« PreviousContinue »
imon cheaply on a large scale, in so many different districts,-as, for instance, in Wales, Staffordshire, Yorkshire, Durham, and Scotland, -has also doubtless been one of the principal causes of our material prosperity, more particularly during the last half century. The great value of iron compared with other metals, consists in the immense variety of uses to which it is capable of being applied. First and foremost is its use in the form of tools, without which man were indeed but a 'poor, bare, forked animal.' Every improvement in tools has marked a new stage in civilisation, until at length, since tools have become organized as machines, results of the most extraordinary magnitude have been achieved. But, besides the use of iron in the form of tools and machines, it has of late years been applied to an infinity of useful purposes, such as ship-building, bridge-building, and works of construction of various kinds, as well as to the purposes of locomotion ; while at the same time it is used for purposes so delicate and so various as the main spring of a watch, the needle of a mariner's compass, the lancet of a surgeon,
pen of a scribe, and the crinoline of a lady. This extraordinary variety in the applicability of iron is mainly due to its power of entering into combination with carbon under different circumstances and in varying proportions.
Of all the compounds of iron,' says Dr. Percy, 'none are to be compared with those of carbon in practical importance ; and, in a scientific point of view, none possess greater interest. The influence of this element in causing variation in the physical properties of iron is one of the most extraordinary phenomena in the whole range of metallurgy. Under the common name of iron are included virtually distinct metals, which in external characters differ far more from each other than many chemically distinct metals. Without carbon the manifold uses of iron would be greatly restricted; and, so far as is yet hown, no other metal or mixtures of metals could be applied to these uses. When carbon is absent, or only present in very small quantity, we have wrought iron, which is comparatively soft, malleable, ductile, weldable, easily forgeable, and very tenacious, but not fusible except at temperatures rarely attainable in furnaces, and not susceptible of tempering like steel; when present in certain proportions, the limits of which cannot be exactly prescribed, we have the various kinds of steel, which are highly elastic, malleable, ductile, forgeable, weldable, and capable of receiving very different degrees of hardness by tempering, Even so as to cut wrought iron with facility, and fusible in furnaces; and lastly, when present in greater proportion than in steel, we have cast iron, which is hard, comparatively brittle and readily fusible, but pot forgeable or weldable. The differences between these three well known sorts of iron essentially depend upon differences in the proportion of carbon, though, as we shall learn hereafter, other elements may and often do concur in modifying, in a striking degree, the qualities of this wonderful metal. Ours is emphatically the iron age; and it may be confidently asserted that no other element has contributed so largely to the civilisation and happiness, and may we not also add, paradoxical as it may seem, to the misery of mankind. But let us not forget that carbon has done its share in this good and evil work.'
It is probable that the first iron ever made was in the form of malleable iron, highly carbonised in consequence of the manner of its production. The methods of smelting iron ore to this day practised by the natives of Central Africa are probably in most respects the same as those adopted by the ancient iron workers. Mungo Park thus describes the process employed at Kamalia on the Niger: A circular hollow tower of clay, about 10 feet high and 3 feet diameter, was erected to serve as a furnace, being bound round with withes to prevent the clay cracking and falling to pieces through the heat. Numerous tubes of clay were placed near the hollow bottom of this tower, through which air was admitted into the lower part of the furnace. A bundle of dry sticks was first put in, then a quantity of charcoal, over that a stratum of iron-stone, then more charcoal, and so on until the furnace was full. Fire was then applied through one of the tubes at the bottom, and kept up by blowing with bellows made of goats' skins, until the flame appeared above the furnace. The people who attended kept filling in more charcoal. This went on for three days, when the fire was allowed to go down ; and some days after, when the whole was cool, part of the furnace was taken down, and the iron appeared in the form of a large irregular mass at the bottom, with pieces of charcoal adhering to it. The mass was sonorous, and when any portion was broken off the fracture exhibited a granulated appearace, like broken steel. This iron, or rather steel,' says Park, 'is formed into various instruments by being repeatedly heated in a forge, the heat of which is urged by a pair of double bellows of a very simple construction, being made of two goat-skins, the tubes from which unite before they enter the forge, and supply a constant and very regular blast.'
Dr. Livingstone also found the African tribes on the Zambesi well acquainted with the use of iron, and making it after a like simple process. Speaking of the neighbourhood of Killimane, he says:
The only other metal, besides gold, we have in abundance in this region, is iron, and that is of excellent quality. In some places it is obtained from what is called the spicular iron ore, and also from black oxide. The latter has been well roasted in the operations of nature, and contains a large proportion of the metal. It occurs generally in tears or rounded lumps, and is but slightly magnetic. When found in the beds of rivers, the natives know of its existence by the quantity of oxide on the surface, and they find no difficulty in digging it with pointed sticks. They consider English iron “ rotten ; ” and I have seen, when a javelin of their own iron lighted on the cranium of a hippopotamus, it curled up like the proboscis of a butterfly, and the owner would prepare it for future use by straightening it cold with two stones. I brought home some of the hoes which Sekeletu gave me to purchase a canoe, also some others obtained in Kilimane, and they have been found of such good quality that a friend of mine in Birmingham has made an Enfield rifle of them.' *
Dr. Livingstone adds, that on sending specimens of this iron to a practical Birmingham blacksmith, he pronounced it to be highly carbonised, strongly resembling Swedish or Russian, and added, that when chilled, it had the properties of steel.
Du Chaillu gives a similar account of the native methods of producing iron among the Fans, who are said to be among the cleverest blacksmiths in Africa. They will not use European or American iron in making their knives or arrow-heads, but prefer their own, which has greater tenacity, and in many respects possesses the properties of steel. The Fans have plenty of ironstone and wood fuel ; and when they want iron, their process of smelting is very simple. They build a pile of wood over a hearth in the open air, heap on a quantity of the ore broken into bits, then more wood, and when the pile is complete, it is set on fire. Wood continues to be thrown on for several days, until there are signs that the iron has been smelted, when the whole is allowed to cool, after which they find the iron in a lump on the hearth at the bottom. This is subjected to a tedious process of repeated heatings and hammerings, until at last, by patience and labour, a very excellent piece of metal is obtained.
The process adopted by the natives of Hindostan, of Madagascar, and Borneo, is of like simplicity and rudeness. They all obtain the malleable iron direct from the ore, instead of by the indirect modern process in which cast iron is first produced. It is probable that a like primitive method of producing iron was adopted in the infancy of most nations. Indeed, the simplicity of the process of smelting iron direct from the ore, compared with the manufacture of bronze, in which much greater skill and knowledge are required, leads Dr. Percy to dispute the favourite theory of antiquarians, that the age of Bronze preceded that of Iron.
The ancient Egyptians appear to have been familiar with
* Livingstone's 'Africa,' 650.
the use of both metals. Mr. Rhind found in the tomb of Seban at Thebes, a place of sepulture which he had reason to believe had not been opened during 2000 years, iron hasps and nails on the massive doors of the inner repositories, ' as lustrous and as pliant as on the day they left the forge.' The Egyptians also possessed an art which seems to have been lost, of making bronze of a particularly fine temper, capable of taking and keeping a sharp edge. Sir Gardiner Wilkinson remarks that some of the bronze daggers found by him in Egyptian tombs were so beautifully tempered that, after having lain buried for 3000 years, they possessed, when dug up, an elasticity almost equal to that of steel.
• That the Assyrians,' says Dr. Percy, 'were well acquainted with iron is clearly established by the explorations of Mr. Layard, who has enriched the collection of the British Museum with many objects of iron from Nineveh of the highest interest. Amongst these may be particularly specified tools employed for the most ordinary purposes, such as picks, hammers, knives, and saws; there is 'a saw similar in construction to that now used by carpenters for sawing large pieces of timber across. It has been described and figured by Mr. Layard. It consists of a blade three feet eight inches long, and four and fiveeighths inches broad throughout its entire length, except at one end, where it is narrowed, and was, no doubt, let into a handle of wood, the rivets being visible upon it; the other end was probably similar, but unfortunately it has been broken off. The metal seems to be almost wholly converted into oxide, yet sufficient remains strongly to attract the magnetic needle; that is supposing no magnetic ozide of iron to be present. There is no evidence to show whether it originally consisted of iron or steel, though this point might possibly be ascertained by a very careful chemical investigation. As an illustration of ancient metallurgy, there is no object in the Museum of greater interest than this rusted saw, which has only recently been exposed to public view. It was found in the North-West Palace at Nimroud; and it is computed that, while it could not be later in date than 880 B.C., it may have been considerably earlier. The fact of iron having been applied to common hammer-heads, for which bronze might have proved a tolerably good substitute, indicates that iron was certainly as cheap, if not cheaper, in those days than bronze; and the correctness of this inference is strikingly confirmed by many other objects from the same locality, consisting of cores of iron round which bronze has been cast: ..
· The iron was employed either to economise the bronze, for the purpose of ornament, or because it was required in the construction. If the former, iron must have been cheaper than bronze, and, therefore, probably more abundant than has generally been supposed. No satisfactory conclusion can be arrived at on this point, from the fact that bronze antiquities are much more frequently found than those of iron : for the obvious reason, that bronze resists destruction by ozilation much better than iron.
Other Assyrian antiquities of iron, which deserve particular attention, are portions of chain armour and two helmets ornamented with bronze. These helmets are greatly corroded by rust, but they are sufficiently perfect in form to indicate excellence in the quantity of the iron, and no ordinary skill in working the metal.'
The early history of the art of extracting and making iron in this country is very obscure. It is possible that the ancient Britons smelted it after the same primitive methods as those above described ; but if they did, no remnant nor indication of the manufacture has been preserved, as has been the case with the ironwork of Egypt and Assyria. It is more probable that the art was introduced by that wonderful people the Romans, of whose extensive works in the Forest of Dean, in Sussex, and in Northumberland, there are numerous traces. From the remains of their works, it appears that they obtained the metal direct from the ore, with charcoal as fuel. Quite recently, the traces of one of their ironworks have been brought to light at Risingham in Northumberland, on the line of the great Roman wall, from which it is to be inferred that they carried on their mining operations on an extensive scale :
In the neighbourhood of Habitancum (near Risingham),' says Dr. Ernce, “large masses of iron slag have been found. It is heavier than what proceeds from modern furnaces, in consequence, probably, of the imperfect reduction of the ore. In the neighbourhood of Lanchester the process seems to have been carried on very extensively. On the division of the common, two large heaps were removed, the one containing about 400 cartloads of iron slag, the other 600. It was used in the construction of some new roads which were then formed, a purpose for which it was admirably adapted. In the neighbourhood of one of these heaps of scoriæ, a pair of iron tongs was ploughed up, much resembling those at present used by blacksmiths. During the operation of bringing this common into cultivation, the method adopted by the Romans of producing the blast necessary to smelt the metal was made apparent. "Two tunnels had been formed in the side of a hill; they were wide at one extremity, but tapered off to a narrow bore at the other, where they met in a point. The mouths of the channels opened towards the west, from which quarter a prevalent wind blows in this valley, and sometimes with great violence; and the blast received by them would, when the wind was high, be poured with considerable force and effect upon the smelting furnaces at the extremity of the tunnels.' *
The manufacture of iron was continued subsequent to the
* Rev. J. C. Bruce's 'The Roman Wall,' pp. 422-3.