Accession No
1752
Brief Description
universal equinoctial ring dial, English, 2/2 18th C
Origin
England
Maker
Class
dials
Earliest Date
1750
Latest Date
1800
Inscription Date
Material
metal (brass)
Dimensions
length 142 mm; diameter 117 mm
Special Collection
Holden-White collection
Provenance
On loan from The Fitzwilliam Museum, University of Cambridge. Donated by Charles Holden-White to the Fitzwilliam Museum. C. Holden-White collection no. 1935-106.
Inscription
Description Notes
Meridian ring calibrated for all latitudes, divided 90˚ - 0 - [90˚], numbered by 10˚, subdivided to 1˚. Suspension shackle with brass suspension ring. Equinoctial ring divided I - XII, I - XII, numbered by I, subdivided to 7 1/2 minutes; similarly divided on inner face; reverse of equinoctial ring carries altitude quadrant divided 0 - 90˚, numbered by 10˚, subdivided to 1˚. Pierced bridge with date scale divided to named (initialled) month, subdivided to 5 days; on reverse a declination scale divided SD[23˚ 30] - 0 - [23˚ 30´]ND, numbered by 10˚, subdivided to 1˚; also a zodiac scale (1st Aries = 20 March). Sliding pinhole gnomon.
Condition: good; complete.
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:43198
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