92 G. K. Gilbert— The Colorado Plateau Province. 
All the processes of erosion are affected directly by the 
amount of rainfall, and by its distribution through the year, 
All are accelerated by its increase and retarded by its diminu- 
tion. When i 
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Weathering is favored by abundance of moisture. Frost ac- 
complishes most when the rocks are saturated ; and solution, 
the annual rainfall is concentrated into a limited season, a larger _ 
share of the water fails to penetrate, and the gain from tempo- 
rary flooding does not compensate for the checking of all solu- 
Transportation is favored by increasing water supply as 
greatly as by. increasing declivity. When the volume of a 
well as by the increment to volume. Hence the increase 10 
power of transportation is more than proportional to the in- 
crease of volume. 
It is due to this fact chiefly, that the transportation of a 
stream which is subject to floods is greater than it would be if 
its total water supply were evenly distributed in time. 
The indirect influence of rainfall and temperature, by means 
of vegetation, has different laws, Vegetation is intimately re- 
i as a distributing reservoir for the 
water of rains, and tends to re et the flow of streams. 
ra) 
great rainfall is the acceleration 
In arid regions of which the declivities ient ive 
; are sufficient to give 
thorough drainage, the absence of vegetation is cone by = 
