A Robinson washery in Alabama is reported to treat 700 to 800 tons a day of which 40 per cent is shipped as lump and nut coal; the re mainder, about 400 tons, is washed. A plant of this sort costs f rom $5,000 to $8,000; the cost of washing the coal for labor at washer is $2 per day; for labor at boilers, fuel, etc, $4; for repairs and supplies, $3. This figured for 400 tons would be 2% cents a ton. The 1,vater required is 35.1 gallons per ton of coal washed.
Anthracite coal comes from the mine in all sizes from large lumps down; the larger lumps must be broken and then the coal is screened into the commerdal sizes known as steamboat, egg, stove, chestnut, pea, etc., and the slate. bone, dust, etc., are separated by hand pick ing and mechanical means.
Trade Sizes for Anthracite The table shows the distance between the screen bars or the diameter of screen opening which deter mines the various sizes of anthracite coal as Icnown to the trade.
It will be at once noticed that the market requires many more sizes of anthracite than of bituminous coal. This is because anthracite
requires that its lu.mps shall be all nearly of the same size in order that they shall burn freely upon a grate. The anthracite breaker, as it is called, consists of a systematic grouping to gether of screens, rolls, where breaking is required, of picking chutes from which the boys pick the slate as the coal slides past them, and of shipping bins to which the differ ent sizes are led and from which the coal is loaded into cars to be shipped by train to the market. Besides hand picking, several mechan ical slate pickers have been devised which de pend upon some .physical feature of the slate, as for example, its tendency to come in thin, flat plates, while the coal is more cubical in form; they have the disadvantage that a thin, flat piece of coal ranks as slate and is lost. For the smaller sizes of anthracite the jigs have done very good work and are standard for cleaning those sizes. See Com..