Roman pillar dial

[Fred Sawyer]

At long last, Hester Higton’s book Sundials: An Illustrated History of Portable Dials is now in print.  In reading it, I was particularly pleased to learn in the very first chapter of a dial that was totally new to me – although perhaps I should have known of it earlier.  Higton discusses a Roman cylinder dial – essentially a ‘shepherd’s dial’ from the first century AD.  Evidently, an 1884 excavation of a gravesite at Este, near Padua in Northern Italy turned up a number of items, including something that was initially cataloged only as a ‘case’.  The item has been on display in the Museum of Este, but in 1984 it was identified as a cylinder dial – a bone pillar with engraved hour lines, and a bone cap with two hinged bronze gnomons that could fit into the pillar when not in use.  The dial worked just as a modern shepherd’s altitude dial – except that its hour lines were calibrated for seasonal hours.  This discovery extends the invention date of the cylinder dial back at least 8 centuries – previously it had been thought to be an invention of the 9th or 10th century.  Mario Arnaldi and Karlheinz Schaldach have published an article on this dial: “A Roman cylinder dial: witness to a forgotten tradition”, Journal of the History of Astronomy, 1997, 28:107-117.