TOPOGRAPHICAL RELATIONS OP GLACIAL RIVERS. 321 



scratches and bowlder trains. I see no admissible interpretation but this: 

 Osars for long distances are transverse to the recorded glacial movements, 

 and probably even the latest ice movements were not parallel with them. 

 In the coast region, as near Belfast, there are iisually one or more systems 

 of glacial scratches that diverge progressively more and more from those 

 that mark the time of deepest ice, the latter being parallel to the scratches 

 found on the tops of the highest hills. Here we find the systems of dis- 

 continuous gravels approximately parallel to the scratches last made, and 

 convergent like them, to Belfast Bay. 



The great divergence of the glacial rivers, both for short and long 

 distances, from the recorded movements of the ice suggest many questions 

 as to the causes that determined the courses of the rivers. The subject is 

 briefly treated in the following chapter. 



RELATIONS OF GLACIAL RIVERS TO RELIEF FORMS OF THE LAND. 



The general facts as to the topographical relations of the osar rivers 

 have already been stated. These rivers often flowed over the lower hills, 

 but not over hills higher than 200 feet except in western Maine, where many 

 gravel series go over hills a little more than 200 feet, and over one hill 400 

 feet, above the ground on the north. 



A question of detail arises whether the glacial streams were determined 

 to the low passes before the hills adjoining the passes emerged from the 

 ice, premising that it is only rarely in Maine that ridges are parallel with 

 the direction of ice movement. Almost always they are transverse. 



The phenomena of delta branches proves that a single glacial river 

 sometimes either used too widely diverging channels simultaneously or 

 abandoned one of the channels for another. This phenomenon is very com- 

 mon in southwestern Maine and over most of the State. But these delta 

 branches go over no higher hills than the tributary branches or main osars, 

 and they throw no light on the time the glacial rivers were established in 

 the low passes. 



The hills adjoining the low passes penetrated by the glacial rivers rise 

 to a height of 100 to 1,000 or more feet above the passes. If at or near 

 the time that the ice melted over the transverse- hills bordering the passes, 

 glacial streams crossed them, we ought under certain conditions to find 

 traces of such streams. 



MON XXXIV 21 



