THE WORK OF SNOW AND ICE. 



293 



Most of the debris gathered by ice is acquired at its bottom. While 

 such material is basal at the outset, some of it may find itself above the 

 bottom a little later. Thus when ice passes over a hill (Fig. 267) the 

 bottom of the ice rends debris from the top of the hill. When it descends 

 from one level to another there is a similar result (Fig. 268). To the 

 lee of the hill the ice from either side may close in under that which 



Fig. 266. — Alaskan fiords. The shaded areas represent land. (From charts of the 



C. & G. Surv.) 



came over the top, in which case the debris derived from the top of 

 the hill by the bottom of the overriding ice will be well up in the ice. 

 It has passed from an initial basal to a subsequent englacial position. 

 The change does not usually involve an actual rise of the material, 



