. A dictionary of arts, manufactures and mines : containing a clear exposition of their principles and practice. 332 than in the roasting furnace. The long axis of the oval hearth is 14 feet; its short asis10 feet; its mean height 2 feet. The principal ore smelted at Chessy isthe azure copper, which was discoveredhy accident in 1812. Red copper ore, also,has come into operation there since average metallic contents of the richestazure ore are from 33 to 36 per cent.; ofthe poorer, from 20 to 24. The red orecontains from 40 to 67 parts in 100. Theore is sorted, so that the mea
. A dictionary of arts, manufactures and mines : containing a clear exposition of their principles and practice. 332 than in the roasting furnace. The long axis of the oval hearth is 14 feet; its short asis10 feet; its mean height 2 feet. The principal ore smelted at Chessy isthe azure copper, which was discoveredhy accident in 1812. Red copper ore, also,has come into operation there since average metallic contents of the richestazure ore are from 33 to 36 per cent.; ofthe poorer, from 20 to 24. The red orecontains from 40 to 67 parts in 100. Theore is sorted, so that the mean contents ofmetal may be 27 per cent., to which 20per cent, of limestone are added; whencethe cinder will amount to 50 per cent, ofthe ore. A few per cents, of red copperslag, with some quicklime and gahrslag, areadded to each charge, which consists of200 pounds of the above mixture, and150 pounds of coke. When the furnace(fourneau a manche, see the Scotch smelting hearth, under Lead) is in good action,from 10 to 14 such charges are worked in 12 hours. When the crucible is full of metalat the end of this period, during
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