Accession No
0151
Brief Description
Standing 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, steel); glass
Dimensions
height 355mm; breadth 260mm; depth 250mm; base plate 215 mm; feet protruding 35 mm; compass 113 mm
Special Collection
Robert Whipple collection
Provenance
Purchased by Robert Stewart Whipple from T.H. Court on 21/05/1924.
Inscription
Description Notes
Brass; set on 3 feet with milled head levelling screws; base plate with an index and vernier ´reading to 5´. The whole dial rotates within the base (operating screw not extant). Central plate divided [0] - 90˚ - [0], 90˚ - 0 - 90˚, numbered by 10˚, subdivided to 1˚. Also on central plate an equation of time marked ‘WATCH FASTER WATCH = SLOWER’ by minutes with associated date scale divided to named month, numbered by 10 days and subdivided to 1 day. Inset compass with silvered rim divided [0] - 360˚, numbered by 10˚, subdivided to 1˚. Also divided [0] - [90˚] - [0] - [90˚] - [0], numbered by 10˚. 8-point rose with fleur-de-lis for North. Two bubble levels inset into the compass rose at right angles.
Meridian ring set within fixed outer ring set on the dial plate. Divided ‘N.0.S.’ - 90˚ - [0] - 90˚ - [0], numbered by 10˚, subdivided to 30´, with vernier on the suspension shackle reading to 5´ and marked ‘Alt Lat’. Reverse carries a list of towns and latitudes (see history file). Sights for sun’s altitude missing, meridian ring tapped.
Equinoctial ring divided I - XII, I - XII, numbered by I, subdivided to 2 minutes (calibrations on face and inside ring). Reverse carries a list of towns and latitudes.
Pierced bridge with date scale divided to named month, subdivided to 2 days; also declination scale and zodiac scale. Single pinhole gnomon.
Signs of silvering on hour ring and meridian ring and on bridge.
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:40012
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