The tuyeres are but fifteen inches above the bottom stone. In this furnace, pine charcoal is burnt; the ore used is a yellow hydrate of iron, soft and friable, somewhat resembling common yellow loam. A very fine foundry iron, remarkable for its liquidity, running into the finest sand moulds, is the product of this furnace. From this metal the greater part of the fine Berlin castings are manufactured. This furnace is remarkable on account of the small amount of coal it uses.

c. Fig. 45 exhibits a German blast furnace for the smelting of bog ores by charcoal. Though the bog ores of southern Prussia are celebrated for producing very cold-short iron, yet from this furnace a large number of good cannon have been cast for the use of government. The form of the inside of this furnace varies remarkably from that of other furnaces. The height of the furnace is thirty feet. The crucible a is at the bottom seventeen, and at the top eighteen, inches in width; its height is five feet six inches. The concave boshes measure, at the widest part, b, seven feet. The top, c, is three feet four inches in diameter, and forms a cylinder of two

feet five inches in length. A very small amount of pine charcoal is sufficient to supply this furnace.

d. Fig. 46 shows the inside of a furnace at Eisenerz, in Styria -the locality of the iron mountain of which we have previously spoken, where sparry carbonates are smelted. For want of wood, there are at this spot but thirteen furnaces, mostly of this description. In fact, all the furnaces of the carbonate ore region, that is, Styria, Carinthia, and Carniola, are constructed on the same principle. The crucible a is generally from ten to thirteen feet high; the boshes b eight feet nine inches in diameter; the top d from two feet seven to two feet nine inches wide. The height of the furnace is from thirty to thirty-eight feet; so that the upper part of its interior is from twenty to twenty-four feet in height. The blast is produced in square wooden bellows, driven by waterwheels, and conducted to the furnace in two copper tuyeres. The hearth is frequently built of limestone, dry marble, or of Jura lime, for reasons which we shall explain hereafter. The application of hot blast has never succeeded. So greatly does it injure the quality of the metal, that the forges cannot work it without extreme difficulty. These furnaces seldom have a damstone; the breast is walled up, and a taphole for the iron left at the bottom. But in many cases, the cinders flow perpetually from a kind of dam erected on the left side of the breast. The iron is taken out, at short periods, in quantities of 200 or 300 pounds, and commonly run into chill moulds. The pigs are in the form of plates of from five to six feet in length, twelve inches wide, and from two or three inches thick. Such plate iron may be used for making either steel or bar iron; but if designed for bar iron alone, and if the very best bar iron is desired, another mode of casting the metal is practiced. The founder digs a circular hole, from twenty-four to thirty inches in diameter, not far from the tapping-hole, into which the iron falls. The surface of the iron is kept very clean, by throwing off the rubbish and cinder. By sprinkling it with a little water from the nose of a small watering-pot, in a very short time the iron on the surface crystalizes, chills, and a plate in the form of a rosette, from one-half to three-fourths of an inch thick, is lifted off by means of an iron fork shaped like a hay fork, and laid aside. The freshly opened surface of the liquid iron is treated in the same manner as before; and thus the iron contained in the basin is converted into rosettes, which decrease in diameter as the amount of metal diminishes. These thin plates, of a very rough surface, are excellently adapted

for the manufacture of bar iron, as well in the charcoal forge as in the puddling furnace. In the next chapter we shall make some additional remarks on this subject. This plate iron is generally beautifully crystalized, and is of a whitish or mottled color, in which a somewhat reddish tinge is sometimes perceptible. The thicker plates are generally full of little cavities of a round form, occasioned by the disengagement of gases in the liquid iron.

Fig. 47.

e. The old furnaces in Sweden generally had the form of two elliptical crucibles-one put upon the other, as shown in the annexed figure. They were often thirtyfive feet high, and, in most instances, worked slowly; they consumed but little coal, but yielded only from two to three tons of metal per week. Still, this metal was of good quality, though only from one hundred to one hundred and ten pounds of charcoal were required for one hundred pounds of iron. The modern form of the Swedish blast furnaces closely resembles the form in general use at the present time. They are often from thirty-five to forty feet in height. In Russia, the same principle of construction prevails. The furnaces are generally large, with weak blast, and adapted to economize fuel. The method of constructing these furnaces was borrowed from Germany. In fact, the Germans Interior of a Swedish blast started the iron business in Russia and Sweden, which may account for the great similarity in apparatus.

furnace.

Before we leave this method, we shall describe a furnace recently built by the Prussian government on the banks of the Rhine. This furnace is designed for the making of foundry metal from brown iron ore, hydrated oxide of iron, of the transition formation. The metal is of good quality, and is used for castings for machinery and cannon; from this metal, also, the finest specimens of ornamental and statuary designs are cast.

f. Fig. 48 shows a section of the furnace, damstone, and work arch. The height of the furnace is thirty-five feet; nine feet eight inches wide at the boshes: the hearth is five feet high, two feet six inches wide at the top, and two feet at the bottom. The tuyeres

are eighteen inches from the base. The top of the furnace is four feet in diameter. The boshes measure, from the upper part of the hearth to its widest part, four feet six inches. The rough masonry of the stack is made of sandstones, strongly secured by iron binders. The hearth was formerly made of sandstone; but at present,

I believe it is made of fire brick. Boshes and lining of fire brick. There are two linings, one within the other, between which is a little space, for the purpose of giving room for expansion and contraction; this space is filled with small fragments of furnace cinder. The furnace is built against the hill-side, and the trunnel head bridge sprung upon a wall, raised against the hill. The blast is produced by three iron cylindrical bellows, of double stroke, which so far equalize the blast as to make the application of a regulator super

fluous. These bellows are driven by a waterwheel. Two, sometimes three, tuyeres conduct the blast into the furnace, which works with remarkable regularity, and economizes fuel and blast. The hot air apparatus is at the top; and the air is conducted through a system of half circular pipes. The casting-house is built entirely of iron, in a noble Gothic style. It is one hundred feet long, the roof resting upon iron columns of twenty-four inches in diameter. These columns serve as supports for cranes, by which heavy casting and flasks are lifted. In the centre of the building, supported by two rows of columns twenty-four feet in height, runs a strong iron carriage, which serves the purpose of transporting castings from the interior towards the main door, and of lifting them on

wagons.

Before closing this article, we shall give the dimensions of some American charcoal furnaces.

g. The furnace at Cold Spring, New York, is forty feet in height and nine feet in width at the boshes. Its hearth is six feet six