INTRODUCTION 42 the double triode type, and consumed about 150kW of electr1cal power. To keep all these circuits in operation at the same time is said to have been extremely difficult but, if this could be done for one hour, ENIAC (Electronic Numerical Integrator and Calculator) could do more work than ASCC would do in a week. Despite the success of ENIAC, computer engineers did not long have to depend on thermionic valves for in 1948 the point-contact transistor of Bardeen and Brattain and the junction transistor of William Shockley both emerged from the laboratories of the Bell Telephone Company in the USA. The transistor was much smaller than the thermionic valve, consumed less power and was far more reliable. The controlled flow of electrons in crystalline substances was also used in other semiconductor devices, such as the varistor, the thermistor, the phototransistor and the magnetic memory. From printed circuits, the technology soon moved on to integrated circuits in which the transistors and associated components are formed and interconnected in situ as thin films on a chip substratum. Up to 20,000 transistors can be integrated on a chip 6mm×3mm and 0.5mm thick. It is little over a hundred years since Alexander Graham Bell invented the telephone (1876) and Edison and Swan the incandescent lamp (1879). In the century that followed electronics has given us radio, television, the tape recorder, the video recorder, the pocket calculator, automation and robotics, the electron microscope, the heart pacemaker, myo-electrically controlled artificial limbs, the automatic aircraft pilot, the maser and the laser, computer-aided design and manufacture, solar cells, satellite communication and, with the rocket, man in space and unmanned space probes. Science and technology have combined to accelerate us into the Electronic Age. As J.G.Crowther wrote, ‘Faraday, Henry and Maxwell would have had little influence in the world without Bell, Edison and Marconi.’ Science and technology, the two arms of progress, have combined to leave us on the shore of a vast ocean of possibilities brought about by electronics. Before and during the Industrial Revolution the ingenious powers of man were devoted to saving labour and to enhancing the capabilities of the paltry human frame. As we approach the last decade of the twentieth century, a new vista is opening before us, one in which at least the drudgery of brainwork is taken over by the electronic machine, the computer. This has already happened in fields such as accountancy and banking, in such affairs as stocktaking, engineering design and many others. But according to modern research programmes we are only at the beginning. The door is scarcely ajar, the door which opens on to life in a society where knowledge, the most prized possession, is freely available to all. The Japanese, in a joint programme between government, industry and academics, are deliberately co-ordinating resources to develop a fifth generation BASIC TOOLS, DEVICES AND MECHANISMS 43 of computers, computers which would be endowed with ‘artificial intelligence’, that is, computers which can think for themselves. This is a concept that to many people appears ridiculous and to many others a threat to the dignity of themselves as members of the human race or worse, a threat to the very existence of humanity as the only reasoning animal living on the planet. Americans who, up to now, have dominated the computer market world-wide, both technically and commercially, are expressing concern about the Japanese attack on their leadership. Perhaps the situation on a global basis is best summed up by the following quotation from Professor Edward Fredkin of Massachusetts Institute of Technology: Humans are okay. I’m glad to be one. I like them in general, but they’re only human. It’s nothing to complain about. Humans aren’t the best ditch-diggers in the world, machines are. And humans can’t lift as much as a crane. They can’t fly without an airplane. And they can’t carry as much as a truck. It doesn’t make me feel bad. There were people whose thing in life was completely physical — John Henry and the steam hammer. Now we’re up against the intellectual steam hammer. The intellectual doesn’t like the idea of this machine doing it better than he does, but it’s no different from the guy who was surpassed physically. FURTHER READING Armytage, W.H.G. A social history of engineering (Faber & Faber, London, 1961) Boorstein, D.J. The discoverers (Dent, London, 1984) Braudel, F. Civilisation and capitalism, 15th–19th centuries: volume 1, the structures of everyday life (Fontana, London, 1985) Burstall, A.F. History of mechanical engineering: technology today and tomorrow (Faber & Faber, London, 1963) Derry, T.K. and Williams, T.I. A short history of technology (Oxford University Press, Oxford and New York, 1960) Dunsheath, P. A history of electrical engineering (Faber & Faber, London, 1957) Feigenbaum, E.A. and McCorduck, P. The fifth generation: artificial intelligence and Japan’s computer challenge to the world (Addison-Wesley, Reading Mass., 1983; Pan, London, 1984) Gimpel, J. Mediaeval machine: the industrial revolution of the middle ages (Wildwood House, Aldershot, 1988) Lilliey, S. Men, machines and history (Lawrence & Wishart, London, 1965) Oakley, K.P. Man the toolmaker (British Museum—Natural History, London, 1972) Pannell, J.P.M. An illustrated history of civil engineering (Thames & Hudson, London, 1964) Sprague de Camp, L. Ancient engineers (Tandem Publishing, London, 1977) Strandth, S. Machines: an illustrated history (Nordbok, Gothenburg, 1979; Mitchell Beazley, London, 1979) Thomson, G. The foreseeable future (Cambridge University Press, Cambridge, 1957) White, L. (Jr) Medieval technology and social change (Oxford University Press, Oxford, 1962) PART ON E MATERIALS 47 1 NON-FERROUS METALS A.S.DARLING NEOLITHIC ORIGINS The birth of metallurgy is shrouded in obscurity, although weathered crystals of native copper might well have attracted the attention of ancient man because of their remarkable green colouration. Beneath this superficial patina copper in metallic form would have been discovered. Decorative and practical applications would undoubtedly have been sought for this relatively hard, heavy material, and primitive man would have been most impressed by the malleability of copper, which allowed it, unlike wood and stone, to be hammered into a variety of useful shapes. The sharp distinction between the brightness, lustre and ductility of the interior of a crystal of native copper and the brittleness and stonelike characteristics of the green patina with which it was encrusted, would also have been noted. From this, the first users of metal might have concluded that all non-living primordial matter had originally been in this pure, bright, noble and amenable metallic state, although it had, like human beings, a natural tendency to fall from grace and, by contact with nature and the passage of time, to assume a degraded form. Differing conclusions can, however, be drawn from the same set of evidence, and some of the earliest metallurgists, it appears, favoured a more optimistic interpretation which suggested that the natural tendency of most metals was towards rather than away from perfection. This tendency was encouraged by contact with nature so that metals buried deep in the bowels of the earth tended to mature and improve. Silver, according to this interpretation, was regarded as an unripened form of gold. PART ONE: MATERIALS 48 COPPER Cold forging of native copper The archaeological evidence indicates that although lead was also known at a very early date, the first metal to be practically utilized was copper. Small beads and pins of hammered copper found at Ali Kosh in Western Iran and Cayönü Tepesi in Anatolia date from the period between the 9th and 7th millennia BC and were made from native, unmelted copper. During the later stages of the Neolithic period more significant metallurgical developments appear to have originated in the mountainous regions north of the alluvial plains where the civilizations of the Tigris and Euphrates subsequently developed. Much use was then made of native copper which was hammered directly into small articles of jewellery or of ritual significance. At a later stage larger artefacts such as axe- heads were made by melting together native crystals of copper in a crucible and casting the molten metal to the required shape. Finally, however, copper was extracted from its ores by pyrometallurgical methods. The period during which copper was known to Neolithic man but not extensively employed is known as the Chalcolithic Age. The beginning of the Copper Age is associated with the emergence of smelting processes which allowed copper to be extracted from its ores. Native copper must undoubtedly have been worked in sites which were close to the outcrops where the metals had been found. It seems logical to assume, therefore, that copper ores were first reduced to metal, quite fortuitously, in the fires where native crystals were annealed at temperatures well below their melting point to soften them after cold forging, or in the furnaces where crystals were melted together. Apart from gold, silver and the other noble metals, copper is the only metal which is found as native crystals in metallic form. This is because its affinity for oxygen is lower than that of most other common metals, and as a result native crystals, although not always abundant, can usually be found in weathered out-crops of copper ore. The native copper which is still abundantly available in the vicinity of the Lake Superior deposits in North America, was worked from 3000 BC until shortly after the arrival of the Spanish invaders by the North American Indian: Giovanni Verazzano, who visited the Atlantic Coast in 1524, commented upon the vast quantities of copper owned by the Indians, and in 1609 Henry Hudson found them using copper tobacco pipes. Although unaware that copper could be melted and cast, they were working large lumps into weapons and jewellery. The burial mounds of the pre-Columbian Indians of the Ohio valley contained many copper implements such as adzes, chisels and axes, which from their chemical composition appear to have been made from Lake Superior copper (see Figure 1.1). In more recent times the Indians on the White River in Alaska used caribou picks to dig copper nuggets out of alluvial gravels. Eskimos living in the Coppermine district on the Arctic shore of Coronation Gulf were using native NON-FERROUS METALS 49 copper as late as 1930, when it was reported that nuggets were occasionally found which were large enough to forge into knives with 20cm (8in) blades. The implements and weapons produced in North America from native copper all appear to have been produced by cold forging with frequent annealing at temperatures below 800°C. After an approximation to the final shape had been obtained in this way, the articles were finished by cold working. The cutting edges were hardened as much as possible by local hammering, and the craftsmen who produced these artefacts were obviously well aware that copper could be hardened by deformation and softened by annealing. It is difficult to understand, however, why they never succeeded in melting copper. In Asia Minor, however, where copper was far less accessible, metallurgical development was very rapid. Cities and civilizations, which produce both wealth and demand, seem far more effective than natural resources in stimulating successful technical innovation. Melted and cast native copper Most of the larger copper artefacts produced in the Middle East between the seventh and fourth millennia BC have a micro-structure which is far from Figure 1.1: Adze blade from an unmelted nugget of native copper forged by preColumban Indians of the Ohio Valley Hopewell culture. Found in a burial mound at Mound City, Ohio, USA. Date 200 BC–AD 600. Note how internal flaws in the nugget have spread to the surface and failed to weld during forging. Courtesy of the British Museum Laboratory. PART ONE: MATERIALS 50 uniform. It consists of crystals which appear to have grown from the melt by throwing out arms into the surrounding liquid. From these arms secondary branches and spines have grown, thus producing a ‘dendritic’ structure characteristic of cast metal. Because of this structure, and their generally high purity, such articles could have been produced only by melting together crystals of native copper. This technique marks a great step forward, although the evidence available is very limited and it cannot be said when copper was first melted or even when the first attempts were made to utilize the effect in a practical manner. During the long period when native copper was being worked and annealed, some of the smaller crystals would, inevitably, have been accidently melted. The early coppersmiths would have attempted, instinctively, to avoid such unfortunate accidents, and would soon have developed an appreciation and recognition of those fiery conditions which would encourage copper to renounce the solid state and become mobile. It seems most probable that when native copper was first intentionally melted it would have been heated from above by a heaped charcoal fire, and encouraged to run together and form a lens-like ingot in a clay-lined saucer- shaped depression in the ground immediately beneath the fuel bed. This arrangement might possibly have required forced draught, from bellows, to attain the temperatures required, although with suitable chimney arrangements this may not have been essential. Crucible furnaces must soon have been employed, however, to produce items such as flat axes or mace heads which were cast directly to size. The earliest crucible furnace remains so far identified were found at Abu Matar, near the old city of Beersheba in Israel on a site used between 3300 and 3000 BC (see Figure 1.2). These furnaces appear to have had a vertical cylindrical clay shaft, supported in such a way that air could enter freely at the lower end, providing the necessary draught. The hemispherical clay crucible, about 10cm in diameter, was supported about half-way up the shaft by charcoal packed into the base of the furnace. The slags produced by such melting processes appear, in general, to be far more enduring than the furnaces themselves. The earliest vitrified copper- bearing slags were found at Catal Huyük in Anatolia at a site dating from 7000– 6000 BC, where specimens of beads and wire which appear to have been made from native copper were found. The first copper artefacts which, from their purity, appear almost certainly to have been produced by forging melted and cast native copper were found at Sialk in Iran, at a site dated around 4500 BC. These contained substantial quantities of copper oxide, and from their microstructure appeared, after casting, to have been either hot forged or cold worked and annealed. The earliest Egyptian artefacts produced from cast and wrought native copper appear to date from the period between 5000 and 4000 BC. The archaeological evidence suggests that the technique of melting and casting native copper originated in Anatolia, and between 5000 and 4000 BC spread rapidly over much of the Middle East and Mediterranean area. Three NON-FERROUS METALS 51 flat axes produced by this approach were found between 1908 and 1961 in the Eneolithic Italian sepulchral cave Bocca Lorenza, close to Vicenza. Because of their high purity, these axes can be clearly distinguished from artefacts produced from smelted copper. Smelting of oxide and carbonate copper ores It seems that towards the end of the fourth millennium BC, the supplies of native copper accessible to the ancient world were incapable of satisfying a rapidly increasing demand. Most of the copper artefacts produced after 3500 BC contain substantial quantities of nickel, arsenic, iron, or other base metal impurities which indicates that they had been produced from copper which had been extracted from ore. Systematic copper mining was being undertaken well before this time, however, as early as the first half of the sixth millennium. The Copper Age began when improved copper extraction techniques meant that primitive copper workers were no longer dependent upon supplies of Figure 1.2: A reconstruction based on the remains of the earliest known crucible furnace, dating from 3300–3000 BC, found at the Chalcolithic site at Abu Matar, near Beersheba, excavated by J.Perrot in 1951. This appears to have been a natural draught furnace used for remelting impure copper in a hemispherical crucible which was supported on and immersed in a bed of charcoal halfway up the furnace shaft. After J.Perrot. . after the arrival of the Spanish invaders by the North American Indian: Giovanni Verazzano, who visited the Atlantic Coast in 1524, commented upon the vast quantities of copper owned by the Indians,. and during the Industrial Revolution the ingenious powers of man were devoted to saving labour and to enhancing the capabilities of the paltry human frame. As we approach the last decade of the. point-contact transistor of Bardeen and Brattain and the junction transistor of William Shockley both emerged from the laboratories of the Bell Telephone Company in the USA. The transistor was much