DRESSING OF ORES 



151 



The stamp work must not flow on a feeding board above a foot in width. 



The length of stroke and number of blows vary according to the stuff to be treated ; 

 the coarser the material, the longer, stronger, and fewer blows are necessary. The 

 quantity of water containing mineral in suspension, to be fed on a single table, 

 is of coarse stuff 1-2 gallon, containing 4 pounds of sand and of slimes, three- 

 quarters of a gallon of water, containing about 13 ounces of sand in suspension. 

 The action of these tables is precisely that of the vanning shovel ; and any ore 

 which can be cleaned upon the shovel can be dressed in a superior manner upon the 

 table. 



Two tables, making 120 blows per minute, require to be driven by a 15-feet water- 



wheel, and 50 gallons of water per minute. Each additional table will take 30 gallons 

 of water per minute to drive it. 



The shaking table shown in fig. 752 has the merit of being extremely light, re- 

 quiring little power, and of performing its work in a highly satisfactory manner. 

 A, table swung by chains, B B', its width being 3 feet and length 12 feet. A greater 

 or less inclination is given to the table by raising or lowering the screws c d. At the 

 upper end of the table is a buffer, D, which acts against a counter-buffer, E. A sliding 

 bar, F, is also fitted between the table and percussion lever G. This lever is struck 

 by cams fitted on the axis H, driven by the runner j. The slimes to be treated 

 flow into the cistern K, 30 inches long, 13 inches wide, and 18 inches deep. Into 

 this box a tormentor is introduced for the purpose of breaking up the slimes. The 

 bottom is fitted with a launder L, 7 inches long and 5 inches wide. From this laundei 

 proceeds a head-board M, expanded to the width of the table, and fitted with buttons, 

 for the purpose of dispersing the slimes equally on the head of the table. 



About five tons of rough slime are enriched per day on four tables, whilst from 

 nine to ten tons of enriched slime are despatched in a similar period. 



Skewing Tables. Figs. 75S, 754 represent a set of sleeping tables. Fig. 753 is the 

 plan, and Jig. 754 a vertical section. The ores, reduced to a sand by stamps, pass into 

 a series of launders, a a, b b, c c, which form three successive runs below the level 

 of the floor of the works. The sand taken out of these launders is thrown into the 

 cells q; whence they are transferred into the trough e, and water is run upon them 

 by turning two stop-cocks for each 

 trough. The sand thus diffused 753 



upon each table, runs off with the 

 water by a groove /, comes upon a 

 sieve h, and spreads itself upon the 

 board q, and thence falls upon the 

 sleeping table t Jc. The under sur- 

 face k of this chest, is pierced with 

 holes, which may be stopped at plea- 

 sure with wooden plugs. There is a 

 launder m, at the lower end of each 

 table to catch the light particles 

 carried off by the water out of the 

 chest i k, through the holes properly 

 opened, while the denser parts are deposited upon the bottom of the chest A general 

 launder n, passes across at the foot of the tables i k, and receives the refuse of the 

 washing operations. 



In certain mines of the Hartz, sweeping tables are employed. The whole of the 

 process consists in letting flow, over the sloping table, in successive currents, water 



