The Margin of the Cornell Glacier. 151 
or by the clown cutting of tlie stream bed where it is eating 
its way through a morainic dam. Tlie different elevations 
are plainl}'^ evident from the absence of lichens on the rocks, 
the clay clinging to the rocky shores, and the beach terraces 
along the old shore lines. In one case, at the western end of 
mount Schurman, a lake of this type, with a depth of at least 
100 feet has recently been drained. Where these extinct lake 
beds exist one sees revealed an expanse of muddy bottom 
with scattered blocks of rock. No chance was found of de- 
termining the depth of these clay beds, but in some cases 
they were evidently several feet deep, perliaps even several 
fjcores of feet. 
In the deposits now being made along the margin of this 
glacier there were two extremes, the bouldery material and 
the claj'' beds. No sand or gravel deposits were seen. Hence 
Ijere is another of the many differences between the present 
results of the Greenland glaciation, and the more ancient de- 
posits that were made by the American glacier. 
Jforaiuic Complexity. By the study of the moraines and 
marginal lakes along the ice front, one sees enough to help 
him to a satisfactory conception of the manner of formation 
of the irregular moraines in the United States, where the drift 
supply was greater and the oscillation of the ice front more 
easily possible. Co-operating with the normal dragging of 
materials to the margin, and with some possible shoving of 
materials at the end, accompanied by the accumulation of ta- 
lus deposits at the base of the glacier front, there was the ac- 
tion of streams over the ice surface, and possibly from be- 
neath, and the presence of the lakes and freqviently changing 
marginal drainage. Lakes appear and disappear, being caused 
by cojiditions now in part absent. With a complex interaction 
of these various causes the topography and structure of the 
American moraine seems easily possible to one who has travel- 
ed along the edge of the Greenland ice cap. All that is needed 
is a little imagination which will permit the ice to change its 
front more frequently and to bring a greater supply of debris. 
As has been described above, the land moraine of this 
Greenland glacier is generally a ridge; but sometimes it be- 
comes a series of choppy hills, quite like those of the Ameri- 
can moraines, due to the presence of several ridges with diff- 
