282 



GEOLOGY 



in the hard bottom over which it flows. It would seem that 

 competency on the part of a viscous body to do this peculiar cla-s 

 of work so distinctive of glaciers, should be demonstrated before 

 the viscous theory of glacial movement is accepted as even a good 

 working hypothesis. In contrast with viscous movement, it is 

 conceived that a glacier is thrust forward rigidly by internal elonga- 



Fig. 238. Shearing plane in glacier well denned; a Spitzbergen glacier. 



(Hamberg.) 



tion, and that it is sheared forcibly over its sides and bottoms , 

 leaving its distinctive marks upon them. 



Auxiliary Elements 



Shearing. In the lower part of a glacier, where the thrusts are 

 greatest, normally, where the granules are fewest and their inter- 

 locking most intimate, shearing takes place within the ice. This 

 is illustrated by Figs. 238 and 239. The shearing results in the 

 foliation of the ice, and in the dragging of debris along the planes of 

 shear. Thus the ice becomes loaded in a special englacial. or l>a><>- 

 englacial fashion, as previously mentioned and illustrated. 



