VIII RIVERS AND LAKES 815 
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 striz 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 Rhine itself, is 
mainly the result of this ice-waste, and that is 
