VIII RIVERS AND LAKES 315 



the sea, and 2000 feet deep, so that its 

 bottom is really below the sea level. The 

 Italian Lakes are even more remarkable. 

 The Lake of Como, 700 feet above the sea, 

 is 1929 feet deep. Lago Maggiore, 685 feet 

 above the sea, is no less than 2625 feet 

 deep. 



If the mind is at first staggered at the 

 magnitude of the scale, we must remember 

 that the ice which is supposed to have scooped 

 out the valley in which the Lake of Geneva 

 now reposes, was once at least 4000 feet 

 thick; while the moraines were also of 

 gigantic magnitude, that of Ivrea, for in- 

 stance, being no less than 1500 feet above 

 the river, and several miles long. 



Indeed it is obvious that a glacier many 

 hundred, or in some cases several thousand, 

 feet in thickness, must exercise great pressure 

 on the bed over which it travels. We see 

 this from the striae and grooves on the solid 

 rocks, and the fine mud which is carried down 

 by glacial streams. The deposit of glacial 

 rivers, the "loess" of the Ehine itself, is 

 mainly the result of this ice-waste, and that is 



