336 University Geological Survey of Kansas. 
effect of the table. The action is more marked on large and 
light than on small and dense material. 
The capacity of such sizing apparatus depends on two con- 
ditions, namely: First, the rate of feeding the apparatus ; 
and second, the velocity at which the grains can be made to 
pass the apparatus, together with the difference in velocities 
of light and heavy grains. 
- Sorting. 
Sorting is a separation of particles by the action of water 
current, according to their falling velocity. Sorting may be 
accomplished by jigs or tables, and therefore by pulsating 
water current, or thin sheets of flowing water. 
By far the greater part of concentrating is done in this dis- 
trict by jigging, although slime tables and other forms of 
slime-treating apparatus are being introduced. 
USE OF JIGS AND TABLES. 
By the use of jigs the separation of ore particles by pulsat- 
ing water current is accomplished. The water is made to 
rise and fall through the jig screens by means of a side pis- 
ton. (See description of jig, page 273.) The supply of 
water is maintained in the plunger cell by a feed spout above 
the plunger. By this arrangement, an inch or so of water 
is kept above the plunger, which prevents air from entering 
and collecting under it. Ina few instances, valves are placed 
in the plunger to allow the escape of any air which might 
have been sucked in; also to reduce the suction in jig bed 
on the upward movement of plunger. Figure 64. The water 
rising and falling through the jig sieve or screen is called the 
‘*under water’’ and is an essential part in the jigging proc- 
ess. The ‘‘feed water’’ is that which is introduced into the 
feed launder to facilitate the passage of the crushed material 
to and over the jig. No definite rule can be laid down as 
to the amount of under water to be used, which varies 
greatly with conditions, such as water supply, position of 
mill, character of material to be treated, method of treat- 
ment, etc. Usually too much water, by far, is used, thereby 
producing a waste of ore by abrasion and wash—the former 
