Watermill

• 1. Introduction

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  A watermill turns flowing water into work. Hold back your hand from the mill, you grinding girls, wrote the Greek epigrammatist Antipater of Thessalonica around 20 BC. He was celebrating a wheel that could grind grain while the workers slept. For Demeter has imposed the labours of your hands on the nymphs, he went on, who leaping down upon the topmost part of the wheel, rotate its axle. If we learn to feast toil-free on the fruits of the earth, we taste again the golden age. Behind that praise sits a deceptively simple structure. A wheel or turbine catches the force of a river. An axle turns. A mechanical process begins, grinding, rolling, or hammering. From that one idea came flour, lumber, paper, textiles, and a long list of metal goods. So who built the first water wheels, and why did France keep inventing new uses for them? How did a single wheel learn to drive four millstones at once? And why did cheap electricity eventually leave these machines standing silent across the developed world?

• 2. Two Wheels, Two Worlds

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  Wheel orientation is the great dividing line among watermills. One kind turns a horizontal wheel on a vertical axle, with no gearing between the wheel and the stone. The other drives a vertical wheel through a gear mechanism. The horizontal design, sometimes called the Greek Mill, is the older and simpler of the two. It works well only with high water velocities and small diameter millstones. Its weakness is the absence of gearing. The speed of the water sets the maximum speed of the runner stone directly, which sets the rate of milling. The vertical-wheeled design, the so-called Roman Mill, is more complicated. It needs gears to carry power from a shaft with a horizontal axis to one with a vertical axis. That complexity bought flexibility. Vertical wheels themselves split into types according to where the water strikes the paddles: undershot, overshot, breastshot, and pitchback, which is also called backshot or reverse shot. The Romans used both fixed and floating wheels and carried water power into other provinces of their empire.

• 3. The Greek And Roman Dawn

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  Philo of Byzantium, the Greek engineer who lived around 280 to 220 BC, left the earliest evidence of a water-driven wheel in his treatises Pneumatica and Parasceuastica. The British historian of technology M.J.T. Lewis showed that the passages describing water wheels, once dismissed as later Arabic interpolations, actually date to the Greek 3rd century BC original. The Greeks invented the two core components, the waterwheel and toothed gearing. Lewis assigns the horizontal-wheeled mill to the Greek colony of Byzantium in the first half of the 3rd century BC, and the vertical-wheeled mill to Ptolemaic Alexandria around 240 BC. The sakia gear appears fully developed in a 2nd-century BC wall painting in Ptolemaic Egypt. The Greek geographer Strabo reports a water-powered grain-mill near the palace of king Mithradates VI Eupator at Cabira, in Asia Minor, before 71 BC. The Roman engineer Vitruvius wrote the first technical description of a watermill, dated to between 40 and 10 BC, fitted with an undershot wheel and a gearing mechanism. He also seems to indicate water-powered kneading machines. Pliny mentions water-powered trip hammers across much of Italy in his Naturalis Historia of around 70 AD. A fulling mill is attested at Antioch, in Roman Syria, in 73 or 74 AD.

• 4. Scale, Saws, And Turbines

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  Barbegal, in southern France, has been called the greatest known concentration of mechanical power in the ancient world. This 2nd century AD complex featured 16 overshot waterwheels driving an equal number of flour mills. Estimates put its capacity at 4.5 tons of flour a day, enough bread for the 12,500 inhabitants of the town of Arelate. A similar complex stood on the Janiculum hill. Its flour supply for Rome mattered enough that emperor Aurelian included it inside the Aurelian Walls in the late 3rd century. The Hierapolis sawmill of the 3rd century AD is the earliest known machine to use a crank and connecting rod. Later water-powered stone sawmills at Gerasa and Ephesus, attested for the 6th century AD, used the same mechanism. Ausonius, in his 4th century AD poem Mosella, refers to water-powered marble saws in what is now Germany, and the Christian saint Gregory of Nyssa from Anatolia seems to point to them about the same time. The earliest turbine mill was found at Chemtou and Testour, in Roman North Africa, dating to the late 3rd or early 4th century AD. A possible water-powered furnace has been identified at Marseille. In 537 AD the East Roman general Belisarius used ship mills when the besieging Goths cut off his water supply, mounting a wheel on a boat moored in a fast river.

• 5. The Medieval Surge

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  The Domesday Book, compiled in 1086, records 5,624 watermills in England alone. Later research suggests a less conservative 6,082, treated as a minimum because the northern reaches of England were never properly recorded. By 1300 the number had risen to between 10,000 and 15,000. Documentary evidence climbs sharply in the Middle Ages because new genres, monastic charters, Christian hagiography, and Germanic legal codes, were more inclined to address a rural work process than the urban-centered ancient literary class had been. By Carolingian times, references in Frankish records had become innumerable. Watermills were well established in Ireland by the early 7th century, and a century later began spreading across the former Roman Rhine and Danube frontier into other parts of Germany. The Irish coast also holds the earliest tide mills. A 6th century vertical-wheeled tide mill sat at Killoteran near Waterford. A twin flume horizontal-wheeled tide mill dating to around 630 was excavated on Little Island, alongside another powered by a vertical undershot wheel. The Nendrum Monastery mill of 787, on an island in Strangford Lough in Northern Ireland, had millstones 830 mm in diameter, with an even earlier mill at the site dated to 619.

• 6. France's Inventive Streak

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  Adam Lucas, in a 2005 survey, traced the first appearances of industrial mill types across medieval Europe between 770 and 1443. France stands out for introducing new uses of water power again and again. The malt mill appears in France in 770, the fulling mill in 1080, the tanning mill around 1134. Forge mills show up around 1200 in England and France, the tool-sharpening mill in France in 1203, the hemp mill in 1209. Bellows are recorded in 1269 and 1283 in Slovakia and France. The paper mill appears in Spain in 1282, the sawmill in France around 1300, and the ore-crushing mill in Germany in 1317. The blast furnace arrives in France in 1384, and the cutting and slitting mill again in France in 1443. Lucas also noted the dearth of studies in several other countries, a gap that leaves the record uneven. The pattern in his table is a steady widening of what a turning wheel could be asked to do.

• 7. Eastern Currents

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  In China the waterwheel appears from 30 AD onward, powering trip hammers, the bellows for smelting iron, and in one case the rotation of an armillary sphere for astronomy, linked to Zhang Heng. The British sinologist Joseph Needham speculated that a water-powered millstone could have existed in Han China by the 1st century AD, but firm literary evidence waits until the 5th. In 488 AD the mathematician and engineer Zu Chongzhi built a watermill inspected by Emperor Wu of Southern Qi. The Sui engineer Yang Su was said to run hundreds by the start of the 6th century. A source from 612 AD records Buddhist monks quarreling over mill revenues. The Tang Ordinances of the Department of Waterways, written in 737 AD, held that mills should not interrupt river transport, and the government demolished many that flouted the rules. A eunuch serving Emperor Xuanzong owned a mill by 748 AD with five waterwheels grinding 300 bushels of wheat a day. The watermill reached Japan via the Korean Peninsula by 610 or 670 AD, and Tibet by at least 641 AD. India, by Greek tradition, received water-mills from the Roman Empire in the early 4th century AD, when a man named Metrodoros introduced water-mills and baths, unknown among the Brahmans till then. Engineers under the Caliphates adopted the technology from former Byzantine provinces. By the 11th century every province of the Islamic world ran industrial watermills, and along the Tigris and Euphrates in 10th-century Iraq, ship mills of teak and iron could produce 10 tons of flour a day for the granary in Baghdad.

• 8. How A Mill Thinks

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  Water diverted along a flume, head race, leat, lade, or penstock drives the blades of a wheel or turbine, which spins an axle that runs the rest of the machinery. Spent water leaves by a tail race, which may itself become the head race for the next wheel. Sluice gates control the flow and offer some flood control, and large complexes may have dozens feeding interconnected races. The overshot wheel was around two and a half times more efficient than the undershot. An undershot wheel, set into the flow, fights itself: it enters the water behind the main thrust and lifts out ahead of it. The overshot wheel brings water to the top, filling buckets whose weight turns the wheel, so the water never impedes its speed. Its drawback is that it reverses the wheel's rotation. The pitchback or backshot wheel solved that with a launder at the end of the flume, turning the water without much loss while keeping the direction of rotation. Daniels Mill near Bewdley, Worcestershire, originally a breastshot mill, was converted to pitchback and today runs as a breastshot mill. In corn mills the waterwheel turns a pit wheel, which meshes with the wallower, which turns the great spur wheel, which drives a stone nut on the runner stone's shaft. By the 19th century a single wheel could drive as many as four stones. The earliest illustration of one waterwheel driving more than one set of stones was drawn by Henry Beighton in 1723 and published in 1744 by J. T. Desaguliers.

  In 1870 watermills still produced two-thirds of the power for British grain milling. Toward the end of the 19th century, the Pelton wheel encouraged some owners to swap over- and undershot wheels for turbines driven through penstocks. Then cheap electrical energy arrived, and by the early 20th century the watermill was obsolete in developed countries, though some small rural mills kept working commercially. A different logic powers the tide mill, which traps the incoming tide behind a mole and releases it through a sluice to drive the wheel. It works best where the tidal range is great, like the Bay of Fundy in Canada, where tides can rise fifty feet. Two restored working tide mills in the United Kingdom can be visited at Eling, Hampshire, and Woodbridge, Suffolk. Historic mills such as the Water Mill, Newlin Mill, and Yates Mill in the US, and The Darley Mill Centre in the UK, still run for demonstration. Small-scale commercial milling continues at Daniels Mill, Little Salkeld Mill, and Redbournbury Mill, boosted by flour shortages during the Covid pandemic. In the developing world the old machines still earn their keep. An estimated 25,000 operate in Nepal and 200,000 in India, and between 2003 and 2007 the Centre for Rural Technology in Nepal upgraded 2,400 of them by replacing wooden parts with better metal ones.