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Inventory no. 34585 - Former Display Label

German MECHANICAL EQUINOCTIAL DIAL
Between 1703 and 1726

Gilt and silvered brass. Signed, "Johann Willebrand, in Augspurg."; undated.

This instrument is used like the majority of mechanical equinoctial dials. After orientating and levelling the instrument, and adjusting it for latitude, the index-arm bearing the minute scale is turned until the gnomon under the minute scale casts its shadow on the line marked on the projecting bar behind it.

There is an unusual means of orientating this sundial. Within the meridian ring is a moveable ring in which is a plate in the plane of the ecliptic. On this plate is an index-arm moving over a calendar scale. The index is set to the date and the position of the instrument and the ring adjusted until the index is directed towards the sun.

[G. 537]
Lewis Evans Collection.

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