364 GLACIAL GEAVBLS OF MAINE. 



be by enlarging the channel. Such enlargements must constantly be 

 forming where superficial streams bring warmed waters and pour them 

 down a crevasse into the glacial river. 



Here are a number of physical causes capable of doing the required 

 work, and perhaps no two of the kames were formed in exactly the 

 same way. 



I have many times examined the country adjacent to the isolated 

 eskers for signs of glacial streams beyond the limit of the gravels them- 

 selves. Thus far I have found no ravine of erosion in the till or glacial 

 potholes, either north or south of these eskers. They begin and end 

 abruptly, and beyond them we pass into regions covered by ordinary till. 

 But it may fairly be urged that the channels of subglacial streams, being 

 underneath the ice, are now covered by the upper or englacial till, while in 

 the region that was beneath the sea we have the search further embarrassed 

 by the deep sheets of marine clays which cover almost all that part of the 

 State. Indeed, it would be possible for a ridge to end in a fan-shaped delta 

 and yet be so covered by the clay that only the top of the highest part of 

 the ridge appeared. 



The problem of the short isolated osars in the region that was under 

 the sea is so nearly related to that of the discontinuous osars that it will be 

 further discussed in connection with that class of gravels. Above the 

 former level of the sea, and especially in the northern part of the State, 

 the first and third of the above-mentioned hypotheses appear to me to be 

 more probable than the second. Yet where the material is quite fine the 

 second method may also have been employed. It is not necessary to 

 premise that all the eskers were formed in the same manner. 



These eskers are situated where no ordinary stream of land drainage 

 could have deposited' them. There is no way of accounting for them 

 except that they were deposited between solid walls that have now disap- 

 peared, and ice is the only admissible solid with that property. The ice- 

 berg theory of the drift has no adequate explanation of them. 



HILLSIDE OSARS OR ESKERS. 



The only deposits of this class of which I have note are found in a 

 broad belt extending northeastwardly across the State. Its southern bor- 

 der lies about 50 miles from the coast, and its breadth is perhaps 75 miles. 



