earliest known machine to combine a crank with a connecting rod. The watermill is shown on a raised relief on the sarcophagus of Marcus Aurelius Ammianos, a local miller. A waterwheel fed by a mill race is shown powering two frame saws via a gear train cutting rectangular blocks. Further crank and connecting rod mechanisms, without gear train, are archaeologically attested for the 6th-century AD water-powered stone sawmills at Gerasa, Jordan, and Ephesus, Turkey. Literary references to water-powered marble saws in Trier, now Germany, can be found in Ausonius's late 4th-century AD poem Mosella. They attest a diversified use of water-power in many parts of the Roman Empire. A complex of mills also existed on the Janiculum in Rome fed by the Aqua Traiana. The Aurelian Walls were carried up the hill apparently to include the water mills used to grind grain towards providing bread flour for the city. The mill was thus probably built at the same time as or before the walls were built by the emperor Aurelian (reigned 270–275 AD). The mills were supplied from an aqueduct, where it plunged down a steep hill. The site thus resembles Barbegal, although excavations in the late 1990s suggest that they may have been undershot rather than overshot in design. The mills were in use in 537 AD when the Goths besieging the city cut off their water supply. However they were subsequently restored and may have remained in operation until at least the time of Pope Gregory IV (827–44). Many other sites are reported from across the Roman Empire, although many remain unexcavated. See also List of Roman watermills Roman agriculture Roman metallurgy Roman mining Roman technology References Bibliography Further reading Cuomo, Serafina. 2008. "Ancient written sources for engineering and technology." In The Oxford handbook of engineering and technology in the classical world. Edited by John P. Oleson, 15–34. New York: Oxford Univ. Press. Greene, Kevin. 2003. "Archaeology and technology." In A companion to archaeology. Edited by John L. Bintliff, 155–173. Oxford: Blackwell. Humphrey, John W. 2006. Ancient technology. Westport, CT: Greenwood. McNeil, Ian, ed. 1990. An encyclopedia of the history of technology. London: Routledge. Oleson, John P., ed. 2008. The Oxford handbook of engineering and technology in the classical world. New York: Oxford Univ. Press. Rihll, Tracey E. 2013. Technology and society in the ancient Greek and Roman worlds. Washington, DC: American Historical Society. White, Kenneth D. 1984.