STAMPING MILLS. In cases where a degree of fineness, intermediate between the results obtained from the crusher and horizontal mill is required, a machine termed a stamps is generally employed. This consists of a series of wooden pestles, each fitted with a lump of cast iron, which is lifted to a certain height and permitted to fall upon the material to be pulverized. These pestles or stamp-heads are elevated by cams arranged spirally on a barrel of wood or cast iron, and to which motion is communicated either by steam or water power. Each pestle or lifter usually makes from 50 to 70 blows per minute. The lower portion of these lifters, where the iron head comes in contact with the mineral to be broken, is enclosed in a wooden trough, termed the cofer, fitted both in the front and ends with perforated iron plates. A small stream of water flows continuously into this trough; so that when the stuff operated on is reduced sufficiently small, it is carried through the gratings into a catch-pit, where it becomes deposited by subsidence. The form of the cofer, exit for the stuff, weight and speed of the stamps, and quantity of water employed, should be varied according to the peculiarities of the ore and matrix operated on. The best machines of this class are to be found in the tin mines of Cornwall. At Polberro a 36-inch engine, working at 55 horse-power, stamped, in the year 1854, no less than 30,201 tons of tin stuff. This was effected by an average of 84 revolutions per minute, each revolution lifting 72 stampers 9 inches high, weighing respectively 600 lbs. The greatest number of blows was 50 per minute, but the average of the whole 45. The entire cost of stamping, including maintenance of engine, wear and tear of machinery, wages of all kind, coal, oil, grease, hemp, &c., amounted to £1,950. or 1s. 3 d. per ton of stuff. Each head stamped 420 tons per annum, or 28 cwts. per 24 hours, whilst the whole number reduced 100 tons per day, at a total cost of £6. 9s. 2d., or 2s. 4d. per horse-power. The stampers weighed, collectively, 19 tons; and as they were lifted 9 inches high, 45 times per minute, it follows that a mass equal to 877 tons was displaced 67 ft. 6 inches in a corresponding period. The total number of grates was 72, the front grates having an exposed area 9 × 6 inches, and end grates 8 × 6 inches, with 140 holes to the square inch. The two fly wheels, each 30 feet diameter, weigh 34 tons, which weight, with cranks, shafts and bolts, is increased to 42 tons. This machine stamped, in 1855, 29,663 tons, and in 1856, 31,411 tons of stuff, which yielded only, on an average, 17 lbs. of merchantable tin ore per ton. At Great Hewas, where the stuff appears to be more readily pulverized, 3 tons of stuff per head are said to pass through grates having 70 holes per square inch per 24 hours. The following particulars of cost have been supplied by the manager of these mines : Coals for engine (per 24 hours) £1 4 0 0 3 6 £1 16 0 This sum, divided by the quantity crushed, gives 3d. per ton of stuff, without allowance for wear and tear. During the last few years, many improvements have been introduced in the mechanical arrangements of stamping-mills, but no course of experiments has apparently been undertaken to ascertain with accuracy their relative values. Much attention has been given to the construction of these machines by the Messrs. Taylor, of Queen Street Place, who have designed some of the best models, both for home and foreign use. Mr. Jordan has also introduced some novelties in the construction of stamping-mills, and proposes to employ the principle of Nasmyth's steam hammer for the pulverization of hard materials, and thus to avoid the torsion resulting from long shafting, and the friction caused by the cam movement. ROUND BUDDLE. This machine is said to have been first introduced into Cardiganshire, but has now become general in almost every important mining district. It serves to separate particles of unequal specific gravities on a circular space inclined from the centre towards the circumference. Its construction will be seen from the annexed representation, in which a, is a conical floor, formed of wood, about 18 feet in diameter, on which the stuff is distributed; B, is a cone effecting the regular distribution of the orey matter, and supporting the upper part of the apparatus; c, is a cap-piece forming the centre of motion; D, a mitre wheel for giving motion to the buddle; E, a funnel perforated with holes, and furnished with an annular trough on the top; F F, are arms for carrying two brushes, which may be balanced by weights, G G, as shown, or raised by a small arbor placed on the top of the beam; H, is a launder for conveying slimes from pit, I; K, is a receptacle in which the orey slime, mixed with water, is worked up by the tormentor, which is a cylinder of wood carrying a number of iron knives; L, is a pulley taking motion from a water-wheel or other prime mover; M, is a circular sieve fixed on the arbor, N. The slimes at K are gradually worked over a bridge forming the side of a catch-pit between the sieve, M, and the tormentor, from whence the stuff passes into the sieve, and by its rotation the finer particles are strained into the pit, I, whilst the coarser are discharged, with chips or other extraneous matter, upon the incline floor, communicating with the launder, o. From the pit, I, the slime flows by the launder, н, into the funnel, E E, and, after passing through the perforated holes, trickles down the sides of the fixed cone, B, when it commences to flow off towards the circumference, leaving, by degrees, in its downward progress, the heavier constituents, whilst the surface is constantly swept smooth by the brushes which revolve, together with the funnel and vertical shaft; so that the particles of different densities will be arranged in concentric circles. The speed of the arms is usually from 3 to 4 revolutions per minute, and a machine, with a bed 18 feet diameter, will work up from 15 to 20 tons of stuff per day of 10 hours. The round buddles employed at the Devon Consols Mines are 18 feet diameter, exposing an area of 254 square feet. The brushes make 2 revolutions per minute, and the stuff washed per buddle amounts to 18 tons per day of 9 hours, or 2 tons per hour. LISBURNE BUDDLE. This machine was invented and first erected, about the end of the year 1855, by the agents at the Lisburne Mines, in Cardiganshire. The idea involved in this arrangement is that of the primitive hand process still employed in Wales for dressing ores. The illustration shows a side elevation and ground plan of this apparatus, in which a represents the raking frame; B, the buddle table; c, head supplying water; D, rod connecting the rake frame with crank of wheel; E, rakes set obliquely to the line of motion, F, supply hopper; F', bin to contain clean ore; &, launder conveying part of the waste water from wheel to the supply hopper; &', bin to receive second class ore; H н, catch-pits for collecting slimes from buddle; K, launder; L, water wheel for giving motion to the machine; M, guides; N, beam balancing frame, o o', carrying the rake frame wheels, the arbor of which forms the axis of motion for the rakes E; P P, catches for supporting rakes in the downward stroke; R rake rest. The table, B, has an inclination towards the pits, H, and also a very slight depression in the direction of the ore bins, F' G'; the water from the wheel flows over the buddle head, and by its admixture with the stuff in the box, F supplies the buddle. The rakes disturb the stuff against the flow of water, and in the opposite direction are elevated so as to pass over it, this is done in the first place by the tops of the catches, P P, striking against the projections, s, and permitting the rake rest to fall, |