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FLUXING   AND   S LAGGING   OUT   KU KNACKS.              67
twenty feet deep, and all the slag" made by the furnace is dumped by the steam shovel into cars and used by some railroads as ballast, and filling up dumps.
Mineral wool is made from slag by rein citing furnace slag in a cupola, under patents obtained by Wood Brothers, of Wheatland, Pa. The process consists of charging the slag in connection with coke after the plan of melting iron. As the slag flows out it is met at the outlet of the slag-hole by three flat streams of steam, which divide its particles into threads of mineral wool and blow the same into a large building about one hundred feet long and thirty feet wide, prepared for its reception. Variations in the character of slags create different grades of wool, which is sorted and packed according to its commercial value. The wool may often be of such a coarse, poor quality as to be unfit for commercial purposes. There is always a difference in the density of the wool at every cast. The lightest is deposited or blown farthest from the cupola and the heaviest grade nearest to the cupola. The wool is eh icily used as a non-conductor of fire, packed between, the walls and floor spaces of fire-proof buildings, etc. This mineral wool resembles in. character that which the founder finds coming from cupolas which are slagged out*
For every tap oi iron made from a furnace, there are generally two taps for slag. This is termed " flushing a furnace." In the furnace shown, Pig. 6, page 34, the number of taps for iron during twenty-four hours generally ranges from four to five. In about the middle of every tap the furnace is " flushed " and then again about twenty minutes before tapping for iron. The old way of tapping to flush a furnace isnager. The pit used is about twenty feet square byurther why the appearance of fractures in pig iron is so often deceptive.mina in proportion to the amount of heat or friction they are                                                 if j