The same period saw the evolution of the fortified stronghold from the Anglo-Saxon motte-and-bailey, a timber tower encircled by a timber and earth wall, to the formidable, fully developed masonry castle that had become an anachronism by the end of the Middle Ages because of the development of artillery. Intrinsic to this innovation were the invention of gunpowder and the development of techniques for casting metals, especially iron. Gunpowder appeared in western Europe in the mid-13th century, although its formula had been known in East Asia long before that date. It consists of a mixture of carbon, sulfur, and saltpetre, of which the first two were available from charcoal and deposits of volcanic sulfur in Europe, whereas saltpetre had to be crystallized by a noxious process of boiling stable sweepings and other decaying refuse. The consolidation of these ingredients into an explosive powder had become an established yet hazardous industry by the close of the Middle Ages.

The first effective cannon appear to have been made of wrought-iron bars strapped together, but although barrels continued to be made in this way for some purposes, the practice of casting cannon in bronze became widespread. The technique of casting in bronze had been known for several millennia, but the casting of cannon presented problems of size and reliability. It is likely that the bronzesmiths were able to draw on the experience of techniques devised by the bell founders as an important adjunct to medieval church building, as the casting of a large bell posed similar problems of heating a substantial amount of metal and of pouring it into a suitable mold. Bronze, however, was an expensive metal to manufacture in bulk, so that the widespread use of cannon in war had to depend upon improvements in iron-casting techniques.

The manufacture of cast iron is the great metallurgical innovation of the Middle Ages. It must be remembered that from the beginning of the Iron Age until late in the Middle Ages the iron ore smelted in the available furnaces had not been completely converted to its liquid form. In the 15th century, however, the development of the blast furnace made possible this fusion, with the result that the molten metal could be poured directly into molds ready to receive it. The emergence of the blast furnace was the result of attempts to increase the size of the traditional blooms. Greater size made necessary the provision of a continuous blast of air, usually from bellows driven by a waterwheel, and the combination increased the internal temperature of the furnace so that the iron became molten. At first, the disk of solid iron left in the bottom of the furnace was regarded as undesirable waste by the iron manufacturer; it possessed properties completely unlike those of the more familiar wrought iron, being crystalline and brittle and thus of no use in the traditional iron forge. But it was soon discovered that the new iron could be cast and turned to profit, particularly in the manufacture of cannon.

Transport

Medieval technology made few contributions to inland transport, though there was some experimentation in bridge building and in the construction of canals; lock gates were developed as early as 1180, when they were employed on the canal between Brugge (now in Belgium) and the sea. Roads remained indifferent where they existed at all, and vehicles were clumsy throughout the period. Wayfarers like Chaucer’s pilgrims traveled on horseback, and this was to remain the best mode of inland transport for centuries to come.

Sea transport was a different story. Here the Middle Ages produced a decisive technological achievement: the creation of a reliable oceangoing ship depending entirely on wind power instead of a combination of wind and muscle. The vital steps in this evolution were, first, the combination of the traditional square sail, used with little modification from Egyptian times through the Roman Empire to the Viking long boats, with the triangular lateen sail developed in the Arab dhow and adopted in the Mediterranean, which gave it the “lateen” (Latin) association attributed to it by the northern seafarers. This combination allowed ships so equipped to sail close to the wind. Second, the adoption of the sternpost rudder gave greatly increased maneuverability, allowing ships to take full advantage of their improved sail power in tacking into a contrary wind. Third, the introduction of the magnetic compass provided a means of checking navigation on the open seas in any weather. The convergence of these improvements in the ships of the later Middle Ages, together with other improvements in construction and equipment—such as better barrels for carrying water, more reliable ropes, sails, and anchors, the availability of navigational charts (first recorded in use on board ship in 1270), and the astrolabe (for measuring the angle of the Sun or a star above the horizon)—lent confidence to adventurous mariners and thus led directly to the voyages of discovery that marked the end of the Middle Ages and the beginning of the expansion of Europe that has characterized modern times.

Communications

While transport technology was evolving toward these revolutionary developments, techniques of recording and communication were making no less momentous advances. The medieval interest in mechanical contrivances is well illustrated by the development of the mechanical clock, the oldest of which, driven by weights and controlled by a verge, an oscillating arm engaging with a gear wheel, and dated 1386, survives in Salisbury Cathedral, England. Clocks driven by springs had appeared by the mid-15th century, making it possible to construct more compact mechanisms and preparing the way for the portable clock. The problem of overcoming the diminishing power of the spring as it unwound was solved by the simple compensating mechanism of the fusee—a conical drum on the shaft that permitted the spring to exert an increasing moment, or tendency to increase motion, as its power declined. It has been argued that the medieval fascination with clocks reflects an increased sense of the importance of timekeeping in business and elsewhere, but it can be seen with equal justice as representing a new sense of inquiry into the possibilities and practical uses of mechanical devices.

Even more significant than the invention of the mechanical clock was the 15th-century invention of printing with movable metal type. The details of this epochal invention are disappointingly obscure, but there is general agreement that the first large-scale printing workshop was that established at Mainz by Johannes Gutenberg, which was producing a sufficient quantity of accurate type to print a Vulgate Bible about 1455. It is clear, however, that this invention drew heavily upon long previous experience with block printing—using a single block to print a design or picture—and on developments in typecasting and ink making. It also made heavy demands on the paper industry, which had been established in Europe since the 12th century but had developed slowly until the invention of printing and the subsequent vogue for the printed word. The printing press itself, vital for securing a firm and even print over the whole page, was an adaptation of the screw press already familiar in the winepress and other applications. The printers found an enormous demand for their product, so that the technique spread rapidly and the printed word became an essential medium of political, social, religious, and scientific communication as well as a convenient means for the dissemination of news and information. By 1500 almost 40,000 recorded editions of books had been printed in 14 European countries, with Germany and Italy accounting for two-thirds. Few single inventions have had such far-reaching consequences.

For all its isolation and intellectual deprivation, the new civilization that took shape in western Europe in the millennium 500 to 1500 achieved some astonishing feats of technological innovation. The intellectual curiosity that led to the foundation of the first universities in the 12th century and applied itself to the recovery of the ancient learning from whatever source it could be obtained was the mainspring also of the technological resourcefulness that encouraged the introduction of the windmill, the improvement and wider application of waterpower, the development of new industrial techniques, the invention of the mechanical clock and gunpowder, the evolution of the sailing ship, and the invention of large-scale printing. Such achievements could not have taken place within a static society. Technological innovation was both the cause and the effect of dynamic development. It is no coincidence that these achievements occurred within the context of a European society that was increasing in population and productivity, stimulating industrial and commercial activity, and expressing itself in the life of new towns and striking cultural activity. Medieval technology mirrored the aspiration of a new and dynamic civilization.