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A watermill or water mill is a mill that uses hydropower. It is a structure that uses a water wheel or water turbine to drive a mechanical process such as milling (grinding), rolling, or
hammer A hammer is a tool, most often a hand tool, consisting of a weighted "head" fixed to a long handle that is swung to deliver an impact to a small area of an object. This can be, for example, to drive nails into wood, to shape metal (as w ...
ing. Such processes are needed in the production of many material goods, including
flour Flour is a powder made by grinding raw grains, roots, beans, nuts, or seeds. Flours are used to make many different foods. Cereal flour, particularly wheat flour, is the main ingredient of bread, which is a staple food for many culture ...
, lumber, paper, textiles, and many metal products. These watermills may comprise gristmills, sawmills,
paper mill A paper mill is a factory devoted to making paper from vegetable fibres such as wood pulp, old rags, and other ingredients. Prior to the invention and adoption of the Fourdrinier machine and other types of paper machine that use an endless belt, ...
s, textile mills, hammermills, trip hammering mills, rolling mills, wire drawing mills. One major way to classify watermills is by wheel orientation (vertical or horizontal), one powered by a vertical waterwheel through a gear mechanism, and the other equipped with a horizontal waterwheel without such a mechanism. The former type can be further divided, depending on where the water hits the wheel paddles, into undershot, overshot, breastshot and pitchback (backshot or reverse shot) waterwheel mills. Another way to classify water mills is by an essential trait about their location: tide mills use the movement of the tide; ship mills are water mills onboard (and constituting) a ship. Watermills impact the river dynamics of the watercourses where they are installed. During the time watermills operate channels tend to sedimentate, particularly backwater. Also in the backwater area, inundation events and sedimentation of adjacent floodplains increase. Over time however these effects are cancelled by river banks becoming higher. Where mills have been removed, river incision increases and channels deepen.


History

There are two basic types of watermills, one powered by a vertical-waterwheel via a gear mechanism, and the other equipped with a horizontal-waterwheel without such a mechanism. The former type can be further divided, depending on where the water hits the wheel paddles, into undershot, overshot, breastshot and reverse shot waterwheel mills.


Western world


Classical Antiquity

The Greeks invented the two main components of watermills, the waterwheel and toothed gearing, and used, along with the Romans, undershot, overshot and breastshot waterwheel mills. The earliest evidence of a water-driven wheel appears in the technical treatises ''Pneumatica'' and ''Parasceuastica'' of the Greek engineer
Philo of Byzantium Philo of Byzantium ( el, , ''Phílōn ho Byzántios'', ca. 280 BC – ca. 220 BC), also known as Philo Mechanicus, was a Greek engineer, physicist and writer on mechanics, who lived during the latter half of the 3rd century BC. Although he was f ...
(ca. 280−220 BC). The British historian of technology M.J.T. Lewis has shown that those portions of Philo of Byzantium's mechanical treatise which describe water wheels and which have been previously regarded as later Arabic interpolations, actually date back to the Greek
3rd century BC In the Mediterranean Basin, the first few decades of this century were characterized by a balance of power between the Greek Hellenistic kingdoms in the east, and the great mercantile power of Carthage in the west. This balance was shattered ...
original. The sakia gear is, already fully developed, for the first time attested in a 2nd-century BC
Hellenistic In Classical antiquity, the Hellenistic period covers the time in Mediterranean history after Classical Greece, between the death of Alexander the Great in 323 BC and the emergence of the Roman Empire, as signified by the Battle of Actium in ...
wall painting in Ptolemaic Egypt. Lewis assigns the date of the invention of the horizontal-wheeled mill to the Greek colony of
Byzantium Byzantium () or Byzantion ( grc, Βυζάντιον) was an ancient Greek city in classical antiquity that became known as Constantinople in late antiquity and Istanbul today. The Greek name ''Byzantion'' and its Latinization ''Byzantium'' cont ...
in the first half of the 3rd century BC, and that of the vertical-wheeled mill to
Ptolemaic Ptolemaic is the adjective formed from the name Ptolemy, and may refer to: Pertaining to the Ptolemaic dynasty * Ptolemaic dynasty, the Macedonian Greek dynasty that ruled Egypt founded in 305 BC by Ptolemy I Soter * Ptolemaic Kingdom Pertaining ...
Alexandria around 240 BC.; ; The Greek geographer
Strabon Strabo''Strabo'' (meaning "squinty", as in strabismus) was a term employed by the Romans for anyone whose eyes were distorted or deformed. The father of Pompey was called "Pompeius Strabo". A native of Sicily so clear-sighted that he could see ...
reports in his ''Geography'' a water-powered
grain-mill A gristmill (also: grist mill, corn mill, flour mill, feed mill or feedmill) grinds cereal grain into flour and middlings. The term can refer to either the grinding mechanism or the building that holds it. Grist is grain that has been separat ...
to have existed near the palace of king Mithradates VI Eupator at
Cabira Cabira or Kabeira (; el, τὰ Κάβειρα) was a town of ancient Pontus in Asia minor, at the base of the range of Paryadres, about 150 stadia south of Eupatoria or Magnopolis, which was at the junction of the Iris and the Lycus. Eupatoria ...
, Asia Minor, before 71 BC. The Roman engineer Vitruvius has the first technical description of a watermill, dated to 40/10 BC; the device is fitted with an undershot wheel and power is transmitted via a gearing mechanism.; He also seems to indicate the existence of water-powered
kneading In cooking (and more specifically baking), kneading is a process in the making of bread or dough, used to mix the ingredients and add strength to the final product. Its importance lies in the mixing of flour with water; when these two ingredient ...
machines. The Greek epigrammatist
Antipater of Thessalonica Antipater of Thessalonica ( grc-gre, Ἀντίπατρος ὁ Θεσσαλονικεύς; c. 10 BC - c. AD 38) was a Greek epigrammatist of the Roman period. Biography Antipater lived during the latter part of the reign of Augustus, and perha ...
tells of an advanced
overshot wheel A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a wheel (usually constructed from wood or metal), with a number of blades or bucket ...
mill around 20 BC/10 AD.; He praised for its use in grinding grain and the reduction of human labour: The Roman encyclopedist Pliny mentions in his '' Naturalis Historia'' of around 70 AD water-powered trip hammers operating in the greater part of Italy.; ; There is evidence of a
fulling mill Fulling, also known as felting, tucking or walking ( Scots: ''waukin'', hence often spelled waulking in Scottish English), is a step in woollen clothmaking which involves the cleansing of woven or knitted cloth (particularly wool) to elimin ...
in 73/4 AD in Antioch,
Roman Syria Roman Syria was an early Roman province annexed to the Roman Republic in 64 BC by Pompey in the Third Mithridatic War following the defeat of King of Armenia Tigranes the Great. Following the partition of the Herodian Kingdom of Judea into tetr ...
. The 2nd century AD multiple mill complex of Barbegal in southern France has been described as "the greatest known concentration of mechanical power in the ancient world". It featured 16 overshot waterwheels to power an equal number of
flour Flour is a powder made by grinding raw grains, roots, beans, nuts, or seeds. Flours are used to make many different foods. Cereal flour, particularly wheat flour, is the main ingredient of bread, which is a staple food for many culture ...
mills. The capacity of the mills has been estimated at 4.5 tons of
flour Flour is a powder made by grinding raw grains, roots, beans, nuts, or seeds. Flours are used to make many different foods. Cereal flour, particularly wheat flour, is the main ingredient of bread, which is a staple food for many culture ...
per day, sufficient to supply enough bread for the 12,500 inhabitants occupying the town of
Arelate Arles (, , ; oc, label= Provençal, Arle ; Classical la, Arelate) is a coastal city and commune in the South of France, a subprefecture in the Bouches-du-Rhône department of the Provence-Alpes-Côte d'Azur region, in the former province of ...
at that time. A similar mill complex existed on the Janiculum hill, whose supply of flour for Rome's population was judged by emperor
Aurelian Aurelian ( la, Lucius Domitius Aurelianus; 9 September 214 October 275) was a Roman emperor, who reigned during the Crisis of the Third Century, from 270 to 275. As emperor, he won an unprecedented series of military victories which reunited t ...
important enough to be included in the Aurelian walls in the late 3rd century. A breastshot wheel mill dating to the late 2nd century AD was excavated at
Les Martres-de-Veyre Les Martres-de-Veyre (, literally ''Les Martres of Veyre''; oc, Las Martras) is a commune in the Puy-de-Dôme department in Auvergne in central France. Population See also *Communes of the Puy-de-Dôme department The following is a list of ...
, France. The 3rd century AD
Hierapolis water-powered stone sawmill The Hierapolis sawmill was a Roman water-powered stone sawmill at Hierapolis, Asia Minor (modern-day Turkey). Dating to the second half of the 3rd century AD, the sawmill is considered the earliest known machine to combine a crank with a conne ...
is the earliest known machine to incorporate a
crank Crank may refer to: Mechanisms * Crank (mechanism), in mechanical engineering, a bent portion of an axle or shaft, or an arm keyed at right angles to the end of a shaft, by which motion is imparted to or received from it * Crankset, the compone ...
and
connecting rod A connecting rod, also called a 'con rod', is the part of a piston engine which connects the piston to the crankshaft. Together with the crank, the connecting rod converts the reciprocating motion of the piston into the rotation of the cranksh ...
mechanism. Further sawmills, also powered by crank and connecting rod mechanisms, are archaeologically attested for the 6th century AD water-powered stone sawmills at Gerasa and
Ephesus Ephesus (; grc-gre, Ἔφεσος, Éphesos; tr, Efes; may ultimately derive from hit, 𒀀𒉺𒊭, Apaša) was a city in ancient Greece on the coast of Ionia, southwest of present-day Selçuk in İzmir Province, Turkey. It was built in t ...
. Literary references to water-powered marble saws in what is now Germany can be found in Ausonius 4th century AD poem Mosella. They also seem to be indicated about the same time by the Christian saint Gregory of Nyssa from Anatolia, demonstrating a diversified use of water-power in many parts of the Roman Empire. The earliest turbine mill was found in
Chemtou Chemtou or Chimtou was an ancient Roman- Berber town in northwestern Tunisia, located 20 km from the city of Jendouba near the Algerian frontier. It was known as Simitthu (or Simitthus in Roman period) in antiquity. History Chemtou was foun ...
and
Testour Testour ( ar, تستور ') is a small town located in the north of Tunisia. The town is perched on the hills of Medjerda Valley, south-west of Medjez-el-Bab, the crossroads between Tunis, Béja, and the north of Tunisia. It was known during th ...
,
Roman North Africa Africa Proconsularis was a Roman province on the northern African coast that was established in 146 BC following the defeat of Carthage in the Third Punic War. It roughly comprised the territory of present-day Tunisia, the northeast of Algeria, ...
, dating to the late 3rd or early 4th century AD. A possible water-powered
furnace A furnace is a structure in which heat is produced with the help of combustion. Furnace may also refer to: Appliances Buildings * Furnace (central heating): a furnace , or a heater or boiler , used to generate heat for buildings * Boiler, used t ...
has been identified at Marseille, France. Mills were commonly used for grinding grain into flour (attested by Pliny the Elder), but industrial uses as fulling and sawing marble were also applied. The Romans used both fixed and floating water wheels and introduced water power to other provinces of the Roman Empire. So-called 'Greek Mills' used water wheels with a horizontal wheel (and vertical shaft). A "Roman Mill" features a vertical wheel (on a horizontal shaft). Greek style mills are the older and simpler of the two designs, but only operate well with high water velocities and with small diameter millstones. Roman style mills are more complicated as they require gears to transmit the power from a shaft with a horizontal axis to one with a vertical axis. Although to date only a few dozen Roman mills are archaeologically traced, the widespread use of aqueducts in the period suggests that many remain to be discovered. Recent excavations in Roman London, for example, have uncovered what appears to be a tide mill together with a possible sequence of mills worked by an aqueduct running along the side of the River Fleet. In 537 AD, ship mills were ingeniously used by the East Roman general Belisarius, when the besieging Goths cut off the water supply for those mills. These floating mills had a wheel that was attached to a boat moored in a fast flowing river. File:Undershot water wheel schematic.svg, Undershot water wheel, applied for watermilling since the 1st century BC Image:Overshot water wheel schematic.svg, Overshot water wheel, applied for watermilling since the 1st century BC Image:Breastshot water wheel schematic.png, Breastshot water wheel, applied for watermilling since the 3rd century AD


Middle Ages

The surviving evidence for watermills sharply increases with the emergence of documentary genres such as monastic
charter A charter is the grant of authority or rights, stating that the granter formally recognizes the prerogative of the recipient to exercise the rights specified. It is implicit that the granter retains superiority (or sovereignty), and that the rec ...
s, Christian
hagiography A hagiography (; ) is a biography of a saint or an ecclesiastical leader, as well as, by extension, an adulatory and idealized biography of a founder, saint, monk, nun or icon in any of the world's religions. Early Christian hagiographies migh ...
and Germanic
legal code A code of law, also called a law code or legal code, is a systematic collection of statutes. It is a type of legislation that purports to exhaustively cover a complete system of laws or a particular area of law as it existed at the time the cod ...
s. These were more inclined to address watermilling, a mostly rural work process, than the ancient urban-centered literary class had been. By
Carolingian The Carolingian dynasty (; known variously as the Carlovingians, Carolingus, Carolings, Karolinger or Karlings) was a Frankish noble family named after Charlemagne, grandson of mayor Charles Martel and a descendant of the Arnulfing and Pippin ...
times, references to watermills had become "innumerable" in Frankish records. The Domesday Book, compiled in 1086, records 5,624 watermills in England alone. Later research estimates a less conservative number of 6,082 that should be considered a minimum as the northern reaches of England were never properly recorded. In 1300, this number had risen to between 10,000 and 15,000. By the early 7th century, watermills were also well established in Ireland. A century later they began to spread across the former Roman Rhine and Danube frontier into the other parts of Germany. Ship mills and tide mills, both of which yet unattested for the ancient period, were introduced in the 6th century. ; Tide mills In recent years, a number of new archaeological finds has consecutively pushed back the date of the earliest tide mills, all of which were discovered on the Irish coast: 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. Alongside it, another tide mill was found which was powered by a vertical undershot wheel. The
Nendrum Monastery mill The Nendrum Monastery mill was a tide mill on an Mahee Island in Strangford Lough now in Northern Ireland. It is the earliest excavated tide mill, dating from 787 AD. Its millstones are 830mm in diameter and the horizontal wheel is estimated to hav ...
from 787 was situated on an island in Strangford Lough in Northern Ireland. Its millstones are 830mm in diameter and the horizontal wheel is estimated to have developed 7/8HP at its peak. Remains of an earlier mill dated at 619 were also found at the site. ; Survey of industrial mills In a 2005 survey the scholar Adam Lucas identified the following first appearances of various industrial mill types in Western Europe. Noticeable is the preeminent role of France in the introduction of new innovative uses of waterpower. However, he has drawn attention to the dearth of studies of the subject in several other countries.


Ancient East Asia

The waterwheel was found in China from 30 AD onwards, when it was used to power trip hammers, the bellows in
smelting iron Smelting is a process of applying heat to ore, to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including silver, iron, copper, and other base metals. Smelting uses heat and a ch ...
, and in one case, to mechanically rotate an
armillary sphere An armillary sphere (variations are known as spherical astrolabe, armilla, or armil) is a model of objects in the sky (on the celestial sphere), consisting of a spherical framework of rings, centered on Earth or the Sun, that represent lines of ...
for astronomical observation (see
Zhang Heng Zhang Heng (; AD 78–139), formerly romanized as Chang Heng, was a Chinese polymathic scientist and statesman who lived during the Han dynasty. Educated in the capital cities of Luoyang and Chang'an, he achieved success as an astronomer, ma ...
). Although the British chemist and sinologist
Joseph Needham Noel Joseph Terence Montgomery Needham (; 9 December 1900 – 24 March 1995) was a British biochemist, historian of science and sinologist known for his scientific research and writing on the history of Chinese science and technology, in ...
speculates that the water-powered millstone could have existed in Han China by the 1st century AD, there is no sufficient literary evidence for it until the 5th century AD. In 488 AD, the mathematician and engineer Zu Chongzhi had a watermill erected which was inspected by
Emperor Wu of Southern Qi Emperor Wu of Southern Qi (南齊武帝) (440– 27 August 493), personal name Xiao Ze (蕭賾), courtesy name Xuanyuan (宣遠), childhood name Long'er (龍兒), was the second emperor of the Chinese Southern Qi dynasty. He is generally considere ...
(r. 482–493 AD).Needham (1986), Volume 4, Part 2, 400. The engineer Yang Su of the
Sui Dynasty The Sui dynasty (, ) was a short-lived imperial dynasty of China that lasted from 581 to 618. The Sui unified the Northern and Southern dynasties, thus ending the long period of division following the fall of the Western Jin dynasty, and layi ...
(581–618 AD) was said to operate hundreds of them by the beginning of the 6th century. A source written in 612 AD mentions Buddhist monks arguing over the revenues gained from watermills. The Tang Dynasty (618–907 AD) 'Ordinances of the Department of Waterways' written in 737 AD stated that watermills should not interrupt riverine transport and in some cases were restricted to use in certain seasons of the year. From other Tang-era sources of the 8th century, it is known that these ordinances were taken very seriously, as the government demolished many watermills owned by great families, merchants, and Buddhist abbeys that failed to acknowledge ordinances or meet government regulations. A eunuch serving
Emperor Xuanzong of Tang Emperor Xuanzong of Tang (; 8 September 685 – 3 May 762), personal name Li Longji, was the seventh emperor of the Tang dynasty in China, reigning from 712 to 756 CE. His reign of 44 years was the longest during the Tang dynasty. In the early ...
(r. 712–756 AD) owned a watermill by 748 AD which employed five waterwheels that ground 300 bushels of wheat a day. By 610 or 670 AD, the watermill was introduced to
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
via Korean Peninsula.Needham (1986), Volume 4, Part 2, 401. It also became known in Tibet by at least 641 AD.


Ancient India

According to Greek historical tradition, India received water-mills from the Roman Empire in the early 4th century AD when a certain Metrodoros introduced "water-mills and baths, unknown among them
he Brahmans He or HE may refer to: Language * He (pronoun), an English pronoun * He (kana), the romanization of the Japanese kana へ * He (letter), the fifth letter of many Semitic alphabets * He (Cyrillic), a letter of the Cyrillic script called ''He'' in ...
till then".


Islamic world

Engineers under the Caliphates adopted watermill technology from former provinces of the Byzantine Empire, having been applied for centuries in those provinces prior to the Muslim conquests, including modern-day
Syria Syria ( ar, سُورِيَا or سُورِيَة, translit=Sūriyā), officially the Syrian Arab Republic ( ar, الجمهورية العربية السورية, al-Jumhūrīyah al-ʻArabīyah as-Sūrīyah), is a Western Asian country loc ...
, Jordan, Israel, Algeria, Tunisia, Morocco, and Spain (see
List of ancient watermills This list of ancient watermills presents an overview of water-powered grain-mills and industrial mills in the classical antiquity from their Hellenistic beginnings through the Roman imperial period. The watermill is the earliest instance of a ...
). The industrial uses of watermills in the Islamic world date back to the 7th century, while horizontal-wheeled and vertical-wheeled watermills were both in widespread use by the 9th century. A variety of industrial watermills were used in the Islamic world, including gristmills, hullers, sawmills, ship mills,
stamp mill A stamp mill (or stamp battery or stamping mill) is a type of mill machine that crushes material by pounding rather than grinding, either for further processing or for extraction of metallic ores. Breaking material down is a type of unit operatio ...
s,
steel mill A steel mill or steelworks is an industrial plant for the manufacture of steel. It may be an integrated steel works carrying out all steps of steelmaking from smelting iron ore to rolled product, but may also be a plant where steel semi-finish ...
s,
sugar mills A sugar cane mill is a factory that processes sugar cane to produce raw or white sugar. The term is also used to refer to the equipment that crushes the sticks of sugar cane to extract the juice. Processing There are a number of steps in prod ...
, and tide mills. By the 11th century, every province throughout the Islamic world had these industrial watermills in operation, from al-Andalus and North Africa to the Middle East and Central Asia. Muslim and Middle Eastern Christian engineers also used
crankshaft A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecting ...
s and water turbines, gears in watermills and water-raising
machine A machine is a physical system using Power (physics), power to apply Force, forces and control Motion, movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to na ...
s, and dams as a source of water, used to provide additional power to watermills and water-raising machines. Fulling mills, and steel mills may have spread from Al-Andalus to Christian Spain in the 12th century. Industrial watermills were also employed in large factory complexes built in al-Andalus between the 11th and 13th centuries. The engineers of the Islamic world used several solutions to achieve the maximum output from a watermill. One solution was to mount them to piers of bridges to take advantage of the increased flow. Another solution was the ship mill, a type of watermill powered by water wheels mounted on the sides of ships moored in midstream. This technique was employed along the Tigris and
Euphrates The Euphrates () is the longest and one of the most historically important rivers of Western Asia. Tigris–Euphrates river system, Together with the Tigris, it is one of the two defining rivers of Mesopotamia ( ''the land between the rivers'') ...
rivers in 10th-century Iraq, where large ship mills made of teak and iron could produce 10
ton Ton is the name of any one of several units of measure. It has a long history and has acquired several meanings and uses. Mainly it describes units of weight. Confusion can arise because ''ton'' can mean * the long ton, which is 2,240 pounds ...
s of flour from corn every day for the granary in Baghdad.Hill; see als
Mechanical Engineering


Persia

More than 300 watermills were at work in Iran till 1960.Conference of Qanat in Iran - water clock in Persia 1383
in Persian
Now only a few are still working. One of the famous ones is the water mill of Askzar and the water mill of the Yazd city, still producing flour.


Operation

Typically, water is diverted from a river or
impoundment Impoundment may refer to: Water control * The result of a dam, creating a body of water ** A reservoir, formed by a dam ** Coal slurry impoundment, a specialized form of such a reservoir used for coal mining and processing * Impounded dock, an enc ...
or mill pond to a turbine or water wheel, along a channel or pipe (variously known as a flume, head race, mill race, leat, leet, lade (Scots) or penstock). The force of the water's movement drives the blades of a wheel or turbine, which in turn rotates an axle that drives the mill's other machinery. Water leaving the wheel or turbine is drained through a tail race, but this channel may also be the head race of yet another wheel, turbine or mill. The passage of water is controlled by
sluice Sluice ( ) is a word for a channel controlled at its head by a movable gate which is called a sluice gate. A sluice gate is traditionally a wood or metal barrier sliding in grooves that are set in the sides of the waterway and can be considered ...
gates that allow maintenance and some measure of flood control; large mill complexes may have dozens of sluices controlling complicated interconnected races that feed multiple buildings and industrial processes. Watermills can be divided into two kinds, one with a horizontal water wheel on a vertical axle, and the other with a vertical wheel on a horizontal axle. The oldest of these were horizontal mills in which the force of the water, striking a simple paddle wheel set horizontally in line with the flow turned a runner stone balanced on the rynd which is atop a shaft leading directly up from the wheel. The bedstone does not turn. The problem with this type of mill arose from the lack of gearing; the speed of the water directly set the maximum speed of the runner stone which, in turn, set the rate of milling. Most watermills in Britain and the United States of America had a vertical waterwheel, one of four kinds: undershot, breast-shot, overshot and pitchback wheels. This vertical produced rotary motion around a horizontal axis, which could be used (with cams) to lift hammers in a
forge A forge is a type of hearth used for heating metals, or the workplace (smithy) where such a hearth is located. The forge is used by the smith to heat a piece of metal to a temperature at which it becomes easier to shape by forging, or to th ...
, fulling stocks in a
fulling mill Fulling, also known as felting, tucking or walking ( Scots: ''waukin'', hence often spelled waulking in Scottish English), is a step in woollen clothmaking which involves the cleansing of woven or knitted cloth (particularly wool) to elimin ...
and so on. File:Undershot water wheel schematic.svg, Undershot water wheel, applied for watermilling since the 1st century BC Image:Overshot water wheel schematic.svg, Overshot water wheel, applied for watermilling since the 1st century BC File:Pitchback water wheel schematic (2).svg, Pitchback water wheel, often used to increase the power generated by a breastshot wheel Image:Breastshot water wheel schematic.png, Breastshot water wheel, applied for watermilling since the 3rd century AD


Milling corn

However, in corn mills rotation about a vertical axis was required to drive its stones. The horizontal rotation was converted into the vertical rotation by means of gearing, which also enabled the runner stones to turn faster than the waterwheel. The usual arrangement in British and American corn mills has been for the waterwheel to turn a horizontal shaft on which is also mounted a large
pit wheel Pit or PIT may refer to: Structure * Ball pit, a recreation structure * Casino pit, the part of a casino which holds gaming tables * Trapping pit, pits used for hunting * Pit (motor racing), an area of a racetrack where pit stops are conducted ...
. This meshes with the wallower, mounted on a vertical shaft, which turns the (larger) great spur wheel (mounted on the same shaft). This large
face wheel A watermill or water mill is a mill that uses hydropower. It is a structure that uses a water wheel or water turbine to drive a mechanical process such as milling (grinding), rolling, or hammering. Such processes are needed in the production o ...
, set with pegs, in turn, turned a smaller wheel (such as a lantern gear) known as a stone nut, which was attached to the shaft that drove the runner stone. The number of runner stones that could be turned depended directly upon the supply of water available. As waterwheel technology improved mills became more efficient, and by the 19th century, it was common for the great spur wheel to drive several stone nuts, so that a single water wheel could drive as many as four stones.Gauldie. Each step in the process increased the gear ratio which increased the maximum speed of the runner stone. Adjusting the sluice gate and thus the flow of the water past the main wheel allowed the miller to compensate for seasonal variations in the water supply. Finer speed adjustment was made during the milling process by ''tentering'', that is, adjusting the gap between the stones according to the water flow, the type of grain being milled, and the grade of flour required. In many mills (including the earliest) the great spur wheel turned only one stone, but there might be several mills under one roof. The earliest illustration of a single waterwheel driving more than one set of stones was drawn by
Henry Beighton Henry Beighton (c. 20 August 1687 – 9 October 1743) was an English engineer and surveyor. He was born at Chilvers Coton near Nuneaton, Warwickshire and worked in the neighbouring village of Griff. In 1717, he published an engraving of the ...
in 1723 and published in 1744 by J. T. Desaguliers.


Overshot and pitchback mills

The overshot wheel was a later innovation in waterwheels and was around two and a half times more efficient than the undershot. The undershot wheel, in which the main water wheel is simply set into the flow of the mill race, suffers from an inherent inefficiency stemming from the fact that the wheel itself, entering the water behind the main thrust of the flow driving the wheel, followed by the lift of the wheel out of the water ahead of the main thrust, actually impedes its own operation. The overshot wheel solves this problem by bringing the water flow to the top of the wheel. The water fills buckets built into the wheel, rather than the simple paddle wheel design of undershot wheels. As the buckets fill, the weight of the water starts to turn the wheel. The water spills out of the bucket on the down side into a spillway leading back to river. Since the wheel itself is set above the spillway, the water never impedes the speed of the wheel. The impulse of the water on the wheel is also harnessed in addition to the weight of the water once in the buckets. Overshot wheels require the construction of a dam on the river above the mill and a more elaborate millpond, sluice gate, mill race and spillway or tailrace. An inherent problem in the overshot mill is that it reverses the rotation of the wheel. If a miller wishes to convert a breastshot mill to an overshot wheel all the machinery in the mill has to be rebuilt to take account of the change in rotation. An alternative solution was the pitchback or backshot wheel. A launder was placed at the end of the flume on the headrace, this turned the direction of the water without much loss of energy, and the direction of rotation was maintained. Daniels Mill near Bewdley, Worcestershire is an example of a flour mill that originally used a breastshot wheel, but was converted to use a pitchback wheel. Today it operates as a breastshot mill. Larger water wheels (usually overshot
steel Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...
wheels) transmit the power from a toothed annular ring that is mounted near the outer edge of the wheel. This drives the machinery using a spur gear mounted on a shaft rather than taking power from the central
axle An axle or axletree is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In the former case, bearing ...
. However, the basic mode of operation remains the same; gravity drives
machinery A machine is a physical system using power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolecule ...
through the motion of flowing water. Toward the end of the 19th century, the invention of the Pelton wheel encouraged some mill owners to replace over- and undershot wheels with Pelton wheel turbines driven through penstocks.


Tide mills

A different type of watermill is the tide mill. This mill might be of any kind, undershot, overshot or horizontal but it does not employ a river for its power source. Instead a mole or causeway is built across the mouth of a small bay. At low tide, gates in the mole are opened allowing the bay to fill with the incoming tide. At high tide the gates are closed, trapping the water inside. At a certain point a sluice gate in the mole can be opened allowing the draining water to drive a mill wheel or wheels. This is particularly effective in places where the tidal differential is very great, such as the
Bay of Fundy The Bay of Fundy (french: Baie de Fundy) is a bay between the Canadian provinces of New Brunswick and Nova Scotia, with a small portion touching the U.S. state of Maine. It is an arm of the Gulf of Maine. Its extremely high tidal range is the hi ...
in Canada where the tides can rise fifty feet, or the now derelict village of Tide Mills, East Sussex. The last two examples in the United Kingdom which are restored to working conditions can be visited at Eling, Hampshire and at
Woodbridge Woodbridge may refer to: Places Australia *Woodbridge, Western Australia formerly called ''West Midland'' *Woodbridge, Tasmania Canada *Woodbridge, Ontario England *Woodbridge, Suffolk, the location of ** Woodbridge (UK Parliament constituency ...
,
Suffolk Suffolk () is a ceremonial county of England in East Anglia. It borders Norfolk to the north, Cambridgeshire to the west and Essex to the south; the North Sea lies to the east. The county town is Ipswich; other important towns include Lowes ...
. ''Run of the river'' schemes do not divert water at all and usually involve
undershot A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a wheel (usually constructed from wood or metal), with a number of blades or bucket ...
wheels the mills are mostly on the banks of sizeable rivers or fast flowing streams. Other watermills were set beneath large bridges where the flow of water between the stanchions was faster. At one point London bridge had so many water wheels beneath it that bargemen complained that passage through the bridge was impaired.


Current status

In 1870 watermills still produced 2/3 of the power available for British grain milling. By the early 20th century, availability of cheap electrical energy made the watermill obsolete in developed countries although some smaller rural mills continued to operate commercially later throughout the century. A few historic mills such as the Water Mill, Newlin Mill and
Yates Mill __NOTOC__ Yates Mill is a fully restored, circa 1756 gristmill located five miles (8 km) south of downtown Raleigh, North Carolina, United States. It is the centerpiece of Historic Yates Mill County Park, in central Wake County. The park featu ...
in the US and The Darley Mill Centre in the UK still operate for demonstration purposes. Small-scale commercial production is carried out in the UK at Daniels Mill, Little Salkeld Mill and
Redbournbury Mill Redbournbury Mill, is a Grade II* listed flour mill in Redbournbury, Hertfordshire, England, which is thought to have been first built in the early 11th Century. Having operated as a watermill on the River Ver, the mill is now powered by a dies ...
. This was boosted to overcome flour shortages during the Covid pandemic. Some old mills are being upgraded with modern hydropower technology, such as those worked on by the
South Somerset Hydropower Group The South Somerset Hydropower Group (SSHG) is a group of 10 owners of former watermills in the South Somerset area of England who are installing micro-hydro turbines for electricity generation. The Group was founded as a result of an initiative b ...
in the UK. In some developing countries, watermills are still widely used for processing grain. For example, there are thought to be 25,000 operating in Nepal, and 200,000 in India. Many of these are still of the traditional style, but some have been upgraded by replacing wooden parts with better-designed metal ones to improve the efficiency. For example, the Centre for Rural Technology in Nepal upgraded 2,400 mills between 2003 and 2007.Ashden Awards case study on upgrading of watermills by CRT/Nepal


Applications

* Bark mills ground
bark Bark may refer to: * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Places * Bark, Germany * Bark, Warmian-Masurian Voivodeship, Poland Arts, ...
, from oak or chestnut trees to produce a coarse powder for use in
tanneries Tanning may refer to: *Tanning (leather), treating animal skins to produce leather *Sun tanning, using the sun to darken pale skin **Indoor tanning, the use of artificial light in place of the sun **Sunless tanning, application of a stain or dye t ...
. * Blade mills were used for sharpening newly made blades. *
Blast furnace A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally pig iron, but also others such as lead or copper. ''Blast'' refers to the combustion air being "forced" or supplied above atmospheric ...
s, finery forges, and tinplate works were, until the introduction of the steam engine, almost invariably water powered. Furnaces and Forges were sometimes called iron mills. *
Bobbin mill A bobbin or spool is a spindle or cylinder, with or without flanges, on which yarn, thread, wire, tape or film is wound. Bobbins are typically found in industrial textile machinery, as well as in sewing machines, fishing reels, tape measures, ...
s made wooden bobbins for the cotton and other textile industries. * Carpet mills for making carpets and rugs were sometimes water-powered. * Cotton mills were driven by water. The power was used to
card Card or The Card may refer to: * Various types of plastic cards: **By type ***Magnetic stripe card *** Chip card *** Digital card **By function ***Payment card ****Credit card **** Debit card ****EC-card ****Identity card ****European Health Insur ...
the raw cotton, and then to drive the spinning mules and ring frames.
Steam engine A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be trans ...
s were initially used to increase the water flow to the wheel, then as the industrial revolution progressed, to directly drive the shafts. * Fulling or ''walk'' mills were used for a finishing process on woollen cloth. * Gristmills, or ''corn mills'', grind
grain A grain is a small, hard, dry fruit (caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and legum ...
s into
flour Flour is a powder made by grinding raw grains, roots, beans, nuts, or seeds. Flours are used to make many different foods. Cereal flour, particularly wheat flour, is the main ingredient of bread, which is a staple food for many culture ...
. * Lead was usually smelted in smeltmills prior to the introduction of the cupola (a reverberatory furnace). *
Needle mill Needle may refer to: Crafting * Crochet needle, a tool for making loops in thread or yarn * Knitting needle, a tool for knitting, not as sharp as a sewing needle * Sewing needle, a long slender tool with a pointed tip * Trussing needle, a long s ...
s for scouring needles during manufacture were mostly water-powered (such as Forge Mill Needle Museum) * Oil mills for crushing
oil seeds Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of fruits. Like animal fats, vegetable fats are ''mixtures'' of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or fat ...
might be wind or water-powered *
Paper mill A paper mill is a factory devoted to making paper from vegetable fibres such as wood pulp, old rags, and other ingredients. Prior to the invention and adoption of the Fourdrinier machine and other types of paper machine that use an endless belt, ...
s used water not only for motive power, but also required it in large quantities in the manufacturing process. * Powder mills for making gunpowder -
black powder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). Th ...
or smokeless powder were usually water-powered. * Rolling mills shaped metal by passing it between rollers. * Sawmills cut timber into lumber. * Slitting mills were used for slitting bars of iron into rods, which were then made into nails. * Spoke mills turned lumber into spokes for
carriage A carriage is a private four-wheeled vehicle for people and is most commonly horse-drawn. Second-hand private carriages were common public transport, the equivalent of modern cars used as taxis. Carriage suspensions are by leather strapping an ...
wheel A wheel is a circular component that is intended to rotate on an axle Bearing (mechanical), bearing. The wheel is one of the key components of the wheel and axle which is one of the Simple machine, six simple machines. Wheels, in conjunction wi ...
s. *
Stamp mill A stamp mill (or stamp battery or stamping mill) is a type of mill machine that crushes material by pounding rather than grinding, either for further processing or for extraction of metallic ores. Breaking material down is a type of unit operatio ...
s for crushing ore, usually from non-ferrous mines * Textile mills for spinning yarn or weaving cloth were sometimes water-powered.


See also

*
Horse mill A horse mill is a mill, sometimes used in conjunction with a watermill or windmill, that uses a horse engine as the power source. Any milling process can be powered in this way, but the most frequent use of animal power in horse mills was for grin ...
* List of watermills * Mill (heraldry) *
Molinology Molinology (from Latin: molīna, mill; and Greek λόγος, study) is the study of mills and other similar devices which use energy for mechanical purposes such as grinding, fulling or sawing. Mill technology The term "Molinology" was coined in 1 ...
* Scoop wheel * Sutter's Mill * Windmill


Notes


References

* * * *Gauldie, Enid (1981). ''The Scottish Miller 1700 - 1900.'' Pub. John Donald. . * * * *Lewis, M. J., ''Millstone and Hammer: the origins of water power'', University of Hull Press 1997. . * * * *Needham, Joseph. (1986). ''Science and Civilisation in China: Volume 4, Physics and Physical Technology; Part 2, Mechanical Engineering''. Taipei: Caves Books Ltd. . * * *Pacey, Arnold, ''Technology in World Civilization: A Thousand-year History'', The MIT Press; Reprint edition (July 1, 1991). . *Reynolds, Terry S. ''Stronger Than a Hundred Men: A History of the Vertical Water Wheel''. (Johns Hopkins University Press 1983). . * * * Spain, Rob
"A possible Roman Tide Mill"
Paper submitted to the ''Kent Archaeological Society'' * * * *


External links


Mill database with over 10000 European millsThe International Molinological Society (TIMS)The Society for the Preservation of Old Mills (SPOOM)U.S. mill pictures and informationMills in Hampshire, EnglandWindmills and watermills of the East Grinstead area
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