Crane.| Prospecting, Mining and Milling Machinery. 283 
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Fig. 59. Wooden grate for support of screen in power jig. 
Slime Washing and Concentrating Apparatus. 
In all mining districts there is a certain amount of fine or 
flour mineral, produced by close crushing, which escapes from 
the large capacity and more or less rough concentrating ap- 
paratus and is lost in the slimes, which are always present in 
ore concentration. An excess of fine (float) mineral may 
be due to—first, too close crushing ; second, very friable min- 
eral. The mineral may be so disseminated throughout the 
gangue or country rock as to require close or fine crushing. 
Special forms of apparatus have been devised for saving 
the flour mineral from the slime. 
Only two forms of slime treating apparatus, the Wilfley 
table, and buddles, have been in use to any great extent in 
the Galena district, while two other forms, the round table 
and the hydraulic separator, have been hardly more than 
tried. The hydraulic separator has, however, had more ex- . 
tensive use than the round table. 
The first two mentioned, namely, the Wilfley table, and bud- 
dles, have been used quite extensively, and will be described 
in detail below. 
19—vili 
