INTERIOR LAND CHANGES 



413 



Valley of the Adige. 



pressure of the accumulated waters. In that case, the lake will go on increasing, till, 

 rising to the level of some crevice, or of the summit of the mound, its waters are dis- 

 charged, and thus a beautiful expanse with a cascade is added to the scenery of the valley. 

 It generally happens, however, that such lakes are only temporary, owing to the looseness 

 of the rampart being unable to withstand the enormous and increasing pressure of the 

 arrested waters, or owing to its materials consisting of snow and ice, which are gradually 

 wasted. The consequence is, that the barrier is forced, and the valley below is subject to 

 the action of a mighty deluge, largely altering its features by its rapid and resistless rush, 

 destroying the dwellings of its inhabitants with the monuments of their industry, and 

 sometimes involving a fearful sacrifice of life, the flood at last subsiding into a peaceful 

 stream, but wending its way in a different channel to that pursued before the waters were 

 dammed up, a bed constructed by the powerful sweep of the newly emancipated torrent. 

 One of the most memorable instances of this kind occurred in the year 1818 in the Val 

 de Bagnes, one of the transverse branches of the great longitudinal valley of the Rhone, 

 above the lake of Geneva. The valley, or rocky glen, extends from thirty to forty miles, 

 and presents steep and rugged mountain walls, the summits ascending above the limit of 

 perpetual snow, and exhibiting glaciers on their slopes. At the top of the valley, the 

 river Dranse has its origin in the two glaciers of .Chermontane and Mont Durand, and 

 flows along its course to its termination at Martigny, where it joins the Rhone, of which 

 it is one of the chief affluents. Not far from the upper end of the Val de Bagnes, it is 

 formed into a narrow gorge by the approximating flanks of Mont Pleureur on one side, 

 and Mont Mauvoisin on the other, between which is the glacier of Getroz. From this 

 glacier large masses of ice are continually detached, which, falling into the ravine, tend 

 to fill up the contracted channel, and arrest the progress of the Dranse. For several 

 years previous to the time referred to, the river had been much obstructed by blocks of 

 ice and snow, which at length accumulated so as to resist the heats of summer, and 

 ultimately form a conical projection of the glacier itself completely across its bed to the 

 height of about a hundred feet. In the month of April 1818 the Dranse was dammed* up, 



