400 GLACIAL GKAVELS OF MAINE. 



ice. They would be retreatal, capping older sediments, and but rarely 

 would they form an isolated mass by themselves, as I conceive. 



While admitting that some marginal submarine ice probably exists, 

 and that it might act in the manner indicated, I have found no certain 

 field evidence of this form of ice action. 



Were the discontinuous coastal gravels begun as a series of subglacial 

 tide-level deposits during a gradual rising of the seal 



The answer to this question is short and positive. The discontinuous 

 systems cross valleys and hills and gently rolling ground. North of the 

 hills the water in the stream channels, no matter whether they were super- 

 glacial or subglacial streams, would be dammed by the hills in front. The 

 rising of the sea could produce no effect beneath the surface of this glacial 

 dam. On a continuous southern slope we might admit as a possibility a 

 series of tide-level deposits as inaugurating sedimentation at intervals, but 

 by no means on the north sides of hills in confined channels in the ice. 

 But in another way we may have proof of the action of the subglacial sea, 

 if we may so term the body of glacial water that filled the cavities of the 

 ice-sheet up to sea level. The East Machias osar shows a series of broad 

 reticulated ridges at the highest sea level, but no delta proper. In Lagrange 

 and Orneville, in the Penobscot Valley, and in Canaan and Cornville, in the 

 Kennebec Valley, we find near the highest sea level that the long osars 

 that follow these valleys for 50 miles expand into plains with some of the 

 characters of narrow marine deltas and also of the broad osar terraces. 

 Here it is probable that these plains or partial deltas were formed at sea 

 level, but at some distance back from the ice front, so that no delta proper 

 could be formed. If so, this would prove that enlargements of glacial 

 channels and sedimentation took place at the point where the stream flowed 

 into the permanent subglacial and submarine body of water. Such deposits 

 are, however, very difi'erent in structure from the discontinuous gravels of 

 the coast region. 



In three instances in Maine osars are conspicuously discontinuous on 

 level ground at long distances from the coast. The first instance is that 

 of the Katahdin osar near South Lincoln; the second, that of the Moose- 

 head Lake osar in Abbott, Guilford, Sangerville, and Dover; the third, the 

 Anson-Madison osar in the northwestern part of Anson. In all these cases 

 the discontinuous deposits are below the highest sea level, or in a glacial 

 lake. A similar coincidence occurs in central New York, where Mr. G. K. 



