112 DRESSING OF ORES 



table. A fixed launder or trough coincident with the periphery of the table is divided 

 so as to receive the ore and orey stuff. 



In addition to the machines already described, a slime or sludge dressing apparatus 

 has been designed by Mr. Borlase. Fig. 737 represents an elevation, and jvj. 738 a, 

 plan of this machine. 



It is described by the inventor as follows : The mineral from which it is desired 

 to separate the metallic ore having been crushed or pulverised, is conducted through 

 a pipe or channel into a revolving cylindrical sieve, A A. The larger parts pass into 

 a shoot or launder B, and from thence into a self-acting jigging machine. The 

 slime or fine portion passes through the meshes of the sieve into a shoot, c, and is 

 discharged into an annular launder, from whence it falls either into a stationary or 

 revolving distributor, D D. From thence it flows through suitable channels into the 

 outer part of the machine, E. The apparatus is fixed on a perpendicular axis, F, and 

 is kept in a continual oscillatory motion by means of cranks and connecting rods, o, 

 the speed of the cranks being adjusted so as to keep the slime in continual motion, 

 and at the same time cause the ore to descend and deposit itself at the bottom, whilst 

 the waste or lighter portion is carried towards the inner part of the machine, where 

 it passes over a moveablo ring, H, which is raised mechanically, and in proportion as 

 the ore rises in the apparatus. The waste is discharged through the outlet i, and 

 conveyed away in launders. When the machine is filled with ore, it can be settled, 

 as in the dolly machine, by means of percussive hammers, j j. The ore can be 

 collected either by reversing the gear and lowering the ring H, or it may be washed 

 into a receiver as convenient. 



Motion is given to the vertical bar K, which is made to vibrato so as to turn by 

 means of a ratchet the wheel L, fitted on a horizontal shaft, M. The ratchet is 

 raised or lowered by a worm screw, in order to increase or decrease the speed ren- 

 dered necessary by the quality of ore operated upon. On the horizontal shaft M 

 is a worm pinion, that works a wheel on a perpendicular shaft, N, on which is fixed 

 a second worm pinion, raising or lowering the tooth segment on the end of the beam 

 o. This segment can be shifted out of gear. The opposite end of the beam o is 

 attached to the rod P, and connected with the crossbar R, as also with the ring H, 

 which has a reciprocatory motion in the centre of the perpendicular shaft F. 



From the foregoing description it would appear that Mr. Borlase has combined in 

 this apparatus the principles of the round buddle with that of the dolly tub. 



Slime Trunking Apparatus. The illustration,^. 739, shows the apparatus employed 

 in some of the lead-mines of Cardiganshire. The slimes are lodged in the several 

 settling pools marked A, and flow through the channels B. At c the slimes pass into 

 the launder D to the box E, where they are comminuted, and from thence progress 

 into the trommel F. From the circular cistern o, V-shaped launders diverge to the 

 trunks K, which are divided by partitions i. Upon the axis j in each buddle head, 

 paddles rotate, and flush the slimes over a head board, where a partial separation is 

 effected. The wheel L is driven by water from the pools A, and any excess is carried 

 off by the launder N. At o o two hand-buddies are shown; these are intended for 

 the concentration of the heads and middles produced in the trunk K. The axis at P 

 is furnished with spikes for the purpose of breaking up the slimes. After the 

 water has passed over the wheel L, it flows into the launder E, and from thence 

 into Q. 



At the Minera lead-mines, where the ore produced is very massive and capable of 

 a high degree of enrichment, the slimes average 9 per cent., and are concentrated by 

 means of this apparatus, together with a round buddlo and dolly tub, to 75 per cent, 

 of metal. With six trunks, one round buddle, one man, and four boys, about nine 

 tons of clean ore are obtained monthly. 



Attempts have been made by Brunton and others to separate metalliferous ores 

 of different specific gravities by allowing them to descend at regular intervals in 

 still water. By reversing the operation and causing the current to ascend uniformly, 

 the particles may be much more conveniently and accurately classified. This has 

 been done in a machine designed by the lato Mr. Herbert Mackworth. Suppose a 

 funnel-shaped tube, larger at the top ; with a current of considerable velocity flowing 

 upwards through it, grains of equal size of galena, pyrites, and quartz, when thrown 

 in, will be suspended at different heights depending on the velocity of the current at 

 each height. Thus cubical grains of galena, iron pyrites, and quartz, of -fa inch 

 diameter, will be just suspended by vertical currents moving at velocities of 12 inches, 

 7 inches, and 5 inches linear per second ; flat or oblong particles require rather less 

 velocities to support them, inasmuch as they descend more slowly in still water than 

 the cubical or spherical particles. 



A simple form of applying this principle is presented by the vertical trunks shown 

 in Jigs. 740 and 741. Metalliferous ore, after being classified by sifting, or tin ore 



