Several forms are in use. Their dimensions vary according to the duty required. In some cases it is desired to save and settle together all the pulp, including the slimes, when there is too much water present for subsequent concentration. In such event the pointed box should be about 6 feet deep, and 3 feet by 7 feet at the top, the longest sides sloping till they meet at the bottom.

Such a box will settle and save about six tons of ore in twenty-four hours, discharging it automatically and continuously from the bottom by a siphon hose, with the proper amount of water for subsequent concen

tration.

This form is used when the tailings from pan amalgamation are to be concentrated, after leaving the settlers and agitators, for they contain a large excess of water, which must be gotten rid of, so that the tailings are of the proper consistency for concentration.

The accompanying cut shows a form of point box used in cases where the slimes are to be separated from the pulp and saved. Each box is 40 inches square at the top, and 40 inches deep, coming to a point at the bottom; and one box will handle from 6 to 10 tons of pulp in twenty-four hours, making a good separation.

The pulp from the battery, entering the box at the top, is confined by partition E, until it passes into the box proper, near its bottom. Clear water is conveyed from above through a half-inch pipe, which delivers it into the box at the bottom. Care must be taken that this pipe is kept full, so that no air bubbles are carried through it, as they create agitation, and cause sand, etc., to pass off with the slimes.

The amount of clear water needed varies, so it is a good plan to have a cock in the pipe just below the clear water box, or else partially close, with a wooden plug, the opening of the pipe in the clear water box. At D is a hollow plug, and to it is attached a piece of hose, which is used as a siphon, so that the pressure is lessened and too violent discharge of the pulp is prevented.

Without the siphon hose, inches opening would not be too small, while with it inches opening is about right, and the end of the hose is plugged accordingly. Inasmuch as foreign coarse material occasionally gets into the box (prevented as much as possible by a screen over the top), it is advisable to use in place of the hollow wooden plug shown, a 14-inch iron tee with one end plugged, and with inch side outlet, attaching the siphon hose by nipple.

Thirty-five years ago, concentration in California consisted simply in saving the placer gold, and the appliances used were the rocker and sluice. Various grades were given to the sluice; its bottom was formed in various ways, some using plain riffle bars, some preferring blocks of wood sawed across the grain; others liked boards, full of round holes, undercurrent riffles, etc. Sometimes quicksilver was used to catch the gold; sometimes none was used.

When gold was discovered in quartz in California, and reduction works for the same were to be constructed, Californians knew nothing of the required means, and had to adopt the old square wooden stem Cornish stamp, the arrastra, etc., but with our ingenuity, native to Americans, improvements were rapidly made, and to-day American (United States) machinery for mining and reduction of gold and silver ores is the best in the world.

The old fashioned stamp was replaced by the round iron stemmed stamp, revolving as it is lifted by the cam, and with cams, tappets, shoes, and dies of cast-steel, the wear has been reduced to a minimum, and the

present standard American stamp mill is a very different crushing appliance from the clumsy stamps first used by us.

Most of the quartz veins worked in early days were either much decomposed on the surface, or were clean quartz containing the bright yellow gold. As depth, however, was attained, the decomposed ores changed, and sulphurets of iron and copper, with galena, blende, and other minerals, were found. The ore did not yield as much of its gold as the surface ore; there was some gold in the tailings, and further examinations showed that a large part of the loss was in the sulphurets, hence we began to realize that there was money in the sulphurets, and two problems arose:

First-How to save the sulphurets.

Second-How to realize the money contained in them after they were

saved.

In regard to the second problem it was soon known, that if rich enough they could be sold to parties who would send them to or other smelting works in Europe, while in some cases quite a proportion of the gold could be saved by thorough amalgamation in pans or barrels, and about 1867 it was proved that a high percentage of the gold could be profitably extracted from the sulphurets by roasting and chlorination.

As regards the first problem, "How to save these gold-bearing sulphurets," here the necessity of concentration became apparent, as the only economical method was by taking advantage of their greater weight and separating them accordingly.

Labor being very high, automatic concentrators became a desideratum, stimulating the inventive faculties of many who were engaged in mining. Various machines were devised and tested; most of them proved to be of little value, and the appliances in general use for saving sulphurets in California in 1875 were few in number, being as follows:

The sluice with blankets or burlaps.

The sluice with riffles and the buddle.

The raising gate.

The Hendy concentrator.

The grade of the sluice, using blankets or burlaps, was generally about inch to the foot. A double set was used; the blankets or burlaps in one set being taken up and washed, while the other set was in use. By very frequent washings the sulphurets were obtained fairly clean, but this took so much labor that they were seldom washed, and the ordinary product contained much sand, and the sulphurets contained were coarse, the finer sulphurets passing off, although nearly equal in quantity and frequently much richer than the coarse sulphurets.

The grade of the sluice with riffles was about inch to the foot, and was generally of the following type: Two sets are used; each riffle is formed by a half-inch strip of wood, fitting across the sluice, and about ten feet from the next riffle. At stated periods, according to the amount to be collected (varying in different ores), another strip is placed on top of the previous one, and this is continued until the sluice is nearly full at each riffle, when the tailings from the mill are turned into the other set of sluices for similar treatment, and the material accumulated in the first set of sluices is collected, and further concentrated in a buddle, of which there are several styles.

The accompanying cut shows one used frequently, and may be described briefly, as follows: It is circular, with concave bottom, and the discharge for the tailings is in the center, where there is a hollow iron cylinder, shown in the cut, with its top or rim even with the bottom of the buddle. In this position everything will flow out of the buddle, but this ring or

cylinder is attached to an upright spindle and by the gear at the top is gradually raised, retaining in the buddle the sulphurets as they accumulate, and constantly raising the discharge of the tailings; the arms, also, from which the brushes hang, are gradually raised at the same time by the mechanism.

The material to be buddled is delivered from above the center through six pipes at the periphery of the buddle. Very little water is used, and there is no agitation except that made by the brushes, which are constantly moving around the circle, resting on the pulp, and being dragged around by the arms.

By means of the step pulleys above, the gradual raising of the discharge cylinder and of the brushes are regulated as required for the material operated on. When the buddle is full of sulphurets, it is stopped and cleaned out.

This system of sluice with riffle and buddle does very fair work if carefully attended to, but requires a large amount of labor, and does not save the finest sulphurets.

The raising gate may perhaps be best described as the sluice with riffles, improved by having the riffle raised gradually by machinery. The accompanying cut shows the raising gate down, or open; by the gear above it is gradually raised, the speed being changed at will by the step pulley.