Hemispherical Sundial

The scaphe was found at Kölner Strasse in Neuss-Gnadenthal in the area of the canabae legionis, the civilian settlement outside the gates of the legionary camp. It is the oldest known timepiece of the Rhineland. Its dial face is inside a hollow hemisphere with a horizontal edge that is conceived as a reflection of the visible part of the celestial sphere. In the middle of the hemispherical bowl is the gnomon, the shadowcasting rod. The incised vertical lines show the position of the twelve hours of the daytime in dependence on the time of the year. Since the calendar reform introduced by Julius Caesar the day was divided into 24 hours. But in daily life the Romans counted the hours differently. The Romans always divided the sunlit part of the day into 12 horae (hours). This meant that their “hour” lasted only around 40 minutes in the winter and up to 90 minutes in the summer.