in breadth. A rivulet meanders amongst them, and loses BOOK itself in a gulf. The verdant foliage of trees and shrubs is XVIII. mingled with the grey masses of the rocks. This labyrinth is evidently the remains of a mountain, the less solid parts of which have crumbled down, and been carried off by currents of water. The famous stones of Carnac, which the vulgar regard as a Druidical temple, appears to us only a labyrinth of Aderbach in miniature. Other countries present similar pictures: such as Stonehenge in England, Griffenstein in Saxony, the rocks of Svit-Feene in China, and several assemblages of enormous stones in the Cordilleras of Peru. The primitive nations chose such places, stamped with the impress of divine power, to solemnize the rites which they dedicated to beings of a superior nature. effects of The slow, but continual and combined action of all the Combined causes which we have specified, is followed by the most as these tonishing catastrophes. The remains of the mountains called Diableret, in Switzerland, present, it is said, a very picturesque scene; portions of wood and pasturage, which have escaped the common disaster, rocks, shivered, dismantled, cleft from top to bottom, and seeming to announce new desolations,―torrents, which are forced to scoop out for themselves a new bed, wear away the trunks of birch trees and firs, half buried in their waves. Such are the varied adorn this theatre of devastation. groupes which It was, according to the History of the Academy of Sciences, in the month of June 1714, but, according to M. Bourrit, and other Swiss writers, the 23d September 1718, that the summits of the Diablerets suddenly fell, and covered the extent of a square league with their fragments, which often form a bed of stones 30 yards and more in thickness. Although several hundred cottages were buried in the ruins, fortunately only 18 persons perished. Cows, goats, and sheep, were the principal victims. The dust which was raised by the fall of the mountain occasioned for some moments a darkness like that of night, although the causes. BOOK XVIII. The sliding event took place at three o'clock in the afternoon, and in fine weather.* We have a more satisfactory account of the falling down of a mountain, which took place in 1751, near Sallenche, in Savoy. The naturalist Donati thus describes this event: A great part of the mountain, situated below that which fell down, was composed of earth and stone, not arranged in strata or beds, but confusedly heaped up. The rolling down of these stones, in former times, had left by degrees the principal rock of the greater mountain without support. This mass was composed of five horizontal and distinct strata, the two first were of a slaty and brittle kind, the two following presented to view a shelly marble, cleft transversely in its beds. In the fifth, the slate reappeared, but its lamina were in a vertical position, and entirely disunited, The waters of three lakes, formed in this last stratum, continually penetrated through the chinks of the mountain. The abundant snow of the year 1751 augmented the force of these waters, and determined the fall of 648 millions of cubic feet of rocks, bulk enough to have formed a great mountain. The fall of this mountain was accompanied by a quantity of dust uncommonly subtile, and which was taken for smoke, because it supported itself in the air for several days. A report was spread that a new volcano had broken out in the midst of the Alps, where the ravages of subterraneous fires had never been known. But Donati, having been sent to the spot, soon dissipated these groundless fears.† There is also another kind of catastrophe, which is not of rocks. less extraordinary in its causes, than destructive in its effects-it happens when one bed of earth or rock slides over another bed without breaking, or separating into pieces. Some years ago, the commencement of an event of this kind was observed at Solutré, near Macon. After some great rains, the strata of earth which lay upon the moun *Bourrit, Description des Alpes Pennines, &c. Ebel, Itinéraire, ii. 26. tain of Solutré, slid along over couches of calcareous stones, BOOK which constitute the body of the mountain. They had al- XVIII. ready advanced several hundred yards, and the village was about to be buried in ruins, when the rain ceased, and this moving mass of earth was arrested in its progress.* A still more astonishing fact of this kind is related: a part of the mountain Goima, in the Venetian State, detached itself during the night, and glided along, with several houses, which were carried into the neighbouring valley; in the morning the inhabitants, who had felt nothing, were extremely astonished, when they awoke, to see themselves at the bottom of a valley, and for a long time imagined that a supernatural power had transported them through the air into some distant climate, until, upon examining the environs, they perceived the traces of the revolution which had so wonderfully spared them. Various disasters are often connected together: inundations originate from the fall of masses of earth, and occasion such falls in their turn. In 1772, the mountain of Piz, in the marche of Treviso, Effects of in the State of Venice, was cleft in two; a part was overfalling down. turned, and covered three villages, together with their inhabitants. A rivulet, stopped by the rubbish, in three months formed a lake. The remaining part of the mountain precipitated itself on that side, the lake overflowed its banks, and many people perished. Several villages were also buried under the waters.† This brief sketch is sufficient to show the difference that exists between a subsiding or falling down, and a shaking of the earth, or earthquake, catastrophes too often confounded by the ancients, and even now by the vulgar. The effects are often the same, but the mode of action and the causes are different. There are fallings down without volcanic shocks, but these shocks often occasion them. The only point of necessary coincidence is, that great rains, * Delamétherie, Théorie de la Terre, vol. v. sect. 1420. down. BOOK which succeed great droughts, equally bring on displaceXVIII. ments and earthquakes. They occasion earthquakes, by evolving in the bosom of the earth elastic and inflammable gases; and they occasion the fall of large masses by cracking, softening, and detaching the different strata of the mountains. The ancients imagined that they could prevent earthquakes, by digging in the towns and surrounding country, ditches and deep wells, to give vent to the subterraneous vapours. It is more certain that men may, with a little care, avoid the destructive effects of fallings down. Whether it At first, in choosing the site of a town, or of a village, we be possible to prevent ought to level the neighbouring heights, and examine the or foresee nature of the rocks, whether they are solid and durable, or fallings the contrary; it is then, generally speaking, easy to place the buildings beyond the reach of such accidents. A Greek naturalist foretold to the Spartans the fall of a projecting part of Mount Taygetus, which soon after overwhelmed in ruins a considerable portion of the city of Lacedemon. Canals and drains, to carry off from the mountains their superabundant waters; reservoirs, where these waters may be collected for distribution over the country, to irrigate the fields and to drive machinery; dikes, walls, and perhaps deep ditches, to stop and weaken the shocks of avalanches; these are the barriers which human industry can oppose to such alarming and disastrous occurrences, one of the most salutary effects of which is to awaken our dormant powers, and to heighten our courage, by giving scope for its exercise. Effects of running water. In tracing out terrestrial hydrography, we have already noticed the very considerable force of running water; and the precipitation of parts of mountains, which we have just been describing, serves to exemplify some of its effects. Its action is still more general; the wandering torrents which roll down rocks, and root up forests, the deep stream which gradually undermines the mountains at whose base it flows, the vast and powerful river which shifts at pleasure the place of its bed, and sometimes creates, by the matter it deposits, a Delta of Egypt, and sometimes, by swallowing up extensive districts, forms new lakes, as, for example, the BOOK Lake Biesboch in Holland; these are the powers which, set in motion by the hand of nature herself, in whose operations ages are accounted as moments, have been able to produce a very great proportion of the changes which the secondary and ternary soils have undergone. tions in We shall now produce some examples of very singular Excavachanges, arising solely from the action of running water. rocks, by Upon Mount Limur, in Norway, we see two roads worn in water. a rock of marble, the one above the other. The marble itself which separates them, and which is only three inches thick, allows you to perceive, through its clefts, a river flowing in the lower road. It appears that the waters of a lake, situate some hundred feet higher, have by degrees hollowed out for themselves these two openings through the rock. It was thus, that the river Gaulen, in the same country, lost itself in 1344, and re-appeared some years afterwards with extreme violence, driving before it the ruins of the subterraneous prison into which it had descended.* Mount Jura, and in general all calcareous mountains, present facts of the same kind. The lake of Joux, and that of Grand-Vaux, and many others, have worn in the rock the funnels through which their waters flow. Sometimes, when the sides of the passage which the waters had made for themselves, become in part worn away and excavated, the roof falls down; it then forms an outlet, cut perpendicularly, through which the waters escape, as near Orgelet, upon the road of Saint Claude; or the mouth of the valley, blocked up by the rubbish, forces the waters to give birth to a lake, such as that of Sillan, near Nantua.‡ Another singular phenomenon occurs in the funnels with Funnels. no outlet, called in Sweden Giants' Cauldrons. These are circular excavations, sometimes of a spiral form, having their sides very smooth, situate for the most part on the Pontoppidan, Natural History of Norway. + Bertrand, Nouv. Principes de Géologie, p. 175. |