STATE GEOLOGIST. 269 
no rubbing on the rock. By attaching separators, either screens or wind 
separators, to the machine, it can produce material quite fine in size. 
The speed of the machine is 180 revolutions, its capacity is from 2 to 8 
(ei F=ED HOPPER 
ADJUSTING 
PRESSURE 
SCREWS 
Fig. 40. Crots section of Kent mili. 
Fig. 40a. Exterior view of Kent mill. 
tons per hour according to material and fineness, and the power required 
is 25 horsepower. In grinding limestone the capacity is quite close to 8 
: tons per hour, but is considerably less for grinding quartz. The journals 
