ON THE ACTION OF TORRENTS. 439 



Masses of ice having fallen towards the upper part of 

 this valley, and accumulated there, raised a dike suffi- 

 ciently compact and strong to block up the course of the 

 Dranse. The waters of this river, rapid and pent up in 

 certain parts of its course, as are all those of the high 

 Alps, accumulated above this barrier of ice, and formed 

 a lake which attained, at its maximum, 130 metres of 

 mean breadth, from 3000 to 4000 metres of length, and 

 36 of mean depth, and consequently a volume of water esti- 

 mated at about 29,000,000 cubic metres. Although, by 

 means of operations conducted with equal skill and cour- 

 age, about the third part of this volume was let off 

 without danger, the remaining part having suddenly 

 broken through the barrier of ice, was precipitated with 

 an almost unexampled impetuosity of 11 metres in the 

 second, into the Vallee de Bagne. In the first part of 

 its course, and in the space of half an hour which the 

 mass of water took in traversing a league, it carried 

 away trees, dwellings, enormous masses of debris, and 

 rocks already separated from their mass, as M. Es- 

 cher, expressly says ; it covered all the broad parts of 

 the valley with rubbish, pebbles and sand, and carried 

 the remainder of the substances which it had swept away, 

 as well to the extremity of the valley, towards Martigny, 

 as into the bed of the Rhone. The mass of water 

 took an hour and a half in rushing from the glacier to 

 Martigny. The same event took place from the same 

 cause, and with nearly similar results, in 1595. 



Torrents may therefore scoop out ravines in certain 

 formations, and produce effects which appear considera- 

 ble, because we judge of them by comparison with our 



