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formed by fusion; I hope that I shall give the most satisfactory proof
of that truth: Consequently, here at least there is no occasion for the
action of water in dissolving siliceous substances in one place, in
order to concrete and crystallise it in another.

In these cavities of the solid granite rock, where crystal is found
regularly shooting from a basis which is the internal surface of the
cavity, we find the other constituent substances of the granite also
crystallised. I have those small cavities, in this rock, from the island
of Arran, containing crystal, felt-spar, and mica, all crystallised in
the same cavity[34]. But this is nothing to the _druzen_ or crystalline
concretions, which are found in a similar manner among metallic and
mineral substances in the veins and mines; there, every species of
mineral and metallic substance, with every variety of mixture and
composition, are found both concreted and crystallised together in every
imaginable shape and situation.

[Note 34: The Chevalier Dolomieu makes the following observation.
Journal de Physique, Juillet 1791.

"J'ai été étonné de trouver au centre d'un énorme massif de granit, que
l'on avoit ouvert avec la poudre pour pratiquer un chemin, des
morceaux, gros comme le poing et au dessous, de spath calcaire blanc,
très-effervescent, en grandes écailles, ou lames entrecroisées. Il
n'occupoit point des cavités particulières, il n'y paroissoit le
produit d'une infiltration qui auroit rempli des cavités, mais il étoit
incorporé avec les feld-spath, le mica, et le quartz, faissoit masse
avec eux, et ne pouvoit se rompre sans les entraîner avec lui."

This great naturalist is convinced that the spar had not been here
introduced by infiltration, although that is the very method which he
employs to form concretions, not only of spar but of crystal, zeolite,
and pyrites, in the closest cavities of the most solid rocks of
basaltes. These four substances in this stone were so mixed together
that nothing but the fusion of the whole mass could explain the state in
which they appeared; but, thinking that such a supposition could not
be allowed, this naturalist, like a man of science when his data fail,
leaves the matter without any interpretation of his own. This however is
what he has not done in the case of basaltes, or that which he mistakes
for proper lavas, as I shall have occasion to show.]

Here is an infinite operation, but an operation which is easily
performed by the natural arrangement of substances acting freely in
a fluid state, and concreting together, each substance, whether more
simple or more compound, directing itself by its internal principle of
attraction, and affecting mechanically those that are concreting around
it.

We see the very same thing happen under our eye, and precisely in the
same manner. When a fluid mass of any mineral or metallic substance is
made to congeal by sudden cooling on the outside, while the mass within
is fluid, a cavity is thus sometimes formed by the contraction of the
contained fluid; and in this cavity are found artificial _druzen_, as
they may be called, being crystallizations similar to those which the
mineral cavities exhibit in such beauty and perfection.

Petrification and consolidation, in some degree, may doubtless be
performed, in certain circumstances, by means of the solution of
calcareous earth; but the examples given by M. de Luc, of those bodies
of lime-stone and agate petrified in the middle of strata of loose or
sandy materials, are certainly inexplicable upon any other principle
except the fusion of those substances with which the bodies are
petrified[35].

[Note 35: Vid. Lettre 28 et Lettre 103. Lettres Physiques et Morales.]

This subject deserves the strictest attention; I propose it as a
touchstone for every theory of petrification or perfect consolidation.
First, There are found, among argillaceous strata, insulated bodies of
iron-stone, perfectly consolidated; secondly, There are found, in strata
of chalk and lime-stone, masses of insulated flints; thirdly, There
are found, in strata of sea sand, masses of that sand cemented by a
siliceous substance; fourthly, In the midst of blocks of sand-stone,
there are found masses of loose or pure sand inclosed in crystallised
cavities; and in this sand are found insulated masses of crystallised
spar, including within them the sand, but without having the sparry
or calcareous crystallization disturbed by it. There are also other
globular masses of the same kind, where the sparry crystallization is
either not to be observed, or appears only partially[36]: And now,
lastly, In strata of shell-sand, there are found masses of consolidated
lime-stone or marble. In all those cases, the consolidated bodies are
perfectly insulated in the middle of strata, in which they must of
necessity have been petrified or consolidated; the stratum around the
bodies has not been affected by the petrifying substance, as there
is not any vestige of it there; and here are examples of different
substances, all conspiring to prove one uniform truth. Therefore, a
general theory of petrification or consolidation of mineral bodies must
explain this distinct fact, and not suffer it any longer to remain a
_lusus naturae_.

[Note 36: Mem. de l'Académie Royale des Sciences, an. 1775.]

Let us now consider what it is that we have to explain, upon the
supposition of those concretions being formed from a solution. We have,
first, To understand what sort of a solution had been employed for the
introducing of those various substances; secondly, How those concretions
had been formed from such solutions within those bodies of strata; and,
lastly, How such concretions could have been formed, without any vestige
appearing of the same substance, or of the same operation, in the
surrounding part of the stratum. Whatever may be the difficulty
of explaining those particular appearances by means of fusion and
mechanical force, it is plainly impossible to conceive those bodies
formed in those places by infiltration, or any manner of concretion from
a state of solution.

Naturalists, in explaining the formation of stones, often use a chemical
language which either has no proper meaning, or which will not apply to
the subject of mineral operations. We know the chemical process by which
one or two stony concretions may be formed among bodies passing from
one state to another. When, therefore, a change from a former state of
things in mineral bodies is judged by naturalists to have happened, the
present state is commonly explained, or the change is supposed to have
been made by means of a similar process, without inquiring if this had
truly been the case or not. Thus their knowledge of chemistry has led
naturalists to reason erroneously, in explaining things upon false
principles. It would be needless to give an example of any one
particular author in this respect; for, so far as I have seen, it
appears to be almost general, every one copying the language of another,
and no one understanding that language which has been employed.

These naturalists suppose every thing done by means of solution in the
mineral kingdom, and yet they are ignorant of those solvents. They
conceive or they imagine concretions and crystallizations to be formed
of every different substance, and in every place within the solid body
of the earth, without considering how far the thing is possible which
they suppose. They are constantly talking of operations which could only
take place in the cavities of the earth above the level of the sea, and
where the influence of the atmosphere were felt; and yet this is the
very place which we have it in our power to examine, and where, besides
the stalactite, and one or two more of the same kind, or formed on the
same principle, they have never been able to discover one of the many
which, according to their theory, ought always to be in action or
effect. So far from knowing that general consolidating operation, which
they suppose to be exerted in filling up the veins and cavities of the
earth by means of the infiltrating water of the surface, they do not
seem fully to understand the only operation of this kind which they see.
The concretion of calcareous matter upon the surface of the earth is
perhaps the only example upon which their theory is founded; and
yet nothing can be more against it than the general history of this
transaction.

Calcareous matter, the great _vinculum_ of many mineral bodies, is in
a perpetual state of dissolution and decay, in every place where the
influences of air and water may pervade. The general tendency of this
is to dissolve calcareous matter out of the earth, and deliver that
solution into the sea. Were it possible to deny that truth, the
very formation of stalactite, that operation which has bewildered
naturalists, would prove it; for it is upon the general solubility of
calcareous matter exposed to water that those cavities are formed, in
which may be found such collections of stalactical concretion; and the
general tendency of those operations is to waste the calcareous bodies
through which water percolates. But how is the general petrifaction or
consolidation of strata, below the surface of the sea, to be explained
by the general dissolution of that consolidating substance in the
earth above that level? Instead of finding a general petrifying or
consolidating operation in the part of the earth which we are able to
examine, we find the contrary operation, so far at least as relates to
calcareous spar, and many other mineral bodies which are decomposed and
dissolved upon the surface of the earth.

Thus in the surface of the earth, above the level of the sea, no
petrifying operation of a durable nature is found; and, were such an
operation there found, it could not be general, as affecting every kind
of substance. But, even suppose that such a general operation were found
to take place in the earth above the level of the sea, where there might
be a circulation of air and percolation of water, How could the strata
of the earth below the level of the sea be petrified? This is a question
that does not seem to have entered into the heads of our naturalists
who attempt to explain petrifaction or mineral concretion from aqueous
solutions. But the consolidation of loose and incoherent things,
gathered together at the bottom of the sea, and afterwards raised
into rocks of various sorts, forms by far the greatest example of
petrification or mineral operation of this globe. It is this that must
be explained in a mineral theory; and it is this great process of
petrifaction to which the doctrine of infiltration, whether for the
mechanical purpose of applying cohesive surfaces, or the chemical one of
forming crystallizations and concretions, will not by any means apply.

Nothing shows more how little true science has been employed for the
explanation of phenomena, than the language of modern naturalists, who
attribute, to stalactical and stalagmical operations, every superficial
or distant resemblance to those calcareous bodies, the origin of which
we know so well. It is not a mere resemblance that should homologate
different things; there should be a specific character in every thing
that is to be generalised. It will be our business to show that, in the
false stalactites, there is not the distinctive character of those water
formed bodies to be found.

In the formation of stalactical concretions, besides the incrustation as
well as crystallization of the stony substance from the aqueous vehicle
by which it had been carried in the dissolved state, we have the other
necessary accompanyments of the operation, or collateral circumstances
of the case. Such, for example, is that tubular construction of the
stalactite, first formed by the concretion of the calcareous substance
upon the outside of the pendant gut of water exposed to the evaporation
of the atmosphere; we then see the gradual filling up of that pervious
tube through which the petrifying water had passed for a certain time;
and, lastly, we see the continual accretion which this conducting body
had received from the water running successively over every part of
it. But among the infinite number of siliceous concretions and
crystallizations, as well as those of an almost indefinite variety of
other substances, all of which are attributed to solution, there is not
the least vestige of any collateral operation, by which the nature of
that concretion might be ascertained in the same manner. In all
those cases, we see nothing but the concreted substances or their
crystallizations; but, no mark of any solvent or incrusting process is
to be perceived. On the contrary, almost all, or the greatest part
of them, are so situated, and attended with such circumstances, as
demonstrate the physical impossibility of that being the manner in which
they had been concreted; for, they are situated within close cavities,
through which nothing can pervade but heat, electricity, magnetism,
etc.; and they fill those cavities more or less, from the thinnest
incrustation of crystals to the full content of those cavities with
various substances, all regularly concreted or crystallised according to
an order which cannot apply to the concretion of any manner of solution.

That there is, in the mineral system, an operation of water which may
with great propriety be termed _infiltration_, I make no doubt. But this
operation of water, that may be employed in consolidating the strata
in the mineral regions, is essentially different from that which is
inconsiderately employed or supposed by mineralists when they talk
of infiltration; these two operations have nothing in common except
employing the water of the surface of the earth to percolate a porous
body. Now, the percolation of water may increase the porousness of that
body which it pervades, but never can thus change it from a porous to a
perfect solid body. But even the percolation of water through the strata
deposited at the bottom of the sea, necessarily required, according to
the supposition of naturalists, must be refused; for, the interstices of
those strata are, from the supposition of the case, already filled with
water; consequently, without first removing that stagnant water, it is
in vain to propose the infiltration of any fluid from the surface.

This is a difficulty which does not occur in our theory, where the
strata, deposited at the bottom of the sea, are to be afterwards heated
by the internal fires of the earth. The natural consequence of those
heating operations may be considered as the converting of the water
contained in the strata into steam, and the expulsion of steam or
vapour, by raising it up against the power of gravity, to be delivered
upon the surface of the earth and again condensed to the state of water.

Let us now conceive the strata, which had been deposited at the bottom
of the sea, as exhausted of their water, and as communicating with the
surface of the earth impregnated with water. Here again we have the
power of gravity to operate in carrying down water to that place which
had been before exhausted by the power of heat; and in this manner, by
alternately employing those two great physical agents, we cannot doubt
that nature may convey soluble substances from above, and deposit them
below for the purpose of consolidating porous bodies, or of filling with
saline and earthy matter those interstices which had been originally
filled with water, when the strata were deposited at the bottom of the
sea. How far any marks of this operation may be perceived, by carefully
examining our mines and minerals, I know not; I can only say that, on
the contrary, whenever those examined objects were clear and distinct,
with the concomitant circumstances, so as to be understood, I have
always found the most certain marks of the solid bodies having concreted
from the fluid state of fusion. This, however, does not exclude the case
of infiltration having been previously employed; and I would intreat
mineralists, who have the opportunity of examining the solid parts of
the earth, to attend particularly to this distinction. But do not let
them suppose that infiltration can be made to fill either the pores or
veins of strata without the operation of mineral heat, or some such
process by which the aqueous vehicle may be discharged.

Not only are mineral philosophers so inconsiderate, in forming
geological theories upon a mere supposition or false analogy, they
have even proceeded, upon that erroneous theory, to form a geological
supposition for explaining the appearances of strata and other stony
masses in employing a particular physical operation, which is, that
of _crystallization_[37]. Now crystallization may be considered as a
species of elective concretion, by which every particular substance, in
passing from a fluid to a solid state, may assume a certain peculiar
external shape and internal arrangement of its parts, by which it is
often distinguished. But, to suppose the solid mineral structure of the
earth explained, like an enigma, by the word _crystallization_, is to
misunderstand the science by which we would explain the subject of
research; and, to form a general mineral theory thus upon that term,
is an attempt to generalise without a reason. For, when it were even
admitted that every solid body is crystallised, we thus know no more of
the geology of this earth, or understand as little of the general theory
of mineral concretion, as we did before; - we cannot, from that, say
whether it be by the operation of solution or of fusion which had
produced the perceived effect.

[Note 37: Journal de Physique; Avril 1753.]

M. de Carosi has wrote a treatise upon certain petrifactions[38]. In the
doctrine of this treatise there is something new or extraordinary. It
will therefore be proper to make some observations on it.

[Note 38: Sur la Génération du Silex et du Quartz en partie.
Observations faites en Pologne 1783, à Cracovie.]

The object of this treatise is to describe the generation of silex and
quartz, with their modifications or compositions, formed within mineral
bodies of a different substance. The natural history contained in this
little treatise is well described and sufficiently interesting. But It
is chiefly in order to examine the means which, according to the theory
of this treatise, are employed in petrifying bodies, that I consider it
in this place.

The first section of this treatise has for title, _Génération du Caillou
et du Quartz de la terre calcaire pure_. It may be worth while to
compare the natural history of this part of the earth with the flint and
chert found in our chalk and lime-stone countries. I shall therefore
transcribe what is worth observing upon that subject (p. 5.).

"Nous rencontrons chez nous dans les parties le plus montagneuses, et
les moins couvertes de terreau, ou tout-au plus de sable, entre de purs
rochers calcaires une quantité incroyable de cailloux (silex) tant en
boules, que veines, couches, et débris. Au premier coup d'oeil l'on
s'imagine que ce font des débris de montagnes éloignées, qui y furent
amenés par les eaux, mais, en examinant la chose de plus pres, on est
convaincu, que ce sont tout au contraire, des parties détachées des
montagnes de la contrée. Car il y a sur presque toute l'étendue de nos
montagnes calcaires une couche, ou pour mieux dire, un banc composé
de plusieurs couches de base calcaire, mais qui ou sont parsemées
irrégulièrement de boules, de rognons, de veines, et de petits filons
de silex, ou qui contiennent cette pierre en filon, veines, et couches
parallèles, et régulièrement disposées. Les boules et rognons de silex
y font depuis moins de la grandeur d'une petite noisette, jusqu'au
diamètre de plus de six pouces de nôtre mesure. La plupart de ces boules
tant qu'elles sont dans l'intérieur caché de la roche vive, et qu'elles
n'ont rien souffert de l'impression de l'air, ont, pour l'ordinaire, une
croûte de spath calcaire, au moyen de la quelle elles sont accrues à
la roche mere; ou pour mieux dire la croûte spatheuse fait l'intermède
entre le silex, et la roche calcaire, par où se fait le passage de l'une
à l'autre. Mais ceci ne vaut que de boules de silex entièrement formées.
C'est dont on peut même se convaincre à la vue, par beaucoup de pierres
dont le pavé de la ville de Cracovie est composé. Mais là, ou le silex
n'est pas encore entièrement achevé, la croûte spatheuse manque, en
revanche on y voit évidemment le passage par degrés successifs de la
roche calcaire au silex qui y est contenu, et les nuances de ce passage
sont souvent si peu marquées que même les acides minéraux ne suffisent
pas à les déterminer, ce n'est que le briquet, qui nous aide à les
découvrir. On voit bien ou la pierre calcaire s'enfonce en couleur, l'on
s'apperçoit, où sa dureté, ses cassures changent, mais, comme elle y
souffre encore quelque impression des acides, l'on ne sauroit déterminer
au juste le point, ou elle a déjà plus de la nature du silex, que de
celle de la chaux, qu'en la frappant du briquet.

"Tels sont les cailloux en boules et rognons avant leur état de
perfection, il y aura même au milieu une partie de pierre calcaire non
changée.

"Ceux au contraire, ou la nature à achevé son ouvrage, ont une croûte de
chaux endurcie, et sont purement du silex fini, mais de toutes couleurs,
d'un grain et d'une texture plus ou moins fine, qui passe assez souvent
par degrés dans les différentes variétés du noble silex. Ils ont, pour
l'ordinaire, dans leur intérieur une cavité, mais pas toujours au
centre, et qui vient apparemment de la consommation de cette partie
calcaire qui y resta la dernière, et n'en fut changée ou dissolute et
séparée, que lorsque le reste du silex étoit déjà entièrement fini. Ces
cavités sont toujours, ou enduites de calcédoine en couche concentriques
recouverte de petits cristaux fort brillans et durs de quartz, ou bien
seulement de ces derniers-ci. Par-fois il y a aussi du spath calcaire
crystallisé, mais cela est extrêmement rare. Quelque-fois enfin ces
cavités sont remplies d'une noix de calcédoine. Je n'ai réussi qu'une
seule fois en cassant un pareil silex en boule d'y trouver encore le
reste de l'eau de crystallisation."

The only remark that I would here make is this, that, if the
crystallization of those close cavities in the _silex_ had at any time
required water of solution, it must always have required it. But, if
there had been water of solution contained in those close cavities, for
the crystallization of the various things which are often found within
them, How comes it that this water is almost never found? I have good
reason to believe that water contained within a solid flint will not
make its escape, as does that contained in the _anhydrites_ of Mount
_Berico_, which are composed of a porous calcedony. But the siliceous
crystallizations within close cavities is a curious subject, which we
shall have occasion to examine more particularly in treating of agates.
We now proceed to the next section, which is the generation of silex and
quartz in marl, (p. 19.)

"Il y a des contrées, chez nous, qui out des étendus assez considérables
en long et en large, de montagnes de pierre de marne calcaire, dans
lesquelles on rencontre le même phénomène que dans celles de chaux pure;
c. a. d. nous y trouvons du silex de différentes variétés, et dans tous
les degrés successifs de leur formation, et de leur perfection. Outre
cela, nous y voyons encore quelque chose, qui semble nous conduire à
la découverte des moyens, dont se sort la nature pour effecteur cette
opération, et qui nous étoit caché dans les montagnes de chaux pure: ces
bancs de pierre marnesilicieuse, contiennent une partie considérable de
pyrites sulfureuses, qui non seulement y forment une grande quantité
de petits sillons, mais toute la masse de la montagne est rempli de
parcelles souvent presqu'imperceptibles de ce minéral. Ces pyrites sont
évidemment des productions du phlogistique et de l'acide contenu dans la
montagne.

"L'eau, qui s'y trouve ordinairement en assez grande abondance, en
détacha, extraha d'un et l'autre, et les combina après tous les deux
ensemble. Cette même eau les dissout derechef, et en fait de nouvelles
combinaisons. C'est ce qu'on voit évidemment là, ou la nature, ayant
commencé ses opérations, il n'y est resté de la pyrite, qu'une portion
de la partie inflammable liée à une base terrestre. Dans ces endroits



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