Volume 2

Ure's dictionary of arts, manufactures, and mines : containing a clear exposition of their principles and practice / by Robert Hunt. ; assisted by F.W. Rudler.

  • Ure, Andrew, 1778-1857.
Date:
1878-1979
Catalogue details

Licence: Public Domain Mark

Credit: Ure's dictionary of arts, manufactures, and mines : containing a clear exposition of their principles and practice / by Robert Hunt. ; assisted by F.W. Rudler. Source: Wellcome Collection.

    96/1060 (page 80)
    G48 the apparatus are of great strength, and the amount of wear and tear is comparatively small In mines where it is requisite to reduce large quantities of vein-stuff, either lor tlio cohhers, coarse sand jiggers, or crushing mill, this machine will prove'an im- portant and valuable auxiliary. The jaw pieces of stone-breakers should bo formed of double chilled iron: soft and badly-hardeued iron is highly objectionable, since with the early inefficiency of the jaw pieces, together with cost and delay attending their re- placement, the cost of reducing stone must be materially increased. A pair of hard jaws 12 inches by 9 inches will break from 2,000 to 3,000 tons of siliceous vein-stone. In large dre.'sing establishments the stone-breaker is driven directly by a steam-engine. Small breakers, with jaws 7^ inches deep and 4 inches wide, are also frequently used for reducing orey vein-stone, derived from the 'coarse sand' jiggers. Cobbing, fig. 648.—This work is generally performed by women, young girls, or boys. It consists of picking the best work from the dradge, and with a peculiarly shaped hammer, detaching from each piece the inferior portions, and thus forming either prill or best dradge ore. An expert cobber will manage to prepare about 10 cwts. of tolerably hard stuff per ten hours. Sizing Apparatus.—In the various processes of dressing, no point is of greater im- portance than that of correctly sizing the vein-stuff, neither is there one demanding the exercise of a more correct judgment. If the particles of ore be reduced below their natural size a source of loss is immediately created, whilst if they are not brought within the limit of their size a portion of waste will probably adhere to each atom, forming a serious difference in the aggregate quantity of castaways, although such waste may afford but a low percentage of metal. The holes in the sieves or trommels should therefore be proportioned to the nature of the ore, but such apparatus should also be introduced wherever necessary. To the crushing mill, trommels are essential, whilst it will be found highly advantageous to employ them for the purpose of dividing the stuff whenever it may be intermixed. The simplest form of sizing is perhaps by 649 the hand riddle, fig, 649, which is formed of a circular hoop of oak, fths of an inch thick and 6 inches deep. Its diameter ranges from 18 to 20 inches. The bottom is made of a meshwork of copper or iron wire. The weight of an iron wire riddle is about seven pounds, and its cost 4s. 6d. Fig. 650 represents a swing sieve employed in mines on the Continent, a, box into which the stuff to be sifted is introduced; b, regulating door ; c. pendulating rod attaching the sieve frame to the frame e; /, friction roller carrying the sieve frame g. At h springs are fitted to each side of the frame, in order to give it a vibratory action; i, rod, giving motion to the apparatus. The width of the sieve frame is about one- third its length, but the sieve bottom only extends from the box, a, two-thirds of the length. The bottom of the sieve frame is subsequently contracted so as to form a sboot. Fig. 651 is a swing sieve employed in the Hartz, for sifting the small fragments of the ores of argentiferous lead. Such an apparatus is usually set up on the outside of a stamps or washing mill. The two moveable chests or boxes a b, of the sieve, are connected together, at their lower ends, with an upright rod, which terminates at one of the arms of a small balance beam, mounted between the driving shaft of the stamps and the sieve, perpendicularly to the length of both. The opposite arm of this beam carries another upright rod, witb cams,—placed so as to be pushed down by thQ