mining now in use on the Pacific slope, and to add such notices of machines used abroad for similar purposes, and to make such comparisons as would be likely to interest and instruct those engaged in mining, and to furnish the data for a general reply to the natural inquiry, what is the position of the United States in this respect, compared with that of European countries.

The writer desires to make special acknowledgment to the Union Iron Works of San Francisco for drawings of stamp-mills, hoisting works, and other machinery, from which many of the illustrations have been reduced for these pages. He is also indebted, for valuable information, to Mr. Irving M. Scott, to Mr. Moore, of the Vulcan Foundery, and A. S. Hallidie, esq., president of the Mechanics' Institute.

For information concerning the machinery now in use abroad, he has consulted his own notes upon the machinery at the Paris Exposition, and elsewhere, and the works of Burat upon the machinery of the Belgian and French collieries. Having recently, in part, rewritten the report upon mining in the series of reports upon the Paris Exposition, he has felt at liberty to make free use of those pages and of many of the illustrations, electrotyped copies of which had been secured for the purpose. *Report on mining and the mechanical preparation of ores, by Henry F. Q. D'Aligny' and Alfred Huet, F. Geyler, and C. Lepainteur. Washington: Government Printing Office. 1870.

SECTION I.-AGENCIES AND INSTRUMENTS OF BREAKING DOWN ROCKS AND ORES.

CHAPTER LXIV.

WATER-HYDRAULIC MINING.

The placer miner avails himself of the results of forces which have been acting for unnumbered ages. Frost, ice, and mountain torrents, aided by the decay of rocks, have broken down the veins and liberated the gold, leaving it distributed under the gravel and sand in the beds of ancient and existing streams. The force required for breaking up the rocks and veins has been expended and the work of the placer miner is rather to clean up, or harvest, what nature has already mined for him. But the operations of nature have been so vast, and so gigantic have been the deposits made by rivers and floods, that the pick, shovel, and pan are inadequate for the profitable collection of the gold, and other mechanical appliances are brought to bear. Powder and nitro-glycerine are used to blow up and disintegrate the deep and consolidated deposits; water under pressure is made to undermine and wash away high banks of gravel; powerfal cranes and hoisting apparatus, and for some of the harder cemented gravels massive stamp-mills, are required.

As water was Nature's principal instrument in preparing these earth deposits, so, also, is water the surface miner's great agent for breaking down and reassorting them. It is brought to bear directly upon the materials, either with the momentum it acquires in falling from a considerable elevation, or with the gentler force of a shorter fall as it runs down a sloping channel. The first is the hydraulic process, and the second is sluicing. The operation of the first is to break and disintegrate, and of the second to separate, assort, and concentrate. In hydraulic mining, the two are necessarily connected and form one continuous operation. Water falling through pipes from a height of from 100 to 200 feet is delivered through nozzles in continuous streams against the base of a bank of earth. It undermines the bank; the overhanging masses fall to the base and are broken apart and loosened; the water penetrates every crack and pore; large boulders are thrown aside like pebbles; the whole mass is stirred and mingled, while the accumulated waters flow away down the slope thick with sand and earth, leaving the larger boulders and the gold resting clean-washed upon the surface of the bed-rock.

This process is applicable wherever deposits have accumulated to such a depth upon the lower stratum holding the gold that they cannot be economically removed by digging. For its successful operation there are two essential conditions: first, sufficient head or height and quantity of water; second, a rapid fall or slope from the base of the bank, so that the water will flow swiftly away and carry the loosened gravel, sand, and earth with it. In California there is comparatively little difficulty in attaining these conditions by an adequate expenditure of money. The high mountains give numerous streams flowing toward and across the gold region, and the deep valleys and ravines permit of ample fall and

drainage. But the streams have to be diverted from their courses and carried in ditches and flumes for many miles along the hillsides, while in most cases the best gold deposits are in trough-like or basin-shaped depressions, hemmed in by rocky walls, through which artificial outlets must be cut, so as to give the requisite drainage.

Thus, when the position, depth, and richness of a deposit are ascer tained, and it is decided to work it by the hydraulic method, the first operation is to provide an outlet for the water. This is done by cutting a tunnel through the rim-rock from an adjoining ravine or valley, so as to tap the lowest part of the basin, and, if possible, to secure a vertical fall of fifty to one hundred feet from the base of the deposit. Such tunnels are usually costly and laborious undertakings; they require great engineering skill for their proper projection, and often many years of time. In driving some of the longer tunnels, from five to seven years have been consumed and an expenditure of from $10 to $60 per linear foot incurred. They vary in length from a few hundred feet to a mile, and are usually from six to eight feet in width by seven in height.

MINING DITCHES IN CALIFORNIA.

In the year 1867 there were 5,328 miles of artificial water-courses for mining purposes in the State of California, besides the subsidiary branches, estimated at over 800 miles more. These water-courses are ditches cut, wherever possible, into the earth of the hillsides, and crossing rocky points and deep valleys by means of flumes, or, better, in iron pipes. The ditches are usually about eight feet wide at the top, six at the bottom, and three feet deep. The grade varies from twelve to eighteen feet to the mile. Formerly flumes were constructed on a large scale and at great cost; but now large sheet-iron pipes are substituted with great advantage in durability and economy. Some of the flumes were of great length and height; one near Big Oak Flat, in Tuolumne County, being 1,300 feet long and a part of it 256 feet above the surface and supported upon wooden towers. Upon the Truckee ditch there were, at one time, 13 miles of flume, eight feet wide and four feet deep, hung upon the side of a deep cañon. Upon the Pilot Creek ditch there was one piece of flume 300 feet long and 95 feet high.

The boards used for making flumes are usually from one and a quarterto one and a half inch thick. They are laid down rough and then battened. Sills are placed at intervals of two and a half feet, with posts and a cap for the support of the flume-box. The sills are four inches square, the posts three by four, and the caps one and a half by four inches. In addition to the first cost of a flume, it is expensive to keep in repair, and is liable to a great many accidents. It may be burned or blown down, and if it is left dry for several months, all the boards curl up and split so that they cannot be used again. It is said that the repairs of a flume cost 90 per cent. more than those of a ditch. For all these reasons, flumes are not now constructed where they can possibly be avoided, and iron pipes are substituted. These pipes are made of stout sheet-iron or boiler-iron, and vary in size from 10 to 40 inches in diameter, according to the quantity of water to be carried. From 7 to 11 inches is a common diameter for the smaller pipes, and these are made of No. 20 iron. A sheet two feet wide and six feet long will make two joints of 11-inch pipe. These joints are put together to form sections 20 feet long, and these sections are united upon the ground and secured by means of strong wire wound around two projecting ears or hooks of iron, one upon each section. The whole pipe is also firmly fastened to the surface

by posts securely set in the ground, to prevent its weight from carrying it down the steep slopes. The examples of the successful use of pipes for carrying water across depressions and ravines are numerous. Upon the South Fork Canal, in Eldorado County, a pipe is used to carry 50 inches of water across a valley 1,600 feet wide and 190 feet deep. This pipe is 10 inches in diameter, the iron about one-sixteenth of an inch thick, and the supply end is ninety feet higher than the delivery. On the Excelsior Company's ditch, near Smartsville, there are five miles of low flume, 6,000 feet of 40-inch pipe, 3,000 feet of 20-inch pipe, and half a mile of 38-inch pipe. The 40-inch pipe crosses a depression 150 feet deep, and with a head of thirty-two feet carries 2,500 inches of water. Upon the Dutch Flat ditch there are 3,500 feet of 31-inch iron pipe and 837 feet of 32-inch pipe.

The aggregate cost of the ditches in California for the supply of water is reported as $15,575,400.* They are generally built by companies and owned distinct from the mining companies; and the water is sold to the miners at so much per inch per day of ten hours.

THE MINER'S INCH OF WATER.

The miner's inch of water is not a very definite and fixed quantity, for the methods of delivering it differ in different places. It varies according to the pressure or head and the height of the aperture. Usually the pressure is six inches, and the aperture is a horizontal slit one inch high and about twenty-four inches long, which can be closed to any desired degree so as to leave an opening one inch long, giving one inch of water, or ten or twelve inches long, giving corresponding numbers of inches of water. It is thus usual to consider the miner's inch as that quantity which will pass through an opening of one square inch area under a mean pressure or head of six inches. The quantity discharged from such an opening (one miner's inch) in twenty-four hours is equal to 2274 cubic feet. A cubic foot is equal to 7.49 United States gallons, or thirty-eight miner's inches.

The Eureka Lake and Canal Company deliver water through an aperture two inches high and under a pressure of six inches. The amount delivered by them through an aperture twenty inches long and two inches high is considered to be forty inches. Upon the Excelsior ditch, and also upon the Sear's ditch, water is delivered under a pressure of ten inches, measured from the center of the orifice. Upon the Mokelumne Hill and Campo Seco ditch, water is delivered under a pressure of four inches. The Phoenix ditch Company deliver it through an orifice three inches high and under a pressure of four inches over the orifice. Upon the Gold Hill ditch, El Dorado County, a miner's inch has been measured out through an orifice two inches high and an inch wide under a four-inch pressure. Another ditch in El Dorado County has sold for an inch of water the amount that escapes through an orifice three inches high and an inch wide without pressure.

At Smartsville water is sold with a head of nine inches with a fourinch opening 125 inches long, giving 11.8 per cent. for an "inch more than is usually given. The quantity discharged through an opening four inches deep, with a nine-inch head over the middle of the opening with the coefficient of discharge =.0615 is 106.6 cubic feet per hour, or 1.7767 cubic feet per minute.

A "head of water" is 500 inches daily for ten hours, and is the quantity required for a first-class hydraulic operation.

*Langley's Directory, 1867.