124 



DRESSING OF ORES 



The arrangement of another separating box is shown in fiys. 705 and 706. Tho 

 slimo water flows in at M ; and water still holding a considerable portion of slime flows 

 away from the opposite end. It is necessary that pieces of chip, small lumps, or other 

 extraneous matter should be intercepted previous to entering this apparatus, also that 



the slimo should be evenly sized by means of a 

 trommel or sieve. The heaviest portion of the 

 slime water in which the sand and ore are con- 

 tained, is discharged at the hole o, about an 

 inch square. The launders pp, are for the pur- 

 pose of conveying the slimo water cither to 

 buddies or shaking tables. The dimensions of 

 the cistern No. 1 are : length, 6 feet ; width, 

 15 feet; depth 12 inches. But two other cis- 

 terns of similar form are attached. No. 1 cistern 

 will work about 10 tons of stuff in 24 hours, and 

 by widening the box from 18 to 27 inches it will 

 get through 20 tons in 24 hours. Affixed to one 

 side of the boxes are hammers so contrived as to 

 give 30 blows per minute in the manner of a 

 dolly tub. Care must be taken in the construc- 

 tion of these classifiers that the sides forming the 

 pyramids be neither too steep nor too flat ; if too 

 flat, the sand is apt to settle until a quantity 

 has accumulated, when it would suddenly sink 

 and choke the discharge pipe o' ; and if too steep 

 tho classifiers would become of inconveniently large dimensions. A gradient of 50 to 



the horizon is found to be the most suitable. The chief dimensions of two cisterns, 

 viz. one working 10, and the other 20 tons, arc given in the following Table : 



