Accession No
1091
Brief Description
universal equinoctial ring dial, English, 1737
Origin
Maker
Class
dials
Earliest Date
1737
Latest Date
1737
Inscription Date
1737
Material
metal (brass)
Dimensions
length 103mm; diameter 87mm
Special Collection
Provenance
On loan from St. John’s College, University of Cambridge from 08/1951. Presented to St. Johns College by H.G. Hadfield esq. in 1927. Originally owned by J. Colemare of St. John’s, c. 1737.
Inscription
‘J. Colemare 1737 Soph at St. John’s Cambridge’ (owner’s inscription on reverse of hour ring, accompanied by 3 scallop shells)
Description Notes
Meridian ring calibrated for northern latitudes, divided Æ (0˚) - [90˚] (only visible to 81˚; 17-1-2000), numbered by 10˚, subdivided to 1˚ . Suspension shackle (suspension ring missing)(there is a suspension ring; 17-1-2000). Equinoctial ring divided III - XII, I - X (I - IX; 17-1-2000), numbered by I, subdivided to 15 minutes; similarly divided on the inner face. Pierced bridge with date scale divided to named (initialled) month, subdivided to 5 days; on reverse a declination scale divided 24˚ - 0 - 24˚, numbered by 10˚, subdivided to 2˚ (1st Aries = 9 March); pinhole gnomon.
Reverse of meridian ring carries altitude quadrant, divided [0] - 90˚, numbered by 10˚, subdivided to 1˚.
Condition: good.
References
Events
Description
The universal equinoctial ring dial was designed by the English mathematician William Oughtred in the first half of the seventeenth century. It could be used at any latitude, so was a popular timekeeper for sailors and other travellers. It was really a much simplified version of the armillary sphere, only keeping the parts which were needed for telling the time.
The universal equinoctial ring dial consists of two rings and a bridging bar inside the inner ring. The outer ring represents a circle passing through the North and South celestial poles. The inner ring is called the ‘equinoctial’ ring because it represents the celestial equator. The bridging bar represents the axis of the world, just as the gnomon on an ordinary horizontal dial does. So the instrument is a very simple model of the heavens.
01/02/2001
Created by: Dr Hester Higton on 01/02/2001
FM:40005
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