The feed box at the back of the table extends from end to end, and is divided by a movable gate, the pulp being fed in one end and clear water along the rest of the length, keeps the headings clean, so that the operator can tell at a glance how the table is working.

A set of cleats, 2 to 7 in number, according to the character of the ore, is nailed along the table parallel to its length. These cleats taper gradually from inch thick at

the upper, or tailings, end of the table to a feather edge at their lower end. The first and longest cleat is put on towards the lower edge of the table and runs up to within 2 feet of the head. The other cleats are successively shorter, the top one being about 4 feet long. The pulp is fed in as near the tailings end as possible, and the heavier mineral sinks to the bottom and clings there. The cleats prevent it from sliding straight across the table and off, and at the same time allow the particles of lighter minerals, which are held in suspension in the water by the jerk of the table, to pass over and off. The tapering of the cleats provides for a considerable range in the size of the particles of gangue and renders the extremely careful sizing, which must be done for most concentrators in order to get the best results, altogether unnecessary. The finer gangue, which is held in suspension in the stream of water, is carried over the cleats with it, but the coarser particles sink. At each jerk of the table, however, they are thrown momentarily into suspension, and as they work towards the end of the cleat, they finally come to some portion which is low enough to allow them to pass over. This operation must be repeated at each cleat. The space between the end of the lowest cleat and the head of the table allows the middlings, or unseparated ore and gangue, to pass over the edge of the table into a middlings trough, through which they flow to a wheel conveyer, which raises them into a launder returning to the feed trough, to be retreated. This insures a clean heading and at the same time prevents the loss of the mineral in the middlings. An inclined shield prevents the tailings from entering the trough. This table has shown a

remarkable saving, taking the ore right from the stamps, like the bumping table, without previous classification; and it has been proved that it can compete, at least on even terms, with the best of the belt vanners on coarser products and has a much larger capacity-15 to 25 tons in 24 hours, or equal to the best bumping tables, with a much better separation.

8. Cammett Concentrator. This machine is constructed on the Rittinger model and has recently received

FIG. 3

It has also come

much praise for accomplishing good work. into prominence owing to its being able to closely separate different metal minerals, such as zinc, iron, lead, and copper sulphides, from each other. The designer of the Wilfley concentrator imagined that the Cammett was an infringement upon his table, and so brought suit against the latter. While the suit was pending the Wilfley people bought out the Cammett people, whereupon the Court decided in favor of the former against the latter. The table is shown from the operating side in Fig. 3.

9. Construction of the Cammett Table.-The top of the table consists of redwood boards a, in which longitudinal riffles are cut. These riffles are said not to warp,

break off, turn up at the ends, or split. It will be noticed that the riffles are continuous from end to end of the table and that they gradually become flattened until, at the discharge end, the grooves are scarcely noticeable. The pulp distributing box b is constructed on the principle of delivering the coarse ore at the head of the table and the fine ore near the tail end. The box is suspended on brackets and moves with the table top, thus insuring agitation necessary for classifying and to prevent clogging. The table is moved by the cone pulley c, which is connected by a belt 2 inches wide to a similar pulley on a countershaft, which should make about 250 1evolutions per minute. The floor space occupied by this table is 6 feet 4 inches wide by 16 feet 1 inch long. The height of the table over all is 34 inches. To further insure that the table top retain its original shape while in motion under its load of pulp and water, the proper points at which to place the bearings were determined by a system of balancing, by which parts remote from the bearings balance each other, producing equal pressure on each bearing and relieving the middle portion of the table top from strains. The satisfactory result obtained can be seen in the absolutely quiet state of the water on the table top when the table is in operation.

The pulp distributing box is one of the special features of the table and has been designed after many extensive experiments and practical working tests. This distributing box is a modification of the well-known spitzkasten, which classifies the pulp, delivering the coarse at the head end of the table and the fine near the tail end. The box is suspended on brackets and moves with the table top. This insures the necessary agitation requisite for a classifying action and also prevents clogging at the discharge outlets, a grave difficulty encountered in other forms of distributing boxes. With each box is provided a set of various sized outlets, made of a non-wearable material.

The wash-water pipes, three in number, are connected to the main water supply pipe by angle valves, enabling the flow of wash water to be regulated to any degree and for any

part of the table. These pipes discharge the water into separate compartments of a wooden trough, which distributes the water in a uniform sheet over the table surface.

It requires one-half horsepower to drive a Cammett concentrator by an electric motor, and this power will give about 10 tons of fine slimes in 24 hours, while on coarse ore the product will be very much increased. The size of the pulp may be from 3 mesh to the finest slimes, although such a mixture cannot be treated without previous sizing, as slimes are more difficult to concentrate than coarser material. The water required for this table will vary from 5 to 20 gallons per minute. Middlings must be recrushed before placing them back on the table.

10. Belt Vanners.-Belt vanners are of two types: the side-shaking and the end-shaking. The principle, however, is the same in both. The end-shaking vanner is comparatively little used, as the side-shaking machine is the better, both in principle and construction. End-shaking machines, however, are still used in some mills where the conditions are such that they do practically as good work as the side-shaking machines; but they require a larger amount of water, a greater inclination of the belt, or a more rapid shaking motion than the side-shaking machines, in order to do the same work.

11. Frue Vanner.-The Frue vanner, shown in Fig. 4, is the original side-shaking machine, and is typical of the class. It consists essentially of a continuous rubber belt traveling slowly up a slight incline and shaking rapidly back and forth sideways. The belt is usually 4 feet widethough 6-foot belts have been used—and has elastic raised edges. It runs over two large galvanized-iron rollers A, 13 inches in diameter and 12 feet apart from center to center, set at either end of a slightly inclined frame. This frame is supported from the fixed frame or table of the machine by eight flat steel rods or springs, which allow it to swing back and forth laterally, and eccentrics on a