The patented machinery of Messrs. Petherick and Kingston, is, we are informed, in successful operation at the Lancscot and other Cornish mines.

Diamonds, gems, and the precious metals being scattered in minute quantities over extensive surfaces of ground, chiefly of alluvial soil, the process of obtaining and separating them from the matrices and earths with which they are naturally combined, is extremely tedious when conducted by the ordinary processes of washing, stamping, and picking; any improvements, therefore, in the apparatus, by which the labour can be considerably abridged, is of essential importance to those who are interested in such pursuits. The improvements which have been patented by Mr. Harsleben, appear to us to be deserving of that character; and having been informed that they have been very successfully introduced in some of the gold mining districts of America, we shall here annex a detailed description of his apparatus, prefacing our account with the observation, that its application is not confined to the more precious metals, but may be advantageously employed in the separation of other solid substances of dissimilar specific gravities.

If the matrices in which metals are found are of a hard and stony nature, they must, in the first instance, be reduced by hammers, or by the operation of an ordinary stamping-mill, to powder or dust; for the smaller the particles are, the more effectually will they be separated by the subsequent process. The materials so prepared are put into a deep conical or cylindrical tub, with a quantity of water sufficient to permit the whole of the ore, soil, or other powdered materials, to float about in a perfectly free and liquid state whenever the water is stirred round by the agitators, which we shall presently describe; and with a force and velocity so as to drive the water up the sides of the tub in such manner, that a hollow space, in the shape of an inverted cone, may be formed in the water within the tub. Fig. 1 of the previous engravings, is a side view of the apparatus; Fig. 2 a plan of the same; and Fig. 3 a section of the tub, to show the form of the agitator, and the means used to suspend and move it; the same letters of reference are used to denote the same parts in all the figures.

A is the tub, quite smooth in the inside, supported upon a platform B, forming a part of the frame of the machine, and from which the two standards, C C, rise that support the horizontal cross-frame D D, which carries the agitator F G H I. This agitator may be made of wood or iron, according to the magnitude of the machine, and consists of four double arms F F F F, which support and carry the stirrers 1111, which hang vertically. These stirrers may be screwed or morticed into the double arms F F F F, which are in like manner screwed or morticed into the strong central block G; through the centre of this block (which is also the centre of the agitator), the iron spindle H passes, being fixed by a nut and screw beneath the block, and terminating at its upper end in the handle k, which serves to turn the agitator round; on which account the spindle has two turned bearings, which run in brass boxes a a. As the power and velocity of the winch K would not be sufficient in large machines, a rigger is hung at L, upon the iron spindle H, so that the agitator may be turned by a band passing round it; and round a large rigger moved by a horse-wheel (or any sufficient power) as shown in Figs. 1 and 2, where M is the band, and N the large rigger fixed upon the vertical shaft O, the bevel pinion of which at P takes into the teeth of a large horse-wheel, not shown in the drawings because it does not constitute any part of the invention.

By this mode of working any required number of machines can be placed round the horse-wheel, and be worked at the same time. The external bars of the stirrers 11 come very nearly in contact with the sides, and their extremities very near to the flat bottom of the tub, so as to insure the agitation of the whole quantity of material that may be mixed with the water, and prevent, as far as possible, the deposit of any part of the same, either on the bottom, or on the sides of the tub; and for the due adjustment of the ends of the stirrers to the bottom of the tub, the horizontal cross-frame D D is movable up and down in long morticed grooves, made for that purpose at Q Q, near the tops of the two standards C C, (as distinctly seen in Figs. 1, 2, and 6,) and is fixed at the required height by means of the iron screw-bolts R R, which pass into any of the series of holes made in the side of the standards, Figs. 3 and 5. A temporary elevation of the agitator may, at times, be necessary in first setting the machine to work, if the powdered ore or sand put into the water is of such a dense or heavy nature as to prevent the agitator from moving; while, by lifting it in the first instance, and then setting it in motion, and afterwards lowering it gently while in motion, it will gradually lay hold of the materials, and soon put them into a whirling motion.

In the underneath Fig. 4, a perspective figure is given of the agitator, detached from the other parts of the machine; and for the purpose of so detaching it, the cross-frame D D, together with its brass boxes, are made to take asunder longitudinally, as seen in Figs. 1 and 2, but are bolted together whilst the machine is in use. S is a cock, or spigot and fauset for drawing off the water from the tub whenever it may be necessary; in addition to this, the centre of the bottom of the tub is furnished with a peculiar valve, the use and construction of which forms one of the leading features of this invention. This valve admits of different constructions, as will appear when its use has been described. One form of it is shown in section at Fig. 3, and another form at Fig. 5. In Fig. 3 c c is a brass or other metal cylinder, which must be bored in its inside like a pump barrel, in order that the piston d, which is packed with hemp, leather, or other fit Fig. 4 material, may move in a water-tight manner within it; e f is an iron lever turning on the fulcrum f for the purpose of moving the piston with which it is connected by the rod g; and h is an iron loop or guide, which not only causes the lever efto move up and down without external action, but also regulates and restrains its quantity of motion, which is necessary, because when the end e of the lever is drawn up to its highest possible elevation, the piston d should be at the top of the barrel cc, with its convex upper surface just projecting into the tub, as shown by the curved dotted line; and when the end e of the lever is at its greatest depression, the piston must be at the bottom of the said barrel, but must never move out of it; and when the said piston is in its lowest situation, as shown in the figure, its upper surface must be just below a row of large holes, which are formed round the said barrel as at ff; consequently, while the piston is in its position, any fluid that may happen to be in the tub will flow out of it, through these holes, into a shallow tub E, placed underneath to receive it; but if the piston is raised rather more than its own thickness, it will cover all the said holeff, and prevent the discharge of anything from the tub, although it will leave all the upper part of the barrel c c open, as a well or receptacle to receive anything that may fall into it; and this well, or receptacle, may, in a moment, be annihilated by pushing the piston upwards.