“ The breaker is often as much as 150 feet high, and rarely less than 80 feet. The coal, as it is hoisted out of the mine, is carried up to the top of the breaker and discharged into a hopper, whence it passes downward over bars, through screens and crushers, and is finally discharged into bins at the bottom. The admixed slate is separated partly by special screens, and the slaty coal (bone coal) is picked out by boys as it slides down the chutes, in the more modern breakers water-jigs are used very successfully to separate the slate and coal. ”