120 



PHYSIOGRAPHY 



grades of coarseness, from the finest earth up to huge masses many 

 feet in diameter (Figs. 125 and 126). 



Fig. 125. Bowlders on the terminal moraine of the Okanagan glacier, Wash. 



Fig. 126. A large bowlder in northwestern Illinois. 



How debris is carried. The larger part of the material carried 

 by a glacier is carried in its lower part; but some is carried in the 

 ice above its bottom, and some on the surface. 



The material in the base of the ice is readily understood from 

 the way in which it is gathered. The material above the bottom 

 reaches its position in various ways. Some of it falls down from the 

 top through crevasses, but more of it is worn from hills over which 

 the ice has passed, as illustrated by Fig. 127. Under some circum- 

 stances, too, ice moves up from the bottom of the glacier (Fig. 2, 

 PL XXXIV, p. 113), and carries debris with it. 



The material on the surface of a glacier, like that in the ice, 

 reaches its position in more ways than one. Where the slopes above 



