A gilt and patinated brass mechanical equinoctial dial, Austrian, early 18th century,
Lot 143
A gilt and patinated brass mechanical equinoctial dial,
Austrian, early 18th century,
£14,000 - 18,000
US$ 24,000 - 30,000
Lot Details
A gilt and patinated brass mechanical equinoctial dial, Austrian, early 18th century,
the elongated octagonal base-plate, the shorter sides lobed, the plate with engraved scallop decoration, is carried by three turned levelling feet. A rigidly mounted plummet holder and bob is attached at the end opposite that on which the dial is mounted. Along the centre length of the base is a latitude scale (33°-63°against which the equinoctial plate may be set by a strut and holder. This holder is adjusted by loosening a wing-nut below the plate. The equinoctial plate has a toothed circumference, is symmetrically pierced, has rubricated formal leaf engraving, and a double hour scale (III-XII-IX). Mounted at the centre is an alidade engraved at one end with a minute scale and carrying a vertically mounted calendar scale against which the sighting arm is adjusted. In use, the dial is oriented along the local meridian, the sighting arm is set for date against the calendar scale and turned, with the help of a key working on the extended arbor of the minute hand which turns a six-leaf pinion against the toothed edge of the hour plate, until a spot of light falls through the upper vane of the onto the centre of the lower vane. Time can then be read off from the two scales. 8 by 5½in (20.3 x 14.2cm)

Footnotes

  • Of the several forms of mechanical equinoctial dial developed throughout Europe during the 18th century following invention of the device, probably by Claude Dunod c. 1680, the example offered here resembles most closely the instruments produced by Franz Antoni Knitl (1671-1754), who from 1708 was a staff member of the Engineering School at Linz and from whom several instruments are known dating between 1708 and 1721.
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  1. Jon Baddeley
    Specialist - Scientific Instruments
    Bonhams
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