DRESSING OF ORES 131 



The table of the buddle has an inclination towards the bins F F*, and catch pits H H. 

 This machine makes about 12 strokes per minute, and may be furnished -with any 

 number of rakes. With 22 rakes, 40 tons of stuff may be concentrated in 10 hours, so 

 as to afford ore for the deluing sieve, whilst the blende will be sufficiently cleaned for 

 the market. The cost of this apparatus complete is about 30^. 



Figs. 722 and 723 represent plan and side elevation of the knife or impellor buddle. 

 The water-wheel A, is 6 feet diameter, and is constructed of wood, with sheet-iron 

 buckets. The speed of the trommel is carefully adjusted to the character of the stuff 

 intended to be treated. This is effected by shifting the band on the driving cones B B. 

 Straw, heath, and other extraneous substances are prevented from entering the sepa- 

 rating table by means of an iron grating c, fixed near the top of the hopper. The 

 trommel, D, is formed of 3 iron hoops braced together by flat lateral bars, 6 feet 

 in length. Into these bars are inserted the scrapers, which are set spirally in the form 

 of a screw. The hoops may be from 2 to 4 feet diameter, |ths inch thick, by 1 inch wide. 

 The scrapers are made of light sheet iron, and are 9 inches wide by 4 inches deep, 

 with shanks 3 inches long. Twelve rows of scrapers are mounted on the periphery 

 of the trommel. The first, fifth, and ninth rows contain nine, and the remaining rows 

 are fitted with eight scrapers. Each scraper is adjusted by slightly rotating the stem, 

 and tightening the nuts over and under the trommel-ring. 



The trommel is rotated against the flow of water. From the vertical axis of the 

 trommel, the table F is more or less inclined, according to the density of the minerals 

 to be separated. The enriched stuff is collected in the side-bin, 2 feet in width by 

 8 feet in length. From this receptacle the sand may be transferred to jigging sieves, 

 round buddies, or other suitable dressing apparatus. The stuff deposited in the 

 strake H is either subjected to additional mechanical treatment, or, if sufficiently free 

 from ore, taken to the refuse heap. 



The ' work ' to be enriched enters at c, on one side of the table, and is propelled 

 against the flowing water by the action of the scrapers. The heavier portion is pro- 

 gressed across the table, and passed into an ore bin, through an opening 18 inches 

 long and 3 inches deep. The lighter materials are drifted into the strake, and in this 

 way a separation is effected. Great care must be taken to distribute the stream of 

 water equally upon the surface of the table, and to proportion its volume so as to 

 divide the inferior from the more valuable minerals. The water flowing from the 

 wheel may serve not only to supply the table, but a part of it may also be diverted 

 into the feed-hopper c, and any excess discharged by the launder j. The quantity of 

 stuff which can be passed through this apparatus in a period of 10 hours will vary with 

 the densities of the minerals to be separated. The impellor buddle has recently been 

 improved by Mr. Henry E. Taylor of Aberystwyth, and applied to the washing of 

 coal and ores. See Specification 889, A.D. 1874. At Eestronquet Mine in Cornwall, 

 the Messrs. Taylor and Sons employ this buddle successfuly in the treatment of tin ores. 



At Wildberg in Germany, the floor of the buddle was divided by moveable ledges, 

 and the stuff diverted to enriching tables. 



SAND AND SLIME DEESSING MACHINEBT. 



In most mines a large proportion of the ore is composed of dradge, and has to be 

 brought to a fine state of subdivision either by the crushing mill or stamps. In this 

 condition the ore is freed from sterile matter, and rendered fit for metallurgic treat- 

 ment. A variety of machines have been invented and applied to this division of 

 dressing, in which the leading principle is to produce a separation by subsidence, ac- 

 cording to the density of the substances. In connection with this principle, the stuff 

 is not permitted to have a vertical fall, but is traversed by a flow of water, on a table 

 or bed set at such an angle to the horizontal plane as may be found expedient. "With 

 extremely fine stuff, apparatus including both of these features are sometimes sub- 

 jected to a mechanical jar or vibration, so as to loosen and eject, as it were, the worth- 

 less matter with which it may be charged. In concentrating crushed or stamped ore, 

 a certain quantity will often exist in a very minute state of division, unable to 

 withstand the currents and volume of water necessary for the separation of the larger 

 particles. 



The amount and richness must necessarily depend upon the united produce and 

 character of the ore, as well as the mode of treatment observed. A good dresser will 

 form as little slime as possible, since when the ore is brought to this condition it is 

 usually associated with a large mass of worthless matter ; and not only so, but the 

 expense of extracting it is materially increased. The loss under the most favourable 

 manipulation is very large, whilst the machinery requisite is probably more compli- 

 cated and expensive than any other section of the dressing plant. Although several 



