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richest verdure, and studded with beautiful groups of houses and barns, shaded by lofty trees.

The southern chain of the valley, setting out from the separation of the Val de Bagne from the valley of Entremont, which leads to the Hospice of St Bernard, rises very soon to the elevation of perpetual snow, and forms the most northerly point of the icy peaks of Mount Combin. The northern chain does not rise so abruptly, and only reaches the line of perpetual snow at Mount Pleureur, situated six miles distant from the entrance of the valley. Thus far this chain separates the Val de Bagne from the great valley of the Rhone; but, at that point where it rises to the line of perpetual congelation, it takes a southerly direction, and then separates the Val de Bagne from the valley of Hyères, which, like the former, is a lateral branch of the great valley of the Rhone. Mount Pleureur descends very rapidly into the valley of Bagne, and there forms with Mount Mauvoisin, which rises opposite to it, a pretty long gorge, in which the Dranse is confined in a channel of from twenty to forty feet in breadth, and whose sides shoot up vertically to the height of about a hundred feet, so that the bridge of Mauvoisin, which connects the two sides of the valley, rests upon perpendicular rocks eighty feet above the bed of the river.

By the side of Mount Pleureur, towards the bottom of the yalley, rises Mount Gétro, whose steep sides, formed into steps by the strata of the rocks composing the mountain, and having but little inclination, are in some parts covered with pasturage, where there are many chalets in very lofty situations. A very narrow and pretty deep channel separates Mount Gétro from Mount Pleureur. The glacier of Gétro is situated at the top of it, and forms the most advanced point, towards the north, of that great uninterrupted range of glaciers which, from the Great St Bernard, as far as the Simplon, crown the vast chain of the Alps which divides Switzerland from Piedmont.

At all seasons, the water of the glacier of Gétro falls in cascades into the ravine, which descends with a very rapid fall into the Dranse, at the upper end of that gorge in the valley where the bridge of Mauvoisin is situated.

For some years back, however, the glacier of Gétro has advanced so far upon the ridge of the rocks which form the upper side of this extensive channel, that enormous masses of ice are constantly falling into it from the glacier above, and are swept over by the waters of the cascade with a tremen

dous crash. Part of them are caught upon the steep ledges of the rocks of the gorge; the remainder falls down into the bottom of the valley, where these fragments accumulate more or less, according to the quantity of ice which the glacier furnishes, and the season accelerates or retards the melting of them.

It is now five years since the accumulation of these blocks of ice, falling from the edge of the glacier of Gétro into the bed of the Dranse, began to form a new glacier in the shape of a half cone, whose summit is in the ravine, about a hundred feet above the bed of the river, and whose base so completely fills up this part (always a narrow one) of the Val de Bagne, that the side of this icy cone, inclined to about forty-five degrees, leans, to the extent of two hundred feet, against the almost perpendicular base of Mount Mauvoisin, which is opposite to the glacier of Gétro, in the chain on your right hand as you ascend the valley of Bagne.

This new glacier, which thus absolutely closes up the bottom of the valley, is certainly not exclusively composed of fragments of ice fallen from the top of the glacier of Gétro: avalanches of snow seem to have had a part in the formation of it; and after this collection of ice and snow became once thick enough to resist tlre transient heat of the preceding summer, it is clear that the snow of the following winter, added to the new avalanches of ice and snow collected in this fatal ravine, was more than sufficient to enlarge the new glacier, which, by means of rain water and melted snow filtering into it and freezing anew, composed at last a honogeneous mass of ice, of so enormous a bulk, that the period of its destruction cannot be calculated.

In the meanwhile, the waters of the Dranse, which are supplied by the glacier of Tzermotane and some others at the head of the valley, and which already form a pretty large torrent, still

found an outlet under the glacier, the base of which was doubtless thawed by the heat of the earth, and that of the water passing under it. Already, in the course of last year, the river had been obstructed by the glacier for a considerable time; but it suddenly opened for itself a passage, which did considerable damage in the lower part of the valley, even as far as Martigny. It was in the month of April last, however, that the waters of the Dranse were observed to be dammed up in the bottom of the Valley of Bagne, forming a lake of half a league in length. The danger of a sudden efflux of the lake, the surface of which was rising and extending every day, was too imminent not to lead to the adoption of every possible means to prevent such a disaster. It was resolved to cut a subterraneous gallery through this enormous cone of ice, sixty feet lower than the line of contact of the new glacier with the side of Mount Mauvoisin, a level at which the new lake, which was always increasing, would necessarily pour itself into the lower part of the valley, if the opposing glacier could resist the enormous pressure of the mass of water accumulated above it. The point at which the draining gallery was carried through the glacier, was fixed at the elevation which the lake was expected to reach at the period of its completion. It was expected that, in consequence of this artificial outlet, the water, in passing through it, would gradually furrow the bottom, and, of course, lower it, while the surface of the lake, by that means, would subside in the same proportion, thus daily diminishing the risk of the rupture of the glacier, and the sudden efflux of the water which it retained. This operation, which was admirably calculated to obviate the impending danger, was executed under the direction of Mr Venetz, an engineer of the Valais, with unshaken perseverance and courage, in spite of the difficulties which every day presented themselves, and the danger of working in a place where blocks of ice were constantly falling from the upper glacier, and in a mass which was liable at every instant to be undermined by the lake, or rent in pieces and carried off by the enormous pressure of the water. This perilous undertaking was begun on the 10th of May, and VOL. IV.

finished on the 13th of June. During these thirty-four days the lake rose sixty-two feet; but during eight days, the increase of its waters having, on account of the falling of the temperature of the atmosphere, only raised the level four feet, the upper entrance of the gallery was still many feet above the level of the lake; and the intrepid Mr Venetz had thus time to sink the floor of that opening several feet, in order to accelerate the efflux of the lake, and thereby diminish the mass of water which was indefinitely accumulating.

During the dangerous working of this gallery, extending to 608 feet in length, through the thickness of the glacier, masses of ice, of many thousand cubic feet, were detached from the base of the glacier on the side of the lake. The fragments, after falling into it with a crash, ascended to the surface, forming small floating ice islands. These accidents shewed the risk which the workmen in the gallery ran, at every instant, of being crushed to pieces and buried under the glacier.

On the evening of the 13th of June, at the moment when the water began to issue from the gallery, now happily finished without any serious accident, the lake was from ten to twelve thousand feet long; its medium breadth, at the surface, might be seven hundred feet, and at the bottom one hundred feet. Thus its absolute medium breadth was four hundred feet, and its absolute medium depth two hundred. The lake, therefore, contained, at the period of its greatest height, at least eight hundred millions of cubic feet.

From the evening of the 13th of June, to the 14th at eleven o'clock in the forenoon, the lake still continued to rise a little, notwithstanding the outlet by the gallery. After this period the bottom of the gallery began to wear down, owing to the melting of the ice over which the water flowed; and by five o'clock of the evening of the same day the lake had descended a foot. On the 15th of June, at six o'clock in the morning, the floor of the gallery was so much lowered, that the height of the lake was diminished ten feet, and twenty-four hours after was less by thirty feet. On the 16th of June, at six o'clock in the evening, being the moment at whic

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the water opened a passage for itself by breaking the glacier, its level had sunk forty-five feet below the greatest height which it had ever reached.

This diminution of the lake having taken place at the top, that is, at the point where it had the greatest breadth, it follows, estimating the breadth at only six hundred feet, that the gallery had effected a diminution of the water of the lake of two hundred and seventy millions of cubic feet at least: so that, at the moment of the breaking up, it did not contain more than five hundred and thirty millions of cubic feet of water, in place of the eight hundred millions which it contained three days before.

At the moment when the gallery began to produce the desired effect, the water which ran through it, rushed out of the outlet in a cascade, into the old bed of the Dranse, below the glacier, quickly melted the ice, and eat away the floor of the gallery at its mouth. The water which had insinuated itself into the rents and crevices, which penetrated the glacier in some places, especially at the edges, caused enormous masses of ice to fall with a crash from the lower sides of it. By these various united causes the gallery lost considerably in length; and the cascade hollowing out a very deep furrow, the mass of the glacier, which at this point formed the retaining wall of the lake, diminished so much in thickness, that the floor of the gallery, which at the outset was six hundred feet in length, was reduced to eight feet at the moment the whole lake forced the passage.

It was not, however, the giving way of this wall of ice, now become so slight, which was the immediate cause of the frightful deluge-that was caused by another accident. After the cascade had formed a channel some hundred feet deep, in the lower mass of the glacier, and, after penetrating more and more, had at last fallen upon the base of Mount Mauvoisin, which passed under the glacier, and against which the latter rested-the base of the mountain not being at that point composed of rocks, but of a thick mass of debris covered with vegetable mould; the cascade, I say, attacked this loose mass and carried it off by degrees; and thus the water filtering into the earth, which it liquified, and which

was continually growing weaker, found itself at last sufficiently strong to push forward this soft soil from the foot of Mount Mauvoisin, and to wear itself a passage between the glacier and the layers of the rocks which composed the mountain. Immediately the lake rushed out all at once; the ice, which still remained between the gallery and Mount Mauvoisin, gave way with a horrible crash; and the body of the water forced its way out with such impetuosity, by the great opening which it had thus forced between the glacier and Mount Mauvoisin, that in half an hour the lake was completely emptied, and the five hundred and thirty millions of cubic feet of water which it contained, thundering down into the valley with a rapidity and violence of which no idea can be formed, destroyed every thing in their course. It is probable, that the rushing out of the lake would have been still more rapid, had it not been for the existence of a narrow gorge immediately below the glacier, between Mount Pleuseur and an advanced point of Mount Mauvoisin. The water rushed into this gorge with such force, that it swept away the bridge of Mauvoisin, situated 90 feet above the level of the Dranse, and rose many toises above the projecting mass of Mount Mauvoisin. After leaving this narrow channel, the enormous mass of water spread itself over a broader part of the Val de Bagne, which forms a pretty large bason, contracted at the bottom by another gorge of the valley, through which it again escaped with such violence, that it carried off every thing which covered the rocks, even detached some of these, and hurled them into the abyss. A new bason in the valley then received this tremendous liquid mass, which swept on every side the foot of the mountains, carrying thence forests, detached rocks, houses, barns, cultivated land, and laying waste even the base of those steep, but more or less cultivated, sides of the two chains of mountains bounding this unfortunate valley. Many contractions, farther down the valley, raised the water to a considerable height, and increased the fury with which it inundated the lower plains, where every obstacle was overthrown and swept away. Enormous heaps of pebbles and rocks, which the floods had carried off higher up, were deposited in the plains,

which, but a moment before so beautiful and so populous, were now converted in a moment into a dreary desert. On reaching Chable, one of the principal villages of the valley, the water was confined between the piers of a strong bridge; the body of the flood, which appeared to contain even more debris than water, rose more than fifty feet above the ordinary level of the Dranse, and began to encroach on the inclined plain, upon which the church and the greater part of the village are built. A few feet more, and the water would have reached the village and destroyed it. At that important moment the bridge gave way, the houses at its two extremities were swept away; and the passage being now clear, the frightful mass of water and rubbish spread itself over the wide part of the valley, as far as St Branchier; every thing in its course was undermined, destroyed, and carried off. Houses, highways, fields covered with the finest crops, noble trees loaded with fruit, every thing was swallowed up and devoured. The moving chaos, charged with all these spoils, now throws itself into the narrow valley of St Branchier à Martigny, through which lies the road of St Bernard; as yet nothing resists the merciless torrent; all the parapets built along the edge of the Dranse are precipitated into the flood, which, reaching Martigny, and escaping from the narrow valley, diffuses itself over the plain, forming the great valley of the Rhone; covers the fields and orchards; runs through the town of Martigny; carries off from thence houses and barns; covers the whole plain with thick mud; thousands of trees torn up by the roots; wrecks of houses and furniture; dead bodies of men and animals; and, branching out, at last it precipitates itself into the bed of the Rhone. That river being at the time little affected by the water of the mountain snow, which had not yet begun to melt, received, without farther injury, all that remain ed moveable of that terrible flood, which had just laid waste one of the finest vallies of the Alps, to the extent of ten leagues in length.

According to the unanimous testimony of the inhabitants, the flood took up half an hour in passing every point which it reached; thus, in the short space of thirty minutes, the whole mass

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of the water of the lake, drawing with it all the debris, and forming a column of more than 530 millions of cubic feet, passed every part of the valley. The flood then furnished in every second 300,000 cubic feet of water. Rhine, below Basle, where all its waters, from the Tyrol to the Jura, are united, gives, during the season when its waters are highest, about 60,000 cubic feet of water per second. The flood of the unfortunate valley of Bagne, then, must have contained five times more water than the Rhine bears when at its height. This comparison may aid us to form some idea of the prodigious mass of water which produced such dreadful effects.

Agreeably to the information I collected, the flood took up thiry-five minutes in coming from the glacier to Chable. The distance between these two points, following the bed of the Dranse, is about 70,000 feet. The water, then encumbered with all the rubbish, moved with the velocity of thirty-three feet in a second. The velocity of the most rapid rivers is from six to ten feet per second; very few attain to the velocity of thirteen; thus, in the rectilineal and perfectly regular canal of Mollis, the Linth, after this canal is full, flows with a velocity of twelve feet per second. That of the torrent of the Val de Bagne, multiplied by the half solid mass which was in motion, explains extremely well the force with which forests, houses, and rocks, have been swept off and carried to a distance.

In passing from Chable to Martigny, the flood must have occupied about fifty-five minutes. The distance between those two places, following the windings of the valley, may be about 60,000 feet; the medium velocity of the current then, in this extent, was about eighteen feet per second. The inclination of that part of the valley being less than the upper portion of it, and the water having lost a part of the impulse resulting from its fall by the open gorge in the glacier, we may suppose that the velocity of the current was considerably diminished in this valley, which was lower and of a more uniform breadth; the time which the flood took up in passing through it, therefore, was in all probability longer than that occupied in traversing the upper valley.

From Martigny to St Maurice, the

water of the flood, now contained in the bed of the Rhone, arrived in seventy minutes, the distance being about 50,000 feet; thus, the velocity of the river was necessarily from eleven to twelve feet per second. The flood being much diffused and divided in the plain of Martigny, the time occupied in crossing that district was of course longer than that occupied in its passage through the higher vallies.

Finally, from St Maurice to the Lake of Geneva, a distance approach ing to 80,000 feet, the water and the rubbish took up about 230 minutes, which gives a velocity of about six feet per second. This velocity was, no doubt, much greater immediately below St Maurice, and much less near the Lake of Geneva; but the velocity of six feet per second expresses the medium velocity of the whole of this passage.

We should deceive ourselves, were we only to estimate the advantage which resulted from the formation of the gallery through the new glacier, by the mass which passed through it in the course of three days; for not only did it draw off from the lake the 370 millions of cubic feet which issued by it, but it prevented the elevation of the level of the water to the height of the point of contact of the glacier with Mount Mauvoisin, a limit which, as we have seen, was sixty feet higher than the gallery; the lake would therefore have increased 15,000 feet in length, and its breadth would have exceeded 1000 feet. Again, sixty feet of additional surface height would have furnished a body of 900 millions of cubic feet of water; which, added to the 800 millions in the lake before the opening of the gallery, would have raised the entire volume of water in the lake to 1700 millions of cubic feet. Now, as the breaking up of the glacier only gave 530 millions of cubic feet of water, its mass was reduced to less than a third of the water which would have been accumulated in the lake, but for the judicious steps taken by the government of the Valais, by the advice and assistance of Mr Venetz,

There can be no doubt, that if these 1700 millions of cubic feet of water had accumulated in the lake, and had the latter begun to exceed the limit of contact between the glacier and Mount

Mauvoisin, the cascade which would have been thus formed, and which would have tumbled at once upon the loose earth which covered the rocky strata of Mount Mauvoisin, would have immediately decomposed and carried off this loose mass of rubbish and vegetable mould, and the lake would thus have forced a passage equally abrupt with that which took place. But a threefold mass of water suddenly escaping from this great reservoir, would certainly not have left the vestige of a habitation either in the valley of Bagne or St Branchier, and most probably all Martigny would have been utterly destroyed. There is still another circumstance to be considered, in order completely to appreciate the extent of the advantage which resulted from that gallery which was so cleverly executed. We have seen that the lake rose daily, during its execution, nearly two feet. After arriving at a height where its surface would have been increased in a greater proportion, this rising would no doubt have diminished in spite of the extraordinary melting of the snow and the ice, occasioned by the greatest heat. But, granting that the lake would have continued to rise at the same rate, the moment of the breaking up would have been delayed at least a month, and would thus have happened at the time the waters of the Rhone are highest. The 530 millions of cubic feet of water which it furnished to the river, were run off without causing damage on the 16th June, a period when the water of the river was still pretty low. But if these 1730 millions of cubic feet had been thrown into the bed of the Rhone when full, assuredly the whole of the bottom of the broad valley of the Rhone, from Martigny to the Lake of Geneva, would have shared, more or less, the disastrous fate of the valley of Bagne.

The new glacier of Mauvoisin, however, still exists in the channel of the Dranse. The mass which has been carried off by the effect of the gallery, and the bursting of the ice, forms but a very small portion of it; the channel by which the lake escaped is even shut up by the blocks of ice which have fallen from the upper glacier, and by masses which are occasionally detached from the edges of the new one. This accumulation of ice-blocks in the

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