Theory of the Earth Volume I Part 15

Here is a supposition of our author that corresponds to nothing which has yet been observed any where else, so far as I know. It is concerning a mineral vein, one which does not appear to differ in any respect from other mineral veins, except in being worked in that open manner which has given our author an idea of its being a valley. He then supposes that valley (or rather empty vein) to have been in this mountain when at the bottom of the sea, and that this mineral vein had then been filled with those materials which now are found in that s.p.a.ce between the two sides of the separated rock. This is a very different operation from that of infiltration, which is commonly supposed to be the method of filling mineral veins; but, we shall soon see the reason why our author has here deserted the common hypothesis, and has adopted another to serve the occasion, without appearing to have considered how perfectly inconsistent those two suppositions are to each other. That mineral veins have been filled with matter in a fluid state, is acknowledged by every body who has either looked at a mineral vein in the earth, or in a cabinet specimen; mineralists and geologists, in general, suppose this to have been done by means of solutions and concretions, a supposition by no means warranted by appearances, which, on the contrary, in general demonstrate that the materials of those veins had been introduced in the fluid state of fusion. But here is a new idea with regard to the filling of those veins; and, I would now beg the reader's attention to the facts which follow in this interesting description, and which have suggested that idea to our author.

"Quand cette matiere accidentelle est enlevee, on voit la coupe du _schiste_ des deux cotes de la _fente_, faisant un _toit_ et un _mur_, parce que la _fente_ n'est pas absolument verticale: des qu'il y a un peu d'inclinaison, on distingue un _toit_ et un mur, comme j'ai l'honneur de l'expliquer a V.M. On ne connoit point encore l'etendue de ce filon, ni dans sa profondeur, ou l'on ne peut pas s'enfoncer beaucoup de cette maniere, ni dans la longueur, selon laquelle on continue a l'exploiter.

"Voila donc un _filon_, a la rigueur de la definition que j'en ai donne a V.M. c'est a dire, une _fente_ dans la montagne naturelle, _comblee_ de _matiere_ etrangere. Mais ce qu'il y a d'extraordinaire ici, c'est que cette _matiere_ vient de la _mer_: ce sont differentes _couches aquiformes_, dont quelques unes sont remplies de _corps marins_. Il y a des _couches_ d'une _terre martiale_ fort brune et sans liaison: d'autres, au contraire toujours _martiales_, sont tres dures et renferment de tres beau jaspe sanguin: d'autres enfin sont de vrai _marbre_ gris veinees de rouge. C'est dans ce marbre que font les _corps marins_, savoir des coquillages et des spongites; et il est lui-meme martial comme tout le reste: les mineurs le nomment _Kubrimen_, et ne l'employent que comme un _fondant_ pour d'autres _mineraux de fer_.

"A ce _filon_, s'en joignent d'autres plus embarra.s.sans. Ils viennent du _toit_, qu'ils divisent par de larges _fentes_ comblees, aboutissantes au _filon_ princ.i.p.ale. Ils font de meme _calcaires_ et marins faits par _couches_; mais ces _couches_ ont une si grande inclinaison, que je ne puis les comprendre: il faut qu'il y ait eu d'etranges boulevers.e.m.e.ns dans ces endroits-la[27].

[Note 27: Here, no doubt, are appearances which it is impossible to explain by the theory of infiltration; it is the filling of mineral veins, and their branches or ramifications, with marble containing marks of marine objects. But, if we shall suppose this marble to have been in the fluid state of fusion, as well as the iron-ore and jasper, we may easily conceive it introduced into the princ.i.p.al vein and its branches.

The description here given of those appearances is by no means such as to enable us to judge particularly of this case, which surely merits the most accurate investigation, and which, I doubt not, will give physical demonstration of the fusion of those mineral substances. I know that sh.e.l.ls have been found within the body of veins in Germany; but, a stratification of those materials in a vein was never heard of before, so far as I know.]

"Ces _fentes_ se sont faites, et ont ete remplies, dans la _mer_; puisque les matieres qui les remplissent sont de la cla.s.se de ses depots tres connoissables, et qu'il contiennent des _depouilles marines_. Mais ce qui embarra.s.se alors c'est que les autres _filons_ ne soyent pas dans le meme cas. N'est ce point la encore un indice, que ces _fentes_ out ete d'abord et princ.i.p.alement remplies de matieres, poussees du fond par la meme force qui secouoit les montagnes[28].

[Note 28: But what is this power by which matter is to be forced from the bottom of the sea to the top of the mountains? For, unless we can form some idea of that power which, as a cause, we ascribe to the perceived effect, we either say nothing to the purpose, or we employ a preternatural cause. It is not sufficient to imagine a power capable of raising from the bottom of the sea the materials deposited in the abyss; it is also necessary to find a power capable of softening bodies which are hard, and of thus consolidating those ma.s.ses which are formed of loose or unconnected materials. Such a power, indeed, the present theory a.s.sumes; and, so far as this shall be implied in the supposition of our author, it will thus have received a certain conformation.]

"Ce _filon_ n'est pas le seul dans le _Hartz_ qui donne des signes _marins_. Il y en a un autre, qui meme se rapproche davantage de la nature du commun des _filons_, et ou l'on trouve aussi des _coquillages_. C'est celui de _Haus-Hartzbergerzug_, pres de _Clausthal_, ou, dans les _Halles_ de quelques mines de plomb abandonnees, et dans une forte _d'ardoise_, on trouve de pet.i.tes _moules_ ou _tellines_ striees, d'une espece particuliere que j'ai vue dans des _ardoises secondaires d'Arotzen_ en _Waldek_ et de _Sombernon_ en _Bourgogne_. Il y a donc certainement quelques _filons_ faits par les depots de la _mer_ dans les _fentes_ de montagnes _primordiales_; comme au contraire il y a des _filons_ metalliques sans indices _marins_, dans des montagnes evidemment _secondaires_, telles que celles de _Derbys.h.i.+re_, ou les _filons_ de _plomb_ traversent des couches de _pierre a chaux_."

Here again our author seems to me to refute his own supposition, That a chasm in the schistus rock may have existed at the bottom of the sea, and been then filled from above with such materials as were transported by the moving water to that place, is not impossible; but n.o.body, who knows the nature of a common metallic vein, can ever suppose it to have been filled in that manner. Our author then adds, "On ne fait reellement que commencer dans ce genre d'observations, considerees quant a la Cosmologie; ainsi il ne faut point desesperer que tout cela ne se devoile un jour, et que nous n'acquerrions ainsi un peu plus de connoissance sur ce qui se pa.s.soit dans la _mer ancienne_.

"En revenant vers _Elbingerode_, nous retrouvames ces _schistes_, qui paroissent au travers des _marbres:_ ils sont donc la continuation de la ma.s.se _schisteuse_ a laquelle appartient le _filon_, dont je viens de parler. Ce _filon_ a ete forme dans une _fente_, restee ouverte et vide: les depots de la _mer_ l'ont comblee, en meme tems qu'ils formoient les couches de _marbre_, qui sont a l'exterieur. En effet, ce _filon_ contient des _couches marines ferrugineuses_, de la meme nature que celles des collines calcaires voisines formees sur le schiste.

"Nous partimes _d'Elbingerode_ dans l'apres midi pour nous rapprocher de Clausthal. Notre chemin fut encore quelque tems sur des sommites _calcaires_; et avant que d'en sortir, nous trouvames une autre mine singuliere a _Arenfeld_. C'est encore un vrai _filon_; mais dans une montagne de _pierre a chaux:_ C'est a-dire, que cette montagne a aussi ete _fendue_, et que la _fente_ a ete remplie d'une _gangue_. La matiere de ce _filon_ est encore _calcaire_ en plus grande partie; mais cette _pierre a chaux_ distincte est _ferrugineuse_, et pa.r.s.emee de concretions de _jaspe_ comme celles _d'Elbingerode:_ on y trouve aussi une matiere verdatre, qui, comme le _jaspe_, ne fait pas effervescence avec l'eau forte."

Here is a phenomenon which is altogether incompatible with the theory that this author has given us for the explanation of those appearances.

He supposes empty crevices in the schistus mountains at the bottom of the sea; these crevices he supposes filled by the deposits of the sea, at the same time, and with the same materials with which the lime-stone strata were formed above the schistus mountains; but we find one of those same veins in these secondary calcareous strata. Now, tho' we should be disposed to allow, that, in the primordial mountain, of which we are supposed not to know the origin, there might have been empty crevices which were afterwards filled with materials transported by the sea, this cannot be admitted as taking place in the loose or incoherent materials deposited above the schistus. Consequently, this theory of our author, which is evidently erroneous with regard to the veins in the lime-stone, must, in the other case, be at least examined with a jealous eye.

"Le haut de cette partie des montagnes _calcaires_ etoit encore recouvert de _sable_ et de gres _vitrescibles_: et continuant a marcher, sans aucune inflexion sensible, nous nous trouvames subitement sur les _schistes_; d'ou nous montames plus rapidement. Puis traversant quelques pet.i.tes vallees nous arrivames sur les montagnes qui appartiennent au prolongement du _Brocken_ ou _Blocksberg_. La matiere dominante est alors le _granit_; mais il est tout en blocs le long de cette route, et ces blocs se trouvent a une telle distance de tout sommite intacte de cette pierre, qui est aise de juger non seulement qu'ils ne sont pas dans leur place originaire, mais encore qu'il ne sont arrives la par aucune des causes naturelles qui agissent dans les montagnes; savoir, la pesanteur, la pente, et le cours des eaux. Ce sont donc de violentes explosions qui ont disperse ces blocs; et alors ils deviennent un nouveau trait cosmologique de quelque importance: car rien ne se meut, ni ne paroit s'etre mu depuis bien des siecles, dans ces lieux qui montrent tant de desordre: un tapis de verdure couvre tout, en conservant les contours baroques du sol. Le betail ne sauroit paturer dans de telles prairies; mais l'industrieux montagnard fait y faucher[29].

[Note 29: M. de Saussure endeavours to explain those appearances of transported blocks of granite by another cause; this is a certain _debacle_ of the waters of the earth, which I do not understand. M. de Luc again attempts to explain it by violent explosions; I suppose he means those of a volcano. But he has not given us the evidence upon which such an opinion may be founded, farther than by saying that those blocks could not have come there by the natural operations of the surface. By this must be meant, that, from the nearest summit of granite, there is not, at present, any natural means by which these blocks might be transported to that place. But it is not with the present state of things that we are concerned, in explaining the operations of a distant period. If the natural operations of the surface change the shape of things, as is clearly proved by every natural appearance, Why form an argument against a former transaction, upon the circ.u.mstances of the present state of things? Our author does not seem to perceive, that, from this mode of reasoning, there is is an insuperable objection to his violent explosions having been employed in producing those effects. For, had there been such a cause, the evidence of this must have remained; if the surface of the earth does not undergo great changes: If, again, this surface be in time much changed, How can we judge from the present shape, what might have been the former posture of things?

This author, indeed, does not allow much time for the natural operations of the globe to change its surface; but, if things be not greatly removed from the state in which the violent operations of the globe had placed them, Why does he not point out to us the source of this great disorder which he there perceives? From what explosion will be explained the blocks of granite which are found upon the Jura, and which must have come from the ma.s.s of _Mont Blanc_? If these dispersed blocks of stone are to be explained by explosion, there must: have been similar explosions in other countries where there is not the smallest appearance of volcanic eruptions; for, around all our granite mountains, and I believe all others, there are found many blocks of granite, traveled at a great distance, and in all directions.]

"_Oberbruck_, ou nous avions ete la precedente fois, se trouva sur notre route, et nous y pa.s.sames aussi la nuit, dans l'esperance de pouvoir monter le lendemain sur le _Brocken_; mais il fut encore enveloppe de nuages; ainsi nous continuames a marcher vers _Clausthal_, pa.s.sant de nouveau par le _Bruchberg_, ou le _sable_ et ses gres recouvrent le _schiste_; puis arrivant a une autre sommite, nous y trouvames la meme pierre _sableuse_ par couches, melee de parcelles de _schiste_, que nous avions vue sur les montagnes _calcaires d'Elbingerode_. Il est donc toujours plus certain que le sol primordial de toutes ces montagnes existoit sous les eaux de l'ancienne mer; puisqu'il est recouvert de diverses fortes de depots, connus pour appartenir a la _mer_; et que les _fentes_ des _filons_ existoient dans cette _mer ancienne_; puisqu'elle en a rempli elle-meme quelques unes, et qu'elle a recouvert de ses depots quelques autres _filons_ tout formes. Quant a celles des matieres de ces _filons_, qui ne paroissent pas etre _marines_ (et c'est de beaucoup la plus grande quant.i.te), j'ai toujours plus de penchant d'en attribuer une partie a l'operation des _feux souterreins_, a mesure que je vois diminuer la probabilite de les a.s.signer entierement a _l'eau_.

Mais quoi-qu'il en soit, ces gangues ne font pas de meme date que les montagnes[30].

[Note 30: I most willingly admit the justness of our author's view, if he thus perceives the operation of fire in the solids of our earth; but it is not for the reasons he has given us for discovering it here more than in other places; for there is not a mineral vein, (so far at least as I have seen), in which the appearances may be explained by any thing else besides the operation of fire or fusion. It is not easy to conceive in what manner our author had conceived the opinions which he has displayed in these letters. He had no opinion of this kind, or rather he was persuaded that subterraneous fire had no hand in the formation of this earth before he came to this place of the Hartz; here he finds certain appearances, by which he is confirmed in his former opinion, that water had operated in forming mineral veins; and then he forms the idea that subterraneous fire may have operated also. But, before the discovery of the chasms in the schistus mountains having been filled with the stratified materials of the sea, How had he supposed veins to be filled? If this philosopher had before no opinion of subterraneous fire, as instrumental in that operation, How comes he now to change that former opinion? For, unless it be the extraordinary manner of filling these open crevices in the mountains by matter deposited immediately from the sea, there is certainly no other appearance in this mineral country of the Hartz, that may not be found in any other, only perhaps upon a smaller scale.]

"Le lendemain de notre arrivee a _Clausthal_, qui etoit le 13e, nous allames visiter d'autres mines de _fer_ en montagnes secondaires, situees au cote oppose du Hartz. Elles sont aupres de _Grund_ l'une des _villes de mines_, et pres du lieu ou sortira la nouvelle _galerie d'ecoulement_ a laquelle on travaille, etc.

"Arrives a _Grund_ les officiers mineurs vinrent, comme a l'ordinaire, accompagner Mons. de _Reden_ aux _mines_ de leur departement. Celles-ci, sans etre plus extraordinaires que celles qui nous avions vues a _Elbingerod_, ou sans aider mieux jusqu'ici a expliquer ce qu'elles ont toutes d'extraordinaire, nous donnent au moins des indices probables de grands accidens. Ces montagnes de _Grund_ sont encore de l'espece remarquable, dont la base est de _schiste_, et le haut de _pierre a chaux_. Les mines qu'on y exploit sont de _fer_, et se trouvent dans cette matiere _calcaire_; mais elles y sont sous des apparences tout-a-fait etranges. La montagne ou nous les vimes princ.i.p.alement le nomme _Iberg_. On y poursuit des ma.s.ses de _pierre a fer_, de l'ensemble desquelles les mineurs ne peuvent encore se rendre compte d'une maniere claire. Ils ont trouve dans cette montagne des _ca__vernes_, qui ressemblent a l'encaiss.e.m.e.nt de _sillons_ deja exploites, ou non formes; c'est-a-dire, que ce sont des _fentes_ presque verticales, et vides, Le _minerai_ qu'ils poursuivent est en _Rognons_; c'est a dire, en grandes ma.s.ses sans continuite decidee. Cependant ces ma.s.ses semblent se succeder dans la montagne suivant une certaine direction; tellement que les mineurs savent deja les chercher, par des indices d'habitude.

La substance de cette _pierre a fer_ particuliere renferme des crystallizations de diverses especes. Il y a des _druses de quartz_, ou de pet.i.ts cristaux de quartz qui tap.i.s.sent des cavites; il y a aussi du _spath_ commun, et de celui qu'on nomme pesant; on y trouve enfin une forte de crystallization nommee _Eisenman_ (_homme de fer_) par les mineurs; se sont des amas de cristaux noir-atres, qui ressemblent a des groupes de grandes lentilles plattes, et ces cristaux sont _ferrugineux_.

"Entre les signes de boulevers.e.m.e.nt que renferme ce lieu, est un rocher nomme _Geb.i.+.c.hensten_, qui est en _pierre a chaux_, ce que _l'Ebrenbreitstein_ de _Coblentz_ est en pierre sableuse: c'est-a-dire, que ses _couches_, remplies de _corps marins_, sont presque verticales; ceux de ces corps qu'on y trouve en plus grande quant.i.te, sont des _madrepores_. Ce rocher s'eleve comme un grand obelisque, au-dessus des _cavernes_, dont j'ai parle; montrant par le cote ses _couches_, qui se trouvent, comme je l'ai dit, dans une situation presque verticale. Sa base est deja bien minee, tant par les _cavernes_, que par la _pierre a fer_ qu'on en tire; et je ne me hasardai dessus, que parce que je me dis, qu'il y a des millions contre un a parier, que ce n'est pas le moment ou il s'enfoncerait. Mais je n'en dirois pas autant, s'il s'agissoit de m'y loger a demeure.

"Quoique tout ce lieu la soit fort remarquable, il se pourrait que ce ne fut qu'un phenomene particulier. Les _cavernes_ peuvent devoir leur origine a la meme cause que celle de Schartzfeld; et le derangement des rochers superieurs a des enfoncemens occasionnes par ces _cavernes_.

Rien n'est si difficile que de retracer aujourd'hui ces fortes d'accidens a cause des changemens que le tems y a operes. S'ils sont arrives sous les eaux de la _mer_, on concoit ais.e.m.e.nt les alterations qui ont du succeder; et si c'est depuis que nos continens sont a sec, les eaux encore, tant interieures qu'exterieures, et la vegetation, en ont beaucoup change l'aspect."

This author has a theory by which he explains to himself the former residence of the sea, above the summits of our mountains; this, however, is not the theory by which we are now endeavouring to explain appearances; we must therefore be allowed to reason from our own principles, in considering the facts here set forth by our author.

Nothing, I think, is more evident, than that in this mineral country of the Hartz, we may find the clearest marks of fracture, elevation, and dislocation of the strata, and of the introduction of foreign matter among those separated bodies. All those appearances, our author would have to be nothing but some particular accident, which is not to enter into the physiology of the earth. I wish again to generalise these facts, by finding them universal in relation to the globe, and necessarily to be found in all the consolidated parts of our land.

It was not to refute our author's reasoning that I have here introduced so much of his observations, but to give an extensive view of the mineral structure of this interesting country. This therefore being done, we now proceed to what is more peculiarly our business in this place, or the immediate subject of investigation, viz. the distinction of primary and secondary strata.

"Dans le voisinage de cette montagne, il y a une autre fort interessante, que je vis le jour suivant. Quoiqu'en traitant des volcans, j'aie demontre que la formation des montagnes, par soulevement, etoit sans exemple dans les faits, et sans fondement dans la theorie, je ne laisseroi pas de m'arreter au phenomene que presente cette montagne; parce qu'il prouvera directement que les _couches calcaires_ au moins, ont ete formees _a la hauteur ou elles sont_; c'est-a-dire qu'elles n'ont pas ete soulevees.

"Voulant prendre l'occasion de mon retour a _Hanovre_, pour traverser les avant-corps du _Hartz_, dans quelque nouvelle direction; je resolus de faire ce voyage a cheval, et de prendre ma route droite vers _Hanovre_, au-travers des collines; ce qui me conduisit encore a _Grund_ puis a _Munchehof Brunshausen, Engelade, Winsenburg_ et _Alfeld_, ou enfin, traversant la _Leine_ j'entrai dans la grande route.

"Je quittai donc _Clausthal_ (et avec bien du regret) le 14 au matin; et revenant d'abord a _Grund_, je le laissai sur ma droite, ainsi que _l'Iberg_; et plus loin, du meme cote, une autre montagne nommee _Winterberg_ dont la base est _schiste_, et le sommet plus haut que Clausthal, entierement compose de _couches calcaires_. De _Grund_ je montai vers une montagne nommee _Ost Kamp_; et je commencai la a donner une attention particuliere au sol. Le long de mon chemin, je ne trouvai longtemps que des schistes, qui montroient leurs points en haut, comme a l'ordinaire, et avec tous leurs tortillemens de feuillets. Mais arrive au haut de la montagne, j'y vis des carrieres de _pierre a chaux_, ou les couches absolument regulieres, et qui ont peu d'epaisseur sur le _schiste_ suivent parfaitement les contours du _sommet_. Ces lits de _pierre a chaux_ n'ont certainement pas ete souleves du fond de la _mer_ sur le dos des schistes; lors meme qu'a cause de la grande inclinaison des feuillets de ceux-ci on voudroit le attribuer a quelque revolution telle que le _soulevement_; (ce que je n'admettrois point). Car si ces lits _calcaires_, ayant ete faits au fond de la _mer_, avoyent ete souleves avec les schistes, ne feroient-ils pas brises et bouleverses comme eux? Il est donc evident, que quoiqu'il soi arrive au schiste qui les porte, ces lits, et tous les autres de meme genre qui sont au haut de ces montagnes, ont ete deposees au niveau ou ils sont; et que par consequent la _mer_ les surpa.s.soit alors. Ainsi le systeme de soulevement perd son but, s'il tend a expliquer pourquoi nous avons des _couches_, formees par la mer, qui se trouvent maintenant si fort au dessus de son niveau. Il est evident que ces _couches_ n'ont pas ete soulevees; mais que la _mer_ s'est _abaissee_. Or c'est la le grand point cosmologique a expliquer: tous les autres, qui tiennent a la structure de certaines montagnes inintelligibles, n'appartiendront qu'a _l'histoire naturelle_, tant qu'ils ne se lieront pas avec celui-la."

Here are two things to be considered; the interesting facts described by our author, and the inference that he would have us draw from those facts. It would appear from the facts, that the body of schistus below, and that of lime-stone above, had not undergone the same disordering operations, or by no means in the same degree. But our author has formed another conclusion; he says, that these lime-stone strata must have been formed precisely in the place and order in which they lie at present; and the reason for this is, because these strata appeared to him to follow perfectly the contour of the summit of this mountain. Now, had there been in the top of this mountain a deep hollow encompa.s.sed about with the schistus rock; and had this cavity been now found filled with horizontal strata, there might have been some shadow of reason for supposing those strata to have been deposited upon the top of the mountain. But to suppose, _first_, that sh.e.l.ls and corals should be deposited upon the convex summit of a mountain which was then covered by the sea; _secondly_, that these moveable materials should remain upon the summit, while the sea had changed its place; and, _lastly_, that those sh.e.l.ls and corals left by the sea upon the top of a mountain should become strata of solid limestone, and have also metallic veins in it, certainly holds of no principle of natural philosophy that I am acquainted with. If, therefore, such an appearance as this were to be employed either in ill.u.s.tration or confirmation of a theory, it would itself require to be explained; but this is a task that this cosmologists does not seem willing to undertake.

He has formed a hypothesis for explaining the general appearance of that which was once the bottom of the sea being now found forming the summits of our mountains; but surely this philosopher will acknowledge, that those natural appearances, in any particular place, will be the same, whether we suppose the bottom of the sea to have been raised, as in the present theory, or the surface of the sea to have sunk according to his hypothesis. For, it is equally easy to suppose a portion of the earth to have been raised all this height, as to suppose all the rest of the surface of the globe to have sunk an equal s.p.a.ce, while a small portion of the bottom of the sea, remaining here and there fixed in its place, became the highest portion of the globe. Consequently, whatever evidence this philosopher shall find in support of his theory of the present earth, (a subject which it is not our purpose to examine) it cannot be allowed that he has here brought any argument capable of disproving the elevation of the bottom of the sea; a supposition which other theories may require.

I would now observe, in relation to the present theory, that so far as this author has reasoned justly from natural appearances, his conclusions will be found to confirm the present supposition, that there is to be perceived the distinction of primordial, and that of secondary, in the ma.s.ses of this earth, without altering the general theory either with respect to the original formation of those ma.s.ses, or to their posterior production.

Here one of two things must be allowed; either that those strata of schistus had been broken and distorted under a ma.s.s of other superinc.u.mbent strata; or that those superinc.u.mbent strata had been deposited upon the broken and distorted strata at the bottom of the sea.

Our author, who has examined the subject, inclines to think, that this last has been the case. If, therefore, strata had been deposited upon broken and bare rocks of schistus, it is probable that these had been sunk in the sea after having been exposed to the atmosphere, and served the purpose of land upon the globe.[31]

[Note 31: This is also supported by another very interesting observation contained in this letter. M. de Luc observes, that in this country the schistus is generally covered by strata of lime-stone, and that these lime-stone strata are again covered with those of sand-stone, in which are found a great many fragments of schistus lying flat. Therefore, while those sand-stone strata were collecting at the bottom of the sea, there had been rocks of schistus in some other place, from whence those fragments bad been detached.]

An example of the same kind also occurs in the _Discours sur l'Histoire Naturelle de la Suisse_; and this author of the _Tableaux de la Suisse_ has given a very distinct description of that appearance, which is perhaps the more to be valued as a piece of natural history, as this intelligent author does not pretend to any geological theory, but simply narrates what he has seen, with such pertinent observations on the subject as naturally must occur to a thinking person on the spot.--(Discours, etc. page 228. Entree au pays de Grisons).

"Du village d'Elen on continue a monter le reste du pet.i.t vallon pendant une lieue et demie parmi les memes especes de pierres qu'on vient de decrire; en pa.s.sant au travers de bois et de forets de sapins et de quelques paturages dont ce haut est couvert, on parvient au pied du Bundnerberg, montagne des grisons, qui forme la tete du vallon. On laisse a droite un fond ou espece d'entonnoir, entoure de tres-hautes montagnes inaccessibles, pour s'enfourrer a gauche entre des rochers qui font fort resserres, ou coule un torrent. Ce lieu seroit horreur si on ne se trouvoit accoutume, par degres, a voir de ces positions effrayantes: tout y est aride, il n'y a plus d'arbres ni de vegetaux ce sont des rochers enta.s.ses les un sur les autres; ce lieu paroit d'autant plus affreux que le pa.s.sage a ete subit, et qu'en sortant de bois et des forets, on se trouve tout-a-coup parmi ces rochers qui s'elevent comme des murailles, et dont on ne voit pas la cime; cette gorge ou cette entree qui se nomme Jetz, est la communication du Canton du Glaris aux Gritons; on a dit precedemment qu'il y en avoit une plus aisee par le Gros-Thal ou le grand vallon. Ce pa.s.sage est tres-curieux pour la Lithogeognosie, il est rare de trouver autant de phenomenes interessans ra.s.sembles, et des substances aussi variees par rapport a leurs positions; c'est le local qui merite le plus d'etre examine en Suisse, et la plus difficile que nous ayons parcouru. On se souviendra que nous avons continuellement monte depuis Glaris, et que nous nous trouvons au pied de ces montagnes ou de ces pics etonnans qui dominent les hautes Alpes; on trouve ici la facilite peu commune de pouvoir examiner, et voir le pied ou les fondemens de ces colosses qui couronnent le globe, parce qu'ils sont ordinairement entoures de leurs debris et de leurs eboulemens qui en cachent le pied. Ici c'est une roche de schiste bleuatre, dure et compact, traversee de filons de quartz blanc, et quelquefois jaunatre, dans laquelle on a taille un sentier pour pouvoir en franchir le pied. Cette roche s'eleve a une hauteur prodigieuse, est presque verticale, et ces couches sont a quatre-vingt degres d'inclinaison. L'imagination est effrayee de voir que de pareilles ma.s.ses ayent pu etre ebranlees et deplacees au point d'avoir fait presque un quart de conversion. Apres avoir monte et suivi cette roche parmi les pierres et les decombres, une heure et demie, on trouve cette roche de schiste surmontee d'autres rochers fort hauts qui sont calcaires, et dont les lits sont fort horizontaux. Les schistes, qui sont directement sous les roches calcaires, conservent la meme inclinaison qu'elles ont a leur pied."

Here is an observation which certainly agrees with that given by M. de Luc, and would seem to confirm this conclusion, that strata had been deposited upon those _schisti_ after they had been changed from their natural or horizontal position, and become vertical; at the same time, this conclusion is not of necessary consequence, without examining concomitant appearances, and finding particular marks by which this operation might be traced; for the simply finding horizontal strata, placed above vertical or much inclined schiste, is not sufficient, of itself, to const.i.tute that fact, while it is acknowledged that every species of fracture, dislocation, and contortion, is to be found among the displaced strata of the globe.

Since writing this chapter, I am enabled to speak more decisively upon that point, having acquired more light upon the subject, as will appear in the next chapter.

CHAP. VI.

The Theory of interchanging Sea and Land ill.u.s.trated by an Investigation of the Primary and Secondary Strata.

SECT. I.--A distinct View of the Primary and Secondary Strata.

Having given a view of what seems to be the primary and secondary strata, from the observations of authors, and having given what was my opinion when I first wrote that chapter, I am now to treat of this subject from observations of my own, which I made since forming that opinion.

From Portpatrick, on the west coast, to St Abb's Head, on the east, there is a tract of schistus mountains, in which the strata are generally much inclined, or approaching to the vertical situation; and it is in these inclined strata that geologists allege that there is not to be found any vestige of organised body. This opinion, however, I have now proved to be erroneous.

There cannot be any doubt with regard to the original formation of those stratified bodies, as having been formed of the materials that are natural to this earth, viz. the detritus of former bodies; and as having been deposited in water, like the horizontal strata: For the substances and bodies of which they are visibly composed are no other than those which form the most regular horizontal strata, and which are continually traveling, or transported at the bottom of the sea, such as gravel, and sand, argillaceous and micaceous bodies.

On each side of this ridge of mountains, which towards the east end is but narrow, there is a lower country composed of strata in general more horizontal; and among which strata, besides coal, there are also found the relics of organised bodies.

Abstracting at present from any consideration of organised bodies among the materials of those strata, it may be affirmed, that the materials which form the strata in the mountains and in the low country, are similar, or of the same nature; that they have, in both places, been consolidated by the same means, viz. heat and fusion; and that the same or similar accidents have happened to them, such as change from their original position, and mineral veins traversing them in various shapes.

Yet still there is a distinctive character for those two bodies, the alpine and the horizontal strata; for, while the horizontal position appears natural to the one, and the changes from that particular state to be only an accident, the vertical position appears to be more natural to the other, which is seldom found horizontal.

Therefore, altho' it is unquestionable that the strata in the alpine and low countries had the same or a similar original, yet, as the vertical position, which is the greatest possible change in that respect, is more natural to the alpine strata, or only necessary in the natural order of those bodies, we are to consider this great disorder or change from the natural state of their original formation, as the proper character of those alpine strata. But then it is also necessary to include in this character a general hardness and solidity in those vertical strata, otherwise they would not have been properly alpine, or have resisted the wearing and was.h.i.+ng powers of the globe, so as to have remained higher than the others; for, the vertical position, or great inclination of those strata, should rather have disposed them the more to dissolution and decay. Let us now see how far we shall be justified in that general conclusion, by the examination of those bodies.