THE ARAPAHOE GLACIER 



849 



Where the ice is snow-covered and on the smaller segments 

 which do not take on the nature of perfect glacier ice, there 

 often results from the surface drainage a peculiar hummocky 

 surface. The process by which these hummocks or knobs come 

 into existence is somewhat indirect. The water draining from a 

 very steep surface of uncompacted nev6, produces at first a 





Fig. 8. — Lake within the present terminal moraine. The prominent lines in the 

 ice at the left are shearing planes. 



system of small parallel channels, which may be a yard or two 

 apart. The water in these channels percolates to some extent, 

 and in freezing produces under the channel a rib which is harder 

 and more ice-like than the snow between channels. Differential 

 melting next leaves what was once a channel exposed as a ridge. 

 This ridge has at no time an even crest, and soon comes to 

 appear as a line of small icy hummocks regularly spaced at 

 intervals of a few feet. The isolated patches of neve attending 

 the Arapahoe glacier, which are just too small to take on com- 



