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THE LIBRARY
OF

THE UNIVERSITY

OF CALIFORNIA

PRESENTED BY

PROF. CHARLES A. KOFOID AND
MRS. PRUDENCE W. KOFOID




PETRALOGY.



vcntt5C on llocfts,



BY



^ PINKERTON.



VOL. I.



Uontron:



PUBLISHED BY WHITE, COCHRANE, AND CO.

1800,

J*. Af /}' V; / /. 7V A/ ^- ^W'^*

. ____ , 7. ' ' '-*



PETRALOGY.
A TREATISE ON ROCKS.



INTRODUCTION.

1. Illustrations of the present Arrangement.

J. HE study of natural history has been divided by the most
esteemed authors, and by the general voice, into three King-
doms, the Animal, Vegetable, and Mineral. These have
again been subdivided into Classes, Orders, Genera, Species,
and Varieties. These terms may be considered as strictly pro-
per with regard to animals and vegetables ; but as their com-
mon meaning implies a vital or animated principle, their
application to the mineral kingdom, to which they have
passed rather by habitual use than after a due examination,
has become dubious ; and has given rise to many variations
and contradictions, and not a little obscurity. It is confessed
that human systems have but a very remote connexion with
the great operations of Nature, and are to be regarded as
mere artificial memories : hence in mineralogy some eminent
writers entirely reject Genera j while others, with Dauben-
ton, say that there are no Species ; and Dolomieu has in vain
exhausted his acuteness and science to prove that real Species
exist in this department. With all his metaphysical prolixity
he has no disciples in this doctrine j and the idea of a Species
remains dark, even to the most enlightened minds, because
it is false and unnatural, as in the other branches of natural
history a Species produces a similar progeny.
VOL, i. a.






Division of
natural
history.



Some termi
inapplicable.



INTRODUCTION.

Other Thus^some \vriters have been contented to divide minerals

into* Classes, Orders, and Genera j while others, instead of
the last, have only Species. Soipe have Varieties j and Wer-
her, with a truly German want of taste, has added Sub-specief
and Sub-varieties ; while, as the terms are merely arbitrary,
he might have chosen far more classical words to express his
distinctions.

The cause of this embarrassment, as has often happened in
the progress of science, is owing to the pursuit of a routine,
of a form, which has become antiquated 3 while the dis-
coveries being wholly new, a new phraseology was indispen-
sable. Thus in natural history Linnaeus having established
the received classification in botany and zoology, the same
terms were introduced into mineralogy, without the simple
reflection that the subjects were wholly distinct: for the
terms, indicating animal and vegetable life, could not without
manifest absurdity be applied to dead and inert matter. The
consequence was, that as the terms conveyed no idea they
were used indifferently, and what was Class with one author
became Order with another ; while the Genus of a third, as
has been already mentioned, became the Species of a fourth :
and a few of deeper sagacity began at last to doubt the pro-
priety of one or other of these appellations.

In fact the terms class, order, genus, and species, convey
real and vivid ideas of life. We say a class or an order of
men, a genus or species of animals, with complete perspicuity
and propriety. Nor is the transition to plants in the least
violent, as the word species in particular may be here used
with some classical authority. But when applied to minerals
they become wholly arbitrary, and convey none of these sub-
stantial ideas which belong to real knowledge, and which the
mind grasps, so to speak, as solid and tangible : for as the
characteristics are here of a totally different kind from those
of animal or vegetable life, they should be distinguished by
new and appropriate appellations. As we shall never describe
*an animal Trom its texture, fracture, or other distinctions of
minerals, so it is equally absurd to describe these by attri-



INTRODUCTION.

butes which are peculiar to living substances. The terms
become wholly useless if they do not serve to distinguish and
discriminate; and numerals, chemical marks, or any other
arbitrary symbols, would serve the purpose equally well.

The impropriety of the present phraseology is often ad-
mitted, while it is considered as bold and adventurous to
hazard a new series of appellations j but in literature, as in
war, he who shrinks from the path of danger will never attain
the wreath of praise.

In an attempt to establish a new nomenclature of arrange- New system,
ment, the first requisite is, that it be conformable to the
simplicity and harmony of nature j and that it be free from
affectation, as even the novelty itself is apt to displease. For
this purpose it is necessary to revert to first principles, and
if possible to establish the edifice upon foundations univer-
sally admitted. Natural history, as already mentioned, has
been well and popularly divided into three Kingdoms, the
Animal, the Vegetable, and the Mineral. In the two former
the kingdom consists of living subjects, who of course may
be well considered as divided into Classes, Orders, Genera,
and Species j but in the Mineral Kingdom the territory alone
constitutes the subject of discussion. It must therefore be
received as a fundamental truth or axiom, that the mineral
kingdom, being wholly inert, cannot admit distinctions which
belong to vital energy ; and that an identity of appellations
cannot therefore be allowed, either in a grammatical or
philosophical view. But the very term Mineral Kingdom
may of itself lead to a new and more proper nomenclature :
for as a kingdom may be regarded as either vivified with
animal and vegetable life, or as an inert tract of country,
with certain geographical, chorographical, and topographical
divisions ; so the latter point of view can alone apply to mi-
neralogy, while the former belongs to zoology and botany.

This simple induction will, it is hoped, lead of itself to easy
and natural, though new denominations. For what is more
usual than the division of a kingdom into provinces, districts,
domains, &c. ? while, as it would not only be pedantic, but



IV



iNTRQCUfcTION.



Grand
provinces






inadequate to the subject, to carry this species of metaphor
too far, some lesser divisions must be borrowed from the
nature of the objects, as they present themselves to the
observer.

I would propose, therefore, in the present advanced state
of the science, that the mineral kingdom be considered as
divided into three provinces: 1. PETRALOGY, or the know-
ledge of rocks, or stones which occur in large masses,

2. LITHOLOGY, the knowledge of gems and small stones.

3. METALLOGY, or the knowledge of metals. Each of these
branches is even at present so important, and offers such
numerous topics of disquisition and research, that in the
course of no long period a professor of each will appear in

t universities 3 and each might occupy the sole pursuit of an
author who is zealous to make discoveries, or to compose
complete and classical works. One of the chief causes of the
slow progress of the science is, that it is too wide for one
mind ; and as zoology has been divided into ornithology,
ichthyology, entomology, &c. so mineralogy, to be duly stu-
died, should have grand subdivisions.

These provinces may again be viewed as divided into DO-
MAINS, corresponding with the Orders of some writers and
the Genera of others, as the Provinces supply what are called
Classes. This term DOMAIN is preferred to District, &c. as
it not only implies a subdivision of a province, but, in another
acceptation, a ruling or preponderating power, strictly appli-
cable in mineralogy, where it is often the preponderance,
and not the universality, which imparts the denomination.
Thus in the siliceous, calcareous, and other domains, it is
only understood that the denominating portion preponderates,
as few or no rocks are pure, and unmixed with other sub-
stances.

Petrology, a province of mineralogy, may therefore be re-
garded as divided into Twelve .Domains ; of which the first
six, being distinguished by the substances themselves, may
Substantial, be called SUBSTANTIAL: while the remaining six, being distin-
guished by circumstances or accidences of various kinds, may



Domains.



INTRODUCTION.

be called CIRCUMSTANTIAL, or ACCIDENTIAL ; but this last
division is of little moment.

The first six domains of Petralogy comprise, 1. The Si-
derous Rocks, or those in which iron predominates, not in
the comparative quantity when analysed, but in the quality
and essential difference which it imparts. 2. The Siliceous,
denominated as usual from the quantity of silex. 3. The
Argillaceous. 4. The Magnesian : these two are again de-
nominated from predominance. 5. The Calcareous. 6. The
Carbonaceous.

The remaining six domains, derived from circumstances or Accidential
accidences, are, 7. The Composite, or Aggregated Rocks, as
calcareous spar with schorl, quartz, and garnets, felspar and
siderite or hornblende, &c. This domain has often been con-
founded with the granites, however alien from that descrip-
tion. 8. The Diamictonic, or rocks in which the substances
are so completely mingled, that it is difficult, even upon an
analysis, to pronounce which preponderates. 9. The Ano-
malous, or those which contradict the common order of
nature, and present unexpected and unusual combinations.
Some of these domains, though they afford few objects at
present, may, in the progress of the science, be greatly
enriched and enlarged j and the utility of such divisions will
be more perceptible as the study advances towards perfection,
the greatest obscurity at present arising from the want of
necessary subdivisions.

The remaining three domains are generally admitted in
geological works, namely, 10. The Transilient Rocks, an
interesting series, in which one substance gradually passes
into another, as granite into porphyry, trap into wacken,
and the like. 11. The Decomposed Rocks, which gradually
decay into sand, clay, or productive soil. 12. The Volcanic,
which require no other description.

Having thus established the Domains, or Great Divisions, Modes,
of Petralogy, the smaller distinctions can be derived only
from the objects themselves, as we now arrive at what are
by most mineralogic authors denominated Species, though in



VI INTRODUCTION-.

their arbitrary and unnatural systems, as Dr. Townson has
observed, the Genera and Species are often confounded.
" Thus in the improved edition of Linnaeus, the characters
which constitute the Species in gypsum form Genera in the
carbonate of lime; for the pulverulent, fibrous, spathous,
and compact kinds of gypsum form but so many Species,
whilst the pulverulent, fibrous, spathous, and compact kinds
of carbonate of lime form so many different Genera"*
Now these very appearances, which constitute the arbitrary
Species and Genera of former authors, what would they be,
in the eyes of a philosopher or grammarian, except different
modifications, or modalities, of the same substance, and which
by a shorter term may be denominated Modes? Hence the
term MODE, which is universally applicable and unobjection-
able, to distinguish such objects in mineralogy, is here ad-
mitted instead of Species f.

To put the propriety of this new appellation to the test,
examples may be produced of what are called Species by the
most celebrated minemlogic writers. Wallerius, among the
species of garnet, first mentions that of an undetermined
figure, composed of granular particles ; and his next species
is of an undetermined figure, but laminar. What are these
but different modifications, or modes, of the same stone?
His ripe asbestus, consisting of fibres which may be sepa-
rated, forms one species ; while that of which the fibres can-
not be separated constitutes another. What are these but
different modifications of the same substance? In the last
edition of Linnaeus by Gmelin the term modes (modi} has
been applied to various appearances of petrification : but
what are sometimes called Genera, and sometimes Species (as
already observed from Dr. Townson), are, in strict language,
mere modifications of matter. If we pass to one of the most
exact of the French mineralogists, we shall find the sapphire
arranged as the tenth species of the siliceous, and the topaz

* Philosophy of Mineralogy, p. 1*3.
f Et&ef implies modus, as well as species.



INTRODUCTION.

as the eleventh j while in fact they merely differ in colour.
In the magnesian division, what are bole, fullers' earth, &c.
but different modifications of the same mixtures ? Mr. Kir-
wan presents no exact arrangement, but uses Classes, Fami-
lies, and Branches, in such a manner as greatly to perplex
the reader : but all his species and families are mere modifi-
cations, and the simple division into modes would convey a
far clearer idea*.

The term Mode is therefore here adopted instead of what
are called Genera by some writers, and Species by others j
this uncertainty, of itself, having demonstrated that there
are neither Genera nor Species in mineralogy.

But as it is now universally allowed by all mineralogists, Chemical,
however different their systems, that the whole science rests
upon chemistry alone, and that no certainty can be found
except by chemical analysis, the word Mode, as finally admit-
ted into the present system, must be chiefly understood to
refer to the CHEMICAL MODE OF COMBINATION, upon which
the nature of the substances, as is now allowed by the
greatest chemists, is yet more dependent, than even upon the
ingredients combined. It is the MODE OF COMBINATION
which distinguishes a diamond from carbon, and a sapphire
from argil combined with a little iron : the essence of a mi-
neral consisting not only in the constituent earths, but in
the peculiar way in which the mixture is modified; and this
modal influence also prevails in many artificial mixtures and
compounds -K In short, the pretended species of former
authors are merely different MODES OF COMBINATION.

* Dr. Thomson, in his valuable Chemistry, has preferred the families of
Werner, and discarded the old genera; iv. 247. Mr. Jameson tells us that
there is in fkct only ONE species in mineralogy, namely the globs; but even
this may be doubted till it shall have produced another, at least as round and
as wicked.

f- This may be exemplified from the Arragon spar, in which the ingre-
dients are the same as in calcareous spar, yet it differs in many properties, not
from composition but from modification, the gangart of red clay or gypsum pro~
pably imparting a tincture of iron.



Vlll



INTRODUCTION.



Structures. This, the most important part of the arrangement,, being
thus borrowed from chemistry, which, like a guardian angel,
should always hover round and direct the labours of mine-
ralogy -, the other subdivisions only require a characteristic
clearness to assist the memory (the chief object in any system
of natural history), and an appropriation to the subject, so
as to satisfy the judgement and imagination. From the
earliest productions of Linnseus to the present time, the
word STRUCTURE has been applied, with classical propriety,
to denote a most striking and characteristic distinction be-
tween mineral substances, whether on a great or on a small
scale. Linnseus has observed that there are only three great
roads which can conduct the curious traveller through the
mineral kingdom 5 that of Physics, or Natural Philosophy,
which treats of the obscure generation of stones -, that of
Natural History, which examines their evident structures;
and that of Chemistry, which considers their analyses*. A
term thus strictly appropriated, and, as it were, consecrated
to the science, has therefore been selected for the next cha-
racteristic subdivision.

Aspects. But as Werner and his disciples not only admit the various

earths as so many Genera j and their Modes, or the modifi-
cations of the mixtures, and even colours, as so many Spe-
, cies 5 but also what are, with great penury and uncouthness



* " Via triplex tantum per Regnuna Lapideum curiosos ducit : Physica quae
descendit per Lapidum obscuras Geneses. Naturalis quae exeurrit per Lapidarn
apricas Structuras. Chemica quae adscendit per Lapidum destructives Analyses."
Linn. Min. a Gmelin, p. 14.

In the edition of his System, Holmue 1768, Linnaeus has the following
among the external characters : " The Structure, foliated, fissile, convergent,
in fragments." Werner says limestone is of & simple structure. Dr. Thomson,
in his valuable Chemistry, says that gneiss differs in its structure from granite;
and that the structure of mica slate is thinly schistose. It is chiefly judged by
the fracture ; and is as applicable to small specimens, if well chosen, as to the
rocks themselves : it may be earthy, compact, columnar, large-grained, &c. &c.
In classical Latin structura is not only applied to the largest edifices, but in very
minute senses, as structura versuum, structura verlvrwn.






INTRODUCTION. IX

of language, styled Sub-species, with still smaller divisions of
Varieties and Sub-varieties; so there remains a necessity for
more minute discriminations in this new arrangement. In
his excellent and elaborate system of chemistry Dr. Thomson
seems to have hit upon the just and natural term, when he
uses the word ASPECT as a chief characteristic. " The parti-
cular characters, says he, are the following: 1, Aspect of
the surface j 2. Aspect, of the fracture j 3. Aspect of the
distinct concretions ; 4. General aspect, &c." As therefore
the most important object in the study of minerals is to
distinguish them by their external characters, and especially
by those apparent to the eye, the aspect becomes of such
radical importance that it may with the greatest propriety
be admitted into the distinctive nomenclature. The verb
aspecto signifies to view with great attention or earnestness,
and aifords a hint to the student that these subdivisions called
aspects require strict attention and discrimination. Thus,
while the Mode chiefly expresses the difference of chemical
composition, &c. and the Structure the grand characteristic,
the Aspect refers to more minute features. The term variety Varieties, &c.
is unobjectionable, as it is equally applicable to objects of ani-
mated or inert matter j and diversity may be used to imply a
still greater difference than the variety presents. A very
faint shade of difference might, if necessary, be called a
lineament.

Having thus briefly explained the present system, the
result of the reflections and meditations of many years (for
it is well known that simplicity in a plan, or a machine, as
it is the most perfect quality, so it is the last which is dis-
covered), it may not be unnecessary to illustrate its necessity
and utility by some further observations.

The embarrassments of the former systems cannot be more
forcibly evinced than by the following discussion by Wer-
ner, in his important work on the External Characters of
Minerals.

" I shall here add some remarks upon the division or natu- Werner's
ral order of bodies in general, as well for example, as expla-

* * * '

r-



X INTRODUCTION,

nation of this paragraph. When we wish to arrange st,
system ; or, which is the same thing, when we wish to deter-
mine the natural order of bodies, we must first find a princi-
ple on which to ground that determination. But this prin-
ciple should be taken from the nature of the bodies, as being
the consequence of it ; and since it is by that we determine
in what degree these bodies are similar or unlike, it should
show equally the principle of their difference. We perceive
in these bodies certain resemblances which are the foundation
of their differences, and as these several resemblances are
more or less allied or varied, so it is with the bodies which
produce them ; this then is the only principle on which we
can determine the class or order of these natural bodies. It
remains now to show where relations are found in natural
bodies ; but here we find a difference between them, for they
are divided into two principal species, these relations in one
consisting in the conformation, and those of the other in the
composition. The first comprising animals and vegetables,
as the second embraces meteors and the mineral kingdom.
It is true that, as being natural bodies, they are at the same
time aggregated and composed j but the first are formed of
parts differing one from another, and which we call organs t
which constitute their relations -, the last, on the contrary,
are simple, or formed of similar parts, and consequently can
have no relationship in their aggregation. Now, as they
nevertheless really differ, that is to say they have different
characters, we must endeavour to recover them in some man-
ner j and, as I have already said, this can be only by their
composition. As a proof of which, when I have divided into
as small parts as possible, a substance of one of the first two
kingdoms, for example a plant, I cannot affirm that each
separate part is the same plant -, because not any of these
parts have the same relationship as in their state of aggrega-
tion, that is to say in their entire plant, and that it is this
total which forms this or that plant. It is then in this re-
union that we must show the character of this plant, since it
is destroyed by the division. On the contrary, I can divide



INTRODUCTION 1 ,

any mineral whatever as I will j the smallest particle that can
be obtained by mechanical instruments, will always be the
same mineral ; for each particle, be it ever so small, preserves
the same properties as would the whole in their collective
state. These qualities consequently are not confined to the
aggregate, since they do not cease with it. But if I destroy
the composition of a mineral, that is to say, if 1 reduce it to
its constituent parts, then each separate constituent part is
no longer the same mineral, because it has not the same pro-
perties as when in composition. When, for example, I de-
compose the glassy silver ore (glaserz sproede) in separating
the silver, the sulphur, and the arsenic ; or cinabar, in with-
drawing separately the mercury and the sulphur ; I cannot
then say of these constituent parts, that they are still the
mineral in the composition of which they formerly existed.
Thus there is no doubt that the relations of minerals consist
in their composition, since they cease with it.

f< In the second place, the gradation of natural bodies into
one another (which is the most infallible sign of the natural
order), shows us that the different relations of the bodies of
the two former kingdoms consist in their aggregated state, by
means of which they pass as it were the one into the other ;
as likewise that the relations of bodies of the two latter
kingdoms, that is to say, minerals and meteors, are in their
composition, because it is only by reason of this composition
that they pass the one into the other : as, for example, in the
mineral kingdom, the glassy silver ore passes to another kind
(the brittle) ; this to the red silver ore (Rothgultig) ; and
this again to the white silver ore (Weissgultige) ; according
as to the first is joined arsenic, to the second raw iron, and
to the third copper. In fine, we have a sufficient number of
examples of passages of the animal kingdom into the vegeta-
ble, and of the mineral kingdom into that of meteors ;
whereas, with regard to the passage of the animal and ve-
getable kingdoms into the mineral, we have no proof: and
indeed, as we have before observed, that can never be, be-
cause in the first the natural order of relations follows their



INTRODUCTION,

aggregation, while in the latter it follows their compo-
sition.

< ' But the following question may still be raised concern-
ing the order and system of minerals : * As it is certain that
minerals, when their composition changes, are also changed
in their exterior, cannot we in this exterior find characters
to determine their natural order or sequence, as well as those
that are taken from their affinities of composition ?' Here
is the answer : We can, it is true, discover the different rela-
tions of composition in minerals by their different external
characters, when they are both determined beforehand -, but
we cannot discover the order of these conformities, because
nature employs indifferently sometimes one character, some-



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