120 



DRESSING OF ORES 



The coarse raggings having passed through the seatings, falls into the portion of 

 the hutch which is divided by thin wooden partitions \v, and passes out through 

 holes v. 



5. Coarse ore should be placed upon the sieves, in grains twice the size of the sieve 

 holes, and of the same ore, or mineral as that which is to bo treated. The bed should 

 be kept about ^ inch thick ; but in case of rich stuff, the thickness, should be less, vary- 

 ing to h inch ; and \rithpoor stuff greater, extending to 1 inch, or even more if found 

 necessary. 



6. Clear water and a supply of stuff being furnished, and the machines started, the 

 stop bolts, M, should be adjusted by turning them down until they are found to regu- 

 late the motion of the plunger N, so that each stroke shall bo of equal length. The 

 speed should be about 120 strokes per minute. 



7. The degree of force operating upon the stuff may be increased by elevating nearer 

 to the rocker s, the adjustible thimble o, on the top of the plunger, or stem p, or by 

 increasing the supply of clear hutch water, or both. The stroke stiould vary from 

 % inch to 1 inch. 



8. The spiral springs K should be just strong enough to strike the plunger against 

 the stop bolts M, before the down stroke, but not stronger. Irregularity of stroke, 

 viz., alternately long and short, may be remedied by attending to the adjustment in 

 connection with the springs. 



These jiggers have been introduced by Messrs. John Taylor and Sons, to whom the 

 miner is indebted for the round and impeller buddies. 



Hundfs Stream Separator. This apparatus consists of an arrangement for sepa- 

 rating, washing, or sorting ores and other substances according to the size or specific 

 gravity of the particles. This is effected in a continuous manner by the agency 

 of a body of water rotating in a horizontal direction, through which the sub- 

 stances are made to fall ; and which are collected at distances increasing in inverse 

 proportion to their size or specific gravity. For this purpose an annular vessel (Jig. 701 ) 



a, placed in a larger cylinder b, is caused to rotate round a central vertical axis c, by 

 means of a pulley or cone n. This annular vessel is open at top and bottom, and 

 placed in the slightly larger and cylindrical vessel d, which is kept full of water 

 during the action of the apparatus. Tho bottom of this vessel is divided into com- 



