Theory of the Earth Volume Ii Part 6

There is at present no question concerning the particular shape in which the mountains of the earth had come out of the waters of the sea. We are considering the wasting of those mountains, in being exposed to the atmosphere and waters of the earth; and the operation that the sea may have had upon their surface, is a subject for judging of which we have not the smallest data, unless by taking the thing for granted, or supposing that the present state of things is that former shape after which we inquire. Now, this is a species of reasoning that M. de Luc would certainly explode; for he admits, as we shall afterwards find, great changes among the mountains of the Alps, from the influences of the atmosphere, perhaps more rapid changes than we are disposed to allow. Therefore, to call in the aid of the ocean, for the degradation of these secondary calcareous mountains, holds of no reason that I can see, unless it be that of diminishing the time which otherwise would have been required in bringing about those changes by the atmosphere alone.

To conclude: Whether we examine the mountain or the plain; whether we consider the degradation of the rocks, or the softer strata of the earth; whether we contemplate nature, and the operations of time, upon the sh.o.r.es of the sea, or in the middle of the continent, in fertile countries, or in barren deserts, we shall find the evidence of a general dissolution on the surface of the earth, and of decay among the hard and solid bodies of the globe; and we shall be convinced, by a careful examination, that there is a gradual destruction of every thing which comes to the view of man, and of every thing that might serve as a resting place for animals above the surface of the sea.

CHAP. V.

_Facts in confirmation of the Theory respecting the Operations of the Earth employed in forming Soil for Plants._

I have distinguished the mineral operations of the earth, by which solid bodies are formed of loose materials, as well as the resolving or decomposing operations which are proper to the surface exposed to the sun and atmosphere. I have also pointed out the end or intention of those several operations, and likewise the means by which they have been brought about. We may now turn our view to that part of the system in which an indefinite variety of soils, for the growth of plants and life of animals, is to be provided upon the face of the earth, corresponding to that diversity which, in the wisdom of nature, has been made of climates.

In this last view, now to be considered, some confirmation should be given to the Theory, in finding the soil, or travelled materials upon the surface of the land, composed of earth, that is, of sand and clay, of stones and gravel; the earth and stones as arising from the resolution and separation of the solids in the neighbourhood of the place; the gravel, again, as having often travelled from more distant parts.

It would be very improper to adduce any example of a particular, where the force of the argument lies in the generality alone. It is enough to have mentioned the facts which are to be examined: Every person of inquiry and observation will judge for himself how far those facts are true.

But there is one general remark that may be made on this occasion, where the operations of the surface are concerned, and which may a.s.sist the investigation of this subject; it is with regard to the gravel or stones worn by attrition, which may have come from a distance. In proportion as hard and insoluble stones are near to their natural beds, they will be found with the sharp angles of their fracture, unless there may have been a cause of agitation and attrition on the spot; they will also be in greater quant.i.ty, _cet. par._ in this place; whereas the farther they may have travelled, they will naturally incline to be more rounded, and, in equal circ.u.mstances, will always be more scarce.

We have thus principles by which to judge of every appearance in relation to the travelled materials of our soil. When, for example, we find an immense quant.i.ty of the hardest stones worn round by attrition, and collected not far distant from their native place, we cannot suppose that they have acquired their shape by the attrition in the distance they have travelled, but in an agitation which they must have received nearly in the place from whence they came. Such is the gravel in the chalk country of England. Around London, in all directions, immense quant.i.ties of gravel are round, which consists almost entirely of flint worn or rounded by attrition; but this is the very centre of the chalk country, at least of England; and no doubt the same appearances will be found in France. We must therefore conclude, that the south of England was under water when that gravel was formed; and that immense quant.i.ties of the chalk above had been destroyed by the agitation of the sea in preparing such quant.i.ties of gravel which still remain upon the land; besides the immense quant.i.ties which must have been dispersed all around during the operation, as well as carried into the sea by the rivers since the elevation of our land. It is not uncommon to find this gravel twenty or thirty feet deep; and ma.s.ses are found of much greater thickness. Were these ma.s.ses of gravel formed in a deep hollow place, they would draw to no conclusion beyond the appearance itself; but they are, on the contrary, in form of hills; and therefore they serve as a kind of measure or indication of what had been carried away when these were left remaining.

We may observe a series or a progress in those forming and destroying operations, by which, on the one hand, the flinty bodies, already formed in the mineral region, were again destroyed, in being diminished by their mutual attrition; and, on the other hand, those diminished bodies were again consolidated into one ma.s.s of flinty stone, without the smallest pore or interstice. This example is to be found in the puddingstone of England. It consists of flint pebbles, precisely like Kensington gravel, penetrated or perfectly consolidated by a flinty substance. Here are the two opposite processes of the globe carried on at the same time and nearly in the same place. But it must be considered, that our land was then in the state of emerging from the sea, and those operations of subterranean fire fit for elevating land was then no doubt exerted with great energy; at present, no such thing appears in this place. But, from the momentary views we have of things, it would be most unphilosophical to draw such absolute conclusions.

The argument now employed rests upon the ident.i.ty of the substance of the gravel with that of the entire flint, which is found in the chalk country; and it goes to prove that the sea had worn away a great deal of that chalk country above the place upon which this body of gravel is now resting; consequently that the sea had formerly flowed over that country covered with gravel, and had dispersed much of that gravel in transporting it to other regions, where that species of flint was not naturally produced. By a parity of reasoning, the gravel produced in the neighbouring regions, and which would be proper to those places, as consisting of their peculiar productions, must have been likewise dispersed and mixed with the surrounding bodies of gravel. But as in the country of which we are now treating, there are considerable regions, the different productions of which are perfectly distinct, we have a proper opportunity of bringing those conclusions of the theory to the test of observation.

For this purpose, let us examine the different countries which surround the chalk regions of England, France, and Flanders; if the gravel upon those neighbouring countries contain flint which the country does not naturally produce; and if the mixture of this flint among the gravel, which is proper to the country itself, be with regard to quant.i.ty in proportion to the vicinity of the flint country, the Theory will then be confirmed; and there is no doubt that this is so. On the other hand, let us examine the gravel about London, which is far distant from any place that produces quartz; if we shall find a very small proportion of quartz gravel in this flinty soil, we may be a.s.sured that the quartz has travelled from a distance, and that the Theory is thus approved. This is actually the case, and I have seen puddingstone containing quartz gravel among the flint.

In confirmation of this view of the travelled soil, it may be observed, that in lower Saxony about Hamburgh, and for a great way to the south-west, the gravel is mostly of broken flint, such as is around the chalk countries: Yet it is at a distance from the chalk of Flanders; there is however at Luxemburgh chalk with flint, the same as in England and France. Therefore the flinty soil of that country, in like manner, demonstrates the great destruction of the solid parts, and ill.u.s.trates the formation of soil by the remainder of the hard parts below, and the alluvion of other parts.

There is most undoubted evidence that the solid body of our land had been formed at the bottom of the sea, and afterwards raised above the surface of the water; but, in the case which has now been described, it appears that the travelled soil of the surface of our land had been lately under the surface of the sea. We have thus therefore traced the different steps in the operations of nature, of which the last step may be considered as thus exposed to our view almost as much as the operations of man in building the Pyramids of Egypt. But surely there are other doc.u.ments to be found in examining the different coasts of this island with attention; and there must be a consistency in the general appearance which never fails to attend on truth.

From the south to the north of this island, there are, in many places, the most evident marks of the sea having been upon a higher level on the land; this height seems to me to amount to about 40 or 50 feet perpendicular at least, which the land must have been raised. Some of those facts may now be mentioned.

Upon the banks of the Thames, I have found sea sh.e.l.ls in the travelled soil a considerable height above the level of the sea. In low Suffolk there are great bodies of sea sh.e.l.ls found in the soil which the farmers call _crag,_ and with it manure their land. I do not know precisely the height above the sea; but I suppose it cannot exceed 100 feet. In the Frith of Forth there are, in certain places, particularly about Newhaven, the most perfect evidence of a sea bank, where the washing of the sea had worn the land, upon a higher level than the present. The same appearance is to be found at Ely upon the Fife coast, where the sea had washed out grottos in the rocks; and above Kinneel, there is a bed of oyster sh.e.l.ls some feet deep appearing in the side of the bank, about 20 or 30 feet above the level of the sea, which corresponds with the old sea banks. I have seen the same evidence in the Frith of Cromarty, where a body of sea sh.e.l.ls, in a similar situation, was found, and employed in manuring the land. There are many other marks of a sea beach upon a higher level than the present, but I mention only those which I can give with certainty.

We have been considering an extensive country more or less covered with gravel; such is England south of Yorkshire; both upon the east and west sides of the island. This country having no high mountainous part in the middle, so as to give it a considerable declivity towards the sh.o.r.es and rivers, the gravel has remained in many places, and in some parts of a considerable thickness. But in other parts of the island, where the declivity of the surface favours the transportation of gravel by the currents of water, there is less of the gravel to be found in the soil, and more of the fragments of stone not formed into gravel. Still, however, the same rule holds with regard to tracing the gravel from its source, and finding particular substances among the gravel of every region, in proportion to the quant.i.ty of country yielding that substance, and the vicinity to the place from whence it came.

Here are principles established, for the judging of a country, in some respects, from a specimen of its gravel or travelled stones. In this manner, I think, I can undertake to tell from whence had come a specimen of gravel taken up any where, at least upon the east side of this island. Nor will this appear any way difficult, when it is considered, that, from Portland to Caithness or the Orkneys, there are at least ten different productions of hard stone in the solid land which are placed at proper distances, are perfectly distinguishable in the gravel which is formed of them, and with all of which I am well acquainted. Let us suppose the distance to be 600 miles, and this to be divided equally into 10 different regions of 60 miles each, it must be evident that we could not only tell the region, which is knowing within 60 miles of the place, but we could also tell the intermediate s.p.a.ce, by seeing an equal mixture of the gravel of two contiguous regions; and this is knowing within 30 miles of the place. If this be allowed, it will not seem difficult to estimate an intermediate distance from the different proportions of the mixed gravel. This is supposing the different regions to be in all respects equal, which is far from being in reality the case; nevertheless, a person well acquainted with the different extent and various natures of those regions, may make allowances for the different known circ.u.mstances that must have influenced in those operations, although it is most probable there will be others which must be unknown, and for which he can make no allowance.

The author of the Tableaux de la Suisse has entered very much into this view of things; he has given us some valuable observations in relation to this subject, which I would here beg leave to transcribe[7].

[Footnote 7: Discours sur l'Histoire Naturelle de la Suisse, p. 27.]

Nous avons dit precedemment que c'etoit entre Orfiere et Liddes que nous avions vu les derniers granites roules, on n'en rencontre plus dans tout le reste de la route jusqu'au haut du Mont St. Bernard. Les rochers qui dominent ce sommet ne sont pas composes de granites, et quoiqu'on ne puisse aborder jusqu'a leur plus grande elevation, on peut juger de leurs especes, par les ma.s.ses qui s'en precipitent. D'ou peuvent donc provenir ces ma.s.ses roulees de granites qui se trouvent jetes et repandus sur le penchant et au bas de ce mont? Il y a peut-etre quelque montagne ou rocher de granite que nous n'avons pas ete a portee de voir: il faudroit plus d'un mois pour faire un pareil examen et parcourir les montagnes environnantes, et faute de pouvoir parvenir a certains sommets, examiner scrupuleus.e.m.e.nt les fonds pour juger des hauts. De pareilles recherches sont plus difficiles et plus longues qu'on ne le croit communement quand on veut reellement voir et observer. Beaucoup de vallons sont combles a des hauteurs prodigieuses, par les amas et les debris provenant des montagnes superieures: ils cessent d'etre des vallons, pour former ou faire partie de montagnes. Ces deplacement et des boulevers.e.m.e.ns, changeant la direction et le courant des torrens, entrainent dans des parties bien opposees des debris qu'on croiroit devoir chercher et trouver ailleurs. On seroit induit en erreur, en voulant suivre toujours le cours actuel des eaux qui descendent des montagnes. Ce n'est pas dans cette occasion seul mais l'Allemagne, la Corse, la Sardaigne, et beaucoup de pays de hautes montagnes, nous out fourni egalement des exemples de ma.s.ses de rochers roules de differentes especes dont il n'existoit pas de rochers pareils, dans toutes les parties elevees environnantes, a plusieurs lieues, a plusieurs journees de chemin, et souvent totalement inconnus dans les pays d'alentour.

Si nous avons remarque les meme especes de rochers faisant corps, et attaches au sol, a une ou plusieurs lieues de distance; nous avons vu souvent que des montagnes plus hautes etoient entre ces ma.s.ses roulees et les rochers, d'ou on auroit pu supposer qu'elles ont ete arrachees: il repugne a croire que des ma.s.ses, d'un poids prodigieux, ayent ete transportees et roulees en travers d'un vallon profond, pour remonter et pa.s.ser de l'autre cote d'une montagne. Nous abandonnons, a ceux qui travaillent dans le cabinet, a l'arrangement du globe, la recherche des moyens que la nature a employe pour produire de pareils effets. Nous nous contenterons, ainsi que nous avons promis, de rendre compte de ce que nous avons vu et observe, et d'engager ceux qui auront la facilite de faire des remarques a.n.a.logues de constater leurs observations en indiquant toujours les lieux fidelement, ainsi que nous le faisions pour la Suisse.

Here the experience of our naturalist amounts to this, that, in those operations by which the solid land is wasted, and the hard materials worn by attrition and transported, it is not always evident from whence had come every particular body of stone or mineral which had travelled by means of water; nor the particular route which, in descending from a higher to a lower place, the protruded body had been made to take, although, in general, these facts may be discovered without much difficulty. Now, this state of things is no other than the natural consequence of the great wasting of the surface and solid parts of our land, and the unequal degradation of this surface, by which means the shape of the earth is so changed, that it would often be impossible, from the present state, to judge of the course in which many bodies had been travelled by water.

M. de Saussure has described a very curious appearance of this kind: It is the finding the travelled materials of Mont Blanc, or fragments detached from the summit and centre of the Alps, in such places as give reason to conclude that they had pa.s.sed through certain openings between the mountains of the Jura. This is a thing which he thinks could not happen according to the ordinary course of nature; he therefore ascribes this appearance to some vast _debacle_, or general flood, which had with great impetuosity transported all at once those heavy bodies, in the direction of that great current, through the defiles of the Alps, or the openings of those mountains.

In giving this beautiful example of the wasting and transporting operations of this earth, this naturalist overlooks the principles which I would wish to inculcate; and he considers the surface of the earth, in its present state, as being the same with that which had subsisted while those stones had been transported. Now, upon that supposition, the appearances are inexplicable; for, How transport those materials, for example, across the lake of Geneva? But there is no occasion to have recourse to any extraordinary cause for this explanation; it must appear that all the intervening hollows, plains, and valleys, had been worn away by means of the natural operations of the surface; consequently, that, in a former period of time, there had been a practicable course in a gradual declivity from the Alps to the place where those granite ma.s.ses are found deposited. In that case, it will be allowed that there are natural means for the transportation of those granite ma.s.ses from the top of the Alps, by means of water and ice adhering to those ma.s.ses of stone, at the same time perhaps that there were certain summits of mountains which interrupted this communication, such as the Jura, etc.

through the openings of which ridges they had pa.s.sed.

In this case of blocks of alpine stones upon the Jura, the question is concerning the transportation of those stones; but, in other cases, the question may be how those blocks were formed.

That many such blocks of stone are formed by the decay of the rock around them, is clearly proved by the observations of M. Ha.s.senfratz, published in the _Annales de Chimie_, October 1791. He has particularly mentioned a place on the road from Saint-Flour to Montpellier, where an amazing collection of these blocks of granite is to be seen. It is here particularly that he observes these blocks to be the more durable parts which remain after the rock around them is decayed and washed away. The proof is satisfactory; the operation is important to the present theory; and therefore I shall give it in his own words.

Tous les blocs de granit dur degages et sortis entierement des ma.s.ses qui forment les montagnes, posent immediatement sur le granit friable ou sur d'autres blocs durs qui eux-memes sont sur le granit friable.

Quoique la plupart des blocs de granit dur, que l'on observe sur toute l'etendue de ce terrain granitique, soient entierement sortis et degages de la ma.s.se de pierre qui forme la montagne, on en rencontre cependant qui ne sont pas encore tout-a-fait degages. Et c'est ici l'observation essentielle qui conduit directement a l'explication du phenomene de l'arrangement, de l'enta.s.s.e.m.e.nt, et de _l'amoncellement_ des blocs d'une maniere simple et absolue.

On voit sur la surface du terrain des portions de blocs durs qui semblent sortir peu a peu, et se degager de la ma.s.se de granit friable; celui-ci se decompose et se reduit en poussiere tout autour de cette ma.s.se dure que les causes de decomposition du granit friable semblent respecter.

Quelques-uns de ces blocs durs, sortans de la montagne granitique, sont deja considerable; on distingue qu'ils n'y tiennent plus que par une tres-pet.i.te partie; d'autres commencent a paroitre se degager, ils ne _saillent_, ils ne sortent encore que de quelque pieds, et meme de quelques pouces. Enfin, en examinant soigneus.e.m.e.nt et attentivement toute la surface de ce terrain granitique, on appercoit tous les intermediaires entre un bloc de granit dur contenu et encha.s.se dans la ma.s.se totale du granit friable et un bloc entierement degage.

Ces observations, suivies avec attention, ne laissent aucun doute que les blocs de granit que l'on observe sur toute l'etendue de ce terrain granitique, n'aient fait autrefois partie d'une couche considerable de granit decomposable qui couvroit ces montagnes et exhaussoit leur sol; que cette couche, dont il semble impossible d'apprecier la hauteur, malgre les blocs considerable qui restent et qui attestent son existence, a ete decomposee par l'air et l'intemperie des saisons; que la poussiere, le sable resultans de cette decomposition, ont ete entraines par les eaux, et deposes a divers points de la surface de la globe; et que ces blocs ont ete peu-a-peu degages de la couche, ainsi qu'il s'en degage encore tous les jours.

To enable the reader to form a notion of what these blocks are, I shall farther give what our author has said in describing this place where they are found.

C'est apres avoir quitte le terrain volcanique, c'est dans le terrain granitique que j'ai trouve des blocs enormes de granit, qui ont fixe mon attention.

Toute l'etendue du terrain granitique que j'ai traversee, se trouve presque couverte de ces ma.s.ses; les uns sur les sommets des montagnes les plus elevees, les autres sur la pente et dans les vallees. Plusieurs de ces ma.s.ses sont arrangees les uns sur les autres avec un art inimitable, les autres sont isolees et epa.r.s.es.

Peu de ces ma.s.ses m'ont presente un spectacle plus beau et plus imposant que celles que l'on rencontre a 6 heures de marche de S. Flour, a une pet.i.te demi heure avant d'arriver a la Garde.

La, sur le sommet d'une montagne, est un amas considerable de blocs de granit, etonnans par leur volume et leur nombre. La grande route pa.s.se a travers, et circule autour de ces ma.s.ses que les constructeurs des chemins n'ont pas ose attaquer.

Le voyageur est penetre d'admiration en voyant l'ordre et l'arrangement symetrique de ces blocs monstrueux par leur ma.s.se, et qu'il ne cesse d'observer en suivant la trace tortueuse du chemin qui les contourne.

Quelques-uns de ces blocs sont poses purement et simplement les uns sur les autres, et forment une colonne isolee; le plus gros sert de base, et les autres, graduellement plus pet.i.ts, son poses dessus. On voit jusqu'a trois de ces blocs immediatement l'un sur l'autre.

D'autres fois, le bloc qui sert de base est beaucoup plus pet.i.t que celui qui le couvre immediatement; et s'arrangement de ces deux blocs presente l'aspect d'un champignon.

Plus souvent plusieurs blocs separes les uns des autres, forment la base, et un ou plusieurs blocs sont poses immediatement dessus, sans ordre constant, tantot inclines, mais toujours d'une maniere stable et fixe, propre a resister aux plus grands efforts.

Enfin, par fois, des ma.s.ses plus pet.i.tes placees entre les grosses, semblent a.s.surer la situation fixe de l'ensemble des blocs; mais ces rencontres sont fort rares.

Here is a distinct view of this part of nature; a view in which the present state of things plainly indicates what has pa.s.sed, without our being obliged to raise our imagination to so high a pitch as is sometimes required, when we take the mountains themselves, instead of these blocks, as steps of the investigation. Here is a view, therefore, that must convince the most scrupulous, or jealous with regard to the admitting of theory, first, that those mountains had been much higher; secondly, that they had been degraded in their present place; thirdly, that this continent has subsisted in its present place for a very long s.p.a.ce of time, during the slow progress of those imperceptible operations; and, lastly, that much of the solid parts of this earth has been thus travelled by the waters to the sea, after serving the purpose of soil upon the surface of the land.

But though M. Ha.s.senfratz has thus given us a most satisfactory view of the natural history of those blocks of stone which are now upon or near their native place, this will not explain other appearances of the same kind, where such blocks are found at great distances from their native places, in situations where the means of their transportation is not to be immediately perceived, such as those resting upon the Jura and Saleve, and where blocks of different kinds of stone are collected together. These last examples are the records of something still more distant in the natural history of this earth; and they give us a more extensive view of those operations by which the surface of this earth is continually changing. It is, however, extremely interesting to this Theory of the Earth, to have so distinctly ascertained some of those first steps by which we are to ascend in taking the more distant prospect; and these observations of M. Ha.s.senfratz answer this end most completely.

Thus all the appearances upon the surface of this earth tend to show that there is no part of that surface to be acknowledged as in its original state, that is to say, the state in which it had come immediately from the mineral operations of the globe; but that, every where, the effects of other operations are to be perceived in the present state of things. The reason of this will be evident, when we consider, that the operations of the mineral kingdom have properly in view to consolidate the loose materials which had been deposited and ama.s.sed at the bottom of the sea, as well as to raise above the level of the ocean the solid land thus formed. But the fertility of the earth, for which those operations were performed, and the growth of plants, for which the surface of the earth is widely adapted, require a soil; now the natural, the proper soil for plants, is formed from the destruction of the solid parts. Accordingly, we find the surface of this earth, below the travelled soil, to consist of the hard and solid parts, always broken and imperfect where they are contiguous with the soil; and we find the soil always composed of materials arising from the ruin and destruction of the solid parts.

CHAP. VI.

_A View of the Economy of Nature, and necessity of Wasting the Surface of the Earth, in serving the purposes of this World_.

There is not perhaps one circ.u.mstance, in the const.i.tution of this terraqueous globe, more necessary to the present theory, than to see clearly that the solid land must be destroyed, in undergoing the operations which are natural to the surface of the earth, and in serving the purposes which are necessary in the system of this living world.