390 ON THE NATURE AND ORIGIN OF 



pouring into the crevasses, but as this process is beyond the 

 reach of observation, it can only be considered as a theory 

 wdth the probabilities in its favor. 



Formution of Eskers. — When in the latest stage of ice 

 melting, local glaciers took the place of the continental ice 

 sheet, those ice sheets on level ground naturally ceased to 

 move while those on sloping ground continued their motion. 

 The result could onh^ be that these eskers on sloping ground 

 continued to move and were eroded or modified, while those 

 on level ground remained unaltered, except here and there 

 by stream erosion. 



How far the local and general slopes, or local and central 

 watersheds of a country acted as a cause in the formation 

 of crevasses, remains for future investigators to decide. 



Emergence of Eskers. — Until distinctly contrary evidence 

 shall be brought to bear, I shall feel justified in claiming that 

 the evidence so far adduced points to the theory that nearly 

 all, if not all of our eskers, were formed in the crevasses of a 

 continental ice sheet. This ice sheet moving toward the 

 lower ground carries with it the contents of the crevasses, 

 eroded and gathered up as it proceeds. Crevasses, usually 

 formed on watersheds, in valleys, or on the edge of declivities, 

 may have moved one or one hundred miles with their load 

 of debris before the increasing temperature dissolved the 

 enclosing ice walls and disclosed the material within. In 

 short, the subglacial drainage system had nothing to do with 

 the origin of eskers and only denuded them in the latest stage 

 of the glacial age. 



Only Reasonable Theory. — This is the only explanation 

 that will solve the puzzle of the uneroded and unmoved 

 eskers so often seen in positions exposed particularly to 

 erosion. 



In eskers we have an example of the rarest and oldest of 

 glacial deposits, the first to be formed but the last to be laid 

 bare to aerial erosion, hence their preservation and their 

 peculiar characteristics. 



