MANUFACTUEE OF SUPEEPHOSPHATE. 



85 



Grijiding Machines — Edge Bunners. — Edge runners consist 

 generally of two stones turning on a circular plate round a 

 vertical shaft ; at the same time each stone turns round its own 

 horizontal axis, and grinds the material both by crushing and 

 rubbing. The horizontal axes of the two mills are independent of 

 one another, and each connected with the vertical shaft by means 

 of a hinged crank. The stones can thus be raised or lowered inde- 

 pendently the one of the other. The material is fed into the mill 

 directly, by the shovel or by an elevator ; it is drawm continually 



Fig. 1. — Vertical Edge Runner. 



under the stones by collectors, and when it is sufficiently ground, 

 it is evacuated by the automatic discharge, sifted and bagged up. 

 Fig. 1 shows a pair of edge runners. Tw^o men suffice to attend to 

 the mill, the elevator and the sifting machinery. 



Flatstone Mills.— Ylntstone mills are built either with the upper 

 stone stationary or the lower stone stationary, according as it is 

 the upper or lower stone that revolves. Mills of the first kind are 



is not standing idle. A manure work at Forres away in the " Farther North " 

 has recently been equipped with automatic shifting machinery for removing 

 manure from the " den". — Tr. 



