480 GLACIAL GRAVELS OF MAINE. 



retreated northward to the bottom of an east-and-west valley, all the sedi- 

 ments derived from the drainage of the ice on the north side of the valley 

 would be swept into the stream, which then would flow in the bottom of the 

 valley substantially parallel with the ice front of that time. As the ice 

 retreated northward up the hill more or less sediment would be poured out 

 on the open hillside below the ice, whence much of it would be carried 

 down the hill to the bottom of the valley. 



6. In some east-and-west valleys hillside eskers are found. These 

 were deposited by glacial streams that flowed down the southern slopes of 

 rather high hills and left their coarser sediments on the sides or near the 

 bases of the hills. Sometimes here they are lost and the streams must 

 have escaped superglacially or in channels too narrow to permit sedimen- 

 tation. In other cases this class of gravels expand into deltas and finally 

 merge into the alluvium of their valleys. Evidently this valley drift dif- 

 fers in no essential from that not associated with the osar gravel, except that 

 we can trace its glacial origin more directly. 



RELATION OF THE VALLEY DRIFT TO THE MARINE BEDS. 



We now approach a series of phenomena very difficult to interpret. 

 In a paper read at the Boston meeting of the American Association for the 

 Advancement of Science, in 1880, I estimated the elevation of the sea in 

 the interior of Maine at 300 to 350 feet. The highest fossils I had been 

 able to find in the interior valleys were at 215 to 230 feet in Palmyra. I 

 had also discovered certain high deltas, as that at Curtis, Leeds, that were 

 from 300 to 350 feet in elevation. My estimate was based on the deltas, 

 assuming that the higher marine beds were nonfossiliferous. Later, when I 

 discovered (1885-86) that the elevation of the beaches along the outer 

 coast-line did not exceed 200 to 230 feet, I became quite doubtful where to 

 place the limit in the interior. It even seemed possible to interpret the- 

 highest deltas as formed in lake-like bodies that toward the south opened on 

 land bare of ice, while the basal clay of the vallej-^s would on this hypothesis 

 be a form of valley drift analogous to the loess. 



The observations of Baron De Geer, made in 1891, cover most of the 

 area of the elevated marine beds. They make it evident, in a way that 

 local observations could not do, that the apparent rise of the sea in late 

 glacial time was due to a general subsidence of the glaciated area. From 



