EARLY HISTORY. Articles of stone, bronze, and iron have been found together on the site of the Swiss lake dwellings. but the most ancient speci mens of iron at present known come from Egyp tian and Assyrian ruins. There is in the British Museum a piece of iron taken from the Pyramid of Gizeh, which is believed to date from about me. 4000, and also an axe-head of Egyptian maim facture dating from me. 1370. Though the earli est pieces of iron now known came from Egypt, it is thought that probably the Assyrians were the first to use the metal freely in the manu facture of tools, weapons. and ornaments. Nu merous samples of iron implements dating from n.e. 800, and including the fragment of a saw 44 inches long. were obtained from the ruins of Nimrod. In India. the famous iron pillar at Entub. near Delhi, standing 22 feet above ground and weighing about 6 tons, dates from fix. 400. It was made by welding disks of metal together, indicating a remarkable degree of skill on the part of those early iron-workers.
The Greeks were familiar with the uses of ircn at least six hundred years before the Christian Era, although the metal was very scarce. It was not until the Roman Empire was fairly estab lished that the use of iron became general over civilized Europe. The Romans made both wroirld iron and steel, using the latter metal for swords and other edged implements. The ancient Britons. at the time of the invasion of Britain by Julius Cesar, n.e. 55, were found to use swords, spears. hooks, and scythes of iron. indicating a familiarity with the metal for a considerable period previous. During the Roman occupation iron manufacture was vigorously de veloped. and in the succeeding Saxon age it seems also to have flourished. After the Norman Conquest little attention was paid to iron manu facture in England. In Germany. however, the art flourished vigorously, iron implements being exported to other countries in considerable plan titles. Until about the middle of the fourteenth century all iron was produced by the direct pro cess. the product being wrought iron nr steel. the ease might lie. aceorsling to the details of the process. About I 3.i11, however. cast iron began to he made in Germany. and the beginning of the modern process of iron and steel manufacture was inaugurated.
The succeeding history of iron and steel manu facture will be continued in the article following under Cast Iron, Wrought Iron, and Steel.
Iron (symbol, Fe: atomic weight. :Ai), in the eliemically pure state. is a sil•er-white metal that crystallizes in the isometric system. Its specific gravity is 7.s14. and its melting-point between 1400° and 15ou' (2.5(to" and •7011° F.). It is the most tenacious of all the this-tile metals, and it may be rolled into sheets so thin that the weight of a sheet of given size will he less than the weight of a sheet of paper of the smile size. The magnetic properties are well known. Pure iron may be prepared by the pro longed action of a weak current of electricity on a solution containing pure ferrous sulphate and sal ammoniac or sulphate of magnesium, and beating the precipitated metal with it view of freeing it from 'occluded' hydrogen :slid di minishing its brittleness. Another method of obtaining chemically pure iron consists in pre paring pure ferric hydroxide by adding am monia to the solution of some pure iron salt. and then heating the hydroxide in a stream of hydrogen gas. Iron and platinum are the only metals that may be soldered to gether immediately. i.e. without the use of any soldering material. \Vith mercury iron refuses to combine directly. the iron amalgam that has been used for electrical machines living made by a somewhat complicated process with the aid of the amalgam of sodium. When immersed in fuming acid, iron becomes coated with insoluble oxide, and as it then refuses to dis solve in as-ids (unless the coating be removed), it is said to be in a passim state. Dry air or oxygen gas has no effect on iron. The 'rust ing' of iron in ordinary atmospheric air is due to the presence of moisture; the fact that the rust thus formed is invariably found to contain ammonia would seem to indicate that iron reacts chemically with the moisture of the air. combin ing with its oxygen and setting free its hydrogen, which, in the nascent state, forms ammonia with the nitrogen of the air. Rusting may accordingly be prevented by covering iron with a waterproof coating or some paint or varnish. or with a coat ing of some metal like lead, tin, copper, nickel, or preferably zinc.