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HUNTINGTON AND GOLDTHWAIT: THE HURRICANE FAULT. 243 
than tliree thousand feet, stated above. 
Accordingly in the ideal (Fig. 10), we 
have drawn the pre-faulting surface of 
Colob four hundred feet below the pres- 
ent level. The Pine Valley mountains, 
on the other hand, certainly stood at a 
height of seven or eight thousand feet, 
and then, even more than now, domi- 
nated the landscape for scores of miles 
on every side. 
If the steps of our reasoning thus far 
have been correct, the master stream of 
the region, the Colorado, must at this 
time have been astrong but thoroughly 
graded river, with a descent of from one 
to two feet per mile. Such a stream 
would probably have ceased to deepen 
its channel, because the heavy load 
which it received from the highlands 
would be deposited in the lowlands, 
and would act as a cloak protecting the 
underlying strata from further erosion. 
In this way the river would be held for 
a long time at nearly the same level, 
and would have an opportunity to swing 
over a wide valley floor, although the 
strength of the current would prevent 
the formation of meanders. The tribu- 
tary streams would act in the same way 
in their lower courses, and thus the 
Mohave peneplain would be formed. 
Farther toward their heads we know 
that the streams flowed in more pro- 
nounced valleys, which had a depth of 
hundreds of feet, although the sides 
were of very moderate slope and thor- 
oughly graded. In the larger valleys 
hard and soft strata alike were evenly 
truncated without reference to their 
texture or attitude. In the middle 
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