CROSBY : ORIGIN OF ESKERS. 
379 
mately parallel are simultaneously forming — one in the middle of 
the tunnel and one on each side. When the ice has fully melted 
away, this debris will present all the complications of interlacing 
ridges with numerous kettle-holes and knobs characterizing the 
kames [eskers] ; and these will be aj^proximatelj^ parallel with the 
line of glacial motion. The same condition of things exists about 
the head of the subglacial stream on the east side, also near the 
junction of the first branch glacier on the east with the main stream, 
as also about the mouth of the independent glacier shown on the 
map lower down on the west side of the inlet.” 
We have clearly indicated here a type of eskers in the formation 
of which running water is no^ an immediately active agent; and, 
moreover, at the time of their filling by superglacial detritus, the sub¬ 
glacial tunnels have become gorges open to the sky and the deposits 
are not in any proper sense subglacial. Undoubtedly this is a true 
explanation of some kame-like and hummocky forms of modified 
drift; and it appears that, in general, deposits formed under these 
conditions would be more properly classed as kames than as eskers, 
and no one, perhaps, supposes that the more typical eskers of New 
England and other districts covered by the Pleistocene ice sheet 
have had this origin. 
The search for eskers along the borders of the Greenland ice cap 
and its dependent lobes or glaciers has been even more fruitless ; 
and Chamberlin (’95, p. 215), among recent competent observers in 
that field, has expressly noted the practical absence of this class of 
phenomena, attributing it chiefly to the inadequate drainage, but in 
part also, to the fact that the glacial streams are mainly lateral, 
coursing along the margins of the ice lobes, while the medial tunnels 
of Alaskan and Alpine glaciers are wanting. , According to Russell, 
the drainage of the glaciers of the St. Elias range, above their 
confluence with the Malaspina glacier, is also largely or chiefly by 
marginal streams, which, like the lateral moraines, unite at the lower 
ends of the mountain ridges and pass' into or beneath the piedmont 
glacier. 
Nowhere, apparently, have esker-like deposits been formed by the 
subglacial streams of alpine glaciers, owing in part to the high 
gradients of the valleys, and in part to the paucity of detritus and 
the consequent absence of deposits at the lower end of the tunnels of 
sufficient volume efficiently to clog the outlets and lead to aggrading 
of the floors of the tunnels. 
