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Sierra Club Bulletin. 



interglacial epochs and during postglacial time. It is 

 true that we cannot measure the nonglacial work, which 

 consisted of a general reduction of surface without nota- 

 ble change of form; but whatever the amount, we may- 

 assume that it would have been the same on both slopes 

 of the same ridge, had there been no glaciers. The visible 

 ice-made hollows therefore represent the local excess of 

 glacial over nonglacial degradation. 



