Theory of the Earth Volume I Part 13

Professor Playfair was to pa.s.s through c.u.mberland. I begged that he would inquire of Mr Wright, at the Low-wood Inn, for those objects which he was to endeavour to procure for me, and to examine the limestone quarry in which I had found the specimen with entrochi. He went through another part of those primary mountains, and has found examples of this kind in the schisti; concerning which he has written me the following account.

"In a visit which I made to the Lakes of c.u.mberland in September 1791, in company with the Hon. Francis Charteris, I met with a limestone full of marine objects, though from its position it is certainly to be reckoned among the primary strata. The place where we found this stone was in the district of Lancas.h.i.+re, that is west of Windermere Lake, on the road from Ambleside to the north end of Coniston Lake, and not far from the point when you come in sight of the latter. Just about this spot we happened to meet with one of those people who serve as guides to travelers in those parts, and who told us, among other things, that stones with sh.e.l.ls in them were often found not far from where we were then walking. We immediately began to look about for specimens of that kind, and soon met with several; the most remarkable of which was in a rock that rose a little above the surface, about 300 or 400 yards to the right of the road. It was a part of a limestone stratum, nearly vertical, and was full of bivalves with the impressions as strong as in a common secondary limestone. The strata on both sides had the same inclination, and were decidedly primary, consisting of the ordinary micaceous schistus. This however I need not remark to you, who know so well from your own observations that the whole of the country I am now speaking of has every character of a primary one. I, only mention it, that it may not be supposed that the rock in question was some fragment of a secondary stratum that remained, after the rest was washed away, superinc.u.mbent on the primary.

"After I had seen this rock, I recollected that you had told me of something of the same kind that you saw in a quarry at Low-wood Inn; and it may be that both belonged to the same stratum or body of strata; for the direction of the strata, as nearly as I could observe, was from S.W.

to N.E.; and this also is nearly the bearing of Low-wood from the place where we now were. I send you a specimen, which you can compare with those you brought from the lime quarry at Low-wood."

I have examined this specimen, and find it to be the common schistus of that country, only containing many bivalve sh.e.l.ls and fragments of entrochi and madrapore bodies, and mixed with pyrites.

I have already observed that one single example of a sh.e.l.l, or of its print, in a schistus, or in a stone stratified among those vertical or erected ma.s.ses, suffices to prove the origin of those bodies to have been, what I had maintained them to be, water formed strata erected from the bottom of the sea, like every other consolidated stratum of the earth. But now, I think, I may affirm, that there is not, or rarely, any considerable extent of country of that primary kind, in which some mark of this origin will not be found, upon careful examination; and now I will give my reason for this a.s.sertion. I have been examining the south alpine country of Scotland, occasionally, for more than forty years back, and I never could find any mark of an organised body in the schistus of those mountains. It is true that I know of only one place where limestone is found among the strata; this is upon Tweed-side near the Crook. This quarry I had carefully examined long ago, but could find no mark of any organised body in it. I suppose they now are working some other of the vertical strata near those which I had examined; for, in the summer 1792, I received a letter from Sir James Hall, which I shall now transcribe. It is dated at Moffat, June 2. 1792.

"As I was riding yesterday between n.o.ble-house and Crook, on the road to this place, I fell in with a quarry of alpine limestone; it consists of four or five strata, about three feet thick, one of them single, and the rest contiguous; they all stand between the strata of slate and schist that are at the place nearly vertical. In the neighbourhood, a slate quarry is worked of a pure blue slate; several of the strata of slate near the limestone are filled with fragments of limestone scattered about like the fragments of schist in the sandstone in the neighbourhood of the junction on our coast.[22]

[Note 22: This has a reference to very curious observations which we made upon the east coast where these mountains terminate, and which I am to describe in the course of this work.]

"Among the ma.s.ses of limestone lately broken off for use, and having the fractures fresh, I found the forms of c.o.c.kles quite distinct; and in great abundance.--I send you three pieces of this kind," etc.

It may perhaps be alleged that those mountains of c.u.mberland and Tweedale are not the primary mountains, but composed of the secondary schistus, which is every where known to contain those objects belonging to a former earth. Naturalists who have not the opportunity of convincing themselves by their proper examination, must judge with regard to that geological fact by the description of others. Now it is most fortunate for natural history, that it has been in this range of mountains that we have discovered those marks of a marine origin; for, I shall afterwards have occasion to give the clearest light into this subject, from observations made in other parts of those same mountains of schist, by which it will be proved that they are the primary strata; and thus no manner of doubt will then remain in the minds of naturalists, who might otherwise suspect that we were deceiving ourselves, by mistaking the secondary for the primitive schistus.

I have only farther to observe, that those schisti mountains of Wales, of c.u.mberland, and of the south alpine part of Scotland, where these marine objects have been found, consist, of that species of stone which in some places makes the most admirable slate for covering houses; and, in other parts, it breaks into blocks that so much resemble wood in appearance, that, without narrow inspection, it might pa.s.s for petrified wood.

We are therefore to conclude that the marks of organised bodies in those primary mountains are certainly found; at the same time the general observation of naturalists has some foundation, so far as the marks of organised bodies are both rarely to be met with in those ma.s.ses, and not easily distinguished as such when they are found.

But this scarcity of marine objects is not confined to those primary mountains, as they are called; for among the most horizontal strata, or those of the latest production, there are many in which, it is commonly thought, no marine calcareous objects are to be found; and this is a subject that deserves to be more particularly considered, as the theory may thus receive some ill.u.s.tration.

Sandstone, coal, and their accompanying strata, are thought to be dest.i.tute of calcareous marine productions, although many vestiges of plants or vegetable productions are there perceived. But this general opinion is neither accurate nor true; for though it be true that in the coal and sandstone strata it is most common to find marks of vegetable production, and rarely those calcareous bodies which are so frequent in the limestone, yet it is not unusual for coal to be accompanied with limestone formed of sh.e.l.ls and corals, and also with ironstone containing many of those marine objects as well as wood. Besides, sandstone frequently contains objects which have been organised bodies, but which do not belong to the vegetable kingdom, at least to no plant which grows upon the land, but would seem to have been some species of zoophite perhaps unknown.

I have also frequently seen the vestige of sh.e.l.ls in sandstone, although in these strata the calcareous bodies are in general not perceived.

The reason of this is evident. When there is a small proportion of the calcareous matter in the ma.s.s of sand which is pervious to steam and to the percolation of water, the calcareous bodies may be easily dissolved, and either carried away or dispersed in the ma.s.s; or even without being thus dispersed by means of solution, the calcareous matter may be absorbed by the siliceous substance of the stratum by means of fusion, or by heat and cementation. The fact is, that I have seen in sandstone the empty mould of marine sh.e.l.ls with some siliceous crystallization, so far as I remember, which corresponded perfectly with that idea. The place I saw this was in a fine white sandstone accompanying the coal, upon the sea side at Brora in Sutherland.

Mineralogy is much indebted to Mr Pallas for the valuable observations which he has given of countries so distant from the habitations of learned men. The physiology of the globe has also been enriched with some interesting observations from the labours of this learned traveller.

But besides giving us facts, Mr Pallas has also reasoned upon the subject, and thus entered deep into the science of Cosmogeny; here it is that I am afraid he has introduced some confusion into the natural history of the earth, in not properly distinguis.h.i.+ng the mineral operations of the globe, and those again which belong entirely to the surface of the earth; perhaps also in confounding the natural effects of water upon the surface of the earth, with those convulsions of the sea which may be properly considered as the accidental operations of the globe. This subject being strictly connected with the opinions of that philosopher with regard to primitive mountains, I am obliged to examine in this place matters which otherwise might have come more properly to be considered in another.

M. Pallas in his _Observations sur la formation des montagnes_, (page 48) makes the following observations.

"J'ai deja dit que _la bande de montagnes primitives schisteuses_ heterogenes, qui, par toute la terre, accompagne les chaines granitiques, et comprend les roches quartzeuses et talceuses mixtes, trapezodes, serpentines, le schiste corne, les roches spathiques et cornees, les grais purs, le porphyre et le jaspre, tous rocs feles en couches, ou presque perpendiculaires, ou du moins tres-rapidement inclinees, (les plus favorables a la filtration des eaux), semble aussi-bien que le granit, anterieure a la creation organisee. Une raison tres-forte pour appuyer cette supposition, c'est que la plupart de ces roches, quoique lamelleuse en facon d'ardoise, n'a jamais produit aux curieux la moindre trace de petrifactions ou empreintes de corps organises. S'il s'en est trouve, c'est apparemment dans des fentes de ces roches ou ces corps ont ete apportes par un deluge, et encastrees apres dans une matiere infiltree, de meme qu'on a trouve des restes d'Elephans dans le filon de la mine d'argent du Schlangenberg.[23] Les caracteres par lesquels plusieurs de ces roches semblent avoir souffert des effets d'un feu-tres-violent, les puissantes veines et amas des mineraux les plus riches qui se trouvent princ.i.p.alement dans la bande qui en est composee, leur position immediate sur le granit, et meme le pa.s.sage, par lequel on voit souvent en grand, changer le granit en une des autres especes; tout cela indique une origine bien plus ancienne, et des causes bien differentes de celles qui ont produit les montagnes secondaires."

[Note 23: This is a very natural way of reasoning when a philosopher finds a fact, related by some naturalists, that does not correspond with his theory or systematic view of things. Here our author follows the general opinion in concluding that no organised body should be found in their primitive strata; when, therefore, such an object is said to have been observed, it is supposed that there may have been some mistake with regard to the case, and that all the circ.u.mstances may not have been considered. This caution with regard to the inaccurate representation of facts, in natural history, is certainly extremely necessary; the relicts of an elephant found in a mineral vein, is certainly a fact of that kind, which should not be given as an example in geology without the most accurate scientifical examination of the subject.]

Here M. Pallas gives his reason for supposing those mountains primitive or anterior to the operations of this globe as a living world; _first_, because they have not, in general, marks of animals or plants; and that it is doubtful if they ever properly contain those marks of organised bodies; _secondly_, because many of those rocks have the appearance of having suffered the effects of the most violent fire. Now, What are those effects? Is it in their having been brought into a fluid state of fusion. In that case, no doubt, they may have been much changed from the original state of their formation; but this is a very good reason why, in this changed state, the marks of organised bodies, which may have been in their original const.i.tution, should be now effaced.

The _third_ reason for supposing those mountains primitive, is taken from the metallic veins, which are found so plentifully in these ma.s.ses.

Now, had these ma.s.ses been the only bodies in this earth in which those mineral veins were found, there might be some species of reason for drawing the conclusion, which is here formed by our philosopher. But nothing is so common (at least in England) as mineral veins in the strata of the latest formation, and in those which are princ.i.p.ally formed of marine productions; consequently so far from serving the purpose for which this argument was employed, the mineral veins in the primitive mountains tend to destroy their originality, by a.s.similating them in some respect with every other ma.s.s of strata or mountain upon the globe.

_Lastly_, M. Pallas here employs an argument taken from an appearance for which we are particularly indebted to him, and by which the arguments which have been already employed in denying the originality of granite is abundantly confirmed. It has been already alleged, that granite, porphyry, and whinstone, or trap, graduate into each other; but here M. Pallas informs us that he has found the granite not only changed into porphyry, but also into the other alpine compositions. How an argument for the originality of these mountains can be established upon those facts, I am not a little at a loss to conceive.

The general mineralogical view of the Russian dominions, which we have, in this treatise, may now be considered with regard to that distinction made by naturalists, of primitive, secondary, and tertiary mountains, in order to see how far the observations of this well informed naturalist shall be found to confirm the theory of the earth which has been already given, or not.

The Oural mountains form a very long chain, which makes the natural division betwixt Europe and Asia, to the north of the Caspian. If in this ridge, as a centre of elevation, and of mineral operations, we shall find the greatest manifestation of the violent exertion of subterraneous fire, or of consolidating and elevating operations; and if we shall perceive a regular appearance of diminution in the violence or magnitude of those operations, as the places gradually recede from this centre of active force; we may find some explanation of those appearances, without having recourse to conjectures which carry no scientific meaning, and which are more calculated to confound our acquired knowledge, than to form any valuable distinction of things. Let us consult M. Pallas how far this is the case, or not.

After having told us that all those various alpine schisti, jaspers, porphyries, serpentines, etc. in those mountains, are found mutually convertible with granite, or graduating into each other, our author thus continues, (p. 50).

"On entrevoit de certaines loix a l'egard de l'arrangement respectif de cet ordre secondaire d'anciennes roches, par tous les systemes de montagnes qui appartiennent a l'Empire Russe. La chaine Ouralique, par exemple, a du cote de l'Orient sur tout sa longueur, une tres-grande abondance de schistes cornes, serpentins et talceux, riches en filons de cuivre, qui forment le princ.i.p.al accompagnement du granite, et en jaspres de diverses couleurs plus exterieurs et souvent comme entrelaces avec les premiers, mais formant des suites de montagnes entieres, et occupant de tres-grands es.p.a.ces. De ce meme cote, il y parait beaucoup de quartz en grandes roches toutes pures, tant dans la princ.i.p.ale chaine que dans le noyau des montagnes de jaspre, et jusques dans la plaine.

Les marbres spateux et veines, percent en beaucoup d'endroits. La plupart de ces especes ne paraissent point du tout a la lisiere occidentale de la chaine, qui n'est presque que de roche melangee de schistes argileux, alumineux, phlogistique, etc. Les filons des mines d'or melees, les riches mines de cuivre en veines et chambrees, les mines de fer et d'aimant par amas et montagnes entieres, sont l'apanage de la bande schisteuse orientale; tandis que l'occidentale n'a pour elle que des mines de fer de depots, et se montre generalement tres-pauvre en metaux. Le granit de la chaine qui borde la Siberie, est recouvert du cote que nous connaissons de roches cornees de la nature des pierres a fusil, quelquefois tendant a la nature d'un grais fin et de schistes tres-metallieres de differente composition. Le jaspre n'y est qu'en filons, ou plans obliques, ce qui est tres-rare pour la chaine Ouralique, et s'observe dans la plus grande partie de la Siberie, a l'exception de cette partie de sa chaine qui pa.s.se pres de la mer d'Okhotsk, ou le jaspre forme derechef des suites de montagnes, ainsi que nous venons de le dire des monts Ourals; mais comme cette roche tient ici le cote meridionale de la chaine Siberienne, et que nous ne lui connaissons point ce cote sur le reste de sa longueur, il se pourrait que le jaspre y fut aussi abondant. Il faudrait, au reste, bien plus de fouilles et d observations pour etablir quelque chose de certain sur l'ordre respectif qu'observent ces roches."

I would now ask, if in all this account of the gradation of rock from the Oural mountains to the sandy coast of the Baltic, there is to be observed any clear and distinctive mark of primitive, secondary, and tertiary, mountains, farther than as one stratum may be considered as either prior or posterior to another stratum, according to the order of superposition in which they are found. We have every where evident marks of the formation of strata by materials deposited originally in water; for the most part, there is sufficient proof that this water in which those materials had been deposited was the sea; we are likewise a.s.sured that the operations of this living world producing animals, must have, for a course of time, altogether inconceivably been exerted, in preparing materials for this ma.s.s; and, lastly, from the changed const.i.tution of those ma.s.ses, we may infer certain mineral operations that melt the substance and alter the position of those horizontal bodies. Such is the information which we may collect from this mineral description of the Russian Dominions.

If we compare some of the Oural mountains with the general strata of the Russian plains, then, as to the contained minerals, we may find a certain diversity in those two places; at the same time, no greater perhaps than may be found betwixt two different bodies in those same plains, for example, chalk and flint. But when we consider those bodies of the earth, or solid strata of the globe, in relation to their proper structure and formation, we surely can find in this description nothing on which may be founded any solid opinion with regard to a different original, however important conclusions may perhaps be formed with regard to the operations of the globe, from the peculiar appearances found in alpine.

From this detail of what is found in the Oural mountains, and in the gradation of country from those mountains to the plains of Russia, we have several facts that are worthy of observation. First extensive mountains of jasper. I have a specimen of this stone; it is striped red and green like some of our marly strata. It has evidently been formed of such argillaceous and siliceous materials, not only indurated, so as to lose its character, as an argillaceous stone, but to have been brought into that degree of fusion which produces perfect solidity. Of the same kind are those hornstein rocks of the nature of flint, sometimes tending to the nature of a fine sandstone. Here is the same induration of sandstone by means of fusion, that in the argillaceous strata has produced jasper. But oblique veins of jasper are represented as traversing these last strata; now this is a fact which is not conceivable in any other way, than by the injection or transfusion of the fluid jasper among those ma.s.ses of indurated strata.

All this belongs to the east side of the mountains. On the west, again, we find the same species of strata; only these are not changed to such a degree as to lose their original character or construction, and thus to be termed differently in mineralogy.

Our author then proceeds. (p. 53.)

"Nous pourrons parler plus decisivement sur les _montagnes secondaires et tertiaires_ de l'Empire, et c'est de celles-la, de la nature, de l'arrangement et du contenu de leurs couches, des grandes inegalites et de la forme du continent d'Europe et d'Asie, que l'on peut tirer avec plus de confiance quelques lumieres sur les changemens arrives aux terres habitables. Ces deux ordres de montagnes presentent la chronique de notre globe la plus ancienne, la moins sujette aux falsifications, et en meme-tems plus lisible que le caractere des chaines primitives; ce font les archives de la nature, anterieures aux lettres et aux traditions les plus reculees, qu'il etoit reserve a notre siecle observateur de feuiller, de commenter, et de mettre au jour, mais que plusieurs siecles apres le notre n'epuiseront pas.

"Dans toute l'etendue de vastes dominations Russes, aussi bien que dans l'Europe entiere, les observateurs attentifs ont remarque que generalement la band schisteuse des grandes chaines se trouve immediatement recouverte ou cottee par la _bande calcaire_. Celle-ci forme deux ordres de montagnes, tres-differentes par la hauteur, la situation de leurs couches, et la composition de la pierre calcaire qui les compose; difference qui est tres-evidente dans cette bande calcaire qui forme la lisiere occidentale de toute la chaine Ouralique, et dont le plan s'etend par tout le plat pays de la Russie. L'on observerait la meme chose a l'orient de la chaine, et dans toute l'etendue de la Siberie, si les couches calcaires horizontales n'y etaient recouvertes par les depots posterieures, de facon qu'il ne parait a la surface que les parties les plus faillantes de la bande, et si ce pays n'etoit trop nouvellement cultive et trop peu exploite par des fouilles et autres operations, que des hommes industrieux ont pratique dans les pays anciennement habites. Ce que je vais exposer sur les deux ordres de montagnes calcaires, se rapportera donc princ.i.p.alement a celles qui sont a l'occident de la chaine Ouralique.

"Ce cote de la dite chaine consiste sur cinquante a cent verstes de largeur, de roche calcaire solide, d'un grain uni, qui tantot ne contient aucune trace de productions marines, tantot n'en conserve que des empreintes aussi legeres qu'epa.r.s.es. Cette roche s'eleve en montagnes d'une hauteur tres-considerable, irregulieres, rapides, et coupees de vallons escarpes. Ses couches, generalement epaisses, ne sont point de niveau, mais tres-inclinees a l'horizon, paralleles, pour la plupart, a la direction de la chaine, qui est aussi ordinairement celle de la bande schisteuse;--au lieu que du cote de l'orient les couches calcaires sont au sens de la chaine en direction plus ou moins approchante de l'angle droite. L'on trouve dans ces hautes montagnes calcaires de frequentes grottes et cavernes tres-remarquables, tant par leur grandeur que par les belles congelations et crystallizations stalactiques dont elles s'ornent. Quelques-unes de ces grottes ne peuvent etre attribuees qu'a quelque boulevers.e.m.e.nt des couches; d'autres semblent devoir leur origine a l'ecoulement des sources souterraines qui ont amolli, ronge et charrie une partie de la roche qui en etoit susceptible.

"En s'eloignant de la chaine, on voit les couches calcaires s'aplanir a.s.sez rapidement, prendre une position horizontale, et devenir abondantes en toute forte de coquillages, de madrepores, et d'autres depouilles marines. Telles on les voit par-tout dans les vallees les plus ba.s.ses qui se trouvent aux pieds des montagnes (comme aux environs de la riviere d'Oufa); telles aussi, elles occupent tout l'etendue de la grande Russie, tant en collines qu'en plat pays; solides tantot et comme semees de productions marines; tantot toutes composees de coquilles et madrepores brisees, et de ce gravier calcaire qui se trouve toujours sur les parages ou la mer abonde en pareilles productions; tantot, enfin, dissoutes en craie et en marines, et souvent entremelees de couches de gravier et de cailloux roules."

How valuable for science to have naturalists who can distinguish properly what they see, and describe intelligibly that which they distinguish. In this description of the strata, from the chain of mountains here considered as primitive, to the plains of Russia, which are supposed to be of a tertiary formation, our naturalist presents us with another species of strata, which he has distinguished, on the one hand, in relation to the mountains at present in question, and on the other, with regard to the strata in the plains, concerning which there is at present no question at all. Now, let us see how these three things are so connected in their nature, as to form properly the contiguous links of the same chain.

The primary and tertiary ma.s.ses are bodies perfectly disconnected; and, without a medium by which they might be approached, they would be considered as things differing in all respects, consequently as having their origins of as opposite a nature as are their appearances. But the nature and formation of those bodies are not left in this obscurity; for, the secondary ma.s.ses, which are interposed, partic.i.p.ate so precisely of what is truly opposite and characteristic in the primary and tertiary ma.s.ses, that it requires nothing more than to see this distinction of things in its true light, to be persuaded, that in those three different things we may perceive a certain gradation, which here takes place among the works of nature, and forms three steps distinguishable by a naturalist, although in reality nothing but the variable measure of similar operations.

We are now to a.s.similate the primary and tertiary ma.s.ses, which are so extremely different, by means of the secondary ma.s.ses, which is the mean. The primary and tertiary differ in the following respects: The one of these contains the relicts of organised bodies which are not observed in the other. But in the species containing these distinguishable bodies, the natural structure and position of the ma.s.s is little affected, or not so much as to be called into doubt. This, however, is not the case with the other; the species in which organised bodies do not appear, is in general so indurated or consolidated in its structure, and changed in its position, that this common origin of those ma.s.ses is by good naturalists, who have also carefully examined them, actually denied. Now, the secondary ma.s.ses may be considered, not only as intermediate with respect to its actual place, as M. Pallas has represented it, but as uniting together the primary and tertiary, or as partic.i.p.ating of the distinguis.h.i.+ng characters of the other two. It is h.o.m.ologated with the primitive mountains, in the solidity of its substance and in the position of its strata; with the tertiary species, again, in its containing marks of organised bodies. How far this view of things is consistent with the theory of the earth now given, is submitted to the consideration of the unprejudiced.

Let us see what our learned author has said farther on this subject, (page 65).

"Je dois parler d'un ordre de montagnes tres-certainement posterieur aux couches marines, puisque celles-ci, generalement lui servent de base.

On n'a point jusqu'ici observe une suite de ces _montagnes tertiaires_, effet des catastrophes les plus modernes de notre globe, si marquee et si puissante, que celle qui accompagne la chaine Ouralique ou cote occidentale fur tout la longueur. Cette suite de montagnes, pour la plupart composees de grais, de marnes rougeatres, entremelees de couches divers.e.m.e.nt mixtes, forme une chaine par-tout separee par une vallee plus ou moins large de la bande de roche calcaire, dont nous avons parle. Sillonnee et entrecoupee de frequens vallons, elles s'eleve souvent a plus de cent toises perpendiculaires, se repand vers les plaines de la Russie en trainees de collines, qui separent les rivieres, en accompagnant generalement la rive boreale ou occidentale, et degenere enfin en deserts sableux qui occupent de grands es.p.a.ces, et s'etendent surtout par longues bandes paralleles aux princ.i.p.ales traces qui suivent les cours des rivieres. La princ.i.p.ale force de ces montagnes tertiaires est plus pres de la chaine primitive par-tout le gouvernement d'Orenbourg et la Permie, ou elle consiste princ.i.p.alement en grais, et contient un fond inepuisable de mines de cuivre sableuses, argileuses, et autres qui se voient ordinairement dans les couches horizontales.

Plus loin, vers la plaine, sont des suites de collines toutes marneuses, qui abondent autant en pierres gypseuses, que les autres en minerais cuivreux. Je n'entre pas dans le detail de celles-ci, qui indiquent sur-tout les sources salines; mais je dois dire des premieres, qui abondent le plus et dont les plus hautes elevations des plaines, meme celle de Moscou, sont formees, qu'elles contiennent tres-peu de traces de productions marines, et jamais des amas entiers de ces corps, tels qu'une mer reposee pendant des siecles de suite a pu les acc.u.muler dans les bancs calcaires. Rien, au contraire, de plus abondant dans ces montagnes de grais stratifie sur l'ancien plan calcaire, que des troncs d'arbres entieres et des fragmens de bois petrifie, souvent mineralise par le cuivre ou le fer; des impressions de troncs de palmires, de tiges de plantes, de roseau, et de quelques fruits etrangers; enfin des oss.e.m.e.ns d'animaux terrestres, si rares dans les couches calcaires. Les bois petrifies se trouvent jusques dans les collines de sable de la plaine; l'on en tire, entr'autres, des hauteurs sablonneuses aux environs de Sysran sur la Volga, changes en queux tres-fin, qui a conserve jusqu'a la texture organique du bois, et remarquables sur-tout par les traces tres-evidentes de ces vers rongeurs qui attaquent les vaisseaux, les pilotis et autres bois trempes dans la mer, et qui sont proprement originaires de la mer des Indes."

This philosopher has now given us a view of what, according to the present fas.h.i.+on of mineral philosophy, he has termed _montagnes primitives, secondaires, et tertiaires_. The first consists in ma.s.ses and strata, much indurated and consolidated, and greatly displaced in their position; but the character of which is chiefly taken from this, that they contain not any visible mark of animal or vegetable bodies.

The second are formed in a great measure of marine productions, are often no less consolidated than those of the first cla.s.s, and frequently no less changed in their natural shape and situation.

The third again have for character, according to this learned theorist, the containing of those organised bodies which are proper to the earth, instead of those which in the second cla.s.s had belonged to the sea; in other respects, surely there is no essential difference. It is not pretended that these tertiary strata had any other origin, than that of having been deposited in water; it is not so much as suspected, that this water had been any other than that of the sea; the few marine bodies which M. Pallas here acknowledges, goes at least to prove this fact: and with regard to the mineral operations which had been employed in consolidating those water formed strata, it is impossible not to be convinced that every effect visible in the other two are here also to be perceived.

From this view of mineral bodies, taken from the extensive observations of the Russian dominions, and from the suppositions of geologists in relation to those appearances, we should be led to conclude that the globe of this earth had been originally nothing but an ocean, a world containing neither plant nor animal to live, to grow and propagate its species. In following a system founded on those appearances, we must next suppose, that to the sterile unorganised world there had succeeded an ocean stored with fish of every species. Here it would be proper to inquire what sustained those aquatic animals; for, in such a system as this, there is no provision made for continuing the life even of the individuals, far less of feeding the species while, in an almost infinite succession of individuals, they should form a continent of land almost composed of their _exuviae_.

If fish can be fed upon water and stone; if siliceous bodies can, by the digesting powers of animals, be converted into argillaceous and calcareous earths; and if inflammable matter can be prepared without the intervention of vegetable bodies, we might erect a system in which this should be the natural order of things. But to form a system in direct opposition to every order of nature that we know, merely because we may suppose another order of things different from the laws of nature which we observe, would be as inconsistent with the rules of reasoning in science, by which the speculations of philosophy are directed, as it would be contrary to common sense, by which the affairs of mankind are conducted.

Still, however, to pursue our visionary system, after a continent had been formed from the relicts of those animals, living, growing, and propagating, during an indefinite series of ages, plants at last are formed; and, what is no less wonderful, those animals which had formed the earth then disappear; but, in compensation, we are to suppose, I presume, that terrestrial animals began. Let us now reason from those facts, without either constraining nature, which we know, or forming visionary systems, with regard to things which are unknown. It would appear, that at one period of time, or in one place, the matter of the globe may be deposited, in strata, without containing any organised bodies; at another time, or in another place, much animal matter may be deposited in strata, without any vegetable substance there appearing; but at another period, or at another time, strata may be formed with much vegetable matter, while there is hardly to be observed any animal body. What then are we to conclude upon the whole? That nature, forming strata, is subject to vicissitudes; and that it is not always the same regular operation with respect to the materials, although always forming strata upon the same principles. Consequently, upon the same spot in the sea, different materials may be acc.u.mulated at different periods of time, and, conversely, the same or similar materials may be collected in different places at the same time. Nothing more follows strictly from the facts on which we now are reasoning; and this is a conclusion which will be verified by every appearance, so far as I know.

Of this I am certain, that in a very little s.p.a.ce of this country, in many places, such a course of things is to be perceived. Nothing so common as to find alternated, over and over again, beds of sand-stone without animal bodies, beds of coal and schistus abounding with vegetable bodies, beds of lime-stone formed of sh.e.l.ls and corals, and beds or particular strata of iron-stone containing sometimes vegetable sometimes animal bodies, or both. Here, indeed, the strata are most commonly inclined; it is seldom they are horizontal; consequently, as across the whole country, all the strata come up to the day, and may be seen in the beds of our rivers, we have an opportunity of observing that great variety which is in nature, and which we are not able to explain.

This only is certain, from what we see, that there is nothing formed in one epoch of nature, but what has been repeated in another, however dissimilar may be the operations which had intervened between those several epochs.