The Archimedes screw may have been watering Babylon's gardens before Archimedes
Tradition credits Archimedes with the water screw, supposedly after a visit to Egypt. But one Assyriologist argues that an inscription of the Assyrian king Sennacherib describes bronze screws irrigating the Hanging Gardens centuries earlier. A BBC documentary even built one from the inscription to test the idea.
The device is simple: a helical blade wound around a shaft inside a pipe, set at an angle. As the shaft turns, the lower end scoops up water and the spiral carries it upward until it spills out the top. The seal between blade and pipe need not be watertight, because any water that leaks back into a lower section is simply lifted again by the next turn. In some versions blade and casing are fused and rotate together, sealed with pitch or cast as one piece of bronze.
The earliest firm mention comes from Moschion, writing between 250 and 220 BC, who described a screw pumping bilge water on a great ship built for Hiero II of Syracuse. Posidonius recorded screws draining Spanish mines. Vitruvius, writing between 27 and 22 BC, detailed a wooden screw with eight blades, and the oldest known picture is a fresco in a Pompeii villa painted before 79 AD. Remains turn up across the Roman world, in Egypt, Spain, France and Italy, but the device largely fell out of European use in the third century.
It returned in the Renaissance. Konrad Kyeser illustrated it in his manuscript Bellifortis in 1405, Leonardo da Vinci drew it, and Galileo explained how it worked. Dutch polder mills used windmills to turn screws and drain land during the Golden Age. Daniel Bernoulli studied the pocket of water each turn carries in 1738, and in 1932 the Dutch engineer Joan Muysken worked out a formula for the screw's rotational speed.
Today screw pumps move wastewater through treatment plants and drain low-lying land. Run backward, the same design becomes a small hydroelectric turbine: it copes with heads as low as 0.1 metres and flows from 0.01 to 14.5 cubic metres per second, conditions where conventional turbines struggle. A patent for the screw turbine was filed in 1991.
Source: Archimedes' screw
