322 GLACIAL GRAVELS OF MAINE. 



1. If subglacial, they aught to have left channels of erosion in the till 

 or deposits of glacial gravel, at least on the south sides of the hills, like the 

 hillside eskers. 



2. If superficial, there would come a time when the top of the thinning 

 ice did not rise so far above the hills but that the channels would cut down 

 through the ice to the till. Erosion of the till would follow until the hill 

 emerged from the ice. The eroded matter would be left somewhere as 

 glacial gravel. Or if the surface streams disappeared down crevasses at the 

 tops of the hills, they ought, while escaping as subglacial streams, to erode 

 the till and leave gravels. 



3. The lowering of the ice to the top of a hill would necessarily 

 deflect to some neighboring pass any stream previously crossing the hill. 

 The deflection might take place in various ways. It might happen some 

 miles to the north, or a pool might be formed on the north slope of the hill 

 which would in fact so far check the force of the stream that it would 

 deposit onlj^ scanty sediments that might since have been wholly or partly 

 eroded. But w^e can at least conceive of a stream thus deflected leaving 

 gravel terraces to mark its new channel along the northern slope of the hill 

 or at some point north. One such case would be very significant. As 

 elsewhere recorded, there are cases on the north sides of hills of lateral 

 deflection from the general course of large glacial rivers, as at South Albion 

 and in Montville and elsewhere, but no gravels on the hills marking more 

 ancient channels than those in which the osars proper were deposited. 



The Greenland and Alaskan glaciers show prominent bulging on their 

 surface, presumably due to passing over hidden hills. Such bulgings must 

 appear while the tops of the obstacles are a considerable distance beneath 

 the ice. Whenever bulging of the surface is accompanied by deep crevasses 

 it would be possible for surface streams here to escape beneath the ice as 

 subglacial streams, but it must often have happened that the raising of the 

 ice over the hills would cause the surface water to gather in the lower parts 

 of the ice surface, i. e., over the low passes of the underlying hills. How 

 far such bulging over transverse hills helped establish the courses of the 

 rivers through the passes is uncertain. 



Numbers of the hillside kames are situated on the south slopes of hills 

 higher than 200 feet above the ground on the north. The small size of the 

 gravel deposits does not call for large streams or long-continued flow. In 



