Geol.— Vol. I.] TURNER— ORIGIN OF YOSEMITE VALLEY. 27 1 



glacial action other than form exists there or not. This is 

 practically to deny that such canyons could be formed by the 

 action of water in a region which had been subjected to great 

 uplift. The existence of hanging valleys^ is sometimes con- 

 sidered an evidence of ice action, but if we picture the 

 Sierra Nevada as being a region greatly worn down, so that 

 the physiographic forms were those characteristic of an old 

 topography, and then sharply uplifted as was probably the 

 case, the streams would certainly cut narrow and deep can- 

 yons, and many of the earlier small shallow valleys draining 

 into these canyons would form hanging valleys, the whole 

 work being purely that of water and weather. If we sup- 

 pose the deep, narrow canyons of the southern Sierra 

 below the known limit of glacial action to be dug out by ice, 

 we must likewise ascribe to the northern canyons of the 

 Sierra, some of which are nearly as deep, the same origin, 

 for the entire range has been subjected to the same influ- 

 ences. Take for example the canyon of the North Fork of 

 the Feather River. There is no evidence that any portion 



Fig. 2. — Cross-sections of the canyon of the North Fork of- the Feather River. 

 ^.— West of Buck's Mt. 5.— Two miles north of Bear Ranch Hill. 



of the canyon of this river, in the area of the Bidwell Bar 

 quadrangle, ever contained glacial ice; yet the canyon is 

 nearly a mile deep at one point and a number of the tribu- 

 tary streams tumble down into it over escarpments from 

 hanging valleys lying above. Moreover, the general form 

 of this canyon, which along here is almost entirely in gran- 

 itic rock, does not differ greatly from that of some of the 

 canyons farther south, which have been occupied by the 

 ice. Small glaciers did exist on the sumit of the plateau in 

 the Bidwell Bar quadrangle to the east and west of the can- 

 yon of the North Feather, but they were of the hanging 



1 Valleys on plateaus near escarpments. 



