Accession No
0294
Brief Description
universal equinoctial ring dial, by J. Sisson, English, 1/2 18th Century
Origin
England; London
Maker
Sisson, J.
Class
dials
Earliest Date
1700
Latest Date
1750
Inscription Date
Material
metal (brass)
Dimensions
Special Collection
Robert Whipple collection
Provenance
Purchased from R. Beard, London, in 09/1926.
Inscription
‘I Sisson Fecit’ (meridian ring)
Description Notes
Meridian ring calibrated for all latitudes, divided in opposite quadrants 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 5 minutes; similarly marked on inner face. Pierced bridge with date scale divided to named month, subdivided to 2 days; reverse carries zodiac scale divided to sign and subdivided to 1˚ (1st Aries = 10 March) and decination scale divided 23˚ 30´ - Æ - 23˚ 30´, numbered by 10˚, subdivided to 30´.
Case covered with black shagreen and lined with red velvet.
good condition
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:39650
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