LINDQREN.] WATER SUPPLY AND WORKABLE GROUND. 677 



7. Anderson ditch. Takes water from Elk Creek below Boulder mine. 



8. Cuddy ditch. Takes water from Elk Creek below Boulder mine. 



9. Dunn ditch. Takes water from Elk Creek below Boulder mine. 



GRIMES CREEK. 



The water supply is here largely controlled by the Wilson Company. 

 The principal ditches are as follows: 



1. Wilson ditch. 12 miles long, on west side of Grimes Creek. Dam located 1 



mile below Charlotte Gulch. Capacity, 2,000 miner's inches. 



2. Gold Trap ditch. 7 miles long, also on west side of Grimes Creek. 



3. American ditch. 6 miles long, west side of Grimes Creek. Dam at Charlotte 



Gulch. 



4. Mountain ditch. 8 miles long, west side of Grimes Creek. Also two shorter 



ditches from Clear Creek. 



GRANITE CREEK. 



The water supply is here controlled by the Ranch Company and 

 the Kennedy Company. The Ranch Company's ditch is 14 miles long, 

 and takes water from Granite Creek above Quartzburg. Capacity, 

 1 ,000 miner's inches. Other ditches lead from West Fork, Fall Creek, 

 and Canyon Creek. 



The hydraulic washings use a pressure of from 100 to 350 feet. 

 There are rarely more th/in 600 miner's inches used in each monitor. 

 Hydraulic elevators have been used by the Wilson Company to work 

 low-bench gravels and tailings. The gravel is elevated from 10 to 25 

 feet. Five hundred miner's inches are here used for the monitors. 



GROUND AVAILABLE FOR FUTURE WORK. 



The largest amounts of gravel remaining near Idaho City are on 

 East Hill and Gold Hill. Though some of the bench gravels remain 

 they are getting rapidly worked out. In the Grimes Creek drainage, 

 some bench gravels still remain near Pioneerville. In the Granite 

 Creek drainage there is a considerable area of low-bench gravels yet 

 untouched near Granite, on both sides of the creek. Considerable 

 gravel remains at the Ranch Company's ground near Placerville. If 

 the conclusions in this paper are correct, there is also a large amount 

 of gravel on the ridge between Wolf Creek and Graniteville. 



In all three drainage branches there are vast amounts of tailings 

 which, with suitable appliances, may be worked over again. But 

 there is no doubt that the placers in course of time will be exhausted. 

 That they are not already exhausted is due to the limited water 



supply 



THE MONAZITE SANDS. 



The sand of the gravels and lake beds of the Idaho Basin is entirely 

 derived from the granite and associated dike rocks. It consists of 

 relatively angular and sharp-edged grains, indicating its manner of 

 formation by extremely rapid accumulation from ,the deeply disinte- 



