the South and Middle Yuba, California. 11 
miner’s measurement, the second to 2280 miner’s inches.* The 
Kureka Lake Water r Company’ s works, commenced in 1858, have 
cost about one million of dollars. 
Experience has demonstrated that the larger the volume of 
water employed in the process of washing, the more the efficiency 
and greater the economy of the operation. The proper a mi om 
tion of the great mechanical force furnished by large volum 
water under a great pressure was a problem solved. satisfactorily 
only after many abortive trials and hg experience. This pro 
lem involves the following conditi 
Ist, The whole mass of neriferous gravel must be moved, 
whatever its depth, quite down to the ‘bed rock.’ 
2d, This must be accomplished by the action of water alone, 
human labor being confined to the application of the water, 
and the preliminary preparations it involves, the amount of 
material to be m isposed of in every day of ten hours 
being from 1500 to 3000 cubic yards for each first class opera- 
tion, involving the use of 400 inches of water. 
, The mechanical disintegration of the compact conglome- 
rate as a part of the uninterrupted operation of the whole system. 
4th, The contemporaneous saving of the gold, without inter- 
rupting the continued flow o 
5th, The disposal of the accumulations resulting from the 
removal of such vast masses of auriferous grave 
These conditions are in practice met by the following steps, 
The nesta ground being selected, a tunnel is projected from 
the nearest and most convenient ravine, so that starting in 
the ‘bed rock’ on the face of the ravine, it shall approach the 
center of the gravel mass to be moved at a gradient of about one 
in twelve to one in twenty. The dimensions of this tunnel are 
La 
tion. These tunnels vary in length from a few hundred feet to 
_* The miner’s inch of water, in California is that quantity of water which will 
pass through an opening of one square inch area under a mean pressure or head of 
six il . In practi i asuri 
inches. In tice the water from the canal is conducted into a m ig 
box (see the accompanying map for a figure of this ) twelve or = urteen 
the sides of which openings are made t 
and extending across three of the sid ones are cl 0 ide 
ves when not in use. The sectional area ander’ which the water flows deter- 
nes of course the volume by rement. us 
slit by two inches in depth, under a head of six inches, is called te — miner's 
A ones foot (=7 749 U. S. gallons) eq s inches. 
any “working y le ten hours, 1,098 cubic feet. The average consumption of © 
ing claim ia active work is equal to three hundred mane s inches. 
oar me as sere flowing ten hours i is equal to 329,400 cubic fee: or 2.4 70,500, 
Uni aed a a greater quantity than is feanieet for the fry of the city 
population of over one ‘hundr api e—Black. 
