alley is the most productive gold-quartz mining district in the world. al yield of an area drawn by a radius of four miles is $3,500,000. The laborers employed in the mines and mills is 2,000, showing an average oduction for each person of $1,750, and the average yield of the rock $30 to $35. The lodes are narrow, none of them exceeding seven dth, and most being less than a foot. They contain much pyrites, act contributes with the narrowness of the veins to make the 'average extraction and reduction high-about $15 per ton. Some of the works sunk to a depth of 400 feet, but most of the pay-quartz is obtained 0 feet of the surface.

9.—PULVERIZATION OF QUARTZ.

in processes of quartz mining are extraction, Crushing, and amalgamae extraction of auriferous quartz from the vein is like that of ores Any person familiar with copper mining can in a few days learn to gold miner. The quantity of copper ore can usually be discovered ce, but in auriferous quartz it is often necessary to pulverize a piece artz, and wash the powder in a spoon or little basin to see whether it o extract. The cost of tunnels and shafts for opening mines in such usually found about the auriferous lodes is from ten to fifteen dollars foot.

five per cent. of all the crushing in California is done with stamps. p is a block of iron, weighing from 300 to 1,500 pounds, fastened to a - iron shaft, usually iron. A battery consists of several stamps standing de, and in most mills the number of stamps is five or a multiple of

five. The stamps are successively lifted by machinery, and then allowed on the quartz. The height to which they are raised is from ten to inches, and each stamp falls from forty to eighty times in a minute. I culated that each stamp should crush a ton of quartz of ordinary qu twenty-four hours. The mills usually run night and day. Of course, the of quartz crushed depends to a considerable extent on the hardness of t the weight of the stamp, the height of the fall and the rapidity of the bl The fineness to which the roek must be pulverized depends on circum The particles of gold may be very fine, so that the quartz must be rec an impalpable powder before they can be liberated; but if the particles and the grain of the rock are coarse, or if the pulp is to go through a pan, the quartz may be allowed to escape when many of the particles are a as sea-sand, or even coarser. The battery has on one side a screen of wi or perforated sheet-iron, with apertures of the size of the largest partic must be permitted to escape. A steady current of water runs through the so as to carry away the quartz dust as soon as it is fine enough. The sh screens are punched with needles, and are known by the numbers. No. is punched with a cambric needle; No. 3 with a darning needle.

In Grass valley most of the mills use Nos. 3 and 4 screens; elsewh 4 and 5 and 6 are preferred.

A multitude of crushers have been tried to break up the quartz be given to the stamps or other pulverizing apparatus, but the number very small. Those principally in use consist of two heavy iron jaws, w wide apart at the top, and close together at the bottom, and as they w and forth, the quartz is smashed between them. The quartz is usually not larger than goose eggs when delivered to the battery, and it is bro size either by sledge-hammers, or by a large stamp, kept for the pu breaking up the large stones.

The musket-ball pulverizer has been tried as a substitute for stamps. report is favorable, but the trial has not been sufficient to command t dence of miners. It is an iron barrel which revolves twenty-four times ute on a longitudinal, horizontal axis. Inside of the barrel are a nu chilled iron balls weighing an ounce each. The quartz is introduced in not larger than a grain of wheat, and in two hours it is reduced to an im powder.

Another pulverizer, that has been tried without attaining favor, is star or wheel without a rim, which makes 1,000 or 1,500 revolutions p in an iron casing. The quartz is thrown with great force by the arm the casing and is dashed into fragments by the concussion. The cas made with little offsets that the quartz strikes at right angles.

10.-AMALGAMATION OF GOLD.

Much of the gold is caught or amalgamated in the battery. The st into an iron box or mortar, into which an ounce of quicksilver is th every ounce of gold supposed to be in the quartz. If the rock is cru in the battery, two-thirds or three-fourths of all the gold saved may there, leaving one-third or one-fourth that escapes through the screen. After leaving the battery, the pulverized quartz in most mills runs d copper plate which has been washed over with diluted nitric acid, rubbed with quicksilver till the whole surface is covered with amalga particles of gold running over this surface adhere and form amalgam; the plate is covered with gold it operates far more effectually than quicksilver is fresh. Gold unites more readily with gold amalgam pure quicksilver. The copper plate, which is the bottom of a trough may be fifty or a hundred feet long. Kustel in his book on Nevada

ocesses of silver and gold extraction (page 16) says, copper plates as a amalgamation are "very imperfect and mostly abandoned." Impermay be, but they are still used in most of the quartz mills of the State, me of the best, or at least in some of those which produce the largest

of bullion.

n the copper plates in many mills are troughs, in the bottom of which parse blankets, or gunny-bag, or even cow-hide with the hair on and the inst the stream. Gold amalgam and sulphurets are caught in the face of the blanket, gunny-sack, or hide, which must be taken up and t intervals, which are usually not more than half an hour long. aking table used in amalgamation is a long box with transverse diviaining quicksilver. It is set horizontally and is shaken longitudinally, from 100 to 200 short jerks in a minute. By these jerks the pulp is ck upon the quicksilver.

Hayward mine the pulp runs out from the amalgamating battery over ne board, across the grain, and the appearance of the amalgam on this upposed to give the best indication whether the proper quantity of quickbeing used in the battery. If too much, most of the amalgam runs off, little caught on the board is in brilliant round globules; and if not he amalgam has a rusty look.

rastra is extensively used for amalgamating, and it has the merits of , grinding well, adaptability to any place, kind of power, economy of l facility of working; but it is slow, and is therefore not in favor in

8.

's amalgamator, used in many mills at Grass valley, consists of level ith quicksilver at the bottom; and over the troughs are horizontal reylinders with projecting spikes, which stir up the quicksilver and the he latter passes over the trough.

e coming into use slowly in the gold quartz mills-at least in some of nes lately erected in Grass valley. Küstel says of pan amalgamation at present the most perfect gold manipulation," and by it "gold is as close as ninety-five per cent. of the fire assay"-that is, if there are. rets. (Nevada and California processes, page 63.) The general that from twenty to forty per cent. of the gold is lost in the ordinary The pans used are mostly like those that will be described as being e silver mills of Nevada. There is, however, one pan not used for siltion that has found some favor with gold miners. This is Baux and an, which has a tight-fitting cover. The pulp runs constantly with a water down into the pan through a tube at the side, and the light mateing ground runs up and out through a tube in the centre. There is thus t feed and discharge, while in nearly all the other pans a batch of ore and worked, and then taken out to make room for another batch. yerson amalgamator is an air-tight chamber in which quartz that has hed very fine by some dry process is subjected to the influence of su1 steam for half an hour as a preparation for the quicksilver, which is duced and converted by the heat into a vapor, in which form it is suppervade the pulp and get access to all the gold. Cold water is injected" se the quicksilver, and the pulp is drawn up to be separated.

11.-SULPHURETS AND CONCENTRATION.

er the pulp has passed through all the amalgamating processes cusgold quartz mills, it is found that in many ores much of the gold is use of the presence of sulphurets of iron and copper. The presence phurets appears to chill the quicksilver and prevent it from taking hold Id, and many particles of gold appear to be enveloped by them. The

gold can be separated from the pyrites, but heretofore the separation effected mainly in establishments specially devoted to that purpose, an the ordinary mills. It is customary to save the sulphurets and sell the sulphuret works, or keep them until there may be a sale for them. the purpose of saving them, they must be separated from the earthy an matter in the pulp, and this is called concentration. The sulphurets ha cific gravity of 4.5, while quartz has a specific gravity of 2.6. difference in density, it is possible to separate the two.

There are several patent concentrators in use, all made of iron, an like shallow pans. The one more used than any other has a bottom from the edge to the centre, where there is an outlet through which th material runs away. This butlet is, of course, not so high as the rin pan turns on a perpendicular axis, and is shaken back and forth by dred short jerks per minute. A hole in the side is left open for the the sulphurets, which flow out in a steady stream; and lower down is hole, which is opened when the heavier matter is to be taken out.

One of the best cheap concentrators is a long and wide rocker wi bottom and a slight inclination. A boy can work one of these conc rockers for a large mill, and the cheapness of the machine and the slig required for it are great advantages. The sulphurets are arrested by the bottom of the rocker, and need to be taken out at intervals of half Any sluice serves also, to some extent, for concentration.

12.-CHLORINATION.

The most approved method of reducing auriferous sulphurets is chlo As a preparation for this process the sulphurets are roasted. They a in an oven brought to a red heat, retained in that condition for about s or until the smell of sulphur has disappeared. After they have cooled phurets are sprinkled with water, shovelled over, and put into wooder boxes, so made that chlorine gas can be introduced at the bottom and rise all through the mass. The tub or box is kept closely covered, and of gold, which is soluble in water, is formed. After the lapse of for hours water is let in, and the chloride of gold is dissolved by it; the s drawn off into glass vessels, and some sheets of iron are put in; the unites with the iron, and the gold falls as a purplish-brown powder to tom of the vessel.

13.-GOLD IN LOOSE STATE.

Gold mines are divided into the two main classes of quartz and plac Whiskey Hill, near the town of Lincoln, in Placer county, about thi from Sacramento, a large mass of loose slate rock is found, containing able pyrites and about six dollars of gold to the ton. The material that eight tons can be crushed by a stamp in a day. It is supposed t the water-line a vein of hard auriferous copper ore will be found. The auriferous slate in the hill is large, and the mine is considered very one-half of it having been sold for $175,000. Similar bodies of aurife mixed with clay are found at Lander's ranch, Placer county, and at 1 City, in Calaveras county.

14.-PLACERS.

Placer mining is decreasing every year. Every month witnesses the e of some rich placer district, or its exhaustion at least for the pre may be that in the future, when laborers can be employed for fifty day, claims which cannot be worked now will be in demand.

There are large bodies of gravel that contain just gold enough no