JOHN WEST, ICY J'OWEW, DAVIS 



result of persistent erosion by rain and rivers during prolonged 

 still-stands of the region in ancient geological periods ; but the 

 phraseology adopted for the peroration, in which the history 

 of these buried lands is set forth, must leave the uninformed 

 reader in some doubt as to the precise nature of the facts and 

 inferences there presented. A simpler statement is given for 

 the plateau-like highlands of crystalline schists, flanked by 

 upturned sedimentaries in the Colorado Front Range, which 

 had made a "deep impression" on Powell when he crossed 

 them in his first Western journey in 1867. He afterward re- 

 calls that he had then "dimly conjectured that tens of thou- 

 sands of feet had been eroded from some of the ranges, and 

 that the table or plateau like character of the ranges was due 

 to some epoch of this later denudation of the ranges when they 

 were planed down to a common level. . . . Such a planing 

 down occurs when the channels of the eroding streams remain 

 for a great length of time at a general base level" (Uinta, 27). 

 It would thus appear that the first observer to recognize this 

 fundamental process in the origin of the Front Range of the 

 Rocky Mountains was not Marvine, to whom it has elsewhere 

 been credited, but Powell. True, he does not explicitly state 

 that the planed-down surface of the Front Range was after- 

 ward broadly uplifted to its present highland altitude in order 

 to excite its streams to erode the gorges by which it is now dis- 

 sected ; but no one who reads his reports can doubt that he 

 understood the uplift as clearly as the planing down. Fol- 

 lowing the principles so well and so early applied in Colorado, 

 he afterward perceived that the ranges of the Great Basin, 

 though composed of Eozoic and Paleozoic rocks, are moun- 

 tains of very late upheaval, and that before upheaval their 

 region was "a comparatively low plain, constituting a general 

 base level of erosion to which that region had been denuded in 

 Mezosoic and early Tertiary time when it was an area of dry 

 land" (Uinta, 32). He was thus led to say: "Mountains can- 

 not long remain as mountains ; they are ephemeral topographic 

 forms. Geologically all existing mountains are recent ; the 

 ancient mountains are gone" (Uinta, 196). I can well recall 

 the exclamatory vigor that Powell gave to a statement at a 

 scientific meeting in 1884, and the emphasis that he added with 



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