Abbildungen der Seite
PDF
EPUB

shepherds seek shelter from the snow-storm, * and seem not hurled by a natural catastrophe, but as if balanced in sport by giant hands. For how came they thus to light upon the steep, and there remain ? What force transported them, and when transported, thus lodged them high and dry 500 feet at least above the plain? We reply, a Glacier might do this. What other inanimate agent could do it, we know not.'(P. 51, 52.)

In examining the higher valley of the Sallenche, before this stream forms the cascade of the Pissevache, Professor Forbes found that the vertical precipices, which form the mural angle between that valley and the valley of the Rhone, are scored by horizontal grooves or flutings, which are clearly the result of superficial attrition.

• But what (asks our author) could have worn it in this position? Could a current of water 1500 feet deep have borne boulders on its surface, which should leave these plain horizontal markings? What could have been moved with a steady pressure as a carpenter presses his cornice plane on the wood, or as a potter moulds with a stick his clay, pressed laterally too with a perpendicular face of 1500 feet beneath? Nothing that I am acquainted with save a glacier, which at this day presses, and moulds, and scores the rocky flanks of its bed, extending to a depth often certainly of hundreds of feet beneath. A torrent, however impetuous—a river, however gigantic-a flood, however terrific, could never do this,'-(P. 53.)

As a record of travels and personal adventure, the main purpose of Professor Forbes's work was to describe that part of the Alpine chain, which was called by the ancients the • Pennine Alps.' It extends from the west side of Mont Blanc to Monte Rosa inclusive, and thus composes the most elevated land and the highest mountain groups in Europe. Distinguished by the number and extent of its glaciers, it was a field peculiarly suited for the principal object of Professor Forbes's researches ; while it has enabled him at the same time to carry his readers among scenes at once wild and picturesque; through frozen gorges as well as through romantic dells; across passes seldom trodden even by native feet, as well as along beaten tracks and patent highways, where nature had been often viewed but never studied,

* One of these afforded shelter to a monomaniac disappointed in love, whose sad story is known to many of the inhabitants of the valley, who recollect him. The block, which is figured in De Charpentier's work, is named, from the poor man who lived, I think, forty years under it, Pierre à Milan.'-P. 53, note.

and where rocks and stones bore testimony to great events, but which, like other witnesses to truth, had testified in vain.

We could have wished to retrace some of the instructive journeys to which we refer ; but our limits will permit us only to glean a few interesting occurrences and descriptions. On the margin of the Mer de Glace, and stretching along the face of the rocky chain which extends from the Aiguille de Dreux to the point called Les Echelets, are some fine grassy slopes, where it is the practice to graze cows during several weeks of summer. How such una wieldy animals can be conveyed to these pastures across passes in the glacier, which an unloaded man feels it difficult to accomplish, must appear surprising. Stray goats are often found bewildered among the crevasses, and bleating for help ; and our author mentions the case of a hotel-keeper and his companion, who, in transporting by means of ropes a mule across the Mer de Glace, were both pulled into a crevasse--they themselves escaping with difficulty, and abandoning the mule to its fate. The march of the cows, however, seems to be conducted with great skill.

• The most usual way of transporting the cows is by the glacier, at the foot of the Mauvais Pus, where, as I have already said, the ice is in the very act of tumbling headlong down. There, by the aid of hatchets and planks, a sort of small pathway is constructed the day before the ascent or descent of the cattle is to be performed, and then about thirty peasants assemble to pass as many cows, and, by the aid of ropes, succeed, usually without any loss, in compelling the poor animals to traverse the rude gangways which they have prepared.'=(P. 69.)

On the 16th February 1842, an American traveller had ventured without a guide to climb the granite peaks which rise almost vertically above the glacier of Irelaporte. These solitary precipices were but casually visited by the shepherd, and still more rarely by the chamois hunter; but our adventurous traveller had succeeded in mounting to a commanding eminence. His foot, however, slipped. He fell over the rock, and being caught in some bushes by his clothes, his fall was checked, and he found himself safely deposited on a narrow ledge of rocks,

in a perfectly hopeless prison,' from which there was no escape. Here he passed the whole night; but in the morning his cries were accidentally heard by some young men from Chamouni, who were at a great distance below on their way across the glacier. The two boldest had with difficulty climbed to a position above him, but were unable to give him help. Fortunately, however, Professor Forbes and his guide, Balmat, had gone to this remote spot, where he had one of his surveying stations,

*

*

*

and when the guide was seeking for water, he came within sight of the young men attempting to relieve the traveller.

· Balmat (says he) instantly joined them, and by great personal courage, as well as strength, succeeded in dragging the man up by the arm, from a spot whence a chamois could not have escaped alive. Balmat told me, that while he bore the entire weight of the man on the slippery ledge to which he himself clung, he felt his foot give way, and for a moment he thought himself lost. * I returned with Balmat to view the exact spot of the adventure, and a more dreadful prison it is impossible to conceive. It was a ledge about a foot broad in most places, and but a few feet long, with grass and juniper growing upon it. It thinned off upon the cliff entirely in one direction, and, on the other, terminated abruptly against a vertical portion of the solid rock, at least ten feet high, so that no man unassisted could have climbed it.

* The ledge was about twenty feet below the top of a smooth granitic precipice, to which a cat could not have clung; and below, the same polished surface went sheer down, without a break, for a depth of at least 200 feet, where it sinks under the glacier, where yawning crevasses would have received the mangled body, and would never have betrayed the traveller's fate.(P. 83, 84.)

In his journey from Chamouni to Val Pelline, Professor Fors bes visited the Val de Bagnes, a wild and lonely valley, and well known as the scene of three awful inundations, which destroyed life and property to an enormous extent. These inundations were occasioned by the fall of the Glacier 'of Getroż, which blocked up the river Drance, and formed a lake, which subsequently burst its icy barrier and desolated the plains below. The first of these inundations took place in 1545, when one hundred and forty persons perished in the flood. In 1595, the valley above the bridge of Mauvoisin was completely shut up by the descent of huge avalanches of ice. The dammed up waters rose to an enormous height, till, under the influence of the hot weather, the icy barrier gave way, on Sunday the 4th of June. The accumulated water rushed out with irresistible force, bearing along with them masses of rock of enormous size, tearing up every thing in their course, desolating the plains of Bagnes, St Branchier, and Bovernier, and destroying the whole town of Martigny. The wretched peasantry were reduced to abject poverty, and no fewer than from sixty to eighty perished in the torrent.

For some years previous to 1818, blocks of ice and avalanches of snow, from the Glacier of Getroz, began to obstruct the river Drance. When this accumulation had acquired sufficient size and solidity to resist the summer heats, it increased every winter, till it became a huge conical mass of homogeneous ice.

The apex of the cone lay in the ravine about 100 feet above the river, and descending with an inclination of 45°, it crossed the Drance, and its base rested upon the precipitous Aanks of Mount Mauvoisin, on the opposite side of the valley. The waters of the Drance, however, still found channels for themselves till the month of April, when these channels were closed, and a lake about half a league long quickly formed. The danger of an inundation was now apparent, and means were instantly taken to prevent it. M. Venetz, an able Engineer of the Valais, and the founder of the modern geological theory of glaciers,' suggested the idea of cutting a subterraneous gallery or tunnel, for the purpose of effecting a gradual discharge of the water. The lower end of the tunnel was to be fifty feet below the line of contact of the cone of ice with the flank of Mount Mauvoisin, while its upper end was fixed to be at the height to which the lake might be supposed to have risen when the tunnel was finished. By this contrivance it was expected that the water entering the tunnel would deepen it by degrees, and then permit the surface of the lake to descend gradually till it was nearly empty. This bold and dangerous experiment, during which the workmen ran the constant risk of being buried under the glacier, or crushed to pieces by the falling blocks of ice, was begun on the 10th of May, and completed on the 13th of June. During the thirty-four days which were required to finish this tunnel, which was sixty-eight feet long, the lake had risen sixtytwo feet; but from particular causes, the mouth of the tunnel was still many feet above the surface of the lake. M. Venetz, therefore, sunk the floor of the tunnel several feet at its mouth, and the water began to enter it on the 13th of June. At this time the lake was about 11,000 feet (more than two miles) long ;-its average breadth at the surface about 700 feet; and at the bottom 100 feet. Its absolute average breadth was therefore 400 feet, its average depth 200 feet, and its contents at least 800 millions of cubic feet.

The floor of the tunnel began to wear down on the 14th of June at eleven o'clock, and at five o'clock the lake had sunk one foot. At six A.M. of the 15th of June, the lake had sunk ten feet. In twenty-four hours more, it had sunk thirty-six feet; and twelve hours after that, the total descent of the lake was forty-five feet. Hence the whole had been reduced from 800 to 530 millions of cubic feet. At the outlet of the tunnel the ice was rapidly melted ; and enormous fragments, owing to the absorption of water, fell away from the lower sides of it, so as to diminish the body of the glacier which formed the retaining wall of the lake. Hence the tunnel was gradually reduced to a few feet in length. When the cascade had thus cut through the cone of VOL, LXXX, NO, CLXI,

I †

ice, it attacked the mound of debris at the base of Mount Mauvoisin, against which the cone rested ; and having carried it off by degrees, it pushed away the soft soil at the same place, and excavated a passage between the glacier and the rocky beds of which the mountain is composed.

The water now rushed out—the ice gave way with a tremendous crash, and the lake was discharged in half an hour. The rapidity and violence of the flood were indescribable. It was first stayed by a narrow gorge below the glacier; and when thus pent up, it carried away the bridge of Mauvoisin, ninety feet above the level of the Drance. After spreading itself over a wider part of the valley, it was again stemmed by another gorge; and thus, rushing from one basin to another, it acquired new force, and swept along with it forests, rocks, houses, barns, and cultivated lands. At the village of Le Chable, the flood, containing more debris than water, was pent up between the piers of a solid bridge, nearly fifty feet above the Drance; and began to attack the inclined plane of earth, on which stood the church and principal part of the village. An increased rise of a few feet would bave undermined them had not the bridge given way, carrying along with it the houses at both its extremities. The food now spread itself over the wide part of the valley between Le Chable and St Branchier, undermining and hurrying away the houses, the roads, the richest crops, and the finest trees, loaded with fruit. Thus armed with new powers of mischief, it entered the narrow valley below St Branchier, and, after ravaging Le Bourg and the village of Martigny, it fell with comparative tranquillity into the Rhone ; leaving the plains around covered with the wreck of houses and of furniture, with thousands of trees torn up by the root, and with the bodies of men and of animals which it had swept away.

M. Escher de la Linth has calculated that the velocity of the torrent from the Glacier to Le Chable was thirty-three feet per second, and that the efflux of water was five times greater than that of the Rhine below Basle.*

We must now take leave of this most interesting work; and we cannot do so more appropriately, than by extracting the following striking passage with which it closes.

• Poets and philosophers have delighted to compare the course of human life to that of a river ; perhaps a still apter simile may be found

* Professor Forbes bas given a very brief notice of this remarkable catastrophe. We have abridged the preceding account of it from a more detailed one, with plans and drawings, by the late Professor Pictet.See Edin. Phil. Jour. vol. i. p. 187.

« ZurückWeiter »