Carbono, ferro, cobre, zinco e estanho o em Mumford (1934)

Iron‘s principal virtue lies in its combination of great strength and malleability. While varying amounts of carbon change its characteristics, from toughness to brittleness, as steel or wrought iron it has greater strength than any of the other common metals; and since, in suitable cross section, an I-beam of iron is as strong as a solid block, it matches its strength with relative lightness and transportability as compared for example with stone. But not merely is iron strong under compression, like many varieties of stone: unlike stone, it is strong in tension and when used in chains and cables, as the Chinese were the first to use it, its characteristic properties come out perhaps most clearly. One must pay for these excellent qualities by working iron under a more intense heat than copper, zinc, or tin: whereas steel. melts at 1800 degrees Centigrade, and cast iron at 1500, copper has a melting point of 1100 and certain types of bronze only half that heat: so that the casting of bronze long preceded the casting of iron. On a large scale, iron-making demands power production: hence, while wrought iron dates back at least 2500 years, cast-iron was not invented until the fourteenth century when the water-driven bellows finally made the high temperature needed in the blast furnace possible. To handle iron in large masses, conveying it, rolling it, hammering it, all the accessory machinery must be brought to an advanced stage of development. Though the ancients produced hard implements of copper by hammering it cold, the cold rolling of steel awaited advanced types of power machinery. Nasmyth’s steam hammer, invented in 1838, was one of the final steps toward iron working in the grand style which made possible the titanic machines and utilities of the later half of the nineteenth century. (Mumford 1934:166)

MUMFORD, Lewis. 1934. Technique and civilization. New York: Harcourt, Brace and Company.