What is Archimedes' screw?
[[File:Archimedes screw.JPG|thumb|Archimedes' screw]] [[File:Arkimedes skruv i Huseby.JPG|thumb|An Archimedes screw in Huseby south of Växjö Sweden]] [[File:Archimedes-screw one-screw-threads with-ball 3D-view animated small.gif|thumb|200px|Archimedes' screw was operated by hand and could raise water efficiently]] '''Archimedes' screw''' is a [[hydraulics|hydraulic]] [[machine]]. It is a type of [[pump]] used for raising water up. It is a screw inside a fairly tight-fitting [[cylinder]]. With the bottom end in water, the screw lifts water up to the top, where it pours out of a spout. The screw can be turned by hand, or by a [[windmill]], or by an [[engine]]. The screw is often used for filling [[irrigation]] ditches. [[Archimedes]] wrote about it when he was in [[Alexandria]], [[Egypt]]. It is not known for certain whether he did invent it, but it is always attributed to him.<ref>Oleson, John Peter 1984. ''Greek and Roman mechanical water-lifting devices: the history of a technology''. Dordrecht: D. Reidel. {{ISBN|90-277-1693-5}}</ref><ref>Dalley S. & Oleson J.P. 2003. Sennacherib, Archimedes, and the water screw: the context of invention in the ancient world. ''Technology and Culture'' '''44''' (1) 1-26. [http://mwbdvjh.muse.jhu.edu/dynamic/article.cgi?aid=40151&format=pdf]{{Dead link|date=January 2021 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> The Archimedes screw is still much in use all over the world. There is also a kind of reverse Archimedes' screw. Water poured in on top turns the screw. The turning drives an [[electric generator]], which makes [[electricity]]. It is good for rivers with modest water drops ('low heads'). The reverse screw has the same benefits as using the screw for pumping: it can handle very dirty water and widely varying rates of flow, with high efficiency. == References == ** P. J. Kantert: „Manual for Archimedean Screw Pump“, Hirthammer Verlag 2008, {{ISBN|978-3-88721-896-6}}. ** P. J. Kantert: „Praxishandbuch Schneckenpumpe“, Hirthammer Verlag 2008, {{ISBN|978-3-88721-2