7 2 
The Ohio Naturalist. 
[Yol. 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 
rapidly 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 60 feet, more or less, could retain their position and sink grad¬ 
ually down during the general ablation of the ice sheet.” ( n ). 
Let us consider the only way of superficial water origin of 
eskers conceivable to Geikie, viz.: ‘‘deep trenches,” that is, 
streams 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 was reached. The result would be not a long com¬ 
paratively uniform ridge, as we find, but a ridge of perhaps only 
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 Icc Age, 3rd Edition, p. 174. 
