In the finery process, the hearth or crucible of the furnace is filled with coke ; then six pigs of cast iron are laid hori zontally on the hearth, namely, four of them parallel to the four sides, and two in the middle above ; and the whole is covered up in a dome-form, with a heap of coke. The fire is now lighted, and in a quarter of an hour the blast is applied. The cast iron flows down gradually, and collects in the crucible ; more coke being added as the first quantity burns away. The operation proceeds by itself; the melted metal is not stirred about, as in some modes of refinery, and the temper ature is always kept high enough to pre serve the metal liquid. During this stage the coals are observed continually heaving up, a movement due, in part, to the action of the blast, and in part to an expansion caused in the metal by the discharge of gaseous oxyde of carbon. When all the pig iron is collected at the bottom of the hearth, which happens commonly at the end of two hours, or two and a half, the tap-hole is opened, and the fine metal flows out with the slag, into the loam-coated pit, on a plate 10 feet long, and 3 broad, and from 2 inches to 20 thick. A portion of the slag forms a small crust on the surface of the metal ; but most part of it collects in a basin scooped out at the bottom of the pit, into which the fine metal is run. A large quantity of water is thrown on the metal, with the view of rendering it brittle, and perhaps of partially oxydiz ing it. This metal, suddenly cooled, is very white, and possesses in general a fibrous radiated texture ; or sometimes a cellular, inelnding a considerable number of small spherical cavities, like a decom posed amygdaloid rock. If the cast iron be of bad quality, a little limestone is oc casionally used in the above operation. Three samples of cinder, analyzed by Berthier, gave : 1. Silica, 0.276 ; protox. of iron, 0.612 ; alumina, 0.040; phosp. acid, 0.072, Dud ley.
2. Silica, 0.368; protox. of iron, 0110; alumina, 0.015; puddling of Dowlais.
3. Silica, 0.421; protox. of iron, 0.520; alumina, 0'033 ; puddling of Dowlais.
The remarkable fact of the presence of phosphoric acid, shows how important this operation is to the purification of the iron. The charge varies from a ton and a quarter to atop and a half of pigs ; and the loss by the process varies from 12 to 17 per cent.
The fine metal thus obtained is broken in pieces, and sent to the puddling fur nace. This is a reverberatory furnace, which is charged by shovelling in the fine metal, and layilig it all round the sides of the earth, raising the heap to the roof; the middle of the hearth is left clear. The fuel is then placed in the grate, and the doors closed ; in 20 minutes the metal becomes white, melts, and falls in drops to the sole of the furnace • the fire is then gradually checked, and the pieces separated so that the whole may not be come too fluid, but remain as a pasty mass • as the heat is continued and stir red, the mass gets drier, and carbonic ox ide, which at first was freely given, now gradually lessens, and ultimately ceases.
The workman, with his paddle, now works the mass into lumps or balls of 70 lbs. weight. The balls are lifted out, and are fit for being hammered. The whole object of the puddling has been to remove the carbon out of the iron, to which its fluidity was due ; as the carbon escapes, the fusibility of the mass di minishes.
The puddled balls have now to under go the next process, which is that ef ham mering or condensing the fibres, of weld them, and giving the mass the form of 'a bar.
In England there are employed for the forging and drawing out of the iron, east iron hammers of great weight, and cylin-1 ders of different dimensions, for beating out the balls, or extending the iron bars, as also powerful shears. These several mechanisms are moved either by a steam engine, as in Staffordshire, and in almost all the other counties of England, or by water-wheels when the localities are fa vorable, as in many establishments in South Wales. We shall here offer some details concerning these machines.
The main driving shaft usually carries at either end a large toothed wheel, which communicates motion to the different machines through smaller toothed wheels. Of these, there are commonly six, four of which drive four different systems of cylinders, and the two others work the hammer and the shears. The different cylinders of an iron work should never be placed on the same arbor, because they are not to move together, and they must have different velocities, according to their diameter. In order to economize time and facilitate labor, care is taken to associate on one side of the motive ma chine the hammer, the shears, and the reducing cylinders ; and, on the other side to place the several systems of cylin ders for drawing out the iron into bars. For the same reason the puddling fur naces ought to be grouped on the side of the hammer ; and the reheating furnaces on the other side of the works.
The hammers are made entirely of cast iron ; they are nearly 10 feet long, and consist usually of two parts, the helve and the head or pane. The latter enters with friction into the former, and is re tained in its place by wedges of iron or wood. The head consists of several faces or planes receding from each other ; for the purpose of giviny, different forms to the ball lumps. A ring of cast-iron call ed the cam-ring bag, bearing movable cams, drives the hammer, by lifting it up round its fulcrum, and then letting it fall alternately. In one iron work, this ring was found to be 3 feet in diameter, 13 inches thick, and to weigh 4 tons. The weight of the helve (handle) of the cor responding hammer was 3 tons and a half, and that of the head of the hammer, 8 hundred weight.
The anvil consists also of two parts ; the one called the pane of the anvil, is the counterpart of the pane of the ham mer; it likewise weighs eight hundred weight. The second, named thestock of the anvil, weighs 4 tons. Its form is a parallelopiped, with the edges rounded. The bloom or rough ball, from the puddle furnace, is laid and turned about upon it, by means of a rod of iron welded to each of them, called a potter. Since the weight of these pieces is very great, and the shocks very considerable, the utmost precautions should be taken in setting the hammer and its anvil upon a stantial mass of masonry, as shown in the figure, over which is laid a double, or even quadruple flooring of wood, formed of beams placed in transverse layers close to each other. Such beams possess an elastic force, and thereby partially destroy the injurious reaction of the shock. In some works, a six-feet cube of east iron is placed as a pedestal to the anvil.