and fuel that fill the interior. For ores that melt easily and fast they are made steeper than for those which are slowly reduced. The boshes open below into the hearth-the central contracted space which the French name the crucible of the furnace. The walls of this are constructed of the most refractory stones of large size, carefully selected for their power to resist the action of fire, and seasoned by exposure for a year or more after being taken from the quarry. Being the first portion to give out, the stack is built so that they can be replaced when necessary. The hearth is reached on each side of the stack by an arch, extending in from the outside. On three sides the blast is introduced by iron pipes that pass through the hearthstones, and terminate in a hollow tuyere, which is kept from melting by a current of water brought by a lead or block-tin pipe, and made to flow continually through and around its hollow shell. The fourth side is the front or working-arch of the furnace, at the bottom of which access is had to the melted materials as they collect in the receptacle provided for them at the base of the hearth or crucible. This arch opens out into the casting-house, upon the floor of which are the beds in the sand for moulding the pigs into which the iron is to be cast. Upon the top of the stack around the central cavity are constructed, in first-class furnaces, large flues, which open into this cavity for the purpose of taking off a portion of the heated gaseous mixtures, that they may be conveyed under the boilers, to be there more effectually consumed, and furnish the heat for raising steam for the engines. A portion of the gases is also led into a large heating-oven, usually built on the top of the stack, in which the blast (distributed through a series of cast iron pipes) is heated by the combustion. These pipes are then concentrated into one main, which passes down the stack and delivers the heated air to the tuyeres, thus returning to the furnace a large portion of the heat which would otherwise escape at the top, and adding powerfully to the efficiency of the blast by its high temperature. The boilers, also conveniently arranged on the top of the furnace, especially when two furnaces are constructed near together, are heated by the escape gases without extra expense of fuel, and they furnish steam to the engines, which are usually placed below them. On account of the enormous volume of air, and the great pressure at which it is blown into the furnace, the engines are of the most powerful kind, and the blowing cylinders are of great dimensions and strength. Some of the large anthracite furnaces employ cylinders 73 feet diameter, and 9 feet stroke. One of these running at the rate of 9 revolutions per minute, and its piston acting in both directions, should propel every minute 7,128 cubic feet of air (less the loss by leakage) into the furnace-a much greater weight than that of all the other materials introduced. It is, moreover, driven in at a pressure (produced by the contracted aperture of the nozzle of the tuyeres in relation to the great volume of air) of 7 or 8 lbs. upon the square inch. Two such cylinders answer for a pair of the largest furnaces, and should be driven by separate engines, so that in case of accident the available power may be extended to either or both furnaces. It is apparent that the engines, too, should be of the largest class and most perfect construction; for the blast is designed to be continued with only temporary interruptions that rarely exceed an hour at a time, so long as the hearth may remain in running order—a period, it may be, of 18 months, or even 4 or 5 years. Furnaces were formerly built against a high bank, upon the top of which the stock of ore and coal was accumulated, and thence carried across a bridge, to be delivered into the tunnel-head or mouth of the furnace. The more common arrangement at present is to construct, a little to one side, an elevator, provided with two platforms of sufficient size to receive several barrows. The moving power is the weight of a body of water let into a reservoir under the platform when it is at the top. This being allowed to descend with the empty barrows, draws up the other platform with its load, and the water is discharged by a self-regulating valve at the bottom. The supply of water is furnished to a tank in the top either by pumps connected with the steam engine or by the head of its source. The furnaces of the United States, though not congregated together in such large numbers as at some of the great establishments in England and Scotland, are unsurpassed in the perfection of their construction, apparatus, and capacity; and none of large size are probably worked in any part of Europe with such economy of materials. The Siemen's regenerating furnace is adopted in those more recently built, wherever an intense heat is required for the reduction of the ores. WROUGHT IRON. It has been, in the past, a just ground of complaint against the producers of wroug it iron and steel, that they could not reduce either directly from the ore-but must go through the long and tedious processes of first making pig or cast iron, then eliminating the carbon from the cast iron by a still more tedious process to produce the wrought iron, and then restore a part of the carbon to make steel. It was said with truth that the half civilized Hindoo tribes and even the barbarous Fans of West Africa, made their native wrought iron (the wootz of India) directly from the ore of an excellent quality, and by a much simpler process than was adopted either in Europe or the United States. There has been, until within the past fifteen or eighteen years, a spirit strongly adverse to progress or improvement among iron producers. By their rude and wasteful processes and their adherence to traditional methods and tests, they succeeded in making a fair though not very uniform quality of wrought iron, at a pretty high cost, but they deprecated any change even if it were for the better. The philosophy and chemistry of iron-making were not well understood, and the time and way of its "coming to nature" a term which conveys the idea of a mystery, was a secret which could only be learned, it was thought, by some supernatural inspiration or some extraordinary skill, only to be acquired by long experience and careful observation. ganese, powdered charcoal, or spiegeleisen, or in some cases silica, to act as flux and remove the sulphur, phosphorus, or other impurity, and to destroy the excess of carbon. He knows, too, just what heat is requisite, and how long it must be continued to produce a certain result every time. Here is no guess-work, no "rule of thumb,” no uncertainty. If he requires the best steel for rails, he can furnish it of precisely standard quality every time; if he is producing steel for the finest cutlery he can produce that; if he desires a wrought iron which shall be so tough and flexible that it can be bent double cold without any symptoms of flaw or crack, he knows just what percentage of the different ores, what eliminating processes, and what amount and duration of heat is neces、 sary to produce it. Now, as in the past, there are different grades and qualities of cast iron, wrought iron, and steel, intended for different purposes, made from different ores, and possessing different degrees of tenacity, hardness, and ductility; but the iron-maker who cannot produce from a given ore, or ores, that description of iron which he desires, without failure, does not understand his business. Cast iron contains, according to the pur pose for which it is intended, from five to six and a half per cent of pure carbon, either chemically or mechanically combined, and except the combination of iron with hydrogen, which is its normal condition, it is not the better for any admixture of other metals or elements, though for some purposes a small percentage of manganese, tungsten, or even a little silicon, are not disadvantageous. As a matter of practical fact, however, both sulphur and phosphorus are usually present, though in good samples in very small amount. By sufficient care they can be almost entirely eliminated, and are so in the best steel and wrought iron. The Bessemer process, invented and put in practice about 1852, first disturbed this popular idea; but in its earlier history this process was not entirely free from guess-work and the coming-to-nature theory by some sudden and unexplicable change; subsequent discoveries and experiments removed this mystery entirely, and there is not, to-day, in practical chemistry and metallurgy a more thoroughly- Steel, according to the purpose to which defined science than that of making iron is to be applied, contains, in chemical comThe iron master, who is fully educated for bination it is believed, from six-tenths to one his business, having before him an accurate and six-tenths per cent. of carbon, and should analysis of his ores, and knowing, as he can have no other ingredient. Wrought iron, if he will, that they are constant in their apart from its ordinary combination with composition, proceeds with the utmost cer- hydrogen, should be entirely free from sultainty to add other ores, or to permeate the phur, phosphorus, or silicon, and though for molten ore with atmospheric air, or to force some purposes, a little manganese, tungsten, additional oxygen through it by means of and a very small percentage of carbon may nitrate of soda, nitrate of potassa, peroxide not prove disadvantageous, yet practically a of iron, or other oxygen-yielding compound, pure iron is preferable to any alloy. Yet it or introduces a definite quantity of man-is seldom actually free from impurities. What is usually denominated pure iron, melts with great difficulty and only at a very much greater heat than either steel or cast iron. În actual practice it is never melted, but when the mass attains a pasty or semi-glutinous condition, it is by one process or another, either hammered, pressed, or squeezed till the impurities are forced out of it. Absolutely pure iron, i. e. iron free from hydrogen as well as other impurities, is one of the rarest metals in the world, and was isolated completely for the first time in 1860. It is a white metal very ductile, and tenacious and so soft as to be easily cut with a knife. The Bessemer process for eliminating the carbon both for producing wrought iron and steel, as now conducted, is as follows: A quantity of pig iron of some grade whose percentage of carbon is known, is melted in one or more reverberating furnaces, according to the size of the converting vessel to be used, which varies in capacity from five to twelve tons. When the metal becomes fluid, it is run into the converting vessel, to which is applied a strong blast of air, which combines with the carbon at an intense white heat. This is continued for about eight or ten minutes, until the whole of the carbon is consumed, when the blast is stopped. It is now wrought iron, requiring only to be squeezed or hammered to force out whatever impurities there may be in it. If, as is generally the case, it is deemed desirable to make it into the Bessemer steel or homogeneous steel or iron, as it is called on the continent, a quantity of metal, usually a pure pig iron, with a known quantity of carbon, is melted and run into the converting vessel to furnish carbon in the exact proportion to make the quality of steel desired, and this combining with the refined iron gives to the mass all the properties and characteristics of steel. This process, though practically a very rapid one, is liable to the objection which held against the old processes, that there is a time in the process of eliminating the carbon from the pig iron when the mass of iron has just enough carbon to form good steel; and that by this process that point is passed and the whole of the carbon expelled, the mass reduced to the condition of wrought iron, and then brought up to the condition of steel by the addition of a percentage of cast iron. This elimination and restoration of the carbon involves waste of time, of heat, and of iron; and hence efforts have been made to convert pig iron and iron ore into steel by a single process. Most of the methods proposed and abiding the test of actual manufacture are intended for the reduction of pig iron or ore to steel, and so come more properly under the head of steel; but a few of them are equally applicable to the production of wrought iron. Among these were the ingenious suggestions of a New York chemist, Prof. A. K. Eaton, at first applied to the malleable cast iron to partially decarbonize it. He proposed the use of the native carbonate of zinc as a flux to furnish the oxygen to consume the excess of carbon. The objection to this process was two-fold-that the zinc combined in a small proportion with the iron, and that the process was too expensive to be successful.. He afterward proposed to substitute crude soda-ash for the zinc-a suggestion in the right direction; for the sodium will combine with the sulphur and phosphorus, and thus help to remove the impurities from the iron; but the crude soda ash is too uncertain in its composition, too full of impurities, and does not yield its oxygen with sufficient readiness to be practically the best flux for this purpose. The process of Messrs. Whelpley & Storer seems one of the best of the numerous American processes. The oxide of carbon, i. e. coal gas, half or imperfectly burned, is the grand agent for making iron and steel from all the German and English furnaces, but the great difficulty has been to apply the powerful agent in such a way as to reduce directly from the ore without going through the pig iron manufacture, the wrought or bar iron, or steel, and free it from the impurities which exist more or less in all ores as well as in much of the pig iron. Messrs. Whelpley & Storer effect this by means of a machine of their own invention, which is really nothing less than the chemist's blow pipe on a grand scale. The oxide of carbon is generated at the moment of using it upon the mass of ore, by the injection of a column of hot air carrying an excessively fine dust of coal or charcoal. The ore spread out upon the floor of a common reverberating furnace receives the red hot blast, while it is rapidly stirred by the workman, and pure iron in minute grains is produced in any desired quantity, from 100 to 2,000 pounds or more at a heat. If the mass is balled up, squeezed, and passed through roller it is bar iron of superior quality. If the time of is what is called a base-burner, the openings the process is extended one hour, or even for introducing the coal being on the top or less, the iron absorbs carbon from the blast roof of this chamber, and the air which enand becomes a light sponge of steel, which ters through the grate effects the combustion melts in the crucible or steel puddling fur- of the coal at the lowest points of the chamnace, and is cast into ingots of sound and pure ber. The products of this combustion rise metal. If continued still longer larger quan- and are decomposed by the superposed strata tities of carbon are absorbed and the mass is of coal above them; they are, moreover, converted into cast iron. The steel and cast mixed with a quantity of steam which is iron as well as the bar iron are of superior drawn in through the grate from a constant quality, and remarkable tenacity and strength. supply of water maintained underneath the Steel is made in this process in eight hours latter. The steam in contact with the infrom crude ore to finished bar; and bar iron candescent coal also decomposes and produin little more than half that time. It is re- ces hydrogen and carbonic oxide gas, which quisite to the success of the process that the are mixed with the gases produced by the carbon should be pulverized to an impalpa- coal direct. The whole volume of these ble powder of the last degree of fineness, that gases is then conducted to the furnace itself thus infinitely subdivided and blown upon by means of wrought iron pipes. The gases the mass it may carry condensed upon its enter one of the regenerators. The regensurface nearly oxygen enough to consume erators are chambers packed with fire-bricks, it, and thus produce extreme rapidity, in- which are built up in walls, with interstices tensity, and thoroughness of combustion. and air-spaces between them (cob-house fashThis pulverization is effected, for the first ion as we should say) allowing of a free pastime, by an ingenious machine invented by sage of gas around each brick. Each regenMessrs. Whelpley & Storer. What Messrs. erator consists of two adjoining chambers of Whelpley & Storer accomplish by their great this kind, with air-passages parallel to each blow-pipe and minute pulverization of car- other, one passage destined for the gaseous bon, Mr. C. W. Siemens effects in an en- fuel, and the other for the supply of atmostirely different way by his regenerating fur-pheric air required for combustion. Each nace; an apparatus requiring, in the first furnace has two such regenerators, and a place, a somewhat more extensive and costly structure, but in the end accomplishing the same result of producing a rapid and intense heat and an atmosphere of oxide of carbon with a comparatively small expenditure of fuel. The necessity that the furnace linings should be almost absolutely indestructible by the intense heat generated makes the first cost of a regenerating furnace very heavy. There are three distinct principles embodied in the Siemens' furnace, viz: the application of gaseous fuel; the regeneration of heat by means of piles of bricks alternately passed over by the waste gases and by the atmospheric air entering the furnace before their combustion; and the chemical action of these gases in combining with the impurities of the ore or the pig iron, and in modifying the quantity of carbon in combination with the iron, for the production of steel. The gas producer is a brick chamber of convenient size, say six feet wide by twelve long, with its front wall inclined at an angle of 45° to 60°, according to the nature of the fuel used. The inclined plane is solid about half way down, and below this it is constructed as a grate with horizontal bars. It set of valves is provided in the main passages or flues, which permit of directing the gases from the producer to the bottom of either of the two regenerators. The gases after passing one regenerator arrive at the furnace, where they are mixed with the air drawn in at the same time, and produce a flame of great heat and intensity within the body of the furnace itself. They then pass, after combustion, into the second regenerator which forms a set of down flues for the waste gases, and ultimately leads them off into a common chimney. On their way from the furnace to the chimney the heated products of combustion raise the temperature of the fire-bricks, over which they pass, to a very high degree, and the gases are so much cooled that, at the base of the chimney, they do not produce a temperature of much more than 300° Fahrenheit. After a certain time the fire-bricks close to the furnace obtain a temperature almost equal to that of the furnace itself, and a gradually diminishing temperature exists in the bricks of the regenerator proportionate to their distance from the furnace. At this moment the attendant, by reversing the different valves of the furnace, opens the heated regenerator for the entrance of the gaseous fuel and atmospheric air, at the same time connecting the other regenerator with the chimney for taking off the products of combustion. The entire current of gases through the furnace is thus reversed. The cold air from the atmosphere, and the comparatively cold gases from the producer, in passing over bricks of gradually increasing temperature as they approach the furnace become intensely heated, and when they are mixed in the furnace itself, enter into combustion under the most favorable circumstances for the production of an intense heat, often rising to 4000° Fahrenheit in the furnace. By changing the relative proportion of air and gas admitted through the flues, the nature of the flame may be altered at will. A surplus of oxygen from the introduction of more than half the volume of atmospheric air will produce an oxidizing flame, suited to the production of very pure bar iron. By the admission of a surplus of gas, on the contrary, the flame can be made of a reductive character and used accordingly for deoxidation. taken by the first, and so the process is carried on continuously with two portions of iron-one freshly introduced and acted upon by the oxidizing flame, the other partly converted into steel and exposed to the neutral flame passing away from the first. M. Berard states that by protracting his process, and by adding spiegeleisen he can remove sulphur and phosphorus from the iron, and make steel from inferior pigs. The Messrs. Martin of Sireuil, France, have, with a Siemens furnace, succeeded in melting with pig iron, old iron rails, wrought iron scrap, puddled steel, &c., in the proportion of two-thirds old rails to one-third pig iron, and have made from the compound an excellent and low-priced steel for rails. Mr. Siemens himself patented, in 1868, and has since that time worked, a process for making natural or "raw" steel directly from the ore by means of a modification of his furnace. This can only be done successfully it is said by the use of the purest and best ores. Of other processes we may mention that of Mr. James Henderson, an eminent founder, of Brooklyn, N. Y., who, using the Bessemer process, has improved it by charging the blast furnace with a mixture of iron and Manganese ores, or any of the Manganiferous iron ores, thus incorporating the indispensable manganese, and causing it to exert its beneficial influence in purifying and refining the iron, at the beginning, instead of the end of the pneumatic process. Mr. John Heaton of Nottingham, England, has been successful in oxidizing and removing the carbon and other impurities with great rapidity by the use of nitrate of soda with the molten metal in the following way: The "converter" consists of a large wrought Berard's process for making steel by gas, directly from pig iron, or ore, requires the Siemens furnace, which he constructs with the bottom formed into two parts each hollowed out like a dish, with a bridge between them, upon which the pigs introduced into the furnace receive a preliminary heating. The flame is maintained with a surplus of oxygen, and a quantity of pig iron is melted in one of the chambers or dishes. The oxidizing action of the flame decarbonizes and refines the pig iron, and after a certain time a second quantity of pigs is thrown into the second dish and melted there. The flame is now reversed in its direction; the oxidiz-iron pot, lined with fire clay; into the boting flame is made to enter at the side where the fresh pig is placed. In passing over this, and oxidizing the carbon, silicon, and other impurities in the iron, the flame loses its surplus oxygen, and becomes of a neutral, or at least only slightly oxidizing character. In this state it passes over the other bath of molten iron, now partly refined, and it continues to act upon the impurities without attacking the iron itself. At a certain moment this portion of iron is completely converted into steel, and that part of the furnace is then tapped, so as to make room for a fresh charge of pigs in that place. After that, the current of gases is again reversed, the second bath now entering into the position previously tom of this a suitable quantity (about 6 per cent. usually of the weight of the pig iron or ore), of crude nitrate of soda combined with silicious sand, is introduced, and the whole covered with a cast-iron perforated plate. The molten pig is then poured in and in about two minutes the reaction commences; at first, brown nitrous fumes are evolved, and after a lapse of five or six minutes, a violent deflagration occurs attended with a loud roaring noise, and a burst from the top of the chimney of brilliant yellow flame, which, in about a minute and a half subsides as rapidly as it commenced. When all has become tranquil the converter is detached from the chimney and its contents emptied |