"Une de plus haute montagnes du Vallais, et situee sur une terrain tres-eleve, est la Gemmi; elle fait partie de la grande chaine qui separe le Canton de Berne du Vallais. Elle est remarquable, a cause de l'importance du chemin qu'on y a pratique, des grandes difficultes qu'il a fallu surmonter, et qu'elle est la seule communication entre les deux Cantons. Nous parlerons de ce chemin, apres avoir decrit la nature de ce prodigieux rocher. La Gemmi est la partie la plus haute de cette chaine qui commence aux galleries; elle est en general calcaire. On commence a monter insensiblement en sortant de Loiche; on traverse beaucoup de paturages; on voit quelques champs de seigle qui etoient encore sur pied et a moitie verts, des bosquets et de petits bois de sapins. Des masses considerables des rochers, des monceaux de pierres entassees descendues des hauteurs, couvrent cette superficie qui devient d'autant plus rapide qu'on approche plus du pied du rocher: cette pente qui est au pied de l'escarpement et de toutes les autres montagnes, est forme des pierres et des sables qui tombent des hauts et produisent, a la longue, des talus formes en pain de sucre, adosses contre les parties escarpees; les plus grosses pierres roulent et se precipitent plus bas, servent de point d'appui aux nouveaux materiaux qui s'y arretent, augmentent la hauteur des talus, en elargissant les basis, et finissent par devenir des montagnes tres considerables qui ont augmente en raison de la quantite des debris qu'ont pu fournir les parties plus elevees; c'est ce qu'on nomme montagnes de troisieme formation, composees des ruines de celles qui dominent ces talus; ces eboulemens sont ordinairement plus fertiles, plus couverts de vegetaux, d'arbres et de forets, sur-tout s'ils sont composes de differentes especes de debris. Nous avons deja vu que les montagnes calcaires sont elles-memes assises sur des couches et des lits d'ardoise ou de schiste, qui, par l'arrangement de leurs feuillets et de leurs couches, paroissent aussi avoir ete arranges et formes successivement; quelle est donc la base primitive sur laquelle sont appuyees et reposent ces masses qui etonnent l'imagination, a quelle profondeur faudra-t-il l'aller chercher? Si nous concevons la formation et la maniere dont se sont accrues et elevees ces troisiemes montagnes, pouvons-nous imaginer comment se sont arrangees celles qui sont si elevees au-dessus d'elles, ce tout que rien ne domine. C'est en examinant en considerant ces grands spectacles que ces reflections nous viennent; nous nous arretons, pour continuer a decrire ce que nous avons vu et remarque, qui est la tache que nous nous sommes imposee.

"En arrivant au pied de l'escarpement, le premier objet qui frappe la vue, ce sont des bancs de schistes ou d'ardoises bleuatres, meles de larges filons de quartz qui forment la base, et les fondemens sur lesquels est eleve ce mur de pierres calcaires. Car cette roche est elevee de meme a pic; ce lit d'ardoises est un peu incline vers le couchant, ainsi que tout ce qui repose dessus; la destruction de ce lit a cause, ainsi qu'aux galeries, la chute des rochers superieurs, et leur a occasionne cet a-plomb. Avant ces eboulements, ces couches schisteuses devoient etre decouvertes a une grande hauteur, etre exposees aux injures du tems et des saisons, se detruire et se decomposer plus aisement. Peut-etre que l'enveloppe calcaire les couvroient entierement, et que ces schistes n'ont commence a se detruire qu'apres la ruine de la pierre calcaire. Actuellement ces schistes sont enterres et couverts; ce n'est qu'en peu d'endroits qu'on les appercoit; appuyes soutenus et couverts par ces immenses debris en talus, ce sont des contre forts qui les aiderons a supporter plus longtemps les prodigieuses masses sous lesquelles ces schistes sont ensevelis. Nous allons placer par ordre les differentes substances, telle qu'elle se presentent en montant.

"1. Base de schiste ou d'ardoise feuilletee bleuatre, traverse, de larges filons de quartz. On ne voit, on ne peut estimer son epaisseur dont partie est enterree.

"2. Immediatement dessus pose la pierre calcaire, elle est d'une grain fin, serre, couleur grise-jaunatre, ainsi que toute le reste.

"3. Des filons de differentes epaisseurs, d'un spath calcaire jaunatre.

"4. Quelques petits filons ou renules de schiste pur.

"5. De la pierre calcaire d'un grain plus grossier.

"6. D'autres couches d'un grain plus fin.

"7. Couches de pierres calcaires melees d'une quantite suffisante de sable pour faire feu avec le briquet, sans cesser de faire effervescence avec les acides.

"8. De petits filons ou couches ondoyantes de spath.

"9. De la pierre calcaire dans laquelle sont deposes des especes de noyaux oblongs, quelques fois par couches, mais sans suite, composes d'un sable fin de couleurs grisatre, plus blanc que la pierre calcaire, tres-durs, faisant feu au briquet, et sans effervescence avec les acides.

"10. On retrouve encore des couches minces sablonneuses melees de parties calcaires.

"11. D'autres de pierre calcaire compacte et d'une epaisseur considerable.

"12. Alternativement de moins compactes. Dans l'une de ces couches il y a de la pyrite vitriolique decompose, qui teint en jaune les parties du rochers sur lesquels a flue la decomposition martiale.

"13. Quelques filons de spath jaunatre, entremeles de veines de schiste pur, ne faisant pas effervescence.

"14. De la pierre calcaire.

"15. Des schistes meles de parties calcaires.

"16. De la pierre calcaire pure.

"17. De larges filons de spath calcaire jaunatre meles de quartz, faisant feu au briquet, et une peu d'effervescence.

"18. De la pierre calcaire pure grise, plus foncee que dans le bas.

"19. Des couches calcaires jaunatres.

"20. Enfin tout le haut n'est que pierre calcaire grise et denaturee. Cette partie superieure du monte est fort etendue. Tout ce qui est sur le local qui va en pente assez douce vers le milieu, n'a pas ete assujetti a de roulis et a des frottemens, il n'y a que la longueur du tems qui l'ait degrade, et lui ait imprime le caractere de la vetuste. On ne voit que des pierres calcaires, elles sont remplies de trous, de fentes, et de crevasses; beaucoup, paroissent poreuses comme de la la pierre ponce grossiere; le sejour des neiges des eaux, la gelee, et l'intemperie des saisons a tout fait. On voit de tous cotes que l'eau s'y infiltre et s'y perd. L'arrangement de cette espece de pierre par couches, facilite l'entree des eaux dans l'interieur de la montagne pour aller donner naissance a des sources, a des torrents, et quelquefois a d'assez fortes rivieres qui sortent du pied de ces montagnes calcaires; lors de la fonte des neiges, l'eau ne se verse point des sommets de ces sortes de montagnes comme de dessus les autres especes de rochers qui absorbent moins les eaux. Dans le milieu de ce haut il y a un petit lac d'un grand quart de lieue de long de forme ovale, ou se rassemblent les eaux des neiges fondues; il n'y a point d'issues a ce lac, ses eaux sont absorbees, et se perdent dans l'interieur de la montagne; il n'y avoit que peu de glace alors sur ce lac, mais il y avoit encore beaucoup de neiges aux environs; un glacier est sur la droite, se prolonge et va fermer le sommet du vallon ou est Loiche; c'est le meme glacier qu'on appercoit derriere les sources chaudes. Deux aiguilles de rocher en cone, fort hautes s'elevent au-dessus du sommet; elles sont toujours couvertes de neiges: leur ressemblance et leur proximite a donne le nom de Gemmi Jumeaux, a cette montagne—On voit a ses pieds a une profondeur immense le village de Loiche, qui paroit etre tout au pied du rocher; il faut cependant une grand heure et demie pour s'y rendre, tant la hauteur diminue le point de perspective. Le chemin qui est pratique dans ce rocher, y a ete par-tout taille; il le contourne certains endroits, dans d'autres il est creuse de facon qu'il forme une voute couverte, et qu'on a le rocher suspendu au-dessus de soi. Il est rare de trouver l'occasion de pouvoir examiner de detailler avec autant de facilite une montagne d'une pareille hauteur. A compter des galleries jusqu'aux glaciers de la Gemmi, ces rochers perpendiculaires et a pic ont plus de trois lieues d'etendue; ils diminuent en hauteur a mesure que le pays s'eleve, et se confond dans les plus hautes alpes, qui sont surmontees d'autre masses de rochers.

"De l'autre cote du vallon, et vis-a-vis des montagnes qui forment celles de la Gemmi, est la montagne du midi, separee par la Dala, torrent qui vient du glacier a la tete du vallon, dont les eaux paroissent avoir creuse le lit etroit et profond. Cette montagne est calcaire comme la Gemmi, et paroit en avoir fait partie: je n'ai pu verifier nulle part si elle etoit posee sur des schistes: tout est dans un grand bouleversement sur sa pente qui est fort rapide. A environs trois quarts de lieue des bains, un sentier fort difficile, qui passe sur les decombres de cette montagne et dans des bois de sapins fort obscurs, conduit par un pente fort rapide a un rocher perpendiculaire, comme sont presque tous ceux du canton on y trouve des echelles appuyees contre; on parvient a la premiere, en grimpant par les avances et les saillies du rocher; d'autres roches facilitent le moyen d'arriver a la seconde; on trouve ainsi sept echelles dont quelques-unes sont fort hautes, et par lesquelles on se guide au sommet de ce rocher; on est bien surpris d'y trouver un terrain en pente, ou il y a des champs laboures et des vignes qui entourent le village d'Albinien, dont les habitans ont place ces echelles pour raccourcir le chemin qui conduit a Loiche, ou ils vont vendre leurs denrees.

"Nous quittons les bains de Loiche pour nous rapprocher du Rhone: on repasse par Inden, on ne trouve ensuite que des pierres, des rochers, des escarpemens; c'est un chemin des plus mauvais jusqu'au bourg de Loiche; c'est pour eviter ce chemin qu'on a fait celui des galleries. Le bourg de Leuck, ou Loiche, est un des principaux endroits du Vallais, bati en pierres, dans une position fort elevee et tres-forte; l'art avoit encore ajoute anciennement a la force de son assiette, il y a encore d'anciens forts et des tours; toute cette hauteur est calcaire; on a la plus belle vue de ce lieu, elle s'etend sur tout le bas Vallais jusqu'au dela de Martigny; nous avons donne une foible idee de cette vue, avant d'arriver aux bains de Loiche, car les expressions manquent pour rendre ces grands tableaux. Un spectacle bien interessant pour ceux qui etudient les changemens qui arrivent journellement a la surface du globe, est la vue du Kolebesch, montagne fort elevee en face du bourg de Leuck, et de l'autre cote du Rhone; cette montagne est calcaire ainsi que la chaine sur la rive gauche du Rhone, du moins la partie avancee qui forme le vallon ou coule ce fleuve. Des chutes, des eboulemens y ont produit de grands changemens; les eaux et les torrens qui viennent des parties elevees, ont entraine ces debris, les ont deposes aux pieds de la montagne, et en ont forme une colline qui a plus d'une demie-lieue jusqu'au Rhone, et plus d'une grande lieue de large, en forme circulaire; elle s'etend vers le haut et le bas Vallais; la partie superieure est couverte de pres et des paturages; celle du cote du bas Vallais est couverte d'une foret; elle va en pente douce; la grosseur des arbres prouve combien la formation de ce terrain est ancienne. Depuis la consolidation de ce terrain des torrens nouveaux y ont creuse un ravin large et profond, par lequel s'ecoulent actuellement les eaux des montagnes, et les pierres qu'elles en arrachent. Le Rhone mine et emporte le pied de cette colline qui resserroit son cours, avec ces materiaux il va plus loin former des atterrissemens composes des matieres les plus pesantes; les parties les plus fines le limon suspendu dans ces eaux servent ensuite a couvrir les anciens atterrissemens, au moyen desquels ils deviennent susceptibles de toute espece de vegetation; ses eaux finissent de s'epurer dans le lac Leman, d'ou il sort clair et limpide, ainsi que toutes les rivieres qui sortent des lacs jusqu'a ce que d'autre torrens, tombant des montagnes, viennent les troubler de nouveau."

Here is a most satisfactory view of the structure of this country on each side of the Rhone; strata of lime-stone and schisti, almost horizontal or little inclined, compose the mountains from their most lofty summits to the deepest bottom of those valleys. Such mountains cannot have been formed in any other manner than by the waste and degradation of their horizontal strata; consequently, here we are certain, that, from the summit of the Gemmi to those upon the other side of the Rhone, all the solid substance had been hollowed out by water. Thus were formed the valleys of the Rhone, the Dala, and a multitude of others.

M. de Saussure has given us a description of a tract of alpine country of the same kind with that of the Vallais now considered, so far as the strata are here in a horizontal position, instead of that highly inclined situation in which those primary bodies are commonly found. It is the description of Mount-Rosa Journal de Physique, Juillet 1790.

Here the same interesting observation may be made with regard to the immense destruction which must necessarily have taken place, in the elevated mass of solid earth, by the dissolving or wearing power of running water; and this will be clearly explained by the formation of those mountains and valleys, which, while they correspond with mountains and valleys in general, have something particular that distinguishes them from most of the Alps, where the strata, being much inclined, give occasion to form ranges of peaks disposed in lines according to the directions of the inclined strata. Here on the contrary, there being no general inclination of the strata to direct the formation of the peaks, they are found without any such order. I shall give it in M. de Saussure's own words.

"En effect toutes les hautes sommites que j'avois observees jusqu'a ce jour sont ou isolees comme l'Etna, ou rangees sur des lignes droites comme le Mont-Blanc et ses cimes collaterales. Mais la je voyois le Mont Rose compose d'une suite non-interrompue de pics gigantesques presqu'egaux entr'eux, former un vaste cirque et renfermer dans leur enceinte, le village de Macugnaga, ses hameaux, ses paturages, les glaciers qui les bordent, et les pentes escarpees qui s'elevent jusqu'aux cimes de ces majestueux colosses.

"Mais ce n'est pas seulement la singularite de cette forme qui rend cette montagne remarquable; c'est peut-etre plus encore sa structure. J'ai constate que le Mont-Blanc et tous les hauts sommets de sa chaine sont composes de couches verticales. Au Mont-Rose jusqu'aux cimes les plus elevees, tout est horizontal ou incline au plus de 30 degres.

"Enfin il se distingue encore par la matiere dont il est construit. Il n'est point de granits en masse, comme le Mont-Blanc et les hautes cimes qui l'entourent; ce sont des granits veines et des roches feuilletees de differens genre qui constituent la masse entiere de cet assemblages de montagnes, depuis bases jusqu'a ses plus hautes cimes. Ce n'est pas que l'on n'y trouve du granit en masses, mais il y est purement accidentel, et sous la forme de rognons, de filons, ou de couches interposees entre celles des roches feuilletees.

"On ne dira donc plus que les granits veines, le gneiss et les autres roches de ce genre, ne sont que les debris des granits rassembles et agglutines au pied des hautes montagnes, puisque voila des roches de ce genre dont la hauteur egale a tres-peu-pres celle des cimes granitiques les plus hautes connues, et ou l'on ferois bien embarrasse a trouver la place des montagnes de granit dont les debris out pu leur servir de materiaux; sur-tout si l'on considere la masse enorme de l'ensemble des murs d'un cirque tel que celui du Mont-Rose. En effet, ce seroit une hypothese inadmissible que de supposer, qu'anciennement il a existe dans le vuide actuel du cirque une montagne de granit, et que ce cirque est le produit des debris de cette montagne. Car comment ne resteroit-il aucun vestige de cette montagne? On concoit bien que sa tete auroit pu se detruire, mais son corps, la base du moins, protegee par les debris de sa tete accumules autour d'elle qu'est ce qui auroit pu l'aneantir; d'ailleurs les parois interieures du cirque quoique tres-escarpees ne sont pourtant pas verticale; elles s'avancent de tous cotes vers l'interieur; et le fond, le milieu meme du cirque n'est point du granit, il est de la meme nature que ses bords. Enfin nous avons reconnu que les montagnes qui forment la couronne du Mont-Rose se prolongent au dehors a de grandes distances en sorte que leur ensemble forme une masse incomparablement plus grande que celle qui auroit rempli le vuide interieur du cirque.

"Il faut donc reconnoitre, comme tous les phenomenes le demontrent d'ailleurs, qu'il existe de montagnes de roches feuilletees, composees des memes elemens que le granit, et qui sont sorties comme lui des mains de la nature sans avoir commence par etres elles-memes des granits[22]."

[Footnote 22: M. de Saussure, upon the evidence before us, might have gone farther, and maintained that the masses of granite, which here traverse the strata in form of veins and irregular blocks, had been truly of a posterior formation. But this is a subject which we shall have afterwards to consider in a particular manner; and then this example must be recollected.]

Here is an example the most interesting that can be imagined. Those mountains are the highest in Europe, and their lofty peaks are altogether inaccessible upon one side. They had all been formed of the same horizontal strata. How then have they become separated peaks? And how have the valleys been hollowed out of this immense mass of elevated country?—No otherwise than as we may perceive it, upon every mountain, and after every flood. It is not often indeed, that, in those alpine regions, any considerable tract of country is to be found, where an example so convincing is exhibited. It is more common for those mountains of primary strata or schistus to rise up in ridges, which, though divided into great pyramids, may still be perceived as connected in the direction of their erected strata. These last, although affording the most satisfactory view of that mineral operation by which land, formed and consolidated at the bottom of the sea, had been elevated and displaced, are not so proper to inform us of the amazing waste of those extremely consolidated bodies, as are those where the strata have preserved their original horizontal portion. It is in this last case, that there are data remaining for calculating the minimum of the waste that must have been made of those mountains, by the regular and long continued operations of the atmospheric elements upon the surface of this earth.

It is the singularity of these horizontal strata in that extensive alpine mass, which seems to have engaged M. de Saussure, who has inspected so much of those instructive countries, to make a tour around those mountains, and to give us a particular description of this interesting place. Now, from this description, it is evident, that there is an immense mass of primary or alpine strata nearly in the horizontal position, which is common to all the strata at their original formation; that this horizontal mass had been raised into the highest place of land upon this globe; and that, in this high situation, it has suffered the greatest degradation, in being wasted by the hand of time, or operations of the elements employed in forming soil for plants, and procuring fertility for the use of animals. Here is nothing but a truth that may almost every where be perceived; but here that important truth is to be perceived on so great a scale, as to enable us to enlarge our ideas with regard to the natural operations of this earth, and to overcome those prejudices which contracted views of nature, and magnified opinions of the experience of man may have begotten,—prejudices that are apt to make us shut our eyes against the cleared light of reason.

Abundant more examples of this kind, were it necessary, might be given, both from this very good observator, and from M. de Luc[23].

[Footnote 23: Vid. Discours sur l'Histoire Naturelle de la Suisse, passim; but more particularly under the article of Route du Grindle wald a meiringen dans le pays de Hasti: Also Hist: de la Terre, Lettre 30. p. 45, et Lettre 31. page 68, etc.]

I will now only mention one from this last author, which we find in the Journal de Physique, Juin 1792.

"Entre Francfort et Hanau, le mein est borde sur ses deux rives, de collines dans lesquelles la lave se trouve enchassee entre des couches calcaires. Ces couches sont tres-remarquables par leur contenue, qui est le meme au-dessus et au-dessous de la lave, et qu'on retrouve dans les couches d'une grande etendue de pays, ou, comme d'ordinaire, on voit leurs sections abruptes dans les flancs de collines, mais sans lave, excepte dans le lieu indique."

The particular structure of those lime-stone strata, with the body of basaltes or subterraneous lava which is interposed among them, shows evidently the former connection of those two banks of the river, by solid matter, the same as that which we see left there, and in the flanks of those hills. That which is wanting, therefore, of those stratified masses, in that great extent of country, marks out to us the minimum of what has been lost, in having been worn by the attrition of travelled materials.

I would now beg leave, for a moment, to transport my reader to the other side of the Atlantic, in order to perceive if the same system of rivers wearing mountains is to be found in that new world, as we have found it in the old.

Of all the mountains upon the earth, so far as we are informed by our maps, none seem to be so regularly disposed as are the ridges of the Virginian mountains. There is in that country a rectilinear continuity of mountains, and a parallelism among the ridges, no where else to be observed, at least not in such a great degree.

At neither end of those parallel ridges is there a direct conveyance for the waters to the sea. At the south end, the Allegany ridge runs across the other parallel ridges, and shuts up the passage of the water in that direction. On the north, again, the parallel ridges terminate in great irregularity. The water therefore, that is collected from the parallel valley, is gathered into two great rivers, which break through those ridges, no doubt at the most convenient places, forming two great gapes in the blue ridge, which is the most easterly of those parallel ridges.

Now, so far as mountains are in the original constitution of a country, the ridges of those mountains must have been a directing cause to the rivers. But so far as rivers, in their course from the higher to the lower country, move bodies with the force of their rolling waters, and wear away the solid strata of the earth, we must consider rivers as also forming mountains, at least as forming the valleys which are co-relative in what is termed mountain. Nothing is more evident than the operation of those two causes in this mountainous country of Virginia; the original ridges of mountains, or indurated and elevated land, have directed the courses of the rivers, and the running of those rivers have modified the mountains from whence their origin is taken. I have often admired, in the map, that wonderful regularity with which those mountains are laid down, and I have much wished for a sight of that gap, through which the rivers, gathered in the long valleys of those mountains, break through the ridge and find a passage to the sea. A description of this gap we have by Mr Jefferson, in his notes on Virginia.

"The passage of the Potomac, through the Blue Ridge, is perhaps one of the most stupendous scenes in nature. You stand on a very high point of land. On your right comes up the Shenandoah, having ranged, along the foot of the mountains, an hundred miles to seek a vent. On the left approaches the Potomac, in quest of a passage also. In the moment of their junction, they rush together against the mountain, rend it asunder, and pass off to the sea.

"The first glance of this scene hurries our senses into the opinion, that this earth had been erected in time; that the mountains were formed first; that the rivers began to flow afterwards; that in this place particularly they have been dammed up by the Blue Ridge of mountains, and have formed an ocean which filled the whole valley; that, continuing to rise, they have at length broken over this spot, and have torn the mountain down from its summit to its base. The piles of rock on each hand, but particularly on the Shenandoah, the evident marks of this disrupture and avulsion from their beds, by the most powerful agents of nature, corroborate the impression. But the distant finishing which nature has given to the picture is of a different character. It is a true contrast to the foreground. It is as placid and delightful as that is wild and tremendous. For the mountain being cloven asunder, she presents to your eye, through the cleft, a small catch of smooth blue horizon at an infinite distance in the plain country, inviting you, as it were, from the riot and tumult roaring around, to pass through the breach, and partake of the calm below. Here the eye ultimately composes itself; and that way too the road happens actually to lead. You cross the Potomac above the junction, pass along its side through the base of the mountain for three miles, its terrible precipices hanging in fragments over you, and within about twenty miles reach of Frederick town, and the fine country around it. This scene is worth a voyage across the Atlantic. Yet here, as in the neighbourhood of the natural bridge, are people who have passed their lives within half a dozen of miles, and have never been to survey these monuments of a war between the rivers and mountains, which must have shaken the earth itself to its center."

To this description of the passage of the Potomac may be added what Mr Jefferson, in the appendix, has given from his friend Mr Thomson, secretary of Congress.

"The reflections I was led into on viewing this passage of the Potomac through the Blue Ridge were, that this country must have suffered some violent convulsion, and that the face of it must have been changed from what it probably was some centuries ago; that broken and ragged faces of the mountain on each side of the river; the tremendous rocks which are left with one end fixed in the precipice, and the other jutting out, and seemingly ready to fall for want of support; the bed of the river for several miles below obstructed, and filled with the loose stones carried from this mound; in short, every thing on which you cast your eye evidently demonstrates a disrupture and breach in the mountain, and that before this happened, what is now a fruitful vale, was formerly a great lake, or collection of water, which possibly might have here formed a mighty cascade, or had its vent to the ocean by the Susquehanna, where the Blue Ridge seems to terminate. Besides this, there are other parts of this country which bear evident traces of a like convulsion. From the best accounts I have been able to obtain, the place where the Delaware now flows through the Kittatinny mountain, which is a continuation of what is called the North Ridge, or mountain, was not its original course, but that it passed through what is now called the Wind-gap, a place several miles to the westward, and above an hundred feet higher than the present bed of the river. This Wind-gap is about a mile broad, and the stones in it such as seem to have been washed for ages by water running over them. Should this have been the case, there must have been a lake behind that mountain; and, by some uncommon swell in the waters, or by some convulsion of nature, the river must have opened its way through a different part of the mountain, and meeting there with less obstruction, carried away with it the opposing mounds of earth, and deluged the country below with the immense collection of waters to which this new passage gave vent. There are still remaining, and daily discovered, innumerable instances of such a deluge on both sides of the river, after it passed the hills above the falls of Trenton, and reached the champaign. On the New Jersey side, which is flatter than the Pennsylvania side, all the country below Croswick hills seems to have been overflowed to the distance of from ten to fifteen miles back from the river, and to have acquired a new soil, by the earth and clay brought down and mixed with the native sand. The spot on which Philadelphia stands evidently appears to be made ground. The different strata through which they pass in digging for water, the acorns, leaves, and sometimes branches which are found above twenty feet below the surface, all seem to demonstrate this."

How little reason there is to ascribe to extraordinary convulsions the excavations which are made by water upon the surface of the earth, will appear most evidently from the examination of that natural bridge of which mention is made above, and which is situated in the same ridge of mountains, far to the south, upon a branch of James's River. Mr Jefferson gives the following account of it.

"The natural bridge, the most sublime of nature's works, is on the ascent of a hill, which seems to have been cloven through its length by some great convulsion. The fissure, just at the bridge, is by some admeasurements 270 feet deep, by others 205; it is about 45 feet wide at the bottom, and 90 feet at the top; this of course determines the length of the bridge, and its height from the water. Its breadth in the middle is about 60 feet, but more at the ends; and the thickness of the mass at the summit of the arch about 40 feet. A part of its thickness is constituted by a coat of earth, which gives growth to many large trees. The residue, with the hill on both sides, is one solid rock of lime-stone. The arch approaches the semi-elliptical form; but the larger axis of the ellipsis, which would be the cord of the arch, is many times longer than the transverse. Though the sides of the bridge are provided in some parts with a parapet of fixed rock, yet few men have resolution to walk to them, and look over into the abyss. You involuntarily fall on your hands and feet, and creep to the parapet, and look over it. Looking down from this height about a minute gave me a violent headache. If the view from the top be painful and intolerable, that from below is delightful in the extreme. It is impossible for the emotions arising from the sublime to be felt beyond what they are here. On the sight of so beautiful an arch, so elevated, so light, and springing as it were up to heaven, the rapture of the spectator is really indescribable! The fissure, continuing narrow, deep, and straight, for a considerable distance above and below the bridge, opens a short but very pleasing view of the north mountain on one side, and blue ridge on the other, at the distance each of them of about five miles. This bridge is in the county of Rockbridge, to which it has given name, and affords a public and commodious passage over a valley, which cannot be crossed elsewhere for a considerable distance. The stream passing under it is called Cedar Creek: it is a water of James's River, and sufficient in the driest seasons to turn a grist mill, though its fountain is not more than two miles above[24]."

[Footnote 24: Upon this occasion it may be observed, the most wonderful thing, with regard to cosmology, is that such remnants, forming bridges, are so rare; this therefore must be an extraordinary piece of solid rock, or some very peculiar circumstances must have concurred to preserve this monument of the former situation of things.]

Thus both in what is called the Old World and the New, we shall be astonished in looking into the operations of time employing water to move the solid masses from their places, and to change the face of nature, on the earth, without defacing nature. At all times there is a terraqueous globe, for the use of plants and animals; at all times there is upon the surface of the earth dry land and moving water, although the particular shape and situation of those things fluctuate, and are not permanent as are the laws of nature.

It is therefore most reasonable, from what appears, to conclude, that the tops of the mountains have been in time past much degraded by the decay of rocks, or by the natural operations of the elements upon the surface of the earth; that the present mountains are parts which either from their situation had been less exposed to those injuries of what is called time, or from the solidity of their constitution have been able to resist them better; and that the present valleys, or hollows between the mountains, have been formed in wasting the rock and in washing away the soil.

If this is the case, that rivers have every where run upon higher levels than those in which we find them flowing at the present, there must be every where to an observing eye marks left upon the sides of rivers, by which it may be judged if this conclusion be true. I shall now transcribe a description of a part of the Vallais by which this will appear. (Discours sur l'Histoire Naturelle de la Suisse.)

"Apres avoir passe le village de Saint-Leonard, on commence a monter la montagne de la Platiere; cette route est on ne peut plus interessante pour le naturaliste Etc.

"On se trouve fort eleve au-dessus du Rhone quand on est sur le haut de ce chemin, dont on decouvre un de plus singuliers, des plus riches, et de plus varies passages qu'on puisse imaginer. On voit sous ses pieds le Rhone serpenter dans le lit qu'il se creuse actuellement, car il change et tout prouve qu'il en a souvent change; une quantite prodigieuse de petites isles le separent et le coupent en une multitude de canaux et de bras; ces isles sont couvertes les unes d'arbres, d'arbustes, de paturages, de bosquets et de verdure, d'autres de pierres, de sable, et de debris de rochers; quelques-unes sont formees ou occasionnees par un amas de troncs d'arbres entasses avec de grands sapins renverses dont les long tiges herissees de branches droites et nues representent des chevaux de frise, et donnent l'idee de ces abatis destines a preserver un pays contre l'approche de l'ennemi. Du cote du bas Vallais, on suit a perte de vue le fleuve dans ses sinuosites et ses detours, on l'appercoit egalement dans le haut Vallais; des avances de montagne le cachent quelquefois: il reparoit et diminue insensiblement en approchant de ces monts eleves ou il prend sa source: le fond du vallon paroit etre de niveau, s'abaisser seulement d'une pente douce du cote du bas Vallais: des mamelons, des hauteurs des monticules isoles, quelquefois groupes de differentes manieres, sont repandus dans cet espace, et rappellent la vue d'une pre devaste par les taupes; plusieurs de ces hauteurs sont surmontees des ruines d'antiques chateaux, d'eglises, et de chapelles; des villages distribues ca et la enrichissent ce fond, qui d'ailleurs est couvert de paturages, de champs d'arbres, de bois, et de bosquets; les enclos des possessions le coupent en mille figure bizarres et irregulieres. Ces monticules avec leurs fabriques s'elevent au-dessus de tous ces objets varies; quelques-unes se distinguent par leur cotes ecroules qui sont a pic; la blancheur de ces eboulemens contraste singulierement avec les verts qui sont les couleurs dominantes du vallon. Au-de-la des coteaux, des montagnes s'elevent et vont s'appuyer et s'adosser a ces masses, a ces colosses enormes de rochers a pic eleves comme des murailles et d'une hauteur prodigieuse qui forment cette barriere qui separe le Vallais de la Savoie. Les contours du pied de ces monts forment des entrees de vallons et de vallees d'ou descendent et se precipitent des torrens qui viennent grossir les eaux du Rhone; la vue cherche a penetrer et a s'etendre dans ces espaces, l'imagination cherche vainement des passages dans effrayantes limites, parmi ces ecueils et ces rochers amonceles, elle est arretee partout; de noires forets de sapin sont suspendues parmi ces rochers blancs-jaunatres, qui se terminent enfin par une multitude d'aiguilles et de pyramides qu'on voit percer au travers des neiges et des glaces, s'elancer dans les nues, s'y cacher et s'y perdre.

"En examinant de plus pres ces mamelons repandus dans le vallon, on voit qu'ils sont composes de pierres, de sables, et de debris rapportes et amonceles sans ordre depuis des temps dont rien ne peut fixer l'epoque: on voit que les eaux du Rhone ont coule a leurs pied, qu'il en a mine plusieurs et a occasionne leurs chutes et leurs ruines. On voit actuellement quelques mamelons qui subissent ces memes degradations, et fournissent au Rhone les materiaux dont il va former plus loin ces atterissemens dont nous avons parle. La confusion et le desordre qui se remarque dans la composition interieure de ces mamelons prouvent qu'ils ne sont pas le produit de la mer ou des eaux qui ont travaille successivement et lentement a la formation de la plupart des terrains; mais que le fond de ce vallon a ete rempli des decombres et des debris des montagnes superieures, qu'ils y ont ete entraines par des inondations et des debordemens subits; que les eaux du Rhone ensuite ont parcouru ce vallon qu'il a souvent change de lit; que c'est en tournant et en circulant dans ce terrain nouvellement forme, qu'il a creuse les espaces qui sont entre ces mamelons, et que c'est en creusant le terrain qu'ils se sont eleves; leurs formes et leurs pentes allongees vers le bas Vallais, sont de nouvelles preuves que ce sont les eaux actuelles qui ont change la surface de ce terrain, nous verrons de nouvelles preuves de ce que nous disons en avancant d'avantage vers le haut Vallais; il n'y a peut-etre point d'endroit plus propre a etudier le travail des eaux que ce vallon qu'on a la facilite de voir et d'examiner sous des aspects differentes."

Another example of the same kind, with regard to the bed of the Rhine, we have from the same author. (Discours, etc. page 259.)

"De Richenau a Coire, Troyen, et Saint-Gal.

"Pour aller a Coire on passe le port qui est sur le haut Rhin; en cotoyant ce fleuve, qui coule dans un fond, on entre dans une plaine de niveau, qui n'a qu'une pente tres insensible de trois quarts de lieue; le fond du terrain n'est qu'un amas de pierres roulees de toutes especes. Les deux cotes sont bordes de montagnes calcaire qui courent parallelement entr'elles. Celle de la gauche, au pied de laquelle coule le Rhine, est tres rapide et perpendiculaire a son sommet; celle qui est a droite de la plaine ou petit vallon, puisqu'il se trouve entre des montagnes, est moins haute, plus boisee, et couverte de sapins. Le vallon est aussi couvert, en partie, de tres-grands et beaux pins; mais ce qu'on y voit de plus remarquable, c'est une douzaine de gros mamelons ou butes, elevees de cinquante a soixante toises, plus ou moins isolee, et a differentes distances les unes des autres; ces butes sont rondes, la plupart allongees dans le sens du vallon, et composees de debris calcaires et de sables; le fond du vallon est mele de plus d'especes de galets. On ne croit pas se tromper en disant que ce vallon a ete rempli de matieres apportees par les eaux jusqu'a la hauteur ou sont encore actuellement les mamelons; que de nouvelles inondations ont ensuite creuse et entraine ce qui manque de terrain a ces mamelons; que c'est en circulant autour de ces mamelons que les eaux leur ont donne la forme ronde; et surtout allongee dans le sens du vallon, et que c'est par le moyen de ces memes eaux que le fond actuel de cette plaine a pris ce niveau et cette pente insensible vers un pays plus ouvert qui est au-dela. On a deja fait mention de pareils mamelons qui se trouvent dans le vallon du Vallais parcouru par le Rhone."

These examples may also be supported by what this author observes in another place[25].

[Footnote 25: Discours, etc. page 201.]

"Le vallon ou est situe Meiringen, est visiblement forme par le depot des eaux, il est de niveau, et s'etend trois lieues en longueur jusqu'au lac de Brientz, a la suite duquel est le meme terrain nivele, qui va jusqu'au lac de Thun, dont on a parle. Une autre observation qui concourt a favoriser ce sentiment, c'est que toutes les roches calcaires, qui entourent le vallon, sont a pic, qu'on y remarque des cavites circulaires et des enfoncemens a meme hauteur et a differents points, qui constatent la fouille et le mouvement des eaux contre ces parois."

Thus we have seen the operation of the atmospheric elements degrading mountains, and hollowing out the valleys of this earth.

The land which comes from the mineral region in a consolidated state, in order to endure the injuries of those atmospheric elements, must be resolved in time for the purposes of fertilising the surface of this earth. In no station whatever is it to be exempted from the wasting operations, which are equally necessary, in the system of this world, as were those by which it had been produced. But with what wisdom is that destroying power disposed! The summit of the mountain is degraded, and the materials of this part, which in a manner has become useless from its excessive height, are employed in order to extend the limits of the shore, and thus increase the useful basis of our dwellings. It is our business to trace this operation through all the intermediate steps of that progress, and thus to understand what we see upon the surface of this earth, by knowing the principles upon which the system of this world proceeds.



CHAP. XI.

Facts and Opinions concerning the Natural Construction of Mountains and Valleys.

The valley of the Rhone is continued up to the mountain of St. Gothard, which may be considered as the centre of the Continent, since, from the different sides of this mountain, the water runs in all directions. To the German Sea it runs by the Rhine, to the Mediterranean by the Rhone, and to the Adriatic by the Po. Here it may be proper to take a general view of this mountainous country, or that great mass of rock or solid strata which has been either formed originally in its present shape, or has been excavated by the constant operation of water running from the summit in all the different directions.

On the one hand, it is supposed that the forming cause which had produced those mountains, in collecting their materials at the bottom of the sea, had also determined the shape in which their various ridges are at present found; on the other hand, it is supposed that the destructive causes, which operate in degrading mountains, have immediately contributed to produce their present forms, and that it is only mediately or more remotely that this shape has been determined by mineral operations and the constitution of the solid parts, which thus oppose the wearing operations of the surface with different degrees of hardness and solidity. Whether natural appearances correspond with the one or the other of those two different suppositions, every person who has the opportunity of making such an examination, and has sufficient knowledge of the subject to judge from his observation, will determine for himself.

I will here give the opinion of a person who has had great opportunities for this purpose, who is an intelligent as well as an attentive observator, and who has had particularly this question in his view. It is from 'Tableaux de la Suisse'[26].

[Footnote 26: "Discours sur l'Histoire Naturelle de la Suisse."]

"Quand nous nous sommes trouve sur ces points eleves, nous avons toujours considere le total des montagnes prises ensemble, leurs situations respectives, les unes par rapport aux autres; afin de reconnoitre, s'il y avoit quelque chose de constant dans leurs position; rien n'est plus varie. Dans la grande chaine de montagnes qui separe le canton de Berne du Vallais d'un cote, et les Alpes qui separent le Vallais de la Savoie de l'autre, en considerant le course du Rhone sous differens points de vue, on n'a point vu que les angles saillans de ces tres hautes montagnes fussent opposes aux angles rentrans des montagnes qui sont vis-a-vis; Le fameux vallon qui est sur le haut du Saint-Gothard, le point le plus eleve de l'Europe, contredit egalement cette observation, aussi que les positions de la plus grande partie des montagnes qui forment son vaste circuit. Le vallon de Scholenen, qui a plus de huit lieues, et dans lequel la Reusse coule du sommet du Saint-Gothard jusqu'au lac de Lucerne, offre a peine quelques exemples d'angles rentrans opposes a des angles saillans. Les nombreux vallons que nous avons constamment traverses ceux qui conduisent au Grindelwald, et celui qui mene au pays de Hasli qui sont sous nos yeux, n'etablirent pas d'avantage cette correspondance d'angles saillans et angles rentrans, qu'on regarde comme si constante. Dans les montagnes basses, du troisieme et quatrieme ordre, ou inferieures, on remarque plus souvent cette correspondance, encore n'est-elle pas constante: les eaux ordinaires ont forme ces vallons; mais si on veut donner une theorie generale, c'est assurement dans les plus hautes montagnes qu'il faut prendre ses exemples. Ce qui se trouve au-dessous de ces points les plus eleves, a pris sa forme de la disposition meme des plus hauts sommets."

M. de Saussure, in his second volume of Voyages dans les Alpes, gives the strongest confirmation to the theory of the gradual degradation of mountains by the means of rain.

"Sec. 920. Je reviens aux observations. Il en est une tres importante pour la theorie de la terre, dont on peut du haut du Cramont apprecier la valeur, mieux que d'aucun autre site; je veux parler de la fameuse observation de Bourguet sur la correspondance des angles saillans avec les angles rentrans des vallees. J'ai a deja dit un mot dans le 1er. volume, Sec. 577, mais j'ai renvoye a ce chapitre les developpemens que je vais donner.

"Ce qui avoit fait regarder cette observation comme tres-importante, c'est que l'on avoit cru qu'elle pourroit servir a demontrer que les vallees ont ete creusees par des courans de la mer, dans le temps ou elle couvroit encore les montagnes; ou que les montagnes qui bordent ces vallees avoient ete elles-memes formees par l'accumulation des depots rejetes sur les bords de ces memes courans.

"Mais l'inspection des vallees que l'on decouvre du haut du Cramont demontre pleinement le peu de solidite de ces deux suppositions. En effet, toutes les vallees que l'on decouvre du haut de cette cime sont fermees, au moins a l'une de leurs extremites et quelques-unes a leurs deux extremites, par des cols eleves, ou meme par des montagnes d'une tres-grande hauteur: toutes sont coupees a angles droits par d'autres vallees, et l'on voit enfin clairement que la plupart d'entr'elles ont ete creusees, non point dans la mer, mais, ou au moment de sa retraite, ou depuis sa retraite, par les eaux des neiges et des pluies.

"On a d'abord sous ses yeux la grande vallee de l'Allee-Blanche, qui etant parallele a la direction general de cette partie des Alpes, est du nombre de celles que je nomme longitudinales; et l'on voit cette vallee barree a l'une de ses extremites par le Col de la Seigne et a l'autre par le Col Ferret. En se retournant du cote de l'Italie, on voit plusieurs vallees a-peu-pres paralleles a celle-la, comme celle de la Tuile, celle du Grand Saint Bernard, qui toutes aboutissent, par le haut, a quelque Col tres-eleve, et par le bas, a la Doire, ou elles viennent se jeter vis-a-vis de quelque montagne qui leur correspond de l'autre cote de cette vallee.

"Si l'on considere ensuite cette meme vallee de la Doire, qui descend de Courmayeur a Yvree, on la verra barree par le Mont-Blanc et par la chaine centrale, qui la coupent a angles droits dans la partie superieure. On verra cette meme vallee s'ouvrir, dans un espace de sept ou huit lieues, deux ou trois inflexions tout-a-fait brusques; et on la verra enfin coupee a angles droits par une quantite de vallees qui viennent y verser leurs eaux, et qui sont elles memes coupees par d'autres, dont elles recoivent aussi le tribut. Or quand on reflechit a la largeur et a l'etendue des courans de la mer, peut-on concevoir que ces sillons etroits, barres, qui se coupent en echiquier a de tres-petites distances, aient pu etre creuses par de semblables courans.

"L'observation de la correspondance des angles, fut-elle aussi universelle qu'elle l'est peu, ne prouveroit donc autre chose, sinon que les vallees sont nees de la fissure et de l'ecartement des montagnes, ou qu'elles ont ete creusees par les torrens et les rivieres qui y coulent actuellement. On voit un grand nombre de vallees naitre, comme je l'ai fait voir au Bon-Homme, Sec. 767, sur les flancs d'une montagne; on les voit s'elargir et s'approfondir a proportion des eaux qui y coulent; un ruisseau qui sort d'une glacier, ou qui sort d'une prairie, creuse un sillon, petit d'abord, mais qui s'agrandit successivement a mesure que ses eaux grossissent, par la reunion d'autres sources ou d'autres torrens.

"Il n'est meme pas necessaire, pour se convaincre de la verite da ces faits, de gravir sur le Cramont. Il suffit de jeter les yeux sur la premiere carte que l'on trouvera sous la main, des Pyrenees, de l'Apennin, des Alpes, ou de quelqu'autre chaine de montagnes que ce puisse etre. On y verra toutes les vallees indiquees par le cours des rivieres; on verra ces rivieres et les vallees dans lesquelles elles coulent, aboutir par une de leurs extremites au sommet de quelque montagne ou de quelque col eleve. Les replis tortueux d'un grand fleuve, indiqueront une vallee principale, dans laquelle des torrens ou des rivieres qui indiquent d'autres vallees moins considerables, viennent aboutir, sous des angles plus ou moins approchans de l'angle droit. Or ces rivieres qui viennent de droite et de gauche se jeter dans la vallee principale, ne s'accordent pas pour se jeter par paires dans le meme point du fleuve; elles sont comme les branches d'un arbre qui s'implantent alternativement sur son tronc, et par consequent, chaque petite vallee se jette dans la vallee principale vis-a-vis d'une montagne. Et de plus on verra aussi sur les cartes que meme les plus grandes vallees ont presque toutes des etranglemens qui forment des ecluses, des fourches, des defiles.

"Je ne pretends cependant pas que l'erosion des eaux pluviales, des torrens et des rivieres, soit l'unique cause de la formation des vallees: le redressement des couches des montagnes nous force a en admettre une autre, dont je parlerai ailleurs; j'ai voulu seulement prouver, ici que la correspondance des angles, lorsqu'elle a lieu dans les vallees, ne prouve point que ces vallees soient l'ouvrage des courans de la mer."

The place to which M. de Saussure here remits us is where he afterwards, in describing the Val d'Aoste, makes the following observation.

"(Sec. 960.) Au-dela de Nuz, les montagnes qui bordent au midi la vallee, et dont on voit d'ici tres-bien la structure, sont composees de grandes couches appliquees les unes contre les autres, et terminees par des cimes aigues, escarpees contre le midi, elles tournent ainsi le dos a la vallee, dont la direction est toujours a 10 degres de l'est par nord. Celles de la gauche que nous cotoyons, et qui sont de nature schisteuse, tournent aussi le dos a la vallee en s'elevant contre le nord. Je crois pouvoir conclure de la, que cette vallee est une de celles dont la formation tient a celle des montagnes memes, et non point a l'erosion des courans de la mer ou des rivieres. Les vallees de ce genre, paroissent avoir ete formees par un affaissement partiel des couches des montagnes, qui ont consenti, dans la direction qu'ont actuellement ces vallees."

Here I would beg leave to differ a little from this opinion of M. de Saussure, at least from the manner in which it is expressed; for perhaps at bottom our opinions upon this subject do not differ much.

M. de Saussure says that the formation of this valley depends upon the mountains themselves, and not upon the erosion of the rivers. I agree with our author, so far as the mountains may have here determined the shape and situation of the valley; but, so far as this valley was hollowed out of the solid mass of our earth, there cannot be the least doubt that the proper agent was the running water of the rivers. The question, therefore, comes to this, How far it is reasonable to conclude that this valley had been hollowed out of the solid mass. Now, according to the present theory, where the strata consolidated at the bottom of the sea are supposed to be erected into the place of land, we cannot suppose any valley formed by another agent than the running water upon the surface, although the parts which are first to be washed away, and those which are to remain longest, must be determined by a concurrence of various circumstances, among which this converging declivity of the strata in the bordering mountains, doubtless, must be enumerated.

With regard to any other theory which shall better explain the present shape of the surface of the earth, by giving a cause for the changed position of the strata originally horizontal, I cannot form a judgment, as I do not understand by what means strata, which were formed horizontally, should have been afterwards inclined, unless it be that of a power acting under those strata, and first erecting them in relation to the solid globe on which they rested.

Besides, in supposing this valley original, and not formed by the erosion of the rivers, What effect should we ascribe to the transport of all those materials of the Alps, which it is demonstrable must have travelled through this valley? Whether is it more reasonable to suppose, on the one hand, that the action and attrition of all the hard materials, running for millions of ages between those two mountains, had hollowed out that mass which originally intervened; or, on the other, that this valley had been originally formed in its present shape, while thousands of other valleys have been hollowed out of the solid mass?

But to put this question out of doubt, with regard to this very valley of the river Doire, M de Saussure has given us the following decisive fact, Sec. 881: "Immediatement au-dessus de cette source, est un rocher qui repond si precisement a un autre rocher de la meme nature, situe de l'autre cote de la vallee de Courmayeur, qu'on ne sauroit douter qu'ils n'aient ete anciennement unis par une montagne intermediaire, detruite par les ravages du temps."

Now, to see how little the situation of the strata influences the shape of the valleys, I shall transcribe the two paragraphs immediately following that which has given occasion to the present discussion.

"Un peu au-dela de Nux, la vallee cesse d'etre large et plane, comme elle etoit dans le environs de la cite; elle devient etroite et tres variee; la sterile et sauvage, ici couverte de vergers et de prairies arrosees par la Doire.

"Sec. 961. Les couches des montagnes a notre gauche, qui depuis la cite avoient constamment couru a l'est et monte au nord, paroissent changer a un quart de lieue du village de Chambaise, qui est a une lieue et un quart de Nux. Elles montent d'abord au sud-est, et peu plus loin droit au sud, tandis que l'autre cote de la vallee elles paroissent monter a l'est."

In every mountain, and in every valley, the solid parts below have contributed in some manner to determine the shape of the surface of the earth; but in no place is the original shape of the earth, such as it had first appeared above the sea, to be found. Every part of the land is wasted; even the tops of the mountains, over which no floods of water run, are degraded. But this wasting operation, which affects the solid rock upon the summit of the mountain, operates slowly in some places, compared with that which may be observed in others. Now, it is in the valleys that this operation is so perceptible; and it is in the valley that there is such a quick succession of things as must strike the mind of any diligent observer; but this is the reason why we must conclude, that at least all the valleys are the operation of running water in the course of time. If this is granted, we have but to consider the mountains as formed by the hollowing out of the valleys, and the valleys as hollowed out by the attrition of hard materials coming from the mountains. Here is the explanation of the general appearance of mountain and valley, of hill and dale, of height and hollow; while each particular shape must have its dependence, consequently its explanation, upon some local circumstance.

But, besides the general conformation of mountains and valleys, there may be also, in the forms of mountains, certain characters depending upon the species of substances or rocks of which they are composed, and the general manner in which those masses are wasted by the operations of the surface. Thus there is some character in the external appearance of a hill, a mountain, or a ridge of hills and mountains; but this appearance is generally attended with various circumstances, or is so complicated in its nature, as to be always difficult to read; and it is but seldom that it affords any very particular information; although, after knowing all the state and circumstances of the case, I have always found the appearances most intelligible, and strictly corresponding with the general principle of atmospheric influence acting upon the particular structure of the earth below.

M. de Saussure has given us an observation of this kind, in describing the mountains through which the Rhone has made its way out of the Alps, at the bottom of the Vallee.

"Sec.. 1061. Plus loin le village de Juviana ou Envionne on voit des rochers qui ont une forme que je nomme moutonnee; car on est tente de donner des noms a des modifications qui n'en ont pas, et qui ont pourtant un caractere propre. Les montagnes que je designe par cette expression sont composees d'un assemblage de tetes arrondies, couvertes quelquefois de bois, mais plus souvent d'herbes, ou tout au plus de brousailles. Ces rondeurs contigues et repetees forment en grand l'effet d'une toison bien fournie, ou de ces perruques que l'on nomme aussi moutonnees. Les montagnes qui se presentent sous cette forme, sont presque toujours de rochers primitives, ou au moins des steatites; car je n'ai jamais vu aucune montagne de pierre a chaux ou d'ardoise revetir cette apparence. Les signes qui peuvent donner quelque indice de la nature des montagnes, a de grandes distances et au travers des plantes qui le couvrent, sont en petit nombre, et meritent d'etre etudies et consacres par des termes propres."

When philosophers propose vague theories of the earth, theories which contain no principle for investigating either the general disorder of strata or the particular form of mountains, such theories can receive no confirmation from the examination of the earth, nor can they afford any rule by which the phenomena in question might be explained. This is not the case when a theory presents both the efficient and final cause of those disorders in bodies which had been originally formed regular, and which shows the use as well as means for the formation of our mountains. Here illustration and confirmation of the theory may be found in the examination of nature; and natural appearances may receive that explanation which the generalization of a proper theory affords.

The particular forms of mountains depend upon the compound operation of two very different causes. One of these consists in those mineral operations by which the strata of the earth are consolidated and displaced, or disordered in the production of land above the sea; the other again consists in those meteorological operations by which this earth is rendered a habitable world. In the one operation, loose materials are united, for the purpose of resisting the dissolving powers which act upon the surface of the earth; in the other, consolidated masses are again dissolved, for the purpose of serving vegetation and entertaining animal life. But, in fulfilling those purposes of a habitable earth, or serving that great end, the land above the level of the sea is wasted, and the materials are transported to the bottom of the ocean from whence that consolidated land had come. At present we only want to see the cause of those particular shapes which are found among the most elevated places of our earth, those places upon which the wasting powers of the surface act with greatest energy or force.

In explaining those appearances of degraded mountains variously shaped, the fact we are now to reason upon is this; first, that in the consolidated earth we find great inequality in the resisting powers of the various consolidated bodies, both from the different degrees of consolidation which had taken place among them, and the different degrees of solubility which is found in the consolidated substances; and, secondly, that we find great diversity in the size, form, and positions of those most durable bodies which, by resisting longer the effects of the wearing operations of the surface, must determine the shape of the remaining mass. Now so far as every particular shape upon the surface of this earth is found to correspond to the effect of those two causes, the theory which gave those principles must be confirmed in the examination of the earth; and so far as the theory is admitted to be just, we have principles for the explanation of every appearance of that kind, whether from the forming or destroying operations of this earth, there being no part upon the surface of this earth in which the effect of both those causes must not more or less appear.

But though the effects of those two causes be evident in the conformation of every mountainous region, it is not always easy to analyse those effects so as to see the efficient cause. Without sections of mountains their internal structure cannot be perceived, if the surface which we see be covered with soil as is generally the case. It is true, indeed, that the solid bodies often partially appear through that covering of soil, and so far discover to us what is to be found within; but as those solid parts are often in disorder, we cannot, from a small portion, always judge of the generality. Besides, the solid parts of mountains is often a compound thing, composed both of stratified and injected bodies; it is therefore most precarious, from a portion which is seen, to form a judgment of a whole mass which is unexplored. Nevertheless, knowing the principles observed by nature both in the construction and degradation of mountains, and cautiously inferring nothing farther than the data will admit of, some conclusion may be formed, in reasoning from what is known to what is still unknown.

It is with this view that we are now to consider the general forms of mountains, such as they appear to us at a certain distance, when we have not the opportunity of examining them in a more perfect manner. For, though we may not thus learn always to understand that which is thus examined, we shall learn, what is still more interesting, viz. that those mountains have been formed in the natural operations of the earth, and according to physical rules that may be investigated.

We are to distinguish mountains as being either on the one hand soft and smooth, or on the other hand as hard and rocky. If we can understand those two great divisions by themselves, we shall find it easy to explain the more complex cases, where these two general appearances partially prevail. Let us therefore examine this general division which we have made with regard to the external character of mountains.

The soft and smooth mountains are generally formed of the schisti, when there is any considerable extent of such alpine or mountainous region. The substance is sufficiently durable to form a mountain, or sufficiently strong, in its natural state, to resist the greatest torrent of water; at the same time this fissible substance generally decays so completely, when exposed to the atmosphere, as to leave no salient rock exposed by which to characterise the mountain.

Of this kind are the schisti of Wales, of Cumberland, of the isle of Man, and of the south of Scotland. I do not say absolutely, that there is no other kind of material, besides the schisti which gives this species of mountain, but only that this is generally the case in alpine situations. It may be also formed of any other substance which has solidity enough to remain in the form of mountains, and at same time not enough to form salient rocks. Such, for example, is the chalk hills of the Isle of Wight and south of England. But these are generally hills of an inferior height compared with our alpine schisti, and hardly deserve the term of mountain.

This material of our smooth green mountains may be termed an argillaceous schistus; it has generally calcareous veins, and is often fibrous in its structure resembling wood, instead of being slatey, which it is in general. There is however another species of schistus, forming also the same sort of mountain; it is the micaceous quartzy schistus of the north of Scotland. Now it must be evident that the character of those mountains arises from there being no part of those schisti that resists the influence of the atmosphere, in exfoliating and breaking into soil; and this soil is doubtless of different qualities, according to the nature of those schisti from which the soil is formed.

Such mountains are necessarily composed of rounded masses, and not formed of angular shapes. They are covered with soil, which is more or less either stoney or tender, sterile or fertile, according to the materials which produce that soil. The fertile mountains are green and covered with grass; the sterile mountains again are black, or covered with heath in our climates.

Thus we have a general character of smooth and rounded mountains; and also a distinction in that general character from the produce of the soil indicating the nature of the solid materials, as containing, either on the one hand calcareous and argillaceous substances, or, on the other, as only containing those that are micaceous and siliceous.

With regard again to the other species of mountain, which we have termed rocky, we must make a subdistinction of those which are regular, and those in which there is no regularity to be perceived. It must be plain that it is only of those which have regularity that we can form a theory. It is this, that the regularity in the shape of those mountains arises from the rock of the mountain being either on the one hand an uniform solid mass, or on the other hand a stratified mass, or one formed upon some regular principle distinguishable in the shape. In the first of these, we have a conical or pyramidal shape, arising from the gradual decay of the rock exposed to the destructive causes of the surface, as already explained in this chapter. In the second, again, we find the original structure of the mass influencing the present shape in conjunction with the destructive causes, by which a certain regularity may be observed. Now, this original shape is no other than that of beds or strata of solid resisting rock, which may be regularly disposed in a mountain, either horizontally, vertically, or in an inclined position; and those solid beds may then affect the shape of the mountain in some regular or distinguishable manner, besides the other parts of its shape which it acquires upon the principle of decay.

In distinguishing, at a distance, those regular causes in the form of mountains, we may not be able to tell, with certainty, what the substance is of which the mountain is composed; yet, with regard to the internal structure of that part of the earth, a person of knowledge and experience in the subject may form a judgment in which, for coming at truth, there is more than accident; there is even often more than probable conjecture. Thus, a horizontal bed of rock forms a table mountain, or such as M. Bouguer found in the valley of the Madelena. An inclined rock of this kind forms a mountain sloping on the one side, and having a precipice upon the upper part of the other side, with a slope of fallen earth at the bottom; such as the ridges observed by M. de Saussure from the top of the Cramont, having precipices upon one side, which also had a respect to certain central points, an observation which draws to more than the simple structure of the mountain. Were it vertical, again, it would form a rocky ridge extended in length, and having its sides equally sloped, so far as the other circumstances of the place would permit.

Therefore, whether we suppose the mountains formed of a rock in mass, or in that of regular beds, this must have an influence in the form of this decaying surface of the earth, and may be distinguished in the shape of mountains. It is but rarely that we find mountains formed altogether of rock, although we often find them of the other sort, where little or nothing of rock is to be seen. But often also we find the two cases variously compounded. This is the source of the difficulty which occurs in the reading of the external characters of mountains; and this is one of the causes of irregularity in the form of mountains, by which there is always some degree of uncertainty in our judgment from external appearances.

We may form another distinction with regard to the structure of mountains, a distinction which depends upon a particular cause, and which will afford an explanation of some other appearance in the surface of the earth.

Mountains in general may be considered as, being either on the one hand associated, or on the other insulated; and this forms a distinction which may be explained in the theory, and afford some ground for judging of the internal structure from the external appearance.

The associated mountains are formed by the wearing down of the most decayable, or softer places, by the collected waters of the surface; consequently there is a certain similarity, or analogy, of the mountains formed of the same materials, and thus associated. The highest of those mountains should be near the center of the mass; but, in extensive masses of this kind, there may also be more than one center. Nor are all the associated mountains to be of one kind, however, to a certain extent, similarity may be expected to prevail among them.

It must now be evident, that when we find mountains composed of very different materials, such as, e.g. of granite, and of lime-stone or marl, and when the shape of those mountains are similar, or formed upon the same principle, such as, e.g. the pyramidal mountains of the Alps, we are then to conclude, as has already been exemplified (chap. 9. page 306.) that those consolidated masses of this earth had been formed into the pyramidal mountains in the same manner. We have there also shown that this principle of formation is no other than the gradual decay of the solid mass by gravity and the atmospheric influences. Consequently, those pyramidal mountains, though composed of such different materials, may, at a certain distance, where smaller characteristic distinctions may not be perceivable, appear to be of the same kind; and this indeed they truly are, so far as having their general shape formed upon the same principle.

We come now to treat of insulated mountains. Here volcanos must be mentioned as a cause. By means of a volcano, a mountain may be raised in a plain, and a volcanic mountain might even rise out of the sea. The formation of this species of mountain requires not the wearing operations of the earth which we have been considering as the modifier of our alpine regions. This volcanic mountain has a conical shape, perhaps more from the manner of its formation which is accretion, than from the wasting of the surface of the earth. It is not, however, of this particular specie of mountain that I mean to treat, having had no opportunity of examining any of that species.

The genus of mountain which we are now considering, is that of the eruptive kind. But there is much of this eruptive matter in the bowels of the earth, which, so far as we know, never has produced a volcano. It is to this species of eruption that I am now to attribute the formation of many insulated mountains, which rise in what may be termed low countries, in opposition to the highlands or alpine situations. Such is Wrekin in Shropshire, which some people have supposed to have been a volcano. Such are the hundred little mountains in the lowlands of this country of Scotland, where those insulated hills are often called by the general term Law; as, for example, North Berwick Law.

When masses of fluid matter are erupted in the mineral regions among strata which are to form our land; and when those elevated strata are, in the course of time, wasted and washed away, the solid mass of those erupted substances, being more durable than the surrounding strata, stand up as eminences in our land. Now these often, almost always, form the small insulated mountains which are found so frequently breaking out in the lowlands of Scotland. They appear in various shapes as well as sizes; and they hold their particular form from the joint operation of two different causes; one is the extent and casual shape of the erupted mass; the other is the degradation of that mass, which is wasted by the influences of the atmosphere, though wasted slower than the strata with which it was involved.

When the formation of this erupted mass has been determined by the place in any regular form, which may be distinguished in the shape of a mountain, it gives a certain character which is often not difficult to read. Thus, our whin-stone, interjected in flat beds between the regular strata, often presents its edge upon, or near the summit of our insolated mountains and eminences. They are commonly in the form of inclined planes; and, to a person a little conversant in this subject, they are extremely distinguishable in the external form of the hill.

We have a good example of this in the little mountain of Arthur's Seat, by this town of Edinburgh. This is a peaked hill of an irregular erupted mass; but on the south and north sides of this central mass, the basaltic matters had been forced also in those inclined beds among the regular strata. On the north side we find remarkable masses of whin-stone in that regular form among the strata, and lying parallel with them. The most conspicuous of these basaltic beds forms the summit of the hill which is called Salisbury Craig. Here the bed of whin-stone, more than 60 or 80 feet thick, rises to the west at an angle of about 40 degrees; it forms the precipicious summit which looks to the west; and this is an appearance which is distinguishable upon a hundred other occasions in the hills and mountains of this country.

Rivers make sections of mountains through which they pass. Therefore, nothing is more interesting for bringing to our knowledge the former state of things upon the surface of this earth, than the examination of those valleys which the rivers have formed by wearing down the solid parts of alpine countries. We have already seen that the wide extensive valley of the Rhone, between Loiche and Kolebesche, as well as the whole extensive circus of the Rosa mountains, has on each side mountains of the same substances, the strata of which are horizontal; consequently, here the valley must have been hollowed out of the solid rock; for there is no natural operation by which those opposite mountains of horizontal strata could have been formed, except in the continuation of those beds. We are therefore to conclude, that the solid strata between those ridges of lofty mountains had been continuous.

The most perfect confirmation which this theory could receive, would be to find that those ridges of mountains, which the Rhone divides in issuing from the Alps into the plain, had been also united, in forming one continued mass of solid rocks. But the observations of M. de Saussure, who has most carefully examined this subject, will leave no room to doubt of that fact.

This view of the entry to the valley of the Rhone is too interesting not to give it here a place. It follows immediately after that which we have last transcribed.

"Ces montagnes que j'allai sonder au haut des prairies qui les separent de la grande route, sont composees d'un melange tres ressemblant au precedent, et ce sont-la, les derniers rochers primitifs que l'on rencontre en sortant des Alpes par cette vallee. Le village de Juviana, dont ils occupent les derrieres, est encore a une lieue de St Maurice.

"Sec. 1062. A l'extremite de ces rochers, on voit une grande ravine, ou plutot une vallee ouverte du nord au midi, dans laquelle coule le torrent de St. Barthelemi. Cette vallee termine les montagnes primitives que je viens de decrire: au-dela commencent les montagnes calcaires. Cependant le pied de la montagne primitive, coupe par le torrent, est demeure engage sous les premieres couches de la montagne calcaire.

"Au travers de cette vallee, on voit de hautes montagnes couverte de neige, situees derriere celles qui bordent notre route. La plus haute et la plus remarquable de ces montagnes se nomme la Dent ou l'Aiguille du Midi. De l'autre cote du Rhone, on voit une autre cime aussi tres-elevee, qui se nomme la Dent ou l'Aiguille de la Morele. Ces deux hautes cimes ont entr'elles une correspondance de hauteur, de forme, et meme de matiere tout-a-fait singuliere. L'une et l'autre presentent leurs escarpemens a la vallee du Rhone. Leurs cimes crenelees sont de la meme couleur brune. Sous ces cimes brunes, on voit de part et d'autre une bande grise, qui paroit horizontale, et au-dessous de cette bande grise, le rocher, dans l'une comme dans l'autre, reprend sa couleur jaunatre. Ces montagnes sont surement secondaires, les bandes grises paroissent etre de pierre a chaux, et les jaunes de schiste argilleux et de gres, a en juger du moins a cette distance, car je ne les ai point observees de plus pres. Elles paroissent aussi appartenir a des chaines secondaires qui passent derriere les chaines primitives, que nous avons observees sur les bords du Rhone, et quoique les bandes jaunes et grises que l'on y observe, semblent horizontales, je ne doute point que les couches memes, dont ces bandes sont les sections, ne descendent en arriere avec assez de rapidite; le escarpemens de ces montagnes en font une preuve a-peu-pres certaine.

"Ces hautes montagnes auroient-elles ete anciennement liees entr'elles par des intermediaires de la meme nature, que couvroient, et les primitives que nous avons observees, et toute cette vallee dans laquelle coule aujourd'hui le Rhone? Je me garderois bien de l'affirmer, mais je ferois tente de le croire.

"Sec. 1063. Depuis la vallee dont je viens de parler, et qui termine au couchant les montagnes primitives, celles qui suivent jusques a St. Maurice, sont de nature calcaire a couches epaisses et suivies. Ces couches s'elevent contre les primitives que nous avons cotoyees; et celles qui en sont les plus voisines paroissent fort tourmentees; ici flechies, la rompues. Apres une interruption, ces rochers sont suivis d'autres rochers, aussi calcaires, coupes a pic du cote de la vallee, et composes de grandes assises horizontales. Ces rochers forment une enceinte demi-circulaire, qui vient presque se joindre a ceux qui bordent la rive droite du Rhone, et former ainsi l'entree de cette vallee, dont le fleuve ne sort que par une issue tres-etroite.

"La ville de St. Maurice est ainsi renfermee par cette enceinte de rochers, dont les bancs epais, bien suivis, separes par des cordons de verdure, et couronnes par des forets, avec un hermitage niche entre ces bancs, presente une aspect singulier et pittoresque.

"Sec. 1064. Les rochers correspondans de l'autre cote du Rhone, ou sur la rive droite de ce fleuve sont aussi calcaires. La montagne qui domine cette rive, un peu au-dessus de St. Maurice, est composee de couches contournees, froissees et repliees de la maniere la plus etrange. Ce qu'il y a encore de remarquable, c'est que ces couches ainsi repliees en ont d'autres a cote d'elles qui sont planes, presque verticales, et d'autres sous elles, qui sont horizontales. Il faudroit avoir observe de pres ce singulier rocher, et avoir determine comment et jusqu'a quel point ces couches sont unies entr'elles pour former les conjectures sur leur origine. Car la vallee est trop large pour que l'on puisse en juger avec precision d'une rive a l'autre.

"On voit avec peine que cette large vallee soit aussi peu cultivee; elle est presque partout couverte, ou de marais, ou de debris des montagnes voisines.

"Sec. 1065. Avant de quitter cette vallee, je jetterai un coup-d'oeil general sur la singuliere suite de rochers qui composent la chaine que nous venons d'observer.

"Les deux extremites sont calcaires, avec cette difference, que celle qui est la plus pres de Martigny est melee de mica, tandis que celle de St Maurice n'en contient point. Entre ces calcaires sont refermees des rochers que l'on regarde comme primitives; et au milieu de ces roches on trouve des ardoises et des poudingues. On fait que ce dernier genre est ordinairement classe parmi les montagnes tertiaires, ou de la formation la plus recente. Mais ces poudingues-ci, qui ne contiennent aucun fragment de pierre calcaire, qui ne sont meme point unis par un gluten calcaire, ne sont vraisemblablement pas posterieures a la formation des montagnes calcaires, ou du moins ils ne doivent point etre confondus avec ces gres et ces poudingues de formation nouvelle, qui entrent dans la composition des montagnes du troisieme ordre.

"Quant aux ardoises que se trouvent interposees au milieu de ces gres et de ces poudingues, Sec. 1054, elles sont de nature argilleuse, et dans l'ordre des pierres que l'on nomme secondaires.

"Ces ardoises, de meme que toutes les pierres de ces montagnes, ont leurs couches dans une situation verticale: mais nous avons vu qu'il y a lieu de croire qu'elles ont ete anciennement horizontales."

It is singularly fortunate that such remarkable appearances, as are found in the rocks of this place, had called the attention of M. de Saussure to investigate a subject so interesting to the present theory; and it is upon this, as well as on many other occasions, that the value of those observations of natural history will appear. They are made by a person eminent for knowledge; and they are recorded with an accuracy and precision which leaves nothing more to be desired.

From Martigny to St. Maurice, about three leagues, there is a most interesting valley of the Rhone, through which this river makes its way from the Vallais, or great valley above, among those mountains which seem to have shut up the Vallais, and through which the river must pass in running to the lake. M. de Saussure found some singular masses, which attracted his attention, in examining the structure of the rocks on the left side of this little valley. Like a true philosopher, and accurate naturalist, he desired to compare what was to be observed in the other side of this valley of the Rhone, which he had found so singular and so interesting on that which he had examined. Accordingly, in Spring 1785, he made a journey for that purpose. In this survey he found the most perfect correspondence between the two sides of this valley, so far as rocks of the same individual species, and precisely in the same order, are found upon the one side and upon the other.

This author, after describing those particular appearances, sums up the evidence which arises from this comparison of the two sides of the valley; and he here gives an example of just reasoning, of accuracy, and impartiality, which, independent of the subject, cannot be read without pleasure and approbation. But when it is considered, that here is a matter of the highest importance to the present theory, or to any other system of geology, no less than a demonstration that the rocks, of which the mountains on both sides of the valley of the Rhone are formed, are the same, and must have been originally continued in one mass, the following observations of our author will be most acceptable to every person who inclines to read upon this subject.

"Sec. 1079. On voit par cet expose, que bien que la vallee du Rlione ait dans ce trajet pres d'une lieue de largeur moyenne, les montagnes qui la bordent sont en general du meme genre, et dans la meme situation sur l'une et l'autre rive.

"Il y a cependant trois differences que je dois exposer et apprecier en peu de mots.

"La plus importante est dans ces couches de pierre calcaire, Sec. 1073, que j'ai trouvees sur la rive droite, et que je n'ai point vue sur la gauche. Mais il est possible qu'elles y soient, et qu'elles m'ayent echappe, masquees par des debris ou par d'autre causes accidentelles; cette supposition est d'autant plus possible, que l'epaisseur de ces couches n'est que de quelques pieds. D'ailleurs il arrive souvent, que des filons, tel que paroit etre celui dont je parle, ne s'etendent pas a de grandes distances, quoique la nature de la montagne demeure la meme. Enfin ce qui diminue l'importance de cette difference, c'est que ces couches calcaires se trouvent dans le voisinage de l'ardoise qui passe, comme la pierre calcaire, pour une pierre de nature secondaire, et qui alterne tres-frequemment avec elle.