278 GLACIAL GEAVELS OF MAINE. 



against the solid rock were held embedded hi the ice, it was solid enough 

 to deserve the name of ice. If they were rolled or dragged beneath it, 

 only solid ice could furnish the necessary friction. No matter what theories 

 we indulge as to basal melting or semifluidity under sufficient pressure, or 

 as to the conditions prevailing at any given point when it was a place of 

 deposition of stationary ground moraine, we must admit that over the area 

 of erosion at any period in the history of the ice-sheet there was a body of ice 

 beneath which, under the enormous pressure extended, terranes were 

 turned to dust. The marks of this tremendous conflict are conspicuously 

 shown by the lower till and not by the upper. Plainly they are what 

 should be expected of material that has been beneath the ice. 



Again, the deeper accumulations, such as the drumlins and the sublen- 

 ticular sheets on the hillsides, have a rounded outline. Under the action of 

 Avater waves a sand or gravel bar assumes the form most favorable to its 

 stabilit)-, and a mass of d(^bris ought to assume a corresponding form while 

 ice flowed over it. The drumlins often show beautiful curves and billows, 

 and the type of ground-moraine scenery is very different from that of 

 moraines either of surface or englacial debris. The latter show more variety 

 of form and gradient of slope and have a more or less heaped appearance. 



It is perhaps now impossible for us to form an accurate picture of the 

 relations of the englacial and subglacial morainal matter to each other and 

 to the subjacent rock. We know that the englacial till is but little glaciated, 

 and hence must have entered the ice liefore being rolled or dragged between 

 the ice and the rock. We do not know in detail the manner of its entrance 

 into the ice, though that must have occurred soon after the flow was 

 established, or possibly even before the flow of consolidated ice began. 

 We do not know the relation of this assumption of englacial matter to the 

 history of the adjacent regions. We do not know certainly whether the 

 stones and particles of the ground moraine were from the first and con- 

 stantly beneath the ice, or whether each particle was at one time within the 

 ice and was subsequently torn from its grasp, or whether both kinds of 

 matter are now a part of the subglacial till, though there is a strong proba- 

 bility that the last-stated hypothesis is the true one. How much of the 

 ground moraine was stationar}^ during the time of the accumulation! We 

 do not know the height in the ice attained by the englacial debris, nor. its 

 vertical and horizontal distribution. In a general way we know that it got 



