until the wheels carrying it are supported by the wooden frame or rail beneath. On approaching the termination of the upstroke, the wheels of the rake rest ascend inclined bosses on the top of the wooden frame, until the catches (which are furnished with little balance weights) fall under the scraper frame, and thus retain the rakes in this position during the return stroke. From the inclination of the scrapers the orey matter is passed from one side of the buddle to the other, and in its progress the gangue is so far separated that clean ore is discharged in the first bin, whilst good seconds are found in the adjoining one. This machine makes 24 strokes per minute, and is provided with 15 rakes. It requires 67 gallons of water for the wheel and buddle during the same period, and washes 40 tons of stuff per 10 hours, yielding 12 tons of best and 4 tons of second ore. The waste averages 2 per cent. of ore. Its cost is as follows:

Smith's work, including materials; work of

first quality

Timber and Carpenters' work, complete

£18 10 0

13 0 0

£31 10 0

This machine has been found highly advantageous for separating blende from lead ore; its construction and mechanical action reflect great credit on the inventors.

GERMAN ROTATING BUDDLE.

The object of this machine is to separate the earthy matters from ores, in a finely divided state, more readily than by the ordinary round buddle. To effect this, the slime is introduced at a point near the centre of a large, rotating, slightly conical table, and, flowing down towards its periphery, a small portion of the upper part or head becomes directly freed from extraneous substances. Beyond this line of separation in the direction of the circumference, the stuff is subjected to the cutting action of a series of brushes or rakes, and by means of a sheet of water flowing over the agitated slime, clean ore is said to be produced almost at a single operation.

The illustration represents this machine as first erected at Clausthal; but it may be remarked that its mechanical details have since been judiciously modified, without affecting its principle, by Mr. Zenner of Newcastle: A is an axis supporting and giving motion to the table; B, conical table 16 feet diameter, rising towards the centre one inch per foot; o, small cast iron tooth-wheel 14 feet diameter; D, tangent screw operating on wheel c; E, drum receiving motion from water-wheel; F, tooth-wheel driving small wheel, f, the

K

axis of which has a crank giving motion to a rod fitted with brushes; G, annular receiving box 4 inches wide, 6 inches deep; a, circular trough of sheet iron, supported on the axis of the table an inch or two above its surface, and so divided that one quarter of it serves for the reception and equal distribution of the slimes, whilst the remaining three-quarters supply clean water; b, launder for conveying the slime ore, behind which there is another, not shown, for giving water to the buddle; o, bent trough, affording additional water to the stuff cut by the brushes. One end of this water trough is fixed about mid-distance between the outer edge and centre of the buddle; the other end advances in a circular direction, nearly to the circumference of the table. The following abstract of a statement made by Mr. Zenner, gives the results obtained by his improved apparatus as compared with the ordinary round buddle.

A lot of slime ore weighing 619.1 cwts. was divided into two equal portions. The rotating buddle finished its portion including re-washing the tailings in 86 hours, whilst the ordinary buddle required 609 hours to perform the same work. The time consumed was therefore in the proportion of 1 hour to 7. The ore operated upon contained about 8 per cent. of lead, and the results of the dressing operation were as follows:

ROTATING BUDDLE.

Washed Conts. of Lead
Ore

:

ORDINARY ROUND BUDdle.

Washed Conts. of Lead.
Ore

The rotating buddle, therefore, cleaned its portion of slime ore to 62.4 per cent. and left only 1.8 per cent. in the waste; the ordinary buddle cleaned its ore to 52.6 per cent. and left 20 per cent. in the waste; the rotating buddle consumed rather less than 4th of the time to effect this.

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DRESSING OF COPPER ORES AT DEVON GREAT CONSOLS.

Through the kindness of Captain Isaac Richards we have been favoured with sketches and particulars of some of the machinery employed in concentrating the inferior ores raised at the above mines. Although the yield of ore is exceedingly large, it may not be generally known that much of it is derived from stuff affording no more than from 2 to 1 per cent. of metal. To readily separate the worthless matter, at a remunerative cost, is a problem which has been ably treated by Capt. Richards, and it must be admitted that the present prosperity of the undertaking has been considerably influenced by the excellent system of machinery introduced by him into the dressing department.

The vein stuff, on arriving at the surface, is cobbed and divided into two classes; the first going to market without experiencing any further manipulative process; whilst the second, or inferior class, is variously treated as may be found expedient. The whole of the latter description is, however, crushed to such a degree of fineness as to pass through a sieve perforated with 1-inch holes.

SIZING SIEVES.-These consist of an arrangement of inclined sieves, four in number, each 6 feet long 24 inches in diameter at the larger end, and 18 inches diameter at the smaller. The mesh-work of A and B is th, cth, and Dth of an inch in diameter. The stuff from the crushing mill is introduced into A

along with a stream of water; that portion of it which falls into the bins, FF, is conveyed to the dressing-wheel, whilst the remainder of the stuff which runs through the coarser meshes is passed into a hopper communicating with jigging machinery placed beneath. The sieves make 20 revolutions per minute, and altogether afford an area of about 6,000 square inches.

SLIME SEPARATOR.-This apparatus is the invention of Captain Isaac Richards, and is almost similar in its construction to the ordinary overshot water-wheel. The slimes or fine particles of ore, &c., which have passed through the circular sieves, A and B, are conveyed from the cisterns, F F, by means of a launder upon a wheel, thereby giving it a slow rotatory motion. Whilst this is turning, time is afforded for the minerals to settle according to their several densities; the result obtained is, that the heavier particles are found at the bottom of the buckets, whilst the lighter matter held in suspension flows away through a launder placed for that purpose. The stuff in the bottom of the buckets is washed out by means of jets of water obtained from a pressure column 10 feet in height, when the whole passes into a round buddle. The wheel A, is 4 feet diameter, 2 feet 6 inches in breast, has 24 buckets, and makes 5 revolutions per minute; B, launder for supplying the slimes; c, pressure column; D, jet piece; E, launder for conveying off the slime overflow of the wheel; F, launder for conveying separated stuff to round buddle.