Eskers of the Kavsan Epoch. — Hershey. 249 
a. There is never the slightest evidence of water action, 
either in eroding the material from its parent ledges or in de- 
positing it. 
b. The eastern end of a given ridge or mound is usually a 
gentle slope, while the western end is almost invariably 
abrupt. 
c. The sliarp contours, especially of the isolated cone-shaped 
mounds, negative the idea that they were ever overridden by 
the ice, and show that they are not preglacial in age. 
d. Except in a very few instances, practically no drift peb- 
bles whatever have been found within the body of these de- 
posits, whereby they are denied admittance into the ground 
moraine as unusually stony portions of the till. 
e. There are generally a few boulders of the englacial drift 
scattered over them, demonstrating that they are not post- 
glacial or even post-Kansan in age (except the sliarp ridge 
southwest of Pecatonica). 
f. The almost total absence of foreign drift within them 
clearl}'' proves that they were not lifted up and carried in the 
ice-sheet as englacial drift. 
g. The occurrence of the deposits as high ridges and cone- 
shaped mounds, in the center of valleys and overlying strati- 
fied drift, shows that they are not now in situ, but have been 
transported from some distant ledge. 
h. Their situation, in the majority of cases, west of the 
crest of a high rock ridge, indicates their derivation from it, 
and we are thus enabled to determine that they have some- 
times been forced up a slope to a considerable hight above the 
parent ledges. 
I think that the glacial origin of these peculiar gravel de- 
posits will not be disputed. It has been suggested that simi- 
lar agglomerates of broken rock might be produced by a land 
slide, or even by the slow "creeping" of the strata down a 
slope. This, however, requires that the parent ledges shall be 
situated at a hight considerably above the finished deposit. 
As we have seen, there are deposits in the Pecatonica basin 
which rest on the summit of esker knolls higher than any 
rock ridges in the vicinity. 
The glacial age of the angular gravel beds having been 
demonstrated, it remains to determine the precise mode by 
