Volume 1 / Part 1 — CHAPTER II. (continued 4)

CHAP. VII.

Opinions examined with regard to Petrifaction, or Mineral Concretion.

The ideas of naturalists with regard to petrifaction are so vague and indistinct, that no proper answer can be given to them. They in general suppose water to be the solvent of bodies, and the vehicle of petrifying substances; but they neither say whether water be an universal menstruum, nor do they show in what manner a solid body has been formed in the bowels of the earth, from that solution. It may now be proper to examine this subject, not with a view to explain all those petrifactions of bodies which is performed in the mineral regions of the earth, those regions that are inaccessible to man, but to show that what has been wrote by naturalists, upon this subject, has only a tendency to corrupt science, by admitting the grossest supposition in place of just principle or truth, and to darken natural history by introducing an ill conceived theory in place of matter of fact.

M. le Comte de Buffon has attempted to explain the crystallization of bodies, or production of mineral forms, by the accretion or juxtaposition of elementary bodies, which have only form in two dimensions, length and breadth; that is to say, that mineral concretions are composed of surfaces alone, and not of bodies. This however is only an attempt to explain, what we do not understand, by a proposition which is either evidently contradictory, or plainly inconceivable. It is true that this eloquent and ingenious author endeavours to correct the palpable absurdity of the proposition, by representing the constituent parts of the mineral bodies as "de lames infiniment minces;" but who is it does not see, that these infinitely thin plates are no other than bodies of three dimensions, contrary to the supposition; for, infinitely thin, means a certain thickness; but the smallest possible or assignable thickness differs as much from a perfect superficies as the greatest.

M. de Luc has given us his ideas of petrifaction with sufficient precision of term and clearness of expression; his opinion, therefore, deserves to be examined; and, as his theory of petrifaction is equally applicable to every species of substance, it is necessary again to examine this subject, notwithstanding of what has been already said, in the first part of this work, concerning consolidation and mineral concretion from the fluid state of fusion.

He then illustrates this operation of nature by those of art, in building walls which certainly become hard, and which, as our author seems to think, become solid. But this is only an imperfect or erroneous representation of this subject; for, mortar does not become hard upon the principle of petrification adopted by our author. Mortar, made of clay, instead of lime, will not acquire a stony hardness, nor ever, by means of water, will it be more indurated than by simply drying; neither will the most subtile powder of chalk, with water and sand, form any solid body, or a proper mortar. The induration of mortar arises from the solution of a stony substance, and the subsequent concretion of that dissolved matter, operations purely chemical. Now, if this philosopher, in his Theory of Petrifaction, means only to explain a chemical operation upon mechanical principles, why have recourse, for an example in this subject, to mineral bodies, the origin of which is questioned? Why does he not rather explain, upon this principle, the known concretion of some body, from a fluid state, or, conversely, the known solution of some concreted body? If again he means to explain petrifaction in the usual way, by a chemical operation, in that case, the application of his polished surfaces, so as to cohere, cannot take place until the dissolved body be separated from the fluid, by means of which it is transported from place to place in the mineral regions. But it is in this preliminary step that lies all the difficulty; for, could we see how every different substance might be dissolved, and every dissolved substance separated from its solvent at our pleasure, we should find no difficulty in admitting the cohesion of hard bodies, whether by means of this doctrine of polished surfaces, or by the principle of general attraction, a principle which surely comprehends this particular, termed a cohesive power.

It must not be alleged, that seeing we know not how water dissolves saline bodies, therefore, this fluid, for any thing that we know, may also dissolve crystal; and, if water thus dissolves a mineral substance in a manner unknown to us, it may in like manner deposit it, although we may not be able to imagine how. This kind of reasoning is only calculated to keep us in ignorance; at the same time, the reasoning of philosophers, concerning petrifaction, does not in general appear to be founded on any principle that is more sound. That water dissolves salt is a fact. That water dissolves crystal is not a fact; therefore, those two propositions, with regard to the power of water, are infinitely removed, and cannot be assimilated in sound physical reasoning. It is no more a truth that water is able to dissolve salt, than that we never have been able to detect the smallest disposition in water to dissolve crystal, flint, quartz, or metals. Therefore, to allege the possibility of water being capable of dissolving those bodies in the mineral regions, and of thus changing the substance of one body into another, as naturalists have supposed, contrary to their knowledge, or in order to explain appearances, is so far from tending to increase our science, that it is abandoning the human intellect to be bewildered in an error; it is the vain attempt of lulling to sleep the scientific conscience, and making the soul of man insensible to the natural distress of conscious ignorance.

But besides that negative argument concerning the insolubility of crystal, by which the erroneous suppositions of naturalists are to be rejected, crystal in general is found regularly concreted in the cavities of the most solid rock, in the heart of the closest agate, and in the midst of granite mountains. But these masses of granite were 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.

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.

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.

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 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 la marne n'est que fort peu sensible aux acides, et de blanche qu'elle étoit, sa couleur est devenue presque noire. C'est là qu'on observe les différens degrés du changement de la marne en silex, contenant, même encore, par fois, de parties pyritéiques non détruites dans son intérieur. Et comme la nature forme ici, de même, que dans la chaux pure les silex, la plupart en boules ou rognons; comme les différent degrés de métamorphoses de la marne en silex, sont ici beaucoup plus nombreuses que là, de sorte qu'il y a des bandes entières, qui mériteroient plutôt d'être appellés bandes silicieuses, que marneuses; comme il y a, enfin, une grande quantité de pyrites, qu'ailleurs, il est très probable qu'elle se serve là du même moyen qu'ici pour opérer la métamorphose en question.

"Ne nous précipitons, cependant, pas à en tirer plus de conséquences; poursuivons plutôt le fil de notre récit.

"Le silex, qui se trouve ici, est non seulement de différents degrés de perfection, il est de plus d'une espèce. Il y a de la pierre à feu, 2 de la calcédoine, 3 des agathes, et 4 différentes nuances et passages des espèces ordinaires aux fines du silex.

"La pierre à feu, est, ordinairement dans son état de perfection d'un grain assez fin, d'une couleur grise plus ou moins foncée, et même donnant, dans le noirâtre, plus ou moins diaphane; ses cassures sont concentriques ou coquillées, 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, même au milieu d'une boule de silex parfait.

"Les calcédoines et agathes de ces couches sont toujours (au moins, je ne les ai pas encore vues autrement) de coraux et autres corps marins pétrifiés. Donc, il faut que les couches de pierres roulées, d'où j'ai tiré ma collection citée plus haut, soyent des débris de montagne» détruites de cette espèce. Il y en a qui sont très parfaites comme celles qui composent ma collection, d'autres méritent plutôt d'être rangées parmi les passages du silex ordinaire, et ses espèces plus fines; d'autres encore sont, en effet, de vraies agathes, mais qui renferment dans leur intérieur 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 opacité, par leur mollesse respective, et souvent même par leur sensibilité pour les acides minéraux. 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 brunâtres, verdâtres, rougeâtres, jaunâtres, bleuâtres, tachetées, veinées, etc. Leur clarté n'est pas moins variable, que leur couleur, il y en a de presqu'opaques, comme aussi de presque transparentes, sur tout là, ou la calcédoine prédomine.

"Le quartz s'y trouve comme dans les pierres de la premiere section, c, a, d, crystallisé, en groupes dans de petites cavités; quelquefois aussi en veines. La calcédoine y est de même, ou bien en mamelons, ou bien en stalactites, lorsqu'elle a de la place pour s'y déposer.

"Un phénomène encore plus curieux que cela est cette belle pyrite sulphureuse jaune, comme de l'or, qui est quelquefois parsemée par tout la substance de pétrifications agathisées, et qui apparemment y fut déposée après la dite métamorphose à la faveur des petits pores, qui y étoient restés ouverts."

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 sçait, qu'une pierre calcaire contenant du bitume.

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

"Le caillou, ou silex qui s'y génère, forme, tantôt de gros blocs informes, qui occupent des cavités dans l'intérieure des montagnes, tantôt, enfin, en forme de filons.

"J'ai remarqué cette métamorphose sur trois endroits différens, dans chacun des quels la nature a autrement opéré.

"Sur l'un, la pierre puante fait un banc horizontal dans une montagne de pierre calcaire crystalline, ou d'une espèce de marbre, qui contient des couches et filons de métal. Ce banc de pierre puante y fait le toit d'une couche de galène de plomb et de pierre calaminaire, et dans ses cavités et fentes il y a non seulement des blocs de grandeur différente, mais aussi des veines et petites bandes courtes de silex, tant ordinaire, que noble c, a, d, de la pierre à feu, de calcédoine, d'agathes, et même d'une espèce de cornaline jaune et rouge pâle. Je ne m'arrêterai pas à en détailler les variétés, parce qu'elles sont trop accidentelles. Je ne les connois pas même toutes, il s'en faut de beaucoup, parce qu'elles se trouvent dans des anciennes mines négligées, peut être depuis plus d'un siècle, et par conséquent 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 cité. Parmi ce silex, il y a aussi de petites groupes et de petites veines de quartz solide et crystallisé.

"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'égales de l'épaisseur de trois aunes à peu près. La montagne, ou cela se voit est aussi une ancienne mine de cuivre et de plomb, consistant en plusieurs variétés de marbre, différent en couleur et en grain, déposées par couches les unes sur les autres. Le filon de silex est formé de feuilles alternatives de pierre puante et de silex, tous les deux de couleur brun de bois à peu prés; mais le silex est plus foncé que sa compagne. Ces feuilles alternatives, consistent d'autres bien plus minces encore, qui souvent n'ont pas l'épaisseur d'une ligne, mais ce qu'il y a de plus curieux, c'est que la même feuille est d'un but de pierre porque, qui, vers le milieu, passe successivement en silex, qui, à son tour, vers l'autre but, qui étoit exposé à l'air repasse par les mêmes gradations en une espèce de tuffe calcaire. Ce qui nous fait voir évidemment la génération et la destruction du silex, même avec une partie des moyens par lesquels elle s'opère. Comme l'endroit de cette découverte n'est accessible qu'à la superficie, je ne saurois dire s'il y a d'autres variétés de silex outre la dite. Il l'est à supposer autant par analogie, que par quelques morceaux qui ont de petites veines transversales d'une espèce de calcédoine, et qui sont, même, sur leur fentes, garnis de petits cristaux de roche. Mais ce qu'il y a de sur c'est que ce filon, parvenu à une certaine profondeur, s'ennoblit et contient du métal, c. a. d. de la galène de plomb, et de la pyrite cuivreuse, j'y en ai trouvés 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'étincelles au briquet, mais ses cassures sont écailleuses.

"La montagne calcaire du troisième lieu a une couche de pierre puante épaisse de plusieurs aunes, qui, derechef contient de petites couches irrégulières et des bandes transversales de silex, qui ont jusques à six pouces passés d'épaisseur. La pierre puante est d'une couleur gris-brune, d'un grain assez fin, et d'un tissu assez dur; ses cassures sont irrégulières, mais plus la pierre s'approche du silex, plus elles donnent dans le coquillé. Le silex ordinaire est d'un brun de bois, d'un grain assez fin, et d'un tissu résistant, et ses cassures sont égales à la pierre porque. Ce n'est pas là la seule variété, il y a, aussi, de la calcédoine et des agathes de couleurs différentes. Même la pierre à feu est assez souvent traversée de veines de calcédoine, de quartz crystallisé, et de spath calcaire blanc en feuilles et en crystaux. Il arrive que la même veine est composée de ces trois espèces de pierres à la fois, de sorte que l'une semble passer dans l'autre, parce que les limites réciproques sont, souvent, assez indistinctes. Il est évident, que le silex est formé de la pierre puante, parce qu'on remarque ici les mêmes phénomènes dont j'ai parlé 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 à changer dans une autre doit, avant toute chose, être rendue réfractaire ce qui ne peut se faire qu'en la saturant avec un acide. Mais une terre simplement, saturée d'un acide, est d'une réduction fort aisée, vu que l'acide n'y tient pas trop fort, d'ailleurs ce n'est qu'un sel neutre terreux fort facile â dissoudre dans une quantité suffisante d'eau. Or pour rendre cette union plus constante, il faut que la terre alcaline s'assimile intimement à l'acide, ce qui ne se sera jamais sans un intermedeliant, qui homogène les parties de ce nouveau corps, et pour que cela ce fasse il est indispensable, qu'il s'opère une dissolution foncière des parties terrestres de la chaux, qui facilite l'ingress à l'acide, et à l'intermède 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 liberté, ouvre les interstices des parties qui constituent la terre alcaline, qu'apres cela cette liqueur savonneuse ayant l'entrée libre s'assimile à la terre en proportion requise, que l'eau, qui servoit de véhicule dans cette operation, s'évapore successivement, et emporte le superflu des ingrediens, pour qu'il se puisse opérer le rapprochement le plus exacte des parcelles ou molécules homogénées de nouveau corps qu'enfin les molécules les plus pures et les mieux affinées soyent réunies en forme liquide dans des cavités, et que par l'évaporation et séparation 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 intérieurs."

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.

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 progénéré de chaux, détaché de son lieu natal, et exposé aux changemens de saisons, s'amollit, reçoit de crevasses, perd sa transparence, devient, enfin, tout-à-fait opaque, le phlogistique s'en évapore, l'acide en est détaché, lavé, et de terre vitrescible, qu'il étoit, il redevient chaux, comme il étoit 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 Grès, ou Pierre Sabloneuse.

"Tout grès est susceptible de cette métamorphose quant au grain et quant à la couleur; depuis la bréccia quartzeuse jusqu'à la pierre à rasoir; et depuis le grès blanc jusqu'au brun et presque noirâtre, tient ou non tient, dur, ou presque friable, c'est indifférent, toutes ces variétés donnent du silex, et surtout de la calcédoine, de la cornaline, et des agathes. Quant au ciment je l'y ai toujours remarqué calcaire et faisant effervescence avec les acides dans les endroits de la pierre qui n'étoient point encore changés; et jamais je n'ai vu ce changement dans du grès dont le ciment fut ou quartzeux ou argileux et réfractaire. Ainsi le ciment entre pour quelque chose dans ce changement.

"Le commencement de cette métamorphose paroit (autant que j'ai pu l'observer dans mes débris roulés) se faire par le ciment, qui dissout là, où les agens eurent l'accès libre, rend les grains en quartz mobiles, les emporte, les mêle avec sa masse dense-liquide, les dissout, même en partie, et forme, dans cet état, des veines et de masses calcédonieuse, carneoliques, ou d'une autre espèce de silex, au milieu du grés peu, ou pas du tout, changé. Car autant que je puis voir, ce n'est pas par couches ou veines qu'elle s'opère, mais par boules et masses rond-oblongues. Au commencement ces veines et tâches sont fort minces, et le reste du grés n'est point du tout, ou à peine sensiblement changé hormis qu'il gagne, plus de consistance, à proportion du changement souffert. Mais à mesure que le silex y augmente et se perfectionne, on y apperçoit les degrés par lesquels a passé cette operation. Les nuance du passage d'une pierre à l'autre deviennent plus visibles, les veines et masses de silex grandissent au point, même, qu'il y a jusqu'aux trois quart du grés changé en silex clair comme de l'eau n'ayant que fort peu de grains de sable nageants dans sa masse. Des morceaux de cette espèce sont rares à la vérité, mais j'en ai, cependant, trouvé quelques uns. Ordinairement, dans les beaux morceaux, le silex fait la base, et le sable y est, comme nageant tantôt en grains séparés tantôt en parties et flocons. Dans les pieces moins belles, le sable fait la base, et le silex sert à 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 grès à gros grains, ou de la breccia, alors le reste prend la nature silicieuse mêlé de sable fin, et les gros grains de quartz restent tels, qu'ils étoient, sans changer. J'ai déjà remarqué que cette métamorphose semble s'opérer, comme celle des cailloux d'origine calcaire en forme approchans la sphérique, il faut encore y a jouter, que j'ai lieu de croire, qu'elle se fasse aussi du dedans en dehors, tout, comme la décomposition se fait du dehors au dedans.

"Il arrive dans cette pierre, comme dans toute autre, qu'il se forme des crystallisations dans les cavités. Lorsqu'elles sont de silex, leur figure est toujours mamelonnée, mais leur eau ou pureté, leur grandeur et leur couleur n'est pas par tout égale. Il y en a qui sont grands, et de la plus pure calcédoine, d'autres sont petits et chaque goutte ou mamelon contient un grain de sable, de facon que cela a l'air d'un grès crystallisè en mamelons ou stalagmitique. D'autres encore sont, de calcédoine, mais recouverts d'une croûte, tantôt blanche qui fait effervescence avec l'acide minéral, et qui est, par conséquent, de nature calcaire; tantôt cette croûte est bleue foncée nuancée de bleu-celeste; tantôt, enfin, elle est noire, mais toutes les deux réfractaires. 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.

"Après tout ceci, l'on conviendra j'espère, que nôtre grais est une pierre bien singulière, et surpassant, à bien des égards, le grais, faussement dit crystallisé, de Fontainebleau. La raison de la figure du grais François est fort évidente, c'est le spath calcaire, qui lui sert de ciment, qui la lui fit prendre; mais qu'est-ce qui opère les métamorphoses racontées dans notre grai siliceux? Seroit-ce son ciment calcaire ou marneux par les mêmes raisons, qui font changer la marne en silex? La chose est très-probable, et je n'en saurois pas même, deviner d'autre. En ce cas la nature auroit un moyen d'opérer par la voie humide, ce que nous faisons dans nos laboratoires en quelque façon, par la voie sèche, c, a, d, de fondre et liquéfier la terre vitrescible, au moyen des alcalis; secret que nous lui avons déjà arraché en partie, en faisant la liqueur silicieuse."

"Je n'ose, cependant, décider pas même hypothétiquement, sur cette matière, pour n'avoir pu observer la nature dans ses ateliers, et parce que je ne possède que des pièces, qui détachées de leur lieu natal, depuis un très long-tems, furent exposées aux intempéries des saisons, où 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 Minéralogique 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 collines sont formées d'un hornstein gris qui paroit se convertir en pierre calcaire par l'action des météores; car tout celui qu'on prend hors du contact de l'air donne les plus vives étincelles, et ne fait pas la moindre effervescence avec les acides, même après avoir été calciné; et l'on observe celui qui est à découvert, passer, par nuances insensibles, jusqu'à l'état de pierre calcaire parfaite de couleur blanchâtre."

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'église de la fonderie, a son arrête composée de ce hornstein qui se décompose en pierre calcaire; mais ici, les parties, qui sont ainsi décomposées, offrent une substance calcédonieuse disposées par zones concentriques, comme on l'observe dans les agates d'oberstein; mais ce ne sont point ici des corps parasites formés par infiltration dans des cavités pré-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 régulière (que ce mot de crystallisation ne révolte point, j'appelle ainsi toute tendance à prendre une forme constante, polyèdre ou non polyèdre.) Les couches les plus voisine du centre sont nettes et distinctes; peu-à-peu elles le sont moins, et enfin elles s'évanouissent et se confondent avec le fond de la roche. Chaque assemblage de ces zones a une forme ronde ou ovale plus ou moins régulière de sept à huit pouces de diamètre.

"Cela ressemble en grand à ce qu'on observe dans les pierres oeillées, et la cause est vraisemblablement la même. Je le répète, je regarde cette disposition régulière comme une véritable cristallisation, qui peut s'opérer et qui s'opère en effet dans l'intérieur des corp les plus solide, tant qu'ils sont fournis à l'action des agens de la nature.

"Tous ceux qui visitent l'intérieur de la terre savent que les roches mêmes le plus compactes y sont intimement pénétrées d'humidité, et ce fluide n'est certainement pas l'eau pure; c'est l'agent qui opère toutes les agrégations, toutes les cristallisations, tous les travaux de la nature dans le règne minéral. On peut donc aisément concevoir qu'à la faveur de ce fluide, il règne, dans les parties les plus intimes des corps souterrains, une circulation qui fait continuellement changer de place aux élémens de la matière, jusqu'a ce que réunis par la force des affinités, les corpuscules similaires prennent la forme que la nature leur a assignée."

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 minéralogique, etc. Journal de Physique Aoust 1784.

"Il y a loin de cette pierre, que je regarde comme une variété de roches ardoisées, aux véritable ardoises. La composition de toutes ces pierres est due aux terres quartzeuses et argileuses, et à la terre talqueuse, que je démontrerai un jour être une espèce particulière et distincte des autres, qui constitue les bonnes ardoises, et fait, ainsi que le quartz, qu'elles résistent aux injures de l'air, sans s'effleurir, comme je ferai voir que cette terre, qu'on désignera sous la dénomination de terre talqueuse, si l'on veut, résiste au grand feu sans se fondre. Les différences de toutes ces pierres, quoique composées des mêmes matières, mais dans des proportions différentes, sont frappantes, et pourroient faire croire qu'elles n'appartiennent pas à ce genre. Mais qui ne voit ici que toutes ces différences, ou ces variétés, ne sont dues qu'aux modifications de la matière première, qu'elle a éprouvées, soit en se mêlant avec des matières hétérogènes, prévenantes du débris des êtres qui ont existé, 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 mêlant avec de la matière déjà solidifiée depuis long-temps? Or nous ne craignons pas de dire, ce que nous avons dit plusieurs fois quand l'occasion s'en est présentée, que cette matière unique, que se modifie selon les occasions et les circonstances, et qui prend un caractère analogue au matières qu'elle rencontre, est l'eau, que beaucoup de naturalistes cherchent vainement ailleurs. Ils ne peuvent comprendre, malgré les exemples frappans qui pourroient les porter à adopter cette opinion, que ce fluide général soit l'élément des corps solides du règne minéral, comme il est de ceux du règne végétal et du règne animal. L'on cherche sérieusement, par des expériences chimiques, à découvrir 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'état fluide à l'état solide. Voyez le spath calcaire et le quartz transparens; est il à présumer qu'ils ne sont que le résultat du dépôt des matières terreuses fait par les eaux? Mais, dans ce ca-là encore, il faut supposer que l'eau qui est restée entre ces partie s'est solidifiée; car, qu'est-elle donc devenue, et quel est donc le lien qui a uni ces parties et leur a fait prendre une forme régulière? Il est vrai qu'on nous parle d'un suc lapidifique; mais c'est-la un être de raison, dont il seroit bien plus difficile d'établir l'existence, que de croire à la solidification de l'eau. On nous donne cependant comme un principe certain que l'eau charie d'un lieu à un autre les matières qu'il a dissoutes, et qu'elle les dépose à la maniere des sels. Mais c'est supposer une chose démentie par l'experience; savoir, que l'eau ait la propriété de dissoudre les matières terreuses, telles que la quartzeuse. A la vérité, 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 été l'exactitude de ceux qui ont répété les expériences de M. Auchard, on n'a pu réussir à imiter la nature, c'est-à-dire, à former des cristaux quartzeux, comme il a annoncé. Que l'eau ait la faculté 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-même y concoure pour sa part; car ce seroit conclure quelque fois que la partie seroit égale au tout. Voyez ces géodes calcaire et argileuses, qui renferment des cristaux nombreux de quartz ou de spath calcaire; ne sont ils que le résultat du dépôt de l'eau qui y a été renfermée, ou que la cristallization pure et simple des molécules que vous supposez avoir été tenues en dissolution par cette eau? Il naîtroit de cette opinion une foule d'objections qu'il seroit impossible de résoudre. Cependant M. Guettard, dans la minéralogie du Dauphiné, qui vient de paroître, ouvrage très-estimable à beaucoup d'égards, explique, selon cette maniere de penser, la formation de cristallizations quartzeuses qu'on trouve dans certaines géodes de cette province, et celle des mines de cristal des hautes montagnes. En supposant même comme vraie l'explication qu'il en donne, on trouveroit en cela un des plus grands problème, et des plus difficiles à résoudre qu'il y ait en minéralogie; car d'abord il faudroit expliquer comment un si petite quantité d'eau que celle qui a été renfermée dans les géodes, et celle qui est parvenue dans les fentes des rochers, ont pu fournir un si grande quantité de matière que celle qui constitue ces cristallisations, et ce qui n'est pas le moins difficile à concevoir, comment l'eau a pu charrier cette matière à travers tant de matières différentes, et la conserver précisément pour cette destination; comment, par exemple, l'eau est venue déposer de la terre quartzeuse dans les masses énormes de pierres calcaires, qui forment la côté qui domine le village de Champigny, à quatre lieues de Paris, au delà de Saint-maur; car s'il nous faut citer un exemple frappant de cette singularité, et à portée d'être vue des naturalistes qui sont dans la capitale, je ne puis mieux faire que de citer cette côté, une des plus curieuses de la France, et que je me propose de fair connoître en détail dans la troisième partie de la minéralogie de la France. On verra, dis-je, dans cette bonne pierre à chaux, et une de plus pure des environs de Paris, de très-abondantes cristallisations de quartz transparent, et quelque fois de belle eau, que les ouvriers sont forcés de séparer de la partie calcaire, à laquelle elles adhèrent fortement. Mais c'est trop nous arrêter à combattre une opinion qui doit son origine aux premières idées qu'ont eues les premiers observateurs en minéralogie, qui se détruira d'elle même comme tant d'autres dont il nous reste à peine le souvenir."

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.

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.

We have had but two theories, with regard to the transformation of those bodies which have had a known origin, or to the change of their substance and consistence; the one of these which I have given is that of heat or fusion; the other, which I wish to be compared with mine, is that of water and infiltration. It is by this last that all authors hitherto, in one shape or another, have endeavoured to explain the changes that those strata must have undergone since the time of their first formation at the bottom of the sea. They indiscriminately apply the doctrine of infiltration to those strata of mineral coal as to any other; they say that bituminous matter is infiltrated with the water, impregnates certain strata of earth with bituminous matter, and thus converts them into mineral coal, and bituminous strata. This is not reasoning physically, or by the inductive method of proceeding upon matter of fact; it is reasoning fantastically, or by making gratuitous supposition founded merely on imagination. It was thus that natural philosophers reasoned before the age of science; the wonder now is, how men of science, in the present enlightened age, should suffer such language of ignorance and credulity to pass uncensured.

The subject which I am now to treat of consists of peculiar strata of the earth, bodies which we may investigate through all the stages of their change, which is extreme; for, from vegetable bodies produced upon the habitable earth, they are now become a mineral body, and the most perfect coal,—a thing extremely different from what it had been, and a thing which cannot be supposed to have been accomplished by the operation of water alone, or any other agent in nature with which we are acquainted, except the action of fire or heat. It is therefore impossible for a philosopher, reasoning upon actual physical principles, not to acknowledge in this a complete proof of the theory which has been given, and a complete refutation of that aqueous operation which has been so inconsiderately supposed as consolidating the strata of the earth, and forming the various mineral concretions which are found in that great body.

To see this, it will be sufficient to trace the progress of vegetable and animal substances, (bodies which had certainly lived by means of a former earth), to this changed state in which they have become perfect mineral bodies, and constitute a part of the present earth. For, as these changes are perfectly explained by the one theory, and absolutely inconsistent with the other, there arises from this a conviction that must be irresistible to a person who can give proper attention to a chain of reasoning from effect to cause.

But if we thus succeed to illustrate the theory of the earth by the natural history of those particular strata, we have but one step farther to make in order to bring all the other parts of the earth, whether stratified or not, into the most perfect consistence with the theory; now this step, it will be most easy to make; and I shall now mention it, that so the reader may keep it in his view: Pyrites is a sulphureo-metallic substance, which cannot be produced by means of water, a substance which the influences of the atmosphere decomposes or separates into its elements, and which even our imperfect art may be considered as able to produce, by means of fusion in our fires. Therefore, the finding of this creature of fire intimately connected with those consolidated strata of mineral coal, adds the greatest confirmation, were it necessary, to the doctrine of those mineral bodies having been consolidated by fusion. This confirmation, however, is not necessary, and it is not the only thing which I am at present to illustrate in that doctrine. What I have now in view is, to homologate the origin of those coal strata, with the production of every other mineral substance, by heat or fusion; and this is what the intimate connection of pyrites with those strata will certainly accomplish. This will be done in the following manner:

Pyrites is not only found in great masses along with the coal strata; it is contained in the veins which traverse those strata, and in the minute ramifications of those veins, which are occasioned by the contraction of the mass, and generally divide it into small cubical pieces; but besides that extrinsic connection, (as it may be called,) with the stratum of coal, pyrites is found intimately connected with that solid body, in being mixed with its substance. If, therefore, it were proved, that either the one or other of those two substances had been consolidated by fusion, the other must be acknowledged as having had the same origin; but now I am to prove, from the natural history of mineral coal, that pyrites had been there formed by fusion; and then, by means of the known origin of that sulphureo-metallic substance, we shall extend our knowledge to the origin of every other mineral body.

The process of this argument is as follows: Every mineral body, I believe, without exception, will be found so intimately connected with pyrites, that these two things must be concluded as having been together in a fluid state, and that, whatever may have been the cause of fluidity in the one, this must have also caused the fluidity in the other; consequently, whatever shall be proved with regard to the mineral operations of pyrites, must be considered as proved of every other mineral substance. But, from the connection of pyrites with mineral coal, it is to be proved that the origin of this metallic body had been fusion; and then it will appear, that all other mineral bodies must have been more or less in fusion, or that they must have been consolidated by means of heat, and not by any manner of solution or aqueous infiltration. I therefore now proceed to take a view of the natural history of coal strata,—a subject which mineralogists seem not inclined to engage with, although the most ample data are to be found for that investigation.

SECT. II.—Natural History of Coal Strata, and Theory of this Geological Operation.

Fossil coal is the species of stratum best understood with regard to its accidents, as being much sought after; at least, this is the case in many parts of Britain, where it supplies the place of wood for burning. This fossil body has the most distinguished character; for, being inflammable or combustible in its nature, there is no other species of stratum that may be confounded with it.

But, though coal be thus the most distinguishable mineral, and that which is best understood in the science of mining, it is perhaps the most difficult to be treated of in the science of mineralogy; for, not having properly any distinguishable parts, we have nothing in the natural constitution of this body, as we have in most other strata, to lead us to the knowledge of its original state or first formation.

The varieties of coal are distinguished by their different manner of burning; but, from appearances of this kind, no perfect judgement can be formed with regard to the specific manner in which those strata had been made; although, from chemical principles, some conclusion may be drawn concerning certain changes which they have undergone since they had been formed.

Thus we have one species of coal which is extremely fusible, abounds with oil, and consequently is inflammable; we have another species again which is perfectly fixed and infusible in the fire; therefore, we may conclude upon principle, that, however, both those coals must have undergone the operation of heat and fusion, in bringing them to their present state, it is only the last that has become so much evaporated as to become perfectly fixed, or so perfectly distilled, as to have been reduced to a caput mortuum.

The argument here employed is founded upon this fact; that, from the fusible species of coal, a caput mortuum may be formed by distillation, and that this chemical production has every essential quality, or every peculiar property, of the fixed and infusible species; although, from the circumstances of our operation, this caput mortuum may not have precisely the exterior appearance of the natural coal. But, we have reason to believe, it is not in the nature of things to change the infusible species, so as to make it fusible or oily. Now, that this body was not formed originally in its present state, must appear from this, that the stratum here considered is perfectly solid; but, without fusion, this could not have been attained; and the coal is now supposed to be infusible. Consequently, this fixed substance, which is now, properly speaking, a perfect coal, had been originally an oily bituminous or fusible substance. It is now a fixed substance, and an infusible coal; therefore, it must have been by means of heat and distillation that it had been changed, from the original state in which this stratum had been formed.

We have thus, in the examination of coal strata upon chemical principles, received a certain lesson in geology, although this does not form a proper distinction by which to specify those strata in general, or explain the variety of that mineral. For, in this manner, we could only distinguish properly two species of those strata; the one bituminous or inflammable; the other proper coal, burning without smoke or flame. Thus it will appear that, as this quality of being perfectly charred is not originally in the constitution of the stratum, but an accident to which some strata of every species may have been subjected, we could not class them by this property without confounding together strata which had differences in their composition or formation. Therefore, we are led to inquire after some other distinction, which may be general to strata of fossil coal, independent of those changes which this substance may have undergone after it had been formed in a stratum.

Perfect mineral coal being a body of undistinguishable parts, it is only in its resolution that we may analyse it, and this is done by burning. Thus, in analysing coal by burning, we have, in the ashes alone, that by which one species of coal may be distinguished from another; and, if we should consider pure coal as having no ashes of itself, we should then, in the weight of its ashes, have a measure of the purity of the coal, this being inversely as the quantity of the ashes. Now, though this be not accurately true, as the purest coal must have some ashes proper to itself, yet, as this is a small matter compared with the quantity of earthy matter that may be left in burning some species of coal, this method of analysis may be considered as not far removed from the truth.

But, in distinguishing fossil coal by this species of chemical analysis, not only is there to be found a perfect or indefinite gradation from a body which is perfectly combustible to one that is hardly combustible in any sensible degree, we should also fall into an inconveniency similar to that already mentioned, of confounding two things extremely different in their nature, a bituminous body, and a perfect charcoal. Thus, if we shall found our distinction upon the fusibility and different degree of having been charred, we shall confound fossil coals of very different degrees of value in burning, or of very different compositions as strata; if, again, we found it upon the purity of composition, in judging from the ashes, we shall confound fossil bodies of very different qualities, the one burning with much smoke and flame, the other without any; the one fusible almost like wax, the other fixed and infusible as charcoal.

It will now appear, that what cannot be done in either the one or other of those two methods, may in a great degree, or with considerable propriety, be performed in employing both.

Thus, whether for the economical purposes of life, or the natural history of fossil coal, those strata should be considered both with regard to the purity of their composition as inflammable matter deposited at the bottom of the sea, and to the changes which they have afterwards undergone by the operation of subterranean heat and distillation.

We have now considered the original matter of which coal strata are composed to be of two kinds; the one pure bitumen or coal, as being perfectly inflammable or combustible; the other an earthy matter, with which proper coal may be variously mixed in its composition, or intimately connected, in subsiding from that suspended state by which it had been carried in the ocean. It is a matter of great importance, in the physiology of this globe, to know that the proper substance of coal may be thus mixed with heterogeneous bodies; for, supposing that this earthy matter, which has subsided in the water along with coal, be no farther connected with the combustible substance of those strata, than that it had floated in the waters of the ocean, and subsided pari passu with the proper materials of the coal, we hence learn a great deal with regard to the state in which the inflammable matter must have been at the time of its formation into strata. This will appear by considering, that we find schistus mixed with coal in the most equal or uniform manner, and in almost every conceivable degree, from the purest coal to the most perfect schistus. Hence we have reason to conclude, that, at the formation of those strata, the bituminous matter, highly subtilised, had been uniformly mixed with the earth subsiding in the water.

Not only is the bituminous matter of coal found mixed in every different proportion with the earthy or uninflammable materials of strata, but the coaly or bituminous composition is found with perhaps every different species of substance belonging to strata. This is certain, that we have the coaly matter intimately mixed with argillaceous and with calcareous strata.

Thus it will appear, that it is no proper explanation of the formation of coal strata, to say that vegetable matter is the basis of those strata; for though, in vegetation, a substance proper for the formation of bituminous matter is produced, it remains to know by what means, from a vegetable body, this bituminous matter is produced, and how it comes to be diffused in that subtile state by which it may be uniformly mixed with the most impalpable earth in water. Could we once resolve this question, every other appearance might be easily explained. Let us therefore now endeavour to discover a principle for the resolving of this problem.

There are two ways in which vegetable bodies may be, in part at least, resolved into that subtilised state of bituminous matter after which we inquire; the one of these is by means of fire, the other by water. We shall now consider these severally as the means of forming bituminous strata, although they may be both employed by nature in this work.

When vegetable bodies are made to burn, there is always more or less of a fuliginous substance formed; but this fuliginous substance is no other than a bituminous body in that subtilised state in which it is indefinitely divided, and may be mixed uniformly with any mass of matter equally subtilised with itself. But this is precisely what we want, in order to compose the strata of coal in question. If, therefore, there were to be found in the ocean such a fund of this fuliginous substance as might suffice for the formation of bituminous strata, no difficulty would be left in explaining the original of fossil coal. But tho' sufficient quantity of this fuliginous matter might not be found for the explanation of natural appearances, yet there cannot be a doubt that more or less of this matter must be produced in the mineral operations of the globe, and be found precisely in that place where it is required for the forming of those strata of coal.