414 



PHYSICAL GEOGIIAPHY. 



and a lake began to form, which soon attained a considerable magnitude. It was 

 obviously in the highest degree probable that the icy barrier would not be able to hold 

 out long against the increasing pressure of the waters, and the sudden efflux of such a 

 mighty volume as was collected, would as certainly desolate the Val de Bagnes. To 

 avoid this calamity, which every day became more impending, an engineer started the 

 bold scheme of tunnelling the rampart of ice, and was employed by the government of 

 the canton for that purpose. This scheme, says the memoir of M. Escher upon it, " was 

 begun on the 10th of May, and finished on the 13th of June, under the direction of 

 M. Venetz. The gallery was sixty-eight feet long, and during its formation the workmen 

 were exposed to the constant risk of being crushed to pieces by the falling blocks of ice, 

 or buried under the glacier itself. " The lake at this time contained at least 800 millions 

 of cubic feet of water, which in three days was reduced to 530 millions, by the discharge 

 from the gallery. The sequel may best be related in the words of the memoir : 



" As soon as the water flowed from the lower end of the gallery the velocity of the 

 cascade melted the ice, and thus wore away the gallery at its mouth. The water which 

 had penetrated the crevices of the glacier caused enormous fragments of ice to fall from 

 the lower sides of it ; so that owing to these causes the body of the glacier, which formed 

 the retaining wall of the lake, was so much diminished in thickness that the floor of the 

 gallery was reduced from its original length of 600 to 8 feet. As soon as the cascade 

 had cut through the cone of ice, it attacked the debris of the base of Mauvoisin, upon 

 which the cone rested ; that is to say, the torrent undermined the glacier by washing away 

 the loose materials forming the bed of the stream, on which the mass of ice had been piled 

 up ; and having carried it off by degrees, it became able to push the soft soil from the 

 foot of Mont Mauvoisin, and excavate for itself a passage between the glacier and* the 

 rocky beds which compose the mountain. As soon as this happened, the water rushed 

 out, the ice gave way with a tremendous crash, the lake was emptied in half-an-hour, 

 and the sea of water which it contained precipitated itself into the valley, with a rapidity 

 and violence which it is impossible to describe. The fury of this raging flood was first 

 stayed by the narrow gorge below the glacier formed between Mont Pleureur and a 

 projecting breast of Mont Mauvoisin ; here it was engulfed with such force that it carried 

 away the bridge of Mauvoisin, ninety feet above the Dranse, and even rose several 

 fathoms above the advanced mass of the mountains. From this narrow gorge, the flood 

 spread itself over a wider part of the valley, which again contracted into another gorge ; 

 and in this way, passing from one basin to another, it acquired new violence, and carried 

 along with it forests, rocks, houses, barns, and cultivated land. When it reached Le Chable, 

 one of the principal villages of the valley, the flood, which seemed to contain more debris 

 than water, was pent up between the piers of a solid bridge, nearly fifty feet above the 

 Dranse, and began to attack the inclined plane upon which the church and the chief part 

 of* the village is built. An additional rise of a few feet would have instantly undermined 

 the village ; but at this critical moment the bridge gave way, and carried off with it the 

 houses at its two extremities. The flood now spread itself over the wide part of the 

 valley between Le Chable and St. Branchier, undermining, destroying, and hurrying 

 away the houses, the roads, the richest crops, and the finest trees, loaded with fruit. 

 Instead of being encumbered with these spoils, the moving chaos received from them new 

 force ; and when it entered the narrow valley extending from St. Branchier to Martigny, 

 it continued its work of destruction till its fury became weakened by expanding itself 

 over the great plain formed by the valley of the Rhone. After ravaging Le Burg and the 

 village of Martigny, it fell with comparative tranquillity into the Rhone, leaving behind it 

 the wreck of houses and of furniture, thousands of trees torn up by the roots, and the 

 bodies of men and of animals whom it had swept away." 



