Greece, Ancient Greek Technology

Portable disc sundial (The "any climate" portable clock) . Photo : Augusta Stylianou Artist

An upright disc (with a base revolving around the centre and an indicator consisting of a vertical gnomon and a curved rod graduated to six estimated distances - scale of the hours) bares an arc also graduated to six spaces corresponding to the six pairs of the zodiacal points (months) for the alignment of the gnomon base according to the current season. On its periphery it bears graduations of a 90╬Ž arc, so that the instrument could be hung from the point corresponding to the angle indication of the geographical latitude of the area. During its operation the sundial turns (vertically around the hypothetical perpendicular line) to the East for the indication of the 6 ante meridian hours and to the West for the indication of the 6 post meridian hours. The sunrise and the sunset coincide with the gnomon base while midday with the opposite peak.