The Archimedes screw – also known as the water screw, Egyptian screw and the hydrodynamic screw – is a machine used to raise and transport water. The technology typically features a spiral within a hollow tube which, when rotated, positively displaces water from the bottom to the top of the cylinder.
Though the technology is often credited to the 3rd-century Greek mathematician and inventor, Archimedes of Syracuse, there’s evidence that screw pumps were in use centuries earlier, in both Egypt and Assyria. In fact, some scholars theorise that screw pumps were used as irrigation tools as early as the 7th century BC.
So, how exactly does the Archimedes screw work, when was it invented and why is it credited to Archimedes?
How does the Archimedes screw work?
The Archimedes screw is essentially a hollow tube that contains a spiral or helix that winds its way up the cylinder. The bottom end of the tube is then placed in a body of water, and the tube is rotated. As the screw turns, it scoops up some of the water. Further turns raise the water through consecutive pockets of the helix until it reaches the top of the tube.
In this way, water from a lower source (say, a river) could be easily raised to a different source (such as an irrigation ditch flowing to agricultural lands).
Methods of rotating the screw pump have varied widely over the centuries. In some civilisations, the shaft would be turned by way of manual labour. In others, by cattle or windmills. Eventually, motors were employed to power screw pumps.
Who invented the Archimedes screw?
There’s evidence that the Archimedes screw was in use during the Hellenistic period of ancient Egyptian history, in around the 3rd century BC. At that time, the Archimedes screw was used to raise water from the Nile, functioning as an irrigation tool. Some scholars have theorised, however, that ancient civilisations were in possession of the technology far earlier than the 3rd century BC.
Assyriologist Stephanie Dalley, for example, has theorised that water screws were in use in the Neo-Assyrian Empire during the reign of King Sennacherib (704-681 BC). Dalley cites a cuneiform inscription as evidence, hailing the artefact as proof that the Assyrians were casting screw pumps in bronze in around the 7th century BC.
Dalley’s theory aligns with the writings of ancient Greek historian Strabo, who wrote that the Hanging Gardens of Babylon – the most elusive of the ‘7 wonders of the ancient world’ – had been irrigated using screws.
The gardens have never been definitively located: some theorise they were situated in Babylon but destroyed in the 1st century AD, while others posit they may have been built in Nineveh under King Sennacherib. So, as yet, there’s no definitive way of knowing how exactly they were irrigated – whether with screw pumps or not.
Why is it popularly known as the Archimedes screw?
So, if the Assyrians and the ancient Egyptians may have been in possession of the technology before the 3rd century BC, why is it named after a 3rd-century Greek mathematician and inventor, Archimedes of Syracuse?
One theory posits that Archimedes invented the screw pump himself, independently. The story goes that King Hiero had Archimedes invent a tool that could remove water from the hull of a ship, which led Archimedes to create the screw pump.
Another theory posits that Archimedes travelled from Greece to Egypt in around 234 BC, where he discovered the technology that was already in use there. He then set about tweaking and improving the invention to his own parameters. Indeed, the evidence suggests that Archimedes never claimed the invention as his own, but rather it was credited to him two centuries later, by the 1st-century BC Greek historian, Diodorus.
How has the Archimedes screw impacted society?
The Archimedes screw served as a vital aid for irrigation across the ancient world, typically as a means of raising water from rivers and lakes into agricultural lands.
To this day, screw pumps are used in water treatment plants around the world to move water and sewage. The technology can also be found in some amusement park rides and in chocolate fountains.
If water is directed into the top of an Archimedes screw, rather than the bottom, it forces the screw to rotate. This can then be utilised as a form of electricity generation. Hydro-generating pumps of this sort are in use on the River Thames in England, the power generated by which is then fed into Windsor Castle.