How it began
The machine is known from a relief on the lid of the sarcophagus of Marcus Aurelius Ammianos at Hierapolis in Phrygia, in present-day Turkey. The epigrapher Ritti dated the tomb to the second half or the end of the third century CE. One end of the stone lid shows the outline of a technical device, a water-powered twin stone saw, with an inscription beside it. Klaus Grewe and Paul Kessener, who published a study of the relief, noted that one may only speculate whether Ammianos himself invented the mechanism.
Before it existed
A waterwheel turns, but a saw has to move back and forth. Turning rotary motion into straight line motion was one of the most disputed questions in the study of ancient waterpower. According to the historian Schiøler, historians of technology had agreed that the one-armed crank was unknown in Roman times, and they placed its introduction much later. The only written hint of powered stone saws was a poem by Ausonius of 371 CE about marble sawmills on the Ruwer.
How it works
The relief shows a large vertical waterwheel with a long horizontal shaft. Water reached the wheel by a chute aimed at about half its height. A gear on the wheel shaft drove a second wheel, and that wheel carried cranks: a disk on the shaft with a pin set off center. A connecting rod ran from each pin to a saw. As the disk turned, the rods pushed and pulled two frame saws, each with a blade held in tension by a wooden frame, through blocks of stone at the same time.
How it spread
The use of the crank and connecting rod for sawing was not confined to Hierapolis. Remains of a water-powered stone sawmill of the sixth or early seventh century CE were found at Ephesus, with blocks about 2.2 meters long bearing two parallel saw cuts. At Gerasa in Jordan, Jacques Seigne found a sixth century mill with limestone drums bearing four cuts each. Both are later than the Hierapolis relief.
What lasted
The relief showed beyond doubt that the crank was known and applied in the third century CE, and it predates the poem of Ausonius by a hundred years. It moved the documented history of the crank and connecting rod, the linkage that turns rotation into reciprocating motion, back into the Roman period. The study of the relief was published in 2007 in a volume on hydraulic energy in antiquity.
