284 W. LINDGREN — TWO NEOCENE RIVERS OF CALIFORNIA. 



river and the lower part by tunnels from Nary Red, or from certain parts 

 of Canyon creek. It is doubtful whether this channel extends up to 

 Emigrant Gap. The relations of the bed-rock to tbe lava at this place 

 lead me to believe that it is ratherthe Omega channel, which extends up 

 by Bear Valley house, near Emigrant Gap, and from there connects with 

 the short distance of channel clearly indicated some distance south of 

 ( lisco. Tbe steepness of the sides of this channel, which is remarkable, is 

 illustrated in section F F. In a distance of three miles it has a grade of 

 four hundred feet, or 133 feet to the mile. The channels above Emigrant 

 (Jap do not. I think, carry gold enough to make their exploitation 

 profitable. 



Grades : 

 Dutch Flat to Nary Red, one mile, about 225 feet. 

 Nary Red to Blue Bluffs, four miles, about 125 feet to tbe mile. Tbe 

 bed-rock at Blue Bluffs slopes in toward the ridge. 



The Neocene American River. 



Ridges of older rocks separated the watershed of tbe Neocene American 

 river from that of the Yuba. The North fork of the American drained 

 the region of Forest bill, and its sources are found near Summit valley, 

 at the crest of the range. The South fork drained the Placerville region, 

 and it appears to have headed among the peaks south of lake Tahoe. 

 Only part of the latter drainage system has been mapped. 



THE SOUTH FORK. 



From the Sacramento Valley to Diamond Springs. — The accumulations 

 along the lower part of tbe Neocene American river are to a very great ex- 

 tent destroyed by subsequent erosion, and to reconstruct that part of tbe 

 river is consequently not very easy; moreover, it has only a theoretical 

 interest, since nearly all of the auriferous gravels along it are swept away. 

 In discussing tbe direction of the river from near Diamond Springs, the 

 lowest point to which he traced it down to the plains, \\\ A. Goodyear 

 expresses the opinion that it probably passed through the gap al Pilot 

 Hill and thence to Folsom, where large accumulations of gravel occur* 



Any other course than by Pilot Hill is indeed out of the question on 

 account of high bed-rock ridges. That it followed the windings of the 

 canyon of the South fork where it cuts through these ridges is so improb- 

 able a proposition that it may be left out of the discussion. No remnants 

 of gravels or volcanic flows, however insignificant, are found along this 

 course to give probability to such a view. That the river continued from 



* Aurilerous GravelSj p. 004. 



