Portable Vertical Sundial
Constantinople (?), 5th-6th century
Brass, D. 110 mm
The instrument consists of a circular plate with a central hole and a suspension-arm with a triangular pointer. One side of the plate is engraved with the names in Greek of thirty-six cities and provinces of the Byzantine world, together with their latitudes, rendered in the Greek alphanumeric system. The other side is engraved with a quadrant scale ranging from nought to ninety degrees (every third degree labelled alphanumerically) and a pair of scales relating to the months of the Julian calendar (January to June and July to December). A pin to fix the arm to the plate is missing, as is a gnomon, presumably with an hour-scale. The pointer of the suspension-arm would have been set to the correct latitude and the gnomon to the scale appropriate to the current month. The instrument would then have been suspended from the ring on the suspension-arm and rotated until the gnomon cast its shadow on the hour-scale.