Biennial report for 1913 and 1914; administrative report and economic and geological papers . R 8 W. W. R6 W. Fig. 2.—Map of Gillespie quadrangle showing structure contours on coal Xo. 6. absent. Farther east, particularly in the neighborhood of Hillsboro, thecoal though generally present is entirely absent from distinctly channel-shaped areas, being cut off along a curving line in the mine workings by asteeply sloping surface which has been attributed to faulting. Drilling in COAL IX GILLESPIE AND MOUNT OLIVE QUADRANGLES 57 one case, however, has demonstrated very clearly that the coal wa
Biennial report for 1913 and 1914; administrative report and economic and geological papers . R 8 W. W. R6 W. Fig. 2.—Map of Gillespie quadrangle showing structure contours on coal Xo. 6. absent. Farther east, particularly in the neighborhood of Hillsboro, thecoal though generally present is entirely absent from distinctly channel-shaped areas, being cut off along a curving line in the mine workings by asteeply sloping surface which has been attributed to faulting. Drilling in COAL IX GILLESPIE AND MOUNT OLIVE QUADRANGLES 57 one case, however, has demonstrated very clearly that the coal was not dis-placed, but entirely absent for a width of about three-fourths of a mile,beyond which the coal is again present in undisturbed continuity at the sameor nearly the same level. The cutting out of the coal is due probably to its W. W. W. W. W. Fig. 3.—Map of Mount Olive quadrangle showing structure contours on coal No. 6. erosion a short time after its deposition and to the subsequent filling of thechannels with shale and sand. Logs of oil holes drilled north of Butler failto report coal No. 6 in this area, but the unreliability of oil wells in relationto the coal has already been mentioned. It is not improbable, however, that 58 BIENNIAL REPORT FOR 1913 AND 1914 coal No. 6 may be found to be thin or absent in a considerable part of ButlerGrove Township, though there is reason to believe that some of the lowerbeds are present in workable thickness. The limestone mentioned as overlying coal No. 6 is a very valuablefactor in the cheap mining of the coal. In parts of the area, however, thislimestone is not present, and as the roof of the coal is difficult to hold in itsabsence, considerable areas in which the character, thickness, and continuityof the coal is otherwise satisfactory, are not at present co
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