Page:Encyclopædia Britannica, Ninth Edition, v. 13.djvu/306

290 IRON implements manufactured in prehistoric times are so numerous as to leave no room for doubt as to the extreme antiquity of the use of that metal instead of the yet earlier stone implements of primeval man. There is every reason to believe that the earliest methods of iron smelting essentially consisted in placing lumps of ore in a fire of wood or char coal, and, after the lapse of a sufficient length of time to permit of their more or less complete reduction, hammer ing the mass of spongy metal thus formed ; so that what is known as the "Catalan forge" of modern times is but a comparatively slight modification of and improvement upon the oldest metallurgical appliances for the extraction of iron, the main difference being in the size of the apparatus and the use of an artificial air blast. Tradition assigns a very remote period to the first discovery of the possibility of extracting iron or crude steel from its ores, Tubal Cain (who has been compared with Vulcan) being the first name mentioned in connexion with the metallurgy of this substance. In the time of the Assyrians iron appears to have been in somewhat extensive use, saws, knives, and other analogous tools having been found by Layard at Nineveh, many of which are very similar to those in use at the present day. Both Homer and Hesiod refer to the forging of iron, whilst the hardening and tempering of steel also appear to have been operations in common use amongst the early Greeks ; indeed the employment of a rough kind of bellows for the forging of tools (probably of iron) is figured in Egyptian sculpture of 1500 years and upwards B.C., the inflation being accomplished by the aid of cords worked by the hand, whilst the pressure of the foot caused the expulsion of the air thus drawn in, much in the same way as is still practised by some almost savage Eastern nations, e.g., the Burmese. In the time of Pliny (about 50 A.D.) the existence of large masses of iron ore in Spain, Elba, Styria, and elsewhere was well known, these minerals being described by him as largely employed in the manufacture of iron and steel; whilst evidently the conditions requisite to produce the best temper of the latter had been carefully examined at that epoch, as he states that the quality of the steel depends on the nature of the water used to harden it, and that oil is preferable for small articles. Prior to this the discovery of cast iron or cast steel appears to have been made, for Aristotle (about 350 B.C.) describes the preparation of the fused or fritted steely iron still prepared in India and known as ivootz, whilst Galen refers to cutting knives made of this steel, and mentions that they are apt to be brittle through excessive hardness. Through the agency of the Romans the manu facture of iron was introduced almost all over the then known world, and into those regions where it had not been previously practised; this, however, does not appear to have been the case with Britain, as the use of iron was probably known there before the Roman invasion ; the knowledge, however, may very possibly have been originally derived from the Romans through the Gauls. The earliest kind of iron forge or bloomery was probably simply an excavation on the windward side of a hill ; the application of an artificial stream of air doubtless soon followed, the blast being either produced by the alternate dilatation and compression of a bladder or goat skins, &c. (as still practised in India and elsewhere), or by means of a fan propelling air through a hollow tube, the fan developing into a kind of loosely fitting piston as still employed in Orissa, Borneo, Madagascar, and elsewhere ; so that the modern bellows and cylinder blowing machine are merely advanced and Improved forms of these crude contrivances. The construction of a clay chamber to contain the fuel and ore, with the employment of a tuyere at the base, so as to be independent of the direction of the wind and of the nature of the ground, was doubtless an early improvement, and probably was the kind of forge used by the Eomans, as it still is substantially that used by various Eastern races. 1 The use of valved single bellows is attributed to the 1 For a description of the different kinds of rude furnace in use in Borneo and other Eastern districts, see Percy s Metallurgy. Romans in the 4th century by Franquoy ; when these developed into double-acting bellows is uncertain, although it is known that such blowing machines were in use in the Harz and elsewhere about the beginning of the 17th century. The date of the invention of the trompe (or air blast, due to the fall of water and the carrying down of air with it) is also uncertain, but was probably a little later, near 1640 (Frangois) ; its use was probably almost confined to the Pyrenees and similar districts where the requisite fall of water was readily obtainable from natural rivulets and torrents. Cylinder blowing machines were introduced at the Carron iron-works about 1760, water-power being usually employed when practicable at that period ; some twenty or thirty years later, when the steam engine came into use, a great impetus was thereby given to the iron industry, as to most other trades, owing to the increased facilities in all directions given by the increased command of power thus obtained. The precise date of the introduction of cast iron is unknown ; probably it was an accidentally formed product in the first instance, due to the employment of larger furnaces and increased blowing power ; in the 14th and 15th centuries it appears to have been known, castings of this period made in Sussex (especially of the later date) being said to be still extant, whilst in the 16th century cannon ot some 3 tons weight each were cast by Johnson. About the end of the century the iron-works of Sussex and neighbouring counties had attained to such dimensions that their consumption of timber for fuel became a serious matter, so that an Act was passed in Elizabeth s reign prohibiting their further extension. Probably this restriction was the cause of attempts being made to utilize coal as fuel in iron smelting, a patent for this purpose being granted in 1611 to Simon Sturtevant, who, however, does not seem to have been successful. Somewhat later Dud Dudley succeeded in producing both cast iron and malleable iron by the aid of coke, but met with so much opposition from the charcoal smelters that he abandoned the process ; a similar result befell Strada in Hainault about the same time ; a century later, however, about 1735, Abraham Darby of Colebrookdale reintroduced coke as fuel with complete success. About 1766-1784 great improvements in the mode of working malleable iron and of transforming cast iron into wrought iron were introduced, partly by Thomas Cranage of Cole brookdale, and Peter Onions, but more particularly by Henry Cort, who patented the use of grooved rolls so as to supersede hammering in 1783, and of the puddling forge in 1784. Since the invention of puddling, and its improvement by Rogers by the introduction of iron instead of sand bottoms, the main improvements in the iron manufacture are the use of the hot blast instead of cold air, due to Neilson, and patented in 1828 ; the employment of the waste gases from blast furnaces for raising steam, &c. (and subsequently for superheating the blast), first patented by Aubertot in France in 1811, and subsequently largely employed in most iron -producing districts, Scotland and Staffordshire excepted ; the invention of the steam hammer by Nasmyth, patented in 1842 ; and the introduction of the Bessemer-Mushet process for steel making (1856) by blowing air through molten cast iron so as to burn out the carbon, and then adding spiegeleisen so as to produce a metal of any required degree of carbonization. In every department of the iron industry, how ever, numerous improvements have been made, amongst which must be specially mentioned the Siemens regenerative furnace and gas producer, and the improved processes for making steel thence resulting ; the use of machinery in lieu of hand labour for puddling, introduced at first unsuccessfully by Tooth and Menelaus, and several others, but brought to a considerable degree of practical suc cess by Danks, Crampton, and others ; the casting of steel under great pressure, due to Sir Joseph "Whitworth ; the application of waste gases and the Siemens regenerative principle to the super heating of the blast by the Cowper-Siemens and Whitwell stoves ; and the recently introduced improvements in Bessemerizing due to Snclus and to Thomas and Gilchrist, whereby even highly phos- phorizcd pig is rendered capable of furnishing a fairly good quality of steel. 2 8. General Classification of Methods employed for the Extraction of Iron from its Ores.- The various modern developments of the earliest methods of iron extraction, consisting of the heating of iron ores with fuel until more or less complete reduction was brought about, and hammer ing the mass, may be conveniently divided into four classes, viz.: (1) those in which cast iron is produced by a smelting process ( 9-21), and subsequently transformed into steel or wrought iron by decarbonizing the resulting pig iron ( 22-28) ; (2) those in which malleable iron or steel is obtained direct from the ore at one operation without 2 A lengthy series of papers on the "History of Modern Invention in the Manufacture of Iron " has appeared in Iron, 1876 and follow ing years, from which much detailed information on the subject may be obtained.