CLAYS OF NEW YOKE: 657 



rapidly reduced to a fine state of division, tlie whole operation 

 taking not over one or two seconds. Tlie material is then dis- 

 charged on an endless belt, and carried to the screens. The dis- 

 integrator is inclosed in a metal case. The series of drums, the 

 velocity with which they revolve, and the strength and the arrange- 

 ment of the staves depend on the hardness, of the material tO' be 

 pulverized, and also on the degree of fineness to which it is to be 

 reduced. By varying the velocity of the disintegrator a coarser or 

 finer product is obtained. 



The capacity of this type of machine is very great, but it also 

 requires considerable power to operate it. According to capacity 

 disintegrators can pulverize in one hour from 8000 to 28,000 

 pounds of material, such as shale, gypsum, etc. They require 2-| to 

 4 horse power for every ton of material pulverized in an hour. 



Ball mills. These consist of a large drum which revolves on a 

 horizontal axis. This drum contains balls of varying diameter 

 which roll over each other, and as the drum revolves .comminute 

 the particles of material. The material is introduced through a 

 door in the side of the drum, the door is then closed, and the drum, 

 being set in motion, isi turned till th© material is ground to suffi- 

 cient fineness. It is then discharged on the sieve, and particles 

 which will not pass through are returned to the drum together with 

 fresh material. 



Ball mills were at first constructed with a comparatively small 

 capacity, but recently mills have been constructed that discharge 

 the pulverized material continuously. A still more recent modifi- 

 cation consists in introducing the charge at one end of the cylinder, 

 allowing it to pass the whole length of the mill and issue at the 

 opposite end. As the breaking up of the particles in the ball mill 

 is the result primarily of the action of the balls rolling over them, 

 it will easily be seen that the product of this machine will show a 

 considerable variation in the size of its grains, and that the thorough 

 pulverization will be obtained only by keeping the material a long 

 while in the mill. This objection therefore, adapts the ball mills 



