DRESSING OF ORES 



147 



fall, so as to produce the greatest regularity in its flow over tables fixed upon a given 

 incline, each table having a sufficient drop from the table above. When the tables 

 are sufficiently charged, clean water is introduced to pass over the table. The 

 surfaces of the tables are subject to the action of brushes or brooms during a part or 

 the whole time of both operations until the ore is sufficiently cleaned. In some 

 cases the use of such brushes or brooms are dispensed with. The ore (on the tables) 

 thus cleaned is washed off into cisterns by the action of water passing over the 

 surfaces of the tables after they are raised to nearly perpendicular positions. 



Fig. 745 represents, 1, framework to carry the gear on each side of the machine ; 

 2, the stretcher or pivot piece on which all the tables are resting ; 3, centre bearings 

 of the tables, to which is attached an adjusting screw for raising or lowering them ; 

 4, a slide valve, which admits or shuts off, as required, the ores, which are previously 

 brought into a thin consistency with water; 5, launder through which the ores, 

 pass to the heads, which are divided into sections and numbered ; 6, the ores, &c., 

 dropping from the heads into a launder, 7, the working edge of which is made level 

 by an adjusting screw at each end for the ores to pass over ; 8 is a stretcher, passing 

 over the heads in both ends, bolted to 1, from which 6 and 7 are supported by three 

 adjusting screws ; 9 are four tables over which the ores have to pass, first receiv- 

 ing the deposit of the cleanest or best ores, and the rest in gradation ; 10, the drop or 

 fall from one table to another ; 11, the balance cistern, into which the refuse from the 

 tables passes, and when full, by lifting the catch 12 it forms a balance for turning up 

 the tables to be washed down, each table being connected with rods and lever A ; this 

 done, such catch is lifted up, and 13 forms a returning balance for the tables; at 14 a 

 stream of water is introduced, passing into 15 as a receiver ; on the turning up of the 

 tables, valves 16 are lifted by lever and rod 17, and admit the water into perforated 

 launders 18 to wash off the ores into receivers 19, through which it passes out into 

 deposit hutches. The slide valve 4 having admitted a sufficient quantity of ore, which 

 has been deposited on the tables, is now closed, and the valve 20 is opened by the 

 dresser at rod handle 21, through which a supply of water passes into launder 

 22, and flows over the tables for the purpose of cleaning the ores. The framework 

 for the brushes 23 is carred on four wheels 24, each table being supplied with a brush 

 25, which brushes its respective table upwards, and on arriving at the heads of the 

 tables, the brushes being all connected, are lifted by lever and 26 slips into the catch 

 27, and the brushes pass back over the tables without touching until the lever of the 

 catch is struck out by 28, and the brushes drop again on the tables. Each brush is 

 adjusted by screws and carried on arbors running across the frame. This frame with 

 its appendages is propelled by a rod 29, attached to a beam 30, that can be worked 

 by any sufficient power that may be applied. 



The ores passing from the third and fourth tables through the two lower receivers 

 19 into a cistern, are lifted by a plunger B, attached to beam 30, by a rod 31, and 

 passes back by launder 32 to be readmitted into slide valve 4, and repass the tables. 

 In 11 balance cistern is a valve 33, which on the dropping of the table lets out the 

 contents. 34 is a catch for holding the frame and brushes during the time of turning 

 down and washing the tables. The machine is to be worked with or without brushes, 

 as the character of the ores may require. It may be extended or diminished to any 

 number of tables, and their size may vary as may be found necessary on the same 

 principle, c is a wheel acting as a parallel motion for the plunger pole and running 

 on a bar of iron. 



This machine was in constant use at the Great Polgooth Mine for some time, 

 and it is said effected a saving of 30 per cent, in the dressing of slime ore. It is 

 not so well adapted for rough as for the treatment of fine slimes. 



Percussion Table. The diagrams, figs. 746, 747, 748, exhibit a plan, vertical sec- 

 tion, and elevation of one of 



these tables. The arbor or 746 



shaft, is shown in section per- 

 pendicularly to its axis, at A. 

 The cams are shown round 

 its circumference, one of them 

 having just acted on n. 



These cams, by the revolu- 

 tion of the arbor, cause the 

 alternating movements of a 

 horizontal bar of wood, o, u, which strikes at the point u against a table d, b, c, u. This 

 table is suspended by two chains t, at its superior end, and by two rods at its lower 

 end. After having been pushed by the piece, o, u, it rebounds to strike against a 

 block or bracket B. A lever p, q, serves to adjust the inclination of the moveable 

 table, the pivots g being points of suspension. 



L2 



