G. K. Gilbert—The Colorado Plateau Province. 19 
humid region, would reward only protracted and laborious ob- 
servation and patient generalization. There is no need to search 
for exposures where everything is exposed. Dr. Newberry, 
speaking of one of the southern plateaus, says, “On our way 
to the Moqui villages we passed through a region singularly 
favorable for accurate geological investigation; where there 
is no vegetation to poi ihe the view; where the strata are 
entirely undisturbed, and are cut by valleys of erosion, in the 
wall-like sides of which every inch of the series may be exam- 
ined. In this journey we ascended in the geological scale from 
the summit of the Carboniferous to the base of the Cretaceous 
series. Of this interval there is no portion of which the expos- 
ures are not as complete as could be desired.” (Geol. Ives’ 
Exped., p. 77. 
This aridity is not peculiar to the plateaus: it pertains to the 
Basin Ranges, and in a less degree to the plains. But in the 
mountain ridges, and these are filled with monotonous Quater- 
nary gravels and clays, which hide all other beds, while the 
ranges themselves, which are of more interest to the geologist, 
catch all the precipitation, and are in some degree clothed with 
ing benches decay more rapidly than they are undermined, an 
their rounded outlines are clothed with soil. But the Colorado 
uous velocity and sweep out the detritus. The rocks of the 
upland are removed as fast as they decay, and soil cannot accu- 
mulate. Thus does thorough drainage conspire with aridity to 
prepare for the geologist a land of naked rock. 
