EEOSION. 15 



improbability, though the proofs are difficult beyond a certain amount. 

 The great value of the Plateau Country is the certainty and fullness of the 

 evidence. Nature here is more easily read than elsewhere. She seems at 

 times amid those solitudes to have lifted from her countenance the veil of 

 mystery which she habitually wears among the haunts of men. Elsewhere 

 an enormous complexity renders the process difficult to study; here it is 

 analyzed for us. The different factors are presented to us in such a way 

 that we may pick out one in one place, another in another jjlace, and study 

 the effect of a single variable, while the other factors remain constant. The 

 land is stripped of its normal clothing; its cliffs and canons have dissected 

 it and laid open its tissues and framework, and "he who runs may read" if 

 his eyes have been duly opened. As Dr. Newberry most forcibly remarks: 

 "Though valueless to the agriculturist, dreaded and shunned by the emi- 

 grant, the miner, and even the adventurous trapper, the Colorado Plateau 

 is to the geologist a paradise. Nowhere on the earth's surface, so far as we 

 know, are the secrets of its structure so fully revealed as here." 



In the new era, beginning with the desiccation of the lake, we have 

 the history of a process which resulted in the destruction and dissipation 

 of those great bodies of sediment which had been gathered and stratified 

 during Mesozoic and Eocene time. Then, too, appears to have begun in 

 earnest the gradual elevation of the entire region which has proceeded from 

 that epoch until the present time, and which even yet may not have cul- 

 minated. The two processes of uplifting and erosion are here inseparably 

 connected, so much so, that we cannot comprehend the one without keeping 

 constantly in view the other. 



From the very inception of the process the drainage system of the 

 Plateau Province has been that plexus of streams which unite in the Colo- 

 rado River. This is the trough through which the waste of the land has 

 been carried to the Pacific. Its origin goes back to the emergence of the 

 land now drained by it from its lacustrine condition. Even prior to that 

 we may conjecture the existence of a Cretaceous-Eocene strait connecting 

 with the ocean that area which was covered by the Laramie beds and the 

 brackish water deposits at the base of the local Eocene ; and many consid- 

 erations lead to the inference that this Hellespont occupied the same position 



