Drawing of an Egyptian seagoing ship, c. 2600 bce based on vessels depicted in the bas-relief discovered in the pyramid of King Sahure at Abū Ṣīr, Cairo.Courtesy of the Science Museum, London
Irrigation
Techniques of food production also showed many improvements over Neolithic methods, including one outstanding innovation in the shape of systematic irrigation. The civilizations of Egypt and Mesopotamia depended heavily upon the two great river systems, the Nile and the Tigris-Euphrates, which both watered the ground with their annual floods and rejuvenated it with the rich alluvium they deposited. The Nile flooded with regularity each summer, and the civilizations building in its valley early learned the technique of basin irrigation, ponding back the floodwater for as long as possible after the river had receded, so that enriched soil could bring forth a harvest before the floods of the following season. In the Tigris-Euphrates valley the irrigation problem was more complex, because the floods were less predictable, more fierce, and came earlier than those of the northward-flowing Nile. They also carried more alluvium, which tended to choke irrigation channels. The task of the Sumerian irrigation engineers was that of channeling water from the rivers during the summer months, impounding it, and distributing it to the fields in small installments. The Sumerian system eventually broke down because it led to an accumulation of salt in the soil, with a consequent loss of fertility. Both systems, however, depended on a high degree of social control, requiring skill in measuring and marking out the land and an intricate legal code to ensure justice in the distribution of precious water. Both systems, moreover, depended on intricate engineering in building dikes and embankments, canals and aqueducts (with lengthy stretches underground to prevent loss by evaporation), and the use of water-raising devices such as the shadoof, a balanced beam with a counterweight on one end and a bucket to lift the water on the other. Urban manufacturing
Manufacturing industry in the early civilizations concentrated on such products as pottery, wines, oils, and cosmetics, which had begun to circulate along the incipient trade routes before the introduction of metals; these became the commodities traded for the metals. In pottery, the potter’s wheel became widely used for spinning the clay into the desired shape, but the older technique of building pots by hand from rolls of clay remained in use for some purposes. In the production of wines and oils various forms of press were developed, while the development of cooking, brewing, and preservatives justified the assertion that the science of chemistry began in the kitchen. Cosmetics too were an offshoot of culinary art.
Pack animals were still the primary means of land transport, the wheeled vehicle developing slowly to meet the divergent needs of agriculture, trade, and war. In the latter category, the chariot appeared as a weapon, even though its use was limited by the continuing difficulty of harnessing a horse. Military technology brought the development of metal plates for armour. Building
In building technology the major developments concerned the scale of operations rather than any particular innovation. The late Stone Age communities of Mesopotamia had already built extensively in sun-dried brick. Their successors continued the technique but extended its scale to construct the massive square temples called ziggurats. These had a core and facing of bricks, the facing walls sloping slightly inward and broken by regular pilasters built into the brickwork, the whole structure ascending in two or three stages to a temple on the summit. Sumerians were also the first to build columns with brick made from local clay, which also provided the writing material for the scribes.
In Egypt, clay was scarce but good building stone was plentiful, and builders used it in constructing the pyramids and temples that remain today as outstanding monuments of Egyptian civilization. Stones were pulled on rollers and raised up the successive stages of the structure by ramps and by balanced levers adapted from the water-raising shadoof. The stones were shaped by skilled masons, and they were placed in position under the careful supervision of priest-architects who were clearly competent mathematicians and astronomers, as is evident from the precise astronomical alignments. It seems certain that the heavy labour of construction fell upon armies of slaves, which helps to explain both the achievements and limitations of early civilizations. Slaves were usually one of the fruits of military conquest, which presupposes a period of successful territorial expansion, although their status as a subject race could be perpetuated indefinitely. Slave populations provided a competent and cheap labour force for the major constructional works that have been described. On the other hand, the availability of slave labour discouraged technological innovation, a social fact that goes far toward explaining the comparative stagnation of mechanical invention in the ancient world. Transmitting knowledge
In the ancient world, technological knowledge was transmitted by traders, who went out in search of tin and other commodities, and by craftsmen in metal, stone, leather, and the other mediums, who passed their skills to others by direct instruction or by providing models that challenged other craftsmen to copy them. This transmission through intermediary contact was occurring between the ancient civilizations and their neighbours to the north and west during the 2nd millennium bce. The pace quickened in the subsequent millennium, distinct new civilizations arising in Crete and Mycenae, in Troy and Carthage. Finally, the introduction of the technique of working iron profoundly changed the capabilities and resources of human societies and ushered in the Classical civilizations of Greece and Rome. Technological achievements of Greece and Rome (500 bce–500 ce)
The contributions of Greece and Rome in philosophy and religion, political and legal institutions, poetry and drama, and in the realm of scientific speculation stand in spectacular contrast with their relatively limited contributions in technology. Their mechanical innovation was not distinguished, and, even in the realms of military and construction engineering, in which they showed great ingenuity and aesthetic sensibility, their work represented more a consummation of earlier lines of development than a dramatic innovation. This apparent paradox of the Classical period of the ancient world requires explanation, and the history of technology can provide some clues to the solution of the problem. The mastery of iron
The outstanding technological factor of the Greco-Roman world was the smelting of iron, a technique—derived from unknown metallurgists, probably in Asia Minor, about 1000 bce—that spread far beyond the provincial frontiers of the Roman Empire. The use of the metal had become general in Greece and the Aegean Islands by the dawn of the Classical period about 500 bce, and it appears to have spread quickly westward thereafter. Iron ore, long a familiar material, had defied reduction into metallic form because of the great heat required in the furnace to perform the chemical transformation (about 1,535 °C [2,795 °F] compared with the 1,083 °C [1,981 °F] necessary for the reduction of copper ores). To reach this temperature, furnace construction had to be improved and ways devised to maintain the heat for several hours. Throughout the Classical period these conditions were achieved only on a small scale, in furnaces burning charcoal and using foot bellows to intensify the heat, and even in these furnaces the heat was not sufficient to reduce the ore completely to molten metal. Instead, a small spongy ball of iron—called a bloom—was produced in the bottom of the furnace. This was extracted by breaking open the furnace, and then it was hammered into bars of wrought iron, which could be shaped as required by further heating and hammering. Apart from its greater abundance, iron for most purposes provided a harder and stronger material than the earlier metals, although the impossibility of casting it into molds like bronze was an inconvenience. At an early date some smiths devised the cementation process for reheating bars of iron between layers of charcoal to carburize the surface of the iron and thus to produce a coat of steel. Such case-hardened iron could be further heated, hammered, and tempered to make knife and sword blades of high quality. The very best steel in Roman times was Seric steel, brought into the Western world from India, where it was produced in blocks a few inches in diameter by a crucible process, melting the ingredients in an enclosed vessel to achieve purity and consistency in the chemical combination. Mechanical contrivances