530 



THE MONNIER PROCESS OF REDUCING ORES. 



The crude diy ore in lumps (1) is mixed with sulphate of soda (5) and 

 passed by the shovelful into the rock-breaker and thence between Corrish 

 rollers (2). The proportion of the mixture is 20 lbs. soda to 80 lbs. ore. 

 Through one elevator (3) the crushed mixture passes to a wire sieve with 21 

 holes to the linear inch, {. e., 576 to the square inch. From this sieve the 

 coarser particles return by a chute to the rock-breaker, the finer pass 

 through it into a second elevator (3), which conducts the finely pulverized 

 and dry material into a large box (4), whence it is passed regularly through 

 a small chamber of brick and iron into the huge revolving iron cylinder (6)> 

 which is five feet in diameter by 40 long. 



Ground Plan of Providence Reduction Works. 



The roasting is here accomplished. This cylinder is revolved very slowly 

 l)j water power. Its upper end (a) is raised six inches above the level of the 

 lower end (b). This elevation can be increased, according to the proportion 

 of the sulphur in the ore. The cylinder has now" been revolving without 

 intermission for a month. Its slow motion causes the roasting mixture to 

 gravitate gradually towards the lowest level, and some 12 hours are required 

 for the crushed sulphates to pass from the upper to the lower end of this 

 revolving cylinder. It thus contains at one time about seven and one-half 

 tons of the ore, since about 15 tons are reduced by this method every 24 

 hours. 



