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66                         METALLURGY   OF   CAST   IRON.
The percentage of silica slag contains, sometimes as high as 60.00, as seen in Tahle 13, shows us ways in which silicon can be carried off or reduced in smelting or remelting iron. The weight of slag produced is dependent upon the character of the ore, fuel, and flux used. The furnace can produce a greater weight of slag than iron, but, as a rule, 600 to 1,000 pounds of slag are made to the ton of iron. The richer the ore, the less slag in the normal working of a furnace. The slag created at a furnace must be disposed of. We find machinery utilized in this work, as in other manipulations of furnace practice. Some have it conveyed in large receptacles, which are hauled by power to cars or dumping ground. When overturned, they release the slag in a molten form, or solidified state. Another plan is to let it run from the spout Y, Fig. 18, page 90, to furrows in the ground, which may be run for a length of two or three hundred feet, often covering an acre of ground. This slag is pulled out of its furrows by hooks in the hands of men before it has thoroughly solidified. In removing the slag from the ground it is shoveled into carts and teamed to the dump, or thrown 011 cars to be transported and used for railroad ballast, or for making roadways. Then again, the slag is run into a deep pit, after being granulated by a stream of water issuing from a pipe in the trough, which strikes the slag as it leaves the trough to drop into the pit. This granulated slag is hoisted by a steam shovel and dumped into cars, doing away with much hand labor. This plan is used at the Alice Furnace, Sharpsville, Pa., and Ella Furnace at West Middlesex, Pa., after plans designed by Mr. E. H. Williams, the general manager. 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