contained a large number of very fine colors to the pan, but of inconsiderable weight. The gravel from the remaining eighty-seven feet, sunk to the bed-rock, contained coarser and heavier gold, the last eight feet averaging from 5 to 20 cents per pan. Drifts opened from the bottom of this shaft were systematically sampled and compared with equal quantities taken from the layers of the upper bank. The several samples aggregated two and a half tons, all of which were panned out carefully in two hundred and forty tests; and the results obtained showed that the blue or lower gravel stratum contained $1 50 per ton, while the white or upper gravel gave a large number of fine colors, but of insignificant weight.

From 1870 to 1874 the North Bloomfield Mining Company washed three and one-quarter million cubic yards of top gravel, which yielded only 2.9 cents per cubic yard and a gross profit of $2,232 84. In 1877 a rough estimate was made of the comparative yield of the upper and lower gravel washed during the year. The top gravel was

assumed to be from a few feet to over two hundred feet deep, and the bottom gravel sixty-five feet deep.

The results obtained were that 1,591,730 cubic yards of top gravel yielded 3.8 cents per cubic yard, and 702,200 cubic yards of bottom gravel returned 32.9 cents per cubic yard.

Patricksville Light Claim.-To investigate more thoroughly the question a test of top and bottom gravel was made at the Light claim, Patricksville: 58,340 cubic yards of top gravel yielded $1,200, or 2 cents per cubic yard. The bottom gravel (four feet deep) was then washed, when it was discovered that two thirds of this gravel had been drifted extensively; but notwithstanding this fact 4.965 cubic yards yielded $2,775 07, or 55 cents per cubic yard.

La Grange Light Claim.-A trial of top dirt was also made at the Light claim, La Grange: 41,038 cubic yards of top dirt yielded $1,500, or 3.7 cents per cubic

yard. The ground, in both of the last mentioned instances, was surveyed and the returns per cubic yard are as accurate as it is practicable to obtain.

Polar Star Mine.-In the appendix to the "Auriferous Gravels of the Sierra Nevada of California," Professor W. H. Pettee estimates the value of the top gravel at the Polar Star Mine to be about 11 cents per cubic yard, and at Quaker Hill the yield of the top gravel is supposed to approximate 6 cents per cubic yard. The yield of the bottom gravel, however, is not given, and the estimates of the upper gravel are approximates based on the statements of others, and not the results of accurate detailed surveys.

1

CHAPTER V.

AMOUNT OF WORKABLE GRAVEL REMAINING IN

CALIFORNIA.

THE quantity of auriferous gravel remaining on the flanks of the Sierra Nevada is very great, but necessarily the amount available for hydraulic mining is limited.

Minimum Pay Yield.-The minimum yield per cubic yard of material which can be mined profitably, must be considered in determining the extent of workable deposits. This cannot be stated in advance without a knowledge, in any given case, of the other factors: as area of ground, character and depth of deposit, facilities for working and dump, supply and cost of water, price of labor and amount of capital invested. In certain localities, even under very disadvantageous circumstan ces, it has paid to work gravel yielding only four cents per cubic yard; and Mr. Skidmore states that, within his personal knowledge, a claim near Iowa Hill, Placer County, in 1879 paid "a fair profit" when the product was only three cents per cubic yard.

With an abundance of cheap water, four per cent. grades, good dump, banks of light gravel one hundred and fifty feet in height and over, a large area of ground, labor at one dollar per diem, and good management, the total running expenses ought not to exceed three cents per cubic yard at the present time, and with present methods. Therefore under these conditions gravel yielding more than three cents per yard ought to pay a greater or less rate of interest on the capital invested in the purchase of the claim and water rights, the building of necessary ditches, flumes, pipes, etc., and in the other appliances requisite for commencing active operations.

The reports of the State Engineer of California (1880) and of Lieut.-Col. Mendell, U. S. A. (1882), give the following data of the estimated amounts of workable gold deposits remaining along the rivers of the principal hydraulic region on the west flank of the Sierra Nevada in California:

The Upper and Lower Feather, large amounts......
The Yuba and its tributaries, about..

Cub. yds. of Gravel.
Unestimated.

700,000,000

The Cosumnes, principally at Hill Top, from 11,000,

"The quantity of auriferous gravel now remaining on the flanks of the Sierra Nevada is practically unlimited. Only a comparatively small portion of the whole can be regarded as workable under existing conditions." *

Since Mr. Hague's report upon Eureka Lake property (1876), wherein it is stated that the quantity to be mined between the Yubas was 700,000,000 cubic yards (roughly estimated), explorations have proven that this estimate is too large. It is true that there was that quan tity of gravel, and perhaps more, in that locality. But since then a quantity, possibly exceeding 100,000,000 yards, has been mined out, and the result of the work has proven that a portion of this gravel channel can never be mined profitably, for the reasons, 1st, that it is capped with lava and cannot be hydraulicked, and it will not pay to drift; and, 2d, another portion is so situated that it is impossible to drain it, or it is too far from the streams to dispose of the débris. It is now estimated that not more than 400,000,000 cubic yards of gravel remain here available for washing.

* Report on Mining Debris in Cal. Rivers, by Lieut.-Col. G. H. Mendell, U.S. A., p. 35.

CHAPTER VI.

THE DIFFERENT METHODS OF MINING GOLD-PLACERS.

THE gold alluvions occur in many different forms: in river channels, in basins and on flats, as surface deposits of sand and gravel, or as accumulations of detritus (consisting of clay, sand, gravel, pebbles, and boulders of all sizes) covered with varying thicknesses of lava and other volcanic products.

Miners' Classification of Deposits.-Miners classify the deposits in various ways, according to their mode of occurrence and topographical position, and according to the mining systems employed in working them. The term "shallow placers" is applied to deposits whose depth varies from a few inches to several feet, to distinguish them from "deep placers," which often cover large areas and have a depth varying from one hundred to several hundred feet.

"Hill Claims," or deposits of gravel on hills; "Bench Claims," or placers occurring in bench form on declivities and above the level of existing rivers; "Gulch Diggings," found in gulches and ravines; "Flat Deposits," on small plains or flats; "Bar Claims," or bars of sand and gravel on the sides of streams, generally above the waterlevel; and "Beach Sands," or the auriferous sands of the sea-shore, are terms in common use, as well as the names "sluice," "drift," and "hydraulic " diggings.

Classification of Mining Operations.-The mining methods in common use may be divided into two general classes-viz., Surface-Mining and Deep-Mining.