inches high; one foot nine inches wide at the bottom, and three feet six inches at the top. In this furnace, magnetic ores from the neighborhood, mixed with a small portion of brown hematite, and a small quantity of bog ore, are those chiefly smelted. These ores are somewhat expensive, averaging three dollars per ton. The gray pig iron manufactured is of superior quality, very fusible and uniform. Two tons and a third of ore, and 120 bushels of charcoal, are required to make one ton of metal. The wages of workmen. average about three dollars per ton of iron. A very small amount of coal supplies this furnace.

h. Fig. 50 represents one of the Eastern Pennsylvania furnaces, all of which are constructed in a similar manner. The height of this furnace is thirty-two feet; width of boshes nine feet six inches; hearth five feet high, two feet in width at the bottom, and two and a quarter feet at the top. The rich hydrates, pipe ores, fossil ore, &c., are generally used. Two tons and a half produce, on an average, one ton of metal. For each ton 180 bushels of charcoal are required. Wages of workmen average two dollars per ton. At some places, the ore is cheap; while at others, it often costs three dollars per ton. There are places where but one dollar per ton is paid for ore, and but four cents per bushel for charcoal. This is the case at Lebanon, and at some adjoining counties. The furnaces in operation at the oldest establishments west of the Alle: ghany Mountains, such, for instance, as the Dover furnace at the Cumberland River, Tenn., are almost a true copy of those in use in Eastern Pennsylvania. Both require the same amount of fuel, and both yield similar results. But the further we move west, the greater is the amount of coal we find used to produce a given amount of iron. For instance, at the Alleghany and Ohio furnaces, as far down as Hanging Rock and Portsmouth, 170 or 180 bushels of charcoal are considered sufficient to make a ton of iron; while in Kentucky and Tennessee, from 200 to 250 bushels of charcoal are required to produce the same amount.

V. The Modern Charcoal Blast Furnace.

At the present time, the blast furnaces are reduced, in a greater or less degree, to a general principle. While they slightly vary according to ore, fuel, locality, in all of them the hearth is narrow and high, the boshes more or less steep, and the trunnel head, or throat, from twenty inches to four feet wide. The outward form varies greatly; and every owner or builder follows whatever arrangement

is most conformable to his taste. We shall give the result of our own experience, and point out the material points on which the success of smelting mainly depends. Fig. 51 represents a section through

work and back arches of a charcoal furnace. This furnace has two tuyeres, and is designed to smelt hydrates of the oxides of iron, such as hematite, brown iron stone, pipe ore, and bog ores. This form, with more or less alterations, will serve as a general model. The exterior may, in all cases, be the same, and the interior altered according to circumstances. The whole height of the furnace is thirty-five feet. The hearth measures from the base to the boshes five feet six inches; its width at the bottom is twenty-four inches, and at the top thirty-six inches. The tuyeres are twenty inches

above the base. The boshes are nine feet six inches in diameter, and measure from the top of the crucible four feet, thus giving about 60° slope. The blast is conducted through sheet iron or cast iron pipes, laid below the bottom stone, into the tuyeres. The top is furnished with a chimney, by which the blaze from the trunnel head is drawn off. Around the top is a fence of iron or wood; Wood, however, is preferable. Fig. 52 shows Fig. 52.

sometimes of stone.

Section of a charcoal furnace through the tuyere arches.

the same furnace in a section across the two tuyere arches and the tuyeres.

a. The Building of a Blast Furnace.-A furnace should be located on a dry spot, free from springs and water of any kind, and not exposed to floods after heavy rains. The ground should be then excavated, until the bottom is sufficiently solid to bear the heavy

weight of the stack. The foundation should be at least one foot larger in each direction than the base of the furnace; that is to say, if the furnace is thirty feet at the base, the foundation ought to be thirty-two feet square. Any kind of hard, large stones may be used to fill the excavation. No mortar should be used in the stone work. We should be careful to leave some channels through which rain or spring water, in case it should penetrate the foundation, may flow off. Such a drain should be carefully walled up and covered. The cavities or channels for the blast pipes are to be placed level with the ground; and the four pillars of the furnace then laid out. Fig.

Fig. 53.

53 shows the arrangement of the pillars, and that of the channels for the blast pipes a, a. If the stack is thirty feet at the base, the work arch b may be fourteen feet wide. Eight feet are thus left on each side of the pillars. The tuyere arches c, c, c measure ten feet, which leaves ten feet pillars. The size of the room in the centre is to correspond with the diameter of the boshes; that is, nine and a half feet. This is to be measured from the centre of the stack by drawing a circle of four feet and three-quarters ra

dius. The inside of the pillars is to be built plumb; on this the lining rests. The walls towards the arches should also be plumb; but the outside should be beveled according to the general tapering of the stack. The height of this stack is thirty-five feet; its width is fifteen feet seven inches at the top, and thirty feet at the base, thus leaving a slope of two and a half inches to the foot. The material of which a stack is built has but little influence on the operation in the furnace. Building stones of any kind, as granite, graywacke, sandstone, or even slate, will answer; but limestone is not adapted for this purpose. The pillars are to be built with great solidity, with good mortar, and may be raised to the place in which the arches are set. The arches are turned of brick, which ought to be hard-burned. Fig. 54 represents the work arch; this commences seven feet above the ground, and forms just the half of a circle. The arch, from

fourteen feet at its outside, contracts to five feet at the timp. The tuyere arches are but ten feet wide, and twelve feet high; they contract, towards the interior, to three feet. The binder a may be walled in at the height of ten feet, and of course crosses the arch. The stone work above the brick arches should be arched, that some of the pressure on the latter may be relieved. The brick

Stone

arches have some advantage over other arrangements. arches are very apt to crack and split; and if, as often happens, the blast works out at the timp or tuyeres, the stones crack and fly in such a manner that it is dangerous to go near the fire. Iron joists are very expensive; besides, by their expansion and contraction, they weaken the stack. The brick arch is very strong, safe, and durable. When the pillars all around are seven feet high, the