116 



DRESSING OF ORES 



partments ; /, g, k, j, discharge holes, which may bo fitted with regulators ; n, o, %>, 

 inclined sieves ; q, horizontal sieve ; r, driving gear ; v, discharge shoot from main 

 sieve ; w, waste waggon ; x, drip receptacle ; y, door through which stuff is withdrawn 

 from hutch ; z, launder for receiving contents of hutch. When using the jigger, tho 



693 



smaller divisions c, d, and e, are partly filled with equivalents, or grains of mineral 

 having equal velocity of fall in water, and of a certain determinate size, observing that 

 the proportionate size or density of the equivalents contained in every successive sieve 



694 



? 



must be increased. Further, as a preliminary to the effective separation of stuff, it is 

 expedient that it should bo sorted or classified according to tho varying size of its con- 

 stituents, or, if necessary reduced to a specified size. At the zinc-mines at Iserlohn, 

 where the stuff consists of galena, blende, calamine, and carbonate of lime, a sieve 24 



