WILKIE ON TIIE MANUFACTURE OF IRON IN GREAT BRITAIN. ° TIIE

principle of making iron—that is, of extracting the metal from the ore and separating from that metal the dross or refuse— is, like the principles of most other arts, simple enough. The difficulty lies in properly applying the principle—and, in these times, cheaply.

"The method formerly everywhere adopted for obtaining iron from the ore, and which method is still in use in some parts of the Continent of Europe, in America, India, &c., was to break the ore into small pieces, and heat it in contact with wood-charcoal,—the fire being urged with bellows worked by hand or water-power,—until the iron was deoxidized or reduced into a metallic state, and softened into a pasty mass; it was then taken out of the fire, and being placed under a hammer, the cinder or earthy matter was forced out, and the iron to some degree condensed. It was then again heated and hammered until the desired form was obtained.

"A small quantity only of material can be operated upon by this method; and it is necessary not only that the iron ore should be rich and comparatively pure, but a large quantity of wood-charcoal is required in the process; and even under these conditions a large amount of metal is wasted, and the labour is great in proportion to the quantity of iron procured."

This simple and primitive method turns out the best metal ; and, with all our science, when iron of a very superior quality is wanted, we now import it : but the mode above described is with us dear, wasteful, and impracticable. The charcoal cannot be furnished in a country like this, or indeed in one far less populous and advanced in cultivation. A scarcity of wood for smelting purposes began to be felt in England towards the end of the sixteenth century. Under James the First and his successor, one of the Dudleys made money by substituting coal for wood in smelting—the Lord Dudley and Ward of our day was a great ironmaster, as is, we believe, the present Lord Ward. The Dudley process, however, fell out of use for nearly a century. In 1713 it was revived by Abraham Darby at Colebrokedale in Shropshire; but till the close of Pie last century, large importations were necessary for the consumption of the country, though Protectionists clamoured as loudly about iron as latterly about corn. The substitution of coke for coal or charcoal, the invention of the steamengine, and improvements in the manufacture, especially Cort's • The Manufacture of Iron in Great Britain ; with Remarks on the Employment of Capital in Iron-Works and Collieries. By George Wilkie, Anse, Inst. C.E., Civil Engineer. Published by Fullerton.

invention of " puddling," towards the end of the last century, gave a wonderful stimulus to the home trade ; which was further increased by the introduction of the hot-blast at a later date.

" In the year 1740 the quantity of oharcoal -iron made in England

and Wales was 17,000 tons ' • in 1788 it was 13, tons, but in the latter

year the pig-iron made with the coke of fossil coal funounted to 48,000 tons, making a total of 61,000 tons. The improvement of the steam-engine by Watt, and the introduction of the process of puddling, for the conversion of cast-iron into wrought-iron, by Cott, in 1783, gave great impetus to the manufacture; and in the year 1796 the make of pig-iron rose to 126,000 tons, and in 1830, including Scotland, to 678,000 tons. In the year H29, James B. Neilson obtained his patent for the use of hot blast, the most important modern improvement in iron manufacture, causing both great economy of fuel and increased production of iron in a given tune and in 1839 the make of pig-iron in Great Britain was 1,248,000 tons, which increased to 1,999,000 tons in 1847, and to 2,700,000 tons in 1862."

Whether iron be made in the primitive mode by charcoal and a pair of bellows, or by the expensive and elaborate processes of the modern hot-blast furnace the principle and object are of course the same. The foreign earthy substances mixed with the metal in the ore or iron-stone must be got rid of by heat, as well as the impurities this process leaves, and the metal finally brought to a state that shall be infusible at a white heat, which constitutes " bar " or wrought iron. This, we have seen, is done under the primitive plan though with waste of metal, fuel, and "men's time. Notwithstanding the science that has been brought to bear upon the subject, this cannot be done by the blast-furnace, which only turns out pig or cast iron, subsequently made wrought or bar iron, by several processes in which remelting and puddling (stirring) form the most important features. The whole process cannot be minutely followed without the drawings and descriptions of Mr. Wilkie's volume, though an actual inspection of works in and out of blast would ho still better. Speaking generally, the furnace is a lofty closed chimney, with access from the bottom, but fed with fuel, ore, and flux from the top. Every step, from the lighting of the fire, or at least supplying it, till the escape of the pig-iron in a molten state, depends upon chemical processes, though known to those who work theta only by rote and experience. After the ore has been calcined, the first step is a proper mixture of the ores with the flax which is intended to facilitate their melting, to make them/tow. This is an important stage because some of the earths in the ore aro infusible in themselves, but can be made readily fusible with proper admixture, while on the other hand a kindly earth may be made refractory or even infusible by an injudicious combination. It is possible that a field of improvement is open in this direction ; Mr. Wilkie conceives there is a wide scope in a proper selection of various ores so as to make the earths in a measure do the work of fluxes. The great modern bugbear cheapness rises up in these cases : the expense of testing and the payment of the requisite skill might be more than the saving of metal or fuel.

The fire is a matter of nicety, which only practice can attain.

"If the heat is insufficient the operation will not succeed—if the hoot is too great or too suddenly applied, the materials will fuse into a slag or cinder, and become nearly or wholly unmanageable. What is required is, first, a gentle heat to expel the water, carbonic acid, ; then an increase of temperature, but not amounting to a melting-heat, while the deoxidizing process is proceeding. After the iron is reduced to a metallic state, the particles may be made to adhere together in the form of wroughtiron, or the metal may be further subjected to saturation with carbon, and it will then pass into earhuret of iron or cast-iron. What is termed working too fast' at a blast-furnace consists in carrying the heat too high up in the stack, and thus melting the materials into stag or cinder, instead of producing such a temperature as will allow of the proper gradual chemical actions taking place. "The hottest part of the furnace must be at the tuyeres, the heat gradually decreasing upwards, so that the throat of the furnace may be Comparatively cool,—for if a furnace is too hot at or near the filling-place, the mine [ore properly prepared for smelting by atmospheric exposure and fire] will become fused before it hue been sufficiently acted upon by the reducing gases, and the iron and earthy matter in combination will run down towards the tuyeres in the form of a slag, front which but little or none of the iron will be revived, and the metal will be carried -away in the cinder, instead of passing into the hearth in the form of cabaret of iron. A furnace too hot at the top will not produce good grey iron, and will also

cause more or leas loss of metal." I

The "blast," whether "hot" or "cold," enters from the bottom of the furnace through an arrangement of pipes, and is driven by the power of steam. The hot-blast is a " saving " ; the cold draught of air rushing upon the fiery mass of the furnace abstracts heat and causes a great " waste " of fuel. There are other advantages in this direction ; but the cold-blast makes the best iron, "cold-blast pig-iron is usually 16s. per ton [about twenty per cent] higher in price than the same description of hotblast pig iron." Like the fire, of which, indeed, it almost forms a part, much of the success depends upon the management of the blast.

When all the processes have been properly gone through, the ores brought by heat and the atmosphere to a mine "—the mine mixed with a right flux—the fire duly applied to the raw material so as chemically to change its nature and separate the earths from the iron and form the two distinct bodies of metal and slag—the lower part of the furnace is reached, and the fused matter falls upon the hearth or crucible according to its specific weight, the iron taking the lowest place, the slag on the top of it. When the slag or " cinder " reaches a certain height, it flows through an opening expressly contrived for it, in a condition like molten lava. The iron is let off in a melted state, by cutting away the stopping of the tapping-hole, and conducted into moulds formed of sand on the floor of the casting-house.

The chemical actions in converting cast-iron into wrought are not so numerous as in separating the metal from the ore. In,

technical language, cast-iron is carburet of iron—a combination of iron with carbon; and wrought-iron is the decarbureted castiron.

"Wrought-iron differs from cast-iron in its mechanical structure, and in containing less impurities. The greater the amount of carbon that iron con tains, the more fusible is the metal; as the quantity of carbon is lessened, the more infusible the iron becomes ; and after the carbon is expelled from the iron it no longer melts on being subjected to a white heat, but becomes soft and

iron, and the particles of metal adhere together' allowing of the malleab e iron being shaped into any required form, and also giving rise to the remarkable property of welding, by which pieces of malleable iron may be joined to each other at a high temperature."

After remelting, the process of conversion mainly consists of stirring ("puddling") to allow the escape of the gas, and hammering to get rid of impurities ; for the rolling into " bar " is a form of convenience. The process is not so well fitted for generalized description as that of making east-iron.

Notwithstanding the scientific and practical struggles after "cheapness," waste still goes on in the manufacture of iron. The coal loses from twenty-five to forty per cent in weight during conversion into coke ; and there seems no help for it. Gas, it appears, cannot practically be supplied from long distances, and there is no town to use it on the spot. To transport the coal to a gaswork and bring back the coke' would cost more than it would save. A good deal of fuel, or at least the heat it furnishes, is wasted by passing out of the " throat " (top) of the furnace into the air, and though methods of turning it to account have been devised, opinions differ as to their utility ; and we conceive they are scarcely so useful as Mr. Wilkie thinks, on account of the first contrivance and subsequent management necessary to render them available. Besides the loss of metal in the slag, the whole of the slag itself is an encumbrance to the earth, all efforts to turn it to account having failed. We know not whether this effort to waste or reject nothing is not struggling against Nature ; most assuredly, a good deal of so-called waste goes on in her processes. The quantity of fruit is small compared with the blossoms ; a large proportion of the embryo or young of many creatures never reach maturity ; what looks like the solid matter of the great globe, philosophers tell us, could be compressed into a small compass ; and what a waste there is in space It is the same in human productions. What sort of works would a painter or a poet produce who used up all his artistical matter ? Even in the iron-trade, " waste " is essential to excellence : the best iron costs the most, in a measure through the rejecting or losing process ; our system of using up everything not only lowers the quality of the article but the national reputation. It seems that a good many capitalists have of late engaged in the "hot-blast" business without understanding it, and have as a consequence burnt their fingers. TO people of this class Mr. Wilkie 's Manufacture of Iron in Great Britain is primarily addressed ; and it will ho found very useful as a warning guide. Besides an historical sketch of the trade, it gives a brief mineralogical account of British iron ores, and of the chemical questions involved in their transmutation. It furnishes a description accompanied with plates of the various buildings necessary in the manufacture of iron, with critical remarks on their structure. The different processes employed are sufficiently explained, as well as some of the subsequent operations to which iron for use as a material is subjected. Mr. Willde concludes with some remarks on the employment of capital in iron-works and collieries, with which last the manufacture of iron ought to be connected for cheap fuel. Though occasionally technical, the book is plain, brief, and it may be recommended as a succinct yet sufficient account of the iron-trade. To a. man intending to embark his money in the business, a course of chemistry in connexion with mining, and a visit to an iron-furnace district, will probably be of more use than any reading that can be put before him ; but Mr. Wilkie's book would form an excellent introduction and help to his practical studies.