« AnteriorContinuar »
richest verdure, and studded with For some years back, however, the beautiful groups of houses and barns, glacier of Gétro has advanced so far shaded by lofty trees.
upon the ridge of the rocks which The southern chain of the valley, form the upper side of this extensive setting out from the separation of the channel, that enormous masses of ice Val de Bagne from the valley of Entre- are constantly falling into it from the mont, which leads to the Hospice of glacier above, and are swept over by the St Bernard, rises very soon to the ele- waters of the cascade with a tremenvation of perpetual snow, and forms dous crash. Part of them are caught the most northerly point of the icy upon the steep ledges of the rocks of peaks of Mount Combin. The northern the gorge; the remainder falls down chain does not rise so abruptly, and into the bottom of the valley, where only reaches the line of perpetual these fragments accumulate more or snow at Mount Pleureur, situated less, according to the quantity of ice six miles distant from the entrance which the glacier furnishes, and the of the valley. Thus far this chain season accelerates or retards the meltseparates the Val de Bagne from the ing of them. great valley of the Rhone ; but, at It is now five years since the accuthat point where it rises to the line of mulation of these blocks of ice, falling perpetual congelation, it takes a south- from the edge of the glacier of Gétro erly direction, and then separates the into the bed of the Dranse, began to Val de Bagne from the valley of form a new glacier in the shape of a Hyères, which, like the former, is half cone, whose summit is in the a lateral branch of the great valley ravine, about a hundred feet above the of the Rhone. Mount Pleureur de- bed of the river, and whose base so scends very rapidly into the valley of completely fills up this part (always a Bagne, and there forms with Mount narrow one) of the Val de Bagne, that Mauvoisin, which rises opposite to it, the side of this icy cone, inclined to a pretty long gorge, in which the about forty-five degrees, Jeans, to the Dranse is confined in a channel of extent of two hundred feet, against from twenty to forty feet in breadth, the almost perpendicular base of Mount and whose sides shoot up vertically to Mauvoisin, which is opposite to the the height of about a hundred feet, so glacier of Gétro, in the chain on your that the bridge of Mauvoisin, which right hand as you ascend the valley of connects the two sides of the valley, Bagne. rests upon perpendicular rocks eighty This new glacier, which thus absofeet above the bed of the river. lutely closes up the bottom of the
By the side of Mount Pleureur, valley, is certainly not exclusively towards the bottom of the yalley, rises composed of fragments of ice fallen Mount Gétro, whose steep sides, formed from the top of the glacier of Gétro: into steps by the strata of the rocks avalanches of snow seem to have had composing the mountain, and having a part in the formation of it; and but little inclination, are in some parts after this collection of ice and snow covered with pasturage, where there became once thick enough to resist are many chalets in very lofty situa- tlre transient heat of the preceding tions. A very narrow and pretty deep summer, it is clear that the snow of channel separates Mount Gétro from the following winter, added to the new Mount Pleureur. The glacier of Gétro avalanches of ice and snow collected is situated at the top of it, and forms in this fatal ravine, was more than the most advanced point, towards the sufficient to enlarge the new glacier, north, of that great uninterrupted range which, by means of rain water and of glaciers which, from the Great Št melted snow filtering into it and Bernard, as far as the Simplon, crown freezing anew, composed at last a hothe vast chain of the Alps which di- nogeneous mass of ice, of so enormous vides Switzerland from Piedmont. a bulk, that the period of its destruc
At all seasons, the water of the gla- tion cannot be calculated. cier of Gétro falls in cascades into the In the meanwhile, the waters of the ravine, which descends with a very Dranse, which are supplied by the rapid fall into the Dranse, at the upper glacier of Tzermotane and some others end of that gorge in the valley where at the head of the valley, and which the bridge of Nauvoisin is situated. already form a pretty large torrent, still
found an outlet under the glacier, the finished on the 13th of June. During base of which was doubtless thawed these thirty-four days the lake rose by the heat of the earth, and that of sixty-two feet; but during eight days, the water passing under it. Already, in the increase of its waters having, on the course of last year, the river had account of the falling of the temperabeen obstructed by the glacier for a ture of the atmosphere, only raised the considerable time; but it suddenly level four feet, the upper entrance of opened for itself a passage, which did the gallery was still many feet above considerable damage in the lower part the level of the lake ; and the intrepid of the valley, even as far as Martigny, Mr Venetz had thus time to sink the
It was in the month of April last, floor of that opening several feet, in however, that the waters of the Dranse order to accelerate the efflux of the were observed to be dammed up in lake, and thereby diminish the mass the bottom of the Valley of Bagne, of water which was indefinitely accuforming a lake of half a league in mulating. length. The danger of a sudden ef- During the dangerous working of flux of the lake, the surface of which this gallery, extending to 608 feet in was rising and extending every day, length, through the thickness of the was too imminent not to lead to the glacier, masses of ice, of many thouadoption of every possible means to sand cubic feet, were detached from prevent such a disaster. It was re- the base of the glacier on the side of solved to cut a subterraneous gallery the lake. The fragments, after fallthrough this enormous cone of ice, ing into it with a crash, ascended to sixty feet lower than the line of con- the surface, forming small floating ice tact of the new glacier with the islands. These accidents shewed the side of Mount Mauvoisin, a level at risk which the workmen in the galwhich the new lake, which was al- lery ran, at every instant, of being ways increasing, would necessarily crushed to pieces and buried under pour itself into the lower part of the the glacier. valley, if the opposing glacier could On the evening of the 13th of June, resist the enormous pressure of the at the moment when the water began mass of water accumulated above it. to issue from the gallery, now happily The point at which the draining gale finished without any serious accident, lay was carried through the glacier, the lake was from ten to twelve thouwas fixed at the elevation which the sand feet long; its medium breadth, lake was expected to reach at the pe- at the surface, might be seven hunriod of its completion. · It was ex- dred feet, and at the bottom one hunpeeted that, in consequence of this ar- dred feet. Thus its absolute metificial outlet, the water, in passing dium breadth was four hundred feet, through it, would gradually furrow and its absolute medium depth two the bottom, and, of course, lower it, hundred. The lake, therefore, conwhile the surface of the lake, by tained, at the period of its greatest that means, would subside in the same height, at least eight hundred millions proportion, thus daily diminishing the of cubic feet. risk of the rupture of the glacier, and From the evening of the 13th of the sudden efflux of the water which June, to the 14th at eleven o'clock in it retained. This operation, which was the forenoon, the lake still continued admirably calculated obviate the to rise a little, notwithstanding the impending danger, was executed un- outlet by the gallery. After this peder the direction of Mr Venetz, an riod the bottom of the gallery began engineer of the Valais, with unshaken to wear down, owing to the melting perseverance and courage, in spite of of the ice over which the water flowthe difficulties which every day pre- ed; and by five o'clock of the evening sented themselves, and the danger of of the same day the lake had descenda working in a place where blocks of ice ed a foot. On the 15th of June, at were constantly falling from the upper six o'clock in the morning, the floor glacier, and in a mass which was lia- of the gallery was so much lowered, ble at every instant to be undermined that the height of the lake was dimiby the lake, or rent in pieces and car- nished ten feet, and twenty-four hours ried off by the enormous pressure of after was less by thirty feet. On the the water. This perilous undertaking 16th of June, at six o'clock in the was begun on the 10th of May, and evening, being the moment at which Vol. IV.
the water opened a passage for itself was continually growing weaker, found by breaking the glacier, its level had itself at last sufficiently strong to sunk forty-five feet below the greatest push forward this soft soil from the height which it had ever reached. foot of Mount Mauvoisin, and to
This diminution of the lake having wear itself a passage between the glataken place at the top, that is, at the cier and the layers of the rocks which point where it had the greatest breadth, composed the mountain. Immediateit follows, estimating the breadth at ly the lake rushed out all at once ; only six hundred feet, that the gallery the ice, which still remained between had effected a diminution of the water the gallery and Mount Mauvoisin, of the lake of two hundred and seventy gave way with a horrible crash ; and millions of cubic feet at least : so the body of the water forced its way out that, at the moment of the breaking with such impetuosity, by the great up, it did not contain more than five opening which it had thus forced behundred and thirty millions of cubic tween the glacier and Mount Mauvoifeet of water, in place of the eight sin, that in half an hour the lake was hundred millions which it contained completely emptied, and the five hunthree days before.
dred and thirty millions of cubic feet of At the moment when the gallery water which it contained, thundering began to produce the desired effect, down into the valley with a rapidity the water which ran through it, rush- and violence of which no idea can be ed out of the outlet in a cascade, into formed, destroyed every thing in their the old bed of the Dranse, below the course. It is probable, that the rushglacier, quickly melted the ice; and ing out of the lake would have been eat away the floor of the gallery at its still more rapid, had it not been for mouth. The water which had insinuated the existence of a narrow gorge immeitself into the rents and crevices, which diately below the glacier, between penetrated the glacier in some places, Mount Pleuseur and an advanced point especially at the edges, caused enor- of Mount Mauvoisin. The water rushmous masses of ice to fall with a crashed into this gorge with such force, from the lower sides of it. By these that it swept away the bridge of Mauvarious united causes the gallery lost voisin, situated 90 feet above the level considerably in length; and the cas- of the Dranse, and rose many toises cade hollowing out a very deep fur- above the projecting mass of Mount row, the mass of the glacier, which at Mauvoisin. After leaving this narrow this point formed the retaining wall of channel, the enormous mass of water the lake, diminished so much in thick- spread itself over a broader part of the ness, that the floor of the gallery, Val de Bagne, which forms a pretty which at the outset was six hundred large bason, contracted at the botfeet in length, was reduced to eight tom by another gorge of the valley, feet at the moment the whole lake through which it again escaped with forced the passage.
such violence, that it carried off every It was not, however, the giving way thing which covered the rocks, even of this wall of ice, now become so detached some of these, and hurled slight, which was the immediate cause them into the abyss. A new bason in of the frightful deluge that was the valley then received this tremendcaused by another accident. After ous liquid mass, which swept on every the cascade had formed a channel side the foot of the mountains, carrysome hundred feet deep, in the lowering thence forests, detached rocks, mass of the glacier, and, after pene- houses, barns, cultivated land, and laytrating more and more, had at lasting waste even the base of those steep, fallen upon the base of Mount Mau- but more or less cultivated, sides of the voisin, which passed under the gla- two chains of mountains bounding this cier, and against which the latter unfortunate valley. Many contractions, rested—the base of the mountain not farther down the valley, raised the wabeing at that point composed of ter to a considerable height, and inrocks, but of a thick mass of debris creased the fury with which it inuncovered with vegetable mould; the dated the lower plains, where every cascade, I say, attacked this loose obstacle was overthrown and swept amass and carried it off by degrees; way. Enormous heaps of pebbles and and thus the water filtering into the rocks, which the floods had carried off earth, which it liquified, and which higher up, were deposited in the plains, which, but a moment before so beau- of the water of the lake, drawing with tiful and so populous, were now con- it all the debris, and forming a column verted in a moment into a dreary de- of more than 530 millions of cubic feet, sert. On reaching Chable, one of the passed every part of the valley. The principal villages of the valley, the food then furnished in every second water was confined between the piers 300,000 cubic feet of water. The of a strong bridge ; the body of Rhine, below Basle, where all its wathe flood, which appeared to contain ters, from the Tyrol to the Jura, are even more debris than water, rose united, gives, during the season when more than fifty feet above the ordi- its waters are highest, about 60,000 nary level of the Dranse, and be cubic feet of water per second. The gan to encroach on the inclined flood of the unfortunate, valley of plain, upon which the church and Bagne, then, must have contained five the greater part of the village are times more water than the Rhine bears built. A few feet more, and the when at its height. This comparison water would have reached the village may aid us to form some idea of the and destroyed it. At that important prodigious mass of water which promoment the bridge gave way, the duced such dreadful effects. houses at its two extremities were Agreeably to the information I colswept away; and the passage being lected, the flood took up thiry-five now clear, the frightful mass of water minutes in coming from the glacier to and rubbish spread itself over the wide Chable. The distance between these part of the valley, as far as St Bran- two points, following the bed of the chier ; every thing in its course was Dranse, is about 10,000 feet. The undermined, destroyed, and carried off water, then encumbered with all the Houses, highways, fields covered with rubbish, moved with the velocity of the finest crops, noble trees loaded thirty-three feet in a second. The with fruit, every thing was swallowed velocity of the most rapid rivers is from up and devoured. The moving chaos, six to ten feet per second; very few charged with all these spoils, now throws attain to the velocity of thirteen ; itself into the narrow valley of St Bran- thus, in the rectilineal and perfectly chier à Martigny, through which lies regular canal of Mollis, the Linth, afthe road of St Bernard; as yet nothing ter this canal is full, flows with a veresists the merciless torrent; all the locity of twelve feet per second. That parapets built along the edge of the of the torrent of the Val de Bagne, Dranse are precipitated into the flood, multiplied by the half solid mass which which, reaching Martigny, and es- was in motion, explains extremely caping from the narrow valley, dif- well the force with which forests, fuses itself over the plain, forming the houses, and rocks, have been swept off great valley of the Rhone; covers the and carried to a distance. fields and orchards; runs through the In passing from Chable to Martigtown of Martigny; carries off from ny, the flood must have occupied about thence houses and barns; covers the fifty-five minutes. The distance bewhole plain with thick mud; thou- tween those two places, following the sands of trees torn up by the roots; windings of the valley, may be about wrecks of houses and furniture ; dead 60,000 feet; the medium velocity of bodies of men and animals; and, branch- the current then, in this extent, was ing out, at last it precipitates itself in- about eighteen feet per second. The to the bed of the Rhone. That river inclination of that part of the valley being at the time little affected by the being less than the upper portion of water of the mountain snow, which it, and the water having lost a part had not yet begun to melt, received, of the impulse resulting from its fall without farther injury, all that remain- by the open gorge in the glacier, we ed moveable of that terrible flood, may suppose that the velocity of the which had just laid waste one of the current was considerably diminished finest vallies of the Alps, to the extent in this valley, which was lower and of of ten leagues in length.
a more uniform breadth; the time According to the unanimous testic which the food took up in passing mony of the inhabitants, the flood took through it, therefore, was in all proup half an hour in passing every point bability longer than that occupied in which it reached ; thus, in the short traversing the upper valley. space of thirty minutes, the whole mass From Martigny to St Maurice, the water of the flood, now contained in Mauvoisin, the cascade which would the bed of the Rhone, arrived in seven- have been thus formed, and which would ty minutes, the distance being about have tumbled at once upon the loose 50,000 feet; thus, the velocity of the earth which covered the rocky strata river was necessarily from eleven to of Mount Mauvoisin, would have imtwelve feet per second. The flood be- mediately decomposed and carried off ing much diffused and divided in the this loose mass of rubbish and vegetaplain of Martigny, the time occupied ble mould, and the lake would thus in crossing that district was of course have forced a passage equally abrupt longer than that occupied in its pas- with that which took place. But a sage through the higher vallies. threefold mass of water suddenly es
Finally, from St Maurice to the caping from this great reservoir, would Lake of Geneva, a distance approach- certainly not have left the vestige of a ing to 80,000 feet, the water and the habitation either in the valley of rubbish took up about 230 minutes, Bagne or St Branchier, and most prowhich gives a velocity of about six bably all Martigny would have been feet per second. This velocity was, utterly destroyed. There is still anno doubt, much greater immediately other circumstance to be considered, below St Maurice, and much less near in order completely to appreciate the the Lake of Geneva; but the velocity extent of the advantage which resultof six feet per second expresses the ed from that gallery which was so medium velocity of the whole of this cleverly executed. We have seen that passage.
the lake rose daily, during its execuWe should deceive ourselves, were tion, nearly two feet. After arriving we only to estimate the advantage at a height where its surface would which resulted from the formation have been increased in a greater proof the gallery through the new gla- portion, this rising would no doubt cier, by the mass which passed have diminished in spite of the exthrough it in the course of three traordinary melting of the snow and days; for not only did it draw off the ice, occasioned by the greatest from the lake the 370 millions of heat. But, granting that the lake cubic feet which issued by it, but it would have continued to rise at the prevented the elevation of the level of same rate, the moment of the breakthe water to the height of the point of ing up would have been delayed at contact of the glacier with Mount least a month, and would thus have Mauvoisin, a limit which, as we have happened at the time the waters of seen, was sixty feet higher than the the Rhone are highest. The 530 gallery ; the lake would therefore millions of cubic feet of water which have increased 15,000 feet in length, it furnished to the river, were run off and its breadth would have exceeded without causing damage on the 16th 1000 feet. Again, sixty feet 'of ad- June, a period when the water of the ditional surface height would have river was still pretty low. But if furnished a body of 900 millions of these 1730 millions of cubic feet had cubic feet of water; which, added to been thrown into the bed of the Rhone the 800 millions in the lake before the when full, assuredly the whole of the opening of thegallery, would have raised bottom of the broad valley of the the entire volume of water in the lake Rhone, from Martigny to the Lake to 1700 millions of cubic feet. Now, of Geneva, would have shared, more as the breaking up of the glacier only or less, the disastrous fate of the valgave 530 millions of cubic feet of ley of Bagne. water, its mass was reduced to less The new glacier of Mauvoisin, howthan a third of the water which ever, still exists in the channel of the would have been accumulated in the Dranse. The mass which has been carlake, but for the judicious steps tak- ried off by the effect of the gallery, and en by the government of the Valais, the bursting of the ice, forms but a by the advice and assistance of Mr very small portion of it; the channel Venetz,
by which the lake escaped is even shut There can be no doubt, that if these up by the blocks of ice which have 1700 millions of cubic feet of water fallen from the upper glacier, and by had accumulated in the lake, and had masses which are occasionally detachthe latter begun to exceed the limit of ed from the edges of the new one. contact between the glacier and Mount This accumulation of ice-blocks in the