J. LeConte—Ancient Glaciers of the Sierra Nevada. 135 
blue of the deep water extends to within 100 to 150 feet of the 
shore-line. At this distance, me bottom could see be seen. 
least 100 feet. The slope of the bottom is, therefore, seu y 
or quite, 45°. It seems, in fact, a direct continuation beneath 
the water of the moraine slope. he materials, also, which 
may be examined with ease through the wonde rfully trans- 
parent water, are exactly the same as that composing the 
moraine, viz: earth, pebbles, and boulders of all sizes, some of 
them of enormous dimensions. Tt seems almost certain that 
the margin of the great Lake Valley glacier, and of the lake itself 
when this glacier had melted and the tributaries first began lo run 
into the lake, was the series of rocky points at the head of the three 
little lakes, about three or four miles back from the present margin 
of the main lake; and that all ap pele from these points has 
been jilled in and made lan by the action of the three glaciers 
tory, projecting: a into the lake, beyond which was another 
e bay, which has been similarly filled in bas débris brought 
down by a north of this point. The moraines of 
these glaciers are plainly visible from the oe pace but 
have not examined them. Thus, all the land, for three or four 
miles back from the lake- SS pe pcos both north and south of 
Rubicon Point, is composed of confluent glacial deltas, and on 
these deltas the moraine ridges are the natural levées of these 
ice-streams. 
e. Parallel Moraines.—The moraines described above are 
peculiar and almost unique. Nowhere, except about Lake Tahoe 
and near Lake Mono, have I seen moraines in the form of parallel 
ridges lying on a level plain and terminating abruptly without 
any signs of transverse connection (terminal moraine) at the lower 
Nor have I been able to find any description of similar 
moraines in other countries. They are not terminal moraines, 
for the glacial asp is open below. They are not lateral 
moraines, for thes sit rne on the glacier itself, or else 
stranded on the aa ‘call sides. Neither do I think mo- 
raines of this kind a pe formed by a glacier emerging 
from a steep narrow cafion and running out on a level plain; 
for in such cases, as soon as the confinement of the bounding 
walls is removed, the ice stream spreads out into an ice lake. 
oes SO as naturally and a asi as does water under 
similar circumstances. The deposit Goals be nearly transverse 
to the direction of motion, and, therefore, more or less erescen- 
tic. There must be something peculiar in the conditions under 
