456 CEMENTS, LIMES, AND PLASTERS. 



hose secured to the dust casing by a wooden frame and clamping-screws. 

 The current of air created in the shaft carries off the moist vapors 

 arising during the grinding process, prevents dust flying from the feed- 

 hopper, and likewise prevents the mill and material being ground from 

 becoming unduly warm. In order that the current of air may be regu- 

 lated according to the weather it is advisable to fit a damper in the 

 shaft. 



FIG. 101. Automatic ball-mill feeder. (Smidth & Co.) 



" Those parts of the mill which are subject to wear and tear, i.e., the 

 balls, grinding, and side-plates, are made of extremely resistant well- 

 tested material, so that the wear and tear is reduced to a minimum. 



"The various parts of the mill may be readily renewed. For this 

 purpose a manhole closed by a wrought-iron cover is provided in the 

 side of the drum opposite to the hopper, so as to admit of easy access 

 to the interior. 



