HIGH GRADES OF THE TRIBUTARIES. 293 



Blacksmith flat to Russian ravine (on similar assumptions), 7 miles, 

 93 feet to the mile. 



The Duncan Peak Tributary. — A short distance from Big Flume, on the 

 northern side of the ridge, there is a deep trough exposed, and known as 

 Marshall's claim. It is, according to my measurements, 50 feet higher 

 than the bed-rock in Russian ravine on the southern side, and it is filled 

 to a depth of about 100 feet with gravel, of which a little has been 

 hydraulicked. This place is evidently near the confluence of a tributary 

 (•(lining down with steep grade from the vicinity of the old Neocene 

 mountain of Duncan peak. From Flat ravine, on the south side of 

 Duncan peak, it runs down almost as a steep ravine to near the Gray 

 Eagle tunnel ; from here it must have connected across Duncan canyon 

 with the main channel of the American river by way of Marshal Is inlet. 

 Abrams tunnel on Duncan canyon is probably in the same channel. 



Grades : 



Flat ravine to Gray Eagle tunnel, 2 miles, 350 feet to the mile. 



Gray Eagle tunnel to Marshalls inlet, 6 miles, 200 feet to the mile. 



The Canada Hill Tributary. — On the northern side of Duncan peak 

 there exists another equally steep channel with thin angular gravel. 

 Starting from Canada hill it runs down in a northeasterly direction to 

 Sterrett's claim in Sailor canyon. From there its course is not deter- 

 mined beyond doubt, but it most probably curved around southeast- 

 ward and joined the main channel near French meadows. 



Grade : 



Canada hill to Sterrett's claim, in 3 miles, 1,000 feet, or about 333 feet 

 to the mile. 



The upper Course. — From Big Flume the channel makes a curve toward 

 the east and crosses the present Middle fork at French meadows, near 

 Ralston dam. At this point the modern river is higher than the bottom 

 of the old channel, but the distance along which there is no bed-rock 

 exposed is short and there is no reason to believe that the deepest part 

 of the channel is very far below the present river-bed* Very little 

 gravel is exposed from here up toward Summit valley; the rhyolitic 

 flows have also changed character, containing more massive rhyolite and 

 less of tuffs than before. They increase in depth, their thickness at 

 French meadows being 600 feet, and south of Summit valley a maximum 

 thickness of almost 1,000 feet is reached. 



Whether the channel from Big Flume up toward Summit valley will 



* Mr J. H. Hammond, in the Ninth Annual Rep. State Min. of California, plate 2, gives a cross- 

 section from this vicinity where some prospecting has been done by tunnels ami inclines. He, 

 however, places the channel below the North fork, which certainly is incorrect. 



