DAVIS: MOUNTAIN RANGES OF THE GREAT BASIN. 145 
in relief as residual mountains in which the streams and rivers have cut 
sharp V-section ravines and notches. The resistance of the sandstones, 
on which the survival of the sharply limited mountain ridge depends, is, 
therefore, also the cause of the narrowness of the ravines and notches 
cut in it by the streams; and it may be added that the sharpness of 
these forms is in part due to the relatively recent uplift that the middle 
Appalachian belt has suffered. 
All the higher Basin ranges that I saw in the summer of 1902 are 
characterized by sharp-cut V-section ravines and canyons, narrow-floored 
and steep-walled down to their very mouths; typical examples are 
shown in Plate 5, from the Pueblo range, described below. All these 
canyoned ranges are so unlike in structure to the ridges of the strati- 
fied Appalachians that it is utterly out of the question to explain the 
former by the theory that is appropriate for the latter. 
Rock canyon in the Wahsatch near Provo, Plate 4, a, has a narrow 
gravel plain near its mouth, probably the result of delta building in front 
of the mountain base during the presence of Lake Bonneville ; but after 
going up the canyon a few hundred feet, its stream is found cascading 
on the more resistant strata, whose rising outcrops form prominent ribs 
on the steep canyon wall. The same features are observable in Slate 
canyon, Plate 4, B, three miles further south, except that the stream 
here being smaller, its descent is steeper, and it has accumulated hardly 
any gravels up stream from its Bonneville delta on the mountain front. 
The beds of both these streams have a rapid descent, and are not cut 
down as low at the canyon mouth as might be expected in view of the 
much lower level of the broad piedmunt plain a little way forward from 
the mountain base. Some detention of their down-cutting must be 
ascribed to the temporary rises of the local baselevel during Bonne- 
ville time, and to the work of removing high-level delta gravels in 
post-Bonneville time ; but this cause of detention does not seem nearly 
sufficient to account for the height of the stream beds over the plain. 
Hence not only the steepness of the canyon walls, the narrowness of 
their floors, and the rapid descent of their stream, but also the relatively 
high level of their mouths suggest recent uplift of the mountain block. 
The general form of these two steep-walled canyons suggests not only 
that the up-faulting of the mountain block has been continued into rela- 
tively recent time, but that the uplift of the block by an amount equal to 
the height of the summits over the base (in the Provo Wahsatch) has been 
accomplished since the latter part of Tertiary time. The canyons have 
a much younger expression than that of the narrow valleys in the up- 
