414 SUPPLEMENTARY INVESTIGATIONS IN THE GRAVEL REGION, 
underneath it. The main lava ridge rises to an altitude of about 400 feet higher than the upper 
bench. 
The water for these mines is brought from the South Yuba River. The Blue Tent Company 
owns a ditch which, we have already seen, extends above Omega.* The Sailor Flat Company buys 
from the Blue Tent Company, or from the South Yuba Water Company, which has an office at 
Nevada City. At Sailor Flat 1,300 inches of water are used per day, under 300 feet pressure. The 
nozzles are five and six inches in diameter. At the Blue Tent mines the ordinary nozzles are from 
six and a half to seven or eight inches in diameter. Nozzles of nine inches in diameter have been 
sometimes employed. 
Since the organization of the English company at Blue Tent, careful records have been kept of 
the amount of water used, the amount of gravel moved, and the yield of gold. Through the 
kindness of Mr. Hughes I was allowed to take the following data from the company’s records :— 
(1.) Between Sept. 1, 1876, and Aug. 15, 1877, the gravel removed at the South Yuba claim 
(Gopher Hill) amounted to 632,533 cubic yards, which was an average of 54% cubic yards per 
twenty-four-hour inch of water. The yield was 12,8; cents per cubic yard of gravel. 
(2.) For the year 1878, at the same claim, the gravel removed amounted to 501,028 cubic yards, 
or an average of 6,35 yards per twenty-four-hour inch of water. The yield was 14 cents to the 
yard, 
(3.) In 1878, at the “Blue Lead,” there were removed 235,703 cubic yards of gravel, an 
average of 5459; yards per inch of water, which yielded 7 cents per cubic yard. 
(4.) From September, 1876, to August, 1877, there was a very large quantity of top gravel 
moved at the Enterprise ground. The gravel was fine, loose, and sandy, and easily moved. The 
amount removed was 1,398,963 cubic yards, at the rate of 10,1; cubic yards to the inch of water, 
but the yield was only 2,85 cents to the yard, barely sufficient to cover expenses. 
(5.) In 1878, at Gopher Point, a mass of hard, indurated, clayey gravel, which could neither be 
washed nor blasted with ease, was removed at the rate of only 2,°,8, cubic yards per daily inch of 
water. 
From the above figures it will be seen that the average yield lias not been quite as much as was 
estimated at the time of the formation of the company. In Raymond’s report for the year 1873, 
page 115, it is stated that up to that time there had been removed, according to the surveys of Mr. 
Bradley, 5,101,150 cubie yards of gravel. The yield up to that time was estimated at $770,000, 
equivalent to fully 15 cents per cubic yard, —and that to a large extent from the upper strata of 
the gravel, at some considerable distance from the bed-reck. 
Mr. Hughes’s estimate of the probable loss of gold in the hydraulic washings is fifteen per 
cent. 
I have already t alluded to the difficulty of determining the precise position of the old channel 
at Blue Tent, and to the hypothesis adopted by Mr. Hughes, and I might have mentioned at the 
same time another view which is held by some well-informed persons, namely, that the channel 
extends under and across the ridge to a connection, by way of Scott’s Flat, with the enormous 
deposits of gravel at Quaker Hill and You Bet. I was not able to make any personal examination 
of the intervening ground, but from what I could learn by inquiry of persons acquainted with 
the country, and from what I saw at Blue Tent and Quaker Hill, taken in connection with the 
relative altitudes of the bed-rock at the two places, I feel confident that no such channel exists. 
That there was, however, once a connection between the Blue Tent gravel and that at Columbia 
Hill, and, in general, that on the divide between the South and Middle Yubas, cannot be denied. 
The identity of bed-rock level at Gopher Hill and Grizzly Hill has already been alluded to. There 
is also a practical identity in the level of the upper surfaces of the gravel on the two sides of the 
South Yuba. Columbia Hill and Blue Tent are in plain sight of each other with no intervening 
* According to Raymond’s report for 1873, page 115, the Blue Tent Company brings its water through 274 
miles of ditch from Culbertson’s Bridge on the South Yuba River. 
+ See ante, p. 411. 
