The top, there is a space of three inches all around. The depth of the fire-pit, from the top of the gratebars to the floor, is twenty-four or twenty-six inches. The flue leading from the furnace to the stack is three and a half by six inches in a single, and three and a half by nine inches in a double furnace. crucible stands on a sple-piece of two or three inches high; this may be either a piece of fire-brick, a lump of fire-clay, or the bottom of an old crucible. The in-walls of the furnaces are made originally of firebrick, but are repaired with mud, taken from the roads where a certain kind of quartz, called "ganis ter," is used in macadamizing. The grate-bars are square bars of wrought-iron, seven-eighths or one inch in thickness, and are loose, so as to admit of being pulled out if necessary. A very hard shingling coke is used in these furnaces, broken to the size of an egg. The grate is supplied with air by natural draught, which is very strong in these furnaces, as there is an almost vertical ascent of the burnt gases. A crucible full of metal requires four hours for melting, and three heats are made in a day. The first operation is to put the fresh crucibles upon their stand, and kindle a small fire around them; or, as is generally the case, to put the crucible upon its solepiece in the gently heated furnace. The crucibles are generally taken from the annealing fire, and, while still warm, set in the furnace. The heat upon the crucible is gradually but slowly raised, by charging more coke, until it assumes a white heat, which operation requires more than an hour's time. When the crucible is hot, and of course glazed, the furnace top-plate-a sort of iron trap-door-is raised, and a tapered sheet-iron pipe is inserted into the hot pot. Through this pipe the pieces of blistered steel are gently lowered into the bottom of the crucible. The pots are usually of the capacity of thirty pounds, though a large sized pot will readily contain forty pounds of pieces. A cover made of pot-clay, which fits the crucible, is now laid upon it, fresh coke given to the fire, and the heat gradually raised to the melting point of steel. This operation requires from one to two hours; and in the mean time the furnace is frequently opened, and fresh coke charged, so that the fuel may be higher than the top of the crucible. Before the steel is melted, the lid is removed, and a little bottle-glass, or pounded blast-furnace slag, is thrown in. This will form a vitreous cover on the surface of the melted steel, and exclude the access and influence of atmospheric air, in case the cover of the crucible is not sufficiently tight for that purpose. A great deal of fresh air draws in at the furnace door, even if it fits well. After the fusion of the steel, the crucible is still kept standing in the fire, to fuse it perfectly, and give time for the interchange of atoms in the fluid mass. As the melting process is chiefly for the purpose of making a uniform grain, those portions of the steel which have more carbon than others, have to dispose of a portion of it, and thus equalize the whole mass. When sufficiently fused, the crucible is lifted from the fire to the floor, when the cover is removed, and the scoria taken off by an iron rod, with a scraper attached to it. The tongs with which the crucible is lifted are provided at their fire-end with arched claws, like basket tongs, to fit the circle of the crucible. The workmen, in getting ready for casting, cover their hands, arms and legs with coarse bagging, formed into narrow sacks, which they saturate with water before putting on; they are thus protected against the intense heat. When all are ready, one smelter grasps the pot in the furnace, and conveys it to a certain spot on the floor. Other hands are ready to take off the cover, remove the scoria, and carry the crucible to the mould, into which it is cast as quickly as possible. The smelter in the meanwhile gets his furnace ready for the returning crucible; for there may be coke on the sole-piece, and, if so, it is necessary that it should be removed. As soon as the crucible is emptied, it is returned to the furnace, and the fire put in a condition to make another heat. The operation is now somewhat shorter, but very much like the first. 13 THE MOULD Is a hollow cast-iron prism, in two halves; it is either a square or an octagon-the latter for round steel. Steel designed to be rolled in sheets, for saws, &c., is cast in flat moulds. The two halves of the mould, while casting, are held together by hooks; and it is set vertically in a narrow pit, so as to project but little above the floor of the building. The mould is well polished on the inside, and, shortly before casting, is covered with a film of oil and finelyground charcoal. It is perhaps three times the weight of the cast, and about three feet long. The upper end of the mould, into which the fluid steel is poured, is open, and of a bell-mouthed shape. Fig. 27 is a section of the mould. The pouring of the hot steel into the mould requires some dexterity and skill, if we expect to make a sound and uniform bar. The liquid metal is cast down in the centre of the hollow mould, so that none of Fig. 27. it shall touch the mould before it reaches the bottom. There are also larger moulds than those we have described, which take more than the contents of one crucible at a time, and |