- G. KE. Gilbert—The Colorado Plateau Province. 101 
is as great as that of the Colorado, and it wouid have carved 
cafions of imposing depth, if only the material of its banks were 
sufficiently coherent to stand in walls. As it is, the loose sands 
of the bordering plains are washed and blown into the river, 
and, its energy being consumed in their transportation, the cor- 
rasion of its channel can proceed no faster than the general 
degradation of the plain. Having little work to perform be- 
side the transportation of its load, it maintains an almost un- 
varied slope from the foot of the mountains to its mouth. 
n that portion of the Colorado which is contained in the 
Plateau province, the load consumes a share of the energy of 
the stream and leaves to corrasion the remainder. The slopes 
of the stream-bed are varied, but not so greatly as those of the 
Niagara. Where the bed-rock is soft, the declivity is small. 
Where it is hard, the declivity is relatively great; but in the 
nats he hornblende rock the mean angle of slope does not ex- 
ceed three degrees. 
The Problem of Inconsequent Drainage. 
There is a third problem of erosion now under investigation 
in the Plateaus that promises results of value and novelty. It 
was propounded by Major Powell, and is set forth on pase 162, 
et seq., of his “‘ Exploration of the Colorado River.” The ques- 
System of displacements. Streams will rise along the crest of 
each satialines 
dip, will unite in the synclinals, and will follow them length- 
e axis of each synclinal will be marked by a water- 
course; the axis of ‘each anticlinal by a watershed. Such a 
System is said to be consequent on the structure. 
f, however, a system of displacements affect a rock series 
after the series has become continental, it will have already ac- 
quired a system of waterways, and, unless the displacements 
are produced with unusual rapidity, the waters will not be 
diverted from their accustomed ways. The effect of local ele- 
vation will be to stimulate local corrasion, and each river that 
crosses an uplifted block will, inch by inch as the block rises, 
deepen its siaasel and valorously maintain its original course. 
It will result that the directions of the drainage lines will be 
Am. Jour. Sc1.—Tarrp Series, Vou. XII, No. 68,—Aveust, 1876. 
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