The heat weakened or fractured the rock on account of thermal growth or other processes, according to the sort of rock and ore. Crude ventilation and pumping systems were being used in which essential. Hoisting up shafts and inclines was carried out with a windlass; haulage was in “vans” and https://hectorkrtxz.blogunok.com/36400492/the-basic-principles-of-jewelry-sector