Accession No
0886
Brief Description
universal equinoctial ring dial, by Benjamin Martin, English, third quarter 18th century
Origin
England; London
Maker
Martin, Benjamin
Class
dials
Earliest Date
1750
Latest Date
1775
Inscription Date
Material
metal (brass, iron)
Dimensions
length 199mm; diameter 155mm
Special Collection
Robert Whipple collection
Provenance
Purchased by Robert Stewart Whipple in 03/1939.
Inscription
‘B Martin London’ (inscription on meridian ring)
Description Notes
Meridian ring calibrated for all latitudes, divided in adjacent quadrants, 90-0-[90], numbered by 10˚, subdivided to 30´. Suspension shackle with iron suspension ring. Equinoctial ring divided I - XII, I - XII, numbered by I, subdivided to 5 minutes; similarly divided on the inner face. Pierced bridge with date scale divided to named (initialled) month, subdivided to 5 days; reverse carries zodiac scale divided to sign of zodiac (1st Aries = 20 March), also declination scale divided ‘SD 23˚ 30´ - Æ - 23˚ 30´ ND’, numbered by 10˚, subdivided to 30´; pinhole gnomon. Reverse of meridian ring carries an altitude quadrant divided 0 - 90˚, numbered by 10˚, subdivided to 30´. Decoration at each end of the bridge.
Condition: good/fair (heavily tarnished brass)
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:40010
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