118 THE LAKE-BASINS OF IARCONN AUGHT. 



ing in different places along the excavation, the detritus 

 carried down is distributed more or less evenly on 

 each bank, forming piled-up, artificial-looking heaps. 

 Each stoppage also adds to the force of the torrent, 

 as the pent-up water, when a dam bursts, rushes down 

 with increased velocity. 



The work done by the same or a similarly circum- 

 stanced torrent when it reaches a flat would be differ- 

 ent, as there, instead of excavating a channel, it would 

 build up a bar extending out from the hill-side, and 

 in some cases even reaching across a valley, thereby 

 damming up the drainage, and forming a lake. In 

 many cases the streams, for reasons somewhat ana- 

 logous to those just mentioned when describing the 

 descent of a torrent down a hill-side, will keep on the 

 top of its bar, and thereby increase its length ; but not 

 always, as sometimes it will break over to one side or 

 another; after which, if it breaks over on the upper 

 side, it will begin to denude away the bar. Remark- 

 able examples of bars of this class occur at the, Lake 

 of Geneva, especially on the flanks of the great snow- 

 hills between Clarens and Yilleneuve, each bar or 

 mound having the torrent that formed it still flowing 

 along its summit. Lakes due to the formation of a 

 meteoric bar across a valley are usually shallow, both 

 on account of the form of the ground, and also because 

 the bars are more or less porous ; the sheet of water, 

 therefore, is seldom considerable, except during heavy 



