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TRANSACTIONS

OF THE

GEOLOGICAL SOCIETY,

ESTABLISHED NOVEMBER 138, 1807.

VOLUME THE SECOND.

Quod si cui mortalium cordi et cure sit, non tantum inventis herere, atque iis uti,
sed ad ulteriora penetrare; atque non disputando adversarium, sed opere naturam
vincere; denique non belle et probabiliter opinari, sed certo et ostensive scire;
tales, tanquam veri scientiarum filii, nobis (si videbitur) se adjungant.

Novum Organum, Prefatio.

LONDON:
PRINTED AND SOLD BY WILLIAM PHILLIPS, GEORGE YARD, LOMBARD STREET.

1814,

Digitized by the Internet Archive
in 2011 with funding from
California Academy of Sciences Library

http://www.archive.org/details/transactionsofge21 geol

OFFICERS AND COUNCIL OF THE GEOLOGICAL SOCIETY,
ELECTED FEBRUARY 4, 1814.

a

OFFICERS.

PRESIDENT,

The Hon. HENRY GREY BENNET, M.P. F.R.S.

VICE-PRESIDENTS,
WILLIAM BLAKE, Esq. F.R.S. \ GEORGE BELLAS GREENOUGH, Esq. F.R-S.
Sir HENRY ENGLEFIELD, Bart. F.R.L. & A.S.. | JOHN MacCULLOCH, MD. E.LS.

. SECRETARIES,
ARTHUR AIKIN, Esq. | HENRY WARBURTON, Esq. F.R.S.
FOREIGN SECRETARY,

SAMUEL SOLLY, Esq. F.R.S.

TREASURERS,

WILLIAM HASLEDINE PEPYS, Esq. F.R.S. | SAMUEL WOODS, Esq.

COUNCIL.
The Hon, LORD COMPTON, M.P. PETER ROGET, M.D.
SAMUEL DAVIS, Esq. F.RS. SMITHSON TENNANT, Esq. F.R.S.

ROBERT FERGUSON, Esq. F.R.S. Prof. Chem. Camb.
JAMES LAIRD, M.D. SAMUEL TURNER, Esq.

ALEXANDER MARCET, MD. F.R.S. JOHN WHISHAW, Esq.

WILLIAM HYDE WOLLASTON, M.D.

THOMAS MURDOCH, Esq. F.R.S.
Sec. R.S.

JAMES PARKINSON, Esq.

KEEPER OF TIE MUSEUM AND DRAUGHTSMAN,
Mr. THOMAS WEBSTER.

TRUSTEES OF THE GEOLOGICAL SOCIETY.

GEORGE BELLAS GREENOUGH, Esq.
Sir ABRAHAM HUME, Bart. M.P.
FRANCIS HORNER, Esq. M.Ps
WILLIAM BABINGTON, M.D.
ROBERT FERGUSON, Esq.

DAVID RICARDO, Esq.

SAMUEL WOODS, Esq.

ADVERTISEMEN'.

THE Editors of the Transactions of the Geological Society
are directed to make it known to the Public, that the Authors alone are

responsible for the facts and opinions contained in their respective papers.

Geological Society,
September 1, 1814.

ERRATA,

Some of which it will be necessary to correct, as materially affecting the sense of the

passages, where they occur.

169,
187,
213,
438,
440,

Line 14,
simian Mik
ies thy
eee
Bean Os
arate,
Louie &,
en
phe:
eof 4,
eee ws

for difficulty read difficultly
iconocolasts —— iconoclasts

two chanels ——- one channel

—— PI. 9. —— Pl. 11.
found — formed

—— has — have
petrefactions petrifactions

dele (;) after Agglestone

for may read might

after Fig. 3 insert Plate 32, Fig. 1.
after the word figures, insert Pl. 31, !eft hand figure at top,

The Papers referred to in pages 475, 476, and 478, were intended to be included in
the present volume, when those pages were printed: their publication has been deferred
to the 3d Volume of the Society’s Transactions.

In the list of Donations to the Collection of Maps, insert 12 Copies of a new Map of
England, in 4 Sheets, from A, Arrowsmith, Esq.

CONTENTS.

I. On certain Products obtained in the Distillation of Wood, with some
account of Bituminous Substances, and Remarks on Coal. By
J. Mac Culloch, M.D. FL.S. Chemist to the Ordnance, and Lecturer
on Chemistry at the Royal Military Academy at Woolwich, and Vice-
President of the Geological Society p- 1

II. Mineralogical Account of the Isle of Man. By J. ¥. Berger, M.D.
Member of the Geological Socicty. p- 29

III. On the Granite Tors of Cornwall. By J. Mac Culloch, M.D.
F.L.S. Chemist to the Ordnance, and Lecturer on Chemistry at the
Royal Military Academy at Woolwich, and Vice-President of the
Geological Society. p- 66

IV. Notes on the Mineralogy of the Neighbourhood of St. David's, Pem-
brokeshire. By John Kidd, M.D. Professor of Chemistry in the
Unicersity of Oxford, and Member of the Geological Society. p. 79

V. Account of the Brine Springs at Droitwich. By Leonard Horner, Esq.
F.R.S. and Member of the Geological Society. p- 94

VI. On the Veins of Cornwall. By William Phillips, Esq. Member of
the Geological Society. p- 110

VII. On the Freshwater Formations in the Isle of Wight, with some Obser-
cations on the Strata over the Chalk in the South-east part of England.

By Thomas Webster, Esq. Member of the Geological Society. p- 161

LE I LLL Le

WIG

IX.

CONTENTS,

Remarks on the Vitrified Forts of Scotland. By J. Mac Culloch,
M.D. F.L.S. Chemist to the Ordnance, and Lecturer on Chemistry
at the Royal Military Academy at Woolwich, and Vice-President
of the Geological Society. p- 255

On the Sublimation of Silica. By J. Mac Culloch, M.D. F.L.S.
Chemist to the Ordnance, and Lecturer on Chemistry at the Royal
Military Academy Y at Woolwich, and Vice-President of the Geological
Society. ver p. 275

X. Observations on the Specimens of Hierurites from Sicily, presented

XI.

XL

XIIL

to the Geological Society by the Hon. Henry Grey Bennet. By
James Parkinson, Esq. Member of ihe Geological Society. p. 377

An Account of the Coalfield at Bradford, near Manchester. By Robert
Bakewell, Esq. commenicated to the Society by Dr. Roget, Member
of the Geological Socicty. p. 282

Some account of the Island of Teneriffe: By the Hon. Henry Grey
Bennet, MP. F.R.S. and President of the Geological Society. _ p. 286

On the Junction of Trap and Sandstone, at Slirling Castle. By
J. Mac Culloch, 17.D. F.L.S. Chemist to the Ordnance, and Leciurer

on Chemistry at the Royal Military Acadeny ai Vi Caletied, and Vice-

XVI.

President of the Geological Society. p- 505
On the Economy of the Mines of Cornwall and Devon. By John.
Taylor, Esq. Member of the Geological Society. | p. 309

On the Origin of a remarkable class of Organic’ Impressions occur-

ring in Nodules of Flint. By the Rev: William Conybeare, of
Christ Church, Oxford, and Member of the Geological Society. p. 528

A Description of the Oxyd of Tin, the production of Cornwall ; of °
the Primitive Crystal and its Modifications, including an atlempt.to

ascertain with precision, the adimeasurement of the angles, by means

. of the, reflecting Goniometer of Dr. Wollaston: to which is added,

a series of its crystalline forms and varieties. By William Phillips,

Esq. Member of the Geological Socicty. . - p. 536

CONTENTS.

XVII. On some new Varieties of Fossil Alcyonia. By Thomas Webster,

Esq. Member of the Geological Society. p.

XVIII. Miscellaneous Remarks accompanying a Catalogue of Specimens
transmitted to the Geological Society. By J. Mac Culloch, M.D.
F.R.S. Chemist to the Ordnance, and Lecturer on Chemistry at the
Royal Military Academy at Woolwich, and Vice-President of the

Geological Society. p:

XIX. Remarks on several parts of Scotland which exhibit Quartz Rock,
and on the Nature and Connexion of this Rock in general. By J.
Mac Culloch, W.D. F.L.S. Chemist to the Ordnance, and Lecturer
on Chemistry at the Royal Military Academy at Woolwich, and Vice-

President of the Geological Society. p-

XX. Notice relative to the Geology of the Coast of Labrador. By the

Rev. Mr. Steinhauer. p.

*

XXI. Memoranda relative to Clovely, North Devon, By the Rev. J. J.
Conybeare, Member of the Geological Society. In a Leiter addressed

to G. B. Greenough Esq. Vice-President of the Geological Society. p.

XXII. On Stafa. By J. Mac Culloch, M.D. F.L.S. Chemist to the
Ordnance, and Lecturer on Chemistry at the Royal Military Academy

at Woolwich, and Vice-President of the Geological Society. p:

XXIII. On Vegetable Remains preserved in Chalcedony. By. J. Mac
Culloch, 1.D. F.LL.S. Chemist to the Ordnance, and Lecturer on
Chemistry at the Royal Military Academy at Woolwich, and Vice-

' President of the Geological Society. Pp
XXIV. On the Vitreous Tubes found near to Drigg, in Cumberland. p.
List of Donations. p:

Index, ; p.

317

450

488

A95

501

510
528
533

547

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TRANSACTIONS

OF THE

GEOLOGICAL SOCIETY.

I. Ox certain Products obtained in the Distillation of Wood, with
some account of Bituminous Substances, and Remarks on Coal,

By J. Mac Currocu, M.D. F.L.S.

Chemist to the Ordnance, and Lecturer on Chemistry at the Royal Military
Academy at Woolwich.

iE is well known that when wood and other vegetable substances
are submitted to destructive distillation, there is produced, among
other matters, a black dense fluid resembling molasses or common tar.
My connection with the Ordnance powder-mills having compelled
‘me to examine some of the properties of this substance, which is
obtained in large quantities in the process of making charcoal, I was
induced to extend my enquiries, in consequence of finding that the
nature of the compound has not hitherto been understood.
VoOruIt A

2g Dr. MAc CuLLocn on certain products

As it is commonly called ¢av by the workmen, I shall use this term
for want of a better.

This tar is very inflammable, and so liquid that it may be burnt in
a lamp.

Although it appears to be an uniform fluid, it contains a great
quantity of acetic acid, in a state of loose combination or mixture.
For, by washing with water, a great part of this is separated; the |
water at the same time acquiring a colour from a portion of the tar
which is retained in solution by the acid. Boiling water takes up a
larger portion, and the tar acquires from this operation a thicker and
more pitchy consistence.

Lime and the carbonated alkalies separate the acid with ease, car-
rying away also a portion of the tar which continues united to the
solution. With subcarbonate of potash it thus forms in the first
instance an uniform solution of a brown colour, but a continuance
of trituration or boiling renders it pitchy and tenacious, after which
it forms no further union with the mild alkalies.

It is perfectly and readily soluble in alcohol, in ether, in the pure
alkaline lixivia, in acetic acid and in the mineral acids. ‘The fat oils
and the new essential oils dissolve only a small portion of it; but the
drying oils and the latter when thickened by age act more readily.
Coloured oil of turpentine dissolves a good deal of it. Naphtha
hardly exerts any action, acquiring a scarcely sensible brown colour.
If heat be applied to assist the solution, the portion taken up is again
deposited on cooling.

When it is subjected to distillation in a heat sufficient to keep it
in a gentle ebullition, an oily looking matter passes over in consider-
able proportion, which sinks to the bottom of the water into which
the tube is inserted. It is first of a pale colour, resembling oil of
peppermint, but becomes gradually darker as the operation advances,
till it acquires a deep brown hue,

obtained in the distillation of Wood, 'Sc. 3

If the operation be pushed by increasing the heat of the retort to
redness, there remains at length only a mass of spungy charcoal,
and the substance is totally converted into the following new com-
pounds, namely, the residuary charcoal, the oily matter, and the
matter held in solution in the water of the apparatus. This latter
proves to consist of a large portion of acetic acid, with which is
combined a very little ammonia.

There is no inflammable gas given out in this process unless the
heat be carelessly managed. If the vapour of the oily matter as it
arises be exposed to the sides of the retort elevated to a high tem-
perature, it is decomposed, and instead of oil there are thus obtained
by a violent distillation in a naked fire, scarcely any products but
acetic acid and an inflammable gas. This fact is analogous to
those occurring in the ordinary process for decomposing such in-
flammable bodies as can be made to put on the gasseous state—and we
ought, in fact, to consider every process of this kind, where a rapid |
distillation with a hot fire is used, as a succession of decompositions;
the matter first produced being afterwards exposed to another pro-
cess of destruction. It is not therefore perhaps very correct lan-
guage, to say that vegetables yield a great quantity of inflammable
gas on distillation with a naked fire; this is the produce of a second
distillation which by the common mode of operating is confounded
with the first. As this reasoning applies equally to all other similar
processes, it would be desirable to use a more accurate mode of des-
cribing this common operation by which we might in some import-
ant instances be led to a more correct practice. ‘Thus, for example,
in the common mode of distilling coal to produce the inflammable
gasses, this double operation is carried on at once by the application
of the petroleum and naphtha at first produced to the heated iron
of the retort. It is in consequence of this imperfect mode of ex-

A 2

4 Dr. Mac CuLiocn om certain products

posing the fluids thus generated to a second heat, that so large a
portion of the petroleum is distilled unchanged. By causing it to
pass a second time in contact with heated iron, while in the state of
vapour, it may be resolved completely into inflammable gas and
charcoal, andthe produce of gas be thus considerably increased.
This circumstance explains also the contradictory accounts given by
different persons of the relative products of distillation, as applied to
the various compound inflammables. ‘To instance the case of cam-
phor, which according to the mode of managing the process, may
be caused to yield essential oil or inflammable gas or a mixture of
both in various proportions. 1 need scarcely point out the advan-
tages so obviously to be derived from this consideration in the ceco-
nomical process of procuring light from pit-coal, an operation at
present conducted with less skill than it demands,

I distilled a portion of this tar in such a way as to obtain inflam-
mable air only, and took the gas in five portions. The first burnt
very faintly, the second rather better, the third and fourth portions
with a good white flame, and the fifth burnt feeble and blue. No
portion of it was equal in brilliancy of inflammation to the gas from
pit-coal. On examination, it was found to contain much carbonic
oxide, by which its nature, as far as it differs from the gas of coal,
is readily understood. ‘The cause of this difference will be apparent
when the other circumstances in the constitution of this substance
have been detailed. I thought it superfluous to examine accurately
the nature of these gasses, but they probably consist of different
mixtures of carbonic oxide, with light and heavy hydrocarbonate
and olefiant gasses, if indeed, (as I much doubt) there be any real
boundary by which the composition of these three last gasses can be
defined. |

If the process of distillation which I have now described be

abtained in the distillation of Wood, %&c. 5

stopped when the oily matter begins to acquire a brown colour, and
when the production of acetic acid is less perceptible, the matter in
the retort will be found when cold, to have assumed a solid con-
sistence. In this state it resembles either pitch or asphaltum, accord=
ing to the degree of heat it has undergone after it became capable
of solidifying.

I will describe this substance as it appears when it first becomes
solid, the reason of which will soon be apparent.

Previously to its arriving at this state, it bears a considerable
resemblance to maltha, being of a consistence intermediate between
that of petroleum and asphaltum, but I did not completely examine
its chemical properties in this condition because they appeared not
to differ from what might be expected, and its history will be
sufficiently full without it. In the solid state it is brilliant and
shining and breaks with a conchoidal fracture and some external
resembiance to obsidian. It has a pungent burning taste and the
well known smell of wood smoke. It is heavier than the specimen
of asphaltum with which I compared it, having a specific gravity
of 1.254, while that of the asphaltum was 1.202. It is fusible and
readily inflammable, burning with a white flame. It is electric
and exhibits the same electricity as the resinous bodies. When
heated in an open vessel, it smokes, and if kept in fusion till it
ceases to smoke, it at length ceases to be fusible and is ultimately
converted into acoal. During this progress it becomes more bril-
liant and less fusible, its fracture also from conchoidal becomes more
splintery, and it puts on the appearance of asphaltum so accurately
that the eye cannot detect the difference. Its specific gravity also
diminishes, and its chemical properties vary in the way I am now
about to detail.

I have described the perfect solubility of the tar in alcohol. The

6 Dr. Mac CuLLocu on certain products

softest specimens of the pitch are nearly as soluble, leaving only
a small residuum, which is infusible and powdery. The harder
Specimens become in proportion less soluble, and leave a larger
residuum ; and those which have been the longest exposed to heat
scarcely give a stain to the alcohol, resembling in this respect the
driest specimens of asphaltum. The analogy is here very apparent,
for asphaltum may approach more or less to petroleum, and the
various specimens of it are found to exhibit various degrees of
solubility in alcohol. ‘That which is least fusible in the fire, is, in
both cases, the least soluble in alcohol. And by this consideration,
the jarring accounts which have been given of the solubility of as-
phaltum in alcohol may be reconciled, and it will be seen in the sequel,
that the history of this substance illustrates, in every respect, the true
nature of the several varieties of the bitumens, substances whose
mutual relations, and the causes of whose chemical diversity have
hitherto not been understood.

If a perfectly soluble specimen be dissolved in alcohol, it is ob-
tained unchanged by evaporating the spirit. In any other case, the
matter which the alcohol has taken up is precisely similar to the
pitch in its first state, and the residuum resembles that which is the
result of fusion when it refuses longer to melt. Alcohol therefore
separates the pure pitch from that, which by a process of decom-
position has been nearly carbonized. Ether acts upon this sub-
stance as readily and in the same manner as alcohol does. In
lixivium of pure potash it is more completely soluble than in alcohol,
and forms with it an intensely brown solution which is diffusible in
water without change, and which, on the addition of an acid,
deposits the matter in a powdery form and apparently unchanged.
It is also soluble in water of ammonia with similar appearances.
It is scarcely soluble in the pale oil of turpentine, but more readily

obtained in the Distillation of Wood, *&c. 7

in the darker. It is slightly soluble in the fat oils, in tallow and in
wax, but is considerably more soluble in drying oil. In all these
cases its solubility varies, from the same causes as those which affect
its solubility in alcohol, Naphtha, whether pale or brown, has no
action on it when cold and takes up but a very minute proportion
even with the assistance of heat. It fuses into an uniform mass with
sulphur, with resin and with asphaltum.

Acetic acid, which dissolves so many of the compound inflam-
mables, effects a compleat solution of it and in large proportion,
and this compound is precisely similar to the empyreumatic acid as
it proceeds from the iron retorts in which the charcoal is distilled.
It would be desirable in an ceconomical point of view, to discover a
method of freeing the acid from the pitch. After many trials, by
combining the foul acid with various bases and again separating it,
it was always found to retain the overpowering smell of wood-tar.
If the acid is combined with the pitch at a high temperature, a large
proportion of it separates in the form of tar on cooling. Muriatic
acid, after long boiling on the pitch, became brown and dissolved a
little of it. |

By digestion with sulphuric acid it was dissolved forming a brown
oily looking fluid, sulphureous acid being at the same time disen-
gaged. By dilution with water, a smell resembling peppermint was
produced, as happens in a similar case with camphor, and the pitch
was thrown down. The action of the red nitrous acid on it is
violent ; the acid is decomposed with great ebullition and a portion
of the pitch is converted into coal. In diluted nitric acid it dissolves
and produces an uniform brown fluid. On continuing to apply
nitrous acid according to the process of Mr. Hatchett, solutions
similar to those which he has described as having been obtained from
the resins and bitumens, are produced,

8 Dr. Mac CuLtocn on certain products

I exposed a quantity of the pitch to a careful distillation through
water. As might be expected from what I described before in the
distillation of the tar, this process gave results neatly similar to the
former. The oily matter differed in being of a brown colour and
in having a greater specific gravity, and much less acid was pro-
duced; the residuum was charcoal. ‘The whole process of distila
lation appears, therefore, to be a decomposition by which the pitchy
substance is converted into oil, acetic ecid, ammonia and charcoal.

I proceeded next to examine the oil. It has a violently pungent
taste and smelk_ It is scarcely heavier than water ; so that it sinks in
that fluid with difficulty, leaving generally some drops on the sur-
face. It is perfectly soluble in alcchol, in ether, in caustic alkali, in
olive oi!, and in linseed oil. It will unite neither to naphtha, nor
to the recent essential oils, but is soluble in the old ones. From
these properties, it belongs to the class of the essential oils, but ex-
hibits at the same time other qualities by which it is distinguished
from the whole of them.

Having thus examined the most remarkable chemical properties
of ‘this substance, it will not be irrelevant to point out its differences
from and its analogies with those substances which it most re-
sembles, namely resin and the bitumens. Resin, as is well known,
is eminently soluble in all the substances in which this is dissolved,
and also in those with which this refuses to unite, even naphtha.
But the general analogy between essential oil, turpentine and resin,
is so close to that of the three substances which I have described,
that it will not perhaps be superduous here to make some remarks
on the nature of common resin and the substances connected with
it, pitch, tar, turpentine and essential oil, as their history will also
illustrate that of the substance I am describing, and as it appears, like
that of the bitumens, to have been somewhat mistaken.

obtained in the distillation of Wood, '&c. 9

If turpentine, as it flows from the fir in a liquid state, be exposed
for a considerable time to the action of the atmosphere, it becomes
brittle, and is converted into resin, in consequence as it is supposed
of the absorption of oxygen. If the same turpentine be exposed to
the action of the fire, a colourless volatile oil is separated, and resin
remains in the retort. This however is not a mere case of the
separation of a more volatile from a fixed substance, for a decompo-
sition takes place, and acetic acid is generated. Nor can turpentine
be again reproduced by mixing together the essential oil and the
resin—it then forms a varnish. ‘The essential oil is in fact a new
compound, produced from the vegetable elements by the action of
fire; and although properly enough classed with those essential oils
which are vegetable secretions, differs from them in some of its
chemical properties. It is, for example, difficulty soluble in alcohol,
but on exposure to air it becomes thick and yellow, and is then easy
of solution in the same substance.

If the resin, which is the residuum of this distillation be still fur-
ther heated, it gives over a thick and high coloured oil, gradually
increasing in weight, till it equals, and at length exceeds the specific
gravity of water. The residuum becomes ultimately black, and
very brittle, remaining soluble in ether and in lixivium of potash,
but refusing to dissolve in alcohel.

Common tar differs from turpentine in containing a portion of
the vegetable tar now under review, mixed with common turpen-
tine and with the acetic acid which is formed in the distillation to
which the wood is subjected for the purpose of obtaining it. Eva-
poration converts this into pitch, by decomposing it.

In this process, an essential oil, compounded of the oil of turpen-
tine and the oil of wood, together with a portion of acetic acid, is
separated, and the residuum or common pitch, is a compound of

Vorc Tr. B

10 Dr. Mac CuLLocn on certain products

-resin and the wood pitch which [ have been describing. To this
admixture, and not to that of adventitious charcoal pruduced in
combustion, is the black colour of common pitch owing.

The analogy between this wood pitch and the bitumens is
equally striking, and the preceding history of these compounds will
throw light on the several varieties of the bituminous substances.

Assuming the tar as the medium form, it is seen that when ex-
posed to heat it gives over oil, and that pitch remains. Thus,
petroleum yields naphtha and asphaltum ; and thus too, asphaltum
exhibits all the gradations which I have described in the pitch, its
properties varying in a similar manner, according to its particular
‘state. In the process of distillation the principal difference will be
found to consist in the relative quantities of acetic acid and ammonia,
which they severally yield; the former chiefly characterizing the
wood tar, and the latter the petroleum. From the same chemical
cause which produces this effect arises also the difference in the
nature of the inflammable gasses which are produced from these
-different substances. /

The sensible qualities of the bitumens (their taste and smell) are
in all states utterly and entirely different from those of the vegetable
tar. Petroleum is also much less soluble in alcohol, and further
differs from the vegetable tar in being perfectly soluble in naphtha.
In their solubilities in oil of turpentine they resemble each other, as
well as in their habitudes with acetic acid and the alkaline lixivia,
although the vegetable tar will be found the more readily soluble of
the two. I need not repeat the circumstances in which the essential
oil of wood differs from naphtha. It is a sufficiently characteristic
one, that it forms no union with this latter.

It has been already shown that the difference between the pitch
and asphaltum is considerable, when the former is in its first state,
particularly with regard to its solubility in alcohol.

obtained in the distillation of Wood, *8c. 11

But if we compare the most brittle specimens of the pitch with
common specimens of asphaltum, the differences, except as far as
smell and taste are concerned, are not so apparent, and the reason
of this will be obvious on considering their fundamental similarity
of composition. ‘The chief ingredients of both are carbon and
hydrogen. By the application of heat, the proportions of these
substances are altered in both cases, the hydrogen being abstracted
in the greatest ratio, to form the new compound (the oil) in which
hydrogen predominates. The ultimate result of both is charcoal.
Asphaltum will be found to combine pretty nearly in the same way,
with all the substances I have above enumerated as combining with
the pitch. Its essential difference however consists in its solubility
in naphtha, and by this test they are readily distinguished. *

The chemical difference to which these different properties of
substances so similar are owing, will be evident on considering some
of the circumstances before related. The disproportion of acetic
acid and carbonic oxide produced from the wood pitch, when com-
pared with the produce of the bitumen, proves that it contains oxy-
gen and azote in proportions different from those in which the same
substances exist in the bitumens; and that in particular it contains
a considerable quantity of the former. The result would not repay
the toil required to investigate these proportions, which are probably
also subject to considerable variation.

It is obvious that this substance is a new compound, formed by
the action of fire on vegetable elementary matter ; but all that we
can determine of its nature is, that in conformity to modern chemical
nomenclature, it is formed of carbon, hydrogen, oxygen, and azote.
The carbon and hydrogen constitute its basis, as they do that of
the bitumens, and the large proportion of oxygen appears to give
it the peculiar properties by which it is distinguished from them.

Be

<—

12 Dr. MAc CuLiocu on certain products

It seems evident however, that no very great change is wanting to
convert the one of these into the other.

The question so much agitated, of the conversion of vegetables
into coal, would appear to receive some illustration from the history
of the compound which I have been describing, and since (as I shall
by and by show) it has actually been confounded with bitumen,
and has been adduced as an instance of the artificial production of
coal by the action of fire, I shall make no apology for pursuing this
subject. Indeed the general chemical resemblance between the mi-
neral bitumens and this vegetable bitumen, if it may be so called, is
so striking, that we may, at first sight, be easily led to suppose that
the same agent has produced both, and excuse the mistakes which
seem to have occurred on this subject. But a cursory view of the
several substances which have been classed under the head of bitu-
mens, may enable us to form a clearer notion of the limited extent
of this analogy, at the same time that it will perhaps assist us
in correcting some errors which have crept into our arrangements
of them.

It is necessary to separate from the bitumens three or four mineral
substances, which differ completely both in chemical and ordinary
characters, but which are approximated to each other by some
general resemblance. These are, amber, mellilite, and the subter-
raneous resins of Cologne, Bovey, and Highgate. The two first are
more nearly associated by the property they have of yielding a
peculiar acid ; and of the three last, it may perhaps be fairly doubted,
whether they are more entitled to be ranked among the mineral
substances strictly so called, than the other vegetable matters which
are found in alluvial soils.

The nature and relations of naphtha, petroleum, maltha, and
asphaltum, will, I trust, appear sufficiently clear from what I have

obtained in the distillation of Wood, 'c. 13

above related, but I cannot forbear remarking on some false hypo-
theses which have been held respecting these substances, and their
relation to other bodies. It is evident, from considering the products
of their decomposition, that the basis of naphtha and of all the
intermediate stages of bitumen, down to asphaltum, are carbon and
hydrogen, modified by certain small proportions of oxygen and azote.
It is in the relative proportions chiefly of these two ingredients that
naphtha differs from petroleum, petroleum from maltha, and maltha
from asphaltum. If we distill either of these more solid substances
with a very gentle heat, we obtain naphtha, in which the proportion
of the hydrogen to the carbon is increased to a maximum ratio.
If the heat is greater, we obtain a substance of a darker colour, in
which that ratio is less ; and, for this reason, the distillation of as-
phaltum affords a darker oil than that of petroleum, because its
composition cannot be dissolved but in a higher temperature,

For the same reason also petroleum is easily rectified into naph-
tha. Asphaltum, in its ordinary state, contains the two ingredients
in a ratio in which the carbon bears a large proportion to the
hydrogen, and that ratio is reduced to the minimum, or becomes
evanescent, when by the continuance of distillation, charcoal alone
remains behind. A large portion of the oxygen, and also of the
azote, is disengaged during this process, but not the whole, since
the darker compounds still give it over on repeating the process,
The naphtha is probably entirely exempt from oxygen. With this
view we cannot accede to the notion, that the absorption of oxygen
is capable of converting naphtha or petroleum into asphaltum ; or
that the harder bitumens originate from the oxygenation of the
more liquid. It is more consonant to the nature of these sub-
stances.to suppose, that the change consists in the alteration of the
relative proportions of the hydrogen and carbon, but whether this is

14 Dr. Mac Cutrocn on certain products

performed by the action of heat, or of other causes volatilizing the
hydrogen, or by the contact of oxygen converting it into water,
cannot now be determined by any facts that we are acquainted with.
Experiments on the induration of the essential oils may throw some
light on this question. It will here perhaps be remarked, that there
is a difference in the substances as they are produced artificially by
the distillation of coal, and as they are found in nature. Thus, for
example, the artificial petroleum of coal differs from that of nature,
in being much more soluble in alcohol. Yet, this circumstance may
arise from the insensible gradation of difference which I have above
remarked in the similar compounds, and thus in the series of grada-
tion, specimens absolutely corresponding, whether artificial or natural,
may exhibit the same chemical characters.

Thus, as I have shown that there is a sort of gradation from
naphtha to asphaltum, through a series of undefinable petrolea, so
this analogy may be extended to the next general variety of the
bitumens, coal.

The several varieties of coal are supposed to consist of charcoal
and asphaltum, or of charcoal and bitumen, combined in as many
different proportions. Charcoal is undoubtedly found mixed with
coal, but it does not appear correct to consider pit coal as either a
mixture or combination of any bitumen with charcoal. The action
of naphtha on its varieties, often none and always sparing, shows
that bitumen does not exist in it in a mixed state. It will be
more consonant to the analogies of the other bituminous substances,
to consider coal in its several varieties as a bitumen, varying in its
composition, from the fattest specimens of Newcastle to the driest
of Kilkenny, and owing its compactness, as well as the other modi-
fications which it exhibits, to the peculiar circumstances under which

it has been formed, the changes it may subsequently have under-

obtained in the distillation of Wood, °c. 15

gone, or the substances with which it has accidentally been mixed.
The power of yielding naphtha on distillation, is rather to be re-
sorted to as the distinction between the one end and the other of the
series ; and it would be surely equally correct to call coal a com-
pound of charcoal and naphtha, as a compound of charcoal and
asphaltum. |

Its several varieties will moreover be found to vary from each
other by containing greater or less proportions of carbon, compared
with their other ingredients ; just as in asphaltum the relative pro-
portions of the hydrogen, azote, and oxygen, to the carbon, are
found to differ from those which constitute petroleum or naphtha.

The last link of the chain of coal (chemically considered) is
anthracite, which contains only carbon, if we reckon the earths
mixed with it as adventitious matter. So the last result of the dis-
tillation of asphaltum is charcoal, and the intermediate steps through
which asphaltum passes in its progress to charcoal, resemble pre-
cisely the corresponding changes which occur in the distillation
of coal till coak is formed, and confirm by their chemical analogy
the view here held forth of the chemical composition of coal, and
the gradation to be traced in nature from fat coal, to anthracite.
If asphaltum be subjected to distillation it gives petroleum. By
degrees its solubility in naphtha diminishes, in consequence of its
carbonaceous ingredient becoming more disproportioned to its hy-
drogen. At a particular period of this distillation it will be found
to resemble fat coal; by and by, it resembles blind coal, and gives
no stain to naphtha; ultimately, pure charcoal remains. All these
bituminous compounds may therefore properly be said to belong to
one genus or family, of which the principal chemical ingredients are
carbon and hydrogen, and it is chiefly to the difference in the
relative proportions of those two substances that we are to look

16 Dr. Mac CuLtocu on certain products

for the differences which characterize the several bitumens, from
naphtha placed at one extreme, to anthracite placed at the other.
The chasm in this series from asphaltum to fat coal, is in fact, rather
apparent than real, being more properly a mechanical or accidental,
than a chemical or essential one. I cannot here avoid taking notice
of the very loose experiments of Mr. Kirwan on the analysis of coal,
(which consisted in projecting portions of coal on melted nitre) as
his deductions are at war with this view of the subject, although not
more so than with all chemical reasoning. ‘They were founded on
an assumption, that coal was carbon impregnated sometimes with
maltha and sometimes with asphaltum—a distinction quite unneces-
sary if the supposition were true. If we conceive coal to be com-
pounded in this way, it would be more obvious to consider it as
formed of carbon and petroleum, since by a regulated heat it can be
separated into those two substances. The theory of the experiment
is equally assumed and the conclusions equally groundless, when it
is inferred that of this compound, (coal) the carbon alone possesses
the power of decomposing the nitre, and that the proportions of these
supposed ingredients may thus be determined. The varying tem-
perature of the nitre, would necessarily produce considerable varia-
tions and uncertainty in its action, and in the consequent accuracy of
the results; but it is plain, that the effect of this contrivance was to
separate by a sort of distillation the petroleum which fire elicits from
coal, and that the method could neither be so accurate as that of
ordinary distillation, from the greater irregularities to which it was
subject and the difficulty of conducting it, and that it proves nothing
with regard to the composition or nature of coal. _In the examina-
tion of maltha, and asphaltum, the defect of this method is still more
apparent. If heat and flame be applied to these bitumens, with

access Of air, they are either consttmed without leaving any carbun,

obtained in the distillation of Wood, Sc. 17

or that carbon which there is not oxygen enough present to burn, is
deposited in a state of very minute division in proportion as it is
volatilized, during the formation of the naphtha or petroleum, the
more hydrogenous part of the compound. But if this part is sepa-
rated without flame, either by a more moderate heat, or by excluding
oxygen from it, the carbon is rendered apparent by its affinity of
aggregation, which causes it in the end to assume comparatively
refractory powers, and a more solid form,

Such are the views I would entertain of the bituminous genus, in
which as it is found in Nature, all traces of organization or re-
semblance to vegetable and animal inflammable matter, have so
thoroughly ceased, that we are entitled to give its several species
a fair rank among minerals. But there is yet another division of
inflammable and subterraneous substances connected with these,
of which the claims may appear doubtful. Retaining as they do, the
traces of organization, and that sometimes in great perfection, it may
be often questioned whether they do not more properly rank with
the fossil remains, than with the minerals properly so called. They
are well distinguished by the name of Lignites. At one end of this
series is placed jet, in which the traces of vegetable origin are nearly
obliterated. Surturbrand and the several varieties of brown coal,
including Cologne earth, connect it gradually with submerged wood
and peat. ‘The experiments I have already related prove that the
substance resembling bitumen, which is produced by the action of
fire in the ordinary way on vegetables, differs from it essentially,
and it has been seen that solubility in naphtha is the readiest crite-
rion by which these substances can be distinguished. To assure
myself of the accuracy of this test I mixed the petroleum of coal
with the black oil of wood in several proportions, and by the appli-
cation of naphtha separated the one from the other. By this simple

VOL. II. c

18 Dr. Mac CuLLocu on certain products

method therefore I expected to detect not only the progress.of bitu-
minization from simple turf to jet, but to assure myself whether in
the examinations hitherto made by others of these different substances,
any mistake had arisen from confounding the vegetable bitumen with
true bitumen when distillation was used to investigate their nature,

Vegetable turf in all its varieties, as well as brown coal, gave a
considerable colour to lixivium of potash, but the same menstruum
produced no effect on jet, or surturbrand. Nor had naphtha or alco-
hol any action except on the resinous lignite of Bovey, from which
they extracted the resinous matter which that variety contains.

I therefore subjected these different substances to distillation, trust-
ing that by the produce, I should ascertain, not only the fact, but
the progress of bituminization.

Submerged wood, from peat mosses in Cumberland, gave a brown
oil, smelling of the wood tar and refusing to dissolve in naphtha,
In this case therefore, no appearance of a change towards bitumen
was exhibited. A compact pitchy looking peat gave an oil which
had a fetid smell, neither resembling that of wood tar, nor bitumen,
and which was very slightly soluble in naphtha.

The Bovey brown (board) coal, produced an oil of a peculiar
smell, but most resembling that of wood tar, and much more soluble
in naphtha than the preceding. Having a larger quantity of this,
I separated the soluble part by naphtha, and in the remainder, or
insoluble oil, the smell of wood tar was powerful, notwithstanding
the strong odour of the naphtha. Here then the progress of bitu-
minization had advanced another step. The resin of this wood, on
which a particular name has lately been bestowed, I consider as an
adventitious and accidental substance, and the natural produce of the
tree, now probably unknown, which occupies these alluvial strata,
as other lost productions of Nature are detected in other alluvial soils.

obtained in the distillation of Wood, &c. 19

A specimen of black lignite from Sussex gave an oil which re-
sembled the former in smell, and perhaps did not differ much from
it in its solubility in naphtha, but I had not enough of the substance
to institute an accurate comparison, neither in fact, could it serve
any purpose. A similar substance from Bovey gave similar results.

The oil which was distilled from jet was of a greater specific
gravity than any of the preceding, and smelled strongly of petroleum.
It seemed to be soluble in naphtha as readily as the specimen of
petroleum with which I compared it. Indeed had it not been that
a greater quantity of acid was given over in this process than from
any of the varieties of coal, I know not that any chemical distinction
between the two would have existed. "The mineralogical one is still
considerable. ‘The several specimens above enumerated, yielded each
a large portion of acetic acid, marking as clearly as the peculiar sort
of oil did, the remains of unchanged vegetable matter.

Examining therefore the alteration produced by water on common
turf, or submerged wooed, we have all the evidence of demonstration
that its action is sufficient to convert them into substances capable of
yielding bitumen on distillation.

That the same action having operated through a longer period
has produced the change in the brown coal of Bovey, is rendered
extremely probable by the geognostic relations of that coal. From
this to the harder lignites, surturbrand and jet, the transition is so
gradual, that there seems no reason to limit the power of water to
produce the effect of bituminization in all these varieties, nor is there
aught in this change so dissonant from other chemical actions, as to
make us hesitate in adopting this cause. In the ordinary process of
vegetable putrefaction and destruction, a variety of compound gases
are formed by the reaction of their elements, and carbon alone, or

rather carbon united to a portion of hydrogen, remains behind.
c2

20 Dr. Mac CuLLocn om certain products

Here the oxygen is completely dissipated, together with the azote,
and the greater portion of the hydrogen. Analogous circumstances
determine the putrefaction of animal matter, but in this case the play
of affinities is so intricate, that a large portion of the carbon is vola-
tilized in the gaseous form. By the constant affusion of water
however, this process may be so modified, that the greater part of
the hydrogen and carbon will be retained, and eater, together with
minute portions of other gases, into a new compound resembling fat,
which has obtained the name of adipocire. The analogy is strong,
and the gradual deoxydation of the wood in this process is visible
in the different stages of bituminization.

Such, as far as observations have yet gone, is our knowledge of
this process and of the power of water in producing it. To repeat
such an experiment in the laboratory seems impossible, since the
necessary element of time must be wanting to complete it. But the
action of fire being of shorter duration, and affording us also readier.
means of imitating Nature in those operations in which she has
wrought with the same agent, it is worth our while to consider, if
by it we can produce from vegetables the bituminous matters under
review. It is not necessary to say how intimately this question is
connected with our speculations on the origin of coal, since Sir
James Hall’s experiments were expressly intended to illustrate this
view of the subject. In this, it is related that “ coal”? was produced
from “ fir saw dust” by the usual method employed in these ex-
periments, and that pieces of wood were changed “ to a jet-black
and imflammable substance, generally very porous,” in some spe-
cimens of which “ the vegetable fibres were still visible.’ There
is no reason to doubt that the substance produced in these experi-
ments, was that black matter which I have described in the first part
of this paper, which, however resembling bitumen in colour and

obtained in the distillation of Wood, Fc. 21

inflammability, I have proved to be a different substance, and that
the igneous theory of the origin of coal will receive no support from
them, as far at least as relates to the conversion of vegetable matter
into bitumen. I need take no notice of the modifications derived
from a mixture of animal matter in these experiments, as it is not
my desire to enter into a discussion of the general question, but to
state such chemical facts as arose in the experiments I undertook.
And since it is certain that vegetables alone are competent to the
production of bitumen, and that the geological history of coal does
not justify a supposition that animals have been concerned in its
production, it is perhaps unnecessary to investigate that question
further.

To satisfy myself whether any essential chemical difference would
result from the experiments performed by simple heat, and those
performed by heat under pressure, I repeated these trials, by heating
wood in close gun barrels, introducing occasionally lime, clay, or:
other matters to absorb the acid generated, and give the greater
chance for the disoxygenation and bituminization of: the wood.
But the produce only differed from that of the experiments in open
vessels, by the circumstance which is mentioned in Sir James Hall’s
paper, namely, the mixture of a porous charcoal, or a half destroyed
vegetable structure. In all cases the bituminous looking matter was
vegetable tar, not bitumen.

Thus far then perhaps we are justified in concluding that the
action of water, and not that of fire, has converted the vegetable
matters into bitumen. It is another question to determine how that
bituminous matter in its several forms of peat or lignite, has been
converted into coal, into a substance differing mechanically, rather
than chemically from it, if, without misleading, I may use the con-
trast of these terms.

22 r Mac CuLiocu on certain products

There is a wide interval between the external characters of the
lignites and of coal, and though we cannot presume to state the
period which Nature has used in her operations, nor during how
long a space the causes have continued to act, before the vegetable
matter has undergone its ultimate change into coal, nor therefore
whether the long continued agency of water and pressure may
not have produced the required changes, yet, since Philosophers of
high reputation have supposed that fire has been a probable cause
of this conversion, and that this theory is supported by considerable
evidence in some analogous cases, it is our duty to examine by ex-
periment, what effects conducing to this end may result from our
limited trials. The foregoing experiments show that the fire of our
furnaces does not convert wood into bitumen, and the processes of
‘Nature seem to prove that water can produce this effect, and that
jet, the bituminous lignite which approaches nearest to coal in its
chemical characters, is the result of this action. Yet there is an
interval between jet and coal as I have already observed, requiring
explanation. The chemical characters may be identical, but the
mineralogical resemblance is still wanting. It is possible that the
agency of fire may account for this ultimate change, and that its
action on beds of lignite and peat has converted not wood but vege-
table matter already bituminized by water into coal. Pursuing this
train of investigations I was induced to try if jet, the most perfectly
bituminized lignite, could by the application of heat under pressure
be converted into coal. For this purpose I introduced powdered
jet into gun barrels, placing it between two portions of rammed
Stourbridge clay, with the view of absorbing a part of the distilled
petroleum when it might be formed in greater quantity than was
requisite for the success of the experiment, and where by its con-
version into hydrogen, it might endanger the bursting of the appa~

obtained in the distillation of Wood, ce. 23

ratus. The barrels, which were Swedish, were held in a moderate
red heat till they burst, when they were instantly withdrawn and
cooled im water to prevent the further volatilization of the bitumi-
nous matter. As the opening was generally no larger than a pin
hole there was no difficulty in cooling the apparatus in time. In
this way, among some failures, I procured a perfect fusion of the jet,
which exhibited the true characters of coal, and was taken out with
the impression of the irregularities in the barrel. I need not add
that in this case the produce had not merely the colour and inflam-
mability but the fracture of coal and its odour on burning. It is not
unlikely that by a sufficient repetition of these experiments with
better regulated heats and more leisure than I possessed, several
varieties of coal might have been in this way produced. Indeed
some of the specimens exhibited a dry, and others a fat appearance,
but it was impossible in general to detach them from the barrels
without reducing them to small fragments. Two other circum-
stances occurred deserving of notice. In one or two cases where
the heat had been too great, a portion of the jet was reduced to
charcoal, which continued attached to the coaly matter, and the clay
was in every instance blackened to a considerable distance from the
jet, and converted into a hard compact substance resembling bitu-
minous shale in its smell and consistence.

Reverting to the chemical nature of the other lignites, there is
very little reason to doubt that those among them which approach
the nearest to a state of perfect bituminization, would have given
results nearly similar, but I could not pursue the investigation for
want of sufficient specimens. From peat we should expect but a
mixed matter, varying between the bitumen of wood and true
bitumen, according to the degree of change previously undergone ;
for that the process of bituminization is the effect of water, and not

24 Dr. MAc CuLLocu on certain products

of fire, is rendered probable, as much by these trials as by the geo-
logical observations above mentioned. ‘The conversion of bitumi-
nized wood into true coal may possibly be the effect of a consolida-
tion produced by the agency of fire, but I shall leave this argument
in the hands of those who have undertaken the defence of this
theory—having entered into this train of reasoning, not by design,
but from the unavoidable concatenation of experiments.*

A circumstance occurred in the coaly residuum of the wood tar
which it is worth while to notice, although of an accidental nature,
and not essentially affecting the history of the vegetable bitumen or
pitch which I have described. It bore no resemblance to common
charcoal, but was more like black lead. It was as glossy, and
although not so soft, marked paper with a similar streak. It was
inflated, and therefore minutely scaly, and porous, and was attracted
by the magnet. Muriatic acid took up a portion of iron from it,
as it does from many varieties of plumbago, and the remainder
resembled plumbago after it had been submitted to the action of acids.

* That I may not interrupt the text, I will add, in a note, a cursory account of the
black matter which is deposited in bogs, and which seems to be the substance giving
the pitchy appearance to the more compact varieties of peat. I have not scen it in the
soft state in which it is first procured.

When dry, it is black, sometimes dull, sometimes with the lustre of asphaltum. It is
heavier than water. It is not electric. It is brittle, and breaks with a fracture inter-
mediate between the splintery and conchoidal, resembling asphaltum generally in its
external characters. Exposed to a red heat it is incinerated, giving a smoke possessing
a modified smell of vegetable (pyroligneous) acid. It is not acted upon by boiling
alcohol, ether, or naphtha; and in this latter circumstance, its difference from asphal-
tum is marked. Neither is it soluble in boiling water. It is readily dissolved in lixivium
of potash, and by nitrous acid. It appears to be formed of the vegetable elements in
the state of transition to bitumen, the carbon having been first held in solution, as it is
in the water of dunghills, by the other matters with which it was combined, and being
at length consolidated by the dissipation of a portion of them. ‘The produce of its

combustion shows it is combined with both hydrogen and oxygen.

obtained in the distillation of Wood, °&c. 95

It was also exceedingly difficult to burn, requiring a long con-
tinued red heat, after which it left an oxide or rathera carbonat- of
iron, such as remains from the combustion of plumbago. It is in
fact to be considered as an artificial plumbago, a substance of whose
nature all the charcoals of difficult combustibility partake, deriving
their resemblance apparently from the same cause.

The formation of this plumbaginous substance serves to shew a
very powerful affinity between iron and carbon, even where the
proportions are very different from those which enter into the com-
position of steel. But to effect this combination, it is necessary
that the carbon be in a state of previous union with other substances,
and that it be applied to the iron in that state. It will be in vain
that we attempt to combine iron with charcoal for this end, unless
the charcoal or carbon be in that state of very minute division in
which it exists when precipitated by a new affinity from some pre-
vious combination. :

It is necessary now to account for the iron in this compound.

This distillation of wood for charcoal is carried on in iron vessels,
and hence is derived the iron which enters into the composition of
the pitch. I will not say that it is solely derived thence, as it is
probable that if there were iron contained in the vegetable matter,
it would also be found in the same place. When the acetic acid
has been separated the iron remains united to the pitch. This fact
may shew us, that if in the destructive analysis of vegetable (and
probably animal) matter, we trust to find the iron they may con-
tain in the residual matter of the distillation, we may be disappointed,
since it may be carried over, together with the substances I have now
been describing, in the act of ebullition, as happens in this very

case, its tendency being to combine with them, in preference to the
charcoal.

WOE.- It. D

26 Dr. Mac Cuttocu on certain products

As it was no part of my design to examine the vegetable elements,
I did not pursue any experiments with this substance distilled in
earthen vessels so as to ascertain whether in this case also it would
contain iron, but I did enough to satisfy myself that the pitch was
essentially the same in which ever way produced.

It is already known that a substance resembling plumbago is
formed in water, it having been discovered by Fabroni in the coun-
try round Naples. It is equally known to be formed in the iron
foundries, and the advocates for the igneous origin of coal have also
contended for that of plumbago, and have supposed it to have been
produced by the contact of melted greenstone with beds of coal. But
even if we admit this cause of its formation, something else seems
necessary for the production of the substance, and some other mode
of applying the heat required before it can be produced. Nor
indeed does the explanation sufficiently correspond with the general
geological position of plumbago.

In numerous trials to combine iron with charcoal so as to form
this substance, I have uniformly failed of success, except where as in
the case above related, the charcoal or carbon has been ina state of
previous combination, or was actually held in solution. In many
trials on this principle, the results have been tolerably successful. If
therefore we are to adopt an igneous theory of the formation of
plumbago, it will be as easy to suppose that the action of subterra-
neous fire on mixtures of bitumen and iron has produced the com-
pound of charcoal and iron, on the principles I have described, and
this supposition will be more consonant to the chemical facts. But
we are too little acquainted with the geological relations of plum-
bago to lay much stress at present upon this or any other hypothesis.
It is evident that plumbago may be a produce of art, and could it be
produced in as solid and compact a state as Nature affords it, the

obtained in the distillation of Wood, &&c. 27

discovery would form a material addition to those useful ones for
which the arts have been indebted to chemistry. |

As nothing tends more to confusion of ideas than confusion of
terms, I may be excused for proposing a name to the pitch of dis-
tilled wood, a name in familiar use, though hitherto unappropriated
by chemists. It is in fact that which is well known to painters by
the name of Bistre, although the nature of bistre has I believe never
yet been examined; and the importance of it to the arts of design
induces me to extend this article for a few lines. According to Dr.
Lewis, bistre is produced from the soot of all wood, other receipt
books give us the same account, but limit the sort of wood to
beech without seeming aware of its real nature; but the colourmen
use the soot of all wood indiscriminately.

Those artists who have made the tour of the highlands of Scot-
land, are well acquainted with that variety of it which varnishes
the interior of a highland cottage.

In all these cases it is a very variable article, and the colour-maker
being unacquainted with its real nature, is unable to rectify its faults,
in consequence of which it is often unfit for use, notwithstanding
the various operose and mysterious purifications it undergoes in his
workshop. The causes of these varieties will be very evident to
those who have read the foregoing experiments. An imperfect
separation of essential oil and a consequent tenacity arising from its
too near alliance to the tar, will appear to be its most common vice,
and it is this which gives it that disagreeable gumminess and dis-
position to return to the pencil which is destructive of its best
qualities. At times also from the same causes it is offensively yellow.
So valuable is a brown colour that will work freely and with
transparency, that the artists will be much obliged to him who shall

render bistre equal in freedom and force to seppia. By distilling
pd 2

28 Dr. Mac CuL_ocu on certain products, Sc.

or evaporating the oil from the pitch, according to the process des-
cribed above, a colour may be produced varying in tone from the
warmest bistre brown down to black. At the same time the sub-
stance loses a great portion or the whole of its disagreeable tenacity,
according to the degree of boiling it has undergone. By treatment
in alcohol, results in some measure similar are produced, and the
residuum of this solution is equal in colour to seppia, and totally void
of tenacity. In either or both of these ways may the quality of this
colour be improved.

It might perhaps be a matter worthy of trial, whether useful
varieties in colour and quality might not be produced by the distilla-
tion of different woods. That which I used was procured either
from willow or alder—the two woods chiefly used in the royal
powder mills, but I cannot ascertain from which of them. The
solution in lixivium of potash or of soda, a substance analogous to
the resinous soaps, answers the purpose of ink, possessing a colour
sufficiently intense and flowing freely from the pen without re-
quiring gum. As it is indestructible by time, by the common acids
or by the alkalies, perhaps it may be found a valuable substitute
for this useful but fugacious substance. ‘The compound of bistre
and soda appears peculiarly well fitted for drawing in monochrome,
since as it does not consist of a powder suspended in a vehicle, it is
free from the peculiar defects, so well known to artists, which occur
in colours thus compounded.

I may also add that it forms a substitute for asphaltum in drying
oil where such a coloured varnish is wanted, and that it makes a very
good japan varnish for metal if dissolved in spirit of wine, and
heated strongly after its application. It is for practical men to see
whether by combining it with asphaltum, lac, or the gums, some

‘more useful and cheap compounds of this sort may not be produced,

II. Mineralogical Account of the Isle of Man,

By J. F. Bercer, M.D. M.G5S.

INTRODUCTION.

Tar the name of the Isle of Man should be owing to its
situation, does not appear at all improbable. Such is the con-
jecture of the learned Bishop Wilson in his short but valuable
“‘ History of the Isle of Man.”

The appellation of the island, says that respectable prelate, is pro-
bably derived from “ the Saxon word Mang, among, as lying almost —
at an equal distance between the kingdoms of England, Scotland
Ireland and Wales,” *

With the exception of the work just mentioned, we scarcely find
in the tours that have since been published any information directly
bearing on the mineralogy and physical structure of this island till
we come to the late publication of Mr. Geo. Woods, where indeed
these topics are more fully detailed than is usually the case in gene-
ral topographical descriptions. +

In enlarging upon the same subject, I hope that I shall not oc-
cupy in vain the time and attention of the Geological Society: for

* Bishop Wilson’s Works—Second Edition—Two Vol. fol. Lond. 1782. Vol. I.
p. 449.
+ An Account of the Isle of Man, by George Woods, London 1811.

30 Dr. BERGER on the Isle of Man.

a minute investigation both of the rocks and simple minerals had
never been yet instituted, and the arrangement and examination o
the Ligh land, the most conspicuous and extensive part of the isle,
still remained a field quite unexplored.

The grotesque and unfaithful attempt of Fannin to lay down
the mountains in his map of the island published in 1789, can hardly
be considered as an improvement upon the much earlier and rough
sketches of Collins, Durham and Speed.

From the materials and documents which I collected when in the
Isle of Man, I have since my return from Ireland constructed a map
chiefly expressive of the features and appearances of the mountain-
ous tract, which I now present to the Society; acknowledging at
the same time the able and kind assistance afforded me by Mr.
Webster, draughtsman to the Society.*

The height of Snei-feldt was a long time ago determined by
means of the barometer, by Bishop Wilson, + and it has been since

* This map however is neither complete nor as perfect as I wish I had been able to
execute it. Mr, Wm. Geneste (a gentleman of Douglass, to whom I am much indebted)
has had the complaisance to undertake last Summer at my request, a trigonometricay
survey of the Isle of Man, conjointly with Mr. James Kewley, a person who has for-
merly practised as a Surveyor. But I fear the result of their labours, which Mr. W. G.
intended with a great liberality to put at my disposal, will not be ready to be published in
this volume of the Transactions of the Geological Society.

+ The height of Snafield (says the Bishop) as taken by an exact barometer, is about
five hundred and eighty yards, the mercury subsiding two inches and one tenth. Vol. I.
p-» 449. ;

This is very probably the first application that was made of the barometer in Great
Britain to determine the elevation of a mountain,

The original experiment pointed out by Pascal, was performed by Perier (his brother-
in-law) on the “ Puy de Dome,” 19th Sept. 1648. Bishop Wilson came over to the Isle

of Man in April 1698, where during his long residence, he made the experiment that led
him to the elevation of Snei-feldt.

Dr. BERGER on the Isle of Man. 31

included along with that of North Bor-roilva, in the trigono-
metrical survey of England by Lieut. Col. Mudge. But with these
exceptions, no other elevations in the island were ascertained. A
barometical measurement which I have made of nearly ‘all the
mountains and other remarkable places, has amongst other advan-
tages, enabled me to give a vertical section of the chain throughout
its whole extent, which agrees very well with a profile view of the
island, taken by Murdoch McKenzie from the Mull of Galloway.

The spelling of the Manx names along with their pronunciation
and signification has been furnished me by several persons in the
isle, well versed in the knowledge of their native language, but I
am particularly indebted for it to the Revds. H. Stowell, T.
Howard, and Wm. Fitz-Simmons.

The length of the island is computed at upwards of thirty Eng-
lish miles, of which about five-sixths are occupied by a large body
of mountains stretching from North-East to South-West ; its breadth
varies from fifteen to eight miles.

The chain spreads or swells out to the northward contracting
itself to the southward into the Calf or Barrow of Man, which
latter is rather less than six hundred acres in superficial extent,
offering thus a gradual slope of fifteen hundred and forty feet from
the top of Snei-feldt down to Burchet’s house on the southern cliff
of the Calf, that is to say, a depression of nearly a quarter of a mile
in twenty-one miles taken in a straight direction, or, on a mean
average, of about seventy-three feet per mile.

Estimating the mean breadth of the mountainous belt at four
miles and a half, and its length at twenty-five, we should have for
its superficial extent one hundred and twelve square miles and a
half, which when referred to the whole area of the island, on the
supposition of its being on a mean average, eleven miles and three

52 Dr. BERGER on the Isle of Man.

quarters broad, by thirty miles long, or three hundred and fifty-two.

square miles and a half, would give one third, by approximation,
for the ratio of the moory and uncultivated Jand to the land that is
under tillage; there can be no doubt however, but a considerable
proportion of the former is susceptible of being reclaimed.*

Parallel to each other, but at a distance respectively different, and
nearly vertical to the main direction of the chain, there are three trans-
verse vallies, the bottom of which, if not on a dead level with the
sea, comes at least very near to it. The first of these is situated in
the middle part of the chain, and the road leading from Douglass to
Peel town passes through it. Its watershed is one hundred and
twenty-six feet above the level of the sea, from which on the
northern side rises a steep slope of 1352 feet to the top of the
North-Greebah, and on the southern side a nearly vertical preci-
pice of 609 feet to the top of the North Slieau-Aalyn above the
hamlet of Mullin-y-Chlea, which stands 93 feet only above the sea.

The second transverse valley is about ten miles in a direct line to
the south of the first, between Purl-Keill-Moirrey and Port Erin.
Its watershed is 81 feet above the level of the sea, and is a low

* According to Mr. J. C. Curwen’s calculations, the Isle of Man contains 245,760
Acres. viz.

100,400 of mountain

69,045 for grazing

30,158 in oats

15,079 under barley

14,761 under green crop, 710 of which may be considered as potatoes

9,047 in wheat

7,270 in roads, rivers, houses

Total 245,760 Acres

Report of the Agricultural Society in the Isle of Man.—Workington, 1810,

Dr. BERGER on the Isle of Man. 33

ridge of land, formed by the gradual slope of Slieau-y-Carnane and
the high land of Spanish head.

Two miles farther to the south, the narrow channel of the Calf,
about two furlongs in breadth, forms the last transverse valley.
The small Isle of Kitterland lies in the middle of the Strait, con-
nected by shelving rocks discernable only at low water, both with
the main of the Isle of Man, and with the Calf itself.

It is a remarkable fact that the trifling elevation of these three
sections decreases southwards, down to the last which is below the
level of the sea.

A fourth flat, more considerable indeed than any already spoken
of, may be said to exist on the outskirt of the chain northwards,
occupying that fenny plain anciently called ‘‘The Curragh,” and now
transformed into one of the most fertile tracts of the whole island.*

The chain of mountains that forms the middle part of the Isle of
Man, considered in itself, might perhaps with more propriety be
denominated a group than a chain. It is arising “‘ en masse’’ of the
land, a common broad basis or foundation on which rest several
mountains otherwise unconnected with each other, though dis-
posed in some regular order.

The narrow Glen of Mullin-y-Chlea, may serve to distinguish
the mountainous group into two divisions, the one north, the other
south. Inthe northern district of the group, two extensive lines of
mountains and a central one, may be traced without difficulty. The

* Very large trees of oak and fir have been found buried in the peat of the Curragh,
some two fect and half in diameter, and 40 feet long. The oaks and firs do not lie pro-
miscuously, but where there is plenty of one sort, there are generally few or none of the
other.—W iilson’s [History of the Isle of Man.

Mr, J. C. Curwen seems to think that the area of the flat country comprehended be-
tween Ramsay and Kirk-Michael, Jurby-point and Airc-point, may be rated at 40,000
acres, that is to say, according to his above referred to calculations, to a little less than
1-6th part of the whole area of the island.

Agricultural Report, p. 153, —-Workington, 1810.

VOL.« Ble E

34 Dr. BERGER on the Isle of Man.

latter having Snei-feldt almost in the centre, comprehends the
highest ground and the mountains of North Bor-roilva, Gob-y-
Scioot, little and big Snei-feldt, Bein-y-phot, Kanaghyn and North-
Greebah.

A boggy and elevated table-land lies on both sides of the central
line of mountains, separating it from the two exterior ones. The
summits of the extensive mountains do not all of them greatly sur-
pass the elevation of the intervening table-land itself.

In the southern district of the group, the two exterior and skirting
lines of mountains do not exist, but the eastern side of the moun-
tains is rather scooped out and smoothed into a gentle and gradual
declivity; whereas the western side constitutes a range of cliffs
abrupt in most of its extent.

The steepness of the exterior mountains is nearly the same on
each side. ‘The northern boundary of the group terminates almost
abruptly, and beyond the Curragh, lie the Balla-chyrrim hills, a
low range formed of loose sand and gravel, facing the northern
escarpment of the group, and then passing southwards in a parallel
direction between the coast and the western exterior line of moun-
tains.

A little to the north of the Balla-chyrrim hills, is a shingly beach,
insensibly declining towards the sea, and formed of water-worn
pebbles and sea-sand. The latter is hardened and binds the pebbles
strongly together. It is the opinion of several persons in the isle,
that the land in this quarter is gaining sensibly upon the sea. Some
go so far as to say that the increase is not less than two yards in a
year.

There are but few water-courses of any magnitude and extent in
the Isle of Man. Sulby River the largest of all, irrigates the
Curragh, and from the village of Sulby to Ramsey* where it

* Roms-waay-wide or roomy bay.

Dr. BERGER on the Isle of Man. 35

empties itself into the sea has but a very inconsiderable fall. From
Crammag-bridge down to Sulby the stream runs at the rate of 452
feet within three miles; from thence higher up near to its source
no computation of the kind can be made, as it 1s no longer one
regular body of water but an assemblage of many little rivulets
flowing down from the slopes of the mountains in every direction,
particularly from the mountainous pasturage called Mowmt-Pellier.

The watershed of the elevated and boggy table-land that separates
Mullach-Oure from the central line of mountains, gives rise to two
other water courses, which from their common origin run in a con-
trary direction. The Bright-river after it has watered the Baldwin-
valley empties itself into the sea at Douglass. The Laxey river
flows through the valley of that name. Allowance being made for
the windings of the Bright-river, it falls at the rate of 1395 feet
within six miles, a fall rather considerable. |

Both the Black-water and the Peel-river that issue from the water-
shed between Douglass and Peel-town are inconsiderable streams.

From the southern group of mountains come out two or three
rivers, Glen-Moy, Cass-ny-Hawin and Castle-town rivers ; the two
latter flowing into the eastern part of the Irish Channel, and the
first into the western.

The vale that is irrigated by the Moy river (Muigh a Druid) is
extremely picturesque, the windings, which are short and frequent,
expose unexpectedly to the traveller’s eye, scattered cottages along
the sides of the river. Cass-ny-Hawin and Castle-town rivers have
a course much more open, owing to the character of the country
which they traverse. Several other streams indent the coast of the
island, which from the shortness of their course and the diminutive
quantity of water they discharge into the sea, do not seem éntitled

to any farther notice.
Te

36 Dr. BerGER on the Isle of Man.

I shall speak first of the Compound Rocks, and secondly of some
Simple Minerals, as they occur /oose or in situ, mentioning besides
in each division under a particular head the primitive rocks, and those
that belong either to the class of Transition, or to that of the
Floetz-Rocks.

I. Compound Rocks in Situ.
(a) Primitive Rocks.
+ Granite.

Very little of the oldest member of the primitive class of Rocks
is to be seen in the Isle of Man in Stu, nor is it the genuine old
granite. Some doubts therefore may be entertained whether in the
places where it occurs it does not lie in beds, rather than forming
the universal foundation of the Isle.

Along the slope of Dun How, on the road from Laxey to
Ramsay, and in the middle feeder of a stream that runs into the
sea, occurs a small grained granite much decomposed, the quartz
bearing but a very small proportion to that of the felspar: when
breathed upon, the rock emits a strong argillaceous smell.

The same small granite, but in a sound state, is to be seen at
Dun-bridge.

The spot where it comes to the surface may be three or four
hundred feet above the level of the sea, but I have made no
observation that enables me to determine accurately.

Another small grained granite was found in the working of a
lead mine at Foxdale, a place situated nearly in the middle of the
island, and 346 feet high.

If the information I received from an old English miner who

Dr. BERGER on the Isle of Man. 37

had been employed the whole time the works were carried on be
correct, they came to the primitive rock in sinking a shaft forty
yards deep. ‘There the granite was found to form the north side*
of the vein, the galena adhering to it, while the south side was a
stratified rock, which I shall hereafter mention. Whatever may be
the depth at which the primitive rock was first remarked, there can
be no doubt as to its existence, from the multiplicity of pieces of
all sizes I found among the rubbish of the mine, and which were
pointed out to me as such by the miner himself.

The rock is of a coarse grained texture, somewhat loosened,
chiefly composed of quartz concretions, with reddish and decayed
felspar along with some plates of white mica.

The mean specific gravity of the different sorts of granite above-
mentioned, is 2, 81. From the granite above described, we come
at once to the clay slate formation. The subsequent or intermediate
members to granite in the series of the primitive rocks, viz. gneiss
and mica slate, being either wanting absolutely, or if they exist at
all, having escaped my attention, or being for the present concealed

from our sight.

t+ Clay-Slate.

The clay slate formation in the Isle of Man does not appear to
belong to the oldest kind of Werner. It is almost limited to the
high ground occupying Snei-feldt, Bein-y-phot, South Bor-roilva,
and Cronk-ne-liry-Lhaa. It also occurs at Mount Pellier as hone
stone; at Peel-hill and Balla-Gawn, as roofing slate ; and as a reddish

* The miner from whom I received my information is a Yorkshire man, and used the
technical word cheek instead of that of side; an expression which I understand is

likewise employed amongst the Derbyshire miners,

38 Dr. BERGER on the Isie of Man.

half-decomposed slate along the mountainous road that runs from
Ramsay to Donglass, between Slieau-Lhearn and little Snei-feldt.

The clay-slate of Snei-feldt has a close texture. Its basis is
remarkably fine, the gloss not very resplendent: it fuses into a
brownish enamel, and is traversed by slender veins of granular
and whitish quartz.

The clay slate of Bein-y-phot has a dull black-brown colour,
while that of Cronk-ne-liry-Lhaa is sometimes so glossy as to
resemble plumbago, is soapy to the feel, fusible into a yellowish and
bubbly enamel, the fracture is foliated, with some minute specks of
white mica.

On the slope of South Bor-roilva the clay slate assumes a more
flinty character, the grain is also very close. At Peel-hill, in a
situation still lower than on the slope of South Bor-roilva, we come
to another flinty clay slate, in the basis of which are distributed
extremely minute specks of mica; it fuses into an olive brown
enamel. The rock is quarried, but the beds that are used for
roofing alternate with two others of a different nature. The one
is a greyish compact felspar, the structure of which is rather thick
slaty, with a close texture, the fracture is short scaly, it contains
dispersed specks of mica, and fuses into a white frothy enamel.
The strata run nearly East and West, dipping at an angle from 75°
to 90°. The other bed alternating with the roof slate is called the
Knobby Side, and forms the wall of the quarry itself. It has a silky
lustre, and the planes of the strata, which are nearly vertical, instead
of being even, offer little cavities smoothened and adapted for the
reception of prominent parts similar in dimensions that exist on
the contiguous bed. There is another roof slate at Balla-Gawn
of a dark grey colour, rising by flags and of a fissile texture.

The clay slate of Mount Pellicer has a structure rather thin slaty,

Dr. BERGER on the Isle of Man. 39

it is ferruginous on the joints, but the colour of the basis is greenish
grey, of a very fine grain, and full of cubic iron pyrites. Itisa
fact worth noticing, that the parts of the rock contiguous to the
pyrites are whitish and earthy.

The last sort of clay slate mentioned as occurring between
Slieau-y-Carnane and little Snei-feldt, has a violet reddish tinge.
The structure is fine slaty, the texture more clayey; talcose linings
impart to the spontaneous joints a glossy character. Its readier
decomposition makes it a better support for vegetation. ‘The mean
specific gravity of the different sorts of clay slate enumerated here,
1s 2ioT.

(2) Lransition Rocks.

We pass from the clay slate formation to transition rocks through
the most insensible gradations, and in this instance it is to be
remarked, that it is the grey-wacke and not the limestone which
forms the oldest member of the series.

Grey-Wacke.

In the Isle of Man this rock, as far as my observation has gone,
never contains organic remains. It is farther to be observed that
the tract of land occupied by the grey-wacke is less elevated ge-
nerally speaking, than that appertaining to the clay slate. We can
trace the grey-wacke all along the contour of the island, and,
except those places where it slopes down gradually, and is out-
skirted by the floetz-limestone receding into the sea, it forms a
range of bold cliffs; at Maughold-head, Banks-how, Douglas’-
head, Walberry-how, Spanish-head, the Calf of Man, Brada-head,

40 Dr. BERGER on the Isle of Man.

Dauby-point, and in the intervening space between Peel-town and
Kirk-michael.

Cronk-dhoo is the highest place where I have observed the
grey-wacke. ‘The shade indeed that seems to discriminate it from
the clay-slate is so delicate, that were I to speak decidedly it would
be rather unphilosophical. It has a grey colour inclining to a
greenish hue, the joints ferruginous; it possesses a silky lustre
which it seems to derive from talc intimately blended or inter-
woven with the basis itself, but there are besides a good many
small specks of mica.

At Banks-how the grey-wacke has a much more. decided
character. It is rather thick slaty and of a granular texture,
traversed by veins of white quartz standing out in relief. The
basis has a greenish tinge approaching to grey, contains no spangles
of mica and comes near to quartz sandstone. When disintegrated
it forms but a meagre soil, fit for little else than oats.

Large tabular masses distinguish the grey-wacke of Clay-head.
The fracture in the small is granular-scaly, the colour greenish
grey, passing to ferruginous on the natural joints, it does not fuse
unless where there are spangles of mica.

Near Laxey there is a grey-wacke-slate used as flags for flooring
houses, it is scarcely fusible but for the mica there is in it, thin
coatings of an ash-grey colour over-run the surface.

The following beds of grey-wacke-slate, alternating with each
other, appear on the south quay of Douglass,

First variety. Texture earthy, of a dirty grey colour, contains
spangles of mica, fuses into a whitish enamel.

Second variety. Striated, of an hard and dry aspect, infusible, or
merely glazed from the mica that enters sparingly into its com-
position. The colour varies from greyish to olive-grey.

Dr. BERGER oa the Isle of Man. 41

Third variety. Granular quartz forms the basis of it, in which
are interspersed some small grains or nodules of transparent quartz,
and some specks of white mica.

The Fourth and last variety, is a granular quartz over-run by
veins of the same substance. ‘There are in it but a few specks
of mica.

The grey-wacke of St. Ann’s-head is distinctly stratified, the
planes of the strata being quite even, a mode of structure which
originates from an accumulation of specks of mica, which render
the rock readily fusible into a brown-greyish enamel, while it is
infusible in those parts where the mica is wanting.

Along the shore between Kirk-michael and Peel-town, the
grey-wacke is rather thick-slaty, traversed by slender and parallel
veins of white quartz, coeval with the rock itself since they occur
along the seams of stratification. The mean specific gravity of

seven specimens of grey-wacke is 2.702.

C. Flaetz-Rocks.

+ Limestone.

It would seem as if the appearance of the limestone was con-
nected with the absence of the exterior line of mountains on the
eastern side of the South Group. We trace it from Cass-ny-Hawin
River to Purl-Keill-Moirrey (Langness-point excepted) but it never
reaches to any elevation on the slope of the mountains; it is
confined to the shore or its vicinity.

It lies conformably over the most superficial of the produced
strata of grey-wacke, but the dip becomes less as the strata retreat
farther back from the land into the sea. It may be comprehended
between 10°. and 20°.

Vou. i. F

42 Dr. BERGER on the Isle of Man.

.

This secondary limestone is accompanied by the magnesian
limestone, but I cannot say that the one overlies the other. They
rather seem -to occur by separate beds, or sometimes by patches,
the one within the other. ‘The magnesian limestone does not put
on that regular stratified appearance which is so conspicuous in
the other, nor have I observed in it any organic remains but in
one single instance, and they are similar in their composition to
the stone itself.

Mr. Parkinson has most obligingly furnished me with a list of the
organic remains contained in the limestone of the Isle of Man, and
he farther remarks, that the whole much resemble those found in
Westmoreland, Cumberland, Durham, and, as far as he can judge,
those of Kilkenny in Ireland.

The following are the organic bodies contained in the specimens
that were submitted to his examination.

A large madrepore from two to three inches in diameter with
distinct branches, a small madrepore with distinct branches, minute
madrepores and entrochite, large trochite and terebratule, the
latter varying from two inches to half an inch in diameter, large
entrochi, small fragments of minute trochite.

The limestone of Castle-town, Scarlet, Pool-vash, and Ball-
Fhallack is of a grey, or more generally of a dark grey colour:
the texture compact with some lamellar concretions. It is traversed
by slender veins of calcareous spar, and the dip-joints* are coated

* This is an expression I beg leave to introduce, and refer to the judgment of
Geologists. All the stratified rocks, but particularly those that have been deposited in
a rather horizontal situation, are divided by rents perpendicular to their direction,
corresponding therefore with their dip, into solids of dimensions more or less regular,
and usually similar in the same individual strata. Thus if the structure of a rock be
middle thick-slaty, it will divide itself spontancously into rectangular solids. When

.

Dr. BERGER ov ihe Isle of Man. 43

with crystallized calc spar. As the texture becomes more compact
it gets harder and of a more intense colour, approaching to black ;_
the fracture at the same time approaching to conchoidal. Iron
pytites dispersed through the mass is not uncommon, and when
scratched the smell of sulphuretted hydrogen is rendered sensible :
it burns very white, a circumstance which shows that the colouring
matter, being volatile, is of an animal or vegetable origin. In diluted
muriatic acid it makes a rapid and brisk effervescence, leaving
rather a considerable residuum. ‘The mean specific gravity, as
resulting from eight specimens, I found 2,704.

I am not aware that the dark marble-limestone cf Pool-vash
contains organic remains; I have seen stripes or veins of lamellar
and greyish limestone full of petrifactions alternating with the
darker variety that remained quite freed from those exuviz.

Thin and crumbling strata intervene between the solid strata of
limestone. ' They are called So/es in the Isle of Man, but generally
Partings among the miners.

The magnesian limestone in the places where it occurs, differs
enough in itself to induce me to give a particular description of it.
At Cass-ny-Hawin it is either finely granular or in lamellar and well
determined crystals. In the latter case it abounds with small ca-

vities filled with crystallized rhomb spar, the crystals of which

the thickness of the strata bears a more equal proportion to the length or respective
distance of the dip-joints, the natural divisions will come to a cubical form. If on the
contrary, the structure be thin-slaty, the rocks will rise spontancously under the form
cither of flags or slates. Whatever may be the shape of these natural blocks, their two
contiguous sides are constantly coated with the predominating ingredient of the rock
itself in its present state. Thus if the rock be quartzose, the coatings of the dip-joints
will be veins of pure white quartz; if it be calcareous, the coatings will be crystallized
calcareous spar, but unless we cause artificially the splitting of the rocks to take place,
secing bat a vertical or a horizontal section of the coatings, we are apt to adopt the
wreng opinion they are veéns instead of layers.

EQ

44 Dr. BERGER on the Isle of Man.

turn quite brown before the blowpipe. The texture of the lamellar
variety is not so close as that of the other. The specific variety of
the latter is 2.7777, and that of the first 2.820.

The magnesian limestone that appears along Castle-town river
from Ball-Fhallack towards Athol-bridge, is remarkable for a cir-
cumstance that has not as far as I can remember been yet noticed.
I mean the occurrence of quartz- nodules, sometimes above the size
of a pea and even of a bean. ‘The quartz is quite glassy, and the
concretions perfectly distinct, as if they had been water-worn and
subsequently imbedded in the limestone itself. This is not however
a conclusion I should adopt, as it seems to me that their existence
may be better accounted for by way of crystallization. The colour
of this magnesian limestone varies from bluish-grey to dirty-yellow ;
it makes a very slow effervescence with diluted muriatic acid, con-
tains rhomb spar either in lumps or on the seams of stratification,
and sometimes sparry iron ore; the latter before the blowpipe as-
sumes the character of a slag, which acts sensibly on the magnet,
whereas the bitterspath, though it turns brown, is not attractable.
The powder of the sparry iron ore of a brown colour efiervesces
briskly with diluted muriatic acid. The specific gravity from three
specimens is 2.81.

At Scarlet point the magnesian limestone has a yellowish-grey
colour, and is close in its texture. Patches of compact greyish
lime-stone are imbedded in it.

A dyke occurs in the limestone formation at Scarlet point, upon
which I shall say no more for the present, as it is a subject which I
intend at some future period to bring before the attention of the
Society.

In the little bay of Purl-Keill-Moirrey, the limestone on account
of its low retreating strata, imitates a sort of causeway, ending to-
wards the high land of Spanish head.

Dr. BERGER on the Isle of Man. 45

tt Amygdaloid.

Kaal-Farane and Cromwell’ walk, two places that separate Scarlet
point from the entrance of Pool-vash bay, present an unstratified
bed of amygdaloid that overlies the limestone itself.

The basis of the amygdaloid is a wacke of an earthy texture, dull
and of a greenish-grey colour, emitting a strong argillaceous smell
when breathed upon. There are in the powder a few particles that
‘effervesce with acids; the rock however fuses readily into a dark
olive bead that is attracted by the magnet. ‘There are in the basis
nodules of lamellar calcareous spar, lined on their periphery with
iron pyrites: the cavities they are imbedded in are smooth. When
by the action of external agents the more tender nodules have been
washed away, the rock partakes of the appearance of a slag, inas-
much as the basis is itself of a dirty red brown colour. The mean

specific gravity from three specimens is 2.592.

ttt Sandstone.

It occurs both under the form of fine granular and of conglo-
merate, of a red and grey-white colour, a little to the north of Peel
town on the shore, and also on Langness isthmus. In the first place
the strata run south-west and north-east, dipping north-west at 39°.
At Langness, as we approach towards the south point of the isthmus,
the conglomerate strata get higher and more thick-slaty. The ma-
terials entering into its composition are of a large size and much
loosened. Along the Castle-town River, the sandstone overlies the

limestone.

46 Dr. BERGER on the Isle of Man.

Il. Compound Rocks not in Situ.
(a) Primitive Rocks.

Granite.

I am aware but of two modes of explaining the existence of loose
blocks of rocks that are spread over the face of a country, what-
ever may be the nature of the blocks themselves, either to suppose »
theyare extraneous to the places where they nowlie, or that, howsoever .
unconnected they may appear to be with the materials that surround
them, they are nevertheless in their dirtb-flace, and have been dis-
integrated in sé/w, covering and resting upon solid and continuous
strata similar to themselves.

The only criterion perhaps applicable to the determination of
this important question is the following. When by farther inves-
tigations we have found that the hidden and continuous rocks are
similar to the blocks themselves, we may safely venture to say that
the latter are zzdigenous.

I am inclined to think that several of the loose blocks I am going
to describe, whenever they occur in any number, are in their birth-
places.

On the beach towards Aire-point there are innumerable loose
blocks of granite, one of which, rather large in its dimensions, I ob-
served on Aire head at the elevation of 271 feet. ‘They all in their
characters differ but little the one from the other. The rock is a
small-grained granite, composed of white felspar, quartz and black
mica, with a few incidental plates of the latter that are white. In
one of the specimens I collected, there is a rectangular piece one
inch in length by half an inch broad, of very minutely grained
granite with a predominance of mica.

Dr. BERGER o# the Isle of Man. 47

On the slope both of South Bor-roilva and Cronk-ne-liry-Lhaa,
in the southern part of the group of mountains, occur abundant
blocks of rather decayed granite, composed of yellowish and white
felspar turning to a state of earth, and disseminated plates of white
mica. ‘The texture is loosened to such a degree that large frag-
ments often yield under the pressure of the hand.

I traced blocks of the same granite in Glen-Moy, though the
bed of the stream is hollowed out in the grey-wacke formation.

The central stone of a Druidical barrow* in Kirk Ballaugh, is
a small grained granite of white felspar, quartz, mica, and a great
deal of hornblende.

t+ Mica-Slate.

A vast number of blocks of mica-slate exist on the slope of
Slieau- y-Carnane, another hill in the southern district of the group.
The quartz is finely granular, and has a silky lustre, which it pro-
bably derives from a superficial covering of tale. The plates of
mica are white and sparingly dispersed, sometimes crystallized.

I met at the village of Craig-neash with a large settled block of
mica-slate. The quartz is of a dirty-grey colour. The plates of

mica very few and falling into decay.

ttt Porphyry.

Very numerous blocks of this rock occur on the beach at Aire-
point. The basis is compact felspar of a flesh-red colour, turning

* All the Runic or Danish monuments so frequent in the Isle of Man, are (as far as
my observation has gone) of greywacke, without one single exception. The inscriptions
they bear are said to be written in the old Norwegian language: they are placed on the
edges of the stones, whereas the carvings are on their flat surfaces. The latter appeared

to me to bear some resemblance to the form of a snake,

43 Dr. BERGER on the Isle of Man.

yellowish and earthy when going to decay. ‘There is some horn-
blende disseminated throughout the mass: a few crystals of lamellar
and transparent felspar are also imbedded in the basis. ‘The rock
acts strongly on the magnet. It emits when breathed upon a sen-

sible argillaceous smell.

ttt Szenite.

I noticed but one block forming part of the Druidical barrow
already spoken of. ‘The texture is unusually close. ‘The two in-
gredients are crystallized and intimately blended together. The
felspar fuses, but not readily, into a transparent enamel which is
not frothy. There are besides in the mass some very minute crys-
tals, of an yellowish colour with a vitreous lustre. (Qu. garnets ?)

Specific gravity 2.932,
TTtttt Quartz.

Several blocks of white and greasy quartz, some of which contain
yellowish talc, form one of the circles of the Druidical barrow in

Kirk Ballaugh. Sp. gr. 2.536.

+tt++++ Garnet Rock.

This rock, of an unusual occurrence I believe, I found under the
form of water-worn pebbles on the shore at Kirk-michael, and as
this is no place for vessels to lie at anchor, I have no reason to
think they could have been taken as ballast and thrown away
where I retnarked them. The rock is highly magnetic, very hard
and tough. The mean specific gravity 2.967, the extremes being
3.085 and 2.846. The mass is of a liver-brown colour, with many
crystals of an orange or reddish-brown cast imbedded in it. Their

Dr. BERGER on the Isle of Man. 49

fracture is vitreous, but sometimes displays a sort of lamellar tex-
ture. The crystallized garnets are much less fusible than the basis
or massive garnet: the latter passes into a brownish bead. There
_are besides in one of the specimens some nodules of radiated zeolite
_or mesotype. In another the mass of garnet is blended with white
felspar.

At B. Wodden I noticed a large block of granular quartz with
garnets? and hornblende. The rock has a greenish-grey colour.
The fracture in the small is granular scaly. Another rock, related
to the preceding, is amongst the Druidical stones of Kirk Ballaugh.

(2) Lransition-rocks not in Situ.
+ Greywacke.

Between Ramsay and Aire-Point I saw in some heaps of stones
a number of pieces and blocks of greywacke, passing from large
grained into a small grained texture. The basis is greyish, the im-
bedded fragments are mostly nodules of white quartz with scraps
of a dull and black sort of slate, fusible into a whitish enamel, and
abraded plates or broad spangles of mica. The cavities that receive
the nodules of quartz when freed from them, appear smooth and
even. ‘The pieces of slate turn sometimes clayey, micaceous, and

of a brown ferruginous colour.

(c) Fletz-Rocks.
+ Limestone.

I shall merely speak here of some water-worn limestone pebbles
found in great plenty from Kirk-michael to Jurby point, though
no solid strata of this kind can be seen in situ. They are picked

VOLs If. 6

50 Dr. Bercer on the Isle of Man.

up and burnt for lime, which I was informed is preferred by the
northern farmers to the Castletown lime for manuring the land.
The colour of these pebbles is smcke-grey, the texture granular
with lamellar crystals; they are soluble with a brisk effervescence
in acids, leaving behind only an inconsiderable residuum. ‘They

contain organic remains,

Til. Staple Minerals in Situ.
+ Lead Glance or Galena.

Lead glance or galena is the most conspicuous of all the simple
minerals [ have to mention here. It forms three limited reposito-
ries, one at Laxey, the other at Foxdale, and the other at Brada
head.

No workings are carried on at present.

As to the precise time those mines were first opened there ‘is, I
think, some uncertainty. It would appear from the following
passage taken from Bishop Wilson’s History of the Isle of Man,
that there had been mines wrought at an early period; “ Mines of
** coal there are none, though several attempts have been made to
“ find them. But of lead, copper, and iron, there are several, and
** some of them have been wrought to good advantage, particularly
“© the lead ; of which many hundred tons have of late been smelted,
“* and exported. As for the copper and iron-ores, they are certainly
‘* better than at present they are thought to be; having been often
‘“* tried and approved of by men skilled in those matters. How-
** ever, through the ignorance of the undertakers or by the un-

Sy

Dr. BERGER on the Isle of Man. 51

** faithfulness of the workmen, or some other cause, no great mat-
** ter has as yet been made of them.” *

.These three repositories of lead lie in a grey-wacke formation,
with the exception before mentioned, when speaking of a small
grained granite found in the sinking of a shaft at Foxdale.

From the direction of the metallic veins, they seem to intersect
‘at a greater or lesser angle the greywacke-strata. The direction of
the metallic vein at Laxey is West South West, and East North
East; at Brada head, the shafts have been opened in a line that

keeps nearly the same direction.
The inclination of the metallic vein with respect to the horizon,

both at Laxey and Foxdale, is two yards in six.

* Page 449. Vol. I.
Since the above was written, a Jetter which I received from Mr. William Geneste of

Douglass, answering some inquiries I made, contains the following more precise infor-
mation on this subject.

‘¢ Mr. Fitz-Simmons, who is preparing to publish an extensive work on the ancient
History of the Isle of Man, states, that mention is made of the mines of the Isle, in the
time of Sir Stanley * Ist and 2d. Those at Brada, he believes, were first wrought ;
whether those at Foxdale were then opened may be doubted; those at Laxey were
opened and wrought by a mining company of Cumberland, about the commencement of

the last century.”
“¢ Mr. William Scott of Douglass conjectures, that the mines at Brada were wrought

previous to the discovery of gunpowder, from Feather-wedges (a contrivance for break-
ing asunder rocks, which is now performed by gunpowder) having becn found in those
m nes.”

Mr. William Geneste informs me farther, that he lately found in some books (titled
Charge of the Revenue) in the Duke’s office, in Douglass (called the Seneschal’s office)
“ that the Jast Earl of Derby had the mines wrought, paying the workmen at the rate
of £3 manx { per ton, for the ore (lead) raised. In the year 1709, he paid the
miners for about 70 tons; from the year 1709 to 1713, about 30 tons yearly. A new
smelting house was built in the year 1711. The working of the mines was totally

suspended about three years ago.”

* The first Sir Stanley appointed King of Man, was by grant from King Henry 4th, im the year 1497.
+ The manx money is to the British in the proportion of seven to six,

eg

52 Dr. BERGER on the Isle of Man.

The breadth of the main metallic vein at Foxdale, the partings
being included, was computed to be full six yards.

In all the three places the vein appears adherent to the contigu-
ous rock, whether it be greywacke or small grained granite.

At Foxdale a cross metallic vein of lead also was found running
a few points from the North and South, that is to say, intersecting
the main vein at a great angle; at the junction or counter, the ore
grew richer, and many fwockings, shods, or balls occurred. The
cross course was as fertile as the main vein itself, if the information
I received be correct. Its inclination likewise, with respect to the
horizon, was fully as considerable.

According to Mr. Wood’s statement, it would appear that the
ore at Brada-head was chiefly sulphuret of copper. *

I shall now enter into a more minute examination of the several

substances which accompany the lead-ore at those three places.

Laxey-Mine.

The galena of Laxey, when pure, is possessed of the lustre cha-
racteristic of common lead-ore. Its specific gravity is 7.652. +

Sex octogonal carbonat of lead, along with efforescent and fibrous
carbonat of copper, are the various minerals attending the lead-ore.
A button of copper may be easily obtained by exposing the carbo-
nat of copper with borax to the heat of the blowpipe.

The vein-stone or Rider, is a greywacke breccia, composed of
pieces of silky-greywacke, quartz, and bitterspath, with much
brown blende.

* An Account of the Isle of Man, by George Woods, London, 1811.
+ The Bishop of Landaff states the produce in silver on some Manks ore, to have
amounted to 20 ounces ina ton of lead. By some of the workmen it is asserted that
the quantity of silver has occasionally amounted to 35 ounces in the ton.
Watson’s Chem. Essays, Vol. 3. p. 328. 7th Edit.

Dr. Bercer on the Isle of Man. — 53

The walls of the vein are formed of silky greywacke with pieces
of bitterspath, and a few flesh-red and lamellar crystals of calc spar.

Foxdale Mines.

The specific gravity of a rather impure specimen of lead-ore, I
found 6.095.

Amongst the stony substances that fill up the vein, I remarked
the following varieties.

A semitransparent and bluish ealcedony passing to white ; it is
zoned, but the zones are not apparent without the assistance of a
magnifying glass; common galena and some iron pyrites are dis-
seminated throughout the mass.

Sometimes the calcedony verges into white quartz, blended with
sparry iron-ore scarcely effervescent with nitric acid, turning almost
black before the blowpipe and acting very powerfully on the mag-
net. It is likewise accompanied by iron-pyrites.

The sparry iron-ore in larger lamellar crystals appears of a dark
colour, and contains so much of iron as to act by itself on the
magnet. Galena adheres to it.

The greywacke that forms the South side or cheek of the vein,
is of a greyish colour with a silky lustre; the common lead-ore
adheres to it. In a granular and drusy quartz filling up the vein,
I noticed a few garnets.

Brada-head Mines.

The specific gravity of a less impure specimen of lead-ore than
that of Foxdale, was 6,622. .

The principal vein-stone through which the ore is disseminated, .
is a yellowish granular quartz that includes iron pyrites.

54 Dr. BERGER on the Isle of Man.
++ Dun Earth.

On the part of Dun How where the granite appears at the sur-
face, and in a natural excavation, but which I believe has been en-
larged by art, there is a brown sort of powder, said to be used by
the inhabitants for the cleaning of plate.* It feels rather soft to
the touch; does not effervese with acids; fuses fer se, but not

readily, into a greyish enamel.

ttt Marl.

All over the curragh, and on the beach also at Kirk-michael, a
substratum of marl several feet deep, underlies a light and sandy
soil. 7

B.Vodden marl.

Calcareous marl of a light flesh colour, soft enough to be cut
with a spade, feels almost greasy to the touch, basis extremely fine,
texture dull and earthy; no other discernible particles in the mass
but very small spangles of white mica; adheres to the tongue strongly,
is soluble with a brisk effervescence in diluted muriatic acid, leaving
a considerable residue readily fusible into a slightly magnetic olive
enamel.

Kirk-Michael-beach.

Calcareous marl of a grey-reddish colour, not so soft as the pre=
ceding, owing to some sandy particles immersed in the basis ; leaves
in diluted muriatic acid a more abundant residue, not so easily
fusible ; the enamel of an olive-green colour.

There is another variety of calcareous marl in the same place of
an ash-grey or of a dun colour.

* Mr. Wood’s account of the Isle of Man.

;

Dr. BERGER on the Isle of Man, 55

The farmers in the northern part of the isle make use of the
above marls, particularly of that from B. Wodden to manure their
land. According to their expressions, marling strengthens the land,
whereas lime purges it, two different ways of obtaining the same
end, the one by adding what is supposed to be wanting to the land
to make it good, the other by getting rid of what is reckoned to be
hurtful to it. Marling once in twenty years, is considered as suf-
ficient to keep the land in good order under a proper course of
crops: eight or nine of which may be taken successively immediately
after the operation.* —

One hundred and fifty tons of marl are computed to be necessary
for an acre of land. The expences, supposing the carriage not to
exceed a mile, will amount to six pounds sterling. The cost of
liming, a practice chiefly used in the southern part of the isle, is
nearly the same. Ninety bushels of lime is the quantity allowed for
covering an acre of land.f Sea weeds previously made into a com-
post, are also much used in the south district of the island. The
marl by lying at the surface sometimes becomes considerably
lighter. When dung mixed with hot lime is put upon a marled
ground, the fermentation that ensues produces a very surprizing
effect.

ttTtt Coals.

It is unfortunately more as a warning against the delusive ac-
counts that have circulated abroad with respect to the discovery of

* Mr. Curwen’s Agr. Report, p. 153.

+ In Mr. Thomas Quayle’s ‘“‘ General View of the Agriculture of the Isle of Man,”
it is said that from 1807 to 1811, 84,992 barrels of lime have been sold from the several
kilns fitted up for that purpose in the south-eastern part of the island.

56 ‘Dr. Bercer on the Isle of Man.

coals in the Isle of Man, that the present topic is introduced here,
than to prove their real existence. ‘To preclude however, farther
investigations and observations on the score that coals cannot pos-
sibly be discovered, would be presumptuous and imprudent, but
nobody has yet, that I am aware of, substantiated their existence,
The only serious attempt I believe to find coals in the isle, was
made at Derby-haven, many years ago by a speculator from Cum-
‘berland.* After having gone to a certain depth, not finding traces
of them, he gave up the search as fruitless,

While I was in the isle (June 1811), two or three spots in the
north-western part, were particularly pointed out to me as places
where coals did actually appear, or were cropping out. But when
the matter was strictly enquired, the reports turned out unfounded.+
While on the subject of coals, I shall beg leave to present here an
account of the coals imported into the Isle of Man from Whitehaven
in the county of Cumberland, arranged under the form of two
series; the one comprehending ten years from 1781 to 1790, the
other including twelve years from 1798 down to 1809. Both
étatements may be relied on, the first was inserted in a scarce book,
the second in a late and though local, most respectable publication
often already referred to.§

The increased consumption of coals in the Isle of Man will not

* Mr. Curwen’s Agr. Report, p. 112. .

+ During the whole of my excursion through the isle of Man, I had the pleasure of
being accompanied by Mr. ‘Thomas Scott, brother to the much celebrated Scotch Poet of
that name. Mr, Wm. Geneste, a well informed gentleman, and a native of the isle,
joined our party while we were examining the southern part of the isle. From the twe
above mentioned gentlemen, and generally from all those to whom I was introduced in
that island, I received the most ready and kind attentions as well as much information.

{ The Report of the Commissioners of Inquiry for the Isle of Man, 1792.

§ Mr. Curwen’s Report of the Agricultural Society.

Dr. BERGER on the Isle of Man. 57

so much show an increase of population* as an increase of com-
forts amongst the inhabitants at large, the consequence of a more
extensive system of cultivation, and the diminishing number of
fishing boats that used to take out in the months of harvest upwards
of 2000 of the most active inhabitants of the labouring class.+

,_ An account of the coals imported into|| An account of the coals imported into
the Isle of Man for ten years, ending the\|the Isle of Man within twelve years ; viz.
5th January 1791. rom the 5th January 1798, to the 5th

July 1810.

Years. Chaldrons.t | Bushels. Years. Chaldrons. Bushels.
1781 9728 18 1798 5559 18
1782 2652 Q7 1799 5258 9
1783 2853 18 - 1800 5693 ras
1784 m 3236 9 1801 61350 0
1785 3585 1802 6379 QT
1786 35796 18 1803 7041 16
1787 3379 18 1804 T7244 97
1788 8719 o7 1805 68238 92
1789 3659 18 1806 6937 35
1790 A321 9 1807 TAGL 25

1808 8807 A
1809 9020 A
Total 33932 18 Total 82357 34

——

As to the great advantage the inhabitants would derive, were
coals to be discovered on their isle, I should entertain some doubt,
when I consider that the inhabitants of the city of Dublin have
their coals put into their cellars at less expence than the persons
who live in the County of Cumberland, twelve miles distant from

* The Census of 1792, returned 28,000 inhabitants nearly, but Mr. Curwen observes
that all the estimates of the population of the Isle of Man published at different periods,
have been much overated. He hardly thinks it can exceed 23,000 or even so much, viz.
6000 inhabitants at Douglass, 2000 at Castle-town, 2000 at Peel, and 1500 at Ramsay,

besides 11,000 spread over the island, considering how few villages there are, and how
small their sizes are.

+ Ibid.
+ A chaldron is a measure of 36 bushels.
Won. 1.

58 Dr. BERGER on the Isle of Man.

the coal-pits of Whitehaven. In the present state of affairs in the
Isle of Man, any thing, I should apprehend, that would have a ten-
dency to diminish the number of hands that may be employed in
extending the culture of the land, would rather operate as a check
on the farther improvement of the island itself.

IV. Szmple Minerals not in Situ.

It is very doubtful whether the minerals mentioned here, do
really belong to the Isle of Man. They made part of a collection
that was in the possession of the late Lord Henry Murray, and
were obligingly communicated to me by Mr. Wm. Scott, the Col-
lector of the Custom-house at Douglass. Many of them had no
labels afixed to them. The informations I received concerning
them, I shall here communicate. .

Wolfram, either in detached pieces or fragments, or adherent to
quartz: supposed to have been found in loose pieces at the surface
of the ground, on the slope of South Bor-roilva, two miles from the
mines of Foxdale.

Tin-Stone. Great doubts may be entertained as to its occurience
in the Isle of Man.

Earthy talc. Said to have been found on Mount Murray.

Could we depend on the locality of the earthy talc here, its oc-
currence would rather favour the possibility of that of tin, as the
two substances often accompany each other.*

I consider myself warranted to deduce the two following con-
clusions.

1. That it appears extremely probable that at some period or

* Jameson’s Mineralogy. Vol. 1. p. 431,

Dr. BERGER om the Isle of Man. 59

other, a subsidence to the south of the whole chain ‘ en masse”
took place, which caused the three dislocations referred to in the
course of this paper, and which are nearly at right angles with the
direction of the chain itself.*

2. That the same subsidence may be supposed to have produced
the general dip of the stratified rocks to the southwards.

¢

* At Spanish head, on the spot called Kione-Gogan, (a head resembling a noggin) the
strata have been rent asunder in two contrary directions. The contiguous sides being
now several yards distant the one from the other. The principal rent runs north and
south, the transverse one east and west, presenting an assemblage of four large square
compartments.

Is this referable to the great subsiding pointed out above? ormore likely, to the cause
that gave origin to the metallic veins, and particularly to the cross course at Foxdale?

The grey-wacke slate of Spanish head splits naturally into long beams 12 or 15 feet
long, fit for mantle-trees, and strong enough to bear the weight of the highest ace of
chimnies.—Wilson’s History of the Isle of Man.

H 2

60 Dr. BERGER on the Isle of Man.

Temperature of several Springs in the Isle of Man, to deduce by
approximation the mean temperature of the climate of that island.

Elevations in feet above | Temperature of
the level of the Sea. the Springs.

Names.

——

Farane-y-phing ; pronounced ‘ 1964 feet 45° + Fabr.
Faraan-e-fing .. -° . «+ «
On S. Bor-roilva slope é undetermined ; 45° 3
Near to the top of Slieau-y-Carnane 960 by paar ee 46°
Cass-ny-hawin, Head of the river 422 wile AGe
St. Patrick’s well; Kirk Lonan undetermined A7e i
=pave between Glen- Pee and ‘ ideeceuieed AT°
en-Laxey . . : aes
South-Quay Douglass | 6 ia a A8°
Ditto : Oi +> Steal War, A8°
Pigeon-Spring, 0 on Walberry How undetermined Ase 2
Hampton-house . is ius Age
Ditto . Th 49°
Vinch’s well, Douglass-bay | debe AQ? 2
Kirk St. Ann’ Glebe . 235 5iP
Hamilton-bridge 220 . 50°
Fleshick bay. Buns! 50° 2
Kirk Lonan’s Glebe . ; Ne 50° +
Burchet’s well; Calf of Man undetermined 50° £
Creggawell . .. . uudetermined 50° 4
Calf spring tte a ord es x
Mill-town spring 5 undetermined 51° 2
South-quay, Douglass OF tee 51° t
Langness spring. ee EO ee 51° s
Ball-Fhallack spring , pronounced deietoca Se
Balla-Salley, the royal residence mb Staal oe
South-quay Douglass 0 hee en 520
Balla cregga’ How . | undetermined 5Q°
Douglass-bridge, on the road to ae
Castletown : 0 52° 3
Flax-mill Spring undetermined 52° £
Fyshtel . . ; 59° £
Parl. Keill- Moirrey, Port- le-Mur ray 0 52° 3
Mr. Gurley’s well; CalfofMan . | 206 . 53°
Kirk-Oncan . : : 904 . 54° 0
Mean 49.99

———— Gaeu——— eees

Dr. BerGer on the Isle of Man. Gl ©

If we rate at 50° Fahr. the mean annual heat in the Isle of Man,
we shall have it differing from that of London merely by 1° fora
difference of 2°,41’ of north latitude. Comparing the same annual
heat of the Isle of Man with that of Edinburgh, we shall find it
surpassing the latter by 2°, 2’ Fahr. though the latitude of the Isle of
~ Man be only 1°,45’ more to the south than that of Edinburgh.

‘ ‘The mean temperature of the month of June, 1811, in the Isle
of Man, deduced from 128 thermometrical observations, I found to
be 55°.81’ Fahr. but as most of the observations were made on
the tops of mountains, the mean must be lower than it would have
been had the observations been made in the plain. Thus I find
that thirty-nine thermometrical observations (out of the series of
128) made by the sea side give for the mean 57°.37’, which when
compared to the mean of 22 thermometrical observations made at
the apartments of the Royal Society on correponding days, is
deficient by 4°.35’. The London mean being 61°.72’, and that
of the Isle of Man 57°.37’. At Belfast the mean is 64°.90’ Fahr.
The mean height of the barometer for the same month of June,
1811, is as follows.

London - - 30.13295

Isle of Man - 30.11895

The frosts are short in the Isle of Man, and the snow does not
lie long on the ground, especially near to the sea. I was informed
by the Rev. Mr. William Fitz Simmons, that on the top of Snei-
feldt it does not remain longer than two or three weeks, from
Christmas generally, to the second or third week of January.

62 Dr. Bercer on the Isle of Man.

Mountains and other Places in the Isle of Man, together with their heights,

*

determined by the Barometer: * the whole arranged alphabetically,

with References to the Numbers in the Map.

Number| Elevation in feet

Mame and Situation. Signijication. in the | above the level of
Map. the Sea.
BT 27 Li lea el rae ES lip ellie ies i I ioe, 1 271
Aire-how . . FETE RTY YT SED TRL * OG 2 Isst
Aire-brow (sea- -mark) cl Te, te ee geen 2 en ae 106

MIMGE EERE lee et ele ste CeCe A5 1452

Balawin Valley bead...) <3 ew a we Peer ei
‘Balla-cragea how tie tug) . Rocky farm... . AL 412
Balla-chirrym ; about the :

middle of the range. Dry TALGh fey] <2 Gees =) epee’ 177
Balla-gawn ; about 2 Pofa mile

south of Kirk- Michael . :
Balla-stowell . . . . .| Stowell’s farm . . . ll 500
Balla-wodden; about ! mile

south of Kirk-Andrew
Banks-how .. . : ; 25 392t
Beary mountain. -_ t Beiree, tops of hills ? ; 27 900
Bein-y-phot . . . . . .| The Pot mountain . . 20 1750
Bool-benney ; highest ridge

on the road from ( Castletown

to Douglass, between the

6th and 7th mile-stone . .| a place where furze grows} 39 538
Bor-roilva, Baroil, Barroole,

or Bourrul ; North Wild mountain . . . 12 1850+
osedeleehs suvecesescceediieaate Sowele| !LO0S FDA TH, 54 36 1545
Brada-head ; LTT OF a Pie AT 707
seve eveserereneenee low point, si en ot cee AG 412

Burchets’ Her mitage ; highest
spot in the Calf of Man Uy cde a he ack pene AQ A61

Cairn . . BCE US NG) SR RE AT pig ee o4 1430
Calf of Man; Mr. Gurley’s
HOUCOMT AEWA coms a tk Gk ek Sane | 206

“* For the calculation of these heights I have made use of Professor Leslie’s Sliding Scale.
+ In the trigonometrical Survey, North-Berule, 1804 feet.

Dr. BERGER on the Isle of Man, 63

. Number, Elevation in feet
Name and Situation, Signification. in the | above the level of
Map. the Sea. °

Caiait Tail Cece ha bet ea aan eek. of the head? } 10 984
Gardens 2 SeO%S. oxee: 2 ERY Ue . 96 1535
@arrick-bill 3) 0). RH poole tilt 6 Rey 6 627

Cass-ny-hawin; taken at the
head ofthe river. . . .| The foot ofthe river . dual aed 429

Clarke’s-hill ew RIES NS fi 889

Clay-head i is the hill that lies
N.E. of Banks how

Cloven - stone; a Druidical
monument, 1! mile from
Laxey, on the Douglass
Teade) #:

Corrin’s tower? highest point ;
of Peel-hill . . . Ne SoBe a cel@ lan Wes le. Sica e 54 675

Crammag-bridge on Sulby e
river. BS a era's Shake coe ct ohh cits vt ees A52

Cregneish or Craig-neash .| Neash, rock oobsids Bly Men eo Taree

Cr onk- dhoo' WEL. By ae) aa a 13 705

Cronk - ne - liry- Lhaa, or

Cronk-ny-irrea-Laa. . .| Break of day hill . . 37 1445
Watershed, between Cronk- .

ne-liry-Lhaa and 8S. Bor-

roilva on the road from

Castletoww¥ Peoltown- |||... - 50 see te atte es | 9898
Six mile-stone betweenCastle-

town and Peeltown; lower

limit of the Turbary in that

part of the island 3 eRe edie bie Movies Na motiMh’s ta. le Gee
Cronk-Ouyr, or Cronk Owre Ouyr dun colour . . 3 186

Owvre, brown

Cronk-Shamrock, or Primrose

Pale et ve ee eer Our MIM Ob pents oI 5 2732
PVOuUetass- CMe ee Moe bln oa oe es we ns AQ 315
Doug TAseeNOW pee eo La ee gas) ol Me Al A66
Dun- ao EDEN ps hom OME Gls, Ae CaN ae Ba 15 757
Dun-bridge; at the foot of Sines

Dun-how

Foxdale or Foxtal mines,
CSREEE, REO LHP UY PO RA bs or int oh ah 8H 4 on ale 32 346

Glen-roy ; at the Rev. W. Fitz
Simmons’ house; one of
the highest habitations in
the island 27°20"... SRA 4 RO I RS AGE

64 Dr. BERGER on the Isle of Man.

Number | Elevation in feet
Signification. in the | above the level of
Map. the Sea.

Gob-y- Sclagph, or Ghub-y-| Ghub is point; canton :

Name and Situation.

Scioot . . ye .| spouts are called Ghub-ny- 1820
spoots 2
Gob-y-vullea, Ses vulley

or voilee : -| Gob, a beak ;
vully, a height 8 TATE
vollee, eye-brow

Greebah or Greebey, North} Grice, grey . . . . 28 1478
esitetiencawaapatioe meer wes Souths orglnternsivnree tend 29 1355
Hlampton House; about 2!

miles from Douglass, on the

Castletown road . " AOT
Ilamilton bridge 220
Jurby point 117
Kar raghyn, or Karaghan ; 31 1520
Kennish’s Hill. Z 4 508
Kione Gogan ; the hill N. W.

of Spanish head 5
Kirk Onchan 204
Kirk Lonan; Keak Dechert

in the map 365
Kirk St. Anne; Kirk St. Ag-

nes in the map Su ke 235
Laxey mines. haw se ‘ ogo oe se ppc. Coe
Laxey-valley alas). ee .-4,| Dae ~waay or waag j 1964

Saimon-bay werk?

Maughold Head... sk? eee) = 14 AT5

Middle hill, about 14 mile
from Douglass, on the
Castletown roads. Ae ee 2 al Re fg! | shee

Mount Murray; the hill be-
tween K. Braddan and K.

Marrown .. . -| Black hill «foe 2 TAQL

MommtePellier) re aoe ee ge af

Mullach Oure;

Southern parcaay 6) i Oe. iar es 23 1540
saeadestetenesicwss Northern partof| . .. iat

and lower limit of the

POY Eee Rie eB od Ge cle a gs mon Ng 23 1378

Mullin-y-chlea . . . . .| The concealed mill .

Mullin-y-chleigh . . . .| the millonthe Boundaries ail 98

Mullin-e-Cleii . . . . the playing mill .

Dr. BERGER on the Isle of Man.

Number
Name and Situation. Signification. in the
Map.
Peel-Hill, high point . 34
sieghietotes. low point 33
Sartyl). . “ . 30
Slieau-Aalyn, or Aalyn, heauiiel
oo : .| The Witches maounitair
Serapees sions . North Sh eh ie BUH 35
rasta SPOOL? al OK, tier) eet wo ae) te 35
Sliean-Chiann. . ...| the Lord’s mountain . 9
Slieau-dhoo .)}the black mountain. 18
Slieau-Lhearn ..}the broad mountain . 21
Slieau-y-Carnane, or
Slieau-y-Carnaane . ae 38

Head of Land, or over hanging
cliff between Slieau-y-Car-
nane and Cronk-n he-Liry-
Lhaa .. :

Snei-feldt, Snioghtey, or
Snawble ; great :

Sicuigeoeee. little... ;

Boggy Table-land, N.W. o
Sneifeldt

Upper limit of the ante land,
betrveen Little Snei-feldt
and Slieau-Lhearn

Spanish-head

St. Anne’s head; low point .

St. John’s chapel the Tinn-
wald't . : 2

penow=telde: fies) 620 3 16
O19SS. 02 TD ¥ 17

.
°
e

Walberry How. . .
Watershed between Peeltown
and Douglass ,
Watershed between Pu ae Keil-
Moirrey and Port-Erin. .| The harbour of St. Mary’s
church, Irish Port . oy al

* Snea-fell, from the trigonometrical Survey, 2004
Snafield, from Bishop Wilson 1740

+ Tinnwald from the Danish word Ting,
on an artificial mount, near the middle of the island, in the open air.

a court of justice, and wald, fenced.

65

Klevation in fect ;
above ihe level of
the Sea.

7024

9774
1068
1215
1533

990

S772

2016
; 1990
1775

mean
2000 *

154

9372
550
126%

It is held

UI. On the Granite Tors of Cornwall,

By J. Mac Cutzocu, M.D. Chemist to the Ordnance, and Lecturer om.
Chemistry at the Royal Military Academy at Woolwich.

/

I Have the honor of presenting to the Society three drawings:
which I have selected from my portfolio, for the purpose of
illustrating the changes which the influence of time and weather
produces on certain varieties of granite. The subjects are alk
chosen among the granites of the west of England ; and that I might
at the same time preserve memorials of circumstances which aré
remarkable independently of their geological interest, I have taken.
two of my examples from places which have called forth more
admiration from the common spectator than even from the phi-
losopher, and which form two points of attraction for the curious’
or idle who annually visit Cornwall. Not only indeed have idle
curiosity and ignorant speculation busied themselves in accounting
for phenomena which many of the vulgar have deemed little less
than miraculous, but learned antiquaries have tortured their iny
ventions and have: constructed religious systems for the purpose of
explaining these very simple and intelligible natural appearances,
by the rites of a mysterious and Druidical worship. I trust I shall
be pardoned, if while I deduce from these facts the geological
consequences which depend on them, I likewise give a more .
particular detail of the appearances themselves which have excited
so much of the attention of all visitors, é

2

Dr. Mac Cuxtocu on the Granite Tors of Cornwall. 67

The Logging rock (Pl. III.) is situated on a peninsula of granite,
in the parish of St. Levin, which stretches out about 200 yards into
the sea, its isthmus still exhibiting remains of the ancient fortification
of Castle Trereen. The mass of granite which forms this peninsula
is split both perpendicularly and horizontally by numerous fissures,
and is thus divided into a number of cubical and prismatic masses.
A similar disposition in all the rocks of this shore-has caused them
to assume those singular forms which are sojconspicuous at the
Land’s End, The appearance of the perpendicular fissures on
approaching the Logging rock from the isthmus is so remarkable,
that we might fer a moment fancy it the effect of stratification, as
geologists have in other instances been tempted to suppose. Crys-
tals of tourmaline are found in this granite, which has supplied the
cabinets of collectors with so many specimens as to be too well
known to need description.

The general height of the mass of rock on which the logging
stone is placed varies from 50 or 80 to 100 feet, and it exhibits
almost all round a perpendicular face to the sea. It is divided into
four summits, on one of which, near the centre of the promontory,
the stone in question lies. If the whole peninsula be viewed
laterally, the conformity of the rocking stone to the mass on which
it stands and to the other small stones which crown the summits,
is such that the eye cannot detect it, so perfectly it seems in its
place. It is in the front view only that it appears detached, as if
occupying an accidental and not its natural and original place. Its
general figure is irregularly prismatic, and foursided, having at its
lower part that protuberance on which it is poised. So inclined is
the plane on which it rests, that it appears at first sight as if a slight
alteration of its position would cause it to slide along the plane into

the sea, standing as it does within two or three fect of the edge of
12

68 Dr. Mac Cuxiocn on the Granite Tors of Cornwall.

the precipice. The breadth of the apparent contact between the
plane and the centre of motion of the stone is about a foot and a
half. As this support is curved only in one direction, being of a
cylindrical and not of a spheroidal figure, the motion of the stone
is consequently limited to a vibration in one direction, which is
nearly at right angles to its longest dimensions. The general
aspect of the stone would scarcely enable a cursory spectator to
assign the reason of its vibratory power, as from the point of view
in which it is usually seen, the centre of gravity would appear
placed rather above than below the centre of suspension. It is said
that the motion is now much more limited than it has been within
the memory of those who live near it; a circumstance rendered
very probable by the progress of disintegration at those points of
contact where water can be detained. A continuance indeed of the
very process to which it owes this property, must ultimately destroy
its motion if it operates by bringing a wider surface into contact,
thus defeating the enlarged vibration which would otherwise follow
from the increasing distance between its centres of suspension and
of gravity. A quantity of loose quartz gravel may be generally
found near the points of contact, marking the progress of this
disintegration.

In the trials which I have at different times made on it, the
greatest force that three persons could apply to it was sufficient to
make its outer edge describe an arc whose chord was 3 of an inch
at 6 feet distance from the centre of motion. When suffered to
return it vibrates for a few seconds before it falls again to rest. A
force of a very few pounds is however sufficient to bring it into a
state of vibration, and to maintain a visible motion. Even the
wind blowing on its western exposed surface produces this effect in
a very sensible degree. It is the largest of its kind at present

—_

Dr. Mac Cutiocu on the Granite Tors of Cornwall. 69

moveable in Cornwall. I made an attempt to ascertain its weight
by measurement. It may without much inaccuracy be resolved
into two frusta of pyramids, on a common trapezoidal base, their
union forming an irregular four-sided prismatic figure, 17 feet in
length, and 321 feet in circumference about the middle part.
Comparing the solid content of the stone, as deduced from this ap-
" proximated measurement, with the sp. gr. of the granite of which it
is composed, the weight appears to be 65,8 tons, a deduction if not.
precise, sufficiently accurate at least to satisfy general curiosity.

It would be superfluous to combat the opinion of those, who like
the Iconocelasts of Cromwell’s time, in the instance of the rocking
stone of Merramber, fancied these stones to be the productions of
art directed to religious purposes. The accidental coincidences
which give rise to their formation, will be considered when I have
reviewed the other tors which are the subject of this paper.

The Cheese-wring, (Pl. 1V.) of which the second drawing is a
representation, occupies the highest ridge of a hill to the north of
Liskeard, one of that collection of hills which decline from Rough-
tor, and Brown-willy, and which form the most elevated part of
Cornwall. The summits of all these hills are covered with granite
cairns in different states of ruin and disintegration, and their sides are
strewed to great distances with the bowlders which have fallen from
them at different times.

The migration of stones is here readily to be traced upon a scale
easily comprehended The granite of which these hills are com-
posed is well known, and has been often described.

It is not far from the Cheese-wring that the first traces are found
of the asbestos and steatites which are known to be so abundant and
conspicuous in the parish of St. Cleer.

The inspection of the drawing will show that this remarkable cairn

70 Dr. Mac Cuttocu on the Granite Tors of Cornwall.

consists of five stones, of which the upper ones are so much the
largest as to overhang the base on all sides. The collective height
of the whole pile is about 15 feet, from which compared with the
drawing, the sizes of the different masses composing it are easily
appreciated.

The rounding of the angles in this instance, has proceeded in some
parts so far as almost to give an appearance of convexity to the
touching surfaces from certain points of view; a state which once
attained will speedily compel the Cheese-wring to join its former
companions in the plains below. It is evident enough, that the cairn
of which this is now the only remaining memorial, has been of
considerable dimension.

An abstraction of its support, occasioned probably by the gradual
disintegration and sliding ofthe summit of the hill, has permitted
the lateral parts to fall away, leaving, in its present whimsical position,
that part which happened to be best poised. It is unnecessary to
suppose that the chisel of Druidism has been employed to reduce it
to an image of Saturn. Natural causes are sufficient to account for
its appearance. Dr. Borlase reports that the upper stone of this pile
had been a logging stone, and thus attempts to strengthen his
Druidical system. It would doubtless be a great improvement on the
statue of Saturn, to be furnished with a moveable head, but an in-
spection of the upper stone is sufficient to show that its centre of
eravity is placed much too high to admit of the conditions requisite
for the production of that effect.

The last of these tors which I have chosen for the purpose of
this illustration, is the Vixen Tor on Dartmoor. (Pl. V.) There is
nothing extraneous or traditional connected with this rock to render
it an object of interest in any other point of view than that for
which I have selected it.

The granite of this county is known to be in general split by fis-

Dr. Mac Cutiocn on the Granite Tors of Cornwall. "71

sures in different directions, but most commonly tending to the per-
pendicular and horizontal. By those it is divided into masses of-a
cubical and prismatic shape. Of the exceptions to this rule there is
one among many other instances, in Shaugh rick near Plymouth, If
we examine a rock of this kind near the surface of the soil, we shall
find that the fissure is a mere mathematical plane, separating the two
‘parts, and that the angles are sharp and perfect. If we turn our
attention to granites which from their greater elevation above the
present soil appear to have been longer exposed to air and weather,
we shall find, as the first step to change, a gentle rounding of the
angles, such as is exhibited in the drawing last cited, the Vixen
Tor. By degrees the surfaces which were in contact become sepa-
rated to a certain distance, which goes on to augment indefinitely.
As the wearing continues to proceed more rapidly near the parts
which are most external, and therefore most exposed, the masses
which were originally prismatic acquire an irregular curvilinear boun-
dary, and the stone assumes an appearance resembling the pieces
which constitute the Cheese-wring. If the centre of gravity of the
mass chances to be high and far removed from the perpendicular of
its fulcrum, the stone falls from its elevation, and becomes constantly
rounder by the continuance of decomposition, till it assumes one of
the various spheroidal figures which the granite bowlders so often
exhibit. A different disposition of that centre will cause it to pre-
serve its position for a greater length of time, or in favourable cir-
cumstances may produce a logging stone.

It is not necessary to call in the aid of long continued friction or
distant transportation to account for the rounded form of these
granite bowlders. ‘The changes which they undergo in their places
of rest, by their more rapid disintegration at the angles than at the -
sides, are sufficient to prove that this spheroidal shape may be pro-

72 Dr. Mac Cutrocu on the Granite Tors of Cornwall.

duced by chemical action of air and water, without the necessity of
any mechanical violence. However difficult it may be to give a
very satisfactory account of this peculiarity, the fact is undoubted.

There is less difficulty in accounting for their separation from each
other at their surfaces of ccntact, after the fissure has been formed,
if we consider that they are liable to lodge water where the surface
is horizontal, or to detain moisture where it is vertical.

That the wearing of these granites on the surface arises from the
action of water, will be evident on examining the stones themselves,
and the result of their disintegration Wherever a stone is disin-
tegrated by the most usual process, the oxidation of the iron
which it contains, a change may always be observed to have taken
place from the surface downwards to a more or less considerable
depth in the stone. Sometimes even the whole mass of rock will
appear to have undergone this gangrenous process at once, and to
have become a bed of clay and gravel. But in the case of the
granite now under view, it is evident that the change is merely super-
ficial, and that no process of oxidation has taken place. Indeed,
many of the varieties of which the mica and felspar are nearly white,
contain so little iron that they are hardly subject to decomposition
from this cause, however much they may, in such particular cases as
that of the St. Stephen’s granite, resolve entirely into gravel and
porcelain clay. The most satisfactory proof however that the mere
agency of water is sufficient to disintegrate this granite, is presented
by those objects which perhaps in consequence of the Druidical spe-
culations of Dr. Borlase are best known by the name of rock basons.

On the flat surfaces of these stones are frequently to be observed
excavations, assuming some curved figure with rounded bottoms.
Occasionally they are circular in their boundary, and as regularly

spheroidal internally as sf they had been shaped by a turning lathe.

Dr. Mac Cunzocn on the Granite Tors of Cornwall, 73

They are of various depths, and they may be sometimes observed to
communicate with each other. Their artificial appearance was suf-
ficient to convince of the truth of his system regarding them, this
strenuous supporter of a worship which must on his hypothesis have
required a priesthood sufficient to exclude all other population, if
every rounded cavity which the granite exhibits was a pool of lus
tration.

Their true origin is easily traced by inspecting the rocks them-
selves. On examining the excavations, they will always be found
to contain distinct grains of quartz and fragments of the other con-
stituent parts of the granite. A small force is sufficient to detach
from the sides of these cavities additional fragments, showing that a
process of decomposition is still going on under favourable cir-
cumstances. ‘These circumstances are the presence of water, or the
alternate action of air and water. If a drop of water can make an
effectual lodgment on a surface of this granite, a small cavity is sooner
or later produced. This insensibly enlarges as it becomes capable of
holding more water, and the sides as they continue to waste, neces-
sarily retain an even and rounded concavity, on account of the uni-
form texture of the granite. In time, the accumulated gravel is
blown away by the winds, although in the deeper hollows it may
often be found forming considerable accumulations.

The same solubility of granite in water, (to speak generally) is the
cause of that wasting of the surface which these rocks undergo, and
to which I have before attributed the enlargement of the vacuities at
the surfaces of contact, .and the separation of the prisms into detached
masses.

We need not hesitate in admitting the solution of granite in water
to an extent capable of producing this effect of disintegration, since we
know that silex is soluble in that fluid by natural means, however we

VOL. Ii. K

74 Dr. Mac Cutiocn on the Granite Tors of Cornwall.

have been unable to imitate the process in our laboratories. It is also
not improbable, that the quantity of potash which enters into the com-
position of felspar, may confer on it a similar property, and that even
in a greater degree, although direct experiments are wanting to prove
this fact. Whichever of these bodies is acted on in the case of this
disintegration, the quantity of matter actually dissolved is probably
very little; we can even conceive it possible that the mere alternation
of the states of moisture and dryness, combined with frequent
changes of temperature at the surface, may be sufficient to pro-
duce this effect without any actual solution of the substance of the
rock. It is a matter of more difficulty to assign the cause of the
change of figure which the masses undergo, by what process Nature
‘* mutat quadrata rotundis.”

Whatever disputes and doubts may have existed relating to the
stratification of granite in general, I believe there is no one now who
conceives the granite of Cornwall more than that of Arran or Mont
Blanc to be stratified. ‘The favourers of different hypotheses, must
each be allowed for the present to adopt the opinions which to them
seem the best founded, and it must depend on the conclusions which
shall ultimately be adopted, relative to the aqueous or igneous origin
of granite, whether these fissures are to be considered as the effects of
contraction produced in the mass by the evaporation of water, or by
the abstraction of heat. The cause of their peculiar form remains for
the present involved in the same difficulties which attend on the
more regular prismatic figures found in the trap rocks. But the
fissures themselves having been formed in whatever way we
chuse to suppose, we have still a difficulty unsolved, and that is the
tendency which they exhibit to wear more rapidly on the angles and
edges than on the sides, and thus to assume the spheroidal forms
which facilitate the ultimate ruin and migration of the summits.

Di. Mac Curiocn on the Granite Tors of Cornwall, = 75

That this would be the consequence of a gradual action merely me-
chanical is undoubted, as the mass must ultimately acquire that
figure which, being the last result of the action of decomposition
is the one which will offer the greatest resistance to further
change. Ina chemical view, the same must also to a certain extent
hold true; since any given particle, supposed cubical and placed at
‘the angle or edge, will be exposed to the action of the solvent on
two or more surfaces, while that on the side of the mass is exposed but
on one, hence the angular body must ultimately change its figure, and
approximate to a spheroidal form: it is easy however to see that the
influence of this cause will be retarded in a quickly increasing ratio,
and that it is insufficient to account for the extreme change of form
suffered by granitic masses. If it were sufficient in the case of granite,
it should equally produce in sandstones of prismatic fracture a determi-
nation to the spheroidal form. But in these we see that the process of
superior waste at the angles and edges, soon ceases to produce an effect
in modifying the figure of the mass, and that sandstone never assumes
the decidedly spheroidal forms which are exhibited by granite.
Mechanical causes of change are here out of the question. If we
now suppose the hardness of a mass of granite, or its resistance to
the disintegrating power of air and water, to vary in any given ratio
at certain distances from the centre, it is evident that the effect of
chemical action on the surface, will be to change the figure of that
mass, and that the ultimate effect will be to disclose the sphere
inscribed within that cube. Let us consider how far the facts bear
us out in this supposition.

De Luc has observed in his Geology, that granite sometimes de-
composes into spheroidal forms, and he describes piles of this rock in
Silesia, resembling, as he says, Dutch cheeses. J need not quote more
authorities for a fact witnessed by innumerable observers. In our

K 2

"6 Dr. Mac Cuxxocu on the Granite Tors of Cornwall.

own island of Arran (that little abridgement of the world) nodules of
spherical granite are found in the valleys which descend from Geat-
field, decomposing on the surface in crusts, and marking decidedly
the very construction which my supposition requires, in a much
greater degree than is requisite for the purpose. Similar granite
balls have been seen in other places, so that their existence is well
ascertained, and this is one of numerous instances, where the decom-
position of a rock gives us most useful information with regard to
its structure, and where without that aid, we should never have
divined the secret of itsformation. It is certain that these balls, now
rendered spherical by decomposition, have been quadrangular masses,
and hence we may step, without any great hazard of unsound
footing, to this general conclusion, that these masses of granite,
which show marks of wearing on their surface with rapidities pro-
portioned to their distance from a central point, have had their
hardness, and probably their crystallization or formation, determined
from that centre.

The analogy of this circumstance to the similar balls formed in
basaltic rocks is illustrative of both the cases, and probably both will
equally tend to confirm the opinions which have been held relating to
the igneous origin of these substances. Thus, if for the sake of
argument I may be allowed to assume that granite is of igneous
origin, it will be easy to explain the peculiar appearances exhibited
by that formation of granite, which, like those of Cornwall and Arran
and many others, is separated into cuboidal masses.

Here we must conceive, that in a homogeneous mass of fluid matter,
erystallization had commenced from numerous centres at the same
time. While there was yet space for the formation of successive
ssolid deposits round any set of these imaginary centres, a sphe-
rical .or spheroidal figure would be the result, As the surfaces

Dr. Mac Cutrocnu on the Granite Tors of Cornwall. TT

of these spheroids approached each other, the successive crusts would
interfere, and the remaining intervals would be filled by portions of
spheroidal crusts, until the cuboidal figures of all the contiguous
masses ,;were completed, thus forming that aggregated mass of cuboids,
which we witness in the granites of this aspect which remain unin-
J ured in their places. We need not be surprised that this regularity
is not more constant, nor the forms more perfect, as we are unac-
quainted with the numerous circumstances which may determine the
several centres of crystallization, or which may interfere with the
ultimate regularity of the resulting masses. It is certain from che-
mical experiments, that the fact which is the basis of the foregoing
supposition, Occurs in various instances of the cooling of slags and of
rocks artificially fused, as Mr. Watt’s experiments have so well
shown. But in these experiments, certain as they are, we are
unacquainted with the causes which determine the places of the
several centres of crystallization, and though equally unacquainted
with those which may have influenced the centres on which the
granite masses were formed, we may yet from analogy understand
how the irregularity of these masses may have been caused by a
corresponding irregularity in the position of their centres.

We can also easily conceive that in certain cases, the peculiar
circumstances of which lie equally hid from us, the approximation of
the spheres of crystallization may have caused the crystalline polarity
of the several masses to interfere with each other,.so as to have pro-
duced in many cases an irregularity still greater than this, and in
some instances even entirely to have obliterated the appearance of
central tendencies. To the chemical facts above adduced in support
of this explanation, I might subjoin, what every one’s mind will
immediately suggest, the illustration which the commenced spheroidal

78 Dr. Mac Cutiocu on the Granite Tors of Cornwall.

forms of the Cheshire rock salt, and the igneous explanation of the
forms of basaltic columns, add to this supposition.

On a smaller scale, a phenomenon of rare occurrence in Nature
may also be suggested in aid of it. I mean the spherically disposed
granite of Corsica, which exhibits the various constituents of granite
formed round numerous centres, and producing those beautiful speci-
mens still so rare in the cabinets of collectors. Similar radiating
tendencies in the smaller parts have been noticed by Saussure, and
although I had not the good fortune to see them in Arran, my friend
Professor Jameson has described them as existing there. I have also
witnessed a similar disposition in the mica which is included in the
granite veins near Portsoy, and the same structure is well known to
exist in that variety of granite which is called Tyger granite, where
the hornblende or shorl forms radiating spheres.

It is sufficiently apparent from the history of this granite, and
from its progress in decomposition now described, that the migration
of stony masses may to a certain extent be explained, at least as far as
this variety of granite is concerned, even without having recourse to
any very violent mechanical action. But the decision and complete
explanation of this very common and puzzling phenomenon, must in
most cases rest upon a question of a different nature, and of greater
difficulty, namely, the alterations which the surface of the earth has
undergone at different eras, as well as the comparative antiquity
of those changes. ‘This phenomenon is only one of many, which
prove the former existence of a different distribution of those parts of
the globe which are at this present time land and sea, hill and valley.

IV. Notes on the Mineralogy of the neighbourhood of St. Davia’s,

Pembrokeshire.

By John Kipp, M.D. Prof. Chem. in the University of Oxford, M.G.S.

—— a

Tne following notes are arranged under separate heads, de-
scriptive of particular points of the country adjacent to St. David’s,
which were visited during a stay of a few days at that place in the
summer Of 1811: and for obvious reasons, such points were selected
as might from description be easily referred to by others inclined to
examine the same ground.

No order has been adopted in the distribution of these heads than
was required for the convenience of description; for there did not
on the spot, and to an unprejudiced observer, appear to be any
obvious and natural chain of connexion between the several points
here described.

The country round St. David’s, when viewed from an eminence,
presents the appearance cf an extensive uneven plain, interspersed
with numerous detached hills or rocky summits of an irregularly
conical shape. ‘The rocks which constitute these hills bear no
marks of regular stratification ; rarely support even a slight degree
of vegetation; and when compared with the surrounding surface,
appear as so many nuclei, about which is arranged a very curiously
diversified series of highly inclined strata of a kind of slate. The
‘constituent parts of these insulated rocks are felspar and hornblende ;

80 Dr. Kipp on the Mineralogy of St. David's.

and the general character of them is crystalline: but the felspar
rarely if ever occurs in distinct crystals; and even the hornblende,
though usually the most accurately defined of the two, is sometimes
not discernible from the felspar. Again, though the mass often
appears upon the whole to have been of chemical origin, yet at the
same time it is, partially, of a structure to the eye decidedly mechani-
cal; and in some instances the character is so extremely equivocal as
to leave the judgment in a very difficult state of suspense. The
predominating colour of these crystalline rocks is a brownish green.
The two highest of these hills, called Carnllidy and Penberry, are
situated to the north of St. David’s: they rise less abruptly from
the plain than the similar hills of the neighbourhood; and are in a
manner connected with each other, and with a third summit not far
distant from the last mentioned, by a slightly elevated ridge which
passes in a south-westerly direction from one hill to the other ;
Penberry being at its north-eastern extremity. From the summit
of Carnllidy the ground gradually slopes towards the west for a few
hundred yards, and then, again rising, forms the promontory called
St. David’s Head. ,
“The ascent to the two hills above mentioned, both on the north
and on the south side, is formed by highly inclined strata of a slaty
rock which would be commonly called grau-wacke, a term in the
present instance used only for the purpose of general description ;
and the nearly precipitous cliffs, by which the greater part of the
adjoining coast is bounded for some miles, appear to consist
principally of the same kind of rock. The massive tabular laminz
of this schist rise abruptly from the sea, with a highly elevated
degree of inclination towards the land, over the edge of which they
are sometimes folded in the form of a broad mantle, or are occasion-
ally broken into natural arches and caverns; giving to the outline

Dr. Kipp on the Mineralogy of St. Davia’s. 81

of the cliffs which they compose a bold but graceful curvature, very
characteristic of a coast of this kind, and productive of scenery the
most magnificent. A very striking illustration of this effect, though
it is not clear whether it proceed from rocks of this class or from
those more immediately belonging to the coal grits, occurs at
Saunders’ Foot, a small cove situated about four miles to the north.
east of Tenby.

It not unfrequently happens that the partial removal of the
superincumbent lamin of the schist, from the surface of those
placed relatively beneath them, has given rise to that appearance of
a succession of broad flat steps or stairs which suggested to the
Swedish mineralogists the term Trapezius; a term applied by them
to that class of rocks, in which from the action of the weather and
other causes, there is a tendency to assume an appearance of this
kind. .

These slaty strata are occasionally traversed by beds of clay
porphyry ; and by veins of quartz affording very large and beautiful
specimens of rock crystal.

It is worth noticing that in none of the stratified or unstratified
rocks of this neighbourhood, did the extemporaneous test of an acid
give any evidence of the presence of carbonate of lime: nor did
there occur in them, with the exception of one equivocal instance,

the smallest trace of any organic remains,

St. David’s Head.

The rock which forms this promontory consists of a mixture
of blackish green hornblende and white felspar; but the pro-
portion of the hornblende often so far predominates, and its cry-
stalline form is so regularly developed, that the felspar appears rather

Vo, II. ES

$2 Dr. Kipp onthe Mineralogy of St. David's.

as an accidentally connecting medium of the former, than as an
essentially constituent part of the whole rock. ‘The crystals of the
hornblende, though generally small, sometimes exceed two or three
inches in length; in which instances they are not of a proportional
breadth: in general also they are closely compacted with the body
‘of the rock ; but occasionally, and especially when larger than usual,
they are easily separable from the mass, leaving a smooth impression
of their surfaces. These impressions, as well as the crystals them-
selves, have commonly a dull iridescent semi-metallic lustre ; arising,
perhaps, from an increased oxydation of the iron of the hornblende,
which by loosening the attachment of the crystals to the mass in
which they are imbedded, has disposed the compound to assume
that regularity in its fracture. A similar appearance often presents
itself in parts of the Malvern rock ; and it is probable that the kind
of lustre here noticed is very characteristic of peculiar states of horn
blende, and may serve to ascertain its presence in a compound rock
where no traces of its crystalline form are evident.

Carnllidy.

The hornblende of the summit of this hill is indistinctly crystallized,
and of a dark and dull olive green colour; generally very uniform
in its character; and so closely compacted with the felspar that the
fracture passes indiscriminately through both. The rock itself is re-
markably hard, and has that degree of toughness which is character-
istic of the class of rocks called by WalleriusSaxaCornea, andCorneus
Trapezius ; which rocks, as may be collected from the volcanic disser-
tations of Dolomieu and Ferrara, contain hornblende as a principally
constituent part. It occasionally contains particles of pyrites; and
insensibly passes into a greyish green coarse and soft slate, which in

if

Dr. Kipp on the Mineralogy of St. David's. 83

the mass is remarkably disposed to separate into flat rhomboidal
fragments, the surfaces of the lamine of which are sometimes inter-
spersed with a few small specks of white mica.

Penberry.

The rock constituting this summit, as may be satisfactorily ascer-
tained by insensibly graduating specimens, is of the same nature with
those already spoken of ; though at first sight, and especially in par-
ticular parts, apparently very different. ‘The hornblende gradu-
ally dsminishing in its proportion, or being intimately blended with
the substance of the felspar, often merely imparts an obscure shade
of green to the whole mass; the presence of which colour princi-
pally assists the eye in recognizing the true nature of the rock; and
but for which it might be confounded with a compact sandstone or
felspar. "The same observation holds, but still more strongly, with
respect to the rock on which stands Roche Castle; a ruin situated to
the north of the turnpike road, about half way between Haverford-
west and St. David’s. This rock has, much more decidedly than
Penberry, the character of a compact sandstone: but in its geogra-
phical relation to the surrounding country, it exactly corresponds
with the preceding rocks, and with the numerous similar rocks of
the neighbourhood. However this may be, the surface of the
ground between Roche Castle and St. David’s is scattered over with
numerous large boulders, as they might be called, very closely re-
sembling in their general character one or other of the three rocks
already described ; and all of them bearing strong marks of having
been the result of chemical formation.

The rock of which Penberry is composed shews occasionally a
slight tendency to concentric disintegration ; and the external part

L 2

84 Dr. Krpp on the Mineralogy of St. David's.

of it is here and there altered by the action of the weather, after the
manner of ferrilite.

On the coast, a little to the north-east of Penberry, is a slate
quarry ; worked out of a mass of schist, which forms remarkably
bold and nearly perpendicular cliffs, the strata of which are occasio-
nally much contorted. ‘The surfaces of the laminz of the slate have
sometimes an ochry tarnish, and abound with minute particles of
mica.

St. David’s Slate Quarry.

This quarry is situated between St. David’s Head on its north,
and a beach called the White Sands on its south side. The slate is
of nearly a black colour, and is here and there traversed by veins of
brownish white compact and indurated clay, containing tarnished
cubical crystals of iron pyrites. The slate is employed in roofing ;
but does not thoroughly resist the action of the weather, perhaps
from the effect produced on pyritical matter disseminated through
it: wherefore it is customary in all this part of the country to white-
wash the roof as well as the walls of their houses.

The laminz of this slate are sometimes wrinkled or wavy. It
contains but faint traces of mica; and sometimes approaches to the
character of siliceous schist.

The White Sands.

This name is given to a beach of about one-third of a mile in
length, which at its northern extremity is separated from St. David’s
slate quarry, by a low and narrow ridge of rocks projecting into the
sea; and is terminated at its southern extremity by high cliffs.
Towards the land it is bounded principally by heaps of sand; inter-

Dr. Kipp on the Mineralogy of St. David's. 85

spersed with low rocky cliffs, which rise higher and higher in ad-
vancing to the southern extremity ; at which point the rocks are
particularly interesting from their variety; passing, sometimes
abruptly, from the coarsest grained conglomerate, as from its appear-
ance it might be called, to the finest schist.

The prevailing colours of these rocks are green and brownish
‘purple; those colours alternating occasionally as in striped jasper.
The cement of those parts which resemble a conglomerate appears
to be in a great measure of chemical origin; containing minute
crystals of semitransparent felspar, with small particles of glassy
quartz. It seems worthy of remark, that in those parts of the rock
which resemble a conglomerate, the pebble-shaped nodules of quartz
are very frequently of the same purple colour as the schist. The
sand of this beach when viewed through a microscope is seen to be
a mixture of fragments of shells with small particles of variously
coloured quartz and slate. A portion of it weighing 200 grains,
which had been collected in July 1811, and had been kept in a
room without a fire till March 1812, only lost one grain of its
weight by exposure to a heat of 212°: after which, having been
boiled in diluted muriatic acid, and then filtered, washed, and dried
by the same heat, it weighed 157 grains; having lost 75 or rather
more than + of its weight, which may be considered as very nearly
the proportion of calcareous carbonate contained in this sand. The

sand is extensively used as a manure,

Porthclats.

This is a small fishing harbour situated to the south or south east
of St. David’s, and is the termination of a narrow shallow valley,
which extends two or three miles inland, and is longitudinally

86 Dr. Kipp on the Mineralogy of St. David's.

divided by the river Alun; the mouth of the river emptying itself
into this harbour.

The rocks constituting the rising ground on the left bank of the
mouth of this river appear to be a compound of felspar or quartz;
or both, with hornblende: the predominating colour is brownish
white, arising from the great proportion of the two first mentioned
component parts.

On the right bank of the mouth of the river the strata are
distinctly schistose, and very various in their appearance. “Within
the distance of two feet the rock assumes the following characters.

Brick red slate, nearly siliceous.

Brownish purple slate, with streaks of green.

Red slate, with an incrustation between some of the laminz
resembling blackish green scaly chlorite.

Greenish grey compact sandstone.

Stratified sandy slate, partly greenish grey, partly purple.

Traces of steatite and serpentine occur in the rocks of this neigh-
bourhood.

Rock in the Close of the Cathedral.

The cathedral is situated in a part of the narrow valley through
which the river Alun winds from the north east ; the descent to its
eastern and south eastern extremity is steep, and is formed by a
rock which might be called a small grained green-stone porphyry,
in a high state of disintegration.

The general colour of this rock varies between a brownish white
or yellow, and a very obscurely greenish brown: where most com-
pact it has nearly a homogeneous appearance, and would by many
be described as a soft compact felspar ; but commonly it is in a very
loose state of aggregation.

Dr. Kipp on the Mineralogy of St. Davia’s. 87

Parts of this rock resemble Fullers’ earth ; but from the occasion-~
ally green colour and the peculiar direction of the natural rifts,
giving it a tendency to separate into rhomboidal or into wedge-
shaped fragments, it possesses a characteristic mark which serves to -
connect it with the prevailing rock of the neighbourhood.

Many parts of this rock easily crumble into the state of an
earthy gravel, and are commonly used as a substitute for common
gravel in and about St. David’s. .

I shall readily be excused for mentioning here, that there is in,
the Ashmole Museum a specimen from Jersey so very like in its
general character to the part of the St. David’s rock now under
consideration, that even an experienced eye might be deceived as
to its separate identity : and it adds to the interest of the comparison
of the specimens in question, that they both occur amongst a suite
of rocks composed principally of hornblende and felspar, and are
both used for the same economical purpose.

Fortification near St. David's.

To the south west of St. David’s are the remains of an old
entrenchment, situated near the edge of the adjacent cliff; and from
the further extremity of the entrenchment the cliffs run out at right
angles to the general bearing of this part of the coast, forming a
tongue of land which projects into the sea. In this projecting point
a natural arch exists, which has been probably excavated by the
gradual washing away of part of the rock ; presenting an appearance
somewhat like that represented in the third of Dr. Mac Culloch’s
plates, in the first volume of the Society’s Transactions.

Near the extremity of this tongue of land is a vein of clay

88 Dr. Kipp on the Mineralogy of St. David's.

porphyry of a light drab colour, containing small crystals of felspar
nearly of the same colour, together with completely tarnished cu-
bical crystals of iron pyrites: there is also in this vein an occasional
appearance of decaying hornblende or chlorite. The base of this
porphyritic vein wears away by the action of the weather, and
leaves the crystals of the felspar projecting from the surface of the
weathered part.

This vein of porphyry is inclosed in a stratum of friable schist,
neither the character nor position of which are at all altered by the
immediate contact of the vein. The adhesion between the schist
and the vein is so very slight that it is extremely difficult, if at all
possible, to separate a specimen which shall unequivocally shew the
junction of the two.

The schist, which is traversed by filamentous veins of quartz,
appears to the eye of a very delicately laminated structure, yet does
not readily separate in the direction of the planes of the laminz.
The surfaces of many of the natural rifts have a brownish black
tarnish.

Carvay.

The cliffs in the neighbourhood of this spot, the precise situation
ef which is not recollected, but it is not far distant from the fore-
going, consist of highly inclined strata of indurated greenish-grey
freestone; of red and coarsely laminated slaty freestone, which
is used in building ; and of a soft argillaceous freestone with nume-
rous veins of sparry quartz. Traces of chlorite are very frequent
in the rocks of this neighbourhood, and the slaty freestone is
often interspersed with particles of a substance intermediate in
its character to mica and chlorite,

Dr. Kipp on the Mineralogy of St. Davia’s. 89

Not far from Carvay I met with two insulated masses, one of
which, bearing a very close resemblance to the mill-stone grit of
Derbyshire, was made up of small particles of white and reddish-
white semitransparent quartz cemented together by white earthy
felspar: the other was also a kind of grit-stone, consisting almost
entirely of particles of quartz, occasionally interspersed with specks
of white earthy felspar. Though I saw no rock iz situ to which
these masses could be directly referred, yet as they did not much
differ from some of the rocks of this district, excepting in the size
of their component particles, and as there was nct any ground for
supposing they had been brought there by art, they probably belong
to the suite already described.

Treginnys.

This is a broad headland, about three miles to the south-wes: of
St. David’s. It is frequented by trading vessels on account of «
fresh-water spring which rises near the edge of the adjacent cliffs,
beneath which is a convenient harbour.

The general character of the rocks in the neighbourhood of
Treginnys is of that equivocal nature alluded to in the beginning
of these notes: here and there they assume the appearance of a
compact earthy felspar of an olive-green colour, and then probably
often contain epidote, compact veins and crystals of which I saw
in more than one instance. In one place this compact green rock
occurs in angular columns horizontally aggregated, and forming a
part of the cliffs on the north side of the harbour. The number of
the columns is not above eight or ten; their form irregularly pen-

tagonal, and their diameter less than a foot. This was the only
Wor. tl, M

50 Dr. Kipp ov the Mineralogy of St. Davia’.

appearance of the kind observed in the neighbourhood of St.
David’s.

The internal texture of many of the racks about Treginnys, and
in the road between that place and St. David’s, resembles that of a
very compact mechanical aggregate, the particles of which are
however obscurely defined: the predominating colours are green,
greenish-white and pale purple: the character of the recent fracture
is like that of coarse steatite. A close inspection brings to view
numerous crystalline surfaces of semitransparent laminated felspar,
and particles of glassy quartz; and it is worth noticing that the
felspar and quartz now and then occur in the substance of the im-
bedded particles as well as in the cementing medium, shewing a
probably cotemporaneous formation of the whole mass.

Some of the rocks of this neighbourhood approach to serpentine
in their general character, and contain veins of indurated steatite.

Ramsey.

This is by far the largest of a number of rocky islands lying off
the coast of St. David’s, and is separated from the main land by a
channel of about two or three miles in breadth. The greatest ex-
tent of the island is from north to south, and at each extremity
in this direction is an elevated summit, or beacon, of considerable
height, the general character of each of which is similar to that of
the corresponding summits on the main land. The intervening
rocks are principally slaty, The western front of each of these two
summits projects into the sea far beyond the intermediate space of
land; and it appears probable that the bay interposed between the
promontories has been cut out by the dashing of the waves against

Dr. Kipp on the Mineralogy of St. Davia’s. 91

the crumbing schistus which is here opposed to them, and that
consequently in process of time, as this schistus is extended across.
the island to the eastern shore, the island may eventually be sepa-
rated into two.

The harbour of Ramsey is a small cove excavated in a mass of
black schist, and situated near the southern extremity of the eastern
front ; advancing from which towards the west, and then ascending
the southern beacon from its northern side, you pass over an ap-
parently conglomerate rock made up almost entirely of large pebble-
shaped masses of white quartz. From the uniformity of colour in
this rock, and from its general appearance, a doubt at first sight
arises whether it is really a mechanical conglomerate or the result
of a peculiar chemical conformation.

On and near the summit of the southern beacon the rock in many
places resembles coarse chert, from which it passes into the state of
indurated clay containing small crystals of felspar and of dodeca-
hedral quartz, the latter in general very imperfectly defined.

The composition of the rock forming the northern beacon is
felspar and hornblende, sometimes assuming nearly a homogeneous
appearance, and sometimes, though rarely, inclining toa porphyritic
structure.

With the island of Ramsey these notes on the Mineralogy of the
neighbourhood of St. David’s terminate, in drawing up which it
has been my object to avoid as much as possible the language of
hypothesis, and to detail the appearances which I met with in terms
strictly descriptive: and though I feel strongly persuaded, on
grounds which have not been taken up hastily, that all the rocks
which I have been describing are essentially allied to each other,
and are all of chemical and cotemporaneous origin; yet, conceiving

M 2

92 Dr. Krpp on the Mineralogy of St. David's.

it would be improper on the present occasion to enter into the par-
ticulars or on the defence of those grounds, I think it respectful to
the Society to be silent on those points.

I may however with propriety add, that from communications
with very competent Judges, aided by the inspection of specimens
which they had themselves collected, it is clear to me that the
geological phenomena above described are of very extensive occur-
rence. In Jersey and Guernsey for instance, in various parts of
Devonshire and Cornwall, in North Wales and Cumberland, in the
neighbourhood of Mount Sorrel in Leicestershire, in all these places
severally, is found an assemblage of rocks of a decidedly crystalline
character, and consisting of hornblende and felspar, associated with
rocks either of a schistose structure or resembling a more or less
fine-grained conglomerate, intersected not unfrequently by masses
of a porphyritic character, and sometimes passing into serpentine. *

In the decidedly crystallized rocks of these suites, consisting of
hornblende and felspar, the felspar sometimes predominates and is of
a red colour, in which case the compound is usually, I believe, called
sienite ; but the same term seems justly applicable where the horn-
blende predominates and the compound is of a black or of a green
colour, for the two varieties insensibly pass into each other.

The opinion which I have here ventured to express of the natu-
ral alliance between the various rocks above described is strongly
supported by its correspondence with the opinion entertained by
M. Godon respecting a similar class of rocks occurring in the

* The transition of the natural compound of hornblende and felspar into serpentine
has been observed in Cornwall, and is satisfactorily shewn in specimens brought from
thence and deposited in the Ashmole Museum; and the opinion of the natural alliance
of these two rocks is strongly confirmed by the inspection of numerous specimens brought
from the coast of Labrador and deposited in the same Museum.

Dr. Kipp on the Mineralogy of St. David's. 93

vicinity of Boston in North Ametica ;* and should it ever receive
general confirmation, it might I think be fairly applied to the cor-
rection of one part of the present nomenclature of Geology. I
would in that case, for instance, propose that the term szenite should
be generally applicable to the whole series, and that the slaty or
granular forms of it should be specifically described by those epi-
thets ; and thus, in a few instances at least, we should attain the
desirable object of banishing the term grauwacke from the language
of mineralogy ; a term not only offensive from its harshness but still

more from its want of precision.

* There is a paper on this subject by M. Godon in the 15th vol. of the Annales da
Muséum d@’Histoire Naturelle, p. 455, the perusal of which will amply repay those who
may be induced to read it.

V. An Account of the Brine Springs at Droitwich,

By Leonarp Horner, F.R.S. M.G.S.

Si Tue town of Droitwich is situated nearly in the centre
of Worcestershire, about six miles from Worcester, on the road to
Birmingham. For a very long time* the manufacture of salt has
been carried on to a great extent in this place, and as 1 am not aware
of the existence of any detailed account of the natural and chemi-
cal history of the brine springs from which it is procured, I take the
liberty of laying before the Society some observations which I made
on the spot in October, 1810, together with the results of some
experiments I have since made, with the view of determining the
chemical composition of the brine.

* In 816, Kenulph, King of the Mercians, gaye Humilton and ten houses in Wick,
with salt furnaces, to the church of Worcester.

‘¢ At the time of Domesday Survey,”? which was finished in 1087, ‘ the only fuel
used for boiling the brine was wood, and the demand for it much greater than the neigh-
bourhood of Droitwich could supply, especially as the brine was of a weaker quality in
those days, and required to be boiled longer than it does at present.””—Nash’s History
of Worcestershire.

+ In the Philosophical Transactions for 1678, there isa short account of the salt-
works of Droitwich by Dr. Thomas Rastcl. At that time there were three pits made
use of, the greatest of which was thirty feet deep. He found that the brine yielded
above one-fourth of its weight of salt.

Mr. Horner ox the Brine Springs at Droitwich. 95

§ 2. The brine-pits are in the centre of the town, situated in a

narrow valley, in the bottom of which runs the small river Sale
warp. ‘The sides of the valley rise rather abruptly from the river.
Doder Hill, on the right bank, which appeared to me to~be the
highest of the two sides, I measured with the barometer, and
found it to be about eighty feet above the bed of the river.
‘ § 3, The prevailing rock around Droitwich is a fine-grained cal-
careo-argillaceous sandstone, of a brownish red colour, with occa-
sional patches and spots which are greenish blue. . At Doder Hill,
where a vertical section of it is exposed, it contains beds of a greenish-
grey colour, and of a more indurated texture, but which do not appear
to differ materially in composition from the red sandstone. These
contain slender veins of crystallized gypsum, the forms of which are
very distinct, where the widening of the vein has produced small
cavities. I did not observe any gypsum in the red sandstone. The
stratification is horizontal, and both the red and the grey rocks, where
they are exposed to the air, crumble down into small pieces, I did
not discover any traces of organic remains.*

This sandstone is the same as that which Mr. Aikin has described
as occurring to so great an extent in Shropshire and Staffordshire,
and which he considers to be the old red sandstone of Werner. He
has also stated that it is found in this district, but as he does not trace
it to any particular spot beyond Droitwich, I may here observe, that
it appears to me to be the same as that which I found on the banks of
the Severn,{ between twelve and thirteen miles from this place; and
I have great reason to believe that it continues without interruption

* Dr, Rastel says, “‘ I never observed any shells.”—Phil, Trans..
+ Trans. of the Geol. Society, vol. 1, p. 191,
{ Trans. of the Geol. Society, vol. 1, p. 312.

96 Mr. Horner on the Brine Springs at Droitwich.

throughout the whole of that extent, and even for some miles to the
south of the spot I have just named.

Mr. Aikin observes that the red sandstone of Shropshire does not
effervesce with acids: in this respect, therefore, it differs from that
of Droitwich, for both varieties of the sandstone effervesce pretty
briskly for a short time, but that which is of a grey colour appears to
contain the greatest proportion of calcareous matter. .

The extensive beds of rock-salt, and the brine-springs of Cheshire,
according to Dr. Holland,” are situated in strata of a similar nature.

§ 4. The surface soil which covers the red sandstone, contains
large pebbles, generally about the size and shapeof a goose’s egg, but
often larger. Those which I examined consisted of compact bluish-
grey quartz, very much resembling some varieties of flint and cal-
cedony, and different varieties of coarse and fine-grained quartzose
sandstones. These pebbles are not found in great quantity, for, as
I was informed by a labourer, they are picked off the surface of the
fields for the purpose of mending the roads, no spot having been
found in the neighbourhood, where they are sufficiently abundant
to pay the expence of digging for them.

§ 5. With regard to the nature of the rocks through which the
brine-pits were sunk, I have not been able to obtain any very distinct
information, as no new pit has been made for the last thirty years.
Allthat I have in my power to lay before the Society on this subject,
is the account contained in Nash’s History of Worcestershire, to-
gether with some details I received from an inhabitant of Droitwich,
who was on the spot at the time the last pit was dug. The follow-
ing is the information given by Dr. Nash.

* Trans. of the Geol. Society, vol. 1, p. 38—Sce also his Agricultural Survey of
Cheshire,

Mr, Horner on the Brine Springs at Droitwich. 97

* Until 1725 the pits had not been sunk very deep, but in that
“¢ year the talc was sunk through, and soon after every one sunk’
** his pit through the talc, and obtained such a profusion of strong
“ brine that not one-tenth part of it hath ever been used, but ran to
“ waste. In 1773 Joseph Priddey, of Droitwich, informed me that
“ he had sunk several pits, and generally found it about 35 feet to
“the talc, through the stratum of talc 150 feet, under the talc a
“ river of brine 22 inches deep, under this river a hard rock of
** salt. When the hole is bored through the talc, the brine bursts
‘* up with amazing violence to the surface of the ground. In the
“ year 1774 he sunk another pit, and found it to the talc 53 feet,
** through the talc 102 feet, the brine river 22 inches, then a rock
* of salt: he bored 24 feet into this rock, and found it still the
“ same. In 1779 a hole was bored previous to a brine pit being
“* sunk in the. yard of Richard Norris, Esq. The strata were,
*“* mould 5 feet, marl 35, talc 40, a river of brine 22 inches;
“ under the brine, talc 75 feet, and a rock of salt, into which the
“© workmen bored 5 feet.* I have been informed, likewise, by
‘* persons employed in sinking these pits, that immediately above
** the river of brine is a thin crust, easily perforated, and, next to
** that, a very soft substance, perhaps two feet thick, and then the
“talc. ‘This talc, or rather gypsum, or alabaster, is a shining
“* fissile species of stone, of a whitish colour. It is so hard that
“* the workmen never sink the pit through it; they bore a hole,

tal

i
* The account of the sinking of this pit differs so materially from the rest, that I
suspect it must be inaccurate. In the accounts of the sinking of the other pits, the
brine flows over rock-salt ; but here 75 feet of gypsum interveue between the brine and
the salt. As all the pits are situated within the space of a square furlong, it is not
probable that so remarkable a change should take place in the relative position of the

gypsum and the rock salt.

Von. il. N

98 Mr. Horner on the Brine Springs at Droitwich.

‘¢ four inches in diameter, through which the brine rises and fills
see’ pit.”

I was informed by an old man who assisted in sinking Walker's
pit, that they sunk through soil, gravel, red marly clay, blue and
white stone, hard rock, and talc, and that they came to the brine
at the depth of 50 yards from the surface ; that for the first 15 yards
they cut out a shaft, about 8 fect square, this they coated with clay,
and afterwards lined with planks, to prevent the springs of fresh
water, which are found at that depth, from mixing with the brine.*
At this depth of 15 yards they found the hard rock, and they then
bored a hole of about 4 inches in diameter through this hard rock
until they came to the brine, which they found at the depth of 35
yards farther ; when they came to the brine, the borer suddenly fell
22 inches, thus indicating the depth of it. As soon as the rock
was penetrated, the brine rushed rapidly through the hole, the
mouth of which the workmen were obliged to stop, until they got
out of the pit. When the plug was withdrawn, the brine quickly
rose to the surface and overflowed.

§ 6. Although the information contained in the preceding state-
ments is not very precise, yet they convey a general idea of the na-
ture of the rocks sunk through, and it is very probable that they are |
similar to those exposed at Doder Hill, immediately contiguous to
the pits, and which I have already described. We learn, however,
with tolerable certainty, that these springs are impregnated from a
body of rock salt ; and we obtain an additional testimony in support
of the observation, that rock salt is invariably accompanied by gyp-
sum. From the rapidity with which the brine rises to the surface,

* In different places in the town of Droitwich, the water in the wells is brackish,

while in others, that are sunk to the same depth, it is quite fresh.

Mr. HoRNER o# the Brine Springs at Droitwich. 99 .

it is evident that the source of these springs must be situated in much
higher ground than that in which the pits are sunk.

§ 7. There are several pits on both sides of the river, but chiefly
on the south side. The greater number of them, however, are not
used, and the whole of the present extensive works are supplied
from four pits.* Indeed, the quantity of brine that is used bears
but a small proportion to that which is allowed to run to waste;
for, except when the reservoirs are filling, the brine is constantly
flowing into the adjoining canal, through a channel cut for the pur-
pose, near the mouth of the pits,

§ 8. The four pits that are worked at this time are distinguished
by the names of Walker’s Pit, Walwyn’s Pit, Romney’s Pit, and
Stuckey’s Pit. From each of these I obtained a bottle of the brine,
for the purpose of submitting it to chemical examination. I also
procured a bottle of the brine from Farley’s Pit, on the north bank
of the river, but which is not now worked.

I shall now lay before the Society the details of the process I
adopted in this analysis.

Analysis.

§ 9. The brine from all the pits is perfectly limpid, and when
held in a tumbler is colourless ; a greater body of it, however, has a
pale greenish hue, similar to that of sea-water. It has remained
equally clear at the end of a year anda half in a bottle closely corked,

* Through the kindness of ‘Thomas Farley, Esq. the -principal proprietor of these
works, I have learned, that the quantity of salt, annually made at Drvitwich, is about
16,090 tons.—The principal part of this is consumed in England, and pays a duty of
about *£320,000.—The present market price of the salt is £31 per ton, £30 of which
is duty.

N 2

100 Mr. Horner on the Brine Springs at Droitwich,

and no change of transparency was produced, when left exposed to
the air in an open vessel, for several days.

Its taste is intensely saline, but without any degree of bitterness ;
neither is there any bitter taste in the crust which is deposited at the
bottom of the pans, after several successive portions of brine have
been evaporated.

The temperature of the brine in the pits, a few feet below the
surface, differed very little from that of springs in general. It
was 55°. *

~ §10. Specific Gravity, and Amount of the solid Contents.

The specific gravity of the several brines I found to be as fol-
lows :

Walkers pu, 7. . «>. Leva.lit
Walwyn’s pit, . . . . 1203.83
Romney’s pit, . . - 3200.15
Stuckey’s pit, ..... » 1184.67
Parley's pityo. . - fe) RATE

* J omitted to note down the temperature of the air, but it was a warm day for the
season of the year.

+ This is not an absolutely saturated solution, for by adding salt to the brine at a
boiling heat, and allowing it to cool to 60¢, I obtained a perfectly limpid solution of the
specific gravity of 1210.39. This sp. gr. almost exactly corresponds with that of
Hassenfratz, An. de Chemie. vol. 28, p. 298. In the sixtieth volume of the Philo-
sophical Trans. Dr. Watson, the present Bishop of Llandaff, has given a valuable
paper, entitled, ‘* Experiments and Observations on various Phenomena attending the
Solution of Salts.”—He has constructed a table of the specific gravity of water im-
pregnated with different quantities of common salt, from 4 down to the 1024th part of
the weight of the water, at a mean temperature of 50°. The salt used was sea-salt,
of the finest kind, and extremely dry.

The highest specific gravity which he gives, is 1206, which very nearly corresponds
with that of Walker’s pit; but from what has been said above this is not the specific
gravity of a fully saturated solution,

Mr. Horner ov the Brine Springs at Droitwich. 101

Four cubic inches of brine were evaporated to dryness very slowly,
in a heat which was not suffered to rise above 212°, and towards the
close of the evaporation it was kept between 170° and 180°. The
residuum was reduced to powder, and again kept for an hour in a
heat of about 180°. The different brines yielded the following

quantities of entire salt.

Walker’s pit, . . 317.14 grs. = 2289.75 grs. ina pint.
Walwyn’s pit, . . 31340 — = 2262.75
Romney’s pit, . . 311.00 — = 2245.42
Stuckey’s pit, . . 283.50 — = 2046.87
Farley’s pit, . . 266.34 — = 1922.97

This variation in the strength of the different brines is probably
owing to the mixture of the fresh-water springs in different propor-
tions. Farley’s pit, which is the weakest, is perhaps so on account of
the brine not being agitated by pumping, whereby the lighter fresh
water will only mix with the brine in the upper part of the pit: the
bottle of it which I obtained was from near the surface.

“But a solution of this specific gravity he states to contain 4 of its weight of salt;
whereas I have found (B. a.) that three ounces of the brine of Walker’s pit, weighing
16284 grs. yielded only 431,86 grs. of salt, which is not equal to two-sevenths of the
weight.

The difference between the results which I have obtained, and Dr. Watson’s tables,
(if it is not owing to error on my part,) may probably arise from the degree of purity
of the salt which he used, and also from the state of it with regard to dryness, before
it was added to the water.

Dr. Holland, in his Agricultural Report of Cheshire, states, that salt, after as much
water as possible has been previously drained from it, loses about one-seventh of its
weight, when heated and dried before the fire, without being allowed to decrepitate.

102. = Mr. Horner on the Brine Springs at Droitwich.

§ 11. Preliminary Experiments with Reagents.

a. Tincture of red cabbage—no change produced.*

5. Litmus paper—no change.

ce. Turmeric paper—no change.

ad. Lime water—no change.

e. Nitrate of barytes—a considerable white precipitate.

jf: Oxalate of ammonia—a white precipitate.

g.» Ammonia—a slight turbidness.

hb, Neutral carbonate of ammonia—a white precipitate.. This
was separated by filtration, and onthe addition of phosphate
of soda to the clear liquor, a slight turbidness was produced,
and, after a little time, a rod drawn along the glass vessel
left white streaks.

Succinate of ammonia—no change.

“oe
°

k. Tincture of galls, a turbidness, but no blackness.

=

Prussiate of potash—no change, even after the addition of
muriatic acid.

m. After the brine was boiled briskly for some minutes, it re-
mained perfectly transparent, and had deposited no sedi-
ment.

The brine, therefore, does not contain any uncombined acid,
(by Exp. a. 6. d..) nor uncombined or carbonated alkali, (by Exp.
a.c.) nor earthy carbonate or oxide of iron, (by Exp. m.) nor
iron in any other state of combination, (by Exp. i. &. /.)

As a farther proof that it does not contain either an earthy car-
bonate, or oxide of iron, the crust left at the bottom of the pan

* 'This experiment was made on the spot.
+ This turbidness was evidently owing to the alcohol of the tincture,

Mr. Horner on the Brine Springs at Droitwich. (108

after the evaporation of successive portions of the brine, called
by the workmen fickings, and of which I procured specimens, is
entirely soluble in water.

The brine appears to contain, besides muriate of soda,

1. A sulphate, or sulphates, (by Exp. e.)

2. Lime, (by Exp. f )
‘ 3. Magnesia, (by Exp. g. 4.)

The sulphuric acid may be’ in combination either with lime,
magnesia, or soda, or with all the three.

The lime and magnesia may be in combination either with sul-

phuric or muriatic acid, or with both.

§ 12. These preliminary experiments were made upon the
‘brine from the five different pits; and as all the specimens gave
the same results, I considered it only necessary to determine the
proportions of the several ingredients in one of them. I em-
ployed for this purpose the brine from Walker’s pit, as being the
strongest.

A. Zo determine the Amount of the Muriates.

From one ounce measure of brine weighing 542.8 grs. I pre»
cipitated the sulphuric acid by nitrate of barytes, separated the
precipitate, and washed it with distilled water, until no change
was produced in the washings by nitrate of silver, and taking care
to add all these washings to the brine. I now precipitated the
muriatic acid by nitrate of silver, which last I added in excess.
The muriate of silver was washed with distilled water until no
change was produced in the washings by muriate of soda. It was
then dried in a low sand heat over a lamp, until it became of a

104 Mr. Horner on the Brine Springs at Droitwich,

purple hue throughout. It now weighed 339.63 grs. which is
equal to 64.7 grs. of acid, taking the composition of muriate of
silver to be 19.05 acid and 80.95 base, according to the deter-
mination of Dr. Marcet, and which, from its close coincidence with
that of Gay Lussac, appears most entitled to confidence. ;

B. Zo separate the Earthy Muriates.

a. Three* ounce measures of the brine, weighing 1628.4 ers.
were evaporated to dryness in a heat not exceeding 200°, and
which was reduced to 180° towards the close of the operation.
The residuum was reduced to powder, and again exposed to a
heat of about 180° until no farther moisture was given off. It
now weighed 431.86 grs.+

b. This residuum finely powdered, I put into a flask, and poured
on it two ounce measures of alcohol nearly boiling. It stood forty-
eight hours, during which time it was frequently shaken. It was
then filtered, and the salt left on the filter was washed with two
ounces of fresh hot alcohol.

c. The filtered liquor was evaporated to dryness in a very
gentle heat, and a small quantity of fresh alcohol was added to
the residuum, to separate the earthy muriates from the muriate of
soda taken up by the alcohol in the process 2. ‘This was filtered,
and the liquor being evaporated to dryness yielded 0.32 gr. of
residuum. 7

* As all the other salts, besides the muriate of soda, were shewn by the preliminary
experiments to exist in comparatively small quantities, I used a larger proportion of
the brine in the determination of these, to avoid as much as possible the crrors of
too minute manipulations.

+ So that the brine contains 26.53 per cent. of salt.

Mr. Horwer on the Brine Springs at Droitwich. 105

d. This residuum was dissolved in distilled water, and as it was
unnecessary to attempt to ascertain the proportions of muriate of |
lime and muriate of magnesia in so small a quantity, supposing
them both to be contained, all I could do was to determine the
existence of each.

e. To one portion of this solution I added oxalate of ammonia,
which produced no change.

jf: To another portion I added pure ammonia, which immediately
eccasioned a flocculent precipitate.

g- To a third portion I added neutral carbonate of ammonia
and phosphate of soda; a precipitate was produced, and a rod
drawn along the glass left white streaks.

The whole therefore of this residuum was muriate of magnesia,
with perhaps a minute quantity of muriate of soda.

C. To estimate the Amount and Nature of the Sulphates.

a. To three ounce measures of brine, weighing 1628.4 grs,
I added nitrate of barytes in excess. The precipitate was well
washed, dried over a lamp, and afterwards heated to redness in a
platina crucible. It weighed 22. grs. which is equal to 7.37 grs.
of acid, or 2.46 gers. in an ounce; according to the proportions of
Berthollet,* of 33.5 acid and 66.5 base in 100 parts of sulphate
of barytes.

This acid might either be combined with lime; magnesia, or
soda, or with all the three. To determine what it was. combined
with, I dissolved the salt which had been freed from the earthy
muriates by the process B. J. in distilled water.

* Memoires d’Arcueil, vol. ii,
Won. fis ra)

106 Mr. Horner on the Brine Springs at Drotiwich.

b. To this solution I added oxalate of ammonia in excess: the
precipitate after being well washed, and dried in a heat not
exceeding 165°, weighed 5.68 grs. which is equal to 2.01 gers. of
lime, or 0.67 gr. in an ounce, according to the proportions of Dr.
Thomson* of 35.5 of lime in 100 parts of the oxalate.

c. To the clear solution from which the lime had been thrown
down, I added ammonia, and as it produced no change I concluded
that no sulphate of magnesia exists in the brine. |

But as 2.01 grs. of lime will only take up 2.9 ers. of sulphuric
acid, | infer that the remaining 4.47 grs. of acid must be combined
with soda.

Recapitulation.

1. By Exp. A. it has been shewn that one ounce measure of
the brine contains 64.7 grs. of muriatic acid, and as by Exp. B.e.
it has been shewn that there is no muriate of lime, the whole of
this muriatic acid must be in combination with soda, with the
exception of the small quantity of muriate of magnesia found by
Exp. B. f' g. Muriate of magnesia, according to Dr. Marcet,-+-
contains 56.01 per cent. of acid, therefore deducting 0.15 gr. for
the acid contained in the 0.32 gr. of muriate of magnesia obtained
in Exp. B. from three ounces of the brine, or 0.06 for that con-
tained in one ounce, there will remain 64.64 grs. of muriatic acid,
which is equal to 140.52 grs. of muriate of soda in one ounce of
the brine, according to the proportions of Dr. Marcet of 46 acid
and 54 soda in 100 parts of salt.

2. By experiment C. d. it has been shewn that three ounces of
brine yielded 5.68 grs. of oxalate of lime, dried at 165°; and by

* Henry’s Elements of Chemistry, sixth edition, vol. ii. page 141.
t Analysis of the Dead Sea, Phil. Trans. 1907.

Mr. Horner on the Brine Springs at Droitwich. 107

Exp. C.a..and B.¢. the lime has been shewn to be in combination
with sulphuric acid: 5.68 grains of oxalate of lime, according to.
Dr. Henry,* are equal to 7,1 grs. of sulphate of lime, both salts
being dried at 160°: there are therefore 2.37 grs. of sulphate of
lime in one ounce of the brine.

3. From the several experiments made with the view of
détermining the amount and nature of the sulphates, it has been
inferred that there are 4.47 ers. of sulphuric acid in combination
with soda in three ounces of the brine, which, (according to the
proportions of Kirwan. of 25.52 acid, 18.48 soda, and 58 water,)
are equal to 7.98 grs. of dry} sulphate of soda, or 2.66 in
one ounce. |

4, By Exp. B. it has been shewn that there are 0.32 er. of
muriate of magnesia in three ounces of the brine or 0.11 in
one ounce.

Therefore the several salts contained in the ounce of the brine
consist of

1. Muriate of soda. . 140.52 grs. = 2248.32’ ers, in a pint.

2. Sulphate of lime . AST — —" SB T.92
8. Sulphate of soda. 2.65 — — 42.40
4, Muriate of magnesia. 0.11 — — 1.76

145.65** 2330.40 *

* Phil. Trans. 1810.

* I calculate the sulphate of soda in the dry state, because in the estimate of the
quantity of entire salt, in the brine (with which the gross amount of the several
ingredients obtained separately will be compared) the residnum was dried in a heat
sufficient to drive off the water from the sulphate of soda. To prove this, I exposed
152 grs. of the entire salt which had been dried in the same way, to a strong red heat
in a platina crucible, and there was only a loss of about 3ths of a grain, and that loss
must have arisen from the water that would be separated from the sulphate of lime.

** This exccss in the amount of salt obtained by the estimate of the several ingredients,
may probably arise from the difficulty of drying the different salts to the precise point

o2

108 Mr. Horner on the Brine Springs at Droitwich.

Or Muriate of soda . . . 96.48 per cent.
Sulphate of lime . . . 1.63
Sulphate of soda . . . 1.82
Muriate of magnesia. . 0.07

100.00

By Exp. B. a. it has been shewn that three ounces of the brine
yielded by evaporation 431.86 grs. of entire salt, which is equal
to 143.95 grs. in one ounce.

Before concluding this paper, I shall compare the results I have
obtained, with the accounts of the Cheshire Brine Springs, given
by Dr. Holland in his Agricultural Survey of that county, and
subsequently by Dr. Henry in the Philosophical Transactions
for 1810.

The densities of the different brines in Cheshire and at Droitwich
are very nearly alike. In general, the former seem to contain
rather a larger proportion of pure muriate of soda. The Droitwich
brine is free from carbonate of lime, oxide of iron, and muriate of
lime; all which are contained in that of Cheshire, though in very
minute quantity. But the most remarkable difference between the
two is, that the brine of Cheshire contains no sulphate of soda,
which I have found in that of Droitwich, in the proportion of
nearly 2 per cent.

implied in those experiments by which the proportions of their constituent parts haye
been determined.

* I have already stated, § 10. that there are 2289.75 grs. of entire salt in a pint of
the brine from Walker’s pit. In estimating that quantity, I made use of a cubic inch
measure, whereas in the other case (by inadvertence) an ounce measure was employed,
The difficulty of measuring the quantity very accurately in both cases is very great, and
in a saturated solution, an imperceptible variation in bulk would become yery sensible
in weight,

Mr. Horner on the Brine Springs at Droitwich. 109:

I was disposed to doubt the accuracy of my experiments, until
I found that Nicolas,* in his memoir “Sur les Salines des De--
partemens de Ia Meurthe, du Jura, du Doubs, & du Mont,”
Hassenfratzt in his memoir “ Sur le Sel Marin, and Montignyt in
his memoir “ Sur les Salines de Franche Comté,” state sulphate of
soda as a constituent part of all the brine springs they examined.
There is therefore no reason why this salt should not exist in the
brine at Droitwich; especially as it is one so commonly met with
in mineral waters.

It is foreign to the object of this paper to describe the process
adopted in the manufacture of salt at Droitwich. It does not differ
in any material respect from that employed in Cheshire, of which
Dr. Holland has already laid before the public a very full account.
in his excellent work already alluded to.

* Annales de Chimie, vol. 20. + Annales de Chimie, vol. 11.
+ Memoires de l’ Academie des Sciences, 1762.

VI. Ox the Veins of Cornwall.

By Witu1am Puiturrs, Member of the Geological Society.

A Visit to the county of Cornwall in the year 1800, the induce-.
ments to which were the objects of mining and mineralogical inquiry,
afforded me many opportunities of conversing with practical miners,
The subject was new to me; and it was with considerable pleasure
that I listened to the many striking and interesting facts detailed by
men ever ready to communicate the information they possess, and
whose minds, as repeated visits to the County have since confirmed
to be their characteristic, are habitually disposed to industrious inge-
nuity. It may well be supposed that the foremost of these subjects
was the nature and peculiarities of veins, or as they are technically
termed, loads, or courses.* Having learned that the run, or direc~-

* T have been at some pains to discover the original meaning of the term lode, or loads
as the technical appellation of the cast and west, or metalliferous veins of Cornwall,
Borlase in his natural history of the county treats at page 146 of the Fissure, and the
next chapter begins thus: ¢ From the Fissures let us proceed to that which they contain,
whatever fills them, we calla lead;’ making a distinction between the fissure or vein and
the substances it contains, He says in the same chapser ¢ where the load is barren, it may
serve to /ead us to what is rich;’ and in a note, concludes the term lode to be an old
Anglo-Saxon word, meaning Jead ; thus Joad-stone, meaning leading-stone,’ and refers to
Lye’s Junius wd verbum. Without going so far back for an authority which nevertheless
may be correct, I am induced to belicve the term Jode, though thus spelt by Borlase and
Price, originally meant the burthen or foad of the metalliferous vein. Carew, whose

Mr. WILLIAM Puivurps on the Veins of Cornwall. 111

tion of the regular metalliferous veins is about east and west, and that
in some districts, the same vein is known actually to pass through
several mines, it occurred to me, as being within possibility, that at
Jeast some veins might extend the whole length of the county ; and
that if the situations of such mines as were then working, or had lately
been worked, were accurately described on a map, it might throw
some light on the idea. With this view therefore, after visiting
many of the mines, particularly those of the mining district of which
Redruth may be said to be the centre, that object was accomplished
by the assistance of some friends. ‘The result by no means con-
firmed the idea in which it originated: for although it evinced that
in the year 1800 there were about 120 mines in the county, either
then working, or which had lately been worked, few of the east and
west or metalliferous veins, from causes that will be explained in the
following pages, have been explored, or even satisfactorily traced more
than two or three miles. The map was however preserved merely
with a view to private gratification; but several gentlemen, whose
zeal for geological inquiry induced them to consider this attempt to
shew the localities of mines as in some degree worthy of attention,
urged my offering it to the notice of the Geological Society, accom-
panied by a memoir on the subject of the Veins of Cornwall.

The map not being of course adapted to the present state of the
mines, nor even sufficiently exact in regard to their several localities
at the time at which it was compiled, to meet the public eye, its pub-
lication is laid aside for the present, not however without expecta-

* survey’ was published almost a century ago, not only so spells it, but at p. 8, in speak-
ing of the effects of the flood on the rocks of the county, says it carried away so much of
the oad as was contained therein.’ Besides it is to be noticed, that the north and south
veins, which are not metalliferous, are uniformly termed courses, making a clear technical

distinction between unproductive and mctalliferous veins.

12) Mr. Wititam Puituiips on the Veins of Cornwall.

‘tion of its being given in some future volume of the Transactions, in
the most accurate and satisfactory manner.

But the ascertaining of the local and relative situations of mines,
though of unquestionable interest to the geologist, can only be
regarded as a linkin the chain of inquiry. In order to render its
value complete, it should be accompanied by a memoir, or rather a
comprehensive history of each mine and of its connexion with those
immediately contiguous to it on the same veins. But this could only
be attained by years of unceasing and laborious inquiry on the spot.
In the counting-houses of the most successful mines the only infor-
mation ever committed to paper, in regard to the workings of the
veins are the expenditure and income, together with a section of the
vein from which the profit is reaped, without a single notice in regard
to the tract of country through which it passes. Of the generality
of unsuccessful mines, which form by far the greater proportion, all
that is registered is the loss or expenditure; other information can
only be obtained by a recourse to personal inquiries of the conductors
or captains. |

The following pages are principally intended to exhibit an outline
of general facts relative to the veins of Cornwall, arranged under
separate heads. In drawing up this sketch, such advantage has been
taken of what has already been published on the subject as seemed
consistent with the present object, carefully rejecting every thing
doubtful, or hypothetical, and having in constant view the advantage
of corroborating every assertion to the extent of my limited informa-
tion, by a recourse to the peculiar circumstances of individual veins or
mines. Though thus limited in its object and extent, it will I trust be
found both consistent with its intention and accurate in its detail ; nor
wil its service be trifling if, upon a subject so interesting, and on
which little is known, it should be the means of inducing some of the

Mr. WititAM Puituips on the Veins of Cornwall. 113

numerous and well-informed men, who are immediately concerned
in mines, to gratify the increasing interest which is felt on geolo- .
gical subjects, by giving to the world occasional details of the many
curious facts that almost daily occur in practical mining.

Almost every mine of any considerable depth or extent, is de-
serving of the notice of the geologist, because each has its peculi-
arities :—for when two or more mines are on the same vein or veins,
there is frequently but little else that is common to each ; and even
in the same mine, situated beneath a few superficial acres, there is
often a strange variety in the dimension, contents, and direction of
its veins, and in the country * through which these run.

Direction and Length of Veins.

It has already been remarked that the regular or metalliferous
veins generally take the direction of about East and West; there
are others both in the same and in different directions, most of
which are very rarely found to produce any metallic substance ;
the nature and peculiarities of these will be noticed hereafter. The
regular veins are almost uniformly of considerable length; some
are known to extend two or three miles, having several mines on
their run; and though the idea of their extending the whole length
of the county may be judged to be hypothetical, it ought to be
noticed that the most experienced miner never satisfactorily wit-

nessed the termination of a vein either on the East or West. Many

* T have used the word Country in the sense in which it is employed by the miner,
and shall hereafter so use it, conceiving it to be well adapted, if not better than any
other I have been able to find, to convey the intended idea. Ifa miner be driving an

‘adit North and South, or in any other direction than that of the Load,-he says he
is “ driving through the country.”

Vor, Ik P

114. Mr. WitiraM Pariuies on the Veins of Cornwall.

circumstances of disaster, and more particularly that of poverty,
occur to prevent their extent from being known; but that there are
instances of their appearing not to exceed a few fathoms in length,
is evinced by the ground plans of Herland and Drannack mines,
accompanying this paper. In reality however the veins of those
mines did not terminate as represented on that plan, but continued
both East and West, to an unknown extent, in strings so very
small, as to be only just perceptible, and therefore not worth the
attention of the miner, whose experience induces him to believe
that when a vein diverges in metalliferous strings, however small,
they would, if pursued, be found ultimately to increase in size, or
to converge again, or to diverge to other veins, which are generally
found to be, as it were, increased in size and value thereby. The
East and West veins are sometimes found diverging from the straight
line, even when apparently unaccompanied by any circumstance
that might be assumed as the cause, but they generally return and
resume their customary direction. In Huel Fanny, I think, the
vein suddenly took a course to the South-East, in a few fathoms it
was found to alter its course again, nearer East; afterwards it ran
about East, and then elbowing again, it resumed its usual direction,
nearly if not quite in a straight line. But circumstances of this
kind are by no means common.

Underlie of Veins.

With the exception of those alluvial depositions of tin, found in
vallies and low grounds in many parts of the county, and in the
working of which the tin is separated from its accompanying earthy
substances by means of passing a stream of water over it, whence

they have been called stream works, neither copper nor tin is found

siellieestitiatiadteeeennadiitiiiee an —

Mr. WiLLiAMm Puitirps on the Veins of Cornwall. 115

in Cornwall in layers or beds.. The veins, in which only they are
found, have a downward direction, not perfectly perpendicular to |
the horizon, but inclining more or less to the North or South;
this inclination is called the underlie of the load, which in some
veins does not exceed a few inches in a fathom from the perpen-
dicular, but in others is a fathom in a fathom, or even more.

When two metalliferous veins underlie in opposite directions,
that is, one North and the other South, and meet underground,
the result is not always favourable to the miner; for even though
they might have been rich when separate, they generally are found
to be poor at and after their junction. But when two lodes un-
derlie in the same direction, and one of them quicker than the
other, it is generally found that when the latter overtakes the
former, they seem mutually to enrich each other.

Veins are not very frequently found to separate in the downward
direction, so as to make branches forming distinct veins, having an
opposite underlie. Instances of this however occurred in Tin
Croft Mine, of which a Section is given.

Depth of Veins.

Not an instance, I believe, has occurred of a vein having been
cut out in depth. When the working of a mine is relinquished, it
is mostly either on account of its poverty, or the expense of sink-
ing to a greater depth, being to a larger amount than the product.
The mine called Crenver and Oatfield is 200 fathoms deep ; Cook’s
Kitchen is 210; and Dolcoath 228 fathoms; these are the deepest
Inines in the county now at work.

Pa

116.0 Mr. WiittiAM Puiuuirs on the Veins of Cornwall,

Width of Veins.

The East and West, or metalliferous veins, are generally from

one to three feet in width, but vary to 30 feet. In the old work-
ings of Relistian mine for tin, there are chasms, both open to day*
and underground, full 30 feet wide. A vein from one to three feet
in width is preferred, because, though many instances of the con-
trary have occurred, it is found that the product is generally as
good as in wider veins, on account of there being, for the most
part, less admixture of foreign substances with the ore.
A vein sometimes varies in width in the same mine very materi-
ally, and is often found to increase in that respect in going down.
One of the lodes in Huel Alfred { varies from 9 to 24 feet: there
is a peculiarity in its direction which is noticed in speaking of that
description of irregular veins called Contres. As opposed how-
ever to the width of that vein, those of Herland and Drannack and
Prince George mines, which are separated from Huel Alfred only
by a brook and a cross vein, may be cited.. There, instead of con-
tinuous veins of a somewhat irregular width, they are remarkably
small, most cf them varying only from 2 to 6 inches in the widest
part, which was about the middle, and going away East and West
in mere strings. A tin vein in Whealan Coates mine, not 3 inches
wide, was very rich, and found to be worth working.

If in working on the course of a vein, or in sinking through the
load, the country is found to assume a greater hardness in a very
considerable degree, the vein generally becomes narrower.

* Ore is said to be discovered near the day, when it lies near the surface.

$ Huel signifies a Mine, according to the Cornish-English Vocabulary of Borlase.
It is commonly, though erroneously spelt, Wheal.

Mr. WiLu1AM Puiiiips on the Veins of Cornwall. 117

Denominations of Metalliferous Veins.

The substances which form the contents of the metalliferous’
veins differ very materially ; nor are veins distinguished simply by
the name of the ore for which they are wrought, as a Copper Load,
or a Tin Load; but they have obtained various appellations, ac-
cording to the nature of the substances found to predominate in
them. For as the greater proportion of the contents of most of
them, is neither the ore of copper nor that of tin, the miner in
speaking of them, gives them the appellation which is technically de-
scriptive of the vein-stones :—as a gossany, sparry,mundicky, peachy,
flucany, scovan, caply, pryany, black jack, and a grouany Load.

Gossan is a friable ferruginous substance, consisting generally of
clay, or of some siliceous matter of a loose texture, coated or tinged
with iron, in various proportions, arising probably from the decom-
position of pyrites; it varies in colour, from pale yellow to. deep
red, sometimes inclining to black. A Gossany Lode is more com-
mon than any other, and most promising both for tin and copper.
Gossan has been plentifully found at small depths. in many mines
that produced considerable quantities of one or the other metals,
both beneath as well as mingled with it; as of tin in Huel Sparnon
and Pednandrae, and of copper in Huel Gorland, and in East and
West Huel Virgin.

When the load or contents of a vein is termed sparry, this does
not imply that it is of solid spar or quartz, but that quartz predomi-
nates. A vein in which this substance is considerably compact is
very unpromising ; and if at the same time the vein becomes nar-
rower as it descends, it is generally relinquished as a hopeless under-
taking; which was the case in Huel Gorland, as noticed in my memoir
on the red oxide of copper.* A vein abounding in fluate of lime

* Geological Transactions, vol. 1,

11S Mr. WitirAM Purtuips on the Veins of Cornwall.

is often termed a sparry loau. Quartz is sometimes called hard spar
by the Cornish miner, and fluate of lime, sugary spar.

If iron pyrites abound, the load is said to be mundicky, and when
this occurs at a shallow level it is not always unpromising: even if
it continue in depth, and be somewhat compact, particularly if
mingled with portions of yellow copper ore, there are many in-
stances of such veins proving rich beneath. No distinction is made
by the miner between iron pyrites and arsenical pyrites. The latter
is however rarely very abundant.

A vein that contains a great proportion of chlorite is termed a
peachy load: it promises for tin rather than copper, which is rarely
accompanied by chlorite. ‘Tin was found in it, in Pednandrae,
Polgooth, Relistian, Huel Unity, and in many other mines. I have
specimens of the yellow copper ore in chlorite from Relistian and
from the Wherry mine, the workings of which were under the sea
in Mounts’ Bay.

A vein is said to be flucany when either one or both its sides, or
walls, are lined with a whitish or bluish clayey substance, or when
this substance is interspersed through the vein itself. Flucan in
some few instances has abounded so greatly, that it has been difficult
to prevent its running in upon the miner in working the mine.
This was the case in the early working of the productive copper
mine called Huel Alfred, as is noticed in the annexed description
of some of its veins. ep -

When tin ore is intimately mingled with quartz and chlorite,
the vein is termed a scovan load, which is of a dark brown or of
a greenish hue, but not very hard, or compact. A load of this
description rarely exceeds 12 or 14 inches in width, but it some-
times occurs in a vein the contents of which are not solid, thence
by the miners termed a sucked stone. A load so circumstanced is
often several feet wide.

Mr. Wi1LL1AM Puirurps on the Veins of Cornwall, 19

A vein is termed a cafly load when consisting of a hard, com-
pact and unpromising substance, which seems principally to be
quartz intermixt with minute portions of chlorite, giving a green-
ish, or brownish green tinge to the mass. ‘Tin is often found in
it, copper rarely. But if a branch of copper ore, or a gossan be
found to take its course down the vein, it commonly makes a
durable copper mine.

A vein is said to be a pryany load, when the tin or copper ore
does not occur in a compact state, but when the stones containing
either of them are found mixed loosely with other substances, such
as gossan or flucan. Pry in the Cornish language signifies clay.

A vein that abounds in blende is called a black jack load, which
is generally unpromising for tin, but is considered a good omen for
copper. It is rarely found that blende continues to any consider-
able depth. It is also called mock-lead by miners.

Grouan * is the common technical term for granite, so that when
a vein abounds in that substance, either in masses or blocks, or in
a decomposed state, it is called a growany load, which is rarely
found except in a granite country. Grouan is more promising for
tin than for copper; though veins containing the latter have often
of late been found in the granitic districts of Cornwall, of which
the western part of West Huel Virgin, Carharack, and Huel Damsel,
all rich copper mines, are instances.

It must be remarked that veins generally take their names from
the substances which abound but a little way below the surface.
But, the circumstances of veins change so often, and their contents
frequently participate so largely of the nature of the country they
traverse, that the same appellation will not often hold for them in

* Grouan signifies Gravel, in the Cornish language, Borlase.—It seems therefore
probable that Grouan, correctly speaking, is decomposed Granite.

120.) Mr. WirrraM Puituirs on the Veins of Cornwall.

depth. A satisfactory trial of their nature and value can rarely be
made, without sinking 30, 40, or even 60 fathoms below the sur-
face, and driving, at various depths, east and west on the “ course
of the load.”

Symptoms in Veins.

In the whole range of the employments of man, there is not
perhaps another in which experience and ingenuity are more
often and completely baffled than in mining. Not unfrequently
the appearances in a vein considered to be of the most promising
kind, lead on the most experienced miners during the lapse of
many years only to ultimate and immense loss ;- while on the other
hand, from the product of veins, which by men of not less experi-
ence have been declared to promise no advantage, large profits have
been reaped. The great copper mine called North Downs, in the
working of which no less a sum than £90,000 was lost, may be
considered as an instance of the first, and Huel Alfred, from which
a greater sum has been gained, is an instance of the second. There
is scarcely one symptom on which the miner most relies that has
not occasionally deceived him. It may be curious however to add
some of the symptoms in favour of which the miner is greatly pre-
judiced. ‘There is no one more favorable in his estimation than
a gossany load. I remember that of North Towan Mine was of
this description, and of so great promise, that several of the most
experienced practical miners did not hesitate to declare it superior,
in that respect, to any other they had seen; and that, if compelled
to venture all they possessed, in the working of any one vein, it
should be that of North Towan ; but, after much time and expense
had been bestowed in trying it, it was found to be very poor, and
was therefore abandoned.

Mr. WILLIAM PHILLiPs on the Veins of Cornwall, 121

The early discovery of iron pyrites and portions of yellow cop-
per ore mingled with a large quantity of blende is considered a
favorable omen for copper. Blende, as has already been noted, is
by the miner called Black Jack; and ‘ Black Jack,’ he says, ‘ rides
a proud horse,’ a phrase become proverbial, from blende being often
found to lie above, in a vein rich in copper beneath. Vast quanti-
ties of it were found above the ore in the productive copper mine
Huel ‘Towan, as well as in that called North Bennar. The early
discovery of lead is also considered a good symptom; very many
tons of it were sold from Huel Alfred in the states of sulphuret and
carbonate. Iron pyrites at a small depth is also considered a favor-
able symptom for copper in depth, as was proved among many
others in the rich mines of Crenver and Huel Virgin’; but when it
proves solid, it has often discouraged the miner and induced him to
abandon the vein. The cutting of a ‘ good course of water’ is es-
teemed no unfavorable circumstance, especially if it be warm, and
it is not uncommon to find water issuing from one part of a vein
of a temperature sensibly higher than that in other parts of it. So
greatly indeed does water abound in rich veins, that on extensive
and deep mines are mostly seen two, three, and even four steam-
engines, for the purpose of drawing it, the cylinders of which are
from 30 to 66 inches in diameter. If a vein be particularly rich,
it is considered to omen well for the parts of other veins immedi-
ately north and south of its riches ; to express which the phrase of
“‘ ore against ore” has been adopted.

It would scarcely be correct to say that the early discovery of
tin in a vein is a good promise for copper in depth, but it is cer-
tainly true that tin is frequently, if not mostly, found at a small
depth in veins, afterwards proving rich in copper. Among many

other instances of this that might be quoted, are the two deep and
WOOL: If Q

122 Mr. WituiAM PuItutres on the Veins of Cornwall,

extensive copper mines called Huel Unity and Cook’s Kitchen, both
of which were, I believe, worked for tin at first, without any
suspicion of their veins being rich in copper beneath it. In both
the tin was soon exhausted ; but it should be noticed as an uncom-
mon circumstance, that in the latter mine, after working to the depth
of 180 fathoms, first through tin and afterwards through copper,
tin was found again, and has continued down to the present depth
of the mine, which is about 210 fathoms from the surface. It
ought however to be noticed that some parts of that portion of the
load which principally contained copper ore, had been left, on the
presumption of their not yielding ore of any sort; in the phrase of
the miner they were considered as deads. Some of these have since
been found to produce tin, which may consequently be said to have
prevailed more or less from the surface to the bottom of the present
working. A considerable proportion, if not the chief part of the
copper ore of this mine, was the sulphuret.

Among the favorable symptoms to which the miner is attached
there is still another, which ought not to be forgotten. There are
some among them credulous enough to believe that they hear, while
employed under ground, another pick at work, which is imme-
diately referred to the agency of an invisible spirit, or what they
term a piskey, or small man. This is esteemed an omen of the
most favorable kind, and which induces the full belief of having
nearly arrived at the desired object, the discovery of ‘ a good course
of ore.’ It seems as though the sound which the miner hears, may
reasonably be accounted for "by presuming him to be at work in the
immediate nighbourhood of a cavity, or as he terms it, a voog,
which returns the sound of the stroke of his own pick.

Mr, WiLL1AM Puituips oa the Veins of Cornwall. 123

Discovery of Veins.

The discovery of metalliferous veins is effected in various ways.
Amongst the foremost of these, Pryce places that of the Virgula
Divinatoria ; but, after a long account of the mode of cutting, tying
and using the rod, interspersed with observations on the great dif-
ference existing in the discriminating faculties of constitutions and
persons in its use, altogether rejects it, because * Cornwall is so
plentifully stored with tin and copper lodes, that some accident
every week discovers to us a fresh vein,’ and because ‘ a grain of
metal attracts the rod as strongly as a pound,’ for which reason ‘ it
has been found to dip equally to a poor as to a rich lode.’ These,
it must be acknowledged, are substantial reasons for the neglect and
disuse into which the rod has fallen. There are not however
wanting even now, in Cornwall, some who maintain the value of
it. Iam acquainted with one person who has repeatedly declared
to me that, while using it in his own shop in the town of Redruth,
he discovered a vein which has since formed a part of the workings
of Pednandrae mine for tin. On the other hand, an intimate friend
wejl conversant with mining concerns was present in Somersetshire
with some noblemen and gentlemen, the proprietors of land in that
county, anxious for the discovery and working of veins supposed
to run through their estates, when a person who professed the
skilful use of the divining rod assured them he could effect their
wish. During one of his attempts, my friend, as though by ac-
cident, took his station immediately facing the professor of the rod,
who advanced with the rod dipping as he declared to the run of a
vein; my friend retreated, and in his retreat made a circuit, which
as he had in some degree caught the attention of the person hold-

Q 2

124 Mr. WitiraM Puituips on the Veins of Cornwall.

ing the rod, was followed by kim; and the pegs that were inserted
in the places his feet had touched proved the circuit he had made.
If a vein actually ran in that direction, it is certainly wholly dif-
ferent from that of any known vein. It is almost needless to add,
that the discovery of the supposed veins as indicated by the means
of the divining rod, was not attempted.

The ancient mode of shoding for tin-veins, consisted in tracing
certain stones, of which tin formed a proportion considerable
enough to excite attention, and found at or a little below the sur-
face, to the vein from which they had been accidentally detached,
so as to have passed in a sort of succession down the side of a hill.
Another mode of seeking tin veins is by sinking pits through the
superincumbent earth down to the solid rock, and driving a trench
from one to another, north and south, so as to meet with every
vein in the track through which it passed. This method, which is
also esteemed to be very old, is called costeening.

The former of these methods for the discovery of tin veins is now
rarely resorted to; but the second, as well as another which differs
not much from it, that of working drifts across the country from
north to south, is sometimes practised. Many tracts of the mining
part of Cornwall are however so amply stored with veins in the
direction of East and West, that there is little occasion to employ
either of the above mentioned modes of discovery. There are com-
paratively but few mines which are known to have within their
boundary only a single vein; in some there are 5, 6, or even 7.
As the driving of an adit home to a vein is one of the first and
most important tasks of the miner, he sometimes embraces the op-
portunity of so doing from a neighbouring valley along a cross
course, or North and South vein, and for two reasons ; the first, that
the expense is less than if he were to drive through the solid coun-

Mr. WILLIAM PuiLuips on the Veins of Cornwall, 125

try ; the second, that he has at least a good chance of meeting with
all the veins between the extremity of the adit and the vein to which
he intends to drive it. Yet of this he is not altogether certain, for
the east and west vein is sometimes so greatly disordered by the
cross vein, as that it might wholly escape the notice of the miner ;
besides, cross veins often divide into branches, so that the miner
runs the hazard of following the wrong branch, and_ thereby
of missing altogether the metalliferous vein. But although the
mode of discovering veins, by driving an adit along the run of a
cross course is at once the cheapest and most expeditious method, it
is not always practised, as the foresight of the experienced miner
sometimes induces him rather to drive through the solid country
than to hazard the chance of being obliged to draw the water of the
country all around him, which he is aware the cross vein would
prevent from troubling him on one side.

Accident often occasions the discovery of veins. That of the
mine called Huel Maggot, or Velenoweth in the parish of Phillack,
was first seen by workmen employed in digging a trench for the
foundation of a garden wall ina valley. It there consisted of a rich
gossan, which in the phrase of the miner was very kindly. On
driving into the hill, a few fathoms on the ‘ course of the load,’ it
produced abundance of sulphat of lead in well defined crystals, some-
times accompanied by the sulphuret, and sometimes deposited on the
gossan, and, a little deeper, copper ore in considerable quantity.
Both were however soon exhausted, and the mine was abandoned.
The run or course of an east and west vein may sometimes be traced
on the surface, by loose fragments or portions of earthy or stony
substances, having generally more or less of an ochreous tinge, but
this, which is called the ‘ bryle of the load,’ has rarely a regular
separation from the country on each side of it. But in sinking a

1269 Mr. Wititam Puiires on the Veins of Cornwall.

few fathoms below the surface, it assumes more determinate markg

of being a fissure.

Contents of East and West or Metalliferous Veins.

The contents or load of the generality of veins, if at all attached to
their sides, are for the most part easily separated. A dark ochreous
crust occasionally covers one or both sides of the vein, technically
called the walls of the load; and when these, or at least one of them,
is regular and determinable, they are more encouraging to the
miner than when rough and uneven. A thin coating of flucan is
found on one, or occasionally on the other wall, or sometimes on
both walls of a metalliferous vein, as described by pl. 6. fig. 4. but it
is said that this coating or vein of flucan is most commonly found
on that which, in regard to the underlie of the vein, may be called
the upper wall.

It has been already noticed, in speaking of the denominations
of metalliferous veins, that there is a great diversity in their loads
or contents, and that the same vein exhibits so little uniformity in
that respect, at different depths, as to assume various characters.
Near the surface the load consists for the most part of a sort of
ochreous rubble, probably the debris of the neighbouring country ;
beneath which, though rarely nearer grass than 20 or 30 fathoms,
are found some metalliferous indications. These, if gossan be the
prevailing substance, consist of the ores of tin or copper. But iron
pyrites, blende, fluate of lime, quartz, and sometimes chlorite, or
flucan, frequenily prevail for many fathoms, occasionally mixed
with portions of the country through which the vein passes, though
frequently with but slight traces either of tin or copper. A vein is
sometimes found to consist of little else than a bed of hard and un-

Mr. Witt1aM Puiutes on the Veins of Cornwall, 127

promising iron pyrites, which occasions its being abandoned ; in
others are found the ores of tin or copper, sometimes both, inter
mingled with some, or even most of the foregoing substances ;
but if they occur together, the copper for the most part prevails to
such an amount, as that all traces of tin are lost indepth. In some
veins however they continue to be found, even to a considerable
depth, though not often much intermingled but in separate bunches;
this as has already been noted, was the case in Cook’s Kitchen Mine;
the neighbouring mine, Tin Croft, also furnished a somewhat similar
instance, though not I believe in the same vein; but these must be
considered as somewhat rare occurrences.

Tin iscommonly found much nearer the surface than copper.
When either is very near, especially if abundance, it is in the esti-
mation of the miner an indication that it will not continue to a very
considerable depth, of which Cornwall furnishes numerous instances.
There is a tract of country situate about midway between Truro
and Redruth on the north of the high road, in most of the mines of
which, and amongst them the great mine called North Downs, the
ore for the most part occurred near the surface, and was almost
uniformly found to extend but to a small comparative depth.

Although there are veins in various parts of the country which
have yielded copper in its pure state in considerable abundance, in
masses interspersed through them, and but little intermingled with
other substances, or even with the ores of copper, yet the most com-
mon state in which this metal is found is that called yellow copper
ore. It is more continuous and lasting than any other. There are
veins which yield only the grey sulphuret, but this rarely or never
continues, being found only in bunches. It is sometimes mingled with
the yellow ore. As a proof of the great difference in the value of
the ores of veins, it may be noticed that there are many which

128 3=Mr. Witi1AM Puituips om the Veins of Cornwall.

seldom yield it of a greater price than £4 or £5 per ton. A few
tons were lately sold from the United Mines at £100. The general
average perhaps does not exceed about £7. 10s. or £8 per ton.

In few metalliferous veins does the ore prove so continuous, as
after it has been taken away to leave a large hollow load. The in-
termediate spaces between the ore are mostly filled with what the
miner terms deads, which consist of quartz, fluor, gossan, iron
pyrites and other substances, as well as occasionally portions of the
country through which the vein runs; but the walls of the vein are
nevertheless generally determinable. The deads are not always a
disadvantage to the miner, as they serve to keep apart the coun-
try on either side the vein; but for this purpose, when the vein has
been left hollow by taking away a large body of ore, strong timbers
are made use of; these are not however always found to be of
strength sufficient to prevent the falling in of the cavity. An
instance of this occurred in the copper mine called Huel Alfred ;
one of the veins of which was hollowed out for about 100 fathoms
in depth, 80 fathoms in length at bottom, and 30 fathoms above,
and varying in width from 9 to 24 feet. Notwithstanding great
labour, skill and expense had been bestowed, and the most substantial
timber employed in order to keep apart the walls of the vein, many
thousands of tons came down in an instant; fortunately seventeen
men who had been working in the very place on which the whole
fell, had left it half an hour before the accident. The whole has
been supported, and they are now working beneath it.

It has sometimes happened that in a large load, and where it is
largest, the miner has suddenly arrived at a piece of dead ground in
the middle of it, which in depth spreads wider so as to occupy
nearly the whole of the vein, leaving on each side only a small
connecting string of ore. This has been known to extend many

Mr. Witti1am Puriitps on the Veins of Cornwall, 129

fathoms in length and depth, and from its being narrow above
and widening below, it has obtained from the miner the name of a-
horse. The phrase on meeting with it is, ‘ the load has taken horse..,

The riches of a mine have in many instances proved the cause of
great speculation, and consequent disappointment to those con~
cerned in the mines immediately contiguous east and west, and om
the same vein or veins. This has been but too unfortunately veri-
fied in the instance of East Towan Mine, which joins Huel Towan
on the east; in the latter, which has during the last 10 or 12
years, from one large and unusually continuous bunch of yellow
copper ore (the discovery of which was the result of a search of at
least 30 years at a greater expense) yielded a very large profits
There were 50 fathoms of good ore-ground in the vein at about 66
fathoms under the adit, which adit is 42 fathoms from the surface;
or in the technical language of the miner, from grass. The bunch
of copper ore continued to that depth from near the adit level, and
as in length it extended east towards East Towan Mine, expecta-
tions were raised that the load in passing through that mine would
prove equally rich. Great speculation and expense of course
ensued ; but in vain. For it was found that in several of the levels
in Huel Towan, the ore ceased within a very few fathoms of East
Towan Mine, and in some places as suddenly as if it had been cut
away by a hatchet. This was not the effect of a cross vein, but
purely one of those accidental circumstances to which copper loads
are very liable. The ore of Huel Towan is of a none any ae
sll and generally pretty compact, but not hard.

Adits.

When it has been determined to try a vein, one of the first
Vou. Il, oe

130) Mr. WiLL1AM Pui tips on the Veins of Cornwall.

objects of the miner is to bring home an adit to it. An adit is a
water course, or rather an underground passage, about 6 feet high
and 2} wide, and is begun at the bottom of a neighbouring valley
and driven up to the vein, for the purpose of draining it of water
above their point of contact. In the event also ofthe mine having a
steam engine upon it to raise the water from a still greater depth, it
is not raised by the engine to the surface, but delivered into the
adit. The general level of the mining-country east and west of
Redruth is, according to Dr. Berger, from 350 to 450 feet above
that of the sea, except where the granite overtops the schist, as in
the instances of Carn-brae, Carn-math, and some few other hills, the
summits of which are at a considerably greater elevation, This
general level of the country is intersected by frequent vallies, which
afford great advantages for the formation of adits, and consequently
for the carrying away of the water from the mines. One adit fre-
quently serves this purpose, for 2, 3 or more mines. Pryce, who
published his work, entitled Mineralogia Cornubiensis, about 30
years ago, says p. 148, * Though we seldom see an adit half a mile in
length, there are 2 or 3 of three times that length, these are the
longest I know of.’ But since his time, one has been driven through
a considerable tract of country at the lowest possible depth, as its
mouth or extremity is nearly on a level with the water in one of the
creeks of Falmouth harbour, into which it empties ; and being below
all other adits in that neighbourhood, it is called the deep adit. It does
not run in one course, either direct or circuitous, the whole of its
way; but taking into calculation its various branchings in and
through the numerous mines (those of Gwennap) which it relieves
of their water, it may be said to be about 24 miles in length.

Taking into consideration the purpose of an adit, it might be
presumed that it is wrought on an inclined plane from the place at

Mr. WILLIAM PHILLIPS on the Veins of Cornwall, 131

which it joins the vein to the extremity in the valley. This may
perhaps be the case with some, but the practice is not uniform.
By making them on an inclined plane, a freer current would be
given to the water, yet much of their benefit would be lost, even
although their declination were not to exceed one inch in a fathom.
For, in supposing this plan to have been pursued in the driving of
the deep adit above mentioned, which, from its extremity to North
Downs mine, is about four miles or 3520 fathoms long, it will be
obvious that if a declination of one inch in a fathom be allowed,
the elevation of the adit at North Downs mine would be about
300 feet above its extremity; an elevation nearly if not quite
equal to that of the surface of the mine. If therefore in the
driving of an adit any allowance be made for the current of water
it may be presumed that the interest of the miner will induce him
to make it as small as possible.

Country.

Veins containing copper, as well as those containing tin are found
both in granite and in schist, though until within the last 50 years,
it was esteemed in Cornwall a hopeless expectation to find a vein
containing copper in the former of these rocks. Experience has
however in many instances, in the parishes of Redruth and Gwen-
nap, as well as in some others, proved that veins of copper ore are
found in granite. In both of those parishes granite and schist have
in some mines been found to alternate ; this alternation has not, as
I conceive arisen from their stratification, but from the casual uneven-
ness of the first being supplied by a deposition of the second. It has,
I believe, been but rarely noticed that the course of a vein has been
along their junction; but some instances of this have certainly

RZ

132) Mr. Witi1am Puiirps.on the Veins of Cornwall.

occurred ; and I was informed by Capt. William Davey, of Redruth,
one of the most skilful and intelligent practical miners of the present
day, and who was the principal manager of Huel Gorland mine, that
for some fathoms both in length and depth one wall of one of its
veins was of granite and the other of schist ; another instance is men-
tioned in the annexed notice of the accompanying section of Tin
Croft mine. b otis

The alterations in the country from schist to granite and back
again to schist, are very frequent in some of the mining districts of
Cornwall, so that it is impossible in a word to say in which some of
the mines are situated, but I suspect this to be principally the case with
those mines that are at the foot, or in the immediate neighbourhood
of granite hills. I have not noticed any instances of the junction of
these two substances in which the granite has not shewn a tendency
to decomposition: it is sometimes separated from the schist by a
slight ferruginous seam.

It will of course be understood that great variations in the texture
and hardness both of granite and schist are observable. Of the for-
mer there seems every possible difference in hardness between the
decomposed granite of Tol Carn mine, which, as well as that of several
others, it was impossible to keep apart without lining the adit or
the level with boards close to each other, both above and on each
side, and the compact and fine grained granite, of which quartz forms
a principal ingredient, and which in hardness is almost equal to por+
phyry. Of the great difference in the hardness of schist, I shall
notice one instance in Huel. Alfred ; in the sinking of two shafts in
that mine, not much exceeding the distance of 50 fathoms from each
other, the pay to the miner was in one instance £55 per fathom, but
in the other only £5.

_ These frequent variations in the country through which the miner

Mr. Witi1aM Puixuiips on the Veins of Cornwall, 133

is under the necessity of passing in the usual course of his occupa
tion in the sinking of shafts and driving of levels and adits, often
‘prove the occasions of great hindrance and loss. There is a narrow
channel of a remarkably fine grained substance consisting of compact
felspar and chlorite, running in the direction of east and west, a little
north-west of Redruth, which is so exceedingly hard as to have ob-
tained the technical name of Ire-stone or Iron-stone. It was met
with in driving an adit towards a mine, the Old Pool, I believe,
and it has often been told me, that it was so remarkably compact in
one place as immediately to turn the point or edge of every tool,
so that it was found impossible to drive a hole deep enough to em~
ploy the blast by gun-powder: the miner was compelled little by
little to pick through that part of it, in doing which the seat-board
‘was not once moved forward during the space of 12 months.

The schist of Cornwall varies much in colour as well as in
hardness. It passes from lightish grey through the shades of slate
«<olour to that inclining to a reddish hue, which is considered to be
promising as to the occurrence of tin. But that which is esteemed
the most kindly both for copper and tin, as well as the least expensive
in the working, is of a light grey colour inclining to slate. This
kind of schist is easily broken, and may be left without much sup-
port, and is therefore what the miner terms feasible ground, but it
often passes in depth into a far more compact kind, of a dark colour,
inclining to blue.

Cross or North and South Veins,

It has already been noticed that there are veins in Cornwall,
which as they are found almost uniformly to traverse the east and

1384 Mr. WititAM Paitiips on the Veins of Cornwall.

west or metalliferous veins* in the direction nearly of north and
south, are technically termed Cross Courses. ‘They rarely produce
copper or tin, or any other metallic substance. They vary from
half an inch to a few feet in width: the underlie of some is east, of
others west ; others again have little or no perceptible underlie, but are
nearly perpendicular to the horizon. In some tracts of the mining
‘country they are of very frequent occurrence, as the accompanying
ground plan of Herland mine will evince.

- Cross Courses, or north and south veins, may be subdivided into
Ist. a Quartzose vein, to which the general term of Cross Course
-has been given—2nd. a vein containing a soft marly or clayey sub-
stance of a bluish or whitish appearance, called a Flucan; and 3d, a
vein containing a substance of an ochreous and friable nature and of a
yellow colour, called by the miner a Cross Gossan. Every cross course
or cross gossan is however accompanied by a flucan. In speaking
of these veins the miner sometimes gives them their technical appel-
lations, but he is more habitually disposed, whatever the substances of
these veins may be, to call them by the familiar term of cross courses.

The principal advantage derived from the north and south veins is
that, when their substance is flucan, or even when a continuous vein
of flucan, however thin, accompanies the quartz or gossan, they pre-
vent the water of the neighbouring country from troubling a mine,
and they are sometimes left to perform that useful office, as was the
case between Huel Sparnon and East Huel Sparnon, near Redruth.
But their disadvantages are numerous ; for although the regular me-
talliferous veins are occasionally found to be but little or not at all dis-
turbed by the passing of the substance of. the, cross vein through
them, except by the mere division of the load, it more often happens

* A rare exception (the only one I am acquainted with) has been found in the mine
called Huel Alfred; a description of some of its veins is annexed.

Mr. WILLIAM Puixuips on the Veins of Cornwall. 135

that it is as it were broken into small strings or branches. By a care-
ful examination of the nature and direction of these, the miner is .
indeed sometimes enabled to find pretty readily that part of the load
which is on the other side of the cross vein, but he is often baffled.
Instances have occurred in which the load has, as it were, been
turned by the cross vein, so as to form what the miners term an
elbow. )

Not only does the substance, whatever it may be, of the cross
vein, almost uniformly pass through that of the metalliferous vein,
but it is often found so to interrupt its course, as, in the phrase of
the miner, to Aeave that part of the vein, east or west of it, a few
inches, or even many fathoms north or south: and as the metal-
liferous vein is frequently found to be poor on one side of the
cross vein, though rich on the other, its occurrence sometimes
not only baffles the skill of the most experienced miners, but also
causes much loss and vexation, as the annexed account of some
peculiarities in the veins of Tol Carn, Huel Jewel, and Huel
Damsel mines, will shew.

Though the cross courses, or north and south veins, are rarely
found to be metalliferous, or even to yield any of the ore of the
east and west veins through which they pass, a general exception
was found to exist in those of the great tin mine near St. Austle,
called Polgooth, in which, I believe, they universally produced
tin. Two of the cross veins in Herland and Drannack mines
yielded silver—one of them: very sparingly, in the other it was
accompanied by other metallic substances: the quantity of silver
amounted in value to 8 or £9000. Pryce says* that-cobalt has
been found in veins of this description, that others have been
worked for lead, and } that the direction of antimonial veins is

* Min. Cornub. p. 50. + Ibid. p. 50,

1860 Mr. WitttaMm PuiLuips on the Veins of Cornwall.

mostly north and south, but that he hdd not known ‘ any produ-
cing that mineral of more than fourteen fathoms deep.’ The mine
called Huel Boys, which formerly produced the triple sulphutet,
is now worked for antimony, which occurs in bunches of various
dimensions in a vein, the direction of which is nearly north and
south, and of about five feet in width. The antimony is accom:
panied by blende only, and is not now found ina state of crys+
tallization. The country through which the vein runs is schist.

- Slide.

-. Veins, not of a metalliferous kind, but which contain gossan,
or flucan, are sometimes found running north and south, with aa
east or west underlie, generally very quick, one of which will be
noticed on a reference to the section of the Manor OldVein. Veins
of this description are also found in the direction of the metalliferous
or east and west veins, having an underlie north or south. But
whether their direction be east and west,.or north and south, and
whatever their underlie, they are frequently the cause of much
expense and vexation to the miner. When the underlie of this
species of vein is in the same direction as that of the metalliferous
vein, but quicker, so as to overtake it in depth, the latter is ge-
nerally divided by the former, and, as it were, removed from its
regular course. The load of the metalliferous vein is also some-
times altered in respect to its value, above or below its section,
and the space between a and 4, P1. 6. fig. 2. as it regards the load, is
as it were lost. This kind of vein, from its direction, has obtained
the name of S/ide, and the phrase is, ‘ the load is cut out by a
slide ;’ its flucan or gossan, generally traverses that of the north and
south, as well as the east and west veins.

Mr. WitiiAM Puitiips on the Veins of Cornwall, 137

Heave.

But when the underlie of this species of vein is in opposition to
that of the metalliferous vein, the effect of it is immediately the
reverse of that of the Slide, and is called the Heave. Pryce has
noticed a remarkable instance of this which occurred in the Goon
Laz and Pink tin mines, in the parish of St. Agness. The tin
load underlaid north, the gessan vein south. (PI1. 7. fig.7.) At
62 fathoms in depth, it separated the tin load at a, heaving the
other part of it up to 4, 22 fathoms in perpendicular height, and
19 fathoms horizontally north. Another gossan vein afterwards
cut the tin load at c, heaving it up to d. The tin load then
resumed its course, until another gossan vein separated it at ¢,
heaving it up to f-

It will be observed that the effect of the heave is that of affording
a greater portion of the tin load at a given depth from the surface,
than would have been the case had the vein pursued its regular
downward direction. But this is not always a compensation to the
miner ; for the vexation and expense accruing to him in searching
for the tin vein generally exceed any advantage to be gained by
the heave. It was, I believe, principally the effect of a heave that
baffled the skill and experience of the most eminent practical miners
in Muel Peever; in which mine they were, during about 40 years,
in search of the load, and which was at length discovered. Per-
haps the history of that mine, and of the long and vexatious
search, occasioned by the loss of the vein, would prove the most
satisfactory evidence that can be obtained of the strange pheno-
mena occasioned by the heave; and I have the satisfaction of

knowing that it is the intention of a gentleman, who has nearly
Voimil, S

1388 Mr. WiirraMm Paivuips on the Veins of Cornwall.

completed an account of it, to present it to the Geological So-
ciety.

In describing that effect produced by the interruption of one
vein by another, called the heave, it ought to be noticed that a
copper vein going down with a quicker underlie than a tin vein,
always passes through it, and sometimes interrupts its regular course.
And if the underlie of the copper vein be south, and that of the
tin vein north, or vice versa, the copper vein continues its course,
but interrupts that of the tin vein, heaving it out of its first direc-
tion; and although Pryce has merely given the appellation of
‘ Gossan’ to those veins that heaved the tin veins, as just noticed,
it seems to me probable that these ‘ Gossans’ were veins containing
copper, which is rendered the more so, as the term ‘ Gossan’ is
frequently given to a copper vein, merely from its being the pre-
vailing substance. The heave of a tin by a copper vein was, I
believe, one of the remarkable and complicated disasters which

befel the veins in Huel Peever.

Feeder.

A small metalliferons vein or string is sometimes found to take
the same course as the east and west vein, (PI. 6. fig. 3.) “When its
underlie is so much quicker than that of the latter, as to overtake
it in going down, the metalliferous vein is generally found to in-
crease in size, not merely in the proportion of the addition of the
lesser vein, but very much more, so as to make a great body of
ore, called by the miner a gulph of ore at their junction. This
species of vein is therefore termed a Feeder.

Leader.

While working in the course of a load, small metalliferous

Mr. WittiAMm PHILLIPs on the Veins of Cornwall. 139

branches or strings are occasionally observed to strike into the vein
from the north or south, which, it seems probable, have before ’
diverged from the same, or some neighbouring vein, (PI. 6. fig. 5.)
It is not certain that copper veins are equally subject to this cir-
cumstance as are those of tin. In Polgooth and Carnmeal tin
mines, their effect was the sudden enlargement of the load to
what is termed a floor of tin, twelve feet or more in breadth, but
without the determinate walls usually observable in regular veins.
A floor of tin rarely continues for any considerable length or depth,
and the load is generally soon found to resume its usual size and
appearance. From the common effect of this kind of branch or
string, it is generally known by the term /eader,

The Contre.

There occurs still another species of vein, of which the course
or direction is generally about north-east and south-west, and
which therefore is oblique in respect to all other veins; from this
circumstance I presume it to have obtained the name of Conére or
Caunter. ‘They are mostly, if not always, metalliferous; several
instances have occurred of their being remarkably rich. Two in-
stances will be noticed in the annexed descriptions of Huel Alfred
and Herland mines, in both of which they were very productive
of copper ore.

It may here be noticed, that in the former of those mines, the
regular or east and west vein was disturbed by the contre, and for
some distance totally disappeared on the west. Inthe latter, both
the load of the regular vein and that of the contre were enlarged,
and became more productive by uniting.

s 2

140) 39=~-Mr. Witt1Am PaiLuips on the Veins of Cornwall. ;

Elvan.

Elvan is one of the three grand distinctions made in regard to
rocks by the Cornish miner. Whatever is not grouan (granite) or
kill as (schist), is of course with him elvan. So that, in fact, it is
extremely difficult to say what it is or even what it is not, with the
exception of granite and schist. ‘The substance to which it is
most commonly applied occurs frequently in Cornwall, not as
forming tracts of country, but interposed between the schist, in
what is termed by the miner a channel. I know of no instance
of its thus occurring in granite. The situation of these channels is
not horizontal : they generally dip at various angles with the horizon,
and in various directions. ‘The colour of elvan is bluish-grey, or
yellowish. It does not always disturb the contents of the metal-
liferous vein, which generally continues through it, though the load
is mostly narrower than when in the schist ; but it sometimes has
the effect of dividing it into small branches. By the accompany-
ing section, of Pleasure, Fancy, and, North Herland veins, Pl. 8.
fig. 10. it will be seen that a large channel of elvan took a course
opposed, though not opposite, to that of the metalliferous vein,
and that two other channels took similar directions by the section
of the Manor Old Vein, fig. 11. The examination of some speci-
mens induced me to consider the elvan of these mines to consist
of crystals of quartz and felspar imbedded in compact felspar; in
one specimen, the latter was intermixed with compact quartz.

Mr. WiLi1AM Puivurps on the Veins of Cornwall. 141

In the preceding pages I have aimed at giving a mere general
outline of facts, which, considering the imperfect state of geology,
seems to be rendering better service to science than could be de-
rived from a feeble attempt. to raise upon their basis any theory
explanatory of their occurrence. Nor indeed is the knowledge of
insulated facts sufficient to authorize such an attempt on this im-
portant and difficult subject, comprehending operations on so grand
a scale, of a date so remote, and throughout a country so greatly
diversified. Before such an explanation can be satisfactorily ac-
complished, we have much to explore and to learn. The task
seems to require a combination of talent and of information, which
but rarely exists. But that a faithful detail of mining facts may
contribute to assist the geologist in his inquiries, can no more be
doubted, than that the science of mineralogy is absolutely essential
to assist him in his researches.

It is to be regretted that the practical miner, in every part of
England, is almost wholly ignorant of the principles and facts of
mineralogy and geology. Even the conductors of the mines,
termed captains, are men generally of little or no education, who
have risen to that station by a superior attention to their art, in
which they have been incessantly occupied from the early age of
five or six years. A century ago among the miners of Cornwall,
whatever was not tin was heedlessly thrown aside; and within that
period, on the discovery of copper ore beneath the tin, it was no
uncommon observation, that the ‘ ore came in and spoilt it.’ It is
an undoubted fact that many roads in the county were mended with
copper ore. The discovery of the native silver in Herland mine
would have passed unnoticed, but for the vibrations of some ca-
pillary portions having accidentally attracted the notice of a work-
man; and it is confidently believed that much of that precious

142 fr, WILLIAM PuriLiips on the Veins of Cernwall.

metal has been thrown away on the neglected heaps of that mine.
Even now, whatever is not manifestly tin or copper, or is not sus-
pected of yielding those metals, is paid little attention to ; and the
practical miner sees no value in the inquiry into the run of veins,
the nature of the country they traverse, their contents, or uniformity,
further than relates in his own estimation to the immediate benefit of
his occupation ; and he smiles at the nice discriminations of the mi-
neralogist. If an inquiry into the phenomena of veins be made
of him, he refers, by one short cut, to the universal deluge.

The total ignorance of almost every thing relating to the sciences
of geology and mineralogy, and above all of chemistry, in the con-
ductors of mines, and their agents, is not only matter of regret, but
it can scarcely be doubted, is also the cause of much loss to the ad-
venturers in mines, to the lords of the soil, and to the buyers of the
ore. If a spirit of inquiry had existed, which some knowledge of
these sciences could not have failed to produce, much cobalt would
not have been thrown away on the heaps of Dolcoath and some
other mines, nor would bismuth in Huel Sparnon have been mis-
taken for cobalt, nor would the roads have been mended with copper
ore, nor would the ponderous ore, which contained silver in Her-
land mine, have been left to the chance that discovered its value,
nor would many miners, in opposition to all the known principles
and properties of mineral bodies believe, even to this day, in the
regeneration of metals.* While in France, and in Germany, there

* “ Whether tin doth grow again, and fill up places which have been formerly
wrought away, or whether it only separateth itself from the consumed offal, hath been
much controverted, and is not to this day decided.” And ‘* whether—dead !odes—
that have not one grain of tin in them—may not hereafter be impregnated, matured,
and prove a future supply to the country, when the present lodes are exhausted, I think
well deserves our highest consideration.”” Notes to Carew’s Survey of Cornwall, edit.
1811, by Tonkin, edited by Lord de Dunstanville. It must be confessed that these
inquiries still prevail amongst practical miners.

Mr. WitttaMm Paicuirs on the Veins of Cornwall. 148

are national institutions for the education of those intended to con-
duct the working of mines, in the three important branches of”
science before alluded to, and which are so intimately connected
with their occupation, in this country all is left to accident, and
the rich gifts which nature has bestowed upon us, are consequently
often neglected, or lavishly thrown away.

“The ores of copper, as sold at the mine, though some of them
are richer, do not in most instances contain more than one-twelfth
of copper, frequently not one-fifteenth, some of them not one-
twentieth. The accompanying substances are a heterogeneous
mixture of earths and metals, amongst which arseniates of various
kinds often bear a considerable proportion. It needs not to be in-
sisted upon that much attention ought to be given to free copper
from arsenic, which is so very liable to render it brittle. When a
pound or two of the ore is given to the sample-trier, as a fair sample
of 50 or 100 tons, his report is but too often grounded on the
weight of the pri// he has obtained from a given quantity of the
ore, without reference to the substances with which it may be al-
loyed, which indeed his skill does not enable him to detect. When
the ore is taken from the mine, it is for the most part deposited, not
that of each mine separately, but mixed with that of many others,
without regard to the great difference that must of course exist in
the ore of veins, circumstanced so variously as are those of Corn-
wall.* And strange as it may seem, it is notwithstanding true, that
even the interest of the buyer seldom tempts him to swerve from

* In reply to this observation, it has been said that the ores of some mines are found
to smelt more easily when mingled with those of certain other mines than alone. This
will not perhaps be doubted. All that is now contended against is, the common
practice of mixing indiscriminately ores of copper of any, or rather of every de-
scription.

144.9 Mr. Witzt1aM Puixutps on the Veins of Cornwall.

the hacknied practice of his predecessors, in making purchases to an
enormous amount on the reports of those whose skill only extends
to the extracting of the heaviest prill, without possessing a know-
ledge of chemistry sufficient to enable them to discover of what it
is compounded,

Enough has been said in the preceding pages of the uncertainties
attending the pursuit of the miner, to amount to evidence that skill
and ingenuity are often exerted in vain:—all they can do is to
determine on, and put in practice the speediest and most effectual
methods of ascertaining the value of a vein, at the least expense.
When assisted by the best experience, they are utterly unable to
form a conjecture, grounded on reasonable certainty, that the great
expenses attending the trial of a vein will be repaid, If indeed the
reverse of this were the case, there would not be as there now are,
so many skilful captains of mines who have lost money by their
adventures. If experience avails so little, theory cannot be ex-
pected to avail any thing; and it may fairly be doubted whether all
that science could bestow on the practical miner, would, in this
branch of his occupation, be found to be of the slightest advan-
tage.

The habits of the miner are those of industry and perseverance,
which often tempt him to exploits that excite astonishment at his
venturous hardihood. The very idea of a descent beneath the surface
of the earth has something in it of the terrible, at which those
shudder who are unacquainted with practical mining. But such is
the force of habit, that rarely does any other employment tempt a
miner to forsake his own. ‘The occasional perils of his occupation
are scarcely noticed, or if noticed are soon forgotten. He walks
often in the middle of the night, and in all weathers, two or three
or more miles to the mine, undresses, and puts on his underground

Mr. WititAM Puituips on the Veins of Cornwall. 145:

clothes, and with his tools slung over his shoulder, descends by
ladders a depth of 1000 or 1200 feet, assisted by the light of a ~
small candle, and works in the bottom of the mine six or eight
hours, amidst the noise of the working of the pumps in drawing
the water, with as much alacrity, and with as little sense of danger,
as he would feel amidst his ordinary occupations above ground.
We should be inclined to feel pity for the wretch who, as an atone-
ment for his crimes, should be compelled to undergo what the
Cornish miner voluntarily undertakes for a small pittance, and that
even of an uncertain amount. ‘ The mine of Huel Cock, in the
parish of St. Just, is wrought eighty fathoms in length under the:
sea, below low water mark; and the sea in some places is but three
fathoms over the back of the workings, insomuch that the tinners
underneath hear the break, flux, ebb, and reflux of every wave,
which, upon the beach overhead, may be said to have had the run
of the Atlantic ocean for many hundred leagues ; and consequently
are amazingly powerful and boisterous. They also hear the rum~-
bling noise of every nodule and fragment of rock, which are con-
tinually rolling upon the submarine stratum ; which altogether make
a kind of thundering roar that would surprise and fearfully engage
the attention of the curious stranger. Add to this, that several
parts of the load which were richer than others, have been very
indiscreetly hulked and worked within four feet of the sea ; whereby
in violent stormy weather the noise overhead has been so tremendous
that the workmen have many times deserted their labour, under the
greatest fear lest the sea might break in upon them.’

The account of Huel Cock above cited, is extracted from the
Mineralogia Cornubiensis of Pryce, page 21. I have made some
use of the mining information contained in that work, which,
though it is often confused, and sometimes scarcely intelligible, is,

Vora. .

146 © Mr WittiraM Puiturps on the Veins of Cornwall.

apart from its reasonings and its philosophy, a valuable production.
I have not thought it necessary to acknowledge my obligations to it
in every particular instance ; nor, on the other hand, have I been
willing to quote its authority, without verifying it by an appeal to
some of my numerous friends among practical miners.

As an appendix, it seemed to me that some account of the veins
of certain mines, remarkable either for their peculiarities or some
striking geological fact, might therefore be an acceptable addition
to the geologist, as well as in corroboration of what has preceded.
I have however to express my regret that these relations are imper-
fect, inasmuch as little is said on the subject of the countries in which
these mines lie. For as the information on that head could only. be
obtained from the practical miner; and as he notices the country
merely as respects the ease or difficulty with which his operations
are carried forward, or at most no further than regards his three
grand distinctions of grouan, killas, and elvan, little or nothing
satisfactory could be obtained, on that important part of their his-

tory.

Ground Plan of Herland and Drannack and Prince George
Copper Mines.

Pl. 8. fig. 9.

Herland and Drannack mines are situated in a hill that rises sud-
denly on the west for some distance, but which is afterwards nearly
on a level for about half a mile, the highest ground being about
the center of that vein termed the Manor Old Load, having a gra-
dual fall to the south of the middle mine. The country is schist,
but in some places so hard as to require the blast by gun-powder.

Mr. WiLL1AM Puixures on the Veins of Cornwall. 147

The general direction of the metalliferous veins is a little from
the north of the east to the south of the west, and of the north.
and south veins or Cross Courses, a little from the west of the
north to the east of the south. :

Herland and Drannack and Prince George mines, and that called
Huel Alfred, a description of some peculiarities in which is annexed,
claim peculiar attention, as well on account of their being in im-
mediate contact with each other, as because their situation in a
schistose country, seems almost the only circumstance decidedly
common to both. In almost every thing that respects their veins,
it would perhaps be difficult to point out two mines more com-
pletely at variance, except that in each there occurs one of that
denomination which is termed a contre.

Most of the east and west or metalliferous veins of Herland and
Drannack mines varied from 2 to 6 inches in width, and whenever
found to exceed the latter size, it proved an indication that they
were about to diminish, and in the language of the miner, to pass
away in the run of some fathoms in mere strings—a circumstance
of extremely rare occurrence in the veins of Cornwall: they were
consequently abandoned, because they no longer paid the expense
of pursuing them east or west. It may well be supposed that con-
sidering the narrowness of these veins they were extremely rich ;
in fact they were so rich that it was frequently the practice of the
miner, after taking away one side of the vein, to spread canvas to
receive the load. That vein called the Manor Old Load exceeded
the rest in width, being in the largest parts from one foot to one foot
and a half in width, and the ore was occasionally found in floors ot
two or three feet wide, a circumstance more common in tin loads
than in those of copper.

The direction of the contre is somewhat to the north of the west

TZ

148 Mr. WiLLiAM PuiLuips on the Veins of Cornwall,

and south of the east: it produced a considerable quantity of cop-
per ore, and varied from one to three feet in width. Near the
surface great quantities of blende and iron pyrites were found in it.
Wherever it intersected the east and west veins, their contents
formed together one load at the junction for about eight fathoms in
length and three or four in width. That part of the contre west
of the cross vein called the Privateer Flucan was heaved by it north-
wards two or three fathoms, and the substances of both were min-
gled together. By Harvie’s cross course it was heaved eight fathoms,
and the substance of the cross course between the divided parts of
the contre was found to be nearly twice its usual size, and consisted
not of quartz only but of quartz mingled with iron pyrites, blende
and copper ore, so that both the cross course and the contre in
part lost their peculiar characters. The contre continued both N.W.
and S. E. beyond its working, but was poor.

The substances of the numerous north and south veins or cross
courses of these mines were quartz or flucan, or both. By the
ground plan some variations will be observed in their directions, as
being more or less to the west of north and south of east: it will
also be seen that their general effect is to alter the course of the
veins they traverse, by heaving, in the phrase of the miner, the
western parts of them higher north, but with some exception, for
the reverse was the fact in respect to those parts of the Manor Old
Load and Middle Mine Load traversed by Chambers’s Flucan and
the Great Cross Course. )

The discovery of silver in one of the north and south veins of
these mines has already been made known by the publication of
Mr. Hitchins’s paper on that subject in the Philosophical Trans-
actions. It may however not be amiss to take some notice of that

peculiar circumstance. It was found in that part of Convocation

Mr, WILLIAM PuHILuips on the Veins of Cornwall. 149

Cross Course which traversed the Manor Old Load, and was first
noticed at about 116 fathoms from the surface: the Cross Course’
was at that place about 21 feet wide, but was narrower above, and
consisted of quartz accompanied by a continuous flucan, which also
was found with the silver. For some fathoms in depth after the
first discovery of the silver, the Cross Course consisted for about 8
or 9 feet, and in some places for 3 fathoms, north and south of its
junction with the Manor Old Load, of silver mingled with sulphuret
of lead, iron pyrites, bismuth, cobalt, wolfram, &c. and these sub-
stances continued to abound and to traverse the copper load so long
as it was rich while in contact with the cross vein.

It was noticed in the paper of Mr. Hitchins above alluded to,
that the Rusty Cross Course, next on the east to Convocation Cross
Course, also produced some silver, although not in sufficient quan-
tity to pay the expenses of procuring it. This cross course con-
sisted of quartz accompanied by a vein of flucan, sometimes on one
side of it and sometimes on the other, together with iron pyrites
occasionally.

The extent north and south of the channel of porphyry, or, to
use the miners term, of elvan, which forms sc conspicuous a feature
in the section of Pleasure, Fancy and North Herland veins, is not
known. Its effect in compressing the east and west veins is worthy
of attention, and is noted on the ground plan, which, together with
the accompanying sections are given from original documents now
in my possession. |

Section of Pleasure, Fancy, and North Herland Copper Mines.

Pl. 8. fig. 10.
The mines united under the name of Herland and Drannack

were formerly worked separately, but were united on account of

150 Mr. WitiiaM Puitiips on the Veins of Cornwall,

the drawing of the water being performed by the engines on Her-
land mine, and the name Drannack was added to Herland because
two of the Mines (Fancy and North Herland) united with it were
situated in a tenement of that name. ‘This section therefore is that
of the workings of the veins designated on the ground plan by the
names of Pleasure, Fancy, and North Herland, north, middle and
south branches. It is on the course of those veins, and supposes
the country on the south side of them to be taken away, and of
course in looking at this section we look north.

The shafts and levels which constituted the workings of these
mines are not laid down, because they were not completed on the
original, and even had they been so the present object can be as well
accomplished without them. This section, together with the ac-
companying section of Herland mine, exhibits several striking
geological facts.

By this section the underlie of the several north and south veins,
or cross courses and flucans, which intersected the mines, will be
observed.

It will also be seen that, to use the miners language, a large chan-
nel of elvan took its course with a very quick underlie towards the
west : near the surface it was about 15 fathoms thick, but diminished
gradually in depth. Its precise direction or extent on the surface
towards the north and south was not ascertained. From some
specimens of this channel in my possession, and of that passing
through Herland mine, they appear to consist of crystals of quartz
and felspar imbedded in compact felspar, which in one or two in-
stances is mingled with compact quartz.

It merits particular notice that the substance of each cross course
(viz. quartz) uniformly traversed the channel of elvan, but, while
in it was much smaller and more compact than when in the schist.

Mr. WILLIAM Puitiips on the Veins of Cornwall. 151

‘That of the flucans, which consisted, when in the schist, of two
veins of flucan or soft marl with portions of schist between them, -
were while in the elvan very much smaller, and: their substance
appeared to be either a mere seam of flucan, or was of a sandy
nature resembling pulverized porphyry. |

The metalliferous veins likewise passed through the channel of
porphyry, which had no other effect upon them than that of dimi-
nishing the load in size; it therefore appeared to be richer.

The north and south vein, called Convocation Cross Course, was
not found to produce any silver in this mine.

Section of the Manor Old Vein.
Pls. fig. la.,

This section is on the course of the vein called the Manor Old
Vein, on the ground plan of Herland and Drannack mines. It was
originally worked: as a separate mine, under the name of Herland.
Its greatest depth was about 150 fathoms from the surface.

The several cross courses and flucans correspond with those in
the ground plan. Halfpenny Little Flucan and Chambers’s Flucan,
were nearly, if not quite, perpendicular to the horizon; the under-
lie of the others will be seen. It will be observed on consulting
the ground plan, that Williams’s or Penberthie’s flucan traversed
the veins both of this mine and that of Pleasure, Fancy, and North
Herland mines. North and South veins generally take the name
of the shaft they most nearly approach. ‘The flucan in this mine
was nearest to a shaft called Williams’s, and therefore obtained the
name of Williams’s flucan. In the other, it approached nearest to
Penberthie’s shaft, and was therefore called Penberthie’s flucan.
Both names are therefore given on the ground plan.

152.9 Mr. WILLIAM PHILLIPS on the Veins of Cornwall.

It was in this mine, as has been already noticed, that silver was
discovered in Convocation Cross Course, as well as a very small
quantity in Rusty Cross Course.

Two channels of porphyry also occurred in this mine ; their effect
onthe N. and §. and E. and W. veins was similar to that produced by
a channel of the same description in Pleasure, Fancy, and North
Herland mine ; their underlie and thickness are also about the same.

The underlie of the Side is in the same direction as that of the
channel of porphyry, but not so quick. Its substance was flucan of
three or four inches in thickness ; it passed through the cross courses
and flucans. It also traversed the metalliferous vein, the course of
which it interrupted, and heaved about fifteen inches, but whether
to the north or south I know not. The load of the metalliferous
vein was found to be richest a fathom or two along the run of the
slide, both above and beneath it.

Transverse or North and South Section of Tin Croft Mine.
Pl. 7. fig. 8.

Tin Croft mine has been worked many years; and has yielded
large profit both to the lord of the soil and to the adventurers.
It was first worked for tin, principally, I believe, if not wholly, on
the two most northerly veins. ‘The country in which the mine is
situate is for the most part schistose, but some remarkable alterna-
tions of schist and granite were discovered while working the two
veins on the south, the probable cause of which appears to be this,
that as these veins run parallel with and at the foot of the hill called
Carn-brae, which is wholly of granite, the irregularities in the granite
were supplied by a deposition of the schist. In no other part of the
mine does granite appear, except that in following down two of
the veins, as is noted on the accompanying section, they were

Mr. WILLIAM PuHiI.urPs on the Veins of Cornwal, 153

found to traverse a mass of it at about 73 fathoms from the surface,
above and beneath which schist only was observed.

The veins of this mine are worthy of attention in regard to their
number, underlie, dimensions, and contents. In number they are
seven; the other two may rather be called off-sets from a vein
than veins. If however they be considered as veins, there are in
this mine five of copper, three of tin, and one of tin and copper,
in about a furlong and half of country from north to south. The
general irregularities of their underlie, both individual and regard~
ing each other, are very remarkable: only the Old Tin vein and
Bodilly’s vein proceed in a straight line, and it will be noticed
that the New Tin vein proceeds in five directions, the second more
inclining to the perpendicular than the first, the third more than
the second, and so on. ‘The South vein varies in width from
one to six feet, and was rich in copper from about 35 fathoms
until about 70 fathoms from the surface; that is, through the
lower part of the upper deposition of granite, and the subjacent
schist ; but at about the place where it entered the granite again
it was hard and poor. It was pursued for about 100 fathoms in
depth. The ore was a mixture of yellow and grey, and like that
of every other vein in the mine, was so extremely bunchy, that a
regular course of ore, as it is technically termed, could scarcely be
said to have existed in any part of it. Dunkin’s vein varied from
one to twelve feet in width, and its general underlie differed so
little from the perpendicular, that advantage was taken of that
circumstance to sink the shaft on its course. It was poor at the
points of junction with Martin’s and Bodilly’s veins, but some ore
was found in it between them. It was richer below the latter, and
was worked to the depth of about 125 fathoms from the surface.
Martin’s vein was from about 3 to G feet wide, and yielded abun-

VoObe Tl. U

154 Mr, Wittram Puiturps on the Veins of Cornwall.

dance of yellow ore (from which brilliant specimens were selected
in tetrahedral crystals of considerable size) and was worked to about
100 fathoms from the surface. Bodilly’s vein varied from one to
six feet in width, the ore was yellow, the vein was for the most
part poor and hard, and was worked to the depth of about 125
fathoms. The load, or substance, of the South and Dunkin’s veins,
passed through the New Tin vein, which, a little below the latter of
them, yielded a considerable quantity of tin, as it did also at about
70 fathoms from the surface; in the intermediate space it likewise
yielded tin, with a very small quantity of copper, but was far from
rich. It was pursued for about 90 fathoms in depth. In the
small vein on the south of Chapple’s vein some tin was found, but
the quantity was not considerable. Chapple’s vein varied from one
to three feet in width, and yielded yellow copper ore, interspersed
with large quantities of iron pyrites. It was worked to about 100
fathoms from the surface, as was also the Highburrow vein, which
varied from six to twelve feet in width, and yielded both tin and
copper, either intermixed or running side by side down the vein:
the latter was both yellow and grey, and very abundant. The old
vein is very large, and was very productive of tin for about the
depth of 45 fathoms from the surface, when it became poor, and
was found to contain little else than iron pyrites. But as this
vein, during many years, proved immensely rich in copper when
passing through Cook’s Kitchen mine, which is contiguous to Tin
Croft on the west, little doubt is entertained by miners that it
will also be found rich in copper at a greater depth than it has
hitherto been proved in this mine. ‘To Captain Thomas Teague,
of Redruth, an experienced and very intelligent miner, and who
during many years has principally conducted the working of Tin
Croft. mine, I am indebted for the Section. He informed me

Mr. WILLIAM Puixurps on the Veins of Cornwall, 155

that in some part of Dunkin’s vein, granite was found on one side
of it and schist on the other, and that detached masses of each sub--
stance were found both in it and in the South vein ; and frequently,
that where granite formed the country on each side of the vein,
the masses were of schist, and vice versa.

Description of some of the Veins in the Mines called Tol Caru,
HMuel Jewel, and Huel Damsel, near St. Die.

Pl. 6. Fig. 1.

The veins of these mines are remarkable in several respects.
A small brook was the boundary between Huel Jewel, which had
been worked about fifty years at an immense profit, and that of an
untried mine called Tol Carn, near St. Die. The veins of Huei
Jewel were very rich in those parts which adjoined Tol Carn
mine. ‘This, of course, raised the expectation of the adventurers
in the latter to an extraordinary pitch, and they set to work in the
full belief that they should be at little trouble and expense in
realizing on their side the brook, a continuation of the riches on
the other side, as the veins of Huel Jewel made immediately for
Tol Carn mine. On sinking a shaft in order to cut one of them
at a certain depth, they were surprised at not doing so, since from
knowing the precise run of the vein, the miner is generally able to
inake nice calculations in point of depth and distance in the
sinking a shaft. After this had been done, as far as it was deemed
proper, they drove through the country, at right angles with the
shaft, from north to south, several fathoms without finding the vein,
It was then attempted, by sinking shafts, to cut the other two veins

which formed a pait of the workings of Huel Jewel, but withaut
u 2

156 9 Mr. WitiiaM Puiturps on the Veins of Cornwall.

success. After much labour and expense had been bestowed, it
was discovered that underneath the brook forming the boundary
between the two mines ran a cross vein of flucan, varying from a few
inches to a few feet in thickness; this vein is believed to run quite
across the country from sea to sea, heaving, in the phrase of the
miner, all those parts of the veins, which it is known to intersect, on
the western side of it, higher north than those on the eastern side ;
so that those parts of the veins in Tol Carn mine had been heaved
by it full eighty fathoms higher north than the other parts of them
in Huel Jewel, which however were found to correspond with
those in Tol Carn not only in their respective distances but also in
dimension. One circumstance however that added materially to
the strange consequences of the cross vein was, that although the
veins in Huel Jewel were rich quite to the cross vein, those in Tol
Carn mine were almost without a speck of ore in them: it was
therefore abandoned after a great expense, and consequently a
great loss has been incurred.

Parallel with the veins of Tol Carn mine, but on the south of it,
run the veins of the rich copper mine called Huel Damsel ; these
have not, I believe, been wrought quite home to the Great Cross
vein. By the annexed ground plan it will be seen that a vein of
flucan, varying from 2 inches to 2 feet in thickness, but without
any perceptible underlie, that is to say, going down in a direction
about perpendicular to the horizon, ran nearly north-east and
south-west, intersecting the veins of Huel Jewel, the Great Cross
vein, and the veins of Huel Damsel, and, to use the miner’s phrase,
heaving them, in the directions laid down in the plan about two
fathoms from their strait courses. This vein is by the miner
ealled a flucan.

It should be noticed that in the working of the above mines,

Mr, Witi1AM Puituips on the Veins of Cornwall. 157

their veins were discovered to be intersected near the Great Cross
vein apparently by two or three smaller cross veins, between
which parts of the east and west veins have been seen; as however
the Great Cross vein is known in other parts of it to divide into
branches (a circumstance very common in veins of this description)
it is believed that these small veins are only branches of the large
oné. . The whole of these mines are situated in granite.

Ground Plan of some of the Veins in the Copper Mine called
Fluel Alfred.

Pl. 6. Fig. 6.

This mine is situated on a schistose hill, in the parish of Phillack,
about three miles south-east of Hayle Copper-house. It had been
worked previously to the year 1800, but was abandoned principally
on account of the surrounding country having fallen in, and filled
up or destroyed the only shaft that had been sunk. This circum-
stance was, most probably, the cause to which the successful
working of the mine may be attributed. For, being compelled to
sink another shaft, it so happened that the chosen spot was
immediately above a vast body of ore which has never failed since
its discovery. But as copper ore had been left at the bottom of
the shaft that had fallen in, a level was carried to that place ; it was
however found to be a mere bunch, which circumstance, it is most
probable would have deterred the miner from an effectual search
after the great riches pitched upon by sinking the new shaft about
100 fathoms west of the former one.

Notwithstanding Huel Alfred is one of the richest and most

158 Mr. WitLiaAM PuiLuips on the Veins of Cornwall.

profitable copper mines that Cornwall has now to boast of, a
particular description of some of its veins would not have been
now attempted, but for some circumstances worthy of particular
notice, viz. that one of its veins is of that description termed a
contre, remarkable for its magnitude and riches as well as its direc-
tion, and on account of the effects produced by its traversing an
east to west vein, and a north and south vein, or cross course.
Both the shafts above alluded to were sunk on the contre, the
direction of which is 28 degrees south of east and north of west.
It varies from 9 to 24 feet in width, its underlie is 2 feet in a
fathom to the east of north. At a small depth this bore the
appellation of a ‘Flucany Load.’ Flucan prevailed very much
between the depth of 50 and 70 fathoms from the surface, and
burst out occasionally with such vehemence as to drive away the
workmen. Captain Samuel Grose, an intelligent captain of the
mine, informed me that he was once carried away 7 fathoms by its
sudden irruption. But little flucan was seen at much greater
depth. Beneath it and above the copper very great abundance of
sulphuret and carbonate of lead occurred, together with iron
pyrites, blende and quartz. The greatest extent to which the
contre has been worked is 160 fathoms from its junction with the
east and west vein towards the south east; 90 fathoms of which,
at about 130 from the surface, are good ore. ‘The only place at
which the contre was rich when in contact with the east and west
vein, was at about 117 fathoms from the surface. North-west of
its junction with that vein the contre was small, and for more than
100 fathoms in depth consisted of strings of flucan, but at about
the depth of 120 fathoms it enlarged to twelve feet in width and
yielded some ore, mingled with fluor, blende, and iron pyrites in
abundance; at 130 fathoms in depth, it was poor for 20 fathoms

Mr. Witi1Am Puiuips on the Veins of Cornwall. 159

from its junction with the east and west vein, and then succeeded
40 fathoms of what the miner terms orey ground.

It seems to be the opinion of a very intelligent and experienced
miner, Captain John Davey, who was a captain in Herland mine,
and is now the managing captain of Huel Alfred, that the contre of
the latter is a continuation of that of Herland.

The east and west, or regular metalliferous vein averages about
2> feet in width, and runs 10 degrees south of east and north of
west: it underlies 24 feet in a fathom towards the north, The ore
was about 110 fathoms in length east of its junction with the
contre, but the east and west vein is poor every where when in
contact with it, except at the only place at which also the contre is
rich, viz. at about 117 fathoms from the surface.

West of the contre the east and west vein is lost for nearly
30 fathoms; and when discovered again, it varies from 18 inches
to 4 feet in width and its load was found chiefly to consist of
flucan with some blende.

The ore of the contre is yellow and occasionally compact, but it
is for the most part approaching to black externally; and where
richest, is loosely intermingled with small portions of quartz, blende,
and iron pyrites, which prevailed very much near the surface.

The ore of the regular vein east of the junction with the contre
is also yellow, and for the most part hard; but it is occasionally
loose.

The common effect of a cross or north and south vein is that it
passes through the east and west or metalliferous vein, and mostly
alters its course, of which numerous instances are shewn on the ground
plan of Herland, Drannack and Prince George Mines. A cross vein
occurs in Huel Alfred; its effect on the east and west vein is not

yet known, but a rare exception to the general rule of north and.

160) 9 Mr. WittiAM Puiiutps on the Veins of Cornwall.

south veins traversing metalliferous veins is here exhibited, for the
load of the contre, which, as has been said, is rich in copper, not
only passes through the north and south vein, but also heaves it
out of its regular direction four fathoms. This is the only instance
of the kind that has come to my knowledge. On consulting the
ground plan of Herland and Drannack mines, it will be seen that
the effect of the cross vein on the contre in that mine was exactly
that of the contre on the cross vein in Huel Alfred.

The run of the cross vein is direct north and south ; it underlies
west about one foot in a fathom; is nine feet wide, and close to the
contre (where only it has been seen) is chiefly filled with quartz,
accompanied by blende and carbonate of lead in very small quantities,
but in it there is no flucan; at and below forty fathoms from the
surface, the quartz assumed the form of a fine sand, and the water
from the cross vein was so powerful as to wash the sand 90
fathoms into the contre, so as occasionally to choak the pumps.
It should be remarked that no ore was seen in the latter while
passing through the cross vein for more than 100 fathoms from the
surface.

About 45,000 tons of copper ore, the produce of Huel Alfred,
have been sold since the beginning of 1801, for the sum of about |
£350,000. The number of men women and children, employed
underground and on the surface, amounts nearly to 1500. There
are three large steam engines for drawing the water, and two steam
whims for drawing the ore, now onthe mine. The monthly expenses
for labour, coals, ropes, timber, &c. amounts now to about £5300.
The profit hitherto divided amongst the adventurers amounts to
about £120,000.

VII. On the Freshwater Formations in the Isle of Wight, with some

, Observations on the Strata over the Chalk in the South-east part
of England.

By Tuomas WexsstTer, Member of the Geological Society.

en NEI

INTRODUCTION.

Aone the geological researches which have lately been made
in various parts of the globe, none have been more interesting than
those of M. M. Cuvier and Brongniart in the environs of Paris.

These naturalists have described a series of mineral strata differing
in many respects from all that were formerly known, and particularly
distinguished by their numerous and singular organic remains. The
animals whose exuvie had hitherto been more commonly noticed
in regularly stratified rocks were the inhabitants of an ocean: but
many of the Parisian fossils belonged to freshwater lakes and marshes,
thus developing new and unsuspected agents in the forming of mi-
neral beds.

The strata described by the French naturalists are deposited in a
cavity in the chalk stratum which extends through a considerable
part of the north of France. The bottom of this hollow is extremely
irregular ; and before it was covered by the materials now found in
it, must have presented partial cavities and projections, the latter

appearing as so many islands piercing through the other strata; and
VoL. Il. x

162 Mr. WEBSTER on the Strata lying over the Chalk,

it is an important observation that there is no correspondence be-
tween the irregular form of the bottom and that of the present sur-
face of the country.

Although the number of distinct beds or layers in this basin is
very considerable, yet the authors of the memoir have reduced them
to eleven principal classes.

1. Chalk.

2. Plastic clay.

S. Coarse limestone and sandstone.

4. Siliceous limestone.

5. Gypsum and marl, containing bones of animals, forming the
lower freshwater formation.

6. Marles of marine origin.

7. Sand and sandstone without shells.

8. The superior marine sandstone.

9. Buhr or millstone formation without shells, and argillaceous
sand.

10. The upper freshwater formation, comprehending marles and

buhrs with freshwater shells.

11. Alluvium or earth of transportation, both ancient and modern,

analogous to our gravel, &c. comprehending rounded peb-
_ bles, pudding stones, argillaceous marles and peat moss.

Of these the three first above the chalk are of marine origin, and
they cover the whole of the bottom of the basin.

The gypsum and accompanying marles they imagine to have been
formed chiefly in fresh water, from the fossils contained in them.

The next series of marles and sandstones containing only marine
shells, shows the sea to have again covered the last formed strata.

Lastly, the upper freshwater formation demonstrates this place to

have been a second time converted into a lake.

Mr. WessTER on the Strata lying over the Chalk. 163

Such are the leading features of these remarkable strata.

It is the object of the present paper to describe a similar series of -

formations ; from which it will appear that the circumstances which
gave rise to the alternation of marine and freshwater strata were
subject at distant places to the same general laws, and were therefore
extensive in operation: conclusions in themselves not uninteresting,
and tending to throw some light on the later revolutions which our
planet has undergone. idetf

Sir Henry Englefield was the first who observed a range of chalk
hills running from east to west across the middle of the Isle of Wight,
and inclined at an angle of from 60° to 80°. An account of these
strata appeared in the Transactions of the Linnean Society, 1802 ;*
but circumstances having prevented him from prosecuting these
geological researches in person, at his request in the summer of 1811
I examined the connexion of the vertical strata of the Isle of Wight
with those on each side which are horizontal, and also the con-
tinuation of this range to the west on the opposite shore of Dorset-
shire.

The general result of this enquiry will be best understood from
the following section across the Isle of Wight from north to south ;
see plate 9, fig. 1.

The inclined strata A, B, C, D, E, compose a range of hills that
divides the island into two parts, extending from the Needles at the
west end of the island to the Culver cliff at the east : at which places
may be seen vertical sections at right angles to the direction of the
range.

* A detailed description of the Isle of Wight is now preparing for the press by Sir
Henry Englefield, who has permitted me to communicate to the Society many of the
observations which I made at his request with the view of completing his work.

Die

©

164 Mr. WEBSTER on the Strata lying over the Chalk.

The stratum marked A, is chalk with flints,* which at the
north side is in nearly vertical layers, the inclination becoming gradu-
ally less and less towards the south side, where they dip about 60>.

Bis chalk without flints,

C chalk marl.

D calcareous sand-stone, with subordinate beds of limestone and
chert.

E__ bluish-black marl.

F _ ferruginous sand and sand-stone, with potters’ clay, slate clay,
argillaceous limestone, wood-coal, &c. The part of this stratum in
the middle ranges of hills inclines only a few degrees, extending to
the south side of the island, where it is horizontal. It is to be re-
marked, that towards this side of the island there is a higher range
of hills H, composed of horizontal strata which correspond ex-
actly with a part of those of the highly inclined series of the middle
range, not only in their nature, but in their order of superposition ;
thus irresistibly forcing upon us the conclusion, that they belonged to
the same formation, and that they had probably at some period been
continuous.

The strata G, to the north of these already mentioned, consist of
a numerous alternating series in a vertical position, and are com-
posed chiefly of sand and clay. These may be seen to great advan-
tage in Alum bay, where they form cliffs about 200 feet in height.

The whole of the most northern part of the island, I, consists of
nearly horizontal strata, which come up abruptly against those that
are vertical, but are slightly curved at their junction with the latter.
These, however, proved to be entirely different in their mineralogi-
cal characters and in the fossils which they contained, from the strata

* It was this chalk, together with the vertical strata of Alum bay, and the horizon-
tal strata on each side, that were first observed and described by Sir H. Englefield.

Mr. WEBSTER on the Strata lying over the Chalk. 165

that I have described on the north side of the island, under the
chalk.

Several of them were composed of a calcareous rock, either of a
loose or compact texture; and an attentive consideration of this
section, together with those of the opposite coasts of Dorsetshire,
Hampshire, and Sussex, convinced me that the date of their origin
was posterior to that of the chalk.

No distinct limestone stratum had been hitherto observed above
any part of the chalk in this country, although it was well known
that such were frequent in France. That this is the real position
of the limestones near Paris could not’ be doubted, since the chalk is
always reached in sinking to great depths. But the geognostic place
of the strata on the north side of the Isle of Wight, was more diffi-
cult to ascertain ; and it was only from many combined considerations
that I was led to the conclusion, that they might be found to agree
with some of those lately described by Cuvier and Brongniart, as.
contained in the basin of Paris.

These considerations were the following :

' The chalk of England, although it appears upon the surface only
in detached hills and patches, is actually continuous through con-
siderable tracts of country, where it exists at great depths, as is now
ascertained by numerous wells and other sinkings. In the order of
position, which the strata of the chalk itself, and those which lie
above and below it, bear severally to one another, there has been
observed in distant places a remarkable agreement. And although
occasional varieties may be noticed, in consequence of the defect or
redundance of any one stratum, yet the law of the Wernerian school
seems to hold good ; viz. that the order of the beds is never inverted.

This agreement renders it extremely probable that the correspond-

ing strata, found in different parts of the same country, arose from

166 Mr. WEBSTER on the Strata lying over the Chalk.

the same cause, and at the same time; and favours the idea, that
many of these, although now broken and unconnected, were origi-
nally continuous.

A part of the series which I deduced from observations made in
the south-eastern part of England, is as follows, beginning with the
uppermost.

1. Alluvium, consisting of gravel, loam, sand, &c. and forming
the surface or soil.

2. Sand seen chiefly in the neighbourhood of Bagshot.
| 3. Blue clay, with septaria and marine fossils, commonly called
the London clay.

‘ 4, Sand, plastic clay, &c.

5. Chalk with flints,

G. Chalk without flints.

7. Chalkmarl, including what is called the grey chalk.

8. Sandstone with green earth and mica, cemented together by
calcareous matter, and containing subordinate beds of limestone and
chert. This includes the firestone of Ryegate, and Kentish rag.

9. Blueish black marl.

10. Sand and sandstone, highly ferruginous, containing subordinate
beds of clay, fullers earth, shale, bituminous wood, and limestone.
This stratum forms the wealds of Kent and Sussex.

11. A series of strata of shelly limestone, known by the name of
the Purbeck stone, alternating with shale and marle. Some of the
fossils of these strata strongly resemble freshwater shells: they ap-
pear to be the Cyclostoma, Planorbis, &c.

12. Clay with gypsum.

13. Portland oolite.

Mr. WessTer on the Strata lying over the Chalk. 167

14. Clay with limestone and bituminous shale, containing the
Kimeridge coal.* |

The strata of Alum bay, now seen in a vertical position, must
have been originally quite horizontal, or nearly so. For it is not
only extremely improbable that beds of such materials should have
been found in any other manner, but a circumstance which I no-
ticéd in Alum bay renders certain the original position of the sand
and clay strata. In one of the vertical beds, consisting of loose
sand, are several layers of flints, extending from the bottom to the
top of the cliff ; these flints have been rounded by attrition ; are from
one inch to eight inches in diameter, and appear to have belonged
to the chalk. Now it is inconceivable that these flint pebbles should
have been originally deposited in their present position; and they
distinctly point out the original horizontality of this series. ‘There
are no signs of partial disturbance in the several beds, and it appears
therefore that the whole has been moved together, either by ele-
vation or subsidence into the vertical situation.

The strata of chalk have evidently suffered a change of position
at the same time with the clay and sand; and since the vertical beds
of Alum bay, c, are next to the stratum of /lizty chalk, which, accord-
ing to the regular order of superposition, is known to have been. the
uppermost of the chalk series, it follows, that they are of posterior.
formation. Moreover, the most northern of these vertical beds is.
a blue clay, agreeing with the London clay, a bed which always

lies over the chalk.

* Other divisions of these strata have been made, and the cause of the differences has
already been alluded to. Not every member of the series is perfectly continuous or
of uniform thickness ; so that when any one is wanting, beds, usually separate, are
brought into immediate contact. In making a classification of these beds, those should
be considered as principal members, which are most rarely deficient in an extensive tract

of country.

168 Mr. WeBsTER on the Strata lying over the Chalk.

The chalk of the middle hills of the Isle of Wight dipping to
the north, and that of the South Downs dipping to the south, it
was an obvious inference that it might pass under the channel called
the Solent, thus forming a basin. This idea was rendered still
more probable on finding that the bottom of this channel consisted
mostly of the London clay, which stratum is found under Ports-
mouth, whence it may be traced eastward, forming the lowermost
bed next the sea all along the shore of Sussex to Pagham and Bognor,
and westward to Stubbington cliff, and along the coast of Hamp-
shire to Hordwell and High cliffs. In all its characters and fossils,
this bed was found to agree with the blue clay which lies over the
chalk, in the counties of Kent, Surrey, Middlesex, Essex, &c. and
with the most northerly of the vertical beds of Alum bay.* Besides,
the chalk itself lies at no great depth from the surface in all that
part of Sussex south of the South Downs, and is even found on
the shore at lowwater-mark at Middleton, two miles east of Bognor.

It appears, therefore, that between the vertical chalk-hills of the
Isle of Wight and the South Downs there is a basin or hollow,
occasioned by the disturbance of the whole mass of strata from
below the chalk to the London clay, inclusive: and also that this
disturbance took place at a period subsequent to the deposition of the
last-mentioned stratum, since it is amongst those which have suf-
fered a change of position.

From this it will be readily admitted, that all the beds situated
within this basin lie above the London clay, and are posterior to it.
Of this description are the horizontal beds of the most northerly
part of the Isle of Wight; and since they come almost into contact

* Having by the kindness of Mr. Holloway, of Portsmouth, become familiar with
the fossils of Stubbingtou, 1 readily perceived their agreement with the above-mentioned
stratum in Alum bay.

Mr. WexgsTER on the Strata lying over the Chalk. 169

with the vertical beds without suffering any considerable change in
their dip, it should seem that they have been deposited on the sides
of this basin subsequently to the disturbance of the strata already
spoken of.

The above conclusions are confirmed by other circumstances.

These horizontal beds have no agreement with any of those
beneath the chalk, nor indeed with any others yet observed in Great
Britain ; their mineralogical characters, and their fossils, are peculiar
and distinctive. ‘The calcareous beds contain numerous petrefactions
of freshwater shells, and in others are found marine fossils agreeing
with those described by Lamarck in the strata of the Paris basin.
But fortunately, the inspection of specimens from the basin of Paris
enabled me no longer to depend upon conjecture only as to the
similarity of these formations. ‘They had been given by M. Brong-
niart himself, in illustration of his memoir, tothe Count de Bournon,
who had deposited them in the museum of the Geological Society.
The agreement of the strata of the two basins, not only with re-
spect to the external characters of the calcaire d'eau douce, but also
to its fossils, was thus rendered evident: and these specimens, so
well authenticated, added one more proof (if more could be want-
ing) of the utility of such collections, and of the advantages to be
derived from a liberal communication between men of science.

It is unnecessary to inform the Society that this circumstance
produced another visit to the Isle of Wight and its vicinity, for the
purpose of examining more particularly its basin, and the remains
of its antient lake. From this, compared with my former survey, I
was enabled to add to the British strata the following, of later for-
mation than the London clay.

1. A calcareous stratum, containing only freshwater shells.

2. Greenish marl, with marine shells,

Wor. 1s . ¥

170 Mr. WEBSTER on the Strata lying over the Chalk,

3. Marl with freshwater shells.

4, Dark blue clay without shells.

These must be placed between the alluvium and the London clay,
of the former list. .

In the subsequent pages I shall describe more minutely the form of
the basin of the Isle of Wight ; and also that of a similar basin on
which London is placed. I shall enumerate the strata and principal
Organic remains contained in each, and conclude by pointing out
such circumstances of agreement or difference as I have been able to
observe between them and the Paris basin.

II. Extent of the Isle of Wight Basin.

In tracing the margin of the cavity in which these horizontal
depositions of the Isle of Wight are found, I shall begin with the
south side.

The middle range of chalk hills in this island, together with the
other highly inclined strata of Alum bay, form part of the ancient
border. If we sail west from the Needles in the Isle of Wight, to
Handfast point in Dorsetshire, we shall find that this vertical chalk
range again makes its appearance in that coast, and may be traced
thence through Corfe Castle to some distance beyond Lulworth ; and
from the correspondence in the line of direction of the Isle of Wight
hills with those of Dorsetshire, and the general agreement in the
position and nature of the strata, (the section of the Isle of Purbeck
corresponding nearly to that of the Isle of Wight,) it appears
extremely probable that at some former period these places were
united.

The clay however over the chalk, and part of the chalk itself,

Mr. WEBSTER on the Strata lying over the Chalk. = 171

in Dorsetshire, is horizontal, differing in this respect from their
position in Alum bay. There must, therefore, have been some
twist in the chalk stratum, a remarkable instance of which I dis-
covered at the other end of the chalk range beyond Lulworth.*

Since I shall have a future opportunity of making some remarks
on the very singular stratification of these places, I shall only at
present observe, that the highly inclined chalk from the Culver cliffs
at the east end of the Isle of Wight to White Nose, in Dorsetshire,
5 miles west of Lulworth, formed the southern side of this depression
in the chalk stratum. The north side of it may be traced in that
range of hills called the South Downs, extending from Beechy Head,
in Sussex, to Dorchester, in Dorsetshire. The strata of which
these hills are composed, dip generally from 15° to 5° to the south ;
the inclination varying in different places. The south side of the
basin therefore must have been extremely steep, while the slope
of the north side was very gentle. The closing of this basin at the
west is obscure, and cannot be distinctly traced ; but the east is now
entirely open, the sea passing through it.

Ill. Extent of the London Basin.

This extensive basin, like that of the Isle of Wight, is probably
owing to a depression in the chalk stratum.

Its south side is formed by a long line of chalk hills, including
those of Kent, Surrey, and Hampshire, called the North Downs,
extending through Basingstoke to some distance beyond Highclere

* The drawings and description of this, as well as of many other parts of this
remarkable coast, will be found in the above-mentioned work now preparing for publi-
cation, by Sir H. Englefield.

y¥2

172 Mr. WessTer on the Strata lying over the Chalk,

Hill, in Berkshire. Its western extremity is much contracted, and
seems to lie somewhere in the vicinity of Hungerford. Its north-
western side is formed by the chalk hills of Wiltshire, Berkshire,
Oxfordshire, Buckinghamshire and Hertfordshire. ‘The most north-
ern part of this boundary has not yet been well determined. On
the east it is open to the sea, the coasts. of Essex, Suffolk and Nor-
folk, being sections of the strata deposited in it.

The dip of the chalk of the North Downs from Dover to Guild-
ford is from 15° to 10°, but in the narrow ridge of chalk called
the Hog’s-back, extending from Guildford to Farnham, the dip is
very considerable being above 45°.* On the dip of the other sides
U have had no opportunity of making any observations.

The depth of the chalk below the surface at London must be very
considerable, since though wells have been sunk several hundred
feet it has never been reached; but at a few miles south of the
metropolis the chalk is frequently come to.

IV. Description of the Strata composing and contained in the Isle of
Wight and London Basins ; with a comparison between them and
those in the Basin of Paris.

The authors of the French memoir, in order to obtain their
general section, have collected the sections of various places ; and by
comparing them together have developed those alternations of marine
and freshwater deposits, which are analogous to those we are now
considering. I shall follow nearly the same method ; but for greater
simplicity I shall divide the formations composing our basins into

* For the pointing out of this fact, as well as for much important information respecting
the extent of the chalk, I am indebted to G, B. Greenough, Esq. V.P.G.S,

Mr. WEBSTER on the Strata lying over the Chalk. 173

1. Chalk formation.*

2. The lowest marine formation over the chalk, including the plastic
clay and sand, together with the London clay.

3. The lowest freshwater formation.

- 4, Lhe upper marine formation.
5. The upper freshwater formation.

‘6. Alluvium.

Fortunately the complete series of these alternations may be seen at
one place in the Isle of Wight, which leaves us no room to doubt
their superposition ; and when their characters have been studied in
this spot, it is more easy to become acquainted with them in other

places.

§ 1. Chalk Formation.

The south-east coast of England and that of the Isle of Wight
afford us many excellent opportunities of examining the chalk. In
numerous natural sections formed by cliffs, as well as in chalk pits,
I have observed it as distinguished into at least three strata, each of
which has peculiar and distinctive characters.

The lower stratum is more or less argillaceous, and constitutes
what is called the chalk marl. "Together with the other strata it
frequently forms cliffs of considerable height, and though differing
little from them in colour is easily distinguished by its constantly
shivering with the frost, which always pulverizes a mass of it when
exposed to the air for a few months; whereas the others resist the
weather in a much greater degree, and are often even employed as a

material for building.

* In using the word formation I have followed the example of M, M. Cuvier and
Brongniart, who have employed it to express an assemblage of beds of the same nature,
or of a different nature but formed during the same epoch.

174 = Mr. Wesster ow the Strata lying over the Chalk.

This chalk marl is never quite so white as chalk, having generally
a tinge of yellow, and sometimes of grey and brown. It also con-
tains nodules and beds of a more indurated marl, which is usually
called the grey chalk from its dark colour, which varies from a
light to a dark grey and brownish grey. Like all argillaceous lime-
stones it possesses in a considerable degree the property of setting
under water when calcined and made into mortar; and it has been
used with great success for this purpose in building the London
Docks.. The part easily reducible to the pulverulent state by the
moisture and frost is a most valuable manure when employed judi-:
ciously in certain soils, This stratum contains no flints.

The middle and upper strata consist of chalk of extreme white-.
ness and purity, and are chiefly distinguished from each other by the
upper one containing layers of flint nodules which do not occur in
the lower. The chalk without flints is most frequently somewhat
harder than that wth flints, and hence they are sometimes distin-
guished as the bard and soft chalk; but from some observations
which I have made in Dorsetshire, it will appear that the hardness,
or degree of induration, does not always mark a particular bed,
the flint chalk being in some places much harder than that without
flints in others.

On the subject of the nodules and lamine of flint in the upper
chalk, the observations of Sir Henry Englefield have thrown great
light, and will be mentioned in his intended work on the Isle of
Wight. |

The several beds of these chalk strata, which vary in thickness
from a few inches to several feet, are frequently separated from each
other not only by layers of flint nodules but frequently also by a
marl containing a considerable proportion of clay, and this substance

also sometimes fills up the diagonal fissures which cross the strata.

Mr. WexsTeEr on the Strata lying over the Chalk. 175

The workmen take advantage of this circumstance in quarrying
the chalk.

The description given by M. M. Cuvier and Brongniart of the
chalk of France appears .to agree generally with that detailed above.
‘They mention nodules of a harder chalk as-occurring in layers in a
softer. They observe that Werner has enumerated grey and brown
among the colours belonging to chalk: and that in a great part of
Champagne the chalk contains no flint,* but it does not’ appear
whether these varieties of chalk are on the continent confined to
particular strata.

M. M. Cuvier and Brongniart remark that the chalk which forms
the bottom of the Parisian basin, appears to have been consoli-
dated before the deposition of the clay which covers it: a circum-
stance which they inferred from there being no transition of these
into each other. A breccia is described as occupying the lower
part of the basin at Meudon, composed of water-worn fragments
of solid chalk cemented by a paste of clay, and situated be-
tween the chalk and the plastic clay. ‘This circumstance, together
with the irregular form of the bottom of their basin, seems to indi-
cate a considerable action of water upon its surface, so as to render
it now difficult to ascertain what might have been the last deposi-

* A singular circumstance is mentioned respecting the chalk of France to which we
have nothing analogous in this country. In Champagne there are immense plains of.
chalk absolutely deprived of vegetation, except where patches of the calcaire grossier
occur as islands or oases in the midst of these deserts. And M. Cuvier observes that
many parts of this tract have not perhaps been visited for ages by any living being: no
motive existing that could induce any to wander there. In England every part of our
chalk is completely covered by vegetable soil, which although very thin on many parts.
of our downs or smooth hills, yet affords support to peculiar grasses and other vege-
tables, on which are pastured vast quantities of sheep. The chalk of France is said
to contain 11 per cent. of magnesia, to which the barrenness may be owing.

176 Mr. WessTER on the Strata lying over the Chalk.

tions of the chalk formation, or those which immediately suc-
ceeded it. |

Some appearances shew that a similar action had taken place on
the original surface of our chalk. Many very interesting sections
may be seen in the County of Kent, where the chalk being at no
great depth, its junction with the strata over it may be very conve-
niently studied. At Woolwich, on the top of the chalk, and be-
tween it and the superimposed sand, there are a number of flint
nodules heaped on each other, which have evidently been displaced
from their original matrix. In the numerous chalk pits, and where
the roads are cut through the chalk along the south side of the
Thames, as at Rochester, Gravesend, North Fleet, Greenhithe, &c.
the junction of the chalk with the sand and gravel is remarkable for
the deep indentations in the surface of the former, which upon ex-
amination I ascertained to be the sections of long furrows and of
wells ; these were apparently occasioned by the powerful action of
water prior to the deposition of the sand and gravel which now fills
up these hollows: the same may be seen still better at Purfleet.

The present surface of the chalk stratum is also frequently covered
by water-worn pieces of chalk and flint imbedded in clay or alluvial
deposits. )

The cliffs between Brighton and Rottendean are of a singular
character, and merit a particular description. The shore consists of
the solid chalk, which is seen running out to a considerable distance
into the sea, and dipping a few degrees tothe scuth. This stratum
forms six or seven feet of the lower part of the vertical cliff; and
on that are placed several layers of loose flints, evidently rounded
by attrition and piled on one another. Over this is an irregular
bed consisting of pieces of chalk and smaller pieces of flints, both
of which have undergone the same process; and the interstices are

Mr. WEBSTER on the Strata lying over the Chalk. 177

filled up with clay and loose chalk or marl: over this is. another
layer of pebbles, and again clay and chalk and fragments of flints; ©
and these follow in succession, but very irregularly, to the top of
the cliff, which is at least seventy or eighty feet in height. ‘These
materials are in general quite loose, being simply heaped or Jaid on
each other; but sometimes masses of it are cemented together by
stalactitical matter, and when the cliff falls, form blocks of great
size and hardness.

It is impossible to see this cliff without immediately perceiving
that it does not owe its existence to original stratification ; but that
it is simply the section of an immense heap of fragments of chalk
and flints mixed with clay and sand, the whole of which has at
some distant period been subjected to the action of water ; and that
it has been thus deposited upon the solid chalk stratum which
is now seen below it.

In tracing this vast collection of water-worn materials, we find
that it forms a considerable hill behind the town, and that it joins
to the side of the range of hills called the South Downs.

In Alum bay in the Isle of Wight, however, the stratum imme-
diately next to the flinty chalk, and consequently deposited upon
it, consists of a white chalk marl without flints. Its nature is
sufficiently shewn by its pulverizing with the frost; and the rains
wash it down, so that its situation is marked by a deep hollow.
There is some appearance here therefore of a transition of the
last portions of the chalk into the clay which succeeded it; and,
the usual rounded flint pebbles over the chalk and the other signs
of disturbance being there wanting, it is possible that we have in
that place the original succession of depositions. In many parts of
Sussex also, south of the South Downs, as at Emsworth, Lavant,
Siddlesham, South and North Bersted, Middleton, &c. I found

VOL. Ii. Z

178 Mr. WEBSTER on the Strata lying over the Chalk.

pits of a marle without flints, and which is evidently over the
chalk. The same marl is also to be found in Dorsetshire west of
Corfe Castle. I have not however heard of its existence in the
London basin.

The agreement of the fossils of our chalk with that of France has
been already pointed out by Mr. Parkinson in his Memoir “ on
some of the Strata in the neighbourhood of London,” in the first
volume of the Transactions of this Society. In the following lists
I have been favoured by his assistance in the endeavour to apiro-
priate the fossils to their peculiar beds.

In the Chalk with Flints.

Asteriz resembling
Pentagonaster semilunatus

regularis

Pentaceros lentiginosus

Stella lumbricalis, lacertosa, corpore spherico.
Echini of the following families :

Cidaris, >

Cassis,

Spatangus, \ several species.
Fibula,

Conulus, |

Spines of the foregoing: sist catarle those resembling the belem-
nites as described by Mr. Parkinson.
Serpulz, particularly the serpula of Mr. Parkinson’s organic
remains, vol. 3. pl. 7. fig. 11.
Cardium.
Spondylus.
Ostrea, several species.

Mr. WEBSTER on the Strata lying over the Chalk. 179

Pecten, several species.

Chama ?

Terebratula, many species.

A longitudinal transversely rugose ostrea-form bivalve of a fibrous
structure.

Fragments of another fibrous shell of a large size, of an unknown
gerius. See Park. Organic Rem. pl. 5. fig. 3.

Alcyonia, sponges, and numerous unknown zoophytes.

A ramose madrepore. .

Several species of minute encrini, figured by Mr. Parkinson.

In the Chalk without Flints.

Echini: several of the same families as those in the chalk with
flints. Many of them, however, particularly the Cassides,
differing much in their forms from the above.

Spines of echini: and particularly those described by M. Braard

as resembling the belemnite.
Patella.

Trochus.

Serpulz, several species.

Belemnites.

Lima?

Fish, too much mutilated to ascertain the genus.
Palates, scales, vertebree and teeth of fish.
Cancri.

In the Chalk Marl.*

Ammonites: the contour of the spiral varying from the circular
to the long-elliptical.

* On the authority of Mr. Parkinson I notice that the supposition of having

discovered a specimen of Trigonia in chalk is erroneous. This belongs only to inferior
strata.

72,

180 Mr. WessTER on the Strata lying over the Chalk.

Scaphites: a new genus by Mr. Parkinson. See his Organic
Remains, vol. 3.

Turrellites, three species.

Trochus.

Madrepore.

It has been remarked by the French naturalists that in their chalk
there is not any univalve shell with a simple and regular spire. In
the chalk of this country, univalves, as the trochus, do sometimes
occur. ‘They may probably however be rather the fossils of the
green sand below the chalk, which have been enveloped in some of
the depositions of the chalk formation, or in the chalk marl, for
they are frequently accompanied by green earth. ©

The following Fossils are found in the Chalk in the Environs
of Paris.

Belemnites - - - - = Perhaps two species: they appear
to be different from those in the
compact limestone.

Lenticulites rotulata.

Lituolites nautiloidea.

difformis.

Pinna- - - - = =- = It is not certain that the large frag-
ments of 12 millimetres in thick-
ness and of a fibrous texture, which
are found in the chalk belong to
this genus. M. Defrance has por-
tions of a hinge which indicate a
different genus. Cuv. p. 11.

Mr. WEBSTER on the Strata lying over the Chalk. 181

Mytilus - - - - - = very different from those of the
g calcaire grossier.

Cardium ?

Ostrea vesicularis.

deltoidea.
Pectten - - - = = = M. Defrance has observed 2 species.
Crania - - - = = = It was adherent and differing in
that from known species.
Perna?
Terebratula, many species.
Spirorbis.
Serpula.

Ananchites ovatus - - - The shell is changed into calcareous

spar, and the internal part is con-
; verted into flint.

Spatangus Cor anguinum Kl.

Porpites.

Caryophyllia

Millepora- - =- = - - These are often in the state of
brown oxide of iron.

Alcyonia.

Shark’s teeth.

§ 2. Lowest Marine Formation over the Chalk.

The clay and sand cliffs of Alum bay afford one of the most
interesting natural sections that can well be imagined. They ex-
hibit the actual state of the strata immediately over the chalk before
any change took place in the position of the latter. For, although
the beds of which they are composed are quite vertical, yet, from

182 Mr. Wrsster on-the Strata ling over the Chalk.

the nature and variety of their composition, from.the great tegu~
larity and numerous alternations of the layers, and the other
circumstances which have been already mentioned, no; one» who
has viewed them with attention can doubt, that.they have suffered
no change except that of having been moved with the chalk from
the horizontal to the vertical position.

The whole of these strata have evidently been formed at the
bottom of an ocean, from the nature of the fossils contained in
them, which, although entirely different from those of the. chalk,
are yet all of marine origin.

The chalk, A, which forms the side of Alum bay, (Plate 11.
Fig. 2.) is somewhat harder than usual, and the flints are shivered,
so as to come to pieces on being taken out.*

Next to the chalk, on the north, stands the bed of chalk marl
a, which has been already mentioned.

To this succeeds a thick bed of clay, b, of a dark red colour,
often streaked or mottled with yellow and white; towards the
south side is a thin layer of greenish-grey sand. This is divided
by a bed of yellowish white sand, c, from a- very thick bed of
dark blue clay, d, which contains much green earth; and also
nodules of a dark coloured limestone, in which I found a few
fossil shells: this bed, however, I am inclined to think, is not con-
tinuous for a great extent, as in a part of the cliff farther inland
and in the line of its direction, it had almost disappeared.

Next follows a vast succession of beds of sand of different
colours, which, though not distinctly separable from each other,
yet may be considered as divided into the following :

* See the paper on this subject, by Sir Henry Englefield, in the Transactions of the

Linnean Society.

e,
f,
gs
h,
i,

k,
I,

Mr. WessTER on the Strata lying over the Chalk. 183

Greenish yellow sand.

Yellow sand with ferruginous masses.
Greenish sand, like e.

Yellow, white, and greenish sand.
Whitish sand, with thin stripes of clay.
White and yellow sand.

Light green sand.

m, Ferruginous sand stone.

n,

0,
Ps
>

Yellow sand with a few red stripes.
Next to this, and in the middle of the bay, is a very nu-
merous succession of beds, which contain a large proportion
of pipe-clay of various colours, white, yellow, grey, and
lackish. These alternate with beautifully coloured sands.
The clay is sometimes in beds several feet in thickness,
without any admixture, and sometimes in laminz not a
quarter of an inch thick with sand between them. They are
generally as follows :
Blackish clay with stripes of white sand.
Sand intensely yellow.
Very white sand. In the middle of this there is a layer of
small siliceous nodules, quite white, easily frangible, and of
an earthy texture; they are water-worn, and seem to have
been derived from decomposed flints.
Sand of a crimson colour.
Pipe clay with sand stripes. Here it runs into the sea, and
may be traced across the beach.
Yellow sand with some crimson.
Pipe clay, white and black, with stripes of sand. In the
middle there are three beds of a sort of wood coal, the
vegetable origin of which is distinctly pointed out by the

%

184 Mr. WeBstTER on the Strata lying over the Chalk.

fruits and branches still to be observed in it. It sometimes
splits into irregular layers in the direction of the bed, and
the cross fracture is dull and earthy. It burns with difficulty,
and with very little fame, giving out a sulphureous smell.

v, Yellow and white sand, with crimson and grey stripes.

w, Five beds of coal similar to that above-mentioned, each a
foot thick.

x, Whitish sand and brownish pipe-clay.

y, Whitish sand with stripes of deep yellow.

z, Several layers of large water-worn black flint pebbles, im-
bedded in deep yellow sand.

B, A stratum of blackish clay, with much green earth and sep-
taria. In this green earth are a prodigious number of fossil
shells, but in a very fragile state. They correspond exactly
with those of Stubbington and Hordwell.

A stream of water from the adjoining hill has worn a deep

channel through the stratum, and affords a path down to the bay.

To the north of this, the strata C consist of yellowish sand; and
it is not easy to see what is really the position of those beds which
lie immediately next to the blue clay, but they appear to dip about
45° to the north; and the sand D lying on them is nearly hori-
zontal.

The north side of Alum bay is bounded by a hill called Headen,
about 400 feet high, considerably loftier than the vertical cliffs,
and composed of the same part of that series of horizontal strata
of which the north side of the island consists. In this hill only
do we distinctly see the alternation, I have mentioned of marine
and fresh water deposits. It is in a state of constant ruin, and by
its section affords lofty vertical cliffs, where its strata may be ex-
amined with the utmost facility.

Mr. WEBSTER on the Strata lying over the Chalk. 185

The last mentioned sand is the lowest stratum there visible. It
is above 30 feet in thickness, beautifully white, and in it several
pits are annually dug, from which the manufactories are supplied ;
with their materials for the best flint glass. This sand may be
traced round the foot of the hill on the north side, and forms the
bottom of Totland and Colwell bays, dipping gradually to the north.

Aver it lies a horizontal bed of black clay E which contains
fossil shells, and sometimes selenite.

Upon reviewing the whole of this lower marine series of strata
in Alum bay, and comparing it with other sections of the strata im-
mediately over the chalk, we shall find it useful, for the present at
least, to separate it into two great divisions: 1. Sand and _ plastic
clay, 2d. London clay. From the irregularities in the beds in the
few places where there are good sections, these divisions however
can as yet scarcely be considered as distinctly determined. Thus
much is certain, that the plastic clay and sand is always below and
never above the London clay. Other sub-divisions may be intro-
duced when future observations shall shew them to be sufficiently
important.

1, Sand and Plastic Clay. Yrom the constant and abundant sup-
ply of water which is found on boring through the London clay,
and from the accounts of the proprietors of the numerous pits of
plastic clay in Dorsetshire, the sand must be considered as the
most extensive and continuous formation, and the clay as filling up
basins or hollows in it. Hence, as may naturally be expected,
we find each of these substances in different places in immediate
contact with the chalk. In the Isle of Wight clay is next to it, but
in the numerous sections on the banks of the Thames, sand is the
lowest, or the clay is wanting.

The beds of plastic clay in the Isle of Wight are of unusual ex-
VOL. Il. 2A

186 Mr. WeBsTER on the Strata lying over the Chalk.

tent and thickness. They extend quite across the island in a vertical
position, keeping parallel to the chalk, and appearing again at White-
cliff bay on the east end, where they are however much concealed
by grassy slopes.

All along the north side of the range of chalk hills which extends
from Handfast-point through Corfe Castle, there is an extensive
stratum of pipe clay ina horizontal position. It contains a bed of
coal so exactly resembling that of Alum bay, that this circumstance,
added to the quality of the clay and its geognostic position, is suf-
ficient to identify it.

I have been favoured by Alexander Jaffray, Esq. with the follow-

ing section of the clay pits of Norden, near Corfe.

Sand onthe top - - - 10 feet
Blackish brown clay - 14

Wood coal” - =" - "= 3
iherase ‘clay "=P F200 5

Fine white potter’s clay 6

Dark brownclay - - 2

Fine white potter’s clay 64

A6t

The same stratum of clay, though not of equal quality, may be
traced in the hills near Poole ; and is found in many parts of that
extensive tract called the trough of Poole.

Potter’s clay, white, yellow, or greyish white, similar to that in
the Isle of Wight, is also frequently found in the London basin:
some of it is of considerable fineness, as on the east bank of the river
Medway, near Rochester.

The plastic clay is frequently of a deep red colour, or red and
white mottled, as in Alum bay: a similar red clay is dug near
Portsmouth and other places along the South Downs. It also ap-
pears at Reading.

EE

Mr. WEBSTER on the Strata lying over the Chalk. 187

In the Isle of Wight basin, both in Dorsetshire and Alum bay,
beds of iron stone and ferruginous sand occur connected with this
clay, and generally lying over it. Considerable rocks of it are seen
about Studland, and the Druidical monument, called the Agglestone ;
near that place is a huge block of this bed.

A stratum of sand, containing green particles, frequently occurs
near the chalk. It is seen in Alum bay without fossils; at Read-
ing it is found containing oyster shells. ‘This green sand is easily
distinguished from that below the chalk, as it is never indurated.

2. London or Blue Clay. The stratum which has received this de-
denomination is found immediately under the gravelly soil on which
the metropolis is situated. Of all the strata over the chalk in this
country, it is of the greatest extent and thickness : and the number,
beauty, and variety of the organic fossils which it contains, renders
it the most interesting and the most easily recognizable.

It consists generally of a blackish clay, sometimes very tough, at
other places mixed with green earth and sand, or with calcareous
matter.

It contains also numerous flat spheroidal nodules of indurated
marl, or argillaceous limestone, which lie in regular horizontal
layers, at unequal distances, generally from four to ten feet apart.
These nodules are well known by the name of Ludus Helmontii, or
Septaria, from ‘their being divided across by partitions or veins
of calcareous spar, which are generally double. In their ca-
vities are frequently found crystals of calcareous spar and of sulphat
of barytes. ~The septaria are surrounded by crusts which contain
a smaller proportion of carbonat of lime than the central part. They
often include organic remains.

Besides the clay, marl, sand, and carbonat of lime, of which the

main body of this stratum consists, several other substances are dis-
Zt

168 Mr. WesstTer on the Strata lying over the Chalk.

persed through it in smaller quantities. Of these the chief is sul-
phuret of iron, which is frequently the mineralizing matter both of
the vegetable and animal remains included in the blue clay.

Selenite is also very abundant; and sulphat of iron frequently
effloresces when the clay is exposed to the air, from the decompo-
sitionof the pyrites contained in it. Phosphat of iron is also some-
times found.

On account of these salts, the water which is contained in, or
which passes through this stratum, is not fit for domestic purposes.*
Wells are therefore generally sunk entirely through it to the sand
below.

In the country round London, this sand which belongs to the
plastic clay, is the great reservoir of water, which generally bursts
out with great violence when broken into.

Sulphat of magnesia has long been known in the springs at Epsom,
which has given its name to this salt, Its origin however does not
appear to have been clearly ascertained, although from its situation
it may be supposed to belong to some of the beds above the chalk.
I derive from Mr. Tennant the information, that the London clay
abounds in Epsom salts. The bricks of old buildings in London,
after fine dry weather, are covered with an efflorescence of this salt.
This may be seen in the walls of the Temple.

In the Isle of Wight, as well as the London basin, this stratum
occupies the same situation, and does not appear to differ materially
in each of these places. In Alum bay it is seen forming the most
northerly of the vertical strata. On the opposite shore of the Solent
it occurs in a horizontal position. Sections of it are formed by the
cliffs between Lymington and Poole. Of these, Hordwell cliff,

* Hence the country on the northern side of London is so thinly inhabited.

Mr. WEBSTER on the Strata lying over the Chalk, 189

below Christchurch, is well known, on account of its fossils, which
are found in a very perfect state. ‘They have been collected and
very accurately described by Mr. Brander and Dr. Solander.

At Stubbington, a few miles west of Portsmouth, the same stratum
of blue clay with much green earth is visible, in a low cliff, with
the same fossils as at Alum bay and Hordwell: the strata being
horizontal. The fossils here, as at Alum bay, though numerous,
are in a very fragile state; minute nummulites are extremely
abundant.

Portsmouth is built upon this stratum, and several deep wells
sunk there afford us much information. James Hay, Esq. F.L.S.
kindly furnished me with the following account of the sinkings at
that place.

“1, Vegetable mould.

2. Yellow loam, of which excellent bricks are made.

3. Yellow gravel, composed of rounded siliceous pebbles and
sand, from 4 ft. 6 in. to 10 feet thick. . In some places, towards the
bottom, the sand abounds; and, generally, within a few feet of the
blue clay, is very fine, and in many places is of a greenish colour.
In the yellow gravel are found many organic remains, siliceous, and
all rounded by attrition. In a few instances singular bones have
been discovered. |

4. An immense bed of blue clay, which in many places at the
surface is mixed with sand strata. At the depth of 30 feet it is
traversed by a thin stratum of white pebbles. Many wells are
dug to this stratum, which contains water, but of a hard quality.
At the depth of 60 feet another similar stratum is found, containing
water also, and of a softer quality. No wells had been sunk lower
than this last stratum, until within 15 years ago, when a well was
dug in the Dock Yard, to the depth of 202 fect. Excellent

190 Mr. WessTER on the Strata lying over the Chalk.

water was then found. Another well was dug about a quarter
of a mile north from Portsmouth, where water of a good quality
was obtained at a depth of 126 feet from the surface. Two years
ago a well was sunk in the town of Portsmouth, to the depth of
266 feet, without getting through the blue clay, and they left off
without finding water. This is the greatest depth they have gone
to in this place. The fossils dug up from these wells eine oT
with those found in other parts of the same stratum.’

I traced this blue clay west of Portsmouth by Emsworth and
Chichester harbours to Brackelsham ; and thence round Selsey Bill
to Pagham harbour.

At Bognor it assumes a new character; instead of a blue clay,
we find here a number of rocks, now appearing as detached masses
in the sea, though evidently forming portions of a stratum once
continuous. The lowest part of these rocks is a dark grey lime-
stone, or perhaps rather a sandstone, containing much calcareous
matter, enclosing many fossils belonging to the blue clay. The
upper part is a siliceous sandstone Bognor rocks resemble much
the nodules and beds of limestone that are found in the blue clay in
Alum bay, and no doubt are owing to the great abundance of cal-
careous matter in this part of the bed.

The Barns rocks between Selsea and Bognor, the Houndgate and
Street rocks on the west, and Mixen rocks to the south, of Selsea,
are portions of the same bed; and | found similar but smaller
masses at Stubbington.

From this place to Brighton the shore is quite flat, and the chalk
lies at no great depth.

The coast at Brighton has been already mentioned. At Rotten-
dean the cliff towards the sea consists of chalk, and this continues
to Newhaven. At this place a series of beds above the chalk occurs,

é

Mr. WEBSTER on the Strata lying over the Chalk. 191

forming to the west of the river a hill, the greatest part of which is
now destroyed by the action of the sea. At this place the chalk is
about 50 feet in height, and is covered immediately by a bed of sand
20 feet thick. Over this are thin strata of yellow marl and clay,
containing a coal much resembling that of Corfe and Alum bay.
H. Warburton, Esq. Secretary to the Geological Society, who first
noticed and pointed out to me these interesting strata, found im-
pressions of leaves in the marl which exactly resemble those engraved
in one of the plates of the Essay on the Mineralogy of the Environs
of Paris: and I have since recognised among the specimens brought
from that place, a fruit of one of the palm tribe, with the vegetable
fibres quite distinct. Shells belonging to the Genera Cerithium, Cy-
therea and Ostrea, together with pyritous casts of the same, also occur.

With this coal are found thin masses of gypsum both selenitous
and fibrous; and over all is a thick bed of blue clay with marine
fossils, which are different from those usually found in the London
clay.

It was here that I found the singular substance which the experi-
ments of Dr. Wollaston ascertained to be a new mineral, a subsul-
phat of alumine. It lies immediately upon the chalk, and fills up a
hollow in it. About a mile on the east side of Newhaven the chalk
cliffs rise again to an equal height and continue to Cuxhaven, where
there is a similar interruption, and thence extend to Beachy Head,
increasing regularly in altitude, and forming tremendous precipices
of several hundred feet in height.* The chalk here is covered
only by a thin layer of sand and gravel.

* One of these prodigious falls of the chalk cliffs, which make a residence near them
frequently so dangerous, occurred a few days before my visiting this spot, accompanied
by a remarkable circumstance. The clergyman of East Dean, who was walking near
the brink of the precipice, perceived the ground to give way under him, and had the

192 Mr. WEBSTER on the Strata lying over the Chalk.

Turning round this promontory, the lower chalk and chalk
marl are seen at the bottom of the cliff and rising to the north-east,
where they soon take place of the chalk, forming a mouldering
slope at South Sea houses; they there give place to the green sand,
which continues some way, then dips, and is covered by a flat
beach extending many miles along Pevensey bay. It is almost
needless to observe that the cliffs from Rottendean to Beachy head
are oblique vertical sections of the South Downs, and have been
formed by the action of the sea.

On entering the London basin at the south side from the sea,
after passing the chalk cliffs at North Foreland and Margate, the
blue clay makes its first appearance at Reculver; and at Swale cliff
and Whitstable it is again seen.

But the Isle of Sheppey, consisting entirely of this stratum, and
whose lofty cliffs on the north side furnish very extensive sections,
affords the best opportunity for studying it.

Of this island, the northern half consists of a range of hills, of
above 200 feet in height. These are cut down vertically by the
action of the sea, which occasions the cliffs continually to fall:
whole acres of land sometimes coming down at once; in conse-
quence of which, the island must in a course even of a few centuries

presence of mind to escape over the rent that was forming at some distance:from the edge
of the cliff. In a few seconds, the mass of chalk which he had stood on, to the extent
of 300 feet in length, and 70 or 80 in breadth, fell with a tremendous crash. In going
from Newhaven round Beachy Head, under the cliff at low water, I passed over these
ruins, which were truly terrific, and observed that their fal] had been occasioned by the
sea acting on the chalk marl, and thus undermining the chalk ; the former from the dip
of the strata, just begins to appear at the bottom of the cliff at this spot. It may be
proper to mention that this place is highly deserving to be visited, on account of the
fossils to be seen in the chalk and green sand; among these I remarked many large
madrepores, and some very large and entire shells of the fibrous kind, the fragments of

which are so numcrous in the chalk,

Mr. WrsstTer on the Strata lying over the Chalk. 193

have suffered considerable diminution. The southern half of the
island is entirely alluvial, being only a few feet above the level of .
the sea; and owes its origin to the gradual filling up of the channel
which separates the Isle of Sheppey from the rest of Kent. It now
consists of flat marsh land, which has been gained from the sea by
embankments.

A little to the north of the eastern point, called Shellness, from
the great number of recent shells that lie on the shore, a low cliff
exhibits the section of the alluvial soil, which consists of clay and
gravel. At Warden the high cliff begins on the east, and extends
towards Sheerness on the west above six miles in length.

The clay of which these cliffs are composed is in all respects similar
to that which has been cut through in the neighbourhood of London
at Highgate, and at the Regent’s Park; and this place is particularly
known on account of its furnishing abundance of the septaria, from
which that excellent material for building under water and for stucco
is made, known by the name of Parker’s cement. These nodular
concretions of stone-marl are separated from the clay by the action of
the sea, and are collected upon the beach, and exported to various
places, where they are calcined and ground.

At Sheerness a well was sunk 330 feet through the blue clay, an
account of which is in the Philosophical Transactions: and from this
we may obtain an idea of the thickness of the stratum: for to this
must be added 200 feet, the height of the cliffs, making in all 550
feet.

The cliffs of Sheppey have long been celebrated for the numerous
organic remains found in them, a list of which, added by Mr. Jacob
to his Plante Favershamienses, is well known. But a much more
extensive collection has since been formed by Mr. Francis Crow, of
Feversham, who has enriched it by the addition of above 700 dif-

ferent species of fossil fruits, berries, and ligneous seed vessels,
WOLi1r, 2B

194 Mr. WesBsTER on the Strata lying over the Chalk.

This ingenious and indefatigable collector has also lately ascertained
a number of fossil bodies found among them to be the excrescences
produced by insects on the branches of various trees ; and I have been
since favoured by him with a portion of the jaw of a crocodile found
in Sheppey ; a fossil extremely interesting, since it is the only instance
yet observed of the bones of this animal having been found in the
London clay.

Almost the whole of the vegetable and animal remains are en-
tirely impregnated with sulphuret of iron, and the vestiges of shells
are chiefly casts in this substance. The quantity of fragments of
pyritous branches* and fruits is very great.

Among the pyritous casts of shells I found one that much resembled
the lymneus, and another the planorbis, but too imperfect to decide
the species. It is proper however to mention, that in a late number
of the Journal de Physique, in a paper on freshwater shells by M.
Braarde, mention is made of three freshwater shells from Sheppey,
‘the lymneus, melania, and nerita.

These shells however, which are very few in number, do not
prove the existence of a freshwater formation in this place similar to
those of the basins of Paris and of the Isle of Wight: being found
among the remains of vegetable and of marine animals, we may sup-
pose that they were carried down together with the branches of trees
and fruits by the numerous streams and rivers that must have flowed
into this gulph. .

Most of the best preserved organic remains are enclosed in the

* Tt will be an interesting investigation for the experienced botanist to trace the living
analogues of these ancient productions of this part of the earth, Such of them as have
been recognized are found to belong to species now growing only in the torrid zone;
thus adding to the evidence afforded by the animal remains of the great change that must
have taken place in the climate.

Mr. WezsTeER on the Strata‘lying over the Chalk. 195

septaria: in these the shells often retain their hs pearly lustre.
The nautili are particularly fine.

Boughton hill, between Feversham and Canterbury, consists of
the London clay. Still nearer to Feversham fossil shells are found,
which are entirely siliceous. They lie loose in a thin bed of greenish
siliceous sand that occupies a situation lower than the blue clay, and
are separated from the chalk by a thick bed of yellow sand. Mr.
Crow has collected here the strombus pes pelecani, a murex, a
species of cucullea, and several other bivalves.

One of the most interesting sections above the chalk is to be seen
at Woolwich, near the banks of the Thames. At this place the junc-
tion of the chalk with the strata over it is plainly to be seen. Over
the chalk is a stratum about 30 feet thick of very fine white sand ;
and towards the top there is a thin bed of clay. Next succeeds a
stratum of about 10 or 12 feet, composed whoily of flint pebbles,
which have been worn by water into their present forms, and lie in
the utmost confusion piled on each other, having a vast number of
fossil shells lodged in the interstices.

The whole has the appearance of having been at some period a
heap washed up on the sea shore, similar to our modern beaches.
The shells are entirely whitened, and having lost their animal matter,
are extremely brittle: their species however may be in general ascer-
tained, although very few are to be found entire. They have been
already described by Mr. Parkinson.

The bottom of this stratum of pebbles is now about 30 feet above
the level of the sea. Over this is a layer of sand with some fer-
ruginous masses, and then several thin strata of clay alternating with
sand. In this clay are vast numbers of bivalves, locked into each other

so. close that this must doubtless have been their original bed.
2.3.2

196 Mr. WEBSTER on the Strata lying over the Chalk.

Other beds of sand succeed, and on the top there is a stratum of
dark blue clay a few feet thick. :

This bed, which is frequently referred to by Woodward in his
history of fossils, has also excited the particular attention of Mr.
Parkinson: but its fossils differ so much from those usually found
in the London clay, that it is not easy to decide upon the place to
which it ought to be referred ; particularly since it is not even covered
by a bed that can be identified with the London clay. Bivalves, re-
sembling those of Woolwich, have been brought up in digging wells
at other places on the banks of the Thames, but I am not aware that
cerithia and the other fossils of this stratum have been so found,
This bed is known to extend for a considerable distance on the south
of the Thames, in the counties of Kent and Surrey. It is found at
Bexley and Plumstead, at which latter place a thin stratum of mi-
nute fossil shells was laid open a few years ago, but which now
appears to be lost.

At Bromley, which is not far above the chalk, vast quantities of
oysters are found imbedded in a calcareous cement and forming, to-
gether with rounded pebbles, a sort of rock. It has been observed
that these oysters are found adhering to the pebbles, indicating the
formation of the latter previous to the growth of the former.

Woodward, in his catalogue, frequently mentions a bed of stone
as occurring at Stifford in Essex, and containing fossil shells which
agree with those at Woolwich and Bexley. In a late visit which I
made to that part of the country for the purpose of ascertaining this
fact, I was not fortunate enough to procure specimens of the rock.
It is not indeed now to be seen where it is described by that author,
being probably concealed by cultivated ground: but I learned that a
stone did exist under the soil, which the labourers frequently came
to in ditching, and I mention this in the hope that some one residing
in that neighbourhood may examine into this matter.

Mr. WEBSTER on the Strata lying over the Chalk. 197

It is said that thin strata of a calcareous rock are found in sinking
wells through the London clay; but of this I have not seen any -
well authenticated specimens. The circumstance however is far from
being improbable.

The extensive works now carrying on in the neighbourhood of
the metropolis, as the cutting the hill at Highgate, the tunnel
lately carried under the Thames at Rotherhithe, one under Hyde
Park, the canal now forming in the Regent’s Park, and several
others of a similar kind, have thrown great light upon the nature
of the London clay and ‘its fossils, and furnish daily opportunities
for observation highly useful to all those who are interested in the
‘examination of our upper strata.

At Highgate-hill the beds consist of
1. Vegetable mould.
2. Several feet of loose gravel and highly ferruginous masses of sandstone.
3. Yellow clay. .
4. Blue clay, in which great numbers of marine shells and parts of fish
were found.

On the south side of the River Thames near Rotherhithe, a shaft
sunk for a tunnel proposed to be carried under the Thames, exhibited
the following strata.

Feet
6 9 Vegetable mould.
9 O Brown clay.

26 8 Gravel with water.
3 0 Blue clay.
5 1 Loam.
3 9 Blue clay with bivalve shells.
7 6 Gravel stones imbedded in a calcareous rock.
4 6 Light blue soil with pyrites.
1 9 Green sand.
8 4 Leafy clay.

198 Mr. WeEBSTER ow the Strata lying over the Chalk.

The bottom of the shaft was 30 feet under the bed of the river
Thames. The unfortunate failure of the project, from the river
bursting in before they had completed a drift, is well known.

At Reading there are several pits dug for the purpose of procuring
brick clay, some of which reach to the chalk; an account of the
strata at this place is given us by Dr. Brewer in the Phil. Trans. 1800.

Immediately incumbent on the chalk is a stratum 2 feet thick of
green sand containing numerous oyster shells. Many of these are
entire, having both their valves united ; but the animal matter being
entirely gone, and the shell not having undergone the process of
petrifaction, they are white and extremely brittle, and separate into
laminz. Fishes teeth are also found with them. Over this is a bed
3 feet thick of a bluish rough clay, then fuller’s earth 23 feet,
and fine white sand 7 feet. Next is a stiff red clay, probably the
plastic clay, of which tiles are made. This is much thicker than any
of the other beds; and over is the alluvial soil. These strata are
known to extend for several miles with little variation.

At Brentford, on the borders of the Thames, about 6 miles from
London, many important discoveries have been made in the grounds
of Mr. Trimmer; an account of which has lately been read before
the Royal Society. Here the chalk lies at a great depth, as they
have dug 200 feet through the blue clay without coming to it. Im-
mediately upon this clay are a few feet of sand and gravel with
water; over that from 1 to 9 feet of calcareous loam ; then sandy
gravel 7 feet, and lastly calcareous loam or common brick earth
9 feet. In the blue clay were found the usual fossils of this
stratum, being entirely marine. The three beds just over it con-
tained a vast collection of the bones of elephants, both African and
Indian, of the hippopotamus, the horns and jaws of oxen, the horns
of deer, and both land and freshwater shells.

Mr. WessTER on the Strata lying over the Chalk. 199

- Richmond Park is on this stratum, and Woodward frequently
refers to this place in his History of Fossils; but there are no longer
any sections to be seen there, the spot being covered by buildings.

Wells of 70.feet deep have been dug at Harrow-on-the-hill; and
several in Londen between 200 and 300 feet deep. At other places on
Fising grounds the depth of this stratum is much greater. In digging
a well for Lord Spencer, at Wimbledon, they were obliged to go
530 feet deep before they got through it to the sand which con-
tained water. At Primrose-hill, near Hampstead, a well was dug
some years ago to the depth of 500 feet without success.

This considerable formation may not only be traced on the north

side of Kent and Surrey, but almost the whole counties of Middle-
sex and Essex are composed of it. At South-end, and Leigh in
Essex, there are good sections of it. But not having an opportunity
of visiting the coast farther to the north, I am unable to speak with
certainty respecting the various strata to be observed there.
- The cliffs at Walton and Harwich, in Essex, have been best de-
scribed. From various accounts the lowest part consists of blue clay,
the fossils of which agree generally with those of Hordwell, Sheppey,
&c. This clay is covered by deep beds of gravel, sand and marl,
containing not only great quantities of fossil shells but also the
remains of land animals. |

From the confused manner in which these shells and: pebbles lie,
as described by Mr. Dale in his history of Harwich, there can be
no doubt but that the strata containing them are frequently alluvial ;
though in the cases where he describes them as lying in patches of
particular genera, we may suppose that portions of the original: strata
remain undisturbed.

Many of these latter fossil shells must belong to some of our latest
strata: they are described as scarcely mineralized, very friable, and
of a dead white colour.

200 Mr. WEBSTER on the Strata lying over the Chalk.

The counties of Suffolk and Norfolk have been little explored, and
still present a wide field for research. They will I have no doubt
amply reward those members of the Society who have opportunities
of examining them. ,

I shall now proceed to point out those particulars in which I have
observed the marine formation which we have been examining to
be analogous to some of the strata in the basin of Paris.

The plastic clay of the Paris basin is described as sometimes con-
sisting of two beds separated by a bed of sand. The lower bed is
properly the plastic clay. It is unctuous, tenacious, containing
some siliceous but no calcareous matter ; and absolutely refractory in
the fire when it has not too great a portion of iron. It varies much
in colour, being very white, grey, yellow, grey mixed with red,
and almost pure red. ‘This clay is employed, according to its qua-
lity, in making coarse or fine pottery and porcelain.

The corresponding beds of clay in this country agree well with
this description. The clays of Dorsetshire are extremely pure, and
are much employed in the potteries of Staffordshire and other parts
of England. In Alum bay we see clays of all the colours just
described. Some of them appear very promising, so much so that
the late Mr. Wedgewood had pits opened there; but although ex-
tremely refractory, they were found upon trial not to burn sufhciently
white for the purposes required. ‘The deep red clays we have seen
are very common in many parts of the country over the chalk.

No fossil shells have been found in this bed of clay in the French
basin, nor in the clay pits of Dorsetshire ; nor are there any in the
pure clays of Alum bay.

The uppermost bed of potters’ clay in France is sandy, blackish,
and contains sometimes fossil shells of the genera cytherea and turri-
tella, and the sand is often coloured red or bluish grey.

q

Mr. WusstTer on the Strata lying over the Chalk. 201

In the stratum of blue clay, next to the deep red clay that adjoins
the chalk of Alum bay, there are septaria with fossil shells, among
which I found cythere and turritelle ; the rest were too much mu-
tilated. Hence it would appear, that no fossil organic bodies are
disseminated through the pure plastic clays of either basins, but that
they are to be found in such beds of this clay as are impure.

A species of imperfect coal also occurs in the lower strata of the
Paris basin, and is probably analogous to that of Corfe, Alum bay,
and Newhaven. .

The French sands are of a great variety of colours. The sands of
Alum bay may correspond to that between their chalk and the plastic
clay, which is described as very. pure, though often coloured red or
blueish grey. It is refractory, and often in very large grains,

In the lower marine formation of the Paris basin, the most re-
markable and best characterized stratum is that of the coarse shelly
limestone or calcaire grossier.. ‘This is generally separated from the
chalk by the clay and the sand just described; or, when that is
wanting, it rests immediately upon the chalk. It is sometimes, also,
separated from the clay by a bed of sand, more or less thick, in
which no shells have been found.

The description given by the French of this calcareous forma-
tion is extremely precise, and corresponds toits importance. From
this it appears to be composed of alternate beds of limestone, more
or less hard, of argillaceous marl, of laminated clay, in very thin.
beds, and of calcareous marl. These are of great extent, and
preserve constantly the same order of superposition, although all
the beds are not continuous. Each bed is also characterized by
its peculiar fossils. The lower are often more sandy than cal-
careous, and when solid they fail to pieces on exposure to the air.
They frequently contain a considerable quantity of green earth,

WoL. ii. Ze

202. Mr. Wester on the Strata lying over the Chalk,

and this is found only in the lower beds, a circumstance which
they have pointed out as particularly indicative of them.

The lowest bed is also particularly distinguished by the vast
number of fossil shells contained in it; the greatest part of which
are more unlike the recent shells than those of the superior beds.
The fossil shells of this bed are often well preserved, and are easily
detached from their matrix; and many of them have still their
original pearly lustre.

The middle beds also inclose a great many shells ; one of them is
called the green bank, from its colour. It often contains impres-
sions of leaves and stalks of land vegetables, mixed with cerithia,
ampullariz, and other marine fossils.

The next bed of calcaire grossier has less variety of fossil shells
than those just mentioned, but the cerithia are very abundant in it:
and towards the top there is a thin bed, containing a prodigious
quantity of corbule, long shaped, and striated. Above these are
the marls, both calcareous and argillaceous ; with calcareous sand,
sometimes agglutinated, and which contains hornstone with hori-
zontal zones.

The uppermost beds of this system have much fewer shells ; and
these are generally altogether wanting at the top.

In passing over in review all the strata which we know above the
chalk in England, there does not appear to be any one that can be
considered as exactly corresponding to this considerable and well-
marked stratum in the basin of Paris; and in instituting a com-
parison between the English and French strata, were we to require
a perfect agreement in all the beds, we should here totally fail.

Yet although we cannot point out a calcareous rock precisely
similar, and possessing the same importance of character, I think a
sufficient number of circumstances may be shewn to justify our

Mr. WEBSTER ox the Strata lying over the Chalk. 203

considering the greatest part of the materials of this formation as
existing in the English basin, but differently modified.

For this purpose I shall consider the organic remains, which the
French have observed to belong peculiarly to these beds, as very
important.

The general correspondence between the fossil shells of Grignon
and those of Hampshire, has been already pointed out by several
able naturalists, and in particular lately by Mr. Parkinson. I should
therefore scarcely have considered it necessary to state here what is
already so well known, had I not been enabled during my late
journey to the Isle of Wight, to add several not hitherto observed,
and which bring the agreement still closer; and since organic re-
mains furnish one of the best methods of identifying strata, or
rather perhaps formations, it may at present be interesting to bring
into one view the most characteristic fossils that have been observed
in this formation in England.

The liberal assistance of Mr. Parkinson has enabled me not only
to give the scientific names of Lamarck to the several fossil shells
which I found, but also to add the corresponding Linnean names,
by which they are chiefly known in this country. This however
could not be done in every case, since many of the fossils of
Lamarck were not known to former naturalists.

22

204

Mr. WessTer on the Strata lying over the Chalk.

Organic remains in the Lower Marine formatian above the Chalk in

England.

Places where they have

Names given by sega bi

Astroite -
Calyptrea tr ochiformis

Conus .. . Ae
Cyprea pediculus —

T erebellum convolutum
liva . ° .
Voluta spinosa. .
musicalis
bicorona abl.
crenulata

Buccinum undatum. .
Harpa ys) ceteris
Cassis carinata F
Rostellaria macroptera
Murex tripterus .
tricarinatus
tubifer ..

Fusus longevus . . .
— clavellatus
— rugosus
~Pyrula nexilis
Pleurotoma? . . .
Cerithium gigantum
Cerithium, nanutlier va-
riety, but too mu-
tilated to ascertain
the species
Trochus agglutinans
monilifer
Solarium caniculatum
or
Delphinula: ?
‘Turritella fercbellata
imbricatoria .
multisulcata .

Ampullaria patula . .

F path ofies

Linnean names.

Trochus aper tus, Brander

Conus . . E
Cyprea esha: :
Bulla di pita, Brand.
Voluta sc, 4 F tor
Strombus spinosus .
luetatora as v4
ambiguus . .
Murex suspensus .
Voluta ampullaria .
Buccinum nodosum, Bran.
Strombus amplus) ..
Murex tripterus .

asper :

pungens . ..

contrarius b

— — whiris the right
way

——longevus’ ..
——— deformis . .
= DORNEGHIS | Jl le
mexilis) 19.9.

Murex .°. .
Loe) ae sae ee

Trochus umbilicaris, Bran.
—— nodulosus
Turbo, tab, 1. fig. 7&8.
Brander
Turbo, tab. 1. fig.7. Brand.
Turbo terebra . . ‘

editus .

vagus

Helix mutabilis

Sheppey

been found

Hordwell, Bognor, Wool-
wich, Plumstead

Hordwell, Stubbington

Stubbington, Highgate

Hordwelt

Alum-bay

Alum-bay

Hordwell

Hordwell

Hordweil, Alum-bay

Brentford, Alum-bay

Alum- bay

Brentford

Stubbington, Highgate

Hordwell, Highgate

Hoxduedl.

Hordwell

Hordwell

Hordwell
Hordwell
Hordwell
Hordwell
Alum-bay
Stubbington

Sheppey

Stubbington, Hordwell
Hordwell

Hordwell

Hordwell

Hordwell, Stubbington,
Alum- bay, Selsea

Hordwell, Stubbington,.
Bognor

Mr. WesBsTER on the Strata lying over the Chalk.

205

Names given by Lamarck

Dentalium elephaniinum
entalis
dentalis

— striatulum

Serpula... .. cisy +
Nautilus imperialis .

pompilius .

centralis
Lenticulina rotulata
Nummulites levigata
Pinna, 2 species
Mytilus modiola .

Pectunculus pulvinatus

Cardium porulosum
asperulum
-obliquum
Crassatellata lamellosa .
Venericardia planicosta
Capsa rugosa .

Chama Lier etlesid
calcarata .

suleata .~.

etvds edulis .
Pyrus bulbiformis
Caryophillia

Teredo navalis . . .

Jaw ofa Crocodile .

Testudo or Turtle

Various Fish, but too
mutilated to ascertain
the species ..

Fish teeth, supposed by
some to belong to the
shark Aas

Molar teeth of fish,
called Bufonites .

Palatum Scopuli and
other palates of fish

Linnean names

Dentalium elephantium 9
— entalis
————— dentalis

———- striatal:

Serpula .

Pian! ie aie i gee
Mytilus are ar

Arca glycemeris .

now. a, ae
Cardium porulosum

asperulum .
—- obliquum .
Tellina sulcata

Venus deflorata .
Chama squamosa

Ostrea edulis .

Turbinated Madrepores

Teredo navalis . .

Places where they have
been found

Hordwell, Sussex

Hordwell, Bognor,
Sheppey

Sheppey, Highgate,
Brentford

Sheppey, South-end,
Highgate, Brentford

Richmond

Stubbington

Brackelsham in Post

Bognor

Bognor, Highgate

Bognor, Stubbington,
Essex

Stubbington

Hordwell
Hordwell

Stubbington, Selsea
Pa cham

Hordwell

Hordwell

Hordwell, Stubbington,
Aium-bay

Bognor, Selsea, Essex

Hordwell, Stubbington,
Alum- -bay

Sheppey

Stubbington, Portsmouth,

Sheppey. Bognor.
Highgate A,
Sheppey—
Sheppey

Sheppey

Sheppey, Stubbington,
Highgate

Sheppey
Selsea, Sheppey

206 Mr. WassTER on the Strata lying over the Chalk.

Names given by Lamarck

Tongue of a fish of the
genus Raiai 2) ;
Tail of the Sting Ray .

Scales of fish .
Vertebre of wakides
species of fish
Cancer, above20 species
of Crabs
Gammarus or
Lobster
as or
Prawn: 14

Wood, often pierced :

the Teredo navalis &
filled with pyrites or
calcareous spar
Fruits, bbianiches, ex-
crescences, ligneous
seed vessels and ber-
ries impregnated with
Pyettes.ie. ese

Places where they have
Linnean names been found

Sheppey
bi ie nkie” 122-25 re pe
SO IF olhar aepce Shepp ey

Sussex, Sheppey, High-
euicf gate

¢- 6 « « 6 (04 SHeppes
s+ © © « es | ODeppeE

e « « « ¢ «| Sheppey

Portsmouth, Sheppey,
. . . . ° . { ighgate

Sheppey, Emsworth in
Sussex

Although nearly 600 species of fossil shells have been described
by M. Lamarck as belonging to the calcaire grossier, Messrs.
Cuvier and Brongniart have selected the following as particularly
characteristic of the several beds.

Lower beds.

Nummulites lavigata Cerithium giganteum
——— scabra Lucina lamellosa
————— numismalis Cardium porulosum
&e. Voluta cithara
Madrepora Crassatella lamellosa
Astrea Turitella multisulcata
Caryophyllia Ostrea Flabellula
Fungites Cymbula

Mr. WeBsTeER on the Strata lying over the Chalk. 207

Middle beds.
Cardita avicularia Citherza nitidula
Orbitolites plana elegans
Turritella imbricata Miliolites
Terebellum convolutum Cerithium ?
Calyptrea trochiformis Articulated bodies
Pectunculus pulvinatus resembling vegetables

Upper beds.
Miliolites Cerithium lapidum
Cardium lima or obliquum ——- petricolum
Lucina saxorum _ Corbula anatina ?
Ampullaria spirata — striata
Cerithium tuberculatum Impressions of leaves

————- mutabile

Messrs. Cuvier and Brongniart remark that the nummulites are
found only in the lowest beds of the calcaire grossier, to which
belongs also the cerithium giganteum. I am enabled by the
information of Mr. Holloway, who pointed out to me these fossils
at Bracklesham in Selsea, and also in Stubbington cliff near Ports-
mouth, to add this very strong circumstance of agreement with the
French strata.

It is impossible not to be struck with the identity of the fossil
shells of the sandy beds of Liancourt with those of Stubbington.

At the former of these places are found :

Nummulites lenticularia

-—-— levigata
Turritella terebellata
imbricataria
Crassatella sulcata
Venericardia planicosta
Sharks’ teeth
The whole of which are to be found at Stubbington.

208 Mr. WessTeR on the Strata lying over the Chalk.

These beds of Liancourt contain also masses of sandy limestone
filled with chlorite: and Stubbington is remarkable for the quantity
of green earth which it contains.

A circumstance is mentioned by the French authors which
appears to point out a remarkable era in the history of these strata.
They observe, that in the beds of the lower marine formation, and
particularly in those of Liancourt, natural wells of considerable
size are sometimes found, filled with ferruginous and sandy clay
and water-worn siliceous pebbles. ‘These wells do not pierce
through all the beds of the calcaire grossier; but begin at the
same level, and are covered and closed by the uppermost beds:
shewing that they were formed after the period of the formation
of the lowest, and before that of the upper beds ; which points out
a very long interval, and the action of viclent causes during
this time.

It may be remarked, that this is exactly the period to which we
must look for the subversion of the strata of the Isle of Wight, and
the formation of its basin. If therefore the deposition of the
upper beds of the calcaire grossier was general, and extended to
this part of the globe, it must be placed at the lowest part of the
Isle of Wight basin, and probably therefore at an inaccessible depth.

The rocks of Bognor and Selsea appear to be the most easily
referable to some of the beds of the calcaire grossier of France.
The correspondence in their geognostic situation, in the nature of
their materials, and in the fossils which they contain, sufficiently
justify the supposition.

Although in general the beds of the calcaire grossier maintain a
regularity remarkable and distinctly to be traced, yet that is not
always the case, the quarries of Saillancourt being cited as an

exception to this rule: all the beds are there united, and nearly of

Mr. WEBSTER on the Strata lying over the Chalk. 209

the same quality, which appears to be owing to calcareous spar
cementing the parts together. In our blue clay there is a con-
siderable quantity of carbonat of lime in a sparry state, as is evi-
dent from the septaria. |

The middle and upper beds of the French calcaire grossier
frequently contain a sandstone, with marine shells which agree,
though not entirely, with those of the calcaire. This sandstone is
sometimes white and friable, and sometimes shining and almost
translucent. ‘The shells are frequently white, calcareous, and well
preserved, though sometimes broken and mixed with pebbles.

The sandstone which forms the uppermost beds of the rocks of.
Bognor, already described, do not differ much from this description.
Tt contains some fossil shells of the same species, though not in
such numbers as the lower beds; and some of those in the lower
beds, as the pinnz, are not met with in the upper beds; the shells
also are frequently whitened.

By connecting all the above circumstances it would appear,
that if we could suppose a blending or mixture between the French
plastic clay, which is blackish and contains organic bodies, and the
lower beds of the calcaire grossier with its green earth and fossils,
we should have a compound agreeing sufficiently near with our
London clay under all its varieties; with this difference, that that
of the French basin would have a greater proportion of calcareous,
and ours of argillaceous matter. We may therefore fairly infer
that they belong to the same epoch. But with respect to the
upper beds of the calcaire grossier of France, no strata have yet
been discovered in this country that correspond to them. Whether
any such ever existed, and whether any traces yet remain, may

perhaps prove a fit subject for future enquiry.

Wou. 11. 25

210 Mr. Wexster on the Strata lying over the Chalk.

§ 3. Lower Freshwater Formation.

This formation is to be seen most distinctly in the section of
the hill called Headen, which forms the northern boundary of
Alum bay, in the Isle of Wight. It appears there in a series of
beds of sandy calcareous and argillaceous marls; sometimes with
more or less of a brownish coaly matter. Some of them appear to
consist almost wholly of the fragments of freshwater shells, many
of which are however sufficiently entire to ascertain their species.
These are the lymneus, planorbis and cyclostoma, and perhaps the
helix ; with a bivalve resembling the freshwater mytilus.

These beds lie immediately upon the black clay that covers the
white sand, described in the account of Alum bay. They are
extremely irregular, and are not to be traced distinctly from each
other for more than about a few hundred yards, the remaining
part being so hid by the mouldering slope, that the formation can
only be observed in mass. It may be seen however extending
round the north side of Headen into Totland bay, where it forms
the upper part of the cliff: and at the point called Warden-ledge,
it is found in a more uniform and indurated state. Here, when
the clay upon which it rests gives way from the rain and frost,
large masses of it fall down, which are employed for the purposes
of building, though the stone is not of a good quality. Pursuing
it farther into Colwell bay, it dips to the north, and is soon lost ;
nor is it to be seen any more on that side of Yarmouth. At the
bottom of these beds, and between them and the black clay, there
is frequently a layer of two inches or more in thickness of a dark
brown coaly matter, much like what is usually found at the bottom
of peat bogs, and it appears to be a similar substance that tinges
many of the beds.

Mr. WEBSTER on the Strata lying over the Chalk. 211

On a careful examination I was not able to discover any
mixture of marine shells in this series of beds. Had they ever
existed I think their remains would have been evident, considering
how much thicker and stronger marine shells in general are than
those of freshwater.

The quantity of shells, and the regularity and extent of the
strata in which they are found, are much too considerable to
suppose that they could have been carried by rivers or streams into
an arm of the sea; and in this case there would also most probably
have been a considerable intermixture of marine shells. We are
compelled therefore to admit that the spot where they now are,
was once occupied by freshwater, in which these animals existed in
a living state.

The mutilated condition in which these shells appear, seems to
denote that they had not become mineralized sufficiently to preserve
their forms, or that the place in which they were accumulated was
occasionally subject to agitations.

Freshwater strata occur occasionally in other parts of the west
and north coasts of the Isle of Wight, but in such an irregular
manner that it is not easy to say to what formation they belong.

Among those at Cowes and Ride there are none that I can
completely identify with these beds. But I am at present inclined
to think that the same formation exists at these places, though
under a character considerably different.

The quarries of Binstead, near Ride, were formerly of great
celebrity, and furnished the materials for many ancient edifices,
both civil and religious, in the Isle of Wight and the counties
contiguous to it. They are now very little worked; but their
extent may be traced by the broken ground where they have been
filled in.

2D2Z

212 Mr. WessTeER on the Strata lying over the Chalk.

The section of the strata is as follows, beginning at the bottom.

Feet.
1s—-Blue clay pron. siaoil caupuit Slecave ateleeieedgaste se eRey Sneeaen
Peete) MR meee geht ae I Re ONS bev Lp pwn. rum CR

3.—A Siliceous limestone called rag
4,—Sand

5.—Siliceous limestone . ....
6.—White shell-marl

7.—Siliceous liméstone . rer ees ee ee
8.—Limestone composed of the fragments of freshwater shells
9.—Ditto, the fragments more apparent . . . . .«
10.—Ditto, the fragments still larger

wo fF WOK KK OCC SO
>

1].—Ditto, fragments still coarser . Pim A
12,—-Blue Clay, in which are many large and loose masses which
appear to belong to the upper Freshwater formation.

At East Cowes Lord Henry Seymour had the goodness to point
- out to me a quarry which he had caused to be opened in his
grounds, the strata of which were almost exactly the same as those
of Binstead. The rag from this quarry his Lordship had employed
in the construction of his mansion; and also in the fine wall
which he has built to keep off the encroachments of the sea.

In the strata of East Cowes the casts of the shells are frequently
entire, and appear to belong to the genus Cyclostoma Lam.

The fragment stone of Binstead, when examined with a mag-
nifier, has a very singular appearance. In some specimens the
fragments themselves remain, though in a sparry state; but in
general the substance of the shell has disappeared, leaving a cavity
where it formerly existed; so that in fact, instead of being frag-
ments cemented together by calcareous spar, the stone consists of
the hollow moulds of fragments held together by that matter. It
would seem as if the shells themselves had been gradually absorbed
into the substance of the cement.

Mr. WEBSTER on the Strata lying over the Chalk. 218
The whole of the ncrth shore of the Isle of Wight has been

for ages in a state of constant ruin by the action of the sea and the
sliding down of the soil. It is difficult therefore to find any part
of the strata in their original situation ; on this account freshwater
and marine shells are frequently found together in confusion. I
have however observed some places where they occur in alternate
layers.*

The cerithia, cyclades, cytherza, oysters, and other fossil shells,
which are so numerous on the shore near Cowes, are derived from
the blue clay of the upper marine formation, which is situated
above that which we are now considering, and of which the
sloping banks chiefly consist.

That occasional alternations and mixture of marine and fresh-
water shells should occur, may, a priori, be expected. They
would denote either the gradual nature of the change that has
taken place in an arm of the sea before it became completely a lake
of freshwater, or the occasional irruptions of the ocean at a sub-
sequent period. |

These beds may be traced a considerable way eastward of Ride,
and I believe as far as Nettlestone, but I have not had an opportu-
nity of ascertaining their precise boundaries. Neither haveI been
able to learn with certainty that any part of this formation is to be
found on the coasts of Hampshire on the opposite side of the
Solent; and I do not find it eastward on the Sussex side.

Woodward, however, in his valuable catalogue of fossils, fre-

quently makes mention of freshwater shells in a marly stone from

* The only shells which I noticed thus alternating with those ef freshwater, appeared
to belong to the genus Cerithium, but not having specimens of them it has since occurred
to me, and it will deserve future observation, whether these were not the Potamides
Lamarkii. They are abundant at Gurnet Point.

214 Mr. WEBSTER on the Strata lying over the Chalk.

the Hordwell cliff. It is very probable therefore that traces of
this formation may be found there, if this spot were well examined
for the purpose.*

- Land and river shells have been repeatedly discovered in various
parts of England; and often at some depth under beds of sand
and gravel. They are then often accompanied by the bones of land
animals as those of the elephant, hippopotamus, &c. and may be
referred to a very ancient period probably connected with some of
these formations. None of them however had as yet been dis-
covered imbedded in a stratum of rock. When they have been
found under peat bogs they have been most probably produced in
some of the later states of the earth.

It is in this formation, in the Paris basin, that the gypsum beds
are placed. ‘Three series of gypseous strata are described: the
lowermost consists of thin beds of gypsum, often selenitous, of solid
calcareous marls, and foliated argillaceous marls ; and they observe,
that these are sometimes deposited on the marine shelly calcareous
sand, and then they contain marine shells. In these are also beds
of white marl, containing a great quantity of freshwater shells of
the genera limneus and planorbis. ‘These lower beds, with the
white marl, constitute the oldest freshwater formation; and, ac-
cording to the observations of M.M. Cuvier and Brongniart,
appear to have been formed during the passage or change of the
Paris basin from the state of a marine bay to that of a freshwater
lake. The second mass of beds differs from the above mentioned

* Since the reading of this paper I have been favoured by the Rev. William Buck.
land, Prof. of Mineralogy, Oxford, with specimens of freshwater shells which he has
collected at Hordwell cliff. They consist of the lymneus, planorbis, cyclostoma, and
a bivalve resembling a freshwater mytilus. From the state of the fossils, and the
nature of the stratum in which they were imbedded, they would appear to belong to
the lower freshwater formation.

Mr. Wesster on the Strata lying over the Chalk. 215

in the gypsum being thicker, and in the occurrence of a bed of
very indurated clay containing fossil fish. The third or uppermost -
mass is the most important, the beds of gypsum being very thick ;
it is here alone that the bones of unknown birds and quadrupeds
are met with. Freshwater shells are also found in it, though rarely.

Over the gypsum are very thick beds of calcareous and argil-
laceous marls ; one of the latter, which is white and friable, contains
silicified trunks of palm trees, and in the former are found many
freshwater shells. In this freshwater formation are found neither
the meulieres, nor any other flints, except the silex menilites, and
the hornstone of the upper gypsum beds.

The total absence of beds of gypsum and of the remains of qua~
drupeds, in this formation in the Isle of Wight, (at least as far as
my observations extend) exhibits a striking proof, that although
probably of contemporaneous origin, yet the circumstances ac-
companying its formation were very different from those under
which that of the basin of Paris was produced. The gypsums of
Montmartre are well known; and they are considerably different
in their appearance from those of England, which belong only to
strata far below the chalk. It has been already observed, that
selenite is very abundant in our blue clay ; but this arises from the
decomposition of the pyrites contained in it.

§ 4. Upper Marine Formation.

Over the lower freshwater formation in the Isle of Wight, a
stratum occurs, consisting of clay and marl, which contains a vast
number of fossil shells wholly marine. Few of these shells agree
with the species that have been found in the London clay, and they
are also considerably different from them in their state of preserva-

216 Mr. WEBSTER ox the Strata lying over the Chalk.

tion; most of them appearing to have undergone but little change,
and some are even scarcely to be distinguished from recent shells.
The situation of this bed, distinctly placed above the vestiges of a
freshwater lake, would seem to indicate some great revolution in
the relative level of the land and sea, since the time of the marine
deposit which we have already considered; and the above circum-
stances, combined with its position as regards the vertical beds of
Alum bay, point out in strong characters a later period.

The spot where this stratum is best examined is Headen, near
Alum bay. It there appears half way up the cliff; is about 36 feet
thick, and dips a few degrees to the north. It passes from thence
all round Totland and Colwell bays.

The substance of the stratum is chiefly marl of a light greenish
colour, and the fossil shells are so numerous that they may fre-
quently be gathered by handfulls, and are in general extremely
perfect. I did not observe that the several species occupied separate
beds, although they were much thicker together in some places
than in others, and were then oftener accompanied by rounded
nodules of greenish indurated marl. From the delicacy of the
shells and their perfect preservation, it is evident that they could
not have been brought from great distances, but must have lived
near to the spots where they are now found. This greenish marl
is separated from the upper freshwater formation only by a bed of
sand a few inches in thickness.

In Colwell bay, at a fissure called Bramble’s chine, there is in
this stratum a very large bank of fossil oyster shells; the greater
part of which are locked into each other in the way in which they
usually live, and many have their valves united. It is therefore
clear that this oyster bed has never suffered a removal.

This stratum may be traced, with various interruptions, all round

Mr. WEBSTER on the Strata lying over the Chalk. 217

the north side of the Isle of Wight, and may be seen at Cowes,
Ride, and Bembridge.

In the enumeration of the various strata in the basin of Paris, our
attention is particularly called to a thin bed of bivalve shells cover-
ing the upper beds of gypsum and gypseous marls of the lower
freshwater formation, the shells of which are placed close, and as
it were locked into each other. This bed, though apparently of
little importance, is remarkable by its great extent; having been
observed over a space of more than 10 leagues in length, and more
than 4 in breadth, and always retaining the same situation and
thickness. It is still farther distinguished as marking out the be-
ginning of the new series of strata deposited by the sea.

Over this thin bed of bivalves there is one of greenish marl with-
out fossils; and then several alternating beds of argillaceous and
other marls and sands, containing marine fossils, shells, and bones
of fish. ‘Two beds of oysters are particularly noticed; and it is
observed that these must have lived upon the spot where they now
are, because they are locked into each other as in their natural beds,
with many of their hinges entire. The uppermost beds of marls
are however not constant; sometimes, as at Chellis, there is only
a thin bed of sand between the green marl and the upper fresh-
water formation. It is in these marls that the silex menilite is
found.

The changes which the surface of the earth has experienced have
no doubt destroyed so much of the Jast depositions in the London
as well asin the Isle of Wight basins, that it is impossible to say
what the complete series was originally.

Of the existence of this upper marine formation therefore in
the London basin, I must speak with diffidence, more particularly
since an extensive freshwater formation might never have existed

VOL. I. ZE

218 Mr. WEBSTER on the Strata lying over the Chalk.

there, and consequently the last marine deposits would be placed
immediately upon the lower ones, and would be less easily distin-
guished, as is frequently the case in the basin of Paris, where we
are informed that the sandstone without shells, which is over the
marls belonging to this formation, is placed immediately upon the
siliceous limestone of the lower marine formation, on the heights
to the east of Melun and of Samoineau; the gypsum being wanting
there. But as it forms the summits of almost all the hills and plateaux
where the gypsum beds are found, they form a separation between
the upper and lower marine strata, and render their distinction no
longer uncertain. In the counties of Suffolk and Norfolk, there
are very extensive beds of marine shells, imbedded chiefly in a
ferruginous sand, and lying above the London clay, which have
been described under the name of Crag pits. Among the fossils
which have been enumerated as belonging to these beds, many
agree with those in the upper marine formation in the Paris basin,
and others do not appear to differ from the recent shells of the
neighbouring seas.

Fossil shells agreeing with the recent occur also in many other
parts of the kingdom, now considerably removed from the sea,
and are often buried under beds of gravel. These probably belong
to the last states of the earth, and might serve as a clue to unravel
geological mysteries.

If we depend upon fossils as a principal means of identifying
strata, we shall see great reason to believe that the last of our marine
depositions are nearly allied to the upper marine formation of the
basin of Paris.

In this stratum in the Isle of Wight I found the following
fossils,

Mr. Wasser on the Strata lying over the Chalk. 219

Names given by Lamarck.
Cerithium plicatum

Linnean Names.

- - - lapidum

- - - mutabile

- = - semicoronatum Murices
= /= ‘cinctum

- - = turritellatum

- - = tricarinatum

Cyclas deltoidea . : : . Venus

Cytherea scutellaria ore oe . Venus

Ancilla buccinoides : ; . Voluta

-~= “subulata “-. ; ; . Voluta

Ampullaria spirata 5 - i elces
= hie" = Mtlepressa f : .

Murex reticulatus . : 3 :

Bivalve apparently of the genus Erycina

Helicina?

Murex nodularius

Melania? They are however too much in-
jured about the mouth to determine
their genus with certainty

Another species of Melania corresponding to
those of Plumstead

Natica Canrena , :

Ostrea, approaching to deltoidea

- - - specific characters not evident, but

different from the last

Zin Z

. Nerita

220 Mr. WEBSTER ow the Strata lying over the Chalk.

Fossils found at Harwich in Essex.

Names given by Lamarck. Linnean Names.
Patella ungaria
--- levis
Patella spirorostris --- fusca
Fissurella labiata : : . Patella
- = -emarginula : . --- fissura
Calyptrea sinensis. ; . --- sinensis
Eburna glabrata : . . Buccinum glabratum
eh Ee Murex corneus
sl thee - - - erinaceus
= 5 fay PO - - = contrarius

eg te a Trochus sulcatus
etal - - - - alligatus
Ampullaria rugosa
Natica canrena

- - glaucina

Mactra
Venericardia senilis . 3 . Arca senilis
Lucina . : . : . Venus gallina
sete Solen siliqua
Pholas crispata ,

rhonda one Ostrea deformis
Pecten plebeius

- - - infirmatus
Balanus

Some of these however may belong to the lower marine blue clay.

Mr. WEBSTER on the Strata lying over the Chalk. 221

M. Brongniart mentions the following as being found in the
various beds of the upper marine marls,

Cytherea (om-bees ) Ostrea Hippopus

- - = plana - - Pseudochama

- - - elegans - - longirostris

- - - semisulcata - - canalis
Cerithium plicatum - - cochlearia

- - - cinctum - - cyathella
Ampullaria patula - - spatulata

Cardium obliquum | -- - linguatula

Nucula margaritacea Bones and parts of Fishes

Patella spirorostris—Cuv. p. 187.

In the upper marine sand stones.

Oliva mitreola Pectunculus pulvinatus
Fusus, resembling longevus Crassatella compressa ?
Cerithium cristatum Donax retusa?

- - - lamellosum Cytherea nitidula

- - - mutabile? - - - levigata
Solarium ? - - - elegans?
Melania costellata ? Corbula rugosa
Melania ? Ostrea flabellula

I have already mentioned that considerable difficulties appear to
me to exist in assigning a place to the Woolwich beds. The actual
lowness of their level, appearing to dip under the London clay,
and their situation near the chalk without the intervention of that
bed, at first seem to determine their geognostic position. Whilst
the circumstances of their not being seen in any part covered by

222 Mr. WeBsTER on the Strata lyinig over the Chalk.

the London clay, nor having been actually identified with any
strata which have been found in sinking through it with certainty,
leave the question still undetermined; and the agreement of the
fossils of the Woolwich and Plumstead beds with those of the upper
marine formation in the Isle of Wight, not only in their species
but in their state of preservation, is sufficiently striking to suggest
the idea of a similarity in the circumstances of their production. __

The considerably greater elevation of Highgate-hill, and of other
places known to consist of the London clay, above the Woolwich
beds, is scarcely of itself a satisfactory reason for supposing that
the latter. exist under the former, since the changes to which this
part from the chalk upwards has been subjected at various periods,
are sufficiently pointed out by the extensive banks of pebbles of
very ancient date, and. the other proofs of the agency of water.
The great irregularity in the surface of the chalk stratum is obvious
from its disappearing so suddenly on the north bank of the
Thames; and it is not difficult to imagine that from currents and
other local causes, the deposition of the London clay might not
have taken place in certain spots, which might yet have been co-
vered by the sea that gave rise to the upper marine stratum on the
Isle of Wight. It must be confessed however, that for want of proper
sections, we have not yet sufficient data for determining this point
with accuracy, and I shall content myself at present with having
described such facts as I have myself noticed, leaving this subject
to future investigation. Ly bs,

Mr. WEBSTER on the Strata lying over the Chalk. 223

Mr. Parkinson enumerates the following as found at Woolwich.

Names given by Lamarck,

Cerithium turritellatum

- - - denticulatum
- = <= serratum
-’- - claviculatum
- - - mutabile
as, CUCU

- - - semicoronatum

Cytherea scutellaria
Cyclas deltoidea

Calyptrea trochiformis

to which I have added

Ancilla Buccinoides

Melania

Arca

Ampullaria

Calyptrea trochiformis
Cyclas

and Mr. Parkinson has since found

Nucula margaritacea
Teeth of fishes

Cerithium denticulatum
Cytherea scutellaria
Ostrea

At Plumstead.

At Newhaven.

Linnean Names.

Murices

Venus
Trochus apertus

Voluta

Helix
Arca
Helix

Arca nucleus

Murex
Venus
Ostrea

224 Mr. WessTeER on the Strata lying over the Chalk.

In the Paris basin the marine marls are covered by a very ex-
tensive and thick bed of sand, entirely without animal exuviz,
which has nearly filled up all the cavities which still existed on the
surface of the basin, covering the partial formations of marine
gypsums, the lower freshwater marls, together with all the other
strata, and reducing the surface nearly to a level.

This sand frequently contains beds of sandstone of the same
nature with itself, which frequently form the flanks of the hills in
the neighbourhood of Paris; and great blocks of these have fre-
quently rolled down into the valleys, the sand having been carried
away; such are the sandstones in the forest of Fontainebleau,
Palaiseau, &c. The sand of this stratum is often an extremely
pure white quartz, and is much used in the arts; but sometimes it
is coloured by oxides of iron, or impregnated by carbonat of lime,
It forms all the soil of Beauce. The sandstone is very hard, pure,
and homogeneous.

This bed is usually covered only by the burr stones without
shells, or by the upper freshwater formation. Over it however
there is in some parts a sandstone containing marine shells, agree-
ing nearly with those of the middle beds of the calcaire grossier,
or rather with those already observed in this upper marine forma-
tion ; and in other places a calcareous stratum with shells.

The London clay is in many places covered by an extensive bed
of sand, usually called the Bagshot sand. It extends over Bagshot,
Frimby, and Purbright heaths, in the county of Surrey, and that
on Hampstead heath belongs also to it.

At Purbright, and many parts of the surrounding country, loose
blocks of a stone is found similar to what has been called the grey
weathers. This stone, composed of siliceous particles cemented

together without any intervening substance, may be considered as

Mr. WEBSTER on the Strata lying over the Chalk. 225

a granular quartz. It has more the appearance of an original for-
mation, or peculiar crystallization of siliceous matter analogous to
that of sugar, than to a substance composed of the detritus of other
rocks.

Numerous large and loose masses of this rock lie scattered over
the surface of the chalk country, particularly in Berkshire and
Wiltshire, but a bed or continuous stratum of it has not yet been
observed. ‘These stones were much employed by our ancestors
in building, and before the ground was cleared for the purposes of
agriculture they were much more numerous than at present. ‘The
huge erections of Stonehenge, which have so much exercised the
conjectures of our antiquaries, are chiefly* composed of it, and
the blocks were no doubt found on the spot.

This granular quartz bears a close resemblance to the siliceous
cement of the Hertfordshire pudding-stone, which also is often found
in loose masses above the London clay. There appears no ne-
cessary connexion between the pebbles of this beautiful conglome-
rate and their cement, but the dates of their origins were very
different ; the siliceous deposition, when it did not envelope any
foreign substance, forming the rock called the grey weathers ; and
when it fell among pebbles of any kind, composing a pudding-
stone. Accordingly we sometimes find in the grey weathers

common chalk flints.*

* It is not a little singular that some of the smaller upright stones of Stonehenge
consist of a sort of greenstone, and must therefore have been brought from a very

great distance, no such rock occurring in the neighbourhood.

+ Specimens of these collected in the neighbourhood of High Wycombe, by the Hon.
Henry Grey Bennett, Pres. G. S. are deposited in the Museum of the Society.

VOnTT. OF

226 Mr. WEBSTER ow the Strata lying over the Chalk,

§ 5. Upper Freshwater Formation.

r

I have now to describe the most remarkable and best charac-
terized of all the strata in that hill in the Isle of Wight called
Headen, which has so frequently come under our examination.

Here, immediately over the last-mentioned formation, there is a
thin bed of sand of 6 inches, upon which rests immediately a
very extensive calcareous stratum 55 feet in thickness, every part
of which contains freshwater shells in great abundance, without
any admixture whatever of marine exuviz. ;

The substance of which this stratum consists is of various cha-
racter, although it cannot be described as being subdivided into
smaller beds. A great part is composed of a yellowish white marl,
sufficiently indurated to remain in blocks when fallen down, but
extremely friable, and which, like other marls, will not endure
the frost. In this, and disposed without any regularity, are hard
masses of a rock which appears to contain a greater proportion of
calcareous matter; and to be in about an equal quantity with the
marl. This stone is very durable, and is employed as a building
material. Between these two extremes there are many parts of
intermediate degrees of hardness and durability.

Many of the shells which are found imbedded in this stratum
are quite entire, and these are mixed with numerous fragments of
the same species. They consist, like the lower freshwater forma.
tion, of several kinds of lymnei, helices, and planorbes, and from
the perfect state of preservation in which they are found, must
evidently have lived in the very spots where they now are, the
shells of these animals being so friable that they could not have

Mr. WeBsTER on the Strata lying over the Chalk. 227

admitted of removal from their original situations without being
broken.

These organic remains therefore most distinctly mark the nature
of the place where the strata enveloping them have been deposited.
It must unquestionably have been the bosom of an extensive lake
in some period of the earth far antecedent to human history ; nor
can we refrain from emotions of extreme astonishment when this
conviction is forced upon us, nor help indulging in speculations
on the revolutions which the earth must have undergone, when
we consider how very differently these strata are now situated.
Instead of being found in a hollow, they now compose the upper
part of a hill; nor are they any more surrounded by those eleva-
tions which must have been essential to the confinement of the
vast body of fresh water which furnished a habitation to myriads
of animated beings, and of which we have nothing to demonstrate
the former existence, except the nature of its depositions, which
remain a faithful record.

Over this bed is a stratum of clay 11 feet in thickness, con-
taining numerous fragments of a small bivalve shell. The hinge
of this shell is of so peculiar a structure that Mr. Parkinson was
not able to refer it to any known genus. ‘The shells are thin, and
unmixed with any other species whatever. It is impossible there-
fore to say whether they have belonged to marine or freshwater
animals, and I have preferred for the present to keep them among
the latter, rather than to suppose another alternation of which
there is no direct proof.

Upon this lies another bed of yellow clay without shells, and
then a stratum of friable calcareous sandstone, also without shells.

To this sandstone succeed other calcareous sirata having a few

freshwater shells. In these, which, like those mentioned above,
2¥F2

228 Mr. WeBsTe_R on the Strata lying over the Chalk.

are not subdivided into distinct beds, are parts of extreme com-
pactness, so as to acquire a porcellanous character. Other parts
contain masses of loose chalky matter, most of which are of a
roundish form ; and among these also are many beds of a cal-
careous matter, extremely dense, and much resembling those
incrustations that have been formed by deposition from water on the
walls of ancient buildings in Italy.

Through all these last strata are veins, frequently several inches
in thickness, of very pure carbonate of lime, which is crystal-
lized, frequently in a radiated form.

This stratum may be seen in many parts of the Isle of Wight,
north of the middle range of chalk hills. On the western coast it
does not extend farther than Totland bay, but occurs again at
Warden point, forming the summit of the cliff.

Numerous blocks of it lie loose in the soil in many parts about
Cowes, Binstead, and Bembridge. But in the neighbourhood of
Calbourne, and between that place and Thorley, several quarries
are opened in it, and afford an excellent stone. The fossil shells
are here larger than I have observed them in any other part, the
planorbes being full two inches in diameter, and the cyclostomz
nearly as large. ‘The rocks at Bembridge ledge and Whitecliff
bay, on the east side of the island, must also be referred to this
formation. 7

It appears therefore to have originally extended over the whole.
of the northern half of the island; but I have not yet been able
to find it on this side of the water, and it is still uncertain whether
it ever existed here, or whether it has disappeared amidst the last
revolutions to which the surface of the earth has been subjected.

This formation may be considered as the latest in this country
which we have as yet been able to detect: and of all those above

Mr. WessTER on the Strata lying over the Chalk. 229

described it agrees most nearly with its corresponding formation in
the Paris basin, with this difference however, that none of ours is
siliceous ; I shall therefore, in the succeeding comparison, confine
myself to the calcareous part.

The external characters of this in both countries are sufficiently
different from every other known rock to render them distinguish-
able even without the shells. That of France is described as white,
or yellowish ; sometimes as tender and friable as chalk or marl,
and sometimes very hard, compact and solid, with a fine grain and
conchoidal fracture. In the latter case it breaks into sharp fragments
like flint, and cannot be worked as stone; sometimes it will even
admit of being polished as marble. It is also frequently filled with
infiltrations of calcareous spar.

This description corresponds very nearly with the freshwater rock
of the Isle of Wight, and an examination of the specimens from both
places leaves no room to doubt of the similarity of the strata.

The fossil shells which I found in the upper freshwater formation,
and which have been described by Mr. Parkinson, are the following.

Names given by Lamarck. Linnean names.
Planorbis, much resembling that which
Brongniart says approaches to
P, cornu
Planorbis, two other species
Planorbis, much resembling P.
prevostinus

Ampullaria - - - - - - - - - Helix
- Helix

- Helix stagnalis

Helix planorbis

Cyclostoma += - - = - - =

Limneus longiscatus - - - = -
= - - - acuminatus

230 Mr. WessTER on the Strata lying over the Chalk.

Limneus corneus
perhaps a large specimen of L.
longiscatus

Gyrogonites

Striated seeds of a flattened oval form, with
parts of coleopterous insects.*

M. Brongniart has enumerated the following fossils as belonging
to this formation.

Cyclostoma elegans antiquum — Limneus inflatus
Potamides Lamarckiit Bulimus pygmeus
Planorbis rotundatus - - terebra

- = cornu Pupa Defrancii i

- - prevostinus Helix lemani
Limneus corneus - Desmarestina

- - fabulum Gyrogonites

- = ventricosus

The last mentioned fossil, to which Lamarck has given the name
of Gyrogonites, is a small globular canellated body about the size
of a mustard seed. ‘The specimens of the French fossils of this
species, in the possession of the Society, are extremely perfect, and
correspond exactly to those which I found. They are very nume-
rous in the freshwater stone at Gurnet point; but they are there

* These were found in some specimens cf clay containing also freshwater shells
which were dug out of a deep well at Newport. But as no distinct account was kept of
the strata passed through, it is not certain to which of the freshwater formations they

belong.

+ It is proper to observe chat the Potamides of Lamarck is a Cerithium. But having
considered the cerithia as marine shells, he thought it proper, on finding a species among
the freshwater shells, to regard this as of a distinct genus; founding the distinction not
on any difference in its form, but on the difference of the water in which it had lived.

Mr. Wesstrr on the Strata lying over the Chalk. 231

only to be seen as casts. In the numerous portions of a thin calca-
reous bed of a highly crystalline structure which lie scattered on the
shore at Cowes, (but which I have not been able to find in situ),
these Gyrogonites are found mixed with cerithia, bivalves, and a
species of serpula ; all these shells being in a whitened state. This
fossil was formerly placed by the French naturalists among the mul-.
tilocular shells, but from a late number of the Journal de Physique,
it appears that recent observations have shown it to be the petrified
seed of a species of chara.

It is singular that the Calcaire d’eau douce of the basins of Paris
and of the Isle of Wight, though found so abundantly in both
countries and constantly used as a building material, should have so
long escaped the observation of naturalists. At the latter place it has
been employed for building from time immemorial, not only in that
island but in many places on this side of the channel, as at Ports-
mouth, Southampton, Lymington, &c.

§ 6. Alluvium.

Under this title may be comprehended all those collections of
various materials, which have been transported at some former
period from different parts of the globe, and deposited on the surface.

The whole of it is evidently composed of the detritus or fragments
of substances which have been originally formed into regular strata,
but which have been torn up and confusedly mixed together by
violent and extraordinary causes, or gradually accumulated by
rivers or meteoric agents. It is therefore, as might be expected,
extremely various, according to the nature of the strata from which it
has been derived.

Considered in this point of view the study of it becomes particu-

232 Mr. WessteR on the Strata lying over the Chalk.

larly interesting, since it enables us to trace back, in some degree,
the great changes which have taken place upon the surface of the
earth.

In that part of our island which we are now considering, this
alluvium or covering is of a nature peculiar to it. Besides the
vegetable earth, clays, marls, and sands, which it possesses in com-
mon with other places, it is distinguished by a vast quantity of
rounded siliceous pebbles of various kinds and sizes, which lie dis-
tributed in a very unequal manner, sometimes forming thick beds
intermingled with clay, sand, and small sharp fragments of flints, at
other places mixed with shells of various kinds, and sometimes
almost without any other substance. This compound is termed
Flint gravel.

When we observe a heap of these pebbles, we easily see that they
consist of a great variety of kinds, and upon attentively examining
them we are able to reduce this variety to several classes.

Some are evidently fragments of the flinty nodules originally be-
longing to the chalk strata. This is evinced by their mineralogical
characters, their sharp conchoidal fracture, peculiar black colour, and
by portions of the white crusts with which they were invested while
in the chalk beds still remaining attached to them.

In others this origin is not so evident, the crusts having been
entirely worn off, and the fragments themselves rounded by attrition.
Yet their fracture, colour, and other circumstances, oblige us to sup-
pose that these also were derived from the chalk. In many places
the whole or the greater part of the gravel consists of these rounded
chalk flints; and hence probably some have been induced to sup-
pose that all the pebbles of the London gravel have proceeded from
the same source.

But besides these other siliceous nodules occur, the origin of

Mr. WessTER on the Strata lying over the Chalk. 233

which is not so evident, as they differ in many respects from the
chalk flints in their usual state. Of these some are of a deep red
colour with a great degree of transparency resembling carnelian :
others are of a yellow calcedony often translucent and even botryoidal,
and they pass into a kind that is yellow, opake, and of a waxy lustre.
Others again appear to be nearly allied to hornstone, and are fre-
quently of irregular shapes, which are probably those of the original
nodules.

Another remarkable class of siliceous pebbles is found either
mixed with all those above mentioned, or alone, or cemented
together into a pudding-stone. ‘These appear to have been origi-
nally formed of concentric coats or layers of different colours,
which vary in almost every specimen. The colours are for the
most part yellow, brown, red, bluish-black, grey, and white: but
these run into each other by an infinite number of shades. Others
are spotted or clouded with different tints, and have much the
appearance of Egyptian pebbles. They take an excellent polish,
and are then often extremely beautiful.

These last appear rather more to resemble agates than chalk
flints. ‘They are never found of a large size, seldom exceeding
two inches in diameter, and generally are not more than one inch:
they are of an oval or flattened form, which appears to have been
their original figure, although they have evidently been subjected
to a certain degree of attrition.

All the above mentioned pebbles are sometimes surrounded by
crusts; and it does not appear clear whether these are not some-
times original, though perhaps stained by the ochreous substances
in which they have been imbedded, or whether they are generally
the effect of decomposition. Flint appears to be one of the most
unchangeable substances with which we are acquainted. We see

VoL. I. 26

234 Mr. WEBSTER on the Strata lying over the Chalk.

buildings constructed with flints that have resisted the agency of
the atmosphere for many centuries without undergoing the smallest
visible alteration, or having become whitened in the least degree. It
is however well known to be liable to decomposition under certain
circumstances ; and it must be allowed that the combined action of
moisture and various decomposing causes whilst a mineral remains
buried in the soil, may produce effects which we can scarcely estimate.

Upon the whole, however, it appears to be extremely improbable,
that any species of imaginable action could have converted a
fragment of chalk flint into a substance so very different as one of
the rounded concentric pebbles of the London gravel.

To assist us in endeavouring to obtain a just-idea with respect
to the origin of the different accumulations which are found in our
gravel, it may be useful to consider the various changes which
have taken place in our upper strata. Of these, although ignorant
of their causes or their extent, we yet perceive the traces written
in characters sufficiently legible.

Although the chalk has been originally formed at the bottom of
the ocean, yet from some change which took place either in the
level of the sea, or in the state of the strata, part of it probably ai
an early period has been above, and part below, the surface of the
water, as at present; and this before the deposition of those strata
which we now see immediately superimposed upon it.

From that date, and by the same cause as we see still producing
this effect, did probably the formation of rounded flint pebbles
begin. The chalk itself, being easily acted upon by the waves,
became disintegrated, while the siliceous nodules were better able
to resist this abrasion, though yet liable to be broken and rounded
by friction against each other.

This effect takes place chiefly upon the margin of the sea. In

Mr. Wester on the Strata lying over the Chalk. 235

deep water it may in some degree be produced by the action of
the tides; but it is by the irresistible force of the billows and
breakers that it proceeds with the utmost rapidity. Hence all
geologists, in examining the history of the strata, have considered
rounded pebbles as proofs of the existence of land elevated above
the water.

At this remote period of the earth, when the outline of the
coasts were, as now, deeply indented by gulphs and bays, but
_ whose forms and situations had but little if any correspondence
with the present, great changes must have taken place by the
gradual action of the sea; and vast accumulations of pebbles of
different materials, formed by attrition, would be thrown upon
the shores.

In the ancient Parisian gulph this phenomenon is distinctly pointed
out; nor are similar appearances wanting to demonstrate the action
of the same causes in the Isle of Wight and London basins.

“We have seen that in Alum bay there are layers of rounded
pebbles in the vertical sand strata, which must have been formed
prior to the subversion of the chalk, and before the deposition of
the London clay. Similar rounded flints, and often of a whitened
appearance, are found in the sand strata at the bottom of the blue
clay in various parts of the London basin.

Ail these belong to the most ancient flint pebbles, formed by the
same sea that deposited our blue clay and the calcaire grossier of
France.

The thick bank of flint pebbles at Woolwich and Blackheath,
separated from the chalk only by sand, appears like the section of
an ancient beach, it being not far distant from the shores of the
ancient marine gulph or bay which now forms the London basin.
The fossil shells which we see in such numbers among these peb-

262

236 Mr. WEBSTER on the Strata lying over the Chalk.

bles are almost all partly broken, and lie exactly in that confusion
in which they appear when thrown up by the sea upon the shore.
Water-worn pebbles are mentioned as occurring in the lower beds
of the French calcaire grossier, and a number of other examples
might be adduced; but these are sufficient to shew the contem-
poraneous agency of similar causes in different places. Prodigious
banks of such pebbles are thrown up on our shores at the present
time, and may serve very well to explain the origin of these
ancient formations of flint gravel.

But with respect to the concentric pebbles above described,
conceiving it to be improbable that they have been derived from
chalk flints, I am compelled to look for their origin to some other
source.

Considering them, as well as all the other bodies composing the
alluvium, as detritus or ruin, a circumstance sufficiently shewn by
the confused manner in which they lie, and by the water-worn
appearance of a great part of them, it is unnecessary for us to
confine ourselves to the chalk in seeking for the beds to which they
originally belonged.

Siliceous nodules are frequent in other limestone strata; an
excellent instance of which may be seen at Tillywhim quarry in
the Isle of Purbeck. Trap also, as is well known, forms the matrix
from which many agates are derived. Various silices, such as the
carnelian, onyx and agate, invested with the usual crusts, are
described by De Luc as being spread over the hills near a part of
the course of the Rhine, while there are not in Europe any known
natural strata that contain these stones.

One of the most remarkable circumstances in which the basin
of the Isle of Wight differs from that of Paris, is the absence in the
former of those siliceous formations so abundant in the latter.

Mr. WEBSTER on the Strata lying over the Chalk. 237

The siliceous limestone, which contains also a burr-stone, covers
half the bottom of the Paris basin. In the middle and upper beds
of the calcaire grossier they have hornstone, and the nectic and
lenticular quartz. The singular substance, called silex menilites, is
well known to all mineralogists: it is found in the foliated
argillaceous marls of the gypsums. In these marls they have also
siliceous nodules, which are white, opake, flat, and mammillated,
and also beds of flint. Stilicified trunks of trees are also described.
The meuliere without shells, above the upper marine formation,
passes often into the state of flint, sometimes white and opake,
and sometimes grey and translucent.

In their upper freshwater formation, a siliceous part containing
the same shells as the calcareous is very abundant. The description
of the several varieties of flints in these beds is as follows.

1. Flint, of a grey colour, translucent, fracture close and waxy,
and even horny.

2. Flint, yellow, very translucent, very easy to break, fracture
conchoidal and smooth.

3. A jasper flint of an opake whiteness like wax, fracture
waxy and scaly, possessing little frangibility.

4. An opake jasper flint, a little cellular, and having all the
characters of a compact burr-stone.

Such is the imperfection of language, that a correspondence
merely in the general description of two mineral substances, is not
sufficient to enable us to ascertain their identity. It must be allowed
however, that most of the characters above enumerated will apply
very accurately to many of the flints which I have described as
composing the greatest part of some heaps of our gravel. I have
also found among these many water-worn fragments of a siliceous
stone that bears a considerable resemblance to the French meuliere
or burr-stone,

238 Mr. WeBsTER on the Strata lying over the Chalk.

If therefore we admit that the pebbles of our gravel are derived
from the destruction of former strata, that many of them differ from
any other siliceous bodies with which we are acquainted, and that
these bear perhaps a stronger resemblance to the flints of the Paris
beds than to those of the chalk (judging from some specimens
of French flints in the Museum of the Geological Society), and if
we have reason to believe that some of those beds formerly existed
in this country, will it be considered as a conjecture rash and un-
warranted, should I imagine that the substances in question have
derived their origin from siliceous nodules, originally formed in
strata which existed over our blue clay, but which have been dis-
integrated, and carried off, in one of those revolutions to which
this part of the earth has been subjected ?*

The formation of the nodules of flint in chalk has frequently,
and will probably much longer continue to excite the speculations
of philosophers. But whatever was the mode in which they origi-
nated, we may fairly imagine that these siliceous masses in question
now found in our gravel, (but which I have supposed to have
belonged originally to regular strata) were formed in a similar
manner.

The coats of the flints in chalk have been found by chemical
analysis to consist of chalk mixed with the flint ; and it appears that
all nodules formed in a matrix have crusts or coats, composed of a
combination between the matter of the nodule and the enveloping
substance.

The coats of these pebbles may be supposed therefore to exhibit
a similar phenomenon; and in them we may perhaps see a part of
the stratum which they were at first imbedded in.

* The Egyptian pebbles are said to occur in a similar situation.

Mr. WesBsTER on the Strata lying over the Chalk. 239

If it be asked what has become of the supposed matrix in which
these flints were formed, and how could strata so considerable as
they must have been, have disappeared without leaving a single
trace of their existence? It may be answered, that the difficulty is
exactly the same in supposing them to be derived from the chalk ;
for no remains of this rock are to be found with these pebbles ; and
it is’ equally impossible to discover what has become of the chalk
that must have belonged to the flint pebbles that are undoubtedly
derived from it.

But when we see rolled pieces of granite, of quartz, and other pri-
mitive rocks, occurring frequently in the alluvium of this part of
the country, though so far removed from the places where these
substances are in situ, we feel so assured of the extensive nature
and violent action of the cause that has occasioned such destruction,
that we need not wonder if many strata have been reduced to a
state of impalpable division, and have been scattered over the surface,
so that not a fragment remains entire; or have been deposited in the
depths of the ocean, where they may have formed new combina-
‘tions that may at some distant period be exposed to view, and afford
matter for the contemplation of future generations. The Herttord-
shire pudding-stone has been already mentioned. It is composed
of these concentric pebbles united by a granular quartz, and is
most abundant in the neighbourhood of St. Alban’s, but is found
in many other places above the chalk. It occurs in large irregular
masses in the gravel; but I am not aware that it exists any where
in an extensive bed in situ.

_ To account for the appearance of this pudding-stone we have
to suppose, Ist, the existence of a stratum superior to the chalk,
containing under some form, the substance of which these pebbles
are composed, 2d, the agency of some power capable of breaking

240 Mr. WussTeER on the Strata lying over the Chalk.

up this stratum, of reducing it to fragments, and of disintegrating
it, by removing the matrix containing the siliceous matter. And
3d. the deposition, either partial or general, of a solution of
siliceous earth capable of cementing the whole together into one
mass.

This formation is no doubt of ancient date, and long anterior to
that of the present surface of the earth; a circumstance which is
rendered probable by our finding masses of this pudding-stone
itself water-worn, indicating, that since its cementation it has been
subjected to some of these revolutionary processes, of which we
have seen so many other proofs.

That all the ancient pebbles were not cemented together in a
similar manner, is shewn by those in Alum bay, which are in
loose sand; and by those which are found in the beds of sand in
the blue clay, both in the neighbourhood of London and at Ports-
mouth.

But that some of the gravel may have been at a former period
in the state of pudding-stone, and may have been disintegrated, is
a circumstance also highly probable. Yet there does not appear
any necessity for supposing that all our gravel has been originally
pudding-stone, any more than that all sand has been sand-stone.

Another species of pebble which is very common, is a striped
flint, or rather a kind of hornstone. These appear never to have had
crusts, but owe their rounded forms entirely to the action of water.
They may be supposed to have been derived from a bed of such a
substance, which has been reduced to fragments. Beds of a striped
chert very analogous to this I have seen in the island of Portland,
alternating with the oolite.

Turf, so abundant in the north of France, is much less frequently
seen in this part of England. The practice of draining, and the

Mr. Wessrer on the Strata lying over the Chalk. 241

great attention paid to agriculture in our country, have much di-
minished the quantity of morasses and ancient depositions of this
kind; and the great superiority of coal as a fuel, and which gives us
a natural advantage over other nations, has rendered turf of little
value,

In Lincolnshire however the quantity of marsh land is prodigious;
and the well known and accurately described submarine forest, yet
to be seen in that county, has already excited the attention of some
of our naturalists.

The subject of the Fossil organic remains, found in the gravel, has
been already so ably treated by a naturalist eminently qualified to
do it justice, that I should have left the subject in better hands, did
it not form so essential a part of an account of our upper strata, that
to have omitted it entirely would have rendered some of the follow-.
ing observations less intelligible.

From the view which I have taken of the subject, it will be seen
that I consider the fossil shells found in the gravel, as well as the
gravel itself, as exhibiting proofs of the detritus or ruin of ancient
strata. Hence specimens of all those fossils which belonged to the
strata over the chalk may be expected to be found in it.

I am aware that the perfect state in which many of these fossil
shells yet remain, has been considered as a proof that they have
never suffered a removal, but that they have lived and died upon
the spots where they now are.

That this is the case with some of the upper beds containing fossil
shells, as the thin clay strata of Woolwich, Plumstead, &c. and per-
haps of other places with which I am not acquainted, there can be
no doubt. But the same argument will not apply to such as are
surrounded by, and enveloped in, beds of water-worn pebbles and
sand, which is evidently a confused mass, the consequence of ancient

Wool, TI. 24H

242 Mr. WEBSTER on the Strata lying over the Chalk.

and violent changes, or the action of causes similar to what we per-
ceive at the present day.

And if we reflect upon the manner in which the most delicate
recent shells are buried when thrown upon the shore, in the sand
and shingles of a beach, without being much mutilated, we shali not
find it difficult to comprehend how very perfect specimens may
sometimes be met with even in our gravel.

By attending to the revolutions that have happened to these upper
strata, this subject will perhaps be less difficult to understand. Beds
of gravel and sand containing fossil shells will be esteemed as the
monuments of ancient changes though of different periods. But
those shells grouped in families and contained in beds of foliated
clay and marl, may be considered as still remaining in their original
situations.

By this distinction we shall be able to separate real alluvial fossils,
or such as have been washed out of regular strata from those that
have never been disturbed ; and the various states of violent con-
vulsion, as well as of quiescence, which the ocean must have ex-
perienced during the several eras, the geological history of which
we have been considering, are sufficient to account for these ap-
pearances.

In a work lately published by an eminent fossilist, I have met
with an opinion, that all the spoils of terrestrial and submarine pro-
ductions which we find buried in the strata in this country over the
chalk, have been transported from distant climates, and have been
deposited in a tumultuous manner by some great convulsion that
blended them in one common grave. I should not have thought it
necessary to allude to this idea, if I had not understood that it has
been considered by some as demonstrating that all the strata over
our chalk are alluvial.

ww

Mr. WEBSTER ox the Strata lying over the Chalk. 943

The grounds upon which this supposition is made, is the obser-
vation that the recent analogues of most of these fossils are now in-
habitants of the torrid zone. The extreme delicacy however of
most of these shells, as well as their perfect preservation (as Mr.
Parkinson has already observed,) precludes entirely the possibility of
their having been brought from distant places, and they serve merely
to shew that this part of the globe must be very different, relatively
to such species of animals, from what it was at the period of. their
entombment.

In some beds of pebbles and gravel fossil shells are very numerous,
as in those of Woolwich, Harwich, &c. and with these alternate fre-
quently beds of clay and sand, containing shells regularly distributed,
entire, and apparently undisturbed. Of these shells Mr. Parkinson
observes, some belong to species now only found in distant seas, and
others appear “ not to differ specifically, as far as their altered state
“ will allow of determining, from the recent shells of the neigh-
“ houring sea.”

But granting, as we must, that the formation of pebbles has taken
place at different periods, it must be extremely difficult, and per-
haps impossible in all cases, to distinguish whether they are now to
be seen in the places where they were at first deposited, or whether
they may not have repeatedly been moved.

In many beds of gravel delicate shells are so abundant that the
cause which placed them there could not have been very violent ;.
whilst others are found totally destitute of organic remains, except
such as are impressed upon the substance of the pebbles themselves.
Among the latter may be enumerated, pectines, anomie, the inte-
rior casts of echini, and impressions of the spines and plates ; zoo-
phytes of unknown genera, some resembling alcyonia, are also fre-
quent. It does not appear certain whether all these may not have

ZH 2

244 Mr, WepstTER on the Strata lying over the Chalk.

belonged to the chalk strata, but Mr. Parkinson is of opinion that:
some differences are observable between these echini and those
of the chalk, M. Desmarets has described in the lower gypsums
of Montmartre fossils similar to those of Grignion, many of which
are echini of the genus spatangus, but different from the spatangus
cor anguinum found in the chalk. At Grignion too, there are
echini which belong to the genus clypeastra.

Impressions of organic remains very rarely occur in the concentric
pebbles, particularly those of the Hertfordshire pudding-stone ; *
but the yellow calcedonic flints frequently contain alcyonia.

The Fossil-bones of quadrupeds are frequently found in the allu-
vium of this part of England, and they appear to be of several dates.

The most ancient are entirely petrified, and where found in the
gravel, appear to have been washed out of the strata in which they
were originally imbedded, which, from the part of the matrix still
adhering to them, appears to have been calcareous. Mr. Parkinson
has described some of those found at Walton and Harwich, which
however were too much broken to enable him to ascertain distinctly
the animal to which they belonged, but he conjectures them to
be parts of the Mastodon of Cuvier.

The next class contains the bones of the elephant, rhinoceros,
hippopotamus, and the Irish elk, which are no longer natives of this
climate. ‘These however are not petrified, and though generally in
a state of decay yet are sometimes quite perfect. They are particu-
larly abundant in Suffolk and Norfolk ; but have also been found at
Brentford, in the Isle of Sheppey, and several other places. And it
is particularly important to remark that these are never found iz the

* A very fine example of one occurs in a specimen in the museum of the Geological
Sgciety, presented by Leonard Horner, Esq, It is a small bivalve resembling a pecten.

Mr. WEBSTER on the Strata lying over the Chalk, 245

stratum of London clay, but always ufo it, and frequently accom~-
panied by marl and freshwater shells.

Other bones of ruminating animals, as those of the horse, ox,
and stag, not different from the living species, are frequently dug
up at small depths, and are covered by peat, gravel, loam, &c.

In the freshwater formations of the basin of Paris the bones of
terrestrial animals are found, which do not belong even to known
genera, and many of those found near the surface in their alluvium,
belonged also to animals of great size, and which are now found
only in countries very remote.

We see therefore that a similar succession of animals has lived ia
this portion of the earth, during the various stages of its habitable

state.

V. Concluding Observations.

One of the most interesting consequences deducible from the
above examination of the last formed strata of this country, is,
perhaps, the view which it seems to afford us, of establishing, in
some degree, a series of epochs between the deposition of the chalk
strata and the formation of the present surface of the land; not
indeed to be distinguished by computable time, since no date can be
affixed to any of the changes to which I have alluded, but an order
of succession of the great events at least appears more than hypo~
thetical, which it may be useful still further to consider.

The origin of the calcareous matter of which the chalk formation
is composed remains one of those hidden mysteries on which all the
speculations of geologists have not thrown any certain light.

In the several strata of chalk however, although their sources were
probably not very different, we may perceive several circumstances
which indicate the action of modifying causes in each deposition,

246 Mr. WesBsTER ow the Strata lying over the Chalk.

that seem to have had considerable influence upon organic life.
The almost entire absence in the lower beds of those siliceous
nodules that are so numerous in the upper one, and the remarkable
differences in their animal remains, furnish sufficient reasons for this
supposition.

Calcareous, argillaceous and siliceous matter, the whole or a part
of which was in a state of solution, originally formed the mass of
this formation. Of these the argillaceous seems to have subsided
first, but more or less mixed with calcareous earth. The silex now
occupies the upper division, but whether separated by the action of
chemical affinities, or introduced subsequently, does not yet appear.
The tranquil state of the ocean during this period may be inferred
from the perfect preservation of the numerous delicate fossil organic
bodies now found in the chalk,

An era of turbulence seems to have succeeded; during which
however the depositions of the plastic clay and sand denote certain
intervals of repose. The surface of the chalk already solidified was
in a certain degree, though irregularly, subjected to the agency of
water in motion; and other causes might have combined in
destroying the original horizontality of its position. But where the
vast bed of London clay subsided, the sea must have regained its
former tranquility.

The numerous vestiges of vegetables as well as of animals to be
found in this stratum, whose recent analogues are now seen only
in tropical countries, involuntarily leads the mind to contemplate
with wonder the altered condition of this portion of the globe.
Have the laws which regulate the place and motions of this earth
in the system of the universe been subjected to change ?- Are there
in these any sources of irregularity or gradual alteration, the proofs
of which can be detected? these are questions for astronomers.

Mr, WessTer on the Strata lying over the Chalk. 247

If we consider that the flinty chalk is somewhat above the level
of the sea at Woolwich and Gravesend ; that it dips under the Isle
of Sheppey and disappears; that at Margate it has been so elevated
that a considerable part of the lower chalk is now seen, the whole
of the upper or flinty chalk being gone; that at Dover it rises to a
vast height; that on the north side of the Thames it appears at
Purfleet opposite to Gravesend, but immediately disappears to rise
no more on the coasts of Essex and Suffolk.—If we reflect on the
rapid dip of the chalk at the Hog’s back, between Guildford and
Farnham, with the many hills and hummocks of chalk to be seen in
the counties of Suffolk, Norfolk, &c. we may perceive evident
proofs of the great irregularity of the ancient surface of this stratum,
and a part of the elements which may enable us to trace the
limits of the land and sea at that period,

In speaking of the formation of the gravel, the probable mode
has been detailed, by which the mountains of chalk originally,
appearing above the sea may have been worn away, cliffs have been
formed, and the flints broken and rounded into pebbles. Of the
early existence of this process, we have seen proofs in the vertical
bed of pebbles of Alum bay, and in those frequently found in the
sand of the plastic and blue clay in many other places. And also
in the lower beds of the calcaire grossier of the basin of Paris.

We have seen also that the extraordinary event of the elevation
or subsidence of the chalk of the Isle of Wight and Dorsetshire
must have taken place after the deposition of the great stratum of
blue clay.

A change of this kind, of which we have no parallel in human
record, it would be in vain to endeavour to account for; but it
must have been an event of itself sufficient to produce great changes
in this part of the globe, and must have been accompanied by the most

248 Mr. Wester on the Strata lying over the Chalk,

extraordinary phenomena. From the correspondence in the situa-
tion of the chalk and the accompanying strata in the Isle of Wight
and Dorsetshire, it should seem, that the range of chalk hills in
each of these places was at first united; and thus a marine gulph
was formed, open to the east, in which a part of the depositions at
that time going on in the ocean subsided.

The observations of several geologists have shewn the natural
tendency which the sea has to fill up estuaries, and to throw up
bars across their mouths by the accumulation of pebbles and sand,
Many remarkable instances of this process have been observed on
the shores of the Baltic, and even in this country. It appears also
that such gulphs and bays are frequently converted into freshwater
lakes, of which Loo Poole in Cornwall is an excellent example.

As it is most philosophical to seek for the solution of natural
phenomena from known causes, might we not suppose that a similar
circumstance has converted the gulph we have contemplated (now
partly occupied by the Solent) into a lake of fresh water? If the
size of the bar necessary for this purpose should appear extraordi-
nary, we have only to recollect the Chesil bank, which now joins
the Isle of Portland to the main land; and many others of the
same description.

With this subject in my mind, while examining the cliff at
Brighton, which has been already described, I could not resist the
idea that it might possibly be the remains of this ancient inclosure
of the lake. That it exhibits the vestiges of a vast and ancient ac-
cumulation well fitted for this purpose, there can be little doubt; and
it is evident, that it has extended in the necessary direction,
it being now a vertical section of what must have run out far into
the sea.

Whether such a supposition as this can afford a solution of the

Mr. WEBSTER on the Strata lying over the Chalk. 249

phenomenon of strata formed in freshwater appearing over marine
strata, I shall leave to be determined by those who are competent
to such a task. /

Of the unfathomable antiquity of these great and numerous col-
lections of freshwater in the ancient world we have however abund-
ant proofs, in the admirable researches of Cuvier on the extinct
genera of animals which inhabited their borders.

It would perhaps be impossible for us now clearly to ascertain
what could have furnished the prodigious quantity of calcareous,
and still more the siliceous matter which they held completely in
solution; in modern lakes we have examples of strata now forming
of marle arising from the shells of the numerous freshwater animals
which inhabit these shells, but these beds (as far as is yet known) are
not consolidated.

Was a portion of the calcareous part of these ancient strata
derived from the surrounding calcareous hills, which might have
been lofty? If we examine the section of the Isle of Wight, the
probability appears considerable, that the strata of chalk must have
stood at a considerable height above the lake ; although it has sub-
sequently undergone the same levelling process, to which all the
surface of the island has been subjected.

As connected with this subject, I shall quote a passage from
Bergman’s Physical Geography published in Swedish in 1769.

** At Langesaltza in Thuringia, they find under the vegetable
“ earth a calcareous and porous tufa; in other parts a fine white
“ sand mixed with river shells ; below, a bed of hard stone, under
“‘ which is a bank of porous stone or sand. Lower stiil they find
** a bed of hard stone, then tender stone and sand; afterwards peat
“* formed of a mixture of leaves, barks of wood, roots, river shells,

“* &c. Lower, yellow sand; and finally, grey fullers’ earth mixed
Vol. 11. 25

250 Mr. WEBSTER on the Strata lying over the Chalk.

“* with marine bodies. The thickness of the beds of stone varies
“ from 6 to 12 feet. They contain river shells, bones, sculls of ani-
“ mals, kernels of fruits, ears of corn, &c. These strata extend
* quite under the city to the borders of the Unstrutt, near to which
“ are seen strata of alabaster and limestone, the detritus of which
** has probably given origin to these beds. It is to be remarked
“¢ that no remains of marine animals are found above the clay where
“‘ the ancient beds commence.” .

A very interesting account has been given by Von Buch of a
freshwater formation in Locle in the district of Jura. It is con-
tained in 4 high inclosed valley surrounded by mountains of white
compact limestone; and consists of various alternating beds of
marly limestone whitish and somewhat friable, bituminous shale,
coal, hornstone of a smoke grey colour, and of a fine splintery or
imperfectly conchoidal fracture, and containing crystals of quartz ;
also of opal of a brownish black colour, glistening lustre, and perfect
conchoidal fracture. Both the limestone and hornstone contain fresh-
water shells, among which may be distinguished the helix cornea
and bivalves.

From these and other accounts it appears probable that these
freshwater formations were purely local, and there appears no
necessity for supposing that the others were any thing more than
local deposits in a former state of the earth.

I am aware that such formations have lately been traced on the
shores of the Baltic, in the south of France, Spain, Germany, and
Silesia ; but this can only prove that fresh water lakes were in for-
mer times as at present very numerous and often extensive.

One of the most striking differences between these ancient lakes
and modern ones, as has been remarked by Messrs. Cuvier and
Brongniart, is the property possessed by the former of forming
siliceous strata.

Mr. WEBSTER oa the Strata lying over the Chalk. 951

It would seem to have been a circumstance accompanying the last
great revolution which the earth has undergone, that siliceous earth
has been held less abundantly in solution since that period. That
event appears to have been accompanied by a process of destruction
merely ; but former changes were alternately destructive and reno-
vating or conservative. The animal and vegetable remains of the
ancient world are frequently impregnated with siliceous matter.
But I believe no well authenticated instances can be adduced of such
a process going on in our times. Petrifaction, indeed, in the proper
sense of the word, seems now to have entirely ceased.

In the strata over the chalk in France silicified organic “bodies are
abundant: in our upper strata they are rare, if we except those
found in the gravel whose original situation is yet questionable.
Indeed the only instance with which I am acquainted in this country
in the strata over the chalk, are the siliceous fossils of Feversham
already mentioned : some of these are entirely calcedonic.

‘The existence of the marine strata placed above the lower fresh-
water formation in this country, as well as in France, is a circum-
stance much more difficult to explain, and would seem to require
either a rising of the sea or a sinking of the land in this part of the
globe.

Alterations in the shape of the coasts, and the accumulation of
sand and pebbles in various parts of the sea, affect the tides so
considerably, as to occasion them to rise to very different heights at
the same places at different periods ; yet no change of this kind can
be imagined sufficiently great to account for an effect so considerable
as has been produced.

Instances of marine strata placed over those formed in fresh water
have been observed not only here and in the basin of Paris, but in
other places. One is mentioned by Professor Herman, of Strasburgh.

212

252 Mr. WeBsTeER on the Strata lying over the Chalk.

The strata are situated in the department of the lower Rhine, in the
mountains of St. Sebastian, one of the lowest in the chain of the Vosges.

The great quantities of white calcareous marl with freshwater
shells, so frequently found on the top of the London clay, and en-
veloping the bones of land animals, would seem to denote a marshy
country, and one containing a great deal of stagnant water. This
seems to have been the first state of the country at the time of the
emerging of the land after the deposition of the blue clay.

In this marl and over the clay is the first appearance of land
quadrupeds, agreeing in this respect with the same observation made
by Cuvier on the calcaire grossier, above which in France their
remains are found in abundance.

The changes preceding or accompanying the upper marine for-
mation perhaps destroyed part of the superior strata, and deposited
many of those extensive beds of shells now to be found over the
London clay. But the nature of the last original marine strata of
this country, the revolutions they may have undergone even in the
ancient state of the earth, are circumstances which can probably no
longer be explained.

Whether the existence of the second freshwater formation in the
Isle of Wight will admit of the same solution as has been proposed
for the first, must be left, like it, undecided: but it appears to have
taken place in a lake possessing the utmost tranquility.

Upon the whole it must be allowed that the points of resem-
blance which have been enumerated between the superior strata of
this part of our island and the adjoining part of the continent, are
too numerous and striking to be the result of accidental causes, and
demonstrate in the clearest manner that they were occasionally sub-
jected to the same general laws. Whilst at the same time the
variations are so considerable, that the effects of these causes appear
to have been much modified by local circumstances.

Mr. WEBSTER on the Strata lying over the Chalk. 253

But I shall now venture with less hesitation to draw an important
conclusion from the section of the Isle of Wight, which has been
already described, and which of itself forms a volume in which we
may read the geological history of several of the latest revolutions
which our earth has experienced.

The idea I allude to is, that the last freshwater formation, as
well as all the other strata which we have been considering, is
anterior to the great event which gave the last shape and surface to
our land.

In the highly inclined and vertical positions of the strata of
Alum bay, we see the effects of some great convulsion of nature,
previous to the formation of the last strata.

In the horizontal deposits of the North side, we see strata of
great extent and antiquity yet formed at a later period. But in the
outline exhibited by the surface of the island, and which has no
reference whatever to that of the strata, is plainly to be perceived
the effect of a general and powerful agent, which. has subsequently
formed the whole of the contour by one bold and sweeping outline.

It may be interesting to see how the same result can be obtained
by a careful survey of different portions of the globe.

Messrs. Cuvier and Brongniart have laid considerable stress on
the observation, that the outline of the present surface has no re-
semblance whatever to the undulations of the strata derived from
the irregularity of the bottom of the basin. But how much. more
striking is this in the Isle of Wight? By no ingenuity of reasoning
can the present form of its surface be derived from the bottom of
that ocean which deposited the chalk; nor would it be produced
by any of the causes now acting; and nothing remains for us but
to admit that it has been the effect of an extraordinary and an ex-
tensively aeting cause.

254 Mr. WessTER on the Strata lying over the Chalk.

In the smooth and undulating surface of the chalk hills, in the
banks of gravel of great extent, in the deep hollows often filled
up again by the detritus of regular strata, in the direction of the
principal ridges and valleys, we cannot but recognize the effect of
water, the only agent which we know to be capable of producing
such appearances.

But under what influence has this power, fully equal to such a
purpose, been directed? What could give sufficient energy to a
body at other times so tranquil? These are questions of which the
complete solution will perhaps ever remain in obscurity.

Yet already we have had sufficient proofs that the sea has not
always maintained the same relative level; that it has alternately
risen and fallen ; although to ascertain the distance of time between
these changes be absolutely beyond the reach of human sagacity.

Let us then imagine an ocean in a violent state of agitation. The
hills of chalk, and the last depositions of the globe are torn to
pieces; the flints are dispersed and rounded by attrition against
each other; finally, currents carry them to great distances, and
lodge them in hollows worn by the waters, or form them into
ridges and other accumulations. Fragments of other rocks are in-
termixed ; forests are torn up and levelled, and, with the vegetable
soil, formed into morasses. The inhabitants of the land are de-
stroyed and buried deep in this dreadful ruin. But a more sur-
prizing revolution ensues. Disorder ends; the waters retire; the
northern continents are disclosed, become fitted for vegetation, and
are peopled by the tribes of animals which now inhabit them.

VIII. Remarks on the Vitrified Forts of Scotland.

By J. Mac Curtocn, M.D. F.L.S. Chemist to the Ordnance, and Lecturer
on Chemistry at the Royal Military Academy at Woolwich.
V. Pr. Geol. Soc.

‘Vue contest about the vitrified forts of Scotland having for
some time ceased from an apparent want of new matter, it may be
deemed superfluous to revive it by the description of any more
of these extraordinary structures. But some appearances which
seemed to have been overlooked having occurred to me in ex-
amining these works, I thought it might yet be interesting to those
who took a part in the former discussion, to receive any additional
remarks which might assist in clearing up the points in dispute.

As far as archzology is concerned in the question, I deem it
useless to enquire to what era they are to be referred. That they
belong to a people who had not learned the Roman arts is probable,
since they contain no calcareous cement. But that this is a certain
conclusion I am not inclined to admit, as the knowledge of a simple
fact among a savage people does not necessarily imply the power to
direct it to use. The ability to detect calcareous stones, the means
of quarrying them in certain situations, and the power of trans-
porting them from great distances to places where they do not
naturally exist, must have been possessed by these people before
they could have directed to any useful purpose this naked truth de-
rived from their conquerors. ‘To instance only those vitrified forts
which are found in Galloway. There is no limestone to be pro-

256 Dr. Mac Cuttrocs on the Vitrified Forts of Scotland.

cured in that country but by a very distant land carriage, or a very
circuitous route by sea. It is evident that a commercial system of
some sort must have been established before the inhabitants of these
countries could have cemented their buildings with lime, however
they might have been acquainted with its properties. It is equally
a matter beyond the power of modern investigation to discover
whether they were the works of the aboriginal Caledonians or of
their Danish invaders. Neither analogy nor examination of the
remains throws the least light on the subject, a subject which as it
is beyond the reach of historical or traditional evidence, seems
equally divested of all those circumstances from which truth is
sometimes elicited. It is nevertheless a general opinion that they
are remains of the earliest works of ancient inhabitants. This too
is a proposition which appears to rest on a very vague sort of rea-
soning. The same Antiquaries suppose that the well known circular
Pictish towers were built before the use of iron, but admit that they
are of more modern date than the vitrified forts, from the greater
artifice apparent in them. It will however be clear to any one who
shall examine the vitrified fort near Amwoth in Galloway, that the
ditch which has been excavated for the purpose of giving the fort
a scarp all round, has been cut down by iron, or at least by a tool of
metal. It is from the greater accumulation of soil on the ruins of
-the vitrified walls, an accumulation often sufficient to conceal them
entirely from the view, that we are (if from any thing) entitled to
consider them as erections of a date more ancient than the towers
of Glen Elg or Dun Dornadilla, or than any of the works as yet
examined in which unvitrified inasonry has been used. But it is
superfluous to pursue these archzological difficulties further.

The question on which the two contending parties have been
most at issue, was, whether the vitrification was the result of design

Dr. Mac Cuttocn on the Vitrified Forts of Seotland. 257

or accident. While one party asserted that a regular process had
-been carried on for the purpose of making a solid wall, the other
supposed that these walls might have been originally constructed of
stone and wood united, and that accidental fire, or the attack of
an enemy, had destroyed the compound structure, producing in
consequence the vitrification now to be traced in them. Mr.
Williams and Mr. Fraser Tytler are the most conspicuous leaders
on each side,

It seemed to me that light might be thrown on the question, by
examining with mineralogical accuracy the. substances of which
these structures were composed, and noting the changes which
each had undergone from the operation of the fire, and also by
observing whence the stones had been derived which were used in
them; and that the question of accident or design might be illus-
trated by examining in the laboratory the degree of heat necessary
to produce the requisite appearances in the stones which actually
exist in these structures.

_ In the present more diffused state of mineralogical and geological
knowledge, it is unnecessary to refute the notion of their volcanic
origin in a paper addressed to a Society like this. For the pur-
pose of the ordinary spectator, that refutation may be trusted to
the increasing progress of natural knowledge.

The hill of Dun Mac Sniochain, which lies in the plain, now
supposed by some to be the site of the ancient Beregonium, has
been long noticed as the seat of one of these extinguished volcanoes.
Having seen specimens of pumice and lava (as they were called)
collected from it, I was glad to have an opportunity of investigating
a very accessible specimen of what I concluded to be a vitrified fort.
Such it proved.

The drawing, pl. 2. fig. 1, which accompanies this paper, contains

VOL, Il. 2k :

258 Dr. Mac Curtocn on the Vitrified Forts of Scotland.

a ground plan of the work, as well as I could determine it by pacing,
and without tools to clear away the sod. Those who have seen simi-
lar works know how completely they are sometimes covered with
the soil ; a circumstance which, as I have just noticed, perhaps more
decidedly than any other, marks their high antiquity. Imperfect
however as their traces generally are, the drawing will serve to
show a very peculiar form in that which is the subject of the
present paper, and a plan differing much from the uniformity of
structure and rudeness of design which have been supposed to dis-
tinguish these works.

The long narrow hill on which it stands is nearly precipitous
along three quarters of its circumference; at the other end it rises
from the plain with a very accessible acclivity. By inspecting the
plan, it will be seen that a series of parallelogramic works have
been constructed so as nearly to cover the principal and precipitous
part of it to the very edge. ‘The greater portion of the hill being
thus occupied by two of these works, the strongest part was cut off
by a wall from the more accessible end, thus forming a sort
of citadel or place of retreat at the last extremity, a practice very
common in the ancient peninsular fortifications of Cornwall, in
Castle Trereen for example, and in a similar castle at Zenor. To
occupy and defend the vulnerable side of this position, the outer
work appears to have been placed without the principal area, that
from it the enemy might be seen and opposed in every part of his
ascent. This disposition bears incontrovertible marks of military
design and experience. Were a modern engineer to defend Dun
Mac Sniochain, he could do little more than build a fort to occupy
the ground and contain his men, erecting an out-work to command
the approach.

I have thus particularly detailed the military relations of this

Dr. Mac Curtocn on the Vitrified Forts of Scotland. 259

work, to show that these forts very probably belong to an age of
some talent and improvement, a notion adverse to the suppositions
of those who. have conceived them to be the efforts of the rudest
barbarians. But the ignorance and rudeness attributed to nations
of mere warriors and hunters is falsely assigned.

The history of infant society shows on the contrary instances of
acute reasoning, of ready invention, of perseverance and prowess,
which would be in vain sought among the enlightened populace of
modern times, nay even among those who are far removed above
that rank. But this ability and vigour of mind have been neces-
sarily directed to those objects only, which were useful or honour-
able, or were then in fashion. The abilities of infant nations
require to be compared with their necessities, and to be measured
by their best works, not by their worst.

The whole length of ground enclosed beyond the cross wall
is about 200 yards, and its breadth is about 60. Within this space
are two works, the one containing a perimeter of 153 yards, and
the other one of 110. These, according to the modern military
computation for the defence of a redoubt, are capable of holding
more than 500 men. The perimeter of the external work is 96
yards, a space nearly capable of disposing of a hundred more. We
are unable, from ignorance of their weapons and modes of warfare,
to determine in what way these works were occupied or defended,
but on any supposition it appears that this must have been a mili-
éary fort of some magnitude and consequence.

I have entered into the details of the magnitude, and figure, and
military importance of this work, for the purpose of setting aside
another hypothesis with regard tothe vitrified forts. They have
been supposed by some to be merely beacons, and that the vitrifi-
cation has been the result of the combustion of those heaps of wood

2K2

260 Dr. Mac Cutiocn on the Vitrified Forts of Scotland.

which were used for signals. The supporters of this opinion have
asserted that they always occupy the highest elevation, and that
many of them are so placed as to be visible from each other. This.
is not true. The fort at Amworth is not on the highest ground
it might have occupied, nor is the fort of Dun Mac Sniochain so.
situated: but they are both on the strongest ground. Where the
strongest and highest ground coincide, a case very common in hilly:
countries, (I speak of military strength of ground as connected with
ancient modes of warfare) there, as at Craig Phadric, they naturally
occupy the sumntit. I may add, that no fort has hitherto been dis-
covered between this and Craig Phadric, except that at Dun
Dheairduihl, nor have any been observed in its neighbourhood in
other directions. I might strengthen this argurmfent by referring
to the descriptions of other similar works, but I prefer arguing
from those which I have seen.

It now remains to enquire, if by any examination of the walls.
of Dun Mac Sniochain, light can be thrown on the causes of its
vitrified appearance, and whether it was the result of design or
of accident.

The remains of walls in the other vitrified forts, noticed by dif-
ferent observers, have been so well described, as far as relates to their |
general appearance, that little can be added on this head. It may be
sufficient to say, that they appear in the present work to be about
twelve feet in thickness, and are now nearly buried under the soil.

One circumstance however requires attention, as some false spe-
culations have been founded on it. Both the outside and inside of
the walls near the ground are rendered much thicker than their true
measurement shows, by a heap of loose stones accumulated against
them, and this renders it difficult in the present state of things
to ascertain their real dimensions, It has been supposed that this

Dr. Mac Cutiocu on the Vitrified Forts of Scotland. 261

was done with a view to strengthen the work, or else that it was
an effect of the rude manner in which they were supposed to be
erected. It would have been an extraordinary system of defence
which should have heaped up a pile of loose stones on the outside
of a wall. Modern warfare is satisfied when its ordnance has
produced such an addition to the face of an enemy’s. bastion.
A little attention also to the angle which loose stones assume when
they are at liberty, might have shown that such a system would not
caly have prevented the defenders from approaching their own
walls, but would in fact in small works, such as those of this fort,
have occupied a very considerable portion of the included area.

It is the dilapidation of the unconsolidated parts of the building
which has produced this appearance. The thickness of the walls of
this fort, as nearly as it can be appretiated, is, as I have already stated,
twelve feet. They bear the marks of vitrification throughout their
whole extent, but in some places it is more complete than in others,
In no case does it seem to have extended more than a foot or two from
the foundation, and the most perfect slags are found at the bottom of
the wall. As we proceed upwards, we find a mixture of porous slag
with stones which having been but partially fused have adhered: toge-
ther in a mass. Higher still we meet with stones which though un-
vitrified are roasted by the action of the heat, and at length the marks of
hre diminish until they almost entirely disappear, leaving only a heap
of loose and unconnected stones. The loose part of the wall
having fallen through time, has caused that accumulation, of rubbish
which we find about the vitrified parts. On account of this mixed
construction, we have no means of ascertaining the original height
of these works ; but if a judgment may be formed from the quantity
of loose stones which are found at the base of the walls, it was

262 Dr. Mac Cuttocu on the Vitrified Forts of Scotland.

probably not considerable. Nor indeed would a work which was
intended for defence from within admit of a greater height of wall
than five feet, or that over which a man might look, a height which
is equal to that of the ancient British field works, if this may be
determined from some of the perfect fragments which remain in
Cornwall.

Of one of the most remarkable of these, I have given an account
to the Antiquarian Society. It is the fort known by the name of
Castle an Dinas, in the parish of Ludgvan, in that county. Here
the altitude of the work is determined by the perfect finish of part
of the remaining wall, which consists of well-fitted dry masonry,
the strength and solidity of which show that it was not a temporary
enclosure, but a sort of citadel, or work of permanent defence.
The wall is here only five feet high, and from this I am inclined to
conjecture that the vitrified forts did not exceed this height. Nor
indeed are the accumulated ruins about them sufficient to give rea-
son for suspecting that they ever were of a greater elevation. It is
deserving of remark, that the vitrification of the outer work is not
so complete as that of the inner ones.

Before examining the materials of which the wall is composed,
it is necessary to mention the mineralogical nature of the rock on
which it stands, and that of the immediate vicinity. The hill of
Dun Mac Sniochain is formed of limestone, lying in schistus, similar
to that which constitutes the neighbouring island of Lismore. The
schistus and the limestone alternate, but the latter is the predominant
rock. The hill itself is perfectly insulated in a great alluvial plain.
To the west this plain is bounded by the mountains of Benediraloch,
which descend abruptly into it, approaching at their nearest point
within half a mile or less of the fort. These mountains are formed

of the old rocks common to this country, granite, gneiss, mica-slate,

Dr. Mac Cutiocu on the Vitrified Forts of Scotland. 263

quartz rock, and porphyry. A long mountain of trap rising at the
borders of Loch Etive, skirts the edges of these hills for a considera-
ble space, terminating on the plain of Connel by a trap breccia, that
pudding-stone well known to tourists as occurring in various places
from Connel to Oban. ‘This breccia, where nearest the fort, is at
least half a mile distant from it. As the geological site of the rock
does not concern the present inquiry, I will limit myself to its mine-
ralogical description.

Tt consists of rounded pebbles of different magnitudes, cemented
by a paste of a mixed white and brown colour. ‘The pebbles are
generally small, and are much more numerous under the size of an
orange than above it. ‘There are very few of considerable magni-
tude. They exhibit for the most part different varieties of trap,
or greenstone, all of which have been rounded previously to
their entanglement. Of these there are purple, red, gray, and
dark blue specimens, varying as much in solidity of texture as
they do in colour, and more or less homogeneous in their appear-
ance. Many of them are of an amygdaloidal structure, containing
imbedded grains of calcareous spar, zeolites, and green earth, and
some are perfectly cavernous and scoriform. Besides these pebbles
of trap, there are rounded pieces of quartz of different colours, white,
gray, and red, cemented in the common ground. In the specimens
which I examined I could not trace any other kind of rock. The
paste by which the whole is cemented is of a peculiar quality. It
is either dark purple, or brown, or mottled, or gray, or a dirty mix-
ture of brown, white, and dull green, It may be scratched with the
knife, has an earthy smell when breathed on, and effervesces with
nitrous acid. Its fracture is not properly granular, but rather of the
small splintery. Before the blow-pipe it is fused into a dark glass.

On a minute examination it appears to consist chiefly of frag-

264 Dr. MAc CuLiocu on the Vitrified Forts of Scotland.

ments of trap cemented by a whitish substance, which proves to be
the hard variety of calcareous spar, mixed with a sand of trap.
This trap sand is generally of a dark purple colour, resembling
many of the imbedded pebbles. Although this sand is the pre-
dominant ingredient in the paste, there are also found in it grains
of quartz, minute zeolites, garnets, crystals of calcareous spar, and
here and there prehnite, diallage, and chlorite slate, as far as it is
possible to speak decidedly of objects so very minute. The spar
which cements this sand into a common paste surrounds every
grain so as to form them into a perfect breccia, and enable the
whole to break with the splintery fracture above noticed, instead of
a granular one. Here and there the paste occupies large interstices
which have been formed by the approximation of two convex
surfaces of considerable extent, and from these it may be traced
insinuating itself through all the grains of the mass. It is evident
that the calcareous spar has been introduced while in a state of
fluidity among the sand and gravel, as the larger pieces of paste
may be observed to envelope the grains of trap. Generally there-
fore we may consider the pudding-stone of Lorn as a congcries of
trap sand and trap pebbles, cemented by calcareous spar, a rock
often designated by the improper name of trap tufo. This how-
ever is not the place to enquire into the means by which the mass
was consolidated. ‘That it is a case of an agglutinated rock differing
greatly from the ordinary sandstone breccia, or the ferruginous and
argillaceous pudding-stone, is very apparent. It resembles them
indeed only superficially and in its mechanical texture, and it will
be worthy the labour of geologists to direct their attention to the
pudding-stones of this coast with more care than they have
hitherto done. The other rocks are too well known to need any

description.

Dr. Mac Cutrocu on the Vitrified Forts of Scotland. 265

The walls of the fort are found on examination to consist partly
of the old rocks before enumerated, and partly of that which I have
now mentioned. Gneiss, quartz, granite, mica-slate, clay-slate, pud-
ding-stone and pyritical slate are seen entangled together, with a very
small proportion of the particular rock on which the fort itself is
founded. ‘The source whence these rocks were derived is evident,
with the exception of the pyritical slate, which I could not trace in
the neighbourhood.

T have now to enquire what motive could induce the builders of
this work to reject the stone which lay at their feet, and to fetch
from such a distance the large quantities required to raise their walls.
It is particularly remarkable, that although the plain and shore are
covered with fragments, yet these are almost entirely fragments of
the primary rocks. I state this for the purpose of obviating a sup-
position that may be adduced to nullify the argument which Iam about
to derive of a previous intention in the builders to vitrify their work,
from their having neglected to use that rock on which the building
was erected, and which was not adapted for the purposes of vitrifi-
cation. It might otherwise be suggested that they collected the
loose rolled stones of the plain, as being ready broken to their hands.
But besides that the pudding-stone is rare among these fragments,
the pieces of the wall which have not felt the fire are angular and
not rolled stones, showing pretty clearly that they were not collected
on an alluvial plain, but broken from the rocks where they were
formed.

Now, in the walls, the pudding-stone which we shall presently
find to be the only vitrifiable ingredient, predominates to such a de-
gree as to occupy the greater part of it. Hence it appears at least
a probable conclusion, that the builders were acquainted with the
effect of fire in destroying limestone, and that intending to erect a

VOL. Il. 21

266 Dr.Mac Cutrocn on the Vitrified Forts of Scotland.

vitrified wall, they rejected that which was unfit for their purposes,
however conveniently placed. Had the object been to erect a dry
wall of stone and wood the limestone would have equally answered
their intentions. This notion of a design to vitrify seems to receive
additional strength from the apparent solicitude and labour employed
in introducing so much pudding-stone into the work. It is very
likely that accident had taught them the vitrifiable nature of this
ingredient ; a piece of knowledge the more probable, if, as there
seems little reason to doubt, they were acquainted with the art of
making iron, an art which we need not deny to them when it is
known to many of the inhabitants of Africa who are in a very low
state of civilization.

Such are the consequences I would try to deduce from the mine-
ralogical considerations belonging to this question..

It is now proper to examine the changes which the several sub-
stances have undergone, that we may, if possible, form some rational
conjecture on the degree of heat to which they have been subjected,
and on the probable means by which that heat was produced.

Where the quartz has been most exposed to the fire it has become
brittle and easily pulverizable. The granite too is brittle and crumbles
to pieces. The gneiss and mica-slate are also rotten where they have
contained much iron, in consequence of the oxidation of that metal.
Where purer they have remained unchanged, as we might expect
from the well known properties of some of the varieties of mica-slate.
Often where their flat surfaces have been in contact they are agglu-
tinated from the superficial vitrification of the quartz which they
contain when united to the potash produced by the fuel. This is
also the cause of the glazed surface which covers the clay-slate and
which has frequently occasioned numerous small pieces to adhere in

one lump. In many places the mica-slate has been so softened by

Dr. Mac Cuxtrocu on the Vitrified Forts of Scotland, 267

the application of heat as to have bent and conformed itself to the
neighbouring protuberances, undergoing at the same time no great |
change of texture, unless when much impregnated with iron; an
appearance perhaps assisting to confirm that explanation of the con-
tortions of the gneiss beds which attributes this effect to the action
of heat.

Very little change appears in the specimens of common slate which
I have taken from it. If any limestone has found its way into the
wall, it has probably been calcined, and subsequently assisted to
bring into fusion the refractory earths. It is to the pudding-stone
however, that the main part of the vitrification is to be attributed.
Without this it would have been only a mass of burnt rocks, and spe-
cimens of it may be taken from the wall in every state, from that of a
black glass, to a spongy scoria capable of floating in water. ‘There
are also many pieces, which having been exposed to a lower heat,
exhibit a gradual succession of changes, from incipient calcination to
complete fusion. This therefore is the cement of the building ; and
it has been so mixed through the whole, that there is scarcely a part
(I speak of the foundation) which has not been united into a con-
tinuous mass by the fusion of this substance. ‘The last stone of
which the changes are worth noticing, is the pyritical slate. In
general it has become disintegrated in consequence of the sublima-
tion of the sulphur contained in the pyrites. But many specimens
may be taken from the wall, where the pyrites has felt no change,
proving evidently that it has scarcely undergone the action of
heat. In the vitrification therefore of the pudding-stone, and
the integrity of the pyrites, we are furnished with the two extreme
points of temperature under which this work has been raised. How
these are to be reconciled is a new difficulty. It is unnecessary to
examine the highest temperature at which pyrites can maintain its

Z2L2

268 Dr.Mac Cuxinocs on the Vitrified Forts of Scotland.

integrity, as it is known to be low. It is equally useless to ex-
amine into the powers of the granite and quartzy rocks to resist heat,
as they also are well known,

The fusibility of the pudding-stone arises partly from the fusible
nature of the substance which I have described as forming its proper
paste, but in some measure also from that of the amygdaloids
and greenstones imbedded in it, It is in consequence of the
carbonic acid contained in the calcareous crystals which these
amygdaloid pebbles exhibit, that the inflated scoria are produced ; for
it may be easily traced to them through a regular gradation. ‘Fo
pursue this subject experimentally, I thought it necessary to submit
various parts of this rock to the furnace, that I might ascertain the
degree of heat necessary to effect the corresponding changes in
it, and the fragments were accompanied by one of Mr. Wedgwood’s
pyrometer pieces.

The spongy scoria remained unchanged, and the natural amygda-
loid was sometimes unaltered, and sometimes disintegrated by the
calcination of its lime, without undergoing any mark of fusion
in a heat of 20°; a heat at which brass is melted. From 20° to 30°
the amygdaloid underwent no change except a slight vitrification
on the surface; at 40° it was much affected, and was fused into a
glass at 60°.

Having excited the fire to 100° I exposed to it various parts of
the pudding-stone, which had not been affected in the heat at which
the amygdaloid was changed. Some of these were vitrified, and
became precisely similar to many of the specimens taken from the
wall, whilst others continued to resist, for a long time, even this
intense heat; a heat at which many varieties of earthenware are
baked. It is unnessary to relate all the experiments which I per-
formed on the different substances, as it is not my object to state
these matters for the purposes of chemistry. Those which have been

Dr. Mac Cuttocu on the Vitrified Forts of Scotland. 269

adduced are sufficient to prove that some of the fused substances must
have been brought to that condition in a heat not less than 60 degrees
or upwards of Wedgwood’s scale. Such then, at least, is one tem~-
perature at which the walls of this fort have been fused. It may have
been much greater. It is perfectly evident that if a temperature of
60° existed in one part of the wall, pyrites lying near it must have been
decomposed. There could be no such discordancy of temperature
existing simultaneously, and so near, in a mass of this construction.
Fience then it follows, that the wall could not have put on its
present appearance by one heating, if it were all actually built pre-
viously to the application of the heat. This precludes the possibility
of the supposition contained in Mr. Tytler’s hypothesis. Had the
fire, which he supposes the cause of vitrification, been produced by
the burning down of the wooden part of the compound wall which
he has imagined, it could not have happened that a vitrification
requiring a temperature of 60° should have taken place in one part,
while in another such a substance as pyrites remained unchanged.
The great heat requisite to effect the vitrification of the pudding-
stone, is an additional argument against this hypothesis, as it could
not have been produced by any quantity of wood capable of enter-
ing into such a wall, unless the wood had predominated to an
extent incompatible with any idea we can form of its architecture.
It is not indeed easy to conceive a plan capable of producing these
effects, and certainly none more feasible than the suggestion of Mr.
Williams. With him I should rather be inclined to suppose that a
sort of furnace was constructed of a double earthen wall, in which
the materials were placed, with such a quantity of wood as was suf-
ficient to excite a strong heat, and that this operation was repeated
till the wall had gained its wished for elevation. The earthen fur-
nace in which the Africans fuse their ores, scems to countenance

this supposition. The imperfect ustion of the upper parts may be

270 Dr.Mac Cuttocn on the Vitrified Forts of Scotland.

easily conceived to have arisen from a partial neglect of the fire
after the wall had nearly attained its requisite height; nor is there
any reason why it should not have been increased in height by the
addition of cold stones after a firm foundation had been obtained.

One other circumstance in the appearance of the burnt stones is
deserving of notice before quitting this subject. The changes which
the mica slate has undergone, appear to be such as could not have
been produced but by long torrefaction, or by such a repetition of
the heat as I have supposed to be the result of design. The tran-
sient effects which would follow from burning down a wooden
wall, would scarcely have been sensible on stones of so refractory a
nature, which exhibit changes in many instances ’as great as if they
had been exposed for a long time to the heat of an ardent furnace.

Such are the observations to which a consideration of the fort of
Dun Mac Sniochain has given rise.

As this was the only one of these mysterious fabrics which I had
seen when the above remarks suggested themselves to me, I was
afterwards glad to have an opportunity of examining the fort on
Craig Phadric, it being that one on which most labour had been
bestowed, and that which I thought might possibly either confirm
or refute my notions on the subject.

Its general appearance and military structure having been fully
and carefully described, I shall only indulge in a very few remarks
on its physical composition. ,

The hill of Craig Phadric, on which it stands, is one of a numerous
set of pudding-stone rocks, which may be traced from Fyers, and
for aught I know, beyond it. At Fyers they lie above the primary
rocks, which they doubtless separate as usual from the secondary
strata, as they may be seen near Inverness, succeeded by sandstone-
breccia and common sandstone. On the top of the rock there is a
deep deposit of rounded stones, consisting of fragments of the older

Dr. Mac Cuxttocn on the Vitrified Forts of Scotland, 271

rocks. The pudding-stone of Craig Phadric differs completely from
that of Lorn. It contains no fragments of the greenstone amyg-
daloid, there being no greenstone beds in its vicinity, as there are
on the Oban coast. The pebbles which it does contain are of quartz,
gneiss, granite, and the other associated rocks. ‘The paste which
cements them is of a granular texture, entirely and essentially dif
ferent from that of the Lorn pudding-stone, and belonging to a very
different class of substances. It is agglutinated by adhesion, as
the sandstones are, without a.common binding paste; and con-
sists of fragments of the same rocks which form the nodules,
exhibiting generally a gritty mixture of horn-blende, mica, fels-
par and quartz, with a considerable portion of ferruginous fels-
par clay. The difference in the vitrification of the wall arising
from this cause is obvious, since the scoria of Craig Phadric
contain none of that very light and spungy sort capable of floating
in water, and which I have shown to arise from the fusion
of the calcareous amygdaloid. It differs also in these respects, that
it contains no pyritical slate, and that it contains fragments of sand-
stone. The heat has operated on these stones so as to roast and
crack the quartz, granite, gneiss, mica-slate, common slate, and
sandstone, producing appearances similar to those of the specimens
in Dun Mac Sniochain. The gneiss only which contains much
hornblende, and passes into hornblende-slate, is partially fused.
The mica-slate, containing also in some instances layers of horn-
blende, has been split in sunder by the vitrification of these laminz,
and in other cases it is bent and contorted in a very amusing and
instructive manner. But the cementation of the wall is produced
by the vitrification of the paste which forms the pudding-stone. By
this, not only its own pebbles are united, but the neighbouring
stones have been entangled in the general mass.

It is plain that no additional argument to support the notion of

272 Dr, Mac Cuttocn on the Vitrified Forts of Scotland.

a design to vitrify can be deduced from this specimen, except that
of the great heat required to fuse it, which applies as well to this
case as to that of Dun Mac Sniochain.

Having in these two instances detected the existence of a vitrifi-
able substance in the rocks from which the walls were constructed,
I was in hopes that all the other vitrified forts would be found to
occur in the vicinity of vitrifiable rocks. No mineralogical notice
has accompanied the accounts of those which have been observed
in Aberdeenshire, in Ross-shire, and other situations, nor had I an
opportunity of inspecting them. But I have since learnt that three
or four exist in Arisaik, a country consisting of gneiss and granite
rocks only. The refractory nature of these substances would almost
lead us to doubt that the buildings are actually vitrified, unless
hornblende or other unnoticed vitrifiable matters abound in them.

It is but of late that similar structures have been detected in the
southern parts of Scotland. Three of them are found in Galloway ;
but I had an opportunity of examining only that which lies in the
parish of Amworth. It is a rectangular and simple wall, occupying
the summit of a steep and strong but low hill, and exhibiting the
usual general appearances.

As the whole of this part of the country consists of common
grauwacke and grauwacke-slate, I was I confess incredulous about
the reported vitrification, on account of the refractory nature of
those substances.

On examining the wall, it appeared that although it bore very
generally the marks of fire, the vitrification had occurred in very
few places and in distant patches. I was at a loss to account for
this circumstance, till on accurate examination of the surrounding
rocks, I found some places where the grauwacke assumed a peculiar
character, exhibiting distinct grains of imbedded carbonate of lime,

Dr. Mac Cuttocn on the Vitrified Forts of Scotland. 2713

This variety is fusible, and from this unquestionably the vitrified
portions had originated. It is here that a part of the rock has been
cut down, very certainly by sharp tools, for the purpose of scarping
one side of the fort. There is no bed of foreign fragments on the
top of the grauwacke, and no covering but the common soil. I
know not what conjectures we can form about this fort, except that
the same attempt has been made, but has failed from the deficiency
of proper materials. I confess that the consideration of the requisite
heat inclines me as much in this case as in the former to the original
supposition, and confirms in my mind the notion that the vitrified
forts of Scotland are the effects of design.

Since the above account was written, two circumstances have
occurred to me which seem to afford additional evidence of the
truth of the opinions I have held respecting the vitrification of
these buildings.

The first is an article in the 12th vol. of Nicholson’s Journal, ©
p. 313, quoted from the report of a French engineer (M. Legoux
de Flaix), describing a method of building practised in Hindustan.
In this process a wall of brick earth is erected, which is then sur-
rounded by a coffer filled with combustibles. As the combustion
proceeds fresh fuel is added, until the whole wall is baked into one
solid brick. ‘The coincidence of the effects of this actually existing
precess with those of one long since forgotten, seems to prove al-
most to demonstration, that similar means have been practised in
the ancient military works of Scotland to produce structures so
analogous to those now commonly used in India, and that the
*‘ baking” of buildings in this country must be considered in the
light of a lost art.

The other is to be found in the history of Gatacre-house in
Shropshire, (now unfortunately pulled down) of which a slight and

WOOL. Tis 2M

974 Dr. MAc Curtrocsa on the Vitrified Forts of Scotland.

not perfectly correct account is given by Owen Salisbury Brereton
Esq. in the third volume of the Archzologia. On applying to the
present most respectable octagenarian proprietor, (descendant of this
ancient family,) to whose regard for the superior comforts of a
modern house we are indebted for the destruction of this singular
and venerable remain, I was informed that the west end alone had
been vitrified. The vitrification was so entire and continuous, as to
form one uniform glassy surface over the whole of the wall, and
thus to conceal even the joints of the masonry. The wall itself was
of grey mottled sandstone, about 18 inches thick. I have examined
the vitrified crust in a specimen transmitted to me. It is scarcely
the twentieth part of an inch in thickness, and consists of a green
transparent glass, perfectly superficial. Its appearance would lead
me to conclude that it had been produced by the application of
alkali or salt to the surface of the wall, previously to the process of
firing by which the vitrification was effected. The proprietor is
inclined to think that the vitrified wall was of greater antiquity than
the rest of the building, but offers no conjecture relative to the time
of its erection. It is only known that the family can be traced
on the same spot to a period as far back as that of Edward the
Confessor.

We have here then additional accessory evidence to prove that the
art of vitrifying buildings after their erection, was an art practised
in Britain. In this case it was evidently intended for the purpose of
excluding the weather, and certainly a more effectual expedient
could not have been devised. The vitrified forts of Scotland, more
solid and less exposed to the ravages of art, have but partially
yielded to the universal enemy, time. The more slender structures
intended for habitation, have disappeared in the lapse of years, or
have suffered from the taste of other improvers.

IX. On the Sublimation of Silica.

By J.Mac Cuttocu, M.D. F.L.S. Chemist to the Ordnance, and Lecturer
on Chemistry at the Royal Military Academy at Woolwich.
V. Pr. Geo. Soc.

SOME years ago, being in pursuit of another object, a mixture of
the oxides of tin and lead was exposed to the heat of an air furnace in
an English crucible, to the top of which was luted another of the
same sort. ‘This apparatus was allowed to remain in the fire for
some hours. No account of the heat was taken, but I have on for-
mer occasions produced in the same furnace a heat sufficient to con-
tract one of Mr. Wedgwood’s original clay pieces to the 130th and
140th degree of his scale. On removing the crucibles, the insides
of both from the bottom of the lowermost to within a third part of
the top of the uppermost, were found covered with white brilliant
filamentous crystals crossing each other in all directions. I con-
cluded that they consisted of the oxide of tin, or perhaps that of
lead, and subjected them to the obvious experiments necessary for
ascertaining this circumstance. Failing to confirm this supposition,
I then conjectured that they might consist of silex. ‘The quantity
I procured scarcely amounted to halfa grain, and I therefore divided
it into two parts, that I might have the satisfaction of confirming or
refuting my own trials by comparison with those of some chemical
friend. Mr. Aikin was so good as to undertake the examination of
the reserved portion, and from his well known accuracy, the Society

will naturally place confidence in our mutual results. On igniting
2M 2

276 Dr. Mac CuLLocu on an Accidental Sublimation of Silica.

them in successive portions of borax and of pure potash, they were
dissolved. The solution was then neutralized, and a few light
flakes fell down, which were redissolved in muriatic acid.
This solution being evaporated to a transparent jelly, was ignited
by the blowpipe, and became insoluble in acids. I was very
desirous of obtaining a second specimen, and repeated the same
process many times for that end, but in vain, I can not pretend to
account for this accidental appearance, and only regret that I was
unable to ensure it at will. ‘There can be no doubt that they were
crystals of silica, however difficult we may find it to form them at
pleasure, and the rarity of the occurrence only serves to prove that
there are properties and relations of this substance with which we
are as yet unacquainted. An agreeable confirmation of this fact ap-
peared some time after in an observation of Vauquelin, copied in
Tilloch’s journal for 1809, with which the members of this Society
are doubtless well acquainted. In a geological view it may per-
haps be worthy of record as not only establishing the volatility of
silica, but serving to prove that this substance may be crystallized
from the state of vapour, as sulphur, some neutral salts, and some
metals are known to be. How far this property of vaporization and
crystallization from that state may be possessed by the other earths,
or by earthy compounds, as it undoubtedly is by all the metals, must
be determined by future observations. Possibly we may thus gain a
step on which to rest, in the investigation of the difficult subject of
mineral veins, and the arrangement of the crystallized substances
which occupy their cavities. The possibility also of explaining by
this process the crystallization of the delicate filamentous zeolites
which occupy the cavities of amygdaloids, will readily occur to every
mineralogist.

X. Observations on the Specimens of Hippurites from Sicily,
presented to the Geological Society by the Hon. Henry Grey Bennet.

y By Jamzes Parkinson, Mem. Geol. Soc.

Tue examination of the excellent series of Hippurites, from
Cape Passaro, in Sicily, presented to the Society by the Hon.
H. G. Bennet, has occasioned the present endeavour to add to the
knowledge of the nature and ceconomy of the animal, whose re-
mains are thus beautifully preserved. ‘The specimens are indeed
such as demand, that they should obtain the particular attention
of the Society, since they possess those characters which will
probably serve to correct some erroneous opinions respecting the
nature and habits of the animals of which these shells were the
dwellings. ,

These fossils exactly agree with the description of M. Lamarck,
being straight or bowed conical shells, furnished internally with
transverse septa, and with two longitudinal, lateral, obtuse and
converging ridges. ‘These characters are distinctly observable in one
of the specimens* which contains,.with several other remains of these
fossils, a nearly perfect shell, longitudinally divided, so as to dis-.
play very beautifully the two ridges, with the numerous septa and
chambers. In another, a longitudinal section of one of these
fossil shells, the same parts are shewn, and the extreme thinness
of the septa, and the closeness with which they are placed to each
other, are particularly observable.

©

* No, 1. of the Scries. + No.

2°18 Mr. PARKINSON on Hippurites.

M. Lamarck concludes his description of this fossil by saying,
that che last chamber is closed by an operculum ; a circumstance which
M. Picot de la Peyrouse had supposed that he had frequently ob-
served, whilst examining the numerous specimens which he had
found onthe Pyrenees. ‘The existence of this operculum is however
positively denied by M. Denys de Montfort, who considers this
supposed operculum as only one of the septa bearing the impression
of the posterior part of the animal. Two specimens” contain
sections of these fossils, towards their superior termination ; and
shew, perhaps, the inner side of this last septum or supposed oper-
culum ; but do not appear to yield any marks which may assist
in determining on the real nature and office of these parts.

M. Picot de la Peyrouse, besides finding several of these bodies
of a conical form, whose length did not exceed their diameter,
found others of a cylindrical form, some of which were a foot and
a half in length, though not more than an inch in diameter; and
of course nearly as large at one end as at the other. ‘The regular
manner in which he found these fossils arranged by the side of each
other led him to describe them as resembling the pipes of an organ.
M. Denys de Montfort has thought proper to place the fossils of
this description under a new and distinct genus, which he names
Batolites organisans, (Le batolite tuyau d’Orge.) The bippurite he
remarks is constantly bowed and short, and possesses a very thick
shell ; whilst the Ja¢olite on the contrary is straight and long, and
has a very thin shell. 3

In another specimen? a section of one of these fossils is seen
possessing a much greater degree of curvature than that which is
seen in No. I. which indeed departs but little from the straight
line. These two fossils may be regarded as intermediate in their

* No.2 & 4. ta NOs os

Mr. PARKINSON on Hippurites, 279

Jength and form, between those which have been placed by M.
Denys de Montfort in the two different genera, Aippurites, and
Batolites organisans; and if this connection be admitted, it
may then appear that those differences which that assiduous
naturalist has assumed as the foundation of generic distinction,
should be considered as at most only marking the distinction of

species.

No attempt has hitherto been made to explain the uses of the
several parts of this fossil, or to infer from them any thing respect-
ing the habits of the animal itself. M.Picot de la Peyrouse gives
the following observations on the subject: ‘* Nous ne connoissons
que trés imparfaitement l’analogue marin des Orthoceratites. Ceux
que Plancus a découverts dans les sables de Rimini, et que Gualtiert
a fait graver, grossis aux microscope, suffisent pour convaincre les
plus incrédules, que les orthocératites sont de véritables corps marins
pétrifiés: mais non pour nous faire connoitre usage du siphon, de
la gouttiére, des concamérations, &c. Il faudroit, pour y parvenir,
découvrir les analogues marins des principales espéces de grands Or-
thocératites, avoir étudie leurs moeurs, leurs habitudes, leur maniére
d’étre. Que des difficultés désesperantes ne présente pas ce projet !
dit il méme étre rempli, serions nous, pour cela, mieux instruits
de usage de cette partie essentielle de organisation de cette animal ?
Le nautile chambré est un des coquillages les plus connus. Nous
avons la description, on la voyoit en troupes sur la surface des mers,
voguer jusques dans les ports les plus frequentés (voyez description
du cap. de B. E. tome If. p. 154) ; nous savons qu'il a des cloisons,
et un siphon; nous n’en ignorons pas moins Pusage qu'il en fait ?
Je crois donc ne mériter aucune blame, si je ne hazarde point de
conjectures sur l’organisation des différentes parties de ces orthocéra-

tites; parcequ’il me seroit impossible de les étayer d’aucune preuve

280 Mr. PARKINSON on Hippuriies.

satisfaisante.” (Description de plusieurs nouvelles espéces d’ortho-
ceratites, &c. p. 15.)

A due attention however to their peculiar organization would, it
may be supposed, have prevented the multilocular shells from having
been considered as pelagian shells. But M. Denys de Montfort,
with most of the French oryctologists, is disposed to believe that all
those shells which are known to us only in a fossil state, and which
have therefore been supposed to belong to animals: which are now
extinct, do actually belong to animals which constantly inhabit the
bottom of the sea, never rising to the surface, or appearing on the
shores. ‘Thus the orthoceratites, ammonites, and belemnites, not-
withstanding their possessing different modifications of that organi-
zation by which the nautilus is enabled to raise itself to the surface of
the water, are all considered as petrified pelagian shells, whose recent
analogues have not yet been brought to view. ‘Thus speaking of
the simplégade couleuvreé (simplegades colubratus), a fossil shell
hitherto considered as an ammonite, but which this author has
thought right to place under a distinct genus, he says, “ Il est trés
probable que les simplégades, comme beaucoup d’autres mollusques
pelagiens, vivent dans le fond des hauts mers, et qu’une cause
physique quelconque ne leur permet point de paroitre a la surface des
eaux.”’ (Conchologie Systematique, &c. p. 84.)

Having already opposed this opinion in a general way, in my
Examination of the organic remains of a former world; and having
shown that in all the known multilocular fossil shells such an orga-
nization existed as was well calculated to enable the animals to raise
themselves occasionally to the surface of the water, I shall here
endeavour to determine how far the specimens presented to the
Society will show, that this property was possessed by the hippurites.

On examining those parts of this fossil, which have been hitherto

Mr. PARKINSON on Hippurites. 281

spoken only of as lateral ridges passing through the chambers and
septa, they will be found in most specimens to be formed of a solid
spathose substance. But in the specimen No. VI, in which is a
transverse section of one of these shells near to its upper extremity,
these ridges will be seen, in consequence of the cavities not having
been filled by the infiltration of calcareous matter, to have originally
possessed a singular organization: a substance of extremely loose
and light texture is disposed in plates, which radiate towards the
sides of the containing tubes, leaving interstices between them, nearly
equal in size to that of the radiating substance itself.

It is indeed impossible to speak decidedly as to the manner in which
this peculiar organization could influence the buoyancy of the animal
and its dwelling. It is however not difficult to conceive that the
animal might possess the power of contracting and of expanding
this radiating substance; and might, by thus admitting or expelling
the water, produce that change in the specific gravity of the whole
mass as might occasion it to sink or rise according as the necessities
of the animal might direct.

The great substance of this shell, it being generally about half an
inch in thickness, does not, it must be acknowledged, appear at
first sight to be favourable to the opinion of its having been capable
of being rendered buoyant. But the appearances offered to our ob-
servation by the specimen No. VII. give reason for supposing that
the texture of the shell was such, that its size might rather promote
than prevent its buoyancy. In this specimen the looseness of the
texture of the shell is very remarkable ; it must however be admitted,
that it is difficult to ascertain how much of this depends on the
original lightness of structure, the interstices not having been filled
up by calcareous matter, and how much on subsequent decom-
position.

VOL. II. 2°N

XI, An Account of the Coalfield at Bradford, near Manchester.
By Rosert Bakewet1,

Communicated to the Geological Society by Dr, Roget, M.G.S.

Tne Coalfield which I have undertaken to describe is of very
limited dimensions, extending little more than two miles in length,
and about 2000 yards in breadth. (See Pl. ii. fig. 2.) The form of
its area is oval. ‘The greatest depth to which the workings have been
carried is 140 yards. Ten seams of coal rise to the surface, some of
which are greatly deteriorated by an intermixture of pyrites. The
river Medlock flows nearly at right angles with the line of bearing of
the strata and a section is exposed on its banks to a considerable dis-
tance.

The strata which alternate with the beds of coal are the same that
are usually found under similar circumstances in Lancashire, Che-
shire, and the west of Derbyshire, viz. argillaceous and bituminous
shale with vegetable impressions, and ironstone sometimes in beds
sometimes in nodules. There occurs also over the first coal what is
more uncommon, limestone not containing I believe any organic
remains; it lies in three several strata from 2 to 6 feet in thickness.
It is of a reddish brown colour, and resembles the magnesian variety
of Derbyshire in appearance, though it differs from it in its compo-
nent parts.

The coalfield is bounded (except at its eastern extremity) by red

Mr. BAKEWELL on the Coalfield near Manchester. 283

siliceous sandstone, similar to that on which the town of Manchester
stands, and it is remarkable that within 15 or 16 yards of its contact
with that rock, the coal is soft and hardly worth working. This
rock stretches through the south of Lancashire into Cheshire and
Shropshire, and appears to agree in some respects with the old red
sandstone of Werner. I have been told by a considerable proprietor
cf coal-mines in these counties, and I believe it is an opinion very
generally entertained, that this sandstone always cuts off the coal-mea-
suves, and that it is useless to search for coal beyond or beneath it.

The Bradford coalfield appears at first sight to offer an exception
to this rule; but upon more attentive examination it will be found,
that what covers the coal-measures there is not the rock itself, but
only a portion of it, washed down from the higher lands, and spread
over the surface.

The coal-measures dip to the south at an angle of about 30°, and
wherever they have been proved, on the southern side of the field,
abut against the sandstone; but on the northern side, at the distance
of ten yards from the red rock, a most striking change in the position
of the strata is discovered. A bed of coal, four feet in thickness,
here rises up to the surface perpendicularly, and terminates the coal-
measures, the intermediate space between this bed and the red rock
being filled with broken stones or rubble without any appearance of
stratification. ‘This perpendicular bed has been worked to the depth
of forty feet, and is of the same quality and general appearance as a
four-feet bed which rises near the middle of the field. The stone
that lies over the one agrees with that adjoining to the other, which
the proprietor does not doubt is a portion of the inclined bed broken
off, and thrown into its present position. The distance of the per-
pendicular bed of coal from the rise of the last bed, that preserves its
inclination of 30°, is 325 yards, and between these no fracture or

fault has been found to explain the difference in their angles of ele-

284 $$Mr. BAKEWELL on the Coalfield near Manchester.

vation. ‘There is indeed a dyke in one part of the field, filled with
a stone nearly similar to the red rock, but it does not affect the
position of the strata on either side of it.

Fourteen hundred yards to the north of the Bradford coalfield,
and separated from it by the red sandstone, is the coalfield of Droyls-
den. The first coal that rises there at the distance of 60 yards from
the red rock, is similar to the bed which rises at the distance of 3.50
yards from the perpendicular coal in the Bradford field.

In the middle figure of Pl. 2.

AA represents the length of the Bradford coalfield.

BB its breadth.

CCCCC. different beds of coal which rise to the surface, and
would be visible along their line of bearing parallel to AA, but are con-
cealed by soil and gravel, except on the banks of the river Medlock.

P P the perpendicular bed of coal.

LL the limestone.

RRR the red sand rock.

SS two beds of coal 20 inches thick, one of them situated in
Droylsden coalfield.

The lower figure of Pl. 2. represents a section of the same strata
on a vertical plane perpendicular to A A.

It appears probable that the strata in these two fields were once
united, and have been separated by some convulsion of nature; in
consequence of which the red rock has been interposed like a wedge
between them, a sliding motion being given to the strata by lateral
pressure ; for a force acting in a direct line from above or beneath
could not produce the bending or folding of the four-feet coal.

The red sandstone has not, I believe, been sunk through in any
part of our island, so that its immediate substratum is yet unknown.

If it should prove to be the metalliferous limestone, it will occupy
the same geognostic situation as the red shale of Derbyshire and

Mr. BAKEWELL on the Coalfield near Manchester. 285

Yorkshire. There is, generally speaking, a considerable difference
in the external characters of these two beds; but at Alderley edge*
some parts of the red rock, containing mica, bear a greater resem-
blance to the shale than I have found in any other situation where
I have examined it.

. Mr. Whitehurst observed that a species of grit-stone, which he
denominates the Mill-stone grit, is found under the coal, but never
over it. This bed of rock, which in some situations is not less than

140yards in thickness, varies in quality from a coarse-grained grit;
approaching toa breccia, to a fine-grained siliceous sandstone. 5o0me
varieties of it are red, and bear a greater resemblance to the sand-
rock of Lancashire and Cheshire than the red shale, which lies be-
neath the mill-stone grit.

It is not improbable that in distant places the same stratum may
assume different characters, particularly when it belongs to that class
of rocks which have been considered by geologists as mechanically
deposited by the action of the tides. Strata thus formed may reason-
ably be supposed to alter with the materials of which they were
made; materials that have been washed from the different parts of
extensive ranges of mountains variously composed. I am not aware
that this view of the subject has before been taken by geologists,
although we may thus account for the gradual transition of rocks
into one another, and may often give a more natural solution of the
sudden changes we observe, than by the supposition of faults, of
whose existence some evidence should always be given, independent
of the difficulties which their admission would explain.

In thus comparing the geognostic position of the Red sandstone
with that of the Mill-stone grit, I do not wish to advance any
opinion of my own as to their identity, but merely to direct the
attention of future enquirers to this subject.

* For the account of Cobalt ore contained in the Red rock at this place vide Monthly
Magazine, February, 1811.

XI. Some account of the Island of Teneriffe.

By the Hon. Henry Grey Benner, M.P. F.R.S. Pres. Geological Society.

Tur island of Teneriffe is the principal island of the seven in
the Western Ocean, that are called generally by the name of the
Canaries. It lies north-east by south-west, and is in length from
the Punta del Hidalgo to the Montana Roxa, its northern and
southern extremities, about 70 English miles; its greatest breadth
not exceeding 30. ‘The superficies may be considered as containing
80 square leagues.

The island narrows at its north-eastern and widens considerably at
its south-western extremity. About the centre of the latter, or per-
haps to describe more accurately, to the westward of the central
point, is the mountain called by the Spaniards e/ Pico di Tiéde, but
better known by the name of the Peak of Teneriffe, and which is
the highest land not only in the island, but in all the Canaries; the
mean of various observations making it 12,500 feet above the level
of the sea. It is visible at a great distance ; we saw it perfectly dis-
tinct thirty-four leagues off by chronometrical observation, when it
appeared rising like a cone from the bed of the ocean; and I have
heard that it has been clearly distinguished at a distance of 45 leagues.

The rocks and strata of the Island of Teneriffe are wholly vol-
canic ; a long chain of mountains, which may be termed the central
chain, traverses the island from the foot of the second region of the

Mr, BENNET on the plana of Teneriffe. 287

Peak sloping down on the eastern, western, and northern sides, to-
the sea. Towards the south, or more properly the 8.S.W. the
mountains are nearly perpendicular, and, though broken into ridges
and occasionally separated by deep ravines that are cut transversely
as well as longitudinally, there are none of those plains nor that
gradual declination of strata that the south-eastern and north-western
sides of the island exhibit.

From the Barranco Seco, in the neighbourhood of Santa Cruz,
to the northerly point called Punta del Hidalgo, a series of steep and
abrupt mountains form headlands to the sea, separated from the
central chain by the valley of Laguna; these mountains are rugged
and peaked, drawn up, if the term may be used, in a column, and
are divided by deep ravines. The sides of these mountains are steep,
being in many places cut nearly perpendicular to the horizon, and
are all composed of lava generally of the basaltic formation, mixed
with. beds of tufa and pumice. From Adalgo point to that of
Teno, the most westerly point of the island, the strata vary from
beds of pumice and decomposed lava and ash, which. form the
plains of Laguna Ticaronte and Songal, to streams and currents
and headlands of lava similar to those of the Barranco Hundo, San
Ursula, Las Horcas, and Las Guanchas. ‘The slope from the central
chain is here gradual, intersected by ravines and streams of lava.
The soil famed for its fertility and which produces the Teneriffe wine,
is composed of lava and ash in a state of decomposition. Head-
lands, some of them from two to three hundred feet in height,
project into the sea between Saaz Ursula and Oretava, forming
perpendicular cliffs. At the western extremity of the island
from Punta di Teno to. Puerto de los Christianoz, the strata
rise in a broken ridge to the Peak, the land ascending gra-
dually from. Punta de Teno by a chain of small peaked hills ;. the

288 Mr. Benner on the Island of Teneriffe.

point itself being very low and projecting as a promontory into the
sea. The declination of the strata is similar from the Peak to Puerto
de los Christianos. This south-westerly chain is broken into many
abrupt ridges, and is cut nearly perpendicular down to the sea. I
could not perceive any base or shelf as on the other sides of the
Peak, from which the cone arose, but the fall is regular though steep.
From Puerto de los Christianos to Santa Cruz, comprising the south-
ern and south-eastern sides of the island, the form is similar to that
in the vicinity of Orotava, but it is barren and desolate, laid waste
by streams of lava. In theshort space of a few leagues I counted no
less than seven cones of extinct volcanoes, and the country is covered
with scoria, exhibiting no appearance of culture, and hardly any of
vegetation ; it is more broken into ravines and more intersected by
lava torrents than on any of the other sides of the island. Numerous
peaked and conical mountains rise upon the slope of the chain, and
the whole country is covered by scoria, and is one continued stream
of lava. The Montana Roxa itself is a singular example of the dis-
location of strata so commonly found in countries of volcanic for-
mation ; it is evidently a slip or fall of semi-columnar lava, and
slopes into the sea at an highly inclined angle.

The ordinary strata of the island are as follows, reckoning
from below upwards-: Ist. the porphyritic lava covered by scoria
and sometimes by pumice. This lava-is composed of hornblende
and feldspar, and contains no other substance. The next stratum
graduates into what the Spaniards call Roccaverde or greenstone, and
is composed of feldspar and hornblende; upon this is generally a thick
stratum of pumice, and last of all towards the surface is the basaltic
lava covered also by tufaand ash. This lava decomposes the soonest.
It also contains the greatest variety of extraneous substances, and is
sometimes divided by a layer of large crystals of olivine some inches

Mr. BENNET on the Lland of Teneriffe. 289

long, and towards the north-east is often intersected by strata of por-
phyritic slate. These lavas are more earthy and cellular than those
which I have had an opportunity of observing elsewhere, yet they
contain fewer extraneous substances than those of A’tna and Vesuvius ;
they are in some places exposed to view in the vallies sitnilar to those
of the Corral in the island of Madeira. The valley of Las Guanchas
on the north-west side of the Peak, contains according to M. Escolar*
above 100 strata of lava, the one reposing upon the other, at times
alternating with pumice and tufa. The depth of these strata varies.
M. Escolar has seen one of basaltic lava between 100 and 150
feet in depth in one solid mass, cellular at the surface, but gradually
becoming more compact towards the bottom. This basaltic lava con-
tains olivine and hornblende, and, in the caves on the coast, zeolite,
This substance is also found in stalactites and in masses, sometimes
in layers spread between the strata and diffused over the rock.
Nodules of chalcedony are sometimes also found, but these sub-
stances occur only in the chain of mountains towards the north-east,
from the northern extremity of Santa Cruz to the point of Hidalgo.
The lavas of the island are of an endless variety, and the number
of streams that have flowed are much beyond all enumeration. The
whole surface is either ash, or solid or decomposed lava, which seems
again and again to have been perforated by volcanic eruptions ; the
number of small extinct volcanoes is prodigious, they are to be found
in all parts of the island, but the stream that has flowed from even
the largest of them, such as the lava of the Peak called ef Mal Pais,
is trifling in comparison with that immense mass of lava mountains

* M. Escolar was sent out by the Spanish government to examine the political, com-
mercial and mineralogical state of the Canaries; he has well performed his task, and it is
to be regretted that the situation of his native country has hitherto deprived the public of
the interesting facts he is able to communicate.

VOU. tk 20

290 Mr. BeNNET on the Island of Teneriffe.

which constitute the central chain of the island, and which stretch
out as headlands like those of /as Horcas and San Ursula.

I never found in situ those masses of columnar basaltic rock that
are so common in the island of Madeira: but in the valley cf /as
Esperanzas, in the chain of hills to the north-eastward of the town
of Santa Cruz, they lie scattered about in considerable numbers,
and M. Escolar told me that he had seen strata of them to a con-
siderable extent, exhibiting with precision the columnar basaltic
form; the modern lavas of the peak are all basaltic, that
of 1704 is decidedly so, as well as that of 1798, though not
exhibiting any prismatic form. Prisms of basaltic lava are yet
found on the peak: I picked up one, though there are no strata of
them to be met with. The metals are rare, and afford but little
variety: specular and micaceous iron, black and grey manganese
are all that have hitherto been discovered. The salts that are so
common on Vesuvius, are here seldom met with. Augite is also
rare, and mica and leucite, though carefully sought after, have
hitherto not been found.

In that part of the island between Laguna and Tacaronte, where
there are few streams of lava, the soil is evidently volcanic. I
examined many of the clods that were turned up by the plough, and
found them all alike: they contained much strong clay, with
crystals of feldspar, olivine, and specular iron. Dr. Gillan, who
accompanied Mr. Barrow and Sir G. Staunton, has advanced an
opinion, that between Laguna and Matanzos there are no signs
of volcanic formation. That the currents of Java occur but seldom
is most true ; but the mountains in the vicinity of Laguna are all
volcanic, and one has a visible crater ; besides, the assertion would
prove too much ; for it would go to maintain that the Campagna
Felice, as well as the plains of Catania, were not created by the

Mr. Bennet on the Island of Teneriffe. 291

ash and pumice eruption of Vesuvius and /Etna. The bed of
soil is here very deep. I examined some ravines that the rains had
laid open to the depth of 30 or 40 feet: the strata were
indurated at the bottom, and resembled the tufa in the vicinity of
Naples, and all contained the substances mentioned above. This
tufaceous character changes as you ascend the hili that separates
Laguna from Santa Cruz; the hill itself, and the whole neigh-
bourhocd of the latter city is one continued stream of lava,
hardly at all decomposed, with little or no vegetation ; but here and
there in the hollows some few stunted plants of the aloe algarvensis,
and the cytisus.

Having given a general account of the island, I shall now
attempt to describe the country of the peak, which mountain I
ascended on the 16th of September, 1810. The road from Puerto
Orotava to the city of Orotava, is a gradual and easy slope for three
or four miles, through a highly cultivated country. The soil is
composed of volcanic ash and earth, and to the eastward of the
town of Puerto di Orotava are the remains of a recent volcano, the
crater and cone being distinctly visible. Leaving the town of Oro-
tava, after a steep ascent of about an hour through a deep ravine, we
quitted the cultivated part of the slope or valley, and entered into a
forest of chesnuts ; the trees are here of a large size. This forest of
chesnuts is mixed with the erica arborea, or tree heath, which shrub
rises to the height of 18 or 20 feet. Some of the stems are as thick
asthe arm of a man, joined together in bunches or tufts like the
common heath. The form of this forest is oblong, it covers the
flank of those hills which I have already denominated the central
chain, from their summit to half their elevation from the plain. The
soil here is deep, and formed of decomposed lava, small ash, and

pumice, I examined several channels in the strata or ravines
ZO 2

292 “Mr. Benner on the Island of Teneriffe.

worn by the rains, and there was no appearance of any other rock.
Leaving this forest, the track passes over a series of green hills which
we traversed in about two hours, and at last halted to water our
mules at a spot called e/ barranco del pino de la meruenda, where there
is a small spring of bad and brackish water issuing from a lava rock.
The ravine is of considerable depth. After the vegetable earth,
which is 2 or 3 feet deep, a layer of tufa succeeds, which is fol-
lowed by a lava of a greyish-blue colour, 30 or 40 feet in depth.
It is compact, contains olivine, and the strata lap over each other,
but shew no appearance of columnar formation. The range of
green hills extends a mile or two further, the soil shallowing by
degrees, more lava and scoria shewing themselves on the surface,
the ravines or channels, worn by the rains, becoming more common,
the trees and shrubs gradually dwindling in size, and of them all
the Spanish broom alone at length covers the ground. Leaving
behind us this range of green hills, the track still ascending leads for
several hours across a steep and difficult mass of lava rock, broken
here and there into strange and fantastic forms, worn into deep ra-
vines, and scantily covered in places by a thin layer of yellow pumice.
The surface of the country, for miles and miles around, is
one continuous stream of lava; the rents or ravines of which seem
to be formed partly by the torrents from the hills flowing for so many
ages, and partly from that tendency, characteristic of a lava current,
to keep itself up in embankments, and in its cooling process to open
out into those ‘hollows which I have uniformly found in every
eruption of lava that I have had an opportunity of examining.
This lava is cellular beyond any I have ever seen, is of a clayey
earthy porphyritic composition, and contains few, if any, pieces of
olivine, though here and there felspar in a semicrystallised form.
As we proceeded on our road, the hills on our left, though broken at

Mr. BeNNeET on the Island of Teneriffe. 293

times in deep ravines, gradually rose in height till the summits.
were lost in those of the central chain, while on our right we were
rapidly gaining an elevation above the lower range of the peak.
This range forms one flank of the plain or valley of Orotava,
stretching from south-east to north-west, and is broken into steep
precipices, cut down in some places perpendicular to the horizon,
and called /as Horcas: it joins the central chain at the high eleva-
tion of the pumice plains, sweeps down the side of the valley, and
forms a headland near 200 feet high, projecting into the sea, some
miles from Ovotava ; we traversed this country an hour or two, till
we reached the point of intersection of /as Horcas with the plains of
pumice. On the road are several small conical hills or mouths of
extinct volcanoes, the decomposed lava on the edges of these craters
having a strong red ochreous tint ; by degrees the lava becomes more
and more covered by a small ash, and the masses or heaps of pu-
mice gradually increase, till the surface is completely concealed. At
length an immense undulated plain spreads itself like a fan, on all
sides, nearly as far as the eye can reach, and this plain is bounded
on the west south-west, and south south-west, by the regions of the
peak ; and on the east and north-east by a range of steep perpendi-
cular precipices and mountains, many leagues in circumference,
called by the Spaniards Las Faldas. M. Escolar informed me that
the wall could be traced for many leagues, the whole circumference
of which evidently formed the side of an immense crater. This tract,
called Las Canales, contains, according to the same authority, 12
square leagues. As we entered this plain from the south-west, there
are to be seen several declivities of lava and strata, broken inwards
towards the plain, and evidently a continuation of the above-
mentioned line of wall and the remains of the original crater. There

294 Mr. Bennet on the Island of Teneriffe.

is here no appearance of columnar formation, the lava being earthy
and porphyritic ; this continuity of wall, at present so easy to be
traced, may be considered as forming the sides of one immense
crater, from which perhaps originally the lavas of the island flowed,
which might have thrown up the cone of the peak, and covered
these wide-spreading plains or c/anuras with the deep beds of ashes
and pumice. On this plain or desart, for we had long left all shew
of vegetation, except a few stunted plants of Spanish broom,a sensible
change was felt in the atmosphere ; the wind was keen and sharp,
and the climate like that of England in the months of autumn. All
here was sad, silent, and solitary. We saw at a distance the fertile
plains on the coast, lying as it were under our feet, and affording a
cheerful contrast to the scenes of desolation with which we were
surrounded ; we were already 7 or 8000 feet above the level of the
-sea, and had reached the bottom of the second region of the peak.
Immense masses of lava, some of them many hundred tons in
weight, lie scattered on these pumice plains. Some are broken by
their fall, and all wear the appearance of having been projected by
volcanic force. ‘Their composition is uniformly porphyritic, with
large masses cf feldspar ; the whole compact and heavy, and bear-
ing no resemblance to the earthy lava we had seen in such abundance
prior to our entering these pumice plains. Many of these masses
are completely vitrifed, while others only shew marks of incipient
vitrification ; but from their site and fracture, from the insulated state
in which they lie, from there being no appearance of lava in a stream,
from the pumice bed being very deep, (and in one place I saw it ex-
posed to a depth of between 20 and 30 feet) from all these facts
taken together, there can be little doubt that these masses were thrown
out of the mountain when that lava fowed, which is of similar sub-
stance, and which is called by the Spaniards 7 Mal Pais.

Mr. Bennet on the Island of Teneriffe. 295

Having reached the end of the plain we found ourselves at the _
bottom of a steep hill, at the foot of which is a mass or current of
lava which has flowed from the higher regions of the peak, and
which constitutes the eastern branch of the lava of Mal Pais. We
began to ascend this steep and rapid part of the mountain which is
composed of a small white or yellowish ash mixed with masses of
pumice and fragments of lava similar to that found in the plains, of
which several small pieces that I picked up were in a state of vitri-
fication. After a laborious not to say hazardous ascent of about an
hour, the pumice and ash giving way and the mule sinking knee
deep at each step, we arrived at about five in the afternoon at the
other extremity of the stream of lava, which descending from the
summit of the second region of the peak divides at the foot of the
cone into two branches, the one running to the north-east and
the other to the north- north-west; at the extremity of this
latter are several immense blocks or masses of lava which bear
the name of La Estancia di los Ingleses, and are rocks, not caves
as has been stated by some writers. It was here we were to pass
the night, so, lighting a fire made of the dry branches of the Spanish
broom and stretching part of a sail over a portion of the rock, we
ate our dinner and laid ourselves down to sleep. I however passed
the best part of the night by the fire, the weather being piercing
cold; as I stood by the fire the view all around me was wild and
terrific, the moon rose about ten at night, and though in her third
quarter gave sufficient light to shew the waste and wilderness by-
which we were surrounded: the peak and the upper regions which
we had yet to ascend towered awfully above our heads, while below,
the mountains that had appeared of such a height in the morning
and had cost us a day’s labour to climb, lay stretched as plains at
our feet ; from the uncommon rarity of the atmosphere the whole»

296 Mr. Bennet on the Island of Teneriffe.

vault of heaven appeared studded with innumerable stars, while
the valleys of Orotava were hidden from our view by a thin veil
of light fleecy clouds, that floated far beneath the elevated spot we
had chosen for our resting place; the solemn stillness of the night
was only interrupted by the crackling of the fire round which we
stood, and by the whistling of the wind, which coming in hollow
gusts from the mountain, resembled the roar of distant cannon.
Between two and three in the morning we resumed on foot our
ascent of the same pumice mountain, the lower part of which we had
climbed on horse-back the preceding evening; the ascent became
however much more rapid and difficult, our feet sinking deep in the
ashes at every step. From the uncommon sharpness of the acclivity
we were obliged to stop often to take breath ; after several halts we at
last reached the head of the pumice hill at its point of intersection
with the two streams of lava, the direction of which I have before
described. This is the commencement of that division of the
mountain called e/ Mal Pais; after resting some short time here,
we began to climb the stream of lava stepping from mass to mass,
the ascent is steep, painful and hazardous, in some places the
stream of lava is heaped up in dykes or embankments, and we
were often obliged to clamber over them as one ascends a steep
wall, this lava is of the same porphyritic appearance as the masses
we found in the plains, it is not covered with a thick scoria, and
seems never to have been in a very fluid state, but to have rolled
along in large masses. The felspar is crystallized in the lava itself,
which is slightly cellular at its surface, yet though I searched
carefully I was unable to discover any extraneous substance. ‘The
whole composition of the stream seems to be felspar imbedded in
a brown clayey paste, remarkably hard, of a close texture and
heavy ; judging from the sharp declivity of the mountain it appears

—

Mr. Bennet on the Island of Teneriffe. 297

surprising that the lava should have flowed so short a distance ; as it
does not exceed 2! or three miles from the base of the cone to the
point of union with the pumice hill; the mass of lava as well as
its depth is prodigious; M. Escolar told me that its greatest
breadth was above two miles, its depth it is not easy to
determine, there are however several ravines or valleys in the
course of the stream, some of which may be from 60 to 100
feet deep. The fusion of the mass does not appear to have been
‘perfect ; it is very earthy, and though vitrified pieces are found, there
is no general appearance of vitrification; there are some pieces that
exhibit an union with the pumice and the gradation from the
stony structure to the vitrified, and thence to pumice. Immense
heaps of this latter lie scattered on the surface of the lava, some of
them containing large crystals of felspar, which abounds in, or
more properly forms the constituent part, of the lava of the Mal Pais.

We halted several times during the ascent, and at last reached a
spot called La Cueva, one of the numerous caves that are found on
the sides of the mountain; this is the largest of them, and is filled
with snow and the most delicious water, which was just at the point
of congelation, the descent into it is difficult it being thirty or forty
feet deep. One of our party let himself down by a rope, he could
not see the extent of the cave, but the guides declared it to be
300 feet in length and to contain thirty or forty feet of water in
depth, the roof and sides are composed of a fine stalactitic lava
-similar to that found on Vesuvius, and it is of the same nature as
that which flowed on the surface. We rested here about half an
hour, during which we had an opportunity of observing the rising
of the sun and that singular and rapid change of night into day, the
consequence of almost an entire absence of twilight. As we ascended
the north-east side of the mountain this view was strikingly beautiful,

VOL. II. 2P |

298 Mr. Bennet on the Island of Teneriffe.

at first there appeared a bright streak of red on the horizon, which
gradually spread itself, lighting up the heavens by degrees, and
growing brighter and brighter till at last the sun burst forth from
the bed of the ocean, gilding as it rose the mountains of Teneriffe
and those of the great Canary; in a short time the whole country to
the eastward lay spread out as a map, the great Canary was easily to
be distinguished and its rugged and mountainous character, similar to
that of the other islands, became visible to the naked eye. The cold at
this time was intense, the wind keen and strong, and the thermometer
sunk to 32 degrees ; after a short though rapid ascent we reached the
summit of the second stage of the mountain, we passed over a small
plain of white pumice on which were spread masses of lava,
and at length atrived at the foot of the cone. This division of
the mountain forms what is generally termed the Peak of
Teneriffe; it resembles the present crater of Vesuvius, with this
difference, however, that while the surface of that mountain is
composed of a black cinder or ash, the superficies of this
appears to be a deposit of pumice of a white colour, of scoria and
of lava, with here and there considerable masses that were probably
thrown out when the volcano was in action. ‘Towards the north-
west on the right hand of our ascent, there is a small current of
lava shewing itself above the pumice, the composition of which is
similar to that at the bottom, though of.a redder tinge ; it is broken
on the surface and is in a rapid state of decomposition. Numerous
small cavities on the side of the mountain emitted vapour with con-
siderable heat. Here begins, in my opinion, the only fatiguing
part of the ascent; the steepness of the cone is excessive, at each
step our feet sunk into the ash, and large masses of pumice and
tava rolled down from above; we were all bruised and our
feet and legs were cut, but none materially hurt; at last we

Mr. BENNET on the Island of Teneriffe, 299

surmounted all difficulties and seated ourselves on the highest ridge
of the mountain. This uppermost region does not appear to ~
contain in superficies more than an acre and an half, it is composed
of a lava similar to that on its sides, though decomposed and
changed white or grey by the action of the sulphurous acid; this
acre and an half is itself a small crater, the walls of which are the
different points on which we sat, and are plainly visible from
below. Within, the lava is in the most rapid state of decomposition ;
losing its brown colour and shade of red, and acquiring a whitish
grey almost the colour of chalk; large masses of sulphur are
depositing, which are crystallized in minute though distinct forms ;
there is also a coating of alum produced by the union of the
sulphurous acid with the argil of the lava; the surface is hot to the
feet and the guides said it was dangerous to remain long in one
spot ; as it was, some of us sunk to our knees in the hot deposit of
sulphur; upon striking the ground with the feet the sound is*
hollow, similar to what is produced by the same impulsion on the
craters of Vesuvius and Solfaterra, estimate the depth of the crater
to be, from the highest ridge to the bottom, about 200 feet
forming an easy and gradual descent, the whole being in
a state of rapid decomposition, and charged with sulphur, large
masses of which are every where depositing. I searched in vain
for any of the arseniats so common on Vesuvius, nor could I find
those siliceous stalactites resembling strung pearls, which are met
with in the island of Jschia, in the crater of the So/faterra, and in
the Maremma of Tuscany. The sulphur is pure and fine, and is
sold for a considerable price at Orotava. We were not able to go
all round the walls or exterior summit of the crater, and hence could
not distinguish its southern or western declivity; M. Escolar
assured me they are similar to, though more rapid than the side by
2P2

300 Mr. Bennet on the Island of Teneriffe.

which we ascended; from this side flowed the basaltic lavas of
1704, and of the last eruption in 1797; this latter stream of
lava flowed in a remarkably slow current, for notwithstanding the
sharp descent of the mountain, and the length of the lava not
exceeding three miles, several days elapsed before it reached the
spot where it stopped ; how little fluid this lava must have been is
evident, when it is remembered that the lava of Vesuvius in L794;
which destroyed Torre del Greco, reached the sea from the bottom
of the cone, a distance of eight miles, in little more than six
hours. M. Escolar further told me that there is on this south-
western side of the Peak an ancient lava, at present not at all
decomposed, of several miles in length, and in a perfect state of
vitrification; the whole of this stream has the appearance of
obsidian. All these lavas appear to have flowed from the bottom
of the cone, and to have run from its base in the same manner as
that of Vesuvius in 1794, the crater of which vomited out ash and
pumice, and large pieces of rock, while the current of lava issued
from its side. It is not however improbable that the cone itself is of
anterior formation to this vitrified lava, as the summit of the Peak
is similar to the lava of the Ma/ Pais, and that being porphyritic is
considered as of more ancient date than the one above mentioned,
“which is basaltic.

If one might hazard a conjecture upon a subject where the data
are so few, I should be inclined to suspect that the Peak itself, as well
as the whole of the country around it which forms its base, were
produced by that immense crater called Las Canales, the shape and
magnitude of which I have before taken notice of when traversing
the pumice plains; it is also well worthy of remark that there is
no volcano in action at all to be compared in size of crater to those
that are extinct. The ancient crater of Vesuvius is considerably

-

Mr. BeNNeET on the Leland of Teneriffe. 301

larger than the present, and those in the vicinity of Naples, the erup-
tions of which probably created that district of Italy, are of enormous
extent. The crater of the Camaldoli is somewhat more than two
leagues in circumference, and the superficies of the Cumales is esti-
mated at 12 square leagues. ‘These vast craters were probably capable
of, ejecting from their bosom those stupendous beds of lava,
which being so much more extensive than any that have flowed
from more recent eruptions have led some persons to deny the
former to be the effects of a central fire. That all the Island
of Teneriffe was volcanically produced no man who examines
it can have any doubt, and though the smallness of the exist-
ing crater of the Peak may lead one to imagine that it alone could not
be the effective cause of all the phenomena, yet the innumerable
volcanoes on all sides of the island, the appearance of Las Canales,
and its elevation, are able to account for the extent of the streams and
beds of lava and of the deposits of tufa and pumice, of which the island
is composed. Having no data to proceed upon but what is given by
the measurement of the eye, it is not easy to determine the magnitude
of the cone at its base ; one may say at a venture, it is about three miles
in circumference, though towards the S.S.W. the descent is much more
abrupt, and the plain from which the cone springs not perceptible.
The view from the summit is stupendous, we could plainly discover
the whole form of the island, and we made out distinctly three or four
of the islands, which together are called the Canaries ; we could not
however see Lancerotte or Fuerteventura, though we were told that
other travellers had distinguished them all.

From this spot the central chain of mountains that runs from south-
west to north-east is easily to be distinguished. These with the suc-
cession of fertile and woody vallies, commencing from San Ursula

and ending at Las Horcas, with the long line of precipitous lava rocks

302 Mr. BENNET on the Island of Teneriffe.

that lay on the right of our ascent, and which traverse that part of
the island, running from east to west from their point of departure
at the Canales to where they end in an abrupt headland on the coast,
with their forests and villages and vinyards, the port with the shipping
in the roads, the towns of Orotava with their spires glittering as the
morning sun burst upon them, afforded a chearful contrast to the
streams of lava, the mounds of ash and pumice, and the sulphur-
ated rock on which we had taken our seat. The sensation of ex-
treme height was in fact one of the most extraordinary I ever felt,
and though I did not find the pain in my chest arising from the
rarity of the atmosphere, near so acute as on the mountains of
Switzerland, yet there was a keenness in the air independent of the
cold that created no small uneasiness in the lungs. The respiration
became short and quick, and repeated halts were found necessary.
The idea also of extreme height was to me more determinate and
precise than on the mountains. of Switzerland; and though the
immediate objects of vision were not so numerous, yet as the
ascent is more rapid, the declivity sharper, and there is here no
mountain like Mont Blanc towering above you, the 12,000
feet above the level of the sea appeared considerably more
than a similar elevation above the lake of Geneva. We re-
mained at the summit about three-quarters of an hour, our ascent
had cost us a labour of four hours, as we left the Estancia at
ten minutes before three and reached the top of the peak before
seven ; many indeed of our halts were needless, and M. Escolar
told me that he had twice ascended to the summit in somewhat less
than three hours. Our thermometer which was graduated to the
scale of Fahrenheit was during our ascent as follows: at Orotava
at eight in the morning, 74°; at six in the evening at La Estancia,
50° ; at one in the following morning 42°; at La Cueva at half-past

Mr. BENNETT on the Island of Teneriffe. 303

four 32°; at the bottom of the cone 36°; at the top of the Peak one
hour and a half after sun-rise 38°. The descent down the cone is -
difficult from its extreme rapidity, and from the fall of large stones
which loosen themselves from the beds of pumice. Having at
last scrambled to the bottom, we pursued our march down the other
course of the lava, that is to say down its westerly side, having
ascended its eastern. The ravines and rents in this stream of lava
are deeper and more formidable; the descent into them was always
painful and troublesome, often dangerous, in some places we let our-
selves down from rock to rock. I can form no opinion why there
should be these strange irregularities in the .surface of this lava; in
places it resembles what sailors term the trough of the sea, and I
can compare it to nothing but as if the sea in a storm had by some
force become on a sudden stationary, the waves retaining their
swell. As we again approached La Cueva there is a singular steep
valley, the depth of which from its two walls cannot be less than
100 to 150 feet, the lava lying in broken ridges one upon the other
similar to the masses of granite rock that time and decay have tumbled
down from the top of the Alps ; and, except from the scoria or what
Milton calls “ the Fiery Surge,” they in no degree bear the marks
of having rolled as a stream of liquid matter. This current like
that of the eastward branch has no resemblance to any lavas I have
seen elsewhere, it is hardly at all decomposed, full of ‘laminz of
feldspar, the fracture conchoidal, and the texture porphyritic, the
colour brown like that of the other branch ; it is but slightly cellular,
and contains no extraneous substances.

We descended the pumice hill with great rapidity almost at a
run, and arrived at La Estancia in little more thantwohours. We
then mounted our mules, and following the track by which we had

304 Mr. BenNneET on the Island of Teneriffe.

ascended the preceding day, we reached about four o'clock the
country house of our hospitable friend Mr. Barry.

The difficulties of this enterprise have been much exagerated, the
ascent on foot is not a labour of more than four hours at most, and
the whole undertaking not to be compared in point of fatigue to
what the traveller undergoes who visits the Alps. That the ascent
must be hazardous in a storm of hail and snow there can be no
doubt, but to cross Salisbury plain may sometimes be dangerous.
Yet stripped of poetical terrors and divested of the eloquent des-
cription of some writers, there is perhaps no mountain in Europe,

the ascent of which does not furnish more difficulties than the Peak
of Teneriffe.

5 XIIl. On the Junction of Trap and Sandstone,
at Stirling Castle.

By J. Mac Cuttocu, M.D. Chemist to the Ordnance, and Lecturer on
Chemistry at the Royal Military Academy at Woolwich.

V. Pr. Geo. Soc.

qT HAVE herewith transmitted a sketch of one of those circum-
stances in the mutual relation of greenstone and sandstone, from
which the Huttonian. theory is presumed by its advocates to derive
so material a support. The particular instance, of which this sketch
is intended to give a general notion, has been lately brought to
light, and has not, as far as I know, been observed by the geolo-
gists of Edinburgh. It does not indeed differ so greatly from the
same class of facts in the neighbourhood of that city, as to require
very particular attention; but I have been induced to preserve this
notice, and drawings of it, (Pl. 12,13) partly on account of its
decided and clear disposition, and partly, lest the same operations by
which it was first exposed, may, at no distant period, again remove
or overwhelm it. Nevertheless, it may have its use in extending
the analogy between those classes of rocks in which this appearance
is found, and in rendering it probable that the same cause, whatever
it was, presided at the formation of all similar phenomena.

The rock on which Stirling Castle is built, and on which the town
also is founded, resembles so strongly that on which Edinburgh
stands, that it would be superfluous to describe it very particularly.

VOL. Tr. Ze

306 Dr. Mac Cuxtocn on the Junction of Trap

It forms a large stair, having its escarpement towards the west,
and its inclination similar to that of the great rocks which are
not only found in the vicinity of Edinburgh, but are to be seen
rising above the general level through the whole interval between
Edinburgh and Stirling. The hill of Stirling, and that of Craig
Forth, are, I believe, the most western of this class of rocks, which
are connected here, as at Edinburgh, with the coal district.

It was in cutting a new road through the castle hill that the
appearance in question was laid bare.

The trap stratum consists of a dark blueish black compact green-
stone, varying to umber brown, and it is accompanied by tufo ; but
the former alone is in contact with that part of the sandstone
stratum which is exposed.

On inspecting the drawing, it will be seen that the sandstone
stratum has been split into two parts in the direction of its stratifi-
cation. ‘The upper portion is then separated by a perpendicular
fracture, and bent upwards, terminating abruptly. It is in this
position involved, supported, and covered by the greenstone.
The broken end is irregularly fractured, but all its cavities are per-
fectly filled up with greenstone. The different laminz of which
the sandstone stratum is composed, are not broken to accommo-
date themselves to this new position, but are irregularly waved
and bent, preserving their continuity every where.

A little additional disturbance appears on the lower side of the
bent portion, as if formed by the separation of fragments ; but
the drawing will render the appearance more intelligible than any
description could do. The state of the rock did not, when I was
there, allow me to examine the other portion of the upper part of
the bed from which the broken end had been disrupted: future
operations on the rock may hereafter lay bare further portions to
illustrate this interesting appearance.

and Sandstone ait Stirling Castle Rock. 307

The sandstone bed itself consists of different laminz, varying.
in colour, but generally slate-coloured, yellowish, and grey. The
two lowermost and thickest beds differ little or nothing in texture,
colour, or quality, from ordinary calcareous sandstones, and they
are (as the drawing shews) of considerable thickness compared
with those which immediately follow them.

These thinner beds are separated from each other by laminz, of a
clay slate, very much confounded with the sandstone, and those
two substances alternate frequently and irregularly, till they ap-
proach the thicker beds which lie in contact with the greenstone.
As they approximate to it they become more indurated, and assume
a texture approaching to that of hornstone. The lowermost of
the two upper beds thus exhibits a kind of hornstone of which the
fracture is occasionally granular, and occasionally passes into the
splintery and conchoidal. The uppermost bed exhibits the cha-
racters of perfect hornstone. It is of an ochre-brown colour, its
fracture is conchoidal, or splintery, with an even shining surface,
and the thin fragments transmit light.

As the specimens are before the Society, I need not enter into
more minute details, particularly as, if taken together with the draw-
ing, they will shew the regular gradation from the ordinary cal-
careous sandstone to the perfectly characterized hornstone. I may
just be allowed to point out the resemblance which this change
bears to that gradation from sandstone to a jaspideous rock, which
occurs in a similar situation at Salisbury Craig. Considering merely
the mechanical position of the sandstone, I confess myself unable
to comprehend how by any combination of accidental abrasion or
fracture, and successive deposition by precipitation, the present,
and similar appearances can be produced. Although the projecting
portion of the sandstone might have been able to maintain its place

2Q2

808 Dr. Mac Cuttocu on the Junction of Trap, Sc.

during the deposition of the greenstone bed, yet some other
expedient must be resorted to before the curvature of the sandstone
stratum can be accounted for. The explanation afforded by the
Huttonian hypothesis is too apparent to require notice.

Whether this hypothesis be esteemed well founded or not, it
must rest on a much wider basis than that of the mere phenomena
which accompany the trap rocks. But if we consider those rocks
with the appearances which I have now described, and which they
so often exhibit, we may safely conclude that no hypothesis is
competent to explain geological phenomena at large, which does
not admit of the forcible displacement of the strata which ac-
company them, and on which the marks of violence are so evi~
dently impressed.

XIV. Ox the Economy of the Mines of Cornwall and Devon.

By Joun Taytor, Mem. Geol. Soc.

Tas miners of many countries have engaged the care and
attention of their governments, and have received support from
national treasuries, or grants and immunities operating in favor of
such undertakings. In some instances officers regularly educated
to the profession of mining, are appointed and paid by the state
for managing the executive departments. With such advantages it
is probable that poorer mines may be worked, than in countries
destitute of them, and where they must be undertaken entirely at
private risk ; yet it is found that the enterprize and ingeauity of
individuals is equal to very considerable efforts, and that their cal-
culations of real profit are often more unquestionable than in
government undertakings, |

If the spirit which is excited by the prospect of gain can be in-
fused into a great portion of the persons employed on any object of
this sort; and if the interest of the proprietors of mines can be
made to go hand in hand with that of their workmen in their ope-
rations, a great degree of united effort may be reasonably expected
to follow such a system, which being advantageous to all parties in
proportion to their exertion, enlists at once their combined efforts
into the service of the common good.

310 Mr. TAYLOR on the Economy

The mines of England have no assistance from the government,
but must rely for their success upon their own resources, and the
spirit and energy of their owners; and it is probably to this cause
that we may attribute the activity and economy which, when their
constitutions are duly examined, may be found to prevail in the
principal mining districts.

The peculiar system invented and gradually improved to its
present state in the mines of Cornwall, and more recently adopted
in the undertakings of the same kind in the adjoining county, so
completely answer the purpose of combining the interests of the
working miner with those of his employer, that if benefit is to be
expected from sucha plan, it is worth describing, as a detail which
may furnish hints that may prove useful to all who are interested
in the subject.

The economy of a mine may be considered under the following
general heads :

1.—The nature of the agreements between the owner of the soil

and the mine adventurers.

2.—The atrangements between the partners or adventurers

themselves, and the system of controul and management
appointed by them.

3.—The mode of employing and paying the miners and work-

men, in use among the agents of the principal concerns.
4,—The purchase of materials for carrying on the undertaking.
5.—The sale of the ores from the mine adventurers to the
smelting companies.

In reviewing the whole system, it may appear that there are parts
subject to censure as well as others worthy of imitation ; but the
detail will not be the less useful on this account, and it is to be un-
derstood that different mines in the Stannaries vary from each

of the. Mines of Cornwall and Devon. 311

other in these respects, and of course some may be said to be more
perfect than others.

The result however of the whole has been the execution of
works of extraordinary magnitude, with unparalleled dispatch ;
the pursuit of the difficult task of discovery with the greatest effect,
and a vast increase in the produce of the metals, more particularly
of copper, in the last fifty years.

The mines of Cornwall have furnished such supplies that the
British manufacturers are no longer dependent on other countries
for an article of raw material of the first importance to their trade,
while in the space of less than a century, an increase, amounting to
the annual value of near a million sterling, has made England one of
the sources whence the world is now supplied with copper, instead
of relying for this article upon the mines of Germany or Sweden.

1. The Nature of the Agreements between the Owner of the Soil
and the Mine Adventurers.

The grant for working a mine is called a set, and is usually taken
by one or more persons from the proprietor of the land in which a
load may be found, except in such cases of tin-mines as are anciently
embounded according to the provisions of the stannary laws, whereby
a tight of working for this metal is obtained. No custom or an-
cient law however prevails as to copper or lead in the stannaries, and
therefore all agreements for searching for, or working these metals,
are made upon such terms as are decided on by the contracting
parties. The owner of the land, in the technical language of the
district, is called the Jord, and the parties who engage to work the
mine are called adventurers.

312 Mr, TAYLor on the Economy

The lord grants a lease or set for 21 years, reserving a power to put
an end to the term, if the mine should not be effectually worked ;
he likewise agrees for a certain proportion of the ores to be de-
livered to him on the mine in a merchantable state, or their value in
money: he provides for a power of inspecting the works at all
times, and binds the adventurers to maintain and leave at any de-
termination of their grant all the shafts, adits, and levels, perfect,
and in good condition, as to timber, where required.

The proportions of ore paid to the land-owner, called the /ora’s
dues, vary considerably, according to the circumstances of different
mines, and the nature of the prospects under which they may be
undertaken. A deep old mine which has been abandoned, is un-
dertaken with a chance of less profit and a certainty of greater risk,
than a new and promising discovery. In the first case encourage-
ment is often held out, by fixing very moderate dues, while in the
other, so much is too frequently demanded and given, as to prevent
that share of profit accruing to the adventurers which is due to the
great risk constantly attendant on all mining pursuits.

In the deep expensive mines the lord’s dues do not often exceed a
fifteenth or eighteenth part of the whole produce of ore, and some-
times they do not amount to more than a twenty-fourth, or even a
thirty-second proportion.

In the newer mines the dues are often as much as a tenth or twelfth
part of the produce, and there are mines which pay an eighth ; but
this is the case only in such as were undertaken when the prices of
metals were much higher than at present, and where an unusual pro-
duce has enabled the concerns to exist in spite,of such a heavy deduc-
tion from their produce, The dues are delivered to the lord, or to
his agent on the mine, free of all expense, or are commuted for a

proportionate part of the money arising from the sale of the whole.

of the Mines of Cornwall and Devon. 313

Hence it will be seen that the land-owner risks nothing but a little -
injury to the surface of his fields, which will appear trifling when
it is considered that if the mine is unsuccessful, the work is soon
stopped ; and that on the other hand many cases exist, where, by
the sacrifice of an acre or two of land, an income of two or three
thousand pounds has been obtained for several years.

The mode of levying the dues on the gross produce of a mine,
tends to discourage enterprize, where considerable expense is in-
curred by the adventurers without an immediate return. It seems
reasonable that the land-owners should contribute something in
favor of that exertion which so often leads to their great advantage.

If an equitable mode of assessing the dues in some proportion to
the net profit, could be devised, and was liberally and fairly acted
upon, it would probably tend more than any thing else to the en-
couragement of mining.

As’ it now stands, the land-owner often derives a great revenue
from a mine, which is swallowing up the money of the adventurers.

oT Be Arrangements between the Partners or Adventurers them-
selves, and the System of Controul and Management appoinied by
them.

?

The parties who take the set, after reserving such shares in the
adventure for themselves as they are disposed to carry on, generally
allot the remainder to such of their friends as are inclined to join
them. The whole concern is usually divided into 64 shares or
doles, which division admits of its being held in various proportions,
so that one person may have an eighth of the mine, another a six-
teenth, and so on, until the whole is taken up.

VOL, | 2R

314 Mr. TAYLOR on the Economy

The disbursements or costs are added up at the end of certain
periods, seldom exceeding three months, but more generally at the
end of every two months, at which times the adventurers meet and
examine the accounts ; each contributes his quota of money in time
for the pay-day, which takes place regularly soon after.

When the mine becomes productive, the accounts are closed at
the same periods, and the profit divided to the adventurers in the
same manner. A balance to answer the advances made to the men,
and other contingencies, is usually left in the hands of the purser
or principal agent.

The general detail of management is often- delegated to one
person, who controuls and superintends the whole affairs of the
mine ; most commonly this person is one of the parties concerned
in the undertaking, and one who from having made the profession
his regular pursuit, and having, as is often the case, the care of
several mines, is well fitted for so important a task. Some mines
have the conduct of their affairs more divided, by the financial part
being entrusted to a purser, and the management of the works to
the principal captain acting under the direction of the meetings of
the adventurers.

The agents who attend regularly to the operations, and who
govern the executive part, are called captains, and are practical
miners, selected for their skill and character, and who frequently
pass from situations of subordinate trust and importance to those of
great responsibility. Their general character is well known to those
who have had occasion to visit the mining districts now under con-
sideration ; and it would be unjust not to notice here, how much of
the perfection of the system of management in the mines has been
owing to the zeal and intelligence of this respectable class of men,
and how much its useful application constantly depends on their
knowledge and activity.

of the Mines of Cornwall and Devon. 315

The captains take different departments of duty in such mines as ©
are sufficiently extensive to require it. ‘The principal or managing
captain has the superintendance of the whole, and gives his attention
to every thing that may demand it, either underground or on the
surface.

“Most of the other captains are employed in viewing and controling
the operations of the miners, and are called zzderground captains ;
they regularly visit different parts of the mine for this purpose, by
night as weli as by day, relieving each other in turn. They assist
the managing captain in valuing the various prices of work to be
offered to the men, and enforce the due performance of the
contracts made with them. ‘Their opinion is most important on all
questions relating to the operations to be pursued, whether for dis-
covery or for the best means of working what is already discovered ;
and they possess generally so much knowledge of practical mecha-
nics applicable to mining, as to be able to direct in all common cases
what is necessary to be done in the erection or repair of much of the
machinery employed.

A grass captain or dresser is appointed, who has charge of the
processes going on at the surface, and who regulates every thing
relating to the preparation of the ores for sale.

The captains are assisted in other departments by an engineer
who often superintends the engines of several mines, and by clerks
to keep the accounts. They have likewise under them a fitman,
who looks after the pumpwork in the shafts, and the underground
machinery in general, a ¢imberman or binder, who takes care that
the ground is properly secured by supports of wood, and that the
casings and ladders in the shafts are well put in, and kept in good
repair.

The establishment of a mine likewise includes often a material

ZR2

316 Mr. TAYLOR on the Economy

man who looks to the receipt and due delivery of articles used in
working the mine, and a principal carpenter and blacksmith, though
the two latter are often employed by contract.

3. The Mode of employing and paying the Miners and Werkmen in
Use among the Agents of the principal Mines.

We now come to that part of the economy of the Cornish mines,
which is most deserving of consideration from the effects it has pro-
duced, not only by procuring regularly a great deal of effective
labour in proportion to the money paid for it, but also by turning
that Jabour into such a direction as to make it the interest of the
workmen to increase the discoveries of ore, and to work it and
make it saleable in the most economical manner. ‘Thus the owners
of the mine have the advantage of all the intellect and skill that the
men collectively possess, and have only to guard against the chances
of fraud which such a system may be supposed to be subject to,
but which are in fact under intelligent and faithful agents of too.
trifling a nature to be accounted of any importance.

_ The work of the mines, on the surface as well as underground, is
universally performed by contract, and in this particular the practice:
of this district is probably similar to that of .other mining establish-
ments in different parts of the kingdom. Day work is in general
disrepute in the stannaries, and is seldom resorted to, but where jobs
are to be performed which either hardly admit of a previous estimate,
or are too trifling to be worth contracting for; so that the charges
under this head, among all the various operations of a large and
well-managed mine, usually amount to but a very small proportion
of the whole.

The plan of making the contracts with the miners, which it is

of the Mines of Cornwall and Devon. 317

believed is peculiar to Cornwall and Devon, and which holds a dis-.
tinguished place in the economy of the mines, is that of periodically
bringing all the work to a kind of public auction. Thus sucha de-
gree of competition among the workmen is constantly excited as to

cause the price of labour always to bear on the whole, a fair pro-

portion to the demand, combined with the considerations connected

with the varying expenses of living. Thus superior skill and in-

dustry have'their due advantage ; and thus arethe adventurers even

guarded in some degree against want of skillin their captains, whose

judgment is always corrected by the results of the settimg. The

only danger to be apprehended is from a combination of the men ;

but this is effectually prevented by the captains reserving the power of
offering the bargain upon their own terms after the men have ceased

to bid, if no one is found to go as low as they deem proper, or to

withdraw the bargain altogether.

The act of contracting with the workmen is called a setting, and
this in general takes place at the end of every two months, the
auction is denominated a survey, and is held in the open air before
the counting-house of the mine, which is generally provided with
an elevated stage for the captains to stand on.

. Three descriptions of contracts are put up at the surveys, ac-
cording to the kind of labour to be performed, which is compre-
hended under the denominations of ¢u/work, tribute, and dressing.

Tutwork includes work done by measure, such as sinking shafts,
driving levels, or stoaping ground; the first being paid for by the
fathom in depth, the second by the fathom in length, and the
third by the cubic or solid fathom.

Tribute is payment for raising or dressing ore by a certain part of
its real value when merchantable, and it is this part of the system

that is deserving of most attention, both on account of the excitement

318 Mr. TayLor on the Economy

it produces to discover ore and to raise it cheaply, as already noticed,
and on account of the perfect state to which the arrangements with’
the working miners under this head have been brought.

Dressing contracted for at the surveys is seldom for more than
the waste or leavings of the tributors, the ores raised on tribute
being made merchantable under the same contract ; but as the men
working on the terms usually made, cannot often afford to dress
the coarser parts of what they raise, they reject it, and it is let to
others who stamp and clean it, having a proportional price likewise
in the way of tribute.

The tutwork is divided into lots, called dargains ; each bargain
requiring a certain set of men, and the gang so employed is always
called a pair of men, let the number be what it may. Shafts have
from 4 to 12 men, levels from 2 to 6 men ina fair: one usually
agrees for the whole, and he is called the taker.

The tribute is set in pitches, each including a certain defined
space of ground, limited very accurately, and each pitch employs
from 2 to 6 men.

Dressing is set in bargains, and generally each to one man wha
employs the women and boys who assist him.

The day or two before the setting is occupied by the captains in
measuring all the work done on tutwork in the shafts, levels, &c.
and in carefully viewing the tribute pitches, so as to estimate nearly
what each ought to set at. From these observations an accurate
list and statement is made out, which the managing captain refers
to in conducting the setting.

About the middle of the day the men are summoned and assemble
in considerable numbers, as not only those who worked in the
mine the former two months, but all such as are in want of employ
attend on these occasions, which indeed is the cause of the com-
petition so often observed.

of the Mines of Cornwall and Devon. 319

The business begins by reading over what is called a general
article, or set of rules and conditions subject to which every con-
tract is made, and which article prescribes fines for fraud or neglect
in the performance of the work.

When this is read the managing captain generally begins with the
tutwork, and puts up a shaft or level, declaring the number of men
required, and sometimes limiting the extent of the bargain to a
certain depth or length. The men who worked it last usually put
it up, asking frequently double what they mean to take ; this they
do, not so much in the expectation that it will influence the agents,
as with the view of deterring other men from opposing them.
Offers are then made at lower prices, which go on until no one is
inclined to bid less, when the captain throws up a small stone,
and declares who is the last offerer. It seldom happens that the
price bid is so low as the agents deem equivalent, therefore it is
understood that the last man is only entitled to the option of closing
the contract upon the terms to be named by the captain ; these are
therefore immediately proposed, and if refused, are tendered to the
others in the order of their offers.

This plan reserves the power to the agents of withholding, in
case of combination, while the men, though they may not in the
first instance bid down to the price they mean to work for, seldom
risk a refusal when the captain’s offer is made, if they think it near
the mark, least others should instantly accept it.

The tribute pitches are set in the same way, the place intended
to be worked being described, with a stated number of men, and
the offer being made at so much in the pound, that is, a certain
sum out of every twenty shillings worth of ore raised and sold.
The tribute may vary from threepence in the pound to fourteen or
fifteen shillings,

320 Mr. TAyLor on the Economy

’ The Tutwork men divide their pairs into lesser gangs, called
corps or cores,® each corps consisting of two or three men; they
work alternately, relieving each other throughout the twenty-four
hours. ‘Thus a pair of six men will divide into three corps, each
working eight hours a day.

An account is opened at the counting-house with the taker or
principal man of the pair, wherein he is debited with the value of all
tools delivered to him by the smith, and the expences of sharpening
and repairing them during the taking, or term of the contract, also,
with the candles, gunpowder, and other articles used by him and his
partners, with the charges on hauling up the waste to the surface, and
likewise with cash advanced, called szbsist. After the taking is out,
the account is eredited with the amount arising from the measure-
ment of the ground at the agreed price, and with the tools and other
articles returned unemployed. ‘The pay-day is generally about a
fortnight after the taking ends, when the balances are paid.

Tribute pitches require much more calculation in estimating
the price at which they can be worked, and a more complicated set
of accounts during their progress.

The proportion of the value of the ore to be allowed the work-
men, must depend on the amount they can procure in a given time
and at a given expense. Therefore the size and productiveness of
the lode, the hardness of the ground, the quality of the ore, and the
cost of hauling to the surface, as well as dressing it for sale,
and the market price of the metal, are important elements in the
calculation. |

To the habit of investigation induced by this plan of payment
may probably be attributed a great deal of the intelligence obser-’
vable among the Cornish tributers, and to the desire of making

* See Pryce.

/

of the Mines of Cornwall and Devon. 321

the most of their talents by looking after pitches, which though
unproductive in present appearance, may improve in working, is :
Owing a great proportion of the lesser discoveries constantly made,
and which contribute in no small degree to the profit of the adven-
turers. |

The tribute work of Cornwall may be thought to be similar
to what is done in many other mines, as in Derbyshire, where the
men raise the ore at what is called a cafe, or at a certain sum for
every ton of ore they may produce. But it will appear that though
this approaches to the Cornish plan, yet that it falls very short
of it. .

The payment in Cornwall being in exact proportion to the
selling value of the ores, which is there settled very accurately
according to the metal contained’ in them, not only instigates the
miner to dicover and produce as much as he can, but leads him
to consider every circumstance which may diminish the expence
of returning it, or may enable him to produce the.greatest quantity
of each metal at the lowest charge of dressing as well as raising.

The tributor’s account is charged with tools, materials, and
money, in the same way as that of the tutwork men, and they
are likewise debited with the wages of the persons employed to
dress their ores. The credit side of their account is not closed until
the ore is actually sold and weighed off to the smelting companies
who may purchase from the mine, as the value of every tributor’s
parcel is compared with the aggregate assay and sale, before they
are settled with, and the differences, if any, divided among the
whole, by an increase or drawback on each.

In the copper mines, when a tributor’s parcel of ore is ready,
it is weighed off by one of the captains, and turned over to the
general heap, or as it is called, the public parcel, at the same time

WAC IER Li Zs

322 Mr. Taytor on the Economy

samples are very accurately taken and sealed up. One of these
samples is delivered to an assay master for the mine, another the
miner takes to have it assayed if he chooses, and a third is reserved
for re-trial in case of dispute. After the market-price of copper
has been determined by the result of the sale which governs the
settling, the price of each parcel is made up according to the assay,
and from the amount of the whole the tribute is carried to the
credit of the taker, and the balance settled at the following pay-day.

The rate of earnings in tribute is extremely uncertain, and the
employment is consequently speculative in a great degree. Ifa set
of men working on a poor part of the lode where they may have
agreed for seven or eight shillings in the pound, discover a bunch
of ore rich enough to set at two or three shillings, they earn money
very rapidly, and instances have often occurred where a set of
miners have divided more than one hundred pounds a man for two
months work. On the other hand, when the lode fails, and becomes
poor, being obliged to go on with the contract, the men may at the
end have their account in debt, not having even enough to pay for
the articles they consume.

The cases of extraordinary earnings probably benefit the owners
of the mine much more than those in which the men are indiffer-
ently paid. They are not likely to happen often, and when they
do, they are attendant on some discovery favourable in the first
instance to the men, but eventually much more so to the owners.
They produce great energy and activity not only in those who
benefit from them, but animate all the others, who increase their
exertion in hopes of some similar discovery ; they encourage com-
petition, and frequently bring neglected parts of the mine into
effective and profitable working.

Dressing the ores by tribute tends to produce accurate calculation

of the Mines of Cornwall and Devon. 323

as to the amount of labour which can be afforded to all the different
varieties, and it has become therefore the common practice to re- ,
gulate these processes by a constant reference to the assay, which
prevents a waste of metal on the one hand, or a useless expence on
the other.

“4, The purchase of the Materials employed jor carrying on the
undertaking.

This part of the economy of the mines of Cornwall has been cen-
sured, inasmuch as the concerns are often supplied by a part of the
adventurers who are dealers in the articles required, and who there-
fore have a concurring interest in allowing exorbitant prices and an
unlimited consumption.

Where the majority of the property of a mine is in the hands of
those who look to their contracts for the supply of materials as a source
of profit, no check can well be devised to guard the interest of the
other adventurers, and it might become a question with any person
about to engage in a mine under such circumstances. But where
the mercantile part of the adventurers hold a smaller part of the
property, contracts of this sort, and the appointment of agents
being under the controul of the majority, they may easily take
measures to secure the purchase of all articles at a fair price, with-
out depriving their fellow adventurers of that preference which
their interest in the mine fairly entitles them to.

5. The Sale of the Ores from the Mine Adventurers to the
Smelting Companies.

Tin ores are smelted in Cornwall at smelting-houses belonging to
different persons who are likewise generally adventurers in tin mines.
2s 2

324 Mr. Taytor on the Economy

Copper ores are mostly smelted in South Wales, near Swansea,
being carried there on account of the great quantity of coal required.
There is however one copper smelting establishment on the northern
coast of Cornwall.

The sale of tin ores is not very well conducted, as the miner is
obliged to carry them to the smelting-house where they are assayed,
and the parties make the best bargain they can.

The smelting copper ores is a much more difficult operation than
that of tin, and requires a very expensive establishment and the
investment of an immense capital.

There are about 15 copper companies, and they have all agents
and assay officers in Cornwall; there is a weekly meeting at some
place near the great mines, called a ticketing, where all the agents of
the copper companies attend. At these ticketings the ores of different
mines allotted in suitable parcels are offered tor sale.

Due notice having been given of the ores intended to be sold on
a particular day, an agent of the smelting companies attends at the
mine some time before the day of sale to take samples of the different
parcels. ‘The ores are prepared for this purpose by being placed in
regular heaps called doles, each lot of ore being equally and carefully
divided into six doles. One of them is fixed on by the buyers’
agent, which after being well turned over and accurately mixed, is
rounded into a regular form, and then a trench is cut through the
middle, from the sides of which the sampler scrapes uniformly a
certain quantity. A portion of this is then taken, bruised and sifted,
and from it a sufficient number of samples are packed up in bags,
which are carefully sealed and sent to the assay masters of all the
copper companies.

The buyers are thus furnished with the exact produce of fine
copper in each parcel which will be submitted for sale at the ticket-

of the Mines of Cornwall and Devon. 325

ing, and by calculating the market price of the metal and the smelt-
ing charges they govern their affairs.

The meeting is attended by the agents and adventurers of the
mines as well as by the agents of the copper companies, and one of the
former usually presides. The offers for each parcel of ore are made
by the buyers’ agents handing to the chairman a note or ticket con-
taining a fixed price per ton, he opens and reads out the whole,
when the ‘highest offer is at once declared the purchaser.

The ores remain on the mine for a given time, when an agent of
the copper company attends to weigh them, and they are afterwards
conveyed to the coast for shipping to Wales.

Copper ores do not bear a price exactly proportioned to the
quantity of metal they contain, some ores being more intractable in
the fire than others or yielding copper of an inferior quality.

From repeated experiment the smelting companies know the effect
that the mixture of particular ores has in the furnace upon each
other, depending on the nature of the mineralizing substance or the
kind of matrix which enters into the mass. On this account they
regulate their offers by the quality of the stock they have on hand,
or they manage so as to purchase ores from mines which may best
suit to mix with others which they have previously bought. Thus
it is well known that the produce of some mines does not bring the
price that its proportion of metal would entitle it to, while that of
others, more esteemed by the smelters, always bears a higher relative
value.

It remains to say a few words on the subject of mines considered
as property, particularly as shares in these undertakings are now fre-
quently bought and sold at a distance from the districts in which
they are situate, and as their value is not often appreciated according
to correct data,

326 Mr. TAyLor on the Economy

From what was said of the arrangements between the parties who
undertake a mine by a joint adventure, it may be concluded that a
share in a new concern costs no more to the original holders than
the proportion of the expences actually incurred. As the mine pro-
ceeds, every adventurer may value his share according to his own
opinion of the prospect of success, and therefore considerable diver-
sity in this respect may arise. In some concerns the value of shares
may rapidly improve by the discovery of ore or favourable symp-
toms, and be soon estimated at much more than the amount of cost
paid; in others, the chance of success may be constantly lessening,
and a reduction in the value of shares will be proportional.

The value of property even in mines that are established and
productive, cannot be determined by any definite rule. ‘They are
liable to great and important changes, leading from great gains some-
times even to considerable loss, and on the other hand emerging from
a state of nearly balanced cost and return to that of great and rapid
profit.

The rate of gain for any given time forms no true criterion by
which to judge of the value of mines, though it is the one by which
most who purchase or sell without sufficient experience are usually
guided. A concern still profitable to a considerable degree, may have
all the symptoms of speedy decay, while on the other hand mines
which are producing but little, or are even yet burdensome to their
proprietors, may be those in which the greatest chance of ultimate
success is probable.

Mining has often got into great disrepute as a mode of employing
money, from a want of due consideration of all these circumstances
in the persons who have engaged their property in this way ; artful
men may have aided the delusion in many instances, and in many
others a pertinacious adherence to adventures of but little hope may
have aggravated the disappointment.

of the Mines of Cornwall and Devon. 327

On the whole probably mining does not yield any great profit to .
the adventurers, but there are numerous cases of extraordinary gain,
and these are probably nearly balanced by more numerous concerns
in which loss is incurred, the latter however, if taken individually,
being generally much less in amount than the former.

From this it will follow that the chances of success are against any
single mine at its first undertaking, and on the whole in favour of a
greater number, when conducted. with skill and honor.

XV. On the Origin of a remarkable class of Organic Impressions
occurring in Nodules of Flint.

By the Rev. -Wittram Conysearr, of Christ Church, Oxford, M.G.S.

Te suite of specimens accompanying the following notice are
submitted to the inspection of the Geological Society, as illustrating
the history of certain organic impressions which are found occur-
ring in the flinty nodules of the chalk strata, and of which the real
origin had previously escaped detection.

Mr. Parkinson, is I believe, the first naturalist who has noticed
similar specimens ; the following description of them is given in the
second vol. of his valuable work on organic remains, and it is not
possible to convey a more accurate idea of their external characters.

“* Small round compressed bodies not exceeding the eighth of an
inch in their longest diameters, and horizontally disposed, are con-
nected by processes nearly of the fineness of a hair which pass
from different parts of each of these bodies, and are attached to the
surrounding ones; the whole of these bodies being thus held in
connection.” Page 75, 76.

Mr. Parkinson proceeds to conjecture “ that the formation of
these bodies has been the work of some animal of a nature similar
to the polypes by which the known Zoophytes are formed.” He
therefore classes them among fossil corals of unknown genera,
acknowledging at the same time that the circumstances which in-
duced him thus to arrange them were very slight, and that they

Mr. CONYBEARE on the origin of Organic Impressions, ce. 329

differed essentially from every zoophyte, recent or fossil, with which _
he was acquainted.

The impressions in question are generally found in a state
of such indifferent preservation, and afford such insufficient data on
which any conjectures concerning their formation can be founded,
that we shall not be surprised to find the more perfect specimens now
submitted to the Society, decidedly militating against the hypothesis
proposed by the able fossilist above cited, and proving that the real
origin of these bodies is widely different from that which he has
assigned, they being in fact siliceous casts moulded in little hollow
cells excavated in the substance of certain marine shells ; the work
perhaps of animalcules preying on those shells and on the vermes:
inhabiting them. It is almost unnecessary to add that these casts,
like the screw stones of Derbyshire, must have been formed by the
infiltration of the siliceous matter while yet in a fluid state into’
the cavities of the shells which it enveloped, and that they have
been laid open and denuded in the specimens at present under con-
sideration, by subsequent exposure to some agent capable of dis="
solving and removing the calcareous matter of the shell which
formed the matrix, while the siliceous impression resisted it and re-
mained unaltered.

My first suspicion of these facts arose from a minute examina-
tion of the specimen represented in the drawings by fig. 1, Pl. 14.
It presented several appearances which seemed to indicate the fol-
lowing conclusions. .

1, That the flat surface of flint over which the globules are in
that specimen distributed, had been originally occupied by a large
piece of the striated shell, the fragments of which occur so abund-
antly in the chalk-strata and accompanying flints, being very com-
monly considered as mutilated portions of a fossil pinna.

VOL. Il. 2T

330 Mr. ConyBEAre on the Origin of a remarkable

2. That the globules themselves were casts moulded (in the
manner already described) in cavities existing in the substance of
the shell in question.

The most important of the appearances from whence these con-
clusions seemed to be deducible were the following.

The flat surface occupied by the globular bodies at one extre-
mity of fig. 2. is terminated by the perpendicular face or escarpment.
(if I may so employ that term) formed by a portion of the flint
elevated a little above the rest; and this escarpment will be found
marked with minute vertical striz, seeming to indicate that it had
been moulded against the edge of a fragment of the striated shell,
already alluded'to; similar strie are observable round the edges of
another elevated portion towards the centre of the specimen, in some
degree resembling the mill-marks round the edge of a coin, and
they again occur on both sides of a small vein, or rather dyke of
flint traversing a cluster of globules, and cutting many of them
through the middle. This striated dyke had therefore all the cha-
racters of an impression formed ina long and narrow fissure of the
shell in question, and was connected with the globular bodies in
such a manner that the formation of the latter could scarcely be as-
signed to any other cause than that which produced the former.

In order to represent these appearances more clearly to the eye,
several slight liberties have been taken in the drawing fig. 1. the
relative position of some parts of the original specimen has been
changed, and to the indications in question, a more prominent cha-
racter than they really possess has been given. The small scale of
the general outline fig. 1. not exceeding one of the original: size, has
rendered this more necessary ; but in fig. 2. a detached representa-
tion of the siliceous dyke traversing the globular bodies has been
added, on a scale rather larger than the original.

class of Organic Impressions, se. 331

Desirous of pursuing the indications afforded by the circum- |
stances above specified, I proceeded to examine many specimens of
flint containing fragments of the striated shell in which the substance
of the shell itself was still preserved, and in several instances ob-
served evident traces of the siliceous globules of the cast, imbedded
in- their testaceous matrix ; by submitting such specimens to the
action of a diluted acid, that matrix was easily removed, and the
casts themselves thus laid open by the destruction of their envelope,
exhibited a perfect resemblance to the specimens previously de-
scribed ; the origin therefore which: my former conjectures had
induced me to attribute to those specimens now received the con-
firmation of a decisive experiment.

The two compartments of fig. 3, exhibit representations of a
specimen of the kind last described, before and after its denudation
by the action of the acid. The specimen itself from which the
latter draught was made, is submitted to the Society, together with
the remainder of the mass of flint from which it was broken in an
unaltered state.

The succeeding figure (4.) exhibits, on a scale rather enlarged,
a section carried vertically through a part of the specimen just de-
scribed. Thecellules forming the matrices of the globular casts will
be seen in this section to have occupied nearly the whole thickness
of the plate of shell. ‘The numerous filaments extending between
the globules in every direction, preserve the traces of as many minute
tubes in which they must originally have been moulded, and
it will be farther perceived that each globule is connected with the
flinty envelope immediately above and below its centre by two
thicker stems resembling the extremities of a projecting axis.

The next specimen of the suite (fig. 5.) is a large fragment of

some nondescript shell of the same striated structure ; on a part of
2.02

332 Mr. ConyBEARE on the Origin of a remarkable

its fractured margin a range of hollow cellules will be observed
similar to those which in the earlier specimens have been occupied
by the infiltration of silex. In the present instance the specimen
has been imbedded in chalk only, and the removal of that soft sub-
stance has exposed the ccllules in their empty state.

_ I have assigned the succeeding figure (6.) to a very interesting
specimen, for the use of which I am indebted to Mr. Parkinson ;. it
exhibits nearly the entire cast of a striated shell supposed by Mr. P.
to be similar to that which Walch has described under the name of
the Ostreo-Pinnite ; the shell in which this cast was formed, must
have become in places almost entirely cellular in its texture from
numerous perforations of the kind so often alluded to, since the in-
ferior margin of the upper valve is completely studded with a con-
geries of their globular casts of every size from that of the head of
the smallest pin to discs of the eighth part of an inch in diameter.

Fig. 7. represents a very delicate groupe of minute globules,
which requires the assistance of a magnifying lens before its ana-
logy with the preceding specimens can be perceived. To the naked
eye it rather assumes the appearance of a coralloid ; a magnified
delineation of the same groupe is added, it is copied from a part of
a large white flint found at Heytesbury, in Wiltshire, over the sur-
face of which many such groupes are scattered, accompanied with
impressions of fragments of the striated shell described by Da Costa
as a patellite (Elements of Conchology, p. 142.): it is the flatter
variety of the two which he describes, and it resembles that figured
by Mr. Parkinson. Organ. Rem. Vol. 3. Pl. 5. fig. 3.

In all the preceding instances, the shells in which the cellules have
been originally formed, have belonged to one class of fossil sheils,
the class (namely). which is distinguished by a striated texture
similar to that of the recent pinna marina.

class of Organic Impressions, &c. 333

Owing to the great brittleness resulting from this texture, the
specimens of such shells hitherto obtained have been found in too
mutilated a state to authorise any definitive opinion with regard to
their systematic classification. We may however securely venture to
pronounce from the data in our possession, that there must certainly
have existed more than one species, and most probably more than
one genus of shells in which this structure prevailed; some of the
fragments found may perhaps have belonged toa fossil pinna, others
appear rather to resemble parts of a shell of the genus ostrea. Da
Costa’s conjecture formerly cited, which refers them to the patella
does not seem to be grounded on sufficient evidence.

Had the cellular excavations occurred only in shells of this class,
concerning which our information is so imperfect, it might have
been conjectured perhaps that they resulted from an original pecu-
liarity in the organization of such shells, but the occurrence of an
impression evidently moulded in similar cellules on the surface of a
cast of the echinus has proved that this cannot be the case. The
specimen alluded to is represented in fig. 9, the conjecture there-
fore originally proposed, namely that these cellules were the work
of animalcules preying on the shells, and on the vermes inhabiting
them seems to be the simplest manner of accounting for their for-
mation.

I might perhaps cite the specimen represented in fig. 8, for
the same purpose with that last referred to, as affording another ex-
ample of a similar cast formed in a body distinct from the striated
shell ; in this specimen a beautiful groupe of globules is seen occupy-
ing a conical hollow sunk into the substance of a flint pebble, and
apparently formed by the impression of the pointed end of a belem-
nite. It is fair however to state, that together with fragments of
the striated shell, certain testaceous bodies of a tapering cylindrical

334 Mr. ConyBEARE on the Origin of a remarkable

figure (which have seemingly constituted processes attached to such
shells) are not unfrequently found in the chalk strata, and that the
last in question may possibly have been moulded in a fragment of
this. The specimen itself is from the collection of Mr. Parkinson,
to whose kind assistance during the course of these enquiries, I am
happy to acknowledge myself much indebted.

I cannot conclude without apologizing to the Society for having
occupied so much of its attention, by minute details which I fear
may have appeared extremely jejune and uninteresting, as they are
confined to the illustration of an insulated fact in the history of
organic remains, in itself of very inferior importance, and cannot be
said to throw any additional light on the general views even of that
branch of geological science with which they are connected.

Since writing the above I have received from my friend Mr.
Buckland the following observations relative to this subject, accom-
panied by a recent specimen which appears to illustrate them in a
very satisfactory manner.

“The hollows that afforded a mould for the formation of these
singular bodies, appear to me to have been the work of some minute
parasitical insect. The small aperture, the cast of which now forms
the projecting axis of each globule, was probably perforated by this
intruder as the entrance to his future habitation ; having completed
this passage, and excavated at its termination a cell suited to his shape
and convenience, he appears by the aid of a delicate auger or pro-
boscis to have drilled many minute and almost capillary perforations
into the substance of the shell on every side around him, taking
care to leave always partitions sufficient to support the thin ex-
ternal plate of shell which formed the roof of his apartment.
Having exhausted all the nourishment which could in this manner
be procured with safety from the vicinity of this first establishment,

class of Organic Impressions, °c. 335

the insect appears to have emigrated, and after working for itself a
lateral passage to a sufficient distance, to have formed a new settle-
ment in the midst of fresh supplies. In the recent oyster shell which
I have transmitted, you will perceive that this process has been car-
ried on to a great extent, in the intermedial matter between two or
three sets of the pearly plates comprising it ; and yet without effecting
the destruction of the exterior crust, or in any degree injuring the
inner surface of the shell, which remains untouched, and, notwith-
standing these attacks, still equally adapted to every purpose required.
by the ceconomy of its inhabitant.

XVI. A Description of the Oxyd of Tin, the production of Cornwall ;
of the Primitive Crystal and its modifications, including an attempt
to ascertain with precision, the admeasurement of the angles, by
means of the reflecting Goniometer of Dr. Wollaston: to which is
added, a series of its crystalline forms and varieties,

By Mr. Wit11am Puttutrs, Member of the Geological Society.

"Tar oxyd of Tin, Etain oxyde of the French, Zinnstein of the
Germans, has for many centuries given to Cornwall an important
place in the economical history of nations. It is asserted by Pliny*
that the Phoenicians visited its coasts, and carried on a lucrative
commerce in tin with its inhabitants.

Cornwall is justly celebrated not only for its inexhaustible stores
of this valuable substance, but for the superior quality of the sub-
stance itself; for, according to Klaproth, it is purer than that of
Bohemia and Saxony, as it contains both less iron and less arsenic:
and although the oxyd of tin is or has been found in almost every
district of Cornwall, it is nevertheless one of those substances which
are the least abundantly dispersed throughout the globe.f Many
considerable countries are entirely without it; but it is found in
Gallicia in Spain, in Bohemia, in Saxony, in Banca and Malacca in
the East Indies, and in Chili in South America.

* Lib. iv. cap. 34. + Brongniart, p. 192.

Mr. Witir1aAm PuiLuips on the Oxyd of Tin. 337

Brongniart says,* that “ tin belongs exclusively to primitive coun-
tries, and even to those of the oldest formation ; for not only is it
found in veins and beds in granite, but also in masses, or dissemi-
nated in beds of gneiss, of micaceous shistus, and of porphyry. Veins
of tin adhere very often to the walls of the lode, by the rock which
encloses them; they are always divided by other veins, and never
divide them. ‘Tin therefore seems to be one of the metals of the
oldest formation: it is accompanied by substances which belong to
the same age, such as wolfram, arsenicated iron, topaz, quartz, fluated
lime, phosphated lime, hornblende, green and black mica, chlorite,
&c. whilst carbonated lime, sulphated barytes, zinc, lead and silver,
substances which frequently accompany other metals, are rarely
found with it.” All this may perhaps be true, in so far as it regards
depositions of tin in other countries, but I am induced to believe it
is not wholly so in regard to Cornwall, where veins producing tin
often occur in districts, both granitic and schistose, which it seems
difficult to ascribe to the primitive formation.

Dr. Berger} in his paper on the physical structure of Devonshire
and Cornwall, says, “ Here (Cornwall), as in the Hartz, it (grau-
wacke) is very rich in ore.” In the term grauwacke, Dr. Berger,
following the example of Werner, seems to include every species of
that rock, usually called schist, and by the miner killas. He further
says{, ‘‘ Grauwacke is one of the oldest of the secondary rocks.”
Again,§ in speaking of the discovery of uranium in Tin Croft
taine, which is situated at the foot of a granitic hill, but partly in
eranite and partly in schist, its “* being found in this district proves
that, contrary to the opinion of Werner, it may be met with in
secondary mountains.”

* Traité Elem. p. 191. + Geolog. Trans, yol. 1. p. 113.
fp. 111. - §p. 176.
VOL. Ii. Zu

338 Mr. W1LL1AM PuILuiPs on the Oxyd of Tin.

The above quotations from Dr. Berger’s valuable paper are
given solely with a view of shewing it to be his opinion that at
least one district of Cornwall, producing tin, is not primitive.
This has long been my opinion of that district, as well as of other
parts of that county in which tin is found: and I cannot doubt
but some specimens of granite in my collection from different
places, enclosing tin, tend to confirm that opinion, But it may
be well to await the developement of many facts, which yet
remain requisite to the better understanding of the geology of the
county, as well as the light that might be thrown on the subject
by a more perfect agreement in the use of geological language.

The existence of tin in the native or pure state is no longer
believed. It was admitted by Romé de Lisle to have been so found,
from the examination of a specimen from Cornwall under that name,
which, by the description he has given of it, seemed to partake of
the exterior appearance of molybdena. I possess a specimen of
tin, found in the neighbourhood of St. Austle in that county, which
with two or three others was arranged in the collection of my late
uncle, now in my possession, under the name of native tin. It is
almost coated by a ferruginous rust, and on one of its larger sides
there are numerous portions of a very hard substance resembling
iron, in which are embedded minute pieces of quartz; on this side
I presume it to have been deposited. ‘I'he fracture in some places
is that of the finest steel-grained sulphuret of lead. The more
pure parts of it easily flatten under the hammer, and fall off in small
scales, which crackle between the teeth and easily yield to the
knife. This specimen seems very much to agree with some found
in France by Schreiber, an account of which he has given in the
Journal des Mines, except that those were accompanied by a
white substance, which proved to be the white muriate of tin.

Mr. WitirAM PHILurps on the Oxyd of Tin. 339

Those specimens which heretofore were called native tin, are now
generally believed to have been accidentally left by the smelters
of the ore, and wherever it is discovered, the place may fairly be
supposed to be the site of a smelting-place. It has now obtained
the name of Jews-house tin.

The oxyd of tin is rarely found in Cornwall free from an
admixture with other substances, but in this state it has been
produced in masses of considerable size. From the mine called*
Polberrow in St. Agness, one block of tin ore was raised weighing
1200lbs. which produced more than one half of metal. The oxyd
of tin seems to occur almost uniformly in a state of crystallization,
with whatever substances it is intermingled, or however minute its
portions, in the common tin-stone of the mines. It is rarely found
in shapeless masses, except, indeed, the rounded grains of alluvial
deposition; and even amongst these many appearances of crys-
tallization, but mostly of the macle, may be noticed. Not only are
the same crystalline forms generally apparent on each cabinet specimen,
but even entire veins seem to be productive principally of the same
varieties. In the tin-stone of Polgooth near St. Austle, I have rarely
seen any other than minute crystals of the form of fig. 66, Pl. 18.
That produced by Pednandrae, an extensive tin mine close by the
town of Redruth, is almost uniformly of the macle described by
fig. 208. Pl. 25. From Huel Fanny mine, which produced tin
only in the shallow part of the copper vein," I have never observed
any other forms than those described by figs. 108. Pl. 20. and 160.
and 162. Pl. 22. and many of the crystals figured in the series of
the 7th and 9th modifications, have, I believe, only been brought
from Relistian mine. If it should hereafter more generally appear

* Pryce, Min. Corn. p. 68.

Zing 2

340 Mr. Wini1AMm Puiiuips of the Oxyd of Tin.

that some modifications of the primitive crystal of this substance are
principally the production of particular districts, as I am led to
suspect will be the case, might not an investigation of the nature and
peculiarities of the veins, and of the country through which they
pass, tend to throw some light on the circumstances, or laws, by
which the several modifications are produced: may not these cir-
cumstances be supposed in some degree to depend on the purity of
the substance itself, or to be affected by the various proportions of
other substances entering into combination with it? The Bohemian
oxyd has not hitherto been observed to assume so great a diversity
of crystalline forms as the Cornish, which by the analysis of
Klaproth already noticed, appears to be by far the most pure.

The crystals of this substance from Bohemia are generally much
larger than those from Cornwall, but Pryce mentions one he had
seen that weighed upwards of two ounces. Very large crystals,
mostly of the macle, I believe, were found in Seal-hole and Trevonance
mines in St. Agness; in the former they were lying loose in the
vein, and were conveyed without first breaking or purifying them,
immediately from the mine to the smelting-house. Some have also
lately been brought from a mine in the neighbourhood of the
Tamar, and others from near the Land’s End; but instances of this
kind are by no means common. The crystals of this substance are
generally in part imbedded in the matrix; they are not commonly
so disposed as to shew both paramids, and are sometimes confusedly
grouped, but this appearance of confusion principally arises from a
circumstance which will be hereafter explained in speaking of the
macle, to which the oxyd of tin is so liable. The crystals are rarely
disposed in radii, but I have one specimen on which they are so
disposed. Radiated schorl has often been mistaken for tin, to
which it frequently bears considerable resmblance.

Mr. Wini1am Purtires on the Oxyd of Tin. 341

The oxyd of tin sometimes occurs in form and appearance very |
similar to the hematitic iron ore, from which it is easily dis-
tinguished by its superior weight. In this state it is mostly in
fragments, either straight or diverging, wedge shaped or splintery,
rarely rounded and reniform ; those fragments of which the fracture
is fibrous, have a silky lustre; its colour is brown of different
shades, passing into brownish-yellow, which are ranged in alternate
bands; it gives a’shining yellowish-brown streak, and is opaque,
hard, brittle, and easily frangible; its spec. grav. is 6.45. This
mineral from its occasional resemblance to wood, has obtained the
name of wood tin, and is the Kornisches zinnerz of Werner, the
Etain oxydé concretionné of Hatty. Before the blowpipe it
becomes brownish-red and decrepitates, but is not fused or reduced
to a metallic state: when strongly heated in a charcoal crucible, it
affords, according to Klaproth, 73 per cent. of reguline tin. It has
hitherto been found only in Cornwall, in the parishes of St. Columb,
St. Roach and St. Dennis, in alluvial beds accompanied by stream
tin; it is rare, and occurs only in small pieces.*

Klaproth mentions “a kind of wood tin, from Maddern in
Cornwall. This is only found in small separate hemispheres, of
the size of a divided shot. The surface is smooth and brown, but
the inside or nucleus is of a light brown and of a whitish-yellow
colour, and slightly radiated. These stalactitical hemispheres,
which, as one may see, have been fixed to other bodies, are similar
to the small spherical protuberances of wood tin, except that the
latter are not so hemispherical, but flatter.” + This substance, I do
not remember to have seen in the form above described, but some

rounded portions of tin were given to me by a Cornish gentleman

* Aikin Chim, Dict. art. Tin. + Klaproth on Fossils of Cornwall, p. 21.

342 Mr. WILLIAM PHILLIPS on the Oxyd of Tin

some years ago, under the name of pea tin, perhaps from their
size. ‘They have evidently been rounded by attrition, and appear
to be a species of wood tin from the variation in colour on the
surface, which is generally of a hair-brown.

There is in my collection, a specimen, which I took from the
heaps of tin on Poldice mine, that is of remarkable character.
The general mass is of a light brown colour; minute veins of
different shades of brown and black tin alternate in bands in the
same direction. It is compact and hard, but not brittle, and gives
sparks with a steel; its fracture is uneven. It may be well sup-
posed from its great weight, to consist almost wholly of the oxyd
of tin. It is accompanied by the black oxyd on one side, and
very minute veins, apparently of quartz, traverse it in various
directions.

Alluvial depositions of tin of considerable extent and depth have
been found in several parts of Cornwall, which it is believed, is the
only part of Europe in which tin occurs under these circumstances.
The grains of it, which it may be presumed, are for the most part
crystals rounded by attrition, are mostly very small, and sometimes
exhibit marks of crystallization, generally of the macle. Stream
tin affords from 65 to 75 per cent. of the purest grain tin. Its
freedom from arsenic perhaps arises from the ore collected in the
stream works being detached portions of the pure oxyd. And its
presence in the regulus of tin procured from the ore of the veins
may be supposed to arise from its being frequently accompanied
by arsenicated iron, It is somewhat remarkable that the only
traces of gold to be found in Cornwall, are in the stream works,
in which it sometimes occurs in small grains, mostly detached, but
occasionally accompanied by quartz. A few years ago, a specimen

of considerable size was discovered, I believe in Carnan stream

Mr, WiLL1AM PuiLuips on the Oxyd of Tin. 343

work, containing it is said the value of ten or eleven guineas in
weight of gold. It is in the collection formerly belonging to the
jate Philip Rashleigh, Esq. of Menabilly.

Tin is not found mineralized by any other metal, and rarely in
intimate combination with any other, except with copper in that
mineral which is known by the name of sulphuret of tin. This
substance has also obtained the names of bell-metal ore and
pyritous tin. It is the Zinnkies of the Germans, the Etain
pyriteux of the French, and has hitherto only been discovered in a
mine called Huel Rock in the parish of St. Agness, in mass, never
crystallized.* According to Klaproth, it contains tin 34, sulphur
25, copper 36, iron 2. Its colour is steel-grey, passing into
bronze-yellow, in some parts inclining to silvery. Its fracture is
unequal and granular. According to Klaproth, its specific gravity
is 4.350; under the blowpipe it emits a sulphureous odour, and
passes into a blackish slag: it gives a yellow tinge to glass of borax.
Its lustre is metallic. It is brittle and easily frangible.

Among the specimens of oxyd of tin in my collection, it may be
observed occurring
In Granite—in minute crystals interspersed through granite, from the

south-west side of St. Michael’s Mount—in granite, with chlorite

and schorl from the south side of Redruth Church-town—with
schorl in granite from near St. Just. In decomposing granite
from Polgooth mine.

* Kirwan has described this mincral as “‘ Tin mineralized by sulphur and associated
with copper.” On this definition Hatiy has the following remark, ‘* It may be proved
by other examples, that this celebrated chemist is of opinion, which appears to me to be
well founded, that a principle that presides in regard to quantity, may be only an
accessary. Mineralogy will have made a great stride towards perfection, when this
distinction between essential principles and those which are only accidental, shall be
correctly applied to all minerals to which it strictly appertains.”

344 Mr. WiLi1aM PHILuips on the Oxyd of Tin.

In Schist—both micaceous, and of other descriptions from St.
Agness—in small veins passing in various directions through light-
coloured schist from St. Agness—crystallized, on rounded masses of
aggregated fragments of schist (grauwacke) from Relistian mine.

In Chlorite—from Polgooth mine—in compact chlorite with im-
bedded crystals of mispickel from Relistian mine—on crystallized
chlorite from Huel Unity.

In Schorl—from Huel Unity, and some mines in St. Just.

In Carbonate of Lime—very compact and semi-transparent, from
Polgooth—with rhomboidal crystals of carbonate of lime from
the same place—and with schiefer spar, also from Polgooth.

In Topaz—with quartz and topazes of a light yellow; on topaz in
mass, as I suspect, in which are imbeded crystals of tin and
quartz—with topazes of a greenish cast, imbedded in mica on
decomposing granite—with topazes and chlorite, on granite—
with white topazes, crystallized phospbate of lime, and silvery
mica on granite, from St. Michael’s Mount. Fom what districts
the other specimens were brought is unknown, but they are from
Cornwall.

In Calcedony—covered by white decomposing calcedony and by blue
calcedony ; both from Pendnandrae mine.

In Fluat of Lime—disseminated through brownish fluor, intimately
mixed with chlorite from Pendnandrae—disseminated through
a mass of white fluor, transparent and cpake, and very fusible,
from Huel Unity—with fluor, purple on the surface, quartz and
chlorite on schist, from St. Agnes—imbedded in *Chlorophane,

* The mine called Pednandrae is, I believe, the only one in this country, in. which
chlorophane has been found. I obtained this specimen from it in 1805, which together
with another, also in my possession, in which the chlorophane is almost completely
imbedded in semi-transparent calcedony, is the only specimen that has been neticed. It is

Mr. WitiiaAM Puixuiips on the Oxyd of Tin. 345

accompanied by calcedony from Pednandrae. In searching the
heaps of that mine for the chlorophane, I found several varieties
of remarkably compact fluor *—also enclosing crystals of oxyd
of tin, or accompanied by them.

In Yellow Copper Ore—imbedded with it—coated with yellow cop-
per ore, and accompanied by chlorite—with yellow copper ore
on micaceous schistus—with yellow copper ore, quartz, and
chlorite, from Huel Fanny.

With Blende on quartz, from St. Agness.

In Mispickel—with mispickel on schist.

In Wolfram—with wolfram and dark brown gossan—with wolfram
and chlorite from Pednandrae mine—with the primitive crysta
of wolfram, mispickel and yellow copper ore, from Huel Fanny.

The science of mineralogy is so intimately connected with some
branches of the mathematics, that he who pretends to the former,
unassisted by a knowledge of the latter, may perhaps be considered
as pursuing it rather as an amusement, than as an object of scientific
research. I confess myself to be exactly so circumstanced. The
want of an attachment to the study of the mathematics, led me to

traversed in various directions by minute veins of chlorite, oecasionally imbedding
yellow copper ore and oxyd of tin. It is hard; scratches glass easily ; its fracture is
shattery and splintery. Its general colour is purplish; it is transparent at the edges,
and the fragments are very transparent ; a thin piece held for a short time in the flame
of a candle, emits a brilliant green light, which becomes very brilliant by placing it on
a live coal, from which, if it be taken at about the height of its light, it may be
repeated, though with diminished effect; by frequent repetition it becomes nearly
colourless. It does not fly even in the centre of a common fire.

* Some of these fluors deserve particular notice on account of their exhibiting some
peculiar characteristic differences when compared with common fluor. One large spe-
cimen is of a bluish colour, and is traversed in various directions by veins of what I

Vern. AL Ox

¢

346 Mr. WiLL1AM PHILuips on the Oxyd of Tin.

neglect them in early life, which I have now occasion to regret,
not only as it forbids the pursuit of mineralogy to an extent which
alone would have enabled me to illustrate its objects in a manner
wholly pleasing and satisfactory, but also as it renders me incom-
petent to reap the pleasure and instruction, which the works of those
celebrated men the Abbe Haiiy and the Count de Bournon, are
calculated to convey. It must of course follow, that the only evidence
I can offer in regard to the admeasurement and value of the angles
of crystals, must be wholly mechanical.

I have given much attention in the endeavour to ascertain pre-
cisely the value of the angles of this substance, by the help of that
admirable instrument the reflecting goniometer of Dr. Wollaston,
having been previously assisted in its use by some hints and per-

conceive to be calcedony of a still lighter blue, though where most free from those veins,
the general colour and appearance considerably resembles the chlorophane already de-
scribed. It seems to have formed the principal part of a vein, being accompanied on
each side by decomposing fluor, which has an ochreous crust similar to the gossan of
the mines. On being placed on a live coal it gives a green light, nearly as splendid as
the chlorophane, and does not fly ; but flies when placed in the fire. It scratches glass
easily.

Another kind of fluor also encloses tin, which is of a light but dull brown colour, and
greasy lustre, and is somewhat transparent at the edges. Its fracture is shattery, It
gives nearly the same light as the chlorophane, but flies in the fire, though not when —
placed on a live coal. One specimen, about an inch in thickness, has on one side, a

smaller vein of fluor, enclosed between two minute veins of chlorite, and on the other

side, compact white fluor; attached to each side, is a blue schist, the country of the
mines From the numerous crystals of tin imbedded in some specimens, I am induced to
believe that it ran beside tin in the vein.

~ I found also several other singular varieties of fluor, much harder and more compact
than fluor generally is, of which the fracture is shattery and the colour purplish. When
placed on a live coal, some of them begin by giving a greenish light, which soon changes
to purplish, and afterwards ends in a dark purple. Others, give only a purplish
light, and these do not fly even in the fire. Others give only a light green when placed
ona coal, without flying, but fly when placed in the fire.

Mr, W1uL1AM Puiips on the Oxyd of Tin. 347

sonal instructions from the ingenious and scientific inventor. Be-
fore I had arrived at some tolerable knowledge in its use, so as to be
assured that the smaller crystals only can be relied on, the great
differences which I found to exist in the same angles of the larger
crystals, even though their planes appeared by the assistance of the
magnifying glass, to be undeviating and polished surfaces, almost
tempted me to doubt the utility of the instrument itself. These
differences amounted in many instances to as much as 15’, fre-
, quently 10’; while on the other hand, small crystals, having clear
and perfect reflections, gave a coincidence in the admeasurement

of the same angle.*
I feel therefore warranted in the conclusion that, although occa-

* The reflecting goniometer is so delicate an instrument, that great care is requisite in
the choice of the crystals subjected to it for the admeasurement of their angles. It
often happens that those of apparently the most beautiful surfaces are unfit for this
purpose; the most clear reflections alone can be relied on, and even then only by com-
paring the results of trials on many crystals. Some of the first attempts gave an inci-
dence of 2 on 2 over the apex of the fig. 27. Pl. 16. one way of 92°, 55'. the other way
93°. 20’. or even 93°, 25', and this induced the suspicion that the bases of the two
pyramids composing the primitive octohedron, were not square. The crystals on which
those admeasurements were taken, were, comparatively, large, and thcir reflections were
by no means so clear as those since obtained on much smaller ones, which have con-
firmed the real incidence both ways to be 92°. 55’. and therefore that the common base
of the two pyramids is square.

The crystals of this substance are likewise subject to another difficulty, that of a
double reflection, even on faces which, by the assistance of the lens, appear of the
most perfect kind. I possess a crystal giving two reflections on three of the four faces,
2, 2 fig. 27. which are those of the pyramid commonly observed on the crystals of this
substance. The incidence obtained one way over the apex, with the two strongest re-
flections was, 92°. 55'. with the two weaker 93°. 10’. but with a strong reflection on
one face and a weaker on the other 93°. 5’. On one of the other two opposed faces of
the pyramid, one reflection only was given, but on the other, two were visible; with
the strongest reflection, the incidence obtained was 93°. 35’, with the other, 93°, 25%.

the least of them 30’, above the real value of the angle.

pa Cogs 7 igi : :

348 Mr. WILLIAM PHILLIPS on the Oxyd of Tin.

sional exceptions certainly exist, reliance cannot be placed but on
crystals so small, or rather so minute, as that it may reasonably be
doubted whether it be possible for the most skilful hand to obtain with
accuracy the admeasurement of the angles formed by the meeting of
their facets by means of the common goniometer. The larger crystals
are certainly best adapted to the use of this latter instrument, and
hence, as I conceive, must have arisen, at least in part, the differences
in the results obtained by it, and by the reflecting goniometer.

The admeasurement of the angle formed by the meeting of the
planes 1 and 2 Fig. 27, Pl. 16. is prominently noticed by Hail.
This angle is first given in his Traité as 135°, and secondly in his
Tableau as 133° 29’; the value of almost if not of every other angle
in any degree connected with this, likewise differs very materially.
These circumstances induce the supposition that having assumed
the value to be first 135° and afterwards 133° 29’, the rest were
arrived at by calculation in both instances, and if so, were, of course,
dependent on the truth and accuracy of this single determination.
It is not therefore surprising that they should be made to differ so
essentially in the two works.

In attempting the admeasurement of the angle above noticed,
viz. that of 1 on 2 fig. 27. Pl. 16. the reflecting goniometer I first
employed, being graduated only te 5 minutes, never satisfactorily
gave an incidence of 133, 30, or 133. 35, but generally approached
as nearly to the one as to the other. This caused the suspicion that the
true value lay somewhere between them, and induced the wish fora
goniometer more highly divided ; and I have obtained one graduated
to half a minute, from Mr. Carey, whose ingenuity led him to add to
it some apparatus with a view to precision in its use. By this instru-
ment, I have repeatedly found the angle in question to be 1330 32’.
30”.—being 1°. 27’. 30”. less than the former determination of

Mr. WILLIAM Puiutps on the Oxyd of Tin. 349

Haiiy; and 3’. 30”. more than the latter. It may therefore be

presumed that the value of other angles connected with this, as”
obtained by the reflecting goniometer, differ from those given by

Haiy, both in the Traite and inthe Tableau. I am perfectly aware

that it becomes me to speak with great deference on this subject.

I offer only the results of a mechanical attempt to ascertain the angles

of this substance, being incapable of verifying or of detecting their

fallacy by a recourse to calculation.

The angle formed by the meeting of the planes P P. of the pri-
mitive crystal, fig. 18. Pl. 15. is given by Haity as 67° 42’; by the
reflecting goniometer, I have uniformly obtained from clear re-
flections, an incidence of 67°. 50°. making a difference of 8 minutes.

The incidences subjoined, are, for the most part, the result of
many perfect agreements of each, on different crystals. In no in-
stance has an average result been noticed. All are not to be relied
on with equal confidence. The plane forming the 9th modification
of the primitive octohedron is always so striated, and those of the
3d and 10th, are always so dull, that the incidences of those planes

with any other in the subsequent series can only be considered as

approximations,

Incidence of P on P fig. 18. Pl. 15 - - - 67°. 50’
— P of either. pyramid on its opposed plane over the apex 112°. 10’
———_——— lon P fig. 21. Pl. 16: - - = 14139259
—————- l on 1 fig. 21 - > - - 90°.
—___——_ 1 on 2 fig. 26 d . - - 133°, 32, 30.
————- 2 on P fig. 26 - - - =i 150°. 45%
——-—— 2 on 2 of either pyramid over the intervening edge, fig. 27 121°. 40’.
—————_ 2 on its opposed plane 2, over the apex, fig. 27 . Zee aie
——— ——- 2 on 2 over the plane 1, fig. 27 - - - 87°. 5’
————. 3 on 2 fig. 33 : 2 3 ~ 136°, 35'.2
———_——- 4 on P fig. 39. Pl. 17 5 - - its th Bae = 5

5 on | fig. 49 A » - Fs = 161 35:

350° Mr. WILLIAM PuILuips on the Oxyd of Tin.

Incidence of 5 0n 4 fig. 49 - - - ° - 253° oa
5 on 5 over the plane 4 fig. 49 - - » ». 196°. Aa
——__————. 5 on 5 over the plane | fig. 49 - - ~ 143% 10
——.——— 6 on 1 fig. 60. Pl. 18 - - - . \ioe's aur
—————. 6 on 5 fig. 60 - - - - - (172°. 50
——-——~—— 7 on 1 fig. 66 - - - - Sind? 92h
a One fiz. 70 : - : : ~ 154°, 15'
—_——_———_ 7 0n 7’ fig. 66 - - - - - 159°. 5’
——_——_— 7'0n 7’ fig. 66 - - - - 2 WT TSt OF
————— 9on 1 fig. 114 Pl. 20 - - - wr AGRO ope
————_— 9 on 2 fig. 114 - - - - ~ of ASL, 1088
——-————10 on 2 fig. 164 Pl, 22 - - - =, 150°. 30° 2
—————— 10 on 9 fig. 167 - - - - 498". 15°

Specific Characters.

Primitive crystal—an octohedron composed of two obtuse quadran-
gular pyramids joined at their bases, which are square.

Fracture—mostly shattery, often vitreous; sometimes conchoidal,
sometimes lamellar.

Aspect—non metallic.

Specific gravity*—6,9009—6,9348 according to Hay.
of the crystallized grey tin-stone 6,84, Klaproth.

of stream tin - = - -. - 6,56, ditto.
of another ditto - - - - 6,97, ditto.
of wood tin - - = = - 6,45,- ditto.

Hardness—brittle and easily frangible ; gives sparks with a steel.

* ¢¢ ’t is remarkable enough that tin, which, in the metallic state, is one of the lightest
metals, surpasses in specific gravity, when in the state of oxyd, the greater part of other
substances of the same class, whether simple oxyds or composed of an oxyd with a
mineralizing substance. The weight of oxydated tin is such, that its difference with that
of metallic tin is but about one-twentieth at least ; whilst other metals offer, in analogi-
cal instances, differences which amount to one-half or one-third.” Hauy.

Mr, WILLIAM PHILLIPs on the Oxyd of Tin. 351

Electricity—the coloured portions, when placed in communication
with an electrified conductor, emit bright sparks on the approach
of the finger. Haiiy.

Colour—whitish, cither translucent or opake; it is sometimes of a
resin yellow, but more often of a deep brown somewhat reddish,
more frequently blackish, or black; occasionally brick-red, but
in that case generally bears in some respect marks of having been
exposed to the action of fire.

‘Transparency—the more colourless crystals are generally somewhat
transparent, in which respect they sometimes almost equal com-
mon quartz.

Lustre—resinous or vitreous.

Dust—of a dull ash grey.

Analysis—77,5 tin, 21,5 oxygen, 0,25 oxide of iron, 0,75 silex.
Under the blowpipe it decrepitates; becomes pale and opake;
is reducible in part to a metallic state, but with difficulty.
When heated and melted with glass, it imparts to it a milk white
colour.—Brongniart.

Primitive Crystal.

The Abbé Haiiy in his * Traité de Minéralogie” assigned the
cube to the oxyd of tin as its primitive form, because he thought
he “ perceived the natural joints parallel with the faces of that solid,
although they were not sufficiently determinate to remove all
doubt.” This opinion was combated by Mr. Day in a paper on
this substance, published in an early volume of the Philosophical
Magazine, in which he assumed as its primitive crystal an octo-
hedron composed of the two quadrilateral pyramids commonly seen

352 Mr. WiLiiAM PHILuips on the Oxyd of Tin.

on the crystals of the oxyd of tin, Joined base to base, being those
of 2,2. fig. 27. Pl. 16.

In 1809, a new work of the Abbé Hatiy’s made its appearance,
entitled ‘Tableau Comparatif, &c.” in which he says (p. 285)
that a revision of his researches on the subject of the oxyd of tin,
in consequence of his having obtained some crystals from Cornwall,
proved to him that the true primitive form is, not as he formerly
supposed, the cube, but a rectangular octohedron, of which the
faces answer to 0 0, Pl. Ixxx, fig. 179 and 180 of his former work,
or, which is the same thing, to those of PP, fig. 26, Pl. 16 of the
series attached to this paper. He says further, tnat the joints which
gave this octohedron are extemely sensible on exposing fractures of
tin to a vivid light ; and again, that he has been led to the adoption
of this octohedron as the primitive form by the results of me-
chanical division.

What the circumstances in the mechanical division of the crys-
tals of this substance leading to this result were, have not been
explained, but having been unexpectedly led to the same conclusion
by the cleavages I have obtained, I shall proceed to describe them.

While preparing this paper, with a view of presenting it to the
notice of the Geological Society, and while an attempt at the me-
chanical division of the crystals of the oxyd of tin was on my list
of agenda, Dr. Wollaston informed me that he had succeeded in
obtaining it, in a direction parallel with the faces of the prism, and
I have since had the same success in numerous instances, so as to
procure on the planes of the fracture an incidence of 90° by the
reflecting goniometer,

Thus is the conjecture of Haity before cited, that he perceived the
natural joints parallel with the planes of the prisms verified. I have
also obtained numerous cleavages parallel with the diagonal of the

Mr. Witt1AM Purxuips on the Oxyd of Tin. 3538

prism, but have in vain attempted it in a direction perpendicular to _
its planes. |

In pursuing this subject, it occurred to me that the exposure of
the crystals of this substance to the action of heat, might possibly
lead to some further discoveries. Accordingly, some were placed in
the centre of a common fire during an hour or two, and being after-
wards left to cool I found that a slight touch with a,hammer imme-
diately reduced them into small pieces: a research among these
afforded very many of the above cited cleavages, which I had pre-
viously obtained from crystals that had not been subjected to the
action of heat.

Let fig. 1. Pl. 15. represent the cleavages, which are easily obtained
parallel with the faces of the prism, and fig. 2 its diagonal cleavages.
By a combination of all these in fig. 3, it will be seen that the prism
is divisible into right-angled triangular prisms, of which I have
numerous instances.

In pursuing a research among the fractures, I found several qua-
drangular prisms with oblique terminal faces, parallel with each
other, as represented by fig. 4, and others similar to fig. 5 ; which it
will be obvious differ only from each other in these respects, that the
edges fg and 6 c are replaced by the planes a and 4, and that the
two other edges, a d and e¢ 4, are also replaced by similar planes, all
which planes are parallel with one or other of the diagonals of
fig. 4.

I have other fractures described by fig. 7, which are the result of
a mechanical division of fig. 4 in the direction of its diagonal a 6
and c d, and along the edges c and ad. It follows that fig. 7 is
a right-angled triangular prism with oblique terminal faces, which
in some of these fragments are perfectly brilliant.

If also a section of fig. 4 be made in the direction of its other

VOL. II. 2Y

354 Mr. WILLIAM PuiLuips on the Oxyd of Tin.

diagonal, shewn by the dotted lines e f and g 4, and aiong the
edges fg and e 4; it will be divided into four parts, one of which
will be represented by fig. 8, which is a right-angled triangular
prism with inclined terminal faces: several of these are in my
possession. .

The fractures represented by figs. 5, 7, 8, prove the mechanical
division of the.crystals of this substance, in the direction of both
diagonals; and what has before been said of that in a direction
parallel with the faces of the prism, would suffice without further
proof. If however evidence were wanting, the cleavage described
by fig. 6, decides its practicability beyond a doubt. Having placed
in the fire a macle represented by the dotted lines of that figure,
and of about the same size, I afterwards obtained from it a nucleus
similar to the fig. a 6 c d, represented within it, and of about the
same size, with faces well defined and very brilliant; it is now in
my collection. This nucleus, it will be seen, is of the same form
as that of the macle described by fig. 208, Pl. 25, and resulted
from a cleavage of fig. 6, (which is of the same form as fig. 209)
in a direction parallel with each of its six larger faces; and, as
hereafter will be shewn in describing the formation of those macles,
consequently parallel with the faces of the prism.

Among the fragments obtained from crystals that had been placed
in the fire, I found some quadrangular prisms having one terminal
face similar to that of the upper one of fig. 4, but with indications
of the lower terminal face in the opposed direction as represented
by fig. 9.

On applying the goniometer to the face P and along the edge bc
of fig. 9, I was somewhat surprized at finding that there is no per-
ceptible difference. between their incidence on each other and that
of the plane P, and along the edge 4 ¢ of a crystal similar to fig. 11 ;

Mr. Wittiam Putixips on the Oxyd of Tin 855

and in some instances I obtained perfect co-incidences by the reflect- -
ing goniometer between the faces P and a fig. 9. and those of
P and a, fig. 11. having eight fractures of the figs. 4. and 9. which
permit the use of that goniometer.

On three fragments similar to fig. 9. I have attempted a mecha-
nical division in the direction of the small planes a f ¢ fig. 10.
and have succeeded in obtaining one or the other on each, so as to
warrant the conclusion of the practicability of the whole. It will
be noticed that if a division were still pursued in the direction of
the planes a fe, the consequence would be that the planes on the
summit of fig. 10 would become in form similar to those of
PP fig. 11.

The cleavages obtained by the planes a f ¢ demonstrate the
possibility of a mechanical division parallel with each terminal face
of a crystal similar to fig. 11. The probability of this in two out
of the four directions may be argued from what is known respect-
ing the formation of the macles of this substance.

It was long since determined by L’hermina that the common
macle represented by fig. 186. Pl. 24. as will hereafter be further
noticed, is the result of a section of a common prismatic crystal,
fig. 27. Pl. 16. in a direction parallel with one or the other of the
edges of its pyramid. The planes forming the pyramid of fig. 11.
Pl. 15. are usually considered to be the effect of a decrement on
those edges, but the reverse is the fact ; for, by figs. 18,19, 20, 21,
25,26,27, it will be seen that the pyramid of fig. 27. is the result of
a modification of the primitive crystal described by the planes 2,2 on
fig. 22; and it will be equally obvious that if the section determined by
L’hermina be parallel with one or other of the edges of the pyramids
of fig. 27. it must also be parallel with one or the other of the planes
of the primitive octohedron, consequently with one or the other of

Bye

356 Mr. WILLLIAM PHILLIPS on the Oxyd of Tin.

the planes composing the pyramid of fig. 11. It will hereafter be
shewn in describing the apparently dodecahedral macle, fig. 188.
that it results from a section of the prism, both in the direction
described by L’hermina, and in the opposite direction. Let these
sections be described by the dotted lines, dg dh and fg ch, fig. 11.

Now, it may be noticed that by a practicable cleavage each way
through the centre of a crystal similar to fig. 11. but parallel with
the planes of the prism, it is divisible into four parts, similar in form
to the fracture described by fig. 9. On one of these portions
similar to that figure let the sections given on fig. 11. be repre-
sented by the lines gdh and cg dh, fig. 12. and it will be seen
that 2 cd on that figure will represent a fracture similar to fig. 4,
If this be pursued still further it may be observed by representing
the lines of section 6 g dh fig. 12. on fig. 13. that by the parallel
section dc g, a tetrahedron adc g is obtainable.

The fragments represented by fig. 8. were obtained by a cleavage
of others represented by fig. 4. in the direction of its diagonal ¢i/.
If therefore a section of fig. 9. be made in the direction of that
diagonal, one portion of that figure so divided, will agree in form
with fig. 14. which figure exactly corresponds with one fourth
part of a crystal represented by fig. 15. by a section along the
edges both of the prism and the pyramids, the planes PP and 4
resembling each other. The planes PP and 4 fig. 15. also cor-
respond with those of PP 4, fig. 16. which planes are usually
supposed to arise from a decrement on the edges of a crystal
similar to fig. 27. Pl. 16.

I presume it has been satisfactorily demonstrated, that by the
fractures represented. by figs. 4, 5,.6, 7, 8, and 9, PL 15. a
mechanical division of the oxyd of tin is unquestionably obtainable,
parallel with the planes of the prism, as well as, by figs. 5, 7, and 8,

Mr. WILLIAM Pui tips on the Oxyd of Tin. 357

with both its diagonals. I presume also that it has been shewn,
by the agreement in the incidences of the plane P on the edge dc
of the fracture, fig. 9. with the plane P on the edge dc of the
crystal, fig. 11. as well as of the plane P with the plane a of each
of those figures; that the plane P of the former figure, is really the
result of a cleavage parallel with the plane P of the latter figure ;
and also, by fig. 10. that a mechanical division is equally practicable
parallel with each of the four planes P, composing the pyramid of
the crystal fig. 1]. Let therefore all these cleavages be represented
on fig. 15. and it will be seen that the result is a mechanical
division of it into tetrahedrons.

It has already been said that in the first instance the Abbé Haiiy,
was induced to believe the cube to be the primitive form of the
oxyd of tin, but that he was afterwards led to adopt the flattened
octohedron composed of the two pyramids of fig. 15. joined base
to base. In this latter opinion, there seems to me, from the
evidence now offered, no room for doubting his correctness. For
whatever has been said tending to shew a connexion between the
fractures that have been described, and a crystal delineated by
fig. 15. relates, with equal aptitude, to one having either a longer
or a shorter prism, and equally well to one having no prism at all:
for it will be seen by fig. 17. that the form of fig. 15. is merely
the result of a decrement on the edges of an octohedron formed by
the meeting of its two pyramids base to base ; which octohedron is
given by itself fig. 18. as the primitive form of the oxyd of tin.
But it has not hitherto been seen unmodified; nor has any crystal
been noticed approaching it more nearly than that delineated by
fig. 21. Pl.16.*

* On the subject of the integrant molecule I do not feel competent to say more, than
that it has been already shewn, by a combination of all its known cleavages, that the

primitive crystal is mechanically divisible into tetrahedrons; but as these tetrahedrons

will necessarily be irregular or rather unequal in their form, it may not be satisfactory

358 Mr. WILLtAM PHILLIPS on the Oxyd of Tin.

First Modification.*

This modification is represented by fig. 19. Pl. 16. and consists
in a decrease on the four lateral solid angles of the primitive form,

by which each is replaced by a plane, perpendicular to the axis |

passing through those angles.

Fig. 20. shews this modification in a more advanced state, and
has been added not because it has been thus observed, but in order
that the combination of the planes of this modification with those
of the primitive form, may be the more readily traced in fig. 21.
in which it occurs, though but rarely. In the fine collection of
tins, in the possession of Mr. Sowerby, there is a specimen of

to adopt it as the integrant molecule. Indeed, it may fairly be doubted, whether,
considering the present state of mineralogical knowledge, much benefit has accrued from
the attempts that have been made to determine that of many other substances.

* The crystals of this substance, when on the matrix, have so greatly the appearance
of being confusedly grouped, that little can be done towards describing them, on
account of their splendour and numerous facets, without first detaching them from the
matrix, which on account of their brittleness requires considerable care. The mode best
adapted for preserving as well as for observing them, I first noticed in the scientific
collection of the Count de Bournon, in which, insulated crystals are placed on wax.
For this purpose I have used the common green taper cut into pieces of about an inch
in Jength, and placed the crystal at one end. There are between 4 and 500 crystals of
this substance so arranged in my collection, including every one described in the series
belonging to this paper, and, being placed in that serics according to the method adopted
by the Count de Bournon (that is, according to their modifications) little or nothing
need be said upon any of the individual crystals.

But in order to render the scries more perfectly intelligible, I have taken especial care
to place the drawing of every crystal throughout the series in the same point of view,
except in a few instances, for the sake of illustration. I am aware that an attention to
this circumstance affords material facility to those who may desire to become acquainted
with the crystallization of the substanee, in tracing the modifications through their
various combinations: and the same care has been observed, not to introduce in the
series of any modification, the figure of a crystal exhibiting the planes of any other

modification, that has not preceded it. ‘

Mr. WiLxi1aM PuiLuips on the Oxyd of Tin. 359

considerable size, almost covered with well defined crystals repre-
sented by figs. 21. and 25.

Neither the planes of this, nor of any other modification have
I believe been found in simple combination with those of the
primitive crystal. They are thus given preceding the series of each
modification, in the hope of thereby rendering each the more
intelligible; to this I have generally added a figure representing
their combination with the planes of the secondary octohedrons,
being those of the second modification, because the planes of that
modification form the pyramid most commonly found on the
crystals of this substance.

Second Modification.

Each of the four solid angles formed by the meeting of the two
pyramids of the primitive form base to base, is by this modification
replaced by two triangular planes; each plane being placed on an
edge of the pyramid, but inclining on the axis passing through the
solid angles, fig. 22. Pl. 16.

This modification is represented in an advanced state, by the
dotted lines of fig. 23. shewing by the lines within it, that when
complete, it produces a secondary pyramid considerably more
acute than that of the primitive form. The secondary pyramid
produced by this modification is that commonly observed on the
crystals of this substance, and by fig. 24. is represented within the
dotted lines of the primitive form.

Fig. 25, shews the first and second modifications in combination
with the planes of the primitive crystal. The lines on the faces of
this figure denote the direction in which the striz are sometimes
to be observed on the crystals.

360 Mr. WILLIAM Puituips on the Oxyd of Tin.

Fig. 26. shews the passage into the secondary pyramid, which
is complete in fig. 27.

Fig. 28. represents an elongated crystal ; its elongation proceeds
from a regular deposition of crystalline laminz on one face of the

upper and on one of the lower pyramid, and on the intermediate

plane of the first modification. On the crystals represented by
fig. 29. a deposition of lamine has taken place on two opposed
planes of the first modification, gradually diminishing, so as to
preserve the lengthened faces of the second modification perfect
planes. On fig. 30. this species of deposition has taken place, after
the crystal itself had been formed similar to that of fig. 28. Fig. 31.
shews a crystal on which a regular deposition has taken place on
two opposed faces of the upper and the two corresponding faces of
the lower pyramid, so as to diminish two of the four triangular
planes of each, and to give the other two the form of irregular

hexahedral planes.
Third Modification.

This modification consists in a decrease on each apex of the
primitive form, by which each is replaced by a quadrangular plane,
perpendicular to the axis passing through the apices, Fig. 52. Pl. 16.
The planes of this, though not uncommonly found in combination
with those of other modifications, are rarely so well defined as
to be depended on for accurate admeasurement, owing to an
unevenness on their surfaces. I have not succeeded in finding
crystals that have satisfactorily allowed the incidence of the planes
of this modification with those of the primitive form.

Fourth Modification,

This modification consists in a decrease on each of the edges of
the primitive crystal, formed by the meeting of the two pyramids

—

Mr. WitttaM Puiuures on the Oxyd of Tin. 361

base to base, by which each is replaced by a plane, perpendicular to
the axis passing through those edges, fig. 34. Pl. 17.

The planes of the primitive crystal are rarely found in combination
with those of this modification, except when they seem only to be
the result of a decrease on the edges of the secondary pyramid as in
fig. 39. Fig. 35. shews the combination of the planes of this modi-
fication with those of the secondary pyramid, which is thus given,
because, as the secondary pyramid is that commonly observed on the
crystals of this substance, it seems to facilitate the tracing of the
various combinations in the succeeding figures.

Fifth Modification.

The fifth modification arises from a decrease on each of the solid
angles caused by. the meeting of the two pyramids base to base, by
which each is replaced by two triangular planes placed on the edges
formed by the meeting of the two pyramids, but inclining on the
axis passing through the lateral solid angles, fig. 45. Pl. 17.

The planes of the primitive crystal are also shewn by the dotied
lines of fig. 46. together with the planes of this modification in a
more advanced state. ‘The latter are also exhibited in combination
with those of the secondary pyramid, by the lines within that
figure.

It will be noticed how nearly the crystals given by fig. 55.
approach the cube, and that of fig. 47. the secondary octohedron.
The crystal represented by the latter figure does not exceed in size
the head of a small pin, but all its planes are remarkably brilliant
and well defined.

A OWisrhs 27

362 Mr. Wittiam Puitrirs on the Oxyd of Tin.

Sixth Modification.

This modification, like the preceding, consists in a decrease on each
of the solid angles, caused by the meeting of the two pyramids of
the primitive form base to base; by which each is also replaced by
two triangular planes placed on the edges formed by the meeting
of the two pyramids, but inclining on the axis passing through
the angles, more than those of the fifth modification, fig. 58.
Pl. 18. The planes of this modification are shewn in combination
with those of the primitive form by the dotted lines of fig. 59. and
with those of the secondary octohedron by the lines within it.

Seventh Modification.

This modification consists in a decrease on each of the four
solid angles caused by the meeting of the two pyramids of the
primitive form, by which each is replaced by four triangular planes,
placed on the faces of the primitive form, but inclining on the axis
passing through the lateral solid angles, fig. 63. Pl. 18.

By fig. 64. the planes of this modification are shewn in a more
advanced state, which renders the first figure in the series, that
of 66, perfectly intelligible. Fig. 65. shews them in combination
with the secondary pyramid, and will, without pursuing the
series from fig. 66. to fig. 70. cause the latter figure to be at once
understood. |

I have not satisfactorily obtained the incidence of the planes
of the primitive form with those of this modification.

The principal part of the crystals delineated in the series of this
modification, in which the prism is long and the facet of the 7th
modification is small, are from Relistian tin mine, and are about a
line in thickness. I have not seen them from any other mine. -

Mr. Witt1aM Puiuips on the Oxyd of Tin. 363
The crystals represented by figs. 66, 68, 69, 70, 71, 79, are about |

the size of a common quill, and were presented to me by a gentle-
man of Penzance, who knew not whence they were brought ;
judging, however, from a superb specimen in my collection, on
which there are some of the above varieties in form, and of about
the same size, and which is from Gavrigan stream works in St.
Mewan, I presume them to be from the same place.

The crystals delineated by figs. 72, 73, and 86, are singularly
beautiful, and present, though scarcely a line in length, both
terminations complete. They were all taken from the same spe-
cimen, which is the only one of the kind that I have seen, but
from what mine it was brought I am unable to say, it having
accidentally been left in London by the captain of a Cornish
trading vessel. ‘The crystals represented by fig. 67. were found
detached in a vein near the Land’s End.

Of the singular variety, fig. 98. I have four crystals, their form
is occasioned by the elongation of one plane of the second modifica-
tion on one pyramid, and of the opposed face on the other; they
are of a light brown colour, and translucent.

Eighth M odification.

This modification, like the preceding, consists in a decrease on
each of the four solid angles, caused by the meeting of the two
pyramids of the primitive form, by which each is replaced by four
triangular planes, placed on the edges, but inclining more than
those of the preceding modification on the axis passing through
the solid angles, fig. 106. Pl. 20. By fig. 107. the planes are
shewn in an advanced state.

The two figures which alone compose the series of this modi-

222

eal oa

364 Mr. Witxiram Puiurips on the Oxyd of Tin.

fication, exhibit its planes very differently, and on all the crystals
represented by these two figures, they are so uneven, or irregularly
striated, as to render it wholly impossible to subject them to the
reflecting goniometer, This modification is extremely rare. The
crystals described by fig. 10S. have I believe been brought only
from the mine called Huel Fanny, west of Redruth.

Ninth Modification.

By the ninth modification, as well as by the second, each of the
four solid angles formed by the meeting of the two pyramids of the
primitive form, is replaced by two triangular planes, placed on the
edges of the pyramid, and inclining on the axis passing through
the solid angles ; but in this modification they incline more on that
axis than those of the second modification, fig. 110. Pl. 20.

Fig. 111. shews the planes of this modification in a more
advanced state; and fig. 112. shews them in combination with the
secondary pyramid. ‘They are generally so minute or so consider-
ably striated, as to prevent their incidence either with the planes of
the primitive form, or with those of any other modification, from
being satisfactorily obtained.

The greater part of the crystals delineated in the series of this
modification, of which the planes of the first modification are long,
and on which those of the seventh modification are observable, were
taken from the surfaces of rounded portions of grauwacke, found
in the hollow parts of the vein in Relistian mine. I have not
noticed any macles on the specimens from that mine; all the
crystals from it are nearly black, and of remarkable brilliancy.

Mr. Witt1aAM Purbxips on the Oxyd of Tin. 365

Tenth Modification.

The planes of this modification replace the lateral solid angles of the
primitive crystal, in the same manner as those of the second and
ninth, but are still more inclined on the axis passing through those
angles, fig. 155. Pl. 22 By fig. 156. the planes of this modifica-
tion are shewn in a more advanced state, and by fig. 157. in com-
vination with the secondary pyramid. Although the planes are of
considerable size on many crystals, they are generally rough, or so
>much rounded, as hitherto to have prevented my obtaining a satis-
factory admeasurement of their incidence on the planes of any other
modification.

The crystals represented by figs. 158. and 159. were I believe
found loose in a vein near the Land’s End. Those of figs. 160.
and 162. are from Huel Fanny. That of fig. 166. from Gunnis
lake mine; it is about three quarters of an inch in length, and is
perfect at both terminations. The crystals delineated by figs. 163,
164, 167, 168, 169, 170, and 171, are from Relistian mine. On
the crystals, fig. 167. the planes of the first, sixth, and tenth modi-
fications were evidently the consequences of a second deposition, as
their natural joints with those of the fourth and ninth modifications

are visible on every side.

Eleventh Modification.

This modification consists in a decrease along the edges of the
two pyramids of the primitive crystal, by which each is replaced
by a plane; fig. 172. Pl. 23. This plane, by a deeper replacement
of those edges, would produce, it will be evident, another and more
obtuse octohedron, fig. 173, the apices of which are visible in com~

366 Mr. WILLIAM PuiLiips on the Oxyd of Tin.

bination with the planes of the primitive form, and with those of
the first and second modifications in fig. 174. I regret the not
having been able to ascertain the incidence of the planes of this on
those of any other modification.

All the specimens on which I have noticed the planes of this mo-
dification, were long since brought from Cornwall, but from what
mine it is impossible now to ascertain.

Twelfth Modification.

The twelfth modification consists in a decrease on those edges of
the primitive crystal which are formed by the meeting of the two
pyramids base to base, by which each edge is replaced by two
planes, placed on the primitive faces, but inclining on the axis,
passing through the edges, fig. 182. Pl. 23. By fig. 183, the
planes of this modification are represented in combination with the
secondary pyramid, as will be evident on consulting fig. 184, which,
together with fig. 185, represents the only crystals on which I have
noticed the planes of this modification. I have not been able to

ascertain their incidence on those of any other.

Macles.

Most of the crystals delineated in the series annexed to this paper,
are defined with great neatness and beauty: but there is generally
much seeming confusion among the crystals of the oxyd of tin,
arising principally from a circumstance or law, not altogether pe-
culiar to it, by which similar portions of two or more crystals are
regularly united, so as to form what have been termed macles, one

of which has been described by De Lille by that name, and by Hatty

Mr. WILL1AM PuiLuips on the Oxyd of Tin. 367

by that of bemitrope. The seeming confusion produced by the
macle,* is very often much augmented by circumstances apparently
resulting from no law, by which parts of crystals are jumbled to-
gether, so as to form a whole, that can only be understood by a
long and patient investigation, which in the end serves only to
satisfy the observer of the absence of all regularity in the disposition
of the several constituent parts, although each may be separately
defined. |

But even the regular macles of the oxyd of tin seem, at first
sight, to form no very intelligible part of the series of its crystalli-
sation, although they are in fact very interesting. To understand
them it needs only to become well acquainted with some of the most
simple; as, for instance, with those of figs. 186, 187, 188, and
189, Pl. 24, which will serve as a ready clue to the comprehending
of all such as are of regular formation ; and by these it will be seen
that they all proceed from the same law of section.

The macle first described by De Lille, who ascribes to Lhermina
the developement of the law by which it takes place, is that of fig.
186, and will be understood by referring to fig. 190, on which the
dotted lines a 4c de represent a section of it, parallel with the
edges e f of the upper and g 4 of the lower pyramid+ dividing the
crystal into two parts. ‘The upper part is represented in the same

* [ have retained the term mac/e in preference to that of hemitrope, because the
latter does notin fact apply to any one of them, It does not seem to me that the term
macle is objectionable, because it has been given toa substance. In this case it only
denotes a circumstance, and no one would think of asking for macles, without adding,
of tin, of the ruby, &c.

+ The section by which this, as well as the succeeding macles, takes place, being
parallel with the edge of the secondary pyramid, it follows of course, as a reference to
the series of the second modification will shew, that this section must also be parallel
with the faces of the primitive octohedron.

368 Mr. Wi1LLIAM PHILLIPs on the Oxyd of Tin.

direction in fig. 186, and the same proportion of another crystal
having been turned half round, and reversed in its direction, is, in
that figure, thus attached to it. The incidence of the edge a 6 on
the edge ¢ d, fig. 186, is 112°. 10’.*

The series of this macle, which is the most simple of all in its
combination, is described by figs. 203, 204, 205, and 206,
Pl. 25; and as the planes on each are numbered with those of the
several modifications to which they respectively belong, they will be
readily understood, except perhaps that of fig. 206. This latter, as
a reference to fig. 52 will evince, is composed of similar parts of
two crystals ; but as the section of the two portions of which it
consists took place parallel with a face P of each, which do not ap-
pear in the macle itself, it follows of course, that this section must
be immediately opposed to that of the three preceding figures. The
existence of this section will be explained and confirmed in speaking
of the formation of the macle described by fig. 188,

Double Macles.

The macle described by fig. 184, Pl. 24, may be termed a double
macle, because it is terminated at each end by a macle similar to
that described by fig. 191, which resembles that described by fig.
186, except that the planes 1, 1, which are those of the prism,
are shorter.

If we were to suppose fig. 187 to consist of two macles similar
to fig. 191, simply reversed, it would be obvious that a re-entering

* The Abbé Haiiy in his Tableau comparatif, has given this incidence, as 112°, 16°. 44”,
but I have been induced to quote it as above, because I have uniformly so obtained it Dy
means of the reflecting goniometer, on macles having the edges ab and cd replaced by
the plancs of the fourth modification,

Mr, Wittiam Puiiuips on the Oxyd of Tin. 369

angle, described by the dotted lines, must exist between the planes _ -
2, 2, of each, which are those of the second modification; in-
stead of which the whole space between those planes is occupied
by an elongation proceeding from each, so as to connect and form
the two upper planes, 2, 2, into one plane; the same effect takes
place in regard to the two lower.

The series of this double macle is given by figs. 216 and 221,
Pl. 25, placed in the position in which they are most commonly
found: they usually present but one termination, the other being
imbedded in the matrix. Fig. 217, represents a crystal similar to
that of fig. 190, but with a shorter prism, so placed as to shew

most advantageously the section described on fig. 190, and

thereby serve as a clue to the more ready comprchension of the
series, On each figure the planes of the several modifications are
pointed out, by the number of the modification itself being placed
on them. On figs, 218, 219, and 221, the planes of the primitive
form are visible. These macles are generally defined with great
neatness, and mostly allow of the perfect use of the reflecting
goniometer, which has been employed to corroborate what has
been said of their construction, the truth of which it places be-
yond a doubt. I possess macles represented by figs, 218 and 220,

on which both terminations are complete.
Incidence of 4 on 4, on the summit of fig. 218—112°. 10’

This macle seems to verify the conclusion of Lhermina, that the
section a 4c d, fig. 190, takes place parallel with the edges e f and
& 4, which are those of the secondary pyramid. If the termina-
tions £& of fig. 187, were complete, or, in other words, if the
planes of the second modification were not visible, fig. 187 would
take the form of fig. 192. Of fig, 192, Ict a section along the

VoL. II. 3A

370 Mr. WILLIAM PHILLIPS on the Oxyd of Tin.

edges a b and c d, be represented by fig. 193, and the dotted line
e f will represent the line of junction of the upper and lower parts
1, 2, 1 and 1, 2, 1 of fig. 192, and consequently also the plane of
section a bc d, of fig. 190, which being parallel with the secondary
edge ef of that figure, is therefore parallel with the planes of the
primitive form, as a reference to figures 18 to 27, Pl. 16, will
evince. In place of the edge a b, fig. 192, which is the edge of
the secondary pyramid, the primitive plane P is seen on fig. 218,
Pl. 25, which plane gives on its opposed plane P of the same figure
(not visible on the figure, but which, as it were, replaces the edge
cd of fig. 192) by the reflecting goniometer an exact incidence of
180°. It follows of course that the edges a 6 and c d, fig. 193, are
parallel with each other; and also that the intermediate line of
section ¢ f must be parallel with each, and therefore with the edge
of the secondary pyramid ¢ f, fig. 190.

For the discovery of the construction of that macle of the oxyd
of tin, which, when viewed in the direction in which it generally
occurs, and in which it is delineated by fig. 188, Pl. 24, appears to
take the form of a dodecahedron with triangular faces, I was prin-
cipally indebted to the direction of the striz on its planes.
Having noticed them to be mostly visible as described on that figure,
a suspicion arose that this macle was composed of equal parts of
the prism formed by the planes of the first modification, and I
found by the common goniometer that the incidence of any plane
of the upper, on its connected plane on the lower pyramid, exactly
corresponded with that of 1 on 1, fig. 27, being 90% The idea of
its being composed of similar and equal portions of several crystals,
was further corroborated by observing, in almost every instance,
their natural joints along the edges from one apex to the other.

This apparently dodecahedral macle, fig. 188, Pl. 24, at first

Mr, WILLIAM PHILuips on the Oxyd of Tin, 371

sight, seems to have no analogy with the preceding macles, but
that it results from the same law of section as those described by
figs 186 and 187, may be readily shewn, Let the section a dc d,
fig. 190, which is parallel with the edges ef and g 4 of that figure
be represented by a section abcd, fig. 194, parallel with the
edges ef and g # of that figure; then let ¢4 4d bea section in
the opposite direction parallel with the edges fa and eg. By
placing the prism so that the edge £42 of fig. 194 shall be repre-
sented by £42, fig. 195, it will be seen that the lines of section
abed and ebhd are the same on each figure, and that by these
sections two equal portions b4da and bcde are obtained from
the prism, the former of which is shewn by fig, 196; and it will
also be seen that the planes 1, 1, of the latter figure, correspond -
with those of 1,1, fig 188. It will be understood therefore that
this macle consists of a number of equal portions of the prism,
described by fig. 196, and that the planes of the first modification
alone are visible.

But there is a circumstance relating to the formation of this
macle that deserves attention. If it were, as it seems to be, a
dodecahedron with triangular faces, the two pyramids, of which
it would be composed, being divided horizontally, would each
have for its base a regular hexahedral plane, divisible into six
equilateral triangles, fig. 197, and the six angles of the plane would
necessarily be 120° each. If a diagonal section of a crystal,
fig, 194, be made along the edges of the pyramids e fa andcgh,
and along those of the prism ec and a4, the plane given to each
portion by that section would also be a hexahedral plane, fig. 198.
But since it has been shewn that the two sections on fig. 194,
(represented by the lines az ¢ and ez A, fig. 198) are parallel with
the edges ¢ fand g 4, and f a ande g; and since the incidence

BAZ

372 Mr. WiLL1AM Pui tips on the Oxyd of Tin.

of the edge ef, on the edge fa over the apex of the crystal, is
112°, 10’, and that of fa on ah 123°, 55’, it will follow that the
triangular planes ai and eic are not equilateral, but isosceles,
triangles, of which the outer sides a # and ec are the longest,
the two others being equal. Now, six isosceles triangles, similar
to those of a7 and ezc, fig. 198, are not equal to the comple-
ment of a regular six-sided plane, fig. 197, as will be seen by fig.
199. The macle delineated by fig. 188, therefore cannot be a
regular dodecahedron with triangular faces. By an attentive ex-
amination it will be generally found to exhibit only three or four
sections of the prism similar to fig. 196: and although this circum-
stance is commonly attributed to interrupted crystallisation, that is
not in fact the cause of its assuming that appearance.

In my collection there is a macle obligingly presented to me by
Mrs. Lowry, of about half an inch in diameter, and almost per-
fect, which as it demonstrates that six sections of the prism, fig.
196, are not equal to the complement of the dodecahedron, is highly
interesting. It is represented by fig. 189, which shews, that in-
stead of exhibiting, as in the preceding figure, equal and similar
planes 1, 1, of equal portions of fig. 196, it has only 3, each of
them, alternating with facets of another form, having between them
a re-entering angle.

Let fig. 201 represent a close combination of three isosecles
triangles, abc, acd and ade, similar to those produced by the
lines of section on fig. 198. Then let afcdg represent one of
those triangles, and one-half of each of the other two. By com-
paring the plane afecdg with afcdg of fig. 200, which is the
plane that would be the base of each pyramid of the macle des-
cribed by fig. 189, by a section between them, it will be seen that
there is a perfect agreement between each ; and it will also be seen

Mr. Witt1aAM Pui ures on the Oxyd of Tin. 373

that a bik g and ah/lmf are similar planes, each consisting of one
isoscele and two halves, of similar triangles. It follows therefore ©
that this macle is composed of three sections of the primitive prism,
fig. 196, alternating with six halves, two and two, of the same
figure.

It should be noticed that the angle / mc, fig. 200, to which there
are five others similar, is about 120° by the common goniometer ;
but as the edges of the macle are very uneven, it cannot be relied
on for admeasurement. The angle /m fj like which there are also
five others, nearly agrees, but is not accurate for the same reason
with that of aec, fig. 193, which is the result of a close com-
bination of two similar isosceles triangles.

It will be understood that fig. 208, Pl. 25, and the seven succeed-
ing figures, comprehending the series of that which is commonly
termed the dodecahedral macle, (each being numbered with the figures
of the several modifications of which it shews the planes) are not in-
tended to represent dodecahedrons, as the macles themselves consist
only of what is visible in the respective drawings, or at most of only
one-third more, that is, of three or at most of only four sections of the
prism, fig. 196, Pl. 24. Yet the apices of several of them are perfect,
as for instance, the plane on the summit of fig. 210, which is perfectly
defined, and which therefore indicates the regular combination of
six sections of that figure, unitedly exhibiting a decrease on the
apex by the plane of the fourth modification. As a corroborative
proof, however, that these macles, under the most favourable cir-
cumstances for perfect crystallization could never become perfect
dodecahedrons, it may be observed that several in the series which
exhibit those planes of the fourth modifications which give to fig.
210 the form of a short prism, give uniformly an incidence of 4 on 4
by the reflecting goniometer of 112°. 10’.; whereas if they were

374 Mr. WILLIAM PHILuips on the Oxyd of Tin.

perfect dodecahedrons, the incidence would necessarily be 120°,
Supposing the macles represented by fig. 188, pl. 24, or fig. 208,
pl. 25, to consist of four sections similar to fig. 196, the plane that
would be given to the upper and lower faces by a horizontal section,
would resemble fig, 202, the angles of which are 112°. 10’, and it
will be obvious that this figure could not be made to agree with the
plane of section of the perfect dodecahedron fig. 107, the angles of
which are 120°, by adding to it triangles of a similar description,

Macles of Macles.

The figures in this series occupying pl. 26, are extremely com-
plex, as except the latter, each consists of four, or a greater number
of similar parts of some one of the macles already described, for
which reason I have termed them macles of macles.

That which is described by fig. 222, Pl. 26, consists of four similar
parts of macles, fig. 188, Pl. 24, which by fig. 223, Pl. 26, is placed
in such a position as to shew that section of fig. 188, which forms
one-fourth part of fig. 222, as will be readily seen by noticing the
figures 1, 1, on each, the planes on which they are placed, being
those of the first modification, or in other words, of the common
prism. ‘The striz on these macles uniformly take the direction
given by the lines on fig. 222. I have several that shew both ter-
minations, and the natural joints of the four portions of which they
are constituted are always visible on the direction of the stronger
lines down the center of the faces of what may be termed the prism
of the macle. As the incidence of the planes 1, on 1 of this macle,
give by the common goniometer exactly 90°, it follows that a
horizontal section of this macle would give a square plane to

each part so divided, Let this plane be represented by fig, 224,

Mr. WILttam PHILLIPS on the Oxyd of Tin. 375

Pl. 26, and as fig. 222 is composed of four equal parts of macles
similar to fig. 223, it will follow that the lines a, b. and 4, c, fig. 224,
will represent that portion of the whole plane, occupied by the con-
stituent part of one macle, and further, the lines of section, a 6 and
6 c, being perpendicular to the lines a d and ¢ d, that the section of
each of the four macles constituting that described by fig. 222, takes
‘place parallel with the planes of the common prism; and it has
been shewn, in treating of the primitive crystal, that in this direction
a cleavage is easily obtained.

Those described by figs. 225 and 226 differ only from fig. 222, in
this, that the planes of some other modifications are visible, the re-
spective numbers of which are placed on them.

That described by fig. 227, consists of four macles similar to that
delineated by fig. 211, except that in this, each is elongated in the
direction shewn by fig. 228. Fig 229 represents one composed of
four elongated macles fig. 214.

By fig. 230, Pl. 26, is represented a singular combination of the
four macles composing the preceding figure, placed on the edges of the
‘prism of a crystal similar to fig. 42, pl. 17. This combination may
‘be quoted in evidence to the truth of what has been said of the con-
struction of common macles, for it will be observed that-the faces
1, 1, on the prism of the crystal itself, and on the macles placed on
its edges, are all planes of the first modification. Both terminations
of fig. 230, as well as of the two preceding figures are visible on the
macles.

Fig. 231, Pl. 26. represents a macle composed of 16 portions of
the prism, fig. 196, Pl. 24, each elongated, the whole forming an
octangular prism, of which a horizontal section is described by
fig. 233. The striz are uniformly in the direction represented.

The construction of this macle will be obvious by consulting fig.

376 Mr. WILLIAM PHILLIPs on the Oxyd of Tin.

234, by which it will be seen that the triangular faces correspond
with those of 1, 1, fig, 232, which is that of a common prismatic
crystal, fig. 27, Pl. 16, placed in such a point of view, as most easily
shews the section shewn on fig. 194, Pl. 24, Each of the eight solid
angles of this figure, therefore, is composed of two portions of the
common prism, fig, 196; giving, by the common goniometer, along
the edges a 6c, an angle somewhat more than 112°, which, gene-
rally speaking, is the same as that / m_f, fig. 200; the plane 1 on I,
over the edge between them, which is that of the common prism,
also gives an incidence of 90° corresponding with that of the planes
lonl, fig. 196, That part of fig. 234, comprehended within the
dotted lines, is supplied in the macle itself, by an elongation pro-
ceeding from the upper and lower triangular planes,

Fig. 235, Pl. 26, represents a macle, in which two halves of one
similar to fig, 218, are attached so as to give an incidence of the
planes P on P, which are not visible in the drawing, but which are
parallel with the planes P P, which are given, of 112°, 10’, by the
reflecting goniometer, over the angle between them, corresponding
with that of the planes 4 on 4 on the summits of the same figure,
and of course with that of the planes 4 on 4 on the summits of
fig. 210.

XVIII. On some new Varieties of Fossil Alcyonia.
By Tuomas Wezster, Member of the Geological Society.

qo REESE

To Sir Henry EnGuerriexvp, Bart.

London, August 2d, 1811.
DEAR SIR,

I Obey with pleasure your request that I would give a particular
account of the singular fossil organic body which I observed in the
green sandstone stratum under the chalk, during my late examination
of the Isle of Wight, and which appears not to have been hitherto
described by any naturalist.

Whilst viewing the rocks about Ventnor Cove, and in various
parts of the Undercliff, I remarked a great number of small pro-
minences that at first sight appeared like harder pieces of the stone
which resisted the effects of the weather after the rest had mouldered
away. But examining them more particularly, I observed that most
of them had exactly the form of branches of trees; and frequently
the resemblance was so complete, that if they had been carved by a
sculptor, he could scarcely have made a better imitation. Sometimes
they were tolerably sharp and perfect, but most generally were a
good deal decayed; and they then bore that sort of likeness to real
branches which sculpture would after having been jong exposed to
the weather. Pl. 27, fig. 1.

VoL. Il. 3B

378 Mr. WEBSTER on some new Varieties of Fossil Alcyonia.

They were of various sizes, from half an inch in diameter to three
or four inches, but were more usually about an inch and a half or
two inches. Their substance was sandstone of the same kind as the
rock they were in; but the part resembling the bark was somewhat
harder, which enabled it to endure longer than the rest of the stone,
and thus project above its surface.

The colour of the outside was sometimes of the same yellowish
tint as the other parts of the rock, but was more frequently dark
grey, owing to their greater durability permitting the lichens to grow
upon them. When the dark coloured pieces were broken, the in-
ternal part was yellow. Often a piece of the bark appeared wanting,
and then the central part of the branch, or that corresponding to the
wood was smocth, but the outside of the cortical part was rough
and corrugated. Some were straight, others a little crooked, and in
a few instances I observed them forked. Others again had much
the appearance of roots, having frequently holes as if branches had
been broken out.

While in the rock their forms were sufficiently distinct ; but they
were so friable in their structure, that I could not detach pieces of
any great length; and when so detached, they seldom conveyed the
same idea. ‘The appearance of the largest and finest specimens,
therefore, which were imbedded in rocks of considerable magnitude,
must be imagined from the drawings.

Notwithstanding that the resemblance of these forms to branches
of trees was so striking that it was impossible not to imagine at first
sight that this had been their origin, yet considering the difficulties
attending the supposition that wood had heen converted into sand-
stone, it seemed to me much more probable that they had been de-
rived from some of those animals assuming a vegetable form and
distinguished by the name of Zoophyte.

Mr. WEBSTER on some new Varieties of Fossil Alcyonia. 379

Examining farther the limestone contained in this stratum, both
in the bed and in those masses which had fallen down, and lay about
the shore, I observed a great many smooth cylindrical forms as
perfect and sharp as though they had been sculptured. Pl. 27, fig. 2.
These penetrated the rock in all directions, many projecting above
the surface as if carved in basso and alto relievo, and exhibit ing
sections in every direction according to the fracture of the rock.
They were also frequently broken out, leaving a cylindrical cavity
where they had been.

These cylinders varied in size from one inch in diameter to the
eighth of an inch, were sometimes straight, generally crooked, hav-
ing much the appearance of eels in motion. They were exceedingly
smooth on the outside, often slightly tapering, and, as well as the
last mentioned forms, had evidently been inclosed in the rock at the
time of its formation. When these cylinders were examined care-
fully, they appeared also to have an external coating or cortex, but
it had been extremely thin, and was always worn off when they had
been exposed by being on the surface. .

Although I first noticed these beautiful cylindrical bodies in the
limestone, yet I could afterwards trace them in the other parts of the
sandstone stratum, although from the softness of the stone they were
there almost obliterated ; and I concluded them also to be some fossil
organic remains, probably belonging to the class of Zoophytes ; but I
could not ascertain that they were parts of the same species as those
I first mentioned, since in no instance could I find them distinctly
connected together. Some rocks contained only one class, and some
had both confusedly intermixed.

I found fragments of these fossils in every part of the island
where the sandstone stratum can be seen, and even in the walls of
buildings constructed of this stone ; but it was only among the

3BZ

380 Mr. WEBSTER on some new Varieties of Fossil Alcyonia,

stupendous and difficultly accessible masses of rock lying under the
romantic cliffs of Western lines that I observed the singular parts of
these organic beings which I shall now mention.

In this place I not only met with the stems above described in
great abundance and perfection, but also having frequently attached
to them heads or bulbous terminations, in form somewhat resem-
bling a closed lily or rather tulip, Pl. 28, fig. 3. These, like the
stems, although sufficiently distinct as to the general shape, were
commonly so wasted by the weather, that good specimens were
exceedingly rare. In some I found the distinct traces of organic
structure.

All these heads possessed nearly the same form, but varied in
length from five or six inches to half an inch; and I think it pos-
sible they may belong to several varieties of the same species, some
differences being observable among them.

Pl. 28, fig. 4. & 5. are the heads attached to the branches so much
resembling the parts of trees. In these the cortical part is often
equally evident in the head as in the stem ; but being in soft sand-
stone I could very seldom observe the organization. I remarked
that some of the stems had also tumid parts not unlike the bulbous
terminations. Pl. 28, fig. 6.

Heads similar in shape, but generally much smaller, were at-
tached to the smooth cylinders in the limestone ; and in these the
cortical part was scarcely visible ; whilst certain lines on the sides
sometimes gave the appearance of petals, Pl. 28, fig. 7,8,9. On
breaking them, slender tubes were seen passing through in a lon-
gitudinal direction ; and one specimen displayed the internal struc-
ture very distinctly, fig. 10. From this it appeared, that these
heads consisted of a group of tubuli now converted into and en-
veloped with stony matter ; and in some of the specimens, as fig. 11.

Mr. WEBSTER on some new Varieties of Fossil Alcyonia. 381

one end was pierced externally with several sma!l holes placed in -
a regular order, which probably communicated with the tubuli I
have mentioned, and by the contraction and dilatation of which the
animal was enabled to draw in the water from which it extracted
its nourishment.

Besides these extraordinary shapes which projected in relief, I
observed a variety of very regular white figures as if painted upon
the rock, being even with its surface, Pl. 29, fig. 12. They con-
sisted of circles, of ellipses with various eccentricities, and of parallel
lines, both straight and curved. These I considered to be the different
sections of some cylindrical and perhaps tubular bodies inclosed in
the stone: the figures being always such as would be produced by.
the varicus sections of a hollow cylinder both straight and crooked.
The circles were generally from two inches to half an inch in
diameter, and were of a whitish yellow colour, the rest of the stone
being of a greenish yellow, or greenish brown. They were smooth
on the inside, but the outside was radiated, as if the original body
had been covered with spiculz.

The substance which filled up the area of these figures was gene-
rally the same as that surrounding the outside, but sometimes it was
a little different.

Although I had no doubt but that these singular figures owed
their origin to some organic body, yet I did not at first suspect that
they were in any way connected with the cylinders in relief that I
have just described. Fortunately however an illustrative specimen in
the limestone convinced me that both these appearances so different
from each other were derived from the same source. Pl. 29, fig. 13,
represents the specimen to which I allude. In this on one side
may be seen a perfect example of the white radiated circles, and,
in consequence of some of the stone being broken away, the in-

382 Mr. WEBSTER om some new Varieties of Fossil Alcyonia.

ternal part is exposed, and corresponds exactly with the smooth cy-
linders. Having seen this in one complete instance, I was able to
trace it in others ; and was now convinced that the smooth cylinders
were only the internal parts of the same body whose various sections
formed the white circular and elliptical figures.

When these forms are enclosed in a very soft sandstone, although
the sections are very evident from their colour, yet they are seldom
seen in relief, because the cylinders themselves are soon destroyed
by the abrasion of the surface; whereas the hardness of the lime-
stone permits them to remain.

Besides the prodigious quantity of fine specimens of these fossils
to be found at the Western lines, Pl. 30, there is another circum-
stance peculiar to the place, arising from the position of the rocks
forming the cliffs. These consist entirely of the green sandstone
formation, which has slid down in a mass into the sea at the time
when the great failure of the stratum took place which occasioned
the under-cliff. The stratification of these rocks dips considerably
towards the land, and from the action of the sea on the lower part,
large portions have been detached, leaving the upper part over-
hanging frequently twenty or thirty feet. ‘These masses have sepa-
rated from the rest of the rock, and exhibit in the divisions between
the beds a view of their upper and under surfaces. Attached to
these surfaces are vast layers of these fossils heaped upon each
other, and lying prostrate in every possible direction, and in frag-
ments of various sizes. Their substance is always sandstone of
very soft quality, and having suffered much from the weather, they
appear like sculpture almost defaced. It is not difficult however to
trace multitudes both of the stems and heads, varying from four
inches in diameter to the eighth of an inch, In the joints between
the beds where they are still not separated, they may also be dis-

Mr. WEBSTER on some new Varieties of Fossil Alcyonia. 383

tinctly seen. The number is indeed truly astonishing, almost .
every block of stone contains many, and some of the rocks appear
entirely filled with them,

Whether those having a thick cortical part, and the smooth cy-
linders with a spiculated cortex, are different parts of the same
species, representing in one case the stems and in the other the
branches, I must leave to be decided by future observers; at present
I am not in possession of any facts that would connect them to-
gether. They both agree in the great length of the stems, and in
the general forms of the heads attached to them; but I never found
the smooth cylinders of larger diameter than one inch, although I
frequently observed the other four or five inches in diameter. The
cortex of the former, when it was at all discernible, was always ex-
tremely thin, but that of the latter was nearly equal to the internal
part ; and I never found the sections of the last sort in the green
sand like rings.

With respect to the smooth cylindrical fossils, whose sections
formed white radiated circles, I cannot help thinking that the
originals were tubular bodies, or that the animal matter which:
originally filled them was gelatinous, or consisted of some: sub-
stance not sufiiciently dense to undergo the process of silicifi-
cation 3 in consequence of which the fossils were at first hollow,
and admitted the matter which enveloped them also to fill the in-
side; since I constantly found the material within the radiated ring,
whether sandstone or limestone, the same or very nearly so with
that which surrounded it.

Although by giving full scope to the imagination, one might
easily be led astray in contemplating a phenomenon so curious, yet
I have no doubt but that these appearances will warrant the con-
clusion, that there must have existed here an immense bed of these
wonderful animals, of the most gigantic size, growing like asub-

384 Mr. WEBSTER on some new Varieties of Fossil Alcyonia.

marine and animated forest; and from the infinite variety of

‘curvilinear forms in which the branches are found, it is probable
that they were possessed of the power of moving their arms in
every possible direction, for the purpose of searching for and ob-
taining their food, which they extracted from the sea-water.

But if we reflect upon the changes which these extraordinary
creatures have undergone, our wonder must increase. From some
mysterious cause the animal membrane becomes converted into si-
liceous matter ; and we have then to contemplate the idea of their
still retaining their original forms and situations but changed into
stone. By subsequent convulsions of nature the silicified animals
are broken to pieces, whilst the fragments are scattered in all di-
rections. These are enveloped and covered by sand and calcareous
matter, the alternate depositions of each with these fossils forming
the vast mass of strata we have been examining. Had the animals
been overwhelmed by the sand while in their living state, they
must have been crushed quite flat by the superincumbent weight ;
but in no instance is this the case; their cylindrical forms remain
perfect, and do not appear to have suffered from pressure,

You will no doubt perceive that in thus supposing the first change
‘of the animal into silex, I have followed the theory of Mr. Par-
kinson, as stated in his work on organic remains ; and the above
observations may perhaps tend to confirm the justice of his con-
clusions. That these fossils contain generally more siliceous matter
than the investing stone, appears probable from their greater dura-
bility, and indeed in some instances I found them almost wholly
siliceous.

Having noticed the extensive distribution of this fossil, I en-
deavoured to ascertain the several strata in which it is found. In
the ferruginous sand, below the green sandstone, I could not find

Mr. WEBSTER on some new Variettes of Fossil Alcyonia. 385

any specimens. In the blue marl on which the sandstone rests, I
found only two or three fragments of cylinders with the cortical
part easily detaching itself, the substance being of the same nature
as the stratum containing them. The green sand and the lime-
stone were the chief repositories. I traced them upwards into the
chert ; but they there became rare, and they totally disappeared in
the chalk marl. But in the fragments of flint with which the shore
from Dunnose to Ventnor is covered, I found many of the cylin-
ders enclosed, and sometimes exhibiting both the internal and
cortical part. Frequently I observed white circles in the flint,
somewhat resembling those above-mentioned in the green sand-
stone, having in the internal part flint of the same kind as the
envelope; and it is not improbable that these are sections of the
cylindrical forms I have been describing.*

Since my return to London, the drawings and specimens
above described have been seen by several gentlemen skilled in or-
ganic remains, and particularly by Mr. Parkinson. It was his
opinion that they all belonged to the genus Alcyonium, but were of
three if not four different species, not one of which had hitherto
been described. ‘The circumstances which he pointed out in which
the first-mentioned differed from any known fossil Alcyonia are the
following.

The heads vary in form from any other, being longer or more
tulip-shaped.

* In a subsequent excursion to Dorsetshire, I observed evident traces of an aleyonium
nearly similar in the Purbeck stone, and another apparently somewhat different in the
limestone rocks between Weymouth and Sandsfoot Castle. I found in great abundance
the appearances of the white radiated circular and elliptical figures in the Isle of Port-
land, and have since noticed that these are extremely common in the blocks of stone
brought from that place to London. They may be seen very distinctly in the Portland
slabs in the door-ways of most of the large houses in this metropolis,

WoL. Tl. 3°e

386 Mr. WEBSTER on some new Varieties of Fossil Alcyonia.

In the fossils of this genus yet noticed, the pedicle sor stalks have
been very short; and although numerous fragments of these have
been found, it was not certain that they belonged to the heads, the
portions of stalk attached generally not exceeding an inch or two;
whereas in those which are the subject of the present paper, we see
stems of considerable length, frequently extending four or five feet.
All the fossil aleyonic heads which have been described as approach-
ing to a globular form, are characterised by a considerable opening in
the end; but the species we have been considering has no such struc-
ture. From the circumstance of the heads appearing in shape much
like the closed buds of the tulip, and from their being attached to
long smooth stalks, perhaps the name Tulip Alcyonium may not
be improperly applied to this species.

In the stratum containing the white radiated circles, and fre-
quently in the same block with them, I noticed another species of
cylindrical and tubular organic body, somewhat resembling them,
but differing essentially in some particulars. Fig. 14, Pl. 29, ex-
hibits the appearance they assume. They are usually about half an
inch in diameter, the inside nearly cylindrical, or rather shghtly
elliptical, and the body much thicker on one side than on the other
so as to make the form of the outside very irregular; but they
never have the radiated character of the others. They do not vary
much in diameter, and are frequently several feet in length. They
do not taper, and I found no branching nor bulbs. Their substance
is calcareous, of a whitish colour, and the matter with which they
are filled is the same with that in which they are enveloped.

Fig. 15, Pl. 29, represents a fossil organized body, which I found
to occur frequently in the stratum of blue marl immediately under
the sandstone, or rather in the part where both these strata pass into
each other.

Mr. WEBSTER o” some new Varieties of Fossil Alcyonia. 387

This appears as blackish streaks in the ash-coloured marl, much
resembling in form some plant. They frequently project above
the surface, being a little more compact than the marl, though
they are also calcareous; they lie in all possible directions, ex-
hibiting sections sometimes at right angles to their axis, sometimes
oblique, and sometimes longitudinal. ‘Their stems appear to have
been hollow, and they have some parts attached to them extremely
thin, like leaves. 1 found nothing like bulbs or heads to these..
They are also very extensively distributed, occurring at every place
where I observed this stratum.

Sic Z

XVIII. Miscellaneous Remarks accompanying a Catalogue of Specimens
. transmitted to the Geological Society.

By J. Mac Curtocs, M.D. F.L.S. Chemist to the Ordnance, and Lecturer
on Chemistry at the Royal Military Academy at Woolwich.
V. Pr. Geol. Soc. 6

Havinc had an opportunity during the Society’s late recess of
collecting some specimens of the mineral productions and rocks of
Scotland, I have transmitted them with a hope that other members
who may have the means of so doing, will make still greater exer-
tions in aid of this very necessary department of our museum.
Such collections, however useless in an insulated state, acquire a real
importance from their union, and form by their accumulation one of
the leading objects of such an institution, a point of reference for
authority whether geographical or mineralogical.

To these specimens I have been induced to add the miscellaneous
remarks which form the present paper, with a view of attaching to
them more interest than would accrue from the mere mention of a
naked /abitat, and for the further purpose of rendering the catalogue
which must accompany them, more intelligible. ‘These remarks
include such geological observations on the nature and connections
of the rocks from which the specimens were detached, as occurred
to me at the time, or were the result of comparison with the obser-
vations of other writers who have treated the same subjects. Where
the specimens themselves are deficient in the requisite purposes of

Dr. Mac Cutiocn on the Geolgy of various parts of Scotland. 389

elucidation, the references to the places where they were found will
enable future visitors to verify or correct them. In this view the
remarks which I have hazarded are even more necessary than in that
of perfecting a catalogue of hand specimens, since of many important
geological facts, itis impossible to preserve a sufficient record in a
mere collection of rocks. A great portion of the country which is
the subject of this miscellaneous notice, has been already surveyed
by various geologists, and particularly by Professor Jameson in his
tour to the Western Isles. ‘Those who are accustomed to geological
investigations will be as little surprised to find me occasionally differ-
ing from those observers as I shall be to find future observers differing
from me. ‘The science is as yet far removed from the class of accu-
rate ones, and must still owe a great deal to that free enquiry which
alone can lay the foundation of a precise and stable induction. It is
peculiarly necessary in its present state that the labours of many
should co-operate, as the wide diffusion and difficult accessibility of
its leading facts put it out of the power of any single observer to add
much from his own stock.

To the more extended geological remarks which seem to be called
for by the peculiar circumstance of some of the rocks included in the
catalogue, I have added a few words on specimens which scarcely
involved any novelty either of a mineralogical or geological nature.
Yet it will not be useless to describe their situation, since our Society
among other objects offers itself as a deposit of miscellaneous infor-
mation on those subjects, and of such detached facts as must other-
wise perish in the portfolios or memories of those whose fortune it
has been to notice them. It is not one of its least advantages that it
forms a school of practical knowledge for those whose opportunities
are circumscribed by the scarcity of scientific institutions or schools
of this nature, and with this view, even the humble offering of a
new habitat is deserving of record,

390 Dr. Mac Cuttocu on the Geology of

In the mass of geological reading which is in the hands of every
one, most of the places referred to for characteristic examples are in
foreign cotntries, always of difficult access to the many, and ren-
dered more so at present from the circumstances of the times.

Our own country, perhaps, exhibits a greater variety of mineralo-
gical products and geological facts than any equal space on the globe,
condensed in their position and easy of access. It is desirable there-
fore that a record should be kept of such circumstances, that the
student may not be sent to Siberia or Bohemia for that information
which he may acquire in Arran or the Grampians; and that the
humble task of recording the domestic Aabitats of interesting par-
ticulars may be countenanced by a Society which we trust is destined
to add somewhat to the interest already taken in this pursuit, and to
the general progress of geological knowledge.

In matters of terminology I have felt an inconvenience not peculiar
to myself, which I have been unable to remedy without appearing
to attack hypotheses that I would willingly have let alone, as the
language of controversy is unpleasing, and appears rather cal-
culated to retard than promote the progress of an infant science ;
not only by warping the impressions which the mind receives, but
by diverting it from legitimate observation to the more amusing
occupation of attack and defence.

I allude here chiefly to Werner’s great divisions of rocks. If we
describe the several rocks by the terms which he has applied to
them, we begin by admitting the very matter to be proved. A worse
consequence follows; the adoption of the terminology insensibly
leads to a belief in the hypothesis, and becomes inimical to that in-
dependent and free spirit of observation which the infancy of any
physical investigation more especially requires. ‘To describe ap-
pearances without adopting this systematical language requires a cir-

various parts of Scotland. 391,

cumlocution which it would be desirable to avoid, yet till either a
system is firmly established on a wide and fair induction, or a set of
terms can be produced independent of all system, such circumlocution
is perhaps inevitable.

I have only to add, that since the following remarks did not admit
of any useful or methodical arrangement, they are placed with little
regard to order, and as the subjects of them occurred. ‘That they
are so detached, and often so superficial, must be imputed partly to.
want of knowledge, partly to want of time, and still more to the
uncontroulable elements, to which the best laid projects of the mine-
ralogist as of the husbandman must bend.

Rona.

I should scarcely have introduced any remarks on Rona, were it
not for the purpose of mentioning that wolfram, hitherto unnoticed,
in this spot, is found in the granite veins that traverse the gneiss
of which this island is principally formed. I may however re-
mark at the same time, that these veins exhibit that variety of
granite called graphic, a rock of much more frequent occurrence
than it was once supposed. ‘The graphic granite of Rona is. dis-
tinguished by the great size of the crystals of felspar which enter
into its composition, and consequently by the equal magnitude and
distinctness of the quartz which fills their intervals. An accurate
survey of Rona is still a desideratum for future mineralogists, as the
number, magnitude, and peculiar character of the granite veins might
give us hopes of detecting in them some of the rarer minerals known
to be inmates of such veins, and observed in similar situations in
other parts of the earth, I cannot however dismiss this subject of

592 Dr. Mac Cutrocu on the Geology of

Rona without pointing out to future observers the singular contor-
tions exhibited as well by the gneiss as by the hornblende rock —
where they come into contact. I may also venture to suggest that
the rock of Blue Bay, described as a mixture of hornstone, chal-
cedony and quartz, appears to be a modification of gneiss, exceed-
ingly intersected by veins of quartz and felspar, and probably of
granite. It exhibits no genuine hornstone; that part of it which
has at first sight this appearance, being an intimate mixture of
quartz and felspar. The chalcedony too is only that modification
of quartz which occurs in graphic granite, and which is well cha-
racterized by its peculiar waxy look. Exposure to the weather pro-
duces on its surface a glossy enamel, of an opacity and lustre still
more nearly resembling that of chalcedony, but which does not
penetrate into the stone. A similar enamel is to be observed in-
vesting the sandstone of Jura and of Schihallien, and I have also
specimens of the granite of Rockall, which exhibit the same appear-
ance. It seems to arise from a partial solution of the silex on the
surface, and has been observed in certain foreign sandstones, being
quoted as an instance of the solubility of silex in water. This
quartz occasionally assumes a high red hue, which is evidently to
be traced to the penetration and intimate mixture of red felspar. In
some places it is of a green colour, being penetrated by threads and
laminz of a substance bearing a resemblance to steatite rather than to
hornblende. It thus forms a greenish stone, probably different from
quartz coloured by actinolite which is called prase, from the same
stone penetrated by epidote which has obtained no name, or from
quartz tinged by green earth, which occurs in Rum and which, as
well as chalcedony when similarly coloured, is known by the name
of heliotrope. Yet, as it possesses the external characters and aspect
of prase, it may be safely referred to a species of which colour

various parts of Scotlnnd. 393

seems the only very discriminating character. I think it necessary
also to mention that the hornblende rock exhibits the two sub-
ordinate varieties of hornblende slate and greenstone slate.

Since I have already indulged in some cursory remarks on that
sort of nomenclature which tends to mislead, by confounding sub-
stances, I may be excused for suggesting a reformation in the terms
primitive greenstone and greenstone slate. These consist of mix-
tures of felspar and hornblende, in the latter case disposed in a
laminated form, and in the former without that regular structure.
Their title to greenstone, as far as colour is concerned, is still less
than that of the varieties of the trap family, as the felspar is (in
Scotland at least) always of a red colour. By the use also of the
term greenstone, and by the series which is formed of primitive,
transition, and floetz greenstones, the mind is naturally led to look
for a geological and natural connection between these rocks, But
the primitive greenstones belong to that class in which gneiss and
mica slate form the principal features, and which constitute that
great system of rocks of which hornblende in its several modi-
fications of hornblende rock, primitive greenstone, hornblende
slate, and greenstone slate, is only a subordinate and occasional
member. The geological character of the floetz greenstones, is
their independence with respect to the rocks with which they are
associated, and their intrusion, if I may so call it, among a regular
system of stratified bodies. The transition greenstones are, I con-
ceive, of a character merely arbitrary, and only so called because
occupying the same situation with regard to the ¢ramsition, as the
former do with regard to the fletz rocks.

Thus also, greenstones may be classed among the primitive, where
they occupy similar positions among primitive rocks.

But the primitive greenstones to which I now allude, and which

VOL, Il. 3D

594 Dr. Mac Curtrocu on the Geology of

constitute a class of rocks entirely different, have been evidently
formed together with the rocks which they accompany, and are,
like them, referable to the same epoch, never intruding to their
disturbance, but occupying situations and maintaining characters,
in every respect conformable to them. It would tend to the accuracy
of geological language, if they were to receive designations derived
from their simple parent, hornblende rock, and it is to be desired
that the occasional mixture of felspar with hornblende, whether that
rock be massive or slaty, should be designated by a term, if it
requires a distinct one, derived from its true basis, so as to prevent
the confusion which their present names introduce into our ideas
and descriptions.

Shiant,

The Shiant isles having escaped the notice of mineralogists, I
shall make no apology for giving such a cursory description of
them as my opportunities of observation allowed me to draw up,
for the purpose of explaining the specimens which I have trans-
mitted.

These islands are situated to the north of Ruhunish point, in
Sky, from which they are distant about 15 miles, and they lie
about 8 miles nearly south-east of the entrance of Loch Brolum,
in Lewis. There are three principal islands, forming a nearly equi-
lateral triangle, besides a few subordinate rocks of considerable
height, but of small superficial dimensions. The names of the
three largest are Gariveilan, Eilanakily, and Eilan Wirrey. Of
these the two former are about a mile and half in circumference, and
the latter appears to be less than a mile. They constitute one farm,
the house appertaining to which is situated on Eilanakily. In ap-

various parts of Scotland. 395

proaching them on any side they exhibit high columnar precipices,
surmounted by grassy irregular plains, and surrounded by rocky
shores of difficult access, which are whitened by a rapid and ge-
nerally turbulent sea. It is easy to perceive that they are all of a
trap formation, and with that general knowledge of two of them,
Kilanakily and Eilan Wirrey, I was obliged to remain content, as a
gale of wind with thick weather coming on soon after I landed on
Gariveilan prevented me from extending my examination further,
without endangering the boat and her crew. I trust that some
future mineralogist, with better fortune, may complete the investi-
gation which I was obliged to leave undone, and fill up the blanks
which will be found in my brief account of this very picturesque
and interesting spot.

The boat landed in a bay on the north side of Gariveilan, where
a noble facade of columnar trap descends perpendicularly and
without a break into the sea, rising to an elevation, as I should
guess, of 200 feet. In picturesque effect, and in continuous pro-
fundity of shade, it excels even the celebrated cliffs of Staffa. The
columns are however neither so regular nor so perpendicular as
those of that island, but rather resemble the obscurely formed ones
which occur on the shores of Ulva. <A few here and there present
nearly the same degree of regularity as those well-known specimens
on the south side of Arthur’s seat. This colonnade extends along
a great part of the northern shore, plunging under the water to the
eastward, while towards the west it is so elevated as to allow an
examination of several strata, which lie beneath it. At the south
side of the island the ground slopes so as nearly to meet the sea.
It is on this south side, and at the eastern end, that these different
strata come into view. ‘The lowermost bed is a dark purple horn-
stone, of which the thickness cannot be determined, as nothing is

3D 2

396 Dr. Mac Cuttocu on the Geology of

seen below it. The accompanying specimens will preclude the
necessity of describing a rock of no uncommon occurrence, whe-
ther the name by which I have designated it be one about which
mineralogists are agreed, or not. It has unfortunately been ap-
plied to so many different stones, that it is utterly impossible to
steer clear of difficulties. Among the reforms of nomenclature,
in the departments of rocks, the term hornstone, and the va-
rious substances which have been classed under it, call loudly for
examination. The adoption of petrosilex might have gone some
way to remove this gonfusion, as we should then have had two
names instead of one, by which to designate four or five different
substances; but as this latter appellation has been equally misap-
plied with the former, and different authors have called the same
substance by both these names, the confusion has, if any thing,
been increased. Mineralogists may inquire whether by a due appro-
priation and limitation of the three terms, hornstone, chert, and
petrosilex, already in use, some progress may not be made in re-
moving this obscurity without any material additions to our no-
menclature. I forbear even to hint at the apparently, and only
apparently, corresponding French terms, pierre de corne, and
cornéene, lest I should drive the reformer to despair.

But to return. This bed dips to the south-west, and appears to
have about 15 degrees of elevation. Immediately above it lies a
bed of rock, about 20 feet in thickness, and of a structure so
peculiar as to require a more detailed description.

It is formed of globules, every where adhering together, not
merely by their touching surfaces, like most of the pisolites, but in
general by large segments, similar to the globular limestone of
Sunderland. These are occasionally compressed as if by a super-
incumbent weight, but in many places are absolutely spherical, and

various parts of Scotland, 397

by their accumulation become botryoidal, smaller spheres growing
out as it were from the larger ones. Detached specimens that have
been washed by the sea, exhibit the appearance of a bunch of
grapes, but in their native bed the intervals are filled with an ochry
clay. Their fracture shows the uniform aspect of siliceous schist,
being neither coated nor radiated; and the rock agrees in every
respect, except its structure, with the bed of siliceous schist, which
is found not far off.

I have only observed one other instance of a rock similar to this,
and it occurs also under amygdaloidal trap at Talisker, in Sky.* I
have reason to suppose it- of rare occurrence. In various parts of
the rocks which I have now described there are found natural joints,
which on being separated exhibit two smooth surfaces, absolutely
flat, and appearing as if they had been cut through by a sharp tool.
The globular bodies themselves are divided in various parts, just as
they happened to interfere with the section. In the greater number
of the sections which I examined, no substance was interposed be-
tween the touching faces. But in some I found wavellite, a mineral
as yet not so common, but that this new /aditat will be acceptable to
the mineralogist. It is remarkable that the circles of wavellite oc-
cupy precisely the surface of each segment of the several spheres,
varying in size according to the varying dimensions of these seg-
ments, ‘This bed is covered by one of trap, or to use the term in
its present great latitude, of greenstone, forming a parallel bed of a
more considerable thickness, but with the same inclination as the
subjacent strata. ‘This bed of greenstone weathers so as to exhibit
distinct globular concretions, although in its entire state the eye can

* T have since observed a similar modification in the schist of Devonshire in which
wayvellite is found.

398 Dr. Mac Cuttocu on the Geology of

trace no difference between the amorphous portion and the columnar
mass which forms the upper part of the island. This very com-
mon fact should serve to convince us how little information we can
obtain of the true and fundamental structure of rocks, from their
natural fracture, while in a state of integrity.

The bed of. trap which I have now described, is followed by a
bed of schistus, which may be called a siliceous schistus, a term
likewise under which many substances have been very improperly
confounded, although the characters of this rock are sufficiently de-
fined to render such carelessness of description inexcusable.

But it is not only in mineralogy that the desire of accounting for
that of which the cause is unknown, and of describing that which
is not understood, predominates over those severer habits of investi-
gation, which can alone render scientific description accurate.

It is too hopeless a task to attempt to develope the confusion of
rocks to which the terms cornéene and trap have been applied, names
which will probably be given to this rock by those who follow the
French nomenclature. I believe I go along with Mr. Jameson, in
calling it flinty slate, or siliceous schist, and it will perhaps be con-
sidered a variety of that which is called Lydian stone. It breaks
naturally into prismatic and rhomboidal fragments, but its forcible
fracture is flat, approaching to the conchoidal, with a small degree
of lustre, and without grain. It is exceedingly brittle, and cuts
the hands like glass. Its gives fire readily with steel, and the file
scarcely touches it. Its colour is a dark lead grey.

Natural joints, similar to those I noticed in the botryoidal
schistus, (if I may venture thus to distinguish the rock described
above) occur also in this schistus, and circular stains may be ob-
served upon the planes of contact. I did not find any specimen of
wavellite in this variety; but I cannot pass on without remarking

various parts of Scotland, 399

that the habits of this rock, and its connections, in all the cases
where I have had an opportunity of seeing it, seem to point it out
as an argillaceous schist, altered and indurated in consequence of its
proximity to greenstone. :

The last bed is the immense mass of columnar trap already men-
tioned, which surmounts the whole. The character of this rock is
not that of a greenstone, to use the word in its more restrained
sense, as it does not contain distinct grains of hornblende and
felspar, but is an obscure mixture of hornblende, felspar, and
quartz. | :

I have therefore both here and in other places, (where I have had
occasion to describe the varieties of this rock, of which the charac-
ters are not so decided as to admit of their being placed either under
the heads of basalt, wacke, or greenstone,) preferred the general
name of trap to the use of a specific one with which the characters
of the individual cannot be made to agree. In so doing I have left
out of view the confusion which must arise if the siliceous schist,
and Lydian stone, which appear to be the trap of some authors, be
considered as forming a part of this great natural division, and have
taken the term, as I imagine, in the sense intended by the followers
of Werner. It is thus used by them as the title of a family, in-
cluding basalt, wacke, greenstone, and clinkstone, a family well
expressed by the vernacular term whiz, now, I believe, and perhaps.
unfortunately, obsolete. The characters of basalt, wacke, green-
stone, and clinkstone, are tolerably decided, and the geological
relations of the trap family are so remarkable that we ought to find
little difficulty in assigning proper terms of distinction to its respec-
tive members. But, independently of these four well characterized
rocks, innumerable varieties occur not properly referable to either,
and which cannot even be truly expressed without much circumlo-

400 Dr. Mac Cutiocn on the Geology of

cution, and reference to those well-known members which they may
chance to resemble. If in these cases we apply the name of any of
their species in place of a generic term, we render our description
of individuals unintelligible, and often contradictory and absurd.
‘Thus the name basalt has been given to greenstone, as well as to
many other modifications of trap, to which no name has, or perhaps
ever can be applied. But the chief confusion has resulted from the
application of the term greenstone, as a generic term for these rocks.
In this way we have had greenstones of all colours, from red to
white, and in which neither hornblende nor felspar were to be dis-
tinguished, ‘

It would assuredly be better in describing the geological appear-
ances of these rocks, when the description of individuals is not
necessary, to make use of a generic term which should distinguish
the character of the family, without confounding the individuals.
The peculiar aspect of the rocks of this family renders the name of
trap as expressive as any which can be applied, and in this sense,
if it be limited to that well-known class of unstratified rocks which
includes the above-named individuals and their numerous modifica-
tions, we shall escape the confusion which must otherwise ensue,
and which unfortunately already exists too much.

It is evident that the other modifications of this rock consisting
of amygdaloid and of the various trap porphyries, are still further
subordinate species, if I may style them so, ranking according to
their particular basis, under the several species above enumerated.

It is said that in the Shiant islands ammonites and other animal
remains are discovered in beds under the trap, but I did not ob-
serve them. ‘They may very probably however exist here, as they
are of frequent occurrence in Sky.

Among the rolled pebbles on the shore I met with specimens of

various parts of Scotland, 401

pink coloured quartz. I did not observe any foreign matters im= _
bedded in the trap, except minute drusy veins of calcareous spar.

Such are the very limited observations, which an inspection un-
avoidably much hurried, enabled me to make on this part of the
group. Although the general aspect of the other two islands would
lead me to expect in them an identity of structure, yet they may
afford differences worthy of further investigation.

Rum.

A stormy sea, a dangerous shore, want of harbours, a trackless
country, and a scanty and wretched population, render it as dif-
ficult a task to reach this island as to examine it.

It forms one mountainous tract of rugged and barren aspect, and
of considerable extent, although its highest mountains, which lie
towards the west, do not appear to exceed two thousand feet in
elevation. My observations were limited to the only two parts of
the island which aretolerably practicable, Loch Skresort, and Scuir-
more.

Loch Skresort forms a semicircular indented bay, from which
the land shelves gradually upwards by a moderate acclivity, till it
approaches the middle region of the mountains, from whence the
further ascent is steep, rugged, and often precipitous to the very
summits. These terminate in craggy and broken points, exhibiting
abrupt faces, and piles of ruins. The rock which incloses the bay
of Loch Skresort, is a reddish argillaceous sandstone, disposed in
beds and elevated to a low angle, varying from ten to fifteen de-
grees, occasionally fractured, bent, and displaced. It appears to
be the result of the decomposition of granite, since the argillaceous
grains are often found to consist of felspar in a state of integrity,

VoL. Il. 3 E

402 Dr. Mac CuLiocn on the Geology of

although at times putting on the appearance of clay. The quartz
is of a brownish red colour. My examination of it was by no
means sufficiently extensive to enable me to say what varieties may
exist in different places, but it has an aspect and disposition so per-
fectly analogous to that of the sandstone which lies under the Cu-
chullin mountain on the opposite shore of Sky, and which forms the
greater part of the island of Soa Vretil, that I consider them as
belonging to one bed. As I shall have occasion to describe this
rock again in the remarks which I propose to offer on Sky, I for-
bear to dwell on it here. The basalt veins, so common through-
out all the islands of this coast, traverse this sandstone, but are not
so abundant immediately about Loch Skresort, as is common on
these shores. Where the sandstone terminates on ascending to-
wards the mountain, it is succeeded by a inass of rock, which
bears the general aspect and features of the mountain trap rocks,
of the rocks for example which constitute the Cuchullin moun-
tains, and which are perfectly distinguished in their general cha-
racters from those which, on account of their bedded and parallel
appearance, are well designated by the term /loetz trap.

But the composition of this rock is peculiar, and, as far as I
know, resembles no other in Scotland. It consists of two ingre-
dients only, and has at first sight the aspect of those syenitic traps
so common in the Cuchullin, which are formed of hornblende
and felspar, in large crystals: but instead of hornblende it contains
augite. ‘These substances, the felspar and augite, are confusedly
crystallized together; and although the concretions vary much in
size, they are most generally large, and appear to increase in di-
mensions on approaching nearer to the summit of the mountain.
The crystals of augite are not unfrequently an inch or more in
length. Although I traversed a considerable space over these

various parts of” Scotland. 403

mountains, I did not discover any variation from this general -
character. I should add, that the felspar is the glassy variety.

The cliffs from Loch Skresort to Scuir-more, exhibit the same
general appearances of sandstone skirting the shores, and intersected
by trap veins, or with masses of trap rocks superimposed on them.
A more particular knowledge of this coast is scarcely attainable either
from sea or land. At Scuir-more a small beach affords a point of
access, and here some variations occur which are worthy of notice.

The sandstone is in this place elevated at very high angles,
varying from forty to sixty degrees and upward, and it appears to
dip uniformly toward the west. In composition it differs more
materially, being ferruginous from oxide of iron, and in place of
clay, containing calcareous earth. It is also traversed by numerous
minute veins of calcareous spar, and is intersected by innumerable
basaltic veins, of different sizes, and often of great magnitude. By
these and the subsequent disintegration of the rocks, it is hollowed
into caves, and wrought into arches, producing strange and _pic-
turesque scenes of ruinous grandeur. I may remark, that the junction
of these different rocks does not appear to be attended with any
change in the nature of either. In one of the veins there is a portion
containing a compound of an uncommon nature, but somewhat
resembling the rock above described, being a mixed mass of crystals
of augite, hornblende, and felspar. Loose specimens of black
pitch-stone are also found on the beach, arising in all probability
from some vein of that substance. But the production for which
it is most remarkable is the green chalcedony, or heliotrope as it is
generally called.

This substance, which exists in large masses, is also found
occupying cavities in the basaltic amygdaloid, in nodules varying
from the size of a mustard seed to that of a pea. These are

SEZ

404 Dr. Mac Cuttocn on the Geology of

accompanied by similar nodules of calcareous spar, often also
penetrated by green earth (chlorite baldogée.) This amygdaloid
accompanies the larger masses of green chalcedony, and seldom
extends many inches beyond them. The great masses are either
in the form of irregular nodules, reaching from the size of an egg
to that of a man’s head, or they resemble short veins, of which the
opposing sides are flat, and somewhat parallel, and which might
perhaps more properly be called angular nodules. Their colour is
as various as their other external characters, but the most frequent
varieties are comprehended in the following list.

1., White chalcedony ? approaching to quartz,-and sometimes to
hornstone, in its aspect, fracture, and other qualities.

2. Pure chalcedony of a more or less milky hue, constituting the
chalcedony and the white carnelian of lapidaries.

3. The first variety of chalcedony, of a brown colour with nar-
row parallel stripes of green.

4, The same, irregularly mottled with green, white, and brown.

5. The opaque, or first variety of chalcedony, of an uniform dark
sap green, with the dull fracture and aspect of wax, and like that
substance, translucent on the thin edges.

6. The translucent variety, similarly coloured, but with a more
conchoidal fracture, and of a glassy aspect.

7. Varieties which in one specimen exhibit a perfect gradation
from pure white or colourless chalcedony, to the deepest green.

All these varieties contain imbedded spherical bodies, varying
from the size of the minutest poppy seed, to that of a mustard seed.
These are frequently formed of pyrites, and although they are
often entirely decomposed, yet they now and then exhibit the
remains of a crystal of pyrites within them, and their external
surfaces retain a ridgy and crystallized aspect, the remains of the —

various parts of Scotland. 405

edges of the plates which have formed them. But the most -
common of the spherical bodies are, when fresh broken, of a white
colour, becoming at first yellow by exposure to air, and subsequently
of a dark brown. Their internal texture, as far as it can be deter-
mined by high magnifying powers, appears platy, and although it
is difficult to speak with certainty of bodies so minute, and so much
out of the reach of examination, they seem greatly to resemble
brown spar; a conclusion rendered more probable, by the changes
which they undergo on exposure to the air. The whole of these
chalcedonies are occasionally penetrated by lamine of calcareous
spar, which are often so numerous as to form nearly one half
of the stone, and which from its yielding in their direction,
rather than in that of the chalcedony, do often seem on a su-
perficial view to form the whole of it. In the rifts of these
chalcedonies, we may occasionally find detached masses of green
earth, which by its combination with the stone itself appears
beyond all doubt to be the colouring ingredient. Its unequal
diffusion through the stone, is equally demonstrative of the same
supposition. )

We have now to compare the green chalcedony of Rum, with
the stone known by the name of heliotrope, and commonly called
oriental, since that name has been applied to it, and as it will appear,
with perfect propriety. The fracture and translucency of the true
oriental heliotrope, show, as Brongniart has well remarked, that
it has been improperly ranked among the Jaspers; and the de-
scription and natural analysis, if I may so call it, which I have
now given of the stone of Rum, confirm the propriety of his
remark, and refer it to its true place among the varieties of
chalcedony. It is true, that the stone of Rum very rarely exhibits
the red spots which so often occur in the oriental kinds, but these

406 Dr. Mac Cuttocu on the Geology of

are purely accidental. An examination of many specimens of the
latter in my possession, has proved the existence in it of variations
in regard to lustre, and other characters, precisely similar to those
IT have noticed in the stone of Rum. In these too, the fracture is
now and then waxy, flat, and dull; occasionally it is conchoidal,
shining, and highly translucent, but it never approaches to the
earthy aspect of true jasper. The irregular diffusion of the green earth
is also equally remarkable in some of the oriental specimens, since
among those which have fallen under my examination the green
colour is often diffused in partial stains through a pure chalcedony,
so that the distinct grains of green earth are discernible by the lens.
These also being accompanied by the blood marks esteemed
characteristic of this stone, leave the determination of its name free
of doubt.

We may therefore conclude, that the green stone of Rum is
the true heliotrope of lapidaries, and that this stone is merely
a mixture of green earth with chalcedony, its external characters
varying either from the variations in the quality of its base, or
from the quantity of the green matter with which it is combined.

I did not perceive among the green chalcedonies of Rum any
specimen resembling the plasma of the Italians, unless perhaps
that in some of them small parts of a more remarkable transparency
might occasionally be traced. Yet, as among specimens of the
real plasma which I received from Egypt, there are green spots in
the stone, resembling minute crystals of chlorite, independent of
the general green stain which pervades the whole, I think it
not unlikely that this substance is also the colouring matter
of plasma, and that the only difference between that mineral and
heliotrope, will be found to consist in the different transparency
of the siliceous stone which receives the colour. It is not therefore

various parts of Scotland. 407

improbable but that plasma as well as heliotrope may be an inmate .
of the trap rocks of Scuir-more.

_ A substance is occasionally brought from India, known to lapi-+
daries by the name of brown carnelian, and it is esteemed peculiarly
rare. This substance also is found among the chalcedonies of Rum,
occupying. the same situation as the green varieties, and differing
from them only in colour. It probably owes its stain to iron.
Motley mixtures of brown, and green, of considerable beauty, add
to the variety of ornamental stones which these rocks contain.

The apparently inaccessible nature of the southern shore of Rum,
prevented me from extending further my observations on this
interesting island. But in coasting it slowly along, it offered the
same general appearance as the cliffs I have now been describing
which look toward the island of Canna, exhibiting one formidable
wall of basaltic aspect, reposing on a base of sandstone. It will be
for more successful geologists to examine whether circumstances
equally interesting, and of a different nature, may not be found
among the caverns and ruins of this repulsive, if not absolutely
inaccessible coast.

Ege.

I have little to add to the description of Egg given in the
“« Mineralogy of the Scottish isles,’ but the following fact relating
to the situation of the promontory called the Scuir of Egg, which
is not noticed in that work. The columns which form this most
magnificent precipice, exceeding in grandeur and picturesque effect
even the far famed Staffa, are of a black pitchstone porphyry.
They are disposed in various perpendicular, inclined, and horizontal
directions, and are either straight, or curved, but never jointed.
The felspar which they contain is the glassy variety. The lines

408 Dr. Mac Cutrocu on the Geology of

which separate the different sets of columns, together with the
varying inclinations of these beds, seem to mark different sets of
deposits. ‘The whole promontory lies on a bed of compact grey
limestone, generally indeed approaching to the character of a stone
marle. This bed is three or four feet thick, and rests on a still
lower bed of hard reddish sandstone, beneath which nothing is
visible. Large masses of wood, bituminized and penetrated with
carbonat of lime, are found in the marle stratum, not at all flattened.
Portions also of trunks of trees retaining their original shape, are
seen in the same bed, silicified, and their rifts filled with chalcedony,
approaching in aspect to semi-opal.

Assynt.

I have separated the account of the limestone which accompanies
the quartz rock of Assynt hereafter to be described, and which
forms so conspicuous a range of hills, because its connection with
that rock is tolerably obvious, and throws no light on its history.
But its peculiarity of character, and the great space which it occupies,
render it highly deserving of notice, as I believe Scotland no where
affords a tract of limestone so extensive.

“A low chain of hills commences about Achamore, and accom-
panies the Tain road towards the east for four or five miles, lying
as it were in a large valley bounded on both sides by an interrupted
range of quartz mountains. It appears to rise gradually as it extends
eastward, and about the Kirk of Assynt attains a height of 1200 or
1400 feet, forming a large and magnificent continuous mountain
ridge, exhibiting a great mural face of precipitous rock to the south,
and shelving away to the northward. ‘The dip and direction of
the quartz mountains appear in this place to be similar to those of

various parts of Scotland. 409

the limestone. The uppermost part of this ridge seems to consist
of one great uninterrupted bed of limestone, some hundreds of
feet in thickness, or rather, of an accumulation of beds ; well marked
horizontal lines being observed to extend in a parallel direction along
the precipice. It is also completely traversed by perpendicular fis-
sures.

Below this great mass a bed of quartz or sandstone, of consider-
able thickness, is to be seen running parallel with, and separating
the incumbent from a similar subjacent body of limestone. I did
not observe whether this alternation is carried further, but it is
probable that it might be discovered in some other parts of the ridge.
The limited extent of my investigation also prevented me from
determining the position of the limestone relative to the great
sandstone or quartz formation; whether it lies upon the’ sandstone
which rises to the south of it, and under that which rises to the
north, or whether it is a partial deposit, occupying the valley alone,
and incumbent on the whole mass. The examination of an ex-
tensive tract of very difficult access, would be requisite to decide
this question, as well as to ascertain the magnitude of its extent, and
the nature of the limits by which it is bounded. Yet, the appear-
ance of a quartz bed alternating with it, renders it probable that it is
also interposed among some of the larger masses. The beds which
I have described are elevated to a considerable angle, and although
in some places their section forms a continuous and even line, in
others they are curved and broken, and tossed about to such a
degree, that their stratified position can scarcely be perceived. The
stone itself is a dark grey or nearly black bituminous limestone, of an
earthy aspect, and minute granular fracture, smelling offensively when
rubbed. I did not any where observe animal remains in it. In many
places it is fissured into small fragments, the intervals of which

VoL. f1. SF |

410 Dr. Mac Cutrocn on the Geslogy of

having been subsequently filled up by red or white sparry matter, a
beautiful variety of marble is produced, which is now wrought for
the purposes of ornament. Its cavities also occasionally contain
large and perfect crystals of that form of calcareous spar called
equiaxe. Its surface is in most parts covered with a loose calcareous
tufo, which in some places being solidified by an infiltration of cal-
careous matter, forms beds of solid breccia. It contains grains of
sand dispersed throughout, and for this reason, commonly gives fire
with steel, a circumstance of very frequent occurrence in all stratified
limestones, whether referred to the rocks called fletz, or ¢ransiticn,
and generally most conspicuous in those which contain animal
remains in abundance. Such are the circumstances of chief im-
portance in the character and position of this limestone.

I shall now, perhaps, be expected to assign a place to this rock in
the usual division of primary, transition, and flatz, distinctions which
T am inclined to think are more easily made in the closet than in
the field. In the present state of geological science, it would appear
a safer practice in this case, as in many others, to describe that which
actually exists, without the use of hypothetical terms, which only
serve to perplex the observer, and to mislead the student, who either
boldly pronounces on the character which suits his particular creed,
or modestly supposes himself incapable of sound observation, because
he is unable to see that which is not visible. If the quartz rock of
this tract be a primitive rock, then the limestone is necessarily a
primitive rock also, notwithstanding its bituminous nature, and
accurately stratified structure, since it alternates with it. But, if this
rock is not a primitive, but a transition rock, then the limestone also
must be removed from the first class of rocks to the second.

In examining its right to a place among the transition rocks, we
must compare its characters with those which have been assigned as.

-various parts of Scotland. 411

the essential distinction of those rocks. I read in the exposition of
the Wernerian system best known to us, that “ transition limestone
contains petrifactions of marine animals,” and “ that it rests imme-
diately on newer clay slate,” and in the numerous distinctions assem-
bled for the purpose of defining it, these are the only two which
appear capable of being rendered truly definitive. Certainly neither
of those characters is found in this limestone. Equal difficulties op-
pose its admission among the fztz rocks, when we consider its con-
nection with the quartz rock, which, whatever division it may be
referred to of the older formations, can scarcely be supposed to
belong to this class. Having no anxiety on this head, and con-
ceiving that we are still deficient in information, both on the nature
-of this district, and on the subject at large, I shall willingly leave
the determination of its artificial place to those who are either better
acquainted with the unwritten laws by which these matters are re-
gulated, or to a period of further information.

To a mere observer, uninfluenced by systems, it exhibits the re-
mains of a disposition originally stratified and horizontal, but dis-
turbed, inclined, and broken, by subsequent changes ;—a disposi-
tion, which however uniform in more distant times, has been
altered to its present one with a partial, not a total loss of its
original character, by revolutions of which the antiquity and mag-
nitude are unknown to us, and by agencies which we are ill able to
explain. Any system of arrangement may be useful, which, al-
though artificial, assists us in classing and describing phenomena
more satisfactorily; but if we are to adopt the system of arrangement
to which I have alluded above, it is much to be desired that geolo-
gists would furnish us with such characters as shall enable us to
decide on the different bodies appertaining to the several divisions
of their system, without which, .an artificial arrangement is not

3F2

412 Dr. Mac CuLLocu on the Geology of

merely nugatory, but injurious to correct observation, chaining
down our conclusions in an obedience to particular dogmas, and
producing impediments destructive to the progress of legitimate
science.

Another tract of limestone, of a distinct character, occurs in the
same valley, occupying a position nearly parallel, at some distance
from it. Of this I have unfortunately nothing to record beyond
the detail of specimens. The whole inclination of the hill on this
side of the valley is covered with a deep bed of soil, such as to
render it impossible to trace the position of the rock, of which, all
that 1s visible appears in the form of detached masses, apparently
without order or semblance of stratification, rising through the grass.

The rock itself is an object worthy of attention from its cecono-
mical qualities, affording various specimens of marble, of a colour
from pure white to grey, which have already been introduced into
commerce, and for which a premium has been assigned to Mr.,
Joplin, of Gateshead, from the Society of Arts. It is the same
marble described by Williams. ‘The principal varieties are the
following :

1. Pure white of a milky opaque aspect, with a crystalline tex-
ture, and large grained granular fracture, approaching to the splin-
tery. Acquires a smooth surface on the polisher, but remains of a
dead hue like the marble of Iona, reflecting no light. Hence its
uses as an ornamental marble are much circumscribed. ,

2. White mottled with gray, of a large platy fracture, and
capable of receiving a high polish, forming a marble of some
beauty.

3. Highly crystalline and translucent, with a large platy fracture,
and of a gray colour, capable of being applied to the purposes of
ornament in sepulchral sculpture.

various parts of Scotland. 413

4, Of an uniform dove colour, very compact and translucent,
‘assuming an excellent polish.

5. Pure white,’of a large platy fracture, and translucent appear-
ance, capable of being used in plain ornaments, but too transparent
for sculpture.

6. White, with irregular yellow stains, from serpentine inter-
mixed ; extremely fine, compact, and fine grained splintery.

7. Intersected by thin lamine of schiefer spar, of an exceed-
‘ingly splendent appearance.

Isla.

My object in Jaying before the Society the series of specimens
collected in Isla, is the correction of some mistakes which have been
entertained about the nature of its limestone district ; a district of
some importance in more than a speculative view, as it forms a
“mining field in which lead ores have been wrought to a consider-
able extent. My researches in Isla having been limited to this
particular part of it, I shall confine myself to that which I
have seen, referring to Mr. Jameson’s book for such further infor-
mation as may be found in it. I may, however, venture to point
out this island as a spot in which the very important circumstance
alluded to in another place, of the connection of the quartz rock
with the mica slate, and clay slate, might be studied to great ad-
vantage. This deduction is not drawn from my own observations,
which were not sufficiently numerous to enable me to decide on a
question so important, but from the narrative of Mr. Jameson,
who appears to describe frequent alternations of those different
classes of rocks. Extensive and correct observations on Isla, would

probably determine the true relative xra of the quartz rock, and

414 Dr. MAc CuLtocn on the Geology of

elucidate still further the disposition of Schihallien, of Jura, and of
the north of Scotland. I shall merely indulge in a few very cursory
remarks on this part of the formation of Isla.

I have stated in another place that in Jura the quartz rock assumes
towards the shores a disposition far less regular than that which it
exhibits in the elevated districts. On the sides of the narrow strait
which separates this island from Isla, this irregularity is particularly
remarkable, and it is also very easy of access. ‘These rocks possess
all the varieties of structure which I have formerly described, and
with them mica slate and clay slate are found in beds, which, even
if this question had not already been decided by evidence drawn
from other places, I should have no hesitation in calling alternate.

The shores of Isla which form the other side of this narrow strait,
resemble those of Jura so perfectly, and correspond with them so
nicely in their various characters, that a spectator would not, with-
out a geographical mark for his guide, be able to determine which
of the two he was examining. We may, without hazarding
too strong a conjecture, look back to a time when these islands
formed one continuous tract. Veins of basalt and granite are to be
observed in both, the former by their superior permanence bearing
a resemblance to high walls, which at a distance emulate ancient
ruins ; appearances similar to that which forms the supposed volcanic
amphitheatre of Mull, so highly pictured by Faujas de St. Fond.
Some varieties of this basalt exhibit by an incipient decomposition,
a structure consisting of thin lamellae, and occurring, although in
a less remarkable degree, at the:Giant’s Causeway. ‘There is an
‘example of this structure among the specimens which are the subject
of the present brief commentary.

But to proceed to the great limestone district of Isla, Mr. Necker’s

various prris of Scotland. 415:

map in the possession of the Society, founded on the general opinion
of the mineralogists of Scotland, calls it a fleetz limestone.

A very cursory survey of it is sufficient to show, that it consists
of irregular and broken fragments of beds disposed in every possible
position. Occasionally it is flat, but is now and then elevated at a
small angle, and often appears. as if it consisted of strata perfectly
vertical, Almost every where it is disturbed and contorted to
a great degree. The beds are easily traced in several places,
where quarries have been dug, or mines wrought; and in many
others the inclination of the soil and the action of water, have laid
the edges bare for some hundreds of yards together. The perfect
similarity of its disposition to that of the limestone which accom-
panies clay slate all over the Highlands of Scotland, and more par-:
ticularly to that of the island of Lismore, would suffice to determine
its true character,. even without the detail of specimens. There are
two predominant varieties of it. Of these, one is dark blue, and
the other greyish white. They are both compact, and hard, but
the aspect of the whiter varieties is more crystalline than that of
the dark, which indeed often possess a merely earthy and granular
appearance.. In many places the blue varieties, where most crystal-
line, are traversed by numerous veins of a white colour, producing
an ornamental marble worthy of attention.

The blue varieties of this limestone appear to be deposited in con-
tact with clay slate, the white on the contrary, which are much more:
rare, are found in contact with a micaceous slate.

When the blue variety approaches the clay slate, it first assumes a
schistose fracture. Shortly after it appears penetrated with delicate
lamine of straight or undulating silky schistus, which by degrees
increase in number, and at length so predominate, that it is only
by examining the cross fracture, and even with some care, that the

o

416 Dr. Mac CuLLocu on the Geology of

presence of limestone is discovered in the mass. Ultimately the
limestone disappears from the schistus.

The whiter varieties, which I have described as more rare, are
found in contact with a micaceous schistus consisting of thick flexu-
ous lamin of quartz separated by thin layers of mica. Here the
gradation from the limestone to the micaceous slate takes place, by
an alternation of the layers of mica with the limestone, forming a
rock easily mistaken for mica slate, and resembling the Cipolino
marble of the Italians. ‘These limestones are no where bituminous,
and it is scarcely necessary to say, that I did not observe in them
any animal remains. A breccia formed of both the varieties is found
here and there, and I observed detached specimens of a variety filled
with minute pores, which although it exhibits no decided animal
appearances, has yet a suspicious character. A specimen is before
the Society for the examination of those who possess superior expe-
rience in these modifications.

It now remains to determine the place of this limestone in the
system of Werner: a determination which probably involves the
character of all the limestones so frequent in the Highlands of
Scotland, which, like this, are deposited with schistus. The in-
stances which occur at Balahulish, at Loch Earn, at Lismore, at Dun
MacSniochain, and at numerous other places, are too familiar to be
pointed out to those who are acquainted with Scottish mineralogy.

It is evident that the character of the limestone must, in this case,
depend on that of the rocks which it accompanies, and not on the
mixture of mica or other foreign minerals which it may contain.
if the clay slate and mica slate of Isla are both considered primitive,
as they probably will be, then this limestone must also be ranked
among the primitive rocks. In all the other instances in which I
have observed this kind of limestone, it has appeared to me to ap-

various parts of Scotland. 417

pertain to the same system of rocks. Yet I have reason to suppose
that the beds of it which exist in the district of Aberfoyle, alternate
with a sort of intermediate rock, which I am inclined to consider as
the latest of the primitive, or the oldest of the transition series, a
rock approaching at least as near to the character of graywacke, as
to that of micaceous schist, if it be possible, as I suspect it is not,
to draw any line between these two classes of rocks. In this case,-
the same limestone will, like clay slate, bear a share in both these
artificial divisions, for artificial I must needs consider divisions which
nature has separated by a boundary so feeble and so undefinable.

Ailsa.

The craig of Ailsa, from which the specimens now exhibited are
taken, resembles the summit of a huge mountain rising abruptly out
of the deep. Such in fact it is, and not a mere rock, as its name
might induce one to suppose. It shelves rapidly into the sea, and
is surrounded by deep water on all sides except the south eastern,
where a small beach has been formed by the accumulation of its
ruins. I regret that the derangement of my barometer, a derange-
ment unfortunately too frequent, prevented me from ascertaining
its altitude; but by comparing its appearance with that of Arthur’s
seat, and computing from the time it required to ascend it, it cannot
be much less than 1000 feet in height. Jt is called 940 in some of
the sea charts, but on what authority I do not know.

Its circumference cannot be less than two miles, and it therefore
forms a large island, which is covered with verdure, and is the
habitation of gulls, awks, gannets, goats and rabbits. Its shape is
round and cumbrous when viewed from the north-west, but when
seen from the north it assumes an elegant conical figure.

VOL: Il. 3G

418 Dr, Mac Cutiocn on the Geology of

It is bounded on the north-west by perpendicular cliffs, 200 or
300 feet in height, but on the other sides it declines by a rapid
grassy slope to the sea, intermixed however with rocky faces, and
covered with heaps of fragments, which are perpetually falling from
the bare rock. ‘The square ruined tower which remains at about a
third part of its elevation, offers nothing interesting to the antiquary,
but the botanist will be delighted with the profusion of lychnis
dioica and silene amzna which covers it with a dense coat of
flowers; to the exclusion of even the grass. It contains springs at
about 200 feet below its summit, which unite in a small marshy
plain, covered with enormous plants of hydrocotyle vulgaris.

The rock which forms this insular mountain is in general amor-
phcus, and breaks into large irregular masses, sometimes approach-
ing to a rectangular shape, sometimes without that tendency, and
resembling the fragments of quartz rock. In many places it ap-
proaches to an obscure columnar structure, and this occasionally
acquires great regularity. It is on the north-west side that the
columns are most perfect. They are here well defined in their
angles, yet adhere together, so as to appear to form one continuous
mass, their true structure being only detected by the occasional!
falling of the huge fragments which strew the narrow beach on this
quarter of the island. They vary in the number of their sides, but
like basaltic columns, the most general forms are the pentagonal and
hexagonal. I could not any where perceive that they were jointed,
but they break at right angles to their axes, forming those flat sum-
mits which are tenanted by clouds of gannets. Their dimensions
are universally large, as they are from six to eight feet in diameter,
and extend in’ height as far as the eye can judge, to a continuous
altitude of 100 feet and upwards. Nothing can exceed the magni-

ficence of the columnar wall on this side of the rock; even the -

various parts of Scotland. 419

high faces of Staffa sink into insignificance on a comparison with
the enormous elevation and dimensions of Ailsa. With that eleva-
tion is combined an air of grandeur, arising from the simplicity of
their aspect, which the pencil and pen are equally incapable of des-
cribing. To the lover of picturesque beauty, they possess a requi-
site, of which the want is perpetually felt in contemplating the
basaltic columns cf Staffa, or Egg. This is their gray colour,
catching the most varied lights and reflections, when the iron cliffs
of basalt are confounded in one indiscriminate gloom. He is an
incurious geologist, or a feeble admirer. of fine nature, who is con-
tent to pass Ailsa unseen.

This rock is traversed in various parts by large veins of green-
stone or basalt. Among these I observed one which was horizon-
tal, but the greater number are vertical, and of large dimensicns:
these lie on the west side. ‘There is no apparent alteration in the
rock at the points of contact. The whole of this island consists of
one substance, in which slight differences of appearance here and
there occur, but are unworthy of particular notice, and scarcely suf-
ficient to constitute a variety. Its basis isan even and small grained
mixture of white felspar, and transparent quartz, in which the
former appears to predominate. This mixture constitutes more
than three-fourths of the stone, and is mottled by minute and in-
distinct stains of a black colour, which through the magnifying glass
are seen to consist of small grains of hornblende. These appear as
if diluted through the stone, and arising from a common centre; and
as they vary in proportion to the other constituents, so the rock
assumes various shades of colour, from a whitish to a blackish gray,
but the lighter varieties predominate.

The stone which I have described may safely be called a syenite,
as it accords with Werner’s definition of that compound rock, and

3G2

420 Dr. Mac Cutrocn on the Geology of

is a term pretty generally admitted. We may, however, venture
to question the propriety of applying to rocks of this nature, a term
borrowed from the ancient naturalists, when it seems certain that
the rock of Syene was, in fact, a true granite, containing hornblende
merely as an occasional and accidental ingredient. Yet, as we are in
want of a generic term for the various rocks which consist of horn-
blende and felspar, and which are not considered as greenstones, it
may be advisable to admit of its use for this purpose, and to sacrifice
a little of our classical accuracy for the sake of convenience, rather
than by the introduction of another new term, to introduce new
confusion into that which already reigns in the denominations of
rocks. I hold it necessary however that the word syenite, if it is
to be used as a generic term, should be limited, as rigidly as the ever
varying and mingling composition of rocks will admit, to those
compound rocks which are akin to greenstone in their chemical and
essential characters, or consist of certain notable and distinct propor-
tions of felspar and hornblende, but in which the felspar is either
the predominating ingredient, or is crystallized in masses so large
and distinct as to remove the compound from those similar compo-
sitions now generally known by the name of greenstone. When
the condition of the stone is of that intermediate nature which ren-
ders its precise place uncertain, the modified term of syenitic green-
stone is easily applied. In difficult cases where these rocks are still
more varied in their composition, and in all others where a multi-
plication of terms would lead to an unbounded and unnecessary
nomenclature, it will even be preferable to distinguish the variation
from the more rigid form by a detailed description rather than to
encumber the science with a useless neology. It is easily under-
stood that no doubts respecting the place of these rocks in a system,
need arise from the intermixture of quartz, or even of mica in the

various parts of Scotland. 42)

stone, provided their proportions are not conspicuous, nor their in-
fluence on its general aspect remarkable.

But the rocks themselves, to which I am thus desirous of limiting
the name of syenite, are so associated in their habits and formation
with the rocks of the trap family, and with those perphyries which
appear to have originated in similar circumstances, that they have
a strong claim on us for one generic term, as well from their geo-
logical, as their chemical, or mineralogical relations. If then we
consider the term syenite as founded on this double view of the
nature and position of the rocks to which I allude, it will be ob-
viously convenient, if not absolutely necessary, to separate from
them the rocks of a granitic character; of these the most simple
in its construction is that which consists of quartz, felspar, and
hornblende, or of those three ingredients with mica. Such rocks
are not of uncommon occurrence, nor is it uncommon to meet a
rock in which quartz, felspar and mica are so compounded, as to
form a true granite with crystals of hornblende superadded to the
compound. Great confusion must follow the separation of these
from the granites, and their union to the syenites above described.
Their structure and characters are in all cases granitic, nor does the
eye readily detect the difference till the darker parts are minutely
examined, when the crystals of hornblende may, and that often
only with much care, be distinguished from the mica. Their geo-
logical affinities associate them also with the granites, and never with
the greenstones, since they occur in the formations of the granite
zera, as hornblende rock and hornblende slate are known to do. The
obvious distinction would be to call these compounds syenitic
granites, thus preserving their analogy with the syenitic greenstones,
and preventing us from confounding into one mass two formations
of widely different characters and epochas, merely from the acci-
dental presence of a single ingredient.

422 Dr. Mac Cuttocu on the Geology of ;

But to return to our subject. We have here an example of the
columnar form existing in a very perfect manner in a rock, which
however it may bear a considerable analogy to greenstone, and
through that to those rocks which more commonly exhibit the
columnar shape, is still sufficiently distinguished from them all by
the great predominance of the felspar. There is no difficulty in
conceiving that the same causes presided at the formation of both,
when we consider the similarity of geological structure and position
which pervades all the rocks distributed under the heads of basalt,
greenstone, and syenite.

The insulated position of this rock precludes all possibility of
tracing its connection with the contiguous ones, and the chasm
which exists between Ailsa and the neighbouring shores, is such as
to insulate it as much in a geological view, as it is in its geographical
position.

As yet nothing resembling it in structure has been observed in
the neighbouring islands, nor on the main land of Scotland, yet the
syenites and greenstones of the motley island of Arran, with the
porphyry of Devar, and the extensive trap formation of the neigh-
bouring shores, point out to us its natural affinities, and enable us
to guess at a connection possibly once more intimate, but long since
submerged in the depths of the sea.

I cannot entirely quit the Craig of Ailsa, without remarking that
it possesses in a high degree one of the conditions requisite to the
solution of the interesting problem of the earth’s density. This is,
the absolute uniformity of its structure, which, with the exception
of the few basaltic veins above described, is of one unvarying rock.
Its mass is also sufficiently considerable to fulfil another of the con-
ditions required for this problem, while its form and situation would

appear to afford sufficient facilities for measuring its solid contents.

‘various parts of Scotland, ~ 423

As this idea had not suggested itself to me when on the rock, I did
not examine, and cannot now recollect, whether it affords situations
adapted for the erection of the requisite observatories, a condition
without which its other conveniences would be of no avail.

y Devar.

The beautiful specimens of porphyry taken from this rock may
render a short description of the rock itself interesting, and I shall
therefore make no apology for occupying the Society a few minutes
with an account of it. It is the more worthy of notice, as it is the
most accessible, and the best characterized mass of porphyry which
I have seen in the various parts of Scotland that I have visited.
It is an island and a peninsula alternately, according to the state of
the tides, and lies off the harbour of Campbelltown, which it covers
from the south and east winds. It is about half a mile in length,
and a quarter in breadth. From the N.W. it rises in a pretty rapid
slope, and terminates to the S.E. in a precipitous face, reaching as
far as the eye can guess, from one to four hundred feet. It consists
of one entire mass cf porphyry, which however varies much in its
colour and texture in different places. It contains no other rock or
vein, nor is its contact or connection with any other to be traced,
but it appears to extend on all sides below the water. On a first
and cursory view, it seems to be formed of upright beds, but a more
accurate examination shows that this appearance is a deception, and
arises from the tendency which the rock has to split in a vertical
direction. Such is its outline and general aspect that it might at a
distance be taken for a mass of trap, similar to those in the vicinity
of Edinburgh, its leading features being the abrupt face and perpen-
dicular fracture. On examining this great fracture more closely we

424 Dr. MAc CutLocn on the Geology of

may perceive that it is of a large lamellar form, or such that one of
the lateral dimensions is always much greater than the other, the
leading lines being nearly vertical. The cross fracture by which it
is separated into small masses and becomes detached, is compara-
tively so rare as not to give any general feature. If it is possible
to transfer a term from a hand specimen toa rock, I might say that
it was formed of distinct lamellar concretions, and a perfect idea
may be acquired of it by conceiving the lamellar pitchstone of
Arran magnified to the requisite size. It contains some caverns,
formed in a vertical direction, but whether by a falling cut of some
parts, or a subsidence and consequent separation of contiguous ones
T could not determine. I have already said that its texture and
aspect are very various, its varieties occurring as far as I could per-
ceive without any certain order or regularity. Its basis appears ta
be a felspar, occasionally of the compact sort, but more generally
crystallized in a confused manner. It differs much in colour, and
offers the following remarkable varieties, brown red, umber brown,
iron grey, purple brown, ash colour, yellow green, olive green,
pale grey green, and grass green. The crystals of felspar which
are imbedded in the mass are of a small size, rarely exceeding the
tenth of an inch, and are either grass green, brown, or white.
Nodules of green earth are also found imbedded in it, and the
green varieties appear to derive their colour from this substance.

I have contented myself according to the established language
with calling this rock by the simple name of porphyry, a name so
vague, and so carelessly applied to rocks of widely different charac-
ters, as to be a cause of unspeakable confusion. Since the term por-
phyry is now applied to all rocks, whatever they may be, which in
a given base contain imbedded crystals of felspar, or of any other
substance, it is evident that it can determine nothing with regard to

various parts of Scotland. 425

the nature or true place of these rocks. An accident common to
many species is not the characteristic of any. As well might gra-
nites and micaceous limestones form one species from their partici-
pation in a common ingredient. Thus we are told that Cruachan
consists of porphyry, that the Ochil hills consist of porphyry, that
the Calton hill consists of porphyry, and that Rona consists of por-
phyry. Yet these four rocks are essentially different, and separated
from each other as widely in composition as they are in geological
relations, bearing, in short, no resemblance except in the
common and unessential circumstance of imbedded felspar. For,
the hornstone, the claystone, the trap and the felspar, which
constitute the bases of these several rocks, although often containing
crystals of felspar, are yet perhaps as frequently destitute of that
accidental substance. Iam not an advocate for increasing words,
and encumbering our language with unnecessary terms, but that
confusion which arises from applying one term to many substances,
is at least as faulty and a greater cause of error than the accumu-
lation of an unweildy stock of synonymous ones. If we must
retain the ill applied term of porphyry, let it at least be returned to
its place among the adjectives, and used as the trivial name to those
species, which, for the purpose of description, can only be truly
characterized by their permanent composition, not by their acci-
dental features. Thus we shall have porphyritic traps and clay-
stones, or, if our grammatical ears are not offended by it, we may
have felspar porphyry, and hornstone porphyry. These are as-
sociations of substantives at least as tolerable as that of a@ line of
battle ship.

I trust it will not be considered beneath the dignity of the Society
if I here take notice of the assistance which the arts may derive
from some of these porphyries. The green specimens are capable

VOL. Il 3H

426 Dr. Mac Cuttocu on the Geology of

of assuming a good polish, and form ornamental stones of equal
novelty and beauty. We have long been indebted to foreign
countries for substances which our own island produces in abun-
dance, and in no instance have the powers of established habits and
prejudices been carried further than in the preference given to many
of their insignificant marbles and porphyries, while our own, either
similar or superior, have been neglected. ‘To encourage commerce
and the arts is not unworthy of a Society, which, like ours, has in
view among other objects, the investigation of an important branch
of the natural history of our own country. Let us not suffer our-
selves to be misled by the imposing aspect of independence and
disinterestedness which philosophy assumes when employed in
investigating general principles, and, contented with the splendour
by which science is surrounded, refer to others the humble task
of converting it to useful purposes. It is the chief boast of
science, that while it occupies the mind in pursuits by which it is
exalted and interested, it tends at the same time to better the con-
dition of life, by adding to its enjoyments, or taking from its incon-
veniences,

Arran. Goatfild.

The general disposition, as well as the particular details of the
geology of Arran being universally known, I need not enter into
any description of them. I may merely remark, that the group of
mountains which constitutes the most elevated part of this island,
consists of a mass of granite, of which Goatfield is the highest
point. Various ridges, separating deep vallies of sudden declivity,
branch from the higher parts of the group in different directions.

various parts of Scotland. 427

These mountains are succeeded by a very systematical arrangement
of consecutive rocks, terminating at length, on one side, in the
sandstone which forms the shore from the Cock to Brodick Bay,
and on the others, in various alternations of rocks, which it is
foreign to my purpose to describe.

The granite of this group differs essentially in external features
from that of the central highlands, and it equally differs from it in
character, resembling almost precisely, in hand specimens, the well
known granite of Devon and Cornwall.

Like that also it has the bedded appearance which in detached
parts so much resembles stratification, and has not unfrequently
been mistaken for it. If we were to be guided by the look of a single
rock or jutting mass, taken here or there, it would be very difficult
to avoid being misled by the impression of stratification which it
gives. But if we examine it in a wider view, we shall see that this
appearance is fallacious, and that the lamina, rather than beds, in
which it is disposed, are placed in every possible direction ; exhibit-
ing even in the immediate neighbourhood of each other, an irregu-
larly tabular form, or lamellar texture, and not a stratified deposition.
It is not even possible that these masses should be portions of dis-
rupted strata, as their positions are complicated in a way in which
no subsidence, or other subsequent disturbance could have placed
them. At any rate it has no better claim to stratification than the
granite of Dartmoor and Cornwall—with these it must be classed
in geological as it is in mineralogical character.

As the stratification of granite has been a subject of much con-
troversy, it is worth our while to examine those doubtful cases
which may be explained by other considerations, and to see what
analogies in the disposition of other rocks can be brought to bear

3H 2

428 Dr. MAc CuLtocn on the Geology of

on this question. Thus we may possibly find that this disputable
appearance forms part of a series of very common phenomena, and
that although it may possess a certain general resemblance to the effects
of mechanical action, it is, in fact, produced by chemical agencies.
There are two circumstances to be regarded in describing the frac-
ture and texture of a rock, its small or artificial fracture and micro-
scopic texture, and its large or natural fracture and texture, as they
are determined and exhibited by the effects of time or decomposition.
The instances which might be adduced to illustrate these differ-
ences are sufficiently familiar. In the case particularly of the large
disposition and fracture of rocks, a striking difference occurs in the
often approximated beds of trap and sandstone. Both form parallel
beds, and both on the application of force break into nearly similar
fragments, yet the natural division of the sandstone bed shows an
horizontal tendency, or one parallel to the plane of the bed, while
that of the trap is vertical to it. From the vertical fracture a series.
of gradations occurs which at length assumes the perfectly geometrical
form of polygonal columns. In this case then, we have a form still
more perfectly mechanical and regular than that of the most even
stratification, and produced by a species of crystallization, a tendency
to decided forms in those particular rocks, with the laws and causes
of which we are at least as well acquainted as we are with the laws
that determine the figure of a quartz crystal. At present they are
both equally inexplicable. There is no further difficulty in con-
ceiving that a rock may constitute a huge bed separable into hori-
zontal laminz as regular as the strata of a mechanical deposit, than
in conceiving that the island of Staffa is separable into columnar
fragments, or the rock of Devar into vertical laminz. It is true that
we have not yet produced any instance of continuous, horizontal
laminar concretions, which are incontrovertibly not mechanical, yet

various parts of Scotland. 429

its existence implies no chemical impossibility. That which occurs
on a small scale may occur on a large. The terms are but com-
parative, and the works of Nature are not to be limited by a measure
taken from our own confined dimensions.

Thus we find on the small scale, that antimony is divisible into
laminz, while its sulphuret splits into columns; that mica has a
lamellar texture, and asbestos a fibrous one. Should a mountain of
the size of Goatfield occur, formed of a solitary crystal of mica, we
should not be entitled to call it stratified, while we considered a
neighbouring mountain of asbestos to be columnar.

‘Such I conceive to be the analogies by which we may safely
guide our reasonings on this subject. Nor is the great lamellar
texture which has so often been considered as the effect of stratifica-
tion, peculiar to granite. In examining the Cuchullin hills in Sky, I
have observed that the syenite and greenstone are bedded as it were in
layers, either curved or straight, either horizontal or slightly inclined,
resembling so much the disposition of granite beds, that even an
experienced eye would at a distance be deceived by them. It is
not necessary to illustrate this view by any further analogies, as
every person’s memory will afford examples in the disposition of
some kinds of porphyry. My design is merely to suggest the
necessity of considering the greatness of the scale on which Nature
operates, and the probable occurrence of a chemical texture, if
I may use such an expression, different from, and additional to that
which may be observed in the smaller masses, and probably as
constant in the larger masses which constitute the different rocks,
as the minuter crystallization is in the smaller parts which unite to
form them.

Thus far I have only argued on the probability that Goatfield
does not consist of stratified granite, by analogical reasoning and

430 Dr. MAc Cutrocn on the Geology of

arguments drawn from theoretical principles. We have, however
a perfect certainty (as far as we have any certainty in geological
induction) that it is not stratified, because veins are found arising
from it, and entering the mass of incumbent schistus in the well
known junction at Loch Ranza.

I have not thought it necessary to take notice of the probable
cause of the prismatic form which occurs so frequently on the
summits of the high ridges in this granite, having before spoken
of them in my remarks on that of Cornwall and Devonshire.

I cannot quit this subject without mentioning that many of the
masses of granite on the summit of Goatfield, are magnetical,
affecting the poles of the needle in situ, and influencing it also even’
in detached pieces. This occurrence may probably be more common
in granite than we are aware of, but as yet, I believe it has been
observed only in the Hartz mountains.*

Boharm.

The sappare (disthéne) said to have been originally discovered
in this place, is now known to be inherent in many different
rocks. ‘Thus, it has been found in granite, in mica slate, and in
talc. The specimens of it seen here, occur in a vein of quartz,
which traverses a talcy clay slate, a slate accompanied by a
singular rock, which I will also describe. It only offers the
common aspect of this mineral, which hitherto has exhibited no
remarkable varieties, and is of a very decided character. The
crystals of disthéne occur in the quartz vein, as well as in the clay
slate which bounds it, and pass indifferently through both, without

* T have since observed it in the mountain Cruachan.

various parts of Scotland. 431

any change of their direction or appearance, marking clearly a
common condition in the schist and the quartz, at the period of
their formation. It is also worthy of remark, as I have observed,
in another place, in speaking of the rutile of Killin, that although
the crystals of disthéne in general penetrate and impress the quartz,
they are sometimes bent and waved as if they had accommodated
themselves to its irregularities. Ignorant as we still are of the
mode in which various minerals are crystallized together, it is not
uaworthy of our attention to collect all the facts which may tend
ultimately to throw light on this obscure process.

The clay slate which I have mentioned above, constitutes a large
portion of the mountains which here form the termination of one
of the Grampian branches in this direction; it is succeeded by a
hard quartzy sandstone, similar to the rock of Assynt, before
described, and by an exceedingly hard quartz breccia, in which
the paste is red, and the fragments white, and which is noted for
containing agates and jaspers. Immediately after this follows the
red sandstone, which constitutes a great part of the flat tract of
Moray, and bounds the course of the Spey in this place. It is
accompanied by the singular rock above alluded to, which I am
about to describe. This rock consists of a talcy clay slate, so
penetrated with hornblende as to render its character for an instant
doubtful. On an accurate examination, it will be seen that the
body of the rock is a clay slate, and that it is interspersed throughout
with lamellar and thin crystals of hornblende. These lamellz
are generally disposed at right angles to the lamelle of the schist,
and are sometimes short and straight, and variously placed, inter-
fering with each other in every direction. More commonly they
diverge from a sort of central axis, in curved planes, so that their
section according to the lamellz of the schist, exhibits an appearance

432 Dr. Mac Cuttocu on the Geology of

of curved penicilliform groups of acicular crystals frequently an
inch in length, assuming an aspect of great singularity. In this
direction the schist is visible, and appears to form the largest part
of the stone, while in the cross fracture the lamelle of hornblende
alone being seen, the whole rock seems to consist of this mineral.
Occasionally the hornblende displays crystals disposed in so many
different ways, that the schist is discernible even in the cross fracture,
but this variety is the least common.

Portsoy.

The veins of granite found at Portsoy are well known, not only
for the peculiar character of their crystallization, called graphic,
but also because they contain crystals of schorl (tourmaline) of
great magnitude. The singular disposition, and mutual relations
of the crystallized substances which form this compound rock, are
known to have afforded Dr. Hutton an argument for its igneous
origin, and its peculiar character has been supposed to arise from a
simultaneous, or nearly simultaneous crystallization of the several
substances contained in it. The specimens which I have to
enumerate, are such as not only throw considerable doubt on this
explanation, but are in fact, sufficient to prove a sequence of
epochas even in this limited space, and to show that the compound
rock in question has been formed by successive operations, the
nature of which however I fear we shall not easily determine.
I would entreat the pardon of the Society for occupying so much
of its time on the fracture of a schorl crystal, were I not persuaded
that much light must at some period inevitably be thrown on the
greater geological phenomena, by considering the chemical and
mechanical relations existing among the smaller portions which

various parts of Scotland. 433

constitute them, and that the language of Nature is often as in-
telligibly spoken in the minute space of an inch, as in the immensity
of a mountain. It is scarcely necessary to add, that the other prevail-
ing theory, that of aqueous formation, supposes the substances which
constitute this rock to have been crystallized from a watery solution,
and that the fundamental objection to the igneous explanation, is
the apparently chemical impossibility, that of a rock compounded
of two crystallized substances, the one which is fusible at the lowest
temperature, and therefore would be the last to crystallize, should
by crystallizing first, have made its impression on the other. An
analogy has, I know, been offered in explanation of this difficulty,
but it will immediately be seen that it is at least incompetent to
explain the particular case under review.

The first specimen which I have to describe is a detached crystal
of a flattened and irregular figure. It has been broken into four
parts, by transverse fractures, which have again united without the
intervention of any intermediate substance. Previous to this re-
union however, they have all been slightly shifted, in such a way
that the several parts of the fractures project, and the whole crystal
has undergone a slight deviation from its original straight line. If
it be alledged that this appearance could arise from a disturbed
crystallization, the next specimens will remove any doubt on this
head.

In these, the crystals have not only been fractured in the same
way, across their axes, but the fractures are filled by the quartz and
felspar which constitute the body of the rock. The granite veins
of Arran do not show more clearly the ramification of a central
substance through the fractures of the neighbouring rock, than
these specimens show the veins of quartz proceeding from the
mass, and penetrating every fissure which had been formed in the

VOL. 51. 31

434 Dr. Mac CuLocn on the Geology of

crystal. It is perfectly evident, that whatever is true of the above
cited granite veins, must also be true of this rock, that the schorl
has been crystallized, then broken, and penetrated by quartz in a
state of fluidity. Nor is there any intermixture of the matter of
quartz, with the matter of schorl, but the line of separation is
most accurately drawn between them. It follows then from these
circumstances, that the rock in question is not a simultaneous
formation from a state of fusion, nor can we readily understand
how it can be the effect of fusion at all, consistently with the
chemical principles we acknowledge. Had such a mass of fused
quartz invaded the minute fragments of schorl which the specimen
exhibits, the latter must either have been fused into a shapeless
mass, or at least the asperities of fracture could not have remained
in a substance whose fusibility is so much lower than that of
quartz. Those who attribute the formation of this rock to aqueous
solution, will perhaps in the above mentioned specimens find
arzuments in favour of their hypothesis. I will not repeat the
often quoted difficulties which attend this theory also, but request
from it an explanation of the remaining specimens.

The first of these is from the same vein at Portsoy, and contains
an acicular and detached crystal of schorl, which is bent without
fracture, so as to form a considerable curvature.

As chemistry produces no examples of incurvated crystallization,
I may safely conclude that this crystal has been bent by external
force after its formation. ‘The noted fragility of schorl will not
allow us to suppose that it could be bent without breaking, unless it
had been previously rendered flexible by some chemical agent
possessed of powers which we have not hitherto discovered in water.

The other specimens :are not from Portsoy, but from an interior
part of the country, and exhibit appearances equally irreconcilable

various parts of Scotland. 435

with the theory of the aqueous formation: but the objection on this
ground has been urged before. In one a crystal of schorl passes
through the centre of a garnet, and the whole is suspended (if I may
use such a phrase) in the quartz. In others the crystals of schorl
are simply suspended in the quartz or felspar, and have perfect
terminations. It is evident in the first, and strongest case, that the
schorl crystals must have been supported in a fluid of equal gravity,
possessing no action chemical or mechanical on it, while a garnet
was allowed to crystallize round it, and that this extraordinary state
of things must have continued during the time which it would
require to deposit a mass of quartz from a watery solution around
the whole, a period, which if we may judge from the slow formation
of chalcedonies from water, involves a supposition little short of
miraculous.

Such are the difficulties which beset this very simple and probably
very common occurrence. Ido not mean by adducing it, to say,
that no theory is worthy of attention which cannot explain all the
phenomena. My wish is rather to excite the industry of those
who cultivate geology, to the investigation of the still recondite
chemical actions, from which alone we can hope for the solution
of these and numerous other difficulties which attend us.

Loch Laggan.

I am merely desirous of pointing out under this title a bed of
limestone, lying in a country so little visited, that it has not yet
been observed by mineralogists, and of sufficiently rare occur-
rence to render it an object of notice.

The whole country about Loch Laggan is of that composition
which forms the far larger part of the highland districts, namely

micaceous schistus. 312

436 Dr. Mac Cutiocu on the Geology of

The bed of limestone bas been quarried near the eastern end of
the lake, and if the reports of the quarry-men are to be trusted,
extends in a direct line for many miles. This part of its history
merits investigation, as the limestones which lie in the highland
schistus, are generally of very limited extent. The stone itself is
remarkable for containing hornblende. The sides of the bed are in
contact with hornblende slate, or rather with that unnamed and
common rock, consisting of a slaty mixture of quartz, mica, and
hornblende.

Where the limestone comes in contact with the schist, the
hornblende crystals penetrate it in such quantity as to blacken the
compound. ‘Towards the centre of the mass they diminish in
number, and at length disappear. / |

Mica also accompanies the hornblende to a certain extent within
the bed, and the limestone being itself of a pure white, a marble
is thus produced of an ornamental nature, and bearing a consider-
able resemblance, as well as analogy, to the celebrated marble of
Tirey. A substance very much resembling massive garnet may be
perceived here and there united with it, but in so small a quantity
as to render the determination of its true nature difficult. It is
worthy of notice, that the limestone is frequently of a large platy
fracture where in contact with the hornblende schistus, and that
these plates are not straight but flexuous. —

Craig Cailleach near Killin.

This summit forms a part of the ridge separating the vales of
the Tay, and Lyon, and is the next highest in elevation to Ben
Lawers, the most conspicuous part of that ridge. The predominant
rock of this ridge, is a very well characterized chlorite slate, which

various parts of Scotland. 437

is, however, intermixed with rocks, consisting of hornblende, and
felspar, and of micaceous schist mixed with hornblende. It exhibits
therefore, specimens of the syenite of Werner, but such as are evi-
dently associated with the mica slate family, and perfectly distinguished
in their connexions, from the greater bodies of syenite occurring in
Scotland, which appear in an independent position, resembling that
of the trap family. The mica slate is often remarkable for contain-
ing numerous and very large cubical crystals of pyrites, an occur-
rence much less frequent in this rock than in clay slate.

Veins of quartz traverse it in innumerable places, and it is also
interspersed with compressed nodules of quartz, which bear no
marks of attrition, but are intimately united to the mica slate, or
chlorite slate, in which they occur. They are frequently character-
ized by a beautiful transparent brown colour, which renders them
objects of much research and high price among lapidaries.

Massive chlorite also appears in abundance, and it is generally
interposed between the chlorite slate and quartz nodule. But the
object for which I have chiefly noticed this mountain, is the occur-
rence in it of Rutile, a mineral as yet of sufficient rarity to deserve
a record of all its baditats. It is found in the larger, as well as in
the smaller quartz nodules, and exhibits many of its well known
varieties.

The crystals generally penetrate the quartz, and often appear to
have their bases fixed in the investing chlorite. It is worthy of re-
mark, that although they most commonly penetrate the quartz, as if
crystallized at perfect liberty, yet they are frequently bent, so as to
accommodate themselves to its occasional elevations and depressions,

Our knowledge of the chemical laws by which mixed minerals are
crystallized together is as yet so imperfect, that we can offer no
conjecture on an appearance so complicated as this, which however,
is not the less deserving of our attention,

438 Dr. Mac Cuttocn on the Geology of

Loch Lomond,

The formation of a new road on the banks of this lake, has ex-
hibited some instances of the contortions of mica slate, which are

deserving of notice. I have attempted to give a notion of them

in the accompanying sketches (Pl, 31. fig. 1, 2—PI. 31}, fig. 3.) /

as it is not possible to procure specimens of the magnitude requi-
site for that purpose.

It would be superfluous to add any thing to the observations on
the inflexion of strata, in the “ Illustrations of the Huttonian theory,”
where this subject is ably treated. But as they consist chiefly of re-
marks on the continuous inflexions of extensive strata, it will not be
useless to notice the more complicated curvatures which take place in
the smaller masses. In a brief notice on certain waving lines of colour
occurring in killas at Plymouth Dock, transmitted last year to the
Society, I suggested the difficulties which attended a solution of this
question, the disposition of the colour having no relation to the
laminz of the schist. But in the contortions of the mica slate, the
laminz themselves are waved, and we have only therefore to enquire
into the conditions requisite to the production of this appearance.

It is evident on inspection of the sketches, and will be equally so
to those who shall inspect the rocks themselves, that, if the several
lamine which compose any given mass, were to be now rendered
flexible, they could not be reduced to continuous straight lines,
without materially changing the relations of their several lengths, and
thus altering the figures of the rocks which now contain them.
It is therefore evident, that no general force acting on a large mass
has been the cause of these curvatures, but that they have been pro-
duced by the application of numerous partial forces acting on different
parts, and capable of stretching those sets of laminz on which the

various parts of Scotland. 439

forces have acted, independently of the neighbouring ones. It is
equally evident, that a mere state of softness in the stratum of schist
is insufficient to account for this partial and complicated effect, but
that it must have taken place when the rock was in a state of
tenacious fluidity. The effect produced by mechanical disturbance
on fluid slags which consist of differently coloured laminz, will il-
lustrate my meaning, or, to leave out of the question any illustration
which may appear to involve a cause, similar appearances may be
produced by the disturbance of tenacious compounds of clay and
water, or of other semifluid mixtures. - It is not perhaps essential to
the igneous theory, that this fact should be explained by an igneous
softening ; but it is necessary that the aqueous theory should admit
of a disturbing force capable of producing a mechanical effect of this
‘nature, since nothing short of mechanical force acting on yielding
matter is capable of explaining it.

I may here add a fact somewhat illustrative of these partial con-
tortions in schist, which is to be observed occurring in the basalt
that forms the hill of Dun Can, in Raasa. Innumerable instances
prove to us that the decomposition of basaltic as well as of granitic
and other rocks, detects in them that structure which we should in
vain seek in the fresh and entire mass. ‘The weathered basalt to which
I allude discovers appearances of contortion similar to those now
under review, its surface exhibiting parallel prominences, separated
by deep lines, which are waved in very complicated curves, and
give reason to suspect a mechanical disturbing force, acting in this
case also, upon a semifluid mass. As analogous appearances of cur-
vature are also of frequent occurrence both in veins of quartz, and
in veins of granite which traverse mica slate and gneiss, I have
given figures of a few among the most remarkable ef the innume-
rable specimens to be seen all over Scotland (PI. 31 +). I have

440 Dr. Mac Cuttocu on the Geology of

nothing to add in explanation of them; they merely suffice to
prove, that these substances like the schistose rocks, have been in a
state which admitted of bending; the capricious and intricate con-
tortions visible in some of the figures (which were drawn with great
care) not admitting of any fissure of this form to be subsequently
filled either by injection or infiltration. One of the figures’ is per-
haps particularly worthy of notice, on account of the distinctness.
with which it demonstrates the action of partial forces, by the re-
markable difference of curvature occurring in two veins so nearly

approximated,

Burnt Island.

A specimen of a compound vein is before the Society, which
traverses the well known amygdaloid of this shore. This vein con-
sists of a highly crystalline brown limestone, mixed with a ramified
compact earthy black basalt. These substances are so intermingled,
that it is scarcely possible to conceive that the basalt is posterior to
the limestone, or that a basalt vein should have found its way into
a vein of limestone without also traversing the amygdaloid. It is
probable that the whole vein is of simultaneous formation, and that
the substances have separated from each other in consequence of
those obscure chemical affinities which regulate the crystallizations
of compound rocks. This however is a subject deserving of fur-
ther investigation, as, if it is admitted, it will prove that the same
cause, whatever that be, may preside over the formation of basaltic
veins, and those veined limestone deposits in trap rocks, which are
called calc sinter, and are held to arise from the posterior effects of
a watery infiltration.

In the same rocks a singular circumstance accompanies the im-
bedded calcareous nodules. Their surfaces are occasionally marked

various parts of Scotland. 441

with sets of concentric circles, consisting of fine black lines most
mathematically drawn, with their intervals often filled up by por-
tions of parallel circular segments, an appearance similar to that
produced on the surface of some of the agates imbedded in trap,
and which on that account are called ocular. ‘These black lines

are perfectly superficial.
Crinan.

The land about this harbour is remarkably. disposed in small
elevated hillocks, producing an irregularity of aspect similar to that
of the Oban shore. The mode adopted in making the canal, by
cutting away the edges of these hills, so as to form a continuous
embankment against them for a considerable space, has brought
their structure to light, and given great facility to the investigation
of their composition. ‘They are formed of a continued alternation
of beds, elevated to an angle of 80° or upwards, and in a general
view appearing to be nearly vertical. On examining these beds,
they are perceived to consist of the following substances.

1. Coarse graywacke, very well characterized, and precisely cor-
responding to the definition, inasmuch as it consists of grains of
quartz cemented by clay slate.

2. The same rock, in which grains of felspar as well as of quartz
are cemented by clay slate.

3. Coarse grained graywacke of a slaty fracture, or graywacke
slate.

4, A similar rock of a much finer texture.

5. A perfectly homogeneous clay slate, not to be distinguished
from the finest varieties of the primitive sort.

6. A similar slate of a pale greenish gray colour, and silky lustre,
approaching in character to chlorite slate.

Wor. 2: 3K

442 Dr. Mac Cuirocn on the Geology of )

All these beds are traversed by numerous veins of quartz, and
they alternate with each other without any regular order, the beds
not forming a series passing from the coarse to the fine grained, but
a fine clay slate often following close upon a coarse graywacke, and
being succeeded by a similar rock.

Here then we have an instance of a fact, of which the observa-
tions of every geologist will furnish many other examples, namely,
the occurrence of clay slate among those rocks called rocks of tran-
sition, their alternation rendering this part of the fact indisputable,
The nomenclature of rocks therefore which is derived from geolo-
gical situation, is here at variance with that which results from
mineralogical character. If the unnecessary multiplication of dis-
tinctions and names in mineralogical nomenclature is productive of
toil by introducing a cumbrous apparatus into the science, it has at
least the merit of conducing to accuracy of description. That is a
much worse extreme, which by rejecting all such distinctions con-
founds together under one sweeping term, all sorts of substances,
which, however differing in individual character and however con-
stant and uniform in the character each severally assumes, are
associated by only one common circumstance, the accidental one of
position. A mineralogical nomenclature, like that of the other
branches of natural history, must either be derived from the appear-
ances and properties of the individual species, or from the character
of the species combined with some generic or family character, either
natural or artificial, which may render it of more easy classification
and description. But we are not at liberty in the nomenclature of
mineralogy, to derive our terms sometimes from the appearance of
the species, and sometimes from the accidental circumstances which
are found to belong to it. This is to acknowledge two distinct
principles of nomenclature, and to claim a privilege of using that

various parts of Scotland. 443

which happens to suit any particular hypothesis which we may wish
to support. The accurate description of mineralogical species, must
be the base of all geological reasonings, but if we intermix charac-
ters derived from geological circumstances with true mineralogical
characters, we set out upon a fefiiio principii, and end by reasoning in
a cirele. In the case of limestone, the chemical properties and well
known popular characters of which have given it a very decided and
eonstant name, we act rightly. The name of the species is retained,
be its geological situation what it may, and its geological accidents
are distinguished by the addition of that name which suits its posi-
tion, whether primitive, transition, or floetz. But on the other
hand, a mineral equally common, whose characters too are suf-
ficiently familiar, is distinguished by two names, although
even more identical in structure than the different tribes of
limestone, and it is called clay slate, or graywacke slate, for no
other reason than that in the one case it is associated with the rocks
called primitive, and in the other with those which go by the name of
transition. It is obviously necessary that the same practice should be
adopted in this case as in the former, and that, adhering to the name
of the species, we should distinguish its geological position, if re-
quired, by the superaddition of the corresponding term. We shall
thus have primitive clay slate, and transition clay slate, if we find it
necessary to retain these geological distinctions.

It is almost superfluous to quote instances of the existence of genuine
clay slate occurring together with well characterized graywacke slate,
as they may be seen in all the slate counties of England, and among
others remarkably in Cornwall. I trust that the geologists who
have attended to these rocks, will see, with me, the necessity of
adopting this distinction ; a distinction, without which all accuracy

3K 2

A444 Dr. Mac Cuttocu on the Geology of

of discrimination will otherwise be sacrificed to the maintenance of
an hypothesis, and the student whom it is a duty incumbent on our
Society to assist, will learn to adopt that hasty and slovenly nomen-
clature, which is destructive of correct description, and scarcely less
inimical to accurate observation.

Having said thus much on the very ill apprehended and often
ill applied term graywacke, I shall be pardoned for suggesting
the propriety of limiting it by a certain fixed definition. Dif-
ferent observers have classed under it, substances the most dis-
cordant, looking either to their general geological hypothesis, or
finding it a convenient repository of rocks for which no other
name was at hand. ‘Thus it has become a chaos of ill associated
substances. Because Cumberland and Wales are supposed countries
of transition, almost every rock found in those districts has been
occasionally called graywacke, and thus we have had breccias of all
possible modifications, sandstones, and clay slates, comfounded
with genuine graywacke under one common designation.

The definition of Werner appears precise, and I believe I do
not misapprehend it, when I state that its essential part is to possess
clay slate as the cement of certain mechanically altered grains or
fragments of different rocks. ‘These may vary materially in size,
and thus form the two leading varieties of fine and coarse graywacke,
and if they also possess a fissile structure, they will then constitute
fine and coarse graywacke slate. It is true that in the definition
of Werner, as given us by Jameson, the grains are stated to be
quartz, indurated clay slate, and flinty slate, but since felspar
and fragments of other rocks do occasionally occur in the best
characterized graywacke, it would probably be desirable to extend
this part of the character so far as to include all grains and fragments,
of whatever nature they may be, and to consider the cementing

~

various parts of Scotland, 445

substance, and obviously mechanical structure, as the essential part
of the definition. I shall take an opportunity in some remarks on
another district, to enquire whether it would not be also convenient
to extend the definition so far as to permit mica slate to participate
with clay slate in the office of cement, the other parts of the
character remaining the same. ;

Whatever definition be ultimately adopted, we cannot too strongly
inculcate the necessity of accuracy in the application of terms.
Accurate mineralogical knowledge is an indispensible condition to
accurate geological description, and the errors of very modern and
celebrated authors, arising from the want of this fundamental
quality, are too well known to call for the invidious task of pointing
them out.

The cacophony of the term graywacke has excited a desire in
some late observers to discard it altogether, and substitute one more
vernacular, and less liable to that objection.

The multiplication of synonyms is itself an evil of so crying a
nature, and has unfortunately become a disease of such magnitude
in our science, that we ought to consider well before we venture
to add another to the unwieldy and vexatious stock. It is so great
an advantage to possess one term well understood, and understood
as the language of philosophy should be, in all countries, that we
can scarcely find a motive sufficiently powerful to induce us to
change this received name. Under these circumstances we have
every reason to retain the term graywacke, however jarring to
English ears, and it is the excess of fastidiousness to reject on
account of its sound, one word from such a polyglott of unmelo-
dious and ill compounded Greek, French, and German terms, as
assail the mineralogist on every side. If there is in any case’a
choice among equally established terms, it is in our power to chuse

446 Dr. Mac Currocu on the Geology of

the most musical, but we are not justified in changing them for so
slight a convenience. The late introduction of a new chemical
nomenclature, has possibly, in conjunction with other causes,
excited a taste for neology, which it behoves us to restrain by every
method in our power, and it is the duty of our Society to watch
over and protect the science from those changes which will, if not
restrained, shortly inundate us with as many names as we have
writers.

The word &illas, a vernacular and Cornish term, has been proposed
as a substitute for graywacke. If killas were actually graywacke,
we might have a fair plea for using the name given to it by a
Cornish miner, in lieu of the corresponding one of a German miner.
But this is not the fact, as those who are conversant with Cornish
terms, well know that killas is applied to all the soft and fissile rocks
occurring in Cornwall, whether clay slate, or graywacke slate ;
and that it is never used for either when they acquire the more
compact and laminated form of roofing slate, a term as commonly
applied to this variety in that county, as in other parts of England.
The harder and more granular graywacke, is also called elvan, in
common with trap, and other hard and dark blue stones.

Aberfoyle.

Tt is well known that the ridge of which Ben Lomond forms a
part, consists of micaceous schistus,* which terminates near Drymen
in the highly elevated range of breccia that separates the primitive
from the secondary country, and which may be traced from this

* In the Mineralogy of the Scettish isles, it is said that the summit of Ben Lomond
consists of gneiss. It is necessary to correct this oversight, the whole of the mountain
being formed of micaceous schistus, and no gneiss occurring in the neighbourhood.

various parts of Scotland. 447

point in various places round by the east coast to Troup Head. It
is visible at the pass of Aberfoyle, and possesses a character and
situation similar to that which it exhibits at Drymen.

A ridge, parallel to that of Ben Lomond, is separated from it by
the valley which includes the Forth. A second parallel valley con-
tains Loch Ard and Loch Chon, which pour into the Forth at Aber-
foyle a tributary stream of equal magnitude. To the east this is
again bounded by a second ridge, nearly parallel to the first, of
which Ben Venu is the principal elevation. The valley which lies
at the foot of this ridge, contains Loch Ketterin, having for its
eastern boundary a double ridge, of which Ben Ledi is the chief
eminence. These four tidges appear to ramify from a central point,
situated between the top of Loch Ketterin and that of Loch Lomond.

The whole of this country has been supposed to be of the same
formation as Ben Lomond, namely micaceous schistus, a suppo-
sition which I have found to be groundless. I am ignorant of the
nature of the ridge which separates the vale of Loch Ard from that
of the Forth, the nearest in order to the ridge of Ben Lomond.
But on examining the vale of Aberfoyle, as far as from the breccia
to the bottom of Loch Chon, I found it to consist of alternations of
graywacke, and graywacke slate, with clay slate, similar to those I
have described as occurring at Crinan, and placed with equal ir-
regularity of alternation. The beds are also elevated to high angles,
but I believe that the positions are various. In traversing the ridge
which separates Loch Ard from Loch Ketterin, the same rocks
appear, and quarries of fine roofing clay slate are wrought in various
parts of it. These, I believe, are of the same class, and belong to
the transition clay slates, but the whole ridge is so extensive and
broken, that it is extremely difficult, if not impossible, to obtain

access to it, except in a few places. On reaching the shores of Loch

448 Dr. Mac Cutiocu on the Geology of

Ketterin,* the nature of the rock alters, and it assumes an aspect
approaching here and there to mica slate, but it is still characterized
in most places by the true graywacke structure, that is to say, by
grains united by a cement, the cement in this case consisting of |
micaceous schist instead of clay slate. At Ben Ledi the structure
still more resembles that of mica slate, insomuch that but for the
previous examination of the adjoining district, we should not sus-.
pect it to consist of any thing but genuine mica slate. Beyond this,
and to the east of Loch Lubnaig, occurs true mica slate which
constitutes the whole of this district as far as Perth. I may
remark too, that the graywacke of which the character is so perfect
in the lower parts of the vale of Loch Ard, becomes micaceous as
we ascend the course of the stream, and that in the upper parts of
the valley, it is often very difficult to ascertain under which head it
is to be ranked.

Those who have been engaged in similar observations on an
extensive tract of country, well know how difficult it is to fill up
all the chasms which the nature of the ground forms in the pursuit
of a series of rocks. Yet I have very little doubt that a true gra-
dation exists here, between mica slate and graywacke slate, and that
the usual intermediate member, primitive clay slate, does not occur
as a necessary part of the series, but that it is irregularly alternated
with the graywacke. It was with a view to these rocks, that I
suggested the propriety of extending the definition of graywacke, so
as to include those which contain mica slate, talc slate, and chlorite
slate, as the cement of the grains, instead of limiting it to clay slate
alone. In many of the rocks which occur here, the cementing in-
gredient appears to consist of these several substances, the rock in

* Ketterin the same as Kerne used by Shakspeare—banditti; hence Loch Ketteria
and not Kathrine or Catharine as it is erroneously spelled.

various parts of Silane. 449

other respects preserving a perfect graywacke character, and being
composed of distinctly rounded as well as crystallized grains of
quartz, joined by a common cement.

It is plain that there will be a point of gradation where it will be
impossible to say to which of the two the rock in question ought to
be referred, although the extremes are perfectly characterized, in
the one case by the laminar form of the quartz and mica, in the
other by its granular disposition. I shall not be surprised if future
observers discover that the rocks of the graywacke structure alter-
nate here with those of the micaceous schist. Should this be the
case, it will confirm the supposition which I have suggested in
other parts of these papers, that no real and well defined line of
distinction exists between the transition and primitive rocks, but
that they form a graduating series of one single formation ; a series
so gradual as to render it expedient once more to return to the
most simple division of rocks, into primary and secondary.

VoL. Il. ul,

XIX. Remarks on several Parts of Scotland which exbibit Quartz
Rock, and on the Nature and Connexions of this Rock in general. -

By J. Mac Cuttocu, M.D. Chemist to the Ordnance, and Lecturer on
Chemistry at the Royal Military Academy at Woolwich.
V. Pr. Geo. Soc.

Jura.

As I considered that the mineralogical history of Jura had al-
ready been amply detailed, I ascended its well-known mountains
rather to gratify my love of the picturesque, than with the hope of
acquiring any new ideas on the subject of its structure.

Yet as the predominant opinions seemed to have determined that
the tract in question was composed of a granular quartz, and as it
had been compared with the northern part of Scotland asserted to
consist of the same rock, with the ridge of Schihallien, amply
described as such by Professor Playfair, and with numerous other
foreign rocks described by various authors under this designation,
I had with others admitted the term, and the era of formation which
this term implied. My own researches having given me reason to
differ in opinion from these authorities, I have thought it necessary
to describe the appearances which I saw; the question of its rank
in the great society of rocks can only be determined after all its cir-
cumstances have been fully investigated.

The whole island extending to a length of 30 miles, and varying ~

Dr. MAc CULLOCH on Quarts: Rock. 451

in breadth from one mile to six, is fundamentally composed of this
one rock, which is also to be found extending through Scarba on
its northern, and through a great portion of Isla on its southern
shore. The other rocks which occur, with the exception of an
important series to be immediately described, either occupy small
spaces apparently subordinate to the general mass, or consist of veins
which traverse it. ‘The highest part of this tract forms an irregular
elevation, of which the three well-known Paps of Jura attaining
the height of 2500 or 2600 feet, are the most remarkable and
prominent features. These occupy a point in the island much
nearer to the southern than to the northern extremity. The in-
terval between them and the southern shore is low, the mountains
declining with a tolerably uninterrupted slope to the sea. But
that between the Paps and the northern side is occupied by a suc-
cession of hills which also decline gradually from the highest
elevation, and form a broken ridge extending to the northern shore
of the island. If we look from any of the highest summits to-
wards the north, a view of almost unexampled singularity and
grandeur is afforded. A series of ridges and brceken elevations ap-
pears under the eye, but so far beneath it that their irregularities
are nearly lost in the continuity of the straight lines which guide
the sight to the further extremity of their range. These seem to
rise from beneath the feet, and to converge to a distant centre, ac-
cording to the strict laws of perspective. On investigating the
cause of this striking disposition, it is easy to perceive that the
effect is produced by the disrupted edges of strata of rock rising
from the east at a considerable angle, and broken away towards
the west. |

However much the continuity be here and there apparently in-
terrupted by the predominance of some particular hill, it is obvious

oL2

452 Dr. MAc CuLLocn om Quartz Rock.

on comparing these apparent interruptions with the actual causes
which produce them, that the fundamental evenness and direction
of the strata is no where altered, and that their discontinuities are
only the effects of partial elevations interfering with the visual line,
all the strata being straight and parallel to each other through
their whole extent. This line extends to the north north-west, and
the strata dip to the east north-east. In the Outlines of the mi-
neralogy of Jura, this angle is said to be 45°. It appeared to me
considerably less, but this sort of observation is not easily made,
except in favourable circumstances of position, and I was at no
pains to verify it accurately, considering it of no importance in a
case like this, whether the elevation were 10 or 12 degrees more
or less. It is only in cases where it is necessary to compare parti-
cular strata, either with the neighbouring ones or with each other,
that accuracy is required, and this accuracy is I fear much less fre-
quently attained than pretended to. These strata are generally
thin, often not exceeding six or eight feet in thickness, and I no
where observed that they were distorted or interrupted by veins of
any magnitude, or that they alternated with other rocks. It is true
that at an inaccessible part of the summit of the one on which I
stood, I observed a mass of dark-coloured rock, which the guide
informed me was a slaty stone. Future observers may find de-
tached specimens of it, and thus ascertain that which I attempted
in vain to investigate, but which the sequel of these remarks will
prove to be more than probable.

Such is the appearance of the rocks as observed from the Paps of
Jura. In descending to the lower grounds, the stratified disposition
becomes more obscure, in consequence of the interruption to the
continuity of the rock from the thick covering of heather, and
from the irregular form of the surface which prevents a connected

Dr. Mac CuLiocn on Quartz Rock. 453

view of large tracts. In many parts of the shore, however, the
disposition of the strata is evidently changed, and they are ob-
served occupying every possible variety of position, from the
horizontal to the vertical. The steps by which these changes
succeed each other eluded my observation, and perhaps are not to
be traced.

I will now describe the principal modifications which this rock
assumes, so as to give an idea of its mineralogical character, before
I attempt even to conjecture its place in a geological system.

It exhibits the following varieties: ~

I. An extremely compact granular stone, consisting of grains of
quartz, of unequal sizes, united without cement.

2. The same, containing grains of clay, which appear to be
decomposed felspar.

3. The same, with more numerous grains of felspar, which
appear on examination generally to consist of rounded fragments.

These rocks are traversed by veins of quartz, of which the
aspect is also granular, but they are distinguished from the body of
the rock by their snow white colour. ‘They often appear so
incorporated with the rock that the line of separation cannot be
distinguished.

4. A similar rock containing angular grains of quartz of half an
inch in diameter, and bearing every mark of having been formed
from a disintegrated granite, except that it exhibits no traces of
mica.

5. The same rock containing a flattened oval pebble of quartz,
perfectly smooth, and having uniform curved surfaces, as if from
long attrition. The pebble is two inches in length, and one and a
half in breadth. It was so firmly united to the rock, that on one
side it has been broken in the attempt to separate it.

454 Dr. Mac CuLiocu on Quartz Rock.

6. Grey quartzy rock, with a basis of a compact splintery ap-
pearance, containing imbedded grains of transparent quartz.

7. Small grained breccia, of which the basis is an earthy-looking
mixture of felspar and quartz, resembling claystone, or compact
felspar, and uniting angular and rounded fragments of quartz.

8. An uniform aggregate of large grains of felspar and of trans-
parent quartz, without the aspect of granite, since all the grains —
appear to have been mechanically rounded and re-united.

This quartz rock in the several varieties now described, although
as I have already remarked, it forms the essential and fundamental
part of the island, does not occupy it to the exclusion of all others.
Beds of a rock resembling both mica slate and graywacke, of com-
mon graywacke, of finer graywacke slate, and of perfectly fine
and uniform clay slate, together with beds of chlorite slate, appear
in various places, all difficult to trace through their whole bearings,
yet all apparently superimposed on the quartz rock. It is necessary
to describe these rocks somewhat more particularly, as they are inti-
mately connected with the quartz rock, and serve to illustrate its
history. The following are the most remarkable varieties :

1. A mixture of quartz in grains, with mica slate, of a character
intermediate between quartz rock and mica slate, or rather resem-
bling some of the varieties of that graywacke which I have described
in my account of Aberfoyle, (p. 447.)

2. The same, of a much larger grain, with distinct scraps of
mica slate.

3. The same, with the mica slate so predominant that the com-
pound forms a dark rock, in which the grains of felspar and quartz
bear a small proportion to the slate.

4, The mica slate still increasing, and the texture still granular.

5. The same, with a slaty fracture.

Dr. Mac CuLtocu on Quartz Rock. 455

6. Coarse graywacke slate.

7. Fine ditto.

8. Perfectly fine and uniform clay slate, of a dark blue colour.

It is important to remark, that the beds which are found at the
foot of the mountain, are of a coarser texture than those at the
summit, and these are probably the uppermost beds of the deposit.
Many of them are nearly black from the quantity of clay they con-
tain; in others are found grains of mica, and in some there are
imbedded large fragments of clay slate and chlorite slate.

In hand specimens a gradation may-be traced from the finest and
most compact quartz rock, down to a perfect breccia, containing
fragments of slate, although the ground does not admit of our tracing
the sequence of the beds.

If therefore we consider the circumstances which I have described
as existing in the finest quartz rock, the rounded pebbles of quartz.
which it contains, and the gradation that may be traced in it through
all the series which I have above noticed, and which are generally
confounded under the term graywacke, we need not hesitate to
conclude that the quartz rock of Jura is a mechanical deposit, or a
rock recomposed from the fragments of older ones. I know that
authors have talked of primitive sandstone, and even of primitive
‘breccia, but the awkward nature of this compound renders it de-
sirable that we should, if possible, discard a phraseology which
involves a contradiction in terms. It is perfectly true that many of
the beds in Jura contain large tracts of a granular quartz, often very
pure and compact, and which from its crystalline texture might in
the hand be supposed a primitive and chemical deposit ; but the
occurrence of blunted fragments, and of rolled pebbles, suffice to
shew, that like many other rocks it possesses at least the compound
structure both of a chemical and of a mechanical deposit. Neither

456 Dr. Mac Cuitocu on Quartz Rock.

is the perfect crystalline texture of quartz any proof of a primitive
formation ; since the strata of Kirkaldy, which belong to the fleetz
and coal formation, contain beds of highly crystalline and translu-
cent quartz, alternating with coal and organic limestones.

The mode in which the felspar exists in this rock proves also
its mechanical construction, and shews that it has very probably
been derived from the wearing and deposition of antient granites,
by whatever means we may attempt to account for its present
highly compacted and often crystalline structure.

Having thus, as I trust, clearly proved that the rock of Jura is
a recomposed rock, as far as regards its structure, and that it cannot
from its compound nature be properly entitled to the name of a
granular quartz, it is our business to consider its geological appear-
ances, and the probable nature of the process by which it acquired
its present disposition.

Before examining this question, it is requisite to premise an ob-
servation of professor Jameson, whose accuracy is not doubted.
He remarks that the “ Quartz rock rises at an angle of 45 degrees
from under the micaceous schistus.”” Here then we have a rock
formed of a mixed mechanical deposit, lying under a rock which
is held to be primitive, and the third in succession from the first and
fundamental of all rocks, granite. I did not observe this fact, but
have perfect reliance on his observations, because they coincide
with what I have myself observed in other places. Either then
this mechanical deposit must be considered as a primitive rock, or
micaceous schistus is a rock of more recent formation than it has
heen generally esteemed.

This latter supposition may perhaps admit of further proof, but
I cannot enter into it in this place.

Leaving this additional difficulty out of discussion at present, it is

Dr. Mac CuLtocu on Quartz Rock. 457

obvious that there is no provision made for this rock in Werner’s
classification, if I have succeeded in proving that it is as little entitled
to the name of quartz, as to that of granite, and that it is not a
purely primitive and chemical deposit. Its mechanical structure
deprives it of a right to the latter title, and its connexions and dis-
position prevent us equally from arranging it with the latest stratified
or “floetz” rocks. If it is a necessary condition of the “transition”
rocks to contain organic remains, then this rock is also excluded
from the intermediate or transition class, as much by this as by its
position in respect of the mica slate, universally esteemed among the
primitive, or to speak more properly among the most ancient rocks.

Such are the inconveniences of artificial arrangements, whether
they are groundless, or founded on partial views of natural pro-
ductions. It has been proposed indeed to call this rock graywacke,
a quartzose graywacke. But this is in fact to confound all dis-
tinctions for the sake of an adherence to a system, which may
without disgrace admit a new member into any of its series, should
it appear that a member hitherto unobserved does actually exist.
The name grayvwacke has been already too much abused, and is
become a fruitful source of confusion and error. It is incumbent on
us to diminish instead of increasing this evil, by a more careful
application of that, as well as of other geological terms, and by
limiting its use within the rigid compass of definition. On that
definition I need not now insist; nor will I attempt at present to
assign the true place of the quartz rock in the general arrangement.
It will be done with greater facility when I have described its
connexions in the other places where I have observed it.

VOL. i. 3M

458 Dr. MAc CuLLocnu on Quartz Rock.

Assynt.

Although I have to regret the limited extent of my observations
on this district, yet as they tend to illustrate the nature of the rock
which forms the subject of this notice, I am unwilling to suppress
them. They may at least serve, in conjunction with the remarks
which I have made on this rock in other places, to extend its history |
and connexions, as. well as to stimulate future observers possessed of
better opportunities, to continue this inquiry, and to assist in
determining the composition of that extensive and as yet little
known country which constitutes the-northern mountainous division
of Scotland.

The mountains which form the districts of Coygach and Assynt
may be distinguished even from the island of Sky, by their peculiarly
smooth and conical outlines, and by the whiteness of their summits,
so dazzling in the sunshine, that to a spectator unaware of their
composition, they appear as if for ever retaining the snows of winter.
Their strong resemblance to the Paps of Jura, both in the even
unbroken line which forms their summits, and in the peculiarity of
their colour, immediately however, explains their composition and
confirms their similarity ; for, like those mountains, they are formed
of a rock which has here also been called “ granular and primitive
quartz.” In a distant view they are remarkable too for another
peculiarity, which in other situations has been supposed characteristic
of the mountains of this class, and that is, their detached position.
The accompanying sketch of the coast, Pl. 32. fig. 2. will better ex-
plain than words can, both the singularity of their form and that
independence of position which they assume; circumstances which
when compared with the irregular outlines and crowded groups of

eranitic and schistose hills, will strike the most careless observer. The

Dr. Mac Cuntocu on Quartz Rock. 459

sketch to which I refer, will doubtless also remind the spectator of
the view given in Dr. Fitton’s paper, of the hills in the vicinity
of Dublin. The conical form of these hills appears to arise partly
from the rapidity of their decomposition, as far as regards their
mountainous bulk, and partly from the permanent nature of the
resulting fragments. ‘To the same cause also is owing that particular
and arid appearance of sterility, which is so characteristic of this
class of mountains, an appearance which those who have seen Jura
will readily recognize, combined with a difficulty in ascending them,
which the geologist who has laboured in the attempt will not easily
forget. The peculiar whiteness which the surfaces of the fragments
show is however adventitious, as the fresh rock exhibits a variety of
grey, yellow, and brown tints, which long exposure to the atmosphere
will ultimately bleach. A narrower examination of unaltered spe-
cimens would possibly have prevented mineralogists from ever
applying to this rock the improper designation of granular quartz,
how much soever the weathered surfaces may resemble this substance.

On a nearer inspection, these mountains appear to consist of a
stratified rock, or to be formed of various beds of grit, which, where
the declivities are so steep as not to admit the lodgment of fragments,
become easily visible. In my remarks on Jura, I have described a
distinct and continuous bearing of the strata, but I was unable by
the aid of a spying-glass to perceive at any of the various points
from which I viewed the mountains of this coast, a similar tendency
through any considerable space. I should conceive their tendencies
to be exceedingly various, and that no general system of inclination
or direction predominated among them. But of this I must needs
speak with much diffidence, as I had no opportunity of ascending
any of the summits, from whence alone an accurate observation of
this nature could be made. Those who have been occupied in

gu Zz

460 Dr. Mac Cutiocn on Quartz Rock.

similar investigations well know how difficult it is to ascertain the
disposition of large tracts of country unless observed from situations
so elevated as to raise the spectator above all the obstructions which
the varying forms of high ground throw in the way of this great
natural perspective. The remarks of Saussure on the highest
summits of the Alps, which relate to this subject, are well known.
It is not material to the purpose of determining their stratified —
structure, whether this stratification be continuous for a large space
or whether it be various and interrupted ; however desirable it might
otherwise be to ascertain its disposition over the whole extent which
these mountains occupy. From the low positions in which I was
compelled to view those strata which I saw at hand, they appeared
to be in some places horizontal, in others occupying various angular 3
elevations, sometimes inclining to the north, and sometimes in a
direction the very reverse. Such perhaps would also have been my
opinion of the strata of Jura, had I not attained its highest summits.
Future observers who shall ascend the Cuniack hills, the Sugar-loaf
mountain, or Ben More, will be able to ascertain what I have left
undone. Want of roads, want of horses, want of population, want
of every thing, render this country among the most impracticable of
Scotland. |

The nature of this rock is exceedingly various. It is often a |
compact stone of a yellowish colour, and uniform texture, resembling
a granulated quartz, simple in its composition, and breaking with an
imperfect conchoidal fracture. Occasionally it assumes a coarser
and looser texture, and in these cases the weathered surface becomes
white, and acquires a harsh and sandy feel and aspect. However
uniform the fresh specimens appear when broken, they almost
invariably disclose some internal mechanical arrangement on weather-
ing, which betrays the nature of their original formation, a circum-

Dr. Mac Cutxiocn on Quartz Rock. 461

stance highly instructive with regard to the composition of many
other rocks. Of these natural analyses, a very common one is the
appearance of laminz of red and white matter, alternating either in
flat plates, or in that peculiar undulating form so well known in the
floctz sandstones, and marking the action of water on loose sand.
An occurrence of equal importance and greater singularity is that. of
imbedded cylindrical bodies which they occasionally exhibit. I may
previously remark that they have a frequent tendency to break into
rectangular solid masses, similar to those which occur in many floetz
sandstones. In these fragments the weathered surfaces present on
the upper part, or that which forms the plane of the stratification, a
number of circular protuberant spots, apparently arising from the
circumstance of their hardness being greater than that of the general
mass. ‘The lateral plane of the same fragments exhibits on the
other hand a similar number of corresponding cylinders, of a hard-
ness in the same way superior to that of the surrounding parts. If
I might venture on a comparison as vulgar as it is explanatory of
this appearance, I would compare it to the two sections of a piece
of larded meat. I may further add, that in these cases the cylindrical
bodies are of a much whiter colour, as well as of a more compact
texture than the rest of the stone; and that on breaking the stone to
examine further into this structure, the whole disappears, and an
uniformity of texture is exhibited throughout.

This peculiar appearance is familiar to all those who are conversant
in the varieties of /loefz sandstone, and the superior hardness of the
cylindrical or vermicular bodies in the sandstones of this class is
equally notorious, as they often continue to project for the space of
even half an inch beyond the decomposing rock, appearing as if
nails had been driven into it. The coast of Fife about Burnt Island
affords excellent examples of this fact. I know not that any attempt

462 Dr. MAc CuLiocu on Quartz Rock.

has been made to explain this circumstance in the foefz sandstones,
but it probably arises from the remains of some animal, a Sabella, or
other marine worm. Whatever it be, it is sufficient to establish the
similarity in the original structure of this mountain rock, with that
of the present floetz formation. I am the more particular in calling
the attention of the Society to these resemblances, because I am
unable to produce such decided instances of rolled pebbles as I have
described in the rock of Jura, and am therefore apprehensive that
the arguments by which I would prove the recomposed structure of
this rock, may not appear sufliciently conclusive. But I have little
doubt that many instances even of this occurrence, will be found by
those who may have more time to bestow on the investigation, and
who with better fortune may collect such specimens as might easily
have eluded my cursory search. Proofs however are not wanting
of mechanical attrition in the component parts of many beds of this
rock, although the fragments do not absolutely reach the size of a
pebble. A rock resembling ferruginous sandstone, of a highly
compacted nature, is found in beds, alternating with the finer and
more compact quartz rock, the grains of sand and gravel bearing
most evident marks of attrition ; and the whole mass being indurated
to such a degree, that a hammer makes no more impression on it than
it would on a mass of iron. It is still more satisfactory to find in
certain positions, strata of absolute and perfect breccia, similar in
aspect to those which now alternate with our older /lcetz sandstones,
but possessing the same extraordinary degree of hardness which
I have just noticed. If there are any marks of organic remains in
this rock less equivocal than the vermicular structure which I have
described above, I did not see them, nor do I consider them necessary
to establish its character, since our oldest floetz sandstones are equally
destitute of them. Under all these circumstances both of position

Dr. Mac CuLztocu on Quartz Rock. 463

and of structure which I have detailed, I think that I am justified
in considering this rock, like that of Jura, to be a recomposed, and
not a purely chemical deposit, being with it equally ill entitled to
the name of granular quartz. Its characters would seem to prove
that it has originally been a stratified sandstone, which by some of
the revolutions of this globe has been both chemically and mecha-
nically altered, consolidated in some places to the apparent loss of
its original texture, and so changed in its position as to show but
faint indications of its former regularity.

It now remains to enquire into the connexion of this rock with
those which accompany it, a part of the subject, and a very im-
portant one, on which I must regret that I have so little precise
information to offer. On the sea shore at Kylescuagh, and on the
shores of Loch Lowie, a very indurated and compact gneiss appears
to lie immediately. below the quartz rock, but I could not discover
their connexion. In the very centre of the district I found horn-
blende slate, gneiss, mica slate, and syenitic granite, together with
numerous veins and detached masses of compact epidote. Here
also, unfortunately, I could not trace their connexion. Such is
the meagre account I have to render of what it would be of prime
importance to ascertain, whether these rocks are every where
inferior in position to quartz rock, or whether the older schistose
rocks do not here, as in other places, alternate with it. Circum-
stantial evidence renders the latter probable. In the description of
Jura I have remarked that mica slate does, according to Professor
Jameson, lie above the quartz rock, and Williams considers the rock
I have described, which he also calls granular quartz, to be, like
granite, the rock on which micaceous schist usually rests. Professor
Playfair also in his J//ustrations, (P. 166,) speaks of a “ granitic sand~

stone in vertical beds,” and mentions its alternation with “* micaceous

464 Dr. Mac CULLOCH on Quartz Rock.

and other varieties of primitive schist.” Since this paper was
originally drawn up, I have seen the country he here quotes,
(Arisaik) and have confirmed that his “ granitic sandstone” is the
rock which I have been describing, and that it is the same rock
which he has also described as constituting the ridge of Schihallien,
a place of which I shall presently have occasion to speak. Possibly
these authors, impressed with the notion that this rock was a
‘“‘ granular quartz,’ and that granular quartz was a primitive rock,
have not thought it necessary to push their investigations as far
as they might have done, nor made the important deductions
which must needs follow from this fact if proved. On the geo-
logical consequences which would result from its being established
it would be useless to speculate till the fact be fully ascertained,
as I trust it will be in the sequel of this paper, but it is obvious
that it would occasion the removal of mica slate out of the chemical
deposits of the Wernerian system, and place it among ‘the me-
chanical, or at least the mixed ones: a change which seems to
be called for by many other circumstances attending the forma-
tion of mica slate. But I must leave this part of the subject for
future consideration.

The true nature of this rock being now, as I trust made out with
regard to Jura and the western part of Sutherlandshire, we are
next led to inquire what evidence there is to prove that all the
mountains of “ granular quartz” are not of a similar nature, and
do not belong to some of the ancient recomposed rocks. The
mountains of Scuraben and Morven are cursorily described by
Jameson, the former as having a summit of quartz, the latter as
possessing the peculiar white aspect so characteristic of the hills I
have noticed on the western coast; and in his work on Geognosy,
they are actually quoted as examples of quartz rock. Mr. Pennant

Dr. Mac Cutrocu on Quariz Rock. 465

too, although not an authority in a case’ of this nature, describes
quartz about Loch Broom, and more cursory observers have given us
reason to think that the generality of the higher mountains of this
northern tract of Scotland are composed of “ quartz.” There is
little doubt that the whole of this elevated tract is of the same for-
mation as that under consideration, and it ought therefore perhaps
(according to the remarks I have already made on Jura) to be
renked with the Transition rocks, if we adopt the divisions of
Werner. fii ;

f this be proved it will be highly interesting to ascertain the
positions of ‘all the strata throughout this whole district. Of the
unstratified rocks it will always be difficult to determine what pox-
tion has been removed, or what changes of the original position
may have taken place, as we have no guide to conduct us in our
judgment, ignorant as we must generally remain of their original
forms. With the stratified rocks the case is otherwise, their exist-
ing forms furnishing us with a palpable index, by which we may
discover either the changes of position they have suffered, ‘or the
waste they have undergone. Certainly the north-west coast of
Scotland gives evidence of an enormous waste of the surface, and
opens an ample field for the speculations of those who have at-
tempted to assign the causes of that waste: to them I must at
present leave it.

I have already, at the beginning of this paper, remarked the simi-
larity which the outline of the mountains of Sutherlandshire bears
to that of the Wicklow mountains. These, in the paper of Dr.
Fitton, above mentioned, are also called granular quartz. As I have
meither seen the mountains themselves, nor any specimens from
them, I am unable to decide whether they are actually similar in

structure and geological character to the Scottish quartz mountains,
Wor. I 3N

466 Dr. Mac CuLtocn on Quartz Rock.

and I can only suggest their suspicious aspect, as a reason for a
further examination of them. I am inclined to entertain the same
doubts relative to the quartz mountains described by authors in
various parts of the world, most of which exhibit the detached
and conical forms so often mentioned, and from some of which
specimens have come to my hand precisely similar in their minera-~
logical characters to those which I have described. If such should
be the fact, the necessity of finding a place for this rock in the list
of formations will be more apparent than before, and it will be the
duty of those geologists who lay stress on such distinctions, to
ascertain the true rank it ought to bear in their system.

Schihallien.

This mountain, already highly interesting from the important
geometrical operations performed on it by Dr. Maskelyne, and
the subsequent mathematical computations of Dr. Hutton, has
again been called into notice by Professor Playfair, in his Lithological
Survey, established for the purpose of correcting the results deduced
from the labours of those mathematicians.

As Mr. Playfair’s remarks on the geological structure of this moun-
tain, although chiefly referring to the particular physical object he
had in view, seem to involve some important conclusions respecting
the rock described in the two foregoing memoirs, I shall, I trust, be
excused for stating the considerations to which they have given rise,
and to which I have already alluded, since they may-serve to call some
further attention to its mineralogical and geological history.

The mountain itself forms the most elevated part of a ridge which
may be considered as rising near Fascally, and extending in a south-
westerly direction till it meets that complicated group from which

Dr. Mac Cuttocu on Quartz Rock. 467 ~

the ridge bounding the southern side of Glenco takes its rise. This
ridge contains the other considerable elevation of Ferrogon, and
separates, not the “ valley of the Tay” but that of the Lyon from
that of the Tumel. The reason for making this correction will
appear in the sequel.

Mr. Playfair’s accurate description of the spaces occupied by the
rocks which constitute the summit of Schihallien, renders it unneces-
sary for me to enter into any such detail. I may merely remark,
that by his report. the whole of the mountain, except the central
ridge, consists of the various modifications of mica slate, hornblende
slate, and the usual associated limestone, which are so well known
as constituting the greatest tracts of the highland mountains. The
result of my own examination, which was however exceedingly
limited, coincides with his. All these strata are vertical, or very
nearly so, and the central ridge, or the “ granular quartz,”’ appears
to be placed in a position absolutely perpendicular.

This quartz rock is stratified, although vertical, in beds which, as
far as they can be seen, appear absolutely and nicely parallel, their
lines of separation being defined with a most mechanical exactness.
They have a tendency to break into rhombic and prismatic fragments,
by fissures perpendicular to their stratification, and being thus
broken, they have fallen on all sides around the summit, producing
the same appearances as those exhibited by the Paps of Jura, and
the mountains of Assynt, and, for the reasons which I have assigned
in my observations on these hills, contributing to form that elegant
conical outline for which the summit of Schihallien is so remarkable.

An ample account having been given by Mr. Playfair of all the mo-
difications of this rock which he could observe, it will be superfluous
for me to enter into its history, particularly as I have already pointed
out its leading characters in describing the rock which forms the

3.N Z

468 Dr. Mac CuLiocn on Quartz Rock.

summits of Jura. There is, in fact, no essential difference between:
them, as they consist in both cases of highly compacted grains of
quartz, with interspersed grains of felspar, often earthy, and never,
I believe, so perfectly crystallized as they are in granites and por-
phyries, but having the aspect of fragments rather than of crystals.
I did not meet with any specimens on Schihallien of a formation so
decidedly mechanical as those which I have described as occurring in
Jura, but must rest the proofs I am desirous to bring forward of the
mechanical and therefore secondary structure of this rock, on other
and more circumstantial evidence. Possibly future observers, bearing
this doubt in their minds, may with more time and opportunity dis-
cover such positive proofs of this nature as I failed to find, since
our acquisitions in specimens are generally in proportion to our
previous knowledge. :

It will doubtless be admitted that if of two rocks precisely similar
in the generality of hand specimens, similar also in structure and
position, and possessing the same characters in general aspect and
disintegration, the one is proved to be a mechanical deposit by its
containing rounded pebbles or beds of breccia, it affords a very
strong presumption that the other is of the same nature. But we
have yet to see what further evidence of this may be found in the
neighbouring rocks, as the occurrence of a single bed of a recom-
posed rock in a situation so remarkable as the ridge of Schihallien,
might excite rational doubts, unless we could discover a greater
extent of similar rocks connected with it. It is here necessary to
remark that the whole country to the north of this ridge consists for
a considerable space of rocks of the class called primitive. The
vale of Tumel and the hills which bound it are composed chiefly of
mica slate, which continues till it meets the granite of the central
Grampians. The case is different on the southern side of Schihallien.

Dr. Mac Currocs on Quartz Rock. 469

The ridge of Ben Lawers, it is true, (that ridge which does actually
bound the valley of the Tay) consists of chlorite slate, with mica
slate, and the other rocks of this character which need not be des-
cribed. But the valley of the Lyon exhibits a formation totally different.
The river Lyon runs with a very gentle fall through the greater part

“of its course into the Tay, proving that there is no very great differ-
ence of level between their respective vallies. In passing through Glen
Lyon, the mica slate may be seen terminating on the south side of
the river, in some places indeed long before it meets the bottom of
the southern side of the valley. It is also obvious that the boundary
of almost the whole northern side, as far at least as from Meggarney
to Fortingall, consists of a sort of compact sandstone or “ granular
quartz,’ a rock in no way differing from many of the varieties of
quartz rock already described. ‘This is the ridge which declines
from the south of Schihallien, and which is intimately connected
with the main ridge of that mountain. The sandstone itself exhibits
a texture of infinite variety, but in all cases it possesses the same
aspect of antiquity and induration which characterizes the rocks of
Jura and Schihallien. It would be necessary to traverse the whole
of this ridge to the top of Schihallien before we could ascertain
positively whether the rock which forms its summit is connected
with that of Glen Lyon, and what is the mode of this connexion ;
a task of considerable difficulty. Yet I have very little doubt that
they are parts of one great deposit, similar to that which constitutes
the north of Scotland and the Island of Jura.

Future and more extended investigations may perhaps enable us
to assign even from this spot the relative antiquity and position of a
rock hitherto but ill understood, and possibly from the more accessi-
ble parts of Schihallien determine the very important fact of its
inferiority to, or alternation with, mica slate, a fact which however

470 Dr. Mac Cuttocu on Quartz Rock.

will appear fully determined by the other examples of this rock,
which are described in the supplement to this communication. But
this circumstance, already mentioned as being supposed to occur in
Jura, does really appear to receive further confimation here, since if
the central ridge of Schihallien is surrounded by mica slate, a fact of
which Mr. Playfair entertains no doubt, and if this ridge is connected
by any system of alternation with the sandstone of Glen Lyon,
mica slate will appear to be a rock formed posteriorly to, or alter-
nately with a rock of recomposed structure. Thus a “* primitive”
rock will be found to alternate with a “ transition” one, an anomaly
which either renders this distinction as useless as it is artificial, or
compels us to modify the definition of transition rocks, or to form
that total change of arrangement which I have more than once
suggested with regard to the primitive and transition classes. It is,
I trust, quite superfluous to say that it can have no title to the name
of “ granite,” with which it certainly does not possess any one

common feature.

Supplementary Remarks on Quartz Rock.

Having had an opportunity since I presented the foregoing
memoir last year, of examining some other parts of Scotland where
a similar rock occurs, I have thought it right to lay these supple-
mentary observations before the Society, partly for the purpose of
correcting the errors and supplying the defects of that communica-
tion, but principally for the sake of elucidating the history of a
substance as yet but imperfectly understood, and but ill arranged,
although it must already be obvious that it occupies a considerable
space among the older rocks, and is entitled to rank as a principal

Dr. Mac Cutzocu on Quartz Rock. 471

member among them. In the former notices I have already in
some measure described its general aspect and connections, although
the limited extent of my researches prevented me at that time from
pronouncing decisively as to the latter. I am now, from more
recent observations, enabled to confirm the suppositions there made
“with regard to its place among the older rocks, and to add such a
further description of its mineralogical character as to include many
more varieties. I shall content myself with merely pointing out
its geographic situation in those places which I was prevented from
examining more particularly, in the hope that some future observer
may direct his attention to them, and ascertain that which I have
left undone.

This rock may be seen in Mar accompanying the Dee during
part of its course through a country consisting of granite, followed
by the usual covering of micaceous and clay slate, a country even in
the Wernerian use of the term, primitive. It appears to be stratified,
but of its more immediate connexion with the schistus I can say
nothing, as IT had no means of examining into it. Following the
military road which extends from Braemar to Tomantoule it may
be observed in various places, and appears to form the whole or
considerable portions of the hills which, declining from the granite
ridge of Cairn Gorm, accompany the courses of the Don and
the Avon, and are principally constituted of different kinds of
schistus. Pursuing this line northwards, it occurs more sparingly,
but may still be occasionally observed, together with the schist, till

the hills decline into the plain country about Fochabers. I can pro-
duce no observations through any part of this course to prove that
it is a member of this class of schistose rocks ; but from its mine-
ralogical character and general appearance, and from the resemblance

which it bears to those quartz rocks whose connexions with the

472 Dr. Mac CuLiocu on Quartz Rock.

older schists are apparent in other places, I think future observations
will confirm my supposition that it isa member of this class of rocks.
A highly indurated breccia may be seen near Boharm, on the line
now described, consisting of angular fragments of red and white
quartz, so compacted that they do not separate from the bed on
breaking the rock, but the whole gives way together, as if it were
one continuous mass. ‘The same rock now and then contains
jaspers dispersed through it in the form of fragments. As I have
observed similarly indurated breccias accompanying a similar quartz
rock in other places, I suspect that this breccia is a portion of the
same formation, bearing such a relation to this quartz rock, or com-
pact sandstone (since it may be often better described by this appel-
lation) as the softer and better known breccias occurring on the
borders of the floetz strata do to these latter. I also suspect that
greater simplicity of composition and more perfect induration will
be found to be leading characters of the breccias of this class, the
causes of which must be sufficiently obvious, and that portions of
breccia or large grained mechanical formation, will generally be
found accompanying the older schistose strata whenever these ex-
hibit the smaller grained mechanical disposition. It is to these that
the unfortunately constructed term of primitive breccias has been
applied. If we could securely adopt the names of breccias and
sandstones. of transition, this contradiction in terms would be
aveided, but if as I have already shown, and shall presently I hope
more fully prove, the quartz rock under review does actually alter-
nate with the rocks called primitive, it is plain that we cannot
have recourse to this expedient, but must be content, if we use the
term primitive, to bear with the unseemly compound. The adop-
tion of the word primary, in lieu of primitive (a change already

recommended) removes this apparent contradiction, since it is only

Dr. Mac CuLtocu on Quartz Rock. 473.

the correlative of secondary, and involves no hypothesis with regard
to the absolute eras of rock formations. But I must pass on to
further matter of fact, leaving to the labours of future geologists,
the actual connections and origin of these breccias, and the distinc-
tions to be drawn among this very intricate class of rocks.
“ In the district of Appin the quartz rock may be observed in va-
rious parts, and although I have not been able in this place any
more than in Mar, sufficiently to trace its connexion with the mica
slate of the country, I have little doubt that it immediately follows,
and possibly alternates with it. It may be seen not far from the
castle of Bercaldine, and forms a large detached rock at Airds. Here
it is of a highly indurated character, and bears the marks of a dis-
turbed stratification. I do not think it necessary to describe the
particular aspect which each rock assumes, as it most frequently
happens that various modifications of it are to be met with in the
same spot, and I prefer delaying the general description till I have
mentioned the several places in which it is found.

The same rock occurs in the district of Arisaig. It occupies there
a considerable portion of the shore, and may be traced forming low
hills and interrupted projections, from the point of Arisaig, nearly to
Loch Morrer. It seems here to alternate with mica slate, as I have
already mentioned in another place, where I have quoted Professor
Playfair’s remarks on it; but possesses much less of the appearance
of stratification than in the other instances which I have enumerated.

In the island of Sky it occupies a considerable space, and forms
that large mountain mass which projects from the general eastern
boundary of the island, so as to produce, together with the main
land, the narrow passage of the *Kyle rea. Here it assumes a

* Kyle rea the smooth strait, Kyle ree the King’s strait, but both are corrupt ety-
mologies. Kyle rich, the swift strait.

WOE: il. 30

474 Dr. Mac Cutiocn on Quariz Rock.

character considerably different from that which it exhibits either in:
Jura, in Assynt, or in the other places which I have described.
Its aspect is more uniform, and its texture more compact. Its
fracture is rather more splintery than granular, and it rarely con-:
tains felspar, a mineral seldom absent for a long space in the ge-
nerality of the quartz rock. It is here of various colours, brown,
grey, yellowish, reddish, and white, but its predominant tint is a
blueish grey. Its marks of stratification are obscure, yet they may,
however disturbed, be traced, and its true character is I think de-
termined by a compact breccia, which in some places may be ob-
served separating it from the schistose rocks, the micaceous and ar-
gillaceous slate. It occurs again in Sky under another form, namely,
in disrupted portions, forming the tops of low hills in the district
of Slate, of a snowy aspect and compact texture, with irregular
grains of felspar imbedded, and in intimate connexion with the
micaceous schistus.

I have reason to think that the same rock will be found to form
a large portion of that ridge of mountains which extends in a
curved line to the south of Ben Nevis, so as to constitute the
southern boundary of Glen Nevis; but as this conclusion is only
founded on a distant observation, and on the peculiar aspect and
mode of decomposition which these hills exhibit, I lay no stress on
it. Yet as it actually occurs in that part of the declivity of this
group which descends into Loch Eil, and is to be found consti-
tuting a considerable mass of mountain at Balahulish, I shall not
be surprised if future observers assign to it a very considerable ex- .
tent in this district. It is at the edges of the road between Balahu-
lish and Fort William, that it may be conveniently examined, and
it will there also be seen to alternate with a compact argillaceous
schist. | :

Dr. Mac Cuttocn on Quartz Rock. 475

On the borders of Loch Leven, and on its northern side, it is
most abundant, and appears to constitute large portions of the
mountains, having an evident similarity of direction and dispo-
sition, to those masses of it which form the principal parts of the
mountains of Ben-na-vear on the opposite or southern side of this

“Jake, and which I am now about to describe. |

I have already had occasion to mention in a note supplementary
to the account of Cruachan, that granite is found at the base of
the group of mountains called Ben-na-vear, extending from Bala-
hulish towards Glenco in one direction, and for a considerable
space along the Appin road in the other. On ascending this group,
the granite continues for some way. This is followed by a rock,
which, although it forms here as in many other places, considerable
portions of mountain masses, has scarcely received a name and an
establishment in the system of rocks. It is a sort of schistose
quartz; it is not graywacke, nor is it micaceous schist, though it
contains grains of quartz, and mica, and clay: neither is it gneiss,
although it contains grains of felspar. Previous prejudices might
perhaps find it a place among either of these, according as the
predominant system dictated. But the best idea of its general
structure may be conveyed by saying, that if it was a floetz rock it
would be called a schistose sandstone. ‘There is in many cases so
strong an affinity between the rocks of the primary and of the
secondary, or floetz, classes, that it can scarcely lead to error, if,
pursuing this analogy, I should call it a schistose quartz rock. — It
will in fact be found to form the same connexion between the mi-
caceous or clay slate and the quartz rock, as the schistose sandstones
which alternate with thin laminz of clay slate. do between the latest
clay slates or shales and common sandstone. And thus, as in other

3.0.2

476 Dr. Mac Cutxiocu on Quartz Rock.

instances, a connexion in structure and habits is established between
certain rocks of the primary and of the secondary classes. In all
cases the mica is disposed in lamellz parallel to the strata or lamine
of the rock; it is never as in gneiss partially disposed in different
directions, still less as in granite indifferently placed. This rock is
succeeded by quartz rock in large masses. Some beds of a hard or
compact schistus, of a character often approximating to hornblende
slate, are also found to all appearance alternating with it, and I
have already noticed in the paper above alluded to,* that granite
veins are found to traverse this particular schist. The hill is, on its
accessible face, so covered with soil, that no very positive evidence
can easily be procured of the alternation which I suspect ; and the
precipitous faces are generally inaccessible, always hazardous of
access, As we approach the summit of the mountain, the quartz
rock becomes established to the exclusion of the schist, and it con-
tinues to the top, where it offers. that aspect of complete disinte-
gration before described under the heads of Jura and Assynt, which
covers the tops of the quartz. mountains with ruins, and gives. them
that acute apex and regularly conoidal declivity, which, as far as I
have yet observed in Scotland, is. sufficient even at a distance to in-
dicate the nature of the rock of which they are composed. The
laminated or stratified structure is by no means so evident in this ex-
ample as in those I have before adduced: from Jura, Schihallien,
and Assynt; but it still bears the marks of a broken and disturbed
stratification. Such being the case, and such the infinite variety of
position, direction, and elevation, assumed by this rock, I think it
unnecessary to enter into any details on these heads. I may only
remark generally, that it stands at an angle not far deviating from

* Vide paper on Cruachan,

Dr. Mac Cuirocn on Quartz Rock. 477

the vertical position, and that this angle is similar to that held by
the schistus with which it is accompanied.

The composition of this rock offers through different parts of its:
mass different varieties, and it will not be useless to enumerate the
most leading ones, merely for the purpose of proving in this, as in
“some of the other instances described, that many of the most re-
markable mineralogical varieties exist under the same geologica]
position. Thus the identity of the rocks as an order or division is
established, and thus we may legitimately deduce those general con-
clusions from which its place in the system may be assigned, how-
ever in different situations its aspect and composition may vary.

It is often composed of mere grains of quartz, of an aspect ex-
tremely various, sometimes highly crystalline, though never defined
by geometrical forms; sometimes shapeless and opaque. These are
more or less strongly agglutinated, and are occasionally compacted to
such a degree that the granular appearance is nearly lost. It con-
tains now and then grains of felspar, imbedded in a compact quartzy
basis, thus bearing a general resemblance to porphyry. These
sometimes appear to be crystallized in an obscure manner, but more
frequently they exhibit no regular figure. At times the felspar and
quartz are so nearly equal in quantity, that the whole forms a pink~
coloured granular mass, often so loose as to crumble in the hand,
and in this case the grains seldom bear any mark of crystallization,
but are rounded as if they had undergone attrition previously to
their aggregation : occasionally, but rarely, it contains imbedded frag-
ments of quartz. It is not often traversed by quartz veins, but
wherever these occur they are much confounded at their edges with
the mass of the stone. Here then, as in other instances, we see that
it exhibits the ambiguous or rather double appearance of a mecha-
nical and of a crystallized deposit, a mixture of character, which,,

478 Dr. Mac Cuiiocn oz Quartz Rock.

as I have elsewhere remarked,* is not the least important eaicalty
which yet remains for geologists to explain.

I have reason to think that this rock will be found to occupy a
very considerable space among the mountains in the vicinity of
Glenco. In many places the fragments assume a dirty reddish ap-
pearance, which at a distance gives them the aspect of granite.
Having in various instances made this rash conclusion myself, I
think it right to suggest to those who may have an opportunity,
the propriety of actualiy examining the rocks themselves before
any opinions are formed of their nature from distant observations.
From such investigations, not to be pursued without much leisure
and favourable seasons, I have little doubt that the quartz rock will
often be found where it was previously little suspected, and that it
will be placed in a very leading situation in the system of the older
rocks.

The last place which I shall now describe as affording an ex-
ample of the quartz rock, is Tyndrum. The whole of this tract
of country from Killin to Glenorchy in one direction, and from
Luss to Loch Tulla at right angles to it, as far as it is visible from
the road side, consists of mica slate, and is part of a most exten-
sive district to all appearance formed exclusively of this rock. It
is at the lead mine where the quartz rock is visible, and although
I did not examine the summits of the neighbouring hills, I think
it very probable that it will be found in other places among them.
Its alternations with the schist are here not only perfectly satisfac-
tory, but very frequent and numerous, and the works connected
with the mine afford the greatest facility in observing them. ‘The
characters of both rocks are perfectly definite, and that of the

* Observations on Glen Tilt.

Dr. Mac CuLLocn on Quartz Rock. 479

quartz rock is sufficiently various in different parts to establish its
identity in the principal leading features, with the more extended
masses which I have already described. It is also worthy of re-
mark, that in some cases the same gradation which I have before
noticed through schistose quartz rock takes place at the line of
‘alternation. This instance therefore offers a proof easily inspected,
and quite satisfactory, of its forming part of the same system of
deposits as mica slate, and establishes its rank among the rocks of
this class.

‘ The mine of Tyndrum has long been known as a lead mine.’
Of the ores of this metal it affurds only galena, but it also pro-:
duces brown blende. It is in the quartz rock that the ore is at
present found, the mine being wrought by open levels, lighted’
and aired from above by small shafts. ‘Thus we see that this rock
is also entitled to a place among the metalliferous ones, a circum-
stance which, with many cthers, should caution us against im-°
plicitly adopting those general rules respecting metalliferous rocks,
which have been too decidedly laid down.

The nature of this paper has compelled me to chuse a geogra-
phical form of detail, which I have further preferred, that others
may have an oppertunity of examining the evidence on which
these conclusions are grounded. But it has necessarily led to an
account of the circumstances attending this rock, so detailed and
divided, that it will not be useless for the purpose of mineralogical
discrimination, to bring under one general view a description of all
its leading varieties, and for the purpose of geological science, all
the leading facts connected with its history. From the former
(perhaps indispensible) details, future observers will be enabled to
satisfy themselves of the truth of these fundamental remarks, and

from the latter, opportunity will be afforded for a more easy ge-

430 Dr. Mac Cuttocn on Quartz Rock.

neralization to those who may wish to assign its place in a system.
I have selected for description all the most prominent varieties
which have fallen under my notice, distinguishing their geological
and geographical position whenever they were known to me, and
marking at the same time the several gradations by which quartz
rock appears to pass into mica slate, into clay slate, or into gray-
wacke.

1. Pure white granular rock, consisting of amorphous grains of
quartz, strongly agglutinated :—a perfect granular quartz. Al-
though the grains separately taken are transparent, the mass is
necessarily opaque. From Balahulish.

2. The same rock, but containing angular fragments of white
felspar dispersed (although rarely) throughout it. From the same
place.

8. The same rock, with extremely minute amorphous frag-
ments of felspar in abundance. From the same place.

The rock whence these specimens were taken alternates with a
very compact micaceous schistus, and the flat surfaces which have
long been exposed to the weather, assume a sort of enamelled ap-
pearance, not much inferior to the polish given by the lapidary’s
wheel.

4. Pure white quartz, formed of semitransparent amorphous
grains, but the mass has a fracture intermediate between the gra-
nular and splintery. From Sky, and alternating with micaceous
schist.

5. A similar rock from Balahulish, of a pink colour, but with
an aspect more harsh and dry, resembling common secondary sand-
stone. In the same situation.

6. Pure granular quartz in the same situation, but the grains
of large size, and the fracture consequently very coarse. From
Portsoy.

Dr. MAc CuLLocu on Quartz Rock. 481

7. White quartz, with a fracture almost purely splintery, the
granular texture being invisible to the naked eye, but sufficing to
render the stone dull and opaque; alternating with micaceous schist.
At Balahulish.

8. Granular quartz, of a dull aspect, in the same situation, and

‘from the same place, with atoms of mica dispersed here and there
throughout it.

9. Granular quartz disposed in parallel stripes, alternately white
and brown, but containing no foreign substance. From Balahulish,
and in the same situation.

10. The same with pyrites, and in the same situation.

11. Granular quartz, deeply stained by iron, from Assynt, of
various colours, yellow, red, and brown, but the grains of quartz
transparent ; reposing on gneiss.

12. Granular quartz of a pale blue colour, containing pyrites ;
alternating with talc slate. Near Inverara.

13. Granular rock, formed of large grains of quartz of various
dark colours, and generally transparent. It contains here and there
rounded and distinct grains of red opaque quartz, and of glassy
felspar. From Jura.

14. Dark-gray rock, of a granular splintery fracture, with
pyrites. From the same place.

15. Dark greenish-gray, of a similar aspect, without pyrites,
extremely compact. From Sky; following mica slate.

16. The same, of a darker colour, and from the same place.
The influence of the weather whitens it, detecting what the mag-
nifying glass cannot, the existence of felspar as an ingredient, and
which is probably the glassy variety, since it cannot be distinguished

VObendhs 3 P

482 Dr. Mac CuLLocn ox Quartz Rock.

from the transparent quartz grains with which it is intimately united
in the fresh rock.

17. The same rock in point of external aspect, ‘but evidently
formed of highly compacted and rounded grains of many different
colours. From the same place.

18. Brown quartz rock, of which the fracture is so little gra-
nular that it almost approaches to common quartz ; semitransparent.
From the mountains of Mar, Angus, and elsewhere, alternating
with micaceous schistus.

19. The same rock, in the same sitwations, of various shades
of red.

20. An almost equal granular mixture of pure transparent
quartz, and snow-white felspar, the grains amorphous. From
Arisaig and Balahulish, with micaceous schistus.

21. The same, but with fragments of felspar, bearing obscure
marks of crystallization. From the latter place.

22. Waxy and perfectly compact quartz, having a porphyritic
aspect from imbedded fragments of felspar ; accompanying the same
rocks.

23. White granular quartz rock of a moderately fine grain, con-
taining at the same time large angular pieces of quartz, of a diame-
ter from half an inch to many inches. In the same series at Balahulish.

24. White granular rock consisting of felspar and quartz tra-
versed by veins of pure white granular quartz, resembling in colour
and texture the finest sugar. From Jura and elsewhere.

25. Distinctly rounded grains of the purest transparent quartz,
imbedded in a mass of very fine grained white quartz. From the
Cape of Good Hope.

26. An uniform mixture of grains of transparent white quartz and
opaque reddish felspar, containing rounded pebbles and fragments

Dr. Mac CuLLocu on Quartz Rock. 483

of purple and-of white quartz, the pebbles being from half an inch
to two inches in diameter. In Jura, forming part of the series of
the purer quartz rock.

27, A brecciated mass of felspar and quartz of various colours,
compacted by a cement of transparent quartz, forming part of the

“series at Balahulish. | |

28. Specimens from Arisaig, from Assynt, Mar, Balahulish,

Airds, Sky, Schihallien, and numerous other places, which consist
of variable mixtures of reddish felspar, and transparent quartz, some-
times appearing to be nearly all quartz, and at others to contain
a large proportion of felspar. The grains are of various dimen-
sions, and the texture of the stone is consequently various. At times
it has the aspect of a fine reddish sandstone, at others of a coarse
grit ; and where the grains are very unequal in dimensions it resem-
bles a breccia. The grains have never a defined form.
. 29. A rock consisting of narrow and alternating parallel layers,
of fine and coarse granular quartz. Large grains of felspar are
found in the coarse layer, but none at all in the fine one. From Ba-
lahulish. |

30. A scarcely coherent combination of large grains of quartz.
and felspar, the interstices either empty or filled with clay. Part of
the series at Balahulish.

31. Compact extremely fine granular splintery quartz, alternating
in thin layers with clay slate. From Cowal.

32. Fine sandstones, not to be distinguished from the floetz
sandstones, and like many of them striped in endless alternations by
black clay. From the series of Balahulish. These belong to that
quartz rock which alternates with clay slate, and show the transitions
between those two substances.

33, Fine grained granular quartz, alternating with layers of

3P 3

484 Dr. Mac CULLOCH on Quartz: Rock,

parallel mica, so thin as not to be discovered in the cross fracture.
From Fassafern, Balahulish and Tyndrum.

34. The same rock, but the layers of mica more conspicuous and
undulating. From Balahulish.

35. The same passing into mere mica slate. From the series at
Balahulish and Tyndrum. ‘These demonstrate the alternation of
the quartz rock with mica slate.

36. A large grained breccia consisting of fragments of quartz
cemented by a mass of earthy white felspar, approaching to por-
celain clay. From Jura.

37. A rock consisting of felspar and granular quartz, with here
and there an atom of blue slaty clay interspersed among the grains.
From Jura.

38. Various specimens of the same, with the clay slate increasing,

39. The same approaching still nearer to graywacke, with a basis
of clay slate, and ultimately terminating in it. ‘These two from
Jura. °

These specimens show the transition into common graywackeslate..

40. The same composition of rock, but in which mica slate holds
the place of clay slate.

Different specimens of this variety demonstrate the passage of
quartz rock into that sort of graywacke which I have described
under the head of Aberfoyle. From Jura.

41. The same rocks passing by insensible degrees into a conglo-
merate, which will by some be ranked with common graywacke.
From the same place.

From a comparison of the several characters under which this
rock appears in the same place, from the similarity of these
characters or of a majority of them in the different situations in
which it occurs, there need be no hesitation in concluding that

Dr. Mac CuULLOcH on Quartz Rock. 485

quartz rock wherever occurring is generically the same, and that it
differs no more from itself than the numerous varieties of gneiss,
of mica slate, or of graywacke are found to do. It ought therefore to
be designated in a geological system by one general name, since, as the
designations of rocks are intended for the purposes of geology, rather
“than of mineralogy, it is preferable that one common term should be
applied to the rock in question, than that the several varieties should
each receive a separate one, a circumstance tending as much to con-
fuse geological reasonings, as to render them tedious and intricate.
It has already received various names, out of which it would be desi-
rable to agree on one. It has been called granular quartz, transition
sandstone, quartzose graywacke, and quartz rock. ‘The first of these:
sufficiently expresses the character of one of its varieties ; but its par-
ticularity excluding those modifications which are not granular, as well
as those which contain felspar, is not well adapted for the purposes of
geological description. Could we prove that it was in every case a rock:
of transition, and that the theory which the term transition implies
was well founded, the name of transition sandstone would perhaps
be the most applicable. But as I have ascertained that it alternates
at times with rocks, which the system here alluded to calls primitive,
and asit is at all times desirable to keep clear of those terms which
involve an hypothesis, I think we are bound to reject this name.
The same argument is valid against the appellation of quartzose
graywacke, a term in other respects perfectly inapplicable, since the
very definition of graywacke decidedly excludes it; and there can
be no greater evil than to confound under one name, substances of dif-
ferent qualities, particularly when that name itself, from its con-
nection with an hypothesis, tends to blind our judgment and _per-
vert our reasonings. I should therefore suggest the superior propriety
of the term quartzy or quartz rock, a term involving no hypothesis,
and which, at the same time that it is sufficiently general to include

486 Dr. Mac CuLtocn oz Quartz Rock.

all the varieties which consist of mere quartz, does not exclude
those which contain a mixture of other ingredients, more than the
terms sandstone or limestone exclude the various bodies which so
often are mixed with, or constitute an integrant part of them.
When more particular description is required, a term so general
admits of being easily combined or modified.

We have now to enquire into the rank which this rock bears in
the generally received arrangement, and into its claims on a place
in either of the classes of chemically crystallized or mechanically
deposited rocks, or of that which is conceived to be a mixture of
both; to use language more hypothetical, we must try to assign it
a situation in the primitive, transition, or floetz divisions. It
appears that it is found, as at Tyndrum and Loch Leven, alternating.
with micaceous schist, and in many other places with what is called.
primitive clay slate. Thus its claim to a rank among the first
division of rocks is established. Its connection with graywacke in
Jura, equally establishes its claim to a place among those rocks
which are assigned to the second division. It is thus, like clay
slate, a member of both these formations. I have already shown,,
that at Balahulish, as well as in Jura and in Assynt, the quartz
rock contains mechanical deposits, from which it must follow that
the existence of a mechanical deposit is not a decisive character for
the rocks of transition, since a rock of which one of the charac-
teristic circumstances is mechanical arrangement, is found to exist
among the rocks called primitive. As I have also shown in
describing the country about Aberfoyle, that a gradation from
mica slate to graywacke takes place by insensible degrees, I think
we may conclude that no valid distinction, nor any constancy of
character, such as ought to constitute a class, is to be found in the
rocks of transition; and that it would be preferable to return to the

Dr. Mac CuLLocn on Quartz Rock. 487

ancient division of primary and secondary, as far at least as relates
to those rocks which bear marks, however obscure, of stratification.
It will be a separate consideration by what means we can divide
those of the former class which contain organic remains, from
those which are without them; a distinction, perhaps not less
requisite in the one than in the other of these two leading classes,
since, however many members of the floetz or secondary division
may be characterized by the existence of these remains, a certain
set are as invariably free from them.

It is perhaps beyond the bounds of the present notice, to suggest
the propriety of separating the unstratified rocks, such as granite,
porphyry, and trap, from this two-fold arrangement. Should such
a measure be ultimately adopted, it will be further necessary to
consider how far any one of the several unstratified rocks is peculiar
to the one set of stratified ones, and how far it is common to both.
A more accurate knowledge of the various rocks designated under
the loose name of porphyry, will be particularly requisite ta the
forming of this arrangement.

XX. Notice relative to the Geology of the Coast of Labrador.

By the Rev. Mr. Srernaaurr.

Tue coast of Labrador is a part of the British territories so
little known, and possessing so few inducements to attract the
visits of strangers, that every fragment of information concerning
it may be esteemed in some degree valuable. This is the only ex-
cuse for offering the following observations in their present very
imperfect state. .

The only English accounts of this country, as yet published, are
the memoir of Lieut. (afterwards Sir Roger) Curtis, and Mr.
Cartwright’s journal. The first-mentioned gentleman reconnoitred
the coast from the Straits of Belle-Isle to lat. 58°, 10’, (according to
Arrowsmith’s chart, 57° 25’,) in the year 1773, by command of
Governor Schuldham. His account is inserted in the Philosophical
Transactions. The latter person does not appear to have gone farther
north than lat. 54°, and his observations refer to little farther than
the fishery and peltry trade. At the request of the British go-
vernment, and particularly of Sir Hugh Palliser, then governor of
Newfoundland, the United Brethren made several voyages of dis-
covery to this coast; and in 1772, formed a settlement in lat.
56° 38’, (56° 24’ Arrowsm.) called Naim; and subsequently two

Mr. STEINHAUER’S Geology of the Coast of Labrador. 459

others, Okkak and Hopedale, im lat. 58° 43’, and 55° 36’. Hence
they have made several excursions, and last year doubled Cape
Chudleigh, in lat. 60° 20’, and descended on the opposite or western
side of the promontory as far as lat. 58° 36’.

The missionaries, assiduously occupied with the great aim for
“which they are sent, may be supposed to have but little time for
objects of mere science; they have however not been neglectful of
the opportunities their stations afforded, but have improved them as
far as their abilities allowed. They have kept meteorological tables
of the barometrical and thermometrical variations,* a tolerably com-
plete flora has been collected; they have from time to time sent
specimens of the minerals of the country ; and their diaries and
verbal accounts furnish some idea at Icast of the principal mountains
on the coast. It is tobe regretted that their observations are of such
a nature as to throw little light on the geology of the country ; even
the specimens sent have not always their habitats affixed, or get con-
founded on board of the vessel. The general aspect of the country is
else such as to promise interesting results, and the examination of the
different strata is not liable to those obstructions from the enve-
loping mantle of vegetation and alluvial mould which so often
baffle all research in our countries. According to the descriptions
of those who have had an opportunity of contemplating this in-
hospitable region, it consists almost entirely of barren rock, towering
in craggy eminences, on which even the hardy lichen in vain en-
deavours to fix a habitation; for moisture enters the rock with its
fibres ; the intense cold of winter congeals that moisture, and the
summer's thaw precipitates the loosened fragment with its tenant to

* In Nain the extremities of cold and heat in the year Nov. 1, 1772, to Nov. 1, 1773,
were—Jan. 16, 3h. A.M. 42 under Farenheit’s O, and Aug. 2, 2h. P.M. 86. Fron
Jan. 11 to Jan. 27, the thermometer was never above Farenhcit’s O.

VOE, EI. 3 Q

490 Mr. STEINHAUER’s Geology of the Coast of Labrador

the foot. These fragments, mouldering into sand, afford in some
places support to a few species of pines, and the annual decompo-
sition of their leaves stains this earth to the depth of a few inches
with a blackish hue. In other spots where the thawing snow oc-
casions an accumulation of water, sphagva and other mosses form
a species of turf, and conceal the barrenness of the land; but
every where the plucking up a tuft of vegetation, or removing the
withered leaves, discovers either the bare rock or a bright silicious
sand. In several parts of the country the rocks are intersected by
chasms running generally in a right line to a considerable distance,
as if intended to be the receptacles of future veins ; the floor, as I
am informed, is composed of a different species of stone from the
sides, and generally of a lighter colour; but I could not, from the
description, ascertain whether it was calcareous or not. These clefts
when covered with snow in the winter, sometimes prove dangerous
pitfalls to the unwary wanderer, who does not know how to avoid
them by the line of bushes (vaccinia, ledum, Sc.) which fringe
their margin. Indeed the narrow passages which divide the coast
into numberless islands, almost seem to be similar chasms occupied
by the sea, few, if any, of these islands being alluvial, but high
barren rocks, appearing from the sea like continuous land.

The highest mountains seem to extend along the eastern coast ;
the names and situations of the principal, known to the mission-
aries, are

The Nachwak chain, about lat. 59°.

The insulated mountain, Tupperlik, (the tent) lat. 58° 15’.

The Kaumayok chain terminating in the high island of Cape
Mug ford or Grimmington, lat. 58°.

The high land of Kiglapyed, in lat 57°.

The Mealy mountains \aid down on Lane’s survey of the coast of

Mr. STEINHAUVER’S Geology of the Coast of Labrador. 491

Labrador, in lat. 53° 30’, and said to be never free from snow ; they
have not been visited by the missionaries, who now seldom go far
to the south of Hopedale.

With respect to their actual height little can be said with ceraimey
but as Mount Thoresby, on an island south of Kiglapyed was ascer-
tained by the officers of H.M.S. Medusa and Thalia, to be 2733
feet, and the Kiglapyed is evidently higher, yet inferior to the Kau-
mayok and Nachwak heights, the latter cannot be assumed at less
than 3000 feet. ‘This supposition gains additional probability,
from the circumstance that the Kaumayok has been seen by Capt.
Frazier,* at a distance of upwards of 30. leagues from land.
The mountains to the west of Cape Chudleigh are much lower,
and, according to the accounts of the missionaries, of a different!
nature; but wherein the difference consists we are unable to de-
termine.

It would, doubtless, be highly interesting to ascertain the consti-
tuent strata of these elevations ; but the attention of the missionaries
being more directed to mineralogical than geological specimens, and
being apt to esteem nothing worth notice, but what, by form or
colour attracted notice, we have little more than hints to guide our
suppositions.

From the islands near Cape Chudleigh we have received speci-
mens cf large-grained pale granite, with garnets. The island of
Ammitok (about lat. 59° 20’) ‘is described as consisting almost
entirely of a crumbling granite, sometimes mixed with hornblende.
The mountains of Nachwak, about Nachwak bay, furnish con-
siderable quantities of /apis ollaris, generally of the grey kind, (of
which a specimen is sent) but sometimes of the semi-transparent

* The master of the ship annually sent with provisions to the missionaries.

a O.2

492 Mr. STEINHAUER’S Geology of the Coast of Labrador.

green variety. The missionaries describe the southern part of this
chain, as exhibiting a very singular appearance towards the sea,
being composed of alternate layers of black and white rock in a
vertical position, which makes the cliffs seem striped; the black
strata are about 5 feet in thickness, the white double that breadth.
‘Nulletartok bay, still farther south, and probably near the extremity
-of the same chain, has been called Slate Bay, from a stratum of
slate which appears there a little above high-water mark; from this
stratum the travellers write, that an acrid liquid, of a strong sul-
phureous smell, exudes, which seems to indicate an impregnation
with sulphuric acid. Below high-water mark, in the same bay,
they noticed a stratum, which they describe as resembling cast iron,
with a glossy, somewhat reddish, surface, and extremely hard,
(qu. a haematitic iron ore?) The north side of the Kaumayok
mountains consists of a white stone, with black or grey veins, re-
sembling statuary marble, but very hard. Of the productions of
the Kiglapyed we have no account, but to the south of this chain
the district commences, where the Labrador felspar is found. This
stone was first distinguished by the late Rev. B. Latrobe,* among
a number of specimens sent to him ; it occurs not only in pebbles
on the shore, but in spots in the rocks in the neighbourhood of
Nain, and particularly near a lagoon, about 50 or 60 miles inland,
in which Nain north river terminates. Its colours darting through
the limpid crystal of the lake, and flashing from the cliffs more
especially when moistened by a shower of rain, changing continually
with every alteration in the position of the boat, are described as
almost realizing a scene in fairy land. The same district produces

* President of the Society for the furtherance of the Gospel established by~ the
Brethren.

Mr. STEINHAUER’S Geology of the Coast of Labrador. 493

also the Labrador hornblende, (Hypersténe) and the white stone
-striped with green, which seems to constitute a rock on an island
near Nain, and was first noticed by the Rev. C. J. Latrobe, among
other fragments, which induced him to cause large Swe to be
broken off and brought over.

One of the mountains in the vicinity of Nain, as well as several
others in different parts of the coast, exhibits a species of Mam-tor,
continually crumbling away and shivering down into the valley
below; a splinter of this rock is sent for the inspection of the
Society.

The island of Ukusiksalik or freestone island, has derived its
name from the quantities of lapis ollaris found there. It is pro-
bably the most southern place on the coast where this mineral
occurs, as the missionaries, who first visited the Eskimos in Chateau
Bay, in the Straits of Belle Isle, were told by them that they pro-
cured the stone of which their lamps, pots, &c. were made from
this island.

At Hopedale the secondary limestone seems to come in ; at least
we have received from this place fragments of reddish carbonate of
lime, calcareous spar, and schiefer spar. Mr. Latrobe also pos-
sesses a madrepore, said to have been found there. It is remarkable
that the river abounds in fragments of stone, worn into the most
fantastic shapes, in which the imagination without great exertion
may trace the rude resemblance of birds, crocodiles, &c. They
sometimes form rings six or eight inches in diameter, and three
quarters of an inch thick. Their great abundance precludes the
possibility of their being the work of art.

With respect to the land, west of Cape Chudleigh, as it has
been but once visited, we cannot expect to learn much about it.
The mountains of Yorngarsuit, (the evil spirit) in lat. 60°, are

494 Mr. STEINHAUVER’s Geology of the Coast of Labrador.

described as rugged, barren, and black, and containing a huge
cavern which the heathen Eskimos fable to be the habitation of the
devil. The rocks farther north are light-coloured, but there appear
to be no mountains of considerable height on this part of the
coast which is called Ungava. On almost every part of it frag-
ments of a red jasper, impregnated with iron, are frequent, and
in some places haematites and cubical pyrites. It may be worth
remark, that the tides rise here no less than 40 to 50 feet, while
they seldom exceed 8 or 10 on the eastern coast. The current sets
from west to east round Cape Chudleigh.

The specimens of rocks from Labrador, which Mr. Latrobe has
desired me to select for the Society, will enable them to form any
further conjectures with respect to the geology of this country far
better than I should be able to do it, and I shall esteem myself
happy if future opportunities enable me to discover any thing
which may be able to throw a more direct light upon the subject.

The specimens marked merely Labrador, are from one or other

of the three settlements, consequently found between lat. 55° 30’,
and 57° 40’,

XXI. Memoranda relative to Clovelly, North Devon.
By the Rev. J. J. Conyzearz, Member of the Geological Society.

In a Letter addressed to G. B. Grrenovcn, Esq. V. Pr. G.S.
My Dear Sir,

iF either the enclosed memoranda relative to the neighbourhood
of Clovelly, or the drawings which accompany them possess any
interest, they can derive it only from the consideration that the
geological features of that remarkable spot do not hitherto appear
to have attracted the attention of any person engaged in those
studies which it is the object of our Society to promote. The
former, though, I trust accurate, are, I fear, extremely scanty. The
latter I can only offer as faithfully copied from sketches made upon
the spot, they will furnish their own apology by shewing at once
that they are the work of one who is uninstructed and almost
entirely unpractised' in that art.

The small Fishing Town of Clovelly is situated in a narrow and
precipitous. ravine on the north coast of Devon, about 22 miles
to the westward of Ilfracombe, and has attracted some notice from
the singularly picturesque scenery of itself and its more immediate
environs, the general character of which much resembles that of
Linton, upon the same coast, so frequently described by modern
tourists.

Having understood that, in addition to this recommendation, the

496 Mr. CONYBEARE on the Strata near

cliffs near the town presented very ample and numerous sections of
the stratified rock of the country; Mr. Buckland and myself were
induced to visit it in the course of an excursion which we made in
the west during last summer.

The best access to the town from the Hartland road is by a
private carriage way which has been cut through the grounds of
Sir James Hamlyn. This not only commands several advantageous
views of the lofty and well wooded ravine along the declivity of
which it winds, but offers in many places, where the rock has been
cut away for the purpose of levelling the road, striking instances of
that remarkable configuration of the strata, which is said to be
characteristic of the grauwacke formation. To that class all the rocks
ef this neighbourhood may probably be referred. The principal
varieties are those known throughout Devonshire by the appellation
of dunstone and shillat; the former answers pretty accurately to
the description usually given by mineralogists of that species of
grauwacke in which the fragments, supposed to be cemented
together by the intervention of a paste resembling the matter of
clay slate, are too small to be discerned even by the aid of a
considerable magnifier. The latter alternates with the former and
is evidently the finer grauwacke slate of the same nomenclature.
Of these rocks the coast between Clovelly presents the most
magnificent and interesting sections which-we met with in the
course of ourtour. Both varieties sometimes alternating in distinct
and well defined strata, sometimes appearing to graduate into each
other, and the compact species assuming the external configuration
of greenstone or serpentine. The strata inclined in every direction
and describing the most capricious and picturesque forms, both
curved and angular, open an abundant field of instruction to the
geologist, while they present difficulties of which neither the theory

Clovelly, Norib Devon. 497

of original deposition on an unequal surface, or of subsequent
dislocation, appear to promise any plausible solution.”

The average height of the cliffs, as far as we could judge by the
eye, is 130 or 140 feet; they are traversed in many places by steep
ravines running from north to south, and numerous outlying masses

“of rock shew themselves above the sea at a small distance from low-
water mark, a character uniformly presented by the stratified rocks
along the whole of the Northern coast.

In some parts the compact grauwacke was wanting for a consider-
able distance, in such cases the forms which the slate had assumed
were rather angular than curvilinear. In the sections of those which
have been called saddle-shaped strata, we observed usually that the
dip was more precipitous on the western side. In neither variety of
the rock could we discover any traces of organic remains, nor could
we perceive any imbedded fragments that should indicate their hav-
ing been formed from the debris of an earlier rock. ‘The strata are
traversed by numerous veins of opaque white quartz, but no appear-
ances of any other mineral substances occurred.

The Drawings annexed, (Pl. 33 and 34,) indifferently executed as

* Professor Jameson (Syst. of Min. vol. 3.) has ascribed these appearances to crystal-
lization. As we are always accustomed to regard terms of science as retaining (where
the coutrary is not expressly stated) the precise sense in which they have hitherto been
uniformly received, the use of this expression is perhaps not strictly correct. The ex-
ternal appearance of these rocks is certainly not that of a mass of crystallized matter ;
and that the phenomenon itself is not invariably connected with the process of crystal-
lization is evident from the consideration that those rocks which are the most highly
crystalline in their texture are the most free from these singular configurations. That
these appearances, however, may have been effected by a process of Nature, somewhat
analogous to crystallization, and depending possibly upon the same remoter causes, is
perhaps the most satisfactory hypothesis that has hitherto beeu offered on the subject,
and such I apprehend to be the opinion of the school of Werner, though somewhat ob-
scured by the adoption of a term implying identity of operation, in a case where the
utmost which can be fairly assumed to exist, appears to be a striking analogy.

VOU. Ir. 3R

498 Mr. CoNYBEARE on the Strata near

they are, will perhaps convey a clearer notion of the singular con-
figuration of these rocks than could be done by words alone. With
the exception of one, which gives a faithful resemblance of some
remarkable curvatures in the grauwacke of Hartland Point, the whole
of the subjects are selected from those which occurred within the
first four miles of our walk from Clovelly westward.

Although these singular contortions are not entirely confined to
the dunstone and shillat of Devonshire, they yet occur much more
constantly in that rock than in the metalliferous schist of Cornwall.
In travelling westward we appeared to lose them gradually. At
Bosscastle where the rock evidently approaches nearer to the cha-
racter of killas, (as it is termed by the miner) they still appear pretty
frequently : at St. Agnes they are much rarer and less capricious.

It is possible that more accurate and minute researches may carry
the subdivision of the stratified rocks of this country much further
than the present state of our knowledge appears to authorize; but I
cannot think that, even with the limited information which we al-
ready possess on this subject, it would be assuming too much to
establish a line of separation between the rock, which under the pro-
vincial names, already mentioned, of dunstone and shillat covers so
large a portion of the North of Devon, and that metalliferous slate
which lying immediately upon the granite of Dartmoor and Cornwall
forms the most considerable portion of the mining tract in both
counties. *

The former of these, besides the peculiarities already noticed, is

* J would wish to be understood as speaking cxclusively of the metalliferous slate.
That which alternates with limestone at Vesyan, at Padstow, (where it is accompanied
by greenstone) and some other spots in Cornwall, will probably be regarded as belonging
to a distinct formation.

Clovelly, North Devon. 499

destitute of metallic veins, It alternates with transition limestone,
and where it does so, occasionally contains organic remains. It alter-
nates also, in one instance at least, with large beds of a species of
culm. Its veins contain few or no extraneous substances besides
common quartz and, though less frequently, calcareous spar. *

‘ The latter (the Killas of Cornwall) has generally the silky charac-
ter ascribed to clay slate.f It is traversed almost throughout its
whole extent by frequent veins, or rather dykes, of a porphyritic
rock, which forms one variety of the Elvan of the Cornish miners,
and which does not occur either in the dunstone or shillat. It has
been found to contain at St. Agnes, the topaz, and in various places
the tourmalin and the garnet: the veins are frequently occupied by
chlorite, by mica, and by crystallized felspar. A considerable part of
the tin of Cornwall is obtained from the killas, and the grey ore of
cobalt has repeatedly been found in it. All these minerals haye
usually been considered as characteristic of the earlier rocks, and
none of them are, I believe, stated by the writers of our most es-
teemed mineralogical systems to occur in that to which they assign
the name of grauwacke. [

It is not without the greatest difidence in my own knowledge of
the subject and powers of observation that I venture to dissent, even
on a mere point of nomenclature, from the opinion of my able and
experienced friend Dr. Berger. I cannot however but conceive that

* In the neighbourhood of Bideford, a little to the west of Ilfracombe, the rock is
said to be much traversed by this mineral.

+ May it not be added that its siliceous varieties are of a texture much finer and more
compact than that of Dunstone?

+ The following substances also which appear (although less positively) to be restricted
to primitive formations by the school of Werner, occur in the killas; wolfram, native
silver, horn silver, schiefer spar, actinolite. I believe that the chiastolite has also been
found in it.

ZRZ

500 Mr. ConyBEARE on the Strata near Clovelly.

the marked difference between the two great varieties, which appear
to include by far the larger part of the stratified rocks occurring in
the west of England, is such, as to render it by no means desirable
that they should both be designated by the common name of grau-
wacke ;* a name perhaps the more liable to misapplication as it is
somewhat indefinite.

* If the reasons which I have ventured to suggest for the propriety of considering the
dunstone and shillat as of a formation distinct from that of the killas be not entirely void
of foundation, it is perhaps the more desirable that the attention of geologists should be
called to the examination of the subject, as it is understood that a large and respectable
body of mineralogists are disposed to apply the name of killas to those stratified rocks in
the northern part of Great Britain, which have hitherto been considered by the most accu-
rate observers as indisputably belonging to the grauwacke formation. Is it not possible
that the frequent, for I apprehend we are scarcely yet entitled to say the ¢ota/ absence
of gneiss and mica slate in the mountain groups of Cornwall may have contributed to
give rise to this opinion? This character however they appear to possess in common with
the Hartz, in which Professor Jameson states the clay slate to rest immediately upon the
granite.

4

/

XXII. On Staffa.

By J. Mac Cutiocn, M.D. ELS. Chemist to the Ordnance, and Lecturer
on Chemistry at the Royal Military Academy at Woolwich.
V. Pr. Geol. Soc.

LE the “ Description and Natural History” of Staffa, by Faujas
de St. Fond, or the various other descriptions which have been
‘published of this island by naturalists and by tourists, had exhausted
the subject, I should have forborn to have troubled the Society with
any remarks on a place which ought now to be well known.

But a visit to this celebrated island having given me an oppor-
tunity of remarking a circumstance before unnoticed, and of some
importance in its natural history, I think it my duty to lay it before
the Society. In so doing, I find it difficult to avoid entering rather
minutely into the general description of the island, particularly since
a second examination, besides confirming the remarkable fact [ at first
noticed, has enabled me to investigate its structure more completely.
I shall doubtless still leave something to be corrected by those who
may come after me. A multiplicity of objects pressing at once for
regard, a visit always necessarily hurried from the impossibility of
remaining long on the island, a boisterous sea, and a stormy atmos-
phere, are hostile to that accuracy of observation which may pre-
clude future corrections.

The circumference of Staffa is estimated at about two miles. It

forms a sort of table land of an irregular surface, bounded on all

502 Dr. Mac Cuttocn on Staffa.

sides by perpendicular cliffs, varying in altitude and broken into
numerous recesses and promontories.

It is intersected by one deep cut, scarcely to be called a valley,
which divides the higher and more celebrated columnar part from
the remainder of the island. At the highest tides this more re-
markably columnar part which forms its southwestern side, appears
to terminate almost abruptly in the water, but the retiring tide
shows a causeway of broken columns forming a sort of beach at its
foot. Round the other sides of the island there is also a beach of
varying breadth, consisting of detached fragments, and of rocks
jutting out into the sea in many irregular directions. This beach,
when the weather is perfectly calm, and the swell off the shore,
will, under due precautions, afford landing in various places, but it.
is on the eastern side that the most numerous landing places occur,
Various narrow creeks sheltered by the island itself from the predo-
minant western swell, admit of easy access in moderate weather,
provided the wind is in any direction from SW. to NW. and for
the encouragement of the mineralogist, who may be terrified at the
exaggerated reports of this difficulty, I can assure him that I have
landed on Staffa when the vessels that navigate this sea have had
their sails reefed, and the boatmen of Iona and Ulva have called it
impracticable. The love of the marvellous has conferred on Staffa
a terrific reputation, which a greater resort has discovered to be
somewhat akin to that of Scylla and Charybdis.

It is easy to perceive from the southward, that with this flat dis-
position of its surface, and notwithstanding its irregularities, Staffa
possesses a gentle inclination towards the N.E. although no oppor-
tunity is afforded for ascertaining the precise dip. It is not of im-
portance to ascertain it, nor can it amount to more than 5 or 6 deg.
of variation from the horizontal plane.

Dr. Mac CuLLocn on Staffa. 503

The highest of the perpendicular faces which bound it, rise about
60 or 70 feet above the high water mark, and these are on the south-
western side, where the most remarkable columns and where the
great caves exist.

The greatest elevation of the island cannot be more than 120 feet

“above the level of the sea. There are no sunk rocks round it, but
the water deepens rapidly from the shore, and admits of large.
vessels coasting it close at hand, provided they have a leading wind.

There is a soil of considerable depth on the surface, and it is
covered with herbage.

It is almost superfluous to say that the whole island consists of a
mass of basalt. I have indeed been told, that a sandstone bed has

_been seen at low water on the southwestern side, but I had not
an opportunity of observing it. ‘This is the part of the island, where,
if in any place, it should, from the inclination of the strata, be per-
ceived, and there is no reason to doubt the assertion, as we find most
of the trap rocks of the Western Islands lying on beds of sandstone.
It is equally superfluous to describe the basalt, since specimens of
it are in every one’s possession. It may be sufficient to remark, that
its texture is more compact, more crystalline, and less earthy than
that of basalt in general, and that it is at the same time less homo-
geneous, less black, more fragile, and more sonorous. But it would
be idle to attempt to apply different terms to the endless varieties of
the rocks of this tribe.

This basalt exhibits two modifications, the columnar, so often
described, and the amorphous which is generally more or less amyg-
daloidal, containing imbedded zeolites of different sorts. I saw no
examples of basaltic breccia, or of trap tuff, as it is improperly called.

It is in the amorphous basalt that the zeolites are most abundant. —
The nodules vary from the size of a pea to that of an hen’s egg and

504 Dr. Mac CuLiocu on Staffa.

upwards, and generally exhibit specimens of radiated mesotype and
of analcime. The cubical zeolites (chabasite) are of rare occurrence,
and the mesotype is seldom granular, and never, as far as I saw,
capillary. The lamellar variety of stilbite, is occasionally found filling
the intervals of approximate columns. I did not observe any zeo-
lites in the larger and more perfect.columns, but in the smaller and
more irregular ones they occur, though rarely.

If we were to view the island only from the southwestern side,
and at half tide, we should conclude that it has been formed of
three distinct deposits, or beds of basalt. Of these the lowermost
appears in some places amorphous, but it is not easy to see enough
of it to judge whether it actually forms a continuous bed. It is
only from the analogy of Canna, and the other basaltic islands of
this sea, that we should be tempted to generalize this conclusion.

The next bed, is that which is divided into those large columns
which form the most conspicuous feature of Staffa, and it varies
from 30 to 50 feet in thickness. ‘The upper one appears at a
distance to be an uniform mass of amorphous basalt, but on a
nearer inspection it is found to consist of small columns, laid and
entangled in every possible direction, often horizontal, and generally
curved. It is this bed which forms the ponderous cap (as it is
called) which crowns the summit of the grand facade.

Although the great columnar bed occupies but a small portion of
the whole exterior face of the island, the columnar form is perhaps
predominant throughout the whole. Yet it would be equally
difficult, as useless, to attempt to determine its proportion to the
amorphous part where they are irregularly mixed, as they are at
the northern and eastern sides. On these sides also the division
into distinct beds such as I have described above, is by no means
easy to trace, and possibly it does not exist.

!

Dr. Mac CuLiocn on Staffa. 505

To those who have seen the beautifully regular columns of the
Giant’s Causeway, those of Staffa will appear rude and compara-
tively shapeless. They no where exhibit that accuracy of design
which is so conspicuous in the former, and are rarely seen of any
considerable length without some incurvation. But their thickness is

“much greater, since they often attain a diameter of four feet. They
vary perpetually in the number of their angles, the pentagonal and
hexagonal being the most common, and those of an inferior num-
ber of angles being less common than those of a superior. Their
joints are very irregularly placed, and are frequently wanting
through a considerable length. When separated, the touching
surfaces are either flat, or marked by a slight respective concavity and
convexity. In many places, and most conspicuously in the great cave,
the angles of the upper joint are considerably and obliquely trun-
cated at the point of contact with the lower one. But I did not
perceive any instance where a corresponding projection of the end
of the inferior angle rose to cover the truncation, a circumstance of
such frequent occurrence at the Giant’s Causeway. I may add,
that the articulated columns are most remarkable in the great cave,
and that the straightest columns generally exhibit the most frequent
articulations. The curved columns visible at the cave called the
Clamshell cave, extend for 40 or 50 feet without a joint.

The disposition of the variously curved columns above this small
cave, is perhaps one of the most striking features of the whole
island. But it will be time enough to speculate on the formation
of a curved basaltic column, when we have something rational to
offer on that of a straight one.

A very extraordinary aggregation of columns lies off this cave,
forming a conical detached rock, corruptly called Boo sha la. The
Gaelic name Buachaille (Bouxéacs?} the herdsman, is commonly ap-

Vou, i 3s

506 Dr. Mac Cutrocu on. Siaffa.

plied to conspicuous single rocks all over the country. This rock
consists of variously inclined columns resting against each other, and
meeting till they form a conical body, which appears to repose
on a bed of curved and horizontal columns.

It is superfluous to attempt a description of the great cave. The
language of wonder has already been exhausted on it, and that of
simple description must fai! in an attempt where hyperbole has
done its utmost. I may however remark, that its dimensions
appear to have been over-rated, in consequence of the mode of
measurement adopted, and that the drawings of it which have been
engraved, give it an aspect of geometrical regularity which it is far
from possessing. Its superiority in point of effect to the greatest
efforts of architecture, might admit of dispute if there were any
disputing about feelings. Another cave occurs at a short distance
westward, of inferior dimensions, and inaccessible unless when it
can be entered in a boat, an event requiring a combination of
circumstances of no very common occurrence at Staffa. Large
fissures are seen above this cave, with an incipient detachment of
considerable masses, threatening a ruin which is perhaps not far
distant. Beyond this there is still another cave which appears to
pass through the promontory in which it lies, but equally or
even more difficult of access, and still involved in uncertainty.
Many other caves of less note are to be seen in various parts of
the cliff around the island, into which the sea breaks with a noise
resembling that of heavy and distant ordnance.

In a letter transmitted last year to the Secretary of this Society,
I took notice of a fact of considerable importance in the natural
history of this island, which had before escaped the remarks of
visitors. This is, the occurrence of a bed of alluvial matter on

some parts of its surface, containing fragments of the older

Dr. Mac Currocu on Staffa. 507

rocks. It is most easily seen at that side of the island which
faces lona, and on the summit of ‘the cliffs of a semicircular bay
opening in that direction. The bed is here broken at the edge of
the cliff, so as to expose its whole thickness for a considerable
extent. But the same appearance may also be observed immediately
“above the ordinary landing place, where the bed has also been
broken. ‘The stones which it contains are all rounded, and of va-
rious, often considerable dimensions, and they exhibit specimens
of granite, gneiss, micaceous schistus, quartz, and red sandstone.
Together with these, are some rolled pieces of basalt.

Here then is a circumstance in the mineral history of Staffa,
adventitious it is true, but involving difficulties of no small impor-
tance. If we cast our eyes on the map, (Pl. 35.) we shall perceive
that it is embayed in a large sinuosity, formed in the island of
Mull, and nearly enclosed on the opposite side by Iona, and the
Treshanish islands. Beyond the latter, a second line is drawn by
Tirey, and Coll; while to the north, but at a greater distance, are
placed the islands of Muck, Rum, Egg, Canna, and Sky. The
whole island of Mull, with the exception of the Ross, is of a trap
formation, containing however some partial tracts of sandstone
and other rocks which I need not notice. The islands of Ulva
and the Treshanish, with their dependent rocks, are also of trap
formation. So are the islands which lie to the north, and which
I have enumerated above. Iona however, together with Coll and
Tirey, consists principally of gneiss and mica slate traversed by
granite veins, rocks which also form the chief parts of the coasts of
Lorn, Appin, Morven, and Ardnamurchan.

It is to the former then, that we must look for the origin of the
rolled stones which cover Staffa, if, limiting the great operations of

nature by our own narrow views, and the ages which have con-
382

508 Dr, Mac CuLLocu on Staffa.

tributed to change the face of the globe by our own short span, we
are led to seek for that solution which may appear the least difficult.
Even then, we must admit that Staffa has formed part of one con-
tinuous land with the islands of Coll, Tirey, and Mull, since no
transportation could have been effected without the existence at
some period of a continuous declivity between them.

The language which this circumstance speaks, is not obscure, and
the nature of these changes ailows of little dispute. If we admit
this obliteration of so large a portion of solid land, and consider
that a deep sea now rolls above the foundations of former mountains,
we have no further difficulties to obstruct us in accounting for the
numerous and distant accumulations of transported materials which
occur over the whole surface of the earth. The same power,
whatever it was, that hollowed the great sinuosity of Mull, might
well remove the solid matter that once filled the valleys which now
separate Mont Blanc from the ridge of Jura.

But if appalled at the supposed magnitude of those changes, and
at the period of time which must have elapsed to complete them,
we suppose that the island of Staffa was elevated from the bottom
of the sea in its present detached form, and retaining on its summit
a portion of the bed of loose matter deposited under the present
waters, another order of phenomena crowds on us, no less impor-
tant, and involving circumstances almost equally repugnant to the
visible operations of nature. .

The appearances are perhaps insufficient to enable us to decide
between two difficulties of equal magnitude, nor is it here necessary
to enter further on that question. I may also leave it to those who
have engaged moredeeply in such investigations, to determine whether
in the supposition of the first of these causes, whether the wasting of
the land has arisen from the gradual action of natural operations, or

Dr. Mac Cutxocy on Staffa. 509

the more violent efforts of an occasional destroying force. It is my
humble task to point out a fact, as a contribution to that mass of
accumulating information on which a consolidated fabric may at
some future time be erected. Yet the idle spectator or enthusiastic
lover of Nature who shall hereafter view this interesting spot, may,
when he contemplates these grand revolutions, learn to wonder less
at the efforts of that power which has hollowed the cave of Fingal,
and submerged in the depths of the ocean those columas which
seemed destined for eternicy.

XXIIL On Vegetable remains preserved in Chalcedony.

By J. Mac Cuttocu, M.D. Chemist to the Ordnance, and Lecturer on
Chemistry at the Royal Military Academy at Woolwich.
V. Pr. Geo. Soc.

In examining the agates which are found on the shore at Dunglas
in Scotland, in the summer of 1811, I was struck with the appear-
ance of organized vegetable substances contained in many of them
It seeming to me impossible that any metallic or earthy matter could
put on these forms, I was at some trouble to make a collection of
stones exhibiting similar appearances, and to ascertain as far as cir-
cumstances permitted, the genera at least of the plants contained in
them. The gradual increase and ultimate accumulation of numerous
specimens, having enabled me to trace their analogies to plants
actually existing, I considered that a detail of the most leading va-
rieties would not be unacceptable to the Society. For the purposes
of a more accurate and convenient illustration than the inspection of
the specimens alone would convey, I also transmit some enlarged
drawings, made by the aid of the microscope, exhibiting the prin-
cipal varieties. |

I did not know when I was first engaged in this investigation that
the subject had already attracted attention, and that a detailed account
of some well ascertained plants involved in chalcedony had been
given by Daubenton.* More lately a letter from Blumenbach has

* Memoires de l’Academic Royale des Sciences, 1782, p. 668.

Dr. Mac. Cutitocn. on. Vegetable remains 5LI:

been quoted in Dr. Thomson’s journal, noticing the same fact, and
professing the remoyal.of his former doubts. It will be a sufficient
apology for not recalling this notice after having thus, discovered
that the inquiry had not the merit of novelty, that so many should
have overlooked, and. so many others refused their assent to.a fact
of no uncommon occurrence.

The metallic arborizations emulating the vegetable form which
occur in the fissures of many stones, and the similar well-known
figures in the chalcedonies distinguished by the name of mochas,
with the lively though superficial resemblance they bear to plants,
have led to the hasty conclusion that all these appearances were of
a metallic nature, and have probably prevented that accurate inves-
tigation of them which they deserved. The want of botanical
knowledge has perhaps also assisted in concealing from most mine-
ralogists their true origin, but I may now hope that the possessors
of such specimens will hereafter by a more attentive examination
confirm the frequency of an occurrence so interesting.

Another circumstance has assisted in this case in deceiving mine-
ralogists, and that is the obscurity in which the vegetable is often
involved either by the accidental mixture of metallic oxides in the
same stone, or by the actual investment of the whole plant with a
thick crust of carbonat of iron. Many of the specimens, and most
commonly those which contain conferve, exhibit at first sight
nothing but a confused and entangled fibrous mass of oxide or car-
bonat of iron. It requires a patient observation to detect in these
the existence of a real vegetable structure contained in the stone,
and modifying the deposition of metallic matter. It will be found
in fact that the whole plant is incrusted with the metallic deposit,
and that it exhibits only here and there its true nature. An accurate

512 Dr. Mac Cuttocu on Vegetable remains

examination will always detect in these the vegetable disposition,
and the sections of the stone will, by cutting through the branches
in various oblique directions, lay bare the true structure and dis-
tinguish the plant from its adventitious and metallic covering.

A third, and the most common source of deception and obscurity,
will be found in the whimsical and fibrous disposition occasionally
assumed by chlorite, its colour often imitating the natural hue of a
plant as perfectly as its fibrous and ramified appearance does the
disposition and form of one. It is by this substance particularly
that appearances strongly resembling conferve are produced, and
nothing but a very accurate investigation, with considerable ex-
perience in the various forms which this substance puts on, as
well as with the aspect and characters of the plants imitated, is
sufficient to enable us to distinguish them. In many cases even
the most scrupulous attention will fail, a fact which need excite no
surprize when it is considered with what difficulty the examination
must often be conducted, from a deficiency of light when trans-
mitted through these stones, and from the impossibility of bringing
into view any considerable portion of the imbedded substance.
Here we must have recourse to the chemical means which I shall
presently describe.

It is I believe from the deception to which those specimens have
exposed mineralogists, that so much incredulity on the subject
exists, every green fibre having been supposed to be chlorite, be-
cause it was apparent that chlorite sometimes assumed the form of
green fibres. However difficult the distinction, it will be found real,
and with sufficient care, generally practicable. The subjoined draw-
ings contain representations of some specimens which are undoubt-
edly chlorite, and of others which present a very suspicious aspect.

Among them however will be found some exhibiting an organization

preserved in Chalcedony. 513

so decided, that no mode of crystallization or inorganic arrangement
can be conceived capable of imitating it.
While on this subject it may not be useless to notice the various
modifications under which chlorite when mixed with chalcedony
presents itself. It is now I believe perfectly well understood (as I
“have already assisted in showing, in some observations on the island
of Rum) that the colouring matter of heliotrope is chlorite diffused
uniformly through the mass, From some specimens in my pos-
session, I think it probable that plasma is indebted for its colour to
the same substance; the different nature of the siliceous base alone
constituting the difference of aspect. In these specimens (brought
from Egypt) distinct grains of green matter may be observed in-
dependent of the general green stain which pervades the stone ; and
this probability is rendered still stronger from the colour and ap-
pearance which is occasionally assumed by the more transparent
flinty matter associated with the chalcedony, the latter acquiring
from the chlorite the aspect of heliotrope, while the more trans-
parent parts put on the semblance of plasma. But of a substance
sO rare it is necessary to speak with hesitation. In quartz the chlo-
rite is well known often to assume a contorted appearance resem-
bling the intestines of animals, but in which the regular crystal-
lization and superposition of the plates can be easily traced. Similarly
contorted fibres occurring in chalcedony do not exhibit the crystal-
lized structure, but appear to consist of very minute or of invisible
particles, or even of a mere colour diffused in that particular form.
At times the coloured fibre contains grains of chlorite attached to
its sides or interspersed through its course, thus emulating the im-
bedded seeds or jointed appearance of real conferve, and I have
reason to think often mistaken for them. Iam uncertain whether
I should rank under the head of chlorite certain contorted fibres
VOL. 11. 3T

514 Dr. Mac Cuttocn on Vegetable remains

which occur in carnelian, and (though much more rarely) in the
agate nodules of trap. These are of a colour sometimes ochry yel-
low, sometimes white, and sometimes brown. ‘Their forms, so
similar to the chlorite fibres, would induce us to class them together,
and it is probable that they actually consist of this substance, having
undergone some decomposition by which the green colour has be-
come brown, from affections of the metallic colouring matter. It is
at present impossible to account for this very singular disposition of
the chlorite. In some cases it evidently forms the centre of a fine
stalactite, of which the minute ramifications, afterwards preserved
in further additions of chalcedony, put on the appearance well
known in the green stained chalcedonies of Faroe. But that it is
not necessarily stalactitical is certain, from its assuming the very
same disposition when existing in quartz crystals. It is probably
the result of a species of arborization, that obscure circumstance in
crystallization which appears to depend on a sort of polarity be-
tween distinct crystals, or throughout the interrupted parts of the
same one. Thus water on freezing, and various metallic substances
on crystallizing, ramify in certain directions. Thus it will often be
found that fibres of mesotype will hold their straight and radiating
course across stilbite or other associated minerals, the continuity of
direction in the portions of any crystal remaining unchanged, how-
ever the crystal itself may be interrupted by. obstacles occurring in
its course. ‘The same appearance may frequently be observed in
quartz and other crystallized substances, and it affords among the
various phenomena of the obscure process of crystallization, not
the least curious subject of inquiry.

It is in the transparent chalcedonies that the fibrous structures
are most visible, but they are also of common occurrence in the

Opaque ones or agates, as they are usually called, although from the

preserved in Chalcedony. | 515

impossibility of transmitting a ray of light through these specimens,
our sight of them is limited to that portion which happens to run
along the fractured or polished surface. Numerous red, white and
yellow agates are every where to be found among collectors and
dealers, in which the appearance of fibres is such as to render it
very probable that they are portions of vegetables incrusted by
oxides of iron, although the obscurity of the specimens must neces-
sarily render this uncertain until they are submitted to chemical
trials. If these are vegetable fibres there is no difficulty in account-
ing for this concealment of the vegetable by the metallic deposit,
since it is easy to understand how from a compound solution of
flint and iron in water, the iron might first be precipitated on the
vegetable, in the same way as we daily see it deposited in chalybeate
springs, and how the subsequent deposition of flinty matter might
involve and penetrate the whole. It is besides known to botanists,
that many plants possess the property of attracting from their state
of combination the earthy base of some of the salts which are dis-
solved in natural waters, a property which may be subservient to
some purpose in the economy of the plant, unknown to us. Such
is the case with Chara vulgaris, which is always found incrusted
with a coating of chalk or calcareous subcarbonate, and such appears
also to be the case with Byssus nivea.

It is worthy of remark that in almost all the specimens of chal-
cedony which appear to contain aquatic conferve, not only the
vegetable structure is perfectly preserved, but the plant, however
light and yielding its texture, is disposed in as free a manner as if
still living and floating in the water which was its native element.
Together with these circumstances, the natural colour is often
equally well preserved, and the various specimens of the conferve
in particular, which are the plants of most common occurrence,

av 2

516 Dr. Mac Cutrocn on Vegetable remains

exhibit all the different tones of colour, from the most brilliant grass
green to the darkest sap or lightest yellow green which at present
characterize the different living specimens with which we are
acquainted. At times however the fibre assumes a whitish aspect,
or the yellowish and reddish hue which those delicate plants ex-
hibit when dead, an appearance perhaps even more characteristic of
their vegetable nature than their natural colour, since we cannot
easily understand how it could be imitated either by chlorite or by
metallic oxides.

Botanists who are conversant with the difficulty of ascertaining the
species of most of the plants contained in the troublesome class of
Cryptogamia, and the uncertainty in particular, which, notwith-
standing the meritorious labours of many modern authors, still hangs
over the individuals of the genus Conferva, will not be surprized that
I have made no attempt to ascertain the species occurring in chal-
cedonies. They well know the obscurity which attends this pursuit,
even where access to numerous examples of the living plant, with
the power of turning it in every direction, of viewing it in all its
states of growth, and of dissecting it into all its ramifications, facilitate
the investigation. With regard to the greater number of species in-
deed, it is known that no distinction can be traced, nor any accurate
character laid down, even by moderate magnifying powers. It is
only from those highly magnified views of the living specimen
which are capable of exhibiting the peculiarities of its internal struc-
ture, and the disposition of its fructification, that characters can be
formed or individuals distinguished. This sort of investigation can-
not be applied to the remains in question, as the loss of light which
necessarily follows the attempt to apply high powers, added to the
great diminution of it when transmitted through the chalcedony, en-
tirely deprives us of a sight of them. But in the paper of Daubenton,

preserved in Chalcedony. 517

to which I have already referred, several species are actually described
as having been well ascertained ; and when we read of two plants
in particular, whose characters are so strong and so decided as
Lichen digitatus and Lichen rangiferinus, we cannot suppose it
possible that he or any other observer could have been deceived.
The execution of the plates which accompany his paper has unfor-
tunately not rendered justice to the apparent accuracy of his obser-
vations.

It will be seen on inspection either of the specimens or of the
drawings, that probably all the plants belong to the Cryptogamia
class, and are limited to certain species of them. ‘The explanation
of this is sufficiently obvious. It is evident that the siliceous depo-
sitions which contain these remains must have been formed in ca-
verns and clefts of rocks, situations only occupied by a few species
of this class of plants, and these chiefly Byssi, Conferve, Junger-
manniz, and the Mosses most commonly so called, plants which re-
quire very little light. All the specimens which I have figured will
accordingly be found to belong to one or other of these families,
with the exception of a few which appear to be fragments of plants,
and which I have been unable from their mutilated state to compare
with any known species.

It may be asked whether the plants thus preserved are specimens
of existing species, or whether they are, like those found entangled
in the secondary strata, the remains of a former set of organized
beings. ‘The limited number of the specimens which I possess, and
the obscurity which attends not only these remains but the present
living species, prevents me from attempting an answer to this question
on botanical evidence, and on my own knowledge. But the obser-
vations of Daubenton appear sufficient to decide that in some instances:
at least they consist of existing species. Since too the formation of

518 Dr. Mac Cuttocn on Vegetable remains

flinty matter by deposition from water is a daily occurrence, there is
no reason to doubt that they may be specimens of plants now actually
existing. But it is also necessary to consider their geological connex-
ions before a full answer can be given to such a question. This is
unfortunately attended with considerable difficulty, as the greater
number of specimens are only to be found in the hands of lapidaries
and jewellers, in circumstances which render it impossible even to
trace the country from whence they have been brought, and much
less the geological situations in which they have occurred. I have only
one meagre fact to offer on this subject. I have said in the com-
mencement of this paper, that many of the specimens found at
Dunglas contain remains of vegetables. ‘These specimens appear
to have been detached from a breccia inferior to the lowest sandstone,
of which a part is visible at St. Abb’s Head, and which is probably
a portion of the extensive breccia found in so many parts of Scot-
land, interposed between the primitive rocks and the whole series
of floetz strata. These then contain remains of organized substances
of an epocha at least equally ancient with that in which the vegetable
remains found in the /loetz strata existed. As the species ascertained
by Daubenton have in all probability been preserved in recent for-
mations of chalcedony, so it is probable that those which I am now
describing have been preserved in the chalcedonies of former days.

It is said that chalcedonies of this nature are found in the Dutchy
of Deux Ponts, in Siberia, and in other situations, but there is no
information sufficiently accurate respecting these en which to ground
any reasoning. I ought however, to add, that in many of the
Siberian specimens which are known to lapidaries by the name of
Moss agates, 1 have ascertained by chemical means that the green
fibres consist of chlorite.

It would indeed have been unpardonable not to have used the aids

preserved in Chalcedony. 519

with which chemistry furnishes us to distinguish these obscure sub-
stances. Chemical analysis is often the only method by which the
very doubtful specimens can be ascertained, and if it be necessary to
determine precisely all the specimens which bear the semblance of
organization, it is the only trial which can be fully depended on, a¢
-least itis the only one on which mere chemical mineralogists will be
inclined to place any reliance. A considerable experience in the
several substances known by the name of Moss agates, combined
with some chemical trials on the most leading varieties, and the
habits of botanical investigation, may indeed produce that ¢ac¢ in this
examination which is well known to mineralogists in other cases; a
judgment founded on circumstances so evanescent and minute as
to be incapable of communication by words. ‘The inconvenience
which follows chemical trials is such as necessarily to preclude its:
application in many instances, and to render it desirable that accurate.
descriptions of all the varieties could be formed. The destruction
of the specimen, often rare and almost always expensive, must in-
evitably follow this mode of investigation. I have not therefore
subjected to this fiery trial every specimen which I have examined,
but have selected such a number of the principal varieties as weré
sufficient to confirm that evidence which had appeared to result from
botanical considerations, and to define in most of the difficult cases
the obscure boundary between the real vegetable fibre, and its mimic.
resemblance, chlorite.

The immediate object of chemical trial being to ascertain the pre--
sence of carbon in the chalcedony, the two following obvious modes.
were adopted. It was previously determined that ail silicified wood.
had the property of blackening and decomposing sulphuric acid, and:
of giving over carbonic acid on distillation with nitre. It was also

ascertained that chlorite (chlorite baldogée or green earth) did not

520 * 2D. Mae CULLOCH on Vegetable remains

possess the first of these properties, and that neither of these effects
resulted from thus treating common chalcedony. Previously to these
trials the precaution was also taken of boiling the specimens for a
considerable time in a solution of pure potash, to remove in the po-
lished ones all possibility of the adhesion of the lapidary’s oil, a cir-
cumstance which would inevitably have led to fallacious results. In
these experiments ample confirmation appeared of the deductions
which had been made from botanical examination, and I was further
enabled to detect many specimens of chlorite, where I had not
suspected its existence. ‘The same trials afforded a test which I
found in many instances to be very easily applicable to the object of
this distinction. ‘This test consisted in the effervescence which is
produced when boiling sulphuric acid is applied to those chalcedonies
which contain chlorite, while those which contain vegetable fibres
blacken the same substance without exciting effervescence. I need
scarcely add that I laid no stress on the method of distillation when
the stone appeared to contain carbonat of iron. It was not necessary
to examine into the cause of the effervescence produced by the action
of the sulphuric acid on the chlorite, a circumstance on which the
very uncertain and contradictory analyses of Meyer, Hopfner, and
other chemists throw no great light.

It would be a waste of time to attempt a description of the charac-
ter of each individual stone which is found to contain a vegetable
substance. However desirable it might be to find a specimen at-
tached to its native place of growth, it has not, as I have before re-
marked, yet occurred to me, nor do I find that it has occurred to any
of those who have noticed the same facts. Yet the appearance of
many of the chalcedonies which contain well ascertained specimens
of plants, is such as to render it likely that they do now occur 77 situ.
Many of the specimens, and among others those which contain t he

preserved in Chalcedony. 521)

hypnum figured at No.7, have the mammillated appearance which
implies that they have been formed by the stalagmitic process. And in
these the plant is broken, compressed, and deranged, though it pre-
serves its natural colour. In many others no mechanical texture or
disposition can be discovered in the stone, but the whole appears one’
semitransparent mass of chalcedony. These are the specimens in’
which the conferve preserve that freedom of arrangement and that
perfection beth of colour and structure which seem to imply that they ,
had been so suddenly involved in a mass of siliceous matter as to
have been preserved from all future changes. Many other specimens
have that mixed aspect of jasper and chalcedony to which among
other varieties of ornamental stones the lax term of agate has been
applied. Jn some specimens we may observe that zoned appearance
which so generally characterizes the chalcedonies occupying the ba-
saltic geodes, the zones always respecting the various parts of the
plant, and forming round it parallel, angular, or curved figures.
From this we may infer that the zoned disposition of those chal-
cedonies which go by the name of onyxes, may as well have pro-
ceeded by a successive deposition from the centre towards the circum-
ference, as in the reverse order, an arrangement supposed by some
mineralogists to have been the cause of this structure in the nodules
found in trap. ”

The fact of the existence of entire vegetable remains in chalce-
dony. being thus established, it may be said that it is analogous to
the well-known instances of silicified wood, and of animal remains
similarly situated. Yet it offers some important differences which
may throw light on certain disputed points, and lead to conclusions
of no small consequence, conclusions not so universally resulting

from those facts. It has been maintained on one hand that the

Vou. Te Sa

522 Dr. Mac Cuttocn on Vegetable remains

result of silex injected in a state of igneous fusion. I know not
that it is necessary for the theory which offers this explanation, that
this solution should be admitted, since the existence of that theory
is not necessarily implicated in the universal proof of this suppo-
sition. It will scarcely be asserted that substances of so tender a
structure as those I have described, substances so evidently involved
in siliceous matter while freely exposed to light and air, could have
undergone this change by any process of compression connected
with igneous fusion. Nor could any theorist invent a scheme
of this nature which should involve the remains of a land animal,
so fragile as is that chrysalis of an insect figured in the plate
No. 29, with so little change of structure. A watery solution
of silex seems so indispensible for this purpose, that it is super-
fluous to insist upon it. Of such watery solutions there are abun-
dant examples existing, examples which it is unnecessary to quote ;
but the instances under examination offer to our consideration views
still more wide and more interesting, however difficult their ex-
planation may be. It is plain on reviewing some of the cases
above described, that a process different from the tedious one of
infiltration and gradual deposition, must have produced the ap-
pearances in question. Neither the free disposition nor the forms
of the delicate vegetable structures could have been preserved during
so slow a process, nor could their colour have remained unaltered.
The loss of colour must have followed the death of the plant, and
the total loss of its figure would have resulted from the gradual
changes which it must needs have undergone during the continu-
ance of a process so tedious. ‘The remains are in fact (if I may
use such an expression) embalmed alive. To produce this effect,
we can. only conceive a solution of silex in water, so dense as to
support the weight of the substance involved, a solution capable of

preserved in Chalcedony. 523

solidifying in a short space of time, or capable at least of suddenly
gelatinizing previously to the ultimate change by which it became
solidified into stone. I need not point out the extreme importance
of this supposition, I had almost said of this fact, to any general
theory of the earth. It is for chemistry yet to investigate experi-
mentally the mode of imitating this unknown process. Those who
know the present state of this science will not hesitate to admit its
imperfections, and those who have attended to its rapid progress
will not despair.

Description of Figures. Pl. 36. 37.

No. 1. I think the peculiar membranes and defined structure
seen in this.figure can only arise from a plant, although I am not
acquainted with any analogous living vegetable. I had not enough
to subject it to chemical trial.

2. This figure exhibits one of the most common forms in which
chlorite is disposed in chalcedonies, a form not very likely to mis-
lead an observer.

3. I have figured this for the purpose of shewing the remarkable
imitation of a conferva, which may be produced by chlorite; that
part of the drawing which is most highly magnified, exhibiting a
chain which consists of distinct scales of this substance.

4, Is drawn from a specimen which appears to contain fragments
of two plants; a conferva, and the leaves of some other plant,
perhaps a moss.

5. That this drawing is made from a plant, I have ascertained
by chemical trial, and the green spots which seem disseminated
along the fibre are probably the fructification.

6. This specimen exhibits an internal structure, not very unlike

3U 2

524 Dr. MAc Cu.tocn on Vegetable remains

that of conferva zgagropila, although its size is such as to preclude
it from belonging to this species, not to notice the other important
distinctions between them. ;

7. The seventh figure exhibits the decided character of a moss,
and probably of a hypnum: I have selected two of the most entire
branches, the greater number having the leaves folded and con-
fused, as if by external force, a circumstance in itself important.
Fibres, appearing to be those of a conferva, may be observed in the
same stone, which is a transparent chalcedony, with the mammil-
lated appearance that determines it to have been a stalagmite.

8. A larger specimen of a plant very like No. 6.

9. Very delicate fibres of chlorite, but much resembling the
conferva tortuosa. They were ascertained to be chlorite by the
chemical means already described.

10. The pale colour which surrounds the dark line in this figure,
appears to arise from some metallic crust, investing a simple fibre...

11. In this figure nothing but a reticulation of minute yellow
fibres can be discerned, and it is toa similar disposition of fibres
that a great proportion of the red and yellow agates owe their
colour. I believe that this particular description of agate has never
been suspected to contain vegetable fibres, nor to owe the dispo-
sition of its colouring matter to the effect of these fibres in modify-
ing the deposition of iron. The agates of this tribe generally
exhibit a muddy uniform yellow colour; at times, though more
rarely, a lively red, and are very common among lapidaries. It
is only when in thin plates, and by the assistance of transmitted
light, that the existence of fibres is detected in them. When sub-
jected to the action of sulphuric acid they blacken and decompose
it in the way I have before described.

12. This figure is intended to convey a notion of the mode in

which oxides of iron invest the vegetable fibre.

preserved in Chalcedony. . 525

_- 13, Exhibits a remarkable instance of a deposit of reddish oxide
of iron, modified by a white central fibre, with whose nature I
am unacquainted.

14. I suspect that this consists of grains of chlorite, become
brown from some of the changes to which I alluded in the paper,
and surrounded with an additional metallic covering.

15. The ramified structure of this is too decided to admit of its
being any thing but a vegetable substance; possibly it is the root of
some moss.

16; In the chalcedonies, which go by the name of Mochas,
brown: arborizations are known to be very common, and often to
assume appearances which render these stones much sought after
for ornaments. I have here figured one which bears so strong.a
resemblance to the imbricated Jungermanniz, that it is difficult at
first. sight to distinguish them. The detached scales render the de-
ception still stronger, their appearance being that of leaves which
have been broken off. But it will I believe be found that all these
are metallic. -How much soever, the bases or middle parts of the
pretended plants may put on an appearance difficult to discriminate,
it will almost always be found that the extremities of the branches
are undefined and shapeless, while in the Jungermanniz the regular
imbrication of the scales is continued to the minutest extremity.
The eye of a botanist will also with care discover an irregularity in
the superposition of the scales, which never occurs. in the plants
themselves, and a decision in the setting on of the branches in the
real plants, which is ill imitated by the clumsy way in which the.
ramifications are disposed in the metallic arborization, I do not
however mean to deny that these stones may not contain organized
bodies, as I have below given a figure of such an one.

17. Fibres, very common in chalcedonies, and bearing a consi-

derable resemblance to Byssus nigra,—conferva ebenea of Dillwyn.

526 Dr. Mac CuLtocn on Vegetable remains

18. Fibres of a brown colour, with whose nature I am unac-
quainted. They are possibly vegetable, but I had not enough to
apply the chemical test to the specimen.

19, 20, 21. Were drawn for the purpose of shewing various
coloured fibres which are among the most common of those found
in chalcedonies. The generally great decision and character of
their ramifications seem to establish them as vegetable fibres, and
which, as I observed in the paper, have lost their colour by the pro-
cess of death going hand in hand with their lapidification.

22. Appears to consist of fragments of a lichen of the foliaceous
imbricated kind, akin to centrifugus and saxatilis, and bearing a
considerable resemblance in colour and general appearance to Parme-
lia Borreri, as figured in the Linnean Transactions. The fragments
are too insufficient in extent, and too deeply bedded in the stone to
admit of any very accurate judgment respecting their affinities.

23. Is another example of a moss, apparently of the same family
with that figured at No.7. I have drawn it precisely as it appears.
It differs from the former in the more orbicular and obtuse form of
the leaves. It is contained in a large nodule of chalcedony, which
exhibits much colour and the zonular disposition.

24, 25, and 26. Brown ramified fibres of the same apparent
nature as 19, 20, and 21. For these drawings I am indebted to
Mr. Blore, and they are from specimens in his possession which I
have not had an opportunity of examining very particularly.

27. These are contained in an criental chalcedony or mocha.
They are evidently hollow tubes, of which various aspects are-ex-
hibited by the chance section of the stone.

28. Similar tubular bodies which appear equally to belong to the
same class of beings. I have figured these because they had been

preserved in Chalcedony. 527

supposed by some of my friends to be examples of the fact under
review. ‘They appear to belong to the tribe of Zoophytes.

29. The singularity of this occurrence has induced me to give a
figure of it. I know not indeed that any other example than the
present one has been produced of an animal substance of this nature

“preserved in chalcedony. The stone which contains it is a striped

onyx agate, and is part of a ring in the possession of the Earl of
Powis. Its fortuitous section by the lapidary has exposed the in-
ternal as well as the external side of the chrysalis, from which the
fly had escaped previously to its lapidification. Its structure points
it out to be the pupa of a lepidopterous insect, probably of a
moth.

30. I have figured this, although I conceive it to be another ex-
ample from the Zoophytes, because I suspect that it has been
mistaken for the fructification of a moss.

It is proper to remark that the figure attached to each specimen
is intended to express the number of times it is magnified in the
drawing.

Independently of the figures which I have now given, I possess
numerous other varieties, which I thought it superfluous to repre-
sent, as they afforded no striking peculiarities. I have chosen the
figures among the most perfect, as well as among the most obscure,
for the purpose of illustrating the one by the other; and I have
also added the mimic resemblances to guide, if. possible, the in-
vestigations of others, and to prevent them from attributing too
much to any bias which. might be supposed to have warped my
own observations.

XXIV. On the Vitreous tubes found near to Drigg, in Cumberland.

Compiled by the Secretaries from several Communications.

i the hillocks of drifted sand, which lie between the mouth of
the river Irt and the sea near to Drigg, in Cumberland, hollow tubes
of a vitreous substance were discovered rising above the surface per-
pendicularly through the sand.* They were found three in num-
ber, within an area of fifteen yards, upon a single hillock, about
forty feet above the level of the sea. The diameter of each was
about an inch and a half. An excavation being made around one
of them, it was found to descend perpendicularly through the sand
about thirty feet. At the depth of about twenty-nine feet the sand
was interrupted by a bed of pebbles, appearing to be the continua-
tion of the sea-beach. The tube here came in contact with a frag-
ment of hornstone-porphyry, glanced off from it at an angle making
about 45° with the horizon, and then returned to its former vertical
position. » Below this fragment the tube, becoming extremely deli-
cate, was frequently broken ; and at the distance of a foot, during

_* The first notice of these substances was transmitted to the Society in the year 1812
by E. L. Irton, Esq. of Irton Hall, in Cumberland, and was accompanied by specimens.
This gentleman removed the sand from around one of the tubes to the depth of 15 feet.
Messrs. Greenough and Buckland, Members of the Society, examined the sand hills in
company with Mr. Irton in the autumn of the year 1813, and finding the surface lowered
more than 15 feet by drifting since the year 1812, resumed the excavation, The obser-
vations of these three gentlemen are introduced irto the present paper.

On the Vitreous Tubes found near Drigg, in Cumberland, 529

an attempt to recover it, the sand fell in and prevented further in-
vestigation. The lowest part of the last piece, that was detached,
was not closed, and did not exhibit any peculiarity of structure,
from which it could be inferred that the extremity had been reached.
The tube appears to have tapered in its descent, its diameter at the
“bottom of the excavation being reduced to half an inch. One spe-
cimen in the collection of the Society is bi-furcated ; whence it is
probable, that the stem was divided into two branches, one of which
may have escaped observation. Small lateral branches proceeded
from different parts of the stem, not exceeding two or three inches
in length, nor a quarter of an inch in diameter at the points of
insertion. ‘They were conical, and ended in points, gradually
bending downwards. Internally they were hollow, and opened
into the principal duct, which, except in dimensions, they perfectly
resembled.

The outside of the tube is coated with an agglutinated sand, which
viewed with a lens is found to consist of black and opaque white
grains mixed together, and rounded, as if by incipient fusion; the
white grains, when farthest from the centre of the tube, having a
reddish tint. The stem is irregularly angular, like a vegetable stalk
much contracted by drying, and is rugged with deep longitudinal
interrupted furrows, like the bark of the elm or of the cork tree.
The sides of the tube are about the twentieth part of an inch thick,
and are very hard and rigid.

On proceeding inwards, their substance gradually loses the appear-
ance of sand, and becomes vitreous, the whole interior being covered
with a smooth glaze. This vitrified matter is whitish or limpid,
containing specks of a dark olive colour and a few air blebs. It is
sufficiently hard to scratch glass.

The irregular form of the interior surface corresponds to that of

VOL. 11, 3X |

530 On the Vitreous Tubes found near Drigg, in Cumberland.

the exterior, and the whole tube has the appearance of being creased
by compression, while in a soft state. ‘The opposite sides of a crease
are often brought into contact and welded together, and thus the
tube is sometimes so flattened as to be entirely closed. In this way
the irregular furrows on the outside have been produced.

The tube on touching the pebble of hornstone porphyry above
mentioned, was welded to it; but on the side adjacent to the pebble
the substance of the tube was wanting, and in the place of it was
found an unglazed rust-coloured mark, passing across one of the flat
faces of the stone. In parts of this mark thin laminz were standing
up from the surface, and two small patches of an olive coloured glass
were adhering to the edges of two natural fissures in the pebble. *

Since the substances that have been described had all the marks of
fusion, it was not improbable that they might be imitated by sub-
mitting to the action of heat the sand and the pebble with which
the tube came in contact. With this view the following experiments
were made.

A fragment of the pebble, of a greenish slate colour, heated to a
dull red before the blowpipe, became rust-coloured, and when urged
by a strong flame, was melted into an olive-coloured glass, similar
to that observed on the surface of the pebble.

The sand of which the hillocks are composed, viewed through a
lens, appears to consist of grains of white or reddish quartz, mingled
with a few grains of hornstone porphyry.} The latter, when picked
out of the sand, are fusible before the blowpipe like the pebble of
the same substance, but they are not in sufficient quantity to act

* A similar appearance is noticed by Saussure (1153) on the Dome de Gouté, and is
by him referred to the action of lightning. The pebble above mentioned is in the cabinet
of the Society ; the adhering tube was unfortunately broken off in its way to London.

+ A few fragments of shell are also to be seen here and there.

‘On thé Vitreous Tubes found near Drigg, in Cumberland. 531

as a flux on the entire sand heated in the usual manner. The
sand so treated is reddened in the first instance, changes afterwards
to an opaque white, and finally is very slightly agglutinated, resem-
bling in its shades of colour and in its cohesion that which adheres
to the outermost coating of the tube. |

The sand was exposed to the flame of a spirit lamp, urged by a
stream of oxygen gas, in which flame Dr. Marcet has shewn that a
thick wire of platina may be melted. The grains of hornstone por-
phyry first began to flow, and presently acting upon the grains of
quartz, formed a clear glass mingled with portions of an olive colour.
Even thus however the fusion was partial, and the utmost intensity
of the flame was required to support it.

The glass thus formed resembled that of the tube in its external
characters, in being very hard and difficult of fusion, and in contain-
ing a great excess of siliceous matter: for it was ascertained that a
fragment of the tube was scarcely softened at the edges by the same
flame that had melted the sand; and that the substance of the tube
contained a large portion of silica, had been determined by one of
the members.

From what has been stated, it appears that the tubes have all the
marks of fusion, and that their substance can be imitated in some
measure by subjecting the sand to intense heat. That they are of
very recent date is certain from the shifting nature of the sand hil-
locks in which they are found, and from their inability to remain
alone and unsupported by the sand without breaking. Lightning
seems to be the only agent that could at once supply the heat and
the force requisite to make them. Inthe familiar experiment of
perforating a quire of paper by the Leyden battery, a mechanical
effect of electricity analogous to the present is exhibited, and in-
stances of fusion by the same instrument it is not necessary to enu-
merate, 3x2

532 On the Vitreous Tubes found near Drigg, in Cumberland.

The sand hillocks of Drigg, though of inconsiderable elevation,
are not unfavourably situated for promoting a discharge, since they
present themselves as the first and highest object in front of the
marshes of the Irt to clouds coming from the sea. Should the ex-
planation of the Sand Tubes, which is now offered, be admitted,
some judgment may be formed of the intensity of the heat developed
in great electrical explosions.

A LIST OF DONATIONS
TO THE LIBRARY;

TO THE

COLLECTION OF MAPS, PLANS, SECTIONS,
DRAWINGS, AND MODELS;
AND TO THE
_ CABINET OF MINERALS,
BELONGING TO THE

GEOLOGICAL SOCIETY,

‘From the Commencement of the Fifth Session in November, 1811,

to the Close of the Seventh Session in June, 1814.

TOGETHER WITH THE DATES AT WHICH THEY WERE RESPECTIVELY MADYF,,.

AND THE

NAMES OF THE DONORS.

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18il. DONATIONS. DONORS.
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The Journal de Physique in continuation, 13num. Robert Ferguson, Esq.
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Nicholson’s Journal in continuation. 8° Leonard Horner, Esq.

Sec. G. Soc.

Outlines of Mineralogy; by J. Kidd, M.D. Pro. The Author,
fessor of Chemistry in the University of Oxford,
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Tableau comparatif des resultats de Ja Crystal- James Laird, M.D.
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by Mr. John Farey, sen, from the Philosophi-
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534

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Nov. 1. Observations on the Charts of _the Islands of.

Dec. 6.

20,

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Jan. 33:

Nefe

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Mar. 6.

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Guernsey, Alderney, Serk, Herm, and Jethon,
made from an actual survey taken by Nicholas
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respective strata ; by White Watson, F.L.S. 8°
Allan’s Alphabetical list of Minerals. 8°

Second Report of the Commissioners of Bogs in
Ireland. 1811.

Analysis of the Meteoric stone which fell in the
County of Tipperary.

Report by Mr. Telford relative to the proposed
Railway between Glasgow and Berwick.

An engraved Portrait of M. de Saussure,

An engraved Portrait of M. Haiiy.

A coloured Plate, representing the carbonate of
zinc found at Matlock.

Organic remains of a former world; by James
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third. 4°

No. 139. Nicholson’s Journal, 8°

Travels in Iceland; by Sir George Stuart Mac-
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Supplement to Vol. 30, Nicholson’s Journal. 8°

Catalogue of the Library of the Royal Institution.

Statistical account of the County of Cork. 8°

Statistical account of the County of Antrim. 8° -

Histoire dela France meridionale; par M. L’ Abbé
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Exotic Mineralogy, N° 1 to6.; by Jas. Sowerby. 8°

Catalogue des Huit Collections qui composent le
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Essai d’une déscription Minéralogique des en-
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Observations relative to the mineralogical and
chemical history of the Fossils of Cornwall ;
by Martin Henry Klaproth. $°

Treatise on the external characters of Fossils,
translated from the German of A. G. Werner ;
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J. G. Children, Esq.
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R. J. Griffith, Esq.
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Leonard Horner, Esq.
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M. L. A. Necker,
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L. Horner, Esq.
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James Sowerby, Esq.
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Managers of the Royal
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Dublin Society.

James Laird, M.D.
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The Author.

Count de Bournon.

A. Apsley, Esq.
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1812,

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Baron Boru’s Travels through the Bannat of
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The University of Dublin.

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536. LIST OF DONATIONS.

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mons, containing an account of the Eruption Pr. G. Soc.
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PV TOeCUteR DOCOWRECE we hn ak Oe eee «
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2 Vols. Memb. G. Soc.
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1814.
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Q1
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Mar. 4.

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May 6.

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VOL ir:

LIST OF DONATIONS.

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British Testacea; by W. Maton, M.D. and the

Rey. 'T. Rackett. From the Transactions of
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Charpentier ov the Geology of Upper Saxony.

—_— SS

of Lower Saxony.
Transactions of the Royal Society of Hdinburgh.
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Transactions of the Asiatic Society. 11 Vols. 4°
Journal de Physique, for May, June, July, and
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Postchaise Companion through Ireland.

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Memoirs of the Wernerian Society, vol. 2. part 1.

3 Y

537

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J. F. Berger, M.D.
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The Hiitor,

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J. F. Berger, M.D.
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The Editor.

G. B. Greenough, Esq.
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The Author.
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J. H. Vivian, Esq.
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Royal Society of Edinburgh

Asiatic Society.

R. Ferguson, Esq.
Memb. G. Soc.
H. Warburton, Esq.
Sec. G. Soc.

Lord Compton,
Memb. G. Soc.

S. Parkes, Esq.
Memb. G. Soc.

J.F. Berger, M.D.
Memb. G. Soc.

P: Neill, Esq. ian
Sec. Wern, Nat. Hist.Soc,

The Wernerian Society.

538

1814.
June 3.

17.

LIST OF DONATIONS.

DONATIONS,

Annals of Philosophy; by Dr. Thomson, N° 15,
8°

16, 17, 18. .

Journal des Mines from the commencement to
the present time. 8°

A Manual of Mineralogy ; by Arthur Aikin, Sec.

to the Geological Society. 8°
Specchio delle Scienze o Giornale.
Enciclopedico di Sicilia. Palermo, 1813. 8e

Traité Klémentaire de Minéralogie, par M. Brog-

niart 8?
Regenfuss on Shells fol.
Appendix to Aikin’s Chemical Dictionary 4°

Practische Gebirgskunde von I. C. Voigt,
Journal de Physique, in continuation to
February, 1814.

Seven books on Mineralogical Subjects.

DONORS.
The Editor.

L’ Administration des
Mines de Ja France
The Author

The Editors.

H. Warburton, Esq.
Sec. G. Soc.

W. Phillips, Esq.
Memb. G. Soc.

W. Sheflield, Esq.

R. Ferguson, Esq.
Memb. G. Soc.

M. Etter.

II. Donations to the Collection of Maps, Sections, &c.

View of the Soufriére of Guadaloupe, by Mons.
Coussin, jun.

. Drawing of the rock of Stirling Castle, and Map

of the United States of America.

Drawing of the disturbance of some Coal Strata,
six miles south-east of Hexham.

Section shewing the mode of blasting rocks at
Newcastle.

Section of the Strata at Coalcleugh, Alston Moor.

* Plan of the Mines at Alston Moor.

1812.

Jan. 17.

Section of the Strata at Allon Heads near Alston
Moor.
Drawing of Curvatures in the Killas near Ply-
_Inouth, —
Drawing of Limestone Strata at Chepstow.
Drawing of a Curvature in the Coal Strata in the
Coalfield at Tenby.

Sections of the Strata at Bradford, near Manchester.

Sections of Strata at East Rainton Colliery.

= - - = at Engine pit, Percymain Col-
liery

at Wall’s end F. pit.

at Engine pit, Willingworth.

from the High main to the Low
main coal seam, at Charlotte
pit, Walker colliery.

at Coxlodge,

N. Nugent, M.D.
Hon. Memb. G. Soc.
G. B. Greenough, Esq.
Pres. G. Soc,
Rey. W. Turner,
Ilon. Mem. G. Soc.

G. B. Greenough, Esq.
Pres. G. Soc.
Thomas Crawhall, Esq.

J. MacCulloch, M.D.
Memb. G. Soc.

Robert Bakewell, Esq.
John Buddle, jun. Esq.
Hon. Memb. G, Soc.

oe
oe at oe ois

oe e «© ©

see eo @

1812.

LIST OF DONATIONS.

i DONATIONS.
Sections of Strata at Hepburn B. pit.

- at Gateshead Fell.
- at Bigges main Colliery.
- ~« at Lanchester Common.

March 6. Diagram of the ‘Triangles of the Trigonometrical

_ Survey of Great Britain.
Map of England, with a sketch of the Mountains
Drawings of Alcyonia, in the Isle of Wight.

Drawings of a Vein in a Lime Stone.

June 19, Ordnance Map of Kent.

Nov. 6

Dec.

Drawing of Meteorolites.

. Nine Maps of England with the principal Strata

sketched in.

4. Sundry Sections and Plans accompanying Mr.

Phillips’s paper on the Veins of Cornwall.

18. Two Drawings of the junction of the Sandstone

1813.
Jan.

and Greenstone in the rock of Stirling Castle.
A Plan of the Vitrified Fort of Dun MacSniochan.

Three ‘Perspective Views and a Plan of different
parts of Switzerland.

A vertical Section of the Strata in the Forest of
Dean.

Section of Horbeck stone pit at Wilsford, in
Lincolnshire.

1. Six Maps and Plans witha Description of the Great

Copper mine at Fahlun in Dalecarlia,

15. Map of the Azores.

Map of the Caledonian Canal.
Nine Maps of various parts of Sweden and Nor.
way.

Feb, 19. Gardner and Yeakell’s Map of Sussex.

Nine Drawings of the Rocks of Clovelly.

Plans and Sections of the Ashover denudation.
Drawing of the Rocks at Lydstop.

April 2. Section of the Strata at Darlstone Bay, Dorsetshire.

Engraved View of Handfast Point, Dorsetshire.

. 23, Map and Section of the Isle of Man.

May 7. Ten Geological Drawings of Parts of Scotland.

21. Fourteen Priuts of Geological Subjects.

3 v2

539

DONORS. ~2)e3
John Buddle, jun. Esq.
Hon. Memb. G. Soc.

J. MacCulloch, M.D,
Memb. G. Soc, -
W. Conybeare, Ksq.
Thomas Webster, Esq.
Memb. G. Soc.
J. Mac Culloch, M.D.
Memb. G. Soc.
KE. W. Rundell, Esq.
Mem. G. Soc.
James Sowerby, Esq.
Mem. G. Soc.
G. B. Greenough, Esq.
Pres. G. Soc.
William Phillips, Esq.
Mem. G. Soc.
J. MacCulloch, M.D.
Mem. G. Soc.
G. B. Greenough, Ksq.
Pres. G.'Soc.

David Mushet, Esq.
Hon. Mem. G. Soc.

Sir A. Hume, Bart.
V.P. G. Soc.

S. Solly, Esq.
Treasurer, G. Soc.

W. Conybeare, Esq.
Mem. G. Soc.

S. Solly, Esq.
Treas. G. Soc.

A. Apsley, Esq.
Mem. G. Soc.

Rev. I. J. Conybeare,
Mem. G. Soc.

J. Farey, Esq.

J. Mac Culloch, M.D.
V.P. G. Soc.

T. Webster, Ksq.

Keeper of the Mus. G.S.

Sir H. Englefield, Bart.
¥ iP. G. Soe.

J.F. Berger, M.D.
Mem. G. Soc.

J. MacCulloch, M.D.
V..P..G. Soc.

G. B. Greenough, Esq.
Mem. G. Soc,

540

1313.

June 18.

Nov. 19.

Dec. 3.

17
1814,
April 1,

May 20.

June 3.

1811.
Noo. 1.

LIST OF DONATIONS.

DONATIONS.
Drawing of a Curvature in Lias, ncar Shepton-
Mallet.
Seven Drawings of Rocks on the Coast from St.
Agnes to Cligga point
General Sections of the [sle of Wight and of Alum

Bay.
Map of the County of Wicklow.

Two Drawings of Undulating Veins of Granite
aud Quartz.

Drawings of the Clay Cliffs of Sheppey, and of
a Chalk-pit at Northfleet.

Nineteen Maps of the North of Europe.

M.S. Map of the County of Donegal.

M.S. Survey of the Malvern Hills.

Hydrographical Survey of the West Coast of
Ireland

Fennin’s Map of the Isle of Man.

Arrowsmith’s Map of !reland.

Rocque’s Map of the County of Dublin.

Baugh’s Map of Shropshire.

Sections of the Strata at Jacob’s Whim Shaft,
Arkindale.

Diagram of threws and protrusion of schist into a
vein.

Section of Belton Shaft near Blanchland,

Sections and Drawings of the Pentowan Stream
Works, near St. Austle, Cornwall.

III.

Specimens of the Strata at Folkestone.

Crystallized Sulphate of Barytes fromCumberland.
Collection of Specimens from the Isle of Man.

Specimens from the neighbourhood of Weymouth.

Specimens of Toad-stone, &c. from Micklewood,
in Gloucestershire.

Series of Specimens from the neighbourhood of
Bristol.

Specimens of Sulphur from the Souffriére of
Montserrat, aud of specular Iron Ore from
Guadaloupe.

Jasper Agate from Palermo.

Specular Iron Ore from the Lipari Islands,

DONORS.
Rev. Wm. Conybeare,
Mem. G. Soc.
Rey. I. J. Conybeare.
Mem. G. Soc.
T. Webster, Esq.
Keeper of the Mus.G.S.
J. F. Berger, M.D.
Mem. G. Soc..
J. MacCulloch, M.D.
V,.P. 4G. Boe:
T. Webster, Esq. Keeper
of the Museum G. Soc.
M. Etter.
Earl of Londonderry
Lieut. Colonel Mudge
Mem. G. Soc.
J. F. Berger, M.D.
Mem. G. Soc.

Hon. H. Grey Bennet,
Pres. G. Soc.

A. Carlisle, Esq.
Mem. G. Soc.

Edward Smith, Esq.

Donations to the Cabinet of Minerals.

Robt. Ferguson, Esq.
Vice Pres. G.S.

~J. F. Berger, M.D.

Mem. G. Soc.

James Laird, M.D.

; Sec. G. Soc.

G. Cumberland, Esq.
Memb. G. Soc.

R. Bright, Junr. Esq.
Memb. G. Soc.

N. Nugent, M.D.

Hon. Memb. G. Soc.

W. Franklin, M.D.
Memb. G. Soc.

1811.

15.

“Dec. 6.

LIST OF DONATIONS.

DONATIONS,
Specimens from Dinmore-hill, in Herefordshire.

Slab of Limestone with Organic Remains from
Charmouth.

Specimens from the Island of Bourbon.

Specimens from the Alum #ine of Hurlet, near
Paisley.

Sulphat of Strontian from Knaresborough.

Specimen of Witherite from Shropshire.

Specimens from Yorkshire and Cumberland.

Series of Speciniens from Allonheads, Alston
Moor -

20. Specimen from Warwickshire.

1812.
Jan. 17.

Feb. 21.

Mar. 20.

April 3.

Specimen of Witherite from Merton Fell, West-
moreland.

Specimen of Pure Clay from Halle, and of Mela-
nite from Frascati,

Specimens of Fossil wood from the ‘Tunnel at
Blisworth in Northamptonshire,

Specimens of Vegetable Remains on Coal Slate
from Somersetshire.

Part of a hollow ball of Ferruginous Sandstone
from a hill 400 miles east of the Cape of Good
Hope.

Specimens from Northumberland.

Specimens from Ireland.

Specimen of supposed Native Lead from Holy-
well, North Wales.
Series of Corundum from China and India.

Septarium from Hertfordshire.

Specimen of undescribed Alcyonium from
Brighton.

Specimen of Statuary Marble rendered elastic by
heat.

Tron Ore from Botany Bay.

Specimens from Labrador,

Specimens of Slickenside.

Specimens of the Nautilus nummularia, from
Kgypt, Spain, &c.

An undescribed Fossil Shell from Shropshire.

Specimens from the Paris mine in Anglesea.

Specimen ofGarnetRock fromHuntly,inBanffshire

541

DONORS. -
Henry Warburton, Esq.
Memb. G. Soc.
G. B. Greenough, Esq.
Pres. G. Soc.
A. Aikin, Esq.
Sec. G. Soc.
J. Ridout, Esq.
Memb. G. Soc.
James Sowerby, Esq.
Memb. G. Soc.
A. Aikin, Esq.
Mem. G. Soc.
G. B. Greenough, Esq.
Pres. G. Soc.
Thomas Crawshall, Esq.

Leon. Horner, Esq.
Sec. G. Soc.
J. G. Children, Esq.
Memb. G. Soc.
A. Champernowne, Esq.
Memb. G. Soc.
Ch. Harvey, Esa.
Memb. G. Soc.
W. James, Esq.
Memb. G. Soc.
W. Richardson, D.D.
Hon. Memb. G. Soc.

Hon. H. G. Bennet.
Memb. G. Soc.

G. B, Gteenough, Esq.
Pres. G. Soc.

T.R. Jones, Esq.

Sir A. Hume, Bart.
Vice Pres, G. Soc.
Sir H. Englefield, Bart.
Mem. G. Soc.
J. Mac Calloch, M.D.
Memb. G. Soc.
Rev. Mr. Latrobe.
A. Champernowne, Esq.
Memb. G. Soc.

James Sowerby, Esq.
Memb. G. Soc.

YD Aikin, Esq.
Sec. G. Soc.

° °

5AQ

1812

LIST OF DONATIONS.

DONATIONS.

Apr. 17. Specimens in illustration of Dr. Mac Culloch’s

May 1.

15,

June 5.

19.

June 5.

Nov. 6.

paper on Bitumen.

Specimens in illustration of Mr. Horner’s paper
on Droitwich.

Specimen of Fibrous Rock Salt from Northwich.

Specimens of Calcareous Spar from Tavistock.

Specimen of recent Pentacrinus from Guadaloupe.
Specimens of the Aluminous Strata from Campsie.
Specimens from Derbyshire.

Specimens of Magnesian Limestone from Sunder-
land.
Series of Corundum, Oriental Ruby, and Spinelle.

Specimens of the Calcaire d’eau douce, and of
the Meuliere d’eau douce from the neighbour-
hood of Paris.

Specimen of Hippurites from Cape Passaro in
Sicily.

Specimens of Alcyonia from the Isle of Wight.

Specimens of Tubes found in the sand at Drigg in
Cumberland,
Series of Specimens from Vesuvius.

Specimens of Chalk with Fossil Palates from
Cherry Hinton.

Specimens from Barbadoes.

Specimens from Yorkshire.

Specimens from Alderney.

Specimen of Coral from the East Indies.
Specimens from Mount Sorrel in Leicestershire.

Large Fossil Vertebra from Dry Sandford, Berk-
shire,
Specimens from France, Hungary, Siberia, &c.

Specimens in illustration of Dr. MacCulloch’s
paper on the Vitrified Forts.

Specimens from Leicestershire.

Specimens of the Sand tubes from Drigg.

Specimens from North America.

Specimens of Flint from Norfolk.

_ Specimens from Bristol}.

Specimen of Carbonate of Lead from Shropshire.

Spec'men of Asbestos and of black Chalk from
Treland, .

-

DONARS,
J. Mac Culloch, M.D.
Memb. G. Soc.
L. Horuer, Esq.
Sec. G. Soc.
A. Aikin, [sq.
Sec. G. Soc.
J. Taylor, Esq.
Memb. G. Soc.
Joseph Skey, M.D.
C. Mackintosh, Esq.
W. Milnes, Esq.
Hon. Memb. G. Soc.
Sir A. Hume, Bart.
Vice Pres. G. Soc.
Count de Bournon,
Foreign Sec. G. Soc.

ey 6) ete hold

Hon. H. G. Bennet,
Memb. G. Soc.

T. Webster, Esq. '
Keeper of the Mus. G.Ss
E. Irton, Esq.

Hon. H. G. Bennet,
Memb. G. Soc.
H. Warburton, Esq.
Memb. G. Soc.
Joseph Skey, M.D.
Capt. Richardson,
63d Regiment.
Capt. Loch.
H. Warburton, Esq.
Memb, G. Soc.
Rev, W. Buckland.

H. Heuland, Esq.
3 Mem. G. Soc.

J. MacCulloch, M.D.
Mem. G. Soc.
Robert Bakewell, Esq.

k. L. Irton, Esq.

Dr. Bruce.

H. Reeve, M.D.

G. Cumberland, Esq.
Hon. Mem. G. Soc.

Thomas Dugard, M.D.
Hon. Mem. G, Soc.

Rey, T. Hincks,
Hon. Mem. G. Sow

1813.

Nov. 20.

Dec. 4.
18.

1814.

Jan. 1.

15?

Feb. 19.

LIST OF DONATIONS.

DONATIONS.
Specimens from Sicily.

Specimens of Coal and Greenstone from Walsall
in Staifordshire.
One Ton of Coals from Wyken near Coventry.

One ditto from Pelsall, Staffordshire.
Specimens from Cornwall.

Specimens from Ireland and Scotland.

Specimens of Cobalt ore from Alderley edge,
Cheshire.
Fossil Shark’s teeth from Malta.

Specimens from Sweden.
Specimens from Cornwall.

Specimens from South America, from Cheshire,
and Somersetshire.

Specimens illustrating the junction of Greenstone
and Sandstone, Stirling Castle.

Organic Remains illustrative of Mr. Parkinson’s
paper on the Strata noar London,

Specimens of Jct from Whitby, and of Agate
from Scotland.

Specimens of Organic Remains from Shropshire.

Specimens from Cornwall.

Crystallized Felspar and Bituminous Marle Slate.

Siliceous Petrifactions, from Tisbury, Wiltshire.

March 19.Specimens from Rutlandsiire and Harrowgate.

April 23.

Organic Remains from Hordwell Cliff, Hampshire.

Specimen of Calcarcous Incrustation found in
the pipe of a steam engine,

Specimens from Doxsetshire and the Isle of Wight.

Specimen of Chalcedony, from Charmouth,

Siliceous Petrifactions of Corals, from Antigua,

Specimens from the neighbourhood of Paris,

Fossils from the Crag Pits, Aldborough,in Suffolk.

Specimens of Volcanic Ash, from the Island of
Bourbon.

543

DONORS.
James Franck, M.D. -
Mem. G., Soc.
A, Aikin, Esq.
Sec. G.S.
Wm. James, Esq.
Mem. G. Soc.

Rev. I. J. Conybeare,

and Rev. Wm. Buckland.

J. MacCulloch, M.D.
Mem. G. Soc.

Rev. K, Stanley.

Capt. Beaufort,

lion. Mem. G. Soc.
S. Solly, Esq.

Treas. G. Soc.
Rev. J. J. Conybeare,
and Rev. J. Buckland.
T. Meade, Esq.

Hon. Mem. G. Soc.
J. MacCulloch, M.D.

VEP.G. SoG.
James Parkinsow, Esq.

Mem. G. Soc.
Right Hon. Lord Dundas,

Mem G. Soc.
Hon. H. G. Bennet,

Pres. G. Soc.

Rev. I. J. Conybeare,
Mem. G. Soc. and
Rev. Wm. Buckland.
A. Champernowne, Esq.
Mem. G. Soc.
Miss Bennett.
H. Warburton, Esq.
Mem. G. Soc.
Miss Bennett.
Hlon. H. G. Bennet,

Pres. G. Soc.

Sir H. Englefield, Bart.
Vice Pres. G. Soe,
Rey. Wm. Buckland,
Memb. G. Soc.
N. Nugent, M.D.

Hon. Memb. G. Soc.
Hon. H. G. Bennet,

Pres. G. Soc.

H. Warburton, Esq.

Memb. G. Soc.

Sir Gilbert Blane, Bart.

M.D.

5AaA

1813.

LIST OF DONATIONS.

DONATIONS,

April 23. Specimen of Actynolite, from Cullen Point.

May 7.

21.

June 4.

Nov. 5.

19,

Dec 3.

Slate, with Organic Remains, from ‘Tintagel,
Cornwall.
Specimen of Euclase, from Brazil.

Specimen of Topaz and Apatite, St. Michael’s
Mount, Cornwall.

Specimens of Zeolites, from Ferroe and Perth-
shire.

Specimens from the Archipelago.

Specimens from Cambridgeshire.

Specimen of native Arsenic, from the Hartz.

. Specimens, containing Organic Remains, from the

summit of Snowdon.

Specimens of Tremolite, from Clicker Tor, Corn-
wall.
Specimens from Hucl Maudlin Mine, Cornwall.

Volcanic Specimens from the Rhine, and Mi-
nerals from Sweden
Specimens of simple Minerals,

Specimens of a supposed Fossil Crocodile, from
Charmouth

Specimen of Organic Remains, from Wiltshire,
Hampshire, and Dorsetshire.

Specimens of Zeolitic Amygdaloid, from Ferroe.

Specimen of Calcareous Spar, from Shropshire.

Fossil Wood, from the Isle of Portland.

Nummulites, from Selsea.

Large Crystal of Felspar, from Catharineberg,
in Siberia,

Specimens and Fossils illustrative of Mr. Webster’s
Paper cu the Strata above the Chalk.

Specimen of Strata and of Organic Remains.

Organic Remains from Corwen, in North Wales,

Specimens of Granite and Gneiss, from North
Wales, Westmoreland, and Leicestershire.
Specimens from Glen Tilt, in Aberdeenshire,
illustrative of his paper.

Specimens from Russia.

17. Specimens from Cornwall

DONORS.
Rev. W. Serle,
Memb. G. Soc.
Rey. f. J. Conybeare,
Memb. G. Soc.
E. W. Rundell, Esq.
Memb. G. Soc.
S. Solly, Esq.
Forcign Sec. G. Soc,
Leonard Horner, Esq.
Sec. G. Soc.
Wm. Mac Michael, M.D.
Memb. G. Soc.
H. Warburton, Esq.
Memb. G. Soc.
A. Champernowne, Esq.
Memb. G. Soc.
Rev. J. Hailstone,
Woodwardian Prof.
Memb. G. Soc.
Rey. W. Gregor,
Hon. Mem. G. Soc.
W. Rashleigh, Esq. :
Memb. G. Soc.
S. Solly, Esq.
Treasurer G. Soc.
H. Heuland, Esq.
Memb. G. Soc.
G. EB. Greenough, Esq.
Memb. G. Soc.
Miss Bennett.

T. Allan, Esq.

T. Dugard, M.D.

G. Cumberland, Esq.
Memb. G. Soc.

James Parkinson, Esq.
Memb. G. Soc.

H. Heuland, Esq.
Memb. G. Soc.

T.. Webster, Esq.

Keeper of the Mus. G.S.

B. Bevan, Esq.
Hon. Memb. G. Soc.

O. Tudor, Esq.
Memb. G. Soc.

G. B. Greenough, Esq.
Memb. G. Soc.

J. Mac Culloch, M.D.
Vice Pres. G. Soc.

M. Etter.

Rev. I. J. Conybeare,
Memb. G. Soc.

1813.

LIST OF DONATIONS.

DONATIONS.
Specimens from Lauren Hil, Galloway.

- Specimens of Strata and Organic Remains illus-

1814.
Jan. 7.

31.

trative of his paper
Specimens of Siliceous Petrifactions, from Antigua.
Specimens of Shells in Marl, from Fifeshire.
Specimens of Flints from the London Gravel.
Specimens of Brazilian Topaz.

Specimens from Guadaloupe.

’ Specimens of Pitch Stone from ‘the Hebrides,

‘eb. 18.

March 4.

18.

April 1,

VOL. II.

and of Strata from the Coal Field of Fifeshire

Specimen of Corundum, from Gellivara, in Swe-
dish Lapland.

Specimens from Northumberland and Roxborough-
shire.

Specimens from the Vale of the Tweed.

Nodule of Tron Stone.
Specimens from Scotland.

Specimens of English Rocks.
Specimens of English, Scottish, and Irish Rocks,

Specimens from Palermo.
Fossil Nautilus and Crystallized Selenite.
Specimens from Petworth and Mount Sorrell.

Specimens of Puddingstone from Hemel Hemp-
stead.

Specimens of Coal and Coal Slate, from Sweden.

Specimens of Magnesian Limestone, &c. from
Cumberiand.

Specimens of Molybdena in Granite, from Shap,
in Westmoreland. ig

Specimens from Northumberland.

Fossils from English Strata.
Vein Stones from English Strata.

Specimens of simple Minerals.

Fossil Shells arranged systematically.

32Z

DONORS.
Rev. Wm. Buckland,
Memb. G. Soc.
T. Webster, Esq.
Keeper of the Mus. G.S.

N. Nugent, M.D.
Hon. Bomb. G. Soc.
H. Warburton, Esq.
Memb. G. Soc.
T. Webster, Esq.
Keeper of the Mus.G.S.
Hon. H.G. Bennet,
Pres. G. Soc.
Rev. J. Gilding,
Memb. G. Soc.
G. B. Greenough, Esq.
. Memb. G. Soc.
M. Swedenstierna,
Hon. Memb. G. Soc.
Hon. H. G. Bennet,
Pres, G. Soc.
H. Warburton, Esq.
Memb. G. Soc.
Royal Society.
H. Warburton, Esq.
Sec. G, Soc.

G. B. Greenough, Esq.
Vice Pres. G. Soc.

Hon. H. G. Bennet,
Pres. G. Soc.

A. Sutherland. M.D.
Memb. G. Soc.

Wm. Blake, Esq.

’ Vice Pres. G. Soc.

H. Warburton, Esq.
Sec. G. Soc.

Rey. Wm. Buckland,
Memb. G. Soc.

G. B. Greenough, Esq.
Vice Pres. G. Soc.

Wm. Lowndes, Esq.
Memb. G. Soc.

Hon. H. G. Bennet,
Pres. G. Soc.

Miss Bennett.

G. B. Greenough, Esq.
Vice Pres. G. Soc.

W. Sheffield, Esq.
Memb. G. Soc.

James Parkinson, Esq.
Memb. G. Soc.

546,

1812.
April 1.

15.

May 6.

10.

June 3.

1813.
Now. 5.

LIST OF DONATIONS.

DONATIONS.
Specimens illustrative of Mr. 'Taylor’s section of
the Tunnel of the Tavistock Canal.
Specimens of English and Scottish Rocks.
Specimen of Labrador Felspar.
Specimens of Fossil Wood and recent Shells.
Specimen of White Marble from Strath, in the
island of Sky.
Alcyonia from Stokenchurch Hill, Oxfordshire.
Specimens from Hudson’s Bay.
Sulphate of Strontian, from Bristol.

Fossil Belemnites from Bosworth, Leicestershire

Specimens from the Geyser spring, and other Mi-
nerals, from Iceland

DONORS.
J. Taylor, Esq.
Memb. G. Soc.
G. B. Greenough, Esq.
Vice Pres. G. Soc.
O. Tudor, Esq.
Memb. G, Soc.
. Turner, Esq.
Memb. G. Soc.
J. Mac Culloch, M.D.
Vice Pres. G. Soc.
Rev. P. Serle,
Memb. G. Soc,
Karl of Selkirk,
Memb. G. Soc.
G. Cumberland, Esq.

wn

Hon. Memb. G. Soc.

B. Bevan, Esq.
Hon: Memb. G. Soc.

H. Holland, M.D.
Memb G. Soc.

( Hon. H. G. Bennet,

|

Specimens & Organic Remains, from Stonesfield, yy
Oxfordshire.

Specimens from the Pentowan Stream Works,
near St. Austle, Cornwall,

Fossils from Cambridgeshire.

Fossils from Cambridge.

Fossil Belemnites,

Fossit Bones and Specimens, from the Basin of
Paris.

Specimens of Chrysocolle, from the Vale of
Newlands, near to Keswick.

IV. Apparatus.

A Clinometer.

Pres. G. Soc.
Lord Compton,
Memb. G. Soc.

1G. B. Greenough, Esq.

Vice Pres. G. Soc.
Edward Smith, Esq.

Rev. J. Hailstone,
Woodwardian, Prof.
Memb, G, Soc.

H. Warburton, Esq.

Sec. G. Soc,
C. Stokes, sq.
Memb. G. Soc.
G. B. Greenough, Esq.
Vice Pres. G. Soc.
W. E. Sheffield, Esq.
Memb. G. Soc.

Lord Webb Seymour,
Memb, G, Soe.

‘

INDEX.

Aberfoyle, on the Rocks in the Neighbourhood of
Adits, in the mining District of Cornwall : ;
Ailsa Craig, Mineralogical Observations on
Alcyonia, Fossil, on some new Varieties of
Strata in which they are found
oS — of Purbeck, Weymouth and Portland
Alluvial Depositions of Tin in Cornwall

above the Basalt of Staffa

around London

; Fossils pS in the

Alum Bay, in the Isle of Wight. deccr Olio Of - andy eo .
Alumine, Sub-sulphat of, found at Newhaven in Sussex és
Amworth, Vitrified Fort of : : : :
Amygdaloid of the Isle of Man. : °

—.of Burnt-Island, remarkable ven in the

Appin, District of, Quartz Rock in the

Arisaig, District of, Quartz Rock in the- ‘ }

Arran, Island of, Observations on the Granite of Goatfield i in ae
Assynt, District of, Mineralogical Observations on the .
Limestone of the-

——__—— — Quartz Rock of the

Augite, Rock composed of, with Felspar, in the iaad ah gies

—_—_—-

Bagshot Heath, Sand of |
Baxewe tt, Mr. R. An account of the Coalfield at pretends
near Manchester : $
Basalt of Raasa, Contortigns of the
——— of Staffa, Different varieties of the
Basaltic,. Columnar, forms of the Lava of Teneriffe
Basin, Hampshire or Isle of Wight, extent of the )
London, extent of the , $8 : : 5 ji
Paris, description of the . £ g
Beachey Head, Strata at
Bell-metal Ore, a Sulphuret of Tin (oma in Comvall
3 2:2

PAGE
AAG
129
AIT
Sie
384
385
342
506
23k
241
181
191
278.

AS
AAO
A73
AT,
A26
A08
A0S
A58.
A0Z

224

282
439
502
290
170
171
161
192
343:

548 INDEX.

PAGE:
Bennet, the Hon.H.G. Some account of the Island of Teneriffe 256
Brrcer, Dr. Mineralogical account of the Isle of Man , : 29
Binstcad, Isle of Wi ght, Strata at . ‘ ; « 212
Bistre, on the nature of ‘ 27
Bitumens, Analogy between these _— certain Pandas ob-

tained in the Distillation of Wood ; ; 3 : 8
Bognor, Rocks at H F ‘ . : 190—208
Bogs, Account of the black matter depositeat in : 24
- Boharm, Mineralogical Observations on the Neighbourhood of A3O
Bowlders, Observations on the Formation of : : . 71—78
Bradford, Coalfield of, account of the 282
Brentford, Strata at 198
Brighton, Ciifls at ; 176
Brine Springs at Sbectiwich, w account of the _ 3 94
Bromley, Strata at : : 196
Burnt-Island, Compound veils of Listeabdnd and Batals, tra-
versing the Amygdaloid at. : : AAO
Calbourne, Isle of Wight, Quarries at. j ‘ j : 228
Calcaire Grossier, in the Paris -Basin oP Hg , : 201
Chabasite of Staffa e : ; : . : : 504
Chalcedony, Vegetable Remains preserved in ° : . 510
—————Green, of the Island of Rum é . A403
Chalke, on the Strata lying over the d ’ : : 161
of the South of England : 173

digo flints, 174—with flints, 174—Gteys VeAthard
and soft, 174—of France, 175
Chalk Marl, in the South of England 173
Cheese Wring, one of the Granite:Tors of Carnal quaiviied 69
Chlorite, peculiar forms of, in Chalcedony. ‘ 2 . 512
Chlorophane, found in Cornwall. : : : 344
Chrysalis of a lepidopterous Insect inclosed in wiGhatcedany 527
Clay, Plastic, above the Chalk in England 5 ‘ 4 166
—London, description of the } f . . > 187
Clay Porphyry, Vein of, near St. David’s ’ ‘ . 8&8
Clay-slate of the Isle of Man : , i 5 : . 37
—— Remarkable variety of : : . . . 43]

INDEX. 549

PAGE
Clay-slate, alternating with Graywacke : : 2 A42—A47
Clovelly, North Deyon, Memoranda relative to. : . 495
Coal, on the Composition of 4 : ‘ : ‘ : 14
—— on the Origin of . . ‘ : : ‘ , 20
—-— Strata, remarkable position of, at Bradford . G- ae 283

Coalfield at Bradford, account of the , ; 4 : . 282
Colwell Bay, Fossil Oyster Shells at . : A : . 216
Columnar Structure of the Syenite of Ailsa Craig P : A19
Conyszears, the Rev. W, On the Origin of a remarkable Class of .
Organic Impressions occurring in Nodules of Flint . 328

Conyszrary, the Rev. J. J. Memoranda relative to Cloveily . A95
Contortions in Mica Slate, Basalt, Veins of Grayite and Quartz A38
Corfe Castle, Clay Pits near ‘ i spies . ° 186
Cornwall, on the Granite Tors of - . s 66

—on the Veins of 3 F “ ° ; x 110
——— on the Economy of the Mines of = “ A S09

-—on the Oxyd of Tin foundin . . : “ 336
Country, meaning of the term as used by the Cornish Miners 113

Nature of in Cornwall, where different Veins occur 131
Cowes, Isle of Wight, Strataat . 5 : siboiamuind 211—212
Crag Pits in Suffolk . “ ¢ “ . - 2 218
Craig Phadric, Vitrified Fort on the Hill Obis« ‘ . 270
Crinan Harbour, Rocks in the Neighbourhood of : : AAT
Cross Courses, or North and South Veins, in Cornwall . P 133
‘Crystallization from vaporized Minerals . “ “ ; 276

-—:—Observations on some Phenomena of 431, 432, 437, 514
Culver Cliff, Isle of Wight : ‘ . ‘ ‘ r 163:
Devar, near Campbelitown, Porphyry of : : : ~ 423
Devonshire, on the Economy of the Mines of . : ‘ 309
Divining Rod, still used in Cornwall. 5 ‘ : ' 124
Dorsetshire, Chalk Hills of . 4 . 5 3 ‘ 170
Prannack Copper Mine in Cornwall, description a ‘ : 146
Drigg, in Cumberland, Vitreous Tubes found near . e 5Y8
Droitwich, Account of the Brine Springs at . . . 94
Droylsden, Coalfield of ; : : 2 ° 283

Dunglas, Agates of, containing Wesabe Remains : ‘ 510

550 INDEX.

Dun Mac Sniochain, Vitrified Fort of the Hill of . :

——_—___ —————. Mineralogical Examination of . ‘
Egg, Island of, Mineralogical Observations on the r :
ENGLEFI£LD, Sir Henry, Observations on the Chalk of the Isle
of Wight e . . = . . e . e
Fancy Copper Mine, Description of d : 3 : ;
Fluor, some remarkable Varieties of —. ‘ g 3 :
Fossil, Organic Remains, in Chalk : . . : ‘
—_——- in the lower Marine Formation above

the Chalk ; é e

in the lower Freshwater ee
in the upper Marine Formation above
the Chalk . A = \ 3
——— in the upper Freshwater Formation
_——————— —____-——. in the Alluvium around London .

—_——_————_ Siliceous, at Feversham 3 :
——— of Hippurites d : . .
————_— ————. Remarkable Class of in Flint -
2 ae of some new Varieties of Alcyonia
Freshwater Formation in the Isle of Wight, Lower :
Upper
— -in the Basin of Paris J z :

——-— Conjectures respecting the Origin of

Garnet Rock in the Isle of Man = aE | ke

Gatacre House, Vitrified Wall of : ! :
Globular Siliceous Rock in the Shiant Isles thes in Sky
Gold found in Cornwall i ‘ 2 ‘ 4
Goniometer of Dr. Wollaston, great aititivy of the : :
Granite, of the Isle of Man, containing Galena. :
- of the Island of Arran, not stratified .

en ee Magnetic 4 : :

——- of Labrador, containing Garnets . ; °

- on the Decomposition of and its Disposition to split
into blocks.

ad

INDEX.

peculiarity of their Structure i a i g0~— §3——

551
PAGE
Granite Graphic, of Rona, . ann ids , 391
Hutton’s Theory of, oleate to ‘ . 432
- Veins of, at Portsoy, Observations on the P . A33
— Contortions of : P : . : A39
- Tors of, in Cornwall, Remarks on the 7 , " 66
Gravel around London, Remarks on the “ : ° ° 231
Graywacke, of the Isleof Man . ; 4 ‘i : 3 39
—of Aberfoyle. ‘ ’ : : AAT
of Clovelly, Contortions in ms ‘ : A97
— alternating with Clay Slate ; , . 449—447
— Observations on the term . ; - : 93—444
Greenstone Porphyry, near St. David’s . . 3 4 A 86
Greenstone, Observations on the term . ‘ : ‘ 393
Green Sandstone Stratum, in the Isle of Wight 382
Grey Weathers, Description of the : : . ° ‘ 224
Gypsum accompanies the Salt Springs at Droitwich : 95
of the Isle of Purbeck . . ; . 8 ‘ 166
——— of Newhaven, in Sussex F J . . : 191
of thei Pavis, Basin.) < i J " 7 " 214
Hart, Sir James, Observations on his Experiments on the Action
of Heat modified by Compression, on Vegetable Matter. 20
Hampstead Heath, Sand of . A : A . : 224.
Headon Hill, {Isle of Wight, Description of : : ° 184
Heat, modified by Compression, its Action on Vegetable Matter 2]
—— Effect of, on the Rocks at the Vitrified Fort of Dun Mac
Sniochain . é é . ‘ ; ‘ . 266
Heliotrope of the Island of Bi ; . : . AO3
Herland Copper Mine, Description of . ° : ; - 146
—_____— ————---—_ North, Description of ; : 149
Hertfordshire Pudding Stone, Description of the . : ‘ 925
Highgate Hill, Account of the Strata of é q . : 197
Hippurites, Observations on some Specimens of . : O77
Hogs-Back, near Guildford, Description of the Chalk of the 172
Hordwell Cliffs, Fossils of . 5 ; : % 189
Horner, Mr. L. Account of the Brine Springs at pata 94
Hornblende avd Felspar, Rocks near St. David’s composed of, and
89,

552 INDEX.

Hornstone of the Shiant Isles ; ‘ $ é : 5
Observations on theterm . ‘ é : $
fuel Alfred Copper Mine, Description of . 3 ‘ ‘
Huel Jewel Mine,

Huel Damsel Mine,

\ Description of some of the Veins in

Hurron’s Theory of Graphic Granite objected to . :
Isla, Island of, Mineralogical Observations on the : ‘
Isle of Man, Mineralogical Account of the : : :

Isle of Sheppey, Description of the. : : : .
Isle of Wight, On the Freshwater Formations in the . ,

Basin of the : : ° 4 ‘

Some new varieties of Alcyonia leased in the
Jura, Island of, Mineralogical Observations on the . .

Kentish Rag, Description of the :

Kipp, Dr. Notes on the Mineralogy of the ili dviseiclecied of
St. David’s, Pembrokeshire. 7 J 5 ‘ ;
Killas, the term, an improper substitute for Graywacke °
of Cornwall, Observations on the. c : :

Killin, Mineralogical Observations in the Neighbourhood of
Kimmeridge Coal, the bed containing it : 4 : :

Labrador, on the Geology of the Coastof . . ; °
Felspar, Locality of . A 7 : s
Hornblende, Locality of . 2 : :

Lapis Ollaris, found in Labrador . : , °
Lava, peculiar Species of, in the Island of Teneriffe. °
Lead Mines of the Isle of Man. - : - ; :
Lead Mine of Tyndrum : : ; are
Lightning supposed to have vielen Sand : ° :
Lignites, on the Nature of . : - : : : :
Limesione of the Isle of Man ° : : - . :
—— of the District of Assynt . : : . .
-- of Isia, not a Floetz Limestone - '
—— ---— of Loch Laggan, containing Hornblende . ‘

Lode, Etymology of . . : ‘ ‘ : : :

‘

INDEX. 553

PAGE
Loch Laggan, Limestone of : : : : : . A35
Loch Lomond, Contortions in the Mica Slate at . 6 ° A38
Logging Rock of Cornwall, Description of the. " . 67
London Clay, Description of the : A : 3 : 187
#ondon Gravel, Remarks onthe . : : A 3 : 234
Lorn, Puddingstone of : : ° ‘ : . : 264
Mac Cuttocn, Dr. On certain products obtained in the Dis-
tillation of Wood, with some account of Bi-
tuminous Substances and Remarks on Coal b
—_— On the Granite Tors of Cornwall . . 66
~————— Remarks on the vitrified Forts of Scotland 235
_— On the Sublimation of Silica A 975
—_— ———— On the Junction of Trap and Sanstone
at Stirling Castle. : x : SOX
——-~————— Miscellaneous Remarks accompanying a
Catalogue of Specimens . . . 388
pee Remarks on several] parts of Scotland which
exhibit Quartz Rock, and on the nature
and connexion of this Rock in general . 450
oe On Staffa : - ‘ : 4 ; 501

: On Vegetable remains preserved in Chalcedony 510
Macles of Oxyd of Tin : . : . . : ° 366
Magnesian Limestone of the Isle of Man : 2 . A3
Man, Isle of, Mineralogical Account of the ; : . 29
- General Description of the Extent and Form,

31, 34 ;—Rivers of 34 ;—Compound Rocks in situ, 36 ;—
Compound Rocks not in situ, 46, 50 ;—Simple Minerals

in situ, 50, 58;—Simple Minerals not in situ, 58 ;—
Temperature of Springs, 60 ;—Height of Mountains, 62

Manor Old Vein, in Cornwall, Description of . : : 15k
Mar, District of, Quartz Rock in the m é 2 2 A73
Marble in the District of Assynt . : : : ° 412
Marine Formation over the Chalk, Lower . - : : 181

oe wPper . . : : 215.
Marl of the Isle of Man : 5 ; 54

- under the Pitchstone Porphyry of the and of es gz 408

B54 INDEX.

Marl in the South-east part of England : ; :
Greenish, in the Isle of Wight. . ° :
Chalk, Description of z
Meteorological Observations on the Coast of ue ae
Mica Slate, Contortions of, at Loch Lomond
Mines of Cornwall and Devon, on the economy of the
The nature of the agreements
between ‘the owner of the soil and the mine adventurers
-—- The arrangements between the
partners or adventurers themselves : 5
— The mode of employing and
paying the miners and workmen
The purchase of the cael
employed for carrying on the undertaking. R
— The Sale of the Ores from the
mine adventurers to the Smelting Companies
Mountains in the Isle of Man, Height of the
-— in Labrador : P P « P

Needles, Isle of Wight, Strataat the. . A
Newhaven, Sussex, Strata at ‘ F 3
the Fossils of the
Nodules, Calcareous, in the London Clay .

Siliceous, in the Stone of Tillywhim, Daweh
Nomenclature, the imperfections of in Rocks :
Proposed modifications of in the terms

Gray wacke . 2 bs 9S—444—A48—499

Greenstone and Greenstone Slate . . $93
Hornstone a , : . 7 369
Killas : : 2 : ; - 446—A99
Porphyry A . “ AQ4
Quartz Rock .. A . : é A57--485
Rocks of Transition . : : é AAQ-——470
Sienite ‘ » : - J : 95—419
Trap . : . . 399
North Downs, Hills composing the . 171

INDEX. 555
PAGE
Organic Impressions, a remarkable class of, in Flint 2 <2 328
Paris, Basin of, Description of the ‘ L 161
Parkinson, Mr. J, Observations on some Speshabne of ivr
from Sicily . d : ; ; : ; 277
Peak of Teneriffe, Besant of the d , 286
en Description of an ascent to thie top of the 291
Pebbles of the London Gravel : : - : ° 232
— Concentric . [ ; : 233
Puitires, Mr. W. On the Veins of Cornwall : 2 : 110

A Description of the Oxyd of Tin . 3 336

Plasma, supposed to exist in the Island of Rum X ; AOT
- probably owes its colour to Chlorite 5 : ; 513
Plastic Clay of the South of England . ‘ ‘ : ‘ 185
of the Paris Basin. A G , . 3 200

Pleasure Copper Mine, Description of : : ‘ ; 149
Plumstead, Fossils at. . - 223
Piumbago, a substance resembling, obtained by artitioioks means Q4
Portland Stone, Fossil Alcyonia in the ; : t 385
Porphyry, Objections to the term as commonly tised ; : AQ4
Portsoy, on the Granite Veins at : : : : E A32
Portsmouth, Strata under . ; : : : 189
Prase, a variety of, found in the Island of ina : - 392
Prince George Copper Mine, Description of ‘ : , 146

Purbeck, Isle of, Freshwater Formation of the. A : 166

Quadrupeds, Fossil Bones of, in the South of England . : Q44

Quartz Rock,

Quartz, granular, called Grey Weathers : ¢ gor
found in Scotland, and on the iitare aed Cor-
nexion of this Rock in general : ’ ohm
its principal modifications 5 . : 453—A80
is a mechanical deposit . , é P A55—ASS
lies under primitive rocks ‘ . : 2 456
alternates with primitive rocks, . 463—A70—486
peculiar appearance of the mountains composed of 458
of Assynt 4 ; if ; : . ‘ ABS
of Schihallien ; ? : 2 : : AGG
of the District of Mar . ; oe ae , A71

4a

556 INDEX.

; PAGE
Quartz Rock of the District of Appin : ; . . AT3
—_—— Arisaig A73
—- of the Island of Sky AT3
——-— of Tyndrum, containing galena 479

—_—_—---——— Schistose, in the group of mountains called
Ben-na-Vear, Argylleshire ‘ 475
Reading, Strata at . ‘ : 198
Rock-Salt, the Brine Suilen at Deoiteich derived pny 98
Rona, Island of, Mineralogical Observations on the 391
Rotherhithe, Strata at . ( . 197
Rum, Island of, Mineralogical Qbiarssitionsrs on the 401
Rutile, found near Killin ‘ A37
Ryegate Fire Stone, Description of the 166
St. David’s, On the Mineralogy of the neighbourhood of 79
Sand, White, of Alum Bay F 1gs5
- Green, over the Chalk : i 187
- Vitrified, supposed to be the effect of lishtaind i 531
Sandstone, Old Red, the Droitwich Brine Springs occur in the 95
cuts off the Coal Measures at Bradford 283
——_——--—under the Chalk in the South of England . 166
—-—- over the Chalk in the South of England 227
Sappare, found at Boharm : 430
Schihallien, Mountain of, Rocks composing the AGG
Septaria in the London Clay . 187
Sheppey, Isle of, Description of the : 192
Shiant Isles, Description of the. : . boa 394
Silica, on the sublimation of ; : J 275

—Appearances of a partial solution of, on the hes a
some Rocks . 392
Silicified Wood, in the fiona oe fige , : ; A08
Sky, Island of, Quartz Rock in the . : : . ° A7T3
Slaty Rock, peculiar kind of, near St. Devitt S : ° 79—85
South Downs, Hills composing the é 171
Springs, Temperature of, in the Isle of Man ; ‘ . 60
Staffa, Remarks on : . : ° . ° . 501

INDEX. 557

. PAGE
Staffa, a bed of alluvial matter on the surface of ; . 506
Srernnaver, the Rev. Mr. Notice relative to the Geology of

the Coast of Labrador . ‘ : : ; x A8$
Stifford, Strata at : 4 : - ; 196
Stirling Castle, Junction of the tap ret Rene an at : 305

Spheroidal Forms in the structure of Rocks, and their tendency to
assume these forms when decomposing, Observations on the 76

Stonehenge, Nature of the Stones at ; ‘ - : : 225
Stream Tin, Occurrence of in Cornwall : : : 342
Strata, General. Order of the, in the South-east part of England 166

— posterior to the London Clay. : : : : 169
die ebbifizion:, near Portsmouth, Strata at , : sae 2 189
Sulphur of Teneriffe. , ¢ ; 3 : ic 299
Salphuret of Tin found in ee ae 4 : : ; 4 343
Syenite, associated with Mica Slate 7 " ; , ; A437

Tayior, Mr. J. On the Economy of the Mines of Cornwall and Devon 309

Leneriffe, island of, some account of the : : ; : 286
Tides, great height.of, on the Coast.of Labrador . i : AQA
Lin, Oxyd of, Deeapeon of the . : ‘ : - 336
: Not.confined to primitive Hock: : é : 338

—————— Uniformity of the crystalline forms of in parti-
cular Veins , é ; : z 339
—_—_———— Alluvial Depositions of thie : Z ; . 342
—— ———— Rocksthat contain the . : C ¢ , 343
——_—_——_—- Specific Characters of the : : : 350
eee Primitive Crystal and Modifications of ‘tie p S51
: —— Macles of the. ‘ ‘ , : 366
Tin Croft Copper and Tin Mine, Desatiption of 3 ‘ . 152
Tol Carn Copper Mine, Description of ; : ; j 155
Tourmaline, in the Granite of Portsoy i F A33
Peculiar appearances in some Gesstels a : A33—A34
Transition Rocks, Objections to such a division. ; AA9—~486.

‘Trap and Sandstone, Junction of, and Induration of the Sandstone 305
‘

Vegetable Remains found in Chalcedony : : - s 510
-——_—_—__ ———_——- Mode ofdetccting . 518

4a.Q2

558 INDEX.
; PAGE
Veins of Cornwall, Description of the : i ‘ 110
— Direction and length of the 113
——- —. Underlie of the 114
—_-—_—_—_—-—_—_ Depth of the . : : 115
—— —_ —_ ——_ —— Width of the { 3 116
—_—___—__———. Denominations of the Metalliferous 117
—_—____—. —— Symptoms in the 120
——-— Discovery of the . f ° : 123
——_—_—_—+—_——. Contents of the Metalliferous 126
—_—_——_———_— North and South, or Cross Courses 133
—_ —__——__—— Slide P F : ‘ ¢ d 136
ee Heave of the . t 137
——————. Feeder 138—Leader 138—the eunne’ 139
Vein of Limestone and Basalt traversing Amygdaloid . 440
Vitreous Tubes found near Drigg ; J 4 528
Vitrificd Forts of Scotland, on the ' , . . 255
——-— Fort of Dun Mac Sniochain 257
———- of Craig Phadric : 270
——-——— of Amworth : ; ¢ 272
Vitrified Wall of Gatacre House : ‘ 273
Vixen Torr, on Dartmoor, Description of the 70
Volcanic Rocks of the Island of Teneriffe 288
Walton, in Essex, Cliffs at. ‘ ‘ . 199
Water, Action of, on Turf or Busdcecad Wood, converting
them into substances capable of yielding Bitumen on
Distillation ‘ é ; 19
Wavellite, found in the Shiant Isles 397
Wesstrer, Mr. T. On the’ Freshwater Hilinaioie in a Isle
of Wight, with some Observations on the Strata over the
Chalk in the South-east part of England 161
————-——— On some new varieties of Fossil Alcyonia ST
Western Lines, Isle of Wight, Fossils at 380
Wight, Isle of, On the Chalk and more recent Strata of ee 161
Wolfram, in the Granite of Rona 391
Wood, on certain products, obtained in the Distillation of I
Wood Tin, a particular form of the Oxyd SAL
Woolwich, Strata at. ‘ ’ : ; . 176—195—221

London: Printed by W. Phillips, George-yard, Lombard-street.

CAD OF SCIENCES LIBRARY

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