GLACIER EROSION 



III 



and the former presence of them in regions whence they have 

 long vanished. The erosive capabilities of moving ice have been 

 and still are the subject of dispute, but much remains that can- 



FlG. 38. — Rock polished by glacial ice, near Englevvood, N.J. 



Salisbury.) 



(Photograph by 



not be questioned. Thick glaciers, moving with comparative 

 rapidity down the steeper slopes, will sweep away the soil and 

 other loose materials which cover the ground. The surface is 



RlG. 39. — Scored and smoothed limestone from Montreal, Canada. 



