Ancient Sundials

Dialface ID 137

ObjID139-1

Holder:: Ephorie Rhodos, Kamiros, Greece
Site:: Rhodes, Greece
Material:: Marble, White
Dating:: unknown
Type:: Cone, Conical
Site Geolocation:: Lat.: 36.42, Long.: 28.2

Abstract

Gibbs: Traces of a gnomon hole 50 mm x 55 mm remain in the top surface to a depth of 40 mm. Its monumental size distinguishes this dial from others of similar shape (rounded sides rising from a plinth base) found on the islands of Rhodes and Kos. The mount hole in the bottom center (45 mm x 50 mm, 55 mm deep) contains a trace of lead.

Measurements

Measurement record: pipeline ObjID 139, matched to this dialface by inventory number.

Quality grade	B (completeness 84 %)
Dial surface	cone (decisive) · fit residual mm: cone 0.49, cylinder 3.94, sphere 11.65
Latitude φ	39.02 ± 0.85° (consensus of witnesses)
Klima	Athens, Delos
Engraved lines	6 hour lines, 3 day lines
Cone half-angle α	41.7 ± 0.30° (cone residual on all points 0.49 mm)
Measured	2026-06-12 20:23

What the dial shows at this latitude

	Winter solstice	Equinox	Summer solstice
Noon altitude of the Sun	27.3°	51.0°	74.7°
Noon shadow (gnomon heights)	1.94	0.81	0.27
Length of the day	9.2 h	12.0 h	14.8 h
Length of a seasonal hour	46 min	60 min	74 min

Computed for the measured latitude with the obliquity of the JPL ephemeris at 101 BC (year -100). The latitude is the one the dial was made for, not a find-spot coordinate.

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References

– Dyggve, Ejnar, Poulsen, Vagn, Lindos : fouilles de l'acropole, 1902-1914 et 1952. 3, Le sanctuaire d'Athana Lindia et l'architecture lindienne, Copenhagen and Berlin, 1960, p. 344, figure 7, no. 24 (photograph of base).
– Gibbs, Sharon L., Greek and Roman Sundials, New Haven and London, 1976, p. 257.