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Inventory no. 78442 - Former Display Label

English EQUINOCTIAL RING-DIAL
c.1730

Brass, silvered and gilt brass, and silver. Signed, "T * Heath Fecit"; undated.

This instrument consists of a large equinoctial dial mounted on a stand in which is a compass. The three adjustable feet, and the two spirit-levels set in the compass, together with the compass, enable the instrument to be levelled and accurately orientated. The silvered base-ring can be turned within the outer brass ring of the stand by a rack and pinion drive. The silvered ring has, on the outer edge, a scale of degrees and this scale moves against a vernier scale on the outer ring.

The instrument can be set for use in any latitude by means of another rack and pinion mechanism which turns the silvered meridian-ring (engraved with Northern and Southern latitude scales) within the outer brass meridian ring (engraved with a vernier scale).

The silvered base ring is engraved with a scale giving the equation of time throughout the year.

On the inner (silvered) meridian ring are two sights which could be used in conjunction with the vertical or horizontal scales of degrees on the instrument for determining angular elevations directions, etc. and would be of use if the instrument were used for surveying or dialling purposes.

[100]
Lewis Evans Collection

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