Reverse Overshot Water-Wheel

The reverse overshot water wheel was a Roman innovation used to raise water out of the lowest levels of underground mine workings. It consists of a large wheel fitted with boxes around its rim that fill with water as they dip into a source at the bottom of the rotation, then carry that water up and tip it out at the top, in effect running an overshot wheel backward to lift water rather than being driven by its fall. Because a single wheel could only lift water so far, Roman engineers arranged multiple reverse overshot wheels in a sequence to raise water considerably higher, a technique documented by the Roman architect and engineer Vitruvius around 25 BC and used chiefly to drain mines and, in some cases, agricultural land.