pubington.] HYDRAULIC MININO. 145 
to save the gold. The sluice has a grade of 14 inches to 12 feet, and 
90 pounds of quicksilver were used in charging the sluice. 
The percentage of gold in the upper 120 feet of the sluice was as 
follows: 
Per cent. 
In upper 1 foot 75. 
In upper 10 feet 8. 4 
In next 50 feet 9. 6 
In next 60 feet 2. 
This portion of the sluice was cleaned up monthly, and was fur- 
nished with old car wheels, regarded as the best riffle, and with iron 
Hungarian riffles. 
The upper 1,000 feet of the sluice was cleaned up once in three 
months, and the whole sluice and undercurrents annually. Five per 
cent of the total product was obtained from the lower 2,380 feet paved 
with quartz stones, and it is estimated that an amount equal to 2 per 
cent of the total product escaped into the canyon below. It was stated 
that one-half mile of this canyon was leased to the Chinese for $5,000 
per annum, who cleaned up at a profit the gold which had escaped. 
The undercurrent was not regarded as of great value, except for the 
saving of excessively fine gold and free quicksilver and gold with 
quartz attached. 
Mr. W. M. Johnson informed the writer that in Nevada County, 
Cal., in the case of a sluice 1^ miles in length, the first live out of a 
total of seven undercurrents proved an economic success, the last two 
hardly paying to clean up. It was found best to clean the five under- 
currents at intervals of two weeks. 
The experience on Pine Creek, Atlin, in the matter of saving gold 
is not so satisfactory as on McKee Creek, according to operators' 
statements. PL XXIII, A (p. 132) shows one of the 120-foot sluices of 
the Pine Creek Power Company. It is 5 feet b} 7 40 inches, has a grade 
of 5 inches in 12 feet, and is paved with block riffles. The under- 
current, 14 by 24 feet, on a 10-inch grade, was one of the few instal- 
lations of the kind seen in the northwest. It was understood to be 
but the beginning of experiments aiming to save the fine gold that 
escaped with an excessive amount of black sand. The amount of gold 
recovered is 43 cents per cubic yard, as stated, and the Opinion was 
expressed that a large percentage of fine gold escapes. The under- 
current itself had not been installed a sufficiently long time to 
determine its efficiency. 
The Atlin gold is derived from older gravels through which the 
present streams cut. The gold is for the most part coarse, but is well 
rounded. That a certain percentage of it is tine, specimens collected 
show. It is very probable that an undue proportion of such bench 
|gold will escape from a sluice of the short dimensions figured. 
Bull. 263—05 10 
