THE WORK OF SNOW AND ICE. 



291 



the debris is carried: (1) the basal or subglacial, (2) the englacial, and 

 (3) the superglacial. The material picked up or rubbed off from the 

 surface over which the ice moves is normally carried forward in the base 

 of the ice; while that which falls on the surface is usually carried in 

 the form of surface moraines. In the former position the drift is basal; 

 in the latter, superglacial. It is doubtful if much debris is moved along 

 beneath (that is, strictly below the bottom of) the ice, though the move- 

 ment of the latter would have a tendency to drag or urge along with it 



Fig. 263. — A hanging valley. 



The water falls (Bridal Veil) from a hanging valley, 

 (Wineman.) 



the loose material of its bed. If drift were carried forward in such 

 positions, it would be strictly suhglacial. 



The basal load of a glacier is constantly being mixed with new acces- 

 sions derived from ground over which the ice is passing, and this admix- 

 ture tells the story of the work done by the bottom of the ice. The 

 englacial and superglacial material, on the other hand, is normally 



