I find no space in the present volume for a discussion at length of the principles of the concentration and separation of ores, which I hope to publish next year. Meanwhile, I desire to describe and recommend a continuous jig, designed by Dr. F. M. Stapff, M. E., a Swedish engineer of skill and experience, who, having tested its efficiency in practice, offers it for trial and the free use of the American mining community, at the same time preventing its being patented by publishing this description. He does not claim the entire invention of an apparatus which is a combination of parts frequently and successfully used in jigs of different construction, it being easy enough for experts to recognize those new and essential features in arrangement and construction by which his machine surpasses similar ones of older date.

The cut subjoined represents a machine built in full accordance with Dr. Stapff's designs, which was constructed at Bethlehem, Pennsylvania, for the Dolores lead mine, Mexico. The ores from this mine, galena and black carbonate of lead, are associated with small quantities of zinc-blende, copper and iron pyrites; they contain calcspar as essential gangue, and are easily dressed. But in Sweden good use has been made of quite similar jigging-apparatus for dressing copper-ores, containing copper pyrites, iron pyrites, and blende in a gangue of quartz, hornblende, and other silicates.

Sizing. It should be understood that the jigger is constructed for the. treatment of sized stuff. We cannot here enter into a description of sizing-machines, and will only mention that the size of meshes in the sizing-screens, and the number of screens subsequently used, must be made dependent upon the specific gravity of the minerals to be separated by the jigging process. For the separation of calcspar and zinc. blende from galena, (Dolores,) the width of meshes in successive sizingscreens should be about 1.00, 0-64, 0.41, 0.26, 0.17, 0.11, 0.07, 0.04 inches, when perforated plates, with round holes, or, 0.70, 0.44, 0.29, 0.18, 0.12, 0.07, 0.05 inches, when wire-gauze with square holes is used. Stuff passing through 0.04-inch meshes is too fine, and stuff remaining upon to 1 inch meshes is too coarse for proper treatment by this jig, which, however, by some slight alterations in constructive details, can be made fit also for the working of coarser or finer stuff. All material fed on the jig should be free from dust.

General arrangement and modus operandi.―The main box contains six compartments, viz: A, open for the circulating water; B' and B", concontaining the pump-pistons E and E"; C', and C", receptacles for the jigged products; D, a space for filtration of the water from the refuse. The raising pistons press water through the sieve-beds, F' and F", while they draw water from A through the valves, e' and e", to the chambers B' and B". A consequence of the water's rising in B' and B", and of its sinking at the same time in A, is a current from left to right along the sievebeds to D, and thence through the holes, k' and k", back to A, by which the medium water-level in the whole vessel is restored. The valves, d", d", allow the water to pass through the sinking pistons, so that there is no suction against the sieve-beds, and no current from right to left is

effected by the back-stroke of pistons. Sized stuff fed upon the sievebed F', from hopper G, is jigged by the thrusts of water from below; but at the same time being exposed to the horizontal water-current, its lighter particles are carried across the ridge c', and after being exposed to a new jigging operation on sieve-bed F", the refuse is carried across the ridge c" to the chamber D. The heaviest parts of the jigged ore move close along the sieve-beds F' and F", and enter the receptacles C" and C", through the gates g' and g", respectively. Screens of woven wire, attached before the holes and k", prevent the refuse from being carried to chamber A. Along the inclined screen ", the refuse is led to a discharge-opening, m". Continual feeding from hopper G is regulated by moving the plate f, which allows more or less stuff to be


drawn from the hopper by the fluctuations of the water. The regular horizontal movement of the ore from left to right is promoted by a slope of sieve-beds of 1 to 36. By slides h' and h", in front of the openings g' and g", the quantity of products entering the receptacles C' and C", is so regulated that the upper surface of the ore in process of treatment is about level with the ridges C' and C". If plenty of water (one cubic foot per second) can be disposed of, the discharge through the holes m', m", m", from the chambers C', C", and D, should be continual; but if water is scarce, the receptacles C' and C" are emptied periodically. The

refuse-hole m' should never be totally closed, in order to allow the refuse to escape continually with a certain quantity of water, which has to be replaced from above.

The pistons, by through-rods and cross-heads connected with levers. O, receive their movement from cams L, working against the lever. It being favorable for the

jigging process that the pistons sink slowly, but rise rapidly, the downstroke is caned directly by cam, and the upstroke effected by a counterpoise Q, on the end of lever O. By alteration of the weight of this counterpoise, the velocity of the rising pistons may be changed at pleasure. Fine ore must be jigged by short strokes, coarse ore by long ones. For chang ing the length of stroke at pleasure, a set-screw, t, is placed over the guide-bar v of the lever O. By this means the back-arm of lever O can be raised so much that the cam L does not catch the head of the other lever-arm at all. Then the piston will rest, though the cam-axle is rotating; or it can be lowered so much as to allow the cam to catch the lever-head 3 to 4 inches above the releas

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ing points, and then the stroke will be about 3 inches. The set-screw can be moved along the guide-bar while the machine is in full motion. An elastic cushion of rubber, r, is applied above the set-screw, to moderate the shocks of the falling lever.

All other circumstances unchanged, the quantity of ore jigged in a certain time depends essentially upon the number of piston-strokes. But this number must not be increased so much that the ore on the bed has not time enough to settle between two strokes, consequently the jig should be run slowly, (about 60 strokes a minute,) if coarse ore is jigged by long strokes, and fast, (about 180 strokes a minute,) if the finest ore is jigged by very short strokes. The most favorable number of strokes in any case can easily be produced by running the drivingbelt on one of the three pulleys of different diameter on the same camshaft.

From the preceding it is easy enough to see the wide applicability of this jig. If the hopper is regularly filled, and everything else regulated in accordance with the nature of the ore jigged, viz, supply of water,

number and length of strokes, feeding (by regulator f,) discharge, (by regulators, g' g',) outlet of water, products and refuse, (by holes, m' m" m",) the receptacle C' will receive the heaviest ore, receptacle C an intermediate class of ore, box D gangue, or rock fit for the stamp-mill. The products of the jigging process, and the further operations they have to pass through, vary in accordance with the mineralogical character and the size of the treated material.

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Fine Dolores ore will give galena and lead carbonate in receptacle C', blende in receptacle C", and calcspar in box D; coarse Dolores ore, galena and carbonate in C', blende, mixed with galena, carbonate and spar in C", spar, with little blende, and traces of leadore in D. In this case it is necessary to submit the crushed products from C" and D to further dressing operations.

The power necessary to drive this jigger depends upon the area of pistons, and upon the number and length of piston-strokes. Half a horse-power is in all cases sufficient to work a jigger of 18 by 18 inches piston area. The quantity of material worked in a certain time is greatest if the stuff is rich and of middle size. Of poor copper-ore, 6 to 7 cubic feet are worked in an hour. Some details of construction.—Most of the constructive details of a jigger built of wood can be seen from the cut, without further explanation. If acid water is to be used for the jigging operation, wood is the best material; and, besides, it is the cheapest. Leaks in a well-constructed wooden jigger-box are usually calked by dirt after the jiggerhas been used for some time, and, besides, it is of no practical account if a few drops of water leak from a vessel through which to 1 cubic foot is run per second. The outside walls of the jigger-box should be at least 3 inches thick, the interior partition-walls 2 to 23 inches. The planks forming these walls should be united by hard-wood wedges filling grooves. It must be remembered that soft and dry wood expands transversely about 3 inch per foot by soaking. A wooden box constructed in accordance with the cut remains not only tight enough, but it can also be easily taken apart, and put together. Grooves in the side walls hold the bottom, which is stiffened by transverse rails; the end walls are fastened in the bottom and side walls, the long partition in the bottom and the end walls, the short partitions in the bottom, long partition, and front walls. Bottom rails and posts form a frame around the box, and by pieces between the rear wall and long partitionwall the whole construction is secured. The discharge-holes m' m'' m''' should not be closed otherwise than by wooden.plugs or exterior trapdoors, which by weights working on knee levers are pressed against nozzles. Close above the bottom are gates i for cleaning the chambers A B' B" D' when they become obstructed by dirt.

The pistons do not slide directly on the walls of partitions B' and B",

but on hard-wood linings, which can be replaced, piece by piece, if necessary. The main valves c' and c", of rubber, are stiffened by thin sheet-covers; their wooden valve-seats are kept in place by buttons. Each piston is covered by four light rubber valves.

The meshes in sieve-beds F F" and in. screens must be fine enough to prevent the ore from passing through. But it is not necessary to use as many different sets of sieve-beds and filtrating screens as there are sizes of ore. Two sets answer all practical wants. Wire gauze, with very fine meshes, which has to be used if the finest stuff is worked, should always be protected against too speedy abrasion by wrappers of coarser gauze. The frames covered with wire cloth (F' F",

rest loosely upon and behind wooden strips, and are kept in position by the large frame H, which is common for all compartments in the front part of the jigger. This frame contains the ridges and c", and the gates f, h', h", which move in grooves; f is kept in position by friction only, h' and h" by wing-screws besides.

Behind frame II and sieve-beds F' and F" move the piston-rods in spacious grooves. The lever-heads receiving the motion from cams L must be covered with steel; the counter-weights Q are made of disks of metal, kept in place by eye-bolts. By replacing one or more of those metal disks by wooden disks, and by moving them nearer to or farther from the fulcrum o, it is easy to change the velocity of the rising pistons at pleasure.

H. Ex. 211-32

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