OCR Text |
Show WHAf IS COAL LAND? ' V (From last week) v If, therefore,1' any producing., coal . fi-'ld is examined there will usually be found a belt of outcrop in which the coal-bearing rocks rise to the surface of the ground, arid outside of that belt an area, wnich may amount to thousands thous-ands of square miles, where the coals are all below the surface and the (surface (sur-face rocks may -.even be : of entirely I different age and perhaps "not coal bearing at all. In Indiana shafts ! have been sunk to coal bed's at a depth' Si 250 feet without any preliminary drilling w,here the coal bed did not outcrop out-crop nearer than 15 miles, and many of I the mines of Illinois are -25 to 50" miles from the nearest outcrop of the coal 1 they are working. In classifying land as to its coal character a few general principles are i.ivolved: '1. If the land is kflown to-be underlain under-lain only by groups of rocks known nowhere no-where to contain coal, the land is assumed as-sumed not to be underlain by coal and to be noncoal land. 2. If land, is known tor be ; underlain by one or more groups of rock known to contain workable beds of coal, and a study of the dips shows that those groups are not too deep for the. coals they contain to be worked, the land may be presumed to be coal land. In nearly ill cases where public lands have been withdrawn pending examination and classification it is known or believed that the land is underlain by groups 6f rocks known ' lsewhere to contain workable beds of coal. In probably a majority of cases it is also known or later examinalion demonstrates that coal does not outcrop out-crop on most of the land withdrawn but underlies it, perhaps at a considerable consider-able dep th. . The evidences obtained by the Sur vey consists of observed outcrops and measured sections, properly located and described on the spot, and analyses made in the Government laboratories from coal samples collected in a definite defi-nite prescribed way, supplemented when .necessary by such second-hand d ita as appear to be accurate and reliable re-liable and to be in accord with the personal observations of the field men. |