GLACIATION OF THE UINTA MOUNTAINS 797 
ice sheet. The mere fact that the area in which the data must be 
found, to prove distinct epochs for a given canyon, is so small, 
enhances the difficulties in the problem, and greatly reduces the 
chance of a demonstration. Where the later ice did not advance as far 
as the earlier, the case is more hopeful. In fact, in every case where 
distinct epochs have been determined in the western mountains, so 
far as the writer is aware, the earlier ice was more extensive than the 
later. In such cases the outer moraines have been subject to the 
processes of weathering and erosion for a longer period than the later 
or inner moraines. ‘There may also be, associated with the two dis- 
tinct systems of moraines, distinct outwash-deposits. These out- 
wash-deposits must have a genetic relationship with the terminal 
moraines of the two epochs, and the older alluvium or valley-train 
may be expected to have suffered greater erosion than the younger. 
The composition of the glacial drift in a mountain canyon will be 
essentially the same each time that ice descends to a given point. 
But if the drift contains some easily weathered material, such as the 
coarsely crystalline rocks, the difference in the amount of weathering 
or disintegratio nof the bowlders may become a strong argument. 
Among the Wasatch Mountains the older and the younger moraines 
may be easily distinguished by the difference in the amount of weath- 
ering. Among the Uintas this line of evidence is almost entirely want- 
ing. The drift among the Uintas is composed largely of quartzite, in 
fact so largely that in most cases it is difficult to find a specimen of any 
other kind of rock in the drift. The drift of certain canyons is com- 
posed entirely of quartzite. Furthermore, the quartzite of the Uintas 
is so hard that the bowlders in preglacial conglomerates, derived 
largely from this formation, appear nearly as fresh as those in the 
youngest glacial deposits. The only difference that can be made out 
in the amount of weathering of the preglacial quartzite conglomerate 
and the quartzite moraines is that in the former there are more and 
larger bowlders that have been fractured, presumably by changes in 
temperature and by frost. 
The determination of two epochs of glaciation among the Uintas 
rests chiefly upon these points: 
1) There are two distinct systems of moraines in each of the main 
canyons. 
