202 \Y. LIXDGREX — TWO NEOCENE RIVERS OF CALIFORNIA. 



present Middle fork should be noted, as well as the bend in its lower 

 course, which closely follows the curve of Long canyon. 



The Lower ( iourse. - < >n the Long canyon divide — i. c., from the Ralston 

 mine to the place called Big Flume on the map — the deposits in the 

 channel preserve about the same characteristics. The general form of 

 valley and depth of deposits are illustrated in section ////(plate 7). 



It appears as if the channel in the Long canyon divide had in mosl 

 places a broad, flat profile. On the bed-rock, as a rule, lies from twenty 

 to forty feet of non-volcanic gravel, composed of quartz. quartzite and 

 granite. Above this rests a series of alternating rhyolitic tuffs and 

 gravels with rhyolitic pebbles, which ranges in depth from L50feet at the 

 western end of the ridge to 400 or 500 feet up toward Big Flume. In 

 the western part of the divide the volcanic gravels are heavier, reaching 

 80 or 100 feet at the Ralston mine. Toward the east they grow thinner 

 and the rhyolitic tuffs begin to predominate. Above the rhyolitic tuffs 

 lie from 700 to 800 feet of andesitic breccia. The center of the channel 

 evidently lies on the southern side of the ridge toward Long canyon, and 

 an almost continuous fringe of gravels and tuffs are exposed along this 

 line. At Blacksmith fiat the bed-rock is propably not far above the 

 deepest depression in the center of the channel, which here reaches its 

 most southerly point. A smaller tributary at this place came in from 

 the south by way of Corcorans diggings and Clydesdale, the bed-rock at 

 the latter place, near the point between Long and Wallace canyons, being 

 a little higher than that of Blacksmith fiat. Again, at Russian ravine. 

 one mile south of Big Flume, the bed-rock is probably nearly as low as 

 that of the deepest channel. 



Numerous attempts have been made on a small scale to mine these 

 gravels. At Ralstons the upper gravels have been hydraulicked with 

 satisfactory results ; many small diggings are found along the rim on the 

 southern side of the divide as far up as Big Flume, hut nowhere, so far as 

 1 am aware, has any systematic and extensive work been undertaken in 

 order to open up tins magnificent channel by means of tunnels. It 

 would seem very likely that some paying ground would he found along 

 it: some risk must he taken, for it is of course impossible to predict 

 whether a certain gravel channel will pay for drifting or not without a 

 trial. That the channel exists and that it is of great dimensions is quite 

 certain, hong canyon is said to have been rich in early days as far up 

 as Russian ravine, while the Middle fork contained less gold. 



( rrades : 

 Ralston mine to Blacksmith fiat (assuming thai the bed-rock at the 

 latter place is hut little higher than in the deepest channel), 5 miles. 65 

 feet to the mile. 



