Water screw

I made my second example (above left) at one of the largest water screw pumping stations in Europe, which was built at Kinderdijk, The Netherlands, in the 1970s.

The water screw of the novel's subtitle operates in a cavern under Catava's supervision somehow pulling molten gold from below the surface to be used as tribute to the Egyptians.

The screw thread is not, he explains, a spiral but a helix, "a three-dimensional curve that twists around a cylinder at a constant inclined angle." The earliest known helix was the water screw developed in the third century B.C., probably by Archimedes: "Only a mathematical genius like Archimedes could have described the geometry of the helix in the first place, and only a mechanical genius like him could have conceived a practical application for this unusual shape."