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Drainage wheel from Rio Tinto

mines

Reverse overshot water-wheelFrom Wikipedia, the free encyclopedia

Frequently used in mines and probably elsewhere (such as agricultural drainage), the reverse overshot water wheelwas a Roman innovation to help remove water from the lowest levels of underground workings. It is described byVitruvius in his work De Architectura published circa 25 BC. The remains of such systems found in Roman minesby later mining operations show that they were used in sequences so as to lift water a considerable height.

Contents

1 Vitruvius

2 Pliny the Elder

3 Examples

4 The Cochlea

5 Water wheels6 See also

7 References

Vitruvius

The Roman author Vitruvius gives explicit instructions on the construction ofdewatering devices, and describes three variants of the "tympanum" inChapter X of De Architectura. It is a large wheel fitted with boxes, which inthe first design, encompass the whole diameter of the wheel. Holes arebored in the boxes to allow water into them, so that as a box dips into thewater, it enters and is raised as the wheel turns. When it reaches to the topof the turn, the water runs out into a channel. He then describes a secondvariant where the boxes are only fitted to the ends of the wheel, so thatalthough the volume of water carried is much smaller, it is carried to agreater height. The final variant is an endless chains of buckets, and muchgreater lifts can be achieved, although greater effort is needed.

Pliny the Elder

Pliny the Elder is probably referring to such devices in a discussion ofsilver/lead mines in his Naturalis Historia. Spain produced the most silver inhis time, many of the silver mines having been started by Hannibal. One ofthe largest had galleries running for between one and two miles into the mountain, "water-men" (in Latin "aquatini")draining the mine, and they

stood night and day in shifts measured by lamps, bailing out water and making a stream.

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Sequence of wheels found in Rio Tinto

mines

Roman screw used to dewater mines in Spain

That they stood suggests that they operated the wheels by standing on the top to turn the cleats, and continuousworking would produce a steady stream of water.

Examples

Fragments of such machines have been found in mines which werere-opened in the Victorian era in Spain, especially at Rio Tinto,where one example used no less than 16 such wheels working inpairs, each pair of wheels lifting water about 3.5 m (12 feet), sogiving a total lift of 30 m (96 feet). The system was carefullyengineered, and was worked by individuals treading slats at the sideof each wheel. It is not an isolated example, because Oliver Daviesmentions examples from the Tharsis copper mine and Logroño inSpain, as well as from Dacia. The gold deposits in Dacia, nowmodern Romania were especially rich, and worked intensively afterthe successful Roman invasion under Trajan. According to OliverDavies, one such sequence discovered at Ruda in HunedoaraCounty in modern Romania was 75 metres in depth, or over 200feet. If worked like the Rio Tinto example, it would have needed atleast 32 wheels.

One such wheel from Spain was rescued and part of it is now ondisplay in the British Museum. Some of the components arenumbered, suggesting that it was prefabricated above ground before assembly in the underground passages. In the1930s, a fragment of a wooden bucket from a drainage wheel was found in deep workings at the Dolaucothi goldmine in west Wales, and is now preserved in the National Museum of Wales in Cardiff. It has been carbon dated toabout 90 AD. From the depth of 160 feet below known open workings, it can be inferred that the drainage wheelwas part of a sequence just like that found in Spain. The shape of the edge of one of the lifting buckets is almostidentical with that from Spain, suggesting that a template was used to make the devices.

The Cochlea

Another device which was used widely was theArchimedean screw, and examples of such drainagemachines have also been found in many old mines.Depictions show the screws being powered by a humantreading on the outer casing to turn the entire apparatus asone piece. They were also used in series, so increasing thelift of water from the workings. However, they must havebeen more difficult to operate since the user had to stand ona slanting surface to turn the screw. The steeper the incline,the greater the risk of the user slipping from the top of thescrew. No doubt the reverse water wheel was easier to usewith a horizontal treading surface. On the other hand, thescrew could be operated by a crank handle fitted to thecentral axle, but would be more tiring since the weight of theoperator does not bear on the crank, as it does when trod from above.

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Like the reverse water wheel, the cochlea was used for many other purposes apart from draining mines. Irrigationof farmland would have the most popular application, but any activity which involved lifting water would haveemployed the devices.

Water wheels

The use of multiple sequences of water wheels was used elsewhere in the Roman Empire, such as the famousexample at Barbegal in southern France. This system was also a stack of 16 wheels but worked like a normalovershot wheel, the wheels driving stone mills and used to grind corn. The water mills were worked from a masonryaqueduct supplying the Roman town at Arles, and the remains of the masonry mills are still visible on the groundtoday, unlike the underground drainage systems of the mines, which were destroyed by later mining operations.Other such sequences of mills existed on the Janiculum in Rome, but have been covered and changed by laterbuildings built on top of them.

See also

De ArchitecturaDolaucothiFrontinus

List of ancient watermillsNaturalis Historia

NoriaPliny the Elder

Roman engineeringRoman technology

Vitruviuswatermill

water wheel

References

Boon, G. C. and Williams, C. The Dolaucothi Drainage Wheel, Journal of Roman Studies, 56 (1966),

122-127.Palmer, RE, Notes on some Ancient Mine Equipment and Systems, Transactions of the Institute of Mining

and Metallurgy, 36 (1928), 299-336.

Davies, Oliver, Roman Mines in Europe, Oxford (1935).

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