220 MmilsG mDUSTEY. 



p. A vertical pin passes downward tlirougli tlie center of the step-box, in 

 contact with the shaft and resting its lower end on the lever, j. This lever 

 may be raised or lowered shghtlj by the hand-wheel, on the rod, k, thus rais- 

 ing the muUer from the dies, if desired. The shaft, C, is also furnished with 

 a screw by means of which the muller may be raised up entirely above the 

 rim of the pan for the purpose of cleaning up or of changing the shoes and 

 dies. The hoisting apparatus required in the absence of this screw is thus 

 avoided. In order to impart an upward current or movement to the pulp 

 there are inclined ledges, I, on the rim of the pan ; and smaller ledges, w, on 

 the periphery of the muller, but incHned in the opposite direction. The pan 

 is also provided with wings, or guide-plates, n, four in number, which serve 

 to direct the moving pulp toward the center. They are fitted into and may 

 be removed, at pleasure, from a T-shaped projection on the pan-rim. The 

 muller is caused to make, usually, about 60 revolutions per minute. It re- 

 quires from two and a half to three horse-power. Its ordinary charge is 800 

 to 1,000 pounds. In some mills a still larger charge is worked. The capa- 

 city of the pan is sometimes increased by adding a rim of sheet iron so as to 

 increase the height of the side. The treatment of the charge usually 

 requires four hours. The shoes and dies wear out in from three to six 

 weeks, though they are made to last longer in some miUs, their duration 

 depending greatly upon the order in which the pan and all its principal work- 

 ing parts are kept. On this condition the economy in the wear of iron and 

 the efficient operation of this and other pans chiefly depend. Neglect in oil- 

 ing the working parts of the running gear is apt to cause unequal wear, the 

 vertical shaft gets loose and out of line, the grinding surfaces cease to work 

 together evenly, and the efficiency of the pan is greatly impaired, while the 

 costs of working are very much increased. Mill-men generally prefer a shoe 

 and die of moderate rather than excessive hardness. The former wear out 

 faster, but are thought to grind more efficiently. Such are usually cast of an 

 equal mixture of white and soft iron. 



aREELEY's Pan.— A pan known as Greeley's, which is used in some 

 mills and which is highly spoken of, possesses the essential features of 

 "Wheeler's, but differs from it in minor details and has larger capacity. In 

 the Petaluma mill, where ten of these pans are employed, the charge of ore 

 consists of 2,200 pounds. 



