188 
THE GEAND CA^ON DISTRICT. 
part of its basin. The gradual elevation of the entire region was the cause 
of the gradual desiccation of the lake, and the channel through which its 
waters escaped, once established, could not have been changed without leav- 
ing some indication of the process which could have effected such a change. 
A powerful river traversing a region which is undergoing a great amount of 
uplifting must ever sink its channel deeper and deeper in the strata, and its 
position must be growing more and more immutable. 
The present position of the Grand and Marble canons, therefore, is the 
locus of the deepest part of the Eocene lake. This conclusion is reached by 
another course of reasoning. If we restore the strata to the condition of 
horizontality, if we replace in imagination the bodies of Mesozoic and lower 
Eocene strata which have been denuded, we shall be led to infer the exist- 
ence of a vast and nearly level platform coextensive with the great areas now 
draining into those canons. But if we supjiose the strata to have thickened 
as they approached their shore-lines we should also infer the existence of 
two converging slopes, one descending from the northwest, the other from 
the southwest, and meeting in a line very near and perhaps exactly in the 
position of these canons. Thus, the law of persistence of rivers and the 
analysis of the vertical movements of the region bring us to the same con- 
clusion. The study of the tributaries also tends to the same result. The 
Kanab and Paria rivers are plainly independent of the inequalities of 
uplifting, and must be older than the displacements. 
These tributaries shed further light upon the earliest condition of the 
Kaibab area. The Kanab and Paria are apparently as old as the Colo- 
rado, and had their origin in the same train of events. Each represents a 
subordinate and lateral drainage basin, and between the two lay a certain 
extent of higher ground. Just at the base of the East Kaibab flexure is 
House Rock Valley, which once held a river which has long since van- 
ished, though leaving well-marked traces of its former action. This inter- 
mediate valley divides the interval between the Kanab and Paria basins 
into two masses ; the western is the Kaibab, the eastern is the Paria, pla- 
teau. None of the great displacements which traverse these masses had 
any existence at that remote epoch. 
The earliest condition of the Kaibab, then, is inferred to have been 
