3938 University Geological Survey of Kansas. 
The feed and discharge may be regulated in several ways, 
namely: First, by special feeding devices ; second, by crusher 
. feed; and third, by a large area of screening surface engaged. 
Only the two latter are employed in this district, and, of the 
two, the former is the more common. 
Work is usually not begun until sufficient dirt is on the 
crusher platform, or there is a certainty of enough accessible 
material to last throughout the shift. Two feeders are usu- 
ally employed to a crusher, and are usually able to maintain 
a fairly constant stream of ore over the jig screens, unless the 
leanness or coarseness of the ore requires much hand pick- 
ing and reduction by sledge. If too many and long delays 
occur in the feeding, there will be corresponding variations 
in the richness of the concentrate on the screens, as the close- 
ness of the separation varies somewhat with the thickness of 
the bed of ore. The best results are obtained when the jig 
is working at full capacity. 
The discharge of tailings is effected and regulated by the 
feed and under waters. The speed of the plunger also ma- 
terially affects the speed of the waste particles across the jig, 
but the speed of stroke should not be increased for this pur- 
pose alone, which would seriously affect the separation on the 
screen. 
The dischargeof theconcentrateis accomplished intwoways : 
First, through the bed on the screen; and, second, by gates 
in the front of the jig, 7. e., discharging from the top of the 
bed. Figure 63. Unlesscareis taken, the concentrate through 
the gate will be poor. The discharge depends upon the mo- 
bility of the ore on the jig bed, and, if anything disturbs 
this, the discharge will be imperfect. The product passing 
through the bed or the hutch, as it is commonly called, will be 
clean only in a few of the last cells of the rougher and in all 
of the cells of the cleaner. If there are a large number of 
cells in a jig, there will be a large number of cells producing 
clean hutch, while in a jig with a few cells the separation is 
difficult, especially when several minerals occur together. 
Usually, the last one or two cells are employed as ‘‘guard’’ 
cells, to prevent a waste of mineral and to insure perfect sepa- 
ration. The hutch from the guard cells, which catch the 
