Cooperative Mining Series; Bulletin Volume 15 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1916 edition. Excerpt: ...the two beds is commonly least where the upper coal is thickest, and where the coal becomes thinner in the southeast part of the district the interval between the two coals becomes greater. It is suggested that possibly the distribution of thickness is casually related to variations in interval between the two coals. If, as was probable, the surface of the lower coal was originally approximately flat lying, the necessity of assuming the existence of an uneven floor upon which the upper coal accumulated seems un avoidable in view of the differences in interval between the two coal beds. Whether this difference in interval is due to erosion of the strata overlying coal No. 5 prior to the deposition of coal No. 6, or whether it is due to non-deposition is not known. The floor of such a basin as is believed to exist was 50 to 75 feet lower along the west side of the district than the surface upon which the coal accumulated in the east part of the area; yet in view of the great amount of shrinkage to which peat is subject upon consolidation into bituminous coal, it is not improbable that the irregularities became entirely obscured before the end of the period of peat formation, and that a flat-lying surface underlain by peat extended over this entire area. The thickest coal should, therefore, be found where originally had been the deepest parts of the basin, and this in general seems to be the case. In the series of diagrams on Plate VI is shown graphically the conditions of accumulation of coal No. 6 as outlined in the preceding paragraph. The differential shrinkage of the thick and thin coal deposited within and without the basin respectively have much to do apparently with the position of the "blue band" within the coal bed...