The Yield of Coal Seams

Abstract

AN important paper on the yield of coal seams was read by Messrs. Booking and Bailey before the South Staffordshire and Warwickshire Institute of Mining Engineers in February last, and a separate copy has just reached us. The main object of the paper appears to be to point out that the generally adopted basis of calculation of the yield of coal seams, namely, 1200 tons per foot thickness per acre (or, as it is often put, 100 tons per inch thickness per acre), is too low and that it would be safe to substitute a higher figure. The authors explain that by the thickness of a coal seam they mean not the true thickness as measured between roof and floor at right angles to the seam itself, but the vertical thickness of the coal seam. This method of calculation is of course quite sound and has the advantage that the dip of the coal seam need not enter into the calculation. The generally accepted figure is one that has been used for a very long time; among the interesting manuscripts in the library of the North of England Institute of Mining and Mechanical Engineers, one of the most interesting is the journal of John Watson, a local mining engineer of considerable reputation and eminence in the latter part of the eighteenth century. This journal contains the following entry under date of July 19, 1746: