402 
TURNER. 
habit of the streams would be reversed, and the canons we 
see would result. That such a change in inclination has 
taken place is rendered probable by other considerations. 
In the first place, the western face, which is far broader than 
the eastern, is, as described by Whitney and others, an in¬ 
clined plane, interrupted only by the narrow canons of the 
modern streams. Its plateau character is not given by a 
continuous stratum of hard rock parallel to the general 
surface, but has been produced by the uniform erosion of a 
system of plicated strata. Such uniform erosion could only 
have been accomplished by streams flowing at a low angle- 
Second, the eastern boundary of the range or plateau is a 
line of faulting; and the orographic movement producing 
the range consisted of a displacement along this fault line, 
and a consequent inclination of a plateau-like mass to the 
westward.” 
In 1886 Professor Le Conte wrote a paper on the “ Post- 
Tertiary Elevation of the Sierra Nevada ” (XIII). On page 
173 he says: 
“ The old river beds were probably established at the be¬ 
ginning of the Cretaceous, when the Sierra range was born 
from the sea and were being cut and shaped throughout 
the whole Cretaceous and Tertiary. By the end of that 
time * * * the rivers seem to have reached their base 
level and had ceased to deepen their channels, but rain 
erosion still continued to widen the valleys and cut down 
the divides. The river system had therefore assumed the 
form characteristic of old topography. Then came the lava 
flood, displacing the rivers, and the contemporaneous eleva¬ 
tion changing the base level and enormously increasing the 
erosive power of the rivers. These, therefore, without loss 
of time, commenced cutting anew, and in comparatively 
short time have cut far lower than before. * * * It is 
impossible to explain this except by supposing a great rise, 
probably several thousands of feet, with increased slope of 
the range at the end of the Tertiary.” 
