. First century of national existence; the United States as they were and ipitous walls of rock alongthe livers; or it is indicated by peculiar in-dentations, known as benches, around theirline of outcrop, caused by their crumblingand wearing away more rapidly than theharder strata above and below them ; andagain by the recurrence of springs of water and wet places at the foot of the benches,which point to an impervious stratum with-in the hill that prevents the water percolat-ing any further down; and lastly, in thelittle gorges worn by the runs, the bedsare often uncovered, and loose
. First century of national existence; the United States as they were and ipitous walls of rock alongthe livers; or it is indicated by peculiar in-dentations, known as benches, around theirline of outcrop, caused by their crumblingand wearing away more rapidly than theharder strata above and below them ; andagain by the recurrence of springs of water and wet places at the foot of the benches,which point to an impervious stratum with-in the hill that prevents the water percolat-ing any further down; and lastly, in thelittle gorges worn by the runs, the bedsare often uncovered, and loose pieces of coalwashed down lead to their original sourceabove. However discovered, the method ofworking them is simple. A convenient placeis selected upon the side of a hill, and an ex-cavation called a drift, usually about fourfeet wide, is made into the coal-bed. Theheight of the drift is governed by the thick-ness of the coal-bed and the nature of theoverlying slate. Miners sometimes work indrifts only 2^ feet high. Coal-beds three orfour feet thick are very common, and are.
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Keywords: ., bookauthorhodgejam, bookcentury1800, bookdecade1870, bookyear1874
