Semi-circumferentor

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A semi-circumferentor (a semicircular graphometer) is a surveying instrument used for measuring angles. This brass example was made around 1775, probably by Jacques Baradelle, a scientific instrument maker based in Paris.

The instrument has an inset compass and is pierced and engraved with floral scrollwork. The outer edge is divided into 180 degrees in both directions. The alidade terminates in verniers with aperture sights and is signed 'Baradelle Paris'.

Instruments of this type were in general use on the Continent, especially in France, during the 18th and 19th centuries. Although it appears to be only half an instrument, the moving alidade allows measurements to be taken through a complete circle, while economising on brass.

Record details

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• Online ID: 000-100-104-232-C
• Image Rights Holder: National Museums Scotland
• Project: National Museums Scotland
  Project description   View all records in project
• Ref: National Museums Scotland  T.1967.77
• Date: Around 1775
  c. 1775
  
• Material: Brass / silvered scale. Inscription: Baradelle Paris; NORD / N. N. Ouest / O. N. Ouest / OUEST
  Circumferentor
  
• Dimensions: 7.19" H; 11.50" D; 9.94" D
  
• What: Circumferentor
  
• Subject: 5. CARTOGRAPHY, Surveying (Departmental Classification)
  
• Who: Baradelle, Paris (Maker)
  
• Where: France, Paris
  
• Event:
• Description: Brass half circle circumferentor by Baradelle of Paris, c. 1775
  
• References:
  • Daumas, M., Scientific Instruments of the 17th and 18th Centuries and their Makers. London: 1972, p 288 
  • Phillips, P., The Collectors' Encyclopedia of Antiques. London: 1973, p 604 
• Translations:
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