366 GLACIAL GRAVELS OF MAINE. 



Again, if the hillside osars were due to local deposition in the channel 

 of a long north-and-south glacial river, we ought to find similar gravels 

 forming a system or connected series along the course of the hypothetical 

 glacial liver. But with a few exceptions the eskers of this class can not be 

 brought into any kind of linear arrangement with other eskers or osars. 

 In most cases hills higher than 200 feet lie to the south of these eskers, 

 sometimes within a mile or two, sometimes 10 or 20 miles away. The 

 great rivers that have left their g-ravels for a hundred miles could not flow 

 over hills more than about 200 feet high. No reason can be assigned why 

 streams that have left gravels for less than 2 miles should be able to flow 

 over any higher hills, or, if so, why they have not left gravels to mark 

 their channels. 



All the facts point to the conchision that the hillside eskers were 

 deposited very late in the Ice period. They are found in regions abounding 

 in rather high hills lying transverse to the direction of glacial movement. 

 These hills stopped the motion as a whole after the depth of ice came to be 

 less than about 500 feet, though local movements would continue along 

 north-and-south valleys like that of the Kennebec. So, too, there Avould be a 

 limited flow from north to south between the successive ranges of transverse 

 hills, especially on the southern slopes of the hills. There would still be a 

 surface gradient of the ice, since in general the melting was most rapid toward 

 the south and the thickness of the ice had originally increased northward. 



Some of the hillside ridges beg-in on the slopes of long hills and have 

 1 or 2 miles of hill north of them. In such cases it is jDossible that the 

 osar streams were wholly supplied by melting ice and other drainage of 

 the hill itself. But generally these ridges begin at or near the tops of the 

 southern slopes of the hills, where the supply of local drainage would be 

 yevj small. Yet the streams had considerable volume at the north, as, for 

 instance, the esker near Wilton. Such streams plainly derived their waters 

 in great part from the regions lying' to the northward. 



The best interpretation of the facts seems to be as follows: The ice front 

 had retreated to near the point of the formation of the streams, but the ice 

 north of the hills was still high enough to enable its drainage waters to flow 

 southward over the hills. The absence of erosion channels or glacial sedi- 

 ments on the tops and northern slopes of the hills can be accounted for on 

 the following suppositions: 



1. That superficial streams flowed over the hills from the north. 



