. Bulletin of the Geological Society of America. Geology. Figure 2.—Sketch of detailed Structure of Part of a 3-foot U-inch Coal Bed locally thickened to 12 feet. expected, the coal which is obtained at such points simply crumbles into slack when mined. At one point the strata in general have suffered until the two coal- beds worked in this area, which normally are 20 to 30 feet apart, are brought to within 6 inches of each other, the lower bed being at that point thickened up to 4? feet and the upper bed from 4 to 6% feet. In a third direction the evidence comes from the peculiar joint struct
. Bulletin of the Geological Society of America. Geology. Figure 2.—Sketch of detailed Structure of Part of a 3-foot U-inch Coal Bed locally thickened to 12 feet. expected, the coal which is obtained at such points simply crumbles into slack when mined. At one point the strata in general have suffered until the two coal- beds worked in this area, which normally are 20 to 30 feet apart, are brought to within 6 inches of each other, the lower bed being at that point thickened up to 4? feet and the upper bed from 4 to 6% feet. In a third direction the evidence comes from the peculiar joint structure com- mon in this area. As stated above, this area lies in the ''block" coal-field, where joint structure is developed in the greatest perfection. Figure 3 shows the normal joint structure of block coal. Figure 4 shows the way the same structure appears over most of this area. In some parts of the mines of this disturbed district the. Figure 3.—Diagram showing normal Structure of the upper Block Coal about Brazil, Indiana. normal block structure is developed, though with this slight difference, that the butt slips or joints are not quite perpendicular, but incline a little. More gener- ally, though, the face slips disappear and the butt slips become strongly inclined to the north, dipping as low as 55 degrees, as far as measured, and where the action has been still stronger a second set of slips are developed as shown in the right of figure 4; so that when mined the coal comes out having the shape of a huge Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Geological Society of America. [New York : The Society]
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1890
