DISPLACEMENT OF GRAVEL BEDS. 271 



THE NORTH FORK. 



Another series of auriferous gravel deposits which can be connected 

 with North San Juan begins at Camptonville. That this is extremely- 

 probable has been sufficiently pointed out by Mr Pettee.* I may add 

 that here, too, high bed-rock on either side of Oregon creek prohibits 

 any other outlet excepting that cut by the modern canyon. 



From Camptonville this Neocene stream, which corresponds to the 

 present North fork, continued to Depot hill by way of Galena hill and 

 Weeds point (p. 428), and then undoubtedly connected with Indian 

 hill, on the brink of the North Yuba canyon. Near this point it prob- 

 ably forked again, the more important stream crossing the present North 

 fork to Brandy City and Council hill and continuing up toward La 

 Porte and Gibsonville. This branch of the old river will not be followed 

 any further northward in this paper. Toward its sources, near the center 

 of volcanic activity in Sierra and Plumas counties, evidences of disturb- 

 ances of the gravel beds by faulting became very frequent. 



At Depot hill the Neocene stream flowed through a canyon, the walls 

 of which rose about eight hundred feet on the western side and one 

 thousand feet on the eastern side, with a slope often or eleven degrees. 



Grades : 



North San Juan to Camptonville, 91 feet per mile (from a supposed 

 point of junction one and a half miles above North San Juan). 

 Camptonville to Depot hill, 3£ miles, 135 feet per mile. 

 Depot hill to Indian hill, 1 mile, 100 feet per mile. 

 Depot hill to Brandy City, 3 miles, 126 feet per mile. 



THE MIDDLE FORK. 



Badger Hill to North Bloomfield. — It has never been seriously ques- 

 tioned that there is a continuous channel between these points ; its 

 lower course is approximately outlined by the gravel area extending 

 between Lake City and Badger hill by way of North Columbia and 

 Cherokee. The gravel beds here attain the enormous thickness of five 

 hundred feet, and up toward Lake City become covered by thick de- 

 posits of clays and volcanic (lows. 



Grade : 

 For reasons stated later on it is not probable that there is an even 

 grade between North Bloomfield and Badger hill. It is altogether more 

 probable that for the first four and a ball' miles from Badger bill the 

 ^rade is very gentle, about 14 feet per mile, and that the sleeper grade 

 of the North Bloomfield channel begins at a point somewhat east of 



* Auriferous Gravels, p. 428. 



