Watermill

Watermill of Braine-le-Château, Belgium (12th century)

This article is about a type of structure. For other locational uses see: Milldam

A watermill is a structure that uses a water wheel or turbine to drive a mechanical process such as flour or lumber production, or metal shaping (rolling, grinding or wire drawing). A watermill that generates electricity is usually called a hydroelectric plant

History

India

The early history of the watermill in India is obscure. According to Terry S. Reynolds, "Joseph Needham noted in 1965 that certain ancient Indian texts from around 350 BC mentioned a cakkavattaka (turning wheel) which commentaries explained as arahatta-ghatĩ-yanta (machine with wheel-pots attached)", on which basis Needham "suggested that the machine in question was a noria and that it was the first water powered prime mover." However, Reynolds also writes that "the term used in Indian texts is ambiguous and does not clearly indicate a water-powered device. In fact, as Thorkild Schiøler has noted, it is far more likely that these passages refer to some type of tread- or hand-operated water-lifting device, instead of a water-powered water-lifting wheel."

Irrigation water for crops was provided by using water raising wheels, some driven by the force of the current in the river from which the water was being raised. This kind of water raising device was used in ancient India.

Around 1150, the astronomer Bhaskara Achārya observed water-raising wheels and imagined such a wheel lifting enough water to replenish the stream driving it, effectively, a perpetual motion machine.

The construction of water works and aspects of water technology in India is described in Arabic and Persian works. During medieval times, the diffusion of Indian and Persian irrigation technologies gave rise to an advanced irrigation system which bought about economic growth and also helped in the growth of material culture.

Greco-Roman world

Reconstruction of a Roman water lifting machine found during excavations in Aldersgate Street, London

The ancient Greeks and Romans were the first to have used water for powering mills. In the early 1st century BC, the Greek epigrammatist Antipater of Thessalonica made the first clear reference to the waterwheel which he praised for its use in grinding grain and the reduction of human labour. It should be noted that this mill was already of the advanced vertical type featuring gears:

Hold back your hand from the mill, you grinding girls; even if the cockcrow heralds the dawn, sleep on. For Demeter has imposed the labours of your hands on the nymphs, who leaping down upon the topmost part of the wheel, rotate its axle; with encircling cogs, it turns the hollow weight of the Nisyrian millstones. If we learn to feast toil-free on the fruits of the earth, we taste again the golden age.

However, there is evidence that the watermill was already well known by then. The British historian of technology M.J.T. Lewis has shown that 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 original. The Greek author Strabo mentions in his Geography another early watermill, located near the palace of king Mithradates VI Eupator (r. 120-63 BC) at Cabira.

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, evidenced by a quotation from the fourth century AD author Ausonius.

Drainage wheel from Rio Tinto mines

Sequence of wheels found in Rio Tinto mines

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.

A particularly large and sophisticated Roman era watermill is the 2nd century site at Barbegal in southern France. This complex, which has been described as "the greatest known concentration of mechanical power in the ancient world", featured 16 overshot waterwheels to power an equal number of flour mills. The capacity of the mills has been estimated at 4.5 tons of flour per day, sufficient to supply enough bread for the 12,500 inhabitants occupying the town of Arelate 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 important enough to be included in the Aurelian walls in the late 3rd century. Much later in 537 AD, ship mills were ingeniously invented by the East Roman general Belisarius, when the besieging Goths cut off the water supply for those mills.

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.

Water lifting machines were common during the Roman period to dewater deep underground mines. Several such devices are described by Vitruvius, including the reverse overshot water-wheel and the Archimedean screw. Many were found during modern mining at the copper mines at Rio Tinto in Spain, one system involving 16 such wheels stacked above one another so as to lift water about 80 feet from the mine sump. Part of such a wheel was found at Dolaucothi, a Roman gold mine in south Wales in the 1930's when the mine was briefly re-opened. It was found about 80 feet below the surface, so must have been part of a similar sequence as that discovered at Rio Tinto. It has recently been carbon dated to about 80 AD, and since the wood from which it was made is much older than the deep mine, it is likely that the deep workings were in operation perhaps 30-50 years after. It is clear from these examples of drainage wheels found in sealed underground galleries in widely separated locations that building water wheels was well within their capabilities, and such verticals water wheels commonly used for industrial purposes.

China

The different variety of watermill was known in China during the Han dynasty (202 BC - 220 AD), but initially only in order to pound grain (to dehusk it).

In the text known as the Xin Lun written by Huan Tan about 20 AD (during the usurpation of Wang Mang), it states that the legendary mythological king known as Fu Xi was the one responsible for the pestle and mortar, or tilt-hammer device (see trip hammer). Although the author speaks of the mythological Fu Xi, a passage of his writing suggests that the waterwheel was in widespread use by the 1st century AD in China (Wade-Giles spelling):

Fu Hsi invented the pestle and mortar, which is so useful, and later on it was cleverly improved in such a way that the whole weight of the body could be used for treading on the tilt-hammer (tui), thus increasing the efficiency ten times. Afterwards the power of animals—donkeys, mules, oxen, and horses—was applied by means of machinery, and water-power too used for pounding, so that the benefit was increased a hundredfold.

A Northern Song era (960–1127) water-powered mill for dehusking grain with a horizontal wheel.

In 31 AD, a Chinese engineer named Du Shi (Wade-Giles: Tu Shih) "invented the first water-powered bellows. This was a complicated machine containing gears, axles, and levers that was powered by a waterwheel," according to Mary and Michael Woods. In essence, Du Shi's invention aided the forging of cast iron smelted from the blast furnace. Du Shi's invention was continued by Chinese living in subsequent dynastic periods of China, although the bellows of his device were improved upon in later periods (from leather bellows to wooden-fan bellows). Early Chinese mills featured mostly horizontal wheels, but vertical wheels were also employed.

Islamic world

Muslim engineers adopted the water wheel technology from the hydraulic societies of the Middle East, where it had been applied for hundreds of years prior to the Muslim conquest. As early as the 7th century, excavation of a canal in the Basra region discovered remains of a water wheel dating from this period. Hama in Syria still preserves one of its large wheels, on the river Orontes, although they are no longer in use. The largest had a diameter of about 20 metres and its rim was divided into 120 compartments. Another wheel that is still in operation is found at Murcia in Spain, La Nora, and although the original wheel has been replaced by a steel one, the Moorish system during al-Andalus is otherwise virtually unchanged. The flywheel mechanism, which is used to smooth out the delivery of power from a driving device to a driven machine, was invented by Ibn Bassal (fl. 1038-1075) of al-Andalus, who pioneered the use of the flywheel in the chain pump (saqiya) and noria.

The industrial uses of watermills in the Islamic world date back to the 7th century, while horizontal-wheeled and vertical-wheeled water mills were both in widespread use by the 9th century. A variety of industrial watermills were used in the Islamic world, including gristmills, hullers, paper mills, sawmills, shipmills, stamp mills, steel mills, sugar mills, 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 engineers also used crankshafts and water turbines, gears in watermills and water-raising machines, and dams as a source of water, used to provide additional power to watermills and water-raising machines. Fulling mills, paper mills and steel mills may have spread from Islamic Spain to Christian Spain in the 12th century. Industrial water mills were also employed in large factory complexes built in al-Andalus between the 11th and 13th centuries.

Muslim engineers used two solutions to achieve the maximum output from a water mill. The first solution was to mount them to piers of bridges to take advantage of the increased flow. The second solution was the shipmill, a type of water mill powered by water wheels mounted on the sides of ships moored in midstream. This technique was employed along the Tigris and Euphrates rivers in 10th century Iraq, where large shipmills made of teak and iron could produce 10 tons of flour from corn every day for the granary in Baghdad.

In the 13th century, Muslim engineers al-Jazari and Taqi al-Din depicted many water-raising machines in their technological treatise.

Medieval Europe

Snettisham Watermill in Norfolk, England

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.

First Appearance of Various Industrial Mills in Medieval Europe, AD 770-1443
Type of mill	Date	Country
Malt mill	770	France
Fulling mill	1080	France
Tanning mill	ca. 1134	France
Forge mill	ca. 1200	England, France
Tool-sharpening mill	1203	France
Hemp mill	1209	France
Bellows	1269, 1283	Slovakia, France
Sawmill	ca. 1300	France
Ore-crushing mill	1317	Germany
Blast furnace	1384	France
Cutting and slitting mill	1443	France

An early tide mill was recently excavated at the Nendrum Monastic Site in Northern Ireland. The complex is dated by dendrochronology to 787 AD.

Operation of a watermill

Roblin's Mill, a watermill, at Black Creek Pioneer Village in Toronto

Watermills in Bosnia

Typically, water is diverted from a river or impoundment 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 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.

The interior of a functional water mill

Watermills can be divided into two kinds, one with a horizontal waterwheel 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 three kinds: undershot, overshot and breast-shot. This produced rotary motion around a horizontal axis, which could be used (with cams) to lift hammers in a forge, fulling stocks in a fulling mill and so on. 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. 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, 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. In many mills the great spur wheel turned only one stone, but there might be several mills under one roof. 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. 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.

Dalgarven Mill, Ayrshire, Scotland

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.

A Breastshot waterwheel at Dalgarven Mill

Toward the end of the 19th century, the invention of the Pelton wheel encouraged some mill owners to replace over- and undershot wheels with penstocks and Pelton wheel turbines.

By the early 20th century, availability of cheap electrical energy made the water mill obsolete although some smaller rural mills continued to operate commercially into the 1960s. A few historic mills (for example, at the Wayside Inn (USA)) still operate for demonstration purposes to this day, or even maintain small-scale commercial production as at Little Salkeld (UK).

A different type of water mill 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 in Canada where the tides can rise fifty feet, or the now derelict village of Tide Mills in the UK. A working example can be seen at Eling Tide Mill.

Other water mills can be set beneath large bridges where the flow of water between the stanchions is faster. At one point London bridge had so many water wheels beneath it that bargemen complained that passage through the bridge was impaired.

A final, rather elegant, water wheel innovation places the wheel in a boat anchored in midstream. The flow of the river past the boat turns the wheel and drives the millstone.

"Run of the river" schemes do not divert water at all and usually involve undershot wheels, and some types of water wheel (usually overshot steel wheels) mount a toothed annular ring near the outer edge that drives machinery from a spur gear rather than taking power from the central axle. However, the basic mode of operation remains the same; gravity drives machinery through the motion of flowing water.

Types of watermills

• Gristmills, or corn mills, grind grains into flour. These were undoubtedly the most common kind of mill.
• Fulling or walk mills were used for a finishing process on cloth.
• Sawmills cut timber into lumber.
• Bark Mills stripped bark from trees or ground it to powder for use in tanneries.
• Spoke mills turned lumber into spokes for carriage wheels.
• Cotton mills were usually powered by a water wheel at the beginning of the industrial revolution.
• Bobbin Mills made wooden bobbins for the cotton and other textile industries.
• Carpet mills for making rugs were sometimes water-powered.
• Textile mills for weaving cloth were sometimes water-powered.
• Powder mills for making gunpowder - black powder or smokeless powder were usually water-powered.
• Blast Furnaces, finery forges, and tinplate works were until the introduction of the steam engine invariably water powered. Furnaces and Forges were sometimes called iron mills.
• Blade mills were used for sharpening newly made blades.
• Slitting mills were used for slitting bars of iron into rods, which were then made into nails.
• Rolling mills shaped metal by passing it between rollers.
• Lead was usually smelted in smeltmills prior to the introduction of the cupola (a reverberatory furnace).
• Paper mills used water not only for motive power, but also required it in large quantities in the manufacturing process.

See also

• Hydropower
• Micro hydro
• Millstone
• Mill machinery
• Molinology
• The International Molinological Society
• Renewable Energy
• Roman engineering
• Sustainable living
• Sutter's Mill
• Watermills in the United Kingdom
• Water wheel

• Claverton Pumping Station – a waterwheel-powered pumping station
• Scottish Rural Life, History Dictionary - a Dictionary which includes many milling terms.(right)

References

• Gauldie, Enid (1981). The Scottish Miller 1700 - 1900. Pub. John Donald. ISBN 0-85976-067-7.
• Lewis, M. J., Millstone and Hammer: the origins of water power, University of Hull Press 1997. ISBN 085958657X.
• Needham, Joseph (1986). Science and Civilization in China: Volume 4, Part 2. Taipei: Caves Books, Ltd.
• Pacey, Arnold, Technology in World Civilization: A Thousand-year History, The MIT Press; Reprint edition (July 1, 1991). ISBN 0262660725.
• Reynolds, Terry S. Stronger Than a Hundred Men: A History of the Vertical Water Wheel. (Johns Hopkins University Press 1983). ISBN 0801872480.
• Woods, Michael and Mary (2000). Ancient Machines: From Wedges to Waterwheels. Minneapolis: Twenty-First Century Books.

External links

• 17 Jun 2003, Deutsche Welle: The World's First Underwater Windmill Starts Turning
• U.S. Mill Pictures and Information
• Tidal power station
• Mill database with over 10000 european mills
• Watermills in Norfolk, England
• Mills in Hampshire, England
• Upwey Mill, Weymouth, Dorset
• The International Molinological Society (TIMS)
• The Society for the Preservation of Old Mills (SPOOM)
• Tidal mill in London]