DRESSING OF ORES 



111 



ticularly intended to supersede the operation of jigging in separating ores from their 

 refuse or waste. ... In the separators, the sieves containing the ores to be cleaned 



687 



are placed in suitable apertures in the fixed coffer of a vessel filled with water, connected 

 with which is a plunger or piston working in a cylinder. The motion of the plunger 

 causes the water to rise and fall alternately 

 in the sieves, and effects the required sepa- 

 ration in a more complete manner than 

 can be performed by jigging. The variety 

 in the extent and quickness of the motion 

 required for the treatment of different de- 

 scriptions of ores is easily produced by a 

 simple arrangement of the machinery. 



A principal advantage in this separator 

 is derived from the sieves being stationary 

 (in jigging, the sieve itself is moved) dur- 

 ing the process ; thereby avoiding the in- 

 discriminate or premature passing of the 

 contents through the meshes, which neces- 

 sarily attends the operation of jigging, 

 whether by the brake or hand sieve. Greater 

 uniformity of motion in the action of the 

 water, in producing the required separation, 

 is also obtained ; and superior facility af- 

 forded to the deposit in the water vessel (especially in dressing crop ores) of the 

 finer and richer particles, which in jigging are principally carried off in the waste water. 



The superiority of the patent separators over the ordinary means of cleaning ores 

 will perhaps be best shown by reference to their actual performance. At the Fowey 

 Consols and Lanescot Mines in Cornwall, where they were extensively used, seventeen 

 distinct experiments were made on copper ores of various qualities from different 

 parts of the mines, to ascertain the extent of the advantage of this mode of separation 

 over the operation of jigging. Seventeen lots of ores, amounting together to about 

 300 tons, were accurately divided, one half was jigged, and the other half cleaned by 

 the separator. A decided advantage was obtained by the latter in every experiment; 

 the aggregate results being shown in Tables at top of next page. 



It must be obvious to those who are practically acquainted with the subject, that 

 the poorer the stuff containing the ores, the greater must be the relative value of 

 any improvement in the process of cleaning it. This was satisfactorily demonstrated 

 by the trials made in the mines before mentioned, in dressing the tailings, which are 



