sometimes to be taken out and rebuilt. Under these circumstances, introduction of the charges of ore and fuel becomes an important matter. A measure often used, similar to the above, is constructed of two half-inch round iron-bars, so connected at one end that one bar sinks into the furnace, while the other serves as a handle; b

forming the handle; c the measure, and the iron plate, a, prevents the sinking of the rod into the materials. There are various other devices to effect the same object, but these are the most common and simple.

The philosophical principles of the blast furnace, or the causes which separate the several substances with which it is charged and precipitate the metals of the ore, are by no means easily disclosed. While the effects produced are generally well understood, the nature of those chemical and mechanical changes and combinations, formed by the decomposition of the combustible material in the blast, during the various stages of ignition through which it passes, is not easily explained. The engraving on page 121 exhibits Mr. Overman's theory of the blast, according to which it appears that, at a, (the points where the blast is received,) the first operation of ignition commences. Here the chemical composition of the material in the furnace undergoes an important change, the immediate result of which is a new combination of fiery matter, which is borne along with great force by the ascending draft. The iron ore, being less combustible, is thrown against the walls of the furnace, where it is liable to form benches or projecting arms of clinker. The fiery draft, by its peculiar chemical qualities, penetrates the

MANUFACTURE OF IRON.

121

pores of the iron ore, and uniting with its combustible parts, precipitates the metal in a fluid state. The metal, as it sinks, still bears off a certain quantity of the gases, as well as more or less of the earthy matter originally conglomerated with it-hence the lava which always floats upon the surface of the pure metal. To thoroughly perform this operation in the fur

nace requires a due mixture of fuel and fluxes with the ore, while the ore itself has often to be mixed with other ores, combining different chemical or mineral qualities, to secure safe and easy working in the furnace, as well as pure metal. What is known, therefore, as rich ore, (or ore which yields a large per centage of metal,) is really not rich when estimated in reference to economical working in the furnace, for such ores are necessarily heavy, compact, and hard to penetrate by the blast, thereby consuming more fuel, and exposing the furnace to irregularities and other dangers. In short. rich ores have generally to be mixed with poor ores, and, in point of economy for smelting, one is scarcely more valuable than the other. The furnace is usually tapped at intervals of twelve hours. The cinders or lava is first allowed to escape, after which the metal flows out, and travels through iron troughs, or canals made in damp sand, and reaching the beds prepared for it, is cut off into pieces of about two feet in length, and probably eight inches in circumference. Here the metal is imbedded in moulds, and becomes cool in a short time. This is what is called pig iron, and here ends the whole process of smelting the ore in the furnace.

One of the most interesting and beautiful sights which the varied arts of civilized man can afford, is the operation of tapping the metal from the furnace. The metal wildly issues forth in a red translucent

liquid, leaping along the little banks and curvatures of the canals, as if right glad to escape from the prison where

Black spirits and white,
Blue spirits and gray,
Mingle, mingle, mingle,
They that mingle may!

Thus released from the clay and rock with which it was lately associated in the "bowels of the earth," it comes forward, crackling and sparkling, to play a very important part in the progressive and varied scenes of man. To see the stubborn, cold, hard rocks thus turned into threads of molten iron, leaping and creeping submissively at our feet, is, indeed, a scene interesting alike to our sight and pride, and gratifying to contemplate. Such scenes undoubtedly raise the human family still higher in the scale of moral grandeur—for it is here where civilized man forges his thunderbolts against ignorance and oppression; it is here where he asserts the majesty of mind and the glory of labour; it is here where, by the metals raised from the caverns of mountains, “he obtains strength for his hands, and subjects all nature to his use and pleasure."

After the metal leaves the furnace, it is subjected to various manipulations, depending on the use and form to which it is to be applied. The immediate object of these manipulations, is to render the metal purer and stronger, as well as to put it in size and shape for still further working. Pig iron is always converted into blooms, and this is done either in the forge-fire or the puddling furnace. The forgefire is the oldest made, as well as the most simple-there being no material difference between it and the common fire of the blacksmith, except in the heavier character of the former. A mass of metal is thus melted and carried to the forge-hammer, which is moved by machinery, and gives a tremendous blow. Whatever impurities are in the metal, will be pretty well hammered out under this huge hammer, and the metal, as it cools, is formed into rounded pieces, about a foot in length, which are called blooms. In the annexed figure, p. 123, a is the hammer, weighing from one hundred to four hundred pounds. It is strongly wedged to the helve, b, which is moved by the projecting teeth h, of the cylinder k. This cylinder is made to revolve by the water or fly-wheel, m. The hot metal is laid under the hammer, upon the platform d. The metal is temporarily connected with an

iron handle, so as to guide it under the hammer, and is cut off after the bloom is perfected.

After leaving the forge-hammer, the bloom is ready for conversion into rolled or bar iron of every description, preparatory to which it undergoes some additional working in the puddling or heating furnaces-especially the pig metal of the anthracite furnaces of the eastern counties of Pennsylvania, which is much more impure than charcoal iron. This iron, in fact, is not forged at all; but after being puddled is taken to the squeezer, formed into blooms, and is then ready, after re-heating, for the rollers. The puddling-furnaces are always erected in the interior of rolling-mills, and their tall chimneys are seen projecting all around the building. They are built singly and doubly, of various dimensions, but on one general principle. By their aid iron, otherwise valueless, can be made perfectly good, which