and gave off its alcohol Nine grains
alcoate were reduced by the application of sufficient heat to
7.65 grains. . Hence the alcoate consisted of 7.65 chloride of
zinc, and 1 .85 alcohol. But the atomic weight of chloride of zinc
is 8.75.

• 7.65 : L85 : : 8.75 : 1.544.

1 .544 slightly exceeds 1 .4375, or half an atomic proportion
of alcohol. It is probable that the excess was owing to the dif-
ficulty of freeing the alcoate completely from the viscid solu-
tion. According to this view, the alcoate of zinc consists of

Two atoms chloride of zinc, . . 17.5
One atom alcohol, 2.875

20.375

Besides these alcoates, similar compounds of chloride of mag->
nesium and of protochbride of iron and alcohol were formed,
although in quantities too minute to enable me to ascertain
their proportions. Alcohol is retained with great force by chlo-
ride of iron, and is partially decomposed when heated, as is the
case with many metallic chlorides*

As I had it only in my power to present the fixed alkalies to
absolute alcohol in the state of hydrates, no alcoate appeared to
be formed. The same was the case with the vegetable aci^b so-
luble in alcohol.

It is probable that many more alcoates of salts may be formed,
particularly of the metallic chlorides. The great obstacle to

Mr Graham's Aecwnt qfthe Formation qf Alcoates. 191

their formation is the difficulty, and frequently the impossibility,
of rendering the salts perfectly anhydrous, before their solution
in alcohol is attempted.

I am not aware of any other compounds in the solid form of
the same class as the hydrates and alcoates. But there is an
oxide, classed by Dr Thomson in bis System of Chemistry,
with water and other neutral and unsaleable oxides, the habi-
tudes of which with certain salts are exceedingly remarkable,
and have been looked upon as anomalous, but on which the es-
tablished properties of hydrates and alcoates appear to me to
throw some light. I refer to the deutoxide of azote or nitrous
gas. 100 volumes pure water are capable of absorbing only 5
volumes of this gas, according to the experiments of Dr Henry.
But Dr Prjestixi and Sir H. Davy ascertained that certain
metallic salts, particularly the protosalts of iron, are capable of
absorbing this gas in large quantities; and again emit the
greater part of it unaltered, on being heated. That the absorp-
tion of deutoxide of azote by these salts, is not dependent upon
the oxygen of their bases, or the water which they contain, I
have proved in two ways, in the case of protorpuriate of iron.
By heating this salt to redness in a glass-tube, it is reduced to
the state of protochloride of iron. Now, J find that this chloride
in the dry state absorbs deutoxide of azote, although in a com-
paratively small proportion. And the alcoholic solution of the
chloride, where neither oxygen nor water interferes, appears to
exceed the aqueous solution of the protomuriate in its capacity
for deutoxide of asote.

Deutoxide of azote, formed by the action of dilute nitric acid
en copper, was conduoted into a globular receiver surrounded
by eold water, and thence through a glass~tube of two feet in

192 Mr Graham's Account of the Formation of Alcoates.

length, filled with small fragments of chloride of calcium. Thus
dried, the deutoxide of azote was passed slowly over carefully
prepared protochloride of iron in the state of powder, and con-
tained in a glass-tube of small diameter. The protochloride im-
mediately became darker in colour ; and upon being withdrawn,
after exposure to the current of gas for some time, was found to
retain the smell of nitrous gas, and to have increased in weight.
In one case, 30 grains chloride had increased to 31.1 grains ;
and in another case, 25 grains chloride to 25.5 grains. On be-
ing gently heated, the deutoxide of azote was evolved, and the
chloride restored to its former colour.

The solution of protochloride of iron in absolute alcohol, ab-
sorbed a much greater quantity of deutoxide of azote, and be-
came nearly black. A solution saturated with gas began to boil
at 100°, evolving gas in great abundance, which, being collect-
ed in the pneumatic trough, proved to be pure deutoxide of
azote. The greater part of the gas was expelled before the al-
cohol rose to its boiling point, and after the solution was in the
state of ebullition for a few seconds gas ceased to rise, and the
alcoholic solution recovered its original colour, which was ge-
nerally a chocolate-brown, from the presence of a little bichloride
of iron. The quantity of gas evolved from a solution of one part
protochloride of iron in five parts absolute alcohol, amounted to
23 times the volume of the alcohol.

I think it probable that the absorption of deutoxide of azote
by protochloride of iron, is analogous to the absorption of alco-
holic and aqueous vapours by the same body. For I find that
protochloride of iron absorbs alcohol-vapour as well as the va-
pour of water. The absorption of deutoxide of azote may de-
pend upon a tendency of chloride of iron to deliquesce in like
manner, in an atmosphere of that neutral oxide. At a very low
temperature, which it is perhaps out of our power to reach,
protochloride of iron would probably absorb this gas in sufficient

Mr Graham's Account if the Formation of Alcoates. 198

quantity to exhibit the appearance of deliquescence, and might
form with it a neutral compound, similar to its alcoate or hy-
drate.

»

A reason can also be given for the superiority of the aqueous
and alcoholic solutions of this chloride over the dry chloride it-
self, in absorbing deutoxide of azote. We formerly saw that
the alcohol of the alcoate of chloride of calcium was completely
expelled by a heat of 250°, when no water was present ; but
that, whea a considerable quantity of water was present, alcohol
was retained by that chloride at the temperature of 400° or 500°.
Now, chloride of iron might be enabled to retain deutoxide of
azote more powerfully, by the assistance of alcohol or water, in
the same manner. But the retaining power we have formerly
found in a similar case to be an index of the absorbing power.
Hence solutions of protochloride of iron might absorb
of azote more powerfully than the chloride itself.

VOL. XI. paet i. b b

( 194 )

XL An Aewwt <f the Tracks and Footmark* qf Animate found
impressed m Sandstone in the Quarry of Corncockle Muir,
in Dumfriesshire. By the Rev. Henry Duncan, D.D.

Minister of Ruthwell.

m

(Read January 7. 1898.)

J. he sandstone quarry of Corncockle Muir is situated between
the rivers Annan and Kinpel, about a mile and half above their
confluence, and not quite three miles from the town of Loch*
maben in Dumfriesshire. It is near the tpp of a low, round-
backed hill, which stretches about half a mile in a westerly di-
rection, almost in the line of the rivers. This hill rises out of a
valley of irregular surface, terminated, at the distance of some
miles, on the north and north-west, by a mountainous range of
transition rock ; on the south by an arm of the same range ; and
on the east, at a greater distance, by lower elevations, consist-
ing, according to Professor Jameson *, partly of flcetz-trap and
partly of the independent coal-formation. The valley itself is
said by the same authority to be of the independent coal-forma-
tion, lying on the transition rock, and contains considerable
quantities of sandstone interspersed in various parts, and stretch-
ing as far as the bottom of the mountains.

The sandstone of which the quarry in question is composed
is, like most other sandstone in the county, of a reddish-brown
colour, and is believed to be what is called in England the new
red sandstone. Its texture is friable, and its strata of very un-

* In his Mineralogical Survey of Dumfriesshire.

Br Duncan on the Footmarks of Quadrupeds m Sandstone. 193

equal thickness. It lies in the direction of the greater part ©f
the sandstone of the district, which is from west^no* thkwest to
east-south-east, with its dip southerly at an angle of 38°.

The remarkable phenomenon which I am now about to de-
scribe as existing in this quarry, is that of numerous impressions,
frequently distinct and well defined, bearing, both in their shape
and in their position with relation to each other, so close a re-
semblance to the foot-prints of quadrupeds, as to leave no doubt
respecting their identity, which have been found by the workmen
on the surface of certain strata, when the superincumbent layers
have been removed in the progress of quarrying. This fact, so
extraordinary, and I believe unique, has not hitherto attracted
the share of public attention which it deserves, and indeed has
not as yet been noticed in any scientific work, though it is fif-
teen or sixteen years since the discovery was first made.

The casts and specimens which accompany this will convey
an accurate idea of the nature of the impressions ; but it may be
necessary to mention, that considerably greater variety than I
have yet been able to procure, has been observed, not only in
their dimensions, but shape, the magnitude varying from the
size of a hare's paw to that of a foal's hoof.

Description of the accompanying Casts.

No. I, represents part of a slab *, formerly in the possession of
Mr Carruthers of Dormont, who procured it about four years
3go from the quarry, and is now built into a summer-house in the
garden belonging to the manse of Ruthwell. On the slab, which
is 5 feet 2 inches in length, there are twenty-four continuous

^•m

* The accompanying engraving (Plate VIII.) is taken from the cast No. 1,

and is on a reduced scale.

Bb2

196 Dr Duncan on the Foot-marks of Quadrupeds

impressions of feet, forming a regular track, which make twelve
of the right feet and as many of the left, being of course six
repetitions of the mark of each foot. The impressions of what
I take to be the fore-feet, are a little more than two inches in
diameter, both from claw to heel and across ; and those made by
what appear to be the hind-feet are of much the same size, but
somewhat differently shaped. The marks of five claws are dis-
cernible in each fore-foot, the three in front being particularly
distinct. The three front claws of the hind-foot may also be
plainly traced, and are placed nearer to each other than those
on the fore-foot. There has obviously been no division in the
sole of the foot, as is the case in the canine and feline species,
as well as in some other quadrupeds ; but a gentle convexity of
surface may be observed, especially in the fore-paw, occasioned
chiefly perhaps, by the act of sinking in the wet sand. The
depth of the . strongest impression is about half an inch, and it is
observable that, in this specimen, the fore-feet have made some-
what deeper marks than those behind, — a fact which may either
indicate a considerable length in the animal's neck, or the more
than ordinary weight of its head and shoulders ; for had it not
been for one or other of these circumstances, the chief pressure
would have been thrown on its hinder paws ; because the surface
up which it appears to have been moving was of considerable
steepness.

The distance from the claw of the hind-foot to the heel of

the nearest impression of the fore-foot on the same side, varies
from an inch to an inch and a half. This, however, merely
marks the position of the two feet when the hinder one was
brought forward. in moving; and if we would ascertain the ani-
mal's step, that is, the length between the hind and fore foot
when the former was thrown back and the latter advanced *, we

* It is not meant that the quadruped has actually been in this position ; for the
hind-foot would of course be moved forward before the fore-foot was lifted.

found in Sandstone in Dumfriesshire. 197

must measure from the hind-foot forward to the second impres-
sion of the fore-foot oh the same side. Now, this gives a dis-
tance of between 13 and 14 inches, which is considerably more,
however, than would have been the case had the animal been
standing still. If we compare this with the distance between
the line of the right and left feet (which is as to the fore-feet
nearly 6£ inches, and as to the hind-feet something more than
7£ inches), we shall see that an extraordinary thickness of the
animal's body in proportion to its length, is clearly indicated.

No. 2. is a cast from another slab of sandstone, which was
taken from the quarry under my own eye, and which is also fix-
ed in the wall of the summer-house at Ruthwell Manse. It con-
tains the track of a smaller quadruped, perhaps a variety of the
same species ; for in some respects a resemblance may be traced.
In both of them the sole of the foot is undivided ; and in both,
a more than ordinary thickness of the body, in proportion to its
length, is shewn by an unusual distance between the marks of
the right and left feet, before as well as behind. In this speci-
men, however, the latter peculiarity is not proportionally so
great as in that of No. 1. nor do the feet appear to have been
of a similar shape, except in the circumstance already men-
tioned ; and indeed the relative proportions of the two are far
from corresponding throughout. Nor is it less worthy of obser-
vation, that although in No. 1, as has already been remarked, the
unusual length of the neck, or weight of the head and shoulders,
seems to be indicated by the deep sinking of the fore-feet, the
very reverse appears in No. 2, the impression of the fore-feet
being in this specimen only very slight, while that of the hind-
feet is strong and well defined. Whether or not these differences
can be accounted for by a difference of age in' two animals of
the same family, I must leave to more skilful inquirers to de-
termine.

The measurements are as follow :

198 Dr Duncan o* the Foot-marks of Quadrupeds

Breadth of the impressions across the toes, 1| inch.

Length of the step, as above explained *, 8

Distance directly across between the line of
the right and left fooUmarks behind and
before, about 3

Distance from the claws of the hind-foot to
those of the nearest mark of the fore-foot,
about 2

In both of the specimens already mentioned, the track of the
animal was in an upward direction, that is, from the bottom to the
top of the quarry, almost in a direct line, along a smooth surface,
inclining like the rest of the strata of the sandstone at an angle of
38°. This at least I can aver, from personal observation, to have
been the case with No. 2, which I saw removed from its original
bed. The track continued along the whole face of the flag as it
lay in the quarry till it disappeared in the earth at the top. It
had been recently uncovered in the course of working, by the re-
moval of a thick superincumbent layer, which, I was informed,
had, in this as in other instances, the counter prints distinctly
marked in relief on its under surface, these upper projections
corresponding to the cavities below as exactly as a cast to its
mould. The whole length of the track, which was quite re-
gular, was from 14 to 16 feet, scarcely visible at first, as if the
sand had been too dry to receive the impression, but becom-
ing in a few steps perfectly well defined, and continuing so to
the very top. The surface on which the footsteps were im-
pressed was what the workmen technically call a clay-face, be-
ing, from a more copious admixture of clay than ordinary in
its outer coat, harder than the rest of the rock, and the seam
between it and the upper stratum having less adhesion, and con*

* That is, when the fore-foot was advanced, and the hind-foot thrown back in
the act of moving forward.

found in Sandstone in Dumfriesshire* 199

taining sometimes, though not in the present instance, a thin
layer of soft clay altogether distinct from the stone. I was told
by the son of the tacksman of the quarry, a person of some in-
telligence, that the tracks never appeared on a surface not of
this kind. Another remark of some importance, derived from
the same source, is, that all the tracks are constantly in a direc-
tion either up or down, sometimes inclining a very little either
to the right or left, but never running across the slope in any
considerable degree. This my own observation, so far as it goes*
fully confirms.

No. 3. is a cast taken from a block which was also removed
from the quarry while I was present, and, like the other two, is
in my possession. The impressions it contains seem to be those
of an animal's feet in the act of descending the steep face of the
moist sand. The inclination of the slab as it lay in the quarry,
was I think greater than the ordinary inclination of the rest of the
strata, and might be upwards of 40°. It was at all events so steep
as to render it necessary for. an animal descending the declivity
to insert its fore-feet firmly in the sand before it could move with
safety ; and this the quadruped in question appears to have done,
by cautiously sliding one paw downwards, till its footing became
secure, and then extending the other in the same way, while its
hinder feet, following alternately, rested on the surface of the
sand. Assuming this to be the case, we might expect to see
the prints of the hind-feet also ; and accordingly, in the very
places where such marks might naturally be looked for, slight
depressions of the stone are discoverable, sufficiently well defined
ic justify the opinion that they are foot-marks. If it be objected
that these depressions are too slight to correspond with the deep
cavities supposed to be made by the fore-feet, it must be remem-
bered that the weight of the animal's body would »ec«jsiai;ily he
thrown much forward, and that the whole of its security would
lie on the efforts made with its fore-feet, the hind-feet being

200 Dr Duncan on the Foot-marks of. Quadrupeds

merely used to keep it steady ; so that the comparative slight-
ness of these impressions is just what might have been antici-
pated. It may be proper to mention, that the block from which
this specimen was taken was but a few feet in length, and con-
tained two other sliding impressions, precisely similar to those
which I carried away, affording the strongest conviction to my
mind that they were a continuation of the same track. I have
in my possession other specimens of similar prints, taken from
a different part of the quarry, one of which I transmit * ; but
these are not so deep, and I have in vain endeavoured to disco-
cover any depressions in them corresponding to those which I
take to be made by the hind-feet of this animal. It is probable
that in these instances the weight with which the hind-feet rested
on the surface was too little to make a durable impression on
the sand in its half indurated state.

I persuade myself that a simple inspection of the casts and
specimens I transmit along with this, will be sufficient to satis-
fy any reasonable inquirer that the cavities they contain are
the actual foot-marks of quadrupeds, and justify me, without
farther proof^ in having assumed them to be so ; but should any
doubts on the subject remain, I must refer to the quarry itself,
where several specimens are still left exposed, and others are oc-
casionally uncovered, of a nature to remove all scepticism, though
it is greatly to be regretted that so many of the very finest have,
by the carelessness of the quarrymen, who regarded them as of
no value, been utterly destroyed.

One of the tracks still to be found in the quarry is too re-
markable to be passed over without notice, being considerably
larger than any of those I have mentioned. The prints are so
much filled up, indeed, as to leave the shape of the foot unde-
fined ; but yet the nature of these impressions cannot be mis-

* Specimen marked A.

found in Sandstone in Dumfriesshire. 201

taken, when they are compared with those which are more dis-
tinct. I have unfortunately taken no accurate measurement of
this track ; but from an imperfect specimen now transmitted *,
it appears that the distance from. the hind to the fore foot, when
most nearly in contact, was about 1 foot 9 inches, while the
breadth across from the line of the right foot . track to that of
the left, was somewhat more than 7 inches ; and if I might be
allowed to speak from recollection, I should say that what I
have loosely called the animal's step, for want of a better word,
that is, the distance between the fore and hind feet, supposing
them to be at their stretch, could not be less than five feet. The
layer on which the impressions are made, happens to be only a
little more than half an inch thick, and it has naturally no ad-
hesion to the under stratum. In attempting, however, to raise
a specimen from its bed, I found that the two strata were so in-
timately united wherever the Sprints of the feet occurred, that it
was impossible to separate them without breaking. It seemed
as if the weight of the animal, or its efforts in ascending, had
occasioned the thrusting of its feet entirely through the upper
into the under layer ; and on forcing the strata asunder, this
supposition was confirmed by the curious fact, that the matter
of the under layer, displaced doubtless by the sinking of the feet,
was discovered to be heaped up in a ridge-like form round the
insertion of the animal's heel, having made way for itself, when
forced back, by causing a corresponding concave impression on
the under face of the upper stratum.

With regard to the species of animals whose tracks have
been so wonderfully preserved, I do not think myself competent
to offer any conjectures of my own ; but having been in corre-
spondence with one of the first geologists of the age (to whom I

* Specimen marked B, on which there is also the track of a small animal ascend-
ing.

VOL. XI. PART I. C C

202 Dr Duncan on the Footmarks of Quadrupeds

sent casts similar to those now transmitted, besides a small spe-
cimen of the rock itself, containing one or two foot-prints), I
think it may be interesting to state the opinion with which his
politeness has favoured me as to three of the tracks.

Concurring with Mr Jameson, as he assures me he does, in
the belief that the rock is what is called the new red sandstone,
which is supposed to have been deposited at an era when it is
the received opinion that no quadrupeds existed on our earth of
a higher order than reptiles, he was induced to look to our pre-
sent crocodiles and tortoises as the species most nearly resembling
those whose footsteps have marked the stone. This led him to
make a rough experiment with some live tortoises which he has in
his possession, the result of which was to make him conjecture
that the impressions must rather belong to the tortoise than the
crocodile tribe. He did not, however, speak positively ; — not
that he thought the prints too indistinct to enable him to form an
opinion, but because he had not sufficient time and opportunity

for examination *. As to the deep tracks occasioned, as I had sug-

- ■ ■- - —

* Since the above was written, I have .had the pleasure to receive a letter from
Professor Bctcklakd, containing the following account of his experiments :

« Oxjbrdy liih Dec. 1887.

" 1st, I made a crocodile walk over soft pye-crust, and took impressions of his
feet, which shew decidedly that your sandstone foot-marks are not crocodiles.

" 2d, I made tortoises, of three distinct species, travel over pye-crust, and wet
sand and soft day ; and the result is, I have little or no doubt that it is to animals
of this genus that your impressions on the new red sandstone must be referred,
though I cannot identify them with any of the living species on which I made my
Experiments. The form of the footstep of a modern tortoise corresponds sufficiently
well, but the relative position of the impressions to each other does not entirely co-
incide, and this I attribute to the different pace at which the animal was proceeding ;
for I found considerable variety in these positions as my tortoises moved more or less
rapidly ; and as most animals have three distinct kinds of impression for their three
paces of walk, trot, and gallop, so I conceive your wild tortoises of the red sandstone

found in Sandstone in Dumfriesshire. 203

gested, by the sliding of the animal, he fully adopted my theory
of their origin. The track of the large animal I had not then
described to him ; and any account of it I am even now able to
give, is so vague as to lead to no certain conclusion. The only
thing yet discovered which can afford any idea of the nature of
the foot, is the ridge formerly mentioned as curling round the
animal's heels, on the surface of the under stratum, correspond-
ing to which, but a little above it, there is, in one instance, on
the surface of the upper layer, a depressed line of the shape
and dimensions marked below :

a fact which contradicts the commonly received opinion of
geologists respecting the position of sandstone in its original

age would move with more activity and speed, and leave more distant impressions,
from a more rapid and more equable style of march, than my dull torpid prisoners
on the present earth in this to them unnatural climate.

" I found, also, that, on walking down hill on soft sand, my tortoise scooped out
long and somewhat oval cavities, like those of which you sent me a cast, leaving no
impressions of the toes or heeL Each foot successively floundered forwards to the
lowest point of the groove, producing the posterior part of the excavation, and was
then dragged out, producing a similar removal of the sand from the anterior part of
the groove in question. The difficulty is to explain why sand so soft did not sub-
aide and obliterate the cavities, before or during the arrival of the next superincum-
bent bed of sand, which filled up and preserved these impressions. Elongated exca-
vations similar to those last spoken of are made by hares and other quadrupeds, in
moving over soft and half consolidated snow."

In a subsequent letter of 17th March, Professor Bucxland, in relation to the
elongated and imperfect impressions, which Dr Duncan attributed to the dragging
of the animals as they were moving with difficulty down hill, observes, " The cause
of this variety of impressions I would interpret otherwise, and rather refer them to

cc 2

204 Dr Duncan on the Footmarks of Quadrupeds

state, seems to be deducible from the appearances connected
with these impressions. It has been alleged that the materials
of which sandstone is composed, were accumulated by succes-
sive depositions from the sea or other extensive waters, and that
therefore the strata must have been, while in a soft state, nearly
horizontal; It seems almost demonstrable, however, that the
strata must in this instance have been in a greatly inclined po-
sition, if not altogether as inclined as at present, when the im-
pressions were made. On this subject an observation or two
may suffice. On inspecting the casts and specimens sent, it
will be observed that there are evident remains of the matter
displaced by the footsteps. This is the case with almost all the
impressions I have seen; and wherever such an appearance
occurs, that matter is found to have been carried downwards,
with reference to the present inclination. In the case of No. 2, *
for instance, the track of the animal was directly up the face of
the steep ; and it will be seen that the sand is therefore thrown
back, immediately behind the foot-marks. In the case of No. 1,
however, the track had inclined a little to the right, and this
slight variation is indicated by the direction of the displaced
sand, which has precisely such a position as this circumstance

■ ■ ill* — — — ——m — . ■ ■ ■ I i ■ I ■ I ■ ,n , . . ^ n , , |

the more than usual soft condition of the sand at the time and place where these im-
perfect marks were made. Marks exactly like those made by my living tortoises,
on sand that was wetted too much for a sound impression, viz. holes into which the
foot had sunk so deep that it could not be lifted out and moved forward by the ad-
vancing animal without displacing by its toes a quantity of the sand that was in front
of i the line of motion of each foot, and the result being a series of scoopings such as
the track of a hare or rabbit exhibits in soft and deep snow. If this idea be correct,
the impressions may have been made on horizontal beds of soft sand, ere they had
received the high degree of inclination they now possess. Thus the problem will be
relieved of some portion of its difficulty, namely, that which attends the hypothesis
of all the impressions having been made on the sand-beds whilst inclined at the same
angle they exhibit at present.7'

* The casts and specimens here alluded to are deposited in the Museum of the
Society, and may be inspected by application to any of its members.

found in Sandstone in Dumfriesshire. 205

accounts for ; while in the case of No. 3, the wet sand has evi-
dently run down before the descending prints. It will be ob-
served, too, that the claws and fore-part of the ascending foot
have been more deeply inserted into the sand than would have
been natural, had the surface been nearly horizontal ; and indeed
a slight glance at the sliding foot-marks in No. 3, seems to settle
the question. But there is another circumstance already men-
tioned, which can scarcely be accounted for, but on the supposi-
tion that the surface of the sand had a very considerable inclina-
tion,—I mean the fact that the tracks run all from the bottom to
the top of the slope, or vice versa, and never across. An inclina-
tion of 38° is so considerable, that it could only be with extreme
difficulty that an animal could make its way across the steep ;
but it would obviously find a much less effort necessary in moving
up and down.

With regard to the state of the sand, in point of tenacity and
moisture, at the time the impressions were made, a few remarks
seem to be called for. In the first place, the surface could not
have been entirely dry, otherwise the displaced sand would have
been rough and uneven, whereas it is quite smooth, indicating a
state inclining to mud, which may be explained on the supposi-
tion already mentioned, of a considerable mixture of fine particles
of clay ; but on the other hand, had the matter been very soft, it
could not have retained its precipitous face, nor could the animals
have moved over it, without sinking much deeper than they ap-
pear to have done, neither could the impressions have remained
so distinct as we find them actually to be. There seems to be an
indication, too, of a certain degree of toughness in the. surface.
This is particularly remarkable in No. 2, where it would appear
that the clayey sand had already become slightly indurated ex-
ternally, having been skinned over, as it were, with a stiffening
coat ; for it will be observed . that the claws of the animal as it

• ♦ «

ascended, seem to have rent the surface asunder at every step of

^

206 Dr Duncan on the Footmarks of Quadrupeds

its hind-feet, forcing it downwards by the pressure. It may be
noticed, too, that, in Nos. 1. and 3, where no such disruption ap-
pears to have taken place, a similar tenacity is indicated ; for,
when the hind-feet of the animals have happened to rest on the
sand that had been newly displaced by the fore-feet, their pres-
sure has not altogether obliterated the appearance of superadded
matter, but has merely caused a depression of the part rested
on. These indications are precisely what would have taken
place on a surface composed of stiffening putty or other tena-
cious matter, and mark with curious precision the peculiar state
of the sand.

There is a circumstance not yet adverted to, which cannot
fail to make a strong impression on those who are not familiar
with the wonders of geology. I allude to the position of these
impressions, with relation to the superincumbent strata. In the
direction of the dip of the strata, the rock is continuous for at
least a quarter of a mile from the quarry where the impressions
are found. Now, as the strata in the whole of this extent are
nearly parallel to those of the quarry, it is obvious that they
must lie upon each other like volumes in the shelf of a li-
brary when all inclining to one side ; and as these strata rest
on others in which the foot-marks are found, they must of course
have been deposited since the animals whose tracks they indi-
cate moved on the sand then forming the surface of the ground.
This fact leads the mind into the remotest antiquity, and per-
plexes it in a maze of interminable conjectures as to the state
of the earth's materials when these living creatures walked on
its surface, and bathed in other waters, and browzed on other
pastures, and not less as to the extraordinary changes and con-
vulsions of nature which have since taken place, and which have
broken up, overturned, and remodelled all things.

Nor will our surprize and perplexity be lessened, when we
attend to other facts connected with this remarkable phenome-

found in Sandstone in Dumfriesshire* 207

non. The quarry has been worked to the depth of about 45 feet
from the top of the rock, and as far down as the labours of the
quarrymen have hitherto extended (I speak on the concurrent
testimony of several eye-witnesses), similar impressions have
been found, and those equally distinct and well defined with
such as are nearer the surface. But this is far less remark-
able than another fact which I give on the same authority.
Although the sandstone at the place where the quarry was ori-
ginally opened, contained no foot-marks, as it consisted of what
is called by the workmen solid (i. e. imperfectly stratified) rock,
yet it soon changed its character, and whenever it assumed the
form of regular layers, the impressions began to occur. From
this period, as the workmen proceeded irr their labours, they
have continued to find numerous impressions, particularly in one
part of the quarry, and that not on a single stratum, but on
many successive strata ; that is to say, after removing a layer
which contained foot-prints, they found perhaps the very next
clay-face stratum, at the distance of a few feet, or it might be of
less than an inch, exhibiting a similar phenomenon. Since the
foot-marks were first discovered, about forty yards of sandstone
have been removed in a direction perpendicular to the line of
the strata, and throughout the whole of that extent, impressions
of precisely the same . kind have, at frequently recurring inter-
vals, been uncovered, and are still continuing to be uncovered.

This seems to prove incontestably that the process, whatever
it may have been, by which the impressions were buried in the
sand, has not been occasioned by any sudden and isolated con-
vulsion of nature, but has been carried on through many succes-
sive years, or rather ages. Nor has it been the result of tides
on the shore of the sea, which can scarcely be supposed to have
flowed to the height of between forty and fifty feet ; and, even
if they had done so, would certainly have swept away or filled up

208 Dr Duncan on the Footmarks of Quadrupeds

any impressions which animals might have made at low water,
by moving over the surface of the sands they were depositing.

In the midst of so much difficulty, it is not easy to form
even a plausible . conjecture as to the manner in which the sand
composing the rock was originally accumulated. It might,
however, be perhaps worth while to inquire whether or not this
successive accumulation could be the effect of the drifting occa-
sioned by violent winds from the south-west. Supposing a sand*
hill to be thus formed, a period of rainy weather following the
stormy season would soften and diffuse the particles of clay,
which may easily be believed to have mingled with the sand-
drift, and would not only prevent the sand from being again
moved by the wind,*but would form it into a substance of some
tenacity, resembling mortar, well fitted for preserving any im-
pression it might receive. If, during or immediately after the
rainy season, animals were to traverse a hill thus formed, their
tracks would be either altogether obliterated, or partially filled
up, of which latter state many traces are to be found in the
quarry ; but when the surface had begun to dry, the foot-marks
impressed on it would remain for a considerable time quite dis-
tinct and well defined. Now, supposing the stormy monsoon
again to commence, the neighbouring sands, which had not yet
been fixed by any strong mixture of clay, and which happened,
from their situation, to be easily dried by a few days of favourable
weather, would be suddenly drifted on the hill in question, form-
ing a layer which may easily have covered over the half-indurated
surface, without being incorporated with it, and without in any
way injuring the form of the foot-steps imprinted on it. Let the
monsoon be now supposed to continue during the whole course of
a dry summer : Fresh layers of sand would be drifted, compara-
tively pure at first, but mingled again towards the close of the
season with the clayey dust swept from an arid soil, which mix-
ture would form the materials of what the quarrymen know in

found in Sandstone in Dumfriesshire. 209

its present state by the name of a clay-face^ and would once
more, when subjected to the operation of the returning period of
rain, both fix the sand, and prepare it for the reception of per-
manent impressions of the tracks of wandering animals. Thus,
from year to year, the same round would be continued, and the
same appearances would take place, till, after the revolution of
many ages, what was originally sand would be converted, by a
common process of nature, into sandstone, and being exposed,
in common with the rest of our globe, to those mighty but mys-
terious convulsions of which there are every where such incon-
trovertible proofs, would at last, by the submersion of the uni-
versal deluge, be buried under its present covering of soil.

Ruthwell, 15th Dec. 1827.

VOL. XI. FART I. I> d

( 210 )

XIL On the Combination of Chlorine with the Prussiate of Potash,
and the presence of such a compound as an impurity in
Prussian Blue. By James F. W. Johnston, A. M.

(Read January 7. 1828.)

It has been long known that the Prussian blue of commerce
contains an admixture, in greater or less quantity, of alumina,
sulphate of potash, and common alum, one or all of them being
easily detected in every specimen. The sulphate of potash and
the alum may be separated by frequent boiling in water, but they
are seldom in such quantity as to render this process necessary.
The alumina may be removed by digestion in muriatic acid, and
the washing consequent upon this mode of treatment will free
it from all the soluble impurities.

When the alkalies or earths are digested with Prussian blue,
in order to form the common Prussiates, and the yellow solution
is evaporated, it almost uniformly happens that after the first or
second crop of crystals is separated, there remains a dark brownish-
red liquid, which either does not crystallize at all, or gives crys-
tals of the required prussiate of a dirty brown colour, and mixed
with a greater or less portion of a red matter, either massive, or
in small, red, four-sided needles and prisms. This may be ob-
served in preparing the prussiates of lime or soda by the com-
mon process, but has been more frequently taken notice of in
forming the cyanide of mercury ; because the least colouring
matter in this salt is at once perceptible, and because in the pre-
paration of it, a partial loss is of greater consequence. To the
presence of a portion of this red salt, particularly in extempo-
raneous prussiates, I attribute those differences in the colour of

Mr Johnston on the Combination cf Chlorine. 211

the precipitates which they give with the metallic oxides, and
which have, led some to doubt the accuracy of their indications.
The grounds of this opinion will appear in the sequel of the
present paper.

In Brewster's Journal (vol. v. p. 247.), Dr Turner has
shown, that, by previously digesting the Prussian blue in dilute
muriatic acid, all loss in the preparation of the cyanide of mercury
may be avoided ; but as he found the acid to have taken up only
iron and alumina, he leaves it to be inferred that one or both of
these is the cause of the impurity above referred to. What is
its true nature, I proceed to show.

To obtain it in a separate state, let the common Prussian
blue of the shops be digested in boiling water, a bright greenish*
yellow solution will be formed, perfectly neutral, and having the
following properties :

With Caustic Alkalies, Sulphate of Soda, Benzoate of Ammonia, Lime-
water, and Salts of Lead, it gives no precipitate.
Nitrate of Silver,... it gives a bright brick-red.

Sulphate of Copper, a brown or dirty brownish-yellow.

Sulphate of Zinc, light yellow, sometimes brownish.

Bichloride of Meitury, slight, yellowish, becoming blue.

Sulphate of Nickel, yellow.

Cobalt, blood-red. ^

Nitrate of Bismuth, chrome-yellow.

Muriate of Gold, alight, yellowish.

Sulphate of Cadmium, chrome-yellow.

Muriates of Tin, beautiful white.

Sulphates of Iron,..*. deep blue.

Pernitrate of Uranium, slight greenish-yellow.

Sulphate of Manganese, dirty brown.

Sulphate of Cerium, none.

Muriate of Platinum, yellow, soluble in hot water.

Hydrosulphuretof Potash,. ..white powder.
Tincture of Galls, brown.

If several ounces of Prussian blue be digested in this way
with repeated affusions of hot water, and die several solutions be

ndS

212 . Mr Johnston on the Combination of Chlorine

added together and evaporated, a small quantity of a dark thick
liquid is obtained, similar in appearance to that occurring in the
preparation of the cyanide of mercury, having a peculiar smell,
approaching to that of weak chlorine, and being of a blackish by
reflected, but of a deep red by transmitted light. By farther
concentration, this liquid is partly decomposed, depositing a
green sediment, and by slow cooling gives crystals of a deep red
colour, in doubly oblique four-sided prisms, terminated some-
times by two or three planes, and not unfrequently acuminated
into pyramids. These crystals are insoluble in alcohol, unless
considerably diluted, but very soluble in water ; and the solu-
tion, which, even when very weak, is of a bright greenish-yellow
colour, has all the properties above mentioned. Sometimes the
crystals are deposited in very minute needles, when they are of a
bright golden-yellow colour, and sometimes in beautiful red tables.

If this salt be reduced to powder, and treated with concen-
trated sulphuric acid, it gives off chlorine, and on the application
of heat hydrocyanic acid. Its solution with tartaric acid gives
crystals of bi-tartrate of potash ; and heated per #e, in an open
crucible, it leaves an oxide of iron. It contains therefore chlo-
rine, cyanogen, potash, and iron. In having the first of these
for one of its constituents, it differs from the common prussiate
of potash.

Having shown this salt to Dr Thomson, I was referred by
him to a paper by Leopold Von Gmelin in Schweigger's
Journal, N. S. vol. iv. p. 825, in which he describes a salt in red
prisms, having properties precisely the same as those above stated.
The angles of the rhombus, which I find, by careful measurement,
to agree with those of the salt obtained as above, he states at 81°
48' and 98° 12', and their diagonals as 2 : v/S. The salts are
therefore identical, though, as we shall afterwards see, Von
Gmelin has mistaken its composition.

To obtain this salt, he passes a stream of chlorine gas through

with the Prussiate of Potash. SIS

a solution of the prussiate of potash : the liquor gradually loses
its yellow tint, becomes of a dark greenish-yellow, and, when fully
saturated, of a deep brownish-red colour. From this solution the
salt is obtained in regular crystals, though with considerable dif-
ficulty, owing to its tendency to decompose, and to deposit a
green sediment. I have never been able by this process to pro-
cure crystals either so large or so permanent as those I got
at first from the Prussian blue. By another process, however,
which I shall presently describe, it may be formed with great
ease, and in beautiful crystals.

Gmelin calls this salt a peculiar Cyanide of. Iron and Potas-
sium (besonderes Cyan Eisen Kalium), and gives the following
as its composition :

By Experiment.

Potassium, = 35873-v

Iron, - = 17/22 > = 102093

Cyanogen, = 49*0 )

taking the mean of his results ; and from this he deduces, as its
atomic constitution,

Potassium, = 3 atoms, = 117*6 = 35*89 per cent.
Iron, = 2 ... = 540 = 16*49

Cyanogen, =6 ... = 156*0 = 47*62

1 atom, = 327*6 = 10000
which, by correcting the atomic weights, becomes

Potassium, 3 atoms, = 15*0 = 120 == 36*1445 per cent..
Iron, 2 ... = 70 = 56 = 16*8674

Cyanogen, 6 ... = 19*5 =156 = 46*9879

1 41*5 382 99*9

214 Mr Johnston on the Combination of Chlorine

Now from the way in which the salt is formed, it is evident
that no such change of composition can have taken place. For
we have here the cyanogen (= 6 atoms) and iron (= 2 atoms)
of 2 atoms of the common prussiate *, contained in each atom
of the new salt in combination with only 8 atoms of potassium ;
so that to form it we have only to deprive the common prussiate
of its water, and of half an atom of potash. Upon what principle
of affinity, then, can the action of chlorine produce this separa-
tion ; and, if produced, what becomes of the potash, since the
liquor may be made to .crystallize to the last drop ? It cannot
be in the green powder, which, during concentration, is often
deposited ; for its quantity is variable, and it is plainly the result
of decomposition. The ratio of the atoms, therefore, must be
different from what he states it to be, and there is no reason why
it should not be the same as in the original salt.

Again, this statement throws no light on the action of the
in forming the new salt. This gas must act in one of

* There are various ways of stating the composition of this salt. According to
Berzblius, who considers the prussiates as compounds of 1 atom of cyanide of iron
-I- 2 atoms cyanide of another metal, it consists of

Potassium 2 atoms, =10*0

Iron l - = 8'5 V = 26-625

Cyanogen 8 ... = 9*75

Water 8 = 8-875

2. According to Dr Thomson, it is composed of

2 atoms potash, - =12*0 ^

1 ... protoxide of iron, = 4»5 > 26*625

8 ... hydrocyanic acid, = 10*125 J

8. While Mr Phillips states it thus :

1 atom ferro-cyanic acid, = 14*625 )

2 ... potash, - =12*0 J86685

Bbbzslius considering the water present to be merely that of crystallization, and
Mr Phillips viewing the iron as a constituent of the acid, coinciding in this point
with Mr Pobbett.

with the Prussiate qf Potash. 215

two ways. Either it mugt combine with the elements of the salt,
or it must decompose the water, imparting to these elements an
atom of oxygen, and combining itself with the hydrogen to form
muriatic acid. But of the presence of this acid there is no trace,
nor does the analysis take account of the addition of oxygen ; for
it does not allow the presence of a single atom in the salt. The
chlorine, therefore, cannot have acted by decomposing the. water ;
it must consequently have combined with the elements of the
salt.

This conclusion, which is fairly deducible from the pheno-
mena attending the preparation of the salt, is confirmed by ex.
periments, both analytic and synthetic, which I proceed to state.

1 . The dry crystals reduced to powder, and treated with con-
centrated sulphuric acid, give off chlorine gas. This is abun-
dantly perceptible by the smell, though. I have not hitherto been
able by this means to obtain satisfactory results as to the quan-
tity of chlorine present.

2. When the same powder, which is of a bright yellow colour,
is heated in a glass tube or small retort by means of a spirit-lamp,
it is changed into a dark brown colour, giving off during this
change a gaseous product, soluble in water, and having the cha-
racter of the chloro-cyanic acid, accompanied sometimes by a
small quantity of cyanogen.

3. By Gmelin's analysis, the salt is anhydrous ; and accord-
ingly, when heated to 300° on the sand-bath, it loses nothing,
nor, when exposed to a red heat in a tube, does it give off any
moisture or trace of ammonia, if the crystals employed have been
perfectly dry. We have ascertained two points of difference,
then, between this taLfrand the common prassiate of potash, that
it contains chlorine, and is destitute qf water . .

216 Mr Johnston on the Combination of Chlorine

Now the chlorine may either have united itself to the entire
elements of the salt, or it may have expelled a portion of the
cyanogen, and have taken its place. The whole loss of gaseous
matter, which he concluded to be all cyanogen, but which was in
reality the sum of the two gases, Gmelin found to amount to
49 per cent. Now 3 atoms of cyanogen — 38*2 per cent, leaving
upwards of 10 per cent, for the chlorine added to the original
constituents. This is not far from half an atom (=8*82 per
cent.), which we shall afterwards see is the true quantity.

4. Failing to satisfy myself by analysis of the true amount of
the chlorine, I endeavoured to ascertain how much the prussiate
of potash would absorb. And first, as the new salt contains no wa-
ter, 40*3 grs. of the anhydrous prussiate, — the three atoms of wa-
ter being previously expelled by a gentle heat, — were introduced
into a glass tube, and exposed for several days to an atmosphere
of chlorine : the white powder became of a beautiful bright yel-
low colour, and had gained 1*4 grs. Dissolved in water, it gave
a bright yellow solution, and by evaporation crystals partly red
and partly yellow, being a mixture of the new salt and the com-
mon prussiate. The powder, therefore, had not been saturated
with chlorine.

5. I now introduced 1 50 grs. of the crystallized prussiate, re-
duced to a fine powder, conceiving that the presence of the 3
atoms of water might facilitate the combination. And to ascer-
tain if any gas were disengaged from the salt, I caused the one
end of the apparatus to terminate in a solution of the prussiate
of potash, through which the passage of chlorine would be indi-
cated by a change of colour ; while at the other, the chlorine was
generated and made to pass over chloride of calcium. As soon
as the gas came in contact with the powder, it gave it a deep
chrome-yellow colour, and a deposition of moisture took place on

tttth the Prussiate of Potash. 217

the inside of the tube, opposite the portion whose colour was
changed. The deposition of moisture and change of colour pro-
ceeded together along the tube (no moisture being deposited at
either extremity beyond the amianthus by which the salt was
confined), till the whole had assumed the new colour, when the
powder was evidently in a moist state. On introducing the chlo-
rine, a portion of common air was expelled, after which no gas
came over, the chlorine being slowly generated. That it was in
contact with the liquid into which the extremity of the appara-
tus was plunged, was manifested by the formation of a dark ring
at its surface* within the terminating tube.

There being in this process, then, no loss, all increase of
weight will be due to the absorption of chlorine. Out of a mul-
titude of experiments with similar results, I select the following:

52 grs. gained 4*4 grs. = 2*253
153-2 grs. ... 129 - 2-248
2775 grs. ... 235 =2*254

• . •

. • •

Now these come all so neat 2*25, — half an atom of chlorine,
as to leave no doubt that such is the true quantity absorbed.

When the chlorine is passed over the powder very slowly,
little apparent moisture is disengaged, the water, though freed
from combination, remaining in contact with the salt ; but if it
be generated with -great rapidity, as by the direct action of mu-
riatic acid on peroxide of manganese, the water of crystallization
is also rapidly disengaged, and forms on the sides of the tube in
very considerable drops ; and if the quantity of powder acted
upon be large, there is at the same time a considerable elevation
of temperature caused by the condensation of the gas.

6. If the yellow powder thus saturated with chlorine be
spread out in the open air, and dried without artificial heat, it
loses in weight a quantity exactly equal to 3 atoms of water.

VOL. XI. part i. e e

SI 8 Mr Johnston on the Combination of Chlorine

m

Thus, for example, 564 grs. lost 6*6, as near 6*591 which 3 atoms
of water amount to as possible ; and after this loss, being heated
to 300°, it lost only *08 of a grain. The chlorine, therefore, in
combining with the prussiate to form this yellow powder, expels
from its previous state of combination the three atoms of water
which enter into its constitution.

7. There only remains, then, to ascertain the relation be-
tween this yellow powder and the red crystals, which, as men-
tioned above, are the state in which the salt under consideration
occurs. If the dry powder be dissolved in a small portion of
distilled water, carefully evaporated, and a gentle heat continued
till the whole moisture be driven oft, the salt will be obtained
in beautiful crystals, and of the same weight as the powder em-
ployed. Or if the moist and newly saturated powder be dissolved
and crystallized, the loss of weight will amount as before to that
of 3 atoms of water.

Thus, 87*7 grs. gave 33*6 grs. of dry crystals.
80 grs, ... 71
80 grs. ... 267
50 grs. ... 44*2

... ...

. . .

... ...

The 1st lost 4*1 grs.,

should have lost 4*4

%cl • *• y • • •

'••• •••• J7 clO

3d ... 3*8 ...

... ... 9 o

4th ... 5*8 •••

• . . ... 5*886

in which the approximation is as close as can be looked for in
such a process. There is therefore no difference between the
yellow powder and the red crystals, except the crystalline ar-
rangement of the particles ; the elementary constitution of both
is the same.

the Pmssiate of Potash. 219

8. The composition of the salt may therefore be stated as
Mows :

1 atom anhydrous prussiate of potash, = 28'25 *) _
£ ... chlorine, - = 2*25 ) "~

Or,

Per Cent

Chlorine, ± atom, = 225 = 88235 \ _ 47#OJ5fifi

Cyanogen, 3 atoms, = 975 = 382353 ) ~ 4 ' °588

Iron, 1 ... = 35 =13725

Potassium, 2 ... = 100 = 39-215

255 9999

or, by doubling the quantities, we shall get rid of the half atom,
and the atomic weight will be 51 .

In this statement, the sum of the chlorine and cyanogen ap-
proaches very near to the amount of cyanogen assigned by Gme-
i/iN : in the potassium there is a difference of 4 and in the iron
of 3 per cent.

9. There are three different modes of combination, according
to which the chlorine may be supposed to have arranged its ele-
mentary particles in forming the new compound we have been
considering. Either it may have united with the cyanogen con-
tained in the cyanide of iron, forming a chloro-cyanide, in which
the acid consists of

1 Chlorine, =4'5|

2 Cyanogen, = 6*5 )

united to two atoms of iron. Or it may have united itself to
that which is combined with the potassium, forming an acid con-
taining double the quantity of cyanogen, namely,

e e 2

220 Mr Johnston on the Combination of Chlorine

1 Chlorine, 4-5 )

17'5

•o)

2 Cyanogen, 13

united to 4 atoms of potassium. Or, lastly, it may have united
with the whole of the cyanogen and the iron, as they exist in
the ferro-cyanic acid, forming a new acid, composed of

1 atom chlorine, = 4*5
6 ... cyanogen, zzl9'5\=3l.

2 ... iron, = 7'0

and our new salt will consist of

1 atom chloro-ferro-cyanic acid, = 31 \
4 ... potassium, - - =20 J

forming a chloro-ferro-cyanide of potassium.

The last of these views of the constitution of the salt is that
which I am inclined to adopt. For this preference various rea-
sons might be stated, but I am mainly influenced by the circum-
stance, that, when the chlorine combines with the prussiate of
potash as above detailed, it expels all the water, and therefore
seems to combine with the whole assemblage of elements as one
compound atom.

10. The acid, as it exists in the above salt, can, it is obvious,
contain neither oxygen nor hydrogen. It may be obtained in a
separate state by various processes, some of which I shall ex-
plain in a future communication. I may here, however, men-
tion, that, when pure, it forms beautiful red four-sided needles,
not differing in appearance from those of any of its salts. In this
state it contains either water or its elements, and may be viewed
as a hydracid, though in the salt of potassium it acts precisely at
chlorine does in the chlorides.

I have formed the various salts resulting from the union of

with the Prussiate qf Potash. 221

acid with the bases, and' shall conclude this paper with a de-
tail of their general properties, reserving the particular history ,
of each till I shall have more fully explained the nature and com-
position of the cry stallized acid.

1st, They are all of a deep red colour, crystallizing in four-
sided pyramids and rhomboidal prisms. In minute needles they
assume a golden-yellow colour.

Zd, In the moist state, the crystals are liable to decomposi-
tion by the agency of heat and light, becoming externally of a
greenish colour, and in solution depositing a green sediment.

3d, They are very soluble in water, but insoluble in alcohol,
unless considerably diluted.

4th, Their solutions when hot and concentrated have a pecu-
liar smell, approaching to that of weak chlorine, and, with the
exception of the salt of lead, they have all a bitterish taste ; that
of lead has the sweet taste of its other salts.

5th, These solutions are decomposed by sulphuretted hydro-
gen, becoming green, and depositing sulphur. Some of the hy-
dro-sulphurets have a similar effect, but they are not changed by
hydrogen gas.

6th, Treated in powder with sulphuric acid, they give off
chlorine gas. From the salts of barytes, strontian and lead, it is
also partially driven off by a gentle heat.

7th, Their solutions are also decomposed by metallic mer-
cury, being changed into green, becoming greenish-yellow, and
letting fall a blue precipitate ; the solution no longer giving a
red but a white with nitrate of silver. They have likewise a
strong action upon metallic iron, coating it immediately with
Prussian blue.

Sthy They all give similar precipitates with the metallic

oxides.

9th, When dry, they undergo no change by exposure to the
air, the salt of cadmium excepted, which deliquesces.

2££ Mr Johnston an the Combination of Chlorine.

10/A, Most of them decrepitate when heated, and in the flame
of a candle are combustible, throwing oat bright white sparks,
and leaving a dark brown residue. The salt of barytas melt*
without sensibly burning ; and that of lead bums silently like
tinder, giving minute globules of metallic lead.

Claypath, Durham, )
January 1888. J

( SS3 )

XIII. On a Mass of Native Iron from the Desert ofAtamaca in
Peru. By Thomas Allan, Esq. F. R. S. £.

(Read 4th February 182&J

When in London in spring last year, Mr Parish had the
kindness to show me some specimens which he had just received
from his son, Mr Woodbine Parish, his Majesty's Consul-Ge-
neral at Buenos Ayres, among which I was surprised and much
pleased to find two masses of native iron, exactly similar to the
Skated Siberian block, made know, to the science world
through the exertions of Pallas, having the same vesicular struc-
ture, and con taining the same straw-yellow coloured olivine firm-
ly imbedded.

I immediately suggested to Mr Parish the propriety of losing
no time in making this discovery known, and thereby secure to
his son the merit of bringing it before the public ; and in order
to do this in the most effectual manner, I advised him to pre-
sent one of the masses to the Royal Society of London, and
the other to the Royal Society of Edinburgh ; and it is with
pleasure that I now find myself deputed to carry his wishes with
respect to this Society into execution, by presenting one of the
masses as a donation to this institution in the name of his son.

Hitherto the Siberian mass has stood unrivalled, and quite
unique. A mass found in Poland in 1809, was said to have re-
sembled it, being vesicular, and having the cavities covered inter-
nally with a yellowish-green vitreous substance ; but it would
have required the cavities in the iron to be filled with that sub-
stance, to have rendered it similar to the Siberian mass. The
other native irons, have I believe, uniformly presented a solid

224 Mr Allan on a mass of Native Iron

structure, or else, though technically termed spongy, were wholly
composed of metallic iron, alloyed as they all are with nickel.
It is consequently interesting to find that a mineral so entirely
similar to that of Siberia, should have been found abounding in
the opposite hemisphere, as appears by the following very curious
statement contained in the extracts of two letters from Buenos
Ayres, and so abounding as to render it a matter of great asto-
nishment.

" Account received by Dr Redhead ; of the Native Iron from the

Province of Atacama.

" The specimens were taken from a heap of the same nature,
esteemed at about three quintals. They exist at the mouth of
a vein of solid iron (barra), half a yard wide, situated at the foot
of a mountain. The opposite plain is strewed with similar frag-
ments. The Indian who brought these, calls them " Reventa-
zones" supposing them to be produced by explosions from the
mines. He had been charged to bring a piece of the vein itself,
and some of the rock in which it is imbedded ; but this he says he
could not effect for want of tools. He therefore contented him-
self with picking up some pieces that were at the foot of the hill,
where the mouth of the vein opens. If it be true, as, from the
probity of the Indian, who is well known from previous informa-
tion, and from general report, we must believe it to be, that the
metal is in a vein, it ought to be considered as the first pheno-
menon of this nature that has occurred. vWhat Margraff found
found in Saxony was probably not of this kind."

Extract of a Letter from Woodbine Parish, Esq. Buenos Ayres,

April 1827.

* • • * *

The account given by Dr Redhead has since been fully
confirmed, by other accounts from different persons. This iron

from the Desert of Atacama in Peru. 225

is found in the province of Atacama in Peru, at a distance" of
about twenty leagues from the port of Cobija, in large masses
imbedded in a mountain, in the neighbourhood of the village of
San Pedro, and scattered over the plains at the foot of the moun-
tain in question for a distance of three or four leagues, in frag-
ments similar to that sent herewith, but some of them of consi-
derable magnitude."

From this statement it appears that the accounts are yet im-
perfect, and that we have only the authority of an Indian to de-
pend upon. It was by the same species of authority, obtained from
a Cosaque named Medvedef, who was found to be accurately cor-
rect, that Pallas was led to his mass. The apology of the Indian
for not bringing a portion of the vein attached to the rock, as he
was desired to do, is a very plausible one ; but the structure of
this iron is so entirely dissimilar from the product of any vein of
iron that we are acquainted with, that it is highly probable the
scattered fragments will be found to differ entirely from any ore
which the veins of that country may produce. It was the theory
of the Indian, that these fragments, which, according to Mr Pa-
rish's subsequent statement, appear to be scattered over a dis-
trict extending to three or four leagues, were produced by explo-
sions from the veins. He had consequently a theory to support ;
and we know here something of the difficulty with which geolo-
gical opinions are abandoned. Our Indian, therefore, who is ad-
mitted to be a man of observation, would probably decline to pro-
duce specimens calculated to overset his former assertions, as it is
very improbable that he would be sent for the purpose of ob-
taining specimens without the tools necessary to secure the suc-
cess of his mission.

The Desert of Atacama, as it is termed in the maps, is si-
tuated on the shore of the Pacific, between Chili and Peru. The
town of Atacama lies in Lat. 23° 8(f S., and Long. 69° SO* W.

VOL. XI. PART I. F f

226 Mr Allan on a mass qf Native Iron

about half-way between the ocean and the volcanic range which
runs along the western edge of the great peninsula.

Connected with, though independent of, this notice, I may
mention, that it is also to Mr Woodbine Parish that the Bri-
tish Museum is indebted for another remarkable mass of native
iron, presented some time ago in the name of that gentleman by
Sir H. Davy. The history of it is unfortunately not given in de-
tail. It is considered by Mr Parish to be the same mass de-
scribed in the Philosophical Transactions of 1788 by Reuban de
Cblis, which was foiuuHn the province of Chaco Galamba. But
there is a great discrepancy in the weight. It is rather sur-
prising that no accurate description of this mass has as yet met
the eye of the public, although it is itself placed under its as-
pect on the steps of the great stair of the Museum.

the Society last met, Dr Turner has accomplished a
examination of this mass, in which he has found nic-
kel, the admitted testimony of meteoric iron, and also traces of
cobalt.

Examination of the Specimen presented to the Society by Mr Air
lan in die name qf Mr Woodbine Parish, his Majesty }s Con-
sul-General at Buenos At/res. By Dr Turner.

Externally it has all the characters of meteoric iron. The
metal in the specimen is tough, of a whiter colour than common
iron, and is covered on most parts with a thin film of the oxide
of iron. The interstices contain olivine.

The specific gravity of some clean fragments is 6*687 ; and
the density of a portion which has been forged into the form of
a nail, is 7488.

To ascertain if the specimen before the Society is analogous
to meteoric iron in composition, as well as in its appearance,

Jrom the Desert of Atacama in Peru. 227

28*77 grains of it were exposed to the action of nitro-muriatic
acid, and were completely dissolved by that menstruum. The
solution, after being moderately diluted with cold water, was gra-
dually neutralized by the bi-carbonate of potash, with the view
of precipitating the iron, and retaining the cobalt and nickel in
solution by the excess of carbonic acid.

The hydrated red oxide of iron, after being carefully washed,
dissolved without residue in oxalic acid, and therefore did not
contain any nickel or cobalt. The peroxide of iron was then
thrown down by ammonia, collected, and heated to redness. Its
weight was 38*39 grains, equivalent according to the atomic tables
of Dr Thomson, to 26*87 grains, or 93'40 per cent of metallic
iron.

The solution from which the iron had been removed by the
bi-carbonate of potash, had a green tint ; and on expelling the
free carbonic acid by heat, the hydrous carbonate of nickel sub-
sided. The precipitation was completed by the aid of pure pot-
ash. The precipitate, after being washed, was treated by a solu-
tion of oxalic acid, and was thus converted into the granular oxa-
late of nickel. The acidulous solution of oxalic acid did not
strike a blue colour with the ferrocyanate of potash, nor yield a
precipitate when neutralized with ammonia, and consequently
was free from iron.

The oxalate of nickel was dissolved in pure ammonia ; and
after it had separated from the liquid by the gradual dissipation
of the alkali, the remaining liquid had a pale pink colour, and
on evaporation yielded a minute residue, which, after being heat-
ed to redness, weighed 0*22 of a grain, and formed a blue bead
when fused with borax. Regarding it as the peroxide of cobalt,
and as composed of 26 parts of metal and 12 parts of oxygen,
the quantity obtained by analysis indicates 01 54 of a grain, or
0#535 per cent, of metallic cobalt.

The oxalate of nickel was decomposed by heat, and yielded

Ff2

228 On a mass of Native Iron.

2*49 grains of the protoxide ; equivalent, according to the atomic
numbers of Dr Thomson, to 1'904 grains, or 6*618 per cent, of
metallic nickel.

I could detect no trace of chromium, manganese, copper, or
any other substance ; and therefore, the specimen presented to
the Society by Mr Allan, consists of iron, nickel and cobalt, in
the Mowing proportions :

Iron 934

Nickel 6-618

Cobalt 0585

100-558

The result of this analysis is, I apprehend, decisive concern-
ing the origin of the specimen before the Society ; for while it
differs from any compound hitherto discovered in the earth, it
corresponds exactly both in appearance and composition with
other masses of meteoric iron. Professor Stromeyer some years
ago detected the presence of cobalt in a specimen of meteoric
iron from the Cape of Good Hope ; and he informs me, that, in
an elaborate investigation of these singular metallic masses, he
has detected cobalt as well as nickel in every specimen which he
has analysed.

PLATE IK

r™«iA» St.* E**. m xi fim

( 229 )

Observations on the Structure of the Fruit in the Order* of
Cucurbitacece. By Francis Hamilton, M. D. F. R. S.
& F. A. S. Lond. & Ed.

(Read *th February 1828J

m

XttB fruit in this natural order does not appear to have been
well understood by most botanists ; and I shall therefore attempt
to give a general view of what appears to me to be its structure ;
and most of the parts are visible in the section .which js here
given (Plate IX. Fig. 1.) of the beautiful but insipid Indian Me-
lon (Cucumis Mela) called Phuti.

The outer parietes (Fig. 1. a,) when young, are thick, fleshy,
and undivided by sutures, with an uniform rind, not separable
from the fleshy part. As ' the fruit ripens, the rind in some
cases becomes so thin as to be unable to contain the pulpy mat-
ter, and bursts either gradually, as in the melon, or with elasti-
city as in the Momordica and Elaterium of Tournefort. At
other times, the rind hardens either into a thin substance like
leather or strong paper, as in the Luffu, or into a strong ligneous
covering, as in the Cucurbita leucanthema or gourd. In these
cases, it sometimes opens horizontally, by means of an operculum,
which falls off and leaves an aperture for the seeds, as in Fig. 2.
representing the summit of the Luffu called Picinna in the Hor-
tus Malabaricus.

The fruit is divided into three loculi or cells, by three mem-
branous . septa, proceeding from the outer parietes towards the
centre (Fig. 1. 6), and in the young fruit accompanied by a thick
covering of parenchymatous, substance, like that of the parietes,

280 Dr Hamilton on the Structure of the Fruit

only softer, and more gelatinous, especially towards the seeds,
which it every where surrounds. In general, the septa entirely
disappear before the fruit ripens, as in Fig. 3. representing a sec-
tion of the picinna in a half ripe state, or at least the septa can-
not be readily traced among the thick substance by which they
are surrounded, and which originally proceeded from them.

This soft substance consists sometimes of fibres intermixed
with juice, and more or less spongy, which, when the fruit ripens,
sometimes becomes either a corky mass, in which the seeds nestle,
as in the Cucurbita leucanthema, or a dry fibrous texture, leaving
a longitudinal cavity, in which the seeds are disposed loose, their
umbilical cords having disappeared, as in Luffh (Fig. 5.). At
other times, again, the fibrous pulp, as it ripens, undergoes less
change, only it becomes more succulent, as in the Cucurbita Pepo,
at more fibrous, as in the Cucumis Colocynthk. Instead of fibres,
again, this soft substance is sometimes divided by membranes
proceeding transversely from the septa, so as to form vertical
cells, separating from each other the seeds, which appear in the
transverse section, and which lie surrounded by a gelatinous fluid
contained within the cells, as in Fig. 1. or as better represented
by Gjertneb (t. S3.) in his figure of the Cucumis mtivus. Fi-
nally, this soft fibrous or membranous substance entirely sepa-
rates from the septa, and a portion of it forms an arillus to cover
each seed, as in several species of Trichosanthes, and as repre-
sented by Gartner in the figure of the Momordka Balsamina
and Bryonia bwiniosa (t. 38.)

The fruit has three receptacula, to which the young seeds ad-
here generally by short umbilical cords, as in the Melon and Cu-
cumber ; but they are sometimes sessile, as in a singular kind of
Tricho$anthes, called Theba by the Bengalese, the receptacula of
which, so long as discernible, envelope with their fleshy reflected
edges the single ovum which each edge nourishes, as in the sec-
tion (Fig. 4.) of its enlarged germen.

in the Order of Cucurbitacece. 281

Each receptaculum in these fruits consists (Fig. 1. c) of two
half membranes, uniting at the centre of the fruit ; so that each
membrane, embracing the inner end of a septum in its central
fold, has one half in one cell, and the other half in another cell
As these receptacula, consisting thus of a double membrane, are
usually thicker than the real septa, and continue longer conspi-
cuous, being less surrounded by the pulpy or fleshy nature of the
fruit, they have often been considered as the true septa dividing
the fruit into three cells, having entirely that appearance, as in
Fig. 3. Still, however, when fully ripe, they often disappear, as
even in the fruit now mentioned, the two rows of seeds that ad-
hered to each septum in the half ripe fruit, when this ripens ape
lodged in a cavity formed by a dry fibrous texture, which sue?
ceeds to the fleshy substance secreted from the true septa (Fig. 5.)
In other cases, as in the Momordica Bahamina (Gjbrtnsb, t. 8&),
all vestiges of both^ septa and receptacula disappear, and the loose
seeds remain floating in a gelatinous fluid, which squirts out when
the fruit bursts.

Sometimes the receptacula do not extend to the parietes, but
terminate in the middle of the cell, in which case they sometime?
have only a single row of seeds annexed to their margin, as in
the species of Luffa called Ghoza by the Bengalese (Fig- &),
sometimes a double row (as in Fig. 3.) ; and rarely only on$ se$4
of each row comes to maturity, as in several species of Bryonia,
and in the Trichomnthes called Theba by the Bengalese (Fig. 4.)

In general, however, the receptacula reach to the outer pa-
rietes, to which they adhere ; and as the portion between the
centre and parietes often disappears before the fruit i$ ripe, what
remains adhering to the parietes is considered as a parietal re-
ceptaculum, and the seeds are considered as centrifugal (Gjeetn.
torn. i. Praef. xlvill directly contrary to fact. This appearance
is very plain in the ripe fruit of the Tricfmwthe* ar^ui^ or
Chichingya of the Bengalee (Fig. 7.), which, when ripe, is per-

282 Dr Hamilton on the Structure of the Fruit

fectly unilocular, with three pair of Ibngitudinal reoeptacula ad-
hering to the parietes.

In some cases, the two membranes of which each receptacu-
lum consists, continue united, until they terminate at the parie-
tes by one or two thickened longitudinal margins, as may be seen
in the common cucumber (Fig. 8.), as usually eaten when half
ripe. In others, the membranes separate, sometimes before they
reach the parietes, and then extending at an angle to each other,
leave a surface on each side towards the general cavity of the
cell, on which surface the seeds are inserted, as in the Cucumis
called Gurmi by the Bengalese (Fig. 9.) At other times the
membranes do not separate until they reach the parietes, when
they are turned back towards the centre of the general cell, and
have the seeds inserted either on their sides (Fig. 1. d)9 or on
their edges, as in the Trichosanthes called nby the Bengalese
Bhungi kumra (Fig. 10.) *

I have said that very often the central parts of the mem-
branes composing the receptacula disappear, leaving only the
parts next to the parietes, to which the seeds adhere ; but in other
cases the whole membranes remain ; and, separating from each
other in the centre as the fruit ripens, leave there an empty
space, with the pulpy matter included in three cells, as it were,
between three portions of the parietes and the three membranes
of the receptacula. Traces of this structure may be observed in
Gartner's figure of the Cueurbita Pepo (t. 88.) ; but in sections
of the Cucumis Melo and C. sativus, when fully ripe, it is very re-
markable (Fig. 11.) Finally, in other cases, the receptacula and
septa entirely disappearing in the ripe fruit, leave the central parts
of the parenchymatous matter in form of a columnar receptacu-
lum, having the seeds imbedded among pulp, between it and the
external parietes. These rows are sometimes six in number, a
row having proceeded from each side of each receptaculum. In
other cases, as in the Momordica called Khaska by the Benga-

in the Order of Cucurbitaceee.

233

lese (Fig. 12.), there are twelve rows, each edge of such recep-
taculum having supported two rows.

The seeds, so far as I have observed, are horizontal, except
in the Trichosantkes called Theba, already mentioned, in which
they are placed vertically ; but this plant apparently differs a
great deal from all the others that I have seen, in having a kind
of bilocular nuts in place of seeds, one cell in each nut being
empty. Besides, the seeds of this plant are covered with a
spongy albumen, unless, from analogy, this may perhaps be con-
sidered as a thick inner membrane investing the seeds, while the
nut may be called a thick outer integument, several other spe-
cies having the outer membrane crustaceous and brittle- In ge-
neral the seeds are flat ; but in several there is a thick edging,
around which, in the Bryonia laciniosa, is enlarged into a ring
somewhat like the" setting of a reading-glass. The embryo is
straight, with thick cotyledons, and a small radicula placed at the
end next the receptaculum.

END OF PART I.

VOL. XI. PART I.

Gg

^

( 235 )

XV. Some Experiments on the Milk of the Cow- Tree. By Tho-
mas Thomson, M. D. F. R. S. L. & E. &c. Professor of
Chemistry in the University of Glasgow.

(Read 17th Starch 1828J

A phial full of this liquid, one of the first specimens, I believe,
that ever made its way to Great Britain, was lately sent to Dr
Hooker by Sir Ralph Woodford, Governor of Trinidad. It
had been collected in Laguayra by Mr Lockart, Director of the
Botanic Garden in Trinidad. Dr Hooker having been good
enough to put this rare specimen into my possession, I made a
few experiments to determine its constituents. The singular
nature of the production, rather than any thing very striking in
the results which I obtained, led me to suppose that they would
not be unacceptable to the Royal Society.

This curious vegetable production was first made known to
the scientific world by M. de Humboldt. But from the very
imperfect account which he gives of the Galactodendron utile *,
there is reason to conclude that he had never seen it. It is cer-
tain at least that he had never seen it in blossom. The atten-
tion of MM. Bou88ingault and Mariano de Rivero was drawn
to this important liquid by M. de Humboldt. They collected
it accordingly, and subjected it to a chemical examination. They
found its constituents to be wax, fibrin, sugar, a magnesian salt,
which was not an acetate, and water. They could neither de-
tect in it casein nor caoutchouc. The ashes after incineration

* This is the name given by Humboldt to the tree which yields the cow-tree
milk.

VOL. XI. FART II. H h

236 Dr Thomson's Experiments on the

consisted of a mixture of silica, lime, phosphate of lime, and
magnesia #.

The Galactodendron utile grows abundantly in the mountains
situated on the north-west part of Venezuela, in South America,
at a height, according to Humboldt, of nearly 10,000 feet above
the level of the sea, and consequently in a climate that cannot
differ much from our own. The tree, from Mr Lock art's ac-
count, is a very large one, with leaves similar to those of the fig.

The juice of this tree* obtained by incision, is known by the
name of the milk of the cow-tree. In the state in which I re-
ceived it, it was a white opaque liquid, of the consistence of
cream. When thrown upon a filter, a small quantity of a red-
dish-brown transparent liquid passed through, leaving a great
quantity of white solid matter on the filter, the surface of which,
as it dried, assumed a reddish-brown colour. The filter itself
became gradually tinged of the same colour. It was found im-
possible to wash this solid matter. It attached itself to the fil-
ter, and rendered it quite impervious to water.

Another portion of the cow-tree milk was left for six weeks
in a state of rest in a tall cylindrical glass. No deposite took
place ; the milk remained unaltered, excepting that its surface,
where in contact with the air, assumed a reddish-brown colour.
But after four months, the white matter had separated, and left
a little brownish liquid at the bottom of the dish.

It had a sour smell, not the same with that of vinegar, but
peculiar. Different individuals formed different opinions re-
specting this smell : some considering it as offensive, others as
rather agreeable. The milk reddened vegetable blues. It had
a very slightly acid taste, but in other respects bore considerable
resemblance to the taste of cream.

Its specific gravity was found to be 1.01242.

* See an abstract of their experiments in the Ann. de Chirru et de Phys. xxiii. 219>

s

Milk of the Cow- Tree. 237

A portion of it was put into a small retort, and left ex-
posed to a heat so regulated as never to exceed 212°. A trans-
parent, colourless liquid gradually distilled over. This liquid
had an acid but at the same time a sweetish taste. It redden-
ed vegetable blues, and had the peculiar smell which characte-
rized the cow-tree milk. To determine the nature of the acid,
I put the liquid into a flask, with some pure carbonate of lime
in powder, and digested the mixture till the liquid had lost
the property of reddening vegetable blues. The portion of
calcareous-spar which remained undissolved had assumed a red-
dish-brown colour, and a slimy consistence. The liquid, which
was colourless, was filtered, evaporated to dryness, and the
saline residue exposed to a heat somewhat higher than 300°,
to decompose any vegetable matter with which the calcareous
salt might be mixed. The brown residue was again digest-
ed in water, and the filtered liquid was a second time evapo-
rated to dryness. A small quantity of white calcareous salt was
obtained, on which a little sulphuric acid was poured, and heat
applied. A strong odour of acetic acid was exhaled, showing
that the small quantity of uncombined acid in the tree milk is
the acetic.

When the cow-tree milk is mixed with caustic potash ley, or
with dilute nitric, muriatic, or sulphuric acids, and then thrown
on a filter, a dark brown coloured liquid passes through, and a
white substance, not unlike wax, remains on the filter. But I
could not succeed by this method in freeing the waxy matter
fmm all impurities.

When the cow-tree milk is exposed to a low heat in an open
vessel, the moisture is gradually dissipated, and a solid, grey
waxy matter remains. When this matter is digested in water,
it becomes white and opaque, while the water assumes a yellow
colour, and, when concentrated, acquires the same dark reddish-
brown colour which characterizes the liquid which passes through
when the cow-tree milk is thrown on a filter. This liquid, how

ii h 2

288 Dr Thomson's Experiments on the

soever concentrated, possesses no agglutinating properties like
those of a solution of gum or sugar. When it was evaporated
to dryness, a shining brown coloured matter remained, having
an acrid taste, and somewhat altered by the heat. This sub-
stance bore a closer resemblance to ulmin than to any other ve-
getable principle, though its properties were different in some
respects. Thus, its solubility in water was promoted by acids,
which is not the case with ulmin. This brown substance is so
scanty, that I never could procure more of it than one grain.
It was therefore impossible to examine it minutely, or to deter-
mine its exact nature.

The white waxy substance left by the water being repeatedly
digested in hot alcohol, was all dissolved, with the exception of a
few pink-coloured flocks, which, after being thoroughly washed in
hot alcohol, and then left to dry in the open air, assumed a dark
brown colour. These flocks were tasteless, and insoluble both
in water and alcohol. When digested in nitric acid, they swelled
up, and assumed the same appearance as a piece of cork would
have done, if placed in similar circumstances. By continuing
the digestion, a solution was obtained. Being evaporated to
dryness, the yellow coloured residue was bitter, and scarcely so-
luble in water. It was three times successively dissolved and di-
gested in nitric acid ; but no crystals of oxalic acid were formed.

In muriatic acid, this substance became soft and spongy like
cork, but did not dissolve. In sulphuric acid, it gradually dis-
solved, blackening the acid, and, when water was added, a black
deposit gradually subsided. In caustic potash ley, it became
soft, and almost gelatinous, but did not dissolve.

I was more minute in my examination of this substance, be-
cause it seems to be what MM. Boussingault and Mariano de
Rivero have distinguished by the name of fibrin. It exists in
the cow-tree milk only in small quantity. It approaches much
more nearly to cork than to any thing else. None of its charac-

Milk of the Cow-Tree. 289

ters have any close resemblance to those of fibrin. It is not un-
likely that it was derived from the inner bark of the cow-tree.

But by far the most abundant constituent of the cow-tree
milk is the substance which was dissolved in the hot alcohol.
When the alcoholic solution cools, it becomes white and opaque
like milk, and gradually deposits abundance of snow-white flakes.
If we pour the alcoholic solution upon a filter, these snow-white
flakes are retained, and the liquid passes through colourless-like
water. When the matter thus retained is exposed to a mode-
rate heat it melts, and on cooling assumes the form of a yellow-
ish-white, opaque, wax-like substance, which I shall distinguish
by the name of gallactin.

The alcohol thus freed from gallactin was put into a retort,
and drawn off at a low heat, till only a small quantity of fluid
remained. A transparent liquid substance gradually separated,
as the alcohol was drawn off. This liquid was at first of the con-
sistence of oil, and very adhesive. When left exposed to the air,
it became gradually more and more viscid, and at length assumed
the consistency of turpentine. A cuticle formed on its surface
by degrees, which was not in the least adhesive. But the liquid
below, when the cuticle was broken, continued as adhesive as
ever. Six weeks9 exposure to the air produced no farther change ;
but when I spread it thin on a plate of glass, it gradually as-
sumed the appearance of a stiff, but soft transparent varnish.

The substance to which I have given the name of gallactin,
has been described by MM. Boussingault and Mariano de
Rivero, under the name of wax, to which it certainly bears a
very striking resemblance ; but as it differs from wax in some of
its most remarkable properties, I have thought it better to dis-
tinguish it by a particular name, which I have borrowed from
the generic name assigned by Humboldt to the Cow-tree.

Gallactin, after it has been deposited from hot alcohol, and
melted into a cake, is a solid substance, having a light yellowish-

240 Dr Thomson's Experiments on the

white colour, and the opacity and consistence of wax. It is not
brittle like bees-wax, but plastic, at least when the temperature
is not lower than 60°, which was the heat of my laboratory when
I was engaged in examining the properties of gallactin.

Like wax, it becomes a transparent liquid when exposed to
heat. This liquid has many of the characters of a fixed oil, ren-
dering paper transparent, and burning with great brilliancy when
kindled by means of a wick. As the change from solidity to a
state of liquidity takes place gradually, it is not easy to assign
the true melting point of gallactin. At 117° it was solid, at 137°
it was fluid. Between 117° and 137° it passes through an infi-
nite number of different degrees of softness, before it becomes as
liquid as possible. When we heat the white flocks which are
deposited from alcohol, they emit abundance of aqueous vapour,
and the gallactin does not become a transparent liquid till kept
for some time in the temperature of 170°, showing that these
white flocks consist of water and gallactin united together.

Gallactin is as tasteless as wax ; but when put into the mouth
it becomes soft and plastic, and adheres strongly to the teeth,
having no bad resemblance, in point of consistency, to the gluten
of wheat, when just freed from the starch. But the colour of
this plastic gallactin is snow-white.

When gallactin is heated on a platinum or silver spoon, it
melts, and then frothes strongly. When the frothing is at an
end, the colour has become brownish-yellow. On increasing the
heat to 640°, the gallactin begins to boil, and the vapour catch-
ing fire, burns with a bright yellow flame, giving out smoke, and
ultimately disappears, leaving behind a minute quantity of white
ashes.

This white residue has no action on vegetable blues, showing
that it contains neither a fixed alkali nor lime. It dissolved in
nitric acid, with the exception of a very minute portion, which
was probably silica, though its quantity was too minute to admit

Milk of the Cow- Tree. 241

of examination. The nitric acid solution, so far as could he
judged from the action of re-agents, consisted of a mixture of
magnesia and phosphate of lime.

Gallactin, at the temperature of 60°, has a specific gravity of

0.969.

It dissolves in considerable quantity in alcohol and sulphuric
ether, when assisted by heat. But it is again deposited in fine
white flocks, when the solutions are allowed to cool.

Oil of turpentine dissolves it with facility ; and when the oil
is cautiously driven of£ a yellow transparent varnish remains.

Olive oil dissolves it likewise with facility, and in consider-
able quantity before its consistency is sensibly altered*

In the properties hitherto enumerated, gallactin agrees with
wax, excepting that it is more soluble both in alcohol and ether.
But in the following properties, there is a marked difference be-
tween these two bodies.

1. Gallactin does not combine with the fixed alkalies, and
does not seem capable of forming soap ; whereas wax, as is well
known, combines with facility with the alkalies, and readily forms
with them a soap. It is true that MM. Boussingault and
Mariano de Rivero say expressly that the wax of the cow-tree
combines with the alkalies, and forms soap. But I digested gal-
lactin in caustic potash ley for three days, and kept the mixture
boiling for several hours, without any appearance of combination.
When the ley was allowed to cool, the gallactin was found float-
ing on its surface in the state of a solid cake, not sensibly altered
in its properties. When wax is subjected to the same treatment,
it forms a milky liquid with the ley in the course of a few mi-
nutes, and this liquid may be employed as a detergent, and of
course possesses the properties of soap.

2. Cold nitric acid does not act sensibly on gallactin ; but
when heat is applied, an effervescence takes place, the gallactin
assumes an orange colour, and gradually dissolves. If we pour

242 Dr Thomson's Experiments on the

water into the solution, the gallactin precipitates, apparently
little altered except in colour. But if we cautiously evaporate
the nitric acid solution to dryness, a yellow, brittle, bitter-tasted
substance remains, which is soluble both in water and in alcohol.

The aqueous solution of this substance is not affected by
prussiate of potash or infusion of nut-galls ; but with nitrate of
lead, or nitrate of mercury, it gives a white precipitate. The
precipitate with the former is scanty, with the latter abundant

The alcoholic solution is yellow and very bitter tasted. Wa-
ter occasions a precipitate, which, however, is re-dissolved on agi-
tating the liquid. It is precipitated by nitrate of lead, nitrate
of mercury, sulphate of zinc, sulphate of manganese, muriate of
barytes, muriate of strontian, muriate of lime, and muriate of
magnesia.

3. When gallactin is put into sulphuric acid, the liquid as-
sumes a fine brownish-red colour, which gradually deepens. The
acid appears green by reflected light, and deep brownish-red by
transmitted light. The gallactin becomes soft and dark brown.
When sulphuric acid is heated in contact with gallactin, it frothes
and assumes a black colour, sulphurous acid being given out
abundantly.

4. When gallactin is heated in water, it does not float on the
top of the liquid, under the form of a transparent oil, as is the
case with wax ; but it imbibes a great deal of water, and assumes
the form of a white, opaque, viscid matter, not unlike the gluten
of wheat in its appearance and adhesive nature, but much more
fluid.

Some of these characters approach those of the volatile oils ;
but gallactin is devoid of smell, and likewise of taste, and the
temperature at which it boils is certainly not lower than 600°.
By my thermometer it was 640°. In combustibility and consis-
tence it resembles wax ; but the action of alkalies, nitric acid,

Mfflc of the Caw-Tree. 243

sulphuric acid, and water, is quite different from the action of
these bodies on bees-wax.

The transparent liquid matter which remains when the cold
alcoholic solution from the cow-tree milk is distilled off in a re-
tort, possesses very nearly all the characters of gallactin, if we
except the liquid form under which it appears. It is equally
fixed, and equally combustible. It is destitute of taste and smell,
stains paper like an oil, does not combine with potash, but dis-
solves in nitric and sulphuric acids with the same phenomena as
gallactin. It is lighter than water, but from its extremely adhe-
sive nature, I could not determine its specific gravity exactly.
Perhaps, therefore, it may be only another modification of gallac-
tin. The two most striking circumstances in which it differs
from gallactin, are its solubility in cold alcohol, and its liquidity.
It remains to be seen whether, by long enough exposure to the
open air, it will assume the appearance of gallactin. As far as I
can judge hitherto, it never loses its transparency, but dries into
a kind of varnish like the drying oils.

Boussingault and Mariano de Rivero mention sugar as
one of the ingredients of the cow-tree milk. The boiling alco-
hol, after being freed from the gallactin, both solid and liquid,
was found to hold a small quantity of matter in solution. It
would not crystallize, neither was it separated by the addition of
water. When the liquid was distilled off at a low heat, a white
flocky matter remained, having a slightly sweetish taste, and so-
luble both in water and alcohol. This is probably the substance
which these chemists have called sugar. If the property of crys-
tallizing and of sweetening water be considered as belonging to
sugar, this substance cannot claim the name. It is probably ana-
logous to sarcocol in its nature.

. VOL. XI. part 11. 1 i

*

( 244 )

XVI. Account of the Constituents of various Minerals. By Tho-
mas Thomson, M. D. F. R. S. L. & E. Professor of Che-
mistry in the University of Glasgow.

(Read Ytth March 1828. J

I have been occupied for about two years past, assisted by the
practical pupils in the laboratory belonging to the College of
Glasgow, in analysing the most important specimens in my mi-
neral cabinet, which seemed to me to require further elucidation.
As my practical pupils are seldom fewer than six, and as they are
employed the whole day, from nine in the morning till dinner-
time, during the whole year, about six weeks in the summer ex-
cepted, which I have been in the habit of spending in the coun-
try, the number of analyses which has accumulated within that
time, has become so great, and some of the results are so curious,
that I have selected a few out of the number, for the gratifica-
tion of the mineralogical public. It may be requisite to mention,
in the first place, that when a pupil comes into my laboratory, the
first thing which he does is to transcribe a set of practical rules,
which 1 have drawn up for the benefit of my pupils. He is then
set to analyse an easy mineral, with the composition of which I
am already acquainted. I either shew him myself the different
steps of the analysis, or request some of the farther advanced pu-
pils to superintend the progress of the analysis, and ensure its
accuracy. This method of superintendence is persisted in, till
the pupil has familiarised himself with the different steps in die
analysis of minerals, and till he has become well acquainted with
the appearances of the different precipitates, and knows how to
determine the complete separation and the purity of the diner-

On the Constituents qf Various Minerals. 245

ent earths, &c. I need hardly remark, that the analysis of the
magnesian minerals is the most difficult, and requires the long-
est practice. As soon as I find that the pupil has acquired suffi-
cient skill, he is left entirely to himself. All the precautions I
think necessary to take, is to give him two or three rather diffi-
cult minerals, which I have previously analysed myself. This
enables me to judge how far I can depend upon the accuracy
and sagacity of the pupil. It has sometimes happened, in these
cases, that the pupil has detected substances in the * mineral
which I myself had overlooked. In such cases, I repeat the ana-
lysis again myself, and generally find that the analysis of the pu-
pil was more correct than the one that I had originally made.
The pupil is always exercised in these kinds of investigations for
a considerable time, and I do not give him new minerals (ne-
ver before investigated) to analyse, till I have had ample evi-
dence of his skill and accuracy.

The minerals of which I mean to give the analysis in this pa-
per, were analysed in the laboratory of Glasgow College, almost
all of them since July last. I shall take them up without any
order, being guided, in some measure, by the comparative im-
portance of each.

1. Sillimanite.

This mineral was found at Petty Pog, in the township of Say-
brook, Connecticut. It was described and analysed by Mr
Bower (Journal of the Academy of Sciences of Philadelphia,
p. 875). For the specimens which I was enabled to subject to
analysis, I was indebted to Mr Nutall.

It occurs in long four-sided prisms, generally bent, in a mica-
slate rock ; but the portion in which the Sillimanite is found is
quartz ; perhaps a vein.

ii 2

246 Dr T. Thomson's Account of the

The faces of the prism are too rough and uneven to admit the
application of the reflecting goniometer. By my measurement
with the common goniometer, they gave 110°, and 70° for their
angles. But Mr Bower, who probably was in possession of spe-
cimens better adapted for examination, states the angles of the
prism to be 106° SO7, and 78° 80'. The base of the prism, he
says, is inclined on the axis at an angle of 1 IS0. In none of the
crystals, in my possession, could the inclination of the base be%
observed at all.

Colour dark-grey, passing into clove-brown.

The crystals have a fibrous structure.

Lustre vitreous.

Brittle, and easily frangible.

Translucent on the edges.

Harder than quartz. It even scratches topaz.

We found the specific gravity to be 8.1636. But the quanti-
ty weighed was only 5.64 grains. Mr Bower states it at 3.41.

Infusible before the blowpipe per se, and also with borax. Not
acted on by acids.

5.64 grains of this mineral were subjected to a very careful
analysis by Mr Thomas Muir. He found the constituents as
follows :

Silica, 88.670

Alumina, 35.106

Zirconia, 18.510

Protoxide of iron, .. 7.216

99.502

When the zircon was detected by Mr Muir, I requested him
to subject it to a rigid examination, to be sure that it was nei-
ther yttria, nor glucina, nor alumina. This was easily done by
means of caustic potash, and sulphuric acid.

Constituents qf various Minerals. 247

Mr Bower's analysis approaches pretty nearly to that of Mr
Muir, only he confounded together the alumina and zirconia.
He obtained

Silica, 42.666

Alumina, 54.111

Oxide of iron, . . . 1.999
Water, 0.510

99.286

The constituents found by Mr Muir give us for the chemical
constituents of the mineral,

15 atoms silicate of alumina,
3 atoms silicate of zirconia,
1 atom silicate of iron.

Were the silicate of iron to be considered as accidental, Sil-
limanite would be a compound of

5 atoms silicate of alumina,
1 atom silicate of zirconia.

2. Cummingtonite.

This mineral, likewise, I owe to the kind attention of Mr Nu-
tall. It was found at Cummington, Massachussets, where it
occurs in a rock composed of quartz, garnet, and Cummingtonite.
Mr Nutall expressed his suspicion that it would prove merely
a variety of Sillimanite. But it is much softer, and in its che-
mical constitution is quite different.

It occurs in fine needles, constituting tufts of crystals, in
which the needles diverge slightly from each other.

Colour greyish-white. Lustre silky.

248 Dr T. Thomson's Account of the

Easily scratched by the knife ; but not* by calcareous spar.

Opaque, or only translucent on the edges.

Specific gravity 8.20 14.

Infusible per se before the blowpipe. With carbonate of soda
it fuses with effervescence into a dark glass. Fuses with borax
and with biphosphate of soda into a black glass, showing the pre-
sence of much iron and manganese.

It was analysed by Mr Thomas Muir, who found the consti-
tuents to be

Silica, 56.543

Protoxide of iron, . .21 .669
Protoxide of manganese, 7.802

Soda, 8.439

Driven off by red heat, . 3.178

97.631

As the loss in this analysis amounted to almost 2.5 per cent.,
I requested Mr Muir to examine the mineral for fluoric acid
and phosphoric acid ; but no traces of either of them could be
found. If we suppose the loss of weight to be soda, the chemi-
cal constitution of Cummingtonite will be

9 atoms tersilicate of iron,

3 atoms tersilicate of manganese,

5 atoms tersilicate of soda.

If the mineral contain no more soda than was found by Mr
Muir, it will be composed of

3 atoms of tersilicate of iron and manganese,
1 atom tersilicate of soda*

I think it most likely that this last view is the nearest the truth.

Constituents of various Minerals. 249

3. Corundum.

The specimen chosen for the analysis was a beautiful
semitransparent crystal from Madras, constituting a six-sided
prism of considerable sifce. It was evidently vtty pure, and had
a distinctly foliated structure, The feces of cleavage were so
brilliant, that the specimen approached pretty closely to a sap-
phire. The specific gravity was 8.951 1. Thi* mineral was
analysed with great cate by Mr Thomas Mum. During the
trituration in the agate mortar, there was a quantity of silica
abraded from the mortar, and mixed with the pouhded corun-
dum. The constituents Were found to be,

Alumina, . . . 98.46
Silica, .... 1.54

100.00

But the quantity of silica abraded from the mortar was 1.56.
Hence it is clear that the corundum is composed of alumina
alone, without any silica whatever. The whole of the alumina,
tn make sure of its Duritv, was converted into alum.

4. Hyacinth from Expailly.

For the analysis of this mineral, very pure crystals were pick-
ed out. I requested Mr Thomas Muir, who made the analysis,
to heat the crystals to redness, and select those that had become
colourless. When pounded in the agate mortar, no loss of
weight was sustained by the mortar, showing that the hyacinth

250 Dr T\ Thomson's Account of the

is much softer than corundum. The analysis was conducted by
heating the pounded mineral with carbonate of soda, in a plati-
num crucible. Much of the success depends upon the fineness
of the powder to which the hyacinth is reduced. The fused
mass was softened by water, and dissolved in muriatic acid. The
portion not taken up by the muriatic acid, was again heated
with a new portion of carbonate of soda, and the solution in mu-
riatic acid repeated. A third heating with carbonate of soda,
and digestion in muriatic acid, furnished a complete solution of
the whole mineral. The rest of the analysis was obvious and
easy. The constituents were found to be

Silica, . . . 33.82

Zirconia, . . 66.00 with a trace of iron.

99.32

The specific gravity of the crystals analysed was 4.6811.
It is plain from this analysis, that hyacinth is a sesquisilicate
of zirconia, or a compound of

1£ atom silica, 3

1 atom zirconia, .... 6

9

5. Chrysoberyl from Brazil.

Mineralogists are aware, that two different analyses of this mi-
neral have been laid before the public, within these few years ;
one by Arfvedson, and another by Mr Seybert.

Constituents of various Minerals. 251

According to Arfvedson, its constituents are,

Alumina, . . . . 81.43
Silica, 18.73

100.16 (Kongl. Vetens. Acad.

Handl. 1822, p. 90).

While Seybert found the composition in two different speci-
mens as follows :

Alumina, . . . . 73,60 . . . 68.666
Glucina, .... 15.80 . . . 16.000

Silica,

4.00 . .

5.990

Protoxide of iron,

o.oo

4.733

Oxide of titanium, .

1.00 . .

2.666

Moisture, . . . .

0.40 . .

. 0.666

98.18 . . . 98.780

The first of these specimens was from Hoddam ; the second from
Brazil. (Silliman's Jour. 8. 109.)

M. Arfvedson's analysis was conducted, by fusing the pound-
ed chrysoberyl with caustic potash, and digesting the matter in
muriatic acid. This process was repeated, and the portion
which ultimately resisted the action of the muriatic acid, he con-
sidered as silica. This was very unlikely to be a correct view
of the case. The silica, if any be present, ought to be more
easily removed by fusion with caustic potash, than any of the
other constituents. I analysed chrysoberyl immediately after
seeing Seybert's analysis, and foimd that the portion remaining,
after the first fusion of the mineral with caustic potash, and di-
gestion in muriatic acid, is a combination of glucina and oxide

VOL. XI. PART II. Kk

£52 Dr T. Thomson's Account of the

of iron. Mr Thomas Muir repeated my analysis last summer
and I give his in preference to mine, because 1 consider it as
more carefully made.

Good crystals were selected for the analysis, the specific gravi-
ty of which was found to be 8.7112. A portion of silica was
abraded from the agate mortar. This silica was detected in the
powder ; but if it be abstracted, then chrysoberyl contains no si-
lica whatever. Its constituents were found to be

Alumina, ....

. 76.752

Glucina, ....

. 17.791

Protoxide of iron,

. 4.494

Driven off by heat,

. 0.480

99.517

The last portion, which is so difficult of decomposition, was
found to yield to ignition, with a sufficient quantity of carbonate
of soda. A good deal of the success depends upon reducing the
mineral to a very fine powder. Neither Mr Muir nor myself
found any oxide of titanium, though we looked for it carefully.

If we consider all the constituents found in the chrysoberyl to
be chemically combined, it will be a compound of

6 atoms sexaluminate of glucina.
1 atom sexaluminate of iron.

The alumina in this mineral seems to act the part of an acid.

6. Brewsterite.

It is known to mineralogists that Mr Brooke first constituted
this mineral (Edin. Phil. Journ. vi. 112) a peculiar species, and
named it in honour of Dr Brewster, Secretary to this Society.

Constituents of various Minerals. 253

It had previously been considered as a stilbite, and as an apo~
phylite. Mr Brooke, in the paper just referred to, has describ-
ed the primary form and modifications of its crystals.

Its colour is white ; its lustre vitreous. It is transparent, and
has a specific gravity of 2.628. It fuses with great facility be-
fore the blowpipe, like the zeolites, to which it has obviously an
affinity. This mineral was analysed with much care by Mr Wil-
liam Muir, but he obtained an excess of about 3£ per cent. I
therefore requested Mr Richard Mitchell, who was a much
more experienced analyst, being in my laboratory for the second
year, to repeat the analysis, with every attention to accuracy.
The result of his analysis almost coincided with that of Mr
Muir, and there was the same excess of 3£ per cent. Upon exa-
mining the silica, I found that it cohered strongly before the
blowpipe. It had, therefore, retained a little soda : for the ana-
lysis had been conducted by igniting the powdered Brewsterite
with carbonate of soda, and dissolving the fused mass in muria-
tic acid. It was obvious from this, that the excess was chiefly
owing to the state of the silica.

The constituents are as follows :

Silica, .... 58.800
Alumina, . . . 18.9 IS
Lime, .... 12.384
Potash, .... 1.500
Water, .... 11.700

103.896

If we admit a slight excess in the silica, from the cause
specified, the constituents of the mineral seem to be

2AZSf+(C,K)S*+3A0;

k k 2

254 Dr T. Thomson's Account of the

or it consists of

2 atoms bisilicate of alumina.

1 atom tersilicate of lime, with some tersilicate of potash.

8 atoms water.

Mr Mitchell, at my request, tested the alkali for soda in the
following manner : The alkaline solution in muriatic acid was
mixed with an excess of muriate of platinum, and the mixture
was evaporated to dryness on the sand-bath, by a gentle heat.
The dry mass was digested in spirits, and the liquid, holding in
solution muriate of platinum, was evaporated to dryness in a pla-
tinum crucible, having been previously mixed with some sulphu-
ric acid. The dry mass was ignited to reduce the platinum to
the metallic state. The matter in the crucible was now digested
in water. This liquid being slowly evaporated to dryness, no
sulphate of soda appeared ; nothing indeed was found but a trace
of sulphate of lime, too small to admit of being weighed. Thus
it appears that Brewsterite contains no soda.

7. Amianthus from Sardinia.

The beautiful white amianthus from Sardinia, composed of
threads, which can be easily teazed from each other, and admit
of being spun, is well known to mineralogists. As it possesses
no marked characters, it is only by analysis that we can form an
opinion of the mineral species with which it is connected. I
therefore requested Mr Richard Mitchell to analyse a spe-
cimen of this beautiful amianthus, for which I was indebted to
my friend Charles Macintosh, Esq. of Crossbasket. Its spe-
cific gravity was 1.551.

Constituents qf various Minerals. 255

The result of the analysis was as follows :

Silica, 55.908

Magnesia, .... 27.068

Lime, 14.632

Alumina, 1.820

Protoxide of iron, . . 6.528

105.956

I believe the excess in this analysis to be chiefly owing to the
magnesia, which had in all likelihood been mixed with a por-
tion of the double carbonate of potash and magnesia : For the
method which I employ to analyse minerals containing lime,
magnesia and alumina, is to throw down the alumina and oxide
of iron by bicarbonate of potash. The liquid thus freed from
alumina, &c. is neutralised by muriatic acid, and the lime thrown
down by oxalate of ammonia. The liquid thus freed from lime,
is heated to the boiling temperature, and gradually mixed with
carbonate of soda, while kept boiling briskly, to throw down the
magnesia. If the carbonate of soda be added too rapidly, or if
the liquid be not made to boil briskly, the compound salt is apt
to make its appearance, in which case, it is exceedingly difficult
to get the magnesia in a state of purity.

Whoever will take the trouble to compare the preceding ana-
lysis of amianthus with the numerous analyses of amphibole by
Bonsdorf, in the Memoirs of the Stockholm Academy for 1821,
p. 192, will see at once that it is merely a variety of that very
proteus-looking mineral.

One of the most common varieties of amphibole consists of

3 .MS2 + CSS;

256 Dr T. Thomson's Account of the

or it is a compound of

3 atoms bisilicate of magnesia.
1 atom tersilicate of lime.

Now, this is the variety of amphibole to which the amianthus
approaches nearest.

8. Nutattite.

mineral was brought into this country some years ago by
Mr Nut all. Its locality is Bolton, Massachusetts. It was
considered in America as elaeolite. Mr Brooke examined it in
1 824, found the crystals much softer, and obtained by cleavage
a right square prism, which he considered as the primary form.
He named the mineral after Mr Nutall, who first brought it
to this country. For the specimens in my possession, I am in-
debted to Mr Nutall, who was so obliging as to send me two or
three ptetty pure pieces of it, one of which was submitted to
analysis. The crystals are imbedded in a rock composed of cal-
careous spar, and a green coloured mineral, in grains having the
aspect of amphibole.

The crystals of Nutallite in my possession, are eight-sided
prisms, which cleave in the direction of the faces of a right square
prism.

The colour is white ; in some parts of the crystal yellowish, in
others bluish or greenish. The yellowish-white parts of the
crystal are transparent ; the bluish nearly opaque ; showing evi-
dently the presence of some foreign matter. Streak white.
Lustre vitreous.
Easily scratches by the knife.

Specific gravity in different specimens was found to vary from
2.748 to 2.758.

Constituents of various Minerals. 257

By the analysis of Mr Thomas Muib, Nutallite is composed
of

Silica, 37.808

Alumina, . . . 25.104

Lime, 18.386

Protoxide of iron, . .. 7.892

Potash, 7.805

Water, 1.500

97.945

Were we to consider these constituents as all essential to the
chemical constitution of the mineral, it would consist of

3A/S + 2(*C + i/+iK)S;

that is to say, of

3 atoms silica of alumina.

1 atom of a triple silicate of lime, peroxide of iron and pot-
ash, in the proportions given in the formula : viz.

4 atoms silicate of lime.

1 atom persilicate of iron.
1 atom silicate of potash.

But whether any of these (and how many) be not accidental in-
gredients, can only be determined when we have an opportunity
of analysing Nutallite from other localities.

9. Pipestone.

I give this name to a mineral from North America, which the
Indians use for making tobacco-pipes. The specimen in my pos-

258 Dr T. Thomson's Account of the

session, which is of considerable size, I got from my friend and
former pupil Dr Scouler ; who some years ago passed a summer
on the north-west coast of America, between Nootka Sound and
Columbia River ; and, among many other natural productions of
the country, he brought home specimens of this pipestone. He
procured it from the Indians, and was ignorant of the part of the
country where it occurs, or the kind of rock with which it is as-
sociated.

It constitutes an amorphous compact stone, through which a
few scales of mica are scattered, having much the appearance of
claystone ; but softer.

Fracture earthy.

Colour light-greyish blue. Powder very light smalt blue.

It is rather harder than gypsum; but soft enough to be
scratched by the nail. Sectile. Opaque.

The particles, when scraped off with a knife, feel gritty be-
tween the teeth.

Specific gravity, 2.606.

It does not melt per se before the blowpipe.

Mr Thomas Muir made an analysis of it at my request, and
found the constituents to be

Silica, ....

. 55.620

Alumina, . . .

. 17.208

dooa, •

. 12.160

Peroxide of iron,

7.612

Lime, 2.256

Magnesia, .... 0.112
Water, 4.600

99.568

It consists of four silicates ; namely, of alumina, soda, peroxide
of iron, and lime. Were we to consider the bisilicates of iron

Constituents of various Minerals. 259

and lime to be only accidental substances, then the mineral
would be 2 A IS* + NS2, or it would consist of

2 atoms bisilicate of alumina.
1 atom bisilicate of soda.

There is a slight excess of silica and alumina ; but we have no
data to determine its chemical constitution with certainty. In
its composition, this stone bears some resemblance to the anal-
cime.

1 0. TersUicate of Lime.

This mineral has been hitherto found only at Gjellebak, four
Swedish miles (26f English miles) south from Christiania in Nor-
way, in a transition limestone, which extends to the south along
the sea-coast. It was taken for a tremolite, till Hi singer sub-
jected it to an analysis in 1823, and ascertained its real nature.
(Kongl. Vetens. Acad. Hand. 1823, p. 177.)

When occupied about a year ago in arranging my mineral ca-
binet, I found among my tremolites a specimen which struck me
as peculiar. I requested Mr Richard Mitchell to analyse it.
The result was, that it was a tersilicate of lime, in a much purer
state than the specimen subjected to analysis by Hisinger.
I do not recollect how the mineral came into my possession, and
there is no label on the specimen. But probably its locality is
the same as that of the tersilicate of lime analysed by Hisin-
ger.

Colour white.

Fracture fine radiated, giving the mineral a good deal of the
appearance of tremolite. The specimen is not crystallised.

Phosphoresces strongly when rubbed or struck; but only
slightly when heated.

Easily frangible, and reduced to powder.

VOL. XL PART II. L 1

260 Dr T. Thomson's Account of the

Opaque.

Dull.

About the hardness of calcareous spar.

Specific gravity, 2.2055.

Does. not effervesce in acids. In this respect my specimen dif-
fers from that analysed by Hisinger, which effervesces weakly
in acids, when in masses ; but strongly when in powder.

Before the blowpipe it fuses with difficulty on the edges (like
table-spar), into a colourless, semitransparent glass. With bo-
rax it fuses easily, and forms an amethyst-coloured glass.

Its constituents, as determined by Mr R. Mitchell, are as
follows :

Silica, 55.200

Lime, ...... 34.284

Alumina, 4.160

Protoxide of iron, . . 2.896

Moisture, 3.400

99.940

The constituents, as determined by Mr Hisinger, are as fol-
lows:

Silica, 43.868

Lime, 38.438

Protoxide of Manganese, 4.962
Protoxide of Iron, . . 1.484
Carbonic acid, ... 1 1 .368

99.565

If the carbonic acid was combined with lime, as it must hare
been, it would require 14.46 grains, reducing the lime in combi-

Constituents qf various Minerals. $61

nation with the 43.368 gr. of silica, to about 24 grains. This
approaches pretty nearly the ratio of 55.2 to 34.284, found by
Mr Mitchell in my specimen.

In my specimen there is a slight deficiency, and in Hisinger's
a slight excess of silica. It is obvious, from a comparison of the
two analyses, that the other constituents are accidental. The
mineral is CS3, or a compound of

3 atoms silica, . . 6
1 atom lime, . . 3.5

9.5

My specimen of tersilicate of lime was accompanied by a snow-
white, amorphous, soft matter, bearing a good deal of resem-
blance to the tersilicate, but entirely without the radiated struc-
ture. Its specific gravity was found to be 2.839. Mr Mitchell
analysed it at my request, and found it composed of

Silica, 56.67

Lime, 39.00

Alumina, .... 2.355 slightly tinged with iron.

98.025

There is a slight increase of the lime ; but it is obviously the
same mineral with the tersilicate of lime, making allowance for
the alteration produced on its texture by the action of the wea-
ther.

l12

262 Dr T. Thomson's Account of the

11. Leelite of Dr Clarke.

I got a specimen of this mineral, which occurs at Grythittan
in Nerike, many years ago from Mr Svedenst jerna. I had
arranged it in my cabinet as a specimen of compact felspar.

Its colour is flesh-red ; its structure compact ; its fracture
splintery, and also conchoidal ; its transparency that of horn ;
its specific gravity 2.606. Mr R. Mitchell analysed it at my
request, and obtained

Silica,

81.91

Alumina, ....

6.55

Protoxide of Iron, .

6.42

Potash, . . , .

8.88

108.76

Dr Clarke had analysed it, and he states its constituents to
be

« •

Silica, . . . . . 75.0

Alumina, .... 22.0

Manganese, ... 2.5

Water, 0.5

* * * • .

100 *

It is possible that the specimen analysed by Dr Clarke
might have differed from mine ; but no great confidence can be
put in Dr Clarke's analyses, as he had not much practice, and
was not probably able to determine the purity of the substance^

See Jnnals of Philosophy y xi. 867.

Constituents of various Minerals. 263

which he separated, with sufficient accuracy to be sure of his re-
sults. The art of analysis is soon learnt, when the pupil has pre-
viously made himself acquainted with the general principles of
chemistry. I have had pupils who could analyze with great ac-
curacy very difficult minerals, after less than a year's practice.

Leelite is obviously a compound of octosilicates, consisting of
2AlS*+fS8+KS8; or

2 atoms octosilicate of alumina,
1 atom octosilicate of iron,
1 atom octosilicate of potash.

It certainly differs from compact felspar.

12. Bucholzite.

The first account of this mineral was published in 1819 by
Dr Brandes, in the 25th volume of the first series of Schweig-
ger's Journal. He had obtained it from Professor Weiss, and
its locality was the Tyrolese Alps. Brandes gives an analysis
and very imperfect description, and I have seen no farther ac-
count of the mineral in any mineralogical treatise since publish-
ed. . About three years ago, Mr Nutall was kind enough to
send me some minerals from the United States. One of these
from Chester on the Delaware, south-west from Philadelphia, he
called Bucholzite, on the authority of Mr Heuland. About a
year ago, I got new specimens from him from the same place,
which were larger, purer, and better characterized.

The colour of Bucholzite is greyish-white, with a very slight
tinge of yellow, not recognizable in the purest specimens.

It is composed of fibres which in some places appear curved,
and, when viewed through a glass, assume the appearance of
plates or imperfect crystals.

Lustre silky.

264 Dr T. Thomson's Account of the

Not scratched by quartz, and scarcely by topaz, but easily by
sapphire.
Brittle.
Easily frangible ; fragments sharp-edged.

Specific gravity 3.193.

It was analysed by Messrs Hilton and Mitchell, and its
constituents found to be,

Silica, 46.40

Alumina, .... 52.92 slightly tinged with iron.

99.32

Brandes's analysis gave

Silica, ... ... 46

Alumina, 50

Protoxide of Iron, ... 2.5
Potash, 1.5

100

It is clear from the analysis, that the American specimens ana-
lysed in my laboratory were much purer than those in the pos-
session of Dr Bbandes.

Buchohsite is obviously a silicate of alumina, or a compound
of

1 atom silica, 2 ... or 46.4

1 atom alumina, 2.25 .... 52.2

numbers which approach very nearly to the result of the analysis.

13. Calcareo-sulphate of Barytes.
This mineral occurs pretty abundantly in the lead-mine of

Constituents of various Minerals.

265

Strontian, where tt is one of the various substances which serve
as a gangue to the ore.

The colour is snow-white.

The mineral is massive. Structure foliated, or at least scaly.
Fracture even.

Rather softer than common sulphate of barytes* Indeed it
is scratched by the nail.

Sectile.

Lustre pearly.

Translucent on the edges.

Specific gravity 4.1907-

It waa analysed by Mr Thomas Muib, who found the con-
stituents as follows i

. .

Sulphuric Acid,

Barytes,

Lime,

Silica,

Alumina,

Protoxide of Iron,

Strontian, .

Carbonic Acid,
Moisture, .

34.640
48.945
6.605
4.140
8.460
0.450
0.790
0.334
0.565

99.829

The mode of analysis followed was to heat the pounded mi-
neral with carbonate of soda, till complete decomposition was in-
duced. The heated mass was softened in water, and digested in
that liquid till every thing soluble was taken up. The alkaline
liquid was saturated with muriatic acid, and evaporated to dry-
ness to obtain the silica. The dry mass was digested in water,
acidulated with muriatic acid. The silica left behind was edul-
corated, ignited, and weighed. The muriatic acid solution was
mixed with a sufficient quantity of muriate of barytes to throw

266 Dr T. Thomson's Account of the

down the sulphuric acid. The sulphate of bary tes was edulco-
rated, ignited, and weighed.

The carbonates of barytes, lime, &c. were dissolved in mu-
riatic acid, and the alumina and oxide of iron were precipitated
by caustic ammonia. The liquid thus freed from alumina and
iron, was evaporated to dryness, and the dry salt digested in al-
cohol, which dissolved the muriates of lime and strontian, and
left the muriate of barytes. This last muriate was dissolved in
water, and the barytes thrown down by sulphate of soda, and its
weight determined in the usual way.

The muriates of lime and strontian were converted into ni-
trates. The dry nitrates were digested in alcohol, which dissol-
ved the nitrate of lime, and left the nitrate of strontian.

The quantity of carbonic acid was not determined experimen-
tally, but deduced from the quantity of strontian present in the
mineral. .

.It is obvious that the mineral consisted of

Sulphate of Barytes, . . {£* JJJJ} . 74.046

Sulphate of Lime, ... {££ *£} . 16.041

Carbonate of Strontian, . . {** JJJj} . 1.124

Silica, Alumina, Protoxide of Iron, 8.050

Moisture, 0.565

99.825

If we consider the carbonate of strontian, the silica, the alu-
mina, protoxide of iron, and moisture, as accidental substances,
then the mineral is a compound of

5 atoms sulphate of barytes,
2 atoms sulphate of lime.

Constituents of various Minerals. £67

14. Green Carbonate of Strontian.

It is well known to mineralogists, that, in the lead-mine of
Strontian in Argyleshire, two different varieties of carbonate of
strontian occur, the one green coloured, the other yellowish-
brown. ' But though these varieties have been long known, I am
not aware that they have hitherto been subjected to a chemical
examination, or that their true chemical constitution has been
determined. I had, indeed, analysed both several years ago ; but
the results of my investigation have hitherto lain by me unpub-
lished. Last summer, Mr Thomas Muir repeated the analysis
of both varieties with very great accuracy, and I shall here state
the result of his investigation.

It is well known that the green variety has an asparagus-
green colour, and that it is composed of imperfect prisms, slight-
ly diverging from a common centre. The specific gravity is
3.713. The constituents are,

Carbonate of Strontian, . . 93.493

Carbonate of Lime, . . . 6.284

Carbonate of Manganese, trace.

Oxide of Iron and Alumina, 0.01 0

99.787
or almost exactly of

1 atom carbonate of lime,
10 atoms carbonate of strontian.

To what is the green colour of this mineral owing ?

15. Brown Carbonate of Strontian.
This variety, judging from the number of specimens in my

VOL. XI. PART II. m m

368 Dr T. Thomson's Account of the

possession, seems to be almost as abundant in Strontian mine as
the preceding.

Its colour is yellowish-brown.

It is composed of needlea much finer than those of the green
variety, and,aa in it, slightty diverge
Specific gravity 8.6$ 1.

Its constituents^ as determined by Mr Thomas Muir, are,

Carbonate of Strontian, . . 91.171

Carbonate of Lime, - . . 8.642

Carbonate of Manganese, . 0.099

Oxide of Iron and Alumina, 0.078

99.990

It is a compound of

1 atom carbonate of lime*

7 atoms carbonate of strontian.

16. Quatersilicate of Alumina.

About two years ago, I received from Mexico, among a va-
riety of minerals, one which I set aside for a chemical exami-
nation. It was ticketed, " Piedran Barras ? Dipiro de Hauy ?
De Cymophan." It was obvious at first sight that the mineral
was neither the Dipyre of Hauy nor Cymophane ; nor could I
assign it a {dace in my cabinet.

Its colour is yellowish-white.

Its structure w initiated; for it is composed of imperfect, ob-
lique four-sided prisms, diverging slightly as from a centre. The
surface of the prisms is striated longitudinally ; and I could dis-
cover no cleavage to lead to any inference respecting the pri-
mary form.

Constituents of various Minerals. 26#

Lustre pearly. When pounded, it appears to be partly com-
pact, and partly composed of pearl coloured flakes or scales, ha-
ving somewhat the appearance of talc. Lustre shining*

Opaque, or only slightly translucent on the edges.

It is softer than calcareous-spar, but harder than gypsum.
The nail makes an impression on it with difficulty.

Specific gravity 2.688.

Infusible before the blowpipe.

The specimen was interspersed with iron-pyrites.

I requested Captain Lehunt to analyse this mineral, which
he did with great care> examining both the compact and scaly
portion separately ; but he found the constituents of both exact-
ly the same, namely,

Silica, . 72.52

Alumina, 20.44

Protoxide of Iron, . . 2.40

Water, 3.40

98.76

If we exclude the iron and water as accidental ingredients,
it is obvious that the mineral is Al S4, or composed of

4 atoms silica,
1 atom alumina.

It is therefore a quatersilicate of alumina*

17. Cinnamonhstone.

Whoever compares the cinnamon-stone with garnet, will, I
think, be under no hesitation about concluding that the two mi-
nerals belong to the same species* The crystalline shape of both
is the same, the hardness the same, the specific gravity the same,

Mm2

270 Dr T. Thomson's Account of the

and the chemical constitution the same. The only difference
that can be laid hold of is the shade of colour, which constitutes
too insignificant a distinction to be adopted as a specific diffe-
rence. Whoever will compare the constituents of cinnamon-
stone, as determined by Klaproth, Arfvedson, Nohdenskiold,
C. G. Gmelin, with the analyses of the different varieties of gar-
net by Trolle-Wachmeister, will be satisfied that the chemical
constitution of both is the same.

Captain Lehunt analysed at my request a very fine specimen
from North America sent me by Dr Torrey of New York, which
had the colour of cinnamon-stone, and the crystalline figure and
hardness of garnet Its specific gravity was 3.631. Its consti-
tuent parts were as follows :

Silica, 89.826

Lime, 80.574

Alumina, 29.141

Protoxide of Iron, . . 9.459

100

My opinion respecting the garnet, founded on a pretty co-
pious induction of facts, is, that there exist in nature three dis-
tinct species, composed as follows :

.1 atom silicate of alumina,
atom silicate of iron,
atom silicate of alumina,
atom silicate of lime,
atom silicate of lime,
atom silicate of iron.

greater number of garnets
of these three species in vi

Constituents of various Minerals. 271

mon-stone obviously belongs to the second species, or it is com*
posed of

1 atom silicate of alumina,

1 atom silicate of lime.

18. Marmolite.

This mineral occurs in veins in the serpentine of Hoboken in
New Jersey, and in the same situation in the Bare Hills near
Baltimore. It was first described and named by Mr Nutall.

Its colour is pale green or greenish-grey.

Texture foliated, with the laminae thin, and often parallel, as
in diallage.

It cleaves parallel to the sides of an oblique and compressed
four-sided prism.

Lustre pearly. Powder unctuous or shining.

Translucent.

Specific gravity, as determined in my laboratory, &4J0. Mr
Nutall states it at 2.470.

Before the blowpipe, it decrepitates, hardens, and slightly
exfoliates, without shewing any signs of fusion.

Mr Nutall analysed it, and found its constituents to be,

Silica, 36

Magnesia, 46

Water, 15

Lime, 2

Protoxide of Iron and Chromium, . 0.5

99.5

#

* Siilimafia Journal, iv. 19.

S7£ Dr T. ThoM&o*'b Account of the Constituents of Minerals.

Mr Nutall was good enough to send me several specimens
of it, one of which was analysed at my request by Mr Thomas
Steel. The result of two successive analyses were as follows :

Silica, ...... 41.256

Magnesia, .... 41.720

Alumina, 1.000

Peroxide of Iron, . . 0.400

Water, 17.680

^mmm

102.056

It is therefore a hycb-ous sesquisilicate of magnesia, or a va-
riety of the precious serpentine* or picrolite of Haushakk.

I have already extended this paper to a greater length than
I intended. Yet I have been able to introduce but a very small
number of the many analyses made by my practical pupils during
the course of the two last years ; and I have omitted altogether a
pretty numerous set of analyses made by myself during that time.
These I may perhaps lqy before the public &t some future oppor-
tunity. Meanwhile it is highly requisite to attend to the adage
of Terence, " Ne quid nimis"

( 273 )

XVII. Account qf a remarkable peculiarity in the Structure qf

Glauberke, which has one Axis qf Doable Refraction
for Violet, and two Aoces for Bed Light By David
Brewstxx, LL.D. F.R.S. Lond. & Em*.

(Read 1th January 1820 J

In the optical and mineralogical classification of crystals which
I published in the article Optics in the Edinburgh Encyclopae-
dia, I hare arranged Glauberite among those in which I dia-
covered two axes 'of double refraction. The specimen which
I used, however, was so small and imperfect, that I could not
measure the inclination of the lines of no polarisation, or ascer-
tain with any accuracy the laws of its action upon light. Mr
William Nicol, whose ingenuity is already well known to this
Society, put into my hands two specimens of Glauberite, which
he had skilfully prepared for showing its system of polarised
rings ; and, by the use of these, I have been enabled to detect a
very remarkable property in this mineral

When examined by common polarised light, the tints of its
rings are exceedingly anomalous, and we seek in vain for the
two poles where the double refraction and polarisation generally
disappear. The cause of this irregularity immediately shews it*
self, when we expose the crystal to homogeneous rays. In the
red rays, we observe the phenomena of two distinct axes, the in»»
clination of the resultant axes being about 5°. This inclination
gradually diminishes in the orange, yellow, and green rays, and in
the violet the two poles coincide, exhibiting the system of rings
round a single axis of double refraction, In all these cases, the
character of the principal axis is negative. It seems to be per-

t

£74 Dr Brewster on a remarkable peculiarity

pendicular to one of the faces P of the primitive form, as given
by Hauy, and the plane of the axes at right angles to a line bi-
secting the acute angle of the same face.

When Mr Herschel discovered the very remarkable pro-
perty in Apophyllite, in virtue of which it exercised a negative
influence over the red rays, a positive influence over the blue
rays, and no influence at all over the yellow ones, I shewed in
a paper read before this Society, and printed in their Transac-
tions #, that these apparently irreconcileable actions, related, as
they seemed to be, to a single axis of double refraction, could be
calculated in the most rigorous manner, by supposing the crystal
to have three positive axes at right angles to each other, each of
which exercises a different dispersive action upon the differently
coloured rays. This result, which is of considerable importance
in the theory of double refraction, is strikingly confirmed by the
phenomena of Glauberite, while these at the same time present
us with a new and still less equivocal case of the composition of
axes.

In the case of Glauberite, observation exhibits to us one ne-
gative axis A, which is the single axis for the violet light, and
the principal axis for the red and the other less refrangible rays ;
and, at the same time, it presents to us a second axis B, which
may be either negative or positive, but which must be 90° distant
from A. If it is negative, it must be in a plane perpendicular to
the plane passing through the two resultant axes for red light ;
and it must bear to A the ratio of the square of the sine of 2£°
(half the inclination of the resultant axes) to unity. If it is po-
sitive, it must lie in the plane passing through the resultant
axes, and it must bear to A the ratio of the square of the sine,
to the square of the cosine of 2£°. But whether it be positive
or negative, it exercises no action whatever upon violet light, a

♦ Vol. IX. p. 817.

in the Structure qf Glauberite. 275

supposition so absurd, that it cannot for a. moment be received.
Since the combination of axes, therefore, indicated by experi-
ment for the single system of rings in violet light, and for the
double system in the other rays, involves a physical absurdity,
we must seek for a new combination, not liable to such an ob-
jection.

If we suppose that the axis A for violet light is the result-
ant of other axes, and that these other axes are two posi-
tive axes B and C at right angles to each other, and also to
the apparent axis A, we shall obtain an explanation of all the
phenomena. If the axes B, C, exercise the same action on
the violet rays, they will produce a single negative axis at A for
violet light, as given by observation ; and if the relative intensi-
ties of their action upon red light are in the ratio of the square
of the cosine of 2£° to unity, the intensity of the weakest gra-
dually diminishing to zero for the rays between the red and the
violet, then we can calculate, with mathematical precision, all
the phenomena of double refraction and polarisation exhibited
by Glauberite.

The structure of Apophyllite and Glauberite, therefore, fur-
nishes us with two unequivocal examples of minerals where the
real axes of double refraction are not pointed out by observation.
Their crystallographic structure does not indicate, with any cer-
tainty, the locality of the axes which we have now inferred from
the laws of double refraction ; but we have no doubt that the
results of crystallography and optical structure will ultimately
coincide, when our knowledge of the primitive and secondary
forms of minerals shall have attained a higher degree of perfec-
tion #.

While repeating these experiments on Glauberite during a
low state of temperature, I was surprised to observe, that the

* The following paragraphs have been added since the paper was read.
VOL. XI. PART II. *M m

£76 Dr Brewster on a remarkable peculiarity in Glauberite.

tint between the two resultant axes diminished with the heat of
the hand. I immediately increased the temperature, and before
it reached that of boiling water, the weaker axis for red light
disappeared altogether, so that the crystal had only one axis for
red light. The axis, however, re-appeared, but the plane pass-
ing through the resultant axes was now at right angles to what
it was at first.

By the application of artificial cold, a new axis was created
for violet light, and the plane of the two resultant axes coincided
with the plane of the two resultant axes for red light at the or-
dinary temperature.

Results analogous to these have been obtained by Professor
Mitscherlich for other minerals ; but I am not aware that he
has observed such marked changes produced by such a slight in-
crease of temperature, or that he has made any observation at
all upon Glauberite. As the subject belongs to him, I have
merely noticed the very singular fact which so unexpectedly pre-
sented itself

( 277 )

XV IU. Experimental Inquiries concerning the Laws qf Magnetic

Farces. By William Snow Harris, Esq.

(Read April 1828.)

1. In the following investigation, it has been my endeavour to
elucidate some of the complicated phenomena observable in all
the known operations of Magnetic Forces : The labours of so
many profound inquirers in this important department of physical
science, are indeed such as almost to discourage those less gifted
with similar powers of research from engaging in the same pur-
suit ; but knowledge is progressive, and the splendid researches
which have displayed the highest efforts of genius serve rather
to assist than to deter others in more humble endeavours to pro-
mote the advancement of science.

2. Many excellent writers have well observed, that, to arrive
at a perfect knowledge of the laws of magnetic action, we should
have it in our power to submit magnets and ferruginous bodies
to the test of experiment, but that the combined effects which
these forces exhibit have at all times rendered such experiments
very difficult and precarious ; so that it has been almost impos-
sible to obtain from them simple results.

3. It may not therefore be altogether useless to describe an
instrument calculated to obviate some of the difficulties which
have thus impeded the efforts of experimentalists in their endea-
vours to investigate the laws of magnetic forces, in which, by the

m m 2

278 Mr Harris's Experimental Inquiries concerning

application of a very simple principle, aided by an easy and deli-
cate mechanism, I have sought a means of observing the action
of one magnet on another, or that of magnetised upon unmagne-
tised iron or steel, so as to estimate either the final result of the
compound action, or the separate forces of which such action is
compounded.

4. Plate X. Fig. 1. represents an instrument which may be
considered as a species of balance with equal arms. There is a
light wheel of brass abed, Figs. 1. & 2. about two inches diame-
ter, whose centre t is placed in that of an arc MIN. This arc is
the quarter part of a circle, having a radius of between six and
seven inches : it is divided into 180 equal parts ; 90 in the di-
rection IN, and 90 in the direction IM ; the point I being the
bisection of the arc, and marked zero. There is a short steel pin
which projects at b for about half an inch from one of the arms
of the wheel, through the circumference : this pin sustains an
index bl, Fig. 1. formed of a light straw, which being tubular, is
easily placed on it, so as to fit sufficiently tight ; the distant ex-
tremity of this index is cut in the manner of a common writing
pen, and is carefully tapered to a fine point. From the opposite
arm at d, a similar pin projects, on which is screwed a very
small brass ball, which being adjusted either nearer to or farther
from the centre, is made so nicely to counterbalance the index,
that the wheel, when resting on its axis, is almost indifferent as
to position, the index remaining on any part of the arc, or nearly
so.

5. The axis of this wheel abed is formed for a short distance
at each extremity into fine cylindrical pivots, which. rest upon
the angles formed by four lesser or friction-wheels : these are al-
so about two inches in diameter, are constructed in the lightest
way possible, and are placed two of them before, and two behind

PLATE S

fi,,v»/ .!«-. Tr.,» I,./ 37 p

the Laws of Magnetic Forces. 279

the frame which sustains the graduated arc ; they are mounted
on very delicate pivots, terminating in fine points #.

6. The five wheels just described, with the graduated arc, are
sustained by a projecting frame of brass ABD ; and the whole is
supported by a vertical column of wood or brass DE, about four-
teen inches high. The frame of brass ABD projects six inches
from the column, and is united to it at D by means of a small
nut and screw. The column DE is screwed, at its lower extre-
mity, into & circular base B', of 10 inches diameter, supported on
three adjusting screws, g> h, k. There are two lines of silk, each
three inches in length, bcm, ban, Figs. 1. & 2., which pass from
the point b in opposite directions, over the circumference of the
wheel abed, and terminate in two small hooks m, n : these lines
are secured close to the point b on each side of it, by means of
a small knot, and by passing them through holes drilled in the
circumference, as in Fig. 2. The circumference is slightly grooved
to receive these lines, and prevent them from slipping over the
edge of the wheel.

The line bem sustains a small cylindrical piece of soft iron, or
otherwise a small cylindrical magnet #, Fig. 1., which being first
attached to a loop of silk f , is suspended on the hook at m. From
the opposite hook n there is suspended in a similar way a cylin-
drical counterpoise of wood W, the lower half of which is im-
mersed in distilled water. The water is contained in a cylindri-
cal vessel of glass, whose interior diameter is so great that any

* The opposite extremities of the pivot-holes are faced with small portions of
fine watch-spring, as at ef> Fig. 1 . which mark the centres of the two front wheels.
Thus all friction which might possibly arise from the occasional contact of the shoul-
der of the pivot is prevented.

+ The loop is formed by a doubled piece of fine silk, inserted in a small hole
drilled vertically into the centre of the upper part of the cylinder -r, and secured
there by a small peg of wood passed down into the hole between its two extremities.

280 Mr Harris's Experimental Inquiries concerning

change in the altitude of the water, in consequence of the im-
mersion or emersion of a small portion of the cylinder W, does
not sensibly influence the indications on the arc M IN.

7. The cylindrical counterpoise just mentioned is made of fine-
grained mahogany : it must be turned very accurately, and must
be perfectly free from grease or varnish of any kind, so that be-
coming readily wetted by the water, it moves in it with great free-
dom. The body of this counterpoise is from two and a half to three
inches in length : its lower extremity terminates in a short stem
p, on which is fastened a brass ferule, having a screw at its lower
part, by which means a small hollow ball of brass b', from three
to six-tenths of an inch in diameter is attached to it, being
previously so loaded as to balance the suspended body a?, and
bring the index b\ within the range of the arc IN, when the
lower half of the cylinder W is about one-half immersed in the
water. The upper extremity of the counterpoise terminates al-
so in a short stem at o, and in a small hemispherical cup ; this
cup is intended to receive the additional weight requisite to
bring the index to aero ; and thus, by means of some fine shot,
which are very convenient for the purpose, the index may be
regulated with great precision *

8. It appears evident from the nature of this arrangement, that
the gravity or weight of the body w being as it were destroyed

* It is requisite to have several of these cylinders of different diameters, namely,
from 0.2 of an inch, to an inch, each increasing in diameter about 0.1 of an inch.
They should be very accurately turned, and, before being used, should be freely
wetted throughout their whole length, which is best effected by allowing them to
remain for a short time immersed in water as high as the upper stem. They are
suspended in their situation by means of a loop of silk, inserted in the bottom of the
hemispherical cup into a small hole drilled through its centre into the stem, and se-
cured there with a small peg of wood in the way already described in note on p. 5279.

the Laws of Magnetic Forces. 281

by a contrary and equal force, it may be considered as existing
in free space, devoid of weight, and it will therefore remain quies-
cent, until some new force be applied to it ; and thus the action
of the force we seek to investigate will become so far evident and
unimpeded by any obstacle arising from gravity, except the fric-
tion and inertia of the wheels, and the resistance of the air **
which in this case need not be taken into account.

Thus, if an attractive force cause the body #, Fig. 1., to de-
scend, then the index b\ will move forward in the direction IN,
until a portion of the cylinder W drawn out of the water, ceases
to displace as much of the fluid as is equivalent to the force ap-
plied; andthusweobtainaconstantandkno^
new force, within a given range, which will be more or less ex-
tended, according to the dimensions of the cylindrical counter-
poise W, the intensity of the force, and the rate of its increase.
In like manner, if a repulsive force act on the body w in a con-
trary direction to the former, then the index bl will move in the
direction IM, until a ntew portion of the cylinder W becomes
immersed in the water ; and thus an equivalent to the force of
repulsion is obtained in a converse way to the preceding.

9. Previously to suspending the cylindrical counterpoise just
described (7-), the body w is to be put in equilibrio with an equal
and similar weight x', Fig. 1*, in order to observe, if when loaded
with the whole, the index is indifferent as to position on any
part of the arc, or nearly so, after carefully bringing it to rest.
(The weight of the silk, which is necessarily transferred from
one side to the other by the motion of the wheel, being consi-
dered of no value). For this purpose, there is a small hollow
{ylinder of brass <xf> Fig. 1*, about the same dimensions as the

* These weights being placed under the same circumstances as the weights in
the celebrated machine of Mr Atwood.— See Atwood on Rectilinear Motion.

282 Mr Harris's Experimental Inquiries concerning

cylinder x : it is closed at each end, but has a small hook strew-
ed into the upper part, which can be occasionally removed, so as
to load the interior with as much weight as shall make it exactly
equal to the weight of the iron or magnet a?, when weighed in
an accurate balance. The machine, with the iron #>, thus put in
equilibrio, will be sufficiently delicate, if, when loaded with a
weight of 500 grains, about one-tenth part of a grain will set it
in motion.

To retain the wheel a be, Fig. 1. in its situation at the time of
removing either of the suspended bodies, there is a small brass
prong, Fig. 4. occasionally inserted in two holes drilled through
the quadrant, so as to enclose the steel point b which carries the
index : thus the wheel cannot fall either to one side or the other.

. 10. In order to regulate the distance at which an attractive or
repulsive force may be caused to operate on the body a?, there is
an adjusting apparatus represented in Fig. 1. by means of which
a magnetic bar H, or a horizontal plane AB, Fig. 9. (PL XI.),
may be elevated or depressed through any required space.

It consists of a vertical screw ST, Fig. 1., eight inches in
length, which passes through a corresponding nut at $, resting
finally upon the metallic foot at T : this foot is secured to a cir-
cular base of a convenient size. The nut at s is fixed to a small
horizontal plane of brass, sy9 an inch and three quarters in length,
and an inch wide : this plane is preserved in its position by the
guide SA, which also assists in supporting the circular top S ;
there is a brass, rod of about three-tenths of an inch in diameter,
and eight inches long, which passes freely through a small pro-
jecting ring at S, and is screwed beneath into the brass plane at
A' ; the use of this rod is to sustain the square band of brass V,
through which passes the magnet H and scale my. The band V
is united to the upper part of the brass-rod by a nut and screw
at r, and incloses a space an inch wide, eight-tenths of an inch

PLATE XI.

the Laws qf Magnetic Farces. 383

lo&g, and about half an inch in depth #. The magnet and scale
which pass through this opening rest in a corresponding band y
below ; this lower band being fixed to the brass plane. Each
band has two small screws, the milled heads of which are seen
projecting at V and y : these are to retain the magnet and scale
firmly in their place by slight pressure. When small magnets
are used, they are easily secured in their situation against the
scale my, by a slight pressure of the screw V. The magnet and
scale being fixed, we are enabled, by turning the head of the ver-
tical screw at S, to raise or depress them through any required
interval within the range of the screw, and so adjust the distance
between the upper pole of the magnet and the lower pole of the
suspended body w, with great accuracy.

11. Besides these means of adjustment, there are one or more
detached bands of brass, Fig. 3., somewhat similar to the fixed
bands already described, which are occasionally applied to any
part of the divided scale, so as to fix a magnet, or a mass of iron, at
any required distance from each other, as shewn in Figs. 5. & IS.,
or otherwise allow of pressure being made about the centre of the
bar, as at H, Fig. 1 ., by which means it can be elevated on the
scale if necessary. These bands also serve to sustain a magnet
or a mass of iron in an horizontal position, as in Fig. 11., there
being two spaces, hh> Fig. 3., through the sides.

12. When it is required to examine the force of a magnet in a
vertical position, it is placed in the situation just described (10.),
and then transferred immediately under the suspended body w,

there being a portion of the circular base B', Fig. 1., removed

... .. . ^ —

* The spaces are sufficiently large to receive one or more magnetic bars of a con-
venient size, the interval, when only one is employed, being filled up by a piece of
wood placed behind the scale, to keep it steady. The scale extends about three
inches above the magnet* and through its whole extent below: it can therefore be
raised between the magnet and wood to any further altitude required.

VOL. XI. FART II. N n

284 Mr Harris's Experimental Inquiries concerning

for this purpose, so that the adjusting apparatus rests on a base
independent of that which sustains the rest of the machine ; and
when it is required to examine the same force, the bar being
placed in an horizontal position, it is then laid on the horizontal
plane before mentioned (10.), and represented in Fig. 9, the
divided scale my being now a detached piece of wood or brass,
fixed against one of the perpendicular sides of a right-angled
triangle, it can thus be transferred to any part of the bar. There
is a small spirit-level occasionally placed on the plane AB, in or-
der to indicate, as nearly as possible, the horizontal position, when
adjusting the distance by means of the screws S, S, Fig. 9.

IS. The iron or magnet #, Fig. 1, and the cylindrical counter-
poise W, being accurately suspended, and the index adjusted at
zero, if the least impulse be communicated to either side, a long
continued and delicate oscillation will take place before the in-
dex again returns to its point of rest, which it finally does at
zero, thus evincing great freedom of motion.

The accuracy of the whole machine should now be finally
examined, by placing successively small weights of a grain or
more, according to the dimensions of the cylindrical counter-
poise, first on the suspended body #, and afterwards in the he-
mispherical cup at o. Thus, if one grain moves the index in ei-
ther direction 5 degrees, two grains should move it 10 degrees,
and so on ; and the motion on each side of zero should corre-
spond.

Beside the certainty we thus obtain of the accuracy of the in-
strument, or the error to which it is liable, we are enabled to
refer the force indicated to a known standard of weight, which
is every where the same, it being only necessary to state the dis-
tance at which the force acts, and the dimensions of the body #,
supposing it to be of soft iron of the ordinary kind. Thus, if
the distance should be an inch, and the index marking 25°, we

the Laws of Magnetic Forces. 285

might say the magnetic bar at an inch distance exerted on our
suspended iron w a force of 5 grains, supposing 5° = 1 grain ; and
thus the indications of such a machine, like the thermometer,
become universal *.

14. Experimental inquiries concerning the laws of magne-
tic forces being, as already observed (2.), much embarrassed
by the complicated action which such forces exhibit, we are
first led to examine the absolute attractive force exerted be-
tween a magnet and a mass of iron, when placed at various dis-
tances from each other, in which case, we may consider that a
permanent magnetic developement exists only in one substance ;
but in this inquiry, it is essential to understand clearly the laws
and operation of induced magnetism, that is to say, the influence
which magnetised steel exerts upon ferruginous bodies not mag-
tic, so as to induce in them a developement of magnetic proper-
ties, such effect being the most simple case of magnetic action.

15. For this purpose, the cylindrical piece of soft iron (13.
Note) was suspended from the wheel of the instrument, Fig. 1. :
it weighed 123 grains. The cylindrical counterpoise W being
about three-tenths of an inch diameter, which, by experiment,
gave 5° of attraction, equal to one grain. A mass of soft iron,
6c, Fig. 5., two inches in length, eight-tenths of an inch wide,
and three-tenths of an inch thick, was then affixed by means of a
brass band n to the divided scale ; and immediately under this

* There should be several small cylinders prepared of very soft iron, for general
use, being about two inches in length, and one quarter of an inch in diameter. The
iron-wire of commerce is convenient for the purpose. They should be accurately
turned, and great care should be observed in freeing them from any permanent po-
larity, which is readily done by making them red-hot in a clay tube, or in fine sand
in a small crucible, so as to keep them out of contact with the air. They may be
considered sufficiently free from polarity, if, when immersed in fine filings of soft
iron, there is no tendency to adhesion, or polar arrangement of the filings about
their extremities.

N n 2

286 Mr Harris's Experimental Inquiries concerning

was placed a magnet m, nine inches long, and of the same breadth
and depth as the iron above ; the whole was then transferred
under the suspended cylinder «r, as in Fig. 5, it being previously
ascertained that the magnet m might be alone approximated
within two inches of the iron #, without any sensible effect being
produced on the index. In this arrangement, therefore, the in-
dex could not become influenced, except by the magnetic de-
velopement induced in the intermediate substance b c ; and thus,
by varying the distance cd, and at the same time preserving the
distance ab9 by means of the screw at S, constant, it was easy to
determine the law according to which the magnetic developement
in the iron proceeded ; the force of the magnet m being consi-
dered a constant quantity, but its distance from the iron a va-
riable one.

16. For it will be readily admitted, that any polarity which
the attracting masses of iron be and oc could be supposed to ac-
quire by position might be considered as invariable and fixed
throughout the experiment, and therefore could not affect the
result, and must be otherwise a quantity so small in relation to
the means by which the other forces were made sensible, that it
could not have any assignable value, as the masses of iron oc and
be would not alone evince any attractive force, so as to be sen-
sible by the index, however near they were approximated.

17. For similar reasons, the operation of the distant polarities,
as they became developed in the attracting masses of iron x and
be, could not be supposed to exert any sensible influence in com-
plicating the result, as will also appear by considering the cir-
cumstances under which these polarities are placed. Thus, when
two magnets A and B, Figs. 6, 7. &. 8. are opposed to each other at
their dissimilar poles, then, in a purely theoretical sense, and ac-
cording to the most evident of magnetic experiments, N attracts

the Laws qf Magnetic Farces. 287

s, but repels n ; and S attracts n, but repels * ; so that the final
resultant is very complicated. We may, however, imagine these
forces to be so circumstanced in relation to a means by which
their action is evinced, and by which they are measured, that at
some distance N#, Fig. 6. the action vanishes. Let then the line
CD represent the limit at which their influence, thus estimated,
ceases : in this case, the effect of the polarity of BN upon that
of An must be considered as having no assignable value, until
some point in An, Fig. 8., upon the other side of the magnetic
centre A passes the limit CD. The same may be said of the in-
fluence of the polarity of BS upon that of As, so long as the
points in BS remain without the limit CD ; that is to say, at a
distance from the points in A* greater than N#. If the magnets
be only hardened and magnetised about their extremities, or if
they be small, and of weak intensity, then there may arise a Case in
which the action is so weak in every other part except the extre-
mities, that the result is not sensibly deranged until the pole n
actually arrives at CD, Fig. 8. There are some further conside-
rations as to the limit CD, not necessary here, which will hereaf-
ter be given.

18. Now, in the experiment under examination, the masses of
iron x and cb9 Fig. 5, during the time they are operated on by
induction, may be considered as two magnets whose intensities
increase at each approximation of the bar m. It is, therefore,
only necessary to determine the limit CD, Fig. 6, of their action,
when the induced magnetic force is the greatest ; and we imme-
diately ascertain if any disturbance arises from the influence of
the opposite polarities. This limit, in the present case, was
found not to exceed an inch and a half ; and it not being requi-
site to approximate the distant poles within that space, the re-
sult might so far be considered free from this source of error.

288 Mr Harris's Experimental Inquiries concerning

, 19. The experiment being, therefore, arranged, as before ex-
plained (15), it was observable, that, when the magnet m and
iron be were an inch apart, and the distance ab adjusted to two-
tenths of an inch, the index moved forward to S° ; on diminish-
ing the distance cd between the iron and magnet to half an inch,
and again adjusting the distance a b to two-tenths, the index
pointed to 6° ; on removing the intermediate iron, the index re-
turned to zero, thereby shewing that it was not acted on except
by the magnetic development induced in the iron be *.

In the following Table is given the results of this experiment
in relation to other decrements of the distance between the
iron and magnet, in which D signifies the distance cd between
the iron and magnet, and F the corresponding force induced in
the iron bc> the distance a b being always adjusted to two-tenths

of an inch.

TABLE I.

D

F

1.0

3.0

0.8

4.-

0.6

5.0

0.5

6.0

0.4

7.5

O.S

10.0

0.2

15-

It may be perceived by reference to the above Table, that the
magnetic development induced in the iron, increased in an in-
verse simple ratio of its distance from the magnet

* The distance cd between the iron and magnet is readily varied, either by ele-
vating the magnet m9 or depressing the iron be, the brass bands allowing them to
slide beneath with sufficient ease, but yet, at the same time, exerting a sufficient de-
gree of pressure to retain the iron and magnet in the required position.

the Laws of Magnetic Forces. 289

20. The truth of this result was in a great measure confirmed,
by ascertaining the absolute weight required to overcome the
attractive force induced in a mass of iron at different distances
from a magnet. The requisite apparatus for such an experi-

of wood cd> Fig. 10, sustained at a convenient height on two or
three columns ef, by means of a horizontal plane d, the columns
ef being screwed into a circular base *, of a convenient size.
The magnet AB, and iron a b9 to be submitted to experiment,
are secured in the required position by the moveable bands
of brass before described (11), the iron passing below through
the plane at d. There is a portion, a B, of the vertical support
c d, divided into inches and tenths of an inch, to mark the re-
lative distances by which the iron and magnet are separated.
A ring of soft steel r, about an inch and a half in diameter, ha-
ving a light brass pan S attached to it, is suspended from the
point r by the attractive force induced in the iron ab; a slender
rod of brass passes through this ring r, being supported at each
extremity in the columns ef, in order to prevent the ring from
falling an unnecessary distance when the force of the attraction
is overcome by weights placed in the pan at S *

21. A magnetic bar being selected, two feet in length, an inch
and a half wide, and half an inch thick, it was placed, by means
of this contrivance, at different distances from a mass of iron of
the same breadth and thickness, but not exceeding three inches
in length. When the magnet and iron were two inches apart, it
reauirecL as determined bv various trials, between 190 and 210

* The point r consists of a very short piece of soft iron, about two-tenths of an
inch in diameter. It is screwed firmly into the centre of the iron ab, so as to have
a perfect contact, and projects vertically for about the one-tenth of an inch from its.
lower extremity ; thus the steel ring r becomes always attached in the same place.

890 Mr Harris's Experimental Inquiries concerning

grains to separate the ring; when the distance was an inch and a
half, between 250 and 280 grains overcame the contact ; on di-
minishing the distance to an inch, between 390 and 400 grains
were required to separate the ring ; and on again diminishing
the distance to half an inch, it sustained a little less than 800
grains. The weights and corresponding distances may be there-
fore expressed as in the following Table, considering the weights
as a fair measure of the attractive force.

TABLE II.

D

F

4

S
2
1

200
265
400
800

The weights, therefore, are in an inverse simple ratio of the dis-
tances, or very nearly so *.

Although this mode of experimenting is not so delicate as the
former, it is still sufficient to shew that the force induced in the
iron was not, in any inverse ratio, greater than that of the simple
distance between the iron and magnet.

22. A similar result was obtained when, instead of placing the
magnet and iron in a vertical position, as in Fig. 5, they were
placed horizontally, as in Fig. 9, the suspended cylinder w being
immediately over the distant extremity a of the iron a b. In
this form of the experiment, we may consider the attractive
force as proceeding from that point (a) of the iron, immediately

* The weight of the steel ring and brass pan S, with the silk lines, was just 100
grains. It was consequently taken into the account at each trial ; and the weights
finally added before the contact was broken, did not exceed 10 grains at a time,
these being placed carefully in the pan.

the Laws of Magnetic Forces.

291

under the suspended cylinder x ; for it is not difficult to shew,
that, in consequence of the other forces being small, and other-
wise caused to act at very small angles, the resultant cannot
differ materially from that of the force a x, and thus we approxi-
mate very nearly to a simple result. Moreover, it could be at
all times ascertained experimentally if any other point fc Fig. 9,
exerted an influence on the index, by withdrawing the iron and
magnet until a arrived at 6, the induced force in the iron being
the greatest. In this instance, the index was not influenced
when the iron a b was withdrawn for a very short distance from
under the suspended cylinder w ; so that the force of the attrac-
tion might, without any considerable error, be supposed to ema-
nate from the point a, the magnet M being preserved at all times
without the attracting limit

28. The magnet and iron described (21) being placed hori-
zontally, with a small moveable scale my, to indicate the con-
stant distance a oc, as in Fig. 9 ; the same process was repeated
as before explained (19). The results are given in the next
Table, the distance aoc being constantly made equal to two-
tenths of an inch.

In this Table, D signifies the distance 6 c, and F the corre-
sponding forces in degrees, 5° being equal to one grain.

TABLE III.

D

F

1.0

5.5

0.8

7.0

0.6

9.0

0.5

11.0

0.4

14.0

0.3

18.0

The trifling differences observable in some of the numbers are

VOL,. XI. PART ii. o o

I

£92 Mr Harris's Experimental Inquiries concerning-

so very small, as to leave no doubt concerning the law we have
endeavoured to investigate. It will, however, be necessary to
remember, that, in these experiments, we have not examined the
absolute attractive force exerted between a mass of iron and a
magnet, at different distances, but merely the law of the influ-
ence of a magnet upon a mass of unmagnetized iron, so as to in-
duce in it a development of magnetic action.

24. This simple law of magnetic induction is observed to pro-
ceed uniformly from the distance at which the force first becomes
measurable, until the iron and magnet are very nearly approxima-
ted, but then begins to vary. Thus, in the preceding experiments
(19. 23), when the iron and magnet were approximated within
the tenth of an inch, the increments in the attractive force be-
gan to diminish. It would appear from this circumstance, either
that the similar and distant polarities begin in this case to exert
a sensible influence in disturbing the result, or that a limit ex-
ists, approaching saturation, beyond which the inductive effect
on the iron does not proceed with the same facility as before. In
either case, this limit may be supposed to vary with the power
of the magnet. This was made evident by employing magnets
of different degrees of intensity in succession. Thus, it was ob-
served, that, although the induced effects on a mass of iron
were at first respectively proportional to the powers of the mag-
nets, yet the increments in the attractive force acquired by
approximation began to diminish at a greater or less distance
from the magnet, according as the original magnetic force was of
greater or less intensity.

25. The attractive force of magnets by induction at their dis-
tant poles is, all other things remaining the same, inversely pro-
portional to the lengths of the iron, and, as just observed, at

the Laws of Magnetic Forces.

293

given distances, proportional to the powers of the inductive *
magnets ; but which will be further shewn.

In the following Table is given the results of some experi-
ments on masses of iron similar to those before employed (15,
21, 22), and whose lengths were equal multiples of each other ;
the masses of iron being each placed in succession at a constant
distance from the inductive magnets, as in Figs. 5. and 9.

The distance cd between the magnets and masses of iron was
made equal to three-tenths of an inch, and the distance at which
the induced force operated on the suspended iron #, as ab,
Fig. 5, made equal to two-tenths of an inch.

In this Table, L signifies the length of the iron, and F the cor-
responding force of attraction, each 5° being equal to one grain.

TABLE IV.

Position Vertical, Fig. 5.

Position Horizontal, Fig. 9.

L

F

L

F

1.0

20

8

18

1.5

H

2.0

10

6

9

3.0

7

26. A curious fact here presented itself in the course of these
experiments, namely, that, whether the masses of iron were acted
on through their lengths, Fig. 5, or through their breadths, as in
Fig. 11, still the induced force of the superior pole did not in
either case materially differ; and it became further evident,
that, although the magnetic bar m, Fig. 1 1, was occasionally ap-
proximated.within a distance of the suspended cylinder, at which
it could alone influence the index, yet the intervening mass ap-
propriated to itself the attractive power; and thus intercept-

* I employ this term to distinguish more particularly the magnets inducing the
temporary development of magnetic properties in the unmagnetised iron.

oo2

294 Mr Harris's Experimental Inquiries concerning

ed all the effect which the bar of itself could otherwise produce ;
so that the bar being, as it were, insulated by the intervening
iron, the final force of attraction might be considered to depend
exclusively on the iron.

27. Although the distant poles of magnets by induction
evince an attractive force inversely proportional to the length of
the iron ; yet the pole immediately opposed to the inductive
magnet would seem to possess the same force in all cases, with-
out any relation to the length of the iron ; since by substituting
a small magnet #, Fig. 1 , for the cylinder of soft iron, and placing
immediately under it in succession, at a constant distance, masses
of iron of different lengths, the force of attraction indicated on
the arc was observed to be in each case the same. The force,
therefore, induced in each mass of iron must have been alike,
since the total attractive force, as will be further shewn (37), is
observed to vary with the force induced in the iron ; the power
of the magnet remaining unchanged, and all other things re-
maining the same.

This result is quite consistent with the general effect observed
in opposing a long mass of iron to the pole of a magnet, in which
case the distant extremity of the iron does not appear, except
by very delicate tests, to be at all magnetic; whilst shorter
lengths, as already shewn (19, 20), exert a considerable attrac-
tive force #.

* It may be from this circumstance that some profound investigators of magne-
tic phenomena have found, that a hollow sphere of iron exerted as much effect on a
compass needle as a solid mass of the same dimensions ; which might be reasonably
supposed to be the case, as the iron could only become magnetic by induction, in which
case the force of the proximate poles would be always the same. The force which
such ball or shell, however, could exert on some third mass, not previously magne-
tic, would probably be found to be very different.

the Laws of Magnetic Forces. 295

28. As the iron bc9 Fig. 5, receives a magnetic developement
inversely proportional to its distance from the magnet m, we
may consequently, by varying this distance, alter the relative
magnetic intensity of be at pleasure ; and thus, by fixing a se-
cond mass of iron de, Fig. 12, immediately above be, at a con-
stant distance eb> this mass de can be caused to operate on the
suspended cylinder or, by a sort of second induction ; so that,
by preserving the distances nd and eb, and at the same time va-
rying the distance ca, we have all the conditions required for de-
termining the law of the inductive influence, when the force of
a magnet be, Fig. 12, is made to vary, but its distance from the
iron de preserved constant. The experiment being thus ar-
ranged, it was found, as might have been previously anticipated,
that the second mass of iron de received an attractive force di-
rectly proportionate to the magnetic intensity of the mass be be-
low.

The same result was obtained when, instead of varying the
magnetic force by induction, it was varied by means of magnets,
whose forces were to each other in a known ratio, applied suc-
cessively, at a constant distance cd, under the iron 6c, Fig. 5.

The following Table contains the results of these experiments,
in which F signifies the relative magnetic intensities ; /the cor-
responding force of induction ; the distance dn, Fig. 12, and a b,
Fig. 5, at which it operated on the suspended cylinder #, being
two-tenths of an inch ; as also the distance eb, Fig. 12. The
distance c d, Fig. 5, in which the induced force in b c was varied
by magnets, being made constantly equal to half an inch, each
fi° of attraction, being in both cases equal to one grain.

296 Mr Harris's Experimental Inquiries concerning

TABLE V

Force varied by Induction, Fig. 12.

Force varied by Magnets, Fig. 5.

F.

/•

F.

/•

1
2
3

3

6
9

1

•

5
10
15

29. From these experiments, therefore, we may conclude, that
the magnetic development in masses of iron by induction is di-
rectly proportionate to the power of the inductive force, and in-
versely proportional to the distance, all other things remaining
the same ; and that thfe attractive forces which magnets can de-
velope in masses of iron at a given distance, may be considered,
within certain limits (24), as a fair measure of their respective
intensities.

30. It will be here proper to examine the curious phenome-
non of the increased force which a magnet apparently gains at
one of its poles, by placing a mass of iron in contact with the
opposite one ; so that, in this case, it can sustain a much greater
weight, and hence its power is said to be increased. This
circumstance, recorded by almost every writer on magnetic at-
traction, may be readily explained on the generally received hy-
pothesis of magnetic developement, which supposes in every
magnet the existence of two opposite forces ; the magnetic cen-
tre being a point where these forces are in a state of neutraliza-
tion, whilst the intensity of the separate forces varies in some
direct ratio of the distance as they recede from each other. The
intensity of the magnetism thus set free, will, therefore, be the
greatest somewhere near the extremities of the bar ; so that, if
a portion of the magnetism at one extremity becomes neutra-
lized, the effect is more or less sensible at the other ; and thus a

the Laws of Magnetic Forces. 297

further magnetic developement is induced by neutralizing a por-
tion of the opposing force.

The force thus neutralized will, from what has been stated
(29), depend on the inductive force of the magnet, and its dis-
tance from the iron ; so that the increased attractive power of
the magnet at its opposite pole, is still a measure of the induc-
tive effect.

31. The fact itself (80) is very well illustrated by placing a
short magnetised piece of steel b c, Fig. 5, to act on the suspend-
ed cylinder x at a constant distance ; and, after observing the at-
tractive force ; by subsequently opposing a mass of soft iron m very
near the inferior pole, in which case the index will be found to
advance. The effect is more decided when the iron m is brought
into contact. The law of this action is, as in the former case,
directly proportionate to the power of the magnet, and inverse-
ly proportional to the distance. Thus, a small magnetised piece
of hardened steel b e, Fig. 5, three inches long, eight-tenths of an
inch wideband three-tenths of an inch thick, being caused to act on
the suspended cylinder x at four-tenths of an inch distance, the
indicated attraction amounted to 1 2°. On approximating a si-
milar mass of iron m, within two-tenths of an inch of its inferior
pole, the index moved forward 1° ; on diminishing the distance
to the one-tenth of an inch, the index moved forward another
degree-

32. The effect thus produced by approximating a mass of iron
toward the opposite pole of a magnet, has not any relation to
the dimensions of the iron, all other things remaining the same ;
thus furnishing an additional confirmation of the curious fact
before mentioned (27), — that the proximate poles of magnets by
induction are of equal intensity.

298 Mr Harris's Experimental Inquiries concerning

33. In the experiment just described (31), the increments of
the attractive force of the magnet were necessarily very small,
since they depended exclusively on the iron, which had no per-
manent magnetism, and which operated at the distant pole. In
order, therefore, to allow of an increased action, and at the same
time observe the immediate operation of the iron on the pole to
which it was opposed, the experiment was transformed as follows.
A magnetic bar m, Fig. 1 3. (PL XII.), being placed in a horizontal
position, with one of its extremities immediately under the sus-
pended cylinder #, and the number of degrees of attraction being
noted at a constant distance, a mass of iron n was approximated
toward the same extremity. In this case such portions of the
free magnetism of this extremity would become neutralized as
were proportional to the magnet's inductive effect, and this
would be evinced by the number of degrees which the index
declined. Thus we might come to determine experimentally all
the particular cases hitherto considered, a method of experi-
menting which, although not entirely free from objection, is still
useful, and sufficiently accurate to confirm the preceding results.

34. The experiment being arranged as in Fig. 13, the effect of
the iron was, as in the former cases, directly proportional to the
power of the magnet m, and inversely proportional to the dis-
tance a b. In the following tables are given the results actually
obtained. The magnetic bars and iron employed being similar
to those before described (15). In these tables, D signifies the
distance a b between the iron and magnet, F the intensities of
the magnets, and /the force as expressed by the number of de-
grees which the index declined. The distance between the sus-
pended cylinder oo and the magnet m being, in Table VI., six-
tenths of an inch, and in Table VII. eight-tenths of an inch ;
the constant distance a b, at which the variable magnetic forces
were applied in Table VII. being two-tenths of an inch.

PLATE XII.

the Laws qf Magnetic Forces.

299

TABLE VI.

TABLE VII.

Magnetic Force constant

Magnetic Force variable.

D.

/

F.

/•

0.6

8.

i

2

0.4

4.5

2

4

0.8

6.

8

6

0.2

9.

4

8

35. In these, as in the former experiments (32. 87), the ef-
fect produced on the index was quite independent of the dimen-
sions of the iron, and was observed to be nearly the same,
whether opposed to the magnet m through its length, as in Fig.
13, or through its breadth, as in Fig. 14, the proximate induced
polarity of the iron appearing to be in each case alike. Similar
results were also obtained to those before noticed (24), in em-
ploying magnets of powerful intensities ; it being observable,
that, at very near approximations, the effect on the index was
not precisely proportional to the powers of the magnets.

36. The general results of the foregoing experiments (34)
became further shewn, when the magnetic forces employed were
those induced in a mass of iron, as in Fig. 15. Thus, a mass of
soft iron d a, not exceeding three inches in length, being placed
with one of its extremities immediately under the suspended
cylinder oc, a magnetic bar bm was opposed to its opposite extre-
mity a, so as to induce in the iron a magnetic developement ;
the number of degrees of attraction, and the distance of the cy-
linder <r, being noted, a second and similar mass of iron en was
then opposed to the induced pole ; and thus, by making the dis-
tance a b always the same, and varying the distance c d, the mag-
netic developement in d a remained the same, whilst the dis-
tance of the opposed iron n c became variable ; and by making
distance c d always the same, and varying a b, we are enabled to

VOL. XI. PART II.

p p

300 Mr Harris's Experimental Inquiries concerning

vary the magnetic developement in da (19), whilst its distance
from the opposed iron n c is constant.

The actual results are given in Tables VIII. and IX., the
distance of x being made constantly equal to three- tenths of an
inch. In Table V1IL, D signifies the variable distance c d, and
/ the corresponding force, as expressed by the number of de-
grees which the index declined, the constant distance a b be-
ing two-tenths of an inch. In Table IX., F signifies the va-
riable magnetic intensities produced by approximating the mag-
netic bar b m, through the respective distances 0.6, 0.3, 0.2, 0.15
of an inch, in order to obtain the relative forces 1, 2, 3, 4, (9) ;
/is the force of induction as before ; the constant distance cd
being in this case also two-tenths of an inch.

TABLE VIII.

TABLE IX.

ftfagnetic. Force pjr Induction constant.
Distance variable.

Magnetic Force of Induction variable.
Distance comrtant.

D.

/•

D.

/•

0.6
0.4
0.S
0.3

3.

4.5 N
6.
9.

1
2
3
4

3
6

9
IS

37. Having considered some of the principal phenomena of
induced magnetism, we may now investigate more particularly
the force made up of the reciprocal attraction between a magnet
and a mass of iron, when placed at different distances from each
other. It may be observed (19), that this combined force exert-
ed between a mass of iron 6 c, Fig. 5, in a temporary magnetic
state, and the suspended body w9 which must be considered also
in a temporary magnetic state, is, at a given distance, directly
proportional to the intensity of the inductive magnet m, and in
an inverse proportion to the distance cd, the magnet m remain-
ing unchanged. From which we may conclude, considering

the Laws of Magnetic Farces. 801

the iron be as a magnet, that the distance ab between a mag-
net and a mass of iron being constant, the absolute attractive
force will be directly proportional to the power of the mag-
net be, and consequently to the force induced in the irdn w.
Thus, if two magnets, whose separate forces of induction on a
mass of soft iron, at a constant distance, have been previously
well determined, be opposed to the suspended iron *, as in Fig. 1,
then the respective attractive forces, at a constant distance, as
shewn by the index, will be observed to vary in the same ratio
as before ; and if both the magnets be now conjoined and op-
posed to the suspended iron oc, at the same distance, then the
indicated attractive force will be the sum of the two former
forces, or very near it.

38. That the absolute force of attraction exerted between a

• »

magnet and a mass of iron should vary with the power of the
magnet, and consequently with the force induced in the iron,
all other things remaining ' the same, is what might have been
previously supposed ; but the ratio in which this same force of
attraction might be expected to vary, when the force induced
in the iron x, Fig. 1, is a constant quantity, whilst its distance
from a magnet H is variable, the magnetism of H being either
temporary or permanent, is not so apparent ; nor has such a case,
as far as I am aware, been yet contemplated ; beside, that the
possibility of obtaining satisfactorily all the conditions of such an
experiment would appear at first somewhat doubtful. The re-
sults, however, before given (19)) enable us to investigate expe-
rimentally such a case. Thus, by varying the distance erf, Fig. 5,
between a magnet and a mass of iron, we can, as before ob-
served (24), within certain limits, obtain any relative magnetic
intensity required ; and by varying the distance ab between the
temporary magnetic pole of the iron be, and the iron #, we can
preserve the force induced in oc constant. Thus, if we dimi-

p p 2

802 Mr Harris's Experimental Inquiries concerning

nish cd one-half, we double the force in be ; and if the dis-
tance a b was preserved, the force in x would become likewise
doubled (29) ; but if, whilst we diminish cd one-half, we double
ab9 then (19) the force in x will remain as before. We may
thus preserve the induced force in the iron x a constant quan-
tity, whilst its distance from the inductive magnet Ac is a va-
riable one ; and hence arrive at the reciprocal force of attrac-
tion under these conditions. The experiment being thus ar-
ranged, it was clearly shewn, that the absolute force varied with
the distance, the induced force in the iron being a constant quan-
tity. Thus, by diminishing cd one-half, so as to double the
magnetic intensity of be, and at the same time doubling the dis-
tance a b9 the number of degrees marked by the index were as
two to one. By decreasing cd to one-third, and trebling a 6,
the observed forces were as three to one ; and so on.

This curious fact was not only apparent when the magnetic
force was varied by induction, but was also satisfactorily shewn,
when varied by magnets whose relative powers of induction were
previously ascertained.

Thus, two magnetic bars being selected, whose inductive
powers were as two to one, they were placed in succession im-
mediately under the suspended iron x, as in Fig. 1, but in such
way that their respective distances from x should, as in Fig. 16,
be inversely proportional to their powers of induction, the stronger
magnet 2m being placed at double the distance ; hence the want
of power in the weaker bar m was compensated by its diminished
distance a b (19) ; so that the force induced in x was in each ar-
rangement the same ; the forces, however, marked by the index
were inversely proportional to the distances a b and cd*.

* Although this result, as disconnected with the previous investigations concern-
ing induced magnetism, it may be readily imagined, must happen, admitting the

the Laws of Magnetic Forces. 808

»

39. We may conclude from these investigations (37, 38), that
the actual force exerted between a magnet and a mass of iron
is directly proportional to the force induced in the iron, and in-
versely proportional to the distance, all other things being the
same ; and this leads us more immediately to consider the abso-
lute attractive force of a magnet and a mass of iron, the dis-
tances between the iron and magnet, and the force induced in
the iron, being both variable.

This case of magnetic attraction, which applies immediately to
the general law, as determined by the celebrated Coulombe, and
likewise by many other profound inquirers, is readily investigated,
by placing a magnet to act directly on the suspended cylinder of
soft iron #, as in Fig, 1 ., at different distances, by which means
we vary the induced force in the iron oc, and the distance simul-
taneously. Thus, if we decrease the distance, Fig. 1, one-half,
we double the force induced in oc (19), whilst we diminish the
distance in the ratio of 2 : 1 . If we decrease the distance to one-
third, we treble the force in the iron #, and at the same time dimi-
nish the distance in the ratio of S : 1, and so on : the absolute or
total attractive forces will consequently, from what has been al-
ready stated (37, 38.), be respectively in the ratio of 4 : 1 and
9:1; and hence we obtain a final force, which is observed to
vary in the inverse ratio of the squares of the distances between
the attracting bodies. Thus, when a long cylindrical magnet in
Fig. 1 . not greatly exceeding the suspended iron oc in diameter,
was placed immediately under it, the distance being an inch, the
force indicated amounted to 5°. On diminishing the distance
to half an inch, the index moved forward to 20°.

general law of magnetic attraction about to be demonstrated, namely, that of the
inverse square of the distance ; yet, on examination, and as will be further shewn, it
will be found to depend exclusively on the operation of induction, and that where
this operation does not proceed, the law abovq named no longer obtains.

304 Mr Harris's Experimental Inquiries concerning

The following are the results of two series of experiments, in
which the distances and forces were compared by decrements of
the tenth of an inch, and it will be perceived, that the trifling
irregularities occasionally observed in some of the numbers, are
not of such importance as to leave any doubt concerning the law
we have been endeavouring to determine, and are, besides, in
many instances not appreciable by the instrument. In these ex-
periments, two magnets were employed, designated by A and B,
and were such as to ensure, as far as possible, accurate results,
the conditions before explained (17) being fully considered: D
signifies the distance between the iron and magnet, and f the
corresponding force of attraction ; the distances being adjusted
by the apparatus before described (10).

TABLE X.

Showing the Attractive Force of a Magnet and Iron
on each other at various distances.

A, north pole.

*

c

I

II

a

*

2

B, south pole.

D.

/• '

D.

/•

1.0

0.9
0.8
0.7
0.6
0.5

4.5
5.5
7.0
9-5
1S.0
18.0

1.0

0.9

0.8

0.7
0.6
0.5

6.0

7.5

9.5

13.0

17.0

24.0

40. The law observable in the preceding experiments may be
generally observed by approximating the pole of any magnet to-
ward the suspended iron #, whether a small cylinder of precisely
the same dimensions, or otherwise a powerful magnet of any form
and length. The variation in the angles at which the attractive
force of the latter may be supposed to act on the suspended iron,
where the opposed surface is more extensive, not having for a
short distance any material influence in disturbing the uniformity

the Laws of Magnetic Forces.

305

of the result. The sapie law may be likewise made evident, in
substituting for the suspended iron oe a email magnet, and approxi-
mating toward it a ipass of soft iron, as in the following Table,
which are the actual results obtained from an experiment *o ar-
ranged.

TABLE XI.

Showing the Attractive Force9 by opposing
a Maes of Iron to a Magnet

D.

/

0.6
0.4
0.8
0.2

1.6
3.6
6.0
18. + •

41. It has been observed (24) that the ratio of the inductive
effect of a magnet on a mass of iron begins to vary when the iron
and magnet are very nearly approximated. The precise point
depending on the magnetic intensity ; we may therefore suppose
that a small mass of iron opposed to the pole of a very powerful
magnet, would become magnetised, nearly to saturation, even be-
fore the magnet and iron were brought into contact, so that, for
a short distance, the increments of the force induced in the iron
would be so very small, that, in such case, it might be considered
as constant ; and hence the reciprocal attractive force would, for
near approximations, no longer vary in the duplicate inverse ra-
tio of the distances, but in an inverse ratio very near that of the
distance only, — the induced force in the iron being considered
constant {38) ; and such is found to be the case, as will be fur-
ther shown (47.)-

42. We have more immediately considered, in the preceding
inquiries, the attractive force exerted between a magnet and a
mass of magnetized iron, in which case a permanent magnetic de-

306 Mr Harris's Experimental Inquiries concerning

velopement is supposed to exist only in one substance : we have
now to consider very similar phenomena evinced in the action
of one magnet on another, in which case there is a permanent
magnetic developement in both substances, — a case of magnetic
action somewhat more complicated than the former, but which
is still susceptible of a similar experimental examination, the in-
ductive action being observed to proceed, whether the bodies be
permanently magnetic or not, or whether opposed, at their similar
or dissimilar poles *. We have consequently to investigate the
operation of this inductive influence when the bodies under exa-
mination have a permanent magnetic developement of greater
or less extent.

43. In order to examine the inductive action of one magnet
on another, a magnetised piece of steel be, Fig. 5. was placed un-
der the suspended iron «r, and the attractive force at a given dis-
tance duly noted. A magnetic bar m was then placed under it ;
first the similar poles, and secondly the dissimilar poles, being
opposed, having previously ascertained the force of the magne-
tized steel be at each pole, and made them equal, and having al-
so equalized the poles of the magnet m, and ascertained their
force. The results obtained from a series of experiments thus
arranged, appeared to show in a satisfactory way that the forces
acquired or lost by the magnet be, at its superior pole, in conse-
quence of the inductive action, were, within certain limits, in the
inverse ratio of the distance between the two magnets ; after
which the increments or decrements began to diminish. In the
following Table, are seen the results of a series of experiments

* Although by opposing two magnets at their dissimilar poles, we in great mea-
sure destroy their permanent magnetism, yet the inductive influence by which this is
effected must still be considered as a new force induced in the magnets, since it has
been capable of producing a certain effect.

the Laws of Magnetic Forces.

307

with different magnets, marked 1, 2, 3, 4. D signifies the dis-
tance cdy Fig.* 5. ; and / the corresponding force of induction, as
measured by the increments in the attraction in the case of the
opposite poles being opposed, and by the decrements when the
similar poles were opposed.

TABLE XII.

D.

Dm sikilak Poles.

*

Similak Poles.

1.

8.

3.

4.

1.

8.

3.

4.

/•

/

/•

/

/•

/

/.

/•

2.0

1.0

8 —

2

4

1.0

2 —

8

4

1.5

1.5

2.5

8.5+

5.5

1.5

2.5

8£ +

5.5

1.0

2.0

3.5

4

7

8

3.5

4

7.5

0.5

3.5

6.0

7

10

3.5

4.5

5

11 —

0.3

4

7

10

4

5

6

0.2

5

9.5

11.5

* +

6 +

7

0.1

8

11

14.5

...

4.5

5.5

7.5

The limits within which the inductive action varied accord-
ing to a uniform law, would, from these experiments, appear to
depend on the magnetic intensities, *and on the circumstances
before observed (24.) ; so that the precise distance at which it
becomes irregular in its action, is not the same for each magnet ;
and it may be further observed, that, when the inductive action
operates in a contrary sense to the poles of the magnets, the de-
crements vary at last more rapidly than the increments, sup-
posing in the latter case the induction to operate in the same
sense. These are points of great consequence in all experimen-
tal researches concerning the reciprocal attractive or repulsive
force, as exerted between two magnets.

44. Similar variations from a regular law are observable, when
the force of a magnet is made to vary, the distance between the
two magnets remaining the same. Thus a magnet of a double
force, opposed to the inferior pole of another magnet, ckcum-

VOL. XI. PART II.

Qq

808 Mr Harris's Experimental Inquiries concerning

stanced as before explained (42), does not, at all distances, exert
an inductive influence proportionate to its power on unmagne-
tised iron.

In the following Table are given the results of two series of
experiments with magnets, whose inductive powers on unmagne-
tised iron were as 2 : 1 ; and it will be seen that this ratio is not
the same at all distances from the magnetised steel. The mag-
nets are denoted by A and 2 A, placed over the respective forces
of induction ; D being the corresponding distance.

TABLE XIII.

D.

A.

2 A.

2.0

2

4

1.5

2.5

5

1.0

4

7.5

0.5

6

11

These experiments shew that a variety of cases may exist in
which the intensities of the magnets become so circumstanced,
in relation to each other, that the inductive action no longer
proceeds.

45. The absolute attractive or repulsive force exerted be-
tween two magnets at various distances, will materially depend
on the operation of the inductive influence, the induced forces and
the distances being both variable ; for we have already seen (89.),
that the absolute force exerted between a magnet and a mass of
iron, varies with these quantities conjointly. The same may
therefore be inferred of the absolute force exerted between two
magnets ; for a very little reflection will serve to show, that, in
estimating the absolute force exerted between them, it is still
the same compound action which we measure (39). Thus, as
already observed, when only one of the bodies B, Fig. 6. is per-
manently magnetic, the absolute force is directly proportional to

the Laws of Magnetic Forces. 809

the force induced in A, and inversely proportional to the distance
Ns (87, 38.) ; and this must be still true, though A be supposed
also a magnet, seeing that the inductive action still proceeds
(43.) ; and thus the absolute force of B upon A will vary as be-
fore (39.) ; but A being now supposed also permanently magne-
tic, it exerts a similar force on B, and which will consequently
vary in the same way. Therefore^ the whole attractive force be-
tween A and B will still be found to vary in an inverse ratio of
the square of the distance, supposing the inductive action to go
on uniformly. And this will be true, whatever be the relative
magnetic intensities, the only difference between this action and
that exerted between a magnet and a mass of iron, arising from
the circumstance, that, in the latter, there is only one primary
inductive action in the operation, whilst in the other there are
two.

46. In order to investigate the absolute force of attraction
or repulsion, as exerted between two magnetised bodies, the dis-
tances and induced forces being both variable, it is only neces-
sary to substitute a small magnet for the cylinder of soft iron a?,
Fig. 1., and observe the attractive or repulsive forces by approxi-
mating toward it either the similar or dissimilar poles of another
magnet, in the way before described (39.)

We have already considered (17.) some of the circumstances
likely to interfere with the accuracy of an experiment thus ar-
ranged, and we have shewn that a limit may be determined,
without which the action of the other poles may be supposed of
no assignable value. It remains, however, still to be considered,
what subsequent change is likely to be produced in this limit
cdj Fig. 6, 7, 8., by the inductive action of the similar or dissimi-
lar polarities on each other. Now, it was shown (33.), that the
inductive influence of dissimilar polarities lessens their free ac-
tion : the approximation of the polarity N towards s will there-

Qq2

310 Mr Harris's Experimental Inquiries concerning-

fore, supposing them of an opposite kind, tend to neutralize each
other's force, and thus extend the limit CD. It is therefore ex-
tremely probable, that, in some cases, the opposed polarities N and
s may so neutralize each other's action in regard to the other po-
larities n, S, that the force may be considered as ultimately reduced
to that of two insulated points. A similar result may be supposed
to follow, when the polarities are of the same kind ; for although
the approximation of similar polarities would seem to reduce the
limit CD, yet the inductive influence (43.) tends to reverse the
repelling poles ; and thus the forces of the distant polarities be-
come also neutralized. The limit CD may be therefore extend-
ed in both cases, and in many instances may vanish altogether.

In the following Table . are the results of a series of experi-
ments with the attracting and repelling poles. The magnets
employed are indicated by the letters a, b, c, d> i, their dimensions
being as follows :

a, A small cylindrical magnet two inches long, 0.2 of an inch

in diameter, and similar in every respect to the sus-
pended magnet x.

b, Four and a half inches long, and four-tenths of an inch

square.

e, Seven inches in length, and seven-tenths of an inch dia-
meter.

dy Nine inches long, eight-tenths of an inch wide, and three-
tenths thick.

€, Fourteen inches long, one inch wide, and half an inch
thick.
, signifies the distance ; whilst the letters a, b,c,d,e are
placed over the respective forces.

the Laws of Magnetic Forces.

311

TABLE XIV.

>x

DlSUMILAK POLM.

Similar Poles.

a.

C.

<L

€n

a.

b.

<%

<L

«.

4

1 • • • • •

• • •

8 +

• • i

• • • •

• • •

8 +

8.5

l • • • • •

• • •

4 +

■i

»•

■ • • •

• • •

4 +

9$

> • • • • •

• • •

6 —

M

•

> • • •

• • •

6 —

2.5

1 • * • • •

• • •

8.5

4)

• •

• • • •

• • •

8 +

2

2.5

3

13

o

• •

2

2.5

13

1.8

... 8 +

3.5+

16.5

1

r^4

• •!

&5

8 +

15 +

1.6

4

4.5+

21

0>

• •

3

4 +

18.5

1.5

4.5

5.5

23

o
.2

• • <

4

5

20

1.4

5.5—

6 +

28

g

• •

4.5

5.5

23 •

1.2

7

8.5

88

is

• •

5.5

7

28

1.0

1.5

5

I 10

12

49

O

1.5

2

7

9

83

0.8

« +

i

I + 15

21

o

2

3

10

11

42

0.6

4

(

}_ 25 +

82

3 +

5

14

14

56

0.5

6

i

i 33

40

4

6.

5 15.5

14 +

60

0.4

9

11

..5

• • •

6

9

17

18 *

58 ♦

0.3

15

It

i

• • •

8

11

11 •

47. These experimental results are quite consistent with the
operations of the inductive influence before explained (48.) We
immediately perceive, by referring to the attractive forces, that
the law of the inverse square of the distance is manifest through
all the approximations, except a few of the last, the occasional ir-
regularities observed being very inconsiderable ; so that when the
magnets are very nearly approximated in relation to their respec-
tive intensities (44.), the increments in the forces begin to de-
cline,— a circumstance of considerable importance in our endea-
vours to investigate the laws of magnetic attraction ; for it may
be supposed that the inductive influence which thus begins to
vary, may at last so far vanish, even before contact, that the ab-
solute force, at near approximations, may, in some instances, as
already stated (41.), be in an inverse simple ratio of the distance,
and which was observed to happen with the bars marked d and e~

* At these distances the repulsive force was superseded by attraction.

SI 2 Mr Harris's Experimental Inquiries concerning

a

For although the cylindrical counterpoise employed in these ex-
periments did not admit of the forces being examined at nearer
approximations than those marked in the table ; yet, by substi-
tuting one of large dimensions, the forces may be carried on
nearly up to the point of contact, so as to be estimated in terms
of the preceding progression, since the degrees of attraction may
be always compared and valued in grains of absolute weight (13.)
In the following Table are the results of the experiments so
continued with the magnets d and e ; the counterpoise employed
being one inch in diameter, 1° of attraction corresponding to 10°
of the former, and being equal to two grains of absolute weight.

TABLE XV.

Dissimilar Poles.

D.

<L

e.

0.4
0,8
0.2

6

8.5
18

18
24
W

It may be perceived in this table, that the corresponding forces,
at near approximations, do not materially vary from a simple in-
verse ratio of the distance.

48. This deviation from the law of the inverse square of the
distance, observed in all the near approximations of the magnets in
Tab. 1 4. may happen, as before observed (24.), either in consequence
of the distant polarities having passed a certain limit, or otherwise
from the inductive action not going on with the same freedom
at some point approaching saturation. The latter would seem to
be extremely probable, for it has already been shown (33.), that
when two dissimilar polarities are opposed to each other, their
free action becomes more or less neutralized. In examining,
therefore, the inductive action upon a mass of iron be, Fig. 5.
(19.), the polarity d would have its free action so much reduced,

the Laws of Magnetic Forces. 318

that the polarity b may be considered as always without the limit
of its influence. If we add, at the same time, the neutralizing
effect of x upon b, then the action of b upon d may vanish alto-
gether. With respect to the distant polarity of m, that may,
when m is a very long bar, be always considered without the li-
mit of the action. In this case, therefore, the decrements of the
inductive force in be, as already stated, would seem to be altoge-
ther independent of any disturbance arising from the action of the
similar poles, although, in examining the reciprocal force exerted
between a mass of iron and a magnet, or between two magnets,
both these causes of disturbance may probably be in operation
within certain limits ; and they sufficiently explain the anomalous
results arrived at by different philosophers in their attempts to in-
vestigate the law of the absolute force exerted between two mag-
nets, or between a magnet and a mass of iron, when placed at diffe-
rent distances from each other : some asserting that it decreased
in the inverse ratio of the squares, and others in that of the
simple distance ; whilst many concluded, that it followed no re-
gular law whatever, but was different for different magnets.

49. The results of the experiments with the repelling poles,
are equally interesting with those of the attracting, as furnishing
useful illustrations of the causes which operate in deranging the
uniformity of the result. The deviations, as may be anticipated
from what has already been shewn (43.), are more considerable
than in the former case. It will be perceived, that a few of the
first approximations in each case differ very little from the law
of the inverse square of the distance ; but they soon become very
irregular, and afterwards approximate to the inverse ratio of the
distance, until, in some instances, the pole of the weaker magnet
is apparently changed by the inductive influence, and the repul-
sive force is superseded by attraction. The most prominent
feature, therefore, in these experiments with the repelling poles,

814 Mr Harris's Experimental Inquiries concerning

is the circumstance of the force becoming less and less, until the
polarity of the weaker magnet appears to be so counteracted by
induction, that the repulsion is at length superseded by attrac-
tion *. Hence, the repulsive power of one magnet, as measured
by its force on the similar pole of another, will never be equal
to the attractive power, as measured by its force on the same
pole, except the magnets happen to be of very powerful intensi-
ties, or opposed to each other nearly at the limit of their action,
when the tendency of the inductive influence begins to be felt,
without the polarity of the magnets having undergone a sensible
change.

50. The curious phenomena of magnetic repulsion, which fol-
low when two similar polarities are opposed to each other,
would hence seem to arise from the tendency of the inductive
influence to cause a new polar arrangement, which action the
established polarities resist ; so that the repulsion will be more
or less evident, as the magnets are of greater or less intensity,
or are separated by a greater or less distance. Thus, when one
of the poles of a weak magnet is opposed to the same pole of a
magnet having a great intensity, the pole of the weak magnet,
if the distance between them be small, is instantly reversed, and
the impulsion is not apparent, but a weak attractive effect is ob-

* Although the polarity of the small magnet in these experiments seemed to be
reversed, inasmuch as the repulsion was superseded by attraction even before con-
tact, yet the new polarity by induction did not appear to be permanent, since the re-
pulsion again obtained when the distance was increased. Thus, both the phenomena
of attraction and repulsion ensued, merely by varying the distance in a small degree
between the magnets. The forces indicated at near approximations with the repell-
ing poles, are only given in illustration of the curious fact, that the pole of the weaker
magnet becomes reversed before contact. We cannot consider them as quite accu-
rate for any purpose of calculation, as the suspended magnet, in consequence of the
great repulsive force, is thrown out of its perpendicular direction.

the Laws of Magnetic Forces. 315

served to take place. If the distance be increased, the repulsion
is evident ; for the strong magnet operating at a greater distance,
the inductive effect is diminished (19) ; so that it now proceeds
with less energy, and only to a certain extent. If the magnets
be supposed equal, then the repulsive effect will be evident at
all distances, and the tendency to a new polar arrangement will
never pass the limits of equal distribution in each bar, supposing
the opposed poles actually in contact.

The inductive action, therefore, according as it proceeds in
the same or in an opposite sense to the polar arrangement al-
ready existing in two magnets, will either tend to increase or
diminish their force ; an effect so well understood practically,
that, to preserve the power of the magnets perfect, they are
usually arranged with their dissimilar poles in contact.

5 1 . Our observations have been hitherto exclusively directed
to the action of a magnet on soft iron, or to that of one magnet
on another ; but it may not be improper, before concluding
them, to consider the law of the magnetic distribution in an ar-
tificial magnet of a regular figure ; since, in assimilating these
phenomena with terrestrial magnetism, it is of great consequence
to determine the law according to which the forces are developed
in different points of the longitudinal magnetic axis between
the centre and poles.

For this purpose, two bars were selected, regularly hardened
throughout, and magnetized, the poles of each separate bar be-
ing equal, and the magnetic centre or point of indifference
equally distant from either pole. The centres and poles were
carefully ascertained by means of filings of soft iron, which were
sifted immediately over them on a sheet of paper strained tight
on a hollow frame of wood. The line which divided the mag-
netic curves was observed and noted, and equal successive por-
tions were marked off on each side of it toward the poles.

VOL. XI. PART ii. b r

316 Mr Harris's Experimental Inquiries concerning

The cylinder of soft iron a?, Fig. 17, being suspended as in
the ibrifaer experiments, and the bars placed immediately under
it in succession, the intensity of different points between the
centre and poles were carefully ascertained, by moving along the
magnet under examination, so aa to bring these points succes-
sively under the suspended iron ; and the constant distance as-
certained and preserved by means of the moveable, scale and the
adjusting screws, as in the former experiment (23).

In this experiment, it is essential to reduce the action to the
point a immediately under the suspended iron, a condition which,
in a purely theoretical sense, is not possible to be fulfilled ; in-
asmuch as the attractive force will be involved in the combined
action of all the other points of the bar. We may, however, un-
der the circumstances already considered (22), approximate so
nearly to it, that the resultant will not differ very materially
from that of the force at a ; so that, for a long series of points,
we may obtain a uniform law, as appears evident by the fol-
lowing Table, in which D signifies the distance from the centre
in half inches, and F the corresponding forces of attraction ; the
constant distance of the suspended iron x being placed imme-
diately after the letters AB, which denote the respective bars.

TABLE XVI.

A3.

B2.

D.

F.

O.

F.

1
2
8
4
5
6

1

4

9
16
25
36

1
2
3

4

0.5
2.0

4 +
8.0

From these results, it would appear, that the law of the dis-
tribution varies directly as the square of the distance from the

the Laws of Magnetic Farces. 817

magnetic centre ; and this law can always be made apparent in
a bar of steel regularly hardened and magnetized throughout
The results, however, are by no means certain in bars whose tem-
perament and texture is irregular, or which are only hardened
at the extremities : in the one case the magnetism is irregularly
retained, in the other it is only sensible at the poles of the bar.

52. In order to avoid the interference of the angular forces to
a still greater extent, so as to have the action reduced as far as
possible to that of an isolated point, the attractive force was
made to operate through a small cylindrical piece of iron, about
two inches long, a b, Fig. 18. Thus, the suspended iron x was
preserved always without the influence of the bar. In this case,
we may suppose, from what has been before shewn respecting
magnets by induction, that, in consequence of the other points
of the bar acting at angular distances upon the cylindrical mass
of iron a b> the induced force arising from these points would, in
certain cases, not exert a sensible influence on its distant extre-
mity ; and thus the attractive force by induction would approxi-
mate very closely to that resulting from the point b of the mag-
net in contact with the iron, which would thus, compared with
the other points acting at a distance, and under different
angles, be very great, whilst a fair measure would still be ob-
tained of the magnetic intensity ; for we have already seep
(29), that the masses of iron under the influence of a magnet
generally exhibit, at their distant extremities, an attractive force
directly proportionate to the magnetic intensities, all other
things remaining the same. Now, the successive points of a
magnetic bar between the centre and poles, may be considered
as so many distinct magnets, varying in intensity : the inductive
effect on the iron in contact with them is, therefore, a fair mea-
sure of their force. In the following Table are given the results
of a series of experiments thus arranged : the magnetic bar be-

Br 2

318 Mr Harris's Experimental Inquiries concerning

ing regularly hardened and magnetized, and the centre poles as-
certained as before ; it was 17 inches long, 1 inch wide, and 0.2
of an inch thick ; the constant distance aoc at which the attrac-
tive force acted on the suspended cylinder oc, was 0.2 of an inch,
and the distances are expressed in inches.

TABLE XVII.*

D.

F.

1

0.5

2

2.

3

4.5

4

8.

5

18 +

6

18.

7

25.—

8

32.

53. As all the known operations of nature are generally of the
most simple kind, it is not unreasonable to suppose, that where-
ever we find a compound law, that law may be resolved finally
into two or more elementary ones. Thus, we have found, that
the absolute force of attraction exerted between a magnet and a
mass of iron, or between one magnet and another, and which
has been found to increase in an inverse ratio of the square of
the distance, is resolvable into two simple elementary actions
(37, 38), one depending on the induced force in the iron, the
other on its distance from the magnet. We may, therefore, sup-

* In a series of experiments of this description, where the forces are at first very
inconsiderable, but afterwards increase rapidly, it becomes necessary to vary the di-
mensions of the cylindrical counterpoise W, Fig. 1, by which means we are enabled
to examine the force in any point of the bar at a small distance ; whilst the degrees
being previously estimated in grains of absolute weight, the whole can be expressed
as if the same counterpoise had been employed throughout the experiment, as before
explained (47), a certain number of degrees with one counterpoise corresponding
to a given number with the other.

the Laws of Magnetic Forces, 819

pose, that the magnetic distribution in an artificial magnet, the
intensity of which increases in a direct ratio of the square of the
distance from the centre, is still to be resolved into two simple
actions, which may possibly be discovered by a little reflection
on the manner of producing magnetic disturbance in bars of
steel, and the laws according to which the opposite magnetic
forces operate on each other.

54. Without stopping to inquire into the nature of the cause
of magnetic phenomena, we shall only assume what is, in fact, evi-
dent by the most simple experiments, that in every magnet there
are two opposite forces developed, whether we suppose them to
be merely different states of the same principle, or whether we
imagine them to be separate and distinct agents. These forces
are observed to neutralize each other when united, and to exert
more or less of free action as they become separated.

Some considerations concerning this free action have been al-
ready entered upon (30) ; but it will be requisite here to deter-
mine the free action developed, by separating the two opposite
magnetic forces ; the original magnetic intensities and the dis-
tances being both variable. For this purpose, two masses of
iron be, da', Fig. 19, 2 inches in length, 0.75 of an inch wide, and
0.3 of an inch thick, were placed under the influence of the dis-
similar poles of two magnetic bars N, N', so as to induce in them
the same magnetic intensities, as measured by the attractive
force on the suspended iron x, in the way before explained (36),
by bringing the opposite polarities c and d of the induced mag-
nets in contact, their free action would be reduced to zero ;
whilst, by withdrawing them from each other, we could estimate
the force of the free action in either of them ; 1° when the in-
duced magnetic force was a constant quantity, and the distance
cd variable, the distance a b9 a'b' from the original magnets being
the same ; 2° when the distance cd was a constant quantity, but

320 Mr Harris's Experimental Inquiries concerning

the induced force variable, the distances a b, a' V being varied
(36) ; and 3°, when both the distances and forces were varied ;
that is to say, when the distance c d, and the distances a 6, a'V
were varied simultaneously. The experiment being thus ar-
ranged, the forces set free, as expressed by the index, at the ex-
tremity d of one of the masses of iron, were found to vary with
the distance c d, when the induced forces were the same, and
with the induced forces when the distance c d was the same ;
and, finally, with these quantities conjointly, when they were both
made variable.

55* Now, by whatever artificial method we suppose a bar of
steel to be made a magnet, whether by the single or double
touch, it would not be difficult to shew, that the first states of
the magnetic disturbance, as measured from the magnetic centre,
would be in an arithmetical progression. Thus, if we suppose a
bar of steel a b. Fig. 20, to have been magnetized, then the
forces impressed on each side of zero may at first be conceived
to go on in the arithmetical progression 1, 2, 3, or 1', 2', 3', &c.
If we conceive these forces to be all united in the centre, their
free action would be zero. Let us now suppose these opposite
forces to be withdrawn through the distances 1 1', 2 2', 3 3', &c.
successively ; then, by the preceding experiments (54), the forces
set free in the points 1, 2, 3, &c. 1', 2', 3', &c. would vary direct-
ly as the square of the distances from the magnetic centre, since
they vary directly with the magnetic intensities, and directly
with the distances.

In the few theoretical illustrations found in the preceding
observations, it has been my endeavour to wander as little as
possible from experimental facts. I have not the vanity to sup-
pose that my researches are such as to defy the scrutiny of a
critical examination, or that, in so difficult an inquiry, I have
obtained perfection. It is only by examining nature in a great

the Laws qf Magnetic Forces. 821

variety of ways, that we can ever hope to arrive at an accurate
knowledge of her laws. 1 therefore submit the results which
I have obtained to the scientific world as matter for candid
consideration, having, at the same time, a proper sense of my
own limited powers of research *.

Plymouth, i
July 1. 1827. j

* It may not be improper to state, that, in the preceding inquiries, the attracting
or repelling forces have been supposed to act in parallel lines. This appears to be an
essential condition of this species of force ; since the reciprocal influence of any two
points directly opposed to each other, as a 6, Fig. SI, 22, 24, must be such as to
neutralize each other's action in relation to any other point more distant ; the action,
therefore, between the points immediately opposed to each other is exclusive, being
the nearest, and consequently the forces are parallel.

It is, therefore, only when the attracting surfaces are of unequal extent* that it be-
comes necessary to take into the account any other force, as cd and ef% Fig. 22,
which, in a great variety of instances, are of no assignable value ; but to obviate any
error which can arise from this cause, it is requisite, when very powerful magnets are
employed, to give the attracting extremity of the bar an armature of soft iron, as re-
presented in Fig. 28. A, which, in diminishing from its base, terminates in a cylin-
drical surface exactly equal to that of the suspended body x ; by which means the an-
gular forces, as cd, ef, Fig. 22, are so intercepted and reduced, as to be of no as-
signable value.

When the attracting surfaces are spherical and equal, it is requisite to determine a
fixed point in each opposed hemisphere, as x and y, Fig. 24, from which the sum of
all the attractions would produce the same effect as if those attractions were exerted
from every point of the hemispheres ; so that, in varying the distances, the intervals
may be estimated from these points, and not from the immediate point of contact.
These points I have found by numerous experiments fall within the opposed hemi-
spheres, at a distance equal to one-fifth of the radius of the spheres, supposing them
equal.

( 322 )

XIX. On certain new Phenomena of Colour in Labrador Fel-
spar, with Observations on the nature and cause of its Change-
able Tints. By David Brewster, LL.D. F.R.SS. L. & E.

(Read May 20. 1829.)

Sir Isaac Newton's theory of the colours of natural bodies, is
perhaps the most ingenious and lofty of all his speculations. It
was devised, however, at a time when the doctrine of light had
made comparatively but little progress, and before the disco-
very of various principles on which the colours of bodies must
depend, or by which, at least, they must be extensively modified.
The different dispersive powers of transparent substances ; — the
irrationality of the spectrum ; — the action of striated surfaces ; —
the decomposition of polarised light ; — the reflection of coloured
light at the confines of equally refracting media ; — and the ab-
sorption of common and of polarised rays, — are principles which
embrace within their individual range a great variety of facts to
which the Newtonian theory of colours bears no relation. In
that theory, indeed, we recognise more the flight of a transcen-
dant genius, than the patient and anxious step of inductive re-
search ; and so firmly has it entrenched itself among the strong-
holds of modern science, that no regular attempt has been made
to unsettle it, or even to submit to a rigorous analysis the va-
rious phenomena of colour, as displayed in mineral and vegetable
bodies, and in the artificial combinations of the laboratory. Such
a task I should not have presumed to undertake ; but in the
course of an extensive examination of minerals, the subject has
been forced upon my attention, and having extended the inquiry
to vegetable bodies, as well as to chemical combinations, I pro-

PLATE X1H.

*WJ S* ft™ .|i * J, ..,.,

SS8

4

in Labrador Felspar. 328

pose, in a series of papers, to submit the results to the Royal So-
ciety.

In my account of the Cavities in Topaz, and other minerals, I
have mentioned the frequent occurrence of strata of cavities, so
minute that they are scarcely capable of being resolved by the
most powerfiil microscope. In the larger cavities, their depth is
sometimes very small, compared with their other dimensions ;
but in the more minute pores, as they may be called, there is
a greater equality in their length, breadth, and thickness, and I
have never been able to recognise any thing like the colours of
thin plates reflected from the strata which they compose.

In seeking for the new fluids in Labrador felspar, the fine
changeable tints of that mineral could not fail to excite particu-
lar attention ; and after examining some specimens, I discovered
a new set of colours, which seemed to be capable of a distinct
analysis. When these colours are seen by a microscope, and un-
der strong illumination, they form a highly beautiful phenome-
non, somewhat resembling Fig. 1. Plate XIII.

The coloured portions have the form of parallelograms, some-
times complete, sometimes truncated at the angles, and some-
times so rounded as to have no regular outline. Their longest
sides are generally parallel to one another, and they are some-
times arranged in groups, with their homologous lines in diffe-
rent directions. The parallelograms are not distributed in a
single stratum. They appear at different depths; and those
which are much below the surface have little brilliancy, owing
to the imperfect transparency of the mineral. These coloured
spaces vary from the 40th or 50th of an inch in length, to the
most minute point which the microscope can descry.

The tints reflected from these spaces are generally very bril-
liant. They are sometimes white, and sometimes all of one co-
lour, but I have never found them below the blue of the se-
cond order of Newton's scale. The surface which reflects them,

VOL. XI. PART II. S 8

324 Dr Brewster on certain new Phenomena of Colour

generally displays throughout the very same tint ; but in some
cases, the same parallelogram exhibits different colours at the
same angle of incidence, owing sometimes to the mixture of the
tints of superposed parallelograms, and sometimes to the variable
thickness of the space by which the colours are occasioned*

The parallelograms which produce the colours now described,
may be crystallized laminae disseminated through the felspar,
and giving the colours of thin plates ; or they may be slender
crystals, which, like the veins of calcareous-spar, develope the
tints of polarised light ; or they may be crystallized cavities, ei-
ther entirely empty, or containing solid, fluid, or gaseous sub-
stances.

The exceeding toughness of the mineral renders it impracti-
cable to obtain good cleavage planes, passing through the paral-
lelograms, for the purpose of shewing their interior, or of dis-
charging their contents, as I succeeded in doing while examining
the topaz cavities, so that I had no other resource but that of op-
tical analysis.

As it was necessary to examine the light transmitted through
the parallelograms, I detached a very thin splinter from the mi-
neral, and placed it in Canada balsam * between two plates of
glass. It was so thin at one edge, that it did not give the co-
lours of polarised light, and at its greatest thickness, it developed
only the red of the third order. It had fortunately only one
stratum of parallelograms, so that their reflected and transmit-
ted tints could be observed with the greatest distinctness. The
reflected tints were uncommonly brilliant and pure, but the
transmitted ones were very faint, and of a yellowish, reddish, or
greenish-brown colour, varying with the obliquity of the incident
ray. I now placed the splinter on the base of a prism, with Ca-
- - — — ' — ■ — - . ._ - .

* Oil of Cassia would have been preferable in other cases, but as it has a colour
of its own, and disperses light so powerfully, it was unsuitable where delicate tints
were to be observed.

in Labrador Felspar. 835

tiada balsam interposed, and I found that the tint diminished as
the angle of incidence increased, and that the same effect took
place in the same degree in all azimuths. This experiment
proved incontestibly that the colours were not those of polarised
light. That the cavities do not contain a gas or a fluid of any
kind, is obvious from the fact, that the felspar does not decre-
pitate or burst with heat Hence, it follows, that the parallelo-
grams must be either empty, or must contain indurated matter.

In order to ascertain, upon the supposition of the parallelo-
grams being solid, whether the colour arose from the thinness of
the solid matter, or from the thin open space which separated
the surface of the parallelograms from the adjacent felspar *, I
observed the particular tints which a number of individual pa-
rallelograms produced at a given incidence ; and upon reversing
the specimen, I found, that, in every case, the very same tints
were developed at the same angle of incidence. This result
clearly proves, that the tints were due to the thickness of the
cavity, whether they were empty or filled with indurated mat-
ter.

The examination of individual parallelograms presents some
instructive peculiarities. While the greater number give an
uniform uninterrupted tint, several have the appearance shewn
in Fig, 2. In No. 1, the parallelogram is imperfect. In No. 2,
it is more so, though the individual patches of colour fill up
its outline. In No. 8, they are smaller still, and more un-
equal. In No. 4, we can still discover the outline of each in-
dividual patch ; but in No. 5, the patches are so minute, that the
surface of the parallelogram produces all the variety of mottled
colours. These phenomena indicate a general resemblance to

* It is from this cause that the splendid colours arise which accompany the den-
dritic crystallizations of titanium in mica, which I have examined with much atten-
tion.

s s 2

326 Dr Brewster on certain new Phenomena of Colour

indurated matter, but, when minutely examined, this resemblance
disappears. The spaces between the individual patches are in
almost every case dark, like the adjacent felspar ; and when the
microscope is capable of separating the individual patches, it be-
comes quite obvious, that, if they are grains of indurated matter,
they are not disseminated through an empty cavity, but are im-
bedded in the felspar. We have no hesitation, therefore, in con-
cluding, that all these little patches and specks of colour are
empty cavities, like the large parallelograms, for the intensity of
the light reflected from the small patches in Nos. 8, & 4. of Fig. %
is the same as that reflected from the parallelograms. This light,
indeed, is so strong, that nothing but a metallic substance filling
the cavities, and in optical contact with their sides, could reflect
it. If this were the feet, the analysis of the mineral could not
fail to exhibit it, and I am not aware that any metallic ingre-
dient, except titanium, has been detected in felspar. M. Pe&-
chier has announced this fact, but whether it was found in com-
mon Felspar or Labradorite, I have not the means of ascertain-
ing. Professor Rose of Berlin, however, who carefully analysed
the Labradorite of various localities, has not been able to disco-
ver any such ingredient. But even if titanium were a constant
element of Labradorite, the parallelograms could not contain
that metal ; for I have ascertained that titanium in optical con-
tact with mica reflects much less light than the parallelograms ;
and since mica has a refractive power greatly inferior to felspar,
titanium in optical contact with felspar, will reflect much less
light than in contact with mica, and consequently much less light
than the parallelograms.

Having thus determined that all the colours under our consi-
deration are those of thin plates produced by minute cavities
within the mineral, varying in magnitude from the 40th of an inch
down to the most minute speck which the microscope can descry*
we are entitled to refer the other phenomena of colour in the

in Labrador Felspar. 327

same mineral to similar cavities, though we are no longer able to
see their individual outline, or to recognise them in any other
way but by their united influence.

The coloured parallelograms above described are, in general,
parallel to the face P, Fig. 8, of the primitive form, as given by
Hauy ; and in no specimen which has come under my examina-
tion, have I ever found them coincident with the plane of the
common changeable colours which have been so long admired in
Labrador Felspar. The largest generally occupy one plane ;
but I have found another set arranged in another plane, while
others have their reflecting edges in a variety of different posi-
tions. This effect will be understood from Fig. 4. which repre-
sents the images reflected from all the different colorific planes
in a specimen in my possession. When we look into the speci-
men, we see the image C of the candle formed by the ordinary
polished surface cut at random. Let the felspar be now turned
round till AC, the line joining the candle C, and the great mass
of changeable colour A is in the plane of reflection, A being seen
by rays incident at a greater angle than C. When this is done,
we shall see a series of nearly coincident coloured images of the
candle at D, which are the reflections from the parallelograms
shewn in Fig. 1. At E, there is another set of nearly coincident
images, fainter and less coloured than those at D. At B there
is a third set, but they are still fainter and more indefinite.
Through these three sets of images there passes an arch of red-
dish-brown light, extending on each side towards F and G, and
formed by minute needle-shaped cavities, which being nearly of
equal diameter in every direction except their length, must re-
flect light in whatever direction it is incident, provided it fall
nearly in a plane perpendicular to their length.

We come now to the examination of the changeable colours
of the spar, which, so far as I know, have never been submitted

838 Dr Brewster on certain new Phenomena of Colour

to a physical analysis. So little attention, indeed, have they ex-
cited, that Hauy, Mohs, and other writers, describe them as ly-
ing in planes parallel to the feces of cleavage ; and in this cir-
cumstance Hauy finds an easy explanation of their origin, by as-
cribing them to accidental fissures between the natural joints of
the mineral #.

Although Labradorite abounds in fissures, I have never disco-
vered any parallel to the general plane of changeable colour, and
I possess a specimen in which the colours lie in various curve
planes, cutting, at a great angle, all the natural joints of the
crystal.

The first point which I was desirous of determining, was the
position of the plane of changeable colour. For this purpose, I
effected a tolerably good cleavage parallel to P, Fig. 8, and ha-
ving placed the crystal on the goniometer, I turned it round in
azimuth till the white image reflected from the face of cleavage,
and the mass of coloured light from the plane of changeable co-
lour, were both in the plane of reflection, the latter being formed
by rays nearer the perpendicular. Let the surface of cleavage
P, Fig. 8, be represented by DC, Fig. 5, and let RC be a ray of
light from a candle incident at C. This ray will be refracted in
the direction CA ; and if CDQ is the inclination of the plane of
changeable colour, the refracted ray GA will be reflected at A in
the direction AB, and will emerge from the spar in the direction

* Elles proviennent, comme dans Fopal, des legeres fissures qui interrompent le
tissue de la pierre ; mais l'opale etant fendill& dans toutes sortes des directions, pre-
sente des reflets qui se succedent, k mesure qu'on la fait mouvoir, ail lieu que dans le
feldspath, dont les fissures coincident sur un seul plan ; en sorte qu'ils se montrent tout
entiers, lorsque la lumiere est reflechie par ce plan, sous Tangle favorable pour la
renvoyer k Poeil, et disparoissent, des qu*on donne k la pierre un inclination diffe-
rente. «Tai reconnu en observant un morceau de feldspath opalin de Norwege, qui
tn'a 6t6 envoys par M. Esm ark, que les plans d1ou partoient les reflets dont je viena
de parler, etoient dans le sens des faced T qui sont les plus etendues. — Traiti de
Miner alogie, torn. ii. p. 613.

in Labrador. Felspar. 329

BE. The eye at £ will therefore see the reflected image of the
candle in the direction ECN, and the mass of coloured light re-
flected at A, in the direction EBM. By measuring the angles,
I found that when FCR was 78±°, the angle NEM, or the dis-
tance of the coloured image from the common image, was 57°>
Calling this distance D, and making m the index of refraction
for felspar, A the angle of refraction at C corresponding to the
angle of incidence I or FCR, and B, the angle of refraction for
a ray EB incident at B (which is equal to the angle of incidence
ABn, when the ray passes out of the felspar), and w the inclina-
tion of the plane of colour, or CDQ, then we shall have

a sin I • r> sin I — D

sinA = -— - > sin B = — >

tn hi

and a — ^ *.

which will give 10° 52' for the inclination of the plane of colour
to the face of cleavage P, Fig. 8. The common section of these
two planes nearly bisects the acute angle of the face P.

The changeable colours of felspar generally vary from the blue
to the red of the second order. In the same specimen, the tint
frequently shades off at the edges to the blue of the second or-
der ; and when we view it at an oblique incidence, by cement-
ing a prism on the polished surface, they diminish from the
maximum tint to the blue, and sometimes to the purple of the
second order. The colours are not produced by a single plane,

* The demonstration of this is very simple. Through C and B draw Bn, and
FCQ perpendicular to DC, and through A draw AF perpendicular to DQ, and
meeting Bn in n. Then x = CDA =r AFQ = AnB, and BAF = ABn + A»B=s
B + a?. But FAC = ACQ — AFC ; consequently, since FAC = BAF, and
ACQ = A, we have

B AE = B + x, and B AE = A — x. Hence,

A — B

B + # = A — .r, and 07 =

%

380 Dr Brewster on certain new Phenomena of Colour

but by an infinite number ; and when we chip off the smallest
fragment, it gives the same colour as the thickest mass. If we
have been successful in obtaining an extremely thin edge, we
shall find that the brightness of the tint suffers an evident dimi-
nution, though the colour itself never changes ; and at the very
edge of the splinter, we can descry, with a good microscope, the
individual specks from which the colour is reflected. •

We have already seen, that the light transmitted through the
coloured spaces in Fig. 1, does not exhibit distinct complementary
tints ; and the same indistinctness takes place in the light trans-
mitted through extremely thin splinters that give the change-
able colours. But when the spar is the 10th or 20th of an inch
thick, the transmitted complementary tint is exceedingly dis-
tinct, and, by varying the incidence, it changes from yellow, the
complement of the blue of the second order, to blue, the comple-
ment of the red of the second order.

Many of the larger cavities, which have a distinct outline, re-
flect a white tint, or a mixture of all the prismatic colours, an effect
analogous to the white reflections of the Moon-stone, or Feldspath
nacree of Hau y. " Some lapidaries," says Hauy, a give the name
of Argentine to specimens of this variety whose pearly reflections,
in place of proceeding from the interior, emanate from the sur-
face, as in pearls *." The effect here described I have examined
in a specimen from Norway, but the light certainly proceeds
from the interior, though, from the imperfect transparency of
the mass, it appears to a careless observer to be produced at or
near the surface. In this specimen, the white light is reflected
from planes parallel, or nearly so, to one of the cleavage planes ;
while in another face of cleavage, we observe an infinite number
of small coloured specks of irregular outline pervading the whole
of the specimen, but all parallel to one another, and inclined to

• Tratoky torn. ii. p. 606.

in Labrador Felspar. 331

the cleavage plane. The pearly light reflected from this speci-
men seems to be owing to a want of homogeneity in the mineral,
in virtue of which portions of different refractive densities are in
contact. The existence of such a structure is clearly proved by
the great nebulosity that accompanies the images of luminous
objects, and by the dimpled surface of its cleavage planes, when
examined by the microscope. This variety of felspar differs as
widely ftoJthe conunon lLadorite. » Chafcedony does ft™
Quartz, and the distinctive character arising from its heteroge-
neous structure is as easily appreciated.

In a fine specimen of felspar belonging to Mr Allan, there
are, besides the plane of changeable colour, two other planes,
which reflect a silvery white light from long and narrow paral-
lelograms. Each of these last planes is formed of portions not
accurately parallel to each other, and hence the reflected light is
divided into separate masses. These masses are bounded by the
prismatic colours, which disappear when the trace of the plane
of reflection is parallel to the common section of the reflecting
plane and the surface of the specimen, and reach their maximum
when these lines are at right angles to each other. Hence, the
prismatic colours are produced by the prism of felspar bounded
by that surface, and by the plane that reflects the silvery tints.
By ascertaining the angle of a prism of felspar which connects
the maximum prismatic tints, we obtain the inclination of the
reflecting plane to the surface of the specimen.

In many specimens of felspar, I have observed with the micro-
scope minute crystals and very small spheres of a metallic sub-
stance, which I have no doubt is titanium, and which has pro-
bably given rise to the peculiarities of M. Peschier's analysis.

VOL. XI. PART II. T t

( 332 )

XX. On the Composition of Blende. By Thomas Thomson, M. D.
F. R. S. L. & E., Professor of Chemistry, Glasgow.

{Read M February 1829.)

It is nearly a century since chemists began to suspect the nature
of the well known mineral usually distinguished by the name of
Blende or Pseudo-Galena. Brandt, in 1735, showed that zinc
was one of its constituents*. In 1744, Funck demonstrated
that it was an ore of zinc f . Margraaff soon after actually ex-
tracted zinc from it p It was impossible to subject it to heat in
an open vessel, without perceiving that it contained sulphur. But
chemists did not succeed in their attempts to combine zinc and
sulphur together. This led them to conclude, that in blende
the zinc and sulphur were united together by the intervention
of iron. This opinion was stated by Cronstedt in the first edi-
tion of his Mineralogy. In 1779 Bergman attempted an ana-
lysis of blende, and drew, as a conclusion from his experiments,

* Bergman. Opusc. ii. 813.

t Kongl. Vet* Acad. Handl. 1744, p. 57.

I Opusc ul. de Mabgraaff, i. 190.

Dr T. Thomson on the Composition of Blende. 333

that it was composed of

Sulphur, 29

Arsenic, 1

Water, • ••.... 6

Lead, 6

Iron, • • 9

Zinc, 45

Silica, 4

100*

But his mode of analysis was so bad, that it is obvious he could
draw no legitimate conclusion respecting the constitution of
blende from his experiments.

About the beginning of the present century, it was generally
admitted by chemists and mineralogists, that blende is a sul-
phuret of zinc. But the unsuccessful attempts to combine sul-
phur and zinc together by heat, induced Morveau to believe
that the zinc in blende was in the state of oxide. Proust, how-
ever, showed, that when blende is mixed with charcoal, and ex-
posed to a red heat, no sulphurous acid whatever is given off f ;
which led him to conclude, that in blende the zinc is in the me-
tallic state. This opinion, in consequence of the progress which
chemical science has made, has been for these twelve or fourteen
years universally adopted. Though I am not aware of any mo-
dern chemist who has attempted to determine the proportions
of its constituents with rigid accuracy except Abfwedson, who
has given us an analysis of a very pure specimen of blende in
the Memoirs of the Stockholm Academy for 1822, p. 438.

Abfwedson employed for his analysis yellow-coloured and

* Opusc ii. 330. + Jour, de Phys. lvl 79.

Tt2

334 Dr T. Thomson on the Composition of Blende.

crystallized blende. And his method of proceeding was as fol-
lows :

1.758 grammes (27.15 grains) of pulverized blende were di-
gested in aqua regia, which had been previously heated till it
began to give out fumes of chlorine gas. When all action was
at an end, the undissolved portion was separated by the filter,
washed and dried. It weighed 0.393. Being exposed to a red
heat a good deal of sulphur was driven off, but a portion of un-
decomposed blende remained, which, being again heated with
aqua regia, was completely dissolved.

The solution thus obtained was diluted with water, raised to
the boiling temperature, and mixed with an excess of carbonate
of potash. The heat being continued till all excess of carbonic
acid was driven off, the precipitated carbonate of zinc was col-
lected on the filter. After being washed, dried, and ignited, it
weighed 0.146. It was oxide of zinc, equivalent, according to
Berzelius's formulas, which Arfwedson follows, to 0.117 parts
of metallic zinc. From this Arfwedson concludes, that the
0.393 parts of residue were composed of

Zinc, 0.117

Sulphur, 0.276

0.893

The sulphuric acid in the original aqua regia solution was
precipitated by muriate of barytes. The ignited sulphate of
barytes obtained weighed 2.288, equivalent, by Berzelius's for-
mula, to 0.786 sulphuric acid, or 0.316 sulphur.

The liquid thus freed from sulphuric acid was raised to the
boiling temperature, and precipitated by carbonate of potash,
the heat being continued till all excess of carbonic acid was
driven off; the oxide of zinc obtained, weighed after ignition

Dr T. Thomson on the Composition of Blende. 335

1.311, and was pure, with the exception of a trace of iron.
1-311 oxide of zinc, according to Berzelius's tables, are equiva*
lent to 1.05 metallic zinc. Thus, by Arfwedson's analysis,
1.758 blende are composed of

Zinci . . • . 1.167 or 66.382
Sulphur, . . 0.592 83.675

1.759 100.057

When we correct Arfwedson's analysis by my formulae,
which I consider as more accurate than those of Berzelius, the
result is as follows :

Zinc, • . . 1.17947 or 67.091
Sulphur, . . 0.58523 83.290

1.76479 100.881

Now, this is equivalent to

Zinc, . . 4.25

Sulphur, 2.1087

4.25 is the atomic weight of zinc But 2.1087 exceeds 2
(= atom of sulphur) by rather more than drth of an atom. Con-
sequently, if Arfwedson's analysis be correct, blende is not a
simple combination of an atom of zinc and an atom of sulphur,
but contains an excess of this last substance.

There are two circumstances connected with Arfwedson's
analysis that prevent me from trusting implicitly in its accu-
racy.

1 . The 0.393 of matter which did not dissolve in aqua regia,
must have been dried at a very low heat, because sulphur begins
to sublime at a temperature considerably under that of boiling

1

336 Dr T. Thomson on the Composition of Blende.

wate*. But at so low a temperature it is not probable that the
powder would be deprived completely of water. Yet Akfwed-
80n estimated the weight of the sulphur, by subtracting the
weight of the zinc obtained from the original weight of the pow-
der. The remainder he considered as sulphur. Now, certainly,
this remainder was not all sulphur, a portion of it must have
been water ; therefore the quantity of sulphur which Arfweq-
son gives is greater than what was actually present in the
blende.

2. From a very great number of experiments which I have
made on the various modes of obtaining zinc from its acid solu-
tions, I am satisfied that, by the method employed by Arfwed-
son, the whole of that metal cannot be obtained. It is plain,
then, that the blende analyzed by him contained more zinc and
less sulphur than he gives. Had the proportions been

Zinc, . 68

Sulphur, 32

100

* •

the blende would be a compound of 1 atom zinc and 1 atom
sulphur.

That I might acquire some additional information on the
subject, I requested Mr Thomas Muir *, of whose uncommon ac-
curacy as an experimenter I had had ample proof, to analyze a
specimen of crystallized blende with which I furnished him.
The crystals had the diamond lustre, were blackish, and almost

* The premature death of this excellent young man, since this paper was written,
is an event very much to be deplored. He had wrought as a practical chemist for
several years in my laboratory ; and, to much practical knowledge, had added so
much neatness and dexterity, joined to uncommon industry, that he would certainly
have speedily distinguished himself as a chemist

Dr T. Thomson on the Composition of Blende. 387

opaque. But the powder was light brown. The specific gra-
vity was 4.076. The blende, previously reduced to powder,
was digested in aqua regia till a complete solution was obtained.
The sulphuric acid was thrown down by muriate of bary tes ; the
peroxide of iron, by benzoate of ammonia ; and the oxide of zinc,
by adding an excess of carbonate of soda, and evaporating the
mixture to dryness. The residual matter was digested in water,
and the carbonate of zinc was collected on the filter. The result
of the analysis was as follows :

Zitic, 65.280

Iron, 0.748

Sulphur, 33.364

99.392

65.28 zinc requires 30.837 sulphur,
0.748 iron requires 0.854, to form bisulphuret.

31.691

Thus, there is an excess of sulphur in the blende analyzed by
Mr T. Muir amounting to 1 .673 per cent. But there is a loss
in Mr Mum's analysis, amounting to .608 per cent., and this loss
was undoubtedly zinc. If we add it, the quantity of zinc in the
blende will be 65.888, which will require 31.123 sulphur. This
would reduce the excess of sulphur to 1 .387 per cent. This is
less than in Arfwedson's analysis, in which the excess of sul-
phur amounts to 1 .986 per cent.

Mr Muir's analysis serving to confirm the accuracy of Arf-
wedson's, I was naturally led to consider it as established that
blende contains an excess of sulphur, amounting to about 1£
per cent. Now, such an excess can only exist on the supposition
that zinc is capable of combining with sulphur in various pro-
portions. For example, if we were to consider blende as a com-

388 Dr T. Thomson on the Composition of Blende.

pound of 24 atoms sulphuret of zinc and 1 atom bisulphuret of
zinc, its constitution would agree very nearly with the analysis
of Mr T. Muir. For

24 atoms zinc =102

1 atom zinc = 4.25

Total zinc - 106.25

24 atoms sulphur, ... 48
2 atoms sulphur, ... 4

52

Now,

Zinc, . . 106.25 is the same as 67.15
Sulphur, .52 32.85

158.25 100.00

Such a composition would be analogous to what Stromeyer
has shewn to be the constitution of magnetic pyrites, which al-
ways contains an admixture of bisulphuret of iron. It was with
a view to ascertain how far zinc and sulphur are capable of en-
tering into various combinations, that the following experiments
were made.

I mixed as intimately as possible 2 1 grains of pure oxide of
zinc with 20 grains of flowers of sulphur. This mixture was
put into a porcelain crucible, which, being covered with its lid,
was exposed over a spirit-lamp, to a heat at first very moderate,
but gradually increased till the crucible became red hot, and it
was kept at that temperature till the whole excess of sulphur
had been driven off. It was then allowed to cool. The matter
remaining in the crucible was a white pulverulent powder, having

Dr T. Thomson on the Composition of Blende. 889

a slight tinge of yellow. It was tasteless and insoluble in water,
and, when examined before the blowpipe, exhibited precisely
the characters of blende. When digested in muriatic acid, it
dissolved with effervescence, giving out abundance of sulphu-
retted hydrogen gas, and leaving a very small quantity of undis-
solved sulphur. Blende, when dissolved in muriatic acid, gave
out the same gas, and likewise left a very small quantity of sul-
phur undissolved. The weight of the sulphuret of zinc which I
had thus formed, was exactly 25 grains.

Now, 21 grains of oxide of zinc are composed of,

Zinc, . . 17

Oxygen, 4

21

17 zinc are equivalent to 4 atoms, and 4 atoms sulphur weigh 8.
Thus it appears that the sulphuret of zinc formed artificially was
composed of

Zinc, 17 or 4.25

Sulphur, .... 8 2

25 6.25

This experiment corresponds exactly with those which I had
previously made to determine the atomic weight of zinc and of
sulphur, and serves to confirm them, if any confirmation had
been wanting.

The very same sulphuret of zinc is obtained when oxide of
zinc and flowers of sulphur are heated together in a green glass
retort.

I made many attempts to form a super-sulphuret of zinc, by
heating sulphur and oxide of zinc in various proportions, and at

VOL. XI. PART II. U u

S40 Dr T. Thomson on the Composition of Blende.

various temperatures, but all these attempts were quite unsuc-
cessful. I always got a simple sulphuret of zinc, and nothing
else, in what way soever the process was varied. When anhy-
drous sulphate of zinc is decomposed by hydrogen gas, in a glass
tube, a portion of the sulphur is driven off, and there remains a
mixture of oxide of zinc and sulphuret of zinc, as was first ascer-
tained by Arfwedson *. If we substitute the acid sulphate of
zinc, which I have described elsewhere f , the result is the same.

My attempts to form a super-sulphuret of zinc, by means of
sulphuretted hydrogen, were equally unsuccessful. But it may
be worth while to state one or two of the experiments somewhat
in detail, on account of the facts which they furnish.

21 grains of pure anhydrous oxide of zinc were dissolved in
acetic acid, and a current of sulphuretted hydrogen gas was
passed through the solution (which was nearly neutral), as long
as any precipitate fell. The precipitate was white and flocky.
Being collected on a filter, washed (a tedious process), and dried,
it weighed 26 09 grains. The liquid from which this matter
had fallen, being evaporated to dryness, left 3.15 grains of a mat-
ter quite similar to the precipitate. Thus the whole substance
obtained, when a solution of 21 grains of oxide of zinc is treated
with sulphuretted hydrogen, amounted to 29.24 grains.

This matter, when dry, assumed a dark green colour. It
was tasteless and insoluble in water, but dissolved in acid, with
the evolution of much sulphuretted hydrogen gas. When
heated to redness it emitted a white smoke, smelling strongly of
sulphur, and assumed a yellow colour ; but, on cooling, it
changed to white. The weight was now reduced to 28-86
grains. It dissolved in muriatic acid without effervescence,

* Kongl. Vetens. Acad. Handl. 1822, p. 346.
■f- First Principles of Chemistry, i. 55.

Dr T. Thomson on the Composition of Blende. 341

though it gave out, at the same time, a perceptible smell of
sulphuretted hydrogen ; and paper, moistened with acetate of
lead, held over it, became brown. Muriate of barytes being
dropt into the solution, 2.089 grains of sulphate of barytes were
obtained, equivalent to 0.706 grain of sulphuric acid.

The green substance thus obtained was obviously an anhy-
drous hydro-sulphuret of zinc, composed of 1 atom oxide of
zinc, and 1 atom sulphuretted hydrogen. For 21 grains of oxide
of zinc being equivalent to 4 atoms, would require 4 atoms of
sulphuretted hydrogen, amounting to 8.5 grains ; for the atom

of sulphuretted hydrogen is 2.125. Thus, we have,

»

4 atoms oxide of zinc, 21

9 atoms sulphuretted hydrogen, 8.5

.Total, ... 295

Now, the quantity which I obtained was 29.24 ; and I find by
the notes of the experiment, that a few flocks of the hydro-sul-
phuret were accidentally lost. Hence, if the whole had been
collected, it would have amounted very nearly to 29.5 grains.

This hydro-sulphuret, when heated, gives out almost the
whole of its sulphuretted hydrogen, while blende may be ignited
in close vessels with very little change. A small portion of the
sulphur was acidified by the heat, and a little of the hydro-sul-
phuret was probably converted into sulphuret of zinc. .

The white flocks precipitated by the sulphuretted hydrogen,
constituted a hydrated hydro-sulphuret of zinc.

Sulphuretted hydrogen gas does not form a sulphuret of
zinc at all, unless it be passed through hot oxide of zinc in a
tube ; and, in that case, nothing is obtained but common sul-
phuret of zinc.

Being thus foiled in all my attempts to form a super-sulphu-

u u2

[

342 Dr T. Thomson on the Composition of Blende.

ret of zinc, it became necessary to examine the composition of
blende again with as much attention to accuracy as possible, in
order to ascertain whether the supposed excess of sulphur really
exists in it.

An analysis of the crystals of blende, obtained from the spe-
cimen which Mr T. Muir had examined, gave me the following
result:

Zinc, 65.7

Iron, 0.740

Sulphur, .... 32.628

99.076

The amount of iron was exactly the same as Mr Muir had ob-
tained ; but the quantity of zinc was 0.42 grains more, while the
sulphur was 0.736 grains less than in his analysis. My loss
amounted to 0.924 per cent., and was undoubtedly zinc ; for I
was at so much pains to obtain all the sulphur, that none of it
could well be lost. The real quantity of zinc, then, in 100
grains of the blende, was,

66.629 gr., requiring . . 31.352 sulphur
0.748 gr., iron requiring 0.354 sulphur

Total, . . 32.206

The quantity of sulphur which I actually obtained exceeds
this quantity by only 0.422. Here the excess is less than one-
third of that in Mr Muir's analysis.

I analyzed another specimen of brown blende, having the
diamond lustre, and a specific gravity of 3.9779. The consti-
tuents obtained were,

Dr T. Thomson on the Composition of Blende. 348

Zinc, 65.5

Iron, 1.372

Sulphur, .... 82.628

99.500

If we allow the loss to be zinc, we have

66 zinc, requiring . . 31.0588 sulphur
1.372 iron, requiring . . 1.5394 sulphur

Total, . . . 32.5982

This exceeds the quantity of sulphur actually found by no more
than 0.03 grain, or less than 1000th of the whole.

Another variety of blende was subjected to analysis. It was
opaque, splendent, dark coloured, crystallized, and had a specific
gravity of 4.2434. Its constituents were found to be,

Zinc, 64.83

Lead, .... 5.215

Iron, 1.33

Sulphur, .... 82.915

103.79

64.33 zinc require of sulphur, . 30.27

5.215 lead, 0.80

1.83 iron, 1.52

Total, .... 32,59

The quantity of sulphur actually found exceeded this by 0.32
grains.

I analyzed two other specimens of blende ; but the results
accord so nearly with those already given, that it seems super-

344 Dr T. Thomson on the Composition of Blende.

fluous to state them. The sulphur rather exceeded the theore-
tical quantity ; but the excess was exceedingly small.

These analyses seem to me to leave no doubt, that the zinc
in blende is combined with 1 atom of sulphur only. Blende is
a simple sulphuret of zinc, but never entirely free from an ad*
mixture of bisulphuret of iron; but the proportion of this last
substance is so small and so variable, that it cannot be considered
as a chemical constituent of blende, but rather as a mechanical
mixture. In the second of my analyses the blende contains the
greatest proportion of iron-pyrites of any of the varieties which
I subjected to analysis. It consist? of about

4

52 atoms sulphuret of zinc,
, 1 atom bisulphuret of iron.

While, in the first variety analyzed, the constituents are nearly

74 atoms sulphuret of zinc,
1 atom bisulphuret of iron.

These variations are inconsistent with chemical combination.

( 345 )

XXI. Notice regarding a Time-Keeper in the Hall of the Royal
Society of Edinburgh. By John Ro bison, Esq. Sec. R. S. Ed.

(Read 1th February 1881.)

A here being some peculiarities in the construction of the
Clock lately set up in this room, which may prove to have consi-
derable influence on the performance of such instruments, and
also on their cost and duration, it is presumed that a short notice
of them, together with a few preliminary observations, may not
be deemed uninteresting to the Society.

An eminent philosopher, in a work recently published, has
defined a clock to be " nothing more than a piece of mechanism,
for counting the oscillations of a pendulum." This definition
cannot be considered as complete, as besides having to register
the oscillations of its pendulum, a clock has to communicate suc-
cessive impulses to it, to enable it to overcome the friction of its
suspension, and the resistance of the air. If a maintaining power
were not exerted by the clock, the pendulum would soon be
brought to a state of rest.

There are therefore two principal points which require to be
attended to in the construction of a good time-keeper. One, that
the pendulum shall perform all its oscillations in equal times, in
spite of the variations of temperature it may be exposed to ; and
the other, that the clock or mechanism shall communicate un-
varying impulses to the pendulum during long periods of time.

346 Notice regarding a Time-Keeper in the Hall

Many ingenious contrivances have been fallen on by men of
science, and by mechanicians, to attain these ends, but some
causes of error, which appear to be inseparable from the ma-
terials employed, still remained to be removed* As an endea-
vour has now been made to get rid of these difficulties, by some
changes in the mechanism of the clock, and in the material of
the pendulum, I shall proceed to explain the peculiarities in
their construction.

The principal circumstances in which this time-keeper differs
from the usual constructions are these; 1st, In having an es-
capement which requires no oil ; 2d, In having the pendulum
and ball formed of a material not hitherto Used for this purpose ;
and 3d, In having the mechanism entirely secured against the
effects of dust, and in a great degree against those of hygrome-
tric changes in the atmosphere.

First as to the Escapement. — It is no doubt known to most
persons now present, that, in the usual forms of clock-escape^
ments, the teeth of the scape-wheel act alternately on two pal-
lets, or inclined planes, which are placed at the extremities of
brandies proceeding from an axis^ which axis has a third branch
or tail, by which it communicates to the pendulum the impulses
which it receives from the wheel-work, through the pallets. Thus
in Plate XIV., Fig. 1 ., which is an enlarged drawing of the most
commonly used escapement, A is the scape-wheel, which is urged
round, in the direction of the arrow, by the maintaining power
of the clock ; B B are the two pallets ; C is the axis from which
they proceed ; and D is a part of the third branch or tail, by
which the successive impulses are communicated to the pendu-
lum.

The chief cause of irregularity in this, and in all other forms
of escapements where the teeth of the scape-wheel act on in-
clined planes, is the oil which is necessarily introduced to dimi-
nish the friction of the rubbing surfaces. In good clocks this

of the Royal Society qf Edinburgh. 347

friction is reduced as much as possible, by forming the scape-
wheel of steel, and the pallets of jewels ; but oil is still neces-
sary, and however pure, it must be liable both to chemical
change, and to a gradual admixture with dust ; its effect there-
fore on the rubbing parts must vary, and the impulse given to
the pendulum must vary with it.

The escapement, which I shall now proceed to describe, is
the invention of Mr Whitelaw, a very ingenious artist in this
city, who has been employed to make the clock. His escape-
ment possesses the advantage of not requiring oil in any part of
its mechanism, and therefore is free from one great cause of ir-
regularity.

In the drawings, at Figs. 2. 8. and 4., A is a scape-wheel,
which need not vary much from the usual form ; it acts alter-
nately on the pallets D and E. These pallets are not attached to
an intermediate axis, as in the former case, but are fixed to the
pendulum itself (by which arrangement some sources of irregu-
larity are suppressed). C C are the branches which carry the
pallets ; and B is the knife-edge on which the pendulum oscil-
lates.

The pallets D and E, instead of being inclined planes along
which the teeth of the scape-wheel would be required to slide
while giving impulse to the pendulum, are portions of the sur-
faces of cylinders which revolve (or rather oscillate) on delicate
pivots in ruby holes. When a tooth of the scape-wheel drops
on one of these cylinders during the motion of the pendulum,
the cylinder is turned partly round by the continued action of
the tooth, until the pendulum has swung so far that the tooth
escapes past the cylinder, having descended through a space equal
to half of its diameter : at the moment of its escape, a tooth on
the opposite side of the wheel is arrested by the other pallet,
and a similar escape takes place with that tooth on the returning
swing of the pendulum.

VOL. XI. PART II. x x

348 Notice regarding a Time-Keeper in the Hall

Here, it will be obvious, there can be no friction between
the teeth and the pallets, and that oil would he superfluous.
The rubbing has been transferred from the surfaces of the pal-
lets tto their centres, where, from the slowness of the motion and
the smaUneasof the space moved through, there can be no appre-
tiable resistance between the pivots and their ruby holes, and
therefore no oil can be required.

It will be observed, on inspection of the dmwing, that the
diameter of the pallets is nearly as great as the distance between
the teeth of the wheel ; the teeth, however, advance only half of
that space at each vibration, and if the pallets were solid cylin-
ders, the returning motion of the pendulum would be opposed
by their striking against the teeth on the entering side. In or-
der to prevent this, a portion of the cylinder is cut away in the
middle part, leaving only .enough of surface for the teeth to act
on during their descent of half the diameter. A third part of the
circumference is sufficient for this action, and any thing less than
a half will leave a free passage for the disengaged tooth. In
Fig, 2, at d e, the pallets are drawn as detached from their frames,
and as if half of the circumference ivere cut away from the mid-
dle part. In Fig. 3. and 4. the pallets are shewn in section in
their proper positions : in these figures, w is a small counter-
poise, to bring hack the pallet to its position for receiving the
next succeeding tooth, after it has been turned aside by the es-
caping one.

To persons who have paid attention to the subject of Horo-
logy, I need not point out the great value of this improvement,
nor the benefits which may arise from it in those departments of
science where an exact measure of time is a desideratum #.

* The maintaining power in this clock is a weight of 41b. 4oz., descending
through about 40 inches in 7 days ; the weight of the pendulum and ball 1££ lb.,
and of vibration 4.4 inches.

of the Royal Society qf Edinburgh. 349

I may mention here, that in Fig. £. the pendulum is sop-
posed to be in the middle of an oscillation, with a tooth of the
scape-wheel pressing on the pallet D. In Fig. 8. the oscillation
has been completed to the left i the pallet D has allowed the
tooth to escape past it, and a tooth of the opposite side of the
wheel has been arrested by the pallet E.

In Fig. 4. the pendulum has swung to the right; the tooth
which rested on £ has in its turn escaped, and another, on the
opposite side of the wheel, has dropped on I>.

The next peculiarity in this clock which merits attention, is
the material of which the pendulum rod and ball have been made.
Marble has been adopted for this purpose, in consequence of
a suggestion made to me by Dr Brewster, and since repeat-
ed by him in the Philosophical Transactions for 1880, page
94, where, in speaking of Mr Mitscherlich, he says, u This
eminent philosopher has found, by direct experiment, that heat
expands a romb of calcareous spar in the direction of its axis, and
contracts it in directions at right angles to that axis." Dr
Brewster adds, in a note : " It follows from this fact, that mas-
sive carbonate of lime, in which the axes of the molecules have
every possible direction, should neither contract nor expand by
heat, and would therefore form an invariable pendulum*."

In constructing this pendulum, care has been taken to ex-
clude every thing which could interfere with its principle, and
the whole of the pendulous portion, from the point of suspen-
sion downward, is continuously of marble, without the interven-
tion of mgtal, and even the convenience of an adjusting screw
at the bottom has been sacrificed to insure this. A method of

* Some experiments made since this paper has been read, seem to shew, that a
rod of Carrara marble, on being measured at 32° and at 21 1° Fahrenheit, will be
found to have expanded 5?§0. A rod of Lucullite marble, y gg0.

xx2

350 Notice regarding a Time* Keeper in the Hall

adjustment has been substituted, which has the advantage of be-
ing applied without stopping the vibrations.

If experience shall confirm the accuracy of Mr Mitscher-
lich's experiment, and verify Dr Brewster's inference from it,
an important advantage will have been gained by this applica-
tion, as a pendulum invariable in its own nature, must have a
great superiority over a compensation one, which, however well
adjusted to isochronism under differences of temperature, when
all its parts are affected simultaneously, must always be liable to
derangement from partial currents and changes. The small ex-
pense at which such a pendulum can be procured, would, in that
case, lead to making good time-keepers come into more general
use.

The last peculiarity which I shall notice is of less import-
ance than those above mentioned, but, nevertheless, merits some
remark, as it tends to obviate another cause of irregular action in
the mechanism of time-keepers, viz. the gradual accumulation
of dust in the interior of the case. In order to understand
the utility of the contrivance which has been resorted to, to
prevent this, it is necessary to explain the way in which the ac-
cumulation of dust takes place. If a clock-case be closed up
when the air of the apartment is of a medium temperature, air
will be drawn into the case through the readiest apertures, as
soon as a diminished temperature causes a contraction of bulk in
the included air* The air which enters will carry with it a por-
tion of the dust which is always floating (as we see distinctly
when a sunbeam shines through a small aperture into a dark-
ened room). This dust is soon deposited, from the comparative
stillness of the air within the case, and when, by increase of tem-
perature, air is pressed out of the case, it leaves the dust behind
it ; by which means a small addition is made to the quantity of
dust in the case every time a contraction takes place, and thus,
in process of time, the action of the mechanism is impeded by

of the Royal Society of Edinburgh. 851

the accumulated deposit. To prevent this process taking place
here, the case has been made carefully air-tight against mode-
rate pressure, excepting in one place, where a short tube is fixed
in an opening from which it projects externally about two inches.
On this projection a half distended air-bag is made fast * It
follows from this arrangement, that when a contraction takes
place within the case, the pressure of the external air will com-
press the bag, and make a portion of its contents enter the case
to make uj5 for it; and when, on the contrary, an expansion
takes place, the expressed air will enter the bag and distend it ;
in this way, if the capacity of the bag be great enough, no fo-
reign air (if it may be so termed) can enter the case, but the
equilibrium will be kept up by a circulation of the same air be-
tween the bag and the case, Hke the mercury in the basin and
tube of a barometer, and no dust can ever be added to the quan-
tity originally shut up with the clock. It is evident that this
must conduce essentially both to regular performance and to the
durability of the clock, and as the application of the contrivance
occasions little expense or inconvenience, there is no reason why
it should be omitted in any observatory clock-case.

* The air-bag is concealed within the pediment of the top of the clock-case.

1

( 352 )

XXIlOn Asbestos, Chlorite, and Talc. By Thomas Thomson,
M. D., F.R.SS.L. & E. &c, Regius Professor of Chemistry in
the University of Glasgow.

(Read \6th February 1999.)

J\I ot withstanding the great progress which Mineralogy has
made of late years, towards the division of minerals into accu-
rate and well defined species, there are several groups which
occur in the oldest mineral systems extant, and which have con-
tinued to the present time with very little alteration or improve-
ment. I allude to the minerals classed under the names of As-
bestos, Chlorite, and Talc. As these minerals, with the excep-
tion of certain varieties of talc, have never been observed in
crystals, the important labours of the crystallographer have not
been able to throw any light upon them. But, as all mineral
species are chemical compounds, and as each species consists of
1lie same constituents united in the same proportions, I thought
it not unlikely that an accurate chemical analysis of the different
varieties of minerals, at present classed under the names Asbes-
tos, Chlorite, and Talc, would be likely to throw considerable
light on their nature, and would inform us whether they consti-
tute peculiar mineral species, or are only varieties of species
already well defined and characterized. I propose, in this paper,
to give an account of the result of this investigation.

Dr T. Tnousov an Aebestus, Chlorite and Tale. 858

I. ASBESTUS.

Asbestos was known to the ancient*. Pliny gives a pretty
long account of it- He says, that a " kind of linen is found,
which is not consumed by the fire. It is called Vivum, and we
see table-cloths of it heated red hot in the fires of convivial par-
ties, and the stains being thus burnt oflj they lode much cleaner
than they could have been made by means of water. Such
pieces of cloth are employed to wrap up the bodies of kings, be-
fore they are placed on the funeral pile, and thus separate the
ashes of the dead body from those of the fuel. This flax is
produced in the deserts of India burnt up by the sun, where no
rain falls, amidst direful serpents. It becomes accustomed to
live by burning. It k rarely found, and is difficult to weave on
account of the shortness of the threads*." Pliny mentions (he
amianthus among stones, says it resembles alum, and that it
loses nothing in the firef. Agricola, in his fifth book, De
Natura Fossilium, gives a long account of it, chiefly taken from
the ancients ; but he informs us, that it existed in his time in
great abundance in the mines of Noricum, and that it could
therefore be obtained at a very cheap rate.

Konig, in his Regnura Minerale, published in 1687, gives a
description of amianthus, and says, that it is rendered fit for
being spun into thread, by being boiled for a quarter of an hour
in an alkaline leyj:. In the first edition of Linnjkus's Systema
Natura, published in 1736, amianthus, asbestos, talcum, and mica,
constitute the four subdivisions of the order Apyrse. Cron-
stedt, in his Mineralogy, first published in 1758, introduced the
same minerals under the division Terra Aebeetinff. Bergman

* Lib. xix. cap. 1. f Lib. xxyi. cap. 19. \ P. 120.

354 Dr T. Thomson on Asbestos, Chlorite, and Tak.

subjected a good many varieties of asbestus to a chemical ana-
lysis, shewed that they were not composed of a particular earth,
but that they all contained magnesia, and therefore arranged
them under Magnesian Earth * This arrangement was followed
by Werner, and has in consequence passed into almost all the
modern systems of mineralogy.

There are usually reckoned five varieties or subspecies of As-
bestus ; namely, Amianthus, Common Asbestus, Rock-wood,
Mountain Leather, and Mountain Cork.

1. Amianthus.

As a specimen of amianthus, I chose a variety from
very like the well known Corsican amianthus, which is suffi-
ciently pure, and so abundant, that Dolomieu made use of it
for packing his minerals. It is composed of very fine threads of
considerable length, and easily teased from each other. Its lustre
is silky, it has a greenish-white colour, is very soft, and has a
specific gravity of 1.551. Its constituents, analyzed in the usual
way for treating magnesian minerals, were found to be as follows :

Silica, . . . .
Magnesia, . . .
Lime,

Protoxide of iron,
Alumina, • . .

55.908

27.068

14.682

6.528

1.820

105.956

or 35 atoms,

. . 13£ atoms,

5 atoms,

2 atoms,

1 atom.

We see from this analysis, that amianthus contains four

# Opus. iv. 160.

Br T. Thomson an Asbestus, Chlorite, and Talc. 355

bases, all of which are in combination with silica. The atoms
of silica being 85, and those of the bases only 21£, it is clear
that some of the bases must be in the state of simple silicates,
and others in that of bisilicates. If the magnesia be a bisilicate,
while the lime, protoxide of iron, and alumina, are simple sili-
cates, then all the atoms, both of the silica and bases, will be in
combination. So that we might consider amianthus as compo-
sed of,

13£ atoms bisilicate of magnesia,
5 atoms silicate of lime,
2 atoms silicate of iron,
1 atom silicate of alumina.

But, if we compare the constituents of amianthus with the
numerous analyses of amphibole given by Bonsdorf, in his in-
structive paper upon the chemical constitution of that compli-
cated mineral species, we cannot avoid seeing a very close re-
semblance. Now, pure amphibole is composed of C S8 + 3 M Sf .
But it would appear from the researches of Bonsdorf, that
part of the silica is occasionally replaced by alumina, and part of
the magnesia by protoxides of iron and manganese. If we ad-
mit these substitutions in the present case, we shall have,

36 atoms of silica and alumina,
15.5 atoms magnesia and protoxide of iron,
5 atoms lime.

This is equivalent to,

7.2 atoms silica and alumina,

3 atoms magnesia and protoxide of iron,

1 atom lime.

VOL. XI. part II. y y

356 Dft T: Thomson on Asbestos, Chlorite, and Tab.

The ratio between the lime and magnesia is the same as in
amphibole ; but there is a deficiency of silica amounting tQ 1 .8
atoms. But I believe that deficiency of silica to be only appa-
rent, and to be owing to the excess of 6 per cent, in the weight
of the constituents. Such an excess is very apt to take place in
the analysis of magnesian minerals, and is chiefly owing to the
formation of certain double magnesian salts, unless great care be
taken in precipitating the magnesia. I generally precipitate
the magnesia by carbonate of soda, and, after boiling the mixture
for some time in a flask, to drive off the excess of carbonic acid,
evaporate the whole to dryness in a porcelain, dish. The mag-
nesia remains when the residue is washed with water. This
magnesia is edulcorated, dried, heated to redness, and weighed.
Now, I generally begin my analysis of magnesian minerals, by
adding to thfe muriatic solution (formed after fusing the portion
of pounded mineral, subjected to analysis with carbonate of soda,
and getting rid of the silica), a quantity of bicarbonate of potash,
which throws down the alumina and oxide of iron, but retains
in solution the lime and magnesia. This method was first prac-
tised by Vauquelin, during his analysis of the chrysolite. After
numerous comparative trials I adopted it as the most effectual
method of freeing the magnesia from alumina, and have accus-
tomed my practical students to employ it in their analyses of
magnesian minerals. The only objection to it is, that unless
care be taken, a double, carbonate of potash and magnesia is apt
to be obtained, instead of pure carbonate of magnesia, as was
first pointed out by Berzelius. If we allow the formation
of a little of this double salt in the preceding analysis, then the
constituents of amianthus will agree exactly with those of some
varieties of amphibole. We may represent it as consisting o£

CS' + 8(M,C)*[r

Djl T\ Thomson on Abestus, Chlorite, and Told 357

Amianthus, then, appears noil tcf constitute a particular species,;
but to be' merely a variety of amphibole.

2. Amianthus, from Bleyberg, in Carinthia.

This variety has a greenish-white colour. Its lustre is some-
what silky, but less so than the preceding variety. It feels soft
and unctuous, and consists of fine threads, which are flexible,
but too easily broken to be capable of being spun into threads.
It is opaque, and its specific gravity is 1.899. Its constituents
were found to be,

Silica, ....... 52.512

Magnesia, 19.112

Protoxide of iron, . . 18:652

Lime, 7.960

Alumina, 4.808

Water, 4.080

* 0

102.124

This is equivalent very nearly to

r

•

58 atoms silica,
17 atoms magnesia,

6£ atoms protoxide of iron,

5 atoms lime,

4| atoms alumina,

8 atoms water.

• *

Now, if we make an allowance for a slight over estimate of
the quantity of magnesia, indicated by an excess of 2£ per cent,
in the analysis, we shall find that these constituents may be

Yy 2

358 Da T. Thomson on Asbestus, Chlorite, and Talc.

made to come under the formula for amphibole. We must ad-
mit the alumina to replace a portion of silica ; and the protoxide
of iron partly to replace lime, and partly magnesia : 1£ atoms
replacing lime, and 5 atoms magnesia. The formula will be

(Ci/)8l+8(Mf/)5[rf+liAy.

This variety of asbestus, then, like the preceding, is an am-
phibole. The water is probably only mechanically mixed, and
not a chemical constituent of the mineral.

8. Asbestus, from Irkutzky, in Siberia.

This specimen had a yellowish-white colour. It was com-
posed of long straight fibres, grouped together so as to give the
mineral the appearance of a congeries of imperfect prisms, in-
clined irregularly to each other.

The fibres were easily separable from each other. They were
not elastic, and might be bent somewhat ; but were too frangible
to admit of being converted into threads. It is this want of
flexibility, together with a greater specific gravity, which consti-
tutes the principal distinction between common asbestus and
amianthus.

Opaque or nearly so.

Soft enough to be scratched by the nail.

Streak white.

Specific gravity 2.888.

The constituents of this mineral, found by analysis, were as
follows :

Dr T. Thomson an Aibertus, Chlorite, and Talc. 359

Silica, 58.804

Magnesia, 2&S26

Protoxide of iron, . . 9.479

Lime, ...... 5.926

102.445'

* This is equivalent to

34£ atoms silica,
IS atoms magnesia,

2£ atoms protoxide of iron,

2 atoms lime.

If we allow a small surplus of magnesia, indicated by the ex-
cess in the analysis, it is evident that the atoms of silica are just
double those of the bases, so that the mineral must consist of
bisilicates. It would appear at first sight, therefore, to differ
essentially from amphibole, which consists of C Ss + 8 M S*. But
the analogy between the constituents and those of amphibole is
striking. And, if we were allowed to consider about 1 atom of
the protoxide of iron to be accidental, and the rest to replace
the lime, we would have

(C,/)S8 + 3MS',

which constitute the constituents of amphibole. I am disposed,
therefore, to consider the common asbestus, of which the mine-
ral analyzed was a specimen, as constituting a variety of amphi-
bole ; and in this respect agreeing with amianthus.

300 Db.T Thomson on Asbestus, Chlorite, and Talk,

4. Aebeetous Rode, from the Island of Bernera.

The colour Was light green. The mineral was composed
of fibres, having some breadth, and running in general longi-
tudinally, though rather irregularly. When examined by a mi-
croscope, it appears to consist of white and green coloured fibres
alternating ; the lustre of the green fibres being glassy, and
that of the white silky. Perhaps these appearances may be
owing to different sides of the fibres presenting themselves to
the eye.

Scratched by the nail.

Opaque, or nearly so.

Feels rather harsh to the touch.

Streaks white.

Specific gravity 2.984.

On being subjected to analysis, its constituents were found
to be as follows :

Silica,

Magnesia, . .

Lime, ....

Protoxide of iron,

Alumina, . •

Protoxide of manganese, 0.280

Moisture, 0.250

56.480

23.256

13.636

4.098

0.516

98.466

Dr T. Thomson on Asbestus, Chlorite, and Tak. 861

This is .equivalent to

21 1 atoms silica,

7.2 atpips magnesia,

3 atoms lime,

0.7 atom protoxide of iron,

0.05 atom protoxide of manganese,

0.17 atom alumina.

If we take the protoxides of iron and manganese along with
the magnesia, it is evident that the atoms of magnesia are al-
most three times as numerous as those of lime. So far there is
an agreement between the composition of the Bemera asbes-
tus and amphibole ; but there is a slight deficiency in the silica,"
even if we add to it the alumina which the mineral contains.'
For, if we divide the atoms just given by three, we have,

1 atom lime,

2.65 atoms magnesia, protoxide of iron and manganese,

7.3 atoms silica and alumina.

• 4

But, to judge of the deficiency accurately, we must take a lit-
tle of the lime, and add it to the magnesia, that the atoms of
magnesia may be thrice as many as those of lime. This will
give us

1 atom lime,

3 atoms magnesia, lime, and protoxide of iron and manganese,

8 atoms silica.

* - 1 * ■ *

To form tersilicate of lime and bisilicate of magnesia, we would
require 9 atoms of silica and alumina ; while the. mineral con-
tains only 8 atoms. So that, to constitute

862 Dr T. Thomson on Asbestos, Chlorite, and Tak.

CSs + 8(M,C,/ro»)S'

there is 1 atom of silica wanting.

In all probability the mineral analyzed was a mixture of am-
phibole and some other magnesian mineral, containing a smaller
proportion of silica.

5. Rock-Wood.

The specimen selected for analysis was from the Tyrol. It
had much of the aspect of common asbestus. The colour was
yellowish-brown ; the texture was distinctly fibrous ; and the
fibres, from their disposition, gave the mineral a good deal of re-
semblance to wood.

Opaque, soft. Specific gravity, 2.724.

Its constituents were found to be,

Silica, ....

54.920

Magnesia, . . .

26.084

Protoxide of iron,

12.600

Alumina, . . •

1.640

Water, ....

5.280

100.524

is equivalent to

76 atoms silica,

29 atoms magnesia,

7| atoms protoxide of :

iron,

2 atoms alumina,

13 atoms water.

Dr T. Thomson on Agbestus, Chlorite, and Talc. 863

The first remarkable circumstance in this mineral is the total
absence of lime. Almost all the varieties, both of amphibole and
pyroxene, have been analyzed in my laboratory ; and we have
an ample collection of both analyzed by Bonsdorf and Rose ;
and not one of either has been met with that did not contain
lime as one of its constituents. I think, then, that we are en-
titled to consider lime as an essential constituent of both of these
species. If so, the specimens of rock-wood which I analyzed,
can neither be an amphibole nor a pyroxene.

The atoms of the bases added together make 38.75, and the
atoms of silica are 76. Now, 38.75 x 2 = 77.5. It would ap-
pear from this that rock-wood is composed of bisilicates.

Farther, the atoms of magnesia and alumina, taken together,
amount to 31, which is just equal to 7.75 (the atoms of pro-
toxide of iron) X 4. Hence the constituents would seem to be

4 atoms bisilicate of magnesia with alumina,
1 atom bisilicate of iron.

The water is 1^ atom ; but the £ atom may be considered as
owing to the presence of water mechanically lodged in the in-
terstices of the fibres. According to this view of the constitu-
tion of the mineral, it may be represented by the following sym-
bol:

4(§M^A/)S'+/S'+1A<?.

The mineral which resembles rock-wood most closely in its
constituents, is hyalosiderite, discovered by Dr Walchner, in an
amygdaloid in the Kaiserstuhl, near Sasbach, in Brisgau, and
which is crystallized in octahedrons with a rectangular base.
But hyalosiderite coritaihs less silica, much more protoxide of
iron, and rather more magnesia. Its symbol being

VOL. XI. PAKT ii. z z

364 Dr T. Thomson an Asbestos, Chlorite, and Talc.

SMS-f/'S.

In the present state of our knowledge we cannot avoid con-
sidering rock-wood as a distinct species. All my specimens of
rock-wood being from the same locality as the one subjected to
analysis, no farther light would have been thrown upon the sub-
ject, by multiplying analyses.

6. Mountain-Leather.

The specimen of this well known mineral, which I selected
for examination, was from the lead-mine of Strontian, where it is
pretty frequently, met with. The colour was light buff. It was
composed of exceedingly fine flexible threads, felted together
like a hat, and not capable of being separated from each other.

Feel very soft ; quite flexible, but tough ; imbibes water
very readily, and then assumes very much the appearance of wet
leather.

Opaque,

Specific gravity 1 .834.

Before the blowpipe, curls up and fuses easily into an opaque
bead. Fuses with carbonate of soda into a transparent yellow
bead* Melts with borax into a colourless transparent glass.

Its constituents were found, by two very careful analyses, to
be the following :

Silica, 51.650

Alumina, . . 9.505

Lime, 10.005

Magnesia, 2.065

Protoxide of iron, with some manganese, . 5.805
Water, 21.700

100.780

Br T. Thomson on Asbestus, Chlorite, and Talc. 865

It is obvious at first sight that this mineral is quite distinct
from amianthus, asbestus, and rock-wood ; for it is almost desti-r
tute of magnesia, which in all of them constitutes the most
abundant of the bases.

It is not easy to decide whether the water which exists in
such abundance in mountain-leather, be chemically combined or
not ; for it imbibes water as readily as a sponge. It was kept
in a dry room, till it ceased to lose any more weight, and in this
state was subjected to analysis* When exposed to redness, it
altered its appearance very much, and no longer bore its former
resemblance to leather. I am disposed, from this, to admit wa-
ter as a chemical constituent of this mineral.

The constituents of mountain-leather are equivalent to

80 atoms

1 3 atoms alumina,

9 atoms lime,

2 atoms protoxide of iron,

1£ atom magnesia,
60 atoms water*

The four bases taken together amount to £5& atoms, while
the silica amounts to 80 atoms ; therefore the alumina and lime
must be combined each with three atoms of silica, while the
protoxide of iron and magnesia must be in the state of quater-
silicates.

Farther, the atoms of quatersilicates being 3£, while those of
tersilicates are 21, it is obvious that there exist in the mineral
6 times as many atoms of tersilicates as of quatersilicates. For
3.5x6 = 21.

The ratio of 1£ to 2 is the same as that of 3 to 4 ; and that
of 9 to 13 approaches very nearly to the same. Hence the

z z 2

366 Dr T. Thomson on Asbestos,; Chlorite, . and . Talc.

constitution of mountain-leather may be represented by the fol-
lowing symbol :

6 (fC + *A/) S3 + (*M + tf ) S< + 17Ag.

• #

It is obvious that it constitutes a distinct mineral species.

7. Mountain-Cork.

* «

/ The specimen of this mineral, selected, for analysis, was from
Piedmont; but I do not know the exact locality.

Its colour was . light buff : it was . composed of fibres so fine
as to be scarcely visible before a common magnifying glass.

It was soft enough to be indented by the nail : it had the
same elastic feel which characterizes. common cork.

Lustre silky ; nearly dull ; opaque ; very tough. Specific
gravity 2.442.

Before the blowpipe fuses into a black glass. When heated
to redness it loses 1.2 per cent, of its weight, which; is pure wa-
ter, and assumes a dark brown colour.

Its constituents, after ignition, were found to be as follows :

» * •

Silica, . . .... 51.75

Lime, ......... . .. 14.05

Magnesia, 10.85

Protoxide of iron, . • > 18.90 •
Alumina,'; . . . . . 1.95
Protoxide of manganese, 1 .85

99.35

. •

Da T. Thomson on Asbestos, Chlorite, and Tale. 867

This is equivalent to

SO atoms silica,
4.5 atoms lime,
5 atoms magnesia,
4.5 atoms protoxide of iron,
1 atom alumina.

• i

The atoms of the bases amount to 15, and those of silica to
30. Hence it is obvious that the mineral is composed of bisili-
cates. If we admit a little of the lime and of the protoxide of
iron to be replaced by alumina, then rock-cork will be a com*
pound of

1 atom bisilicate of lime,
1 atom bisilicate of magnesia,
1 atom bisilicate of iron.

Its symbol will be CS" + MS* +/S*.

It is therefore most probably a variety of pyroxene.

If any confidence can be placed in the preceding discussion,
it follows that the minerals hitherto arranged as subspecies of
asbestus, constitute in reality four distinct species.

1 . Amianthus and common asbestus are varieties of am-
phibole.

2. Rock-wood is 4.(§M + JjA/) S' +/S* + \Aq.

• *

* *
8. Mountain-leather 6 (jfi + yA/) Ss + Qm + 1/) S4

+ 17 Aq.

»

4. Mountain-cork is a variety of pyroxene.

• t ♦ r

• t

I

368 Dr T. Thomson on Asbestos, Chlorite, and Tate.

8. Nemalite of Nutall.

For the specimen of this mineral which I subjected to ana-
lysis, I am indebted to the kindness of Professor Nut all. It
occurs in veins in the serpentine rocks of Hobpken, New Jersey,
and had always been taken for a variety of amianthus, till its
real nature was determined by Mr Nutall *.

. Its colour i* white, with a slight shade of yellow, or some-
times of blue. It is composed of long straight fibres, easily se-
parable, and bearing a close resemblance to asbestus.
. Soft enough to be scratched by the nail of the finger.

Specific gravity 2.353.

Opaque, or only slightly translucent.

When exposed to a red heat it assumes a brown colour, re-
tains its fibrous texture, but becomes friable, and easily reducible
to powder. By this treatment it loses 29*66 per oent. of its
weight. The matter driven off is pure water.

It dissolves in nitric acid, without effervescence, leaving be-
hind a little silica.

By a careful an&lysis I found its constituents as follows :

Magnesia, . . . ... 51.721

Silica, 12.568

Peroxide of iron, . . 5.874

Water, 29.666

+*0mm+^

This is equivalent to

99.829

104 atoms water,
25 atoms silica,

4 atoms peroxide of iron,
83 atoms magnesia;

* See Sillimax's Journal, iv. 19.

Dr T. Thomson oh Asbestos, Gdorite, and Tale. 369

The water, silica, and peroxide of iron, are probably all com-
bined with the magnesia, constituting in all probability

5 atoms silicate of magnesia,
1 1 atoms bihydrate of magnesia,
1 atom ferrate of magnesia.

Were we to consider the peroxide of iron as replacing a por-
tion of silica, the constitution of nemalito would be

1 atom silicate of magnesia,

2 atoms bihydrate of magnesia; an4 its symbol would be

MS + 2 MA?2.

Nemalite, therefore, constitutes a taew species of magnesian
minerals, which may be distinguished by the name of hydro-sili-
cate of magnesia.

The marmolite of Nutaix, found in the same place with his
nemalite, would seem, from the analysis of Notall, to be a hy-
drous silicate of magnesia, composed of MS -f- 1 Aq. But I find,
bya careful analysis of some specimens of it, for which I am in-
debted to the kindness of Professor Nutall, that its composi-
tion is exactly the same with the picrolite of Haussman, or the
precious serpentine of other mineralogists. Precious serpentine
is composed of

1£ atom silica,
1 atom magnesia,
1 atom water ;

Or it is a hydrous sesquisUicate of magnesia.

■370 Dfe T. Thomson on ■ AtbestUs, Chlorite,

II. CHLORITE.

«

The name Chlorite was first introduced into mineralogy by
Werner, and applied by him to a mineral, which preceding
mineralogists had confounded with mica, and which Hauy after-
wards considered as a variety of talc

I employed, as a specimen of chlorite for analysis, a very
pure piece of common chlorite from the Isle of Bute.

Its colour was very dark green. It was composed of very
small scales, attached to each other without any visible cement.
These scales were so small, that I could not distinguish their
shape by means of a common magnifying-glass. Streak light-
green.

Opaque. Soft enough to be scratched by the nail.

Lustre silky, approaching to resinous.

Sectile. Easily frangible.

Specific gravity 2.828.

Its constituents were found to be as follows :

Silica,

, . 27.634

Protoxide of iron, .

. . 27.544

Magnesia, . . .

. . 10.960

Water, . . .

. . 9.160

98.996

equivalent to

•

16 atoms silica,

7 atoms protoxide of in

on,

12 atoms alumina,

5 atoms magnesia,

9 atoms water.

This is equivalent to

Da T. Thomson on Asbestos, Chlorite, and Tak. 371

It is obvious at once that chlorite differs essentially in its
chemical constitution from all the varieties of asbestus. For
the atoms of silica are to the atoms of the bases, with which it
must be united in the mineral, as 2 to 3.

Chlorite is a compound of three subsesquisilicates* and, if we
suppose the subsesquisilicates of iron and magnesia to be pre-
viously in combination with each other, before they united to
the subsesquisilicates of alumina, the symbol for chlorite will be
as follows :

&

a/*s+(£m + £#*s + ia*

Common chlorite, then, appears to constitute a peculiar mineral
species. *

2. Chlorite Earth.

The specimen of chlorite earth, which I selected for analysis,
was given me many years ago by the Rev. Mr Headrick of
Dunnichen. He had picked it up somewhere in the Highlands
of Scotland, but I am not sure of the locality. It consisted of
small brown-coloured loose scales, having a silky lustre and a soft
feel. The specific gravity was 2.801. The constituents, after a
very careful analysis, which was twice* made, were found to be as
follows :

Silica, 48.166

Alumina,* ..".*•". 16.851

Peroxidedof iron, " .* . 19.100

Potash, *...•.'. 6.558

Magnesia, .... 2.916

Lime, 2.675

Water, 2.850

98.616

VOL. XI. PART II. 3 A

372 Dr T. Thomson on Asbestos, Chlorite, and Talc

A little lead was found in the scales, which was obviously a
foreign substance. It was separated with much care ; though
it is not impossible that it may have affected die weight of some
of the constituents a little. From the care taken to separate
the lead, and from the repetition of the analysis, t believe that
the error resulting from it, if any, must be very trifling.

It is obvious at first sight, that the constitution of this mine-
ral is quite different from that of chlorite. I believe it to be a
variety of rhomboidal mica. From the analysis of mica by Kla-
proth and Rose, there cannot be a doubt, that at least three dif-
ferent species of mineral are at present confounded together
under the name of' ftiica. One of the most common of these
species crystallizes in oblique rhomboidal prisms, with the fol-
lowing angles :

P on M" 98° 4CT,
P on M 81° 20',
M'onM60°.

i

*

I analyzed a very pure crystallized mica of this ki
United States, and found its composition as follows ;

Silica, . 49.380

Alumina, ..... 23.668

Protoxide of iron, . . 7.812

Lime, ... . . , 6,134

Potash, . ' . . . . 15.292

iithia, ... . . . 0.060

101.846

% . ...

Dfc T. Thomson tm Asberfu*, Chlorite, and Tale, 373
This is equivalent to

»

SO atoms silica,
18 atoms, alumina,

3 atoma protoxide of iron,

aatoaelime,

3 &tojna peftash.

It is obvious that the atoms, of silica are to those of the bases as
3 to 2. Henoe all the bases must be in the .state of sesquisili-

cates.

■ » . *

From the analyses of K&apro-tp and Rose, it appears, that
as the protoxide of iron in mica increases the alumina diminish-*
es. If we take the atoms of alumina and protoxide of iron to-
gether, as also those of potash and lime, they are to each other
as S to 1. We may therefore consider the constitution of rhom-
boidal mica to be

The atomic coi^tit^eiit^ of pie chloritp earth are obviously*

24 atoms silica,
7i; atoms alumina,
4" atoms peroxide of iron,
1 atom potash,
1 atom magnesia.
1 atom lime.

Now, these proportions of silica and bases approach those of sesh
quisilicates. The mineral appi

WM\\~\

* GSr* + i^O s" + O + tM + 1 c) s1'

It belongs, therefore, to rhomboidal mica. Whether this be the
constitution of all the varieties of chlorite earth I do not know.

3a2

374 Dr T. Thomson on Asbestos, Chlorite, and Tak.

III. TALC.

The terms Talc and Mica seem originally to have been ap-
plied indifferently to the same minerals ; namely those which
could be split into thin layers or plates. When the plates were
large, the mineral was called Talc, when they were small it was
called. Mica. Common talc, or Venetian talc as it is called, .seems
first to have been constituted a peculiar species by Werner.
Cronstedt has considered it as, a variety of mica. Hau y, in the
first edition of his Traits de Mineralogie, published in 1801, ar-
ranged under talc several other minerals that are probably dis-
tinct species ; namely, Chlorite, Agalmatolite, Steatite, &c.

1. Venetian Talc.

<

This mineral is found imbedded in serpentine, in the moun-
tains of Saltzburg and the Tyrol, and was formerly carried to
Venice as an article of commerce, being employed in medicine.
Hence the name Venetian Talc. It was chiefly employed as a
cosmetic. It was reduced to & fine powder by heating it to red-
ness, and afterwards pounding it in a hot mortar.

Colour apple-green, It is composed of thin flexible plates,
having a silvery appearance and a pearly lustre, and easily sepa-
rable from each other. These plates are not elastic. It varies
from semitransparent to translucent. Very sectile. Soft enough
to be scratched by the nail of the finger. Specific gravity 2.697.
Infusible before the blowpipe per se.

I have never seen a specimen of true Venetian talc in crys-
tals.

A very pure specimen of this mineral being subjected to ana-

i

j

Da T. Thomson on Asbestos, Chlorite, and. Talc. 375
lysis, the constituents were found to be,

t ■

Silica, . . . . . . 62.588

Magnesia, . . . . « 30.828

Protoxide of iron, . . 8.848

Water, . . . . ' . 8.400

100.864

•

This is equivalent to,

5.21 atoms silica,
2 atoms magheaia,

0.14 atoms protoxide 6f iron;
0.5 atoms water.

If we allow for the presence of a small quantity of bisilicate of
iron (probably accidental), thlc' mfcy be considered as composed
of

• *

• A

£ atoms silica, .
& atoms magnesia.

• * * i * . *

It is, therefore, "a compound of,

#

1 atom bisilicate of magnesia,

1 atom tersilicate of mAghesia. -

Thus its chemical constitution differs from that of every other
mineral hitherto examined. Venetian talc, then, is entitled to
rank as a distinct mineral species.

376 Db T. Thomson on Asbestos, Chlorite, and Tak*

% Talc-Slate.

The mineral called Talc-Sfate is obviously closely allied to
Venetian talc ; though there are many particulars in which the
external characters of the two differ. *

The specimen whi^h I selected for analysis was from Novar-
da in Piedmont.

Its colour was white, with a slight shade of yellow. Massive
and slaty. Composed of impalpable particles without any cleav-
age. Fracture flat conchoidal. Opaque, or only translucent
on the edges. Sectfkk • Luatpe silky. Hardness about the
same as that of gypsum. Specific gravity $J

Its constituents were found to be,

» •. ■ i •

•» • i

* ,.

. •• , >*

Magnesia,

Protoxide of iron.
Water, . * .

». *

m • •

♦ « ' ••

57*560
37,216
7.^44
4.7S0
4;716
1,600

100,756

This is equivalent to,

5 atoms silica,

2 atoms magnesia,

0.21 atom silica,

0.41 atom lime,

0.14 atom alumina,

0.19 atom protoxide of iron,

0.25 atom water-

X>b T. Thomson on Asbetfu*, Chlorite, and Tok> 877

It is obvious at once, that talc-slate consists essentially of
MS8 + MS3 ; but that it is mixed also with a small quantity of
silica, lime, alumina, protoxide of iroii, and water. These bodies,
in all probability, are not. chemically combined, but merely me-
chanically mixed with the pure talc ; thus disguising its exter-
nal character somewhat. The slight difference in the specific
gravity probably depends upon the laminated texture of the talc.

3. Pvtefime from Sweden.

I got the specimen which I subjected to analysis from my
friend Mr Lora*o of Gottenburg. It was polished, which pre*
vents me from describing its characters with much accuracy.
When examined with a glass, it exhibited a mixture of small sil-
very plates, like talc, and black-looking crystalline grains. It
was opaque ; the hardness nearly that of talc ; the specific gra-
vity 2.88. It was sectile, and bore a considerable resemblance
to a mineral which I have seen described by the Wernerians un-
der the name of CMtfite-slate. Its constituents were as follows :

Silica, 49.01

Magnesia, 80.20

Protoxide of iron, . ♦ 11.40
Alumina, 6.08

Water, • ■ * 4.20

•»

100.89
This is equivalent to,

5 atoms silica,
2£ atoms magnesia,

£ atom protoxide of iron,

£ atom alumina,

£ atom water.

378 Dr T. Thomson on Asbestus, Chlorite, and Talc.
Thus the composition of Swedish potstone is,

2 atoms talc + 1 atom magnesia,

+ 1 atom protoxide of iron,
+ 1 atom alumina,
-f- H atom water.

It is probable that the black crystalline grains were composed
o£

1 atom magnesia,

1 atom alumina,

1 atom protoxide of iron.

»

They constitute, therefore, a new mineral species. But I found
it impossible to separate them from the white portion of the mi-
neral apparently constituting the talc, or to subject them to a
separate analysis.

Swedish potstone would seem, from the above analysis, to be
a mixture of pure talc and of a black' mineral hitherto unex-
amined.

4* Hexagonal. Tak.

The mine™! which i subject* Jo ^ya* wa, from AU in
Piedmont. It constituted large six-sided plates in a granular
stone, usually distinguished by the name of granular talc.

The colour of the crystals was dark green. The texture fo-
liated. The crystals had the appearance of very short regular
six-sided prisms, about an inch. in diameter, but the edges were
not smooth nor well defined ; which prevented the possibility
of measuring the angles.

Streaks white. Soft enough to be scratched by the nail.
Specific gravity 2.772.

Dr T. Thomson on Asbestos, Chlorite, and Talc. 379

The constituents of these crystals ware found to be as fol-
lows :

Silica, • • . .
Alumina, . . ♦
Lime, • . . .
Magnesia, . .
Protoxide of iron,
Water, . . •

29.364
17-808
3.092
12.144
26.016
11.200

99.624

If we allow a little of the magnesia in this mineral to be re-
placed by lime, we have its atomic constituents as follows :

5 atoms silica,

■■ atom, magnesia with lime,

2 1 atoms alumina,

2 atoms protoxide of iron,

2£ atoms water.

The silica and magnesia exist in the same proportions as in
talc. But more than half the weight of the mineral consists of
alumina and protoxide of iron and water. The probability is, that
these crystals consist essentially of talc ; but so much contami-
nated with foreign matter as greatly to disguise the characters
of the mineral.

5. Indurated Talc.

The specimen of indurated talc which I selected for analysis
was from Sweden, but I do not know the locality.
Its colour was light bluish-green.

VOL. XI. PART II. 3 B

380 Dr T. Thomson an Asbestus, Chlorite, and Talc.

The texture was foliated and curved, and the folia were ra-
ther thick.

Lustre pearly, or between pearly and resinous.

Slightly translucent on the edges.

Feel soft. Rather sectile.

It does not scratch calcareous spar ; but it scratches sulphate
of lime very readily.

Has an earthy smell when breathed on.

Specific gravity 2.512.

Its constituents were found to be,

Silica, 39.524

Magnesia, .... 35.080
Protoxide of iron, • . 11.528
Alumina, ..... 6.200
Volatile matter (water ?) 8.120

100,452

It is obvious at a glance that this mineral differs entirely in
its contitution from talc. Its atomic constituents are very near-

7 atoms silica,

5 atoms magnesia,

1 atom protoxide of iron,

I atom alumina,

I I atom water.

Hence it consists of simple silicates, and is obviously a com-
pound of,

5 atoms silicate of magnesia,
1 atom silicate of iron,
1 atom silicate of alumina,
1£ atom water.

Da T. Thomson on Asbestus, Chlorite, and Talc. 381

It is undoubtedly connected with the mineral to which the
name of Nephrite has been given. I subjected to analysis the
well known nephrite, found on the shores of Iona, and which ap-
pears to have formed a part of a limestone-bed in that island,
long since wrought out Its specific gravity is 2.595, and its
constituents were found to be,

Silica, 40.7

Magnesia, 48.156

Protoxide of iron, . * 3.528

Water, 13.200

100.584
This is equivalent to *

6 atoms silica,
5 atoms magnesia,
0.2 atom protoxide of iron,
8£ atoms water.

Which may be reduced to

25 atoms silicate of magnesia,
1 atom quintosilicate of iron,
16| atoms water.

While the indurated talc consists of

25 atoms silicate of magnesia,
5 atoms silicate of iron,

5 atoms silicate of alumina,

6 £ atoms water.

Thus the water in nephrite is just thrice as much as in indu-

3b2

382 Dr T. Thomson on Asbestus, Chlorite, and Talc.

rated talc ; but the talc contains a quantity of silicate of iron
and of silicate of alumina, not to be found in the nephrite.

We may consider what has hitherto been called indurated
talc as an impure variety of nephrite.

6. Cornish Talc.

This is a mineral which I got many years ago from Cornwall,
under the name of Talc. The locality was not given ; but I sus-
pect it to have been found in the lode of one of the mines near
St Austle.

It has a white colour, with a slight shade of yellow, and con-
tains interspersed through it grains of dark purple fluor-spar,
and of another mineral which seems to be apatite.

It is composed of small foliated masses, laid upon each other
irregularly. Each of these grains (not above the size of a mus-
tard seed) has an imperfect resemblance to a crystal. I fancy I
can distinguish in some of them the rudiments of octahedrons,
but this may be imagination.

Lustre rather pearly.

Translucent ; sectile.

About the hardness of fluor-spar.

Specific gravity 2.648.

Its constituents, from two careful analyses, are as follows :

Silica, 45.155

Alumina, ..... 40.110

Lime, 4.170

Magnesia, 1.900

Protoxide of iron, . . 2.430

Water, 4.250

98.015

Da T. Thomson on Asbestus, Chlorite, and Talc* 383

It is obvious at first sight, that this mineral has no connexion
either with asbestus, or talc, or chlorite, as it is almost destitute
of magnesia, which constitutes an essential constituent of all
these minerals. The atomic constituents are,

19 atoms silica,
15 atoms alumina,

1 atom lime,

0.6 atom magnesia,

0.4 atom protoxide of iron,

8£ atoms water.

The atoms of silica amounting to 1 9, while those of the bases
are only 17, it is obvious that the lime, magnesia, and protoxide
of iron must be in the state of bisilicates. The constitution of
the mineral may be represented thus :

15 A/S + CS2 + (§M +lf) S* + $Aq.

Thus it appears that the Cornish talc is nothing else than a
hydrous silicate of alumina, mixed or combined with a little bisi*
licate of lime, bisilicate of magnesia, and bisilicate of iron. I
propose to distinguish this mineral by the name of Gilbertite, in
honour of Mr Davies Gilbert, late President of the Royal

Society.

The mineral called Bucholzite, from the Tyrol, imperfectly
described and analyzed by Dr Brandes, is an anhydrous silicate
of alumina. I am indebted to the kindness of Professor Nutall,
for very pure specimens of it from Chester on the Delaware.

Its colour is greyish-white. It is composed of fibres often
curved, and which, when viewed through a microscope, assume
the appearance of flat and rather irregular four-sided prisms.
Lustre silky ; about . the hardness of quartz. Specific gravity
3.193. Infusible before the blowpipe.

384 Dr T. Thomson on Asbestos, Chlorite, and Talc.
I found its constituents to be,

Silica, 46.40

Alumina, 52.92

99.32

So that it is a simple anhydrous silicate of alumina. The
Cornish specimen differs from bucholzite, in containing water,
and in being contaminated with a little bisilicates of lime, mag-
nesia, and iron. Its lower specific gravity and inferior hardness
are probably owing to the presence of water. We may dis-
tinguish it by the name of Hydrous Silicate of Alumina, or Gil-
bert ite.

IV. SOAPSTONE.

The mineral called Soapstone or Rocksoap* occurs in the Pe-
ninsula of the Lizzard, partly in a vein in serpentine at the
Lizzard Point, and partly near Mullyan Churchtown. The co-
lour is greenish-white, or almost white, often mottled with green
and red. The white portion often traverses the red in a kind
of irregular veins. When first extracted from the vein, it is soft,
but when left exposed to the air, it loses part of its moisture ;
becomes translucent on the edges, and harder ; though it is still
soft enough to be scratched by the nail.

Feel unctuous or soapy ; histre resinous.

Sectile : opaque, or nearly translucent on the edges.

I found the specific gravity of a white specimen 2.396 : of a
red specimen 2.411. Both of them had been about sixteen
years in my cabinet.

The following table exhibits the constituents of these two
specimens. The first was mottled red and white, the second
was white, and consequently purest :

Dr T. Thomson on Asbcstus, Chlorite, and Talc. ,385

.• *> •

Silica, .
Magnesia, . . .
Alumina, . . .
Lime, . . . .
Protoxide of iron,
Water, . . . .

42.820

25.680

9.384

4.680

1.083

16.960

100.107

43.884

24.144

9.872

...

...

21.228

99.128

Klaproth's analysis of this mineral approaches very closely
to mine. It is as follows :

Silica, ....
Magnesia, • . .
Alumina, .
Peroxide of iron, .
Potash, . • . .
Water, ....

45

24.75
9.25
1.00
0.75

18.00

98.75

If we calculate from the second of my specimens, which I
consider as the purest, the atomic constituents of soapstone are,

25 atoms silica,
12 atoms magnesia,
5 atoms alumina,
21£ atoms water.

It is obvious, at first sight, that the atoms of silica are to
those of the two bases as 8 to 2. Hence it follows that soap-
QtrmA is o nnmnound of two sesauisilicates, namely of magnesia

* Beitrage, v. 22.

986 Dr T. Tqomson on Asbestus, Chlorite, and Talc.

and alumina, with a certain quantity of water. We may state
the constituents as follows ;

12 atoms sesquisilicate of magnesia,
5 atoms sesquisilicate of alumina,
2l£ atoms water.

«

Soapstone thus constitutes a peculiar species. It resembles
mica, in being a compound of sesquisilicates. But the number
of salts combined in it is much fewer, and mica (at least rhom-
boidal mica) contains no magnesia, which constitutes so conspi-
cuous an ingredient in soapstone.

# *

2. Agalmatolite.

This mineral, which comes from China, usually cut into va-
rious figures, and on that account called figurestone, bildstein,
has been classed along with soapstone, though the resemblance
which it bears to the characters of that mineral is not very close.

Its colour varies considerably ; but that of the specimen
which I subjected to analysis was white, with a shade of bluish-
green.

Lustre waxy and nearly dull. It acquires some lustre in the
streak.

Fracture splintery ; rather sectile.

Translucent ; tough ; feel soft.

Not scratched by calcareous spar ; but readily by fluor-spar.
It seems to have nearly the hardness of calcareous spar.

Specific gravity 2.895.

Dr T. Thomson on Asbestos, Chlorite, and Talc. 387

Its constituents were found to be,

Silica, 49.816

Alumina, 20.596

Lime, 6.000

Potash, 6.800

Protoxide of iron, . . 1.500

Water, 5.000

99.212

with a trace of manganese.

If we calculate the composition of agalmatolite from the pre-
ceding analysis, we obtain,

149£ atoms silica,
71 atoms alumina,
10 atoms lime,

7 atoms potash,

% atoms protoxide of iron,
28 atoms water.

We might therefore consider it as composed o£

35? atoms sesquisilicate of alumina,

5 atoms bisilicate of lime,

8£ atoms tersilicate of potash,

1 atom silicate of iron,
14 atoms water.

From the analysis of Klaproth, and John and Vauquelin,
it is obvious that the lime and oxide of iron are not always found
in agalmatolite. They cannot therefore be essential ingredients.
If we leave them out, and consider the silica united with them
as in combination with the alumina, agalmatolite will be a com-

VOL. XI. PART II. 3 c

388 Dr T. Thomson on Asbestus, Chlorite, and Talc.

pound o£

10 atoms bisilicate of alumina,
1 atom bisilicate of potash,
4 atoms water. -

Agalmatolite approaches most nearly to nacrite in its compo-
sition. It differs by containing 1 atom bisilicate of potash, and
4 atoms water. Nacrite is an anhydrous bisilicate of alumina,
and agalmatolite may be considered as a hydrous bisilicate,
mixed or combined with a little bisilicate. of potash.

I intended in this paper to have investigated likewise the
chemical constitution of Steatite ; but I have already trespassed
so far upon the usual length of papers presented to the Society,
that I think it better to delay that part of the subject to a fu-
ture opportunity.

( 889 )

XXIII. Observations to determine the Dentition of the Dugong;
to which are added Observations illustrating the Anatomical
Structure and Natural History qf certain qf the Cetacea.
By Robert Knox, F. R. S. Ed. and Lecturer on Ana-
tomy.

(Read 18th January 1830.)

Jt he following observations as to the dentition of the Dugong
were made rather more than two years ago, and the inquiry as
to the succession and character of the teeth in this interesting
animal, and as to the exact composition of its skeleton, was then
fully gone into, and all the facts to be now stated proved satis-
factorily to myself at least. Notices of these opinions and facts
more or less perfect, have been in several ways submitted to the
public, both in this country and on the continent ; but, as the
whole matter was in some measure controversial, tending to call
in question the accuracy of a theory as to the dentition of the
dugong, promulgated and supported by an anatomist of the
highest reputation #, I hesitated whether or not the matter to
be discussed merited being brought before this Society. Recol-
lecting, however, that the opinions and statements opposed to
my own views, had found their way into the pages of a work f ,
of such importance and authority in itself, as to impress readily

* Sir Eveeaed Home, Bart. f The Philosophical Transactions.

3c 2

390 Dr Knox on the Dentition of the Dugong, and on the

in the minds of most readers an easy credence as to the exact-
ness of whatever researches there find a place, I hesitated no
longer as to the course to be adopted.

A considerable time ago, Mr Swinton, to whom this Society
owes so many rare and valuable presents in anatomy and zoology,
transmitted to this country the head of an apparently full grown
dugong from the Indian Seas, clothed with all the soft parts, and
seemingly, in every respect, uninjured. Together with the head,
which was preserved in strong spirits, and quite fresh when it
reached this country, Mr Swinton had taken the trouble to for-
ward in like manner to the Society the heart* stomach, and or-
gans of generation, which appertain to the female, from which
one may reasonably conjecture that these preparations belonged
to the same individual, and, if so, that the cranium of the
dugong, now in the possession of the Society, belonged to the
female.

Our Secretary and Treasurer, who do me the honour to
consult me as to the disposal and arrangement of the anato-
mical and zoological presents to the Society, were so kind as to
inform me early of the arrival of these, and to put them at my
disposal, directing me to dissect and prepare them in whatever
way I should deem most fit for the interests of the Museum and
of science.

This communication afforded me the greatest pleasure. I
knew, indeed, that some coarse dissections of the dugong had been
made in this and in other countries, and that a theory as to the

* In the excellent anatomical account of the Lamantin, drawn up by Dauben-
ton merely from a foetus, preserved for some time in spirits, and under great disad-
vantages therefore, that careful observer first discovered and described the bifurca-
tion of the heart, and partial separation of the ventricles of that organ from each
other. A similar structure was afterwards found to exist in the dugong.

Anatomical Structure of certain of the Cetacea. 89 1

dentition of the animal had been brought forward and supported
with great ingenuity by the eminent anatomist and physio-
logist already named, whose labours have contributed so much
to support the cause of comparative anatomy in England ; but I
knew also that something doubtful was mixed up with these re-
sults, notwithstanding their seeming ingenuity ; and I was aware
also, and was the first to point out, long ago, that the osteology
of the dugong, contained in the justly celebrated " Ossemens
Fossiles" had been drawn up from an imperfect skeleton, sent
to its distinguished author by MM. Diard and Duvauceal *.
I felt, therefore, that any well ascertained fact must be a valuable
addition to the history of the animal, and such appeared to me,
whatever observations should result from a careful inspection of

* There are no proofs whatever that there now exists any where in Europe, a
perfect skeleton of the dugong ; by perfect, I mean a skeleton prepared under the
immediate superintendence of an anatomist The engraving of the skeleton in the
Ossemens Fossiles, from which M. Cuviee drew up his account of the osteolo-
gy of this interesting animal, represents it to be without a sternum. Now, it mat-
ters not whether the bones were sent home in this condition to M. Cuviee by the Na»
turaliste Voyageur, or whether the animal reached him entire, preserved in spirits,
or otherwise, and the bones of the sternum were afterwards lost in preparing the
skeleton ; I insist chiefly on the fact, that the skeleton is, from some cause or other,
imperfect. Extensive experience as to those matters has convinced me, that no ske-
leton can be properly prepared and in a way to be entirely depended on, with a view
to anatomical and zoological inquiry, which has not been dissected and prepared un-
der the immediate superintendence of a good anatomist Mr Robison, who did me
the honour to convey personally to M. Cuviee a memorandum from me, containing
an outline of this inquiry, has since informed me that Baron Cuviee assured him
that he now possessed five complete skeletons of the dugong ; they must, of course,
have come into his possession since the publication of the last edition of the " Osse-
mens Fossiles " in 1825 ; but it remains to be shewn before we agree to these skele-
tons being complete, by whom they were prepared, and if the separate bones were
sent to Europe, or the entire animals

892 Dr Knox on the Dentition of the Dugong, and on the

the head and cranium, put into my hands by the politeness of
this Society.

When Mr Swinton transmitted the preparations and parts
of the dugong, to which I have already alluded, to this country,
he at the same time sent the separate bones of another dugong,
which had been macerated and prepared in the East Indies.
These bones, seemingly an entire skeleton of an adult animal,
came accidentally into the hands of the curators of the Univer-
sity Museum, and Professor Jameson, Keeper of that Museum,
very readily granted my request, that he would allow these
bones to be articulated by my assistant, Mr F. Knox, who, being
much conversant with these matters, would take every care that
the workmen employed by him should in no shape injure the
skeleton, as had happened to a deplorable extent to the skeleton
of a young dugong, at present deposited in the Museum of the
University *.

* The animal to which the young skeleton I now speak of belonged, reached
this country several years ago, and, as I have been assured, entire. It was the mu-
nificent gift of some patron of science to the Museum of the University. I many
years ago pointed out, from a cursory and hasty view of the skeleton, when prepared,
that a highly blamable neglect had been shewn in its preparation, inasmuch as the
bones of the sternum and rudimentary pelvis had evidently been lost or destroyed.
My brother, somewhat more than a year ago, having had occasion to re-examine this
skeleton, discovered that the original teeth (probably all milk-teeth, as the skeleton
must evidently have been that of a young animal) had been lost, and their place sup-
plied by the workman to whom the articulation of this invaluable skeleton was en-
trusted, who had substituted for the absent teeth those of a variety of other animals,
and even pieces of ivory. So that all that remains of this splendid gift is a muti-
lated skeleton, which ought not to be exhibited in any museum. I trust that no-
thing contained in this note will be construed by any one into censure of the Cura-
tors of a museum, which is really a private collection ; on the contrary, we may re-
gret with them that the person to whom they entrusted the dissection was found to
be altogether unfit for real anatomical research. I mentioned these facts, first dis-
covered by my brother, to several persons, and they, somehow or other, have got in-
to the public journals ; but this was not originally intended.

Anatomical Structure of certain of the Cetacea. 398

I had thus before me the crania of two adult specimens of
the dugong, for such I presumed them to be, one prepared by
myself, and one by some persons abroad. A little dissection
brought to light a most unexpected fact, viz. that the tusks of the
crania before me differed from each other in shape and general
appearance ; and that, whilst one of these resembled in all re-
spects the tusk which Sir Everard Home had characterised as
belonging to the adult or complete animal, the other resem-
bled entirely the tusk which he considered as a milk-tusk.
Here, then, were two crania, evidently adult, possessing dif-
ferently formed tusks, which difference in form could not pos-
sibly depend on age, as had been advanced by Sir E« Home,
but must depend on some other cause. Before we consider what
that cause may be, 1 shall take the liberty of briefly and rapidly
reviewing what has been done as to the anatomy of the dugong,
by those anatomists who have preceded me in this inquiry,
stating in the first place, succinctly and briefly, those facts (and
the conclusions drawn from them by myself), which may be veri-
fied by the Members of this Society and by others, by simply
inspecting the two crania, I have had an opportunity of describ-
ing. '

The cranium of the skeleton at present in the possession of
the University, is somewhat smaller than that now before the
Society. Tlie length of the skeleton is fully 7 feet 3 inches
English ; the bones are extremely hard, and the head dense and
heavy. < In the crania I observed differences as to the shape of
various bones, when compared with each other, which, upon the
whole, however, hardly amounted to what I should venture to
call Specific differences. They do not exactly resemble each
other. In the upper jaw there are two tusks in the intermaxil-
lary bones, and three molar teeth on each side, opposed to those
occupying a similar situation in the lower jaw-bone. The ante-

r

394 Dr Knox on the Dentition of the Dvgong, and on the

cLor part of this bone slopes greatly, and is of vast strength, and
there are cavities for eight rudimentary teeth, which teeth, how-
$yer, are. not present It will be quite obvious to every onet
that the teeth may have been lost by maceration, or have been
intentionally removed, or accidentally dropt out ; to me it seems
probable that they occasionally remain in the jaw during the
whole period of the animal's existence. Upon the whole I do
not reckon this a question of any moment. The right tusk of
the nnrwal (whioh \ a„ iodri™ tooth) rcn^n, Lays im-
bedded in the jaw, and seldom shews itself even beyond the
gums, and, were it not for this, I should imagine, by what we see
take place in man* that the alveolar cavities would be absorbed
and disappear, and thus cause a great loss of depth and strength
in this part of the jaw. If we apply this reasoning to the jaws
and small rudimentary incisive teeth of the dugong, we shall find
the natural conclusion to be, that they probably get entangled
in the alveolar cavity, and may possibly thereby prevent its ab-
sorption and disappearance, which, according to the physiologi-
cal laws prevalent in other animals, would most certainly take
place, were the teeth entirely removed. Those who talk of the
filling up of the alveolar cavities, after the removal of the teeth,
either by a natural process or otherwise, employ a language ex-
ceedingly incorrect, and at total variance with the whole history
of dentition, and the changes which take place in the maxillary
bones of animals, from a variety of causes.

Without pretending, therefore, to consider it as a view finally
settled, I deem it merely probable that the incisive teeth in a
rudimentary state are retained, and lodged in the alveolar cavities
of the lower jaw-bone, throughout the life of the animal, for the
reasons assigned. Should it be afterwards shewn that an oppo-
site law prevails in the dugong, to what takes place in other ani-
mals ; should it hereafter be shewn that the alveolar processes
of the maxillary bones can and do retain all their depth and

Structure of certain of the Cetacea. 895

strength, even after the teeth which were lodged in them have
been thrown off by the ordinary processes of dentition, I dball
not be in any. way surprised at this, knowing as I do the infinite
power of Nature, which adapts and modifies all structure accord-
ing to the wants and habits of the animal

The cranium now on the table of the Society is somewhat
larger, and of a different shape, from the one I have just de-
scribed, and which I presume is still preserved in the University
Museum. The tusks or teeth, supported by the intermaxillary
bones, correspond in every respect to those which have been de-
scribed as milk-tusks by Sir E. Home, and yet they are not milk*
tusks. They are as long as the so-named permanent ones of the
other head. To suppose them milk-tusks, we should be forced
to have recourse to conjectures totally inadmissible in anatomi-
cal inquiry. We might suppose them to be milk-tusks, which,
by some extraordinary accident, had not been thrown off at the
usual time, but had grown up and taken on the functions of the
permanent ones, which, in this individual, had not been deve-
loped. Now, conjectures of this kind lead to error, and are
altogether unnecessary in the present case. The tusks differ
as much in form in the two crania, as the tusks of the Asia-
tic elephant differ from those of the African one, and, there-
fore, naturalists would say that these animals must be specifi-
cally different * I hesitate, however, in asserting this positively,
and would say rather that it amounts with other data, such as
the belief on the part of the Malays, in whose seas these ani-
mals reside, that, to a great probability, there are two distinct
species of the dugong now inhabiting the Eastern Ocean. I

* The difference in the tusks of the African and Asiatic Elephants is not cfflfe
filed to mere form ; Mr Robisok informs me that the ivory is much finer and mow
dense in the former than in the latter.

VOL.. XI. PAET II. 8 D

896 Dr Knox an the Dentition qftk? Dugong, and on the

do not at the present moment remember any facts tending to
shew that these very obvious differences may be merely sexual ;
and that they do not depend on difference as to age, I think has
tieen clearly made out by the preceding observations *.

It may be observed, moreover, with a reference to the tusks
of the cranium now an the table, that there are no appearances
of permanent or other tusks behind these; no vestiges of the
roots, or such other appearances as indicate their probable ulti-
mate replacement by others. The molar teeth correspond in
both jaws, and in the. lower jaw of this cranium we find the al-
veoli for the reception of the imperfect rudimentary incisive
teeth formerly spoken of These teeth are mostly present, but
,not all, a circumstance which may either arise from some of them
having been thrown aftj or by their having become encrusted
with bone. All this part of the jaw was covered with a dense
and almost horny semicartilaginous substance. A similar sub-
stance was found encrusting the palate above, and these sub-
stances seemed to me placed there, to supply the deficiency of
incisive teeth f .

The dugong seems then to have originally, and, whilst yet

* I observe, in a late number of the Annates des Sciences ^Observation that a
new species of fossil Hyaena has been established, merely from a slight variety of
form occurring in one of the molar teeth.

f There is rather a vagueness in what Sir E. Home says about the milk-mofar
teeth in an animal Jour feet eight indies Jong ; it seems reasonable to have expected
that the molar teeth in such an animal should have been proved to be miDc-molar
teeth, by laying open the jaw and shewing the germs of the permanent ones below.
The same distinguished anatomist has, besides, from an accidental oversight no
doubt, given a representation of the upper jaw of a dugong, which must obviously
have been adult, there being two molar teeth on one side, and three on the other,
and has described this jaw as belonging to a young one, and has called these teeth
milk-molar teeth.

Anatomical Structure of certain of the Cetaeea. 897

young, incisive teeth in both jaws, in addition to the tusks in the
upper. Of these incisives, the upper smaller or mesial ones, are
thrown off at an eariy period, and not replaced. The tusks are
probably m replaced by permanent teeth. No tusks are found in
the lower jaw..

As regards the other parts of the skeleton, I found, in the
one so often alluded to during the course of this memoir, twen-
ty-six cervical and dorsal vertebra, aAd twenty-eight caudal
The sternum is very remarkable ; but its appearance cannot be
altogether depended on, for this reason, that we know not how:
the bones were originally prepared, nor what violence, or injury,
or loss, they may have sustained. That they are not quite per-
fect, is obvious from what I discovered had happened to the tern*
poral bone, where, very obviously, the knife or chisel had been
at work, to extract the small bones of the ear. Whether this
happened previous to the bones being sent from India, or merely
prior to their being inspected by me, I shall not take it upon me
to determine. The adult sterntam, in a perfect state, may not as
yet have been seen by any anatomist.

From the hasty glance I had of the soft parts, I will venture
to predict, that the arrangement of the hybid bones, and their
connexion with the tongue, have been totally misunderstood ;
but I am unwilling to bring forward any viewB as to this part of
the animal, until another opportunity shall occur of inspecting
these parts.

In the bones of the fore-arm we meet with an unexpected
resemblance to the elephant, in a structure hitherto deemed
unique. " The ulna is the stronger bone at the carpal joint ; but
it is quite probable that this structure prevails in several pachy-
dermatous marine mammalia.

3d2

$&8 Dr Knox on the Dentition of the Dugong, and&t the

< »

Zoological Arrangement of the Dugwng.

In the inquiry, which, at the Meeting oi the ^1 si Decem-
ber 1829, I had the honour to submit to the Society, the denti-
tion of the dugong was considered. It was shewn in that me-
moir, that an insuperable objection lay against the views as to the
succession of the tusks of the dugong, promulgated first by the dis-
tinguished EngHsh anatomist, Sir Everard Home, and adopted,
so far as I know, by most continental ones. The observations
which were then submitted to the Society shewed, that in two
adult crania of the dugong, there were two kinds of tusks, quite
distinct from eaeh other in their form, and that this difference
seemed specific, as not being referrible to age. In considering
the character I speak of as specific, I do not go beyond the or-
dinary rule of zoological investigation ; but, whether or not this
determination be the correct one, I feel yet assured, that these
differences in tlte form of the tusks, in the adult crania of the du-
gong, do not depend on age> and this is all I contend for at pre*
sent.

There is a fact to which I beg leave to call the attention of
the Society, before I quit this subject. The milk-tusks of the
dugong have never been seen by any one ; that is, I have not
heard of the existence of any preparation shewing the germs of
the milk or permanent teeth, together or in succession, and in
such a way as to leave no doubt on the subject. They may
exist, inasmuch as there is nothing in the economy of this inte-
resting animal forbidding such a belief; but I repeat that they
never have been seen by any one ; so that it seems to me but
right, that, previous to all further speculations as to the natural
history of the animal, efforts were made to perfect, in some mea-
sure, its anatomy, on which alone can the zoologist found any
rational inquiry.

Anatomical SkvOure ^terUm qf the Cetmxd, 899

The remarks I have to make as to the zoological arrange-
ment of the dngQBgg, are of less interest than those regarding its
dentition, as being a question merely of nomenclature and sys-
tem. The dngaAg was firet arranged with the : walrus. Cam-
pbb, in his natural history work, called in question the propriety
of this arrangement. He was followed by others, and, finally, by
Baron Cuvijbb, who determined the dugong, lamantin, and the
animal' of SrauusR, to belong naturally to the Cetacea, and they
were accordingly arranged under the head of Herbivorous Ceta-
cea. I confess that, from the time I oommeneed these inquiries
into the anatomy of the dugong, I felt much inclined to question
the propriety in their haying separated this animal from others
to which it seemed naturally allied. The external form, it is
true, so far as regards the caudal termination of the body, greatly
resembles the dolphin, porpoise, and whales generally ; and there
are facts in the anatomy of the bones composing the skeleton of
this part of the body, such as the form of the bones of the pel-
vis, the presence of the bones having the form of the letter V,
found on the ventral aspect of the caudal vertebrae, which, taken
together with the complete enclosure of all the bones of the up-
per extremity, so as to render the articulations of the limb of
probably little use to the animal, are facts, it may be admitted,
in favour of its arrangement with the Cetacea ; but, when we re-
flect on the form of the cranium of the dugong, on the structure
of the molar teeth and tusks *, on the dentition of the animal
generally, on the structure of its stomach, position of the mam-
mae of the female so different from that of the Cetacea, one
cannot but be convinced, - reflecting without prejudice on these
facts, that the dugong may be more naturally grouped with the
walrus, than with any of the whale tribe as yet described by na-

* The teeth in the true Cetaoea, when present, are uniform.

400 Dr Knox on the Dentition of the Dugong, and oh the

turalists. The Scapulas of the dugong, have no resemblance to
those of any of the Cetacea I have examined, but they approach
those of the walrus. The great strength of the zygomatic arch,
and, indeed, the whole anterior part of the body, shews the
natural affinity with the tribe of the walrus ; so that here, as in
so many other zoological cases, I fear it will be found that consi-
derations, drawn chiefly from external characters, lead only to
false conclusions.

True Cetacea.

We owe to Mr John Hunter most of the best made out ana-
tomical facts in the history of the Cetacea : above all, we owe to
him the history of their mode of dentition ; and the facts and ob-
servations, together with the conclusions drawn from them, have,
so far as I know, never been directly questioned by any one. Mr
Hunter, I think, was the first to prove that, in their mode of
dentition, whales do not strictly resemble other mammalia. He
shewed, as far at least as the field of his inquiry extended, that
nothing that had been made out regarding the succession of the
teeth in the other mammalia, was at all applicable to the Cetacea.
In them we have no permanent teeth following milk-teeth, but
one set only which are at once temporary and permanent, that is
to say, the anterior ones, together with the small part of the jaw
containing them, are constantly worn away and lost during the
life of the animal, and these are replaced by others, which grow
up from behind, precisely as in the elephant. Now, I had
thought that this mode of dentition described by Mr Hunter,
and which 1 had myself verified in a very considerable number
of the Cetacea, might, without venturing on a rash analogy, be
held as applicable to all the Cetaoea ; but it would seem some
have thought differently, and, among these, the immediate sue-

Anatomical Structure of certain of the Cetacea. 401

cessor of Mr Hunter, Sir Everard Home, who, in a paper
published in the Transactions of the Royal Society of London,
speaks familiarly of the milk-tusks of the narwals*. That it was
possible, I repeat, that the dentition of this animal might really
differ from the other Cetacea, in the having temporary teeth fol-
lowed by permanent ones, was a circumstance which, in so far
as regards its possibility, could not be questioned ; but still I
doubted the fact, and this doubt seemed confirmed by a note
subjoined to the history of the narwal, in the Fossil Remains
of Baron Cuvier, which note, though rather obscure in its style,
impresses my mind with a belief that that distinguished anato-
mist holds opinions similar to those I now submit to the So-
ciety ; and, as the zoology of this remarkable cetaceous animal is
as yet extremely imperfect, I shall take the liberty of submitting
to the Society a few remarks as to the structure of its skeleton.

Skeleton of the Narwal.

When Baron Cuvier published the last edition of the " Osse-
mens Fossiles," he had not seen a skeleton of this remarkable
whale.

* All anatomists will readily admit the possibility that the mode of dentition of
the narwal might be found, on inquiry, to differ from that prevailing in the ordi-
nary Cetacea, inasmuch as the anatomical facts, and the inferences from them, can-
not, as I had the honour to demonstrate to the Society on a former occasion, be
transferred by d priori reasoning to any other species, even though that species be
strictly congenerous ; at least th js has been the impression under which I have now,
for a very considerable number of years, carried on extensive inquiries into the ana-
tomical structure of animals. And here I may take the liberty of remarking, that
this does teem to me to have been the impression under which all anatomists of any
reputation have acted, notwithstanding the observations to die contrary which hare
been lately brought before this Society and the public, by a distinguished British

403 Da Knox an the Dentition of the Dugong, and en the

If any proofs were a wan ting that natural science requires
protection, that it never has, nor ever can, make any progress
in the hands of others than strictly scientific men, it will be
found that the facts required to demonstrate this may be best
drawn from the history of the Cetacea.

Since the period when the commercial nations of Europe
first navigated the icy seas of Greenland, to obtain by the cap-
ture of the whale, and others of the tribe Cetacea, whalebone
and oil, for the purposes of traffic, hundreds of vessels, admirably
equipped, commanded by persons not wholly illiterate, and (I
regret to make the avowal) provided with surgeons, whose edu-
cation ought, assuredly, always more or less, to lead to a fond*
ness for natural historical pursuits, have annually visited these
frozen coasts; have assisted in the capture of thousands of
whales ; have been now, for some centuries past, under circum-
stances the most favourable for the observation of the peculiar
history of these most interesting animals, without the addition
of a single well ascertained fact, so far as I can learn, to those
published nearly a hundred years ago by a gentleman in no way
commercial, the Honourable Paul Dudley, who published, in
the Philosophical Transactions for 1730, some Observations on
the Natural History of several of the larger Cetacea.

There is something, then, in the spirit of trade and com-
merce hostile to real science, and to the progress of scientific
pursuits ; nor do I think this hostility limited to the sciences
termed Natural merely, but to every kind of knowledge with
which I am acquainted. These remarks I do not make with a
view to hurt the feelings of any one, but simply to explain the
difficulties which anatomists and naturalists have experienced in

naturalist, Dr Fleming ; an erroneous conception of which, without doubt, mint
have arisen in his mind from his little acquaintance with anatomical science.

Anatomical Structure of certain of the Cetacea. 408

completing the history, or rather, I should say, in obtaining fects
sufficient for a mere outline of the structure of these animals *,
and as an excuse for wishing to record in the Transactions of
this learned body a few facts regarding the anatomy and physio-
logy of whales, which, compared with the mass of unexplored
inquiry, must be deemed comparatively meagre and scanty, and
of which fact I may venture to presume few can be better judges
than myself.

Mr Hunter, in the work I have just alluded to, says, " From
ipy want of knowledge of the different genera of this tribe of
animals, an incorrectness in the application of the anatomical ac-
count to the proper genus may be the consequence ; a tolerably
correct anatomical description of each species, with an accurate
drawing of the external form, would lead us to a knowledge of
the different genera, and the species in each ; and, in order to

# Mr Hunter, whose position in life enabled him more than any other person
to investigate the structure of the Cetacea with advantage, has remarked, in those
admirable " Observations on the Structure and Economy of Whales," that he has
availed himself as much as possible of all accidental opportunities of ascertaining the
anatomical structure of large marine animals ; " and, anxious to get more extensive
information, engaged a surgeon, at a considerable expense, to make a voyage to
Greenland in one of the ships employed in the whale-fishery, and furnished him with
such necessaries as I thought might be requisite for examining and preserving the
more interesting parts, and with instructions for making general observations ; but
the only return I received for this expense was a piece of whale's skin, with some
small animals sticking upon it"— P. 372.

For my own part, I may say that all accidental opportunities of dissecting the
larger species of whales in this country have been denied me by a curious arrange-
ment, which I wish I could believe altogether accidental; for, notwithstanding the
fact, very generally known, that all my leisure moments were constantly jemployed
in ascertaining the anatomical structure of various animals, it has uniformly happened
that the requisite information as to the stranding of any of the larger whales has
been brought to me last. And thus has it happened with almost all the opportuni-
ties which have from time to time occurrtd for the anatomical examination of the
rarer animals which have reached this country during the last ten years.

VOL. XI. PART II. 3 £

404 Dr Knox on the Dentition of the Dugong, and on the

forward so useful a work; I propose at some future period to lay
before the Society descriptions and drawings of those which have
come under my own observations." Mr Hunter, by these re-
marks, means, no doubt, to state that he had in his possession
anatomical descriptions or monographs of the various individuals
of the whale tribe examined by him. These monographs un-
happily, so far as I know, have never been communicated to the
public *. This is extremely to be regretted, inasmuch as, until
the publication of proper monographs of each species, drawn up
from dissections made by experienced anatomists, almost every
thing said regarding the Cetacea, or of any other tribe of ani-
mals, must be matter of pure conjecture.

Delphinus Phocana.

I am indebted to my brother for certain of the following ob-
servations on some parts of the anatomy of the porpoise.

The ribs have always been found to be thirteen on each side^
when the specimen came uninjured into his hands at first, a fact
the more remarkable, I think, that all the artificially articulated
skeletons 1 have seen have twelve only on each side, shewing
how easily errors arise when the setting up of a skeleton is en-
trusted to persons altogether ignorant, or altogether regardless,
of anatomical science. In one specimen which is now in. the
Museum, about the middle of the dorsal vertebrae, there is a

* As I have not the honour of a personal acquaintance with the person into
whose hands Mr Hunter's Papers came on the demise of that great man, I here
take tne liberty of suggesting to him the propriety of publishing those Memoirs of
the Cetacea spoken of by Mr Hunter, which assuredly will be found to contain
highly important facts and observations.

• • •

Anatomical Structure of certain of the Cetacca, 405

vertebra which carries no rib, and this fact is undoubted, in-
asmuch as the skeleton was prepared as a natural skeleton ; but
this is seemingly only an individual variety, since in the skele-
ton of several others, and more particularly in that of the foetus
of the porpoise, no such appearance is met with.

The skeletons of several specimens, of various ages, of the
Delphinus Phoctena, prepared with great care by my brother, and
whose skeletons are still in the Museum, shew that there are se-
ven cervical vertebras.

Other specimens of the genus Delphinus.

The want of symmetry in the bones of the cranium of the
narwal does not extend to all the Cetacea. We have seen
that it scarcely exists in the Delphinus Phoccena and Delphis.
There is in the Barclayan Museum the skeleton of a grampus,
which was stranded in the Frith,

9

Cervical vertebrae, 7

Dorsal and caudal, . . . 56

63

Cranium very nearly symmetrical

Teeth ~^ : the two anterior teeth slope much forward ;

21.21 x

they are small, and solid.

There are twelve ribs on each side : and of these, eight are
articulated with the transverse processes of the vertebrae only.

There is the cranium of a large description of grampus in
the same museum, in which the want of symmetry is very re-*

Se2

406 Dr Knox on ihe Dentition of the Dugong, and on the

markabie. There are alveolar cavities for six teeth in the upper
jaw on each side, and a similar appearance : in the lower jaw ;
these teeth may once have been conical, but, by use, they are
much flattened above, and sloped. These anatomical differences,
found to exist in animals so greatly resembling each other, are
remarkable.

Qf the Size of the Fcetus of the Cetacea at the time of Birth.

Naturalists, I presume, must have few well authenticated
facts on this point, otherwise it would not happen that so able a
naturalist as the author of the British Zoology should have de-
scribed the foetus of the Delphinus Phoccena as being only seven
inches in length shortly before birth * I have put on the table
of the Society the skin of the foetus of a common porpoise, of the
usual length (about five feet two inches), and which was caught
in the Frith of Forth. It was removed from the uterus, toge-
ther with its membranes, in presence of a numerous class. The
length, even in its present dried state, is two feet six inches, and
I see no reason, from the state of the parts, to suppose that the
birth of the young was about to happen at the moment of the
capture of the mother. The foetus of the seal is, in like manner,
of a disproportionate size to its parent f . Its birth is provided
for by a remarkable mechanism connected with the fibro-cartila-
ginous and ligamentous structure of the symphysis of the pubis,
which, previous to, and during parturition, elongates to the ex-
tent of nearly two inches. The effects of this, in enlarging

* British Animals.

f The foetus of a seal shortly before birth was found to be about £ feet 6 inches
in length, that of the mother being about 5 feet 2 inches.

Anatomical Structure of certain of the Cetacea. 407

the capacity of the pelvic apertures, may be readily judged of
by reflecting on the elongated square form of the pelvis of the
seal ; but it is equally obvious, that the artificial separation of
the bones of the human pelvis, by a section of the ligamentous
symphysis, cannot produce the same results, by reason of the cir-
cular form of the cavity of the human pelvis. The pretended
reasoning from analogy, then, on the part of those who have
proposed imitating a process of nature, in dividing the human
symphysis pubis during laborious or difficult parturition in wo-
men, argues merely a want of accurate observation on their
part, and is an attempt to supply one animal with a mechanism,
which Nature exclusively intended for another, whose structure*
was originally entirely different*.

The total length of the skeleton of the narwal, apparently
that of an adult animal, in the Barclayan Museum, as now arti-
culated, and which is said to have been presented to Dr Bar-
clay by Captain Scoresby, is 16 feet 8 inches. Length of the
head 2 feet ; of the tusk 6 feet 1£ inches, being that remarkable
single tooth which has in all ages characterized this animal ; it
being also well known that, in the male, the left tusk only is
developed so as to protrude beyond the gums, whilst the right
remains imbedded in the jaw for life ; in the female both tusks
remain in this latter state ; the part imbedded within the socket

• In an Essay on the History of Whales, by the Honourable P. Dudley, Phil.
Trans. 1725, the following observations occur as to the bulk of the foetus of the
Whale.

" Whalebone Whale.— This fish, when first brought forth, is about 20 feet
long, and of little value : the full-grown animal is 60 or 70 ; say as 1 to 8.

" Spermaceti Whale. — The calf, or young whale, has been found perfectly
formed in the cow when not above 17 inches long, and white; yet, when brought
forth, it is usually 20 feet, and of a black colour."

408 Da Knox on the Dentition of the Dugong, and oh the

10 inches. The tusk is rolled spirally throughout its whole ex-
tent, with the exception of about 8£ inches at the point where
the tusk is smooth, and resembles strongly the young teeth. On
looking into the cavity for the reception of the pulp, we perceive
the spiral twisting to be as well marked as on the outside, and we
find the tooth to be hollow throughout the whole extent of the
cavity for its reception in the jaw. With the exception of a
small space in the centre, we are sure that the remaining part is
solid.

The animal has a distinct vertebra dentata, almost as large
as the atlas, and, in this respect, differs much from the com-
mon porpoise of the coast, which has the dentata united to the
atlas by bone, and not to be distinguished from it ; and the spi*
nous process, which is distinct, is a mere plate of bone. With
reference, then, to these two vertebrae, the narwal differs
from all the Cetacea I have examined ; and of whom it may be
said generally, that the vertebrae of the neck run much together,
and are so united as not to admit of any motion in this part of
the vertebral column. The neck of the narwal is therefore
somewhat longer proportionally than in the other whales ; and
the flexibility of its neck must enable it to be much more agile
than others of its kind. In short, we find moveable vertebra?
with distinct or peculiar surfaces, appearances which do not exist
in this part of the column in any of the other true Cetacea I
have seen or read of.

There is no opening for the vertebral artery. The junction
of the first and second vertebrae is by two surfaces, as in man and
other animals. In looking into the vertebral canal, no processus
dentatus is seen, so that it presents an appearance as if the pro-
cessus dentatus had been cut slopingly off on its superior sur-
face, leaving only its articulating surface, as seen in other ani-
mals. The dentata and atlas are equal as to breadth, viz.
8 inches. They are almost equal as to strength. The third

' Anatomical Structure of certain of the Cetacea, 409

vertebra is remarkably thin and anchylosed to the second. There
are no openings in the transverse processes. The fourth, fifth,
sixth, and seventh cervical vertebrae are distinct, having interver-
tebral cartilages interposed, and none of these is so weak as the
third. There are characters in which the narwal differs from
other Cete. No vestiges of openings for the vertebral arte-
ries in any of them- . There are . eleven dorsal vertebra^ and
eleven ribs on e^ch side. . But Captain Scqresby, whose autho-
rity in these matters is unquestionable, says, that there are twelve
dorsal vertebrae, and, of course, twelve ribs, so that these bones,
in the skeleton now under consideration, may have been lost

In the Cetacea, apparently, the transverse processes of the
vertebrae undergo a sudden elongation, about the termination of
the dorsal ones, that is the thirteenth vertebra. This we find to be
the case in the narwal under consideration.

There are thirty-two remaining vertebrae in the Barclayan
narwal, and twelve bones in the form of the letter V, which
bones may be considered as spinous processes on the ventral as-
pect of the vertebrae. They are, however, placed upon the ver-
tebral substances, which renders their presence altogether ano-
malous. There are then in the narwal,

Cervical vertebra^ 7

Dorsal, carrying ribs, 11

Lumbar and caudal, 82

50

The caudal may not be all present.; and as Mr Scoresby says
that there are in the narwal he examined fifty-four vertebrae,
it is more than probable that four, bones of the Barclayan spe-
cimen have been lost

410 Da Kvox on the Dentition iff the Dugqng, anHonihc

The length of each pectoral extremity is 17 indies ; these
are imperfect, however, inasmuch as few of the fingers are pie-
sent. The bones of the pelvis are entirely wanting ; * that is, I
presume, they have been lost in the original preparation of the
animal.

Feet. Inches.

Length of head, . . . . /. .... . 2 0

♦Breadth, 0 17

The tusks are carried in the maxillary bone. The summit
at the top of the head is removed to the left side to the distance
of about an inch "from' the mesial plane, so that, looking at the
head from behind, it has a singular asymmetrical appearance, the
right side of the occipital bone appearing so much broader than
the left side ; whilst looking at the face oh the' upper surface, the
left side again preponderates over the right, in consequence of
the much greater size of the left maxillary bone, as it requires to
carry the fully developed tooth. This difference in breadth and
depth does not extend to the inter-maxillary bones, or very
slightly ; and indeed, superiorly, the inter-maxillary bone of the
right side is the larger of the two ; so that the want of symmetry
follows a different law in the cranium and upper part of the face
from what it does in the lower part of -the fkce. The distance
between the orbit of the right side and the anterior margin of
the blow Jhole of the same side, being nearly an inch greater than
on the left. The law, therefore, seems to be, that the greater
development with regard to the cranium is on the right side, and
with regard to the face, on the left side, and the head has alto-
gether a twisted appearance. This singular want of symmetry
in the bones of the cranium and face has not been remarked by
M. Cuvieb, though in the engraving .of the cranium of .the nar-
wal the appearance I speak of has been very accurately repre-
sented by the engraver. The capacity of the cranium is large,

Anatomical Structure of certain qfthe Cetacea. 411

analogous to what we find in the porpoise and dolphin, and the
squamous or ascending plate of the occipital bone is imperfectly
ossified, and very thin. The jaw where the developed tooth is
contained is slightly reticulated on the upper surface. The
symphysis of the lower jaw has been originally united by syn-
condroses, and a shallow groove runs along, for a short distance,
the upper margin of the lower jaw, obviously analogous to the
deep groove in the porpoise, dolphin, and many other Cetacea,
containing in them the sharp conical teeth, but, as is well known}
there are no teeth of this kind in the narwaL The maxillary
bones are loose and spongy; the inter-maxillary firmer and
denser, more resembling in structure the inferior maxillary
bones.

Mr Hunter's admirable account of the dentition of the
ordinary Cetacea may be corrected apparently in one point;
the groove, or elongated cavity for the reception of the young
teeth, cannot b^fonned by the sinking down of the teeth in it*
for the teeth are already deeply imbedded in it in the foetus.
In many species of animals, moreover, the osseous partitions of
the alveolar cavities are by no means complete. It is probable,
therefore, that the gams of the teeth are developed in this
elongated alveolar cavity, much in the same way as they are in
other Mammalia; but, as Mr Hunter remarks, they do not
succeed each other by germs placed above or below each other
in the jaw (according to the jaw spoken of), but rather from be-
hind forwards, the anterior ones, together with the portion of
the maxillary bone carrying them, gradually wasting away by a
law in the economy of the animal The inter-maxillary bones

1 •

carry -y te6th apparently in many of the Cetacea, as in all the

*

porpoises.

In the adult animal, and no doubt in many others of the Ce-
tacea, this elongated groove for the reception of the teeth may,

VOL. XI. NO. II. 3 F

'412 Dr. Knox on the Dentition of the Dugang, and an the

and does actually become, partially divided into a number of
<*>mpartme»ts by osseous division or ridges »

It is, moreover, probable that the inferior * dentar canal,
.which more resembles a great cavity, contains numerous blood,
vessels and nerves, calculated to allow of, and supply,, the waste
of the jaw, and the succession and loss of teeth ; and the same
structure may prevail even in the narwal, since being of an
analogous nature with the other Cetacea, the jaws may waste
away in it although there be no teeth present, with the excep-
tion of the left tusk and the aborted tooth f of the right side.

Since the period of the earliest voyages to the Arctic Seas,
the narwal, from the remarkable projecting and single tooth,
carried in the upper jaw, has attracted the attention even of
those least interested in zoological inquiries- The facts, that it
is the left tooth only which is developed in general — that some*
times the right is also found to extend, more or less, beyond the
gums, but more usually remains in the socket, imbedded in the
jaw, probably for the whole life of the animal — and that, in the
female, both these teeth remain in the jaw, and never shew
themselves external to the gums ; — these are facts known to
.every one. But I do not believe that these aborted teeth,
which remain imbedded in the jaw, viz. the right tooth in the
male and both in the female, are milk tusks, or merely tempo-
rary teeth ; neither is there a single observation in the history
of the narwal to shew that there really exists any true succes-

* There is a species of Rhinoceros in which two incisive teeth remain below the
gum during the whole period of the natural life of the animal : they are not to be
seen then so long as the head is covered with soft parts. Thus the permanent
residence of teeth within the alveolar cavities, or not visible beyond the gums, as
assuredly happens in the narwal, and, as I supposed, might also occur in the cafe
of the lower incisives in the dugong, is a fact not confined to the Cetacea.

f An expression employed by M. Ctjviee.

Anatomical Structure of certain of the Cetacea. 413

sion of the teeth as in most of the Mammalia. The crania of
two foetuses of the narwhale now before me show no such appear-
ances. On each side of the upper jaw, and in the usual place,
there ares two hollow teeth, obviously the extremities of the
spiral permanent tooth of the male. These teeth are complete-
ly imbedded in the jaw in the young narwhale ; observation tells
us, that if the animal be a male the left tooth continues to grow,
the right, after a time, fills up, its central cavity for containing
the pulp disappears, and, after attaining a growth of 5 or 6
inches, the jaw elongates, to correspond with the growth of the
animal and of the other tooth, and the aborted tooth remains
imbedded in the jaw for life.

Digestive Organs #.

Inquiries into this system of organs are by no means so com-
plete as they ought to be. My own very limited field of inquiry
has presented but few novel facts, if any ; but I feel inclined to
view differently from those who have preceded me in this in-
quiry, that structure in the second stomach of the porpoise and
dolphin, which many have considered as glandular merely*
That it bears a considerable resemblance to the tubular portion
of the kidney of some animals cannot be overlooked, but this, for
obvious reasons, does not seem to remove the difficulty we have
in considering the whole structure as merely glandular. The

• I have not observed the muscles in any of the whale tribe or Cetacea to stiffen,
nor the blood to coagulate after death. Others, however, whose opportunities for
observation may have been more extensive, may have noticed these phenomena
•The muscles are, compared with other Mammalia, soft and easily lacerated. The
anterior filaments of the spinal nerves are greatly more numerous or larger than the
posterior;

3f2

41 4 Dr Knox on the Dentition of the Dugong, and on. the

following are the few brief remarks I have been able to make re-
garding it

r

In accordance with the language of all or most anatomists, I
shall speak of this species of the Cetacea as having four stomachs,
this being the usual language held with reference. to the sto-
machs termed complex, lily own opinion, • as explained more
fully in a memoir I had the honour to submit, to the Royal So-
ciety of Edinburgh, on the Structure of the Stomach of the La-
ma, is, that no animal possesses more than one stomach, divided
more or less by compartments, and thus assuming the appear-
ance of one or more cavities, which anatomists have unhappily
spoken of as being one or more stomachs. Now, in accordance
with this language, which, however .inaccurate, demands respect
from its universality, I shall speak of the second cavity in the
stomach of the porpoise as being the second stomach.

The gullet of the porpoise, composed of the usual membranes
or tunics common to it with other Mammalia, terminates in a
•somewhat elongated, tolerably capacious pyramidal-shaped bag,
known by the name of the first stomach. In this we find, ex-
ternally, and immediately invested by the peritoneal tunic, a
strong coat of muscular fibres, spread uniformly over the sur-
face, continuous upwards with the muscular layers of the gullet,
and downwards with those which, in a similar fashion, envelope
the second stomach, occupying the same situation relatively to
the peritoneal tunic in it as in the first. This muscular tunic
of the first stomach is composed of two layers, separated from
each other by a layer of cellular membrane ; the fibres are chief-
ly longitudinal and circular. Within these there is the usual
vasculo-cellular layer, and it has within it a mucous, membrane,
covered by a strong epidermic covering. By maceration a double
epidermic covering may be separated from the mucous surface of
the gullet, but one only seems to invest the first stomach.

- Anatomical Structure of certain of the Cetacea. . 415

To this cavity the branches of the nervi vagi (which are
large, and distinct) do not proceed in any great abundance, their
course is rather, towards the second cavity or stomach, whose
structure I shall now endeavour to describe. The capacity of
the second stomachal cavity, is less than that of the first, and its
structure differs remarkably from it. The aperture of commu-
nication betwixt these cavities admits readily enough the fore-
finger, and here the internal textures of the first stomach sud-
denly cease ; the epidermic covering and subjacent mucous mem-
brane cease, and there is substituted for them a perfectly smooth
membrane, without villosities or glandular structures; it has a
good deal the appearance of a serous membrane. This closely
invests a series of fibres, which externally are covered by an ex-
tremely vascular and cellular tunic. These fibres are. placed per-
pendicularly betwixt the two membranes I have spoken of, and
quite close to each other. They may be considered, then, as
placed on the outer surface of the internal membrane of the sto-
mach like a pile of velvet enclosed by thin laminae or plates *
Outside the vasculo-cellular layer, muscular layers exist, continu-

* I here take the liberty of subjoining a microscopical examination of the struc-
ture by Dr Brewster. " I have examined the piece of stomach you have sent me
of one of the Cetacea. It seems, in its wet state, to consist of tubes or fibres, per-

pendicular to the two membranes which enclose them, thus : aD^ ^e

upper surface of one of the membranes is covered with hollows or depressions, cor-
responding with the extremities of the tubes or fibres. A more minute examination,
conducted in a different way, proves these perpendicular portions to be tubes. In
order to dry it, I pressed it between folds of paper, and the effect of the compres-
sion was, to press together nearly all the tubes, and make the whole one dense mass
of a dark brown colour ; but when it became dry, and slightly indu rated, I drew it
out as if it had been India rubber, and the tubes opened and the the mass became

white, thus * :

* See Edin. PhiL Journal by Dr Bbewstxb.

416 Dr Knox on the Dentition qfthc Dugimg, and on the

ous, as I have already said, with those of the first stomach, and
transmitted over the second, which they, in like manner invest,
to the third. The interior of this second cavity, when kid open,
presents a series of longitudinal and transverse elevations, which
resemble the interlocking of the fingers with each other. To
this stomach most of the branches of the nervi vagi are distri-
buted.

The third and fourth cavities have been very carefully de-
scribed by Baron Cuvier, and by most systematic writers on
comparative anatomy, The questions raised by Camper as to
the number of the stomachs in this animal, do not merit notice.
The accompanying sketch will perhaps explain in an easier way
than I have done, to the non-professional reader, the structures
in question. I forbear for the present all speculation as to the
nature of these fibres, which are obviously not muscular, and
can hardly be considered merely glandular ; future observation
and experiment will, no doubt, one day determine whether or
not I am correct in supposing them analogous to the electric
organs of certain fishes.

Anatomical Structure of certain of the Cetacea. 417

• ♦

EXPLANATION OP PLATE XV.

Fig. 1. Cranium of the adult narwal seen from the upper surface.

Fig. 2. The same cranium seen from below. These sketches were made with great
care.

Fig. S. The same cranium seen from behind. The want of symmetry is remark,
able.

Fig. 4. The atlas, dentata, and third cervical vertebra of the same narwal.

Fig. 5. Cranium of a young narwal (supposed to be a foetus), seen from above.

Fig. 6. One of the teeth withdrawn from the socket The young narwal seems
uniformly to have two such, of. nearly jequal length ; one only comes to
perfection in the male ; neither in the female.

Fig. 7. Inner surface of one of the compartments of the porpoise, in which there
prevails a peculiar structure, tubular or fibrous, and perhaps electrical.

Fig. 8. Figure shewing the remarkable regularity of the tubes or fibres placed be-
tween two tunics of the stomach.

< 418 )

XXIV. Remarks explanatory > and Tabular Results of a Meteoro-
logical Journal kept at Carlisle by the late Mr William
Pitt daring twenty-four years. By Thomas Barnes,
M.D. Physician to the Fever Hospital and Public Dis-
pensary at Carlisle, &c.

(Bead 1st Feb. 1830. j

*

The Royal Society of Edinburgh having taken great interest in
meteorological observations, it has occurred to me, that the ac-
companying Meteorological Journals would be acceptable to the
Society. I therefore transmit them, in the hope that they may
be of some service, in prompting the laudable object of the So*
ciety, the science of meteorology.

These journals include a period of twenty-four years, and
were kept by the late Mr Pitt of Carlisle, who was long a care-
ful and accurate observer of many atmospherical phenomena.

Mr Pitt did not avail himself of the new instruments that are

» *

used in meteorology, but understood well the nature and appli-
cation of those he employed. The thermometer, barometer, and
rain-gauge, were the instruments he made use of, and they are
probably more important than any other. For many years Mr
Pitt had no particular occupation, and meteorology was his
hobby. He devoted a great portion of his time to astronomical
and meteorological observations, took great delight in keeping
his journals, and was scrupulously accurate. From my personal
knowledge of his diligence, of his habits of making correct obser-
vations, and the systematic fidelity with which he recorded them,
I think I can with great safety vouch for the accuracy of the
statements contained in his journals.

Dr Barnes's Remarks on a Meteorological Journal. 419

These meteorological journals were commenced on the 1st of
January 1801, and regularly continued up to the end of December
1824. Observations were made of the thermometer, barometer,
quantity of rain, direction and force of the wind, clouds, and the
appearance of the sky. These are followed with general remarks
on the state of the weather, the occurrence of thunder, of me-
teors, and of the aurora borealis. In some places there are added
the appearance of the country, the height of the neighbouring
rivers, the progress of vegetation, and the migration of birds.
The state of the barometer and thermometer, and some other
phenomena, were regularly observed and entered in the journal
three times a-day, with a mechanical exactness. Mr Pitt was
seldom absent from home ; and whenever any unavoidable cir-
cumstance obliged him to go to a distance, he always appointed
a confidential person to take the observations for him.

At the end of each month, the observations are summed up,
the means of each of the three daily observations of the thermo-
meter and barometer are given ; the quantity of rain stated ; the
number of west and east winds; the number of wet days; the
highest and. lowest degrees of temperature; the mean tempera-
ture of all the observations ; the highest and lowest state of the
barometer; and the mean height of the barometer of all the
daily observations are mentioned.

At the end of each year, the yearly results are stated. We
have the annual average height of the thermometer, the annual
average height of the barometer, the annual quantity of rain, and ;
the -number of westerly and easterly winds.

The register contains a daily account of the direction and
force of the wind. In the monthly and annual summaries, the
winds are arranged into two classes, which are called East and
West winds. Mr Pitt began with the W. and went round by
the S. to the E., and all the winds between these two points he
classed with the west winds. He then reckoned from E. to W.,
and classed the NE. N. and NW. and all the winds from the in-

VOL. XI. PART II. 3 G

420 Dr Barnes's Remarks on, and Tabular Results qf>

termediate points with the east. This classification, though it be
not the best, and may be regarded as fanciful and arbitrary, conn
tains a good. general division of the winds. It would not be difficult
to look over the register, and make any other arrangement that
might be thought better. No instrument has been used to mea-
sure the force of the wind. Mr Pitt has contented himself with
a verbal description of it. The winds, it may be proper to state,
were registered from the weathercock of the Carlisle cathedral

During the first three years of the journals, Mr Pitt has
given daily observations of the state of the hygrometer. Not
being aware what instrument he used, I am not able to say any
thing respecting it, except from the imperfect state of hygrome-
ters at that period, little or no dependence, I think, can be placed
on his observations. If Mr Pitt had considered his hygrometer
a good one, he would in all probability have continued to use it,
and would have entered his observations in the journals.

The description of the appearances of the sky and clouds, is
vague and unsatisfactory. Had Mr Pitt availed himself of Mr
Howard's ingenious nomenclature of clouds, this part of the re-
gister would have been more explicit and definite. Mr Pitt
had probably commenced his observations before the publication
of Mr Howard's Natural History of Clouds, or before he be-
came acquainted with Mr Howard's nomenclature, and found
great difficulty in adapting it to his register.

In order to render the accompanying Journals more intelli-
gible and interesting, it may be proper to give some account of
the situation of Carlisle, and the instruments Mr Pitt em-
ployed.

Carlisle, the county town of Cumberland, is situate on a
gentle rise near the conflux of three rivers, the Eden, the Cal-
dew, and the Peterill, and has a fine champaigne country stretch-
ing out on each side. Its latitude is 54° 53' 38" N., and longi-

a Meteorological Journal kept at Carlisle. 421

tude 2° 57' SO* West of Greenwich. The river Eden runs on
the east side of the city towards the north, and the Caldew on
the west, towards the north? where they unite. The PeteriU
joins the Eden a little way above the eity, towards the south-
east. The high mountains of Cumberland are between twenty
and thirty miles distant from Carlisle. Skiddaw lies to the SW.
and Cross Fell to the SE. Mr Pitt resided and took his obser-
vations at Shaddongate, which is in the suburbs of Carlisle, and
stands on ground rather lower than the city, SW. of Carlisle
Castle. Its height above the level of the dea is about 40 feet,
and its distance from the sea twelve miles.

Mr Pitt was in possession of several thermometers and ba-
rometers, which were of a superior kind, and he prided himself
much upon their goodness. Though he generally examined
them all every day, the observations in his journals were usually
made from one thermometer and one barometer.

The thermometer he used latterly was made by Charles
Aiano. It has been constructed and graduated with great care,
and has Reaumur's scale on one side, and Fahrenheit's on the
other. It hangs upon the garden-wall, in a glass cylinder, which
is open at each extremity. It is not in contact with the wall,
and is sheltered from the heavens, and the falling vapours. It
is placed in a north-eastern aspect, about six feet from the ground.
A good situation has been chosen for the instrument. There is
at all times a free circulation of air, and it is so placed as to be
in flie shade the whole day, and cannot be influenced by re-
flected heat.

The barometer was made by Nairne, London, and has an
open and capacious cistern. The column of mercury seems very
free from air and moisture. It hangs in the stair-case, in a per-
pendicular position, about twelve feet from the ground, and
equally free from the sun's rays and the effects of artificial heat.
The temperature of the situation is not liable to any great or

42£ Dr Barnes^ Remarks on, and Tabular Mesulte of,

sodden venation, so as to have muck influence on the instru-
ment, though Mr Pitt, I have reason to know, always made the
necessary corrections for the capacity of the cistern and the ten**
perature of the mercury. .

During the first six; or eight years of these journals (for I
have not . been able to ascertain the exact period), the hours of
registering the thermometer and barometer, in the winter months,
viz. January, February, March, November, and . December, were
8 o'clock in. the morning, 1 at noon, and 10 at night. In the
summer months, via. April, May, June, July, August, September,
and October, half-past 7, morning; half-past 1, noon; and half-
past 10, night. Since; then, thd observations of the. thermometer
and batotneter were mbde three times in the day, viz. at 8 o'clock
A.M., 1 o'clock p. Hi, and at 9 o'clock , p.m. These hours are par-
haps not the best adapted to obtain the * meati temperature and
pressure of the atmosphere of a day , . month, or year, nor is the
form of the register the? best) calculated to elicit all the advan-
tagesof meteorological observations q: yet a. register containing
three daily observations* itegAlarly continued for twenty-four years,
without the omisstcm of a siagle day, or even a single observa-
tion, it is hoped, will not be found' destitute of interest . It must
afford a near approximation to the monthly and annual means,
and will give pretty correctly the character of the climate and
weather of Carlisle.

The Rain-gauge is a copper vessel, and consists of a funnel
inserted into a tube, with a narrow communication, to prevent
evaporation. The cylinder is four inehes diameter, and the area
of the funnel is ten times that of the cylinder, consequently,
when there is ten inches of rain in the cylinder, it is one inch of
surface. The rain-gauge stands in an open situation upon the gar-
den-wall, about twelve feet above the surrounding ground. The
water in the gauge, as appears from the registers, was not mea-
sured at regular periods. He measured it more frequently, when
he thought it was likely to suffer diminution by evaporation.

a Meteorological Journal kept at Carlisle* 42S

In an abstract of the Journal for 1801 *, which was the iret
year of this series, Mr Pitt states, that " the barometer • and
thermometer used in keeping this Journal was made by Messrs*
Jones, Holborn, London. The barometer is <rf the Torricellian
construction ; its scale is not foil inches* but something less, ow-
ing to the rising and falling of the surface of the reservoir ; the
nonius moves by a key, placed in front of the barometer, and it
has a floating-gauge, for the purpose oTadjusting it to its jfroper
height The thermometer is divided, into half degrees, and i»
properly graduated. The times of' registering were 6 o'clock in
the morning, 1 at noon, and 10 at night in the winter months,
and half-past 7, halfcpa&t 1, amd UalftpAst'lG in suinmer, Tlie
rain-gauge is a tin vessel ; the trunk is to the funnel as & to l,aad
has a floating-index to ascertain the • quantity." At what time
he discontinued the use of these insthimeilts, and began to use
the present ones, I have not been able to learn ; but I have no
doubt that he would take great care' to. have them constructed
and graduated in such a manner as not to aflfect the continuity
and correctness of his journals* Mr Pitt, I, know, was in the
habit of verifying the accuracy of the instalments he used, by
comparing them with other instruments; made by the best artists.

METEOROLOGICAL RESULTS.

The results of the -Meteorological Journals, for twenty-four
years, I have arranged into the subsequent Tables. To Mr
Taylor of Carlisle, I beg to express my obligation for his kind
assistance in calculating some of the averages. Should the Jour-

* Monthly Magazine, vol. xiii. p. 8. A brief abstract of the journal was pub-
lished annually in the Monthly Magazine.

424 Dr Barnes's Remarks on, and Tabular Results of,

nal£ and the Tables be found useful in promoting the advance-
ment of the science of Meteorology, I shall feel highly gratified,
by having contributed my mite to so desirable an object.

It is not improbable that these meteorological journals might
be made useful and valuable, by comparing them with similar
journals kept at the same time by other observers, at different
and distant places. They would shew the agreement and diffe-
rence of atmospheric phenomena in different regions of the
earth ; and perhaps important conclusions may be drawn from
their comparison. As I have had few opportunities of examining
journals of this kind, I shall not offer any opinion respecting
them, neither shall I at present attempt to draw any conclusions
from the comparisons I have made. I shall merely observe, that
I have met with some instances of remarkable simultaneous fluc-
tuations of the barometer, occurring in places at a considerable
distance from one another. Among them, the following may be
mentioned. On the 30th of November 1816, the barometer at
Carlisle stood uncommonly high. According to the register, it
was as high as 80,77, morning; 80,77, afternoon; and 30,80,
night, — wind north-west. On the same day, at Edinburgh, there
was the greatest elevation of the barometer that had been ob-
served for several years. The mercury, 135 feet above the level
of the sea, stood at 30,640 in the morning, and 30,602 in the
evening, — wind west *. On the night of the 4th of March 1818,
the barometer at Carlisle was unusually low. It was as low as
28,24 ; the following morning 28,43 ; in the afternoon 28,60 ; and
at night, 28,81, — wind south-west. The weather had been very
stormy, with violent hurricanes, and heavy showers of hail and
snow for several days. A hurricane occurred during that night
At Edinburgh, there was similar weather, with hurricanes ; and
on the 5th of March, at 8 o'clock of the morning, the barometer

* Edinburgh Encyclopaedia, vol. xiv. p. 162.

a Meteorological Journal kept at Carlisle. 425

stood at 27,970, — wind south-west. This was the greatest de*
pression of the barometer that had been observed there for many
years *. On the 8th and 9th of January 1 820, the barometer
stood extremely high at Carlisle, and also at London. At Car*
lisle, on the morning of the 8th, it stood at 80,74 ; in the after-
noon, 30,80 ; and at night, 50,87. The following morning, 30,94 ;
afternoon, 30,86 ; night, 30,75. At London f, on the morning
of the 8th of January, the barometer was at 30,42 ; in the after-
noon, 30,44 ; at night, 30,52. On the morning of the 9th, 80,59 ;
afternoon, 30,51 ; night, 80,32. The mercury had risen at Car-
lisle at the afternoon observation of the 8thlT^th of an inch ; and at
night T^ths more. At London, it had risen T^ths in the afternoon,
and fifths more at night. It rose exactly ^ths of an inch during
the night of the 8th at both places ; and fell ^ths of an inch at
both places in the forenoon, which are striking coincidences.
The barometer had fallen ^ths of an inch at the night observa-
tion at Carlisle, and ^ths of an inch during the same time at
London ; — wind north-east on both days, at both places. The
extraordinary height of 30,94, which the barometer attained on
the morning of the 9th of January 1 820, is higher than has been
observed at Carlisle at any other period of the register. On
comparing Mr Pitt's journal with Mr Daniell's, I find that
the barometers used at Carlisle and London generally rose and
fell with great regularity at the same time, sometimes in the
same ratio, and that the maxima and minima results were often
on the same day.

On the 25th of December 1821, a very great depression of
the barometer took place at Carlisle. It was so low as 28,26,
both in the morning and in the afternoon, and 28,35 at night.
It appears that there was a remarkable fall of the barometer,

* Edinburgh Encyclopaedia, vol. xiv. p. 168.

f Meteorological Essays and Observations, by J. F. Danijell, F.fiLS. p. 400.

426 Dr Barnes's Remarks on, and Tabular Results 6f>

on the same day, both at Geneva and throughout all Scotland *.
At the same time, a corresponding fall of the barometer was also
observed at London f. During the latter part of November and
the first three weeks of December 1821, Carlisle was visited by
several violent hurricanes, accompanied with heavy showers of
hail, and torrents of rain. On the 1 8th of December, there was a
dreadful thunder-storm, and extremely vivid lightning, followed
by hail and rain. On the 20th, a violent hurricane, with heavy
rain in the night. During the three or four following days, there
were several showers of hail and rain, and snow upon the neigh-
bouring mountains. On the 25th, the day on which the great-
est depression of the barometer occurred, the weather was fair
and pleasant, and continued fair, mild and pleasant until the end
of the month. The average of the barometric pressure of this
month, 29,321, is the lowest monthly average in the journals.
The average temperature of the month, 42°, 1, is higher than the
December average of any other year, excepting December 1806,
when it was 48°,5. The average height of the barometer of
December 1806, was 29,377, which is the next lowest average
for December. The barometer also sunk so low as 28,48 in De-
cember of this year ; and there was great similarity of weather
during the month, — a violent storm of thunder, lightning, hurri-
canes, and showers of hail and rain. The minimum of the ba-
rometer occurred on the 2d of December, — wind north-west.
During the thunder-storm which took place on the 18th, the ba-

»

rometer stood at 28,55, — wind south. In the intervening days,
the mercury was comparatively low. In 1821, the thermometer
ranged from 55° to 30°, in the month of December, and the ba-
rometer from 30,23 to 28,26. In December 1806, the range of
the thermometer was from 54° to 26°, and of the barometer from
30,48 to 28,48.

* Edinburgh Philosophical Journal, vol tl p. 888.

Essays, fee. by J. F. Daxiell, p. 44ft

«r Meteorological Journal kept at Carlisle.

427

TABLE I.

EXHIBITING XBE MAXIMUM XK» MIKfMOK TBUPCBAXCBK OP BACH K0MTH FOE. 24 TltAHS.

Yetrs.

JAN.

FEB.

MABCH.

APRIL.

HAY.

JUNK.

JULY.

AUG-

SEPT.

OCT.

NOV.

DEC.

•

M

•

C
•-*

3

4

•

OS

•

m.

K
:«

•

C

S

i.

.a

S

•

9

s

m

M

•

C

3

*

•

C

•**

M

•

e

•

ct

S

A

3

2

.5

•

H

OS

2

•

s

1801,

o

51

J
o

25

0

64

o

80

>

9

00

O

28

O

68

1

28|

68

0

36

70

m

a

0

43

75

■

0

49

71

36

64

33

o

55

204

o

44

o

17*

1802,

52

12

51

24

58

25

59

34

80

28

65

44

65

45

78

51

71

40

65

35

52

20

51

23

1803,

48

18

50

23

61

24

73

32

68

37

75

41

81

48

81

41

68

32

63

34

52

24

54

8

1804,

55

5

49

18

fid

ai

64

29

70

Sfr

77

47

rt-

50

76

50

75

40

63

33

54

27

47

rt
I

1805,

47

23

48

22

55

30

63

37

69

34

70

38

77

53.

72

54

76

.40

63

23

57

20

52

21

1806,

50

25

51

17

52

21

64

32

72

40

71

43

70

52

75'

48

67

40

62

26

56

34

54

26

1807,

49

17

9*9

21

5£

22

71

25

85

86

68

4T

73

50

7*

50

'64

33

65

82

51

18

50

16

1808,

50

17

52

24

51

27

56

25

72

47

76

48

84

46

71

40,

67

$0

58

31

57

25

52

17

1809,

45

14

50

29

54

SO

57

27

76

34

70

39

76

51

70

'51

68

33

61

36

51

20

51

31

1810,

51

18

53

14

52

25

68

35

71

27

78

M

71

49

74

49

73

44

66

ai

51

28

51

22

1811,

49

18

50

24

57

31

68

26

78i

40

77

43

76

50

69

50

73

43

65A

34

57

32

53

20

1812,

50

10

52

3*

53

23

51

80

72

S#

76

46

68

47

68

47

64

38

60

33

53

20

48

15

181*3,

50

25

52

34

54

26

64

31

66

42

7»

1

48

7*

48

65

42

63

86

59

27

54

24

50

20

1814,

41

-2

47

20

56

24

65

35

62,

34

67

38

78

47

69

42

69

37

61

30

53

18

55

21

1815,

45

13

51

31

60

32

73

81

68

44

76

47

68

46!

70

47

71

38

60

40

55

13

49

2

1816,

49

21

50

10

50

23

63

28

63

35

71

.« .

71

44

65

46

62

35

60

36

52

18

49

25

1817,

54

24

50

32

50

22

60

24'

62

39

81

>

43

65

48

62

43

75

35

54

28

57

34

50

16

1818.

52

27

51

18

50

32

60

SI

Tl

41

79

48

79

48

76

43

68

40

65

40

59

36

53

26

1819,

52

30

50

25

57

30

59

34

66

34

64

46.

76

47

,77

50

68

37

66

22

52

20

53

3

1820,

47

0

52

25

55

11

70

34

73

30 1

80

42

74

45

66

40

74

37

56

32

55

30

55

29

1821,

55

12

50

24

52

27

71

32

62

S2

69

40

76-

89

78

50

73

50

63

33

58

30

55

30

1822,

48

24

54

33

53

32

70

35

70

86

80

48

71

46

72

47

66

37

60

35

57

32

46

22

1823,

45

11

48'

12

54

25

56

31

71

38

64

39

61

44

66

43

66

35

61

28

54

27

51

24

1824,

52

25

50

28

55

25

68

25

72

30

78

41

75 48

70

41

75

29

63

26

58 25

52

15

The Maximum Temperature that has taken place during 24 years, was at the noon observation of
May 25. 1807; thermometer then stood at 85°. In the general remarks for this day, it is stated, the
weather was intensely hot ; there was distant thunder, and a continued flame of lightning all night.

The Minimum Temperature during 24 years, took place on the morning of January 17. 1814 ; the
thermometer was then 2° below zero, — 2°.> Among the general remarks, it is stated, that, at this time,
there occurred the most severe frost on record. The thermometer was unusually low daring the whole
of the month, but particularly on the 4th, 8th, 13th, 17th and 20th. On the morning of the 4th, the
thermometer was at 10°, and in the evening at 11°. On the morning of the 8th, it was at 10°, and in
the evening at 9°. On the 13th, morning at 15% and at night 5°. On the 17th, 2° below zero ; morn-
ing; 14° at noon ; and 3° at night. On the 20th, it was 15° in the morning, and 10° at night

The average temperature of the whole month, 24*47, is the lowest monthly mean temperature during
the whole period of the journal.

VOL. XI. PART, II. 3 H

428

Dr Barnes's Remarks on, and Tabular Results of,

TABLE II.

CONTAIKIKG THB MBAM TETOERATVBE OP BACH MONTH JOE 24 YEABS, AMD THE ANKCAL MEAN

TEMPERAT0BE OF EACH TEAS.

Years.

Jan.

Feb.

March.

April

May.

June.

July.

Aug.

Sept.

Oct.

Nor.

1 Mean

Dec 1 Temp, of
1 each year.

1801,

40,8

o

41

4S°,7

46*,6

53,1

55,8

59*7

60,8

55,5

49,5

39,8

S3°,6

48£

1802,

35,4

87,03

42,48

47,1

50,3

54,8

55,63

61,63

55,93

50,68

41,07

38,47

47,54

1803,

85,17

38,06

42,71

47,15

50,32

55,56

63,40

60,00

52,25

48,55

39,10

87,20

47,456

1804,

41,3

36,9

39,89

48,8

55,7

60,32

60,07

59,4

58,1

51,6

42,7

34,6

48,656

1805,

86,5

38,2

48,67

47

50,66

55,4

61,4

60,78

57,67

45

40,5

38,8

47,965

1806,

87,70

88,37

40,70

45,70

53,40

56,90

59,50

59,38

55,40

51,08

46,70

43,50

48,944

1807,

87,83

87,84

36,24

44,95

51,96

56,05

60,40

61,22

48,20

51,51

35,29

36,08

46,464

1808,

87,4

87

37,43

41,51

55,4

59

64

61,2

53,92

43,92

41,46

86,58

47,8406

1809,

82,6

41

42,95

41,21

54,7

55,07

59,35

57,91

53,6

51,22

40,41

89,83

47,4875

1810,

36,9

37,62

38,7

46,68

48,4

59,35

59,28

59,02

56,29

48,4

39,6

88,2

47,37

1811,

84,98

39,3

48,7

47,5

54,8

57,22

60,6

57,67

55,25

53,4

46,12

37,87

49,00

1812,

86

41,05

36,65

40,97

51,3

55,8

56,81

57,8

54,4

48,5

40,2

84,72

46,142

1818,

35,8

42,41

44,5

45,1

51,4

56

58,15

56,24

53,20

44,72

39,23

37,24

47

1814,

24,47

35

88,21

48,7

47,18

53,32

59,5

57,74'

55,7

45,85

40,07

38,1

45,82

1815,

32,85

42,71

43,6

46,8

58,7

57

58

58

55,3

50

36,86

34,08

47,4

1816,

86,4

35,6

37,4

42,4

48,87

53,68

55,3

55,7

51,4

48,86

38,6

36,8

45,085

1817,

40

41,8

40,43

48,1

47

57,8

56,6

55

55

41,3

47,83

35

47,12

1818,

39,3

86,7

38,63

42,4

53

60,3

62,1

57.2

54,1

53,4

48,55

40,06

48,812

1819,

39,53

88,5

48,05

46,5

52,3

54,8

60

63,8

54,5

46,6

87,5

32

47,4

1820,

30,4

38,20

38,40

47,60

51,10

54,70

59,20

56,5

58,3

45,4

41,8

40,8

46,42

1821,

88,2

37

40,8

48,4

47

54

57,1

59,8

57

50

45,4

42,1

48,06

1822,

40

42,45

44

46

53,4

61,14

58,5

58,3

52

49,5

45,8

36

49

1823,

81,7

85,6

40,4

48

52,7

52,3

56

55,3

53

45,5

45,1

40

45,9

1824,

40,50

40,00

39,80

45,60

53,00

56,00

59,70

57,80

55,60

48,00

42,50

40,00

48,21

The annual means of the thermometer for 24 years, divided into periods of six and twelve
years each, give the following results :

The average or mean temperature of the first six years, viz. 1801, 1802,

1803,1804,1806,1806,

The mean temperature of the second six years, viz. 1807, 1808, 1809, 1810,

1811,1812,

The mean temperature of the third six yean, viz. 1813, 1814, 1815, 1816,

1817,1818,

Mean temperature of the last six years, viz. 1819, 1820, 1821, 1822, 1823,

1824,

Mean temperature of the first twelve years, ending 1812,
Mean temperature of the last twelve years, ending 1824,
Mean temperature of the twenty-four years,

48°, 1435

47,8886

46,7895

47,4983
47,7685
47,144

47,4587

a Meteorological Journal kept at Carlisle.

429

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Dr Barnes's Remarks on, and Tabular Results of,

In

29,796
29,8175
29,895
29,8619
29,859
29,7706
29,8192
29,875
29,817
! 29,8563
29,81425
29,856
£9,903
29,8763
29,8676
29,78
29,83
29,841
29,84
29,877
29,804
29,89
29,77
29,83

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431

TABLE V. — EXHIBITING THE QUANTITY OF BAIN OF EACH MONTH FOB 24 YEARS, AND THE

ANNUAL QUANTITY OF EACH YEAR.

■

Annual

Yean.

Jan.

Feb.

March.

April.

May.

June.

July.

August.

Sept

Oct.

Nov.

Dec.

quantity of
each year.

Inches,

Inches.

Inches.

Inches.

Inches.

Inches.

Inches.

Inches.

Inches.

Inches.

Inches.

Inches.

Inches.

1801,

3,000

2,456

2,874

0,862

1,931

0,325

5,627

0,908

4,804

4,702

1,496

2,481

31,466

1802,

1,970

2,623

0,840

2,566

0,470

2,343

5,308

2,509

2,344

4,420

0,670

2,441

28,504

1803,

1,042

3,556

1,472

1,980

2,940

2,524

0,755

3,694

2,322

2,030

2,450

2,775

27,520

1804,

5,335

1,995

2,400

1,885

2,475

2,660

3,275

6,270

1,010

5,500

2,040

1,000

35,845

1805,

1,950

2,455

2,300

0,630

1,740

2,380

5,060

3,130

2,170

0,470

0,460

3,610

26,355

1806,

3,26

2,10

0,77

0,89

1,47

1,26

3,21

5,57

3,50

1,25

5,32

2,94

31,54

1807,

0,80

3,17

0,76

1,88

2,41

1,59

2,45

1,93

5,37

3,36

2,53

1,50

27,75

1808,

2,10

1,57

0,20

1,20

2,86 .

0,82

3,90

4,48

1,84

3,95

3,06

1,88

27,86

1809,

3,50

2,53

0,56

1,20

3,75

2,85

1,84

5,19

4,95

0,38

1,84

3,18

31,77

1810,

1,84

1,22

3,80

1,01

0,53

1,60

3,24

3,22

1,70

3,12

3,15

4,30

28,73

1811,

1,30

3,80

2,20

1,60

6,02

2,25

2,40

2,88

2,35

2,47

4,00

3,26

34,53

1812,

1,41

4,62

2,75

1,12

1,71

2,81

1,61

2,58

2,91

2,72

2,02

0,61

26,87

1813,

2,02

3,67

0,81

1,68

4,01

1,00

3,11

1,08

1,98

3,12

2,23

0,97

25,68

1814,

0,44

1,12

0,93

4,31

0,51

1,50

3,61

2,09

0,96

3,01

4,16

4,92

27,56

1815,

0,82

1,54

4,05

0,86

3,86

3,13

1,66

2,54

3,38

3,77

2,22

3,93

31,76

1816,

1,85

0,78

1,88

1,38

2,31

1,51

4,57

1,33

3,32

2,36

2,04

2,44

25,77

1817,

1,57

3,20

2,13

0,31

2,71

3,06

3,64

5,71

1,46

1,17

2,80

2,75

30,51

1818,

3,51

1,67

6,10

2,56

1,11

1,75

4,11

1,85

3,66

3,49

3,30

1,60

34,71

1819,

3,62

3,10

1,58

1,68

1,87

2,11

3,66

1,60

2,27

5,15

3,28

3,34

33,26

1820,

2,25

1,80

2,47

1,00

3,40

3,64

2,02

4,01

3,11

2,45

1,60

2,42

30,17

1821,

1,65

0,75

3,68

2,74

1,26

1,11

1,55

1,74

3,45

4,67

4,70

A fjf}

31,93

1822,

1,53

2,87

4,01

1,90

1,34

1,05

5,33

5,33

1,33

4,06

4,31

2,35

35,38

1823,

2,68

2,02

1,96

1,64

4,61

1,57

5,12

5,18

3,80

2,84

1,62

2,47

35,51

1824,

1,63

0,77

2,50

0,85

1,23

2,23

2,55

2,95

3,85

3,01

5,53

5,63

32,73

Total,

51,077

55,385

53,026

37,133

56,526

47,072

79,605 77,771

67,840

73,472

66,826 J 67*427

733,71

The following are the mean results of the Fall of Rain during 24 years, divided into periods similar to those
of the Thermometer and Barometer :

The mean quantity of rain of the first six years, 1801 — 1806, .... 30,205 incites.

Mean quantity of rain of the second six years, 1807 — 1812, 29,585

Mean quantity of rain of the third six years, 1813— 1818, 29,83

Mean quantity of the last six years, 1819— 1824, . 83,163

Mean quantity of the first twelve years, 1801 — 1812, 29,895

Mean quantity of the last twelve years, 1812 — 1824, 31,246

Mean for the first eighteen years, 1801—1818, 29,706

Mean of twenty-four years, 1801— 1824, 80,571

The highest annual mean height of the barometer that has occurred is 29,903. This was in the year 1813,
and the quantity of rain during that year, 26,87 inches, was the least that has fallen in one year during the
period of the journals. . . .*

The lowest annual mean of the barometer, 29»77, was in 1823, and the quantity of rain of that year, 35,51
inches, the greatest in the journal, except in the year 1804, when the quantity was 35,845; barometer 29,8619.
It may be remarked, that an unusually large quantity of rain fell at Carlisle during the last seven years.
The greatest fall of rain in one month during 24 years, took place in August

1804: mean barometric pressure of the month, 29,89, 6,270 inches.

The least fall of rain in one month during 24 years, was in March 1808 ; mean

barometric pressure of the month 30,20, 0,20

432

Dr Baknes on a Meteorological Journal, Sfc.

TABLE VI.

SHEWING THE QUANTITIES OF RAIN PUBING THE 6 SUMMER AND 6 WINTER MONTHS

OP EACH TEAR FOR 29 YEARS.

Ymn.

From beginning
of April to ena
ox September.

From beginning
of October to end]
of March next
following.

Yflftn.

From beginning
of April to end
of September.

From beginning
ofOctobertoend
of March next
following.

1801,
1802,
1808,
1804,
1806,
1806,

Incbe*.

14,457

15,540

14,215

17,575

15,110

16,900

Inches.

14,112

13,601

16,965
15,245
10,670
14,240

1813,
1814,
1815,
1816,
1817,
1818,

Inches.

12,860

12,980

15,430

14,420

16,890

15,040

Inches.
8,810
18,500
14,430
13,740
18,000
16,690

Mean fori
6 years, J

15,466

14,139

Mean fori
6 yean, J

14,603

15,028

1807,
1808,
1809,
1810,
1811,
1812,

15,630
15,100
'19,780
11,300
17,540
12,740

11,260
15,480
12,260
17,870
• 18,510
11,850

Mean for\
18 years, J

16,139

14,568

1819,
1820,
1821,
1822,
1823,

13,190
17,180
11,860
16,250
21,920

18,290
12,560
22,410
17,380
11,830

Mean for \
6 yean, J

15,348

14,538

Mean fori
5 years, J

16,078

16,492

Mean fori
12 years,/

15,407

14,338

Mean for 1
23 years,/

15,344

14,986

The Average or Mean Quantity qf Rain qfeaeh month for 24 years:

The mean quantity of rain of the month of January for 24 years,

. 2,128 inches.

February for do, . . .

2,308

March for do. . . .

2,209

April for do. •

1,560

May for do. ...

. 2,355

June for do. ...

. 1,960

July for do. . . .

8,317

August for do. . ,

. 8,8«

September for da

. 2,827

October for da

. 8,061

November for do.

. 2,784

December for da

. 2,809

( 483 )

XXV. On Mudarine, the Active Principle qfthe Bark qfthe Root
of the Calotropis Mudarii, Buch.; and the singular influence
of Temperature upon its solubility in Water. By Andrew
Duncan, M. D., F. R. S. Ed. Professor of Materia Medica in
the University of Edinburgh.

(Read SQth December 1830 J

JL o the professional zeal and liberality of my lamented friend
Dr Adam, late Secretary to the Medical Board at Calcutta, I am
indebted for many interesting specimens of the Materia Medica
of Hindostan. Among these was a large supply of the powder
of the bark of the Mudar or Mudhar, the Calotropis Mudarii of
Dr Hamilton, which, with a nearly allied species, had been for*
merly referred to the genus Asclepias, under the trivial name of
gigantea.

The high reputation which the Mudar Powder enjoyed
among the natives of India, as a specific for the cure of various
cutaneous diseases, induced Mr Playfair, Mr Robinson, and
Dr Vos, to investigate its action as a medicine. These gentle-
men gave favourable reports of its effects in India, in cutaneous
diseases, syphilitic affections, and tape-worm.

Dr Adam was desirous that it should be tried in the diseases
of this country, and that it should be subjected to chemical ana*
lysis, in order to ascertain the nature of its active constituent
principles. I lost no time in proceeding with both investigations.
The results of my first experiments were accordingly communi-
cated to the public, in a paper published in the Edinburgh Me*
dieal and Surgical Journal in July 1829. Since that time, greatly

434 Dr Dunca** oh Mudarifie.

enlarged experience has satisfied me, that mudar possesses bo
specific virtue ; but that it is infinitely more valuable, from its
common medicinal properties, which correspond in every re-
spect, both in kind and in degree, with those of ipeeacuan. In-
deed) I have no doubt, that, from the facility with which any
quantity may be supplied from the province of Bahar, the use
of the Brazilian root may be altogether dispensed with in our
East Indian settlements, and that mudar may even become, in a
commercial point of view, a valuable export from Bengal to Eu-
rope. As such I feel myself justified in recommending it to the
notice of the Honourable East India Company, and to the pri-
vate merchants trading with India.

In the paper to which I have already alluded, I gave an ac-
count of the analysis of mudar, so far as I had then carried it. - I
merely indicated the singular property possessed by one of its
constituents, Mudarine, which it is the object of this paper to
explain more fully. In a note, I mentioned that I had disco-
vered it to possess the very singular property of being very solu-
ble in cold water, and gelatinizing when the solution was heated
to 85° or 90° Fahrenheit.

Since that time I have frequently repeated and varied my
experiments upon the mudar powder ; but I have not yet com-
pleted my general analysis, which, upon the whole, coincides
with what I published from my first experiments in 1829.
Having, however, satisfied myself that the principle to which I
gave the name of Mudarine possesses a property which has not
been observed in any other principle, organic or inorganic, and
constitutes a very striking exception to the general law of the
power of solvents being increased by increase of temperature, I
have thought it deserving of being communicated to the Royal
Society, and, through the medium of its Transactions, of be-
ing made known to scientific chemists, as it is not imjfrbbable
that it k possessed, in a greater ot less* degree, by gofae other

Dm Duxcax m Mudarine, 435

organic principles, and that its discovery may lead to consider-
able modifications in our methods of analyzing organic sub-
stances.

Mudarine is very easily obtained, in a state of considerable
purity, from the tincture of mudar, made by macerating the
powder of the root in cold rectified spirit The greater part of
the spirit may be recovered by distillation, and the remaining so-
lution, which acquires a much deeper colour, but remains per-
fectly transparent, is then allowed to cool. As the temperature
declines, a white granular resin is deposited by a species of crys-
tallization, from a transparent coloured solution. The whole is
now allowed to dry spontaneously, that all the resin may con-
crete. The dry residuum is then treated by water, which dis-
solves the coloured portion, and leaves the resin untouched. It
is to this principle, dissolved by cold water from the resinous ex-
tract, that I have given the name of Mudarine.

By exposure to the air, it dries readily, forming a mass of a
pale-brownish colour, perfectly transparent and homogeneous in
appearance, having no tendency to crystallize, but becoming full
of cracks, diverging from the centre, exceedingly brittle, and ha-
ving no adhesion to the capsule containing it, from which it peels
off spontaneously. It has no smell, and is intensely bitter, with
a very peculiar nauseating taste.

It is exceedingly soluble in cold water, at the ordinary tem-
perature of the atmosphere. On the contrary, it is insoluble in
boiling water. It is also soluble in alcohol, but the power of
this solvent is increased by increase of temperature. It is inso-
luble in sulphuric ether, oil of turpentine, and olive-oil

It is in the solution in water, when nearly saturated, that the
peculiar property of mudarine is most easily exhibited.

At ordinary temperatures this solution is quite fluid and
transparent When heat is gradually applied, already at 74°, a
change in its constitution begins to be observable, indicated by

VOL. XI. PART II. Si

4&S Dfe Duncan an Mudarine.

a slight diminution of transparency and limpidity. As the tern*
perature is raised, these changes increase, and at 90° it has in a
great degree lost its transparency, and has acquired the consis-
tence of a tremulous jelly.

If the heat be now withdrawn, and the vessel allowed to cool,
the jelly gradually, but very slowly liquefies, so that a day or
two elapses before it has entirely recovered its original limpidity
and transparency.

If, instead of withdrawing the heat when it has risen to 90°,
we continue to raise it, further changes occur.

At 95° it is fully gelatinized, and now there appears to be a
separation taking place into two parts, a soft brownish coagu-
lura and a liquid nearly colourless, not unlike the separation of
the serum from the crassamentum of the blood, as it spontaneous-
ly contracts.

At 98° the coagulum is evidently contracted in size, while
the fluid increases in proportion.

At ISO0 the coagulum seems to dissolve ; probably, however,
it only is reduced in size by contraction.

At 185° the coagulum is very small, and has a tenacious
pitchy consistency.

At 212° little further change.

The alterations which in this state it undergoes on cooling,
are next to be observed.

At 140° the fluid is very turbid. The coagulum has not
diminished in size, and is now very hard and brittle.

At 110° fluid less turbid, coagulum remarkably brittle, with
a resinous fracture.

At 100°, fluid more transparent, with thin detached pellicles
on the surface. When cooled down, even to the freezing tem-
perature, the coagulum remains unaltered, and very much re-
sembles colophony ; but, after the lapse of several days, it gra*

Dr Duncan on Mudarine. 437

dually liquefies in the portion of fluid in contact with it, with-
out passing through the intermediate form of a jelly.

The coagulum, when separated from the fluid, is a transparent
brown mass, exceedingly brittle, not deliquescent, fragments an-
gular lustre resinous, taste bitter, nauseous, adhering to the
teeth.

In this state it seems at first not to be soluble in distilled
water, but after some days it is dissolved in it, with the same
phenomena as in the fluid from which it was separated by boil-
ing, and the solution has acquired its original properties. The
dry mudarine is readily soluble in rectified spirit, and is not pre-
cipitated from the alcoholic solution by the addition of water.
As long as any considerable proportion of spirit remains, it is
not coagulated by increase of temperature, but, on allowing the
spirit to evaporate by exposure to the air, it remains dissolved in
the water, and has reacquired its original properties.

It would therefore seem that its tardy solubility, after being
contracted, is owing to the state of increased aggregation, for
when this is removed by alcohol, its solubility is quickly re-
stored.

Mudarine is also extracted, by the action of cold water, from
the powder, but it is not so easily separated from a gummy mat-
ter, also dissolved, as from the resin extracted along with it by
rectified spirit.

Its presence is, however, sufficiently demonstrated by the
cold infusion gradually losing its transparency as its tempera-
ture is increased, tod in this case it regains its former transpa-
rency, even after having been subjected for some time to the
boiling temperature.

We therefore see, that, in this instance, a very active princi-
ple is more readily dissolved by cold than by boiling water ; and
it is probable that there are other instances in which heat is im-
properly empldyedf~ with the view of extracting the active princi-
ples of vegetable substances.

Si2

438 Da. Dtixtf a» on Mndarinc,

If iMt IKi-

The influence of temperature upon the power of solvents it
exceedingly curious and interesting. It haa bag been reeog.
nized as a general law, that the proportion of solid pri
which are dissolved in fluids, is more or less increased by the
sistance of heat. Hence water, by decoction and digestion* com-
monly dissolves more speedily and more abundantly, than by odd
maceration, the soluble! principles of compound bodies*.

Various exceptions, however, to this general iule> have suc-
cessively been discovered. Sea-salt has long been known to be
equally soluble in cold and in boiling water. Afterwards, it was
found that lime and magnesia were actually more soluble in cold
than in boding water ; and a still more remarkable relation be-
tween the solubility of certain saline substances and heat has
more recently been discovered. Sulphate of soda, and the nitrate
and muriate of barytes, by successive augmentations of tempera-
ture, have their solubility first slightly increased, then greatly
diminished, and again very rapidly increased. This phenomenon
is the less likely to be soon explained, that each salt follows in
this respect a different law, or that the curve of their solubilities
in relation to temperature in each is different. All the known
exceptions to the general law have been observed in the mineral
or inorganic kingdom, and from analogy we may conjecture that
many others exist in similar bodies, although not yet detected.
It is also necessary to remark, that when, in consequence of the
diminished power of the menstruum, whether by increase or di-
minution of temperature, the solvend is separated by precipi-
tation or crystallization, its nature is not altered, and it is equally
soluble in the menstruum as before, by diminishing or increasing
the temperature, or by adding an additional quantity of the sol-
vent.

But, in regard to the organic kingdom, the law of increased

solubility, by increase of temperature, has been hitherto hefclto

be universal, except when the nature of the solvend is altogether

i

Br Duncan a* Mudarine*

altered by heat, so that it h*s become no longer soluble in* the
menstruum, either by restoring the original temperature, or by foi-
cwqsing the quantity of the menstruum, Thus albumen, once
coagulated by heat, is rendered permanently insoluble in water.
hTZttetotomo^ debility of c*L prmciplesia «*.
posed to be increased by increase of temperature. By heating
the menstruum, it commonly acts more- quickly and more com-
pletely, the soluble principles are more speedily extracted from or-
ganic compounds, and in larger quantity, and the solution is more
liquid and perfect; while, on the contrary, on cooling, the prin-
ciple dissolved separates from a hot saturated solution either by
precipitation or crystallization, or by becoming viscid, or forming
a jelly, and in all these cases the principle thus separated is re-
dissolved by again increasing the temperature, shewing that its
nature is not altered, and that they are simple examples of the
rule that the solubility of bodies is increased by increase of tem-
perature. The relative solubility of animal gelatine and of pec-
tic acid, at different temperatures, may be specified with peculiar
propriety as forming a striking contrast with the subject of this
paper. Gelatine is sparingly Soluble in water at the ordinary
temperature of the atmosphere, so that cold water is incapable
of extracting it from bones, horn, membranes, tendons, or even
flesh. By increase of temperature, it becomes rapidly more so-
luble, and most of these substances yield it very readily to boil-
ing water. Nay, by increasing the temperature of water above
the bailing point in Papin's Digestor, it becomes progressively
still more soluble ; and, accordingly, this method is employed by
D'Arcbt to extract gelatine from the hardest bones. On cool-
ing, the water is no longer capable of retaining the whole gela-
tine dissolved, and the solution, by reduction of temperature,
forms a; trdmuiobS' jelly* more or less solid in proportion to its
condetntration, wiikh'is again readily dissolved into a fluid by the
application of heat, prdpdrties veey nearly the reverse of those

440 Db, Duncak on Mudarine.

I have stated to belong to mudarine. Nearly the same pheno-
mena are observed with regard to pectic acid

I must postpone to another opportunity the changes which
mudarine undergoes from various chemical re-agents, as well as
the general analysis of the mudar powder, because I think, that,
by limiting the present communication to the singular exception
which mudarine presents to the solubility of organic principles
being increased by increase of temperature, it is more likely to
attract the notice of scientific chemists, and to lead to the in-
quiry, whether other vegetable principles possess any analogy in
this respect.

( 441 )

1VL Description and Analysis of some Minerals. By Thomas
Thomson, M. D., F. R. S. L. & Ed. &c, Professor of Che-
mistry, Glasgow.

(Read SI rf Jpril 1828.)

1. Anhydrous Silicate qf Iron.

JL his mineral was given me for examination by Patrick
Doran, an Irish mineral-dealer, who discovered it in Slavcorrach,
one of the Morne Mountains, on the north-east coast of Ireland,
forming so conspicuous an object at the southern extremity of
the county of Down.

The colour is dark brown, with something of the metallic
lustre.

The mineral is foliated, and breaks easily into four-sided
prisms, seemingly right ; though the summits are very obscure.

. The fragments are strongly attracted by the magnet, but
they have no poles.

Hardness 4.

Opaque.

Easily frangible.

Specific gravity 8.8846.

When heated in a glass-tube, it gives out ammoniacal va-
pours, and loses 1.97 per cent, of its weight.

Infusible per se before the blowpipe, but in the reducing
flame acquires the metallic lustre, and assumes very much the
appearance of magnetic iron-ore.

In muriatic acid it dissolves by the assistance of heat, without
effervescence, leaving behind a quantity of silica in fine flocks,

442 Dr T. Thomson's Analysis qfsome Minerals.

but not gelatinous ; 20 grains being treated in this manner, left a
quantity of white siliceous matter, which, after ignition, weighed
5*535 grains. This matter being fused with twice its weight of
carbonate of soda, dissolved in muriatic acid, and treated in the
usual way, was found composed of,

Silica, ...... 4.861

Peroxide of iron, . . . 0.290

0

Red oxide of manganese, 0.384

5.535

The muriatic solution was evaporated to dryness, and the
dry residue digested in water, acidulated with muriatic acid, till
every thing soluble was taken up. There remained undissolved
a quantity of silica, which weighed after ignition 1 .059 grains.

Suspecting the presence of manganese in the muriatic acid
solution, I neutralized it with ammonia, and threw down the
iron (it had been peroxidized by digestion with nitric acid ), by
benzoate of ammonia.

The benzoate of iron, after edulcoration and drying, was
burnt in an open crucible, and kept red hot till the iron was
brought into the state of peroxide. It weighed . 1 4.95 grains,
equivalent to 1 3.46 grains of protoxide of iron.

The residual liquid was mixed with an excess of carbonate
of soda, and boiled in a flask. Nothing was obtained except a
trace of alumina too small to be weighed.

Thus the constituents of the mineral, by this analysis, are,

Silica, 9.92 or 29.60

Protoxide of iron, . . n.460 67.80

Peroxide of iron, . . 0.290 1.45

Red oxide of manganese, 0.384 1 .92

20.054 100.27

Dr T. Thomson's Analysis of some Minerals. 448

There is a slight excess, which would be diminished by re-
ducing the peroxide of iron and the red oxide of manganese
to protoxides ; for that is the state in which they probably
exist in the mineral. This reduction being made, the consti-
tuents of the mineral will be

Silica, . .... . 29.60

Protoxide of iron, . . 68.605
Protoxide of manganese, 1 .857

100.062

This is equivalent to

14.8 atoms silica,
15.24 atoms protoxide of iron,
6.40 atoms protoxide of manganese.

If we admit the 0.4 oxide of manganese to have been united
with 0.4 protoxide of iron, there will remain

14.8 atoms silica,

14.8 atoms protoxide of iron.

It is obvious from this that the mineral is a simple anhydrous
silicate of iron, composed of

1 atom silica, 2

1 atom protoxide of iron, 4.5

6.5

This mineral adds another species to the family of silicated
iron already so numerous; though there can be little doubt
that many more species will be added hereafter. The following

VOL. XI. part ii. 3k

444 Br TV Thomson's Analysis of some Mineral*.

enumeration of the species at present known may not be unac-
cept^blQ to qrineralogists :

1. Sp. Sideroschisolite, or disilicate of iron, discovered in
Brazil, and described by Dr Warnekikk*. It is composed of

1 atom silica, 2

2 atoms protoxide of iron, . . 9

1 atom water, 1.125

12.128

2. Sp. Chamoisite, occurring in beds at Chamoisin, in the
Vakris, and described and analyzed by Berthierf. Its consti-
tuents are, *

1 atom silica, ...... 2

2 atoms protoxide of iron, . . 9

2 atoms water, 2.25

13.25

3. Sp. Cronstedtite, discovered at Przibram in Bohemia, de-
scribed by Zippe, and analysed by Professor Steinmann $. Its
constituents are,

1 atom silica, 2

1 atom protoxide of iron, . 4.5

1 atom water, ...... 1.125

7.625

» - *

i

* Poggebtdorff's Annalen, i. 387.

f Ann. des Min. V. 393.

I Schweigger's Jahrbuch, ii. 69.

Dk T. Tflo^oN's 4iriy*k qf^me Minerals. 44fr

4. Sp. Anhydrous silicate of, wpij.frpm theAM<SJiie Moun-
tains, described and analyzed in this paper.

5. Sp. Hedenbergite, found at,XiUM)l^&>i]l;Sodennanland,
Sweden, and described and analyzed by Hedekberg *. Its con-
stituents seem to be,

8 atoms silica, 6

1 atom protoxide of iron, . . 4.5

2 atoms water, ...... 2.25

12.75

6. Sp. Chloropal, discovered by Joseph Jotf as, near Unghwar,
in Hungary, along with the opal, and described and analyzed by
Bebnhardi and Brandes f .. Its. constituents are,

>

3 atoms silica, t 6

1 atom protoxide of iron, . . 4.5
2£ atoms water, ..... 2.8125

13.3125

7. Arfwedsonite, so called by My Brooke, but formerly known
by the name of Ferruginous Hornblende, brought from Kargard-
luarduk in Greenland, by Sir Charles Giesecke'. it was ana-
lyzed several years ago in ray, laboratory, and found composed of

15 atoqis, silica,
4 atoms peroxide of iron,
1 atom deutoxide of manganese.

i. ■ ■. !■

* 4fhandKngary ii. 164. f Schwbiggb&'s Jahtbuch, ▼. 29.

3k2

446 Dr T. Thomson's Analysis of some Minerals.
It is therefore a compound of

4 atoms pertersilicate of iron,
1 atom tersilicate of manganese.

8. Sp. Hisingrite. This mineral was discovered in the iron
mine of Gillinge, in Sodermanland, and was first described and
analyzed by Hisinger in 1810 *.

Its constituents are,

4 atoms persilicate of iron,
1 atom silicate of alumina,
4 atoms water.

9. Sp. Knebilite. This is a name given by Dobereiner to
a mineral of unknown locality, which he described and ana-
lyzed f. Its constituents are,

1 atom silicate of iron,

1 atom silicate of manganese.

10. Sp. Pyrosmalite. Discovered in the iron mine of Bjelke,
Nordmark in Wermland, Sweden, described by Haussmann, and
analyzed by Berzelius and Hisinger £ is composed of,

14 atoms seaquisilicate of iron,
5 atoms sesquisilicate of manganese,
1 atom sesquichloride of iron.

* A/hand. iii. 804. f Schwexggzb's Journ. xxi. 40.

\ 4flumLiv.sn.

Dr T. Thomson's Analysis of some Minerals. 447

Or, if we consider the sesquichloride as replacing a certain por-
tion of sesquisilicate of iron, then the constituents will be,

3 atoms sesquisilicate of iron,

1 atom sesquisilicate of manganese.

11. Sp. Nontronite. Discovered at Nontron, in the Depart-
ment of Dordogne, France, and described and analyzed by Ber-
their * Its constituents are,

7 atoms terpersilicate of iron,

2 atoms bisilicate of alumina,
1 atom silicate of magnesia.

It might be considered as a compound of two distinct mi-
nerals.

The first composed of

1 atom terpersilicate of iron.
1 atom silicate of magnesia.

The second of

9

3 atoms terpersilscate of iron.
1 atom bisilicate of alumina.

One integrant particle of the first of these, combined with
two integrant particles of the second, would constitute nontro-
nite. On this view of its constitution, nontronite might be re-
presented by the following formula :

1 (/S3 + MS) + 2 (3/S8 + A/S«)

* Ann. de Chim. et de Phys. xxxvi. 22.

448 Dr T. Thomson's Analysis qfsome Minerals.

2. Hydrolite.

This mineral seems to have been first discovered by Leman,
in the cavities of araygdaloidal rocks, in the Vicentine. These
specimens were analyzed by Vauquelin, under the name of Sar-
^blitp ; and Havy considered them as mere varieties' of analcime.
Some years ago the mineral was discovered in the oounty of An-
trim, Ireland, lodged in amygdaloidal rocks, precisely as in the
Vicentine. The specimens in my possession were procured from
Patrick Dorak, an Irish mineral-dealer, who had collected
them in this locality. Dr Brewster gave an account of the
physical properties of this mineral in his scientific Journal #, un-
der the name of Gmelinite ; and Haidingejl has described it un-
der the same name, in an appendix added to his English transla-
tion of Moh8* Mineralogy f .

Colour snow-white.

All the specimens which I have seen,
are in double six-sided truncated pyra-
mids, with a short six-sided prism between
them. The inclination of y on y', accord-
ing to Dr Brewster's measurement, is
83° 36'.

Translucent.

Hardness 3.5. Scratches ealcareous spar, but not fluor-spar.
x,x vLiistre vit*eou& '
u .."Specific gravity < 2,054.

Very easily frangible. ...

Before the blowpipe, swells out and assumes the "appearance
of an enamel ; but does not fuse into a transparent glass.

• Vol, ii. p. 9QSL f Vol. iii. p. 174.

Dr T. Thomson's Analysis of some Minerals. 449

When exposed to a red heat, it gives out water, and nothing
else, and loses 29.866 per cent, of its weight • r i v ..;

I Subjected it to analysis ; but, as the quantity of it in my
possession only amounted to 5.8 grains after ignition* it will bt;
necessary to state the steps of the analysis, to enable the reader
to judge of the degree of confidence to which my experiments
are entitled.

The 5.3 grains of the ignited mineral, after having been re-
duced to a fine powder, were intimately mixed with 30 grains
of carbonate of bary tes, in a platinum crucible* and the mixture
was exposed to a strong red heat, and kept at that temperature
for an hour. The whole was then - dissolved in dilute muriatic
add. The undissolved portion having the appeafturae ofi hydro-*
lite undecomposed, was mixed with 30 grama of darbonate of b&~
rytes, and kept in a strong heat for two hours. It was .'then
dissolved in dilute muriatic acid. A few flocks remained undis-
solved ; but they were light and loose, indicating 'that they had
been acted upon by the bary tes. * The tforo solutions were mixed
together, and evaporated to dryness in a porcelain bdsin. , The
dry mass was digested for some time 'in water acidulated with
muriatic acid. The whole was then thrown on the filter, to se-
parate the undissolved silica from the solution. Hie silica on
the filter being washed, dried, and ignited, weighed 4 grains.
It was laid aside for examination. -

The muriatic acid solution was neutralized by caustic am-
monia added slightly in excess. A brown precipitate fell,, weigh*
ing, after ignition, 1.08 grains. Being digested in muriatic acid,
it left undissolved 0.055 grains of a grey matter, which, tested
by the blowpipe, proved to be silica very slightly tinged with
iron.

The muriatic solution thus freed from silica was mixed with
potash-ley in considerable excess, and heated in a flask. There
was precipitated a quantity of peroxide of iron, weighing, af-

450 De T. Thomson's Analysis of same Minerals.

ter edulcoration, drying, and ignition, 0.44 grain. , The potash-
ley had dissolved the alumina of the precipitate, which obviously
amounted to 0.585 grain. Thus the brown precipitate thrown
down by caustic ammonia, was composed of,

Silica, 0.055

Peroxide of iron, . . . 0.440
Alumina, 0*585

1.080

The muriatic solution was now mixed with a sufficient quan-
tity of carbonate of ammonia, to throw down the whole of the
barytes. The filtered liquid was evaporated to dryness, and ex-
posed to a graduated heat, to drive off the ammoniacal salts.
The residue was found to contain lime derived from the filter.
To get rid of it, I added some carbonate of ammonia, heated the
liquid in a flask, then left it in a small glass cylinder till the car-
bonate of lime subsided ; drew off the clear supernatant liquid
by a sucker, edulcorated the carbonate of lime by distilled wa-
ter, which was drawn off in like manner by a sucker. The liquid
was evaporated to dryness in a platinum vessel, and the ammo-
niacal salt driven off. There remained behind a little saline
matter, which weighed, after ignition, 0.84 grain. It was soluble
in water, and the aqueous solution was abundantly precipitated
by muriate of platinum. Hence the salt was chloride of potas-
sium, and contained 0,41 potassium, equivalent to 0.53 potash.

The 4 grains of silica, obtained at the beginning of the analy-
sis, we*e mixed with thrice their Weight of anhydrous carbonate
of soda, and exposed to a strong heat in a platinum crucible. The
mass, which had undergone fusion, was dissolved in muriatic acid,
and the solution was evaporated to dryness. The dry residue was
digested in dilute muriatic acid, and thrown upon a filter, to se-

Dr TV Thomson's 'Analysis qfsome Minerals. 451

parate the silica.' Thte silica, after edulcoration, drying, and igni-
tion, weighed 2.96 grains. . It was a fine white powder, and was
perfectly pure.

The muriatic solution, thus freed from silica, was mixed with
caustic ammonia slightly in excess ; a greyish-brown precipitate
fell, weighing, after ignition, 0.58 grain. By solution in muria-
tic acid, and mixing the solution with caustic potash in conside-
rable excess, it was resolved into

Peroxide of iron, . . . 0.185
Alumina, 0.395

.580

Thus, from the 4 grains of the siliceous-looking matter, se-
parated from the hydrolite, when it was treated with carbonate
of bary tes and muriatic acid, were obtained,

« * a t

9

Pure silica, . . ...... 2.96

Peroxide of iron, . . . 0.155
Alumina, . ... • . 0.395

3.54
Loss, 0.46

»

4.00

This loss could have been owing to nothing but the pre-
sence of a little potash in the siliceous matter (the liquid was
carefully examined, but nothing found), which I ~ could not ob-
tain, because I had fused the 4 grains of siliceous matter with

• • * *

carbonate of soda.

If we now add together all the constituents, we shall find
that 5.3 grains of anhydrous hydrolite are composed of

VOL. XI. PART ii. 3l

452 Dr T. Thomson's Analysis if some Minerals.

Silica, 3.015.

Alumina, 0.980

Peroxide of iron, . . . 0.625

Potash, 0.5S0

■■■■

4.95

As hydrolite contains 29.866 per cent, of water, it is obvious,
that if the 5.8 grains analyzed had retained their water, the
weight would have been 7.53 grains. Consequently the consti-
tuents, according to the preceding analysis, considering the loss
as potash, and converting the peroxide of iron into protoxide,
are as follows :

Silica, 3.015 or 39.896

Alumina, .... 0.980 . . 12.968

Protoxide of iron, . 0.5625 . . 7.448

Potash, 0.7425 . . 9.827

Water, . ... . 2.2050 . . 29.866

pa

7.5050 100.

This is equivalent to

14 atoms. silica,

4 atoms alumina,

1 atom protoxide of iron,

1 atom potash,
18 atoms water.

We may therefore consider hydrolite as a compound of

4 atoms bisilicate of alumina,
1 atom bisilicate of potash,
1 atom quatersilicate of iron,
18 atoms water.

Dr T. Thomson's Analysis qfsame Minerals. 453

So that every integrant particle of the mineral is combined
with three atoms of water.

III. Supersulphuretted Lead.

The first specimen of this mineral which I had an opportu-
nity of seeing, was one said to have been brought from Caith-
ness by Sir John Sinclair. This was more than twenty years
ago. I had no opportunity of analyzing it ; but, when held in
the flame of a candle, it burnt with a blue flame, and emitted a
strong odour of sulphurous acid. I have been told by the over*
seers of the lead mines in the north of England, that this kind
of ore is not uncommon in their district ; but I never was so
lucky as to get a specimen of it till August 1828, when Captain
Lehunt brought several pieces of it from Ireland, which he got
from a mineral-dealer in Dublin ; but unluckily the locality of
these pieces is unknown ; though I am in hopes soon of getting
some accurate information on the subject.

The mineral has much the appearance of fine grained galena.

Colour blue.

Lustre metallic.

Texture fine granular ; opaque.

Scratches common galena ; but, as it is not free from grains
of quartz, it may owe its apparent hardness to these grains.

Sectile.

Specific gravity 6.718.

Before the blowpipe, burns with a blue flame, decrepitates,
melts, and, on charcoal, is reduced to a button of lead.

100 grains, when heated, gave out sulphur, and were redu-
ced to 98.206 grains.

20 grains of this mineral, as free from impurities as possible,
were digested in nitro-muriatic acid, till every thing soluble was

8l2

454 Dr T. Thomson's Analysis of some Minerals.

taken up. The undissolved matter, after ignition, weighed 0.25
grain. It was white and transparent, and, when viewed through
a glass, proved to be small grains of quartz, which had been me-
chanically mixed with the mineral.

The solution, while hot, was mixed with an excess of bicar-
bonate of potash, previously dissolved in water, and the mixture
was digested on the sand-bath for 24 hours. The precipitated
carbonate of lead was then separated by the filter : after being
washed and dried, it was exposed to a red heat It melted, as-
sumed . a yellow colour, and weighed 1 8.52 grains. Being, di-
gested in nitric acid, it dissolved, with the exception of a few
white flocks, which weighed, after ignition, 0.44 grain, and
proved, 'when examined by the blowpipe, to be silica. Hence
the oxide of lead was 18.08 grains, equivalent to 16.79 grains
of metallic lead.

The alkaline solution, from which the carbonate of lead had
been thrown down, was evaporated to dryness, and the residue
digested in water. A small, white powder remained undissolved.
By ignition it became yeDow. It dissolved completely in nitric
acid, and the solution was precipitated orange by chromate of
potash. It was therefore oxide of lead. It weighed, after igni-
tion, 0.48 grain, equivalent to 0.445 grain lead.

The alkaline solution was supersaturated with nitric acid,
and the sulphuric acid thrown down by muriate of bary tes. The
sulphate of bary tes, obtained after edulcoration and ignition,
weighed 21.254 grains, equivalent to 2.881 grains of sulphur.

Thus the constituents of the ore were,

Lead, 17.235 or 86.175

Sulphur, .... 2.881 • . . 14.405
Silica, .... 0.690 . . . 8.450

29.806 104.080

Dr T. Thomson's Analysis qfsome Minerals* 455

I do not, know to what the excess is to be ascribed in this
analysis. I repeated the analysis, and obtained similar results, and
an excess which amounted to 2.5 per cent The silica is an ac-
cidental impurity. The ore is obviously a compound of

Lead, 86.175 or 78 or 156

Sulphur, . • . 14.405 . • 13.04 . 26.08

The atom of lead being IS, and that of sulphur 2, it is obvious
that 156 lead is equal to 12 atoms; while 26.06 sulphur is al-
most exactly equal to 13 atoms. The supersulphuret of lead,
therefore, which 1 analyzed, is a compound of

12 atoms lead,

13 atoms sulphur.

• • •

This is an unexpected combination, nothing similar to which
I have met with before. I have not made any experiments to
ascertain whether lead be susceptible of combining with sulphur
in various proportions. Analogy would lead us to suppose that
it is ; for we generally find, that oxygen and sulphur «iter into
the same number of combinations with most of the metals.
There probably, then, exists a sesquisulphuret of lead ; if so, we
may consider the supersulphuret of lead just analyzed, as a com-
pound of

5 atoms sulphuret of lead,

1 atom sesquisulphuret of lead.

This

V. Chabasite.

This mineral, as is well known to mineralogists, exists rather
abundantly in the neighbourhood of Glasgow. The finest spe-

456 Da T. Thomson's Analysis of some Mineral*;

omens have been found at Kilmacolm in Renfrewshire ; and I
am indebted to my friend and pupil Mr Brown, fbr a very fine
collection of chabasites from that locality. It is in large trans-
parent rhomboidal crystals, constituting the well known primary
form of this mineral. Chabasite has been analyzed thrice by
Berzelius, and once by Arfwedson. The following table ex-
hibits the results of these analyses :

Silica, . .

Alumina, •
Lime,

Magnesia, .

Potash, . .

Soda, • .

Water, . .

50.65 48.80 48.00 49.17

17.00

19.28

29.00

18.90

9.73

8.70

8.35
0.40

1.70

2.50

0.41

2.75

12.19

19.50

20.00

19.30

19.73

98.58# 98.78 f 99.21 J 99.99

The last analysis in the table was made by Berzelius upon
a specimen from Scotland It is very remarkable, from the to-
tal absence of lime, which occurs as a constituent in every other
chabasite hitherto subjected to analysis. Berzelius informs us,
that under the soda a little potash is included.

It was this last analysis that induced me to introduce chaba-
site into this paper. Berzelius has given no other locality ex-
cept Scotland. Nor has he favoured us with any description of
the mineral subjected to analysis ; both of which would have
been very desirable. That the chabasite of Scotland is not al-
ways composed, as Berzelius has found it in the specimen which

* Berzelius ; Af hadL vi. 190. The specimen was from Jutland.
f Arfwedson ; Kong. Vet. Acad. Handl. 1824, p. 866. Prom Faroe.
J Berzelius ; Ibid. The variety called Leveyne, and from Faroe.

Dr T. Thomson's Analysis of some Minerals. 457

he analysed, will appear from the following table, exhibiting the
constituents of a very fine specimen of chabasite from Kilma-
colm, which I subjected to a very careful analysis :

Silica, 48.756

Alumina, 17.440

Lime, 10.468

Potash, 1.548

Water, 21.720

99.932

The potash was carefully examined for soda, but none was
fo^dta* It will appearfrom this analy**, that theKitaa-
colm chabasite, so far from containing no lime, contains in fact
a greater proportion of that substance than any other specimen
hitherto analyzed. Is it not possible that the Scottish specimen
analyzed by Berzelius may turn out to be a new species ?

The formula for chabasite seems to be,

3AZS* + CS2 + 6A0.
Or it is composed of

1 atom bisilicate of lime, with some potash,
3 atoms bisilicate of alumina,

» *

6 atoms water*

The excess of lime in the Kilmacolm chabasite, prevents this
formula from applying quite accurately to its constituents *

* Since this paper was read to the Society, I have analyzed a flesh-coloured cha-
basite from the north of Ireland, and foiled it composed of

458 Da T. Thomson's Analysis qf tome Minerals.

V. WoUastonite.

This name was given by Leman to a mineral which occurs in
the lava of Capo di Bone, near Rome. I have never seen a spe-
cimen of it ; but Mr W. Philips informs us, that, by mechanical
division, it yields a crystal precisely the same with the primary
form of table-spar or bisilicate of lime, of which it can scarcely be
said to be a variety *. But there is a mineral which occurs in
the rock of Edinburgh Castle, to which the Edinburgh mineralo-
gists have given the name of Wollastonite, probably from a no-
tion that it is the same with Leman's mineral. I had an oppor-
tunity of seeing and examining some specimens of this mineral
last September, and was surprised to find it to be a mineral very
different indeed from table-spar, being in fact very pure prehnite.
The total want of the shade of green which usually characterizes
prehnite, seems to have prevented the true nature of this mineral
from being recognised. But abundance of prehnite, quite free
from every tint of green, is met with in the neighbourhood of

Silica, 48.988

Alumina, 19.774

Soda, 6.066

Lime, 4.068

Peroxide of iron, . . . 0.404

Water, JW.700

100.

This approaches Berzelius' specimen, and shews us, that the lime in chabasite
may be replaced by soda. The formula is,

8AJS*+(fN + fC)S» + 6Ag.
* Philip's Mineralogy, p. 211.

Dft T. TmJ*f*o»,« Anatysi* of some Minerals. 459

Glasgow. The following comparison between the Castlehill mi-
neral and prehnite will leave no doubt about its nature.

It is composed of fibres slightly diverging, so is fibrous preb

nite.

Translucent, so is prehnite.

Lustre vitreous, so is that of prehnite.

The hardness is the same as that of prehnite.

Specific gravity 2.900. I found that of a fine specimen of
prehnite from Kilpatrick 2.901.

Before the blowpipe it behaves exactly as prehnite.

Captain Lehunt, at my request, analyzed the Castlehill mi-
neral. The following table contains the result of his analysis.
I have placed, in a second column, the analysis of a pure speci-
men of prehnite from the hills behind Port-Glasgow, which I
made some years ago, to show the identity of the two minerals.

Castlehill ITflmjmolf^

Prehnite. Prehnite.

Silica, . '. . . . 48.084 42.22

Alumina, 23.840 23.68

Lime, 26.164 23.52

Protoxide of iron, . . . 0.640 3.06

Protoxide of manganese, . 0.416

Potash and soda, . . . 1.028

Water, 4.600 5.58

99.772 98.06

■

Potash and soda had been already found in prehnite by
Laugier. They probably existed in the specimen analyzed by
me. The loss being only 2 per cent. I did not suspect the pre-
sence of an alkali, and, therefore, did not search for it. In the
specimens of prehnite analyzed by Gehlen, the lime amounted

VOL. XI. PART II. 3 M

460 JDr T. Thomson's Atodysis qfvme Minerals,

to 26 per cent., as well as in the CasttehiU specimen analysed by
Captain Lbhunt.

Jf we admit a small excess of silica, an4 consider the oxides
of iron, manganese, and the potash and soda, as accidental ingre-
dients, the composition of prehnite will be

10 atoms silicate of alumina,
7 atoms silicate of lime.

Reckoning from the Castlehill variety, all the other Scottish
prehnites, go far as I have analyzed them, contain rather less
lime. The surplus of silica amounting to about one-seventh of
the whole, is probably, in the mineral, united to the oxides of
iron and manganese, and to the potash and soda. How far these
may he essential ingredients remains still to be discovered *•

* The name WoOastonite was given by Hauy to tablMpar, or bisUicaie qfHme ;
but mineralogists in general have refused to adopt this appellation. I have been in-
duced, therefore, in order to commemorate the many obligations which mmeralogy
owes to Dr Wollaston, to apply the term WoUastomte to a mineral which I believe
to be new, and which has a very close relation to the species which Haut designa-
ted by that name.

It occurs in veins in a greenstone which is situated near Kilsyth, on the banks
of the Forth and Clyde. Canal, and possesses the following characters :

Its colour- is white, with a slight shade of green. Its texture is fibrous, and the
fibres are in tufts diverging from a centre, thu3 exhibiting marks of an imperfect
crystallization^ The mineral is translucent on the edges, and has a lustre inclining
to silky. The fracture is splintery, and the fragments are sharp-edged.

The hardness is intermediate between that of selenite and calcareous spar. Its
specific gravity is 2.8760.

Before the blowpipe it melts with some difficulty into a white enamel. This fu-
sion is not accompanied by any froathing. With borax it fuses into a bead-yellow,
while hot, but becoming colourless on cooling. With biphosphate of soda in consi-
derable excess, it fuses into a colourless bead, leaving a silica skeleton. With car-
donate of soda it effervesces, and fuses into an opaque bead, with a reddish-blue
colour.

Dft T. TSoiWOK's Amtyiig qfwme Mit&ah. 461

VI. Sulphate tf Alumina.

The specie of .hi, nOne** in my pos^on oomes fto.
Rio Soldana in South America.. I am indebted for it to the
kindness of Chak&ks Macintosh, Esq, of Cro&basket, who had
got it frorii the late Sir Rauph .WqoqfO^d, Govef ftor of Trinidad.
There is a notice respecting it in the Annates de Chimie et de
Physique *, by M. Boussijtchult, from lyhkh^e learn that it
occurs in the transitknuslate of the Andes of Cohimbia, either in
a state of efflorescence or in crystallized masses. Humboldt ob-
served it in the clay-slate of Araya near Cumana. It is found
also in the clay-slate of Sooono, and in many other places of South
America. It occurs in commerce, in spherical masses, and in the

\*> ■ '. ' ■ * ■ -.»■. 4 II' I

The constituents of this mineral I found to be,

Silica, ......... 52.744

Lime, \ 81.684

Soda, 9.600

Magnesia, Lfiflflf

Peroxide of itan, v 1.200

Alumina, . 0«672

\Vater, 2.000

•

99.420

If we suppose the magnesia to have replaced a little lime, this mineral is a com-
pound of

• 4 atoms bisilicate of lime,

1 atom tersilicate of soda.

» » • *

Thence, its symbol is 4CS* + NSF, add it differs from tabtespar, by contain-
ing 1 atom of tersilicate of soda united to 4 atoms bisilicate of lime ; whereas table-
spar is pure bisilicate of lime.

* Tom. xxx. p. 109.

3m2

462 Dr T. Thomson's Analysis of some Minerals.

country is called ahtmbre (alum), and applied to the same utes as
that salt. Boussingault has analyzed a specimen from the same
locality as mine. He gives its constituents as follows :

Sulphuric acid,
Alumina, . .
Water, • .
Oxide of iron,
Lime, • . .
Clay, . . .

36.4

16.0

46.6

0.4

0.2

0.4

100-0

The colour of the specimen is white, here and there tinged
yellow, obviously from external impurities.

In fine crystalline scales.

Lustre silky.

Taste that of alum, but stronger.

Translucent.

Very soft.

Specific gravity 1.6606.

Before the blowpipte behaves like alum.

Being subjected to a careftd analysis, its constituents were
found as follows :

Sulphuric acid, . . . . 35.872

Alumina, 14*645

Water, 46.875

Peroxide of iron, .... 0.500

Soda, 2.262

Mechanical impurity *, . . 0.100

99.754

* It was very ferruginous silica.

Dr T. Thomson's Analysis of some Minerals. 468

This does not differ very far from the analysis of Boussin-
oault. It is equivalent to

4

1 atom sulphate of alumina.
6 atoms water.
~ atom sulphate of soda.
5 atom per-sulphate of iron.

If we allow the small quantity of sulphate of soda and per-
sulphate of iron found in this mineral to he accidental ingre-
dients, then the salt is composed of

1 atom sulphate of alumina, . , . 7.25
6 atoms water, ,.,.,,, 6.75

14.

VII. Sulphate of Alumina — From Campsie.

Mr Macintosh has an alum-work at Campsie, near Glasgow.
The alum is obtained from the shale of the old abandoned coal
beds in the neighbourhood. At first, nothing more was neces-
sary than to lixiviate the shale, concentrate the liquid, and add
sulphate or muriate of potash in order to obtain alum. This
process being continued for a considerable number of years, a
great quantity of shale thus washed had accumulated in the
neighbourhood of the work. Mr Macintosh found, that, by
burning this washed shale, it might be made to yield a new crop
of alum. In one of my visits to this manufactory, Mr Macin-
tosh pointed out to me thin white bands, which occasionally
present themselves in this burnt shale, and he mentioned how
very productive these bands were when employed in the manufac-

464 Dr T. Thomson's Analysis qfsame Minerals.

taring of alum. After having examined the sulphate of alumina
from Rio Soldano, it occurred to me that the white bands at
Campsie bore a certain resemblance to it. I, therefore, request-
ed Mr Macintosh to procure me a specimen of it for examina-
tion, which, with his usual polite kindness, he speedily did.

Its colour is greyish-white, intermixed with portions having
a yellow colour, and which ate unequally distributed.

Fracture earthy.

Opaque.

Friable.

Taste acid, astringent, and sweet.

Specific gravity 1.887.

When digested in water it dissolved, with the exception of a
white powder, which amounted to 15.81 per Gent of the whole.
This white powder proved, on examination, to be a subsulphate
of alumina.

When heated, it melts somewhat like alum, and gives out
pure water. When heated to redness, it swells up like alum,
and finally leaves a yellowish-white, porous, tasteless matter,
nearly similar to what would be left by alum, making allowance
for the colour.

Being carefully analyzed, its constituents wete foul to be,

1. Matter insoluble in water 15*31, composed of

Sulphuric acid, ..... 10*2
Alumina, . 5.11

&. Matter soluble in water composed of

Dr TV Thomson's Analysis of some Minerals* 465

Sulphuric acid, 80.225

Alumina, 5.372

Peroxide of iron, .... 8.5S0

Potash, 1.172

Water, 86.295

4MMMMM

81.594
Insoluble matter, . . . . 15.310

Total, . . . 96.904
Loss, . . . 3.096

m

100.000

This loss was doubtless water. For the 86.295 per cent of
water were obtained by simply exposing the matter to heat on
the sand bath. I had ascertained, by previous experiments, that
it is impossible to deprive sulphate of alumina of the whole of
its water, without at the same tune driving off some of the sul-
phuric acid.

The constituents thus found are equivalent to

24 atoms sulphate of alumina.
9 atoms bipersulphate of iron. 9
1 atom bisulphate of potash.
42 atoms water.

The American sulphate of alumina differs from that of Camp-
sie in three remarkable particulars. It contains soda, while the
alkali in the Campsie mineral is potash. The Campsie mineral
contains a notable quantity of bipersulphate of iron, while, in the
American mineral, the quantity is trifling. In the American
mineral, all the saline contents were neutral, while in the Camp-
sie mineral almost one-half of the saline contents are in the state
of bisulphates.

466 Dr T. Thomson's Analysis of some Minerals.

VIII. Soda-Alum.

Some years ago Dr Hooker received several specimens of
native alum from Dr Gillies, who resided at the time at Men-
doza, a city near the foot of the Andes, and about 800 miles west
from Buenos Ayres. Dr Hooker was so good as to put some of
the specimens into my possession that they might be analyzed,
and their constitution determined. The specimens were ticket-
ed, " Native alum from the province of St Juan." They are in
irregular nodules, rather smaller than a hen's egg. From the
rocky fragments occasionally attached to them, they seem to
have been imbedded in a slate, having a blue colour, very soft,
and bearing some resemblance to the slate-clay usually accom-
panying the coal beds in this country. But these stony frag-
ments are too minute to enable us to determine with accuracy
the true position of the rock to which they belong.

The alum is white, and composed of fibres adhering longitu-
dinally, and having some breadth, but very little thickness. It
bears some resemblance to fibrous gypsum, but is much harder,
not being scratched by the nail, though it is readily enough by
the knife. It is sectile, the outer fibres are white and opaque,
as if they had lost a portion of their water. But internally the
fibres are transparent, and have a glossy or rather silky aspect,
shewing that they retain a good deal of water of crystallization.
The specific gravity of the transparent portion is 1 .88. It tastes
precisely like alum, but is much more soluble in water. For 100
parts of water, at the temperature of 62°, dissolve 877.8 parts of
it, and boiling water takes up any quantity of it whatever.
When heated it behaves precisely like common alum. 100 parts
of it exposed to a red heat lose 46.55 parts of their weight. But
this is not pure water, but water holding some sulphuric acid in
solution.

4

Dr T. Thomson's Analysis of some Minerals. 467

By a careful analysis, I found that 58.25 grains of it could be
resolved into the following constituents.

Sulphuric acid, 20.000

Alumina, 6.360

Soda, 4.000

Water, 22.209

Silica, 0.012

Lime, 0.136

Peroxide of iron, . . . . 0.110
Protoxide of manganese, with

a little magnesia, . . . 0.423

58.250

It will be observed that the sulphuric acid corresponds exact-
ly with four atoms. Hence it is probable, that the bases which
saturate this acid in the salt amount also to exactly four atoms.
Four constitutes an atom of soda. But the atom of alumina
being 2.25, three atoms of that earth will amount to 6.75 ; where-
as only 6.36 were found in the salt. There is, therefore, a defi-
ciency of 0.39 grains of alumina. But the lime, iron, and man-
ganese, (if the magnesia contained in it be reckoned 0.12), are
together exactly equivalent to 0.39 alumina. Thus, it appears,
that these substances replace a small portion of the alumina in
the salt. 22.209 approaches very nearly to twenty atoms of wa-
ter. We may, therefore, neglecting the minute quantity of silica,
lime, iron, manganese, and magnesia, consider the salt as com-
posed of

4 atoms sulphuric acid, . . 20

3 atoms alumina, .... 6.75

1 atom soda, 4.0

20 atoms water, 22.5

53.25

VOL. XI. PART II. 3 N

468 JDr T. Thomson's Analysis of some Minerals.

Or we may state the composition this way :

S atoms sulphate of alumina, 21.75

1 atom sulphate of soda, . . . 9-0
20 atoms water, 22.5

53.25

The only difference between native and artificial soda-alum
is in the water of crystallization. In the former it amounts only
to twenty atoms, while in the latter it is twenty-five atoms.
Artificial soda-alum crystallizes in regular octahedrons like com-
mon alum. But the native seems to crystallize in prisms. At
least that is the natural inference from its fibrous structure. I
made some attempts to obtain it in more regular crystals, but
they were unsuccessful, owing, I believe, to the heat of the
weather when the trial was made.

IX. Siliceous Hydrate of Magnesia. — From Haboken, New

Jersey, Nemalite of Nutall.

This mineral was sent me some years ago by Mr Nutall,
among many other interesting magnesian minerals from the same
locality of which he had some time before given an account to
the American public

The mineral which I am going to describe occurs in veins in
serpentine, and was taken for amianthus till its true nature was
discovered by Mr Nutall #.

The colour is white, with a slight shade of yellow.

Composed of elastic fibres, easily separable, and bearing a
striking resemblance to the fibres of amianthus.

• • •

* See Silliman's Journal, iv. 19.

Dr T> Thomson's Analysis of some Minerals. 409

Soft enough to be scraped by the nail of the thumb.
Opaque.

Specific gravity 2.853.

By exposure to a red heat its colour was changed into brown.
It retained its asbestous structure, but had become brittle and
easily reducible to powder. 12 grains by this treatment lost
8.56 grains, which is equivalent to 29.66 per cent. This loss was
pure water.

It dissolved in nitric acid, without effervescence, leaving a
little silica.

On subjecting it to analysis, I obtained the following consti-
tuents,

Magnesia, .... 51.721

Silica, 12.568

Peroxide of iron . . 5.874

Water, 29.666

99,829
This is equivalent to

20.75 atoms magnesia,

6.25 atoms silica,

1 atom peroxide of iron,
26.888 atoms water.

This might be considered as,

20.75 atoms protohydrate of magnesia, mixed
6.25 atoms silica,
1 atom peroxide of iron,
5.58 atoms water.

8 n 2

470 Dr T. Thomson's Analysis of some Minerals.

But, probably, the silica is in chemical combination with the
magnesia. I am disposed to consider this curious mineral as
composed of

5 atoms silicate of magnesia,
12 atoms bihydrate of magnesia,
1 atom ferrate of magnesia.

Its symbol, on that supposition, will be,

5MS+ \2MAq* + Mf.

X. Brownspar and Pearlspar.

These names have been applied to a variety of mineral spe-
cies, which have a considerable resemblance to each other, and
the crystalline form of which approaches more or less to that of
calcareous spar. Mohs and Haidinger have done a good deal
to disentangle this chaos, and have constituted several well de-
fined species out of minerals hitherto confounded under the
common name of Brownspar. But it is doubtful whether the
external characters alone afford sufficiently distinctive marks in
all cases, at least, for arranging the different brownspars under
their respective species. At any rate, it would be proper to sub-
ject them, in the first place, to a careful chemical analysis, in or-
der to discover with accuracy the number of true species under
which they should be arranged. It is with a view of forwarding
this desirable object that I shall here state the composition of
such species of brownspar in my own collection as I have hither-
to subjected to chemical analysis.

First Variety.

It is composed of plates which break into rhomboids, similar
in appearance to calcareous spar. But the angle, as has been

Dr T. Thomson's Analysis of some Minerals. 471

long ago shown by Dr Wollaston, is 106° 15', instead of 105°
5' as in calcareous spar.

Colour white, with a shade of red.

Translucent.

Hardness rather exceeds that of calcareous spar.

Specific gravity 2.8 1 5.

Dissolves slowly in muriatic acid, unless heat be applied.

A careful analysis of this mineral gave its composition as fol-
lows :

Carbonate of lime, . . 54.256

Carbonate of magnesia, 47.428

Alumina, 0.680

Protoxide of iron, . . 1 .692

104.056

Excluding the alumina and oxide of iron as accidental, the
mineral is obviously a compound of

1 atom carbonate of lime, » . . . 6.25
1 atom carbonate of magnesia, . . 5.25

11.5

I have found several specimens of the magnesian limestone
from Sunderland exactly similar in composition. This is the
case also with several specimens of Dolomite which I have ana-
lyzed.

This variety of brownspar, then, constitutes a well defined
species, to which the name of M agnesio-carbonate of Lime may
be given, it has been long distinguished as peculiar in minera-
logical systems. Yet nothing is more common than to find in
cabinets varieties of it arranged under the name of brown spar.

472 Dr T. Thomson's Analysis of some Minerals.

Second Variety*

I got this variety from the neighbourhood of Alston Moor,
under the name of Brown Spar.

It has a dirty brown colour. Streak brown.

Consists of small irregular rhomboids, with curve feces, and
entangled in each other.

Lustre pearly, nearly dull.

Opaque.

Scratched by calcareous spar.

_ •

Rather brittle.

Specific gravity 8.404.

The crystals were attached to a thin crust of brown matter,
having a pearly and splendent lustre. It was of the same na-
ture as the crystals, but had not like them been altered by ex-
posure to the weather.

This specimen being subjected to a careful analysis, its con-
stituents were found to be,

Carbonic acid, .... 1&50

Protoxide of iron, . . 80.27

Peroxide of iron, . . . 87.65

Deutoxide of manganese, 4.75

Water, 8.80

99.47

If we allow the manganese to be accidental, then the constitu-
tion of the mineral will be,

1 atom carbonate of iron, . . 7.25
1 atom perhydrate of iron, 6.125

12.875

It therefore constitutes a new species of iron-ore, which may be
distinguished by the name of Hydro-carbonate of iron.

I

Da T. Thomson's Analysis of some Minerals. 478

It is unfortunate that the crystals in the specimen which I
possess do not admit of measurement. The angle of the rhom-
boid constituting common carbonate of iron is known to be 107°.
Probably the measurement of the present species will deviate
somewhat.

Third variety.

This variety is implanted in small sphericles on the points of
long crystals of quartz. Its colour is brownish, $uid its lustre ra-
ther inclined to pearly. But in every other respect its charac-
ters are those of calcareous spar. Its specific gravity is 2.727.
Its constituents were found to be,

Carbonic acid,
Lime, ....
Magnesia, . .
Protoxide of iron,
Alumina, . . .

44.405

56.090

1.650

1.465
1.120

pm

104.73

The carbonic acid is little more than sufficient to saturate the
lime ; I have little doubt, however, that the magnesia is also in
the state of carbonate. The iron and alumina were probably
only accidental. It is obvious that this mineral is not a true
species, but merely a variety of common carbonate of lime. Its
locality was Transylvannia. It was marked Globular Brown
Spar.

Fourth variety.

It was composed of a congeries of small rhomboids with
curved faces.

Lustre pearly.

Surface brown ; but the interior qf the minerfti which had
not been exposed to the Feather snow-white.

Scratches calcareous spar, but not fluor-spar. Hardness 3.5.

Opaque, or only slightly translucent on the edges.

474 Dr T. Thomson's Analysis of some Minerals.

This mineral was from Traversella in Piedmont. I got it
under the name of Convex Rhomboidal Pearl-Spar. Unfortu-
nately the rhomboids are not susceptible of measurement. This
puts it out of our power to determine whether its shape be pre-
cisely the same with that of the first variety or not.

The constituents of this variety were found to be,

Carbonic acid, . , . 47.

Lime, 29.072

Magnesia, 14.140

Protoxide of iron, . . IS. 892

Alumina, 0.720

104.324

This is equivalent to

8 atoms carbonate of lime,
5 atoms carbonate of magnesia,
3 atoms carbonate of iron.

We may consider it as composed of two different minerals,
united together. The first mineral is common carbonate of
lime ; the second a compound of

5 atoms carbonate of magnesia,
8 atoms carbonate of iron.

This compound we may represent thus,

1 atom carbonate of lime,

1 atom carbonate of ({ magnesia + f iron).

This specimen constitutes a peculiar species, not hitherto no-
ticed by mineralogists, which may be termed Calcareo-carbonate
of Magnesia-and-Iron.

Dr T. Thomson's Analysis of some Minerals. 475

IX. Killinite.

«

This mineral' was discovered some years ago by Dr Taylor,
hi coarse granite veins in fine-grained granite at Killiney, Dub-
lin Bay. In the veins it is mixed with a good deab of spodu-
mene. It was analyzed at the time by Dr Barker and Dr
Taylor, who found the constituents as follows :

Silica, ....
Alumina, . . •
Potash, . . .
Protoxide of iron,
Lime, ....
Oxide of manganese,
Water, . . . .

52.49

24.30

5.00

2.49
0.50
0.75
0.50

i*M^

90.53

But I have reason to suspect, both from the description and from
the specimens which I saw some years ago in Dublin, that the spe-
cimens in the possession of these gentlemen were rather impure.

Captain Lehunt and Dr Stokes junior visited Killiney du-
ring the summer of 1828, and procured abundance of very good
specimens. Captain Lehunt was so obliging as to present me
with a very pure crystallized specimen of a large size, and seem-
ingly quite pure. This, together with a good many other spe-
cimens already in my possession, puts it in my power to describe
Killinite with more precision than has yet been done.

The usual colour is brownish-yellow ; though occasionally it
has a tint of green. I have seen specimens of a green colour,
but they are comparatively rare. When heated to redness some
specimens become snow-white, while * others assume a reddish

VOL. XI. PART II. 3 o

476 Dr T. Thomson's Analysis of some Minerals.

tinge ; this may probably depend upon the proportion of iron
which they respectively contain.

Texture foliated. Sometimes it is crystallized. I possess a
crystal 4 inches long, 1.3 inch broad, and 0.9 inch thick. It
constitutes a four-sided prism, which appears perfectly rectangu-
lar, by the most careful measurement. But the crystal has no
regular summit, nor will it cleave in the direction perpendicular
to the axis. We have no means of knowing, therefore, whether
the prism be right or oblique.

Lustre waxy, dull, except when particles of foreign matter

are mixed with it.

Opaque, or only slightly translucent on the edges.

Hardness 3.5 to 6. -

Streak yellowish-white.

Specific gravity £.598,' as determined in my laboratory. Dr
Barker states it to be 2.698.

Before the blowpipe becomes white and friable, and gra-
dually fuses into a white opaque bead, but not nearly so readily
as spodumene. With carbonate of soda it fuses into a transpa-
rent glass ; with borax or biphosphate of soda, into a colourless
glass, leaving a silica skeleton.

It was twice analyzed in my laboratory, first by Captain
Lehunt, and then by Mr William Blythe. The constituents
were as follows,

Silica, 49.08 47.925

Alumina, 30.60 31.041

Potash, 6.72 6.063

Protoxide of iron, 2.27 2.328

Lime, 0.68 0.724

Magnesia with some manganese, 1 .08 0.459

Protoxide of manganese, . . 1.255

Water, 10.00 16.000

100.4$ 99.795

Dr T. Thomson's Analysis of some Minerals. 477

These constituents are equivalent to

22 atoms silica,
1 2 atoms alumina,

1 atom potash,

8 atoms water.

Killinite therefore may be considered as a compound of

12 atoms sesquisilicate of alumina,
1 atom quatersilicate of potash,
8 atoms water.

Its symbol is 12AZS1* + KS4 + 8 Ay.

The alkali was examined with great care, and was found to
be pure potash. This was requisite, because in the vein, killi-
nite is intermixed with spodumene, the alkali of which we found
to be lithia, without any admixture of potash or soda. I was
disposed at first to suspect that killinite might be only a variety
of spodumene. But the external characters and the consti-
tuents are both incompatible with such a supposition. It must
therefore be admitted into the system as a distinct species.

The spodumene which accompanies the killinite was ana-
lyzed two different times by Captain Lehunt. The consti-
tuents found were almost identical with the specimen from Uto,
in Sweden, analyzed by Stromeyer *. I subjoin both, to enable
the reader to compare the two.

Untersuchunger, p. 426.

3o2

478 Dr T. Thomson's Analysis of some Minerals,

Spodumenejrom

Spodumenejrom

Via.

Ktiliney.

Silica, .••%..

63.288

63.312

Alumina,

28.776

28.508

Lithia,

5.626

5.604

• • •

0.728

Protoxide of iron, . .
Protoxide of manganese,

0.794 ")
0.204)

0.828

yy ater, •#•««•

0.775

0.366

99.463

-99.840

( 479 )

XXVII. Observations on the Structure qf the Stomach of the
Peruvian Lama ; to which are prefixed Remarks on the
Analogical Reasoning of Anatomists^ in the Determination
a priori qf Unknown Species and Unknown Structures.
By Robert Knox, M. D^ F. R. S. Ed. and Lecturer on
Anatomy.

(Read 4th January 1830. >

Section I.

The facts and observations I have now the honour to bring be-
fore the Society, were fully made out, and their general correct-
ness ascertained, somewhat more than three years ago. Since,
that time I have been in the habit of alluding to them, and de-
monstrating the strictly anatomical part, in my summer course of
lectures on comparative anatomy ; so that, in short, they may be
considered as having, to a certain extent, undergone the ordeal
of public opinion. I have thought it right to mention this
circumstance, inasmuch as the statements and opinions to be
brought forward this evening are contradictory of others which
have been promulgated by some anatomists of high standing, and
have been received and admitted by naturalists, and by the non-
professional, as observations not to be doubted nor controverted ;
as matters of fact which call for no deeper inquiry ; as statements
on which unerring doctrinal points might be founded #.

* There are exceptions to this remark. The elegant writer of the Zoological Ma-
gazine, whose taste and judgment in every thing affecting zoological inquiry are so
correct, did not give credence to the statements I have alluded to regarding the
structure of the lam&'s stomach.

480 Dr Knox on the Structure of the Stomach '

The facility with which an error in observation may be pro-
pagated is very great, in consequence of there being so few who
make any effort to observe for themselves. A doubt is expressed
by a person having some little acquaintance with the matter dis-
cussed ; and this doubt, as it extends, is changed to " a probabi-
lity," from which the step to * a certainty" is easy, especially if
this third person be altogether ignorant of the nature of the in-
quiries *. An obscure hint is first thrown out by a distinguished
anatomist ; a bolder and much more decided statement is made
by another ; a popular writer and naturalist, of whom it would
be unreasonable to expect anatomical knowledge, considers
the matter as decided, and the stomach of the lama is declared
to be " unlike that of the camel," being unprovided with the
peculiar apparatus by which it is enabled to dispense with the
necessity of a daily supply of water, even in countries where such
supply, from the heat of the climate, may be supposed essential-
ly requisite.

The object of the present memoir is to shew, that the state-
ments denying to the lama a compensating and peculiar structure
as regards the stomach, are without foundation in truth ; and
that errors, for such they assuredly are, have originated in an
unwary application of a principle, which I had thought all ex-
perienced anatomists employed with great caution, viz. the as-
suming the structure of the young or foetal state to be analo-
gous or identical with that of the adult f .

Whoever looks into the structure of an animal, is naturally

* Griffith's Animal Kingdom.

f Sir E. Home has inferred, from the examination of the structure of the sto-
mach of the young lama, that " the stomach has a portion of it, as it were, intended
to resemble the reservoirs for water in the camel ; but these have no depth, are only
superficial cells, and have no muscular apparatus to close their mouths and allow the
solid food to pass into the fourth cavity, or truly digesting stomach, without going
into these cells.*— Comp. Anat. voL v. p. 249*

of the Peruvian Lama. 481

led to guess at the functions or the uses of the organs and parts
successively displayed by mere handling, or by the more intricate
process of dissection. The first, the great object, is a discovery
of the use of the parts, there being no inference so natural to
the human mind, than that every part of the animal economy
must have its use ; but of all inquiries, this is one of the most
difficult, it being impossible to argue the uses of new parts,
which so obviously serve no immediate purpose, and imprac-
ticable to apply the laws which regulate the construction of ma-
chinery, united and fashioned by human hands, to those regu-
lated by the mysterious principle of life.

If the animal he is examining be altogether foreign to him,
if its natural history be unknown, the inquirer can then only
guess at the functions of the parts which present themselves to
him ; and the vagueness of such conjectures will be best under-
stood by remembering that neither Aristotle, nor even per-
haps Hippocrates, knew the uses of the common muscular
masses composing the greater part of animals highly organized ;
that they were ignorant of the nature and functions of nerves,
tendons, and of all the white fibrous textures of the body ; of
the brain, of the heart, arteries, veins, lymphatic vessels ; and
of all those parts which are now known to every tyro in ana-
tomy, and even to the better educated amongst non-profes-
sional persons. It is not now as with the anatomists of former
times ; inquiries so extensive, as to determine the exact nature
of almost every natural family of the animal kingdom, enable
the anatomist to proceed to the dissection of an unknown ani-
mal with an extent of previous knowledge, of which he is not
himself at all times conscious. He determines, by what he has
already seen and read, the names and nature of all the great
and leading organs of the body of the animal ; he even goes
further, — trusting to analogy, he ventures to predict the pro-
bable use of a part he may not have seen before in any animal.

482 Dr Knox on the Structure of the Stomach

But he is bound to do this cautiously, inasmuch as analogies
are deceitful, and previous experience and observation fruitless,
when it attempts to bind down to fixed laws and permanent
forms, structures which, in the hands of an all-powerful Agent,
seem, on most occasions, to be made subservient to function,
and are changed and altered, or, as the physiological phrase goes,
modified and diversified, to an extent harassing to the mind of
the impatient inquirer, and puzzling to all.

To obviate certain of these difficulties, the anatomical in-
quirer resorts to other sources of knowledge, to other means, in
order to come at the desired object. He patiently observes the
habits of animals ; the effects of climate and of domestication ;
the kind of food seemingly enjoined them by Nature ; in short,
their natural history ; and, aided by this, he again returns to his
previous anatomical investigation, hoping confidently to verify
in the body deprived of life the truth of the observations he had
made on the living ; and, by comparing what he already knows
of function with what he sees of structure, to decide on cause
and effect ; give reasons for absence, alteration, or modification of
parts ; in a word, to solve the difficult problem of the uses of the
parts in animal bodies #.

In this complicated and extended inquiry, which has endured
now so many thousand years, it has not unfrequently happened,
that the most experienced observers in the field of inquiry have
forgot the sources of their knowledge, when they fancied them*
selves in possession of laws conclusive as to animal structure ;

* The presence of certain generative organs in the male and female, and of the
hyoid bones, in the Mammalia, together with nearly all rudimentary organs, in-
cluding the swimming-bladder of fishes, urinary bladder in the same animals, &c.
have hitherto defied the attempts of all anatomists to explain. Mr Hunter said that
" Nature was fond of analogy ;" and so, I presume, in sport, placed organs in ani-
mals which seemingly performed no functions ; but these explanations will not pass
current now, I presume, with any one who pretends to any physiological judgment.

of the Peruvian Lama. 488

laws regulating the presence or absence of organs, and sufficiently
accurate and extended, to enable them to decide a priori on
structure ; or, to state the problem in the language of the ma-
thematician, " from a given part of the structure, to describe the
whole/' To me it appears that the question of organization is
not to be solved in this way. We may determine, by such means,
unknown quantities, and the greater number of questions in
physics and mechanics, because their laws are already so well
made out, that, generally speaking, there are no real exceptions
to these laws, and, above all, every possible combination, if I
may so express myself, is already known to the inquirer ; but to
me it seems quite different with living organized bodies. The
possible combinations of form have not been fully determined ;
exceptions which, though not real, have all the force of reality
until they shall be explained, are too numerous ; they exist to a
degree that the memory can no longer retain them, so that
every thing like system and general laws is lost. Let not the
anatomist then deceive himself and others. The high authority
which would persuade us, that from a small portion of bone we
may determine the form, the anatomy, the natural history, the
antiquity of an unknown animal, I altogether disregard, — sup-
porting my seeming neglect of such well-earned reputation, by
the strong conviction which naturally arises in my mind, from an
extent of anatomical inquiry into the structure of almost every
kind of animal at present found to inhabit the earth's surface ;
an inquiry extended now to rather more than fifteen years.

I shall bring these observations to a conclusion by remarking,
that the anatomy and natural history of any species of animal,
fully observed, and made out satisfactorily, may enable us to de-
cide on the anatomy and natural history of an animal unknown
to us, provided they accord entirely, or nearly so ; that, more es-
pecially in some natural families, such as the strictly carnivorous
tribe, a tooth, a fragment of bone, or other remains of structure,

VOL. XI. PART II. 8 P

484 De Knox on the Structure cf the Stomach

may enable us to conjecture, with some shew of probability, that
the animal, whether fossil or otherwise, may have been specifi-
cally or generically allied in a certain degree to those with which
we are already acquainted ; and we may even admit as certain,
that a hoof, such as that of the horse or ox, never yet was com-
bined with other structures implying carnivorous habits. Neither
will it require any great stretch of the imagination to believe
that animals having the bulk of the mammoth could not possi-
bly subsist amidst the frozen regions of Siberia ; nor that plants,
having a seeming resemblance to our present inter-tropical vege-
table kingdom, could possibly grow and flourish in region*
doomed to a comparative absolute sterility, and to a dwarfish
stunted vegetable growth. To theories of this kind we may
fairly object, that heat is essential to life ; and to theorists of an-
other kind, who venture to declare a priori, and without having
any knowledge of the animal previously, its anatomy, and its na-
tural history, from the observance of a portion of the hide, a
fragment of the bones of the foot, a portion of the skull, a tooth,
that they cannot produce a single instance of their having ever
done so in a way so as not to admit of refutation, or at least of
doubt The claws and nail-bones of the sloth indicate nothing
of its peaceful and frugivorous habits ; and to assimilate its habits
and anatomical structure with certain gigantic fossil remains fe»
not to use a harsher style of criticism, eminently imaginative and
fantastic. The molar teeth of bears are not carnivorous molar
teeth ; and it is by the observation of the living species only that
we have become aware of the frugivorous habits of some, and of
the strictly carnivorous habits of the polar species. To speculate
from such facts as these as to the anatomy and natural history of
the extinct Ursus spekeus, must, to every reflecting mind, ap-
pear exceedingly ridiculous. The strength of the zygomatic
arch of the dugong exceeds that of the lion, and yet how op-
posed are these animals to each other in their habits and gene-

if the Peruvian Lama. 48&

nd economy. The habits even of genera closely BesemhKng eaeh
other occasionally do not accord. Antelopes lire in pairs, insniatt
families, or congregated in thousands; the zebra is seen in
groups only of two or three ; whilst the quagga, resembling it so
closely as to be often confounded with it, feeds in flocks on. the
wide extended plains of Africa, Lastly, by what &ct in the in-
ternal or external structure of the hippopotamus could the ana*
tomist have decided a priori that the animal was aquatic *.

Nor can we decide on the relations of different organs or
structures to each other. We cannot predict, for example, that
an animal will necessarily ruminate, because we find its upper
jaw unprovided with incisive teeth, nor that there is any con-
stant relation between these two cureamstance* There is no-
thing in the anatomy of the skeleton or dentition of the hone
which can lead an anatomist to* decide d priori on the probable
form of the stomach of that animal ; and, I would ask, where are
the data by which we could determine the form of the stomach
in the quadrumana, the larger paehydermata, including the pig,
the puzriing animals of Australia, and of numerous others*. unn&»
cessasy to partkidarioe here ? Where is the anatomist who would

* Though the camelopardalis has now been known to man for some thousand
years', na anatomist in the world could have predicted the' form ef its stomach pre-
vjftm to dissection.

The stomach of tie hippopotamus is complex ; that of the rhinoceros simple; jtst
their food is similar. I know of nothing in the form of the skeleton or other struc-
tures which, being presented to the anatomist separately, and unconnected with its
other parte, could enable the anatomist to decide on the nature of any of these am*
mall without air exact examination of die whole of the structure, and a. knowledge
of their habits, drawn from observation of the living species ; andi^ in the *TfiP*Vfflh
tioikof fossil temainsy we venture to pronounce dogmatically on a few of the beat
made out genera, and declare such a bone to belong to the hyaena tribe, such another
to the tiger, elephant, and so on, such opinions are after all but probable conjec-
ture^ unfitted by their nature to form- a basis- for a solid theory of animal
Mourner,, they cannot go beyond mnre generalities.

3p2

486 Dr Knox on the Structure of the Stomach

venture to declare the form of the stomach in any of the Cetacea,
unless he had actually seen it, or read its description by others ?
Surely no one will believe that the mouth of the dolphin, armed
with teeth for catching and holding its prey, and that prey ob-
viously animal, would lead any one to conjecture that the dol-
phin posse** a stomach more complicated than the ox. who*
stomach is declared, foolishly enough, to be quadruple, bemuse
Of its living on vegetable food.

If we now advert to the assigned causes of structure, we shall
find them equally untenable, equally unphilosophical. The
quadruple stomach of the ox and sheep is said to compensate for
the deficiency of the incisor teeth ; but the camel has teeth of this
kind, and its stomach is quintuple. The causes, then, of nearly
all structures are concealed, as yet, by an impenetrable veil from
human sight, leaving only a few great and general laws applica-
ble to animal nature, but so loosely as greatly to diminish their
value. It is not with animal machines as with a watch or other
piece of human mechanism, wherein the purpose of its creation
is expressly known and understood, and the reason, which, more-
over, is purely a mechanical one, for the presence of each wheel
and pivot, chain and box, made known to us by the mechanist,
or discovered on investigation. The animal machine abounds
with structures, the reason for whose presence he cannot guess
at, neither can he calculate what might be the result of their
absence or destruction. That design generally, in the com-
plex machinery of animal bodies, is too obvious to require even
a thought ; but the attempts at particularizing the particular
design connected with separate individual organs, seem to me
hitherto to present a series of the most lamentable failures in
human reasoning. I do not hesitate to declare nearly all the
systems hitherto built on these opinions as so many systems of
false philosophy, of which some are below criticism, and others
of a pernicious tendency. There are persons who believe that

of the Peruvian Lama. 487

the blubber of the whale is placed in the animal by Nature, to
render the animal buoyant ; and that the rudiments of mammas
are placed on the human male breast to warm and cherish the
heart, and also for the sake of ornament. I feel, of course, that
to persons whose physiology is of this cast, all my previous re-
marks must appear puzzling and contradictory ; but they will not,
I trusty appear the less unimportant that they are not fully un-
derstood by those whose habits of loose reasoning induce them
to grasp at the first explanation of a phenomenon which pre-
sents itself to their minds *

Section II.

We are now prepared, divested of the prejudices of ages, and
of false dissections, and of popular, and necessarily false, theories,
to enter on the inquiry of the physiological character of the sto-
mach in two animals, than which, in many respects, there are
none more interesting now inhabiting the globe. The Camel,
known to all antiquity, — the ship of the desert, as it has been
styled by poets and by poetical writers, — the medium of commu-
nication betwixt countries separated by deserts which neither man
nor animal could traverse in safety without its aid : patient un-
der fatigue, and temperate in regions where universal aridity,
eternal drought, and an almost insupportable heat, demands of
every thing living an excess in the use of liquid nourishment ;
these are the qualities known through all ages as characteristic
of this animal. On the other hand, the Lama, performing in mi-

* Mr Huntee used to explain the presence of parts and structures in animal
bodies, whose presence were obviously not requisite, by the highly figurative, and to
me unintelligible, phrase, that " Nature placed them there because she delights in
analogies."

466 Da Kxox-Mi the Structure efthe Stomach

mature, as it were, to the ancient Peruvians those services- red»

*

dered in a much more efficient manner by the congenerous am*
mal of the Old World, but still a kind of earned as I may so ex*
press myself, — a camel of the New World, — a miniature of the
camel of the desert, as the puma is to the Hon, — possessing similar
qualities ; patient under fatigue, and temperate beyond what baa
been told, even in exaggeration, of the ancient animal of the
Arabian desert.

This is the knowledge, the previous knowledge, drawn firom
history and observation, with which the anatomist proceeds to
search for, in the structure of the animal, the reasons for its
temperance. The first essays were to discover the sac or bag
(for the early and even late notions on this matter were extreme-
ly coarse) in which the animal was supposed to deposite the
water drank in large quantities, and at long intervening periods,
aa if really kid np in store for future use. Now^ftmda pass first
into the stomach ; and to this organ, therefore, the anatomist first
directs his researches, delighted, no doubt* to find that these
should exist in it a structure seemingly explanatory of tha theo-
ry, seemingly conformable to the habits of the gniwmly unlike
what exists in other animals, and referable^ therefore, in thai
view, to this cause only. It seems to hove been forgotten^, in
this fanny to explain function from structure, that it was fink
to be proved that a liquid could remain for several days con-
tained within a living organ, adapted apparently for absorption,
without being removed or absorbed, agreeably to the laws of
mucous membranes. This difficulty, however, was readily over-
looked, and yet there are only three experiments recorded, in
which it is pretended that any water was found, after the lapse
of a few days, in the stomach of the camel : the first by Bruce,
with most questionable authority ; the second by Daubenton,
who found water in the stomach of the camel ten days after the
death of the animal ; the third, too rude I fear to figure aa a pin-

of the Penman Lama. 489

loaophical experiment, was made in the apartments of the Royal
College of Surgeons in London, and is thus detailed : " A camel,
in a dying state, was purchased by the College of Surgeons.
The animal gradually grew weaker, and was at length killed,
after being excited to drink three gallons of water, having taken
none for three days previously. Its death was immediate, for it
was pithed, or instantly deprived of sensibility, by passing a
poniard between the skull and first vertebra of the neck. Its
head was fixed to a beam, to prevent the body falling to the
ground after it was dead. The animal was kept suspended that
the viscera might remain in their natural state, and in two hours
the cavities of the chest and abdomen were laid open."

It seems hardly necessary to add, that a good deal of water
was found in the animal's stomach, just as would have happened
in any other animal, treated in a similar way, whatever might be
the structure of the organ. Fluids often disappear, in some ani-
mals, from the stomach with great rapidity, but they also occa,
ri-Dr ren«rfn i-rir-riJd . to quantity »d qLi* , ««l
all this takes place in so capricious a manner, that no anatomist
would venture to predict the actual condition of the contents of
the stomach after death in any case whatever.

It is obvious, then, that the function of the camel's stomaehr
if it really be a function appertaining to it, by which the animal
is enabled to maintain such sobriety amidst the arid wastes of
Africa and Arabia, was not a discovery which flowed from the
examination of structure ; but that the structure being peculiar,
it was inferred that such must be its function, for the only reason
I can discover that no other function could be assigned to it.

Having got rid of these errors, and traced the* hypothesis to
its source, we shall proceed to examine that structure, first in
the camel, and secondly in the lama, proving, I trust, beyond all
doubt, that they strietly and exactly resemble each other, and
that whatever faculty the one possesses the other also must en-

490 Dr Knox on the Structure of the Stomach

joy, if there be the smallest truth in the law, that similar and
analogous parts must perform similar functions.

The Camel.

The discovery of the peculiar anatomy of the camel's sto-
mach is not a discovery of modern times. Perrault, in the
Memoirs of the French Academy, describes the stomach of the
camel with tolerable accuracy ; but it was reserved for Dauben-
ton to finish a monograph, which, for accuracy of detail and
shrewdness of observation, cannot be excelled. The facts disco-
vered by Daubenton were re-examined very lately by Sir E.
Home, and found to be strictly accordant with nature. The
learned and modest assistant of Buffon had absolutely omitted
nothing. M. Cuvier, indeed, has not deemed it necessary to
quote Dau ben ton's description in his great work on Compara-
tive Anatomy, and has given us in its place the dissection of the
stomach of the foetus of a lama ; but this, I trust, in this country
at least, will not be deemed derogatory of Daubenton's merit,
more particularly if it be shewn that his monograph on the sto-
mach of the camel is admirable. But, first, with regard to the
dissections of Perrault and of his colaborateurs, the Parisian
dissectors, as they are sometimes called.

" The ventricle," say they, " which was very large, and di-
vided into parts (39), as in the other animals which ruminate,
had not that different structure which is observed in the sto-
machs of the strictly ruminants, or ox and sheep. They were
only distinguished by some straitenings, which made that the
first ventricle, if large and bent, produced another very small
one, which was followed with a third somewhat less than the
first, but much longer, and this was followed by a fourth like
to the second.

" At the top of the second ventricle, there were several square

of the Peruvian Lama. 49 8

Tioles, which were the orifices of about twenty cavities, made like-
sacs, placed between the two membranes which do compose
the substance of this ventricle. The view of these sacs made us
think that they might well be the reservatories where Pliny
says camels do a long time keep the water which they drink in
great abundance, when they meet with it, to supply the wants
which they may have thereof in the dry deserts, where they are
used to travel, and where it as said that those which do guide
them are sometimes forced, by extremity of thirst, to open their
belly, in which they do find water."

We do not find in this description that remarkable accuracy
and minuteness of description, which so very generally characte-
rize their memoirs. They have not stated, as they ought to
have done, and was afterwards discovered and perfectly described
by Daubenton, that the distended stomach presents an appear-
ance of four stomachs, but, when opened, there are found to be
five ; that the paunch abounds with large cells, as well as the
second stomach (which Dad ben ton also called the reservoir) ;
that the third stomach, which was also discovered by Da uben*
ton*, and admirably depicted in his works, is exceedingly small,
and forms a kind of rudiment of the king's-hood of the strictly
ruminants. Moreover, he explained very beautifully the struc-
ture of those deep square cells, with apertures surrounded by
bundles of muscular fibres, in which he says he found abundance
of fluid, a. structure which seemed to retain the water like a
sponge. Two or three pints of clear and almost insipid water
were found in the cells of the second stomach, ten days after the
death of the animal. He concludes, then, that the second sto-
mach, or reservoir, is a stomach superadded to the others, in. the
camel, for the express purpose of a reservoir. To these descrip-
tions of the stomach of the camel, Daubenton added drawings
of inimitable accuracy. The ingenious and elegant popular wri-
ter of the article " Menagerie," in the Library of Entertaining

VOL. XI. PAST II* 3d

J

492 Dr Knox on the Structure of the Stomach

Knowledge, has fallen into a great error, by not consulting, what
Daobenton has said, and by trusting to the remarks of those
who fancied their interests and vanity served by an ill-judged
and totally erroneous criticism upon the works of that eminent
observer. The transverse contraction of the fourth cavity, where-
by it is obviously divided into two stomachs, distinguished by
this circumstance, which alone, according, to the more generally
received views, would entitle us to consider this elongated ca-
vity to be divisible into a fourth and fifth stomach ; this trans-
verse contraction was discovered by Daubenton, and particu-
larly dwelt on by him ; and, when he offered it as his opinion
that there exist five stomachs in the animal, he grounded that
opinion on views which no real anatomist can possibly call in
question.

The Lama.

I come now to describe the structure of the stomach of the
adult lama. M. Cuvier and Sir E. Home have had opportu-
nities of describing only that of the foetus, and if our descrip-
tions differ, as they do most materially, it will not, I imagine,
surprise any one, for assuredly it must be known to all zoologists,
that the stomach of the foetus and of the adult animal seldom
correspond.

The cavity which we may term the first stomach or paunch,
is, in the adult lama, of great capacity, and seemed to me to
bear the same relation to the bulk of the animal as the paunch
does in other ruminating animals ; it was, in the instance which
came under my notice, filled with oats, on which kind of food
the animal had been last fed. In the structure of this cavity
there was first the external or peritoneal covering, the muscular
tunics more internally, and, still deeper, the cellular and mucous
layers. The inner surface, throughout a considerable extent of

oftiie Peruvian Lama. 493

surface, is smooth, but there likewise are two Tery {considerable
portions occupied by rows of cells, which I shall now describe.

In the larger collection of cells there are sixteen rows, but
the rows vary much in length, and, besides, the cells are of vary-
ing depth. In some of the rows there are twenty cells, and the
depth of each, if the stomachs were distended, may vary from
half am inch to about three-fourths. They all open towards the
stomadh, eeem lined by the general mucous membrane of the ca-
vity, altered however somewhat in its appearance and probably
texture ; the rows are further divided from each other by very
powerful bundles of muscular fibres, whilst each pair of cells is
separated from those which precede and follow by muscular fi-
bres also, which however, as may be observed in the accompany-
ing delineations, ace much weaker than the powerful muscles
which separate and divide the rows of cells from each other.
The action of these muscular fibres must be to shut the mouths
of the cells, .and do form of them at times, it may be presumed,
cavities distinct from the general cavity -of the stomach.

The smaller collection of cells is similar in most respects to
the larger. These are here twenty vows of cells, but they are
much shorter, and the individual cells are obviously much shal-
lower. In other respects their structure corresponds to those
already described. Two powerful muscular bands lead in such
a way from the gullet towards the third stomach, as to enable
the animal at will to cause the food, after remastdcation, to pass
at once (by converting the open groove into a complete canal)
into the third -stomach — a structure at least altogether like this
is found in .the stomachs of the ox, sheep, and camel, and this is
the function which anatomists have assigned to it.

The first stomach communicates with the second by .an aper-
ture, sufficient to allow the hand to pass through. This second
stomach, which is of considerable magnitude, is almost entirely
composed of cells, but they are scarcely so deep. They differ also

8q2

494 Dr Knox on the Structure of the Stomach

somewhat in structure, and the muscular bands for closing their
apertures are not so powerful as in those of the first stomach.

The second stomach opens* into the third by an aperture
somewhat larger than the finger. The third stomach is, toge-
ther with the cellular character of the first and second, that
which in a peculiar way assimilates the camel and lama. It is a
small surface, marked by elevations which cross each other at
right angles, and seem to occupy merely the upper part of what
I call the fourth stomach, there being no contraction betwixt it
and the fourth ; but Daubenton shewed long ago in the camel,
that this surface is actually a stomach, and the fact is now ad-
mitted by all anatomists *. What its nature or function may
be, it seems impossible to conjecture ; there is no natural eon-
traction betwixt it and the stomach which follows, which we shall
call the fourth stomach.

«

This cavity is characterized by longitudinal folds in the
axis of its tube. They are about twenty in number, and of to-
* lerable regularity. Between the fourth and fifth stomachs there
is a natural contraction, and this latter cavity is further charac-
terized by having a smooth, soft, and, as it were, pulpy mucous
surface, destitute of cells, furrows, ridges, or prominences of any
kind. The pyloric orifice of the stomach resembles that in other
ruminants, and the duodenum is at first slightly dilated.

In no part of its anatomy, then, does the lama more closely
resemble the camel than in the structure of its stomach.

It may here be asked, what proofs have we that the lama
possesses the same power of abstinence from drink as the camel ?
To this it may be answered, that a similar structure ought to
produce a similar result ; and although I do not myself consider
it as satisfactorily made out, that the mechanism by which the

* The calling it a rudimentary stomach, analogous to one found in the ox, sheep,
*nd common ruminants, does not elucidate the matter greatly.

of the Peruvian Lama: 495

xamel and lama can each refrain from drinking for so long a pe-
riod, depends altogether on the structure of the stomach ; yet it
is not improbable that it may in part be connected therewith.
Many travellers report that the lama never drinks ; and a fo-
reign writer (Father Feuille') is quoted, as describing the sto-
mach to be not only provided with a large reservoir for carrying
water, but that, like the stomach of the camel, it has the same
machinery for allowing the separation of solid from liquid ali-
ment. I have not been able to find a complete copy of Feu-
ille"s work, so that I cannot support what I have said by his
remarks ; but surely there can be no occasion for this, since the
actual structure I now describe at this moment lies before me.

Section III.

I have hitherto, in conformity with the language used by
anatomists, spoken of single, double, triple, quadruple, and quin-
tuple stomachs, as if there were such in nature ; but I do not
believe so* The stomach of all animals is a single organ : it may
be divided into various compartments, as in the ruminants, the
camels, and in the cetacea, and these may have their specific
uses. One may be intended slightly to affect the alimentary
mass first received into it ; a second to alter it still further by
its juices; a third may be intended merely to prolong its resi-
dence within the canal ; and a fourth finally to convert it into
that semifluid condition, into which it is presumed finally to be
changed, previous to its passage into the intestinal tube, but
still it is but one organ; nor have I ever heard it affirmed by
any one, that the complex quadruple stomach did more than
the simple stomach, in affecting the material of our nourishment,
or bringing it nearer to perfection. I presume, therefore, that
the organ is single in every important sense of the word, and

496 Dr Knox on ike Structure 4f the Stomach

that the phraseology of two, three, or four stomachs m dtogetiher
incorrect. We have seen that no anatonfet <of $nc*eAt pr mo-
dern times could ever predict what kind «tf stotnaoh would tne-
cessaitily be found in any animal previous <to its having actually
been examined. The stomach of the eflephatft presents one
lange cavity ; the elephant has no cutting incisor teeth in drtitar
jaw. (The eftomaeh of the horse is single, us the ijflusse goes, if
We tiequifce (that a stomach to be considered double mvst be di-
vided toy a permanent contracted interval into two cavities, com-
municating with each other by an aperture smaller in diameter
than either ; but if to constitute a double stomachy it be merely
necessary 'that (its interior should present differently organised
surfaces, then the stomach of the horse is double. The hippo-
potamus has, if I remember right, a kind of three cavities or
stomachs,, as they are called, judging !by the number of culs de
sac or compartments ; for I could not observe, in the interior of
these •cavities, any great difference as to structure ; but it seems
to 'me impossible 4o say how many stomachs the seal <or pig may
be considered as /entitled to ; externally, indeed, they seem to
have but one ; internally they present valvular projections and a
diversified structure, setting at defiance all the usual anatomi-
cal nomenclature as to this organ.

Man is considered as having a single stomach, but this is not
unfrequently found contracted about the middle, so as to divide
the cavity, as it were, into two, by means of a narrow contracted
portion. If this be constant during the digestion of the food,
as some have supposed, we might almost venture to call the hu-
man stomach double ; but in truth it is not so, and is a pheno-
menon which takes place only occasionally and in certain indivi-
duals ; it is a deviation from the ordinary human structure, but
of the simplest kind, — an irregularity in man, a regular struc-
ture in certain of the lower animals, that structure being, as it is
so often, persistent in them, which in him is only fugacious.

PLATE XVI.

tf the Peruvian JLa*na> 497

Till anatomists have determined what is to constitute a
double, what a single stomach, or until they have corrected
their nomenclature, let us consider the stomach in all animals as
a single organ, varying with the species, performing a single
function, and not to be determined on a priori, by any doctrine,
anatomical or physiological, nor by any pretended necessary re-
lative dependence upon any other co-existing anatomical struc-
tures.

EXPLANATION OF PLATES' XVI. XVII. and XVIII.

PLATE XVI.

Fig. 1 . A view of the paunch or first stomach laid open : the larger assemblage of
cells is represented with great care, and a portion of the smaller may also
be seen ; the strong muscular bands dividing the rows of cells frojn each
other, and the cross slips of fibres separating the cells individually and
in pairs.

a points out a strong band of muscular fibres, which extends from the gullet
to the extreme of the third stomach ; and

b marks a still stronger assemblage of muscular fibres, which form, as it were,
a base, from whence the numerous bundles of fibres dividing the rows of
cells from each other proceed. The extremity of this bundle of fibres
may also contribute towards the formation of the channel or groove
spoken of in the text at page 15.

0

498 Da Kxox m the Stomach of the Peruvian Lama.

PLATE XVII.

•Pig. 1. Shews the larger assemblage of cells in the paunch, drawn with great care,,
so as to explain their form, size, and, above all, the correct arrangement
of the bundles of muscular fibres.

Pig. 2. Is intended to shew the termination and ultimate course of the muscular
apparatus of the cells. Towards the upper margin the fibres gradually
•widen and separate from each other, sweeping around in concentric circles.
They are ultimately lost in the general muscular tunics of the stomach.

PLATE XVIH.

fig. I. The cells of the paunch of the natural size.

Fig. 2. Points out the- structure of the cells in the second stomach, which has
been laid open ; the narrow contracted passage, leading to the third and
fourth stomachs. The third stomach is marked a, and the upper part of
the fourth is marked b. They are distinguished from each other merely
by their structure, there not being any contracted portion to form them
into distinct cavities.

Pig. 8. Shews the termination of the fourth stomach, and the whole of the fifth, laid
open : the structure of these cavities has been sufficiently described m
the text.

PLATE ZVDI.

. f

mm r£±

VWiZ

PROCEEDINGS

OF THE

EXTRAORDINARY GENERAL MEETINGS,

AND

LIST OF MEMBERS ELECTED AT ORDINARY MEETINGS,

SINCE MAY 1. 1818.

TOL. XI. PART II. 8 R

PROCEEDINGS, &c.

November 87. 188$.

At an Extraordinary General Meeting held this day, Dr Hope
in the Chair, the following Office-Bearers were elected for the ensuing year :

Sir Walter Scott, Bart. President

Vice-Presidents.

Bight Hon. Lord Chief-Baron,

Hon. Lord Glenlee,

Dr T. C. Hope,

Professor Russell,

Dr Brewster, General Secretary.

Thomas Allan, Esq. Treasurer.

James Skene, Esq. Curator of the Museum.

PHYSICAL CLASS.

Hon. Lord Newton, President
John Robison, Esq. Secretary.

COUNCILLOES FEOM THE PHYSICAL CLASS.

Sir William Forbes, Bart Dr Turner.

■ ♦

Dr Home. Sir T. M. Brisbane, K. C. B.

Professor Wallace. Dr Graham.

8 3 r2

502 PROCEEDINGS OF GENERAL MEETINGS,

LITERARY CLASS.

Henry Mackenzie, Esq. President.
P. F. Tytler, Esq. Secretary.

COUNCILLORS FROM THE LITERARY CLA8S.

Right Hon. Sir Wm. Rae, Bart. Dr Hibbert.

Sir Henry Jardine. Lord Meadowbank.

Sir John Hay, Bart. Thomas Kinnear, Esq.

The following Gentlemen were appointed a Committee to audit the Treasurer's Account :

Sir Henry Jardine,

Sir William Arbuthnot, Bart.

On the motion of Mr Allan, the Meeting recommended to the Committee already
appointed for this purpose, to use all diligence in obtaining payment of the Money due
by the College Trustees to the Society.

It was moved by Sir Henry Jardine, and unanimously agreed to, that the
thanks of the Society be given to the Committee for superintending the furnishing, &c.
of the Society's apartments. The thanks of the Society were accordingly given by the
Vice-President to Thomas Allan, Esq., James Skene, Esq., and Robert Steven-
son, Esq., the Members of the Committee.

ORDINARY MEETINGS.

December 4. 1826.
MEMBERS ELECTED.

ORDINARY.

George Moir, Esq, Advocate.
John Stark, Esq.

At this Meeting the President announced that the Library would now be always
open, and accessible to the Members ; but that the privilege of using it must necessa-
rily be confined to the Fellows of the Society.

AND LIST OF MEMBERS ELECTED. 508

On the motion of Mr Stkvemson, C. E., the thanks of the Society were unani-
mously voted to Mr W. H. Playfaik, for the skill and taste he has displayed in the
arrangement of their new premises.

February 5. 1827.
MEMBERS ELECTED.

«

ORDINARY.

James Weddell, Esq. R. N.

John Gardiner Kinnear, Esq. Edinburgh.

William Burn, Esq.

March 5. 1827.

MEMBERS ELECTED.

■

ORDINARY.

Dr James Russell, Edinburgh.

* _ * ■

Prideaux John Selby, Esq.

Henry Witham, Esq.

John Reddie, Esq. LL. D. Edinburgh.

The Rev. Dr Robert Gordon, Edinburgh.

James Wilson, Esq. Edinburgh.

HONORARY,

J. Berzelius, M.D. F.R.S. Lond., Professor of Chemistry at Stockholm.

FOREIGN.

John James Audubon, Esq. M. W. S.

MM PROCEEDINGS OF GENERAL MEETINGS,

il 8. 1827.
MEMBERS ELECTED.

ORDINARY.

The Rev. Edward Bannerman Ramsay, A. B. of St John's College,

Cambridge.
James Walker, D. D. of St John's College, Cambridge.

May 7. 1827.
MEMBERS ELECTED.

ORDINARY.

Alexander Copland Hutchison, Esq. Surgeon.
George Swinton, Esq. Secretary to Government, Calcutta.

November 96. 1837.

At an Extraordinary General Meeting held this day, Sir Wal-
ter Scott, Bart in the Chair, the following Office-Bearers were elected for
the ensuing year :

Sir Walter Scott, Bart President.

Right Hon. Lord Chief Baron,

H<m. Loud Gle#lee,

Dr T. C. Hope,

Professor Russell,

Dr Brewster, General Secretary.

Thomas Allan, Esq. Treasurer.

James Skene, Esq. Curator of the Museum.

Vice-Presidents.

AND LOT OF MEMBERS ELECTED. 9M

PHYSICAL CLASS.

Hon. Lord Newton, President.
John Robison, Esq. Secretary.

COUNCILLORS FROM THE PHYSICAL CLASS.

Professor Wallace. Dr Graham.

Dr Turner. James Hunter, Esq.

Sir T. M. Brisbane, K. C. B. Dr Alison.

LITERARY CLASS.

Henry Mackenzie, Esq. President
P. F. Tytler, Esq. Secretary.

COUNCILLORS FROM THE LITERARY CLASS.

Sir John Hay, Bart. Thomas Kin near, Esq.

Dr Hibbert. Sir William Hamilton, Bart.

Hon. Lord Meadowbank. Rev. Dr Brunton.

Dr Ballinoall, Dr Graham, and Mr Robison were appointed a Committee to
examine and report on the Treasurer's Accounts.

Dr Graham gave notice of a Motion to alter tile 17th Law, in so far " as to do
away the appointment, at future elections, of Presidents to the Physical and Literary
Classes, and to add two to the present number of Vice-Presidents."

Dr Grah4M explained, that, as according to the present practice of the Royal
Society, there never were any separate meetings of these Classes, the persons on whom
the distinction of being appointed Presidents is conferred, can never be called on to
take the Chair, and that it would therefore be better that they should be added to the
number of Vice-Presidents, when they would in turn preside in the absence of the
President

The Motion was ordered to lie on the table until the first Ordinary Meeting in
January.

Mr Allan represented that some means of warming and ventilating the Society's
apartments, by heated air, would be conducive to the comfort of the Members, and to
the preservation of the property of the Society, and suggested that a small Committee

506 PROCEEDINGS OF GENERAL MEETINGS,

should be named to consider and report on the practicability of some plan for this pur-
pose. The Meeting, on considering this suggestion, appointed

Dr Hope, Mr Playfair, and

Mr J. Jakdine, Mr Robison,

to be a Committee for this purpose.

Mr Robison intimated, that he had received a Letter from Mr Watt, of Soho,
mentioning that he was preparing (with the purpose of presenting it to the Royal So-
ciety) a copy of Sir William Beechey's Portrait of his Father, the late Mr Watt.
The Meeting expressed their gratification at this communication, but deferred noticing
it until the arrival of the Picture.

Mr Robison was directed, in the absence of the General Secretary, to open the
Letters, &c. whiph may be received, and to take the necessary steps for forwarding
the business of the Society.

ORDINARY MEETINGS.

January 7. 1828.
MEMBERS ELECTED.

ORDINARY.

Sir Fbancis Walker Drummond, Bart.
Sir William 6. Gordon Cumming, Bart.

The Vice-President communicated to the Society, that the Council had, after due
investigation, adjudged the first Biennial Prize, from the donation of the late Mr Keith,
to Dr Brewster, for his Papers on his discovery of two new immiscible fluids in the
cavities of certain Minerals.

' 2

AND LIST OF MEMBER8 ELECTED. 507

February 4. 1828.
MEMBERS ELECTED.

ORDINARY.

Erskine D. Sandford, Esq. Advocate.
David Maclagan, M.D. Edinburgh.
James Craufurd Gregory, M.D. Edinburgh.
Sir Alexander Keith, Knight Marischal.

Upon the motion of Sir Hbnrt Jardine, it was resolved that the Council shall
be empowered to enter into arrangements with the Council of the Antiquarian Society,
for making such an exchange of any objects in their respective collections as may ap-
pear for the benefit of both.

March 3. 1828.

MEMBER ELECTED,

ORDINARY.

Captain Maxwell, K. D. Guards.
April 7. 1828.

MEMBERS ELECTED.

»

HONORARY.

Davies Gilbert, Esq. M. P. President of the Royal Society of London.

FOREIGN.

Le Chevalier Bouvard, F. R. S. Lond. Member of the Institute of France.

ORDINARY.

John Forster, Esq. Architect, Liverpool

Thomas Graham, Esq. A. M.

Thomas Hamilton, Esq.

David Milne, Esq. Advocate.

DtManson.

William Burn Callender, Esq.

VOL. XL PART II. 3 S

50& PROCEEDINGS OF GENERAL MEETINGS,

EXTRAORDINARY GENERAL MEETING.

November 24. 1828.

At an Extraordinary General Meeting held this day,
Sir John Sinclair, Bart, being called to the Chair,

Resolved, — " That this Meeting approve of the change in the denominations of
the Office-Bearers, recommended by Dr Graham, on the 36th November 1827, and
remit to the Council to make such verbal alterations in the Laws as may be requisite

to put them in accordance with it"

The Meeting proceeded to the election of Office-Bearers, when the fol-
lowing were appointed :

Sir Walter Scott, Bark President.

Right Hon. the Lord Chief Baron,

Hon. Lord Glenlee,

Dr T. C. Hope,

Professor Russell,

Hon. Lord Newton,

Henry Mackenzie, Esq.

John Robison, Esq. General Secretary.

Vice-Presidents.

r% \* t* -o " i Secretaries to the Ordinary Meetings.

Rev. E. B. Ramsay, J

Thomas Allan, Esq. Treasurer.

James Skene, Esq. Curator of the Museum.

AND LIST OF MEMBEK8 ELECTED. 509

COUNCILLORS.

Sir T. M. Brisbane, K. C. B. Dr Alison.

Hon. Lord Meadowbank. Rev. Dr Brunton.

Dr Graham. Dr Brewster.

Thomas Kinnear, Esq. Captain Basil Hall, R. N.

James Hunter, Esq. Sir Henry Jardine.

Sir William Hamilton, Bart. Professor Jameson.

In terms of the 2 1st Law, the following Committee was appointed to audit the
Treasurer's Accounts :

Thomas Kinnear, Esq. (Convener.)
Patrick Neill, Esq.
John Rorison, Esq.

Sir John Sinclair addressed the Meeting, and observed, that it would be impro-
per to allow Dr Brewster to retire from the office he has held (with so much advan-
tage to the Society, and honour to himself,) without testifying their sense of his merits ;
and he therefore moved, " That the Royal Society take the opportunity presented in
the resignation, by Dr Brewster, of the office of Secretary, to offer him their best
thanks for his zealous services, and for the numerous valuable communications with
which he has enriched their Transactions, and by which he has contributed materially
to maintain the reputation of the Society." This Motion was unanimously adopted.

Mr Allan said, that while he heartily concurred in this resolution, he thought
that something more substantial than a vote of thanks should be offered to Dr Brewqter,
in return for the labour he had bestowed on the affair* of the Society; he therefore
proposed " That the Council be requested to consider and report to a Special General
Meeting, to be held in January next, the amount of pecuniary remuneration which
they would recommend should be offered to Dr Brewster." This motion was likewise
unanimously adopted.

Sir John Hay suggested to the Meeting, " That, as it is highly desirable that
the Society should possess a portrait of their illustrious President Sir Walter Scott,
he should be requested to sit to Mr Graham for that purpose." The Meeting approved
of this suggestion, and appointed Sir John Hay, Mr Seene, and Mr RoBison to be
a Committee for carrying it into effect.

Mr Robison intimated to the Meeting, that he intended to offer to the acceptance
of the Society, a portrait of his Father, by the late Sir Henry Raeburn.

3s2

510 PROCEEDINGS OF GENERAL MEETINGS,

January 5. 1829.

At a Special General Meeting, the following communication was made by the
Council :—

" The Council have to report, that, in compliance with the first part of the remit
made to them by the extraordinary General Meeting of the 24th November last, they
have made the required alterations in the Bye-Laws, of which they npw lay a corrected
copy on the Table.1"

" They have further to report, that, after duly considering the second part of
the remit, they unanimously agreed to recommend that the same amount, namely
L.300, which was granted to the former General Secretary, Mr Playfaie, should be
presented to Dr Brewster."

The Meeting unanimously approved of the Report, and adopted the recommen-
dation.

COPY OF THE LAWS, AS CORRECTED BY THE COUNCIL.

I. The Royal Society of Edinburgh shall consist of Ordinary, Foreign, and
Honorary Members.

II. Every Ordinary Member, within three months after his election, shall pay
Five Guineas as fees of admission, and Three Guineas as the first annual contribution ;
and shall farther be bound to pay the sum of Three Guineas annually into the hands
of the Treasurer. All Members who shall have paid Twenty-five years1 annual con-
tributions shall be exempt from further payment.

III. Members shall be at liberty to compound for their annual contribution, by
paying at the rate of ten years1 purchase.

IV. Ordinary Members, not residing in Edinburgh, and not compounding, shall
appoint some person residing in Edinburgh, by whom the payment of the said contri-
bution shall be made, and shall signify the same to the Treasurer.

V. Members Ailing to pay their contribution for three successive years (due ap-
plication having been made to them by the Treasurer), shall be reported to the Coun-

1

AND LIST OF MEMBERS ELECTED. 511

cil, and, if they see fit, shall be declared from that period to be no longer Members,
and the legal means for recovering such arrears shall be employed.

VI. None but Ordinary Members shall bear any office in the Society, or vote in
the choice of Member or Office-bearers, or 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 be entitled to receive from the Publisher, gratis, the Parts of the Society's Trans-
actions which shall be published subsequent to their admission.

IX. No person shall be proposed as an Ordinary Member, without a recommenda-
tion subscribed by One Ordinary Member, to the purport below*. This recommenda-
tion 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.

X. The Foreign Members shall not be subject to the Annual Contributions, 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.

XI. The Honorary Members shall not be subject to the Annual Contribution,
nor to any Fee on admission. They shall be limited to the number of Twenty-one,
and shall consist of persons eminently distinguished in Science and Literature.

XII. Any Three Members may transmit, through the Secretary to the Council,
recommendations of Foreign and Honorary Members. Foreign and Honorary Mem-

• u A. B. a gentleman well skilled in several branches of Science (or Polite literature, as the case
u 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."

This recommendation to be accompanied by a request of admission, signed by the Candidate.

512 PROCEEDINGS OF GENERAL MEETINGS,

bers may also be proposed by the Council, and they shall be elected in the dame man-
ner as the Ordinary Members.

XIII. The election of Members shall take place on the 1st Mondays of the
month during the Session, at the ordinary meetings of the Society. The Election
shall be by Ballot, and shall be determined by a majority of at least two-thirds of the
votes, provided Twenty-four Members be present, and vote.

XIV. The Ordinary Meetings shall be held on the first and third Mondays of
every month, from November to June inclusive. Regular minutes shall be kept of the
proceedings, and the Secretaries shall do the duty alternately, or according to such
agreement as they may find it convenient to make.

XV. The Society shall from time to time publish its Transactions and proceed-
ings. For this purpose the Council shall select and arrange the papers which they
shall deem it expedient to publish in the Transactions of the Society, and shall super-
intend the printing of the same.

The Transactions shall be published in Parts or Fasciculi at the close of each
session, and the expense shall be defrayed by the Society.

XVI. There shall be elected annually for conducting the publications and regu-
lating the private business of the Society, a Council, consisting of a President ; Six
Vice-Presidents, two at least of whom shall be resident ; Twelve Councillors, a Ge-
neral Secretary, Two Secretaries to the Ordinary Meetings, a Treasurer, and a Curator
of the Museum and Library*.

XVII. Four Councillors shall go out annually, to be taken according to the order
in which they stand on the list of the Council.

XVIII. An Extraordinary Meeting for the Election of Office-Bearers shall be
held on the fourth Monday of November annually.

* An Assistant Curator has since been added by a resolution of the Society on the 18th January 18)0.

AtfD LlAT OP MEMBERS ELECTED. 513

XIX. Special Meetings of the Society may be called by the Secretary, by direc-
tion of the Council ; or on a requisition signed by six or more Ordinary Members.
Notice of not less than two days must be given of such meetings.

XX. The Treasurer shall receive and disburse the money belonging to the So-
ciety, granting the necessary receipts, and collecting the money when due.

He shall keep regular accounts of all the cash received and expended, which shall
be made up and balanced annually ; and at the last Ordinary Meeting in January, he
shall present the accounts for the preceding year, duly audited. At this Meeting, the
Treasurer shall also lay before the Council a list of all arrears due above two years,
and the Council shall thereupon give such directions as they may deem necessary for
recovery thereof.

XXI. At the Extraordinary Meeting in November, a Committee of Three Mem-
bers shall be chosen to audit the Treasurer's accounts, and give the necessary discharge
of his intromissions.

The report of the examination and discharge shall be laid before the Society at
the last Ordinary Meeting in January, and inserted in the records.

XXII. The General Secretary shall keep Minutes of the Extraordinary Meetings
of the Society, and of the meetings of the Council, in two distinct books. He shall,
under the direction of the Council, conduct the correspondence of the Society, and
superintend its publications. For these purposes, he shall, when necessary, employ a
clerk, to be paid by the Society.

The Secretaries to the Ordinary Meeting shall keep a regular Minute-book, in
which a full account of the proceedings of these Meetings shall be entered : they shall
specify all the Donations received, and furnish a list of them, and of the donor's names,
to the Curator of the Library and Museum : they shall likewise furnish the Treasu-
rer with notes of all admissions of Ordinary Members. They shall assist the General
Secretary in superintending the publications, and in his absence shall take his duty.

XXIII. The. Curator of the Museum and Library shall have the custody and
charge of all the Books, Manuscripts, objects of Natural History, Scientific Produc-
tions, and other articles of a similar description belonging to the Society ; he shall take
an account of these when received, and keep a regular catalogue of the whole, which
shall lie in the Hall, for the inspection of the Members.

514 PROCEEDINGS OF GENERAL MEETINGS,

XXIV. 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 shall from time to time appoint.

XXV. A Register shall be kept, in which the names of the Members shall be
enrolled at their admission, with the date.

The above Laws were ordered to be printed and distributed among the Members.

ORDINARY MEETINGS.

January 5. 1829*
MEMBERS ELECTED.

ORDINARY.

Andrew Skene, Esq. Advocate.
A. Colyar, Esq.

March S. 1829.
MEMBERS ELECTED.

ORDINARY.

William Gibson Craig, Esq. Advocate.

Charles Ferguson, Esq. Advocate*

James Ewing, Esq. LL. D. Glasgow.

Duncan Macneill, Esq. Sheriff-Depute of Perth.

Rev. John Sinclair, A. M. Pembroke College, Oxford.

Arthur Connell, Esg. Advocate.

Rev. Thomas Sheepshanks, A. M.

James Hope Vere, Esq. of Craigie Hall.

f <

AND LIST OF MEMBERS ELECTED. SIS

April 6. 1829-

MEMBER ELECTED.

«

ORDINARY.

Bindon Blood, Esq. M. R. I. A.

At this Meeting the Keith Prize, lately adjudged to Dr Brewster, was presented
to him, with an appropriate address from the Chair. The Prize consisted, agreeably
to the terms of the donation, of a Medal and a piece of Plate, bearing the devices and
inscription of the medal.

November 23. 1829.

Vice-Presidents.

At an Extraordinary General Meeting held this day, Dr Hope,
Vice-President, in the Chair, the following Office-Bearers were elected for the
ensuing year :

Sir Walter Scott, Bart. President.

Bight Hon. the Lord Chief Baron,
Hon. Lord Glenlee,
Hon. Lord Newton,
Dr T. C. Hope,
Professor Russell,
Henry Mackenzie, Esq.
John Robison, Esq. General Secretary.
Rev. E. B. Ramsay,
Dr J. C. Gregory,
Thomas Allan, Esq. Treasurer.
James Skene, Esq. Curator of the Museum.
John Stark, Esq. Assistant Cutator.
vol. xi. part ii. 8 t

Y, )

[-Secretaries to the Ordinary Meetings.

51* PROCEEDINGS OF GENERAL MEETINGS,

COUNCILLOBS.

James Hunter, Esq. Sir Henry Jardine.

Dr Alison. Professor Jameson.

Sir William Hamilton, Bart. Sir David Milne.

Rev. Dr Brunton. Sir 6. S. Mackenzie, Bart.

Dr Brewster. Dr Duncan.

Captain Basil Hall, R. N. Professor Wallace.

The following Committee was appointed to audit the Treasurer's Accounts :

Patrick Neill, Esq. John Robison, Esq.

J. 6. Kinnear, Esq.

ORDINARY MEETINGS.

December 7. 1829*

MEMBERS ELE€TEt>.

OHDIXAMY.

James Walker, Esq. W. S.
William Bald, Esq. M. R. I. A.
Whitel aw Ainslie, M.D. M. R. A. S.

January 18. 1830.

At this Meeting, a Motion, of which due notice had been given at the Meeting of
the 21st of December 1829, to alter the 16th Law, so iar as to add an Assistant Cura-
tor to the Office-Bearers in Council, was made from the Chair, and agreed to unani-
mously.

AND LIST OF MEMBERS ELECTED. 517

February 1. 18S0.

MEMBER ELECTED.

ORDINARY.

Colonel Pitman, Hon. B. I* G. Sendee.

March 1. 1880.

MEMBERS ELECTED.

ORDINARY.

J. T. Gibson Craig, Esq- W. S.
Archibald Alison, Esq. Advocate.

April 5. 1880.

MEMBERS ELECTED.

ORDINARY.

Hon. Mountstuart Elphinstone.
James Syme, Esq. Surgeon, Edinburgh.
Thomas Brown, Esq. of Langfcie.

St 2

918 PROCEEDINGS OF GENERAL MEETINGS,

November 22. 1830.

At a General Meeting held this day,Dr Hope, Vice-President, in the
Chair, the following Office-Bearers were elected for the ensuing year :

Sir Walter Scott, Bart. President.

Vice-Presidents.

The Hon: Lord Glenlee, - }
The Hon. Lord Newton,
Dr Hope,
Professor Russell,
Henry Mackenzie, Esq..

John Robison, Esq. General Secretary.

^ ' ' I Secretaries to the Ordinary Meetings.

Dr Christison, J '

Thomas Allan, Esq. Treasurer.

James Skene, Esq. Curator.

John Stark, Esq. Assistant Curator.

COUNCILLORS.

Dr Brewster, Dr Duncan.

Capt. Basil Hall, R. N. Professor Wallace.

Sir Henry Jardine. Sir T. M. Brisbane.

Professor Jameson. Dr Greville.

Sir David Milne. James Jardine, Esq.

Sir George Mackenzie, Bart. Dr Hibbert.

The following Committee was appointed to audit the Treasurer's account.

» • t ,'

s

Patrick Neill, Esq. \ John Gardiner Kinnear, Esq.
Joh^ Robison, Esq. Mr Kinnear, Convener.

. AND LIST OF MEMBERS ELECTED. 519

ORDINARY MEETINGS.

December 6. 1830.

MEMBERS ELECTED.

ORDINARY.

*

t
• ♦ • »

James L'Amy, Esq. Advocate.
Thomas Barnes, Esq. M. D. Carlisle.

Notice was given, that a Motion would be made on Monday, Sd January 1831,
to give power to the Council to dispense with the exaction of the fees of entrance and
annual contribution in certain cases.

January 3. 1831.

MEMBERS ELECTED.

HONORARY. (

• « *

«

His Royal Highness The Duke of Sussex.

• • • •

ORDINARY.

James D. Forbes, Esq. Advocate.

» »
* *

The following Motion was made by Mr Robison : —

" That in the event of any case occurring, in which it may appear that it would
tend to the advancement of science, and to the promotion of the general interests of the
Royal Society, it shall be competent to the Council to dispense with the exaction of the
usual fees of admission and annual contribution, by a resolution to be proposed at one
Ordinary Meeting of Council, and to be passed at a subsequent one."

It was at the same time explained to the Meeting, that the object of this Motion
was to enable the Council to arrange for the admission into the Society of persons whose
eminence in scientific pursuits should make their association expedient for the reputa-
tion of the Society, but to whom the amount of the fees might be inconvenient.

The Motion having been put from the Chair, and having been seconded by Dr
Whitelaw Aikslib, was carried unanimously.

530 PROCEEDINGS OF GENERAL MEETINGS, &C.

February 7. 1881.
Migiimpmi ELECTED.

ORDINARY.

The Right Hon. James Abercromby, Lord Chief Baron.
John Abercrombie, Esq. M. D.
Donald Smith, Esq.
Captain Samuel Brown, R.N.

April 4. 1831.
MEMBERS ELECTED.

ORDINARY.

O. Tyndal Bruce, Esq. of Falkland.

David Boswell Reid, Esq. M. D.

The Rev. W. EL Marriot, A. M. Trinity College, Cambridge.

T. S. Da vies, Esq. Bath.

At this Meeting Dr Gkzgoey gave notice of a Motion to aker the 9th Law, so
far as to diminish the period which at present intervenes between the first reading of
the name of a Candidate and the day of his election.

( «ai )

ORDINARY MEMBERS tN THE
THEIR ELECTION.

— - ■ ■ •- — -

His Majesty THE gING Patbok.

Date of
Election.

James Hamilton senior^ M. D. Edinburgh.
Sir William Miller, Baronet, Lord Glenlee.
James Russell, Esq. Prqfessor of Clinical Surgery.

The above Gentlemen were Members qf the Edinburgh Philosophical
Society.

1783. Honourable Baron Hume.

Sir William Macleod Bannatyne, Bart.

The above Gentlemen were associated with the Members of the Philosophical
Society at the Institution of the Royal Society in 1783.

The following Members were regularly elected.

1784. Sir James Hall, Baronet, F. R. S. Loud.
Honourable Lord Eldin.

Reverend Archibald Alison, LL. B. Edinburgh.

1785. James Hare, M. D. late of Calcutta.

1787. James Home, M. D. Prqfessor of the Practice qf Physic.

1788. Thomas Charles Hope, M. D. F. R. S. Lond. Prqfessor qf Chemistry.
Right Honourable Charles Hope, Lord President of the Court qf Session.

1798. Sir Alexander Muir Mackenzie, Bart. qfDelvm.

1795. The Very Reverend Dr George Husband Baird, Principal of the University.

522 LIST OF ORDINARY MEMBERS.

Date of
Election.

1795. Robert Hamilton, Esq. Professor of Public Law.

1796. The Honourable Baron Sir Patrick Murray, Baronet.
Andrew Berry, M. D. Edinburgh.

1797. Andrew Duncan, M. D. Prqfessor of Materia Medica.

1798. Alexander Monro, M. D. Prqfessor of 'Anatomy, fyc.
Right Honourable Sir John Sinclair, Bart.

1799. Thomas Macknight, D. D.
Honourable Lord Robertson.

Sir George S. Mackenzie, Baronet, F. R. S. Lond.
Robert Jameson, Esq. Professor of Natural History.

1800. Gilbert Innes, Esq. of Stow.

Sir Walter Scott, Baronet, of Abbotsfbrd.

1802. Colonel D. Robertson MacdonakL

1803. John Jamieson, D. D.

Thomas Telford, Esq. Civil Engineer.

Reverend Dr Andrew Brown, Prqfessor of Rhetoric.

1804. William Wallace, Esq. Prqfessor of Mathematics.
Honourable Lord Newton.

1805. Thomas Allan, Esq. F. R. S. Lond.

' Thomas Thomson, M. D. F. R. S. Lond. Prqfessor of Chemistry, Glasgow.

1806. Robert Ferguson, Esq. qfRaith, F. R. S. Lond.
George Bell, Esq. Surgeon, Edinburgh.
George Dunbar, Esq. Prqfessor of Greek.

1807. Sir James Montgomery, Baronet, of Stanhope.
John Leslie, Esq. Professor of Natural Philosophy.
John Campbell, Esq. qfCarbrook.

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.

1811. Charles Bell, Esq. Surgeon, London.
Alexander Nimmo, Esq. Civil Engineer.
Reverend Andrew Stewart, M. D.'Ershme.
David Ritchie, D. D. Prqfessor of Logic.
Major-General Sir Thomas Makdougal Brisbane, K. C. B.

1812. General Dyce.

John Thomson, M. D. Edinburgh.
James Jardine, Esq. Civil Engineer.
Captain Basil Hall, R. N. F. R. S. Lond.

3

LIST OF ORDINARY MEMBERS. 523

Dtte of
Election.

1812. 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. Prqfisssor of Humanity.
Sir George Clerk, Bart. M. P. and F. R. S. Lond.
Daniel Ellis, Esq. Edinburgh.
13. William Somerville, M. D. F. R. S.London.
Henry Davidson, M. D. Edinburgh.

1814. Sir Henry Jardine, King's Remembrancer in Exchequer.

Patrick Neill, Esq. Secretary to the Wernerian and Horticultural Societies.

Right Honourable Lord Viscount Arbuthnot.

Reverend John Thomson, Duddingston.

John Fleming, D. D. Flisk.

John Cheyne, M. D. Dublin.

Sir James Macintosh, Bart. London.

Lieut-Colonel Tytler, Edinburgh.

Alexander Brunton, D. D. Professor of Oriental Languages.

Professor George Glennie, MarischaU College, Aberdeen.

1815. Gilbert Laing Meason, Esq. of Lindertis.
Robert Stevenson, Esq. Civil Engineer.

Sir Thomas Dick Lauder, Bart of Fountainhall.
Henry Home Drummond, Esq. of Blair-Drummond, M. P.
Charles Granville Stewart Menteath, Esq. ofCloseburn.
William Thomas Brande, Esq. F. 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 Colbrooke, Esq. Director of the Asiatic Society of Great Britain.

George Cook, D. D. Laurencekirk.

Right Honourable William Adam, Lord Chief Commissioner.

Honourable Lord Fullerton.

Thomas Jackson, LL. D. Professor of Natural Philosophy, St Andrew's

John Robison, Esq. Edinburgh.

Hugh Murray, Esq. Edinburgh.

1817. The Honourable Baron Clerk Rattray.

Right Honourable the Earl of Wemyss and March.
John Wilson, Esq. Professor of Moral PhMosoplty.
Honourable Lord Meadowbank.

VOL. XI. PART II. 8 V

524 LIST OF OBD1NABY MEMBERS.

Bate of
Election*

1817. James Hamilton Dickson, M. D. Clifton.

William P. Alison, M. D. Professor of the Theory of Physic.
James Skene, Esq. of Rubislaw.
Reverend Robert Morehead, Edinburgh.
Robert Bald, Esq. Civil Engineer.
Thomas Sivright, Esq. of Meggctland.

1818. William Richardson, M. D. Harrowgate.
Right Honourable Lord Napier.
Harry William Carter, M. D. Oxford.
Patrick Miller, M. D. Exeter.

John Craig, Esq. Edinburgh.

John Watson, M. D.

John Hope, Esq. Dean of Faculty.

Major James Alston of Aucfienard.

William Ferguson, M. D. Windsor.

Sir William Hamilton, Bart Professor of Civil History.
1819 Right Honourable Lord John Campbell, F. R. S. LoncL and M. R. L

Dr Shoolbred, Calcutta.

Patrick Fraser Tytler, Esq. Advocate.

Patrick Murray, Esq. qfSimprim.

James Muttlebury, M. D. Bath.

Thomas Stewart Traill, M. D. Liverpool.

Mr Alexander Adie, Optician, Edinburgh.
. William Couper, M. D. Glasgow.

Marshall HaU, M. D. Nottingham.

John Borthwick, Esq. Advocate.

Richard Phillips, Esq. F. R. S. London.

Reverend William Scoresby.

George Forbes, Esq. Edinburgh.
1820. James Hunter, Esq. of Thurston.

Right Honourable David Boyle, Lord Justice-Clerk.

James Keith, Esq. Surgeon, Edinburgh.

Right Honourable Sir Samuel Shepherd.

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.

LIST OF ORBfNABY MEMBERS. 53 5

Date of
Election.

1820. John F. W. Herschel, Esq. F. R. S. Lond.

Adam Anderson, Esq. A. M. Rector of the Academy, Perth,

John Schank More, Esq. Advocate.

George Augustus Borthwick, M. IX EtHnburgft.

Robert Dundas, Esq. of Arniskm.

Samuel Hibbert, M. D.

Robert Haldane, D. D. Principal of St Mary's College, St Andrew's.

Sir John Meade, M. D. Weymouth.

Dr William Macdonald of BaByshear.

John Hall, Esq. younger of Dunglass.

Sir John Hay, Bart of Smithfield and Hay Hon.

Sir George Ballingall, M. D. Professor of Military Surgery.

1821. Major-General Straton, C. B. &c. &c.
Robert Graham, M. D. Professor of Botany.
A. N. Macleod, Esq. of Harris.

Sir James M. Riddell, Bart of Ardnamurchan.

Archibald Bell, Esq. Advocate.

John Clerk Maxwell, Esq. Advocate.

John H. Wishart, Esq. Surgeon, Edinburgh.

John Lizars, Esq. Surgeon, Edinburgh.

John Cay, Esq. Advocate.

Sir Charles Gies&ke, Professor of Mineralogy to the Dublin Society.

Robert Kay Greville, LL. D. Edmbicrgh.

Robert Hamilton, M. D. 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, LL. D.

James Buchan, M. D. Edinburgh.

James Ty tier, Esq. of Woodhouseke, W. S.

1822. Francis Chantry, Esq. F. R. S. London, tec.
Edward Troughton, Esq. F. R. S. London, fee.
James Smith, Esq. qfJordanhiU.

William Bonar, Esq. Edinburgh.
Rev. H. Parr Hamilton, Cambridge.
Captain J. D. Boswall, R. N. of Wardie.
George A. Walker Arnott, Esq. Advocate.
Rev. John Lee, M. D. Edinburgh.

4 3 »2

526 LIST OF ORDINARY MEMBERS.

Bate of
Election.

1822. John Ay ton, Esq. of Inchdarhie.

Sir James South, F. R. S. London, &c.

Lieutenant-Colonel Martin Whyte, Edinburgh.

Walter Frederick Campbell, Esq. ofShawJleld, M. P.

George Joseph Bell, Esq. Professor of Scots Law.

Dr William Dyce, Aberdeen.

W. C. Trevelyan, Esq. Wellington.

Robert Abercromby, Esq. younger qfBirkenbog.

Thomas Shortt, M. D. Edinburgh.

Dr Wallich, Calcutta.

1823. The Right Honourable Sir George Warrender, Bart of Lochend.
John Russell, Esq. W. S. Edinburgh.

John Shaw Stewart, Esq. Advocate.
Alexander Hamilton, M. D. Edittfmrgh.
Right Honourable Sir William Rae, Bart, of St Catherine's.
Sir Robert Dundas, Bart. qfBeechwood.
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 qfAUanbank.
Sir Andrew Halliday, M. D.
John Bonar, Esq. qfKimmerghame.

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 Banchory, Advocate.
Liscombe John Curtis, Esq. Ingsdon House, Devonshire.
Robert Knox. M. D. Lecturer on Anatomy, Edinburgh.
Robert Christison, M. D. Professor of Medical Jurisprudence.
. John Gordon, Esq. qfCairnbulg.
1824 George Harvey, Esq. F. R. S. Lond. Plymouth.
Dr Lawson Whalley, Lancaster.
William Bell, Esq. Wf S. Edinburgh.
Alexander Wilson Philip, M. D. London. .

James Hamilton jun.9 M. D. Professor of 'Midwifery in tlie University of Edin-
burgh.
Admiral Adam, R. N.

LIST OF ORDINARY MEMBERS. 587

Date of
Election.

1824. Robert Grant, M. D. Professor of Comparative Anatomy in the London . Uni-

versity.
Claud Russell, Esq. Accountant, Edinburgh,
Rev. Dr William Muir, one of the Ministers qf Edinburgh.
W. H. Playfair, Esq. Architect, Edinburgh.
John Argyle Robertson, Esq. Surgeon, Edinburgh.
James Pillans, Esq. Edinburgh.
James Walker, Esq. Civil Engineer.
William Newbigging, Esq. Surgeon.
William Wood, Esq. Surgeon, Edinburgh.
William Crosbie Mair, M. D. London.
John Campbell, M. D. Edinburgh.
George Anderson, Esq. Inverness.

1825. Rev. John Williams, Rector of the Edinburgh Academy.
W. Preston Lauder, M. D.

Right Honourable Lord Ruthven.
Major Leith Hay qfRannes.
% Edward Turner, M. D. Professor of Chemistry to the London University.
Dr Reid Clanny, Sunderland.
John Archibald Stewart, Esq. younger qfGrantuBy.
Sir William Jardine, Bart. qfApplegarth.
Alexander Wood, Esq. Advocate.
Rev. Dionysius Lardner, London University.

1826. George Macpherson Grant, Esq. 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.
George Moir, Esq. Advocate.
John Stark, Esq. Edinburgh.
1887. James Weddell, Esq. R. N.

John Gardiner Kinnear, Esq. Edinburgh.
William Burn, Esq. Edinburgh.
James Russell Junior, M. D. Edinburgh.
Prideaux John Selby, Esq.
Henry Witham, Esq.
John Reddie, Esq. LL. D. Edinburgh.
The Rev. Dr Robert Gordon, Edinburgh.
James Wilson, Esq, Edinburgh.

588 LIST OF OEDINAHY HEMBE&S.

Bate of
Election.

18*7. The Rev. Edward Bannerman Ramsay, A. B. of St Jthtie CaUege, -CtoMridgt.
James Walker, D. D. of St John's College, Cambridge.
Alexander Copland Hutchinson, Esq. Surgeon* London.
George Swinton, Esq* Secretary to Government, Calcutta.

1828. Sir Francis Walker Drummond, Bart
Sir William 6. Gordon dimming, Bart.
Erskine D. Sandford, Esq. Advocate.
David Maclagan, M. D. Edinburgh.
James Craufurd Gregory, M. D. Edinburgh.
Sir Alexander Keith, Knight Mari&chal.
Captain Maxwell, K. D. Guards.

John Forster, Esq. Architect, Liverpool.
Thomas Graham, Esq. A. M., Glasgow.
Thomas Hamilton, Esq. Edinburgh.
David Milne, Esq. Advocate.
Dr Manson, Nottingham.
William Burn Callender, Esq.

1829. Andrew -Skene, "Esq. Advocate.
A. Colyar, Esq.

William Gibson Craig, Esq. Advocate.

Charles Ferguson, Esq. Advocate*

James Ewing, Esq. LL. D. Glasgow.

Duncan Macneill, Esq. Sherffidepnte -of Perth*

The Rev. John Sinclair, A. M» Pembroke College, Oxford.

Arthur Connell, Esq. Advocate.

James Hope Vere, Esq. of CratgiehaU.

Bindon Blood, Esq. M. R.I. A.

James Walker, Esq. W.S.

William Bald, Esq. M. R. I. A.

Whitelaw Ainslie, M. D. M. R. A. S.

1830. Colonel Pitman, Hon. East India Company's Ser*vice.
J. T. Gibson Craig, Esq. W. S.

Archibald Alison, Esq. Advocate.
Honourable Mountstuart Elphinstone.
James Syme, Esq. Surgeon, Edinburgh.
Thomas Brown, Esq. ofLangfine.
James L'Amy, Esq. Advocate.
Thomas Barnes, M. D. Carlisle.

1831. James D. Forbes, Esq. Advocate*

LIST OF OKMKARY memkebs. 5flg

Bate of
Election.

1881. The Right Honourable James Abercromby, Lord Chief Baron.

John Abercrombie, M. D.

Donald Smith, Esq.

Captain Samuel Brown, R. N.

O. Tyndal Bruce, Esq. qf Falkland.

The Rev. W. H. Marriot, A. M. Trin. College, Cambridge.

T. S. Davies, Esq. Bath.

5S0 LIST OF NON-RESIDENT AND FOREIGN MEMBERS.

LIST OF NON-RESIDENT AND FOREIGN MEMBERS ELECTED

UNDER THE OLD LAWS

Sir Gilbert Blane, M. D. F. R. S. London.

Right Honourable the Earl of Dundonald.

Right Honourable Sir Robert Listen, Bart.

M. Le Chevalier, Paris.

Dr'S. L. Mitchell, New Fork.

Right Honourable Lord Wallace.

John Gillies, LL. D. Historiographer to his Majesty.

M. P. Prevost, Geneva.

Rev. Walter Fisher, Cranston.

Rev. Bishop Gleig, Stirling.

Charles Hatchet, Esq. F. R. S. Lond.

Sir Henry Steuart, Bart. qfAUanton.

Sir William Blizzard, M. D. F. R. S. Lond.

Thomas Blizzard, Esq.

Sir William Ouseley, Bart.

Sir James Macgrigor, M. D.

Richard Griffiths, Esq. Civil Engineer.

LIST OF HONORARY AND FOREIGN MEMBERS. 581

LIST OF HONORARY AND FOREIGN MEMBERS ELECTED UNDER

THE NEW LAWS-

CLASS OF HONORARY MEMBERS LIMITED TO 21.

Baron Cuvier, Secretary to the Institute of France.

M. le Baron Humboldt, Member of the Institute of France.

M. Gray 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.

Robert Brown, Esq. F. R. S. Lond. &c. &c.

Jacob Berzelius, M. D. F. R. S. Lond. Professor of Chemistry 9 Stockholm.

Davies Gilbert, Esq. M. P., F. R. S.

His Royal Highness the Duke of Sussex, President of the Royal Society of London.

CLASS OF FOREIGN MEMRERS LIMITED TO S6.

M. Le Chevalier Legendre, Member of the Institute of France.

M. Poisson, Member of the Institute of France.

M. le Baron de 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.

Count Volta, Como.

M. J. C. L. Simonde de Sismondi.

Baron Degerando.

VOL. XI. PART II. S X

532 LIST OF HONORARY AND FOREIGN MEMBERS.

Baron Krusenstern, Member of the Academy of Sciences at St Petersburg*
M. Oersted, Secretary to the Royal Society of Denmark.
M. Ampere, Member of the Institute of France. >
M. Schumacher, Professor qf Astronomy at Copenhagen.
M. Mohs, Professor qf Mineralogy at Freyberg.
David Hosack, M. D. F. R. S. New York.
Nathaniel Bowditch, Esq. Salem, Massachussets.
M le. Baron Larrey, Member qfthe Institute qfFrarice.

Sir Henry Bernstein, Professor qf Oriental Literature in the University of Berlin*
M. De Candolle, Geneva.
Dr Olbers, Bremen.

M. Frederick Munter, Bishop qf Zealand.
M. Oriani, Milan.

M. le Baron Dupin, Member qfthe Institute of France.
M. Brongniart, Member qfthe Institute qf France.
The Chevalier Burg, Vienna.
M. Bessel, Konigsberg.

M. Thenard, Member qfthe Institute of France.
M. Haidinger, Vienna.

M. Mitscherlich, Prqfessor qf Chemistry in the University qf Berlin.
M. Gustavus Rose, Prtfessor of Mineralogy in the University qf Berlin.
6. Moll, Prqfessor qf Natural Philosophy in the University qf Utrecht.
M. Stromeyer, Prqfessor of Chemistry in the University ofGottingen.
M. Hausmann, Professor of Mineralogy in the University ofGottingen.
John James Audubon, Esq. M. W. S.

Le Chevalier Bouvard, F. R. S. Lond, Member qfthe Institute of France.

1

( 533 )

LIST OF DECEASED MEMBERS, AND OP MEMBERS RESIGNED,

FROM 1826 TO 1830.

(N. B— This List is necessarily incomplete.)

Sir William Drummond, Bart of Logic Aknond.

The Right Honourable the Earl of Traquair.

George Jardine, A. M., Professor of Logic, Glasgow.

Andrew Duncan senior9 M. D. &c

Charles Stuart, M. D.

Dugald Stewart, Esq.

Honourable Lord Hermand.

Robert Blair, M.D.

General Dirom, of Mount Annan.

Rev. Sir Henry Moncrieff Wellwood. Bart.

Sir William Arbuthnot, Bart.

James Bryce, Esq. Surgeon.

Robert Allan, Esq. Surgeon.

Sir William Forbes, Bart qfPiisligo.

John Barclay, M. D.

Rev. Dr William Ritchie.

John Yule, M. D.

Francis Hamilton, M. D. F. R. S.

Sir John Hay, Bart

Major-General David Stewart of Garth.

Alexander Kennedy, M. D.

John Hennen, M. D.

John Veitch, M. D.

Andrew Waddell, Esq.

Alexander Waddell, Esq.

George Eellie, M. D.

H. W. Williams, Esq.

John Hugh Maclean, Esq.

John Hunter, LL. D.

Right Honourable the Earl of Morton,

Mr Jefferson.

The Rev. Thomas Somerville.

Robert Freer, M. D.

3X2

534

LIST OF DECEASED AND RESIGNED MEMBERS.

Major Rennell, F. R. S. Lond.

Richard Chenevix, Esq. F. R. S. Lond.

H. H. Blackadder, Esq. Surgeon.

Dr James Hare,jun. fate of Calcutta.

Thomas Kinnear, Esq.

Henry Mackenzie, Esq.

Colin Mackenzie, Esq. ofPortmore.

Andrew Coventry, M. D. Professor of Agriculture.

Rev. William Traill, LL. D.

Sir Humphrey Davy, Bart, F. R. S. Lond.

W. H. Wollaston, M. D., F. R. S. Lond.

M. Vauquelin, Member of the Institute of France.

Le Marquis de Laplace, Member of the Institute of France.

John Fleming, M. D. M. P.

RESIGNATIONS.

Right Honourable Lord Gray.
Dr Howell

The Rev. Thomas Sheepshanks.
Alexander Munro, Esq.
James Hall, Esq. Advocate.
John Dewar, Esq. Advocate.
Dr Macwhirter.

( 585 )

LIST OP PRESENTS, CONTINUED FROM VOL. X. P. 488.

1826. - . PRESENTS.

Dec. 4. Memorie della Reale Accademia delle Scienze di

Torino, Tom. XXX.
Memoirs of the Academy of Berlin for 1882 and

1828.
ReneTs Astronomical observations for 1824.
WeddelTs Voyage to the South Pole.
Guilding on the Botanic Garden of St Vincent
Flora Batava, Nos. 68, 69, 70, and 71.

South on Right Ascensions.
South on 838 Stars.
Hamilton's Analytical Geometry.
18. The Scapula of a Whale found in sinking a Coal-
Pit in Ayrshire.
Historical Notices of the Roman Law, by John

Reddie, Esq. LL. D.
Specimens of Mineral Waters from St Michael's.
1827.
Jan. 8. Transactions of the Horticultural Society of Lon-
don, Part 8. of Vol. VI.
28. Transactions of do. Part 4. of Vol. VI.
Jan. 28. Flora Batava, No. 72.

Feb. 5. Memoirs of the Astronomical Society of London,

Vol. II. Part 2.
. Asiatic Researches, Vol. XV.
American Journal of Science, Vol. X. No. 2.
Analytical Treatise on Plane and Spherical Tri-
gonometry, by the Rev. Dr Lardner.

BOKOES.

Royal Academy of
Sciences of Turin.

Royal Academy of
Sciences of Berlin.

The Author.

Ditto.

Ditto.

His Majesty the King
of the Netherlands.

The Author.

Ditto.

Ditto.

Thomas Allan, Esq.

The Author.

Lord Napier.

Horticultural Society.

Ditto.

His Majesty the King

of the Netherlands.

Astronomical Society.

Asiatic Society.
Professor Silliman
Dr Lardner.

536

LI8T OF DONATIONS.

1827. PRESENTS.

Feb. 5. The Snout of a Sword Fish.

19. Illustrations of Ornithology, by Sir William Jar-
dine, Bart, and P. J. Selby, Esq.

Various Specimens of Natural History and Manu-
factures from New Zealand, New South
Wales, &c.
Mar. 5. The Tusk of a Mastodon, with some other Bones,

found in Woodhill Quarry, near Kilmarnock.

Observations on Surgery, by Mr Copland Hut-
chisoQ.

On the State of Knowledge in the Highlands of
Scotland, by Mr Anderson

Memoires d'Experiences Electro-Dynamiques, par
•M. Ampere.
19. Memoires de Chirurgie Militaire, par Le Baron
Larrey,

Trigonometrical Survey of Mayo, by W. Bald,

Esq.

Transactions of the Horticultural Society of Lon-
don, Vol. VI. Part 5.

Transactions of the Royal Asiatic Society, Vol. I.
Part 2.
April 2. Transactions of the Society for the Encourage-
ment of Arts, Manufactures, and Commerce,
Vol. XLIV.

Scientific Aphorisms, by Robert Blair, M. D.,
F. R. S. Ed.
Dec. 3. Many Specimens and Objects of Natural History

and the Fine Arts, collected in India by
George Swinton, Esq. Secretary to Govern-
ment, Calcutta.

Theorie des Phenomenes Electro-Dynamiques, par
M. Ampere.

Eulogium on Mr Jefferson.

Transactions of the Geological Society of London,

Vol. II. Parts Land 2.
Memoires de l'Academie Royale des Sciences de

rinstitut de France. Annee 1828. Tom. VI.

DONORS.

George Swinton, Esq.

Calcutta.
The Authors.

Sir T. M. Brisbane,
&• C. B.

Thomas Allan, Esq.

The Author.

Ditto.

Ditto.

Ditto.

Ditto.

Horticultural Society.

Asiatic Society.

The Society of Arts,

The Author.
George Swinton, Esq.

M. Amp&re.

American Philosophi-
cal Society.

The Geological So-
ciety.

The Academy of
Sciences.

LIST OF DONATIONS.

537

1827. PRESENTS.

Dec 3. Distances of the Moon and Four Planets for 18X7.
Lecture on the Zopuron, by Dr Reid Clanny.
Astronomische Beobachtungen, by* M. F. B. Bessel.
Hourly Meteorological Observations on 17th July

1827.
Illustrations of Zoology, No. 1., by James Wil-
son, Esq. F. R. S. Ed.
Philosophy of the Human Voice, by James Rush,

M.D.
Monumenti Etruschi, in 10 vols. 4to.
Plantarum Brasiliensium Nova Genera, 1 vol.

folio.
Saggio de Esperienze Electrometriche del Ike. Ste-

fano Marianini.
Memoria Sopra la Fiaroma*
Abhandlungen der Akademie der Wissenschaften

zu Berlin 1824.
Bericht uber die Natur-historischen Reisen, &c.

1826.
Kupfer an Krystallen.

Travels from, India to England, &c. in 1826-26,

by Lieutenant Alexander.
Descriptions de quelques-uns de Principaux Obser-

vatoires d'Allemagne, by M. Quetilet.
Flora Batava, Nos. 78. and 74.

17. The Hunterian Orations for 1828 and 1826.

Transactions of the Royal Society of Stockholm.

1828.
Jan. 7. Models and Papers connected with the Erection of

the Eddystone Lighthouse, which belonged
to the late Mr Smeaton, Civil-Engineer.
21. A Treatise on Algebra, by the Rev. Dr Lardner.
A Treatise on the Ancient Geometrical Analysis,

by the Rev. Dr Lardner.
Three Orations before the Medico- Botanical So-
ciety of London, by John Frost, Esq.

DOKOA8.

M. Schumacher.

The Author.

Ditto.

Mr Thomson, Belfast

Institution.
The Author.

Ditto.

4

M. Camponi.
Ditto.

Ditto.

G. Libri.

Royal Academy of

Berlin.
Baron Humboldt.

Royal Academy of

Berlin.
The Author.

Ditto.

His Majesty the King
of the Netherlands.

The Hunterian So-
ciety.

The Royal Society of

Stockholm.

The Right Hon. the
Countess of Mor-
ton.

The Author.

Ditto.

Ditto.

538

LIST OF DONAT10N8.

1828. PRESENTS.

Jan. 21. Some Account of the Science of Botany, by John

Frost, Esq.
Dissertatio de Latitudine Specula? Havniensis, by

M. H. C. Schumacher.
Astronomische Nachrichten, Nos. 108. to 120.
Report, of the Transactions of the Academy of
Natural Sciences of Philadelphia during the
year 1824.
Feb. 4. Memoirs of the Astronomical Society of London,

Vol. III. Part 1.
A Mass of Metallic Iron, supposed to be Meteo-
ric.— See a Memoir by Thomas Allan, Esq.
Vol. XI. Part 1. of Transactions of Royal
Society of Edinburgh.
18. Transactions of the Society of Arts of London,
Vol. XLV.
Mar. 8. Physiological Illustrations of the Organ of Hear-
ing, by T. Buchanan, C. M.
17. An Analytical System of Conic Sections, by the
Rev. H. P. Hamilton, M. A., F. R. S.
Dec. 1. Models of the Islands of Clare and Eigg, and

Drawings illustrative of Topographical Mo-
delling and Delineation, by William Bald,
Esq. M. R. I. A. and F. G. S. Lond. &c.
Essay on Light, by J. F. W. Herschel, Esq. M. A.

F. R. S.
Illustrations of Ornithology, by Sir William Jar-
dine, Bart
Transactions of the American Philosophical So-
ciety, Vol. III. Part 1.
Transactions of the Linnean Society of London,

Vol. XV.
Sur la Combinasion de FOxig&ne et de TEau, par

M. TMnard.
Portrait of James Watt, Esq.

Some Proof Sheets of a Map of Mayo.
Transactions of the Horticultural Society of Lon-
don, Vol. VII. Part 2.

DONORS.

The Author.

Ditto.

M. BesseL
The Academy.

The Astronomical So-
ciety.
Mr Parish.

The Society of Arte.

The Author.

Ditto.

William Bald, Esq.

The Author.

The Author.

The American Philo-
sophical Society.
The Linnean Society.

The Author.

Mr Watt of Aston-
Hall, his Son.

W. Bald, Esq.

The Horticultural
Society.

LIST OF DONATIONS.

5S9

1888. PBESENTS.

Dec. 1. Portrait of Mr Murdoch, who first applied Carbu-

retted Hydrogen to the purposes of Illumi-
nation.

1829.
Jan. 5. Transactions of the Royal Academy of Sciences of

St Petersburg, with a Medal in Silver of the
Emperor Nicholas.
19. An Essay on Comets, which obtained the first of
Dr Fellowes's Prizes, by David Milne, Esq.
A. M. F. R. S. Ed.
Feb. 2. Elements of Natural History, by John Stark,

F. R. S. Ed.
Magazine of Natural History, edited by J. C.

Loudon, F. L. S. &c. Nos. 1. to 5. inclusive.
Some Specimens of Minerals.
16. Various Objects of Natural History.

Flora Batava, Nos. 75. and 76.

March 2. Supplement to the Edinburgh New Dispensa-
tory, by Andrew Duncan, M. D. F. R. S. Ed.
Professor of Materia Medica.
Cast of the Skull of a White Bear.

16. Elements of Chemistry, 2d Edition, by Edward
Turner, M. D. F. R. S. Ed., Professor of Che-
mistry in the London University.

Catalogue of Nebulae and Clusters of Stars in the
Southern Hemisphere, observed at Paramatta,
by James Dunlop, Esq.

Approximate Distances of Double Stars in the
Southern Hemisphere, observed at Paramatta,
by James Dunlop, Esq.
April 6. An Historical and Descriptive Account of the Sus-
pension Bridge constructed over the Menai
Strait, with a Brief Notice of Conway Bridge,
from Designs by, and under the direction of,
Thomas Telford, Esq. F. R. S. LoncL & Ed.,
by W. A. Provis, C. E.
Dec. 7. Essay on Evergreen Oaks, by Isaac Weld, Esq.

* VOL. XI. PART II.

DONORS.

Edinburgh Gas Light
Company.

The Academy of
Sciences of St Pe-
tersburg.

The Author.

The Author.

The Editor.

Lieut. Smart, R. N.
George Swinton, Esq.

Calcutta.
His Majesty the King

of the Netherlands.
The Author.

Mr O'Neill, Sculp.

tor.
The Author.

Sir T. M. Brisbane,
Jk. C B.

Ditto.

Thos. Telford, Esq.

The Author.

St

540

LIST OF DOTATIONS.

1899. PRESENTS.

JJec. 7. Abhandlungen der Akademie der Wissenschaften

zu Berlin, 1825.
De Tabulis Macularum Solis Iconographicis.
Astronomische Nachrichten, Nos. 157. and 158.
Asiatic Researches, Vol. XV.
Memoirs of the Astronomical Society of London,

Vol IIL Part 2.
Memoir of De Witt Clinton, by Dr Hosack.
Transactions of the Linnean Society of London.
Transactions of the Royal Society of Literature,

Vol. I. Part 2.
Six Annual Reports of the Whitby Philosophical

Society.
RuppeTs Atlas of Northern Africa, Twelve Parts.

Transactions of the Royal Society of London,—
1827, Parts 1. and 2. ; 1828, Part 1. ; 1829,
Parti.

Travels of Ibn Batuta, translated by the Rev. S.

Lee, B. D.
Extraits des Annales des Sciences Naturelles,

1828.
Flora Batava, Nos. 77, 78, and 79.

Rapport sur les Machines a Vapeur, par M. De

Prony.
Eloge de Marquis de La Place, par M. le. Baron

Fourier.
Eloge de M. Ramond, par M. le Baron Cuvier.
Notice Historique sur Perronet, par M; De Prony.
Rapport au Roi sur la Navigation Interieure de la

France, par M. Becquey.
Transactions of the Plinian Society.
Two Papers by R. I. Murchison, Esq. F. R. S.
Portrait of Sir James Hall, Bart.
Memoires de Mathematique et de Physique, par

M. G. Libri.
Flora Batava, Nos. 80. 81. and 82.

DONORS.

The Academy of
Sciences of Berlin.

M. Soemmering.

M. Bessel.

The Asiatic Society.

The Astronomical
Society.

The Author.

The Linnean Society.

The Royal Society of
Literature.

The Whitby Philoso-
phical Society.

The Frankfort Insti-
tution.

The Royal Society.

The Asiatic Society.
M. Brongniart.

His Majesty the King

of the Netherlands
The Author.

Ditto.

Ditto.
Ditto.
Ditto.

The Plinian Society.
The Author.
John Hall, Esq.
The Author.

His Majesty the King
of the Netherlands.

LIST OF DONATIONS.

541

1829. PRESENTS.

Dec. 7. Observations on the Genus Unio, by Isaac Lee,

M. A. P. S. &c.
Transactions of the Horticultural Society of Lon-
don, Vol. VI L Part 8.
Journal of Meteorological Observations made in
the Garden of the Horticultural Society at
Chiswick, for the Years 1826 and 1827, with
Reports of the Garden Committee, and of the
Instruments employed in these Observations.

Dec. 21. Experimental Inquiries on Electrical Accumula-
tion, by W. S. Harris, Esq.
1830.

Feb. 1. The Phrenological Journal, from its commence-
ment to the present date.

Mar. 15. Transactions of the Agricultural and Horticultural

Society of India, Vol. I.

Transactions of the Society of Arts, &c. Vol.
XLVII.

Mecanique Celeste, by the Marquis de La Place,
translated, with a Commentary, by Nathaniel
Bowditch, LL. D., F. R. S. L. and Ed., Vol. I.

Flora Batava, Nos. 83. and 84.

A German Pamphlet, by Barton Alexander de

Humboldt, on the Systems of Notation.
April 5. Remarques sur la Loi de la Force Elastique de

l'Air, &c. par le Chevalier Avogadro.
Memorie della Reale Academia delle Scienze di

Torino, Vol. XXXII. and XXXIII.
19. Microscopic Illustrations, &c, by R. C. Goring,

M. D., and Andrew Pritchard, Hon. Mem. of

the Society of Arts, Edinburgh.
Memoires de TAcademie Royale des Sciences de

l'lnstitut de France, pour Fannie l825,Tom«

VIII.
Abhandlungen der Akademie der Wissehschaften

zu Berlin, 1826.
Transactions of the Royal Institute of the Nether-
lands, Vol VII.

DOKOBS.

The Author.

The Horticultural

Society.
The Horticultural

Society.

The Author.

Sir G. S. Mackenzie,
Bart.

The Agricultural and
Horticultural So-
ciety of India.

The Society of Arts.

Dr Bowditch.

His Majesty the King
of the Netherlands.
The Author.

The Author.

The Academy of Tu-
rin.
Mr Pritchard.

The Academy of
Sciences.

The Academy.

Royal Institute of the
Netherlands.

Sy2

542

LIST OF DONATIONS.

1880. PRESENTS.

April 19- New Transactions of Ditto, Vols. I. and II.

Transactions of the Geological Society of London,
Second Series, Vol II. Part S. Supplement.

Memoirs of the Astronomical Society of London,
Vol. IV. Part 1.

Transactions of the Cambridge Philosophical So-
ciety, Vol. III. Part 1.

Bijdragen tot da Natuurkandige Wetenschappen,
Amsterdam, Nos. 1, 2, 8, 4.

American Journal of Science and Arts, Vol. XVII.
Nos. 1. and 2.

Astronomische Nachrichten, Nos. 159, 160, and
161.

Histoire Naturelle des Bdemnites, par M. Ras-
pail.
Dec. 6. Flora Batava, Nos. 85. and 86.

Transactions of the Royal Irish Academy, Vol.
XVI. Part 1.

Reflections on the Decline of Science in England,
by Charles Babbage, Esq. F. R. S.

Transactions of the Royal Asiatic Society of Great
Britain and Ireland, Vol. II.

Transactions of the American Philosophical So-
ciety, Vol. III. Part 8.

Elements of Chemistry, by Edward Turner, Esq.
M.D.F.R.S. 1881.

Transactions of the Physical Class of the Asiatic
Society of Bengal, Part 1.

Catalogue of the Library of the Royal Asiatic So-
ciety, and Third Report.

System of Conic Sections, by the Rev. H. P. Ha-
milton.

Observations in Natural History, by G. J. Mulder,
4 Numbers.

Experiments in Electro-Magnetism, by G. Moll.

Observations on the Tyrolese Alps, by R. I. Mur-
rhison, Esq.

DONORS.

Royal Institute of
the Netherlands.

The Geological So-
ciety.

The Astronomical
Society.

The Cambridge Phi-
losophical Society.

The Amsterdam So-
ciety.

Professor Silliman.

M. Bessel.
The Author.

His Majesty the King
of the Netherlands.

Royal Irish Aca-
demy.

The Author.

The Asiatic Society.

The American Phi-
losophical Society.
Dr Turner.

The Bengal Asiatic

Society.
The Asiatic Society.

The Author.

The Author.

The Author.
The Author.

LIST OP DONATIONS.

543

1830. PRESENTS.

Dec. 6. On Spasmodic Strictures of the Colon, by John

Howship, Esq.

Gleanings in Science, published at Calcutta, Nos.
1-12.

American Journal of Science and Arts, Vol. XIX.
Part 1.

A cask containing the greater part of the body of a
Dugong, preserved in spirits.

Specimens of the Edible Nests, from the Eastern
Islands.

Specimens of Amber, from Assam.

Specimens of different qualities of Paper made from
Vegetable Matter in Nepaul.

A large case containing 150 pounds weight of the
Vegetable Matter in a preparatory state, for the
purpose of being tried by Paper-makers in this
country.

Specimens of Lackered Work referred to in the com-
munications published in Gleanings in Science
at Calcutta.

Specimens of the Rocks, &c of the Diamond Mines
in India.

Plaster Cast of a Fossil Animal. From M. Herm.
de Meyer, Frankfort
80. Materia Indica, by Whitelaw Ainslie, M. D. 2 vols.

Observations on the Cholera Morbus of India,
by Whitelaw Ainslie, M. D.

Observations on the Smallpox and Inoculation in
Eastern Countries, by Whitelaw Ainslie, M. D.

Medical, Geographical and Agricultural Reports
of a Committee appointed by the Madras Go*
vernment, to inquire into the Causes of the Epi-
demic Fever in the provinces of Coimbatore,
Madura, Dindigul, and Tinnivelly, &c. during
the years 1809, 1810, and 1811, by Whitelaw
Ainslie, M. D.

Clemenza, or the Tuscan Orphan, by Whitelaw
\nslie, M. D.

A relation of Proceedings concerning the Affairs

DONORS.

The Author.

George Swinton, Esq.

Calcutta.
Professor Silliman.

George Swinton, Esq.

Calcutta.
Ditto.

Ditto.
Ditto.

Ditto.

Ditto.

The Author.
Ditto.

Ditto.

Ditto.

Ditto.

544

LIST OF DONATIONS.

PRE8ENTS.

of the Kirk of Scotland, from August 1637 to
July 1638, by John Earl of Rothes. Printed
for the Bannatyne Club, by James Nairne, Esq.
W.S. f

1831.
Jan. 3. Observations on Fossil Vegetables, accompanied by
Representations of their Internal Structure, as
seen through the Microscope, by Henry Witham,
Esq. F. R. S. Ed., &c.

An Experimental Inquiry into the Number and
Properties of the Primary Colours, and the
Source of Colour in the Prism, by Walter Crum,
Esq.

Part of an Aerolite which fell in the territories of
the Madras Government in 1810.
17. South African Quarterly Journal, Nos. 1, 2, 3.

On the Utility of fixing Lightning Conductors in
Ships, by W. S. Harris, Esq.

Experimental Inquiries on Electrical Accumula-
tion, by W. S. Harris, Esq.

Letter to the Proprietors of Steam- Vessels connect-
ed with the Frith of Forth, and others interest-
ed in the trade carried on by Steam Navigation,
by Captain J. D. Boswell, R. N.
Feb. 7. The Edinburgh Journal of Natural and Geogra-
phical Science, New Series, Nos. 1, 2, conducted
by Henry H. Cheek, Esq. F. L. S., fee.
Mar. 7. Flora Batava, No. 87.

Astronomical Observations of Professor Bessel,

Parts 13. and 14.
SI. Memoirs of the Royal Academy of Turin, Vol.

XXXIV.
Major RennelTs Geography of Herodotus, 2d

Edit. 2 vols.
Etudes Administrative* sur les Landes, by M. le

Baron D'Haussez.

DONORS.

The Editor.

The Author.

Ditto.

Andrew Berry, M. D.

The South African

Institution.
The Author.

Ditto.

»

Ditto.

The Editor.

His Majesty the King
of the Netherlands.
The Author.

The Royal Academy

of Turin.
The Editor.

The Author.

LIST OF DONATIONS.

545

1831. PRESENTS.

Mar. 21. Souvenirs pour servir a la Statistique du Depart-
ment de Tlsere. By M. le Baron d'Haussez.
Address of Earl Stanhope, President of the Medi-
co-Botanical Society, for the Anniversary Meet-
ing, January 1831.
April 4. Account of the Meeting of the Cultivators of Na-
tural Science and Medicine at Hamburgh, in
September 1830. By James F. W. Johnston,
Esq. M.A*
Charges against the President and Councils of the
Royal Society of London. By Sir James South.
April 18. Illustrations of Zoology, No. 9. By James Wil-
son, F. R. S. Ed.
Transactions of the Horticultural Society of Lon-
don, Vol VII. Parts 4 and 5.
Transactions of the Royal Society of London for
1830. Parts 1 and 2.

DONORS.

The Author.

The Honorary Secre-
tary of the Society.-

The Author.

The Author.

The Author.

The Horticultural

Society.
The Royal Society.

PRINTED BT NEILL & CO. OLD PI8HM ARRET, EDINBURGH.