PHYSIOGRAPHY OF BISHOP CONGLOMERATE 617 



greater than that of the temporary streams in loosening and carry- 

 ing material down the slopes, for any such piedmont debris must 

 be removed before the wind can attack the rocks at the mountain- 

 base. In an absolutely rainless region there would be no diflficulty 

 in accepting this explanation, but there seems to be no region 

 which is without its occasional rains, and a slight amount of rain- 

 fall distributed as it is in the deserts in the form of local torrents 

 would be sufficient to bring down a considerable quantity of debris ■ 

 from the bare slopes of the mountain — more it would seem than 

 could be effectively disposed of by the wind. 



From the foregoing lines of reasoning it is thought that the 

 planation was the result of long-continued subaerial denudation 

 under conditions of a moist climate. This belief is not held with 

 great confidence, however, for it is recognized that desert erosion 

 might under certain conditions produce similar results. 



The surface of the gravels, from Miller Mountain northward to 

 near the low area, slopes to the north at the rate of between seventy 

 and one hundred feet per mile. The underlying rock-surface has 

 a slightly lower slope. Judging from the present slope and attitude 

 of the gravel-deposits it seems unlikely that there has been any 

 considerable change in slope of the underlying peneplained surface 

 since they were laid down, though there may have been a general 

 elevation of the whole region. The gravel surface is a graded 

 slope and shows no sign of disturbance since its formation. The 

 transportation of large bowlders such as those on Miller Moun- 

 tain would require a considerable gradient, probably as great as 

 that at present. On the other hand, the development of a pene- 

 plained surface as even as that under discussion would require a 

 more nearly horizontal attitude than at present at the time of 

 planation, at any rate if this were accomplished under conditions 

 of a moist climate, as there seems reason to think was the case. 

 Whether or not such a surface with such a slope could be formed 

 under desert conditions by wind scour is more difficult to deter- 

 mine, but it seems unlikely. The present slope would therefore 

 indicate that, unless planation was the result of wind erosion, this 

 portion of the peneplain when formed was more nearly horizontal 

 than now and that it was tilted toward the north at a time of 



