118 The Phosphates of America. 



B B represent the two opposite heads or cups of the mill hold- 

 ing the two bushings E E, which slightly project into the case. 

 At Z Z, the stone hollow cones are shown (which form themselves 

 in each head by the packing of the rocks being ground after the 

 machine has been run a few moments). The hopper is filled with 

 rocks, which drop into the case of the machine between the two 

 heads. In a few moments after the mill has started the two stone 

 hollow Cones Z Z form themselves and become as hard as the 

 rock. When these hollow cones have formed, the centrifugal force 

 given by their revolution will hurl out of the hollow cones in the 

 general directions indicated by the arrows all the rocks that are 

 forced into them. The iron confining-screen C is of very small 

 diameter, and an important object is accomplished by this arrange- 

 ment. The ground rock is let out of the screen at once. 



We have found it advisable to attach a set of rock-emery 

 stones to this mill for grinding the fine tailings, which amount to 

 about thirty per cent. In this way the average milled product of 

 TO-mesh may be fairly taken as about two tons per hour. 



TJiird. The Griffin mill, which is of the class known as a 

 roller and die mill, in which the material is reduced by being 

 crushed by a roll running within and against the inner surface of 

 a ring or die. 



It is a substantial mill and receives its power by a pulley run- 

 ning horizontally. From this pulley is suspended the roller-shaft, 

 by means of a universal joint, and to the lower extremity of this 

 shaft is rigidly secured the crushing-roll, which is thus free to 

 swing in any direction within the case. 



The illustration on the next page shows that the case consists 

 of the base or pan (24) containing the ring or die (70), against 

 which works the roll (31) and upon the inner vertical surface of 

 which the crushing is done. 



This pan or base has a number of openings through it down- 

 ward outside of the ring or die which lead into a pit or receptacle 

 below. Upon this base is secured the screen-frame (44), which is 

 surrounded with a sheet-iron cover (45) and to the top of which is 

 fastened a conical shield (2&) open at the apex, through which the 

 roll-shaft works. 



To this cone is attached the feeder-arm (34) by means of which 

 the automatic feeder is operated. The crushing-roll is attached to 

 the end of the lower or roll-shaft (1), and just above the roll is the 

 fan (7). On the under side of the roll are shown shoes or ploughs 



