110 Gregory — Progress in Interpretation of Land Forms. 



position or form to the sea or to structural factors. 

 They are the work of existing streams which have eaten 

 their way headwards. Even the valleys of Australia 

 cited by Darwin as type examples of ocean work are 

 shown to be products of normal stream work. Dana 

 went further and gave a permanent place to the Hut- 

 tonian idea that many bays, inlets, and fiords are but the 

 drowned mouths of stream-made valleys. In the same 

 volume in which these conclusions appeared, Hubbard 

 (1850) 19 announced that in New Hampshire the " deepest 

 valleys are but valleys of erosion." The theory that 

 valleys are excavated by streams which occupy them 

 was all but universally accepted after F. V. Hayden's 

 description 20 of Rocky Mountain gorges (1862) and New- 

 berry's interpretation of the canyons of Arizona (1862) ; 

 but the scientific world was poorly prepared for New- 

 berry's statement: 21 



"Like the great canons of the Colorado, the broad valleys 

 bounded by high and perpendicular walls belong to a vast system 

 of erosion, and are wholly due to the action of water. . . . The 

 first and most plausible explanation of the striking surface fea- 

 tures of this region will be to refer them to that embodiment of 

 resistless power — the sword that cuts so many geological knots — 

 volcanic force. The Great Canon of the Colorado would be 

 considered a vast fissure or rent in the earth's crust, and the 

 abrupt termination of the steps of the table-lands as marking 

 lines of displacement. This theory though so plausible, and so 

 entirely adequate to explain all the striking phenomena, lacks 

 a single requisite to acceptance, and that is truth." 



With such stupendous examples in mind, the dictum 

 of Hutton seemed reasonable : "there is no spot on which 

 rivers may not formerly have run. ' ' 



Denudation by Rivers. 



The general recognition of the competency of streams 

 to form valleys was a necessary prelude to the broader 

 view expressed by Jukes (1862) 22 



"The surfaces of our present lands are as much carved and 

 sculptured surfaces as the medallion carved from the slab, or the 

 statue sculptured from the block. They have been gradually 

 reached by the removal of the rock that once covered them, and 

 are themselves but of transient duration, always slowly wasting 

 from decay." 



