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'Academie 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 Generation du Silex et du Quartz en partie. Observations faites en Pologne 1783, a 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, Generation 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 quantite incroyable de cailloux (silex) tant en boules, que veines, couches, et debris. Au premier coup d'oeil l'on s'imagine que ce font des debris de montagnes eloignees, qui y furent amenes par les eaux, mais, en examinant la chose de plus pres, on est convaincu, que ce sont tout au contraire, des parties detachees des montagnes de la contree. Car il y a sur presque toute l'etendue de nos montagnes calcaires une couche, ou pour mieux dire, un banc compose de plusieurs couches de base calcaire, mais qui ou sont parsemees irregulierement de boules, de rognons, de veines, et de petits filons de silex, ou qui contiennent cette pierre en filon, veines, et couches paralleles, et regulierement disposees. Les boules et rognons de silex y font depuis moins de la grandeur d'une petite noisette, jusqu'au diametre de plus de six pouces de notre mesure. La plupart de ces boules tant qu'elles sont dans l'interieur cache de la roche vive, et qu'elles n'ont rien souffert de l'impression de l'air, ont, pour l'ordinaire, une croute de spath calcaire, au moyen de la quelle elles sont accrues a la roche mere; ou pour mieux dire la croute spatheuse fait l'intermede entre le silex, et la roche calcaire, par ou se fait le passage de l'une a l'autre. Mais ceci ne vaut que de boules de silex entierement formees. C'est dont on peut meme se convaincre a la vue, par beaucoup de pierres dont le pave de la ville de Cracovie est compose. Mais la, ou le silex n'est pas encore entierement acheve, la croute spatheuse manque, en revanche on y voit evidemment le passage par degres successifs de la roche calcaire au silex qui y est contenu, et les nuances de ce passage sont souvent si peu marquees que meme les acides mineraux ne suffisent pas a les determiner, ce n'est que le briquet, qui nous aide a les decouvrir. On voit bien ou la pierre calcaire s'enfonce en couleur, l'on s'appercoit, ou sa durete, ses cassures changent, mais, comme elle y souffre encore quelque impression des acides, l'on ne sauroit determiner au juste le point, ou elle a deja 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 etat de perfection, il y aura meme au milieu une partie de pierre calcaire non changee.

"Ceux au contraire, ou la nature a acheve son ouvrage, ont une croute 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 degres dans les differentes varietes du noble silex. Ils ont, pour l'ordinaire, dans leur interieur une cavite, mais pas toujours au centre, et qui vient apparemment de la consommation de cette partie calcaire qui y resta la derniere, et n'en fut changee ou dissolute et separee, que lorsque le reste du silex etoit deja entierement fini. Ces cavites sont toujours, ou enduites de calcedoine 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 crystallise, mais cela est extremement rare. Quelque-fois enfin ces cavites sont remplies d'une noix de calcedoine. Je n'ai reussi 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 contrees, chez nous, qui out des etendus assez considerables en long et en large, de montagnes de pierre de marne calcaire, dans lesquelles on rencontre le meme phenomene que dans celles de chaux pure; c. a. d. nous y trouvons du silex de differentes varietes, et dans tous les degres successifs de leur formation, et de leur perfection. Outre cela, nous y voyons encore quelque chose, qui semble nous conduire a la decouverte des moyens, dont se sort la nature pour effecteur cette operation, et qui nous etoit cache dans les montagnes de chaux pure: ces bancs de pierre marnesilicieuse, contiennent une partie considerable de pyrites sulfureuses, qui non seulement y forment une grande quantite de petits sillons, mais toute la masse de la montagne est rempli de parcelles souvent presqu'imperceptibles de ce mineral. Ces pyrites sont evidemment des productions du phlogistique et de l'acide contenu dans la montagne.

"L'eau, qui s'y trouve ordinairement en assez grande abondance, en detacha, extraha d'un et l'autre, et les combina apres tous les deux ensemble. Cette meme eau les dissout derechef, et en fait de nouvelles combinaisons. C'est ce qu'on voit evidemment la, ou la nature, ayant commence ses operations, il n'y est reste de la pyrite, qu'une portion de la partie inflammable liee a une base terrestre. Dans ces endroits la marne n'est que fort peu sensible aux acides, et de blanche qu'elle etoit, sa couleur est devenue presque noire. C'est la qu'on observe les differens degres du changement de la marne en silex, contenant, meme encore, par fois, de parties pyriteiques non detruites dans son interieur. Et comme la nature forme ici, de meme, que dans la chaux pure les silex, la plupart en boules ou rognons; comme les different degres de metamorphoses de la marne en silex, sont ici beaucoup plus nombreuses que la, de sorte qu'il y a des bandes entieres, qui meriteroient plutot d'etre appelles bandes silicieuses, que marneuses; comme il y a, enfin, une grande quantite de pyrites, qu'ailleurs, il est tres probable qu'elle se serve la du meme moyen qu'ici pour operer la metamorphose en question.

"Ne nous precipitons, cependant, pas a en tirer plus de consequences; poursuivons plutot le fil de notre recit.

"Le silex, qui se trouve ici, est non seulement de differents degres de perfection, il est de plus d'une espece. Il y a de la pierre a feu, 2 de la calcedoine, 3 des agathes, et 4 differentes nuances et passages des especes ordinaires aux fines du silex.

"La pierre a feu, est, ordinairement dans son etat de perfection d'un grain assez fin, d'une couleur grise plus ou moins foncee, et meme donnant, dans le noiratre, plus ou moins diaphane; ses cassures sont concentriques ou coquillees, et sa masse est assez compacte. Outre sa conformation ordinaire en boules et rognons, elle fait presque toujours la noix de ursins marins, qui y font en grand nombre, et dont la coquille est le plus souvent, et presque toujours de spath calcaire, meme au milieu d'une boule de silex parfait.

"Les calcedoines et agathes de ces couches sont toujours (au moins, je ne les ai pas encore vues autrement) de coraux et autres corps marins petrifies. Donc, il faut que les couches de pierres roulees, d'ou j'ai tire ma collection citee plus haut, soyent des debris de montagne" detruites de cette espece. Il y en a qui sont tres parfaites comme celles qui composent ma collection, d'autres meritent plutot d'etre rangees parmi les passages du silex ordinaire, et ses especes plus fines; d'autres encore sont, en effet, de vraies agathes, mais qui renferment dans leur interieur plus ou moins de parties non parfaites presque calcaires, qui s'annoncent d'abord par leur couleur blanche, par leur gros grains relativement au reste, par leur opacite, par leur mollesse respective, et souvent meme par leur sensibilite pour les acides mineraux. Mais celles, qui sont finies, quoiqu'elles ayent, pour la plupart, une couleur presque noire, ne laissent, cependant, pas d'avoir aussi des teintes plus claires comme brunatres, verdatres, rougeatres, jaunatres, bleuatres, tachetees, veinees, etc. Leur clarte n'est pas moins variable, que leur couleur, il y en a de presqu'opaques, comme aussi de presque transparentes, sur tout la, ou la calcedoine predomine.

"Le quartz s'y trouve comme dans les pierres de la premiere section, c, a, d, crystallise, en groupes dans de petites cavites; quelquefois aussi en veines. La calcedoine y est de meme, ou bien en mamelons, ou bien en stalactites, lorsqu'elle a de la place pour s'y deposer.

"Un phenomene encore plus curieux que cela est cette belle pyrite sulphureuse jaune, comme de l'or, qui est quelquefois parsemee par tout la substance de petrifications agathisees, et qui apparemment y fut deposee apres la dite metamorphose a la faveur des petits pores, qui y etoient restes ouverts."

I would beg that mineralists, who use such language as this, would consider if it contains a distinct idea of the operation which they would thereby describe, or if it does not contain either a contradiction or an inconceivable proposition. It supposes a calcareous body to be metamorphosed, somehow by means of the mountain acid, into a siliceous body. But, finding many bodies of pyrites contained within that solid flint, it is said, that, when the calcareous body was flintified, there were left in it cavities which were afterwards filled with pyrites. Let us reflect a moment upon this doctrine. These cavities were first open to the outside of the flinty body; but now the pyrites with which they had been filled is insulated in the solid flint. Here three things are required; first, The calcareous body is to be flintified, at the same time leaving the body full of small cavities open to the outside; secondly, These cavities are to be filled with pyrites; lastly, These mineral bodies are to be so inclosed within the flint, as to leave no vestige of the former processes. This marly mountain itself, which had been formed of loose materials gathered together at the bottom of the sea, was first to be filled with pyrites, in various shapes, by means of the phlogistic and the acid of the mountain. Here is proposed to us an operation which is totally unknown, or of which we have no kind of idea. But, let us suppose pyrites formed in this mountain, (of whatever chemical substances), by means of water; Why should water again undo that pyrites, in order to form other concretions? And, Why should the flint be formed first with cavities, and then made solid, after pyrites had been introduced into those cavities of the agate, and, as our author expresses it, parsemee pour toute la substance? Here are suppositions which are not only perfectly gratuitous, but are also inconsistent with any thing that we understand. This is not explaining nature; it is only feigning causes[39].

[Note 39: The description of those insulated siliceous bodies, containing in their closed cavities all the usual concretions of calcedony and crystals, as well as full of small pyrites floating in the solid flint, are extremely interesting to a mineral system, or such a geological theory as should explain the present state of things in those strata that had been formed by deposits of known materials at the bottom of the sea; they are indeed such appearances as may be found, more or less, in all consolidated strata. But it is this author's explanation of that petrifaction which is our present object to consider; and, as he is so particular in giving us his theory upon the subject, it is easy to detect the error of his reasoning. Were those naturalists who explain things only in general, by saying that water is the agent, and infiltration the means employed by nature;—were these naturalists, I say, to give us as particular a description of their process, it would appear as inconsistent with the nature of things as that which we have from this author, who examines nature very minutely, and who sees distinctly that the infiltrating theory is inapplicable for the explanation of those petrifactions.]

The third section has for title, "Generation du Silex et Quartz de la Pierre Puante." Here we find an example worthy of being recorded, as contributing to throw great light upon those mineral operations; however, the opinion of our author and mine, upon this subject, differ widely. He proceeds thus:

"Cette pierre n'est, comme chacun le scait, qu'une pierre calcaire contenant du bitume.

"Nos montagnes n'en contiennent seulement pas de simples couches, mais il y en a meme de grandes bancs fort epais.

"Le caillou, ou silex qui s'y genere, forme, tantot de gros blocs informes, qui occupent des cavites dans l'interieure des montagnes, tantot, enfin, en forme de filons.

"J'ai remarque cette metamorphose sur trois endroits differens, dans chacun des quels la nature a autrement opere.

"Sur l'un, la pierre puante fait un banc horizontal dans une montagne de pierre calcaire crystalline, ou d'une espece de marbre, qui contient des couches et filons de metal. Ce banc de pierre puante y fait le toit d'une couche de galene de plomb et de pierre calaminaire, et dans ses cavites et fentes il y a non seulement des blocs de grandeur differente, mais aussi des veines et petites bandes courtes de silex, tant ordinaire, que noble c, a, d, de la pierre a feu, de calcedoine, d'agathes, et meme d'une espece de cornaline jaune et rouge pale. Je ne m'arreterai pas a en detailler les varietes, parce qu'elles sont trop accidentelles. Je ne les connois pas meme toutes, il s'en faut de beaucoup, parce qu'elles se trouvent dans des anciennes mines negligees, peut etre depuis plus d'un siecle, et par consequent peu accessibles. Je ne doute, cependant pas, que, si l'on pouvoit mieux sonder le terrain, on y trouveroit bien plus encore du peu que j'ai cite. Parmi ce silex, il y a aussi de petites groupes et de petites veines de quartz solide et crystallise.

"Au second endroit la pierre puante fait un filon, ou si l'on veut, une couche ou bande verticale, qui partage la montagne en deux parties presqu'egales de l'epaisseur de trois aunes a peu pres. La montagne, ou cela se voit est aussi une ancienne mine de cuivre et de plomb, consistant en plusieurs varietes de marbre, different en couleur et en grain, deposees par couches les unes sur les autres. Le filon de silex est forme de feuilles alternatives de pierre puante et de silex, tous les deux de couleur brun de bois a peu pres; mais le silex est plus fonce que sa compagne. Ces feuilles alternatives, consistent d'autres bien plus minces encore, qui souvent n'ont pas l'epaisseur d'une ligne, mais ce qu'il y a de plus curieux, c'est que la meme feuille est d'un but de pierre porque, qui, vers le milieu, passe successivement en silex, qui, a son tour, vers l'autre but, qui etoit expose a l'air repasse par les memes gradations en une espece de tuffe calcaire. Ce qui nous fait voir evidemment la generation et la destruction du silex, meme avec une partie des moyens par lesquels elle s'opere. Comme l'endroit de cette decouverte n'est accessible qu'a la superficie, je ne saurois dire s'il y a d'autres varietes de silex outre la dite. Il l'est a supposer autant par analogie, que par quelques morceaux qui ont de petites veines transversales d'une espece de calcedoine, et qui sont, meme, sur leur fentes, garnis de petits cristaux de roche. Mais ce qu'il y a de sur c'est que ce filon, parvenu a une certaine profondeur, s'ennoblit et contient du metal, c. a. d. de la galene de plomb, et de la pyrite cuivreuse, j'y en ai trouves de morceaux, qui en font de preuves incontestables. Le caillou d'ici est un grain fin d'une texture forte, peu transparent, donne beaucoup d'etincelles au briquet, mais ses cassures sont ecailleuses.

"La montagne calcaire du troisieme lieu a une couche de pierre puante epaisse de plusieurs aunes, qui, derechef contient de petites couches irregulieres et des bandes transversales de silex, qui ont jusques a six pouces passes d'epaisseur. La pierre puante est d'une couleur gris-brune, d'un grain assez fin, et d'un tissu assez dur; ses cassures sont irregulieres, mais plus la pierre s'approche du silex, plus elles donnent dans le coquille. Le silex ordinaire est d'un brun de bois, d'un grain assez fin, et d'un tissu resistant, et ses cassures sont egales a la pierre porque. Ce n'est pas la la seule variete, il y a, aussi, de la calcedoine et des agathes de couleurs differentes. Meme la pierre a feu est assez souvent traversee de veines de calcedoine, de quartz crystallise, et de spath calcaire blanc en feuilles et en crystaux. Il arrive que la meme veine est composee de ces trois especes de pierres a la fois, de sorte que l'une semble passer dans l'autre, parce que les limites reciproques sont, souvent, assez indistinctes. Il est evident, que le silex est forme de la pierre puante, parce qu'on remarque ici les memes phenomenes dont j'ai parle plus haut, c. a. d. les passages successifs de l'une dans l'autre pierre, tant en montant qu'en descendant."

There is nothing particular in the siliceous mixture in this species of lime-stone, except the vein of that substance. It is evident that this vein, traversing the mountain, had been introduced in the fluid state of fusion. I do not mean to say, that, in this particular case now described, the evidence of that truth peculiarly appears; but that, from the general nature of mineral veins breaking and traversing the solid strata of the globe, no other conclusion can be formed; and that in the particulars of this example there is nothing that could lead us to suppose any other origin to the petrifactions contained in this vein of stinking lime-stone. It is plain, that our author has imagined to himself an unknown manner of executing his mineral metamorphoses. He sees plainly that the common notion of infiltration will not at all explain the evident confusion of those calcareous and siliceous bodies which appear to him to be metamorphosing into each other. Nothing, indeed, can explain those phenomena but a general cause of fluidity; and there is no such general cause besides that of heat or fusion.

But to show how mineralists of great merit, gentlemen who have examined systematically and with some accuracy, may impose upon themselves in reasoning for the explanation of mineral appearances from limited notions of things, and from the supposition of these having been formed where they now are found, that is, upon the surface of the earth, I would beg leave to transcribe what this author has said upon this species of petrifaction. It is not that he is ignorant of what mineralists have already said upon the subject; it is because he sees the incompetency of their explanations in those particular cases; and that he would employ some other more effectual means. (p. 50.)

"Toute terre calcaire a changer dans une autre doit, avant toute chose, etre rendue refractaire ce qui ne peut se faire qu'en la saturant avec un acide. Mais une terre simplement, saturee d'un acide, est d'une reduction fort aisee, vu que l'acide n'y tient pas trop fort, d'ailleurs ce n'est qu'un sel neutre terreux fort facile a dissoudre dans une quantite suffisante d'eau. Or pour rendre cette union plus constante, il faut que la terre alcaline s'assimile intimement a l'acide, ce qui ne se sera jamais sans un intermedeliant, qui homogene les parties de ce nouveau corps, et pour que cela ce fasse il est indispensable, qu'il s'opere une dissolution fonciere des parties terrestres de la chaux, qui facilite l'ingress a l'acide, et a l'intermede pour qu'ils s'y lie bien fortement. Supposons qu'il se forme une liqueur savonneuse de l'acide et du phlogistique, que l'air fixe, mis en liberte, ouvre les interstices des parties qui constituent la terre alcaline, qu'apres cela cette liqueur savonneuse ayant l'entree libre s'assimile a la terre en proportion requise, que l'eau, qui servoit de vehicule dans cette operation, s'evapore successivement, et emporte le superflu des ingrediens, pour qu'il se puisse operer le rapprochement le plus exacte des parcelles ou molecules homogenees de nouveau corps qu'enfin les molecules les plus pures et les mieux affinees soyent reunies en forme liquide dans des cavites, et que par l'evaporation et separation de l'eau, ou elles nageoient, il s'en forme des crystaux n'aurons-nous pas une boule de silex, avec de crystaux de quartz dans ses creux interieurs."

The supposed case is this; a calcareous body is to be metamorphosed into a siliceous nodule, having a cavity within it lined with quartz, crystals, etc. M. de Carosi means to inform us how this may be done. Now, as this process requires no other conditions than those that may be found upon the surface of this earth, the proper way to prove this hypothetical theory, would be to exhibit such a mineral body produced by those means. But, even supposing that such a process were to be exhibited, still it would remain to be explained, how this process, which requires conditions certainly not be found at the bottom of the sea, could be accomplished in that place, where the strata of the earth had been deposited, accumulated, consolidated, and metamorphosed.

This mineral process, which has been now described, will no doubt revolt the opinions of many of our chemists as well as naturalists; and I should not have thought of transcribing it, but as an example of that inconclusive reasoning which prevails in mineralogical writings upon this subject.

But this is not all. We have, upon this occasion, a most remarkable example of the fallaceous views that may be taken of things; and of the danger to science when men of sense and observation form suppositions for the explanation of appearances without that strict conformity with the principles of natural philosophy which is requited on all occasions. Both M. de Carosi, and also M. Macquart[40], to whom our author communicated his ideas and proper specimens, assert, that from their accurate experience, they find calcedony growing daily, not only in the solid body of gypsum, etc. while in the mine, but also in the solid stone when taktn out of the mine, and preserved in their cabinet.

[Note 40: Vid. Essais de Mineralogie par M. Macquart.]

What answer can be made to this positive testimony of these gentlemen, by a person who has not seen any such a thing, and who has not the opportunity of examining the cases in which those naturalists may have perhaps been led into some delusion? Were I however to conjecture upon a subject in which I have not any positive information, I should suppose that some part of the calcedony, like the oculus mundi when dipped in water, may be so transparent, while containing some portion of humidity, that it is not easily distinguishable from the gypsum in which it is concreted; but that in having the humidity evaporated, by being taken out of the mine and exposed to the dry air, those portions of calcedony, which did not before appear, may be perceived by becoming more opaque[41].

[Note 41: From the description given in this treatise, and from the drawings both of M. de Carosi and M. Macquart, I find a very valuable inference to be made, so much the more interesting, as I have not found any example of the like before. This arises from the intimate connection which is here to be perceived between agate and gypsum. Now, upon this principle, that the agate-calcedony had been formed by fusion, a truth which, from the general testimony of minerals, I must presume, it is plain, that those nodules of gypsum had been in the fluid state of fusion among those marly strata, and that the gypseous bodies had been penetrated variously with the siliceous substance of the calcedony.

The description of those siliceous penetrations of gypsum is followed by this conclusion: "En voila assez, je crois pour faire voir que le silex ci-decrit est effectivement une emanation du gypse, et non pas une matiere heterogene amenee d'autre part et deposee, ou nous la voyons." In this instance our author had convinced himself that the calcedony concretions had not been formed, as he and other mineralists had before supposed, by means of infiltration; he has not, however, substituted any thing more intelligible in its stead. I do not pretend that we understand mineral fusion; but only that such mineral fusion is a thing demonstrable upon a thousand occasions; and that thus is to be explained the petrification and consolidation of the porous and naturally incoherent strata of the earth.]

There is, however, a subject in which I can more freely accuse this author of being deceived. This naturalist says, that calcareous stones become silex by a certain chemical operation; and that those flinty bodies, in being exposed upon the surface of the earth, out of their natural bed, are again, by a contrary chemical operation, changed from flint to a calcareous substance. I will give it in his own words, (p. 56.)

"Cela dit, venons au fait. Tout silex progenere de chaux, detache de son lieu natal, et expose aux changemens de saisons, s'amollit, recoit de crevasses, perd sa transparence, devient, enfin, tout-a-fait opaque, le phlogistique s'en evapore, l'acide en est detache, lave, et de terre vitrescible, qu'il etoit, il redevient chaux, comme il etoit auparavant."

Here is no question with regard to mere opinion, but to matter of fact; and, in this case, nothing is more evident, than that upon the surface of this earth, that is, in the examinable parts above the level of the sea, there is no transition either of calcareous bodies into flint, nor of flinty bodies into calcareous substance. Calcareous matter is constantly dissolved by water, when it is exposed to the washing of that fluid; and it is even dissolved out of the most perfect union or combination with siliceous substance, and the most solid composition of an insoluble body, as may be perceived in the decaying of feld-spar. A superficial view of flints, which have come out of a body of chalk, may have created such an opinion, which will not either bear the light of chemical or mineral investigation. The subject of these chalk flints will be minutely examined in its proper place.

Our author has carefully examined the subject of flintification; and the country where he makes his observations would seem to be well disposed for such a research. He has had great opportunity and inclination to examine the subject which he writes upon; and he has given a distinct account of what be has seen. His description of the flintification of sand-stone is extremely interesting. I will therefore transcribe it, both as a valuable portion of natural history, and also in order to contrast this author's opinion, with regard to the means employed by nature in petrifying bodies, and that which I maintain to be the general consolidating operation of the globe. It is Section V. Generation du Caillou du Silex du Gres, ou Pierre Sablonneuse.

"Tout gres est susceptible de cette metamorphose quant au grain et quant a la couleur; depuis la breccia quartzeuse jusqu'a la pierre a rasoir; et depuis le gres blanc jusqu'au brun et presque noiratre, tient ou non tient, dur, ou presque friable, c'est indifferent, toutes ces varietes donnent du silex, et surtout de la calcedoine, de la cornaline, et des agathes. Quant au ciment je l'y ai toujours remarque calcaire et faisant effervescence avec les acides dans les endroits de la pierre qui n'etoient point encore changes; et jamais je n'ai vu ce changement dans du gres dont le ciment fut ou quartzeux ou argileux et refractaire. Ainsi le ciment entre pour quelque chose dans ce changement.

"Le commencement de cette metamorphose paroit (autant que j'ai pu l'observer dans mes debris roules) se faire par le ciment, qui dissout la, ou les agens eurent l'acces libre, rend les grains en quartz mobiles, les emporte, les mele avec sa masse dense-liquide, les dissout, meme en partie, et forme, dans cet etat, des veines et de masses calcedonieuse, carneoliques, ou d'une autre espece de silex, au milieu du gres peu, ou pas du tout, change. Car autant que je puis voir, ce n'est pas par couches ou veines qu'elle s'opere, mais par boules et masses rond-oblongues. Au commencement ces veines et taches sont fort minces, et le reste du gres n'est point du tout, ou a peine sensiblement change hormis qu'il gagne, plus de consistence, a proportion du changement souffert. Mais a mesure que le silex y augmente et se perfectionne, on y appercoit les degres par lesquels a passe cette operation. Les nuance du passage d'une pierre a l'autre deviennent plus visibles, les veines et masses de silex grandissent au point, meme, qu'il y a jusqu'aux trois quart du gres change en silex clair comme de l'eau n'ayant que fort peu de grains de sable nageants dans sa masse. Des morceaux de cette espece sont rares a la verite, mais j'en ai, cependant, trouve quelques uns. Ordinairement, dans les beaux morceaux, le silex fait la base, et le sable y est, comme nageant tantot en grains separes tantot en parties et flocons. Dans les pieces moins belles, le sable fait la base, et le silex sert a la fois de ciment, et forme aussi plus ou moins de veines, qui traversent la masse en maintes et maintes directions. Mais si c'est un gres a gros grains, ou de la breccia, alors le reste prend la nature silicieuse mele de sable fin, et les gros grains de quartz restent tels, qu'ils etoient, sans changer. J'ai deja remarque que cette metamorphose semble s'operer, comme celle des cailloux d'origine calcaire en forme approchans la spherique, il faut encore y a jouter, que j'ai lieu de croire, qu'elle se fasse aussi du dedans en dehors, tout, comme la decomposition se fait du dehors au dedans.

"Il arrive dans cette pierre, comme dans toute autre, qu'il se forme des crystallisations dans les cavites. Lorsqu'elles sont de silex, leur figure est toujours mamelonnee, mais leur eau ou purete, leur grandeur et leur couleur n'est pas par tout egale. Il y en a qui sont grands, et de la plus pure calcedoine, d'autres sont petits et chaque goutte ou mamelon contient un grain de sable, de facon que cela a l'air d'un gres crystallise en mamelons ou stalagmitique. D'autres encore sont, de calcedoine, mais recouverts d'une croute, tantot blanche qui fait effervescence avec l'acide mineral, et qui est, par consequent, de nature calcaire; tantot cette croute est bleue foncee nuancee de bleu-celeste; tantot, enfin, elle est noire, mais toutes les deux refractaires. Outre ces crystallisations silicieuses, il y en a, quoique rarement, de quartzeuses, qui ou forment de petites veines de crystal, ou bien des groupes de crystaux quartzeux, ou qui enfin, enduisent les mamelons de silex."

Our author then makes a specification of the different varieties; after which he continues, p. 69.

"Apres tout ceci, l'on conviendra j'espere, que notre grais est une pierre bien singuliere, et surpassant, a bien des egards, le grais, faussement dit crystallise, de Fontainebleau. La raison de la figure du grais Francois est fort evidente, c'est le spath calcaire, qui lui sert de ciment, qui la lui fit prendre; mais qu'est-ce qui opere les metamorphoses racontees dans notre grais siliceux? Seroit-ce son ciment calcaire ou marneux par les memes raisons, qui font changer la marne en silex? La chose est tres-probable, et je n'en saurois pas meme, deviner d'autre. En ce cas la nature auroit un moyen d'operer par la voie humide, ce que nous faisons dans nos laboratoires en quelque facon, par la voie seche, c, a, d, de fondre et liquefier la terre vitrescible, au moyen des alcalis; secret que nous lui avons deja arrache en partie, en faisant la liqueur silicieuse."

"Je n'ose, cependant, decider pas meme hypothetiquement, sur cette matiere, pour n'avoir pu observer la nature dans ses ateliers, et parce que je ne possede que des pieces, qui detachees de leur lieu natal, depuis un tres long-tems, furent exposees aux intemperies des saisons, ou elles peuvent avoir souffert bien de changemens."

There cannot be a more fair exposition of facts; and it is only our author's opinion of this mineral transmutation that I would controvert. I do not pretend to understand the manner of operating that our author here supposes nature to take. I only maintain, that here, as every where in general, the loose and incoherent strata of the globe have been petrified, that is, consolidated, by means of the fusion of their substances; and this I think is confirmed from the accurate description here given of the flintification of sand-stone. Here is described very distinctly an appearance which is very common or general on those occasions; this is the parts or particles of stone floating in the fluid siliceous substance, and there dissolving more or less.

M. de Carosi describes very systematically the generation of silex, calcedony, onyx, and quartz, in calcareous earth, marl, gypsum, sand-stone, and also what he terms terre glaise, ou de l'Argile. It is in this last that we find a perfect analogy with what is so frequent in this country of Scotland. These are the agates, calcedonies, calcareous and zeolite nodules, which are found produced in our whin-stone or subterraneous lavas, that is, the amygdaloides of Crondstedt. Naturalists explain the formation of those nodular bodies differently. The Chevalier de Dolomieu supposes these rocks to have been erupted lavas, originally containing cavities; and that these cavities in the solid rock had been afterwards filled and crystallised, by means of infiltration, with the different substances which are found variously concreted and crystallised within the solid rocks. Our author, on the contrary, supposes these formed by a species of chemical transmutation of calcareous and argillaceous earths, which, if not altogether incomprehensible, is at least not in any degree, so far as I know, a thing to be understood.

This is not the place where that subject of these particular rocks, which is extremely interesting, is to be examined. We shall afterwards have occasion to treat of that matter at large. It is sufficient here to observe, that our author finds occasion to generalise the formation of those petrifactions with the flintifications in calcareous and gypseous bodies. When, therefore, the formation of any of them shall be demonstrated, as having taken its origin in the fusion of those substances, this mode of operation, which is generalised in the consolidation of strata, will be properly inferred in all the rest.

Petrifaction is a subject in which mineralogists have perhaps wandered more widely from the truth than in any other part of natural history; and the reason is plain. The mineral operations of nature lie in a part of the globe which is necessarily inaccessible to man, and where the powers of nature act under very different conditions from those which we find take place in the only situation where we can live. Naturalists, therefore, finding in stalactical incrustation a cause for the formation of stone, in many respects analogous to what is found in the strata of the earth, and which had come from the mineral region in a consolidated state, have, without due consideration, attributed to this cause all the appearances of petrifaction or mineral concretion. It has been one of the objects of this work to show that this operation of incrustation, or petrifaction by means of solution, is altogether ineffectual for producing mineral concretions; and that, even were it capable of forming those mineral bodies, yet that, in the solid parts of this earth, formed by a deposit of travelled materials at the bottom of the sea, the conditions necessary to this incrustating process do not take place.

Those enlightened naturalists who have of late been employed in carefully examining the evidences of mineral operations, are often staggered in finding appearances inconsistent with the received doctrine of infiltration; they then have recourse to ingenious suppositions, in order to explain that enigma. In giving examples of this kind. I have in view both to represent the natural history these mineralists furnish us with, which is extremely interesting, and also to show the various shapes in which error will proceed, when ingenious men are obliged to reason without some necessary principle in their science. We have just now had an example in Europe; I will next present the reader with one from Asia.

M. Patrin, in his Notice Mineralogique de la Daourie, (Journal de Physique, Mars 1791) gives us a very distinct account of what he met with in that region. Describing the country of Doutchersk upon the river Argun, in Siberia, he proceeds thus:

"Ces colines sont formees d'un hornstein gris qui paroit se convertir en pierre calcaire par l'action des meteores; car tout celui qu'on prend hors du contact de l'air donne les plus vives etincelles, et ne fait pas la moindre effervescence avec les acides, meme apres avoir ete calcine; et l'on observe celui qui est a decouvert, passer, par nuances insensibles, jusqu'a l'etat de pierre calcaire parfaite de couleur blanchatre."

Here M. Patrin has persuaded himself, probably from an imperfect examination of the subject, that there takes place a mineral metamorphosis, which certainly is not found in any other part of the earth, and for which he does not find any particular cause. The natural effect of the meteors, in other parts of the earth, is to dissolve the calcareous substance out of bodies exposed to those agents; and the gradation from the one of those two things to the other, which seems to be the data on which he had proceeded in forming his conclusion, is not sufficient to prove the metamorphosis, even were there not so strong a physical objection to it; for, it is by no means unusual for mineral bodies to graduate thus from one substance to another. However that be, this is not the principal object of the example[42].

[Note 42: Here we have well informed naturalists reasoning with all the light of our present mineralogy, and maintaining, on the one hand, that gypsum is transformed into calcedony, by the operation of the meteors, or some such cause; and, on the other, that a siliceous substance is by the same means converted into lime-stone. What should we now conclude from this?—That calcareous and siliceous substances were mutually convertible. But then this is only in certain districts of Poland and Siberia. Every where, indeed, we find strange mixtures of calcareous and siliceous bodies; but neither mineralists nor chemists have, from these examples, ventured to affirm a metamorphosis, which might have spared them much difficulty in explaining those appearances.

This is a subject that may be taken in very different lights. In one view, no doubt, there would appear to be absurdity in the doctrine of metamorphosis, as there is now a days acknowledged to be in that of lusus naturae; and those reasoning mineralists might thus, in the opinion of some philosophers, expose their theory to contempt and ridicule. This is not the light in which I view the subject. I give those gentlemen credit for diligently observing nature; and I applaud them for having the merit to reason for themselves, which would seem to be the case with few of the many naturalists who now speak and write upon the subject.

Let us now draw an inference, with regard to this, in judging of the different theories. Either the received system concerning mineral operations is just, in which case those gentlemen, who employ a secret metamorphosis, may be to blame in laying it aside; or it is erroneous and deficient; and, in that case, they have the merit of distinguishing the error or deficiency of the prevailing system. How far they have seen the system of nature, in those examples which they have described, is another question. In the mean time, I am to avail myself of the testimony of those gentlemen of observation, by which the insufficiency at least of the received mineral system is acknowledged.]

After speculating upon the effect of the ancient ocean upon the mountains of that country, he proceeds as follows:

"Je laisse ces conjectures pour remarquer un fait singulier: la colline, qui est au nord de l'eglise de la fonderie, a son arrete composee de ce hornstein qui se decompose en pierre calcaire; mais ici, les parties, qui sont ainsi decomposees, offrent une substance calcedonieuse disposees par zones concentriques, comme on l'observe dans les agates d'oberstein; mais ce ne sont point ici des corps parasites formes par infiltration dans des cavites pre-existantes comme les agates; on voit que ce sont les parties constituantes de la roche qui, par un travail interne, et par une sorte de crystallisation, out pris cette disposition reguliere (que ce mot de crystallisation ne revolte point, j'appelle ainsi toute tendance a prendre une forme constante, polyedre ou non polyedre.) Les couches les plus voisine du centre sont nettes et distinctes; peu-a-peu elles le sont moins, et enfin elles s'evanouissent et se confondent avec le fond de la roche. Chaque assemblage de ces zones a une forme ronde ou ovale plus ou moins reguliere de sept a huit pouces de diametre.

"Cela ressemble en grand a ce qu'on observe dans les pierres oeillees, et la cause est vraisemblablement la meme. Je le repete, je regarde cette disposition reguliere comme une veritable cristallisation, qui peut s'operer et qui s'opere en effet dans l'interieur des corp les plus solide, tant qu'ils sont fournis a l'action des agens de la nature.

"Tous ceux qui visitent l'interieur de la terre savent que les roches memes le plus compactes y sont intimement penetrees d'humidite, et ce fluide n'est certainement pas l'eau pure; c'est l'agent qui opere toutes les agregations, toutes les cristallisations, tous les travaux de la nature dans le regne mineral. On peut donc aisement concevoir qu'a la faveur de ce fluide, il regne, dans les parties les plus intimes des corps souterrains, une circulation qui fait continuellement changer de place aux elemens de la matiere, jusqu'a ce que reunis par la force des affinites, les corpuscules similaires prennent la forme que la nature leur a assignee."

Those nodular bodies or figured parts which are here inclosed in the rock, are evidently what may be called calcedony agates. M. Patrin is persuaded, from the examination of them, that they had not been formed in the manner of German agates, which he supposes is by mean of infiltration; and he has endeavoured to conceive another manner of operating, still however by means of water, which I suppose, according to this hypothesis, is to dissolve substances in one part, and deposits them in another, There must certainly be some great desideratum in that mineral philosophy which is obliged to have recourse to such violent suppositions. First, water is not an universal solvent, as it would require to be, upon this supposition; secondly, were water allowed to be an universal menstruum, here is to be established a circulation that does not naturally arise from the mixture of water and earth; and, lastly, were this circulation to be allowed, it would not explain the variety which is found in the consolidation and concretion of mineral bodies.

So long, therefore, as we are to explain natural appearances by reasoning from known principles, and not by ascribing those effects to preternatural causes, we cannot allow of this regular operation which M. Patrin alleges to be acting in the interior parts of the most solid bodies. This is indeed evident, that there has been a cause operating in the internal parts of the most solid bodies, a cause by which the elements, or constituent parts of those solid bodies, have been moved and regularly disposed, as this author very well observes must have been the case in our agates or eyed stones; but to ascribe to water this effect, or to employ either an ineffectual or an unknown cause, is not to reason philosophically with regard to the history of nature; it is to reason phantastically, and to imagine fable.

M. Monnet has imagined a petrifying power in water very different from any that has hitherto been conceived, I believe, by natural philosophers, and I also believe, altogether inconsistent with experience or matter of fact; but as it is not without good reason that this naturalist has been induced to look out for a petrifying cause different from any hitherto supposed, and as he has endeavoured very properly to refute the systems of petrification hitherto received, I would beg leave to transcribe his reasoning upon the subject in corroboration of the present theory of consolidation by the means of fusion.

It is upon occasion of describing one of the species of alpine stone or schistus which contains quartzy particles. Nouveau voyage mineralogique, etc. Journal de Physique Aoust 1784.

"Il y a loin de cette pierre, que je regarde comme une variete de roches ardoisees, aux veritable ardoises. La composition de toutes ces pierres est due aux terres quartzeuses et argileuses, et a la terre talqueuse, que je demontrerai un jour etre une espece particuliere et distincte des autres, qui constitue les bonnes ardoises, et fait, ainsi que le quartz, qu'elles resistent aux injures de l'air, sans s'effleurir, comme je ferai voir que cette terre, qu'on designera sous la denomination de terre talqueuse, si l'on veut, resiste au grand feu sans se fondre. Les differences de toutes ces pierres, quoique composees des memes matieres, mais dans des proportions differentes, sont frappantes, et pourroient faire croire qu'elles n'appartiennent pas a ce genre. Mais qui ne voit ici que toutes ces differences, ou ces varietes, ne sont dues qu'aux modifications de la matiere premiere, qu'elle a eprouvees, soit en se melant avec des matieres heterogenes, prevenantes du debris des etres qui ont existe, comme l'argile, par exemple, qui, de l'aveu de presque tous les naturalistes, est le produit de l'organization des plantes, ou soit en se melant avec de la matiere deja solidifiee depuis long-temps? Or nous ne craignons pas de dire, ce que nous avons dit plusieurs fois quand l'occasion s'en est presentee, que cette matiere unique, que se modifie selon les occasions et les circonstances, et qui prend un caractere analogue au matieres qu'elle rencontre, est l'eau, que beaucoup de naturalistes cherchent vainement ailleurs. Ils ne peuvent comprendre, malgre les exemples frappans qui pourroient les porter a adopter cette opinion, que ce fluide general soit l'element des corps solides du regne mineral, comme il est de ceux du regne vegetal et du regne animal. L'on cherche serieusement, par des experiences chimiques, a decouvrir si l'eau est susceptible de se convertir en terre comme si la nature n'avoit pas d'autre moyen que nous de la faire passer de l'etat fluide a l'etat solide. Voyez le spath calcaire et le quartz transparens; est il a presumer qu'ils ne sont que le resultat du depot des matieres terreuses fait par les eaux? Mais, dans ce ca-la encore, il faut supposer que l'eau qui est restee entre ces partie s'est solidifiee; car, qu'est-elle donc devenue, et quel est donc le lien qui a uni ces parties et leur a fait prendre une forme reguliere? Il est vrai qu'on nous parle d'un suc lapidifique; mais c'est-la un etre de raison, dont il seroit bien plus difficile d'etablir l'existence, que de croire a la solidification de l'eau. On nous donne cependant comme un principe certain que l'eau charie d'un lieu a un autre les matieres qu'il a dissoutes, et qu'elle les depose a la maniere des sels. Mais c'est supposer une chose dementie par l'experience; savoir, que l'eau ait la propriete de dissoudre les matieres terreuses, telles que la quartzeuse. A la verite, M. Auchard de Berlin y joint de l'air fixe; mais cet air fixe ne sauroit tenir en dissolution un atome de quartz dans l'eau; et quelle qu'ait ete l'exactitude de ceux qui ont repete les experiences de M. Auchard, on n'a pu reussir a imiter la nature, c'est-a-dire, a former des cristaux quartzeux, comme il a annonce. Que l'eau ait la faculte de tenir en dissolution quelques petites parties de terre calcaire, au moyen de cet air fixe, il n'en faut pas conclure qu'elle puisse former de cette maniere tous les cristaux calcaires, sans que l'eau elle-meme y concoure pour sa part; car ce seroit conclure quelque fois que la partie seroit egale au tout. Voyez ces geodes calcaire et argileuses, qui renferment des cristaux nombreux de quartz ou de spath calcaire; ne sont ils que le resultat du depot de l'eau qui y a ete renfermee, ou que la cristallization pure et simple des molecules que vous supposez avoir ete tenues en dissolution par cette eau? Il naitroit de cette opinion une foule d'objections qu'il seroit impossible de resoudre. Cependant M. Guettard, dans la mineralogie du Dauphine, qui vient de paroitre, ouvrage tres-estimable a beaucoup d'egards, explique, selon cette maniere de penser, la formation de cristallizations quartzeuses qu'on trouve dans certaines geodes de cette province, et celle des mines de cristal des hautes montagnes. En supposant meme comme vraie l'explication qu'il en donne, on trouveroit en cela un des plus grands probleme, et des plus difficiles a resoudre qu'il y ait en mineralogie; car d'abord il faudroit expliquer comment un si petite quantite d'eau que celle qui a ete renfermee dans les geodes, et celle qui est parvenue dans les fentes des rochers, ont pu fournir un si grande quantite de matiere que celle qui constitue ces cristallisations, et ce qui n'est pas le moins difficile a concevoir, comment l'eau a pu charrier cette matiere a travers tant de matieres differentes, et la conserver precisement pour cette destination; comment, par exemple, l'eau est venue deposer de la terre quartzeuse dans les masses enormes de pierres calcaires, qui forment la cote qui domine le village de Champigny, a quatre lieues de Paris, au dela de Saint-maur; car s'il nous faut citer un exemple frappant de cette singularite, et a portee d'etre vue des naturalistes qui sont dans la capitale, je ne puis mieux faire que de citer cette cote, une des plus curieuses de la France, et que je me propose de fair connoitre en detail dans la troisieme partie de la mineralogie de la France. On verra, dis-je, dans cette bonne pierre a chaux, et une de plus pure des environs de Paris, de tres-abondantes cristallisations de quartz transparent, et quelque fois de belle eau, que les ouvriers sont forces de separer de la partie calcaire, a laquelle elles adherent fortement. Mais c'est trop nous arreter a combattre une opinion qui doit son origine aux premieres idees qu'ont eues les premiers observateurs en mineralogie, qui se detruira d'elle meme comme tant d'autres dont il nous reste a peine le souvenir."

We find here an accurate naturalist, and a diligent observer, who, in conformity with what my sentiments are upon the subject, thinks it impossible that the crystallizations in close cavities, and concretions of different solid substances within each other, which so frequently occur in the mineral regions, could have been produced, by means of solution and crystallization, from a fluid vehicle. But what has he now substituted in place of this solution, in order to explain appearances?—a mere supposition, viz. that nature may have the power of converting water, in those secret places, into some other thing; or rather that the substance of water is here converted into every other thing; for, though he has only mentioned quartz and calcareous spar, what mineral substance is there that may not be found in those close cavities? They are actually almost all, not even excepting gold; for, small grains of gold are inclosed within the cavities of a porous stone, in the Siberian mine. Now, for what purpose should nature, (to the power of which we are not to set a limit) have such an object in view as to convert water into every thing, unless it were to confound human understanding? For, so far as human experience has been as yet able to reach, there would appear to be certain elementary substances; and among these is water, or the principles of that fluid[43]. But because water is so generally found in bodies, and so necessarily in most of the operations of this world, why convert it into every other thing? Surely, for no better reason than that there has not occurred to this mineralist any other way of explaining certain natural appearances which aqueous solution could not produce. Here is no dispute about a matter of fact; it is on all hands allowed, that in certain cavities, inaccessible to any thing but heat and cold, we find mineral concretions, which contain no water, and which, according to the known operations of nature, water could not have produced; must we therefore have recourse to water acting according to no known principle, that is to say, are we to explain nature by a preternatural cause?

[Note 43: Water is now considered by men of science, as a compound substance; this doctrine, which seems to follow so necessarily from the experiments of the French philosophers, must be tried by the growing light of chemical science. In the oxygenating operation of inflammable and combustible bodies when burning, those ingenious chemists overlooked the operation of phlogistic matter, which has no weight, and which escapes on that occasion, as I have had occasion to show in a dissertation upon phlogiston, and in the Philosophy of Light, Heat, and Fire. How far this view, which I have given of those interesting experiments, may lead to the explanation of other collateral phenomena, such as that of the water produced, I will not pretend to conjecture. One thing is evident, that if the weight of the water, procured in burning inflammable and vital air, be equal to that of those two gasses, we would then have reason to conclude, either that water were a compound substance, or that vital air, and inflammable vapour were compounds of water and the matter of light, or solar substance.]

I dare say that this is not the view that M. Monnet takes of the subject, when he thinks to explain to himself the concretion of those different substances by means of water; but, according to my apprehension of the matter, his theory, when sifted to the bottom, will bear no other construction; and, unless he shall consider water like the matter of heat, as capable of producing the fluidity of fusion, and of being also again abstracted from the fluid, by pervading the most solid body, which would then be a substance different from water, he must employ this aqueous substance as a menstruum or solvent for solid bodies, in the same manner as has been done by those naturalists whom he he justly censure, and conform to those erroneous ideas which first observations, or inaccurate knowledge of minerals, may have suggested to former naturalists.

It is the dissolution and concretion of siliceous substance, no doubt, that gives such difficulty to our naturalists in explaining petrifaction: they have, however, something apparently in their favour, which it may be proper now to mention.

In the first place, although siliceous substance is not soluble, so far as we know, by simple water, it is soluble by means of alkaline substance; consequently, it is possible that it may be dissolved in the earth.

Secondly, The water of Giezer in Iceland, actually petrifies bodies which are alternately imbibed with that hot water and exposed to the air. This water, therefore, not only contains siliceous substance in a dissolved state, but deposits this again, either by means of cooling, or being aerated, or of evaporating. Consequently, without knowing the principle upon which it proceeds, we here perceive a natural operation by which siliceous petrifaction may be performed.

Lastly, We have another principle for the dissolution of siliceous substance. This is the fluor acid which volatilises the siliceous substance. This, however, requires certain conditions, which cannot be found as a general cause in the mineral regions.

Thus we would seem to have every thing necessary for explaining the concretion and crystallization of siliceous bodies, provided we could find the proper conditions requisite for that operation; for whether it shall be by means of acid or alkaline substances that siliceous matter is to be dissolved, volatilised, and transported from one place to another, it is necessary that those dissolving substances should be present upon those occasions. Nor is it sufficient only to dissolve the siliceous substance which is to be transported; the necessary conditions for the concretion again of the dissolved substances, whatever these may be, are also absolutely required for this operation. Now, though those requisite conditions may be, upon many occasions, allowed in the earth, it is not according to the theory of our modern naturalists, who explain petrifaction upon the principles of simple infiltration of water, that any advantage can be taken of those conditions; nor are natural appearances to be explained without employing more complicated chemical agents in the mineral regions.

To this subject of the petrifactions of Giezier, I may now add the information which we have received in consequence of a new voyage from this country to Iceland.

When Sir Joseph Banks returned from his expedition to Iceland, he landed at this place; and, having brought specimens of the petrifications of Giezer, Dr Black and I first discovered that these were of a siliceous substance. I have always conjectured that the water of Giezer must be impregnated with flinty matter by means of an alkaline substance, and so expressed my opinion in the Theory of the Earth published in the Transactions of the Edinburgh Royal Society. We have therefore been very desirous of procuring some of that water, in order to have it analysed.

An opportunity favourable to our views has occurred this summer. Mr Stanley set out from this place with the same purpose of examining Iceland. He was so good as to ask of Dr Black and I what inquiries we would incline that he should make. We have now, by the favour of this gentleman, obtained specimens of the petrifactions of Giezer; and, what is still more interesting, we have procured some of the water of those petrifying boiling springs.

It appears from these specimens, that the boiling water which is ejected from those aqueous volcanoes, if we may use the expression, is endued with the quality of forming two different species of petrifaction or incrustation; for, besides the siliceous bodies, of which we had before received specimens, the same stream of water incrustates its channel with a calcareous substance. All the specimens which I have seen consist of incrustation, some purely siliceous, some calcareous, and others mixed of those two, more or less.

Dr Black has been analysing the water; and he finds in it siliceous matter dissolved by an alkaline substance, in the manner of liquor silicum[44]. My conjecture has thus been verified.

[Note 44: See Trans. of the Edin. Royal Society.]

It must not be alleged that nature may operate in the mineral regions, as she does here upon the surface in the case of Giezer. Such an argument as this, however sound it may be in general, will not apply to the subject of which we treat at present. There is no question about the limiting the powers of nature; we are only considering nature as operating in a certain determined manner, viz. by water acting simply upon the loose materials of the land deposited at the bottom of the sea, and accumulated in regular strata, one upon another, to the most enormous depth or thickness. This is the situation and condition of things in which nature is to operate; and we are to find the means of consolidating those strata, and concreting every species of substance in almost every possible composition, according to some known physical principle. Here is an operation which is limited; for, we must reason strictly, according to the laws of nature, in the case which we have under consideration; and we cannot suppose nature as ever transgressing those laws.

It is acknowledged, that, by means sometimes of an aeriform, sometimes of an alkaline, perhaps also of an acid substance, calcareous matter is dissolved in the earth, and certain metallic substances, such as lead and iron. This solution also, upon particular occasions, (where the proper conditions for separating the solvent from the dissolved substance exist), forms certain concretions; these are sometimes a mere incrustation, as in the case of the siliceous incrustation of Giezer, sometimes again in a crystallised or sparry form, as in the case of stalactical concretions. But here is no question of those cases where the proper conditions may be found; first, of dissolving the substance which is afterwards to be concreted; secondly, of separating the menstruum from the dissolved substance; and, lastly, of removing the fluid deprived of its solution, and of supplying a new solution in its room; the question is, how far those concretions are formed where those conditions do not take place. Now, this last case is that of almost all mineral concretions.

It must not be here alleged that certain concretions have been found in mines posterior to these having been worked by man; consequently, that those concretions have been formed by nothing but the infiltration of water. In those cases, where such concretions are truly found, I am persuaded that all the conditions proper to that operation will also be found; and it is only, I believe, in those cases where such proper conditions may be found, that this aqueous concretion ever appears. Now, if we shall except calcareous stalactite, and the bog ore of iron, How seldom is it that any appearance of those aqueous mineral concretion ever is found? Those very few cases in which they are found, afford the strongest proof against these being operations general to the globe, or proper mineral concretions; because it is only where all the necessary conditions conspire in each contributing its part, that the effect is accomplished; and this is a thing which cannot possibly take place in the aquiform strata below the surface of the sea. But, without attending to this clear distinction of things perfectly different, naturalists are apt to see false analogies, and thus in generalising to form the most erroneous theories.

I shall now give an example of this fallaceous manner of reasoning; it is in the case of certain mineral appearances which are erroneously considered as stalactical concretions.

The only true stalactical bodies are of a calcareous substance; they are formed by water containing this substance in a dissolved state; and the principles upon which this particular concretion is formed are well known. It is therefore easy to compare other concretions, which may have some superficial resemblance to these stalactical bodies, in order to see if they have proceeded upon the same principle of concretion from a dissolved state, or by water depositing its dissolved substance in a similar manner.

There are two different mineral substances which give appearances of this sort. These are certain concretions of calcedony, and also of iron-ore, which are thought to have such resemblance to stalactical concretions as, by some superficial observers, to be reckoned of the same kind. It is now proposed to show that those conclusions are not well founded; and that, in this case of calcedony and iron-ore, it could not be upon the principle of stalactical concretion that the bodies now in question had their forms.

The principle upon which calcareous substance is dissolved in water, and made to concrete by the evaporation of the acid substance, or fixed air by which it had been dissolved, is too well known to require any explanation in this place; we are only to consider the sensible effects of those operations of which we know so well the proper conditions.

There are just two distinct views under which we may consider all stalactical concretions formed; these are the incrustation of the calcareous substance concreting upon a foreign body, and the incrustation of the same substance upon itself. By the first any manner of shape may be formed, provided there be a solid body, upon the surface of which the calcareous solution is made to pass. By the second, again, we have various forms; but we know the principles upon which they had been made. These are the shape and motions of the fluid which gives the calcareous concretion. Now, these principles are always to be perceived, more or less, in all the bizarre or fantastical, as well as regular shapes which are produced by stalactical concretions. At present, we shall confine our views to one particular shape, which is simple, regular, and perfectly understood wherever it is formed.

Drops of water falling from a roof, and forming stalactite, produce first tubular bodies, and then gradually consolidate and increase those pendulous bodies by incrustation. These appearances are thought to be observed in the calcedony and ferruginous concretions, which has led some mineralists to conclude, that those concretions had been formed in the same manner, by means of water. We are now to show that these mineral appearances are not analogous to stalactites in their formation, and that they have evidently been formed in a different manner.

It must be evident, that, in the formation of those pendulous bodies, each distinct stalactite must be formed by a separate drop of water; consequently, that no more stalactites can be formed in a given space, than there could have subsisted separate drops of water. Now, a drop of water is a very determined thing; and thus we have a principle by which to judge of those mistaken appearances.

Let us suppose the gut of water to be but one eighth of an inch, although it is a great deal more, we should have no stalactites formed nearer to each other than that measure of space. But those mineral concretions, which are supposed to be stalactical, are contained in half that space, or are nearer to each other than the tenth or twentieth of an inch. I have them like needles, and in every degree of proximity or contiguity, at the same time that they are perfectly solid. Therefore, it is plainly impossible that they could have been formed upon this principle of calcareous stalactite. But, it is only by this false resemblance, that any argument can be formed for the concretion of those bodies from an aqueous solution; in every other respect they are true mineral concretions; and, that these have had a very different origin, has been already the subject of investigation, and will be more particularly examined in the course of this work.

The term infiltration, which has been much employed for explaining mineral appearances, is too vague, imperfect, or unexplicit, for science, whether as the means of knowing nature, or the subject of confutation. This is not the case with that of stalactite; here is a term that implies a certain natural operation, or a most distinct process for attaining a certain end; and we know the principles upon which it proceeds, as well as the several steps that may be traced in the general result. It is an operation which has not only been analysed to its principles; it is also a process which is performed by man, proceeding on his acquired knowledge. Now, were this operation common to the mineral regions, as it is proper to the surface of this earth; we could not remain in any degree of suspense with regard to the origin of those mineral bodies; for, having the true clue of knowledge, we should be able to unravel the most intricate and mysterious appearance. But, so far from this being the case, the more we come to inquire into nature, and employ this principle, the less we find it applicable, and the more involved in darkness is our science.

The places where these false appearances of stalactite are found, are precisely those in which, from the nature of things, all possibility for such an operation is excluded. For, How can this take place within a closs cavity in the mineral regions? The term vegetation may as well be employed for the explanation of those appearances: But what would now be said of such an explication? It is high time that science were properly applied to the natural history of this earth, and mineralists not allowed to impose upon themselves with false reasoning, or to please themselves with the vain attempt of explaining visible effects by unknown causes.

Such various inconsistent opinions, respecting petrifaction or mineral concretion, as I have now exposed, opinions that are not founded on any sound physical principle, authorise me to conclude that they are all erroneous. If this be admitted, it will follow that we have no proof of any proper mineral concretion except that which had proceeded by congelation from the fluid state of fusion. This has been the doctrine which I have held out in my Theory of the Earth; and this will be more and more confirmed as we come to examine particular mineral appearances.



CHAP. VIII.

The Nature of Mineral Coal, and the Formation of Bituminous Strata, investigated.

SECT. I.—Purpose of this Inquiry.

In the first chapter, I have given a perfect mark by which to judge, of every consolidated stratum, how far that had been the operation or effect of water alone, or if it had been that of heat and fusion. This is the particular veins or divisions of the consolidated stratum, arising from the contraction of the mass, distended by heat, and contracted in cooling. It is not an argument of greater or lesser probability; it is a physical demonstration; but, so far as I see, it would appear to be for most mineralists an unintelligible proposition. Time, however, will open the eyes of men; science will some day find admittance into the cabinet of the curious. I will therefore now give another proof,—not of the consolidation of mineral bodies by means of fusion, for there is no mineral body in which that proof is not found,—but of the inconsistency of aqueous infiltration with the appearances of bodies, where not only fusion had been employed for the consolidation, but where the application of heat is necessary, and along with it the circumstances proper for distillation.

Short-sighted naturalists see springs of water issuing from the earth, one forming calcareous incrustations, the other depositing bituminous substances. Here is enough for them to make the theory of a world; on the one hand, solid marble is explained, on the other, solid coal. Ignorance suspects not error; their first step is to reason upon a false principle;—no matter, were they only to reason far enough, they would soon find their error by the absurdity into which it lands them. The misfortune is, they reason no farther; they have explained mineralogy by infiltration; and they content themselves with viewing the beautiful specimens in their cabinet, the supposed product of solution and crystalization. How shall we inform such observators; How reason with those who attend not to an argument!

As naturalists have explained all mineral concretions from aqueous or other solution, and attributed to infiltration the formation of those stony bodies in which there are marks of their original composition, so have they explained to themselves, I suppose, the origin of those bituminous bodies which are found among the strata of the earth. In the case of stony substances, I have shown how unfounded all their theories are for the production of those concretions, crystallizations, and consolidated bodies. I am here to examine the subject of inflammable and combustible bodies, which I believe have been little considered by those theorists who suppose mineral bodies consolidated by infiltration. It is here that we shall find an infinite difference between the aqueous and igneous theories; for, we shall find it impossible to explain by the one certain operations which must have necessarily required the great agent generally employed in the other.

The subject of this chapter is a touch-stone for every theory of the earth. In every quarter of this globe, perhaps in every extensive country, bituminous strata are to be found; they are alternated with those which are called aquiform, or which had been evidently formed by subsidence of certain moved materials at the bottom of the sea; so far, therefore, all those strata have had the same origin. In this point I think I may assert, that all the different theories at present are agreed; and it is only concerning certain transformations of those strata, since their original collection, that have been ascribed to different causes.

Of these transformations, which the strata must have undergone, there are two kinds; one in relation to change of place and position; the other in relation to solidity or consistence. It is only the last of those two changes which is here to be the subject of consideration; because, with regard to the first, there is nothing peculiar in these bituminous strata to throw any light, in that respect, upon the others. This is not the case with regard to the transformation in their chemical character and consistence; bituminous bodies may not be affected by chemical agents, such as fire and water, in the same manner as the argillaceous, siliceous, micaceous, and such other strata that are alternated with the bituminous; and thus we may find the means for investigating the nature of that agent by which those strata in general have been transformed in their substance; or we may find means for the detecting of false theories which may have been formed with regard to those operations in which the original deposits of water had been changed.