72 The Ohio Naturalist. [Vol. VII, No. 4, 



of the ice than to arrange it in determinate linear courses, unless, 

 indeed, we are to suppose that the superficial rivers succeeded in 

 rapidlv cutting their way down to the bottom of the ice-sheet, 

 and thus at an early period formed deep trenches into which was 

 shot all the rock-rubbish derived from the ice during its dissolu- 

 tion. If it be hard to conceive such conditions possible, it is not 

 easier to see how river beds filled with detritus to a depth of 50 

 to GO feet, more or less, could retain their position and sink grad- 

 uallv down during the general ablation of the ice sheet." ("). 



Let us consider the only way of superficial water origin of 

 eskers conceivable to Geikie, viz.: "deep trenches," that is, 

 stream.s whose banks were the ice-sheets and whose bottoms were 

 the ground. These streams with the vast amount of water and 

 material cast into them would be nothing short of torrents and 

 would carry the material along and deposit it in approximately 

 longitudinal, horizontal strata. Now take a case of an esker of 

 Maine, which passes beneath the water of a lake, up the side of a 

 valley, over a col or divide of 200 to 400 feet, and thence down 

 the other side. Here the stream (deep trench) would continue 

 to lay down its load in practically horizontal layers until the top 

 of the divide w^as reached. The result would be not a long com- 

 paratively uniform ridge, as we find, but a ridge of perhaps onl\- 

 a few inches in height at the divide and 200-400 feet in height 

 in the valley and with a still greater height across the lake basin. 

 The fact that we have these ridges of practically uniform height 

 extending through lakes, up valleys, across divides and down into 

 other valleys seems to point to but one origin, namely: sub-gla- 

 cial streams flowing under "head" at the maximum extent or at 

 the various stages of retreat of the ice-sheet. 



The writer is under obligation to Dr. George D. Hubbard for 

 many suggestions and criticisms and for the photograph for 

 figure 6 and wishes to express his thanks to him for the courtesies 

 extended. 



11. The Great Ice Age, onl Ediliun, p. 17-1. 



