270 w. i.im><;i;kn — two neocene riveks of California. 



it is met with is at the " Buena Vista slide/"* a few miles east of Grass 

 Valley : it is here covered by heavy masses of rhyolitic sand and tuffs— 

 an overflow from the main South Yuba channel ; from here it passed by 

 Krcs and Union hill across the eroded gap of Grass Valley, and thence 

 on through the volcanic ridge down to Rough and Ready. The possi- 

 bility is not excluded that this Grass Valley channel belongs to a some- 

 what later period than that of Nevada City. 



( trades : 



The average grade from the Manzanita diggings to supposed junction 

 with the main Yuba near Mooney Hat, 16 miles, is 115 feet to the mile. 



The same from Buena Vista to the same junction, 16 miles, is about 

 1 22 feet to the mile. 



The actual grade of the Grass Valley channel from Buena Vista slide 

 to Rough and Ready is about 72 feet per mile. This necessitates a heavy 

 fall for the lower part of the Neocene Deer creek. 



French Corral la North San Juan. — Between these two points the 

 channel is nearly continuous, and the volcanic beds once covering the 

 gravel arc almost completely eroded. This part of the channel has been 

 described in detail in "Auriferous gravels," page 190 et se<p and page 

 .'is.") et seq., and also previously to this by Mr J. D. Hague. f Attention 

 should he called to section B B, which excellently illustrates the topog- 

 raphy of the ancient valley. It is seen that, without allowing anything 

 for subsequent erosion, the northwestern side of the valley rose 1,300 

 feet in a short distance; it culminated in the (not shown) Oregon peak, 

 a high diabase ridge 1,700 feet above the channel. 



Grade : 



From French Corral to North San Juan the grade is pretty regular 

 and averages, in 7 miles, 05 feet per mile. 



North San Juan to Badger Hill. — In seeking to trace the Neocene rivet- 

 further up the slope from North San Juan there are only two places 

 which can he connected with it. The one which doubtless indicates the 

 continuation of the main channel upward is Badger hill. The stream, 

 of which we find the outlet at Badger hill, must in fact have connected 

 with San Juan ; high bed-rock bars any other way. This lias been 

 universally recognized by all investigators of the region. 



Grade : 



North San Juan to Badger hill, 4] miles, 80 feet per mile. 



# 



*The elevation of the bed-rock at this place is somewhat doubtful mi account of sliding masses 

 of claj and sand ; it is probably not far from 2,750 feet. 



fThe Water and Gravel Mining Properties belonging to the Eureka Luke and Yuba Canal Com- 

 pany, 1876. 



