crease the amount of alkali in the cinder; but this object is directly counteracted by brick and stone boshes.

7. Having delineated, though by no means having exhausted, the various matters which relate to puddling, we shall take a critical view of the present mode of refining. We shall also investigate the cause of the improvement which results from the sudden cooling of metal, and shall conclude the chapter by a few general remarks on wrought iron.

The run-out fire, which is generally employed for refining iron, is based upon principles derived from the charcoal forge. Before hot blast was introduced into blast furnace operations, this was doubtless a useful apparatus. Pig metal which, fifteen years ago, would have been considered worthless for the forge, is now employed in the manufacture of iron. The run-out fire labors under the same difficulties which exist in relation to the puddling furnace with iron boshes. For iron which contains carbon in small amount, or in chemical combination, its hearth is too cold. From gray charcoal pig iron, of good quality, the run-out produces a tolerably useful article. But we do not need it for this purpose. Cold blast gray pig may be worked to advantage in the puddling furnace without difficulty. Since the introduction of hot blast-that is, since the use of anthracite and stone coal-quite a revolution has taken place in the chemical constitution of pig iron: the amount of chemically combined carbon has increased; silicon and other reduced matters are more generally present; and even the grayest specimens of metal are not free from unoxidized elements. To these causes, the difficulty of refining hot blast iron may be mainly attributed. Our previous investigations have proved that a high heat is required for the removal of silicon; but a still more necessary element is a cinder which does not too freely yield its oxygen. To what extent does the run-out fire fulfil these conditions? With respect to heat, it is but little better than the puddling furnace; and with respect to cinder, it answers scarcely a better purpose. Analysis has shown that the cinder of the run-out fire contains as much protoxide of iron as the cinder of a puddling furnace. A finery cinder from Dudley, England, contained silex 27.6, protoxide of iron 61.2, alumina 0.4, and phosphoric acid. If we melt very impure pig iron in such a cinder, we cannot produce iron of good quality; this is especially the case should the iron have been smelted by hot blast. For the melting of such iron, we require a cinder containing less alkali. Less alkali is required to make good iron in puddling. From the

amount of iron in this cinder, it is evident that the run-out fire cannot improve bad pig iron in any high degree, unless there is a serious loss in metal. That this loss occurs is shown not only from conclusions theoretically arrived at, but from observation. Whatever advantage the run-out fire, in this case, possesses, is that of a division of labor, which, of course, we are not disposed to rate very highly.

We believe that, in the construction of the run-out fire, but little science and philosophy have been embodied. At all events, but one principle governs the present case; that is, bringing the inferior qualities of metal, in the cheapest possible way, to a higher standard. The idea of making white metal was undoubtedly derived from the ancient method by which such metal was made in the blast furnace. The latter metal, when smelted from good ore, was, and still is, a prime article in the charcoal forge. Since the introduction of coke, anthracite, poor ores, and hot blast, the iron business has undergone a change. At the present time, we cannot avoid producing pig iron, which, a few years ago, would have been considered worthless. This metal it is now our object to bring to as high a standard as the best iron of the ancients. In the accomplishment of this object, it is evident that cautious manipulation and scientific knowledge are required. We cannot believe, that any one doubts that the quality of our worst pig iron is equal to that of the ores from which steel metal is made. If such is the case, it should not be deemed an impossibility to make steel metal from our most inferior pig iron.

There would be no necessity for making white metal were it not for the railroad, boiler-plate, and heavy bar iron which is needed. For these purposes, boiled does not answer so well as puddled iron. But, if such iron is necessary, it should be well made. The run-out fire is imperfectly adapted to accomplish this result. By destroying the carbon in pig iron, without removing its impurities, it fails to produce a metal fit for boiling. Therefore, the run-out fire destroys the element necessary to make metal boil, without producing a metal profitable for puddling. Hot blast iron would be an excellent metal for boiling, were it possible to remove its impurities

without destroying its carbon. Still, it is not impossible to remove impurities and carbon together, and thus make a useful metal for puddling.

The finery is considered a link between the blast furnace and the puddling furnace; that is, it is believed to occupy the same relative position between these furnaces that the blast furnace occupies

between the ore and the finery. The blast furnace is an apparatus designed for the removal of impurities with the least possible loss of iron. It answers the purpose of its construction excellently. But what is the fact with respect to the finery? Simply this: the cinder from the finery contains more iron than that from the puddling furnace; and, when we consider that the contact of coke or anthracite increases the amount of silex in the former, we find that there is a far greater loss of metal in the run-out fire than would result from the same pig iron in the puddling furnace. If this is the only advantage derivable from the finery, it is surely far preferable to take the worst kind of pig iron directly to the puddling furnace.

We trust that some practical men will be sufficiently interested in this subject to endeavor to construct something better adapted to our wants than this exceedingly imperfect apparatus. If heat, and a cinder to protect the iron can be obtained, all the conditions of a good finery will be fulfilled.

m. The philosophy of the improvement of metal consists in the circumstance that a part of its impurities, which are originally in chemical combination, are converted into mechanical admixtures. Iron containing a small amount of carbon, silicon, or phosphorus is always more hard and strong than pure iron. Pure iron is quite soft. Impure iron has the property of crystalizing on being suddenly cooled. The size of these crystals is proportional to the amount of carbon in chemical combination the iron contains, in proportion to other matter. Between the crystals, minute spaces are left, which serve for the absorption of oxygen. By this means, silicon and calcium may be oxidized; but such is not the case with carbon, phosphorus, and sulphur. Therefore, the metal improves in quality in proportion as oxygen finds access to its impurities. For this reason, the habit of running metal, or any kind of pig iron designed for the forge, into iron chills, is a good one, and is worthy of imitation wherever it is applicable. By this means, the absence of sand and the cleanliness of the metal are secured. For the same. reason, the metal is tempered; that is, the plates of metal, or, as in some parts of Austria, rosettes of metal, are piled up with small charcoal, braise, and exposed to a lower temperature than a cherryred heat, for twenty-four or forty-eight hours, in a kind of large bake oven. By this method, the value of the metal is improved for the manufacture of soft and fibrous iron. It is not applicable to plates from which steel is to be made.

n. Wrought iron, if of good quality, is silvery white, and fibrous; carbon imparts to it a bluish, and often a gray color; sulphur a dark dead color, without a tinge of blue; silicon, phosphorus, and carbon a bright color, which is the more beautiful the more the first two elements preponderate. The lustre of iron does not depend principally upon its color; for pure iron, though silvery white, reflects little light. A small quantity of carbon in chemical combination, phosphorus, or silicon increases the brilliancy of its lustre. Its lustre is diminished by silex, carbon in mechanical admixture, cinder, lime, sulphur, or magnesia. Good iron should appear fresh, somewhat reflex in its fibres, and silky. A dead color indicates a weak iron, even though it is perfectly white. Dark, but very lustrous iron is always superior to that which has a bright color and feeble lustre. Coarse fibres indicate a strong, but, if the iron is dark, an inferior article, unfit for the merchant or the blacksmith. But, where the iron is of a white, bright color, they indicate an article of superior quality for sheet iron and boiler-plate, though too soft for railroad iron. For the latter purpose, a coarse, fibrous, slightly bluish iron is required. Iron of short fibre is too pure; it is generally hot-short, and, when cold, not strong. This kind of iron is apt to result from the application of an excess of lime. Its weakness is the result of the absence of all impurities. The best qualities of bar iron always contain a small amount of impurities. Steel ceases to be hard and strong if we deprive it of the small amount of silicon it contains, or if, by repeated heating, that silicon is oxidized. This is the case with bar iron. If we deprive it of all foreign admixtures, it ceases to be a strong, tenacious, and beautiful iron, and becomes a pale, soft metal, of feeble strength and lustre. Good bar or wrought iron is always fibrous; it loses its fibres neither by heat nor cold. Time may change its aggregate form, but its fibrous quality should always be considered the guarantee of its strength. Iron of good quality will bear cold hammering to any extent. A bar an inch square, which cannot be hammered down to a quarter of an inch on a cold anvil without. showing any traces of splitting, is an inferior iron.

CHAPTER V.

FORGING AND ROLLING.

THE machines adapted for forging and condensing wrought iron. vary both in principle and in form. This department of the labors of the iron master is very extensive. But, as our treatise must necessarily be restricted within certain limits, and as this branch of iron manufacture is already highly cultivated in this country-our establishments excelling in finish those of Europe generally, and in some respects particularly-we shall devote the present chapter to a mere enumeration of the machines required in an iron factory, and explain the principles upon which each is constructed. We are satisfied that, if a higher degree of perfection is needed in this department, it will be realized by the intellect, skill, and industry of our practical engineers.

I. Forge Hammers.

a. The most simple machine by which iron is forged is the German forge-hammer, often called the tilt-hammer. This machine, often of a fanciful form, is very extensively employed. The leading principle which we seek to secure in its construction is solidity; and every variety of form has been invented simply to give permanency to the structure, which is mainly endangered by the action and reaction of the strokes. The common form of a forge-hammer with a wooden frame is represented by Fig. 95. a. The cast iron hammer, which varies in weight, according to the purposes for which it is designed, from 50 to 400 pounds. For drawing small iron and nail rods, a hammer of the former size is sufficiently heavy; but for forging blooms of from 60 to 100 pounds in weight, a hammer weighing 300 or 400 pounds is employed. Such a hammer is represented by Fig. 96, in detail. It should be cast from the strongest gray iron, and secured by wooden wedges to the helve b. The fastening of the hammer to its helve is, in many cases, effected