Diptych sundial (closed)

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Diptych sundials have two plates hinged together, and in use open out to form a right angle, with the string hinge operating as a gnomon. This ivory example (pictured here closed) was made in the 17th century in Dieppe in France.

The lid of the instrument has an equinoctial dial marked 1-12 twice for use in spring and summer months. The centre metal rivet has a hole for a pin gnomon, now missing. The ornamentation around the edge is typical of Dieppe dials.

The equinoctial dial is the simplest form of equal-hour sundial. It can be used at any latitude, provided it is inclined correctly.

Record details

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• Online ID: 000-190-001-024-C
• Image Rights Holder: National Museums Scotland
• Project: National Museums Scotland
  Project description   View all records in project
• Ref: National Museums Scotland  T.1924.11
• Date: 17th century
  
• Material: Ivory, paper list, brass strut and disc. Inscription: [On base] List of places and latitudes
  Sundial, universal, portable
  
• Dimensions: 2.75" x 2.25"
  
• What: Sundial, universal, portable
  
• Subject: 20. TIME MEASUREMENT, Sundials (Departmental Classification)
  
• Who:
• Where: France, Dieppe
  
• Event:
• Description: French portable universal sundial in ivory, book form, base with sunk compass, horizontal dial and list of places and latitudes, with equinoctial dial on lid, unsigned, Dieppe, 17th century
  
• References:
  • For a comparable example, see Lloyd, Steven A., Ivory Diptych Sundials 1570-1750. London & Cambridge, Massachusetts: Harvard, 1992. p 136, also pp 19-23 
  • Turner, G. L'E. Antique Scientific Instruments. Poole: Blandford, 1980. pp 22-3 
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