MANUFACTURE OF SUPEEPHOSPHATE. 



99 



position, in such a manner that the teeth of one of the rollers corre- 

 sponds to the rings of the other. The discs resist any test and are 

 readily replaced. The distance between the rollers can be regulated 

 according to the size of the grain desired, by means of a regulating 



Fig. 16.— Stamping Mill. 



screw fitted with a spring stud. This machine reduces the_ bones 

 to the size of a nut, mixed with granules [?| inch bones], which are 

 separated by sifting. The double mill comprises two pairs of rollers 

 in a strong lateral framework. The upper pair is provided with big 

 teeth and turns at a less speed than the lower pair, the teeth of 

 ^hich are finer. These double mills take bigger bones (whole ox 



