. The Americana : a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc. of the world . Fig. 1. at a speed of 360 revolutions per minute; asteel frame made to suit any height of coal;and a drill auger usually ranging from threefeet to six feet, but which may be made of anysize or length, according to requirements. Thetotal weight of a machine suitable for working asix-foot vein of coal is about 188 pounds. Thesemachines are also aranged to be operated bycompressed air, or by hand. The power ma-chines drill in coal at the rate
. The Americana : a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc. of the world . Fig. 1. at a speed of 360 revolutions per minute; asteel frame made to suit any height of coal;and a drill auger usually ranging from threefeet to six feet, but which may be made of anysize or length, according to requirements. Thetotal weight of a machine suitable for working asix-foot vein of coal is about 188 pounds. Thesemachines are also aranged to be operated bycompressed air, or by hand. The power ma-chines drill in coal at the rate of 6 to 12 inchesper Fig. 2. Fig. 2 illustrates the general view of aMorgan-Gardner electric pick machine, andFig. 3, the sectional details of a Sullivan direct-acting undercutter. In these machines a re-ciprocating piston is actuated by a spring andcam — the spring strikes the blow, and the camdriven by the motor draws the piston number of blows delivered range from 175to 250 per minute. These machines are usedto great advantage in entry driving, cuttingnecks, and turning rooms, or in any narrow place
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectencyclo, bookyear1903
