Appletons' cyclopaedia of applied mechanics: a dictionary of mechanical engineering and the mechanical arts (1880)
D. Appleton and Company, Benjamin, Park, 1849-1922 · New York, D. Appleton · leaf 452
ing pillars between them ; supporting the roof of the breast, 6 to 12 ft. wide, with timbers until ithas reached the hanging wall; then withdrawing the timbers and packing the excavation with wasterock; and then extracting the pillars and replacing them also with waste rock. A cross layer of… … ,v*y M//.^ /7 ^ s~ ^/.^/ .■* v% /TV / %/ AA * /V /> > 7v ^ S TJ. ^ . h x_Z_^ O \\ ¥\\ employed at the quicksilver mine of Idria, Carniola, and in various modifications at the zinc minesnear Aix, the coal mines of Le Creuzot and St. Etienne in France, the mines of roofing slate near theRhine,…
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