324 GLACIAL GEAVELS OF MAINE. 



axis of a valley or zigzag' from one side to the other in a way that shows no 

 connection with the inequalities of the land. 



Thus far I have been able to make no generalization, but certainly the 

 determination of the positions of the crevasses is a difficult matter, and per- 

 haps often impossible. Many details in regard to particular places will be 

 found in the descriptions of the gravel systems. 



GLACIAL RIVERS OF MAINE: SUMMARY. 



In the preceding pages we have spoken of the great length and volume 

 of the glacial rivers of Maine as attested by the gravels they deposited. 

 Care has been taken to avoid naming them either subglacial or superficial. 

 From whatever point of view we look, the difficulties are immense in 

 accounting for the branchings of the rivers of the ice-sheet, their directions 

 and their relations to the relief forms of the land, the nature of their sedi- 

 ments, etc., on the theory that we are dealing with subglacial streams alone. 

 To insist that the glacial gravels are wholly due to subglacial streams, or 

 wholly to superficial streams, appears to me to be dangerously like the dis- 

 pute between the followers of Hutton and those of Werner as to whether 

 the earth had come to its present condition by the action of water or fire. 

 Both sides of that controversy were partly right and partly wrong, and 

 probably this is the case in the controversy as to the glacial streams. 

 Those who study the question near the great terminal moraines will every- 

 where see signs of subglacial streams only. Those who study in north- 

 ern New England will also see phenomena that are consistent with the 

 hypothesis of superficial streams. It is too early for anyone to settle finally 

 the moot question of glacial streams. In the following interpretations I 

 have endeavored to correlate the facts in Maine, so far as I have observed 

 them, with those of Greenland. The best interpretation will prevail. 



GLACIAL POTHOLES. 



The process of pothole making has long been well understood in the 

 form in which it appears in the beds of surface streams of the land. If we 

 go to some place where a rapid stream passes over a series of waterfalls 

 and rapids, especially over granite rocks, we can see potholes in all stages 

 of formation An accessible locality is the falls of the Androscoggin River 



