368 



GROUND-ICE AND GLACIERS. 



[Ch. XVI. 



feet high. The frozen mass augmenting from year to year 

 would add indefinitely to the altitude of alpine summits, 

 were it not relieved by its descent through the larger and 



deeper valleys to regions far below the general snow-line. 



To these it slowly finds its way in the form of rivers of ice 

 called glaciers, the consolidation of which is produced by 

 pressure, and by the congelation of water infiltered into the 

 porous mass, which is always undergoing partial liquefaction 



Eig. 22. 



WVMPER 



Glacier with medial and lateral moraines and with terminal cave. 



■ 



on its surface. In a day of hot sunshine, or mild rain, in- 

 numerable rills of Dure and SDarkline water run in icy chan- 



glaciers, which in the nig 



lit 



nels along the surface of the 

 shrink, and come to nothing. They are often precipitated 

 in bold cascades into deep fissures in the ice, and contribute 

 together with springs to form torrents, which flow in tunnels 



at the bottom of the glaciers for many 



d at 



length issue 



at their extremities, from beneath beautiful 





