Watermill
The Greek engineer Philo of Byzantium wrote about water-driven wheels in his technical treatises Pneumatica and Parasceuastica around 280 BC. These documents contain the earliest known evidence of a water-powered wheel, predating later Arabic interpolations by centuries. A wall painting from Ptolemaic Egypt dated to the 2nd century BC shows a fully developed sakia gear mechanism. Historian M.J.T. Lewis confirmed that these portions of Philo's work date back to the original Greek text from the 3rd century BC. The invention of the horizontal-wheeled mill is assigned to the Greek colony of Byzantium during the first half of the 3rd century BC. Vertical-wheeled mills appeared in Ptolemaic Alexandria around 240 BC. Roman engineer Vitruvius provided the first technical description of a watermill in 40/10 BC. His design featured an undershot wheel with power transmitted via a gearing mechanism. Strabo reported a water-powered grain-mill existed near the palace of King Mithradates VI Eupator at Cabira before 71 BC. Antipater of Thessalonica described an advanced overshot wheel mill around 20 BC or 10 AD. He praised its ability to grind grain and reduce human labor. Pliny mentioned water-powered trip hammers operating throughout Italy around 70 AD. Evidence of a fulling mill exists in Antioch, Roman Syria, dating to 73/74 AD. The Barbegal complex in southern France featured sixteen overshot waterwheels powering an equal number of flour mills. This facility produced 4.5 tons of flour per day for the town of Arelate. The Janiculum hill complex supplied flour to Rome's population by the late 3rd century.
The Domesday Book compiled in 1086 recorded 5,624 watermills in England alone. Later research estimates this number should be considered a minimum of 6,082 since northern reaches were never properly recorded. By 1300, the count had risen to between 10,000 and 15,000 mills across the region. Watermills became well established in Ireland by the early 7th century. They began spreading across the former Roman Rhine and Danube frontier into Germany a century later. Ship mills and tide mills were introduced in the 6th century despite being unattested for the ancient period. Archaeological finds on the Irish coast have pushed back the date of earliest tide mills. A 6th century vertical-wheeled tide mill was located at Killoteran near Waterford. A twin flume horizontal-wheeled tide mill dating to c. 630 was excavated on Little Island. Another tide mill powered by a vertical undershot wheel stood alongside it. The Nendrum Monastery mill from 787 sat on an island in Strangford Lough in Northern Ireland. Its millstones measured 830 mm in diameter while the horizontal wheel developed power at its peak. Remains of an earlier mill dated at 619 were also found at that site. Adam Lucas identified first appearances of various industrial mill types in Western Europe during a 2005 survey. France played a preeminent role in introducing new innovative uses of waterpower between AD 770 and 1443. Malt mills appeared in France in 770 while fulling mills emerged there in 1080. Tanning mills arrived around 1134 followed by forge mills circa 1200 in England and France. Tool-sharpening mills appeared in France in 1203 and hemp mills in 1209. Paper mills began operating in Spain in 1282 before sawmills reached France around 1300. Ore-crushing mills started in Germany in 1317 and blast furnaces in France by 1384.
The waterwheel was found in China from 30 AD onwards when it powered trip hammers for iron smelting. It also mechanically rotated an armillary sphere for astronomical observation under Zhang Heng. Joseph Needham speculates the water-powered millstone could have existed in Han China by the 1st century AD though no sufficient literary evidence exists until the 5th century AD. Mathematician and engineer Zu Chongzhi erected a watermill in 488 AD which Emperor Wu of Southern Qi inspected. Engineer Yang Su of the Sui dynasty operated hundreds of them by the beginning of the 6th century. A source written in 612 AD mentions Buddhist monks arguing over revenues gained from watermills. The Tang dynasty Ordinances of the Department of Waterways written in 737 AD stated that watermills should not interrupt riverine transport. Government officials demolished many watermills owned by great families, merchants, and Buddhist abbeys that failed to meet regulations. A eunuch serving Emperor Xuanzong of Tang owned a watermill by 748 AD employing five waterwheels. This facility ground 300 bushels of wheat daily. The watermill reached Japan via the Korean Peninsula by 610 or 670 AD. It became known in Tibet by at least 641 AD. India received water-mills from the Roman Empire in the early 4th century AD when Metrodoros introduced them. Engineers under the Caliphates adopted watermill technology from former Byzantine provinces including Syria, Jordan, Israel, Algeria, Tunisia, Morocco, and Spain. Industrial uses of watermills in the Islamic world date back to the 7th century while both horizontal-wheeled and vertical-wheeled mills were widespread by the 9th century. By the 11th century every province throughout the Islamic world had these industrial watermills in operation. Muslim and Middle Eastern Christian engineers used crankshafts and water turbines alongside gears in watermills. More than 300 watermills worked in Iran until 1960 though only a few remain operational today.
Water is diverted from a river or impoundment along a channel known as a flume, head race, mill race, leat, lade, or penstock. The force of the water's movement drives blades on a wheel or turbine which rotates an axle. Water leaving the wheel drains through a tailrace but this channel may also serve as the head race for another wheel. Sluice gates control passage allowing maintenance and some measure of flood control. Large mill complexes may have dozens of sluices controlling complicated interconnected races feeding multiple buildings. Horizontal mills struck a simple paddle wheel set horizontally in line with flow turning a runner stone balanced on the rynd. Bedstones did not turn in these earliest designs due to lack of gearing. Vertical wheels produced rotary motion around a horizontal axis usable for lifting hammers in forge operations. Overshot wheels were later innovations around two and a half times more efficient than undershot types. Undershot wheels suffered inherent inefficiency because the wheel entered water behind main thrust then lifted out ahead of it. Overshot wheels solved this by bringing water flow to top where buckets filled and weight started turning the wheel. Water spilled out of bucket on down side into spillway leading back to river since wheel sat above spillway. Overshot wheels required construction of dam on river above mill plus elaborate millpond, sluice gate, mill race and spillway. An inherent problem in overshot mill was that it reversed rotation requiring all machinery rebuild if converting from breastshot. Pitchback or backshot wheels maintained direction of rotation without much energy loss using launder placed at end of flume.
Bark mills ground bark from oak or chestnut trees producing coarse powder for use in tanneries. Blade mills sharpened newly made blades while blast furnaces and finery forges remained almost invariably water powered until steam engine introduction. Bobbin mills made wooden bobbins for cotton and other textile industries before steam engines took over. Carpet mills sometimes used water power to make carpets and rugs alongside cotton mills driven by water. Fulling or walk mills finished woollen cloth through a specialized process. Gristmills or corn mills ground grains into flour as their primary function. Lead smelted in smeltmills prior to cupola introduction while needle mills scoured needles during manufacture. Oil mills crushed oil seeds though some were wind-powered instead. Paper mills used water not only for motive power but also required large quantities in manufacturing process. Powder mills making gunpowder black powder or smokeless powder were usually water-powered. Rolling mills shaped metal by passing it between rollers while sawmills cut timber into lumber. Slitting mills split bars of iron into rods then made nails from them. Spoke mills turned lumber into spokes for carriage wheels. Stamp mills crushed ore usually from non-ferrous mines. Textile mills spun yarn or wove cloth sometimes using water power. Ship mills on the Mura river in Slovenia demonstrated floating mill technology. Tide mills built across bay mouths trapped incoming tide inside before draining to drive wheel. The Bay of Fundy in Canada features tidal differentials rising fifty feet making such operations particularly effective.
In 1870 watermills still produced two-thirds of power available for British grain milling. By early 20th century availability of cheap electrical energy made watermill obsolete in developed countries. Some smaller rural mills continued operating commercially later throughout the century. Historic mills like Water Mill, Newlin Mill and Yates Mill in US operate for demonstration purposes today. Darley Mill Centre in UK remains another example of preserved functionality. Small-scale commercial production occurs at Daniels Mill, Little Salkeld Mill and Redbournbury Mill in United Kingdom. This activity boosted flour supplies during Covid pandemic when shortages emerged. Old mills get upgraded with modern hydropower technology by groups like South Somerset Hydropower Group in UK. Developing countries continue widely using watermills for processing grain where infrastructure lacks alternatives. Nepal contains thought to be 25,000 operating mills while India hosts 200,000 similar facilities. Many remain traditional style though some replaced wooden parts with better-designed metal ones improving efficiency. Centre for Rural Technology in Nepal upgraded 2,400 mills between 2003 and 2007 alone. Pelton wheel turbines encouraged mill owners toward end of 19th century to replace older designs. These new turbines drove through penstocks offering greater efficiency than previous overshot or undershot wheels.
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Common questions
When did Philo of Byzantium write about water-driven wheels?
Philo of Byzantium wrote about water-driven wheels in his technical treatises Pneumatica and Parasceuastica around 280 BC. These documents contain the earliest known evidence of a water-powered wheel, predating later Arabic interpolations by centuries.
How many watermills were recorded in England in the Domesday Book compiled in 1086?
The Domesday Book compiled in 1086 recorded 5,624 watermills in England alone. Later research estimates this number should be considered a minimum of 6,082 since northern reaches were never properly recorded.
Where was the Barbegal complex located and how much flour did it produce per day?
The Barbegal complex in southern France featured sixteen overshot waterwheels powering an equal number of flour mills. This facility produced 4.5 tons of flour per day for the town of Arelate.
Which engineer erected a watermill in 488 AD that Emperor Wu of Southern Qi inspected?
Mathematician and engineer Zu Chongzhi erected a watermill in 488 AD which Emperor Wu of Southern Qi inspected. Engineer Yang Su of the Sui dynasty operated hundreds of them by the beginning of the 6th century.
What is the difference between overshot wheels and undershot wheels regarding efficiency?
Overshot wheels were later innovations around two and a half times more efficient than undershot types. Undershot wheels suffered inherent inefficiency because the wheel entered water behind main thrust then lifted out ahead of it.