The water-mill, though known in the Roman Empire from the second century BCE, did not come to enjoy any widespread use until the 4 th or 5 th centuries CE, and then chiefly in the West, which was then experiencing not only a rapid decline in the supply of slaves, but also widespread depopulation, and thus a severe scarcity of labour. For the West -- those regions that came to form Europe -- the water-mill then became by far the predominant 'prime mover': i.e., an apparatus that converts natural energy into mechanical power. The classic study, as a monograph in technological and engineering history, is Terry S. Reynolds, Stronger than a Hundred Men: A History of the Vertical Water Wheel (Baltimore and London, 1983). Indeed he has calculated that even the early medieval watermills provided about 2 hp, enough to liberate from 30 to 60 persons from the wearisome task of grinding grain into flour, the mill's virtually sole use during the first millennium. He, and others, have neglected to note, however, that, apart from providing such economies in labour, water-mills also conserved on the capital and land resources (fodder crops) that would have been required to produce a comparable amount of power with animal-powered mills (horses, mules). The aim of this study is to analyse in greater depth the economic implications and consequences of the application of water-mills, their impact on European economic history up to the Industrial Revolution era, in those areas not well treated by Reynolds and other historians: in the fields of mining, metallurgy, and textiles -- including the cotton industry of the initial phase of the Industrial Revolution. The study also necessarily analyses as well the necessary technological innovations to achieve the productivity gains in these economic sectors: especially in the devices (cam and crankshafts) to convert the basic rotary power of mills into reciprocal power, initially to operate trip-hammers; and the more gradual, if only late-medieval, displacement of the original undershot wheels with the far more effective, if more capital costly, overshot wheels. The study thus begins with the late-medieval technological revolutions in both mining and metallurgy, providing the key transitions to the early-modern European economy. A demonstration of significant productivity gains is counterbalanced, however, in this study by an examination of the physical and economic limitations on the uses of water-power and, particularly in the field of woollen-cloth production, the negative consequences of water-powered machinery, in the form of both fulling-mills and gig-mills (cloth-finishing), in impairing the quality of the finer fabrics. In particular, cost-benefit analyses are provided to show why the late-medieval English cloth industry did indeed achieve significant gains in switching from foot- to mechanical-fulling, while, at the same time, the leading draperies of the late-medieval Low Countries were perfectly rational in eschewing such mills before the 16 th century -- when they did indeed adopt them, for rather different types of textiles. On the other hand, and indeed in striking contrast, the application of water-power in the medieval production of silks and then especially in the 18 th -century production of the new cotton textiles, with those major innovations of the Industrial Revolution era (water-frame and mule) had the opposite result: of greatly improving quality while also radically reducing production costs. Indeed quality-improvements in spinning cotton yarns was the chief goal of these entrepreneurs, with the ambition of displacing fine Asian textiles from world markets.
