366 Glaciers. 



rubbish that the glacier deposits at its lower ends, in 

 some cases almost as fast as it is formed, perhaps, I might 

 rather say, as slowly as it is formed, because day after 

 day we may see scarcely any difference in the details of 

 certain moraines, though, when being worked upon by 

 water, all stones of moderate size that have been shed 

 from the ice are in the long run apt to be carried 

 down the valley by the ever-changing streams that flow 

 from the ends of glaciers along the length of many 

 terminal moraines. In some cases, however, it happens 

 that, from various circumstances, both terminal and 

 lateral moraines have been so well preserved from 

 destruction, that they form long enduring features in 

 the scenery. 



Something remains to be said about moraine-stones 

 before I describe the glacial phenomena of our own 

 island. When an immense weight of glacier ice, in 

 some cases hundreds, or in Arctic and Antarctic regions 

 even two or three thousand feet in thickness, passes 

 over solid rocks, by the pressure of the moving mass, 

 the rocks in the valley over which it slides become 

 smooth and polished not flatly, but in flowing lines, 

 presenting a largely mammillated surface. Further- 

 more, the stones of the surface-moraines frequently fall 

 into fractures called crevasses, and the small debris 

 and finely powdered rocks that more or less cover 

 the glacier are borne into these crevasses by the water 

 that flows upon the surface, and much of this matter 

 finds its way to the bottom of the ice, fig. 78. The 

 bottom of a glacier, therefore, is not simple bare ice, 

 but between the ice and the rock over which it flows 

 there are blocks of stone imprisoned, and fine silicious 

 and often felspathic debris (chiefly worn from the floor 

 itself), which may be likened to emery powder. The 



