{"collection":"earth","html_url":"https://unchartedknowledge.5gfusion.net/browse/earth/toe/toe33.htm","path":"earth/toe/toe33.htm","source_url":"https://sacred-texts.com/earth/toe/toe33.htm","text":"Theory of the Earth, by James Hutton, [1788 and 1795]\nThe Theory Illustrated, with a View of the\n Summits of the Alps.\nThere are two different directions in which we may observe the destruction of our land to proceed; in the one of these, the basis of our continent is diminished by the incroachment of the sea; in the other, again, it is the height of the land above the level of the sea that is lowered. We have been considering the incroachment of the sea upon the continent; let us now examine how far there may also appear sufficient documents, by which we may be led to conclude a long progress in time past, for the destruction of the solid mass of earth above the sea, without diminishing its basis.\nIf we shall suppose this earth composed of horizontal strata, and of one level surface, without the least protuberance remaining by which we might be informed of what had been removed by time in the operation of second causes, we should be ignorant of every thing of cosmogeny but this, That the strata of the globe had been originally formed (by the sea) in the same shape as we had found them on the surface of the land. But this is not the shape of the surface of our continent: We have every where abundance of eminences, sufficient to give us great information with regard to what had passed in former periods of time, if the strata of the globe were in that regular shape which they had originally assumed in being deposited at the bottom the sea.\nThe strata, however, are not in that regular shape and position from whence we might learn, by examining the remaining portions, what had been carried away from the surface in general; they are found variously inclined to the horizon; and this we find both occasioned from the fracture and flexure of those bodies, thus changed from their natural horizontal state. Thus, though there are in many places immense masses of strata cut off abruptly, and exposed to view, without the remainder appearing, we cannot from hence form any estimate of the general quantity of destruction; at the same time, it must be evident, from a general inspection, that there has been an immense quantity removed; and that an immense time had been required in bringing about those revolutions of things, which are not done by violent changes, but by slow degrees.\nBesides that general conclusion with regard to the destruction of the strata, there is also in many places a demonstration of that fact, from a measured minimum of the quantity which had been removed. It is to the mining business chiefly that we are indebted for that demonstration of which we now shall give an example.\nThe coal strata, about Newcastle upon Tyne, dip to the south-east at the rate of one in twelve, or thereabouts. This is but little removed from the horizontal position; at the same time, the strata come all up to the soil or surface in a country which is level, or with little risings. But in those strata there is a slip, or hitch, which runs from north-east to south-west, for 17 or 18 miles in a straight line; the surface on each side of this line is perfectly equal, and nothing distinguishable in the soil above; but, in sinking mines, the same strata are found at the distance of 70 fathoms from each other. Here therefore is a demonstration, that there had been worn away, and removed into the sea, 70 fathoms more from the country on the one side of this line, than from that on the other. It is far from having given us all the height of country which has been washed away, but it gives us a minimum of that quantity.\nThe examination of what is commonly called a secondary country is not sufficient to give us an idea of the immense operation of time in wearing the surface of this earth. It is not that those countries of inferior hardness and elevation have been spared in the course of time, but because we have not, in those levelled countries, such great remainders, by which we are to judge the quantity of what is lost. In the alpine country, again, though it be the same system of things with that which takes place in the lower country, the revolution of things is more marked for our view; and the ravages of time, in destroying the solid parts of the globe, in order to make soil of that which is removed, may be seen in all the steps of that important operation; whereas, in the more level countries, the scale of elevation is imperceptible, and that of time is so slow as renders our examination fruitless. It is the Alps, therefore, chiefly that we are to take for an example, in tracing this operation of nature upon the surface of this earth, and forming some idea of the course of time that must have flowed during that operation in which the height of our land had been diminished.\nOn whatever side we approach the Alps, we find some great river discharging the waters which had been gathered above, and with that water all the waste of earth and stone which had been made among those lofty masses of decaying rock. Now, we find this river running in a valley proportioned, in general, to this vehicle, in which is travelled the wreck of ruinous mountains. Spacious plains attend those mighty streams; and, tho' sometimes we find the greatest rivers much confined between approaching hills of solid rock, the valley opens again, and, on the whole, is always corresponding to the current of water which has successively run in all the quarters of this plain. Here a question occurs; Has this valley been made by the operation of the river itself, or has it been the effect of other causes? Let us now resolve that question.\nIf the valley was made for the river by any other natural cause, either we should tell by what means this work had been performed, or all reasoning upon the subject is at an end, and fancy substituted in its place. If again the river be considered as the means employed by nature in making this valley, then all the solid parts between the bounding mountains must have been removed, and the fertile plains must have been formed by the water depositing those materials which we find in the soil, and which had come originally from the solid mountains. There is no occasion to enter into any argument to prove this fact; nobody that examines the matter will find any reason to doubt; and it would be as unreasonable for those to doubt who have not examined, as for those who find no reasonable subject of doubt to disbelieve.\nWe are now to suppose the great river to have formed the valley and extensive plain in which the water runs,\u2014a valley corresponding to the grandeur of the river by which it has been formed. But, as we ascend this great valley, we find other valleys branching from this main valley; and, in all those subordinate valleys, we find rivers corresponding in like manner with the magnitude of the valley. Here, therefore, is infinitely more than a single river, and a valley corresponding to the river; here is a system of rivers and of valleys, things calculated in perfect wisdom, or properly adapted to each other.\nNow it is just as easy, by our theory, to explain this system of rivers and valleys, as it is to understand the single appearance of a river and a valley. But it is only in this manner that such a complicated operation, of a series in rivers and their valleys, is to be explained; and we can neither suppose the land to be formed with this intention by a supernatural cause, nor imagine any other natural cause so arranging things, upon the surface of the earth, as to form this perfect system, which holds of nothing but itself; a system in which is manifested wisdom, so far as all the parts are properly adapted to each other, and thus made to answer that intention which is so visible in the economy of this world.\nThe direction of the principal valleys of the Alps, or every mountainous region of the globe, may be considered as proceeding from the centre of that region to the plain country in which each river is to terminate; each secondary river with its valley then branches from the primary as from a stem, consequently runs in a direction perpendicular or inclined to the other. But the secondary rivers also have their branches; and subordinate branches still are branched. In thus tracing rivers and their branchings, we come at last to rivulets that only run in times of rain, and at other times are dry. It is here I would wish to carry my reader, in order to be convinced, with his proper observation, of this great fact,\u2014that the rivers, in general, have hollowed out their valleys.\nThe changes of the valley of the main river are but slow, the plain indeed is wasted in one place, but it is repaired in another, and we do not perceive the place from whence that repairing matter had proceeded. Therefore, that which here appears does not immediately suggest to the spectator what had been the state of things before the valley had been hollowed out, or before that plain, through which the river runs so naturally as being in the lowest place, was made. But it is otherwise in the valley of the rivulet; no person can examine this subject without seeing that the rivulet carries away matter which cannot be repaired except by wearing away some part of the mountain, or the surface of that place upon which the rain, which forms the stream, is gathered. In those rivulets, or their little plains, we see the detached parts remaining in the soil, and also the place from whence those detached parts were taken. Here we need no long chain of reasoning from effect to cause; the whole operation is in a manner before our eyes. In this case, it requires but little study to replace the removed parts; and thus to see the work of nature, resolving the most hard and solid masses by the continued influences of the sun and atmosphere. In this state of things, we are easily made to understand how heavy bodies are travelled along the declivity of the earth, by means of water running from the height.\nSuch is the system of rivers and their valleys; nor is there upon the continent a spot on which some river has not run. But, in the Alps of Switzerland and Savoy, there is another system of valleys, above that of the rivers, and connected with it. These are valleys of moving ice, instead of water. This icy valley is also found branching from a greater to a lesser, until at last it ends upon the summit of a mountain, covered continually with snow. The motion of things in those icy valleys is commonly exceeding slow, the operation however of protruding bodies, as well as that of fracture and attrition, is extremely powerful.\nTo illustrate those operations of excavating the valleys of rivers and of thus undermining mountains which fall by their proper weight, I shall transcribe some descriptions of what is to be found among the Alps. But first I would wish to carry my reader to the summit of that country, to examine the state of that part which nothing can have affected but the immediate influences of the sun and air. After having thus formed some idea of the summit of this wasting country, we shall next examine the valleys through which the materials of the degraded summit must have travelled.\nIn order to give a proper idea of this central part of the Alps, which is so interesting a part in the natural history of the earth, M. de Saussure, in the plates of his Voyages dans les Alpes, tom. 2. has given us two views, the one in profile, the other in face, of the Mont-Blanc. I have caused copy those plates, which are necessary to be consulted in reading the following description of this centre of the Alps.\nThis author has taken much pains to form, to himself a proper idea of the object which we have now in view; and he gives a description of the Mont-Blanc as seen from the top of the Cramont. It is that description which I am now to transcribe 17.\n\u00a7 910. \u00abLe premier objet de mon \u00e9tude fut le Mont Blanc. Il se pr\u00e9sente ici de la maniere la plus brillante et la plus commode pour l'observateur. On l'embrasse d'un seul coup-d'oeil, depuis sa base jusqu'\u00e0 sa cime, et il semble avoir \u00e9cart\u00e9 et rejet\u00e9 sur ses \u00e9paules son manteau de neiges et de glaces pour laisser voir \u00e0 d\u00e9couvert la structure de son corps. Taill\u00e9 presqu'\u00e0 pic dans une hauteur perpendiculaire de 1600 toises, les neiges et les glaces ne peuvent s'arr\u00eater que dans un petit nombre d'\u00e9chancrures, et il montre partout \u00e0 nud le roc vif dont il est compos\u00e9.\n\u00abSa forme paro\u00eet \u00eatre celle d'une pyramide, qui presente au sud-est du c\u00f4t\u00e9 du Cramont une de ses faces. L'arr\u00eate droite de cette pyramide du c\u00f4t\u00e9 du sud-ouest, monte au sommet, en faisant avec l'horison un angle de 23 \u00e0 24 degr\u00e9s. L'arr\u00eate gauche du cot\u00e9 du nord-est, monte au m\u00eame sommet sous un angle de 23 \u00e0 24 degr\u00e9s, en sorte que l'angle au sommet est d'environ 130 degr\u00e9s.\n\u00abCette pyramide paro\u00eet elle m\u00eame compos\u00e9e de grands feuillets triangulaires ou pyramidaux. Trois de ces grands feuillets ont leurs bases dans l'All\u00e9e-Blanche, et forment ensemble tout l'avant corps de la base de la pyramide. Chacun de ces feuillets, vu de l'All\u00e9e-Blanche, paro\u00eet une grande montagne, je les ai d\u00e9crits dans le chapitre pr\u00e9c\u00e9dent sous le noms de Mont-P\u00e9t\u00e9ret, Mont-Rouge, et Mont-Broglia, \u00a7 830, 831, 834. Mais du haut du Cramont, on voit plus nettement leur forme, et leur ensemble, on distingue, par exemple, qu'ils sont eux-m\u00eames compos\u00e9s de grandes feuilles pyramidales; on voit que les injures du temps ont d\u00e9truit la pointe du Mont-Rouge, tandis que celles des deux autres pyramides sont demeur\u00e9es enti\u00e8res.\n\u00abCes trois feuillets ne s'\u00e9l\u00e8vent pas jusqu'\u00e0 la moiti\u00e9 de la hauteur du Mont-Blanc; d'autres feuillets plus petits, situ\u00e9s derri\u00e8re et au-dessus d'eux, et plac\u00e9s sur deux lignes principales qui convergent au sommet, ach\u00e8vent de couvrir la face de cette grande pyramide. Ces feuillets sont tous de forme pyramidale; les plus petits sont les plus aigus; j'en ai mesur\u00e9 plusieurs, dont l'angle au sommet n'\u00e9toit que de 70 degr\u00e9s. Tous, absolument tous, ont leurs plans parall\u00e8les \u00e0 l'All\u00e9e-Blanche, et par cons\u00e9quent dirig\u00e9s du nord-est au sud-ouest.\n\u00ab\u00a7 911. Quant \u00e0 la mati\u00e8re dont est compos\u00e9e cette grande et haute montagne, toute sa cime et toute sa base, tant au centre que du c\u00f4t\u00e9 du nord-est, sont indubitablement de granit; mais le c\u00f4t\u00e9 sud-ouest de la base, ou le Mont-Broglia que nous avons vu de pr\u00e8s, \u00a7 834, est d'une pierre moins dure, m\u00e9lang\u00e9e de schorl, de feldspath, de mica, de quartz gras et de pyrites.\n\u00abOn voit tr\u00e8s-bien du haut du Cramont que cette partie de la base n'est point du granit; sa couleur est d'un brun rouge\u00e2tre, elle ne se termine point par des arr\u00eates vives et nettes, n'est point compos\u00e9e de grandes tables planes. Ce font cependant des feuillets pyramidaux, mais petits et press\u00e9s les unes contre les autres; \u00e0 mesure qu'ils s'approchent du sommet, et par cela m\u00eame du coeur de la montagne, ils perdent leur couleur rouge, leurs angles deviennent plus vifs, leurs tables plus grandes et plus planes, et enfin pr\u00e9s de la cime, et \u00e0 la cime m\u00eame, ce sont de vrais granits parfaitement caract\u00e9ris\u00e9s. On peut donc conclure, que le corps entier du Mont-Blanc, et m\u00eame ces bases avanc\u00e9es du c\u00f4t\u00e9 de l'Italie, sont toutes de granit, except\u00e9 la base de l'arr\u00eate ext\u00e9rieure du c\u00f4t\u00e9 du sud-ouest.\n\u00ab\u00a7 912. La montagne qui touche le Mont-Blanc du c\u00f4t\u00e9 du nord-est, et qui, vue de Gen\u00e8ve, forme en quelque maniere le premiere escalier en descendant de la cime, est aussi compos\u00e9e de tables de granit qui paroissent dirig\u00e9es du nord-est au sud-ouest. Mais la sommit\u00e9 qui suit celle-ci en tirant toujours au nord-est, et qui forme le second escalier, paro\u00eet avoir quelques feuillets tournans autour de son corps pyramidal, comme les feuillets d'un artichaux, et comme j'ai d\u00e9peint l'aiguille du Midi, tome I. pl. 6. En tirant plus encore au nord-est, on reconno\u00eet les Jorasses que nous avons vues du haut du Tal\u00e9fre, \u00a7 637, elles paroissent d'ici, apr\u00e8s le Mont-Blanc et ses escaliers, les sommit\u00e9s les plus \u00e9lev\u00e9es de toute cette cha\u00eene, et elles semblent r\u00e9sulter de l'assemblage de plusieurs suites de feuillets pyramidaux convergents vers leur sommet. En g\u00e9n\u00e9ral toutes les cimes \u00e9lev\u00e9es que l'on peut distinguer dans cette chaine, depuis le Mont-Blanc jusqu'au col Ferret, sont soutenues par des augives compos\u00e9es d'une ou de plusieurs suites de feuillets pyramidaux appuy\u00e9s les uns contre les autres; les ext\u00e9rieures ont leurs bases dans le fond de la vall\u00e9e, et les int\u00e9rieures remontent par degr\u00e9s jusqu'au haut des cimes. Les deux escaliers du Mont-Blanc sont les seules sommit\u00e9s qui n'aient pas des augives de ce genre.\n\u00ab\u00a7 913. Je demande \u00e1 present quelle id\u00e9e on peut se faire de l'origine de ces feuillets plans et de toutes ces pyramides grandes et petites qui r\u00e9sultent de leur assemblage, si on ne les consid\u00e8re pas comme les restes ou les noyaux les plus durs des couches qui out r\u00e9sist\u00e9 aux ravages du temps, tandis que les parties interm\u00e9diaires, qui les lioient entr'elles, out \u00e9t\u00e9 d\u00e9truites par ces m\u00eames ravages.\n\u00abMais jusqu'\u00e0 quel point la crystallization a-t-elle contribu\u00e9 \u00e1 d\u00e9terminer ces formes pyramidales? doit-on consid\u00e9rer le Mont-Blanc ou telle autre de ces aiguilles, comme un \u00e9norme crystal? C'est une question de th\u00e9orie que j'examinerai ailleurs. Quant \u00e0 pr\u00e9sent je me contenterai de conclure, que la face m\u00e9ridionale de la cha\u00eene centrale des Alpes est, comme la face septentrionale de cette m\u00eame cha\u00eene, compos\u00e9e, pour la plus grande partie, de couches de granit \u00e0-peu-pr\u00e8s verticales, et dirig\u00e9es pour la plupart du nord-est au sud-ouest.\u00bb\nThis theoretical question of our author is so properly connected with the natural history which he has here given us, that it is not difficult to resolve it in the most satisfactory manner.\nHere is an enormous mass of granite, the origin of which we are not now inquiring after, but the causes of its present form. The internal part of this granite subsists in a state of the most perfect solidity; the external again is evidently in a decaying state. This is a fact which we learn from the nature of feldspar, of which granite is in part composed; this crystallised substance is every where decomposed, where long exposed to the atmosphere. But it is not this gradual decay of the mass of granite perishing equably from its external surface, and resolved into some of its component parts, that we are here to consider; it is only mentioned to show that the mass of granite is subject to decay, when exposed to the influence of the atmosphere, like every other compound mineral body, and to lose that perfect solidity which we find in the centre of the mass.\nWe find the granite masses not only subject to decay from the external surface, by the decomposition of the feltspar, or the dissolution of its constituent parts, but also liable to be separated into blocks of different degrees of regularity, commonly rectangular or approaching to the rhombic shape. This is the consequence, either of larger veins and fissures, filled with matter which is still more dissolvable than is the substance of the granite, or else by imperceptible crevices or cutters, into which the atmospheric influences gradually insinuate, and form at last a visible separation.\nIn examining the tops of granite mountains, or where this rock is exposed to the weather, we may perceive those two species of decay proceeding together. The external surface of the stone, where there is a sufficient mixture of feltspar, is separating into grains which form a species of sand, being nothing but the particles of granite separating by means of the decaying sparry part. But a similar progress may be observed, from the external surface penetrating in lines the mass of solid rock, and dividing that mass into the rectangular blocks into which those exposed places are gradually resolved.\nNow the tops of all those mountains are formed into an assemblage of pyramids, declining in height from the central pyramid; and all those pyramids are again in like manner subdivided into lesser pyramids. But the smallest of those pyramids are no other than the rectangular blocks into which those granite masses always separate by the influence of the atmosphere.\nIt will now be evident, that those mountains, thus resolving into separate blocks, must acquire this series of pyramidal constructions; for, in every particular mass of mountain, there must be a central part, from which the separated blocks cannot be removed, while those around, or towards the sides, are detached by the swelling water upon freezing, and separated from the more central masses which are thus the latest of being removed.\nIt is impossible to see this series of pyramidal relics, without at the same time perceiving that manner of formation, by the gradual resolution of the solid mass of granite, as it comes to be exposed in succession to the influences of the atmosphere, which M. de Saussure has termed les ravage du temps.\nBut if it be in this manner, that time wastes the solid masses of this globe; and if all the solid masses of the earth have acquired their solid state by the same means, i.e. by heat and fusion, as is maintained in the present theory, we should find similar pyramidal mountains formed of different materials. Now there can be nothing more different than masses of lime-stone and those of granite. But pyramidal mountains are equally formed of those two different materials. In plate V, under the letter B, may be seen the calcareous pyramids which are near the col de la Seigne, and which in plate VI. are represented under the letter G.\nHere is a view of the summit of the Alps, from whence we may be allowed to draw the most important conclusions in favour of our theory.\nThis summit is of solid granite, a mass in which there is no stratification, such as is to be perceived in all the other masses of those alpine regions. With regard again to the extent of this mass of granite, its basis is about two leagues in breadth, by at least thrice that space in length; and now we are to consider in what shape this mass of granite presents itself to our view.\nThe summit of Mont Blanc, which may be considered as in the centre of this mass, is a pyramid; and this great central pyramid is surrounded by a number of other great pyramids of the same kind. The points of those pyramids are extremely lofty; and, having sides often vastly steep, if not perpendicular, those colossal pyramids rise from the icy valleys in such a shape as has given occasion to their being named needles. Thus we find the whole space of this granite mass consisting of a mixture of icy valleys, and pyramidal rocks on which hardly any thing rests.\nNow, these lofty rocks or pointed mountains must have been either originally formed of that shape, or posteriorly hewn out by the hand of nature, gradually wasting mountains in the course of time, and operations of the surface. If it is by the first that we are to explain the present state of things, then observation is superfluous, and our reasoning is at an end; for, when even observation should not contradict the proposition, which it actually does, it would be useless, as it can afford no data from a former state, which is supposed to have been no other than it is at present; and reasoning cannot be admitted if we have no data. Therefore, if we are to reason upon the subject, we are obliged to admit, that nature must have hollowed out of the solid rock all those pyramidal mountains, and a system of inclined valleys carrying the ice from the summits.\nLet us now reason from our principles, in order to see how far the present appearances of things would naturally result from those wasting causes acting upon a mass of granite, of a given basis and of sufficient height, during a space of time which is unlimited.\nWe are to suppose our mass of granite without any structure except that of the veins and cutters, formed by the contraction of the solid mass in cooling. Now, those separations will naturally give direction to the operation of the wasting causes, whether we consider these as chymical or mechanical. Hollow tracts would thus be formed in the solid mass; in those hollow ways would flow the water, carrying the detached portions of the rock; and those hard materials, by their attrition upon the solid mass, would more and more increase the channels in which they move. Thus there would be early formed a system of valleys in this rock, and among those valleys a number of central points, or summits over which no running water would carry hard materials to operate upon the solid rock over which it flows.\nHere therefore, in the nature of things, is placed the rudiments of our needles, those colossal pyramids which acquire height gradually as the valleys widen, and whose apices may arrive at an angle of a certain degree of acuteness. But what a waste of rock to have formed all those needles which we find rising from the icy valleys round Mount Blanc!\nUpon the supposition that this had been the origin of those pyramidal mountains, it must be evident, that there is a ne plus ultra of acuteness to which the apex of a pyramid would in time arrive; and that then the decaying summit would tumble by the lump alternately, and regain the acuteness of its point. Now, if this be the case, although we cannot see the process, which is too slow for human observation, we should actually find them in all the stages of this progress. But this is precisely the state in which the summits of those mountains are to be found. M. de Saussure gives a view of one of those pyramids, which will serve to illustrate this subject in the most perfect manner. It is from the Montanvert that this object is to be perceived. (Voyages dans les Alpes, vol. 2.).\nThese high peaks of solid rock demonstrate the manner in which those enormous masses of mountains are degraded, and also the means which are employed by nature for that purpose; but this scene, however well represented, is too far removed, in its appearance, from the ordinary mountains of this earth, to satisfy the doubts of every reader or to generalise a principle which must be universal in the system of this earth. We therefore have occasion for a mean, by which the extreme of those alpine summits shall be generalised or connected with our low inclined plains; and, on this occasion, I will give M. de Saussure's most excellent description of the Breven. Nothing can better suit our present purpose than the subject of this natural history; and I am persuaded that most readers will be better informed by the description of this naturalist, than they would be by their own observation.\n\u00ab\u00a7. 639. J'ai d\u00e9j\u00e0 plusieurs fois nomm\u00e9 cette montagne, qui est situ\u00e9e imm\u00e9diatement au-dessus du Prieur\u00e9 de Chamouni, du c\u00f4t\u00e9 du nord-ouest: elle est li\u00e9e par sa base avec les Aiguilles-rouges, dont j'ai aussi parl\u00e9 dans le premier volume. Mais sa cime est nue, isol\u00e9e, arrondie sur les derri\u00e8res, et coup\u00e9e \u00e0 pic du c\u00f4t\u00e9 de Chamouni. C'est \u00e0 tous \u00e9gards une des montagnes les plus int\u00e9ressantes pour un naturaliste.\n\u00abJ'y montai pour la premiere fois en 1760, et je ne crois pas qu'aucun naturaliste l'e\u00fbt visit\u00e9e avant moi; j'y retournai l'ann\u00e9e suivante; j'y allai encore en 1767, et j'y montai enfin pour la derni\u00e8re fois en 1781, afin de v\u00e9rifier mes anciennes observations, et de me mettre en \u00e9tat d'en donner une description plus exacte.\n\u00ab\u00a7 640. On peut du Prieur\u00e9 monter au sommet du Br\u00e9ven et redescendre dans le m\u00eame jour, mais c'est une course p\u00e9nible, car il faut au moins cinq heures pour monter, et la pente est extr\u00eamement rapide. On peut cependant faire \u00e0 mulet le premier tiers de cette mont\u00e9e. Comme je voulus avoir le tems d'observer tout avec soin, j'y destinai deux jours, et j'allai coucher le premier jour dans un chalet, nomm\u00e9 Plianpra, qui, en partant du Prieur\u00e9, est aux deux tiers de la hauteur totale de la montagne.\n\u00abEn montant \u00e0 Plianpra, on fait pr\u00e8s des trois quarts du chemin sur des d\u00e9bris tomb\u00e9s et roul\u00e9s du haut de la t\u00eate du Br\u00e9ven. La colline m\u00eame sur laquelle est b\u00e2ti le village du Prieur\u00e9 n'est compos\u00e9e que des d\u00e9bris de cette montagne; ces d\u00e9bris ont d\u00e9bouch\u00e9 par une gorge que nous traversons en montant, et se versant ensuite \u00e0 droite et \u00e0 gauche, ils ont pris la forme d'un c\u00f4ne, dont le sommet est au milieu de cette gorge. Les collines de ce genre et de cette forme se rencontrent bien fr\u00e9quemment dans les vall\u00e9es bord\u00e9es par de hautes montagnes.\n\u00abCes d\u00e9bris, qui ne viennent pas seulement de la t\u00eate du Br\u00e9ven, mais de ses flancs et de sa base, sont des roches feuillet\u00e9es m\u00e9lang\u00e9es de quartz, de mica et de feldspath dans toutes les proportions imaginables. De ces diff\u00e9rentes proportions naissent diff\u00e9rens degr\u00e9s de duret\u00e9, depuis le granit feuillet\u00e9 le plus dur jusques \u00e0 la roche micac\u00e9e la plus tendre.\n\u00ab\u00a7 641. Les rochers au pied desquels on passe avant de gravir la mont\u00e9e rapide et herb\u00e9e qui aboutit \u00e0 Plianpra, sont compos\u00e9s d'une roche feuillet\u00e9e assez dure, dont les couches bien parall\u00e8les aux veines int\u00e9rieures de la pierre, suivent la direction de l'aiguille aimant\u00e9e et sont tr\u00e8s-inclin\u00e9es \u00e0 l'horison.\n\u00abLe chalet de Plianpra est situ\u00e9 au milieu d'une assez grande prairie en pente douce du c\u00f4t\u00e9 de la vall\u00e9e de Chamouni, et domin\u00e9e du c\u00f4t\u00e9 oppos\u00e9 par les rocs nus qui forment les sommit\u00e9s de la cha\u00eene du Br\u00e9ven. Du bord de cette prairie, on a une tr\u00e8s-belle vue du Mont-Blanc, de la vall\u00e9e de Chamouni et des glaciers qui y aboutissent. Ces m\u00eames objets se pr\u00e9sentent avec bien plus d'\u00e9clat de la cime du Br\u00e9ven; cependant la vue de Plianpra m\u00e9riteroit bien que ceux qui n'auroient pas la force ou le courage d'aller jusques \u00e0 la cime, montassent du moins jusque l\u00e0 pour s'en former une id\u00e9e.\n\u00abComme je ne voulois monter sur le Br\u00e9ven que lendemain, j'employai le reste de la journ\u00e9e \u00e0 observer les environs du chalet. J'examinai surtout avec soin des rochers situ\u00e9s \u00e0 une demi-lieue au nord au-dessus du chalet, qui de loin paroissent color\u00e9s en rouge, comme plusieurs sommit\u00e9s de cette cha\u00eene: c'est par cette raison qu'elle porte le nom d'Aiguilles-rouges.\n\u00ab\u00a7 642. Je trouvai que c'\u00e9toient encore des granits vein\u00e9s, m\u00e9lang\u00e9s de quartz, de feldspath, de mica et de fer qui colore la pierre en se d\u00e9composant au-dehors: cette teinte p\u00e9n\u00e8tre m\u00eame quelquefois assez avant dans l'int\u00e9rieur. Ces rochers sont divis\u00e9s par couches bien distinctes, \u00e0-peu-pr\u00e8s verticales, et dans la direction de l'aiguille aimant\u00e9e, comme celles que j'avois observ\u00e9es au-dessous du chalet. Ces couches sont coup\u00e9es par des fentes \u00e0-peu-pr\u00e8s perpendiculaires \u00e0 leurs plans, et qui sont pour la plupart parall\u00e8les \u00e0 l'horison, de maniere que ces rochers se trouvent ainsi divis\u00e9s en grandes pieces de forme \u00e0-peu-pr\u00e8s rhombo\u00efdale. Les veines m\u00eames int\u00e9rieures de la pierre sont aussi tr\u00e8s-bien prononc\u00e9es, et exactement parall\u00e8les \u00e0 ses couches; observation g\u00e9n\u00e9rale et de la plus grande importance, parce qu'elle prouve que ces couches sont bien de vraies couches, et non point des fissures produites fortuitement par la retraite ou par un affaissement in\u00e9gal des parties du rocher. Ces veines sont dessin\u00e9es sur le fond blanc de la pierre des feuillets minces de mica noir\u00e2tre; elles sont tant\u00f4t planes, tant\u00f4t ond\u00e9es, mais toujours r\u00e9guli\u00e8res et parall\u00e8les entr'elles, except\u00e9 l\u00e0 o\u00f9 il se rencontre des noeuds; encore reprennent-elles leur direction apr\u00e8s en avoir fait le tour. Comme le mica s'y trouve en petite quantit\u00e9, la pierre est dure, et ne se brise qu'\u00e0 grands coups de marteau. Lorsqu'on l'observe de pr\u00e8s dans sa cassure, on voit que les petites lames ou \u00e9cailles de mica sont constamment couch\u00e9es dans le sens des veines de la pierre. Ces m\u00eames \u00e9cailles n'ont presque aucune adh\u00e9rence entr'elles, en sorte que les feuillets dont la pierre est compos\u00e9e, n'adh\u00e8rent entr'eux que par les points o\u00f9 il ne se trouve point de mica.\n\u00ab\u00a7 643. Je me demandois \u00e0 moi-m\u00eame, en observant cette pierre, s'il \u00e9toit possible qu'elle e\u00fbt \u00e9t\u00e9 form\u00e9e dans cette situation verticale; si ces \u00e9cailles incoh\u00e9rentes auroient pu venir s'attacher \u00e0 ces murs verticaux, et si le mouvement des eaux, clairement indiqu\u00e9 par le tissu feuillet\u00e9 de la pierre, n'auroit pas d\u00fb les d\u00e9tacher et les faire tomber \u00e0 mesure qu'elles se formoient. Je me demandois encore, si les fentes qui coupent ces feuillets, perpendiculairement \u00e0 leurs plans, ne dateroient point d'un tems ou ces couches auroient \u00e9t\u00e9 horisontales, et n'auroient point \u00e9t\u00e9 produites alors par le poids et l'affaissement in\u00e9gal des parties de la pierre. Mais pour admettre cette supposition, il faudroit expliquer comment ces bancs, d'abord horisontaux, ont pu se redresser; pourquoi ce redressement a \u00e9t\u00e9 si fr\u00e9quent, si r\u00e9gulier, etc. etc. Je r\u00e9serve pour un autre tems la discussion de ces grandes questions; mais je ne crois pas inutile de faire apercevoir la liaison qu'ont avec la th\u00e9orie des observations si minutieuses en apparence.\n\u00abEn faisant ces r\u00e9flexions, je retournai au chalet de Plianpra o\u00f9 je passai la nuit sur de la paille que j'avois fait \u00e9tendre aupr\u00e8s du feu, parce que la soir\u00e9e \u00e9toit extr\u00eamement fra\u00eeche.\n\u00ab\u00a7 645 On commence \u00e0 monter par de jolis sentiers peu inclin\u00e9s, pratiqu\u00e9s le long d'un grand rocher semblable \u00e0 ceux que j'avois observ\u00e9s la veille. On a ensuite le choix de monter, ou par des pentes couvertes de rocailles un peu fatigantes, ou par des gazons extr\u00eamement rapides. Ceux-ci paroissent d'abord plus agr\u00e9ables et moins p\u00e9nibles; cependant ces gazons sont si serr\u00e9s et si glissans, qu'ils en deviennent dangereux, au moins pour ceux qui n'ont pas l'habitude des montagnes. Ces rocailles sont d\u00e9bris de roches feuillet\u00e9es, semblables \u00e0 celles que l'on rencontre en montant du Prieur\u00e9 \u00e0 Plianpra.\n\u00ab\u00a7 646. B. Au bout d'une heure de marche, on arrive au pied d'un rocher assez escarp\u00e9, qu'il faut escalader pour parvenir \u00e0 la cime de la montagne. C'est une roche micac\u00e9e, mais qui contient cependant assez de quartz pour avoir de la consistance. Elle se s\u00e9pare par feuillets si d\u00e9cid\u00e9s, que sans employer d'autre instrument que mes mains, j'en d\u00e9tachai une dalle, qui avoit sept pieds de hauteur sur quatre de largeur, et \u00e0 peine un pouce dans sa plus grande \u00e9paisseur.\n\u00abJ'avois quelque desir de descendre de-l\u00e0 au pied des grandes tables verticales qui composent la t\u00eate du Br\u00e9ven, pour les observer de pr\u00e8s et comparer ainsi leur base avec leur cime; mais de cet endroit la chose est impossible, la pente est d'une telle rapidit\u00e9 qu'une pierre m\u00e9diocrement grosse, que je mis en mouvement, roula avec beaucoup de vitesse, en entra\u00eena d'autres, celles-ci d'autres, et elles form\u00e8rent enfin un torrent de pierres qui se pr\u00e9cipita avec un fracas mille fois r\u00e9p\u00e9t\u00e9 par les grands rochers du Br\u00e9ven.\n\u00abComme donc je ne pouvois pas descendre, je montai par le passage ordinaire, qui est une esp\u00e8ce de couloir ou de chemin\u00e9e ouverte, adoss\u00e9e \u00e0 un rocher presqu'\u00e0 pic, de 40 ou 50 pieds de hauteur. Bien des curieux sont venus jusques au pied de ce passage sans oser le franchir; mais je vis en revenant qu'\u00e0 un demi-quart de lieue plus au nord, on trouve un autre passage extr\u00eamement commode, qui m\u00e8ne au m\u00eame but, et qu'il faut par cons\u00e9quent toujours pr\u00e9f\u00e9rer.\n\u00abCe rocher une fois escalad\u00e9, on monte par une pente douce, sans danger et sans fatigue, jusqu'au sommet du Br\u00e9ven.\n\u00ab\u00a7 646. C. En montant le long du bord, du c\u00f4t\u00e9 de Chamouni, j'eus un plaisir inexprimable \u00e0 contempler les magnifiques tables de granit dont est compos\u00e9e toute la t\u00eate de cette montagne. Car bien que les \u00e9cailles du mica noir\u00e2tre dont cette roche est m\u00e9lang\u00e9e, soient parall\u00e8les entr'elles et lui donnent ainsi quelque ressemblance avec une roche feuillet\u00e9e, cependant la quantit\u00e9 de quartz et de feldspath qui entrent dans sa composition, son extr\u00eame duret\u00e9, le peu de disposition qu'elle a \u00e0 se fondre dans le sens de ses feuillets, la placent, sinon pour le nomenclateur, du moins pour le naturaliste, dans la classe des vrais granits 18; et le parfait parall\u00e9lisme de ces feuillets avec les faces des grandes tables, ou des grandes divisions du rocher, d\u00e9montre que ces tables sont des couches, et non des parties s\u00e9par\u00e9es par des fissures accidentelles.\u00bb\n\u00abL'extr\u00eame r\u00e9gularit\u00e9 de ces tables ach\u00e8ve de d\u00e9montrer que ce sont de v\u00e9ritables couches. Leurs plans qui sont ici \u00e0 d\u00e9couvert dans une hauteur perpendiculaire de plus de 500 pieds, sont parfaitement suivis, comme taill\u00e9s au ciseau, dirig\u00e9s tous comme l'aiguille aimant\u00e9e, et verticaux, \u00e0 quelques degr\u00e9s pr\u00e8s dont ils s'appuyent contre le corps de la montagne. On s'assure en montant que cette structure est celle de la montagne enti\u00e8re; on voit les profils d'une infinit\u00e9 de ces couches, on passe sur les sommit\u00e9s de ces tranches verticales, et on les voit se prolonger dans cette m\u00eame direction tout au travers de la montagne. Or je demande si un naturaliste qui aura observ\u00e9 cet ensemble et ces d\u00e9tails pourra regarder cette montagne comme le produit du concours fortuit de grains de sable agglutin\u00e9s entr'eux.\n\u00abCes tables sont coup\u00e9es un peu obliquement \u00e0 leurs plans par des fentes dont la plupart sont \u00e0-peu-pr\u00e8s horizontales et d'autres tr\u00e9s-inclin\u00e9es \u00e0 l'horizon. La pierre se trouve ainsi tr\u00e8s-fr\u00e9quemment coup\u00e9e en parall\u00e9l\u00e9pip\u00e8des obliquangles. Ces m\u00eames fentes rendent raison, d'une observation que j'avois faite en 1776. En examinant avec une bonne lunette, depuis une fen\u00eatre du Prieur\u00e9, les faces verticales des couches de la sommit\u00e9 du Br\u00e9ven, j'avois remarqu\u00e9 un grand dieze bien nettement \u00e9crit sur la face de la montagne, je le vis de pr\u00e9s en 1781, et je reconnus qu'il \u00e9toit form\u00e9 par quatre de ces fentes qui se coupoient obliquement.\n\u00ab\u00a7 647. La cime de la montagne est une pointe mousse, coup\u00e9e \u00e0 pic du c\u00f4t\u00e9 de la vall\u00e9e de Chamouni et arrondie de tous les autres c\u00f4t\u00e9s. Cette t\u00eate est enti\u00e8rement couverte de d\u00e9bris et de blocs confus\u00e9ment entass\u00e9. On est \u00e9tonn\u00e9 de trouver l\u00e0 ces d\u00e9bris, car cette cime est absolument isol\u00e9e, et s\u00e9par\u00e9e par de larges et profondes vall\u00e9es des sommit\u00e9s qui la surpassent en hauteur: il semble que ces d\u00e9bris n'aient pu tomber que du ciel; mais quand on les examine avec soin, on voit qu'ils sont du m\u00eame genre de pierre que la montagne elle m\u00eame; et que tous leurs angles font vifs, leurs faces planes et leur forme souvent rhombo\u00efdale. On reconno\u00eet donc par l\u00e0 que les parties sup\u00e9rieures de la montagne, qui sont plus expos\u00e9es aux injures de l'air et qui ne sont pas assujetties par des masses situ\u00e9es au-dessus d'elles, se d\u00e9litent et se separent. Je trouvai cependant sur la cime une pierre d'une espece diff\u00e9rente; c'\u00e9toit une roche compos\u00e9e de schorl noir en aiguilles, de quartz et de grenats; sa forme \u00e9toit exactement rhombo\u00efdale. Mais ce genre de pierre se rencontre assez souvent en filons dans les roches feuillet\u00e9es et dans les granits vein\u00e9s; il est donc vraisemblable que le filon auquel ce fragment avoit appartenu s'est d\u00e9truit avec la partie sup\u00e9rieure du rocher, du moins n'en ai-je pu trouver aucun indice dans la partie solide de la montagne.\n\u00abL'admirable r\u00e9gularit\u00e9 des couches de cette cime \u00e9lev\u00e9e m\u00e9rite l'attention des amateurs de la g\u00e9ologie, et la vue qu'elle pr\u00e9sente d\u00e9dommageroit seule de la peine d'y monter.\n\u00ab\u00a7 648. Mon but principal dans la premiere course que je fis au Br\u00e9ven \u00e9toit de prendre de l\u00e0 une id\u00e9e juste des glaciers de la vall\u00e9e de Chamouni, de leur forme, de leur position, et de l'ensemble des montagnes sur lesquelles ils sont situ\u00e9s. Comme cette montagne est post\u00e9e \u00e0-peu-pr\u00e8s au milieu de la vall\u00e9e de Chamouni, en face du Mont-Blanc et vis-\u00e0-vis des principaux glaciers qui en descendent, c'\u00e9toit certainement un des meilleurs observatoires que l'on p\u00fbt choisir dans cette intention. J'y montai par le jour le plus beau et le plus clair; c'\u00e9toit mon premier voyage dans les hautes Alpes, je n'\u00e9tois point encore accoutum\u00e9 \u00e0 ces grands spectacles; en sorte que cette vue fit sur moi une impression qui ne s'effacera jamais de mon souvenir.\n\u00abOn d\u00e9couvre tout-\u00e0-la-fois et presque dans un seul tableau les six glaciers qui vont se verser dans la vall\u00e9e de Chamouni, les cimes inaccessibles entre lesquelles ils prennent leur naissance; le Mont-Blanc surtout, que l'on trouve d'autant plus grand, d'autant plus majestueux, qu'on l'observe d'un lieu plus \u00e9lev\u00e9. On voit ces \u00e9tendues immenses de neige et de glaces, dont, malgr\u00e9 leur distance, on a peine \u00e0 soutenir l'\u00e9clat, ces beaux glaciers qui s'en d\u00e9tachent comme autant de fleuves solides qui vont entre de grandes for\u00eats de sapins, descendre en replis tortueux, et se verser au fond de la vall\u00e9e de Chamouni; les yeux fatigu\u00e9s de l'\u00e9clat de ces neiges et de ces glaces se reposent d\u00e9licieusement ou sur ces for\u00eats, dont le verd fonc\u00e9 contraste avec la blancheur des glaces qui les traversent, ou dans la fertile et riante vall\u00e9e qu'arrosent les eaux qui d\u00e9coulent de ces glaciers.\u00bb\nOur object at present is not to see the degradation of that great mass of granite out of which have been hewn, by the hand of time and influences of the atmosphere, these lofty pyramids which surround Mont-Blanc; it is to see the degradation of that immense mass of vertical or highly inclined strata, out of which that great mass of granite rises; and it is to understand the conical and rounded forms which are to be perceived more or less in all the inferior mountains, where apparently the degradation has come to a stand, and where the surface is actually employed in vegetation, or in maintaining the system of living bodies in this world.\nHow high those vertical strata may have been erected, or how much may have been wasted of that mass in forming the mountains and their valleys, is a question which it is impossible to resolve: It is evident, however, that this quantity must have been very great. In the Mont-Rosa we find those strata at present in the horizontal situation, as high as the summits of those granite pyramids that overlook the mass of vertical strata which we are now considering; and, in those mountains of Rosa, the valleys are most profound. It is therefore most reasonable to suppose, that the mass out of which the Breven and all the other mountains had been formed, was once as high, at least, as the summit of Mont-Blanc. It is altogether inconceivable, that this mass of vertical and horizontal strata could have been formed, either originally, or by any mineral operation, into the present shape of things; therefore, we must look out for another cause.\nLet us now suppose them degraded by the hand of time, and all their moveable materials transported in the floods; In what state would they be left for our examination?\u2014Here is a question that must decide the theory of those mountains; for, if it is not possible to conceive the present appearances as arising from any other cause than this gradual degradation which we see operating at present, we must conclude that this is the system of nature established for the purpose of this world. But this is the very state in which they are found; every where the solid parts are going into decay, and furnishing those heaps of earth and stones that form the slopes by which we ascend from step to step. Wherever earth and stones may lie, there they are found to form a bank for vegetation; whenever these loose materials are carried away to a lower; station, the more solid parts above are still decaying in order to furnish more. There is not one step in all this progress, (of the summit of the solid mountain forming earth and stones, and travelling to the sea) that is not to be actually perceived, although it is only scientifically that man, who reasons in the present moment, may see the effect of time which has no end.\nThe summit of the granite pyramids of Mont-Blanc, the summit of the Breven, that of the Saleve 19, and of every little hillock upon the surface of the earth, attest this truth, that there is no other natural means by which this end may be attained. It is true, indeed, that geologists every where imagine to themselves great events, or powerful causes, by which these changes of the earth should be brought about in a short space of time; but they are under a double deception; first with regard to time which is limited, whereas they want to explain appearances by a cause acting in a limited time; secondly, with regard to operation, their supposition of a great debacle is altogether incompetent for the end required. How, for example, accumulate the debris of the Breven, as we have now seen, upon the summit of that mountain, by the force of running water? But this is only one of a thousand appearances that proves the operations of time, and refutes the hypothesis of violent causes.\nFrom the top of those decaying pyramids to the sea, we have a chain of facts which clearly demonstrate this proposition, That the materials of the wasted mountains have travelled through the rivers; for, in every step of this progress, we may see the effect, and thus acknowledge the proper cause. We may often even be witness to the action; but it is only a small part of the whole progress that we may thus perceive, nevertheless it is equally satisfactory as if we saw the whole; for, throughout the whole of this long course, we may see some part of the mountain moving some part of the way. What more can we require? Nothing but time. It is not any part of the process that will be disputed; but, after allowing all the parts, the whole will be denied; and, For what?\u2014only because we are not disposed to allow that quantity of time which the ablution of so much wasted mountain might require.\nv2:17 Voyage dans les Alpes, tom. 2.\nv2:18 \u00abLa d\u00e9nomination de granit vein\u00e9 que j'ai, \u00e0 ce que je crois, employ\u00e9e le premier, a paru tr\u00e8s-heureuse \u00e0 quelques naturalistes, et a, au contraire, souverainement d\u00e9plu \u00e0 quelques autres. Un de ces derniers pr\u00e9tend que ce que je nomme granit vein\u00e9 n'est qu'un amas de gravier graniteux, et par cons\u00e9quent une esp\u00e8ce de gr\u00e8s grossier. Mais je voudrois que ceux qui de bonne foi pourroient croire que j'aie commis une erreur aussi grossi\u00e8re et aussi fr\u00e9quemment r\u00e9p\u00e9t\u00e9e, observassent les granits du Br\u00e9ven; et j'en enverrais volontiers \u00e0 ceux d'entr'eux que le souhaiteroient. Lorsqu'ils verroient que les parties de quartz et de feldspath qui entrent dans leur composition, ont tous leurs angles vifs et tranchans, que ces parties sont intimement unies entre elles et emp\u00e2t\u00e9es les unes avec les autres, comme dans les granits en masse; que leur coh\u00e9rence est aussi grande que dans ces derniers granits, et que cette roche n'en diff\u00e8re absolument, comme je l'ai d\u00e9j\u00e0 dit, que par le parall\u00e9lisme qu'observent entr'elles les lames rares de mica dont elle est m\u00e9lang\u00e9e: je suis persuad\u00e9 qu'ils reconno\u00eetroient qu'elle a tous les caract\u00e8res essentiels du ranit, qu'elle doit avoir la m\u00eame origine, et qu'en un mot elle est au granit proprement dit, ce qu'une pierre calcaire feuillet\u00e9e est \u00e0 une pierre calcaire dans laquelle on ne distingue point de feuillets.\u00bb\nv2:19 See Part II. chap. 30.","title":"Theory of the Earth: Theory of the Earth [1795], Vol. II ...","type":"page"}