Page:The American Cyclopædia (1879) Volume V.djvu/72

68 COLLIERY a FIG. 7. Plications of Anthracite Measures near Pottsville, Pa. a, Sharp mt. ; ft, Pottsville ; c, Deep pits ; c', Hickory and St. Clair pits ; d, Mine hill ; , irregular axis ; /, Broad mt. heavy framework of great elevation and strength, and are used for the fourfold pur- pose of breaking, selecting, separating, and storing the prepared coal. The breaker is built near the mouth of the mine, and the coal cars from the drift, tunnel, slope, or shaft are elevated by machinery to the top of the breaker. Here the coal is dumped into a wide shute provided with bar or flat screens and plat- FIG. 8. Drift with dip and strike f nrrn<a TliA nnol i of inclining coaf beds, forms. I tie coal IS separated by pass- ing over the screens and selected by the work- men on the platforms. The purest and best lump or large coal is thrown into a bin pro- vided for the purpose, while the second size, or steamboat coal, passes into a second bin ; and the remainder, excepting the dirt and slate or impurities, is put through the breaking rolls, which consist of from two to four heavy iron rollers provided with steel or chilled cast-iron teeth. In passing through these, the coal is broken into small pieces, and descends into a system of large circular screens which are con- stantly revolving, and which separate the coal into sizes known as pea, chestnut, stove, egg, and broken coal ; and sometimes a larger size used for large ranges or heaters in hotels, pud- dling furnaces, &c. The sizes above this are steamboat and lump, which last is the largest, and generally used for blast furnaces, though the steamboat size is often mixed with the lump for this purpose. Formerly this prepa- ration of anthracite was exceedingly wasteful, owing to imperfect breaking machinery, and a careless habit of crowding the whole mass, both large and small coal, through the break- ing rolls without regularity or order. It is es- timated that 20 to 25 per cent, of the coal was thus lost. To these defects must also be added that both pea coal and chestnut were wasted in "dirt banks" during the early days of the anthracite trade. Those old banks now yield a large amount of small or screened coal, the re- mainder being converti- ble into pressed blocks of patent fuel, or car- bonic oxide gas as a fuel. The waste is now considerably less, as the chestnut, pea, and some- times lime burners' coal is screened, and only the dust and impurities are rejected, which in well arranged colliery establishments do not much exceed 10 per cent, of the whole. Yet this does not include a much greater waste in the inside of the mines, where a large percentage of small coal is often left in the "goaf," and not less than one third of the whole bed is abandoned as pillars. At the anthracite collieries, where the imperfect systems of " post and stall " and " pillar and breast " are still in general use, not less than one half the entire contents of the coal beds is wasted or lost ; and in some cases the waste is still greater. In comparison with the English bituminous mines, this waste is 25 per cent, greater than that of the longwall and 30 per cent, greater than the bord and pillar systems of mining. The coal breaker was in- vented by a Mr. Batten, who appears to have conceived the idea from the crushing rollers used in Cornwall, England, for the purpose of breaking copper, tin, and other ores. His pat- ent, however, was seriously defective, in not specifying or claiming the combination of the mechanical devices, instead of the direct appli- cation of the toothed rollers to breaking coal, I while his patent fees were thought exorbitant by the colliery owners, and were successfully resisted. The invention ruined the inventor, while it has conferred immense benefits upon the anthracite trade. This method was intro- duced in 1844, before which time the coal was broken to sizes by hand hammers. To break the amount of coal now produced by one of these large collieries would require not fewer than 100 men, and in some cases 200 would be re- quired. There are now more than 400 such coal breakers in use in the anthracite fields. The process is peculiar to the Pennsylvania anthracite mines, where the coal, owing to its great hardness, requires special preparation for economical combustion. It is thought by some that this preparation could be more economi- cally done near the great coal marts, where all the waste, except actual impurities, could be sold, because the coal dust thus wasted is the best portion of the coal. The Pennsylvania anthracite collieries are not only modified by the peculiar structure of the coal measures, but also by numerous distortions and faults which often seriously interfere with mining operations. The form and character of those faults are as peculiar and varied as the litho- logical structure. Dislocations of s-trata and crushed graphitic coal are the predominating forms of fault, but the replacement of the coal by rock and slate or shale is also frequent in the upper and smaller beds ; while small local